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Psychoneuroimmunology FOURTH EDITION Volume I
SECTION EDITORS
Robert Dantzer Department of Animal Sciences University of Illinois at Urbana-Champaign Urbana, Illinois Ronald Glaser Institute for Behavioral Medicine Research The Ohio State University College of Medicine Columbus, Ohio Cobi Heijnen Department of Psychoneuroimmunology University Medical Center Utrecht, The Netherlands Michael Irwin Cousins Center for Psychoneuroimmunology University of California Los Angeles, California David Padgett Institute for Behavioral Medicine Research The Ohio State University College of Dentistry Columbus, Ohio John Sheridan Institute for Behavioral Medicine Research The Ohio State University College of Dentistry Columbus, Ohio
Psychoneuroimmunology FOURTH EDITION Volume I
Edited by
Robert Ader Department of Psychiatry Center for Psychoneuroimmunology Research University of Rochester Medical Center Rochester, New York
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Library of Congress Cataloging-in-Publication Data Psychoneuroimmunology / edited by Robert Ader.—4th ed. p. ; cm. Includes bibliographical references and indexes. ISBN-10: (invalid) 978012088576X (set : hardback : alk. paper) ISBN-10: 0-12-088576-X (set : hardback : alk. paper) ISBN-13: 978-0-12-088577-0 (v. 1 : hardback : alk. paper) ISBN-10: 0-12-088577-8 (v. 1 : hardback : alk. paper) [etc.] 1. Psychoneuroimmunology. I. Ader, Robert. [DNLM: 1. Psychoneuroimmunology. WL 103.7 P9734 2007] QP356.47.P79 2007 616.07′9—dc22 2006010164
British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library ISBN ISBN ISBN ISBN ISBN ISBN
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978-0-12-088576-8X (Two Volume Set) 0-12-088576-X (Two Volume Set) 978-0-12-088577-0 (Volume I) 0-12-088577-8 (Volume I) 978-0-12-088578-7 (Volume II) 0-12-088578-6 (Volume II)
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Contents
7. Crosstalk between Insulin-like Growth Factors and Pro-inflammatory Cytokines . . . . . . . . . . 171 Robert H. McCusker, Klemen Strle, Suzanne R. Broussard, Robert Dantzer, Rose Marie Bluthé, and Keith W. Kelley
VOLUME I Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . ix Preface to the Fourth Edition . . . . . xv About the Editors . . . . . . . . . . . . . . . . . . . xix
8. The Neuroendocrine System and Rheumatoid Arthritis: Focus on the HypothalamicPituitary-Adrenal Axis . . . . . . . . . . . . . . . . . . . 193 Heather E. Gorby and Esther M. Sternberg
Prologue Exploring the Phylogenetic History of Neuralimmune System Interactions: An Update . . . . . 1 Nicholas Cohen and Kevin S. Kinney
9. Sex Steroids and Immunity . . . . . . . . . . . . . . . 207 Maurizio Cutolo and Alessandro Calvia 10. Emerging Concepts for the Pathogenesis of Chronic Disabling Inflammatory Diseases: Neuroendocrine-immune Interactions and Evolutionary Biology . . . . . . . . . . . . . . . . . . . . . 217 Rainer H. Straub, Adriana del Rey, and Hugo O. Besedovsky
I. Neural and Endocrine Effects on Immunity I. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 C. J. Heijnen
11. Neuroendocrine Regulation of Cancer Progression: I. Biological Mechanisms and Clinical Relevance . . . . . . . . . . . . . . . . . . . . . . . 233 Anil K. Sood, Susan K. Lutgendorf, and Steve Cole
1. Glucocorticoids and Immunity: Mechanisms of Regulation . . . . . . . . . . . . . . . . . 45 Onard J. L. M. Schoneveld and John A. Cidlowski 2. Adrenergic Regulation of Immunity . . . . . . . . 63 Virginia M. Sanders and Annemieke Kavelaars
12. Neuroendocrine Regulation of Cancer Progression: II. Immunological Mechanisms, Clinical Relevance, and Prophylactic Measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 Roi Avraham and Shamgar Ben-Eliyahu
3. Cholinergic Regulation of Inflammation . . . . . 85 Christopher J. Czura, Mauricio Rosas-Ballina, and Kevin J. Tracey 4. Significance of Sensory Neuropeptides and the Immune Response . . . . . . . . . . . . . . . . . . . . . 97 Hanneke P. M. van der Kleij and John Bienenstock
II. Immune System Effects on Neural and Endocrine Processes and Behavior
5. Vasoactive Intestinal Peptide: An Anti-inflammatory Neuropeptide . . . . . . 131 Doina Ganea and Mario Delgado
Robert Dantzer
6. Immune-derived Opioids: Production and Function in Inflammatory Pain . . . . . . . . . . . . 159 Halina Machelska and Christoph Stein
II. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 Robert Dantzer
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13. Expression and Action of Cytokines in the Brain: Mechanisms and Pathophysiological Implications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271 Robert Dantzer 14. Cytokines, Sickness Behavior, and Depression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281 Robert Dantzer, Rose-Marie Bluthé, Nathalie Castanon, Keith W. Kelley, Jan-Pieter Konsman, Sophie Laye, Jacques Lestage, and Patricia Parnet 15. The Differential Role of Prostaglandin E2 Receptors in the CNS Response to Systemic Immune Challenge . . . . . . . . . . . . . . . . . . . . . . 319 Michael Lazarus and Clifford B. Saper 16. The Role of Pro-inflammatory Cytokines in Memory Processes and Neural Plasticity . . . 337 Inbal Goshen and Raz Yirmiya 17. Aging, Neuroinflammation, and Behavior . . . 379 Rodney W. Johnson and Jonathan P. Godbout 18. Neuroimmune Interactions and Pain: The Role of Immune and Glial Cells . . . . . . . 393 Linda R. Watkins, Julie Wieseler-Frank, Mark R. Hutchinson, Annemarie Ledeboer, Leah Spataro, Erin D. Milligan, Evan M. Sloane, and Steven F. Maier
24. Psychoneuroimmunology of Depressive Disorder: Mechanisms and Clinical Implications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509 Lucile Capuron, Andrew Miller, and Michael R. Irwin 25. Immune and Neuroendocrine Alterations in Post-traumatic Stress Disorder . . . . . . . . . . . . 531 Gail Ironson, Dean Cruess, and Mahendra Kumar 26. Psychoneuroimmunologic Aspects of Alcohol and Substance Abuse . . . . . . . . . . . . . 549 Steven J. Schleifer 27. Schizophrenia and Immunity . . . . . . . . . . . . . 563 Matthias Rothermundt and Volker Arolt 28. Sleep and the Immune System . . . . . . . . . . . . 579 Mark R. Opp, Jan Born, and Michael R. Irwin 29. Emotions and the Immune System . . . . . . . . . 619 Margaret E. Kemeny 30. Behaviorally Conditioned Enhancement of Immune Responses . . . . . . . . . . . . . . . . . . . . . . 631 Gustavo Pacheco-López, Maj-Britt Niemi, Harald Engler, and Manfred Schedlowski 31. Exercise and Immunity: Clinical Studies . . . . 661 David C. Nieman
19. Cytokines and Non-immune Brain Injury . . . 415 Barry W. McColl, Chris J. Stock, and Nancy J. Rothwell
32. Behavioral Interventions: Immunologic Mediators and Disease Outcomes . . . . . . . . . . 675 Michael H. Antoni, Neil Schneiderman, and Frank Penedo
20. The Interaction between Brain Inflammation and Systemic Infection . . . . . . . . . . . . . . . . . . . 429 Leigh M. Felton and V. Hugh Perry
VOLUME II
III. Behavior and Immunity Michael R. Irwin III. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 449 Michael Irwin 21. Mother-infant Interactions and the Development of Immunity from Conception through Weaning . . . . . . . . . . . . . . . . . . . . . . . . 455 Christopher L. Coe and Gabriele R. Lubach 22. Social Dominance and Immunity in Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 475 Mark L. Laudenslager and Sarah Kennedy 23. Social Context as an Individual Difference in Psychoneuroimmunology . . . . . . . . . . . . . . 497 Edith Chen and Gregory E. Miller
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . ix Preface to the Fourth Edition . . . . . xv About the Editors . . . . . . . . . . . . . . . . . . . xix IV. Stress and Immunity Ronald Glaser IV. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 705 Ronald Glaser 33. Stress: A System of the Whole . . . . . . . . . . . . . 709 Bruce Rabin 34. Bi-directional Effects of Stress on Immune Function: Possible Explanations for Salubrious as Well as Harmful Effects . . . . . . 723 Firdaus S. Dhabhar and Bruce S. McEwen
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35. Positive Affect and Immune Function . . . . . . 761 Anna L. Marsland, Sarah Pressman, and Sheldon Cohen 36. Close Relationships and Immunity . . . . . . . . . 781 Jennifer E. Graham, Lisa M. Christian, and Janice K. Kiecolt-Glaser 37. Stress and Allergic Diseases . . . . . . . . . . . . . . . 799 Gailen D. Marshall and Sitesh R. Roy 38. Stress, Neuroendocrine Hormones, and Wound Healing: Human Models . . . . . . . . . . 825 Phillip T. Marucha and Christopher G. Engeland 39. Stress and Wound Healing: Animal Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 837 David A. Padgett, Phillip T. Marucha, and John F. Sheridan 40. Reactivation of Latent Herpes Viruses in Astronauts . . . . . . . . . . . . . . . . . . . . . . . . . . . 851 Duane L. Pierson, Satish K. Mehta, and Raymond P. Stowe 41. Psychosocial Influences in Oncology: An Expanded Model of Biobehavioral Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . 869 Susan K. Lutgendorf, Erin S. Costanzo, and Scott D. Siegel 42. Stress-associated Immune Dysregulation Can Affect Antibody and T-cell Responses to Vaccines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 897 Mark A. Wetherell and Kavita Vedhara
V. Psychoneuroimmunology and Pathophysiology John Sheridan and David Padgett V. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 917 John Sheridan and David Padgett 43. Psychoneuroimmunological Pathways Involved in Acute Coronary Syndromes . . . . 921 Willem J. Kop and Nicholas Cohen
44. Psychosocial Factors and Coronary Heart Disease: The Role of Psychoneuroimmunological Processes . . . . . . 945 Andrew Steptoe and Lena Brydon 45. Endocrine and Immune Responses to Stress in Chronic Inflammatory Skin Disorder (Atopic Dermatitis) . . . . . . . . . . . . . . . . . . . . . . 975 A. Buske-Kirschbaum 46. Obesity and Immunity . . . . . . . . . . . . . . . . . . . 993 Christopher B. Guest, Yan Gao, Jason C. O’Connor, and Gregory G. Freund 47. Endogenous Extracellular Hsp72 Release Is an Adaptive Feature of the Acute Stress Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1013 Monika Fleshner, Craig M. Sharkey, Molly Nickerson, and John D. Johnson 48. Cold-Restraint–induced Immune and Biochemical Changes Inhibit Host Resistance to Listeria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1035 Rebecca T. Emeny and David A. Lawrence 49. Psychobiology of HIV Infection . . . . . . . . . . 1053 Erica Sloan, Alicia Collado-Hidalgo, and Steve Cole 50. Stress-induced Modulation of the Immune Response to Herpes Simplex Virus Infections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1077 Robert H. Bonneau and John T. Hunzeker 51. Stress-induced Modulation of Innate Resistance and Adaptive Immunity to Influenza Viral Infection . . . . . . . . . . . . . . . . . 1097 Michael T. Bailey, David A. Padgett, and John F. Sheridan 52. Social Stress Alters the Severity of a Virally Initiated Model of Multiple Sclerosis . . . . . . 1107 Mary W. Meagher, Robin Johnson, Elisabeth Good, and C. Jane Welsh
Author Index Subject Index
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1125 1249
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Contributors
Numbers in parentheses indicate the volume number and the chapter(s) where the authors’ contribution(s) begin.
Lena Brydon (2: Ch. 44) Psychobiology Group, Department of Epidemiology and Public Health, University College London, London WC1E 6BT, UK A. Buske-Kirschbaum (2: Ch. 45) Department of Biopsychology, Technical University of Dresden, Dresden D-01362 Germany Alessandro Calvia (1: Ch. 9) Research Laboratory and Division of Rheumatology, Department Internal Medicine, University of Genova, Viale Benedetto XV, 6 16132 Genova, Italy Lucile Capuron (1: Ch. 24) Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, Atlanta, Georgia 30322 Nathalie Castanon (2: Ch. 14) Neurobiologie Intégrative, UMR INRA Université de Bordeaux 2, FRE CNRS, Rue Camille Saint-Saëns, 33077 Bordeaux Cedex, France Edith Chen (1: Ch. 23) Department of Psychology, University of British Columbia, Vancouver BC V6T 1Z4 Lisa M. Christian (2: Ch. 36) Department of Psychology, The Ohio State University, Columbus, Ohio 43210 John A. Cidlowski (1: Ch. 1) Laboratory of Signal Transduction, Molecular Endocrinology Group, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709 Christopher L. Coe (1: Ch. 21) Harlow Center for Biological Psychology, University of Wisconsin, Madison, Wisconsin 53715 Nicholas Cohen (1: Prologue; 2: Ch. 43) Department of Microbiology and Immunology and the Center for Mind-Body Research, The University of Rochester School of Medicine and Dentistry, Rochester, New York 14642
Michael H. Antoni (1: Ch. 32) Department of Behavioral Medicine, University of Miami, Coral Gables, Florida 33146 Volker Arolt (1: Ch. 27) Department of Psychiatry, University of Muenster, 48129, Muenster, Germany Roi Avraham (1: Ch. 12) Department of Psychology, Tel Aviv University, Tel Aviv 69978 Israel Michael T. Bailey (2: Ch. 51) Section of Oral Biology, College of Dentistry, The Ohio State University, Columbus, Ohio 43218 Shamgar Ben-Eliyahu (1: Ch. 12) Department of Psychology, Tel Aviv University, Tel Aviv 69978 Israel Hugo O. Besedovsky (1: Ch. 10) Institute of Normal and Pathological Physiology, University of Marburg, 35033 Marburg, Germany John Bienenstock (1: Ch. 4) Brain-Body Institute and Department of Pathology and Molecular Medicine, St. Joseph’s Healthcare Hamilton and McMaster University, Hamilton, Ontario, Canada L8N 3Z5 Rose-Marie Bluthé (1: Ch. 7, Ch. 14) Neurobiologie Intégrative, UMR INRA Université de Bordeaux 2, FRE CNRS, Rue Camille Saint-Saëns, 33077 Bordeaux Cedex, France Robert H. Bonneau (2: Ch. 50) Department of Microbiology and Immunology, College of Medicine, Milton S. Hershey Medical Center, The Pennsylvania State University, Hershey, Pennsylvania 17033 Jan Born (1: Ch. 28) Department of Neuroendocrinology, University of Lübeck, Lübeck, Germany Suzanne R. Broussard (1: Ch. 7) Integrated Immunology and Behavior Program, Laboratory of Immunophysiology, Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
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Contributors
Sheldon Cohen (2: Ch. 35) Department of Psychology, Carnegie Mellon University, Pittsburgh, Pennsylvania 15238 Steve Cole (1: Ch. 11; 2: Ch. 49) Division of Hematology-Oncology and Department of Psychiatry and Biobehavioral Sciences, and the Norman Cousins Center for Psychoneuroimmunology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095 Alicia Collado-Hidalgo (2: Ch. 49) Cousins Center for Psychoneuroimmunology, UCLA Semel Institute for Neuroscience and Human Behavior, Los Angeles, California 90095 Erin S. Costanzo (2: Ch. 41) Department of Psychology, University of Iowa, Iowa City, Iowa 52242 Dean Cruess (1: Ch. 25) Department of Psychology, University of Connecticut, Storrs, Connecticut 06269 Maurizio Cutolo (1: Ch. 9) Research Laboratory and Division of Rheumatology, Department Internal Medicine, University of Genova, Viale Benedetto XV, 6 16132 Genova, Italy Christopher J. Czura (1: Ch. 3) Laboratory of Biomedical Science, Center for Inflammation and Immunity, Feinstein Institute for Medical Research, Manhasset, New York 11030 Robert Dantzer (1: Ch7, Ch. 13, Ch. 14) Integrative Immunology and Behavior, Department of Animal Sciences, University of Illinois at UrbanaChampaign, Urbana, Illinois 61801 Mario Delgado (1: Ch. 5) Instituto de Parasitología y Biomedicina, Granada, Spain Adriana del Rey (1: Ch. 10) Institute of Normal and Pathological Physiology, University of Marburg, 35033 Marburg, Germany Firdaus S. Dhabhar (2: Ch. 34) Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, California 94305 Rebecca T. Emeny (2: Ch. 48) Laboratory of Clinical and Experimental Endocrinology & Immunology, Wadsworth Center, New York State Department of Health, Albany, New York 12201 Christopher G. Engeland (2: Ch. 38) Department of Periodontics, University of Illinois at Chicago, Chicago, Illinois 60612 Harald Engler (1: Ch. 30) Division of Psychology and Behavioral Immunobiology, Institute for Behavioral Sciences, Swiss Federal Institute of Technology (ETH), CH-8092 Zürich, Switzerland Leigh M. Felton (1: Ch. 20) CNS Inflammation Group, School of Biological Sciences, University of Southampton, Southampton, S016 7PX, UK
Monika Fleshner (2: Ch. 47) Department of Integrative Physiology and the Center for Neuroscience, University of Colorado, Boulder, Colorado 80309 Gregory G. Freund (2: Ch. 46) Integrated Immunology and Behavior, Department of Pathology Division of Nutritional Sciences, University of Illinois, Urbana, Illinois 61801 Doina Ganea (1: Ch. 5) Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140 Yan Gao (2: Ch. 46) Integrated Immunology and behavior, Division of Nutritional Sciences, University of Illinois, Urbana, Illinois 61801 Jonathan P. Godbout (1: Ch. 17) The Ohio State University, Department of Molecular Virology, Immunology, and Medical Genetics and the Institute for Behavioral Medicine Research, Columbus, Ohio 43210 Elisabeth Good (2: Ch. 52) Department of Psychology, College of Liberal Arts, Texas A&M University, College Station, Texas 77843 Heather E. Gorby (1: Ch. 8) Section on Neuroendocrine Immunology and Behavior, Integrative Neural Immune Program, National Institute of Mental Health, National Institutes of Health, Rockville, MD 20852 Inbal Goshen (1: Ch. 16) Department of Psychology, The Hebrew University of Jerusalem, Mount Scopus, Jerusalem 91905, Israel Jennifer E. Graham (2: Ch. 36) Institute for Behavioral Medicine Research, The Ohio State University College of Medicine, Columbus, Ohio 43210 Christopher B. Guest (2: Ch. 46) Integrative Immunology and Behavior, College of Medicine, Division of Nutritional Sciences, University of Illinois, Urbana, Illinois 61801 John T. Hunzeker (2: Ch. 50) Department of Microbiology and Immunology, College of Medicine, Milton S. Hershey Medical Center, The Pennsylvania State University, Hershey, Pennsylvania 17033 Mark R. Hutchinson (1: Ch. 18) Department of Psychology and the Center for Neuroscience, University of Colorado at Boulder, Boulder, Colorado 80309 Gail Ironson (1: Ch. 25) Department of Psychology and Psychiatry, University of Miami, Miami, Florida 33124 Michael R. Irwin (1: Ch. 24, Ch. 28) Cousins Center for Psychoneuroimmunology, University of California, Los Angeles, Neuropsychiatric Institute, Los Angeles, California 90095
Contributors
John D. Johnson (2: Ch. 47) Department of Integrative Physiology and the Center for Neuroscience, University of Colorado, Boulder, Colorado 80309 Robin Johnson (2: Ch. 52) Department of Psychology, College of Liberal Arts, Texas A&M University, College Station, Texas 77843 Rodney W. Johnson (1: Ch. 17) Integrative Immunology and Behavior, Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 Annemieke Kavelaars (1: Ch. 2) Laboratory for Psychoneuroimmunology, University Medical Center Utrecht, Utrecht, The Netherlands Keith W. Kelley (1: Ch. 7, Ch. 14) Integrated Immunology and Behavior Program, Laboratory of Immunophysiology, Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 Margaret E. Kemeny (1: Ch. 29) Health Psychology Program, University of California, San Francisco, California 94143 Sarah Kennedy (1: Ch. 22) Department of Integrative Physiology, University of Colorado, Boulder, Colorado 80309 Janice K. Kiecolt-Glaser (2: Ch. 36) Department of Psychiatry and Institute for Behavioral Medicine Research, The Ohio State University College of Medicine, Columbus, Ohio 43210 Kevin S. Kinney (1: Prologue) Department of Biology, DePauw University, Greencastle, Indiana 46135 Jan-Pieter Konsman (1: Ch. 14) Neurobiologie Intégrative, UMR INRA Université de Bordeaux 2, FRE CNRS, Rue Camille Saint-Saëns, 33077 Bordeaux Cedex, France Willem J. Kop (2: Ch. 43) Department of Medical and Clinical Psychology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814 Mahendra Kumar (1: Ch. 25) University of Miami, Miami, Florida 33124 Mark L. Laudenslager (1: Ch. 22) Department of Psychiatry, University of Colorado Denver & Health Sciences Center, Denver, Colorado 80220 David A. Lawrence (2: Ch. 48) Laboratory of Clinical and Experimental Endocrinology & Immunology, Wadsworth Center, New York State Department of Health, Albany, New York 12201 Sophie Laye (1: Ch. 14) Neurobiologie Intégrative, UMR INRA Université de Bordeaux 2, FRE CNRS, Rue Camille Saint-Saëns, 33077 Bordeaux Cedex, France
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Michael Lazarus (1: Ch. 15) Department of Neurology, Beth Israel Deaconess Medical Center, and Program in Neuroscience, Harvard Medical School, Boston, Massachusetts 02115 Annemarie Ledeboer (1: Ch. 18) Department of Psychology and the Center for Neuroscience, University of Colorado at Boulder, Boulder, Colorado 80309 Jacques Lestage (1: Ch. 14) Neurobiologie Intégrative, UMR INRA Université de Bordeaux 2, FRE CNRS, Rue Camille Saint-Saëns, 33077 Bordeaux Cedex, France Gabriele R. Lubach (1: Ch. 21) Harlow Center for Biological Psychology, University of Wisconsin, Madison, Wisconsin 53715 Susan K. Lutgendorf (1: Ch. 11; 2: Ch. 41) Departments of Psychology and Obstetrics and Gynecology, Holden Comprehensive Cancer Center, University of Iowa, Iowa City, Iowa 52242 Halina Machelska (1: Ch. 6) Klinik für Anaesthesiologie und operative Intensivmedizin, CharitéUniversitätsmedizin Berlin, Campus Benjamin Franklin, 12200 Berlin, Germany Steven F. Maier (1: Ch. 18) Department of Psychology and the Center for Neuroscience, University of Colorado at Boulder, Boulder, Colorado 80309 Gailen D. Marshall (2: Ch. 37) Division of Clinical Immunology and Allergy, Department of Medicine The University of Mississippi Medical Center, Jackson, Mississippi 39216 Anna L. Marsland (2: Ch. 35) Department of Psychology, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 Philip T. Marucha (2: Ch. 38, Ch. 39) Department of Periodontics, University of Illinois at Chicago, Chicago, Illinois 60612 Barry W. McColl (1: Ch. 19) Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK Robert H. McCusker (1: Ch. 7) Integrated Immunology and Behavior Program, Laboratory of Immunophysiology, Department of Animal Sciences, College of Agriculture, University of Illinois at UrbanaChampaign, Urbana, Illinois 61801 Bruce S. McEwen (2: Ch. 34) Laboratory of Neuroendocrinology, The Rockefeller University, New York, New York 10021 Mary W. Meagher (2: Ch. 52) Department of Psychology, College of Liberal Arts, Texas A&M University, College Station, Texas 77843
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Contributors
Satish K. Mehta (2: Ch. 40) National Aeronautics and Space Administration/Johnson Space Center, Enterprise Advisory Services, Inc. Houston, Texas 77058 Andrew Miller (1: Ch. 24) Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, Atlanta, Georgia 30322 Gregory E. Miller (1: Ch. 23) Department of Psychology, University of British Columbia, Vancouver BC V6T 1Z4 Erin D. Milligan (1: Ch. 18) Department of Psychology and the Center for Neuroscience, University of Colorado at Boulder, Boulder, Colorado 80309 Molly Nickerson (2: Ch. 47) Department of Integrative Physiology and the Center for Neuroscience, University of Colorado, Boulder, Colorado 80309 David C. Nieman (1: Ch. 31) Department of Health and Exercise Science, Appalachian State University, Boone, North Carolina 28608 Maj-Britt Niemi (1: Ch. 30) Division of Psychology and Behavioral Immunobiology, Institute for Behavioral Sciences, Swiss Federal Institute of Technology (ETH), CH-8092 Zürich, Switzerland Jason C. O’Connor (2: Ch. 46) Integrative Immunology and Behavior, Division of Nutritional Sciences, University of Illinois, Urbana, Illinois 61801 Mark R. Opp (1: Ch. 28) Department of Anesthesiology, University of Mechigan Medical School, Ann Arbor, Michigan 48109 Gustavo Pacheco-López (1: Ch. 30) Division of Psychology and Behavioral Immunobiology, Institute for Behavioral Sciences, Swiss Federal Institute of Technology (ETH), CH-8092 Zürich, Switzerland David A. Padgett (2: Ch. 39, Ch. 51) Section of Oral Biology, College of Dentistry, Institute for Behavioral Medicine Research, Department of Molecular Virology, Immunology and Medical Genetics, College of Medicine and Public Health, The Ohio State University, Columbus, Ohio 43218 Patricia Parnet (1: Ch. 14) Neurobiologie Intégrative, UMR INRA Université de Bordeaux 2, FRE CNRS, Rue Camille Saint-Saëns, 33077 Bordeaux Cedex, France Frank Penedo (1: Ch. 32) Department of Behavioral Medicine, University of Miami, Coral Gables, Florida 33146 V. Hugh Perry (1: Ch. 20) CNS Inflammation Group School of Biological Sciences, University of Southampton, Southampton, S016 7PX, UK Duane L. Pierson (2: Ch. 40) National Aeronautics and Space Administration/Johnson Space Center, Houston, Texas 77058
Sarah Pressman (2: Ch. 35) Department of Psychology, Carnegie Mellon University, Pittsburgh, Pennsylvania 15238 Bruce Rabin (2: Ch. 33) University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania 15213 Mauricio Rosas-Ballina (1: Ch. 3) Laboratory of Biomedical Science, Center for Inflammation and Immunity, The Feinstein Institute for Medical Research, Manhasset, New York 11030 Matthias Rothermundt (1: Ch. 27) Department of Psychiatry, University of Muenster, 48129 Muenster, Germany Nancy J. Rothwell (1: Ch. 19) Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK Sitesh R. Roy (2: Ch. 37) Division of Allergy and Immunology, Department of Pediatrics, The University of Mississippi Medical Center, Jackson, Mississippi 39216 Virginia M. Sanders (1: Ch. 2) Department of Molecular Virology, Immunology, and Medical Genetics, The Ohio State University School of Medicine and Public Health, Columbus, Ohio 43210 Clifford B. Saper (1: Ch. 15) Department of Neurology, Beth Israel Deaconess Medical Center, and Program in Neuroscience, Harvard Medical School, Boston, Massachusetts 02115 Manfred Schedlowski (1: Ch. 30) Division of Psychology and Behavioral Immunobiology, Institute for Behavioral Sciences, Swiss Federal Institute of Technology (ETH), CH-8092 Zürich, Switzerland Steven J. Schleifer (1: Ch. 26) Department of Psychiatry, UMDNJ-New Jersey Medical School, Newark, New Jersey 07103 Neil Schneiderman (1: Ch. 32) Department of Behavioral Medicine, University of Miami, Coral Gables, Florida 33146 Onard J. L. M. Schoneveld (1: Ch. 1) Laboratory of Signal Transduction, Molecular Endocrinology Group, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709 Craig M. Sharkey (2: Ch. 47) Department of Integrative Physiology and the Center for Neuroscience, University of Colorado, Boulder, Colorado 80309 John F. Sheridan (2: Ch. 39, Ch. 51) Section of Oral Biology, College of Dentistry, Institute for Behavioral Medicine Research, Department of Molecular Virology, Immunology and Medical Genetics, College of Medicine and Public Health, The Ohio State University, Columbus, Ohio 43218
Contributors
Scott D. Siegel (2: Ch. 41) Department of Psychology, University of Miami, Miami, Florida 33124 Erica Sloan (2: Ch. 49) Division of HematologyOncology and Department of Psychiatry and Biobehavioral Sciences, and the Norman Cousins Center for Psychoneuroimmunology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095 Evan M. Sloane (1: Ch. 18) Department of Psychology and the Center for Neuroscience, University of Colorado at Boulder, Boulder, Colorado 80309 Anil K. Sood (1: Ch. 11) Departments of Gynecologic Oncology and Cancer Biology, University of Texas M. D. Anderson Cancer Center, Unit 1362, Houston, Texas 77230 Leah Spataro (1: Ch. 18) Department of Psychology and the Center for Neuroscience, University of Colorado at Boulder, Boulder, Colorado 80309 Christoph Stein (1: Ch. 6) Klinik für Anaesthesiologie und operative Intensivmedizin, Charité-Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany D-12200 Andrew Steptoe (2: Ch. 44) Psychobiology Group, Department of Epidemiology and Public Health, University College London, London WC1E 6BT, UK Esther M. Sternberg (1: Ch. 8) Section on Neuroendocrine Immunology and Behavior, Integrative Neural Immune Program, National Institute of Mental Health, National Institutes of Health, Rockville, MD 20852 Chris J. Stock (1: Ch. 19) Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK Raymond P. Stowe (2: Ch. 40) Microgen Laboratories, La Marqué, Texas 77568
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Rainer H. Straub (1: Ch. 10) Department of Internal Medicine I, University Hospital Regensburg, 93042 Regensburg, Germany Klemen Strle (1: Ch. 7) Integrated Immunology and Behavior Program, Laboratory of Immunophysiology, Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 Kevin J. Tracey (1: Ch. 3) Laboratory of Biomedical Science, Center for Patient Oriented Research, General Clinical Research Center, The Feinstein Institute for Medical Research, Manhasset, New York 11030 Hanneke P.M. van der Kleij (1: Ch. 4) Brain-Body Institute and Department of Pathology and Molecular Medicine, St. Joseph’s Healthcare Hamilton and McMaster University, Hamilton, Ontario, Canada L8N 3Z5 Kavita Vedhara (2: Ch. 42) MRC Health Services Research Collaboration, University of Bristol, Clifton, Bristol, BS8 2PR, UK Linda R. Watkins (1: Ch. 18) Department of Psychology and the Center for Neuroscience, University of Colorado at Boulder, Boulder, Colorado 80309 C. Jane Welsh (2: Ch. 52) Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas 77843 Mark A. Wetherell (2: Ch. 42) MRC Health Services Research Collaboration, University of Bristol, Clifton, Bristol, BS8 2PR, UK Julie Wieseler-Frank (1: Ch. 18) Department of Psychology and the Center for Neuroscience, University of Colorado at Boulder, Boulder, Colorado 80309 Raz Yirmiya (1: Ch. 16) Department of Psychology, The Hebrew University of Jerusalem, Mount Scopus, Jerusalem 91905, Israel
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Preface to the Fourth Edition
Psychoneuroimmunology is a convergence of disciplines—namely, the behavioral sciences, the neurosciences, endocrinology, and immunology—intended to achieve a more complete understanding of the way the interactions among these systems serve homeostatic ends and influence health and disease. As I have previously remarked, psychoneuroimmunology is an interdisciplinary field that has developed and now prospers by exploring and tilling fertile territories secreted by the arbitrary and illusory boundaries of the biomedical sciences. Disciplinary boundaries, codified by bureaucracies, are historical fictions that can restrict the imagination and impede the transfer and application of technologies and lend credence to Werner Heisenberg’s assertion that “What we observe is not nature itself, but nature exposed to our method of questioning.” Today, still, the business of science, by which I mean the training of scientists, the formulation of questions and hypotheses, the implementation of research, the communication among scientists, and even the funding of research, takes place within disciplinary boundaries that represent the disassembled parts of natural phenomena. This is not a representation of nature. It is an expedience that reflects our own intellectual limitations. This theme of disciplinary integration is now being endorsed by the National Institutes of Health (NIH). The NIH Roadmap, a description of new trans-NIH initiatives, argues that, “Biomedical research traditionally has been organized . . . into broad areas of scientific interest and then [grouped] into distinct, departmentally based specialties. But, as science has advanced over the past decade . . . , two fundamental themes are apparent: the study of human biology and behavior is a wonderfully dynamic process, and the traditional divisions within biomedical research may in some instances impede the pace of scientific discovery. To lower these artificial organizational barriers, the
NIH will implement several initiatives designed to facilitate interdisciplinary research collaborations and research training and, ultimately, lead to the development of new hybrid disciplines that will provide a more complete understanding of psychological, social and biological interactions in health and disease.” Psychoneuroimmunology is one such hybrid discipline that should prosper under these NIH initiatives. This is the temporal context in which I proposed a fourth edition of Psychoneuroimmunology. Like previous editions, Psychoneuroimmunology-IV is addressed to a broad audience in a continuing effort to draw attention to the field and promote interdisciplinary research in the laboratory and in the clinic. The primary targets would be laboratory and clinical investigators in endocrinology, immunology, neurochemistry, neurophysiology, pharmacology, psychiatry, psychology, virology, and medical specialists in allergic and infectious diseases, oncology, rheumatology, etc. In contrast to previous editions, the editorial responsibilities for Psychoneuroimmunology-IV were shared among a board of Associate Editors. These individuals, Robert Dantzer, Ronald Glaser, Cobi Heijnen, Michael Irwin, David Padgett, and John Sheridan, are well known and respected investigators who did a superb job in selecting and editing the chapters in their respective parts. Having established that (a) lymphocytes bear receptors for neurotransmitters, neuropeptides, and hormones and that activated lymphocytes can produce these same neuroendocrine signals, and that (b) neurons bear receptors for messenger molecules produced by cells of the immune system and that these cytokines can be released by cells of the neuroendocrine system, current research on the mechanisms involved in this neuroendocrineimmunecircuitry are presented in Part I of this volume. Emphasizing either shared mediators or shared recep-
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tors, these several chapters describe functional neuroendocrine-immune system regulatory pathways at the intercellular, interorgan, and whole body level— and how these circuits might influence health and disease. Continuing and reinforcing this discussion of shared mediators and receptors, Part II illustrates the diversity of effects and the complexity of the circuitry involved that has made research on cytokines and neuroinflammatory processes a rapidly expanding interdisciplinary area of research in the neurosciences, including behavior. Part III details the influence of behaviors, disordered behavioral states, and behavioral interventions, including classical conditioning, on immune functions that bear on health. The premise underlying this research is that psychosocial and stressful life events induce emotional responses that are associated with neuroendocrine and autonomic nervous system changes capable of modulating immune function and, thus, the susceptibility and/or progression of disease. It is further hypothesized that interventions calculated to elicit positive emotions and behaviors might, through alterations in immune states, ameliorate the effects of stressful life experiences on disease. The final two Parts most directly address the perennial issue of whether stress-induced changes in immune function are sufficiently large (and/or of sufficient duration) to influence the health of the organism. Within the context of behavioral medicine or psychosomatic medicine, could changes in immune function serve as mediators of the effects of psychosocial factors, including stressful life experiences, on health and disease? The several chapters in Part IV on stress and immunity affirm, within the immune system, an existing literature indicating that different stressors elicit different physiological responses and, therefore, would have different effects on different disease processes. This part also reviews the effects of positive affect and social relationships on immune function and their possible health consequences; the data on the role of stressful life experiences and associated changes in immune function in allergic diseases, wound healing, reactivation of latent viruses, the progression of malignant disease, and how stressful life experiences are capable of altering the individual’s response to vaccines. Part V provides further examples of how the immune system plays a role in mediating the effects of psychosocial factors on specific disease processes. These chapters review the provocative new studies of immune system involvement in cardiovascular disease, skin disorders, obesity, infectious and autoimmune diseases—and the psychoneuroimmunologic mechanisms that may play a role in host resistance.
Although the nervous, endocrine, and immune systems evolved to serve specialized functions, the premise underlying psychoneuroimmunology, confirmed by the extraordinary amount of research that has been conducted in the past couple of decades, is that each of these “systems” is also capable of responding to information derived from the other. Together, behavioral, neural, endocrine, and immune processes of adaptation constitute an integrated network of defenses and, insofar as immunoregulatory processes are concerned, the assumption of an autonomous immune system is no longer tenable. It is not possible to obtain a full understanding of immunoregulatory processes without considering the organism and the internal and external environment in which immune responses take place. The first edition of Psychoneuroimmunology was published 25 years ago. It described the relatively meager amount of research being conducted on the relationship between the brain and the immune system. However, it was, as one reviewer prophesied, the signature volume of a new field of research. That new field of research has since come of age and is being described as a paradigm shift in the way we view the multi-tiered organization of adaptive processes. Certainly, that is not a universally accepted proposition. Psychoneuroimmunology has been and, in reduced volume, continues to be assailed by gratuitous and uninformed commentaries. That is not altogether surprising. Any number of writers has commented that the everyday business of most scientists does not concern itself with the development or implementation of new ideas and theories—and is often intolerant of such developments by others. “Normal science,” as Thomas Kuhn refers to it in The Structure of Scientific Revolutions (University of Chicago Press, 1970), is concerned with an elaboration of the phenomena that the prevailing paradigm already supplies. And, in accord with the prevailing paradigm, we refer to connections between the CNS and immune system, which is not an especially satisfactory or accurate expression. It does not adequately describe the essence of the integration that the term psychoneuroimmunology is meant to convey. The phrase enables one to retain the historical fiction that these are separate and distinct systems; it is a two-dimensional expression for a threedimensional concept. Psychoneuroimmunology does magnify the complexity of already complex fields of study. That, however, is a small price to pay for a more complete understanding of biological processes that constitute the foundation of the study of health and illness. As we learn more about how behavioral, neural, and endocrine states influence immunologically based dis-
Preface to the Fourth Edition
eases and how immune processes affect behavior and what are presumed to be endocrine or neurologic disorders, there may be a need to redefine the nature of some diseases and, thus, the strategies for therapeutic interventions. Accepting the notion that there is a single, integrated system of adaptive processes pre-
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sents new challenges and new opportunities for approaching the study of health and the treatment and prevention of disease. The authors of Psychoneuroimmunology-IV invite your participation in this venture. Robert Ader
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About the Editors
of Psychoneuroimmunology at the Department of Pathology and Department of Animal Sciences of the University of Illinois at Urbana-Champaign, where he coordinates a program in Integrative Immunology and Behavior. Robert Dantzer has carried out research for many years on the psychobiology of stress, the influence of neuropeptides on behavior, and the interactions between the immune system and the brain. His current research aims at understanding the mechanisms of cytokine-induced sickness behavior and the possible involvement of cytokines in symptoms of depression. He has authored and co-authored 350 original research papers and 100 book chapters on stress, anxiety, neuropeptides, and psychoneuroimmunology. He is also the author or the editor of several books on stress in intensive husbandry, emotions, psychosomatics, and neurobiology of cytokines. He is the Editor-in-Chief of Psychoneuroendocrinology (Elsevier), Associate Editor of Brain, Behavior and Immunity (Elsevier), and was President of the Psychoneuroimmunology Research Society from 2002 to 2003.
Robert Ader, Ph.D., M.D. hc Dr. Robert Ader is Distinguished University Professor at the University of Rochester School of Medicine and Dentistry. He received his Ph.D. in psychology from Cornell University in 1957 and immediately thereafter joined the Rochester faculty, becoming Professor of Psychiatry and Psychology in 1968. He was awarded an honorary M.D. from Trondheim University in Norway in 1992 and an honorary D.Sc. from Tulane University in 2002. Dr. Ader was Visiting Professor at the Rudolf Magnus Institute for Pharmacology in Utrecht, The Netherlands (1970–71), and a Fellow at the Center for Advanced Study in the Behavioral Sciences at Stanford (1992–93). He serves on several Editorial Boards and was Editor-in-Chief of Brain, Behavior and Immunity from 1986 through 2002. Dr. Ader is a past President of the American Psychosomatic Society, the International Society for Developmental Psychobiology, the Academy of Behavioral Medicine Research, and was Founding President of the Psychoneuroimmunology Research Society. Robert Dantzer, D.V.M., Ph.D. Robert Dantzer was born in Saint-Etienne, France. He received his Doctorate in Veterinary Medicine in 1968, his Ph.D in 1972, and his Doctorate es-Sciences in 1977. From 1993 to 2006 he was Director of Research at the French National Institute for Agronomic Research and the Director of the Laboratory of Integrative Neurobiology at the University of Bordeaux, France, an operation funded by the French Scientific Research Council, the French National Institute of Agronomic Research, and the University of Bordeaux 2. He worked there with several senior scientists and technicians on various aspects of the expression and action of cytokines in the brain and their pathological consequences. Robert Dantzer is currently professor
Ronald Glaser, Ph.D. Ronald Glaser is Professor of Molecular Virology, Immunology, and Medical Genetics and Director of the Institute for Behavioral Medicine Research at The Ohio State University College of Medicine. He has published over 282 articles and chapters in the area of viral oncology and in the area of stress and immune function. He is an American Association for the Advancement of Science (AAAS) fellow, a fellow of the Academy of Behavioral Medicine Research, was named Distinguished Scholar by The Ohio State University, and holds the Gilbert and Kathryn Mitchell Endowed Chair in Medicine.
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About the Editors
Cobi Heijnen, Ph.D. Dr. Cobi Heijnen trained in medical biology and basic immunology and defended her thesis on regulation of antibody production by T-cell subsets at the Sorbonne University Marie Curie in Paris in 1982. She began her research in psychoneuroimmunology as a post-doctoral fellow in Utrecht. In 1997, she became a full professor in psychoneuroimmunology. This PNI chair was the first in Europe. In 1998, Dr. Heijnen received the Norman Cousins Award from the PsychoNeuroImmunology Research Society (PNIRS) and, in 2005–06, she served as President of the PNIRS. Michael Irwin, M.D. Michael Irwin, M.D., is Norman Cousins Professor of Psychiatry and Biobehavioral Sciences and Director of the Cousins Center for Psychoneuroimmunology and the UCLA Training Program in Psychoneuroimmunology. His primary research interests focus on the bi-directional relationships between behavioral processes (e.g., depression, disordered sleep) and autonomic and immunological function and their consequences for infectious disease risk and inflammation in humans. Current studies are also examining the neural, autonomic, and immunological mechanisms that underlie the action of mind-body interventions to promote health in older adults and in patients with inflammatory disorders. Dr. Irwin serves on the Advisory Council of the National Center for Complementary and Alternative Medicine, is past President of the Academy of Behavioral Medicine Research and of the Psychoneuroimmunology Research Society, Associate Editor of Brain, Behavior and Immunity, and recipient of numerous awards from the National Institutes of Health. For over a decade, Dr. Irwin has demonstrated leadership in the training of post-doctoral research fellows as Training Director of the UCLA Psychoneuroimmunology Post-Graduate Training
Program at UCLA as well as the Psychoneuroimmunology Research Society Scholars Program that sponsors training in psychoneuroimmunology at the national level. David Padgett, Ph.D. David Padgett received his Ph.D. in 1994 from the Medical College of Virginia and then joined the psychoneuroimmunology research group at The Ohio State University as a post-doctoral fellow. In the decade that he has been at Ohio State, he has risen to Associate Professor and is a member of the Institute for Behavioral Medicine Research. Dr. Padgett’s laboratory embraces the overarching concept that hormonal modulation of transcriptional activators that control gene expression is responsible for modulating innate immune responses to viral infection, the inflammatory phase of wound repair, and the induction of programmed cell death. John F. Sheridan, Ph.D. John F. Sheridan is an Associate Dean for Research, Professor of Oral Biology in the College of Dentistry, and Director of the Comprehensive Training in Oral and Craniofacial Biology program at the Ohio State University. He also holds appointments in the Departments of Molecular Virology, Immunology and Medical Genetics, and the Department of Psychology. He currently holds the George C. Paffenbarger Distinguished Alumni Endowed Chair in Dental Research, and he is an Associate Director of the Institute for Behavioral Medicine Research at the Ohio State University. Dr. Sheridan’s research is devoted to understanding the cellular and molecular mechanisms underlying mind body interactions as they relate to host defense and resistance to infectious disease. Dr. Sheridan is a past President of the PsychoNeuroImmunology Research Society.
PROLOGUE Exploring the Phylogenetic History of Neural-immune System Interactions: An Update NICHOLAS COHEN AND KEVIN S. KINNEY
I. INTRODUCTION 1 II. NEURAL-DEFENSE SYSTEM INTERACTIONS IN INVERTEBRATES 2 III. NEURAL-IMMUNE INTERACTIONS IN TELEOST FISH 6 IV. NEURAL-IMMUNE INTERACTIONS IN AMPHIBIANS 12 V. NEURAL-IMMUNE INTERACTIONS IN REPTILES 20 VI. NEURAL-IMMUNE SYSTEM INTERACTIONS IN BIRDS 22 VII. CONCLUDING REMARKS AND FUTURE RESEARCH DIRECTIONS 25
vertebrate species are serving, or have served, as living tools to probe the evolutionary origins of neuralimmune system interactions. In 2001, we published a comprehensive review of the research from these laboratories (Cohen and Kinney, 2001); the present review updates that information. The reader should bear in mind that the descriptive comparative approach we have taken here allows us only to make educated guesses about the true evolutionary history of the integration of two complex physiological systems. To avoid redundancy with what is presented in the rest of this 4th edition of Psychoneuroimmunology, we will not summarize the voluminous data from research with mammals as we did in our earlier review (Cohen and Kinney, 2001). The main phenomenology emerging from the literature that deals with neural-immune system interactions in rodents and primates, however, still serves as the gold standard for the questions asked by investigators using non-mammalian model systems. Thus, for comparative purposes, the mammalian reference points include the following facts: (1) mammalian lymphoid tissues are richly innervated (Felten et al., 1992; Felten et al., 2003); (2) cells of the mammalian immune system express receptors for neuropeptides, neurotransmitters, and hormones (Sanders et al., 1997, 2001); (3) activation of these receptors by their appropriate ligands affects functional behavior of the cells (Sanders and Straub, 2002; Sanders et al., 2001); (4) the SNS exerts a tonic regulatory role over the immune system as revealed, for example, by experiments
I. INTRODUCTION Psychoneuroimmunology, the study of behaviorally associated immunological changes and immunologically associated behavioral changes that result from reciprocal interactions among the nervous, endocrine, and immune systems, has emerged as a new field of scientific inquiry within the past 2 decades (Ader, 1981; Ader et al., 1991, 2001). It is a field that has been defined phenomenologically and is currently being explored mechanistically, primarily by studying rodents and primates. Although hundreds of investigators are using these and other mammalian species to address basic and clinical facets of psychoneuroimmunology, we are aware of only a handful of laboratories in which invertebrates, avian, and ectothermic (cold-blooded) PSYCHONEUROIMMUNOLOGY, 4E VOLUME I
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Copyright © 2007 by Elsevier, Inc. All rights of reproduction in any form reserved.
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involving sympathectomy (Kruszewska et al., 1995, 1998); (5) cells of the immune system themselves produce, as well as respond to, neuropeptides and hormones (Blalock, 2005; Smith, 2003); (6) cytokines (e.g., IL-1, IL-6, TNF-α) produced by cells of both systems act as signal molecules in the bi-directional dialogue between the nervous and immune systems (Danzer et al., 2002; Goehler, et al., 1997; Maier, 2003; Maier and Watkins, 1998); and (7) behavioral responses to diverse stimuli (stressors) can trigger central neuroendocrine and peripheral autonomic responses that can alter immune parameters and, thereby, under certain conditions, affect the health of the organism (Glaser et al., 1999).
II. NEURAL-DEFENSE SYSTEM INTERACTIONS IN INVERTEBRATES By all current definitions, invertebrates display features of innate immunity in the complete absence of adaptive immunity (e.g., major histocompatibility complex [MHC], immunoglobulin genes, re-arranging T-cell receptor genes, immunological specificity, and memory). In the past 15 years, two major research groups, one in Italy and the other in New York state, have explored the possibility that communication between the neuroendocrine and innate defense systems exists in invertebrates as well as vertebrates. These investigators have used four basic interrelated approaches to address this phylogenetically critical issue. In the following review of their work and the more recent work of others, the generic term hemocyte refers to the invertebrate equivalent of vertebrate blood leukocyte.
A. Synthesis of Neuroendocrine and Neurotransmitter Molecules by Invertebrate Hemocytes The first approach focused on whether endogenous neuroendocrine and/or neurotransmitter substances are synthesized by, and can affect the behavior of, invertebrate blood cells. Hemocytes from several molluscan species (Planorbarius corneus, Lymnaea stagnalis, Mytilus edulis) exhibit immunoreactivity for several vertebrate neuropeptides including met-enkephalin, oxytocin, somatostatin, vasoactive intestinal peptide (VIP), substance P (SP) (Ottaviani and Cossarizza, 1990), ACTH (Ottaviani et al., 1991; Ottaviani et al., 1992a; Smith et al., 1991), and β-endorphin (Ottaviani et al., 1990). ACTH- and TNF-α–like molecules are also found in some types of leukocytes residing in the hemolymph of the dipteran Calliphora vomitoria; staining for both ACTH and TNF-α of the mitotically active
plasmacytes was related to their activated state during the formation of capsules to wall off foreign substances (Franchini et al., 1996b). Immunoreactive met-enkephalin has also been detected in the coelomic fluid of earthworms, and treatment of earthworm coelomocytes with DAMA stimulates coelomocyte migration, much as is seen in human granulocytes and molluscan hemocytes (Cooper et al., 1993). Eleven years ago, Ottaviani et al. (1995a) reported that hemocytes from freshwater snails, Planorbarius corneus and Viviparus ater, express pro-opiomelanocortin (POMC) mRNA as assessed by in situ hybridization with a digoxigenin-labeled human DNA probe. Interestingly, this probe did not detect POMC mRNA in another morphologically distinct hemocyte from these species, a hemocyte that Ottaviani (1992) believes has features of the vertebrate T-cell. This is the same probe mentioned subsequently in connection with detection of POMC mRNA in phagocytic leukocytes from both the edible frog and goldfish, and in lymphocytes from frogs but not fish (Ottaviani et al., 1995a). It also appears that “stress” stimulates invertebrate hemocytes to produce endogenous neural-immune mediators. For example, Stefano et al. (1989b) found elevated levels of endogenous morphine-like material in the hemolymph of Mytilus that had been subjected to electrical shock combined with mechanically preventing closure of their shells. Concurrent with this rise was a substantial increase in the proportion of activated (ameboid, as opposed to rounded or resting) hemocytes (Stefano et al., 1993). With respect to stressors and immunological changes in invertebrates, it is worth noting that Malham et al. (2003) reported that abalone subjected to 15 minutes of mechanical disturbance (i.e., shaking in a rotating box) resulted in an elevation of norepinephrine (NE) and epinephrine (EPI) levels. Whether this increase was causally responsible for the accompanying reduction of numbers of circulating hemocytes, their migratory and phagocytic activity, and respiratory burst is possible, but this component of the regulatory pathway has yet to be studied. Interestingly, these changes in immune parameters were short lived in that the values returned to baseline levels (with the exception of superoxide anion production) 100–480 minutes after stress exposure. In a related study, Malham and co-workers (2002) “stressed” octopuses (Eledone cirrhosa) by handling them and exposing them to air for a few minutes. They found that both NE and EPI were released into hemolymph but that the increased levels returned to basal levels within 30–60 minutes after stressor exposure. They also saw a decrease in the numbers of circulating hemocytes that was followed by a rebound effect (i.e., greater numbers than controls within an hour). In contrast to
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their observations with abalone, the stressor in the octopus effected an increase in hemocyte activity (measured by phagocytosis of heat-killed Vibrio) that peaked at 1 hour and returned to baseline by 2 hours. The production of superoxide anions peaked as early as 5 minutes post stressor exposure and remained elevated for upwards of 2 hours. The norendocrine effectors responsible for these transitory changes are unknown, as is whether such short-lived changes have repercussions with respect to the health of these invertebrate species. There is, however, a very recent study that addresses the long-term health consequences of a stressor exposure in another invertebrate, the fresh water clam Anodonta piscinalis (Saarinen and Taskinen, 2005). These investigators explored the susceptibility of Anodonta to the ergasilid copepod, Paraergasilus rylovi. Clams were field collected from two populations in late summer. They were then transported to the laboratory and marked. The stressed clams were subjected to low oxygen for 25 days, whereas the unstressed control clams were housed in their lakes of origin for the same period. Eleven months after exposure to the stressor, the stressed clams were more intensively parasitized than controls. They also showed lower growth, lower reproduction, and poorer survival than the “unstressed” control clams. Thus, this model suggests that even in an invertebrate, a stressor may evoke long-lasting effects on susceptibility of natural populations to parasitism.
B. Effects of Mammalian Neuroendocrine and Neurotransmitter Molecules on Invertebrate Hemocytes Several investigators have examined the possible influence of exogenous neuroendocrine, neuropeptide, and/or neurotransmitter messenger molecules on the behavior of invertebrate hemocytes. Recent research on crustaceans by Cheng and colleagues (2005) revealed that 4 hours after white shrimp received 10−7 M dopamine, there was a 25% decrease in total hemocyte count, a 15% decrease in phenoloxidase activity, a 21% decrease in respiratory burst, and a 50% decrease in superoxide dismutase activity. Further, the phagocytic activity and clearance of Vibrio also diminished significantly, and bacterial challenge resulted in a higher mortality. Li et al. (2005) reported a similar response to dopamine (except for the change in numbers of circulating hemocytes) in a different host (giant prawn) and parasite combination. Catecholamines have been shown to affect the behavior of hemocytes from bivalves. Specifically, Lacoste et al. (2001) reported that 0.1 μM NE (and higher) inhibited phagocytosis in oysters, an effect that
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was mimicked by isoproterenol, but not by the alpha agonist, phenylephrine. The antagonist, propranolol (a beta-blocker), blocked the NE effect, but an alphablocker did not. Further experiments indicated that the reported effect was mediated via a cAMP-protein kinase A-dependent signal. In the 1990s, Franchini and Ottaviani (1994) and Ottaviani et al. (1992d) published that ACTH induces cytoskeletal and motility changes of phagocytic hemocytes from snails. Genedani et al. (1994) basically confirmed these studies for CRF. They also reported that ACTH fragments (1–24), (1–4), (4–9), (1–13), (1–17), and (11–24) stimulate molluscan hemocyte migration, whereas the entire sequence (1–39) and the fragment (4–11) have an inhibitory effect. Differences between species were noted with respect to the response to individual fragments. Additionally, the (4–11) fragment could antagonize some of the stimulatory fragments (4–9) as well as TNF-α–induced chemotaxis. More recently, Malagoli et al. (2000) again confirmed (in the mollusc Mytilus galloprovincialis) that exogenous CRH provokes changes in the cellular shape of immunocytes and that this response is dependent on extracellular Ca++. By using various inhibitors of transduction signaling pathways, they could completely or partially inhibit these changes. These findings are consistent with the proposition that PKA, PKC, and PKB/Akt are involved in CRH-induced cell shape changes in immunocytes and that the cellular effect of CRH needs the synergistic action of the two second messengers, cAMP and IP(3). In this study, Malagoli and colleagues also reported that immunocytes from the mussel express mRNAs for the CRH receptors, CRH-R1 and CRH-R2. ACTH also causes molluscan hemocytes to release biogenic amines (NE, EPI, and dopamine) that influence chemotactic and phagocytic activities of hemocytes (Franchini and Ottaviani, 1994; Ottaviani et al., 1992d). The greatest release occurred after 15 minutes, but after 45 minutes, the values were similar to those of the controls. Culturing hemocytes with CRF also provoked release of biogenic amines, suggesting that endogenous ACTH mediates this release. These experiments also suggest that molluscan hemocytes have the capacity to bind and respond to CRH in a manner reminiscent of the way in which mammalian leukocytes respond to this releasing factor (Ottaviani et al., 1993a). These authors further demonstrated immunoreactive tyrosine hydroxylase and dopamine betahydroxylase (enzymes involved in biogenic amine biosynthesis) in these hemocytes. Ottaviani et al. (1994) found a similar but less significant catecholamine response when mammalian interleukin-2 (IL-2) rather than ACTH was added to cultures of hemocytes. Inter-
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estingly, pre-incubation of hemocytes with IL-2 or with anti–IL-2 monoclonal antibody significantly reduced or completely eliminated the CRF-induced release of biogenic amines. Further direct evidence of competition between CRF and IL-2 was revealed by immunocytochemical and cytofluorimetric analysis. One explanation favored by these investigators (at least at that time) was the presence of a unique (ancestral?) receptor on molluscan hemocytes that is capable of binding both CRF and IL-2. If this is indeed the case, it would have significant implications for understanding the evolution of neural-immune system interactions. At the very least, these and other observations suggest that in terms of catechol biosynthesis, the invertebrate hemocyte may be a major player in an ancestral stress response that is associated with the HPA axis in mammals. Stefano and colleagues (Dureus et al., 1993) also found that administration of mammalian neuropeptide Y (NPY) to either molluscan hemocytes or to human granulocytes inhibited both spontaneous activation and chemotaxis in response to the chemoattractant synthetic peptide, N-formyl-methionyl-leucylphenylalanine. In a somewhat more recent investigation, Sassi et al. (1998) confirmed that ACTH (1–24) induces cell shape changes in the immunocytes of the mollusc, Mytilus galloprovincialis. Using computer-assisted microscopic image analysis, they reported that a G protein antagonist (suramin sodium), an adenylate cyclase inhibitor (2′,5′-dideoxyadenosine), and a protein kinase inhibitor (staurosporine) inhibited this effect. The highly specific inhibitors H-89 (for protein kinase A) and calphostin C (for protein kinase C) only partially inhibited the morphological alterations, whereas the simultaneous action of H-89 and calphostin C completely blocked them. Thus, mammalian ACTHinduced changes in cell shape appear to involve the adenylate cyclase/cAMP/protein kinase A pathway, as well as the activation of protein kinase C. In a related paper (Ottaviani et al., 1998b), ACTH receptor-like messenger RNA was detected in molluscan hemocytes (and, as a control, in human blood mononuclear cells) using a digoxigenin-labeled bovine cDNA probe. These findings imply that the ACTH receptor gene has been highly conserved during evolution and, according to these investigators, support their hypothesis that there is a phylogenetic relationship between the immune and neuroendocrine systems in invertebrates. Stefano et al. (1989a) reported that opioids can also affect the behavior of hemocytes of the mussel, Mytilus edulis. Specifically, they found that the synthetic enkephalin analogue, DAMA (D-Ala2, met5enkephalinamide), modulated locomotion, adherence,
and conformation of a subset of hemocytes that resulted in their assuming a flattened and elongated conformation with extended pseudopodia. These morphological characteristics of hemocyte activation are similar to those seen following similar treatment of human granulocytes (Hughes et al., 1991b; Stefano et al., 1989a; Stefano et al., 1989b; Stefano et al., 1991a).
C. Effects of Mammalian Cytokines on Invertebrate Hemocytes The third approach to studying invertebrate neuralinnate immune system interactions has involved exploring the impact of molecules, purported to be homologues of mammalian pro-inflammatory cytokines, on hemocyte locomotion and phagocytosis, and on the production of nitric oxide synthase (NOS) and biogenic amines (Ottaviani et al., 1995c; Ottaviani et al., 1997). Some of these studies provide suggestive evidence that the cytokines tested can bind to, and compete with, CRF for the same membrane receptor (Ottaviani and Franchini 1995). However, given the known lack of cross-reactivity of most mammalian cytokines with cells from different mammalian species (Haynes and Cohen, 1991), these results with mammalian cytokines and invertebrate blood cells must remain more provocative than definitive.
D. Production of Cytokine-Like Molecules by Invertebrate Hemocytes The final approach taken by these investigators addresses the production of cytokine-like molecules by invertebrate hemocytes in response to signals that clearly elicit cytokine production by mammalian leukocytes. Like human granulocytes, molluscan hemocytes respond to lipopolysaccharide (LPS) stimulation by assuming the active conformation changes described above (Hughes, et al., 1990; Hughes et al., 1991a; Hughes et al., 1991c). Similar LPS-induced changes of hemocytes from the insect Leucophaea maderae have also been published (Ottaviani et al., 1995e). At least for molluscs, this effect could be blocked by anti-mammalian TNF-α and/or anti–IL-1 antibodies. DAMA also is able to induce molluscan hemocytes to produce immunoreactive (ir)IL-1 (Stefano et al., 1991b). Administration of naloxone blocked the DAMAinduced conformational change by hemocytes, but these cells could still be activated by administration of recombinant human (rh)IL-1α, suggesting that opioid activation may be triggered by an IL-1–like molecule (Stefano et al., 1991b). As mentioned earlier, molluscan hemocytes release biogenic amines when they are cultured with CRF, a
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phenomenon that Ottaviani and co-workers (1991) described as a prototypic stress response. This response is significantly reduced when hemocytes are preincubated with IL-1α, IL-1β, TNF-α, or TNF-β prior to adding CRF to the incubation mixture (Ottaviani et al., 1995b). Ottaviani and Franchini (1995) and Franchini et al. (1996a) used immunocytochemistry to detect immunoreactive platelet-derived growth factor α and β (PDGFα/β) and transforming growth factor (TGF)-β in phagocytic invertebrate leukocytes. The presence of PDGF-α/β–like receptors and TGF-β receptor (type II)-like molecules on the plasma membranes of the immunocytes of the mollusc Mytilus galloprovincialis was also suggested by immunocytochemistry (Kletsas et al., 1998). This latter study also revealed that PDGFα/β and TGFβ1 provoke changes in the shape of the molluscan hemocytes following interactions of these mammalian ligands with their putative receptors and that these extracellular signals are transduced along the phosphoinositide-signaling pathway. Ottaviani et al. (1998a) suggest that in the mussel, the major pathway followed by PDGFα/β and TGFβ in provoking the release of NE, EPI, and dopamine into cell-free hemolymph is mediated by a CRH-ACTH biogenic amine axis. In mammals, microglial cells, like macrophages, are phagocytic and synthesize pro-inflammatory cytokines. Sonetti et al. (1997) argue that the snail, Planorbius corneus, also has a class of glial cells that resemble vertebrate microglia. Interestingly, these cells can be identified by their immunopositivity to anti–POMCderived peptide antibodies. As in the vertebrates, snail microglia exhibit macrophage-like mobility, and when exposed in vitro to LPS or bacteria, they underwent conformational and mobility changes and also became phagocytic. Moreover, when activated, they also expressed TNF-α–like molecules and increased production of NOS, as shown immunocytochemically. Morphine (which appears to bind these cells via a μ3 receptor) inhibited this mobility and phagocytic activity of invertebrate microglia, suggesting to these investigators that opioid-like compounds may influence invertebrate microglia as well as hemocytes. Similar microglial-like cells have also been described in the mussel and the insect Leucophaea maderae (Sonetti et al., 1994). Excitability of a population of nociceptive sensory neurons in Aplysia were influenced by neighboring hemocytes (Clatworthy, 1998); Clatworthy and Grose (1999) suggest that in vitro activation of these hemocytes by LPS causes them to produce cytokinelike factors which modulate expression of injuryinduced sensory nerve hyperexcitability. The aforementioned studies with invertebrates are clearly provocative in terms of their suggesting a
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common evolutionary origin of the immune and neuroendocrine systems with their attendant inflammatory and stress responses (Ottaviani and Franchini, 1995; Ottaviani and Franceschi, 1996, 1997, 1998). However, before accepting the validity of this hypothesis, or even some of the data that led to its formulation, we must emphasize the importance of characterizing all the immunoreactive molecules and their receptors described in the previous paragraphs at the structural and genomic levels to determine if they are true homologues of their mammalian counterparts rather than, for example, an artifact of the detection methods used to identify them (Hahn et al., 1996). A few intriguing studies we encountered in our review of the literature do not fit into the outline we’ve followed for this section on invertebrates. Indeed, they so beautifully reveal the evolutionary conservation of the links between behavior and its neuroimmune consequences that they merit their own paragraph. Mallon et al. (2003) and Riddell and Mallon (2006) presented behavioral evidence indicating a link between the immune system and the nervous system in insects. In brief, bumblebees that were injected with LPS to incite an anti-bacterial response in their hemolymph (Moret and Schmid-Hempel, 2000) have reduced abilities to learn (or recall memory) in a classical conditioning paradigm. Their study further points out that this associative learning deficit occurs only after bees are deprived of pollen (their only protein sources). As will be discussed later in the section on birds, some evolutionary biologists have become interested in the immune system in general (and psychoneuroimmunology in particular) because of an interest in energy trade-offs between immune processes and various behaviors (e.g., reproduction, foraging for food, nest building, sexual displays). With respect to invertebrates, Fedorka et al. (2004) tested the hypothesis that “immune suppression” mediates a phenotypic trade-off between reproduction and immunity by manipulating reproductive effort and measuring immune function and mortality rates in the striped ground cricket, Allonemobius socius. In this species, male crickets provide females with a hemolymphbased “nuptial gift” during copulation. Based on their knowledge that hemolymph contains many immune mediators, these investigators predicted that sexual selection might differentially affect how disease resistance evolves in males and females. Indeed, they found that for both sexes, an increased mating effort resulted in a reduced immune ability. In their words, immune suppression appears to be a link between reproductive effort and cost in this system. Also of note are their observations that males and females differentially invest in several aspects of immunity prior to mating:
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Males exhibit a higher concentration of circulating hemocytes and a superior bacterial defense capability than females. In a related study from this group, Zuk et al. (2004) reported that the ability of seasonal breeding crickets (both in the field and in the lab) to encapsulate foreign material was better in males than females. No sex dimorphism was noted in an aseasonal breeding species; however, when food was restricted, the males again did better. Although an interaction between the endocrine and defense systems are suspect in the results described in this and the preceding paragraph, no mechanisms have been explored formally. No doubt many experimental questions of potential psychoneuroimmunological interest raised by this intriguing line of research will keep these and other investigators gainfully occupied for several years.
III. NEURAL-IMMUNE INTERACTIONS IN TELEOST FISH Given the phylogenetic success of the teleosts (Hickman et al., 1993), it would not be unreasonable to propose that fish, like all other ectotherms discussed in the following sections, display coordinated and integrated immune and neuroendocrine responses to environmental challenges. The information reviewed in this section and elsewhere (Weyts et al., 1999; Yada and Nakanishi, 2002) clearly support this hypothesis.
A. Innervation of Lymphoid Organs and Response of Leukocytes to Biogenic Amines Autonomic innervation in the spleens of cod (Nilsson and Grove, 1974), coho salmon (Flory, 1989), and rainbow trout (Flory, 1990) has been demonstrated. At least for coho salmon, however, splenic innervation appears to be largely associated with the vasculature, with some branching out into the parenchyma (Flory, 1989). Chemical sympathectomy (SyX) of salmon with 6-hydroxydopamine (6-OHDA) depletes noradrenergic (NA) innervation as measured either by HPLC for NE, or by the absence of fluorescent NA nerve fibers (Flory, 1989) using sucrose-potassium phosphateglyoxylic acid-induced (SPG) histofluorescence for catecholamines (de la Torre, 1980). Chemical SyX has also been reported to increase the number and percentage of splenic anti-sheep red blood cell (SRBC) plaqueforming cells (PFCs) in fish denervated prior to immunization; no effect was seen if immunization preceded SyX. These data are consistent with the augmented antibody response seen following SyX of neonatal rats
(Besedovsky et al., 1979) and adult mice (Kruszewska et al., 1995, 1998), but contrast with the decreased antibody and cell-mediated responses seen after SyX in adult mice (Livnat et al., 1985; Madden et al., 1989a; Madden et al., 1989b; Sanders and Straub, 2002). Flory (1990) also demonstrated for rainbow trout that adrenergic and cholinergic agents can alter in vitro antibody response to TNP-LPS. Specifically, the in vitro induction of a primary anti–TNP-LPS PFC response was suppressed by the β-adrenergic agonist, isoproterenol (10−4–10−7 M), whereas it was enhanced by the αadrenergic agonist, phenylephrine. The β-agonist effect could be blocked by propranolol, consistent with receptor mediation, and the α-agonist effect was blocked by yohimbine but not phentolamine. This suggestion of an α–2 adrenoreceptor was confirmed by the demonstration that clonidine (10−7–10−11 M), an α–2 specific agonist, enhanced antibody responses. A cholinergic agonist also enhanced PFC responses over a dose range of 10−5–10−11 M; this was blockable by the muscarinic antagonist, atropine. Subsequent studies have revealed an influence of adrenergic and cholinergic agents on the chemiluminescent and mitogenic responses of trout leukocytes (Bayne and Levy, 1991; Flory and Bayne, 1991). Plytycz and co-workers (Józefowski and Plytycz, 1998; Józefowski et al., 1995) extended Flory’s studies by demonstrating first that there are adrenergic and cholinergic receptors on head kidney leukocytes of the goldfish, Carassius auratus; and second, that high concentrations of the βadrenergic agonist, isoproteronol (10−4 M), and the cholinergic agonist, carbachol (10−5 M), enhanced phorbol myristate acetate (PMA)-induced oxidative burst of goldfish macrophages, effects that could be blocked by equimolar concentrations of propranolol and atropine, respectively. Both EPI and NE enhance the respiratory burst activity of carp anterior kidney macrophages and neutrophils (Verburg-van Kemenade, personal communication). Finally, Narnaware and colleagues (Narnaware and Baker, 1996; Narnaware et al., 1994) observed that both α- and β-adrenergic agonists depress in vitro phagocytosis of yeast by rainbow trout macrophages and that injection of the adrenergic blocker phentolamine can prevent the depressive effects of “stress” on the phagocytic index of cells from the same species. Serotonin (5-HT) is also immunomodulatory in fish. According to a set of detailed experiments (Ferriere et al., 1996), 5-HT suppressed LPS- and PHA-induced proliferation of trout PBLs. This inhibitory effect could be mimicked by an agonist of 5-HT1A receptors (8-OH-DPAT) and was reversed by an antagonist of 5-HT1A and 5-HT1B receptors (spiperone). Scatchard plot analyses confirmed the existence of specific sero-
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tonin receptors on lymphocytes. In a competition study, serotonin inhibited the binding of 3H-5HT to receptors in both resting and mitogen-stimulated lymphocytes. However, the agonists (8-OH-DPAT and buspirone) and antagonist (NAN-190) of the 5-HT1A receptor subtype failed to displace 3H-5HT binding to receptor sites in resting cells, but they did inhibit 3H5HT binding in LPS- and PHA-stimulated lymphocytes. Based on these observations, the authors propose that 5-HT1A receptors are expressed on activated lymphocytes only after mitogenic stimulation. An agonist of 5-HT1B receptors (CGS-12066B) failed to affect 3H5HT binding on either resting or mitogen-stimulated lymphocytes, suggesting that this 5-HT receptor subtype is absent on lymphocytes. A subsequent pharmacological study from the same group (Meyniel et al., 1997), in which additional antagonists of mammalian 5-HT receptors (ICS-205–930 and metoclopramide) were used, suggests that fish 5-HT3 lymphocyte receptors may differ pharmacologically from mammalian receptors.
B. Neuropeptide Production by Cells of the Teleost Immune System Recently, investigators have begun to explore whether fish leukocytes, like mammalian lymphocytes (Blalock, 2005), synthesize hormones typically associated with the hypothalamo-pituitary-interrenal (HPI) gland axis.1 POMC-derived peptides (ACTH, α-MSH, and β-endorphin) have been detected immunocytochemically in goldfish thymic epithelial cells (Ottaviani et al., 1995d), and constitutive and mitogenstimulated production of immunoreactive POMC products by catfish lymphocytes has also been reported (Arnold and Rice, 1997). Since both studies were based on antibody detection of antigenic cross-reactivities, their interpretation may be questioned. However, Ottaviani et al. (1995a) have also reported that goldfish (C. auratus) phagocytic leukocytes express POMC mRNA as determined by in situ hybridization with a digoxigenin-labeled human DNA probe. The same probe also detected POMC mRNA in phagocytic leukocytes and peripheral blood lymphocytes from the frog, Rana esculenta, but lymphocytes from goldfish did not express this gene. A study of different teleost and amphibian species, however, seems necessary before endorsing these authors’ suggestion that expres-
1 Since in fish, the interrenal glands serve the function provided by the adrenal cortex in mammals (Chester Jones et al., 1980), the hypothalamo-pituitary-adrenal axis and the hypothalamo-pituitaryinterrenal axis are functionally equivalent.
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sion of this gene in vertebrate lymphocytes first occurred in the Amphibia. A major contribution to psychoneuroimmunology in the past decade has been research revealing that in mammals communication between the neuroendocrine and immune systems is mediated, at least in part, by pro-inflammatory cytokines (e.g., IL-1, IL-6, TNFα). For example, in rodents, IL-1 can act on the hypothalamus and pituitary to elicit CRH and ACTH, respectively (Parsadaniantz et al., 1994, 1997). Thanks largely to the work of Secombes and colleagues in Scotland, several cytokine genes that include IL-1 (Pleguezuelos et al., 2000; Secombes et al., 1998); IL-8 (Laing et al., 2002); IL-10 (Zou et al., 2003); TNF-α (Zou et al., 2002, 2003); IFN-γ (Zou et al., 2005); IL-6 (Bird et al., 2005); lymphotoxin b (Kono et al., 2006), IL-11 (Wang et al., 2005); and IL-18 (Zou 2004) have been cloned in different species (e.g., salmon, rainbow trout) and, at least for some genes, their products expressed as recombinant proteins (reviewed in Secombes et al., 2001; Secombes and Cunningham, 2004). This major sustained effort has permitted research on the role of cytokines as mediators of neuroendocrine-immune interactions in teleosts. Indeed, there is now solid evidence that in fish, IL-1β is an effector molecule that activates the HPI axis as evidenced by a strikingly elevated level of plasma cortisol in trout receiving an i.p. injection of 0.1–0.6 nmol/kg of the recombinant protein (Engelsma et al., 2002; Holland et al., 2002). Holland et al. (2002) also reported that trout IL-1β peptides (P1 and P3), which are homologous to receptor-binding sequences of human IL-1β, failed to influence the prevailing cortisol concentration even though an equivalent dose was immunostimulatory in vivo. In this study, blockade of endogenous ACTH release by administration of the synthetic glucocorticoid dexamethasone (DEX) prevented the rIL-1β–mediated elevation of plasma cortisol. Inhibition studies with the cloned fish IL-1 receptor-associated protein and IL-1 receptor (Stansberg et al., 2005) have yet to be carried out to further probe the role of this cytokine in the neuroimmune circuitry. Nevertheless, the important phylogenetic take-home message from these studies is that IL-1 signaling between the immune and neuroendocrine systems in mammals is conserved in lower vertebrates. Just how early this neuroimmune regulatory pathway evolved (i.e., is it present in elasmobranchs and agthanans?) remains unresolved. So too does the question of whether, like mammals, other pro-inflammatory cytokines play a signaling role at the teleost level of phylogeny. LPS is known to activate the fish HPI axis (Balm, 1997). Since increased cortisol levels could be induced by either an i.p. injection of LPS or rIL-1β, it is reason-
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able, by extrapolating from the mammalian literature, to conclude that in fish LPS induces an increase in IL-1 that, in turn, effects increased levels of cortisol via activation of the HPI axis. An early literature points out that direct exposure of pituitary tissue to LPS in vitro blunts ACTH and α-MSH release (Balm et al., 1995). Although it is once again reasonable to assume that these changes result from an increase in cytokine secretion following LPS treatment, it should be noted that LPS can also affect endocrine tissues directly (Brunetti et al., 1994; Milton et al., 1993). One of the most important reasons for conducting studies using a homologous system (i.e., trout rIL-1b injected into trout) is that it obviates problems inherent in using mammalian cytokines in fish. Earlier studies like one in which murine IL-1α was reported to inhibit α-MSH release by the HPI axis (Balm et al., 1993) or studies pointing out that mammalian IL-1 has no effect on teleost lymphocytes (see review by Haynes and Cohen 1991; see also Ellsaesser and Clem, 1994; Verburg-van Kemenade et al., 1995) need to be repeated in the homologous system, especially since mammalian and fish IL-1 have minimal identity at the DNA and amino acid sequence levels (Secombes et al., 1998).
C. Glucocorticoids, Neuropeptides, and Stressor Effects on Immunity The neuroendocrine stress response of fish (Wendelaar Bonga, 1997) is quite similar to that of mammals (Chrousos and Gold, 1992) in that it consists, in part, of a stressor-sensitive HPI axis. Cortisol, the major glucocorticoid in fish, is produced by the interrenal gland. Primary mediators of cortisol in teleosts are ACTH (apparently for acute stress situations) and α-MSH (in more chronic situations) (Donaldson, 1981; Lamers et al., 1994; Sumpter et al., 1994). These hormones, in turn, are under hypothalamic control via CRF for ACTH (Olivereau and Olivereau, 1991) or via both CRF and TRH α-MSH (Lamers et al., 1994). Parenthetically, in an in vitro study, Harris and Bird (1998) demonstrated that a 1-hour exposure to α-MSH increases the phagocytic ability of head kidney macrophages and neutrophils from rainbow trout. Although the neuroendocrinology of the stress response in teleosts has been well studied (Huising et al., 2004, 2005; Rotlant et al., 2003; van den Burgh et al., 2005), information that causally relates, in a stepwise and mechanistic fashion, stressor-associated neuroendocrine levels and pathways to changes in immune system parameters and susceptibility to pathogens is relatively fragmentary. This is not to say that there is a dearth of studies that explore the effects of stressors
on selected aspects of immune function and on mortality in agriculturally important teleost species. Quite the contrary (Barton and Iwama, 1991; Ellis, 1981; Ndoye et al., 1991; Pickering, 1981; Wendelaar Bonga, 1997). For example, a 30-second dip net removal of Chinook salmon from the water temporarily elevated plasma cortisol, increased leukocyte numbers in the thymus and anterior kidney, decreased blood and spleen leukocytes, and altered resistance to the fish pathogen Vibrio anguillarum (Maule et al., 1989). Altered resistance was manifested by an increased mortality and decreased time-to-death in salmon exposed to Vibrio 4 hours after stressor exposure and by a decreased mortality (relative to controls) and longer survival times in fish exposed 1 day after this acute stressor (Maule and Schreck, 1990a; Maule et al., 1989). Altered immune function was also reflected by a decreased in vitro anti-TNP antibody production (relative to unstressed fish) by anterior kidney leukocytes 4 hours and 7 days after stressor exposure. At this later time-point, plasma cortisol levels had returned to normal (Maule et al., 1989), indicating that the effects of the stressor persist beyond the time of cortisol elevation. A similar observation was made by Betoulle et al. (1995), who subjected trout to hyperosmotic shock for 7 days or 30 days and measured cortisol, PRL, and anti-Yersinia ruckeri antibodies in the serum. Relatively short-term “stress” was associated with a correlation between high levels of both stress hormones and a delayed production and lower titers of antibody. More chronically exposed animals had no increase in stress hormones but still had low antibody titers. These two reports, among others, are consistent with the idea that the putative immunomodulatory effects of stress hormones impact the earlier phases of antibody production. A recent study (Binuramesh et al., 2006) has convincingly demonstrated that the social environment of fish plays an important role in their adaptive and innate immune responses to pathogens. This research examined the effects of sex ratio of a tilapia (Oreochromis mossambicus) housed for 4 weeks either as same sex or mixed (1:1) sex cohorts on antibody responses to Aeromonas hydrophila; serum lysozyme activity; production of intracellular reactive oxygen species (ROS); on reactive nitrogen species (RNS) by peripheral blood leukocytes; and on disease resistance against live, virulent Aeromonas hydrophila. Their data convincingly showed an enhanced antibody response and increased number of antibody-producing cells in the mixed-sex cohorts relative to fish in monosex ratio groups. Similar enhancement was also observed in non-specific immune parameters such as serum lysozyme level, ROS, and RNS production. The host resistance test
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revealed that enhanced immunity in the equal male and female sex ratio group was protective against Aeromonas hydrophila infection. Hence, natural sex ratios may enhance disease resistance to pathogens in this species; just how it does so is an important but unresolved issue. As indicated in the aforementioned Binuramesh study, stressors can modify various aspects of the innate as well as adaptive immune system of teleosts. In another example from other species (e.g., trout), in vitro respiratory burst activity of fish anterior kidney phagocytes was diminished following handling and exposure to anoxic shock, as well as by crowding (Angelidis et al., 1987; Pulsford et al., 1994; Yin et al., 1995), but it was increased in trout following transfer from fresh to sea water (Marc et al., 1995), indicating a variance across species and/or stress modalities. A social stress paradigm in rainbow trout led to increased in vivo phagocytosis of bacteria by peripheral blood phagocytes (Peters et al., 1991). Transition from fresh to seawater, however, had no effect on activity of natural cytotoxic cells (NCC) isolated from brown trout (Marc et al., 1995). Although decreasing the water temperature in which carp were held enhanced their NCC activity (Le Morvan-Rocher et al., 1995), the in vitro assays were all performed at 28°C, which could have different consequences for cells isolated from fish adapted to different temperatures (Clem et al., 1984, 1991). A social stress paradigm in aggressive fish (Tilapia) resulted in depressed NCC activity and mitogenic responses in the subordinate fish (Ghoneum et al., 1988). As determined by blocking studies with naltrexone, this effect seems to be mediated, at least in part, by endogenous opioids (Faisal et al., 1989). A group of Polish investigators led by Plytycz has demonstrated that endogenous opioids (i.e., morphine) also appear to be involved in reducing numbers, but increasing respiratory burst activity, of thioglycollate-elicited inflammatory cells in peritoneal exudates from goldfish (Chadzinska et al., 1997; Gruca et al., 1996) and salmon (Chadzinska et al., 1999). This morphine-induced increase in respiratory burst activity did not occur if the exudate cells were harvested from stressed salmon (Plytycz et al., 1996). As would be predicted by the results from these studies involving the parenteral administration of morphine and naltrexone, opioid receptors have been identified on teleost head kidney leukocytes cells and characterized by radiolabeled ligand binding (Józefowski and Plytycz, 1997). As in mammals, lysozyme plays a non-specific antibacterial defense role in fish. Plasma lysozyme levels (as well as plasma cortisol and epinephrine) in rainbow trout increased following 30 seconds of handling (Demers and Bayne, 1997). Lysozyme levels were also
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increased in brown trout following their transition from fresh to seawater (Marc et al., 1995) but were unaffected by parr-smolt transformation (see below) in Atlantic salmon (Olsen et al., 1993) and were actually decreased in carp following 30 days of crowding (Yin et al., 1995). These differences may well relate to the duration and severity of the stressor, as was shown by Möck and Peters (1990), who observed that 30 minutes of handling increased lysozyme levels in rainbow trout, whereas a 2-hour transport stressor decreased their levels. It seems clear that many of the effects of stressors on non-specific and specific defense modalities in fish involve the HPI axis and glucocorticoids. Fish leukocytes possess receptors for corticosteroids (Maule and Schreck, 1990a, 1990b; Verburg-van Kemenade et al., 1999; Weyts et al., 1998a). In coho salmon, receptor-like binding of a synthetic corticosteroid analogue (triamcinolone acetonide) to cells isolated from spleen and head kidney was reported (Maule and Schreck, 1990b). Carp peripheral blood cells also express cortisol receptors with a high binding affinity (Kd 3.8 nM). Neutrophilic granulocytes isolated from the carp head kidney contain cortisol-binding sites with the same characteristics (Weyts et al., 1998a, 1998c), suggesting that both PBL and head kidney neutrophils express the same glucocorticoid receptor. Basal receptor densities in both cell types are approximately 500 per cell. Following cortisol treatment in vivo, receptor numbers in carp PBL decrease (Weyts et al., 1997), whereas numbers of corticosteroid receptors in coho salmon spleen and head kidney leukocytes increase following exposure to an acute or chronic stressor or by cortisol treatment in vivo (Maule and Schreck, 1991). These changes in receptor densities have been explained by a stress- or cortisol-induced trafficking of receptor-rich leukocyte subtypes from the circulation into lymphoid organs. However, since corticosteroid receptors in coho salmon head kidney leukocytes are also increased following an in vitro exposure to cortisol (Maule and Schreck, 1991), an actual upregulation of receptor numbers resulting from the cortisol treatment also seems reasonable. The immunosuppressive effects of glucocorticoids have been demonstrated in several studies with teleosts. Anderson et al. (1982) injected rainbow trout with a synthetic glucocorticoid 24 hours after immunizing them with the O-antigen of Yersinia ruckeri and observed depressed in vitro and in vivo antibody production and a reduced number of splenic lymphocytes. A similar reduction in numbers of antibody-producing cells has been described in flounder (Carlson et al., 1993). Ellsaesser and Clem (1987) injected channel catfish i.v. with cortisol (6.7 μg/kg body weight),
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which resulted in a plasma level of cortisol 30 minutes following injection equivalent to that seen 30 minutes following “transport stress” in this species. This increase correlated with decreased numbers of circulating leukocytes, increased neutrophils, and decreased LPS- and Con A-induced lympho-proliferation. This last observation has also been made for salmon by Espelid et al. (1996). Since these Norwegian investigators noted that the addition of physiologic levels of cortisol to normal fish leukocytes in vitro did not alter mitogen responses, they suggested that an indirect mechanism was involved in the observed effects. However, Tripp and colleagues (1987) found that physiological concentrations of cortisol in vitro did, in fact, depress both LPS-induced mitogenesis and the primary anti–TNP-LPS antibody responses of splenic and head kidney lymphocytes from coho salmon. In this paradigm, pronephric lymphocytes were sensitive early in the antibody response, whereas splenic lymphocytes were sensitive throughout the culture period. Although it is unknown whether the aforementioned differences in the in vitro effects of cortisol on salmon and catfish lymphocyte mitogenesis are related to the species used or to methodological considerations, others have also shown that vitro, cortisol inhibits teleost lymphocyte proliferation (Grimm, 1985; Pulsford et al., 1995; Tripp et al., 1987) and reduces antibody production (Tripp et al., 1987; Wechsler et al., 1986). It has been suggested that cortisol may act on fish lymphocytes by inhibiting cytokine production as it does in mammalian cells (Kaattari and Tripp, 1987; Tripp et al., 1987). On the other hand, the observation that in vivo cortisol treatment resulting in plasma concentrations of 400 ng/ml enhances the numbers of apoptotic lymphocytes in the skin of rainbow trout (Iger et al., 1995) suggests that apoptosis may be regulated by cortisol. Indeed, apoptosis appears to have been conserved as an immune regulatory mechanism in fish as well as other ectothermic vertebrates including frogs (Haberfeld et al., 1999; Rollins-Smith, 1998; Rollins-Smith and Blair, 1993; Rollins-Smith et al., 1997a; Ruben et al., 1994) and salamanders (Ducoroy et al., 1999). Cortisol-induced apoptosis of fish leukocytes is mediated by a glucocorticosteroid receptor since the glucocorticoid receptor antagonist RU486 (Weyts et al., 1998a, 1998b, 1998c) could block apoptosis. The low concentration of cortisol (0.1 μM) that was effective in inducing B-cell apoptosis contrasts with the lack of effects of cortisol’s natural conversion product, cortisone. Since the conversion of cortisol to cortisone in fish is highly preferred over the reverse reaction (Donaldson and Fagerlund, 1972), this conversion may
provide the fish with a mechanism to regulate the effects of corticosteroids on cells of the immune system. The lack of apoptosis induction by cortisone correlates with the low affinity of the glucocorticosteroid receptor in carp PBL for cortisone (250 times lower than that for cortisol) (Weyts et al., 1998c). Effects of cortisol on leukocyte viability are cell type-specific. For example, B-cells from carp are especially sensitive to cortisol, whereas thrombocytes and T-cells are insensitive. Induction of apoptosis depends on the developmental state and/or activation state of the lymphocyte. In the periphery, only activated Bcells appear sensitive, whereas in head kidney and spleen apoptosis induction in B-cells is independent of the activation state (Verburg-van Kemenade et al., 1999). Interestingly, in vitro apoptosis of carp head kidney neutrophils was reduced when cells were cultured with cortisol, and this effect of cortisol was also mediated by a glucocorticoid receptor (Weyts et al., 1998b). Analysis of the glucocorticoid receptors in these cells revealed that they may be the same as those detected in PBLs since both have the same affinity and specificity (Weyts et al., 1998c). The inhibition of neutrophil apoptosis by cortisol, combined with the observation that neutrophil respiratory burst activity was not affected by cortisol, would augment the supply of functional neutrophils in stressful conditions. Taking into account that neutrophils, together with macrophages, form the first line of defense against invading microorganisms (Dalmo et al., 1997), mobilization of these cells under stressful conditions may be important for survival. Although cortisol can trigger apoptosis of leukocytes, and stressors elevate this steroid in fish, Alford et al. (1994) observed that confinement stress of channel catfish was associated with a decrease in apoptotic PBLs, and in vitro culture of lymphoid cells with cortisol failed to induce apoptosis. This apparent discrepancy with some of the previously cited literature may relate to the fact these investigators used unstimulated cells in their experiments and, at least in carp, only mitogen-stimulated PBLs are sensitive to cortisolinduced apoptosis (Weyts et al., 1998b). Plasma cortisol concentrations in stressed salmonids and cyprinids range between 100 and 500 ng/ml (Barton and Iwama, 1991), of which approximately 25–125 ng/ml is present in an unbound configuration (Caldwell et al., 1991; Flik and Perry, 1989). Therefore, concentrations in the micromolar range or higher may not be physiological. It appears that in vitro, cortisol does not affect phagocytosis or respiratory burst activity (Narnaware et al., 1994; Weyts et al., 1998b) unless
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supraphysiological concentrations in the micromolar range (or higher) are used (Ainsworth et al., 1991; Pulsford et al., 1995; Stave and Roberson, 1985). Accordingly, respiratory burst activity of a goldfish macrophage cell line was unaffected by up to 10 μM cortisol (Wang and Belosevic, 1995). The inhibition of phagocytosis of SRBC that was described in the same study was again only detected at relatively high (1 μM) cortisol concentrations. Studies of cellular immune functions associated with either stressor administration or in vivo cortisol treatment often fail to consider leukocyte trafficking and redistribution as an explanation of the apparent immunosuppression observed in vitro. A wealth of information reveals that many stressors (e.g., transport, anoxia, social conflict, handling, injection) in several fish species are associated with decreased numbers of circulating B-lymphocytes and increased numbers of circulating neutrophils (Ainsworth et al., 1991; Angelidis et al., 1987; Bly et al., 1990; Ellsaesser and Clem, 1987; Espelid et al., 1996; Faisal et al., 1989; Pulsford et al., 1994; Salonius and Iwama, 1993). These effects are mimicked by in vivo corticosteroid treatment (Ainsworth et al., 1991; Ellsaesser and Clem, 1987; Espelid et al., 1996; Weyts et al., 1997). Increased infiltration of leukocytes into the thymus, head kidney, skin, and gill (Balm and Pottinger, 1993; Iger et al., 1995; Maule and Schreck, 1990a; Peters et al., 1991) has also been observed following either stress or in vivo cortisol administration. Thus, interpretation of data obtained from in vitro functional analysis of leukocytes from stressed fish or from fish injected with cortisol needs to take into consideration the possible (dis)appearance of cell populations rather than simply changes in cell activity. Although there are more data supporting a neuroendocrine-immune link in fish than there are for any other non-mammalian vertebrate, studies to date have used many different species and many different types of stressors. Thus, no “best use” model has emerged to allow an in-depth study of the effects of various sorts of stressors on several immune parameters of a single species. Effects are leukocyte type dependent, and the final outcome may depend on the severity and duration of the stressor, as it does in mammals (Moynihan et al., 1994). The cortisol-mediated rescue of neutrophils from apoptosis shows that cortisol does not suppress all aspects of the fish defense system. Rather, cortisol acts as a regulator, inhibiting some parts of the (specific) immune response and enhancing other (nonspecific) components that may be functional in stressful situations. Stimulation of an innate immune response may be part of an adaptive response neces-
sary to combat potential pathogens under stressful conditions (Weyts et al., 1999).
D. Seasonal Influences on Immunity Smolting, a series of profound physiological changes that prepare juvenile freshwater salmon for entry into salt water, is characterized by increases in plasma thyroxine and cortisol levels (Maule et al., 1987). These hormonal changes correlate with decreased numbers of splenic PFCs in salmon immunized with the Oantigen from V. anguillarum and also with decreased numbers of PBL (although there was an increase in the proportion of small lymphocytes) relative to either erythrocytes or fish body weight. Such changes, together with increased mortality to Vibrio infection, have also been seen following implantation of cortisolcontaining pellets (Maule et al., 1987). Like reptiles and amphibians (discussed in following sections), immune reactivities and lymphoid tissues of teleosts undergo seasonal changes that are unrelated to smolting. For example, Yamaguchi et al. (1981) found that the agglutinating and cytotoxic antibody responses of trout immunized in the spring with the pathogen Aeromonas salmonicida were higher and increased more rapidly than those of fish immunized in the winter, even though animals were held at a constant temperature of 18°C. Seasonal modulation in antibody production in relation to the state of lymphoid tissue development has also been studied in the ovoviviparous marine fish, Sebastiscus marmoratus (Nakanishi, 1986). Fish immunized with SRBC in summer after having been acclimated for at least 2 weeks to 23°C, had higher antibody titers than fish immunized in winter, even when the environmental temperature of acclimation and immunization was constant. A sexual dimorphism was noted in that antiSRBC antibody titers of mature females were lower than that of either males or immature females in the winter spawning season. In addition, the thymus of pregnant and especially post-spawning females was entirely involuted, showing a marked decrease in the number of lymphocytes in both the cortex and medulla. The neuroendocrine regulation of such dramatic changes seems well worth further study. Circadian rhythm has been shown to influence immune responses in fish. The gulf killifish, Fundulus grandis, for example, exhibits a circadian variation in immune reactivity during scale allograft rejection. Specifically, a two- to three-fold higher level of immune activity and cellular destruction occurred during the dark period, resulting in a longer survival time for grafts transplanted at light onset than for those grafted
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at lights off (Nevid and Meier, 1993, 1994). Phase relationships between two circadian neuroendocrine oscillations (daily photoperiod and non-photic daily stimuli) appear to be involved (Nevid and Meier, 1995a), as do levels of hormones and neuropeptides/ neurotransmitters (Nevid and Meier, 1995b). For example, daily rhythms of alloimmune reactivity could be abrogated by treating fish with naloxone or propranolol at light offset only, GH or atropine at light onset only, or PRL at either light onset or light offset. Timed treatments with PRL or GH reduced the length of time needed to completely destroy scale grafts, whereas timed treatments with propranolol or naloxone prolonged graft survival (Nevid and Meier, 1995b).
IV. NEURAL-IMMUNE INTERACTIONS IN AMPHIBIANS Based on a variety of morphological and physiological characteristics that distinguish Amphibia from Teleosteii and Reptilia, this class of vertebrates is generally thought of as a phylogenetically pivotal group. As such, the immune systems of a few (one hopes representative) amphibian species have been exhaustively studied. In the last decade, a few “amphibian immunologists” have broadened their research focus to include neural-immune interactions in both frogs and salamanders. Areas being investigated include: (a) innervation of lymphoid tissues; (b) neuropeptide/ neurotransmitter regulation of immunity; (c) seasonal/ neuroendocrine effects on immunity in adults; (d) neuroendocrine regulation of immunity during metamorphosis; and (e) the impact of environmental stressors on anti-microbial immunity and its implications for the worldwide decline of amphibians.
A. Innervation of Lymphoid Organs Several lines of evidence point to catecholamines as “neuroimmune transmitters” in amphibians. Prior to the published observations in mammals by the Feltens in the 1980s (Felten and Olschowka, 1987; Felten et al., 1987), Nilsson (1978) had used fluorescence histochemistry to reveal sympathetic innervation of the spleen of the cane toad, Bufo marinus, and Zapata et al. (1982) published electron microscopic evidence of direct contacts between nerve endings and lymphoid cells in the jugular body of the leopard frog, Rana pipiens (Manning and Horton, 1982). More recently, Kinney et al. (1994b) described noradrenergic and peptidergic innervation of the spleen of the adult South African clawed frog, Xenopus laevis, using: SPG histofluorescence (de la
Torre, 1980) for catecholamines and immunocytochemistry for tyrosine hydroxylase (TH), the ratelimiting enzyme in the synthesis of catecholamines (Felten and Olschowka, 1987); PGP 9.5 (a general neuronal antigen); and NPY. Spleens of this species, like those of other anurans, have a clearly defined red and white pulp (Manning, 1991; Manning and Horton, 1982). Noradrenergic fibers are almost exclusively restricted to the white pulp in association with the central artery. These fibers have occasional varicosities in the parenchyma, and additional fibers are present in the boundary cell/perifollicular areas where they may come into contact with B-cells and macrophages of the white pulp; non-lymphoid dendritic cells involved in trapping and retention of soluble antigen (Manning, 1991); and possibly the T-cells at the extreme boundary of the white pulp. In some instances, fibers were also noted in the splenic capsule. In short, this innervation pattern in Xenopus is similar to that described for the murine spleen (Felten et al., 1987). The profile of fine varicose nerve fibers staining for NPY in the white pulp of the Xenopus spleen was similar to, but less abundant than, TH+ fibers, an observation that may reflect a difference in sensitivity of the antibody used rather than an actual difference in amount of neurotransmitter present. Substance P-staining fibers were also found around vessels in the splenic white pulp (Kinney et al., 1994b). Although frogs, toads (Anura), and salamanders (Urodela) are all amphibians, the two taxonomic orders differ immunologically in several interesting ways, such as the delayed kinetics of antibody production and allograft rejection characteristic of urodeles relative to anurans (Cohen and Koniski, 1994). In addition, and in sharp contrast to the mammalian-type pattern of innervation that characterizes the compartmentalized Xenopus spleen, SPG histofluorescence analysis of the non-compartmentalized spleens of the salamanders Taricha torosa, Notophthalmus viridescens, and Ambystoma mexicanum revealed a diffuse pattern of innervation associated with the reticular network (Kinney et al., 1994b). The third order of amphibians, the Gymniophiona (Apoda or caecelians), has received only limited attention from immunologists, no doubt because they are difficult to obtain for laboratory research. The spleen of one such apodan, Typhlonectes sp., is elongate like that of salamanders. Unlike salamander spleens, however, the Typhlonectes spleen exhibits some aggregation of lymphocytes into white pulp-like regions that are less organized than the white pulps of the anuran or mammalian spleen (Manning, 1991). The spleen of this species is also characterized by less abundant innervation than the urodele spleen, both in
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immediate proximity to blood vessels and also in areas removed from blood vessels, as shown by SPG histofluorescence. PGP 9.5 staining of the Typhlonectes spleen revealed occasional individual fibers and fiber bundles in a pattern similar to that seen with histofluorescence (Kinney et al., 1994b). The ontogeny of splenic innervation during the larval life of Xenopus has also received some attention. Clothier et al. (1991) reported changes in splenic innervation during the period shortly before metamorphic climax. Specifically, they described a drop in the levels of splenic NE, as assessed by HPLC and SPG histofluorescence at Nieuwkoop and Faber (1967) larval stage 58, a time when lymphocyte mitogen responsiveness is also significantly decreased (Rollins-Smith et al., 1984). Unfortunately, this reported developmental loss of splenic NE was not accompanied by micrographic documentation of a loss of sympathetic nerve fibers in the spleen. The lack of such documentation becomes important in view of our observations (Kinney, 1996) that the larval Xenopus spleen is innervated earlier than stage 58 (i.e., from stage 54 onward), and that the appearance of innervation is very sensitive to the environmental conditions (e.g., temperature, animal density) under which the larvae are reared. We have also reported that chemical SyX during larval life prior to the appearance of splenic compartmentation does not affect the subsequent development of the demarcation into a red and white pulp (Kinney, 1996), and that early larval thymectomy that renders animals T-cell deficient does not influence the normal development of innervation (Kinney et al., 1993; Rollins-Smith and Cohen, 1995).
B. Sympathetic and Neuroendocrine Regulation of Immunity SyX (using 6-OHDA) of adult Xenopus is associated with a significant increase in the in vitro proliferative response by splenocytes cultured with the mitogens LPS, Con A, and PMA (Kinney, 1995; Kinney and Cohen, 2005). A similar increase in in vitro proliferation was noted when splenocytes from frogs that had been parenterally immunized with keyhole limpet hemocyanin (KLH) 2 days after SyX were cultured with KLH (Kinney, 1995). This SyX-associated enhancement of polyclonal- and antigen-driven proliferation of Xenopus splenocytes is similar to observations in mice (Kruszewska et al., 1995, 1998). Unlike these murine studies, our initial (Kinney, 1995) SyX experiments did not reveal any alteration in the primary serum anti-KLH IgM antibody response (assayed 1–55 days post-immunization) in frogs immunized 2 days after 6-OHDA treatment. This apparent lack of effect
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was recently reproduced (Kinney, unpublished). However, when such primed frogs were again treated with 6-OHDA 47 days after the initial SyX and injected with a second dose of KLH 2 days later, the secondary IgY anti-KLH response was increased relative to the appropriate controls. To the best of our knowledge, the impact of SyX on secondary antibody responses in other species has never been examined. SyX does not appear to affect the time-course of skin allograft rejection (Kinney, 1995; Kinney et al., 1994a), a T-dependent immune process in Xenopus (Manning et al., 1976). Specifically, injection of 6-OHDA 2 days before transplantation, and repeated weekly during the course of the experiment, did not affect skin graft survival, regardless of whether donor and hosts differed by MHC plus minor histocompatibility (H) locus antigens or by minor H-antigens only. There was also no effect of SyX on the accelerated second-set rejection of minor H locus-disparate grafts. In confirmation of these data, Józefowski et al. (1996) reported that chronic in vivo administration of β-adrenergic (propranolol) or muscarinic (atropine) antagonists had no effect on skin allograft survival in R. esculenta and R. temporaria. Morphine, too, was without effect. The picture is slightly different, however, when the fate of xenografts rather than allografts was investigated using R. esculenta as hosts. Specifically, repeated injections of propranolol increased the survival time of xenogeneic skin grafts from R. temporaria and B. bomina, injections of atropine significantly accelerated rejection of skin from B. bomina but not R. temporaria, and injections of morphine had no effects regardless of the donor species used. Interestingly, binding of radiolabeled ligands to muscarinic and adrenergic receptors on PBLs was increased significantly in xenografted animals but not on cells from recipients of allografts. It is also noteworthy that unlike classic T-cell–mediated rejection of allografts, xenograft rejection in anurans is thought to primarily involve innate and antibody-mediated immunity (Horton et al., 1992; Józkowicz., 1995). In Xenopus, immunological tolerance characterizes the alloimmune response of perimetamorphic animals to skin grafts from adult donors that differ from the hosts only by minor H-antigens (DiMarzo and Cohen, 1982). SyX of newly metamorphosed recipients of such grafts had no effect on either the induction or maintenance of this non-deletional form of tolerance (Kinney, 1995). As in so-called higher vertebrates, immunological effects of SyX suggest that cells involved in amphibian immunity express receptors for noradrenergic ligands. Indeed, in the late 1970s, an English group (Hodgson et al., 1978, 1979) reported that antigen-binding splenocytes from several species of SRBC-immunized sala-
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manders (T. cristatus, T. alpestris, Cynops hongkongensis, C. pyrrhogaster, N. viridescens) were decreased following their in vitro exposure to both α- and β-adrenergic receptor (AR) stimulation2. In immunized frogs (R. temporaria, X. laevis, R. esculenta, Bufo bufo), α-AR stimulation decreased, whereas β-AR stimulation increased the number of antigen-binding splenocytes. In these early studies, it was erroneously assumed that all antigen-binding cells were antibody-producing cells. Subsequently, this group (Clothier et al., 1989, 1992) used an ELISA to examine the effects of in vivo NE administration on in vitro antibody responses to T-dependent and T-independent antigens. They reported differential effects based on the thymus dependency of the antigen and the timing of immunization relative to NE administration. Implantation of an NE-containing pellet prior to priming with a Tdependent antigen resulted in increased antibody production, whereas pellet implantation at some (unstated) time after priming was without effect. The influence of NE on antibody responses to T-independent antigens was studied by injecting NE rather than implanting an NE-containing pellet. A single injection of an (unspecified) amount of NE at the time of immunization with TNP-LPS effected a reduction of the splenic anti-TNP antibody response. Unfortunately, the difference in routes of administration of the NE between the two experiments makes a general conclusion difficult. Addition of NE (10−6–10−8 M) to cultures of splenocytes from animals primed in vivo with TNP-LPS also reduced the in vitro anti-TNP antibody response. Interestingly, an increase was seen if the cells were exposed to 10−12 M NE, a finding apparent from the data but not pointed out in the text. A low concentration (10−12– 10−15 M) of the β-AR agonist, isoproterenol, also enhanced in vitro antibody production when it was added on day 7 in culture. In contrast, the α2-agonist, clonidine (10−9–10−15 M) resulted in a reduced response, an effect that was blocked by the α-antagonist, yohimbine. β-AR stimulation with 10−10–10−12 M isoproterenol was also reported to reduce PHA-stimulated T-cell mitogenesis, a finding which we were unable to replicate using physiological or even subpharmacological (i.e., less than 10−4 M) concentrations of isoproterenol (Cohen and Kinney, unpublished). Although Clothier and colleagues (1992) also claimed that immunization resulted in a depletion of NE in the spleen, an unex-
To stimulate α receptors, either the specific α-agonist, phenylephrine, or a combination of epinephrine plus the β–receptor antagonist, timolol, were used; to stimulate β–receptors, either the specific β agonist, isoproterenol, or a combination of epinephrine plus the α–receptor antagonist, thymoxamine, was used. 2
plained decrease in splenic NE was also seen in animals injected only with phosphate buffered saline (PBS). In these same studies, Clothier et al. (1989, 1992) suggested reciprocal interactions between splenic NE content and processes involved in antibody production. Treatment with 6-OHDA reduced primary antihapten antibody responses to TNP-SRBC. When TNP was coupled to a T-independent carrier (LPS or Ficoll), the primary anti-hapten response was increased. Most recently, Haberfeld et al. (1999) reported that adrenoceptor agonists modulate in vitro apoptosis of lymphocytes. Although α-2 and β-2 receptor agonists themselves did not induce apoptosis of Xenopus splenocytes cultured for 4 or 20 hours, they did modulate apoptosis of Xenopus splenocytes that were cultured with a calcium ionophore. More specifically, clonidine (α-2 agonist) enhanced ionophore-induced apoptosis of lymphocytes cultured for 4 but not for 20 hours, whereas isoproterenol (β-2 agonist) decreased apoptosis in 4-hour cultures but enhanced this programmed cell death when lymphocytes were cultured for the longer period. By itself, the synthetic glucocorticoid, DEX (10−4–10−6 M), also induced apoptosis of frog lymphocytes cultured for 4 or 20 hours. Whereas clonidine did not affect cell death caused by this synthetic steroid at either time-point, isoproterenol enhanced apoptosis after 4 but not after 20 hours of co-culture. Haberfeld et al. (1999) suggested that their data might reflect a different apoptotic pathway induced by the ionophore and the synthetic steroid. All the aforementioned experiments dealing with noradrenergic modulation of immunity in amphibians were based on the assumption that the agonists and antagonists used were actually binding to bona fide β-AR receptors. Józefowski and Plytycz (1998) used radiolabeled ligand binding to actually characterize β-AR receptors on splenocytes and activated peritoneal leukocytes from frogs (R. temporaria and B. bufo) and splenocytes from the salamander (Salamandra salamandra). Saturation, competition, and kinetic studies revealed a single site with a similar binding capacity. These investigators estimated that there were about 4,000 and 14,000 receptors per frog splenocyte and peritoneal cell, respectively (the difference probably reflects the larger number of phagocytic adherent cells in the peritoneal exudate) and as many as 183,000 such receptors on salamander splenocytes (a number consistent with their greater cell size). Although leukocytes from amphibians and goldfish (see previous section) all have β-AR receptors with similar affinities for the ligands [3H]CGP-12177 and [3H]DHA, competition experiments (Józefowski and Plytycz, 1998) suggest that there may be taxa (class)-specific differences not only for cells of the amphibians and teleosts
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studied, but also relative to birds and mammals. Radiolabeled ligand-binding studies have also revealed cholinergic muscarinic receptors on elicited peritoneal leukocytes from two species of anurans (Józefowski et al., 1996). As discussed in great detail in the first section, which deals with invertebrates, a series of studies published throughout the 1990s by Ottaviani and coworkers used immunocytochemical procedures to investigate whether neuropeptides, neurohormones, and cytokines are produced by vertebrate and invertebrate cells and tissues involved in adaptive and innate immunity. With respect to the Amphibia, POMC-derived ACTH, β-endorphin, and αmelanocyte–stimulating hormone (α-MSH), as well as molecules that show antigenic cross-reactivity with antibodies directed against mammalian IL-1α, IL-1β, IL-2, IL-6, and TNF-α were revealed in PAS-positive epithelial cells of the thymus of the anuran amphibian R. esculenta. Three groups of PAS-positive epithelial cells were identified in subcapsular cortex, inner cortex, and medulla. The cells containing ACTH-, α-MSHand cytokine-like molecules were distributed in the cortex, whereas those containing β-endorphin–like molecules were found in the medulla and inner cortex. Thymic lymphocytes were always negative for POMCderived peptides and “cytokines.” This does not appear to be the case for peripheral lymphocytes, however, since immunocytochemistry and cytofluometry (Ottaviani et al., 1992c, 1995a) detected POMC (or POMC mRNA) in peripheral blood lymphocytes as well as in phagocytic leukocytes from this same species. Ottaviani et al. (1998) also detected CRH and cortisol-like molecules immunocytochemically in the epithelial cells, interdigitating cells and macrophages, but not lymphocytes, in thymuses from fish, frog, chicken, and rat. These data suggest that throughout vertebrate evolution, the thymus can function as a neuroendocrine organ that is fully capable of displaying characteristics of a “stress response.” In a 1992 study, the presence of immunoreactive ACTH and βendorphin molecules in phagocytic basophils and neutrophils of salamanders (S. salamandra, T. carnifex, Speleomantes imperialis) has been established (Ottaviani et al., 1992d); ACTH increased phagocytic activity of these cells. Morphine-induced inhibition of zymosan-induced peritoneal inflammation consistently recorded in several mouse strains and in fish (salmon and goldfish) was not observed in the anuran amphibians R. temporaria, R. esculenta, and Bombina bombina (Kolaczkowska et al., 2000). Given the number of parameters involved in this type of study, however, a negative result cannot be considered as definitive.
In a more recent study, Chadzinka and Plytycz (2004) pre-incubated leukocytes from mice, goldfish, and frogs with agonists of mu, delta, or kappa opioid receptors (morphine, deltorphine, or U-50,488H, respectively), and then recorded their in vitro migration after culturing them in either medium (M), control serum (S), or serum from zymosan-treated animals (SZAS). In all species, migration of control leukocytes was in the order SZAS > S > M. Also for all species, pre-treatment of leukocytes with a mu or delta opioid receptor agonist, but not a kappa agonist, enhanced their migration when they were cultured with either medium or control serum. When the leukocytes were harvested from animals treated in vivo with zymosan to activate them, the migration of mouse and fish leukocytes, but not frog leukocytes, was inhibited. This inhibition could be reversed by specific antagonists of mu and delta opioid receptors (CTOP and naltrindole, respectively). According to the authors, these results imply that the final effects of opioids on cell migration are “dependent on a species-specific balance between up- and down-regulation of leukocyte migration that results from an interplay between receptors for opioids and chemotactic factors.”
C. Seasonal Influences on Immunity The amphibian immune system, like that of reptiles (see next major section), is influenced by seasonal variations (Plytycz and Seljelid, 1996, 1997). Several examples are worth noting: (1) The inguinal lymphoid bodies of toads undergo seasonal cyclic changes in morphology (Plytycz and Szarski, 1987). (2) Gutassociated lymphoid tissues of some anuran species also undergo seasonal changes (Saad and Plytycz, 1994). For example, Wojtowicz and Plytycz (1997) found that the number of lymphoid nodules in the gut was negligible in field-collected B. bufo that were emerging from hibernation. This number increased in spring, reached its highest level in the summer, and declined in autumn. (3) The magnitude of the antiSRBC response and the number of splenic lymphocytes in the toad B. regularis are high in spring, low in summer, high in autumn, and low again in winter (Hussein et al., 1984; Saad and Ali, 1992). (4) The percentage of lymphocytes in peripheral blood and hematopoiesis in the perihepatic subcapsular tissue is strikingly reduced in winter relative to summer in two species of newts: T. carnifex and T. alpestris (Barni et al., 1993). (5) The thymus of the frog R. temporaria undergoes cyclical changes with maximal development occurring during the summer and involution in the winter (Bigaj and Plytycz, 1984; Miodonski et al., 1996; Plytycz, et al., 1991).
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Surprisingly, only a few investigators have examined seasonal effects on the amphibian immune system by modeling the normal winter hibernation of amphibians in the laboratory. In an early study of this kind, Green (Donnelly) and Cohen (1977) found that complement CH50 titers of Rana pipiens kept at 4°C for several months in a hibernaculum decreased to undetectable levels. This finding was confirmed and extended to other components of the immune system by Maniero and Carey (1997). Cooper et al. (1992) performed a more comprehensive study of hibernationassociated changes in the anuran immune system. Leopard frogs (acclimated to 22°C) were placed in a hibernaculum (in the dark) in late autumn. Animals, sampled at days 45 and 90 after initiation of hibernation, underwent a progressive 9- to 10-fold loss of leukocytes in the blood, thymus, spleen, jugular bodies and, to a much lesser extent (1- to 2-fold), in the hematopoietic bone marrow. These changes were reflected by marked aplastic changes in these organs. By the end of the experimental hibernation period (day 135), however, numbers of leukocytes in these organs had begun to increase, even though the photoperiod was unchanged and the temperature remained at 4°C. At day 30 after the frogs had been returned to room temperature, cell numbers had returned to, or were greater than, pre-hibernation values, and the architecture of the organs again appeared normal. Despite the clear importance of temperature effects rather than season on graft rejection discussed below, at least in the case of the R. temporaria thymus, manipulation of the environmental temperature during the period of winter involution and summer growth did not override the endogenous seasonal rhythms (Bigaj and Plytycz, 1984; Zapata et al., 1992). These morphological and functional changes may result from seasonal changes in levels of circulating hormones such as corticosteroids, sex steroids, GH, PRL, and/or thyroxine (Mosconi et al., 1994; Plytycz et al., 1993; Saad and Ali, 1992; Zapata et al., 1992). Indeed, nearly 60 years ago, Holzapfel (1937) reported changes in the gross and histological changes in the adrenals, pituitary, gonads, pancreas, and thyroid during winter hibernation. This yearly pattern of thymic involution and loss of lymphocytes followed by expansion of thymocytes and peripheral lymphocytes in the spring may offer a unique model for studying repertoire development and self-tolerance in the context of neuroendocrine regulation. Regardless of whether cold and/or neuroendocrine changes are responsible for the striking winter-associated depression of lymphoid tissues and specific immune responses (Plytycz and Seljelid, 1997), immunologists still have to contend with the issue of
how such immunosuppressed amphibians survive during such periods. Several possibilities come to mind. First, at least some animals might not survive. Second, at least for amphibians living in temperate climates, low temperature may also suppress the growth of potential pathogens. Third, immunological memory (i.e., memory cells) to pathogens to which amphibians were exposed during the spring, summer, and fall may persist during the winter (Cooper et al., 1992). Finally, components of the non-specific innate immune system may not be depressed during the winter or may recover more rapidly after hibernation than specific adaptive immune responses. With respect to this last possibility, Maniero and Carey (1997) noted that complement activity increased within 2 days after R. pipiens were brought from artificial hibernation to room temperature. Moreover, complement levels continued to increase until, in some instances, they were significantly greater than those of controls held at room temperature. Similarly, Plytycz and Józkowicz (1994) reported that endocytosis of peritoneal macrophages from fish as well as anuran and urodele amphibians was effective in vitro over a wide temperature range and was actually enhanced in cells obtained from cold-acclimated animals. Although the aforementioned studies reveal important seasonal (endocrine) effects on parameters of the amphibian immune system, it is well known that immune responses in this vertebrate class are, like those in other ectotherms, regulated by temperature. In this regard, it is noteworthy that the timing of skin graft survival by anurans grafted during different seasons appears reflective of temperature rather than neuroendocrine changes (Józkowicz and Plytycz, 1998; Saad and Plytycz, 1994). In the Józkowicz and Plytycz (1998) study, the effects of ambient temperature (22°C vs. 10°C) and season (summer vs. winter) on anuran skin allograft rejection were examined in frogs (R. temporaria and R. esculenta) and toads (B. bufo, Bombina variegate, and B. bombina). Mean graft survival times were significantly prolonged at the low temperature regardless of the season. Interestingly, R. esculenta was the most sensitive to the temperature effect, whereas B. bufo was relatively resistant. Rejection of second-set grafts in R. esculenta was accelerated at both 22°C and 10°C, but second-set grafts were less temperature-sensitive than the initial sensitizing ones. In both summer and in winter, R. esculenta rejected allografts promptly at 22°C but slowly at 10°C. In both seasons, B. variegate kept at 22°C rejected allografts chronically. This indicates that amphibian transplantation immunity depends on the donor-host genetic disparity and ambient temperature but is independent of season.
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D. Glucocorticoid Effects on Amphibian Immunity Exogenous administration of a single injection of DEX in Rana perezi caused thymic involution and massive destruction of cortical lymphocytes, diminution in white pulp, and lymphocyte redistribution to the bone marrow from blood and spleen (Garrido et al., 1987). The nature and extent of these changes depended on whether DEX was administered in autumn or winter (Garrido et al., 1989). Pharmacologic concentrations of hydrocortisone suppress antibody responses in Xenopus and cause massive cell death in vivo and in vitro in the thymuses and jugular bodies, but not the spleen, of R. temporaria (Plytycz et al., 1993). In the Plytycz et al. (1993) study, the number of viable cells in the thymus and jugular body returned to normal within 1 week after a single injection of hydrocortisone3. Rollins-Smith and Blair (1993) also reported that physiological (10−5 M–10−9 M) rather than pharmacological concentrations of corticosterone inhibited PHA-induced proliferation of adult Xenopus splenocytes.
E. Neuroendocrine-immune System Interactions During Metamorphosis Thyroxine (T4) and triiodothyronine (T3) play a major role in driving amphibian metamorphosis (Kikuyama et al., 1993; Leloup and Buscaglia, 1977; White and Nicoll, 1981). Circulating levels of these hormones are low at pre-metamorphic stages, increase during pro-metamorphosis, peak during climax, and decline at the end of metamorphosis. Metamorphosis is also accompanied by increases in circulating levels of corticosteroids (Jaudet and Hatey, 1984; Kikuyama et al., 1986), PRL, and GH (Buckbinder and Brown, 1993; Clemons and Nicoll, 1977; White and Nicoll, 1981). Each of these hormones has immunomodulatory effects in mammalian species (Madden and Felten, 1995), and manipulation of at least some of these hormones also influences immune function in amphibians (Rollins-Smith, 1998; Rollins-Smith and Cohen, 1995, 2003). Thyroid hormones: Since metamorphosis is strictly regulated by the availability of thyroid hormones, manipulating their levels makes it possible to inhibit or accelerate metamorphosis and thereby determine the extent to which development of an adult parameter of immunity in frogs requires a normal metamorphic transition. Xenopus larvae reared in the water contain3 It should also be noted that thymic and splenic morphology may be affected by laboratory and/or husbandry conditions regardless of season (Dulak and Plytycz, 1989).
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ing the goitrogen, sodium perchlorate, to inhibit iodine uptake by thyroid follicle cells (Capen, 1994) undergo arrested development and do not metamorphose. Such blocked animals reveal that development of some structural and functional components of the adult Xenopus immune system are dependent on thyroid hormones and a normal metamorphic transition, whereas others are metamorphosis-independent. Specifically, perchlorate-blocked larvae lack the adult pattern of antibody responses to a specific hapten (Hsu and Du Pasquier, 1984), and adult-type MHC class II+ T-lymphocytes do not appear in the periphery (RollinsSmith and Blair, 1990b). Moreover, the thymus does not assume an adult-type morphology (Clothier and Balls, 1985); lymphocytes in the thymus and spleen do not achieve the expanded cell numbers characteristic of post-metamorphic adults (Rollins-Smith and Blair, 1990a, 1990b); adult-type skin allograft rejection does not replace the typical tolerogenic responses of larvae (Cohen and Crosby, unpublished); and, as pointed out previously, splenic innervation and compartmentation of the spleen into a clearly defined red and white pulp is dramatically delayed (Kinney, 1996). Immune system changes that occur in perchlorateblocked tadpoles (i.e., are independent of thyroxine levels) include the expression of MHC class I antigens (Rollins-Smith, 1998; Rollins-Smith et al., 1994), the immigration and expansion of T-cell precursors in the thymus (Rollins-Smith et al., 1992), and the development of high titer IgY antibody production (Hsu and Du Pasquier, 1984). Just how thyroid hormones are related to the maturation of some facets of the Xenopus immune system is unknown. Thyroxine appears to drive the terminal maturation of larval erythrocytes (Galton and St. Germain, 1985) and the expansion of a separate adult erythrocyte population (Flajnik and Du Pasquier, 1988). However, since thyroid hormones have no deleterious effects on lymphocyte viability and inconsistent effects on proliferation (Rollins-Smith and Blair, 1993), the direct action of thyroid hormones does not appear to be responsible for the dramatic loss of larval lymphocytes at metamorphosis. In this regard, it is noteworthy that thyroid hormone deprivation initiated after metamorphosis does not appear to affect lymphocyte populations of post-metamorphic animals or the ability of T-cells from such animals to respond to mitogens (Rollins-Smith et al., 1993). Corticosteroid hormones (CH): In short-term in vitro studies, both adult and larval lymphocytes are killed by concentrations of corticosterone that are comparable to those occurring at metamorphosis (RollinsSmith, 1998; Rollins-Smith and Blair, 1993; Rollins-Smith et al., 1997a). Corticosterone and aldosterone signifi-
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cantly inhibit PHA-induced proliferation of larval and adult spleen cells (Marx et al., 1987; Rollins-Smith and Blair, 1993; Rollins-Smith and Cohen, 1995), and corticosterone induces apoptotic death of larval splenocytes at concentrations as low as 1–10 nM (Rollins-Smith, 1998; Rollins-Smith et al., 1997a). Adult lymphocytes may be protected in vivo from the destructive effects of corticosterone since there is less total corticosterone in the circulation after metamorphosis, and most is in a bound state (Jolivet-Jaudet and Leloup-Hatey, 1986). Since aldosterone levels do not appear to be affected by specific serum-binding factors, the observed elevated levels of aldosterone in plasma of metamorphosing and adult frogs reflect the level of freely available aldosterone. Because larval lymphocyte function is affected by aldosterone at these physiologically relevant concentrations (Rollins-Smith and Cohen, 1995), aldosterone could play a role in the loss of larval lymphocytes. Based on in vitro sensitivities of Xenopus lymphocytes to corticosterone and aldosterone, it is reasonable to propose that the naturally increasing concentrations of these hormones during metamorphosis are causally related to the death of significant numbers of larval splenic lymphocytes (Rollins-Smith and Cohen, 1995). This hypothesis is supported by evidence that the in vitro inhibition of PHA-stimulated splenocyte proliferation by CH can be blocked by the CH-receptor antagonist, RU486 (Rollins-Smith, 1998; Rollins-Smith and Cohen, 1995; Rollins-Smith et al., 1997a), and that in vivo treatment of stage 57–58 larvae with RU486 reveals a dose-dependent inhibition of the loss of splenocytes that normally occurs during metamorphosis (Rollins-Smith, 1998). Thus, corticosterone and/or aldosterone appear to be important regulators of peripheral splenocyte populations at metamorphosis in Xenopus. The putative hormonally induced loss of splenic lymphocytes during metamorphosis is quite important, for if these immunocompetent larval cells were not eliminated, they could potentially be activated by newly emerging adult-specific self-molecules. The role of increasing levels of CH on the viability and development of thymocytes is more difficult to evaluate. Viability of larval thymocytes cultured in 1– 10 μg/ml corticosterone is significantly reduced (Rollins-Smith and Blair, 1993); this reduction can be inhibited by RU486 in vitro (Rollins-Smith, 1998; Rollins-Smith et al., 1997a). However, other studies have reported significant apoptosis of cultured thymocytes from all larval and metamorphic that does not appear to be increased by culture with DEX (Ruben et al., 1994). Regardless of their outcome, these in vitro
studies are difficult to interpret because thymocyte development is critically dependent on influences of the stromal/epithelial microenvironmental. For example, in mammalian systems, thymic epithelial components can synthesize corticosteroids (Vacchio et al., 1994). Thus, thymocytes may constantly receive local corticosteroid signals that influence their viability. Growth hormone (GH) and prolactin (PRL): Although a role for GH and PRL in mammalian immunity is now well established (Dorshkind and Horseman, 2000; Kelly et al., 1992), very little is known about the involvement of these hormones in the development and function of cells of the amphibian immune system. Hypophysectomized tadpoles continue to grow, can usually reject skin or organ allografts differing by presumed or defined MHC antigens (Rollins and Cohen, 1980; Rollins-Smith and Cohen, 1982; Maéno, and Katagiri, 1984) and, like control tadpoles, do not reject minor H-locus disparate grafts or grafts expressing organ-specific antigens (Maéno and Katagiri, 1984; Rollins-Smith and Cohen, 1982). To study the possible role of pituitary-derived hormones in the development of the amphibian immune system, Rollins-Smith and colleagues (2000) hypophysectomized (hypx) early larval stage Xenopus and examined the pattern of immigration of host-derived T-cell precursors into an implanted thymus using a ploidy marker (Rollins-Smith et al., 1992; Turpen and Smith, 1989). There were significantly decreased numbers of lymphocytes in the spleen and thymuses of hypx frogs in comparison with intact controls. However, no apparent delay or inhibition of the repopulation of the triploid donor thymus implanted into a diploid tadpole host was observed (Rollins-Smith et al., 2000). These results suggest that during the larval period, pituitary hormones are not required for either maintenance of the extra-thymic stem cell compartment, for maintenance of the attractiveness of the thymus for precursors, or for the process of thymocyte immigration. Analysis of cell division in the developing thymus populations revealed an inhibition of proliferation in hypx hosts. Thus, pituitary hormones appear to be required for the normal expansion of Tcell precursors after they colonize the thymus. In unpublished studies, we and Rollins-Smith have independently observed that chicken anti-PRL antibodies suppress proliferation of mitogen-stimulated (LPS, PHA, Con A) larval and adult splenic lymphocytes. Thus, PRL may be an essential lymphocyte growth factor that developed early in vertebrate evolution (see discussion in Kelly et al., 1992). To produce sufficient Xenopus PRL to investigate the role of PRL in normal lymphocyte function, Rollins-Smith and
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colleagues (personal communication) have inserted cDNA corresponding to the known sequence for a Xenopus PRL into a bacterial expression vector. The resulting expression products (single peptides of about 26 kDa (including 21 additional amino acids on the amino terminal end) stain with anti-PRL antibodies by immunoblotting. These expressed proteins can enhance PHA-induced lymphocyte proliferation driven by the T-cell mitogen, PHA (Rollins Smith and Reinhart, personal communication). Hypx frogs exhibit a larval-type pattern of expression of MHC class I and class II antigens (Rollins-Smith et al., 1997b). That is, surface expression of MHC class I on spleen cells and erythrocytes is low in comparison with age-matched intact post-metamorphic controls at 1 year of age. The monoclonal anti-T cell antibody XT1 (Nagata, 1988) recognizes determinants that are predominantly on MHC class II negative cells in hypx frogs, whereas the XT-1+ population in age-matched post-metamorphic adults is class II positive. These experiments suggest that the pituitary-derived hormones that orchestrate normal metamorphosis are required for a post-metamorphic T-cell expansion and for development of the adult pattern of MHC expression on cells of the immune system.
F. The Impact of Environmental Stressors on Anti-microbial Immunity and Its Implications for the Worldwide Decline of Amphibians An ecological problem area that is being studied deliberately from a psychoneuroimmunological perspective is the worldwide decline of populations and species of frogs and salamanders (Collins et al., 2005). One cause of these declines and extinctions is clearly the destruction of habitat where amphibians breed and grow. A second cause stems from the introduction of superior predators or competitors that displace native species. At face value, these two explanations would not appear to involve psychoneuroimmunological considerations although they do involve what might be considered environmental stressors. However, we also know that two pathogens, a Chytrid fungus (Batrachochytrium dendrobatidis) and iridoviruses (ranavirus, Ambystoma tigrinum virus), are causally involved (Carey et al., 1999; Rollins-Smith et al., 2002; Woodhams et al., 2006) in the decline; so too are anthropogenic environmental changes or “ecological stressors” that include toxic chemicals (e.g., agricultural pesticides), UV radiation, and/or global climate change. Some pesticides are immunomodulatory in amphibians. For example, immunotoxicological studies have revealed the immunosuppressive capacity of various
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single and combinations of pesticides (e.g., atrazine, metribuzine, endosulfan, lindane, aldicarb, DDT, malathione, and dieldrin) in Xenopus and Rana (Christin et al., 2004; Gilberton et al., 2003). These agents could be immunotoxic by acting directly on cells of the immune system. Alternatively, and from a psychoneuroimmunological perspective, they could be immunosuppressive owing to their action on the neuroendocrine system that, in turn, negatively signals the immune system and increases susceptibility to fungal and/or viral pathogenicity, eventuating in a species decline (Rollins-Smith and Cohen, 2003). Evidence for this latter possibility is scanty since studies of immunity to chytrids and ranaviruses are only in their infancy. Nevertheless, we do know that naturally produced anti-microbial skin peptides of frogs are capable of inhibiting growth of zoospores and mature fungal cells (Rollins-Smith et al., 2002). Secretion of these peptides from amphibian skin glands is regulated by the sympathetic nervous system (i.e., EPI and NE) (Benson and Hadley, 1969; Dockray and Hopkins, 1975; Holmes and Balls, 1978). Could environmental “stressors” (e.g., pesticides) be affecting peptide production/ secretion via their effects on the sympathetics? Although this possibility has yet to be tested in a laboratory environment, it is known that chlorotriazine herbicides decrease the intracellular content and release of DA and NE from PC12 cells, a cell line with neuronal characteristics (Das et al., 2000). Also, a dithiocarbamate compound similar to agents used as pesticides inhibits NE synthesis by suppressing the activity of dopamine-beta-hydroxylase (Goldman et al., 1994). In other words, this possibility may not be so far-fetched. With respect to iridoviruses, we now know that in addition to anti-microbial peptides (Chinchar et al., 2001) and NK cells (Horton et al., 2003), Xenopus uses CD8 T-cells, NK/T-cells, and antibody to deal with laboratory-induced infections with frog virus 3 (FV3) (Gantress et al., 2003; Robert et al., 2005). We also know that x-irradiation increases mortality associated with FV3 infection (Robert et al., 2005). Metamorphosing frogs have a naturally downregulated immune system4, and larval and metamorphosing frogs are much more susceptible to infection with this iridovirus than are adults (Robert et al., 2005). Finally, we know that in amphibians glucocorticoids are highly immunomodulatory, especially during metamorphosis (RollinsSmith et al., 1997a). In this regard, xenobiotic chemicals in the environment can induce increases in circulating 4 It is thought that this downregulation evolved to protect animals from immune responses to adult-specific antigens that are emerging during the metamorphic transition from immunocompetent larva to immunocompetent adult.
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corticosteroids (Gendron et al., 1997; Hopkins et al., 1999). Although we’ve not directly tested this possibility in Xenopus, we do know that elevated levels of corticosteroids have been detected in toads (Bufo terrestris) collected from areas polluted by coal ash (Hopkins et al., 1999) and in mudpuppies (Necturus maculosus) that have been exposed to organochlorine (Gendron et al., 1997) in a setting in which maximal concentrations approximate those associated with the natural glucocorticoid-associated immunosuppression in Xenopus that occurs during metamorphosis (Barker et al., 1997; Rollins-Smith and Blair, 1993).
V. NEURAL-IMMUNE INTERACTIONS IN REPTILES Our very limited knowledge of the interactions of the neuroendocrine and immune systems in reptiles is derived primarily from the following three lines of research by Egyptian and Spanish groups of investigators: (1) lymphoid tissue innervation, (2) seasonal influences on several immunological parameters, and (3) effects of steroids on immunity. Much of what has been accomplished following the last two approaches is the focus of reviews by Zapata et al. (1992) and Saad and Plytycz (1994).
A. Innervation of Lymphoid Organs Saad (1993) described, in turtles, the presence of nerve endings in close proximity to lymphocytes in the spleen, as well as changes in brain catecholamine levels during the course of an immune response. Brain EPI levels were increased 10 hours after immunization with SRBC; they then decreased to below-control levels at 48 hours, after which time they returned to baseline. DA was elevated at 4 hours, decreased at 2–4 days, and then returned to normal values by day 10 (Saad, 1993). Clearly, more details are needed about innervation of lymphoid organs in representatives of various reptilian orders. It is also unknown whether the seasonal waxing and waning of immune reactivity in reptiles described below is associated with seasonal changes in the pattern of innervation of lymphoid tissues.
B. Seasonal Influences on Immunity In the snake (Natrix natrix), a seasonal cyclicity in circulating leukocytes has been reported, with females showing lymphocytopenia and neutrophilic granulocytosis during the time of egg laying, and males also showing similar, but less marked, white cell count cycling (Wojtaszek, 1992). Thymic involution in the
turtle, Mauremys caspica, occurs in April–May, as do diminished antibody responses and delayed graft rejection (Zapata and Leceta, 1986; Zapata et al., 1992). Other investigators (Muñoz and De La Fuente, 2001, 2004), however, reported for the same species that spring is associated with a higher splenic mitogen response and summer with enhanced chemotaxis and cytotoxicity; spring-summer is associated with a higher proportion of splenic and thymic lymphocytes as well as better thymocyte proliferation. Since there is disagreement in these results from the same chelonian species, resolution of the differences awaits further study, as does an understanding of the mechanisms responsible for such seasonal changes. In the lizards Eumeces schneideri and Chalcides ocellatus (Saad et al., 1993), the numbers of lymphocytes in the peripheral blood, bone marrow, thymus, and spleen are lower during the fall and winter than in spring and summer. There also appears to be a trend toward increased humoral immunity (both in vivo and in vitro) in the summer relative to winter (Saad et al., 1993; Zapata et al., 1992). Lizards have also been reported to show seasonal variability in their ability to reject skin allografts in that animals grafted in winter months did not reject until the warmer spring months (Afifi et al., 1993). These winter-spring responses, however, were still slower than those seen in warmer summer months. Reptiles are ectotherms, and high and low environmental temperatures are immunomodulatory in such species (Clem et al., 1984, 1991). Therefore, interpretation of data describing seasonal effects on the immune system is confounded by the possibility that variation in ambient temperature, rather than (or in addition to) neuroendocrine changes associated with seasonality and altered photoperiod, is the important variable. The fact that antibody titers in the turtle Mauremys capsica are higher in autumn than summer in turtles kept at 27°C and at a constant photoperiod (Zapata and Laceta, 1986) argues against this possible confound. Comparable data presented below for a ranid frog (Bigaj and Plytycz, 1984) and for fish (Nakanishi, 1986; Yamaguchi et al., 1981) also support some sort of seasonal cue (e.g., photoperiod?) other than temperature as an important component of this cyclicity of immune responses and lymphoid system changes. The impact of different photoperiods at a constant temperature on immune system parameters still needs to be determined at all seasons.
C. Effects of Steroids on Immunity Some of the aforementioned seasonal changes may be related to seasonal changes in circulating levels of
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corticosteroids and/or gonadal steroids. In this regard, some correlational data on seasonal levels of testosterone, glucocorticoids, and changes in the reptilian immune system are worth highlighting (Zapata et al., 1982; Zapata et al., 1992). Based on observations of a sexual dimorphism in immunity in a snake (Saad and Shoukrey, 1988) and of an increase in testosterone levels in the blood of Chalcides ocellatus during the spring, Saad et al. (1990, 1992) investigated the impact of adult orchiectomy and testosterone treatment on antibody production in Chalcides. Five injections of testosterone propionate (each separated by 5 days) during the summer (animals maintained at ambient and, therefore, fluctuating, temperatures), followed by immunization with SRBC, did not affect in vitro PFC responses but were associated with a significantly diminished serum antibody at some, but not all times, post-immunization. Orchiectomy during the spring effected a marked and long-lived reduction in serum levels of testosterone and was associated with an increased primary PFC and serum antibody response to SRBC. Although antibody responses in orchiectomized lizards that received a course of testosterone did not differ from responses of orchiectomized animals, this reconstitution experiment would have been strengthened had the investigators confirmed the efficacy of the orchiectomy itself by including a group of unmanipulated animals in their protocol. A single injection of testosterone proprionate also resulted in thymic involution and depletion of splenic and PBLs in the turtle Mauremys caspica (Saad et al., 1991a, 1991b; Varas et al., 1992). The immunocompetence handicap hypothesis (ICH) was developed to explain the maintenance of exaggerated male traits under sexual selection in birds. The hypothesis requires that such traits (e.g., bright plumage in birds) (1) are preferred by females; (2) are promoted by testosterone (T); and (3) are maintained as “honest signals” by the presumed immunosuppressive action of testosterone (i.e., only a high-quality male can afford to be so immunosuppressed) (Fostad and Karter, 1992). As might be expected given their close phylogenetic apposition to birds, reptiles have also been the subject of speculations concerning the ICH. Oppliger et al. (2004) found decreased skin response to PHA in testosterone-implanted male lizards (Podarcis muralis) but did not find any effect on the presence of blood or ectoparasites, a common functional measure of immunity in both birds and reptiles. Berger et al. (2005) examined Galapagos marine iguanas during the breeding season and found no overall differences between dominant and subordinate males, but that restraint stress or corticosteroid injection elicited a depressed PHA response. The authors
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argue that this is evidence that corticosteroids, not gonadal steroids, are key immunosuppressive agents during the breeding season and that the ICH needs to be revised to account for this. In an earlier series of studies, the Egyptian group studied the histological, cytological, and immunological consequences of exogenously administered pharmacological concentrations of hydrocortisone acetate in Chalcides during the summer. As would be predicted from studies with mammals, exogenous hydrocortisone acetate caused profound, but seemingly selective, loss of both T- and B-lymphocytes in the thymus, peripheral blood, and spleen. Physiological concentrations of 10−3 M hydrocortisone also led to in vitro destruction of thymocytes, PBLs and, to a lesser extent, splenic lymphocytes (Saad and Bassiouni, 1991; Saad et al., 1984a, 1984b). Long-term corticosteroid administration has also been associated with decreases in lymphocytes and heterophils in juvenile alligators (Morici et al., 1997). More recently, exogenous glucocorticoids have been associated with apoptosis of thymocytes in the wall lizard, Hemidactylus flaviviridis (Hareramadas et al., 2004). In Chalcides, a single injection of 1.0 mg/g body weight of hydrocortisone acetate “caused” a 3-week-long physiological increase in serum corticosterone (peak 2 × 10−7 M) and cortisol (peak 1 × 10−6 M). This was associated with a suppression of the primary antibody response to rat RBC in vivo and in vitro, a delay in allograft rejection, and a reduction in proliferation in mixed leukocyte culture (Saad et al., 1986). An obvious confound in this study is the extent to which the impaired immune response reflects the exogenously administered steroid rather than, or in addition to, endogenously synthesized glucocorticoid. Also, an increase in endogenous steroids in response to exogenous steroids is puzzling if the HPA axis of turtles, like that of mammals, has a characteristic feedback loop. In a somewhat more naturalistic study, environmental stress (density, presence of new conspecifics, altered feeding protocol) was associated with an increase in blood parasite infections in the lizard Lacerta vivipara, a finding which could have implications for understanding the effects of habitat loss (Oppliger et al., 1998) on the survival of lizard populations. Infection with blood-borne parasites has also been associated with a drop in corticosteroid levels (Hanley and Stamps, 2002). An important caveat in interpreting studies in which a correlation is being made between seasonally associated alterations in immune function and in levels of endogenous hormones is whether levels of a given hormone have been determined sequentially during a 24-hour period in each season. In instances of the
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single time-of-day measurements that appear typical of the immunological studies in reptiles, amphibians, and teleosts reviewed in this chapter, a possible seasonal phase shift in the diurnal rhythm associated with a given hormone (Spieler, 1979) could significantly alter interpretation of the published data regarding mechanisms responsible for seasonal changes in immune function. Regardless of the underlying mechanisms, however, seasonal and endocrine-associated changes in lymphoid tissue architecture and cellularity remain real events. In contrast to mammals (and to a lesser extent, amphibians and teleosts), the role of catecholamines in immunity in reptiles has received minimal attention. One recent study, however, indicates that in the lizard Hemidactylus flaviviridis, high doses of catecholamines (as well as 1-hour restraint stress) inhibited phagocytic activity of splenic macrophages, whereas very low concentrations enhanced the response (Roi and Rai, 2004). Clearly, much remains to be examined in this area.
VI. NEURAL-IMMUNE SYSTEM INTERACTIONS IN BIRDS The study of neural-immune system interactions in birds, like the study of avian immunity itself (Sharma, 1991), has lagged behind comparable studies in mammals. Nevertheless, several lines of evidence (Marsh and Scanes, 1994) are totally consistent with neuroendocrine regulation of immune processes in the few commercially important avian species that have been studied.
A. Innervation of Lymphoid Organs and Immunomodulation by Neuropeptides The earliest indication that the bursa of Fabricius, the primary lymphoid organ involved in Blymphocyte ontogeny in birds, is innervated was provided by observations of Pintea et al. (1967), Cordier (1969), and Inue (1971). More recently, Zentel et al. (1991) described peptidergic innervation of the chicken bursa. Specifically, immunoreactivity for tachykinins, calcitonin gene-related peptide (CGRP), and NPY was described in proximity to bursal vasculature and specific cell populations, primarily B-cells. Even though some T-lymphocytes are present in the bursa, these investigators did not find peptidergic fibers near labeled T-cells. Although Zentel and Weihe (1991) were unable to directly demonstrate sympathetic innervation of the bursa, they associated the NPY staining with sympathetic innervation since, at least in
mammals, NPY and NE are co-localized in sympathetic fibers (Bellinger et al., 1990). More recently, Ciriaco et al. (1995) investigated innervation of the pigeon bursa of Fabricius from hatching to 4 months of age, by histochemically staining for noradrenergic- and acetylcholinesterase (AChE)-reactive nerve fibers. NA nerve fibers were largely perivascular, but a small number were also seen in interfollicular connective tissue. In bursas from 30–75-day-old animals, fibers were occasionally observed beneath the bursal epithelium, in the cortex, and at the cortico-medullary border, but not the medullary portion, of the lymphoid follicles. Although no age-associated changes in the density of NA innervation were observed in the vascular areas, there was a progressive increase in the density of non-vascular NA nerve fibers for the first 30 days of life, no variation from 30–75 days, and an apparent regional increase during bursal involution. The distribution and density of perivascular AChE-positive nerve fibers were similar to that for NA fibers. AChE-reactive fibers were also observed in the capsule of the bursa and in the interfollicular septa, and AChE-reactive dendritic-like cells and cell processes were seen subepithelially, in the cortex, and at the corticomedullary border of the lymphoid follicles. No age-dependent changes in AChE staining were noted. Finally, in 1999, Franchini and Ottaviani described the presence of immunoreactive pro-opiomelanocortin derivatives (ACTH, α-MSH, β-endorphin) in both the thymus and bursa of chickens. In the thymus, immunoreactive staining was associated with the thymic epithelium and a few interdigitating cells. In the bursa, staining was associated with cells of the follicle. Immunoreactivity was seen as early as day 4 and increased with age. Given the change with development and the pattern of association, the authors suggest a physiological role in the development and/or involution of the organs. Suggestive evidence for sympathetic modulation of immunity in chickens has been provided by BrownBorg and Edens (1992). These investigators administered 6-OHDA to chicks in ovo on day 18 post-fertilization, immunized the birds with SRBC 25 days post-hatching, and observed a small but statistically significant increase in hemagglutinating antibody titers (relative to vehicle-injected controls) at 6, 8, and 10 days post-immunization. No change, however, was observed in a cutaneous cell-mediated response to PHA measured at the same times as anti-SRBC antibody responses. This suggests that their manipulation of the sympathetic nervous system may differentially affect different arms of the immune system. SyX of adult mice causes an increase in glucocorticoids (Callahan et al., 1998). Although this does not appear
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to be responsible for the SyX-associated immune changes seen in such mice (Kruszewska et al., 1998), this may not be the case in birds. There is also evidence that innervation of primary lymphoid organs plays a role in development of avian immune responses (Franchini et al., 1995). Administration of 6-OHDA to chicks in ovo was associated with reduced expression of IL-2 mRNA and reduced in vitro proliferative response to pokeweed mitogen, as well as alterations in lymphocyte expression of β-AR mRNA expression and response to NE administration (Motobu et al., 2003). That young chickens exhibit a corticosterone-unresponsive phase during the first 2–3 weeks post-hatching (Guellati et al., 1991) also needs to be considered in the context of differential effects of SyX on cellular and humoral immunity described by Brown-Borg and Edens (1992). In rodents, neonatal SyX results in a profound and long-lasting drop in splenic NE (Ackerman et al., 1991a) that is accompanied by increased antibody response to T-dependent antigens (Ackerman et al., 1991a; Besedovsky et al., 1979) and changes in a variety of other in vivo and in vitro immune system parameters (Ackerman et al., 1991b; Chelmicka-Schorr et al., 1992a, 1992b; Madden et al., 1993). Although in chickens, the injection of 6-OHDA in ovo causes central as well as peripheral denervation (Spooner and Winters, 1966), Brown-Borg and Edens (1992) did not directly demonstrate denervation in their 6-OHDA study. Indeed, they could not detect NE (the principal sympathetic neurotransmitter in the chick) (Rome and Bell, 1983) in the thymus or bursa at the time of hatching, and NE was detected only in the brain stem and spleens of fewer than 30% of the control and experimental chicks examined. Moreover, similar levels of EPI and 5HT were found in the brain stem, thymus, bursa, and spleen of both control and 6-OHDA–treated animals. Although the levels of splenic NE increased during the course of the antibody response, at the time of each antibody titration, no differences among levels of splenic NE, DA, and 5HT in controls and experimental birds were seen. The significance of their observation that the peak splenic NE and DA response in 6-OHDA– treated chicks lagged a few days behind that of vehicleinjected controls is unclear. Further studies are needed to clarify the developmental time course of innervation of lymphoid tissues in chicks as well as to provide definitive HPLC, immunohistochemical, and immunocytochemical evidence of peripheral denervation by 6-OHDA treatment in ovo. In chickens, suppression of a PHA-induced cellmediated immune reaction in the wattle (Kelsius et al., 1977) could be effected by a single injection of NE, 5HT, and DA (Lukas et al., 1987) or by continuous DA
administration alone (McCorkle and Taylor, 1994). In vivo DA and 5HT administration also suppressed PFC responses (McCorkle et al., 1986); enhanced migration of PBLs was noted following in vitro exposure of chicken leukocytes to each of these monoamines (McCorkle and Taylor, 1994; McCorkle et al., 1990). In a somewhat more recent study, the same group (Gray et al., 1991) found that parenteral 5-HT and DA increased and decreased plaque formation, respectively; only the DAassociated effect could be mimicked by in vitro administration. No effect of neurotransmitters on IgG PFC formation was seen in either case, but in a related study, Denno et al. (1994) demonstrated a suppression of IgG PFCs by in vivo and in vitro administration of EPI, but an enhancement of IgM PFCs in response to in vitro EPI. In vitro administration of catecholamines has also been demonstrated to alter macrophage functions. For example, an increase in phagocytosis and the percentage of cells expressing FcR was seen following incubation with NE, EPI, or dopamine for 1 hour, whereas a longer exposure (3 hours) to DA only reduced SRBC phagocytosis (Ali et al., 1994). Taken together, these studies indicate a substantial, albeit not easily interpretable, influence on the sympathetic nervous system on immunity in birds.
B. Neuroendocrine Regulation of Immunity In addition to modulation of immunity by peripheral nerves and neurotransmitters, hormones (e.g., corticosterone, thyroid hormone, growth hormone, PRL, and gonadal steroids) all affect in vivo and in vitro immune function in fowl (Bachman and Mashaly, 1986, 1987; Glick, 1984; Haddad and Mashaly, 1990, 1991; Marsh and Scanes, 1994; Mashaly et al., 1998; Skwarlo-Sonta, 1992; Trout and Mashaly, 1995). A few examples should suffice: (1) CRF stimulates chicken macrophages, and to a lesser extent lymphocytes, to secrete ACTH, and concentrations of circulating corticosterone increase following antigen challenge (Hendricks and Mashaly, 1998; Hendricks et al., 1991; Mashaly et al., 1993). The increased corticosterone causes a redistribution of different lymphocyte subpopulations from the blood to spleen (Mashaly et al., 1993, 1998). (2) In mallards, the size of the thymus and bursa are reduced following corticosteroid treatment or blockade of thyroid hormone production (Glick, 1984). In vivo treatment of mallards with DEX suppresses primary antibody responses to SRBC. At the same concentration of DEX, NK cell activity is increased, apparently resulting from the decreased production of PGE-2 by macrophages included in the cultures (Fowles et al., 1993). (3) Castrated chickens, or
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chickens with early lesions of the anterior pituitary, display decreased T-cell–mediated immunity such as GVH in vivo and PHA-induced lympho-proliferation in vitro (Glick, 1984; Mashaly, 1984). (4) Chickens with either a genetic thyroid hormone deficiency (SLD dwarf chickens) or a thyroid hormone deficiency induced by synthesis blockade exhibit depressed antiSRBC antibody responses (Glick, 1984). The genetic deficiency and its associated immune dysfunction can be reversed by administration of thyroxine and growth hormone (Marsh et al., 1984). (5) PRL has a stimulatory effect on avian immunity in that it is associated with increased bursal mitotic activity in leghorns (Glick, 1984), increased bursa weight in hypophysectomized pigeons, enhanced chicken anti-SRBC responses, and enhanced mitogenic activity of chicken thymocytes and splenocytes (Skwarlo-Sonta, 1992). (6) Feeding thyrotropin-releasing hormone (TRH) or triiodothyronine (T3) to 1-day-old chicks for 8 weeks is associated with an increase in bursal weight; T3 but not TRH also increases splenic weight and numbers of white blood cells (Haddad and Mashaly, 1990); T3 treatment also increases the number of resting splenocytes expressing IL-2 receptors as well as the number of CD3-positive cells (Chandratilleke et al., 1996). (7) The bursa of Fabricius, like the thymus, has an endocrine as well as a critical immunological function. Surgical bursectomy (BsX) of 1-day-old chickens reduces the subsequent in vitro corticosterone response of adrenal glands exposed to ACTH (el Far et al., 1994). BsX is also associated with a reduction in testosterone production by Leydig cells (el Far et al., 1994). (8) Humoral immunity to a Tindependent antigen (LPS) has also been associated temporally with a drop in triiodothyronine levels and a rise in CORT levels in immature male chickens (Gehad et al., 2002). One of the most thoroughly examined roles of neuroendocrine regulation of immunity in birds comes from investigations by the group of Georg Wick (Hu et al., 1993), who studied the Obese Strain (OS) of chicken. This strain is characterized by the spontaneous onset of an autoimmune thyroiditis and hypothyroidism (Wick et al., 1990). OS birds exhibit increased corticosteroid-binding globulin, decreased free corticosteroid, and an impaired or even absent increase in plasma glucocorticoids in response to either the intravenous (i.v.) administration of antigen, IL-1, or a conditioned medium from Con-A–stimulated splenocytes that is known to contain factors that increase glucocorticoid levels (GIFs) in birds (i.e., IL-1 but not IL-6 or TNF). This impaired glucocorticoid response is not seen in either normal birds or in the UCD 200 strain of chickens that spontaneously develops a different autoimmune pathology from OS chickens. Given that there
is no strain-associated difference in the ability of mitogen-stimulated splenocytes from the OS and UCD 200 strain to produce conditioned medium with GIF activity (Schauenstein et al., 1986), the reduced glucocorticoid synthesis in OS chickens may well be referable to a neuroendocrine immunoregulatory defect in the HPA axis (Brezinschek et al., 1990; Wick et al., 1990) such as that associated with induced or spontaneous autoimmune diseases in certain strains of rats and mice (Wick et al., 1993). The situation for OS birds, however, is not as clear-cut as it might seem since hypothyroidism itself causes blunted HPA axis responses (Kamilaris et al., 1991). Given their economic importance and public concerns about battery-raised chickens, it is somewhat surprising that relatively little has been published on the effects of stressors on immunity in domestic fowl. What is known, however, holds no surprises (Cunnick et al., 1994). For example, social isolation as a stressor in young domestic fowl led to an increase in the number of leukocytes in the blood, but not in the spleen. This same study reported a time-dependent decrease in T-cell proliferation and an increase in production of an IL-1–like factor by adherent cells in the spleen (Cunnick et al., 1994). Increasing housing density decreased bursal weight in broilers but did not affect anti-SRBC production, cell proliferation, or total white blood cell count (Heckert et al., 2002). In a study examining free-living Adelie penguins, repeated handling had no effect on heterophil/lymphocyte ratios, but nesting status did. The ratio was lowest during the stage of chick care, a change which apparently preceded the rise in CORT associated with fasting at this time (Vleck et al., 2000). Perhaps the most fascinating area of investigation involving neural-immune interactions in birds involves the fields of ecology and evolutionary biology, where a hypothesis has emerged that actually assumes a neuroendocrine-immune system link. The immunocompetence handicap hypothesis (ICH), described in the previous section on reptiles, requires that certain traits (e.g., bright plumage in birds) that are preferred by females are promoted by the immunosuppressive action of testosterone (Fostad and Karter, 1992). Since the ICH was proposed, many studies have focused on demonstrating the immunomodulatory action of testosterone. For example, male house finches implanted with capsules to artificially elevate testosterone prior to immunization with SRBC exhibited a diminished hemagglutinating antibody response 2 weeks following immunization. A diminished cell-mediated response, assessed by a local inflammatory response to PHA, was also seen (Deviche and Cortez, 2005). A similar suppressive response was seen in song spar-
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rows (Owen-Ashley et al., 2004). Since these latter authors also reported that dehydroepiandrosterone did not affect immune responses, a direct effect of androgens is questionable. Further, these authors’ demonstration that CORT levels were elevated in testosterone pellet-implanted birds also argues that this effect is not directly due to the action of testosterone on the immune system. Artificial elevation of testosterone has also been demonstrated to depress immune parameters in dark-eyed juncos (Casto et al., 2001) and European starlings (Duffy et al., 2001). Not all experiments testing the ICH have demonstrated an immunosuppressive action of testosterone. Experiments employing free-living versus captive superb fairy-wrens (Peters, 2000) or examining resistance to viral infection in greenfinches (Lindstrom et al., 2001) have indicated that, at least in some instances, testosterone may be immunoenhancing. At least one other study examining antibody responses to SRBC failed to find any immunological effect of testosterone (Hasselquist et al., 1999). Thus, validation of ICH, and on the immunosuppressive effect of testosterone under naturalistic conditions, requires further investigation.
VII. CONCLUDING REMARKS AND FUTURE RESEARCH DIRECTIONS Although there have been only limited analyses of components of the neural-immune system communication network in the few favorite non-mammalian species, enough data exist to support the proposition that the phylogenetic emergence of a link between these two systems was not a recent event. To find the earliest origins of the integration of these systems and to determine whether the neuroendocrine and immune systems evolved from a “common ancestor” (Ottaviani and Franceschi, 1997) prior to the appearance of a blood-brain barrier (Cserr and Bundgaard, 1984), studies are needed that exploit the most primitive extant vertebrates: the Agnatha (hagfish and lampreys) that lack MHC, Ig, and TCR genes; the elasmobranchs (sharks and rays), in which these critical hallmarks of adaptive immunity emerge for the first time (Du Pasquier and Flajnik, 1999); and, of course, the invertebrates. In the past 5 years, studies of innate immunity have revealed several non-cytokine molecules that are common to the innate defense systems of both invertebrates and vertebrates. Indeed, these data (see reviews by Hoebe et al., 2004; Hoffman et al., 1999; Medzhitov and Janeway, 1998) provide strong evidence of evolutionary parallels and conservation of ancient host defense pathways involving Toll receptors and NF-κB signaling in organisms (e.g., Drosoph-
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ila) that have been separated from mammals by hundreds of millions years. Given the availability of the molecular tools that allowed this new information to be generated, it would seem worthwhile to determine whether such receptors and signaling pathways might be subject to regulation by those mammalian-like neuroendocrine mediators that also appear to have been phylogenetically conserved in invertebrates. Although it is clear that the basic pathways by which the nervous system can regulate the immune system in mammals are operative in teleosts, amphibians, reptiles, and birds, the extent to which products of the immune system can affect the brain and behavior of ectothermic vertebrates is virtually unexplored. Clearly, one of the more exciting developments in our understanding of neural-immune networks in mammals has been the reproducible demonstration that pro-inflammatory cytokines (e.g., IL-1, IL-6, TNFα) induced, for example, by microbial products act as bi-directional communication signal molecules between the immune system and the CNS (Felten et al., 1991; Fleshner et al., 1995; Krueger and Majde, 1994; Parsadaniantz et al., 1994, 1997). There are reports that deliberate infection of lizards (Kluger et al., 1975) or amphibians (Lefcort and Eiger, 1993) with pathogens can evoke behavioral responses consistent with IL-1 mediation (e.g., thermoregulatory behavior resulting in the selection of a higher temperature in the classic study of Kluger et al., 1975). Research on the direct involvement of cytokine homologues in such CNS responses in all classes of ectothermic vertebrates other than teleosts fish (Engelsma et al., 2002; Holland et al., 2002) has yet to be initiated. That recombinant cytokines, appropriate molecular probes, and monoclonal anti-cytokine antibodies will be invaluable for addressing fundamental questions about the phylogeny of neural immune system interactions is sharply revealed by a report that in the frog Xenopus, IL-β and its type 1 receptor, as detected by immunohistochemistry using polyclonal anti-human antibodies, are expressed in neural tissue prior to the development of cells of the immune system (Jelaso et al., 1998). Although these investigators performed Western blotting to “confirm” the IL-1 and IL-1 receptor specificity of the anti-human polyclonal antibodies they used in their Xenopus system, the availability of monoclonal antibodies directed against recombinant Xenopus IL-1 would have eliminated “putative” as a descriptor of the frog “IL-1” they were examining. Until such reagents are available, the issue of whether IL-1 and other pro-inflammatory cytokines were first used (phylogenetically speaking) as regulatory molecules by the nervous system and were subsequently co-
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opted by the adaptive immune system, or vice versa, remains purely speculative. This issue might best be addressed in invertebrates and agnathans in which no true adaptive immune system exists. As previously pointed out, some authors have written extensively about hemocyte-derived homologues of IL-1α and IL1β, IL-2, IL-6, and TNF-α and β (Ottaviani et al., 1995c). Their reports are primarily, if not exclusively, based on cross-reactions with anti-mammalian cytokine antibodies. While these mediators do appear to affect cell migration, phagocytosis, and the induction of biogenic amines and nitric oxide synthase in the species of origin (e.g., freshwater snails), we must reiterate that the appropriate molecular studies confirming that these invertebrate mediators are really cytokine homologues are lacking. Similarly, since we last reviewed this research area (Cohen and Kinney, 2001), we have not become aware of substantive reports that these hemocyte-derived mediators, whatever they are, can affect the nervous system and behavior in the homologous (or even heterologous) invertebrate species. Clearly, appropriate studies in invertebrates and ectothermic vertebrates could prove extremely interesting with respect to the evolution of these mediators themselves as well as to the phylogeny of neural-immune interactions. Information in this area may come from unexpected areas of research. For example, axons of the central nervous system in adult mammals do not regenerate spontaneously after injury, partly because of the presence of oligodendrocytes that inhibit axonal growth (Eitan et al., 1992). This is not the case in fish, where spontaneous regeneration of the optic nerve has been correlated with the presence of factors cytotoxic to oligodendrocytes. This cytotoxic factor from the fish optic nerve has been described by Eitan et al. (1992) as an IL-2–like cytokine. One important outcome of fully understanding neural-immune interactions is the development of behavioral and/or psychopharmacological strategies to maintain optimal health status in humans. There is, however, another related but largely overlooked application of understanding the impact of psychosocial and physical stressors on immune function, namely that eliminating or “controlling” or simply understanding stressors that may be encountered by feral animals may prove important for the health of both captive and wild populations. The following few examples (some of which are discussed elsewhere [Cohen, 2006]) should bring this point home: • Briggs et al. (1996) reviewed the impact of potential immunomodulatory effects of handling stress on the morbidity and mortality of seabirds
•
•
•
•
that are cleaned after having suffered the misfortune of being contaminated by an oil spill. An important method for tracking avian species during their migrations involves capturing the birds (e.g., with mist nets) and then banding them before release. Trapping and handling wild birds clearly influence glucocorticoid levels (Romero and Wingfield, 1999; Romero et al., 1997); the short- and long-term consequences of these well-intentioned manipulations on immune functions of these birds (many of whom are weakened by the flight and lack of feeding) certainly need to be considered by those directing this information-gathering conservation effort. In their paper describing the innervation of the spleen of the beluga whale, Romano et al. (1994) pointed out that in general, the incidence of cetacean strandings, on the rise in recent years, is thought to be associated with an intense but as yet unidentified stressor. As such, the capacity of the immune system to respond to cues from the CNS may prove critical not only for understanding the reasons for such strandings, but also in the rehabilitation of stranded animals. Consequent to certain behavioral circumstances, individual subdominant male wolves may be ostracized from the pack to spend the rest of their lives as solitary animals. Whether this naturally occurring, but forced, isolation of a social animal is accompanied by immunomodulation, and whether the resulting solitary life is then shortened by opportunistic pathogens, is an intriguing scenario that begs to be written. In the section of this chapter dealing with amphibians, we discussed possible connections among environmental contaminants, neuroendocrine function, immunosuppression, and susceptibility to disease-causing pathogens. In a related vein, Herbst and Klein (1995) have speculated that the relationship between environmental contaminants and the increasing prevalence of green turtle fibropapillomatosis (an epizootic, apparently virally induced, disease) may involve immunosuppression associated with environmental contaminants (e.g., endocrine disruptors) or “stressors” such as altered temperature or salinity. Aluru et al. (2004) found that in the Artic char, PCB disrupts the HPI axis. The immunological consequences of the associated downregulation of brain glucocorticoids warrants exploration in normal and stressed fish. Similar considerations apply to other taxa, including mammals (Lawrence and Kim, 2000). These
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speculations certainly provide an ecologically valid rationale for better understanding the mechanisms underlying neural-immune system cross-talk in endothermic as well as ectothermic species. As a rhetorical aside, if fish, amphibians, and reptiles are indeed the pre-verbal canaries in the coal mine, are their warnings being taken seriously enough, in a non-anthropocentric sense, by Homo sapiens occupying leadership positions? • It is well known that environmental temperature modulates immunity in ectothermic vertebrates (Clem et al., 1984, 1991; Józkowicz and Plytycz, 1998). Indeed, a recent study (Alcorn et al., 2002) points out that sockeye salmon reared throughout their entire lifecycle at either 8° or 12°C are quite different creatures in terms of both their innate and adaptive immune response capacity. Scientists are in fundamental agreement about the phenomenon of global warming; ecological consequences are already being noted. What is not known, however, is whether the immune system (e.g., via cytokine mediators) plays a role in the neuroendocrine processes that eventuate in a change in a fish’s or frog’s core temperature and thereby affect its defense systems. If it does, it puts an interesting psychoneuroimmunological twist with an evolutionary spin on one of the world’s most serious and thorny problems. As a final note, captivity can impose potentially stressful environmental conditions (e.g., crowding, isolation, handling, and possible disturbances in circadian activity) (Dulak et al., 1989; Worley and Jurd, 1979) that are immunomodulatory in laboratory animals (Moynihan et al., 1994). Given that zoological specimens are similarly affected by these and other stressors, an understanding of the physiological impact of these conditions would be of benefit to both the animals bred and/or maintained in captivity and to the institutions involved in maintaining them. Minimizing events detrimental to the animals’ selfmaintenance of health status would also minimize the necessity for intervention by animal handlers. As more species from more taxa are being represented primarily by captive specimens, ensuring the individuals’ continued health becomes more critical; one way to ensure this may be to better understand how to enable the organism to maintain its own defense against pathogens.
Acknowledgments This manuscript was written with the support of grants from the NSF (IRCEB-00138) and the NIH (R24-AI-059830).
References Ackerman, K. D., Bellinger, D. L., Felten, S. Y., and Felten, D. L. (1991a). Ontogeny and senescence of noradrenergic innervation of the rodent thymus and spleen. In R. Ader, D. L. Felten, and N. Cohen (Eds.), Psychoneuroimmunology (2nd ed., pp. 72–125). San Diego: Academic Press. Ackerman, K. D., Madden, K .S., Livnat, S., Felten, S. Y., and Felten, D. L. (1991b). Neonatal sympathetic denervation alters the development of in vitro spleen cell proliferation and differentiation. Brain Behav. Immun., 5, 235–261. Ader, R. (Ed.) (1981). Psychoneuroimmunology. San Diego: Academic Press. Ader, R., Felten, D. L., and Cohen, N. (Eds.) (1991). Psychoneuroimmunology (2nd ed.). San Diego: Academic Press. Ader, R., Felten, D. L., and Cohen, N. (Eds.) (2001). Psychoneuroimmunology (3rd ed.). San Diego: Academic Press. Afifi, A., Mohamed, E. R., and el Ridi, R. (1993). Seasonal conditions determine the manner of skin rejection in reptiles. J. Exp. Zool., 265, 459–468. Ainsworth, A. J., Dexiang, C., and Waterstat, P. R. (1991). Changes in peripheral blood leukocyte percentages and function of neutrophils in stressed channel catfish. J. Aquat. Anim. Health, 3, 41–47. Alcorn, S. W., Murra, A. L., and Pascho, R. J. (2002). Effects of rearing temperature on immune functions in sockeye salmon (Oncorhynchus nerka). Fish Shell. Immunol., 12, 303–334. Alford, P. B., III, Tomasso J. R., Bodine, A. B., and Kendall, C. (1994). Apoptotic death of peripheral leukocytes in channel catfish: effect of confinement-induced stress. J. Aquat. Anim. Health, 5, 64–69. Ali, R. A., Qureshi, M. A., and McCorkle, F. M. (1994). Profile of chicken macrophage functions after exposure to catecholamines in vitro. Immunopharm. Immunotox., 16, 611–625. Aluru, N., Jorgensen, E. H., Maule, A. G., and Vijayan, M. M. (2004). PCB disruption of the hypothalamus-pituitary-interrenal axis involves brain glucocorticoid receptor downregulation in anadromous Arctic char. Am. J. Physiol. Regul. Integr. Comp. Physiol., 287, 787–793. Anderson, D. P., Roberson, B. S., and Dixon, O. W. (1982). Immunosuppression induced by a corticosteroid or an alkylating agent in rainbow trout (Salmo gairdneri) administered a Yersinia ruckeri bacteria. Dev. Comp. Immunol., 2, 197–204. Angelidis, P., Baudin-Laurencin, F., and Youinou, P. (1987). Stress in rainbow trout, Salmo gairdneri: effect upon phagocyte chemiluminescence, circulating leukocytes and susceptibility to Aeromonas salmonicida. J. Fish Biol., 31(suppl. A), 113–122. Arnold, R. E., and Rice, C. D. (1997). Channel catfish lymphocytes secrete ACTH in response to corticotropic releasing factor. Dev. Comp. Immunol., 21, 152. Bachman, S. E., and Mashaly, M. M. (1986). Relationship between circulating thyroid hormones and humoral immunity in immature male chickens. Dev. Comp. Immunol., 10, 395–403. Bachman, S. E., and Mashaly, M. M. (1987). Relationship between circulating thyroid hormones and cell-mediated immunity in immature male chickens. Dev. Comp. Immunol., 11, 203–213. Balm, P. H. M. (1997). Immuno-endocrine interactions. In G. K. Iwama, A. D. Pickering, J. P. Sumpter, and C. B. Schreck (Eds.), Fish stress and health in aquaculture. (195–221) Cambridge University Press. Balm, P. H. M., Pepels, P., van Lieshout, E., and Wendelaar Bonga, S. E. (1993). Neuroimmunological regulation of α-MSH release in tilapia (Oreochromis mossambicus). Fish Physiol. Biochem., 11, 125–130.
28
Prologue
Balm, P. H. M., and Pottinger, T. G. (1993). Acclimation of rainbow trout (Onchorhynchus mykiss) to low environmental pH does not involve an activation of the pituitary-interrenal axis, but evokes adjustments in branchial ultrastructure. Can. J. Fish Aquat. Sci., 50, 2532–2541. Balm, P. H. M, van Lieshout, M. E., Lokate, J., and Wendelaar Bonga, S. E. W. (1995), Bacterial lipopolysaccharide (LPS) and interleukin-1 (IL-1) exert multiple physiological effects in the tilapia Oreochromis mossambicus (Teleostei). J. Compar. Physiol. B, 165, 85–92. Barker, K. S., Davis, A. T., and Rollins-Smith, L. A. (1997). Spontaneous and corticosteroid-induced apoptosis of lymphocyte populations in metamorphosing frogs. Brain Behav. Immun., 11, 119–131. Barni, S., Nano, R., and Vignola, C. (1993). Changes in the hemopoietic activity and characteristics of circulating blood cells in Triturus carnifex and Triturus alpestris during the winter period. Comp. Haematol. Internat., 3, 159–163. Barton, B. A., and Iwama, G. K. (1991). Physiological changes in fish from stress in aquaculture with emphasis on the response and effects of corticosteroids. Annu. Rev. Fish Dis., 1, 3–26. Bayne, D. J., and Levy, S. (1991). Modulation of the oxidative burst in trout myeloid cells by adrenocorticotropic hormone and catecholamines: mechanisms of action. J. Leuk. Biol., 50, 554–560. Bellinger, D. L., Lorton, D., Romano, T. A., Olschowka, J. A., Felten, S. Y., and Felten, D. L. (1990). Neuropeptide innervation of lymphoid organs. Ann. N. Y. Acad. Sci., 594, 17–33. Benson, B. J., and Hadley, M. E. (1969). In vitro characterization of adrenergic receptors controlling skin gland secretion in two anurans Rana pipiens and Xenopus laevis. Comp. Biochem. Physiol., 30, 857–864. Berger, S., Martin L. B. II, Wilkeski, M., Romero, L. M., Kalko, E. K. V., Vitousek, M., and Rodl, T. (2005). Corticosterone suppresses immune activity in territorial Galápagos marine iguanas during reproduction. Horm. Behav., 47, 419–429. Besedovsky, H. O., del Rey, A., Sorkin, E., Da Prada, M., and Keller, H. H. (1979). Immunoregulation mediated by the sympathetic nervous system. Cell. Immunol., 48, 346–355. Betoulle, S., Troutaud, D., Khan, N., and Deschaux, P. (1995). Antibody response, cortisolemia and prolactinemia in rainbow trouts Com. Rend. L’Acad. Sciences—Serie Iii, Sciences de la Vie., 318, 677–681. Bigaj, J., and Plytycz, B. (1984). Endogenous rhythm in the thymus gland of Rana temporaria (Morphological study). Thymus, 6, 369–373. Binuramesh, C., Prabakaran, M., Steinhagenb, D. M., and Dinakaran, R. M. (2006). Effect of sex ratio on the immune system of Oreochromis mossambicus (Peters). Brain Behav. Immun. 20, 300–308. Bird, S., Zou, J., Savan, R., Kono, T., Sakai, M., Woo, J., and Secombes, C. (2005), Characterisation and expression analysis of an interleukin 6 homologue in the Japanese pufferfish, Fugu rubripes. Dev. Comp. Immunol., 29, 775–789. Blalock, J. E. (2005). The immune system as the sixth sense. J. Intern. Med., 257, 126–138. Bly, J. E., Miller, N. W., and Clem, L. W. (1990). A monoclonal antibody specific for neutrophilic granulocytes in normal and stressed channel catfish. Dev. Comp. Immunol., 14, 211– 221. Brezinschek, H. P., Fässler, R., Klocker, H., Krömer, G., Sgonc, R., Dietrich, H., Jakober, R., and Wick, G. (1990). Analysis of the immune-endocrine feedback loop in the avian system and its alteration in chickens with spontaneous autoimmune thyroiditis. Eur. J. Immunol., 20, 2155–2159.
Brown-Borg, H. M., and Edens, F. W. (1992). In vivo neurotoxin administration alters immune response in chickens (Gallus domesticus). Comp. Biochem. Physiol., 102C, 177–183. Briggs, K. T., Yoshida, S. H., and Gershwin, M. E. (1996). The influence of petrochemicals and stress on the immune system of seabirds. Reg. Tox. Pharm., 23, 145–155. Brunetti, L., Preziosi, P., Ragazzon, E., and Vacca, M. (1994). Effects of lipopolysaccharide on hypothalamic-pituitary-adrenal axis in vitro. Life Sci., 54, 165–171. Buckbinder, L., and Brown, D. D. (1993). Expression of Xenopus laevis prolactin and thyrotropin genes during metamorphosis. Proc. Natl. Acad. Sci. USA, 90, 3820–3824. Caldwell, C. A., Kattesh, H. G., and Strange, R. J. (1991). Distribution of cortisol among its free and protein-bound fractions in rainbow trout (Oncorhynchus mykiss): evidence of control by sexual maturation. Comp. Biochem. Physiol., 99A, 593–595. Callahan, T. A., Moynihan, J. A., and Piekut, D. T. (1998). Consequences of peripheral sympathetic denervation following injection of 6-hydroxydopamine: activation of the central nervous system. Brain Behav. Immun., 12, 230–241. Capen, C. C. (1994). Mechanisms of chemical injury of thyroid gland. Prog. Clinc. Res., 387, 173–191. Carey, C., Cohen, N., and Rollins-Smith, L. A. (1999). Amphibian declines: An immunological perspective. Dev. Comp. Immunol., 23, 459–472. Carlson, R. E., Anderson, D. P., and Bodammer, J. E. (1993). In vivo cortisol administration suppresses the in vitro primary immune response of winter flounder lymphocytes. Fish Shell. Immunol., 3, 299–312. Casto, J. M., Nolan, V., and Ketterson, E. D. (2001). Steroid hormones and immune function: experimental studies in wild and captive dark-eyed juncos (Junco hyemalis). Amer. Natur., 157, 408–420. Chadzinska, M., Józefowski, S., Bigaj, J., and Plytycz, B. (1997). Morphine modulation of thioglycollate-elicited peritoneal inflammation in the goldfish, Carassius auratus. Archiv. Immunol. Therap. Exp., 45, 321–327. Chadzinska, M., Kolaczkowska, Seljelid, R., and Plytycz, B. (1999). Morphine modulation of peritoneal inflammation in Atlantic salmon and CB6 mice. J. Leuk. Biol., 65, 590–596. Chadzinska, M., and Plytycz B. (2004). Differential migratory properties of mouse, fish, and frog leukocytes treated with agonists of opioid receptors. Dev. Comp. Immunol., 28, 949–958. Chandratilleke, D., Hala. K., and March, J. A. (1996). Effects of in vivo thyroid hormone treatment on the expression of interleukin2 receptors on avian splenocytes. Int. J. Immunopharm., 18, 203–210. Chelmicka-Schorr, E., Kwasniewski, M. N., and Czlonkowska, A. (1992a). Sympathetic nervous system modulates macrophage function. Int. J. Immunopharm., 14, 841–846. Chelmicka-Schorr, E., Kwasniewski, M. N., and Wollmann, R. L. (1992b). Sympathectomy augments adoptively transferred experimental allergic encephalomyelitis. J. Neuroimmunol., 37, 99–103. Cheng, W., Chieu, H. T., Tsai, C. H., and Chen, J. C. (2005), Effects of dopamine on the immunity of the white shrimp Litopenaeus vannamei. Fish Shell. Immunol., 19, 375–385. Chinchar, V. G., Wang, J., Murti, G., Carey, C., and Rollins-Smith, L. A. (2001), Inactivation of frog virus 3 and channel catfish virus by esculentin-2P and ranatuerin-2P, two antimicrobial peptides isolated from frog skin. Virology, 288, 351–357. Christin, M. S., Menard, L., Gendron, A. D., Ruby, S., Cyr, D., Marcogliese, D. J., Rollins-Smith, L., and Fournier, M. (2004). Effects of agricultural pesticides on the immune system of Xenopus laevis and Rana pipiens. Aquat. Toxicol., 67, 33–43.
Prologue Chrousos, G. P., and Gold, P. W. (1992). The concepts of stress and stress disorders. Overview of physical and behavioral homeostasis. JAMA, 267, 1244–1252. Ciriaco, E., Ricci, A., Bronzetti, E., Mammola, C. L., Germanà, G, and Vega, J. A. (1995). Age-related changes of the noradrenergic and acetylcholinesterase reactive nerve fibres innervating the pigeon bursa of Fabricius. Ann. Anat., 177, 237–242. Clatworthy, A. L. (1998), Neural-immune interactions—an evolutionary perspective. Neuroimmunomodulation, 5, 136–142. Clatworthy, A. L., and Grose, E. (1999). Immune-mediated alterations in nociceptive sensory function in Alyssa. J. Exp. Biol., 202, 623–630. Clem, L., Faulmann, E., Miller, N., and Ellsaesser, E. (1984). Temperature-mediated processes in teleost immunity: differential effects of and in vitro and in vivo temperatures on mitogenic responses of channel catfish lymphocytes. Dev. Comp. Immunol., 8, 313–322. Clem, L. W., Miller, N. W., and Bly, J. E. (1991). Evolution of lymphocyte subpopulations, their interactions and temperature sensitivities. In G. W. Warr and N. Cohen (Eds.), Phylogenesis of immune functions (pp. 191–213). Boca Raton, FL: CRC Press. Clemons, G., and Nicoll, C. S. (1977). Development and preliminary application of a homologous radioimmunoassay for bullfrog prolactin. Gen. Comp. Endocrinol., 32, 531–535. Clothier, R. H., and Balls, M. (1985). Structural changes in the thymus glands of Xenopus laevis during development. In M. Balls and M. Bownes (Eds.), Metamorphosis (pp. 332–359). Oxford: Clarendon Press. Clothier, R. H., Ruben, L. N., Balls, M., and Greenhalgh, L. (1991). Morphological and immunological changes in the spleen of Xenopus laevis during metamorphosis. Res. Immunol., 142, 360–362. Clothier, R. H., Ruben, L. N., Johnson, R. O., Parker, K., Sovak, M., Greenhalgh, L., Ooi, E., and Balls, M. (1992). Neuroendocrine regulation of immunity: the effects of noradrenaline in Xenopus laevis, the South African clawed toad. Int. J. Neurosci., 62, 123–140. Clothier, R. H., Ruben, L. N., Tran, K., and Balls, M. (1989). Catecholamine regulation of and by immunity in Xenopus laevis. Dev. Comp. Immunol., 13, 441–442. Cohen, N. (2006). The uses and abuses of psychoneuroimmunology: a global overview. Brain Behav. Immun., 20, 99–112. Cohen, N., and Kinney, K. (2001). Exploring the phylogenetic history of neural-immune system interactions. In R. Ader, D. L. Felten, and N. Cohen (Eds.), Psychoneuroimmunology (3rd ed., pp. 3–25). San Diego: Academic Press. Cohen, N., and Koniski, A. (1994). Axolotl immunology: lymphocytes, cytokines, and alloincompatibility reactions. Axolotl Newsletter, 23, 24–33. Collins, J. P., Cohen, N., Davidson, E. W., Longcore, J. E., and Storfer, A. (2005). Meeting the challenge of amphibian declines with an interdisciplinary research program. In M. Lannoo (Ed.), Declining amphibians: a United States’ response to the global problem (pp. 23– 27). Berkeley: University of California Press. Cooper, E. L., Leung, M. K., Suzuki, M. M., Vicki, K., Cadet, P., and Stefano, G. B. (1993). An enkephalin-like molecule in earthworm coelomic fluid modifies leukocyte behavior. Dev. Com. Immunol., 17, 201–209. Cooper, E. L., Wright, R. K., Klempau, A. E., and Smith, C. T. (1992). Hibernation alters the frog’s immune system. Cryobiology, 29, 616–631. Cordier, A. (1969). L’innervation de la bourse de Fabricius durant l’embryogenèse et de la vie adulte. Acta Anat., 73, 38–47.
29
Cserr, H. F., and Bundgaard, M. (1984). Blood-brain interfaces in vertebrates: a comparative approach. Am. J. Physiol., 146, 277–288. Cunnick, J. E., Kojic, L. D., and Hughes, R. A. (1994). Stress-induced changes in immune function are associated with increased production of an interleukin-1–like factor in young domestic fowl. Brain, Behav. Immun., 8, 123–136. Dalmo, R. A., Ingebrigtsen, K., and Bfgwald, J. (1997). Nonspecific defence mechanisms in fish, with particular reference to the reticuloendothelial system (RES). J. Fish Dis., 20, 241–273. Danzer, M., Schicho, R., Lippe, I. T., and Holzer, P. (2002). Interleukin-1β–induced sensitization of vagal afferent pathways to intragastric acid challenge: a novel experimental model of functional dyspepsia? Gastroenterology, 122, A34. Das, P. C., McElroy, W. K., and Cooper, R. L. (2000). Differential modulation of catecholamines by chlorotriazine herbicides in pheochromocytoma (PC12) cells in vitro. Toxicol. Sci., 56, 324–331. de la Torre, J. C. (1980). Standardization of the sucrose-potassium phosphate-glyoxylic acid histofluorescence method for tissue monoamines. Neurosci. Lett., 17, 339–340. Demers, N. E., and Bayne, C. J. (1997). The immediate effects of stress on hormones and plasma lysozyme in rainbow trout. Dev. Comp. Immunol., 21, 363–373. Denno, K. M., McCorkle, F. M., and Taylor, R. L. (1994). Catecholamines modulate chicken immunoglobulin-M and immunoglobulin-G plaque-forming cells. Poultry Sci., 73, 1858–1866. Deviche, P., and Cortez, L. (2005). Androgen control of immunocompetence in the male house finch, Carpodacus mexicanus (Muller). J. Exp. Biol., 208, 1287–1295. DiMarzo, S. J., and Cohen, N. (1982). Immunogenetic aspects of in vitro tolerance induction during the ontogeny of Xenopus laevis. Immunogenetics, 16, 103–116. Dockray, G. J., and Hopkins, C. R. (1975). Caerulein secretion by dermal glands in Xenopus laevis. J. Cell Biol., 64, 724–733. Donaldson, E. M. (1981). The pituitary-interrenal axis as an indicator of stress in fish. In A. D. Pickering (Ed.), Stress in fish (pp. 11–47). London: Academic Press. Donaldson, E. M., and Fagerlund, U. H. M. (1972). Corticosteroid dynamics in Pacific salmon. Gen. Comp. Endocrinol., Suppl. 3, 254–265. Dorshkind, K., and Horseman, N. D. (2000). The roles of prolactin, growth hormone, insulin-like growth factor-I, and thyroid hormones in lymphocyte development and function: insights from genetic models of hormone and hormone receptor deficiency. Endocr. Rev., 21, 292–312. Ducoroy, P., Lesourd, M., Padros, M. R., and Tournefier, A. (1999). Natural and induced apoptosis during lymphocyte development in the axolotl. Dev. Comp. Immunol., 23, 241–252. Duffy, D. L., Bentley, G. E., Drazen, D. L., and Ball, G. F. (2001). Effects of testosterone on cell-mediate and humoral immunity in non-breeding adult European starlings. Behav. Ecol., 11, 654–662. Dulak, J., and Plytycz, B. (1989). The effect of laboratory environment on the morphology of the spleen and the thymus in the yellow-bellied toad, Bombina variegata (L.). Dev. Comp. Immunol., 13, 49–55. Du Pasquier, L., and Flajnik, M. (1999). Origin and evolution of the vertebrate immune system. In W. E. Paul (Ed.), Fundamental immunology (4th ed., pp. 605–649). New York: Raven Press. Dureus, P., Louis, D., Grant, A. V., Bilfinger, T. V., and Stefano, G. B. (1993). Neuropeptide Y inhibits human and invertebrate
30
Prologue
immunocyte chemotaxis, chemokinesis, and spontaneous activation. Cell. Mol. Neurobiol., 13, 541–546. Eitan, S., Zisling, R., Cohen, A., Belkin, M., and Hirschberg, D. L. (1992). Identification of an interleukin 2–like substance as a factor cytotoxic to oligodendrocytes and associated with central nervous system. Proc. Natl. Acad. Sci. USA, 89, 5424–5428. el-Far, A. A., Mashaly, M. M., and Kamar, G. A. (1994). Bursectomy and in vitro response of adrenal gland to adrenocorticotropic hormone and testis to human chorionic gonadotropin in immature male chickens. Poultry Sci., 73, 113–117. Ellis, A. E. (1981). Stress and the modulation of defence mechanisms in fish. In A. D. Pickering (Ed.), Stress in fish (pp. 147–169). London: Academic Press. Ellsaesser, C. F., and Clem, L. W. (1987). Cortisol-induced hematologic and immunologic changes in channel catfish (Ictalurus punctatus). Comp. Biochem. Physiol., 87A, 405–408. Ellsaesser, C. F., and Clem, L. W. (1994). Functionally distinct high and low molecular weight species of channel catfish and mouse IL-1. Cytokine, 5, 10–20. Engelsma, M. Y., Huising, M. O., van Muiswinkel, W. B., Flik, G., Kwang, J., Savelkoul, H. F., and Verburg-van Kemenade, B. M. (2002). Neuroendocrine-immune interactions in fish: a role for interleukin-1. Vet. Immunol. Immunopathol., 87, 467–479. Espelid, S., Lokken, G. B., Steiro, K., and Bogwald, J. (1996). Effects of cortisol and stress on the immune system in Atlantic salmon (Salmo salar L.). Fish Shell. Immunol., 6, 95–110. Faisal, M., Chiappelli, F., Ahmed, I, Cooper, E. L., and Weiner, H. (1989). Social confrontation “stress” in aggressive fish is associated with an endogenous opioid-mediated suppression of proliferative response to mitogens and nonspecific cytotoxicity. Brain Behav. Immun., 3, 223–233. Fedorka, K. M., Zuk, M., and Mousseau, T. A. (2004). Immune suppression and the cost of reproduction in the ground cricket, Allonemobius socius. Evolution, 58, 2478–2485. Felten, D. L., Ackerman, K. D., Wiegand, S. J., and Felten, S. Y. (1987). Noradrenergic sympathetic innervation of the spleen: I. Nerve fibers associate with lymphocytes and macrophages in specific compartments of the splenic white pulp. J. Neurosci. Res., 18, 28–36. Felten, D. L., Cohen, N. Ader, R., Felten, S. Y., Carlson, S. L, and Roszman. T. L. (1991). Central neural circuits involved in neuralimmune interactions. In R. Ader, D. L. Felten, and N. Cohen (Eds.), Psychoneuroimmunology (2nd ed., pp. 3–25). San Diego: Academic Press. Felten, D. L., Jozefowicz, R. D., and Netter, F. H. (2003). Netter’s atlas of neuroscience. ICON Learning Systems, 310. Felten, S. Y., Felten, D. L., Bellinger, D. L., and Olschowka, J. A. (1992). Noradrenergic and peptidergic innervation of lymphoid organs. Cell. Immunol., 52, 25–48. Felten, S. Y., and Olschowka, J. A. (1987). Noradrenergic sympathetic innervation of the spleen: II. Tyrosine hydroxylase (TH)-positive nerve terminals form synaptic-like contacts on lymphocytes in the splenic white pulp. J. Neurosci. Res., 18, 37–48. Ferriere, F., Khan, N. A., Troutaud, D., and Deschaux, P. (1996). Serotonin modulation of lymphocyte proliferation via 5-HT1A receptors in rainbow trout (Oncorhynchus mykiss). Dev. Comp. Immunol., 20, 273–283. Flajnik, M. F., and Du Pasquier, L. (1988). MHC class I antigens as surface markers of adult erythrocytes during the metamorphosis of Xenopus. Dev. Biol., 128, 198–206. Fleshner, M., Goehler, L. E., Hermann, J., Relton, J. K., Maier, S. F., and Watkins, L. R. (1995). Interleukin-1β induced corticosterone
elevation and hypothalamic NE depletion is vagally mediated. Brain Res. Bull., 37, 605–610. Flik, G., and Perry, S. F. (1989). Cortisol stimulates whole body calcium uptake and the branchial calcium pump in fresh water rainbow trout. J. of Endocrinol., 120, 75–82. Flory, C. M. (1989). Autonomic innervation of the spleen of the coho salmon, Oncorhynchus kisutch: a histochemical demonstration and preliminary assessment of its immunoregulatory role. Brain Behav. Immun., 3, 331–334. Flory, C. M. (1990). Phylogeny of neuroimmunoregulation: effects of adrenergic and cholinergic agents on the in vitro antibody response of the rainbow trout, Onchorynchus mykiss. Dev. Comp. Immunol., 14, 283–294. Flory, C. M., and Bayne C. J. (1991). The influence of adrenergic and cholinergic agents on the chemiluminescent and mitogenic responses of leukocytes from the rainbow trout, Oncorhynchus mykiss. Dev. Comp. Immunol., 15, 135–142. Fostad I., and Karter A. J. (1992). Parasites bright males, and the immunocompetence handicap. Am. Natur., 139, 603–622. Fowles, J. R., Fairbrother, A., Fix, M., Schiller, S., and Kerkvliet, N. I. (1993), Glucocorticoid effects on natural and humoral immunity in mallards. Dev. Comp. Immunol., 17, 165–177. Franchini, A., Kletsas, D., and Ottaviani, E. (1996a). Immunocytochemical evidence of PDGF- and TGF-beta–like molecules in invertebrate and vertebrate immunocytes: an evolutionary approach. Histochem. J., 28, 599–605. Franchini, A., Miyan, J. A., and Ottaviani, E. (1996b). Induction of ACTH- and TNF-alpha–like molecules in the hemocytes of Calliphora vomitoria (Insecta, Diptera). Tissue Cell, 28, 587–592. Franchini A., and Ottaviani E. (1994). Modification induced by ACTH in hemocyte cytoskeleton of the freshwater snail Viviparus ater (Gastropoda, Prosobranchia). Eur. J. Histochem., 38, 145–150. Franchini, A., Ottaviani, E., and Franceschi, C. (1995). Presence of immunoreactive pro-opiomelanocortin-derived peptides and cytokines in the thymus of an anuran amphibian (Rana esculenta). Tissue Cell, 27, 263–267. Galton, V. A., and St. Germain, D. (1985). Putative nuclear triiodothyronine receptors in tadpole erythrocytes during metamorphic climax. Endocrinology, 116, 99–104. Gantress, J., Maniero, G. D., Cohen, N., and Robert, J. (2003). Development and characterization of a model system to study amphibian immune responses to iridoviruses. Virology, 311, 254–262. Garrido, E., Gomariz, R. P., Leceta, J., and Zapata, A. (1987). Effects of dexamethasone on the lymphoid organs of Rana perezi. Dev. Comp. Immunol., 11, 375–384. Garrido, E., Gomariz, R. P., Leceta, J., and Zapata, A. (1989). Differential sensitivity to the dexamethasone treatment of the lymphoid organs of Rana perezi in two different seasons. Dev. Comp. Immunol., 13, 57–64. Gehad, A. E., Lillehoj, H. S., Hendricks, G. L., and Mashaly, M. M. (2002). Initiation of humoral immunity. I. The role of cytokines and hormones in the initiation of humoral immunity using Tdependent and T-independent antigens. Dev. Comp. Immunol., 26, 751–759. Gendron, A. D., Bishop, C. A., Fortin, R., and Hontela, A. (1997). In vivo testing of the functional integrity of the corticosteroneproducing axis in mudpuppy (Amphibia) exposed to chlorinated hydrocarbons in the wild. Environ. Toxicol. Chem., 16, 1694–1706. Genedani, S., Bernardi, M., Ottaviani, E., Franceschi, C., Leung, M. K., and Stefano, G. B. (1994). Differential modulation of inver-
Prologue tebrate hemocyte motility by CRF, ACTH, and its fragments. Peptides, 15, 203–206. Ghoneum, M., Faisal, M., Peters, G., Ahmed, I., I., and Cooper, E. L. (1988). Suppression of natural cytotoxic cell activity by social aggressiveness in tilapia. Dev. Comp. Immunol., 12, 595–602. Gilbertson, M. K., Haffner, G. D., Drouillard, K. G., Albert, A., and Dixon, B. (2003). Immunosuppression in the northern leopard frog (Rana pipiens) induced by pesticide exposure. Environ. Toxicol. Chem., 22, 101–110. Glaser, R., Kiecolt-Glaser, J. K., Marucha, P. T., MacCallum, R. C., Laskowski, B. F., and Malarkey, W. B. (1999). Stress-related changes in proinflammatory cytokine production in wounds. Arch. Gen. Psych., 56, 450–456. Glick, B. (1984). Interrelation of the avian immune and neuroendocrine systems. J. Exp. Zool., 232, 671–682. Goehler, L. E., Relton, J. K., Dripss, D., Kiechle, R., Tartaglia, N., Maier, S. F., and Watkins, L. R. (1997). Vagal paraganglia bind biotinylated interleukin-1 receptor antagonist: a possible mechanism for immune-to-brain communication. Brain Res. Bull., 43, 357–364. Goldman, J. M., Stoker, T. E., Cooper, R. L., McElroy, W. K., and Hein, J. F. (1994). Blockage of ovulation in the rat by the fungicide sodium N-methyldithiocarbamate: relationship between effects on the luteinizing hormone surge and alterations in hypothalamic catecholamines. Neurotoxicol. Teratol., 16, 257–268. Gray, R. S., McCorkle, F. M., Denno, K. M., and Taylor, R. L. (1991). Modulation of chicken plaque-forming cells by serotinin and dopamine. Poultry Sci., 70, 1521–1526. Green (Donnelly), N., and Cohen, N. (1977). The effect of temperature on serum complement levels in the leopard frog, Rana pipiens. Dev. Comp. Immunol., 1, 59–64. Grimm, A. S. (1985). Suppression by cortisol of the mitogen-induced proliferation of peripheral blood leucocytes from plaice, Pleuronectes platessa L. In M. J. Manning and M. F. Tatner (Eds.), Fish immunology (pp. 263–271). London: Academic Press. Gruca, P., Chadzinska, M., Lackowska, B., and Plytycz, B. (1996). Analysis of peritoneal and head kidney phagocytes during thioglycollate-elicited peritoneal inflammation in the goldfish, Carassius auratus. Folia Biol. (Krakow), 44, 137–142. Guellati, M., Ramade, F., Le Nguyen, D., Ibos, F., and Bayle, J. D. (1991). Effects of early embryonic bursectomy and opotherapic substitution on the functional development of the adrenocorticotropic axis. J. Dev. Physiol., 15, 357–363. Haberfeld, M., Johnson, R. O., Ruben, L. N., Clothier, R. H., and Shiigi, S. (1999). Adrenergic modulation of apoptosis in splenocytes of Xenopus laevis in vitro: leucocytes of rainbow trout (Oncorhynchus mykiss) in vitro. Fish Shell. Immunol., 8, 631–638. Haddad, E. E., and Mashaly, M. M. (1990). Effect of thyrotropinreleasing hormone, triiodothyronine, and chicken growth hormone on plasma concentrations of thyroxine, triiodothyronine, growth hormone, and growth of lymphoid organs and leukocyte populations in immature male chickens. Poultry Sci., 69, 1094–1102. Haddad, E. E., and Mashaly, M. M. (1991). Chicken growth hormone, triiodothyronine and thyrotropin releasing hormone modulation of the levels of chicken natural cell-mediated cytotoxicity. Dev. Comp. Immunol., 15, 65–71. Hahn, U. K., Fryer, S. E., and Bayne, C. J. (1996). An invertebrate (molluscan) plasma protein that binds to vertebrate immunoglobulins and its potential for yielding false-positives in antibodybased detection systems. Dev. Comp. Immunol., 20, 39–50. Hanley, K. A., and Stamps, J. A. (2002). Does corticosterone mediate bidirectional interactions between social behavior and blood
31
parasites in the juvenile black iguana, Ctenosaura similes? Animal Behav., 63, 311–322. Hareramadas, B., Rembhotkar, G. W., and Rai, U. (2004). Glucocorticoid-induced thymocyte apoptosis in wall lizard, Hemidactylus flaviviridis. Gen. Compar. Endocrinol., 135, 293–299. Harris, J., and Bird, D. J. (1998). Alpha-melanocyte stimulating hormone (a-MSH) and melanin-concentrating hormone (MCH) stimulate phagocytosis by head kidney leucocytes of rainbow trout (Oncorhynchus mykiss) in vitro. Fish Shell. Immunol., 8, 631–638. Hasselquist, D., Marsh, J. A., Sherman, P. W., and Wingfield J. C. (1999). Is avian humoral immunocompetence suppressed by testosterone? Behav. Ecol. Sociobiol., 45, 167–175. Haynes, L., and Cohen, N. (1991). Phylogenetic conservation of cytokines. In G. W. Warr and N. Cohen (Eds.), Phylogenesis of immune function (pp. 241–268). Boca Raton, FL: CRC Press. Heckert, R. A., Estevez, I., Russek-Cohen, E., and Petit-Riley, R. (2002). Effects of density and perch availability on the immune status of broilers. Poultry Sci., 81, 451–457. Hendricks, G. L., and Mashaly, M. M. (1998). Effects of corticotropin releasing factor on the production of adrenocorticotropic hormone by leukocyte populations. Brit. Poultry Sci., 9, 123–127. Hendricks, G. L., Siegel, H. S., and Mashaly, M. M. (1991). Ovine corticotropin-releasing factor increases endocrine and immunologic activity of avian leukocytes in vitro. Proceedings of the Society for Experimental Biology and Medicine, 196, 390–395. Herbst, L. H., and Klein, P. A. (1995). Green turtle fibropapillomatosis: challenges to assessing the role of environmental cofactors. Environ. Health Perspect., 103, 27–30. Hickman, C. P., Roberts, L. S., and Larson, A. (1993). Integrated principles of zoology (9th ed., pp. 603–657). St. Louis: Mosby-Year Book. Hodgson, R., Clothier, R. H., and Balls, M. (1979). Adrenoreceptors, cyclic nucleotides, and the regulation of spleen cell antigen binding in urodele and anuran amphibians. Eur. J. Immunol., 9, 289–293. Hodgson, R., Clothier, R. H., Ruben, L. N., and Balls, M. (1978). The effects of α and β adrenergic agents on spleen cell antigen binding in four amphibian species. Eur. J. Immunol., 8, 348–351. Hoebe, K., Janssen, E., and Beutler, B. (2004). The interface between innate and adaptive immunity. Nat. Immunol., 10, 971–974. Hoffmann, J. A., Kafatos, F. C., Janeway, C. A., and Ezekowitz, R. A. (1999). Phylogenetic perspectives in innate immunity. Science, 284, 1313–1318. Holland, J. W., Pottinger, T. G., and Secombes, C. J. (2002). Recombinant interleukin-1 beta activates the hypothalamic-pituitaryinterrenal axis in rainbow trout, Oncorhynchus mykiss. J. Endocrinol., 175, 261–267. Holmes, C., and Balls, M. (1978). In vitro studies on the control of myoepithelial cell contractions in the granular glands of Xenopus laevis skin. Gen. Comp. Endocrinol., 36, 255–263. Holzapfel, R. A. (1937). The cyclic character of hibernation in frogs. Quart. Rev. Biol., 12, 64–83. Hopkins, W. A., Mendonca, M. T., and Congdon, J. D. (1999). Responsiveness of the hypothalamo-pituitary-interrenal axis in an amphibian (Bufo terrestris) exposed to coal combustion wastes. Comp. Biochem. Physiol. C, 122, 191–196. Horton, J. D., Horton, T. L., Ritchie, P., and Varley, C. A. (1992). Skin xenograft rejection in Xenopus: immunohistology and effect of thymectomy. Transplantation, 53, 473–476. Horton, T., Stewart, R., Cohen, N., Rau, L., Ritchie, P., Watson, M., Robert, J., and Horton, J. D. (2003). Ontogeny of Xenopus NK cells
32
Prologue
in the absence of MHC class I antigens. Dev. Comp. Immunol., 27, 15–26. Hsu, E., and Du Pasquier, L. (1984). Ontogeny of the immune system in Xenopus: II. Antibody repertoire differences between larvae and adults. Differentiation, 28, 116–122. Hu, Y., Dietrich, H., Herold, M., Heinrich, P. C., and Wick, G. (1993). Disturbed immuno-endocrine communication via the hypothalamo-pituitary-adrenal axis in autoimmune disease. Internat. Arch. Allergy, 102, 232–241. Hughes, T., Chin, R., Smith, E., Leung, M., and Stefano, G. B. (1991a). Similarities of signal systems in vertebrates and invertebrates: detection, action, and interactions of immunoreactive monokines in the mussel, Mytilus edulis. Adv. Neuroimmunol., 6, 59–69. Hughes, T., Smith, E., Barnett, J., Charles, R., and Stefano, G. B. (1991b). Lipopolysaccharide and opioids activate distinct populations of Mytilus edulis immunocytes. Cell Tissue Res., 264, 317–320. Hughes, T., Smith, E., Barnett, J., Charles, R., and Stefano, G. B. (1991c). LPS stimulated invertebrate hemocytes: a role for immunoreactive TNF and IL-1. Dev. Comp. Immunol., 15, 117–122. Hughes, T., Smith, E., Chin, R., Cadet, P., Sinisterra, J., Leung, M., Shipp, M., Scharrer, B., and Stefano, G. B. (1990). Interaction of immunoactive monokines (interleukin 1 and tumor necrosis factor) in the bivalve mollusc Mytilus edulis. Proc. Natl. Acad. Sci. USA, 87, 4426–4429. Huising, M. O., Metz, J. R., de Mazon, A. F., Verburg-van Kemenade, B. M., and Flik, G. (2005). Regulation of the stress response in early vertebrates. Ann. N. Y. Acad. Sci., 1040, 345–347. Huising, M. O., Metz, J. R., van Schooten, C., Taverne-Thiele, A. J., Hermsen, T., Verburg-van Kemenade, B. M., and Flik, G. (2004). Structural characterisation of a cyprinid (Cyprinus carpio L.) CRH, CRH-BP and CRH-R1, and the role of these proteins in the acute stress response. J. Mol. Endocrinol., 32, 627–648. Hussein, M., Badir, N., Zada, S., el Ridi, R., and Zahran, W. (1984). Effect of seasonal changes on immune system of the toad, Bufo regularis. Bull. Fac. Sci. Cairo Univ., 52, 181–192. Iger, Y., Balm, P. H. M., Jenner, H. A., and Wendelaar Bonga, S. E. (1995). Cortisol induces stress-related changes in the skin of rainbow trout (Oncorhynchus mykiss). Gen. Comp. Endocrinol., 97, 188–189. Inue, K. (1971). Innervation of the bursa of Fabricius in the domestic fowl. Acta Anatomica, Nippon., 46, 403–415. Jaudet, G., and Hatey, J. (1984). Variations in aldosterone and corticosterone plasma levels during metamorphosis in Xenopus laevis tadpoles. Gen. Comp. Endocrinol., 56, 59–65. Jelaso, A. M., Acevedo, S., Dang, T., Lepere, A., and Ide, C. F. (1998). Interleukin-1β and its type 1 receptor are expressed in developing neural circuits in the frog, Xenopus laevis. J. Compl. Neurol., 394, 242–251. Jolivet-Jaudet, G., and Leloup-Hatey, J. (1986). Corticosteroid binding in plasma of Xenopus laevis: modifications during metamorphosis and growth. J. Steroid Biochem., 25, 343–350. Józefowski, S., Gruca, P., Józkowicz, A., and Plytycz, B. (1995). Direct detection and modulatory effects of adrenergic and cholinergic receptors on goldfish leukocytes. J. Marine Biotech., 3, 171–173. Józefowski, S., Józefowski, A., Antkiewicz-Michaluk, L., Plytycz, B., and Seljelid, R. (1996). Neurotransmitter and opioid modulation of the amphibian transplantation immunity. In J. S. Stolen, T. C. Fletcher, C. J. Bayne, C. J. Secombes, J. Zelikoff, T. Twerdok, and D. P. Anderson (Eds.), Modulators of immune responses: the evolutionary trail (pp. 281–290). Fair Haven, NJ: SOS Publications. Józefowski, S. J., and Plytycz, B. (1997). Characterization of opiate binding sites on the goldfish (Carassius auratus L.) pronephric leukocytes. Polish J. Pharmacol., 49, 229–237.
Józefowski, S. J., and Plytycz, B. (1998). Characterization of βadrenergic receptors in fish and amphibian lymphoid organs. Dev. Comp. Immunol., 22, 587–604. Józkowicz, A. (1995). Mechanisms involved in allograft and xenograft rejection in anuran amphibians. Herpetopathology, Proceedings of the Fifth International Collequim on the Pathology of Reptiles and Amphibians, 155–160. Józkowicz, A., and Plytycz B. (1998). Temperature but not season affects the transplantation immunity of anuran amphibians. J. Exp. Zool., 281, 58–64. Kaatari, S. L., and Tripp, R. A. (1987). Cellular mechanism of glucocorticoid suppression in salmon. J. Fish. Biol., 31(suppl A), 129–132. Kamilaris, T. C., Debold, C. R., Johnson, E. Q., Mamalaki, E., Listwak, S. J., Calogero, A. E., Kalogeras, K. T., Gold, P. W., and Orth, D. N. (1991). Effects of short and long duration hypothyroidism and hyperthyroidism on the plasma adrenocorticotropin and corticosterone responses to ovine corticotropin-releasing hormone in rats. Endocrinology, 128, 2567–2576. Kelly, K. W., Arkins, S., and Li, Y. M. (1992). Growth hormone, prolactin and insulin-like growth factor; new jobs for old players. Brain Behav. Immun., 6, 317–326. Kikuyama, S., Kawamura, K., Tanaka, S., and Yamamoto (1993). Aspects of amphibian metamorphosis: hormonal control. Internat. Rev. Cytol., 145, 105–148. Kikuyama, S., Suzuki, M. R., and Iwamuro, S. (1986). Elevation of plasma aldosterone levels in tadpoles at metamorphic climax. Gen. Comp. Endocrinol., 63, 186–190. Kinney, K. S. (1995). Sympathetic innervation of the amphibian spleen: structural and functional studies. Doctoral dissertation, University of Rochester, Rochester, NY. Kinney, K. S. (1996). Sympathetic innervation of the amphibian spleen: developmental studies in Xenopus laevis. Dev. Comp. Immunol., 20, 51–59. Kinney, K. S., and Cohen, N. (2005). Increased splenocyte mitogenesis following sympathetic denervation in Xenopus laevis. Dev. Comp. Immunol., 29, 287–294. Kinney, K. S., Cohen, N., and Felten, S. Y. (1994a). Chemical sympathectomy with 6-OHDA does not alter skin graft rejection in the frog, Xenopus laevis. Abst. Soc. Neurosci., 20, 105. Kinney, K. S., Cohen, N., and Felten, S. Y. (1994b). Noradrenergic and peptidergic innervation of the amphibian spleen: comparative studies. Dev. Comp. Immunol., 18, 511–521. Kinney, K. S., Felten, S. Y., Horton, J. D., and Cohen, N. (1993). Chemical sympathectomy and thymectomy effects on splenic anatomy in the frog Xenopus laevis. Abst. Soc. Neurosci, Part 2, 945. Klesius, P., Johnson, W., and Kramer, T. (1977). Delayed wattle reaction as a measure of cell-mediated immunity in the chicken. Poultry Sci., 56, 249–256. Kletsas, D., Sassi, D., Franchini, A., and Ottaviani, E. (1998). PDGF and TGF-beta induce cell shape changes in invertebrate immunocytes via specific cell surface receptors. Eur. J. Cell Biol., 75, 362–366. Kluger, M. J., Ringler, D. H., and Anver, M. R. (1975). Fever and survival. Science, 188, 166–168. Kolaczkowska, E., Menaszek, E., Seljelid, R., and Plytycz, B. (2000). Experimental peritonitis in anuran amphibians is not suppressed by morphine treatment. Pol. J. Pharmacol., 52, 323–326. Kono, T., Zou, J., Bird, S., Savan, R., Sakai, M., and Secombes, C. J. (2006). Identification and expression analysis of lymphotoxinbeta like homologues in rainbow trout Oncorhynchus mykiss. Mol. Immunol. 43, 1390–1401.
Prologue Krueger, J. M., and Majde, J. A. (1994). Microbial products and cytokines in sleep and fever regulation. Crit. Rev. Immunol., 14, 355–379. Kruszewska, B., Felten, D. L., and Moynihan, J. A. (1998). Changes in cytokine production and proliferation following chemical sympathectomy: interactions with glucocorticoids. Brain Behav. Immun., 12, 181–200. Kruszewska, B., Felten, S. Y., and Moynihan, J. A. (1995). Alterations in cytokine and antibody production following chemical sympathectomy in two strains of mice. J. Immunol., 155, 4613–4620. Lacoste, A., Malham, S. K., Cueff, A., and Poulet, S. A. (2001). Noradrenaline modulates oyster hemocyte phagocytosis via a β-adrenergic receptor-cAMP signaling pathway. Gen. Comp. Endocrinol., 122, 252–259. Laing, K. J., Zou, J. J., Wang, T., Bols, N., Hirono, I., Aoki, T., and Secombes, C. J. (2002). Identification and analysis of an interleukin 8–like molecule in rainbow trout Oncorhynchus mykiss. Dev. Comp. Immunol., 26, 433–444. Lamers, A. E., Flik, G., and Wendelaar Bonga, S. E. (1994). A specific role for TRH in release of diacetyl α-MSH in tilapia stressed by acid water. Am. J. Physiology, 267 (Reg. Integrat. Comp. Physiol.) 36, 1302–1308. Lawrence, D. A., and Kim, D. (2000). Central/peripheral nervous system and immune responses. Toxicology, 142, 189–201. Lefcort, H., and Eiger, S. M. (1993). Antipredatory behaviour of feverish tadpoles: implications for pathogen transmission. Behaviour, 126, 13–27. Leloup, J., and Buscaglia, M. (1977). La triiodothyronine, hormone de la métamorphose des Amphibiens. Compte Rendu L’Acad. Sci., Paris, 84D, 2261–2263. Le Morvan-Rocher, C., Troutead, D., and Deschaux, P. (1995). Effects of temperature on carp leukocyte mitogen-induced proliferation and nonspecific cytotoxic activity. Dev. Comp. Immunol., 19, 87–95. Li, J.-T., Lee, P.-P., Chen, O.-C., Cheng, W., and Kuo, C.-M. (2005). Dopamine depresses the immune ability and increases susceptibility to Lactococcus garvieae in the freshwater giant prawn, Macrobrachium rosenbergii. Fish Shell. Immunol., 19, 269–280. Lindstrom, K. M., Krakower, D., Lundstrom, J. O., and Silverin, B. (2001). The effects of testosterone on a viral infection in greenfinches (Carduelis chloris): an experimental test of the immunocompetence-handicap hypothesis. Proc. R. Soc. Lond. B, 268, 207–211. Livnat, S., Felten, S. Y., Carlson, S. L., Bellinger, D. L., and Felten, D. L. (1985). Involvement of peripheral and central catecholamine systems in neural-immune interactions. J. Neuroimmunol., 10, 5–30. Lukas, N. W., McCorkle, F. M., and Taylor, R. L. Jr. (1987). Monoamines suppress the phytohemagglutinin wattle response in chickens. Dev. Comp. Immunol., 11, 759–768. Madden, K. S., Ackerman, K. D., Livnat, S., Felten, S. Y., and Felten, D. L. (1989a). Patterns of noradrenergic innervation of lymphoid organs and immunological consequences of denervation. In E. Goetzl and N. H. Spector (Eds.), Neuroimmune networks: physiology and diseases (pp. 1–8). New York: Alan R. Liss. Madden, K. S., Ackerman, K. D., Livnat, S., Felten, S. Y., and Felten, D. L. (1993). Neonatal sympathetic denervation alters developments of natural killer (NK) cell activity in F344 rats. Brain Behav. Immun., 7, 344–351. Madden, K. S., and Felten, D. L. (1995). Experimental basis for neural-immune interactions. Physiol. Rev., 75, 77–105. Madden, K. S., Felten, S. Y., Felten, D. L., Sundaresan, P. R., and Livnat, S. (1989b). Sympathetic neural modulation of the immune system: I. Depression of T-cell immunity in vivo and in vitro
33
following chemical sympathectomy. Brain Behav. Immun., 3, 72–89. Maéno, M., and Katagiri, C. (1984). Elicitation of weak immune response in larval and adult Xenopus laevis by allografted pituitary. Transplantation, 38, 251–255. Maier, S. F. (2003). Bi-directional immune-brain communication: implications for understanding stress, pain, and cognition. Brain Behav. Immun., 17, 69–85. Maier, S. F., and Watkins, L. R. (1998). Cytokines for psychologists: implications of bi-directional immune to brain communication for understanding behaviour, mood, and cognition. Psycholog. Rev., 105, 83–107. Malagoli, D., Franchini, A., and Ottaviani, E. (2000). Synergistic role of cAMP and IP(3) in corticotropin-releasing hormone-induced cell shape changes in invertebrate immunocytes. Peptides, 21, 175–182. Malham, S., Lacoste, A., Gélébart, F., Cueff, A., and Poulet, S. A. (2003). Evidence for a direct link between stress and immunity in the mollusk Haliotis tuberculata. J. Exp. Zool., 295A, 136–144. Malham, S. K., Lacoste, A., Gélébart, F., Cueff, A., and Poulet, S. A. (2002). A first insight into stress-induced neuroendocrine and immune changes in the octopus Eledone cirrhosa. Resources vivantes aquatiques, 15, 187–192. Mallon, E. B., Brockmann, A., and Schmid-Hempel, P. (2003). Immune function inhibits memory formation in the honeybee Apis melifera. Proc. Roy. Soc., B, 270, 2471–2473. Maniero, G. D., and Carey, C. (1997). Changes in selected aspects of immune function in the leopard frog, Rana pipiens, associated with exposure to cold. J. Comp. Physiol.—Biochem., Systemic, Environ. Physiol., 167, 256–263. Manning, M. J. (1991). Histological organization of the spleen: implications for immune functions in amphibians. Res. Immunol., 142, 355–359. Manning, M. J., Donnelly, N., and Cohen, N. (1976). Thymus dependent and thymus independent components of the amphibian immune system. In R. K. Wright and E. L. Cooper (Eds.), Phylogeny of thymus and bone marrow-bursa cells (pp. 123–132). Amsterdam: North Holland Publishing. Manning, M. J., and Horton, J. D. (1982). RES structure and function of the Amphibia. In N. Cohen and M. M. Sigel (Eds.), The reticuloendothelial system: phylogeny and ontogeny (pp. 423–459). New York: Plenum Press. Marc, A. M., Quentel, C., Severe, A., Le Bail, P. Y., and Boeuf, G. (1995). Changes in some endocrinological and non-specific immunological parameters during seawater exposure in the brown trout. J. Fish Biol., 46, 1065–1081. Marsh, J. A., Gause, W. C., Sandhu, S., and Scanes, C. G. (1984). Enhanced growth and immune development in dwarf chickens treated with mammalian growth hormone and thyroxine. Proc. Soc. Exp. Biol., 175, 351–360. Marsh, J. A., and Scanes, C. G. (1994). Neuroendocrine-immune interactions. Poultry Sci., 73, 1049–1061. Marx, M., Ruben, L. N., Nobis, C., and Duffy, D. (1987). Compromised T-cell regulatory functions during anuran metamorphosis: the role of corticosteroids. Prog. Clin. Biol. Res., 233, 129–140. Mashaly, M. M. (1984). Effect of caponization on cell-mediated immunity of immature cockerels. Poultry Sci., 63, 369–372. Mashaly, M. M., Trout, J. M., and Hendricks, G. L. 3rd (1993). The endocrine function of the immune cells in the initiation of humoral immunity. Poultry Sci., 72, 1289–1293. Mashaly, M. M., Trout, J. M., Hendricks, G. L. 3rd, al-Dokhi, L. M., and Gehad, A. (1998). The role of neuroendocrine immune interactions in the initiation of humoral immunity in chickens. Domestic Animal Endocrinology, 15, 409–422.
34
Prologue
Maule, A. G., and Schreck, C. B. (1990a). Changes in the numbers of leukocytes in immune organs of juvenile coho salmon after acute stress or cortisol treatment. J. Aquat. Anim. Health, 2, 298–304. Maule, A. G., and Schreck, C .B. (1990b). Glucocorticoid receptors in leukocytes and gill of juvenile coho salmon (Oncorhynchus kisutch). Gen. Comp. Endocrinol, 77, 448–455. Maule, A. G., and Schreck, C. B. (1991). Stress and cortisol treatment changes affinity and number of glucocorticoid receptors in leukocytes and gill of coho salmon. Gen. Comp. Endocrinol., 84, 83–93. Maule, A. G., Schreck, C., and Kaattari, S. (1987). Changes in the immune system of coho salmon (Oncorhynchus kisutch) during the parr-to-smolt transformation and after implantation of cortisol. Can. J. Fish Aquat. Sci., 44, 161–166. Maule, A. G., Tripp, R., Kaattari, S., and Schreck, C. (1989). Stress alters immune function and disease resistance in Chinook salmon (Oncorhynchus tshawytscha). J. Endocrinol., 120, 135–142. McCorkle, R. M., Lukas, N., and Taylor, R. L. Jr. (1986). Effect of serotonin on plaque-forming cells in chickens. Poultry Sci., 65, 90. McCorkle, R. M., and Taylor, R. L. (1994). Continuous administration of dopamine alters cellular-immunity in chickens. Comp. Biochem. Physiol. C-Pharmacol. Toxicol. Endocrinol., 94, 511–514. McCorkle, R. M., Taylor, R. L., Denno, K. M., and Jabe, H. M. (1990). Monoamines alter in vitro migration of chicken leukocytes. Dev. Comp. Immunol., 14, 85–93. Medzhitov, R., and Janeway, C. A. Jr. (1998). An ancient system of host defense. Curr. Opin. Immunol., 10, 12–15. Meyniel, J. P., Khan, N. A., Ferriere, F., and Deschaux, P. (1997). Identification of lymphocyte 5-HT3 receptor subtype and its implication in fish T-cell proliferation. Immunol. Lett., 55, 151–160. Milton, N. G., Self, S. H., and Hillhouse, E. W. (1993). Effects of pyrogenic immunomodulators on the release of corticotropicfactor 41 and prostaglandin E2 from the intact rat hypothalamus in vitro. Br. J. Pharmacol., 109, 88–93. Miodonski, A. J., Bigai, J., Mika, J., and Plytycz, B. (1996). Seasonspecific thymic architecture in the frog Rana temporaria: SEM studies. Dev. Comp. Immunol., 20, 129–137. Möck, A., and Peters, G. (1990). Lysozyme activity in rainbow trout, Oncorhynchus mykiss (Waldbaum), stressed by handling, transport and water pollution. J. Fish. Biol., 37, 873–885. Moret, Y., and Schmid-Hempel, P. (2000). Survival for immunity: the price of immune system activation for bumble-bee workers. Science, 290, 1166–1168. Morici, L. A., Elsey, R. M., and Lance, V. A. (1997). Effects of longterm corticosterone implants on growth and immune function in juvenile alligators, Alligator mississipiensis. J. Exp. Zool., 279, 156–162. Mosconi, G., Yamamoto, K., Carnevali, O., Nabissi, M., PolzonettiMagni, A., and Kikuyama, S. (1994). Seasonal changes in plasma growth hormone and prolactin concentrations of the frog Rana esculenta. Gen. Comp. Endocrinol., 93, 380–387. Motobu, M., El-Abasy, M., Na, K. J., Vainio, O., Toivanen, P., and Hirota Y. (2003). Effects of 6-hydroxydopamine on the development of the immune system in chickens. J. Med. Vet. Med. Sci., 65, 35–42. Moynihan, J. A., Ader, R., and Cohen, N. (1994). Stress and immunity: animal studies. In B. Scharrer, E. M. Smith, and G. B. Stefano (Eds.), Neuropeptides and immunoregulation (pp. 120–138). Berlin: Springer-Verlag. Muñoz, F. J., and De La Fuente, M. (2001). The effect of the seasonal cycle on the splenic leukocyte functions in the turtle Mauremys caspica. Physiol. Biochem. Zool., 75, 660–667.
Muñoz, F. J., and De La Fuente, M. (2004). Seasonal changes in lymphoid distribution of the turtle Mauremys caspica. Copeia, 4, 178–183. Nagata, S. (1988). T cell-specific antigen in Xenopus identified with a mouse monoclonal antibody: biochemical characterization and species distribution. Zool. Sci., 5, 77–83. Nakanishi, T. (1986). Seasonal changes in the humoral immune response and the lymphoid tissues of the marine teleost, Sebastiscus marmoratus. Vet. Immunol. Immunopath., 12, 336–342. Narnaware, Y. K., and Baker, B. I. (1996). Evidence that cortisol may protect against the immediate effects of stress on circulating leukocytes in the trout. Gen. Comp. Endocrinol., 103, 359–366. Narnaware, Y. K., Baker, B. I., and Tomlinson, M. G. (1994). The effect of various stresses, corticosteroids and adrenergic agents on phagocytosis in the rainbow trout Oncorhynchus mykiss. Fish Physiol. Biochem., 13, 31–40. Ndoye, A., Troutaud, D., Rougier, F., and Dechaux, P. (1991). Neuroimmunology in fish. Adv. Neuroimmunol., 1, 242–251. Nevid, N. J., and Meier, A. H. (1993). A day-night rhythm of immune activity during scale allograft rejection in the gulf killifish, Fundulus grandis. Dev. Comp. Immunol., 17, 221–228. Nevid, N. J., and Meier, A. H. (1994). Nonphotic stimuli alter a daynight rhythm of allograft rejection in gulf killifish. Dev. Comp. Immunol., 18, 495–509. Nevid, N. J., and Meier, A. H. (1995a). Time-dependent effects of daily thermoperiods, feeding, and disturbances on scale allograft survival in the gulf killifish, Fundulus grandis. J. Exp. Zool., 272, 46–53. Nevid, N. J., and Meier, A. H. (1995b). Timed daily administration of hormones and antagonists of neuroendocrine receptors alter day-night rhythms of allograft rejection in the gulf killifish, Fundulus grandis. Gen. Comp. Endocrinol., 97, 327–339. Nieuwkoop, P. D., and Faber, J. (1967). Normal table of Xenopus laevis (Daudin). Amsterdam: North-Holland Publishing. Nilsson, S. (1978). Sympathetic innervation of the spleen of the cane toad, Bufo marinus. Comp. Biochem. Physiol., 61C, 133–139. Nilsson, S., and Grove, D. J. (1974). Adrenergic and cholinergic innervation of the cod Gadus morhua. Eur. J. Pharmacol., 28, 135–143. Olivereau, M., and Olivereau, J. M. (1991). Responses of brain and pituitary immunoreactive corticotropin-releasing factor in surgically interrenalectomised eels: immunocytochemical study. Gen. Comp. Endocrinol., 81, 295–303. Olsen, Y. A., Reitan, L. J., and Roed, K. H. (1993). Gill Na+, K+-ATPase activity, plasma cortisol level, and non-specific immune response in Atlantic salmon (Salmo salar) during parr-smolt transformation. J. Fish. Biol., 43, 559–573. Oppliger, A., Clobert, J., Lecomte, J., Lorenzon, P., Boudjemadi, K., and John-Adler, H. B. (1998). Environmental stress increases the prevalence and intensity of blood parasite infection in the common lizard Lacerta vivipara. Ecol. Lett, 1, 129–138. Oppliger, A., Giorgi, M. S., Conelli, A., Nembrini, M., and JohnAlder, H. B. (2004). Effect of testosterone on immunocompetence, parasite load, and metabolism in the common wall lizard (Podarcis muralis). Can. J. Zool., 82, 1713–1719. Ottaviani, E. (1992). Immunorecognition in the gastropod molluscs with particular reference to the freshwater snail Planorbarius corneus (L.) (Gastropoda, Pulmonata). Bull. Zool., 59, 129–139. Ottaviani, E., Capriglione, and Franceschi, D. (1995a). Invertebrate and vertebrate immune cells express pro-opiomelanocortin (POMC) mRNA. Brain Behav. Immun., 9, 1–8. Ottaviani, E., Caselgrandi, E., Fontanili, P., and Franceschi, C. (1992a). Evolution, immune responses and stress: studies on molluscan cells. Acta Biol. Hung., 43, 293–298.
Prologue Ottaviani, E., Caselgrandi, E., and Franceschi, C. (1995b). Cytokines and evolution: in vitro effects of IL-1 alpha, IL-1 beta, TNF-alpha and TNF-beta on an ancestral type of stress response. Biochem. Biophys. Res. Communic., 207, 288–292. Ottaviani, E., Caselgrandi, E., Franchini, A., and Franceschi, C. (1993a). CRF provokes the release of norepinephrine by hemocytes of Viviparus ater (Gastropoda, prosobranchia): further evidence in favour of the evolutionary hypothesis of the “mobile immune-brain.” Biochem. Biophys. Res. Communic., 193, 446–452. Ottaviani, E., Caselgrandi, E., and Kletsas, D. (1997). Effect of PDGF and TGF-beta on the release of biogenic amines from invertebrate immunocytes and their possible role in the stress response. FEBS Lett., 403, 236–238. Ottaviani, E., Caselgrandi, E., Petraglia, F., and Franceschi, C. (1992b). Stress response in the freshwater snail Planorbarius corneus (L.) (Gastropoda, Pulmonata): interaction between CRF, ACTH, and biogenic amines. Gen. Comp. Endocrinol., 87, 354–360. Ottaviani, E., and Cossarizza, A. (1990). Immunocytochemical evidence of vertebrate bioactive peptide-like molecules in the immuno cell types of the freshwater snail Planorbarius corneus (L.) (Gastropoda, Pulmonata). FEBS Lett., 267, 250–252. Ottaviani, E., Cossarizza, A., Ortolani, C., Monti, D., and Franceschi, C. (1991). ACTH-like molecules in gastropod molluscs: a possible role in ancestral immune response and stress. Proc. Roy. Soc. Lond., 245, 215–218. Ottaviani, E., and Franceschi, C. (1996). The neuroimmunology of stress from invertebrates to man. Progr. Neurobiol., 48, 421–440, [published erratum appears in Progress Neurobiol., (1996), 49, 285]. Ottaviani, E., and Franceschi, C. (1997). The invertebrate phagocytic immunocyte: clues to a common evolution of immune and neuroendocrine systems. Immunol. Today, 18, 169–174. Ottaviani, E., and Franceschi, C. (1998). A new theory on the common evolutionary origin of natural immunity, inflammation and stress response: the invertebrate phagocytic immunocyte as an eyewitness. Domes. Anim. Endocrinol., 15, 291–296. Ottaviani, E., and Franchini, A. (1995). Immune and neuroendocrine responses in molluscs: the role of cytokines. Acta Biol. Hungar., 46, 341–349. Ottaviani, E., Franchini, A., Caselgrandi, E., Cossarizza, A., and Franceschi, C. (1994). Relationship between corticotropinreleasing factor and interleukin-2: evolutionary evidence. FEBS Lett., 351, 19–21. Ottaviani, E., Franchini, A., Cassenelli, S., and Genedani, S. (1995c). Cytokines and invertebrate immune responses. Biol. Cell, 85, 87–91. Ottaviani, E., Franchini, A., Cossarizza, A., and Franceschi, C. (1992c). ACTH-like molecules in lymphocytes. A study in different vertebrate classes. Neuropeptides, 23, 215–219. Ottaviani, E., Franchini, A., and Franceschi, C. (1995d). Evidence for the presence of immunoreactive POMC-derived peptides and cytokines in the thymus of the goldfish (Carassius c. auratus), Histochem. J., 27, 597–601. Ottaviani, E., Franchini, A., and Franceschi, C. (1998a). Presence of immunoreactive corticotropin-releasing hormone and cortisol molecules in invertebrate haemocytes and lower and higher vertebrate thymus. Histochem. J., 30, 61–67. Ottaviani, E., Franchini, A., and Hanukoglu, I. (1998b). In situ localization of ACTH receptor-like mRNA in molluscan and human immunocytes. Cell. Mol. Life Sci., 54, 139–142. Ottaviani, E., Franchini, A., Sonetti, D., and Stefano, G. B. (1995d). Antagonizing effect of morphine on the mobility and phagocytic activity of invertebrate immunocytes. Eur. J. Pharmacolo., 276, 35–39.
35
Ottaviani, E., Petraglia, F., Montagnani, G., Cossarizza, A., Monti, D., and Franceschi, C. (1990). Presence of ACTH and betaendorphin immunoreactive molecules in the freshwater snail Planorbarius corneus (L.) (Gastropoda, Pulmonata) and their possible role in phagocytosis. Regul. Pept., 27, 1–9. Ottaviani, E., Trevisan, P., and Pederzoli, A. (1992d). Immunocytochemical evidence for ACTH- and beta-endorphin–like molecules in phagocytic blood cells of urodelean amphibians. Peptides, 13, 227–231. Owen-Ashley, N. T., Hasselquist, D., and Wingfield, J. C. (2004). Androgens and the immunocompetence handicap hypothesis: unraveling direct and indirect pathways of immunosuppression in song sparrows. Amer. Natur., 164, 490–505. Parsadaniantz, S. M., Batsche, E., Gegout-Pottie, P., Terlain, B., Gillet, P., Netter, P., and Kerdelhue, B. (1997). Effects of continuous infusion of interleukin 1 beta on corticotropin-releasing hormone (CRH), CRH receptors, proopiomelanocortin gene expression, and secretion of corticotropin, beta-endorphin and corticosterone. Neuroendocrinology, 65, 53–63. Parsadaniantz, S. M., Levin, N., Lenoir, V., Roberts, J. L., and Kerdelhue, B. (1994). Human interleukin 1 beta: corticotropin releasing factor and ACTH release and gene expression in the male rat: in vivo and in vitro studies. J. Neurosci. Res., 15(37), 675–682. Peters A. (2000). Testosterone treatment is immunosuppressive in superb fairy-wrens, yet free-living males with high testosterone are more immunocompetent. Proc. Roy. Soc. Lond. B, 267, 883–889. Peters, G., Nüβgen, A., Raabe, A., and Möck, A. (1991). Social stress induces structural and functional alterations of phagocytes in rainbow trout (Oncorhynchus mykiss). Fish Shell. Immunol., 1, 17–31. Pickering, A. D. (Ed.) (1981). Stress and fish. New York: Academic Press. Pintea, V., Constantinescu, B. M., and Radu, C. (1967). Vascular and nerve supply of bursa of Fabricius in hen. Acta Vet. Acad. Scient. Hung., 17, 263–268. Pleguezuelos, O., Zou, J., Cunningham, C., and Secombes, C. J. (2000). Cloning, sequencing, and analysis of expression of a second IL-1beta gene in rainbow trout (Oncorhynchus mykiss). Immunogenetics, 51, 1002–1011. Plytycz, B., Chadzinska, M., Józkowicz, A., Gruca, P., and Seljelid, R. (1996). Stressing fish before sacrificing affects the in vitro cell activity. Cent. Eur. J. Immunol., 21, 278–280. Plytycz, B., Dulak, J., Bigai, J., and Janeczko, K. (1991). Annual cycle of mitotic activity in the thymus of the frog, Rana temporaria. Herpetopathologia, 2, 23–29. Plytycz, B., and Józkowicz, A. (1994). Differential effects of temperature on macrophages of ectothermic vertebrates. J. Leuk. Biol., 56, 729–731. Plytycz, B., Kusina, E., and Józkowicz, A. (1993). Effects of hydrocortisone on the lymphoid organs of Rana temporaria. Folia Histochem. Cytobiol., 31, 129–132. Plytycz, B., and Seljelid, R. (1996). Nervous-endocrine-immune interactions in vertebrates. In J. S. Stolen, T. C. Fletcher, C. J. Bayne, C. J. Secombes, J. Zelikoff, J. T. Twerdok, and D. P. Anderson (Eds.), Modulators of immune responses: the evolutionary trail (pp. 119–130). Fair Haven, NJ: SOS Publications. Plytycz, B., and Seljelid, R. (1997). Rhythms of immunity. Archiv. Immunol. Therap. Exp., 45, 157–162. Plytycz, B., and Szarski, H. (1987). Inguinal bodies of some Bufo species. J. Herpetol., 21, 236–237. Pulsford, A. L., Crampe, M., Langston, A., and Glynn, P. J. (1995). Modulatory effects of disease, stress, copper, TBT and vitamin E
36
Prologue
on the immune system of flatfish. Fish Shell. Immunol., 5, 631–643. Pulsford, A. L., Lemaire-Gony, S., Tomlinson, M., Collingwood, N., and Glynn P. J. (1994). Effects of acute stress on the immune system of the dab, Limanda limanda. Comp. Biochem. Physiol., 109C, 129–139. Riddell, C. E., and Mallon, E. B. (2006). Insect psychoneuroimmunology: immune response reduces learning in protein starved bumblebees (Bombus terrestris). Brain Behav. Imm., 20, 135–138. Robert, J., Morales, H., Buck, W., Cohen, N., Marr, S., and Gantress, J. (2005). Histopathogenesis and immune responses to FV3 virus infection in Xenopus. Virology, 332, 667–675. Roi, B., and Rai, U. (2004). Dual mode of catecholamine action on splenic macrophage phagocytosis in wall lizard, Hemidactylus flaviviridis, Gen. Comp. Endocrinol., 136, 180–191. Rollins, L. A., and Cohen, N. (1980). On tadpoles, transplantation, and tolerance. In J. D. Horton (Ed.), Development and differentiation of vertebrate lymphocytes (pp. 203–214). Amsterdam: Elsevier/ North-Holland. Rollins-Smith, L. A. (1998). Metamorphosis and the amphibian immune system. Immunol. Rev., 166, 221–230. Rollins-Smith, L. A., Barker, K. S., and Davis, A. T. (1997a). Involvement of glucocorticoids in the reorganization of the amphibian immune system at metamorphosis. Dev. Immunol., 5, 145–152. Rollins-Smith, L. A., and Blair, P. J. (1990a). Contribution of ventral blood island mesoderm to hematopoiesis in postmetamorphic and metamorphosis-inhibited Xenopus laevis. Dev. Biol., 142, 178–183. Rollins-Smith, L. A., and Blair, P. J. (1990b). Expression of class II major histocompatibility complex antigens on adult T-cells in Xenopus is metamorphosis dependent. Dev. Immunol., 1, 97–104. Rollins-Smith, L. A., and Blair, P. J. (1993). The effects of corticosteroid hormones and thyroid hormones on lymphocyte viability and proliferation during development and metamorphosis of Xenopus laevis. Differentiation, 54, 155–160. Rollins-Smith, L. A., Blair, P. J., and Davis, A. T. (1992). Thymus ontogeny in frogs T-cell renewal at metamorphosis. Dev. Immunol., 2, 207–213. Rollins-Smith, L. A., and Cohen, N. (1982). Self-pituitary grafts are not rejected by frogs deprived of their pituitary anlagen as embryos. Nature, 299, 820–821. Rollins-Smith, L. A., and Cohen, N. (1995). Metamorphosis: an immunologically unique period in the life of the frog. In L. J. Gilbert, B. G. Atkinson, and J. Tata (Eds.), Metamorphosis/postembryonic reprogramming of gene expression in amphibian and insect cells (pp. 626–646). London: Academic Press. Rollins-Smith, L. A., and Cohen, N. (2003). Hormones and the immune system of amphibians. In H. Heatwole (Ed.), Amphibian biology: Vol. 6. Endocrinology (pp. 2377–2391). Chipping Norton, Australia: Surrey Beatty and Sons. Rollins-Smith, L. A., and Conlon, J. M. (2005). Antimicrobial peptide defenses against chytridiomycosis, an emerging infectious disease of amphibian populations. Dev. Comp. Immunol., 29, 589–598. Rollins-Smith, L. A., Davis, A. T., and Blair, L. A. (1993). Effects of thyroid hormone deprivation on immunity in postmetamorphic frogs. Dev. Comp. Immunol., 17, 157–164. Rollins-Smith, L. A., Davis, A. T., and Reinert, L .K. (1997b). Effects of early hypophysectomy on development of the immune system of Xenopus laevis. Dev. Comp. Immunol., 21, 152. Rollins-Smith, L. A., Davis, A. T., and Reinert, L .K. (2000). Pituitary involvement in T cell renewal during development and metamorphosis of Xenopus laevis. Brain Behav. Immun., 14, 185–197.
Rollins-Smith, L. A., Doersam, J. K., Longcore, J. E., Taylorm S. K., Shamblin, J. C., Carey, C., and Zasloff, M. A. (2002). Antimicrobial peptide defenses against pathogens associated with global amphibian declines. Dev. Comp. Immunol., 26, 63–72. Rollins-Smith, L. A., Flajnik, M. F., Blair, P., Davis, A. T., and Green, W. F. (1994). Expression of MHC class I antigens during ontogeny in Xenopus is metamorphosis-independent. Dev. Comp. Immunol., 18, S95. Rollins-Smith, L. A., Parsons, S., and Cohen, N. (1984). During frog ontogeny, PHA and Con A responsiveness of splenocytes precedes that of thymocytes. Immunology, 52, 491–500. Romano, T. A., Felten, S. Y., Olschowka, J. A., and Felten, D. L. (1994). Noradrenergic and peptidergic innervation of lymphoid organs in the beluga, Delphinapterus leucas: an anatomical link between the nervous and immune systems. J. Morphol., 221, 243–259. Rome, A., and Bell, C. (1983). Catecholamines in the sympathetic nervous system of the domestic fowl. J. Autonom. Nerv. Syst., 8, 331–342. Romero, L. M., Ramenofsky, M., and Wingfield, J. C. (1997). Season and migration alters the corticosterone response to capture and handling in an Arctic migrant, the white-crowned sparrow (Zonotrichia leucophrys gambelii). Comp. Biochem. Physiol. Part C Pharmacol., Toxicol./Endocrinol., 116, 171–177. Romero, L. M., and Wingfield, J. C. (1999). Alterations in hypothalamic-pituitary-adrenal function associated with captivity in Gambel’s white-crowned sparrows (Zonotrichia leucophrys gambelii). Comp. Biochem. Physiol. Part B, Biochem. Mol. Biol., 122, 13–20. Rotllant, J., Ruane, N. M., Caballero, M. J., Montero, D., and Tort, L. (2003). Response to confinement in sea bass (Dicentrarchus labrax) is characterised by an increased biosynthetic capacity of interrenal tissue with no effect on ACTH sensitivity. Comp. Biochem. Physiol. A Mol. Integr. Physiol., 136, 613–620. Ruben, L. N., Proochista, A., Johnson, R. O., Buchholz, D. R., Clothier, R. H., and Shiigi, S. (1994). Apoptosis in the thymus of developing Xenopus laevis. Dev. Comp. Immunol., 18, 343–352. Saad, A.-H.(1993). Neuroimmunomodulation in reptiles. I. Pathways of neuro-immune interactions in the turtle, Mauremys caspica. J. Egypt. Gen. Soc/ Zool., 10, 81–103. Saad, A.-H., Abdel Khalek, N., and El Ridi, R. (1990). Blood testosterone level: a season-dependent factor regulating immune reactivity in lizards. Immunobiology, 180, 184–190. Saad, A.-H, and Ali, W. (1992). Seasonal changes in humoral immunity and blood thyroxine levels in the toad, Bufo regularis. Zool. Sci., 9, 349–356. Saad A.-H., and Bassiouni, W. M. (1991). Ultrastructural changes in the thymus of the lizard, Chalcides ocellatus following hydrocortisone treatment. J. Egypt. Gen. Soc. Zool., 6, 39–44. Saad, A.-H., and El Ridi, R. (1988). Endogenous corticosteroids mediate seasonal cyclic changes in immunity of the lizard. Immunobiology, 177, 390–403. Saad, A.-H, El Ridi, R., El Deeb, S., and Soliman, M. A. W. (1986). Effects of hydrocortisone on the immune response of the lizard, Chalcides ocellatus. III. Effect on cellular and humoral immune responses. Dev. Comp. Immunol., 10, 235–245. Saad, A.-H, El Ridi, R., Zada, S., and Badir, N. (1984a). Effects of hydrocortisone on the immune response of the lizard, Chalcides ocellatus. I. Response of lymphoid tissues and cells to in vivo and in vitro hydrocortisone. Dev. Comp. Immunol., 8, 121–130. Saad, A.-H, El Ridi, R., Zada, S., and Badir, N. (1984b). Effects of hydrocortisone on the immune response of the lizard, Chalcides ocellatus. II. Differential action on T and B lymphocytes. Dev. Comp. Immunol., 8, 835–844.
Prologue Saad, A.-H, Nabil, M., and Raheem, K. (1993). Neuroimmunomodulation in reptiles. II. Seasonal changes in immune response and brain monoamine levels in the lizard, Eumeces schneideri. J. Egypt. Gen. Soc. Zool., 10, 355–371. Saad, A.-H, and Plytycz, B. (1994). Hormonal and nervous regulation of amphibian and reptilian immunity. Folia Biol., 42, 63–78. Saad, A.-H., and Shoukrey, N. (1988). Sexual dimorphism on the immune responses of the snake Psammophis siblans. Immunobiology, 177, 404–419. Saad, A.-H., Torroba, M., Varas, A., and Zapata, A. (1991a). Structural changes in the thymus gland of turtles following testosterone treatment. Thymus, 17, 129–132. Saad, A.-H., Torroba, M., Varas, A., and Zapata, A. (1991b). Testosterone induces lymphopenia in turtles. Vet. Immunol. Immunopath., 28, 173–180. Saarinen, M., and Taskinen, J. (2005). Long-lasting effect of stress on susceptibility of a freshwater clam to copepod parasitism. Parasitology, 130, 523–529. Salonius, K., and Iwama, G. K. (1993). Effect of early rearing environment on stress response, immune function, and disease resistance in juvenile coho (Oncorhynchus kisutch) and chinook salmon (O. tshawytscha). Can. J. Aquat. Sci., 50, 759–766. Sanders, V. M., Baker, R. A., Ramer-Quinn, D. S., Kasprowicz, D. J., Fuchs, B. A., and Street, N. E. (1997). Differential expression of the beta2-adrenergic receptor by Th1 and Th2 clones: implications for cytokine production and B cell help. J. Immunol., 158, 4200–4210. Sanders, V. M., Kasprowicz, D. J., Kohm, A. P., and Swanson, M. A. (2001). Neurotransmitter receptors on lymphocytes and other lymphoid cells. In R. Ader, D. L. Felten, and N. Cohen (Eds.), Psychoneuroimmunology (2nd ed., pp. 161–196). New York: Academic Press. Sanders, V. M., and Straub, R. (2002). Norepinephrine, the βadrenergic receptor, and immunity. Brain Behav. Immun., 16, 290–332. Sassi, D., Kletsas, D., and Ottaviani, E. (1998). Interactions of signaling pathways in ACTH (1–24)-induced cell shape changes in invertebrate immunocytes. Peptides, 19, 1105–1110. Schauenstein, K., Fässler, R., Dietrich, H., Schwartz, S., Krömer, G., and Wick, G. (1986). Disturbed immune-endocrine communication in autoimmune disease: lack of corticosterone response to immune signals in obese chickens with spontaneous autoimmune thyroiditis. J. Immunol., 139, 1830–1833. Secombes C., and Cunningham, C. (2004). Cytokines: an evolutionary perspective. Dev. Comp. Immunol., 28, 373–374. Secombes, C., Zou, J., Daniels, G., Cunningham, C., Koussounadis, A., and Kemp, G. (1998). Rainbow trout cytokine and cytokine receptors genes. Immunol. Rev., 166, 333–340. Secombes, C. J., Wang, T., Hong, S., Peddie, S., Crampe, M., Laing, K. J., Cunningham, C., and Zou, J. (2001). Cytokines and innate immunity of fish. Dev. Comp. Immunol., 25, 713–723. Sharma, J. M. (1991). Overview of the avian immune system. Vet. Immunol. Immunopath., 30, 13–17. Skwarlo-Sonta, K. (1992). Prolactin as an immunoregulatory hormone in mammals and birds. Immunol. Lett., 33, 105–122. Smith, E., Hughes, T., Leung, M., and Stefano, G. B. (1991). The production and action of ACTH-related peptides in invertebrate hemocytes. Adv. Neuroimmunol., 1, 7–16. Smith, E. M. (2003). Opioid peptides in immune cells. Adv. Exp. Med. Biol., 521, 51–68. Sonetti, D., Ottaviani, E., Bianchi, F., Rodriguez, M., Stefano, M. L., Scharrer, B., and Stefano, G. B. (1994). Microglia in invertebrate ganglia, Proc. Natl. Acad. Sci. USA, 91, 180–184.
37
Sonetti, D., Ottaviani, E., and Stefano, G. B. (1997), Opiate signaling regulates microglia activities in the invertebrate nervous system. Gen. Pharmacol., 29, 39–47. Spieler, R. E. (1979). Daily rhythms of circulating prolactin, cortisol, thyroxine, and triiodothyronine levels in fishes: a review. Rev. Can. Biol., 38, 301–315. Spooner, C. E., and Winters, W. D. (1966). Distribution of monoamines and regional uptake of DL-norepinephrine-7–H3 in the avian brain. Pharmacologist, 8, 189. Stansberg, C., Subramaniam, S., Collet, B., Secombes, C. J., and Cunningham, C. (2005). Cloning of the Atlantic salmon (Salmo salar) IL-1 receptor associated protein. Fish Shell. Immunol., 19, 53–65. Stave, J. B., and Roberson, B. S. (1985). Hydrocortisone suppresses the chemiluminescent response of striped bass phagocytes. Dev. Comp. Immunol., 9, 77–84. Stefano, G. B., Cadet, P., and Scharrer, B. (1989a). Stimulatory effects of opioid neuropeptides on locomotory activity and conformational changes in invertebrate and human immunocytes: evidence for a subtype of ∂ receptor. Proc. Natl. Acad. Sci. USA, 86, 6307–6311. Stefano, G. B., Digenis, A., Spector, S., Leung, M. K., Bilfinger, T. V., Makman, M. H., Scharrer, B., and Abumrad, N. N. (1993). Opiatelike substances in an invertebrate, an opiate receptor on invertebrate and human immunocytes, and a role in immunosuppression. Proc. Natl. Acad. Sci. USA, 90, 11099–11103. Stefano, G. B., Leung, M., Zhao, X., and Scharrer, B. (1989b). Evidence for the involvement of opioid neuropeptides in the adherence and migration of immunocompetent invertebrate hemocytes. Proc. Natl. Acad. Sci. USA, 86, 626–630. Stefano, G. B., Shipp, M., and Scharrer, B. (1991a). A possible immunoregulatory function for [Met]-enkephalin-Arg6–Phe7 involving human and invertebrate granulocytes. J. Neuroimmunol., 31, 97–103. Stefano, G. B., Smith, E., and Hughes, T. (1991b). Opioid induction of immunoreactive interleukin-1 in Mytilus edulis and human immunocytes: an interleukin-1–like substance in invertebrate neural tissue. J. Neuroimmunol., 32, 29–34. Sumpter, J. P., Pottinger, T. G., Rand-Weaver, M., and Campbell, P. M. (1994). The wide-ranging effects of stress on fish. In K. G. Davey, R. E. Peter, and S. S. Tobe (Eds.), Perspectives in comparative endocrinology (pp 535–538). Ottawa: National Research Council of Canada. Tripp, R. A., Maule, A. G., Schreck, C. B., and Kaattari, S. L. (1987). Cortisol mediated suppression of Salmon lymphocyte responses in vitro. Dev. Comp. Immunol., 11, 565–576. Trout, J. M., and Mashaly, M. M. (1995). Effects of in vitro corticosterone on chicken T- and B-lymphocyte proliferation. Brit. Poultry Sci., 36, 813–820. Turpen, J. B., and Smith, P. B. (1989). Precursor immigration and thymocyte succession during larval development and metamorphosis in Xenopus. J. Immunol., 142, 41–44. Vacchio, M. S., Papadopoulos, V., and Ashwell, J. D. (1994). Steroid production in the thymus: implications for thymocyte selection. J. Exp. Med., 179, 1835–1846. van den Burg, E. H., Metz, J. R., Spanings, F. A., Wendelaar Bonga, S. E., and Flik, G. (2005). Plasma alpha-MSH and acetylated betaendorphin levels following stress vary according to CRH sensitivity of the pituitary melanotropes in common carp, Cyprinus carpio. Gen. Comp. Endocrinol., 140, 210–221. Varas A., Torroba M., and Zapata A. G. (1992). Changes in the thymus and spleen of the turtle Mauremys caspica after testosterone injection: a morphometric study. Dev. Comp. Immunol., 16, 165–174.
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Verburg-van Kemenade, B. M. L., Nowak, B., Engelsma. M. Y., and Weyts, F. A. A. (1999). Differential effects of cortisol on apoptosis and proliferation of carp B lymphocytes from head kidney, spleen and blood. Fish Shell. Immunol., 9, 405–415. Verburg-van Kemenade, B. M. L., Weyts, F. A. A., Debets, R., and Flik, G. (1995). Carp macrophages and neutrophilic granulocytes secrete an interleukin-1–like factor. Dev. Comp. Immunol., 19, 59–70. Vleck, C. M., Vertalino, N., Vleck, D., and Bucher, T .L. (2000). Stress, corticosterone, and heterophil to lymphocyte ratios in free-living Adelie penguins. Condor, 102, 392–400. Wang, R., and Belosevic, M. (1995). The in vitro effects of estradiol and cortisol on the function of a long-term goldfish macrophage cell line. Dev. Comp. Immunol., 19, 327–336. Wang, T., Holland, J. W., Bols, N., and Secombes, C. J. (2005). Cloning and expression of the first nonmammalian interleukin-11 gene in rainbow trout Oncorhynchus mykiss. FEBS J., 272, 1136–1147. Wechsler S. J., McAllister, P. E., Hetrick, F. M., and Anderson, D. P. (1986). Effect of exogenous corticosteroids on circulating virus and neutralizing antibodies in striped bass (Morone saxatilis) infected with infectious pancreatic necrosis virus. Vet. Immunol. Immunopath., 12, 305–311. Wendelaar Bonga, S. E. (1997). The stress response in fish. Physiol. Rev., 77, 591–625. Weyts, F., Flik, G., Cohen, N, and Verburg-van Kemenade, B. M. L. (1999). Interactions between the immune system and hypothalamo-pituitary-interrenal axis in fish. Fish Shell. Immunol., 9, 1–20. Weyts, F. A. A., Flik, G., Rombout, J. H. W. M., and Verburg-van Kemenade, B. M. L. (1998a). Cortisol induces apoptosis in activated B cells, but not in thrombocytes or T cells of common carp, Cyprinus carpio L. Dev. Comp. Immunol., 22, 551–562. Weyts, F. A. A., Flik, G., and Verburg-van Kemenade, B. M. L. (1998b). Cortisol inhibits apoptosis in carp neutrophilic granulocytes. Dev. Comp. Immunol., 22, 563–572. Weyts, F. A. A., Verburg-van Kemenade, B. M. L., and Flik, G. (1998c). Characterization of corticoid receptors in carp, Cyprinus carpio L., peripheral blood leukocytes. Gen. Comp. Endocrin., 111, 1–8. Weyts, F. A. A., Verburg-van Kemenade, B. M. L., Flik, G., Lambert, J. G. D., and Wendelaar Bonga, S. E. (1997). Conservation of apoptosis as an immune regulatory mechanism: effects of cortisol and cortisone on carp lymphocytes. Brain Behav. Immun., 11, 95–105. White, B., and Nicoll, C. (1981). Hormonal control of amphibian metamorphosis. In L. Gilbert and E. Frieden (Eds.), Metamorphosis: a problem in developmental biology (pp. 363–395). New York: Plenum Press. Wick, G., Brezinschek, H. P., Hala, K., Dietrich, H., Wolf, H., and Krömer, G. (1990). The obese strain of chickens: an animal model with spontaneous autoimmune thyroiditis. Adv. Immunol., 47, 433–500. Wick, G., Hu, Y., Schwarz, S., and Krömer, G. (1993). Immunoendocrine communication via the hypothalamo-pituitary-adrenal axis in autoimmune diseases. Endocr. Rev., 14, 539–563. Wojtaszek, J. S. (1992). Seasonal changes of circulating blood parameters in the grass snake, Natrix natrix natrix L. Comp. Biochem. Physiol., 103A, 461–471.
Wojtowicz, A., and Plytycz, B. (1997). Seasonal changes of the gutassociated lymphoid tissues in the common toad, Bufo bufo. J. Nutrit. Immunol., 52, 57–65. Woodhams, D. C., Rollins-Smith, L. A., Carey, C., Reinert, L., Tyler, M. J., and Alford, R. A. (2006). Population trends associated with skin peptide defenses against chytridiomycosis in Australian frogs. Oecologia., 146, 531–540. Worley, R. T. S., and Jurd, R. D. (1979). The effect of a laboratory environment on graft rejection in Lacerta viridis, the European green lizard. Dev. Comp. Immunol., 3, 653–665. Yada, T., and Nakanishi, T. (2002). Interaction between endocrine and immune systems in fish. Int. Rev. Cytol., 220, 35–92. Yamaguchi, A., Teshima, C., Kurashige, S., Saito, T., and Mitsuhasi, S. (1981). Seasonal modulation and antibody formation in rainbow trout (Salmo gaidneri). In J. B. Solomon (Ed.), Aspects of developmental and comparative immunology (p. 483). Oxford: Pergamon Press. Yin, Z., Lam, T. J., and Sin, Y. M. (1995). The effects of crowding stress on the non-specific immune response in fancy carp (Cyprinus carpio L.). Fish Shell. Immunol., 5, 519–529. Zapata, A., and Leceta, J. (1986). Seasonal variations in the immune response of the tortoise Mauremys caspica. Immunology, 57, 483–487. Zapata, A., Varas, A., and Torroba, M. (1992). Seasonal variations in the immune system of lower vertebrates. Immunol. Today, 13, 142–147. Zapata, A., Villena, A., and Cooper, E. L. (1982). Direct contacts between nerve endings and lymphoid cells in the jugular body of Rana pipiens. Experientia, 38, 623–624. Zentel, H. J., Nohr, D., Albrecht, R., Jeurissen, S. H. M., Vainio, O., and Weihe, E. (1991). Peptidergic innervation of the bursa fabric: interrelation with T-lymphocyte subsets. Internat. J. Neurosci., 59, 177–188. Zentel, H. J., and Weihe, E. (1991). The neuro-B cell link of peptidergic innervation of the bursa fabric. Brain Behav. Immun., 5, 132–147. Zou, J., Bird, S., Truckle, J., Bols, N., Horne, M., and Secombes, C. (2004). Identification and expression analysis of an IL-18 homologue and its alternatively spliced form in rainbow trout (Oncorhynchus mykiss). Eur. J. Biochem., 271, 1913–1923. Zou, J., Carrington, A., Collet, B., Dijkstra, J. M., Yoshiura, Y., Bols, N., and Secombes, C. (2005). Identification and bioactivities of IFN-gamma in rainbow trout Oncorhynchus mykiss: the first Th1type cytokine characterized functionally in fish. J. Immunol., 175, 2484–2494. Zou, J., Peddie, S., Scapigliati, G., Zhang, Y., Bols, N. C., Ellis, A. E., and Secombes, C. J. (2003). Functional characterisation of the recombinant tumor necrosis factors in rainbow trout, Oncorhynchus mykiss. Dev. Comp. Immunol., 27, 813–822. Zou, J., Wang, T., Hirono, I., Aoki, T., Inagawa, H., Honda, T., Soma, G. I., Ototake, M., Nakanishi, T., Ellis, A. E., and Secombes, C. J. (2002). Differential expression of two tumor necrosis factor genes in rainbow trout, Oncorhynchus mykiss. Dev. Comp. Immunol., 26, 161–172. Zuk, M., Simmens, L. W., Rotenberry, J. T., and Stoehr, A. M. (2004). Sex differences in immunity in two species of field cricket. Can. J. Zool., 82, 627–634.
P A R T
I NEURAL AND ENDOCRINE EFFECTS ON IMMUNITY COBI HEIJNEN
INTRODUCTION This section contains a challenging overview of the developments in the research on mechanisms involved in the neuroendocrine-immune circuitry. Since the intriguing paper of J. Edwin Blalock in 1985, proposing a theory about shared mediators and shared receptors in immune and neuroendocrine systems, the field of psychoneuroimmunology (PNI) has made enormous progress (Blalock et al., 1985). At the time, the major challenge was to prove first of all that leukocytes express bonafide receptors for neurotransmitters, neuropeptides, and hormones, and second, that leukocytes can produce the same mediators that were known as classical neuroendocrine mediators. On the other hand, there was a scientific debate going on around the hypothesis that neurons express receptors for immune mediators like cytokines and that cytokines can be produced by cells of the neuroendocrine system. Nowadays, the dust has settled, and we are no longer questioning the validity of the concept of shared mediators and receptors in neuroendocrine and immune systems. Today’s challenge is to define the functional importance of this neuroendocrine-immune circuitry for health and disease. The chapters in this section show that neuroendocrine-immune communication encompasses complete regulatory circuits on many functional levels: • on the level of the whole organism • on the level of interorgan communication • on the level of intercellular communication within the immune system
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On the level of communication between immune cells, Chapter 5, by Ganea and Delgado, describes the production and function of the neuropeptide vasoactive intestinal peptide (VIP).VIP is described here as a powerful anti-inflammatory neuropeptide that is produced not only by neurons but also by T-cells. Production of VIP can lead to the differentiation of T-cells into so-called T regulatory cells (Treg), which are of paramount importance for the induction and maintenance of tolerance during proinflammatory autoimmune diseases like rheumatoid arthritis. From these data one could hypothesize that the (auto)immune activation of the T-cells may lead to the production of VIP, which will contribute to the induction or activation of Tregs. This will, in turn, suppress the level of activation of the T-cell, which subsequently will lead to less VIP production by the T-cell. Interesting examples of regulatory neuroendocrine-immune circuitries on the level of organ systems are described in Chapter 2, by Sanders and Kavelaars; Chapter 4, by Van der Kleij and Bienenstock; and Chapter 3, by Czura, Rosas, and Tracey. Sanders and Kavelaars start from the original observation of Hugo Besedovsky et al. that immune activation of the spleen leads to catecholamine secretion by sympathetic nerves in the spleen, which subsequently leads to a down regulation of immune activation (Besedovsky et al., 1983). Recent research revealed that the picture is more complex. Sympathetic activation and stimulation of beta2-adrenergic receptors on immune cells is not always immunosuppressive. Both in the innate as well as in the adaptive immune response, it has been shown that, depending on timing and context, beta-adrenergic activation of immune cells can be either stimulatory or suppressive. Elegant work from the Sanders group describes the molecular mechanisms underlying the immunoenhancing effects of catecholamines on both B- and T-cells. Van der Kleij and Bienenstock describe the role of neuropeptides like VIP, Substance P and CGRP for nervous system-immune communication within the mucosal immune system in, e.g., the gastrointestinal tract, the urinary tract, and the airways. These authors elucidate the central role of mast cells not only as a target for neuropeptides, but also as a source for conveying information on inflammatory activity within these organ systems to the nervous system. Neuropeptides activate mast cells, and mast cells secrete mediators that activate neurons in an intricate network of interactions with important consequences for the activity of the end organs like the gut or the airways. Disturbances in these circuitries are related to diseases like asthma or inflammatory bowel disease. The importance of cholinergic signaling as a distinct counter-regulatory mechanism to restrain excessive inflammatory cytokine production for the prevention of endotoxic shock, tissue injury, and perhaps autoimmunity is described in Chapter 3, by Czura et al. The inflammatory reflex is described in this chapter as the capacity of the vagus nerve to respond to low concentrations of cytokines in peripheral tissue with activation of a cholinergic efferent arm that has potent anti-inflammatory capacities in models of, e.g., endotoxemia and ischemia. Acetylcholine stimulation of the alpha-7 subunit of nicotinic acetylcholine receptors on macrophages is identified as the immunosuppressive route of the inflammatory reflex. Clinically, the use of cholinergic agonists to inhibit pro-inflammatory cytokine secretion has numerous possible applications.
I. Neural and Endocrine Effects on Immunity
A more classical hormonal inflammatory feedback mechanism is represented by the loop of cytokine production, activation of the hypothalamus-pituitary-adrenal-axis, and glucocorticoid mediated inhibition of inflammation. In Chapter 8, Gorby and Sternberg describe beautifully the concept that disturbances in this feedback mechanism could be involved in the inflammatory activity in autoimmune diseases like rheumatoid arthritis and the disease-associated behavioral symptoms like sensitivity to stress and depression. Although the role of glucocorticoids in autoimmunity has received most of the attention, we should not forget the importance of sex steroids and their metabolism in autoimmune diseases as described in Chapter 9, by Cutolo and Calzia. The well-known changes in the clinical symptoms of autoimmune diseases during various phases of pregnancy form the most clear-cut example of the regulatory capacity of sex steroids. From the initial discovery that leukocytes produced neuropeptides, including opioids, in vitro after proper stimulation, Machelska and Stein continued to work on this phenomenon, despite a lot of skepticism at the time. Now they show convincingly in Chapter 6 that leukocytes produce these opioids like endorphins and enkephalins in vivo during inflammatory conditions. More importantly, inhibition of production of the leukocyte-derived opioids leads to more pronounced hyperalgesia of the animal and increased inflammation. These in vivo studies clearly show the functional importance of opioid production by the immune system in intra- and inter-organ communication. I think we can consider these findings as another example of a feedback loop using shared mediators and receptors, in this case to dampen inflammatory pain. Until now I have mainly commented on the influence of the production of shared mediators by neurons and cells of the immune system. However, the other important players in the circuitry are the shared receptors. In various chapters of this section, the authors paid attention to the importance of regulation of receptor function for determining the outcome of neuroendocrine-immune communication. In Chapter 1, Schoneveld and Cidlowski elegantly describe the latest state of knowledge on the function and regulation of glucocorticoid receptors (GR) in cells of the immune system. Activation of GR, which are in fact transcription factors, can lead to transactivation and transrepression of genes in the immune cell, depending on the vicinity, availability, and balance of various transcriptional elements in the cell. However, an additional means of regulation occurs at the receptor site itself, e.g., by post-translational modification of the GR via modifications like phosphorylation at different sites or ubiquitination of the GR leading to an alteration of receptor functioning. In Chapter 2, by Sanders and Kavelaars, the regulation of β2-adrenergic receptor expression and sensitivity is described. Here, the authors describe that inflammation can alter the sensitivity of receptors for catecholamines by modulation of the intracellular kinases, like G protein coupled receptor kinases that regulate phosphorylation and internalization of adrenergic receptors. In Chapter 7, McCusker and Kelley make a crucial step forward when considering the consequences of simultaneous activation of more than one receptor on a target cell. The ultimate effect of regulatory hormones, neurotransmitters, and cytokines will be determined by the concerted action of these mediators on multiple receptors expressed by the same cell. The molecular approach used in these studies reveals an important
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level of interaction that, because of the complexity of the phenomenon, has been studied only sparsely. By now we know a lot about the activities of separate hormones and receptors, but in real life, activation of, e.g., sensory neurons will lead to a simultaneous secretion of many neuropeptides like Substance P, calcitonin-gene-related peptide, norepinephrine, acetylcholine, etc. Conversely, the cell or the organ will be bombarded by many immune mediators such as a myriad of pro-inflammatory cytokines. The cell will respond to most of the neuroendocrine and immune mediators since it expresses receptors for these molecules. This will activate several intracellular signaling pathways that will be counteracted or enhanced by each other, leading finally to the net physiological outcome of cellular activity. We are only now beginning to understand this overwhelming complexity, and the challenge in the coming decade will be to use signalomic, metabolomic, and proteomic approaches to further unravel the hierarchy in the neuroendocrine-immune circuitry. The progress of the field of psychoneuroimmunology becomes very clear in this section of Psychoneuroimmunology, Fourth Edition, since nearly every chapter deals with the effect of neuroendocrine-immune circuitry from in vitro to in vivo to translation to pathological conditions. In this respect, it is intriguing to read Chapter 10, by Straub and colleagues, who argue that neuroendocrine-immune circuitry has developed because of its evolutionary importance for the survival of the species. This means that the driving force for development of the circuitry should be understood from the point of view of defense against acute infections in individuals during and before the reproductive age. The authors propose that, in diseases that mostly occur among the elderly, the neuroendocrine-immune circuitry may lose its protective role and transform into a counterproductive system. This hypothesis is important because it may alter our idea of the way the neuroendocrine-immune circuitry should be therapeutically targeted in diseases of the elderly. Chapter 11, by Sood et al., and Chapter 12, by Avraham and Ben Eliyahu, highlight neuroendocrine-immune influences on cancer progression. Sood and co-workers describe elegantly the pivotal importance of angiogenesis for cancer progression and metastasis and the effect of the neuroendocrine mediators, e.g., catecholamines, on this process. Moreover, it appears that tumor cells themselves are sensitive to neuroimmune regulation. Tumor cells express adrenergic receptors and respond to catecholamines with increased metalloprotease production that enhances the invasive capacity of these cells. In Chapter 12, Avraham and Ben Eliyahu continue to describe the negative effects of stress and stress hormones on cancer metastasis. These authors concentrate on the fact that the stress associated with surgery to remove the primary tumor via catecholaminergic suppression of NK cell activity may, in fact, facilitate the dissemination of single tumor cells and the formation of micrometastases. Taken into account that there are now at least two levels described for potentiation of metastasis formation by catecholamines, the need for a randomized trial with beta-adrenergic blockers during surgery for the inhibition of micrometastasis formation is obvious. At the end of my introduction, I would like to stress that as PNI scientists, who have come so far as to
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make the translation from fundamental studies on neuroendocrine-immune circuitry in vitro to the description of this intricate interplay of shared mediators and receptors in pathological conditions, we should now together step forward and enter the field of neuro-immune therapeutic interventions. Cobi J. Heijnen
References Besedovsky, H., Del Rey, A., Sorkin, E., Da Prada, M., Burri, R., and Honegger, C. (1983). The immune response evokes changes in brain noradrenergic neurons. Science, 221, 564–566. Blalock J. E., Harbour-McMenamin, D., and Smith, E. M. (1985). Peptide hormones shared by the neuroendocrine and immunologic systems. J. Immunol., 135, 858s–861s.
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C H A P T E R
1 Glucocorticoids and Immunity: Mechanisms of Regulation ONARD J. L. M. SCHONEVELD AND JOHN A. CIDLOWSKI
I. II. III. IV. V. VI.
INTRODUCTION 45 IMMUNITY 46 GLUCOCORTICOIDS 48 GLUCOCORTICOID RECEPTOR 48 REGULATION OF GENE EXPRESSION BY GR 50 INHIBITORY EFFECTS OF GLUCOCORTICOIDS ON THE IMMUNE SYSTEM 54 VII. PERSPECTIVES 56
nisms, glucocorticoids act at multiple levels in the immune system, including the regulation of cytokine signaling, cytokine receptor synthesis, and other critical mediators of the immune response. Because of their clinical importance and diverse roles as antiinflammatory therapeutics, it is of paramount importance to understand how glucocorticoids affect the immune system. This chapter will provide a concise overview of the immune response as well as glucocorticoid signaling, and how these two systems interact.
ABSTRACT I. INTRODUCTION
Glucocorticoids are among the most effective pharmaceuticals used to treat inflammatory and allergic diseases. Their therapeutic effects are, however, accompanied by a number of severe side effects, including fat redistribution, weight gain, hyperglycemia, and osteoporosis. Glucocorticoids exert their effects mainly through the glucocorticoid receptor, a liganddependent transcriptional regulator that activates or represses target gene expression. While the adverse effects of glucocorticoid treatment are thought to be primarily caused by activation of catabolic genes, the anti-inflammatory effects are largely thought to be mediated by the transrepressive properties of glucocorticoids. Transrepression of gene expression can be achieved by association of GR with either negative regulatory sequences in target genes, or proinflammatory transcription factors such as NFκB, AP1, and NF-AT, thereby preventing the upregulation of pro-inflammatory genes. Via these repressive mechaPSYCHONEUROIMMUNOLOGY, 4E VOLUME I
Glucocorticoids are among the most prescribed immunosuppressive drugs and have been used in the clinic for over 50 years (Dickey, 1976; Galon et al., 2002). When they were initially used in this setting, very little was known about the mechanisms underlying the anti-inflammatory effects of glucocorticoids, although the side effects had already been recognized (Clark, 1968). Years of research in addition to the development of molecular biological tools have led to significant progress in the field. Despite our better understanding and the development of non-steroidal anti-inflammatory and immunosuppressive drugs, glucocorticoids are still among the most prescribed immunosuppressive medications. This chapter will give a concise overview of the immune response and mechanisms of glucocorticoid signaling. In addition we will outline several examples where
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Copyright © 2007 by Elsevier, Inc. All rights of reproduction in any form reserved.
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glucocorticoids elicit a myriad of anti-inflammatory responses at multiple levels in the immune cascade.
II. IMMUNITY To protect against invasion by pathogenic organisms, our body has developed an array of complex protective processes. In principle, two general immune mechanisms exist: innate immunity, in which the host’s existing genes determine responses to pathogens by recognition of molecular patterns that are distinct from the host, and the adaptive immune system, where the response depends on gene rearrangements to generate new receptors that are specific for one particular antigen. The immune response can be divided in three stages: the recognition phase, the activation phase, and the effector phase. Although the innate and adaptive immune systems are very different in terms of rapidity and specificity of the response, there is crosstalk between both mechanisms (Chaplin, 2003).
A. Innate Immunity The innate response is a broadly expressed system and can therefore respond very rapidly to microbial infections. It responds prior to the development of the adaptive immune response and acts as a first response against invading pathogens. By definition, the innate response consists of all the defense mechanisms that are encoded by the host’s germ-line genes. These include (1) the body’s physical barriers like the skin and the gastrointestinal tract, (2) molecules that recognize foreign antigens such as blood proteins of the complement system and cell-surface receptors that recognize molecular patterns, (3) molecules and cells that direct effector cells to the site of inflammation like vascular endothelial cells and cytokines, and (4) effector cells that eliminate foreign pathogens like phagocytes. The innate immune system responds only to molecular patterns found in microbes and products thereof such as dsRNA found in replicating viruses (Alexopoulou et al., 2001), and complex carbohydrates such as lipopolysaccharides (LPS). An important system for recognizing foreign antigens is formed by the complement system (Morgan and Harris, 2003). Its most predominant role involves recognizing pathogens, pathogenic products, or altered host cells, and targeting them for degradation. The complement system consists of over 25 plasma and cell-surface proteins that recognize pathogen-associated molecular patterns and relay this information via a signaling cascade onto the central component C3. Activation of
this system occurs through three pathways (Liszewski et al., 1996): In the classical pathway, C3 becomes activated in response to antigen-antibody complexes that are formed during the humoral response (Reid and Porter, 1981). The mannose-binding lectin pathway is activated upon recognition of pathogen-related molecular patterns by lectin proteins (Reid and Turner, 1994). In contrast, the alternative pathway is not activated by a specific signal, but is turned on by spontaneous activation of C3, or its non-specific interaction with other proteins (Fearon and Austen, 1975). Once activated, target-bound C3 can elicit several responses including (1) induction of cell lysis by the formation of a membrane-bound attack complex, (2) opsonization of the antigen, and (3) targeting of the antigen to the adaptive immune system (Sim and Tsiftsoglou, 2004). Besides the complement system, recognition of microbial antigens also takes place via Toll-like receptors (TLR) located on the membrane of certain subclasses of leukocytes (Pasare and Medzhitov, 2004). To date there are 10 known TLRs, each recognizing a different class of antigens. TLR4, for instance, recognizes LPS, potent inducers of inflammation and cytokine production that are derived from the cell wall of gramnegative bacteria (Janeway and Medzhitov, 2002). Upon activation of TLRs, the TLR-mediated MyD88dependent signaling is initiated, resulting in activation of the nuclear factor κB (NFκB) and activating protein 1 (AP-1) pathways that in turn trigger the host’s innate defense system (Wang et al., 2001). This results in the induction of pro-inflammatory genes and the production of pro-inflammatory cytokines and chemokines. Chemokines stimulate endothelial cells to produce selectins that mediate the loose attachment of leukocytes to the vascular cells at the site of inflammation (Gonzalez-Amaro and Sanchez-Madrid, 1999). Leukocytes are then activated by chemokines produced by the endothelial cells and start producing high-affinity integrins. These molecules recognize intercellular adhesion molecules (ICAMs) and vascular cell adhesion molecule-1 (VCAM-1), which are expressed on endothelial cells in response to pro-inflammatory cytokines (Gahmberg, 1997). Subsequently, the leukocytes can migrate through inter-endothelial cell junctions from the blood into the tissue (Bianchi et al., 1997). At the site of infection, the effector cells of the innate immune system (e.g., neutrophils and macrophages) can “ingest” microbes and kill them in a process known as phagocytocis.
B. Adaptive Immunity In contrast to the innate response, the adaptive immune response develops in reaction to an infection
1. Glucocorticoids and Immunity: Mechanisms of Regulation
by the selection of B- and T-lymphocytes that recognize particular antigens. Because of the large number of potential antigens, the adaptive immune system generates very few cells with specificity for each antigen (Chaplin, 2003). Once activated, the responding cells need to proliferate in order to provide an adequate response. Therefore, this response is much more specific but also much slower than the innate immune system. However, due to its ability to memorize the response to a specific antigen, it is able to react faster and more vigorously after repeated exposures to the antigen (Rocha and Tanchot, 2004; Stockinger et al., 2004). The adaptive immune response is initiated in the peripheral lymphoid tissues (i.e., lymph nodes, spleen, and the cutaneous and mucosal immune systems) where the antigens are concentrated. The first step in the adaptive immune response is the presentation of antigens at the cell surface of so-called antigenpresenting cells, including dendritic cells, monocytes, macrophages, and also B-cells (Del-Val and Lopez, 2002). Among those, dendritic cells are the most predominant class of antigen presenting cells and have the special function to stimulate the proliferation of naïve T-cells into Th1 or Th2 effector cells (Degli-Esposti and Smyth, 2005). Antigens produced intracellularly, such as virus-infected cells, are presented in a complex with MHC-1 molecules to Tlymphocytes. The first step in the presentation of intracellular antigens is the generation of peptide fragments by the proteasome (Bogyo et al., 1997). In the endoplasmic reticulum, these oligopeptides are then tethered to the MHC class I receptors and transported to the cell surface. Antigens of exogenous origin, such as bacteria, need to be ingested by phagocytosis or endocytosis, after which they are cleaved by lysosomal enzymes to generate peptide fragments that can be tethered to MHC class II receptors. The effector cells of the adaptive response are the T- and B-lymphocytes, and the natural killer (NK) cells that can be discriminated by the receptor type they express on the cell surface. T-cells contain receptors that interact with antigens displayed on the MHC receptors of antigen-presenting cells. Besides this antigen-specific T-cell receptor, T-cells express a complementarity domain (CD) on their cell surface that interacts with subunits of the MHC complex. CD8+ T-cells recognize MHC class I molecules and induce a response against intracellular pathogens, whereas T-helper cells (CD4+) recognize antigens that are complexed with MHC class II molecules and evoke the cellular and humoral immune responses (Williams et al., 1991). The identity of the cytokines present at the site of activation determine whether the acti-
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vated CD4+ T-cells differentiate into Th1 or Th2 cells (Mosmann and Coffman, 1989). Th1 cells produce a different set of cytokines than Th2 cells, resulting in a distinct immune response. The Th1 cells induce a cellmediated immune response, whereas the Th2 cells are involved in the humoral and allergic responses. Besides activation of the T-cell receptor complex, a co-stimulatory signal is required for T-cell activation. The first signal, derived from the antigen, determines specificity, while the second signal, which is a product of the innate immune response, ensures that a response is executed when needed. The latter can be a costimulator, cytokine, or breakdown products of the complement system. (Bretscher, 1992). By synergistic activation of the T-cell receptor complex and the co-stimulatory molecules, the transmembrane CD3 complex with which the T-cell receptor associates can initiate a mitogen-activated protein kinase (MAPK) signaling cascade resulting in the activation of genes involved in lymphocyte proliferation and differentiation (Pitcher and van Oers, 2003). B-cells are lymphocytes derived from the bone marrow and are characterized by the production of immunoglobin (Ig) molecules. The variable region of these molecules constitutes the antigen-binding domain, whereas the constant carboxy-terminal end forms the Fc domain that conducts the effector functions. Surface Ig molecules capable of recognizing a specific antigen are assembled in the B-cell receptor complex. Like T-cells, B-cell activation requires the synergistic activation of the B-cell receptor complex by the antigen and by the co-receptor complex through binding of the complement factor C3d (Fearon and Carroll, 2000). This results in activation of a downstream MAPK cascade that activates a set of genes involved in cell proliferation and maturation. In contrast to the phagocytes of the innate immune system, natural killer (NK) cells recognize intracellular antigens, like virus-infected cells. All nucleated cells normally express the class I MHC molecules that inhibit cell lysis by NK cells. Target cells in which the level of MHC molecules is reduced as a result of infection or transformation into a cancer cell can trigger the activation of natural killer cells. Also, the CD16 receptor of natural killer cells can recognize target cells that have been coated with certain classes of IgG antibodies. Once activated, the NK cell can lyse the bound target cell by releasing the content of its granules, which contain perforin and granzymes that make pores and induce apoptosis in the target cells, respectively (Smyth et al., 2005). In addition, the NK cells produce IFN-γ to activate macrophages.
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In contrast to the innate immune system, the adaptive immune response has the ability to generate longterm protection against repeated exposure to a certain antigen. After antigen-stimulation, a subset of the effector B-cells differentiates into memory B-cells and plasma cells, whereas a subset of the T-cells develops into CD4 and CD8 memory T-cells (Rocha and Tanchot, 2004; Stockinger et al., 2004).
III. GLUCOCORTICOIDS Endogenous glucocorticoids are produced by the adrenal gland under the control of the hypothalamus and pituitary, constituting the hypothalamicpituitary-adrenal gland axis (HPA). When activated by stress factors such as exposure to endotoxins, corticotropin releasing factor (CRF) and arginine vasopressin (AVP) are released from the hypothalamus, stimulating the pituitary to release adrenocorticotrophic hormone (ACTH) into the blood (Schreiber et al., 1993). In turn, ACTH stimulates the release of cortisol from the adrenal cortex into the blood, initiating the activation of downstream pathways. Named for their role in maintaining glucose homeostasis, glucocorticoids can regulate many catabolic genes, including phosphoenolpyruvate carboxykinase involved in gluconeogenesis (Scott et al., 1998), and also carbamoylphosphate synthetase that is a key enzyme in the urea cycle (Christoffels et al., 2000). In contrast to these transactivating functions, glucocorticoids have transrepressive activities on inflammatory pathways, and are widely applied to treat inflammatory responses such as asthma, arthritis, and eczema. One of the major drawbacks on the long-term use of glucocorticoids as anti-inflammatory agents is the concomitant catabolic response in many tissues of the body. The enzymes that play a role in protein catabolism often contain glucocorticoid-response elements (GREs) in their regulatory sequences and are upregulated upon treatment with glucocorticoids. In the liver, for example, induction of protein catabolism is accompanied by increases in amino acid-catabolizing, gluconeogenic, and ammonia-detoxifying enzymes. A considerable amount of research is now focusing on dissociating the repressive from the transactivating effects of glucocorticoids. Besides the endogenous glucocorticoids that are produced in the adrenal cortex, many synthetic glucocorticoids have been developed demonstrating a different benefit-risk ratio; however, significant side effects due to upregulation of genes remain (Belvisi et al., 2001; Coghlan et al., 2003).
IV. GLUCOCORTICOID RECEPTOR A. Glucocorticoid Receptor Expression The effects of glucocorticoids are mediated by the glucocorticoid receptor (GR) that is expressed in almost all tissues (Rousseau and Baxter, 1979). Although multiple isoforms exist, GR is encoded by a single gene. This gene is composed of nine exons and is located on chromosome 5 (Encio and Detera-Wadleigh, 1991). Three different promoters drive the expression of this gene resulting in three mRNAs differing in the 5’ untranslated region. Based on their GC-richness and the fact that they are expressed in most cell types, the 1B and 1C promoters have been suggested to act as housekeeping-gene promoters (Breslin et al., 2001). In contrast, the 1A promoter contains a non-consensus GRE directly upstream of a transcription-factor binding site for both c-Myb and c-Ets and is regulated by glucocorticoids. In many cell types, GR expression is downregulated by glucocorticoids (Rosewicz et al., 1988), except in immature thymocytes and Tlymphoblasts where GR is upregulated. Upregulation of GR seems to be important for the pro-apoptotic effects of glucocorticoids in these cells. It has been suggested that depending on the type of transcription factor (c-Myb or c-Ets) that is bound to the response element adjacent to the GRE, the gene is either repressed or activated by glucocorticoids (Geng and Vedeckis, 2004). Splice variants of exon nine give rise to the α and β isoform of GR that, although identical up to amino acid 727, differ at their carboxy termini. GRα, the most predominant isoform, contains a 50 amino acid carboxy terminal end that composes part of the ligand-binding domain. In contrast, in GRβ, the carboxy terminal end is replaced by 15 amino acids that have not been reported to bind any ligand (Yudt et al., 2003). The physiological relevance of GRβ is a topic of controversy. Besides these splice variants, different GR isoforms result from alternative-translation initiation due to the presence of a weak Kozak sequence in front of the first AUG and the presence of multiple AUGs in the GR coding region (Lu and Cidlowski, 2004; Lu and Cidlowski, 2005; Yudt and Cidlowski, 2001). The ratio of the different isoforms varies between cell types, and each of these isoforms regulates a specific set of genes. It has been proposed that this provides an additional mechanism to regulate the glucocorticoid response (Lu and Cidlowski, 2005).
1. Glucocorticoids and Immunity: Mechanisms of Regulation
B. Protein Structure The GR belongs to the steroid receptor family that also includes the estrogen receptors, the androgen receptors, thyroid receptors, and mineralocorticoid receptors. Similar to other steroid receptors, GR is a modular protein, with each domain having separate functions (Figure 1). The N-terminal domain contains activation function 1 (AF-1) that can activate target genes in a hormone-independent fashion (Hollenberg and Evans, 1988; Miesfeld et al., 1987). The central domain harbors the DNA-binding domain and a nuclear-localization signal (NL1). Two zinc ions in the DNA-binding domain are coordinated by two sets of four cysteins to constitute two zinc fingers (Luisi et al., 1991). Three amino acids within the zinc-finger loop constitute the P-box, which contacts the DNA and governs specificity (Eriksson and Nilsson, 1998; Umesono and Evans, 1989). The core nuclear localization motif of NL1 is located adjacent to the DNAbinding domain. In addition, two short clusters of amino acids increase the strength of the nuclearlocalization signal (Savory et al., 1999). The carboxyteminus of GR contains a second but weaker activation function (AF-2), a second nuclear localization signal (NL2), and GR’s ligand-binding domain. Since NL2 is located within the ligand-binding domain, it is not very well defined. However, there are reports suggesting that NL2 is an inefficient nuclear-localization signal (Cadepond et al., 1992; Jewell et al., 1995). Crystalstructure analysis of hGRα has shown that the ligandbinding domain contains α-helices and β sheets that form a hydrophobic pocket in which the ligand can
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bind. In the absence of hormone, GR is localized in the cytoplasm in a complex with HSP90 and other proteins to keep it in a conformation poised to bind its ligand (Pratt and Toft, 1997). Glucocorticoid binding produces a conformational change in GR and causes it to dissociate from this complex and rapidly translocate to the nucleus, where it can regulate expression of target genes (Freedman and Yamamoto, 2004; Howard and Distelhorst, 1988).
C. Post-translational Modifications Post-translational modifications like phosphorylation and ubiquitination can alter protein function and, therefore, provide an additional means for regulation. Bodwell and colleagues have identified seven phosphorylation sites in mouse GR (Bodwell et al., 1991). All but one of these sites were found to be located within the N-terminal transactivation domain of GR. In addition, hormonal induction increased the phosphorylation status at all but two sites, Ser150 and Thr159, suggesting a role of phosphorylation in ligand-dependent transactivation (Bodwell et al., 1995). However, the effects of GR phosphorylation on its capacity to transregulate gene expression were ambiguous. Data from Mason and Housley that were later confirmed by Jewell and colleagues have shown that mutation of all seven phosphorylation sites in mouse GR did not have any major effects on its transactivation capacity from an MMTV reporter construct in COS-1 cells (Mason and Housley, 1993; Jewell et al., 1995; Webster et al., 1997). In agreement Almlof et al. have shown that mutation of all five serine residues in
FIGURE 1 Schematic representation of the hGRα. GR is a modular protein, functionally consisting of three major domains. The N-terminal domain contains the strong activation function, AF1, that is important for relaying the transcription-activation signal onto the basal transcription machinery. The DNA-binding domain contains two zinc fingers that are responsible for receptor dimerization and for contacting the DNA in a sequence-specific manner. Although the hinge region does not act as a functionally important domain, it does contain a nuclear localization signal that is important for receptor translocation to the nuclear compartment. The ligandbinding domain is important for ligand binding, but contains in addition, a second transactivation function, AF2, and a second nuclear localization signal.
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human GR, which are homologous to amino acids that can be phosphorylated in mouse GR, did not result in a significantly different transactivation capacity of AF1 from a 2xGRE-TK promoter in COS-7 cells (Almlof et al., 1995). However, when these experiments were repeated using a 2xGRE-TATA reporter, it was found that mouse GR mutated at single or multiple phosphorylation sites exhibited a decreased transactivation capacity relative to wild type GR in COS-1 cells (Bodwell et al., 1998; Webster et al., 1997). Thus, these results suggested that the phosphorylation status of GR can alter its transactivation potential in a promoterspecific manner. Transcription factors, being part of signal transduction pathways, are mobile proteins within the cell. Cytoplasmic-nuclear shuttling of the GR is mediated by the import and nuclear export machinery that recognizes nuclear-localization signals and nuclearexport signals respectively (Black et al., 2001). Posttranslational modification can mask or reveal such localization sequences, thereby regulating the subcellular distribution of GR. Harreman and colleagues have shown that phosphorylation of residues adjacent to the SV40 nuclear-localization signal can indeed determine the subcellular localization of a recombinant protein (Harreman et al., 2004). However, Jewell and colleagues showed that the nuclear translocation of mouse GR mutated at single, multiple, or all phosphorylation sites in response to dexamethasone was indistinguishable from the wild type receptor, indicating that these phosphorylation sites do not play a major role in hormone-inducible translocation (Jewell et al., 1995; Webster et al., 1997). In contrast, a report by Wang et al. suggested that there might be an effect of GR’s phosphorylation status on its subcellular distribution (Wang et al., 2002). Using phosphorylationsite specific antibodies, they have shown that in stably transfected U2OS cells without hormone treatment, GR proteins phosphorylated at Ser203 or at Ser211 are both confined to the cytosolic fraction. However, following 1hr dex induction, the Ser211 form, which has been associated with the transcriptionally active subpopulation of the receptor, was found both in the cytoplasm and in the nucleoplasm, whereas the Ser203 phosphorylated form of GR was confined only to the cytosolic fraction. The discrepancy between the above findings may stem from differences in the cell types used or from stable versus transiently transfected cells. Besides influencing the transactivation properties and subcellular localization of GR, phosphorylation may affect the stability of the protein. Indeed, Webster et al. have shown that a decreased degree of phosphorylation affects receptor half-life (Webster et al.,
1997). How exactly this takes place is unclear, but it could involve ubiquitination (Wallace and Cidlowski, 2001). In cells transfected with GR constructs in which the cDNA is placed under control of a heterologous promoter, addition of glucocorticoid ligand downregulates GR expression. The absence of regulatory sequences in these constructs suggests down regulation at the post-transcriptional level. Indeed, it has been reported that mouse GR is degraded by the ubiquitinproteasome pathway (Wallace and Cidlowski, 2001).
V. REGULATION OF GENE EXPRESSION BY GR A. Transactivation of Genes Activation of gene expression by GR through DNAbinding involves glucocorticoid-response elements (GREs). These sequences, located in the regulatory regions of target genes, consist of two GRE-half sites separated by a three-base pair linker. The consensus sequence of a GRE has been defined as the imperfect palindrome GGTACAnnnTGTTCT. GR uses amino acids in the P-box of the DNA-binding domain to recognize the GRE’s nucleic acids from the major groove. A GR monomer first binds the most conserved 3’ half of the GRE after which a second monomer binds the 5’ half to form a DNA-bound dimer (Tsai et al., 1988). Once bound, GR can utilize several mechanisms to activate transcription (Figure 2). One mechanism involves the interaction of GR with TFIID, a key component of the basal transcription machinery, providing a means to directly regulate gene expression (Ford et al., 1997). However, in this case the GRE needs to be in direct proximity to the TATA-box. Another mechanism is provided by coactivators that can act as transcriptional bridges to interact with the basal transcription machinery (Glass and Rosenfeld, 2000; Rosenfeld and Glass, 2001). Members of the p160 family of transcription factors, for instance, contain NR-boxes with which they can interact with GR (Ding et al., 1998) and subsequently recruit secondary coactivators that can interact with the basal transcription machinery (Wang et al., 1998). Alternatively, these coactivators can possess histone acetyltransferase activity to loosen the interaction between histones and the DNA and thereby regulate transcription-factor access to the promoter (Vo and Goodman, 2001). As for an example, this is the case in the mouse mammary tumor virus gene (MMTV) promoter that contains positioned nucleosomes that hinder transcriptionfactor binding to the DNA. GR, however, is still able to bind its GRE in this repressive environment and
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FIGURE 2 Mechanisms of transactivation and transrepression by GR. In absence of glucocorticoid hormone, GR is complexed in the cytoplasm with heat-shock proteins and other proteins. Once bound by ligand, the glucocorticoid receptor migrates through the nuclear-pore complex to the nucleus. In the nucleus, GR can employ several mechanisms to regulate transcription. GR can bind directly to GREs and interact with general transcription factors to activate transcription. In addition, GR can recruit coactivators that can activate the basal transcription machinery or it can recruit coactivators with histone acetyltransferase activity to modify the local chromatin structure from a repressive into a permissive state. Transrepression can be achieved by interfering with transcription-factor binding to overlapping response elements. In addition, GR can interact with the DNA-bound transcription factor to render a transcriptionally inactive protein complex, or it can interact with a transcription factor to prevent it from binding the DNA.
recruits a set of coactivators with histone-acetyl transferase activity to the nucleosome-bound DNA. These coactivators displace the nucleosome, enabling transcription-factor binding adjacent binding sites to activate gene transcription (Archer et al., 1992; Blomquist et al., 1996; Deroo and Archer, 2001).
B. Transrepression of Genes When a GRE borders or overlaps with another transcription-factor binding site, the two transcription factors have to compete for DNA binding. Hence, activation of one would result in decreased transregula-
tion of the other. This is nicely exemplified in the rat α-fetoprotein gene where a GRE overlaps with an HNF4 binding site. Activation of GR strongly reduced the activity of this gene (Nakabayashi et al., 2001). Another example is the osteocalcin gene where the GRE overlaps the TATA-box and has to compete with TATA box-binding protein for DNA binding (Meyer et al., 1997). To date, we are only aware of one publication in which the nGRE sequence directs gene repression (Ou et al., 2001). In the neuronal serotonin receptor (5-1HT1A) gene, two directly repeated GRE-half sites are separated by a hexamer. When cells were treated with glucocorticoids, GR could repress expression of
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this gene by 40%. However, when this sequence was modified into a classical GRE, it increased gene expression by three- to four-fold. Besides these direct effects, GR can also exert its repressive effects by interacting with other transcription factors, including NFκB, AP-1, and nuclear factor of activated T-cells (NF-AT). NFκB plays an important role in regulating the expression of several proinflammatory genes (Barnes and Karin, 1997). The NFκB signaling pathway is activated by cytokines such as interleukin 1 (IL-1) and tumor-necrosis factor α (TNF-α) (Janeway and Medzhitov, 2002), but also by lipopolysaccharides (Janeway and Medzhitov, 2002), and UV (Adachi et al., 2003). The NFκB transcription
factor is composed of homo- and heterodimers of subunits from the NFκB/Rel family of transcription factors (p50, p52, RelA, c-Rel, and RelB) (Menetski, 2000). Interaction with the inhibitory subunit IκB retains NFκB in the cytoplasm via its ankyrin motif (Beg and Baldwin, 1993). Phosphorylation of IκB triggers ubiquitination and subsequent degradation by the proteasome (Karin and Ben-Neriah, 2000). Due to its constitutive phosphorylation, IκB has a half-life of only 1 to 2 hours (Rice and Ernst, 1993). Activation of the NFκB pathway activates IκB kinase (IKK) (Figure 3). The resulting hyperphosphorylation of IκB results in an increased rate of IκB degradation and releases NFκB for signaling to the nucleus. In the nucleus,
FIGURE 3 GR-mediated repression of NFκB signaling. In its inactive state, NFκB is retained in the cytoplasm in complex with IκB. Activation of the NFκB pathway by lipopolysaccharides or cytokines activates IκB kinase and leads to phosphorylation and subsequent degradation of IκB. The released NFκB can subsequently translocate to the nucleus to bind its response element in the regulatory regions of pro-inflammatory target genes to activate transcription. Glucocorticoids have been reported to repress NFκB signaling through multiple mechanisms. Activation of GR by glucocorticoid binding results in translocation to the nucleus where it can activate the expression of IκB and shifts the balance of NFκB localization towards the cytoplasmic compartment. GR can also interfere with NFκB signaling by interacting with NFκB and either prevent it from binding its response element or form a transcriptionally inactive protein complex on the DNA. An alternative but less-favored mechanism involves the competition between NFκB and GR for binding CBP/p300 that is present in the cell in limiting amounts.
1. Glucocorticoids and Immunity: Mechanisms of Regulation
NFκB can bind to regulatory regions of target genes and activate transcription of genes involved in the inflammatory process, including cytokines such as TNF-α (Collart et al., 1990) and IL-1β (Cogswell et al., 1994), but also inflammatory mediators such as cyclooxygenase-2 (COX-2) (Inoue and Tanabe, 1998; Nakao et al., 2002), inducible nitric oxide synthase (iNOS), and the cytosolic phospholipase A2 gene (cPLA2) (Morri et al., 1994). Several hypotheses have been postulated as to how glucocorticoids inhibit the pro-inflammatory actions of NFκB. First, due to the presence of a GRE in its regulatory region, glucocorticoids can upregulate the expression of IκB (Auphan et al., 1995; Scheinman et al., 1995a), thereby shifting the balance towards the cytoplasmic-localized NFκB. Second, it has been proposed that GR and NFκB compete for binding to CREB-binding protein (CBP)/p300. Since CBP/p300 is present in the cell in limiting amounts, activation of GR can repress the NFκB pathway. However, since NFκB and signal transducers of activated T-cells (STATs) are also targets for CPB/p300 but do not transrepress AP-1 activity, it is unlikely that such competition is the cause for glucocorticoid-mediated transrepression of these transcription factors (Karin and Chang, 2001). Indeed, McKay and Cidlowski have shown that although GR bound by antagonist RU486 is not able to interact with CBP/p300, it retains its ability to repress NFκB mediated transactivation (McKay and Cidlowski, 2000). These data, therefore, suggest that rather than acting as a coactivator for which NFκB and GR have to compete, CBP/p300 acts as a scaffolding protein that integrates NFκB and GR signaling. In the third model, activated GR can interact with NFκB via protein–protein interactions rendering the NFκB incapable of binding its response elements (McKay and Cidlowski, 1998). This model has become more and more accepted as the predominant mode of GR-mediated repression (Figure 2). Indeed, it has been reported that glucocorticoids can repress NFκB action by disturbing the interaction of p65 with the basal transcription machinery, rather than being dependent on the levels of coactivators in the cells (De Bosscher et al., 2000). Furthermore, it has been shown that GR and NFκB physically interact (Ray and Prefontaine, 1994; Scheinman et al., 1995b). Deletion analysis has shown that multiple GR domains are required for its transrepressive effect on NFκB (McKay and Cidlowski, 1998). An additional mechanism was suggested when it was shown that GR activation does not prevent NFκB from binding its response elements on the IL-8 promoter, but rather acts by recruiting repressor proteins to the target site on the DNA (Nissen and Yamamoto, 2000). Moreover, GR was able to recruit
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the transcriptional coactivator glucocorticoid receptor interacting protein-1 (GRIP-1) to the collagenase gene promoter and inhibit the transcriptional activator NFκB, turning GRIP-1 into a co-repressor (Rogatsky et al., 2001). Similar repressive mechanisms by glucocorticoids have been reported for other pro-inflammatory transcription factors. The AP-1 transcription factor, for instance, is involved in the regulation of several pro-inflammatory genes, including many cytokines (Johnson and Lapadat, 2002). AP-1 proteins are composed of homo- and heterodimeric proteins of the Jun, Fos, ATF, or Maf family of transcription factors (Angel and Karin, 1991). AP-1 dimers containing Jun recognize the AP-1 sequence (5’ TGAGCTCA) in the regulatory regions of target genes, while ATF-containing complexes recognize cAMP-responsive elements (5’ TGACGTCA). Differential expression of the AP-1 subunits allows regulation of the AP-1 activity (Bakiri et al., 2000; Chiu et al., 1989; Passegue and Wagner, 2000; Szabowski et al., 2000). Additional regulation can be achieved through AP-1 phosphorylation (Karin, 1995; Karin, 1998). Activation of AP-1 can be initiated by several stimuli, including growth factors (Quantin and Breathnach, 1988; Ryder and Nathans, 1988), TNF-α (Brenner et al., 1989), IL-1 (Goldgaber et al., 1989; Muegge et al., 1989), phorbol esters, and also by environmental stressors such as UV irradiation (Karin, 1998). These stimuli activate MAPK cascades that phosphorylate AP-1 and increase its activity. Once activated, AP-1 can bind to its response elements and regulate gene transcription of several inflammatory genes, including the collagenase gene (Schule et al., 1990). When the composition of the AP-1 complex is altered, different responses to different stimuli can be elicited. It has been shown, for instance, that a Jun-Fos heterodimer has a higher affinity for DNA than a Jun-Jun homodimer (Halazonetis et al., 1988). Glucocorticoids can negatively regulate the AP-1 mediated inflammatory response. It has been reported that GR can employ similar mechanisms to repress AP-1 as the ones repressing NFκB (Schule et al., 1990). Another transcription factor serving as a target of glucocorticoid action is the nuclear factor of activated T-cells (NF-AT). NF-AT was originally characterized as a transcription factor driving the transcription of the human IL-2 gene (Shaw et al., 1988). Four members of the NF-AT family have been identified so far (Hoey et al., 1995), regulating many genes that are activated upon T-cell activation (Kel et al., 1999). Activation of these genes involves NF-AT binding to its respective sites in regulatory regions, often acting synergistically with other transcription factors, including AP-1 in the IL-2 enhancer (Vacca et al., 1992) and Oct-1 in the IL-3
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enhancer (Duncliffe et al., 1997). In the IL-4 enhancer, NF-AT does not require cooperative interaction to drive transcription. Instead, cytoplasmic NF-AT becomes dephosphorylated in response to calcium and translocates to the nucleus to bind its response element in the IL-4 gene in order to activate transcription. Glucocorticoid treatment induces the formation of a complex between GR and NF-AT in the nucleus, thereby preventing NF-AT from binding the DNA (Chen et al., 2000).
VI. INHIBITORY EFFECTS OF GLUCOCORTICOIDS ON THE IMMUNE SYSTEM A. The Hypothalamic-Pituitary-Adrenal Gland Axis Transcription factors can regulate many genes. Therefore, the inhibition of pro-inflammatory transcription factors by glucocorticoids modulates a myriad of responses. Studies in animal models have suggested that defects in the HPA axis may increase the susceptibility to inflammatory disorders. Lewis rats, for instance, have reduced corticotropin-releasing hormone synthesis, rendering them more susceptible to streptococcal cell wall-induced arthritis (Sternberg et al., 1989a; Sternberg et al., 1989b). In agreement, supplementing glucocorticoids to these rats, thus restoring their physiological level, did reverse this phenotype. Studies in humans have shown that patients suffering from hypocortisolemia exhibit an increase in IL-2 synthesis by T-cells (Sauer et al., 1994). These examples show that defects in HPA-axis function may lead to elevated activation of inflammatory pathways. The central role of glucocorticoids in controlling the immune response suggests that there is a tight mutual regulation between the pro- and antiinflammatory pathways. Indeed, the inflammatory response is equipped with a classical feedback mechanism, triggering the release of the anti-inflammatory glucocorticoids. During the inflammatory response TNF-α, IL-1, and IL-6 mediate most of the feedback regulation on the HPA-axis (Akira et al., 1990; Hesse et al., 1988; van Deventer et al., 1990). These cytokines can independently as well as synergistically stimulate the release of adrenocorticotrophic hormone (ACTH) from the hypothalamus and pituitary, thus resulting in an increased production of glucocorticoids, thereby counteracting the inflammatory response (Adcock, 2001; Chrousos, 1995). Thus, defects in the functioning of the HPA-axis make individuals more susceptible to inflammatory diseases (Morand and Leech, 2001),
stressing the importance for the development of treatments for inflammatory diseases.
B. Upregulation of Anti-inflammatory Genes In the human body, many genes involved in catabolic processes are positively regulated by glucocorticoids, underscoring the role of GR in maintaining glucose homeostasis. However, besides these activating functions, glucocorticoids have an inhibitory effect on the immune system. One mechanism involves the activation of genes that negatively regulate the inflammatory response. For example, the lipocortin-1 (Hayashi et al., 2004), the secretory leukocyte protease inhibitor (SLPI) (Hayashi et al., 2004), and the glucocorticoid-induced leucine zipper (GILZ) (Cannarile et al., 2001; Mittelstadt and Ashwell, 2001; Riccardi et al., 1999) genes are all upregulated by glucocorticoids. However, most of the genes regulated by glucocorticoids and involved in the inflammatory response lack GREs or nGREs in their regulatory sequences. This paradox was reconciled when the major antiinflammatory actions of glucocorticoids were found to be mediated by a direct inhibitory interaction of the GR with pro-inflammatory transcription factors such as NFκB (Ray and Prefontaine, 1994), AP-1 (Adcock, 2001), and NF-AT (Chen et al., 2000). These transcription factors are activated by many stimuli and are considered of paramount importance in the inflammatory response (Baldwin, 2001). Over the years, it has become increasingly clear that, in contrast to NSAIDs, glucocorticoids act on multiple levels in the immune response in order to exert their repressive effects (Figure 4). Although the precise mechanisms in these responses are not always clear, transcription factors are thought to play a central role.
C. Glucocorticoid-mediated Post-transcriptional Regulation Glucocorticoids can increase mRNA turnover of target genes by increasing the expression of certain ribonucleases. These ribonucleases have been reported to act upon AU-rich regions in the 3’ UTR of certain genes, including GM-CSF (Bickel et al., 1990) and COX-2, thereby reducing mRNA half-life and subsequent protein synthesis (Newton et al., 1998; Nishimori et al., 2004; Ristimaki et al., 1996). A similar mechanism has been described for the interferon-β gene, in which the 3’ UTR is a target for glucocorticoids to increase interferon-β mRNA turnover (Peppel et al., 1991).
1. Glucocorticoids and Immunity: Mechanisms of Regulation
FIGURE 4 Glucocorticoids act on multiple levels in the immune response. By activating the expression of antiinflammatory proteins, GR can inhibit the immune response. GR can inhibit the transcriptional activity of pro-inflammatory transcription factors. This leads to altered cytokine production, reduced expression of cytokine receptor. Combined, these modifications affect many processes in the immune response including the development of T cells, but also the migration of leukocyte to the site of inflammation by inhibiting the expression of adhesion molecules.
Interleukin 5 (IL-5) is predominantly produced by Th2 cells to regulate differentiation and proliferation of eosinophils (Clutterbuck et al., 1989; Hamid et al., 1991; Ying et al., 1995). Since asthma is characterized by eosinophil infiltration of the airways, IL-5 is regarded as a major target for anti-asthma therapies (Djukanovic et al., 1990). Glucocorticoids have been shown to inhibit IL-5 synthesis, but the exact mechanism is unknown (Corrigan et al., 1993; Rolfe et al., 1992). Since dexamethasone does not inhibit IL-5 transcription, regulation most likely takes place via a posttranslational mechanism. It has been suggested that glucocorticoids upregulate the synthesis of mRNA destabilizing factor, thereby shortening IL-5 mRNA half-life (Staples et al., 2003).
D. Glucocorticoids Modulate the Innate Immune Response The vascular endothelium plays a crucial role in the immune response by directing leukocytes to the site of inflammation. Endothelial cells express a set of adhesion molecules on their cell surface, including ICAM-1, endothelial-leukocyte adhesion molecule 1 (ELAM-1) (Cronstein et al., 1992), and E-selectin (Brostjan et al., 1997), all of which are involved in directing leukocytes to the site of inflammation (Caldenhoven et al., 1995; Cronstein et al., 1992). Glucocorticoids possess the ability to negatively regulate the expression of these adhesion molecules, thus providing a mechanism of
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inhibiting the inflammatory response. The ICAM-1 and E-selectin genes, for instance, contain NF-κB binding sites in their regulatory regions. Association of GR to NF-κB does not prevent NF-κB from binding the ICAM-1 gene. Instead, a transcriptionally inactive transcription-factor complex is formed on the DNA (Brostjan et al., 1997; Liden et al., 2000). Besides these inhibitory effects of glucocorticoids, certain proinflammatory genes related to the innate immune response are upregulated by glucocorticoids (Galon et al., 2002). TLR-2, for instance, contains binding sites for NFκB, STAT, and GR, which have been shown to synergistically activate gene transcription (Hermoso et al., 2004). Furthermore, microarray analysis using peripheral blood mononuclear cells suggested that while genes involved in the adaptive immune response are downregulated by glucocorticoids, a number of genes of the innate immune response are upregulated by glucocorticoids (Galon et al., 2002). Such upregulation of pro-inflammatory genes by glucocorticoid hormones suggests an interesting mechanistic discrimination between the innate and the adaptive immune response. It has been suggested that glucocorticoids stimulate the clearance of antigens by promoting the innate immune response, while inhibiting the adaptive immune response (Galon et al., 2002).
E. Glucocorticoids Affect Cytokine Production Cytokines, being signaling molecules between different cells, are produced at multiple levels during the immune response. There are many reports indicating a glucocorticoid-mediated inhibition of cytokine expression including, but not limited to, IL-1 through IL-6, IL-8, IL-11, IL-12, IL-16, IFN-γ, and TNF-α (Almawi et al., 1991; Amano et al., 1993; Arima et al., 1999; Blotta et al., 1997; Chen et al., 2000; Culpepper and Lee, 1985; Elenkov et al., 1996; Haynesworth et al., 1996; Kunicka et al., 1993; Paliogianni and Boumpas, 1995; Tobler et al., 1992). T-cell activation, for instance, triggers intracellular signaling cascades, including the NFκB, AP-1 and NF-AT pathways. These transcription factors can regulate the expression of cytokine genes. The IL-2 gene, for instance, has binding sites for all these three transcription factors, allowing synergistic action of the transcription factors (Durand et al., 1988; Paliogianni et al., 1993; Vacca et al., 1992). Administration of glucocorticoids inhibits expression of the IL-2 gene, most likely through protein–protein interaction with AP-1, thereby preventing it from forming a protein complex on the DNA that can activate transcription (Paliogianni et al., 1993).
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F. Glucocorticoids Can Regulate the Expression of Cytokine Receptors Glucocorticoids have been shown to modulate the expression of several cytokine receptors including those for TNF-α, IL-1, IL-2, IL-6, IL-12, IFN-γ, and GMCSF (Almawi et al., 1996; Wiegers and Reul, 1998). The IL-4 receptor, for instance, is downregulated by dexamethasone. Nuclear run-on assays indicated that this regulation did not take place at the transcriptional level. Instead, mRNA stability assays showed that dexamethasone decreased mRNA stability of the receptor (Mozo et al., 1998). Another example is the IL-12 receptor that is primarily expressed on T-cells and NK cells (Desai et al., 1992). IL-12 binding to the receptor induces intracellular signaling cascades regulating the generation and stability of Th1 and Th2 responses. It has been established that dexamethasone can decrease the expression of the IL-12 receptor at the cell surface, although the exact mechanism remains largely unclear (Wu et al., 1998).
G. Glucocorticoids Modulate the Adaptive Immune Response Naïve T helper cells serve as precursors of Th1 and Th2 cells in the adaptive immune response. The differentiation of a Th precursor cell into a Th1 or a Th2 cell depends on the cytokines that are locally present. The production of IL-12 by antigen-presenting cells has been shown to direct the response into a Th1 response (Trinchieri, 1995), whereas IL-4 has been reported to develop the Th2 response (Paul and Seder, 1994). Th1 helper cells produce IL-2, IFN-γ, and TNF-β and are involved in regulation of the cellular immunity by activating cytotoxic T-cells, natural killer cells, and macrophages. In contrast, Th2 cells produce IL-4, IL-5, IL-6, IL-10, and IL-13 cytokines that regulate humoral immunity by promoting the proliferation and activation of mast cells and eosinophils, and by promoting B-cell differentiation into antibody-secreting cells (Mosmann and Sad, 1996). Besides stimulating the response into the Th1 or Th2 direction, these cytokines simultaneously inhibit development of the reciprocal phenotype (Mosmann and Sad, 1996). Glucocorticoids can shift the Th1/Th2 balance into the direction of the Th2-mediated humoral immunity (Elenkov et al., 1996). The main underlying mechanism of this shift results from the selective repression of Th1 cytokine production as well as the upregulation of Th2-cytokine synthesis mainly through inhibition of IL-12 production by antigen-presenting cells (Blotta et al., 1997). In addition, glucocorticoids inhibit the expression of the
IL-12 receptor in T-cells and NK cells (Elenkov, 2004; Wu et al., 1998). Increased glucocorticoid production from endogenous origin due to various stress factors may have a great impact on the outcome of the immune response. Cellular responses to viral infections, such as common cold and Herpes simplex virus, may be seriously impaired in such cases. Psychological stress can, for instance, increase the susceptibility to respiratory infections in humans (Cohen et al., 1991). Furthermore, it has been suggested that impairment of the host’s cellular response by stress-associated immunomodulation can affect the defense against herpes simplex virus (Sainz et al., 2001).
VII. PERSPECTIVES The glucocorticoid receptor acts as a liganddependent transcriptional regulator and plays an important role in the regulation of catabolic genes to maintain glucose homeostasis. In addition, it is also an important negative regulator for counteracting the effects of the immune response. Today, glucocorticoids are among the most powerful antiphlogistic drugs, but their severe adverse effects rival their beneficial therapeutic effects. Research over several decades trying to uncouple the transactivating from the transrepressive effect has led to the development of synthetic glucocorticoids that have lower adverse effects but are usually less effective. It has become increasingly clear that the glucocorticoid receptor employs diverse mechanisms to inhibit pro-inflammatory signaling pathways. First, the receptor itself is the subject of regulation at the transcriptional, post-transcriptional, and post-translational levels. Second, it can positively regulate anti-inflammatory genes and downregulate pro-inflammatory genes by direct binding to its response element on the regulatory regions of target genes. Also, it can inhibit the activity of proinflammatory transcription factors by formation of a protein complex that is either transcriptionally inactive or cannot bind DNA. Furthermore, the effects of the antiphlogistic mechanisms of glucocorticoids become apparent at multiple levels throughout the immune response. A better in-depth understanding of the regulatory mechanisms of the pro- and anti-inflammatory pathways as well as the complex crosstalk between these two pathways may help to develop better therapeutic regimens for the drugs currently available and assist in defining new therapeutic targets for the ongoing development of safe and effective antiinflammatory drugs.
1. Glucocorticoids and Immunity: Mechanisms of Regulation
References Adachi, M., Gazel, A., Pintucci, G., Shuck, A., Shifteh, S., Ginsburg, D., Rao, L. S., Kaneko, T., Freedberg, I. M., Tamaki, K., and Blumenberg, M. (2003). Specificity in stress response: epidermal keratinocytes exhibit specialized UV-responsive signal transduction pathways. DNA Cell Biol., 22, 665–677. Adcock, I. M. (2001). Glucocorticoid-regulated transcription factors. Pulm. Pharmacol. Ther., 14, 211–219. Akira, S., Hirano, T., Taga, T., and Kishimoto, T. (1990). Biology of multifunctional cytokines: IL 6 and related molecules (IL 1 and TNF). FASEB J., 4, 2860–2867. Alexopoulou, L., Holt, A. C., Medzhitov, R., and Flavell, R. A. (2001). Recognition of double-stranded RNA and activation of NFkappaB by Toll-like receptor 3. Nature, 413, 732–738. Almawi, W. Y., Beyhum, H. N., Rahme, A. A., and Rieder, M. J. (1996). Regulation of cytokine and cytokine receptor expression by glucocorticoids. J. Leukoc. Biol., 60, 563–572. Almawi, W. Y., Lipman, M. L., Stevens, A. C., Zanker, B., Hadro, E. T., and Strom, T. B. (1991). Abrogation of glucocorticoidmediated inhibition of T cell proliferation by the synergistic action of IL-1, IL-6, and IFN-gamma. J. Immunol., 146, 3523–3527. Almlof, T., Wright, A. P., and Gustafsson, J. A. (1995). Role of acidic and phosphorylated residues in gene activation by the glucocorticoid receptor. J. Biol. Chem., 270, 17535–17540. Amano, Y., Lee, S. W., and Allison, A. C. (1993). Inhibition by glucocorticoids of the formation of interleukin-1 alpha, interleukin-1 beta, and interleukin-6: mediation by decreased mRNA stability. Mol. Pharmacol., 43, 176–182. Angel, P., and Karin, M. (1991). The role of Jun, Fos and the AP-1 complex in cell-proliferation and transformation. Biochim. Biophys. Acta., 1072, 129–157. Archer, T. K., Lefebvre, P., Wolford, R. G., and Hager, G. L. (1992). Transcription factor loading on the MMTV promoter: a bimodal mechanism for promoter activation. Science, 255, 1573–1576. Arima, M., Plitt, J., Stellato, C., Bickel, C., Motojima, S., Makino, S., Fukuda, T., and Schleimer, R. P. (1999). Expression of interleukin16 by human epithelial cells. Inhibition by dexamethasone. Am. J. Respir. Cell Mol. Biol., 21, 684–692. Auphan, N., DiDonato, J. A., Rosette, C., Helmberg, A., and Karin, M. (1995). Immunosuppression by glucocorticoids: inhibition of NF-kappa B activity through induction of I kappa B synthesis. Science, 270, 286–290. Bakiri, L., Lallemand, D., Bossy-Wetzel, E., and Yaniv, M. (2000). Cell cycle-dependent variations in c-Jun and JunB phosphorylation: a role in the control of cyclin D1 expression. EMBO J., 19, 2056–2068. Baldwin, A. S., Jr. (2001). Series introduction: the transcription factor NF-kappaB and human disease. J. Clin. Invest., 107, 3–6. Barnes, P. J., and Karin, M. (1997). Nuclear factor-kappaB: a pivotal transcription factor in chronic inflammatory diseases. N. Engl. J. Med., 336, 1066–1071. Beg, A. A., and Baldwin, A. S., Jr. (1993). The I kappa B proteins: multifunctional regulators of Rel/NF-kappa B transcription factors. Genes Dev., 7, 2064–2070. Belvisi, M. G., Brown, T. J., Wicks, S., and Foster, M. L. (2001). New glucocorticosteroids with an improved therapeutic ratio? Pulm. Pharmacol. Ther., 14, 221–227. Bianchi, E., Bender, J. R., Blasi, F., and Pardi, R. (1997). Through and beyond the wall: late steps in leukocyte transendothelial migration. Immunol. Today, 18, 586–591.
57
Bickel, M., Cohen, R. B., and Pluznik, D. H. (1990). Post-transcriptional regulation of granulocyte-macrophage colony-stimulating factor synthesis in murine T cells. J. Immunol., 145, 840–845. Black, B. E., Holaska, J. M., Rastinejad, F., and Paschal, B. M. (2001). DNA binding domains in diverse nuclear receptors function as nuclear export signals. Curr. Biol., 11, 1749–1758. Blomquist, P., Li, Q., and Wrange, O. (1996). The affinity of nuclear factor 1 for its DNA site is drastically reduced by nucleosome organization irrespective of its rotational or translational position. J. Biol. Chem., 271, 153–159. Blotta, M. H., DeKruyff, R. H., and Umetsu, D. T. (1997). Corticosteroids inhibit IL-12 production in human monocytes and enhance their capacity to induce IL-4 synthesis in CD4+ lymphocytes. J. Immunol., 158, 5589–5595. Bodwell, J. E., Hu, J. M., Orti, E., and Munck, A. (1995). Hormoneinduced hyperphosphorylation of specific phosphorylated sites in the mouse glucocorticoid receptor. J. Steroid Biochem. Mol. Biol., 52, 135–140. Bodwell, J. E., Orti, E., Coull, J. M., Pappin, D. J., Smith, L. I., and Swift, F. (1991). Identification of phosphorylated sites in the mouse glucocorticoid receptor. J. Biol. Chem., 266, 7549–7555. Bodwell, J. E., Webster, J. C., Jewell, C. M., Cidlowski, J. A., Hu, J. M., and Munck, A. (1998). Glucocorticoid receptor phosphorylation: overview, function and cell cycle-dependence. J. Steroid Biochem. Mol. Biol., 65, 91–99. Bogyo, M., Gaczynska, M., and Ploegh, H. L. (1997). Proteasome inhibitors and antigen presentation. Biopolymers, 43, 269–280. Brenner, D. A., O’Hara, M., Angel, P., Chojkier, M., and Karin, M. (1989). Prolonged activation of jun and collagenase genes by tumour necrosis factor-alpha. Nature, 337, 661–663. Breslin, M. B., Geng, C. D., and Vedeckis, W. V. (2001). Multiple promoters exist in the human GR gene, one of which is activated by glucocorticoids. Mol. Endocrinol., 15, 1381–1395. Bretscher, P. (1992). The two-signal model of lymphocyte activation twenty-one years later. Immunol. Today, 13, 74–76. Brostjan, C., Anrather, J., Csizmadia, V., Natarajan, G., and Winkler, H. (1997). Glucocorticoids inhibit E-selectin expression by targeting NF-kappaB and not ATF/c-Jun. J. Immunol., 158, 3836–3844. Cadepond, F., Gasc, J. M., Delahaye, F., Jibard, N., Schweizer-Groyer, G., Segard-Maurel, I., Evans, R., and Baulieu, E. E. (1992). Hormonal regulation of the nuclear localization signals of the human glucocorticosteroid receptor. Exp. Cell Res., 201, 99–108. Caldenhoven, E., Liden, J., Wissink, S., Van de Stolpe, A., Raaijmakers, J., Koenderman, L., Okret, S., Gustafsson, J. A., and Van der Saag, P. T. (1995). Negative cross-talk between RelA and the glucocorticoid receptor: a possible mechanism for the antiinflammatory action of glucocorticoids. Mol. Endocrinol., 9, 401–412. Cannarile, L., Zollo, O., D’Adamio, F., Ayroldi, E., Marchetti, C., Tabilio, A., Bruscoli, S., and Riccardi, C. (2001). Cloning, chromosomal assignment and tissue distribution of human GILZ, a glucocorticoid hormone-induced gene. Cell Death Differ., 8, 201–203. Chaplin, D. D. (2003). 1. Overview of the immune response. J. Allergy. Clin. Immunol., 111, S442–459. Chen, R., Burke, T. F., Cumberland, J. E., Brummet, M., Beck, L. A., Casolaro, V., and Georas, S. N. (2000). Glucocorticoids inhibit calcium- and calcineurin-dependent activation of the human IL-4 promoter. J. Immunol., 164, 825–832. Chiu, R., Angel, P., and Karin, M. (1989). Jun-B differs in its biological properties from, and is a negative regulator of, c-Jun. Cell, 59, 979–986. Christoffels, V. M., Habets, P. E., Das, A. T., Clout, D. E., van Roon, M. A., Moorman, A. F., and Lamers, W. H. (2000). A single
58
I. Neural and Endocrine Effects on Immunity
regulatory module of the carbamoylphosphate synthetase I gene executes its hepatic program of expression. J. Biol. Chem., 275, 40020–40027. Chrousos, G. P. (1995). The hypothalamic-pituitary-adrenal axis and immune-mediated inflammation. N. Engl. J. Med., 332, 1351–1362. Clark, J. V. (1968). Complications of steroid therapy. Manit. Med. Rev., 48, 454–461. Clutterbuck, E. J., Hirst, E. M., and Sanderson, C. J. (1989). Human interleukin-5 (IL-5) regulates the production of eosinophils in human bone marrow cultures: comparison and interaction with IL-1, IL-3, IL-6, and GMCSF. Blood, 73, 1504–1512. Coghlan, M. J., Elmore, S. W., Kym, P. R., and Kort, M. E. (2003). The pursuit of differentiated ligands for the glucocorticoid receptor. Curr. Top. Med. Chem., 3, 1617–1635. Cogswell, J. P., Godlevski, M. M., Wisely, G. B., Clay, W. C., Leesnitzer, L. M., Ways, J. P., and Gray, J. G. (1994). NF-kappa B regulates IL-1 beta transcription through a consensus NF-kappa B binding site and a nonconsensus CRE-like site. J. Immunol., 153, 712–723. Cohen, S., Tyrrell, D. A., and Smith, A. P. (1991). Psychological stress and susceptibility to the common cold. N. Engl. J. Med., 325, 606–612. Collart, M. A., Baeuerle, P., and Vassalli, P. (1990). Regulation of tumor necrosis factor alpha transcription in macrophages: involvement of four kappa B-like motifs and of constitutive and inducible forms of NF-kappa B. Mol. Cell Biol., 10, 1498–1506. Corrigan, C. J., Haczku, A., Gemou-Engesaeth, V., Doi, S., Kikuchi, Y., Takatsu, K., Durham, S. R., and Kay, A. B. (1993). CD4 Tlymphocyte activation in asthma is accompanied by increased serum concentrations of interleukin-5. Effect of glucocorticoid therapy. Am. Rev. Respir. Dis., 147, 540–547. Cronstein, B. N., Kimmel, S. C., Levin, R. I., Martiniuk, F., and Weissmann, G. (1992). A mechanism for the antiinflammatory effects of corticosteroids: the glucocorticoid receptor regulates leukocyte adhesion to endothelial cells and expression of endothelial-leukocyte adhesion molecule 1 and intercellular adhesion molecule 1. Proc. Natl. Acad. Sci. USA, 89, 9991–9995. Culpepper, J. A., and Lee, F. (1985). Regulation of IL 3 expression by glucocorticoids in cloned murine T lymphocytes. J. Immunol., 135, 3191–3197. De Bosscher, K., Vanden Berghe, W., Vermeulen, L., Plaisance, S., Boone, E., and Haegeman, G. (2000). Glucocorticoids repress NFkappaB-driven genes by disturbing the interaction of p65 with the basal transcription machinery, irrespective of coactivator levels in the cell. Proc. Natl. Acad. Sci. USA, 97, 3919–3924. Degli-Esposti, M. A., and Smyth, M. J. (2005). Close encounters of different kinds: dendritic cells and NK cells take centre stage. Nat. Rev. Immunol., 5, 112–124. Del-Val, M., and Lopez, D. (2002). Multiple proteases process viral antigens for presentation by MHC class I molecules to CD8(+) T lymphocytes. Mol. Immunol., 39, 235–247. Deroo, B. J., and Archer, T. K. (2001). Glucocorticoid receptormediated chromatin remodeling in vivo. Oncogene, 20, 3039–3046. Desai, B. B., Quinn, P. M., Wolitzky, A. G., Mongini, P. K., Chizzonite, R., and Gately, M. K. (1992). IL-12 receptor. II. Distribution and regulation of receptor expression. J. Immunol., 148, 3125–3132. Dickey, R. F. (1976). Parenteral short-term corticosteroid therapy in moderate to severe dermatoses. A comparative multiclinic study. Cutis, 17, 179–183. Ding, X. F., Anderson, C. M., Ma, H., Hong, H., Uht, R. M., Kushner, P. J., and Stallcup, M. R. (1998). Nuclear receptor-binding sites of
coactivators glucocorticoid receptor interacting protein 1 (GRIP1) and steroid receptor coactivator 1 (SRC-1): multiple motifs with different binding specificities. Mol. Endocrinol., 12, 302–313. Djukanovic, R., Roche, W. R., Wilson, J. W., Beasley, C. R., Twentyman, O. P., Howarth, R. H., and Holgate, S. T. (1990). Mucosal inflammation in asthma. Am. Rev. Respir. Dis., 142, 434–457. Duncliffe, K. N., Bert, A. G., Vadas, M. A., and Cockerill, P. N. (1997). A T cell-specific enhancer in the interleukin-3 locus is activated cooperatively by Oct and NFAT elements within a DNase Ihypersensitive site. Immunity, 6, 175–185. Durand, D. B., Shaw, J. P., Bush, M. R., Replogle, R. E., Belagaje, R., and Crabtree, G. R. (1988). Characterization of antigen receptor response elements within the interleukin-2 enhancer. Mol. Cell. Biol., 8, 1715–1724. Elenkov, I. J. (2004). Glucocorticoids and the Th1/Th2 balance. Ann. N. Y. Acad. Sci., 1024, 138–146. Elenkov, I. J., Papanicolaou, D. A., Wilder, R. L., and Chrousos, G. P. (1996). Modulatory effects of glucocorticoids and catecholamines on human interleukin-12 and interleukin-10 production: clinical implications. Proc. Assoc. Am. Physicians, 108, 374–381. Encio, I. J., and Detera-Wadleigh, S. D. (1991). The genomic structure of the human glucocorticoid receptor. J. Biol. Chem., 266, 7182–7188. Eriksson, M. A., and Nilsson, L. (1998). Structural and dynamic effects of point mutations in the recognition helix of the glucocorticoid receptor DNA-binding domain. Protein Eng., 11, 589–600. Fearon, D. T., and Austen, K. F. (1975). Initiation of C3 cleavage in the alternative complement pathway. J. Immunol., 115, 1357–1361. Fearon, D. T., and Carroll, M. C. (2000). Regulation of B lymphocyte responses to foreign and self-antigens by the CD19/CD21 complex. Annu. Rev. Immunol., 18, 393–422. Ford, J., McEwan, I. J., Wright, A. P., and Gustafsson, J. A. (1997). Involvement of the transcription factor IID protein complex in gene activation by the N-terminal transactivation domain of the glucocorticoid receptor in vitro. Mol. Endocrinol., 11, 1467–1475. Freedman, N. D., and Yamamoto, K. R. (2004). Importin 7 and importin alpha/importin beta are nuclear import receptors for the glucocorticoid receptor. Mol. Biol. Cell, 15, 2276–2286. Gahmberg, C. G. (1997). Leukocyte adhesion: CD11/CD18 integrins and intercellular adhesion molecules. Curr. Opin. Cell Biol., 9, 643–650. Galon, J., Franchimont, D., Hiroi, N., Frey, G., Boettner, A., EhrhartBornstein, M., O’Shea, J. J., Chrousos, G. P., and Bornstein, S. R. (2002). Gene profiling reveals unknown enhancing and suppressive actions of glucocorticoids on immune cells. FASEB J., 16, 61–71. Geng, C. D., and Vedeckis, W. V. (2004). Steroid-responsive sequences in the human glucocorticoid receptor gene 1A promoter. Mol. Endocrinol., 18, 912–924. Glass, C. K., and Rosenfeld, M. G. (2000). The coregulator exchange in transcriptional functions of nuclear receptors. Genes Dev., 14, 121–141. Goldgaber, D., Harris, H. W., Hla, T., Maciag, T., Donnelly, R. J., Jacobsen, J. S., Vitek, M. P., and Gajdusek, D. C. (1989). Interleukin 1 regulates synthesis of amyloid beta-protein precursor mRNA in human endothelial cells. Proc. Natl. Acad. Sci. USA, 86, 7606–7610. Gonzalez-Amaro, R., and Sanchez-Madrid, F. (1999). Cell adhesion molecules: selectins and integrins. Crit. Rev. Immunol., 19, 389–429. Halazonetis, T. D., Georgopoulos, K., Greenberg, M. E., and Leder, P. (1988). c-Jun dimerizes with itself and with c-Fos, forming
1. Glucocorticoids and Immunity: Mechanisms of Regulation complexes of different DNA binding affinities. Cell, 55, 917– 924. Hamid, Q., Azzawi, M., Ying, S., Moqbel, R., Wardlaw, A. J., Corrigan, C. J., Bradley, B., Durham, S. R., Collins, J. V., and Jeffery, P. K. et al. (1991). Expression of mRNA for interleukin-5 in mucosal bronchial biopsies from asthma. J. Clin. Invest, 87, 1541–1546. Harreman, M. T., Kline, T. M., Milford, H. G., Harben, M. B., Hodel, A. E., and Corbett, A. H. (2004). Regulation of nuclear import by phosphorylation adjacent to nuclear localization signals. J. Biol. Chem., 279, 20613–20621. Hayashi, R., Wada, H., Ito, K., and Adcock, I. M. (2004). Effects of glucocorticoids on gene transcription. Eur. J. Pharmacol., 500, 51–62. Haynesworth, S. E., Baber, M. A., and Caplan, A. I. (1996). Cytokine expression by human marrow-derived mesenchymal progenitor cells in vitro: effects of dexamethasone and IL-1 alpha. J. Cell Physiol., 166, 585–592. Hermoso, M. A., Matsuguchi, T., Smoak, K., and Cidlowski, J. A. (2004). Glucocorticoids and tumor necrosis factor alpha cooperatively regulate toll-like receptor 2 gene expression. Mol. Cell. Biol., 24, 4743–4756. Hesse, D. G., Tracey, K. J., Fong, Y., Manogue, K. R., Palladino, M. A., Jr., Cerami, A., Shires, G. T., and Lowry, S. F. (1988). Cytokine appearance in human endotoxemia and primate bacteremia. Surg. Gynecol. Obstet., 166, 147–153. Hoey, T., Sun, Y. L., Williamson, K., and Xu, X. (1995). Isolation of two new members of the NF-AT gene family and functional characterization of the NF-AT proteins. Immunity, 2, 461–472. Hollenberg, S. M., and Evans, R. M. (1988). Multiple and cooperative trans-activation domains of the human glucocorticoid receptor. Cell, 55, 899–906. Howard, K. J., and Distelhorst, C. W. (1988). Evidence for intracellular association of the glucocorticoid receptor with the 90-kDa heat shock protein. J. Biol. Chem., 263, 3474–3481. Inoue, H., and Tanabe, T. (1998). Transcriptional role of the nuclear factor kappa B site in the induction by lipopolysaccharide and suppression by dexamethasone of cyclooxygenase-2 in U937 cells. Biochem. Biophys. Res. Commun., 244, 143–148. Janeway, C. A., Jr., and Medzhitov, R. (2002). Innate immune recognition. Annu. Rev. Immunol., 20, 197–216. Jewell, C. M., Webster, J. C., Burnstein, K. L., Sar, M., Bodwell, J. E., and Cidlowski, J. A. (1995). Immunocytochemical analysis of hormone mediated nuclear translocation of wild type and mutant glucocorticoid receptors. J. Steroid Biochem. Mol. Biol., 55, 135–146. Johnson, G. L., and Lapadat, R. (2002). Mitogen-activated protein kinase pathways mediated by ERK, JNK, and p38 protein kinases. Science, 298, 1911–1912. Karin, M. (1995). The regulation of AP-1 activity by mitogen-activated protein kinases. J. Biol. Chem., 270, 16483–16486. Karin, M. (1998). Mitogen-activated protein kinase cascades as regulators of stress responses. Ann. N. Y. Acad. Sci., 851, 139–146. Karin, M., and Ben-Neriah, Y. (2000). Phosphorylation meets ubiquitination: the control of NF-[kappa]B activity. Annu. Rev. Immunol., 18, 621–663. Karin, M., and Chang, L. (2001). AP-1–glucocorticoid receptor crosstalk taken to a higher level. J. Endocrinol, 169, 447–451. Kel, A., Kel-Margoulis, O., Babenko, V., and Wingender, E. (1999). Recognition of NFATp/AP-1 composite elements within genes induced upon the activation of immune cells. J. Mol. Biol., 288, 353–376. Kunicka, J. E., Talle, M. A., Denhardt, G. H., Brown, M., Prince, L. A., and Goldstein, G. (1993). Immunosuppression by gluco-
59
corticoids: inhibition of production of multiple lymphokines by in vivo administration of dexamethasone. Cell. Immunol., 149, 39–49. Liden, J., Rafter, I., Truss, M., Gustafsson, J. A., and Okret, S. (2000). Glucocorticoid effects on NF-kappaB binding in the transcription of the ICAM-1 gene. Biochem. Biophys. Res. Commun., 273, 1008–1014. Liszewski, M. K., Farries, T. C., Lublin, D. M., Rooney, I. A., and Atkinson, J. P. (1996). Control of the complement system. Adv. Immunol., 61, 201–283. Lu, N. Z., and Cidlowski, J. A. (2004). The origin and functions of multiple human glucocorticoid receptor isoforms. Ann. N. Y. Acad. Sci., 1024, 102–123. Lu, N. Z., and Cidlowski, J. A. (2005). Translational regulatory mechanisms generate N-terminal glucocorticoid receptor isoforms with unique transcriptional target genes. Mol. Cell, 18, 331–342. Luisi, B. F., Xu, W. X., Otwinowski, Z., Freedman, L. P., Yamamoto, K. R., and Sigler, P. B. (1991). Crystallographic analysis of the interaction of the glucocorticoid receptor with DNA. Nature, 352, 497–505. Mason, S. A., and Housley, P. R. (1993). Site-directed mutagenesis of the phosphorylation sites in the mouse glucocorticoid receptor. J. Biol. Chem., 268, 21501–21504. McKay, L. I., and Cidlowski, J. A. (1998). Cross-talk between nuclear factor-kappa B and the steroid hormone receptors: mechanisms of mutual antagonism. Mol. Endocrinol., 12, 45–56. McKay, L. I., and Cidlowski, J. A. (2000). CBP (CREB binding protein) integrates NF-kappaB (nuclear factor-kappaB) and glucocorticoid receptor physical interactions and antagonism. Mol. Endocrinol., 14, 1222–1234. Menetski, J. P. (2000). The structure of the nuclear factor-kappaB protein-DNA complex varies with DNA-binding site sequence. J. Biol. Chem., 275, 7619–7625. Meyer, T., Carlstedt-Duke, J., and Starr, D. B. (1997). A weak TATA box is a prerequisite for glucocorticoid-dependent repression of the osteocalcin gene. J. Biol. Chem., 272, 30709–30714. Miesfeld, R., Godowski, P. J., Maler, B. A., and Yamamoto, K. R. (1987). Glucocorticoid receptor mutants that define a small region sufficient for enhancer activation. Science, 236, 423–427. Mittelstadt, P. R., and Ashwell, J. D. (2001). Inhibition of AP-1 by the glucocorticoid-inducible protein GILZ. J. Biol. Chem., 276, 29603–29610. Morand, E. F., and Leech, M. (2001). Hypothalamic-pituitary-adrenal axis regulation of inflammation in rheumatoid arthritis. Immunol. Cell Biol., 79, 395–399. Morgan, B. P., and Harris, C. L. (2003). Complement therapeutics; history and current progress. Mol. Immunol., 40, 159–170. Morri, H., Ozaki, M., and Watanabe, Y. (1994). 5’-flanking region surrounding a human cytosolic phospholipase A2 gene. Biochem. Biophys. Res. Commun., 205, 6–11. Mosmann, T. R., and Coffman, R. L. (1989). TH1 and TH2 cells: different patterns of lymphokine secretion lead to different functional properties. Annu. Rev. Immunol., 7, 145–173. Mosmann, T. R., and Sad, S. (1996). The expanding universe of T-cell subsets: Th1, Th2 and more. Immunol. Today, 17, 138– 146. Mozo, L., Gayo, A., Suarez, A., Rivas, D., Zamorano, J., and Gutierrez, C. (1998). Glucocorticoids inhibit IL-4 and mitogen-induced IL-4R alpha chain expression by different posttranscriptional mechanisms. J. Allergy Clin. Immunol., 102, 968–976. Muegge, K., Williams, T. M., Kant, J., Karin, M., Chiu, R., Schmidt, A., Siebenlist, U., Young, H. A., and Durum, S. K. (1989). Interleukin-1 costimulatory activity on the interleukin-2 promoter via AP-1. Science, 246, 249–251.
60
I. Neural and Endocrine Effects on Immunity
Nakabayashi, H., Koyama, Y., Sakai, M., Li, H. M., Wong, N. C., and Nishi, S. (2001). Glucocorticoid stimulates primate but inhibits rodent alpha-fetoprotein gene promoter. Biochem. Biophys. Res. Commun., 287, 160–172. Nakao, S., Ogtata, Y., Shimizu, E., Yamazaki, M., Furuyama, S., and Sugiya, H. (2002). Tumor necrosis factor alpha (TNF-alpha)induced prostaglandin E2 release is mediated by the activation of cyclooxygenase-2 (COX-2) transcription via NFkappaB in human gingival fibroblasts. Mol. Cell. Biochem., 238, 11–18. Newton, R., Seybold, J., Kuitert, L. M., Bergmann, M., and Barnes, P. J. (1998). Repression of cyclooxygenase-2 and prostaglandin E2 release by dexamethasone occurs by transcriptional and posttranscriptional mechanisms involving loss of polyadenylated mRNA. J. Biol. Chem., 273, 32312–32321. Nishimori, T., Inoue, H., and Hirata, Y. (2004). Involvement of the 3’-untranslated region of cyclooxygenase-2 gene in its posttranscriptional regulation through the glucocorticoid receptor. Life Sci., 74, 2505–2513. Nissen, R. M., and Yamamoto, K. R. (2000). The glucocorticoid receptor inhibits NFkappaB by interfering with serine-2 phosphorylation of the RNA polymerase II carboxy-terminal domain. Genes Dev., 14, 2314–2329. Ou, X. M., Storring, J. M., Kushwaha, N., and Albert, P. R. (2001). Heterodimerization of mineralocorticoid and glucocorticoid receptors at a novel negative response element of the 5-HT1A receptor gene. J. Biol. Chem., 276, 14299–14307. Paliogianni, F., and Boumpas, D. T. (1995). Glucocorticoids regulate calcineurin-dependent trans-activating pathways for interleukin2 gene transcription in human T lymphocytes. Transplantation, 59, 1333–1339. Paliogianni, F., Raptis, A., Ahuja, S. S., Najjar, S. M., and Boumpas, D. T. (1993). Negative transcriptional regulation of human interleukin 2 (IL-2) gene by glucocorticoids through interference with nuclear transcription factors AP-1 and NF-AT. J. Clin. Invest., 91, 1481–1489. Pasare, C., and Medzhitov, R. (2004). Toll-like receptors: linking innate and adaptive immunity. Microbes Infect., 6, 1382–1387. Passegue, E., and Wagner, E. F. (2000). JunB suppresses cell proliferation by transcriptional activation of p16(INK4a) expression. EMBO J., 19, 2969–2979. Paul, W. E., and Seder, R. A. (1994). Lymphocyte responses and cytokines. Cell, 76, 241–251. Peppel, K., Vinci, J. M., and Baglioni, C. (1991). The AU-rich sequences in the 3’ untranslated region mediate the increased turnover of interferon mRNA induced by glucocorticoids. J. Exp. Med., 173, 349–355. Pitcher, L. A., and van Oers, N. S. (2003). T-cell receptor signal transmission: who gives an ITAM? Trends Immunol., 24, 554–560. Pratt, W. B., and Toft, D. O. (1997). Steroid receptor interactions with heat shock protein and immunophilin chaperones. Endocr. Rev., 18, 306–360. Quantin, B., and Breathnach, R. (1988). Epidermal growth factor stimulates transcription of the c-Jun proto-oncogene in rat fibroblasts. Nature, 334, 538–539. Ray, A., and Prefontaine, K. (1994). Physical association and functional antagonism between the p65 subunit of transcription factor NF-{kappa}B and the glucocorticoid receptor. PNAS, 91, 752–756. Reid, K. B., and Porter, R. R. (1981). The proteolytic activation systems of complement. Annu. Rev. Biochem., 50, 433–464. Reid, K. B., and Turner, M. W. (1994). Mammalian lectins in activation and clearance mechanisms involving the complement system. Springer Semin. Immunopathol., 15, 307–326.
Riccardi, C., Cifone, M. G., and Migliorati, G. (1999). Glucocorticoid hormone-induced modulation of gene expression and regulation of T-cell death: role of GITR and GILZ, two dexamethasoneinduced genes. Cell Death Differ., 6, 1182–1189. Rice, N. R., and Ernst, M. K. (1993). In vivo control of NF-kappa B activation by I kappa B alpha. EMBO J., 12, 4685–4695. Ristimaki, A., Narko, K., and Hla, T. (1996). Down-regulation of cytokine-induced cyclo-oxygenase-2 transcript isoforms by dexamethasone: evidence for post-transcriptional regulation. Biochem. J., 318 (Pt 1), 325–331. Rocha, B., and Tanchot, C. (2004). CD8 T cell memory. Semin. Immunol., 16, 305–314. Rogatsky, I., Zarember, K. A., and Yamamoto, K. R. (2001). Factor recruitment and TIF2/GRIP1 corepressor activity at a collagenase3 response element that mediates regulation by phorbol esters and hormones. EMBO J., 20, 6071–6083. Rolfe, F. G., Hughes, J. M., Armour, C. L., and Sewell, W. A. (1992). Inhibition of interleukin-5 gene expression by dexamethasone. Immunology, 77, 494–499. Rosenfeld, M. G., and Glass, C. K. (2001). Coregulator codes of transcriptional regulation by nuclear receptors. J. Biol. Chem., 276, 36865–36868. Rosewicz, S., McDonald, A. R., Maddux, B. A., Goldfine, I. D., Miesfeld, R. L., and Logsdon, C. D. (1988). Mechanism of glucocorticoid receptor down-regulation by glucocorticoids. J. Biol. Chem., 263, 2581–2584. Rousseau, G. G., and Baxter, J. D. (1979). Glucocorticoid receptors. Monogr. Endocrinol., 12, 49–77. Ryder, K., and Nathans, D. (1988). Induction of protooncogene c-Jun by serum growth factors. Proc. Natl. Acad. Sci. USA, 85, 8464–8467. Sainz, B., Loutsch, J. M., Marquart, M. E., and Hill, J. M. (2001). Stress-associated immunomodulation and herpes simplex virus infections. Med. Hypotheses, 56, 348–356. Sauer, J., Stalla, G. K., Muller, O. A., and Arzt, E. (1994). Inhibition of interleukin-2-mediated lymphocyte activation in patients with Cushing’s syndrome: a comparison with hypocortisolemic patients. Neuroendocrinology, 59, 144–151. Savory, J. G., Hsu, B., Laquian, I. R., Giffin, W., Reich, T., Hache, R. J., and Lefebvre, Y. A. (1999). Discrimination between NL1and NL2-mediated nuclear localization of the glucocorticoid receptor. Mol. Cell. Biol., 19, 1025–1037. Scheinman, R. I., Cogswell, P. C., Lofquist, A. K., and Baldwin, A. S., Jr. (1995a). Role of transcriptional activation of I kappa B alpha in mediation of immunosuppression by glucocorticoids. Science, 270, 283–286. Scheinman, R. I., Gualberto, A., Jewell, C. M., Cidlowski, J. A., and Baldwin, A. S., Jr. (1995b). Characterization of mechanisms involved in transrepression of NF-kappa B by activated glucocorticoid receptors. Mol. Cell. Biol. 15, 943–953. Schreiber, W., Pollmacher, T., Fassbender, K., Gudewill, S., Vedder, H., Wiedemann, K., Galanos, C., and Holsboer, F. (1993). Endotoxin- and corticotropin-releasing hormone-induced release of ACTH and cortisol. A comparative study in men. Neuroendocrinology, 58, 123–128. Schule, R., Rangarajan, P., Kliewer, S., Ransone, L. J., Bolado, J., Yang, N., Verma, I. M., and Evans, R. M. (1990). Functional antagonism between oncoprotein c-Jun and the glucocorticoid receptor. Cell, 62, 1217–1226. Scott, D. K., Stromstedt, P. E., Wang, J. C., and Granner, D. K. (1998). Further characterization of the glucocorticoid response unit in the phosphoenolpyruvate carboxykinase gene. The role of the glucocorticoid receptor-binding sites. Mol. Endocrinol., 12, 482–491.
1. Glucocorticoids and Immunity: Mechanisms of Regulation Shaw, J. P., Utz, P. J., Durand, D. B., Toole, J. J., Emmel, E. A., and Crabtree, G. R. (1988). Identification of a putative regulator of early T cell activation genes. Science, 241, 202–205. Sim, R. B., and Tsiftsoglou, S. A. (2004). Proteases of the complement system. Biochem. Soc. Trans., 32, 21–27. Smyth, M. J., Cretney, E., Kelly, J. M., Westwood, J. A., Street, S. E., Yagita, H., Takeda, K., van Dommelen, S. L., Degli-Esposti, M. A., and Hayakawa, Y. (2005). Activation of NK cell cytotoxicity. Mol. Immunol., 42, 501–510. Staples, K. J., Bergmann, M. W., Barnes, P. J., and Newton, R. (2003). Evidence for post-transcriptional regulation of interleukin-5 by dexamethasone. Immunology, 109, 527–535. Sternberg, E. M., Hill, J. M., Chrousos, G. P., Kamilaris, T., Listwak, S. J., Gold, P. W., and Wilder, R. L. (1989a). Inflammatory mediator-induced hypothalamic-pituitary-adrenal axis activation is defective in streptococcal cell wall arthritis-susceptible Lewis rats. Proc. Natl. Acad. Sci. USA, 86, 2374–2378. Sternberg, E. M., Young, W. S., 3rd, Bernardini, R., Calogero, A. E., Chrousos, G. P., Gold, P. W., and Wilder, R. L. (1989b). A central nervous system defect in biosynthesis of corticotropin-releasing hormone is associated with susceptibility to streptococcal cell wall-induced arthritis in Lewis rats. Proc. Natl. Acad. Sci. USA, 86, 4771–4775. Stockinger, B., Kassiotis, G., and Bourgeois, C. (2004). CD4 T-cell memory. Semin. Immunol., 16, 295–303. Szabowski, A., Maas-Szabowski, N., Andrecht, S., Kolbus, A., Schorpp-Kistner, M., Fusenig, N. E., and Angel, P. (2000). c-Jun and JunB antagonistically control cytokine-regulated mesenchymal-epidermal interaction in skin. Cell, 103, 745–755. Tobler, A., Meier, R., Seitz, M., Dewald, B., Baggiolini, M., and Fey, M. F. (1992). Glucocorticoids downregulate gene expression of GM-CSF, NAP-1/IL-8, and IL-6, but not of M-CSF in human fibroblasts. Blood, 79, 45–51. Trinchieri, G. (1995). Interleukin-12: a proinflammatory cytokine with immunoregulatory functions that bridge innate resistance and antigen-specific adaptive immunity. Annu. Rev. Immunol., 13, 251–276. Tsai, S. Y., Carlstedt-Duke, J., Weigel, N. L., Dahlman, K., Gustafsson, J. A., Tsai, M. J., and O’Malley, B. W. (1988). Molecular interactions of steroid hormone receptor with its enhancer element: evidence for receptor dimer formation. Cell, 55, 361–369. Umesono, K., and Evans, R. M. (1989). Determinants of target gene specificity for steroid/thyroid hormone receptors. Cell, 57, 1139–1146. Vacca, A., Felli, M. P., Farina, A. R., Martinotti, S., Maroder, M., Screpanti, I., Meco, D., Petrangeli, E., Frati, L., and Gulino, A. (1992). Glucocorticoid receptor-mediated suppression of the interleukin 2 gene expression through impairment of the
61
cooperativity between nuclear factor of activated T cells and AP-1 enhancer elements. J. Exp. Med., 175, 637–646. van Deventer, S. J., Buller, H. R., ten Cate, J. W., Aarden, L. A., Hack, C. E., and Sturk, A. (1990). Experimental endotoxemia in humans: analysis of cytokine release and coagulation, fibrinolytic, and complement pathways. Blood, 76, 2520–2526. Vo, N., and Goodman, R. H. (2001). CREB-binding protein and p300 in transcriptional regulation. J. Biol. Chem., 276, 13505– 13508. Wallace, A. D., and Cidlowski, J. A. (2001). Proteasome-mediated glucocorticoid receptor degradation restricts transcriptional signaling by glucocorticoids. J. Biol. Chem., 276, 42714–42721. Wang, C., Deng, L., Hong, M., Akkaraju, G. R., Inoue, J., and Chen, Z. J. (2001). TAK1 is a ubiquitin-dependent kinase of MKK and IKK. Nature, 412, 346–351. Wang, J. C., Stafford, J. M., and Granner, D. K. (1998). SRC-1 and GRIP1 coactivate transcription with hepatocyte nuclear factor 4. J. Biol. Chem., 273, 30847–30850. Wang, Z., Frederick, J., and Garabedian, M. J. (2002). Deciphering the phosphorylation “code” of the glucocorticoid receptor in vivo. J. Biol. Chem., 277, 26573–26580. Webster, J. C., Jewell, C. M., Bodwell, J. E., Munck, A., Sar, M., and Cidlowski, J. A. (1997). Mouse glucocorticoid receptor phosphorylation status influences multiple functions of the receptor protein. J. Biol. Chem., 272, 9287–9293. Wiegers, G. J., and Reul, J. M. (1998). Induction of cytokine receptors by glucocorticoids: functional and pathological significance. Trends Pharmacol. Sci., 19, 317–321. Williams, M. E., Chang, T. L., Burke, S. K., Lichtman, A. H., and Abbas, A. K. (1991). Activation of functionally distinct subsets of CD4+ T lymphocytes. Res. Immunol., 142, 23–28. Wu, C. Y., Wang, K., McDyer, J. F., and Seder, R. A. (1998). Prostaglandin E2 and dexamethasone inhibit IL-12 receptor expression and IL-12 responsiveness. J. Immunol., 161, 2723– 2730. Ying, S., Durham, S. R., Corrigan, C. J., Hamid, Q., and Kay, A. B. (1995). Phenotype of cells expressing mRNA for TH2-type (interleukin 4 and interleukin 5) and TH1-type (interleukin 2 and interferon gamma) cytokines in bronchoalveolar lavage and bronchial biopsies from atopic asthmatic and normal control subjects. Am. J. Respir. Cell Mol. Biol., 12, 477–487. Yudt, M. R., and Cidlowski, J. A. (2001). Molecular identification and characterization of a and b forms of the glucocorticoid receptor. Mol. Endocrinol., 15, 1093–1103. Yudt, M. R., Jewell, C. M., Bienstock, R. J., and Cidlowski, J. A. (2003). Molecular origins for the dominant negative function of human glucocorticoid receptor beta. Mol. Cell. Biol., 23, 4319–4330.
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C H A P T E R
2 Adrenergic Regulation of Immunity VIRGINIA M. SANDERS AND ANNEMIEKE KAVELAARS
I. EARLY EVIDENCE THAT THE NERVOUS AND IMMUNE SYSTEMS COMMUNICATE WITH EACH OTHER 63 II. SYMPATHETIC INNERVATION OF LYMPHOID TISSUE AND NOREPINEPHRINE RELEASE 64 III. EVIDENCE FOR ADRENERGIC RECEPTOR EXPRESSION ON IMMUNE CELLS 65 IV. EVIDENCE THAT NOREPINEPHRINE REGULATES IMMUNE CELL ACTIVITY IN VIVO 66 V. EVIDENCE FOR ADRENERGIC RECEPTOR REGULATION OF IMMUNE CELL ACTIVITY IN VITRO 71 VI. RELEVANCE TO HEALTH AND DISEASE 75
tion, epinephrine (EPI) is stored in the adrenal medulla, released systemically in response to stress, and also binds to the β2AR. Thus, both NE and EPI are important regulators of immune cell activity, with NE being released in response to both antigen and stress, and EPI being released primarily in response to stress alone. Thus, mechanisms are in place within lymphoid tissue that allow for a message to be delivered from the brain to cells of the immune system to maintain homeostasis when the host is threatened by antigen entry, and this message can be modified during times of stress or behavioral conditioning. In this way, a neurotransmitter-mediated adjustment in the level of immune cell activity has the potential to limit susceptibility or resistance to disease.
ABSTRACT Changes in immune system structure and function are associated with both stress and behavioral conditioning, suggesting that cells of the immune system are influenced by mediators released from the nervous and/or endocrine systems. The evidence to confirm that a communication exists between the sympathetic nervous system and immune system is well established. First, primary and secondary lymphoid organs are innervated with sympathetic nerve fibers in the parenchyma. Second, the sympathetic neurotransmitter norepinephrine (NE) is released from the nerve terminals following exposure to an antigen. Third, all immune cell types, with the possible exception of Th2 cells, express the beta-2-adrenergic receptor (β2AR) that binds NE to activate signaling intermediates within the cell. And finally, stimulation of the β2AR by NE regulates the level of leukocyte activity. In addiPSYCHONEUROIMMUNOLOGY, 4E VOLUME I
I. EARLY EVIDENCE THAT THE NERVOUS AND IMMUNE SYSTEMS COMMUNICATE WITH EACH OTHER A number of recent review articles have documented and discussed the evidence in support of the existence of a neuroimmune connection (Glaser and KiecoltGlaser, 2005; Harbuz, 2003; Kohm et al., 2001; Lombardi et al., 2002; Schorr and Arnason, 1999; Steinman, 2004). There are three landmark findings that are considered the cornerstone of psychoneuroimmunology. The study by Ader and Cohen, in which they showed the effect of taste aversion conditioning on a humoral immune response (Ader and Cohen, 1975), indicated that behavior influenced immunity and that immunity influenced behavior. These results
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suggested that a bi-directional relationship between behavior and immunity existed, and that such a relationship would have biological relevance for the treatment of disease. The stage was now set to explore the mechanisms responsible for mediating this communication, i.e., the mechanisms by which the immune system alerts the brain that it is responding to an antigen, as well as those mechanisms by which the brain regulates the level of immune cell activity that develops. The study by Besedovsky and Del Rey was the first to show that the activated immune system was able to release a soluble product that precipitated a change in the firing rate of neurons in a specific location within the brain, the hypothalamus (Besedovsky et al., 1977; Besedovsky et al., 1983). The importance of this finding was that the hypothalamus is the brain region that controls activation of organ system pathways that allow for the brain to communicate with the periphery. These organ system pathways include the sympathetic nervous system (SNS), which releases the neurotransmitter NE from nerve terminals and EPI from the adrenal medulla, and/or the hypothalamic-pituitaryadrenal axis, which releases a variety of hormones such as corticosteroids. Besedovsky and Del Rey were also the first to show that the SNS, via the stimulation of a receptor that could bind NE, was able to regulate the magnitude of an antibody response (Besedovsky et al., 1979; Del Rey et al., 1981). Thus, a brain-toimmune circuit was now in place to explain how behavior might affect immunity via the sympathetic nervous system. There is also an immune-to-brain circuit that explains how behavior might be affected by the activated immune system, but this topic will not be discussed herein. Instead, the reader is referred to the following excellent reviews on this topic (Besedovsky and Del Rey, 1996; Tracey, 2002; Watkins and Maier, 2005) and to the appropriate chapter in this book.
II. SYMPATHETIC INNERVATION OF LYMPHOID TISSUE AND NOREPINEPHRINE RELEASE The SNS maintains homeostasis by regulating the activity of organ systems that are not under voluntary, conscious control, e.g., the cardiovascular and respiratory systems. The SNS is associated with the “flight or fight” response, which involves immediate regulation of cardiovascular, respiratory, and metabolic functions during times of critical need, such as when fleeing or fighting an attacker. It seems as no surprise then that the immune system might also be under the regulatory
control of the SNS, especially since the cells of the immune system are involved in guarding against reactions to self and eliminating anything that is non-self. But before this assumption would be proven, it was imperative to first show that lymphoid organs were innervated with sympathetic nerve fibers so that the labile neurotransmitter would be delivered within close proximity to immune cells. Also, because epinephrine is released systemically, primarily during a response to physical or psychological stress, and is less labile than NE, it was necessary to show that a high enough concentration of epinephrine in the plasma would reach the microenvironment of immune cells to exert an effect on immune cell activity. Both human and animal primary and secondary lymphoid organs are innervated with sympathetic nerve fibers (Felten and Felten, 1991; Meltzer et al., 1997; Panuncio et al., 1998). A dense perivascular network of sympathetic nerve fibers is detectable within the splenic white pulp, thymus, and lymph nodes of mice and humans. Nerve endings that terminate in the parenchyma of the white pulp are especially numerous in the periarteriolar lymphoid sheath (PALS) and are found adjacent to both CD4+ and CD8+ T-cells, as well as in the vicinity of macrophages and B-cells (Felten et al., 1987; Felten et al., 1998). The level of NE released at a nerve terminal may reach a local concentration of approximately 1 × 10−5 to 5 × 10−4 M (Shimizu et al., 1994), which becomes lower as NE is either taken back into the nerve terminal, degraded by enzymes, or moves away from the nerve terminal to create a concentration gradient. Also, epinephrine that is released during a stress response can reach a concentration of 1 × 10−7 M in the plasma, which is considerably lower than that of NE due to the systemic nature of its release. Thus, a mechanism was now in place by which NE could be released into, and epinephrine could attain a high enough concentration within, the microenvironment in which immune cells responded to antigen. Consequently, cells in these two compartments, blood vs. lymphoid organs, may be exposed to different concentrations of NE and subsequently may respond differently. It was now important to determine if the introduction of antigen into the body was associated with SNS activation and release of NE within lymphoid tissue, independently of a stress response that induces a release of both NE and epinephrine. Systemic infection, LPS-, or infectious microorganisms increased the rate of NE release in the spleen during the first 12 hours of exposure (Kohm et al., 2001). Non-infectious types of immune stimuli, e.g., particulate or soluble protein antigens, also influenced the rate of NE release in lymphoid organs. Sheep erythrocytes increased the
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level of sympathetic nerve activity and the rate of NE release in the spleen (Besedovsky et al., 1979), without disrupting the homeostatic mechanisms responsible for maintaining a constant level of NE tissue content (Fuchs et al., 1988). Likewise, a soluble protein antigen, TNP-KLH, increased the rate of NE release within the spleen and bone marrow in an antigen-specific manner between 9–18 hours following immunization (Kohm et al., 2000), suggesting that initial antigen distribution, uptake, processing, presentation, and cytokine synthesis/release occurred before the SNS was activated. In the latter study, the increase in sympathetic nerve activity was partially blocked by the ganglionic-blocker chlorisondamine, suggesting that both pre- and postganglionic mechanisms are likely involved in regulating NE release following an immune insult. Thus, activation of the SNS is one mechanism by which the brain appears to communicate with cells of the immune system to potentially regulate the magnitude of an immune response. As a result of an immune response to antigen, SNS activation appears to be initiated from either within the central nervous system (CNS) or outside the CNS at sympathetic nerve terminals and post-ganglionic sites (Straub, 2004). It is interesting to speculate that severe infections, which pose an immediate threat to survival, may require participation of the CNS to orchestrate SNS-mediated immune regulation peripherally, while less severe infections or autoimmune reactions may require the participation of local regulatory mechanisms alone.
III. EVIDENCE FOR ADRENERGIC RECEPTOR EXPRESSION ON IMMUNE CELLS Adrenergic receptors bind catecholamines, such as NE and epinephrine. Adrenergic binding sites have been identified on immune cell subsets that are saturable, reversible, high affinity, and almost exclusively of the β2AR subtype, as determined using radioligand binding analysis (Sanders et al., 2001). In addition, single nucleotide polymorphisms associated with the β2AR gene are becoming evident in cells from rheumatoid arthritis patients (Xu et al., 2005). In contrast, evidence for the expression of the αAR subtype by immune cells appears to be limited to specific cell subsets and is primarily of the α1AR subtype (Kavelaars, 2002).
A. Cells of the Innate Immune System Data show that cells of the innate immune system— i.e., polymorphonuclear cells (PMN), mast cells, monocyte/macrophages, and natural killer (NK)
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cells—express one and/or another AR subtype. Initially, radioligand binding analyses that were performed on isolated subsets of innate immune cells showed that all cells expressed the β2AR (Elenkov et al., 2000). These findings were confirmed recently by analysis of mRNA expression (de Coupade et al., 2004). However, it remains unclear as to whether other βAR subtypes are expressed by PMN. A recent study using human PMN detected no β1AR mRNA (de Coupade et al., 2004), while functional studies using human peripheral blood monocytes and monocyte-derived macrophages revealed the expression of not only the β2AR, but also the β1AR (Speidl et al., 2004). Dendritic cells derived from bone marrow appear to express the α1AR (Maestroni, 2000), α2AR, β1AR, and β2AR (Maestroni et al., 2003). In contrast, NK cells express the β2AR exclusively (Jetschmann et al., 1997). Expression of the AR subtypes on cells of the innate immune system is not static, and is subject to regulation by cell activation and/or various hormones. For example, during sepsis, the β2AR number expressed on a phagocytic liver Kupffer cell is markedly increased (Hahn et al., 1998). Likewise, the β2AR number on a human PMN is higher on cells obtained from females in comparison to cells from males, suggesting that innate immune cell interactions with sexual hormones may regulate expression of the β2AR on these cells (de Coupade et al., 2004). Few data are available with respect to the presence of the αAR subtype on cells of the innate immune system. Cell lines of monocytic origin express a detectable level of the α1AR, as determined on the mRNA level, but this subtype is undetectable on peripheral blood cells from healthy individuals (Heijnen et al., 2002; Rouppe van der Voort et al., 2000). Upon activation, however, the level of the α1AR expressed on monocytic cell lines changes (Heijnen et al., 2002; Rouppe van der Voort et al., 1999), and expression is induced on freshly isolated human peripheral blood monocytes (Kavelaars, 2002). Moreover, there is evidence that in certain clinical conditions, e.g., in children with juvenile idiopathic arthritis, a functional α1AR is expressed on cells in the peripheral blood, as indicated by increased production of IL-6 and TNF-α after exposure of cells to an α1AR agonist. Because the cytokines are likely secreted by monocytes in the peripheral blood, this finding suggests that monocytes represent the immune cell subset that expresses the α1AR (Heijnen et al., 2002; Rouppe van der Voort et al., 2000). Other studies report that murine peritoneal macrophages express a α2AR, as determined functionally, and that human PMN express about 500 α2AR per cell, as determined using radioligand binding analysis (Miles et al., 1996; Panosian and Marinetti, 1983;
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Spengler et al., 1990). In contrast, the α1AR was undetectable on PMN (Panosian and Marinetti, 1983).
B. Cells of the Adaptive Immune System 1. T-Cells CD8+ T-cells have not been studied as much as CD4+ T-cells, but they do express βAR binding sites (Sanders et al., 2001). In contrast, the animal and human CD4+ T-cell has been well characterized for expression of the β2AR (Sanders et al., 2001). However, the CD4+ T-cells analyzed in most of these studies represent a population of cells that may contain all three subsets of CD4+ T-cells, namely the naïve, Th1, and Th2 cell. Because radioligand binding analysis is difficult to perform on a purified population of naïve CD4+ T-cells due to low cell number, RT-PCR analysis was used to show that murine naïve CD4+ T-cells express mRNA for the β2AR (Swanson et al., 2001). Clones of murine Th1 cells express the β2AR and accumulate cAMP upon exposure to a β2AR agonist, but clones of Th2 cells do not (Sanders et al., 1997). The latter conclusion was initially suggested earlier when it was reported that different CD4+ T-cell lines (not necessarily Th1 or Th2) differentially accumulated cAMP in response to a β2AR agonist, even though all of the cell lines accumulated cAMP in response to other ligands such as histamine or PGE2 (Khan et al., 1985a; Khan et al., 1985b). Indirectly, these findings suggested that murine CD4+ Tcell subsets might differentially express the β2AR, even though all subsets express other receptors capable of activating cAMP. Expression of the β2AR on murine primary Th1 and Th2 cells generated from a naïve cell precursor activated under Th1- or Th2-polarizing conditions remains unknown, although preliminary data confirm the findings using clones of differential expression (Sanders et al., unpublished data). These findings may be difficult to confirm using human cells since human CD4+ T-cells do not polarize as clearly as mouse cells do under Th1and Th2-polarizing conditions (Abbas et al., 1996; Romagnani, 1994; Romagnani, 2000). Nonetheless, conflicting data exist when using human cells, with some suggesting the absence of a β2AR (Borger et al., 1998) and others suggesting the presence (Goleva et al., 2004; Heijink et al., 2003). However, as techniques are improved to purify out human CD4+ T-cells that secrete only Th1- or Th2-like cytokines, it may be possible to solve this question. Upon CD4+ T-cell activation, via either mitogen activation, TCR stimulation, or contact sensitization, the level of β2AR expression either increases (Madden et al., 1989; Radojcic et al., 1991; Ramer-Quinn et al.,
1997; Sanders and Munson, 1985b; Westly and Kelley, 1987;) or decreases (Cazaux et al., 1995; Radojcic et al., 1991), but remains undetectable on Th2 cell clones (Ramer-Quinn et al., 1997). Stimulation of the β2AR on a CD4+ T-cell that expresses the receptor increases both the intracellular concentration of cAMP and adenylate cyclase activity (Sanders et al., 2001). Thus, the β2AR appears to be maintained as the naïve T-cell differentiates into a Th1 cell, but is repressed as the naïve cell differentiates into a Th2 cell. The mechanism responsible for mediating the differential expression of the β2AR by these two effector cell subsets remains unknown. 2. B-Cells Radioligand binding analysis shows that a B-cell expresses almost twice as many receptors as a CD4+ T-cell, and that the receptor is of the β2AR subtype (Sanders et al., 2001). Expression of the β2AR by a purified population of naïve antigen-specific B-cells has also been reported, using both radioligand binding, immunofluorescence, molecular, and biochemical analyses (Kohm and Sanders, 1999). Thus far, no data have been reported to show expression of either the β1AR or β3AR on B-cells. A few radioligand binding analyses show expression of the αAR on B-cells (Goin et al., 1991; McPherson and Summers, 1982; Titinchi and Clark, 1984), but the results may be misleading since platelets, which express the αAR at a high level, were not removed from the lymphocyte samples before analysis. The β2AR on a B-cell is functional since exposure to a β2AR agonist enhances both the intracellular accumulation of cAMP and adenylate cyclase activation (Sanders et al., 2001). Taken together, the innate and adaptive immune cell data suggest that all immune cell types, except for Th2 cells, express an AR subtype, and that expression occurs at different densities (see Figure 1).
IV. EVIDENCE THAT NOREPINEPHRINE REGULATES IMMUNE CELL ACTIVITY IN VIVO After infection, immune cells of the innate and adaptive immune system protect the host by destroying the infectious pathogen and by providing longterm pathogen-specific protection. The innate immune system acts almost immediately in an antigen nonspecific manner and does not generate memory cells that would recognize a specific antigen upon reexposure. The adaptive immune system protects the host within a few days of antigen entry in an antigen-
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β2 PMN
β1
Innate Immune Cells β2 β ? β1 β2 α α1 β1 2 α1 α 1 2
Human Mono Mac
Murine Mac
Dendritic Cell
β2 NK Cell
Adaptive Immune Cells β2
β2
?
β2
β2
Naive CD4+ T-cell
CD4+ Th1 Cell
CD4+ Th2 Cell
CD8+ T-cell
B-cell
FIGURE 1 Adrenergic receptor phenotype on cells of the innate and adaptive immune systems. Each cell type shows only the subtype designation for the adrenergic receptor. A question mark indicates that the findings are inclusive in both humans and animals; e.g., murine and human Th2 cells are reported to not express the β2AR, while some human Th2 cells appear to express the receptor (see III. B. 1). The same question holds true for expression of the α2AR by murine macrophages. Mono = monocyte; Mac = macrophage.
specific manner and generates long-term protection in the form of memory. Both arms of the immune system are characterized by either cell-mediated or humoraltype responses. Cell-mediated responses are those that can be passively transferred to an infected host, i.e., in the form of cells from infected donors to promote a protective response in a host either directly via cell– cell contact to kill infected targets or indirectly via the release of cytokines to enhance the activity of other immune cells. On the other hand, humoral responses are those that can be passively transferred in the form of soluble proteins contained in serum, usually in the form of antibodies that are made and released by B-cells. Pharmacological evidence for involvement of the sympathetic nervous system in regulating the level of both cell-mediated and humoral immune responses was initially obtained from studies in which the chemical neurotoxin 6-hydroxydopamine (6-OHDA) was used to reversibly deplete NE from peripheral sympathetic nerve terminals in adult mice. Such NE-depleted mice had either enhanced, suppressed, or unaltered immune responses in response to antigen when compared to mice in which NE remained intact (Kohm et al., 2001), suggesting that NE needed to be released from nerve terminals within the microenvironment of immune cells responding to antigen so that the level of an immune response could be regulated. However, different findings may result from either the initial burst of NE displaced by 6-OHDA as it is taken into a nerve terminal, which may have exerted an effect on
cells before NE depletion was established, the dose and/or time of 6-OHDA administration, and/or the type of immune response being measured. Such caveats have made it difficult to conclude whether the disparate findings reflected different aspects of a related phenomenon or reflected differences in the responsiveness of different cell subsets to NE during different stages of an immune response. Nonetheless, the following data provide evidence that NE plays a role in regulating the magnitude of innate and humoral immunity.
A. Innate Immunity The majority of studies on the effects of acute stress in humans have focused on changes that occur in the number of specific cell subsets that are primarily within the human peripheral blood compartment. The reason for the attention to number changes within peripheral blood as opposed to lymphoid tissue that is commonly used from animals is clear, namely that human peripheral blood is more easily accessible and cell-counting techniques are not very complicated. It is well known that acute stress results in a reliable and rapid increase in the number of circulating NK cells and a slower increase in the number of PMN [reviewed in (Benschop et al., 1996b; Elenkov et al., 2000)]. In contrast, less is known about how stress affects the number and/or distribution of specific innate immune cell subsets during the course of a clinical condition. However, more recent studies have explored the effect of stress and AR stimulation on innate immunity in sepsis and models of NK cell-dependent defense against tumor metastasis. In this chapter, we will focus on the general effects of NE, EPI, and AR stimulation on innate immunity. 1. NK Cells The role of AR signaling in NK cell-mediated killing of tumor cells will be discussed in detail in Chapter 12, authored by Ben Eliyahu and Avraham. The effects of stress on NK cell distribution and function will be discussed here briefly. Acute stress in humans, e.g., the stress experienced during either the delivery of a public speech or a first parachute jump, or the mimicking of acute stress via the infusion of an adrenergic agonist such as EPI, results in a rapid and transient increase in the number of NK cells in peripheral blood (Benschop et al., 1994; Benschop et al., 1996a; Kappel et al., 1998; Schedlowski et al., 1993; Tonnesen et al., 1987). This effect of both acute stress or EPI infusion is evident within 5–30 minutes and is prevented completely by administration of a β2AR antagonist
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(Benschop et al., 1994; Benschop et al., 1996a; Schedlowski et al., 1993). Thus, an increase in the level of circulating NE/EPI results in an increased number of circulating NK cells via stimulation of the β2AR. Although no formal proof exists to show that the effect on NK cell distribution is mediated directly via β2AR stimulation on an NK cell, the consensus is that NE/ EPI binding directly to the β2AR expressed on an NK cell results in the effect. In contrast, the stress-induced increase in PMN number in the peripheral blood was not inhibited completely by administration of a βAR antagonist (Benschop et al., 1996b), suggesting that other endogenous stress signals, such as glucocorticoids, are involved in the PMN distributional response to stress. Despite a vast body of literature describing the effects of acute stress and infusion of βAR agonists on innate immune cell distribution, little is known with respect to the mechanisms underlying this phenomenon. The first question that needed to be addressed concerned the source of the NK cells that enter the circulation, and the second concerned the mechanisms by which β2AR stimulation increased the number of NK cells in the peripheral blood. Based on studies performed in both humans and animals, it is now well established that the major source for the increased number of NK cells is the marginal pool of transiently immobilized leukocytes located along the blood vessel wall, as opposed to cells from the spleen or bone marrow. This transient immobilization results from changes in the interaction of adhesion molecules expressed on both endothelial cells and leukocytes, resulting in cell adherence to the blood vessel wall and creation of a shearing force to the blood flow. Also, because the blood flow is lower in venules than in arterioles, the marginal pool of leukocytes is present predominantly in venules. Although there is no direct evidence that NE/EPI reduce the adherence of cells to a blood vessel wall in vivo, there is evidence from an in vitro study to show NK cell adherence to cultured vascular endothelium is inhibited in the presence of a β2AR agonist (Benschop et al., 1993). 2. PMN/Monocytes/Macrophages/Dendritic Cells Acute administration of NE or EPI changes the number of PMN in the blood, an effect that is not only dependent on the βAR, but also involves the αAR (Dhabhar and McEwen, 1999). However, it remains unclear as to whether the AR subtypes involved in PMN distribution are on the PMN itself or on other cells. On a functional level, NE-depleted non-stressed animals show an enhanced early resistance to the intracellular pathogen Listeria monocytogenes (LM),
presumably due to increased PMN infiltration into infected organs during the early innate immune response (Rice et al., 2001). Similarly, an increase in NE that is induced by acute stress is associated with an increase in LM burden in infected organs at 3 days after infection, which results from reduced PMN migration (Cao et al., 2002). Again, NE depletion prevented this stress-induced increase in LM burden in infected organs. Thus, the possible underlying mechanism responsible for the increase in LM burden appears to involve an inhibitory action of NE on PMN migration and/or activity. As mentioned earlier, behavioral conditioning modulates the level of immune cell activity. In a recent study, the role of the SNS in the conditioning of the PMN response to activation by poly-IC was investigated (Chao et al., 2005). Poly-IC administration to animals, in combination with a specific smell, increases PMN activity. This effect was subsequently evoked upon re-exposure to the smell alone, and was prevented when NE was depleted. Similarly, it has been shown that ablation of the peripheral stores of NE has a marked effect on the defense against bacterial infection. For example, NE depletion prior to infection with Pseudomonas aeruginosa results in an improved phagocytic response of peritoneal cells and an increased influx of monocytes into the peritoneal cavity, leading to reduced dissemination of this microorganism (Straub et al., 2005c). The level of an innate immune response in vivo is modulated not only by endogenous adrenergic agonists such as NE and EPI, but also by pharmacological agents such as β2AR agonists. Interestingly, LPSinduced cytokine production in animals following administration of a β2AR agonist is dependent on the type of cytokine produced and the type of tissue analyzed (Eijkelkamp et al., 2004). In vivo, administration of a β2AR agonist decreases the LPS-induced production of IFN-γ by peritoneal cells in the small intestine and lung. IL-10 production, however, is modulated in a tissue-specific manner so that LPS-induced IL-10 in the peritoneal cavity is increased, but decreased in the ileum and the lung. These tissue site- and cytokinedependent differences in the effect induced of βAR activation is adding information to help better the understanding of how NE depletion either enhances or suppresses susceptibility to infection. Dendritic cells are called Langerhans cells when they reside in the skin. It appears that an NE/EPI may participate in a normal contact hypersensitivity response since the administration of a β2AR antagonist enhanced the normal response, suggesting an inhibitory influence of NE/EPI under normal circumstances (Seiffert et al., 2002). This finding is supported by
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another report that NE inhibited Langerhans cell mobility (Maestroni, 2000).
B. Adaptive Immunity 1. T-Cells Findings indicated that a suppressed Th1 cellmediated contact hypersensitivity response occurred when NE was depleted either before or after sensitization in comparison to NE-intact control mice (Madden et al., 1989), suggesting that NE is needed for the generation of an optimal response at both the naïve and effector T-cell stages. This result was confirmed when mice were genetically deficient for the enzyme dopamine beta-hydroxylase, which is required for the synthesis of NE from dopamine, and which provides another means to deplete NE stores (Alaniz et al., 1999). These NE-deficient mice showed less protection against the Th1-promoting pathogens Listeria monocytogenes or Mycobacterium tuberculosis, and a significant decrease in the level of the Th1 cytokine IFN-γ produced, again suggesting that NE plays a role to upregulate the magnitude of a Th1 cell-mediated immune response. However, a 10-fold higher level of dopamine in these mice (Alaniz et al., 1999) may have caused the decrease in CD4+ T-cell function instead of the lack of NE (Kouassi et al., 1987). In contrast, NE may exert a suppressive effect on Th1 cell activity during a normal contact hypersensitivity response, possibly via an effect on the level of IL-12 produced by dendritic cells or on the ability of the cells to migrate to the lymph node (Maestroni et al., 2003; Seiffert et al., 2002). Taken together, most studies indicate that NE exerts an enhancing effect on either early naïve CD4+ T-cell development into a Th1 cell and/or the amount of IFN-γ secreted by the resulting Th1 cell. Analysis of T-cells that infiltrate the inflamed synovium of RA patients shows that there is a bias to a Th1-like cell phenotype and the production of IFN-γ (Feldmann et al., 1996). Likewise, animal models of arthritis are clearly Th1-cell dependent (Firestein, 2003). Blockade of the β2AR in rodents prior to, and during, arthritis delays the onset and reduces the severity of joint injury (Levine et al., 1988), suggesting that NE stimulation of the β2AR on a Th1 cell may exacerbate the disease process. The latter effect also appears to depend on the time when NE is released during the disease process, the level of sympathetic innervation within a specific tissue compartment, and the induction of anti- versus pro-inflammatory cytokines (Harle et al., 2005). β2AR stimulation on human peripheral blood mononuclear cells from RA patients induces a higher level of cAMP accumulation
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than does the stimulation on cells from healthy individuals (Lombardi et al., 1999). This increased sensitivity of the β2AR appears to be independent of a change in the level of β2AR expression, but may be associated with a 50% decrease in the expression and activity of the G-protein–related kinase 2 (GRK2) (Lombardi et al., 1999), which phosphorylates the β2AR upon agonist binding to desensitize the receptor (Benovic et al., 1986; Ferguson, 2001). Cells from rodents with adjuvant-induced arthritis also express less GRK2, and this effect is specifically found to exist in CD4+, but not CD8+, T-cells (Lombardi et al., 2001). Collectively, these findings in vitro suggest that the increased response to a β2AR agonist by human peripheral blood mononuclear cells from RA patients results from reduced GRK2 expression in immune cells, possibly Th1 cells, indicating that NE may use a similar mechanism in vivo. The role that NE plays in a Th2 cell-mediated response is less clear. When two different strains of mice, C57Bl/6J (Th1 cell-slanted strain) and Balb/c (Th2 cell-slanted strain), were depleted of NE and immunized with KLH, splenic cells from both strains of mice produced significantly higher levels of IL-2 and the Th2 cytokine IL-4 following reactivation in vitro when compared to cells isolated from immunized NE-intact controls (Kruszewska et al., 1995), suggesting that NE may help to produce a normal Th2 response. However, the mechanism by which this effect on Th2 cells occurs may be indirectly mediated by a direct effect on macrophages. In mice receiving a thermal burn injury, elevated plasma NE levels were associated with an increase in the production of the chemokine CCL2 production by macrophages, chemokine CCL3 production by T-cells, and the subsequent development of a predominant Th2-like response, effects that were prevented by NE depletion (Takahashi et al., 2004; Takahashi et al., 2005). This finding suggests that NE may influence susceptibility to infections after a thermal burn by regulating macrophage and T-cell chemokine secretion and a subsequent increase in Th2 cell accumulation at the site of injury, as has been described previously (Kobayashi et al., 1998). To date, few studies have shown a direct correlation between the levels and timing of NE exposure and/or β2AR stimulation with the number of CD8+ T-cells. In one study, administration of a monoamine oxidase inhibitor to tumor-bearing rats increased both NE levels and the percentage of CD8+ T-cells in the spleen (ThyagaRajan et al., 1999). With respect to the effect of NE/EPI exposure and/or β2AR stimulation on CD8+ T-cell activity, a few animal studies have provided some insight into what might be expected in humans.
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When mice were depleted of NE before sensitization with trinitrochlorobenzene (TNCB), the generation of hapten-specific CD8+ T-cell cytotoxicity decreased upon TNCB challenge in comparison to controls (Madden et al., 1989), suggesting that NE is required for the generation of cytotoxicity after initial antigen exposure. In contrast, exposure of mice to restraint stress decreased the generation of a CD8+ T-cell response to either HSV or influenza virus infection, and this effect was partially mediated by a βARinduced mechanism (Dobbs et al., 1993; Sheridan et al., 1998). Thus, a definitive answer about the effect of NE on murine CD8+ T-cell cytotoxicity remains unknown. In humans, certain types of physical and psychological stress have been shown to induce an increase in CD8+ T-cell number that is blocked by the administration of a βAR antagonist, suggesting that both CA release and βAR stimulation are involved in these stress-induced immune changes (Benschop et al., 1996a). In women exposed to a public-speaking stress, CD8+ T-cell number increased along with increased levels of NE, EPI, and cortisol (Mathews et al., 1983), suggesting that a concomitant increase in cortisol with NE does not alter the NE-induced increase on these particular immune parameters. A number of these studies also showed that a β2AR-subtype specificity exists for these effects since they were either induced by a β2AR selective agonist or blocked by a βARselective antagonist, but not by a β1AR-selective antagonist. In contrast, when the β2AR agonist terbutaline was administered to healthy subjects for 7 days, CD8+ T-cell numbers decreased, while cell numbers increased upon acute exposure (Maisel et al., 1990). Chronic exposure to a β2AR agonist in asthmatic individuals did not change the number of bronchial CD8+ T-cells (Roberts et al., 1999), while an increase in number was found in HIV-infected individuals (Sondergaard et al., 2000), suggesting that a disease process may influence the response to β2AR stimulation. Also, CD62L was increased on CD8+ T-cells from individuals exposed to dynamic exercise (Mills et al., 1999), suggesting that more naïve-type T-cells are localized into the circulation during exercise. Thus, in humans, acute exposure to NE/EPI appears to increase CD8+ T-cell number in the circulation, while chronic exposure appears to decrease. Taken together, NE may either enhance or suppress CD4+ and CD8+ T-cell function, depending on the specific type of immune response in which T-cell function was evaluated, the type of antigen-presenting cell involved in the response, the responsiveness of the APC itself to NE, and/or the time at which the AR is stimulated in relation to antigen activation.
C. B-Cell The role played by NE in regulating the magnitude of an antibody response has been implicated in studies conducted in NE-depleted mice. Data show that either a decrease (Ackerman et al., 1991; Cross et al., 1986; Fuchs et al., 1988; Hall et al., 1982; Kasahara et al., 1977a; Kasahara et al., 1977b; Livnat et al., 1985; Madden et al., 1989) or increase (Besedovsky et al., 1979; Chelmicka-Schorr et al., 1988; Miles et al., 1981) in the Th cell-dependent antibody response occurs after NE depletion. In a chronic depression mouse model, IgG levels increased acutely when the NE levels were elevated, but decreased chronically when the NE levels had returned to normal (Silberman et al., 2003). Also, anti-HSV IgM levels increased in young, but not old, mice that were exposed to moderate exercise training, and the increase was inhibited by blockade of the βAR, suggesting that NE was involved in elevating the antibody level (Kohut et al., 2004). Taken together, the majority of results in mice suggest that NE exerts a regulatory effect on the level of antibody produced by enhancing the endogenous activity of the immune cells that generate the response. Thus, the presence and concentration of NE at the time of antigen exposure may be a determining factor in the development of a normal primary and secondary antibody response to a T-cell-dependent antigen. The possibility exists, however, that the initial burst of NE that was released by 6-OHDA may have exerted an effect on immune cells before an NE-depleted state was obtained. To address this possibility, antigen-specific Th2 cells and B-cells were adoptively transferred into severe combined immunodeficient (scid) mice that were depleted of NE by 6-OHDA prior to cell transfer and immunization (Kohm and Sanders, 1999). A lower serum level of antigen-specific IgM and the neutralizing antibody isotype IgG1 was measured in these mice as compared to reconstituted NE-intact mice, an effect that was prevented by the administration of a β2AR-selective agonist at the time of immunization. Secondary immunization of these mice induced serum levels of antigen-specific IgG1 that were delayed in reaching a control level of response. It is important to note that NE depletion did not alter T- and B-cell trafficking to the spleen, but after immunization, NE depletion did decrease follicular expansion and germinal center formation when compared to NE-intact controls. Taken together, these data suggest that NE is needed to obtain a normal level of IgM and Th2 celldependent IgG1 during a primary and secondary Th2 cell-dependent antibody response in vivo. Because the β2AR is expressed on both the Th1 and B-cell, it has been more difficult to determine the effect
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of NE on the IgG2a response that develops due to the effect that NE has on the level of IFN-γ released by the Th1 cell. However, when mice deficient in dopamine beta-hydroxylase were studied, they exhibited normal lymphocyte development, but an impaired ability to produce Th1 cells and IFN-γ–dependent IgG2a (Alaniz et al., 1999), suggesting that NE is necessary for the development of Th1 cell immunity and subsequent IgG2a production, a finding that has been confirmed in vitro (Swanson et al., 2001). A recent study reported that stress diminishes the IgG2a response, but that this diminution appears to result from a stress-induced depletion of splenic NE that can be reversed pharmacologically (Kennedy et al., 2005), again suggesting that NE may exert an enhancing effect on IgG2a production. In contrast, mice exposed to either herpes simplex or influenza virus at the time of restraint stress had decreased numbers of virus-specific IgM-, IgG1-, and IgG2a-secreting cells in the lung, mediastinal LN, and spleen, but increased numbers were found in cervical LN cells, in a partially β2AR-mediated manner (Sheridan et al., 1998). The latter finding suggested that tissue-specific regulation of the antibody response may exist in response to changes in NE levels within lymphoid organs. Few in vivo human studies have shown directly that exposure to either NE or a β2AR agonist alters a specific isotype of antibody. In one study, the administration to asthmatics of either a β2AR agonist alone increased levels of serum IgG, but did not affect the level of any other isotype, including IgE (Manfield and Nelson, 1982). However, if the β2AR agonist was administered with cortisol, an increase in the level of serum IgG was measured. This finding suggests that a synergy may exist in humans between the β2AR agonist- and cortisol-induced signals to affect an immune cell function, such as IgG production. In contrast, peripheral blood cells obtained from women asked to perform a public-speaking task, which resulted in elevated levels of NE but not cortisol, produced less IgM and IgG in response to mitogen stimulation in vitro than when cells were taken before the stressful event (Matthews et al., 1995). At first glance, these findings may seem to contradict each other, in that β2AR stimulation alone appears to increase IgG in one study, but decrease IgG in the other. But again, the study designs need to be taken into account before the data are compared. In the first situation, the study was performed entirely in vivo and in individuals with asthma who had been chronically exposed to a specific allergen. In the other situation, the NE-exposed cells were cultured ex vivo and were activated with a polyclonal stimulant instead of a specific antigen. In addition, disparate results may also stem from variables
such as the tissue source of human cells for study, i.e., peripheral blood B-cells vs. tonsil B-cells. Thus, the effect of NE exposure and β2AR stimulation in vivo on human antibody production remains unclear, but the mechanism by which the effect occurs may depend on the presence or absence of a clinical disease, the presence or absence of another hormone, the type of activation stimulus used to induce a functional response, the length of time for β2AR stimulation, and/or the time of β2AR stimulation in relation to antigen receptor stimulation. The findings summarized thus far suggest strongly that NE is released upon antigen exposure from nerve terminals located within lymphoid tissue to serve as a messenger from the brain to cells of the immune system. This message is heard by the β2AR that is expressed on immune cells and is translated into an intracellular signal that regulates the magnitude of a specific immune cell response.
V. EVIDENCE FOR ADRENERGIC RECEPTOR REGULATION OF IMMUNE CELL ACTIVITY IN VITRO A. Innate Immunity 1. NK Cells Although data in the literature with respect to the in vivo effects of β2AR activation on NK cell activity are somewhat contradictory, in vitro studies clearly suggest that exposure of NK cells to a β2AR agonist reduces NK cell activity (Gan et al., 2002; Hellstrand et al., 1985; Hellstrand et al., 1989; Takamoto et al., 1991). Little is known, however, about the cellular mechanisms responsible for this effect. It has been suggested that treatment of NK cells with NE reduces the ability of NK cells to bind to a target cell, possibly via a mechanism involving reduced CD16 expression on NK cells. In addition, when IL-2–maintained NK cells were exposed to NE, the production of IFN-γ and TNF-α was inhibited, affecting NK cell maturation into fully functional cytotoxic cells (Gan et al., 2002). 2. PMN A key role in host defense against invading microorganisms is played by the PMN, which is a phagocytic cell that releases reactive oxygen species and anti-microbial proteins/peptides to kill bacteria. Activation of PMN by a variety of stimuli results in a “respiratory burst” that results in superoxide anion production, which is suppressed following exposure to a βAR agonist (O’Dowd et al., 2004). Moreover, there
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is evidence that a β2AR agonist inhibits the adhesion of PMN to vascular endothelium cultured in vitro (Bloemen et al., 1997), an effect which may contribute to the reduced tissue infiltration of PMN after treatment with a βAR agonist (Johnson and Rennard, 2001). In contrast, other data suggest that β2AR stimulation on PMN stimulates cell motility, which may result in increased accumulation of PMN at sites of inflammation (de Coupade et al., 2004). In this case, NE was not acting as a chemotactic factor in the classic sense; i.e., NE does not cause directed migration of PMN towards itself. However, NE does enhance non-directed migration, also known as chemokinesis, but inhibits directed migration of PMN, or chemotaxis, toward the chemokine IL-8 (de Coupade et al., 2004). Thus, NE may specifically enhance PMN non-directed, as opposed to directed, migration. 3. Macrophages The best-described effect of an adrenergic agonist on macrophage/monocyte function involves the level of cytokine produced. In most studies, LPS is used to induce the production of both pro- and anti-inflammatory cytokines, such as TNF-α, IL-12, IL-6, and IL-10. Agents that induce an increase in cAMP, including a β2AR agonist, inhibit the LPS-induced secretion of IL12 by monocytes and dendritic cells activated in vitro (Elenkov et al., 1996; Panina-Bordignon et al., 1997). In addition, the production of the pro-inflammatory cytokine TNF-α is sensitive to inhibition by a βAR agonist (Hetier et al., 1991; van der Poll et al., 1994). In contrast, IL-10 IL-8 production is enhanced by the addition of an βAR agonist to LPS-activated human monocytes or mouse peritoneal macrophages (Kavelaars et al., 1997; van der Poll et al., 1997a; van der Poll et al., 1997b). These effects of a βAR agonist on LPS-induced cytokine production by macrophages/monocytes is mimicked by other agents that raise the intracellular level of cAMP (Kavelaars et al., 1997), suggesting that the cAMP/protein kinase A (PKA) signaling pathway is responsible for the observed effects of βAR stimulation on the production of these cytokines and chemokines. There is also evidence that macrophages not only respond to a β2AR agonist, but also to αAR agonists. It should be noted, however, that although the response to a βAR agonist takes place under most circumstances in vivo, special endogenous situations likely occur that cause these cells to respond to an αAR agonist, also. For example, elicited peritoneal macrophages from specific pathogen-free mice respond to an α2AR agonist with increased secretion of TNF-α (Spengler et al.,
1990). In addition, when THP-1 cells, which represent a human monocytic cell line, are exposed to an α1AR agonist, the ERK and NK-κB pathways within the cell are activated to produce IL-6 (Bierhaus et al., 2003). However, when similar experiments were performed using peripheral blood monocytes from healthy individuals, an α1AR agonist did not have any effect on these cells (Rouppe van der Voort et al., 2000). There are, however, conditions in which we can detect an α1AR-induced increase in cytokine production by peripheral blood monocytes. For example, in vitro stimulation with LPS can induce expression of the α1AR, and subsequent triggering of this receptor with a specific agonist results in increased phosphorylation of ERK. Similarly, peripheral blood cells from children with juvenile idiopathic arthritis, a chronic inflammatory disease, express α1AR mRNA and respond to α1AR stimulation in vitro with an increase in production of the cytokines IL-6 and TNF-α (Heijnen et al., 1996). More recently, NE/EPI have been shown to modulate not only cytokine production by monocytes, but also the expression of matrix metalloproteases [(MMPs) (Speidl et al., 2004)]. MMPs degrade collagen, proteoglycans, and elastin, thus playing a role in various disease states, such as joint destruction in arthritic patients, rupture of atherosclerotic plaques, and macrophage-assisted tumor cell invasion into surrounding normal tissue (Speidl et al., 2004). Both primary human monocytes and monocyte-derived macrophages respond to LPS by increasing the secretion of MMPs, which is further enhanced by NE/EPI and inhibited by addition of a β1antagonist, but not a β2AR antagonist. These data suggest that monocyte/macrophages not only express a functional β2AR, but also a functional β1AR. 4. Dendritic Cells In contrast to the large number of studies describing modulation of monocyte/macrophage function by NE/EPI, little is known with respect to dendritic cells. One study shows that NE enhances skin dendritic cell migration from the site of antigen deposition to the draining lymph nodes in an α1/β2AR-dependent manner (Maestroni et al., 2003). In this response, NE may act as a chemotactic factor, although it may be that NE stimulates DC motility, rather than directed migration. In the same study, it was suggested that immature, but not mature, DCs express the αAR. Acute restraint stress in mice increases DC migration to the skin, an effect that is prevented by NE depletion (Maestroni et al., 2003). In addition, exposure of bone marrow-derived DCs to NEs reduces either LPS-
2. Adrenergic Regulation of Immunity
or protein antigen (KLH)–induced IL-12 release, but facilitates IL-10 release (Maestroni, 2002). Thus, in contrast to the effect described for NE on cytokine production by macrophages, the effect of NE on DC cytokine production is not exclusively mediated via the β2AR, since a β2AR antagonist reverses only part of the effect.
B. Adaptive Immunity 1. T-Cells An intracellular elevation in cAMP, the second messenger activated by β2AR stimulation, inhibits mature T-cell proliferation by decreasing IL-2 expression and secretion (Chen and Rothenberg, 1994; Mary et al., 1989; Tamir and Isakov, 1994; Wacholtz et al., 1991) and IL-2 receptor expression (Feldman et al., 1987; Krause et al., 1991; Tamir and Isakov, 1994). These findings suggest that there may be an effect of cAMP alone on naïve T-cell proliferation and IL-2 production, even though naïve CD4+ T-cells were not specifically isolated in these studies. When naïve CD4+ T-cells were isolated and activated, IL-2 secretion was decreased by exposure to NE, an effect that was prevented when a β2AR antagonist, but not β1AR or αAR antagonist, was added to the culture (Ramer-Quinn et al., 2000). These results suggested that NE and β2AR stimulation affect the ability of an activated naïve T-cell to produce IL-2 and, possibly, to expand in number. However, when the NE- or β2AR agonist-exposed naïve T-cells were cultured with either antigen/irradiated APC or antiCD3/anti-CD28, they produced an equal number of viable cells after 5 days in culture even though they produced less IL-2 (Swanson et al., 2001), suggesting that an early decrease in IL-2 after β2AR stimulation may affect initial naïve T-cell expansion, but that this effect on IL-2 may either dissipate over time or simply limit the number of T-cells that will go on to differentiate into an effector cell. In human T-cells activated via CD3, the β2AR inhibits the activation of NF-κB via a mechanism that involves the stabilization of its inhibitor protein, IκBα (Loop et al., 2004). In addition, high levels of NE appear to induce apoptosis and cell death (Bergquist et al., 1998; Del Rey et al., 2003), suggesting that other mechanisms for a diminished immune cell functional response may exist. These findings prompted study designs that would determine if NE and β2AR stimulation affected the ability of a naïve T-cell to develop into a Th1 or Th2 cell. Although the effect on Th2 cell development remains unclear, data show that NE stimulation of the β2AR on a naïve CD4+ T-cell does not affect the number of Th1 cells that develop under defined Th1-driving conditions, but does allow for the Th1 cells that develop
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to produce more IFN-γ per cell upon reactivation (Swanson et al., 2001). IL-12 appears to be essential for β2AR stimulation to exert this enhancing effect on resulting Th1 cell function, suggesting that the IL-12R and β2AR signaling pathways may interact with each other to mediate the enhancing effect. In this particular study, NE and β2AR stimulation had no effect on the level of IL-12 secreted by APC that activated the naïve T-cell, although the effect of NE on IL-12 production and Th1 development has been reported to be suppressed (Panina-Bordignon et al., 1997). Thus, NE may also have an effect on IL-12 production, which must be considered when evaluating any effects of NE on the development of a Th1 response in vivo. The effect of NE, β2AR stimulation, and cAMP on effector cell function itself, as opposed to naïve T-cell function, has been an area of active investigation. In Th1 cells, an increase in intracellular cAMP inhibits the production of IL-2 (Gajewski et al., 1990; Munoz et al., 1990; Novak and Rothenberg, 1990) and IFN-γ (Gajewski et al., 1990). For the mouse Th1 cell that expresses the β2AR, it appears that the timing of β2AR stimulation in relation to cell activation may play a role in determining the effect on Th1 cell activity. For example, exposure of Th1 cells to NE or a β2AR-selective agonist before their activation decreases both IL-2 and IFN-γ production (Sanders et al., 1997). However, stimulation either at the time of, or after, cell activation appears to be either without effect or induces a small increase in IFN-γ (Ramer-Quinn et al., 1997). In contrast, the effect of a cAMP increase in Th2 cells is either no change (Betz and Fox, 1991; Gajewski et al., 1990; Katamura et al., 1995; Novak and Rothenberg, 1990; Paliogianni and Boumpas, 1996; Pochet and Delespesse, 1983; Yoshimura et al., 1998), an inhibition (Borger et al., 1996a; Parker et al., 1995), or enhancement (Betz and Fox, 1991; Borger et al., 1996b; Crocker et al., 1996; Lacour et al., 1994; Naito et al., 1996; Wirth et al., 1996) of IL-4 and IL-5 production. However, it appears that NE has no effect on Th2 cell activity, likely because the Th2 cell does not express the β2AR (Sanders et al., 1997). Thus, an elevation in intracellular cAMP within each effector CD4+ T-cell subset is able to affect T-cell activity, but NE and β2AR stimulation affect only naïve T-cell and Th1 cell activity, with the effect on Th1 cells depending on the time of β2AR stimulation in relation to cell activation. In vitro exposure of human PBMC to dexamethasone, EPI, NE, or terbutaline induced a decrease in IFN-γ production, but an increase in IL-4 and IL-10, due primarily to a decrease induced in IL-12 production by APC (Agarwal et al., 1998a; Agarwal et al., 1998b; Agarwal et al., 2000; Elenkov et al., 1996; PaninaBordignon et al., 1997). These findings indicate that a
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decrease in IL-12 induced by either NE, a β2AR agonist, or cortisol prevents Th1 cell differentiation, resulting in a possible shift to Th2 cell development. However, when human HIV-infected PBMC were exposed in vitro to NE, stimulation of the β2AR decreased IFN-γ, IL-10, and IL-4 production and enhanced HIV replication in T-cells, an effect that was prevented when these cytokines were added exogenously to the cultures (Cole et al., 1998). Thus, the latter finding suggested that NE stimulation of the β2AR on T-cells may enhance HIV pathogenesis by inhibiting the production of all cytokines that would prevent HIV replication, namely IFN-γ, IL-10, and IL-4. Exposure of murine spleen cells to NE increased the generation of CD8+ T-cell lytic activity (Hatfield et al., 1986), perhaps by inhibiting the production of TNF-α, an effect that was reversed by the addition of exogenous cytokine (Kalinichenko et al., 1999). In contrast, EPI and a βAR agonist decreased the generation of CD8+ T-cell lytic activity (Cook-Mills et al., 1995; Strom et al., 1973). However, the timing of exposure to an NE/EPI or agonist in relation to the stage of CD8+ Tcell differentiation may be relevant to the outcome in cell activity. For example, the above-cited studies were conducted using cells exposed to AR ligands during the generation of the CTL response. If ligands were added after the generation of CTL, i.e., during the effector stage of the response to antigen, a decrease in CTL activity occurred (Cook-Mills et al., 1995; Strom et al., 1973) that may have been due to a cAMP-induced decrease in the TCR-dependent release of cytotoxic granules (Takayama et al., 1988). Thus, the role of NE and/or β2AR stimulation in modulating CD8+ T-cell activity remains uncertain in both humans and animals, but may be influenced by the time of β2AR stimulation in relation to the stage of CD8+ T-cell differentiation. 2. B-Cells β2AR stimulation and elevation of cAMP have been shown to affect B-cell proliferation (Blomhoff et al., 1987; Cohen and Rothstein, 1989; Diamantstein and Ulmer, 1975; Holte et al., 1988; Johnson et al., 1981; Muraguchi et al., 1984; Muthusamy et al., 1991; Vischer, 1976; Watson, 1975; Whisler et al., 1992) by either inhibiting early biochemical events and proliferation (Blomhoff et al., 1987; Holte et al., 1988; Muthusamy et al., 1991) or enhancing B-cell proliferation (Cohen and Rothstein., 1989; Li et al., 1989; Whisler et al., 1992). For a comprehensive review of the very early history of findings in this area, please refer to the following review article (Sanders and Munson, 1985a). A pharmacologic characterization of the enhancing effect of NE on the IgM response shows that either NE alone or
NE in the presence of the αAR antagonist phentolamine produced an enhanced IgM response, while in the presence of the βAR antagonist propranolol produced a control level response, suggesting that βAR activation was responsible for the enhancement (Sanders and Munson, 1984a). Selective β2AR stimulation with the agonist terbutaline enhanced the antibody response with a similar magnitude and kinetics to that produced by NE, and this enhancement was blocked with propranolol (Sanders and Munson, 1984b), suggesting that β2AR activation specifically was responsible for mediating the enhancing effect of NE. IgG1 production in vitro by B-cells cultured in the presence of an activating stimulus and a source for IL-4 is enhanced following β2AR stimulation and elevation of cAMP when compared to control cells (Kasprowicz et al., 2000; Podojil and Sanders, 2003; Roper et al., 1990; Roper et al., 2002; Stein and Phipps, 1991a; Stein and Phipps, 1991b; Stein and Phipps, 1992). However, the mechanism by which this enhancement was induced remained unknown until recently. Before one attempts to understand the mechanism by which β2AR stimulation regulates the level of IgG1 produced, a working knowledge of how the production of IgG is regulated at the molecular level is essential. First, Bcell activation in conjunction with specific cytokines induce class switch recombination (CSR) at the DNA level so that a B-cell will differentiate into a cell that produces an antibody isotype other than IgM. The CSR triggers the production of germline γ1 mRNA before the DNA completely rearranges for production of the mature form of IgG1 mRNA and protein that will be secreted from the cell (Stavnezer-Nordgren and Sirlin, 1986). The level of mature IgG1 produced by a B-cell is regulated by activity at the 3′-IgH enhancer region that is contained within the IgH locus in the mouse (Khamlichi et al., 2000). DNA sequences contained within the 3′-IgH enhancer region bind various transcription factors, including the B-cell–specific transcription factor Oct-2, which is known to regulate activity of the 3′-IgH enhancer in association with the coactivator OCA-B (Tang and Sharp, 1999). Both Oct-2 and OCA-B are induced when the activation receptor CD40 is stimulated on the B-cell (Pinaud et al., 2001; Stevens et al., 2000). Deletion of Oct-2 decreases the level of serum IgG1 in mice (Corcoran and Karvelas, 1994; Humbert and Corcoran, 1997), while deletion of OCA-B decreases serum IgG1 and germinal center formation (Kim et al., 1996; Nielsen et al., 1996; Schubart et al., 1996). Taken together, these data indicate that 3′-IgH enhancer activity is regulated by the transcription factor Oct-2 and its co-activator protein OCA-B, and that these proteins determine the rate at which IgG1 is produced after
2. Adrenergic Regulation of Immunity
switching. Therefore, regulation of an IgG1 response can occur at the level of either CSR and/or 3′-IgH enhancer activity. The Th2 cell that helps a B-cell to make IgG1 is not affected by β2AR stimulation since it does not express the receptor. Thus, the effect of β2AR stimulation on the B-cell alone could be ascertained because any contribution of an indirect effect that may be exerted on Th2 cell activity was eliminated. Using a model system of purified splenic naïve B-cells cultured in the presence of CD40L and IL-4, data show that β2AR stimulation increases the amount of IgG1 produced per B-cell, without affecting the number of cells that switch to produce IgG1, as compared to B-cells not exposed to β2AR stimulation (Kasprowicz et al., 2000; Podojil and Sanders, 2003; Podojil et al., 2004). β2AR stimulation mediates this enhancing effect in two ways: first, via a direct pathway from the β2AR that regulates the level of 3′-IgH enhancer activity (Podojil and Sanders, 2003); and second, via an indirect pathway that first upregulates expression of the co-stimulatory molecule CD86 (also known as B7-2), which upon stimulation with CD28, activates another signaling pathway in the Bcell that also regulates the level of 3′-IgH enhancer activity. More specifically, the OCA-B is upregulated by β2AR activation of PKA and subsequent phosphorylation of CREB (Podojil et al., 2004). Using chromatin immunoprecipitation, the increase in OCA-B translated into a higher level of OCA-B binding to the 3′IgH-enhancer region of the IgH locus (Podojil et al., 2004), suggesting that the coactivator was binding to a transcription factor that could activate 3′-IgH enhancer activity directly. Additionally, the level of Oct-2, the transcription factor that binds to the 3′-IgH enhancer, is increased indirectly via β2AR stimulation as a consequence of the β2AR-induced increase in CD86 expression (Podojil et al., 2004). Specifically, CD86 stimulation increases the level of Oct-2 expression and binding to the 3′-IgH enhancer via a newly characterized signaling pathway that involves NF-κB activation (Podojil et al., 2004). Thus, the β2AR-induced indirect increase in the level of the transcription factor Oct-2, along with the β2AR-induced increase in the level of its coactivator protein OCA-B, bind cooperatively to the 3′IgH enhancer region to increase the rate at which IgG1 mRNA is produced (Podojil et al., 2004). If this effect from β2AR stimulation in vitro is what happens normally during a B-cell response to antigen in vivo when NE is released within the microenvironment of B-cells responding to antigen during a Th2–B-cell interaction, then immune reactions studied in vitro in the absence of NE reflect responses that involve immune cells alone, and may not reflect what happens in vivo when
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NE is released to stimulate the β2AR. This probability is supported by in vivo data showing that antigen induces an increase in CD86 expression on a B-cell, but that NE depletion prevents this increase in CD86 from occurring (Kohm et al., 2002), suggesting that NE may regulate the level of a key co-stimulatory molecule that is involved in the co-stimulation of not only T-cells to stimulate cytokine production, but is also involved in direct signaling to the B-cell itself to regulate the level of IgG1 produced. For a more detailed description of how the study of the role played by the β2AR in enhancing the IgG1 response led to the discovery of the signaling pathway activated by CD86, please refer to the following review (Podojil et al., 2005). Taken together, these findings suggest that NE exerts a regulatory effect on the level of IgG1 produced by enhancing the endogenous activity of the B-cells that are activated to generate the response. These findings also suggest that signaling pathways activated in a B-cell through stimulation of an immunoreceptor (CD86) and a neuroreceptor (β2AR) converge to regulate the magnitude of an IgG1 response.
VI. RELEVANCE TO HEALTH AND DISEASE An understanding of the cellular, biochemical, and molecular mechanisms by which NE regulates the level of immune cell activity will potentially lead to the development of therapeutic approaches that will alter the etiology and/or progression of immune system-related diseases. Such therapeutic approaches will be important as one’s immune system encounters a multitude of exogenous and endogenous antigens. It will also be important to understand how one’s level of immunocompetence might affect different components of the nervous system that regulate the level of immune cell activity, e.g., the level of locally secreted NE within lymphoid tissue and/or the level of expression for AR subtypes on immune cells. To date, a few clinical examples support a role for a neuroimmune interrelationship in the etiology or progression of a disease state, and they will be discussed below. As summarized above, expression of the βAR on cells of the innate immune system contributes to suppression of innate immunity. Thus, during acute psychological or physical stress, it is likely that partial suppression of NK cell cytolytic activity and macrophage/PMN anti-microbial activity will occur. Is there evidence that the β2AR-mediated suppression of innate immunity takes place in clinically relevant situations? We think that the answer is yes. For example, the welldescribed effects of acute stress on, or the administra-
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tion of a β2AR agonist to, laboratory animals not only suppresses NK cell function, but also enhances tumor cell metastasis [reviewed in (Ben Eliyahu, 2003)]. In addition, the suppression of NK cell activity and the increase in metastasis formation precipitated by surgical stress is prevented by administration of a βAR antagonist, again indicating the clinical relevance of these findings to cancer therapy (Melamed et al., 2005). Additional details concerning the clinical relevance of βAR stimulation on innate immune cell activity during times of stress are discussed in Chapter 12 of this book, authored by Ben Eliyahu and Avraham. It is known that infections are a common complication of stroke, and that a large part of the mortality in stroke patients is due to complications that develop because of the infection. In an animal model of stroke, immune cell activity is suppressed, particularly the ability of NK and T-cells to produce IFN-γ (Prass et al., 2003). Moreover, the stroke-induced suppression of IFN-γ production was prevented by the administration of a βAR antagonist, as was the level of infection, suggesting that normal regulation of NK and T-cell activity by NE is dysregulated. Also, patients with chronic obstructive pulmonary disease (COPD), who are chronically exposed to a βAR agonist to relax constricted airway smooth muscles, may suffer the effect of β2AR-induced reduction in the number of PMN and an inhibition of PMN activity and mediator release. Moreover, there is evidence that a β2AR agonist promotes PMN apoptosis and reduces integrin expression on the cell surface [reviewed in (Johnson and Rennard, 2001)]. Thus, the effect of sympathetic neurotransmitters on immune cells that are essential for the clearance of infections needs to be considered, especially when the level of neurotransmitter may be more or less than normal. Evidence for the involvement of a neuroimmune interaction in the pathogenesis of an inflammatory disease, such as rheumatoid arthritis (RA), is suggested by a collection of clinical observations. First, the distribution of joint inflammation is mostly symmetric (Mitchell and Fries, 1982), as is the distribution of sympathetic nerves. Second, the joints in a patient with unilateral paralysis are spared from the inflammatory process on the affected side alone, suggesting that arthritis is limited to joints in which the SNS remains intact (Thompson and Bywaters, 1962). Third, NE and immune cells that express the β2AR are involved in regulating the intensity of joint inflammation (Straub et al., 2005a; Straub and Harle, 2005b). And finally, stress often precedes disease exacerbation (Baker, 1982; Herrmann et al., 2000), suggesting that the SNS and HPA are activated to release NE/EPI and/or corticosteroids, respectively. Therefore, in RA patients where
the systemic level of IFN-γ is elevated, as is the local level at the inflammatory sites (Park et al., 2001; Yin et al., 1999), it is possible that disease onset and/or progression is promoted by a mechanism that involves an SNS-induced, β2AR-mediated effect on a naïve CD4+ T-cell to increase the level of IFN-γ produced by the Th1 cells that develop, as has been reported for murine naïve CD4+ T-cells (Swanson et al., 2001). In this manner, Th1 cells secreting a higher level of IFN-γ might accumulate within the synovial fluid to promote the inflammatory process. Such a finding would indicate that a neuroimmune process was involved in the disease process and, therefore, should be controllable via pharmacological therapeutic approaches. Such findings may also have relevance for the design of vaccination protocols in which the goal might be to increase IFN-γ production by a limited number of Th1 cells that may develop under conditions where IL-12 is limited. The administration of a β2AR drug may have beneficial effects for patients with other inflammatory autoimmune diseases. For example, the administration of a β2AR agonist to patients with multiple sclerosis suppresses pro-inflammatory cytokine production, which may help to reduce the inflammatory response in these patients. Interestingly, there is evidence from patients with multiple sclerosis (Giorelli et al., 2004; Vroon et al., 2005), as well as from patients with rheumatoid arthritis, that immune cells are more sensitive for regulation of the immune response by a βAR agonist, an effect which may be beneficial (Lombardi et al., 1999). Based on this information, it was shown that the administration of a βAR agonist to rats with adjuvant arthritis increases production of the anti-inflammatory cytokines IL-10, TGF-β, and IL-1RA, but reduced production of the pro-inflammatory cytokines TNF-α and IFN-γ at mucosal sites (Cobelens et al., 2002). More importantly, however, results show that administration of a βAR agonist to rats with adjuvant arthritis, together with oral administration of a tolerogenic antigen, suppresses disease symptoms, while administration of either the antigen or the β2AR agonist alone did not have an effect. These data suggest that administration of a βAR agonist during an inflammatory disease process may modify the cytokine milieu so that tolerogenic processes can develop. An understanding of the regulatory mechanism by which CD86 and/or β2AR stimulation increases the level of IgG1 produced by a murine B-cell may help to explain how acute stress has been linked to an enhancement of IgG immunity in humans. A recent study reported that the drug ephedrine exacerbates lupus symptoms in lupus-prone mice via a mechanism that appears to involve stimulation of the bAR on a B-cell
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to increase the level of IgG (Hudson et al., 2005), suggesting that NE may regulate the severity of this disease process. In acute stress, an increase in the level of NE/EPI released from lymphoid organ nerve terminals, above that released by antigen alone, might stimulate a higher number of the β2AR on a B-cell to induce the B-cell to produce a higher level of IgG, as reported in mice (Kohm and Sanders, 1999; Podojil and Sanders, 2003; Podojil et al., 2004). While in chronic stress, the β2AR may be downregulated, thus preventing optimal β2AR stimulation on a B-cell and, consequently, preventing optimal IgG production to occur. However, a recent study reported that chronic stress in mice is associated with no change in NE levels, but is associated with an increase in β2AR expression on immune cells and an increased sympathetic effect on T- and B-cell responses (Edgar et al., 2003). The latter findings may have relevance for vaccination protocols in which the goal might be to raise the level of humoral immunity in new recruits to the armed forces, especially when vaccinations occur just prior to deployment when stress levels have been elevated for days. An increase in sympathetic tone that is induced by the anxiety of surgery may suppress immune cell function to slow down wound healing, and thus increase the chance for wound infection (Glaser et al., 1999; Glaser et al., 2005; Kiecolt-Glaser et al., 1998; Rozlog et al., 1999). Likewise, an increase in sympathetic tone during exercise may enhance the intensity and duration of a humoral immune response to antigen, and consequently affect the likelihood of the development of infectious conditions such as colds and flu (Gleeson et al., 2004). Interventions that include exercise may decrease anxiety, depression, and other psychological states, which appear to have a negative effect on immunity, but increase humoral immunity. Also, the activation or suppression of sympathetic tone during psychological and/or behavioral interventions for clinical conditions such as either depression or HIV infection may affect immune status and the ultimate survival of the affected individual (Robinson et al., 2000). Also, if NE plays a role in regulating immune cell function, then an age-related decline in lymphoid tissue innervation (Bellinger et al., 1992; Madden, 2000) may contribute to the age-associated increase in the incidence of autoimmunity, cancer, and susceptibility to infection (Biondi and Zannino, 1997; Caruso et al., 2004; Kiecolt-Glaser and Glaser, 1999). An understanding of this neuroimmune interaction would be useful in the design of targeted therapeutic approaches for aged individuals who might manifest changes in the level of adrenergic receptors and/or their ligands at the time of flu or pneumococcal vaccination.
References Abbas, A. K., Murphy, K. M., and Sher, A. (1996). Functional diversity of helper T lymphocytes. Nature, 383, 787–793. Ackerman, K. D., Madden, K. S., Livnat, S., Felten, S. Y., and Felten, D. L. (1991). Neonatal sympathetic denervation alters the development of in vitro spleen cell proliferation and differentiation. Brain Behav. Immunity, 5, 235–261. Ader, R., and Cohen, N. (1975). Behaviorally conditioned immunosuppression. Psychosom. Med., 37, 333–340. Agarwal, S. K., and Marshall, G. D., Jr. (1998a). Glucocorticoidinduced type 1/type 2 cytokine alterations in humans: a model for stress-related immune dysfunction. J. Interferon Cytokine Res., 18, 1059–1068. Agarwal, S. K., and Marshall, G. D., Jr. (1998b). In vivo alteration in type-1 and type-2 cytokine balance: a possible mechanism for elevated total IgE in HIV-infected patients. Hum. Immunol., 59, 99–105. Agarwal, S. K., and Marshall, G. D., Jr. (2000). Beta-adrenergic modulation of human type-1/type-2 cytokine balance. J. Allergy Clin. Immunol., 105, 91–98. Alaniz, R. C., Thomas, S. A., Perez-Melgosa, M., Mueller, K., Farr, A. G., Palmiter, R. D., and Wilson, C. B. (1999). Dopamine betahydroxylase deficiency impairs cellular immunity. Proc. Natl. Acad. Sci. USA, 96, 2274–2278. Baker, G. H. (1982). Life events before the onset of rheumatoid arthritis. Psychother. Psychosom., 38, 173–177. Bellinger, D. L., Ackerman, K. D., Felten, S. Y., and Felten, D. L. (1992). A longitudinal study of age-related loss of noradrenergic nerves and lymphoid cells in the rat spleen. Exp. Neurol., 116, 295–311. Ben Eliyahu, S. (2003). The promotion of tumor metastasis by surgery and stress: immunological basis and implications for psychoneuroimmunology. Brain Behav. Immun., 17(Suppl 1), S27–36. Benovic, J. L., Strasser, R. H., Caron, M. G., and Lefkowitz, R. J. (1986). Beta-adrenergic receptor kinase: identification of a novel protein kinase that phosphorylates the agonist-occupied form of the receptor. PNAS, 83, 2797–2801. Benschop, R. J., Jacobs, R., Sommer, B., Schurmeyer, T. H., Raab, J. R., Schmidt, R. E., and Schedlowski, M. (1996a). Modulation of the immunologic response to acute stress in humans by betablockade or benzodiazepines. FASEB J., 10, 517–524. Benschop, R. J., Nieuwenhuis, E. E., Tromp, E. A., Godaert, G. L., Ballieux, R. E., and van Doornen, L. J. (1994). Effects of betaadrenergic blockade on immunologic and cardiovascular changes induced by mental stress. Circulation, 89, 762–769. Benschop, R. J., Oostveen, F. G., Heijnen, C. J., and Ballieux, R. E. (1993). Beta 2–adrenergic stimulation causes detachment of natural killer cells from cultured endothelium. Eur. J. Immunol., 23, 3242–3247. Benschop, R. J., Rodriguez-Feuerhahn, M., and Schedlowski, M. (1996b). Catecholamine-induced leukocytosis: early observations, current research, and future directions. Brain Behav. Immun., 10, 77–91. Bergquist, J., Tarkowski, A., Ewing, A., and Ekman, R. (1998). Catecholaminergic suppression of immunocompetent cells. Immunol. Today, 19, 562–567. Besedovsky, H., Del Rey, A., Sorkin, E., Da Prada, M., Burri, R., and Honegger, C. (1983). The immune response evokes changes in brain noradrenergic neurons. Science, 221, 564–566. Besedovsky, H., Sorkin, E., Felix, D., and Haas, H. (1977). Hypothalamic changes during the immune process. Eur. J. Immunol., 7, 323–325.
78
I. Neural and Endocrine Effects on Immunity
Besedovsky, H. O., and Del Rey, A. (1996). Immune-neuro-endocrine interactions: facts and hypotheses. Endocr. Rev., 17, 64–102. Besedovsky, H. O., Del Rey, A., Sorkin, E., Da Prada, M., and Keller, H. H. (1979). Immunoregulation mediated by the sympathetic nervous system. Cell. Immunol., 48, 346–355. Betz, M., and Fox, B. S. (1991). Prostaglandin E2 inhibits production of Th1 lymphokines but not of Th2 lymphokines. J. Immunol., 146, 108–113. Bierhaus, A., Wolf, J., Andrassy, M., Rohleder, N., Humpert, P. M., Petrov, D., Ferstl, R., von Eynatten, M., Wendt, T., Rudofsky, G., Joswig, M., Morcos, M., Schwaninger, M., McEwen, B., Kirschbaum, C., and Nawroth, P. P. (2003). A mechanism converting psychosocial stress into mononuclear cell activation. Proc. Natl. Acad. Sci. USA, 100, 1920–1925. Biondi, M., and Zannino, L.-G. (1997). Psychological stress, neuroimmunomodulation, and susceptibility to infectious diseases in animals and man: a review. Psychother. Psychosom., 66, 3–26. Bloemen, P. G., van den Tweel, M. C., Henricks, P. A., Engels, F., Kester, M. H., van de Loo, P. G., Blomjous, F. J., and Nijkamp, F. P. (1997). Increased cAMP levels in stimulated neutrophils inhibit their adhesion to human bronchial epithelial cells. Am. J. Physiol., 272, L580–587. Blomhoff, H. K., Smeland, E. B., Beiske, K., Blomhoff, R., Ruud, E., Bjoro, T., Pfeifer-Ohlsson, S., Watt, R., Funderud, S., Godal, T., and Ohlsson, R. (1987). Cyclic AMP-mediated suppression of normal and neoplastic B cell proliferation is associated with regulation of myc and Ha-ras protooncogenes. J. Cell. Physiol., 131, 426–433. Borger, P., Hoekstra, Y., Esselink, M. T., Postma, D. S., Zaagsma, J., Vellenga, E., and Kauffman, H. F. (1998). Beta-adrenoceptor– mediated inhibition of IFN-gamma, IL-3, and GM-CSF mRNA accumulation in activated human T lymphocytes is solely mediated by the beta2–adrenoceptor subtype. Am. J. Respir. Cell Mol. Biol., 19, 400–407. Borger, P., Kauffman, H. F., Postma, D. S., and Vellenga, E. (1996a). Interleukin-4 gene expression in activated human T lymphocytes is regulated by the cyclic adenosine monophosphate-dependent signaling pathway. Blood, 87, 691–698. Borger, P., Kauffman, H. F., Postma, D. S., and Vellenga, E. (1996b). Interleukin-4 gene expression in activated human T lymphocytes is regulated by the cyclic adenosine monophosphate-dependent signaling pathway. Blood, 87, 691–698. Cao, L., Filipov, N. M., and Lawrence, D. A. (2002). Sympathetic nervous system plays a major role in acute cold/restraint stress inhibition of host resistance to Listeria monocytogenes. J. Neuroimmunol., 125, 94–102. Caruso, C., Lio, D., Cavallone, L., and Franceschi, C. (2004). Aging, longevity, inflammation, and cancer. Ann. N. Y. Acad. Sci., 1028, 1–13. Cazaux, C. A., Sterin-Borda, L., Gorelik, G., and Cremaschi, G. A. (1995). Down-regulation of beta-adrenergic receptors induced by mitogen activation of intracellular signaling events in lymphocytes. FEBS Lett., 364, 120–124. Chao, H. J., Hsu, Y. C., Yuan, H. P., Jiang, H. S., and Hsueh, C. M. (2005). The conditioned enhancement of neutrophil activity is catecholamine dependent. J. Neuroimmunol., 158, 159–169. Chelmicka-Schorr, E., Checinski, M., and Arnason, B. G. W. (1988). Chemical sympathectomy augments the severity of experimental allergic encephalomyelitis. J. Neuroimmunol., 17, 347–350. Chen, D., and Rothenberg, E. V. (1994). Interleukin 2 transcription factors as molecular targets of cAMP inhibition: delayed inhibition kinetics and combinatorial transcription roles. J. Exp. Med., 179, 931–942.
Cobelens, P. M., Kavelaars, A., Vroon, A., Ringeling, M., van der Zee, R., van Eden, W., and Heijnen, C. J. (2002). The beta 2-adrenergic agonist salbutamol potentiates oral induction of tolerance, suppressing adjuvant arthritis and antigen-specific immunity. J. Immunol., 169, 5028–5035. Cohen, D. P., and Rothstein, T. L. (1989). Adenosine 3′, 5′-cyclic monophosphate modulates the mitogenic responses of murine B lymphocytes. Cell. Immunol., 121, 113–124. Cole, S. W., Korin, Y. D., Fahey, J. L., and Zack, J. A. (1998). Norepinephrine accelerates HIV replication via protein kinase Adependent effects on cytokine production. J. Immunol., 161, 610–616. Cook-Mills, J. M., Mokyr, M. B., Cohen, R. L., Perlman, R. L., and Chambers, D. A. (1995). Neurotransmitter suppression of the in vitro generation of a cytotoxic T lymphocyte response against the syngeneic MOPC-315 plasmacytoma. Cancer Immunol. Immunother., 40, 79–87. Corcoran, L. M., and Karvelas, M. (1994). Oct-2 is required in T cell–independent B cell activation for G1 progression and for proliferation. Immunity, 1, 635–645. Crocker, I. C., Townley, R. G., and Khan, M. M. (1996). Phosphodiesterase inhibitors suppress proliferation of peripheral blood mononuclear cells and interleukin-4 and -5 secretion by human T-helper type 2 cells. Immunopharmacol., 31, 223–235. Cross, R. J., Jackson, J. C., Brooks, W. H., Sparks, D. L., Markesbery, W. R., and Roszman, T. L. (1986). Neuroimmunomodulation: impairment of humoral immune responsiveness by 6-hydroxydopamine treatment. Immunology, 57, 145–152. de Coupade, C., Gear, R. W., Dazin, P. F., Sroussi, H. Y., Green, P. G., and Levine, J. D. (2004). Beta 2–adrenergic receptor regulation of human neutrophil function is sexually dimorphic. Br. J. Pharmacol., 143, 1033–1041. Del Rey, A., Besedovsky, H. O., Sorkin, E., Da Prada, M., and Arrenbrecht, S. (1981). Immunoregulation mediated by the sympathetic nervous system II. Cell. Immunol., 63, 329–334. Del Rey, A., Kabiersch, A., Petzoldt, S., and Besedovsky, H. O. (2003). Sympathetic abnormalities during autoimmune processes: potential relevance of noradrenaline-induced apoptosis. Ann. N. Y. Acad. Sci., 992, 158–167. Dhabhar, F. S., and McEwen, B. S. (1999). Enhancing versus suppressive effects of stress hormones on skin immune function. Proc. Natl. Acad. Sci. USA, 96, 1059–1064. Diamantstein, T., and Ulmer, A. (1975). The antagonistic action of cyclic GMP and cyclic AMP on proliferation of B and T lymphocytes. Immunology, 28, 113–119. Dobbs, C. M., Vasquez, M., Glaser, R., and Sheridan, J. F. (1993). Mechanisms of stress-induced modulation of viral pathogenesis and immunity. J. Neuroimmunol., 48, 151–160. Edgar, V. A., Silberman, D. M., Cremaschi, G. A., Zieher, L. M., and Genaro, A. M. (2003). Altered lymphocyte catecholamine reactivity in mice subjected to chronic mild stress. Biochem. Pharmacol., 65, 15–23. Eijkelkamp, N., Cobelens, P. M., Sanders, V. M., Heijnen, C. J., and Kavelaars, A. (2004). Tissue specific effects of the beta 2adrenergic agonist salbutamol on LPS-induced IFN-gamma, IL-10 and TGF-beta responses in vivo. J. Neuroimmunol., 150, 3–9. Elenkov, I. J., Papanicolaou, D. A., Wilder, R. L., and Chrousos, G. P. (1996). Modulatory effects of glucocorticoids and catecholamines on human interleukin-12 and interleukin-10 production: clinical implications. Proceedings of the Association of American Physicians, 108, 374–381. Elenkov, I. J., Wilder, R. L., Chrousos, G. P., and Vizi, E. S. (2000). The sympathetic nerve—an integrative interface between two super-
2. Adrenergic Regulation of Immunity systems: the brain and the immune system. Pharmacol. Rev., 52, 595–638. Feldman, R. D., Hunninghake, G. W., and McArdle, W. (1987). Betaadrenergic receptor-mediated suppression of interleukin 2 receptors in human lymphocytes. J. Immunol., 139(10), 3355–3359. Feldmann, M., Brennan, F. M., and Maini, R. N. (1996). Role of cytokines in rheumatoid arthritis. Annu. Rev. Immunol., 14, 397–440. Felten, D. L., Felten, S. Y., Bellinger, D. L., Carlson, S. L., Ackerman, K. D., Madden, K. S., Olschowki, J. A., and Livnat, S. (1987). Noradrenergic sympathetic neural interactions with the immune system: structure and function. Immunol. Rev., 100, 225–260. Felten, S. Y., and Felten, D. L. (1991). Innervation of lymphoid tissue. In R. Ader, N. Cohen, and D. L. Felten (Eds.), Psychoneuroimmunology (2nd ed., pp. 27–69). New York: Academic Press, Inc. Felten, S. Y., Madden, K. S., Bellinger, D. L., Kruszewska, B., Moynihan, J. A., and Felten, D. L. (1998). The role of the sympathetic nervous system in the modulation of immune responses. Adv. in Pharmacol., 42, 583–587. Ferguson, S. S. (2001). Evolving concepts in G protein–coupled receptor endocytosis: the role in receptor desensitization and signaling. Pharmacol. Rev., 53, 1–24. Firestein, G. S. (2003). Evolving concepts of rheumatoid arthritis. Nature, 423, 356–361. Fuchs, B. A., Campbell, K. S., and Munson, A. E. (1988). Norepinephrine and serotonin content of the murine spleen: its relationship to lymphocyte beta-adrenergic receptor density and the humoral immune response in vivo and in vitro. Cell. Immunol., 117, 339–351. Gajewski, T. F., Schell, S. R., and Fitch, F. W. (1990). Evidence implicating utilization of different T cell receptor-associated signaling pathways by Th-1 and Th-2 clones. J. Immunol., 144, 4110–4120. Gan, X., Zhang, L., Solomon, G. F., and Bonavida, B. (2002). Mechanism of norepinephrine-mediated inhibition of human NK cytotoxic functions: inhibition of cytokine secretion, target binding, and programming for cytotoxicity. Brain Behav. Immun., 16, 227–246. Giorelli, M., Livrea, P., and Trojano, M. (2004). Post-receptorial mechanisms underlie functional disregulation of beta2-adrenergic receptors in lymphocytes from multiple sclerosis patients. J. Neuroimmunol., 155, 143–149. Glaser, R., and Kiecolt-Glaser, J. K. (2005). Stress-induced immune dysfunction: implications for health. Nat. Rev. Immunol., 5, 243–251. Glaser, R., Kiecolt-Glaser, J. K., Marucha, P. T., MacCallum, R. C., Laskowski, B. F., and Malarkey, W. B. (1999). Stress-related changes in proinflammatory cytokine production in wounds. Arch. Gen. Psychiatry, 56, 450–456. Gleeson, M., Nieman, D. C., and Pedersen, B. K. (2004). Exercise, nutrition and immune function. J. Sports Sci., 22, 115–125. Goin, J. C., Sterin-Borda, L., Borda, E. S., Finiasz, M., Fernandez, J., and de Bracco, M. M. (1991). Active alpha 2 and beta adrenoceptors in lymphocytes from patients with chronic lymphocytic leukemia. Int. J. Cancer, 49, 178–181. Goleva, E., Dunlap, A., and Leung, D. Y. (2004). Differential control of TH1 versus TH2 cell responses by the combination of low-dose steroids with beta2-adrenergic agonists. J. Allergy Clin. Immunol., 114, 183–191. Hahn, P. Y., Yoo, P., Ba, Z. F., Chaudry, I. H., and Wang, P. (1998). Upregulation of Kupffer cell beta-adrenoceptors and cAMP levels during the late stage of sepsis. Biochim. Biophys. Acta., 1404, 377–384. Hall, N. R., McClure, J. E., Hu, S., Tare, S., Seals, C. M., and Goldstein, A. L. (1982). Effects of 6-hydroxydopamine upon primary and
79
secondary thymus dependent immune responses. Immunopharmacol., 5, 39–48. Harbuz, M. (2003). Neuroendocrine-immune interactions. Trends Endocrinol. Metab., 14, 51–52. Harle, P., Mobius, D., Carr, D. J., Scholmerich, J., and Straub, R. H. (2005). An opposing time-dependent immune-modulating effect of the sympathetic nervous system conferred by altering the cytokine profile in the local lymph nodes and spleen of mice with type II collagen-induced arthritis. Arthritis Rheum., 52, 1305–1313. Hatfield, S. M., Peterson, B. H., and DiMicco, J. A. (1986). Beta-adrenoceptor modulation of the generation of murine cytotoxic T lymphocytes in vitro. J. Pharmacol. Exp. Ther., 239, 460–466. Heijink, I. H., Vellenga, E., Borger, P., Postma, D. S., Monchy, J. G., and Kauffman, H. F. (2003). Polarized Th1 and Th2 cells are less responsive to negative feedback by receptors coupled to the AC/ cAMP system compared to freshly isolated T cells. Br. J. Pharmacol., 138, 1441–1450. Heijnen, C. J., Rouppe van der Voort, C., van de Pol, M., and Kavelaars, A. (2002). Cytokines regulate alpha(1)-adrenergic receptor mRNA expression in human monocytic cells and endothelial cells. J. Neuroimmunol, 125, 66–72. Heijnen, C. J., Rouppe van der Voort, C., Wulffraat, N., van der Net, J., Kuis, W., and Kavelaars, A. (1996). Functional alpha 1adrenergic receptors on leukocytes of patients with polyarticular juvenile rheumatoid arthritis. J. Neuroimmunol., 71, 223–226. Hellstrand, K., and Hermodsson, S. (1989). An immunopharmacological analysis of adrenaline-induced suppression of human natural killer cell cytotoxicity. Int. Arch. Allergy Appl. Immunol., 89, 334–341. Hellstrand, K., Hermodsson, S., and Strannegard, O. (1985). Evidence for a beta-adrenoceptor–mediated regulation of human natural killer cells. J. Immunol., 134, 4095–4099. Herrmann, M., Scholmerich, J., and Straub, R. H. (2000). Stress and rheumatic diseases. Rheum. Dis. Clin. North Am., 26, 737–763, viii. Hetier, E., Ayala, J., Bousseau, A., and Prochiantz, A. (1991). Modulation of interleukin-1 and tumor necrosis factor expression by beta-adrenergic agonists in mouse amoeboid microglial cells. Exp. Brain Res., 86, 407–413. Holte, H., Torjesen, P., Blomhoff, H. K., Ruud, E., Funderud, S., and Smeland, E. B. (1988). Cyclic AMP has the ability to influence multiple events during B cell stimulation. Eur. J. Immunol., 18, 1359–1366. Hudson, C. A., Mondal, T. K., Cao, L., Kasten-Jolly, J., Huber, V. C., and Lawrence, D. A. (2005). The dietary supplement ephedrine induces beta-adrenergic mediated exacerbation of systemic lupus erythematosus in NZM391 mice. Lupus, 14, 293–307. Humbert, P. O., and Corcoran, L. M. (1997). Oct-2 gene disruption eliminates the peritoneal B-1 lymphocytes linage and attenuates B-2 cell maturation and function. J. Immunol., 159, 5273–5285. Jetschmann, J. U., Benschop, R. J., Jacobs, R., Kemper, A., Oberbeck, R., Schmidt, R. E., and Schedlowski, M. (1997). Expression and in-vivo modulation of alpha- and beta-adrenoceptors on human natural killer (CD16+) cells. J. Neuroimmunol., 74, 159–164. Johnson, D. L., Ashmore, R. C., and Gordon, M. A. (1981). Effects of beta-adrenergic agents on the murine lymphocyte response to mitogen stimulation. J. Immunopharmacol., 3, 205–219. Johnson, M., and Rennard, S. (2001). Alternative mechanisms for long-acting beta(2)-adrenergic agonists in COPD. Chest, 120, 258–270. Kalinichenko, V. V., Mokyr, M. B., Graf, L. H., Jr., Cohen, R. L., and Chambers, D. A. (1999). Norepinephrine-mediated inhibition of antitumor cytotoxic T lymphocyte generation involves a beta-
80
I. Neural and Endocrine Effects on Immunity
adrenergic receptor mechanism and decreased TNF-alpha gene expression. J. Immunol., 163, 2492–2499. Kappel, M., Poulsen, T. D., Galbo, H., and Pedersen, B. K. (1998). Influence of minor increases in plasma catecholamines on natural killer cell activity. Horm. Res., 49, 22–26. Kasahara, K., Tanaka, S., and Hamashima, Y. (1977a). Suppressed immune response to T-cell dependent antigen in chemically sympathectomized mice. Res. Commun. Chem. Pathol. Pharmacol., 18, 533–542. Kasahara, K., Tanaka, S., Ito, T., and Hamashima, Y. (1977b). Suppression of the primary immune response by chemical sympathectomy. Res. Comm. Chem. Pathol. Pharmacol., 16, 687–694. Kasprowicz, D. J., Kohm, A. P., Berton, M. T., Chruscinski, A. J., Sharpe, A. H., and Sanders, V. M. (2000). Stimulation of the B cell receptor, CD86 (B7-2), and the beta-2–adrenergic receptor intrinsically modulates the level of IgG1 produced per B cell. J. Immunol., 165, 680–690. Katamura, K., Shintaku, N., Yamauchi, Y., Fukui, T., Ohshima, Y., Mayumi, M., and Furusho, K. (1995). Prostaglandin E2 at priming of naïve CD4+ T cells inhibits acquisition of ability to produce IFN-gamma and IL-2, but not IL-4 and IL-5. J. Immunol., 155, 4604–4612. Kavelaars, A. (2002). Regulated expression of alpha-1 adrenergic receptors in the immune system. Brain Behav. Immun., 16, 799–807. Kavelaars, A., van de Pol, M., Zijlstra, J., and Heijnen, C. J. (1997). Beta 2-adrenergic activation enhances interleukin-8 production by human monocytes. J. Neuroimmunol., 77, 211–216. Kennedy, S. L., Nickerson, M., Campisi, J., Johnson, J. D., Smith, T. P., Sharkey, C., and Fleshner, M. (2005). Splenic norepinephrine depletion following acute stress suppresses in vivo antibody response. J. Neuroimmunol., 165, 150–160. Khamlichi, A. A., Pinaud, E., Decourt, C., Chauveau, C., and Cogne, M. (2000). The 3′ IgH regulatory region: a complex structure in a search for a function. Adv. Immunol., 75, 317–345. Khan, M. M., Melmom, K. L., Fathman, C. G., Hertel-Wulff, B., and Strober, S. (1985a). The effects of autocoids on cloned murine lymphoid cells: modulation of IL-2 secretion and the activity of natural suppressor cells. J. Immunol., 134, 4100–4106. Khan, M. M., Silverman, E., Engleman, E. G., and Melmon, K. L. (1985b). Responses of subpopulations of human helper T cells to autocoids. Proc. West. Pharmacol. Soc., 28, 225–228. Kiecolt-Glaser, J. K., and Glaser, R. (1999). Psychoneuroimmunology and cancer: fact or fiction? Eur. J. Cancer, 35, 1603–1607. Kiecolt-Glaser, J. K., Page, G. G., Marucha, P. T., MacCallum, R. C., and Glaser, R. (1998). Psychological influences on surgical recovery. Perspectives from psychoneuroimmunology. Am. Psychol., 53, 1209–1218. Kim, U., Qin, X. F., Gong, S., Stevens, S., Luo, Y., Nussenzweig, M., and Roeder, R. G. (1996). The B-cell–specific transcription coactivator OCA-B/OBF-1/Bob-1 is essential for normal production of immunoglobulin isotypes. Nature, 383, 542–547. Kobayashi, M., Kobayashi, H., Herndon, D. N., Pollard, R. B., and Suzuki, F. (1998). Burn-associated Candida albicans infection caused by CD30+ type 2 T cells. J. Leukoc. Biol., 63, 723–731. Kohm, A. P., Mozaffarian, A., and Sanders, V. M. (2002). B cell receptor- and beta-2–adrenergic receptor-induced regulation of B7-2 (CD86) expression in B cells. J. Immunol., 168, 6314–6322. Kohm, A. P., and Sanders, V. M. (1999). Suppression of antigenspecific Th2 cell-dependent IgM and IgG1 production following norepinephrine depletion in vivo. J. Immunol., 162, 5299–5308. Kohm, A. P., and Sanders, V. M. (2001). Norepinehrine and beta2–adrenergic receptor stimulation regulate CD4+ T and B lym-
phocyte function in vitro and in vivo. Pharmacol. Rev., 53, 487–525. Kohm, A. P., Tang, Y., Sanders, V. M., and Jones, S. B. (2000). Activation of antigen-specific CD4+ Th2 cells and B cells in vivo increases norepinephrine release in the spleen and bone marrow. J. Immunol., 165, 725–733. Kohut, M. L., Thompson, J. R., Lee, W., and Cunnick, J. E. (2004). Exercise training–induced adaptations of immune response are mediated by beta-adrenergic receptors in aged but not young mice. J. Appl. Physiol., 96, 1312–1322. Kouassi, E., Boukhris, W., Descotes, J., Zukervar, P., Li, Y. S., and Revillard, J. P. (1987). Selective T cell defects induced by dopamine administration in mice. Immunopharmacol. Immunotoxicol., 9, 477–488. Krause, D. S., and Deutsch, C. (1991). Cyclic AMP directly inhibits IL-2 receptor expression in human T cells: expression of both p55 and p75 subunits is affected. J. Immunol., 146, 2285–2294. Kruszewska, B., Felten, S. Y., and Moynihan, J. A. (1995). Alterations in cytokine and antibody production following chemical sympathectomy in two strains of mice. J. Immunol., 155, 4613–4620. Lacour, M., Arrighi, J., Muller, K. M., Carlberg, C., Saurat, J., and Hauser, C. (1994). cAMP up-regulates IL-4 and IL-5 production from activated CD4+ T cells while decreasing IL-2 release and NF-AT induction. Int. Immunol., 6, 1333–1343. Levine, J. D., Coderre, T. J., Helms, C., and Basbaum, A. I. (1988). β2-adrenergic mechanisms in experimental arthritis. Proc. Natl. Acad. Sci. USA, 85, 4553–4556. Li, Y. S., Kouassi, E., and Revillard, J.-P. (1989). Cyclic AMP can enhance mouse B cell activation by regulating progression into late G1/S phase. Eur. J. Immunol., 19, 1721–1725. Livnat, S., Felten, S. Y., Carlson, S. L., Bellinger, D. L., and Felten, D. L. (1985). Involvement of peripheral and central catecholamine systems in neural-immune interactions. J. Neuroimmunol., 10, 5–30. Lombardi, M. S., Kavelaars, A., Cobelens, P. M., Schmidt, R. E., Schedlowski, M., and Heijnen, C. J. (2001). Adjuvant arthritis induces down-regulation of G protein–coupled receptor kinases in the immune system. J. Immunol., 166, 1635–1640. Lombardi, M. S., Kavelaars, A., and Heijnen, C. J. (2002). Role and modulation of G protein–coupled receptor signaling in inflammatory processes. Crit. Rev. Immunol., 22, 141–163. Lombardi, M. S., Kavelaars, A., Schedlowski, M., Bijlsma, J. W., Okihara, K. L., van de Pol, M., Ochsmann, S., Pawlak, C., Schmidt, R. E., and Heijnen, C. J. (1999). Decreased expression and activity of G-protein–coupled receptor kinases in peripheral blood mononuclear cells of patients with rheumatoid arthritis. FASEB J., 13, 715–725. Loop, T., Bross, T., Humar, M., Hoetzel, A., Schmidt, R., Pahl, H. L., Geiger, K. K., and Pannen, B. H. (2004). Dobutamine inhibits phorbol-myristate-acetate–induced activation of nuclear factorkappaB in human T lymphocytes in vitro. Anesth. Analg., 99, 1508–1515; table of contents. Madden, K. S., Felten, S. Y., Felten, D. L., Sundaresan, P. R., and Livnat, S. (1989). Sympathetic neural modulation of the immune system. I. Depression of T cell immunity in vivo and in vitro following chemical sympathectomy. Brain Behav. Immun., 3, 72–89. Madden, K. S., Stevens, S. Y., Felten, D. L., and Bellinger, D. L. (2000). Alterations in T lymphocyte activity following chemical sympathectomy in young and old Fischer 344 rats. J. Neuroimmunol., 103, 131–145. Maestroni, G. J. (2000). Dendritic cell migration controlled by alpha 1b-adrenergic receptors. J. Immunol., 165, 6743–6747. Maestroni, G. J. (2002). Short exposure of maturing, bone marrow– derived dendritic cells to norepinephrine: impact on kinetics of
2. Adrenergic Regulation of Immunity cytokine production and Th development. J. Neuroimmunol., 129, 106–114. Maestroni, G. J., and Mazzola, P. (2003). Langerhans cells beta 2adrenoceptors: role in migration, cytokine production, Th priming and contact hypersensitivity. J. Neuroimmunol., 144, 91–99. Maisel, A. S., and Michel, M. C. (1990). Beta-adrenoceptor control of immune function in congestive heart failure. Br. J. Clin. Pharmacol., 30(Suppl 1), 49S–53S. Manfield, L. E., and Nelson, H. S. (1982). Effect of beta-adrenergic agents on immunoglobulin G levels in asthmatic subjects. Int. Arch. Allergy Appl. Immunol., 68, 13–16. Mary, D., Peyron, J.-F., Auberger, P., Aussel, C., and Fehlmann, M. (1989). Modulation of T cell activation by differential regulation of the phosphorylation of two cytosolic proteins. J. Biol. Chem., 264, 14498–14502. Mathews, P. M., Froelich, C. J., Sibbitt, W. L., and Bankhurst, A. D. (1983). Enhancement of natural cytotoxicity by β-endorphin. J. Immunol., 130, 1658–1662. Matthews, K. A., Caggiula, A. R., McAllister, C. G., Berga, S. L., Owens, J. F., Flory, J. D., and Miller, A. L. (1995). Sympathetic reactivity to acute stress and immune response in women. Psychosom. Med., 57, 564–571. McPherson, G. A., and Summers, R. J. (1982). Characteristics and localization of 3H-clonidine binding in membranes prepared from guinea pig spleen. Clin. Exp. Pharmacol. Physiol., 9, 77– 87. Melamed, R., Rosenne, E., Shakhar, K., Schwartz, Y., Abudarham, N., and Ben Eliyahu, S. (2005). Marginating pulmonary-NK activity and resistance to experimental tumor metastasis: suppression by surgery and the prophylactic use of a beta-adrenergic antagonist and a prostaglandin synthesis inhibitor. Brain Behav. Immun., 19, 114–126. Meltzer, J. C., Grimm, P. C., Greenberg, A. H., and Nance, D. M. (1997). Enhanced immunohistochemical detection of autonomic nerve fibers, cytokines and inducible nitric oxide synthase by light and fluorescent microscopy in rat spleen. J. Histochem. Cytochem., 45, 599–610. Miles, B. A., Lafuse, W. P., and Zwilling, B. S. (1996). Binding of alpha-adrenergic receptors stimulates the anti-mycobacterial activity of murine peritoneal macrophages. J. Neuroimmunol., 71, 19–24. Miles, K., Quintans, J., Chelmicka-Schorr, E., and Arnason, B. G. W. (1981). The sympathetic nervous system modulates antibody response to thymus-independent antigens. J. Neuroimmunol., 1, 101–105. Mills, P. J., Rehman, J., Ziegler, M. G., Carter, S. M., Dimsdale, J. E., and Maisel, A. S. (1999). Nonselective beta blockade attenuates the recruitment of CD62L(-)T lymphocytes following exercise. Eur. J. Appl. Physiol., 79, 531–534. Mitchell, D. M., and Fries, J. F. (1982). An analysis of the American Rheumatism Association criteria for rheumatoid arthritis. Arthritis Rheum., 25, 481–487. Munoz, E., Zubiaga, A. M., Merrow, M., Sauter, N. P., and Huber, B. T. (1990). Cholera toxin discriminates between T helper 1 and 2 cells in T cell receptor-mediated activation: role of cAMP in T cell proliferation. J. Exp. Med., 172, 95–103. Muraguchi, A., Miyazaki, K., Kehrl, J. H., and Fauci, A. S. (1984). Inhibition of human B cell activation by diterpine forskolin: interference with B cell growth factor–induced G1 to S transition of the B cell cycle. J. Immunol., 133, 1283–1287. Muthusamy, N., Baluyut, A. R., and Subbarao, B. (1991). Differential regulation of surface Ig- and Lyb2–mediated B cell activation by cyclic AMP. I. Evidence for alternative regulation of signaling
81
through two different receptors linked to phosphatidylinositol hydrolysis in murine B cells. J. Immunol., 147, 2483–2492. Naito, Y., Endo, H., Arai, K., Coffman, R. L., and Arai, N. (1996). Signal transduction in Th clones: target of differential modulation by PGE2 may reside downstream of the PKC-dependent pathway. Cytokine, 8, 346–356. Nielsen, P. J., Georgiev, O., Lorenz, B., and Schaffner, W. (1996). B lymphocytes are impaired in mice lacking the transcriptional co-activator Bob1/OCA-B/OBF1. Eur. J. Immunol., 26, 3214–3218. Novak, T. J., and Rothenberg, E. V. (1990). cAMP inhibits induction of interleukin 2 but not of interleukin 4 in T cells. Proc. Natl. Acad. Sci. USA, 87, 9353–9357. O’Dowd, Y. M., El-Benna, J., Perianin, A., and Newsholme, P. (2004). Inhibition of formyl-methionyl-leucyl-phenylalanine–stimulated respiratory burst in human neutrophils by adrenaline: inhibition of phospholipase A2 activity but not p47phox phosphorylation and translocation. Biochem. Pharmacol., 67, 183–190. Paliogianni, F., and Boumpas, D. T. (1996). Prostaglandin E2 inhibits the nuclear transcription of the human interleukin 2, but not the Il-4, gene in human T cells by targeting transcription factors AP-1 and NF-AT. Cell. Immunology, 171, 95–101. Panina-Bordignon, P., Mazzeo, D., Lucia, P. D., D’Ambrosio, D., Lang, R., Fabbri, L., Self, C., and Sinigaglia, F. (1997). Beta2agonists prevent Th1 development by selective inhibition of interleukin 12. J. Clin. Invest., 100, 1513–1519. Panosian, J. O., and Marinetti, G. V. (1983). Alpha 2-adrenergic receptors in human polymorphonuclear leukocyte membranes. Biochem. Pharmacol., 32, 2243–2247. Panuncio, A. L., De La Pena, S., Gualco, G., and Reissenweber, N. (1998). Adrenergic innervation in reactive human lymph nodes. J. Anat., 194, 143–146. Park, S. H., Min, D. J., Cho, M. L., Kim, W. U., Youn, J., Park, W., Cho, C. S., and Kim, H. Y. (2001). Shift toward T helper 1 cytokines by type II collagen-reactive T cells in patients with rheumatoid arthritis. Arthritis Rheum., 44, 561–569. Parker, C. W., Huber, M. G., and Godt, S. M. (1995). Modulation of IL-4 production in murine spleen cells by prostaglandins. Cell. Immunol., 160, 278–285. Pinaud, E., Khamlichi, A. A., Le Morvan, C., Drouet, M., Nelsso, V., Le Bert, M., and Cogne, M. (2001). Localization of the 3′ IgH locus elements that effect long-distance regulation of class switching recombination. Immunity, 15, 187–199. Pochet, R., and Delespesse, G. (1983). Beta-adrenoceptors display different efficiency on lymphocyte subpopulations. Biochem. Pharmacol., 32, 1651–1655. Podojil, J., and Sanders, V. (2005). CD86 and beta2-adrenergic receptor stimulation regulate B cell activity cooperatively. Trends in Immunology, 26, 180–185. Podojil, J. R., Kin, N. W., and Sanders, V. M. (2004). CD86 and beta2adrenergic receptor signaling pathways, respectively, increase Oct-2 and OCA-B expression and binding to the 3′-IgH enhancer in B cells. J. Biol. Chem., 279, 23394–23404. Podojil, J. R., and Sanders, V. M. (2003). Selective regulation of mature IgG1 transcription by CD86 and beta2–adrenergic receptor stimulation. J. Immunol., 170, 5143–5151. Prass, K., Meisel, C., Hoflich, C., Braun, J., Halle, E., Wolf, T., Ruscher, K., Victorov, I. V., Priller, J., Dirnagl, U., Volk, H. D., and Meisel, A. (2003). Stroke-induced immunodeficiency promotes spontaneous bacterial infections and is mediated by sympathetic activation reversal by poststroke T helper cell type 1–like immunostimulation. J. Exp. Med., 198, 725–736. Radojcic, T., Baird, S., Darko, D., Smith, D., and Bulloch, K. (1991). Changes in beta-adrenergic receptor distribution on immuno-
82
I. Neural and Endocrine Effects on Immunity
cytes during differentiation: an analysis of T cells and macrophages. J. Neurosci. Res., 30, 328–335. Ramer-Quinn, D. S., Baker, R. A., and Sanders, V. M. (1997). Activated Th1 and Th2 cells differentially express the beta-2– adrenergic receptor: a mechanism for selective modulation of Th1 cell cytokine production. J. Immunol., 159, 4857–4867. Ramer-Quinn, D. S., Swanson, M. A., Lee, W. T., and Sanders, V. M. (2000). Cytokine production by naïve and primary effector CD4(+) T cells exposed to norepinephrine. Brain Behav. Immun., 14, 239–255. Rice, P. A., Boehm, G. W., Moynihan, J. A., Bellinger, D. L., and Stevens, S. Y. (2001). Chemical sympathectomy increases the innate immune response and decreases the specific immune response in the spleen to infection with Listeria monocytogenes. J. Neuroimmunol., 114, 19–27. Roberts, J. A., Bradding, P., Britten, K. M., Walls, A. F., Wilson, S., Gratziou, C., Holgate, S. T., and Howarth, P. H. (1999). The longacting beta2-agonist salmeterol xinafoate: effects on airway inflammation in asthma [see comments]. Eur. Respir. J., 14, 275–282. Robinson, F. P., Mathews, H. L., and Witek-Janusek, L. (2000). Stress reduction and HIV disease: a review of intervention studies using a psychoneuroimmunology framework. J. Assoc. Nurses, 11, 87–96. Romagnani, S. (1994). Lymphokine production by human T cells in disease states. Ann. Rev. Immunol., 12, 227–257. Romagnani, S. (2000). T-cell subsets (Th1 versus Th2). Ann. Allergy Asthma Immunol., 85, 9–18; quiz 18, 21. Roper, R. L., Conrad, D. H., Brown, D. M., Warner, G. L., and Phipps, R. P. (1990). Prostaglandin E2 promotes IL-4–induced IgE and IgG1 synthesis. J. Immunol., 145, 2644–2651. Roper, R. L., Graf, B., and Phipps, R. P. (2002). Prostaglandin E2 and cAMP promote B lymphocyte class switching to IgG1. Immunol. Lett., 84, 191–198. Rouppe van der Voort, C., Heijnen, C. J., Wulffraat, N., Kuis, W., and Kavelaars, A. (2000). Stress induces increases in IL-6 production by leucocytes of patients with the chronic inflammatory disease juvenile rheumatoid arthritis: a putative role for alpha(1)adrenergic receptors. J. Neuroimmunol., 110, 223–229. Rouppe van der Voort, C., Kavelaars, A., van de Pol, M., and Heijnen, C. J. (1999). Neuroendocrine mediators up-regulate alpha1b- and alpha1d-adrenergic receptor subtypes in human monocytes. J. Neuroimmunol., 95, 165–173. Rouppe van der Voort, C., Kavelaars, A., van de Pol, M., and Heijnen, C. J. (2000). Noradrenaline induces phosphorylation of ERK-2 in human peripheral blood mononuclear cells after induction of alpha(1)-adrenergic receptors. J. Neuroimmunol., 108, 82–91. Rozlog, L. A., Kiecolt-Glaser, J. K., Marucha, P. T., Sheridan, J. F., and Glaser, R. (1999). Stress and immunity: implications for viral disease and wound healing. J. Periodontol., 70, 786–792. Sanders, V. M., Baker, R. A., Ramer-Quinn, D. S., Kasprowicz, D. J., Fuchs, B. A., and Street, N. E. (1997). Differential expression of the beta-2–adrenergic receptor by Th1 and Th2 clones: implications for cytokine production and B cell help. J. Immunol., 158, 4200–4210. Sanders, V. M., Kasprowicz, D. J., Kohm, A. P., and Swanson, M. A. (2001). Neurotransmitter receptors on lymphocytes and other lymphoid cells. In R. Ader, D. Felten, and N. Cohen (Eds.), Psychoneuroimmunology (3rd ed., vol. 2, pp. 161–196), San Diego, CA: Academic Press. Sanders, V. M., and Munson, A. E. (1984a). Beta-adrenoceptor mediation of the enhancing effect of norepinephrine on the murine primary antibody response in vitro. J. Pharmacol. Exp. Ther., 230(1), 183–192.
Sanders, V. M., and Munson, A. E. (1984b). Kinetics of the enhancing effect produced by norepinephrine and terbutaline on the murine primary antibody response in vitro. J. Pharmacol. Exp. Ther., 231(3), 527–531. Sanders, V. M., and Munson, A. E. (1985a). Norepinephrine and the antibody response. Pharmacol. Rev., 37(3), 229–248. Sanders, V. M., and Munson, A. E. (1985b). Role of alpha adrenoceptor activation in modulating the murine primary antibody response in vitro. J. Pharmacol. Exp. Ther., 232(2), 395–400. Schedlowski, M., Falk, A., Rohne, A., Wagner, T. O., Jacobs, R., Tewes, U., and Schmidt, R. E. (1993). Catecholamines induce alterations of distribution and activity of human natural killer (NK) cells. J. Clin. Immunol., 13, 344–351. Schorr, E. C., and Arnason, B. G. (1999). Interactions between the sympathetic nervous system and the immune system. Brain Behav. Immun., 13, 271–278. Schubart, D. B., Rolink, A., Kosco-Vilbois, M. H., Botteri, F., and Matthias, P. (1996). B-cell–specific coactivator OBF-1/OCA-B/ Bob1 required for immune response and germinal centre formation. Nature, 383, 538–542. Seiffert, K., Hosoi, J., Torii, H., Ozawa, H., Ding, W., Campton, K., Wagner, J. A., and Granstein, R. D. (2002). Catecholamines inhibit the antigen-presenting capability of epidermal Langerhans cells. J. Immunol., 168, 6128–6135. Sheridan, J. F., Dobbs, C., Jung, J., Chu, X., Konstantinos, A., Padgett, D., and Glaser, R. (1998). Stress-induced neuroendocrine modulation of viral pathogenesis and immunity. Ann. N. Y. Acad. Sci., 840, 803–808. Shimizu, N., Hori, T., and Nakane, H. (1994). An interleukin-1–betainduced noradrenaline release in the spleen is mediated by brain corticotropin-releasing factor: an in vivo microdialysis study in conscious rats. Brain Behav. Immun., 7, 14–23. Silberman, D. M., Wald, M. R., and Genaro, A. M. (2003). Acute and chronic stress exert opposing effects on antibody responses associated with changes in stress hormone regulation of Tlymphocyte reactivity. J. Neuroimmunol., 144, 53–60. Sondergaard, S. R., Cozzi Lepri, A., Ullum, H., Wiis, J., Hermann, C. K., Laursen, S. B., Qvist, J., Gerstoft, J., Skinhoj, P., and Pedersen, B. K. (2000). Adrenaline-induced mobilization of T cells in HIV-infected patients. Clin. Exp. Immunol., 119, 115–122. Speidl, W. S., Toller, W. G., Kaun, C., Weiss, T. W., Pfaffenberger, S., Kastl, S. P., Furnkranz, A., Maurer, G., Huber, K., Metzler, H., and Wojta, J. (2004). Catecholamines potentiate LPS-induced expression of MMP-1 and MMP-9 in human monocytes and in the human monocytic cell line U937: possible implications for perioperative plaque instability. FASEB J., 18, 603–605. Spengler, R. N., Allen, R. M., Remick, D. G., Strieter, R. M., and Kunkel, S. L. (1990). Stimulation of alpha-adrenergic receptor augments the production of macrophage-derived tumor necrosis factor. J. Immunol., 145, 1430–1434. Stavnezer-Nordgren, J., and Sirlin, S. (1986). Specificity of immunoglobulin heavy chain switch correlates with activity of germline heavy chain genes prior to switching. EMBO J., 5, 95–102. Stein, S. H., and Phipps, R. P. (1991a). Antigen-specific IgG2a production in response to prostaglandin E2, immune complexes, and IFN-gamma. J. Immunol., 147, 2500–2506. Stein, S. H., and Phipps, R. P. (1991b). Elevated levels of intracellular cAMP sensitize resting B lymphocytes to immune complexinduced unresponsiveness. Eur. J. Immunol., 21, 313–318. Stein, S. H., and Phipps, R. P. (1992). Anti-class II antibodies potentiate IgG2a production by lipopolysaccharide-stimulated B lymphocytes treated with prostaglandin E2 and IFN-gamma. J. Immunol., 148, 3943–3949.
2. Adrenergic Regulation of Immunity Steinman, L. (2004). Elaborate interactions between the immune and nervous systems. Nat. Immunol., 5, 575–581. Stevens, S., Ong, J., Kim, U., Eckhardt, L. A., and Roeder, R. G. (2000). Role of OCA-B in 3′-IgH enhancer function. J. Immunol., 164, 5306–5312. Straub, R. H. (2004). Complexity of the bi-directional neuroimmune junction in the spleen. Trends Pharmacol. Sci., 25, 640–646. Straub, R. H., Baerwald, C. G., Wahle, M., and Janig, W. (2005a). Autonomic dysfunction in rheumatic diseases. Rheum. Dis. Clin. North Am., 31, 61–75, viii. Straub, R. H., and Harle, P. (2005b). Sympathetic neurotransmitters in joint inflammation. Rheum. Dis. Clin. North Am., 31, 43–59, viii. Straub, R. H., Pongratz, G., Weidler, C., Linde, H. J., Kirschning, C. J., Gluck, T., Scholmerich, J., and Falk, W. (2005c). Ablation of the sympathetic nervous system decreases gram-negative and increases gram-positive bacterial dissemination: key roles for tumor necrosis factor/phagocytes and interleukin-4/lymphocytes. J. Infect. Dis., 192, 560–572. Strom, T. B., Carpenter, C. B., Garovoy, M. R., Austen, K. F., Merrill, J. P., and Kaliner, M. (1973). The modulating influence of cyclic nucleotides upon lymphocyte-mediated cytotoxicity. J. Exp. Med., 138, 381–393. Swanson, M. A., Lee, W. T., and Sanders, V. M. (2001). IFN-gamma production by Th1 cells generated from naïve CD4(+) T cells exposed to norepinephrine. J. Immunol., 166, 232–240. Takahashi, H., Kobayashi, M., Tsuda, Y., Herndon, D. N., and Suzuki, F. (2005). Contribution of the sympathetic nervous system on the burn-associated impairment of CCL3 production. Cytokine, 29, 208–214. Takahashi, H., Tsuda, Y., Kobayashi, M., Herndon, D. N., and Suzuki, F. (2004). Increased norepinephrine production associated with burn injuries results in CCL2 production and type 2 T cell generation. Burns, 30, 317–321. Takamoto, T., Hori, Y., Koga, Y., Toshima, H., Hara, A., and Yokoyama, M. M. (1991). Norepinephrine inhibits human natural killer cell activity in vitro. Int. J. Neurosci., 58, 127–131. Takayama, H., Trenn, G., and Sitkovsky, M. V. (1988). Locus of inhibitory action of cAMP-dependent protein kinase in the antigen receptor-triggered cytotoxic T lymphocyte activation pathway. J. Biol. Chem., 263, 2330–2336. Tamir, A., and Isakov, N. (1994). Cyclic AMP inhibits phosphatidylinositol-coupled and -uncoupled mitogenic signals in T lymphocytes. Evidence that cAMP alters PKC-induced transcription regulation of members of the jun and fos family of genes. J. Immunol., 152, 3391–3399. Tang, H., and Sharp, P. A. (1999). Transcriptional regulation of the murine 3′ IgH enhancer by OCT-2. Immunity, 11, 517–526. Thompson, M., and Bywaters, E. G. (1962). Unilateral rheumatoid arthritis following hemiplegia. Ann. Rheum. Dis., 21, 370–377. ThyagaRajan, S., Madden, K. S., Stevens, S. Y., and Felten, D. L. (1999). Effects of L-deprenyl treatment on noradrenergic innervation and immune reactivity in lymphoid organs of young F344 rats. J. Neuroimmunol., 96, 57–65. Titinchi, S., and Clark, B. (1984). Alpha-2–adrenoceptors in human lymphocytes: direct characterization by [3H]Yohimbine binding. Biochem. Biophys. Res. Commun., 121(1), 1–7. Tonnesen, E., Christensen, N. J., and Brinklov, M. M. (1987). Natural killer cell activity during cortisol and adrenaline infusion in healthy volunteers. Eur. J. Clin. Invest., 17, 497–503.
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Tracey, K. J. (2002). The inflammatory reflex. Nature, 420, 853–859. van der Poll, T., Jansen, J., Endert, E., Sauerwein, H. P., and van Deventer, S. J. (1994). Noradrenaline inhibits lipopolysaccharideinduced tumor necrosis factor and interleukin 6 production in human whole blood. Infect. Immun., 62, 2046–2050. van der Poll, T., and Lowry, S. F. (1997a). Epinephrine inhibits endotoxin-induced IL-1 beta production: roles of tumor necrosis factor-alpha and IL-10. Am. J. Physiol., 273, R1885–1890. van der Poll, T., and Lowry, S. F. (1997b). Lipopolysaccharideinduced interleukin 8 production by human whole blood is enhanced by epinephrine and inhibited by hydrocortisone. Infect. Immun., 65, 2378–2381. Vischer, T. L. (1976). The differential effect of cAMP on lymphocyte stimulation by T- or B-cell mitogens. Immunology, 30, 735–739. Vroon, A., Kavelaars, A., Limmroth, V., Lombardi, M. S., Goebel, M. U., Van Dam, A. M., Caron, M. G., Schedlowski, M., and Heijnen, C. J. (2005). G protein–coupled receptor kinase 2 in multiple sclerosis and experimental autoimmune encephalomyelitis. J. Immunol., 174, 4400–4406. Wacholtz, M. C., Minakuchi, R., and Lipsky, P. E. (1991). Characterization of the 3′,5′-cyclic adenosine monophosphate-mediated regulation of IL2 production by T cells and Jurkat cells. Cell. Immunol., 135, 285–298. Watson, J. (1975). The influence of intracellular levels of cyclic nucleotides on cell proliferation and the induction of antibody synthesis. J. Exp. Med., 141, 97–111. Watkins, L. R., and Maier, S. F. (2005). Immune regulation of central nervous system functions: from sickness responses to pathological pain. J. Intern. Med., 257, 139–155. Westly, H. J., and Kelley, K. W. (1987). Down-regulation of glucocorticoid and beta-adrenergic receptors on lectin-stimulated splenocytes. Proc. Soc. Exp. Biol. Med., 185, 211–218. Whisler, R. L., Beiqing, L., Grants, I. S., and Newhouse, Y. G. (1992). Cyclic AMP modulation of human B cell proliferative responses: role of cAMP-dependent protein kinases in enhancing B cell responses to phorbol diesters and ionomycin. Cell. Immunol., 142, 398–415. Wirth, S., Lacour, M., Jaunin, F., and Hauser, C. (1996). Cyclic adenosine monophosphate (cAMP) differentially regulates IL-4 in thymocyte subsets. Thymus, 24, 101–109. Xu, B. Y., Arlehag, L., Rantapaa-Dahlquist, S. B., and Lefvert, A. K. (2005). Beta2 adrenoceptor gene single nucleotide polymorphisms are associated with rheumatoid arthritis in northern Sweden. Ann. Rheum. Dis., 64, 773–776. Yin, Z., Siegert, S., Neure, L., Grolms, M., Liu, L., Eggens, U., Radbruch, A., Braun, J., and Sieper, J. (1999). The elevated ratio of interferon gamma-/interleukin-4–positive T cells found in synovial fluid and synovial membrane of rheumatoid arthritis patients can be changed by interleukin-4 but not by interleukin10 or transforming growth factor beta. Rheumatology (Oxford), 38, 1058–1067. Yoshimura, T., Nagao, T., Nakao, T., Watanabe, S., Usami, E., Kobayashi, J., Yamazaki, F., Tanaka, H., Inagaki, N., and Nagai, H. (1998). Modulation of Th1- and Th2-like cytokine production from mitogen-stimulated human peripheral blood mononuclear cells by phosphodiesterase inhibitors. Gen. Pharmacol., 30, 175–180.
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C H A P T E R
3 Cholinergic Regulation of Inflammation CHRISTOPHER J. CZURA, MAURICIO ROSAS–BALLINA, AND KEVIN J. TRACEY
I. INTRODUCTION 85 II. BRAIN-IMMUNE COMMUNICATION 86 III. THE CHOLINERGIC ANTI-INFLAMMATORY PATHWAY IN MEDICINE 89 IV. PERSPECTIVES 93
in order to prevent shock, tissue injury arthritis, and the other complications of excessive cytokine activity. These redundant anti-inflammatory mechanisms are integral to the host response because they effectively inhibit the release of cytokines by macrophages and other cells. Macrophage deactivating factors accumulate at the local site of infection (e.g., prostaglandin E2 and spermine) and are released systemically (e.g., IL10, TGF-β, glucocorticoids). Local accumulation of prostaglandin E2 (PGE2) inhibits synthesis of proinflammatory cytokines and restrains acute cytokine responses (1). Spermine is a ubiquitous biogenic molecule that accumulates at sites of infection or injury and inhibits the activity of several cytokines at a posttranscriptional level, including TNF, IL-1, and the macrophage inflammatory proteins 1α and 1β (MIP1α, MIP-1β) in macrophages and monocytes (2–5). Anti-inflammatory cytokines such as IL-10 and transforming growth factor β (TGF-β) also serve to downregulate inflammatory responses. IL-10 deactivates macrophages in culture; in trauma patients, TNF levels are higher when IL-10 levels are depressed, an indication of pending septic complications (6–8). Elevated levels of TGF-β, a potent inhibitor of monocyte activation, have been observed in monocytes derived from immunosuppressed trauma patients (9;10). There also are mechanisms to inhibit the activity of cytokines that have already been released. For example, TNF receptor fragments cleaved from the cell surface are released as soluble factors that bind and neutralize the cytokine activity of TNF. Surprisingly, recent evidence now implicates a critical controlling role for the nervous system in both detecting and suppressing inflammation via the
I. INTRODUCTION The innate immune system is the front line of host defense against tissue injury and infection. Infectious agents and tissues damaged by injury release chemotactic factors that recruit leukocytes to the site of injury, which recognize and neutralize endogenous and exogenous cellular debris and invading pathogens. These activated cells release pro-inflammatory cytokines such as tumor necrosis factor (TNF), interleukin (IL)-1, and HMGB1, which amplify the inflammatory response, modulate wound healing and tissue remodeling, and activate specific immune responses. In the majority of cases, these and other inflammatory responses culminate in the resolution of infection and healing of the wound. Occasionally, however, the innate immune response can spiral out of control, leading to widespread cytokine release that spills out of the local environment to cause shock, tissue injury, diffuse coagulation, organ ischemia, and even death. Excessive pro-inflammatory cytokine activity has a causative role in human disease, as evidenced by the success of anti-TNF strategies for treatment of rheumatoid arthritis and Crohn’s disease. Evolution has conferred upon mammals several distinct counter-regulatory mechanisms that “normally” restrain the pro-inflammatory cytokine response PSYCHONEUROIMMUNOLOGY, 4E VOLUME I
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Copyright © 2007 by Elsevier, Inc. All rights of reproduction in any form reserved.
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“inflammatory reflex.” Inflammation is sensed by afferent fibers in the vagus nerve, which innervates the reticuloendothelial system and other major organs. Low levels of cytokines produced in tissues activate an afferent vagus nerve signal that elicits the central nervous system responses to inflammation (e.g., fever, sickness behaviors). Indeed, an intact vagus nerve is required to mount appropriate physiological responses to inflammation, because vagotomy ablates cytokineinduced fever in response to exposure to low doses of IL-1 in the abdomen. Since it innervates the liver, spleen, lungs, and other visceral organs that act as filters or routes of entry for pathogens or their products, the vagus nerve is uniquely positioned to anatomically modulate and integrate a range of potential infectious or injurious threats. The sensory fibers terminate in the dorsal vagus complex in the medulla oblongata; the efferent vagus fibers originate in the dorsal vagus complex (and particularly the nucleus tractus solitarius). Together these vagus nerve nuclei can interact with forebrain regions, the hypothalamus, and amygdala, to sense peripheral physiological activity, including immune status, integrate the information, and coordinate appropriate responses to maintain homeostasis. We discovered that the efferent arm of the inflammatory reflex is a vagus nerve-dependent cholinergic anti-inflammatory pathway which inhibits pro-inflammatory cytokine synthesis in animal models of endotoxemia, ischemia, and other types of inflammation. Electrical stimulation of the vagus nerve inhibits cytokine release and protects animals against local inflammation, as well as systemic inflammation associated with endotoxemia, hypovolemic shock, and septic peritonitis. Pharmacological stimulation of this pathway using either peripheral cholinergic agonists that target cytokine-secreting cells, or using centrally acting compounds that cross the blood-brain barrier and activate efferent vagus nerve activity, exert significant protection against cytokine-mediated diseases (11–13). Acetylcholine, the principal neurotransmitter of the vagus, interacts with the α7 subunit of nicotinic acetylcholine receptors specifically expressed on macrophages to inhibit the release of proinflammatory cytokines including TNF, IL-1, IL-6, IL18, and HMGB1, without affecting the release of the anti-inflammatory cytokines such as IL-10 (13;14). Disruption of this cholinergic anti-inflammatory pathway, either by surgical vagotomy or genetic knockout of the α7 subunit, renders animals more sensitive to inflammatory stimuli than their wild-type counterparts, indicating that the cholinergic anti-inflammatory pathway exerts tonic regulatory effects on innate immune responses (14;15). Cholinergic agonists that inhibit
macrophage release of pro-inflammatory cytokines significantly improve survival in animal models of local and systemic inflammation, together indicating that the α7 subunit of the nicotinic acetylcholine receptor is an experimental therapeutic target for diseases characterized by excessive pro-inflammatory cytokine activity (13;14;16).
II. BRAIN-IMMUNE COMMUNICATION The nervous system is composed of the somatic motor system, which controls voluntary movements, and the autonomic motor system, which controls involuntarily visceral functions. Two divisions of the autonomic nervous system—the parasympathetic and the sympathetic—continuously regulate basic physiological responses, including heart rate and blood pressure, respiratory rate, gastrointestinal motility, and body temperature. The autonomic nervous system detects the physiologic status of the major body systems and relays this information to the primitive brain, including the limbic system, which interprets this information and coordinates sympathetic and parasympathetic neural responses to maintain homeostasis. This physiological regulatory activity occurs subconsciously, with the hypothalamus acting as a gatekeeper, letting less than 1% of ascending information to penetrate to higher brain centers. New insights have revealed a basic neural pathway that reflexively monitors and adjusts the inflammatory response, not unlike the regulation of instantaneous heart rate. Inflammatory stimuli activate afferent pathways within the vagus nerve that are relayed to the hypothalamus. Like the baroreflex, in which the stretching of the carotid or aortic sinuses elicits an efferent response to prolong the time to the next heartbeat, inflammatory input can activate an anti-inflammatory response that rapidly inhibits the subsequent production of pro-inflammatory cytokines. Thus, the nervous system can gather sensory information about inflammatory or invasive events from multiple local sites, and integrate this data with information about other aspects of health and function. Therefore, the central nervous system is a central coordinator of the immunological homeostasis.
A. Anatomy of the Vagus Nerve The vagus nerve, one of 12 pairs of cranial nerves, is the predominant neural effector of the parasympathetic nervous system that comprises 75% of all parasympathetic nerve fibers. The vagus nerve is particularly well positioned to interface the immune and central
3. Cholinergic Regulation of Inflammation
nervous systems because it innervates the organs that are portals of entry or filters for pathogens and their products. The vagus nerve has motor functions in the larynx, diaphragm, stomach, and heart; and sensory functions in the ears, tongue, and visceral organs, including the liver. Inflammatory signals in peripheral tissues activate afferent signals in the vagus nerve, which are relayed to the hypothalamus and stimulate the release of ACTH and the development of fever after administration of endotoxin (17;18). The vagus nerve contains three fiber types: highly myelinated A fibers, which have low activation thresholds; lightly myelinated B fibers; and unmyelinated C fibers, which have high activation thresholds. The B and C fibers have been implicated in regulation of heart rate (19–21); no specific function has been attributed to the vagal A fibers, but our recent results suggest that the A fibers may contribute to the regulation of cytokine release. In agreement with this possibility, vagus nerve inhibition of cytokine release is specific and can be dissociated from the vagus nerve regulation of the heart rate (Huston, J., unpublished data). Moreover, the cholinergic anti-inflammatory pathway has a low activation threshold, as would be expected from an A-fiber dependent pathway. Percutaneous stimulation of the vagus via carotid massage is sufficient to inhibit systemic inflammatory responses to endotoxin challenge (Huston, J., unpublished data). Ongoing studies may delineate an immunologicalregulatory role for the vagus nerve A fibers, which are heavily myelinated and therefore most sensitive to activation.
B. Sensing Peripheral Inflammation The central nervous system receives sensory input from the immune system through both humoral and neural routes. Blalock suggested in 1984 that the immune system functions as a “sixth sense” that detects microbial invasion and produces molecules to relay this information to the brain (22;23). IL-1, TNF, and other immunological mediators can gain access to brain centers that are devoid of a blood-brain barrier, known as circumventricular regions, or can penetrate other regions of the brain by active transport systems. Very low levels of IL-1 and endotoxin in the tissues can also activate afferent vagus nerve signals at thresholds well below the serum levels that are required to achieve signaling to the brain via the humoral route. Activation of the vagus nerve by these extremely low concentrations can mediate sickness behaviors, including food aversion and fever. Both the humoral and neural routes for immune system to nervous system communication have been implicated in the develop-
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ment of fever, anorexia, activation of hypothalamicpituitary responses to infection and injury, and other behavioral manifestations of illness. 1. Humoral Mechanisms of Immune to Brain Communication TNF and IL-1 are actively transported across the blood-brain barrier, and IL-1α directly enters the brain through circumventricular organs such as the pineal gland, area postrema, median eminence, and the neural lobe of the pituitary, where the blood-brain barrier is non-existent or discontinuous (24–26). IL-1α also penetrates these areas of the brain through a putative transport mechanism in the vasculature (25;27). Microglia and endothelial cells of the cerebral vasculature express IL-1 receptors (28;29), as well as the coreceptors for endotoxin, CD14 (30) and Toll-like receptor 4 (TLR4) (31). Once cytokines gain access to circumventricular organs, they can induce widereaching effects through second messengers such as cyclooxygenase (COX2), which processes arachadonic acid to release prostaglandin E2 (PGE2); prostaglandin receptors localize to areas of the brain that play important roles in peripheral inflammatory responses such as activation of the HPA axis and fever (32–34). High molecular weight, blood-borne inflammatory mediators therefore can directly inform the central nervous system of inflammatory conditions in the periphery. The humoral route seems to be a predominant means for immune-to-brain communication when circulating cytokine levels are high. 2. Neural Mechanisms of Immune to Brain Communication The vagus nerve is a mixed nerve composed of approximately 80% sensory fibers relaying information between the brain from the head, neck, thorax, and abdomen. The central nervous system can become informed about the status of inflammation via afferent neural signals, even when blood cytokine levels are low, because locally increased levels of cytokines in tissues can activate an afferent signal in the vagus nerve. Sensory innervation of immune organs by ascending fibers traveling in the vagus nerve, as well as other pain and ascending sensory pathways, provides important input about the status of invasive and injurious challenges in distributed body compartments (19). Importantly, these neural inflammation-sensing pathways function at lower detection thresholds and activate responses even when the inflammatory agents are present in tissues at levels that are not high enough to reach the brain through the bloodstream. Linda
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Watkins and colleagues provided critical insight into the sensory role of afferent vagus nerve fibers by observing that vagotomy blunts the development of fever in animals exposed to low, intra-abdominal doses of IL-1 or endotoxin (18;35–37). It is not entirely clear how the vagus nerve “detects” the presence of inflammatory mediators, but cells isolated from the vagus nerve can express IL-1 receptor mRNA, and discrete IL-1 binding sites have been identified on “glomus” cells (38;39). Electrophysiological studies indicate that vagus nerve signals can also be activated by mechanoreceptors, chemoreceptors, temperature sensors, and osmolarity sensors, each of which can be activated at an inflammatory locus (40). The sensory afferent cell bodies of the vagus nerve reside in the nodose ganglion and transmit information to the area postrema and nucleus tractus solitaries (NTS), two regions that are active during peripheral inflammation. Ascending vagus nerve signals excite second-order neurons within the NTS (41). The NTS forms the apex of a feedback loop that modulates visceral activity through two mechanisms: NTS neurons inhibit a subset of neurons within the dorsal motor nucleus of the vagus (DMV) that activate the viscera and the digestive tract. The NTS also suppresses visceral activity by activating inhibitory DMV efferent neurons. The NTS and DMV both contain blood vessels that lack a functional blood-brain barrier, thereby allowing these brain regions to respond to either diffusible circulating factors such as LPS, TNF, and IL-1 as well as to signals arriving via the ascending vagus nerve (42). Information projecting from the NTS can in turn be relayed to the higher brain via autonomic feedback loops, direct projections to the medullary reticular formations, or through the parabrachial nucleus and the locus ceruleus. Connections from the latter emanate to the hypothalamus, the amygdala (mood regulation), and the entire forebrain [for a review see (43)].
C. The Cholinergic Anti-Inflammatory Pathway The cholinergic anti-inflammatory pathway is a neural mechanism that inhibits pro-inflammatory cytokine release via signals that require the vagus nerve and α7 receptors (12;14;15;44;45). Experimental activation of the cholinergic anti-inflammatory pathway by direct electrical stimulation of efferent vagus nerve inhibits the synthesis of TNF in liver, spleen, and heart, and attenuates serum TNF levels during endotoxemia, ischemia/reperfusion injury, hemorrhagic shock, septic peritonitis, and other dis-
eases associated with excessive cytokine release (12;14;15;44;45). Vagotomy or genetic disruption of the α7 gene significantly exacerbates TNF responses to inflammatory stimuli and sensitizes animals to the lethal effects of endotoxin (15), suggesting that cholinergic anti-inflammatory signals transmitted via the efferent vagus nerve play a role in maintaining immunological homeostasis. The synapse between the cholinergic nervous system and the innate immune system requires the α7 subunit of the acetylcholine receptor, a nicotinic αbungarotoxin-sensitive cholinergic receptor expressed on macrophages and other immunocompetent cells that modulate or participate in the inflammatory response (15). Cholinergic agonists, including nicotine and acetylcholine, significantly inhibit the release of TNF and other cytokines from endotoxin-stimulated human macrophages. Tissue macrophages, not circulating monocytes, produce most of the inflammatory cytokines released systemically during excessive inflammatory responses. The interaction of cholinergic agonists with the acetylcholine receptor inhibits the synthesis of pro-inflammatory cytokines, but not antiinflammatory cytokines (e.g., IL-10) (13–15). Monocytes, which express little or no α7 receptor, are refractory to the cytokine-inhibiting effects of acetylcholine; only supra-physiological concentrations of cholinergic agonists inhibit monocyte cytokine synthesis (14). Macrophage expression of the α7 subunit of nicotinic acetylcholine receptor distinguishes the cholinergic anti-inflammatory pathway from muscarinic receptor activities identified previously on lymphocytes, peripheral blood mononuclear cells, and alveolar macrophages (46;47). Activation of α7 transduction in macrophages inhibits endotoxin-induced NF-κB activation but does not affect the activation of several MAP kinases typically associated with endotoxin signaling (13). Since macrophages are exquisitely sensitive to acetylcholine, it is plausible that other, non-neuronal acetylcholine producing cells (e.g., epithelial cells, T lymphocytes, endothelial cells) might also modulate cytokine synthesis in nearby macrophages (48;49). Most studies to date characterizing the cholinergic– anti-inflammatory pathway have focused on the macrophage/acetylcholine interaction, but other cell types, particularly the endothelium, are also potentially regulated by acetylcholine. Activation of endothelial cells during inflammation, characterized by increased adhesion molecule expression and inflammatory mediator production, plays a critical role in the adhesion and subsequent trafficking of inflammatory leu-
3. Cholinergic Regulation of Inflammation
kocytes. Inflammatory mediators such as chemokines present on the surface of the endothelium progressively activate leukocytes rolling across the vasculature; for example, neutrophils become activated upon binding to endothelium-expressed adhesion molecules (50;51). Human microvascular endothelial cells express the α7 subunit of the acetylcholine receptor on the cell surface, and acetycholine significantly blocks TNFinduced adhesion molecule expression and chemokine expression in a concentration-dependent manner (16). Cholinergic signaling via receptor agonists (e.g., nicotine) or direct electrical vagus nerve stimulation inhibits leukocyte migration across the endothelium in vivo; notably, this effect can be blocked with mecamylamine, a negative allosteric modulator of nicotinic acetylcholine receptors, indicating that the effects of cholinergic agonists are not due to the activity of other receptor interactions (16). Acetycholine also modulates intestinal inflammatory responses and decreases histamine release by airway mucosal mast cells (52). Nicotine has anti-inflammatory effects on several other cell types, including monocytes, epithelial cells, T-cells, and neutrophils, but the role of the α7 acetylcholine receptor subunit in these cells has not been specifically defined (53–57). Our recent studies indicate that electrically stimulating the cholinergic anti-inflammatory pathway significantly inhibits TNF synthesis in spleen. Surgical ablation of the common celiac nerve to spleen abolishes the effects of vagus nerve stimulation on serum TNF levels, whereas transection of other abdominal branches of the vagus does not interfere with the cytokine-inhibiting activity of vagus nerve stimulation (Huston, et al. submitted.)
III. THE CHOLINERGIC ANTIINFLAMMATORY PATHWAY IN MEDICINE It now appears that the vagus nerve is an integral component of a reflex loop that can detect and regulate inflammatory responses in real-time. Inflammation activates an ascending signal that can be relayed to the hypothalamus to activate humoral anti-inflammatory mechanisms; efferent vagus nerve signals can rapidly and specifically inhibit macrophages in tissues (58). Physiological anti-inflammatory mechanisms represent efficient systems that have been selected by evolution to control inflammation. Now perhaps, they can be exploited for the treatment of inflammatory disorders. Several approaches have been used successfully
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to treat or prevent inflammatory disease in animals; some of these may well be adapted for therapeutic use in the clinic (13–15).
A. Electrical Vagus Nerve Stimulation The “hard-wired” connection between the nervous and immune systems functions as an antiinflammatory mechanism in several models of systemic and local inflammation. Rats subjected to bilateral cervical vagotomy are more sensitive to subsequent injection of endotoxin than animals that have undergone sham surgery; vagotomized animals develop endotoxemic shock more quickly and exhibit a more robust systemic inflammatory response, as compared to sham animals. Electrical stimulation of the vagus nerve attenuates the release of pro-inflammatory cytokines, including TNF, and IL-1 in murine endotoxemia, and also protects against endotoxemic shock (hypotension) (14;15). Stimulation of the vagus nerve has similar effects in several animal models of systemic inflammatory disease, including peritonitis/sepsis, ischemia/ reperfusion injury, and hypovolemic shock [(12;44); personal observations]. Interestingly, electrical vagus nerve stimulation also attenuates inflammatory responses in animal models of local inflammation, including carrageenan-induced paw edema and the carrageenan air pouch model; these cutaneous inflammation models are characterized by sustained endothelial cell activation (16). Furthermore, electrical stimulation of the vagus nerve increased gastric emptying, activated STAT3 in intestinal macrophages, and reduced intestinal inflammation as measured by neutrophil infiltration into the muscularis layer of the gut (59). The voltage and frequency parameters sufficient to activate the cholinergic anti-inflammatory pathway are beneath the threshold required to activate cardiac vagal fibers, indicating that vagus nerve stimulation may be a practical and efficient means of therapeutically regulating peripheral inflammation in human disease (personal observations). This approach to regulating systemic or local inflammation may have significant therapeutic potential, because vagus nerve stimulators are clinically approved devices used for the treatment of epilepsy and depression in patients refractory to other treatments. This technology to treat surgically refractory epilepsy was developed based on anecdotal observations that carotid massage, which activates vagus nerve firing, reduced seizure. Vagus nerve stimulators have been safely used in thousands of patients, but their effects on the immune response remain unknown.
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B. a7 Agonists: A New Class of Anti-inflammatory Agents α7 receptors are required for the cytokinesuppressing effects of the cholinergic anti-inflammatory pathway in animals. Activation of α7 with acetylcholine or nicotine activates calcium influx in macrophages and suppresses endotoxin-induced release of pro-inflammatory cytokines, including TNF, IL-1, and HMGB1. These observations indicate that cholinergic agonists may modulate inflammatory responses in vivo and may be an effective approach to treat diseases mediated by cytokine excess. Animal models using cholinergic agonists, including the non-specific agonist nicotine, have provided proof-of-concept data that indicate that such an approach may be successful. Although the antiinflammatory properties of nicotine are well described, the precise mechanism by which nicotine inhibits inflammation had not been previously understood. Nicotine is a relatively non-specific α7 agonist that provides significant survival advantages to animals subjected to endotoxemia or peritonitis/sepsis, and suppresses the progression of experimental ulcerative colitis and cutaneous inflammation (13;60–62). Nicotine suppresses leukocyte migration into carrageenan air pouches and decreases inflammatory infiltrate in the ears of mice subjected to the Shwartzmann reaction. The effect of nicotine on inflammatory cell recruitment is dependent upon cholinergic receptors, because the receptor antagonist mecamylamine reverses the protective effects of nicotine (16). The endogenous α7 agonist, acetylcholine, is a physiological anti-inflammatory modulator of HMGB1 release, suggesting that the cholinergic antiinflammatory pathway can be exploited for the treatment of severe sepsis (13). Nicotine recapitulates the inhibitory effects of acetylcholine on HMGB1 release, through a mechanism that requires the α7 subunit of the acetylcholine receptor to inhibit the NF-κB pathway (13). Novel, more specific α7 agonists are also in development and under study. We have found that α7 agonists are effective inhibitors of NF-κB nuclear translocation, cytokine release, and endothelial cell and macrophage activation, in murine models of local (carrageenan air pouch) and systemic (endotoxemia, peritonitis/sepsis) inflammation (13;16). α7 inhibition of the NF-κB pathway may not be the primary mechanism of action of these agents, and additional signal transduction mechanisms leading to macrophage inactivation are under study. Recent in vitro experiments have demonstrated that activation of peritoneal macrophages through the α7 nicotinic receptor is associated with activation of the transcrip-
tion factor STAT3, through a JAK2-dependent mechanism (59). Nicotine also has proven efficacy in several clinical trials; randomized, placebo-controlled trials showed that nicotine treatment was associated with significant remissions in ulcerative colitis severity (61;63). While the precise mechanism of the anti-inflammatory effects of nicotine is unproven in human disease, recent data from cell culture and animal studies indicate that the protection may have been achieved by decreasing cytokine release. 1. In Vitro Macrophages. The α7 subunit of the acetylcholine receptor is an essential regulator of inflammation in vivo, because transgenic animals devoid of α7 are exquisitely sensitive to inflammatory stimuli, and produce significantly higher levels of proinflammatory cytokines in response to endotoxin challenge than do their wild-type counterparts. In vitro, acetylcholine significantly and dose-dependently inhibits pro-inflammatory cytokine release from endotoxin-stimulated macrophages, but its in vivo use as an anti-inflammatory agent is limited by its extremely short extra-synaptic half-life. Nicotine, which has a half-maximal effective concentration (EC50 = 40 μM) on calcium influx that is three-fold lower than that of acetylcholine (EC50 = 150 μM) (64;65), is a suboptimal therapeutic because of its associated toxicity, short half-life, lack of specificity for α7, and undesirable pharmacokinetics. It is useful as a test agent in animal models of inflammation because it inhibits endotoxininduced release of TNF, IL-1, IL-18, and HMGB1 (and TNF-induced HMGB1 release) from the murine macrophage-like cell line RAW264.7 and differentiated human macrophages in culture. The antiinflammatory activity of nicotine is dependent upon α7 signaling, because transfection of macrophages with antisense oligonucleotides against α7, but not α1, α9, or α10, blocks the effects of nicotine and restores macrophage cytokine responses to endotoxin despite the presence of nicotine in the cell culture medium. Mecamylamine, a general nicotinic receptor antagonist, and α-conotoxin IMI, a selective α7 antagonist, also inhibit the anti-inflammatory effects of nicotine. In an alveolar macrophage cell line (MH-S), nicotine inhibited cytokine release in response to Legionella pneumophila infection and prevented macrophage clearance of the bacteria in vitro. Interestingly, this macrophage cell line does not express α7, and the immunosuppressive effects of nicotine appear instead to be dependent upon nicotinic receptors that include the α4 and β2 subunits. Although the intracellular sig-
3. Cholinergic Regulation of Inflammation
naling cascades activated by α7 in response to ligand have not been fully characterized in macrophages, nicotine inhibits endotoxin- and peptidoglycaninduced activation of NF-κB, but not the MAP kinases Erk, JNK, or p38 (13). Endothelium. The endothelium is an important component of the inflammatory response. Endothelial cell expression of adhesion molecules (e.g., ICAM, VCAM, and E-selectin) and soluble chemokines (e.g., IL-8, MCP-1, and RANTES) recruits macrophages and neutrophils to the site of infection or injury. The expression of α7 on the surface of primary human microvascular endothelial cells in culture suggests that nicotine and other cholinergic agonists may attenuate endothelial cell inflammatory responses. Endothelial cells in culture do not respond to endotoxin, but TNF activates the surface expression of adhesion molecules, as well as the release of chemokines into the cell culture supernatant. Supplementing cell culture media with nicotine in primary human microvascular endothelial cells stimulated with TNF inhibited expression of ICAM, VCAM, and E-selectin on the cell surface; release of IL-8, MCP-1, and RANTES into the cell culture supernatants; and activation of NF-κB with an EC50∼10−7–10−8M. Similar anti-inflammatory effects were seen with a novel cholinergic agonist, CAP55. The activity of these compounds was inhibited with mecamylamine, a non-selective and non-competitive antagonist of nicotinic acetylcholine receptors (16). Microglia. The anti-inflammatory effect of α7 agonists has also been shown in microglial cells, bone marrow–derived cells with phagocytic function present in the central nervous system (66). In vitro, nicotine pretreatment of microglial cells reduces endotoxininduced TNF release, while levels of IL-1, IL-10, and NO remained unchanged. This effect may be mediated through α7, because microglial cells express α7 mRNA, and the TNF-suppressing effect of nicotine was negated by increasing concentrations of αBTx, a selective α7 antagonist. Interestingly, nicotine enhanced the mRNA levels of COX-2 and the synthesis of PGE2 in this neuronal cell type. Increased PGE2 levels may impair microglial activation and, as a consequence, modulate chronic inflammation. Also, since neurodegenerative pathologies are characterized by microglial activation and chronic inflammation, further understanding of α7 activation in these cells could contribute to potential pharmacological modulation of microglia in neurodegenerative disorders. 2. In Vivo: Animal Models Local inflammation. Localized endothelial cell inflammation can be activated in the Schwartzmann reaction,
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in which a small dose of endotoxin is introduced to the pinnae of the ear, followed by a much larger dose 24 hours later. Five hours after the second injection of endotoxin, ear tissue is harvested and analyzed histologically for expression of adhesion molecules on endothelial cells. Treatment with nicotine or CAP55 at each endotoxin injection significantly reduces the expression of VCAM, ICAM, and E-selectin on the surface of endothelial cells in vivo. To determine if cholinergic regulation of endothelial cell adhesion molecule expression leads to reduced macrophage and neutrophil tissue infiltration, animals were subjected to a carrageenan air-pouch model, in which air is injected subcutaneously to create an air pouch. Six days later, carrageenan, an inflammatory component of seaweed, is injected into the pouch. Pouch fluid collected 6 hours later can be analyzed for cell counts and inflammatory cytokines. Treatment with nicotine or CAP55 immediately prior to carrageenan injection significantly reduces inflammatory cell influx into the pouch; the anti-inflammatory effects of these compounds are dependent on nicotinic cholinergic receptors, because mecamylamine renders these compounds ineffective (16). Systemic inflammation (endotoxemia). Endotoxemia, induced by intraperitoneal injection of lipopolysaccharide, induces a lethal pro-inflammatory disease characterized by high blood levels of TNF, IL-1, IL-6, MIF, HMGB1, and other pro-inflammatory cytokines. Treatment with nicotine (400 μg/kg, i.p.) 30 minutes prior to, and 20 hours after, endotoxin administration significantly inhibited accumulation of HMGB1 in serum. In separate studies, continued dosing twice per day for 3 days conferred significant survival advantage (vehicle-treated survival = 44%, vs. 81% survival in nicotine-treated animals). Peritonitis/Sepsis. The therapeutic effects of nicotine also have been tested in a clinically relevant model of sepsis. Anesthetized animals undergo laparotomy; the cecum is isolated, ligated, and punctured; and the animals are sutured, closed, and returned to their cages. Over the following 24 hours, intestinal contents leaking from the punctured cecum cause peritonitis, and induce a systemic inflammatory response leading to organ failure, hypotension, and death. Treatment with nicotine, beginning 24 hours after surgery when animals have developed clinical signs of sepsis, confers significant survival advantage (vehicle-treated survival = 48% vs. 89% survival in nicotine-treated animals). Nicotine treatment was associated with reduced pro-inflammatory cytokines in the circulation, and improved clinical signs of sepsis. Vagus nerve control over inflammation and the anti-inflammatory effect of nicotine were also tested in
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a model of sepsis induced by direct injection of Escherichia coli into the peritoneum (45). Surgical vagotomy prior to bacterial injection was associated with increased TNF, IL-1, and IL-6 levels as compared to sham animals, indicating that the vagus nerve exerts a tonic anti-inflammatory effect during severe bacterial infection. Conversely, oral administration of nicotine prior to injection of E. coli decreased serum cytokine levels. Cholinergic signaling is important for preserving organ function during E. coli peritonitis, because vagotomy led to slight (but non-significant) increases in ALT and AST serum concentration, while nicotine treatment preserved liver function as assessed by these measures. These changes in hepatic injury were accompanied by increased or decreased neutrophil influx by vagotomy or nicotine, respectively. Interestingly, nicotine facilitated E. coli outgrowth in peritoneal lavage fluid, blood and liver, and accelerated mortality, suggesting that attenuation of macrophage function by cholinergic agonists may impair bacterial clearance (45).
C. Pharmacologic Vagus Nerve Stimulators We first identified the cholinergic anti-inflammatory pathway while working with the tetravalent guanylhydrazone CNI-1493, a potent macrophage deactivating agent (67;68). In macrophage cultures, CNI-1493 inhibits phosphorylation of p38 MAP kinase, an enzyme that occupies a critical role in regulating the synthesis of TNF and other cytokines (69). CNI1493 confers protection in lethal endotoxemia, and against the lethality of sepsis in a standardized model of cecal ligation and puncture (70). Following a Phase I trial (71) and a small-scale Phase II clinical trial (72) a large-scale, prospective, randomized clinical trial of CNI-1493 for Crohn’s disease is underway. In the early trials, CNI-1493 induced significant clinical and endoscopic improvement in 80% of the patients, and inhibited the expression of TNF in the colonic mucosa (72). While investigating the potential therapeutic utility of CNI-1493 as a TNF inhibitor in animal models of cerebral ischemia, we made a startling and significant discovery: The fundamental physiologic mechanism of action through which CNI-1493 inhibits inflammation in vivo is to stimulate efferent activity in the vagus nerve. It is now clear that CNI-1493 functions in vivo as a pharmacologic vagus nerve stimulator, and that enhanced vagus nerve activity is required for the macrophage deactivating effects of CNI-1493 when delivered systemically. The first direct experimental insight into the role of the CNS in mediating the anti-inflammatory effects of
CNI-1493 came from analysis of endotoxin-induced shock in animals receiving CNI-1493 via the intravenous or intracerebroventricular routes. While the potential for CNI-1493 as an experimental therapeutic for stroke was examined, animals subjected to middle cerebral artery occlusion (MCAO) received CNI-1493 through either intravenous (i.v.) or intracerebroventricular (ic.v.) routes. The controls for this study included animals that received an i.v. dose of endotoxin (11; 73). Vehicle-treated endotoxemic rats developed significant hypotension and increased serum TNF levels within 1 hour after exposure to a lethal dose of LPS. Pretreatment with intravenous CNI-1493 significantly and dose-dependently inhibited serum TNF release and prevented the development of LPSinduced hypotension, but the lowest i.v. CNI-1493 dose tested (100 mg/kg) failed to prevent TNF release or hypotension. Intracerebroventricular administration of a 100-fold dilution of this ineffective i.v. dose significantly attenuated serum TNF release, and protected against the development of hypotension. Much lower i.c.v. doses of CNI-1493 (10, 1.0, and 0.1 ng CNI1493/kg) conferred significant protection against the development of endotoxin-induced serum TNF and hypotension, suggesting that the CNS participates in the systemic anti-inflammatory action of CNI-1493 during endotoxemia (11). Indeed, i.v. dosing of radiolabeled CNI-1493 led to the accumulation of protective levels of the drug in the brain. Extremely low concentrations of CNI-1493 in the brain inhibited peripheral TNF responses to systemic endotoxin challenge, suggesting that CNI-1493 invoked second messengers to regulate innate immune responses in vivo. We found no evidence of increased ACTH or glucocorticoids following ic.v. administration of CNI-1493, and accordingly hypothesized that CNI-1493 might inhibit systemic TNF through activation of efferent neural signals. It seemed plausible that the autonomic nervous system could modulate immune function; and that of all autonomic nerves, the vagus nerve, which innervates all major reticuloendothelial organs, would be most likely to carry the CNI1493–induced signal. To determine whether an intact vagus nerve is required for inhibition of TNF and protection from endotoxin-induced shock by i.c.v. or i.v. CNI-1493, animals were subjected to either surgical or chemical vagotomy (11;73). Surgical vagotomy eliminated the protective effects of intracerebroventricular CNI-1493 against LPS-induced hypotension. Surgical vagotomy also eliminated the protective effect of intravenous CNI-1493 against endotoxin-induced shock and systemic TNF release, indicating that the protective effects of CNI-1493, whether administered into the brain or the peripheral circulation, require an
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intact vagus nerve. CNI-1493 administered intravenously increased the discharge rate of the vagus nerve starting at 3–4 minutes after CNI-1493 administration, and lasted for 10–14 minutes. These results identified a previously unrecognized role of CNI-1493 in functioning as a pharmacological vagus nerve stimulator: to increase efferent vagus nerve activity and inhibit endotoxin-induced systemic TNF release and shock (11). Ligand-binding studies revealed that CNI-1493 can bind to muscarinic receptors, predominantly the M1 subtype. Therefore, we studied whether activation of central muscarinic receptors can inhibit TNF during lethal endotoxemia (PANS, in press). Administration of muscarine or the specific M1 agonist McN-A-343 prior to endotoxin exposure dose-dependently inhibits endotoxin-induced serum TNF levels, indicating that activation of central muscarinic receptors (M1) is sufficient to inhibit endotoxin-induced serum TNF. Systemic administration of muscarine, which does not cross the blood-brain barrier (BBB), had no statistically significant effect on serum TNF during endotoxemia, suggesting that peripheral muscarinic receptors do not regulate the inflammatory response to endotoxin. Together, our findings identify a central, muscarinic receptor-dependent mechanism that regulates systemic inflammation.
IV. PERSPECTIVES New insights into endogenous mechanisms that control inflammation have arisen from studies at the interface of immunology and neuroscience. The cholinergic anti-inflammatory pathway comprises the efferent arm of an inflammatory reflex, a neural feedback loop through which the central nervous system monitors and regulates immune function. In addition to providing several new therapeutic approaches to control inflammatory disease, the description of the inflammatory reflex suggests that it may be possible to study whether diseases presenting with an inflammatory component have an underlying neurological deficit. It is also possible to hypothesize that rational modulation of vagus nerve tone may have therapeutic benefit in inflammatory diseases. It may also be possible to study whether acupuncture, placebo effects, prayer, and meditation cause a functional response in neural-immune signaling via this pathway.
A. Autonomic Dysfunction in Disease It is now reasonable to suggest a hypothesis that dysfunction of the cholinergic anti-inflammatory
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pathway may predispose some individuals to excessive inflammatory responses, because the cholinergic anti-inflammatory pathway normally provides a brake on the immune system that restrains cytokine production. Animals with insufficient efferent signaling in the cholinergic anti-inflammatory pathway exhibit robust systemic responses to inflammatory disease, suggesting that this neural pathway provides tonic regulation of immunological homeostasis. Clinically, autonomic dysfunction has been associated with a number of inflammatory diseases characterized by increased proinflammatory cytokine activity, including rheumatoid arthritis, Crohn’s disease, lupus, diabetes, and sepsis. It is theoretically possible that autonomic dysfunction contributes to the dysregulated cytokine release in these diseases. In one large clinical trial, the fatality rate of septic patients with abnormal mental status was twice that of patients with normal mentation; loss of heart rate variability, a reflection of autonomic dysfunction, is also associated with increased sepsis mortality (74–77).
B. Biofeedback and Inflammation For centuries, patients and physicians have believed in the vague notion that an individual’s “state of mind” can influence somatic health. Folklore, art, and literature are replete with the themes that grief and depression are associated with increased disease susceptibility, and positive beliefs and expectations augur wellness. A familiar example is the death of a devoted spouse shortly after he or she buries his or her loved one. To many, this fundamental relationship between a sense of well-being and health is indisputable. One implication of the anti-inflammatory activity of the efferent vagus nerve is that subjects may be trained to rationally augment vagus nerve activity, and thus modulate peripheral inflammatory and immune responses. Via a computer interface, subjects can be trained to increase vagus nerve activity. This approach, known commonly as biofeedback, has been used in the treatment of headache (78), temporomandibular joint disorders (79), Raynaud disease (80), hypertension (81), diabetes (82), urinary (83) and fecal incontinence (84), asthma (85), and intermittent claudication (86) with varying success. Electronic sensors and graphic displays that monitor physiologic parameters such as heart rate, skin temperature, and muscle tension are measured. Subjects can learn to associate visual and auditory signals from a computer interface with changes in involuntary functions, and to recognize mental and physical states that induce desired physiologic changes regulated by the parasympathetic (vagus) nervous system (e.g., blood pres-
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sure reduction, warming of extremities, slowing of heart rate). The ability to rationally modulate vagus nerve activity through biofeedback techniques now makes it plausible to consider regulation of cytokine synthesis by voluntarily increasing vagus nerve activity. A treatment for diseases characterized by uncontrolled inflammation may now be at hand, by stimulating the cholinergic anti-inflammatory pathway to turn off cytokine synthesis.
Literature Cited 1. Knudsen, P. J., Dinarello, C. A., and Strom, T. B. (1986). Prostaglandins posttranscriptionally inhibit monocyte expression of interleukin 1 activity by increasing intracellular cyclic adenosine monophosphate. J. Immunol., 137 (10), 3189–3194. 2. Wang, H., Zhang, M., Bianchi, M., Sherry, B., Sama, A., and Tracey, K. J. (1998). Fetuin (alpha2-HS-glycoprotein) opsonizes cationic macrophage deactivating molecules. Proc. Natl. Acad. Sci. USA, 95 (24), 14429–14434. 3. Zhang. M., Caragine. T., Wang. H., et al. (1997). Spermine inhibits proinflammatory cytokine synthesis in human mononuclear cells, a counterregulatory mechanism that restrains the immune response. J. Exp. Med., 185 (10), 1759–1768. 4. Zhang, M., Borovikova, L. V., Wang, H., Metz, C., and Tracey, K. J. (1999) Spermine inhibition of monocyte activation and inflammation. Mol. Med., 5 (9), 595–605. 5. Zhang, M., Wang, H., and Tracey, K. J. (2000). Regulation of macrophage activation and inflammation by spermine, a new chapter in an old story. Crit. Care Med., 28 (4 Suppl), N60–N66. 6. Bogdan, C., Vodovotz, Y., and Nathan, C. (1991). Macrophage deactivation by interleukin 10. J. Exp. Med., 174 (6), 1549–1555. 7. Hauser, C. J., Lagoo, S., Lagoo, A., et al. (1995). Tumor necrosis factor alpha gene expression in human peritoneal macrophages is suppressed by extra-abdominal trauma. Arch. Surg., 130 (11), 1186–1191. 8. Oswald, I. P., Wynn, T. A., Sher, A., and James, S. L. (1992). Interleukin 10 inhibits macrophage microbicidal activity by blocking the endogenous production of tumor necrosis factor alpha required as a costimulatory factor for interferon gammainduced activation. Proc. Natl. Acad. Sci. USA, 89 (18), 8676–8680. 9. Miller-Graziano, C. L., Szabo, G., Griffey, K., Mehta, B., Kodys, K., and Catalano, D. (1991). Role of elevated monocyte transforming growth factor beta (TGF beta) production in posttrauma immunosuppression. J Clin. Immunol., 11 (2), 95–102. 10. Tsunawaki, S., Sporn, M., Ding, A., and Nathan, C. (1988). Deactivation of macrophages by transforming growth factor-beta. Nature, 334 (6179), 260–262. 11. Bernik, T. R., Friedman, S. G., Ochani, M., et al. (2002). Pharmacological stimulation of the cholinergic antiinflammatory pathway. J. Exp. Med., 195 (6), 781–788. 12. Guarini, S., Altavilla, D., Cainazzo, M. M., et al. (2003). Efferent vagal fibre stimulation blunts nuclear factor-kappaB activation and protects against hypovolemic hemorrhagic shock. Circulation, 107 (8), 1189–1194. 13. Wang, H., Liao, H., Ochani, M., et al. (2004). Cholinergic agonists inhibit HMGB1 release and improve survival in experimental sepsis. Nat. Med., 10 (11), 1216–1221.
14. Borovikova, L. V., Ivanova, S., Zhang, M., et al. (2000). Vagus nerve stimulation attenuates the systemic inflammatory response to endotoxin. Nature, 405 (6785), 458–462. 15. Wang, H., Yu, M., Ochani, M., et al. (2003). Nicotinic acetylcholine receptor alpha7 subunit is an essential regulator of inflammation. Nature, 421 (6921), 384–388. 16. Saeed, R. W., Varma, S., Peng-Nemeroff, T., et al. (2005). Cholinergic stimulation blocks endothelial cell activation and leukocyte recruitment during inflammation. J. Exp. Med., 201 (7), 1113–1123. 17. Dantzer, R. (2001). Cytokine-induced sickness behavior, mechanisms and implications. Ann. N. Y. Acad. Sci., 933, 222–234. 18. Maier, S. F., Goehler, L. E., Fleshner, M., and Watkins, L. R. (1998). The role of the vagus nerve in cytokine-to-brain communication. Ann. N. Y. Acad. Sci., 840, 289–300. 19. Jones, J. F., Wang, Y., and Jordan, D. (1995). Heart rate responses to selective stimulation of cardiac vagal C fibres in anaesthetized cats, rats and rabbits. J. Physiol., 489 (Pt 1), 203–214. 20. Nosaka, S., Yasunaga, K., and Kawano, M. (1979). Vagus cardioinhibitory fibers in rats. Pflugers Arch., 379 (3), 281–285. 21. Schwaber, J. S., and Cohen, D. H. (1978). Electrophysiological and electron microscopic analysis of the vagus nerve of the pigeon, with particular reference to the cardiac innervation. Brain Res., 147 (1), 65–78. 22. Blalock, J. E. (1984). The immune system as a sensory organ. J. Immunol., 132 (3), 1067–1070. 23. Blalock, J. E. (2005). The immune system as the sixth sense. J. Intern. Med., 257 (2), 126–138. 24. Gross, P. M., and Weindl, A. (1987). Peering through the windows of the brain. J. Cereb. Blood Flow Metab., 7 (6), 663–672. 25. Johnson, A. K., and Gross, P. M. (1993). Sensory circumventricular organs and brain homeostatic pathways. FASEB J., 7 (8), 678–686. 26. Plotkin, S. R., Banks, W. A., and Kastin, A. J. (1996). Comparison of saturable transport and extracellular pathways in the passage of interleukin-1 alpha across the blood-brain barrier. J. Neuroimmunol., 67 (1), 41–47. 27. Moinuddin, A., Morley, J. E., and Banks, W. A. (2000). Regional variations in the transport of interleukin-1alpha across the blood-brain barrier in ICR and aging SAMP8 mice. Neuroimmunomodulation, 8 (4), 165–170. 28. Cunningham, E. T., Jr., Wada, E., Carter, D. B., Tracey, D. E., Battey, J. F., and De Souza, E. B. (1992). In situ histochemical localization of type I interleukin-1 receptor messenger RNA in the central nervous system, pituitary, and adrenal gland of the mouse. J. Neurosci., 12 (3), 1101–1114. 29. Yabuuchi, K., Minami, M., Katsumata, S., and Satoh, M. (1994). Localization of type I interleukin-1 receptor mRNA in the rat brain. Brain. Res. Mol. Brain Res., 27 (1), 27–36. 30. Lacroix, S., and Rivest, S. (1998). Effect of acute systemic inflammatory response and cytokines on the transcription of the genes encoding cyclooxygenase enzymes (COX-1 and COX-2) in the rat brain. J. Neurochem., 70 (2), 452–466. 31. Olson, J. K., and Miller, S. D. (2004). Microglia initiate central nervous system innate and adaptive immune responses through multiple TLRs. J. Immunol., 173 (6), 3916–3924. 32. Ericsson, A., Arias, C., and Sawchenko, P. E. (1997). Evidence for an intramedullary prostaglandin-dependent mechanism in the activation of stress-related neuroendocrine circuitry by intravenous interleukin-1. J. Neurosci., 17 (18), 7166–7179. 33. Matsumura, K., Watanabe, Y., Onoe, H., Watanabe, Y., and Hayaishi, O. (1990). High density of prostaglandin E2 binding sites in the anterior wall of the 3rd ventricle, a possible site of its hyperthermic action. Brain Res., 533 (1), 147–151.
3. Cholinergic Regulation of Inflammation 34. Parrott, R. F., and Vellucci, S. V. (1996). Effects of centrally administered prostaglandin EP receptor agonists on febrile and adrenocortical responses in the prepubertal pig. Brain Res. Bull., 41 (2), 97–103. 35. Hansen, M. K., Nguyen, K. T., Goehler, L. E., et al. (2000). Effects of vagotomy on lipopolysaccharide-induced brain interleukin1beta protein in rats. Auton. Neurosci., 85 (1–3), 119–126. 36. Hansen, M. K., Nguyen, K. T., Fleshner, M., et al. (2000). Effects of vagotomy on serum endotoxin, cytokines, and corticosterone after intraperitoneal lipopolysaccharide. Am. J. Physiol. Regul. Integr. Comp. Physiol., 278 (2), R331–R336. 37. Milligan, E. D., McGorry, M. M., Fleshner, M., et al. (1997). Subdiaphragmatic vagotomy does not prevent fever following intracerebroventricular prostaglandin E2: further evidence for the importance of vagal afferents in immune-to-brain communication. Brain Res., 766 (1–2), 240–243. 38. Ek, M., Kurosawa, M., Lundeberg, T., and Ericsson, A. (1998). Activation of vagal afferents after intravenous injection of interleukin-1beta: role of endogenous prostaglandins. J. Neurosci., 18 (22), 9471–9479. 39. Goehler, L. E., Relton, J. K., Dripps, D., et al. (1997). Vagal paraganglia bind biotinylated interleukin-1 receptor antagonist: a possible mechanism for immune-to-brain communication. Brain Res. Bull., 43 (3), 357–364. 40. Adachi, A. (1984). Thermosensitive and osmoreceptive afferent fibers in the hepatic branch of the vagus nerve. J. Auton. Nerv. Syst., 10 (3–4), 269–273. 41. Rogers, R. C., McTigue, D. M., and Hermann, G. E. (1996). Vagal control of digestion: modulation by central neural and peripheral endocrine factors. Neurosci. Biobehav. Rev., 20 (1), 57–66. 42. Smith, B. N., Dou, P., Barber, W. D., and Dudek, F. E. (1998). Vagally evoked synaptic currents in the immature rat nucleus tractus solitarii in an intact in vitro preparation. J. Physiol., 512 (Pt 1), 149–162. 43. Pavlov, V. A., Wang, H., Czura, C. J., Friedman, S. G., and Tracey, K. J. (2003). The cholinergic anti-inflammatory pathway: a missing link in neuroimmunomodulation. Mol. Med., 9 (5–8), 125–134. 44. Bernik, T. R., Friedman, S. G., Ochani, M., et al. (2002). Cholinergic antiinflammatory pathway inhibition of tumor necrosis factor during ischemia reperfusion. J. Vasc. Surg., 36 (6), 1231–1236. 45. van Westerloo, D. J., Giebelen, I. A., Florquin, S., et al. (2005). The cholinergic anti-inflammatory pathway regulates the host response during septic peritonitis. J. Infect. Dis., 191 (12), 2138–2148. 46. Kawashima, K., and Fujii, T. (2003). The lymphocytic cholinergic system and its contribution to the regulation of immune activity. Life Sci., 74 (6), 675–696. 47. Sato, E., Koyama, S., Okubo, Y., Kubo, K., and Sekiguchi, M. (1998). Acetylcholine stimulates alveolar macrophages to release inflammatory cell chemotactic activity. Am. J. Physiol., 274 (6 Pt 1), L970–L979. 48. Kawashima, K., Fujii, T., Watanabe, Y., and Misawa, H. (1998). Acetylcholine synthesis and muscarinic receptor subtype mRNA expression in T-lymphocytes. Life Sci., 62 (17–18), 1701–1705. 49. Proskocil, B. J., Sekhon, H. S., Jia, Y., et al. (2004). Acetylcholine is an autocrine or paracrine hormone synthesized and secreted by airway bronchial epithelial cells. Endocrinology, 145 (5), 2498–2506. 50. Ley, K. (2002). Integration of inflammatory signals by rolling neutrophils. Immunol. Rev., 186, 8–18.
95
51. Peters, K., Unger, R. E., Brunner, J., and Kirkpatrick, C. J. (2003). Molecular basis of endothelial dysfunction in sepsis. Cardiovasc. Res., 60 (1), 49–57. 52. Reinheimer, T., Mohlig, T., Zimmermann, S., Hohle, K. D., and Wessler, I. (2000). Muscarinic control of histamine release from airways. Inhibitory M1-receptors in human bronchi but absence in rat trachea. Am. J. Respir. Crit. Care Med., 162 (2 Pt 1), 534–538. 53. Mariggio, M. A., Guida, L., Laforgia, A., et al. (2001). Nicotine effects on polymorphonuclear cell apoptosis and lipopolysaccharide-induced monocyte functions. A possible role in periodontal disease? J. Periodontal Res., 36 (1), 32– 39. 54. Singh, S. P., Kalra, R., Puttfarcken, P., Kozak, A., Tesfaigzi, J., and Sopori, M. L. (2000). Acute and chronic nicotine exposures modulate the immune system through different pathways. Toxicol. Appl. Pharmacol., 164 (1), 65–72. 55. Sorensen, L. T., Nielsen, H. B., Kharazmi, A., and Gottrup, F. (2004). Effect of smoking and abstention on oxidative burst and reactivity of neutrophils and monocytes. Surgery, 136 (5), 1047–1053. 56. Speer, P., Zhang, Y., Gu, Y., Lucas, M. J., and Wang, Y. (2002). Effects of nicotine on intercellular adhesion molecule expression in endothelial cells and integrin expression in neutrophils in vitro. Am. J. Obstet. Gynecol., 186 (3), 551–556. 57. Zhang, S., and Petro, T. M. (1996). The effect of nicotine on murine CD4 T cell responses. Int. J. Immunopharmacol., 18 (8–9), 467–478. 58. Andersson, J. (2005). The inflammatory reflex—introduction. J. Intern. Med., 257 (2), 122–125. 59. de Jonge, W. J., and van der Zanden, E. P. (2005). The FO et al. Stimulation of the vagus nerve attenuates macrophage activation by activating the Jak2-STAT3 signaling pathway. Nat. Immunol., 6 (8), 844–851. 60. Mills, C. M., Hill, S. A., and Marks, R. (1997). Transdermal nicotine suppresses cutaneous inflammation. Arch. Dermatol., 133 (7), 823–825. 61. Pullan, R. D., Rhodes, J., Ganesh, S., et al. (1994). Transdermal nicotine for active ulcerative colitis. N. Engl. J. Med., 330 (12), 811–815. 62. Thomas, G. A., Rhodes, J., Mani, V., et al. (1995). Transdermal nicotine as maintenance therapy for ulcerative colitis. N. Engl. J. Med., 332 (15), 988–992. 63. Sandborn, W. J., Tremaine, W. J., Offord, K. P., et al. (1997). Transdermal nicotine for mildly to moderately active ulcerative colitis. A randomized, double-blind, placebo-controlled trial. Ann. Intern. Med., 126 (5), 364–371. 64. Delbono, O., Gopalakrishnan, M., Renganathan, M., Monteggia, L. M., Messi, M. L., and Sullivan, J. P. (1997). Activation of the recombinant human alpha 7 nicotinic acetylcholine receptor significantly raises intracellular free calcium. J. Pharmacol. Exp. Ther., 280 (1), 428–438. 65. Leonard, S., and Bertrand, D. (2001). Neuronal nicotinic receptors: from structure to function. Nicotine Tob. Res., 3 (3), 203–223. 66. De, SR., jmone-Cat, M. A., Carnevale, D., and Minghetti, L. (2005). Activation of alpha7 nicotinic acetylcholine receptor by nicotine selectively up-regulates cyclooxygenase-2 and prostaglandin E2 in rat microglial cultures. J. Neuroinflammation, 2 (1), 4. 67. Bianchi, M., Ulrich, P., Bloom, O., et al. (1995). An inhibitor of macrophage arginine transport and nitric oxide production (CNI-1493) prevents acute inflammation and endotoxin lethality. Mol. Med., 1 (3), 254–266.
96
I. Neural and Endocrine Effects on Immunity
68. Bianchi, M., Bloom, O., Raabe, T., et al. (1996). Suppression of proinflammatory cytokines in monocytes by a tetravalent guanylhydrazone. J. Exp. Med., 183 (3), 927–936. 69. Cohen, P. S., Nakshatri, H., Dennis, J., et al. (1996). CNI-1493 inhibits monocyte/macrophage tumor necrosis factor by suppression of translation efficiency. Proc. Natl. Acad. Sci. USA, 93 (9), 3967–3971. 70. D’Souza, M. J., Oettinger, C. W., Milton, G. V., and Tracey, K. J. (1999). Prevention of lethality and suppression of proinflammatory cytokines in experimental septic shock by microencapsulated CNI-1493. J. Interferon Cytokine Res., 19 (10), 1125–1133. 71. Atkins, M. B., Redman, B., Mier, J., et al. (2001). A phase I study of CNI-1493, an inhibitor of cytokine release, in combination with high-dose interleukin-2 in patients with renal cancer and melanoma. Clin. Cancer Res., 7 (3), 486–492. 72. Hommes, D., van den, B. B., Plasse, T., et al. (2002). Inhibition of stress-activated MAP kinases induces clinical improvement in moderate to severe Crohn’s disease. Gastroenterology, 122 (1), 7–14. 73. Meistrell, M. E., III, Botchkina, G. I., Wang, H., et al. (1997). Tumor necrosis factor is a brain damaging cytokine in cerebral ischemia. Shock, 8 (5), 341–348. 74. Arons, M. M., Wheeler, A. P., Bernard, G. R., et al. (1999). Effects of ibuprofen on the physiology and survival of hypothermic sepsis. Ibuprofen in Sepsis Study Group. Crit. Care Med., 27 (4), 699–707. 75. Landry, D. W., Levin, H. R., Gallant, E. M., et al. (1997). Vasopressin deficiency contributes to the vasodilation of septic shock. Circulation, 95 (5), 1122–1125. 76 Sprung, C. L., Peduzzi, P. N., Shatney, C. H., et al. (1990). Impact of encephalopathy on mortality in the sepsis syndrome. The Veterans Administration Systemic Sepsis Cooperative Study Group. Crit. Care Med., 18 (8), 801–806. 77. Yien, H. W., Hseu, S. S., Lee, L. C., Kuo, T. B., Lee, T. Y., and Chan, S. H. (1997). Spectral analysis of systemic arterial pressure
78.
79.
80.
81.
82.
83.
84.
85.
86.
and heart rate signals as a prognostic tool for the prediction of patient outcome in the intensive care unit. Crit. Care Med., 25 (2), 258–266. Hermann, C., and Blanchard, E. B. (2002). Biofeedback in the treatment of headache and other childhood pain. Appl. Psychophysiol. Biofeedback, 27 (2), 143–162. Crider, A. B., and Glaros, A. G. (1999). A meta-analysis of EMG biofeedback treatment of temporomandibular disorders. J. Orofac. Pain, 13 (1), 29–37. Middaugh, S. J., Haythornthwaite, J. A., Thompson, B., et al. (2001). The Raynaud’s Treatment Study: biofeedback protocols and acquisition of temperature biofeedback skills. Appl. Psychophysiol. Biofeedback, 26 (4), 251–278. Yucha, C. B., Clark, L., Smith, M., Uris, P., LaFleur, B., and Duval, S. (2001). The effect of biofeedback in hypertension. Appl. Nurs. Res., 14 (1), 29–35. McGrady, A., and Horner, J. (1999). Role of mood in outcome of biofeedback assisted relaxation therapy in insulin dependent diabetes mellitus. Appl. Psychophysiol. Biofeedback, 24 (1), 79–88. Gormley, E. A. (2002). Biofeedback and behavioral therapy for the management of female urinary incontinence. Urol. Clin. North Am., 29 (3), 551–557. Pager, C. K., Solomon, M. J., Rex, J., and Roberts, R. A. (2002). Long-term outcomes of pelvic floor exercise and biofeedback treatment for patients with fecal incontinence. Dis. Colon Rectum, 45 (8), 997–1003. Lehrer, P., Smetankin, A., and Potapova, T. (2000). Respiratory sinus arrhythmia biofeedback therapy for asthma: a report of 20 unmedicated pediatric cases using the Smetankin method. Appl. Psychophysiol. Biofeedback, 25 (3), 193–200. Aikens, J. E. (1999). Thermal biofeedback for claudication in diabetes: a literature review and case study. Altern. Med. Rev., 4 (2), 104–110.
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4 Significance of Sensory Neuropeptides and the Immune Response HANNEKE P. M. VAN DER KLEIJ AND JOHN BIENENSTOCK
I. II. III. IV. V. VI. VII. VIII. IX. X. XI. XII. XIII. XIV.
INTRODUCTION 97 THE IMMUNE SYSTEM 98 THE NERVOUS SYSTEM 99 NEUROPEPTIDES 100 THE ENTERIC NERVOUS SYSTEM 105 THE CHOLINERGIC ANTI-INFLAMMATORY PATHWAY 105 NEUROTROPHINS 105 NEUROPEPTIDE COMMUNICATION: THE DIFFERENT IMMUNE CELLS 106 NERVES IN THE INFLAMMATORY PROCESS 110 NEUROGENIC INFLAMMATION 111 CENTRAL NERVOUS SYSTEM 111 STRESS RESPONSE 112 NERVE-IMMUNE COMMUNICATION IN THE VARIOUS TISSUES 113 SUMMARY 117
will show that local environmental effects may alter many of the functions of all cells present. As a consequence to this outline, the chapter contains some redundancy of information.
I. INTRODUCTION More and more studies are demonstrating interactions between the nervous system and immune system (1–3). It has been established that the central nervous system (CNS) can regulate immune functioning. For instance, lesions in the CNS lead to altered immune responses (4,5). Also, immune responses can be classically conditioned involving a CNS learning paradigm (6,7). Furthermore, it was found that peripheral immune responses could alter the firing rate of neurons in the CNS (8). Accordingly, information can flow not only from the CNS to the immune system, but also in the opposite direction. For instance, immune cells can produce neuropeptides such as substance P and βendorphin (9). Neuropeptides are made by the nervous system and by all types of other cells, e.g., substance P by eosinophils. Acetylcholine (ACh) is made by nonneuronal cells. On the other hand, neurons can make cytokines such as interleukin (IL) 1 (10). In addition, cells of the immune system possess receptors for a host of hormones and neurotransmitters, including receptors for catecholamines, ACTH, opioid peptides, substance P, and vasoactive intestinal peptide (VIP). These receptors have been shown to respond in vivo and/or in vitro to the neurotransmitter substances, and their
The nervous system and the immune system have been clearly shown to be closely related. This chapter will describe how the immune system and the nervous system interact, and address the overlap in compounds they contain and release plus the mutual expression of receptors. We will concentrate on the role of sensory neuropeptides in relation to cells involved in the inflammatory system. First, we will address the immune system and the nervous system from a more general point of view. Second, we will concentrate on the specific cell types and the way sensory neuropeptides interact with the different immune cells on this level. Last, since nerve fibers project into every organ of the body, we will focus on sensory neuropeptide interaction with immune cells in different tissues. We PSYCHONEUROIMMUNOLOGY, 4E VOLUME I
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manipulation can alter immune responses. (11,12). Additionally, the CNS shares receptors with the immune system for neuropeptides and neurotransmitters as well as for cytokines. Thus, the two systems can communicate in a bi-directional fashion as a result of a common set of signal molecules and their receptors (13). Nerves are closely associated with inflammatory cells, especially mast cells and lymphocytes (14,15). Nerve-immune associations were found in the intestine involving mast cells, as well as eosinophils and plasma cells (16). Cells of the immune system and their products have been shown to influence peripheral and central neurotransmission, leading to the conceptualization of a bi-directional neuroimmune communication system. In addition, neuropeptides from sensory nerves can directly modulate the function of Langerhans cells. Further work has demonstrated similar morphologic mast cell-nerve associations in the liver, mesentery, urinary bladder, and skin. These interactions influence a variety of physiologic and pathophysiologic functions including cellular development, growth and differentiation, immunity, leukocyte recruitment, inflammation, as well as tissue repair (17–19). Immune regulation is mediated via a cascade of events requiring cell–cell interactions and subsequent release of their contents, such as cytokines and antibodies, to regulate these responses. The complex interrelationships of the nervous system and the immune system have received increasing attention (a) on their bi-directional nature and (b) on the production of cytokines by the nervous system and neuropeptides by the immune/inflammatory system.
II. THE IMMUNE SYSTEM Immune molecules such as cytokines, chemokines, and growth factors can modulate functioning of the nervous system through multiple signaling pathways. Immunological stressors can engage cytokines and other immune molecules in bi-directional interactions with brain neuroendocrine, peptide, and neurotransmitter systems. There are two major defense responses of the body to immunological triggers. Innate immunity refers to the initial response by the body to defend against and eliminate microbes and prevent infection. Adaptive or acquired immunity refers to antigenspecific defense mechanisms that may take several days to become protective and are designed to react with, neutralize, and remove a specific antigen. Dendritic cells (DCs) and natural killer (NK) cells are the main cellular components of the innate immune
system. NK cells recognize and bind virus-infected host cells and tumor cells and induce their apoptosis (20). Upon activation, NK cells can produce a variety of cytokines and chemokines, which can have a direct effect on tumor growth and induce inflammatory and anti-viral responses (21). In disease states, the first contact between NK cells and DCs most likely occur at the site of infection as both cell types are recruited to tissues in response to infection. Many of the cytokines that are known to enhance NK cell function are produced by DCs in response to microbial infection (22). For instance, DCs are a major source of IL-15, a cytokine essential for NK cell development, that also promotes NK cell survival and proliferation (23). Following priming by pathogen-derived products, their reciprocal interactions result in a potent activating crosstalk regulating the innate immune responses. A second set of NK cells, the natural killer T-cells (NKT), has been more recently identified. NKT cells possess phenotypic characteristics of both NK and Tcells (24). NKT cells are considered to play an intermediary role bridging innate and acquired immunity. They respond to various external stimuli by an early burst of cytokines, especially IL-4 and IFN-γ (25). NKT cells play an important immunoregulatory role through the production of these Th1 (IFN-γ) and Th2 (IL-4) cytokines (24). It has been shown that the communication between NK and NKT cells is mediated primarily by IFN-γ. In addition, the production of IFN-γ has an important role in the cytotoxic response (25). Dysregulation in IL-4 production can result in chronic inflammation and autoimmune diseases (26). Impaired IFN-γ production by NKT cells results in inefficient NK cell cytotoxicity because NKT cells “cross-talk” via IFN-γ to activate NK cells (25). This pathway linking NKT and NK cell functions is important under conditions of low innate cytokine induction (i.e., of IL-12 and/or IFNα/β) during viral or bacterial infections (24). Innate immunity is designed to recognize a few highly conserved structures present in many different microorganisms. Infection by pathogenic microorganisms triggers in the host a set of immune, physiological, metabolic, and behavioral responses known as the acute phase reaction. These responses are mediated by the activation of innate immune cells that recognize bacterial and viral products via membrane Toll-like receptors (TLR). Studies have been showing an essential role for TLR in the activation of innate and adaptive immunity (27). Ligand recognition induces a host defense response, which includes the production of inflammatory cytokines, upregulation of co-stimulatory molecules, and the induction of anti-microbial defense. Activation of dendritic cells by TLR ligands is necessary for their maturation and con-
4. Significance of Sensory Neuropeptides and the Immune Response
sequent ability to initiate immune responses (27). Lipopolysaccharide (LPS), the active fragment of Gram negative bacteria, binds to Toll-like receptor-4 on monocytes and macrophages, which activates complex intracellular signaling pathways resulting in the activation of nuclear transcription factors. It has been shown that intraperitoneal LPS induced IL-1β protein within the vagus in a time frame consistent with signaling of immune activation. This suggests a novel mechanism by which IL-1β may serve as a molecular link between the immune system and vagus nerve, and hence the CNS (28). Furthermore, the systemic administration of LPS or recombinant pro-inflammatory cytokines such as IL-1 to healthy laboratory animals or human volunteers triggers the whole set of responses, including its central component in the form of fever, activation of the hypothalamic-pituitaryadrenal axis, and the behavioral symptoms of sickness (29,30). The same clinical signs can be induced by injection of LPS or interleukin-1 into the lateral ventricle of the brain, which indicates that the brain is able to recognize immune molecular signals. Cytokine-induced sickness behavior can be seen as a neuroimmune response to activation of innate immunity. In the brain, cytokines are produced that are the same as those expressed by innate immune cells, and they act on brain receptors that are identical to those characterized on immune cells. Primary afferent nerves represent the main communication pathway between peripheral and central cytokines (29,30). Recent reports identified and described neural pathways that control and adjust the peripheral immune response. For instance, the two immunomodulatory peptides VIP and the pituitary adenylate cyclase-activating polypeptide (PACAP) are present and released from both nerves and immune cells (31). VIP/PACAP have a general anti-inflammatory effect, both in innate and adaptive immunity. In innate immunity, VIP/PACAP inhibit the production of pro-inflammatory cytokines and chemokines from macrophages, microglia, and dendritic cells. In addition, VIP/PACAP reduce the expression of co-stimulatory molecules on antigen-presenting cells, and therefore reduce stimulation of antigen-specific CD4+ T-cells. In adaptive immunity, VIP/PACAP promote Th2-type responses, and reduce the pro-inflammatory Th1-type responses (31). The adaptive immune system can be divided into humoral immunity, mediated by antibody-producing B-cells, and cell-mediated immunity, mediated by Tlymphocytes. There are different types of T-cells: Thelper cells, Th0, Th1, Th2, T regulatory cells (Treg), and Natural Killer T (NKT) cells, which direct adaptive immune responses. Treg appear to be important in
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the prevention of autoimmune disease and in their response to incoming invaders. Th1 and Th2 cells are thought to derive from a naive Th0 precursor that makes a wide range of cytokines. In the presence of IL-12 and IL-18 (from dendritic cells), Th0 will differentiate into Th1 cells that secrete IL-2, interferon γ (IFN-γ), and TGF-β, or in the presence of IL-4 (from Bcells or lymphoid dendritic cells) they will differentiate into Th2 cells that secrete IL-4, IL-5, IL-6, IL-10, and IL-13. These types of responses are mutually inhibitory, and the switch to one or the other is directly linked with the cytokines generated by innate immune responses. The first step in immune responsiveness is the delivery of antigen in a form that DCs can acquire, process, and present to CD4+ T-cells, CD8+ T-cells, and/or Bcells (32). Immature tissue DCs sense invading organisms by their TLR (33). Upon receiving an activation signal, they undergo phenotypical and functional changes, including increased expression of surface molecules that aid and promote T-cell activation, a changed pattern of release of chemokines and cytokines leading to attraction of T-cells, promotion of Tcell activation, and direction of their ultimate phenotype (Th0, Th1, Th2, or T regulatory [Treg]) (34, 35). DCs treated with TNF, a pleiotropic stimulus of DC activation, and prostaglandin E produce a low level of IL-12 and induce a mixed population of Th0 and Th1 T-cells. DCs secrete high levels of IL-12 and IFN-α leading to a strong Th1 response. The nervous system releases neuropeptides at specific local sites of infection or challenge, which may then influence the direction of the Th1/Th2 response and therefore immune outcome. For instance, calcitonin gene-related peptide (CGRP) can inhibit IFN-γ production markedly in a dose-dependent manner, and substance P and VIP can suppress IL-4 production (36). Catecholamines may play an important role in regulating adaptive immune responses as Th1 cells express adrenergic receptors (37). Furthermore, adrenergic receptors on B-cells suggest that the sympathetic nervous system may also regulate antibody production (37).
III. THE NERVOUS SYSTEM The nervous system can regulate immune function and inflammation. Experimental evidence shows an important role of the autonomic nervous system in the bi-directional communication between the brain and the immune system, underlying the ability of the brain to monitor immune status and control inflammation. The central nervous system and immune system inter-
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act bi-directionally. Neuropeptides, neurohormones, and neurotransmitters of the CNS interact with the immune system which, in turn, feeds back to the brain inducing changes in both behavior such as sickness response and changes in the immune system (38–40). Cytokines produced in the periphery can affect the brain, producing illness behavior and activation of neuroendocrine and autonomic stress-related circuits (41,42). The CNS alerts the immune system to environmental changes using the shared neuropeptide, neurotransmitter, and cytokine receptors on immune cells. An example of this is the effects of stress to dampen immune function. Recognition of stimuli such as viruses and bacteria by the immune systems results in transmission of information to the CNS to cause a physiological response. Upon peritoneal infection with bacteria, changes occur in the body such as fever associated with sickness behavior. These responses are a direct result of immune cell–derived proinflammatory cytokines signaling the CNS via the subdiaphragmatic vagus nerve (13,43). In the autonomic nervous system, nerves are intimately associated with inflammatory cells, especially mast cells (2). The chemical transmitter at both preand post-ganglionic synapses in the parasympathetic system is ACh. Nerve fibers that release ACh from their endings are described as cholinergic fibers. ACh is the neurotransmitter via a nicotinic receptor at the pre-ganglionic synapse. Adrenaline and noradrenaline as well as norepinephrine (NE), the classical sympathetic neurotransmitter, are catecholamines. Noradrenergic nerve fibers of the sympathetic nervous system release NE and other co-localized peptides that signal cells bearing appropriate cell surface receptors. Cells of the immune system, including T and B lymphocytes, NK cells, and macrophages, express α- and β-adrenergic receptors, the receptors for NE (44,45). Activation of the sympathetic nervous system in vivo, or stimulation of lymphocytes with selective receptor agonists in vitro, alters proliferation, differentiation, and cytokine production by lymphocytes and macrophages. Furthermore, cytotoxicity of NK cells is probably suppressed in vivo through their β-adrenergic receptors in response to sympathetic nervous activity (46). The role of catecholamines in immune regulation will be further reviewed elsewhere. In addition to the classical neurotransmitters, acetylcholine and noradrenaline, a wide number of peptides with neurotransmitter activity have been identified in the past few years as being synthesized and released from both autonomic and parasympathetic cholinergic neurons—among them, CGRP and the tachykinins substance P, neurokinin A, neurokinin B, and the newly discovered hemokinin (47,48). The
tachykinins and CGRP also appear to act as mediators of non-adrenergic, non-cholinergic (NANC) excitatory neurotransmission. The excitatory and inhibitory non-adrenergic/non-cholinergic (e-NANC, i-NANC) systems have been extensively studied. The terms excitatory and inhibitory apply to airway smooth muscle, but the neurotransmitters also act on other targets such as blood vessels, glands, and the epithelium, where individual actions may vary. VIP and nitric oxide (NO) co-localize in vagal motor nerves, but they are also found in sympathetic and sensory nerves. In general they have similar actions on target tissues, and their relative importance may vary with the target tissue and the species. Substance P and neurokinin A are also released from sensory nerves, and belong to the family of tachykinins. Finally, it is important to recognize that ACh, substance P, NO, and even other neurotransmitters can be synthesized by non-neuronal cells (49,50). The regulation of synthesis and secretion of these mediators is largely undetermined. Therefore, any description of homeostasis, especially under conditions where immune stimulation or inflammation is present, must by necessity remain incomplete until this knowledge is available.
IV. NEUROPEPTIDES Neuropeptides are produced primarily in the brain, although almost every tissue in the body can produce and exchange neuropeptides. The immunological activity of neuropeptides is mediated through specific receptors. The presence of specific receptors for substance P (51,52), somatostatin (53), CGRP (54), Corticotrophin releasing hormone (CRH) (55), melanocortin peptides (56,57), and VIP and related peptides has been reported in immune cells. The existence of these specific neuropeptide receptors on immune cells represents the framework for neuropeptides functioning as mediators of neuroimmune interactions. Substance P, CGRP, and VIP represent the neuropeptides most involved in neuroimmune modulation. Somatostatin (SOM), CGRP, substance P, and neurokinin A are excitatory NANC neuropeptides. SOM exerts various inhibitory functions on immune responses via specific receptor activation (58). To date, five different receptor types have been cloned and characterized, sst1–5 (59,60). The main sst expressed in cells of the rat immune system were found to be sst3 and sst4 in contrast with the human and murine situations, in which sst2 appears to be the main subtype expressed in the immune system (61). Recently, ten Bokum et al. (61) demonstrated the localization of SOM receptors in inflammatory lesions in rheumatoid
4. Significance of Sensory Neuropeptides and the Immune Response
arthritis. The SSt2 was expressed by endothelial cells of the synovial venules and a subset of synovial macrophages, which are thought to be important effector cells in rheumatoid arthritis. SOM affects the suppression of Ig production in B-cells, including IgE (62), modulation of lymphocyte proliferation, and reduction of eosinophil infiltration in hypereosinophilia. Sensory neurons are characterized by their expression of a certain group of neuropeptides, the tachykinins, and CGRP. For many years, SP, neurokinin A, neurokinin B, and two elongated versions of neurokinin A, neuropeptide γ (NPγ) and neuropeptide K (NPK), were thought to be the only members of the mammalian tachykinin family (63). This family is now expanded by the recent identification of hemokinin (47,48). The only functions so far ascribed to hemokinin are its possible role in lymphopoiesis. In mammals, tachykinins act as neurotransmitters, paracrine or endocrine factors, and neuroimmunomodulators. Important actions include vasodilatation, plasma extravasation, smooth muscle contraction, secretion, neuronal excitation, and processing of sensory information. Substance P, neurokinin A, and neurokinin B are the best described members of the tachykinin family and share a common C-terminal sequence of -Phe-X-GlyLeu-Met-NH2. Two distinct genes called the preprotachykinins A and B encode the tachykinins. Neurokinin B derives from preprotachykinin B, while the others are from preprotachykinin A. The preprotachykinin A has seven exons that can be alternatively spliced to produce α, β, γ, and δ-preprotachykinin A. Recently, an additional tachykinin gene, preprotachykinin C, has been identified that encodes the novel tachykinin-designated hemokinin (64). Neuropeptides exhibit a variety of proinflammatory effects. They are released in response to nociceptive stimulation by pain, mechanical, and chemical irritants to mediate skin responses to infection, injury, and wound healing (65). They are known to activate a variety of immune cells through highaffinity neuropeptide receptors or by direct activation of G-protein–signaling cascades without an intermediary receptor (66,67). Recent reports have also indicated the presence of neurokinin B precursor mRNA in the human and rat placenta (68) and uterus (69,70). These data argue for a broader distribution for these peptides that may not only act as neurotransmitters but also have an endocrine function.
A. Substance P Substance P is an 11 amino acid molecule derived from the preprotachykinin A gene. Substance P is widely distributed in the central, peripheral, and
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enteric nervous systems of many species. Substance P functions in the CNS as a neurotransmitter, and its neurokinin (NK) receptor 1 are localized in distinct areas of the brain important in affecting behavior and the neurochemical response to both psychological and somatic stress. It may also coordinate the response to stress by interacting with the HPA axis and the sympathetic nervous system (71,72). In addition, substance P is involved in sensory and, most notably, nociceptive pathways (73). In the periphery, substance P has been identified in C-type sensory nerve endings and autonomic afferents throughout the body (74). Substance P is present at sites of inflammation, and inflammation can enhance its expression (75–77). Substance P–containing nerves are abundant at mucosal sites and are in ganglia, spinal cord, brain, airways, and skin and around blood vessels (78,79). Some sensory neurons, both intrinsic and extrinsic, produce substance P. Neuronal substance P is stored in vesicles and released from sensory nerves in response to various stimuli such as leukotrienes, prostaglandins, and histamine (79). In addition, substance P can be synthesized and released from immune cells such as macrophages and eosinophils, particularly in disease (80,81). Neutral endopeptidase (NEP) or enkephalinase is a neuropeptide-degrading enzyme expressed on the cell surface of many cell types including neurons, leukocytes, epithelial cells, and smooth muscle cells. NEP has high specificity for substance P and degrades substance P, leaving no biologically active metabolites (82). Blocking NEP delays substance P degradation. NEP transgenic knockout mice develop a markedly increased form of colitis in response to dinitrobenzene sulfonic acid. The administration of substance P receptor antagonists or recombinant NEP prevents the exacerbated inflammation (83). This suggests that a defect in NEP expression with resulting over-expression of substance P worsens the level of inflammation. Guinea pigs are not affected by inhalation of substance P; however, even a small amount of substance P given together with an NEP inhibitor does cause bronchoconstriction in these animals, suggesting that the amount of local NEP may regulate the functional effects of substance P in vivo (84).
B. Hemokinin Recently, the tachykinin family has been extended by the discovery of a third tachykinin gene preprotachykinin-C mRNA encoding a tachykinin called hemokinin-1 (85,86). Like substance P, hemokinin-1 has a high affinity for the NK-1 receptor. An important observation that has been made is the fact that constitutive expression of hemokinin mRNA occurs prefer-
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entially in leukocytes and lymphoid tissue, not in the nervous system (87). Hemokinin-1 has been proposed as a regulator of B- and T-cell lymphopoiesis. PPT-C mRNA was expressed in B-cells from bone marrow, where it promoted the survival and proliferation of Bcell precursors. These observations suggest that hemokinin is an autocrine factor, playing a role in B-cell development. However, NK-1 knockout mice are not lymphopenic, which suggests that hemokinin is not essential for B-cell growth (88). Nelson et al. (87) demonstrated the expression of preprotachykinin-C mRNA by macrophages, dendritic cells, and in a microglial cell line. This implies that microglial cells, described as resident macrophages in the brain, are a potential source of hemokinin-1. There is the possibility that hemokinin-1 could play a significant role in communication between immune cells in the CNS (89), and between immune cells and neuronal cells expressing the NK-1 receptor. Studies have demonstrated the importance of the NK-1 receptor during bacterial (90), viral (91), and parasitic infections (92). The demonstration of preprotachykinin-C mRNA expression by macrophages and dendritic cells also has implications for tachykininmediated host responses against microbial pathogens. The fact that preprotachykinin-C mRNA is preferentially expressed in leukocytes suggests that hemokinin-1 may contribute to the development and/ or activation of the immune response.
C. Capsaicin Capsaicin is the spicy ingredient in red pepper fruits of the genus capsicum, including paprika, jalapeno, and cayenne (93). Capsaicin accomplishes its effects by evoking sharp burning pain sensation when it comes into contact with mucous membranes. Jancso and Porszasz (94) were the first to show that capsaicin selectively and specifically excites a subpopulation of primary sensory fibers. Later, Jancso et al.’s (95) finding that capsaicin injection into neonatal rats results in the loss of capsaicin-sensitive primary sensory neurons provided an excellent tool for studying this subpopulation of sensory neurons. The capsaicin receptor TRPV1 is a nociceptorspecific ion channel that serves as the molecular target of capsaicin (96). As the capsaicin-sensitive receptor also responds to other related molecules with vanilloid moiety, the receptor was named the vanilloid receptor (VR1 or TRPV1) (97). The structure and amino acid sequence of TRPV1 are similar to those of the transient receptor potential (TRP) family of cation channels (98). In addition to TRPV1, three more TRP receptors have been discovered (TRPV2, TRPV3, and TRPV4). There
is not much known so far on the role of these receptors in neurogenic inflammation. In this review we will therefore focus only on TRPV1. TRPV1 can be activated not only by capsaicin but also by noxious heat or protons, all of which are known to cause pain in vivo. TRPV1, in addition to a subpopulation of primary sensory neurons, is expressed by various neurons and non-neuronal cells. The great majority of TRPV1-expressing cells belong to nociceptive cells expressing substance P and CGRP. Both somatic and visceral primary afferents express TRPV1, and the molecule is expressed by peripheral terminals and in many areas of the CNS (99,100). Furthermore, TRPV1 protein and mRNA expression in cultured rat gastric epithelial cell and epithelial cells in the urinary bladder have also been shown to express TRPV1 both at mRNA and protein level (101). Alterations in the sensitivity of VR1 to agonists or its level of expression would be expected to markedly affect the sensitivity of sensory neurons with important implications for inflammatory diseases such as asthma and IBD. Most of the neurogenic effects in the airways, gut, or urinary tract are mediated by a direct action on sensory nerve terminals via the stimulation of VR1 (102). Thus, antagonists of VR1 may be useful for the treatment of a wide range of diseases that affect the sensory nervous system. TRPV1 appears to be upregulated during inflammatory conditions. Nerve growth factor (NGF), bradykinin, and proteases can upregulate the function of VR1 (103). For instance, tryptase, the major protease released from mast cells, excites VR1-positive sensory neurons (104). Factors that downregulate TRPV1 expression include vanilloid treatment and NGF deprivation (105). These findings imply an important role for TRPV1 expression in the development of neuropathic pain and hyperalgesia. Disease-related changes in TRPV1 expression have already been described in IBD and IBS although the mechanisms that regulate TRPV1 gene expression under pathological conditions are unknown.
D. Neurokinin Receptors Tachykinins can bind with different affinities to their potential neurokinin receptors. Three distinct subtypes of mammalian receptors have been identified and denoted as NK-1, NK-2, and NK-3. The NK-1 receptor has the highest affinity for substance P and hemokinin. The NK-1 and NK-2 receptors bind with the highest affinity to neurokinin A and B, respectively (106–108). Tachykinin receptors belong to the Gprotein–coupled receptor superfamily with the structural characteristics of seven transmembrane helices.
4. Significance of Sensory Neuropeptides and the Immune Response
All three neurokinin receptors share a high degree of homology (109,110). Substance P is believed to act as one of the most significant neurotransmitters (111). The NK-1 receptor is widely distributed in both central and peripheral nervous systems and is localized on smooth muscle cells, submucosal glands, blood vessels, and inflammatory cells (108,112). Tachykinin NK-1 receptors have been proposed to be involved in many physiological and pathological conditions such as noxious stimuli, neurogenic inflammation, intestinal motility, vasodilatation, smooth muscle contraction, as well as immune response (77,113). NK-2 receptors have been detected in the central nervous system but are more widely distributed in the periphery such as respiratory, gastrointestinal, and urinary tract. Activation of this receptor subtype results in facilitation of transmitter release, neuronal excitation, and stimulation of certain immune cells (113). The NK-2 receptor is also found on smooth muscle. Animal studies have shown that NK-2 receptors are involved in bronchoconstriction (65,113). However, the exact function of this receptor in the central nervous system has yet to be delineated. Compared with the NK-1 and NK-2 receptors, much less is known about the biological function of the NK-3 receptor. The tachykinin NK-3 receptors are predominantly present in the central and peripheral nervous system (114,115) and have been detected only in certain peripheral tissues, such as the human uterus and skeletal muscle, brain, and certain enteric neurons from the gut of different species (111,116,117). Studies using selective agonists or antagonists point to a central role of the tachykinin NK-3 receptor, which might be involved in depression and anxiety (118). On the contrary, the role of this tachykinin receptor type at the peripheral level remains elusive. Cells of the immune system have also shown to express neurokinin receptors, especially the NK-1 receptor. Moreover, macrophages (119,120), dendritic cells (121), T lymphocytes (51,122), and B lymphocytes (123,124) all have the ability to express NK-1 receptors.
E. Inhibitory NANC Neuropeptides The main transmitters that mediate NANC inhibitory neural transmission are VIP and NO. VIP is found in the CNS and in peripheral nerves, particularly in peptidergic nerves (125). Peptidergic nerves are abundant in mucosal tissues such as the lungs, the upper respiratory and nasal mucosa, and the small and large intestine (126,127). Furthermore, VIP can be found together with substance P in the enteric neurons of the myenteric plexus and submucosal plexus, the lym-
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phoid tissue including the thymus, spleen, and Peyer’s patches (128). The general consensus is that VIP is an important inhibitory NANC neurotransmitter that relaxes airway smooth muscle, as does NO. It can be broken down by local enzymes such as neutral endopeptidase (NEP), and mast cell tryptase and chymase. Three receptors for VIP have been identified belonging to the family of G-protein–coupled, seventransmembrane receptors. Mouse T lymphocytes have been shown to express VIP receptors (129) both on CD4+ and CD8+ T-cells (130). Lymphocytes have been shown to produce VIP upon their activation (131). VIP and its receptors will be discussed in more detail elsewhere. Nitric oxide (NO) is also present in airway nerves and relaxes airway smooth muscle. NO is a signaling molecule with important regulatory functions such as regulation of blood pressure, neurotransmission, and host and immune defense (132). NO, co-released with CGRP, seems to also play a role in the UVB-induced immunosuppression through a yet undiscovered mechanism of action (133). In the respiratory tract, NO is formed and released by various sources including endothelial and epithelial cells, nerves, airway smooth muscle, and inflammatory cells. NO is found in vascular endothelium, in the respiratory epithelium of guinea pigs (134) and asthmatic (135) and possibly healthy humans, in sympathetic motor nerves to the lungs, and even in epithelial nerves, emphasizing the importance of NO as a mucosal mediator (134). The mechanism of release of NO from nerves is unclear. The evidence points to NO being an important or the main inhibitory NANC transmitter, at least in humans. In other species it is present and may play a cooperative role with VIP. Most VIP-containing nerves are also cholinergic, containing choline acetyltransferase, and VIP has also been shown to co-localize with SP or CGRP in mucosal nerves, including probably the epithelium. NO is present in cholinergic motor nerves together with VIP. PACAP belongs to the VIP family of peptides. The two neuropeptides are structurally related and are released within the lymphoid organs following antigenic stimulation, and modulate the function of inflammatory cells through specific receptors (31). So far, three different receptors have been recognized and defined as PAC1–R, VPAC1–R, and VPAC2–R. PACAP, but not VIP, binds to PAC1–R, whereas PACAP and VIP both bind to VPAC1–R and VPAC2–R (136). VIP/ PACAP receptors are expressed in various immune cell populations. VPAC1 seems to be constitutively expressed in both unstimulated and stimulated lymphocytes and macrophages (137). VPAC2, on the other hand, is expressed in lymphocytes and macrophages
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only following stimulation (130, 138). VIP and PACAP are co-expressed in single- and double-positive (CD4+CD8+) thymocytes and in T and B lymphocytes from spleen and lymph nodes (139). They promote Th2-type and inhibit Th1-type responses in vivo and in vitro. Macrophages treated in vitro with PACAP gain the ability to induce Th2-type cytokines (IL-4 and IL-5) and inhibit Th1-type cytokines (IFN-γ, IL-2) in antigenprimed CD4 T-cells. Furthermore, VIP and PACAP inhibit TNF, IL-1β, IL-6, and NO production by lipopolysaccharide (LPS)-activated microglia (140).
F. Calcitonin Gene-related Peptide CGRP is a 37 amino acid neuropeptide. CGRP is synthesized in the body of sensory nerves and transported to the nerve endings, where it is released by voltage-dependent calcium uptake. Sensory nerve fibers are stimulated by noxious stimuli and certain inflammatory mediators like IL-1 and PGE2 (141). CGRP is present in all body surfaces, around all blood vessels and at all internal and external surfaces, where it can influence inflammatory and immune responses. Release of CGRP is often accompanied by release of substance P (142), but CGRP can be found by itself in some motor and enteric neurons (142). There are two isoforms of CGRP, α and β, derived from two distinct genes, one of which also encodes the hormone calcitonin. The CGRP receptors are seventransmembrane domains, G-protein–associated receptors. CGRP receptors have been classified in two major classes, namely the CGRP1 and CGRP2 subtypes. CGRP receptors were identified several years ago in lymphoid tissue. Receptors have been identified on mature T- and B-cells and macrophages, and on developing B-cells in the bone marrow (143–145). CGRP1 is found throughout the body including the nervous and endocrine systems (146–148). CGRP inhibits T-cell proliferation by inhibiting IL-2 production. In macrophages, it inhibits antigen presentation and other macrophage functions including phagocytosis (149). It also stimulates production of a number of cytokines such as IL-6, IL-10, and TNF. In vivo injection of CGRP was shown to inhibit the onset of delayed type hypersensitivity reactions (150) supporting the role of CGRP in systemic regulation of immune activation. Indeed, Hosoi et al. (151) previously showed conclusively that CGRP could inhibit Langerhans cell (LC) activity and the initiation of antigen-induced immune responses. Furthermore, it was shown that intracutaneously injected CGRP participates in the pathogenesis of failed contact hypersensitivity induction after acute, low-dose ultraviolet B radiation (152). These authors showed that CGRP
has the capacity to promote cutaneous tolerance and that the mechanism contributes to the tolerance promoted by acute, low-dose ultraviolet B radiation. Endogenous CGRP may generally modulate immune function, presumably in part, through an inhibitory effect on LC function. This indicates that CGRP is capable of inhibiting both the induction and expression of fundamental cellular immune functions and suggests an interaction between the nervous system and immunological function. These observations imply the likelihood that the CNS may be capable of suppressing the initiation of immune responses, and also be effective in their modulation. Overall, there is substantial experimental evidence demonstrating that CGRP can influence the function and development of inflammatory and immune cells in local microenvironments by specific receptor-mediated mechanisms.
G. Non-neuronal Neurotransmitters Although classically neuropeptides are released from autonomic and sensory nerves, there is increasing evidence that they may also be synthesized and released from inflammatory cells, particularly in disease. Over the last two decades there have been several reports suggesting that lymphocytes produce many different neuropeptides. Substance P has been shown to be a product of human, rat, and mouse leukocytes that can be released at sites of inflammation (50,153,154). Human and mouse eosinophils produce and secrete substance P (153,155), and it is known that T-cells in granulomata in the spleen in murine schistosomiasis express preprotachykinin A mRNA. Furthermore, LPS induces preprotachykinin A mRNA and substance P production from rat peritoneal macrophages (156) as well as rat and human alveolar macrophages (80). Collectively, these studies clearly demonstrate that stimulated leukocytes can express PPT mRNA and the products of PPT genes, although the concentrations are significantly less than those reported for neuronally derived tachykinins. This alternative source of immune cell-derived neuropeptides could represent an additional source of tachykinins in inflamed tissues, providing a non-neurogenic tachykininergic contribution to the local inflammatory process (157). It is so far not clear why leukocytes might express tachykinins. It is likely that the stimuli that induce neuronal production and secretion of tachykinins will be different from the stimuli that would evoke substance P secretion by leukocytes. Furthermore, it is possible that leukocyte-derived neuropeptide production occurs in areas of limited innervation by sensory
4. Significance of Sensory Neuropeptides and the Immune Response
neurons and thus may locally compensate for the relative paucity of the modulatory response. The neurotransmitter Ach has been found in epithelial cells, endothelial cells, muscle and immune cells such as mononuclear cells, granulocytes, alveolar macrophages, and mast cells (49,158,159). The expression of ACh is accompanied by the presence of cholinesterase and nicotinic and muscarinic receptors (49,158,160). This suggests that non-neuronal Ach acts as a local cellular signaling molecule rather than a neurotransmitter. Thus, non-neuronal Ach has to be discriminated from neuronal ACh especially since there are apparent functional differences between the two.
V. THE ENTERIC NERVOUS SYSTEM The enteric nervous system is an independent, though connected network of nerve fibers that innervate the viscera (gastrointestinal tract, pancreas, gall bladder). The enteric nervous system is essential for regulating motility and secretion. It consists of ganglionated plexuses embedded in the wall of the intestine divided into submucosal ganglia and myenteric ganglia distributed between the longitudinal and circular muscles. Neurons within submucosal ganglia can be classified as intrinsic primary afferent neurons (IPANs), interneurons, secretomotor and vasodilator neurons (161,162). Myenteric ganglia also contain motor neurons, innervating the longitudinal and circular muscle layers, and secretomotor neurons, which project to the mucosa (163). With these neural components the enteric nervous system (ENS) can elicit neural reflexes that control and coordinate motility, secretion, and blood flow. The nervous system of the gut is capable of integrative functions independent of the central nervous system. The human GI system, deprived of CNS innervation, is capable of coordinated digestion, motility, secretion, and absorption. The neurons that control bowel functions are located entirely within the gut, and for this reason the ENS is sometimes called the “little brain” (164). Substance P is found predominantly in submucosal IPANs. The presence of NK-1 receptors on isolated colonocytes suggests that appropriate elements are present for axon reflex activation of intestinal epithelial cells (165). MacNaughton et al. (166) characterized tachykinin-evoked secretomotor responses in in vitro submucosal and mucosal-submucosal preparations of the guinea pig ileum using combined intracellular and Ussing chamber recording techniques. Their findings suggest that tachykinin-evoked secretion in guinea pig ileum is mediated by NK-1 and NK-3 receptors on submucosal secretomotor neurons and that capsaicin-
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sensitive nerves release tachykinin(s) that activate the NK-1 receptors.
VI. THE CHOLINERGIC ANTI-INFLAMMATORY PATHWAY Afferent signals to the brain can generate a reflex causing an anti-inflammatory response, which is partly mediated by the efferent branch of the vagus nerve (167,168). This cholinergic anti-inflammatory pathway is mediated primarily by nicotinic ACh receptors expressed upon tissue macrophages and blood monocytes. ACh can interact specifically with macrophage alpha7 subunits of nicotinic ACh receptors, leading to cellular deactivation and inhibition of cytokine release (169). Endotoxin (or LPS) is a product of all gram-negative bacteria, which can cause shock (hypotension) and, ultimately, death. This occurs as a result of LPS activation of macrophages to release TNF, which is a principal mediator of acute LPS-induced shock (169,170). Wang et al. (169) showed the ability of ACh to suppress macrophage TNF production in vitro. Stimulation of efferent vagus nerve activity inhibited the systemic inflammatory response to endotoxin. These findings were the first to demonstrate a previously unrecognized, parasympathetic anti-inflammatory pathway by which the CNS modulates systemic inflammatory responses. The Tracey group termed this the “cholinergic anti-inflammatory pathway.”
VII. NEUROTROPHINS Classical mediators of inflammation are not alone in their ability to influence the interaction between cells of the immune system and nerves. Based on their expression profile, neurotrophins are good candidates for mediating immune-nerve cell interactions. NGF was the first discovered member of the family of neurotrophins in the 1950s, now including brainderived neurotrophic factor (BDNF) and neurotrophins 3/5. NGF is the best characterized neurotrophic protein and is required for survival and differentiation of neuronal cell types in both the peripheral and central nervous system. Functional properties of neurons are also affected by NGF. For instance, NGF was shown to upregulate neuropeptide production in sensory neurons and to contribute to inflammatory hypersensitivity (171). In addition, in cultured nodose ganglion neurons, substance P production is regulated by NGF (172). NGF and BDNF are some of the most effective
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mediators involved in inflammatory hyperalgesia (171). The biological effects of neurotrophins are mediated by binding either to the specific high affinity receptors trkA (for NGF), trkB (for BDNF), and trkC (for NT-3) or the low affinity receptor pan-neurotrophin receptor p75 (NTR). Neurotrophin receptors are widely expressed in the peripheral and the CNS as well as on cells of the immune system (169,173). NGF receptors on mast cells act as autoreceptors, regulating mast cell NGF synthesis and release, while at the same time being sensitive to NGF from the environment. Many immune cells express the high affinity NGF receptor. This allows NGF to promote the release of inflammatory mediators. Several of these mediators such as IL-1, IL-4, IL-5, TNF, and IFN can, in turn, induce the release of NGF (169,174). Therefore, NGF seems to be a mediator with functions on both immune cells and nerve cells and is likely an important factor integrating communication between the nervous and immune systems (175). There is increasing evidence that NGF acts on cells of the immune system, apart from its neurotrophic effects. NGF promotes differentiation, activation, and cytokine production of mast cells and macrophages (176,177), and activates eosinophils (178). Furthermore, NGF is a chemoattractant, thereby causing an increase in the number of mast cells as well as their degranulation (179–181). Injection of NGF causes mast cell proliferation in part by mast cell degranulation (182). NGF also influences activity of basophils, eosinophils, neurophils, macrophages, and T-cells. Both murine and recombinant human NGF enhance histamine release and strongly modulate the formation of lipid mediators by basophils in response to various stimuli (183). This priming effect of NGF on basophils occurs rapidly, is dose-dependent, and requires low concentrations of NGF. In addition, BDNF can trigger histamine release from rat brain mast cells, suggesting that these mast cells contain the TrkA and TrkB receptors (184). The mammalian skin expresses a variety of neurotrophic growth factors that are essential for growth, proliferation, and maintenance of nerves such as NGF. Cutaneous neurotrophins are expressed by sensory and sympathetic neurons and non-neuronal cells, thereby regulating nociception, mechanoreception, epidermal homeostasis, inflammation, and hair growth (185,186). During inflammation, NGF is markedly upregulated in nerves associated with the inflamed area (171). During the inflammatory process, NGF is also produced by a wide range of immune cells. Mast cells (187), T-cells (188) and B-cells (189), eosinophils, lymphocytes (190), and epithelial cells (191) can synthesize
NGF. In vitro, allergen stimulation of mononuclear cells from sensitized mice resulted in enhanced NGF synthesis (192). In addition, NGF production was enhanced by antigen stimulation in murine and human Th2 cells (193,194). BDNF synthesis has been detected in human T-cells, B-cells, macrophages, and mast cells (195,196). There is also evidence for enhanced neurotrophin production in inflammation (192). Activated T-cells and macrophages produce BDNF during allergic inflammation (192). NGF can have pro-inflammatory as well as antiinflammatory effects depending on the situation and concentration of the compound. In mice, Braun et al. have recently shown that nasal treatment of mice with NGF induced airway hyperresponsiveness measured by electrical field stimulation (197). Another study by Braun et al. showed that nasal treatment of mice with anti-NGF prevented the development of airway hyperresponsiveness (192). On the other hand, the expression of NGF is increased after brain injury. There is evidence indicating that the increased production of NGF in the central nervous system (CNS) during brain diseases such as multiple sclerosis can suppress inflammation by switching the immune response to an anti-inflammatory, suppressive mechanism (198). In a compelling study, the injection of CD4+ lymphocytes transfected with the NGF gene either before or after the induction of allergic encephalomyelitis inhibited the onset of demyelination (199). This powerful inhibition of an auto-immune process showed that local expression of NGF prevented the migration of inflammatory cells across the vascular endothelium. Furthermore, the functional role of NGF and NT-3 was studied in a model for experimental colitis. The pretreatment with anti-NGF or anti-NT-3 caused a significant increase in the severity of the experimental inflammation (200). These findings suggest a regulatory role for NGF and NT-3 in experimental inflammation of the gut. The fact that NGF may under different circumstances be either pro-inflammatory or antiinflammatory is an important example of the complexity of interactions between neuroactive molecules and the immune and inflammatory systems.
VIII. NEUROPEPTIDE COMMUNICATION: THE DIFFERENT IMMUNE CELLS A. T and B Lymphocytes Peptidergic nerve fibers are in close approximation to lymphocytes in many lymphoid tissues (201). Indeed, mononuclear cells are modified by neuropep-
4. Significance of Sensory Neuropeptides and the Immune Response
tides. The presence of neuropeptide receptors on lymphocyte surfaces supports this interaction. Substance P may enhance the mitogen-induced proliferation of human (202) and murine lymphocytes and IgA synthesis by cells from the spleen, Peyer’s patches, and mesenteric lymph nodes (203). VIP increased the IgA response in mesenteric lymph nodes and spleens, but inhibited IgA synthesis in lymphocytes from Peyer’s patches. Furthermore, substance P is chemotactic for human peripheral blood T- and B-cells (204). It is also reported that substance P is a growth and differentiation factor for B-cells (192) and it stimulates cytokine production, chemotaxis (78), and a Th1/Th2 phenotype switch in T-cells (205). Murine and human T-cells can express NK-1 receptors, but their expression on B-cells remains controversial. Some of the biological activity of substance P occurs at only high concentration, suggesting pathways independent of NK-1 receptors, whereas some activity could be blocked by NK-1 receptor antagonists. Clear evidence for the importance of the NK-1 receptor on T-cells comes from studies by Blum et al. (206) using a murine model for schistosomiasis. In NK-1 receptor knockout mice, they observed significant reductions in the size of granulomas in comparison with disease in wild-type animals. The limited IFN-γ production by infected knockout mice suggests that T-cells may be an important target for substance P during schistosomiasis. Substance P and VIP have been shown to affect the ability of mature B-cells to secrete immunoglobulins. Braun et al. (192) showed that tachykinins could augment Ig secretion in cytokine-stimulated cultures. NK-1 receptors have been demonstrated on B-cells, and their biological impact was evidenced by the ability of substance P to enhance Ig synthesis in the presence of a second signal. The addition of LPS to varying concentrations of substance P resulted in optimal IgM production at subnanomolar substance P concentrations, whereas elevated concentrations (100 nM) were not effective (207). These events were NK-1 receptor mediated. VIP stimulation of lymphocytes, like substance P, requires a co-stimulatory signal (208). Substance P is found in the highest concentration in the GI tract (209) and in the lungs (210). In Peyer’s patches, evidence suggests that substance P–containing nerve fibers infiltrate T-cell zones and associate with macrophages. For example, in patients with ulcerative colitis, an increased level of T lymphocytes is found together with an increase in substance P– containing neurons. In human inflammatory bowel disease, increased substance P, as well as NK-1 receptor mRNA, in the gut has been shown, which associates with mucosal T-cells (77). Various studies have
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reported increased expression of substance P derived from neurons following inflammation. Several animal models of inflammation and human disease provide evidence that the NK-1 receptor, located on leukocytes, and its ligand, substance P, influence immune responses. For instance, trichinella spiralis, a parasite that induces a Th2-immune response in rat intestine, induces a T-cell–dependent increase in substance P in the muscle-mesenteric plexus, and blocking of the NK-1 receptor reduces the intestinal inflammation (211). In murine schistosoma inflammation, it has been shown that NK-1 and substance P play an important part in the regulatory response. Substance P regulates T-cell IFN-γ production through interaction with the NK-1 receptors expressed on these cells (122). Another recently discovered molecule, hemokinin, belonging to the family of tachykinins, is a selective NK-1 agonist (212). High concentrations of this neuropeptide were shown to stimulate the proliferation of B lymphocytes (85). It has been suggested that hemokinin is an autocrine factor that contributes to the survival of B-cell precursors in the bone marrow (85).
B. Dendritic Cells DCs, the major antigen-presenting cells, play an important role in the immune response against infections. Their function is crucial in both the early innate responses and subsequent adaptive response (213). In the course of inflammation in peripheral tissue, various cytokines and chemokines are released by resident DCs. DCs are reported to contain substance P or the preprotachykinin mRNA which encodes for substance P and neurokinin A (50). As well, Nelson et al. (87) have clearly shown constitutive expression of PPT-C mRNA by cultured DCs. Myeloid DCs express the highest levels of the message encoding hemokinin-1. Similarly, NK-1 or NK-1 mRNA has been detected in DCs (50) as well as VPAC-1 and VPAC-2 receptor expression (149). CGRP, VIP, and somatostatin are being released from DCs (214). Therefore, neuropeptides should be included in any examination of the immune regulation of T-cell function by DCs. Since DCs are the most efficient antigen-presenting cells that stimulate naive T-cells, thus promoting adaptive immunity, it is not surprising that interactions between neuropeptides and dendritic cells take place. DCs are found in peripheral and CNS (215). Using neuropeptide and DC immunostaining, anatomical and functional connections between the two have been shown (151). In the liver, contacts between nerve fiber staining for substance P, VIP, and CGRP were observed (216). In the lung, being a rich source of neuropeptides
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significantly increasing upon inflammation, DCs are located in close proximity to unmyelinated nerve fibers (217). Functionally, pulmonary DCs bound to substance P and displayed increased motility in vitro in response to graded concentrations of substance P. To examine the role of neural influences on the pulmonary immune response to inhaled antigen, rats were pretreated with capsaicin, and challenged with antigen. Neonatal capsaicin treatment inhibited the accumulation of DCs around small pulmonary vessels (217). Peripheral neuropeptides can directly attract immature DCs, and at the same time they may capture mature DCs at sites of neurogenic inflammation. Low neuropeptide concentrations can improve the motility of DCs to the source of the neuropeptides, primarily sensory nerve fibers. Cells that reach these fibers may undergo functional and phenotypical maturation, which will keep them arrested there. This opposite behavior is probably due to changes in signal transduction pathways of neuropeptide receptors in immature and mature DCs (218). There is no difference in neuropeptide receptor expression on immature and mature DCs (219), but differences have been found for several chemokines (220). Thus, the effects are mediated by specific receptors, which switch signal transduction pathways in DCs of distinct maturation stages. These findings provide evidence for a connection between adaptive immunity and the nervous system, as do the observations of Hosoi et al. (151) who showed the importance of CGRP as a potent downregulator of DC function.
C. Macrophages Macrophages have various important functions involving host defense, immunomodulation, and tissue repair. They produce many types of mediators including interleukins, chemokines, and nitric oxide. There is growing evidence that macrophages can produce substance P and express NK-1 receptors (119,221). Substance P can stimulate human macrophages to release TNF, IL-6, and IL-1 (222,223). Substance P inhibits IFN-γ and LPS-induced TGF-β production (224). In addition, murine macrophages produce somatostatin in response to LPS, IL-10, IFN-γ, and TNF. Other reports suggest that substance P works as a priming factor rather than a direct stimulator. Substance P should sensitize macrophages, making them more responsive to LPS (225,226). Macrophages from stressed mice released IL-6 upon exposure to LPS in vitro (227). Substance P was responsible for the activation of the macrophages and primed them for LPSinduced IL-6 release. Macrophages, stimulated by substance P, produce the inflammatory mediators
PGE2, thromboxane B2, and superoxide ions (228,229). Macrophages also have receptors for CRF, and CRF can induce the production of IL-1, IL-6, and TNF (230). The innate immune response can be influenced by neuropeptides, especially since NK-1 receptors have been found on macrophages (119,222) and dendritic cells (121). In vivo studies have demonstrated a role for the NK-1 receptor in the initiation on the host response against bacterial and viral pathogens. Upregulation of NK-1 receptor expression by salmonella may significantly increase the substance P–mediated macrophage response, directly killing the bacteria. In addition, substance P can enhance IL-1, IL-6, and TNF secretion by macrophages (222). Mice deficient in NK-1 receptor expression have also been used to investigate the importance of this neuropeptide receptor in the host response against pathogens. For instance, the significance of the NK-1 receptor during schistosomiasis has been discussed earlier (206).
D. Neutrophils and Eosinophils There are some reports on direct effects of substance P on neutrophils and eosinophils, but the concentrations of substance P are usually not of physiological relevance. Most of the effects require high concentrations of neuropeptides, whereas at low concentrations, neuropeptides prime the response to other stimuli that otherwise would be ineffective (231). CGRP and substance P have a degranulating effect on eosinophils, and substance P, CGRP, and VIP were found to stimulate eosinophil migration (232). In an in vivo study with allergic rhinitis patients, it was shown that substance P enhanced the recruitment of eosinophils after repeated allergen challenge. Furthermore, substance P can induce IL-8 production from human peripheral blood neutrophils (233) and stimulate guinea pig eosinophil peroxidase secretion (234). CGRP is capable of causing eosinophilia in the lung in vivo and may contribute to airway inflammation in patients with asthma (235). A study on eosinophil chemotaxis showed that neuropeptides alone did not have an effect. However, when eosinophils were pre-treated with peptides, chemotactic response to platelet-activating factor (PAF) or leukotriene B4 was significantly enhanced in allergic patients (236). Potentiating effect of substance P and CGRP on PAF-induced eosinophil chemotaxis in allergic subjects was significantly attenuated by a substance P antagonist and by a human CGRP receptor antagonist, respectively. These results suggest that neuropeptides may play a significant role in eosinophil infiltration by priming cells in allergic inflammation.
4. Significance of Sensory Neuropeptides and the Immune Response
Aside from the direct effects, the indirect effects of substance P are more common and better described. Neutrophils migrate into tissue due to neurogenic inflammation resulting from the interaction of substance P with the NK-1 receptor on endothelial cells. In addition, substance P can induce the production of neutrophil chemotactic factor from bovine bronchial epithelial cells (237). Moreover, it stimulates adhesion between cells via induction of adhesion molecules (238).
E. Mast Cells 1. Mast Cell-Nerve Communication Histological studies reveal an intimate association between mast cells and neurons in both the peripheral and central nervous system (2,175). A close anatomical relationship between mast cells and substance P and CGRP-containing sensory nerve endings has been reported in various tissues including skin (239,240), intestine (1), dura mater (241,242), and airway mucosa (16,240). Other than an anatomical link, mast cells also form a functional link between the immune and nervous systems, and mast cells appear to act as bidirectional carriers of information. Neuronal mechanisms are involved in mast cell activation, and mast cells act as principal transducers of information between peripheral nerves and local inflammatory events (243). In an in vitro model of co-culture of mast cells and superior cervical ganglion neurites, selective activation of neurites by scorpion venom has been shown to cause increased calcium uptake in associated mast cells through substance P release and interaction with NK-1 receptors (76), with subsequent focused membrane ruffling at the points of contact (244). Peripheral nerves are highly populated with mast cells, and manipulation of these peripheral nerves causes changes in mast cell densities (245). Mast cells and nerves in many tissues are in constant contact with each other and share a number of activating signals, for some of which both cells express receptors (such as vanilloids) (104). Additionally, both mast cells and nerves respond to stimulation by secretion of preformed mediators, many of which are produced by both cells (NGF, neuropeptides, and endothelin-1). Moreover, a large proportion of primary spinal afferent neurons which contain CGRP and substance P express the proteinase-activated receptor 2 (PAR-2). Proteases such as tryptase from degranulated mast cells have recently been shown to cleave PAR-2 on primary spinal afferent neurons, which causes release of substance P, activation of the NK-1 receptor and amplification of inflammation, and thermal and
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mechanical hyperalgesia (246). This mechanism of protease-induced neurogenic inflammation may contribute to the pro-inflammatory effects of mast cells in human disease. In addition, PAR-2 is also highly expressed in keratinocytes and endothelial cells of inflamed skin (247). Tryptase may in turn activate PAR-2 on keratinocytes and endothelial cells during inflammation. Many studies have shown that mast cell–derived mediators such as histamine, serotonin, and cytokines modulate NANC neurotransmission (248,249). NANC nerve endings express receptors for histamine (H1 and H3) and serotonin (5-HT2a) (250,251), and histamine H1 receptor expression at least is upregulated on primary NANC nerves in inflammation (252). Mast cell mediators like TNF can sensitize afferent C fibers by lowering their threshold (249,253) but can also cause direct release of substance P, neurokinin A, and CGRP from unmyelinated fibers (248). 2. Mast Cell Stimulation In addition to IgE and antigen, cytokines, hormones, and neuropeptides can trigger mast cell secretion (254,255). The latter include somatostatin (256), neurotensin (257), PACAP (258), CGRP (259), and substance P (260). Stem cell factor (SCF) and NGF can promote mast cell growth and can also trigger mast cell degranulation (261). SCF has also been reported to induce mast cells to become responsive to PACAP (262). SCF and NGF are also secreted by mast cells, while substance P has been localized in human skin mast cells, indicating autocrine actions (263,264). Keratinocytes, Langerhans cells, fibroblasts, mast cells, and endothelial cells express functional neurokinin receptors, while G proteins on mast cells can in addition be activated by substance P in a nonreceptormediated fashion (265). Stimulation of G-proteins will eventually lead to mast cell mediator production and release. It has been shown that functional NK-1 receptors are expressed on murine mast cells in vitro in the presence of IL-4 and SCF (266). Very recently, Bischoff et al. examined the expression of tachykinin receptors on human mast cells and found that human mast cells derived from intestinal mucosa do not constitutively express NK-1, NK-2, or NK-3 receptors (267). However, when stimulated by IgE receptor crosslinking, these mast cells started to express NK-1, but not NK-2 or NK-3 receptors, suggesting that specific tissue conditions such as allergic inflammation may lead to mast cell expression of NK-1 receptors. Nerve-mast cell interaction is involved in both homeostatic and pathologic regulations. Because the synaptic cell adhesion molecule (SynCAM), alterna-
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tively named spermatogenic Ig superfamily (SgIGSF), is expressed on both nerves and mast cells and because it binds homophilically, this molecule may be the best candidate to sustain this association (268). In vitro, mast cells with SgIGSF/SynCAM attached to neurites; this was inhibited dose-dependently by blocking Ab to SgIGSF/SynCAM. Mast cells without SgIGSF/ SynCAM were defective in attachment to neurites, and transfection with SgIGSF/SynCAM normalized this, showing that SgIGSF/SynCAM on mast cells predominantly mediated attachment and also promoted communication with associated nerves. The activity of mast cells is clearly more complicated than being an all-or-nothing condition. Janiszewski et al. (393) reported in a patch clamp study that mast cells do not respond to very low concentrations of substance P (in the picomolar range), but that activation and delayed degranulation occurred after a second exposure. Therefore, mast cells can be primed when exposed to physiologically relevant low concentrations of substance P, and lower their thresholds to subsequent activation. It has been proposed that this initial stimulation is the functional correlate of priming. If mast cells are indeed primed by exposure to substance P, it would enable a subthreshold stimulus to initiate mast cell activation. Furthermore, secretion can occur without evidence of degranulation, and even molecules stored within the same granules can be released and secreted in a discriminatory pattern (269). Mast cells have been increasingly implicated in inflammatory processes where explosive degranulation is not commonly observed. Ultrastructurally, a study by Ratliff et al. (270) showed mast cells in close proximity to unmyelinated nerve fibers. These mast cells contained granules showing ultrastructural features of activation or piecemeal degranulation, which have been associated with differential secretion. Marshall et al. (179) showed that NGF at doses as low as 10 ng/ml will induce IL-6 production but inhibit TNF release from rat peritoneal mast cells, indicating that even a single molecular signal can give rise to a balanced proand anti-inflammatory outcome in a single cell type. These data support the potential for mast cell regulation by the central nervous system and suggest that modulation of mast cells can occur in vivo without degranulation.
IX. NERVES IN THE INFLAMMATORY PROCESS Nervous innervation of an organ is a requirement for establishing certain inflammatory reactions (271). Substance P and the related tachykinin peptides are
involved in inflammatory processes and in the transmission of sensory nociceptive information. Organs with a high density of neuropeptide receptors, such as the intestines and the lung, have been proposed to be more susceptible to inflammation (272). For instance, infection of rats with the nematode Nippostrongylus brasiliensis results in mast cell hyperplasia and neuroplasticity of intestinal mucosal nerves during inflammation. This was shown to include early neurodegenerative and late regenerative phases that appeared to correlate with mast cell densities (1). During inflammation, hyperalgesic mediators are produced by invading immune cells or by resident cells (cytokines, chemokines, NGF, leukotrienes, prostaglandins, ATP). It is less well known that analgesic mediators are also produced in inflamed tissue, which counteract pain. These include opioid peptides, somatostatin, and anti-inflammatory cytokines (273). While these mediators contribute to the body’s ability to counteract infection and the destruction of tissue integrity, they also elicit pain by activation of specialized receptors localized on primary afferent neurons “nociceptors.” Opioid peptides are produced in peripheral inflamed tissue by immune cells and can be released upon certain types of stimulation. They bind to peripheral opioid receptors and thereby elicit potent endogenous analgesia (274). Peripheral tissue injury causes a migration of opioid peptide-containing immune cells to the inflamed site. The subsequent release and action of these peptides on opioid receptors localized on peripheral sensory nerve terminals cause endogenous analgesia (275). Opioid peptides secreted from immune cells are so far the best studied peptides in peripheral inflammatory pain control. Immigration of opioidcontaining immune cells is also dependent on neuroimmune interactions (275), since the central inhibition of pain by intrathecal application of morphine reduces the number of opioid-containing immune cells at the site of inflammation and also impairs endogenous peripheral opioid analgesia. Rheumatoid arthritis is an autoimmune disease characterized by inflammation of the synovial membrane of multiple joints. Experimentally, adjuvant arthritis is most severe in joints which are most densely innervated (276). Clinically, it was shown that hemiplegic patients do not have arthritis on their paralyzed side (277). Moreover, if the nerve innervating a joint is cut, arthritis cannot be induced in the denervated joint (276, 278). Miao et al. (279) have shown that impulse activity in vagal afferents has an inhibitory effect on the modulation of bradykinin-induced plasma extravasation by nicotine. Spinal pathways seem to be important in mediating this effect. In rheumatoid arthritis fibroblast-like synoviocytes are at the interface between
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the immune and the nervous systems (280). There is evidence implying that substance P and the NK-1 receptor play a role in arthritic disease. Synoviocytes of patients with rheumatoid arthritis express NK-1 receptor mRNA (281). Substance P potentiates the effect of pro-inflammatory cytokines on the expression of VCAM-1 on these cells, suggesting that substance P increase of cytokine-induced VCAM-1 expression acts via this specific substance P receptor (282). The relationship between nervous innervation and inflammation is observed in other clinical situations such as diabetes in which the inflammatory response is inadequate because the nervous innervation is affected by the disease (diabetic neuropathy).
X. NEUROGENIC INFLAMMATION Neuropeptides released from sensory nerves induce a wide range of inflammatory reactions including vasodilatation, increased plasma extravasation, tissue swelling, and adherence of inflammatory cells to the endothelium, thereby facilitating cellular infiltration (106,283). The effects produced by tachykinins (substance P, neurokinin A, and neurokinin B) and CGRP released from peripheral endings of capsaicinsensitive primary sensory neurons are collectively referred to as neurogenic inflammation (284). Several studies have shown a role for neurogenic inflammation in the airways (285–287), skin (288,289), pancreas (290), urinary tract, and the digestive system (291). Neurogenic inflammation involves a change in function of sensory neurons due to inflammatory mediators, inducing an enhanced release of neuropeptides from the sensory nerve endings (292,293). Sensory neurons play a role in neurogenic inflammation (292). It has become apparent that the mast cell and its mediators also are important in neurogenic inflammation (293). In various studies, tissue mast cells invariably show ultrastructural evidence of activation even in normal healthy conditions, suggesting that these cells are constantly providing information to the nervous system (241). The fact that they are located at sites under constant exposure to the external environment, such as the skin, respiratory and gastrointestinal tract, emphasizes the significance of these associations. Aside from the generation of action potentials, the C-fiber terminal is a secretory system, releasing tachykinins to cause neurogenic inflammation. There is also histological evidence of the presence of cytokines, especially IL-6, within both sensory and autonomic nerves (294). The release of these pro-inflammatory cytokines would cause inflammation in the affected
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area, and indicates a direct link between neurogenic stimulation and the release of pro-inflammatory cytokines (294). Stimulation of these C-fibers by a range of chemical and physical factors results in afferent neuronal condition eliciting parasympathetic reflexes and antidromic impulses traveling along the peripheral nerve terminal. Such communication from one nerve to another, without passing through a cell body, is called the axon reflex and results in local release of tachykinins and CGRP from C-fiber terminals (107). Axon reflexes account for many of the local physiological responses to antigen, for instance, in sensitized lung (295,296) and gut tissues (297,298), and have long been recognized to be involved in local vasodilatation in the skin (299). Antidromic stimulation of guinea pig vagal sensory fibers results in contractions of the isolated airway smooth muscle mediated by tachykinins (300). Further studies indicate that neuropeptide release can also be induced via direct depolarization of the terminal.
XI. CENTRAL NERVOUS SYSTEM The brain, nervous, and immune systems are the major adaptive systems of the body (301). Several pathways have been shown to link the brain and the immune system, such as the autonomic nervous system via direct neural influences and, second, the neuroendocrine humoral outflow via the pituitary. CRH, secreted by the pituitary gland, is a major regulator of the HPA axis and cortisone synthesis, and acts as a coordinator of the stress response (302). CRH is also thought to be involved peripherally in tissue responses to stress in the skin, respiratory tract, and intestine. The central nervous system can and does activate or even inhibit immune and inflammatory events. Stress activation of the hypothalamic-pituitary-adrenal (HPA) axis has such a bimodal effect. CRH activates peripheral mast cells (303), corticosterone may inhibit inflammatory events, and catecholamines have complex effects. Hypnosis has been shown to inhibit the expression of skin reactivity to allergen in classical tests of allergic hypersensitivity (304,305), and we have shown that classical Pavlovian conditioning could cause mast cell secretion (306). In the central nervous system, mast cells may participate in the regulation of inflammatory responses through interactions with the HPA axis. Matsumoto et al. (307) showed that in the dog, degranulation of CNS mast cells evoked HPA activation in response to histamine release and CRH. In this study, dogs were passively sensitized with IgE and challenged with specific antigen centrally or peripherally. Both routes
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resulted in cortisone release from the adrenal glands. The effect could be mimicked by intracranial injection of the mast cell secretagogue compound 48/80, and blocked by CRH antibodies or histamine H1 blockers, but not H2 blockers. These results suggest that intracranial mast cells may act as allergen sensors, and that the activated adrenocortical response may represent a host defense reaction to prevent anaphylaxis. CRH is also thought to be involved peripherally in tissue responses to stress in the skin, respiratory tract, intestine, and bladder. Many, if not all, of the recorded changes have involved mast cells and neuronal activation, the latter being often mediated by neurotensin and/or substance P. Central neuropeptides initiate a systemic stress response by activation of neuroendocrinological pathways such as the sympathetic nervous system, hypothalamic pituitary axis, and the renin angiotensin system, with the release of the stress hormones (i.e., catecholamines, corticosteroids, growth hormone, glucagons, and renin)(308). These effects have been found in a variety of stress models including cold, restraint stress, and water avoidance stress (309–311). The neuropeptide CGRP is present in central structures like the pituitary and is involved in the modulation of inflammation (312). The presence of dense CGRP-like immunoreactivity in vagal nuclei (313) suggests that CGRP may have a functional role in the protective effect in vagal afferents in inflammatory processes. Studies have shown that exposure of experimental animals to immobilization stress increases colonic motility and that these effects are mediated by release
After Dickerson et al., J. Leuk. Biol., 1998 Maier et al., Ann. N.Y. Acad. Sci., 1998
FIGURE 1 Schematic outline after Maier et al. (43) with modifications. This work has shown that if endotoxin is introduced into the peritoneal cavity in vagotomized animals, the fever response of the brain is markedly diminished with consequent downstream effects on cortisol production. This response appears to involve both mast cells and nerves in a complex set of interactions. Reprinted with permission.
of CRH. Pothoulakis et al. (314) demonstrated that CRH released during immobilization stress increases colonic transit via a neuronal pathway and stimulates colonic mucin release via activation of neurons and colonic mast cells. These results provide support for an important role for CRH in stress-mediated colonic responses and a link between the nervous and the immune systems.
XII. STRESS RESPONSE The CNS seems to have the capacity to produce as well as modulate general inflammatory reactions, not only in response to infection, trauma, and tissue damage, but in response to stress as well (38,40). Psychological stress results in the release of chemical mediators including norepinephrine (NE), serotonin, and acetylcholine, which activate cells of the paraventricular nucleus (PVN) of the hypothalamus producing CRH (308). CRH is a major regulator of the HPA axis and principal coordinator of the stress response. Peripheral CRH is thought to have pro-inflammatory effects. CRH also stimulates the locus coeruleus, a dense collection of autonomic cells in the brainstem, to secrete NE at sympathetic nerve endings (315). Although CRH is the major coordinator of the stress response, substance P may also participate in the stress response by activating the HPA axis and the sensory nervous system. Substance P becomes elevated in the brain in response to many different types of psychological stress such as handling (316), restraint (317), and anxiety (318). In the amygdala, there is a marked increase in substance P and its precursor preprotachykinin after various psychological stressors in rats. Two other areas, involved in behavior, innervated with substance P are the substantia nigra and the median raphe. Substance P may stimulate the HPA axis directly or indirectly by increasing arginine vasopressin (AVP), a potent stimulator of HPA activity (319). Immune cells such as macrophages are also involved in certain types of stress. The cold water swim test resulted in the increase of substance P and its receptor in peritoneal macrophages as well as an increase in peritoneal substance P.
A. Acute versus Chronic Stress A general pattern of immunological changes is emerging as part of a result of examination of the effects of stress. As a generalized observation in animal models of stress, acute stress appears to enhance and chronic stress appears to diminish cell-mediated
4. Significance of Sensory Neuropeptides and the Immune Response
immune responses and other immune reactivity (320). The generalized pattern of deficits seen with chronic stressors includes diminished lymphocyte proliferation and diminished production of cell-mediated immune cytokines as IL-2 and IFN-γ (321). These immunological alterations were often accompanied by evidence of elevated production of stress mediators, such as epinephrine and cortisol. Active immune responses themselves represent a source of systemic stress which impacts the brain and modifies various neuroendocrine and behavioral functions. Therefore, the immune system has been conceived of as a potential contributor to stress-related behavioral abnormalities, such as clinical depression (29,322). It is suggested that immunologically induced changes in the brain activate neuropeptides, thereby sustaining an adaptive state of arousal that promotes appropriate behavioral adjustments during infectious illness.
XIII. NERVE-IMMUNE COMMUNICATION IN THE VARIOUS TISSUES A. Skin Both nerve fibers and inflammatory cells are able to release neuromediators and thereby activate specific receptors on target cells in the skin. The dermis is richly innervated by primary efferent sensory nerves, post-ganglionic cholinergic parasympathetic nerves and post-ganglionic adrenergic and cholinergic sympathetic nerves (311). Cutaneous neuromediators include classical neurotransmitters such as catecholamines and acetylcholine being released from the autonomic nervous system. Neuropeptides including substance P, VIP, and CRGP may be released from sensory or autonomic nerve fibers and several epidermal as well as dermal cells. Neuropeptides have been shown to activate a number of target cells including Langerhans cells, endothelial cells, and mast cells (323). Observations of Egan et al. (324) showed that especially unmyelinated axons were associated with mast cells as well as Langerhans cells in primate as well as murine skin.
1. Neuropeptides and Mast Cells Skin mast cells can respond to trauma, releasing a variety of inflammatory mediators through an immediate sensory nerve-stimulated response or via an axon reflex, inducing the release of neuropeptides from peripheral nerve endings, in turn leading to more mast cell activation. Neuropeptides are released in response to nociceptive stimulation by pain, mechanical and
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chemical irritants to mediate skin responses to infection, injury, and wound healing. Substance P effects have been described on keratinocytes including hair follicles, mast cells, fibroblasts, and endothelial cells. Increased epidermal SPimmunoreactive nerve fibers have been observed in certain inflammatory human skin diseases (325). Substance P is one of the main neuropeptides responsible for the skin reaction characterized by erythema, pain, and swelling (239). In addition, substance P can cause the release of histamine (326) and TNF (327) from skin mast cells, which in turn lead to vasodilatation. Capsaicin (which releases neuropeptides from nerves) applied to human skin induces the release of chymase within 6 hours and induction of E-selectin in adjacent microvascular endothelium. These events are consistent with release of substance P from axons and subsequent stimulation of cytokine-mediated mast cell-endothelial interaction. However, identical application of capsaicin to human skin grafted onto immunodeficient mice, and thus experimentally lacking in unmyelinated axons, failed to show similar findings (324). These results demonstrate that unmyelinated axons connect Langerhans cells and dermal mast cells. Immune-nerve interaction has been shown to be involved in the skin during stress. Stress can significantly increase the number of hair follicles containing apoptotic cells and also significantly increase the number of activated perifollicular macrophage clusters and the number of degranulated mast cells, whereas it downregulated the number of intraepithelial T lymphocytes. Substance P seems to be a key mediator of stress-induced hair growth inhibition in vivo. These stress-induced immune changes could be mimicked by injection of the neuropeptide substance P in non-stressed mice (328,329). Increased numbers of substance P-immunoreactive sensory fibers, as seen in the dermis of stressed mice, are a result of transient high levels of NGF (330), suggesting that NGF is a central element in the perifollicular neurogenic inflammation that develops during the murine skin response to stress. So, stress can inhibit hair growth in vivo, probably via a substance P and NGF-dependent activation of macrophages and/or mast cells. Recent studies have suggested that mast cells play a crucial role in the downregulation of immune responses and induction of tolerance after exposure of skin to ultraviolet B (UVB) radiation. Interactions between mast cells and the nervous system appear to be involved in UVB-mediated immune suppression. TNF, reported to be derived from mast cells, has been shown to be a major cytokine implicated in signaling
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Alard, Niizeki, Hanninen et al., 1999
FIGURE 2 Schematic drawing of skin responses to UVB radiation and the consequent immune suppression dependent on mast cells, Langerhans cells, and nerves (331). Modified with permission.
the immunosuppressive effects of UVB (331). Evidence indicates that mast cells are triggered to release TNF in response to the neuropeptide CGRP, which is also released from UVB-damaged cutaneous nerve endings (332). Several inflammatory skin conditions, including atopic dermatitis and psoriasis, are exacerbated by stress. Recent evidence suggests that crosstalk between mast cells, neurons, and keratinocytes might be involved in such exacerbation. CRH and its receptor are present in the skin, and their levels are increased following stress (333). Human mast cells synthesize and secrete CRH in response to immunoglobulin E receptor crosslinking. Mast cells also express CRH receptors, activation of which leads to the selective release of cytokines and other pro-inflammatory mediators (334). CRH receptor antagonists could be used to inhibit stress-induced mast cell activation and provide new therapeutic options for chronic inflammatory conditions exacerbated by stress. 2. Neuropeptides in Nerve-Dendritic Cell Communication Nerve cells may regulate Langerhans cell (LC) function by elaboration of certain neuropeptides, whereas LC may promote the differentiation of nerves by elaboration of interleukin-6 and, possibly, other factors (149). LC functions are modulated by both substance P and CGRP, because these two neuropeptides are often co-localized and co-released by the same cutaneous nerve fibers (335,336). Brain and Williams (336) have shown that injection of CGRP in the human skin together with substance P converts the long-lasting vasodilatation induced by CGRP into a temporary
response. Thus, it may be hypothesized that biological effects occur through the combined action of substance P and CGRP. Furthermore, Brain and Williams (336) showed that this phenomenon is dependent on the action of proteases released from mast cells by substance P, revealing a new mechanism for the inactivation of a neuropeptide due to a direct consequence of mast cell activation. Although substance P seems to be involved in local inflammatory reactions in the skin, it has been shown that substance P may be involved in the inhibition of antigen presentation (265). CGRP is a neuropeptide and vasodilator that modulates some macrophage functions, including antigen presentation in vitro. Many, if not most, epidermal LC appeared to be closely associated anatomically with CGRP-containing nerves as determined by confocal laser scanning microscopy (337). CGRP inhibits the Ag-presenting function of macrophages (338) and Langerhans cells in various systems (151). Nong et al. (338) found that CGRP inhibits macrophage activation induced by IFN-γ. In addition, pretreatment of LC by CGRP before antigen sensitization prevents the ability of the cells to elicit a delayed-type hypersensitivity reaction (151). Furthermore, when injected intradermally, CGRP inhibits the induction of hypersensitivity contact reactions (150), supporting the concept that endogenous CGRP may modulate immune function, presumably in part, through an inhibitory effect on LC function. These findings indicate that CGRP is capable of inhibiting both the induction and expression of fundamental cellular immune functions and suggest at least one inhibitory pathway of interaction between the nervous system and immunological function.
B. Airways Various studies have demonstrated the presence of SP and NKA in the respiratory tract in mammalian nerve fibers. The majority of nerve fibers reach the lung via the vagus nerve. The vagal innervation is divided into vagal afferent (sensory) nerves and autonomic (parasympathetic) nerves. The interaction between the nervous and immune systems in the lung, as in other organs, is bi-directional. Some immune cells in the airways are in intimate contact with nerves. They possess cell-surface receptors for a variety of neurotransmitters. The function of monocytes and macrophages, for example, can be modified by adrenergic and cholinergic receptor activation (339). In addition, neuropeptides including tachykinins and VIP can interact with receptors on macrophages to modify their function (340,341). In the trachea and
4. Significance of Sensory Neuropeptides and the Immune Response
bronchi, SP-immunoreactive fibers have been found in the smooth muscle layer and around local ganglion cells. In the bronchial tree, most of the SP-positive fibers are of vagal origin; but in the lung, the fibers are both of vagal and thoracic spinal origin (342–344). Another important neural network in the lung is the non-adrenergic non-cholinergic (NANC) nervous system. Inhibitory NANC nerves contain vasoactive intestinal peptide (VIP) and nitric oxide (NO). Under normal conditions in the mouse lung, VIP receptors are localized on alveolar macrophages. Immunized and intratracheally challenged mice demonstrated increased levels of VIP and NO receptor expression on mononuclear cells and neutrophils in inflammatory infiltrates (126). VIP is a potent relaxant of the airways and has also been suggested to inhibit mediator release from mast cells (345). In cats, Miura et al. (346) demonstrated that bilateral electrical nerve (vagus) stimulation of i-NANC in atropinized and propanolol-treated animals inhibited antigen-induced bronchoconstriction and histamine secretion from histamine-containing cells. Other direct effects of VIP include inhibition of T-cell proliferation; IL-2, IL-4, and IL-10 cytokine production; and inhibition of IgE release by B-cells (347). A further role of NO is skewing T-cells towards a Th2 phenotype by inhibition of Th1 cells and IFN-γ (348). In addition to inhibitory NANC systems in the airways, there is also an NANC afferent nervous system that protects the airways against inhaled irritants and chemical particles. These excitatory NANC nerves or sensory nerves play a regulatory role in airways. Excitatory NANC system-associated neuropeptides with immunomodulatory functions are SOM, CGRP, the members of the tachykinin family substance P and NKA, present in the airways of various mammals including man (78,106,349). These sensory neuropeptides contract smooth muscle, dilate bronchial arteries, increase vascular permeability, increase mucus production, and modulate ganglionic transmission. Many animal studies show that capsaicin-induced depletion of excitatory NANC neuropeptides prevents airway hyperresponsiveness and pulmonary inflammation. For instance, airway hyperresponsiveness induced by a respiratory viral infection, ovalbumin (350), plateletactivating factor (351), or toluene diisocyanate (352) can be attenuated by interruption or blockade of the excitatory NANC system. Sensory neuropeptides can be released into the airways as a consequence of action potentials (axonreflex pathways)(353). Once released in the airways, neuropeptides participate in the inflammatory response via various mechanisms collectively referred to as neurogenic inflammation (as described above). In addition,
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they are certain to influence the recruitment, proliferation, and activation of inflammatory cells. Specific receptors for CGRP and SOM have been demonstrated on macrophages, monocytes, B-cells, and T-cells (58,354). SOM has various inhibitory effects on immune responses via specific receptor activation (58) and affects the suppression of Ig production in B-cells, including IgE (62). CGRP inhibits substance P–induced super oxide production in neutrophils and the proliferation as well as antigen presentation by peripheral mononuclear cells (355). In allergic rhinitis patients, it was shown that substance P administered after antigen challenge enhanced the recruitment of eosinophils. Forsythe et al. (356) demonstrated that substance P and NKA induce histamine release from human airway mast cells. This is underlined by an in vitro model using trachea from Fischer 344 rats, in which substance P stimulation of mast cells represented a major factor leading to bronchoconstriction (357).
C. Gastrointestinal Tract The main sources of the neuronal tachykinins in the gut are (a) the intrinsic enteric neurons of the myenteric plexus, (b) the intrinsic enteric neurons of the submucosal plexus, and (c) the extrinsic primary afferent fibers. The most quantitatively important source of tachykinins in the gut is the enteric nervous system, which has its cells in the wall of the intestine and supplies all gastrointestinal effector systems. The mammalian gastrointestinal tract contains both substance P and neurokinin A and various extended forms of these tachykinins. The gastrointestinal tract is characterized by a unique accumulation of immune and inflammatory cells. Close approximations between peptidergic nerves and mast cells, lymphocytes, eosinophils, and plasma cells have been reported in the lamina propria (1,16,358,359). Neurotransmitters, neuropeptides, and neuroendocrine hormones can affect immune function, and conversely cytokines can affect neuronal function. As many leukocytes express receptors for neuropeptides and neuroendocrine hormones, this strongly implies the importance of a neuroimmune interaction in the intestine. Neurally mediated epithelial ion secretion is well established, and immunomodulation of epithelial barrier function has become evident (14,360). Epithelial cells can also produce neuroregulatory factors, indicating the communication between nerves, immune cells, and epithelium (361). An example of a neuropeptide-induced inflammatory process is diarrhea induced in rats by clostridium difficile toxin (362–364). Substance P, CGRP, and neurotensin were involved in this inflammatory process.
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The toxin stimulated the release of these neuropeptides from primary C afferents in the lamina propria. This was likely followed by the production of substance P by macrophages and the release of greater amounts of TNF. Furthermore, mast cells were degranulated in the mucosa by substance P, their mediators also contributing to the inflammatory process. Pothoulakis et al. (314) studied the intestinal responses to stress. Increased motility, mucus hypersecretion and intestinal chloride ion secretion, was mediated by CRH. Both mast cells and nerves are involved since the effects were inhibited by NK-1 receptor antagonists and mast cell stabilizers (365). Structural as well as functional alterations of enteric nerves have been reported in both ulcerative colitis and Crohn’s disease. An altered expression of substance P (366) and VIP (367) has been found in both diseases. An increased expression of CRH has been demonstrated in mucosal inflammatory cells in ulcerative colitis (368). Furthermore, NGF immunostaining is significantly increased in Crohn’s disease tissue (369). The consequences for these neuronal changes for mucosal function in IBD have yet to be fully clarified. 1. Mast Cells Intestinal mast cells have been repeatedly reported to communicate with the enteric nervous system. Stead et al. (370) reported an anatomical association between mast cells and nerves in the human intestinal mucosa based on electron microscopy studies. Nerve stimulation has been reported to cause mast cell degranulation in the intestine. First, Shanahan et al. (371) showed that substance P caused mediator release from intestinal mucosal mast cells. Subsequently, substance P and CGRP fibers have been reported to activate peptidergic mast cells in intestinal mucosa of healthy and infected rats as well as in patients with inflammatory bowel disease (1). Mast cell mediators have an effect on the nerves in the intestine. Intestinal mast cell infiltration may perturb nerve function leading to abdominal pain perception in irritable bowel syndrome (372). Recent evidence for activated mast cells associated with enteric nerves in irritable bowel syndrome strongly imply that mast cells are involved in this symptom complex (372). A study by Jiang et al. (373) in an intestinal model for anaphylaxis showed that serotonin and histamine, released from the mast cells after intestinal anaphylaxis, stimulate mesenteric afferents via 5HT3 and histamine H1 receptors. Mesenteric afferent nerve discharge increased approximately 1 minute after luminal antigen challenge and was atten-
uated by serotonin and histamine receptor antagonists. Mast cell-nerve association appears to function as a homeostatic unit in the regulation of gut physiology and in response to antigen (14). Perdue et al. (298) determined the existence of an integral nerve-to-mast cell and mast cell-to-nerve connection during intestinal anaphylaxis. A role for the mast cell-to-nerve connection was also established by increases in the short-circuit current after antigen challenge, in Ussing chamber experiments. The response to antigenic stimulation was reduced in mast cell– deficient mice compared to their littermates and was inhibited by different mast cell antagonists in +/+ but not in W/Wv mice, pointing to mast cell-to-nerve connection. Furthermore, reconstitution of the mast cell deficiency was followed by a restoration of the neural response. In sensitized guinea pig intestine, the short-circuit current secretory response to antigen occurred simultaneously to acetylcholine release and could be blocked by atropine (374). This showed conclusively that nerve excitation and the secretion of the main cholinergic neurotransmitter could be induced by antigen via mast cells through an immunemediated response. It can reasonably be concluded that nerves and mast cells form a physiological unit which presumably maintains and regulates homeostasis of the mucosal epithelial secretory response. This unit is involved in health, in response to stress,
FIGURE 3 Representation of neuroimmune interactions involved in stress-induced functional changes of intestinal mucosa. Activation of mucosal nerves, possibly releasing CRH and/or Ach, leads to the stimulation of mast cells. Mast cells (and possibly neurons) can release bioactive chemicals that enhance epithelial ion secretion and permeability of both the transcellular and paracellular pathway (Modified with permission from Soderholm and Perdue, 2001) (394).
4. Significance of Sensory Neuropeptides and the Immune Response
and also in response to injuries and environmental pathogens.
D. Urinary Tract Bladder function is regulated by complex and interrelated neural circuits involving the peripheral and CNS (375). In addition to the classic neurotransmitters Ach and NE, neuropeptides released from the different innervating nerves and cytokines liberated from mast cells and leukocytes profoundly affect bladder function (376). Dysfunction of these interactions could lead to bladder hyperreactivity and systemic inflammatory symptoms. The distribution of SP and NKA has been extensively studied in the urinary bladder of several species (377,378). Capsaicin treatment results in an almost complete disappearance of the tachykinin-immunoreactive fibers, suggesting that the major sources of tachykinins in the urinary bladder are sensory fibers (379,380). Emotional or physical stress can release CRF or its analogue urocortin (Ucn) from the hypothalamus, which then stimulates the NTS to release Ach or neuropeptides in the bladder, inducing hyperreactivity. CRF/Ucn can also be released from the dorsal root ganglia and can stimulate bladder mast cells, directly or via neuropeptides (376). For instance, stress-induced bladder mast cell activation is inhibited by neonatal capsaicin treatment, which depletes sensory neurons of their substance P (381). Bladder afferents synapsing at the sacral DRG contain CGRP, glutamate, NO, VIP, and substance P (382). Depletion of these neuropeptides by capsaicin reduces bladder pain and irritation (383–385). Moreover, selective NK-1 receptor antagonists block substance P–induced bladder muscle contractions and plasma extravasation (386). An intimate relationship has been demonstrated between mast cells and peptidergic sensory nerves in the bladder. As shown by Keith and Saban (387), mast cells of mucosal and connective tissue type were found within nerves and ganglia and were in close contact with individual nerve fibers displaying substance Pand CGRP-like immunoreactivity in healthy tissue. In the bladder, axon reflexes can cause noninfectious neurogenic inflammation (376,381,388) via the influx of inflammatory cells from the vascular system. Mast cell immigration has been described in urinary bladder disorders such as interstitial cystitis. Interstitial cystitis (IC) has continued to be an unresolved problem in clinical urology. Mast cells were in close contact with nerve fibers displaying substance P- and CGRP-like immunoreactivity (389). Elbadawi demon-
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strated the presence of mast cells, undergoing piecemeal degranulation, in close proximity to intrinsic nerves in the bladder wall (375). Bladder neuronal proliferation has been demonstrated in IC patients, and an increase in nerve fibers containing NPY and CGRP has also been noted (390). In addition, increased mast cell numbers have been reported in a subset of IC patients (391) together with increased concentrations of histamine (389). The data provide evidence for the involvement of neurogenic inflammation in the pathogenesis of interstitial cystitis. Saban et al. (392) showed that NK-1 receptor −/− mice were protected from inflammation, failing to present bladder inflammatory cell infiltrate or edema in response to antigen challenge. This work supports evidence for the role of substance P and the NK-1 receptor in the development of interstitial cystitis.
XIV. SUMMARY The brain and nervous system have a bi-directional communication with the immune system. Over the last decade especially, it has become apparent that many of the cells in these different systems possess the same receptors and can make the same molecules. Thus, the nervous system can make a major pro-inflammatory cytokine, IL-6, and cells of the immune system can make substance P and acetylcholine. Similarly, cells in both systems can synthesize neurotrophins such as nerve growth factor and brain-derived neurotrophic factor. Behavioral changes can be initiated as a result of peripheral inflammation (illness behavior), and pyrexia can be caused by peripheral infections and inflammation as a result of communication with and through the vagus nerve to the brain. In turn the brain routinely receives communication signals from peripheral immune events and can coordinate responses through the HPA axis and the autonomic nervous system. The intimate nature of these connections is exemplified by the consistent finding of associations between non-myelinated nerves and lymphocytes, mast cells, eosinophils, and Langerhans cells, at which locations bi-directional communication clearly occurs. How these events are orchestrated under different circumstances of emotion or inflammation and injury are only just beginning to be worked out. Much remains to be done, but scientific progress promises much greater complexity as well as understanding. What is clear, however, is that immune mechanisms cannot be ignored in dealing with a functional understanding of the nervous system or even behavior, and the reverse is also true.
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References 1. Stead, R. H., Tomioka, M., Quinonez, G., Simon, G. T., Felten, S. Y., and Bienenstock, J. (1987). Intestinal mucosal mast cells in normal and nematode-infected rat intestines are in intimate contact with peptidergic nerves. Proc. Natl. Acad. Sci. USA, 84, 2975–2979. 2. Purcell, W. M., and Atterwill, C. K. (1995). Mast cells in neuroimmune function: neurotoxicological and neuropharmacological perspectives. Neurochem. Res., 20, 521–532. 3. Marshall, J. S., and Waserman, S. (1995). Mast cells and the nerves—potential interactions in the context of chronic disease. Clin. Exp. Allergy, 25, 102–110. 4. Katayama, M., Kobayashi, S., Kuramoto, N., and Yokoyama, M. M. (1987). Effects of hypothalamic lesions on lymphocyte subsets in mice. Ann. N. Y. Acad. Sci., 496, 366–376. 5. Felten, D. L. (1991). Neurotransmitter signaling of cells of the immune system: important progress, major gaps. Brain Behav. Immun., 5, 2–8. 6. Ader, R., and Cohen, N. (1975). Behaviorally conditioned immunosuppression. Psychosom. Med., 37, 333–340. 7. Madden, K. S., Boehm, G. W., Lee, S. C., Grota, L. J., Cohen, N., and Ader, R. (2001). One-trial conditioning of the antibody response to hen egg lysozyme in rats. J. Neuroimmunol., 113, 236–239. 8. Besedovsky, H., Sorkin, E., Felix, D., and Haas, H. (1977). Hypothalamic changes during the immune response. Eur. J. Immunol., 7, 323–325. 9. Carr, D. J., and Blalock, J. E. (1989). A molecular basis for intersystem communication between the immune and neuroendocrine systems. Int. Rev. Immunol., 4, 213–228. 10. Blalock, J. E. (1989). A molecular basis for bidirectional communication between the immune and neuroendocrine systems. Physiol. Rev., 69, 1–32. 11. Plaut, M. (1987). Lymphocyte hormone receptors. Annu. Rev. Immunol., 5, 621–669. 12. Madden, K. S., Sanders, V. M., and Felten, D. L. (1995). Catecholamine influences and sympathetic neural modulation of immune responsiveness. Annu. Rev. Pharmacol. Toxicol., 35, 417–448. 13. Blalock, J. E. (1984). The immune system as a sensory organ. J. Immunol., 132, 1067–1070. 14. McKay, D. M., and Bienenstock, J. (1994). The interaction between mast cells and nerves in the gastrointestinal tract. Immunol. Today, 15, 533–538. 15. Williams, J. M., and Felten, D. L. (1981). Sympathetic innervation of murine thymus and spleen: a comparative histofluorescence study. Anat. Rec., 199, 531–542. 16. Arizono, N., Matsuda, S., Hattori, T., Kojima, Y., Maeda, T., and Galli, S. J. (1990). Anatomical variation in mast cell nerve associations in the rat small intestine, heart, lung, and skin. Similarities of distances between neural processes and mast cells, eosinophils, or plasma cells in the jejunal lamina propria. Lab Invest., 62, 626–634. 17. Steinhoff, M., Stander, S., Seeliger, S., Ansel, J. C., Schmelz, M., and Luger, T. (2003). Modern aspects of cutaneous neurogenic inflammation. Arch. Dermatol., 139, 1479–1488. 18. Luger, T. A. (2002). Neuromediators—a crucial component of the skin immune system. J. Dermatol. Sci., 30, 87–93. 19. Stanisz, A., Scicchitano, R., Stead, R., Matsuda, H., Tomioka, M., Denburg, J., and Bienenstock, J. (1987). Neuropeptides and immunity. Am. Rev. Respir. Dis., 136, S48–S51. 20. Tosi, M. F. (2005). Innate immune responses to infection. J. Allergy Clin. Immunol., 116, 241–249.
21. Wallace, M. E., and Smyth, M. J. (2005). The role of natural killer cells in tumor control—effectors and regulators of adaptive immunity. Springer Semin. Immunopathol., 27, 49–64. 22. Banchereau, J., and Steinman, R. M. (1998). Dendritic cells and the control of immunity. Nature, 392, 245–252. 23. Waldmann, T. A., and Tagaya, Y. (1999). The multifaceted regulation of interleukin-15 expression and the role of this cytokine in NK cell differentiation and host response to intracellular pathogens. Annu. Rev. Immunol., 17, 19–49. 24. Emoto, M., and Kaufmann, S. H. (2003). Liver NKT cells: an account of heterogeneity. Trends Immunol., 24, 364–369. 25. Biron, C. A., and Brossay, L. (2001). NK cells and NKT cells in innate defense against viral infections. Curr. Opin. Immunol., 13, 458–464. 26. Araujo, L. M., Lefort, J., Nahori, M. A., Diem, S., Zhu, R., Dy, M., Leite-de-Moraes, M. C., Bach, J. F., Vargaftig, B. B., and Herbelin, A. (2004). Exacerbated Th2-mediated airway inflammation and hyperresponsiveness in autoimmune diabetesprone NOD mice: a critical role for CD1d-dependent NKT cells. Eur. J. Immunol., 34, 327–335. 27. Pasare, C., and Medzhitov, R. (2005). Toll-like receptors: linking innate and adaptive immunity. Adv. Exp. Med. Biol., 560, 11–18. 28. Goehler, L. E., Gaykema, R. P., Nguyen, K. T., Lee, J. E., Tilders, F. J., Maier, S. F., and Watkins, L. R. (1999). Interleukin-1beta in immune cells of the abdominal vagus nerve: a link between the immune and nervous systems? J. Neurosci., 19, 2799–2806. 29. Dantzer, R. (2004). Cytokine-induced sickness behaviour: a neuroimmune response to activation of innate immunity. Eur. J. Pharmacol., 500, 399–411. 30. Luheshi, G. N., Bluthe, R. M., Rushforth, D., Mulcahy, N., Konsman, J. P., Goldbach, M., and Dantzer, R. (2000). Vagotomy attenuates the behavioural but not the pyrogenic effects of interleukin-1 in rats. Auton. Neurosci., 85, 127–132. 31. Ganea, D., Rodriguez, R., and Delgado, M. (2003). Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide: players in innate and adaptive immunity. Cell Mol. Biol. (Noisy-le-grand), 49, 127–142. 32. Steinman, R. M., and Inaba, K. (1999). Myeloid dendritic cells. J. Leukoc. Biol., 66, 205–208. 33. Akira, S., Takeda, K., and Kaisho, T. (2001). Toll-like receptors: critical proteins linking innate and acquired immunity. Nat. Immunol., 2, 675–680. 34. Liu, Y. J., Kanzler, H., Soumelis, V., and Gilliet, M. (2001). Dendritic cell lineage, plasticity and cross-regulation. Nat. Immunol., 2, 585–589. 35. Wan, Y., and Bramson, J. (2001). Role of dendritic cell–derived cytokines in immune regulation. Curr. Pharm. Des., 7, 977– 992. 36. Kawamura, N., Tamura, H., Obana, S., Wenner, M., Ishikawa, T., Nakata, A., and Yamamoto, H. (1998). Differential effects of neuropeptides on cytokine production by mouse helper T cell subsets. Neuroimmunomodulation, 5, 9–15. 37. Sanders, V. M., Baker, R. A., Ramer-Quinn, D. S., Kasprowicz, D. J., Fuchs, B. A., and Street, N. E. (1997). Differential expression of the beta2-adrenergic receptor by Th1 and Th2 clones: implications for cytokine production and B cell help. J. Immunol., 158, 4200–4210. 38. Black, P. H. (1994). Central nervous system-immune system interactions: psychoneuroendocrinology of stress and its immune consequences. Antimicrob. Agents Chemother., 38, 1–6. 39. Chrousos, G. P., and Gold, P. W. (1992). The concepts of stress and stress system disorders. Overview of physical and behavioral homeostasis. JAMA, 267, 1244–1252.
4. Significance of Sensory Neuropeptides and the Immune Response 40. Maier, S. F., and Watkins, L. R. (1998). Cytokines for psychologists: implications of bidirectional immune-to-brain communication for understanding behavior, mood, and cognition. Psychol. Rev., 105, 83–107. 41. Hori, T., Oka, T., Hosoi, M., Abe, M., and Oka, K. (2000). Hypothalamic mechanisms of pain modulatory actions of cytokines and prostaglandin E2. Ann. N. Y. Acad. Sci., 917, 106–120. 42. Watkins, L. R., and Maier, S. F. (1999). Implications of immuneto-brain communication for sickness and pain. Proc. Natl. Acad. Sci. USA, 96, 7710–7713. 43. Maier, S. F., Goehler, L. E., Fleshner, M., and Watkins, L. R. (1998). The role of the vagus nerve in cytokine-to-brain communication. Ann. N. Y. Acad. Sci., 840, 289–300. 44. Abrass, C. K., O’Connor, S. W., Scarpace, P. J., and Abrass, I. B. (1985). Characterization of the beta-adrenergic receptor of the rat peritoneal macrophage. J. Immunol., 135, 1338–1341. 45. Fuchs, B. A., Campbell, K. S., and Munson, A. E. (1988). Norepinephrine and serotonin content of the murine spleen: its relationship to lymphocyte beta-adrenergic receptor density and the humoral immune response in vivo and in vitro. Cell. Immunol., 117, 339–351. 46. Downing, J. E., and Miyan, J. A. (2000). Neural immunoregulation: emerging roles for nerves in immune homeostasis and disease. Immunol. Today, 21, 281–289. 47. Metwali, A., Blum, A. M., Elliott, D. E., Setiawan, T., and Weinstock, J. V. (2004). Cutting edge: hemokinin has substance P–like function and expression in inflammation. J. Immunol., 172, 6528–6532. 48. Patacchini, R., Lecci, A., Holzer, P., and Maggi, C. A. (2004). Newly discovered tachykinins raise new questions about their peripheral roles and the tachykinin nomenclature. Trends Pharmacol. Sci., 25, 1–3. 49. Wessler, I., Kilbinger, H., Bittinger, F., Unger, R., and Kirkpatrick, C. J. (2003). The non-neuronal cholinergic system in humans: expression, function and pathophysiology. Life Sci., 72, 2055–2061. 50. Lambrecht, B. N., Germonpre, P. R., Everaert, E. G., CarroMuino, I., De Veerman, M., de Felipe, C., Hunt, S. P., Thielemans, K., Joos, G. F., and Pauwels, R. A. (1999). Endogenously produced substance P contributes to lymphocyte proliferation induced by dendritic cells and direct TCR ligation. Eur. J. Immunol., 29, 3815–3825. 51. Cook, G. A., Elliott, D., Metwali, A., Blum, A. M., Sandor, M., Lynch, R., and Weinstock, J. V. (1994). Molecular evidence that granuloma T lymphocytes in murine schistosomiasis mansoni express an authentic substance P (NK-1) receptor. J. Immunol., 152, 1830–1835. 52. McCormack, R. J., Hart, R. P., and Ganea, D. (1996). Expression of NK-1 receptor mRNA in murine T lymphocytes. Neuroimmunomodulation, 3, 35–46. 53. Sreedharan, S. P., Kodama, K. T., Peterson, K. E., and Goetzl, E. J. (1989). Distinct subsets of somatostatin receptors on cultured human lymphocytes. J. Biol. Chem., 264, 949–952. 54. McGillis, J. P., Humphreys, S., and Reid, S. (1991). Characterization of functional calcitonin gene-related peptide receptors on rat lymphocytes. J. Immunol., 147, 3482–3489. 55. Audhya, T., Jain, R., and Hollander, C. S. (1991). Receptormediated immunomodulation by corticotropin-releasing factor. Cell. Immunol., 134, 77–84. 56. Catania, A., Rajora, N., Capsoni, F., Minonzio, F., Star, R. A., and Lipton, J. M. (1996). The neuropeptide alpha-MSH has specific receptors on neutrophils and reduces chemotaxis in vitro. Peptides, 17, 675–679.
119
57. Getting, S. J., Gibbs, L., Clark, A. J., Flower, R. J., and Perretti, M. (1999). POMC gene-derived peptides activate melanocortin type 3 receptor on murine macrophages, suppress cytokine release, and inhibit neutrophil migration in acute experimental inflammation. J. Immunol., 162, 7446–7453. 58. van Hagen, P. M., Krenning, E. P., Kwekkeboom, D. J., Reubi, J. C., Anker-Lugtenburg, P. J., Lowenberg, B., and Lamberts, S. W. (1994). Somatostatin and the immune and haematopoetic system: a review. Eur. J. Clin. Invest., 24, 91–99. 59. Benali, N., Ferjoux, G., Puente, E., Buscail, L., and Susini, C. (2000). Somatostatin receptors. Digestion, 62 (Suppl 1), 27–32. 60. Reisine, T. (1995). Somatostatin receptors. Am. J. Physiol., 269, G813–G820. 61. ten Bokum, A. M., Lichtenauer-Kaligis, E. G., Melief, M. J., van Koetsveld, P. M., Bruns, C., van Hagen, P. M., Hofland, L. J., Lamberts, S. W., and Hazenberg, M. P. (1999). Somatostatin receptor subtype expression in cells of the rat immune system during adjuvant arthritis. J. Endocrinol., 161, 167–175. 62. Kimata, H., Yoshida, A., Ishioka, C., and Mikawa, H. (1992). Differential effect of vasoactive intestinal peptide, somatostatin, and substance P on human IgE and IgG subclass production. Cell. Immunol., 144, 429–442. 63. Liu, L., and Burcher, E. (2005). Tachykinin peptides and receptors: putting amphibians into perspective. Peptides, 26, 1369–1382. 64. Kurtz, M. M., Wang, R., Clements, M. K., Cascieri, M. A., Austin, C. P., Cunningham, B. R., Chicchi, G. G., and Liu, Q. (2002). Identification, localization and receptor characterization of novel mammalian substance P–like peptides. Gene, 296, 205–212. 65. McDonald, D. M., Bowden, J. J., Baluk, P., and Bunnett, N. W. (1996). Neurogenic inflammation. A model for studying efferent actions of sensory nerves. Adv. Exp. Med. Biol., 410, 453–462. 66. Mousli, M., Bronner, C., Landry, Y., Bockaert, J., and Rouot, B. (1990). Direct activation of GTP-binding regulatory proteins (G-proteins) by substance P and compound 48/80. FEBS Lett., 259, 260–262. 67. Mousli, M., Hugli, T. E., Landry, Y., and Bronner, C. (1994). Peptidergic pathway in human skin and rat peritoneal mast cell activation. Immunopharmacology, 27, 1–11. 68. Page, N. M., Woods, R. J., Gardiner, S. M., Lomthaisong, K., Gladwell, R. T., Butlin, D. J., Manyonda, I. T., and Lowry, P. J. (2000). Excessive placental secretion of neurokinin B during the third trimester causes pre-eclampsia. Nature, 405, 797–800. 69. Cintado, C. G., Pinto, F. M., Devillier, P., Merida, A., and Candenas, M. L. (2001). Increase in neurokinin B expression and in tachykinin NK(3) receptor-mediated response and expression in the rat uterus with age. J. Pharmacol. Exp. Ther., 299, 934–938. 70. Patak, E., Candenas, M. L., Pennefather, J. N., Ziccone, S., Lilley, A., Martin, J. D., Flores, C., Mantecon, A. G., Story, M. E., and Pinto, F. M. (2003). Tachykinins and tachykinin receptors in human uterus. Br. J. Pharmacol., 139, 523–532. 71. Malendowicz, L. K., Andreis, P. G., Nussdorfer, G. G., and Markowska, A. (1996). The possible role of endogenous substance P in the modulation of the response of rat pituitaryadrenal axis to stresses. Endocr. Res., 22, 311–318. 72. Jessop, D. S., Renshaw, D., Larsen, P. J., Chowdrey, H. S., and Harbuz, M. S. (2000). Substance P is involved in terminating the hypothalamo-pituitary-adrenal axis response to acute stress through centrally located neurokinin-1 receptors. Stress, 3, 209–220.
120
I. Neural and Endocrine Effects on Immunity
73. Pitcher, G. M., and Henry, J. L. (2004). Nociceptive response to innocuous mechanical stimulation is mediated via myelinated afferents and NK-1 receptor activation in a rat model of neuropathic pain. Exp. Neurol., 186, 173–197. 74. Buck, S. H., Walsh, J. H., Yamamura, H. I., and Burks, T. F. (1982). Neuropeptides in sensory neurons. Life Sci., 30, 1857– 1866. 75. Swain, M. G., Agro, A., Blennerhassett, P., Stanisz, A., and Collins, S. M. (1992). Increased levels of substance P in the myenteric plexus of Trichinella-infected rats. Gastroenterology, 102, 1913–1919. 76. Suzuki, R., Furuno, T., McKay, D. M., Wolvers, D., Teshima, R., Nakanishi, M., and Bienenstock, J. (1999). Direct neurite-mast cell communication in vitro occurs via the neuropeptide substance P. J. Immunol., 163, 2410–2415. 77. Mantyh, P. W. (1991). Substance P and the inflammatory and immune response. Ann. N. Y. Acad. Sci., 632, 263–271. 78. Van, D. V., V, and Hulsmann, A. R. (1999). Autonomic innervation of human airways: structure, function, and pathophysiology in asthma. Neuroimmunomodulation, 6, 145–159. 79. Maggi, C. A. (1995). Tachykinins and calcitonin gene-related peptide (CGRP) as co-transmitters released from peripheral endings of sensory nerves. Prog. Neurobiol., 45, 1–98. 80. Germonpre, P. R., Bullock, G. R., Lambrecht, B. N., Van, D. V., Luyten, V. W. H., Joos, G. F., and Pauwels, R. A. (1999). Presence of substance P and neurokinin 1 receptors in human sputum macrophages and U-937 cells. Eur. Respir. J., 14, 776–782. 81. Weinstock, J. V., and Blum, A. M. (1989). Tachykinin production in granulomas of murine schistosomiasis mansoni. J. Immunol., 142, 3256–3261. 82. Okamoto, A., Lovett, M., Payan, D. G., and Bunnett, N. W. (1994). Interactions between neutral endopeptidase (EC 3. 4. 24. 11) and the substance P (NK1) receptor expressed in mammalian cells. Biochem. J., 299 (Pt 3), 683–693. 83. Sturiale, S., Barbara, G., Qiu, B., Figini, M., Geppetti, P., Gerard, N., Gerard, C., Grady, E. F., Bunnett, N. W., and Collins, S. M. (1999). Neutral endopeptidase (EC 3. 4. 24. 11) terminates colitis by degrading substance P. Proc. Natl. Acad. Sci. USA, 96, 11653–11658. 84. Shore, S. A., Stimler-Gerard, N. P., Coats, S. R., and Drazen, J. M. (1988). Substance P–induced bronchoconstriction in the guinea pig. Enhancement by inhibitors of neutral metalloendopeptidase and angiotensin-converting enzyme. Am. Rev. Respir. Dis., 137, 331–336. 85. Zhang, Y., and Paige, C. J. (2003). T-cell developmental blockage by tachykinin antagonists and the role of hemokinin 1 in T lymphopoiesis. Blood, 102, 2165–2172. 86. Jiang, Y., Gao, G., Fang, G., Gustafson, E. L., Laverty, M., Yin, Y., Zhang, Y., Luo, J., Greene, J. R., Bayne, M. L., Hedrick, J. A., and Murgolo, N. J. (2003). PepPat, a pattern-based oligopeptide homology search method and the identification of a novel tachykinin-like peptide. Mamm. Genome, 14, 341– 349. 87. Nelson, D. A., Marriott, I., and Bost, K. L. (2004). Expression of hemokinin 1 mRNA by murine dendritic cells. J. Neuroimmunol., 155, 94–102. 88. Morteau, O., Lu, B., Gerard, C., and Gerard, N. P. (2001). Hemokinin 1 is a full agonist at the substance P receptor. Nat. Immunol., 2, 1088. 89. Marriott, I. (2004). The role of tachykinins in central nervous system inflammatory responses. Front. Biosci., 9, 2153–2165. 90. Pascual, D. W. (2004). The role of tachykinins on bacterial infections. Front. Biosci., 9, 3209–3217.
91. Bost, K. L. (2004). Tachykinin-modulated anti-viral responses. Front. Biosci., 9, 1994–1998. 92. Weinstock, J. V. (2004). The role of substance P, hemokinin and their receptor in governing mucosal inflammation and granulomatous responses. Front. Biosci., 9, 1936–1943. 93. Holzer, P. (2002). Sensory neurone responses to mucosal noxae in the upper gut: relevance to mucosal integrity and gastrointestinal pain. Neurogastroenterol. Motil., 14, 459–475. 94. Porszasz, J., and Jancso, N. (1959). Studies on the action potentials of sensory nerves in animals desensitized with capsaicin. Acta Physiol. Acad. Sci. Hung., 16, 299–306. 95. Jancso, G., Kiraly, E., and Jancso-Gabor, A. (1977). Pharmacologically induced selective degeneration of chemosensitive primary sensory neurones. Nature, 270, 741–743. 96. Numazaki, M., and Tominaga, M. (2004). Nociception and TRP channels. Curr. Drug Targets. CNS. Neurol. Disord., 3, 479–485. 97. Szallasi, A., and Blumberg, P. M. (1990). Resiniferatoxin and its analogs provide novel insights into the pharmacology of the vanilloid (capsaicin) receptor. Life Sci., 47, 1399–1408. 98. Caterina, M. J., Schumacher, M. A., Tominaga, M., Rosen, T. A., Levine, J. D., and Julius, D. (1997). The capsaicin receptor: a heat-activated ion channel in the pain pathway. Nature, 389, 816–824. 99. Avelino, A., Cruz, C., Nagy, I., and Cruz, F. (2002). Vanilloid receptor 1 expression in the rat urinary tract. Neuroscience, 109, 787–798. 100. Roberts, J. C., Davis, J. B., and Benham, C. D. (2004). [3H]Resiniferatoxin autoradiography in the CNS of wild-type and TRPV1 null mice defines TRPV1 (VR-1) protein distribution. Brain Res., 995, 176–183. 101. Birder, L. A., Kanai, A. J., de Groat, W. C., Kiss, S., Nealen, M. L., Burke, N. E., Dineley, K. E., Watkins, S., Reynolds, I. J., and Caterina, M. J. (2001). Vanilloid receptor expression suggests a sensory role for urinary bladder epithelial cells. Proc. Natl. Acad. Sci. USA, 98, 13396–13401. 102. Bevan, S., and Geppetti, P. (1994). Protons: small stimulants of capsaicin-sensitive sensory nerves. Trends Neurosci., 17, 509–512. 103. Bunnett, N. W., and Geppetti, P. (2003). Mechanisms by which lipid derivatives and proteinases signal to primary sensory neurons: implications for inflammation and pain. In J. Bienenstock, E. J. Goetzl, and M. G. Blennerhassett (Eds.). Autonomic neuroimmunology (pp. 197–214). London: Taylor & Francis. 104. Biro, T., Maurer, M., Modarres, S., Lewin, N. E., Brodie, C., Acs, G., Acs, P., Paus, R., and Blumberg, P. M. (1998). Characterization of functional vanilloid receptors expressed by mast cells. Blood, 91, 1332–1340. 105. Cortright, D. N., and Szallasi, A. (2004). Biochemical pharmacology of the vanilloid receptor TRPV1. An update. Eur. J. Biochem., 271, 1814–1819. 106. Joos, G. F., Germonpre, P. R., and Pauwels, R. A. (2000). Role of tachykinins in asthma. Allergy, 55, 321–337. 107. Solway, J., and Leff, A. R. (1991). Sensory neuropeptides and airway function. J. Appl. Physiol., 71, 2077–2087. 108. Advenier, C., Lagente, V., and Boichot, E. (1997). The role of tachykinin receptor antagonists in the prevention of bronchial hyperresponsiveness, airway inflammation and cough. Eur. Respir. J., 10, 1892–1906. 109. Krause, J. E., Bu, J. Y., Takeda, Y., Blount, P., Raddatz, R., Sachais, B. S., Chou, K. B., Takeda, J., McCarson, K., and DiMaggio, D. (1993). Structure, expression and second messenger-mediated regulation of the human and rat substance P receptors and their genes. Regul. Pept., 46, 59–66.
4. Significance of Sensory Neuropeptides and the Immune Response 110. Buell, G., Schulz, M. F., Arkinstall, S. J., Maury, K., Missotten, M., Adami, N., Talabot, F., and Kawashima, E. (1992). Molecular characterisation, expression and localisation of human neurokinin-3 receptor. FEBS Lett., 299, 90–95. 111. Regoli, D., Boudon, A., and Fauchere, J. L. (1994). Receptors and antagonists for substance P and related peptides. Pharmacol. Rev., 46, 551–599. 112. Baluk, P., Bowden, J. J., Lefevre, P. M., and McDonald, D. M. (1997). Upregulation of substance P receptors in angiogenesis associated with chronic airway inflammation in rats. Am. J. Physiol., 273, L565–L571. 113. Maggi, C. A. (1995). The mammalian tachykinin receptors. Gen. Pharmacol., 26, 911–944. 114. Grady, E. F., Baluk, P., Bohm, S., Gamp, P. D., Wong, H., Payan, D. G., Ansel, J., Portbury, A. L., Furness, J. B., McDonald, D. M., and Bunnett, N. W. (1996). Characterization of antisera specific to NK1, NK2, and NK3 neurokinin receptors and their utilization to localize receptors in the rat gastrointestinal tract. J. Neurosci., 16, 6975–6986. 115. Bannon, M. J., Brownschidle, L. A., Tian, Y., Whitty, C. J., Poosch, M. S., D’sa, C., and Moody, C. A. (1995). Neurokinin-3 receptors modulate dopamine cell function and alter the effects of 6-hydroxydopamine. Brain Res., 695, 19–24. 116. Johnson, P. J., Bornstein, J. C., and Burcher, E. (1998). Roles of neuronal NK1 and NK3 receptors in synaptic transmission during motility reflexes in the guinea-pig ileum. Br. J. Pharmacol., 124, 1375–1384. 117. Mileusnic, D., Lee, J. M., Magnuson, D. J., Hejna, M. J., Krause, J. E., Lorens, J. B., and Lorens, S. A. (1999). Neurokinin-3 receptor distribution in rat and human brain: an immunohistochemical study. Neuroscience, 89, 1269–1290. 118. Massi, M., Panocka, I., and de Caro, G. (2000). The psychopharmacology of tachykinin NK-3 receptors in laboratory animals. Peptides, 21, 1597–1609. 119. Marriott, I., and Bost, K. L. (2001). Substance P receptor mediated macrophage responses. Adv. Exp. Med. Biol., 493, 247– 254. 120. Rasley, A., Bost, K. L., Olson, J. K., Miller, S. D., and Marriott, I. (2002). Expression of functional NK-1 receptors in murine microglia. Glia, 37, 258–267. 121. Marriott, I., and Bost, K. L. (2001). Expression of authentic substance P receptors in murine and human dendritic cells. J. Neuroimmunol., 114, 131–141. 122. Blum, A. M., Metwali, A., Elliott, D. E., and Weinstock, J. V. (2003). T cell substance P receptor governs antigen-elicited IFNgamma production. Am. J. Physiol. Gastrointest. Liver Physiol., 284, G197–G204. 123. Payan, D. G., Levine, J. D., and Goetzl, E. J. (1984). Modulation of immunity and hypersensitivity by sensory neuropeptides. J. Immunol., 132, 1601–1604. 124. van Ginkel, F. W., and Pascual, D. W. (1996). Recognition of neurokinin 1 receptor (NK1–R): an antibody to a peptide sequence from the third extracellular region binds to brain NK1–R. J. Neuroimmunol., 67, 49–58. 125. Dorsam, G., Chan, R. C., and Goetzl, E. J. (2003). Developmental regulation and functional integration by the vasoactive intestinal peptide (VIP) neuroimmune mediator. In J. Bienenstock, E. J. Goetzl, and M. G. Blennerhassett (Eds.), Autonomic neuroimmunology (pp. 75–94). London: Taylor & Francis. 126. Kaltreider, H. B., Ichikawa, S., Byrd, P. K., Ingram, D. A., Kishiyama, J. L., Sreedharan, S. P., Warnock, M. L., Beck, J. M., and Goetzl, E. J. (1997). Upregulation of neuropeptides and neuropeptide receptors in a murine model of immune inflammation in lung parenchyma. Am. J. Respir. Cell Mol. Biol., 16, 133–144.
121
127. Ekblad, E., Winther, C., Ekman, R., Hakanson, R., and Sundler, F. (1987). Projections of peptide-containing neurons in rat small intestine. Neuroscience, 20, 169–188. 128. Felten, D. L., Felten, S. Y., Carlson, S. L., Olschowka, J. A., and Livnat, S. (1985). Noradrenergic and peptidergic innervation of lymphoid tissue. J. Immunol., 135, 755s–765s. 129. Ottaway, C. A., and Greenberg, G. R. (1984). Interaction of vasoactive intestinal peptide with mouse lymphocytes: specific binding and the modulation of mitogen responses. J. Immunol., 132, 417–423. 130. Delgado, M., Martinez, C., Johnson, M. C., Gomariz, R. P., and Ganea, D. (1996). Differential expression of vasoactive intestinal peptide receptors 1 and 2 (VIP-R1 and VIP-R2) mRNA in murine lymphocytes. J. Neuroimmunol., 68, 27–38. 131. Delgado, M., Martinez, C., Leceta, J., and Gomariz, R. P. (1999). Vasoactive intestinal peptide in thymus: synthesis, receptors and biological actions. Neuroimmunomodulation, 6, 97–107. 132. Di Maria, G. U., Spicuzza, L., Mistretta, A., and Mazzarella, G. (2000). Role of endogenous nitric oxide in asthma. Allergy, 55 (Suppl 61), 31–35. 133. Seiffert, K., and Granstein, R. D. (2002). Neuropeptides and neuroendocrine hormones in ultraviolet radiation-induced immunosuppression. Methods, 28, 97–103. 134. Fischer, A., Mundel, P., Mayer, B., Preissler, U., Philippin, B., and Kummer, W. (1993). Nitric oxide synthase in guinea pig lower airway innervation. Neurosci. Lett., 149, 157–160. 135. Hamid, Q., Springall, D. R., Riveros-Moreno, V., Chanez, P., Howarth, P., Redington, A., Bousquet, J., Godard, P., Holgate, S., and Polak, J. M. (1993). Induction of nitric oxide synthase in asthma. Lancet, 342, 1510–1513. 136. Arimura, A. (1998). Perspectives on pituitary adenylate cyclase activating polypeptide (PACAP) in the neuroendocrine, endocrine, and nervous systems. Jpn. J. Physiol., 48, 301–331. 137. Delgado, M., Pozo, D., Martinez, C., Leceta, J., Calvo, J. R., Ganea, D., and Gomariz, R. P. (1999). Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide inhibit endotoxin-induced TNF-alpha production by macrophages: in vitro and in vivo studies. J. Immunol., 162, 2358– 2367. 138. Delgado, M., Munoz-Elias, E. J., Gomariz, R. P., and Ganea, D. (1999). Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide enhance IL-10 production by murine macrophages: in vitro and in vivo studies. J. Immunol., 162, 1707–1716. 139. Delgado, M., Abad, C., Martinez, C., Juarranz, M. G., Leceta, J., Ganea, D., and Gomariz, R. P. (2003). PACAP in immunity and inflammation. Ann. N. Y. Acad. Sci., 992, 141–157. 140. Delgado, M., Leceta, J., and Ganea, D. (2003). Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide inhibit the production of inflammatory mediators by activated microglia. J. Leukoc. Biol., 73, 155–164. 141. Herbert, M. K., and Holzer, P. (1994). Interleukin-1 beta enhances capsaicin-induced neurogenic vasodilatation in the rat skin. Br. J. Pharmacol., 111, 681–686. 142. Rodrigo, J., Polak, J. M., Fernandez, L., Ghatei, M. A., Mulderry, P., and Bloom, S. R. (1985). Calcitonin gene-related peptide immunoreactive sensory and motor nerves of the rat, cat, and monkey esophagus. Gastroenterology, 88, 444–451. 143. Bulloch, K., McEwen, B. S., Nordberg, J., Diwa, A., and Baird, S. (1998). Selective regulation of T-cell development and function by calcitonin gene-related peptide in thymus and spleen. An example of differential regional regulation of immunity by the neuroendocrine system. Ann. N. Y. Acad. Sci., 840, 551–562.
122
I. Neural and Endocrine Effects on Immunity
144. McGillis, J. P., Humphreys, S., Rangnekar, V., and Ciallella, J. (1993). Modulation of B lymphocyte differentiation by calcitonin gene-related peptide (CGRP). I. Characterization of highaffinity CGRP receptors on murine 70Z/3 cells. Cell. Immunol., 150, 391–404. 145. Mullins, M. W., Ciallella, J., Rangnekar, V., and McGillis, J. P. (1993). Characterization of a calcitonin gene-related peptide (CGRP) receptor on mouse bone marrow cells. Regul. Pept., 49, 65–72. 146. Seifert, H., Chesnut, J., De Souza, E., Rivier, J., and Vale, W. (1985). Binding sites for calcitonin gene-related peptide in distinct areas of rat brain. Brain Res., 346, 195–198. 147. Tschopp, F. A., Henke, H., Petermann, J. B., Tobler, P. H., Janzer, R., Hokfelt, T., Lundberg, J. M., Cuello, C., and Fischer, J. A. (1985). Calcitonin gene-related peptide and its binding sites in the human central nervous system and pituitary. Proc. Natl. Acad. Sci. USA, 82, 248–252. 148. Dennis, T., Fournier, A., St Pierre, S., and Quirion, R. (1989). Structure-activity profile of calcitonin gene-related peptide in peripheral and brain tissues. Evidence for receptor multiplicity. J. Pharmacol. Exp. Ther., 251, 718–725. 149. Torii, H., Yan, Z., Hosoi, J., and Granstein, R. D. (1997). Expression of neurotrophic factors and neuropeptide receptors by Langerhans cells and the Langerhans cell-like cell line XS52, further support for a functional relationship between Langerhans cells and epidermal nerves. J. Invest. Dermatol., 109, 586– 591. 150. Asahina, A., Hosoi, J., Beissert, S., Stratigos, A., and Granstein, R. D. (1995). Inhibition of the induction of delayed-type and contact hypersensitivity by calcitonin gene-related peptide. J. Immunol., 154, 3056–3061. 151. Hosoi, J., Murphy, G. F., Egan, C. L., Lerner, E. A., Grabbe, S., Asahina, A., and Granstein, R. D. (1993). Regulation of Langerhans cell function by nerves containing calcitonin generelated peptide. Nature, 363, 159–163. 152. Kitazawa, T., and Streilein, J. W. (2000). Hapten-specific tolerance promoted by calcitonin gene-related peptide. J. Invest. Dermatol., 115, 942–948. 153. Weinstock, J. V., Blum, A., Walder, J., and Walder, R. (1988). Eosinophils from granulomas in murine schistosomiasis mansoni produce substance P. J. Immunol., 141, 961–966. 154. Garssen, J., Nijkamp, F. P., Van Vugt, E., Van V, D., and Van Loveren, H., (1994). T cell–derived antigen binding molecules play a role in the induction of airway hyperresponsiveness. Am. J. Respir. Crit. Care Med., 150, 1528–1538. 155. Metwali, A., Blum, A. M., Ferraris, L., Klein, J. S., Fiocchi, C., and Weinstock, J. V. (1994). Eosinophils within the healthy or inflamed human intestine produce substance P and vasoactive intestinal peptide. J. Neuroimmunol., 52, 69–78. 156. Bost, K. L., Breeding, S. A., and Pascual, D. W. (1992). Modulation of the mRNAs encoding substance P and its receptor in rat macrophages by LPS. Reg. Immunol., 4, 105–112. 157. Maggi, C. A. (1997). The effects of tachykinins on inflammatory and immune cells. Regul. Pept., 70, 75–90. 158. Kawashima, K., and Fujii, T. (2004). Expression of nonneuronal acetylcholine in lymphocytes and its contribution to the regulation of immune function. Front. Biosci., 9, 2063–2085. 159. Kawashima, K., Fujii, T., Watanabe, Y., and Misawa, H. (1998). Acetylcholine synthesis and muscarinic receptor subtype mRNA expression in T-lymphocytes. Life Sci., 62, 1701–1705. 160. Kuo, Y., Lucero, L., Michaels, J., DeLuca, D., and Lukas, R. J. (2002). Differential expression of nicotinic acetylcholine receptor subunits in fetal and neonatal mouse thymus. J. Neuroimmunol., 130, 140–154.
161. Pan, H., and Gershon, M. D. (2000). Activation of intrinsic afferent pathways in submucosal ganglia of the guinea pig small intestine. J. Neurosci., 20, 3295–3309. 162. Timmermans, J. P., Hens, J., and Adriaensen, D. (2001). Outer submucous plexus: an intrinsic nerve network involved in both secretory and motility processes in the intestine of large mammals and humans. Anat. Rec., 262, 71–78. 163. Kunze, W. A., and Furness, J. B. (1999). The enteric nervous system and regulation of intestinal motility. Annu. Rev. Physiol., 61, 117–142. 164. Wood, J. D. (2004). Enteric neuroimmunophysiology and pathophysiology. Gastroenterology, 127, 635–657. 165. Cooke, H. J., Sidhu, M., Fox, P., Wang, Y. Z., and Zimmermann, E. M. (1997). Substance P as a mediator of colonic secretory reflexes. Am. J. Physiol, 272, G238–G245. 166. MacNaughton, W., Moore, B., and Vanner, S. (1997). Cellular pathways mediating tachykinin-evoked secretomotor responses in guinea pig ileum. Am. J. Physiol., 273, G1127–G1134. 167. Tracey, K. J. (2002). The inflammatory reflex. Nature, 420, 853–859. 168. Czura, C. J., and Tracey, K. J. (2005). Autonomic neural regulation of immunity. J. Intern. Med., 257, 156–166. 169. Wang, H., Yu, M., Ochani, M., Amella, C. A., Tanovic, M., Susarla, S., Li, J. H., Wang, H., Yang, H., Ulloa, L., Al Abed, Y., Czura, C. J., and Tracey, K. J. (2003). Nicotinic acetylcholine receptor alpha7 subunit is an essential regulator of inflammation. Nature, 421, 384–388. 170. Borovikova, L. V., Ivanova, S., Zhang, M., Yang, H., Botchkina, G. I., Watkins, L. R., Wang, H., Abumrad, N., Eaton, J. W., and Tracey, K. J. (2000). Vagus nerve stimulation attenuates the systemic inflammatory response to endotoxin. Nature, 405, 458–462. 171. Donnerer, J., Schuligoi, R., and Stein, C. (1992). Increased content and transport of substance P and calcitonin generelated peptide in sensory nerves innervating inflamed tissue: evidence for a regulatory function of nerve growth factor in vivo. Neuroscience, 49, 693–698. 172. MacLean, D. B., Lewis, S. F., and Wheeler, F. B. (1988). Substance P content in cultured neonatal rat vagal sensory neurons: the effect of nerve growth factor. Brain Res., 457, 53–62. 173. Lewin, G. R., and Barde, Y. A. (1996). Physiology of the neurotrophins. Annu. Rev. Neurosci., 19, 289–317. 174. Hattori, A., Hayashi, K., and Kohno, M. (1996). Tumor necrosis factor (TNF) stimulates the production of nerve growth factor in fibroblasts via the 55–kDa type 1 TNF receptor. FEBS Lett., 379, 157–160. 175. van der Kleij, H. P., Blennerhassett, M. G., and Bienenstock, J. (2003). Nerve-mast cell interactions—partnership in health and disease. In J. Bienenstock, E. J. Goetzl, and M. G. Blennerhassett (Eds.), Autonomic neuroimmunology (pp. 139–170). London: Taylor & Francis. 176. Matsuda, H., Kannan, Y., Ushio, H., Kiso, Y., Kanemoto, T., Suzuki, H., and Kitamura, Y. (1991). Nerve growth factor induces development of connective tissue-type mast cells in vitro from murine bone marrow cells. J. Exp. Med., 174, 7–14. 177. Welker, P., Grabbe, J., Grutzkau, A., and Henz, B. M. (1998). Effects of nerve growth factor (NGF) and other fibroblastderived growth factors on immature human mast cells (HMC1). Immunology, 94, 310–317. 178. Hamada, A., Watanabe, N., Ohtomo, H., and Matsuda, H. (1996). Nerve growth factor enhances survival and cytotoxic activity of human eosinophils. Br. J. Haematol., 93, 299–302. 179. Marshall, J. S., Gomi, K., Blennerhassett, M. G., and Bienenstock, J. (1999). Nerve growth factor modifies the expression of
4. Significance of Sensory Neuropeptides and the Immune Response
180.
181.
182.
183.
184.
185.
186.
187.
188.
189.
190.
191.
192.
193.
194.
195.
inflammatory cytokines by mast cells via a prostanoiddependent mechanism. J. Immunol., 162, 4271–4276. Horigome, K., Pryor, J. C., Bullock, E. D., and Johnson, E. M. Jr. (1993). Mediator release from mast cells by nerve growth factor. Neurotrophin specificity and receptor mediation. J. Biol. Chem., 268, 14881–14887. Lindsay, R. M., and Harmar, A. J. (1989). Nerve growth factor regulates expression of neuropeptide genes in adult sensory neurons. Nature, 337, 362–364. Marshall, J. S., Stead, R. H., McSharry, C., Nielsen, L., and Bienenstock, J. (1990). The role of mast cell degranulation products in mast cell hyperplasia. I. Mechanism of action of nerve growth factor. J. Immunol., 144, 1886–1892. Bischoff, S. C., and Dahinden, C. A. (1992). Effect of nerve growth factor on the release of inflammatory mediators by mature human basophils. Blood, 79, 2662–2669. Purcell, W. M., Westgate, C., and Atterwill, C. K. (1996). Rat brain mast cells: an in vitro paradigm for assessing the toxic effects of neurotropic therapeutics. Neurotoxicology, 17, 845– 850. Bergman, E., Ulfhake, B., and Fundin, B. T. (2000). Regulation of NGF-family ligands and receptors in adulthood and senescence: correlation to degenerative and regenerative changes in cutaneous innervation. Eur. J. Neurosci., 12, 2694–2706. Botchkarev, V. A., Botchkareva, N. V., Peters, E. M., and Paus, R. (2004). Epithelial growth control by neurotrophins: leads and lessons from the hair follicle. Prog. Brain Res., 146, 493–513. Leon, A., Buriani, A., Dal Toso, R., Fabris, M., Romanello, S., Aloe, L., and Levi-Montalcini, R. (1994). Mast cells synthesize, store, and release nerve growth factor. Proc. Natl. Acad. Sci. USA, 91, 3739–3743. Mizuma, H., Takagi, K., Miyake, K., Takagi, N., Ishida, K., Takeo, S., Nitta, A., Nomoto, H., Furukawa, Y., and Furukawa, S. (1999). Microsphere embolism-induced elevation of nerve growth factor level and appearance of nerve growth factor immunoreactivity in activated T-lymphocytes in the rat brain. J. Neurosci. Res., 55, 749–761. Solomon, A., Aloe, L., Pe’er, J., Frucht-Pery, J., Bonini, S., and Levi-Schaffer, F. (1998). Nerve growth factor is preformed in and activates human peripheral blood eosinophils. J. Allergy Clin. Immunol., 102, 454–460. Barouch, R., Appel, E., Kazimirsky, G., Braun, A., Renz, H., and Brodie, C. (2000). Differential regulation of neurotrophin expression by mitogens and neurotransmitters in mouse lymphocytes. J. Neuroimmunol., 103, 112–121. Fox, A. J., Patel, H. J., Barnes, P. J., and Belvisi, M. G. (2001). Release of nerve growth factor by human pulmonary epithelial cells: role in airway inflammatory diseases. Eur. J. Pharmacol., 424, 159–162. Braun, A., Lommatzsch, M., Lewin, G. R., Virchow, J. C., and Renz, H. (1999). Neurotrophins: a link between airway inflammation and airway smooth muscle contractility in asthma? Int. Arch. Allergy Immunol., 118, 163–165. Ehrhard, P. B., Erb, P., Graumann, U., Schmutz, B., and Otten, U. (1994). Expression of functional trk tyrosine kinase receptors after T cell activation. J. Immunol., 152, 2705–2709. Lambiase, A., Bracci-Laudiero, L., Bonini, S., Starace, G., D’Elios, M. M., De Carli, M., and Aloe, L. (1997). Human CD4+ T cell clones produce and release nerve growth factor and express high-affinity nerve growth factor receptors. J. Allergy Clin. Immunol., 100, 408–414. Kerschensteiner, M., Gallmeier, E., Behrens, L., Leal, V. V., Misgeld, T., Klinkert, W. E., Kolbeck, R., Hoppe, E., Oropeza-
196.
197.
198.
199.
200.
201.
202.
203.
204.
205.
206.
207.
208.
123
Wekerle, R. L., Bartke, I., Stadelmann, C., Lassmann, H., Wekerle, H., and Hohlfeld, R. (1999). Activated human T cells, B cells, and monocytes produce brain-derived neurotrophic factor in vitro and in inflammatory brain lesions: a neuroprotective role of inflammation? J. Exp. Med., 189, 865–870. Radka, S. F., Holst, P. A., Fritsche, M., and Altar, C. A. (1996). Presence of brain-derived neurotrophic factor in brain and human and rat but not mouse serum detected by a sensitive and specific immunoassay. Brain Res., 709, 122–301. Braun, A., Quarcoo, D., Schulte-Herbruggen, O., Lommatzsch, M., Hoyle, G., and Renz, H. (2001). Nerve growth factor induces airway hyperresponsiveness in mice. Int. Arch. Allergy Immunol., 124, 205–207. Villoslada, P., Hauser, S. L., Bartke, I., Unger, J., Heald, N., Rosenberg, D., Cheung, S. W., Mobley, W. C., Fisher, S., and Genain, C. P. (2000). Human nerve growth factor protects common marmosets against autoimmune encephalomyelitis by switching the balance of T helper cell type 1 and 2 cytokines within the central nervous system. J. Exp. Med., 191, 1799– 1806. Flugel, A., Matsumuro, K., Neumann, H., Klinkert, W. E., Birnbacher, R., Lassmann, H., Otten, U., and Wekerle, H. (2001). Anti-inflammatory activity of nerve growth factor in experimental autoimmune encephalomyelitis: inhibition of monocyte transendothelial migration. Eur. J. Immunol., 31, 11–22. Reinshagen, M., Rohm, H., Steinkamp, M., Lieb, K., Geerling, I., Von Herbay, A., Flamig, G., Eysselein, V. E., and Adler, G. (2000). Protective role of neurotrophins in experimental inflammation of the rat gut. Gastroenterology, 119, 368–376. Felten, D. L., Felten, S. Y., Bellinger, D. L., and Lorton, D. (1992). Noradrenergic and peptidergic innervation of secondary lymphoid organs: role in experimental rheumatoid arthritis. Eur. J. Clin. Invest., 22 (Suppl 1), 37–41. Covas, M. J., Pinto, L. A., and Victorino, R. M. (1997). Effects of substance P on human T cell function and the modulatory role of peptidase inhibitors. Int. J. Clin. Lab Res., 27, 129–134. Stanisz, A. M., Befus, D., and Bienenstock, J. (1986). Differential effects of vasoactive intestinal peptide, substance P, and somatostatin on immunoglobulin synthesis and proliferations by lymphocytes from Peyer’s patches, mesenteric lymph nodes, and spleen. J. Immunol., 136, 152–156. Schratzberger, P., Reinisch, N., Prodinger, W. M., Kahler, C. M., Sitte, B. A., Bellmann, R., Fischer-Colbrie, R., Winkler, H., and Wiedermann, C. J. (1997). Differential chemotactic activities of sensory neuropeptides for human peripheral blood mononuclear cells. J. Immunol., 158, 3895–3901. Levite, M. (1998). Neuropeptides, by direct interaction with T cells, induce cytokine secretion and break the commitment to a distinct T helper phenotype. Proc. Natl. Acad. Sci. USA, 95, 12544–12549. Blum, A. M., Metwali, A., Kim-Miller, M., Li, J., Qadir, K., Elliott, D. E., Lu, B., Fabry, Z., Gerard, N., and Weinstock, J. V. (1999). The substance P receptor is necessary for a normal granulomatous response in murine schistosomiasis mansoni. J. Immunol., 162, 6080–6085. Pascual, D. W., McGhee, J. R., Kiyono, H., and Bost, K. L. (1991). Neuroimmune modulation of lymphocyte function—I. Substance P enhances immunoglobulin synthesis in lipopolysaccharide activated murine splenic B cell cultures. Int. Immunol., 3, 1223–1229. Kimata, H., and Fujimoto, M. (1994). Vasoactive intestinal peptide specifically induces human IgA1 and IgA2 production. Eur. J. Immunol., 24, 2262–2265.
124
I. Neural and Endocrine Effects on Immunity
209. Hokfelt, T., Pernow, B., and Wahren, J. (2001). Substance P: a pioneer amongst neuropeptides. J. Intern. Med., 249, 27–40. 210. Joos, G. F., De Swert, K. O., and Pauwels, R. A. (2001). Airway inflammation and tachykinins: prospects for the development of tachykinin receptor antagonists. Eur. J. Pharmacol., 429, 239–250. 211. Kataeva, G., Agro, A., and Stanisz, A. M. (1994). Substance-P– mediated intestinal inflammation: inhibitory effects of CP 96,345 and SMS 201–995. Neuroimmunomodulation, 1, 350–356. 212. Bellucci, F., Carini, F., Catalani, C., Cucchi, P., Lecci, A., Meini, S., Patacchini, R., Quartara, L., Ricci, R., Tramontana, M., Giuliani, S., and Maggi, C. A. (2002). Pharmacological profile of the novel mammalian tachykinin, hemokinin 1. Br. J. Pharmacol., 135, 266–274. 213. Della, C. M., Sivori, S., Castriconi, R., Marcenaro, E., and Moretta, A. (2005). Pathogen-induced private conversations between natural killer and dendritic cells. Trends Microbiol., 13, 128–136. 214. Lambrecht, B. N. (2001). Immunologists getting nervous: neuropeptides, dendritic cells and T cell activation. Respir. Res., 2, 133–138. 215. Fischer, H. G., and Reichmann, G. (2001). Brain dendritic cells and macrophages/microglia in central nervous system inflammation. J. Immunol., 166, 2717–2726. 216. Markus, A. M., Kockerling, F., and Neuhuber, W. L. (1998). Close anatomical relationships between nerve fibers and MHC class II-expressing dendritic cells in the rat liver and extrahepatic bile duct. Histochem. Cell Biol., 109, 409–415. 217. Kradin, R., MacLean, J., Duckett, S., Schneeberger, E. E., Waeber, C., and Pinto, C. (1997). Pulmonary response to inhaled antigen: neuroimmune interactions promote the recruitment of dendritic cells to the lung and the cellular immune response to inhaled antigen. Am. J. Pathol., 150, 1735–1743. 218. Dunzendorfer, S., Kaser, A., Meierhofer, C., Tilg, H., and Wiedermann, C. J. (2001). Cutting edge: peripheral neuropeptides attract immature and arrest mature blood-derived dendritic cells. J. Immunol., 166, 2167–2172. 219. Carucci, J. A., Ignatius, R., Wei, Y., Cypess, A. M., Schaer, D. A., Pope, M., Steinman, R. M., and Mojsov, S. (2000). Calcitonin gene-related peptide decreases expression of HLA-DR and CD86 by human dendritic cells and dampens dendritic cell-driven T cell-proliferative responses via the type I calcitonin gene-related peptide receptor. J. Immunol., 164, 3494–3499. 220. Dieu-Nosjean, M. C., Vicari, A., Lebecque, S., and Caux, C. (1999). Regulation of dendritic cell trafficking: a process that involves the participation of selective chemokines. J. Leukoc. Biol., 66, 252–262. 221. Bardelli, C., Gunella, G., Varsaldi, F., Balbo, P., Del Boca, E., Bernardone, I. S., Amoruso, A., and Brunelleschi, S. (2005). Expression of functional NK1 receptors in human alveolar macrophages: superoxide anion production, cytokine release and involvement of NF-kappaB pathway. Br. J. Pharmacol., 145, 385–396. 222. Lotz, M., Vaughan, J. H., and Carson, D. A. (1988). Effect of neuropeptides on production of inflammatory cytokines by human monocytes. Science, 241, 1218–1221. 223. Chancellor-Freeland, C., Zhu, G. F., Kage, R., Beller, D. I., Leeman, S. E., and Black, P. H. (1995). Substance P and stressinduced changes in macrophages. Ann. N. Y. Acad. Sci., 771, 472–484. 224. Marriott, I., and Bost, K. L. (1998). Substance P diminishes lipopolysaccharide and interferon-gamma-induced TGF-beta 1 production by cultured murine macrophages. Cell. Immunol., 183, 113–120.
225. Berman, A. S., Chancellor-Freeland, C., Zhu, G., and Black, P. H. (1996). Substance P primes murine peritoneal macrophages for an augmented proinflammatory cytokine response to lipopolysaccharide. Neuroimmunomodulation, 3, 141–149. 226. Lieb, K., Fiebich, B. L., Busse-Grawitz, M., Hull, M., Berger, M., and Bauer, J. (1996). Effects of substance P and selected other neuropeptides on the synthesis of interleukin-1 beta and interleukin-6 in human monocytes: a re-examination. J. Neuroimmunol., 67, 77–81. 227. Zhu, G. F., Chancellor-Freeland, C., Berman, A. S., Kage, R., Leeman, S. E., Beller, D. I., and Black, P. H. (1996). Endogenous substance P mediates cold water stress-induced increase in interleukin-6 secretion from peritoneal macrophages. J. Neurosci., 16, 3745–3752. 228. Hartung, H. P. (1988). Activation of macrophages by neuropeptides. Brain Behav. Immun., 2, 275–281. 229. Peck, R. (1987). Neuropeptides modulating macrophage function. Ann. N. Y. Acad. Sci., 496, 264–270. 230. Agelaki, S., Tsatsanis, C., Gravanis, A., and Margioris, A. N. (2002). Corticotropin-releasing hormone augments proinflammatory cytokine production from macrophages in vitro and in lipopolysaccharide-induced endotoxin shock in mice. Infect. Immun., 70, 6068–6074. 231. Braun, A., and Renz, H. (2003). Neuroimmune control of the pulmonary immune response. In J. Bienenstock, E. J. Goetzl, and M. G. Blennerhassett (Eds.), Autonomic neuroimmunology (pp. 295–317). London: Francis & Taylor. 232. Dunzendorfer, S., Meierhofer, C., and Wiedermann, C. J. (1998). Signaling in neuropeptide-induced migration of human eosinophils. J. Leukoc. Biol., 64, 828–834. 233. Serra, M. C., Calzetti, F., Ceska, M., and Cassatella, M. A. (1994). Effect of substance P on superoxide anion and IL-8 production by human PMNL. Immunology, 82, 63–69. 234. Kroegel, C., Giembycz, M. A., and Barnes, P. J. (1990). Characterization of eosinophil cell activation by peptides. Differential effects of substance P, melittin, and FMET-Leu-Phe. J. Immunol., 145, 2581–2587. 235. Bellibas, S. E. (1996). The effect of human calcitonin generelated peptide on eosinophil chemotaxis in the rat airway. Peptides, 17, 563–564. 236. Numao, T., and Agrawal, D. K. (1992). Neuropeptides modulate human eosinophil chemotaxis. J. Immunol., 149, 3309–3315. 237. Von Essen, S. G., Rennard, S. I., O’Neill, D., Ertl, R. F., Robbins, R. A., Koyama, S., and Rubinstein, I. (1992). Bronchial epithelial cells release neutrophil chemotactic activity in response to tachykinins. Am. J. Physiol., 263, L226–L231. 238. DeRose, V., Robbins, R. A., Snider, R. M., Spurzem, J. R., Thiele, G. M., Rennard, S. I., and Rubinstein, I. (1994). Substance P increases neutrophil adhesion to bronchial epithelial cells. J. Immunol., 152, 1339–1346. 239. Scholzen, T., Armstrong, C. A., Bunnett, N. W., Luger, T. A., Olerud, J. E., and Ansel, J. C. (1998). Neuropeptides in the skin: interactions between the neuroendocrine and the skin immune systems. Exp. Dermatol., 7, 81–96. 240. Alving, K., Sundstrom, C., Matran, R., Panula, P., Hokfelt, T., and Lundberg, J. M. (1991). Association between histaminecontaining mast cells and sensory nerves in the skin and airways of control and capsaicin-treated pigs. Cell Tissue Res., 264, 529–538. 241. Dimitriadou, V., Rouleau, A., Trung, T., Newlands, G. J., Miller, H. R., Luffau, G., Schwartz, J. C., and Garbarg, M. (1997). Functional relationships between sensory nerve fibers and mast cells
4. Significance of Sensory Neuropeptides and the Immune Response
242.
243.
244.
245.
246.
247.
248.
249.
250.
251.
252.
253.
254. 255.
256.
257.
of dura mater in normal and inflammatory conditions. Neuroscience, 77, 829–839. Rozniecki, J. J., Dimitriadou, V., Lambracht-Hall, M., Pang, X., and Theoharides, T. C. (1999). Morphological and functional demonstration of rat dura mater mast cell-neuron interactions in vitro and in vivo. Brain Res., 849, 1–15. Williams, R. M., Bienenstock, J., and Stead, R. H. (1995). Mast cells: the neuroimmune connection. Chem. Immunol., 61, 208– 235. Mori, N., Suzuki, R., Furuno, T., McKay, D. M., Wada, M., Teshima, R., Bienenstock, J., and Nakanishi, M. (2002). Nervemast cell (RBL) interaction: RBL membrane ruffling occurs at the contact site with an activated neurite. Am. J. Physiol. Cell. Physiol., 283, C1738–C1744. Church, M. K., Lowman, M. A., Rees, P. H., and Benyon, R. C. (1989). Mast cells, neuropeptides and inflammation. Agents Actions, 27, 8–16. Defea, K., Schmidlin, F., Dery, O., Grady, E. F., and Bunnett, N. W. (2000). Mechanisms of initiation and termination of signalling by neuropeptide receptors: a comparison with the proteinase-activated receptors. Biochem. Soc. Trans., 28, 419–426. Steinhoff, M., Corvera, C. U., Thoma, M. S., Kong, W., McAlpine, B. E., Caughey, G. H., Ansel, J. C., and Bunnett, N. W. (1999). Proteinase-activated receptor-2 in human skin: tissue distribution and activation of keratinocytes by mast cell tryptase. Exp. Dermatol., 8, 282–294. Michaelis, M., Vogel, C., Blenk, K. H., Arnarson, A., and Janig, W. (1998). Inflammatory mediators sensitize acutely axotomized nerve fibers to mechanical stimulation in the rat. J. Neurosci., 18, 7581–7587. Hua, X. Y., and Yaksh, T. L. (1993). Pharmacology of the effects of bradykinin, serotonin, and histamine on the release of calcitonin gene-related peptide from C-fiber terminals in the rat trachea. J. Neurosci., 13, 1947–1953. Imamura, M., Smith, N. C., Garbarg, M., and Levi, R. (1996). Histamine H3-receptor–mediated inhibition of calcitonin generelated peptide release from cardiac C fibers. A regulatory negative-feedback loop. Circ. Res., 78, 863–869. Sekizawa, S., Tsubone, H., Kuwahara, M., and Sugano, S. (1998). Does histamine stimulate trigeminal nasal afferents? Respir. Physiol., 112, 13–22. Kashiba, H., Fukui, H., Morikawa, Y., and Senba, E. (1999). Gene expression of histamine H1 receptor in guinea pig primary sensory neurons: a relationship between H1 receptor mRNAexpressing neurons and peptidergic neurons. Brain Res. Mol. Brain Res., 66, 24–34. van Houwelingen, A. H., Kool, M., de Jager, S. C., Redegeld, F. A., Heuven-Nolsen, D., Kraneveld, A. D., and Nijkamp, F. P. (2002). Mast cell–derived TNF-alpha primes sensory nerve endings in a pulmonary hypersensitivity reaction. J. Immunol., 168, 5297–5302. Theoharides, T. C. (1996). The mast cell: a neuroimmunoendocrine master player. Int. J. Tissue React., 18, 1–21. Goetzl, E. J., Cheng, P. P., Hassner, A., Adelman, D. C., Frick, O. L., and Sreedharan, S. P. (1990). Neuropeptides, mast cells and allergy: novel mechanisms and therapeutic possibilities. Clin. Exp. Allergy, 20 (Suppl 4), 3–7. Theoharides, T. C., and Douglas, W. W. (1978). Somatostatin induces histamine secretion from rat peritoneal mast cells. Endocrinology, 102, 1637–1640. Carraway, R., Cochrane, D. E., Lansman, J. B., Leeman, S. E., Paterson, B. M., and Welch, H. J. (1982). Neurotensin stimulates exocytotic histamine secretion from rat mast cells and elevates plasma histamine levels. J. Physiol., 323, 403–414.
125
258. Seebeck, J., Kruse, M. L., Schmidt-Choudhury, A., Schmidtmayer, J., and Schmidt, W. E. (1998). Pituitary adenylate cyclase activating polypeptide induces multiple signaling pathways in rat peritoneal mast cells. Eur. J. Pharmacol., 352, 343–350. 259. Piotrowski, W., and Foreman, J. C. (1986). Some effects of calcitonin gene-related peptide in human skin and on histamine release. Br. J. Dermatol., 114, 37–46. 260. Ali, H., Leung, K. B., Pearce, F. L., Hayes, N. A., and Foreman, J. C. (1986). Comparison of the histamine-releasing action of substance P on mast cells and basophils from different species and tissues. Int. Arch. Allergy Appl. Immunol., 79, 413–418. 261. Bienenstock, J., Tomioka, M., Matsuda, H., Stead, R. H., Quinonez, G., Simon, G. T., Coughlin, M. D., and Denburg, J. A. (1987). The role of mast cells in inflammatory processes: evidence for nerve/mast cell interactions. Int. Arch. Allergy Appl. Immunol., 82, 238–243. 262. Schmidt-Choudhury, A., Meissner, J., Seebeck, J., Goetzl, E. J., Xia, M., Galli, S. J., Schmidt, W. E., Schaub, J., and Wershil, B. K. (1999). Stem cell factor influences neuro-immune interactions: the response of mast cells to pituitary adenylate cyclase activating polypeptide is altered by stem cell factor. Regul. Pept., 83, 73–80. 263. Toyoda, M., Makino, T., Kagoura, M., and Morohashi, M. (2000). Immunolocalization of substance P in human skin mast cells. Arch. Dermatol. Res., 292, 418–421. 264. De Paulis, A., Minopoli, G., Arbustini, E., de Crescenzo, G., Dal Piaz, F., Pucci, P., Russo, T., and Marone, G. (1999). Stem cell factor is localized in, released from, and cleaved by human mast cells. J. Immunol., 163, 2799–2808. 265. Staniek, V., Misery, L., Peguet-Navarro, J., Abello, J., Doutremepuich, J. D., Claudy, A., and Schmitt, D. (1997). Binding and in vitro modulation of human epidermal Langerhans cell functions by substance P. Arch. Dermatol. Res., 289, 285–291. 266. van der Kleij, H. P., Ma, D., Redegeld, F. A., Kraneveld, A. D., Nijkamp, F. P., and Bienenstock, J. (2003). Functional expression of neurokinin 1 receptors on mast cells induced by IL-4 and stem cell factor. J. Immunol., 171, 2074–2079. 267. Bischoff, S. C., Schwengberg, S., Lorentz, A., Manns, M. P., Bektas, H., Sann, H., Levi-Schaffer, F., Shanahan, F., and Schemann, M. (2004). Substance P and other neuropeptides do not induce mediator release in isolated human intestinal mast cells. Neurogastroenterol. Motil., 16, 185–193. 268. Furuno, T., Ito, A., Koma, Y., Watabe, K., Yokozaki, H., Bienenstock, J., Nakanishi, M., and Kitamura, Y. (2005). The spermatogenic Ig superfamily/synaptic cell adhesion molecule mast-cell adhesion molecule promotes interaction with nerves. J. Immunol., 174, 6934–6942. 269. Theoharides, T. C., Kops, S. K., Bondy, P. K., and Askenase, P. W. (1985). Differential release of serotonin without comparable histamine under diverse conditions in the rat mast cell. Biochem. Pharmacol., 34, 1389–1398. 270. Ratliff, T. L., Klutke, C. G., Hofmeister, M., He, F., Russell, J. H., and Becich, M. J. (1995). Role of the immune response in interstitial cystitis. Clin. Immunol. Immunopathol., 74, 209–216. 271. Baluk, P. (1997). Neurogenic inflammation in skin and airways. J. Investig. Dermatol. Symp. Proc., 2, 76–81. 272. Weinstock, J. V. (1992). Neuropeptides and the regulation of granulomatous inflammation. Clin. Immunol. Immunopathol., 64, 17–22. 273. Rittner, H. L., and Stein, C. (2005). Involvement of cytokines, chemokines and adhesion molecules in opioid analgesia. Eur. J. Pain, 9, 109–112.
126
I. Neural and Endocrine Effects on Immunity
274. Janson, W., and Stein, C. (2003). Peripheral opioid analgesia. Curr. Pharm. Biotechnol., 4, 270–274. 275. Schmitt, T. K., Mousa, S. A., Brack, A., Schmidt, D. K., Rittner, H. L., Welte, M., Schafer, M., and Stein, C. (2003). Modulation of peripheral endogenous opioid analgesia by central afferent blockade. Anesthesiology, 98, 195–202. 276. Levine, J. D., Clark, R., Devor, M., Helms, C., Moskowitz, M. A., and Basbaum, A. I. (1984). Intraneuronal substance P contributes to the severity of experimental arthritis. Science, 226, 547–549. 277. Sethi, S., and Sequeira, W. (1990). Sparing effect of hemiplegia on scleroderma. Ann. Rheum. Dis., 49, 999–1000. 278. Levine, J. D., Goetzl, E. J., and Basbaum, A. I. (1987). Contribution of the nervous system to the pathophysiology of rheumatoid arthritis and other polyarthritides. Rheum. Dis. Clin. North Am., 13, 369–383. 279. Miao, F. J., Janig, W., Dallman, M. F., Benowitz, N. L., Heller, P. H., Basbaum, A. I., and Levine, J. D. (1994). Role of vagal afferents and spinal pathways modulating inhibition of bradykinin-induced plasma extravasation by intrathecal nicotine. J. Neurophysiol., 72, 1199–1207. 280. Krause, J. E., DiMaggio, D. A., and McCarson, K. E. (1995). Alterations in neurokinin 1 receptor gene expression in models of pain and inflammation. Can. J. Physiol. Pharmacol., 73, 854– 859. 281. Sakai, K., Matsuno, H., Tsuji, H., and Tohyama, M. (1998). Substance P receptor (NK1) gene expression in synovial tissue in rheumatoid arthritis and osteoarthritis. Scand. J. Rheumatol., 27, 135–141. 282. Lambert, N., Lescoulie, P. L., Yassine-Diab, B., Enault, G., Mazieres, B., De Preval, C., and Cantagrel, A. (1998). Substance P enhances cytokine-induced vascular cell adhesion molecule-1 (VCAM-1) expression on cultured rheumatoid fibroblast-like synoviocytes. Clin. Exp. Immunol., 113, 269–275. 283. Maggi, C. A. (1993). Tachykinin receptors and airway pathophysiology. Eur. Respir. J., 6, 735–742. 284. Harrison, S., and Geppetti, P. (2001). Substance p. Int. J. Biochem. Cell Biol., 33, 555–576. 285. Buckley, T. L., and Nijkamp, F. P. (1994). Airways hyperreactivity and cellular accumulation in a delayed-type hypersensitivity reaction in the mouse. Modulation by capsaicin-sensitive nerves. Am. J. Respir. Crit. Care Med., 149, 400–407. 286. Wu, Z. X., and Lee, L. Y. (1999). Airway hyperresponsiveness induced by chronic exposure to cigarette smoke in guinea pigs: role of tachykinins. J. Appl. Physiol., 87, 1621–1628. 287. Fischer, A., McGregor, G. P., Saria, A., Philippin, B., and Kummer, W. (1996). Induction of tachykinin gene and peptide expression in guinea pig nodose primary afferent neurons by allergic airway inflammation. J. Clin. Invest., 98, 2284–2291. 288. Singh, L. K., Pang, X., Alexacos, N., Letourneau, R., and Theoharides, T. C. (1999). Acute immobilization stress triggers skin mast cell degranulation via corticotropin releasing hormone, neurotensin, and substance P: a link to neurogenic skin disorders. Brain Behav. Immun., 13, 225–239. 289. Cao, T., Pinter, E., Al Rashed, S., Gerard, N., Hoult, J. R., and Brain, S. D. (2000). Neurokinin-1 receptor agonists are involved in mediating neutrophil accumulation in the inflamed, but not normal, cutaneous microvasculature: an in vivo study using neurokinin-1 receptor knockout mice. J. Immunol., 164, 5424– 5429. 290. Bhatia, M., Saluja, A. K., Hofbauer, B., Frossard, J. L., Lee, H. S., Castagliuolo, I., Wang, C. C., Gerard, N., Pothoulakis, C., and Steer, M. L. (1998). Role of substance P and the neuro-
291.
292. 293.
294.
295.
296.
297.
298.
299.
300.
301.
302.
303.
304.
305.
306.
kinin 1 receptor in acute pancreatitis and pancreatitisassociated lung injury. Proc. Natl. Acad. Sci. USA, 95, 4760–4765. Sann, H., Dux, M., Schemann, M., and Jancso, G. (1996). Neurogenic inflammation in the gastrointestinal tract of the rat. Neurosci. Lett., 219, 147–150. Barnes, P. J. (2001). Neurogenic inflammation in the airways. Respir. Physiol., 125, 145–154. Baraniuk, J. N., Kowalski, M. L., and Kaliner, M. A. (1990). Relationships between permeable vessels, nerves, and mast cells in rat cutaneous neurogenic inflammation. J. Appl. Physiol., 68, 2305–2311. Nordlind, K., Libing, C., Ahmed, A. A., Ljungberg, A., and Liden, S. (1995). Immunohistochemical localization of interleukin-6–like immunoreactivity to peripheral nerve-like structures in normal and inflamed human skin. Ann. N. Y. Acad. Sci., 762, 450–451. Lundberg, J. M., Martling, C. R., and Saria, A. (1983). Substance P and capsaicin-induced contraction of human bronchi. Acta Physiol. Scand., 119, 49–53. Sestini, P., Dolovich, M., Vancheri, C., Stead, R. H., Marshall, J. S., Perdue, M., Gauldie, J., and Bienenstock, J. (1989). Antigen-induced lung solute clearance in rats is dependent on capsaicin-sensitive nerves. Am. Rev. Respir. Dis., 139, 401– 406. Baird, A. W., and Cuthbert, A. W. (1987). Neuronal involvement in type 1 hypersensitivity reactions in gut epithelia. Br. J. Pharmacol., 92, 647–655. Perdue, M. H., Masson, S., Wershil, B. K., and Galli, S. J. (1991). Role of mast cells in ion transport abnormalities associated with intestinal anaphylaxis. Correction of the diminished secretory response in genetically mast cell-deficient W/Wv mice by bone marrow transplantation. J. Clin. Invest., 87, 687–693. Westerman, R. A., Low, A., Pratt, A., Hutchinson, J. S., Szolcsanyi, J., Magerl, W., Handwerker, H. O., and Kozak, W. M. (1987). Electrically evoked skin vasodilatation: a quantitative test of nociceptor function in man. Clin. Exp. Neurol., 23, 81–89. Undem, B. J., Myers, A. C., Barthlow, H., and Weinreich, D. (1990). Vagal innervation of guinea pig bronchial smooth muscle. J. Appl. Physiol., 69, 1336–1346. Elenkov, I. J., Wilder, R. L., Chrousos, G. P., and Vizi, E. S. (2000). The sympathetic nerve—an integrative interface between two supersystems: the brain and the immune system. Pharmacol. Rev., 52, 595–638. Cromlish, J. A., Seidah, N. G., Marcinkiewicz, M., Hamelin, J., Johnson, D. A., and Chretien, M. (1987). Human pituitary tryptase: molecular forms, NH2-terminal sequence, immunocytochemical localization, and specificity with prohormone and fluorogenic substrates. J. Biol. Chem., 262, 1363–1373. Theoharides, T. C., Singh, L. K., Boucher, W., Pang, X., Letourneau, R., Webster, E., and Chrousos, G. (1998). Corticotropin-releasing hormone induces skin mast cell degranulation and increased vascular permeability, a possible explanation for its proinflammatory effects. Endocrinology, 139, 403–413. Black, S., Humphrey, J. H., and Niven, J. S. (1963). Inhibition of Mantoux reaction by direct suggestion under hypnosis. Br. Med. J., 5346, 1649–1652. Black, S. (1963). Inhibition of immediate-type hypersensitivity response by direct suggestion under hypnosis. Br. Med. J., 5335, 925–929. MacQueen, G., Marshall, J., Perdue, M., Siegel, S., and Bienenstock, J. (1989). Pavlovian conditioning of rat mucosal
4. Significance of Sensory Neuropeptides and the Immune Response
307.
308.
309.
310.
311.
312.
313.
314.
315.
316.
317.
318.
319.
320.
321.
322.
323.
mast cells to secrete rat mast cell protease II. Science, 243, 83–85. Matsumoto, I., Inoue, Y., Shimada, T., and Aikawa, T. (2001). Brain mast cells act as an immune gate to the hypothalamicpituitary-adrenal axis in dogs. J. Exp. Med., 194, 71–78. Black, P. H. (2002). Stress and the inflammatory response: a review of neurogenic inflammation. Brain Behav. Immun., 16, 622–653. Castagliuolo, I., Wershil, B. K., Karalis, K., Pasha, A., Nikulasson, S. T., and Pothoulakis, C. (1998). Colonic mucin release in response to immobilization stress is mast cell dependent. Am. J. Physiol., 274, G1094–G1100. Santos, J., Saperas, E., Nogueiras, C., Mourelle, M., Antolin, M., Cadahia, A., and Malagelada, J. R. (1998). Release of mast cell mediators into the jejunum by cold pain stress in humans. Gastroenterology, 114, 640–648. Rossi, R., and Johansson, O. (1998). Cutaneous innervation and the role of neuronal peptides in cutaneous inflammation: a minireview. Eur. J. Dermatol., 8, 299–306. Skofitsch, G., and Jacobowitz, D. M. (1985). Calcitonin generelated peptide: detailed immunohistochemical distribution in the central nervous system. Peptides, 6, 721–745. Sharkey, K. A. (1992). Substance P and calcitonin gene-related peptide (CGRP) in gastrointestinal inflammation. Ann. N. Y. Acad. Sci., 664, 425–442. Pothoulakis, C., Castagliuolo, I., and Leeman, S. E. (1998). Neuroimmune mechanisms of intestinal responses to stress. Role of corticotropin-releasing factor and neurotensin. Ann. N. Y. Acad. Sci., 840, 635–648. Reul, J. M., Labeur, M. S., Wiegers, G. J., and Linthorst, A. C. (1998). Altered neuroimmunoendocrine communication during a condition of chronically increased brain corticotropinreleasing hormone drive. Ann. N. Y. Acad. Sci., 840, 444–455. Brodin, E., Rosen, A., Schott, E., and Brodin, K. (1994). Effects of sequential removal of rats from a group cage, and of individual housing of rats, on substance P, cholecystokinin and somatostatin levels in the periaqueductal grey and limbic regions. Neuropeptides, 26, 253–260. Rosen, A., Brodin, K., Eneroth, P., and Brodin, E. (1992). Short-term restraint stress and s.c. saline injection alter the tissue levels of substance P and cholecystokinin in the periaqueductal grey and limbic regions of rat brain. Acta Physiol. Scand., 146, 341–348. Fehder, W. P., Sachs, J., Uvaydova, M., and Douglas, S. D. (1997). Substance P as an immune modulator of anxiety. Neuroimmunomodulation, 4, 42–48. Chowdrey, H. S., Larsen, P. J., Harbuz, M. S., Lightman, S. L., and Jessop, D. S. (1995). Endogenous substance P inhibits the expression of corticotropin-releasing hormone during a chronic inflammatory stress. Life Sci., 57, 2021–2029. Dhabhar, F. S., McEwen, B. S., and Spencer, R. L. (1997). Adaptation to prolonged or repeated stress—comparison between rat strains showing intrinsic differences in reactivity to acute stress. Neuroendocrinology, 65, 360–368. Kiecolt-Glaser, J. K. (1999). Norman Cousins Memorial Lecture 1998. Stress, personal relationships, and immune function: health implications. Brain Behav. Immun., 13, 61–72. Konsman, J. P., Parnet, P., and Dantzer, R. (2002). Cytokineinduced sickness behaviour: mechanisms and implications. Trends Neurosci., 25, 154–159. Ansel, J. C., Armstrong, C. A., Song, I., Quinlan, K. L., Olerud, J. E., Caughman, S. W., and Bunnett, N. W. (1997). Interactions of the skin and nervous system. J. Investig. Dermatol. Symp. Proc., 2, 23–26.
127
324. Egan, C. L., Viglione-Schneck, M. J., Walsh, L. J., Green, B., Trojanowski, J. Q., Whitaker-Menezes, D., and Murphy, G. F. (1998). Characterization of unmyelinated axons uniting epidermal and dermal immune cells in primate and murine skin. J. Cutan. Pathol., 25, 20–29. 325. Misery, L. (1997). Skin, immunity and the nervous system. Br. J. Dermatol., 137, 843–850. 326. Church, M. K., Okayama, Y., and el Lati, S. (1991). Mediator secretion from human skin mast cells provoked by immunological and non-immunological stimulation. Skin Pharmacol., 4 (Suppl 1), 15–24. 327. Ansel, J. C., Brown, J. R., Payan, D. G., and Brown, M. A. (1993). Substance P selectively activates TNF-alpha gene expression in murine mast cells. J. Immunol., 150, 4478–4485. 328. Arck, P. C., Handjiski, B., Hagen, E., Joachim, R., Klapp, B. F., and Paus, R. (2001). Indications for a “brain-hair follicle axis (BHA)”: inhibition of keratinocyte proliferation and upregulation of keratinocyte apoptosis in telogen hair follicles by stress and substance P. FASEB J., 15, 2536–2538. 329. Arck, P. C., Handjiski, B., Peters, E. M., Peter, A. S., Hagen, E., Fischer, A., Klapp, B. F., and Paus, R. (2003). Stress inhibits hair growth in mice by induction of premature catagen development and deleterious perifollicular inflammatory events via neuropeptide substance P–dependent pathways. Am. J. Pathol., 162, 803–814. 330. Peters, E. M., Handjiski, B., Kuhlmei, A., Hagen, E., Bielas, H., Braun, A., Klapp, B. F., Paus, R., and Arck, P. C. (2004). Neurogenic inflammation in stress-induced termination of murine hair growth is promoted by nerve growth factor. Am. J. Pathol., 165, 259–271. 331. Alard, P., Niizeki, H., Hanninen, L., and Streilein, J. W. (1999). Local ultraviolet B irradiation impairs contact hypersensitivity induction by triggering release of tumor necrosis factor-alpha from mast cells. Involvement of mast cells and Langerhans cells in susceptibility to ultraviolet B. J. Invest. Dermatol., 113, 983– 990. 332. Yoshikawa, T., and Streilein, J. W. (1990). Tumor necrosis factor-alpha and ultraviolet B light have similar effects on contact hypersensitivity in mice. Reg. Immunol., 3, 139–144. 333. Theoharides, T. C., Donelan, J. M., Papadopoulou, N., Cao, J., Kempuraj, D., and Conti, P. (2004). Mast cells as targets of corticotropin-releasing factor and related peptides. Trends Pharmacol. Sci., 25, 563–568. 334. Cao, J., Papadopoulou, N., Kempuraj, D., Boucher, W. S., Sugimoto, K., Cetrulo, C. L., and Theoharides, T. C. (2005). Human mast cells express corticotropin-releasing hormone (CRH) receptors and CRH leads to selective secretion of vascular endothelial growth factor. J. Immunol., 174, 7665–7675. 335. Bjorklund, H., Dalsgaard, C. J., Jonsson, C. E., and Hermansson, A. (1986). Sensory and autonomic innervation of non-hairy and hairy human skin. An immunohistochemical study. Cell Tissue Res., 243, 51–57. 336. Brain, S. D., and Williams, T. J. (1988). Substance P regulates the vasodilator activity of calcitonin gene-related peptide. Nature, 335, 73–75. 337. Asahina, A., Hosoi, J., Grabbe, S., and Granstein, R. D. (1995). Modulation of Langerhans cell function by epidermal nerves. J. Allergy Clin. Immunol., 96, 1178–1182. 338. Nong, Y. H., Titus, R. G., Ribeiro, J. M., and Remold, H. G. (1989). Peptides encoded by the calcitonin gene inhibit macrophage function. J. Immunol., 143, 45–49. 339. Shen, H. M., Sha, L. X., Kennedy, J. L., and Ou, D. W. (1994). Adrenergic receptors regulate macrophage secretion. Int. J. Immunopharmacol., 16, 905–910.
128
I. Neural and Endocrine Effects on Immunity
340. Brunelleschi, S., Vanni, L., Ledda, F., Giotti, A., Maggi, C. A., and Fantozzi, R. (1990). Tachykinins activate guinea-pig alveolar macrophages: involvement of NK2 and NK1 receptors. Br. J. Pharmacol., 100, 417–420. 341. Litwin, D. K., Wilson, A. K., and Said, S. I. (1992). Vasoactive intestinal polypeptide (VIP) inhibits rat alveolar macrophage phagocytosis and chemotaxis in vitro. Regul. Pept., 40, 63– 74. 342. Lundberg, J. M., Brodin, E., and Saria, A. (1983). Effects and distribution of vagal capsaicin-sensitive substance P neurons with special reference to the trachea and lungs. Acta Physiol. Scand., 119, 243–252. 343. Saria, A., Martling, C. R., Dalsgaard, C. J., and Lundberg, J. M. (1985). Evidence for substance P-immunoreactive spinal afferents that mediate bronchoconstriction. Acta Physiol. Scand., 125, 407–414. 344. Manzini, S., Conti, S., Maggi, C. A., Abelli, L., Somma, V., Del Bianco, E., and Geppetti, P. (1989). Regional differences in the motor and inflammatory responses to capsaicin in guinea pig airways. Correlation with content and release of substance P– like immunoreactivity. Am. Rev. Respir. Dis., 140, 936–941. 345. Undem, B. J., Dick, E. C., and Buckner, C. K. (1983). Inhibition by vasoactive intestinal peptide of antigen-induced histamine release from guinea-pig minced lung. Eur. J. Pharmacol., 88, 247–250. 346. Miura, M., Inoue, H., Ichinose, M., Kimura, K., Katsumata, U., and Takishima, T. (1990). Effect of nonadrenergic noncholinergic inhibitory nerve stimulation on the allergic reaction in cat airways. Am. Rev. Respir. Dis., 141, 29–32. 347. Bellinger, D. L., Lorton, D., Brouxhon, S., Felten, S., and Felten, D. L. (1996). The significance of vasoactive intestinal polypeptide (VIP) in immunomodulation. Adv. Neuroimmunol., 6, 5– 27. 348. Taylor-Robinson, A. W., Liew, F. Y., Severn, A., Xu, D., McSorley, S. J., Garside, P., Padron, J., and Phillips, R. S. (1994). Regulation of the immune response by nitric oxide differentially produced by T helper type 1 and T helper type 2 cells. Eur. J. Immunol., 24, 980–984. 349. Luts, A., Uddman, R., Alm, P., Basterra, J., and Sundler, F. (1993). Peptide-containing nerve fibers in human airways: distribution and coexistence pattern. Int. Arch. Allergy Immunol., 101, 52–60. 350. Ladenius, A. R., Folkerts, G., van der Linde, H. J., and Nijkamp, F. P. (1995). Potentiation by viral respiratory infection of ovalbumin-induced guinea-pig tracheal hyperresponsiveness: role for tachykinins. Br. J. Pharmacol., 115, 1048–1052. 351. Perretti, F., and Manzini, S. (1993). Activation of capsaicinsensitive sensory fibers modulates PAF-induced bronchial hyperresponsiveness in anesthetized guinea pigs. Am. Rev. Respir. Dis., 148, 927–931. 352. Scheerens, H., Buckley, T. L., Muis, T., Van Loveren, H., and Nijkamp, F. P. (1996). The involvement of sensory neuropeptides in toluene diisocyanate-induced tracheal hyperreactivity in the mouse airways. Br. J. Pharmacol., 119, 1665–1671. 353. Barnes, P. J. (1986). Asthma as an axon reflex. Lancet, 1, 242–245. 354. Fernandez, S., Knopf, M. A., Bjork, S. K., and McGillis, J. P. (2001). Bone marrow–derived macrophages express functional CGRP receptors and respond to CGRP by increasing transcription of c-fos and IL-6 mRNA. Cell. Immunol., 209, 140–148. 355. Tanabe, T., Otani, H., Zeng, X. T., Mishima, K., Ogawa, R., and Inagaki, C. (1996). Inhibitory effects of calcitonin gene-related peptide on substance-P–induced superoxide production in human neutrophils. Eur. J. Pharmacol., 314, 175–183.
356. Forsythe, P., McGarvey, L. P., Heaney, L. G., MacMahon, J., and Ennis, M. (2000). Sensory neuropeptides induce histamine release from bronchoalveolar lavage cells in both nonasthmatic coughers and cough variant asthmatics. Clin. Exp. Allergy, 30, 225–232. 357. Joos, G. F., Lefebvre, R. A., Bullock, G. R., and Pauwels, R. A. (1997). Role of 5-hydroxytryptamine and mast cells in the tachykinin-induced contraction of rat trachea in vitro. Eur. J. Pharmacol., 338, 259–268. 358. Feher, E., Fodor, M., and Burnstock, G. (1992). Distribution of somatostatin-immunoreactive nerve fibres in Peyer’s patches. Gut, 33, 1195–1198. 359. Felten, D. L., Felten, S. Y., Bellinger, D. L., Carlson, S. L., Ackerman, K. D., Madden, K. S., Olschowki, J. A., and Livnat, S. (1987). Noradrenergic sympathetic neural interactions with the immune system: structure and function. Immunol. Rev., 100, 225–260. 360. Cuthbert, A. W., and Baird, A. W. (1987). Multiple mediators of type I hypersensitivity reactions in epithelia. Am. J. Physiol., 252, G443–G444. 361. Berin, M. C., McKay, D. M., and Perdue, M. H. (1999). Immuneepithelial interactions in host defense. Am. J. Trop. Med. Hyg., 60, 16–25. 362. Castagliuolo, I., Keates, A. C., Qiu, B., Kelly, C. P., Nikulasson, S., Leeman, S. E., and Pothoulakis, C. (1997). Increased substance P responses in dorsal root ganglia and intestinal macrophages during Clostridium difficile toxin A enteritis in rats. Proc. Natl. Acad. Sci. USA, 94, 4788–4793. 363. Castagliuolo, I., Wang, C. C., Valenick, L., Pasha, A., Nikulasson, S., Carraway, R. E., and Pothoulakis, C. (1999). Neurotensin is a proinflammatory neuropeptide in colonic inflammation. J. Clin. Invest., 103, 843–849. 364. Pothoulakis, C., Castagliuolo, I., LaMont, J. T., Jaffer, A., O’Keane, J. C., Snider, R. M., and Leeman, S. E. (1994). CP96,345, a substance P antagonist, inhibits rat intestinal responses to Clostridium difficile toxin A but not cholera toxin. Proc. Natl. Acad. Sci. USA, 91, 947–951. 365. Santos, J., and Perdue, M. H. (1998). Immunological regulation of intestinal epithelial transport. Digestion, 59, 404–408. 366. Mazumdar, S., and Das, K. M. (1992). Immunocytochemical localization of vasoactive intestinal peptide and substance P in the colon from normal subjects and patients with inflammatory bowel disease. Am. J. Gastroenterol., 87, 176–181. 367. Kubota, Y., Petras, R. E., Ottaway, C. A., Tubbs, R. R., Farmer, R. G., and Fiocchi, C. (1992). Colonic vasoactive intestinal peptide nerves in inflammatory bowel disease. Gastroenterology, 102, 1242–1251. 368. Kawahito, Y., Sano, H., Mukai, S., Asai, K., Kimura, S., Yamamura, Y., Kato, H., Chrousos, G. P., Wilder, R. L., and Kondo, M. (1995). Corticotropin releasing hormone in colonic mucosa in patients with ulcerative colitis. Gut, 37, 544–551. 369. Strobach, R. S., Ross, A. H., Markin, R. S., Zetterman, R. K., and Linder, J. (1990). Neural patterns in inflammatory bowel disease: an immunohistochemical survey. Mod. Pathol., 3, 488–493. 370. Stead, R. H., Dixon, M. F., Bramwell, N. H., Riddell, R. H., and Bienenstock, J. (1989). Mast cells are closely apposed to nerves in the human gastrointestinal mucosa. Gastroenterology, 97, 575–585. 371. Shanahan, F., Denburg, J. A., Fox, J., Bienenstock, J., and Befus, D. (1985). Mast cell heterogeneity: effects of neuroenteric peptides on histamine release. J. Immunol., 135, 1331–1337. 372. Barbara, G., Stanghellini, V., De Giorgio, R., Cremon, C., Cottrell, G. S., Santini, D., Pasquinelli, G., Morselli-Labate,
4. Significance of Sensory Neuropeptides and the Immune Response
373.
374.
375.
376.
377.
378.
379.
380.
381.
382.
A. M., Grady, E. F., Bunnett, N. W., Collins, S. M., and Corinaldesi, R. (2004). Activated mast cells in proximity to colonic nerves correlate with abdominal pain in irritable bowel syndrome. Gastroenterology, 126, 693–702. Jiang, W., Kreis, M. E., Eastwood, C., Kirkup, A. J., Humphrey, P. P., and Grundy, D. (2000). 5-HT(3) and histamine H(1) receptors mediate afferent nerve sensitivity to intestinal anaphylaxis in rats. Gastroenterology, 119, 1267–1275. Javed, N. H., Wang, Y. Z., and Cooke, H. J. (1992). Neuroimmune interactions: role for cholinergic neurons in intestinal anaphylaxis. Am. J. Physiol., 263, G847–G852. Elbadawi, A. (1997). Interstitial cystitis: a critique of current concepts with a new proposal for pathologic diagnosis and pathogenesis. Urology, 49, 14–40. Theoharides, T. C., and Sant, G. R. (2003). Neuroimmune connections and regulation of function in the urinary bladder. In J. Bienenstock, E. J. Goetzl, and M. G. Blennerhassett (Eds.), Autonomic neuroimmunology (pp. 345–369). London: Taylor & Francis. Sharkey, K. A., Williams, R. G., Schultzberg, M., and Dockray, G. J. (1983). Sensory substance P-innervation of the urinary bladder: possible site of action of capsaicin in causing urine retention in rats. Neuroscience, 10, 861–868. Maggi, C. A., Giuliani, S., Santicioli, P., Abelli, L., Geppetti, P., Somma, V., Renzi, D., and Meli, A. (1987). Species-related variations in the effects of capsaicin on urinary bladder functions: relation to bladder content of substance P–like immunoreactivity. Naunyn Schmiedebergs Arch. Pharmacol., 336, 546–555. Maggi, C. A., Santicioli, P., Patacchini, R., Geppetti, P., Giuliani, S., Astolfi, G. M., Baldi, E., Parlani, M., Theodorsson, E., and Fusco, B., et al. (1988). Regional differences in the motor response to capsaicin in the guinea-pig urinary bladder: relative role of pre- and postjunctional factors related to neuropeptide-containing sensory nerves. Neuroscience, 27, 675–688. Maggi, C. A., Geppetti, P., Santicioli, P., Frilli, S., Giuliani, S., Furio, M., Theodorsson, E., Fusco, B., and Meli, A. (1988). Tachykinin-like immunoreactivity in the mammalian urinary bladder: correlation with the functions of the capsaicinsensitive sensory nerves. Neuroscience, 26, 233–242. Theoharides, T. C., Pang, X., Letourneau, R., and Sant, G. R. (1998). Interstitial cystitis: a neuroimmunoendocrine disorder. Ann. N. Y. Acad. Sci., 840, 619–634. Chai, T. C., and Steers, W. D. (1997). Neurophysiology of micturition and continence in women. Int. Urogynecol. J. Pelvic Floor Dysfunct., 8, 85–97.
129
383. Fowler, C. J. (2000). Intravesical treatment of overactive bladder. Urology, 55, 60–64. 384. Lazzeri, M., Beneforti, P., Spinelli, M., Zanollo, A., Barbagli, G., and Turini, D. (2000). Intravesical resiniferatoxin for the treatment of hypersensitive disorder: a randomized placebo controlled study. J. Urol., 164, 676–679. 385. Silva, C., Rio, M. E., and Cruz, F. (2000). Desensitization of bladder sensory fibers by intravesical resiniferatoxin, a capsaicin analog: long-term results for the treatment of detrusor hyperreflexia. Eur. Urol., 38, 444–452. 386. Montier, F., Carruette, A., Moussaoui, S., Boccio, D., and Garret, C. (1994). Antagonism of substance P and related peptides by RP 67580 and CP-96,345, at tachykinin NK1 receptor sites, in the rat urinary bladder. Eur. J. Pharmacol., 251, 9–14. 387. Keith, I. M., Jin, J., and Saban, R. (1995). Nerve-mast cell interaction in normal guinea pig urinary bladder. J. Comp. Neurol., 363, 28–36. 388. Bjorling, D. E., Beckman, M., and Saban, R. (2003). Neurogenic inflammation of the bladder. Adv. Exp. Med. Biol., 539, 551–583. 389. Pang, X., Boucher, W., Triadafilopoulos, G., Sant, G. R., and Theoharides, T. C. (1996). Mast cell and substance P–positive nerve involvement in a patient with both irritable bowel syndrome and interstitial cystitis. Urology, 47, 436–438. 390. Christmas, T. J., Rode, J., Chapple, C. R., Milroy, E. J., and Turner-Warwick, R. T. (1990). Nerve fibre proliferation in interstitial cystitis. Virchows Arch. 416, 447–451. 391. Spanos, C., Pang, X., Ligris, K., Letourneau, R., Alferes, L., Alexacos, N., Sant, G. R., and Theoharides, T. C. (1997). Stressinduced bladder mast cell activation: implications for interstitial cystitis. J. Urol., 157, 669–672. 392. Saban, R., Saban, M. R., Nguyen, N. B., Lu, B., Gerard, C., Gerard, N. P., and Hammond, T. G. (2000). Neurokinin-1 (NK1) receptor is required in antigen-induced cystitis. Am. J. Pathol., 156, 775–780. 393. Janiszewski, J., Bienenstock, J., and Blennerhassett, M. G. (1994). Picomolar doses of substance P trigger electrical responses in mast cells without degranulation. Am. J. Physiol., 267, C138–C145. 394. Soderholm, J. D., and Perdue, M. (2001). Stress and gastrointestinal tract. II. Stress and barrier function. Am. J. Physiol. Gastrointest. Liver Physiol. 280, 67–613.
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C H A P T E R
5 Vasoactive Intestinal Peptide: An Anti-inflammatory Neuropeptide DOINA GANEA AND MARIO DELGADO
I. INTRODUCTION 131 II. VIP PRESENCE IN PRIMARY AND SECONDARY LYMPHOID ORGANS 132 III. VIP RECEPTORS IN IMMUNE CELLS 133 IV. EFFECTS OF VIP ON INNATE IMMUNE RESPONSES 135 V. EFFECTS OF VIP ON T-CELL ACTIVATION, DIFFERENTIATION, AND FUNCTION 139 VI. VIP IN MODELS OF AUTOIMMUNITY, INFLAMMATION, AND BONE MARROW TRANSPLANTATION 143 VII. CONCLUSIONS AND PERSPECTIVES 149 VIII. ABBREVIATIONS 150
in various models of autoimmune diseases and inflammatory conditions both in the CNS and the periphery.
I. INTRODUCTION In addition to the hypothalamus-pituitary-adrenal axis, neuroendocrine-immune interactions occur through peripheral nerve fibers innervating the lymphoid organs, and are mediated by neurotransmitters and neuropeptides. In addition, immune cells express and release various neuropeptides and hormones. Although the factors controlling neuropeptide release from neuronal or immune sources during an inflammatory response remain to be identified, it has been shown that functionally relevant amounts of vasoactive intestinal peptide (VIP), substance P (SP) and calcitonin gene-related peptide (CGRP) are released during an immune response in patients and animal models (Delgado et al., 1999b; Kaltreider et al., 1997; Lee et al., 2002; Mosimann et al., 1993; Nieber et al., 1992). Immune cells and cells of the nervous system share the same specific receptors for neuropeptides, and the presence of both neuropeptides and neuropeptide receptors in lymphoid tissues creates the framework for the immunomodulatory function of neuropeptides. VIP, one of the best studied immunoregulatory neuropeptides, affects both innate and adaptive immune responses, and acts as a major anti-inflammatory factor
ABSTRACT The vasoactive intestinal peptide (VIP) discovered by Said and Mutt more than 30 years ago and characterized as a widely distributed neuropeptide also functions as a potent immunomodulator. Here, we review the evidence supporting the role of VIP as an endogenous anti-inflammatory agent, released by the innervation and by activated immune cells and acting through specific receptors present on macrophages, dendritic cells, microglia, and T lymphocytes. VIP prevents the activation of macrophages, microglia, and dendritic cells, and promotes the generation of Th2 effectors and regulatory T-cells. Due to its pleiotropic effects on both innate and adaptive immunity, VIP is an attractive potential therapeutic agent for the treatment of autoimmune and inflammatory diseases. This review presents recent evidence on the effect of VIP PSYCHONEUROIMMUNOLOGY, 4E VOLUME I
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Copyright © 2007 by Elsevier, Inc. All rights of reproduction in any form reserved.
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in animal models of autoimmune diseases. In this chapter we propose to review the role of VIP in immunity, and to discuss its potential use in the treatment of inflammatory, autoimmune, and neurodegenerative disorders.
peptide synthesis was described initially in neuronal cells, prohormone convertases required for neuropeptide processing have been recently identified in immune cells as well (Decroly et al., 1996).
B. VIP Sources in Lymphoid Organs II. VIP PRESENCE IN PRIMARY AND SECONDARY LYMPHOID ORGANS A. VIP Gene and Protein VIP, a 28 amino acid peptide, belongs to a family of structurally related hormones and neuropeptides, which includes PACAP27, PACAP38, secretin, glucagon, gastric inhibitory peptide, peptide histidine methionine (in humans), and peptide histidine isoleucine (its counterpart in other mammalian species) (Said, 1986) (Figure 1A). The human VIP gene contains seven exons, with exon five coding for VIP (Figure 1B). The mRNA is processed through differential splicing, and the translated preproVIP undergoes enzymatic processing resulting in the mature C-terminus amidated VIP peptide (Bloom et al., 1983; Itoh et al., 1983). Although the biochemical process required for neuro-
1. Neuronal VIP VIP-ergic nerve fibers have been identified in both central and peripheral lymphoid organs. In the thymus, the VIP+ nerve endings are most abundant in the capsule, enter the cortex and occasionally the medulla (Bellinger et al., 1996). In the spleen, VIP+ nerve endings are prominent in the red pulp, extending as free fibers in the parenchyma and the white pulp, as well as in the periarteriolar lymphatic sheath among T lymphocytes (Bellinger et al., 1996). In lymph nodes, the VIP innervation is relatively sparse, being present beneath the capsule and along the vasculature (Bellinger et al., 1996; Fink and Weihe, 1988). VIP+ fibers occasionally leave the vascular plexus to extend among T-cells in the adjacent cortex (Bellinger et al., 1990). In the mucosal-associated lymphoid tissue, an extensive nerve plexus containing various neuropeptides such
cac tet gat gcc gtc ttc aca gat aac tac acc gcg ctc aga aag cee etg gct gtg aag aaa tac ctg aac tcc atc ctg aat gga VIP mRNA His Ser Asp AiA Val Phe Thr Asp Asn Tyr Thr Arg Leu Arg Lys Gin Met Aia Val Lys Lys TyrLeu Asn Ser Iie Leu Asn Gty VIP
FIGURE 1 VIP structure: protein and gene. (A) sequence of VIP family peptides. (B) VIP gene structure.
5. Vasoactive Intestinal Peptide: An Anti-inflammatory Neuropeptide
as VIP, SP, CGRP, cholecystokinin, and somatostatin is present in the intestinal lamina propria (Bellinger et al., 1996). In the Peyer’s patches, the VIP+ nerve fibers are predominantly along the lymphatics and high endothelial venules. The major VIP sources in the gut are the intrinsic enteric VIP-containing neurons found in the myenteric and submucosal ganglionic plexuses, and the extrinsic parasympathetic and sensory fibers (Furness and Costa, 1980). In the bronchus-associated lymphoid tissue, VIP+ fibers are present in the walls of bronchia and bronchioles (Dey et al., 1981). The VIPergic innervation in the lung arises presumably from the vagus and from microganglia present in the walls of the bronchia (Dey et al., 1981; Lundberg et al., 1979). The nature of the signals leading to neuronal VIP release during an inflammatory reaction is not known. However, a strong candidate is nitric oxide (NO), produced at high levels in inflammatory responses and shown to release VIP from enteric ganglia (Grider and Jin, 1993; Matsuyama et al., 2002). In addition, in a murine model of pulmonary delayed–type hypersensitivity, intratracheal antigenic challenge resulted in an increased secretion of VIP, recruitment of T-cells bearing VIP receptors, and upregulation of VIP receptors on the responding T-cells, suggesting that inflammatory signals result in VIP release (Kaltreider et al., 1997). 2. Immune VIP The first evidence for the production of VIP by immune cells was the identification of VIP-immunoreactivity (VIP-ir) in rat mast cells (Cutz et al., 1978). However, the VIP identified in mast cells corresponded mostly to the truncated VIP10–28 fragment, and to a mixture of amino-terminally extended VIPs (Goetzl et al., 1988; Wershil et al., 1993). Further studies showed VIP-ir in blood polymorphonuclear and mononuclear cells, basophils, and eosinophils (Aliakbari et al., 1987; Lygren et al., 1984; O’Dorisio et al., 1980; Weinstock and Blum, 1990). Using different experimental approaches, several studies demonstrated that lymphocytes synthesize and secrete functional VIP. Both thymocytes and peripheral T-cells express VIP mRNA as determined by RT-PCR (Gomariz et al., 1994; Leceta et al., 1994). Northern blot analysis indicated that the 1 kb predominant VIP transcript in lymphocytes resulting from the use of the proximal polyadenylation site in the VIP gene (Chew et al., 1994) differs from the preferentially expressed 1.7 kb transcript found in most tissues (Leceta et al., 1996). Use of HPLC followed by Elisa identified VIP1–28 and two higher molecular weight
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precursors in lysates obtained from lymphocyte cultures (Gomariz et al., 1992). In addition to VIP expression and accumulation of intracellular VIP1–28, T lymphocytes activated through the T-cell receptor were shown to secrete VIP (Martinez et al., 1999). We reported recently that Th2, but not Th1, effectors express and secrete functional VIP following antigenic stimulation (Delgado and Ganea, 2001a; Vassiliou et al., 2001). Since VIP acts as a Th2 differentiation and survival factor (see Section V.A.2 and 3), VIP synthesis and release by activated Th2 cells suggests a positive feedback mechanism leading to the alteration of the Th1/Th2 balance in favor of Th2 immune responses. The role of endogenous, T-cell–derived VIP in T-cell differentiation was confirmed recently through the elimination of VIP with VIPase IgG from cultured TCR-stimulated T-cells, leading to the restoration of the Th1/Th2 balance (Voice et al., 2003).
III. VIP RECEPTORS IN IMMUNE CELLS A. Classification of VIP/PACAP Receptors Following the discovery of PACAP, it became apparent that VIP and PACAP act as endogenous ligands for the same receptors. So far, three VIP/ PACAP receptors have been cloned and classified as VPAC1 and VPAC2 (with high affinity for both VIP and PACAP) and PAC1 (preferred PACAP receptor) (Harmar et al., 1998). The VIP/PACAP receptors are seven transmembrane domain G-protein linked receptors, with highly conserved amino acid residues in the amino-terminal extracellular region, the transmembrane domains, and the first intracellular loop. Recently, a natural VIP deletion variant of the VPAC2 receptor was identified in immune cells (Grinninger et al., 2004). This receptor binds VIP but does not signal. In contrast to VPAC1 and VPAC2, there are multiple variants of PAC1 resulting from alternative splicing (Pisegna et al., 1996; Spengler et al., 1993). Signaling through VIP/PACAP receptors results in the activation of adenylyl cyclase (AC) and of phospholipase C (PLC) and D (PLD) (Delporte et al., 1995; Harmar et al., 1998; McCulloch et al., 2000; McCulloch et al., 2001; McCulloch et al., 2002; Van Rampelbergh et al., 1997). VPAC1 and VPAC2 receptors stimulate PLD less potently than AC (McCulloch et al., 2001). The rat isoform PAC1-TM4, which differs from the canonical PAC1 receptor only by discrete sequences located in transmembrane domains II and IV and in the extracellular domain, is not coupled to AC, PLC, or PLD but mediates increases [Ca2+] via L-type Ca+2 channels (Chatterjee et al., 1996).
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B. VIP/PACAP Receptors in Immune Cells VIP binding sites have been described initially for human, rat, and mouse lymphocytes (Calvo et al., 1986; Guerrero et al., 1981; O’Dorisio et al., 1981; Ottaway et al., 1983; Ottaway and Greenberg, 1984). Following cloning of VPAC1, VPAC2, and PAC1, the expression of these receptors was investigated in various immune cell subpopulations. Due to lack of appropriate specific antibodies, the expression of VPAC1/2 and PAC1 receptors has been followed at the mRNA level. Discrepancies between the results reported by different laboratories can be attributed to the use of different primers and of different culture conditions. In addition, the expression of the three receptors appears to be modulated during activation and differentiation of immune cells, which introduces a new experimental variable. In most immune cells, VPAC1 appears to be constitutively expressed. For example, macrophages and macrophage cell lines such as THP-1 and RAW cells express PAC1 and VPAC1 mRNA constitutively, whereas VPAC2 is induced upon activation (Delgado et al., 1998). In bone marrow–derived dendritic cells, VPAC1 is expressed at higher levels than VPAC2, with no PAC1 expression (Delgado et al., 2004b). Functional VPAC1 and VPAC2 receptors coupled to adenylyl cyclase have been also reported in murine Langerhans cells (Asahina et al., 1995). Similar to macrophages, murine microglia express VPAC1 and PAC1 constitutively (Delgado et al., 2002b; Kim et al., 2000). The best studied immune cells in terms of VIP/ PACAP receptors are the T lymphocytes. Initial localization of VIP and PACAP binding sites in immune organs revealed a high density of receptors in the Tcell areas without identifying the receptor (Reubi, 2000). There is general agreement that VPAC1 is constitutively expressed in murine and human naïve Tcells, and that VPAC2 is expressed primarily in CD4+
TABLE 1
T lymphocytes following TCR-stimulation (Delgado et al., 1996; Lara-Marquez et al., 2001; Pankhaniya et al., 1998). In contrast to VPAC2, VPAC1 transcription after TCR cross-linking and CD28 co-stimulation was reported to be downregulated in human peripheral T-cells and thymocytes (Lara-Marquez et al., 2000; Lara-Marquez et al., 2001). This observation led to a model of opposite regulation for VPAC1 and VPAC2, with VPAC1 being downregulated and VPAC2 upregulated following CD4+ T-cell activation. However, recent studies from our laboratory suggest that this is a rather simplified model that does not take into account the differentiation of CD4+ T-cells into Th1 and Th2 effectors following activation and proliferation. We found that naïve CD4+ T-cells express VPAC1 and very little, if any, VPAC2; however, following several rounds of proliferation and differentiation into Th1 and Th2 effectors, Th2 cells express significantly higher levels of both VPAC1 and VPAC2 receptors, compared to Th1 effectors (Sharma et al., 2006). A final resolution for the regulation of VPAC1 and VPAC2 expression during Tcell activation, proliferation, and differentiation will require quantitative measurements at both message and protein level during the various phases of T-cell activation. The question of the biological role of the various VIP/PACAP receptors has been addressed in functional assays. With the exception of IL-6 inhibition, VPAC1 mediates the inhibition of pro-inflammatory cytokine and chemokine production in LPS-stimulated macrophages and microglia (Delgado et al., 1998; Delgado et al., 1999d; Delgado et al., 1999e; Delgado et al., 1999f; Delgado et al., 2002b; Delgado and Ganea, 1999; Delgado and Ganea, 2001d), the VIP-induced inhibition of hematopoiesis (Rameshwar et al., 2002), and the induction of tolerogenic dendritic cells (Delgado et al., 2005b) (Table 1). In contrast, VPAC2 acts as the major biological receptor in T-cells, promoting Th2-type responses in vivo and in vitro (Goetzl et al., 2001; Voice et al., 2001; Voice et al., 2003).
Receptors, Intracellular Pathways, and Transcription Factors Involved in the Anti-inflammatory Activity of VIP and PACAP
IL-6 IL-10 IL-12 TNF NO CK Hematopoiesis Tolerogenic DCs
Action
Receptor
Intracellular pathways
Transcription factors
Inhibition Stimulation Inhibition Inhibition Inhibition Inhibition Inhibition Induction
PAC1 VPAC1 VPAC1/VPAC2 VPAC1 VPAC1 VPAC1 VPAC1 VPAC1
PKC cAMP cAMP/cAMP indep cAMP/cAMP indep cAMP/cAMP indep cAMP ? cAMP/PKA
ND CREB IRF-1/NF-κB CREB/NF-κB IRF-1/NF-κB NF-κB ? NF-κB
5. Vasoactive Intestinal Peptide: An Anti-inflammatory Neuropeptide
IV. EFFECTS OF VIP ON INNATE IMMUNE RESPONSES
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A. VIP Inhibits the Expression and Release of Pro-inflammatory Mediators from Activated Macrophages and Microglia
To eliminate invading pathogens, the immune system mounts two different but interconnected responses: the innate and adaptive immunity. The innate immune response occurs upon the recognition through Toll-like receptors (TLRs) of foreign patterns characteristic for groups of pathogens. The innate immune response, characterized by phagocytosis, release of oxygen and nitrogen radicals, and production of pro-inflammatory cytokines and chemokines, involves cells such as macrophages, neutrophils, dendritic cells in the periphery, and microglia in the CNS. In addition to their immediate function in killing pathogens, macrophages, microglia, and particularly dendritic cells have the capacity to process antigen and initiate an adaptive immune response, through stimulatory and co-stimulatory contacts with naïve T-cells bearing the appropriate TCR. Although both innate and adaptive immune responses are required for the successful elimination of pathogens, an uncontrolled inflammatory response can lead to serious tissue damage, organ failure, and ultimately to death. Therefore, endogenous anti-inflammatory factors such as glucocorticoids, lipid mediators, anti-inflammatory cytokines, and neuropeptides such as VIP play an important role in the successful resolution of the inflammatory response. The various mechanisms that promote the anti-inflammatory activity of VIP are summarized in Figure 2.
Following signaling through TLRs, macrophages secrete several pro-inflammatory mediators, such as TNF-α, IL-12, IL-1β, IL-6, and NO, followed by secretion of the anti-inflammatory cytokines IL-10 and transforming growth factor β (TGFβ) (Laskin and Pendino, 1995). Despite the beneficial role of proinflammatory factors in host defense, their sustained production can lead to serious pathological conditions (Evans, 1995; Van Snick, 1990; Vassalli, 1992). As one of the endogenous anti-inflammatory factors, VIP inhibits the production of TNF-α, IL-6, IL-12, and the induction of iNOS, and stimulates the production of the anti-inflammatory cytokines IL-10 and IL-1Ra in LPS-stimulated macrophages and macrophage cell lines (Delgado et al., 1999c; Delgado et al., 1999d; Delgado et al., 1999e; Delgado et al., 1999f; Dewit et al., 1998; Martinez et al., 1998; Xin and Sriram, 1998) (Figure 3). The use of specific agonists and antagonists established that VPAC1 is the major receptor involved in the effect on macrophages with the exception of IL6, which is downregulated following signaling through PAC1 (Table 1). Indeed, in vivo experiments in an inflammation disease model using PAC1-deficient mice suggested that VPAC2 and PAC1 are also involved, although minimally, in the anti-inflammatory effect of VIP (Delgado et al., 2000; Martinez et al., 2005).
FIGURE 2 General immunoregulatory effects of VIP. VIP is released from the lymphoid innervation and from activated Th2 effectors and acts on bone marrow cells inhibiting hematopoiesis; deactivates stimulated macrophages, dendritic cells, and microglia; reduces antigen presentation; promotes Th2 responses at the expense of Th1 proinflammatory responses; and induces the generation and/or activation of regulatory T-cells.
FIGURE 3 Effects of VIP on LPS-stimulated macrophages. VIP inhibits the expression of the pro-inflammatory genes TNF-α, IL-6, iNOS, IL-12p40, and chemokines, and stimulates production of the anti-inflammatory factors IL-10 and IL1Ra. Through its effect on IL-12 production, VIP inhibits the release of IFNγ from activated CD4+ T-cells.
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Accumulation of immune cells at the site of pathogen invasion is mediated through inflammatory chemokines released primarily by cells involved in innate immunity, i.e., macrophages/monocytes, dendritic cells, and microglia. Although chemokines usually attract several types of immune cells, there is a certain degree of specificity. For example, CXCL1 (IL-8) and CXCL2 (MIP-2) activate and induce the directional migration of neutrophils, whereas CCL3 (MIP-1α), CCL4 (MIP-1β), CCL2 (MCP-1), and CCL5 (RANTES) are chemotactic for monocytes/macrophages and Tcells (Luster, 1998; Rollins, 1997; Rossi and Zlotnik, 2000). Although several studies have addressed the effects of VIP on lymphocyte adhesion and traffic, there is little agreement beyond the fact that VIP affects lymphocyte traffic. At the present time, there are few reports regarding the effects of VIP on inflammatory chemokine production and only one report showing that VIP prevents the migration of mononuclear cells by phosphorylating and deactivating the chemokine receptor CCR5 (Grimm et al., 2003). We reported that VIP inhibits the expression of two CXC chemokines (CXCL1/KC and CXCL2/MIP2) and four CC chemokines (CCL2/MCP1, CCL3/MIP1α, CCL4/MIP1β, and CCL5/RANTES) in LPS-stimulated mouse macrophages (Delgado and Ganea, 2001b). Similarly, VIP inhibits endotoxin-induced expression of IL-8 (CXCL1) in human peripheral blood monocytes (Delgado and Ganea, 2003b). The inhibitory effect is mediated by VPAC1 and correlates with a reduction in NFκB binding and transactivating activity (Delgado et al., 2003; Delgado and Ganea, 2001f). In agreement with the reported chemoattraction of neutrophils by CXCL1 and CXCL2, and of monocytes/macrophages and Tcells by CCL2, CCL3, CCL4, and CCL5, the VIP treatment of human monocytes resulted in a reduced in vitro chemotactic activity for peripheral blood neutrophils, and the in vivo administration of VIP in a murine model of acute peritonitis led to a significant reduction in the recruitment of neutrophils, macrophages, and lymphocytes to the peritoneal cavity (Delgado and Ganea, 2001c). Microglia, the CNS functional equivalent of mononuclear phagocytes in the periphery, are considered to play a central role in the regulation of immune and inflammatory activities and tissue remodeling in the CNS (Gonzalez-Scarano and Baltuch, 1999; Streit et al., 1988). In response to brain injury, infection or inflammation, microglia are activated similar to peripheral tissue macrophages. Activation of microglia is a histopathological hallmark of several neurodegenerative diseases where inflammation plays a major role. It has been proposed that in response to pro-inflammatory cytokines or antigens, activated microglia secrete
inflammatory mediators such as NO and pro-inflammatory cytokines, including TNF-α, IL-6, and IL-1β, which contribute to neuronal damage and cell death (Bartholdi and Schwab, 1997; Chao et al., 1995; Ding et al., 1997; Lee et al., 1993; Lipton et al., 1994; McManus et al., 1998; Peterson et al., 1997; Streit et al., 1998; Taupin et al., 1993). Since the intensity and duration of inflammatory processes in the CNS depend on the local balance between pro- and anti-inflammatory factors, a number of regulatory molecules termed microglia-deactivating factors have been the focus of considerable research. Recently, VIP was identified as a microgliadeactivating factor. VIP inhibits in a dose-dependent manner the production of TNF-α, IL-1β, IL-6, NO, and of the pro-inflammatory chemokines RANTES, MCP1, MIP-1α, MIP-1β, MIP-2, and KC by LPS-stimulated microglia (Delgado et al., 2002b; Delgado et al., 2003; Kim et al., 2000). At the same time, VIP stimulates the expression of the anti-inflammatory factors IL-10 and IL-1Ra (Delgado et al., 2003). The VIP-mediated inhibition of chemokine production correlates with a decreased microglia-induced chemotaxis for macrophages, lymphocytes, and neutrophils (Delgado et al., 2002b). Similar to macrophages/monocytes, the effects of VIP on activated microglia are mediated primarily through VPAC1 (Delgado et al., 2002b; Delgado et al., 2003; Kim et al., 2000). In addition, VIP also inhibits the expression of several genes involved in the IFNγinduced inflammatory response in microglia, including CD40, CXCL10 (IP-10), and iNOS (Delgado et al., 2003; Kim et al., 2002). The anti-inflammatory effect of VIP has also been described in vivo. I.c.v. administration of LPS caused neurodegeneration accompanied by massive microglia activation and by increases in the microglial expression of TNF-α, IL-1β, and iNOS. Local i.c.v. VIP administration prevented LPS-induced neurodegeneration, microglia activation, and TNF-α, IL-1β, and iNOS expression (Delgado and Ganea, 2003a; Delgado and Ganea, 2003c; Kim et al., 2002).
B. Signaling Pathways Involved in the Inhibitory Effect of VIP VIP affects the expression of pro- and antiinflammatory factors in LPS- and LPS+IFNγstimulated macrophages and microglia by regulating the expression and/or transactivating activity of transcription factors such as IRF-1, NFκB, CREB, and AP-1. LPS binding to TRL4 results in the activation of NFκB and of the three MAPK pathways, i.e., the p38 MAPK, the extracellular signal-regulated kinases, and the cJun N-terminal kinase (JNK) (Pyo et al., 1998; Zhang
5. Vasoactive Intestinal Peptide: An Anti-inflammatory Neuropeptide
et al., 1998). JNK phosphorylation and activation are mediated through the MEKK1/MKK4/JNK pathway, and phosphorylation of c-Jun by JNK increases its transactivating activity. Activation of the MEKK1/ MKK4/JNK pathway by LPS is involved in the upregulation of several pro-inflammatory factors (Cobb, 1999).We showed that VIP treatment of LPS-stimulated macrophages and microglia results in the inhibition of MEKK1/MKK4/JNK phosphorylation and the upregulation and nuclear translocation of JunB (Figure 4A) (Delgado, 2002; Delgado and Ganea, 2000b). Subsequently there is a change in the composition of AP-1 with c-Jun being replaced by JunB and loss of transactivating activity for TNF-α expression (Delgado et al., 1998). The pleiotropic transcription factor NFκB plays an important role in the transcriptional regulation of all pro-inflammatory factors. The most common transcriptionally active NFκB is a p50/p65 heterodimer. In unstimulated cells, NFκB is localized in the cytosol bound to the inhibitor IκB. LPS treatment results in IκB phosphorylation by specific kinases (IKK), ubiquitination, and proteosomal degradation. This is followed by the rapid nuclear translocation of NFκB and binding to specific κB elements within cytokine and chemokine promoters. The transactivating activity of NFκB requires interaction with co-activators that bridge transcriptional activators and components of the basal transcriptional machinery. The CREB-binding protein (CBP) is an ubiquitously expressed nuclear coactivator present in limiting amounts (Goldman et al., 1997). CBP serves to interconnect various transcription factors, including NFκB with TFIIB, a member of the basal transcriptional machinery, which in turn makes contact with the TATA box-binding protein (TBP) (Janknecht and Nordheim, 1996; Kamei et al., 1996). The interaction of p65 with CBP is essential for NFκB transcriptional activity (Gerritsen et al., 1997; Zhong et al., 1998), and this interaction is prevented by competition from other CBP-binding factors such as CREB (Chrivia et al., 1993; Kwok et al., 1994). Our studies indicate that VIP affects NFκB-transactivating activity through a cAMP-independent pathway, which results in the inhibition of IκB phosphorylation by IKK, a cAMP-dependent pathway which prevents MEKK1/ MEK3-6/p38 phosphorylation and subsequent TBP phosphorylation and nuclear translocation, and the cAMP-dependent phosphorylation of CREB, which becomes a high-affinity competitor for CBP (Figure 4B) (Delgado and Ganea, 2001f). Since NFκB is involved in the expression of TNF-α, IL-12, and iNOS, and of the pro-inflammatory chemokines, the VIP-induced reduction in NFκB-transactivating activity affects multiple target genes.
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In addition to LPS, optimal expression of IL-12 and iNOS in macrophages and microglia requires IFNγ signaling. Binding of IFNγ to its receptor induces the assembly of an active receptor complex with subsequent transphosphorylation of Jak1 and Jak2, followed by recruitment and phosphorylation of STAT1 (Darnell, Jr. et al., 1994). Upon phosphorylation, STAT1 forms homodimers which translocate to the nucleus, where they bind to the IFNγ-activated site (GAS) found in the promoter of many IFNγ-induced genes including IRF1 (Sims et al., 1993). Many of the regulatory effects of IFNγ in macrophages and microglia appear to be mediated by IRF-1, which transactivates multiple effector genes including CXCL10 (IP-10), CD40, IL-12, and iNOS (Ma et al., 1997; Martin et al., 1994; Nguyen and Benveniste, 2002; Ohmori and Hamilton, 1993). Our studies indicate that VIP inhibits Jak1/STAT1 phosphorylation in a cAMP-dependent manner, and therefore prevents IRF-1 expression (Figure 4C) (Delgado and Ganea, 2000a). Although the link between cAMP induction and inhibition of Jak1/STAT1 phosphorylation has not been elucidated, preliminary studies in T-cells suggest that VIP inhibits IL-12 signaling through the phosphorylation and activation of the phosphatase SHIP-1, which in turn dephosphorylates some of the Jaks (unpublished data). Therefore, the family of SHIP phosphatases represents an attractive target for the VIP effect on the Jak/STAT signaling pathways.
C. VIP Inhibits the Capacity of Antigen-presenting Cells to Initiate Adaptive Immunity In vertebrates, innate immunity is followed by an antigen-specific immune response which involves B and T lymphocytes. The link between innate and adaptive immunity is built on the capacity of antigenpresenting cells (APCs), such as dendritic cells, macrophages, and microglia, to process antigen, present it to naïve CD4+ T-cells, and induce T-cell proliferation and differentiation. Optimal T-cell stimulation requires co-stimulatory signals aside from signaling through the TCR. In addition, the APCs provide the cytokine microenvironment necessary for the initial stimulation of CD4+ T-cells. Among the co-stimulatory signals involved in the APC/T-cell interactions, the B7 family, primarily CD80 and CD86, as well as CD40, play major roles. Dendritic cells (DCs) express CD80, CD86, and CD40 constitutively, and upregulate their expression following TLR signaling. In macrophages, the co-stimulatory molecules are expressed only following activation. We reported previously that VIP is among the endogenous factors regulating CD80 and CD86 expres-
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FIGURE 4 Signaling pathways involved in the VIP effect on activated macrophages. (A) LPS induces c-Jun phosphorylation through the MEKK1/MEK4/JNK pathway. VIP acts through the VPAC1 receptor, activates PKA, and phosphorylates JunB. VIP also inhibits the MEKK1/MEK4/JNK pathway and subsequently reduces c-Jun phosphorylation. This results in the replacement of c-Jun with JunB in the AP-1 transcription complex and inhibition of TNF-α transcription. (B) LPS induces TATA-box binding protein (TBP) phosphorylation through the MEKK1/MEK3-6/p38 pathway and induces NFkB (p65/p50) nuclear translocation by activating IKK and inducing IkB phosphorylation and degradation. VIP inhibits the MEKK1/ MEK3-6/p38 pathway in a cAMP-dependent manner, resulting in a reduction in TBP phosphorylation. VIP also inhibits IKK activation in a cAMP-independent manner, preventing IkB degradation and NFkB nuclear translocation. In addition, VIP induces CREB phosphorylation in a cAMP-dependent manner, and phosphorylated CREB competes with p65 for the coactivator CBP. All these effects contribute to reduce transcription of NFkB-dependent genes, such as TNF-α, iNOS, IL-12p40, and chemokines. (C) IFNγ signals through the Jak12/STAT1 pathway to induce transcription of IFNγ-activated genes (GAS), including IRF-1. IRF-1 is an essential transcription factor for IL-12p40 and iNOS. VIP inhibits in a cAMPdependent manner Jak1/STAT1 phosphorylation and subsequently inhibits IRF-1 transcription. The effect on Jak/STAT phosphorylation might be mediated through the activation of the phosphatase SHIP1 (see text).
5. Vasoactive Intestinal Peptide: An Anti-inflammatory Neuropeptide
sion in macrophages (Delgado et al., 1999g). Interestingly, VIP affects the expression of co-stimulatory molecules in an opposite manner in resting and activated macrophages. In resting macrophages, VIP upregulates CD86, but not CD80 expression both in vivo and in vitro. In contrast, in LPS/IFNγ-activated macrophages, VIP downregulates both CD80 and CD86 expression. Similar results were obtained recently with bone marrow–derived DCs (Delgado et al., 2004b). The effect of VIP on the expression of co-stimulatory molecules correlates with the effects on the macrophage/DC stimulatory activity for T-cells. The inhibition of CD80/CD86 expression in activated macrophages and DCs results in a significantly reduced capacity to stimulate allogeneic or antigen-specific syngeneic CD4+ T-cells, in vivo and in vitro (Delgado et al., 1999g; Delgado et al., 2004b). This is in perfect agreement with the accepted role of VIP as an endogenous anti-inflammatory agent. In contrast, the upregulation of CD86 in immature DCs and resting macrophages correlates with an increase in the stimulatory activity for T-cells, and with a pronounced bias in the generation of Th2 effectors (see Section V.A.2).
D. Effects of VIP on Hematopoiesis In mammals the immune cells are generated by hematopoiesis in the bone marrow. During an active immune response, hematopoiesis is enhanced mainly through the effect of cytokines. Once the infectious agent is eliminated, immune cell homeostasis is reestablished, in part through a reduction in hematopoiesis. Although peptidergic nerve fibers were identified in the bone marrow (Felten, 1993; Tabarowski et al., 1996), there are few reports regarding the effects of neuropeptides on hematopoiesis. A recent study demonstrated that VIP reduces the number of granulocytic and erythroid colonies, mostly through direct effects on the CD34+ bone marrow progenitors (Rameshwar et al., 2002). The inhibitory effect of VIP on hematopoiesis could contribute to the re-establishment of homeostasis in vivo following an immune response, supporting the general anti-inflammatory role of VIP.
V. EFFECTS OF VIP ON T-CELL ACTIVATION, DIFFERENTIATION, AND FUNCTION Following recognition of antigenic peptides complexed to MHC class I or II, T lymphocytes proliferate and differentiate into effector cells. CD4+ T-cells recognize antigen complexed to MHC class II presented by APCs and differentiate into Th1 and Th2 effectors.
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CD8+ T-cells recognize antigen complexed to MHC class I and become fully functional cytotoxic T-cells. T lymphocytes, particularly CD4+ T-cells, represent major targets for VIP regulation. Both the activation of naïve T-cells and their differentiation into effector and memory cells are affected by VIP.
A. VIP Effects on CD4+ T Helper Cells 1. Effect on CD4+ T-Cell Activation Proliferation of naïve CD4+ T-cells is initiated following contact with APCs, with both stimulatory and co-stimulatory signals required for T-cell activation. Initial reports indicated that VIP reduces T-cell proliferation (Ganea, 1996). The inhibitory effect of VIP can be attributed to the reduction in the expression of costimulatory molecules on APCs and to direct effects on CD4+ T-cells. Indeed, we reported that VIP downregulates CD80/CD86 in LPS/IFNγ-activated macrophages and DCs, and the reduction in B7 expression correlates with a reduction in the proliferation of antigen-specific T-cells (Delgado et al., 1999g; Delgado et al., 2004b; Ganea et al., 2003). VIP was also reported to directly affect IL-2 gene expression in CD4+ T-cells and to inhibit T-cell proliferation (Ganea, 1996; Gomariz et al., 2001). Both VPAC1 and VPAC2 mediate the inhibitory effect of VIP/ PACAP on IL-2 expression, primarily through the induction of intracellular cAMP and subsequent effects on the transcription factors NFAT and AP-1 (Wang et al., 1999; Wang et al., 2000). 2. VIP Promotes Differentiation into Th2 Effectors Following antigenic stimulation and several rounds of proliferation, CD4+ T-cells differentiate into Th1 and Th2 effectors, characterized by different cytokine profiles. The differentiation into Th1 or Th2 effectors is controlled by the cytokine microenvironment, the nature of the APCs, the nature and amount of antigen, and the genetic background of the host (O’Garra, 1998). In addition, endogenous factors such as progesterone and glucocorticoids have been reported to favor Th2 differentiation (Miyaura and Iwata, 2002). Recent studies indicate that neuropeptides, particularly VIP, also favor Th2 differentiation. Macrophages treated in vitro with VIP gain the ability to induce Th2-type cytokine (IL-4 and IL-5) and to inhibit Th1-type cytokine (IFNγ and IL-2) production in primed CD4+ T-cells (Delgado et al., 1999a). Similar results were obtained recently with bone marrow–derived dendritic cells (Delgado et al., 2004b; Ganea et al., 2003). In vivo, administration of VIP to immunized mice results in a reduction in the number of IFNγ-secreting cells and an
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increase in the number of IL-4 secreting cells (Delgado et al., 1999a). Two recent studies confirmed the prevalence of Th2-type responses in transgenic mice overexpressing the human VPAC2 receptor in CD4+ T-cells (Voice et al., 2001) and of Th1-type responses in VPAC2 knockout mice (Goetzl et al., 2001). The studies in mice genetically altered for VPAC2 expression indicate the importance of endogenous VIP for the regulation of Th1/Th2 responses in vivo and the prominent role of the VPAC2 receptor in CD4+ T-cell differentiation and/ or responses. The role of endogenous, Th2-derived VIP in maintaining the Th2 bias was confirmed recently in studies in which elimination of VIP from TCR-stimulated T-cells with VIPase antibodies resulted in the readjustment of the Th1/Th2 balance (Voice et al., 2003). These studies confirm the concept that VIP affects the Th1/Th2 balance in vivo and indicate the prevalent role of VPAC2 in this process. A number of different, non-excluding mechanisms contribute to the VIP-induced Th2 bias (Figure 5). The
neuropeptide may affect Th1/Th2 generation directly or through effects on APCs, or could act on the alreadygenerated effectors by preferentially promoting Th2 proliferation and/or survival. VIP affects APCs in ways relevant to Th1/Th2 differentiation. First, VIP inhibits the production of IL-12, the major Th1inducing cytokine (Delgado et al., 1999e; Xin and Sriram, 1998). This results in the preferential generation of Th2 effectors. Second, the level of co-stimulatory molecule expression on APCs is more important for Th2, compared with Th1 development (Ranger et al., 1996). VIP has been shown to induce CD86 expression in resting macrophages and immature DCs, and the capacity of the VIP-treated macrophages/DCs to induce Th2 cytokines in antigen-primed T-cells was abolished by treatment with neutralizing anti-CD86 Abs (Delgado et al., 1999a; Delgado et al., 2004b; Ganea et al., 2003). VIP also affects differentiating T-cells directly. Indeed, addition of VIP to TCR-transgenic T-cells cul-
FIGURE 5 Effects of VIP on CD4+ T-cell differentiation and survival. VIP promotes Th2 differentiation through effects on APCs (inhibition of IL-12 release and of CD80/CD86 expression by activated macrophages, induction of CD86 in resting macrophages and DCs), and through direct effects on the differentiating CD4+ T-cells such as induction of c-Maf and JunB expression. VIP promotes the survival of Th2 effectors through the reduction in both FasL and granzyme B expression (see text), and their differentiation into memory Th2 cells.
5. Vasoactive Intestinal Peptide: An Anti-inflammatory Neuropeptide
tured with irradiated APCs and antigenic peptide or stimulated with anti-CD3 and anti-CD28 in the absence of APCs, with or without polarizing cytokines (IL-12 for Th1 and IL-4 for Th2 differentiation), leads to increased levels of IL-4 and decreased levels of IFNγ. This suggests that VIP promotes the development of Th2 cells directly by acting on the differentiating CD4+ T-cells (Ganea et al., 2003). Recent experiments indicate that VIP blocks IL-12 signaling in differentiating CD4+ T-cells, preventing Jak2/STAT4 phosphorylation, presumably through the activation of the SHIP-1 phosphatase (unpublished data). A recent report also indicated that VIP induces the expression of the Th2 master transcription factors c-Maf and JunB in differentiating CD4+ T-cells (Voice et al., 2004). Finally, VIP could act on the already-generated Th1/Th2 effectors. Both in vitro and in vivo experiments indicate that VIP supports the survival and possibly the proliferation of Th2, but not Th1, effectors (Delgado et al., 2002c). The in vivo surviving Th2 cells following inoculation with antigen and VIP exhibit memory cell markers (Delgado et al., 2002c) (see Section V.A.3). In addition to promoting Th2 survival, VIP also affects Th1/Th2 migration in a differential manner. Recent studies indicate that VIP promotes Th2 and inhibits Th1 migration in vitro and in vivo, through effects on the production of chemokines. VIP promotes the expression and release of CCL22 (MDC), a Th2-attracting chemokine and inhibits the release of the Th1-attracting chemokine CXCL10 (IP-10) (Delgado et al., 2004a) (see Section V.A.4). The preferential recruitment of Th2 effectors could further contribute to the VIP induction of Th2, as opposed to Th1-type immunity by VIP.
3. VIP Promotes the Survival of Th2 Effectors The majority of Th1/Th2 effectors become apoptotic following a relatively short period of intense activity. The elimination of effector T-cells occurs through either active or passive apoptosis, depending on whether the antigen persists or is eliminated. The few surviving effector T-cells become antigen-specific memory cells and differ from naïve T-cells in terms of homing and activation requirements. Although VIP acts as a survival factor in the CNS, we expected VIP to promote T lymphocyte apoptosis in the peripheral immune system, based on its antiinflammatory function. Surprisingly, VIP was shown to protect activated CD4+ T-cells against active (antigeninduced) cell death (AICD) both in vitro and in vivo. This protection is associated with an inhibitory effect on FasL ligand (FasL) expression (Delgado and Ganea,
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2000c). FasL expression requires a number of transcription factors, including NFκB and Egr2 and 3. VIP inhibits NFκB binding through the stabilization of the IκB inhibitor and retention of p65/p50 in the cytoplasm. In addition, VIP prevents NF-ATp nuclear translocation in a calcineurin-independent manner, inhibiting the NF-ATp dependent expression of Egr2 and 3 (Delgado and Ganea, 2001e). At first glance, the protective effect against apoptosis, resulting in a higher number of surviving effector CD4+ T-cells, could lead to a more intense inflammatory response, in apparent contradiction to the general anti-inflammatory effect of VIP. However, VIP might specifically protect Th2 effectors, to the detriment of Th1 cells, which are the major players in acute inflammation through the mobilization and activation of neutrophils and macrophages. Therefore, the VIPinduced development of Th2 immunity, with its subsequent reduction in Th1 effectors, would have an anti-inflammatory effect. The function of VIP as a specific Th2 survival factor is in agreement with the Th2-type immunity observed in transgenic mice overexpressing the VPAC2 receptor or following VIP administration in wild-type mice (Delgado et al., 1999a; Voice et al., 2001). We confirmed the preferential effect of VIP on the survival of Th2 effectors in a recent report (Delgado et al., 2002c). When thymectomized hosts were reconstituted with Th1 and Th2 cell lines derived from TCR transgenic mice, followed by immunization with the specific antigen and VIP, transgenic CD4+ T-cells could be recovered 62 days later only from hosts that received Th2 cells. When the hosts received transgenic CD4+ Tcells instead of Th1 or Th2 cell lines, the recovered transgenic T-cells exhibited a phenotype typical of memory Th2 cells (CD44hi, L-selectinlo, CD45RBlo, and IL-4 and IL-5, but not IFNγ or IL-2 producers). The preferential survival of Th2 cells in the presence of VIP was also confirmed in vitro, with VIP/PACAP supporting the survival of Th2, but not Th1, cell lines (Delgado et al., 2002c). Mechanistic studies established that AICD in Th1 and Th2 effectors occurs through two apparently independent pathways, initiated by FasL/Fas interactions and through the induction of granzyme B (GrB), respectively (Sharma et al., 2006). Both Th1 and Th2 effectors upregulate FasL and GrB expression following TCR restimulation. There is a significant difference between Th1 and Th2 cells in the expression of VPAC1/2 receptors, with Th2 cells expressing higher levels of VIP receptors. VIP prevents FasL expression in both Th1 and Th2 cells, but inhibits GrB expression selectively in Th2 effectors (Sharma et al., 2006).
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4. VIP Favors the Directional Migration of Th2 Cells The selective recruitment of effector T-cells to an inflammatory site is mediated through chemokines and chemokine receptors. Although chemokines are largely redundant, the homing of Th1 and Th2 cells depends on the expression of different chemokine receptors (Bonecchi et al., 1998; Sallusto et al., 1998). Th1 cells express CXCR3 and CCR5, whereas Th2 cells preferentially express CCR3, CCR4, and CCR8 (Bonecchi et al., 1998; Loetscher et al., 1998; Qin et al., 1998). Among chemokines, IP-10 (CXCL10), MIG (CXCL9), and I-TAC (CXCL11) bind only to CXCR3, whereas MDC (CCL22), TARC (CCL17), and TCA-3 (CCL1) bind to CCR4 and/or CCR8 (Zlotnik and Yoshie, 2000). Activated Th1 and Th2 cells were reported to migrate in response to IP-10 (CXCL10) and MDC (CCL22), respectively (Andrew et al., 1998; Bonecchi et al., 1998; Imai et al., 1999). In a recent study we showed that VIP downregulates CXCL10 and upregulates CCL22 release in spleen cell cultures (Jiang et al., 2002). Similar results were obtained with bone marrow–derived DCs (Delgado et al., 2004a; Ganea et al., 2003). VIP induces CCL22 release in immature and mature DCs and inhibits CXCL10 release from mature DCs. There is a good correlation between the VIP effects on CCL22 and CXCL10 production and chemotaxis for Th2 and Th1 cells, both in vitro and in vivo, where VIP-treated DCs loaded with Ag and inoculated i.p. lead to the preferential accumulation of Th2 effectors in the peritoneal cavity (Delgado et al., 2004a). The selective effect of VIP on Th1/Th2-attracting chemokines represents a new additional mechanism for its Th2-promoting activity.
B. VIP Effects on CD8+ and CD4+ Cytotoxic T-Cells Cytotoxic CD8+ T-cells kill targets through a major, calcium-dependent, perforin/granzyme-mediated mechanism, with a minor contribution from the calcium-independent, FasL-mediated pathway. VIP does not affect the perforin/granzyme-mediated cytotoxicity but inhibits drastically the FasL-mediated lysis of both allogeneic and syngeneic Fas-bearing targets. This results from the VIP-induced inhibition of FasL expression in CD8+ T-cells (Delgado and Ganea, 2000d). Since VIP affects only the minor FasL/Fas-mediated lysis in CD8+ cytotoxic T-cells, their overall effect on CD8+ T-cell cytotoxicity does not have major consequences. In contrast, CD4+ cytotoxic T-cells kill targets solely through the FasL/Fas-initiated pathway (Stalder et al.,
1994), and VIP has a major impact on their cytotoxic function. Cytotoxic CD4+ T-cells are activated by APCs in an MHC II–restricted manner, leading to FasL expression. Subsequently, the activated CD4+ T-cells lyse both cognate APCs (direct targets) and neighboring Fas-bearing cells (bystander targets) (Smyth, 1997; Wang et al., 1996). VIP inhibits FasL expression in CD4+ effectors generated in vivo and reduces the cytotoxicity for both direct and bystander targets (Delgado and Ganea, 2001g). Killing of bystander targets results in collateral damage, which is detrimental particularly in tissues with limited MHC II expression such as the brain. In this context, the fact that endogenous agents such as VIP, a neuropeptide highly expressed in the brain, controls Fas-mediated lysis of innocent bystanders might be highly significant.
C. VIP Contributes to the Generation of Antigen-specific Regulatory T-Cells Dendritic cells are a heterogeneous population of antigen-presenting cells that besides, contributing to innate immunity and initiating adaptive immunity, also play an important role in immune homeostasis, by inducing and maintaining tolerance (Banchereau et al., 2000; Steinman, 2003). Regulatory T-cells (Treg) generated in the thymus and in the periphery are major tolerance enforcers. Although questions regarding Treg generation remain to be answered, recent reports indicate that immature or semi-mature DCs contribute to the induction of Treg. Treg-inducing DCs, called tolerogenic DCs, appear to be generated in a variety of ways. For example, human monocytederived immature DCs secreting IL-10 act as tolerogenic DCs (Levings et al., 2005). Tolerogenic DCs have been generated from human monocyte and murine bone marrow in the presence of 1,25(OH)2D3, the active form of vitamin D3 and of vitamin D3 analogs (Gregori et al., 2001; Piemonti et al., 2000). Also, DCs grown in the presence of TNF and IL-10 function as tolerogenic, and are characterized by a specific phenotype, i.e., CD11clowCD45RBhigh (Menges et al., 2002; Wakkach et al., 2003). We evaluated the capacity of VIP to induce tolerogenic DCs in vitro and in vivo. Bone marrow– derived DCs generated in the presence of VIP are CD11clowCD45RBhigh and do not upregulate the costimulatory molecules CD40, CD80, and CD86 following LPS stimulation. In contrast to control DCs (generated in the absence of VIP), the LPS-stimulated VIP-DCs secrete low levels of pro-inflammatory cytokines and high levels of IL-10. Antigen-pulsed VIPDCs induce IL-10/TGFβ secreting T-cells that suppress
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the response of freshly activated CD4+ T-cells in an antigen-specific manner (Delgado et al., 2005b). The antigen-loaded VIP-DCs induce antigen-specific tolerance in vivo, and generate antigen-specific Treg capable of transferring tolerance to naïve hosts (Delgado et al., 2005b). The in vivo administration of VIP together with low doses of antigen results in a significant increase in the number of CD4+CD25+ Foxp3-expressing Treg. The in vivo VIP-induced Treg transfer antigen-specific suppression, inhibit delayed-type hypersensitivity, and prevent graft-versus-host disease in irradiated hosts reconstituted with allogeneic bone marrow (Delgado et al., 2005a; see Section VI.D). The capacity of VIP to generate tolerogenic DCs and antigen-specific Treg suggests new and exciting therapeutic avenues for the treatment of autoimmune diseases and the potential use of VIP in bone marrow transplantation.
VI. VIP IN MODELS OF AUTOIMMUNITY, INFLAMMATION, AND BONE MARROW TRANSPLANTATION Due to its pleiotropic functions, VIP and VIP analogs are considered for the development of multiple therapies. Here, we review the potential VIP therapeutic applications in immunological disorders, such as autoimmunity, inflammatory conditions, and bone marrow transplantation. Due to the inhibition of macrophage/ microglia activation, and to the ability to promote Th2 immunity and to generate and/or activate antigenspecific regulatory T-cells, VIP is as an attractive therapeutic factor for inflammatory disorders and/or Th1-type autoimmune diseases.
A. Autoimmune Disorders 1. Rheumatoid Arthritis Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by progressive joint inflammation and subsequent cartilage and bone destruction. RA treatments are focused on the decrease of joint inflammation, primarily by inhibiting the secretion or activity of pro-inflammatory cytokines and chemokines. Agents that inhibit TNF-α secretion or block receptor binding are increasingly viewed as therapeutic agents with increased specificity in comparison to traditional drugs (Feldmann, 1996). Since animal models indicated a predominant Th1 role in RA (Joosten et al., 1997; Mauri et al., 1996; Walmsley et al., 1996), alternative therapeutic strategies focus on the alteration of the Th1/Th2 balance.
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VIP is a potent inhibitor of macrophage activation (including secretion of TNF-α, IL-6, and NO; discussed in Section IV.A), and a Th2-promoting factor (discussed in Section V.A), and therefore, an excellent prospect for RA therapy. In fact, several recent reports using the animal model of collagen-induced arthritis (CIA), which shares a number of clinical, histological, and immunological features with human RA, demonstrated that VIP administration to arthritic mice or rats decreases the frequency, delays the onset, and reduces the severity of the disease (Figure 6A) (Delgado et al., 2001; Williams, 2002; Yin et al., 2005). VIP reduces the proliferative response of collagen-specific T-cells, induces a shift towards Th2 cytokines, and reduces the titer of autoreactive anti-collagen antibodies (particularly IgG2a) (Delgado et al., 2001). VIP reduces the inflammatory response by downregulating the production of several pro-inflammatory agents in the inflamed joints and synovial cells, including TNF-α, IL-6, IL-1β, iNOS, IL-12, and IL-18, and of various chemokines (RANTES, MCP-1, MIP-1α, MIP-1β, and MIP2) (Delgado et al., 2001). In addition, VIP increases the production of the anti-inflammatory cytokines IL-10 and IL-1Ra, which have been reported to ameliorate arthritis symptoms (Feldmann, 1996). A similar VIP effect on cytokine/chemokine release by human synovial cells from RA patients was reported (Juarranz et al., 2004; Takeba et al., 1999). A recent study from our laboratory indicates that VIP inoculation in CIA mice after disease onset results in the generation of CD4+CD25+ Treg, which significantly ameliorate the clinical score upon transfer to arthritic hosts. This is associated with a decrease in the expression of IL-12, IFNγ, and TNF-α in the affected joints, and with a decrease in the proliferation and IFNγ and IL-2 production in spleen cells of the arthritic hosts (Gonzalez-Rey et al., 2006a). The capacity of VIP to regulate a wide spectrum of macrophage-derived inflammatory mediators, to switch the Th1/Th2 balance in favor of Th2 immunity, and to contribute to the generation and/or activation of Treg offers an advantage over treatments with neutralizing antibodies and receptor antagonists directed against a single cytokine. Of obvious biological significance is the fact that VIP levels, similar to those of other described antiarthritic neuropeptides and hormones such as CGRP and αMSH (Lipton and Catania, 1997; Takeba et al., 1999), are increased in serum and joints of arthritic mice (Delgado et al., 2001; Delgado et al., 2002a). This suggests that endogenous neuroimmune factors act as natural anti-arthritic agents. Nevertheless, arthritis-induced endogenous VIP levels are two to three orders of magnitude lower
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than the required protective concentrations for exogenous VIP. 2. Crohn’s Disease Crohn’s disease (CD) is an autoimmune inflammatory bowel disease characterized by chronic inflammation in the gastrointestinal tract leading to abdominal pain, rectal bleeding, diarrhea, weight loss, skin and eye disorders, and delayed growth and sexual maturation in children (Hanauer and Present, 2003). The abnormal inflammatory process results in a prolonged and severe inflammation of the intestinal mucosa, uncontrolled production of pro-inflammatory cytoA
kines and oligoclonal expansion, and activation of CD4+ Th1 cells (Blumberg and Strober, 2001). Classical therapeutic agents used in Crohn’s disease are mostly non-specific and exhibit adverse side effects (Hanauer and Present, 2003). Novel, more specific therapeutic strategies include the blockage of some of the pro-inflammatory cytokines (such as TNF-α, IL-6, and IL-12) (Atreya et al., 2000; Fuss et al., 1999; Neurath et al., 2002; Nikolaus et al., 2000; Yamamoto et al., 2000). Since both macrophage-derived inflammatory agents and Th1-derived cytokines are involved in CD, the ideal treatment should address both. In a recent report, Abad et al. (2003) used the murine IBD model induced by intrarectal administration of trinitrobenB
C
FIGURE 6 Effects of VIP in disease models. (A) Collagen-induced arthritis. DBA/J mice were immunized with bovine collagen and treated with VIP (1 and 5 nmol) at different times after immunization (day 28, or at the time of the secondary antigen administration—day 34). Open circles—VIP treatment; closed circles—control (no VIP). (B) Inflammatory bowel disease. IBD was induced in Balb/c mice with TNBS in 50% ethanol. Mice were treated with VIP (5 nmol) 12 hours after TNBS administration, and body weight was measured daily. Open circles—VIP treatment; closed circles—control, no VIP. Numbers in parentheses indicate mortality. (C) Septic shock. Balb/c mice were injected i.p. with a high dose of LPS and VIP or PACAP at the time of LPS administration. Viability was determined at 12-hour intervals. Positive control (D) represents mice injected with LPS and anti-TNF-α Abs.
5. Vasoactive Intestinal Peptide: An Anti-inflammatory Neuropeptide
D
E
FIGURE 6 cont’d. (D) EAE. SJL/J mice were immunized with PLP and injected with VIP either at the time of immunization (left panel) or at different times after immunization (right panel). The mean clinical score was determined at different times after immunization. (E) Graft-versusleukemia. Irradiated Balc/c mice were injected with syngeneic leukemic cells and reconstituted with allogeneic T-cell–depleted bone marrow cells (BM)—closed circles. Open circles—in addition to leukemic and BM cells, the mice received CD4+ T-cells from allogeneic TCR-transgenic mice inoculated with the specific Ag. Closed triangles—in addition to leukemic and BM cells, the mice received CD4+ T-cells from allogeneic TCR-transgenic mice inoculated with specific Ag and VIP. Survival was monitored daily after bone marrow transfer (BMT) (left panel). Leukemic cells (A20) H-2Kd+B220+ cells were monitored in blood as (right panels).
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zene sulfonic acid (TNBS) and demonstrated that treatment with VIP reduced the clinical severity (Figure 6B) and the disease-related histopathology, preventing or reversing body weight loss, diarrhea, and intestinal inflammation. VIP was effective both when administered together with TNBS and when given several days after colitis onset. VIP significantly reduced the inflammatory response by downregulating the expression of the pro-inflammatory cytokines TNF-α, IL-1β, IL-6, IL-12, and IL-18 and chemokines MIP-1α, MCP-1, MIP-2, KC, CXCL12, CXCL13, and CXCL14 (Abad et al., 2003; Abad et al., 2005). As expected from the effect on chemokine expression, the VIP treatment reduced the number of infiltrating immune cells, including neutrophils, macrophages, and CD4+ T-cells in the lamina propria. Spleen and lamina propria CD4+ Tcells from mice treated with VIP showed a preferential Th2 response, with increased production of IL-4 and IL-10 (Abad et al., 2003; Abad et al., 2005). In addition to the described mechanisms for VIP-induced deactivation of macrophages and preferential development of Th2 responses (see Sections IV.A and V.A), a recent report indicates that VIP downregulates the expression of TLR2 and 4 in the murine IBD model (Gomariz et al., 2005). Since GI immune cells are presumed to be chronically activated by local microorganisms in Crohn’s disease, the VIP-induced downregulation of receptors recognizing various groups of microorganisms is certainly relevant. From a therapeutic point of view, it is important to point out that VIP reduced disease severity even when given after the onset of clinical symptoms, and that VIP dramatically reduced disease recurrence upon administration of a second dose of TNBS (Abad et al., 2003). Therefore, VIP could function as a possible multi-step therapeutic agent for Crohn’s disease.
B. Peripheral Inflammatory Disorders 1. Septic Shock Syndrome Septic shock in humans is caused primarily by endotoxins released during severe Gram-negative bacterial infections and carries a staggering 30–50% mortality rate (Danner et al., 1991). High endotoxemia following LPS administration to experimental animals leads to pathological changes similar to human septic shock syndrome. In the last decade our understanding of the pathophysiology of septic shock has increased markedly (Baumgartner and Calandra, 1999; Glauser et al., 1994; Parrillo, 1993). The septic shock follows massive bacterial infections, resulting in the release of bacterial products and the activation of host immune cells and of soluble factors such as complement and clotting molecules. It is generally recognized that the
severe pathology associated with septic shock results from a hyperactive and out-of-balance network of endogenous pro-inflammatory cytokines, including TNF-α, IL-12, IL-6, and IFNγ (van Deuren et al., 1992). The overproduction of inflammatory cytokines generates systemic activation, which affects vascular permeability, cardiac function, and induces metabolic changes that can lead to tissue necrosis and eventually to multiple organ failure and death. Since VIP inhibits the production of pro-inflammatory macrophage-derived cytokines, it was expected to protect against endotoxemia. Indeed, VIP is protective in high endotoxemic models for septic shock (Figure 6C) (Delgado et al., 1999b; Delgado et al., 2000; Martinez et al., 2005; Tuncel et al., 2000). Endotoxemic animals suffer from generalized intravascular coagulation with multiple organ failure as evidenced by severe congestion, hemorrhage, fibrin deposits, edema, thrombosis, massive accumulation of leukocytes in lungs and the intestinal tract, severe congestion of the medullar sinusoids in the spleen, and segmental ischemia of the bowel with regions of hemorrhage or necrosis and an infracted caecum. In contrast, VIPtreated individuals did not present any of the histopathological alterations associated with septic shock (Delgado et al., 1999b). The protective effect of VIP is associated with the downregulation of pro-inflammatory agents released from activated macrophages, i.e., TNF-α, IL-6, IL-12, and NO and immune cell recruitment in target organs (Delgado et al., 1999b; Delgado et al., 2000; Martinez et al., 2005). Studies with specific VIP receptor agonists and the use of PAC1-deficient mice showed that although VPAC1 is the main receptor involved in the protective effect of VIP in septic shock, all three receptors participate in the VIP-induced downregulation of cytokine production and the inhibition of neutrophil recruitment (Delgado et al., 2000; Martinez et al., 2002; Martinez et al., 2005). Whether VIP or VIP analogs might provide a successful therapy in septic shock syndrome remains to be ascertained. The current clinical trials for various therapies have been disappointing. There are several reasons for the lack of success in applying the results obtained in animal models to patients with septic shock syndrome. In animal models, the events starting with the initial stimulus and resulting in the release of the pro-inflammatory cytokine cascade follow a predictable time course. Thus, experimental protocols designed to block the cytokine cascade are relatively straightforward. In contrast, in human septic shock syndrome, the sequence of events is more complex, and the course of the disease generally lasts days rather than hours, as in most animal models. The design of a clinical trial is based essentially on experimental
5. Vasoactive Intestinal Peptide: An Anti-inflammatory Neuropeptide
models using parenteral injections of LPS/bacteria. In contrast, in humans the organisms and site of infections are diverse, and the patients have a variety of underlying diseases. Most important, interventions in animal models have been successful only when applied early, whereas therapy in patients starts during fullblown disease. Since VIP has pleiotropic effects on inflammation, and since it remains protective in the high endotoxemic murine model even when administered 2 hours after LPS inoculation, treatment with VIP or VIP analogs may represent a better biological therapeutic alternative than anti-inflammatory cytokines or anti–TNF-α antibodies, which are effective only at an early stage.
C. Neuroinflammation In addition to multiple sclerosis, the best characterized autoimmune disease in the CNS, recent evidence points towards inflammation as a player in neurodegenerative diseases such as Parkinson’s and Alzheimer’s disease. Also, inflammation is the central player in secondary neuronal cell death occurring in brain trauma and spinal cord injury. Microglia, the CNS equivalent of peripheral mononuclear phagocytes, play a major role in CNS inflammation through the release of pro-inflammatory cytokines and chemokines and the capacity to efficiently present antigen to CD4+ T-cells (Kim and de Vellis, 2005; Minghetti et al., 2005; Nelson et al., 2002). Microglia activation is a hallmark of several neurodegenerative diseases, and microgliareleased inflammatory mediators including TNF-α, IL-6, IL-1β, and NO contribute to neuronal damage (Lipton et al., 1994; Taupin et al., 1993). Since VIP was recently identified as a microgliadeactivating factor (see Section IV.A), we assessed its potential role in models of Parkinson’s, brain trauma, and multiple sclerosis. 1. Parkinson’s Disease In vitro VIP has been shown to prevent LPS-induced neuronal cell death in mixed glia-neuronal cell cultures (Delgado and Ganea, 2003a). This neuroprotective effect was especially relevant for dopaminergic neurons (tyrosine hydroxylase, TH-positive neurons). The LPS-induced neurodegeneration is associated with and probably mediated by increased microglial activation, characterized by morphological changes, increased Mac-1 expression, release of free radicals, TNF-α, and NO (Delgado and Ganea, 2003a). The involvement of activated microglia is supported by the lack of LPS effect on pure neuronal cultures and by the fact that cell-free supernatants from LPS-stimulated microglia induce significant cell death in neuro-
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nal cultures. VIP inhibited the LPS-induced microglial activation and the production of TNF-α and NO, suggesting that the neuroprotective effect of VIP is mediated through its inhibitory effect on microglia activation. In Parkinson’s disease (PD) there is progressive degeneration of the dopaminergic neurons of the substantia nigra pars compacta (SNpc) and subsequent loss of their projecting fibers to the striatum. The etiology of PD remains unknown, and present therapies are successful only short term. Several mechanisms, including mitochondrial dysfunction, oxidative damage, excitotoxicity, and α-synuclein deposition, have been proposed to initiate neuronal cell death (Goedert, 2001; Jenner and Olanow, 1996; Mizuno et al., 1995). In addition, neuronal cell death occurs subsequent to inflammatory processes (Fahrig et al., 2005; Jackson-Lewis and Smeyne, 2005; Nagatsu and Sawada, 2005). Pro-inflammatory cytokines are known to participate in mitochondrial impairment and oxidative stress, and therefore, the inflammatory response may serve as an integral feature in PD pathogenesis. Insights into the pathogenesis of PD have been achieved experimentally by using the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model. MPTP produces irreversible clinical, biochemical, and neuropathological effects that mimic those observed in idiopathic PD, including the dramatic neurodegeneration of the nigrostriatal dopaminergic neurons (Bloem et al., 1990; Grunblatt et al., 2000; Przedborski et al., 2000). We have recently demonstrated that the stereotaxic SNpc administration of VIP in the MPTP mouse model of PD is beneficial, reducing SNpc dopaminergic neuronal degeneration and nigrostriatal nerve fiber loss (Delgado and Ganea, 2003a). VIP prevents MPTPinduced activation of microglia in SNpc and striatum and the expression of the cytotoxic mediators iNOS, IL-1β, TNF-α, and NADPH-oxidase. The VIP effect is mediated through VPAC1 and is PKA-dependent. Based on the correlation between the neuroprotective effect of VIP and its inhibition of MPTP-induced microglial activation, we propose that VIP exerts its neuroprotective activity as a “microglial-deactivating factor.” Interestingly, systemic i.p. administration of VIP also inhibited MPTP-induced loss of TH immunoreactivity, although it required 15-fold higher doses and was 50% less efficient than cerebral VIP administration. 2. Brain Trauma Although there is agreement that the increase in the levels of pro-inflammatory cytokines is an early feature in CNS trauma (Bartholdi and Schwab, 1997b; Streit
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et al., 1998; Taupin et al., 1993), whether inflammation in the injured CNS serves a beneficial or detrimental purpose remains controversial. There is evidence that the administration of inflammatory cytokines to injured areas is neuroprotective and/or promotes axonal regeneration (Schwartz et al., 1999). Bloodderived macrophages were shown to change the nonpermissive environment of the CNS white matter to an axonal growth-promoting environment (David et al., 1990). In contrast, other studies support the involvement of pro-inflammatory mediators such as TNF-α, IL-1β, and NO in neuronal and oligodendroglial cell death (Gonzalez-Scarano and Baltuch, 1999; MorgantiKossmann et al., 2002; Stoll et al., 2002). Whether inflammation plays a beneficial or detrimental role in neuronal degeneration might depend on the type of inflammatory cells, the CNS region involved, or the stage of neuronal degeneration. The source of inflammatory cytokines in the CNS following trauma remains unresolved. Infiltrating leukocytes are obvious candidates, but the CNS influx of leukocytes is delayed compared to other tissues. Thus, neutrophils do not infiltrate appreciably until about 6 hours after lesion, whereas T lymphocytes and monocytes appear 12 to 24 hours later (Frank and Wolburg, 1996; Giulian et al., 1989; Moreno-Flores et al., 1993). This suggests that resident cells in the CNS mount the early inflammatory response in trauma. Microglia have been proposed as the source of the early increase in CNS inflammatory cytokines following injury (Bartholdi and Schwab, 1997; Streit et al., 1988). In a model of murine stab wound brain trauma in the periventricular area, VIP was shown to significantly reduce neurodegeneration, the recruitment of mononuclear phagocytes, and microglia activation (Delgado and Ganea, 2003c). We propose that VIP reduces neuronal cell loss through the inhibition of microglial release of pro-inflammatory mediators such as TNF-α, IL-1β, and of chemokines responsible for the recruitment of blood-derived leukocytes into the brain parenchyma. Whether VIP also acts directly on neurons as a neuroprotective agent, or affects neuronal survival through secondary effects on astrocytes, remains to be established. 3. Experimental Autoimmune Encephalomyelitis Experimental autoimmune encephalomyelitis (EAE) is an inflammatory, autoimmune demyelinating disease of the CNS in rodents, with pathologic and clinical similarities to human multiple sclerosis (MS). EAE is used as a model to study the basic mechanisms of autoimmune demyelination and to test potential therapeutic agents (Steinman, 1999). Development of
EAE involves two main phases, i.e., initiation and establishment of autoimmunity to myelin sheath components, and later events leading to the destruction of myelin sheaths. The autoimmune response involves the development of reactive Th1 cells with encephalitogenic potential, their entry into the CNS, microglia activation and recruitment, and activation of peripheral inflammatory cells (Behi et al., 2005; Owens, 2003; Segal, 2005; Wheeler and Owens, 2005). Various therapeutic approaches address the autoimmune components of EAE and MS, complementing existing anti-inflammatory therapies (Calabresi et al., 2002; Howard and Miller, 2004; Killestein et al., 2005; Mezzapesa et al., 2005; Murdoch and Lyseng-Williamson, 2005; Pease and Horuk, 2005; Steinman, 2005; Yong, 2002). Although available therapies reduce the relapse rate and/or delay disease onset, they do not suppress progressive clinical disability. This illustrates the need for novel therapeutic approaches to prevent the inflammatory and autoimmune components of the disease and to promote repair and regeneration mechanisms. Since VIP acts as a potent “deactivating factor” for both macrophages and microglia, promotes Th2 differentiation, and generates antigen-specific regulatory T-cells (see Sections IV.A and V.A and C) we investigated the potential therapeutic effect of VIP in the chronic C57BL/6 and the remitting-relapsing SJL/J EAE models. A recent report indicated that the structurally related neuropeptide PACAP ameliorates EAE in C57BL/6 mice primarily through its effect on antigen-presenting cells (Kato et al., 2004). Our results indicate that VIP treatment prevents the clinical symptoms when administered at the time of immunization and significantly reduces disease severity when administered post-immunization (Figure 6D) (Gonzalez-Rey et al., 2006b). The therapeutic effect correlates with a significant reduction in the spinal cord expression of the pro-inflammatory mediators TNF-α, IL-6, IL-1β, IL-18, IL-12, iNOS; and of various chemokines including CCL2 (MCP-1); an increase in IL-10, TGFβ1, and IL-1Ra expression; and a significant decrease in the number of encephalitogenic Th1 cells both in the periphery and the CNS (Gonzalez-Rey et al., 2006b). We also observed a bias towards Th2 responses in mononuclear cells isolated from both CNS and periphery. Most important, VIP treatment post-immunization was also effective. Since our results indicate that VIP administration induces the generation and/or activation of efficient CD4+CD25+ Treg, including the appearance of CD4+CD25+ cells with a Treg phenotype in the CNS, we propose that the beneficial effect of VIP is mediated, at least partially, through regulatory T-cells
5. Vasoactive Intestinal Peptide: An Anti-inflammatory Neuropeptide
(Chorny et al., 2005; Fernandez-Martin et al., 2006). The Treg induced by VIP in the periphery apparently cross the blood-brain barrier, accumulate in the CNS, and induce suppression of the encephalitogenic response. Indeed, CD4+CD25+ Treg cells have been reported to play a critical role in the regulation of autoimmune diseases, including EAE and MS (Bynoe et al., 2003; Kohm et al., 2002; Reddy et al., 2004; Viglietta et al., 2004). Attention has been focused lately on repair and regeneration mechanisms as targets for MS therapy, especially in the secondary progressive phase of the disease. Interestingly, the delayed administration of VIP in EAE not only prevented the progression of the disease, but induced significant recovery, suggesting a role of VIP in repair and/or neuroregeneration. In fact, in our study, VIP inhibited oligodendrocyte cell loss and axonal damage. VIP stimulates the release of Tcell–derived brain-derived neurotrophic factor (BDNF) (unpublished data), which has been reported to promote axonal outgrowth and rescue of the degenerating neurons (Murray et al., 2002; Yin et al., 1998). VIP has been also reported to induce the production of astrocyte-derived neurotrophic factors (Gozes and Brenneman, 2000). Therefore, in addition to its antiinflammatory activity, VIP might also contribute to neuroprotection and neuroregeneration.
D. Bone Marrow Transplantation Allogeneic bone marrow transplantation is the treatment of choice in hematopoietic malignancies. Following high dose chemotherapy or irradiation, the host is reconstituted with bone marrow cells, and the donor T-cells are responsible for the graft-versus-tumor (GVT) effects that eliminate the remaining malignant host cells. However, the same donor T-cells can initiate a graft-versus-host reaction (GVHR) that represents the major complication following allogeneic bone marrow transplantation. Therefore, the ideal therapy would allow a graft-versus-tumor response without a graft-versus-host reaction. In mice, regulatory T-cells have been shown to prevent lethal GVHR in lethally irradiated hosts reconstituted with allogeneic bone marrow (Cohen et al., 2002; Hoffmann et al., 2002). Recent studies have also demonstrated that, while controlling GVHR, CD4+CD25+ Treg maintain the graftversus-tumor (GVT) response (Trenado et al., 2003). In recent experiments we demonstrated that the in vivo administration of VIP together with low doses of soluble antigen results in the development/activation of antigen-specific CD4+CD25+ Treg (Delgado et al., 2005a; see Section V.C). Using a similar experimental system, we addressed the question whether VIP-
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induced Treg control GVHR while still allowing the beneficial graft-versus-leukemia response. The potential use of VIP-induced Treg in a model of GVHR was assessed by reconstituting lethally irradiated H-2d recipients with allogeneic (H-2k) bone marrow cells depleted of T-cells. The recipients also received CD4+ splenic T-cells obtained from H-2k TCR-transgenic mice previously inoculated with Ag (CD4-control) or with Ag+VIP (CD4-VIP). Mice receiving CD4-control developed severe GVHR, including weight loss, reduced mobility, hunched posture, diarrhea and ruffled fur, and died within 30 days. In contrast, mice receiving CD4-VIP were protected, and more than 60% survived for more than 75 days. The protective effect was even more pronounced upon use of purified CD25+ T-cells from the Ag+VIP-injected donors (Delgado et al., 2005a). While these experiments proved that VIP-induced CD4+CD25+ Treg prevented GVHR, the question remained whether a beneficial GVT effect would be preserved. Irradiated H-2d recipients were reconstituted with T-cell–depleted allogeneic bone marrow cells (H-2k) plus A20 leukemic cells (H-2d) and either CD4-control or CD4-VIP T-cells. The hosts receiving only bone marrow cells died between days 20 and 30 of leukemia (Figure 6E). The hosts receiving bone marrow and CD4-control died of GVHR between days 5 and 24, although the A20 tumor cells had been eliminated. In contrast, 80% of the mice that received bone marrow and CD4-VIP survived, with no evidence of A20 leukemic cells in blood (Figure 6E) (Delgado et al., 2005a). These studies indicate that the VIPgenerated Treg protect against GVHR, while still allowing GVT to occur, and suggest the possible use of VIP-induced Treg in various pathological conditions, including hematopoietic cell transplantation.
VII. CONCLUSIONS AND PERSPECTIVES Macrophages and dendritic cells in the periphery and microglia in the CNS are major players in innate immunity and serve as a link to adaptive immunity by functioning as antigen-presenting cells. Locally activated macrophages, dendritic cells, and microglia decrease the pathogen load through the release of cytotoxic cytokines, oxygen radicals, and nitric oxide, and recruit additional immune cells through the release of pro-inflammatory chemokines. In response to stimulatory and co-stimulatory signals delivered by APCs, CD4+ T-cells proliferate and differentiate into effector Th1 and Th2 cells. At the conclusion of an immune response, both activated dendritic cells/macrophages/ microglia and T-cells have to be deactivated and/or
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eliminated to avoid excessive tissue and organ damage. VIP, released in the lymphoid organs by the innervation and activated immune cells, modulates the function of inflammatory cells through specific receptors, and affects both innate and adaptive immunity functioning primarily as an endogenous anti-inflammatory agent. VIP exerts its anti-inflammatory function through several different mechanisms: (1) direct inhibition of pro-inflammatory cytokine production (TNF-α, IL-6, and IL-12) by activated macrophages and microglia; (2) upregulation of IL-10 production (a potent antiinflammatory cytokine); (3) inhibition of expression and release of pro-inflammatory chemokines from activated macrophages and microglia; (4) inhibition of CD80/CD86 expression in activated macrophages and dendritic cells, and subsequent inhibition of their stimulatory activity for antigen-specific T-cells; (5) alteration of the Th1/Th2 balance by promoting Th2 responses and inhibiting the pro-inflammatory Th1type response; and (6) generation of antigen-specific regulatory T-cells that inhibit proliferation and cytokine production by effector T-cells. From the point of view of a normal physiological role, the fact that VIP downregulates innate immunity and promotes the generation of Th2 effectors and regulatory T-cells is particularly relevant in view of the concept that immune privilege in organs such as brain and eye, where VIP is abundant, is an active process of immune deviation. From a pathological point of view, these findings open up the possibility of using VIP and its analogs as therapeutic agents. Since it interferes with major signaling pathways, i.e., NFkB, MAPK, and Jak/STAT, VIP represents an attractive target for future drug development strategies, particularly for therapies directed at autoimmune and inflammatory conditions.
Acknowledgments This work was made possible by the following grants: 2RO1A047325 (DG) and AI52306(DG and MD), Spanish Ministry of Health (PI03/0526, MD), and La Caixa Foundation (NE03-009, MD).
VIII. ABBREVIATIONS AC, adenylate cyclase; APC, antigen-presenting cell; CBP, CREB-binding protein; CD, Crohn’s disease; CGRP, calcitonin gene-related protein; CIA, collageninduced arthritis; EAE, experimental autoimmune encephalomyelitis; GrB, granzyme B; GVHR, graft-
versus-host reaction; GVT, graft-versus-tumor; IBD, inflammatory bowel disease; iNOS, inducible nitric oxide synthase; MPTP, 1-methyl-4-phenyl-1.2.3.6tetrahydropyridine; α-MSH, melatonin-stimulating hormone; LPS, lipopolysaccharide; PACAP, pituitary adenylate cyclase activating polypeptide; PAC1, PACAP-preferring receptor; PD, Parkinson’s disease; PLC, phospholipase C; PLD, phospholipase D; RA, rheumatoid arthritis; SP, substance P; TH, tyrosine hydroxylase; TLR, Toll-like receptors; TNBS, trinitrobenzene sulfonic acid; Treg, regulatory T-cells; VIP, vasoactive intestinal peptide; VPAC1/2, VIP receptors.
References Abad, C., Juarranz, Y., Martinez, C., Arranz, A., Rosignoli, F., Garcia-Gomez, M., Leceta, J., and Gomariz, R. P. (2005). cDNA array analysis of cytokines, chemokines, and receptors involved in the development of TNBS-induced colitis: homeostatic role of VIP. Inflamm. Bowel Dis., 11, 674–684. Abad, C., Martinez, C., Juarranz, M. G., Arranz, A., Leceta, J., Delgado, M., and Gomariz, R. P. (2003). Therapeutic effects of vasoactive intestinal peptide in the trinitrobenzene sulfonic acid mice model of Crohn’s disease. Gastroenterology, 124, 961–971. Aliakbari, J., Sreedharan, S. P., Turck, C. W., and Goetzl, E. J. (1987). Selective localization of vasoactive intestinal peptide and substance P in human eosinophils. Biochem. Biophys. Res. Commun., 148, 1440–1445. Andrew, D. P., Chang, M. S., McNinch, J., Wathen, S. T., Rihanek, M., Tseng, J., Spellberg, J. P., and Elias, C. G., III (1998). STCP-1 (MDC) CC chemokine acts specifically on chronically activated Th2 lymphocytes and is produced by monocytes on stimulation with Th2 cytokines IL-4 and IL-13. J. Immunol., 161, 5027–5038. Asahina, A., Hosoi, J., Grabbe, S., and Granstein, R. D. (1995). Modulation of Langerhans cell function by epidermal nerves. J. Allergy Clin. Immunol., 96, 1178–1182. Atreya, R., Mudter, J., Finotto, S., Mullberg, J., Jostock, T., Wirtz, S., Schutz, M., Bartsch, B., Holtmann, M., Becker, C., Strand, D., Czaja, J., Schlaak, J. F., Lehr, H. A., Autschbach, F., Schurmann, G., Nishimoto, N., Yoshizaki, K., Ito, H., Kishimoto, T., Galle, P. R., Rose-John, S., and Neurath, M. F. (2000). Blockade of interleukin 6 trans signaling suppresses T-cell resistance against apoptosis in chronic intestinal inflammation: evidence in Crohn disease and experimental colitis in vivo. Nat. Med., 6, 583–588. Banchereau, J., Briere, F., Caux, C., Davoust, J., Lebecque, S., Liu, Y. J., Pulendran, B., and Palucka, K. (2000). Immunobiology of dendritic cells. Annu. Rev. Immunol., 18, 767–811. Bartholdi, D., and Schwab, M. E. (1997). Expression of proinflammatory cytokine and chemokine mRNA upon experimental spinal cord injury in mouse: an in situ hybridization study. Eur. J. Neurosci., 9, 1422–1438. Baumgartner, J. D., and Calandra, T. (1999). Treatment of sepsis: past and future avenues. Drugs, 57, 127–132. Behi, M. E., Dubucquoi, S., Lefranc, D., Zephir, H., De Seze, J., Vermersch, P., and Prin, L. (2005). New insights into cell responses involved in experimental autoimmune encephalomyelitis and multiple sclerosis. Immunol. Lett., 96, 11–26.
5. Vasoactive Intestinal Peptide: An Anti-inflammatory Neuropeptide Bellinger, D. L., Lorton, D., Brouxhon, S., Felten, S., and Felten, D. L. (1996). The significance of vasoactive intestinal polypeptide (VIP) in immunomodulation. Adv. Neuroimmunol., 6, 5–27. Bellinger, D. L., Lorton, D., Romano, T. D., Olschowka, J. A., Felten, S. Y., and Felten, D. L. (1990). Neuropeptide innervation of lymphoid organs. Ann. N. Y. Acad. Sci., 594, 17–33. Bloem, B. R., Irwin, I., Buruma, O. J., Haan, J., Roos, R. A., Tetrud, J. W., and Langston, J. W. (1990). The MPTP model: versatile contributions to the treatment of idiopathic Parkinson’s disease. J. Neurol. Sci., 97, 273–293. Bloom, S. R., Christofides, N. D., Delamarter, J., Buell, G., Kawashima, E., and Polak, J. M. (1983). Diarrhoea in vipoma patients associated with cosecretion of a second active peptide (peptide histidine isoleucine) explained by single coding gene. Lancet, 2, 1163–1165. Blumberg, R. S., and Strober, W. (2001). Prospects for research in inflammatory bowel disease. JAMA, 285, 643–647. Bonecchi, R., Bianchi, G., Bordignon, P. P., D’Ambrosio, D., Lang, R., Borsatti, A., Sozzani, S., Allavena, P., Gray, P. A., Mantovani, A., and Sinigaglia, F. (1998). Differential expression of chemokine receptors and chemotactic responsiveness of type 1 T helper cells (Th1s) and Th2s. J. Exp. Med., 187, 129–134. Bynoe, M. S., Evans, J. T., Viret, C., and Janeway, C. A., Jr. (2003). Epicutaneous immunization with autoantigenic peptides induces T suppressor cells that prevent experimental allergic encephalomyelitis. Immunity, 19, 317–328. Calabresi, P. A., Wilterdink, J. L., Rogg, J. M., Mills, P., Webb, A., and Whartenby, K. A. (2002). An open-label trial of combination therapy with interferon beta-1a and oral methotrexate in MS. Neurology, 58, 314–317. Calvo, J. R., Molinero, P., Jimenez, J., Goberna, R., and Guerrero, J. M. (1986). Interaction of vasoactive intestinal peptide (VIP) with rat lymphoid cells. Peptides, 7, 177–181. Chao, C. C., Hu, S., Ehrlich, L., and Peterson, P. K. (1995). Interleukin-1 and tumor necrosis factor-alpha synergistically mediate neurotoxicity: involvement of nitric oxide and of N-methyl-Daspartate receptors. Brain Behav. Immun., 9, 355–365. Chatterjee, T. K., Sharma, R. V., and Fisher, R. A. (1996). Molecular cloning of a novel variant of the pituitary adenylate cyclaseactivating polypeptide (PACAP) receptor that stimulates calcium influx by activation of L-type calcium channels. J. Biol. Chem., 271, 32226–32232. Chew, L. J., Murphy, D., and Carter, D. A. (1994). Alternatively polyadenylated vasoactive intestinal peptide mRNAs are differentially regulated at the level of stability. Mol. Endocrinol., 8, 603–613. Chorny, A., Gonzalez-Rey, E., Fernandez-Martin, A., Pozo, D., Ganea, D., and Delgado, M. (2005). Vasoactive intestinal peptide induces regulatory dendritic cells with therapeutic effects on autoimmune disorders. Proc. Natl. Acad. Sci. USA 102, 13562–13567. Chrivia, J. C., Kwok, R. P., Lamb, N., Hagiwara, M., Montminy, M. R., and Goodman, R. H. (1993). Phosphorylated CREB binds specifically to the nuclear protein CBP. Nature, 365, 855–859. Cobb, M. H. (1999). MAP kinase pathways. Prog. Biophys. Mol. Biol., 71, 479–500. Cohen, J. L., Trenado, A., Vasey, D., Klatzmann, D., and Salomon, B. L. (2002). CD4(+)CD25(+) immunoregulatory T cells: new therapeutics for graft-versus-host disease. J. Exp. Med., 196, 401– 406. Cutz, E., Chan, W., Track, N. S., Goth, A., and Said, S. I. (1978). Release of vasoactive intestinal polypeptide in mast cells by histamine liberators. Nature, 275, 661–662.
151
Danner, R. L., Elin, R. J., Hosseini, J. M., Wesley, R. A., Reilly, J. M., and Parillo, J. E. (1991). Endotoxemia in human septic shock. Chest, 99, 169–175. Darnell, J. E., Jr., Kerr, I. M., and Stark, G. R. (1994). Jak-STAT pathways and transcriptional activation in response to IFNs and other extracellular signaling proteins. Science, 264, 1415–1421. David, S., Bouchard, C., Tsatas, O., and Giftochristos, N. (1990). Macrophages can modify the nonpermissive nature of the adult mammalian central nervous system. Neuron, 5, 463–469. Decroly, E., Wouters, S., Di Bello, C., Lazure, C., Ruysschaert, J. M., and Seidah, N. G. (1996). Identification of the paired basic convertases implicated in HIV gp160 processing based on in vitro assays and expression in CD4(+) cell lines. J. Biol. Chem., 271, 30442–30450. Delgado, M. (2002). Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide inhibit the MEKK1/ MEK4/JNK signaling pathway in endotoxin-activated microglia. Biochem. Biophys. Res. Commun., 293, 771–776. Delgado, M., Abad, C., Martinez, C., Juarranz, M. G., Arranz, A., Gomariz, R. P., and Leceta, J. (2002a). Vasoactive intestinal peptide in the immune system: potential therapeutic role in inflammatory and autoimmune diseases. J. Mol. Med., 80, 16–24. Delgado, M., Abad, C., Martinez, C., Leceta, J., and Gomariz, R. P. (2001). Vasoactive intestinal peptide prevents experimental arthritis by downregulating both autoimmune and inflammatory components of the disease. Nat. Med., 7, 563–568. Delgado, M., Chorny, A., Gonzalez-Rey, E., and Ganea, D. (2005a). Vasoactive intestinal peptide generates CD4+Cd25+ regulatory T cells in vivo. J. Leukoc. Biol., 78, 1327–1338. Delgado, M., and Ganea, D. (1999). Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide inhibit interleukin-12 transcription by regulating nuclear factor kappaB and Ets activation. J. Biol. Chem., 274, 31930–31940. Delgado, M., and Ganea, D. (2000a) Inhibition of IFN-gamma– induced janus kinase-1–STAT1 activation in macrophages by vasoactive intestinal peptide and pituitary adenylate cyclaseactivating polypeptide. J. Immunol., 165, 3051–3057. Delgado, M., and Ganea, D. (2000b). Vasoactive intestinal peptide and pituitary adenylate cyclase activating polypeptide inhibit the MEKK1/MEK4/JNK signaling pathway in LPS-stimulated macrophages. J. Neuroimmunol., 110, 97–105. Delgado, M., and Ganea, D. (2000c). Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide inhibit antigen-induced apoptosis of mature T lymphocytes by inhibiting Fas ligand expression. J. Immunol., 164, 1200– 1210. Delgado, M., and Ganea, D. (2000d). Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide inhibit T cell-mediated cytotoxicity by inhibiting Fas ligand expression. J. Immunol., 165, 114–123. Delgado, M., and Ganea, D. (2001a). Cutting edge: is vasoactive intestinal peptide a type 2 cytokine? J. Immunol., 166, 2907–2912. Delgado, M., and Ganea, D. (2001b). Inhibition of endotoxin-induced macrophage chemokine production by vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide in vitro and in vivo. J. Immunol., 167, 966–975. Delgado, M., and Ganea, D. (2001c). Inhibition of endotoxin-induced macrophage chemokine production by vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide in vitro and in vivo. J. Immunol., 167, 966–975. Delgado, M., and Ganea, D. (2001d). Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide inhibit
152
I. Neural and Endocrine Effects on Immunity
expression of Fas ligand in activated T lymphocytes by regulating c-Myc, NF-kappa B, NF-AT, and early growth factors 2/3. J. Immunol., 166, 1028–1040. Delgado, M., and Ganea, D. (2001e). Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide inhibit nuclear factor-kappa B-dependent gene activation at multiple levels in the human monocytic cell line THP-1. J. Biol. Chem., 276, 369–380. Delgado, M., and Ganea, D. (2001f). VIP and PACAP inhibit Fas ligand-mediated bystander lysis by CD4(+) T cells. J. Neuroimmunol., 112, 78–88. Delgado, M., and Ganea, D. (2001g). VIP and PACAP inhibit Fas ligand-mediated bystander lysis by CD4(+) T cells. J. Neuroimmunol., 112, 78–88. Delgado, M., and Ganea, D. (2003a). Neuroprotective effect of vasoactive intestinal peptide (VIP) in a mouse model of Parkinson’s disease by blocking microglial activation. FASEB J., 17, 944–946. Delgado, M., and Ganea, D. (2003b). Vasoactive intestinal peptide inhibits IL-8 production in human monocytes. Biochem. Biophys. Res. Commun., 301, 825–832. Delgado, M., and Ganea, D. (2003c). Vasoactive intestinal peptide prevents activated microglia-induced neurodegeneration under inflammatory conditions: potential therapeutic role in brain trauma. FASEB J., 17, 1922–1924. Delgado, M., Gomariz, R. P., Martinez, C., Abad, C., and Leceta, J. (2000). Anti-inflammatory properties of the type 1 and type 2 vasoactive intestinal peptide receptors: role in lethal endotoxic shock. Eur. J. Immunol., 30, 3236–3246. Delgado, M., Gonzalez-Rey, E., and Ganea, D. (2004a). VIP/PACAP preferentially attract Th2 effectors through differential regulation of chemokine production by dendritic cells. FASEB J., 18, 1453–1455. Delgado, M., Gonzalez-Rey, E., and Ganea, D. (2005b). The neuropeptide vasoactive intestinal peptide generates tolerogenic dendritic cells. J. Immunol., 175, 7311–7324. Delgado, M., Jonakait, G. M., and Ganea, D. (2002b). Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide inhibit chemokine production in activated microglia. Glia, 39, 148–161. Delgado, M., Leceta, J., and Ganea, D. (2002c). Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide promote in vivo generation of memory Th2 cells. FASEB J., 16, 1844–1846. Delgado, M., Leceta, J., and Ganea, D. (2003). Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide inhibit the production of inflammatory mediators by activated microglia. J. Leukoc. Biol., 73, 155–164. Delgado, M., Leceta, J., Gomariz, R. P., and Ganea, D. (1999a). Vasoactive intestinal peptide and pituitary adenylate cyclaseactivating polypeptide stimulate the induction of Th2 responses by up-regulating B7.2 expression. J. Immunol., 163, 3629– 3635. Delgado, M., Martinez, C., Johnson, M. C., Gomariz, R. P., and Ganea, D. (1996). Differential expression of vasoactive intestinal peptide receptors 1 and 2 (VIP-R1 and VIP-R2) mRNA in murine lymphocytes. J. Neuroimmunol., 68, 27–38. Delgado, M., Martinez, C., Pozo, D., Calvo, J. R., Leceta, J., Ganea, D., and Gomariz, R. P. (1999b). Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activation polypeptide (PACAP) protect mice from lethal endotoxemia through the inhibition of TNF-alpha and IL-6. J. Immunol., 162, 1200–1205. Delgado, M., Munoz-Elias, E. J., Gomariz, R. P., and Ganea, D. (1999c). Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide enhance IL-10 production by
murine macrophages: in vitro and in vivo studies. J. Immunol., 162, 1707–1716. Delgado, M., Munoz-Elias, E. J., Gomariz, R. P., and Ganea, D. (1999d). Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide prevent inducible nitric oxide synthase transcription in macrophages by inhibiting NF-kappa B and IFN regulatory factor 1 activation. J. Immunol., 162, 4685–4696. Delgado, M., Munoz-Elias, E. J., Gomariz, R. P., and Ganea, D. (1999e). VIP and PACAP inhibit IL-12 production in LPS-stimulated macrophages. Subsequent effect on IFNgamma synthesis by T cells. J. Neuroimmunol., 96, 167–181. Delgado, M., Munoz-Elias, E. J., Kan, Y., Gozes, I., Fridkin, M., Brenneman, D. E., Gomariz, R. P., and Ganea, D. (1998). Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide inhibit tumor necrosis factor alpha transcriptional activation by regulating nuclear factor-kB and cAMP response element-binding protein/c-Jun. J. Biol. Chem., 273, 31427– 31436. Delgado, M., Pozo, D., Martinez, C., Leceta, J., Calvo, J. R., Ganea, D., and Gomariz, R. P. (1999f). Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide inhibit endotoxin-induced TNF-alpha production by macrophages: in vitro and in vivo studies. J. Immunol., 162, 2358–2367. Delgado, M., Reduta, A., Sharma, V., and Ganea, D. (2004b). VIP/ PACAP oppositely affects immature and mature dendritic cell expression of CD80/CD86 and the stimulatory activity for CD4(+) T cells. J. Leukoc. Biol., 75, 1122–1130. Delgado, M., Sun, W., Leceta, J., and Ganea, D. (1999g). VIP and PACAP differentially regulate the costimulatory activity of resting and activated macrophages through the modulation of B7.1 and B7.2 expression. J. Immunol., 163, 4213–4223. Delporte, C., Poloczek, P., de Neef, P., Vertongen, P., Ciccarelli, E., Svoboda, M., Herchuelz, A., Winand, J., and Robberecht, P. (1995). Pituitary adenylate cyclase activating polypeptide (PACAP) and vasoactive intestinal peptide stimulate two signaling pathways in CHO cells stably transfected with the selective type I PACAP receptor. Mol. Cell. Endocrinol., 107, 71–76. Dewit, D., Gourlet, P., Amraoui, Z., Vertongen, P., Willems, F., Robberecht, P., and Goldman, M. (1998). The vasoactive intestinal peptide analogue RO25–1553 inhibits the production of TNF and IL-12 by LPS-activated monocytes. Immunol. Lett., 60, 57–60. Dey, R. D., Shannon, W. A., Jr., and Said, S. I. (1981). Localization of VIP-immunoreactive nerves in airways and pulmonary vessels of dogs, cats, and human subjects. Cell Tissue Res., 220, 231–238. Ding, M., St Pierre, B. A., Parkinson, J. F., Medberry, P., Wong, J. L., Rogers, N. E., Ignarro, L. J., and Merrill, J. E. (1997). Inducible nitric-oxide synthase and nitric oxide production in human fetal astrocytes and microglia. A kinetic analysis. J. Biol. Chem., 272, 11327–11335. Evans, C. H. (1995). Nitric oxide: what role does it play in inflammation and tissue destruction? Agents Actions Suppl., 47, 107–116. Fahrig, T., Gerlach, I., and Horvath, E. (2005). A synthetic derivative of the natural product rocaglaol is a potent inhibitor of cytokinemediated signaling and shows neuroprotective activity in vitro and in animal models of Parkinson’s disease and traumatic brain injury. Mol. Pharmacol., 67, 1544–1555. Feldmann, M. (1996). What is the mechanism of action of antitumour necrosis factor-alpha antibody in rheumatoid arthritis? Int. Arch. Allergy Immunol., 111, 362–365. Felten, D. L. (1993). Direct innervation of lymphoid organs: substrate for neurotransmitter signaling of cells of the immune system. Neuropsychobiology, 28, 110–112.
5. Vasoactive Intestinal Peptide: An Anti-inflammatory Neuropeptide Fernandez-Martin, A., Gonzalez-Rey, E., Chorny, A., Ganea, D., and Delgado, M. (2006). Vasoactive intestinal peptide induces regulatory T cells during experimental autoimmune encephalomyelitis. Eur. J. Immunol., 36, 318–326. Fink, T., and Weihe, E. (1988). Multiple neuropeptides in nerves supplying mammalian lymph nodes: messenger candidates for sensory and autonomic neuroimmunomodulation? Neurosci. Lett., 90, 39–44. Frank, M., and Wolburg, H. (1996). Cellular reactions at the lesion site after crushing of the rat optic nerve. Glia, 16, 227–240. Furness, J. B., and Costa, M. (1980). Types of nerves in the enteric nervous system. Neuroscience, 5, 1–20. Fuss, I. J., Marth, T., Neurath, M. F., Pearlstein, G. R., Jain, A., and Strober, W. (1999). Anti-interleukin 12 treatment regulates apoptosis of Th1 T cells in experimental colitis in mice. Gastroenterology, 117, 1078–1088. Ganea, D. (1996). Regulatory effects of vasoactive intestinal peptide on cytokine production in central and peripheral lymphoid organs. Adv. Neuroimmunol., 6, 61–74. Ganea, D., Rodriguez, R., and Delgado, M. (2003). Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide: players in innate and adaptive immunity. Cell. Mol. Biol. (Noisy-le-grand), 49, 127–142. Gerritsen, M. E., Williams, A. J., Neish, A. S., Moore, S., Shi, Y., and Collins, T. (1997). CREB-binding protein/p300 are transcriptional coactivators of p65. Proc. Natl. Acad. Sci. USA, 94, 2927–2932. Giulian, D., Chen, J., Ingeman, J. E., George, J. K., and Noponen, M. (1989). The role of mononuclear phagocytes in wound healing after traumatic injury to adult mammalian brain. J. Neurosci., 9, 4416–4429. Glauser, M. P., Heumann, D., Baumgartner, J. D., and Cohen, J. (1994). Pathogenesis and potential strategies for prevention and treatment of septic shock: an update. Clin. Infect. Dis., 18 (Suppl 2), S205–S216. Goedert, M. (2001). Alpha-synuclein and neurodegenerative diseases. Nat. Rev. Neurosci., 2, 492–501. Goetzl, E. J., Sreedharan, S. P., and Turck, C. W. (1988). Structurally distinctive vasoactive intestinal peptides from rat basophilic leukemia cells. J. Biol. Chem., 263, 9083–9086. Goetzl, E. J., Voice, J. K., Shen, S., Dorsam, G., Kong, Y., West, K. M., Morrison, C. F., and Harmar, A. J. (2001). Enhanced delayedtype hypersensitivity and diminished immediate-type hypersensitivity in mice lacking the inducible VPAC(2) receptor for vasoactive intestinal peptide. Proc. Natl. Acad. Sci. USA, 98, 13854–13859. Goldman, P. S., Tran, V. K., and Goodman, R. H. (1997). The multifunctional role of the co-activator CBP in transcriptional regulation. Recent Prog. Horm. Res., 52, 103–119. Gomariz, R. P., Arranz, A., Abad, C., Torroba, M., Martinez, C., Rosignoli, F., Garcia-Gomez, M., Leceta, J., and Juarranz, Y. (2005). Time-course expression of Toll-like receptors 2 and 4 in inflammatory bowel disease and homeostatic effect of VIP. J. Leukoc. Biol., 78, 491–502. Gomariz, R. P., De La F. M., Hernanz, A., and Leceta, J. (1992). Occurrence of vasoactive intestinal peptide (VIP) in lymphoid organs from rat and mouse. Ann. N. Y. Acad. Sci., 650, 13–18. Gomariz, R. P., Leceta, J., Garrido, E., Garrido, T., and Delgado, M. (1994). Vasoactive intestinal peptide (VIP) mRNA expression in rat T and B lymphocytes. Regul. Pept., 50, 177–184. Gomariz, R. P., Martinez, C., Abad, C., Leceta, J., and Delgado, M. (2001). Immunology of VIP: a review and therapeutical perspectives. Curr. Pharm. Des., 7, 89–111. Gonzalez-Rey, E., Fernandez-Martin, A., Chorny, A., and Delgado, M. (2006a). Vasoactive intestinal peptide induces CD4+CD25+ T
153
regulatory cells with therapeutic effect in collagen-induced arthritis. Arthritis Rheum., 54, 864–876. Gonzalez-Rey, E., Fernandez-Martin, A., Chorny, A., Martin, J., Pozp, D., Ganea, D., and Delgado, M. (2006b). Therapeutic effect of vasoactive intestinal peptide on experimental autoimmune encephalomyelitis. Am. J. Pathol., 168, 1179–1188. Gonzalez-Scarano, F., and Baltuch, G. (1999). Microglia as mediators of inflammatory and degenerative diseases. Annu. Rev. Neurosci., 22, 219–240. Gozes, I., and Brenneman, D. E. (2000). A new concept in the pharmacology of neuroprotection. J. Mol. Neurosci., 14, 61–68. Gregori, S., Casorati, M., Amuchastegui, S., Smiroldo, S., Davalli, A. M., and Adorini, L. (2001). Regulatory T cells induced by 1 alpha,25-dihydroxyvitamin D3 and mycophenolate mofetil treatment mediate transplantation tolerance. J. Immunol., 167, 1945–1953. Grider, J. R., and Jin, J. G. (1993). Vasoactive intestinal peptide release and L-citrulline production from isolated ganglia of the myenteric plexus: evidence for regulation of vasoactive intestinal peptide release by nitric oxide. Neuroscience, 54, 521–526. Grimm, M. C., Newman, R., Hassim, Z., Cuan, N., Connor, S. J., Le Y., Wang, J. M., Oppenheim, J. J., and Lloyd, A. R. (2003). Cutting edge: vasoactive intestinal peptide acts as a potent suppressor of inflammation in vivo by trans-deactivating chemokine receptors. J. Immunol., 171, 4990–4994. Grinninger, C., Wang, W., Oskoui, K. B., Voice, J. K., and Goetzl, E. J. (2004). A natural variant type II G protein-coupled receptor for vasoactive intestinal peptide with altered function. J. Biol. Chem., 279, 40259–40262. Grunblatt, E., Mandel, S., and Youdim, M. B. (2000). MPTP and 6hydroxydopamine–induced neurodegeneration as models for Parkinson’s disease: neuroprotective strategies. J. Neurol., 247 (Suppl 2), II95–II102. Guerrero, J. M., Prieto, J. C., Elorza, F. L., Ramirez, R., and Goberna, R. (1981). Interaction of vasoactive intestinal peptide with human blood mononuclear cells. Mol. Cell. Endocrinol., 21, 151–160. Hanauer, S. B., and Present, D. H. (2003). The state of the art in the management of inflammatory bowel disease. Rev. Gastroenterol. Disord., 3, 81–92. Harmar, A. J., Arimura, A., Gozes, I., Journot, L., Laburthe, M., Pisegna, J. R., Rawlings, S. R., Robberecht, P., Said, S. I., Sreedharan, S. P., Wank, S. A., and Waschek, J. A. (1998). International Union of Pharmacology. XVIII. Nomenclature of receptors for vasoactive intestinal peptide and pituitary adenylate cyclaseactivating polypeptide. Pharmacol. Rev., 50, 265–270. Hoffmann, P., Ermann, J., Edinger, M., Fathman, C. G., and Strober, S. (2002). Donor-type CD4(+)CD25(+) regulatory T cells suppress lethal acute graft-versus-host disease after allogeneic bone marrow transplantation. J. Exp. Med., 196, 389–399. Howard, L. M., and Miller, S. D. (2004). Immunotherapy targeting the CD40/CD154 costimulatory pathway for treatment of autoimmune disease. Autoimmunity, 37, 411–418. Imai, T., Nagira, M., Takagi, S., Kakizaki, M., Nishimura, M., Wang, J., Gray, P. W., Matsushima, K., and Yoshie, O. (1999). Selective recruitment of CCR4-bearing Th2 cells toward antigen-presenting cells by the CC chemokines thymus and activation-regulated chemokine and macrophage-derived chemokine. Int. Immunol., 11, 81–88. Itoh, N., Obata, K., Yanaihara, N., and Okamoto, H. (1983). Human preprovasoactive intestinal polypeptide contains a novel PHI27–like peptide, PHM-27. Nature, 304, 547–549. Jackson-Lewis, V., and Smeyne, R. J. (2005). MPTP and SNpc DA neuronal vulnerability: role of dopamine, superoxide and nitric oxide in neurotoxicity. Minireview. Neurotox. Res., 7, 193–202.
154
I. Neural and Endocrine Effects on Immunity
Janknecht, R., and Nordheim, A. (1996). MAP kinase-dependent transcriptional coactivation by Elk-1 and its cofactor CBP. Biochem. Biophys. Res. Commun., 228, 831–837. Jenner, P., and Olanow, C. W. (1996). Oxidative stress and the pathogenesis of Parkinson’s disease. Neurology, 47, S161–S170. Jiang, X., Jing, H., and Ganea, D. (2002). VIP and PACAP downregulate CXCL10 (IP-10) and up-regulate CCL22 (MDC) in spleen cells. J. Neuroimmunol., 133, 81–94. Joosten, L. A., Lubberts, E., Helsen, M. M., and van den Berg, W. B. (1997). Dual role of IL-12 in early and late stages of murine collagen type II arthritis. J. Immunol., 159, 4094–4102. Juarranz, M. G., Santiago, B., Torroba, M., Gutierrez-Canas, I., Palao, G., Galindo, M., Abad, C., Martinez, C., Leceta, J., Pablos, J. L., and Gomariz, R. P. (2004). Vasoactive intestinal peptide modulates proinflammatory mediator synthesis in osteoarthritic and rheumatoid synovial cells. Rheumatology (Oxford), 43, 416–422. Kaltreider, H. B., Ichikawa, S., Byrd, P. K., Ingram, D. A., Kishiyama, J. L., Sreedharan, S. P., Warnock, M. L., Beck, J. M., and Goetzl, E. J. (1997). Upregulation of neuropeptides and neuropeptide receptors in a murine model of immune inflammation in lung parenchyma. Am. J. Respir. Cell Mol. Biol., 16, 133–144. Kamei, Y., Xu, L., Heinzel, T., Torchia, J., Kurokawa, R., Gloss, B., Lin, S. C., Heyman, R. A., Rose, D. W., Glass, C. K., and Rosenfeld, M. G. (1996). A CBP integrator complex mediates transcriptional activation and AP-1 inhibition by nuclear receptors. Cell, 85, 403–414. Kato, H., Ito, A., Kawanokuchi, J., Jin, S., Mizuno, T., Ojika, K., Ueda, R., and Suzumura, A. (2004). Pituitary adenylate cyclaseactivating polypeptide (PACAP) ameliorates experimental autoimmune encephalomyelitis by suppressing the functions of antigen presenting cells. Mult. Scler., 10, 651–659. Killestein, J., Kalkers, N. F., and Polman, C. H. (2005). Glutamate inhibition in MS: the neuroprotective properties of riluzole. J. Neurol. Sci., 233, 113–115. Kim, S. U., and de Vellis, J. (2005). Microglia in health and disease. J. Neurosci. Res., 81, 302–313. Kim, W. K., Ganea, D., and Jonakait, G. M. (2002). Inhibition of microglial CD40 expression by pituitary adenylate cyclaseactivating polypeptide is mediated by interleukin-10. J. Neuroimmunol., 126, 16–24. Kim, W. K., Kan, Y., Ganea, D., Hart, R. P., Gozes, I., and Jonakait, G. M. (2000). Vasoactive intestinal peptide and pituitary adenyl cyclase-activating polypeptide inhibit tumor necrosis factoralpha production in injured spinal cord and in activated microglia via a cAMP-dependent pathway. J. Neurosci., 20, 3622–3630. Kohm, A. P., Carpentier, P. A., Anger, H. A., and Miller, S. D. (2002). Cutting edge: CD4+CD25+ regulatory T cells suppress antigenspecific autoreactive immune responses and central nervous system inflammation during active experimental autoimmune encephalomyelitis. J. Immunol., 169, 4712–4716. Kwok, R. P., Lundblad, J. R., Chrivia, J. C., Richards, J. P., Bachinger, H. P., Brennan, R. G., Roberts, S. G., Green, M. R., and Goodman, R. H. (1994). Nuclear protein CBP is a coactivator for the transcription factor CREB. Nature, 370, 223–226. Lara-Marquez, M. L., O’Dorisio, M. S., and Karacay, B. (2000). Vasoactive intestinal peptide (VIP) receptor type 2 (VPAC2) is the predominant receptor expressed in human thymocytes. Ann. N.Y. Acad. Sci., 921, 45–54. Lara-Marquez, M., O’Dorisio, M., O’Dorisio, T., Shah, M., and Karacay, B. (2001). Selective gene expression and activationdependent regulation of vasoactive intestinal peptide receptor type 1 and type 2 in human T cells. J. Immunol., 166, 2522–2530.
Laskin, D. L., and Pendino, K. J. (1995). Macrophages and inflammatory mediators in tissue injury. Annu. Rev. Pharmacol. Toxicol., 35, 655–677. Leceta, J., Martinez, C., Delgado, M., Garrido, E., and Gomariz, R. P. (1996). Expression of vasoactive intestinal peptide in lymphocytes: a possible endogenous role in the regulation of the immune system. Adv. Neuroimmunol., 6, 29–36. Leceta, J., Martinez, M. C., Delgado, M., Garrido, E., and Gomariz, R. P. (1994). Lymphoid cell subpopulations containing vasoactive intestinal peptide in the rat. Peptides, 15, 791–797. Lee, C. M., Kumar, R. K., Lubowski, D. Z., and Burcher, E. (2002). Neuropeptides and nerve growth in inflammatory bowel diseases: a quantitative immunohistochemical study. Dig. Dis. Sci., 47, 495–502. Lee, S. C., Liu, W., Dickson, D. W., Brosnan, C. F., and Berman, J. W. (1993). Cytokine production by human fetal microglia and astrocytes. Differential induction by lipopolysaccharide and IL-1 beta. J. Immunol., 150, 2659–2667. Levings, M. K., Gregori, S., Tresoldi, E., Cazzaniga, S., Bonini, C., and Roncarolo, M. G. (2005). Differentiation of Tr1 cells by immature dendritic cells requires IL-10 but not CD25+CD4+ Tr cells. Blood, 105, 1162–1169. Lipton, J. M., and Catania, A. (1997). Anti-inflammatory actions of the neuroimmunomodulator alpha-MSH. Immunol. Today, 18, 140–145. Lipton, S. A., Singel, D. J., and Stamler, J. S. (1994). Nitric oxide in the central nervous system. Prog. Brain Res., 103, 359–364. Loetscher, P., Uguccioni, M., Bordoli, L., Baggiolini, M., Moser, B., Chizzolini, C., and Dayer, J. M. (1998). CCR5 is characteristic of Th1 lymphocytes. Nature, 391, 344–345. Lundberg, J. M., Hokfelt, T., Kewenter, J., Pettersson, G., Ahlman, H., Edin, R., Dahlstrom, A., Nilsson, G., Terenius, L., UvnasWallensten, K., and Said, S. (1979). Substance P-, VIP-, and enkephalin-like immunoreactivity in the human vagus nerve. Gastroenterology, 77, 468–471. Luster, A. D. (1998). Chemokines—chemotactic cytokines that mediate inflammation. N. Engl. J. Med., 338, 436–445. Lygren, I., Revhaug, A., Burhol, P. G., Giercksky, K. E., and Jenssen, T. G. (1984). Vasoactive intestinal polypeptide and somatostatin in leucocytes. Scand. J. Clin. Lab. Invest., 44, 347–351. Ma, X., Aste-Amezaga, M., Gri, G., Gerosa, F., and Trinchieri, G. (1997). Immunomodulatory functions and molecular regulation of IL-12. Chem. Immunol., 68, 1–22. Martin, E., Nathan, C., and Xie, Q. W. (1994). Role of interferon regulatory factor 1 in induction of nitric oxide synthase. J. Exp. Med., 180, 977–984. Martinez, C., Abad, C., Delgado, M., Arranz, A., Juarranz, M. G., Rodriguez-Henche, N., Brabet, P., Leceta, J., and Gomariz, R. P. (2002). Anti-inflammatory role in septic shock of pituitary adenylate cyclase-activating polypeptide receptor. Proc. Natl. Acad. Sci. USA, 99, 1053–1058. Martinez, C., Delgado, M., Abad, C., Gomariz, R. P., Ganea, D., and Leceta, J. (1999). Regulation of VIP production and secretion by murine lymphocytes. J. Neuroimmunol., 93, 126–138. Martinez, C., Delgado, M., Pozo, D., Leceta, J., Calvo, J. R., Ganea, D., and Gomariz, R. P. (1998). VIP and PACAP enhance IL-6 release and mRNA levels in resting peritoneal macrophages: in vitro and in vivo studies. J. Neuroimmunol., 85, 155– 167. Martinez, C., Juarranz, Y., Abad, C., Arranz, A., Miguel, B. G., Rosignoli, F., Leceta, J., and Gomariz, R. P. (2005). Analysis of the role of the PAC1 receptor in neutrophil recruitment, acutephase response, and nitric oxide production in septic shock. J. Leukoc. Biol., 77, 729–738.
5. Vasoactive Intestinal Peptide: An Anti-inflammatory Neuropeptide Matsuyama, H., Unno, T., El Mahmoudy, A. M., Komori, S., Kobayashi, H., Thapaliya, S., and Takewaki, T. (2002). Peptidergic and nitrergic inhibitory neurotransmissions in the hamster jejunum: regulation of vasoactive intestinal peptide release by nitric oxide. Neuroscience, 110, 779–788. Mauri, C., Williams, R. O., Walmsley, M., and Feldmann, M. (1996). Relationship between Th1/Th2 cytokine patterns and the arthritogenic response in collagen-induced arthritis. Eur. J. Immunol., 26, 1511–1518. McCulloch, D. A., Lutz, E. M., Johnson, M. S., MacKenzie, C. J., and Mitchell, R. (2000). Differential activation of phospholipase D by VPAC and PAC1 receptors. Ann. N. Y. Acad. Sci., 921, 175–185. McCulloch, D. A., Lutz, E. M., Johnson, M. S., Robertson, D. N., MacKenzie, C. J., Holland, P. J., and Mitchell, R. (2001). ADPribosylation factor-dependent phospholipase D activation by VPAC receptors and a PAC(1) receptor splice variant. Mol. Pharmacol., 59, 1523–1532. McCulloch, D. A., MacKenzie, C. J., Johnson, M. S., Robertson, D. N., Holland, P. J., Ronaldson, E., Lutz, E. M., and Mitchell, R. (2002). Additional signals from VPAC/PAC family receptors. Biochem. Soc. Trans., 30, 441–446. McManus, C. M., Brosnan, C. F., and Berman, J. W. (1998). Cytokine induction of MIP-1 alpha and MIP-1 beta in human fetal microglia. J. Immunol., 160, 1449–1455. Menges, M., Rossner, S., Voigtlander, C., Schindler, H., Kukutsch, N. A., Bogdan, C., Erb, K., Schuler, G., and Lutz, M. B. (2002). Repetitive injections of dendritic cells matured with tumor necrosis factor alpha induce antigen-specific protection of mice from autoimmunity. J. Exp. Med., 195, 15–21. Mezzapesa, D. M., Rovaris, M., and Filippi, M. (2005). Glatiramer acetate in multiple sclerosis. Expert Rev. Neurother., 5, 451–458. Minghetti, L., Ajmone-Cat, M. A., De Berardinis, M. A., and De Simone, R. (2005). Microglial activation in chronic neurodegenerative diseases: roles of apoptotic neurons and chronic stimulation. Brain Res. Brain Res. Rev., 48, 251–256. Miyaura, H., and Iwata, M. (2002). Direct and indirect inhibition of Th1 development by progesterone and glucocorticoids. J. Immunol., 168, 1087–1094. Mizuno, Y., Ikebe, S., Hattori, N., Nakagawa-Hattori, Y., Mochizuki, H., Tanaka, M., and Ozawa, T. (1995). Role of mitochondria in the etiology and pathogenesis of Parkinson’s disease. Biochim. Biophys. Acta, 1271, 265–274. Moreno-Flores, M. T., Bovolenta, P., and Nieto-Sampedro, M. (1993). Polymorphonuclear leukocytes in brain parenchyma after injury and their interaction with purified astrocytes in culture. Glia, 7, 146–157. Morganti-Kossmann, M. C., Rancan, M., Stahel, P. F., and Kossmann, T. (2002). Inflammatory response in acute traumatic brain injury: a double-edged sword. Curr. Opin. Crit. Care, 8, 101–105. Mosimann, B. L., White, M. V., Hohman, R. J., Goldrich, M. S., Kaulbach, H. C., and Kaliner, M. A. (1993). Substance P, calcitonin gene-related peptide, and vasoactive intestinal peptide increase in nasal secretions after allergen challenge in atopic patients. J. Allergy Clin. Immunol., 92, 95–104. Murdoch, D., and Lyseng-Williamson, K. A. (2005). Subcutaneous recombinant interferon-beta-1a (Rebif((R))): a review of its use in relapsing-remitting multiple sclerosis. Drugs, 65, 1295– 1312. Murray, M., Kim, D., Liu, Y., Tobias, C., Tessler, A., and Fischer, I. (2002). Transplantation of genetically modified cells contributes to repair and recovery from spinal injury. Brain Res. Brain Res. Rev., 40, 292–300.
155
Nagatsu, T., and Sawada, M. (2005). Inflammatory process in Parkinson’s disease: role for cytokines. Curr. Pharm. Des., 11, 999–1016. Nelson, P. T., Soma, L. A., and Lavi, E. (2002). Microglia in diseases of the central nervous system. Ann. Med., 34, 491–500. Neurath, M. F., Weigmann, B., Finotto, S., Glickman, J., Nieuwenhuis, E., Iijima, H., Mizoguchi, A., Mizoguchi, E., Mudter, J., Galle, P. R., Bhan, A., Autschbach, F., Sullivan, B. M., Szabo, S. J., Glimcher, L. H., and Blumberg, R. S. (2002). The transcription factor T-bet regulates mucosal T cell activation in experimental colitis and Crohn’s disease. J. Exp. Med., 195, 1129–1143. Nguyen, V. T., and Benveniste, E. N. (2002). Critical role of tumor necrosis factor-alpha and NF-kappa B in interferon-gamma– induced CD40 expression in microglia/macrophages. J. Biol. Chem., 277, 13796–13803. Nieber, K., Baumgarten, C. R., Rathsack, R., Furkert, J., Oehme, P., and Kunkel, G. (1992). Substance P and beta-endorphin–like immunoreactivity in lavage fluids of subjects with and without allergic asthma. J. Allergy Clin. Immunol., 90, 646–652. Nikolaus, S., Raedler, A., Kuhbacker, T., Sfikas, N., Folsch, U. R., and Schreiber, S. (2000). Mechanisms in failure of infliximab for Crohn’s disease. Lancet, 356, 1475–1479. O’Dorisio, M. S., Hermina, N. S., O’Dorisio, T. M., and Balcerzak, S. P. (1981). Vasoactive intestinal polypeptide modulation of lymphocyte adenylate cyclase. J. Immunol., 127, 2551–2554. O’Dorisio, M. S., O’Dorisio, T. M., Cataland, S., and Balcerzak, S. P. (1980). Vasoactive intestinal polypeptide as a biochemical marker for polymorphonuclear leukocytes. J. Lab. Clin. Med., 96, 666–672. O’Garra, A. (1998). Cytokines induce the development of functionally heterogeneous T helper cell subsets. Immunity, 8, 275– 283. Ohmori, Y., and Hamilton, T. A. (1993). Cooperative interaction between interferon (IFN) stimulus response element and kappa B sequence motifs controls IFN gamma- and lipopolysaccharidestimulated transcription from the murine IP-10 promoter. J. Biol. Chem., 268, 6677–6688. Ottaway, C. A., Bernaerts, C., Chan, B., and Greenberg, G. R. (1983). Specific binding of vasoactive intestinal peptide to human circulating mononuclear cells. Can. J. Physiol. Pharmacol., 61, 664–671. Ottaway, C. A., and Greenberg, G. R. (1984). Interaction of vasoactive intestinal peptide with mouse lymphocytes: specific binding and the modulation of mitogen responses. J. Immunol., 132, 417–423. Owens, T. (2003). The enigma of multiple sclerosis: inflammation and neurodegeneration cause heterogeneous dysfunction and damage. Curr. Opin. Neurol., 16, 259–265. Pankhaniya, R., Jabrane-Ferrat, N., Gaufo, G. O., Sreedharan, S. P., Dazin, P., Kaye, J., and Goetzl, E. J. (1998). Vasoactive intestinal peptide enhancement of antigen-induced differentiation of a cultured line of mouse thymocytes. FASEB J., 12, 119–127. Parrillo, J. E. (1993). Pathogenetic mechanisms of septic shock. N. Engl. J. Med., 328, 1471–1477. Pease, J. E., and Horuk, R. (2005). CCR1 antagonists in clinical development. Expert Opin. Investig. Drugs, 14, 785–796. Peterson, P. K., Hu, S., Salak-Johnson, J., Molitor, T. W., and Chao, C. C. (1997). Differential production of and migratory response to beta chemokines by human microglia and astrocytes. J. Infect. Dis., 175, 478–481. Piemonti, L., Monti, P., Sironi, M., Fraticelli, P., Leone, B. E., Dal Cin, E., Allavena, P., and Di, C. V. (2000). Vitamin D3 affects differentiation, maturation, and function of human monocyte–derived dendritic cells. J. Immunol., 164, 4443–4451.
156
I. Neural and Endocrine Effects on Immunity
Pisegna, J. R., Moody, T. W., and Wank, S. A. (1996). Differential signaling and immediate-early gene activation by four splice variants of the human pituitary adenylate cyclase-activating polypeptide receptor (hPACAP-R). Ann. N. Y. Acad. Sci., 805, 54–64. Przedborski, S., Jackson-Lewis, V., Djaldetti, R., Liberatore, G., Vila, M., Vukosavic, S., and Almer, G. (2000). The parkinsonian toxin MPTP: action and mechanism. Restor. Neurol. Neurosci., 16, 135–142. Pyo, H., Jou, I., Jung, S., Hong, S., and Joe, E. H. (1998). Mitogenactivated protein kinases activated by lipopolysaccharide and beta-amyloid in cultured rat microglia. Neuroreport, 9, 871–874. Qin, S., Rottman, J. B., Myers, P., Kassam, N., Weinblatt, M., Loetscher, M., Koch, A. E., Moser, B., and Mackay, C. R. (1998). The chemokine receptors CXCR3 and CCR5 mark subsets of T cells associated with certain inflammatory reactions. J. Clin. Invest., 101, 746–754. Rameshwar, P., Gascon, P., Oh, H. S., Denny, T. N., Zhu, G., and Ganea, D. (2002). Vasoactive intestinal peptide (VIP) inhibits the proliferation of bone marrow progenitors through the VPAC1 receptor. Exp. Hematol., 30, 1001–1009. Ranger, A. M., Das, M. P., Kuchroo, V. K., and Glimcher, L. H. (1996). B7-2 (CD86) is essential for the development of IL-4–producing T cells. Int. Immunol., 8, 1549–1560. Reddy, J., Illes, Z., Zhang, X., Encinas, J., Pyrdol, J., Nicholson, L., Sobel, R. A., Wucherpfennig, K. W., and Kuchroo, V. K. (2004). Myelin proteolipid protein-specific CD4+CD25+ regulatory cells mediate genetic resistance to experimental autoimmune encephalomyelitis. Proc. Natl. Acad. Sci. USA, 101, 15434–15439. Reubi, J. C. (2000). In vitro evaluation of VIP/PACAP receptors in healthy and diseased human tissues. Clinical implications. Ann. N. Y. Acad. Sci., 921, 1–25. Rollins, B. J. (1997). Chemokines. Blood, 90, 909–928. Rossi, D., and Zlotnik, A. (2000). The biology of chemokines and their receptors. Annu. Rev. Immunol., 18, 217–242. Said, S. I. (1986). Vasoactive intestinal peptide. J. Endocrinol. Invest., 9, 191–200. Sallusto, F., Lanzavecchia A., and Mackay C. R. (1998). Chemokines and chemokine receptors in T-cell priming and Th1/Th2-mediated responses. Immunol. Today, 19, 568–574. Schwartz, M., Moalem, G., Leibowitz-Amit, R., and Cohen, I. R. (1999). Innate and adaptive immune responses can be beneficial for CNS repair. Trends Neurosci., 22, 295–299. Segal, B. M. (2005). CNS chemokines, cytokines, and dendritic cells in autoimmune demyelination. J. Neurol. Sci., 228, 210–214. Sharma, V., Delgado, M., and Ganea, D. (2006). Granzyme B, a new placer in activation-induced cell death, is down-regulated by vasoactive intestinal peptide in Th2 but not Th1 effector. J. Immunol., 176, 97–110. Sims, S. H., Cha, Y., Romine, M. F., Gao, P. Q., Gottlieb, K., and Deisseroth, A. B. (1993). A novel interferon-inducible domain: structural and functional analysis of the human interferon regulatory factor 1 gene promoter. Mol. Cell. Biol., 13, 690–702. Smyth, M. J. (1997). Fas ligand-mediated bystander lysis of syngeneic cells in response to an allogeneic stimulus. J. Immunol., 158, 5765–5772. Spengler, D., Waeber, C., Pantaloni, C., Holsboer, F., Bockaert, J., Seeburg, P. H., and Journot, L. (1993). Differential signal transduction by five splice variants of the PACAP receptor. Nature, 365, 170–175. Stalder, T., Hahn, S., and Erb, P. (1994). Fas antigen is the major target molecule for CD4+ T cell-mediated cytotoxicity. J. Immunol., 152, 1127–1133.
Steinman, L. (1999). Assessment of animal models for MS and demyelinating disease in the design of rational therapy. Neuron, 24, 511–514. Steinman, L. (2005). Blocking adhesion molecules as therapy for multiple sclerosis: natalizumab. Nat. Rev. Drug Discov., 4, 510–518. Steinman, R. M. (2003). The control of immunity and tolerance by dendritic cell. Pathol. Biol. (Paris), 51, 59–60. Stoll, G., Jander, S., and Schroeter, M. (2002). Detrimental and beneficial effects of injury-induced inflammation and cytokine expression in the nervous system. Adv. Exp. Med. Biol., 513, 87–113. Streit, W. J., Graeber, M. B., and Kreutzberg, G. W. (1988). Functional plasticity of microglia: a review. Glia, 1, 301–307. Streit, W. J., Semple-Rowland, S. L., Hurley, S. D., Miller, R. C., Popovich, P. G., and Stokes, B. T. (1998). Cytokine mRNA profiles in contused spinal cord and axotomized facial nucleus suggest a beneficial role for inflammation and gliosis. Exp. Neurol., 152, 74–87. Tabarowski, Z., Gibson-Berry, K., and Felten, S. Y. (1996). Noradrenergic and peptidergic innervation of the mouse femur bone marrow. Acta Histochem., 98, 453–457. Takeba, Y., Suzuki, N., Kaneko, A., Asai, T., and Sakane, T. (1999). Evidence for neural regulation of inflammatory synovial cell functions by secreting calcitonin gene-related peptide and vasoactive intestinal peptide in patients with rheumatoid arthritis. Arthritis Rheum., 42, 2418–2429. Taupin, V., Toulmond, S., Serrano, A., Benavides, J., and Zavala, F. (1993). Increase in IL-6, IL-1 and TNF levels in rat brain following traumatic lesion. Influence of pre- and post-traumatic treatment with Ro5 4864, a peripheral-type (p site) benzodiazepine ligand. J. Neuroimmunol., 42, 177–185. Trenado, A., Charlotte, F., Fisson, S., Yagello, M., Klatzmann, D., Salomon, B. L., and Cohen, J. L. (2003). Recipient-type specific CD4+CD25+ regulatory T cells favor immune reconstitution and control graft-versus-host disease while maintaining graft-versusleukemia. J. Clin. Invest., 112, 1688–1696. Tuncel, N., Tore, F., Sahinturk, V., Ak, D., and Tuncel, M. (2000). Vasoactive intestinal peptide inhibits degranulation and changes granular content of mast cells: a potential therapeutic strategy in controlling septic shock. Peptides, 21, 81–89. van Deuren, M., Dofferhoff, A. S., and van der Meer, J. W. (1992). Cytokines and the response to infection. J. Pathol., 168, 349– 356. Van Rampelbergh, J., Poloczek, P., Francoys, I., Delporte, C., Winand, J., Robberecht, P., and Waelbroeck, M. (1997). The pituitary adenylate cyclase activating polypeptide (PACAP I) and VIP (PACAP II VIP1) receptors stimulate inositol phosphate synthesis in transfected CHO cells through interaction with different G proteins. Biochim. Biophys. Acta, 1357, 249–255. Van Snick, J. (1990). Interleukin-6: an overview. Annu. Rev. Immunol., 8, 253–278. Vassalli, P. (1992). The pathophysiology of tumor necrosis factors. Annu. Rev. Immunol., 10, 411–452. Vassiliou, E., Jiang, X., Delgado, M., and Ganea, D. (2001). Th2 lymphocytes secrete functional VIP upon antigen stimulation. Arch. Physiol. Biochem., 109, 365–368. Viglietta, V., Baecher-Allan, C., Weiner, H. L., and Hafler, D. A. (2004). Loss of functional suppression by CD4+CD25+ regulatory T cells in patients with multiple sclerosis. J. Exp. Med., 199, 971–979. Voice, J., Donnelly, S., Dorsam, G., Dolganov, G., Paul, S., and Goetzl, E. J. (2004). c-Maf and JunB mediation of Th2 differentiation induced by the type 2 G protein-coupled receptor (VPAC2)
5. Vasoactive Intestinal Peptide: An Anti-inflammatory Neuropeptide for vasoactive intestinal peptide. J. Immunol., 172, 7289– 7296. Voice, J. K., Dorsam, G., Lee, H., Kong, Y., and Goetzl, E. J. (2001). Allergic diathesis in transgenic mice with constitutive T cell expression of inducible vasoactive intestinal peptide receptor. FASEB J., 15, 2489–2496. Voice, J. K., Grinninger, C., Kong, Y., Bangale, Y., Paul, S., and Goetzl, E. J. (2003). Roles of vasoactive intestinal peptide (VIP) in the expression of different immune phenotypes by wild-type mice and T cell–targeted type II VIP receptor transgenic mice. J. Immunol., 170, 308–314. Wakkach, A., Fournier, N., Brun, V., Breittmayer, J. P., Cottrez, F., and Groux, H. (2003). Characterization of dendritic cells that induce tolerance and T regulatory 1 cell differentiation in vivo. Immunity, 18, 605–617. Walmsley, M., Katsikis, P. D., Abney, E., Parry, S., Williams, R. O., Maini, R. N., and Feldmann, M. (1996). Interleukin-10 inhibition of the progression of established collagen-induced arthritis. Arthritis Rheum., 39, 495–503. Wang, H. Y., Jiang, X., Gozes, I., Fridkin, M., Brenneman, D. E., and Ganea, D. (1999). Vasoactive intestinal peptide inhibits cytokine production in T lymphocytes through cAMP-dependent and cAMP-independent mechanisms. Regul. Pept., 84, 55–67. Wang, H. Y., Jiang, X. M., and Ganea, D. (2000). The neuropeptides VIP and PACAP inhibit IL-2 transcription by decreasing c-Jun and increasing JunB expression in T cells. J. Neuroimmunol., 104, 68–78. Wang, R., Rogers, A. M., Ratliff, T. L., and Russell, J. H. (1996). CD95dependent bystander lysis caused by CD4+ T helper 1 effectors. J. Immunol., 157, 2961–2968. Weinstock, J. V., and Blum, A. M. (1990). Detection of vasoactive intestinal peptide and localization of its mRNA within granulomas of murine schistosomiasis. Cell. Immunol., 125, 291–300. Wershil, B. K., Turck, C. W., Sreedharan, S. P., Yang, J., An, S., Galli, S. J., and Goetzl, E. J. (1993). Variants of vasoactive intestinal
157
peptide in mouse mast cells and rat basophilic leukemia cells. Cell. Immunol., 151, 369–378. Wheeler, R. D., and Owens, T. (2005). The changing face of cytokines in the brain: perspectives from EAE. Curr. Pharm. Des., 11, 1031–1037. Williams, R. O. (2002). Therapeutic effect of vasoactive intestinal peptide in collagen-induced arthritis. Arthritis Rheum., 46, 271–273. Xin, Z., and Sriram, S. (1998). Vasoactive intestinal peptide inhibits IL-12 and nitric oxide production in murine macrophages. J. Neuroimmunol., 89, 206–212. Yamamoto, M., Yoshizaki, K., Kishimoto, T., and Ito, H. (2000). IL-6 is required for the development of Th1 cell-mediated murine colitis. J. Immunol., 164, 4878–4882. Yin, H., Cheng, H., Yu, M., Zhang, F., Lin, J., Gao, Y., Han, B., and Zhu, L. (2005). Vasoactive intestinal peptide ameliorates synovial cell functions of collagen-induced arthritis rats by downregulating NF-kappaB activity. Immunol. Invest., 34, 153–169. Yin, Q., Kemp, G. J., and Frostick, S. P. (1998). Neurotrophins, neurones and peripheral nerve regeneration. J. Hand Surg. [Br], 23, 433–437. Yong, V. W. (2002). Differential mechanisms of action of interferonbeta and glutiramer acetate in MS. Neurology, 59, 802–808. Zhang, P., Hogan, E. L., and Bhat, N. R. (1998). Activation of JNK/ SAPK in primary glial cultures: II. Differential activation of kinase isoforms corresponds to their differential expression. Neurochem. Res., 23, 219–225. Zhong, H., Voll, R. E., and Ghosh, S. (1998). Phosphorylation of NFkappa B p65 by PKA stimulates transcriptional activity by promoting a novel bivalent interaction with the coactivator CBP/ p300. Mol. Cell., 1, 661–671. Zlotnik, A., and Yoshie, O. (2000). Chemokines: a new classification system and their role in immunity. Immunity, 12, 121–127.
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6 Immune-derived Opioids: Production and Function in Inflammatory Pain HALINA MACHELSKA AND CHRISTOPH STEIN
I. INTRODUCTION 159 II. PERIPHERAL OPIOID RECEPTORS 160 III. OPIOID PEPTIDES PRODUCED BY IMMUNE CELLS 161 IV. MIGRATION OF OPIOID-CONTAINING IMMUNE CELLS TO INFLAMED TISSUE 163 V. RELEASE OF OPIOID PEPTIDES FROM IMMUNE CELLS 164 VI. ANALGESIA PRODUCED BY IMMUNE-DERIVED OPIOID PEPTIDES 165 VII. CLINICAL IMPLICATIONS 166 VIII. PERSPECTIVES 166
peptides. These effects occur without central opioid side effects such as depression of breathing, clouding of consciousness, or addiction. Future research should elucidate the selective targeting of opioid peptidecontaining cells to sites of painful tissue injury and the augmentation of opioid peptide and receptor synthesis.
I. INTRODUCTION Acute transient pain serves as a physiological warning to guard the integrity of the organism. An immediate reflex, e.g., withdrawal of a body part from a heat source, prevents tissue damage. If tissue damage occurs, an inflammatory response develops triggered by various pro-inflammatory and pro-algesic mediators. These include protons, hydrogen ions, bradykinin, adenosine triphosphate, prostaglandins, proinflammatory cytokines, chemokines, sympathetic amines, nerve growth factor, and neuropeptides (e.g., substance P, calcitonin-gene–related peptide), which are produced at the site of injury, in plasma, in immune cells, and in the nervous system. In consequence, specialized sensory neurons called nociceptors are activated. Trigeminal and dorsal root ganglia contain nociceptor cell bodies, which give rise to myelinated Aδ and unmyelinated C fibers. Peripheral terminals of Aδ and C fibers transduce and propagate noxious stimuli from peripheral tissues (such as skin, muscles, joints, viscera) to the dorsal horn of the spinal cord
ABSTRACT Endogenous pain control is not only mediated within the central nervous system. In inflammation an interaction between immune cell-derived opioid peptides and peripheral opioid receptors produces potent, clinically relevant inhibition of pain. Opioid receptors are present on peripheral terminals of sensory neurons and are upregulated in inflammation. Their endogenous ligands, opioid peptides, are synthesized in circulating immune cells, which migrate to injured tissues directed by chemokines and adhesion molecules. Under stressful stimuli or in response to releasing agents (e.g., corticotropin-releasing factor, cytokines, catecholamines), immunocytes can secrete opioids. These peptides activate peripheral opioid receptors and produce analgesia by inhibiting the excitability of sensory nerves and/or the release of excitatory neuroPSYCHONEUROIMMUNOLOGY, 4E VOLUME I
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from where these stimuli are transmitted to the brain. At the spinal and supraspinal sites, pro-algesic neurotransmitters, environmental, and cognitive factors contribute to the sensation of pain (Woolf and Salter, 2000). Concurrently, however, endogenous mechanisms which counteract pain develop. They have been well established in the brain and spinal cord where they constitute so-called descending pain inhibitory pathways, which contain mostly opioid peptides, noradrenaline and serotonin, and their receptors (Akil et al., 1998; Terman et al., 1984; Willer et al., 1981). In the peripheral inflamed tissue similar effects can be produced by anti-inflammatory cytokines (Cunha and Ferreira, 2003). However, the best characterized mechanisms of intrinsic pain inhibition (analgesia) directly at the site of injury are based on interactions between leukocyte-derived opioid peptides and peripheral nociceptor endings carrying opioid receptors (Machelska et al., 2002; Stein et al., 2003). This chapter will give an overview of current information on the anatomy and function of peripheral opioid receptors, production and release of opioid peptides from immune cells, mechanisms of opioid-containing leukocyte migration to inflamed tissue, and on analgesia produced by immune-derived opioids.
II. PERIPHERAL OPIOID RECEPTORS A. Localization Opioid peptides are the natural ligands at opioid receptors. Three cDNAs and their genes have been identified, encoding the μ-, δ-, and κ-opioid receptors (MOP, DOP, and KOP), respectively (Kieffer and Gaveriaux-Ruff, 2002). All three receptors can mediate pain inhibition, and they are found throughout the nervous system, including somatic and visceral sensory neurons, spinal cord projection and interneurons, midbrain and cortex. Recent interest has focused on the identification of opioid receptors on nociceptors. All three opioid receptor mRNAs and proteins are expressed in cell bodies of these neurons in dorsal root ganglia (Stein et al., 2001). Opioid receptors are intraaxonally transported into the neuronal processes and are detectable on peripheral sensory nerve terminals in animals and in humans. Colocalization studies confirmed the presence of opioid receptors on neurons expressing substance P and/or calcitonin gene-related peptide, on Aδ- and C-fibers. The latter carry the capsaicin receptor TRPV1 (transient receptor potential vanniloid subtype-1) and are considered the dominant fibers in clinical pain. The binding characteristics
(affinity) of peripheral and central opioid receptors are similar, but the molecular mass of peripheral and central μ-receptors appear to be different (references in Stein et al., 2003). If these findings are confirmed, a search for selective ligands at such distinct receptors may be warranted. It has been suggested that opioid receptors are also located on sympathetic postganglionic neuron terminals. However, there are reports arguing against this notion, and studies attempting the direct demonstration of opioid receptor mRNA in sympathetic ganglia have produced negative results. In addition, thorough morphological investigations have clearly demonstrated the presence of δ-receptors on unmyelinated primary afferent neurons and the absence of such receptors on postganglionic sympathetic neurons in skin, lip, and cornea. Moreover, chemical sympathectomy with 6-hydroxydopamine does not change the expression of opioid receptors in the dorsal root ganglion or the peripheral analgesic effects of μ-, δ-, and κ-receptor agonists in a model of inflammatory pain. Together, these findings have corroborated the notion that peripheral opioid receptors mediating analgesia are exclusively localized on primary sensory neurons (references in Stein et al., 2001). Opioid binding sites and the expression of opioid receptor transcripts have also been demonstrated in immune cells. Opioid-mediated modulation of the proliferation of these cells and of their functions (e.g., chemotaxis, superoxide and cytokine production, mast cell degranulation) has been reported. These immunomodulatory actions can be stimulatory as well as inhibitory and have been ascribed to the activation of opioid receptors (Sacerdote et al., 2003; Sharp, 2003). However, the significance of such effects with regard to pain transmission has not been investigated as yet.
B. Opioid Receptor Signaling in Sensory Neurons All three types of opioid receptors mediate the inhibition of high-voltage activated calcium channels in cultured primary afferent neurons (Figure 1). These effects are transduced by G-proteins (Gi and/or Go) (references in Stein et al., 2001, 2003). Although it is well known that opioids induce membrane hyperpolarization due to increased potassium currents in central neurons, this could not be detected in dorsal root ganglion neurons so far (Akins et al., 1993). Thus, the modulation of calcium channels appears to be the primary mechanism for the inhibitory effects of opioids on peripheral sensory neurons. In addition, opioids—via inhibition of adenylyl cyclase—suppress
6. Immune-derived Opioids: Production and Function in Inflammatory Pain Opioid receptor +
Na channel
Adenylyl cyclase
ATP
TABLE 1 NH2
++
Ca channel
Gi/o COOH
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Structure of endogenous opioid peptides
β-Endorphin
Tyr-Gly-Gly-Phe-Met-Thr-Ser-Glu-LysSer-Gln-Thr-Pro-Leu-Val-Thr-Leu-PheLys-Asn-Ala-Ile-Val-Lys-Asn-Ala-HisLys-Lys-Gly-Gln-OH Methionine-enkephalin Tyr-Gly-Gly-Phe-Met-OH Leucine-enkephalin Tyr-Gly-Gly-Phe-Leu-OH Dynorphin A Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Ile-ArgPro-Lys-Leu-Lys-Tyr-Asp-Asn-Gln-OH Endomorphin-1 Tyr-Pro-Trp-Phe-OH Endomorphin-2 Tyr-Pro-Phe-Phe-OH
cAMP
FIGURE 1 Opioid receptor structure and signaling in primary afferent neurons. Opioid receptors consist of seven transmembrane domains (green). Upon activation by exogenous or endogenous opioids, they couple to inhibitory G-proteins (Gi/o). This leads to direct or indirect (via decrease of cyclic adenosine monophosphate [cAMP]) closing of calcium (Ca++) and/or sodium (Na+) channels, and to subsequent analgesia. Cyclic AMP is produced from adenosine triphosphate (ATP) by the enzyme adenylyl cyclase.
tetrodotoxin-resistant sodium- and nonselective cation currents stimulated by the inflammatory agent prostaglandin E2 (Gold et al., 1994; Ingram and Williams, 1994). Interestingly, tetrodotoxin-resistant sodium channels are selectively expressed in nociceptors; they are important for impulse initiation and action potential conductance; they mediate spontaneous activity in sensitized nociceptors; and they accumulate at the site of injury in damaged nerves, leading to ectopic impulse generation (Laird et al., 2002; Porreca et al., 1999). The latter observations may explain the notable efficacy of peripheral opioids in inflammatory and neuropathic pain (Stein et al., 2001, 2003). Consistent with their effects on ion channels, opioids attenuate the excitability of peripheral nociceptor terminals, the propagation of action potentials, the release of excitatory pro-inflammatory neuropeptides (substance P, calcitonin gene-related peptide) from peripheral sensory nerve endings, and vasodilatation evoked by stimulation of C-fibers (references in Stein et al., 2001). All of these mechanisms result in analgesia and/or antiinflammatory actions.
C. Peripheral Opioid Receptors and Inflammation Peripheral opioid analgesic effects are augmented under conditions of tissue injury such as inflammation, neuropathy, or bone damage (Stein et al., 2001, 2003). One underlying mechanism is an increased
number (“upregulation”) of peripheral opioid receptors. In neuronal cell cultures, μ-receptor transcription is upregulated by the cytokine interleukin (IL)-4 through binding of STAT6 transcription factors to the μ-receptor gene promoter (Kraus et al., 2001). In dorsal root ganglia, the synthesis and expression of opioid receptors can be increased by peripheral tissue inflammation (Ji et al., 1995; Zöllner et al., 2003). Subsequently, the axonal transport of opioid receptors is greatly enhanced, leading to their upregulation and to enhanced agonist efficacy at peripheral nerve terminals (Jeanjean et al., 1995; Mousa et al., 2001). In addition, the specific milieu (low pH, prostanoid release) of inflamed tissue may increase opioid agonist efficacy by enhanced G-protein coupling and by increased neuronal cyclic adenosine monophosphate levels (Ingram and Williams, 1994; Selley et al., 1993; Zöllner et al., 2003). Inflammation also leads to an increase in the number of sensory nerve terminals (“sprouting”) and disrupts the perineurial barrier, thus facilitating the access of opioid agonists to their receptors (Stein et al., 2001, 2003).
III. OPIOID PEPTIDES PRODUCED BY IMMUNE CELLS Three families of these peptides are well characterized in the central nervous and neuroendocrine systems (Akil et al., 1998). Each family derives from a distinct gene and from one of the three precursor proteins proopiomelanocortin (POMC), proenkephalin (PENK), and prodynorphin, respectively. Appropriate processing yields their respective representative opioid peptides, the endorphins, enkephalins, and dynorphins (Table 1). These peptides exhibit different affinity and selectivity for the three opioid receptors μ (endorphins, enkephalins), δ (enkephalins, endorphins), and κ (dynorphin). Two additional endogenous opioid peptides have been isolated from bovine brain:
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endomorphin-1 and endomorphin-2. Both peptides are considered highly selective μ-receptor ligands. Their precursors are not known yet. All of these opioid peptides have been detected in immune cells, but the POMC and PENK families have been studied most extensively.
A. POMC-derived Opioid Peptides POMC-related opioid peptides have been found in immune cells of many vertebrates and non-vertebrates (references in Machelska and Stein, 2002). To determine whether these immune-competent cells actually synthesize POMC rather than simply absorb related peptides from plasma, mRNA-encoding POMC was sought for and demonstrated in many of these studies. The pituitary POMC gene is organized into three exons separated by intervening sequences which are removed during processing following transcription to produce the full-length, 1200 nt transcript. Initially, truncated POMC transcripts were found in leukocytes (references in Machelska and Stein, 2002). Lyons and Blalock re-examined the question of POMC mRNA expression using novel polymerase chain reaction procedures (Lyons and Blalock, 1997). With this exacting and sensitive methodology, they found expression of fulllength transcripts encoding all three POMC exons in rat mononuclear leukocytes. This POMC transcript is spliced in the same way as the pituitary transcript and contains the sequence for the signal peptide, which is necessary for the correct routing into the regulated secretory pathway. The POMC protein is also proteolytically processed in a way consistent with the pituitary gland (Lyons and Blalock, 1997; Mousa et al., 2004). These results unequivocally demonstrate that immune cells can produce full-length POMC transcripts. Apparently this production is stimulated by various immune and inflammatory mediators (Smith, 2003).
B. PENK-derived Opioid Peptides PENK-derived opioid peptides have also been detected in human and rodent immune cells. Both the mRNA and Methionine (Met)-enkephalin protein were detected. Preproenkephalin mRNA was found in Tand B-cells, macrophages, and mast cells. In subpopulations of immune cells, this mRNA was shown to be highly homologous to brain PENK mRNA, abundant and apparently translated, since immunoreactive enkephalin is present and/or released. The appropriate enzymes necessary for post-translational processing of PENK have also been identified in immune cells (references in Machelska and Stein, 2002).
C. Immune-derived Opioid Peptides in Inflammation Immune-derived opioid peptides apparently play a substantial role in the modulation of inflammatory pain (Machelska and Stein, 2002; Stein et al., 2003). Persistent inflammation is a pathophysiological in vivo stimulus for the immune system and represents a condition that is closer to the clinical setting than in vitro studies. POMC mRNA and β-endorphin, as well as Met-enkephalin and dynorphin, were found in cells derived from lymph nodes, and in leukocytes in the blood and within inflamed tissue (Cabot et al., 1997, 2001; Machelska et al., 2003; Mousa et al., 2004). In the pituitary POMC processing begins as the nascent polypeptide enters the endoplasmic reticulum directed by the signal peptide, and POMC cleavage begins in the trans-Golgi network (references in Mousa et al., 2004). The POMC prohormone is directed to the regulated secretory pathway at the trans-Golgi network by binding to a sorting receptor, membranebound carboxypeptidase E. The prohormone convertases PC1 (also called PC1/3) and PC2 cleave POMC within the trans-Golgi network. PC1 mediates the initial cleavage into adrenocorticotropic and βlipotropic hormones. The inactive pro-PC2 is bound to 7B2 (a chaperone-like binding protein) and is transported from the endoplasmic reticulum to later compartments of the secretory pathway, where it matures to active PC2; thereafter, PC2 converts β-lipotropic hormone into β-melanocyte-stimulating hormone and β-endorphin (references in Mousa et al., 2004). Recently, we detected β-endorphin and POMC alone and colocalized with PC1, PC2, carboxypeptidase E, and 7B2 in leukocytes in the blood and within inflamed tissue in a rat model of unilateral hind paw inflammation with complete Freund’s adjuvant (Mousa et al., 2004). This demonstrates that immune cells express the entire machinery required for POMC processing into functionally active β-endorphin. In the same model of inflammatory pain, mRNAs encoding POMC and PENK and the corresponding opioid peptides βendorphin and Met-enkephalin are abundant in cells of inflamed but not in non-inflamed tissue (Przewlocki et al., 1992). Histomorphological procedures and flow cytometry have identified the opioid-containing cells as T- and B-lymphocytes, granulocytes, and monocytes/macrophages (Przewlocki et al., 1992; Rittner et al., 2001). Also, it was shown that β-endorphin is present in activated/memory T-cells within inflamed tissue (Cabot et al., 1997; Mousa et al., 2001). Thus, opioid peptides are processed and present both in circulating and inflammatory cells infiltrating injured tissue.
6. Immune-derived Opioids: Production and Function in Inflammatory Pain
IV. MIGRATION OF OPIOID-CONTAINING IMMUNE CELLS TO INFLAMED TISSUE The recruitment of leukocytes from the circulation into areas of inflammation involves a well-orchestrated set of events. Leukocytes undergo multiple attachments to and detachments from the vessel’s endothelial cells prior to transendothelial migration. This includes slowing and rolling along the endothelial cell wall that is mediated predominantly by the interaction of selectins expressed on leukocytes (L-selectin) and on endothelial cells (P- and E-selectin) with their ligands on endothelium or immune cells, respectively. The rolling immunocytes can then be activated by chemoattractants such as chemokines released from
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inflammatory cells and presented on endothelium. This leads to the upregulation and increased avidity of integrins. These mediate the firm adhesion of leukocytes to endothelial cells via ligands of the immunoglobulin superfamily, e.g., intercellular adhesion molecule-1 (ICAM-1). Finally, the immune cells transmigrate through the endothelial wall mediated by immunoglobulin superfamily members (e.g., platelet-endothelial adhesion molecule-1; PECAM-1) and are directed to the sites of inflammation to initiate a host defense (reviewed by Petruzzelli et al., 1999; von Andrian and Mackay, 2000). Recent findings indicate that these events can also be involved in the endogenous control of inflammatory pain. In the model of unilateral hind paw
FIGURE 2 Migration of opioid-producing cells and opioid secretion within inflamed tissue. Adhesion molecules are upregulated on vascular endothelium of blood vessels (red) and are co-expressed by circulating immune cells producing opioid peptides. These cells also co-express receptors for chemokines which are released from leukocytes and presented on endothelium. Certain adhesion molecules mediate rolling of opioid-containing leukocytes along the endothelium. The rolling leukocytes can then be activated by chemokines which upregulate another class of adhesion molecules mediating adhesion, and finally cells transmigrate through the endothelium. Once extravasated, these cells can be stimulated by stress (e.g., swim stress, surgery) or releasing agents such as corticotropin-releasing factor (CRF), interleukin-1β (IL-1), and noradrenaline (NA) to secrete opioid peptides. CRF, IL-1, and NA (derived from postganglionic sympathetic neurons; PGSN) elicit opioid release by activating CRF receptors (CRFR), IL-1 receptors (IL-1R), and adrenergic receptors (AR) on immune cells, respectively. Opioids bind to peripheral opioid receptors (produced in dorsal root ganglia and transported to peripheral endings of primary afferent neurons; PAN) and lead to analgesia (see Figure 1).
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inflammation, we have shown that integrin α4 and the chemokines CXCL1 (i.e., keratinocyte-derived chemokine) and CXCL2 (i.e., macrophage inflammatory protein-2) are expressed by leukocytes, while adhesion molecules such as P- and E-selectins, ICAM1, and PECAM-1 are upregulated on endothelium in inflamed paw tissue (Brack et al., 2004c; Machelska et al., 2002, 2004; Mousa et al., 2000) (Figure 2). Expression of CXCL1 and CXCL2 mRNAs and protein contents significantly increased in inflamed tissue during the course of inflammation (Brack et al., 2004b, 2004c). Importantly, L-selectin, integrins β2, and the CXC chemokine receptor 2 (CXCR2) are co-expressed by opioidcontaining leukocytes that have migrated to inflamed subcutaneous paw tissue (Brack et al., 2004c; Machelska et al., 2004; Mousa et al., 2000). Furthermore, pretreatment of rats with a selectin blocker (fucoidin), selective antibodies against ICAM-1, integrins α4 and β2, or chemokines CXCL1 and CXCL2 substantially decreases the number of opioid-containing immunocytes infiltrating the inflamed tissue (Brack et al., 2004c; Machelska et al., 1998, 2002, 2004) and in consequence abolishes endogenous peripheral opioid analgesia (see section VI). This suggests that circulating opioidproducing immune cells home to inflamed tissue where they secrete the opioids to inhibit pain. Afterwards they travel to the regional lymph nodes, depleted of the opioid peptides (Cabot et al., 1997; 2001). Thus, local signals apparently not only stimulate the synthesis of opioid peptides in resident inflammatory cells, but also attract opioid-containing cells from the circulation to the site of injury to reduce pain. This is controlled by specific chemotactic and adhesive mechanisms.
V. RELEASE OF OPIOID PEPTIDES FROM IMMUNE CELLS Regulated secretion of peptides requires secretory granules deriving from the Golgi network for transport to the cell membrane. As discussed in Section III.C. immune cells in the blood and in inflamed tissue co-express the entire machinery required for POMC processing into functionally active β-endorphin (Mousa et al., 2004). Furthermore, our ultrastructural observations show that β-endorphin-immunoreactive macrophages, monocytes, granulocytes, and lymphocytes contain rough endoplasmic reticulum and Golgi apparatus, similar to pituitary cells. Immunostaining of βendorphin was detectable in secretory granules, which were grouped in small or large membranous vesicular
structures. The smaller β-endorphin-immunoreactive secretory granules were localized within cytoplasm, and the larger ones were arranged at the cell periphery ready for the exocytosis, similar to the pituitary (Mousa et al., 2004). In the pituitary β-endorphin and other POMC-derived peptides are released by CRF and IL1β (IL-1) (references in Schäfer, 2003). Similar mechanisms can trigger opioid release within peripheral inflamed tissue (Figure 2). CRF is present in immune cells, fibroblasts, and vascular endothelium, and peripheral CRF expression is enhanced in inflamed synovial and subcutaneous tissue of animals and humans (Schäfer et al., 1996). CRF- and IL-1–receptors and their upregulation were demonstrated in inflamed lymph nodes and paw tissue. Their pharmacological characteristics were similar to the high-affinity CRFand IL-1–binding sites in the pituitary (Mousa et al., 1996). Furthermore, the co-expression of CRF-1 and CRF-2 receptors with β-endorphin in monocytes/macrophages, granulocytes, and lymphocytes was recently shown in the blood and in inflamed paw tissue (Mousa et al., 2003). In contrast, CRF-receptors were not detected on peripheral endings of sensory nerves (Mousa et al., 1996, 2003). The activation of CRF- and IL-1–receptors on cells from lymph nodes results in the secretion of opioid peptides. In those studies βendorphin, Met-enkephalin, and dynorphin were dose-dependently released by CRF, while IL-1 released β-endorphin and dynorphin but not Met-enkephalin. These effects were specific to CRF- and IL-1–receptors (Cabot et al., 1997, 2001; Schäfer et al., 1994). Moreover, this release of opioid peptides was calcium-dependent and mimicked by elevated extracellular concentrations of potassium (Cabot et al., 1997, 2001). This is consistent with a regulated pathway of release from secretory vesicles, as in neurons and endocrine cells. Adrenergic-receptor agonists have also been shown to secrete β-endorphin from human peripheral blood mononuclear cells (Kavelaars et al., 1990). Similar mechanisms are involved in β-endorphin release from leukocytes in the rat model of inflammatory pain (Binder et al., 2004) (Figure 2). Double labeling demonstrated adrenergic α1-, β2- and, to a lesser degree, α2-receptors expressed on β-endorphin–containing inflammatory cells in paw tissue. β-endorphin– containing cells and adrenergic α1- and β2-receptor– expressing cells were localized in close proximity to sympathetic nerve fibers, and chemical ablation of these fibers abolished intrinsic opioid analgesia. Finally, noradrenaline induced adrenergic receptorspecific release of β-endorphin from immune cells in vitro (Binder et al., 2004). Taken together, CRF, IL-1, and sympathetic neuron-derived noradrenaline can
6. Immune-derived Opioids: Production and Function in Inflammatory Pain
act on their respective receptors on immune cells, resulting in release of opioid peptides (Figure 2).
VI. ANALGESIA PRODUCED BY IMMUNE-DERIVED OPIOID PEPTIDES A. Analgesic Effects of CRF, Cytokines, and Noradrenaline CRF-, IL-1–, and noradrenaline-induced release of opioids from immune cells also occurs in vivo (Figure 2). CRF and IL-1 injected into inflamed paws produce dose-dependent analgesia reversible by their respective antagonists (Schäfer et al., 1994). CRF can produce analgesia both in early and late stages of inflammation (2 hours to 6 days) and, in accord with anatomical findings (see section V), CRF-analgesia involves both CRF-1 and CRF-2 receptors (Brack et al., 2004c; Machelska et al., 2003; Mousa et al., 2003). Intravenous administration of these agents in locally effective doses does not change pain thresholds, demonstrating a peripheral site of action (Brack et al., 2004c; Machelska et al., 2003; Mousa et al., 2003; Schäfer et al., 1994). Leukocytes apparently are the target for CRF and IL-1 because immunosuppression with cyclosporine A, depletion of granulocytes, blockade of chemokines (CXCL1 and CXCL2), as well as anti-selectin and antiICAM-1 treatments result in a significant reduction of opioid-containing cells and of CRF- or IL-1–induced analgesia (Brack et al., 2004c; Machelska et al., 1998, 2002; Schäfer et al., 1994). Also, cyclosporine A-induced attenuation of CRF-analgesia could be restored by injection of activated lymphocytes (Hermanussen et al., 2004). CRF- and IL-1–induced analgesia is blocked by an antibody against β-endorphin, suggesting that this opioid plays a major role. In addition, Met-enkephalin appears to be involved in CRF-, and dynorphin in IL-1–induced analgesia (Schäfer et al., 1994). These results are in line with other studies on local analgesic effects of CRF (Hargreaves et al., 1989; McLoon et al., 2002) and of the cytokines IL-6 and tumor necrosis factor-α (Czlonkowski et al., 1993) but are in contrast to hyperalgesia induced by IL-1α, IL-1β, IL-6, and tumor necrosis factor-α (Cunha and Ferreira, 2003). Importantly, however, the latter hyperalgesic effects of exogenous cytokines were observed after injections into noninflamed tissue (Cunha and Ferreira, 2003; Safieh-Garabedian et al., 1995; Woolf et al., 1997). Apparently, hyperalgesia in highly inflamed tissue (4 days after complete Freund’s adjuvant) has already reached a ceiling effect (Machelska et al., 2003) and therefore cannot be further increased. Instead, in such tissue opioid-containing immune cells became
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the predominant target for cytokines to produce analgesia. Contribution of endogenous pro-inflammatory cytokines to the generation of pain was mostly observed either in early stages (3–6 hours) when cytokine blockade preceded induction of complete Freund’s adjuvant inflammation (Woolf et al., 1997) or in short-lasting (30 minutes–3 hours) inflammation, e.g., induced with carrageenan, lipopolysaccharide, or acetic acid (Cunha and Ferreira, 2003). Thus, the presence or absence of inflammation and the duration and/or model of inflammatory pain are factors to be taken into consideration. Noradrenaline administered directly into inflamed tissue has been shown to produce analgesia, reversible by α1-, α2-, and β2-adrenergic receptor antagonists. Further, this effect was dose-dependently blocked by μ- and δ-opioid receptor antagonists and antibody against β-endorphin (Binder et al., 2004). These data suggest that this catecholamine produces analgesia via opioid peptides activating peripheral opioid receptors (Figure 2). In noninflamed tissue, noradrenaline did not influence pain behavior in this model, consistent with the lack of opioid-containing cells and with the scarcity of adrenergic receptors (Binder et al., 2004). However, the role of peripheral adrenergic receptors in nociception appears controversial. In noninflamed tissue noradrenaline has been shown to produce hyperalgesia via an α2-adrenergic receptor mechanism. Others found that α2-agonists could also produce peripheral analgesia. It has even been postulated that hyperalgesia is mediated via α2B and analgesia is mediated via α2C receptors (references in Binder et al., 2004). Thus, different receptor subtypes, receptor localization, microenvironment, and the presence or absence of inflammation are important parameters to be considered.
B. Endogenous Opioid Analgesia Stress is a natural stimulus triggering inhibition of pain (Terman et al., 1984; Willer et al., 1981). In rats with unilateral hind paw inflammation, stress induced by cold water (4°C) swim (for 1 minute) elicits potent analgesia in inflamed but not in noninflamed paws (Machelska et al., 2003; Stein et al., 1990a). In early inflammation (6 hours) this swim stress-induced analgesia was only partially attenuated by peripherally selective doses of different opioid peptide antibodies and receptor antagonists but was fully reversed by centrally acting doses of an opioid receptor antagonist (Machelska et al., 2003). At later stages of inflammation (4–6 days) swim stress-induced analgesia was completely abolished by peripherally selective doses
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of antibody against β-endorphin and by μ- and δantagonists (Stein et al., 1990a, 1990b). Together, these data indicate that at early stages of Freund’s adjuvantinduced inflammation, all three families of opioid peptides and receptors are involved, while at later stages β-endorphin acting at μ- and δ-receptors dominates. Whereas at early stages both peripheral and central opioid receptors are involved, at later stages endogenous analgesia is mediated exclusively by peripheral opioid receptors. Thus, peripheral opioid mechanisms of pain control become more prevalent with the duration and severity of inflammation. Endogenous triggers of swim stress-induced analgesia are locally produced CRF and sympathetic nerve-derived catecholamines because this effect is abolished by local neutralization of CRF (Machelska et al., 2003; Schäfer et al., 1996), and by sympathetic blockade (Binder et al., 2004). Various types of immune cells are the source of opioids as demonstrated by the abolishment of stressinduced analgesia by immunosuppression with cyclosporine A or whole body irradiation, and by depletion of monocytes/macrophages (Brack et al., 2004a; Przewlocki et al., 1992; Stein et al., 1990b). Moreover, this effect is also extinguished by inhibiting the extravasation of β-endorphin–containing immune cells following blockade of L- and P-selectins, α4 and β2 integrins, or of ICAM-1 (Machelska et al., 1998, 2002, 2004). These adhesion molecules apparently regulate the migration of opioid-containing immune cells and the subsequent generation of intrinsic pain control in injured tissue (Figure 2). A future challenge is to identify factors that will increase homing of opioidcontaining cells to injured tissue and will enhance analgesia. To this end, we have shown that hematopoetic growth factors strongly mobilized granulocytes in the blood but resulted only in a minor increase in the number of opioid-containing leukocytes in inflamed paws, and in no change of CRF- and swim stressinduced analgesia (Brack et al., 2004b). Another approach was to increase the migration of opioidcontaining cells to inflamed tissue with local injections of chemokine CXCL2. However, this did not result in stronger CRF- or swim stress-induced analgesia either, most probably as a result of the small number of peripheral opioid receptors at this very early (2 hours) stage of inflammation (Brack et al., 2004d). Indeed, our previous studies had shown that intrinsic analgesia increases with the duration of inflammation (2 hours–4 days), in parallel with the number of opioid-containing immunocytes, with the number of peripheral opioid receptors and with the efficacy of opioid receptor-G–protein coupling in sensory neurons (Mousa et al., 2001; Rittner et al., 2001; Zöllner et al., 2003).
VII. CLINICAL IMPLICATIONS Peripheral endogenous opioid analgesia has found many clinical applications. Opioid receptors have been demonstrated on peripheral terminals of sensory nerves in human synovia (Stein et al., 1996), and these receptors mediate analgesia in patients with various types of pain (e.g., in chronic rheumatoid arthritis and osteoarthritis; bone pain; after dental, laparoscopic, urinary bladder, and knee surgery) (references in Stein et al., 2003). Opioid peptides are found in human synovial lining cells, mast cells, lymphocytes, and macrophages. The prevailing peptides are βendorphin and Met-enkephalin, while only minor amounts of dynorphin are detectable (Stein et al., 1993; 1996). The interaction of synovial opioids with peripheral opioid receptors was examined in patients undergoing knee surgery. Blocking intra-articular opioid receptors by the local administration of naloxone resulted in significantly increased postoperative pain (Stein et al., 1993). Taken together, these findings suggest that in a stressful (e.g., postoperative) situation, opioids are tonically released from inflamed tissue and activate peripheral opioid receptors to attenuate clinical pain. Importantly, these endogenous opioids do not interfere with exogenous morphine, i.e., intra-articular morphine is an equally potent analgesic in patients with and without opioid-producing inflammatory synovial cells (Stein et al., 1996). This suggests that, in contrast to the rapid development of tolerance in the central nervous system, the immune cell-derived opioids do not readily produce cross-tolerance to morphine at peripheral opioid receptors.
VIII. PERSPECTIVES Effective control of inflammatory pain can result from interactions between leukocyte-derived opioid peptides and their receptors on peripheral sensory neurons. These findings provide new insights into intrinsic mechanisms of pain control and open strategies to develop new drugs and alternative approaches to treatment of pain. Immunocompromised patients (e.g., in AIDS, cancer, diabetes) frequently suffer from painful neuropathies that can be associated with intraand perineural inflammation, with reduced intraepidermal nerve fiber density and with low CD4+ lymphocyte counts (Polydefkis et al., 2003). Thus, it may be interesting to investigate the opioid production/release and the migration of opioid-containing leukocytes in these patients. The important role of certain adhesion molecules and chemokines in the trafficking of opioid-containing cells to injured tissues
6. Immune-derived Opioids: Production and Function in Inflammatory Pain
indicates that anti-adhesion or anti-chemokine strategies for the treatment of inflammatory diseases may in fact carry a significant risk to exacerbate pain. It would be highly desirable to identify stimulating factors and strategies that selectively attract opioid-producing cells and increase peripheral opioid receptor numbers in damaged tissue. Augmenting the synthesis and/or secretion of opioid peptides and opioid receptor numbers within injured tissue may be accomplished by gene therapy: delivery of PENK-, POMC-, and μopioid receptor-cDNAs has been shown to decrease chronic pain and inflammation (Braz et al., 2001; Lu et al., 2002; Xu et al., 2003). Importantly, opioid analgesia resulting from neuroimmune interactions occurs in peripheral tissues and therefore is devoid of central opioid side effects (such as respiratory depression, nausea, dysphoria, addiction, and high rate of tolerance) and of typical side effects produced by non-steroidal anti-inflammatory drugs (such as gastric erosions, ulcers, bleeding, diarrhea, and renal toxicity). Many efforts have been undertaken to develop peripherally acting analgesics by aiming at individual excitatory receptors or channels on sensory neurons (Simonin and Kieffer, 2002). The major advantage of targeting opioid receptors is their mechanism of action: The inhibition of calcium (and possibly sodium) channels simply renders the nociceptor less excitable to the plethora of stimulating molecules expressed in damaged tissue. Thus, peripherally acting opioids can prevent and reverse the action of multiple excitatory agents simultaneously, in contrast to blocking only one single noxious stimulus. Uncovering mechanisms that can enhance the availability of endogenous opioids within injured tissue and the signal transduction of peripheral opioid receptors will open exciting possibilities for pain research and therapy.
Acknowledgment We wish to thank Christine Voigts for the preparation of the illustrations.
References Akil, H., Owens, C., Gutstein, H., Taylor, L., Curran, E., and Watson, S. (1998). Endogenous opioids: overview and current issues. Drug Alcohol Depend., 51, 127–140. Akins, P. T., and McCleskey, E. W. (1993). Characterization of potassium currents in adult rat sensory neurons and modulation by opioids and cyclic AMP. Neuroscience, 56, 759–769. Binder, W., Mousa, S. A., Sitte, N., Kaiser, M., Stein, C., and Schäfer, M. (2004). Sympathetic activation triggers endogenous opioid release and analgesia within peripheral inflamed tissue. Eur. J. Neurosci., 20, 92–100.
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Brack, A., Labuz, D., Schiltz, A., Rittner, H. L., Machelska, H., Schäfer, M., Reszka, R., and Stein, C. (2004a). Tissue monocytes/ macrophages in inflammation: hyperalgesia versus opioidmediated peripheral antinociception. Anesthesiology, 101, 204– 211. Brack, A., Rittner, H. L., Machelska, H., Beschmann, K., Sitte, N., Schäfer, M., and Stein, C. (2004b). Mobilization of opioidcontaining polymorphonuclear cells by hematopoietic growth factors and influence on inflammatory pain. Anesthesiology, 100, 149–157. Brack, A., Rittner, H. L., Machelska, H., Leder, K., Mousa, S. A., Schäfer, M., and Stein, C. (2004c). Control of inflammatory pain by chemokine-mediated recruitment of opioid-containing polymorphonuclear cells. Pain, 112, 229–238. Brack, A., Rittner, H. L., Machelska, H., Shaqura, M., Mousa, S. A., Labuz, D., Zöllner, C., Schäfer, M., and Stein, C. (2004d). Endogenous peripheral antinociception in early inflammation is not limited by the number of opioid-containing leukocytes but by opioid receptor expression. Pain, 108, 67–75. Braz, J., Beaufour, C., Coutaux, A., Epstein, A. L., Cesselin, F., Hamon, M., and Pohl, M. (2001). Therapeutic efficacy in experimental polyarthritis of viral-driven enkephalin overproduction in sensory neurons. J. Neurosci., 21, 7881–7888. Cabot, P. J., Carter, L., Gaiddon, C., Zhang, Q., Schäfer, M., Loeffler, J. P., and Stein, C. (1997). Immune cell-derived β-endorphin: production, release and control of inflammatory pain in rats. J. Clin. Invest., 100, 142–148. Cabot, P. J., Carter, L., Schäfer, M., and Stein, C. (2001). Methionineenkephalin- and Dynorphin A-release from immune cells and control of inflammatory pain. Pain, 93, 207–212. Cunha, F. Q., and Ferreira, S. H. (2003). Peripheral hyperalgesic cytokines. Adv. Exp. Med. Biol., 521, 22–39. Czlonkowski, A., Stein, C., and Herz, A. (1993). Peripheral mechanisms of opioid antinociception in inflammation: involvement of cytokines. Eur. J. Pharmacol., 242, 229–235. Gold, M. S., and Levine, J. D. (1994). DAMGO inhibits prostaglandin E2-induced potentiation of a TTX-resistant Na+ current in rat sensory neurons in vitro. Neurosci. Lett., 212, 83–86. Hargreaves, K. M., Dubner, R., and Costello, A. H. (1989). Corticotropin releasing factor (CRF) has a peripheral site of action for antinociception. Eur. J. Pharmacol., 170, 275–279. Hermanussen, S., Do, M., and Cabot, P. J. (2004). Reduction of betaendorphin-containing immune cells in inflamed paw tissue corresponds with a reduction in immune-derived antinociception: reversible by donor activated lymphocytes. Anesth. Analg., 98, 723–729. Ingram, S. L., and Williams, J. T. (1994). Opioid inhibition of Ih via adenylyl cyclase. Neuron, 13, 179–186. Jeanjean, A. P., Moussaoui, S. M., Maloteaux, J.-M., and Laduron, P. M. (1995). Interleukin-1β induces long-term increase of axonally transported opiate receptors and substance P. Neuroscience, 68, 151–157. Ji, R. R., Zhang, Q., Law, P. Y., Low, H. H., Elde, R., and Hökfelt, T. (1995). Expression of μ-, δ-, and κ-opioid receptor-like immunoreactivities in rat dorsal root ganglia after carrageenan-induced inflammation. J. Neurosci., 15, 8156–8166. Kavelaars, A., Ballieux, R. E., and Heijnen, C. J. (1990). In vitro beta–adrenergic stimulation of lymphocytes induces the release of immunoreactive beta-endorphin. Endocrinology, 126, 3028–3032. Kieffer, B. L., and Gaveriaux-Ruff, C. (2002). Exploring the opioid system by gene knockout. Prog. Neurobiol., 66, 285–306. Kraus, J., Borner, C., Giannini, E., Hickfang, K., Braun, H., Mayer, P., Hoehe, M. R., Ambrosch, A., Konig, W., and Höllt, V. (2001).
168
I. Neural and Endocrine Effects on Immunity
Regulation of mu-opioid receptor gene transcription by interleukin-4 and influence of an allelic variation within a STAT6 transcription factor binding site. J. Biol. Chem., 276, 43901–43908. Laird, J. M., Souslova, V., Wood, J. N., and Cervero, F. (2002). Deficits in visceral pain and referred hyperalgesia in Nav1.8 (SNS/PN3)-null mice. J. Neurosci., 22, 8352–8356. Lu, C. Y., Chou, A. K., Wu, C. L., Yang, C. H., Chen, J. T., Wu, P. C., Lin, S. H., Muhammad, R., and Yang, L. C. (2002). Gene-gun particle with pro-opiomelanocortin cDNA produces analgesia against formalin-induced pain in rats. Gene Ther., 9, 1008–1014. Lyons, P. D., and Blalock, J. E. (1997). Pro-opiomelanocortin gene expression and protein processing in rat mononuclear leukocytes. J. Neuroimmunol., 78, 47–56. Machelska, H., Brack, A., Mousa, S. A., Schopohl, J. K., Rittner, H. L., Schäfer, M., and Stein, C. (2004). Selectins and integrins but not platelet-endothelial cell adhesion molecule-1 regulate opioid inhibition of inflammatory pain. Br. J. Pharmacol., 142, 772–780. Machelska, H., Cabot, P. J., Mousa, S. A., Zhang, Q., and Stein, C. (1998). Pain control in inflammation governed by selectins. Nat. Med., 4, 1425–1428. Machelska, H., Mousa, S. A., Brack, A., Schopohl, J. K., Rittner, H. L., Schäfer, M., and Stein, C. (2002). Opioid control of inflammatory pain regulated by intercellular adhesion molecule-1. J. Neurosci., 22, 5588–5596. Machelska, H., Schopohl, J. K., Mousa, S. A., Labuz, D., Schäfer, M., and Stein, C. (2003). Different mechanisms of intrinsic pain inhibition in early and late inflammation. J. Neuroimmunol., 141, 30–39. Machelska, H., and Stein, C. (2002). Immune mechanisms in pain control. Anesth. Analg., 95, 1002–1008. McLoon, L. K., Sandnas, A. M., Nockleby, K. J., and Wirtschafter, J. D. (2002). Reduction in vesicant-induced cellular inflammation and hyperalgesia by local injection of corticotropin releasing factor in rabbit eyelid. Inflamm. Res., 51, 16–23. Mousa, S. A., Bopaiah, C. P., Stein, C., and Schäfer, M. (2003). Involvement of corticotropin-releasing hormone receptor subtypes 1 and 2 in peripheral opioid-mediated inhibition of inflammatory pain. Pain, 106, 297–307. Mousa, S. A., Machelska, H., Schäfer, M., and Stein, C. (2000). Coexpression of beta-endorphin with adhesion molecules in a model of inflammatory pain. J. Neuroimmunol., 108, 160–170. Mousa, S. A., Schäfer, M., Mitchell, W. M., Hassan, A. H. S., and Stein, C. (1996). Local upregulation of corticotropin-releasing hormone and interleukin-1 receptors in rats with painful hindlimb inflammation. Eur. J. Pharmacol., 311, 221–231. Mousa, S. A., Shakibaei, M., Sitte, N., Schäfer, M., and Stein, C. (2004). Subcellular pathways of beta-endorphin synthesis, processing, and release from immunocytes in inflammatory pain. Endocrinology, 145, 1331–1341. Mousa, S. A., Zhang, Q., Sitte, N., Ji, R., and Stein, C. (2001). Betaendorphin–containing memory-cells and mu-opioid receptors undergo transport to peripheral inflamed tissue. J. Neuroimmunol., 115, 71–78. Petruzzelli, L., Takami, M., and Humes, D. (1999). Structure and function of cell adhesion molecules. Am. J. Med., 106, 467–476. Polydefkis, M., Yiannoutsos, C. T., Cohen, B. A., Hollander, H., Schifitto, G., Clifford, D. B., Simpson, D. M., Katzenstein, D., Shriver, S., Hauer, P., Brown, A., Haidich, A. B., Moo, L., and McArthur, J. C. (2002). Reduced intraepidermal nerve fiber density in HIV-associated sensory neuropathy. Neurology, 58, 115–119.
Porreca, F., Lai, J., Bian, D., Wegert, S., Ossipov, M. H., Eglen, R. M., Kassotakis, L., Novakovic, S., Rabert, D. K., Sangameswaran, L., and Hunter, J. C. (1999). A comparison of the potential role of the tetrodotoxin-insensitive sodium channels, PN3/SNS and NaN/SNS2, in rat models of chronic pain. Proc. Natl. Acad. Sci. USA, 96, 7640–7644. Przewlocki, R., Hassan, A. H. S., Lason, W., Epplen, C., Herz, A., and Stein, C. (1992). Gene expression and localization of opioid peptides in immune cells of inflamed tissue. Functional role in antinociception. Neuroscience, 48, 491–500. Rittner, H. L., Brack, A., Machelska, H., Mousa, S. A., Bauer, M., Schäfer, M., and Stein, C. (2001). Opioid peptide expressing leukocytes-identification, recruitment and simultaneously increasing inhibition of inflammatory pain. Anesthesiology, 95, 500–508. Sacerdote, P., Limiroli, E., and Gaspani, L. (2003). Experimental evidence for immunomodulatory effects of opioids. Adv. Exp. Med. Biol., 521, 106–116. Safieh-Garabedian, B., Poole, S., Allchorne, A., Winter, J., and Woolf, C. J. (1995). Contribution of interleukin-1 beta to the inflammation-induced increase in nerve growth factor levels and inflammatory hyperalgesia. Br. J. Pharmacol., 115, 1265–1275. Schäfer, M. (2003). Cytokines and peripheral analgesia. Adv. Exp. Med. Biol., 521, 40–50. Schäfer, M., Carter, L., and Stein, C. (1994). Interleukin-1β and corticotropin-releasing-factor inhibit pain by releasing opioids from immune cells in inflamed tissue. Proc. Natl. Acad. Sci. USA, 91, 4219–4223. Schäfer, M., Mousa, S. A., Zhang, Q., Carter, L., and Stein, C. (1996). Expression of corticotropin-releasing factor in inflamed tissue is required for intrinsic peripheral opioid analgesia. Proc. Natl. Acad. Sci. USA, 93, 6096–6100. Selley, D. E., Breivogel, C. S., and Childers, S. R. (1993). Modification of G protein-coupled functions by low pH pretreatment of membranes from NG108-15 cells: increase in opioid agonist efficacy by decreased inactivation of G proteins. Mol. Pharmacol., 44, 731–741. Sharp, B. M. (2003). Opioid receptor expression and intracellular signaling by cells involved in host defence and immunity. Adv. Exp. Med. Biol., 521, 8–105. Simonin, F., and Kieffer, B. L. (2002). Two faces for an opioid peptide—and more receptors for pain research. Nat. Neurosci., 5, 185–186. Smith, E. M. (2003). Opioid peptides in immune cells. Adv. Exp. Med. Biol., 521, 51–68. Stein, C., Gramsch, C., and Herz, A. (1990a). Intrinsic mechanisms of antinociception in inflammation. Local opioid receptors and beta-endorphin. J. Neurosci. 10, 1292–1298. Stein, C., Hassan, A. H. S., Lehrberger, K., Giefing, J., and Yassouridis, A. (1993). Local analgesic effect of endogenous opioid peptides. Lancet, 342, 321–324. Stein, C., Hassan, A. H. S., Przewlocki, R., Gramsch, C., Peter, K., and Herz, A. (1990b). Opioids from immunocytes interact with receptors on sensory nerves to inhibit nociception in inflammation. Proc. Natl. Acad. Sci. USA, 87, 5935–5939. Stein, C., Machelska, H., and Schäfer, M. (2001). Peripheral analgesic and antiinflammatory effects of opioids. Z. Rheumatol., 60, 416–424. Stein, C., Pflüger, M., Yassouridis, A., Hoelzl, J., Lehrberger, K., Welte, C., and Hassan, A. H. S. (1996). No tolerance to peripheral morphine analgesia in presence of opioid expression in inflamed synovia. J. Clin. Invest., 98, 793–799. Stein, C., Schäfer, M., and Machelska, H. (2003). Attacking pain at its source: new perspectives on opioids. Nat. Med., 9, 1003–1008.
6. Immune-derived Opioids: Production and Function in Inflammatory Pain Terman, G. W., Shavit, Y., Lewis, J. W., Cannon, J. T., and Liebeskind, J. C. (1984). Intrinsic mechanisms of pain inhibition: activation by stress. Science, 14, 1270–1277. von Andrian, U. H., and Mackay, C. R. (2000). T-cell function and migration. Two sides of the same coin. N. Engl. J. Med., 343, 1020–1034. Willer, J. C., Dehen, H., and Cambier, J. (1981). Stress-induced analgesia in humans: endogenous opioids and naloxone-reversible depression of pain reflexes. Science, 212, 689–691. Woolf, C. J., Allchorne, A., Safieh-Garabedian, B., and Poole, S. (1997). Cytokines, nerve growth factor and inflammatory hyperalgesia: the contribution of tumour necrosis factor alpha. Br. J. Pharmacol., 121, 417–424.
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Woolf, C. J., and Salter, M. W. (2000). Neuronal plasticity: increasing the gain in pain. Science, 288, 1765–1769. Xu, Y., Gu, Y., Xu, G. Y., Wu, P., Li, G. W., and Huang, L. Y. (2003). Adeno-associated viral transfer of opioid receptor gene to primary sensory neurons: a strategy to increase opioid antinociception. Proc. Natl. Acad. Sci. USA, 100, 6204–6209. Zöllner, C., Shaqura, M. A., Bopaiah, C. P., Mousa, S. A., Stein, C., and Schäfer, M. (2003). Painful inflammation-induced increase in mu-opioid receptor binding and G-protein coupling in primary afferent neurons. Mol. Pharmacol., 64, 202–210.
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C H A P T E R
7 Crosstalk between Insulin-like Growth Factors and Pro-inflammatory Cytokines ROBERT H. McCUSKER, KLEMEN STRLE, SUZANNE R. BROUSSARD, ROBERT DANTZER, ROSE–MARIE BLUTHÉ, AND KEITH W. KELLEY
I. INTRODUCTION 171 II. THE INSULIN-LIKE GROWTH FACTOR (IGF) SYSTEM 172 III. IGF TYPE I RECEPTOR SIGNALING 175 IV. PRO-INFLAMMATORY CYTOKINE SIGNALING 177 V. CYTOKINE-INDUCED IGF RESISTANCE; IN VITRO—MECHANISMS OF ACTION 179 VI. CYTOKINE—IGF INTERACTIONS; IN VIVO— BEHAVIOR AND LEARNING 184 VII. CONCLUSIONS 187
ultimately relate to health and well-being. The chapter is broken into two general sections. The first describes how IGFs and pro-inflammatory cytokines interact at the cellular level, with an emphasis on proinflammatory cytokine-induced hormone resistance. The second section relates these cytokine and hormone interactions to the field of psychoneuroimmunology by presenting evidence of their interactive effects on behavior and cognition. The endocrine and immune systems are biosensors that constantly monitor the body and its environment to fine-tune cellular growth, metabolism, and behavior. These systems coordinate the body’s adaptive mechanisms. This adaptation is necessary for growth and survival, permitting the body to resist the stressors imposed by insults such as environment extremes, exposure to pathogens, or limited nutritional resources. Adaptation requires not only positive actions, but more often than realized, adaptation requires downregulatory, negative actions such as cytokine-induced resistance to the actions of hormones and growth factors. This cytokine-induced resistance is critical to curb the activity of growth factors and to maintain homeostasis. Homeostasis is a carefully controlled balance between responses to the deleterious effects of environmental and pathological stressors (both external and internal) and the drive for normal growth, development, and eventual maintenance of the status quo (Figure 1). The intricate balance maintained by homeostasis is partially coordinated by the secretion and action of hormones (Frystyk, 2004; Valverde et al.,
I. INTRODUCTION The path of least resistance is the path of the loser. H.G. Wells 1866–1946
The immune and endocrine systems interact to control growth, development, health, and mental wellbeing. An important aspect of this interaction is the regulation of immune events by the endocrine system, as we highlighted for growth hormone, insulin-like growth factor-I (IGF-I) and prolactin (Arkins et al., 2001). The two major pro-inflammatory cytokines, TNFα and IL-1β, have now been shown to interact with the IGFs to regulate each others’ actions, such as occurs when cytokines induce hormone resistance (Kelley, 2004). The purpose of this chapter is to highlight this exciting and relatively new area of research by describing the mechanisms underlying how the immune system affects various cellular functions that PSYCHONEUROIMMUNOLOGY, 4E VOLUME I
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Copyright © 2007 by Elsevier, Inc. All rights of reproduction in any form reserved.
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2005) and cytokines (Hehlgans and Pfeffer, 2005; Valverde et al., 2005). For instance, infectious agents are perceived by the immune system, which in turn can initiate stress signals in the form of pro-inflammatory cytokines that act not only on leukocytes but also on other tissues, including the brain. The reliance on hormone and cytokine release for homeostasis is necessary to coordinate the multitude of processes that simultaneously occur in complex organisms. Such a reliance on biosensor systems is uniquely different from growth regulation of simpler organisms that respond to environmental stimuli with only a limited ability to communicate between cells. For decades, the endocrine and immune systems were largely studied independently of one another. However, it is now clear that the two systems interact at several levels to create an intricate network that controls everything from animal behavior to body growth and cancer progression. Pro-inflammatory cytokines act in the brain to cause sickness behavior (Kelley et al., 2003) and contribute to depressive-like symptoms (Schiepers et al., 2005). They act on skeletal muscle to cause wasting (Spate and Schulze, 2004) and on cancer cells to suppress proliferation or induce cell death (Mocellin et al., 2005; Wajant et al., 2005). Although there are differences in the ultimate consequence on cells, all of these effects share one common mechanism: pro-inflammatory cytokine-induced IGF resistance. Hormone resistance may be more common
than first believed as it is now becoming clear that pro-inflammatory cytokines can induce resistance to several important hormones besides IGF, including insulin (Hotamisligil, 2003), glucocorticoids (Avitsur et al., 2005; Silverman et al., 2005), and growth hormone (Lang et al., 2005). Why is there a need for the immune system to induce hormone resistance? The answer is by no means simple. One rudimental possibility is that hormone resistance is needed because the human body has limited resources. A system of checks and balances has evolved to control the use of these resources between tissues, within tissues, and indeed within different compartments of individual cells. Only in developed countries of the current era have humans found themselves in a “protected” environment, with almost unlimited essentials for life, i.e., food, shelter, and medicine. However, throughout most of history, humans have had limited resources. The body adapted to these limited resources by making careful decisions about how to use those resources, with the major choices being aimed at three main processes: (a) growth and nutrient storage, (b) reproduction, and (c) survival processes, such as combating disease. In response to many types of stressors, one of the global consequences of pro-inflammatory cytokines is to depress growth and nutrient storage, making more resources available for more fundamental survival processes. This goal is partially achieved by blocking the anabolic effects of IGF via hormone resistance. With this in mind, this chapter focuses on interactions between two major pro-inflammatory cytokines, TNFα and IL-1β, and an important growth factor, IGF. The main theme is aimed at describing how these pro-inflammatory cytokines indirectly alter normal cellular processes by interfering with the actions of IGF.
II. THE INSULIN-LIKE GROWTH FACTOR (IGF) SYSTEM
FIGURE 1 Adaptation via the interaction of two biosensor systems. The immune and IGF systems act synergistically on some functions yet are in opposition on others. One of the keys to regulating their actions is a clear understanding of how the two systems interact. It is now apparent that intracellular receptor signaling pathways of pro-inflammatory cytokines and IGFs communicate with each other to regulate cellular function.
The IGFs are unique among growth factors. Virtually all cells of the body are responsive to IGF-I and IGF-II, either acting through their own receptor or the insulin receptor. This fact underlies the global importance of these peptides in controlling cellular function. Indeed, IGF-I and IGF-II are key endocrine proteins driving cellular growth, development, and survival (McCusker, 1998). In particular, IGF-I is critical for normal postnatal growth and development. Together with its primary regulator, GH, IGF-I accounts for 83% of postnatal body growth (Lupu et al., 2001). IGF-I and IGF-II drive the growth of essentially every tissue
7. Crosstalk between Insulin-like Growth Factors and Pro-inflammatory Cytokines
within the body, including proper brain size and development (D’Ercole et al., 2002). Although GH regulates serum IGF-I and thereby body growth, it appears that the brain is privileged in this respect. GH deficiency does not reduce brain IGF-I, brain size, or cognitive function, thus creating a protective mechanism for the brain against GH deficiency. Indeed, growth hormone-deficient mice have higher concentrations of IGF-I in the brain than do non-deficient mice (Sun et al., 2005). IGF-I is also necessary for muscle growth and development. Early work clearly established that elevated GH enhances serum IGF-I concentrations, mRNA expression within muscle and overall muscle growth (Frost and Lang, 2003). Similarly, an enhanced GH/IGF axis increases the number of muscle precursor cells (McCusker and Campion, 1986). Until recently, it was believed that, over a large physiological range, the IGFs did not have major adverse consequences. However, from research that began with Caenorhabditis elegans and recently extended to mammals, it has become increasingly clear that postnatal circulating IGF-I is inversely related to life span (Kenyon, 2005) and elevated embryonic IGF-II leads to fetal overgrowth and early postnatal death (Lau et al., 1994). Also, since the IGFs increase proliferation of many cells, serum IGF is positively correlated to progression of several different types of tumors (Foulstone et al., 2005; Hofmann and Garcia-Echeverria, 2005; Khandwala et al., 2000; LeRoith and Helman, 2004). In terms of life span, the divergent outcomes of IGF signaling appear to converge mechanistically at the level of FOXO, a member of the forkhead family of transcription factors that inhibits cell proliferation and is associated with increased resistance to cellular stressors and prolonged life span. Inactivation of forkhead proteins by IGF promotes cell survival. Conversely, IGF activation of PI3-K and subsequently the downstream kinase, Akt, leads to phosphorylation of FOXO, which sequesters it to the cytoplasm and inhibits its transcriptional activity. Despite IGF inactivation of FOXO for cell survival, IGF inactivation of this factor appears to be associated with decreased life span (Kenyon, 2005). This disparate relationship underlies our lack of a comprehensive view of IGF physiology. However, it emphasizes a real and pressing goal of independently controlling the various intracellular signaling pathways of IGF in a specific fashion. The paradox that IGFs, which are necessary for growth and development, are inversely correlated with life span of the whole organism is intriguing and suggests that mechanisms should be present to precisely control IGF activity. Indeed, IGF activity is intri-
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cately regulated by several mechanisms, including binding to three distinct receptors (IGF type 1 receptor, or IGF-1R; the insulin receptor, or InsR; and the IGF type 2 receptor, IGF-2R, which is an inhibitory decoy) and several high-affinity binding proteins (IGFBPs, which control IGF access to cell surface IGF receptors). Pro-inflammatory cytokines from the immune system have now been defined as an IGF-regulating mechanism. An activated immune system, via pro-inflammatory cytokine production, causes IGF resistance by decreasing some aspects of intracellular receptor signaling, as will be described below. These findings indicate that the outcomes of IGF receptor signaling are defined by a complex network of interactions, and also point to the conclusion that there are major gaps in understanding just how IGF and each of its divergent signaling pathways are regulated. To completely grasp the intricate and complex regulation that has evolved to control IGF activity, we need to define the various members of the system (Table 1). IGF-I and IGF-II are both small peptides, 67 to 70 amino acids, respectively, that are present in varying levels in all body fluids. Encoded by separate genes, the two peptides share complete physiological redundancy. The IGFs act through the same receptors and have identical effects on cells, differing only in relative sensitivities. IGF-I binds to the IGF-1R with approximately twice the avidity of IGF-II (McCusker, 1998) and thus has similar activity at half the dose. Insulin binds the IGF-IR with a 200-fold lower affinity. Care must be taken when interpreting in vitro studies using high levels of any of these three ligands (IGF-I, IGF-II, or insulin). Due to receptor cross-reactivity, cellular changes resulting from IGF-1R, IGF-2R, and InsR cross-reactivity may not occur in vivo with physiological levels of ligand. This is especially important for insulin, which is frequently added at > 1 μg/ml to cell culture supplements. For instance, the popular B27 medium supplement used for neuronal serum-free cultures (Gibco) contains 4 μg/ml insulin, which likely activates both the InsR and the IGF-1R. Although most of the work, both in vivo and in vitro, has been done with IGF-I, cytokine-induced IGF resistance would occur for all three ligands—IGF-I, IGF-II, and insulin. Four major mechanisms exist to regulate IGF activity. First and foremost is the distribution of receptors; the presence or absence of receptors determines the ability of a cell to respond. A clear example is presented during development of skeletal muscle. Myoblasts, which are skeletal muscle precursor cells (Wagers and Conboy, 2005), express abundant IGF1Rs but fewer InsRs (McCusker and Novakofski, 2003,
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I. Neural and Endocrine Effects on Immunity TABLE I Size (kDa)
Ligands IGF-I & IGF-II Insulin Receptors IGF-1R
7.6 5.8 303.7
InsR (a/b isoforms)
306.7
IGF-specific regulators IGFBPs (1–6) IGF-2R
∼30.0 540.0
Members of the IGF System Primary role
Metabolism, proliferation, survival, differentiation Nutrient metabolism for storage Ligand activated tyrosine kinase Binds IGF-I > IGF-II >> Insulin at 1 : 2 : 200 ∼relative affinities Ligand-activated tyrosine kinase Binds Insulin ≥ IGF-II > IGF-I at 1 : 2 : 30 ∼relative affinities IGF inhibition/potentiation IGF inhibition
Location: source
All body fluids: all tissues Circulation / pancreas
Transmembrane: one or both receptors are present on most if not all cells of the body
Body fluids, cell surfaces: all tissues
IGF-1R and IGF-2R = IGF type 1 and 2 receptors. IGFBP = IGF binding protein. InsR = insulin receptor. Sizes based on amino acid composition (receptors = size of multimer) but vary with glycosylation. (Entingh et al., 2003; McCusker, 1998).
2004). In contrast, once differentiated, mature myofibers contain abundant InsRs but fewer IGF-1Rs (Brunetti et al., 1989). There is a general correlation of greater IGF-1R expression in rapidly growing cells (and thus transformed cells) and a greater relative InsR expression in post-mitotic cells (e.g., myofibers, hepatocytes, and adipocytes). This general trend in relative receptor expression led to the characterization of IGFs as growth factors, since they act on most mitoticcompetent cells at relatively low concentrations. In contrast, insulin was characterized as a metabolic hormone, since it is active at low concentrations in stimulating nutrient storage (e.g., sugars as glycogen, lipids as fat, and amino acids as protein). Relative receptor expression (IGF-1R/InsR) on a particular cell type is largely predetermined, and relatively little is known about the regulatory mechanisms determining which receptor is expressed on a particular cell. Other than knockout or forced expression of the IGFIR or InsR to study the in vitro and in vivo actions of each respective ligand (Baserga, 2005; Kitamura et al., 2003), there has been little effort devoted toward regulating relative receptor expression as a means of controlling cellular responsiveness among the three ligands. Second is the rate of IGF secretion. Clearly, postnatal secretion of IGF-I is more dynamically controlled than is the secretion of IGF-II. IGF-I secretion is affected by multiple hormones, including growth hormone, insulin, thyroid hormones, and glucocorticoids (McCusker, 1998). Similarly, insulin secretion has been extensively studied. From a physiological standpoint, this is a relatively mature subject. Thousands of research papers and numerous reviews have summarized the regulation of IGF secretion in mammals.
There remains great potential for the therapeutic use of IGF for human maladies, including treatments for wound healing (Grazul-Bilska et al., 2003), pediatric (Rosenfeld, 2005) and adult growth hormone deficiency (Savage et al., 2004), diabetes (Ranke, 2005), neurological disorders (Leinninger and Feldman, 2005), and immunoenhancement (Burgess et al., 1999; Welniak et al., 2002). A recent report established that rats partially deficient in GH for their entire life do not display increased longevity (Sonntag et al., 2005). However, treatment of GH-deficient rats with GH prior to adulthood increases longevity and improves cognitive function later during senescence. In humans, there is positive correlation between IGF levels and progression of cancer (Foulstone et al., 2005; Hofmann and Garcia-Echeverria, 2005) and diminution of life span (Kenyon, 2005). These findings have led to a huge controversy about the role of GH and IGF in human medicine (Consensus, 2001). For example, adults with low IGF-I have reduced risk for a variety of cancers. However, subjects with low IGF-I concentrations also have an increased risk for diabetes and osteoporosis, as well as both heart and neurodegenerative diseases (Yang et al., 2005). Importantly, there is as yet no evidence that reduced IGF-I blood concentration in humans is associated with longer life (Janssen and Lamberts, 2004). The current view is that not enough IGF or too much IGF is detrimental to health, but there is a certain amount of IGF that is required and necessary for optimal health. This conclusion is similar to the classic U-shaped curve in exercise physiology, which reflects the concept that too little or too much exercise can impair health, with moderate exercise being recommended for most of us.
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Third are the IGFBPs. Six high affinity IGFBPs and an additional IGF receptor control IGF activity (see Table 1). The IGF-2R, residing on the cell surface, has no known signaling ability. Instead, it serves to aide internalization and target IGF-II for degradation. By this mechanism, the IGF-2R directly decreases the amount of active IGF-II and thus decreases IGF activity. The IGF-2R is also found in the circulation (McCusker et al., 1989), where it acts as an additional soluble IGFBP with unproven although presumed IGF-delaying activity similar to that of the smaller IGFBPs. In extracellular fluids, the six IGFBPs delay IGF activity, as demonstrated both in vivo and in vitro. By association with the IGFs, the IGFBPs prevent immediate IGF access to the IGF-1R (Arkins et al., 1995; Li et al., 1996; Liu et al., 1998; McCusker et al., 1990; McCusker et al., 1991). The IGFBPs and IGF-2R increase the half-life of circulating IGF and delay IGF activity until the IGF is released, wherein it can then associate with the IGF-1R. Fourth, and most critical to this review, is the regulation of IGF-induced intracellular signaling. The three mechanisms, briefly described above, control overall IGF activity with no specificity regarding the various effector functions of IGF such as cell survival, differentiation, proliferation, or metabolism. However, considering the requirement of IGF activity for these various cellular activities, the ability to specifically and independently control these various actions has the greatest potential to result in therapeutic application. Since all IGF-mediated actions are via the single cell surface receptor, IGF-1R, functional divergence depends on branching of intracellular signaling pathways that are initiated following binding of either IGFI or IGF-II to the IGF-IR.
III. IGF TYPE I RECEPTOR SIGNALING The heterotetrameric IGF-1R is a ligand-activated transmembrane tyrosine kinase composed of two α (105kDa each) and two ß (95kDa each) subunits. Ligand binding to the α-subunits induces conformational changes in the ß subunits and trans-autophosphorylation of critical tyrosine residues in the ß subunit kinase domain/C-terminus of the receptor. These residues allow for docking of IRS and Shc proteins, which are then tyrosine phosphorylated by the IGF-1R. Phosphorylated docking proteins recruit additional signal transducing factors, including the p85 regulatory subunit of PI3-K and Grb2/SOS (Dupont and LeRoith, 2001; Leroith and Nissley, 2005) activating two major signaling cascades, the PI3-K and the MAPK pathways, respectively. Various signaling components
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of these pathways regulate cell metabolism, hypertrophy, proliferation, survival, and differentiation (Figure 2). MAPK Pathway: IGF-1R activation and the subsequent tyrosine phosphorylation of Shc and IRS-1 allow Grb2 to bind to these adaptor proteins via its SH2 domain. Grb2 then recruits SOS, a guanine nucleotide release protein that catalyzes the conversion of inactive Ras-GDP into its active form, Ras-GTP. Ras-GTP promotes membrane localization and activation of Raf-1, which subsequently activates downstream ERK-1/2; components of an MAPK pathway. ERKs, rather than c-jun N-terminal kinase (JNK) or p38 stress-activated protein kinase (SAPK), are the major IGF-activated MAPKs that confer cell-cycle progression/proliferation of a diverse variety of cell types, including myoblasts and many cancer cells. PI3-K Pathway: Unlike the MAPK pathway, the PI3-K pathway does not require guanine nucleotide exchange and is activated by direct binding of IRS-1/2 to the phosphorylated IGF-1R. IGF-1R–induced tyrosine phosphorylation of IRS (pIRS) recruits the p85 regulatory subunit of PI3-K via two SH2 domains. Binding of p85 to pIRS activates PI3-K’s catalytic domain, p110. Activated PI3-K converts membrane 3,4-inositol-diphosphate to 3,4,5-inositol-triphosphate; which activates two distinct PDKs, followed by Akt. Akt is a major divergence point that ultimately regulates IGF-induced cell hypertrophy, proliferation, survival, and differentiation. Distinct Akt-dependent pathways are critical to specific IGF functional outcomes (Figure 2). Although neither the MAPK nor the PI3-K pathways shown in Figure 2 are completely defined, several important points about the pathways are obvious. (1) The two pathways are connected. This is specifically illustrated by showing that both pathways link the IGF-1R to cyclin-dependent kinase (CDK) activation. (2) Both pathways are branched; this is particularly true for the PI3-K pathway, which arborizes extensively after the activation of Akt. (3) Each branch has overlapping functions, but each is involved in specific effects of IGF. The overlapping properties are not necessarily obvious, but each of the branches after Akt has been found to have different functions in different systems. For instance, a cell must survive to differentiate. Hence, to a large degree, the pathways that one laboratory indicates to be involved in cell survival may be found by another laboratory as necessary for differentiation, since dead cells cannot differentiate. Similarly, transcription is necessary for proliferation. To put this another way and iterate this point, induction of a particular pathway does not promote only one particular function, but in many cases just one particu-
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FIGURE 2 A simplified IGF-1R signaling map. Upon IGF binding to the IGF-1R, or insulin to the InsR, a series of intracellular signaling events occurs that result in enhanced cell metabolism, hypertrophy, proliferation, differentiation, or survival. Two major pathways are activated by the IGF-1R: the MAPK pathway (left) and PI3-K pathway (right). The PI3-K pathway diverges after activation of Akt. Interference with any of the steps prior to Akt activation will affect all or part of IGF’s downstream actions. A more detailed signaling pathway and several excellent reviews can be found at STKE Connections Map (White, 2003). IRS—insulin receptor substrates, PI3-K— phosphoinositide 3-kinase, PDK—3-phosphoinositide-dependent protein kinase, Akt—(PKB, protein kinase B), TSC—tuberous sclerosis complex/tuberin, MDM—murine double minute, mTOR—mammalian target of rapamycin, GSK—glycogen synthase kinase; SOS—son of sevenless.
lar pathway may be limiting for that function to occur. (4) It is currently unclear whether a single receptor molecule activates both the MAPK and PI3-K pathways simultaneously; the possibility that specific IGF1R heterodimers promote only the MAPK or the PI3-K pathway is the reason for distinct receptor proteins linked to each pathway in Figure 2. The effect initiated
by IGF signaling may depend on the type of protein scaffolding that occurs at the intracellular face of individual receptors. For example, IGF-I activates the mitogenic ERK1/2 pathway very well in many cell types but poorly in primary hippocampal neurons despite all the hardware for IGF-1R signaling being present (Zheng and Quirion, 2004). (5) Finally, there
7. Crosstalk between Insulin-like Growth Factors and Pro-inflammatory Cytokines
are inhibitors of specific components in the pathway. For example, the tumor suppressors PTEN (phosphatase and tension homolog deleted on chromosome 10) and tuberous sclerosis (TSC) lie upstream and downstream of Akt, both of which act to constrain the activity of Akt (Hay, 2005). Undoubtedly, more activators and inhibitors in the IGF signaling pathway will be discovered, thereby offering new targets for pharmacological interventions. It is important to note that all of the in vitro physiological effects of IGF can be considered positive, i.e., increased cell survival, increased cell proliferation, increased cell differentiation, increased transcription, increased metabolic activity, and increased cell hypertrophy. Although most approaches to modify intracellular IGF actions have focused on early upstream events induced by IGF-1R activation, such as IRS recruitment or PI3-K activation, controlling specific steps along either the MAPK or the PI3-K pathways could yield novel approaches to control a specific effect of IGF. For example, it should be possible to develop a way to depress IGF-induced proliferation of cancer cells without diminishing IGF’s protective actions within the brain or on skeletal muscle.
IV. PRO-INFLAMMATORY CYTOKINE SIGNALING The key aspect of pro-inflammatory cytokine action, relative to this chapter, is duality of action. Unlike the effects of the IGFs that can all be considered positive at the cellular level (i.e., increased in proliferation, differentiation, survival, or hypertrophy), pro-inflammatory cytokines affect cells in both positive and negative ways. Another important point is that various cytokines share many physiological functions and common intermediate receptor signaling molecules (Hanada and Yoshimura, 2002; Liu, 2005), although there are specific and important differences in signaling intermediates between each of the cytokines. With this in mind, TNFα acting through TNF-R1 is used as a prototypical pro-inflammatory cytokine model in this chapter. The multiple redundancies in receptor signaling between cytokine receptors, despite differences in the physiological outcomes of cytokines, is not unlike the remarkable similarity in signaling pathways shared by the IGF-1R and InsR, despite important differences in the perceived major physiological roles of insulin and the IGFs (nutrient storage vs. cell proliferation). These enigmas are most certainly due to lack of clear and complete definition of receptor distribution between cell types within tissues, as mentioned earlier for the IGF-1R and InsR, and additional unknown sig-
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naling differences that occur between and within the context of mammalian cells. TNF-R1 is a homotrimer without intrinsic enzymatic ability, i.e., absence of kinase activity. Ligand binding changes the conformation TNF-R1, leading to exchange of proteins that bind the intracellular face of the trimer. Receptor signaling is usually suppressed by the Silencer of Death Domain (SODD), which prevents association of early upstream signaling intermediates with the TNF-R1. Upon TNFα binding, SODD dissociates from the receptor allowing other proteins to bind to the receptor complex. Since the receptor lacks enzymatic activity, exactly how signaling is initiated upon ligand binding is currently unclear. TNF-R1 has two major domains for signal initiation: the death domain (DD) and the neutral sphingomyelinase domain (NSD). DD was so named because early work indicated that proteins bound to TNF-R1 by this region, such as TRADD and FADD, could initiate apoptosis via caspase activation (Figure 3). Similarly, factor-associated with neutral sphingomyelinase (FAN) binding to the NSD results in neutral sphingomyelinase (N-SMase) activation and ceramide generation. This pathway also can cause apoptosis of certain cells. Albeit TNFα was first characterized by its ability to cause tumor cell death, TNF-R1 signaling can also promote cell survival via NFκß-dependent transcription of anti-apoptotic factors (Sheikh and Huang, 2003). Although the last decade has witnessed remarkable advances in the field, it still remains unclear how cells choose between life and death following TNFα stimulation (Mocellin et al., 2005). TNFα, via the DD and several MAPK pathways, can activate ERK1/2 and p38MAPK, which enhance cell proliferation (Baud and Karin, 2001). However, TNFR1 activation has a notable cytostatic effect (Shen et al., 2002), albeit by largely uncharacterized mechanisms. Activation of TNF-R1 also suppresses differentiation of several cell types, particularly skeletal muscle cells. However, there is no direct signaling pathway associated with either cytostasis or inhibition of differentiation (Figure 3). Although the intricate details associated with IGF-1R signaling relative to a particular function are still being defined, there is consensus that a positive response will occur. However, TNFα action is difficult to predict based upon the seemingly opposing possible effects mediated by TNF-R1; numerous reviews have come to the same conclusion regarding the ambivalent prediction of TNFα activity. The manuscripts cited in the reviews contain excellent experiments attempting to elucidate the specific mechanism associated with a particular effect of TNFα. Most experiments, however, are not designed to consider the possibility that many
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FIGURE 3 A simplified TNFα signaling diagram. Proinflammatory cytokine signaling is a highly arborized process, and the net effect depends on the relative strength of each pathway [adapted from (Mocellin et al., 2005)]. TRADD—TNF-R associated death domain; FADD—Fas-associated death domain; PPA2—protein phosphatase 2A; SMase—sphingomyelinase; MADD—MAPK-activating death domain; RIP—receptorinteracting protein; TRAF—TNFR-associated protein; TNF-R1—TNF receptor type 1/ p55; MAPK—mitogen-activated protein kinase; JNK—c-Jun N-terminal kinase; SODD— silencer of death domain; NSD—N-SMase activation domain.
of the effects induced by TNFα are not direct. To clearly understand TNFα action requires the consideration of its interaction with growth factors and hormones, in particular the IGFs. Most in vitro experiments are conducted using cells grown in the presence of fetal bovine serum (FBS) or one of several medium supplements such as ITS, N2, or B27. FBS contains substantial amounts of both IGF-I and IGF-II, and the three aforementioned supplements contain insulin at
levels that activate the IGF-1R. As discussed below, many of the biological actions associated with TNFα may not be direct but instead may be the result of TNFα causing resistance to IGFs (and/or insulin). Similarly, since all in vivo fluids contain IGF, many of the results that have been reported with animal studies may well be the result of growth factor resistance in addition to direct effects of the pro-inflammatory cytokine.
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FIGURE 4 Signaling pathways for one cytokine and one growth factor. Proinflammatory cytokine and IGF signaling have both distinct and similar effects on cells. Similar pathways may be a means to amplify an action, whereas distinct pathways may either complement each other or be antagonistic.
V. CYTOKINE-INDUCED IGF RESISTANCE; IN VITRO—MECHANISMS OF ACTION In live animals, cells are not under the influence of a single growth factor or cytokine. This is also true in vitro, as many cells secrete several factors in culture, including pro-inflammatory cytokines and either IGF-I or IGF-II. As already mentioned above, few cells in vitro are grown in serum-free conditions, and even then they are generally supplemented with a hormone mixture which usually contains a member of the IGF ligand family. It has been difficult to unravel the particular pathways activated by a single factor due to pathway arborization (see Figures 2 and 3), and few investigators have attempted modeling the interaction of multiple factors within a cell. Diagrams rapidly become complex when simplified pathways for even a single cytokine and growth factor are considered jointly (Figure 4). The intracellular signaling pathways of receptors for pro-inflammatory cytokines and IGF coexist in many cells. Therefore, the undefined negative effects of TNFα (cytostasis, decreased differentiation, altered metabolism, and apoptosis) could be explained by attributing these actions not to a direct effect of the
cytokine but to cytokine-induced IGF resistance. As shown in Figure 4, at least two pro-inflammatory cytokine signaling pathways, FAN-ceramide and MAPKJNK, can depress the IGF-induced PI3-K pathway by interfering with IRS tyrosine phosphorylation or Akt activity. In contrast to the IRS/PI3-K/Akt pathway, it is important to note that TNFα-ERK1/2 and IGFERK1/2 are parallel pathways and thus are unlikely to have negative interactions. Evidence supporting proinflammatory cytokine-induced IGF resistance is presented below, using several distinct in vitro models.
A. Cell Proliferation: A Case for Cancer Therapy Cancer cells provide an excellent model to unravel the role of growth factors and pro-inflammatory cytokines during cell proliferation. Due to their transformation, many cancerous cells are immortal. Most of these cells grow rapidly, thus providing a robust proliferative signal and do not generally differentiate unless they are experimentally induced to do so. Many of these cells are responsive to both growth factors and pro-inflammatory cytokines despite their transformation. In fact, inhibition of IGF-1R activity and
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B. Proliferation; cytokine depressed IGF-induction of cell proliferation, [3H]-thymidine into DNA C Pro yt -i ok nf in lam e Si ma gn to al ry lin g
A.
C. Early signaling; cytokine depressed IGF activation of Akt
D. Cell cycle; cytokine suppressed IGF activation of Cdk2
FIGURE 5 Cytokines depress the proliferation of breast cancer cells by blocking the ability of IGF to enhance CDK activity. The effects of cytokines, IL-1β in this case, entails blockage of early IGF-1R events such as Akt phosphorylation, which blocks IGF-I–induced Cdk-2 enzymatic activity. (Shen et al., 2004a; Shen et al., 2002). Reprinted with permission.
administration of cytokines are two approaches that have been validated in animal models and have entered clinical trials to control some forms of cancer (Dranoff, 2004; Khandwala et al., 2000). IGF-1R activation drives cell cycle progression of several types of cancer cells. Recent studies indicate that components of cytokine receptor signaling pathways interact with an IGF-1R signaling pathway to reduce IGF activity and thereby reduce cell proliferation. 1. IGFs and Cancer The IGF system, particularly the IGF-1R, is closely associated with progression and metastasis of numerous human cancers, including those of the breast, prostate, lung, colon, and bladder (LeRoith and Helman, 2004). Many components of the IGF-activated PI3-K
pathway are constitutively active in cancer cells (Figure 5A). For example, the catalytic p110 domain is persistently activated in many transformed cells (Martin, 2003). Similar observations have been noted with Akt, although this may be due to PI3-K activation. These in vitro studies were confirmed with animal models showing that increased IGF-I promotes tumor number and growth (Baserga et al., 2003; LeRoith and Helman, 2004; Wu et al., 2003). The same appears true in humans. Patients with circulating IGF-I in the upper 25% of a normal range have an increased incidence of breast, bladder, colon, lung, and prostate cancer (LeRoith and Helman, 2004). Conversely, reduced IGF-I levels correlate with increased tumor latency and decreased growth and metastasis (Baserga et al., 2003; LeRoith and Helman, 2004). It should be noted that IGF activity does not cause transformation but instead enhances
7. Crosstalk between Insulin-like Growth Factors and Pro-inflammatory Cytokines
the rate of transformation and/or the growth of transformed cells such that tumors appear earlier. 2. Cytokine-induced IGF Resistance during Cell Proliferation Numerous in vitro studies have confirmed that proinflammatory cytokines inhibit the growth of several types of cancer cells, including melanoma (LazarMolnar et al., 2000), leukemia (Mudipalli et al., 2001), rhabdomyosarcoma (Storz et al., 2000), breast (Rozen et al., 1998), salivary gland (Katz et al., 1999), sarcoma (Shalita-Chesner et al., 2001), and ovarian adenocarcinoma (Simonitsch and Krupitza, 1998). Unfortunately, parenteral administration of pro-inflammatory cytokines leads to development of the systemic inflammatory response syndrome (SIRS), which is often lethal. However, clinical trials attest to the fact that administration of cytokines directly into localized areas has substantial therapeutic benefit (Dranoff, 2004). What is intriguing is that inhibition of IGF activity induces much the same effects as the site-directed administration of cytokines. Until recently, no link has been drawn between these two approaches to treat cancer. One of the contributing factors is that the effect of cytokine treatment was believed to be direct, but most of the studies were done in the presence of serendipitous IGF. For example, most in vitro experiments with primary or transformed cancer cells use culture conditions that maintain cells in medium supplemented with FBS. Consequently, the inhibitory actions of cytokines observed in cancer models could be due to their blocking the IGF activity in the FBS (Figure 5A). Also, since many cancer cells synthesize IGF, the cytotoxic actions of cytokines could blunt the proliferative actions of endogenous IGF. In fact, several studies have reported that in cells grown in medium without serum, the cytostatic actions of pro-inflammatory cytokines were prominent only when the cells were treated with a growth factor (Shen et al., 2002; Shen et al., 2004a; Shen et al., 2004b). Indeed, TNFα, IL-1β, or IL-6 had no effect on cell proliferation when added to cells grown in serum-free conditions (Shen et al., 2002). However, cytokines inhibited proliferation of IGF-I treated cells (Figure 5B). This was one of the first indications that cytokines may suppress cancer cell growth by inhibiting IGF action. As discussed above, IGF binding results in IGF-1R autophosphorylation, recruitment of IRS docking proteins, and activation of downstream molecules. Cytokines alone do not affect MCF-7 cell proliferation, but they do depress the mitogenic effect of IGF (Figure 5B). Cytokines do not change the autophosphorylation state of the IGF-1R, but TNFα and IL-1β both inhibit IGF-induced activation of IRS-1 (Shen et al., 2002). The
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actions of cytokines on upstream IGF-1R signaling are reflected in decreased activation of downstream effector kinases. Thus, cytokines act by blocking IGF-1R induction of the PI3-K pathway including Akt activation (Figure 5C). After the major Akt branching point, cytokine action is reflected as a block in IGF-induced activation of the cell cycle machinery, Cdk2 activity, as assessed by reducing phosphorylation of its substrate, the retinoblastoma (Rb) tumor suppressor (Figure 5D). This occurs by IL-1β depression of PI3-K activity and subsequent lack of stimulus for the formation of Cdk2/ cyclin A complexes (Shen et al., 2002; Shen et al., 2004a). Consequently, one way that the pro-inflammatory cytokines act on breast cancer cells is by inhibiting cytoplasmic signaling components in the IGF cascade, which leads to cytostasis. This cytostatic effect is possible because the PI3-K pathway is limiting for the proliferation of MCF-7 breast cancer cells. However, this limitation is not true for all types of cells. For example, skeletal muscle myoblast proliferation is dependent upon IGF-induced MAPK activity. Apparently, the IGF-dependent MAPK pathway is limiting for myoblast proliferation. In these cells, proinflammatory cytokines, which activate various MAPK pathways, do not induce myoblast cytostasis but actually increase cell cycle progression (Stewart et al., 2004).
B. Differentiation and Hypertrophy: Myogenesis and Cachexia Skeletal muscle development provides an excellent model for the investigation of cellular differentiation and hypertrophy, especially in regard to interactions between cytokines and IGF. There are several wellcharacterized cell lines that faithfully mimic how these processes occur in primary cells. Of particular interest are murine C2C12 cells, which differentiate by cell cycle withdrawal and the upregulation of myogenic regulatory proteins, such as the transcription factor myogenin (Miller, 1990) and myosin, a functional skeletal muscle protein. C2C12 and other myogenic cells are sensitive to both IGF and pro-inflammatory cytokines. Using these cells, the interaction between cytokines and growth factors during differentiation and hypertrophy can be studied in a well-characterized and controlled in vitro paradigm. 1. IGFs and Muscle The anabolic effects of IGF drive differentiation and hypertrophy of skeletal muscle (Rommel et al., 2001) and overexpression of IGF within muscle enhance muscle formation and hypertrophy (Coleman et al., 1995; Musaro and Rosenthal, 1999). Several years ago
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it was shown that the major stimulus for myogenesis was indeed the IGFs (Florini et al., 1991). Using a variety of human, mouse, rat, or avian primary cultures or cell lines, the control of myogenesis (commitment to differentiation followed by fusion of mononucleated myoblasts into myofibers) and muscle hypertrophy (primarily via the synthesis and subsequent accumulation of protein) has been defined. Supporting very early work, it has been repeatedly confirmed that IGF increases myoblast differentiation into myotubes, an effect that requires expression of myogenic regulatory proteins such as myogenin. Subsequently, IGF increases hypertrophy and maturation by increasing synthesis of muscle-specific proteins, including myosin (Florini et al., 1991; Miller, 1990). Both differentiation and hypertrophy (Figure 6A) require IGF activation of the PI3-K pathway (Coolican et al., 1997; Rommel et al., 2001; Tureckova et al., 2001). In contrast, myoblast proliferation requires IGFinduced MAPK activity (Coolican et al., 1997). 2. Cytokines and Muscle Similar to cancer cells, myoblasts and myofibers respond not only to growth factors such as IGF, but they are responsive to a wide variety of proinflammatory cytokines, including TNFα and IL-1β. Pro-inflammatory cytokines markedly diminish both differentiation and hypertrophy of myoblasts (Langen et al., 2001; Li et al., 1998; Stewart et al., 2004; Szalay et al., 1997). Myoblasts differentiate better in low serum compared to serum-free conditions due to poorly defined factors in horse serum that are necessary for myotube formation. Therefore, most of the studies with pro-inflammatory cytokines were performed by switching cells from 10% FBS to 1–2% horse serum to induce differentiation. Until recently, it was believed that the inhibitory effects of cytokines would be attributed to specific signaling pathways that directly inhibit differentiation or hypertrophy. However, as shown in Figure 3, there are as yet no defined signaling pathways induced by cytokines that directly block these events. It is known that TNFα directly stimulates myoblast proliferation via its ability to activate ERK1/2 pathways (Stewart et al., 2004). This later action and mechanism are analogous to that of IGF, but only recently has the mechanism by which cytokines block differentiation and hypertrophy been defined. 3. Cytokine-induced IGF Resistance during Differentiation and Hypertrophy Similar to IGF-induced proliferation of certain cells, skeletal muscle differentiation and hypertrophy
(protein synthesis) are IGF-driven events, requiring activation of the PI3-K pathway. Differentiation and hypertrophy require a common branch of the IGFinduced Akt pathway involving p70S6K activation (Figure 6A). With IGF-1R activation being necessary for myogenesis and the fact that pro-inflammatory cytokines can often act in a fashion opposing IGF, there was probable cause to assume an interconnection between the two. We found that under serum-free conditions and in the absence of added IGF, neither TNFα or IL-1β affect myoblast differentiation or hypertrophy (Broussard et al., 2003; Broussard et al., 2004; Strle et al., 2004). For example, basal myogenin expression is not affected by IL-1β in C2C12 myoblasts, but IGF-I significantly increases myogenin expression (Figure 6B). An interaction was detected by showing that physiological levels of IL-1β, which do not affect basal myogenin expression, dose-dependently diminish the ability of IGF-I to increase myogenin. Similarly, IGF-I increases protein synthesis of C2C12 cells (Figure 6C), whereas TNFα neither stimulates nor depresses protein synthesis when added alone. However, TNFα potently depresses IGF-induced protein synthesis. Thus, both differentiation and hypertrophy are depressed by proinflammatory cytokines, and both effects are a result of diminished IGF activity. The effect of cytokines occurs very early in the IGF signaling cascade, as both IL-1β (Broussard et al., 2004) and TNFα (Figure 6D) depress IRS-1 and IRS-2 tyrosine phosphorylation induced by IGF-I. The inhibition caused by cytokines on both differentiation and protein synthesis requires ceramide synthesis (Strle et al., 2004). A ceramide analog completely mimics the inhibition caused by both TNFα and IL-1β (Figure 6E), as does exogenous sphingomyelinase (which generates ceramide). Blocking ceramide synthesis in C2C12 cells abrogates the ability of both TNFα and IL-1β to inhibit IGF activity. Consequently, one way that the pro-inflammatory cytokines act on muscle is by inhibiting cytoplasmic signaling components in the IGF cascade, with a resultant decrease in hypertrophy and a decrease in the differentiation of precursor cells. As previously mentioned, however, this limitation is not true for myoblast proliferation (Stewart et al., 2004). Thus, cellular differentiation, not proliferation, is inhibited because IGF-induction of the PI3K pathway is limiting for only one of the two processes. This clearly illustrates that cytokines can be used to block only a portion of the IGF signaling cascade. As mentioned earlier, extracellular tools that depress IGF activity, such as the soluble IGFBPs, lack specificity. They block all IGF effects. Similarly, recent pharmaceuticals that block IGF-1R kinase activity such as
7. Crosstalk between Insulin-like Growth Factors and Pro-inflammatory Cytokines
A.
C Pro yt -i ok nf in lam e S i ma gn to al r y lin g
B. Differentiation; IL-1β depresses IGF-induction of myogenesis, as assessed by myogenin expression
C. Hypertrophy; TNFα depresses IGF-induction of protein synthesis in cultured C2C12 muscle cells
D. Early Signaling; TNFα depresses IGF-induction of IRS phosphorylation/activation.
E. Early Signaling; A ceramide analog (Cer) mimics TNFα blockage of IGF→IRS-1
FIGURE 6 Cytokines depress hypertrophy and differentiation of muscle by blocking IGFinduced protein synthesis and myogenin expression. The effects of either TNFα or IL-1β entails blockage of early IGF-1R events such as IRS-1 phosphorylation, which diminishes downstream signaling effects. Ceramide, a signaling intermediate, mimics the cytokine inhibition, and preventing ceramide synthesis can block cytokine activity (Broussard et al., 2003; Broussard et al., 2004; Strle et al., 2004). Reprinted with permission.
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tyrphostins or cyclolignans block all IGF-1R activity (Girnita et al., 2004; LeRoith and Helman, 2004; Levitzki and Gazit, 1995); because they block the first step in IGF signaling. In contrast, cytokines clearly block some but not all of the effects of IGF. A careful dissection of cytokine actions and mechanisms will continue to provide important new insights into the regulation of specific actions of IGF and thus allow tailoring of IGF resistance toward a specific goal.
C. Cell Survival: Lessons from Neurons It has long been established that IGF protects neurons against a variety of excitotoxic/ischemic insults (Cheng and Mattson, 1992; Mattson and Cheng, 1993), reviewed in (Carro et al., 2003; Dore et al., 2000). Considerable evidence supporting the survival properties of IGF justifies the potential use of IGF-I as a treatment for a variety of neurological diseases (Leinninger and Feldman, 2005; Wilczak and de Keyser, 2005). Indeed, overexpression of IGF-I in the cerebellum prevents neuronal death in Weaver mice, and in doing so, prevents ataxia (Zhong et al., 2005), probably by activation of the PI3-K pathway. Unfortunately, genetic models to study IGF depletion in vivo are not available because mice with a null mutation in the IGF-1R die at birth (Liu et al., 1993), and mice with a mutation to IGF-I die perinatally (Powell-Braxton et al., 1993). Hence, most of the mechanistic studies regarding IGF activity on neurons necessitate the use of in vitro models. A general theme has emerged from IGF studies, which is that IGF saves neurons via the PI3-K pathway. A few selective manuscripts indicate that IGF saves cerebellar granule neurons from depolarization (Subramaniam et al., 2005; Wiedmann et al., 2005) and hippocampal neurons from either hypoglycemic damage (Cheng and Mattson, 1992) or growth factor deprivation (Zheng et al., 2002). IGF also saves cortical neurons from corticosterone-induced death (Nitta et al., 2004). All of these actions are apparently mediated via the PI3-K pathway. IGF also is neuroprotective in models of ischemic damage and several other types of death, including dopamine-induced neurotoxicity [a model of Parkinson’s disease (Offen et al., 2001)], N-methylD-aspartate toxicity of cortical neurons (Takadera et al., 1999), and development of sensitivity to kainate neurotoxicity (Leski et al., 2000). IGF-I is a strong activator of the PI3-K pathway in hippocampal neurons, and inhibition of IGF activity in vivo leads to neuronal degeneration (Zheng and Quirion, 2004; Zhong et al., 2002). These data underlie the critical need of the PI3-K signaling cascade in neurons. IGF-I and the phosphatase inhibitor, sodium orthovanadate, appear to exert their neuroprotective
activities in vivo against ischemic damage by enhancing the PI3-K pathway (Fukunaga and Kawano, 2003). This makes the PI3-K downstream protein, Akt, a potential molecular target for ischemic therapy. The PI3-K pathway is also involved in IGF actions during neuronal differentiation. As examples, IGF-I induces the expression of glutamate receptors on neurons (Zona et al., 1995) and potentiates expression of neuronal L calcium channels (Bence-Hanulec et al., 2000; Blair et al., 1999). IGF is necessary for the induction of glutamate sensitivity of developing neurons (Calissano et al., 1993; Gonzalez de la Vega et al., 2001) and enhances field excitatory postsynaptic potentials (Ramsey et al., 2005). With this in mind, IGF-I infusion into old rats increases complexity of synapses within the hippocampus (Shi et al., 2005) and diminishes the age-associated loss of neurogenesis within the hippocampus (Lichtenwalner et al., 2001). All of these findings imply a cognitive benefit associated with IGF signaling in neurons, primarily through activation of the PI3-K pathway. They also suggest that diminished signaling through this pathway will markedly affect neuron activity, including those associated with behavior and learning. Considering this and the ability of cytokines such as TNFα and IL-1β to block IGF-induction of the PI3-K pathway, it was logical to assume that cytokine effects on behavior and cognition may involve antagonizing the positive effects of IGF.
VI. CYTOKINE—IGF INTERACTIONS; IN VIVO—BEHAVIOR AND LEARNING A. IGF Reduces Sickness Behavior Critical to the development of therapeutic approaches to increase quality of life is defining the role of proinflammatory cytokines in the induction of sickness behavior [reviewed in (Kelley et al., 2003; Parnet et al., 2002)]. Several key experiments highlighted in these reviews indicate that induction of cytokine expression within the brain causes a myriad of symptoms collectively defined as sickness behavior. The symptoms include decreased activity, decreased social investigation, anhedonia, general malaise, fatigue, depressed appetite, and changes in sleep pattern. It is now well accepted that pro-inflammatory cytokines act within the central nervous system to modulate behavior, albeit with ill-defined targets. However, with the antagonist relationship between cytokines and IGF described above, a natural extension of these experiments was to determine if IGF would counteract the sickness-inducing properties of LPS. In these experiments, LPS or bovine serum albumin was injected i.c.v. into mice, which was immediately followed by
7. Crosstalk between Insulin-like Growth Factors and Pro-inflammatory Cytokines
A. Behavior; IGF-l reduces TNFαdepressed social exploration of a novel juvenile.
TNFa TNFa
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B. Immobility; IGF-l prevents TNFαinduced immobility.
TNFa TNFa
FIGURE 7 TNFα-induced sickness behavior is antagonized by IGF-I. TNFα, when administered i.c.v., depresses social exploration of a novel juvenile and induces immobility, two well-characterized indices of sickness behavior. Central administration of IGF-I antagonizes the effect of TNFα (Bluthé et al., 2006). Reprinted with permission.
i.c.v. administration of IGF-I (100 ng or 1000 ng). There was no effect of either dose of IGF-I following administration of albumin. As expected, LPS reduced exploration of a novel object, suppressed rearing behavior and increased immobility. In all these cases, the higher dose of IGF-I, but not the lower one, significantly inhibited development of all of these sickness behaviors (Dantzer et al., 1999). Although unproven, the beneficial effect of IGF-I on sickness behavior may be associated with increased glucose utilization throughout the brain (Cheng et al., 2000). This increase in glucose utilization is likely to be a consequence of IGF increasing tyrosine phosphorylation of the critical IRS docking proteins and PI3-K in both neurons and glia following activation of the IGF-1R. The beneficial effects of IGF-I on LPS-induced sickness behavior were interpreted to suggest that IGF-I either reduces the production of cytokines in the brain that are synthesized in response to LPS or that IGF-I impairs the action of these LPS-induced central cytokines (Dantzer et al., 1999). In order to test the possibility that IGF-I interferes with the action of proinflammatory cytokines, mice were injected i.c.v. with either recombinant TNFα or IL-1β. The doses of TNFα (50 ng) and IL-1β (2 ng) were carefully selected in order to induce equivalent degrees of sickness behavior. In the absence of cytokine, IGF-I (100 ng) did not affect behavior, as assessed by investigation of a conspecific juvenile (Figure 7A) or duration of immobility (Figure 7B). As expected, TNFα impaired both these behavioral readouts. However, when mice were pre-
treated i.c.v. with IGF-I, changes in both social investigation and immobility in response to TNFα were ameliorated. Interestingly, this dose of IGF-I did not impair development of sickness behavior induced by i.c.v. injection of a similar sickness-inducing dose of IL-1β. However, a higher dose of IGF-I (1000 ng) significantly attenuated IL-1β-induced sickness behavior. These data extend earlier results in which IGF-I inhibited LPS-induced reduction in several sickness indices, including investigation, rearing, and freezing (Dantzer et al., 1999). These findings offer strong evidence in a whole animal model of the antagonism that exists between pro-inflammatory cytokines and IGF-I by showing that enhanced IGF-1R activation is able to overcome the probable TNFα-induced decrease in IGF signaling in vivo within the brain. Interestingly, IGF-I is more potent in ameliorating TNFα- than IL-1β-induced sickness behavior. Since TNFα-induced IL-1β synthesis is responsible for inducing most symptoms of sickness behavior (Bluthé et al., 1991), at least part of the IGF effect may not be caused by a direct effect on neurons but may involve an impairment in the ability of TNFα to induce central synthesis of IL-1β.
B. Spatial Learning Deficits Are Prevented by IGF Low levels of IGF-I and elevated pro-inflammatory cytokines have been linked to progressive inflammatory neuropathologic disorders, including Alzheimer’s
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disease (Dik et al., 2003; Wilson et al., 2002a). New results indicate that IGF-I protects against the development of amyloid plaques (Carro & Torres-Aleman, 2004; Carro et al., 2002; Dik et al., 2003; Wilson et al., 2002b). Consistent with data in other physiological systems, this neuroprotective effect of IGF-I is antagonized by TNFα (Carro et al., 2002). In this study, TNFα blocked the ability of IGF-I to promote transport of amyloid across the blood-brain barrier. Although the potential role of IGF-I in improving cognitive functions is in its infancy, a review of the literature in 2000 (van Dam et al., 2000) noted the very strong positive relationship between plasma IGF-I and a variety of cognitive functions, particularly in the elderly. Since that time, it has been reported that humans with serum IGF-I < 70 ng/ml have lower information processing speed (Dik et al., 2003). This correlative study is supported by recent cause-and-effect studies with growth hormone–deficient adult humans who suffer from a variety of psychological disturbances (Stouthart et al., 2003). Growth hormone replacement therapy, which causes an increase in circulating IGF-I, reduces anxiety and improves quality of life in these patients. Elevated serum IGF-I is positively related to memory and negatively related to depression, tension, and anxiety. Serum IGF-I is well known to be elevated by moderate exercise, an effect that has now been extended to exercise-induced increases in brain IGF-I and protection of the brain against a variety of insults (Carro et al., 2001). Although natural methods that are associated with healthy lifestyles can increase brain IGF-I, the roles of IGF in regulating both sickness behavior and cognitive events have not been fully defined. More importantly, the intracellular protective mechanisms that are mediated by the IGF-1R must be refined. Antagonizing IGF-II action in the brains of young animals impairs both learning and memory (Lupien et al., 2003) suggesting that other treatments that alter IGF activity, for instance, cytokines, would also result in impaired learning and memory. An in vivo model, kainate (KA, a neurotoxic glutamate receptor agonist)induced deficits in spatial memory, show that the deficits are blocked by an inhibitor of TNFα synthesis (Bluthé et al., 2005). KA-induced spatial memory deficits are also inhibited by i.c.v. administration of IGF-I. Coupled with other data showing that KA induces synthesis of TNFα in the brain (de Bock et al., 1996; Dinkel et al., 2003; Minami et al., 1991) by microglia (Noda et al., 2000), this new work begins to define KA as an inflammatory stimulus. Consistent with this effect, IGF-I promotes neuronal survival following exposure of neurons to glutamate or cytokines (Kenchappa et al., 2004; Vincent et al., 2004; Yadav et
al., 2005). However, unlike cytokine-induced sickness behavior, KA does not diminish general activity of mice when assessed 2 weeks after KA injection (Bluthé et al., 2005). Instead, at a dose of KA that is not neurotoxic (15 mg), KA causes deficits in spatial memory. The cognitive effect of KA, without gross behavioral effects, is due primarily to the localized effect of KA, which is largely limited to the hippocampus (Jarrard, 2002). The hippocampus is directly involved in spatial memory but not necessarily involved in all aspects of sickness behavior. KA induces pro-inflammatory cytokine production within the hippocampus (de Bock et al., 1996; Lehtimaki et al., 2003; Minami et al., 1991; Vezzani et al., 2002) and at higher doses results in neuronal death (Jarrard, 2002). However, under controlled conditions, KA causes spatial memory deficits without concurrent neuronal loss, as assessed by Fluorojade B staining (Bluthé et al., 2005). The cognitive effects of KA are blocked by an inhibitor of TNFα synthesis, pentoxifylline, (Figure 8A) as well as by chronic (5 days), but not acute (1 day) i.c.v. administration of IGF-I (Figure 8B). These findings further support an antagonistic relationship between pro-inflammatory cytokines and IGF within the brain. Although the mechanisms responsible for the CNS effects are ill defined, they are consistent with the idea that pro-inflammatory cytokines reduce IGF activity, causing IGF resistance. This relationship is strengthened by the ability of IGF administration to ameliorate both inflammation and cytokine-induced sickness behavior and cytokine-dependent spatial memory deficits. It is possible that sickness behaviors induced by TNFα can be overcome by maintaining higher levels of IGF in the brain, such as might be induced by exercise. Experimental data, coupled with clinical correlative studies, provide strong evidence for a link between IGF activity, behavior, and cognition in otherwise healthy subjects. The experimental animal trials clearly indicate that sickness behavior and at least some cognitive deficits are mediated by proinflammatory cytokines within the brain. Many of the clinical and experimental changes can be abrogated by treatments aimed at enhancing IGF activity, including GH injection, exercise, or direct i.c.v. IGF injection. Critical to preventing sickness behavior and cognitive deficits is a clear understanding of the mechanisms by which pro-inflammatory cytokines elicit their negative actions within the brain. Based upon these data, investigations on how pro-inflammatory cytokines cause adverse effects in the CNS should include studies directed at understanding the ability of cytokines to interact with the IGFs and possibly other growth factors, such as brain-derived neurotrophic factor.
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A. KA inhibits spatial memory. PTX, B. KA administration depresses which blocks TNFa synthesis, prevents hippocampal-dependent spatial memory. KA-induced spatial memory loss. IGF-l inhibits this TNFα-dependent action.
FIGURE 8 The spatial memory deficit caused by KA requires TNFα and is antagonized by IGF-I. Blocking TNFα secretion with PTX (A) or i.c.v. treatment with IGF-I both prevent the cognitive deficits associated with KA (Bluthé et al., 2005). Reprinted with permission.
VII. CONCLUSIONS Hormone and immune interactions have been classically defined by experiments using synthetic glucocorticoids and the stress- or inflammation-induced release of adrenal glucocorticoids. These hormones have long been known to have a variety of effects on nearly all cells of the immune system. The overall theme of this chapter is that the GH/IGF axis, which controls over 80% of postnatal growth, represents another important example of how the endocrine system interacts with the immune system. A number of examples have been used not only to demonstrate the existence of the interaction between pro-inflammatory cytokines and IGF, but also to provide insights into the mechanism by which this occurs. These data make it clear that advances at any one level of understanding in either the immune or endocrine systems will not be fully understood until there is a more complete understanding of the crosstalk that occurs between these two systems.
Acknowledgment This research was supported by grants from National Institutes of Health to Keith W. Kelley (AI50442 and MH51569) and Robert Dantzer (MH071349).
References Arkins, S., Johnson, R. W., Minshall, C., Dantzer, R., and Kelley, K. (2001). Immunophysiology: The interaction of hormone, lymphohemopoietic cytokines and the neuroimmune axis. In B. S. McEwen (Ed.), Coping with the Environment: Neural and Endocrine Mechanisms, Handbook of Physiology, Section 7, The Endocrine
System, American Physiological Society (vol. 4, pp 469–495). New York: Oxford University Press. Arkins, S., Rebeiz, N., Brunke-Reese, D. L., Minshall, C., and Kelley, K. W. (1995). The colony-stimulating factors induce expression of insulin-like growth factor-I messenger ribonucleic acid during hematopoiesis. Endocrinology, 136, 1153–1160. Avitsur, R., Kavelaars, A., Heijnen, C., and Sheridan, J. F. (2005). Social stress and the regulation of tumor necrosis factor-alpha secretion. Brain Behav. Immun., 19, 311–317. Baserga, R. (2005). The insulin-like growth factor-I receptor as a target for cancer therapy. Expert Opin. Ther. Targets, 9, 753–768. Baserga, R., Peruzzi, F., and Reiss, K. (2003). The IGF-1 receptor in cancer biology. Int. J. Cancer, 107, 873–877. Baud, V., and Karin, M. (2001). Signal transduction by tumor necrosis factor and its relatives. Trends Cell Biol., 11, 372–377. Bence-Hanulec, K. K., Marshall, J., and Blair, L. A. (2000). Potentiation of neuronal L calcium channels by IGF-1 requires phosphorylation of the alpha1 subunit on a specific tyrosine residue. Neuron, 27, 121–131. Blair, L. A., Bence-Hanulec, K. K., Mehta, S., Franke, T., Kaplan, D., and Marshall, J. (1999). Akt-dependent potentiation of L channels by insulin-like growth factor-1 is required for neuronal survival. J. Neurosci., 19, 1940–1951. Bluthé, R. M., Dantzer, R., and Kelley, K. W. (1991). Interleukin-1 mediates behavioural but not metabolic effects of tumor necrosis factor α in mice. Eur. J. Pharmacol., 209, 281–283. Bluthé, R. M., Frenois, F., Kelley, K., and Dantzer, R. (2005). Pentoxifyllin and insulin-like growth factor-I (IGF-I) abrogate kainic acid-induced cognitive impairment in mice. J. Neuroimmunol., 169, 50–58. Bluthé, R. M., Kelley, K. W., and Dantzer, R. (2006). Effects of insulinlike growth factor-I on cytokine-induced sickness behavior in mice. Brain Behav. Immun., 20, 57–63. Broussard, S. R., McCusker, R. H., Novakofski, J. E., Strle, K., Shen, W. H., Johnson, R. W., Dantzer, R., and Kelley, K. W. (2004). IL-1 beta impairs insulin-like growth factor i-induced differentiation and downstream activation signals of the insulin-like growth factor I receptor in myoblasts. J. Immunol., 172, 7713–7720. Broussard, S. R., McCusker, R. H., Novakofski, J. E., Strle, K., Shen, W. H., Johnson, R. W., Freund, G. G., Dantzer, R., and Kelley, K. W. (2003). Cytokine-hormone interactions: tumor necrosis factor alpha impairs biologic activity and downstream activation
188
I. Neural and Endocrine Effects on Immunity
signals of the insulin-like growth factor I receptor in myoblasts. Endocrinology, 144, 2988–2996. Brunetti, A., Maddux, B. A., Wong, K. Y., and Goldfine, I. D. (1989). Muscle cell differentiation is associated with increased insulin receptor biosynthesis and messenger RNA levels. J. Clin. Invest., 83, 192–198. Burgess, W., Liu, Q., Zhou, J., Tang, Q., Ozawa, A., VanHoy, R., Arkins, S., Dantzer, R., and Kelley, K. W. (1999). The immuneendocrine loop during aging: role of growth hormone and insulin-like growth factor-I. Neuroimmunomodulation, 6, 56–68. Calissano, P., Ciotti, M. T., Battistini, L., Zona, C., Angelini, A., Merlo, D., and Mercanti, D. (1993). Recombinant human insulinlike growth factor I exerts a trophic action and confers glutamate sensitivity on glutamate-resistant cerebellar granule cells. Proc. Natl. Acad. Sci. USA, 90, 8752–8756. Carro, E., and Torres-Aleman, I. (2004). The role of insulin and insulin-like growth factor I in the molecular and cellular mechanisms underlying the pathology of Alzheimer’s disease. Eur. J. Pharmacol., 490, 127–133. Carro, E., Trejo, J. L., Busiguina, S., and Torres-Aleman, I. (2001). Circulating insulin-like growth factor I mediates the protective effects of physical exercise against brain insults of different etiology and anatomy. J. Neurosci., 21, 5678–5684. Carro, E., Trejo, J. L., Gomez-Isla, T., LeRoith, D., and Torres-Aleman, I. (2002). Serum insulin-like growth factor I regulates brain amyloid-beta levels. Nat. Med., 8, 1390–1397. Carro, E., Trejo, J., Nunez, A., and Torres-Aleman, I. (2003). Brain repair and neuroprotection by serum insulin-like growth factor I. Mol. Neurobiol., 27, 153–162. Cheng, B., and Mattson, M. P. (1992). IGF-I and IGF-II protect cultured hippocampal and septal neurons against calciummediated hypoglycemic damage. J. Neurosci., 12, 1558–1566. Cheng, C. M., Reinhardt, R. R., Lee, W. H., Joncas, G., Patel, S. C., and Bondy, C. A. (2000). Insulin-like growth factor 1 regulates developing brain glucose metabolism. Proc. Natl. Acad. Sci. USA, 97, 10236–10241. Coleman, M. E., DeMayo, F., Yin, K. C., Lee, H. M., Geske, R., Montgomery, C., and Schwartz, R. J. (1995). Myogenic vector expression of insulin-like growth factor I stimulates muscle cell differentiation and myofiber hypertrophy in transgenic mice. J. Biol. Chem., 270, 12109–12116. Consensus. (2001). Critical evaluation of the safety of recombinant human growth hormone administration: statement from the Growth Hormone Research Society. J. Clin. Endocrinol. Metab., 86, 1868–1870. Coolican, S. A., Samuel, D. S., Ewton, D. Z., McWade, F. J., and Florini, J. R. (1997). The mitogenic and myogenic actions of insulin-like growth factors utilize distinct signaling pathways. J. Biol. Chem., 272, 6653–6662. Dantzer, R., Gheusi, G., Johnson, R. W., and Kelley, K. W. (1999). Central administration of insulin-like growth factor-1 inhibits lipopolysaccharide-induced sickness behavior in mice. Neuroreport, 10, 289–292. de Bock, F., Dornand, J., and Rondouin, G. (1996). Release of TNF alpha in the rat hippocampus following epileptic seizures and excitotoxic neuronal damage. Neuroreport, 7, 1125–1129. D’Ercole, A. J., Ye, P., and O’Kusky, J. R. (2002). Mutant mouse models of insulin-like growth factor actions in the central nervous system. Neuropeptides, 36, 209–220. Dik, M. G., Pluijm, S. M., Jonker, C., Deeg, D. J., Lomecky, M. Z., and Lips, P. (2003). Insulin-like growth factor I (IGF-I) and cognitive decline in older persons. Neurobiol. Aging, 24, 573–581.
Dinkel, K., MacPherson, A., and Sapolsky, R. M. (2003). Novel glucocorticoid effects on acute inflammation in the CNS. J. Neurochem., 84, 705–716. Dore, S., Kar, S., Zheng, W. H., and Quirion, R. (2000). Rediscovering good old friend IGF-I in the new millennium: possible usefulness in Alzheimer’s disease and stroke. Pharm. Acta Helv., 74, 273–280. Dranoff, G. (2004). Cytokines in cancer pathogenesis and cancer therapy. Nat. Rev. Cancer, 4, 11–22. Dupont, J., and LeRoith, D. (2001). Insulin and insulin-like growth factor I receptors: similarities and differences in signal transduction. Horm. Res., 55(Suppl 2), 22–26. Entingh, A. J., Taniguchi, C. M., and Kahn, C. R. (2003). Bidirectional regulation of brown fat adipogenesis by the insulin receptor. J. Biol. Chem., 278, 33377–33383. Florini, J. R., Ewton, D. Z., and Roof, S. L. (1991). Insulin-like growth factor-I stimulates terminal myogenic differentiation by induction of myogenin gene expression. Mol. Endocrinol., 5, 718–724. Foulstone, E., Prince, S., Zaccheo, O., Burns, J. L., Harper, J., Jacobs, C., Church, D., and Hassan, A. B. (2005). Insulin-like growth factor ligands, receptors, and binding proteins in cancer. J. Pathol., 205, 145–153. Frost, R. A., and Lang, C. H. (2003). Regulation of insulin-like growth factor-I in skeletal muscle and muscle cells. Minerva Endocrinol., 28, 53–73. Frystyk, J. (2004). Free insulin-like growth factors—measurements and relationships to growth hormone secretion and glucose homeostasis. Growth Horm. IGF Res., 14, 337–375. Fukunaga, K., and Kawano, T. (2003). Akt is a molecular target for signal transduction therapy in brain ischemic insult. J. Pharmacol. Sci., 92, 317–327. Girnita, A., Girnita, L., del Prete, F., Bartolazzi, A., Larsson, O., and Axelson, M. (2004). Cyclolignans as inhibitors of the insulin-like growth factor-1 receptor and malignant cell growth. Cancer Res., 64, 236–242. Gonzalez de la Vega, A., Buno, W., Pons, S., Garcia-Calderat, M. S., Garcia-Galloway, E., and Torres-Aleman, I. (2001). Insulin-like growth factor I potentiates kainate receptors through a phosphatidylinositol 3-kinase dependent pathway. Neuroreport, 12, 1293–1296. Grazul-Bilska, A. T., Johnson, M. L., Bilski, J. J., Redmer, D. A., Reynolds, L. P., Abdullah, A., and Abdullah, K. M. (2003). Wound healing: the role of growth factors. Drugs Today (Barc.), 39, 787–800. Hanada, T., and Yoshimura, A. (2002). Regulation of cytokine signaling and inflammation. Cytokine Growth Factor Rev., 13, 413–421. Hay, N. (2005). The Akt-mTOR tango and its relevance to cancer. Cancer Cell, 8, 179–183. Hehlgans, T., and Pfeffer, K. (2005). The intriguing biology of the tumour necrosis factor/tumour necrosis factor receptor superfamily: players, rules and the games. Immunology, 115, 1–20. Hofmann, F., and Garcia-Echeverria, C. (2005). Blocking the insulinlike growth factor-I receptor as a strategy for targeting cancer. Drug Discov. Today, 10, 1041–1047. Hotamisligil, G. S. (2003). Inflammatory pathways and insulin action. Int. J. Obes. Relat. Metab. Disord., 27(Suppl 3), S53–S55. Janssen, J. A., and Lamberts, S. W. (2004). IGF-I and longevity. Horm. Res., 62(Suppl 3), 104–109. Jarrard, L. E. (2002). Use of excitotoxins to lesion the hippocampus: update. Hippocampus, 12, 405–414. Katz, J., Nasatzky, E., Werner, H., Le Roith, D., and Shemer, J. (1999). Tumor necrosis factor alpha and interferon gamma—induced cell growth arrest is mediated via insulin-like growth factor binding protein-3. Growth Horm. IGF Res., 9, 174–178.
7. Crosstalk between Insulin-like Growth Factors and Pro-inflammatory Cytokines Kelley, K. W. (2004). From hormones to immunity: the physiology of immunology. Brain Behav. Immun., 18, 95–113. Kelley, K. W., Bluthé, R. M., Dantzer, R., Zhou, J. H., Shen, W. H., Johnson, R. W., and Broussard, S. R. (2003). Cytokine-induced sickness behavior. Brain Behav. Immun., 17, 112–118. Kenchappa, P., Yadav, A., Singh, G., Nandana, S., and Banerjee, K. (2004). Rescue of TNFalpha-inhibited neuronal cells by IGF-1 involves Akt and c-Jun N-terminal kinases. J. Neurosci. Res., 76, 466–474. Kenyon, C. (2005). The plasticity of aging: insights from long-lived mutants. Cell, 120, 449–460. Khandwala, H. M., McCutcheon, I. E., Flyvbjerg, A., and Friend, K. E. (2000). The effects of insulin-like growth factors on tumorigenesis and neoplastic growth. Endocr. Rev., 21, 215–244. Kitamura, T., Kahn, C. R., and Accili, D. (2003). Insulin receptor knockout mice. Annu. Rev. Physiol., 65, 313–332. Lang, C. H., Hong-Brown, L., and Frost, R. A. (2005). Cytokine inhibition of JAK-STAT signaling: a new mechanism of growth hormone resistance. Pediatr. Nephrol., 20, 306–312. Langen, R. C., Schols, A. M., Kelders, M. C., Wouters, E. F., and Janssen-Heininger, Y. M. (2001). Inflammatory cytokines inhibit myogenic differentiation through activation of nuclear factorkappaB. FASEB J., 15, 1169–1180. Lau, M. M., Stewart, C. E., Liu, Z., Bhatt, H., Rotwein, P., and Stewart, C. L. (1994). Loss of the imprinted IGF2/cationindependent mannose 6-phosphate receptor results in fetal overgrowth and perinatal lethality. Genes Dev., 8, 2953–2963. Lazar-Molnar, E., Hegyesi, H., Toth, S., and Falus, A. (2000). Autocrine and paracrine regulation by cytokines and growth factors in melanoma. Cytokine, 12, 547–554. Lehtimaki, K. A., Peltola, J., Koskikallio, E., Keranen, T., and Honkaniemi, J. (2003). Expression of cytokines and cytokine receptors in the rat brain after kainic acid-induced seizures. Brain Res. Mol. Brain Res., 110, 253–260. Leinninger, G. M., and Feldman, E. L. (2005). Insulin-like growth factors in the treatment of neurological disease. Endocr. Dev., 9, 135–159. LeRoith, D., and Helman, L. (2004). The new kid on the block(ade) of the IGF-1 receptor. Cancer Cell, 5, 201–202. Leroith, D., and Nissley, P. (2005). Knock your SOCS off! J. Clin. Invest., 115, 233–236. Leski, M. L., Valentine, S. L., Baer, J. D., and Coyle, J. T. (2000). Insulin-like growth factor I prevents the development of sensitivity to kainate neurotoxicity in cerebellar granule cells. J. Neurochem., 75, 1548–1556. Levitzki, A., and Gazit, A. (1995). Tyrosine kinase inhibition: an approach to drug development. Science, 267, 1782–1788. Li, Y. M., Arkins, S., McCusker, R. H., Jr., Donovan, S. M., Liu, Q., Jayaraman, S., Dantzer, R., and Kelley, K. W. (1996). Macrophages synthesize and secrete a 25-kilodalton protein that binds insulin-like growth factor-I. J. Immunol., 156, 64–72. Li, Y. P., Schwartz, R. J., Waddell, I. D., Holloway, B. R., and Reid, M. B. (1998). Skeletal muscle myocytes undergo protein loss and reactive oxygen-mediated NF-kappaB activation in response to tumor necrosis factor alpha. FASEB J., 12, 871–880. Lichtenwalner, R. J., Forbes, M. E., Bennett, S. A., Lynch, C. D., Sonntag, W. E., and Riddle, D. R. (2001). Intracerebroventricular infusion of insulin-like growth factor-I ameliorates the agerelated decline in hippocampal neurogenesis. Neuroscience, 107, 603–613. Liu, J. P., Baker, J., Perkins, A. S., Robertson, E. J., and Efstratiadis, A. (1993). Mice carrying null mutations of the genes encoding insulin-like growth factor I (Igf-1) and type 1 IGF receptor (Igf1r). Cell, 75, 59–72.
189
Liu, Q., Ning, W., Dantzer, R., Freund, G. G., and Kelley, K. W. (1998). Activation of protein kinase C-zeta and phosphatidylinositol 3’-kinase and promotion of macrophage differentiation by insulin-like growth factor-I. J. Immunol., 160, 1393–1401. Liu, Z. G. (2005). Molecular mechanism of TNF signaling and beyond. Cell Res., 15, 24–27. Lupien, S. B., Bluhm, E. J., and Ishii, D. N. (2003). Systemic insulinlike growth factor-I administration prevents cognitive impairment in diabetic rats, and brain IGF regulates learning/memory in normal adult rats. J. Neurosci. Res., 74, 512–523. Lupu, F., Terwilliger, J. D., Lee, K., Segre, G. V., and Efstratiadis, A. (2001). Roles of growth hormone and insulin-like growth factor 1 in mouse postnatal growth. Dev. Biol., 229, 141–162. Martin, G. S. (2003). Cell signaling and cancer. Cancer Cell, 4, 167–174. Mattson, M. P., and Cheng, B. (1993). Growth factors protect neurons against excitotoxic/ischemic damage by stabilizing calcium homeostasis. Stroke, 24, I136–140; discussion I144–135. McCusker, R. H. (1998). Controlling insulin-like growth factor activity and the modulation of insulin-like growth factor binding protein and receptor binding. J. Dairy Sci., 81, 1790–1800. McCusker, R. H., Busby, W. H., Dehoff, M. H., Camacho-Hubner, C., and Clemmons, D. R. (1991). Insulin-like growth factor (IGF) binding to cell monolayers is directly modulated by the addition of IGF-binding proteins. Endocrinology, 129, 939–949. McCusker, R. H., Camacho-Hubner, C., Bayne, M. L., Cascieri, M. A., and Clemmons, D. R. (1990). Insulin-like growth factor (IGF) binding to human fibroblast and glioblastoma cells: the modulating effect of cell released IGF binding proteins (IGFBPs). J. Cell. Physiol., 144, 244–253. McCusker, R. H., and Campion, D. R. (1986). Effect of growth hormone-secreting tumours on skeletal muscle cellularity in the rat. J. Endocrinol., 111, 279–285. McCusker, R. H., Campion, D. R., Jones, W. K., and Clemmons, D. R. (1989). The insulin-like growth factor-binding proteins of porcine serum: endocrine and nutritional regulation. Endocrinology, 125, 501–509. McCusker, R. H., and Novakofski, J. (2003). Zinc partitions insulinlike growth factors (IGFs) from soluble IGF binding protein (IGFBP)-5 to the cell surface receptors of BC3H-1 muscle cells. J. Cell. Physiol., 197, 388–399. McCusker, R. H., and Novakofski, J. (2004). Zinc partitions IGFs from soluble IGF binding proteins (IGFBP)-5, but not soluble IGFBP-4, to myoblast IGF type 1 receptors. J. Endocrinol., 180, 227–246. Miller, J. B. (1990). Myogenic programs of mouse muscle cell lines: expression of myosin heavy chain isoforms, MyoD1, and myogenin. J. Cell Biol., 111, 1149–1159. Minami, M., Kuraishi, Y., and Satoh, M. (1991). Effects of kainic acid on messenger RNA levels of IL-1 beta, IL-6, TNF alpha and LIF in the rat brain. Biochem. Biophys. Res. Commun., 176, 593–598. Mocellin, S., Rossi, C. R., Pilati, P., and Nitti, D. (2005). Tumor necrosis factor, cancer and anticancer therapy. Cytokine Growth Factor Rev., 16, 35–53. Mudipalli, A., Li, Z., Hromchak, R., and Bloch, A. (2001). NF-kappaB (p65/RelA) as a regulator of TNFalpha-mediated ML-1 cell differentiation. Leukemia, 15, 808–813. Musaro, A., and Rosenthal, N. (1999). Maturation of the myogenic program is induced by postmitotic expression of insulin-like growth factor I. Mol. Cell. Biol., 19, 3115–3124. Nitta, A., Zheng, W. H., and Quirion, R. (2004). Insulin-like growth factor 1 prevents neuronal cell death induced by corticosterone through activation of the PI3k/Akt pathway. J. Neurosci. Res., 76, 98–103.
190
I. Neural and Endocrine Effects on Immunity
Noda, M., Nakanishi, H., Nabekura, J., and Akaike, N. (2000). AMPA-kainate subtypes of glutamate receptor in rat cerebral microglia. J. Neurosci., 20, 251–258. Offen, D., Shtaif, B., Hadad, D., Weizman, A., Melamed, E., and Gil-Ad, I. (2001). Protective effect of insulin-like-growth-factor-1 against dopamine-induced neurotoxicity in human and rodent neuronal cultures: possible implications for Parkinson’s disease. Neurosci. Lett., 316, 129–132. Parnet, P., Kelley, K. W., Bluthé, R. M., and Dantzer, R. (2002). Expression and regulation of interleukin-1 receptors in the brain. Role in cytokines-induced sickness behavior. J. Neuroimmunol., 125, 5–14. Powell-Braxton, L., Hollingshead, P., Warburton, C., Dowd, M., Pitts-Meek, S., Dalton, D., Gillett, N., and Stewart, T. A. (1993). IGF-I is required for normal embryonic growth in mice. Genes Dev., 7, 2609–2617. Ramsey, M. M., Adams, M. M., Ariwodola, O. J., Sonntag, W. E., and Weiner, J. L. (2005). Functional characterization of des-IGF-1 action at excitatory synapses in the CA1 region of rat hippocampus. J. Neurophysiol., 94, 247–254. Ranke, M. B. (2005). Insulin-like growth factor-I treatment of growth disorders, diabetes mellitus and insulin resistance. Trends Endocrinol. Metab., 16, 190–197. Rommel, C., Bodine, S. C., Clarke, B. A., Rossman, R., Nunez, L., Stitt, T. N., Yancopoulos, G. D., and Glass, D. J. (2001). Mediation of IGF-1–induced skeletal myotube hypertrophy by PI(3)K/Akt/ mTOR and PI(3)K/Akt/GSK3 pathways. Nat. Cell Biol., 3, 1009–1013. Rosenfeld, R. G. (2005). The IGF system: new developments relevant to pediatric practice. Endocr. Dev., 9, 1–10. Rozen, F., Zhang, J., and Pollak, M. (1998). Antiproliferative action of tumor necrosis factor-alpha on MCF-7 breast cancer cells is associated with increased insulin-like growth factor binding protein-3 accumulation. Int. J. Oncol., 13, 865–869. Savage, M. O., Camacho-Hubner, R. C., and Dunger, D. B. (2004). Therapeutic applications of the insulin-like growth factors. Growth Horm. IGF Res., 14, 301–308. Schiepers, O. J., Wichers, M. C., and Maes, M. (2005). Cytokines and major depression. Prog. Neuropsychopharmacol. Biol. Psychiatry, 29, 201–217. Shalita-Chesner, M., Katz, J., Shemer, J., and Werner, H. (2001). Regulation of insulin-like growth factor-I receptor gene expression by tumor necrosis factor-alpha and interferon-gamma. Mol. Cell. Endocrinol., 176, 1–12. Sheikh, M. S., and Huang, Y. (2003). Death receptor activation complexes: it takes two to activate TNF receptor 1. Cell Cycle, 2, 550–552. Shen, W. H., Jackson, S. T., Broussard, S. R., McCusker, R. H., Strle, K., Freund, G. G., Johnson, R. W., Dantzer, R., and Kelley, K. W. (2004a). IL-1beta suppresses prolonged Akt activation and expression of E2F-1 and cyclin A in breast cancer cells. J. Immunol., 172, 7272–7281. Shen, W. H., Yin, Y., Broussard, S. R., McCusker, R. H., Freund, G. G., Dantzer, R., and Kelley, K. W. (2004b). Tumor necrosis factor alpha inhibits cyclin A expression and retinoblastoma hyperphosphorylation triggered by insulin-like growth factor-I induction of new E2F-1 synthesis. J. Biol. Chem., 279, 7438–7446. Shen, W. H., Zhou, J. H., Broussard, S. R., Freund, G. G., Dantzer, R., and Kelley, K. W. (2002). Proinflammatory cytokines block growth of breast cancer cells by impairing signals from a growth factor receptor. Cancer Res., 62, 4746–4756. Shi, L., Linville, M. C., Tucker, E. W., Sonntag, W. E., and BrunsoBechtold, J. K. (2005). Differential effects of aging and insulin-like growth factor-1 on synapses in CA1 of rat hippocampus. Cereb. Cortex, 15, 571–577.
Silverman, M. N., Pearce, B. D., Biron, C. A., and Miller, A. H. (2005). Immune modulation of the hypothalamic-pituitary-adrenal (HPA) axis during viral infection. Viral Immunol., 18, 41–78. Simonitsch, I., and Krupitza, G. (1998). Autocrine self-elimination of cultured ovarian cancer cells by tumour necrosis factor alpha (TNF-alpha). Br. J. Cancer, 78, 862–870. Sonntag, W. E., Carter, C. S., Ikeno, Y., Ekenstedt, K., Carlson, C. S., Loeser, R. F., Chakrabarty, S., Lee, S., Bennett, C., Ingram, R., Moore, T., and Ramsey, M. (2005). Adult-onset growth hormone and insulin-like growth factor I deficiency reduces neoplastic disease, modifies age-related pathology, and increases life span. Endocrinology, 146, 2920–2932. Spate, U., and Schulze, P. C. (2004). Proinflammatory cytokines and skeletal muscle. Curr. Opin. Clin. Nutr. Metab. Care, 7, 265–269. Stewart, C. E., Newcomb, P. V., and Holly, J. M. (2004). Multifaceted roles of TNF-alpha in myoblast destruction: a multitude of signal transduction pathways. J. Cell. Physiol., 198, 237–247. Storz, P., Doppler, H., Horn-Muller, J., Mulle, G., and Pfizenmaier, K. (2000). TNF down-regulation of receptor tyrosine kinasedependent mitogenic signal pathways as an important step in cytostasis induction and commitment to apoptosis of Kym-1 rhabdomyosarcoma cells. Cell Death Differ, 7, 955–965. Stouthart, P. J., Deijen, J. B., Roffel, M., and Delemarre-van de Waal, H. A. (2003). Quality of life of growth hormone (GH) deficient young adults during discontinuation and restart of GH therapy. Psychoneuroendocrinology, 28, 612–626. Strle, K., Broussard, S. R., McCusker, R. H., Shen, W. H., Johnson, R. W., Freund, G. G., Dantzer, R., and Kelley, K. W. (2004). Proinflammatory cytokine impairment of insulin-like growth factor I–induced protein synthesis in skeletal muscle myoblasts requires ceramide. Endocrinology, 145, 4592–4602. Subramaniam, S., Shahani, N., Strelau, J., Laliberte, C., Brandt, R., Kaplan, D., and Unsicker, K. (2005). Insulin-like growth factor 1 inhibits extracellular signal-regulated kinase to promote neuronal survival via the phosphatidylinositol 3-kinase/protein kinase A/c-Raf pathway. J. Neurosci., 25, 2838–2852. Sun, L. Y., Al-Regaiey, K., Masternak, M. M., Wang, J., and Bartke, A. (2005). Local expression of GH and IGF-1 in the hippocampus of GH-deficient long-lived mice. Neurobiol. Aging, 26, 929–937. Szalay, K., Razga, Z., and Duda, E. (1997). TNF inhibits myogenesis and downregulates the expression of myogenic regulatory factors myoD and myogenin. Eur. J. Cell Biol., 74, 391–398. Takadera, T., Matsuda, I., and Ohyashiki, T. (1999). Apoptotic cell death and caspase-3 activation induced by N-methyl-D-aspartate receptor antagonists and their prevention by insulin-like growth factor I. J. Neurochem., 73, 548–556. Tureckova, J., Wilson, E. M., Cappalonga, J. L., and Rotwein, P. (2001). Insulin-like growth factor-mediated muscle differentiation: collaboration between phosphatidylinositol 3-kinaseAkt-signaling pathways and myogenin. J. Biol. Chem., 276, 39264–39270. Valverde, A. M., Benito, M., and Lorenzo, M. (2005). The brown adipose cell: a model for understanding the molecular mechanisms of insulin resistance. Acta Physiol. Scand., 183, 59–73. van Dam, P. S., Aleman, A., de Vries, W. R., Deijen, J. B., van der Veen, E. A., de Haan, E. H., and Koppeschaar, H. P. (2000). Growth hormone, insulin-like growth factor I and cognitive function in adults. Growth Horm. IGF Res., 10, S69–S73. Vezzani, A., Moneta, D., Richichi, C., Aliprandi, M., Burrows, S. J., Ravizza, T., Perego, C., and De Simoni, M. G. (2002). Functional role of inflammatory cytokines and antiinflammatory molecules in seizures and epileptogenesis. Epilepsia, 43 (Suppl 5), 30–35.
7. Crosstalk between Insulin-like Growth Factors and Pro-inflammatory Cytokines Vincent, A. M., Mobley, B. C., Hiller, A., and Feldman, E. L. (2004). IGF-I prevents glutamate-induced motor neuron programmed cell death. Neurobiol. Dis., 16, 407–416. Wagers, A. J., and Conboy, I. M. (2005). Cellular and molecular signatures of muscle regeneration: current concepts and controversies in adult myogenesis. Cell, 122, 659–667. Wajant, H., Gerspach, J., and Pfizenmaier, K. (2005). Tumor therapeutics by design: targeting and activation of death receptors. Cytokine Growth Factor Rev., 16, 55–76. Welniak, L. A., Sun, R., and Murphy, W. J. (2002). The role of growth hormone in T-cell development and reconstitution. J. Leukoc. Biol., 71, 381–387. White, M. F. (2003). Insulin signaling in health and disease. Science, 302, 1710–1711. Wiedmann, M., Wang, X., Tang, X., Han, M., Li, M., and Mao, Z. (2005). PI3K/Akt-dependent regulation of the transcription factor myocyte enhancer factor-2 in insulin-like growth factor-1and membrane depolarization-mediated survival of cerebellar granule neurons. J. Neurosci. Res., 81, 226–234. Wilczak, N., and de Keyser, J. (2005). Insulin-like growth factor system in amyotrophic lateral sclerosis. Endocr. Dev., 9, 160–169. Wilson, C. J., Finch, C. E., and Cohen, H. J. (2002a). Cytokines and cognition—the case for a head-to-toe inflammatory paradigm. J. Am. Geriatr. Soc., 50, 2041–2056. Wilson, C. J., Finch, C. E., and Cohen, H. J. (2002b). Cytokines and cognition—the case for a head-to-toe inflammatory paradigm. J. Am. Geriatr. Soc., 50, 2041–2056. Wu, Y., Cui, K., Miyoshi, K., Hennighausen, L., Green, J. E., Setser, J., LeRoith, D., and Yakar, S. (2003). Reduced circulating insulinlike growth factor I levels delay the onset of chemically and
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genetically induced mammary tumors. Cancer Res., 63, 4384–4388. Yadav, A., Kalita, A., and Banerjee, K. (2005). JAK/STAT3 pathway is involved in survival of neurons in response to insulin like growth factor and negatively regulated by suppression of cytokine signaling-3. J. Biol. Chem., 36, 31830–31840. Yang, J., Anzo, M., and Cohen, P. (2005). Control of aging and longevity by IGF-I signaling. Exp. Gerontol., 40, 867–872. Zheng, W. H., Kar, S., and Quirion, R. (2002). Insulin-like growth factor-1–induced phosphorylation of transcription factor FKHRL1 is mediated by phosphatidylinositol 3-kinase/Akt kinase and role of this pathway in insulin-like growth factor-1– induced survival of cultured hippocampal neurons. Mol. Pharmacol., 62, 225–233. Zheng, W. H., and Quirion, R. (2004). Comparative signaling pathways of insulin-like growth factor-1 and brain-derived neurotrophic factor in hippocampal neurons and the role of the PI3 kinase pathway in cell survival. J. Neurochem., 89, 844–852. Zhong, J., Deng, J., Ghetti, B., and Lee, W. H. (2002). Inhibition of insulin-like growth factor I activity contributes to the premature apoptosis of cerebellar granule neuron in Weaver mutant mice: in vitro analysis. J. Neurosci. Res., 70, 36–45. Zhong, J., Deng, J., Phan, J., Dlouhy, S., Wu, H., Yao, W., Ye, P., D’Ercole, A. J., and Lee, W. H. (2005). Insulin-like growth factor-I protects granule neurons from apoptosis and improves ataxia in Weaver mice. J. Neurosci. Res., 80, 481–490. Zona, C., Ciotti, M. T., and Calissano, P. (1995). Human recombinant IGF-I induces the functional expression of AMPA/kainate receptors in cerebellar granule cells. Neurosci. Lett., 186, 75–78.
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C H A P T E R
8 The Neuroendocrine System and Rheumatoid Arthritis: Focus on the Hypothalamic-Pituitary-Adrenal Axis HEATHER E. GORBY AND ESTHER M. STERNBERG
I. INTRODUCTION 193 II. GENERAL CONCEPTS OF NEURAL-IMMUNE INTERACTIONS 194 III. ANIMAL MODELS OF RHEUMATOID ARTHRITIS 196 IV. HPA AXIS FUNCTION FINDINGS IN RHEUMATOID ARTHRITIS PATIENTS 197 V. OTHER NEUROENDOCRINE FACTORS IMPLICATED IN RA PATHOGENESIS 199 VI. SUMMARY 201
lage and bone. Persistent synovial inflammation, chronic pain, joint damage, and progressive disability occur over the course of RA. RA etiology remains unclear. RA is frequently accompanied by a variety of other known autoimmune or autoimmune-associated disorders such as systemic lupus erythematosus and Sjogren’s syndrome that are characterized by autoantibody production, suggesting a generalized autoimmune susceptibility in affected individuals. Indeed, over 20 different regions on 15 different chromosomes, many of which are immunerelated genes, have been linked to inflammatory arthritis in animal studies (Wilder et al., 1999), indicating a multi-genic, polygenic component to this syndrome. Furthermore, the cytokines TNF-α and interleukin-1 (IL-1) are elevated in patients with RA, suggesting that they have a pathological role in the disease (Chikanza et al., 1995; Saxne et al., 1988). Animal studies and human clinical trials using pharmacological agents that block TNF show clinical improvement in RA and decreased rate of progression of erosions (Barrera et al., 1996; Maini et al., 2004; Schiff, 2004; Thorbecke et al., 1992; Williams et al., 1992). There is also abundant evidence that the nervous system and endocrine systems are involved in the pathogenesis of RA (Harle et al., 2005). The interaction of the neural, endocrine, and immune systems in RA will be the focus of this chapter.
I. INTRODUCTION Rheumatoid arthritis (RA) is a chronic inflammatory disease effecting an estimated 0.5–1.1% of the North American population (Alamanos and Drosos, 2005). The age of onset is usually between 20 and 40 years of age with a female:male ratio of 3 : 1. There is a 12–20% concordance rate in monozygotic twins, and a 4–5% concordance rate in dizygotic twins, suggesting that there may be a genetic component in RA predisposition (MacGregor et al., 2000; Silman et al., 1993). The first stage involves the classical signs of inflammation in the synovial lining, including redness, swelling, warmth, pain, and stiffness. Late-stage disease is characterized by a release of cytokines and enzymes in the extracellular matrix that leads to degradation of cartiPSYCHONEUROIMMUNOLOGY, 4E VOLUME I
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II. GENERAL CONCEPTS OF NEURAL-IMMUNE INTERACTIONS A. Interactions between the Immune and Neuroendocrine Systems: Bi-directional Communication Pathways 1. Peripheral Immune System Signaling to the Central Nervous System Peripheral inflammation results in the production of a variety of inflammatory mediators including cytokines, which can signal the brain via several routes. Peripherally released cytokines modulate brain function and can produce fever and sickness behavior (loss of appetite, decreased locomotion, loss of interest in sex and social interactions, and depressed mood). Cytokines produced in the periphery can cross the blood-brain barrier in small amounts at leaky points (the circumventricular organs) or via specific active transport mechanisms (Banks, 2005). Cytokines can also signal the CNS by stimulation of the vagus nerve or through activation of second messengers such as nitric oxide or prostaglandins. In addition, cytokines can also be produced in the brain by glia, neurons, or macrophages and can influence neuronal cell death or survival. 2. CNS Stress Response Effects on the Immune Response: HPA Axis, Sympathetic, Parasympathetic, and Peripheral Nervous System Regulation of Immunity The nervous system regulates the immune system systemically through hormonal routes, regionally in immune organs, and locally at sites of inflammation (Webster et al., 2002b). Endogenous glucocorticoids (GCs) are essential physiological regulators of the immune response and inflammation. Exogenous GCs have been used for several decades as potent suppressors of overactive immune responses. Extensive research has demonstrated the powerful pharmacological and physiological effects of GCs on multiple aspects of immune cell function [reviewed in (Webster et al., 2002b)]. Pharmacological doses of GCs suppress the immune response, including innate immune, cellular, and humoral acquired immune responses. More recently it has been suggested that physiological levels of GCs are immunomodulatory and result in a shift of cytokine production from primarily pro-inflammatory to a primarily anti-inflammatory pattern. Such patterns of cytokine production can be categorized as TH1 or TH2, and roughly correspond to cellular or humoral patterns of immune responses, respectively. A TH1 pattern of cytokines is characterized by production of
largely pro-inflammatory IL-12, with a primarily cellular immune response. A TH2 pattern of immunity is characterized by production of IL-4 and IL-10, and is associated with a primarily humoral or antibody response. At physiological concentrations, GCs inhibit TH1 and enhance TH2 cytokine production (Elenkov and Chrousos, 1999). Thus, immune suppression by GCs provides an important mechanism to prevent the immune response from continuing unchecked. Activation of the stress response also results in increased neural output to peripheral tissues. The sympathetic, parasympathetic, and peripheral nervous systems play important roles in regulating the immune response. The sympathetic and parasympathetic nervous systems modulate inflammatory responses through regional innervation of immune organs including the spleen, thymus, and lymph nodes (Bellinger et al., 1991). In animal studies, sympathetic denervation can have different effects on regional inflammation depending on the site and mode of denervation (Fleshner and Laudenslager, 2004; Madden et al., 1994a; Madden et al., 1994b; Sanders and Kohm, 2002). Natural sympathetic denervation of the spleen that occurs with aging may play a role in some of the immunosuppression seen in aging (Madden et al., 1998). Sympathetic postganglionic neurons are also key in regulating the fluid extravasation component of the early inflammatory response (Green et al., 1998). The parasympathetic nervous system modulates immune responses at a regional level though the efferent fibers of the vagus nerve. The afferent fibers of the vagus nerve also signal the presence of peripheral inflammation to the brain. Thus, during inflammation in the peritoneum, cytokines such as IL-1 bind to IL-1 receptors in paraganglia cells located in the peritoneum, rapidly inducing early gene expression and increasing activity in vagal brain stem centers (Watkins and Maier, 1999). The main parasympathetic neurotransmitter is acetylcholine (ACh), which binds to two general cholinergic receptor sub-types: nicotinic and muscarinic cholinergic receptors. Enhanced parasympathetic tone results in increased ACh, which suppresses production of pro-inflammatory cytokines (Tracey, 2002). Activation of the parasympathetic cholinergic response and its subsequent suppression of inflammation through the vagus nerve has been termed the “cholinergic inflammatory reflex” (Tracey, 2002). Interruption of this important route by cutting the vagus nerve results in exacerbation of inflammation and shock (Tracey, 2002). At sites of peripheral inflammation, peripheral nerves regulate local inflammatory responses through release of neuropeptides that are largely pro-
8. The Neuroendocrine System and Rheumatoid Arthritis: Focus on the Hypothalamic-Pituitary-Adrenal Axis
inflammatory. The peripheral nervous system affects inflammation through neuropeptides, such as substance P (SP) or vasoactive intestinal polypeptide (VIP), a 29-amino acid peptide released from peripheral sensory neurons. These may be released directly from nerve endings and synapses at sites of inflammation, or they can be synthesized and released by immune cells depending on the type of inflammation involved. Peripheral neuropeptides may be pro- or anti-inflammatory. Thus, while SP is primarily pro-inflammatory, VIP is predominantly anti-inflammatory, inhibiting the production of proinflammatory cytokines (Pozo et al., 2000). As would be expected, VIP administration in animal models leads to clinical improvement and suppression of pro-inflammatory cytokine production from T-cells (Delgado et al., 2001; Foey et al., 2003). Studies have also shown that both peripheral sympathetic noradrenergic (NA) nerves and SP-containing nerves play a role in joint inflammation (Keeble and Brain, 2004). 3. Defining Stress and the Stress Response A wide range of physical, psychological, or immune/ inflammatory stimuli, including cytokines, can activate a series of neuroendocrine and neuronal responses, which produce a characteristic series of physiological responses that together comprise the physiological stress response [for review, see (Goldstein and McEwen, 2002)]. These include activation of the hypothalamic-pituitary-adrenal (HPA) axis and of the sympathetic nervous system. Activation of hypothalamic CRH stimulates the stress response, including secretion of ACTH from the pituitary and glucocorticoid secretion from the adrenal gland. Activation of central corticotrophin-releasing hormone (CRH) and the locus ceruleus produce behavioral effects of increased arousal and alertness. Sympathetic nervous system activation leads to increased heart rate, increased muscle blood flow, and sweating. Together these early behavioral and physiological responses comprise the stress or “fight or flight” response. The bi-directional communication between the immune system and the central nervous system (CNS), in which cytokines signal the brain and the brain responds by regulating the immune system in part through the anti-inflammatory effects of GCs released from the adrenal glands, constitutes the main hormonal negative feedback loop for CNS regulation of immunity (Figure 1) (Webster et al., 2002b). In addition to their role in regulating the immune system, GCs also downregulate the HPA axis itself, and are essential for the maintenance of several homeostatic mecha-
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nisms in the body, including the CNS, cardiovascular system, and metabolic homeostasis. A blunted HPA axis is associated with a wide range of autoimmune/inflammatory diseases across species (chickens, mice, rats, humans); and interruptions of the HPA axis in otherwise inflammatory-resistant hosts, through surgical interventions (adrenalectomy, hypophysectomy) or through pharmacological intervention with glucocorticoid antagonists (e.g., RU 486), renders otherwise inflammatory-resistant hosts highly susceptible to inflammation and increased mortality from septic shock [for a more detailed review, see (Webster and Sternberg, 2004)]. Stressful stimuli also activate brain-stem adrenergic pathways and the sympathetic nervous system outflow from the brainstem to the periphery. Several neuronal pathways project from the hypothalamus to noradrenergic areas in the brain stem, such as the locus ceruleus and A2 and C2 regions (Sawchenko et al., 1996), and thus activation of hypothalamic CRH can also stimulate these noradrenergic regions and sympathetic outflow to the periphery. In turn adrenergic outflow from the brain stem can stimulate the hypothalamus to secrete CRH (Figure 1). 4. Relationship between the Nature of the Stressor and the HPA Axis Response: Psychological versus Physical Stress, Acute versus Chronic Stress The components of the stress response that are activated vary with the type of stimulus to which the organism is exposed. Stressors can be categorized as being primarily physical in nature (illness, inflammation, exercise) or psychological (i.e., performance tasks). Different stressors yield different patterns of activation of brain stress response regions. The response to psychological stressors appears to be particularly dependent on the individual’s critical perception of the event (Ehlert and Straub, 1998). Additionally, even within the category of primarily physical stressors, the HPA axis response differs depending on the type of stressor. Thus, intermittent electrical foot shocks in rats activate different stress-responsive neurotransmitter regions and pathways within the brain as compared to a systemic cytokine (IL-1) challenge (Li et al., 1996). With regards to inflammatory stressors, the nature of the immune challenge also determines the degree of the HPA axis response (Nagano et al., 1999). The duration of the stressful stimulus is also an important qualitative and quantitative determinant of the HPA axis response. It is critical to consider the neuroendocrine consequences of any long-standing peripheral immune activation process when studying
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FIGURE 1 Schematic illustration of neural immune connections, including immune signaling of central nervous system via systemic routes and the vagus nerve (Vagus n.) and CNS regulation of immunity via the hypothalamicpituitary-adrenal (HPA) axis, sympathetic nervous system (SNS), parasympathetic nervous system, and peripheral nervous system (PNS). Asterisks within the brain represent cytokine expression within the CNS. Dotted lines represent negative regulatory pathways; solid lines represent positive regulatory pathways. Reprinted with permission from (Marques-Deak et al., 2005) (www.nature.com/mp). CRH, corticotrophin releasing hormone; AVP, arginine vasopressin; ACTH, adrenocorticotrophin hormone, SNS, sympathetic nervous system; PNS, peripheral nervous system; LC, locus ceruleus; A1, C1, A2, C2, brainstem adrenergic nucleii.
the HPA axis in chronic inflammatory conditions such as RA or erosive arthritis in animal models. Chronic stress stimulation results in readjustments of the neurotransmitter and neuroendocrine responses that are activated during acute stress. These physiological changes complicate data interpretation and make it difficult to establish causal relationships between HPA axis hyporeactivity and predisposition to inflammatory disease in the context of already established chronic inflammation. Thus, any observed differences between unaffected and diseased subjects may be a reflection of the illness.
Although not consistent across all rodent species, during chronic stress the control of ACTH secretion may shift from CRH to arginine vasopressin (AVP) in rats (Harbuz et al., 1997). This shift may be related to differential susceptibility of CRH and AVP secretion to negative feedback by corticosterone (Makino et al., 1995). CRH and AVP have synergistic actions as ACTH secretagogues; AVP significantly potentiates the stimulatory action of CRH on ACTH production. Chronic inflammatory conditions in humans are also associated with this shift in ACTH control from CRH to AVP. Thus, patients with multiple sclerosis and significant baseline hypercortisolemia have a blunted ACTH response to AVP with normal ACTH response to CRH. Of note, subjects in this study did not exhibit evidence of increased peripheral inflammation, such as elevated plasma sedimentation rates, or elevated IL-6, or IL-1β levels (Michelson et al., 1994). The neuroendocrine response pattern changes seen in chronic stress may represent central adaptation to a continuous exposure to the stimulus. It is also possible that peripheral immune signaling to and the activation of the CNS evolve as patterns of cytokine production change over the course of chronic inflammation. Certainly, patterns of cytokine production differ in peripheral blood mononuclear cells from patients with early versus chronic RA (Butrimiene et al., 2004; Kanik et al., 1998). In addition to a shift in the stress hormonal response pattern, there is a dampening of the stress response to acute stimulation in animals with chronic inflammation, which varies with the type of acute stressor studied (Aguilera et al., 1997; Shanks et al., 1998). Hypothalamic CRH mRNA expression changes in rats developing adjuvant arthritis (Aguilera et al., 1997). When the nature of the acute stressor is inflammatory, the blunted response is not observed (Harbuz et al., 1997). A pre-existing stressor may dampen the inflammatory response to an immune challenge. Thus, repeated psychological stress is associated with a decreased severity in collagen-induced arthritis in female Lewis (LEW/N) rats (Miller et al., 1995).
III. ANIMAL MODELS OF RHEUMATOID ARTHRITIS A. Animal Models of Neuroendocrine Responses and Resistance and Susceptibility to Chronic Erosive Arthritis Multiple animal models have been developed to study RA, which partially but incompletely mimic the human situation. RA is a multifactorial disease related
8. The Neuroendocrine System and Rheumatoid Arthritis: Focus on the Hypothalamic-Pituitary-Adrenal Axis
to an interaction of genetic susceptibility, infection, and environmental factors. Multiple antigenic and pro-inflammatory triggers have been used to induce RA in rats and mice, including adjuvant and streptococcal cell walls. The most widely used of these is collagen-induced arthritis (Holmdahl et al., 2002). Transgenic mouse models, such as TNFα transgenic mice, have also been developed (Campbell et al., 2001). Evidence from inbred rat strains indicate that a blunted HPA axis plays a role in autoimmune disorders including inflammatory arthritis. Lewis (LEW/N) rats with a hyporesponsive HPA axis are susceptible to autoimmune/inflammatory disease, while Fischer (F344/N) rats, which exhibit a hyperresponsive HPA axis, are relatively resistant to inflammation (Sternberg et al., 1989a; Sternberg et al., 1989b). Interruption of the HPA axis by a variety of methods including RU486, a GR antagonist, renders F344/N rats susceptible to autoimmune/inflammatory diseases (Sternberg et al., 1989a), and conversely, in LEW/N rats, reconstitution of the HPA axis by intracerebroventricular fetal hypothalamic tissue transplantation reverses their susceptibility to autoimmune disease (Misiewicz et al., 1997). Removal of endogenous GCs, through chemical or surgical adrenalectomy, results in increased severity of inflammation and decreased survival (Harbuz et al., 1993) in other animal models of RA, such as adjuvant arthritis, as well as in other autoimmune disease models (Mason et al., 1990). These animal models of RA have been useful in testing neuroendocrine agents as therapies for RA. Treatment with a non-peptide CRH antagonist diminishes synovitis and clinical joint scores in inflammatory arthritis in LEW/N rats, but has no effect on F344/N rats (Webster et al., 2002a). These results suggest that multiple endocrine pathways play a role in rheumatoid arthritis and that peripheral blockade of the pro-inflammatory effects of CRH may play a primary role in the beneficial effects of this agent. Estrogen also plays a role in RA development, and manipulations of the HPA axis have been used in animal models of RA. Ovariectomy in Sprague-Dawley rats increases the susceptibility to collagen-induced arthritis, as well as the severity of erosions and bone loss (Yamasaki et al., 2001), while estrogen replacement reversed this effect. Tamoxifen, an estrogen receptor antagonist, is anti-inflammatory in the carrageenan inflammation in LEW/N rats (Misiewicz et al., 1996), and inhibits receptor activation of NF-κB in human RA (Mitani et al., 2005), suggesting that further study of this category of agents may yield additional anti-inflammatory treatments for RA.
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IV. HPA AXIS FUNCTION FINDINGS IN RHEUMATOID ARTHRITIS PATIENTS As in animal models, accumulating evidence from human studies shows that neuroendocrine abnormalities exist in RA patients, suggesting a link between the neuroendocrine system and the development of human autoimmune disease.
A. HPA Axis Studies in Human Rheumatoid Arthritis Various methods have been used to assess HPA axis function in patients with RA, including plasma ACTH and cortisol levels measured at regular intervals over the circadian rhythm, and after CRH stimulation. 1. HPA Axis Activation Patterns in RA The anti-inflammatory effects of the glucocorticoids (GCs) have been known since the 1940s, and the Nobel Prize was awarded for their use in the treatment of RA in 1950 (Hench et al., 1949). However, it was not until the late 1980s that the important physiological role of glucocorticoids in regulating immunity and in pathogenesis of a susceptibility to inflammatory arthritis was recognized. Overall, RA patients exhibit a blunted HPA axis response (Chikanza et al., 1992; Gudbjornsson et al., 1996; Hall et al., 1994b; Kanik et al., 2000; Neeck et al., 1990; Straub et al., 2002b) and a shift in the circadian rhythm of cortisol production, with cortisol maximum and minimum shifted to earlier times in the day (Neeck et al., 1990). Some RA patients are reported to have increased ACTH, but normal cortisol levels compared to controls (Gudbjornsson et al., 1996; Hall et al., 1994b; Kanik et al., 2000), indicating a relative adrenal insensitivity to ACTH stimulation. RA patients also show disproportionately lower levels of cortisol in response to the pro-inflammatory cytokines IL-6 and TNF-α (Straub et al., 2002b). This suggests an under-responsive HPA axis to increased inflammatory drive. Generally, inappropriately low cortisol secretion is a typical feature of RA patients. It is unknown whether the HPA axis abnormalities in RA patients are merely a consequence of the disease or a predisposing factor. Manipulations of the HPA axis can also effect susceptibility to RA. RA activity is exacerbated by the inhibition of glucocorticoid synthesis with the 11-β hydroxylase inhibitor metyrapone (Panayi, 1992; Saldanha et al., 1986). Patients with Cushing’s disease (characterized by hyperproduction of cortisol) who undergo adrenalectomy, and therefore removal of endogenous GCs, show enhanced susceptibility to RA
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(Uthman and Senecal, 1995; Yakushiji et al., 1995). GCs have long been used as a treatment option in patients with RA. Prednisolone reduces the rate of RA disease progression, and joint destruction resumes when patients discontinue the use of the drug (Hickling et al., 1998; Kirwan, 1995). The development of more specific GC therapeutics, such as time-release formulas and drugs with lower toxicity, may help curb harmful side effects (Bijlsma et al., 2005). For example, selective GC receptor agonists preferentially induce transrepression of GR, which leads to repressed transcription of pro-inflammatory factors (Schacke et al., 2004). This suggests that GCs and their derivatives will continue to be a useful therapy in RA and that new preparations may increase their efficacy, while lowering side effects. 2. Genetic Polymorphisms in the HPA Axis Genes in RA Genetic polymorphisms have been reported in the CRH gene and the glucocorticoid receptor gene in human RA. Recent evidence indicates that CRH gene polymorphisms are present in RA patients and could contribute to RA susceptibility (Baerwald et al., 2000; Gonzalez-Gay et al., 2003). Although no functional abnormality of CRH was reported in these studies, CRH polymorphisms could be a useful genetic marker for RA susceptibility. Impaired glucocorticoid control of inflammation may also result from resistance at the level of the glucocorticoid receptor (GR)—a member of a superfamily of nuclear hormone receptors (including the progesterone, estrogen, androgen, mineralocorticoid, and thyroid hormone receptors) that reside in the cytoplasm or nucleus. When glucocorticoid hormone binds to the ligand-binding domain of the GR, the receptorhormone complex dimerizes and moves into the nucleus and, facilitated by many co-factors and accessory proteins, binds to DNA and activates or inhibits transcription and translation (Webster et al., 2002b). Abnormalities of any of these molecules may lead to impaired GR function and glucocorticoid resistance. There are two forms of the GR, α and β. GRβ is an inactive form of the GR that does not activate DNA (Bamberger et al., 1995). Enhanced expression of GRβ, polymorphisms or impaired function of the GRα, GRβ, or associated co-factors may all contribute to glucocorticoid resistance (DeRijk et al., 2002; Webster et al., 2002b). Glucocorticoid resistance has been increasingly reported in autoimmune/inflammatory allergic diseases [for review, see (Marques-Deak et al., 2005)]. GRβ over-expression may contribute to glucocorticoid insensitivity in RA (Chikanza, 2002). A GRβ polymor-
phism associated with enhanced stability of this receptor has also been reported in RA patients, suggesting a potential source of glucocorticoid resistance in this sub-population of RA patients (DeRijk et al., 2001). Finally, there is some evidence of alterations in GR number in RA patients (Schlaghecke et al., 1992). Some studies report a downregulation of GR number in the early course of the disease (Huisman et al., 2002; van Everdingen et al., 2002). However, studying RA patients previously treated with glucocorticoids may confound these findings, since glucocorticoids downregulate GR expression. Indeed, GC-treated RA patients show decreased GR density in lymphocytes, whereas untreated RA patients do not show changes in GR number when compared to healthy controls (Neeck et al., 2002). Given this finding, evidence of alterations in GC receptor number should be interpreted with caution in GC-treated RA patients.
B. Stress and Depression and RA 1. Stress and RA Anecdotal reports have long linked environmental stressors to precipitation or exacerbation of disease in RA. Minor daily stressors have been linked to increases in inflammation in RA (Affleck et al., 1987; Thomason et al., 1992), and a 5-year longitudinal study found that RA patients with higher daily stress levels had more bony erosions over time (Feigenbaum et al., 1979). Interestingly, major stressors do not appear to be linked to RA, and may even be associated with a decrease in disease activity (Potter and Zautra, 1997). Psychological stress is reported to exacerbate RA (Herrmann et al., 2000; Straub et al., 2005), and stress management may lead to reductions in pain in RA patients (Rhee et al., 2000). 2. Depression and RA More than 50% of patients with RA also experience symptoms of depression (Frank et al., 1988; MarquesDeak et al., 2005; Sternberg, 1993). The underlying mechanisms between these relationships are not well understood; however, recent studies showing dysregulations in the HPA axis in both RA and depressive disorders suggest that a common underlying neuroendocrine dysregulation may underlie both these disorders in patients who experience RA and depression, since both syndromes are associated with dysregulations of hypothalamic CRH responsiveness. RA patients who concurrently experience depressive symptoms and stress also had increased levels of the pro-inflammatory cytokine IL-6 in peripheral blood
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mononuclear cells (Zautra et al., 2004), supporting the hypothesis that an underlying biological process may predispose to both syndromes in some individuals. Indeed, the induction of depressive symptomatology in patients treated with IL-6 for other conditions (cancer, bone marrow suppression) and prevention of these symptoms by pre-treatment with anti-depressants (Musselman et al., 2001) raise the possibility that depression in RA may be, in part, secondary to elevated peripheral cytokine production. Other factors that may contribute to the association include pain and psychosocial factors (Marques-Deak et al., 2005). Chronic pain is often associated with both stress and depression (Blackburn-Munro and Blackburn-Munro, 2001), suggesting that the development of psychiatric symptoms in patients with RA may be partially due to chronic pain (Blalock and DeVellis, 1992). Psychosocial factors such as interpersonal stress may also contribute to neuroimmune dysregulation and worsening of disease severity in RA patients (Zautra et al., 1997).
V. OTHER NEUROENDOCRINE FACTORS IMPLICATED IN RA PATHOGENESIS A. Sex Hormones Females of all species show a higher incidence and/or severity of autoimmune/inflammatory disease compared to males, suggesting a role for sex hormones in the pathogenesis of the disease (Exploring the biological contributions to human health: Does sex matter? 2001). Conditions in which hormone levels are in flux are also associated with remissions or exacerbations of RA (Masi et al., 1995). Thus, pregnancy is associated with remission, while the postpartum period is associated with exacerbations of RA (Silman et al., 1992). During times of estrogen decline or insufficiency (i.e., postpartum and in menopausal women), the incidence of RA is increased. The severity of RA is also increased post-menopause, but this may be age-related rather than related to changes in sex hormone levels alone (Kuiper et al., 2001). The relationship between exogenous hormones, such as oral contraceptives, and rheumatoid arthritis disease progression and pathogenesis is unclear. Early evidence suggested that oral contraceptives were not protective against RA occurrence (Moskowitz et al., 1990), and a more recent study also failed to show that oral contraceptives influence RA expression (Drossaers-Bakker et al., 2002). Clinical trials of hormone replacement therapy showed no improvement in RA (Doran et al., 2004; Hall et al., 1994a; van den Brink et al., 1993). However, a population-based
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study found that oral contraceptives were associated with a decreased incidence of rheumatoid arthritis (Doran et al., 2004). Interestingly, this study also found that women who took oral contraceptives before 1970, when higher doses of estrogens and progestins were used, had a further lowering of risk to RA development. Importantly, synovial tissue from RA patients has been shown to express estrogen receptors (Ushiyama et al., 1995), suggesting that synovial tissue in RA could be responsive to fluctuating hormone levels. It is also possible that changing ratios of other hormones or their receptors in immune cells throughout development may contribute to changes in inflammatory disease expression. Animal studies show changes in ratios of estrogen and glucocorticoid receptors in Bcells throughout early development, with higher ratios of estrogen receptors compared to glucocorticoid receptors during puberty (Igarashi et al., 2001). Since estrogens are generally regarded as immunostimulatory [e.g., estrogen upregulates bcl-2, which interferes with induction of B cell tolerance (Bynoe et al., 2000)], this suggests the possibility that enhanced tissue sensitivity to the immunostimulatory effects of estrogen that occurs during puberty may account for some of the higher incidence for disease in post-pubertal females. In contrast, androgens are generally immunosuppressive (Cutolo et al., 2002). Low levels of androgens have been reported in both male and female RA patients (Cutolo et al., 2002; Masi et al., 2002; Tengstrand et al., 2002). These include reduced levels of dehydroepiandrostenedione (DHEA)/DHEA sulphate, and testosterone/dihydrotestosterone. Low levels of DHEA in RA patients correlates with low waking cortisol values and high levels of the proinflammatory cytokine IL-6 (Cutolo et al., 1999). There is also evidence that low levels of DHEA and a dissociation of cortisol and DHEA occur before the onset of RA in young premenopausal women (Masi et al., 1999). Administration of androgens to these patients improves RA symptoms (Booji et al., 1996). Recent studies have reported normal estrogen levels, and low serum androgen levels in RA patients have been reported (Cutolo et al., 2002; Spector et al., 1988), suggesting that an imbalance in these hormones may contribute to disease in some patients.
B. Sympathetic Nervous System Activation in RA Chemical sympathectomy or surgically cutting the sympathetic nerve in vivo has shown that the SNS plays an important role in regulating regional immu-
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nity in both animal models of inflammatory arthritis and in human RA. Sympathectomy diminishes inflammatory responses in an animal model of arthritis (Felten et al., 1992), and regional chemical sympathetic blockade improves symptoms in human RA (Levine et al., 1986). The primary neurotransmitter released from sympathetic nerves is norepinephrine, which acts through adrenergic receptors (Felten and Felten, 1988). The β2adrenergic receptor (β2AR), a classic 7 membrane Gprotein coupled receptor, is the main adrenergic receptor expressed on lymphocytes (Bishopric et al., 1980). Binding of β2AR by norepinephrine stimulates cAMP and activates protein kinase A, which in turn suppresses cytokine production. Removal of this inhibitory control results in enhanced immune responses. In contrast, stimulation of αAR enhances immune responses through activation of protein kinase C (PKC) (Bergmann and Sautner, 2002). RA patients exhibit several abnormalities of the SNS. These include a decreased β2AR density in blood mononuclear cells, which results in an increase of α1AR-mediated effects (Baerwald et al., 1992; Rouppe van der Voort et al., 2000; Wahle et al., 1999), and alterations in neuropeptide Y (NPY), a neuropeptide that is synthesized and/or released with norepinephrine from sympathetic neurons. Thus, NPY levels in serum correlate with symptom severity in RA patients, with higher levels associated with shorter durations of pain (Holmlund et al., 1991). Synovium from RA patients also shows a loss of NPY-containing fibers (Mapp et al., 1990; Miller et al., 2000). Finally, norepinephrine administration acts synergistically with cortisol to inhibit pro-inflammatory cytokine secretion from RA synoviocytes in vitro (Straub et al., 2002a).
C. Parasympathetic Nervous System in RA Although the parasympathetic nervous system has rarely been studied in RA patients, there is some evidence that parasympathetic regulation in RA may be impaired (Louthrenoo et al., 1999; Maule et al., 1997).
D. Peripheral Nervous System in RA Neuropeptides of the peripheral nervous system may be involved in RA pathogenesis. These include NPY, vasoactive intestinal peptide (VIP), substance P (SP), and calcitonin gene-related peptide (CGRP). SP is released from peripheral sensory nerves and has a pro-inflammatory effect on the immune system. Increased levels of SP have been shown in synovial fluid from RA patients (Agro and Stanisz, 1992). The
primary receptor for SP, the neurokinin 1 (NK1) receptor, is present in both normal synovium and in the synovial membrane of RA patients (Lambert et al., 1998). Evidence from animal models suggest that SP plays a role in joint inflammation (Keeble and Brain, 2004), indicating that SP antagonists may be useful therapeutic agents for RA. Specific NK1 receptor antagonists have been shown to reduce inflammation and pain in rodents, but have not been tested in humans (Keeble and Brain, 2004). The same sensory neurons that release SP also release CGRP, a 37-amino acid peptide. CGRP opposes the pro-inflammatory effects of SP. In rats, immunization with CGRP reduces the severity of adjuvantinduced lesions (Louis et al., 1990). Animal studies also report increased amounts of SP and CGRP in synovial fluid (Bileviciute et al., 1993). CGRP mRNA is contained in synovial cells from RA patients, and exogenous CGRP administration has an inhibitory effect on pro-inflammatory cytokines and matrix metalloproteinase (MMP) production in vitro (Takeba et al., 1999). Similar to CGRP, VIP mRNA is found in synovial cells from RA patients, and exogenous VIP has an inhibitory effect on pro-inflammatory cytokines, chemokines, and matrix metalloproteinase (MMP) production in vitro (Juarranz et al., 2004; Takeba et al., 1999). This suggests that VIP-related agents could play a therapeutic role in RA. Peripheral corticotropin releasing hormone (CRH) is present in higher concentrations in inflamed joints in Lewis compared to Fischer rats. While central CRH suppresses immune responses through activation of the HPA axis and release of glucocorticoids, peripheral CRH released at nerve terminals is pro-inflammatory and its immunoneutralization is associated with decreased cellular infiltration and volume of exudates in chronic inflammation (Karalis et al., 1991). Furthermore, treatment of rats with adjuvant arthritis with the non-peptide CRH antagonist antalarmin reduced arthritis scores by 50% (Webster et al., 2002a). The findings that neuropeptides influence RA pathology suggest that further investigations in their role in RA and inflammation could provide new avenues for treatment of the disease.
E. Prolactin Prolactin is a pro-inflammatory hormone released from the pituitary gland. Prolactin receptors are widely distributed and are found in the CNS, adrenals, and on lymphocytes. Studies in animal models of inflammatory arthritis and lupus have shown that prolactin antagonists inhibit disease activity (Berczi et al., 1984;
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Walker et al., 1998). Elevated prolactin levels have been reported in human RA patients (Chikanza et al., 1992; Ram et al., 2004), and increases in the prolactin diurnal rhythm coincide with RA disease activity. Although the therapeutic effects of prolactin have not been tested in human RA, studies in human SLE indicate that prolactin is elevated in SLE and prolactin inhibitors ameliorate disease course (Walker et al., 1998).
VI. SUMMARY Research in recent decades shows that the HPA axis, the SNS, and the parasympathetic and peripheral nervous systems all play an important role in regulating the peripheral immune/inflammatory response. Advances in our understanding of the molecular, biochemical, and neuroanatomical pathways by which the immune system and the CNS communicate also provide evidence that dysregulations of these connections are associated with and contribute to RA pathogenesis and disease expression. There is no simple cause-and-effect relationship between RA and the responsiveness of these neural and neuroendocrine systems, but dysregulation in the bi-directional communication between the periphery and these axes are certainly present in RA and are likely to contribute to susceptibility, course, and expression of disease. Findings in both animal and human studies show a downregulated HPA axis in RA. While there is no definitive evidence in humans that a hypoactive HPA axis causes or directly contributes to the development of RA, animal studies in which the HPA axis is interrupted do suggest a causal relationship. Recent studies showing glucocorticoid receptor polymorphisms and GC resistance in RA suggest that differences in receptor sensitivity may also be an important factor contributing to disease susceptibility and individual variability in expression of RA. Peripheral neuropeptides and sympathetic and parasympathetic nervous system factors may also contribute to RA pathology, and further exploration of the role of these peptides and neurotransmitters in human RA may lead to additional therapeutic options. Finally, sex hormones and their receptors also play an important role in disease predisposition and severity. These are reviewed elsewhere in this text and in more depth.
References Affleck, G., Pfeiffer, C., Tennen, H., and Fifield, J. (1987). Attributional processes in rheumatoid arthritis patients. Arthritis Rheum., 30 (8), 927–931.
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Agro, A., and Stanisz, A. M. (1992). Are lymphocytes a target for substance P modulation in arthritis? Semin. Arthritis Rheum., 21 (4), 252–258. Aguilera, G., Jessop, D. S., Harbuz, M. S., Kiss, A., and Lightman, S. L. (1997). Differential regulation of hypothalamic pituitary corticotropin releasing hormone receptors during development of adjuvant-induced arthritis in the rat. J. Endocrinol., 153 (2), 185–191. Alamanos, Y., and Drosos, A. A. (2005). Epidemiology of adult rheumatoid arthritis. Autoimmun. Rev., 4 (3), 130–136. Baerwald, C., Graefe, C., Muhl, C., Von Wichert, P., and Krause, A. (1992). Beta 2-adrenergic receptors on peripheral blood mononuclear cells in patients with rheumatic diseases. Eur. J. Clin. Invest., 22 (Suppl 1), 42–46. Baerwald, C. G., Mok, C. C., Tickly, M., Lau, C. S., Wordsworth, B. P., Ollier, B., et al. (2000). Corticotropin releasing hormone (CRH) promoter polymorphisms in various ethnic groups of patients with rheumatoid arthritis. Z. Rheumatol., 59 (1), 29–34. Bamberger, C. M., Bamberger, A. M., de Castro, M., and Chrousos, G. P. (1995). Glucocorticoid receptor beta, a potential endogenous inhibitor of glucocorticoid action in humans. J. Clin. Invest., 95 (6), 2435–2441. Banks, W. A. (2005). Blood-brain barrier transport of cytokines: A mechanism for neuropathology. Curr. Pharm. Des., 11 (8), 973–984. Barrera, P., Boerbooms, A. M., van de Putte, L. B., and van der Meer, J. W. (1996). Effects of antirheumatic agents on cytokines. Semin. Arthritis Rheum., 25 (4), 234–253. Bellinger, D. L., Lorton, D., Lubahn C., and Felten, D. L. (1991). Innervation of lympoid organs—association of nerves with cells of the immune system and their implications in disease. In R. Ader, D. L. Felten, N. Cohen (Eds.), Psychoneuroimmunology (3rd edition) (vol. 1, pp. 55–112). San Diego: Academic Press. Berczi, I., Nagy, E., Asa, S. L., and Kovacs, K. (1984). The influence of pituitary hormones on adjuvant arthritis. Arthritis Rheum., 27 (6), 682–688. Bergmann, M., and Sautner, T. (2002). Immunomodulatory effects of vasoactive catecholamines. Wien. Klin. Wochenschr., 114 (17–18), 752–761. Bijlsma, J. W., Saag, K. G., Buttgereit, F., and da Silva, J. A. (2005). Developments in glucocorticoid therapy. Rheum. Dis. Clin. North Am., 31 (1), 1–17, vii. Bileviciute, I., Lundeberg, T., Ekblom, A., and Theodorsson, E. (1993). Bilateral changes of substance P-, neurokinin A-, calcitonin gene-related peptide- and neuropeptide Y-like immunoreactivity in rat knee joint synovial fluid during acute monoarthritis. Neurosci. Lett., 153 (1), 37–40. Bishopric, N. H., Cohen, H. J., and Lefkowitz, R. J. (1980). Beta adrenergic receptors in lymphocyte subpopulations. J. Allergy Clin. Immunol., 65 (1), 29–33. Blackburn-Munro, G., and Blackburn-Munro, R. E. (2001). Chronic pain, chronic stress and depression: Coincidence or consequence? J. Neuroendocrinol., 13 (12), 1009–1023. Blalock, S. J., and DeVellis, R. F. (1992). Rheumatoid arthritis and depression: An overview. Bull. Rheum. Dis., 41 (1), 6–8. Booji, A., Biewenga-Booji, C. M., Huber-Bruning, O., Cornelis, C., Jacobs, J. W., and Bijlsma, J. W. (1996). Androgens as adjuvant treatment in postmenopausal female patients with rheumatoid arthritis. Ann. Rheum. Dis., 55 (11), 811–815. Butrimiene, I., Jarmalaite, S., Ranceva, J., Venalis, A., Jasiuleviciute, L., and Zvirbliene, A. (2004). Different cytokine profiles in patients with chronic and acute reactive arthritis. Rheumatology (Oxford), 43 (10), 1300–1304.
202
I. Neural and Endocrine Effects on Immunity
Bynoe, M. S., Grimaldi, C. M., and Diamond, B. (2000). Estrogen up-regulates bcl-2 and blocks tolerance induction of naive b cells. Proc. Natl. Acad. Sci. USA, 97 (6), 2703–2708. Campbell, I. K., O’Donnell, K., Lawlor, K. E., and Wicks, I. P. (2001). Severe inflammatory arthritis and lymphadenopathy in the absence of TNF. J. Clin. Invest., 107 (12), 1519–1527. Chikanza, I. C. (2002). Mechanisms of corticosteroid resistance in rheumatoid arthritis: A putative role for the corticosteroid receptor beta isoform. Ann. N. Y. Acad. Sci., 966, 39–48. Chikanza, I. C., Kingsley, G., and Panayi, G. S. (1995). Peripheral blood and synovial fluid monocyte expression of interleukin 1 alpha and 1 beta during active rheumatoid arthritis. J. Rheumatol., 22 (4), 600–606. Chikanza, I. C., Petrou, P., Kingsley, G., Chrousos, G., and Panayi, G. S. (1992). Defective hypothalamic response to immune and inflammatory stimuli in patients with rheumatoid arthritis. Arthritis Rheum., 35 (11), 1281–1288. Cutolo, M., Foppiani, L., Prete, C., Ballarino, P., Sulli, A., Villaggio, B., et al. (1999). Hypothalamic-pituitary-adrenocortical axis function in premenopausal women with rheumatoid arthritis not treated with glucocorticoids. J. Rheumatol., 26 (2), 282– 288. Cutolo, M., Seriolo, B., Villaggio, B., Pizzorni, C., Craviotto, C., and Sulli, A. (2002). Androgens and estrogens modulate the immune and inflammatory responses in rheumatoid arthritis. Ann. N. Y. Acad. Sci., 966, 131–142. Delgado, M., Abad, C., Martinez, C., Leceta, J., and Gomariz, R. P. (2001). Vasoactive intestinal peptide prevents experimental arthritis by downregulating both autoimmune and inflammatory components of the disease. Nat. Med., 7 (5), 563–568. DeRijk, R. H., Schaaf, M., and de Kloet, E. R. (2002). Glucocorticoid receptor variants: Clinical implications. J. Steroid Biochem. Mol. Biol., 81 (2), 103–122. DeRijk, R. H., Schaaf, M. J., Turner, G., Datson, N. A., Vreugdenhil, E., Cidlowski, J., et al. (2001). A human glucocorticoid receptor gene variant that increases the stability of the glucocorticoid receptor beta-isoform mRNA is associated with rheumatoid arthritis. J. Rheumatol., 28 (11), 2383–2388. Doran, M. F., Crowson, C. S., O’Fallon, W. M., and Gabriel, S. E. (2004). The effect of oral contraceptives and estrogen replacement therapy on the risk of rheumatoid arthritis: A population based study. J. Rheumatol., 31 (2), 207–213. Drossaers-Bakker, K. W., Zwinderman, A. H., van Zeben, D., Breedveld, F. C., and Hazes, J. M. (2002). Pregnancy and oral contraceptive use do not significantly influence outcome in long term rheumatoid arthritis. Ann. Rheum. Dis., 61 (5), 405–408. Ehlert, U., and Straub, R. (1998). Physiological and emotional response to psychological stressors in psychiatric and psychosomatic disorders. Ann. N. Y. Acad. Sci., 851, 477–486. Elenkov, I. J., and Chrousos, G. P. (1999). Stress, cytokine patterns and susceptibility to disease. Baillieres Best Pract. Res. Clin. Endocrinol. Metab., 13 (4), 583–595. Exploring the biological contributions to human health: Does sex matter? (2001). Washington, DC: National Academy Press. Feigenbaum, S. L., Masi, A. T., and Kaplan, S. B. (1979). Prognosis in rheumatoid arthritis. A longitudinal study of newly diagnosed younger adult patients. Am. J. Med., 66 (3), 377–384. Felten, D. L., and Felten, S. Y. (1988). Sympathetic noradrenergic innervation of immune organs. Brain Behav. Immun., 2 (4), 293–300. Felten, D. L., Felten, S. Y., Bellinger, D. L., and Lorton, D. (1992). Noradrenergic and peptidergic innervation of secondary lymphoid organs: Role in experimental rheumatoid arthritis. Eur. J. Clin. Invest. (22 Suppl 1), 37–41.
Fleshner, M., and Laudenslager, M. L. (2004). Psychoneuroimmunology: Then and now. Behav. Cogn. Neurosci. Rev., 3 (2), 114– 130. Foey, A. D., Field, S., Ahmed, S., Jain, A., Feldmann, M., Brennan, F. M., et al. (2003). Impact of vip and camp on the regulation of TNF-alpha and IL-10 production: Implications for rheumatoid arthritis. Arthritis. Res. Ther., 5 (6), R317–R328. Frank, R. G., Beck, N. C., Parker, J. C., Kashani, J. H., Elliott, T. R., Haut, A. E., et al. (1988). Depression in rheumatoid arthritis. J. Rheumatol., 15 (6), 920–925. Goldstein, D. S., and McEwen, B. (2002). Allostasis, homeostats, and the nature of stress. Stress, 5 (1), 55–58. Gonzalez-Gay, M. A., Hajeer, A. H., Garcia-Porrua, C., Dababneh, A., Amoli, M. M., Botana, M. A., et al. (2003). Corticotropinreleasing hormone promoter polymorphisms in patients with rheumatoid arthritis from Northwest Spain. J. Rheumatol., 30 (5), 913–917. Green, P. G., Miao, F. J., Strausbaugh, H., Heller, P., Janig, W., and Levine, J. D. (1998). Endocrine and vagal controls of sympathetically dependent neurogenic inflammation. Ann. N. Y. Acad. Sci., 840, 282–288. Gudbjornsson, B., Skogseid, B., Oberg, K., Wide, L., and Hallgren, R. (1996). Intact adrenocorticotropic hormone secretion but impaired cortisol response in patients with active rheumatoid arthritis. Effect of glucocorticoids. J. Rheumatol., 23 (4), 596–602. Hall, G. M., Daniels, M., Huskisson, E. C., and Spector, T. D. (1994a). A randomised controlled trial of the effect of hormone replacement therapy on disease activity in postmenopausal rheumatoid arthritis. Ann. Rheum. Dis., 53 (2), 112–116. Hall, J., Morand, E. F., Medbak, S., Zaman, M., Perry, L., Goulding, N. J., et al. (1994b). Abnormal hypothalamic-pituitary-adrenal axis function in rheumatoid arthritis. Effects of nonsteroidal antiinflammatory drugs and water immersion. Arthritis. Rheum., 37 (8), 1132–1137. Harbuz, M. S., Conde, G. L., Marti, O., Lightman, S. L., and Jessop, D. S. (1997). The hypothalamic-pituitary-adrenal axis in autoimmunity. Ann. N. Y. Acad. Sci., 823, 214–224. Harbuz, M. S., Rees, R. G., and Lightman, S. L. (1993). HPA axis responses to acute stress and adrenalectomy during adjuvantinduced arthritis in the rat. Am. J. Physiol., 264 (1 Pt 2), R179–R185. Harle, P., Bongartz, T., Scholmerich, J., Muller-Ladner, U., and Straub, R. H. (2005). Predictive and potentially predictive factors in early arthritis: A multidisciplinary approach. Rheumatology (Oxford), 44 (4), 426–433. Hench P. S., Kendall, E. C., Slocumb, C. H., and Polley H. F. (1949). The effect of a hormone of the adrenal cortex (17-hydroxy-11dehydrocorticosterone: Compound e) and of pituitary adrenocorticotrophic hormone on rheumatoid arthritis: Preliminary report. Proceedings of the Staff Meeting of Mayo Clinic, 24, 181–197. Herrmann, M., Scholmerich, J., and Straub, R. H. (2000). Stress and rheumatic diseases. Rheum. Dis. Clin. North Am., 26 (4), viii, 737–763. Hickling, P., Jacoby, R. K., and Kirwan, J. R. (1998). Joint destruction after glucocorticoids are withdrawn in early rheumatoid arthritis. Arthritis and rheumatism council low dose glucocorticoid study group. Br. J. Rheumatol., 37 (9), 930–936. Holmdahl, R., Bockermann, R., Backlund, J., and Yamada, H. (2002). The molecular pathogenesis of collagen-induced arthritis in mice—a model for rheumatoid arthritis. Ageing Res. Rev., 1 (1), 135–147. Holmlund, A., Ekblom, A., Hansson, P., Lind, J., Lundeberg, T., and Theodorsson, E. (1991). Concentrations of neuropeptides sub-
8. The Neuroendocrine System and Rheumatoid Arthritis: Focus on the Hypothalamic-Pituitary-Adrenal Axis stance P, neurokinin A, calcitonin gene-related peptide, neuropeptide Y and vasoactive intestinal polypeptide in synovial fluid of the human temporomandibular joint. A correlation with symptoms, signs and arthroscopic findings. Int. J. Oral Maxillofac. Surg., 20 (4), 228–231. Huisman, A. M., Van Everdingen, A. A., Wenting, M. J., Siewertsz Van Reesema, D. R., Lafeber, F. P., Jacobs, J. W., et al. (2002). Glucocorticoid receptor downregulation in early diagnosed rheumatoid arthritis. Ann. N. Y. Acad. Sci., 966, 64–67. Igarashi, H., Kouro, T., Yokota, T., Comp, P. C., and Kincade, P. W. (2001). Age and stage dependency of estrogen receptor expression by lymphocyte precursors. Proc. Natl. Acad. Sci. USA, 98 (26), 15131–15136. Juarranz, M. G., Santiago, B., Torroba, M., Gutierrez-Canas, I., Palao, G., Galindo, M., et al. (2004). Vasoactive intestinal peptide modulates proinflammatory mediator synthesis in osteoarthritic and rheumatoid synovial cells. Rheumatology (Oxford), 43 (4), 416–422. Kanik, K. S., Chrousos, G. P., Schumacher, H. R., Crane, M. L., Yarboro, C. H., and Wilder, R. L. (2000). Adrenocorticotropin, glucocorticoid, and androgen secretion in patients with new onset synovitis/rheumatoid arthritis: Relations with indices of inflammation. J. Clin. Endocrinol. Metab., 85 (4), 1461–1466. Kanik, K. S., Hagiwara, E., Yarboro, C. H., Schumacher, H. R., Wilder, R. L., and Klinman, D. M. (1998). Distinct patterns of cytokine secretion characterize new onset synovitis versus chronic rheumatoid arthritis. J. Rheumatol., 25 (1), 16–22. Karalis, K., Sano, H., Redwine, J., Listwak, S., Wilder, R. L., and Chrousos, G. P. (1991). Autocrine or paracrine inflammatory actions of corticotropin-releasing hormone in vivo. Science, 254 (5030), 421–423. Keeble, J. E., and Brain, S. D. (2004). A role for substance P in arthritis? Neurosci. Lett., 361 (1–3), 176–179. Kirwan, J. R. (1995). The effect of glucocorticoids on joint destruction in rheumatoid arthritis. The Arthritis and Rheumatism Council Low-dose Glucocorticoid Study Group. N. Engl. J. Med., 333 (3), 142–146. Kuiper, S., van Gestel, A. M., Swinkels, H. L., de Boo, T. M., da Silva, J. A., and van Riel, P. L. (2001). Influence of sex, age, and menopausal state on the course of early rheumatoid arthritis. J. Rheumatol., 28 (8), 1809–1816. Lambert, N., Lescoulie, P. L., Yassine-Diab, B., Enault, G., Mazieres, B., De Preval, C., et al. (1998). Substance P enhances cytokineinduced vascular cell adhesion molecule-1 (VCAM-1) expression on cultured rheumatoid fibroblast-like synoviocytes. Clin. Exp. Immunol., 113 (2), 269–275. Levine, J. D., Dardick, S. J., Roizen, M. F., Helms, C., and Basbaum, A. I. (1986). Contribution of sensory afferents and sympathetic efferents to joint injury in experimental arthritis. J. Neurosci., 6 (12), 3423–3429. Li, H. Y., Ericsson, A., and Sawchenko, P. E. (1996). Distinct mechanisms underlie activation of hypothalamic neurosecretory neurons and their medullary catecholaminergic afferents in categorically different stress paradigms. Proc. Natl. Acad. Sci. USA, 93 (6), 2359–2364. Louis, S. M., Johnstone, D., Millest, A. J., Russell, N. J., and Dockray, G. J. (1990). Immunization with calcitonin gene-related peptide reduces the inflammatory response to adjuvant arthritis in the rat. Neuroscience, 39 (3), 727–731. Louthrenoo, W., Ruttanaumpawan, P., Aramrattana, A., and Sukitawut, W. (1999). Cardiovascular autonomic nervous system dysfunction in patients with rheumatoid arthritis and systemic lupus erythematosus. QJM, 92 (2), 97–102.
203
MacGregor, A. J., Snieder, H., Rigby, A. S., Koskenvuo, M., Kaprio, J., Aho, K., et al. (2000). Characterizing the quantitative genetic contribution to rheumatoid arthritis using data from twins. Arthritis Rheum., 43 (1), 30–37. Madden, K. S., Felten, S. Y., Felten, D. L., Hardy, C. A., and Livnat, S. (1994a). Sympathetic nervous system modulation of the immune system. Ii. Induction of lymphocyte proliferation and migration in vivo by chemical sympathectomy. J. Neuroimmunol., 49 (1–2), 67–75. Madden, K. S., Moynihan, J. A., Brenner, G. J., Felten, S. Y., Felten, D. L., and Livnat, S. (1994b). Sympathetic nervous system modulation of the immune system. Iii. Alterations in T and B cell proliferation and differentiation in vitro following chemical sympathectomy. J. Neuroimmunol., 49 (1–2), 77–87. Madden, K. S., Thyagarajan, S., and Felten, D. L. (1998). Alterations in sympathetic noradrenergic innervation in lymphoid organs with age. Ann. N. Y. Acad. Sci., 840, 262–268. Maini, R. N., Breedveld, F. C., Kalden, J. R., Smolen, J. S., Furst, D., Weisman, M. H., et al. (2004). Sustained improvement over two years in physical function, structural damage, and signs and symptoms among patients with rheumatoid arthritis treated with infliximab and methotrexate. Arthritis Rheum., 50 (4), 1051–1065. Makino, S., Smith, M. A., and Gold, P. W. (1995). Increased expression of corticotropin-releasing hormone and vasopressin messenger ribonucleic acid (mRNA) in the hypothalamic paraventricular nucleus during repeated stress: Association with reduction in glucocorticoid receptor mRNA levels. Endocrinology, 136 (8), 3299–3309. Mapp, P. I., Kidd, B. L., Gibson, S. J., Terry, J. M., Revell, P. A., Ibrahim, N. B., et al. (1990). Substance P-, calcitonin generelated peptide- and c-flanking peptide of neuropeptide Yimmunoreactive fibres are present in normal synovium but depleted in patients with rheumatoid arthritis. Neuroscience, 37 (1), 143–153. Marques-Deak, A., Cizza, G., and Sternberg, E. (2005). Brain-immune interactions and disease susceptibility. Mol. Psychiatry, 10 (3), 239–250. Masi, A. T., Chatterton, R. T., and Aldag, J. C. (1999). Perturbations of hypothalamic-pituitary-gonadal axis and adrenal androgen functions in rheumatoid arthritis: An odyssey of hormonal relationships to the disease. Ann. N. Y. Acad. Sci., 876, 53–62; discussion 62–63. Masi, A. T., Chatterton, R. T., Aldag, J. C., and Malamet, R. L. (2002). Perspectives on the relationship of adrenal steroids to rheumatoid arthritis. Ann. N. Y. Acad. Sci., 966, 1–12. Masi, A. T., Feigenbaum, S. L., and Chatterton, R. T. (1995). Hormonal and pregnancy relationships to rheumatoid arthritis: Convergent effects with immunologic and microvascular systems. Semin. Arthritis Rheum., 25 (1), 1–27. Mason, D., MacPhee, I., and Antoni, F. (1990). The role of the neuroendocrine system in determining genetic susceptibility to experimental allergic encephalomyelitis in the rat. Immunology, 70 (1), 1–5. Maule, S., Quadri, R., Mirante, D., Pellerito, R. A., Marucco, E., Marinone, C., et al. (1997). Autonomic nervous dysfunction in systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA): Possible pathogenic role of autoantibodies to autonomic nervous structures. Clin. Exp. Immunol., 110 (3), 423–427. Michelson, D., Stone, L., Galliven, E., Magiakou, M. A., Chrousos, G. P., Sternberg, E. M., et al. (1994). Multiple sclerosis is associated with alterations in hypothalamic-pituitary-adrenal axis function. J. Clin. Endocrinol. Metab., 79 (3), 848–853.
204
I. Neural and Endocrine Effects on Immunity
Miller, L. E., Justen, H. P., Scholmerich, J., and Straub, R. H. (2000). The loss of sympathetic nerve fibers in the synovial tissue of patients with rheumatoid arthritis is accompanied by increased norepinephrine release from synovial macrophages. FASEB J., 14 (13), 2097–2107. Miller, S. C., Rapier, S. H., Holtsclaw, L. I., and Turner, B. B. (1995). Effects of psychological stress on joint inflammation and adrenal function during induction of arthritis in the Lewis rat. Neuroimmunomodulation, 2 (6), 329–338. Misiewicz, B., Griebler, C., Gomez, M., Raybourne, R., Zelazowska, E., Gold, P. W., et al. (1996). The estrogen antagonist tamoxifen inhibits carrageenan induced inflammation in Lew/n female rats. Life Sci., 58 (16), PL281–286. Misiewicz, B., Poltorak, M., Raybourne, R. B., Gomez, M., Listwak, S., and Sternberg, E. M. (1997). Intracerebroventricular transplantation of embryonic neuronal tissue from inflammatory resistant into inflammatory susceptible rats suppresses specific components of inflammation. Exp. Neurol., 146 (2), 305–314. Mitani, M., Miura, Y., Saura, R., Kitagawa, A., Fukuyama, T., Hashiramoto, A., et al. (2005). Estrogen specifically stimulates expression and production of osteoprotegerin from rheumatoid synovial fibroblasts. Int. J. Mol. Med., 15 (5), 827–832. Moskowitz, M. A., Jick, S. S., Burnside, S., Wallis, W. J., Dickson, J. F., Hunter, J. R., et al. (1990). The relationship of oral contraceptive use to rheumatoid arthritis. Epidemiology, 1 (2), 153–156. Musselman, D. L., Lawson, D. H., Gumnick, J. F., Manatunga, A. K., Penna, S., Goodkin, R. S., et al. (2001). Paroxetine for the prevention of depression induced by high-dose interferon alfa. N. Engl. J. Med., 344 (13), 961–966. Nagano, I., Takao, T., Nanamiya, W., Takemura, T., Nishiyama, M., Asaba, K., et al. (1999). Differential effects of one and repeated endotoxin treatment on pituitary-adrenocortical hormones in the mouse: Role of interleukin-1 and tumor necrosis factor-alpha. Neuroimmunomodulation, 6 (4), 284–292. Neeck, G., Federlin, K., Graef, V., Rusch, D., and Schmidt, K. L. (1990). Adrenal secretion of cortisol in patients with rheumatoid arthritis. J. Rheumatol., 17 (1), 24–29. Neeck, G., Kluter, A., Dotzlaw, H., and Eggert, M. (2002). Involvement of the glucocorticoid receptor in the pathogenesis of rheumatoid arthritis. Ann. N. Y. Acad. Sci., 966, 491–495. Panayi, G. S. (1992). Neuroendocrine modulation of disease expression in rheumatoid arthritis. Eular. Congress Reports, 2, 2–12. Potter, P. T., and Zautra, A. J. (1997). Stressful life events’ effects on rheumatoid arthritis disease activity. J. Consult. Clin. Psychol., 65 (2), 319–323. Pozo, D., Delgado, M., Martinez, M., Guerrero, J. M., Leceta, J., Gomariz, R. P., et al. (2000). Immunobiology of vasoactive intestinal peptide (VIP). Immunol. Today, 21 (1), 7–11. Ram, S., Blumberg, D., Newton, P., Anderson, N. R., and Gama, R. (2004). Raised serum prolactin in rheumatoid arthritis: Genuine or laboratory artifact? Rheumatology (Oxford), 43 (10), 1272–1274. Rhee, S. H., Parker, J. C., Smarr, K. L., Petroski, G. F., Johnson, J. C., Hewett, J. E., et al. (2000). Stress management in rheumatoid arthritis: What is the underlying mechanism? Arthritis Care Res., 13 (6), 435–442. Rouppe van der Voort, C., Kavelaars, A., van de Pol, M., and Heijnen, C. J. (2000). Noradrenaline induces phosphorylation of ERK-2 in human peripheral blood mononuclear cells after induction of alpha(1)-adrenergic receptors. J. Neuroimmunol., 108 (1–2), 82–91. Saldanha, C., Tougas, G., and Grace, E. (1986). Evidence for antiinflammatory effect of normal circulating plasma cortisol. Clin. Exp. Rheumatol., 4 (4), 365–366.
Sanders, V. M., and Kohm, A. P. (2002). Sympathetic nervous system interaction with the immune system. Int. Rev. Neurobiol., 52, 17–41. Sawchenko, P. E., Brown, E. R., Chan, R. K., Ericsson, A., Li, H. Y., Roland, B. L., et al. (1996). The paraventricular nucleus of the hypothalamus and the functional neuroanatomy of visceromotor responses to stress. Prog. Brain Res., 107, 201–222. Saxne, T., Palladino, M. A., Jr., Heinegard, D., Talal, N., and Wollheim, F. A. (1988). Detection of tumor necrosis factor alpha but not tumor necrosis factor beta in rheumatoid arthritis synovial fluid and serum. Arthritis Rheum., 31 (8), 1041–1045. Schacke, H., Schottelius, A., Docke, W. D., Strehlke, P., Jaroch, S., Schmees, N., et al. (2004). Dissociation of transactivation from transrepression by a selective glucocorticoid receptor agonist leads to separation of therapeutic effects from side effects. Proc. Natl. Acad. Sci. USA, 101 (1), 227–232. Schiff, M. H. (2004). Durability and rapidity of response to anakinra in patients with rheumatoid arthritis. Drugs, 64 (22), 2493–2501. Schlaghecke, R., Kornely, E., Wollenhaupt, J., and Specker, C. (1992). Glucocorticoid receptors in rheumatoid arthritis. Arthritis Rheum., 35 (7), 740–744. Shanks, N., Harbuz, M. S., Jessop, D. S., Perks, P., Moore, P. M., and Lightman, S. L. (1998). Inflammatory disease as chronic stress. Ann. N. Y. Acad. Sci., 840, 599–607. Silman, A., Kay, A., and Brennan, P. (1992). Timing of pregnancy in relation to the onset of rheumatoid arthritis. Arthritis Rheum., 35 (2), 152–155. Silman, A. J., MacGregor, A. J., Thomson, W., Holligan, S., Carthy, D., Farhan, A., et al. (1993). Twin concordance rates for rheumatoid arthritis: Results from a nationwide study. Br. J. Rheumatol., 32 (10), 903–907. Spector, T. D., Perry, L. A., Tubb, G., Silman, A. J., and Huskisson, E. C. (1988). Low free testosterone levels in rheumatoid arthritis. Ann. Rheum. Dis., 47 (1), 65–68. Sternberg, E. M. (1993). Hyperimmune fatigue syndromes: Diseases of the stress response? J. Rheumatol., 20 (3), 418–421. Sternberg, E. M., Hill, J. M., Chrousos, G. P., Kamilaris, T., Listwak, S. J., Gold, P. W., et al. (1989a). Inflammatory mediator-induced hypothalamic-pituitary-adrenal axis activation is defective in streptococcal cell wall arthritis-susceptible Lewis rats. Proc. Natl. Acad. Sci. USA, 86 (7), 2374–2378. Sternberg, E. M., Young, W. S., 3rd, Bernardini, R., Calogero, A. E., Chrousos, G. P., Gold, P. W., et al. (1989b). A central nervous system defect in biosynthesis of corticotropin-releasing hormone is associated with susceptibility to streptococcal cell wall-induced arthritis in Lewis rats. Proc. Natl. Acad. Sci. USA, 86 (12), 4771–4775. Straub, R. H., Dhabhar, F. S., Bijlsma, J. W., and Cutolo, M. (2005). How psychological stress via hormones and nerve fibers may exacerbate rheumatoid arthritis. Arthritis Rheum., 52 (1), 16–26. Straub, R. H., Gunzler, C., Miller, L. E., Cutolo, M., Scholmerich, J., and Schill, S. (2002a). Anti-inflammatory cooperativity of corticosteroids and norepinephrine in rheumatoid arthritis synovial tissue in vivo and in vitro. FASEB J., 16 (9), 993–1000. Straub, R. H., Paimela, L., Peltomaa, R., Scholmerich, J., and Leirisalo-Repo, M. (2002b). Inadequately low serum levels of steroid hormones in relation to interleukin-6 and tumor necrosis factor in untreated patients with early rheumatoid arthritis and reactive arthritis. Arthritis Rheum., 46 (3), 654–662. Takeba, Y., Suzuki, N., Kaneko, A., Asai, T., and Sakane, T. (1999). Evidence for neural regulation of inflammatory synovial cell functions by secreting calcitonin gene-related peptide and vasoactive intestinal peptide in patients with rheumatoid arthritis. Arthritis Rheum., 42 (11), 2418–2429.
8. The Neuroendocrine System and Rheumatoid Arthritis: Focus on the Hypothalamic-Pituitary-Adrenal Axis Tengstrand, B., Carlstrom, K., and Hafstrom, I. (2002). Bioavailable testosterone in men with rheumatoid arthritis-high frequency of hypogonadism. Rheumatology (Oxford), 41 (3), 285–289. Thomason, B. T., Brantley, P. J., Jones, G. N., Dyer, H. R., and Morris, J. L. (1992). The relation between stress and disease activity in rheumatoid arthritis. J. Behav. Med., 15 (2), 215–220. Thorbecke, G. J., Shah, R., Leu, C. H., Kuruvilla, A. P., Hardison, A. M., and Palladino, M. A. (1992). Involvement of endogenous tumor necrosis factor alpha and transforming growth factor beta during induction of collagen type II arthritis in mice. Proc. Natl. Acad. Sci. USA, 89 (16), 7375–7379. Tracey, K. J. (2002). The inflammatory reflex. Nature, 420 (6917), 853–859. Ushiyama, T., Inoue, K., and Nishioka, J. (1995). Expression of estrogen receptor related protein (p29) and estradiol binding in human arthritic synovium. J. Rheumatol., 22 (3), 421–426. Uthman, I., and Senecal, J. L. (1995). Onset of rheumatoid arthritis after surgical treatment of Cushing’s disease. J. Rheumatol., 22 (10), 1964–1966. van den Brink, H. R., van Everdingen, A. A., van Wijk, M. J., Jacobs, J. W., and Bijlsma, J. W. (1993). Adjuvant estrogen therapy does not improve disease activity in postmenopausal patients with rheumatoid arthritis. Ann. Rheum. Dis., 52 (12), 862–865. van Everdingen, A. A., Huisman, A. M., Wenting, M. J., van Reesema, S., Jacobs, J. W., and Bijlsma, J. W. (2002). Down regulation of glucocorticoid receptors in early-diagnosed rheumatoid arthritis. Clin. Exp. Rheumatol., 20 (4), 463–468. Wahle, M., Krause, A., Ulrichs, T., Jonas, D., von Wichert, P., Burmester, G. R., et al. (1999). Disease activity related catecholamine response of lymphocytes from patients with rheumatoid arthritis. Ann. N. Y. Acad. Sci., 876, 287–296. Walker, S. E., McMurray, R. W., Houri, J. M., Allen, S. H., Keisler, D., Sharp, G. C., et al. (1998). Effects of prolactin in stimulating disease activity in systemic lupus erythematosus. Ann. N. Y. Acad. Sci., 840, 762–772. Watkins, L. R., and Maier, S. F. (1999). Implications of immune-tobrain communication for sickness and pain. Proc. Natl. Acad. Sci. USA, 96 (14), 7710–7713.
205
Webster, E. L., Barrientos, R. M., Contoreggi, C., Isaac, M. G., Ligier, S., Gabry, K. E., et al. (2002a). Corticotropin releasing hormone (CRH) antagonist attenuates adjuvant induced arthritis: Role of CRH in peripheral inflammation. J. Rheumatol., 29 (6), 1252– 1261. Webster, J. I., and Sternberg, E. M. (2004). Role of the hypothalamicpituitary-adrenal axis, glucocorticoids and glucocorticoid receptors in toxic sequelae of exposure to bacterial and viral products. J. Endocrinol., 181 (2), 207–221. Webster, J. I., Tonelli, L., and Sternberg, E. M. (2002b). Neuroendocrine regulation of immunity. Annu. Rev. Immunol., 20, 125–163. Wilder, R. L., Remmers, E. F., Kawahito, Y., Gulko, P. S., Cannon, G. W., and Griffiths, M. M. (1999). Genetic factors regulating experimental arthritis in mice and rats. Curr. Dir. Autoimmun., 1, 121–165. Williams, R. O., Feldmann, M., and Maini, R. N. (1992). Anti-tumor necrosis factor ameliorates joint disease in murine collageninduced arthritis. Proc. Natl. Acad. Sci. USA, 89 (20), 9784–9788. Yakushiji, F., Kita, M., Hiroi, N., Ueshiba, H., Monma, I., and Miyachi, Y. (1995). Exacerbation of rheumatoid arthritis after removal of adrenal adenoma in Cushing’s syndrome. Endocr. J., 42 (2), 219–223. Yamasaki, D., Enokida, M., Okano, T., Hagino, H., and Teshima, R. (2001). Effects of ovariectomy and estrogen replacement therapy on arthritis and bone mineral density in rats with collageninduced arthritis. Bone, 28 (6), 634–640. Zautra, A. J., Hoffman, J., Potter, P., Matt, K. S., Yocum, D., and Castro, L. (1997). Examination of changes in interpersonal stress as a factor in disease exacerbations among women with rheumatoid arthritis. Ann. Behav. Med., 19 (3), 279–286. Zautra, A. J., Yocum, D. C., Villanueva, I., Smith, B., Davis, M. C., Attrep, J., et al. (2004). Immune activation and depression in women with rheumatoid arthritis. J. Rheumatol., 31 (3), 457–463.
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C H A P T E R
9 Sex Steroids and Immunity MAURIZIO CUTOLO AND ALESSANDRO CALVIA
I. INTRODUCTION: SEX HORMONES AND AUTOIMMUNE DISEASES 207 II. PERIPHERAL SEX HORMONE METABOLISM IN AUTOIMMUNE DISEASES 208 III. POSSIBLE MECHANISMS OF IMMUNOMODULATION BY SEX HORMONES 209 IV. PREGNANCY AND AUTOIMMUNITY 211
Sex hormones are implicated in the immune response, with estrogens as enhancers (at least of the humoral immunity), and androgens and progesterone (and glucocorticoids) as natural immune-suppressors on Th0 maturation and Th1/Th2 activities (4,5) (Figure 1). Estrogens in physiological concentrations enhance the Th1 cytokine production, and at pharmacological concentrations exert opposite effects, at least in models (Figure 2). In addition, estrogens enhance antibody production by activated B-cells (Figure 3). Low concentrations of gonadal and adrenal androgen [testosterone (T)/dihydrotestosterone (DHT), dehydroepiandrosterone (DHEA) and its sulphate (DHEAS), respectively] levels, as well as reduced androgens/ estrogens ratio, have been detected in serum and body fluids (i.e., blood, synovial fluid [SF], smears, salivary) of male and female RA patients, as well as in SLE, supporting the possible pathogenic role for the decreased levels of the immune-suppressive androgens (6). However, in respect to serum levels of estrogens, interestingly, they are not significantly changed, which is in strict contrast to androgen levels in RA patients (4). Several physiological, pathological, and therapeutic conditions may change the serum estrogen milieu and/or peripheral conversion rate, including the menstrual cycle; pregnancy; postpartum period; menopause; elderly; chronic stress; inflammatory cytokines; use of corticosteroids, oral contraceptives, and steroid hormonal replacements; inducing altered androgen/ estrogen ratios and related effects (5–7). As a matter of fact, sex hormones can also exert local actions (paracrine) in the tissues in which they are formed or enter the circulation, and both T and 17-β estradiol (E2) seem to exert dose- and time-dependent
I. INTRODUCTION: SEX HORMONES AND AUTOIMMUNE DISEASES Epidemiological evidence indicates that during the fertile age, women are more often affected by rheumatic diseases than men, particularly autoimmune diseases (1). As a matter of fact, rheumatic disorders with autoimmune involvement such as rheumatoid arthritis (RA) or systemic lupus erythematosus (SLE) result from the combination of several predisposing factors, which include the relationships between epitopes of the trigger agent (i.e., virus) and histocompatibility epitopes (i.e., HLA), the status of the stress response system including the hypothalamicpituitary-adrenocortical axis (HPA) and the sympathetic nervous system (SNS), and mainly the effects of the gonadal hormones (hypothalamic-pituitarygonadal, or HPG, axis) (2). The pre- or post-menopausal serum sex hormonal status is a further factor influencing the rate of rheumatic diseases. It is therefore important, whenever possible, to evaluate epidemiologic data broken down into age (for example, 10-year age band) and sexspecific group before making inferences (3). Obviously, sex hormones seem to play an important role as modulators of both disease onset and perpetuation (4). PSYCHONEUROIMMUNOLOGY, 4E VOLUME I
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Estrogens (physiological - low)
Th1 Testosterone
(physiological - low)
Th2
(progesterone)
Th0
Estrogens
IL-2 RA IFN-γγ = MS
Testosterone (progesterone)
Th2
Estrogens
IL-4 IL-10 SLE IL-5 = β TGF-β
(pharmacological - high)
Estrogens Th1
IL-1 TNF-α α IL-6
Testosterone (progesterone)
M0
Estrogens
IL-4 Ab IL-10 = production IL-5 TGF-β β
(pharmacological - high)
FIGURE 1 Sex hormones are implicated in the immune response, with estrogens as enhancers (at least of the humoral immunity), and androgens and progesterone (and glucocorticoids) as natural immune-suppressors on Th0 maturation and Th1/Th2 activities.
(physiological - low)
B cell
IL-4 IL-10 = Ab IL-5 production β TGF-β
IL-1 TNF-α α IL-6
Estrogens (pharmacological - high)
FIGURE 2 Estrogens in physiological concentrations enhance the Th1 cytokine production, and at pharmacological concentrations exert opposite effects, at least in models.
effects on cell growth and apoptosis (2,4). These effects, as well as important influences on gene promoter of Th1/Th2 cytokines and the recently discovered increased SF estrogen concentrations, might suggest interesting new roles for estrogens, at least in RA (8–11).
II. PERIPHERAL SEX HORMONE METABOLISM IN AUTOIMMUNE DISEASES Several findings suggest an accelerated metabolic conversion of upstream androgen precursors to E2 in
FIGURE 3 Estrogens enhance antibody production by activated B cells.
RA and SLE patients. E2, as the aromatic product of the gonadal steroid metabolic pathway and the result of peripheral conversion from the adrenal androgen DHEA, recognizes as upstream precursors different hormones such as DHEA, testosterone, and progesterone. As a matter of fact, a very large number of studies and reviews in the last 20 years have shown reduced serum concentrations of DHEAS, testosterone, and progesterone in both male and female RA/SLE patients (12,13). These data strongly support an accelerated peripheral metabolic conversion of upstream androgen precursors to E2 (see Figure 1). High estrogen concentrations have been found particularly in synovial fluids of RA patients of both sexes. How can one explain the recent detection of lower androgen and higher estrogen levels in both female and male RA synovial fluids? The appropriate explanation might originate from recent studies showing that the inflammatory cytokines (i.e., TNFα, IL-6, IL-1), particularly increased in RA synovitis, are able to markedly stimulate the aromatase activity in peripheral tissues (14,15). As a matter of fact, the aromatase enzyme complex is involved in the peripheral conversion of androgens (testosterone and androstenedione) to estrogens (estrone and estradiol, respectively). In tissues rich in macrophages, a significant correlation was found between the aromatase activity and the IL-6 production, and aromatase has been found also in synoviocytes (16). Therefore, the increased aromatase activity induced by locally produced inflammatory cytokines (i.e. TNFα, IL-1, IL-6) might explain the altered balance resulting in lower androgens and higher estrogens in the synovial RA fluids, as well as their effects on syno-
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vial cells, first described in our research (17) (see Figure 1). The role of local sex hormone concentrations at the level of inflammatory foci is of great value in order to explain the modulatory effects exerted by these hormones on the immune-inflammatory reaction. Men with rheumatoid arthritis (RA) have a higher than normal frequency of low testosterone levels. Interestingly, in a recent study, DHEAS and estrone concentrations have been found lower and estradiol was found higher in male RA patients compared with healthy controls (18). In this study, estrone did not correlate with any disease variable, whereas estradiol correlated strongly and positively with all measured indices of inflammation. Men with RA had aberrations in all sex hormones analyzed, although only estradiol consistently correlated with inflammation (18). The low levels of estrone and DHEAS may depend on a shift in the adrenal steroidogenesis towards the glucocorticoid pathway, whereas increased conversion of estrone to estradiol seemed to be the cause for the high estradiol levels (effect of the 17beta-hydroxysteroid dehydrogenase). In SLE patients, the aromatase activity evaluated in skin and subcutaneous tissue showed a tendency toward an increase when compared to control subjects (19). Among SLE patients, the aromatase activity varied inversely with disease activity, and the patients had decreased androgen and increased estrogen serum levels (19). Therefore, tissue aromatase activity showed significant direct correlation with estrogen levels in SLE patients. These data suggest that abnormal regulation of aromatase activity (i.e., increased activity) may partially explain the abnormalities of peripheral estrogen synthesis (i.e., increased availability of E2 and possible metabolites) in SLE, as well as the altered serum sexhormone levels and ratio (i.e., decreased androgens and DHEAS) (see Figure 1). Similarly, in a recent study by Straub, it is thought that the urinary excretion of hydroxyestrogens (namely, 16α-hydroxyestrone and 2-hydroxyestrogens) reflects the production in the tissues, since no respective hydroxylase activity is expected in the urine (20,21). On the other hand, as recently reviewed, peripheral estrogen hydroxylation was found increased in both men and women with SLE, and the estrogenic metabolites have been reported to increase B-cell differentiation and activate T-cells (22).
A. The Role of Estrogen Metabolites The elevated serum levels of 16α-hydroxyestrone, already described in SLE patients, indicate that dis-
eases in men differ from diseases in women to the extent that only 16 alpha-hydroxyestrone was elevated in men, whereas women had elevations of both 16 alpha-hydroxyestrone and estriol (23). These data suggest abnormal patterns of E2 metabolism, which may lead to increased estrogenic activity in SLE patients. A similar phenomenon is described in the synovial fluids of RA patients where 16α-hydroxyestrone/4hydroxyestradiol were found significantly higher when compared with control fluids (17,20) (see Figure 1). In these studies, molar ratio of free estrogens/free androgens also was found significantly higher in RA synovial fluids. Two important aspects must be considered. Total serum levels of E2 are not typically outside physiologic ranges in RA, as well as in SLE patients of both sexes, and the reported alterations in estrogen metabolism are again observed in both male and female patients, as recently reviewed (24–26). Therefore, it is intriguing that gender may not influence the entire phenomenon and that the gonadal production of the sex hormones is not responsible for the observed metabolic results, since most of the measured metabolites are converted in the periphery which is largely independent of gender. The phenomenon seems only dependent on the inflammatory state of the tissues, and the common mechanisms in both RA and SLE patients might indicate this is also a diseaseunspecific phenomenon. Furthermore, E2 is thought to play a dual proand anti-inflammatory role in chronic inflammatory diseases that were found related to low and high concentrations, respectively. In light of these data, it is possible that the phenomenon might just depend on different dose-related rate of peripheral E2 conversion to pro- or anti-inflammatory metabolites, such as 16αhydroxyestrone or naturally occurring antagonists (i.e., 2-hydroxyestrogens), respectively (27).
III. POSSIBLE MECHANISMS OF IMMUNOMODULATION BY SEX HORMONES A. Clinical Evidence Macrophages release cytokines, such as tumor necrosis factor alpha (TNFα), interleukin-1 (IL-1), and IL-6, which, for example, modulate the symptoms at least of RA. Macrophage release of these cytokines can be modulated by estrogen in different ways. Fc gamma receptor type IIIA (CD16a) is a receptor expressed on macrophages that selectively binds IgG molecules, an important rheumatoid factor in RA. Binding of CD16
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by anti-CD16 monoclonal antibodies stimulates macrophage cytokine release. In a recent study, estrogen can modulate pro-inflammatory cytokine release from activated monocytes and/or macrophages, in particular through modulation of CD16 expression (28). On the other hand, recent studies have shown that 16α-hydroxyestrone was far more potent than E2 in exerting proliferative activities (27). More recently we tested in cultured human myeloid monocytic cells (THP-1), differentiated into activated macrophages (M), the effects of E2 and testosterone in order to evaluate their influence on cell proliferation and apoptosis. The effects were evaluated on the NFk-B activity, as a complex of molecules modulating cellular activation. Testosterone was found to exert pro-apoptotic effects and to reduce M proliferation, whereas E2 induced opposite effects by interfering with NFk-B activities. Therefore, these results might support the hypothesis of a sex hormone modulation of cell growth and apoptosis. The next obvious step will be to test the effects of 16α-hydroxyestrone and 2-hydroxyestrogens on the same cells. In another study, E2 was found to increase IgG and IgM production by peripheral blood mononuclear cells (PBMC) from SLE patients, which leads to elevated levels of polyclonal IgG, including IgG antidsDNA, by enhancing B-cell activity via interleukin-10 (IL-10) (19). These latter results should also be replicated in presence of 16α-hydroxyestrone as well as with the naturally occurring 2-hydroxylated antiestrogen. In fact, in a recent study it has been shown that disease activity in SLE patients was negatively correlated to urinary concentrations of 2-hydroxylated estrogens (21). Estrogens are confirmed as one of the risk factors in autoimmunity. Interesting changes of serum estrogens have been found during pregnancy in SLE patients and have been found to correlate with cytokine variations (29,30) . The major hormonal alteration observed during pregnancy in SLE patients was an unexpected lack of estrogen serum level increase and, to a lesser extent, progesterone serum level increase, during the second and—even more—the third trimester of gestation (29). This lack of increase probably was due to placental compromise. In addition, a lower than expected increase of IL-6 in the third trimester of gestation and persistently high levels of IL-10 during pregnancy seem to be the major alterations of the cytokine milieu in the peripheral circulation of SLE pregnant patients (30). Therefore, these steroid hormone and cytokine variations may result in a lower humoral immune response activation, probably related to a change in
the estrogen/androgen balance, which in turn could account for a more immunosuppressive effect exerted by cytokines on disease activity as observed during the third trimester in pregnant SLE patients (29). Since cyclophosphamide-induced ovarian failure has been reported to be protective against flares of SLE, a recent study evaluated whether patients with SLE experience a decrease in disease activity after natural menopause (31). Differences in disease activity scores (mean and maximum) and the number of visits to a rheumatologist’s office were only significant when the fourth year before menopause was compared with the fourth year after menopause. Disease activity was found mild during the pre-menopausal and postmenopausal periods in women with SLE. A modest decrease, especially in the maximum disease activity, was seen after natural menopause (31).
B. Role of Sex Hormones in Cell Proliferation and Apoptosis Monocytes/macrophages contribute to the autoimmune process, mainly acting as antigen-processing/ presenting cells and sources of inflammatory cytokines, in particular at the level of the synovial tissue in RA (32). Moreover, sex hormones can exert local actions (paracrine) in the tissues in which they are formed, including the synovial tissue (17,20). Activated THP-1 cells differentiate into macrophages for long-term cultures. On the contrary, synovial macrophages are characterized by a short life during in vitro culture. The present study shows opposite effects by sex hormones on cultures of activated monocytic/macrophage cells (THP-1 cells) concerning their modulatory effects on cell proliferation and/or apoptosis. The signaling pathways modulating the pro- and anti-inflammatory mechanisms seem to involve the steroidal hormone receptor activation and the NFk-B complex factors; in addition estrogens may differently regulate NF-kB activation depending on cell type tested (33,34). Therefore, E2 increased the expression of markers of cell growth and proliferation, whereas T induced an increase of the PARP-cleaved expression, indicating DNA damage and apoptosis. In addition, to support the proliferative role exerted by E2, the THP-1 cells pre-treated with the estrogens showed a decrease of staurosporine-induced apoptosis when compared with T-treated and untreated cells. Furthermore, the increased NFk-B p65 expression and the evident NFkappaB-binding to DNA in E2-treated cells, when compared with untreated or T-treated cells, as well as the increased levels of the IkB-•• phosphorylated
9. Sex Steroids and Immunity
form, seem to support the major enhancing role exerted by estrogens on immune/inflammatory response by activating the NF-kB complex. On the contrary, the observed positive upregulation of the IkB-α exerted by T treatment presumably dampens the pro-inflammatory effects mediated by the NF-kB activation and therefore might represent a further mechanism by which androgens exert antiinflammatory effects. Recent studies support these results, showing that E2 inhibits apoptosis in different cell types (cardiac myocytes and others), whereas androgens have been found to induce apoptosis (35,36). The increased concentrations of estrogens (and low androgens) recently described (17) at the level of the synovial fluid of RA patients of both sexes seem to support their possible modulator roles on synovial tissue hyperplasia and chronic synovial cell activation, by considering the estrogenic effects on cell proliferation and apoptosis. These observations have been recently obtained also in human breast cancer cells (37). To explain increased estrogen concentrations in RA synovial fluids, the pro-inflammatory cytokines (TNFα, IL-1, IL-6) have been found to accelerate the metabolic conversion on estrogens from androgens by inducing the synovial tissue aromatases (38–40). As a consequence, locally increased estrogen levels might exert activating effects on synovial cell proliferation, including macrophages and fibroblasts (41). In conclusion, the concentrations for E2 and T tested here seem to modulate the activity of NFk-B molecules in monocytic/macrophage cells line (THP-1) with opposite effects, and interfere with cell growth and apoptosis (42). These observations might provide a further biological link between gender effects and the complex inflammatory process involved in rheumatoid synovitis. Further studies using peripheral metabolites of estrogens and synovial macrophages from RA patients might extend the value of these observations.
IV. PREGNANCY AND AUTOIMMUNITY A. The Immune System at the Placental Level Feto-maternal unit organization starts with the invasion of maternal decidua by trophoblast. The maternal immune system does allow the trophoblast invasion anchoring the placenta to the uterus. In the initial phases, the progesterone produced by the corpus luteum induces the differentiation of Th0
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to Th2 lymphocytes. Th2 cells inhibit Th1 by the production of IL-4, IL-10, and IL-13, as well as the antigenpresenting cells (APC) activity secreting IL-4, IL-6, and IL-10. At the feto-maternal interface, APCs are almost all represented by dendritic cells. Th2 lymphocytes producing IL-4, IL-6, and IL-10 also stimulate differentiation of B-cells to plasma cells, and in particular, they stimulate the synthesis of some trophoblast-protecting antibodies, such as asymmetric IgG and anti-R80K antibodies. IL-4 produced by Th2 lymphocytes inhibits NK cells expressing the “Killer Activator Inhibitor” (KAR). These cells are also inhibited by anti-R80K antibodies. On the contrary, IL-4 stimulates KAR-expressing NK cells. This receptor forms a complex with HLA-G molecules expressed by the trophoblast, and this interaction blocks the killer activity of NK lymphocytes on trophoblastic cells. NK cells start to produce LIF and M-CSF (monocyte-stimulating growth factor), which regulate the invasion of trophoblastic tissue. Th2 cytokines are produced not only by immune cells but also by the placenta. In particular, IL-4, IL-6, and IL-10 stimulate hCG secretion by the placenta, which in turn stimulates the ovarium to produce progesterone. The same cytokines produced by the placenta can directly stimulate the differentiation of Th0 to Th2 lymphocytes. Estrogens at high levels, such as those produced by the placenta during the second and third trimester of pregnancy, can stimulate IL-6 production by the placenta itself or by macrophages. This cytokine plays a very important role during differentiation of Th0 to Th2 lymphocytes. Therefore, at the feto-maternal interface, the Th1/ Th2 shift plays a crucial role: Th1 cytokine reduction results in cell immune response inhibition, and Th2 increments results in humoral immune response stimulation. If Th1/Th2 balance does not shift, abortion can occur. This shift is mainly modulated by progesterone and estrogens (43). Progesterone participates in the first phase of pregnancy, whereas estrogens seem to be more important during the second period of pregnancy, during which they are produced in large amounts by the placenta.
B. Cytokine and Endocrine Network in the Periphery during Pregnancy Hormonal modifications during pregnancy are regulated by the feto-placental unit and depend on interactions between mother and fetus (44). Progesterone has a placental origin, since it is secreted by the corpus luteum during the first 6–8
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weeks of gestation. During physiological pregnancy, progesterone levels are 4–6 times higher than those out of gestation. Progesterone is the fundamental hormone during the first part of pregnancy and the precursor of some fetal hormones, and it also has other functions, some of which are still partially unknown. Deoxicorticosterone, one of its metabolites, is found in concentration 1,000 times higher than that out of pregnancy, but the physiologic role of this hormone is still not known (44). Also, the estrogen concentration is significantly increased during pregnancy, reaching levels 3–8 times higher compared to normal levels (44). This increase results from a unique interchange between mother and fetus. The fetus uses the pregnenolone produced by placenta in order to produce adrenal dehydroepiandrosterone and dehydroepiandrosterone sulphate. These hormones are metabolized to androstenedione and testosterone at the level of the placenta; finally, they are rapidly converted to estrose and estradiol and let into maternal circulation (44). The metabolite of dehydroepiandrosterone, which is 16α idroxilate, is converted to estriol in the fetal liver throughout the same pathways. One of the main side effects of elevated levels of estrogens during pregnancy is the increased protein synthesis in maternal liver, thus increasing the concentrations of several proteins in maternal circulation (44). It has also been shown that the increase of several coagulation proteins is probably responsible for the ipercoagulability state observed during pregnancy. The feto-placental hormones—in particular, progesterone, estrogens, and placental lactogenic hormone— are responsible for an altered metabolism of carbohydrates observed during gestation. In fact, during the second part of pregnancy, the mother develops a slight peripheral resistance to insulin, inducing an increased production and release of insulin by the pancreas (44). Due to glucose tolerance– induced physiological stress, almost 5% of pregnant women develop gestational diabetes during the second part of pregnancy. Probably, the concomitant corticosteroid therapy might predispose to this condition (44). Pregnancy and postpartum represent a paradigmatic example of how the modification of steroid hormone concentration can influence the immune and inflammatory responses in women and can modify the concentrations of immunoregulatory molecules (i.e., cytokines) and thereafter the expression of autoimmune diseases.
The physiological increase of cortisol, progesterone, estradiol, and testosterone during the third trimester of pregnancy seems to be responsible systemically and at the feto-maternal interface of the Th2 cytokines’ polarization (45). In fact, elevated levels of Th2 cytokines, such as IL10, have been found in placenta and amniotic fluid during the third trimester of pregnancy (46). Therefore, the suppression of the immune response mediated by Th1 cytokines seems to be fundamental for fetal survival. It has been suggested that some autoimmune diseases, such as SLE, which are mediated mainly by Th2 cytokines and humoral immune response, tend to develop or relapse during pregnancy (47), whereas Th1-mediated diseases, such as rheumatoid arthritis, tend to improve. In both cases a flare or explosion of disease is shown during the postpartum, when the anti-inflammatory Th2 cytokines collapse. During normal pregnancy the IL-10 production by peripheral lymphocytes progressively increases (48,49). It also has been demonstrated that during pregnancy IL-6 serum levels gradually increase in maternal circulation and even more during labor (50). TNF-α serum levels do not vary during pregnancy, whereas the TNF-α-soluble receptors increase just to protect the fetus from TNF-α dangerous effects (51,52). It is known that glococorticoids inhibit IL-1, TNF-α, IFN-γ, and IL-2 production and that they stimulate IL-10, IL-4, and IL-13 synthesis, confirming a modulatory effect on the balance between the antiinflammatory/immunosuppressive responses during pregnancy (53). At physiological concentration, progesterone stimulates IL-4 (Th2 cytokine) synthesis, whereas estradiol stimulates TNFα production (Th1 cytokine). On the contrary, at pharmacologic levels, such as those observed during the second part of pregnancy, progesterone inhibits TNFα secretion and stimulates the IL-10 production in T lymphocyte clones, leading to an increased humoral immune response (54,55). Increased concentration of prolactin is associated with worsening of renal involvement in animal studies and has been found both in SLE males and females. A study carried out to detect serum autoantibodies in women during premenopausal periods has shown that in 20% of these, the prolactin levels were found increased, and high levels of anti-DNA antibodies were present at the same time. However, many women not diagnosed as SLE and followed at the Hyperprolactinemia Endocrinological Center showed increased levels of anti-nuclear antibodies (ANA) (56).
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C. Cytokine Network in Non-pregnant SLE Patients Cytokine profile has been largely investigated in SLE. In T lymphocytes from SLE patients, an insufficient production of IL-2 in vitro has been observed, probably resulting from several factors, including downregulation of some Th2 cytokines. The recent finding of the IL-10 role in the pathogenesis of SLE supports this hypothesis. IL-10 is a Th2 cytokine that strongly stimulates B lymphocyte proliferation and differentiation, having a potential role as mediator of B-cell polyclonal activation in SLE. Recent studies have demonstrated that the spontaneous IL-10 production by B lymphocytes and peripheral blood mononuclear cells is significantly more elevated in SLE patients compared to controls (56,57). In addition, IL10 concentration in the serum was found higher in SLE patients and correlated with disease clinical and serological activity, as well as with anti-DNA antibodies (58–60). IL-10 increased production may be caused by a reduced Th1 in vitro response of T-cells in SLE. This phenomenon has been suggested in a study showing that the addition of IL-10–blocking antibodies significantly increased the proliferative response of peripheral blood mononuclear cells (61). IL-12 cytokine is a heterodimer produced by B lymphocytes, macrophages, and dendritic cells that promotes cell-mediated immune response and has some inhibitory activity on humoral immune response (62). It has been shown that IL-12 is insufficiently produced by peripheral blood mononuclear cells in SLE patients (62,63). The deficit of IL-12 production is probably characteristic of monocytes rather than B lymphocytes (64). On the contrary, IL-12 addition to SLE peripheral blood mononuclear cells significantly inhibits both spontaneous and IL-10–stimulated production of immunoglobulins and anti-DNA antibodies (65). Therefore, the altered regulation of IL-10/IL-12 balance plays a crucial role in the inadequate cell immune response observed in SLE patients.
D. Immunoendocrine Modifications in SLE Patients during Pregnancy In healthy subjects, the altered immunoregulation induced by pregnancy is manifested mainly at the fetomaternal interface, whereas systemic effects are negligible. The situation is different in patients affected by autoimmune rheumatic diseases (ARDs) during pregnancy. ARDs are already characterized by an altered immunoregulation, and in these patients the maternal immune system modifications can influence the course of the disease.
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One of the most important modifications is the Th1/ Th2 shift. It occurs both at the feto-placental barrier and in maternal circulation, and it is driven by the physiological increase of progesterone and estrogens that occurs progressively throughout pregnancy, with the maximum peak during the third trimester of gestation. In particular, progesterone plays an important role in the first part of pregnancy, and estrogens in the second part. In physiological conditions, it seems that estrogens stimulate both humoral and cell immune responses (Th1 and Th2 cytokines). Nevertheless, at concentrations higher than physiological, such as those reached during pregnancy, it seems that estrogens inhibit cellmediated immune response (Th1 cytokines), whereas they induce antibody production (Th2 cytokines). The polarization of Th2 response may explain why patients affected by rheumatoid arthritis generally improve during pregnancy, whereas those with SLE get worse. In SLE patients, pregnancy has always been considered a risk event both for the mother and fetus since the relapse of the disease is frequent during gestation. As a consequence, fetal loss, prematurity, and underweight babies are more common events in SLE women than in healthy subjects. Nevertheless, during the last years, the number of successful pregnancies has increased, although disease relapse still remains a frequent event during both gestation and postpartum. Recently, a reduced frequency of relapses has been reported during the third trimester of pregnancy compared to the second and postpartum. It has been shown that serum levels of some hormones are lower in SLE patients compared to healthy controls (29). In particular, the concentration of estradiol and progesterone in the serum is unexpectedly low in the second and most in the third trimester of pregnancy, periods during which these hormones are secreted mainly by the placenta. The reduced concentration of estradiol and progesterone may be due to the compromised placental activities, responsible for a lower activation of humoral response and leading to a lower disease activity during the third trimester of pregnancy in SLE patients (30). The effects of steroid hormones on disease activity during pregnancy seem to be mediated by Th2 cytokines. IL-10 strongly stimulates B lymphocytes and anti-DNA production in SLE. In healthy subjects IL-10 progressively increases during pregnancy, whereas in SLE patients IL-10 serum levels remain elevated before and after pregnancy in the case of both active and inactive disease. These effects support the hypothesis that
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SLE IL-10 is constitutively hyperproducted rather than modulated by gonadal hormones (steroids) (30). On the other hand, it is known that IL-6 is involved in Th0/Th2 shift (44). The production of IL-6 seems to be correlated with disease activity. In healthy subjects during pregnancy, IL-6 progressively increases in maternal circulation and even more during delivery. In SLE patients the peak of IL-6 during the third trimester seems lacking (30). The modulation of estrogens on IL-6 production seems dose-dependent; at physiological levels estrogens inhibit IL-6, but at pharmacological levels, such as those reached at the end of pregnancy in physiological conditions, estrogens inhibit IL-6 production (45). The low levels of IL-6 observed during the third trimester of pregnancy in SLE may depend on the low levels of estrogens observed during the same period of gestation and may explain the lower frequency of relapse reported in the same period (30).
References 1. Bijlsma, J. W. J., Straub, R. H., Masi, A. T., Lahita, R. G., and Cutolo, M. (2002). Neuroendocrine immune mechanisms in rheumatic diseases. Trends Immunol, 23, 59–61. 2. Straub, R., and Cutolo, M. (2001). Impact of the hypothalamicpituitary-adrenal/gonadal axes and the peripheral nervous system in rheumatoid arthritis: a systemic pathogenic view point. Arthritis Rheum, 44, 493–495. 3. Cutolo, M. (2003). Gender and the rheumatic diseases: epidemiological evidence and possible biologic mechanisms. Ann Rheum Dis, 62(sp0005) 3. 4. Cutolo, M., Villaggio, B., Craviotto, C., Pizzorni, C., Seriolo, B., and Sulli, A. (2002). Sex hormones and rheumatoid arthritis. Autoimmun Rev, 1, 284–289. 5. Cutolo, M., and Straub, R. (2000). Polymyalgia rheumatica: evidence for a hypothalamic-pituitary-adrenal axis-driven disease. Clin Exp Rheumatol, 18, 655–658. 6. Maestroni, G., Sulli, A., Pizzorni, C., Villaggio, B., and Cutolo, M. (2002). Melatonin in rheumatoid arthritis: a disease promoting and modulating hormone? Clin Exp Rheumatol, 20, 872–873. 7. Cutolo, M. (2003). Solar light effects on relapse/onset circannual/circadian rhythms in rheumatoid arthritis. Clin Exp Rheumatol, 21, 148–150. 8. Cutolo, M., Straub, R. H., Masi, A. T., Bijlsma, J. W. J., Lahita, R., and Bradlow, H. L. (2002). Altered neuroendocrine immune (NEI) networks in rheumatology. Ann NY Acad Sci, 966, xiii. 9. Kawasaki, T., Ushiyama, T., Inoue, K., and Hukuda, S. (2000). Effects of estrogen on interleukin-6 production in rheumatoid fibroblast-like synoviocytes. Clin Exp Rheumatol, 18, 743–745. 10. Li, Z. G., Danis, V. A., and Brooks, P. M. (1993). Effect of gonadal steroids on the production of IL-1 and IL-6 by blood mononuclear cells in vitro. Clin Exp Rheumatol, 11, 157–162. 11. Cutolo, M., Villaggio, B., Montagna, P., Capellino, S., Seriolo, B., Straub, R. H., et al. (2004). Synovial fluid estrogens in rheumatoid arthritis. Autoimmun Rev, 3, 193–198. 12. Bijlsma, J. W. J., Straub, R. H., Masi, A. T., Lahita, R. G., and Cutolo, M. (2002). Neuroendocrine immune mechanisms in rheumatic diseases. Trends Immunol, 23, 59–66.
13. Lahita, R. G., Bradlow, H. L., Ginzler, E., Pang, S., and New, M. (1987). Low plasma androgens in women with systemic lupus erythematosus. Arthritis Rheum, 30, 241–248. 14. Macdiarmid, F., Wang, D., and Duncan, L. G. (1994). Stimulation of aromatase activity in breast fibroblasts by tumor necrosis factor α. Mol Cell Endocrinol, 106, 17–21. 15. Purohit, A, Ghilchic, M. W., and Duncan, L. (1995). Aromatase activity and interleukin-6 production by normal and malignant breast tissues. J Clin Endocrinol Metab, 80, 3052–3058. 16. Le Bail, J., Liagre, B., Vergne, P., Bertin, P., Beneytout, J., and Habrioux, G. (2001). Aromatase in synovial cells from postmenopausal women. Steroids, 66, 749–755. 17. Castagnetta, L., Cutolo, M., Granata, O., Di Falco, M., Bellavia, V., and Carruba, G. (1999). Endocrine end-points in rheumatoid arthritis. Ann N Y Acad Sci, 876, 180–192. 18. Tengstrand, B., Carlstrom, K., Fellander-Tsai, L., and Hafstrom, I. (2003). Abnormal levels of serum dehydroepiandrosterone, estrone, and estradiol in men with rheumatoid arthritis: high correlation between serum estradiol and current degree of inflammation. J Rheumatol, 30, 2338–2343. 19. Folomeev, M., Dougados, M., Beaune, J., Kouyoumdjian, J. C., Nahoul, K., Amor, B., et al. (1992). Plasma sex hormones and aromatase activity in tissues of patients with systemic lupus erythematosus. Lupus, 1, 191–195. 20. Castagnetta, L. A., Carruba, G., Granata, O. M., Miele, M., Cutolo, M., Straub, R. H., et al. (2003). Increased estrogen formation and estrogen to androgen ratio in the synovial fluid of patients with rheumatoid arthritis. J Rheumatol, 30, 2597– 2605. 21. Weidler, C., Harle, P., Schedel, J., Schmidt, M., Scholmerich, J., and Straub, R. H. (2004). Patients with rheumatoid arthritis and systemic lupus erythematosus have increased renal excretion of mitogenic estrogens in relation to endogenous antiestrogens. J Rheumatol, 31, 489–495. 22. Kanda, N., Tsuchida, T., and Tamaki, K. (1999). Estrogen enhancement of anti-double-stranded DNA antibody and immunoglobulin G production in peripheral blood mononuclear cells from patients with systemic lupus erythematosus. Arthritis Rheum, 42, 328–337. 23. Lahita, R. G., Bradlow, H. L., Kunkel, H. G., and Fishman, J. (1979). Alterations of estrogen metabolism in systemic lupus erythematosus. Arthritis Rheum, 22, 1195–1198. 24. Cutolo, M., Sulli, A., Seriolo, B., Accardo, S., and Masi, A. T. (1995). Estrogens, the immune response and autoimmunity. Clin Exp Rheumatol, 13, 217–226. 25. Cutolo, M., Sulli, A., Seriolo, B., Villaggio, B., and Straub, R. H. (2003). New roles for estrogens in rheumatoid arthritis. Clin Exp Rheumatol, 21, 687–690. 26. McMurray, R. W., and May, W. (2003). Sex hormones and systemic lupus erythematosus: review and meta-analysis. Arthritis Rheum, 48, 2100–2110. 27. Cutolo, M. (2004). Estrogen metabolites: increasing evidence for their role in rheumatoid arthritis and systemic lupus erythematosus. J Rheumatol, 31, 419–421. 28. Kramer, P. R., Kramer, S. F., and Guan, G. (2004). 17 betaestradiol regulates cytokine release through modulation of CD16 expression in monocytes and monocyte-derived macrophages. Arthritis Rheum, 50, 1967–1975. 29. Doria, A., Cutolo, M., Ghirardello, A., Zampieri, S., Vescovi, F., Sulli, A., et al. (2002). Hormones and disease activity during pregnancy in systemic lupus erythematosus. Arthritis Rheum, 47, 202–209. 30. Doria, A., Ghirardello, A., Punzi, L., Sulli, A., Gambari, P. F., Cutolo, M., et al. (2004). Pregnancy, cytokines and disease activ-
9. Sex Steroids and Immunity
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41. 42.
43.
44.
45.
46.
47.
ity in systemic lupus erythematosus. Arthritis Rheum, 15, 989–995. Sanchez-Guerrero, J., Villegas, A., Mendoza-Fuentes, A., Romero-Diaz, J., Moreno-Coutino, G., and Cravioto, M. C. (2001). Disease activity during the premenopausal and postmenopausal periods in women with systemic lupus erythematosus. Am J Med, 111, 464–468. Kinne, R. W., Brauer, R., Stuhlmuller, B., Palombo-Kinne, E., and Burmester, G. R. (2000). Macrophages in rheumatoid arthritis. Arthritis Res, 2, 189–202. Ghisletti, S., Meda, C., Maggi, A., and Vegeto, E. (2005). 17βestradiol inhibits inflammatory gene expression by controlling NF-kB intracellular localization. Mol Cell Biol, 25, 2957–2968. Cerillo, G., Rees, A., Manchanda, N., et al. (1998). The estrogen receptor regulates NF-kappaB and AP-1 activity in a cell-specific manner. J Steroid Biochem Mol Biol, 67, 79–88. Pelzer, T., Schumann, M., Neumann, M., De Jager, T., Stimpel, M., Serfling, E., et al. (2000). 17-β estradiol prevents programmed cell death in cardiac myocytes. Biochem Biophys Res Commun, 268, 192–200. Ling, S., Dai, A., Williams, M. R., Myles, K., Dilley, R. J., Komesaroff, P. A., and Sudhir, K. (2002). Testosterone (T) enhances apoptosis-related damage in human vascular endothelial cells. Endocrinology, 143, 1119–1125. Honma, S., Shimodaira, K., Shimizu, Y., Tsuchiya, N., Saito, H., Yanaihara, T., et al. (2002). The influence of inflammatory cytokines on estrogen production and cell proliferation in human breast cancer cells. Endocr J, 49, 371–377. Macdiarmid, F., Wang, D., and Duncan, L. G. (1994). Stimulation of aromatase activity in breast fibroblasts by tumor necrosis factor α. Mol Cell Endocrinol, 106, 17–21. Purohit, A., Ghilchic, M. W., and Duncan, L. (1995). Aromatase activity and interleukin-6 production by normal and malignant breast tissues. J Clin Endocrinol Metab, 80, 3052–3058. Le Bail, J., Liagre, B., Vergne, P., Bertin, P., Beneytout, J., and Habrioux, G. (2001). Aromatase in synovial cells from postmenopausal women. Steroids, 66, 749–757. Cutolo, M., and Lahita, R. G. (2005). Estrogens and arthritis. Rheum Dis Clin North Am, 31, 19–27. Cutolo, M., Capellino, S., Montagna, P., Ghiorzo, P., Sulli, A., and Villaggio, B. (2005). Hormone modulation of cell growth and apoptosis of the human monocytic/macrophage cell line. Arthritis Res Ther, 7, 1124–1133. Straub, R. H., Buttgereit, F., and Cutolo, M. (2005). Benefit of pregnancy in inflammatory arthritis. Ann Rheum Dis, 64, 801–803. Marzi, M., Vigano, A., Trabattoni, D., Villa, M. L., Salvaggio, A., Clerici, E., and Clerici, M. (1996). Characterization of type 1 and type 2 cytokine production profile in physiologic and pathologic human pregnancy. Clin Exp Immunol, 106, 127–133. Munoz-Valle, J. F., Vazquez-Del Mercado, M., Garcia-Iglesias, T., Orozco-Barocio, G., Bernard-Medina, G., Martinez-Bonilla, G., Bastidas-Ramirez, B. E., Navarro, A. D, Bueno, M., MartinezLopez, E., Best-Aguilera, C. R., Kamachi, M , and ArmendarizBorunda, J. (2003). T(H)1/T(H)2 cytokine profile, metalloprotease-9 activity and hormonal status in pregnant rheumatoid arthritis and systemic lupus erythematosus patients. Clin Exp Immunol, 131, 377–384. Opsjon, S. L., Wether, N. C., Tingslad, S., Wiedswang, G., Sunden, A., Waager, A., and Austejuler, R. (1993). Tumor necrosis factor, interleukin-1, and interleukin-6 in normal human pregnancy. Am J Obstet Gynecol, 169, 397–404. Elenkov, I. J., Hoffmann, J., and Wilder, R. L. (1997). Does differential neuroendocrine control of cytokine production govern
48.
49.
50. 51.
52.
53.
54.
55.
56. 57.
58.
59.
60.
61.
62.
63.
215
the expression of autoimmune diseases in pregnancy and the postpartum period? Mol Med Today, 3, 379–383. Russel, A. S., et al. (1997). Evidence for reduced Th1 function in normal pregnancy: a hypothesis for the remission of rheumatoid arthritis. J Rheumatol, 24, 1045–1050. Kupfermine, M. J., Peaceman, A. M., Aderka, D., Wallach, D., Peyser, M. R., Lessing, J. B., and Socol, M. L. (1995). Soluble tumor necrosis factor receptors in maternal plasma and second-trimester amniotic fluid. Am J Obstet Gynecol, 173, 900–905. Branch, D. W. (1992). Physiologic adaptation of pregnancy. Am J Reprod Immunol, 28, 120–122. Lin, H., Mosman, T. R., Guilbert, L., Tntipopipats, S., and Wegmann, T. G. (1993). Synthesis of T helper-2-cytokines at the maternal-fetal interface. J Immunol, 151, 4562–4573. Greig, P. C., Herbert, W. N., Robinette, B. L., and Teot, L. A. (1995). Amniotic fluid interleukin-10 concentrations increase through pregnancy and are elevated in patients with preterm labor associated with intrauterine infection. Am J Obstet Gynecol, 173, 1223–1227. Ramirez, F., Fowell, D. J., Puklavec, M., Simmonds, S., and Mason, D. (1996). Glucocorticoids promote a Th2 cytokine response by CD4+ T cells in vitro. J Immunol, 156, 2406– 2412. Piccinni, M. P., Giudizi, M. G., Biagiotti, R., Beloni, L., Giannarini, L., Sampognaro, S., Parronchi, P., Manetti, R., Annunziato, F., and Livi, C. (1995). Progesterone favors the development of human T helper cells producing Th2-type cytokines and promotes both IL-4 production and membrane CD30 expression in established Th1 cell clones. J Immunol, 155, 128–133. Cutolo, M., Sulli, A., Seriolo, B., Accardo, S., and Masi, A. T. (1995). Estrogens, the immune response and autoimmunity. Clin Exp. Rheumatol., 13, 217–226. Lahita, R. G. (1999). The role of sex hormones in systemic lupus erythematosus. Curr Opin Rheum, 11, 352–356. Llorente, L., Richaud-Patin, Y., Wijdenes, J., Alcocer-Varela, J., Maillot, M. C., Durand-Gasselin, I., Fourrier, B. M., Galanaud, P., and Emilie, D. (1993). Spontaneous production of interleukin10 by B-lymphocytes and monocytes in systemic lupus erythematosus. Eur Cytokine Netw, 4, 421–427. Houssiau, F. A., Lefebvre, C., Vanden Berghe, M., et al. (1995). Serum interleukin 10 titers in systemic lupus erythematosus reflect disease activity. Lupus, 4, 393–395. Park, Y. B., Lee, S. K., Kim, D. S., Lee, J., Lee, C. H., and Song, C. H. (1998). Elevated interleukin-10 levels correlated with disease activity in systemic lupus erythematosus. Clin Exp Rheumatol, 16, 283–288. Grondal, G., Gunnarson, I., Ronnelid, J., et al. (2000). Cytokine production, serum levels and disease activity in systemic lupus erythematosus. Clin Exp Rheumatol, 18, 565–570. Lauwerys, B. R., Garot, N., Renauld, J. C., and Houssiau, F. A. (2000). Interleukin-10 blockade corrects impaired in vitro cellular immune responses of systemic lupus erythematosus patients. Arthritis Rheum, 43, 1976–1981. Horowitz, D. A., Gray, J. D., Behrendsen, S. C., Kubin, M., Rengaraju, M., Ohtsuka, K., and Trinchieri, G. (1998). Decreased production of interleukin-12 and other Th1-type cytokines in patients with recent-onset systemic lupus erythematosus. Arthritis Rheum, 41, 838–844. Liu, T. F., and Jones, B. M. (1998). Impaired production of IL-12 in systemic lupus erythematosus. I. Excessive production of IL10 suppresses production of IL-12 by monocytes. Cytokine, 10, 140–147.
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I. Neural and Endocrine Effects on Immunity
64. Liu, T. F., and Jones, B. M. (1997). Impairment of IL-12 production in SLE is due to defective monocytes, not B cells. Immuol Lett, 56, 314. 65. Houssiau, F. A., Mascart-Lemone, F., Stevens, M., Libin, M., Devogelaer, J. P., Goldman, M., and Renauld, J. C. (1997). IL-12 inhibits in vitro immunoglobulin production by human lupus
peripheral blood mononuclear cells (PBMC). Clin Exp Immunol, 108, 375–380. 66. Kovacs, E. J., Messingham, K. A., and Gregory, M. S. (2002). Estrogen regulation of immune responses after injury. Mol Cell Endocrinol, 193, 129–135.
C H A P T E R
10 Emerging Concepts for the Pathogenesis of Chronic Disabling Inflammatory Diseases: Neuroendocrine-immune Interactions and Evolutionary Biology RAINER H. STRAUB, ADRIANA DEL REY, AND HUGO O. BESEDOVSKY
I. INTRODUCTION 217 II. BALANCE BETWEEN IMMUNE TOLERANCE AND IMMUNE AGGRESSION 217 III. GENES RESPONSIBLE FOR ADVANTAGEOUS REACTIONS TO OVERCOME CHRONIC DISABLING INFLAMMATORY DISEASES WERE NOT EVOLUTIONARILY CONSERVED 219 IV. HOMEOSTATIC MECHANISMS ARE EVOLUTIONARILY CONSERVED FOR TRANSIENT INFLAMMATORY REACTIONS—THEIR MISUSE IN CHRONIC DISABLING INFLAMMATORY DISEASES 220 V. UNCOUPLING OF SUPERSYSTEMS DURING CDIDS 224 VI. THE HEN-AND-EGG PROBLEM OF CDIDs—WHO STARTS THE DISEASE? 226
well-programmed adaptive mechanisms to interfere with the chronicity of pathologies that are expressed after reproductive ages or have a polygenetic background.
II. BALANCE BETWEEN IMMUNE TOLERANCE AND IMMUNE AGGRESSION Immunological models such as “self-nonself” (Burnett, 1959), “infectious-nonself” (Janeway, Jr., 1989), the “danger model” (Matzinger, 2002), “missing self” (Ljunggren et al., 1990), and “altered self” (Medzhitov and Janeway, 2002) explain certain facets of CDIDs (including the relevance of auto-antigen or commensurate foreign antigen). It has been shown that tolerance against an antigen occurs when dendritic cells ingest and present this antigen in the context of low expression of MHC class II and co-stimulatory molecules and in a microenvironment in which the cytokine cocktail is of an anti-inflammatory nature (Lutz and Schuler, 2002). Different subsets of antigenpresenting cells (APCs)/macrophages guide the responses accordingly (Mantovani et al., 2004). In contrast, if this cocktail is pro-inflammatory, an aggressive response will follow (Lutz and Schuler, 2002). It became evident that the presence of self-reactive lymphocytes is rather normal in humans and mice
I. INTRODUCTION This chapter provides an integrated framework of the pathogenesis of chronic disabling inflammatory diseases (CDIDs) combining aspects of evolutionary biology, the main homeostatic supersystems, such as the immune, the nervous, and the endocrine systems, and others such as the reproductive system. The goal of this chapter is the integration of knowledge derived from different fields. The chronic inflammatory disease of rheumatoid arthritis (RA) is used as a prototypic disease to illustrate the proposal that there are not PSYCHONEUROIMMUNOLOGY, 4E VOLUME I
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Copyright © 2007 by Elsevier, Inc. All rights of reproduction in any form reserved.
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many years before the first joint symptoms appeared (Figure 1) (Rantapää-Dahlqvist et al., 2003). Interestingly, such auto-antigens can be products of posttranslational modifications of harmless self-proteins that can allow immune recognition of neo-self epitopes (Anderton, 2004). The epidemiological study from Sweden mentioned above is outstandingly important because it demonstrates that auto-antigenicity is not immediately accompanied by symptomatic joint disease: “The immune response is restricted to hidden players.” When the disease becomes symptomatic, many other cell types such as neutrophils, fibroblasts,
se
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(Agrawal et al., 1991; Tao et al., 1985). In the pre-symptomatic phase of an immune-mediated joint disease, a limited number of cell types are involved. If, as in the case of RA, the etiological concept of an antigen-driven disease (self or foreign) is accepted, T-cells, B-cells, and APCs will play the major role in the pre-symptomatic phase (as easily recognized in animal models, see below). Not many other cell types contribute to the initiation of the joint disease. In this context, it is worth mentioning that increased antibody titers against possible RA auto-antigens (cyclic-citrullinated peptide [CCP] and IgA rheumatoid factor) have been detected
a re inc
hiden players: T- & B-cells and APCs
FIGURE 1 Autoimmune phenomena are present during the pre-symptomatic phase in rheumatoid arthritis. In the pre-symptomatic phase of the disease, T-cells, B-cells, and antigen presenting cells (APCs) dominate the immune response. Since no symptoms appear, a homeostatic balance exists between aggression and tolerance towards a self or foreign antigen. In the symptomatic phase of the disease, aggression outweighs tolerance, and other cell types are involved in the inflammatory process. The inlay demonstrates an opened knee joint. Arrows indicate the proliferation zone of synovium (pannus formation) that destroys the cartilage. The interval between first detection of autoimmune phenomena (auto-antibodies) and first symptoms can last 10 years (Rantapää-Dahlqvist et al., 2003. Arthritis Rheum., 48, 2741–2749).
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10. Neuroendocrine-immune Interactions and Evolutionary Biology TABLE 1
Effect of Various Mediators of the Nervous and Endocrine System on Function of Dendritic Cells
Mediator
Effect on dendritic cells
Refs
norepinephrine substance P calcitonin gene-related peptide vasoactive inflammatory peptide (VIP) cortisol estrogens
Regulates antigen presentation by Langerhans cells Contributes to T-cell proliferation induced by dendritic cells Inhibits B7-2 expression Synergizes with TNF in inducing human dendritic cell maturation Inhibits the maturation of dendritic cells and the presenting capabilities Stimulate dendritic cell function and differentiation
testosterone
Downregulates dendritic cell density in the skin
Seiffert et al., 2002 Lambrecht et al., 1999 Torii et al., 1998 Delneste et al., 1999 de Jong et al., 1999 Komi et al., 2000; Komi et al., 2001 Galasso et al., 1996
leading to an unfavorable preponderance of aggressive factors must occur during aging. Age-related changes of all supersystems might play a critical role.
III. GENES RESPONSIBLE FOR ADVANTAGEOUS REACTIONS TO OVERCOME CHRONIC DISABLING INFLAMMATORY DISEASES WERE NOT EVOLUTIONARILY CONSERVED FIGURE 2 Increased incidence of rheumatoid arthritis during aging in women. It is obvious that incidence particularly increases in the peri- and post-menopausal time.
osteoclasts, endothelial cells, chondrocytes, mast cells, osteoblasts, nerve fibers, stem cells, and fat cells are involved in the local destructive process (Figure 1). The role of the initial secret players—the T-cell, B-cell, and APCs—decreases while other cell types become important and the characteristics of the disease gradually change. Thus, a pre-symptomatic and a symptomatic phase of arthritis can be defined (Figure 1). In most animal models of autoimmune diseases, co-injection of a strong immune stimulus such as Freund’s adjuvant is needed to guarantee a pro-inflammatory condition during ingestion and presentation of the antigen (pre-symptomatic phase). During situations that are not polarized regarding aggression versus tolerance, hormones and neurotransmitters may become decisive (Table 1). If an acute inflammatory disease is not rapidly resolved, aggression will predominate (see below) and the disease will become chronic. The response favored will mainly depend on the antigen (concentration, epitope, antigen receptor density), the dendritic cells involved, involvement of pattern recognition receptors, and the microenvironment (Mantovani et al., 2004; Murray, 1998). In the case of RA, it is interesting that the incidence of the disease increases during aging (Figure 2) (Masi, 1994). It seems rather obvious that homeostatic changes
A. Advantageous Reactions Were Not Conserved At the time of the homo habilis (2 Mio years ago), the reproductive period lasted about 25 years (Baur et al., 2001). However, we know now that many CDIDs appear after the age of 35 years (e.g., RA). This has not allowed retaining specific genes responsible for advantageous reactions to overcome late-manifesting CDIDs. Prolongation of life as consequence of hygienic and nutritive practices and modern medicine were not predicted by biological evolution. In contrast, under natural conditions the development of a chronic disease is a handicap for the individual (e.g., in competition for nutrients and vulnerability to predators), implying a strong negative selection pressure. In addition, systemic inflammatory episodes lead to the production of cytokines that mediate a strong inhibition of the hypothalamus-pituitary-gonadal axis at different levels, resulting in inhibition of reproduction (Adashi et al., 1989). It has been shown that such inhibition also occurs in humans (Tsigos et al., 1999): IL-6, injected into healthy male volunteers in doses that lead to circulating IL-6 levels of a magnitude similar to that observed during severe inflammatory stress, causes a significant decrease in testosterone levels, which return to baseline concentrations only 7 days later (Tsigos et al., 1999). Thus, a long-lasting increase of IL-6 levels, which is typical during RA or juvenile idiopathic arthritis, would hinder testosterone production. Even today under optimal therapy, CDIDs such as juvenile
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idiopathic arthritis significantly diminish the probability of successful conception (Ostensen et al., 2000). Most likely, such linkage between blunted reproductory functions and pro-inflammatory cytokines has not allowed the evolutionary acquisition of well-adjusted immuneneuro-endocrine responses to impede or modulate the chronic development of a disease. A typical example is the adult form of RA, a CDID with severe polyarticular inflammatory symptoms. We hypothesize that under natural conditions this disabling disease would be hardly expressed for a long time (as a chronic disease) because of the need to cope with the environmental threats and to compete for nutrients. However, an individual that would suffer from RA later in life can transmit before to the progeny the genetic background that predisposes to the disease. Conversely, advantageous mechanisms to prevent late-manifesting RA and other CDIDs might not have been evolutionarily conserved because possibly advantageous genes were not retained in the offspring. In addition, genes that may be beneficial in the early period of life (e.g., for reproduction) may be deleterious in an elderly person suffering from a CDID. In aging research, this is called “the pleiotropy theory of aging” (Kirkwood and Austad, 2000), but it can also be applied to CDIDs. To this, it should be added that some evolutionarily conserved programs may be dangerous for the individual but favorable for the species (Box 1).
Box 1 1. The antechinus Antechinus is a marsupial the size of a large mouse, with a pointed snout and a short-haired, medium-long tail. It has short broad feet of buff to yellow-brown color. Copulation occurs during a short season in winter. The males, driven to somewhat frenzied sexual activity due to raised testosterone levels, compete vigorously for females. Copulation can last up to 24 hours. Within 3 weeks, almost all the males in the population are dead. This male die-off is largely brought on by the high stress levels associated with the physiological changes brought on by the breeding period. The animals die due to severe infection, particularly, owing to parasites. Removing male antechinus from the natural habitat leads to a life expectancy similar to female animals. 2. The leaping salmon Salmon spend part of their life as freshwater fish (youth), part as saltwater fish (adulthood), and during reproduction again as freshwater animals. When they return to rivers from the ocean to give birth, salmon do not eat. Spawning salmon live solely on accumulated muscle reserves for
nearly a year. In rivers brimming with food, 20-pound salmon will drive themselves to the edge of starvation. Over the 3 to 5 months between arriving from the ocean, migrating upstream, and spawning in the late fall, salmon expose themselves to predators. Salmon in rivers will jump and roll and swirl on the surface of pools, for no apparent reason, even though this reveals their location to predators and makes them vulnerable to death or injury during that critical period before they mate. After mating, salmon die due to exhaustion and parasitic infections.
B. Prerequisites for CDIDS Are Conserved—The Accumulation Theory It is still necessary to explain why genetic (e.g., HLA-linked) predisposition for CDIDs that appear before or during the reproductive period has been retained. In our view, an explanation for this apparent paradox resides in the fact that CDIDs have a multifactorial genetically polymorph background. For example, HLA-B27 is important for ankylosing spondylitis (relative risk = 90). HLA-B27 could have been retained in the offspring because in most cases the disease does not develop due to the lack of additional factors (genetically inherited or environmental). In RA, many other genetic prerequisites, which depend on the population, have been described (Figure 3, grayshaded area). The genetic prerequisites for a CDID can be retained over generations via individuals that never express the disease because relevant co-factors may either not occur or are expressed following very irregular patterns and only after the reproductive phase. This scenario, which we have called the “accumulation theory” (Straub and Besedovsky, 2003), would allow the appearance of CDIDs in the young.
IV. HOMEOSTATIC MECHANISMS ARE EVOLUTIONARILY CONSERVED FOR TRANSIENT INFLAMMATORY REACTIONS—THEIR MISUSE IN CHRONIC DISABLING INFLAMMATORY DISEASES A. The Versatility of the Immune System—The Dilemma in CDIDs The immune system (including tissue repairing by mechanisms comparable to those used by the reproductory system), the nervous system, and the endocrine system are homeostatic supersystems that integrate many reactions occurring during transient inflammatory events (see Table 2 later in this chapter).
10. Neuroendocrine-immune Interactions and Evolutionary Biology
FIGURE 3 Integrated view of factors influencing chronic inflammatory rheumatic diseases. The basis of rheumatoid arthritis is a genetic background. Several polymorphisms have been suggested to play a role (gray area, left part, abbreviations, see below), and they are a prerequisite for the development of rheumatoid arthritis. During early life, an asymptomatic phase of the disease exists during which serologically detectable autoimmune phenomena are already present (yellow area, autoantibodies can be observed years before disease outbreak). Environmental triggers may contribute to initiate this early phase. Particularly, adaptive immune responses play a predominant role (dendritic cells, T-cells, B-cells). In addition, nervous and endocrine factors can intensely modulate leukocyte migration and distribution. In the symptomatic overt phase of the disease (red area), the role of the initial players—the T-cell, B-cell, and dendritic cell—simultaneously decreases while other cell types become involved in the inflamed area. Various mediators may stimulate the immune response in phase P1, but the same mediators can inhibit immune response in phase P2. These differential effects are due to the different components involved. Furthermore, in the asymptomatic phase of the disease (yellow area), neuroendocrine axes are probably intact, whereas in the symptomatic phase these axes are markedly altered possibly due to inherited deficits in responding to inflammation. Abbreviations: ACE, angiotensin converting enzyme; CRH, corticotropin-releasing hormone; FCγRIIIA, Fc-gamma receptor IIIA; GRβ, glucocorticoid receptor beta; MMP-3, matrix metalloproteinase 3; NK cells, natural killer cells; PADI, peptidylarginine deiminase 4 (initiates cyclic citrullination); SLC22A4, organic cation transporter; TNF, tumor necrosis factor; TNFRII, TNF receptor type II.
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During approximately 109 years, an extremely efficient pattern of receptors for recognition of foreign agents has been evolutionarily conserved in our genome (Marchalonis et al., 2002). Responses triggered by stimulation of these receptors are immediate, non-clonal, independent of gene re-arrangement, and the repertoire of pattern recognition receptors is small. In contrast to innate immunity, the younger adaptive immune system (arising later, particularly with vertebrates 450 Mio years ago) demonstrates a striking dissociation from these evolutionary older elements: Genes in Tand B-cells allow recognition of a huge number of 109 to 1011 antigenic determinants. In antigen-activated peripheral B-cells, every infection leads to a high rate of somatic point mutations (hypermutation, genes are not fixed in the genome), which improves affinity for the antigen. This versatility bears a highly significant risk for errors in the discrimination between self and foreign, which is most likely the dilemma in CDIDs (the starting point). The big advantage of the adaptive immune system is its memory for the antigen, the specificity, and the diversity (that allows the recognition of future emerging antigens) (Abbas et al., 1996; Marchalonis et al., 2002). This has been evolutionarily advantageous since about 94% of the human population profit from the adaptive immune system (during infections, etc.), whereas only 6% suffer from CDIDs. Which are the homeostatic mechanisms that have been evolutionarily conserved for transient inflammatory reactions but are mistaken in CDIDs?
B. The Immune System The evolutionarily conserved reaction against an unwanted antigen is the continuous attack to eliminate it, a process that is obviously beneficial during infection. In the case of a harmless self or foreign antigen, the continuous attack is no longer meaningful. In RA, a large list of self-antigens has been reported (Bläß et al., 1999), and some epitopes are identical for the human disease and in experimental models (Burkhardt et al., 2002). However, whether RA is an autoimmune disease with broken tolerance against self rather than a disease with an inflammatory reaction against a foreign antigen is still a matter of debate. Nevertheless, RA is a severe CDID with a continuous strong proinflammatory and destructive behavior (continuous aggression). In CDIDs, reactions of the immune system are accompanied by a permanent aggressive attack with the purpose of completely eliminating the probably harmless antigen. The evolutionarily conserved reaction used to overcome infectious agents is no longer meaningful in such a situation.
C. The Endocrine System In the early phase of an inflammatory episode, an immediate rise of cortisol, epinephrine, and norepinephrine in plasma is observed (Christeff et al., 1987; Jones et al., 1984; Suzuki et al., 1986). These endocrine reactions were most likely conserved to control inflammatory reactions and cytokine production (Besedovsky et al., 1986). In addition, it has been demonstrated that cortisol and norepinephrine are necessary to establish an adequate immune reaction (Del Rey et al., 2002; Kohm and Sanders, 2000; Madden et al., 1989) and an early mobilization and redistribution of immune cells (Dhabhar et al., 1995; Toft et al., 1994). However, a prolonged increase in the activity of the HPA axis and the sympathetic nervous system during immune processes predispose to severe infections. Furthermore, endotoxin–induced increase of cortisol levels is achieved at the expense of adrenal androgens (Straub et al., 2002d), which are anti-inflammatory (reviewed in Cutolo and Wilder, 2000). Thus, the fast cortisol rise and fall and the loss of adrenal androgens have been evolutionarily conserved to support a strong immune reaction during infection. In the case of a prolonged immune aggression such as in RA, these evolutionarily conserved mechanisms are used in a wrong way: A rapid loss of the anti-inflammatory mediators cortisol and androgens and their continuous inadequate production are unfavorable in CDIDs (Crofford et al., 1997; Cutolo et al., 1988; Masi et al., 1984; Straub et al., 2002c). Prolactin, another important endocrine mediator, should be taken into account. During an infectious disease, the levels of prolactin, a stimulator of the immune system (Matera et al., 1992; Spangelo et al., 1987), sharply increase (Feldman et al., 1989). The evolutionarily conserved increase in prolactin levels during an infectious episode particularly serves to shelter mother and baby during breast-feeding. In RA and other CDIDs, this endocrine response provides a continuous unfavorable pro-inflammatory condition (Jorgensen et al., 1995). Again, the evolutionarily conserved response to transient infectious diseases or other harmless inflammatory episodes has adverse consequences in CDIDs.
D. The Nervous System Following a physical injury of the skin, with or without infectious agents, a typical wound response is observed (Figure 4): (1) The sensory nervous system signals this event to the central nervous system. (2) In parallel, substance P is locally released from sensory
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FIGURE 4 Sequence of local events during wound healing. The normal wound-healing process lasts approximately 3 to 5 weeks. The behavior of sensory and sympathetic nerve fibers is indicated in red. Abbreviations: ECM, extracellular matrix.
nerve terminals and attracts monocytes and neutrophils (Roch-Arveiller et al., 1986; Ruff et al., 1985). Substance P activates these cells to produce pro-inflammatory cytokines such as IL-1β and TNF (Lotz et al., 1988). (3) In a later phase of the wound-healing process, substance P stimulates fibroblasts to generate matrix in order to close the wound (Nilsson et al., 1985). The reaction of the sensory nervous system is accompanied by peripheral and central sensitization that imprints pain pathways (Schaible and Grubb, 1993), an evolutionarily conserved learning phenomenon to heal the wound. (4) On the other hand, sympathetic nerves hinder the wound-healing process (Perez et al., 1987; Wucherpfennig et al., 1990). Thus, during 2 up to 21 days following a wound reaction, the preponderance of sensory over sympathetic nerve fibers was evolutionarily conserved for wound healing (Reynolds et al., 1995; Westerman et al., 1993). In the case of an improper immune reaction such as in RA, the same wound-healing processes (Miller et al., 2000; Pereira da Silva and Carmo-Fonseca, 1990) co-exist with an inadequate cortisol secretion (Straub et al., 2002a; Straub et al., 2002c) supporting the continuation of a local aggressive immune response. This evolutionarily conserved wound reaction is no longer advantageous in a CDID. Another phenomenon occurring during acute infectious disease is sickness behavior, in the form of malaise, fatigue, numbness, coldness, muscle and joint aches, reduced appetite, anxiety, and depressive mood triggered by pro-inflammatory cytokines in the central
nervous system (Bluthe et al., 1994; Reichenberg et al., 2001). The behavioral components of sickness represent, together with the fever response and the associated neuroendocrine changes, a highly organized strategy evolutionarily conserved and beneficial during acute infections. In a CDID such as RA, the same pro-inflammatory cytokines induce comparable symptoms such as depression, anxiety, hypersensitivity, and numbness (reviewed in Herrmann et al., 2000). If this evolutionary conserved behavior is prolonged, it becomes deleterious for the individual.
E. The Reproductive System Before the embryonic blastocyst can enter the mucosa, the mucosa must be prepared by estrogens and progesterone (Shifren et al., 1996). Progesterone and 17β-estradiol are strong stimulators of vascular endothelial growth factor (VEGF) (Shifren et al., 1996). Furthermore, adhesion molecules such as beta 1 integrins and alpha5 beta3 integrin are needed for attachment of the blastocyst (Yoshimura et al., 1998). The 17β-estradiol is a stimulator of these adhesion molecules (Shiokawa et al., 1996). The same adhesion molecules play an essential role in angiogenesis during a wound-healing process, and in leukocyte traffic and homing (Tonnesen et al., 2000). During the transient inflammatory wound-healing process, the repair system is stimulated so that multipotent stem cells can enter the tissue, which is prepared by estrogens and supported by vessel formation. During RA, the inflam-
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matory process leads to the local preponderance of estrogens versus androgens (Castagnetta et al., 2003). These estrogens upregulate adhesion molecules and most probably induce neovascularization via VEGF (Cid et al., 1994) and placental growth factor (PlGF) (Ziche et al., 1997). The same mechanisms are continuously used during an immune aggression against a harmless antigen, which adds to the continuation of inflammation (Bottomley et al., 2000; Koch et al., 1994). It is possible that these “erroneous” mechanisms particularly operate in women with a perfect estrogen/ progesterone-driven reproductive system during a CDID in later life (pleiotropy theory). Interestingly, the above-mentioned factors such as VEGF and PlGF are important repellents of sympathetic nerve fibers (Neufeld et al., 2002). One may speculate that these sympathetic nerve-repellent factors impede the sympathetic innervation of the placenta. Similar mechanisms are likely used during placental growth and wound repair, leading to sympathetic nerve fiber repulsion and preponderance of pro-inflammatory sensory nerve fibers (see above).
V. UNCOUPLING OF SUPERSYSTEMS DURING CDIDS Synchronization and desynchronization of hormonal/neurotransmitter systems have been evolutionarily conserved for normal life and transient inflammatory episodes in order to maintain bodily functions. For example, plasma levels of prolactin, growth hormone, and melatonin are increased and those of cortisol and norepinephrine are decreased during nighttime (evolutionarily conserved desynchronization). This particular desynchronization is thought to be important for circadian rhythms of immune system activation (Born et al., 1997). Compared with wakefulness, early nocturnal sleep induces a shift in the Th1/Th2 cytokine balance towards increased Th1 activity, as indicated by an increased ratio of IFN-γ/IL-4–producing T helper cells (Dimitrov et al., 2004). The nighttime hormonal profile probably supports the Th1 preponderance. Could it be an explanation that during sleep an animal is more susceptible to be attacked and wounded, and therefore, it would be beneficial to promote inflammatory reactions at this time? Another example is the evolutionarily conserved synchronization of cortisol and norepinephrine release during acute stress situations. Since cortisol supports several effects of norepinephrine and vice versa, blood pressure and energy supply are maintained during acute stress responses. These examples indicate that
synchronized and desynchronized programs were evolutionarily conserved to maintain homeostasis during normal life and non–life-threatening episodes (e.g., transient infectious disease). How does this concept apply to CDIDs? It has been recently demonstrated that in patients with Crohn’s disease and ulcerative colitis, two prototypic CDIDs, the synchronization of the sympathetic nervous system and the HPA axis is disturbed (Straub et al., 2002b). Under continuous inflammatory stress in these CDIDs, the sympathetic nervous tone increases, whereas the HPA axis tone remains relatively normal (Figure 5A). Despite direct activation of the adrenal glands by circulating cytokines such as IL-6 (EhrhartBornstein et al., 1998), cortisol secretion is inadequately low in relation to cytokine serum levels (Straub et al., 1998; Straub et al., 2002c). A very similar phenomenon with an increased tone of the sympathetic nervous system and a low normal activity of the HPA axis was observed in patients with RA and systemic lupus erythematosus (P. Härle and R.H. Straub, 2006). An “uncoupling” between the activities of the sympathetic nervous system and the HPA axis was also detected early during ontogeny in an animal model of systemic lupus erythematosus (A. del Rey et al., submitted). It seems that continuous high output steroid hormone secretion is not evolutionarily conserved, whereas continuous activation of the sympathetic nervous system is possible (= uncoupling of supersystems). We hypothesize that the increase of the sympathetic nervous tone may compensate for disturbed cortisol secretion and lower density of sympathetic nerve fibers in inflamed tissue (Figure 5B). In inflammatory diseases, coupling of the HPA axis and the sympathetic nervous system may be important to dampen peripheral inflammation due to cooperativity between cortisol and norepinephrine, which has recently been demonstrated in patients with RA (Straub et al., 2002a). Thus, uncoupling of these supersystems may be deleterious in CDIDs.
A. The Time-point When CDIDs Become Chronic Two, not mutually excluding explanations are provided which indicate a possible time-point when CDIDs become chronic: 1. It should be considered that the above-mentioned adaptation processes to transient inflammatory reactions are terminated within 3 to 5 weeks (Table 2). If the immune reaction against a harmless antigen (self or foreign) is not successful, the antigen is not eliminated after 3 to 5 weeks, but coordinated antiinflammatory responses of the other supersystems may not operate properly after this time. According to
FIGURE 5 Uncoupling of the HPA axis and the sympathetic nervous system. (A) In healthy subjects cortisol levels positively correlate with plasma levels of neuropeptide Y, indicating coupling of the activity of these two systems. In patients with ulcerative colitis, the correlation between these parameters is negative. (B) In the pre-symptomatic phase without overt inflammation, the sympathetic nervous tone is synchronized with the tone of the HPA axis. In the symptomatic phase of the disease, the activity of the two axes is uncoupled. We hypothesize that uncoupling is an important factor that drives to chronicity.
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Problem Infection in general Infection during pregnancy Wound Foreign body reaction Embryonic implantation Unwelcome small inanimate objects (e.g., pollen)
Evolutionarily Conserved Transient Inflammatory Reactions Reaction of the supersystems Continuous attempt to eliminate infectious agents Hormonal support of the immune system Closing of a wound including implantation of adult stem cells in a wounded tissue Continuous attempt to get rid of a foreign body Uterine implantation of the embryonic blastocyst Allergic-type immune response to get rid of the particular allergen
our proposal, this may reflect that anti-inflammatory adaptive neuroendocrine responses were evolutionarily conserved to cope only with transient inflammatory processes. Thus, uncoupling of supersystems after 3 to 5 weeks may be an important prerequisite for chronicity. 2. The responses of the supersystems change with time. In the early phase of a CDID (first weeks, presymptomatic phase), clonal expansion of highly affine aggressive immune cells is most important, and the adaptive immune system is the main player. After appearance of overt clinical symptoms, the local inflammatory process—for example, in a joint— involves many other cell types such as neutrophils, macrophages, natural killer cells, fibroblasts, endothelial cells, nerve fibers, and others (evolutionarily the old players). Since the supersystems affect these two phases of the disease in a different way, their influence on the course of a CDID must change when the local inflammatory process acquires a dominant role. This happens within the first weeks after appearance of clinical symptoms (symptomatic phase of arthritis) (see Figure 3). It is interesting that important hormonal and neuronal factors change during the course of CDIDs so that in the chronic phase (after 5 weeks) the systemic situation and the local micromilieu in the synovium demonstrate predominantly pro-inflammatory patterns (Figure 6).
VI. THE HEN-AND-EGG PROBLEM OF CDIDs—WHO STARTS THE DISEASE? A. The Erroneous Reaction against a SelfAntigen or a Harmless Foreign Antigen Starts the Disease At the beginning of CDIDs (in a pre-symptomatic phase), immune tolerance against self-antigens is
Typical duration of the reaction (days) ≤21 ≤21 ≤21 ≤21 ≤21 (until deep implantation) very fast, short-lasting
broken, or an inadequate immune response to harmless foreign antigens is triggered. T-cells, B-cells, and APCs are hidden players of the disease process in the pre-symptomatic phase of the disease (Figure 5B). Then, the disease, probably because of an additional trigger, strides into the symptomatic phase that involves many other cell types. Continuous aggression against an antigen leads to a dissociation between the immune system and the other supersystems (Figure 5B). Now, CDIDs become chronic due to the aberrant expression of programs that have been preserved to cope only with acute events during transient inflammatory reactions (uncoupling) (Figure 5B).
B. Age-related Changes of Supersystems Start the Disease We have mentioned that aging is an important prerequisite for the development of RA (Figure 2). During aging, adrenal cortisol production remains relatively stable, whereas the production of adrenal and gonadal androgens as well as of gonadal estrogens continuously decreases (more obvious in women than in men, particularly after menopause) (Straub et al., 2001). In addition, plasma levels of norepinephrine increase in relation to other steroid hormones including cortisol (Straub et al., 2001) (Figure 7). Aging is accompanied by a decrease of sympathetic innervation and a general increase of the sympathetic nervous tone (Bellinger et al., 2001; Straub et al., 2001) (Figure 7). Several other forms of uncoupling phenomena, which are beyond the scope of this chapter, are apparent during the aging process. During aging, uncoupling is a slowly progressive process (Figure 7), which may be paralleled by hidden immune phenomena as mentioned above (Figure 1). Autoimmunity seems to be a rather normal phenomenon in a healthy person, which is supported by a specific genetic background and largely controlled in the pre-symptomatic phase of CDIDs. It is conceivable that the uncoupling of homeostatic programs during the process of aging is enough to drive a process
FIGURE 6 Evolutionarily conserved changes of the supersystems related to acute immune challenges, whose maintenance in CDIDs induces an overall pro-inflammatory situation. Timepoint zero indicates the starting point of the overt inflammatory process. Day X indicates a later time-point in the symptomatic chronic inflammatory disease. Changes include inadequate low levels of systemic cortisol (A) (two different time courses of cortisol increase are demonstrated), decreased local androgens, progesterone, and 2-hydroxyestrogens (C), decreased local sympathetic neurotransmitters due to sympathetic nerve fiber repulsion (E), and elevated systemic levels of prolactin (B), locally increased 17β-estradiol and 16-hydroxylated estrogens (D), and high local levels of substance P due to sensory hyperinnervation (nerve fiber sprouting) (F). In relation to the initial levels, the systemic or local level of all mentioned factors changes into an aggressive direction (red zone) and never into an anti-inflammatory direction (blue zone). The larger symbol for the antigen indicates that sometimes access to a self or foreign antigen increases during the symptomatic phase of a CDID. Abbreviations: β-END, β endorphin (from sympathetic nerve terminals); A, adrenaline; NE, norepinephrine; NPY, neuropeptide Y; VIP, vasoactive intestinal peptide.
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FIGURE 7 Uncoupling of the HPA axis and the sympathetic nervous system during the process of aging. This example shows that during early life (until 25 years of age) the activities of the HPA axis and the sympathetic nervous system are synchronized. Evolutionarily conserved synchronization of the response of these two systems is necessary in order to provide cooperative effects, which contribute to prevent overt immune reactions against self or foreign antigens. Uncoupling of the activity of the two systems during aging steadily drives the aggressive immune process. At a certain time-point, with or without an exogenous trigger, the symptomatic phase of the disease starts, and uncoupling of the two supersystems is boosted, leading to further increased uncoupling phenomena.
to a symptomatic disease and chronicity, with or without an additional environmental trigger (Figure 6). Probably both an inadequate immune response and age-related changes of the supersystems play a role in this process. For both theories, genetic prerequisites are important (Figure 3, gray-shaded area). The genetic background is not restricted to genes within the immune system. Background genes controlling the other supersystems are certainly equally important (Masi et al., 2003). The integrated framework provided in this chapter demonstrates that all supersystems concomitantly add to the nature of a CDID.
Acknowledgments This work was supported by several national grants from the Deutsche Forschungsgemeinschaft (DFG), the VolkswagenFoundation (VWS), and the Nationales Genom-Forschungsnetz (NGFN) (Straub: Str 511/5-1,2,3; Str 511/9-1,2,3; Str 511/10-1,2; Str
511/11-1,2; Wi 1502/2-1; SFB 585/B8, Str 511/14-1; Str 511/15-1; Str 511/16-1; Str 511/17-1; VWS I/68950; ReFormC program of the University Hospital Regensburg; Besedovsky and del Rey: RE 1451/2-2; SFB 297/C1; VWS I/67419; (NGFN) NV-S14T02).
References Abbas, A. K., Murphy, K. M., and Sher, A. (1996). Functional diversity of helper T lymphocytes. Nature, 383, 787–793. Adashi, E. Y., Resnick, C. E., Croft, C. S., and Payne, D. W. (1989). Tumor necrosis factor alpha inhibits gonadotropin hormonal action in nontransformed ovarian granulosa cells. A modulatory noncytotoxic property. J. Biol. Chem., 264, 11591–11597. Agrawal, B., Manickasundari, M., Fraga, E., and Singh, B. (1991). T cells that recognize peptide sequences of self MHC class II molecules exist in syngeneic mice. J. Immunol., 147, 383–390. Anderton, S. M. (2004). Post-translational modifications of self antigens: implications for autoimmunity. Curr. Opin. Immunol., 16, 753–758. Baur, M., and Ziegler, G. (2001). Die Odyssee des Menschen—Es begann in Afrika. München: Econ Ullstein List Verlag.
10. Neuroendocrine-immune Interactions and Evolutionary Biology Bellinger, D. L., Madden, K. S., Lorton, D., Thyagarajan, S., and Felten, D. L. (2001). Age-related alterations in neural-immune interactions and neural strategies in immunosenescence. In R. Ader, D. L. Felten, and N. Cohen (Eds.), Psychoneuroimmunology (pp. 241–286). San Diego: Academic Press. Besedovsky, H. O., Del Rey, A., Sorkin, E., and Dinarello, C. (1986). Immunoregulatory feedback between interleukin-1 and glucocorticoid hormones. Science, 233, 652–654. Bläß, S., Engel, J. M., and Burmester, G. R. (1999). The immunologic homunculus in rheumatoid arthritis. Arthritis Rheum., 42, 2499–2506. Bluthe, R. M., Pawlowski, M., Suarez, S., Parnet, P., Pittman, Q., Kelley, K. W., and Dantzer, R. (1994). Synergy between tumor necrosis factor alpha and interleukin-1 in the induction of sickness behavior in mice. Psychoneuroendocrinology, 19, 197–207. Born, J., Lange, T., Hansen, K., Molle, M., and Fehm, H. L. (1997). Effects of sleep and circadian rhythm on human circulating immune cells. J. Immunol., 158, 4454–4464. Bottomley, M. J., Webb, N. J., Watson, C. J., Holt, L., Bukhari, M., Denton, J., Freemont, A. J., and Brenchley, P. E. (2000). Placenta growth factor (PlGF) induces vascular endothelial growth factor (VEGF) secretion from mononuclear cells and is co-expressed with VEGF in synovial fluid. Clin. Exp. Immunol., 119, 182–188. Burkhardt, H., Koller, T., Engstrom, A., Nandakumar, K. S., Turnay, J., Kraetsch, H. G., Kalden, J. R., and Holmdahl, R. (2002). Epitope-specific recognition of type II collagen by rheumatoid arthritis antibodies is shared with recognition by antibodies that are arthritogenic in collagen-induced arthritis in the mouse. Arthritis Rheum., 46, 2339–2348. Burnett, F. M. (1959). The conal selection theory of acquired immunity. Nashville: Vanderbildt University Press. Castagnetta, L. A., Carruba, G., Granata, O. M., Stefano, R., Miele, M., Schmidt, M., Cutolo, M., and Straub, R. H. (2003). Increased estrogen formation and estrogen to androgen ratio in the synovial fluid of patients with rheumatoid arthritis. J. Rheumatol., 30, 2597–2605. Christeff, N., Auclair, M. C., Benassayag, C., Carli, A., and Nunez, E. A. (1987). Endotoxin-induced changes in sex steroid hormone levels in male rats. J. Steroid Biochem., 26, 67–71. Cid, M. C., Kleinman, H. K., Grant, D. S., Schnaper, H. W., Fauci, A. S., and Hoffman, G. S. (1994). Estradiol enhances leukocyte binding to tumor necrosis factor (TNF)-stimulated endothelial cells via an increase in TNF-induced adhesion molecules E-selectin, intercellular adhesion molecule type 1, and vascular cell adhesion molecule type 1. J. Clin. Invest., 93, 17–25. Crofford, L. J., Kalogeras, K. T., Mastorakos, G., Magiakou, M. A., Wells, J., Kanik, K. S., Gold, P. W., Chrousos, G. P., and Wilder, R. L. (1997). Circadian relationships between interleukin (IL)-6 and hypothalamic-pituitary-adrenal axis hormones: failure of IL6 to cause sustained hypercortisolism in patients with early untreated rheumatoid arthritis. J. Clin. Endocrinol. Metab., 82, 1279–1283. Cutolo, M., Balleari, E., Giusti, M., Monachesi, M., and Accardo, S. (1988). Sex hormone status of male patients with rheumatoid arthritis: evidence of low serum concentrations of testosterone at baseline and after human chorionic gonadotropin stimulation. Arthritis Rheum., 31, 1314–1317. Cutolo, M., and Wilder, R. (2000). Different roles for androgens and estrogens in the susceptibility to autoimmune rheumatic diseases. Rheum. Dis. Clin. North Am., 26, 825–839. de Jong, E. C., Vieira, P. L., Kalinski, P., and Kapsenberg, M. L. (1999). Corticosteroids inhibit the production of inflammatory mediators in immature monocyte-derived DC and induce the development of tolerogenic DC3. J. Leukoc. Biol., 66, 201–204.
229
Delneste, Y., Herbault, N., Galea, B., Magistrelli, G., Bazin, I., Bonnefoy, J. Y., and Jeannin, P. (1999). Vasoactive intestinal peptide synergizes with TNF-alpha in inducing human dendritic cell maturation. J. Immunol., 163, 3071–3075. Del Rey, A., Kabiersch, A., Petzoldt, S., and Besedovsky, H. O. (2002). Involvement of noradrenergic nerves in the activation and clonal deletion of T cells stimulated by superantigen in vivo. J. Neuroimmunol., 127, 44–53. Dhabhar, F. S., Miller, A. H., McEwen, B. S., and Spencer, R. L. (1995). Effects of stress on immune cell distribution. Dynamics and hormonal mechanisms. J. Immunol., 154, 5511–5527. Dimitrov, S., Lange, T., Tieken, S., Fehm, H. L., and Born, J. (2004). Sleep associated regulation of T helper 1/T helper 2 cytokine balance in humans. Brain Behav. Immun., 18, 341–348. Ehrhart-Bornstein, M., Hinson, J. P., Bornstein, S. R., Scherbaum, W. A., and Vinson, G. P. (1998). Intraadrenal interactions in the regulation of adrenocortical steroidogenesis. Endocr. Rev., 19, 101–143. Feldman, C., Joffe, B., Panz, V. R., Levy, H., Walker, L., Kallenbach, J. M., and Seftel, H. C. (1989). Initial hormonal and metabolic profile in critically ill patients with community-acquired lobar pneumonia. S. Afr. Med. J., 76, 593–596. Galasso, F., Altamura, V., and Sbano, E. (1996). Effects of topical testosterone propionate on the positive nickel patch test. J. Dermatol. Sci., 13, 76–82. Härle, P., Straub, R. H., Wiest, R., Maier, A., Schölmerich, J., Atzeni, F., Carrabba, M., Cutolo, M., and Sarzi-Puttini, P. (2006). Increase of systemic sympathetic nervous outflow and parallel decrease of hypothalamic-pituitary-adrenal axis activity in patients with SLE and RA. Ann. Rheum. Dis., 65, 51–56. Herrmann, M., Schölmerich, J., and Straub, R. H. (2000). Stress and rheumatic diseases. Rheum. Dis. Clin. North Am., 26, 8–1–8–27. Janeway, C. A., Jr. (1989). Approaching the asymptote? Evolution and revolution in immunology. Cold Spring Harb. Symp. Quant. Biol., 54, 1–13. Jones, S. B., and Romano, F. D. (1984). Plasma catecholamines in the conscious rat during endotoxicosis. Circ. Shock, 14, 189– 201. Jorgensen, C., Bressot, N., Bologna, C., and Sany, J. (1995). Dysregulation of the hypothalamo-pituitary axis in rheumatoid arthritis. J. Rheumatol., 22, 1829–1833. Kirkwood, T. B., and Austad, S. N. (2000). Why do we age? Nature, 408, 233–238. Koch, A. E., Harlow, L. A., Haines, G. K., Amento, E. P., Unemori, E. N., Wong, W. L., Pope, R. M., and Ferrara, N. (1994). Vascular endothelial growth factor. A cytokine modulating endothelial function in rheumatoid arthritis. J. Immunol., 152, 4149–4156. Kohm, A. P., and Sanders, V. M. (2000). Norepinephrine: a messenger from the brain to the immune system. Immunol. Today, 21, 539–542. Komi, J., and Lassila, O. (2000). Nonsteroidal anti-estrogens inhibit the functional differentiation of human monocyte-derived dendritic cells. Blood, 95, 2875–2882. Komi, J., Mottonen, M., Luukkainen, R., and Lassila, O. (2001). Nonsteroidal anti-oestrogens inhibit the differentiation of synovial macrophages into dendritic cells. Rheumatology (Oxford), 40, 185–191. Lambrecht, B. N., Germonpre, P. R., Everaert, E. G., Carro-Muino, I., De Veerman, M., de Felipe, C., Hunt, S. P., Thielemans, K., Joos, G. F., and Pauwels, R. A. (1999). Endogenously produced substance P contributes to lymphocyte proliferation induced by dendritic cells and direct TCR ligation. Eur. J. Immunol., 29, 3815–3825.
230
I. Neural and Endocrine Effects on Immunity
Ljunggren, H. G., and Karre, K. (1990). In search of the “missing self”: MHC molecules and NK cell recognition. Immunol. Today, 11, 237–244. Lotz, M., Vaughan, J. H., and Carson, D. A. (1988). Effect of neuropeptides on production of inflammatory cytokines by human monocytes. Science, 241, 1218–1221. Lutz, M., and Schuler, G. (2002). Immature, semi-mature and fully mature dendritic cells: which signals induce tolerance or immunity? Trends Immunol., 23, 445. Madden, K. S., Felten, S. Y., Felten, D. L., Sundaresan, P. R., and Livnat, S. (1989). Sympathetic neural modulation of the immune system. I. Depression of T cell immunity in vivo and vitro following chemical sympathectomy. Brain Behav. Immun., 3, 72–89. Mantovani, A., Sica, A., Sozzani, S., Allavena, P., Vecchi, A., and Locati, M. (2004). The chemokine system in diverse forms of macrophage activation and polarization. Trends Immunol., 25, 677–686. Marchalonis, J. J., Kaveri, S., Lacroix-Desmazes, S., and Kazatchkine, M. D. (2002). Natural recognition repertoire and the evolutionary emergence of the combinatorial immune system. FASEB J., 16, 842–848. Masi, A. T. (1994). Incidence of rheumatoid arthritis: do the observed age-sex interaction patterns support a role of androgenic-anabolic steroid deficiency in its pathogenesis? Br. J. Rheumatol., 33, 697–699. Masi, A. T., Aldag, J. C., and Chatterton, R. T. (2003). Neuroendocrine immune perturbations in rheumatoid arthritis: causes, consequences, or confounders in the disease process? J. Rheumatol., 30, 2302–2305. Masi, A. T., Josipovic, D. B., and Jefferson, W. E. (1984). Low adrenal androgenic-anabolic steroids in women with rheumatoid arthritis (RA): gas-liquid chromatographic studies of RA patients and matched normal control women indicating decreased 11-deoxy17-ketosteroid excretion. Semin. Arthritis Rheum., 14, 1–23. Matera, L., Cesano, A., Bellone, G., and Oberholtzer, E. (1992). Modulatory effect of prolactin on the resting and mitogen-induced activity of T, B, and NK lymphocytes. Brain Behav. Immun., 6, 409–417. Matzinger, P. (2002). The danger model: a renewed sense of self. Science, 296, 301–305. Medzhitov, R., and Janeway, C. A., Jr. (2002). Decoding the patterns of self and nonself by the innate immune system. Science, 296, 298–300. Miller, L. E., Jüsten, H. P., Schölmerich, J., and Straub, R. H. (2000). The loss of sympathetic nerve fibers in the synovial tissue of patients with rheumatoid arthritis is accompanied by increased norepinephrine release from synovial macrophages. FASEB J., 14, 2097–2107. Murray, J. S. (1998). How the MHC selects Th1/Th2 immunity. Immunol. Today, 19, 157–163. Neufeld, G., Cohen, T., Shraga, N., Lange, T., Kessler, O., and Herzog, Y. (2002). The neuropilins: multifunctional semaphorin and VEGF receptors that modulate axon guidance and angiogenesis. Trends Cardiovasc. Med., 12, 13–19. Nilsson, J., von Euler, A. M., and Dalsgaard, C. J. (1985). Stimulation of connective tissue cell growth by substance P and substance K. Nature, 315, 61–63. Ostensen, M., Almberg, K., and Koksvik, H. S. (2000). Sex, reproduction, and gynecological disease in young adults with a history of juvenile chronic arthritis. J. Rheumatol., 27, 1783–1787. Pereira da Silva, J. A., and Carmo-Fonseca, M. (1990). Peptide containing nerves in human synovium: immunohistochemical evidence for decreased innervation in rheumatoid arthritis. J. Rheumatol., 17, 1592–1599.
Perez, E., Lopez-Briones, L. G., Gallar, J., and Belmonte, C. (1987). Effects of chronic sympathetic stimulation on corneal wound healing. Invest Ophthalmol. Vis. Sci., 28, 221–224. Rantapää-Dahlqvist, S., de Jong, B. A., Berglin, E., Hallmans, G., Wadell, G., Stenlund, H., Sundin, U., and van Venrooij, W. J. (2003). Antibodies against cyclic citrullinated peptide and IgA rheumatoid factor predict the development of rheumatoid arthritis. Arthritis Rheum., 48, 2741–2749. Reichenberg, A., Yirmiya, R., Schuld, A., Kraus, T., Haack, M., Morag, A., and Pollmächer, T. (2001). Cytokine-associated emotional and cognitive disturbances in humans. Arch. Gen. Psychiatry, 58, 445–452. Reynolds, M. L., and Fitzgerald, M. (1995). Long-term sensory hyperinnervation following neonatal skin wounds. J. Comp. Neurol., 358, 487–498. Roch-Arveiller, M., Regoli, D., Chanaud, B., Lenoir, M., Muntaner, O., Stralzko, S., and Giroud, J. P. (1986). Tachykinins: effects on motility and metabolism of rat polymorphonuclear leucocytes. Pharmacology, 33, 266–273. Ruff, M. R., Wahl, S. M., and Pert, C. B. (1985). Substance P receptor-mediated chemotaxis of human monocytes. Peptides, 6(Suppl. 2), 107–111. Schaible, H. G., and Grubb, B. D. (1993). Afferent and spinal mechanisms of joint pain. Pain, 55, 5–54. Seiffert, K., Hosoi, J., Torii, H., Ozawa, H., Ding, W., Campton, K., Wagner, J. A., and Granstein, R. D. (2002). Catecholamines inhibit the antigen-presenting capability of epidermal Langerhans cells. J. Immunol., 168, 6128–6135. Shifren, J. L., Tseng, J. F., Zaloudek, C. J., Ryan, I. P., Meng, Y. G., Ferrara, N., Jaffe, R. B., and Taylor, R. N. (1996). Ovarian steroid regulation of vascular endothelial growth factor in the human endometrium: implications for angiogenesis during the menstrual cycle and in the pathogenesis of endometriosis. J. Clin. Endocrinol. Metab., 81, 3112–3118. Shiokawa, S., Yoshimura, Y., Nagamatsu, S., Sawa, H., Hanashi, H., Oda, T., Katsumata, Y., Koyama, N., and Nakamura, Y. (1996). Expression of beta 1 integrins in human endometrial stromal and decidual cells. J. Clin. Endocrinol. Metab, 81, 1533–1540. Spangelo, B. L., Hall, N. R., Ross, P. C., and Goldstein, A. L. (1987). Stimulation of in vivo antibody production and concanavalinA–induced mouse spleen cell mitogenesis by prolactin. Immunopharmacology, 14, 11–20. Straub, R. H., and Besedovsky, H. O. (2003). Integrated evolutionary, immunological, and neuroendocrine framework for the pathogenesis of chronic disabling inflammatory diseases. FASEB J., 17, 2176–2183. Straub, R. H., Günzler, C., Miller, L. E., Cutolo, M., Schölmerich, J., and Schill, S. (2002a). Anti-inflammatory cooperativity of corticosteroids and norepinephrine in rheumatoid arthritis synovial tissue in vivo and in vitro. FASEB J., 16, 993–1000. Straub, R. H., Herfarth, H., Falk, W., Andus, T., and Schölmerich, J. (2002b). Uncoupling of the sympathetic nervous system and the hypothalamic-pituitary-adrenal axis in inflammatory bowel disease? J. Neuroimmunol., 126, 116–125. Straub, R. H., Paimela, L., Peltomaa, R., Schölmerich, J., and Leirisalo-Repo, M. (2002c). Inadequately low serum levels of steroid hormones in relation to IL-6 and TNF in untreated patients with early rheumatoid arthritis and reactive arthritis. Arthritis Rheum., 46, 654–662. Straub, R. H., Schuld, A., Mullington, J., Haack, M., Schölmerich, J., and Pollmächer, T. (2002d). The endotoxin-induced increase of cytokines is followed by an increase of cortisol relative to dehydroepiandrosterone (DHEA) in healthy male subjects. J. Endocrinol., 175, 467–474.
10. Neuroendocrine-immune Interactions and Evolutionary Biology Straub, R. H., Cutolo, M., Zietz, B., and Schölmerich, J. (2001). The process of aging changes the interplay of the immune, endocrine and nervous systems. Mech. Ageing Dev., 122, 1591–1611. Straub, R. H., Vogl, D., Gross, V., Lang, B., Schölmerich, J., and Andus, T. (1998). Association of humoral markers of inflammation and dehydroepiandrosterone sulfate or cortisol serum levels in patients with chronic inflammatory bowel disease. Am. J. Gastroenterol., 93, 2197–2202. Suzuki, S., Oh, C., and Nakano, K. (1986). Pituitary-dependent and -independent secretion of CS caused by bacterial endotoxin in rats. Am. J. Physiol, 250, E470–E474. Tao, T. W., Leu, S. L., and Kriss, J. P. (1985). Peripheral blood lymphocytes from normal individuals can be induced to secrete immunoglobulin G antibodies against self-antigen thyroglobulin in vitro. J. Clin. Endocrinol. Metab, 60, 279–282. Toft, P., Helbo-Hansen, H. S., Tonnesen, E., Lillevang, S. T., Rasmussen, J. W., and Christensen, N. J. (1994). Redistribution of granulocytes during adrenaline infusion and following administration of cortisol in healthy volunteers. Acta Anaesthesiol. Scand., 38, 254–258. Tonnesen, M. G., Feng, X., and Clark, R. A. (2000). Angiogenesis in wound healing. J. Investig. Dermatol. Symp. Proc., 5, 40–46. Torii, H., Tamaki, K., and Granstein, R. D. (1998). The effect of neuropeptides/hormones on Langerhans cells. J. Dermatol. Sci., 20, 21–28.
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Tsigos, C., Papanicolaou, D. A., Kyrou, I., Raptis, S. A., and Chrousos, G. P. (1999). Dose-dependent effects of recombinant human interleukin-6 on the pituitary-testicular axis. J. Interferon Cytokine Res., 19, 1271–1276. Westerman, R. A., Carr, R. W., Delaney, C. A., Morris, M. J., and Roberts, R. G. (1993). The role of skin nociceptive afferent nerves in blister healing. Clin. Exp Neurol., 30, 39–60. Wucherpfennig, A. L., Chiego, D. J., Jr., and Avery, J. K. (1990). Tritiated thymidine autoradiographic study on the influence of sensory and sympathetic innervation on periodontal wound healing in the rat. Arch. Oral Biol., 35, 443–448. Yoshimura, Y., Miyakoshi, K., Hamatani, T., Iwahashi, K., Takahashi, J., Kobayashi, N., Sueoka, K., Miyazaki, T., Kuji, N., and Tanaka, M. (1998). Role of beta 1 integrins in human endometrium and decidua during implantation. Horm. Res., 50(Suppl. 2), 46–55. Ziche, M., Maglione, D., Ribatti, D., Morbidelli, L., Lago, C. T., Battisti, M., Paoletti, I., Barra, A., Tucci, M., Parise, G., Vincenti, V., Granger, H. J., Viglietto, G., and Persico, M. G. (1997). Placenta growth factor-1 is chemotactic, mitogenic, and angiogenic. Lab. Invest, 76, 517–531.
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C H A P T E R
11 Neuroendocrine Regulation of Cancer Progression: I. Biological Mechanisms and Clinical Relevance ANIL K. SOOD, SUSAN K. LUTGENDORF, AND STEVEN W. COLE
I. INTRODUCTION 233 II. OVERVIEW OF THE STRESS RESPONSE SYSTEM 235 III. CANCER INITIATION 235 IV. CANCER METASTASIS 237 V. NEUROENDOCRINE EFFECTS ON CANCER-RELATED BIOLOGICAL PATHWAYS VI. SUMMARY 242
cellular, and molecular processes that might mediate those relationships.
A. Psychosocial Factors and Cancer Incidence 239
The question of whether psychosocial factors pose risks for development of cancer has been the focus of longstanding attention. (6,7) Galen, the ancient Greek physician, stated that women with a “melancholic” disposition were more likely to develop cancer than their counterparts with a more “sanguine” (positive) disposition. (8) Two recent meta-analyses and a review paper have found no overall link between stressful life events and development of cancer (9,10); and a third meta-analysis indicated that although some significant links were found between stressful life events, personality factors, and development of cancer, the moderate effect sizes suggested that the variance contributed by psychosocial factors to cancer initiation was relatively small. (11) However, when greater specificity is applied to these findings, relationships start to emerge. For example, presence of severe life events, or specific severe circumstances such as death of a child or spouse have been more consistently associated with increased cancer risk (6,9,12,13), with findings differing according to cancer site (14,15). The Lillberg (2003) study was notable for its large sample size of 10,808 women. (13) In a similar vein, Giraldi and colleagues found that the occurrence of severe stressful life events in the 6 months
I. INTRODUCTION Clinical and epidemiological studies over the last 25 years have identified psychosocial factors including stress, chronic depression, and lack of social support as risk factors for the incidence and progression of cancer. (1) Relationships between behavioral risk factors and cancer onset are inconsistent (see review in Chapter 41 of this volume), but behavioral factors are more consistently found to forecast differences in disease progression for already-established cancers. These clinical findings parallel a large animal research literature showing that experimentally imposed stress can alter cancer progression. (2–5) Recent molecular studies have begun to identify specific signaling pathways by which neuroendocrine correlates of behavior might impact tumor growth and metastasis. This chapter will briefly review the clinical relationship between behavioral factors and cancer pathogenesis, and then consider in more detail the neuroendocrine, PSYCHONEUROIMMUNOLOGY, 4E VOLUME I
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before a breast cancer diagnosis was associated with larger tumor volume at surgery (16). In a study unique for its repeated assessments of depression, Penninx and colleagues assessed depression prospectively (in 1982, 1985, and 1988) in 4,825 older adults in a population-based study (17). Those individuals reporting chronic depression (positive at each of the three time-points) had almost a two-fold (1.88) increase in cancer incidence compared to those with no depression. When depression at a single time point was used, it did not predict cancer incidence, suggesting a potential contribution of chronic, but not short-term depression to carcinogenesis (17). Particular combinations of psychosocial factors may be most conducive to the development of cancer. For example, Price and colleagues reported that the combination of a highly threatening life stressor and low social support was related to a nine-fold increase in breast cancer incidence, whereas, individually, neither life stressors nor low social support was related to cancer incidence (18). Furthermore, specific psychosocial risks may act synergistically in combination with biological vulnerabilities, genetic predispositions, or exposure to smoking or environmental toxins to increase the risk for cancer development (19). Examination of these potential risk factor interactions may increase understanding of the complex interactions between these phenomena.
B. Depression, Stress, and Cancer Progression In general, psychosocial factors have more strongly predicted variations in the progression of established cancers than differential risk of cancer onset. A classic prospective study of 2,020 healthy middle-aged men by Shekelle reported that psychological depression was prospectively associated with a two-fold increase in risk of death from cancer (20). This relationship was independent of adjustment for age, smoking, alcohol, family cancer history, and occupational status. In six major studies since 1990, depressive factors have been found to predict cancer progression or mortality (see review in Spiegel, 2003) (1). For example, Everson and colleagues found a dose-response relationship between hopelessness and cancer mortality in a large-scale, prospective population-based study of 2,428 men in Finland (21). During 6 years of follow-up, those men with moderate and high levels of hopelessness had more than a two-fold increase in risk of mortality from cancer (of any site) (21). Stommel (1999) reported that cancer patients with a higher pre-morbid history of depression or functional limitations had a 2.6-fold greater hazard of dying than patients without these
problems, and the combination of these two risk factors increased cancer death risk by 7.6 times (22). These data suggest that chronic psychological or functional problems may convey a vulnerability for cancer development and aggressive tumor behavior. Watson and colleagues (23) found that among 578 women diagnosed with early stage breast cancer, high levels of depression predicted a 3.59 times increased chance of death (23). Depressed mood has been associated with poorer survival in studies of lung cancer and bone marrow transplant patients as well (24,25). In contrast, Tross and associates found no association between distress and disease progression in a cohort of 280 Stage II breast cancer patients followed over a 12–16 year period (26). Other researchers have also failed to find links between depression and survival in lung and in bone marrow transplant patients (27,28). Stressful events have not generally been linked to cancer recurrence or survival (16,29,30). Thus, there are several strong studies supporting a link between depression and cancer progression. Chronicity of negative affect, as manifested in depressed mood or hopelessness, appears to have stronger relationships to outcomes than do stressful events, suggesting that sustained activation of negative affective pathways may be the strongest links to cancer progression. Moderators of stress, such as social support, have been frequently studied with respect to cancer outcomes. Social support refers to an individual’s perceived satisfaction with social relationships, and is thought to play a major role in buffering psychological and biological stress responses (31). Several studies have linked high levels of social support to improved clinical outcomes in cancer patients. In breast cancer patients, social support has been related to longer survival in several large-scale studies (32–36), although negative findings exist as well (16,37). As summarized in Chapter 41, the strongest findings indicate that characteristics such as suppression of negative emotions, hopelessness, denial, and lack of social support are associated with poorer survival. These are generally long-standing trait-like individual difference factors rather than short-term characteristics such as mood or acute stress, and thus likely to exert sustained neurohormonal effects in the body. The biological pathways underlying the links between behavioral factors and cancer incidence or progression remain poorly defined in the human clinical setting, although animal studies have identified some potential mechanisms in the context of tumor cell growth processes and anti-tumor immune responses. The effects of stress on the immune system are reviewed elsewhere in this volume, and their relevance to cancer is considered in Chapter 12. In this chapter, we con-
11. Neuroendocrine Regulation of Cancer Progression: I. Biological Mechanisms and Clinical Relevance
sider in more detail the role of behavioral and neuroendocrine factors in directly regulating the activity of tumor cells. After reviewing basic processes involved in the initiation and progression of malignant cell growth, we consider how the neuroendocrine effects of behavioral dynamics might impact those processes to affect the incidence and progression of tumors. We conclude by considering the implications of those dynamics for the clinical treatment of cancer and the maintenance of health in cancer survivors.
II. OVERVIEW OF THE STRESS RESPONSE SYSTEM Biological responses to stress are mediated by CNS processes that evaluate circumstances as threatening and modulate peripheral neuroendocrine function to respond to that threat (38,39) Two major pathways by which CNS stress responses regulate peripheral function are the HPA and SNS (40,41), and the neuroendocrine mediators of these two systems can modulate cellular function in many of the peripheral tissue sites most relevant to cancer onset and progression. For example, there is emerging evidence that catecholamine neurotransmitters from the SNS (epinephrine and norepinephrine) play physiologically relevant roles in regulating the microenvironment of peripheral organs. The ovary provides one example highly relevant to cancers of the reproductive system. Overall concentrations of catecholamines are substantially higher in the ovary than in the plasma (42). Catecholamine levels in the ovary are known to be increased in response to stress due to increased sympathetic activity, which has been shown to result in appearance of precystic follicles (43–46). Similarly, catecholamines are present at substantially higher levels in the bone marrow microenvironment than in circulation and originate from nerve endings and bone marrow cells (47). Functionally, there is growing evidence that neuroendocrine factors can modulate hematopoiesis within the bone marrow microenviroment (47). The effects of catecholamines on cancer growth and progression are discussed below, but these studies suggest that stress-induced changes in catecholamines are robust enough to alter organ microenvironment and function. Both norepinephrine and epinephrine are known to be elevated in individuals with acute or chronic stress (48–50). Beta-adrenergic receptors (βAR) mediate many effects of catecholamines on target cells and have been identified on several cancer cell types, including breast cancer cells (51) and ovarian cancer cells (52), where the β2 subtype is the dominant adren-
235
ergic receptor present. βARs are G-protein–coupled receptors, whose primary function is the transmission of information from the extracellular environment to the interior of the cell (53). Three distinct βAR subtypes have been identified (β1-AR, β2-AR, and β3-AR) (54– 56), and all three can signal by coupling to the stimulatory G-protein Gαs, leading to activation of adenylyl cyclase and accumulation of the second messenger cAMP. To verify the role of beta-adrenergic activation in mediating stress effects on tumor dynamics, some investigators have used agonists such as metaproterenol to demonstrate dose-dependent increases in, for example, the retention of tumor cells within the lung. Similarly, adrenaline injections have been shown to cause suppression of NK cell activity and promote tumor cell retention (57). Cortisol is a glucocorticoid hormone that is secreted by the adrenal cortex in response to stress (40,58,59). Social support and stress reduction are associated with lower cortisol levels (60,61). Glucocorticoids may have a bimodal effect on tumor cells. For example, Kawamura and colleagues have reported, at lower doses, dexamethasone can stimulate tumor growth, but at higher doses it inhibits tumor growth (62). In addition, cortisol may act in a synergistic fashion with catecholamines. For example, cortisol has been shown to potentiate the isoproterenol-induced increase in cAMP accumulation in lung carcinoma cells (63).
III. CANCER INITIATION Several lines of evidence indicate that tumorigenesis in humans is a multi-step process and that these steps reflect genetic alterations that drive the progressive transformation of normal human cells into malignant cells (64,65). The transformation of a normal cell into a cancerous state appears to require multiple ratelimiting steps including both genetic and epigenetic processes. Even in cultured rodent cells, tumorigenic potential requires at least two introduced genetic changes, and human cells are more difficult to transform (66). Hanahan and Weinberg (64) proposed that there are six essential alterations in cell physiology that dictate malignant growth: (1) self-sufficiency in growth signals, (2) insensitivity to growth-inhibitory (antigrowth) signals, (3) evasion of programmed cell death (apoptosis), (4) limitless replicative potential, (5) sustained angiogenesis, and (6) tissue invasion and metastasis. Each of these acquired capabilities reflects a breach in the normal host defenses against malignant cell growth. In some tumors such as Kaposi’s sarcoma and cervical cancer, viral infections contribute to the acquisition of some of these capabilities by delivering
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new genes into the cell (viral oncogenes). In other cases, physical damage to cellular DNA by carcinogens alters the expression or function of human genes. Regardless of whether tumors are initiated by viral infections or other carcinogens, the result is a somatic cell with enhanced growth capacity and a consequent increase in its ability to “evolve” within the body by acquiring new genetic alterations. Below, we focus on viral oncogenesis as a model for understanding biobehavioral influences on tumor initiation due to the well-characterized influences of behavioral stress and neuroendocrine factors on the activity of oncogenic viruses. However, other pathways for neuroendocrine influence clearly exist. For example, several studies have shown that stress can affect the cellular process involved in the repair of damaged DNA (67–70), providing a generalized mechanism by which behavioral factors might facilitate the establishment of oncogenic mutations. Behavioral factors can also increase tumor incidence via accelerated replication of hormoneresponsive cells, leading to increased opportunities for mitotic errors that may contribute to increased tumorigenesis in stressed animals (71–73). Several other fundamental processes of tumor initiation and evolution will be considered in the context of metastasis later (see also Chapter 12).
A. Viral Oncogenesis Some of the earliest experimental demonstrations that biobehavioral factors could influence cancer came from animal studies of virally induced tumors (74–76). As animal models of malignant cell growth emerged in the 1950s, 1960s, and 1970s, a raft of studies found accelerated growth of virally induced tumors in animals subject to experimental stress (4,5,77), as well as seemingly paradoxical protective effects of handling, fighting, and crowding (76,78–82). As the basic pathogenesis of these virally induced tumors became better understood, biological bases for these conflicting results became apparent in the diverse biology of distinct tumor types. Changes in neuroendocrine function were found to play a central role in stress effects on tumor growth, particularly elevated production of glucocorticoids (e.g., corticosterone, the rodent analogue of primate cortisol). Depending upon the particular viral model, glucocorticoids could modulate viral replication, activate viral oncogenes, enhance tumor metabolism, undermine cellular immune responses, or kill lymphoid cells (83–88). The latter dynamic was particularly significant in determining when stress would manifest paradoxically protective effects: Malignancies of hematopoietic and lymphoid
cells (leukemias and lymphomas) were generally inhibited by experimental stress because those cell types are especially vulnerable to glucocorticoidinduced programmed cell death (apoptosis). In fact, many chemotherapy protocols for lymphoid and hematopoietic malignancies include synthetic glucocorticoids as a central pro-apoptotic component. In contrast to leukemias and lymphomas, animal models of solid tumors were generally found to be exacerbated by stress due to the effects of glucocorticoids and catecholamines in undermining cellular immune responses (89–92) and enhancing tumor metabolism and viral oncogene expression (83–88). Several studies also found that stress effects on tumor growth varied depending upon whether the stress was applied before, during, or after tumor initiation, or depending on the gender or housing conditions of the animal (4,5,75–77). These results are consistent with the multi-step nature of cancer in suggesting that stress-related neuroendocrine dynamics might have different impacts at varying stages of tumor development or on different aspects of the malignant cell growth process. As evidence for viral contributions to human cancer emerged during the 1970s and 1980s (Table 1) (93–95), “stress hormones” have been found to influence the activity of all major human tumor viruses, including both RNA and DNA viruses (Table 2). Seminal studies from the laboratory of Glaser and colleagues found that prolonged psychological stress could induce subclinical reactivation of Epstein-Barr virus (EBV) in healthy people, and similar results have emerged from studies of astronauts and Antarctic research scientists (96–99). In many of these studies, HPA activity increased in parallel (100,101) and glucocorticoid hormones were subsequently found to enhance EBV gene expression in vitro (101,102). Subsequent studies have also shown that glucocorticoids can modulate the TABLE 1
Viral Oncology
• Viral infections contribute to approximately 15% of human cancers worldwide (95). Pathogenic mechanisms include expression of viral oncogenes (e.g., HTLV Tax, EBV EBNAs, and LMP1), inhibition of host cell tumor suppressors (e.g., HPV E6/p53 and E7/pRB), and genomic damage stemming from immune-mediated cell turnover (e.g., HBV, HCV) (93–95). • All human tumor viruses are sensitive to the intracellular signaling pathways activated by the HPA axis and ANS (see Table 2), which can reactivate latent tumor virus, stimulate oncogene expression, and inhibit host cell antiviral responses. • Vaccination is a major primary prevention strategy against viral tumors, and behavioral factors can influence the efficacy of this approach by modulating vaccine-induced immune responses (138–141).
11. Neuroendocrine Regulation of Cancer Progression: I. Biological Mechanisms and Clinical Relevance TABLE 2
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Human Cancer Viruses Influence by Stress Hormones
Human tumor virus Human Papilloma Viruses (HPV-16, HPV-33) Hepatitis B Virus (HBV) Hepatitis C Virus (HCV) Epstein-Barr Virus (EBV) Human T-cell Lymphotropic Virus (HTLV-I, -II) Kaposi’s Sarcoma-associated Herpesvirus (KSHV)
Malignancy
Sensitivity*
Cervical and head/neck cancer Hepatocellular carcinoma Hepatocellular carcinoma Lymphoma, Nasopharyngeal carcinoma Adult T-cell leukemia/lymphoma Kaposi’s Sarcoma, Primary Effusion Lymphoma
HPA HPA HPA HPA ANS ANS
*Presumptive based on in vitro studies.
activity of cancer-causing Human Papilloma viruses (HPVs) by enhancing viral gene expression (103–110), facilitating interactions between viral gene products and cellular proto-oncogenes (111,112), and undermining cellular immune responses by downregulating Class I MHC molecules (113). Glucocorticoid antagonists can inhibit HPV activity in vitro (114–116), providing a potential molecular mechanism for clinical data linking psychological risk factors to the progression of cervical dysplasia in HPV+ women (117,118). Hepatitis B and C viruses (HBV/HCV) come from completely different viral lineages, yet both respond to glucocorticoids by enhancing gene expression and replication (119–127). These dynamics are so pronounced that glucocorticoids have been employed clinically to activate HBV and HCV for eradication by replication-dependent antiviral drugs (125–128). Cancer-related viruses are also sensitive to catecholamines and the cAMP-linked PKA signaling pathway. Virologic mechanisms are especially well defined for Acquired Immune Deficiency Syndrome (AIDS)– associated malignancies. Catecholamines can accelerate HIV-1 replication by enhancing cellular susceptibility to infection (129,130), activating viral gene transcription (129), and suppressing anti-viral cytokines (131). People with high ANS activity show elevated plasma viral load and impaired response to anti-retroviral therapy (129), placing them at increased risk for AIDSassociated B-cell lymphomas (132,133). Catecholamines can also activate the Kaposi’s Sarcoma-associated Herpesvirus (KSHV) via PKA induction of the viral transcription factor Rta (134). The Human T-cell Lymphotropic Viruses (HTLV-I/-II) are sensitive to PKAmediated induction of the oncogenic Tax transcription factor (135). In addition to direct effects on viral gene expression, biobehavioral factors can also indirectly affect tumor viruses by modulating host immune responses. Antiviral vaccines will play a growing role in the primary prevention of cancer (136,137), and biobehavioral modulation of vaccine-induced immune responses
TABLE 3
Steps Involved in Metastasis
1. Proliferation and growth of primary tumor 2. Detachment or shedding of cells from primary tumor into circulation 3. Survival of cancer cells in circulation 4. Transport of cancer cells to new organs with subsequent arrest 5. Extravasation into surrounding tissues 6. Angiogenesis and growth of the metastatic tumor
becomes especially relevant (138–141). Neuroendocrine influences on immune response may also explain why oncogenic viruses so consistently acquire hormone-responsive replication dynamics. Viruses that coordinate their gene expression with periods of hormone-induced immunosuppression should enjoy a significant survival advantage. Similar selective pressures may also shape the evolution of non-viral malignancies (65), as genomic alterations are selected for their ability to evade immune clearance or capitalize on endocrine dynamics to optimize growth and metastasis.
IV. CANCER METASTASIS Cancer is a complex disease in which many basic processes including cell division, apoptosis, and motility are dysregulated. Metastasis is a process by which cancer cells spread from the primary tumor to distant organs followed by relentless growth at those sites (142). Despite improvements in diagnosis and therapy, most deaths from cancer occur due to metastases that are resistant to conventional therapy (143). The process of cancer metastasis consists of a series of sequential, interrelated steps, each of which can be rate limiting (Table 3). To produce clinically relevant lesions, metastatic cells must complete all the steps of this process (144). After the initial transformation and growth of these cells, vascularization must occur for a tumor mass to exceed 2 mm in diameter (145,146). Subse-
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quent steps in the pathogenesis of cancer metastasis include invasion, detachment, embolization, arrest in capillary beds of organs, extravasation into the organ parenchyma, evasion of host defenses, and progressive growth. The production of metastases, therefore, depends on continuous interaction of tumor cells with host homeostatic mechanisms (147,148). Failure to complete any of the sequential steps aborts the process of metastasis. It has long been recognized that some types of cancer show an organ-specific pattern of metastasis. In 1989, Stephen Paget published an influential paper describing the propensity of various types of cancer to form metastases in specific organs and proposed that these patterns were due to the “dependence of the seed (cancer cell) on the soil (the metastatic site)” (149). His analysis indicated a non-random pattern of metastasis, and he concluded that metastases formed only when the seed and soil were compatible. The regulation of metastasis can be considered in terms of a balance between growth-stimulating factors from both the tumor and host cells versus inhibitory signals. To produce metastasis, the balance is weighted toward the stimulatory signals. Even though Paget’s “seed and soil” hypothesis dates back to 1889, the mechanistic role of microenvironment has only recently begun to be defined. Tumor progression is a product of an evolving crosstalk between different cell types within the tumor and its surrounding supporting tissue, tumor stroma (150). The tumor stroma contains a specific extracellular matrix as well as cellular components such as fibroblasts, immune and inflammatory cells, and blood-vessel cells. The interactive signaling between tumor and stroma contributes to the formation of a complex multi-cellular organ (Table 4). For example, the expression of the epidermal growthfactor receptor coupled with the expression of growth factors in the host tissue such as transforming growth factor-α (TGF-α) plays a role in metastatic
TABLE 4
Molecular Regulators of Metastasis*
Biological process Survival Adhesion Migration/Invasion ECM remodeling Immune escape Angiogenesis Homing to target organs
Molecular factors IGF survival factors CAMs, cadherins, integrins c-Met/HGF signaling, FAK MMPs, IPA, heparanase MHC loss VEGF, bFGF, PDGF Chemokines/chemokine receptors, CD44
*This list is meant to be illustrative and not comprehensive with regard to molecular factors regulating metastasis.
growth of colon and other cancer cells in the liver (151). The organ microenvironment can markedly change the gene-expression patterns of cancer cells, and therefore their behavior and growth ability (150). Recent studies regarding chemokines and their receptors provide important clues regarding why some cancers metastasize to specific organs. For example, breast cancer cells frequently express chemokine receptors CXCR4 and CCR7 at high levels. The specific ligands for these receptors CXCL12 and CCL 21 are found at high levels in lymph nodes, lung, liver, and bone marrow, which are common sites for breast cancer metastasis (152,153). Emerging evidence suggests that factors related to certain biobehavioral states such as neuropeptides and neurotransmitters also influence various steps in the cascade of metastasis.
A. Animal Models for Studying Effects of Stress Appropriate animal models play a crucial role in understanding the effects of stress of cancer and other diseases. Restraint stress animal models, using a variety of restraining devices, have been widely used to study the effects of stress on immunity, course of infectious diseases, and cancer (154–158). Physical restraint using 50 ml conical tubes for varying lengths of time has been shown to effectively modulate norepinephrine, epinephrine, and glucocorticoid levels (154–158). Restraint systems have also been demonstrated to consistently result in elevations of IL-6 (159,160). Furthermore, restraint stress has been shown to reduce the anti-tumor efficacy of chemotherapy in C57BL/6 mice bearing Lewis lung carcinoma (161) and has been demonstrated to result in metallothionein induction, which may be responsible for chemotherapy resistance (162). The length of restraint in different studies has ranged from 1 hour to 12 hours daily (155–157,159,161,163,164). In C57BL/6 mice, within 3 hours, there is almost a 50% increase in corticosterone levels, and at 6 hours the corticosterone levels reach a maximal increase of over 100% (155, 157,159,161,164,165). Furthermore, restraint stress has been demonstrated to raise catecholamine levels in murine models by two- to five-fold (45,164,166,167). Other models used for stress studies include swim stress, surgical stress, social confrontation, and hypothermia—these models have also been shown to promote lung metastasis from injected breast cancer cells (57,168–170). Most of these models have been used in the context of effects on the immune system, and specific applications are described in detail in the accompanying Chapter 12. The effects of stress on other biological pathways are described below.
11. Neuroendocrine Regulation of Cancer Progression: I. Biological Mechanisms and Clinical Relevance
V. NEUROENDOCRINE EFFECTS ON CANCER-RELATED BIOLOGICAL PATHWAYS A. Proliferation and Growth of Primary Tumor and Metastases Tumor growth at the primary site depends initially on nutrient and oxygen diffusion. Subsequently, at metastatic sites, signals from autocrine, paracrine, and/or endocrine pathways influence tumor cell proliferation with growth dependent on the net balance of positive and negative signals (144). There are limited data regarding the direct effects of stress hormones on cell proliferation. Most data suggest that catecholamines suppress proliferation of normal cells such as keratinocytes (171), which may contribute to impaired wound healing in the context of stress. The effects of stress-related hormones on tumor cell proliferation may depend on the type of substance and tumor type. In mammary tumors, activation of βARs have been related to accelerated tumor growth (51,172,173). The cAMP responsive element-binding (CREB) protein is an important transcription factor activated by multiple signal transduction pathways in response to external stimuli including stress hormones (174,175). Several studies have revealed a role for the CREB family of proteins in tumor cell proliferation, migration, angiogenesis, and inhibition of apoptosis (174–176). However, in other models, catecholamines appear to inhibit tumor cell proliferation, which may be mediated by alpha-adrenergic receptors. Scarparo and colleagues tested the effects of the α1-adrenergic agonist phenylephrine and reported a dose-dependent decrease in melanoma cell proliferation, which was reversed by the α1-adrenergic antagonist prazosin (177). Similarly, Pifl and associates found that norepinephrine inhibited neuroblastoma cell growth, primarily in cells expressing the dopamine transporter (178). In cells with dopamine uptake, the share of G0/ G1 population of cells was significantly increased after treatment with norepinephrine. Bijman and associates examined the effects of isoproterenol and histamine on head and neck carcinoma cells and found that both agents resulted in a minor inhibition of clonogenicity, which could be reversed with propranolol and cimetidine, respectively (179). In prostate carcinoma, treatment with agents that induce cAMP, such as epinephrine, isoproterenol, forskolin, and dibutyryl cAMP, result in acquisition of neuroendocrine characteristics by epithelial prostate cancer cells (180). The neuroendocrine characteristics were manifested by dense core granules in the cytoplasm, the extension of neuron-like processes, loss of mitogenic activity, and
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expression of multiple neuroendocrine markers. The presence of these neuroendocrine cells has been linked to prognosis in prostate cancer patients (181,182). Interestingly, the neuroendocrine cells have minimal proliferative activity, but yet these cells provide paracrine stimuli for proliferation of surrounding carcinoma cells (183). Among the epithelial tumors, some decrease in proliferation may be reflective of a more invasive phenotype. Next, we will discuss the effects of glucocorticoid hormones on cancer cell proliferation. Zhao and colleagues determined the effects of glucocorticoids on prostate cancer cells (184). Cortisol, and its metabolite cortisone, stimulated the growth of prostate cancer cells in the absence of androgens and increased the secretion of prostate-specific antigen (184). These cells had a mutated androgen receptor. Simon and coworkers examined the effects of several steroid hormones on human mammary carcinoma cells and found that physiological concentrations of glucocorticoids enhanced proliferation by nearly two-fold (185). The role of glucorticoid hormones in the context of other neuroendocrine hormones remains to be studied with regard to effects on proliferation.
B. Adhesion Tumor cell adhesion to the extracellular matrix within tissues greatly influences the ability of a malignant cell to invade and metastasize to outlying tissues (186). The proteins of the extracellular matrix consist of type I and IV collagens, laminins, heparin sulfate proteoglycan, fibronectin, and other noncollagenous glycoproteins (187). Cell adhesion to these proteins is mediated in part by a group of heterodimeric transmembrane proteins called integrins, which are composed of a non-covalently associated α and β subunit that defines the integrin-ligand specificity (188). The upstream factors that regulate adhesion to matrix components are not completely understood, although cAMP has been shown to regulate the small GTPases RhoA and Rac in a protein kinase A (PKA)–dependent manner (189). Cyclic AMP is a common second messenger that regulates many cellular processes. Previously, PKA was thought to be the main target of cAMP in eukaryotic cells. However, recently Epac (exchange factor directly activated by cAMP), a widely expressed exchange factor for the small GTPases Rap1 and Rap2, has been shown to be a receptor for cyclic AMP as well (190,191). Importantly, Epac controls a number of cellular processes previously attributed to PKA. Cyclic AMP controls cell adhesion in many cell types, and recently a link between cAMP, Epac-Rap1, and regulation of cell adhesion has been established (192). Enser-
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ink and colleagues have demonstrated that isoproterenol promotes ovarian cancer cell spreading and adhesion to laminin-5 independent of protein kinase A but rather dependent on Epac 1 (193). Similarly, isoproterenol stimulated adhesion to fibronectin in a cAMPmediated Epac-Rap1 pathway (192). Treatment with isoproterenol induced both activation of Rap1 and phosphorylation of CREB. Isoproterenol-induced adhesion was insensitive to pretreatment with a PKA inhibitor. Thus, stress hormones may promote cellmatrix attachments of cancer cells. Such a mechanism would be particularly relevant for ovarian cancer where cancer cells slough off the primary tumor and then implant at multiple peritoneal sites.
C. Migration and Invasion To reach blood vessels or lymphatics, tumor cells must penetrate host stroma, including the basement membrane. The process of tumor cell penetration of the host basement membrane consists of attachment, matrix dissolution, motility, and then actual penetration (194). There is growing evidence that stress hormones may affect tumor cell motility and invasion. Drell and colleagues demonstrated that norepinephrine not only induces chemokinetic migration, but also attracts breast cancer cells chemotactically (195). Similarly, Masur and associates demonstrated that norepinephrine was a potent inducer of colon cancer cell migration, which was inhibited by beta-blockers (196). Furthermore, they demonstrate that norepinephrinestimulated migration was dependent on phospholipase Cγ and protein kinase Cα activity. Sood and colleagues have examined the direct effects of catecholamines and cortisol on the invasive potential (i.e., capacity of tumor cells to penetrate extracellular matrix) of ovarian cancer cells, and their production of key matrix metalloproteinases involved in tumor cell penetration of extracellular matrix (197). Stress levels of norepinephrine increased the in vitro invasiveness of ovarian cancer cells by 89–198% (198). Epinephrine also induced significant increases in invasion of ovarian cancer cells ranging from 64–76%, but cortisol did not significantly affect the invasive potential of cancer cells. The beta-adrenergic antagonist propranolol completely blocked the norepinephrine-induced increase in invasiveness. Norepinephrine also increased tumor cell expression of MMP-2 and MMP-9, and pharmacologic blockade of MMPs abrogated its effects on tumor cell invasive potential. These findings provide direct experimental evidence that stress hormones can enhance the invasive potential of ovarian cancer cells in vitro.
D. Angiogenesis Hormones associated with SNS activation may favor angiogenic mechanisms in human tumors. Norepinephrine has been shown to upregulate vascular endothelial growth factor (VEGF) in adipose tissue through beta-adrenoreceptor/cAMP/PKA pathway (199) and in two ovarian cancer cell lines (52). VEGF is a direct angiogenic molecule that plays an essential role in embryogenesis, physiologic angiogenesis, and neovascularization of malignancy (200). VEGF stimulates endothelial cell migration, proliferation, and proteolytic activity (201). The effect of norepinephrine with regard to VEGF stimulation was abolished by a beta-blocker, propranolol, and mimicked by isoproterenol and was thus thought to be mediated via βadrenoreceptors (52,199). The effects of stress on tumor angiogenesis have recently been examined using in vivo models. In orthotopic murine models of ovarian cancer, Thaker and colleagues demonstrated that chronic stress induced by daily periods of immobilization results in higher levels of tissue catecholamines, greater tumor burden, and a more invasive pattern of disease (202). Angiogenesis, as reflected by microvessel density counts, was significantly increased in the stressed compared to control mice tumor samples. Furthermore, VEGF mRNA and protein levels were significantly elevated in the stressed tumor samples. Continuous infusion of propranolol (non-selective beta-blocker) ameliorated the effects of stress on tumor burden and pattern of disease, thereby confirming the importance of beta-adrenergic receptors on ovarian cancer cells in an in vivo model (202). In line with these findings, recent clinical studies have shown links between higher levels of social support and lower serum VEGF levels in ovarian cancer patients (203). Furthermore, social support has also been linked to lower levels of interleukin-6 (IL-6), another proangiogenic factor, both in peripheral blood and in ascites from ovarian cancer patients (204). Tumor-produced angiogenic molecules may further contribute to cancer progression by impairing immune cell function. Factors such as VEGF and tumor necrosis factor (TNF) may impair both effector function and early stages of hematopoiesis. Mice receiving transplants of Lewis lung carcinoma cells develop thymic aptrophy (205). VEGF causes a defect in the functional maturation of dendritic cells (DCs) from early hematopoietic progenitor cells (206,207). In addition to DC defects, non-tumor–bearing mice treated with recombinant VEGF have a decreased number of T-cells and a decreased T-cell to B-cell ratio in their lymph nodes and spleen (207). Ohm and colleagues demonstrated
11. Neuroendocrine Regulation of Cancer Progression: I. Biological Mechanisms and Clinical Relevance
profound thymic atrophy accompanied by a marked reduction in CD4+/CD8+ thymocytes after exposure of mice to recombinant VEGF at concentrations similar to those observed in advanced stage cancer patients (208). There is also evidence that other cytokines, such as IL-6, could contribute to peripheral T lymphocyte dysfunction, enabling tumor cells to escape immune surveillance by preventing the anti-tumor TH1 immune responses (209). These findings suggest that stressinduced changes in tumor-associated factors may further promote tumor growth by compromising components of the immune system. There are limited data regarding the effects of cortisol on angiogenesis. In a rat glioma model, dexamethasone (synthetic glucocorticoid) treatment of cancer cells resulted in a 50–60% downregulation of VEGF mRNA, and this effect was dependent on the glucocorticoid receptor function (210). However, this inhibitory effect was markedly reduced by hypoxia, which is a potent VEGF inducer. In ovarian cancer cell lines, cortisol alone had some stimulating effects at lower doses, but inhibitory effects at pharmacologic doses (52). Because stress often involves elevations in both cortisol and catecholamines, costimulation experiments were also performed. While priming with cortisol blunted norepinephrine-induced VEGF production, significant increases were still seen (52). These findings suggest that catecholamine-induced effects are dominant in the context of angiogenic cytokine production.
E. Cell Survival Tumor cell survival or avoidance of apoptosis is essential during the metastatic process. Most of the data with regard to the effects of stress hormones on tumor cell survival have focused on glucocorticoid hormones. Glucocorticoids regulate a wide variety of cellular processes through glucocorticoid receptormediated activation or repression of target genes. Recent studies have demonstrated that while glucocorticoid hormones induce apoptosis in lymphocytes (211), these hormones activate survival genes that protect cancer cells from the effects of chemotherapy (212,213). Herr and colleagues examined the effects of glucocorticoids on human cervical and lung carcinoma cells and found downregulation of pro-apoptotic elements of the death receptor and mitochondrial apoptosis pathways (212). Similarly, Wu and associates found that dexamethasone pretreatment of breast cancer cell lines inhibits chemotherapy-induced apoptosis in a glucocorticoid receptor-dependent manner and is associated with the transcriptional induction of
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serum and GC-inducible protein kinase-1 (SGK-1) and mitogen-activated protein kinase phosphatase-1 (MKP1) (213). Specific inhibition of these two proteins reversed the anti-apoptotic effects of GC treatment (213). Glucocorticoids such as cortisol may also act in a synergistic fashion with catecholamines to facilitate cancer growth. For example, cortisol potentiated the isoproterenol-induced increase in cAMP accumulation; increased βAR density; and markedly increased the effects of IL-1α, IL-1β, and TNF-α in lung carcinoma cells (63). It is thus plausible that stressful situations characterized by both elevated catecholamine and cortisol levels (e.g., uncontrollable stress) may have the greatest impact on cancer-related processes.
F. Other Stress Mediators Other hormones affected by stress include prolactin (214,215), oxytocin, and dopamine (216). Prolactin plays a functional role in tumor cell growth and promotes survival of breast and other cancer cells (217,218). A number of epidemiological studies have demonstrated a consistent correlation between prolactin levels and well-confirmed breast cancer risk factors such as parity and age at menarche (217). Most breast cancer cell lines express the prolactin receptor, and exogenously added prolactin has modest trophic effects on human tumor tissues and cells in vitro (219). Prolactin has been shown to stimulate proliferation in prostate and endometrial cancer cells as well (218). In addition to stimulation of proliferation, prolactin may also actively inhibit apoptosis of mammary tumor cells via stimulation of the Akt pathway (220,221). Oxytocin inhibits the growth of some epithelial cell (e.g., breast, endometrial) tumors and those of nervous or bone origin, but the hormone has a growthstimulating effect in trophoblast and other tumors (small cell lung tumors, Kaposi’s sarcoma) (222,223). The presence of oxytocin receptor has been described in breast cancer cells (224,225). Dopamine, an important member of the catecholamine family, is one of the major neurotransmitters in the mammalian brain and also has important roles in the periphery (226,227). Chronic exposure to stress leads to decreased dopamine release (228,229). Several studies have indicated a direct effect of dopamine in growth inhibition of tumor cells including neuroblastoma, breast, melanoma, and head and neck cancer cell lines (230–234). The growth inhibition may be mediated through dopamine receptors on the tumor cell surface or by auto-oxidation of dopamine, resulting in the generation of reactive oxygen species. However, emerging data suggest that dopamine may have other
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anti-tumor effects as well, such as anti-angiogenic properties. Dopamine is known to inhibit the growth of several types of tumors in in vivo experimental models (235,236). Basu and colleagues reported that at non-toxic levels, dopamine administration inhibited the vascular permealizing and angiogenic activities of VEGF (237). Dopamine acted through D2 dopamine receptors to induce endocytosis of VEGF receptor 2, which is critical for promoting angiogenesis, thereby preventing VEGF binding, receptor phosphorylation, and subsequent signaling steps (237). Similar results were found in gastric cancer models (235). Teunis and co-workers examined tumor growth and angiogenesis in Wistar rats with high or low dopamine reactivity (236). Both tumor size and vessel density were lower in rats with a hyperactive dopaminergic system, again suggesting a link between dopaminergic activity, angiogenesis, and tumor development.
ing neuroendocrine dynamics to undermine their support for the progression of malignant disease. Some biobehavioral intervention studies have shown promise for modifying neuroendocrine dysregulation, and immunologic functions that could potentially have implications for tumor progression (3). As discussed above, beta-blockers have been shown to block many of the deleterious effects of stress. Some clinical studies have shown lower cancer incidence among patients treated with beta-blockers (238,239), while in others the cancer risk was neutral (240–242). Some antidepressant medications also suppress the inflammatory response (243), which may be a beneficial property in cancer patients. While great strides have been made in understanding the influence of behavioral factors on cancer initiation and progression, further research is needed to fully understand the complex underlying mechanisms. However, such work holds promise for novel patient-specific and comprehensive intervention strategies.
VI. SUMMARY Cancer initiation and progression is a complex process that is dependent on multiple steps, including genetic alterations, growth/proliferation, vascularization, invasion, embolization, and survival/evasion of apoptosis. Once a tumor is established, its survival, growth, and metastatic dissemination depends on many interactions with homeostatic factors and mechanisms. The cumulative clinical and pre-clinical work reviewed in this chapter demonstrates the interrelationships between behavioral factors and cancer initiation and metastasis. The effects of behavioral factors on the immune system will be discussed in the accompanying Chapter 12. However, stress-induced changes in tumor factors such as VEGF and IL-6 may also play a role in compromising components of the immune system, thus further tilting the physiologic odds in favor of the tumor. The findings in the current chapter suggest that behavioral process and their endocrine consequences can have multiple and direct effects on the tumor microenvironment, with the potential to generate clinically significant downstream effects on tumor progression. Based on the data reviewed here showing direct effects of “stress hormones” on the function and activity of tumor cells, perhaps the word psychoneuroimmunobiology may be more reflective of the effects of behavioral factors on cancer. The effects of behavioral factors on tumor initiation and progression are likely to be complex and should be studied in the context of the relevant microenvironment. These studies may offer new opportunities for therapeutic intervention based on behavioral and pharmacologic approaches that target tumor-support-
Acknowledgments Portions of the work in this chapter were supported by NCI grants (CA11079301, CA10929801, and CA083639) to Dr. Sood; NCI grants (CA 1045-25 and CA 102515) and NCCAM (P20 AT-756) to Dr. Lutgendorf; and Dr. Cole is supported by NIH grant AI52737 and the Norman Cousins Center at UCLA.
References 1. Spiegel, D., and Giese-Davis, J. (2003). Depression and cancer: mechanisms and disease progression. Biol. Psychiatry, 54, 269–282. 2. Strange, K. S., Kerr, L. R., Andrews, H. N., et al. (2000). Psychosocial stressors and mammary tumor growth: an animal model. Neurotoxicol. Teratol., 22, 89–102. 3. Antoni, M., Lutgendorf, S., Cole, S., et al. (2006). The influence of biobehavioral factors on tumor biology: pathway and mechanisms. Nature Reviews Cancer, 6, 240–248. 4. Justice, A. (1985). Review of the effects of stress on cancer in laboratory animals: importance of time of stress application and type of tumor. Psychol. Bul., 98, 108–138. 5. Riley, V. (1981). Psychoneuroendocrine influences on immunocompetence and neoplasia. Science, 212, 1100–1109. 6. Chen, C. C., David, A. S., Nunnerley, H., et al. (1995). Adverse life events and breast cancer: case-control study. BMJ, 311, 1527–1530. 7. Protheroe, D., Turvey, K., Horgan, K., et al. (1999). Stressful life events and difficulties and onset of breast cancer: case-control study. BMJ, 319, 1027–1030. 8. Dunn, A. J. (1996). Psychoneuroimmunology: introduction and general perspectives. In B. E. Leonard and K. Miller (Eds.), Stress, the immune system and psychiatry (pp. 1–16). Chichester: John Wiley & Sons, Ltd. 9. Duijts, S. F., Zeegers, M. P., and Borne, B. V. (2003). The association between stressful life events and breast cancer risk: a metaanalysis. Int. J. Cancer, 107, 1023–1029.
11. Neuroendocrine Regulation of Cancer Progression: I. Biological Mechanisms and Clinical Relevance 10. Petticrew, M., Fraser, J., and Regan. M. (1999). Adverse lifeevents and risk of breast cancer: a meta-analysis. British Journal of Health Psychology, 4, 1–17. 11. McKenna, M. C., Zevon, M. A., Corn, B., et al. (1999). Psychosocial factors and the development of breast cancer: a metaanalysis. Health Psychology, 18, 520–531. 12. Geyer, S. (1991). Life events prior to manifestation of breast cancer: a limited prospective study covering eight years before diagnosis. J. Psychosom. Res., 35, 355–363. 13. Lillberg, K., Verkasalo, P. K., Kaprio, J., et al. (2003). Stressful life events and risk of breast cancer in 10,808 women: a cohort study. Am. J. Epidemiol., 157, 415–423. 14. Levav, I., Kohn, R., Iscovich, J., et al. (2000). Cancer incidence and survival following bereavement. Am. J. Public Health, 90, 1601–1607. 15. Martikainen, P., and Valkonen, T. (1996). Mortality after death of spouse in relation to duration of bereavement in Finland. J. Epidemiol. Community Health, 50, 264–268. 16. Giraldi, T., Rodani, M. G., Cartei, G., et al. (1997). Psychosocial factors and breast cancer: a 6-year Italian follow-up study. Psychotherapy & Psychosomatics, 66, 229–236. 17. Penninx, B. W., Guralnik, J. M., Pahor, M., et al. (1998). Chronically depressed mood and cancer risk in older persons. J. Natl. Cancer Inst., 90, 1888–1893. 18. Price, M. A., Tennant, C. C., Smith, R. C., et al. (2001). The role of psychosocial factors in the development of breast carcinoma: Part I. The cancer prone personality. Cancer, 91, 679–685. 19. Lutgendorf, S. K., and Costanzo, E. S. (2003). Psychoneuroimmunology and health psychology: an integrative model. Brain Behav. Immun., 17, 225–232. 20. Shekelle, R. B., Raynor, W. J. Jr., Ostfeld, A. M., et al. (1981). Psychological depression and 17-year risk of death from cancer. Psychosom. Med., 43, 117–125. 21. Everson. S. A., Goldberg, D. E., Kaplan, G. A., et al. (1996). Hopelessness and risk of mortality and incidence of myocardial infarction and cancer. Psychosom. Med., 58, 113–121. 22. Stommel, M., Given, B. A., and Given, C. W. (2002). Depression and functional status as predictors of death among cancer patients. Cancer, 94, 2719–2727. 23. Watson, M., Haviland, J. S., Greer, S., et al. (1999). Influence of psychological response on survival in breast cancer: a population-based cohort study. Lancet, 354, 1331–1336. 24. Buccheri, G. (1998). Depressive reactions to lung cancer are common and often followed by a poor outcome. European Respiratory Journal, 11, 173–178. 25. Rodrigue, J., Pearman, T., and Moreb, J. (1999). Morbidity and mortality following bone marrow transplantation: predictive utility of pre-BMT affective functioning, compliance, and social support stability. International Journal of Behavioral Medicine, 6, 241–254. 26. Tross, S., Herndon, J., 2nd, Korzun, A., et al. (1996). Psychological symptoms and disease-free and overall survival in women with stage II breast cancer. Cancer and Leukemia Group B. J. Natl. Cancer Inst., 88, 661–667. 27. Andrykowski, M. A., Brady, M. J., and Henslee-Downey, P. J. (1994). Psychosocial factors predictive of survival after allogeneic bone marrow transplantation for leukemia. Psychosom. Med., 56, 432–439. 28. Faller, H., Bulzebruck, H., Drings, P., et al. (1999). Coping, distress, and survival among patients with lung cancer. Arch. Gen. Psychiatry, 56, 756–762. 29. Barraclough, J., Pinder, P., Cruddas, M., et al. (1992). Life events and breast cancer prognosis. BMJ, 304, 1078–1081.
243
30. Maunsell, E., Brisson, J., Mondor, M., et al. (2001). Stressful life events and survival after breast cancer. Psychosom. Med., 63, 306–315. 31. Cohen, S., and Willis, T. A. (1985). Stress, social support, and the buffering hypothesis. Psychological Bulletin, 98, 310–357. 32. Funch, D. P., and Marshall, J. (1983). The role of stress, social support and age in survival from breast cancer. Journal of Psychosomatic Research, 27, 77–83. 33. Marshall, J. R., and Funch, D. P. Social environment and breast cancer. A cohort analysis of patient survival. Cancer, 52, 1546–1550. 34. Maunsell, E., Brisson, J., and Deschenes, L. Social support and survival among women with breast cancer. Cancer, 76, 631–637. 35. Reynolds, P., Boyd, P. T., Blacklow, R. S., et al. (1994). The relationship between social ties and survival among black and white breast cancer patients. National Cancer Institute Black/ White Cancer Survival Study Group. Cancer Epidemiol. Biomarkers Prev., 3, 253–259. 36. Reynolds, P., Hurley, S., Torres, M., et al. (2000). Use of coping strategies and breast cancer survival: results from the Black/ White Cancer Survival Study. Am. J. Epidemiol., 152, 940–949. 37. Butow, P. N., Hiller, J. E., Price, M. A., et al. (2000). Epidemiological evidence for a relationship between life events, coping style, and personality factors in the development of breast cancer. J. Psychosom. Res., 49, 169–181. 38. Sapolsky, R. (1994). Why zebras don’t get ulcers: a guide to stress, stress-related diseases, and coping. New York: Freeman. 39. Weiner, H. (1992). Perturbing the organism: the biology of stressful experience. Chicago: University of Chicago Press. 40. Chrousos, G. P., and Gold, P. W. (1992). The concepts of stress and stress system disorders. Overview of physical and behavioral homeostasis. JAMA, 267, 1244–1252. 41. Charmandari, E., Tsigos, C., and Chrousos G. (2005). Endocrinology of the stress response. Annu. Rev. Physiol., 67, 259–284. 42. Lara, H. E., Porcile, A., Espinoza, J., et al. (2001). Release of norepinephrine from human ovary: coupling to steroidogenic response. Endocrine Journal, 15, 187–192. 43. Greenwald, G., and Roy, S. (1994). Follicular development and its control. In E. Knobil and J. Neill (Eds.), The physiology of reproduction (pp 629–724). New York: Raven Press. 44. Nankova, B., Kvetnansky, R., Hiremagalur, B., et al. (1996). Immobilization stress elevates gene expression for catecholamine biosynthetic enzymes and some neuropeptides in rat sympathetic ganglia: effects of adrenocorticotropin and glucocorticoids. Endocrinology, 137, 5597–5604. 45. Paredes, A., Galvez, A., Leyton, V., et al. (1998). Stress promotes development of ovarian cysts in rats: the possible role of sympathetic nerve activation. Endocrine, 8, 309–315. 46. Lara, H. E., Dorfman, M., Venegas, M., et al. (2002). Changes in sympathetic nerve activity of the mammalian ovary during a normal estrous cycle and in polycystic ovary syndrome: studies on norepinephrine release. Microsc. Res. Tech., 59, 495–502. 47. Maestroni, G. J. (2000). Neurohormones and catecholamines as functional components of the bone marrow microenvironment. Ann. N. Y. Acad. Sci., 917, 29–37. 48. Schmidt, C., and Kraft, K. (1996). Beta-endorphin and catecholamine concentrations during chronic and acute stress in intensive care patients. Eur. J. Med. Res., 1, 528–532. 49. Rupp, H., Dhalla, K, S., and Dhalla, N. S. Mechanisms of cardiac cell damage due to catecholamines: significance of drugs regulating central sympathetic outflow. J. Cardiovasc. Pharmacol., 24 (Suppl 1), S16–24.
244
I. Neural and Endocrine Effects on Immunity
50. Rupp, H., and Jacob, R. (1995). Excess catecholamines and the metabolic syndrome: should central imidazoline receptors be a therapeutic target? Med. Hypotheses, 44, 217–225. 51. Badino, G. R., Novelli, A., Girardi, C., et al. (1996). Evidence for functional beta-adrenoceptor subtypes in CG-5 breast cancer cell. Pharmacological Research, 33, 255–260. 52. Lutgendorf, S. K., Cole, S., Costanzo, E., et al. (2003). Stressrelated mediators stimulate vascular endothelial growth factor secretion by two ovarian cancer cell lines. Clinical Cancer Research, 9, 4514–4521. 53. McDonald, P. H., and Lefkowitz, R. J. (2001). Beta-arrestins: new roles in regulating heptahelical receptors’ functions. Cell Signal, 13, 683–689. 54. Dixon, R. A., Kobilka, B. K., Strader, D. J., et al. (1986). Cloning of the gene and cDNA for mammalian beta-adrenergic receptor and homology with rhodopsin. Nature, 321, 75–79. 55. Emorine, L. J., Marullo, S., Briend-Sutren, M. M., et al. (1989). Molecular characterization of the human beta 3-adrenergic receptor. Science, 245, 1118–1121. 56. Frielle, T., Collins, S., Daniel, K. W., et al. (1987). Cloning of the cDNA for the human beta 1-adrenergic receptor. Proceedings of the National Academy of Sciences of the United States of America, 84, 7920–7924. 57. Ben-Eliyahu, S., Yirmiya, R., Liebeskind, J. C., et al. (1991). Stress increases metastatic spread of a mammary tumor in rats: evidence for mediation by the immune system. Brain, Behavior, & Immunity, 5, 193–205. 58. Sapolsky, R. M., Romero, L. M., and Munck, A. U. How do glucocorticoids influence stress responses? Integrating permissive, suppressive, stimulatory, and preparative actions. Endocrine Reviews, 21, 55–89. 59. Seeman, T., and McEwan, B. (1996). Impact of Social environment characteristics on neuroendocrine regulation. Psychosom. Med., 58, 459–471. 60. Antoni, M. H., Cruess, D. G., Cruess, S., et al. (2000a). Cognitive-behavioral stress management intervention effects on anxiety, 24-hr urinary norepinephrine output, and T-cytotoxic/ suppressor cells over time among symptomatic HIV-infected gay men. J. Consult. Clin. Psychol., 68, 31–45. 61. Antoni, M. H., Cruess, S., Cruess, D. G., et al. (2000b). Cognitive-behavioral stress management reduces distress and 24hour urinary free cortisol output among symptomatic HIVinfected gay men. Ann. Behav. Med., 22, 29–37. 62. Kawamura, A., Tamaki, N., and Kokunai, T. (1998). Effect of dexamethasone on cell proliferation of neuroepithelial tumor cell lines. Neurologia. Medico-Chirurgica, 38, 633–638; discussion, 638–640. 63. Nakane, T., Szentendrei, T., Stern, L., et al. (1990). Effects of IL-1 and cortisol on beta-adrenergic receptors, cell proliferation, and differentiation in cultured human A549 lung tumor cells. J. Immunol., 145, 260–266. 64. Hanahan, D., and Weinberg, R. A. (2000). The hallmarks of cancer. Cell, 100, 57–70. 65. Vogelstein, B., and Kinzler, K. W. (2002). The genetic basis of human cancer (2nd ed.). New York: McGraw-Hill Companies, Inc. 66. Hahn, W. C., Counter, C. M., Lundberg, A. S., et al. (1999). Creation of human tumour cells with defined genetic elements. Nature, 400, 464–468. 67. Kiecolt-Glaser, J. K., Stephens, R. E., Lipetz, P. D., et al. (1985). Distress and DNA repair in human lymphocytes. J. Behav. Med., 8, 311–320. 68. Glaser, R., Thorn, B. E., Tarr, K. L., et al. (1985). Effects of stress on methyltransferase synthesis: an important DNA repair enzyme. Health Psychol., 4, 403–412.
69. Fischman, H. K., and Kelly, D. D. (1987). Sister chromatid exchanges induced by behavioral stress. Ann. N. Y. Acad. Sci., 496, 426–435. 70. Forlenza, M. J., Latimer, J. J., and Baumi, A. (2000). The effects of stress on DNA repair capacity. Psychology & Health, 15, 881–891. 71. Cavigelli, S. A., and McClintock, M. K. (2003). Fear of novelty in infant rats predicts adult corticosterone dynamics and an early death. Proc. Natl. Acad. Sci. USA, 100, 16131–16136. 72. Parker, J., Klein, S. L., McClintock, M. K., et al. (2004). Chronic stress accelerates ultraviolet-induced cutaneous carcinogenesis. J. Am. Acad. Dermatol., 51, 919–922. 73. McClintock, M. K., Conzen, S. D., Gehlert, S., et al. (2005). Mammary cancer and social interactions: identifying multiple environments that regulate gene expression throughout the life span. J. Gerontol. B Psychol. Sci. Soc. Sci., 60 (Spec No 1), 32–41. 74. Jensen, M. M. (1968). The influence of stress on murine leukemia virus infection. Proc. Soc. Exp. Biol. Med., 127, 610–614. 75. Riley, V. (1975). Mouse mammary tumors: alteration of incidence as apparent function of stress. Science, 189, 465–467. 76. Amkraut, A., and Solomon, G. F. (1972). Stress and murine sarcoma virus (Moloney)-induced tumors. Cancer Res., 32, 1428–1433. 77. Everett, R. (1984). Factors affecting spontaneous tumor incidence rates in mice: a literature review. Crit. Rev. Toxicol., 13, 235–251. 78. Reznikoff, M., and Martin, D. E. (1957). The influence of stress on mammary cancer in mice. J. Psychosom. Res., 2, 56–60. 79. Andervont, H. (1944). Influence of environment on mammary cancer in mice. Journal of the National Cancer Institute, 4, 579–581. 80. Muhlbock, O. (1951). Influence of environment on the incidence of mammary tumors in mice. Acta Unio. Int. Contra. Cancrum, 7, 351–353. 81. Albert, Z. (1967). Effect of number of animals per cage on the development of spontaneous neoplasms. In M. L. Conalty (Ed.), Husbandry of laboratory animals. London: Academic Press. 82. Riley, V., and Spackman, S. (1976). Modifying effects of a benign virus on the malignant process and the role of physiological stress on tumor incidence. Fogarty International Center Proceedings, 28, 319–356. 83. Rowse, G. L., Weinberg, J., Bellward, G. D., et al. (1992). Endocrine mediation of psychosocial stressor effects on mouse mammary tumor growth. Cancer Letter, 65, 85–93. 84. Sapolsky, R. M., and Donnelly, T. M. Vulnerability to stressinduced tumor growth increases with age in rats: role of glucocorticoids. Endocrinology, 117, 662–666. 85. Rapp, F., and Reed, C. L. (1977). The viral etiology of cancer: a realistic approach. Cancer, 40, 419–429. 86. Romero, L., Raley-Susman, K., Redish, D., et al. (1992). A possible mechanism by which stress accelerates growth of virallyderived tumors. Proceeding of the National Academy of Sciences, 89, 11084. 87. McGrath, C. M., and Jones, R. F. (1978). Hormonal induction of mammary tumor viruses and its implications for carcinogenesis. Cancer Res., 38, 4112–4125. 88. McGrath, C. M., Prass, W. A., Maloney, T. M., et al. (1981). Induction of endogenous mammary tumor virus expression during hormonal induction of mammary adenoacanthomas and carcinomas of BALB/c female mice. J. Natl. Cancer Inst., 67, 841–852.
11. Neuroendocrine Regulation of Cancer Progression: I. Biological Mechanisms and Clinical Relevance 89. Kalinichenko, V. V., Mokyr, M. B., Graf, L. H. Jr., et al. (1999). Norepinephrine-mediated inhibition of antitumor cytotoxic T lymphocyte generation involves a beta-adrenergic receptor mechanism and decreased TNF-alpha gene expression. J. Immunol., 163, 2492–2499. 90. Cook-Mills, J. M., Cohen, R. L., Perlman, R. L., et al. (1995). Inhibition of lymphocyte activation by catecholamines: evidence for a non-classical mechanism of catecholamine action. Immunology, 85, 544–549. 91. Cook-Mills, J. M., Mokyr, M. B., Cohen, R. L., et al. (1995). Neurotransmitter suppression of the in vitro generation of a cytotoxic T lymphocyte response against the syngeneic MOPC-315 plasmacytoma. Cancer Immunol. Immunother., 40, 79–87. 92. Melamed, R., Rosenne, E., Shakhar, K., et al. (2005). Marginating pulmonary-NK activity and resistance to experimental tumor metastasis: suppression by surgery and the prophylactic use of a beta-adrenergic antagonist and a prostaglandin synthesis inhibitor. Brain Behav. Immun., 19, 114–126. 93. Buchschacher, G. L. J., and Wong-Staal, F. (2005). RNA viruses. In V. T. J. DeVita, S. Hellman, S. A. Rosenberg (Eds.), Cancer: principles and practice of oncology (pp. 165–172). Philadelphia: Lippincott Williams & Wilkins. 94. Howley, P. M., Ganem, D., and Kieff, E. (2005). DNA viruses. In V. T. J. DeVita, S. Hellman, and S. A. Rosenberg (Eds.), Cancer: principles and practice of oncology (pp 173–184). Philadelphia: Lippincott Williams & Wilkins. 95. zur Hausen, H. (1991). Viruses in human cancers. Science, 254, 1167–1173. 96. Payne, D. A., Mehta, S. K., Tyring, S. K., et al. (1999). Incidence of Epstein-Barr virus in astronaut saliva during spaceflight. Aviat. Space Environ. Med., 70, 1211–1213. 97. Tingate, T. R., Lugg, D. J., Muller, H. K., et al. (1997). Antarctic isolation: immune and viral studies. Immunol. Cell Biol., 75, 275–283. 98. Glaser, R., Kiecolt-Glaser, J. K., Speicher, C. E., et al. (1985). Stress, loneliness, and changes in herpesvirus latency. J. Behav. Med., 8, 249–260. 99. Glaser, R., Pearson, G. R., Jones, J. F., et al. (1991). Stress-related activation of Epstein-Barr virus. Brain Behav. Immun., 5, 219–232. 100. Stowe, R. P., Pierson, D. L., and Barrett, A. D. (2001). Elevated stress hormone levels relate to Epstein-Barr virus reactivation in astronauts. Psychosom Med., 63, 891–895. 101. Cacioppo, J. T., Kiecolt-Glaser, J. K., Malarkey, W. B., et al. (2002). Autonomic and glucocorticoid associations with the steady-state expression of latent Epstein-Barr virus. Horm. Behav., 42, 32–41. 102. Glaser, R., Kutz, L. A., MacCallum, R. C., et al. (1995). Hormonal modulation of Epstein-Barr virus replication. Neuroendocrinology, 62, 356–361. 103. Selvey, L. A., Dunn, L. A., Tindle, R. W., et al. (1994). Human papillomavirus (HPV) type 18 E7 protein is a short-lived steroid-inducible phosphoprotein in HPV-transformed cell lines. J. Gen. Virol., 75 (Pt 7), 1647–1653. 104. Bromberg-White, J. L., and Meyers, C. (2003). Comparison of the basal and glucocorticoid-inducible activities of the upstream regulatory regions of HPV18 and HPV31 in multiple epithelial cell lines. Virology, 306, 197–202. 105. Piccini, A., Storey, A., Romanos, M., et al. (1997). Regulation of human papillomavirus type 16 DNA replication by E2, glucocorticoid hormone and epidermal growth factor. J. Gen. Virol., 78 (Pt 8), 1963–1970. 106. Khare, S., Pater, M. M., Tang, S. C., et al. (1997). Effect of glucocorticoid hormones on viral gene expression, growth, and
107.
108.
109.
110.
111.
112.
113.
114.
115.
116.
117.
118.
119.
120.
121.
122.
245
dysplastic differentiation in HPV16-immortalized ectocervical cells. Exp. Cell Res., 232, 353–360. Mittal, R., Tsutsumi, K., Pater, A., et al. (1993). Human papillomavirus type 16 expression in cervical keratinocytes: role of progesterone and glucocorticoid hormones. Obstet. Gynecol., 81, 5–12. Mittal, R., Pater, A., and Pater, M. M. (1993). Multiple human papillomavirus type 16 glucocorticoid response elements functional for transformation, transient expression, and DNAprotein interactions. J. Virol., 67, 5656–5659. Cid, A., Auewarakul, P., Garcia-Carranca, A., et al. (1993). Celltype–specific activity of the human papillomavirus type 18 upstream regulatory region in transgenic mice and its modulation by tetradecanoyl phorbol acetate and glucocorticoids. J. Virol., 67, 6742–6752. Gloss, B., Bernard, H. U., Seedorf, K., et al. (1987). The upstream regulatory region of the human papilloma virus-16 contains an E2 protein-independent enhancer which is specific for cervical carcinoma cells and regulated by glucocorticoid hormones. EMBO J., 6, 3735–3743. Durst, M., Gallahan, D., Jay, G., et al. (1989). Glucocorticoidenhanced neoplastic transformation of human keratinocytes by human papillomavirus type 16 and an activated ras oncogene. Virology, 173, 767–771. Pater, M. M., Hughes, G. A., Hyslop, D. E., et al. (1988). Glucocorticoid-dependent oncogenic transformation by type 16 but not type 11 human papilloma virus DNA. Nature, 335, 832–835. Bartholomew, J. S., Glenville, S., Sarkar, S., et al. (1997). Integration of high-risk human papillomavirus DNA is linked to the down-regulation of class I human leukocyte antigens by steroid hormones in cervical tumor cells. Cancer Res., 57, 937–942. Pater, M. M., and Pater, A. (1991). RU486 inhibits glucocorticoid hormone-dependent oncogenesis by human papillomavirus type 16 DNA. Virology, 183, 799–802. Kamradt, M. C., Mohideen, N., Krueger, E., et al. (2000). Inhibition of radiation-induced apoptosis by dexamethasone in cervical carcinoma cell lines depends upon increased HPV E6/E7. Br. J. Cancer, 82, 1709–1716. Kamradt, M. C., Mohideen, N., and Vaughan, A. T. (2000). RU486 increases radiosensitivity and restores apoptosis through modulation of HPV E6/E7 in dexamethasone-treated cervical carcinoma cells. Gynecol. Oncol., 77, 177–182. Coker, A. L., Bond, S., Madeleine, M. M., et al. (2003). Psychosocial stress and cervical neoplasia risk. Psychosom. Med., 65, 644–651. Pereira, D. B., Antoni, M. H., Danielson, A., et al. (2003). Life stress and cervical squamous intraepithelial lesions in women with human papillomavirus and human immunodeficiency virus. Psychosom. Med., 65, 427–434. Tur-Kaspa, R., Burk, R. D., Lieberman, H. H., et al. (1986). Hepatitis B virus gene expression in relation to virus replication and HBV-DNA integration. New concepts for antiviral therapy. J. Hepatol., 3 (Suppl 2), S25–S33. Tur-Kaspa, R., Shaul, Y., Moore, D. D., et al. (1988). The glucocorticoid receptor recognizes a specific nucleotide sequence in hepatitis B virus DNA causing increased activity of the HBV enhancer. Virology, 167, 630–633. Gripon, P., Diot, C., Corlu, A., et al. (1989). Regulation by dimethylsulfoxide, insulin, and corticosteroids of hepatitis B virus replication in a transfected human hepatoma cell line. J. Med. Virol., 28, 193–199. Tur-Kaspa, R., and Laub, O. (1990). Corticosteroids stimulate hepatitis B virus DNA, mRNA and protein production in a stable expression system. J. Hepatol., 11, 34–36.
246
I. Neural and Endocrine Effects on Immunity
123. Chou, C. K., Wang, L. H., Lin, H. M., et al. (1992). Glucocorticoid stimulates hepatitis B viral gene expression in cultured human hepatoma cells. Hepatology, 16, 13–18. 124. Magy, N., Cribier, B., Schmitt, C., et al. (1999). Effects of corticosteroids on HCV infection. Int J. Immunopharmacol., 21, 253–261. 125. Chayama, K., Tsubota, A., Kobayashi, M., et al. (1996). A pilot study of corticosteroid priming for lymphoblastoid interferon alfa in patients with chronic hepatitis C. Hepatology, 23, 953–957. 126. Tisone, G., Angelico, M., Palmieri, G., et al. (1999). A pilot study on the safety and effectiveness of immunosuppression without prednisone after liver transplantation. Transplantation, 67, 1308–1313. 127. McHutchison, J. G., Ponnudurai, R., Bylund, D. L., et al. (2001). Prednisone withdrawal followed by interferon alpha for treatment of chronic hepatitis C infection: results of a randomized controlled trial. J. Clin. Gastroenterol., 32, 133–137. 128. Yokosuka, O. (2000). Role of steroid priming in the treatment of chronic hepatitis B. J. Gastroenterol. Hepatol., 15 (Suppl), E41–45. 129. Cole, S. W., Naliboff, B. D., Kemeny, M. E., et al. (2001). Impaired response to HAART in HIV-infected individuals with high autonomic nervous system activity. Proc. Natl. Acad. Sci. USA, 98, 12695–12700. 130. Cole, S. W., Jamieson, B. D., and Zack, J. A. (1999). cAMP upregulates cell surface expression of lymphocyte CXCR4: implications for chemotaxis and HIV-1 infection. J. Immunol., 162, 1392–1400. 131. Cole, S. W., Korin, Y. D., Fahey, J. L., et al. (1998). Norepinephrine accelerates HIV replication via protein kinase Adependent effects on cytokine production. J. Immunol., 161, 610–616. 132. Killebrew, D., and Shiramizu, B. (2004). Pathogenesis of HIVassociated non-Hodgkin lymphoma. Curr. HIV Res., 2, 215–221. 133. Clifford, G. M., Polesel, J., Rickenbach, M., et al. (2005). Cancer risk in the Swiss HIV Cohort Study: associations with immunodeficiency, smoking, and highly active antiretroviral therapy. J. Natl. Cancer Inst., 97, 425–432. 134. Chang, M. (In press, 2005). Beta-adrenoreceptors reactivate KSHV lytic replication via PKA-dependent control of viral RTA. Journal of Virology. 135. Turgeman, H., and Aboud, M. (1998). Evidence that protein kinase A activity is required for the basal and tax-stimulated transcriptional activity of human T-cell leukemia virus type-I long terminal repeat. FEBS Lett., 428, 183–187. 136. Bhopale, G. M., and Nanda, R. K. (2004). Prospects for hepatitis C vaccine. Acta Virol., 48, 215–221. 137. Harper, D. M. (2005). Efficacy of a bivalent L1 virus-like particle vaccine in prevention of infection with human papillomavirus types 16 and 18 in young women: a randomized trial. Obstet. Gynecol. Surv., 60, 171–173. 138. Marsland, A. L., Cohen, S., Rabin, B. S., et al. (2001). Associations between stress, trait negative affect, acute immune reactivity, and antibody response to hepatitis B injection in healthy young adults. Health Psychol., 20, 4–11. 139. Jabaaij, L., van Hattum, J., Vingerhoets, J. J., et al. (1996). Modulation of immune response to rDNA hepatitis B vaccination by psychological stress. J. Psychosom. Res., 41, 129–137. 140. Jabaaij, L., Grosheide, P. M., Heijtink, R. A., et al. (1993). Influence of perceived psychological stress and distress on antibody response to low dose rDNA hepatitis B vaccine. J. Psychosom. Res., 37, 361–369.
141. Glaser, R., Kiecolt-Glaser, J. K., Bonneau, R. H., et al. (1992). Stress-induced modulation of the immune response to recombinant hepatitis B vaccine. Psychosomatic Medicine, 54, 22–29. 142. Fidler, I. J. (2003). The pathogenesis of cancer metastasis: the ‘seed and soil’ hypothesis revisited. Nature Reviews. Cancer, 3, 453–458. 143. Fidler, I. J. (2002). Critical determinants of metastasis. Seminars in Cancer Biology, 12, 89–96. 144. Fidler, I. J. (1990). Critical factors in the biology of human cancer metastasis: Twenty-eighth G.H.A. Clowes Memorial Award Lecture. Cancer Research, 50, 6130–6138. 145. Folkman, J. (1985). Toward an understanding of angiogenesis: search and discovery. Perspectives in Biology & Medicine, 29, 10–36. 146. Auerbach, W., and Auerbach, R. (1994). Angiogenesis inhibition: a review. Pharmacology & Therapeutics, 63, 265–311. 147. Fidler, I. J. (1995a). Critical factors in the biology of human cancer metastasis. Am. Surg., 61, 1065–1066. 148. Fidler, I. J. (1995b). Modulation of the organ microenvironment for treatment of cancer metastasis. J. Natl. Cancer Inst., 87, 1588–1592. 149. Paget, S. (1989). The distribution of secondary growths in cancer of the breast. Cancer Metastasis Rev., 8, 98–101. 150. Mueller, M. M., and Fusenig, N. E. (2004). Friends or foes— bipolar effects of the tumour stroma in cancer. Nat. Rev. Cancer, 4, 839–849. 151. Chambers, A. F., Groom, A. C., and MacDonald, I. C. (2002). Dissemination and growth of cancer cells in metastatic sites. Nat. Rev. Cancer, 2, 563–572. 152. Muller, A., Homey, B., Soto, H., et al. (2001). Involvement of chemokine receptors in breast cancer metastasis. Nature, 410, 50–56. 153. Liotta, L. A. (2001). An attractive force in metastasis. Nature, 410, 24–25. 154. Sheridan, J. F., Feng, N. G., Bonneau, R. H., et al. (1991). Restraint stress differentially affects anti-viral cellular and humoral immune responses in mice. J. Neuroimmunol., 31, 245–255. 155. Padgett, D. A., Marucha, P. T., and Sheridan, J. F. (1998). Restraint stress slows cutaneous wound healing in mice. Brain Behav. Immun., 12, 64–73. 156. Padgett, D. A., Sheridan, J. F., Dorne, J., et al. (1998). Social stress and the reactivation of latent herpes simplex virus type 1. Proc. Natl. Acad. Sci. USA, 95, 7231–7235. 157. Iwakabe, K., Shimada, M., Ohta, A., et al. (1998). The restraint stress drives a shift in Th1/Th2 balance toward Th2-dominant immunity in mice. Immunology Letters, 62, 39–43. 158. Fiserova, A., Starec, M., Kuldova, M., et al. (2002). Effects of D2-dopamine and alpha-adrenoceptor antagonists in stress induced changes on immune responsiveness of mice. Journal of Neuroimmunology, 130, 55–65. 159. Nukina, H., Sudo, N., Aiba, Y., et al. (2001). Restraint stress elevates the plasma interleukin-6 levels in germ-free mice. J. Neuroimmunol., 115, 46–52. 160. Zhou, D., Kusnecov, A. W., Shurin, M. R., et al. (1993). Exposure to physical and psychological stressors elevates plasma interleukin 6: relationship to the activation of hypothalamicpituitary-adrenal axis. Endocrinology, 133, 2523–2530. 161. Zorzet, S., Perissin, L., Rapozzi, V., et al. (1998). Restraint stress reduces the antitumor efficacy of cyclophosphamide in tumorbearing mice. Brain Behav. Immun., 12, 23–33. 162. Ghoshal, K., Wang, Y., Sheridan, J. F., et al. (1998). Metallothionein induction in response to restraint stress. Transcriptional
11. Neuroendocrine Regulation of Cancer Progression: I. Biological Mechanisms and Clinical Relevance
163.
164.
165.
166.
167.
168.
169.
170.
171.
172.
173.
174.
175.
176.
177.
178.
179.
control, adaptation to stress, and role of glucocorticoid. Journal of Biological Chemistry, 273, 27904–27910. Steplewski, Z., Vogel, W. H., Ehya, H., et al. (1985). Effects of restraint stress on inoculated tumor growth and immune response in rats. Cancer Res., 45, 5128–5133. Cao, L., Filipov, N. M., Lawrence, D. A. (2002). Sympathetic nervous system plays a major role in acute cold/restraint stress inhibition of host resistance to Listeria monocytogenes. Journal of Neuroimmunology, 125, 94–102. Steplewski, Z., Goldman, P. R., and Vogel, W. H. (1987). Effect of housing stress on the formation and development of tumors in rats. Cancer Lett., 34, 257–261. Tjurmina, O. A., Armando, I., Saavedra, J. M., et al. (2002). Exaggerated adrenomedullary response to immobilization in mice with targeted disruption of the serotonin transporter gene. Endocrinology, 143, 4520–4526. Kvetnansky, R., Fukuhara, K., Pacak, K., et al. (1993). Endogenous glucocorticoids restrain catecholamine synthesis and release at rest and during immobilization stress in rats. Endocrinology, 133, 1411–1419. Ben-Eliyahu, S., Page, G. G., Yirmiya, R., et al. (1999). Evidence that stress and surgical interventions promote tumor development by suppressing natural killer cell activity. International Journal of Cancer, 80, 880–888. Page, G. G., and Ben-Eliyahu, S. (1999). A role for NK cells in greater susceptibility of young rats to metastatic formation. Developmental & Comparative Immunology, 23, 87–96. Page, G. G., Ben-Eliyahu, S., Yirmiya, R., et al. (1993). Morphine attenuates surgery-induced enhancement of metastatic colonization in rats. Pain, 54, 21–28. Flaxman, B. A., and Harper, R. A. (1975). In vitro analysis of the control of keratinocyte proliferation in human epidermis by physiologic and pharmacologic agents. J. Invest. Dermatol, 65, 52–59. Vandewalle, B., Revillion, F., and Lefebvre, J. (1990). Functional beta-adrenergic receptors in breast cancer cells. J. Cancer Res. Clin. Oncol., 116, 303–306. Marchetti, B., Spinola, P. G., Pelletier, G., et al. (1991). A potential role for catecholamines in the development and progression of carcinogen-induced mammary tumors: hormonal control of beta-adrenergic receptors and correlation with tumor growth. Journal of Steroid Biochemistry & Molecular Biology, 38, 307–320. Abramovitch, R., Tavor, E., Jacob-Hirsch, J., et al. (2004). A pivotal role of cyclic AMP-responsive element binding protein in tumor progression. Cancer Res., 64, 1338–1346. Lang, K., Drell, T. Lt., Lindecke, A., et al. (2004). Induction of a metastatogenic tumor cell type by neurotransmitters and its pharmacological inhibition by established drugs. Int. J. Cancer., 112, 231–238. Jean, D., and Bar-Eli, M. (2000). Regulation of tumor growth and metastasis of human melanoma by the CREB transcription factor family. Mol. Cell. Biochem., 212, 19–28. Scarparo, A. C., Sumida, D. H., Patrao, M. T., et al. (2004). Catecholamine effects on human melanoma cells evoked by alpha1-adrenoceptors. Arch. Dermatol. Res., 296, 112–119. Pifl, C., Zezula, J., Spittler, A., et al. (2001). Antiproliferative action of dopamine and norepinephrine in neuroblastoma cells expressing the human dopamine transporter. FASEB J., 15, 1607–1609. Bijman, J. T., Wagener, D. J., Graafsma, S. J., et al. (1987). Modulation of proliferation of a human head and neck squamous carcinoma cell line (HN-1) by catecholamines and histamine. Anticancer Res., 7, 147–150.
247
180. Cox, M. E., Deeble, P. D., Lakhani, S., et al. (1999). Acquisition of neuroendocrine characteristics by prostate tumor cells is reversible: implications for prostate cancer progression. Cancer Res., 59, 3821–3830. 181. Cohen, R. J., Glezerson, G., and Haffejee, Z. (1991). Neuroendocrine cells—a new prognostic parameter in prostate cancer. Br. J. Urol., 68, 258–262. 182. Theodorescu, D., Broder, S. R., Boyd, J. C., et al. (1997). Cathepsin D and chromogranin A as predictors of long term disease specific survival after radical prostatectomy for localized carcinoma of the prostate. Cancer, 80, 2109–2119. 183. di Sant’Agnese, P. A. (1992). Neuroendocrine differentiation in human prostatic carcinoma. Hum. Pathol., 23, 287–296. 184. Zhao, X. Y., Malloy, P. J., Krishnan, A. V., et al. (2000). Glucocorticoids can promote androgen-independent growth of prostate cancer cells through a mutated androgen receptor. Nat. Med., 6, 703–706. 185. Simon, W. E., Albrecht, M., Trams, G., et al. (1984). In vitro growth promotion of human mammary carcinoma cells by steroid hormones, tamoxifen, and prolactin. J. Natl. Cancer Inst., 73, 313–321. 186. Boudreau, N., and Bissell, M. J. (1998). Extracellular matrix signaling: integration of form and function in normal and malignant cells. Curr. Opin. Cell Biol., 10, 640–646. 187. Hay, E. (1991). Biology of the extracellular matrix. New York: Plenum Press. 188. Hynes, R. O. (1992). Integrins: versatility, modulation, and signaling in cell adhesion. Cell, 69, 11–25. 189. Mercurio, A. M., and Rabinovitz, I. (2001). Towards a mechanistic understanding of tumor invasion—lessons from the alpha6beta 4 integrin. Semin. Cancer Biol., 11, 129–141. 190. Kawasaki, H., Springett, G. M., Mochizuki, N., et al. (1998). A family of cAMP-binding proteins that directly activate Rap1. Science, 282, 2275–2279. 191. de Rooij, J., Zwartkruis, F. J., Verheijen, M. H., et al. (1998). Epac is a Rap1 guanine-nucleotide-exchange factor directly activated by cyclic AMP. Nature, 396, 474–477. 192. Rangarajan, S., Enserink, J. M., Kuiperij, H. B., et al. (2003). Cyclic AMP induces integrin-mediated cell adhesion through Epac and Rap1 upon stimulation of the beta 2-adrenergic receptor. J. Cell Biol., 160, 487–493. 193. Enserink, J. M., Price, L. S., Methi, T., et al. (2004). The cAMP-Epac-Rap1 pathway regulates cell spreading and cell adhesion to laminin-5 through the alpha3beta1 integrin but not the alpha6beta4 integrin. J. Biol. Chem., 279, 44889–44896. 194. Liotta, L. A., and Stetler-Stevenson, W. G. (1990). Metalloproteinases and cancer invasion. Semin. Cancer Biol., 1, 99–106. 195. Drell, T. Lt., Joseph, J., Lang, K., et al. (2003). Effects of neurotransmitters on the chemokinesis and chemotaxis of MDAMB-468 human breast carcinoma cells. Breast Cancer Res. Treat, 80, 63–70. 196. Masur, K., Niggemann, B., Zanker, K. S., et al. (2001). Norepinephrine-induced migration of SW 480 colon carcinoma cells is inhibited by beta-blockers. Cancer Res., 61, 2866–2869. 197. Sood, A. K., Bhatty, R., Landen, C. N. Jr., et al. (In press). Stress hormone mediated invasion of ovarian cancer cells. Clinical Cancer Research. 198. Sood, A. K., Lush, R., Geisler, J. P., et al. (2004). Sequential intraperitoneal topotecan and oral etoposide chemotherapy in recurrent platinum-resistant ovarian carcinoma: results of a phase II trial. Clinical Cancer Research, 10, 6080–6085. 199. Fredriksson, J. M., Lindquist, J. M., Bronnikov, G. E., et al. (2000). Norepinephrine induces vascular endothelial growth factor gene expression in brown adipocytes through a beta-
248
200. 201. 202.
203.
204.
205.
206.
207.
208.
209.
210.
211.
212.
213.
214.
215.
216.
217.
I. Neural and Endocrine Effects on Immunity adrenoreceptor/cAMP/protein kinase A pathway involving Src but independently of Erk1/2. Journal of Biological Chemistry, 275, 13802–13811. Ferrara, N. (1996). Vascular endothelial growth factor. European Journal of Cancer, 32A, 2413–2422. Ferrara, N., and Davis-Smyth, T. (1997). The biology of vascular endothelial growth factor. Endocrine Reviews, 18, 4–25. Thaker, P. H., Lloyd, M., Jennings, N., et al. (2005). Chronic stress promotes angiogenesis in ovarian carcinoma. The 36th Annual Meeting of the Society of Gynecologic Oncologists. Miami, FL. Lutgendorf, S. K., Johnsen, E. L., Cooper, B., et al. (2002). Vascular endothelial growth factor and social support in patients with ovarian carcinoma. Cancer, 95, 808–815. Costanzo, E. S., Lutgendorf, S. K., Sood, A. K., et al. (2005). Psychosocial factors and interleukin-6 among women with advanced ovarian cancer. Cancer, 104, 305–313. Kaiserlian, D., Savino, W., Hassid, J., et al. (1984). Studies of the thymus in mice bearing the Lewis lung carcinoma. III. Possible mechanisms of tumor-induced thymic atrophy. Clin. Immunol. Immunopathol., 32, 316–325. Gabrilovich, D. I., Chen, H. L., Girgis, K. R., et al. (1996). Production of vascular endothelial growth factor by human tumors inhibits the functional maturation of dendritic cells. Nat. Med., 2, 1096–1103. Gabrilovich, D., Ishida, T., Oyama, T., et al. (1998). Vascular endothelial growth factor inhibits the development of dendritic cells and dramatically affects the differentiation of multiple hematopoietic lineages in vivo. Blood, 92, 4150–4166. Ohm, J. E., Gabrilovich, D. I., Sempowski, G. D., et al. (2003). VEGF inhibits T-cell development and may contribute to tumor-induced immune suppression. Blood, 101, 4878–4886. Frassanito, M. A., Cusmai, A., Iodice, G., et al. (2001). Autocrine interleukin-6 production and highly malignant multiple myeloma: relation with resistance to drug-induced apoptosis. Blood, 97, 483–489. Machein, M. R., Kullmer, J., Ronicke, V., et al. (1999). Differential downregulation of vascular endothelial growth factor by dexamethasone in normoxic and hypoxic rat glioma cells. Neuropathology & Applied Neurobiology, 25, 104–112. Distelhorst, C. W. (2002). Recent insights into the mechanism of glucocorticosteroid-induced apoptosis. Cell Death Differ., 9, 6–19. Herr, I., Ucur, E., Herzer, K., et al. (2003). Glucocorticoid cotreatment induces apoptosis resistance toward cancer therapy in carcinomas. Cancer Res., 63, 3112–3120. Wu, W., Chaudhuri, S., Brickley, D. R., et al. (2004). Microarray analysis reveals glucocorticoid-regulated survival genes that are associated with inhibition of apoptosis in breast epithelial cells. Cancer Res., 64, 1757–1764. Dave, J. R., Anderson, S. M., Saviolakis, G. A., et al. (2000). Chronic sustained stress increases levels of anterior pituitary prolactin mRNA. Pharmacol. Biochem. Behav., 67, 423–431. Almeida, S. A., Petenusci, S. O., Franci, J. A., et al. (2000). Chronic immobilization-induced stress increases plasma testosterone and delays testicular maturation in pubertal rats. Andrologia., 32, 7–11. Young, W. S. 3rd, and Lightman, S. L. (1992). Chronic stress elevates enkephalin expression in the rat paraventricular and supraoptic nuclei. Mol. Brain Res., 13, 111–117. Clevenger, C. V., Furth, P. A., Hankinson, S. E., et al. (2003). The role of prolactin in mammary carcinoma. Endocr. Rev., 24, 1–27.
218. Ben-Jonathan, N., Liby, K., McFarland, M., et al. (2002). Prolactin as an autocrine/paracrine growth factor in human cancer. Trends Endocrinol. Metab., 13, 245–250. 219. Vonderhaar, B. K. (2000). Prolactin in human breast cancer development. In Stephen P. Ethier (Ed.), Endocrine oncology (pp 101–120). Totowa: Humana Press. 220. Chen, W. Y., Ramamoorthy, P., Chen, N., et al. (1999). A human prolactin antagonist, hPRL-G129R, inhibits breast cancer cell proliferation through induction of apoptosis. Clin. Cancer Res., 5, 3583–3593. 221. Richert, M. M., Decker, K., and Anderson, S. M. (2001). Mechanisms underlying constitutive activation of Akt in breast cancer cell lines (p. 551). 83rd Annual Meeting of the Endocrine Society. Denver, CO. 222. Pequeux, C., Keegan, B. P., Hagelstein, M. T., et al. (2004). Oxytocin- and vasopressin-induced growth of human smallcell lung cancer is mediated by the mitogen-activated protein kinase pathway. Endocr. Relat. Cancer, 11, 871–885. 223. Cassoni, P., Marrocco, T., Deaglio, S., et al. (2001). Biological relevance of oxytocin and oxytocin receptors in cancer cells and primary tumors. Ann. Oncol., 12 (Suppl 2), S37–39. 224. Taylor, A. H., Ang, V. T., Jenkins, J. S., et al. (1990). Interaction of vasopressin and oxytocin with human breast carcinoma cells. Cancer Res., 50, 7882–7886. 225. Bussolati, G., Cassoni, P. (2001). Editorial: the oxytocin/oxytocin receptor system—expect the unexpected. Endocrinology, 142, 1377–1379. 226. Glavin GB, and Szabo S. (1990). Dopamine in gastrointestinal disease. Dig. Dis. Sci., 35, 1153–1161. 227. Mezey, E., Eisenhofer, G., Hansson, S., et al. (1998). Dopamine produced by the stomach may act as a paracrine/autocrine hormone in the rat. Neuroendocrinology, 67, 336–348. 228. Imperato, A., Angelucci, L., Casolini, P., et al. (1992). Repeated stressful experiences differently affect limbic dopamine release during and following stress. Brain Res., 577, 194–199. 229. Isovich, E., Mijnster, M. J., Flugge, G., et al. (2000). Chronic psychosocial stress reduces the density of dopamine transporters. Eur. J. Neurosci., 12, 1071–1078. 230. Johnson, D. E., Ochieng, J., and Evans, S. L. (1995). The growth inhibitory properties of a dopamine agonist (SKF 38393) on MCF-7 cells. Anticancer Drugs, 6, 471–474. 231. Lai, C. T., and Yu, P. H. (1997). Dopamine- and L-beta-3,4dihydroxyphenylalanine hydrochloride (L-Dopa)-induced cytotoxicity towards catecholaminergic neuroblastoma SHSY5Y cells. Effects of oxidative stress and antioxidative factors. Biochem. Pharmacol., 53, 363–372. 232. Wick, M. M. (1980). Levodopa and dopamine analogs as DNA polymerase inhibitors and antitumor agents in human melanoma. Cancer Res., 40, 1414–1418. 233. Wick, M. M., and Mui, A. (1981). Synthesis and biologic evaluation of the dopamine analog N-acetyldopamine in experimental leukemia in mice. J. Natl. Cancer Inst., 66, 351–354. 234. Fitzgerald, G. B., and Wick, M. M. (1987). Comparison of the inhibitory effects of hydroxyurea, 5-fluorodeoxyuridine, 3,4dihydroxybenzylamine, and methotrexate on human squamous cell carcinoma. J. Invest. Dermatol., 88, 66–70. 235. Chakroborty, D., Sarkar, C., Mitra, R. B., et al. (2004). Depleted dopamine in gastric cancer tissues: dopamine treatment retards growth of gastric cancer by inhibiting angiogenesis. Clin. Cancer Res., 10, 4349–4356. 236. Teunis, M. A., Kavelaars, A., Voest, E., et al. (2002). Reduced tumor growth, experimental metastasis formation, and angiogenesis in rats with a hyperreactive dopaminergic system. FASEB J., 16, 1465–1467.
11. Neuroendocrine Regulation of Cancer Progression: I. Biological Mechanisms and Clinical Relevance 237. Basu, S., Nagy, J. A., Pal, S., et al. (2001). The neurotransmitter dopamine inhibits angiogenesis induced by vascular permeability factor/vascular endothelial growth factor. Nature Medicine, 7, 569–574. 238. Perron, L., Bairati, I., Harel, F., et al. (2004). Antihypertensive drug use and the risk of prostate cancer (Canada). Cancer Causes Control, 15, 535–541. 239. Algazi, M., Plu-Bureau, G., Flahault, A., et al. (2004). Could treatments with beta-blockers be associated with a reduction in cancer risk? Rev. Epidemiol. Sante Publique, 52, 53–65. 240. Li, C. I., Malone, K. E., Weiss, N. S., et al. (2003). Relation between use of antihypertensive medications and risk of breast
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carcinoma among women ages 65–79 years. Cancer, 98, 1504–1513. 241. Meier, C. R., Derby, L. E., Jick, S. S., et al. (2000). Angiotensinconverting enzyme inhibitors, calcium channel blockers, and breast cancer. Arch. Intern. Med., 160, 349–353. 242. Rosenberg, L., Rao, R. S., Palmer, J. R., et al. (1998). Calcium channel blockers and the risk of cancer. JAMA, 279, 1000–1004. 243. Lieb, J. (2001). Antidepressants, eicosanoids and the prevention and treatment of cancer. A review. Prostaglandins Leukot. Essent. Fatty Acids, 65, 233–239.
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C H A P T E R
12 Neuroendocrine Regulation of Cancer Progression: II. Immunological Mechanisms, Clinical Relevance, and Prophylactic Measures ROI AVRAHAM AND SHAMGAR BEN-ELIYAHU
I. IMMUNE-CANCER INTERACTIONS AND THE POTENTIAL ROLE OF CELL-MEDIATED IMMUNITY (CMI) IN RESTRICTING TUMOR GROWTH AND METASTASIS 252 II. THE CRITICAL PERIOPERATIVE PERIOD IN CANCER PATIENTS 253 III. NEUROENDOCRINE MODULATION OF CELL-MEDIATED IMMUNITY AND CANCER DEVELOPMENT IN THE PERIOPERATIVE PERIOD 254 IV. POSTOPERATIVE SUPPRESSION OF NK ACTIVITY AND RESISTANCE TO TUMOR PROGRESSION: MECHANISMS AND PREVENTION BY PHARMACOLOGICAL INTERVENTIONS 254 V. IS THERE EVIDENCE IN CANCER PATIENTS THAT POSTOPERATIVE SUPPRESSION OF CMI CAN INDEED PROMOTE METASTASIS? 257 VI. IMMUNE STIMULATION AS A PROPHYLACTIC MEASURE IN THE PERIOPERATIVE PERIOD: A DOUBLE-EDGED SWORD AND THE POTENTIAL FOR PNI-BASED INTERVENTIONS TO IMPROVE IMMUNOTHERAPY 258 VII. DOES MALIGNANT TISSUE EXPLOIT STRESSFUL PERIODS TO FACILITATE ITS AUTO-EVOLUTIONARY PROCESS? 260 VIII. CLINICAL IMPLICATIONS 261
of a neoplasm within a patient that harbors this disease. In this chapter we focus on the interactions between the malignant tissue and the immune and neuroendocrine systems, considering the ramifications of this interaction to cancer evolvement, progression, and treatment. We start by reviewing evidence supporting the role of the immune system in shaping and controlling cancer progression and metastasis. We argue that, for various considerations, the perioperative period is critical in determining long-term survival, and that the immune system is presented with a unique opportunity to eradicate cancer. We then present clinical evidence indicating that cellular immunity is often limited by neuroendocrine modulation during the perioperative period. From our own studies, we give evidence that immunosuppression that follows surgery can directly promote metastasis. We point at several mechanisms, including local and neuroendocrine responses, by which various aspects of surgery can cause immunosuppression, and introduce possible prophylactic interventions that reduce immunosuppression. We further suggest that the potential beneficial effects of immunotherapy are also jeopardized by patients’ stress responses. Complementing immunotherapy with blockers to stress hormones may thus promote its efficacy. We hypothesize that along the autoevolutionary process of cancer development and metastasis, the malignant tissue capitalizes on neuroendocrine stress responses and synchronizes the
ABSTRACT Common approaches to cancer treatments focus on the malignant tissue itself, rather than on the existence PSYCHONEUROIMMUNOLOGY, 4E VOLUME I
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periods of maximal risk and exposure with periods of suppressed immunity. We conclude this chapter with clinical implications of these insights and of the suggested prophylactic anti-immunosuppressive interventions.
I. IMMUNE-CANCER INTERACTIONS AND THE POTENTIAL ROLE OF CELL-MEDIATED IMMUNITY (CMI) IN RESTRICTING TUMOR GROWTH AND METASTASIS The suggestion that neuroendocrine modulation of immune competence has biological and clinical significance to tumor development depends critically on the ability of the immune system to control malignancies. Whether and under what circumstances such control is implemented has been debated for decades, and we have recently reviewed this issue in detail (Shakhar and Ben-Eliyahu, 2003). Below we present the controversy, a contemporary theory that accounts for the apparently conflicting evidence, and our view that ascribes a significant role for CMI in controlling tumor metastasis under certain clinical conditions.
A. The Controversy over the Role of the Immune System in Controlling Cancer Development, and Its Resolution by Contemporary Theories The involvement of the immune system in controlling cancer has been debated for more than a century, since William Coley used extracts of pyrogenic bacteria to cause sporadic anti-tumor responses (Coley, 1893). Empirical evidence has been brought to support theories advocating immune surveillance, as well as theories negating immune control over malignant tumors. Today, state-of-the-art studies have provided ample evidence in favor of immune-cancer interactions and started to revive enthusiasm in immunotherapy. These studies can be categorized into several non-conclusive domains of research, including identification of immunogenic tumor-associated antigens (TAAs); activation of professional antigen-presenting cells (APCs) for the induction of effective T-cell–mediated immunity; the use of pattern recognition receptors to link innate to adaptive immunity via dendritic cells (DCs); and the role of suppressor or regulatory T lymphocytes in inhibiting responses against tumors. Nevertheless, the clinical significance of these interactions in controlling cancer progression has yet to be shown. Animal studies provided ample evidence for the involvement of the immune system in controlling tumor initiation, growth, and metastasis (Kikkawa
et al., 2000; McCoy et al., 2000; Smyth et al., 2001), and specifically implicated immune effectors such as CTL and NK cells (Brittenden, 1996; Khavari, 1987; Lindauer et al., 1998). Other leukocytes, including dendritic cells (Gilboa et al., 1998; Fong and Engleman, 2000), NKT (Brutkiewicz and Sriram, 2002; Smyth et al., 2002), and T-helper (Toes et al., 1999) cells also seem to be involved in supporting cytotoxic activity against tumors. Nevertheless, it is widely acknowledged that animal models often do not reliably simulate immune-malignant interactions in humans (Shakhar and Ben-Eliyahu, 2003). Models of experimental metastasis are often chosen based on their artificially high immunogenicity, and the course of natural tumor development and metastasis in rodents is markedly shorter and potentially less complex than in humans. Indeed, the evidence in humans is not conclusive. Undermining the suggested role of immunity are the findings that spontaneous remission in cancer patients is rare, immuno-stimulatory regimens have so far yielded limited success, and immuno-suppressed transplant patients hardly show increased frequencies of major cancer types (Penn, 1993). On the other hand, ample evidence in cancer patients supports a role for immunity. Autologous innate and adoptive immunocytes were shown in vitro to lyse tumor cells expanded from excised tumors (Rosenberg, 2001), and many molecular mechanisms of tumor recognition by immunocytes have been recently identified (Khavari, 1987; Long, 2002; Soloski, 2001). Moreover, patients’ leukocyte cytotoxicity (Uchida et al., 1990) or proliferative response (McCoy et al., 2000) to the autologous tumor were shown to be the best independent predictor of metastasis-free long-term survival, better than tumor stage and grade. When cancer appears in already immunosuppressed patients, its clinical course is commonly accelerated and more metastases appear (Barrett et al., 1993; Detry et al., 2000). Last, while it is now evident that the majority of cancer patients harbor micrometastases and circulating malignant cells following the removal of the primary tumor (Yamaguchi et al., 2000), recurrence occurs only in a minority of this population, suggesting a role for immunity in eradicating such minimal residual disease (MRD). This apparent conflicting evidence is reconciled by contemporary theories as follows. A newly transformed tissue is initially exposed to immunocytes only when it attracts blood capillary and emits various danger signals (Fuchs and Matzinger, 1996). By this stage, malignant cells have accumulated sufficient mutations to become immunogenic, and are recognized and destroyed by immunocytes. This starts an auto-evolutionary process through which selection pressure by the immune system, if not eradicating the developing tumor, increases the proportion of resis-
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tant malignant cells. Remaining malignant cells, which are known to intensively mutate, continue to acquire escape mechanisms that can eventually yield an immune-resistant malignancy. In cancer patients, the primary tumor has clearly outmaneuvered the immune system, but the prospect of a transformed cell in a healthy individual is unknown and may be dismal. Most impressive are the findings that human tumor cells can develop mechanisms to escape every known process used by the immune system to recognize or destroy malignant cells (Pawelec, 2004). These findings attest to a rigorous interaction between malignant cells and immunocytes, and to the substantial tumor destruction carried by immunocytes.
B. Cancer Metastases Are More Susceptible to CMI Than the Primary Tumor Although in cancer patients the immune system has clearly failed to eradicate the evolving primary tumor, it is believed to maintain an important role in controlling metastases, particularly after the primary tumor is removed and minimal residual disease (MRD) includes circulating single tumor cells and isolated micrometastases. Following detachment from the primary tumor, single tumor cells are targeted by unfamiliar populations of lymphocytes that employ recognition and destruction strategies that were not used against the primary tumor. Moreover, MRDs are not shielded by the primary tumor, and due to their insignificant mass cannot use escape mechanisms such as the release of immunosuppressive factors (e.g., prostaglandins, IL-10). There is evidence that metastases express more advanced escape mechanisms than the primary tumor, testifying to the strict selection pressure imposed by the immune system on metastasizing cells (Schirrmacher, 1985). Overall, the evidence suggests that immunity has an anti-malignant and anti-metastatic role in the natural course of human cancer, and that suppression of immune functions could thus worsen the prognosis of cancer patients. As indicated below (Section II), the perioperative period may constitute a setting in which immune competence is critical for restricting metastasis.
II. THE CRITICAL PERIOPERATIVE PERIOD IN CANCER PATIENTS A. Surgery as a Risk Factor in the Development of Metastases Surgery for the removal of the primary tumor, although essential, can increase the risk of postoperative metastases through several mechanisms. First, as
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malignant tissue is notoriously non-adhesive, the mechanical manipulation involved in excising the tumor and cutting its blood vessels has been shown to release tumor cells into the circulation (Eschwege et al., 1995; Yamaguchi et al., 2000). Second, growth factors released by the body to facilitate the healing of damaged tissue following surgery also facilitate the growth of pre-existing micrometastasis and the development of new metastases. Third, the removal of the primary tumor commonly terminates the release of anti-angiogenic factors, enabling dormant micrometastases to develop blood vessels and expand beyond a critical size (O’Reilly et al., 1994; O’Reilly et al., 1997). Fourth, stress hormones released perioperatively were shown in vitro to elevate the release of angiogenic factors by tumor cells (e.g., VEGF), potentially promoting the outbreak of dormant micrometastases (Lutgendorf et al., 2003). Last, surgery causes marked suppression of CMI, specifically if the procedure is large, invasive, and physiologically traumatic. These risk factors peak simultaneously during and immediately following surgery, and can act in synergy to promote the spread and seeding of new metastasis and the flare-up of pre-existing dormant micrometastases. At this critical setting, anti-metastatic immunity can become a critical factor restricting metastasis, and interference with its functioning can lead to the development of metastases that would have been prevented if immune competence was not impaired (Shakhar and Ben-Eliyahu, 2003).
B. A Window of Opportunity for Eradicating Cancer On the other hand, surgery opens a window of opportunity for eradicating cancer. The excision of the primary tumor eliminates the major source of mutating and metastasizing tumor cells, and the immune system is thus faced with a lesser challenge. Remaining malignant tissue in the form of MRD is also more susceptible to immunity, as indicated above, and the levels of immuno-suppressive factors often released by the primary tumor subside. Thus, the postoperative period presents the immune system with a second opportunity for eradicating cancer. This window of opportunity will be closed once potential metastases will grow beyond a critical size that enables the use of escape mechanisms originally employed by the excised primary tumor. Taken together, the postoperative period is characterized by a high risk for initiation and progression of metastases, but simultaneously presents an opportunity to eradicate cancer. Both prospects critically depend on immune competence, specifically immune anti-metastatic activity. Therefore, maintaining
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immune competence or/and boosting it during this critical period can impact long-term survival rates in cancer patients.
III. NEUROENDOCRINE MODULATION OF CELL-MEDIATED IMMUNITY AND CANCER DEVELOPMENT IN THE PERIOPERATIVE PERIOD Immunosuppression by surgery is caused by an intricate array of local and systemic physiological responses. As described below, many of these responses involve a CNS-mediated neuroendocrine feedback. Generally, whereas in the vicinity of the wound the predominant response is pro-inflammatory, in the periphery, where the fate of metastases is determined, an opposite picture emerges: There is a drastic reduction in pro-cellular Th1-type responses and suppression of CMI, with minor perturbation to humoral immunity.
A. The Potential Role of the Sympathetic Nervous System (SNS) The SNS innervates lymphoid organs and most leukocytes express adrenergic receptors (Elenkov et al., 2000). During the perioperative period and following psychological stress, catecholamines are released systemically, as well as locally by nerve endings that are believed to form “synapses” with leukocytes (Elenkov et al., 2000). In vitro studies have indicated that catecholamines can act directly to suppress many aspects of CMI, including NK, CTL, and macrophage activity (Elenkov et al., 2000). Catecholamines can also act indirectly to suppress CMI by reducing macrophages and Th production of type 1 cytokines (e.g., IL-12, TNF-α, and IFN-γ), and by stimulating the release of immunosuppressive factors including IL-10 and TGF-β (Platzer et al., 2000; Woiciechowsky et al., 1999).
B. The Hypothalmo-Pituitary-Adrenal (HPA) Axis Surgery activates the HPA axis via a spinal pathway, as well as through the release of IL-1 and IL-6 (Mastorakos et al., 1993). Increased levels of corticosteroids following surgery last for days and correlate with the severity of surgery and the degree of immunosuppression (Tashiro et al., 1996). Corticosteroids are established in vitro immunosuppressors and, when administered in pharmacological doses, cause potent immunosuppression. Indeed, the use of synthesis inhibitors or competitive antagonists of corticosteroids reduced T-cell apoptosis and metastasis following
surgery in rats (Deguchi et al., 1998), and attenuated the suppression of monocyte activity in injured mice (Cech et al., 1994). In addition, stress was shown to suppress various aspects of CMI and promote infection via activation of the HPA axis (Sheridan et al., 1994).
C. Local Factors and Cytokine Responses The response to tissue damage is initiated by local products of cell lysis, humoral factors released by macrophages and other resident cells, and by local neurogenic inflammatory agents. Prominent among these factors are prostaglandins (e.g., PGE2), which are potent in vitro suppressors of CMI and are known to be involved in the initiation of the cytokine response (Faist et al., 1996). In humans, cyclooxygenase inhibitors blunted the cytokine responses (Chambrier et al., 1996) and the suppression of CMI following surgery (Faist et al., 1990; Markewitz et al., 1996), and in rats they were also shown to reduce the promotion of metastasis by surgery (Colacchio et al., 1994). The local neurogenic pro-inflammatory response is initiated by nociceptive afferents. It involves local and spinal reflexes, and promotes erythema and edema around the surgical wound by releasing numerous compounds, including substance P (Rameshwar, 1997; Schaffer et al., 1998). The cytokine response to major surgery includes an immediate surge in systemic levels of pro-inflammatory cytokines (e.g., IL-6 and IL-8), and an increase in plasma levels of type 2 cytokines and other factors that interfere with CMI (e.g., IL-10, IL-1rA, sTNF-αr, and sIL-2r) (Faist et al., 1996; Lin et al., 2000). Additionally, in vitro studies indicated a marked decrease in the production of pro-CMI cytokines (such as IL-2, IL-12, IFN-γ, TNF-α, and IL-1β) by monocytes and Th1 cells, and an increase in the production of factors that interfere with CMI, such as IL10 and IL-1rA (Munford and Pugin, 2001). The cytokine response to surgery is intertwined with the neuroendocrine response described above. For example, IL-1 and IL-6 are critical for initiating the HPA response to surgery, while sympathetic activity was shown to trigger IL-10 release following surgery (Woiciechowsky et al., 1998; Woiciechowsky et al., 1999).
IV. POSTOPERATIVE SUPPRESSION OF NK ACTIVITY AND RESISTANCE TO TUMOR PROGRESSION: MECHANISMS AND PREVENTION BY PHARMACOLOGICAL INTERVENTIONS Major surgeries cause complex perturbations to various physiological processes, including the meta-
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bolic, cytokine, neuroendocrine, and immune systems. Various aspects of the surgical procedure are suspected to mediate the immunosuppressive effects of surgery. These include perioperative stress and anxiety, anesthetic and analgesic agents, tissue damage, blood loss and transfusion, hypothermia, and nociception and pain. The local paracrine mediators and the systemic cytokine and neuroendocrine responses that mediate the immunosuppressive effects of surgery are diverse and only partly understood. We have studied most of the aforementioned aspects of surgery with respect to their impact on rats’ NK activity and resistance to experimental metastasis, and searched for specific endocrine mediators of their impact. In these studies we made use of the mammary adenocarcinoma MADB106 tumor line and the CRNK-16 leukemia line, both syngeneic to the F344 rat. These tumor cells are sensitive in vivo to NK activity (Avraham et al., 2005; Barlozzari et al., 1983; Barlozzari et al., 1985; BenEliyahu and Page, 1992; Ben-Eliyahu et al., 1996), and thus we consider resistance to their metastases an in vivo index for NK activity (Ben-Eliyahu and Page, 1992; Ben-Eliyahu et al., 1996). These models also simulate some aspects of the more comprehensive metastatic process (e.g., extravasation of tumor cells and growth of metastases), or leukemia progression, but clearly suffers from some of the above-mentioned drawbacks of animal cancer models.
Garabal et al., 1993a; Freire-Garabal et al., 1993b). We have also shown that swim stress suppressed circulating NKA and promoted lung metastasis and leukemia progression by activating the SNS and releasing adrenal catecholamines (Figure 1) (Inbar et al., 2003) that activate β1 and β2 adrenoceptors (Ben-Eliyahu et al., 2000). Perhaps more related to human stress and anxiety, we have shown that social confrontation in rats can suppress NK activity and promote MADB106 experimental metastasis and that these effects were attenuated using a β-adrenergic blocker or diazepam (Abitri et al., 2005; Stefanski and Ben-Eliyahu, 1996; Stefanski and Engler, 1998). Interestingly, the coping style in the confrontation paradigm (e.g., type and frequency of submissive behavior) predicted susceptibility to metastasis (Stefanski and Ben-Eliyahu, 1996). Simulating the effects of SNS activation during stress, we also showed that the administration of physiologically relevant doses of a β-adrenergic agonist or adrenaline suppressed NK activity and consequently increased lung metastasis (Ben-Eliyahu et al., 2000; Shakhar and Ben-Eliyahu, 1998) and the progression
1
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1. Perioperative Stress and Anxiety and the Involvement of Catecholamines Most cancer patients experience emotional distress before and after surgery. Distress stems from loss of control, fear from the surgery and progression of the disease, the prospect of chemotherapy or radiotherapy, disfigurement, disability, and death (Lutgendorf and Costanzo, 2003). Psychological stress, especially when chronic, is associated with depressed CMI and increased susceptibility to infectious disease (Cohen and Herbert, 1996). Conducting animal studies, we and others have provided causal evidence that stress suppresses immunity (Moynihan and Ader, 1996) and consequently increases susceptibility to various types of metastasis and to leukemia (Ben-Eliyahu et al., 1991; Ben-Eliyahu et al., 1999; Ishihara et al., 1999). Correspondingly, anxiolytic drugs were shown to reduce postoperative suppression of CMI in mice (Freire-
Stress Nadolol Stress Vehicle
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A. Specific Aspects of Surgery That Contribute to Immunosuppression and Cancer Progression, and Their Mediating Immunological and Neuroendocrine Mechanisms
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0 15 25 35 45 55 65 75 Days FIGURE 1 The effect of swim stress on survival and its attenuation by the β-adrenergic blocker, nadolol. A miniscule number of 60 CRNK-16 leukemia cells were administered before subjecting rats to stress. Swim stress significantly increased mortality rates, and nadolol significantly attenuated this effect.
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of the CRNK-16 leukemia (Inbar et al., 2003). Although perioperative psychological factors may affect neuroendocrine responses less profoundly than intra- and postoperative physiological stressors, they last longer and may thus have a profound effect. 2. Causal Relationship between NK Suppression and Tumor Promotion It is often hard to show causal relationships between two in vivo processes. Strongly suggesting that the immunosuppressive effects of our above stressors underlie their tumor-promoting effects are the following findings: Different stress paradigms suppressed NKA for different durations that corresponded well with the time courses of their tumor promoting effects; metastasis of tumor lines that are sensitive to NKcontrol (MADB106, CRNK-16) were affected by stress, but not those that are not sensitive to NKA (C4047); the same interventions that attenuated the suppression of NKA reduced the promotion of metastasis and leukemia (Melamed et al., 2005); and selective depletion of NK cells eliminated the metastatic-promoting effects of swim-stress and β-adrenergic agonist, but not of surgery (Ben-Eliyahu et al., 1999; Ben-Eliyahu et al., 2000; Inbar et al., 2003; Shakhar and Ben-Eliyahu, 1998). Thus, suppression of NKA is sufficient to promote NK-sensitive metastasis under some stressful conditions, but additional mechanisms could play a role in more complex stressors, such as surgery. 3. Anesthetics and Analgesic Agents, and the Effects of Hypothermia Our studies in rats indicated that some anesthetics (i.e., ketamine, fentanyl, and thiopental) can alone suppress NK activity and promote tumor metastasis, while halothane and propofol have minor or no such effects (Melamed et al., 2003; Shavit et al., 2004). We also found that prolonged and severe hypothermia in rats, but not moderate hypothermia, causes similar effects, and that both the effects of hypothermia and of some anesthetics can be markedly reduced by a β-adrenergic antagonist (Ben-Eliyahu et al., 1999; Melamed et al., 2003). Thus, our surgical paradigm is based on the non–NK-suppressive general halothane anesthesia and is monitored to prevent severe hypothermia. 4. Tissue Damage Several studies in humans and rodents indicated that the severity of postoperative immunosuppression is associated with the degree of tissue damage (Carter, 2001; Lennard et al., 1985; Nelson and Lysle, 1998). Minimally invasive surgeries, such as laparoscopy,
limit postoperative infections in patients (Targarona et al., 2000) and the promotion of metastasis in operated animals (Da Costa et al., 1998). These beneficial effects could be related to attenuation of the local paracrine or systemic neuroendocrine responses, or to a lesser degree of hypothermia, blood loss, nociception, and pain. 5. Blood Loss and Transfusion Blood loss and transfusion were shown to interfere with several aspects of CMI, including cytokine levels, NK cell activity, and T-cell blastogenesis (Klein, 1999). Blood transfusion (BT) was suggested to be an independent risk factor for tumor recurrence in cancer patients (Klein, 1999), although the specific mechanisms are yet unclear. In an ongoing study in rats, we found that BT that is based on standard clinical procedures promotes MADB106 metastasis and the progression of the CRNK-16 leukemia. Surprisingly, our findings also indicate a critical role for red blood cells in mediating these effects of BT, rather than a role for leukocyte or soluble factors. We suspect that donors’ deteriorating red blood cells disrupt the normal host anti-tumor response, presumably through preoccupying host immunocytes (Atzil et al., 2004). 6. Nociception and Pain Pain and nociception are known to activate responses of the SNS, HPA, and the opioid systems via various mechanisms including the activation of spinal ascending and descending pathways. Because pain alleviation and spinal blockade are clinically feasible and were shown to reduce postoperative immunosuppression (Le Cras et al., 1998; Sacerdote et al., 2000), we tested their efficacy in reducing the tumor-promoting effects of surgery. We have established in rats that low analgesic doses of morphine or fentanyl (e.g., up to 5 mg/kg and 40 μg/kg respectively) can reduce the promotion of MADB106 metastasis by surgery (Page et al., 1998; Page et al., 2001). Preemptive analgesia, which is known to abrogate the nociceptive afferent barrage, was as efficient as prolonged postoperative treatment (Page et al., 1998). However, higher doses of narcotics (e.g., morphine 10 mg/kg) were detrimental, inducing immunosuppression and tumor promotion, as was also reported in human and animal studies (Saurer et al., 2004; Shavit et al., 2001; Shavit et al., 2004). Thus, a delicate balance between insufficient analgesia and too much narcotics must be maintained to clinically employ this approach. We therefore assessed another approach—perioperative spinal block by a combination of bupivacaine and morphine. This approach ensures low systemic levels of narcotic with
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superb pain and nociception blockade. Our studies indicated that this approach was more efficient in reducing the tumor-promoting effects of surgery, most likely acting by blocking the HPA and SNS responses to surgery (Bar-Yosef et al., 2001; Page et al., 2001). 7. The Involvement of Prostaglandins in the Immunosuppressive Effects of Surgery Prostaglandins, in particular PGE2, are important local mediators of CMI dysfunction. These substances are potent immunosuppressants, quickly synthesized in damaged tissue by macrophages and other cells, and have been reported by some but not other studies to increase systemically following surgery (Lai et al., 2000; Vitoratos et al., 1996). The administration of cyclooxygenase inhibitors to surgical patients results in blunted cytokine responses (Chambrier et al., 1996) and attenuated suppression of CMI (Faist et al., 1990). We have shown that the administration of PGE2 in physiologically relevant doses to rats suppresses circulating NKA per NK cell. By selective depletion of NK cells, we showed that dysfunction of NK cells induced by PGE2 increased susceptibility to metastasis. Finally, by treating rodents with COX or by selective COX2 inhibitors, we and others were able to reduce the promotion of metastasis by surgery (Colacchio et al., 1994; Page et al., 2003; Yakar et al., 2003). 8. A Unique Role for Marginating Pulmonary-NK Cells in Resisting Syngeneic Tumor Cells Many autologous tumor cells excised from patients are considered NK-insensitive, as patients’ circulating lymphocytes fail to exhibit spontaneous in vitro NK cytotoxicity against them (i.e., no cytotoxicity in a 4 h 51 Cr release assay). However, several tumor lines that are clearly controlled by NK cells in vivo, including the MADB106 line (Barlozzari et al., 1985; Ben-Eliyahu and Page, 1992; Ben-Eliyahu et al., 1996), meet the above “clinical” criterion for being NK-insensitive. Thus, we suspected that there is a unique population of NK cells that act in vivo in a manner that LAK cells act in vitro— recognize a larger spectrum of tumor cells and exhibit greater cytotoxicity than circulating NK cells. Recently, we have found a leukocyte population that seems to contain such an NK population—marginating pulmonary (MP) leukocytes (leukocytes adhering to the lungs’ vasculature). We have established that this population exhibits markedly greater NK cytotoxicity per MP-NK cell against syngeneic and xenogeneic target cells, and has a greater subpopulation of large NK cells (between 16 and 25 μm in size (Melamed et al., 2005) compared to circulating NK cells (30% vs. 10% in the blood) (Melamed et al., 2005). Although MP-NK cells
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are relatively few (approximately 3–10 × 105 cells/rat), they are strategically located to physically interact with circulating malignant cells that have to force their way through the pulmonary capillary system. By purifying MP-NK cells, we are now studying whether their unique capacities are contained within MP-NK cells themselves (as we believe), or whether supporting cells (e.g., NKT cells) are involved. Similar populations of NK cells may reside in other immune compartments (e.g., hepatic vasculature). If such populations exist in humans, then autologous tumor cells that were considered NK-insensitive are actually controlled in vivo by such NK cells.
B. The Prophylactic Use of a Combination B-Adrenergic Antagonist and a PGSynthesis Inhibitor against the Deleterious Effects of Surgery We recently reported the efficacy of a combined use of a β-adrenergic antagonist and a PG-synthesis inhibitor in preventing surgery-induced suppression of circulating and MP-NK activity against the YAC-1 and the syngeneic MADB106 target cells. We also showed that this treatment abolished the MADB106 metastasis-promoting effect of surgery (see Figure 2) (Melamed et al., 2005). Such a combined use of antagonists may be a key to a clinical approach, as blocking only one pathway may be insufficient given that either catecholamines or PGs can alone suppress NK activity by increasing intracellular cAMP levels (Torgersen et al., 1997; Whalen and Bankhurst, 1990). In our study, the interventions were given only postoperatively, as non-selective COX inhibitors can cause complications during surgery. We have also started the use of a selective COX2 inhibitor and a β-blocker that were administered before and after surgery. This approach has already yielded promising results (Avraham et al., 2005) and can be advantageous in the clinical setting, as it can be expected to also alleviate pre-operative immunosuppression caused by potential release of PGs by the primary tumor, and to reduce the effects of SNS responses caused by psychological stress.
V. IS THERE EVIDENCE IN CANCER PATIENTS THAT POSTOPERATIVE SUPPRESSION OF CMI CAN INDEED PROMOTE METASTASIS? Studies in animals cannot be expected to simulate the much longer, different, and complex process of metastasis in cancer patients (Hewitt, 1983; Killion et al., 1998). Thus, evidence in support of the suggestion
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% Lung Tumor Retention (MADB106)
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FIGURE 2 The effects of surgery and their attenuation by the β-adrenergic blocker, nadolol, by the prostaglandin synthesis inhibitor, indomethacin (indo), and by the combined use of these drugs (indo and nadolol) (mean ± SEM). Surgery increased lung tumor retention of the MADB106 tumor and increased the number of experimental MADB106 lung metastases counted 3 weeks later (not shown). Each of the blockers attenuated these effects, and their combined use almost completely abolished them. ¥ indicates a significant effect of surgery (difference between the control saline and surgery saline groups), and * indicates a significant attenuation of this effect by drug treatment (difference between the surgery saline group and the surgery drug group). The combined treatment was significantly lower than each treatment alone.
that postoperative suppression of CMI can promote metastasis in cancer patients should also be obtained in cancer patients. Because surgery is always conducted in patients presenting with operable tumors, potential evidence could only be based on correspondence between variations in the levels of postoperative immunosuppression and subsequent long-term recurrence rates. Studying the literature, we found such correspondence with respect to variations on surgical procedures that exacerbate or lessen postoperative immunosuppression. Specifically, local rather than general anesthesia was shown to reduce postoperative immunosuppression (Galley et al., 2000), and prospective studies showed that this approach also reduces long-term mortality rates in skin cancer patients (Schlagenhauff et al., 2000). Blood transfusion was shown to cause immunosuppression (Klein, 1999), as well as to be an independent risk factor for recurrence (Klein,
1999; Vamvakas and Blajchman, 2001). Repeated surgeries cause more immunosuppression than a single surgery and were reported to worsen prognosis in colon cancer (Fielding and Wells, 1974). Last, minimally invasive surgeries (MIS) are known to cause less immunosuppression (Carter, 2001; Sietses, 1999), and data are now accumulating to suggest that they can reduce recurrence rates (Kaseda et al., 2000; Sugi et al., 2000). Most importantly, local anesthesia, blood transfusion, repeated surgeries, and MIS were shown to predict recurrence rates independently of other factors associated with them, and in some studies subjects were randomly and prospectively allocated to the different studies’ groups. Thus, these positive and negative risk factors should be considered seriously when planning and conducting surgeries in cancer patients. The different levels of postoperative immunosuppression they induce could be the major factor mediating their impact on recurrence rates. Some of these correspondences have been simulated in animal models, and these studies provided more direct support for the mediating role of immunosuppression [for more details, see (Shakhar and Ben-Eliyahu, 2003)]. Because in cancer patients the evidence is still circumstantial, the most convincing evidence that one could strive to achieve in this population seems to be through interventions aiming at specifically blocking postoperative immunosuppression. We feel that our knowledge is now sufficient to start developing these interventions in patients undergoing major surgeries. Such strategies could be implemented in cancer patients once they are proven successful and provided that there are no contraindications.
VI. IMMUNE STIMULATION AS A PROPHYLACTIC MEASURE IN THE PERIOPERATIVE PERIOD: A DOUBLEEDGED SWORD AND THE POTENTIAL FOR PNI-BASED INTERVENTIONS TO IMPROVE IMMUNOTHERAPY In the context of tumor excision, residual circulating tumor cells are potentially immunogenic and are outnumbered by immunocytes outside the protective environment of the primary tumor. This presents an opportunity for immune-activation–based therapies to reduce long-term postoperative metastases. Unfortunately, stress and surgery often cause the release of stress hormones that could potentially interfere with immune responses to immunostimulatory agents. Also, the immunosuppressive effects of surgery could annihilate the beneficial effects of immunostimulation. We have conducted several studies to explore poten-
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tial interactions between stress responses and immunotherapy, and the feasibility to integrate PNI-based interventions with immunotherapy in the perioperative period to reduce postoperative metastasis.
A. Are the Beneficial Effects of Immunostimulation Limited by the Deleterious Effects of Stress and Surgery? Marked postoperative immunosuppression could theoretically annihilate the beneficial effects of preoperative immunostimulation. We believe that while boosting baseline levels of immunity would prove beneficial under no-stress conditions, after severe stress, which can occur postoperatively, the beneficial effects of immunotherapy could be undermined. To explore this notion in the context of stress and surgery, we studied two different agents commonly used in immunotherapy: poly I-C and IL-12. Repeated pre-tumor administration of IL-12 was found in our in vivo studies to potently reduce metastasis in non-stressed rats. However, surgery and stress had the same deleterious effects in IL-12–treated rats as in saline-treated rats. Ex vivo studies indicated that IL-12 induced its favorable effects by increasing total numbers of circulating and marginating pulmonary NK cells, both in the stress and no-stress groups. Surgery caused a marked suppression in NK activity per NK cell, without affecting the numbers of circulating or marginating pulmonary NK cells. Corresponding with the in vivo findings, IL-12 did not protect NK activity per NK cell from suppression by surgery (Avraham et al., 2004). Thus, in our studies IL-12 acted by increasing baseline levels of immunity and tumor resistance, but did not protect the host from the deleterious effects of surgery. A similar paradigm of low doses in repeated administration of Poly I-C was not as effective as IL-12 in reducing metastasis in non-stressed rats. However, the metastasis-promoting effects of stress and surgery were dramatically decreased or completely absent in poly I-C treated rats. Our findings also indicate that poly I-C was not as effective as IL-12 in increasing numbers of circulating and marginating pulmonary NK cells. However, unlike IL-12, poly I-C significantly protected NK activity per NK cell from stress- and surgery-induced suppression (Shakhar et al., 2003). Moreover, we conducted further studies that directly confirmed these ex vivo results; in vivo treatment with poly I-C completely abolished the in vitro suppression of marginating pulmonary NK cells by corticosterone and prostaglandin E2. Taken together, these results suggest that boosting immune functions and protecting immunity from
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postoperative suppression are independent outcomes that seem to act via different cellular mechanisms. While boosting immune function acted in the current studies via increasing numbers of effector cells, protecting immunity from suppression acted at the single cell level. Hence, in cancer patients subjected to immunostimulatory regimens, complementary treatments should be considered.
B. Immunostimulation Can Also Suppress Immune Functions Immunostimulation in and of itself can induce various physiological stress responses that can suppress some immune functions or affect tumor progression via non-immunological mechanisms. For example, poly I-C was found to induce the release of corticosterone (Pruett et al., 2003). In our studies we found that while repeated administrations of poly I-C reduced experimental metastasis, a single dose causes detrimental effects during the first hours following administration. This may be attributed to a specific stress response caused by poly I-C, or may reflect the activation of the hypothalamic-pituitary-adrenal axis by one or more of the cytokines induced by poly I-C (e.g., IL6) (Turnbull and Rivier, 1999). Indeed, in a recent study we were able to significantly attenuate these detrimental effects of poly I-C by administrating a non-selective β-blocker, and to a lesser degree by administrating the non-selective corticosterone antagonist, RU486 (unpublished data). The notion that the sickness syndrome is stressful and potentially immunosuppressive has been previously reflected upon in the realm of PNI. Its biological significance has thus far been reported mainly with respect to psycho-depressive symptoms induced by cytokine therapy or by spontaneous immune responses to environmental challenges (Yirmiya et al., 2000). In the context of immune-stimulations in cancer patients, such effects may bear significant clinical consequences.
C. Immunostimulation Can Directly Promote Tumor Progression Cancer cells are transformed cells of the body, and as such they often express receptors and other surface molecules expressed by their pre-malignant progenitors. Consequently, malignancies that have originated from leukocytes might interact with immunostimulatory agents. In our studies with the CRNK-16 leukemia-line, we administered IL-12 or poly I-C before or after leukemia inoculation. These immunostimulatory agents were effective in reducing mortality rates from
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this leukemia when administered before leukemia inoculation, but not after it. One explanation could be that CRNK-16 cells were triggered to proliferate by IL-12 or by cytokines induced by poly I-C. Given that CRNK-16 cells originate from LGLs (Ward and Reynolds, 1983), they are likely to express receptors to such factors. This phenomenon may present an obstacle to immunotherapy in tumor-bearing patients. The balance between boosting immune activity and stimulating tumor cells should be considered with respect to the specific malignant tissue and the context of treatment.
D. The Potential for Combining Immunostimulation with PNI-Based Interventions Given the above results and considerations, activation of the immune system in the perioperative setting may not suffice if not protected from the massive immunosuppression that follows major surgeries. To this end, we have studied the combination of PNIbased interventions in the form of a β-blocker and COX inhibitor with IL-12 immunotherapy. The in vivo results are summarized in Figure 3. The combined approach was most effective, boosting anti-tumor resistance and protecting it against suppression by surgery. Studying underlying cellular mechanisms, it followed that IL-12 increased the numbers of MP-NK, while the PNI-based intervention prevented NK suppression on a per NK cell basis. These results imply that the two approaches utilize different sets of molecular mechanisms that can complement each other in the postoperative period.
VII. DOES MALIGNANT TISSUE EXPLOIT STRESSFUL PERIODS TO FACILITATE ITS AUTO-EVOLUTIONARY PROCESS? Ample evidence reviewed above indicates that neuroendocrine stress responses can modulate immune competence against metastatic processes and that these modulations bear clinical significance. While metastasis is an advanced stage of tumor progression, the outbreak and growth of cancer is an auto-evolutionary process that is affected by numerous factors and various selection pressures along its course. It is our hypothesis that neuroendocrine perturbations impact the evolvement of the malignant tissue via diverse mechanisms, and that the malignant tissue itself senses neuroendocrine stress responses and uses them to coordinate processes that promote its evolvement and survival. Specifically, we believe that the malignant
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FIGURE 3 The effects of surgery and their attenuation by IL-12, the use of a β-adrenergic blocker and a prostaglandin synthesis inhibitor (nadolol & indo), and by the combined use of all these interventions (combined) (mean ± SEM). * indicates a significant decrease in baseline LTR in the IL-12 treated groups. ¥ indicates a significant effect of surgery (difference between the control saline and surgery saline groups), and ** indicates a significant attenuation of this effect by drug treatment (difference between the surgery saline group and the surgery drug groups). The combined treatment was significantly lower than each treatment alone.
tissue synchronizes stages in which it is maximally exposed or endangered, with periods of minimal selection pressure. Indeed, fulfilling a prerequisite for this hypothesis, evidence from recent years indicates that malignancies express β-adrenergic and PGE2 functional receptors (Park et al., 1995; Wang and Dubois, 2004), which can enable them to detect periods of neuroendocrine perturbations and potential immune suppression. At least three circumstances along tumor evolvement can be considered as critical for malignancies to rely on neuroendocrine signaling to safely initiate their progression: (a) The first major emission of danger signals from hypoxic dividing malignant cells attracts immunocytes (Collingridge et al., 2001; Lewis and Murdoch, 2005) and exposes the tissue to massive selection pressure. Tumor cells were shown to accelerate their proliferative rate and increase resistance to apoptosis when subjected to increased levels of catecholamines and PGs (Park et al., 1995; Romano and
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Claria, 2003; Wang and Dubois, 2004). Thus, tumor cells synchronize this high exposure period with elevated levels of immunosuppressive factors. Similar processes apparently occur with respect to the progression of viruses that were shown to activate gene transcription and to accelerate replication during periods of heightened epinephrine levels (Cole et al., 1998; Cole et al., 2001; Romero et al., 1992). (b) The creation of new blood vessels enables the malignant tissue to grow beyond a critical size, but also markedly exposes the tissue to interaction with newly arrived immunocytes. Tumors were shown to release factors (e.g., VEGF) to facilitate the angiogenic process (Folkman, 1990). Studies have shown that stress-related mediators (e.g., norepinephrine) can directly enhance the production of VEGF by cancer cell lines through tumor ß-adrenergic receptors (Lutgendorf et al., 2003). (c) The metastatic process is another critical stage in which cancer cells detach from the primary tumor and enter the circulation to invade remote organs. Outside the protective environment of the tumor, these single cells are more vulnerable to immune surveillance and are exposed to new populations of immunocytes in target organs. Studies have shown that catecholamines increase the invasiveness of tumor cells (Wang and Dubois, 2004) and tumor cell migration (Lang et al., 2004). Overall, these findings are in agreement with the notion that tumor cells respond to their neuroendocrine milieu in a fashion that synchronizes critical stages of their progression with periods of minimal selection pressure by the immune system. This ability of tumor cells is most likely acquired through random mutation and selection that have eliminated cells that failed to exploit such a potential survival advantage. This characteristic of tumor cells should be considered as an escape mechanism acting at the organism systemic level.
VIII. CLINICAL IMPLICATIONS Today, the medical perspective of cancer is focusing on the neoplasm, addressing its stage, metastatic status, etc. Accordingly, most therapies are directed at the malignant tissue itself (e.g., surgery, chemotherapy, immunotherapy targeting tumor-associated antigens), and the patient’s reaction to the therapy is merely a side effect. In this chapter we emphasize a point of view in which the patient’s natural biological processes have a central role, affecting the progression of the disease and the prognosis. This point of view embraces the notion that cancer evolves within the body through interactions with the immune and neu-
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roendocrine systems. The anti-cancer treatments and the malignant tissue itself can affect the immune and neuroendocrine systems, thereby impacting cancer progression. The following issues are central to this perspective and its implications. It is still controversial whether the theory of immunosurveillance holds and bears clinical significance. While animal studies of immune stimulation have yielded promising results, large-scale clinical trials employing various immunostimulatory agents were mostly inconclusive (Smyth et al., 2001), supporting the view that immune control over cancer progression might be dismal. However, our findings in rats (VI.a) indicate that stress and surgery can cause immunosuppression in immuno-stimulated rats, which might undermine the potential beneficial effects of immunotherapy. Also, the host response to immunostimulating agents may be jeopardized by neuroendocrine responses to stress. Importantly, psychological and physiological stress responses are common in patients, and were not addressed in most animal studies of immunostimulation. Therefore, it is our belief that the controversy over the significance of immune surveillance in cancer patients could be better resolved if clinical trials will assess approaches to prevent immunosuppression in critical periods, as opposed to relying on immunostimulatory approaches. This approach could be implemented by using blockers to stress hormones and PGs during the perioperative period. Such studies will also indicate, for the first time, not only whether the notion of immunosurveillance holds, but also the biological significance of immunosuppression in cancer patients. A few issues should be considered with respect to anti-immunosuppressive therapies: (a) As malignancies evolve and acquire more sophisticated escape mechanisms, immunosurveillance and its neuroendocrine regulation gradually become inconsequential. Encouragingly, early detection of the disease is a major focus of many studies, yielding profound advances in several types of cancer. An early detection may also provide an advantage to anti-immunosuppressive therapy. (b) Cancer patients are often in distress while undergoing immunostimulatory treatments, and the physiological responses to immunostimulation are often stressful in and of themselves. Stress hormones may cause perturbation to specific immune functions, jeopardizing the host response to an immunostimulatory agent. Therefore, stress-alleviating approaches may improve the outcome of immunostimulatory regimens. (c) Such stress-alleviating approaches may also prevent the tumor from capitalizing on neuroendocrine responses that directly accelerate its evolvement (Section VII). (d) In the context of surgery, anti-
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immunosuppressive approaches would, at best, preserve immune competence at baseline levels. Combining immunostimulatory approaches with antiimmunosuppressive approaches could potentially yield synergistic effects, as the two approaches utilize different sets of cellular mechanisms and can thus complement each other. Integrating such a combined approach with surgical treatment might improve longterm prognosis of cancer patients.
References Abitri, N., Greenfeld, K., Atzil, S., Melamed, R., Rosenne, E., Avraham, R., and Ben-Eliyahu, S. (2005). A new frontier for antianxiety drugs?! Israel Bio-Psychology Annual Meeting. Atzil, S., Arad, M., Abiri, N., Rosenne, E., Beilin, B., and Ben-Eliyahu, S. (2004). Blood transfusion suppresses host resistance to experimental tumor metastasis: Effects of histocompatibility and storage time. Annual Meeting of the Psychoneuroimmunology Research Society, Titisee, Germany. Avraham, R., Rosenne, E., Melamed, R., and Ben-Eliyahu, S. (2005). Combining immunotherapy with PNI-based interventions: a win-win approach in the post operative setting. Psychoneuroimmunology Research Society, Denver, Colorado. Avraham, R., Schwartz, Y., Rosenne, E., Melamed, R., and BenEliyahu, S. (2004). IL-12-based immunotherapy reduces postsurgery immunosuppression and metastasis, and increases survival from experimental leukemia. Psychoneuroimmunology Research Society, Titisee, Germany: Elsevier. Barlozzari, T., Leonhardt, J., Wiltrout, R. H., Herberman, R. B., and Reynolds, C. W. (1985). Direct evidence for the role of LGL in the inhibition of experimental tumor metastases. Journal of Immunology, 134 (4), 2783–2789. Barlozzari, T., Reynolds, C. W., and Herberman, R. B. (1983). In vivo role of natural killer cells: involvement of large granular lymphocytes in the clearance of tumor cells in anti-asialo GM1-treated rats. Journal of Immunology, 131 (2), 1024–1027. Barrett, W. L., First, M. R., Aron, B. S., and Penn, I. (1993). Clinical course of malignancies in renal transplant recipients. Cancer, 72 (7), 2186–2189. Bar-Yosef, S., Melamed, R., Page, G. G., Shakhar, G., Shakhar, K., and Ben-Eliyahu, S. (2001). Attenuation of the tumor-promoting effect of surgery by spinal blockade in rats. Anesthesiology, 94 (6), 1066–1073. Ben-Eliyahu, S., and Page, G. G. (1992). In vivo assessment of natural killer cell activity in rats. Progress in Neuroendocrineimmunology, 5, 199–214. Ben-Eliyahu, S., Page, G. G., Yirmiya, R., and Shakhar, G. (1999). Evidence that stress and surgical interventions promote tumor development by suppressing natural killer cell activity. Int. J. Cancer, 80 (6), 880–888. Ben-Eliyahu, S., Page, G. G., Yirmiya, R., and Taylor, A. N. (1996). Acute alcohol intoxication suppresses natural killer cell activity and promotes tumor metastasis. Nature Medicine, 2 (4), 457– 460. Ben-Eliyahu, S., Shakhar, G., Page, G. G., Stefanski, V., and Shakhar, K. (2000). Suppression of NK cell activity and of resistance to metastasis by stress: a role for adrenal catecholamines and betaadrenoceptors. Neuroimmunomodulation, 8 (3), 154–164. Ben-Eliyahu, S., Shakhar, G., Rosenne, E., Levinson, Y., and Beilin, B. (1999). Hypothermia in barbiturate-anesthetized rats sup-
presses natural killer cell activity and compromises resistance to tumor metastasis: a role for adrenergic mechanisms. Anesthesiology, 91 (3), 732–740. Ben-Eliyahu, S., Yirmiya, R., Liebeskind, J. C., Taylor, A. N., and Gale, R. P. (1991). Stress increases metastatic spread of a mammary tumor in rats: evidence for mediation by the immune system. Brain, Behavior, and Immunity, 5 (2), 193–205. Brittenden, J. (1996). Natural killer cells and cancer. Cancer, 77 (7), 1226–1243. Brutkiewicz, R. R., and Sriram, V. (2002). Natural killer T (NKT) cells and their role in antitumor immunity. Crit. Rev. Oncol. Hematol., 41 (3), 287–298. Carter, J. J. (2001). The immunologic consequences of laparoscopy in oncology. Surgical Oncology Clinics of North America, 10 (3), 655–677. Cech, A. C., Shou, J., Gallagher, H., and Daly, J. M. (1994). Glucocorticoid receptor blockade reverses postinjury macrophage suppression. Arch. Surg., 129 (12), 1227–1232. Chambrier, C., Chassard, D., Bienvenu, J., Saudin, F., Paturel, B., Garrigue, C., Barbier, Y., and Bouletreau, P. (1996). Cytokine and hormonal changes after cholecystectomy. Effect of ibuprofen pretreatment. Ann. Surg., 224 (2), 178–182. Cohen, S., and Herbert, T. B. (1996). Health psychology: psychological factors and physical disease from the perspective of human psychoneuroimmunology. Annual Review of Psychology, 47, 113–142. Colacchio, T. A., Yeager, M. P., and Hildebrandt, L. W. (1994). Perioperative immunomodulation in cancer surgery. Am. J. Surg., 167 (1), 174–179. Cole, S. W., Korin, Y. D., Fahey, J. L., and Zack, J. A. (1998). Norepinephrine accelerates HIV replication via protein kinase Adependent effects on cytokine production. J. Immunol., 161 (2), 610–616. Cole, S. W., Naliboff, B. D., Kemeny, M. E., Griswold, M. P., Fahey, J. L., and Zack, J. A. (2001). Impaired response to HAART in HIV-infected individuals with high autonomic nervous system activity. Proc. Natl. Acad. Sci. U.S.A., 98 (22), 12695–12700. Coley, W. B. (1893). The treatment of malignant tumors by repeated inoculations of erysipelas. With a report of ten original cases. 1893. A, J. Med. Sci., 105, 487–511. Collingridge, D. R., Hill, S. A., and Chaplin, D. J. (2001). Proportion of infiltrating IgG-binding immune cells predict for tumour hypoxia. Br. J. Cancer, 84 (5), 626–630. Da Costa, M. L., Redmond, P., and Bouchier-Hayes, D. J. (1998). The effect of laparotomy and laparoscopy on the establishment of spontaneous tumor metastases. Surgery, 124 (3), 516–525. Deguchi, M., Isobe, Y., Matsukawa, S., Yamaguchi, A., and Nakagawara, G. (1998). Usefulness of metyrapone treatment to suppress cancer metastasis facilitated by surgical stress. Surgery, 123 (4), 440–449. Detry, O., Honore, P., Meurisse, M., and Jacquet, N. (2000). Cancer in transplant recipients. Transplant Proc., 32 (1), 127. Elenkov, I. J., Wilder, R. L., Chrousos, G. P., and Vizi, E. S. (2000). The sympathetic nerve—an integrative interface between two supersystems: the brain and the immune system. Pharmacol. Rev., 52 (4), 595–638. Eschwege, P., Dumas, F., Blanchet, P., Le Maire, V., Benoit, G., Jardin, A., Lacour, B., and Loric, S. (1995). Haematogenous dissemination of prostatic epithelial cells during radical prostatectomy. Lancet, 346 (8989), 1528–1530. Faist, E., Ertel, W., Cohnert, T., Huber, P., Inthorn, D., and Heberer, G. (1990). Immunoprotective effects of cyclooxygenase inhibition in patients with major surgical trauma. J. Trauma, 30 (1), 8–17.
12. Neuroendocrine Regulation of Cancer Progression Faist, E., Schinkel, C., and Zimmer, S. (1996). Update on the mechanisms of immune suppression of injury and immune modulation. World J. Surg., 20 (4), 454–459. Fielding, L. P., and Wells, B. W. (1974). Survival after primary and after staged resection for large bowel obstruction caused by cancer. Br. J. Surg., 61 (1), 16–18. Folkman, J. (1990). What is the evidence that tumors are angiogenesis dependent? J. Natl. Cancer Inst., 82 (1), 4–6. Fong, L., and Engleman, E. G. (2000). Dendritic cells in cancer immunotherapy. Annu. Rev. Immunol., 18, 245–273. Freire-Garabal, M., Nunez, M. J., Balboa, J. L., Fernandez-Rial, J. C., Vallejo, L. G., Gonzalez-Bahillo, J., and Rey-Mendez, M. (1993a). Effects of alprazolam on cellular immune response to surgical stress in mice. Cancer Lett., 73 (2–3), 155–160. Freire-Garabal, M., Nunez, M. J., Balboa, J. L., Gonzalez-Bahillo, J., and Belmonte, A. (1993b). Effects of midazolam on the activity of phagocytosis in mice submitted to surgical stress. Pharmacol. Biochem. Behav., 46 (3), 605–608. Fuchs, E. J., and Matzinger, P. (1996). Is cancer dangerous to the immune system? Semin. Immunol., 8 (5), 271–280. Galley, H. F., DiMatteo, M. A., and Webster, N. R. (2000). Immunomodulation by anaesthetic, sedative and analgesic agents: does it matter? Intensive Care Med., 26 (3), 267–274. Gilboa, E., Nair, S. K., and Lyerly, H. K. (1998). Immunotherapy of cancer with dendritic-cell–based vaccines. Cancer Immunol. Immunother, 46 (2), 82–87. Hewitt, H. B. (1983). Second point: animal tumor models and their relevance to human tumor immunology. J. Biol. Response Mod., 2 (3), 210–216. Inbar, S., Rosenne, E., Schwartz, Y., Melamed, R., and Ben-Eliyahu, S. (2003). The impact of stress hormones on progression of CRNK16 leukemia in rats, and the potential immunostressful nature of having leukemia. Brain, Behavior, and Immunity, 17 (3), 182. Ishihara, Y., Matsunaga, K., Iijima, H., Fujii, T., Oguchi, Y., and Kagawa, J. (1999). Time-dependent effects of stressor application on metastasis of tumor cells in the lung and its regulation by an immunomodulator in mice. Psychoneuroendocrinology, 24 (7), 713–726. Kaseda, S., Aoki, T., Hangai, N., and Shimizu, K. (2000). Better pulmonary function and prognosis with video-assisted thoracic surgery than with thoracotomy. Ann. Thorac. Surg., 70 (5), 1644–1646. Khavari, P. (1987). Cytotoxic cellular mediators of the immune response to neoplasia: a review. Yale Journal of Biology and Medicine, 60 (5), 409–419. Kikkawa, H., Imafuku, H., Tsukada, H., and Oku, N. (2000). Possible role of immune surveillance at the initial phase of metastasis produced by B16BL6 melanoma cells. FEBS Lett., 467 (2–3), 211–216. Killion, J. J., Radinsky, R., and Fidler, I. J. (1998). Orthotopic models are necessary to predict therapy of transplantable tumors in mice. Cancer Metastasis Rev., 17 (3), 279–284. Klein, H. G. (1999). Immunomodulatory aspects of transfusion: a once and future risk? Anesthesiology, 91 (3), 861–865. Lai, O. F., Chow, P. K., Tan, S., Song, I. C., Soo, K. C., Aw, S. E., Yu, W. K., Fook-Chong, S. M., Satchithanantham, S., and Chan, S. T. (2000). Changes in prostaglandin and nitric oxide levels in the hyperdynamic circulation following liver resection. J. Gastroenterol. Hepatol., 15 (8), 895–901. Lang, K., Drell, T. L, T., Lindecke, A., Niggemann, B., Kaltschmidt, C., Zaenker, K. S., and Entschladen, F. (2004). Induction of a metastatogenic tumor cell type by neurotransmitters and its pharmacological inhibition by established drugs. Int. J. Cancer, 112 (2), 231–238.
263
Le Cras, A. E., Galley, H. F., and Webster, N. R. (1998). Spinal but not general anesthesia increases the ratio of T helper 1 to T helper 2 cell subsets in patients undergoing transurethral resection of the prostate. Anesth. Analg., 87 (6), 1421–1425. Lennard, T. W., Shenton, B. K., Borzotta, A., Donnelly, P. K., White, M., Gerrie, L. M., Proud, G., and Taylor, R. M. (1985). The influence of surgical operations on components of the human immune system. Br. J. Surg., 72 (10), 771–776. Lewis, C., and Murdoch, C. (2005). Macrophage responses to hypoxia: implications for tumor progression and anti-cancer therapies. Am. J. Pathol., 167 (3), 627–635. Lin, E., Calvano, S. E., and Lowry, S. F. (2000). Inflammatory cytokines and cell response in surgery. Surgery, 127 (2), 117–126. Lindauer, M., Stanislawski, T., Haussler, A., Antunes, E., Cellary, A., Huber, C., and Theobald, M. (1998). The molecular basis of cancer immunotherapy by cytotoxic T lymphocytes. J. Mol. Med., 76 (1), 32–47. Long, E. O. (2002). Tumor cell recognition by natural killer cells. Semin. Cancer Biol., 12 (1), 57–61. Lutgendorf, S. K., Cole, S., Costanzo, E., Bradley, S., Coffin, J., Jabbari, S., Rainwater, K., Ritchie, J. M., Yang, M., and Sood, A. K. (2003). Stress-related mediators stimulate vascular endothelial growth factor secretion by two ovarian cancer cell lines. Clin. Cancer Res., 9 (12), 4514–4521. Lutgendorf, S. K., and Costanzo, E. S. (2003). Psychoneuroimmunology and health psychology: an integrative model. Brain Behav. Immun., 17 (4), 225–232. Markewitz, A., Faist, E., Lang, S., Hultner, L., Weinhold, C., and Reichart, B. (1996). An imbalance in T-helper cell subsets alters immune response after cardiac surgery. Eur. J. Cardiothorac. Surg., 10 (1), 61–67. Mastorakos, G., Chrousos, G. P., and Weber, J. S. (1993). Recombinant interleukin-6 activates the hypothalamic-pituitary-adrenal axis in humans. J. Clin. Endocrinol. Metab., 77 (6), 1690–1694. McCoy, J. L., Rucker, R., and Petros, J. A. (2000). Cell-mediated immunity to tumor-associated antigens is a better predictor of survival in early stage breast cancer than stage, grade or lymph node status. Breast Cancer Res. Treat., 60 (3), 227–234. Melamed, R., Bar-Yosef, S., Shakhar, G., Shakhar, K., and BenEliyahu, S. (2003). Suppression of natural killer cell activity and promotion of tumor metastasis by ketamine, thiopental, and halothane, but not by propofol: mediating mechanisms and prophylactic measures. Anesth. Analg., 97 (5), 1331–1339. Melamed, R., Rosenne, E., Shakhar, K., Schwartz, Y., Abudarham, N., and Ben-Eliyahu, S. (2005). Marginating pulmonary-NK activity and resistance to experimental tumor metastasis: suppression by surgery and the prophylactic use of a betaadrenergic antagonist and a prostaglandin synthesis inhibitor. Brain Behav. Immun., 19 (2), 114–126. Moynihan, J. A., and Ader, R. (1996). Psychoneuroimmunology: animal models of disease. Psychsomatic Medicine, 58 (6), 546– 558. Munford, R. S., and Pugin, J. (2001). Normal responses to injury prevent systemic inflammation and can be immunosuppressive. Am. J. Respir. Crit. Care Med., 163 (2), 316–321. Nelson, C. J., and Lysle, D. T. (1998). Severity, time, and betaadrenergic receptor involvement in surgery-induced immune alterations. J. Surg. Res., 80 (2), 115–122. O’Reilly, M. S., Boehm, T., Shing, Y., Fukai, N., Vasios, G., Lane, W. S., Flynn, E., Birkhead, J. R., Olsen, B. R., and Folkman, J. (1997). Endostatin: an endogenous inhibitor of angiogenesis and tumor growth. Cell, 88 (2), 277–285. O’Reilly, M. S., Holmgren, L., Shing, Y., Chen, C., Rosenthal, R. A., Moses, M., Lane, W. S., Cao, Y., Sage, E. H., and Folkman, J.
264
I. Neural and Endocrine Effects on Immunity
(1994). Angiostatin: a novel angiogenesis inhibitor that mediates the suppression of metastases by a Lewis lung carcinoma. Cell, 79 (2), 315–328. Page, G. G., and Ben-Eliyahu, S. (2003). COX-2 involvement in the tumor-enhancing effects of surgery. Brain, Behavior, and Immunity, 17, 194. Page, G. G., Blakely, W. P., and Ben-Eliyahu, S. (2001). Evidence that postoperative pain is a mediator of the tumor-promoting effects of surgery in rats. Pain, 90 (1–2), 191–199. Page, G. G., McDonald, J. S., and Ben-Eliyahu, S. (1998). Preoperative versus postoperative administration of morphine: impact on the neuroendocrine, behavioural, and metastaticenhancing effects of surgery. Br. J. Anaesth., 81 (2), 216–223. Park, P. G., Merryman, J., Orloff, M., and Schuller, H. M. (1995). Beta-adrenergic mitogenic signal transduction in peripheral lung adenocarcinoma: implications for individuals with preexisting chronic lung disease. Cancer Res., 55 (16), 3504–3508. Pawelec, G. (2004). Tumour escape: antitumour effectors too much of a good thing? Cancer Immunol. Immunother., 53 (3), 262–274. Penn, I. (1993). The effect of immunosuppression on pre-existing cancers. Transplantation, 55 (4), 742–747. Platzer, C., Docke, W., Volk, H., and Prosch, S. (2000). Catecholamines trigger IL-10 release in acute systemic stress reaction by direct stimulation of its promoter/enhancer activity in monocytic cells. J. Neuroimmunol., 105 (1), 31–38. Pruett, S. B., Fan, R., and Zheng, Q. (2003). Acute ethanol administration profoundly alters poly I:C-induced cytokine expression in mice by a mechanism that is not dependent on corticosterone. Life Sci., 72 (16), 1825–1839. Rameshwar, P. (1997). Substance P: a regulatory neuropeptide for hematopoiesis and immune functions. Clin. Immunol. Immunopathol., 85 (2), 129–133. Romano, M., and Claria, J. (2003). Cyclooxygenase-2 and 5lipoxygenase converging functions on cell proliferation and tumor angiogenesis: implications for cancer therapy. FASEB J., 17 (14), 1986–1995. Romero, L. M., Raley-Susman, K. M., Redish, D. M., Brooke, S. M., Horner, H. C., and Sapolsky, R. M. (1992). Possible mechanism by which stress accelerates growth of virally derived tumors. Proc. Natl. Acad. Sci. U.S.A., 89 (22), 11084–11087. Rosenberg, S. A. (2001). Progress in human tumour immunology and immunotherapy. Nature, 411 (6835), 380–384. Sacerdote, P., Bianchi, M., Gaspani, L., Manfredi, B., Maucione, A., Terno, G., Ammatuna, M., and Panerai, A. E. (2000). The effects of tramadol and morphine on immune responses and pain after surgery in cancer patients. Anesth. Analg., 90 (6), 1411–1414. Saurer, T. B., Carrigan, K. A., Ijames, S. G., and Lysle, D. T. (2004). Morphine-induced alterations of immune status are blocked by the dopamine D2-like receptor agonist 7-OH-DPAT. J. Neuroimmunol., 148 (1–2), 54–62. Schaffer, M., Beiter, T., Becker, H. D., and Hunt, T. K. (1998). Neuropeptides: mediators of inflammation and tissue repair? Arch. Surg., 133 (10), 1107–1116. Schirrmacher, V. (1985). Cancer metastasis: experimental approaches, theoretical concepts, and impacts for treatment strategies. Adv. Cancer Res., 43, 1–73. Schlagenhauff, B., Ellwanger, U., Breuninger, H., Stroebel, W., Rassner, G., and Garbe, C. (2000). Prognostic impact of the type of anaesthesia used during the excision of primary cutaneous melanoma. Melanoma Res., 10 (2), 165–169. Shakhar, G., Abudarham, N., Melamed, R., Schwartz, Y., Rosenne, E., and Ben-Eliyahu, S. (2003). Protecting pulmonary NK activity from suppression by surgery: an approach to reduce postopera-
tive metastasis. Annual Meeting of the Psychoneuro-immunology Research Society. Shakhar, G., and Ben-Eliyahu, S. (1998). In vivo beta-adrenergic stimulation suppresses natural killer activity and compromises resistance to tumor metastasis in rats. Journal of Immunology, 160 (7), 3251–3258. Shakhar, G., and Ben-Eliyahu, S. (2003). Potential prophylactic measures against postoperative immunosuppression: could they reduce recurrence rates in oncological patients? Ann. Surg. Oncol., 10 (8), 972–992. Shavit, Y., Beilin, B., Zaidel, A., Smirnov, G., and Bessler, H. (2001). Effects of preemptive analgesia on immune response in the postoperative period (abstract). Brain Behav. Immun., 15 (2), 127. Shavit, Y., Ben-Eliyahu, S., Zeidel, A., and Beilin, B. (2004). Effects of fentanyl on natural killer cell activity and on resistance to tumor metastasis in rats. Dose and timing study. Neuroimmunomodulation, 11 (4), 255–260. Sheridan, J. F., Dobbs, C., Brown, D., and Zwilling, B. (1994). Psychoneuroimmunology: stress effects on pathogenesis and immunity during infection. Clinical Microbiology Reviews, 7 (2), 200–212. Sietses, C. (1999). Immunological consequences of laparoscopic surgery, speculations on the cause and clinical implications. Langenbecks Archives of Surgery, 384 (3), 250–258. Smyth, M. J., Crowe, N. Y., Hayakawa, Y., Takeda, K., Yagita, H., and Godfrey, D. I. (2002). NKT cells—conductors of tumor immunity? Curr. Opin. Immunol., 14 (2), 165–171. Smyth, M. J., Godfrey, D. I., and Trapani, J. A. (2001). A fresh look at tumor immunosurveillance and immunotherapy. Nat. Immunol., 2 (4), 293–299. Soloski, M. J. (2001). Recognition of tumor cells by the innate immune system. Curr. Opin. Immunol., 13 (2), 154–162. Stefanski, V., and Ben-Eliyahu, S. (1996). Social confrontation and tumor metastasis in rats: defeat and beta-adrenergic mechanisms. Physiol. Behav., 60 (1), 277–282. Stefanski, V., and Engler, H. (1998). Effects of acute and chronic social stress on blood cellular immunity in rats. Physiol. Behav., 64 (5), 733–741. Sugi, K., Kaneda, Y., and Esato, K. (2000). Video-assisted thoracoscopic lobectomy achieves a satisfactory long-term prognosis in patients with clinical stage IA lung cancer. World J. Surg., 24 (1), 27–30; discussion, 30–31. Targarona, E. M., Balague, C., Knook, M. M., and Trias, M. (2000). Laparoscopic surgery and surgical infection. Br. J. Surg., 87 (5), 536–544. Tashiro, T., Yamamori, H., Takagi, K., Morishima, Y., and Nakajima, N. (1996). Effect of severity of stress on whole-body protein kinetics in surgical patients receiving parenteral nutrition. Nutrition, 12 (11–12), 763–765. Toes, R. E., Ossendorp, F., Offringa, R., and Melief, C. J. (1999). CD4 T cells and their role in antitumor immune responses. J. Exp. Med., 189 (5), 753–756. Torgersen, K. M., Vaage, J. T., Levy, F. O., Hansson, V., Rolstad, B., and Tasken, K. (1997). Selective activation of cAMP-dependent protein kinase type I inhibits rat natural killer cell cytotoxicity. J. Biol. Chem., 272 (9), 5495–5500. Turnbull, A. V., and Rivier, C. L. (1999). Regulation of the hypothalamic-pituitary-adrenal axis by cytokines: actions and mechanisms of action. Physiol. Rev., 79 (1), 1–71. Uchida, A., Kariya, Y., Okamoto, N., Sugie, K., Fujimoto, T., and Yagita, M. (1990). Prediction of postoperative clinical course by autologous tumor-killing activity in lung cancer patients. J. Natl. Cancer Inst., 82 (21), 1697–1701.
12. Neuroendocrine Regulation of Cancer Progression Vamvakas, E. C., and Blajchman, M. A. (2001). Deleterious clinical effects of transfusion-associated immunomodulation: fact or fiction? Blood, 97 (5), 1180–1195. Vitoratos, N., Hassiakos, D., Louridas, C., Limuris, G., and Zourlas, P. A. (1996). Prostaglandin F1a and prostaglandin E2 plasma levels after transvaginal cervical cerclage. Clin. Exp. Obstet. Gynecol., 23 (1), 21–25. Wang, D., and Dubois, R. N. (2004). Cyclooxygenase-2: a potential target in breast cancer. Semin. Oncol., 31 (1 Suppl 3), 64–73. Ward, J. M., and Reynolds, C. W. (1983). Large granular lymphocyte leukemia. A heterogeneous lymphocytic leukemia in F344 rats. American Journal of Pathology, 111 (1), 1–10. Whalen, M. M., and Bankhurst, A. D. (1990). Effects of betaadrenergic receptor activation, cholera toxin and forskolin on human natural killer cell function. Biochemical Journal, 272 (2), 327–331. Woiciechowsky, C., Asadullah, K., Nestler, D., Eberhardt, B., Platzer, C., Schoning, B., Glockner, F., Lanksch, W. R., Volk, H. D., and Docke, W. D. (1998). Sympathetic activation triggers systemic
265
interleukin-10 release in immunodepression induced by brain injury. Nat. Med., 4 (7), 808–813. Woiciechowsky, C., Schoning, B., Lanksch, W. R., Volk, H. D., and Docke, W. D. (1999). Mechanisms of brain-mediated systemic anti-inflammatory syndrome causing immunodepression. J. Mol. Med., 77 (11), 769–780. Yakar, I., Melamed, R., Shakhar, G., Shakhar, K., Rosenne, E., Abudarham, N., Page, G. G., and Ben-Eliyahu, S. (2003). Prostaglandin e(2) suppresses NK activity in vivo and promotes postoperative tumor metastasis in rats. Ann. Surg. Oncol., 10 (4), 469–479. Yamaguchi, K., Takagi, Y., Aoki, S., Futamura, M., and Saji, S. (2000). Significant detection of circulating cancer cells in the blood by reverse transcriptase-polymerase chain reaction during colorectal cancer resection. Ann. Surg., 232 (1), 58–65. Yirmiya, R., Pollak, Y., Morag, M., Reichenberg, A., Barak, O., Avitsur, R., Shavit, Y., Ovadia, H., Weidenfeld, J., Morag, A., Newman, M. E., and Pollmacher, T. (2000). Illness, cytokines, and depression. Ann. N. Y. Acad. Sci., 917, 478–487.
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II IMMUNE SYSTEM EFFECTS ON NEURAL AND ENDOCRINE PROCESSES AND BEHAVIOR ROBERT DANTZER
CYTOKINES IN THE BRAIN: AN INTRODUCTION Pro-inflammatory cytokines are soluble mediators that are produced by activated innate immune cells to serve cell-to-cell communication within the immune system. These same proteins are also messengers between immune and non-immune cells so as to enable development of an inflammatory response. The main pro-inflammatory cytokines are interleukin-1 (IL-1), tumor necrosis factor-alpha (TNF-α), and IL-6. Shortly after their characterization in the innate immune system, pro-inflammatory cytokines have been found to be expressed in the central nervous system either constitutively or in an inducible manner, e.g., in response to injury or peripheral immune stimulation. The study of the production and action of cytokines in the brain has become a hot topic in psychoneuroimmunology due to the diversity of functions that are mediated by these molecules. During the course of an infection, brain pro-inflammatory cytokines relay the action of peripherally produced pro-inflammatory cytokines on neuroendocrine, metabolic, and behavioral endpoints. For instance, the febrile response that is the main feature of the organism’s response to invading pathogens is mediated by prostaglandindependent action of brain pro-inflammatory cytokines on thermoregulatory neurons located in the anterior part of the pre-optic area of the hypothalamus. Brain proinflammatory cytokines are also produced in pathological circumstances in the injured brain. Normally, the production and action of pro-inflammatory cytokines in the brain are tightly regulated by a wide variety of endogenous molecules termed cryogens. These mediators include anti-inflammatory cytokines such as IL-10, hormonal factors such as glucocorticoids and insulin-like growth factor I, and neuropeptides such as vasopressin and α-melanotropin. When pro-inflammatory cytokines are produced in excess or over a long period of time and endogenous cryogens are deficient, functional and structural
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alterations in cell targets of brain cytokines can develop and give rise to alterations in affect and cognition that culminate in mood and cognitive disorders. The eight chapters that are part of this section aim at reviewing the most recent developments in this new field at the interface between neurosciences and immunology. They specifically discuss the pathophysiological implications of the expression and action of cytokines in the central nervous system. In Chapter 13, Robert Dantzer provides an overview of the mechanisms that mediate the production and action of pro-inflammatory cytokines in the brain and discusses how these cytokines are involved in a variety of brain disorders. He starts with a presentation of the key elements of the brain cytokine system before discussing what is currently known concerning the mechanisms of action of cytokines in the brain. He then summarizes the evidence in favor of the involvement of cytokines in brain development and synaptic plasticity, and the role of these molecules in neuropathology and psychopathology. One of the clearest results of the action of cytokines in the brain is the development of sickness behavior. A sick individual displays decreased motor activity, reduced food and water intake, social withdrawal, and disinterest in the external environment. These changes, when prolonged, can be associated with alterations in mood and cognition. In human beings, these behavioral alterations are accompanied by subjective feelings of malaise and distress. Sick patients also express subjective health complaints including fatigue, reduced appetite, sleep disorders, and depressed mood. In Chapter 14, “Cytokines, Sickness Behavior, and Depression,” Dantzer et al. review the current evidence in favor of the organized character of this response of the host to infection and its relation to other motivational systems. These authors present at different levels of description (from the organism to the molecular level) the mechanisms that underlie the behavioral effects of cytokines, including the modalities of immune-to-brain communication, the receptor mechanisms of the sickness-inducing effects of cytokines and the way cytokine-induced sickness behavior can culminate in major depressive disorders in vulnerable individuals. In this last section, Dantzer et al. show that the mechanisms of cytokine-induced depression can be studied in a translational manner by going from the bench to the bedside and vice versa. Whether the actions of cytokines on brain functions are direct or mediated via the synthesis of intermediate molecules such as prostaglandins has long been difficult to determine, because of the relative non-specificity of the tools available for these studies. To address this problem, Michael Lazarus and Clifford B. Saper, in Chapter 15, describe the use of a combination of neuroanatomical approaches and micropharmacological administration of very specific agonists and antagonists of the different subtypes of prostaglandin receptors (EP1–4) that are expressed in the brain. They propose a fever model in which EP1 and EP4 receptors in the pre-optic area promote thermogenesis, whereas EP4 receptors promote hypothermia. At the level of the paraventricular nucleus of the hypothalamus, EP1 and EP3 appear to be required for synergistic activation of the hypothalamo-pituitary-adrenal response to peripheral immune stimulation. The role of the same receptors in the modulation of pain and sleep-wake cycles is also discussed.
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The regulatory actions of pro-inflammatory cytokines in memory processes and neural plasticity are developed by Inbal Goshen and Raz Yirmiya, in Chapter 16. They present a dual model in which cytokines that are expressed constitutively in the brain, probably in the neuronal compartment, are necessary for the formation of hippocampal-dependent memory, whereas cytokines that are induced in the glial compartment of the brain in response to peripheral immune stimulation impair memory. Of course, the demonstration of the involvement of cytokines in learning and memory in an inverted U manner gives rise to another important question: What is the place of these immune mediators in the myriad of factors that have already been found to modulate learning and memory? Although this point is not addressed in Goshen and Yirmiya’s chapter, it is tempting to propose that many of the observed effects of cytokines could be indirectly caused via the regulation of brain temperature and metabolism. Aging is well known to be associated with an increased risk for alterations in cognition. Since the many physiological changes that develop during aging include a lowgrade inflammatory status, Rodney W. Johnson and Jonathan P. Godbout propose in Chapter 17 that inflammatory mediators might actually mediate the age-associated impairment in cognition. They demonstrate that while brain microglial cells are normally quiescent, they become activated or “primed” in aged individuals, therefore contributing to neuroinflammation in the brain of otherwise healthy animals. These primed microglial cells are hyper-responsive to a secondary stimulus from the peripheral innate immune system and can produce an exaggerated pro-inflammatory cytokine response that translates functionally in an increased sickness behavior. The same mechanisms probably account for the exacerbation of cognitive disorders and neurodegenerative processes that develop in elderly patients during episodes of peripheral infections. The emphasis in previous chapters on the role of pro-inflammatory cytokines in sickness behavior, learning and memory, and fever should not be detrimental to their well-recognized role in the modulation of pain. Pain is one of the four cardinal signs of inflammation and, as detailed extensively by Linda R. Watkins and her colleagues in Chapter 18, pain is powerfully amplified by activation of peripheral immune cells associated with peripheral nerves and by the activation of immune-like glial cells (microglia and astrocytes) within the central nervous system. After reviewing the basics of pain and pain modulation, Watkins et al. focus on chronic pain, which is poorly, if at all, controlled by currently available drugs. They propose that such pain arises as a consequence of immune and glial activation and discuss the very recent finding that glia and their pro-inflammatory cytokine products also oppose the effects of painrelieving drugs like morphine. All these findings provide new and important molecular and cellular targets for clinical pain control. Building on the repeated observation of increased expression of pro-inflammatory cytokines that is associated with brain injury, Barry McColl and colleagues make the point in Chapter 19 that besides the role of these mediators and especially IL-1 in acute damage during brain injury, there is growing evidence in favor of the involvement of
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cytokines in the post-acute phase. This effect most notably occurs in the resolution of acute inflammation and the impact on brain tissue repair and long-term functional recovery. Involvement of cytokines in chronic neurodegenerative disorders is also an area of expanding investigation in light of the discovery of cytokine gene polymorphisms which confer increased risk of developing Alzheimer’s disease. In Chapter 20, the final chapter of this series, Leigh M. Felton and V. Hugh Perry return to the issue of neuroinflammation that is implicit in all the previous chapters. They describe the biological mechanisms underlying central cytokine expression, discuss their physiological relevance in the context of systemic inflammation, and contemplate the recent evidence demonstrating that pro-inflammatory cytokines can exacerbate neuronal death and inflammation in rodent models of CNS disease. Felton and Perry also describe the bi-directional nature of communication between the CNS and peripheral immune system, placing particular emphasis on the acute phase response to brain injury, and the complex role of the liver. The range of immune mediators they consider encompass a number of pro- and anti-inflammatory cytokines, chemokines, and lipophilic mediators of inflammation. They show how the expression of these mediators may exacerbate tissue injury in acute brain injury, multiple sclerosis (MS), and chronic neurodegenerative disease (prion diseases, Alzheimer’s disease). They also describe the impact of repeated systemic infection on the immunological status of the mammalian central nervous system and summarize evidence demonstrating that priming of microglia and other glia by prolonged or repeated exposure to proinflammatory mediators can impact on the progression, severity, and clinical expression of subsequent CNS disease. Even a cursory reading of the chapters in this series on cytokines in the brain will show that this new information creates pioneering insights on a wide variety of clinical conditions affecting brain function and structure, which certainly accounts for the rapid progression of knowledge in this area at the interface between immunology and neurosciences. The elucidation of mechanisms of immune-to-brain communication has become relevant not only for neurology and psychiatry, but also for somatic diseases with an inflammatory component, including cancer, coronary heart disease, and obesity. In the case of these important systemic diseases, the question that is now crucial is whether the non-specific subjective health complaints of patients that have somewhat been neglected by physicians to the profit of the specific signs of the disease are not just another manifestation of their inflammatory status when it invades the brain. This would explain the comorbid nature of many of these symptoms, including fatigue and depression, and the fact that they are often associated with poor prognosis of the underlying pathological process.
C H A P T E R
13 Expression and Action of Cytokines in the Brain: Mechanisms and Pathophysiological Implications ROBERT DANTZER
The brain represents an important target organ for cytokines since it controls fever, another essential component of the host response to infection. Since cytokines are geared to act locally, they do not travel all the way from the injured body site to the brain. The brain actually reconstitutes a cellular and molecular image of the peripheral inflammation, using its own cellular machinery in the form of macrophage-like cells and microglia. The cytokines that are synthesized and released by these brain cells mirror the cytokine response at the periphery and mediate not only the brain response to immune and non-immune injury, but also the central component of the acute phase reaction. However, this is not their only role. In the brain, like at the periphery, cytokines are two-edged swords that in acute situations, or at low levels of expression, help to deal with the injury and ultimately promote healing. When chronically produced at high levels, cytokines can promote cell death and seriously damage the tissue in which they are expressed. In the brain, this is at the origin of functional and structural alterations that culminate in astrogliosis and neuronal death. Until a few years ago, the study of the production and actions of cytokines in the brain was a very restricted scientific area. Since then, the field has literally exploded. The chapters that are part of the present Part aim at reviewing the most recent developments in this new field at the interface between neurosciences and immunology, and discussing the pathophysiological implications of the expression and action of cytokines in the central nervous system.
I. KEY ELEMENTS OF THE BRAIN CYTOKINE SYSTEM 272 II. MECHANISMS OF ACTION OF CYTOKINES IN THE BRAIN 273 III. ROLE OF CYTOKINES IN BRAIN DEVELOPMENT AND SYNAPTIC PLASTICITY 274 IV. ROLE OF CYTOKINES IN NEUROPATHOLOGY 275 V. ROLE OF CYTOKINES IN PSYCHOPATHOLOGY 277 VI. CONCLUSION 277
Inflammation is a defense response of the body against traumatic, infectious, or toxic injury. This response begins at the site of injury but has the potential of leading to a body-wide response. It first mobilizes mast cells and macrophages stationed in the affected tissues before very rapidly recruiting leukocytes from the blood. These cells respond in an innate manner to highly conserved molecules that are associated with pathogens, the so-called pathogen-associated molecular patterns, by releasing a wide variety of inflammatory mediators including histamine, eicosanoids, proteases, chemokines, and newly synthesized cytokines. The local inflammatory response is geared to kill the invading infectious agents at the expense of tissue damage, before switching to a mode that promotes tissue repair and epithelial closure (Nathan, 2002). Cytokines function as paracrine and autocrine communication molecules between immune cells and between immunocytes and other peripheral cells, such as fibroblasts and endothelial cells. They also act at a distance to coordinate the host response to infection. PSYCHONEUROIMMUNOLOGY, 4E VOLUME I
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I. KEY ELEMENTS OF THE BRAIN CYTOKINE SYSTEM Innate immune recognition relies on a limited number of receptors that recognize pathogenassociated molecular patterns and are called Toll-like receptors (TLRs). Stimulation of these receptors by microbial products and, in some cases, by endogenous danger signals coming, for instance, from cells dying from necrosis, in the form of heat shock proteins or from oxidative stress (Gallucci and Matzinger, 2001), leads to the activation of signaling pathways that result in the induction of anti-microbial genes and proinflammatory cytokines (Janeway and Medzhitov, 2002). TLR4s that recognize LPS together with CD14 are constitutively expressed in macrophage-like cells that are present in the circumventricular organs (CVOs), choroid plexus, and leptomeninges (Rivest, 2003). CVOs are devoid of a functional brain barrier and are therefore well suited for responding to signals from the internal milieu. In response to circulating LPS, activation of TLR4 in CVOs leads to the synthesis of pro-inflammatory cytokines that can subsequently invade the brain parenchyma and diffuse toward key brain areas involved in the control of behavior and neurovegetative functions (Konsman et al., 2002). The diffusion of this message into the brain is demonstrated by the rapid transcriptional activation of genes encoding TLR2 in the brain parenchyma (Rivest, 2003). This relatively slow pathway of immune-to-brain communication is complemented by a more rapid pathway involving the neural afferents originating from the site of the body in which the inflammation takes place (Konsman et al., 2002). Circulating cytokines can also get access to the brain via specific saturable transporters (Banks, 2005). The brain inflammatory response to an intraparenchymal injection of LPS is quite different from that of other tissues. In particular, polymorphonuclear cells are largely excluded, and monocytes are recruited only after a delay of several days (Perry and Andersson, 1992). Furthermore, while interleukin-1 (IL-1) administered at the periphery triggers the synthesis of tumor necrosis factor-alpha (TNF-α) and vice versa, this is not the case in the brain parenchyma since IL-1 triggers only its own synthesis but not that of TNF-α (Blond et al., 2002). TNF-α has no effect on its own synthesis, whereas LPS elicits the synthesis of both cytokines. A question that has been disputed for a long time is whether microglial cells that are resident macrophages in the brain parenchyma are formed exclusively locally, are derived from myeloid progenitor cells in the bone marrow, or are actively recruited to
the central nervous system. In a modernized version of the work carried out originally by Hickey and Kimura on the bone marrow origin of perivascular microglial cells (Hickey and Kimura, 1988), the use of lethally irradiated bone marrow chimeric mice, of which the innate immune system was reconstituted with bone marrow stem cells expressing green fluorescent protein, allowed settlement of this issue. These cells were found to immigrate into the brain parenchyma in many regions of the brain and differentiate there in true microglial cells (Kokovay and Cunningham, 2005; Simard and Rivest, 2004). The relative contribution of resident and immigrating cells to brain inflammation was studied by generating bone marrow chimeras using wild-type and TLR4 mutant mice that were unresponsive to LPS (Chakravarty and Herkenham, 2005). In response to systemic LPS, TLR4expressing cells of hematopoietic origin were able to release pro-inflammatory cytokines at the periphery. However, transcription of pro-inflammatory genes in the brain was reduced in duration. Brain-resident TLR4-expressing cells were necessary for the late inflammatory response to LPS. In the normal healthy brain, the macrophage population that includes the microglia and perivascular and meningeal macrophages is switched off. This process that is particularly important for microglia is dependent on several signals including OX2 (CD200), MyD-1 (CD172, a member of the family of signal regulatory phosphatase-binding proteins), and CD47, an integrinassociated protein that binds to the inhibitory receptor signal regulatory protein alpha (Alblas et al., 2005; Hoek et al., 2000). Since the macrophage population in the brain plays a key role in the transduction of immune signals from the periphery to the brain, it is clear that the state of activation of these macrophages influences the severity of this transduction process. There is accumulating evidence showing that in chronic neurodegenerative disorders the macrophages become activated, in the sense that their morphology and phenotype change relative to the resting state. This process and its consequences on the reactivity of the brain to episodes of systemic infection are extensively described in the chapter by Felton and Perry. This is important from the viewpoint of neuropathology since the course of many inflammatory diseases of the brain is well known to be modulated by systemic infections, although this aspect has usually been neglected by pathologists (Holmes et al., 2003; Sibley et al., 1985). A contrario, the enhanced response of the brain to systemic or local immune activation can be taken as evidence of low grade inflammation affecting the brain either directly, such as during chronic neurodegeneration, or indirectly, via the influence of peripheral
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inflammation on brain inflammation. Instances of such phenomena during aging are reported in the chapter by Johnson and Godbout, and during type I and II diabetes by Dantzer et al. in their chapter on cytokines, sickness behavior, and depression (Dantzer et al., 2006). A potent new tool for inhibiting microglial activation and therefore assessing the role of microglial activation in a given condition is the use of lipid-soluble semisynthetic tetracyclines like minocycline. This compound has been found to be neuroprotective in various animal models of central nervous system trauma and several neurodegenerative diseases (Stirling et al., 2005); to attenuate the production of pro-inflammatory cytokines and their consequences on nociception in the spinal cord (Ledeboer et al., 2005); and to reduce the severity of encephalitis, suppress viral load in the brain, and decrease the expression of neuroinflammatory markers in a simian immunodeficiency virus model of HIV (Zink et al., 2005). The microglia are not the only cell type that is involved in brain inflammation. Other glial cells including astrocytes, oligodendrocytes in the central nervous system, and Schwann cells in the peripheral nervous system are also important. These cell types are both the source and target of cytokines and other inflammatory mediators (Baumann et al., 1993; Dong and Benveniste, 2001). Endothelial cells of brain blood vessels play an essential role in inflammation since they respond to circulating cytokines by producing prostaglandin E2 that diffuses into the brain parenchyma and targets neuronal circuits involved in the control of thermoregulation of activity of the hypothalamic-pituitaryadrenal axis (Matsumura and Kobayashi, 2004). The presence of functional IL-1 receptors on brain endothelial cells, of which the activation induces the expression of COX-2, has been confirmed by immunohistochemistry (Konsman et al., 2004). The latest developments in this field are discussed in the chapter by Lazarus and Saper, with a particular emphasis on the subtypes of prostaglandin E2 receptors that mediate the effects of prostaglandins on neurons. Brain mast cells are often forgotten in the list of cell types that can be at the origin of significant amounts of pro-inflammatory cytokines in the brain (Cocchiara et al., 1998). This is unfortunate since mast cells contain high levels of pre-formed IL-1 and TNF-α that can be released upon degranulation (Moller et al., 1998). In one of the rare studies examining the contribution of mast cells to the production of pro-inflammatory cytokines, intraperitoneal LPS was found to lower visceral pain threshold (allodynia) through a mechanism involving mast cell degranulation and resulting in IL1β and TNF-α release (Coelho et al., 2000).
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An important aspect of the expression and action of cytokines in the brain is its temporal dimension. As illustrated in the chapter by Dantzer et al., the expression of cytokines in the brain in response to peripheral activation of the innate immune system is not an instantaneous phenomenon but a gradually developing one that involves several immune-to-brain communication pathways and various cellular and molecular cascades (Dantzer et al., 2006). This is also true when cytokines are expressed in the brain in the absence of peripheral immune signals. For instance, although IL-1β is rapidly synthesized in the rat brain by glial cells after the induction of seizures, its action is conditioned by the expression of type I IL-1 receptors. IL-1RI expression takes place first in hippocampal neurons before spreading to astrocytes localized in limbic and extra-limbic areas (Ravizza and Vezzani, 2006). Communication between the brain and the innate immune system does not flow only from the immune system to the brain, but also from the brain to the innate immune system, as elegantly demonstrated by Tracey (Pavlov and Tracey, 2005). The efferent branches of the vagus nerves originating from the dorsal motor nucleus of the vagus inhibits release of proinflammatory cytokines at the periphery via α7 nicotinic receptors located on peripheral innate immune cells. This communication pathway utilizes probably choline diffusing from the synaptic cleft rather than acetylcholine. Although the relevance of this pathway has mainly been studied in the context of sepsis, it could play a physiological role by being activated by dietary fat (Tracey, 2005).
II. MECHANISMS OF ACTION OF CYTOKINES IN THE BRAIN Fever had long been known to be elicited by endogenous pyrogens from leukocytic origin rather than from microbial products (Dinarello and Wolff, 1982). However, it took a long time to characterize which molecular factors elaborated by leukocytes were responsible for this response. In the mid 1980s, recombinant technology allowed to produce murine and human IL-1β in sufficient quantities for injection to naïve experimental animals (Dinarello et al., 1986; Tocco-Bradley et al., 1986). The demonstration of the pyrogenic effects of IL-1β was followed by that of the pituitary-adrenal activating effects of this cytokine (Besedovsky et al., 1986) and its ability to induce sickness (Tazi et al., 1988). Adriano Fontana and his colleagues in Switzerland were the first scientists to
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propose that IL-1β was produced in the brain in response to peripherally administered LPS as an intermediate step in fever induction (Fontana et al., 1984). They showed that brain extracts from LPS-injected mice stimulated thymocyte proliferation, induced the production of prostaglandin E2 by synovial cells, and caused fever when injected to LPS-naïve mice. They postulated that astrocytes were the cellular source of this bioactive IL-1β. However, this concept remained dormant until molecular biologists were able to use sufficiently sensitive techniques to demonstrate that LPS induces cytokines in the brain and that cytokine receptors are expressed in the brain. The exact mechanisms of the pyrogenic effects of IL-1 and other cytokines that share its action, including TNF-α and IL-6, have not yet been fully elucidated. In addition to endogenous pyrogens, fever can also be caused by direct activation of TLR receptors by circulating pathogen-associated molecular patterns. The final common pathway for these diverse triggering stimuli is claimed to be the generation of prostaglandin E2 (PGE2) intermediates via the induction of cyclooxygenase-2 and the activation of neuronal PGE2 receptors in the pre-optic area of the hypothalamus (Dinarello, 2004). There are, however, many variants to this mode of action. Cytokines could act directly on neurons of the pre-optic area of the hypothalamus. IL-1 receptors have been identified on hypothalamic neurons including vasopressinergic neurons of the paraventricular nucleus (Diana et al., 1999). However, electrophysiological recordings of vasopressinergic neurons showed that their response to IL-1 is mediated by prostaglandins rather than by a direct neuronal action of IL-1 (Ferri et al., 2005). In the same manner, hyperpolarization induced by IL-1 in the dorsal motor nucleus of the vagus was blocked by inhibition of prostaglandin synthesis (Mo et al., 1996). Several studies indicate that IL-6, rather than IL-1, is the cytokine that is responsible for fever in the brain. In particular, IL-1 did not induce a fever in IL-6 knock-out mice (Kagiwada et al., 2004). The role of prostaglandins in the pyrogenic effects of IL-6 is unclear. Prostaglandins have been proposed to mediate the synthesis of IL-6 in response to IL-1 (Kagiwada et al., 2004) or to be responsible for the effects of IL-6 on its neuronal targets (Li et al., 2003). In another system, the paraventricular nucleus of the hypothalamus, neuronal IL-6 receptors have been proposed to mediate the LPS-induced activation of the HPA axis in a prostaglandin-independent manner (Vallieres and Rivest, 1999). Prostaglandin-amplified thermosensitivity of neurons of anterior hypothalamus could still be another possibility for explaining
the fever response to cytokines (Tabarean et al., 2004). Whatever the ultimate mechanism(s), a role for prostaglandins assumes the presence of prostaglandin receptors on target cells of cytokines. The nature of the receptors that mediate the effects of prostaglandindependent responses to cytokines is extensively discussed in the chapter by Lazarus and Saper. Much progress has been achieved during the recent years on the intracellular signaling pathways that mediate the effects of pro-inflammatory cytokines on their target cells (Aggarwal, 2003; O’Neill et al., 2003; Shishodia and Aggarwal, 2002; Wajant, 2003). However, this knowledge has hardly been used for understanding the mechanisms of action of cytokines in the brain. In the case of IL-1, there is evidence that brain IL-1 receptors are identical to those characterized on peripheral immune and nonimmune cells and that, for the generation of sickness behavior, their activation at the blood-brain interface likely involves a nuclear factor-kappaB (NFκB) signaling pathway in contrast to mitogen-activated protein kinases (MAP-kinases) and especially Erk1/2 that mediate the neuronal effects of IL-1 (Nadjar et al., 2005a; Nadjar et al., 2005b; Parnet et al., 2002). The role of MAP kinases on the neuronal effects of IL-1 has mainly been studied in the model of IL-1– induced impairment of long-term potentiation (see section “Role of Cytokines in Neuropathology”). The induction of COX-2 by IL-1β in the brain vasculature is associated with NFκB activation, as demonstrated by co-localization experiments (Konsman et al., 2004; Nadjar et al., 2005c). Activation of NFκB is necessary for induction of COX-2 since antagonism of NFκB in vivo abrogates the synthesis of inducible COX-2 in brain endothelial cells without altering constitutive neuronal COX-2 (Nadjar et al., 2005c). The observation that IL-1 is still able to exacerbate ischemia-induced neuronal damage in the brain of mice deficient in the gene for the type I IL-1 receptor provides indirect evidence for the role of additional IL-1 receptors in the brain (Touzani et al., 2002), as presented in their chapter by McColl et al.
III. ROLE OF CYTOKINES IN BRAIN DEVELOPMENT AND SYNAPTIC PLASTICITY Besides their role in the elaboration of the central component of the acute phase response, cytokines are also involved in brain development and neuronal plasticity. Programmed neuronal cell death is an essential
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factor in the normal development of the brain, since excess neurons that do not form synaptic connections need to be eliminated early in life (Roth and D’Sa, 2001). This process appears to regulated by proinflammatory cytokines such as TNF-α (Bessis et al., 2005). Cytokines are expressed early in brain development and may serve specific roles during the migration of neurons to their targets and the establishment of synaptic connections, for instance, by regulating the expression of adhesion molecules. Cytokines can also regulate the fate of stem cells in neuronal and nonneuronal lineages. For instance, there is evidence that cytokines of the IL-6 family and bone morphogenetic proteins act in concert to promote astrocyte differentiation (Nakashima and Taga, 2002). Chemokines also play a role in the migration, differentiation, and proliferation of glial and neuronal cells (Bajetto et al., 2001). There is evidence, for instance, that the chemokine CXCL12 that binds to the CXCR4 is involved in migration of neural and oligodendrocyte progenitors in the developing brain (Lazarini et al., 2003). Plasticity in the central nervous system is often studied via the model of long-term potentiation (LTP). In this model of memory, a particular pattern of activation of incoming excitatory fibers, presented as mimicking the learning experience, induces long-lasting enhancement of the communication between the presynaptic and post-synaptic elements (representing the memory). As discussed in the chapter by Goshen and Yirmiya, there is evidence that cytokines modulate LTP, with divergent results according to the authors. In the case of IL-1 for instance, endogenous IL-1 has been shown to be necessary for the establishment of LTP (Schneider et al., 1998), whereas exogenous IL-1 impairs LTP (Murray and Lynch, 1998). A possible mechanism for the modulatory effects of IL-1 on LTP is the involvement of prostaglandins E2 in hippocampal synaptic plasticity. Prostaglandins E2 are synthesized in a COX-2–dependent manner in the post-synaptic dendritic spines and function as a retrograde messenger via pre-synaptic EP2 receptors (Sang et al., 2005). A likely explanation for the observation of divergent effects of IL-1 on LTP is the nature of the cellular compartment in which cytokines are expressed and active. Using NFκB as a ubiquitous signaling pathway for the effects of cytokines on their brain targets, Mattson proposed that the expression of this transcription factor in neurons is responsible for plasticity and survival, whereas its expression in glial cells (and probably endothelial cells of blood vessels) is necessary for inducing the production and release of pro-inflammatory cytokines, reactive oxygen molecules, and excitotoxins, contributing to neuronal degeneration (Mattson, 2005). This perspec-
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tive is reinforced by the dual cellular localization of cytokines. For instance, IL-1β is expressed constitutively in neurons and in an inducible manner in the glial compartment (Bartfai and Schultzberg, 1993). Another model of plasticity is represented by sensitization of nociceptive pathways in the dorsal horn of the spinal cord. Cytokines released by activated glial cells sensitize peripheral pain signaling sensory neurons, as presented by Watkins et al. in their chapter.
IV. ROLE OF CYTOKINES IN NEUROPATHOLOGY Cytokines can cause cell death by several processes including apoptosis, necrosis, and autophagy. Apoptosis is a form of programmed cell death that is usually initiated by a stimulus or by removal of a repressor agent and results in self-destruction of the cell. Necrosis, in contrast, is a form of cell death that is caused by injury and involves special enzymes that are released by lysosomes. Autophagy is a dynamic process that occurs in response to nutrient deprivation and involves the rearrangement of subcellular membranes to sequester cytoplasm and organelles for delivery to the lysosome or vacuole where the sequestered cargo is degraded and recycled (Klionsky and Emr, 2000). A role for autophagy in the response of brain cells to pro-inflammatory cytokines has not yet been investigated, despite the fact that the net result of the effect of pro-inflammatory cytokines on many cell types is to interfere with the growth signal transduction that is normally required to direct the utilization of exogenous nutrients to maintain cell functioning and viability, as proposed by Kelley et al., in this book. In a situation of apparent scarcity of nutrients, autophagy is essential for maintaining cell survival, and this process can sustain viability for several weeks. During this time, cells respond to growth factor re-addition by rapid restoration of their ability to take up and metabolize glucose and by subsequent recovery of their original size and proliferative potential (Lum et al., 2005). Rather than directly causing autophagy, proinflammatory cytokines such as IL-1β could actually precipitate this process. Pre-treatment with IL-1β was found to potentiate neuronal death caused by depriving of oxygen and glucose-mixed cortical cell cultures containing neurons and astrocytes (Fogal et al., 2005). AIDS and neurodegenerative disorders like Alzheimer’s or Parkinson’s disease represent the most widely studied group of disorders in which apoptosis has been implicated. For example, the programmed
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cell death of neurons, astrocytes, and endothelial cells that occur in the brain of patients infected with the human immunodeficiency virus has been imputed to neurotoxic substances, including pro-inflammatory cytokines, shed by infected glia and macrophages (Li et al., 2005). In the case of TNF-α, major steps in the cytotoxicity cascade induced by this cytokine include activation of phospholipases, generation of free radicals, and damage to nuclear DNA by endonucleases, leading ultimately to DNA fragmentation and cell death (Larrick and Wright, 1990). There is evidence in favor of an early role of neuroinflammation in the pathophysiology of Alzheimer’s disease (AD) (Benveniste et al., 2001; Eikelenboom et al., 2002; Minagar et al., 2002). The amyloid plaques in AD brains are co-localized with a broad variety of inflammation-related proteins (complement factors, acute-phase proteins, proinflammatory cytokines) and clusters of activated microglia. Amyloid beta (Aβ) deposits in AD brains appear to be closely associated with a locally induced, non-immune–mediated, chronic inflammatory response. Microglial activation precedes the process of neuropil destruction in AD. Increased neuronal COX2 expression also appears to be involved in the cellular changes that take place in pyramidal neurons early in AD. Epidemiological studies indicate that polymorphisms of certain cytokines and acute-phase proteins that are co-localized with amyloid-β plaques are genetic risk factors of AD. In the autosomaldominant inherited forms of AD, the primary factor is the increased production of amyloid-β1-42, resulting into fibrillar amyloid-β deposition that elicits a brain inflammatory response. This state of microglial activation in AD has important functional consequences since animal models show that when activated microglia are further activated by a subsequent systemic infection, this results in significantly raised levels of pro-inflammatory cytokines within the CNS, which may in turn potentiate neurodegeneration, as pointed out in the chapter by Felton and Perry. In particular, a prospective pilot study in AD subjects showed that cognitive function can be impaired for at least two months after the resolution of a systemic infection and that cognitive impairment is preceded by raised serum levels of interleukin 1beta (Holmes et al., 2003). These relations were not confounded by the presence of any subsequent systemic infection or by baseline cognitive scores. Although microglial activation is closely associated with neuronal death, this reaction is not always responsible for neuronal death. It can be protective. In an experimental situation in which microglial cells were repeatedly challenged with lipopolysaccharide or co-
cultured with healthy, apoptotic, or necrotic neuronal cells, microglial cells released immunoregulatory and neuroprotective agents (prostaglandin E[2], transforming growth factor-beta, and nerve growth factor), whereas the synthesis of pro-inflammatory molecules (tumor necrosis factor-alpha and nitric oxide) was inhibited (Minghetti et al., 2005). These findings indicate that signals that are relevant to chronic diseases lead to a progressive downregulation of proinflammatory microglial functions. However, as pointed out by Felton and Perry in their chapter using the example of prion disease, this does not mean that the microglia cannot be re-activated in situations of systemic or local inflammation and actually contribute to neuronal damage (Felton and Perry, 2006). The neurodegenerative effects of pro-inflammatory cytokines are most often indirect via the generation of radical oxygen species and peroxides. Another important mechanism is the potentiation of excitotoxicity. Cytokines can potentiate the effects of glutamate receptor antagonists and, reciprocally, excitotoxicity can lead to the production of pro-inflammatory cytokines. Furthermore, as illustrated in the chapter by McColl et al., cytokines can promote neuronal death at a distance from where they are produced (McColl et al., 2006). The effects of cytokines in the brain involve interactions between many different cellular and molecular events, of which the combination and outcome vary with time. Interactions between the tissue-type plasminogen activator (tPA), N-methyl-daspartate (NMDA) receptors, transforming growth factor-beta1 (TGFβ1), and the type-1 plasminogen activator inhibitor provide a good example of this complex process. The only approved therapy for stroke is early reperfusion by intravenous injection of the thrombolytic agent, tPA. This treatment improves neurological outcome in a great proportion of patients, provided it is performed within the recommended therapeutic time window. However, tPA has the paradoxical effect of enhancing the NMDA receptormediated signaling in neurons, which results in increased excitotoxicity (Benchenane et al., 2004). This effect is mediated by the formation of a direct complex of tPA with the amino acid terminal of the NR1 subunit of the NMDA receptor and the cleavage of this subunit at arginine 260. Transforming growth factor-beta1 is strongly upregulated in the central nervous system following ischemia-induced brain damage. This anti-inflammatory cytokine attenuates ischemia-induced neuronal death in vivo (Buisson et al., 2003). In vitro, TGF-beta1 protects neurons against excitotoxicity by inhibiting the tPApotentiated NMDA-induced neuronal death through a mechanism involving the upregulation of the type-1
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plasminogen activator inhibitor in astrocytes (Buisson et al., 2003).
V. ROLE OF CYTOKINES IN PSYCHOPATHOLOGY Besides their role in neuropathology, cytokines have also been implicated in psychopathology. The macrophage theory of depression proposes that major depressive disorders are actually the consequence of the brain effects of pro-inflammatory cytokines due to the activation of the innate immune system that prevails in depressed subjects (Leonard, 2001; Maes, 1999). This process would lead not only to functional changes in brain functions but also to structural alterations, in the form of death of hippocampal neurons. Neuronal death would be due to the neurotoxic effects of tryptophan derivatives produced as a consequence of the activation of the tryptophan-degrading enzyme indoleamine 2,3 dioxygenase (IDO) by immune stimuli (Wichers et al., 2005). Whatever the attractiveness of this hypothesis, it is unlikely that all instances of major depression are due to activation of the innate immune system. It is certainly more realistic to position this event as another precipitating factor for depression rather than a true causal factor (Capuron and Dantzer, 2003). Instances of the involvement of activation of the peripheral immune system in mood disorders are numerous and range from aging subjects in the general population to patients treated with cytokines for cancer or hepatitis C. As illustrated by Capuron et al. in their chapter, this last condition provides a unique opportunity to assess the clinical features of depressive symptoms associated with activation of the immune system and study the mechanisms that are involved in the relationship between cytokines and depression. In Chapter 14, Dantzer et al. describe the progression from sickness behavior to depression, the problems associated with modeling this condition in experimental animals and the possible mechanisms (Dantzer et al., 2006). It is important to point out that IDO activation by cytokines such as IFNγ and TNF-α is probably not sufficient to explain all the symptoms of depression that develop in response to cytokines, and that other mechanisms are at work, including alterations in dopaminergic and glutamatergic neurotransmission. Cytokines have been proposed to play a role not only in mood disorders but also in psychosis. In schizophrenia for instance, findings from clinical studies and postmortem neuropathology point to disturbances of the blood-brain barrier, presence of auto-antibodies or antibodies against various microbial pathogens, acute
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phase proteins, immunocompetent cells, and activation markers of immunocompetent cells that can be explained either by the infectious hypothesis or the autoimmune hypothesis. The epidemiological findings in favor of an increased risk of psychosis in children born from mothers exposed to influenza virus during early pregnancy have been recently confirmed by a group of American psychiatrists based on measure of influenza antibodies in a nested case-control study of a large birth cohort, born from 1959 through 1966, and followed up for psychiatric disorders 30 to 38 years later (Brown et al., 2004). Animal models confirm that exposure to infectious agents during the perinatal period leads to permanent changes in physiology and behavior that are associated with changes in synaptic regulatory genes (Beraki et al., 2005). Intranasal inoculation of influenza virus to pregnant mice at embryonic day 9.5 that corresponds to the time of neural tube closure produced behavioral and neuropathological alterations in the progeny that mimic those observed in autistic children (Fatemi et al., 2002; Shi et al., 2003). Microarray analysis shows that several genes associated with schizophrenia and autism are altered in the brain. These alterations are associated with the maternal immune response to pathogens since they can be reproduced by administration of double-stranded RNA or IL-6.
VI. CONCLUSION In conclusion, the discovery of cytokines and their receptors, the identification of the molecular mechanisms that mediate their effects, and the characterization of the genes of which they modulate the expression have put neuroinflammation at the front stage in neuroscience and biomedical research. The diversity of disciplines involved in this research (from molecular and cellular neuroscience to neuropathology and psychiatry) is a clear testimony in favor of the interdisciplinary nature of the research on cytokines in the brain. The increasing sophistication of techniques and use of post-genomic approaches will certainly accelerate the rate of acquisition of new knowledge in the field and its relevance to clinical preoccupations. In particular the ability to simultaneously quantify multiple cytokines in the biological fluids, tissues, and cell-culture supernatants thanks to the commercial availability of bead-based immunoassay technology will certainly help to clarify the complex interactions that take place within the cytokine network under different circumstances (Hulse et al., 2004).
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Acknowledgments Supported by INRA, CNRS, University of Bordeaux 2, and the National Institute of Health (MH 71349).
References Aggarwal, B. B. (2003). Signalling pathways of the TNF superfamily: a double-edged sword. Nat. Rev. Immunol., 3, 745–756. Alblas, J., Honing, H., de Lavalette, C. R., Brown, M. H., Dijkstra, C. D., and van den Berg, T. K. (2005). Signal regulatory protein alpha ligation induces macrophage nitric oxide production through JAK/STAT- and phosphatidylinositol 3-kinase/Rac1/ NAPDH oxidase/H2O2-dependent pathways. Mol. Cell. Biol., 25, 7181–7192. Bajetto, A., Bonavia, R., Barbero, S., Florio, T., and Schettini, G. (2001). Chemokines and their receptors in the central nervous system. Front. Neuroendocrinol., 22, 147–184. Banks, W. A. (2005). Blood-brain barrier transport of cytokines: a mechanism for neuropathology. Curr. Pharm. Des., 11, 973–984. Bartfai, T., and Schultzberg, M. (1993). Cytokines in neuronal cell types. Neurochem. Int., 22, 435–444. Baumann, N., Baron-Van Evercooren, A., Jacque, C., and Zalc, B. (1993). Glial biology and disorders. Curr. Opin. Neurol. Neurosurg., 6, 27–33. Benchenane, K., Lopez-Atalaya, J. P., Fernandez-Monreal, M., Touzani, O., and Vivien, D. (2004). Equivocal roles of tissue-type plasminogen activator in stroke-induced injury. Trends Neurosci., 27, 155–160. Benveniste, E. N., Nguyen, V. T., and O’Keefe, G. M. (2001). Immunological aspects of microglia: relevance to Alzheimer’s disease. Neurochem. Int., 39, 381–391. Beraki, S., Aronsson, F., Karlsson, H., Ogren, S. O., and Kristensson, K. (2005). Influenza A virus infection causes alterations in expression of synaptic regulatory genes combined with changes in cognitive and emotional behaviors in mice. Mol. Psychiatry, 10, 299–308. Besedovsky, H., del Rey, A., Sorkin, E., and Dinarello, C. A. (1986). Immunoregulatory feedback between interleukin-1 and glucocorticoid hormones. Science, 233, 652–654. Bessis, A., Bernard, D., and Triller, A. (2005). Tumor necrosis factoralpha and neuronal development. Neuroscientist, 11, 277–281. Blond, D., Campbell, S. J., Butchart, A. G., Perry, V. H., and Anthony, D. C. (2002). Differential induction of interleukin-1beta and tumour necrosis factor-alpha may account for specific patterns of leukocyte recruitment in the brain. Brain Res., 958, 89–99. Brown, A. S., Begg, M. D., Gravenstein, S., Schaefer, C. A., Wyatt, R. J., and Bresnahan, M., et al. (2004). Serologic evidence of prenatal influenza in the etiology of schizophrenia. Arch. Gen. Psychiatry, 61, 774–780. Buisson, A., Lesne, S., Docagne, F., Ali, C., Nicole, O., MacKenzie, E. T., and Vivien, D. (2003). Transforming growth factor-beta and ischemic brain injury. Cell. Mol. Neurobiol., 23, 539–550. Capuron, L., and Dantzer, R. (2003). Cytokines and depression: the need for a new paradigm. Brain Behav. Immun., 17 (Suppl 1), S119–124. Chakravarty, S., and Herkenham, M. (2005). Toll-like receptor 4 on nonhematopoietic cells sustains CNS inflammation during endotoxemia, independent of systemic cytokines. J. Neurosci., 25, 1788–1796. Cocchiara, R., Bongiovanni, A., Albeggiani, G., Azzolina, A., and Geraci, D. (1998). Evidence that brain mast cells can modulate neuroinflammatory responses by tumour necrosis factor-alpha production. Neuroreport, 9, 95–98.
Coelho, A. M., Fioramonti, J., and Bueno, L. (2000). Systemic lipopolysaccharide influences rectal sensitivity in rats: role of mast cells, cytokines, and vagus nerve. Am. J. Physiol. Gastrointest. Liver Physiol., 279, G781–790. Dantzer, R., Bluthe, R. M., Castanon, N., Kelley, K. W., Konsman, J. P., Laye, S., et al. (2006). Cytokines, sickness behavior, and depression. In R Ader (Ed.), Psychoneuroimmunology, 4th ed. San Diego: Elsevier. Diana, A., Van Dam, A. M., Winblad, B., and Schultzberg, M. (1999). Co-localization of interleukin-1 receptor type I and interleukin-1 receptor antagonist with vasopressin in magnocellular neurons of the paraventricular and supraoptic nuclei of the rat hypothalamus. Neuroscience, 89, 137–147. Dinarello, C. A. (2004). Infection, fever, and exogenous and endogenous pyrogens: some concepts have changed. J. Endotoxin Res., 10, 201–222. Dinarello, C. A., Cannon, J. G., Mier, J. W., Bernheim, H. A., LoPreste, G., Lynn, D. L., et al. (1986). Multiple biological activities of human recombinant interleukin 1. J. Clin. Invest., 77, 1734–1739. Dinarello, C. A., and Wolff, S. M. (1982). Molecular basis of fever in humans. Am. J. Med., 72, 799–819. Dong, Y., and Benveniste, E. N. (2001). Immune function of astrocytes. Glia, 36, 180–190. Eikelenboom, P., Bate, C., Van Gool, W. A., Hoozemans, J. J., Rozemuller, J. M., Veerhuis, R., and Williams, A. (2002). Neuroinflammation in Alzheimer’s disease and prion disease. Glia, 40, 232–239. Fatemi, S. H., Earle, J., Kanodia, R., Kist, D., Emamian, E. S., Patterson, P. H., et al. (2002). Prenatal viral infection leads to pyramidal cell atrophy and macrocephaly in adulthood: implications for genesis of autism and schizophrenia. Cell. Mol. Neurobiol., 22, 25–33. Felton, L. M., and Perry, V.H. (2006). The interaction between brain inflammation and systemic infection. In R Ader (Ed.), Psychoneuroimmunology, 4th ed. San Diego: Elsevier. Ferri, C. C., Yuill, E. A., and Ferguson, A. V. (2005). Interleukin-1beta depolarizes magnocellular neurons in the paraventricular nucleus of the hypothalamus through prostaglandin-mediated activation of a non-selective cationic conductance. Regul. Pept., 129, 63–71. Fogal, B., Hewett, J. A., and Hewett, S. J. (2005). Interleukin-1beta potentiates neuronal injury in a variety of injury models involving energy deprivation. J. Neuroimmunol., 161, 93–100. Fontana, A., Weber, E., and Dayer, J. M. (1984). Synthesis of interleukin 1/endogenous pyrogen in the brain of endotoxin-treated mice: a step in fever induction? J. Immunol., 133, 1696–1698. Gallucci, S., and Matzinger, P. (2001). Danger signals: SOS to the immune system. Curr. Opin. Immunol., 13, 114–119. Goshen, I., and Yirmiya, R. (2006). The role of pro-inflammatory cytokines in memory processes and neural plasticity. In R Ader (Ed.), Psychoneuroimmunology, 4th ed. San Diego: Elsevier. Hickey, W. F., and Kimura, H. (1988). Perivascular microglial cells of the CNS are bone marrow–derived and present antigen in vivo. Science, 239, 290–292. Hoek, R. M., Ruuls, S. R., Murphy, C. A., Wright, G. J., Goddard, R., Zurawski, S. M., et al. (2000). Down-regulation of the macrophage lineage through interaction with OX2 (CD200). Science, 290, 1768–1771. Holmes, C., El-Okl, M., Williams, A. L., Cunningham, C., Wilcockson, D., and Perry, V. H. (2003). Systemic infection, interleukin 1beta, and cognitive decline in Alzheimer’s disease. J. Neurol. Neurosurg. Psychiatry, 74, 788–789. Hulse, R. E., Kunkler, P. E., Fedynyshyn, J. P., and Kraig, R. P. (2004). Optimization of multiplexed bead-based cytokine immunoassays for rat serum and brain tissue. J. Neurosci. Methods, 136, 87–98.
13. Expression and Action of Cytokines in the Brain: Mechanisms and Pathophysiological Implications Janeway, C. A. Jr., and Medzhitov, R. (2002). Innate immune recognition. Annu. Rev. Immunol., 20, 197–216. Johnson, R. W., and Godbout, J. P. (2006). Aging, neuroinflammation, and behavior. In R Ader (Ed.), Psychoneuroimmunology, 4th ed. San Diego: Elsevier. Kagiwada, K., Chida, D., Sakatani, T., Asano, M., Nambu, A., Kakuta, S., and Iwakura, Y. (2004). Interleukin (IL)-6, but not IL1, induction in the brain downstream of cyclooxygenase-2 is essential for the induction of febrile response against peripheral IL-1alpha. Endocrinology, 145, 5044–5048. Klionsky, D. J., and Emr, S. D. (2000). Autophagy as a regulated pathway of cellular degradation. Science, 290, 1717–1721. Kokovay, E., and Cunningham, L. A. (2005). Bone marrow–derived microglia contribute to the neuroinflammatory response and express iNOS in the MPTP mouse model of Parkinson’s disease. Neurobiol. Dis., 19, 471–478. Konsman, J. P., Parnet, P., and Dantzer, R. (2002). Cytokine-induced sickness behaviour: mechanisms and implications. Trends Neurosci., 25, 154–159. Konsman, J. P., Vigues, S., Mackerlova, L., Bristow, A., and Blomqvist, A. (2004). Rat brain vascular distribution of interleukin-1 type-1 receptor immunoreactivity: relationship to patterns of inducible cyclooxygenase expression by peripheral inflammatory stimuli. J. Comp. Neurol., 472, 113–129. Larrick, J. W., and Wright, S. C. (1990). Cytotoxic mechanism of tumor necrosis factor-alpha. FASEB J., 4, 3215–3223. Lazarini, F., Tham, T. N., Casanova, P., Arenzana-Seisdedos, F., and Dubois-Dalcq, M. (2003). Role of the alpha-chemokine stromal cell-derived factor (SDF-1) in the developing and mature central nervous system. Glia, 42, 139–148. Lazarus, M., and Saper, C. B. (2006). The differential role of prostaglandin E2 receptors in the response to systemic immune challenge. In R Ader (Ed.), Psychoneuroimmunology, 4th ed. San Diego: Elsevier. Ledeboer, A., Sloane, E. M., Milligan, E. D., Frank, M. G., Mahony, J. H., Maier, S. F., and Watkins, L. R. (2005). Minocycline attenuates mechanical allodynia and proinflammatory cytokine expression in rat models of pain facilitation. Pain, 115, 71–83. Leonard, B. E. (2001). The immune system, depression and the action of antidepressants. Prog. Neuropsychopharmacol. Biol. Psychiatry, 25, 767–780. Li, S., Goorha, S., Ballou, L. R., and Blatteis, C. M. (2003). Intracerebroventricular interleukin-6, macrophage inflammatory protein1 beta and IL-18, pyrogenic and PGE(2)-mediated? Brain Res., 992, 76–84. Li, W., Galey, D., Mattson, M. P., and Nath, A. (2005). Molecular and cellular mechanisms of neuronal cell death in HIV dementia. Neurotox. Res., 8, 119–134. Lum, J. J., Bauer, D. E., Kong, M., Harris, M. H., Li, C., Lindsten, T., and Thompson, C. B. (2005). Growth factor regulation of autophagy and cell survival in the absence of apoptosis. Cell, 120, 237–248. Maes, M. (1999). Major depression and activation of the inflammatory response system. Adv. Exp. Med. Biol., 461, 25–46. Matsumura, K., and Kobayashi, S. (2004). Signaling the brain in inflammation: the role of endothelial cells. Front. Biosci., 9, 2819–2826. Mattson, M. P. (2005). NF-kappaB in the survival and plasticity of neurons. Neurochem. Res., 30, 883–893. McColl, B. W., Stock, C. J., and Rothwell, N. J. (2006). Cytokines and non-immune brain injury. In R Ader (Ed.), Psychoneuroimmunology, 4th ed. San Diego: Elsevier. Minagar, A., Shapshak, P., Fujimura, R., Ownby, R., Heyes, M., and Eisdorfer, C. (2002). The role of macrophage/microglia and astrocytes in the pathogenesis of three neurologic disorders: HIV-
279
associated dementia, Alzheimer disease, and multiple sclerosis. J. Neurol. Sci., 202, 13–23. Minghetti, L., Ajmone-Cat, M. A., De Berardinis, M. A., and De Simone, R. (2005). Microglial activation in chronic neurodegenerative diseases: roles of apoptotic neurons and chronic stimulation. Brain Res. Brain Res. Rev., 48, 251–256. Mo, Z. L., Katafuchi, T., and Hori, T. (1996). Effects of IL-1 beta on neuronal activities in the dorsal motor nucleus of the vagus in rat brain slices. Brain Res. Bull., 41, 249–255. Moller, A., Henz, B. M., Grutzkau, A., Lippert, U., Aragane, Y., Schwarz, T., and Kruger-Krasagakes, S. (1998). Comparative cytokine gene expression: regulation and release by human mast cells. Immunology, 93, 289–295. Murray, C. A., and Lynch, M. A. (1998). Evidence that increased hippocampal expression of the cytokine interleukin-1 beta is a common trigger for age- and stress-induced impairments in long-term potentiation. J. Neurosci., 18, 2974–2981. Nadjar, A., Bluthe, R. M., May, M. J., Dantzer, R., and Parnet, P. (2005a). Inactivation of the cerebral NFkappaB pathway inhibits interleukin-1beta-induced sickness behavior and c-Fos expression in various brain nuclei. Neuropsychopharmacology, 30, 1492–1499. Nadjar, A., Combe, C., Busquet, P., Dantzer, R., and Parnet, P. (2005b). Signaling pathways of interleukin-1 actions in the brain: anatomical distribution of phospho-ERK1/2 in the brain of rat treated systemically with interleukin-1beta. Neuroscience, 134, 921–932. Nadjar, A., Tridon, V., May, M. J., Ghosh, S., Dantzer, R., Amedee, T., and Parnet, P. (2005c). NFkappaB activates in vivo the synthesis of inducible COX-2 in the brain. J. Cereb. Blood Flow Metab., 25, 1047–1059. Nakashima, K., and Taga, T. (2002). Mechanisms underlying cytokine-mediated cell-fate regulation in the nervous system. Mol. Neurobiol., 25, 233–244. Nathan, C. (2002). Points of control in inflammation. Nature, 420, 846–852. O’Neill, L. A., Dunne, A., Edjeback, M., Gray, P., Jefferies, C., and Wietek, C. (2003). Mal and MyD88, adapter proteins involved in signal transduction by Toll-like receptors. J. Endotoxin. Res., 9, 55–59. Parnet, P., Kelley, K. W., Bluthe, R. M., and Dantzer, R. (2002). Expression and regulation of interleukin-1 receptors in the brain. Role in cytokines-induced sickness behavior. J. Neuroimmunol., 125, 5–14. Pavlov, V. A., and Tracey, K. J. (2005). The cholinergic antiinflammatory pathway. Brain Behav. Immun., 19, 493–499. Perry, V. H., and Andersson, P. B. (1992). The inflammatory response in the CNS. Neuropathol. Appl. Neurobiol., 18, 454–459. Ravizza, T., and Vezzani, A. (2006). Status epilepticus induces timedependent neuronal and astrocytic expression of interleukin-1 receptor type I in the rat limbic system. Neuroscience, 137, 301–308. Rivest, S. (2003). Molecular insights on the cerebral innate immune system. Brain Behav. Immun., 17, 13–19. Roth, K. A., and D’Sa, C. (2001). Apoptosis and brain development. Ment. Retard. Dev. Disabil. Res. Rev., 7, 261–266. Sang, N., Zhang, J., Marcheselli, V., Bazan, N. G., and Chen, C. (2005). Postsynaptically synthesized prostaglandin E2 (PGE2) modulates hippocampal synaptic transmission via a presynaptic PGE2 EP2 receptor. J. Neurosci., 25, 9858–9870. Schneider, H., Pitossi, F., Balschun, D., Wagner, A., del Rey, A., and Besedovsky, H. O. (1998). A neuromodulatory role of interleukin-1beta in the hippocampus. Proc. Natl. Acad. Sci. U.S.A., 95, 7778–7783. Shi, L., Fatemi, S. H., Sidwell, R. W., and Patterson, P. H. (2003). Maternal influenza infection causes marked behavioral and
280
II. Immune System Effects on Neural and Endocrine Processes and Behavior
pharmacological changes in the offspring. J. Neurosci., 23, 297–302. Shishodia, S., and Aggarwal, B. B. (2002). Nuclear factor-kappaB activation: a question of life or death. J. Biochem. Mol. Biol., 35, 28–40. Sibley, W. A., Bamford, C. R., and Clark, K. (1985). Clinical viral infections and multiple sclerosis. Lancet, 1, 1313–1315. Simard, A. R., and Rivest, S. (2004). Bone marrow stem cells have the ability to populate the entire central nervous system into fully differentiated parenchymal microglia. FASEB J., 18, 998–1000. Stirling, D. P., Koochesfahani, K. M., Steeves, J. D., and Tetzlaff, W. (2005). Minocycline as a neuroprotective agent. Neuroscientist, 11, 308–322. Tabarean, I. V., Behrens, M. M., Bartfai, T., and Korn, H. (2004). Prostaglandin E2-increased thermosensitivity of anterior hypothalamic neurons is associated with depressed inhibition. Proc. Natl. Acad. Sci. U.S.A., 101, 2590–2595. Tazi, A., Dantzer, R., Crestani, F., and Le Moal, M. (1988). Interleukin-1 induces conditioned taste aversion in rats: a possible explanation for its pituitary-adrenal stimulating activity. Brain Res., 473, 369–371. Tocco-Bradley, R., Moldawer, L. L., Jones, C. T., Gerson, B., Blackburn, G. L., and Bistrian, B. R. (1986). The biological activity in vivo of recombinant murine interleukin 1 in the rat. Proc. Soc. Exp. Biol. Med., 182, 263–271.
Touzani, O., Boutin, H., LeFeuvre, R., Parker, L., Miller, A., Luheshi, G., and Rothwell, N. (2002). Interleukin-1 influences ischemic brain damage in the mouse independently of the interleukin-1 type I receptor. J. Neurosci., 22, 38–43. Tracey, K. J. (2005). Fat meets the cholinergic antiinflammatory pathway. J. Exp. Med., 202, 1017–1021. Vallieres, L., and Rivest, S. (1999). Interleukin-6 is a needed proinflammatory cytokine in the prolonged neural activity and transcriptional activation of corticotropin-releasing factor during endotoxemia. Endocrinology, 140, 3890–3903. Wajant, H. (2003). Death receptors. Essays Biochem., 39, 53–71. Watkins, L. R., Wieseler-Frank, J., Hutchinson, M. R., Ledeboer, A., Spataro, L., Milligan, E. D., et al. (2006). Neuroimmune interactions and pain: the role of immune and glial cells. In R Ader (Ed.), Psychoneuroimmunology, 4th ed. San Diego: Elsevier. Wichers, M. C., Koek, G. H., Robaeys, G., Verkerk, R., Scharpe, S., and Maes, M. (2005). IDO and interferon-alpha–induced depressive symptoms: a shift in hypothesis from tryptophan depletion to neurotoxicity. Mol. Psychiatry, 10, 538–544. Zink, M. C., Uhrlaub, J., DeWitt, J., Voelker, T., Bullock, B., Mankowski, J., et al. (2005). Neuroprotective and anti-human immunodeficiency virus activity of minocycline. JAMA, 293, 2003–2011.
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14 Cytokines, Sickness Behavior, and Depression ROBERT DANTZER, ROSE-MARIE BLUTHÉ, NATHALIE CASTANON, KEITH W. KELLEY, JAN-PIETER KONSMAN, SOPHIE LAYE, JACQUES LESTAGE, AND PATRICIA PARNET
I. II. III. IV. V. VI. VII. VIII.
IX.
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XI. XII. XIII.
metabolism that is necessary for the fever response. At the subjective level, a sick person experiences malaise, fatigue and apathy, and sometimes mental confusion. Hyperalgesia, or enhanced sense of pain, is another important component of sickness (Watkins and Maier, 2000). The symptoms of sickness can be elicited in healthy subjects and experimental animals by systemic injection of the cytokine inducer lipopolysaccharide (LPS) or the pro-inflammatory cytokines that are released by activated monocytes and macrophages during the host response to infection (Dantzer and Kelley, 1989). Similar symptoms can be induced by direct administration of LPS or pro-inflammatory cytokines into the brain of experimental animals. During the last 15 years, the mechanisms of cytokine-induced sickness behavior have been the subject of intense research, carried out at several levels of analysis, from the molecular to the behavioral and clinical levels. The purpose of the present chapter is to review the results that have been obtained in this field. At the behavioral level, cytokine-induced sickness behavior has been demonstrated to be the expression of a central motivational state that reorganizes the organism’s priorities in order to cope with infectious microorganisms. At the organ level, this motivational aspect of sickness behavior is mediated by the action of endogenous signals of sickness that are represented by pro-inflammatory cytokines on neuronal networks integrating the subjective, behavioral, and physiological components of sickness. Cytokine receptors are present in the brain, and they are activated in most cases not by peripheral cytokines that enter the brain, but by cytokines that are produced locally in the brain in response to peripheral cytokines. At the cellular level,
INTRODUCTION 281 THE CYTOKINE NETWORK 282 BEHAVIORAL EFFECTS OF CYTOKINES 282 SICKNESS BEHAVIOR IS THE EXPRESSION OF A CENTRAL MOTIVATIONAL STATE 285 MODES OF ACTION OF CYTOKINES ON THE BRAIN 286 CELLULAR ORGANIZATION OF THE CYTOKINE NETWORK IN THE BRAIN 291 MECHANISMS OF ACTION OF CYTOKINES ON THEIR BRAIN TARGETS 293 SPECIFICITY OF THE INVOLVEMENT OF PERIPHERAL AND CENTRAL CYTOKINES IN DIFFERENT COMPONENTS OF SICKNESS BEHAVIOR 297 MOLECULAR FACTORS OPPOSING THE EXPRESSION AND ACTION OF PROINFLAMMATORY CYTOKINES IN THE BRAIN 298 MODULATION OF CYTOKINE-INDUCED SICKNESS BEHAVIOR BY DIETARY AND OTHER ENVIRONMENTAL FACTORS 303 SENSITIZATION OF THE BRAIN CYTOKINE SYSTEM 303 CYTOKINES, DEPRESSION, AND ANXIETY 304 CONCLUSION 309
I. INTRODUCTION Sickness is a common if not trivial experience that occurs during the course of an infectious process (Dantzer, 2001). At the behavioral level, sick individuals typically display depressed activity and little or no interest in the environment. Body care activities are usually absent, and food intake is profoundly depressed despite the increased PSYCHONEUROIMMUNOLOGY, 4E VOLUME I
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brain cytokines are produced by macrophage-like cells in the meninges and around the blood vessels and by microglial cells in the brain parenchyma. These locally produced cytokines act on other glial cells and ultimately on neurons. At the molecular level, the brain effects of cytokines are mediated by receptors that are similar to those characterized at the periphery. Sickness behavior is normally a reversible process. At the molecular level, this corresponds to the fact that the brain production and action of pro-inflammatory cytokines are downregulated by potent endogenous factors. These factors have been termed cryogens, to contrast them with pyrogens, and they include a wide variety of bioactive molecules, from glucocorticoids to anti-inflammatory cytokines. When the cytokine network remains activated over time, the non-specific symptoms of sickness can become chronic and culminate in mood and cognition disorders. Structural changes can also occur in the brain, in the form of astrogliosis, degeneration of oligodendrocytes that form the myelin sheath, and neuronal death.
II. THE CYTOKINE NETWORK The main pro-inflammatory cytokines that are responsible for the innate immune response to infectious agents are interleukin-1 (IL-1) alpha and beta, interleukin-6 (IL-6), and tumor necrosis factor-α (TNFα). At the periphery, these cytokines are synthesized and released by activated monocytes and macrophages in response to pathogen-associated molecular patterns, and they play a pivotal role in inflammation. A convenient way to induce expression of these cytokines in healthy subjects is to inject lipopolysaccharide (LPS), the active fragment of endotoxin from Gram negative bacteria. Like other pathogen-associated molecular patterns, LPS activates innate immune cells by binding to Toll-like receptors (TLR). Members of the TLR family recognize conserved microbial structures such as Gram negative bacterial LPS for TLR-4, lipoproteins and peptidoglycans for TLR-2, and viral-double stranded RNA for TLR-3. Binding of pathogenassociated molecular patterns to TLR activates a common signaling pathway of which the proximal part involves various adaptor proteins and the distal part activation of nuclear factor-kappa B (NFκB), as well as several mitogen-activated protein kinases (MAPKs) (Barton and Medzhitov, 2003). Although the biological actions of the various proinflammatory cytokines widely overlap, each cytokine also has its own specific properties. IL-1 can be considered as a prototypical pro-inflammatory cytokine (Dinarello, 1998). It exists in two molecular forms, IL-
1α and IL-1β, which are encoded by two different genes. Another member of the IL-1 family is the IL-1 receptor antagonist (IL-1ra). This last cytokine behaves as a pure endogenous antagonist of IL-1 receptors and blocks most biological effects of IL-1α and IL-1β in vitro and in vivo. IL-6 is mainly responsible for the synthesis of acute phase proteins by hepatocytes. This cytokine also plays a pivotal role in the induction of the fever response. TNF-α is a key factor in the pathogenesis of the septic shock syndrome. IL-1α and β bind to two types of receptors belonging to the superfamily of Toll-like and interleukin-1 receptors, the type I and the type II IL-1 receptors. Upon binding with IL-1, the type I IL-1 receptor forms a heterodimeric complex with the IL-1 receptor accessory protein (IL-1RAcP), which activates a cascade of adaptor proteins and kinases that ultimately transduce the signal to the cell nucleus via the activation of NFκB and MAP kinases. This results in the induction of several genes, including the genes for the inducible form of the nitric oxide synthase (iNOS) and the inducible form of cyclo-oxygenase (COX-2). In contrast, the type II IL-1 receptor does not transduce the signal and functions as a “decoy” receptor that binds the excess of IL-1 to downregulate its actions. IL-1ra behaves as an antagonist of IL-1 receptors by preventing the type I IL-1 receptor from associating with IL-1RAcP. Several anti-inflammatory cytokines downregulate the production and action of pro-inflammatory cytokines. They include IL-10, IL-4, IL-13, and transforming growth factor-beta (TGF-β), although many of these cytokines have activities on their own. Other endogenous factors that oppose the production and action of pro-inflammatory cytokines but do not belong sensu stricto to the cytokine network include glucocorticoids, neuropeptides such as vasopressin and alphamelanotropin, and growth factors such as insulin-like growth factor I (IGF-I).
III. BEHAVIORAL EFFECTS OF CYTOKINES Peripheral and central administration of IL-1α, IL-1β, and TNF-α to healthy laboratory animals induces fever (Kluger, 1991), activation of the hypothalamic-pituitaryadrenal axis (Besedovsky et al., 1986), and behavioral symptoms of sickness (Kent et al., 1992b). Depressed activity and apathy are commonly observed, together with decreases in food intake and the adoption of a curled posture. The two behavioral end points that have been mostly used to investigate the mechanisms of cytokine-induced sickness behavior are social exploration and food intake (Figure 1). In the first case, the effects of cytokines are assessed by measuring decreases
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FIGURE 1 Behavioral effects of recombinant IL-1β in rats. Rats were injected intraperitoneally with various doses of recombinant human IL-1β or physiological saline and tested at different times after the injection in a fixed ratio schedule of food reinforcement or in a test of social exploration. In the first case, rats had been previously trained to press an operant lever 10 times consecutively for a food reward (a 45 mg food pellet) and were maintained at 85% of their free feeding body weight for keeping them sufficiently motivated. They were tested for 5 minutes at different time intervals post treatment, and their performance, measured by the number of lever presses, was expressed as percent of response rate just before treatment. In the second case, rats were presented with a juvenile conspecific introduced into their home cage for 5 minutes. Different juveniles were presented on the different occasions of test. Social exploration was measured as the duration of time spent sniffing and following the juvenile. (From Kent et al., 1992b.)
in the duration of exploration of a conspecific juvenile that is temporarily introduced into the home cage of the animal under test. The presentation of this social stimulus normally elicits a full sequence of close following and olfactory investigation that is profoundly depressed in a time- and dose-dependent manner in mice and rats injected with LPS and IL-1 (Kent et al., 1992b). TNF-α is less potent than IL-1 to decrease social exploration, but the effects of IL-1 are potentiated by TNF-α (Bluthe et al., 1994a). Despite its potent pyrogenic effect, IL-6 has no behavioral effect on its own although it is able to potentiate the effects of IL-1 (Lenczowski et al., 1999). Changes in ingestive behavior that develop in sick animals can be measured by the disruption of food intake in animals provided with free food, or the decrease in operant responding in animals trained to press a lever or to poke their nose in a hole for a food reward (Kent et al., 1996; Plata-Salaman, 1995; Plata-Salaman et al., 1996). In both cases, LPS and re-
combinant pro-inflammatory cytokines have profound depressive effects on ingestive behavior whether injected peripherally or centrally. Anorexigenic cytokines include IL-1, IL-6, IL-8, TNF-α, and IFN-α. Based on computerized analysis of meal pattern, low doses of IL-1β were found to reduce meal size and meal duration, and decrease feeding rate. Higher doses of IL-1β also decreased meal frequency and prolonged intermeal intervals (Plata-Salaman and Turrin, 1999; Plata-Salaman, 1999). In contrast, IFN-α induced anorexia by reducing meal size and meal duration but had no effect on meal frequency. In rats trained to eat a meal from separate sources of proteins, fats, and carbohydrates, LPS and IL-1β decreased caloric intake, but increased the relative intake of carbohydrates while decreasing protein intake and keeping fat intake constant (Aubert et al., 1995). This pattern of macronutrient intake differs from what is observed in rats exposed to cold, which increase their caloric intake
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mainly by consuming more fat. This difference between cytokine-treated rats and cold-exposed rats is consistent with the metabolic consequences of the cytokine treatment. Cytokines impair lipid metabolism by decreasing lipoprotein lipase activity and lipolysis (Grunfeld and Feingold, 1996; Spurlock, 1997). They also increase glycogenolysis and glucose oxidation and utilization, and enhance protein breakdown and synthesis of acute phase proteins (Spurlock, 1997). In addition to their direct effects on food and water intake, pro-inflammatory cytokines can alter eating and drinking by inducing conditioned taste aversions. More specifically, if the taste of a new solution is associated with sickness induced by immune activation, subsequent presentation of the taste solution leads to its reduced intake. This occurs whether LPS, peptidoglycan, muramyl dipetide (Goehler et al., 1995), TNFα, or IL-1β are used as sickness-producing agents (Langhans et al., 1990; Mormede et al., 2004; Tazi et al., 1988). However, conditioned taste aversions in animals made sick by immune activation apparently differ from conditioned taste aversions in animals made sick by a toxin (Cross-Mellor et al., 2004). In the former case LPS-treated animals displayed only decreased appetitive taste reactions to the solution paired with sickness. In the second case animals treated with lithium chloride displayed both decreased appetitive and increased aversive taste reactions (Cross-Mellor et al., 2004). However, the possibility of a bias due to the use of an intra-oral perfusion of the taste solution in this experiment cannot be discarded since the amount of sucrose ingested in this way did not vary in LPS-treated rats in contrast to what was observed in lithium chloride– treated rats (Cross-Mellor et al., 2003). Sexual behavior is also disrupted by systemic administration of LPS and IL-1β, and this effect is more marked in female than in male rats (Avitsur et al., 1997a; Avitsur et al., 1997c; Avitsur and Yirmiya, 1999). All components of sexual behavior are affected, including sexual motivation, proceptive behavior (soliciting), receptivity, and attractivity. Although most of the work on the behavioral effects of cytokines has concentrated upon LPS and proinflammatory cytokines, a few studies have addressed the action of other immune stimuli. Bacterial T-cell antigens like staphylococcal enterotoxins A and B induce mainly IL-2, IFNγ, TNF, and IL-6 in a T-cell dependent manner. They activate the HPA axis and reduce food intake, possibly by inducing anxiety since their effect is mainly observed when mice are presented with new food or food in a new environmental context (Kusnecov and Goldfarb, 2005). This aspect is discussed further in “Cytokines, Depression, and Anxiety.” In contrast to LPS, of which the behavioral
effects appear to be mainly dependent on IL-1, the sickness-inducing effects of staphylococcal enterotoxin are mainly mediated by TNF-α (Rossi-George et al., 2005). It is important to note that decreased behavioral activities are not always observed in cytokine-treated animals. For instance, IL-2 and IL-6 can have behavioral-activating effects in mice, in the form of an increase in digging, rearing, exploration of a new object, and, for IL-6, locomotion and grooming (Zalcman et al., 1998). IL-2 was actually able to sensitize mice to behaviorally activating effects of a dopamine agonist (Zalcman, 2001). Conversely, IL-2 induced climbing in mice was blocked by dopaminergic receptor antagonists (Zalcman, 2002). Mice transgenic for a cytokine or the receptor of a cytokine have been used to assess the way cytokines affect brain function. Mice overexpressing pro-inflammatory cytokines in astrocytes or in neurons often develop severe neuropathological alterations (Campbell et al., 1998), which make the study of behavioral activities not very pertinent, except when focusing on early signs of disease progression. Mice in which the gene for a given pro-inflammatory cytokine or its receptors has been deleted by homologous recombination do not show any obvious behavioral alteration, which is in agreement with the redundancy characterizing the biological activity of these proteins. However, subtle behavioral alterations can sometimes be observed. For example, IL-6 knockout mice were found to display a higher degree of aggressive behavior and a lower frequency of affiliative interactions (Alleva et al., 1998). Although the results of behavioral observations in knockout mice are not easy to interpret due to the fact that the expressed phenotype varies according to the genetic background, the fact that in this study mice overexpressing IL-6 specifically in the central nervous system displayed more intense affiliative interactions than their wild-type counterparts was interpreted to suggest that IL-6 might be involved in the regulation of agonistic behavior. In a different experiment controlling for the effect of the genetic background, IL-6(−/−) mice were observed to be less emotional than wild-type mice in the holeboard and the elevated plus-maze, indicating that IL-6 could be involved in the control of emotionality (Armario et al., 1998). Mice overexpressing TNF-α in neurons of the central nervous system displayed alterations of exploration in the hole-board and black/white box, and increased grooming when exposed to highly unfamiliar environmental stimuli (Fiore et al., 1998).
14. Cytokines, Sickness Behavior, and Depression
IV. SICKNESS BEHAVIOR IS THE EXPRESSION OF A CENTRAL MOTIVATIONAL STATE Most of the symptoms of cytokine-induced sickness behavior resemble the expression of physical debilitation and general weakness (Figure 2). During an infection episode, sick individuals usually remain prostrated and engage in little physical activity. They do not care for their physical appearance and bodily condition and refrain from engaging in social interactions. There is accumulating evidence in favor of the adaptive nature of the phenotypic changes that occur in sick individuals. A typical example is provided by the changes in bill color that develop in male blackbirds during immune activation (Faivre et al., 2003). Male blackbirds normally display a black plumage with a yellow to orange bill that serves as a secondary sexual trait of health and vigor. The color of the bill is dependent on the availability of carotenoids, but these compounds are also important for immune defenses. During the course of an immune response, the allocation of carotenoids to immune functioning is detrimental to their role in sexual signaling, so that bill color fades off during immune activation (Faivre et al., 2003). In male zebra finches, manipulation of dietary carotenoids supply invoked parallel changes in cell-mediated immune function and sexual attractiveness (Blount et al., 2003). These results show that immune activation has a cost that impacts on phenotype. In mammals, Hart (Hart, 1988) has convincingly argued that sickness behavior supports the metabolic and physiological changes occurring in the infected organism and
FIGURE 2 Motivational aspects of sickness behavior. The behavioral signs of sickness that develop during an infectious episode can be seen as the result of physical debilitation and weakness (upper pathway) or the expression of a reorganization of the organism’s priorities in face of the immune challenge (lower pathway). The evidence collected during recent years supports this last interpretation.
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increases their efficiency. The increase in body temperature that is needed for mounting a fever leaves little room for expensive activities that are of no use in fighting the infectious pathogens. The reduced behavioral activities that occur in ill individuals would therefore be the expression of a highly organized strategy that is critical to the survival of the organism. A typical example of such a reorganization of behavioral activities is provided by the effect of IL-1 on agonistic behavior in mice. When confronted to an adult conspecific, mice typically engage in offensive behavioral patterns, and this phase of attack is followed by defensive behavior if they are likely to lose the fight. In contrast, IL-1–treated mice displayed no offensive behavioral elements, but still responded to the opponent’s attacks with defensive elements such as upright defensive posture, upright submissive posture, crouching, and fleeing (Cirulli et al., 1998). This reorganization of behavioral activities under the influence of pro-inflammatory cytokines is characteristic of what psychologists call motivational changes (Figure 2). A motivation can be defined as a central state which reorganizes perception and action (Bolles, 1970). In the case of fear, for instance, the individual confronted with a threat focuses his attention on all potential sources of danger, and at the same time, gets ready to engage in the most appropriate defensive behavioral pattern that is available in his behavioral repertoire. In other words, a motivational state does not trigger an unflexible behavioral pattern in response to an internal or external stimulus. Instead of this, motivation enables the subject to uncouple perception from action, and therefore to select the appropriate strategy in relation to the eliciting situation (Bolles, 1970). The first evidence that sickness behavior is the expression of a motivational state rather than the consequence of weakness was provided by Miller in an obscure review paper (Miller, 1964). While he was initially searching for endogenous signals of the thirst motivational system, Miller observed that endotoxin administration made rats stop bar pressing for water. However, this motivational effect was not specific of thirst since the same endotoxin treatment also reduced bar pressing for food and for intracranial selfstimulation in the lateral hypothalamus. This decrease in response rate was not generalized since rats placed in a rotating drum that they could stop for brief periods by pressing a lever increased their bar pressing rate in response to endotoxin instead of decreasing it. The mere fact that endotoxin treatment decreased or increased behavioral output depending on its consequences was for Miller a strong indication in favor of a motivational effect of this treatment (Miller, 1964).
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An important characteristic of a motivational state is that it competes with other motivational states for behavioral output. As a typical example, it is difficult if not impossible to search for food and at the same time court a sexual partner, as the behavioral patterns of foraging and courtship are not compatible with each other. The normal expression of behavior therefore requires a hierarchical structure of motivational states which is continuously updated according to variations in the external and internal milieux. When an infection occurs, the sick individual is at a life or death juncture, and he needs to adjust his physiology and behavior so as to overcome the disease. However, this is a relatively long-term process which must make room for more urgent needs when necessary. If a sick person lying in his bed hears a fire alarm ringing in his house and sees flames and smoke coming out of the basement, he must be able to momentarily overcome his sickness behavior to escape danger. Translated into motivational terms, this means that fear competes with sickness, and fear-motivated behavior takes precedence over sickness behavior. To show that sickness does not interfere with the subject’s ability to adjust his behavioral strategies with regard to his needs and capacities, Aubert and colleagues (Aubert et al., 1997b) assessed the effects of LPS on food hoarding and food consumption in rats that did or did not receive a food supplement in addition to normal amounts of daily food. Briefly, rats were trained to obtain food for 30 minutes in an apparatus consisting of a cage connected to an alley with free food at its end. In this apparatus, rats normally bring back to their home cage the food that is available at the end of the alley, and the amount of food they hoard is lower when they receive a food supplement than when they have no supplement. In response to LPS, food intake was decreased to the same extent whether rats received a food supplement or not. However, food hoarding was unaffected in LPS-injected rats that did not receive a food supplement compared to rats provided with the food supplement. These results are important because they indicate that the internal state of sickness induced by LPS is more effective in suppressing the immediate response to food than the anticipatory response to future needs. Another example of the motivational aspects of sickness behavior is provided by the effects of cytokines on maternal behavior (Figure 3). Rodent neonates are poikilothermic, and they need the thermoregulatory protection of a nest. Maternal behavior is therefore critical for survival of the progeny. In accordance with the motivational priority of maternal behavior, lactating mice that were made sick by an appropriate dose of LPS remained able to retrieve their
pups, which had been removed from the nest, but did not engage in nest building when tested at 22°C. However, when the dams and their litters were placed in cold temperatures (6°C) to increase the survival value of nest building, this last behavior was no longer impaired (Aubert et al., 1997a). Collectively, all these data support the view that sickness behavior is not simply the result of a debilitated state. Instead, sickness behavior represents a motivational state that is shaped by both the internal and external needs of the organism.
V. MODES OF ACTION OF CYTOKINES ON THE BRAIN The fact that sickness is a central motivational state implies that the endogenous signals of sickness act on the brain. However, cytokines are relatively large protein molecules, about 15 kDa for IL-1, and their hydrophilic nature does not allow them to easily cross the blood-brain barrier. It has therefore been proposed that cytokines, like many other centrally acting peptides, enter the brain at the sites at which the bloodbrain barrier is deficient. These privileged sites for communication with the internal milieu are known as the circumventricular organs, because of their anatomical location around the brain ventricles. Based on results of lesion and knife cut experiments, the organum vasculosum of the lamina terminalis (OVLT) has long been considered as the site of action of peripherally released cytokines (Blatteis, 1990). Bloodborne cytokines were initially assumed to diffuse into the brain side of the blood-brain barrier through fenestrated capillaries in these sites, and act on parenchymal astrocytes to induce the synthesis and release of prostaglandins of the E2 series. Prostaglandins would then freely diffuse to nearby target brain areas, such as the median pre-optic area of the hypothalamus in the case of fever. However, there are at least two problems with this proposed mechanism. First, most cytokines have a very limited range of diffusion, and are more tuned to act locally in an autocrine and paracrine manner than to act at distance in a hormonal manner. Second, fully functional cytokine receptors are expressed in the brain (see below), and they mediate the effects of endogenously produced or exogenously injected cytokines. For example, blockade of brain IL-1 receptors has been found to abrogate the effects of peripheral immune stimuli on behavior (Kent et al., 1992a), corticotropin-releasing hormone gene expression in the hypothalamus (Kakucska et al., 1993), and body temperature (Klir et al., 1994). The simplest interpretation for these findings is that
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FIGURE 3 Interactions between LPS-induced sickness behavior and maternal behavior in lactating mice. Schematic representation of the experimental design allowing to test the hypothesis of motivational properties of sickness behavior. If the behavioral alterations that develop in lactating mice are only due to changes in their internal state (the socalled medical hypothesis), their nature and intensity should be solely a function of the changes in internal state. If these behavioral alterations are the expression of a motivational state (the so-called motivational interpretation), their nature and intensity should be a joint function of the changes in internal state and the environmental contingencies. Lactating mice were injected with LPS at a sickness-producing dose (400 μg/kg IP) or apyrogenic saline. Their maternal behavior was assessed before and 2 hours after LPS by measuring their ability to build a nest after replacement of the original nest by surgical cotton and to retrieve their pups after pups had been removed from the nest and aligned along the wall on the opposite side from the nest. LPS-treated dams overcame their sickness to retrieve their pups but did not build a nest when tested at 24°C, whereas they built a functional nest in addition to engaging in pup retrieval when tested at 6°C. (From Aubert et al., 1997a.)
cytokines are actively transported into the brain, as proposed for other peptides. For example, insulin enters the brain by a receptor-mediated, saturable transport process across brain capillary endothelial cells (Baura et al., 1993; Wu et al., 1997). Pharmacokinetic data with radiolabeled cytokines have revealed the existence of specific saturable transport systems for a number of pro-inflammatory cytokines (Banks, 2005). In the case of insulin, the transporter is nothing else than the insulin receptor. However, the molecular identity of cytokine transporters is still unknown, and the efficacy of the transport system varies according to cytokines, brain regions, and physiological conditions. Although such a transporter has been shown to mediate learning impairment induced by an intravenous injection of IL-1α (Banks et al., 2001), it is important to note that the existence of a transport system alone is not sufficient to explain how peripheral
cytokines act on the brain. There is still the problem that in order to be transported, cytokines need to be present in the general blood circulation, or synthesized and released close to their transporter systems. Furthermore, a transport process is apparently not necessary for central effects of peripheral cytokines, since independent experiments have provided evidence for the existence of a brain compartment of cytokines that is inducible by peripheral cytokines (Gatti and Bartfai, 1993; Laye et al., 1994). Systemic administration of LPS induces the coordinated expression of IL-1β, TNF-α, IL-6, and IL-1ra in various brain structures at the mRNA and protein levels (Gatti and Bartfai, 1993; Laye et al., 1994) (Figure 4). The same effect is obtained when IL-1β is injected in place of LPS (Hansen et al., 1998), which is consistent with the concept that IL-1β induces its own synthesis and the synthesis of other cytokines in cascade.
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FIGURE 4 Systemic administration of LPS induces the expression of IL-1β and IL-1ra in the brain of mice. Mice were injected intraperitoneally with LPS (10 μg/mouse) and killed just before or at different times after injection. Total RNA was extracted from the hypothalamus and submitted to comparative RT-PCR to determine transcripts for IL-1β and IL-1ra, using beta2-microglobulin (β2mgl) as an internal standard. Levels of IL-1β were measured in the hypothalamus (pg/mg protein) and plasma (pg/ml) using a validated ELISA (mean of 5 different experiments). (From Laye et al., 1994.)
The same cascade of cytokines can be activated when LPS or pro-inflammatory cytokines are injected directly into the lateral ventricle of the brain (Plata-Salaman, 1999). In order to produce cytokines in a coordinated manner in response to peripheral cytokines, brain cells require a communication pathway for transmission of immune information from the periphery to the brain (Dantzer et al., 2000; Kent et al., 1992b). Neural afferents are good candidates for this role, since they already transmit two sensory components of inflammation, calor and dolor (heat and pain) (Kent et al., 1992b). When LPS or cytokines are injected into the abdominal cavity, an inflammatory response develops locally. The main neural pathway from the abdominal cavity to the brain is represented by the afferent branches of the vagus nerves. The role of vagus nerves in the transmission of the immune information from the periphery to the brain has first been demonstrated based on c-fos mapping experiments. The immediate early gene c-fos is differentially expressed in many regions of the central nervous system following various physiological challenges and can be used as a marker of neuronal activation. Intraperitoneal administration of LPS to rats induced the expression of c-Fos, the protein product of the c-fos gene, in the nucleus tractus solitarius that corresponds to the primary projection area of the vagus nerves, and in the parabrachial nuclei,
the paraventricular nucleus and the supraoptic nuclei of the hypothalamus, the central amygdala, and the bed nucleus of the stria terminalis that all correspond to secondary projection areas of the vagus nerves (Wan et al., 1994). The specificity of the relationship of this labeling to vagally mediated transmission was demonstrated by its disappearance following subdiaphragmatic section of the vagus nerves (Wan et al., 1994). Subdiaphragmatic vagotomy also blocked the depressing effects of LPS and IL-1β on social exploration and food intake in rats and mice (Figure 5) (Bluthe et al., 1994b; Bret-Dibat et al., 1995). Blockade of the effects of peripheral cytokines on the brain by vagotomy was not due to an impaired peripheral immune response since vagotomy had no effect on the LPS-induced increases in the levels of peripheral IL-1β measured in peritoneal macrophages or in the bloodstream (Bluthe et al., 1994b; Hansen et al., 2000b; Laye et al., 1995). The involvement of the vagus nerves in the behavioral effects of cytokines is restricted to cytokines that are released in the abdominal cavity and sensed by afferent vagal terminals since vagotomy did not block sickness behavior induced by subcutaneous and intravenous injections of IL-1β (Bluthe et al., 1996b), and had no effect on sickness behavior induced by central injection of IL-1β (Bluthe et al., 1996a). Based on these results, Romeo et al. proposed that immune stimuli from the posterior oral cavity are sensed by the central nervous system via glossopharyngeal afferents (Romeo et al., 2001; Romeo et al., 2003). In accordance with this hypothesis, they showed that bilateral transection of the glossopharyngeal nerves attenuated the febrile response elicited by injection of LPS or IL-1β into the soft palate of rats but had no effect when LPS and IL-1β were injected intraperitoneally. In the same manner, the febrile response caused by injection of a small dose of LPS into an artificial subcutaneous chamber in guinea pigs was blocked in part by injection of a local anesthetic into the subcutaneous chamber, indicating a participation of cutaneous afferent nerve signals in immune-to-brain communication (Roth and De Souza, 2001). According to the hypothesis of a neural immune-tobrain communication pathway, sectioning of vagal afferents should abrogate induction of brain cytokines in response to intraperitoneal administration of LPS and IL-1β. In accordance with this prediction, vagotomy abrogated LPS- and IL-1β–induced increases in IL-1β mRNA in the hypothalamus and hippocampus but not in the pituitary (Hansen et al., 1998; Laye et al., 1995). Results at the protein level are less clear since vagotomized rats continued to respond to intraperitoneal LPS by an increase in brain IL-1β that was identical to that observed in sham-operated rats (Hansen et al.,
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FIGURE 5 Vagotomy abrogates the depressing effects of systemic LPS on social exploration. The experiment was carried out on rats that had been submitted to subdiaphragmatic vagotomy or sham surgery 4 weeks before the test. Physiological saline (SAL) or LPS (1.25 mg/kg) was injected IP immediately after the first behavioral session that took place at time 0 (baseline), and the same animals were tested again with different juveniles 2, 4, and 6 hours later (n = 4 for each experimental group except LPS-treated sham animals for which n = 3). Each behavioral test lasted 4 minutes. (From Bluthe et al., 1994b.)
2000c). The same phenomenon was observed in rats injected with LPS in the soft palate, since the increase in IL-1β protein levels was the same in LPS-treated rats independently of the transection of the glossopharyngeal nerves (Romeo et al., 2003). One of the reasons for this discrepancy between mRNA and protein levels of IL-1β could be the important contribution of extraparenchymal IL-1β to the amount of IL-1β that is measured in the brain by ELISA, in the form of IL-1β derived from meningeal and perivascular macrophages or that transported across the blood-brain barrier. A potential problem with all the vagotomy experiments is that the vagotomy procedure eliminates vagal afferent as well as efferent fibers. Furthermore, the vagotomy surgical procedure often includes stripping the esophagus from all its nerves, which is likely to remove non-vagal, myenteric nerve fibers that are at the origin of the splanchnic visceral nerves. Although surgical transection of the celiac superior mesenteric complex failed to attenuate the hyperalgesic effects of LPS in contrast to section of the vagus nerves (Watkins et al., 1995), the effects of this surgical manipulation on the inhibitory effects of LPS and IL-1β on behavior have received little attention. In the only experiment that specifically addressed the
question of the role of vagal afferents in the behavioral effects of cytokines, selective vagal rootlet deafferentation of the left vagus nerve associated to subdiaphragmatic section of the right vagus nerve did not alter the suppressive effects of LPS and IL-1β on food intake in rats (Schwartz et al., 1997). Negative results were also obtained when vagal deafferentation was combined with celiac superior mesenteric ganglionectomy (Porter et al., 1998). However, in the absence of a positive control for the effects of conventional vagotomy on the action of LPS and IL-1β, these last results are difficult to interpret. Marvel et al. used another approach to assess the role of vagus nerves in the communication pathway from the immune system to the brain by reversibly inactivating the dorsal vagal complex with a longacting local anesthetic (Marvel et al., 2004). The dorsal vagal complex is a brain stem structure that integrates visceral signals and comprises a circumventricular organ, the area postrema, and the primary projection area of the vagus nerves, the nucleus tractus solitarius. The local injection of bupivacaine totally abrogated LPS-induced reduction of social exploration and attenuated LPS-induced Fos expression in various parts of the brain.
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The involvement of vagal afferents in the transmission of information from the peripheral cytokine compartment to the brain is not restricted to the behavioral effects of cytokines, since vagotomy also attenuated LPS-induced hyperalgesia, fever, and elevated plasma ACTH levels (Watkins et al., 1995). Vagotomy was also found to attenuate activation of locus coeruleus neurons by intraperitoneal injection of LPS and other immune activating substances [peptidoglycan and poly(I):(C) (Borsody and Weiss, 2005)]. The same effect was obtained when transection was limited to the dorsal trunk of the vagus nerve. However, it is important to note that the results concerning the effects of vagotomy on fever and pituitary-adrenal axis activation are not always as clear as the effects of this procedure on cytokine-induced sickness behavior. In an experiment comparing the effects of LPS on social exploration and body temperature in the same rats, subdiaphragmatic vagotomy was found to block LPS-induced social withdrawal but not LPS-induced increased body temperature (Konsman et al., 2000a; Luheshi et al., 2000). Since higher doses of LPS are necessary to induce sickness behavior than fever, these results are consistent with the observation that fever induced by high doses of LPS is resistant to the effects of vagotomy (Hansen et al., 2000a; Romanovsky, 2000; Szekely et al., 2000). Mice have been suggested to be less susceptible than rats to the effects of vagotomy (Wieczorek et al., 2005) although a direct comparison between species is still lacking. Vagal signaling of immune activation occurs fairly rapidly since c-Fos is expressed within 60 minutes of intraperitoneal LPS administration. Sensory structures associated with the abdominal vagus (vagal paraganglia) express binding sites for the IL-1 receptor antagonist (Goehler et al., 1997). Furthermore, IL-1β levels in dendritic cells and macrophages within connective tissue associated with the abdominal vagus nerves increased by 45 minutes after LPS administration, a time frame consistent with signaling of immune activation (Goehler et al., 1999). These cells certainly function as immune chemosensory elements (Goehler et al., 2000) that signal vagal neurons via prostaglandindependent and independent mechanisms. Using neuroanatomy techniques, Ek et al. showed that specific labeling for mRNAs encoding the type I IL-1 receptor and the EP3 subtype of the prostaglandin E2 receptor was detected in situ over neuronal cell bodies in the rat nodose ganglion (Ek et al., 1998). Moreover, intravenously applied IL-1 increased the number of sensory neurons in the nodose ganglion that express the cellular activation marker c-Fos, which was matched by an increase in discharge activity of vagal afferents arising from gastric compartments (Ek et al., 1998). This
response to IL-1 administration was attenuated in animals pre-treated with the cyclooxygenase inhibitor indomethacin, suggesting partial mediation by prostaglandins (Ek et al., 1998). The observation that subdiaphragmatic section of the vagus nerves attenuates the brain effects of systemic cytokines, together with the demonstration of an inducible brain cytokine compartment, has shifted the attention from circumventricular organs to neural pathways in the transmission of immune messages to the brain. Since then, neuroanatomical studies have confirmed the existence of a fast route of communication from the immune system to the brain via afferent nerves innervating the site of the body where the inflammatory response takes place (Figure 6). However, this neural pathway is complemented by a humoral pathway that involves a relay at the level of structures outside the blood-brain barrier, the circumventricular organs and the choroid plexus. These neural structures contain dendritic cells and macrophage-like cells that respond to circulating pathogen-associated molecular patterns by producing pro-inflammatory cytokines (Figure 6). These locally produced cytokines diffuse from their site of production to the adjacent brain parenchyma and from there propagate in the brain parenchyma in a manner that is typical of volume transmission, i.e., by using the extracellular space and following specific routes along the blood vessels and fiber tracts (Konsman et al., 2000b; Vitkovic et al., 2000). The recruitment of microglial cells and perivascular macrophages “en passant” is certainly at the origin of a second wave of cytokines produced in the brain parenchyma. Depending on their source, these locally produced cytokines can activate neurons that project to specific brain areas via prostaglandinindependent or dependent mechanisms. The way the neural pathway of immune-to-brain transmission interacts with this humoral pathway remains to be elucidated, but a likely possibility is that the neural pathway sensitizes the brain structures involved in the production and action of cytokines participating in the humoral pathway (Dantzer et al., 2000). In conclusion, the results of neuroanatomy and vagotomy experiments support the hypothesis that multiple routes of communication transmit the immune message from the periphery to the brain. Neural and humoral pathways together with specific saturable transporters are involved in this communication. This multiplicity of pathways points out to the importance of the involvement of the central nervous system in the host response to infection, not only for triggering a febrile response but also to adapt behavior to the new priorities required by the fight against infectious pathogens.
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FIGURE 6 Schematic drawing of the neural immune-tobrain communication pathway. The upper portion of the figure represents a sagittal section of the rat brain, whereas the lower-right portion of the figure represents the liver. Intraperitoneally administered LPS induces the production of IL-1β (represented by asterisks) by Kupffer cells in the liver, resulting in the activation of vagal afferents. This neural message is transmitted to the NTS, and from there to the parabrachial nuclei (PB), the ventrolateral medulla (VLM), and the forebrain nuclei that are implicated in the metabolic, neuroendocrine, and behavioral components of the systemic host response to infection (Medial Preoptic area, MPO; ParaVentricular Nucleus, PVN; SupraOptic Nucleus of the hypothalamus, SON; Central nucleus of the Amygdala, CeA; Bed nucleus of the Stria Terminalis, BST). Neural activation of these structures is apparent from c-Fos expression. IL-1β, represented by asterisks, is first synthesized and released in the circumventricular organs (Organum Vasculosum of the Lamina Terminalis, OVLT; Area Postrema, AP; SubFornical Organ, SFO; Median Eminence, ME) and the choroid plexus (ChP). In the AP, IL-1β is synthesized and released by perivascular phagocytic cells and then diffused throughout the interstitium to act on IL-1 type I receptors that are present on AP neurons and project to the Nucleus Tractus Solitarius (NTS). This results in a second wave of FOS expression in the NTS and its projection structures. The NTS therefore plays a pivotal role in the integration of peripheral and central IL-1β. A second wave of IL-1β expression occurs on the neural side of the blood-brain barrier and corresponds to the sequential activation of ramified microglial cells. Not represented in this figure is the fact that the actions of IL-1β on many of its target structures are mediated by intermediates such as prostaglandins and NO. (From Konsman et al., 1999.)
VI. CELLULAR ORGANIZATION OF THE CYTOKINE NETWORK IN THE BRAIN The concept that peripheral immune activation induces expression of cytokines at the mRNA and
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protein levels in the brain was initially based on the observation that intraperitoneal administration of the cytokine inducer, LPS, induces IL-1β synthesis in the brain (Dantzer, 2001; Konsman et al., 2002). The brain cells at the origin of this synthesis are meningeal and perivascular macrophages, and ramified microglial cells (Buttini and Boddeke, 1995; van Dam et al., 1992; van Dam et al., 1995). However, IL-1 is not the sole cytokine to be induced in the brain by peripheral immune stimuli. TNF-α is also expressed at the mRNA and protein levels (Breder et al., 1994; Gatti and Bartfai, 1993), and its cellular sources are represented by perivascular cells and neurons. IL-6 mRNA is also induced in the brain in response to peripheral LPS but not IL-1, with a delayed expression in comparison to that of IL-1 (Laye et al., 1994; Vallieres and Rivest, 1997). IL-1β presents the peculiarity of being produced in the form of a biologically inactive precursor, known as proIL-1β, that needs to be clived at an aspartate residue by a specific enzyme, named interleukin-1β converting enzyme (ICE) or caspase-1, to provide biologically active IL-1β. Despite ICE being co-localized with IL-1β in microglial cells, proIL-1β is the predominant form that is secreted by stimulated microglial cells (Chauvet et al., 2001). Like in macrophages, the release of mature IL-1β from microglial cells requires high amounts of ATP that binds to a low-affinity P2X7 purinergic receptor on the membrane of microglial cells (Ferrari et al., 1997). This results in activation of ICE, and maturation and release of IL-1β. ATP derives from dying cells in case of brain injury or from astrocytes, in the absence of cell damage. The mechanism of release of microglial IL-1β in co-cultures of astrocytes and microglia has been elucidated by the use of a biochemical approach integrated with video microscopy experiments in response to astrocyte-derived ATP (Bianco et al., 2005). ATP induced the formation and the shedding of membrane vesicles containing IL-1β. At the periphery, LPS induces first the expression of TNF-α that is responsible for the synthesis of IL-1. IL-1 itself triggers the synthesis and release of IL-6. Using the technique of polymerase chain reaction after reverse transcription (RT-PCR), studies of brain transcripts for mRNA for these different cytokines at various intervals following intraperitoneal administration of LPS revealed that the same sequence of events occurs in the brain. TNF-α and IL-1β mRNAs appeared first and were followed by IL-1ra and IL-6 mRNAs (Laye et al., 1994). The importance of IL-1β in this cascade was apparent from the observation that intracerebroventricular i.c.v. administration of IL-1ra to LPS-treated mice blocked the induction of expression of IL-1β, IL-6, and TNF-α in the hypothalamus and attenuated it in the hippocampus (Laye et al., 2000). Based on in situ
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hybridization studies, IL-1ra mRNA appears to be mainly expressed in the meninges, choroid plexus, and perivascular cells (Wong et al., 1997). At the cellular level, IL-1ra is produced by microglial cells, although it is also present in astrocytes and neurons, perhaps secondary to an internalization process, the nature of which remains to be elucidated (van Dam et al., 1998). The exact cellular targets of pro-inflammatory cytokines in the brain are still elusive. IL-1 receptors have been identified in brain tissues, using radioligandbinding studies, in situ hybridization, and immunohistochemistry. Equilibrium binding of 125I-IL-1α by brain membrane homogenates and brain slices was the first technique that was used to demonstrate the presence of binding sites for IL-1 in the mouse brain (Ban et al., 1991; Parnet et al., 1994; Takao et al., 1990). These binding sites are located almost exclusively in the anterior pituitary, choroid plexus, and dentate gyrus of the hippocampus. However, these findings are inconsistent with proposed sites of action of IL-1 receptor agonists in such areas as the hypothalamus and brain stem. Autoradiography techniques have been unable to reveal the presence of IL-1 binding sites within the rat brain, in contrast to the mouse (Marquette et al., 1995). However, in situ hybridization identified the type I IL-1 receptor mRNA in several regions of the rat brain, including the anterior olfactory nucleus, medial thalamic nucleus, posterior thalamic nucleus, basolateral amygdaloid nucleus, ventromedial hypothalamus nucleus, arcuate nucleus, median eminence, mesencephalic trigeminal nucleus, motor trigeminal nucleus, facial nucleus, and Purkinje cells of the cerebellum (Ericsson et al., 1995). Immunohistochemistry with an antibody directed against the extracellular domain of IL-1RI revealed a predominant vascular localization of this receptor (Konsman et al., 2004). IL-1R1–immunoreactive perivascular cells were mostly found in choroid plexus and meninges. IL-1R1–immunoreactive vessels were seen throughout the brain, but concentrated in the pre-optic area, subfornical organ, supraoptic hypothalamus, and to a lesser extent in the paraventricular hypothalamus, cortex, nucleus of the solitary tract, and ventrolateral medulla. Vascular IL-1R1– immunoreactivity was associated with an endothelial cell marker that was not found in arterioles, corresponded to the induction patterns of phosphorylated c-Jun and inhibitory-factor kappa B mRNA upon IL-1 beta stimulation, and co-localized with peripheral IL-1 beta- or LPS-induced COX-2 expression (Nadjar et al., 2005). These observations indicate that functional IL-1R1s are expressed in endothelial cells of brain venules and suggest that vascular IL1R1 distribution is an important factor determining
prostaglandin-dependent activation of brain structures during infection. The accessory protein of the IL-1 receptor is expressed at high levels in the mouse and rat brain at a much larger extent than IL-1RI, which indicates a possible role of this accessory protein independently of its association with IL-1RI (Gabellec et al., 1996; Greenfeder et al., 1995; Liu et al., 1996). However, such a role has not yet been elucidated. Upon binding of IL-1, IL-1RI forms a dimer with IL-1RAcP, which ultimately leads to the transcription of NFκB and MAP kinases. It is therefore possible to identify the cellular targets of IL-1 by determining in which cell types NFκB is activated. This can be done using either induction of IκB mRNA or nuclear translocation of NFκB (Figure 7). As mentioned above, endothelial cells of blood vessels not only express IL1R1, but they also respond to intraperitional LPS and IL-1β by enhanced expression of IκB transcripts (Nadjar et al., 2003). These cells are supposed to be at the origin
FIGURE 7 The peripheral IL-1 message relays in circumventricular organs before diffusing into the brain parenchyma. Rats were injected intraperitoneally with 20 μg recombinant rat IL-1β before being killed 1–2 hours (upper line) or 3–4 hours (lower line) after. Coronal sections of the brain at the level of the dorsal vagal complex containing the area postrema (AP) and nucleus tractus solitarius (NTS) were made and labeled with an antibody against p65-NFκB subunit (left column) or rat IL-1β (right column). Note that NFκB labeling overlapped with IL-1β labeling and diffused with time from the AP into the NTS. Although not shown, NFκB labeling was seen in all cases in the nuclear compartment of cells present in the defined structures. (From Konsman et al., 1999; Nadjar et al., 2003.)
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of prostanoids in response to IL-1 in the brain (van Dam et al., 1996). However, a careful analysis of the relative importance of endothelial cells and perivascular macrophages revealed that in response to low doses of IL-1 and LPS, perivascular macrophages were the first cells to respond by expressing the inducible enzyme COX-2, whereas endothelial cells responded only to higher doses of LPS (Schiltz and Sawchenko, 2002). Induction of IκB and activation of NFκB have been used further to delineate the neural circuits that are involved in the brain effects of cytokines, as outlined in the next section.
VII. MECHANISMS OF ACTION OF CYTOKINES ON THEIR BRAIN TARGETS The exact mechanisms of action of cytokines on their brain targets are still elusive. There are several aspects to this issue. The first one concerns the brain circuitry that is involved in the response to proinflammatory cytokines. The second one concerns the respective role of brain cytokines and intermediate molecules, such as prostanoids and nitric oxide (NO), in the activation of this circuitry.
A. Functional Neuroanatomy The neuronal circuits that underlie the response to immune stimuli have mainly been studied with regard to the activation of the hypothalamic-pituitary-adrenal axis, the fever response, and the alterations in food intake that develop in animals injected with LPS and IL-1β. Ericsson and colleagues have examined the pathways that mediate activation of the hypothalamicpituitary-adrenal axis in response to an intravenous injection of IL-1β (Ericsson et al., 1994). Using c-Fos immunohistochemistry, they found that c-Fos was induced in C1 noradrenergic neurons in the ventrolateral medulla. These neurons project to the CRH containing neurons of the paraventricular nucleus (PVN) of the hypothalamus. Interruption of the input from the C1 cells to the PVN by knife cuts prevented the CRH response to IL-1β. Quan et al. have proposed another mechanism independent of any neural pathway (Quan et al., 2003). In their model, activation of the PVN is secondary to prostaglandin synthesis by IL-1 activated endothelial cells in the PVN. In the case of fever, Saper and colleagues observed that intravenously injected LPS activated c-Fos in the ventromedial pre-optic area of the hypothalamus (VMPO) (Elmquist et al., 1996). Using retrograde tracing, they found that the VMPO has both direct and indirect (via the anterior perifornical area and
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parastrial nucleus) projections to the autonomic parvicellular divisions of the PVN. They proposed that activation of VMPO efferents following LPS disinhibits PVN neurons that are involved in thermogenesis by inhibition of warm sensitive neurons that are located in the anterior perifornical area, therefore raising the thermostatic set-point for thermoregulation (Elmquist et al., 1996; Plata-Salaman, 1998). In the case of food intake, Plata-Salaman and colleagues showed that IL1β suppressed the neuronal activity of the glucosesensitive neurons in the lateral hypothalamic area, while activating glucose-sensitive neurons in the hypothalamic ventromedial nucleus (VMH) (PlataSalaman, 1998; Plata-Salaman et al., 1988). More modern views on the regulation of food intake and energy expenditure emphasize the role of adiposity signals on food intake and regulation of fat metabolism (Schwartz et al., 2000). Leptin and insulin are adiposity signals, secreted in proportion to body fat content, which act in the hypothalamus to inhibit anabolic and stimulate catabolic effector pathways. These pathways have opposing effects on energy balance (the difference between calories consumed and energy expended) that in turn determines the amount of body fuel stored as fat. A first order brain structure in this process is the arcuate nucleus that is situated adjacent to the floor of the third ventricle and innervates a number of second-order structures directly involved in the regulation of metabolism and/or food intake. The arcuate nucleus transduces the afferent input from circulating leptin and insulin into a coordinated neuronal response thanks to the intervention of two different neuronal populations. One population contains neuropeptide Y (NPY) and agouti-related protein (AGRP) and activates an anabolic pathway, whereas the other population contains pro-opiomelanocortin (POMC) and cocaine and amphetamine-regulated transcript (CART) and regulates a catabolic pathway. The arcuate nucleus appears to be a target brain structure for IL-1–induced anorexia since it contains IL-1RI (Ericsson et al., 1995) and is activated in response to systemic IL-1 challenge, as shown by enhanced c-Fos expression (Herkenham et al., 1998) that is apparent in both POMC- and NPY-containing neurons (Reyes and Sawchenko, 2002). However, lesion of this structure by various techniques did not impair IL-1– induced anorexia but enhanced it instead (Reyes and Sawchenko, 2002). A possible explanation for this somewhat discrepant finding is the priming effect of brain lesions on microglial reactivity to systemic immune stimuli, as discussed in “Sensitization of the Brain Cytokine System.” Although many studies used cytokine-induced social withdrawal as a characteristic indicator of
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sickness behavior, the neuronal basis of this effect remains unknown. One region of the brain that might be involved in generating social withdrawal is the amygdala (Phelps and Ledoux, 2005). A detailed analysis of the effects of systemic IL-1β on c-Fos immunolabeling in rats in the rat amygdala using retrograde tracing revealed that the central amygdala receives a distinct population of IL-1β–activated afferent inputs that are primarily situated in two nuclei, the parabrachial nucleus and the paraventricular thalamus (Buller and Day, 2002). The parabrachial nucleus is a secondary projection area of the vagus nerves via the nucleus tractus solitarius. The paraventricular thalamus is part of the non-specific thalamus that projects to the amygdala and is also activated by anxiogenic stimuli (Kurumaji et al., 2003). Both the central amygdala and the bed nucleus of the stria terminalis form part of the extended amygdala that projects to the periacqueductal gray. This last neural structure is formed of longitudinal neuronal columns that play key roles in the elaboration of neurovegetative and motor components of what some authors call passive and active emotional coping, especially in relation to painful stimuli (Bandler et al., 2000). Immobility and decreased responding to the environment can be considered as passive emotional coping strategies. The periacqueductal gray has also been involved in defensive recuperative behavior and freezing (Jhou, 2005). The exact role of these brain structures in cytokine-induced social withdrawal remains to be tested. Rather than using functional neuroanatomy techniques to identify the neural structures that mediate the behavioral effects of cytokines, some investigators have microinjected minute amounts of cytokines in specific brain areas. Bilateral infusion of IL-1β into the ventro-medial hypothalamic area of rats depressed food-motivated behavior in rats (Kent et al., 1994). These effects required a lower dose than that injected into the lateral ventricle of the brain. However, the same effect was observed when the cannula did not hit the VMH. In a different experiment, IL-1β was found to decrease locomotor activity, and food and saccharin consumption when injected into the PVN, whereas administration into adjacent thalamic locations had no effect (Avitsur et al., 1997b). These limited findings indicate that the techniques of micropharmacology are certainly useful for dissecting out the sites of action of cytokines in the brain. In the cat, microinjection of IL-1β into the medial hypothalamus facilitated the defensive rage response induced by stimulation of the periacqueductal gray, indicating that IL-1 sensitizes the activity of this last brain structure (Hassanain et al., 2005). However, more systematic investigations are clearly needed.
B. Molecular Intermediates Whether cytokines directly act on the abovedescribed neural pathways or activate them via intermediates such as prostaglandins and nitric oxide (NO) is still a matter of controversy. There is no doubt that cytokines are powerful inducers of the expression of cyclooxygenase-2 (COX-2) in the brain (Breder and Saper, 1996; Cao et al., 1996). COX-2 is the rate-limiting enzyme in the conversion of arachidonic acid to prostanoids. This enzyme is induced in brain vascular- and perivascular-associated cells in response to systemic administration of LPS and IL-1β, but not IL-6 (Cao et al., 1996; Konsman et al., 2004; Lacroix and Rivest, 1998). Cytokines also induce NO synthase in the brain (Wong et al., 1996). The inducible form of NO synthase (iNOS), also called type II NOS, is synthesized by macrophages in response to inflammatory stimuli. Using in situ hybridization, Wong et al. reported that there is no detectable expression of iNOS in the brain in basal conditions, but that this enzyme is rapidly induced in vascular cells, glia, and neurons of the rat brain in response to intraperitoneal LPS. The induction of this enzyme in the hypothalamus was confirmed by Satta and colleagues, using RT-PCR (Satta et al., 1998). Since many of the functional neuroanatomical studies on the brain effects of immune stimuli were carried out using the intravenous route, and endothelial cells of the brain microvasculature respond to intraluminar cytokines by producing prostaglandins, Elmquist et al. proposed that these intermediates mediate the CRH and fever responses to immune stimuli (Elmquist et al., 1997). These actions of prostaglandins would take place in different regions of the brain, the C1 noradrenergic neurons for the CRH response, and the VMPO neurons for fever. Stimulation of COX-2 in the brain microvasculature of the MPOA results in an increased local production of prostaglandins. These intermediates would bind to specific receptors expressed on nearby neurons to promote the fever in response to peripheral immune stimuli. In the case of a local inflammation, prostaglandins released at the site of inflammation would activate local sensory fibers, resulting in the transmission of the peripheral immune message to the brain. The postulated association between IL-1 receptor activation, NFκB activation, and COX-2 expression in endothelial cells (Quan et al., 1997) has recently been confirmed by visualization of NFκB translocation together with COX-2 induction in response to intraperitoneal IL-1β (Konsman et al., 2004; Nadjar et al., 2003). IL-1β induced a robust translocation of NFκB in the brain vasculature that was associated with COX-2 induction in the same cells and abrogated by
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pre-treatment with a cell permeant NFκB antagonist peptide administered directly into the lateral ventricle of the brain (Nadjar et al., 2005). The role of prostaglandins in cytokine-induced sickness behavior has been examined by inhibiting the synthesis of these compounds with various nonsteroidal anti-inflammatory drugs. Intraperitonal pretreatment with the non-selective COX inhibitor indomethacin or the COX-1 inhibitor piroxicam blocked the effects of intraperitoneal IL-1β on social exploration and food-motivated behavior in rats, whereas aspirin was ineffective (Crestani et al., 1991). Indomethacin or ibuprofen was also found to attenuate LPS-induced anorexia in rats (Hellerstein et al., 1989; Langhans et al., 1989; Uehara et al., 1989a) and LPS-induced reduction in sweetened milk intake (Dunn and Swiergiel, 2001). Diclofenac, another COX-1 inhibitor, attenuated LPSinduced reduction in response rate in rats trained to press a lever for a food reward (De La Garza et al., 2004). In an attempt to dissect the respective role of COX-1 and COX-2 in the reduction of sweetened milk intake induced by intraperitoneal LPS, Swiergiel and Dunn used mice in which the gene coding for one or the other enzyme had been deleted, together with administration of specific COX inhibitors in normal mice (Swiergiel and Dunn, 2001; Swiergiel and Dunn, 2002). In response to intraperitoneal IL-1β, COX-2 knockout mice were initially not affected but showed less of a decrease in their intake of sweetened milk 90 to 120 minutes after, whereas the reverse was true for COX-1 knockout mice. The COX-2–selective inhibitor, celecoxib, failed to alter the response to IL-1β 30 minutes after administration, but low doses antagonized the effects of IL-1β at 90 to 120 minutes. The COX-1– selective inhibitor, SC560, attenuated both the early and late responses, but with a larger effect at 30 minutes than at 90 minutes. These results indicate that COX-1 is involved in the early stage response to IL-1β, whereas COX-2 becomes more important at later times. Using a similar approach but with measurements of food intake and body weight for longer times, Johnson et al. found that COX-2 inhibition during LPS-induced inflammation resulted in preserved food intake and maintenance of body weight, whereas COX-1 inhibition resulted in augmented and prolonged weight loss (Johnson et al., 2002). The role of nitric oxide in cytokine-induced sickness behavior was examined using pharmacological approaches aiming at blocking nitric oxide synthase. Inhibition of nitric oxide synthase activity by N omega nitro-L-arginine-methyl-ester potentiated the depressive effects of IL-1β on social investigation in mice. This effect was attenuated by L-arginine but not by D-arginine, confirming the protective action of nitric
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oxide in sickness (Bluthe et al., 1992c). Similar effects were obtained in rats when IL-1β was replaced by LPS (Connor et al., 2002), and these effects were obtained only with an antagonist targeting the endothelial isoform of inducible nitric oxide synthase but not the other isoforms. However, administration of the same antagonist into the lateral ventricle of the brain abrogated the impairing effects of intravenous LPS and ICV TNF-α on drinking behavior induced by water deprivation (Calapai et al., 1994), indicating that production of nitric oxide in the brain could mediate some of the sickness-inducing effects of pro-inflammatory cytokines. In conclusion, there are multiple pathways and several intermediates that are involved in the immuneto-brain communication both at the periphery and in the brain itself (Figure 8). The exact pathway and intermediates that are involved depend on the component of the host response to infection and the time course of the response.
FIGURE 8 Schematic drawing of the mechanisms of cytokine-induced sickness. Pathogen-associated molecular patterns induce the production of pro-inflammatory cytokines at the periphery and in macrophage-like cells of circumventricular organs (CVOs) and choroids plexuses. Peripheral cytokines induce the expression of cytokines in the brain via neural afferents or a relay at the level of circumventricular organs and brain vasculature. Prostaglandins of the E2 series are produced locally and diffuse to brain targets to alter the set point for various regulatory processes. Alternatively, brain cytokines propagate by volume diffusion to their neural targets. The relative importance of humoral and neural pathways differs according to the specific component of the host response to infection. The vertical dotted line in the middle of the figure represents the blood-brain barrier, whereas the other dotted lines represent neurally transmitted actions of cytokines to distant targets. (From Konsman et al., 2002.)
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C. Role of Neurotransmitters and Neuropeptides Administration of LPS or cytokines to laboratory animals induces profound alterations in neurotransmitter metabolism in various areas of the brain. LPS, IL-1, and IL-6 stimulate brain noradrenaline (NA) metabolism, and increase tryptophan concentrations and serotonin (5-HT) metabolism (Dunn et al., 1999). Dopamine levels are elevated by LPS in some brain areas such as the paraventricular nucleus and arcuate nucleus (MohanKumar et al., 1999). IL-2 modulates veratrine-evoked release of endogenous dopamine from striatal slices in a biphasic pattern, increasing release at low concentrations and decreasing it at high concentrations (Petitto et al., 1997). TNF-α affects noradrenaline and tryptophan but only at high doses, whereas INFα has no effect. While the neurochemical response to physical stressors is normally distributed in a relatively uniform manner throughout the brain, the neurochemical response to cytokines is more localized and observed mainly in the hypothalamus (Dunn et al., 1999). Most of these effects have been studied in response to single injections of cytokines. Repeated administration of these soluble mediators can have potent effects on brain neurotransmission. For instance, repeated but not single administration of interferon-α to mice drastically reduced the brain levels of dopamine and its major metabolite, 3-4 dihydroxyphenylacetic acid (Shuto et al., 1997), which could account for the Parkinson-like symptoms observed in patients treated with this cytokine (Capuron and Miller, 2004). In view of the various biological effects of cytokines, it is not easy to relate the changes in neurotransmitter metabolism to specific behavioral effects of cytokines. An attempt to do so has been made by Linthorst and colleagues in an elegant series of studies carried out with in vivo microdialysis techniques in animals of which the core temperature, corticosterone, and behavior were monitored continuously (Linthorst et al., 1995a; Linthorst et al., 1995b). These studies focused on 5-HT and NA neurotransmission in the hippocampus and the hypothalamic preoptic area of rats injected intraperitoneally with LPS. LPS induced a dose-dependent increase in hippocampal extracellular levels of 5-HT and its metabolite 5-hydroxyindoleacetic acid (5-HIAA). In contrast to what was observed in the hippocampus, intraperitoneal LPS had no effect on preoptic extracellular levels of 5-HT. Intraperitoneal LPS also increased hippocampal extracellular levels of NA and its major metabolite, 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) (Linthorst et al., 1996),
but this effect was small compared to the huge increase of NA and MHPG that was observed in the preoptic area. ICV administration of IL-1β mimicked the effects of LPS on 5-HT neurotransmission in the hippocampus, whereas ICV TNF-α had no effect on behavior and neurotransmitters. ICV IL-2 affected hippocampal 5-HT neurotransmission only at doses that depressed locomotor activity (Pauli et al., 1998). Based on these findings and the neuroanatomical connectivity of these brain structures, Linthorst and colleagues proposed that the increase in preoptic NA is involved in fever and/or activation of the hypothalamic-pituitary-adrenal axis, whereas the rise in hippocampal 5-HT is associated with the development of sickness behavior (Linthorst and Reul, 1999). This hypothesis still needs to be tested using local infusion of specific agonists and antagonists of 5-HT and NA. Studies on the role of neuropeptides in the behavioral effects of cytokines have mainly concentrated on corticotropin releasing hormone (CRH), cholecystokinin (CCK, a feeding inhibitory factor), neuropeptide Y (NPY, a feeding stimulatory factor), and leptin (a feeding inhibitory factor). Since IL-1 is a potent activator of the hypothalamic-pituitary-adrenal axis, the possibility that CRH mediates some of the effects of this cytokine on anxiety-like behaviors has been assessed, using immunoneutralization of CRH by ICV administration of CRH receptor antagonists and neutralizing antibodies directed against CRH. The results of these experiments have not been very conclusive, and the same applies to the depressing effects of IL-1 on food intake. In one experiment, immunoneutralization of endogenous CRF in the brain attenuated the anorexic effect of intraperitoneal IL-1β (Uehara et al., 1989b), whereas in another experiment, this treatment did not alter the disrupting effect of IL-1β administered intraperitoneally or into the lateral ventricle of the brain on food-motivated behavior (Bluthe et al., 1992a). The anorexic effects of the bacterial T-cell superantigen, Staphylococcal enterotoxin A, were attenuated by intracerebroventricular pre-treatment with α-helical CRH9-41, a non-selective CRH receptor antagonist, but not by astressin-2B, a selective CRH receptor 2 antagonist (Kaneta and Kusnecov, 2005). Discrepant results were also obtained with CCK receptor antagonists since administration of a CCK-A receptor antagonist blocked the effects of IL-1α on food intake and gastric emptying in rats in one experiment (Daun and McCarthy, 1993), whereas in another experiment antagonism of peripheral or CCK-A or CCK-B receptors had no effect on the behavioral changes caused by IL-1 (Bluthe et al., 1997b). The observation that both leptin and IL-1 are able to inhibit the potent orexigenic
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effects of NPY, and conversely that NPY can reverse IL1–induced anorexia (Sonti et al., 1996), led some authors to speculate that a disregulation of leptin-NPY-cytokine interactions might play a pivotal role in the pathophysiology of feeding disorders (Plata-Salaman et al., 1996). IL-1β and other pro-inflammatory cytokines act on adipocytes and induce the synthesis of leptin (Faggioni et al., 1998; Francis et al., 1999; Sarraf et al., 1997). The in vivo effects of LPS on leptin are likely to be mediated by TNF-α since LPS had no effect on leptin secretion by adipocytes, whereas TNF-α increased it (Finck et al., 1998). The first test of the hypothesis of a role of leptin in cytokine-induced anorexia was carried out on leptindeficient (ob/ob) and leptin-receptor–deficient (db/db) mice. Contrary to expectations, these mice were found to remain sensitive to the anorexic effects of LPS (Faggioni et al., 1997). However, the interpretation of these last results is certainly confounded by the lowgrade inflammation that is associated with obesity and sensitizes the cytokine system both at the periphery and in the brain to immune stimulation (O’Connor et al., 2005). Immunoneutralization of circulating leptin decreased the inhibitory effect of LPS on food intake and attenuated LPS-induced expression of brain cytokines (Sachot et al., 2004). Conversely, the inhibitory effect of leptin on food intake was found to be mediated by IL-1 since it was blocked by central administration of the IL-1 receptor antagonist and was no longer present in mice deficient for the type I IL-1 receptor (Luheshi et al., 1999). These results are consistent with the observation that leptin increases hypothalamic IL-1β expression (Hosoi et al., 2003; Wisse et al., 2004). Because the leptin receptor is closely related to glycoprotein 130 (gp130), a common signal transducer among receptors for cytokines of the IL-6 family (IL-6, ciliary neurotrophic factor [CNTF], leukemia inhibitory factor [LIF]), the possibility that CNTF-induced anorexia is mediated by leptin was investigated in rats treated with intraperitoneal leptin and CNTF (Xu et al., 1998). Both molecules induced anorexia and suppressed NPY-induced feeding. However, CNTF decreased leptin mRNA in adipocytes and had a depressing effect on hypothalamic NPY gene expression only at high dosages, suggesting that the effects of CNTF are not mediated by interactions with these endogenous signals.
VIII. SPECIFICITY OF THE INVOLVEMENT OF PERIPHERAL AND CENTRAL CYTOKINES IN DIFFERENT COMPONENTS OF SICKNESS BEHAVIOR Although most of the work on the behavioral effects of pro-inflammatory cytokines has concentrated on
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IL-1, the different components of the behavioral syndrome that develops in sick individuals do not necessarily have an identical molecular basis. Moreover, the role of a given cytokine in sickness is likely to depend on the compartment, peripheral or central, in which it exerts its effects. The evidence that supports this interpretation is based on time course studies of the effect of IL-1β on social exploration and food-motivated behavior, on experiments examining the behavioral effects of LPS in animals pre-treated with various cytokine and cytokine receptor antagonists, and on investigation of the effects of immune stimulation in mice in which the gene coding for a specific cytokine or its receptor has been deleted by the technique of homologous recombination. Time course studies of the behavioral effects of IL-1β show that the changes in social exploration gradually develop within 2 hours following peripheral administration of this cytokine, whereas the changes in food-motivated behavior reach a maximum by 1 hour following treatment (Kent et al., 1996). The behavioral alterations that are induced by central administration of IL-1β usually dissipate faster than those induced by peripheral administration of this cytokine. The identification and cloning of IL-1ra provided a powerful pharmacological tool to attempt to resolve the role of IL-1 in sickness behavior. This cytokine blocks the in vivo biological effects of IL-1 when coadministered at a 100- to 1,000-fold excess dose with IL-1. To determine the importance of IL-1 in the behavioral effects of LPS, rats were injected intraperitoneally with IL-1ra before being administered LPS intraperitoneally. This treatment abrogated the depressing effect of LPS on social behavior (Bluthe et al., 1992b), but not on food-motivated behavior (Kent et al., 1992c) nor on female sexual behavior (Avitsur et al., 1997c). IL-1ra did not antagonize the decrease in milk intake induced by LPS administration in mice (Swiergiel et al., 1997). These results can be interpreted to suggest that peripheral IL-1 is a key cytokine in the network of proinflammatory cytokines that is induced by LPS when it comes to social activities, but not to food intake. To determine the importance of brain IL-1 in the depressing effects of peripherally administered IL-1 on social behavior and food-motivated behavior, rats received an intracerebroventricular injection of IL-1ra before being injected intraperitoneally with IL-1β. The depression of social exploration of a conspecific juvenile that normally occurs within 2–6 hours following IL-1β injection was totally blocked in IL-1ra pre-treated rats. However, in rats trained to press a bar for a food reward in a Skinner box, the same treatment only partially attenuated the decrease in bar pressing that
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normally occurs within 1–8 hours following IL-1β injection (Kent et al., 1992a). This did not appear to be a dose-dependent effect since increasing the dose of IL1ra by nearly nine-fold did not augment this partial blockade. These results indicate that among the different cytokines that are induced in the brain in response to peripheral IL-1, IL-1 is certainly the predominant molecular signal for the depression in social behavior but not for the decrease in food-motivated behavior. This effect of IL-1 appears to be mediated by the type I IL-1 receptor since intracerebroventricular administration of a neutralizing antibody directed against this receptor blocked the decrease in social behavior that was induced in mice by IP IL-1β (Cremona et al., 1998). In accordance with this last result, mice in which the gene for the type I IL-1 receptor or the accessory protein of the IL-1 receptor had been deleted by homologous recombination no longer responded to ICV IL-1β (Bluthe et al., 2000a). The importance of a given cytokine depends not only on the compartment, peripheral or central, and on the behavior under consideration, but also on the immune stimulus. As described above, brain IL-1 mediates the effects of IP IL-1 on social behavior. However, when LPS was injected in place of IL-1 to suppress social behavior, intracerebroventricular administration of IL-1ra was no longer able to abrogate the depressing effect of LPS (Bluthe et al., 1992b), whereas it still attenuated the LPS-induced reduction in food intake (Laye et al., 2000). The involvement of brain IL-1β in the depressing effects of LPS on food intake was confirmed in an experiment using mice in which the gene coding for ICE had been deleted (ICE(−/−)). These mice do not produce bioactive IL-1β. Both wild-type and ICE(−/−) mice responded to peripheral and central IL-1β injection by a decrease in food intake, indicating that the effector mechanisms of this cytokine were not affected by the mutation. However, ICE(−/−) mice were less sensitive than wild-type mice to the depressing effects of central LPS on food intake and food-motivated behavior, whereas they did not differ in their response to intraperitoneal LPS (Burgess et al., 1998). In general, the presence of a network of cytokines acting in a cascade fashion does not make easy the task of assessing the relative importance of individual molecules in the induction of the behavioral symptoms that are characteristic of sick individuals. Since cytokines act in the context of other cytokines, which have agonist and antagonist activities, the conclusions that can be drawn from a particular combination of cytokines induced by a specific immune stimulus does not necessarily apply to a different combination of the same and possibly other cytokines induced by a
different immune stimulus. Even apparently straightforward pharmacological experiments in which the concentration of a given cytokine is artificially modified can lead to erroneous conclusions. For example, peripheral and central administration of recombinant rat IL-6 to rats failed to cause any alteration in social behavior, whereas the same treatments reliably induced fever and activation of the pituitary-adrenal axis (Lenczowski et al., 1999). These results could easily be interpreted to suggest that IL-6 plays no role in sickness behavior. However, intracerebroventricular administration of IL-6 was found to potentiate the effects of a subthreshold dose of IL-1β administered via the same route on social behavior in rats. In accordance with their attenuated sensitivity to sickness associated with influenza pneumonitis (Kozak et al., 1997a), mice which are deficient in IL-6 were found to be less sensitive to the depressing effects of both IL-1 and LPS on social behavior when these molecules were administered either IP or ICV (Bluthe et al., 2000b). These results indicate that IL-6 is behaviorally active only in the context of other pro-inflammatory cytokines. The problem of identifying a major molecular signal for sickness behavior mirrors the difficulties experienced by pathologists in the selection of an appropriate molecular target for developing potential therapies for the treatment of septic shock and other pathological conditions in which cytokines play a critical role. This does not imply that pro-inflammatory cytokines are not important for the condition under examination; it just indicates that the redundant nature of the cytokine network imposes the choice of alternative strategies, based on the investigation of the mechanisms that are responsible for the commonality of action of pro-inflammatory cytokines, e.g., postreceptor mechanisms, and processes that regulate cytokine expression and actions.
IX. MOLECULAR FACTORS OPPOSING THE EXPRESSION AND ACTION OF PRO-INFLAMMATORY CYTOKINES IN THE BRAIN Pro-inflammatory cytokines are often viewed as a two-edged sword. At low concentrations, they have potent biological effects that play a key role in the development of the host response to infection. However, at high concentrations, they can lead to cell death by necrosis or apoptosis. The activity of proinflammatory cytokines therefore needs to be tightly regulated. Two main categories of molecules oppose the expression and action of pro-inflammatory
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cytokines, molecules that are part of the cytokine network and are called anti-inflammatory cytokines, and molecules that are exogenous to the cytokine network and are called cryogens (Kluger, 1991) (Figure 9). Cryogens include neuropeptides, such as vasopressin and alpha-melanotropin, and glucocorticoids.
A. Anti-inflammatory Cytokines Anti-inflammatory cytokines belong to a very heterogeneous family of secreted signaling molecules that all have in common the property of inhibiting to some extent the expression and/or action of proinflammatory cytokines. These cytokines include IL-4, IL-10, IL-13, and transforming growth factors-beta (TGF-β). Although the biological activity of these molecules was initially defined on peripheral immune and non-immune cells, there is evidence that they are also able to regulate the effects of pro-inflammatory cytokines in the nervous system. Most of the studies on anti-inflammatory cytokines in the nervous system have been carried out in the context of neuropathology (Owens et al., 1994; Vitkovic et al., 2001). During the course of an immune response in the brain, antiinflammatory cytokines are mainly produced by T helper 2 lymphocytes, and they downregulate pro-
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inflammatory cytokines produced by T helper 1 lymphocytes (IFN-γ and TNF-α). However, antiinflammatory cytokines can also be produced by macrophages, monocytes, and glial cells, and therefore play a physiological role in the regulation of sickness behavior. TGF-β is constitutively expressed in the brain and is certainly an important factor for the maintenance of the immune privilege of this organ. Whether it is the same for other anti-inflammatory cytokines is still uncertain. Although IL-10, for example, is expressed at the mRNA level in the human pituitary and hypothalamus (Rady et al., 1995), its expression and that of IL-13 do not appear to be very sensitive to the inducing effects of systemic LPS, in comparison to that of IL-1β (Wong et al., 1997). This does not mean that IL-10 has no effect on the brain action of cytokines. In accordance with its ability to protect from the lethal effects of endotoxemia, systemic administration of IL10 was found to abrogate the fever induced in mice by low doses of LPS (Leon et al., 1999). In addition, IL-10 knockout mice developed an exacerbated and prolonged fever and a more marked suppression of food intake in response to a low dose of LPS, when compared to their wild-type counterparts. Central administration of IL-10 abrogated the depressing effects of intraperitoneal LPS on locomotor activity but not on
FIGURE 9 Regulation of the expression and action of pro-inflammatory cytokines in the brain. The production and action of pro-inflammatory cytokines in the brain are regulated by anti-inflammatory cytokines, glucocorticoids, neuropeptides, and growth factors such as IGF-I. Proinflammatory cytokines activate the hypothalamic-pituitary-adrenal axis at the level of the paraventricular nucleus (PVN). The resulting increase in glucocorticoid levels feeds back in a counter regulatory manner not only on the pituitary and hypothalamus, but also on activated immunocytes. Solid arrows represent positive effects, whereas dotted arrows represent inhibitory influences.
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water intake in rats (Nava et al., 1997). Intracerebroventricular administration of IL-10 also abrogated the depressing effects of LPS administered intraperitoneally or into the lateral ventricle of the brain on social exploration in rats (Bluthe et al., 1999a). The reduction of endotoxin-induced hyperalgesia by intraperitoneal IL-10 in mice was associated with a downregulation of LPS-induced increases in levels of TNF-α and IL-1β in the skin of injected hind paws (Kanaan et al., 1998), which indicates that IL-10 might act by inhibiting production of pro-inflammatory cytokines. Centrally administered IL-10 was also able to block sickness behavior induced by intracerebral administration of gp120, a glycoproteic component of the capsid of the human immunodeficiency virus that has potent inflammatory effects in the brain (Barak et al., 2002). Since many anti-inflammatory cytokines play an important role in growth and development, it is possible that more traditional growth factors actually behave as anti-inflammatory cytokines. This was found to be the case for insulin-like growth factor I, which is abundantly expressed in the brain and, when administered centrally, attenuates the behavioral depression induced by intracerebroventricular injection of LPS (Dantzer et al., 1999). Chronic administration of IGF-I into the lateral ventricle of the brain also attenuated the impairing effects of kainate on spatial memory, probably by interfering with TNF-α since the effects of IGF-I were mimicked by pentoxifylline, an inhibitor of TNF-α synthesis (Bluthe et al., 2005). The generality of the anti-inflammatory action of IGF-I and its mechanisms remains to be elucidated.
dependent pathway is also activated during fever (Dantzer and Bluthe, 1992). Central administration of VP attenuated the depressing effects of centrally injected IL-1β on social exploration. Conversely, central injection of an antagonist of vasopressin receptors, which has no biological activity on its own but prevents endogenously released vasopressin to reach its receptors, sensitized rats to the behavioral effects of IL-1 (Dantzer et al., 1991). These last results are important since they suggest that endogenous VP plays a physiological modulatory role in the behavioral effects of IL-1. To determine whether this phenomenon is mediated by an androgendependent or independent pathway, castrated male rats were compared to intact male rats for their sensitivity to the modulatory role of the VP receptor antagonist. Castration by itself potentiated the depressing effects of IL-1β on social exploration. Central administration of VP was more effective in attenuating the behavioral effects of IL-1 in castrated than in intact male rats and, conversely, ICV administration of the VP receptor antagonist was no longer active in potentiating the behavioral effects of IL-1 in castrated male rats lacking vasopressinergic innervation of the lateral septum (Dantzer et al., 1991). Pro-inflammatory cytokines such as IL-1 stimulate the release of vasopressin by acting on a non-specific cationic conductance on vasopressinergic neurons via a prostaglandindependent mechanism (Ferri and Ferguson, 2005; Ferri et al., 2005). Conversely, VP appears to be able to suppress the production of pro-inflammatory cytokines by glial cells via a cAMP response elementbinding protein-element (Zhao and Brinton, 2004).
B. Vasopressin Vasopressin (VP) plays a key role in the regulation of water metabolism. It is produced by hypothalamic magnocellular neurons and accumulates in the terminals of these neurons in the posterior pituitary. It is released in the general circulation and acts as an antidiuretic hormone in response to water deprivation. The release of VP is enhanced during the febrile response, and this enhanced release can be of such a degree that miction does not occur before defervescence. VP also acts as a neurotransmitter in the brain. It is particularly present in neurons whose cell bodies are located in the bed nucleus of the stria terminalis, and whose terminals project to the lateral septum. This vasopressinergic pathway is highly sensitive to circulating androgens in rodents. Castration leads to a dramatic reduction in the content of VP mRNA in the neuronal cell bodies of the bed nucleus of the stria terminalis and to a reduction in immunoreactive VP in the terminal areas of the septum. This androgen-
C. Glucocorticoids The potent activating effects of pro-inflammatory cytokines on pituitary-adrenal activity have already been mentioned. Glucocorticoids feed back on activated immunocytes to downregulate the production and action of pro-inflammatory cytokines (Besedovsky and del Rey, 2000). Glucocorticoids act by binding to the glucocorticoid receptor (GR) that, upon activation, translocates to the nucleus and either stimulates or inhibits gene expression. GR inhibition of many proinflammatory response genes occurs through induction of the synthesis of anti-inflammatory proteins as well as through repression of pro-inflammatory transcription factors, such as NFκB or activator protein-1 (AP-1) (Smoak and Cidlowski, 2004). The downregulatory effects of glucocorticoids on the synthesis and secretion of IL-1, IL-6, and TNF-α by activated monocytes and macrophages (Lee et al., 1988) are physiologically relevant, as demonstrated by adrenalectomy
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(ADX) experiments. LPS-induced increases in plasma levels of TNF-α and IL-6 were much higher in adrenalectomized than in sham-operated animals (Zuckerman et al., 1989). Adrenalectomy sensitized experimental animals to the septic shock syndrome, whereas glucocorticoid supplementation had the opposite effect (Bertini et al., 1988; Ramachandra et al., 1992). To assess the possible influence of endogenous glucocorticoids on cytokine expression in the brain, ADX mice and sham-operated mice were injected with saline or LPS, and the levels of transcripts for IL-1α, IL-1β, IL-1ra, IL-6, and TNF-α were subsequently determined in the spleen, pituitary, hypothalamus, hippocampus, and striatum, using comparative RTPCR (Goujon et al., 1996). Levels of IL-1β were also measured by a specific ELISA in the plasma and tissues of experimental animals. LPS-induced expression of cytokines was potentiated by adrenalectomy in the plasma and other tissues, including several brain structures (Figure 10). Conversely, an increase in
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circulating glucocorticoids induced by a 15-minute restraint stress decreased LPS-induced cytokine gene expression both at the periphery and in the brain (Goujon et al., 1995c). It is important to note that the effects of stress are more complex than this experiment indicates, since increases in IL-1β mRNA levels in the hypothalamus of rats (Minami et al., 1991) and IL-6 levels in the plasma (LeMay et al., 1990; Zhou et al., 1993) have also been reported in stressed animals. Stress can actually increase cytokine expression via a β2 adrenergic receptor mechanism (Hetier et al., 1991). However, this effect is masked by endogenous glucocorticoids when they are released in sufficient quantities, as revealed by adrenalectomy experiments. Inescapable electric shocks increased cytokine expression at the periphery and in the brain in ADX, but not in control rats (Nguyen et al., 2000). As already mentioned, IL-1β is synthesized as an inactive precursor which must be cleaved to be secreted in an active form. The enzyme which is responsible for this cleavage is a protease, called interleukin-1β
FIGURE 10 Adrenalectomy increases expression of IL-1α mRNA in mice. Adrenalectomized (ADX) and sham-operated mice were injected subcutaneously with saline or LPS (10 μg/mouse) and killed 2 hours later. Total RNA was extracted from the hypothalamus, and IL-1α mRNA, expressed as a percentage of beta2-microglobulin mRNA, was measured by comparative RTPCR. The figure represents the mean results of three different experiments. Note that LPS increased IL-1α mRNA in various brain structures, and adrenalectomy increased the expression of this cytokine in saline- and LPS-treated mice. * p < 0.05, ** p < 0.01, *** p < 0.001 with respect to control values. (From Goujon et al., 1996.)
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converting enzyme (ICE). To determine whether glucocorticoids that regulate the expression of IL-1 in immune and non-immune tissues are also able to regulate the expression of ICE, mice were injected with LPS and the levels of ICE mRNA in the spleen, pituitary, and brain of experimental animals were measured by comparative RT-PCR. ICE mRNAs were more abundant in the spleen and hippocampus than in the pituitary and hypothalamus, but they were not significantly altered by LPS treatment. In another experiment, mice were submitted to adrenalectomy or a 15-minute restraint stress and injected with saline or LPS. ADX mice had significantly higher ICE mRNA levels, whereas stressed mice had significantly lower ICE mRNA levels than their respective controls. These results can be interpreted to suggest that endogenous glucocorticoids regulate the expression of ICE in peripheral and brain tissues, in a manner which is commensurate to their effects on IL-1β gene expression (Laye et al., 1996). This regulation of ICE by glucocorticoids was confirmed in vitro using primary cultures of murine microglia cells and a transformed murine microglial cell line (Yao and Johnson, 1997). In addition to their action on the synthesis of proinflammatory cytokines at the periphery and in the brain, glucocorticoids are also able to modulate the expression of IL-1 receptors. Although glucocorticoids induce the expression of IL-1 receptors in various immune and non-immune tissues, mixed results have been reported in the brain (Ban et al., 1993; Betancur et al., 1994). The problem with the radioligand-binding techniques which have been used for these studies is that they do not discriminate between type I and type II IL-1 receptor involvement and do not allow an accurate description of what is going on at the molecular level, since the same effect, in the form, for instance, of decreased binding, can be obtained as a result of very different processes, e.g., downregulation of receptors, or activation of receptors with internalization of receptor-ligand complexes. Binding techniques must therefore be complemented by other techniques, e.g., RT-PCR or western blot. By using specific blocking antibodies against type I and type II IL-1 receptors, in vitro studies on primary cultures of murine astrocytes showed that the synthetic glucocorticoid dexamethasone increased the expression of the IL-1RII decoy receptor at the protein and transcript level without affecting the affinity for IL-1β (Pousset et al., 2001). The downregulatory effects of glucocorticoids on the pro-inflammatory cytokine network at the periphery and in the brain should lead to an increased sensitivity of adrenalectomized animals to the brain actions of these cytokines. This appears to be the case since adrenalectomy increased the febrile response to LPS,
whereas administration of glucocorticoids had the opposite effect (Coelho et al., 1992; Morrow et al., 1993). In the same manner, adrenalectomy enhanced the depression of social exploration induced by peripheral injection of IL-1β or LPS (Goujon et al., 1995a). This effect was mimicked by administration of the glucocorticoid type II receptor antagonist, RU 38486. Chronic replacement with a 15-mg corticosterone pellet which yielded plasma corticosterone levels intermediate between baseline and stress levels, abrogated the enhanced susceptibility of ADX mice to the lower dose of IL-1β but had only partial protective effects on the response to a higher dose of IL-1β and to LPS. Taken together, these findings can be interpreted to suggest that the phasic response of the pituitaryadrenal axis to cytokines has an important regulatory role on the neural effects of cytokines. However, they do not reveal at which level (peripheral or central) glucocorticoids are acting. Central sites of action appear to be involved in the regulatory effects of glucocorticoids on the neural effects of cytokines, since central injection of RU 38486 potentiated fever induced by a peripheral injection of LPS to rats (McClellan et al., 1994). In the same manner, adrenalectomy sensitized mice to the depressing effects of intracerebroventricular administration of IL-1β on social exploration, and this effect was attenuated by corticosterone compensation (Goujon et al., 1995b). Central administration of RU 38486 mimicked the effect of adrenalectomy. The negative feedback provided by glucocorticoids on the production and action of pro-inflammatory cytokines in the brain is not specific of the sickness response since similar effects can be observed on the neurotoxic effects of LPS infused into the striatum of rats (Nadeau and Rivest, 2003). The limiting factors for the negative feedback of glucocorticoids on the production and action of cytokines are not necessarily the amount of glucocorticoids produced by the adrenal cortex or their bioavailability. Another important factor is the development of cortisol resistance. Cortisol resistance can be evidenced by the lower ability of synthetic or natural glucocorticoids to attenuate pro-inflammatory cytokine production by innate immune cells, e.g., monocytes. Cortisol resistance occurs during aging in males in part because of a decrease in testosterone since it can be eliminated by testosterone supplementation (Rohleder et al., 2002). Cortisol resistance can also occur in response to social disruption stress (Quan et al., 2001). The effects of glucocorticoids on pro-inflammatory cytokines in response to immune activation are not always inhibitory. They can also be permissive. This was found to be the case in a murine model of herpes simplex virus encephalitis (Ben-Hur et al., 2001).
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Intracerebroventricular inoculation of HSV-1 in rats induced fever, motor hyperactivity, and aggressive behavior. These clinical signs were not apparent in adrenalectomized rats, although the mortality rate was not altered. Furthermore, despite the fact that adrenalectomy enhanced the expression of brain IL-1β, it was not further increased in response to HSV-1.
X. MODULATION OF CYTOKINE-INDUCED SICKNESS BEHAVIOR BY DIETARY AND OTHER ENVIRONMENTAL FACTORS Dietary supplementation with anti-oxidants and n-3 fatty acids has anti-inflammatory properties. Antioxidants scavenge radical oxygen species and therefore limit the effects of oxidative stress associated with inflammation on target cells. Omega-3 fatty acids are taken up by virtually all body cells and affect membrane composition, eicosanoid biosynthesis, cell signaling cascades, and gene expression. Intraperitonal administration of α-tocopherol for 3 days to mice attenuated LPS-induced reduction in social behavior (Berg et al., 2004). However, the dietary incorporation of this compound together with selenium was less effective in protecting mice against LPS-induced sickness behavior perhaps because the systemic administration of α-tocopherol better targets the brain than the oral route. This effect of α-tocopherol on sickness behavior is consistent with the demonstration that treatment with antioxidants reduces the production of pro-inflammatory cytokines and radical oxygen species by Kupffer cells or peritoneal macrophages stimulated with LPS (Bellezzo et al., 1998; Haddad et al., 2002; Kheir-Eldin et al., 2001). A fish oil diet rich in n-3 fatty acids was found to attenuate the reduction of food intake induced by intraperitoneal IL-1β and this effect was associated with a reduced production of prostaglandins (Hellerstein et al., 1989). The effects of such a regimen are apparently a function of the nature of the inflammatory response (Kozak et al., 1997b). When inflammation was induced locally by subcutaneous injection of turpentine, fever, lethargy, anorexia, and body weight decrease were all inhibited in mice fed the fish oil diet. In contrast dietary n-3 fatty acids prevented fever and attenuated the decrease in body weight caused by LPS but did not affect the LPS-induced lethargy and anorexia. In another series of experiments, mice fed a diet supplemented with n-3 fatty acids for 4 weeks were less sensitive to LPS-induced reduction in food-motivated behavior and social exploration than mice fed a diet supplemented with n-6 fatty acids (Watanabe et al., 2004). However, this protective effect
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disappeared when LPS was injected into the lateral ventricle of the brain rather than intraperitoneally, indicating that dietary supplementation affected only the peripheral cytokine compartment. The way polyunsaturated fatty acids modulate cytokine-induced sickness behavior is far from clear since rats fed with the n-3 fatty acid, eicosapentaenoic acid, displayed reduced behavioral response to ICV IL-1β (Song et al., 2004). In the same manner, eicosapentaenoic acid inhibited the detrimental effects of LPS on long-term potentiation both in vitro and in vivo (Kavanagh et al., 2004), confirming that n-3 fatty acids can act in the brain to regulate the production and action of cytokines. Because of its strong association with energy requirement, sickness behavior is likely to vary with the energy demands of the environment (Nelson, 2004). In seasonal species such as the Siberian hamster, immune functions are tuned to day length information. LPS-induced sickness behavior was found to be less pronounced in Siberian hamsters maintained in short day lengths compared to hamsters in long days (Bilbo et al., 2002). This was associated with a lower expression of IL-1β and TNF-α in the hypothalamus in response to systemic LPS (Pyter et al., 2005).
XI. SENSITIZATION OF THE BRAIN CYTOKINE SYSTEM By analogy with allergy, the term sensitization is used to refer to the development, over time, of an exaggerated response of a biological system to a challenge. The challenge can cause a mild response on the first few exposures, but as the sensitization process develops, the response becomes higher with subsequent exposures. Cross-sensitization occurs when the stimulus at the origin of the sensitization process belongs to a different category from the one which the biological system normally responds to. In neurosciences, sensitization refers to a change in behavior or biological response by an organism that is produced by delivering a strong, generally noxious stimulus. As a typical example, repeated injections of the dopaminergic stimulant cocaine result in sensitization of the locomotor response to this drug (Post and Rose, 1976). Exposure to a stressor such as a single epidose of social defeat produces the same result as the repeated exposures to cocaine (Miczek et al., 1999). In the case of cytokines, a single administration of TNF-α to mice resulted in an enhanced behavioral, neurochemical, and pituitary-adrenal response to the same cytokine when it was re-injected 28 days but not 1 day after the initial injection (Hayley et al.,
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2002b). Sensitization occurred only when TNF-α was administered systemically, but not when it was injected into the lateral ventricle of the brain or when the challenge was carried out into the lateral ventricle of the brain of mice that had been initially injected intraperitoneally. Since this sensitization was abolished by antihistaminergic drugs (Hayley et al., 2002a), the possibility that it was not due to TNF-α per se but to the bovine serum albumin carrier added to the cytokine solution was investigated further but turned out to be negative (Anisman et al., 2003). Repeated administration of IL-1β did not induce behavioral sensitization in rats submitted to a two-way conditioned avoidance learning paradigm (Bonaccorso et al., 2003). In the same manner, repeated injections of IFN-α did not result in an enhanced behavioral effect on locomotor activity and food intake (Segall and Crnic, 1990). However, a single administration of IL-1β was able to sensitize the hypothalamic-pituitary-adrenal axis for a period of up to 22 days post IL-1 (Schmidt et al., 2001). This sensitization was manifest when mice were later exposed to novelty, and it was associated with prolonged activation of CRH and CRH-R1 in the paraventricular nucleus of the hypothalamus (Schmidt et al., 2003). Prior administration of IL-2 or IL-6 was also able to sensitize the locomotor response to amphetamine or to dopaminergic stimulants (Zalcman et al., 1999; Zalcman 2001), making cytokines behave as stressors (Anisman et al., 2002a). A low-grade inflammation condition can also sensitize cytokine-induced sickness behavior. The first test of this possibility took place in cerebellar mutant mice (Bluthe et al., 1997a). These animals develop a cerebellar atrophy that is associated with a chronic inflammatory state both at the periphery and in the brain. Cerebellar mutant mice were found to be more sensitive to the behaviorally depressing effects of intraperitoneal (IP) and intracerebroventricular (ICV) administration of LPS and IL-1β (Bluthe et al., 1997a). A similar increased sensitivity to the behavioral effects of IL-1β was observed in pre-diabetic nonobese diabetic mice (Bluthe et al., 1999b). The rationale for this form of sensitization was elaborated by Perry, in the context of brain inflammation and neurodegeneration (Perry, 2004; Perry et al., 2003). Perry gathered experimental and clinical evidence showing that systemic acute inflammation on a background of ongoing inflammation in the brain can be harmful and contribute to the onset or progression of disease. This can even take place in the context of an antiinflammatory profile such as the one occurring in pre-clinical murine prion disease since under the influence of systemic inflammation it rapidly switches
to a pro-inflammatory profile (Combrinck et al., 2002). The key cellular event that underlies sensitization is the priming of microglia by early or subtle pathological changes. Passage of immune signals from the periphery to the brain during the course of a systemic immune activation further activates microglia and results in aggravated signs of sickness. In contrast, an exaggerated sickness response to a systemic immune challenge or to a direct local stimulation can be used to reveal this priming state of the microglia. This has been demonstrated to be the case in aged mice (Godbout et al., 2005) and in type II diabetic mice (O’Connor et al., 2005).
XII. CYTOKINES, DEPRESSION, AND ANXIETY Uncontrolled inflammation or previous sensitization of the brain cytokine network will lead not only to exaggerated sickness behavior, but also to mood disorders and ultimately neuropathology. In this section, the clinical and experimental evidence showing that activation of the brain cytokine network can induce mood disorders will be presented and the mechanisms discussed. A more detailed discussion of the role of cytokines in mood disorders can be found in Chapter 24, “Psychoneuroimmunology of Depressive Disorder: Mechanisms and Clinical Implications,” by Capuron et al.
A. Depressed Mood Caused by Immune Activation in Human Subjects The first studies documenting the depressive effects of cytokines were carried out clinically (Capuron et al., 2000; Capuron et al., 2001a; Capuron et al., 2001b; Raison et al., 2005). These studies reported that whereas all patients responded to the treatment by manifesting behavioral symptoms of sickness, a significant percentage of them also developed mood disorders. These observations were carried out in patients given cytokine immunotherapy (e.g., IFN-α, IL-2) for the treatment of cancer (kidney cancer and melanoma with metastasis) and viral infections such as hepatitis C. The exact clinical presentation of mood disorders varies according to the immunotherapy treatment and the underlying pathology. Cancer patients display relatively pure depressive disorders, with sadness, decreased selfesteem, and psychomotor retardation, whereas hepatitis C patients develop episodes of depression alternating with episodes of manic symptoms, although not severe or long enough to be catego-
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rized as mania. Irritation and anxiety dominate the clinical presentation in these patients (Capuron and Miller, 2004). In all cases, these psychiatric symptoms develop over a background of neurovegetative sickness symptoms, including fatigue, decreased appetite, and sleep disorders. The fact that mood disorders occur only in about one-third of the patients receiving immunotherapy points to the importance of individual vulnerability factors. Patients who have clinically diagnosed depressed mood at baseline, before the initiation of immunotherapy, are more at risk than patients with normal mood scores (Capuron and Ravaud, 1999). The risk of developing a depressive disorder is also higher in patients whose pituitary-adrenal axis response to the first injection of IFNα is more intense (Capuron and Miller, 2004). Whether these features are characteristic of patients who have the usual risk factors for mood disorders or for a differential activation of the innate immune response (e.g., single nucleotide polymorphisms accounting for higher production of pro-inflammatory cytokines or a decreased production of anti-inflammatory cytokines) remains unknown. Similar relationships between immune activation and depressed mood have been observed in conditions of less drastic immune activation. Volunteers injected with Salmonella abortus equi endotoxin developed mild illness symptoms associated with significant increases in anxiety and mood (Reichenberg et al., 2001). Mild inflammatory stimulation caused by typhoid vaccination of student volunteers led to a significant decline in mood without any neurovegetative sign (Strike et al., 2004). This was associated with increased plasma levels of IL-6, and negative changes in mood following vaccination significantly correlated with increases in IL-6 (Wright et al., 2005).
B. Immune Activation and Depressive- and Anxiety-like Behavior in Laboratory Rodents Indirect evidence for an association between inflammation and depression comes from the demonstration that animal models of depression (e.g., olfactory bulbectomized rats or rats submitted to mild chronic stress) display evidence of chronic activation of the innate immune system (Connor et al., 2000; Kubera et al., 1998; Kubera et al., 2001; Mormede et al., 2004). More direct evidence comes from experimental studies showing that peripheral or central administration of pro-inflammatory cytokines induces depressive-like behaviors in laboratory rodents (Avitsur and Yirmiya, 1999; Merali et al., 2003; Yirmiya et al., 1999). These
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behavioral alterations include social withdrawal, increased duration of immobility in the forced swim test, failure to learn to escape from painful electric shocks (learned helplessness), and decreased sensitivity to reward or pleasure (anhedonia). Anhedonia can be evidenced by an increased threshold for a rewarding electrical stimulation in the brain (Anisman et al., 2002b) or a decreased attraction to sweetened solutions (Yirmiya et al., 1999). These behavioral alterations are associated with decreased brain serotoninergic and dopaminergic neurotransmission, as well as some implications for the noradrenergic system. In general, the behavioral and neurochemical alterations that are assumed to model depression in mice and rats are more profound in aged than in young individuals (Onodera et al., 2000; Schulz et al., 2004; Slotkin et al., 1999), which is consistent with the low-grade inflammation status that characterizes aging (see Chapter 17, “Aging, Neuroinflammation, and Behavior,” by Johnson and Godbout, this volume). In the absence of a fully validated animal model of depression, it is important to note that convergent evidence from several behavioral tests together with pharmacological validation (i.e., the observed alterations in behavior must be alleviated by antidepressant treatment) is required before any conclusion on depressive disorders can be reached (Redei et al., 2001; Willner and Mitchell, 2002). Studies on the so-called anhedonic effects of cytokines provide a good illustration of this issue. As pointed out by Merali and colleagues, it is not easy to dissociate the sickness elicited by cytokines, including anorexia, from effects related to anhedonia since both conditions result in a decreased behavioral performance (Merali et al., 2003). In an attempt to reach this goal, they trained rats in a progressive ratio schedule for a sucrose solution reward, in which rats had to progressively increase their rate of responding in order to gain access to the reward. This had already been done in mice by Larson et al. who showed that intraperitoneal administration of IL-1β decreased the breaking point; i.e., IL-1β–treated animals stopped earlier in the sequence than salinetreated mice (Larson et al., 2002). Merali et al. observed the same effect, but in their experiments rats had free access to laboratory chow at the same time they performed on the progressive ratio schedule (Merali et al., 2003). IL-1β decreased both chow consumption and progressive ratio performance. This by itself was not demonstrative of anhedonia, but the observation that chronic fluoxetine treatment attenuated the disturbance of progressive ratio performance but had no effect on reduced chow consumption allowed them to conclude that it is possible to dissociate the anhedonic from the anorexic effects of IL-1β, since the former but
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not the latter one was sensitive to the effects of an antidepressant drug supposed to abrogate anhedonia. Such results do not necessarily imply that reduced preference for a palatable solution in cytokine-treated animals is a measure of anhedonia. In a detailed analysis of the effects of LPS on preference for saccharin and aversion for quinine using a two-bottle test procedure, LPS was found to decrease the preference for saccharin and attenuate the aversion to quinine, on a background of reduced intake of fluid (Aubert and Dantzer, 2005). Taste reactivity, as assessed by scoring of ingestive and aversive taste reaction patterns to separate solutions of sucrose and quinine, was not altered by LPS treatment. However, LPS decreased the ingestive and increased the aversive taste reaction patterns to a mixture of sucrose and quinine. Although the results on taste reaction patterns to sucrose are consistent with those of other studies showing that LPS decreased sucrose intake but did not alter sucrose palatability (CrossMellor et al., 1999), the data on the taste reactivity to the bitter-sweet solution point to an increased finickiness of sick animals that would prevent them from ingesting any potentially toxic compound even when normally tolerated by healthy animals (Aubert and Dantzer, 2005). Most of the studies on the relationships between depressive-like behavior and cytokines have been carried out in rodents injected with cytokines. However, in an effort to model the depression that is associated with coronary artery disease, Grippo et al. assessed the effects of experimental heart failure induced in rats by coronary artery ligation on responses to rewarding electrical brain stimulation in the lateral hypothalamus (Grippo et al., 2003). Heart failure led 7 days later to a rightward shift in the current-response relationship in the brain self-stimulation paradigm, indicative of reduced rewarding properties of the brain stimulation. This effect was prevented by treatment with a TNF-α antagonist administered 24 hours before brain self-stimulation. Another approach to study the possible contribution of cytokines to the pathogenesis of depression is the use of genetic animal models of depression. For instance, the Fawn-Hooded rat is an inbred strain of rats that has been reported to display many of the proposed animal equivalents of depression, including a higher immobility in the forced swim test, and all these features are corrected by antidepressant treatment (Rezvani et al., 2002). Compared to normal Sprague-Dawley rats, Fawn-Hooded rats displayed augmented behavioral and neurochemical responses to IL-1a (Simmons and Broderick, 2005). The possibility that pro-inflammatory cytokines have anxiogenic effects has been investigated using
various tests of anxiety (Anisman and Merali, 1999). In the elevated plus-maze, mice treated with LPS displayed a reduced frequency of open-arm visits, whereas visits to the closed arms were unaffected. Similar effects were obtained in rats treated with ICV IL-1β and TNF-α, but not IL-2 nor IL-6 (Connor et al., 1998). In the light-dark box, LPS increased the tendency to avoid the illuminated region (Anisman and Merali, 1999). These behavioral alterations were not due to motor deficiency since LPS-treated mice escaped very quickly from the open arms and the illuminated compartment when they were directly exposed to them. Acute administration of IL-2 had no obvious anxiogenic effect, whereas chronic IL-2 attenuated exploration. IL-1β had anxiogenic effects at low doses when injected either systemically or centrally, whereas these effects were replaced by a general depression of activity at higher doses. The same effects as those obtained with low doses of IL-1β were observed with TNF-α. Increased levels of anxiety-like behavior in the elevated plus-maze were also observed in mice infected orally with the Gram-negative pathogen Campylobacter jejuni at a dose that induced a subclinical infection but no immune activation, at least based on circulating IL-6 levels (Lyte et al., 1998). In accordance with a positive action of pro-inflammatory cytokines on anxiety, mice overexpressing the IL-1 receptor antagonist behaved as if they are less anxious. Compared to wildtype mice, they displayed higher locomotion and decreased habituation in an open-field test and spent a longer time in the open arms of an elevated plus maze (Oprica et al., 2005). As mentioned in “Behavioral Effects of Cytokines,” administration of bacterial T-cell superantigens was found to suppress food intake, these effects being more apparent when animals were presented with a new palatable solution or when the already familiar food was presented in a novel context (Kusnecov et al., 1999). These effects were therefore interpreted in terms of increased anxiety. Similarly, mice challenged with bacterial superantigens displayed greater reactivity to a novel object introduced into an openfield (Kawashima and Kusnecov, 2002). However, when mice treated with bacterial superantigens were tested in the elevated plus-maze and light-dark box, they showed no sign of anxious-like behavior and actually spent a longer time in the open arms of the plus maze (Rossi-George et al., 2004). An anxiogeniclike effect was observed only when mice tested in the light-dark box had an intervening consumption test prior to exposure to the apparatus. This obviously points to the shortcomings of explanation of the behavioral consequences of immune activation in terms of anxiety.
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C. Activation of Indoleamine 2,3 Dioxygenase As a Likely Intermediate in the Relationship between Cytokines and Depression In cancer patients treated with IFNα and/or IL-2, there is a rapid drop in plasma tryptophan that is accompanied by an increase in plasma kynurenine, a metabolite of tryptophan (Capuron et al., 2002). This increase in the kynurenine-to-tryptophan ratio is characteristic of conditions associated with activation of the indoleamine 2,3 dioxygenase (IDO) enzyme (Widner et al., 2000). This ubiquitous enzyme degrades tryptophan along the kynurenine/quinolinate pathway and is activated by cytokines such as IFNγ and TNF-α (Alberati-Giani et al., 1996; Robinson et al., 2003). Although a causal role of IDO in the pathogenesis of depressive disorders has not yet been demonstrated, the demonstration of a significant positive linear correlation between the drop in circulating tryptophan levels and increasing depressive scores in clinical studies (Capuron et al., 2002) is very suggestive of such a possibility. Indeed, a link between IDO activation and clinical depression has been proposed by various authors (Capuron and Dantzer, 2003; Schiepers et al., 2005; Widner et al., 2000). The hypothesized mechanism for this link is a cytokine-induced increase in IDO activation, thereby reducing tryptophan bioavailability for the synthesis of serotonin, an important neurotransmitter involved in the regulation of mood (Evans et al., 2005; Nemeroff and Vale, 2005; Owens and Nemeroff, 1994). IDO degrades tryptophan to kynurenine, leading to an increase in kynurenine and quinolinic acid and a decrease in tryptophan bioavailability (Figure 11). IDO is expressed systemically in dendritic cells, macrophages, and endothelial cells, but it is also expressed in the central nervous system in endothelial cells, macrophages/microglia, and astrocytes (Burudi et al., 2002; Cross-Mellor et al., 2004; Guillemin et al., 2005; Kwidzinski et al., 2005; Santoso et al., 2002). In the brain, the tryptophan hydroxylase enzyme that adds a hydroxyl radical to tryptophan, converting it into the intermediate product 5-hydroxy-tryptophan, is only 50% saturated with its substrate. Therefore, increasing or decreasing the level of bioavailable tryptophan has an immediate impact on brain serotonin levels (Fernstrom and Wurtman, 1971; Moore et al., 2000; Young and Gauthier, 1981). Acute depletion of tryptophan in normal subjects can be achieved by consumption of a tryptophan-free amino acid drinking solution. When subjects at risk for depression because of a personal or a familial history of depression are submitted to this procedure, they develop larger deteriorations in mood than control
FIGURE 11 Mechanisms of the effects of cytokines on mood. Tryptophan derived from food proteins is transported into the brain for the synthesis of serotonin or 5-hydroxytryptamine. The enzyme indoleamine 2,3 dioxygenase is upregulated in response to pathogenassociated molecular patterns (PAMPs). The resulting degradation of tryptophan along the kynurenine/quinolinic acid pathway makes tryptophan less available for the synthesis of serotonin while generating glutamate receptor ligands.
subjects (Riedel et al., 2002; Sobczak et al., 2002; Van der Does, 2001). These findings are consistent with the serotonin hypothesis of depression (Hirschfeld, 2000a; Hirschfeld, 2000b). Other evidence for serotoninergic abnormalities in depressed patients includes a reduction in cerebrospinal fluid concentrations of the main metabolite of serotonin, 5-hydroxyindolacetic acid (5-HIAA), decreased serotonin uptake and transporter binding sites in platelets, and blunted neuroendocrine responses to serotoninergic drugs (Owens and Nemeroff, 1994). Studies in postmortem tissues and neuroimaging studies in depressed subjects have confirmed that depression is associated with alterations in serotonin receptors and the serotonin transporter (Stockmeier, 2003). The mechanisms of cytokine-induced depression can be studied in acute and chronic animal models of immune activation. Acute administration of LPS or peptidoglycan increased circulating levels of IFNγ and activated peripheral and brain IDO (Figure 12) (Lestage et al., 2002). Inoculation of Bacillus Calmette-Guerin resulted in a sustained elevation of circulating levels of IFNγ and a chronic activation of peripheral and brain IDO, associated with decreases in plasma and brain tryptophan (Figure 13) (Moreau et al., 2005). Both treatments were associated with depressive-like behavior, in the form of increased duration of immobility in the forced swimming test.
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FIGURE 12 Acute peripheral immune stimulation induces IFNγ production and increases IDO activity in the mouse brain. Mice (n = 5 per group) were injected with LPS (0.83 mg/kg) at time 0 and sacrificed at different time intervals to measure IFNγ in the serum and brain IDO. Note that IFNγ peaked at 6 hours post LPS, whereas brain IDO activity peaked at 24 hours post LPS. * p < 0.05, ** p < 0.01, *** p < 0.001. (From Lestage et al., 2002.)
FIGURE 13 Chronic peripheral immune stimulation induces IFNγ production and increases IDO activity in the mouse brain. Mice (n = 6–8 per group) were inoculated intraperitoneally with 107 colony-forming units of Bacillus Calmette-Guerin, an attenuated form of Mycobacterium bovis, before being killed at different time intervals to measure IFNγ in the serum and brain IDO. Note the prolonged increase in peripheral IFNγ levels and brain IDO enzymatic activity. * p < 0.05, ** p < 0.01, *** p < 0.001. (From Moreau et al., 2005.)
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FIGURE 14 Bi-directional interactions between immune events and psychoneuroendocrine states. Various stimuli including pathogen-associated molecular patterns (PAMPs), danger signals, and stress can lead to an activation of the innate immune system, resulting in an increase in peripheral cytokines. This increase is mirrored in the brain. Brain cytokines activate the hypothalamicpituitary-adrenal axis and the neural circuits involved in the regulation of sleep, appetite, metabolism, affect, and cognition. Cortisol downregulates the production and action of cytokines both at the periphery and in the brain. Changes in affect and various physiological functions including metabolism and sleep can alter immunocompetence, which impacts on the microbial load and ultimately the degree of activation of the innate immune system.
XIII. CONCLUSION Pro-inflammatory cytokines are produced at the periphery by activated monocytes and macrophages in response to pathogen-associated molecular patterns. Via their actions in the brain, they are responsible for the occurrence of the non-specific symptoms of sickness, including apathy, social withdrawal, anorexia, cachexia, anhedonia, fatigue, pain, and alterations in cognition and mood (Figure 14). Peripheral immune activation is transmitted to the brain by several communication pathways that include saturable transporters of cytokines across the blood-brain barrier, humoral transmission via the circumventricular organs, and neural transmission via the afferent nerves that innervate the site of the body in which the inflammatory response takes place. This ultimately results in the synthesis and release of pro-inflammatory cytokines in the brain. Centrally produced cytokines act probably by volume transmission on those neural structures that are involved in the control of thermoregulation, metabolism, and behavior, resulting in the development of the brain components of the host response to infection. Glucocorticoids that are released by the adrenal cortex in response to the hypothalamic effects of proinflammatory cytokines regulate the expression and actions of cytokines not only in the periphery, but also
in the brain. When the cytokine system is uncontrolled, its repeated or chronic activation can lead to the development of mood disorders that are dependent on cytokine-induced alterations in the metabolism of tryptophan. These findings open new perspectives on the mechanisms and means of controlling the nonspecific symptoms of sickness such as fatigue, anorexia, and social withdrawal that develop in a wide variety of pathological conditions associated with inflammation and can culminate in pathological alterations in mood and cognition (Dantzer, 2004). Sickness behavior can itself lead to changes in immune competence that regulates the host sensitivity to external and internal pathogens, therefore influencing the degree of activation of the innate immune system and the production of peripheral cytokines (Figure 13). These intricate bidirectional interactions between immune events and psychological states ultimately determine the degree of wellness and therefore provide a potential target for interventions aiming at preserving or restoring well-being.
Acknowledgments Supported by INRA, CNRS, University of Bordeaux 2, and the National Institute of Health (MH 71349 to RD, MH 51569 and AI 50442 to KWK).
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References Alberati-Giani, D., Ricciardi-Castagnoli, P., Kohler, C., and Cesura, A. M. (1996). Regulation of the kynurenine metabolic pathway by interferon-gamma in murine cloned macrophages and microglial cells. J. Neurochem., 66, 996–1004. Alleva, E., Cirulli, F., Bianchi, M., Bondiolotti, G. P., Chiarotti, F., De Acetis, L., and Panerai, A. E. (1998). Behavioural characterization of interleukin-6 overexpressing or deficient mice during agonistic encounters. Eur. J. Neurosci., 10, 3664–3672. Anisman, H., Hayley, S., Turrin, N., and Merali, Z. (2002a). Cytokines as a stressor: implications for depressive illness. Int. J. Neuropsychopharmacol., 5, 357–373. Anisman, H., Kokkinidis, L., and Merali, Z. (2002b). Further evidence for the depressive effects of cytokines: anhedonia and neurochemical changes. Brain Behav. Immun., 16, 544–556. Anisman, H., and Merali, Z. (1999). Anhedonic and anxiogenic effects of cytokine exposure. Adv. Exp. Med. Biol., 461, 199–233. Anisman, H., Turrin, N. P., Merali, Z., and Hayley, S. (2003). Neurochemical sensitization associated with systemic administration of tumor necrosis factor-alpha: adjuvant action in combination with bovine serum albumin. J. Neuroimmunol., 145, 91–102. Armario, A., Hernandez, J., Bluethmann, H., and Hidalgo, J. (1998). IL-6 deficiency leads to increased emotionality in mice: evidence in transgenic mice carrying a null mutation for IL-6. J. Neuroimmunol., 92, 160–169. Aubert, A., and Dantzer, R. (2005). The taste of sickness: lipopolysaccharide-induced finickiness in rats. Physiol. Behav., 84, 437–444. Aubert, A., Goodall, G., and Dantzer, R. (1995). Compared effects of cold ambient temperature and cytokines on macronutrient intake in rats. Physiol. Behav., 57, 869–873. Aubert, A., Goodall, G., Dantzer, R., and Gheusi, G. (1997a). Differential effects of lipopolysaccharide on pup retrieving and nest building in lactating mice. Brain Behav. Immun., 11, 107–118. Aubert, A., Kelley, K. W., and Dantzer, R. (1997b). Differential effect of lipopolysaccharide on food hoarding behavior and food consumption in rats. Brain Behav. Immun., 11, 229–238. Avitsur, R., Cohen, E., and Yirmiya, R. (1997a). Effects of interleukin1 on sexual attractivity in a model of sickness behavior. Physiol. Behav., 63, 25–30. Avitsur, R., Pollak, Y., and Yirmiya, R. (1997b). Administration of interleukin-1 into the hypothalamic paraventricular nucleus induces febrile and behavioral effects. Neuroimmunomodulation, 4, 258–265. Avitsur, R., Pollak, Y., and Yirmiya, R. (1997c). Different receptor mechanisms mediate the effects of endotoxin and interleukin-1 on female sexual behavior. Brain Res., 773, 149–161. Avitsur, R., and Yirmiya, R. (1999). The immunobiology of sexual behavior: gender differences in the suppression of sexual activity during illness. Pharmacol. Biochem. Behav., 64, 787–796. Ban, E., Marquette, C., Sarrieau, A., Fitzpatrick, F., Fillion, G., Milon, G., et al. (1993). Regulation of interleukin-1 receptor expression in mouse brain and pituitary by lipopolysaccharide and glucocorticoids. Neuroendocrinology, 58, 581–587. Ban, E., Milon, G., Prudhomme, N., Fillion, G., and Haour, F. (1991). Receptors for interleukin-1 (alpha and beta) in mouse brain: mapping and neuronal localization in hippocampus. Neuroscience, 43, 21–30. Bandler, R., Keay, K. A., Floyd, N., and Price, J. (2000). Central circuits mediating patterned autonomic activity during active vs. passive emotional coping. Brain Res. Bull., 53, 95–104. Banks, W. A. (2005). Blood-brain barrier transport of cytokines: a mechanism for neuropathology. Curr. Pharm. Des., 11, 973–984. Banks, W. A., Farr, S. A., La Scola, M. E., and Morley, J. E. (2001). Intravenous human interleukin-1alpha impairs memory
processing in mice: dependence on blood-brain barrier transport into posterior division of the septum. J. Pharmacol. Exp. Ther., 299, 536–541. Barak, O., Goshen, I., Ben-Hur, T., Weidenfeld, J., Taylor, A. N., and Yirmiya, R. (2002). Involvement of brain cytokines in the neurobehavioral disturbances induced by HIV-1 glycoprotein120. Brain Res., 933, 98–108. Barton, G. M., and Medzhitov, R. (2003). Toll-like receptor signaling pathways. Science, 300, 1524–1525. Baura, G. D., Foster, D. M., Porte, D., Jr., Kahn, S. E., Bergman, R. N., Cobelli, C., and Schwartz, M. W. (1993). Saturable transport of insulin from plasma into the central nervous system of dogs in vivo. A mechanism for regulated insulin delivery to the brain. J. Clin. Invest., 92, 1824–1830. Bellezzo, J. M., Leingang, K. A., Bulla, G. A., Britton, R. S., Bacon, B. R., and Fox E. S. (1998). Modulation of lipopolysaccharidemediated activation in rat Kupffer cells by antioxidants. J. Lab. Clin. Med., 131, 36–44. Ben-Hur, T., Cialic, R., Itzik, A., Barak, O., Yirmiya, R., and Weidenfeld, J. (2001). A novel permissive role for glucocorticoids in induction of febrile and behavioral signs of experimental herpes simplex virus encephalitis. Neuroscience, 108, 119–127. Berg, B. M., Godbout, J. P., Kelley, K. W., and Johnson, R. W. (2004). Alpha-tocopherol attenuates lipopolysaccharide-induced sickness behavior in mice. Brain Behav. Immun., 18, 149–157. Bertini, R., Bianchi, M., and Ghezzi, P. (1988). Adrenalectomy sensitizes mice to the lethal effects of interleukin 1 and tumor necrosis factor. J. Exp. Med., 167, 1708–1712. Besedovsky, H., del Rey, A., Sorkin, E., and Dinarello, C. A. (1986). Immunoregulatory feedback between interleukin-1 and glucocorticoid hormones. Science, 233, 652–654. Besedovsky, H. O., and del Rey, A. (2000). The cytokine-HPA axis feed-back circuit. Z. Rheumatol., 59 (Suppl 2), II/26–30. Betancur, C., Lledo, A., Borrell, J., and Guaza, C. (1994). Corticosteroid regulation of IL-1 receptors in the mouse hippocampus: effects of glucocorticoid treatment, stress, and adrenalectomy. Neuroendocrinology, 59, 120–128. Bianco, F., Pravettoni, E., Colombo, A., Schenk, U., Moller, T., Matteoli, M., and Verderio, C. (2005). Astrocyte-derived ATP induces vesicle shedding and IL-1 beta release from microglia. J. Immunol., 174, 7268–7277. Bilbo, S. D., Drazen, D. L., Quan, N., He L., and Nelson, R. J. (2002). Short day lengths attenuate the symptoms of infection in Siberian hamsters. Proc. Biol. Sci., 269, 447–454. Blatteis, C. M. (1990). Neuromodulative actions of cytokines. Yale J. Biol. Med., 63, 133–146. Blount, J. D., Metcalfe, N. B., Birkhead, T. R., and Surai, P. F. (2003). Carotenoid modulation of immune function and sexual attractiveness in zebra finches. Science, 300, 125–127. Bluthe, R. M., Castanon, N., Pousset, F., Bristow, A., Ball, C., Lestage, J., et al. (1999a). Central injection of IL-10 antagonizes the behavioural effects of lipopolysaccharide in rats. Psychoneuroendocrinology, 24, 301–311. Bluthe, R. M., Crestani, F., Kelley, K. W., and Dantzer, R. (1992a). Mechanisms of the behavioral effects of interleukin 1. Role of prostaglandins and CRF. Ann. N. Y. Acad. Sci., 650, 268–275. Bluthe, R. M., Dantzer, R., and Kelley, K. W. (1992b). Effects of interleukin-1 receptor antagonist on the behavioral effects of lipopolysaccharide in rat. Brain Res., 573, 318–320. Bluthe, R. M., Frenois, F., Kelley, K. W., and Dantzer, R. (2005). Pentoxifylline and insulin-like growth factor-I (IGF-I) abrogate kainic acid-induced cognitive impairment in mice. J. Neuroimmunol., 169, 50–58. Bluthe, R. M., Jafarian-Tehrani, M., Michaud, B., Haour, F., Dantzer, R., and Homo-Delarche, F. (1999b). Increased sensitivity of pre-
14. Cytokines, Sickness Behavior, and Depression diabetic nonobese diabetic mouse to the behavioral effects of IL1. Brain Behav. Immun., 13, 303–314. Bluthe, R. M., Laye, S., Michaud, B., Combe, C., Dantzer, R., and Parnet, P. (2000a). Role of interleukin-1beta and tumour necrosis factor-alpha in lipopolysaccharide-induced sickness behaviour: a study with interleukin-1 type I receptor-deficient mice. Eur. J. Neurosci., 12, 4447–4456. Bluthe, R. M., Michaud, B., Delhaye-Bouchaud, N., Mariani, J., and Dantzer, R. (1997a). Hypersensitivity of lurcher mutant mice to the depressing effects of lipopolysaccharide and interleukin-1 on behaviour. Neuroreport, 8, 1119–1122. Bluthe, R. M., Michaud, B., Kelley, K. W., and Dantzer, R. (1996a). Vagotomy attenuates behavioural effects of interleukin-1 injected peripherally but not centrally. Neuroreport, 7, 1485–1488. Bluthe, R. M., Michaud, B., Kelley, K. W., and Dantzer, R. (1996b). Vagotomy blocks behavioural effects of interleukin-1 injected via the intraperitoneal route but not via other systemic routes. Neuroreport, 7, 2823–2827. Bluthe, R. M., Michaud, B., Kelley, K. W., and Dantzer. R. (1997b). Cholecystokinin receptors do not mediate the behavioral effects of lipopolysaccharide in mice. Physiol. Behav., 62, 385–389. Bluthe, R. M., Michaud, B., Poli, V., and Dantzer, R. (2000b). Role of IL-6 in cytokine-induced sickness behavior: a study with IL-6 deficient mice. Physiol. Behav., 70, 367–373. Bluthe, R. M., Pawlowski, M., Suarez, S., Parnet, P., Pittman, Q., Kelley, K. W., and Dantzer, R. (1994a). Synergy between tumor necrosis factor alpha and interleukin-1 in the induction of sickness behavior in mice. Psychoneuroendocrinology, 19, 197–207. Bluthe, R. M., Sparber, S., and Dantzer, R. (1992c). Modulation of the behavioural effects of interleukin-1 in mice by nitric oxide. Neuroreport, 3, 207–209. Bluthe, R. M., Walter, V., Parnet, P., Laye, S., Lestage, J., Verrier, D. et al. (1994b). Lipopolysaccharide induces sickness behaviour in rats by a vagal mediated mechanism. C. R. Acad. Sci. III, 317, 499–503. Bolles, R. C. (1970). Species-specific defense reactions and avoidance learning. Psychol. Rev., 77, 32–48. Bonaccorso, S., Maier, S. F., Meltzer, H. Y., and Maes, M. (2003). Behavioral changes in rats after acute, chronic and repeated administration of interleukin-1beta: relevance for affective disorders. J. Affect. Disord., 77, 143–148. Borsody, M. K., and Weiss, J. M. (2005). The subdiaphragmatic vagus nerves mediate activation of locus coeruleus neurons by peripherally administered microbial substances. Neuroscience, 131, 235–245. Breder, C. D., Hazuka, C., Ghayur, T., Klug, C., Huginin, M., Yasuda, K., et al. (1994). Regional induction of tumor necrosis factor alpha expression in the mouse brain after systemic lipopolysaccharide administration. Proc. Natl. Acad. Sci. USA, 91, 11393–11397. Breder, C. D., and Saper, C. B. (1996). Expression of inducible cyclooxygenase mRNA in the mouse brain after systemic administration of bacterial lipopolysaccharide. Brain Res., 713, 64–69. Bret-Dibat, J. L., Bluthe, R. M., Kent, S., Kelley, K. W., and Dantzer, R. (1995). Lipopolysaccharide and interleukin-1 depress foodmotivated behavior in mice by a vagal-mediated mechanism. Brain Behav. Immun., 9, 242–246. Buller, K. M., and Day, T. A. (2002). Systemic administration of interleukin-1beta activates select populations of central amygdala afferents. J. Comp. Neurol., 452, 288–296. Burgess, W., Gheusi, G., Yao, J., Johnson, R. W., Dantzer, R., and Kelley, K. W. (1998). Interleukin-1beta–converting enzymedeficient mice resist central but not systemic endotoxin-induced anorexia. Am. J. Physiol., 274, R1829–1833. Burudi, E. M., Marcondes, M. C., Watry, D. D., Zandonatti, M., Taffe, M. A., and Fox, H. S. (2002). Regulation of indoleamine 2,3-
311
dioxygenase expression in simian immunodeficiency virusinfected monkey brains. J. Virol., 76, 12233–12241. Buttini, M., and Boddeke, H. (1995). Peripheral lipopolysaccharide stimulation induces interleukin-1 beta messenger RNA in rat brain microglial cells. Neuroscience, 65, 523–530. Calapai, G., Mazzaglia, G., Cilia, M., Zingarelli, B., Squadrito, F., and Caputi, A. P. (1994). Mediation by nitric oxide formation in the preoptic area of endotoxin and tumour necrosis factor-induced inhibition of water intake in the rat. Br. J. Pharmacol., 111, 1328–1332. Campbell, I. L., Stalder, A. K., Akwa, Y., Pagenstecher, A., and Asensio, V. C. (1998). Transgenic models to study the actions of cytokines in the central nervous system. Neuroimmunomodulation, 5, 126–135. Cao, C., Matsumura, K., Yamagata, K., and Watanabe, Y. (1996). Endothelial cells of the rat brain vasculature express cyclooxygenase-2 mRNA in response to systemic interleukin-1 beta: a possible site of prostaglandin synthesis responsible for fever. Brain Res., 733, 263–272. Capuron, L., and Dantzer, R. (2003). Cytokines and depression: the need for a new paradigm. Brain Behav. Immun., 17 (Suppl 1), S119–S124. Capuron, L., and Miller, A. H. (2004). Cytokines and psychopathology: lessons from interferon-alpha. Biol. Psychiatry, 56, 819–824. Capuron, L., and Ravaud, A. (1999). Prediction of the depressive effects of interferon alfa therapy by the patient’s initial affective state. N. Engl. J. Med., 340, 1370. Capuron, L., Ravaud, A., and Dantzer, R. (2000). Early depressive symptoms in cancer patients receiving interleukin 2 and/or interferon alfa-2b therapy. J. Clin. Oncol., 18, 2143–2151. Capuron, L., Ravaud, A., and Dantzer, R. (2001a). Timing and specificity of the cognitive changes induced by interleukin-2 and interferon-alpha treatments in cancer patients. Psychosom. Med., 63, 376–386. Capuron, L., Ravaud, A., Gualde, N., Bosmans, E., Dantzer, R., Maes, M., and Neveu, P. J. (2001b). Association between immune activation and early depressive symptoms in cancer patients treated with interleukin-2–based therapy. Psychoneuroendocrinology, 26, 797–808. Capuron, L., Ravaud, A., Neveu, P. J., Miller, A. H., Maes, M., and Dantzer, R. (2002). Association between decreased serum tryptophan concentrations and depressive symptoms in cancer patients undergoing cytokine therapy. Mol. Psychiatry, 7, 468–473. Chauvet, N., Palin, K., Verrier, D., Poole, S., Dantzer, R., and Lestage, J. (2001). Rat microglial cells secrete predominantly the precursor of interleukin-1beta in response to lipopolysaccharide. Eur. J. Neurosci., 14, 609–617. Cirulli. F., De Acetis, L., and Alleva, E. (1998). Behavioral effects of peripheral interleukin-1 administration in adult CD-1 mice: specific inhibition of the offensive components of intermale agonistic behavior. Brain Res., 791, 308–312. Coelho, M. M., Souza, G. E., and Pela, I. R. (1992). Endotoxin-induced fever is modulated by endogenous glucocorticoids in rats. Am. J. Physiol., 263, R423–427. Combrinck, M. I., Perry, V. H., and Cunningham, C. (2002). Peripheral infection evokes exaggerated sickness behaviour in preclinical murine prion disease. Neuroscience, 112, 7–11. Connor, T. J., Harkin, A., Kelly, J. P., and Leonard, B. E. (2000). Olfactory bulbectomy provokes a suppression of interleukin1beta and tumour necrosis factor-alpha production in response to an in vivo challenge with lipopolysaccharide: effect of chronic desipramine treatment. Neuroimmunomodulation, 7, 27–35. Connor, T. J., O’Sullivan, J., Nolan, Y., and Kelly, J. P. (2002). Inhibition of constitutive nitric oxide production increases the severity
312
II. Immune System Effects on Neural and Endocrine Processes and Behavior
of lipopolysaccharide-induced sickness behaviour: a role for TNF-alpha. Neuroimmunomodulation, 10, 367–378. Connor, T. J., Song, C., Leonard, B. E., Merali, Z., and Anisman, H. (1998). An assessment of the effects of central interleukin-1beta, -2, -6, and tumor necrosis factor-alpha administration on some behavioural, neurochemical, endocrine and immune parameters in the rat. Neuroscience, 84, 923–933. Cremona, S., Goujon, E., Kelley, K. W., Dantzer, R., and Parnet, P. (1998). Brain type I but not type II IL-1 receptors mediate the effects of IL-1 beta on behavior in mice. Am. J. Physiol., 274, R735–740. Crestani, F., Seguy, F., and Dantzer, R. (1991). Behavioural effects of peripherally injected interleukin-1, role of prostaglandins. Brain Res., 542, 330–335. Cross-Mellor, S. K., Kavaliers, M., and Ossenkopp, K. P. (2004). Comparing immune activation (lipopolysaccharide) and toxin (lithium chloride)-induced gustatory conditioning: lipopolysaccharide produces conditioned taste avoidance but not aversion. Behav. Brain Res., 148, 11–19. Cross-Mellor, S. K., Kent, W. D., Ossenkopp, K. P., and Kavaliers, M. (1999). Differential effects of lipopolysaccharide and cholecystokinin on sucrose intake and palatability. Am. J. Physiol., 277, R705–715. Cross-Mellor, S. K., Roberts, S., Kavaliers, M., and Ossenkopp, K. P. (2003). Activation of the immune system in rats with lipopolysaccharide reduces voluntary sucrose intake but not intraoral intake. Pharmacol. Biochem. Behav., 76, 153–159. Dantzer, R. (2001). Cytokine-induced sickness behavior: where do we stand? Brain Behav. Immun., 15, 7–24. Dantzer, R. (2004). Innate immunity at the forefront of psychoneuroimmunology. Brain Behav. Immun., 18, 1–6. Dantzer, R., and Bluthe, R. M. (1992). Vasopressin involvement in antipyresis, social communication, and social recognition: a synthesis. Crit. Rev. Neurobiol., 6, 243–255. Dantzer, R., Bluthe, R. M., and Kelley, K. W. (1991). Androgendependent vasopressinergic neurotransmission attenuates interleukin-1–induced sickness behavior. Brain Res., 557, 115–120. Dantzer, R., Gheusi, G., Johnson, R. W., and Kelley, K. W. (1999). Central administration of insulin-like growth factor-1 inhibits lipopolysaccharide-induced sickness behavior in mice. Neuroreport, 10, 289–292. Dantzer, R., and Kelley, K. W. (1989). Stress and immunity: an integrated view of relationships between the brain and the immune system. Life Sci., 44, 1995–2008. Dantzer, R., Konsman, J. P., Bluthe, R. M., and Kelley, K. W. (2000). Neural and humoral pathways of communication from the immune system to the brain: parallel or convergent? Auton. Neurosci., 85, 60–65. Daun, J. M., and McCarthy, D. O. (1993). The role of cholecystokinin in interleukin-1–induced anorexia. Physiol. Behav., 54, 237–241. De La Garza, R., 2nd, Fabrizio, K. R., Radoi, G. E., Vlad, T., and Asnis, G. M. (2004). The non-steroidal anti-inflammatory drug diclofenac sodium attenuates lipopolysaccharide-induced alterations to reward behavior and corticosterone release. Behav. Brain Res., 149, 77–85. Dinarello, C. A. (1998). Interleukin-1, interleukin-1 receptors and interleukin-1 receptor antagonist. Int. Rev. Immunol., 16, 457–499. Dunn, A. J., and Swiergiel, A. H. (2001). The reductions in sweetened milk intake induced by interleukin-1 and endotoxin are not prevented by chronic antidepressant treatment. Neuroimmunomodulation, 9, 163–169. Dunn, A. J., Wang, J., and Ando, T. (1999). Effects of cytokines on cerebral neurotransmission. Comparison with the effects of stress. Adv. Exp. Med. Biol., 461, 117–127.
Ek, M., Kurosawa, M., Lundeberg, T., and Ericsson, A. (1998). Activation of vagal afferents after intravenous injection of interleukin-1beta: role of endogenous prostaglandins. J. Neurosci., 18, 9471–9479. Elmquist, J. K., Breder, C. D., Sherin, J. E., Scammell, T. E., Hickey, W. F., Dewitt, D., and Saper, C. B. (1997). Intravenous lipopolysaccharide induces cyclooxygenase 2–like immunoreactivity in rat brain perivascular microglia and meningeal macrophages. J. Comp. Neurol., 381, 119–129. Elmquist, J. K., Scammell, T. E., Jacobson, C. D., and Saper, C. B. (1996). Distribution of Fos-like immunoreactivity in the rat brain following intravenous lipopolysaccharide administration. J. Comp. Neurol., 371, 85–103. Ericsson, A., Kovacs, K. J., and Sawchenko, P. E. (1994). A functional anatomical analysis of central pathways subserving the effects of interleukin-1 on stress-related neuroendocrine neurons. J. Neurosci., 14, 897–913. Ericsson, A., Liu, C., Hart, R. P., and Sawchenko, P. E. (1995). Type 1 interleukin-1 receptor in the rat brain: distribution, regulation, and relationship to sites of IL-1–induced cellular activation. J. Comp. Neurol., 361, 681–698. Evans, D. L., Charney, D. S., Lewis, L., Golden, R. N., Gorman, J. M., Krishnan, K. R., et al. (2005). Mood disorders in the medically ill: scientific review and recommendations. Biol. Psychiatry, 58, 175–189. Faggioni, R., Fantuzzi, G., Fuller, J., Dinarello, C. A., Feingold, K. R., and Grunfeld, C. (1998). IL-1 beta mediates leptin induction during inflammation. Am. J. Physiol., 274, R204–208. Faggioni, R., Fuller, J., Moser, A., Feingold, K. R., and Grunfeld, C. (1997). LPS-induced anorexia in leptin-deficient (ob/ob) and leptin receptor-deficient (db/db) mice. Am. J. Physiol., 273, R181–186. Faivre, B., Gregoire, A., Preault, M., Cezilly, F., and Sorci, G. (2003). Immune activation rapidly mirrored in a secondary sexual trait. Science, 300, 103. Fernstrom, J. D., and Wurtman, R. J. (1971). Brain serotonin content: physiological dependence on plasma tryptophan levels. Science, 173, 149–152. Ferrari, D., Chiozzi, P., Falzoni, S., Hanau, S., and Di Virgilio, F. (1997). Purinergic modulation of interleukin-1 beta release from microglial cells stimulated with bacterial endotoxin. J. Exp. Med., 185, 579–582. Ferri, C. C., and Ferguson, A. V. (2005). Prostaglandin E2 mediates cellular effects of interleukin-1beta on parvocellular neurones in the paraventricular nucleus of the hypothalamus. J. Neuroendocrinol., 17, 498–508. Ferri, C. C., Yuill, E. A., and Ferguson, A. V. (2005). Interleukin-1beta depolarizes magnocellular neurons in the paraventricular nucleus of the hypothalamus through prostaglandin-mediated activation of a non selective cationic conductance. Regul. Pept., 129, 63–71. Finck, B. N., Kelley, K. W., Dantzer, R., and Johnson, R. W. (1998). In vivo and in vitro evidence for the involvement of tumor necrosis factor-alpha in the induction of leptin by lipopolysaccharide. Endocrinology, 139, 2278–2283. Fiore, M., Alleva, E., Probert, L., Kollias, G., Angelucci, F., and Aloe, L. (1998). Exploratory and displacement behavior in transgenic mice expressing high levels of brain TNF-alpha. Physiol. Behav., 63, 571–576. Francis, J., MohanKumar, P. S., MohanKumar, S. M., and Quadri, S. K. (1999). Systemic administration of lipopolysaccharide increases plasma leptin levels: blockade by soluble interleukin-1 receptor. Endocrine, 10, 291–295. Gabellec, M. M., Jafarian-Tehrani, M., Griffais, R., and Haour, F. (1996). Interleukin-1 receptor accessory protein transcripts in the
14. Cytokines, Sickness Behavior, and Depression brain and spleen: kinetics after peripheral administration of bacterial lipopolysaccharide in mice. Neuroimmunomodulation, 3, 304–309. Gatti, S., and Bartfai, T. (1993). Induction of tumor necrosis factoralpha mRNA in the brain after peripheral endotoxin treatment: comparison with interleukin-1 family and interleukin-6. Brain Res., 624, 291–294. Godbout, J. P., Chen, J., Abraham, J., Richwine, A. F., Berg, B. M., Kelley, K. W., and Johnson, R. W. (2005). Exaggerated neuroinflammation and sickness behavior in aged mice following activation of the peripheral innate immune system. FASEB J., 19, 1329–1331. Goehler, L. E., Busch, C. R., Tartaglia, N., Relton, J., Sisk, D., Maier, S. F., and Watkins, L. R. (1995). Blockade of cytokine induced conditioned taste aversion by subdiaphragmatic vagotomy: further evidence for vagal mediation of immune-brain communication. Neurosci. Lett., 185, 163–166. Goehler, L. E., Gaykema, R. P., Hansen, M. K., Anderson, K., Maier, S. F., and Watkins, L. R. (2000). Vagal immune-to-brain communication: a visceral chemosensory pathway. Auton. Neurosci., 85, 49–59. Goehler, L. E., Gaykema, R. P., Nguyen, K. T., Lee, J. E., Tilders, F. J., Maier, S. F., and Watkins, L. R. (1999). Interleukin-1beta in immune cells of the abdominal vagus nerve: a link between the immune and nervous systems? J. Neurosci., 19, 2799–2806. Goehler, L. E., Relton, J. K., Dripps, D., Kiechle, R., Tartaglia, N., Maier, S. F., and Watkins, L. R. (1997). Vagal paraganglia bind biotinylated interleukin-1 receptor antagonist: a possible mechanism for immune-to-brain communication. Brain Res. Bull., 43, 357–364. Goujon, E., Parnet, P., Aubert, A., Goodall, G., and Dantzer, R. (1995a). Corticosterone regulates behavioral effects of lipopolysaccharide and interleukin-1 beta in mice. Am. J. Physiol., 269, R154–159. Goujon, E., Parnet, P., Cremona, S., and Dantzer, R. (1995b). Endogenous glucocorticoids down regulate central effects of interleukin-1 beta on body temperature and behaviour in mice. Brain Res., 702, 173–180. Goujon, E., Parnet, P., Laye, S., Combe, C., and Dantzer, R. (1996). Adrenalectomy enhances pro-inflammatory cytokines gene expression, in the spleen, pituitary and brain of mice in response to lipopolysaccharide. Brain Res. Mol. Brain Res., 36, 53–62. Goujon, E., Parnet, P., Laye, S., Combe, C., Kelley, K. W., and Dantzer, R. (1995c). Stress downregulates lipopolysaccharideinduced expression of proinflammatory cytokines in the spleen, pituitary, and brain of mice. Brain Behav. Immun., 9, 292–303. Greenfeder, S. A., Nunes, P., Kwee, L., Labow, M., Chizzonite, R. A., and Ju, G. (1995). Molecular cloning and characterization of a second subunit of the interleukin 1 receptor complex. J. Biol. Chem., 270, 13757–13765. Grippo, A. J., Francis, J., Weiss, R. M., Felder, R. B., and Johnson, A. K. (2003). Cytokine mediation of experimental heart failureinduced anhedonia. Am. J. Physiol. Regul. Integr. Comp. Physiol., 284, R666–673. Grunfeld, C., and Feingold, K. R. (1996). Regulation of lipid metabolism by cytokines during host defense. Nutrition, 12, S24–26. Guillemin, G. J., Smythe, G., Takikawa, O., and Brew, B. J. (2005). Expression of indoleamine 2,3-dioxygenase and production of quinolinic acid by human microglia, astrocytes, and neurons. Glia., 49, 15–23. Haddad, J. J., Safieh-Garabedian, B., Saade, N. E., and Lauterbach, R. (2002). Inhibition of glutathione-related enzymes augments LPS-mediated cytokine biosynthesis: involvement of an IkappaB/ NF-kappaB-sensitive pathway in the alveolar epithelium. Int. Immunopharmacol., 2, 1567–1583.
313
Hansen, M. K., Daniels, S., Goehler, L. E., Gaykema, R. P., Maier, S. F., and Watkins, L. R. (2000a). Subdiaphragmatic vagotomy does not block intraperitoneal lipopolysaccharide-induced fever. Auton. Neurosci., 85, 83–87. Hansen, M. K., Nguyen, K. T., Fleshner, M., Goehler, L. E., Gaykema, R. P., Maier, S. F., and Watkins, L. R. (2000b). Effects of vagotomy on serum endotoxin, cytokines, and corticosterone after intraperitoneal lipopolysaccharide. Am. J. Physiol. Regul. Integr. Comp. Physiol., 278, R331–336. Hansen, M. K., Nguyen, K. T., Goehler, L. E., Gaykema, R. P., Fleshner, M., Maier, S. F., and Watkins, L. R. (2000c). Effects of vagotomy on lipopolysaccharide-induced brain interleukin1beta protein in rats. Auton. Neurosci., 85, 119–126. Hansen, M. K., Taishi, P., Chen, Z., and Krueger, J. M. (1998). Vagotomy blocks the induction of interleukin-1beta (IL-1beta) mRNA in the brain of rats in response to systemic IL-1beta. J. Neurosci., 18, 2247–2253. Hart, B. L. (1988). Biological basis of the behavior of sick animals. Neurosci. Biobehav. Rev., 12, 123–137. Hassanain, M., Bhatt, S., Zalcman, S., and Siegel, A. (2005). Potentiating role of interleukin-1beta (IL-1beta) and IL-1beta type 1 receptors in the medial hypothalamus in defensive rage behavior in the cat. Brain Res., 1048, 1–11. Hayley, S., Kelly, O., and Anisman, H. (2002a). Murine tumor necrosis factor-alpha sensitizes plasma corticosterone activity and the manifestation of shock: modulation by histamine. J. Neuroimmunol., 131, 60–69. Hayley, S., Wall, P., and Anisman, H. (2002b). Sensitization to the neuroendocrine, central monoamine and behavioural effects of murine tumor necrosis factor-alpha: peripheral and central mechanisms. Eur. J. Neurosci., 15, 1061–1076. Hellerstein, M. K., Meydani, S. N., Meydani, M., Wu, K., and Dinarello, C. A. (1989). Interleukin-1–induced anorexia in the rat. Influence of prostaglandins. J. Clin. Invest., 84, 228–235. Herkenham, M., Lee, H. Y., and Baker, R. A. (1998). Temporal and spatial patterns of c-fos mRNA induced by intravenous interleukin-1, a cascade of non-neuronal cellular activation at the bloodbrain barrier. J. Comp. Neurol., 400, 175–196. Hetier, E., Ayala, J., Bousseau, A., and Prochiantz, A. (1991). Modulation of interleukin-1 and tumor necrosis factor expression by beta-adrenergic agonists in mouse ameboid microglial cells. Exp. Brain Res., 86, 407–413. Hirschfeld, R. M. (2000a). Antidepressants in long-term therapy: a review of tricyclic antidepressants and selective serotonin reuptake inhibitors. Acta Psychiatr. Scand Suppl., 403, 35–38. Hirschfeld, R. M. (2000b). History and evolution of the monoamine hypothesis of depression. J. Clin. Psychiatry, 61 (Suppl 6), 4–6. Hosoi, T., Okuma, Y., Wada, S., and Nomura, Y. (2003). Inhibition of leptin-induced IL-1beta expression by glucocorticoids in the brain. Brain Res., 969, 95–101. Jhou, T. (2005). Neural mechanisms of freezing and passive aversive behaviors. J. Comp. Neurol., 493, 111–114. Johnson, P. M., Vogt, S. K., Burney, M. W., and Muglia, L. J. (2002). COX-2 inhibition attenuates anorexia during systemic inflammation without impairing cytokine production. Am. J. Physiol. Endocrinol. Metab., 282, E650–656. Kakucska, I., Qi, Y., Clark, B. D., and Lechan, R. M. (1993). Endotoxin-induced corticotropin-releasing hormone gene expression in the hypothalamic paraventricular nucleus is mediated centrally by interleukin-1. Endocrinology, 133, 815–821. Kanaan, S. A., Poole, S., Saade, N. E., Jabbur, S., and SafiehGarabedian, B. (1998). Interleukin-10 reduces the endotoxininduced hyperalgesia in mice. J. Neuroimmunol., 86, 142–150. Kaneta, T., and Kusnecov, A. W. (2005). The role of central corticotropin-releasing hormone in the anorexic and endocrine effects
314
II. Immune System Effects on Neural and Endocrine Processes and Behavior
of the bacterial T cell superantigen, Staphylococcal enterotoxin A. Brain Behav. Immun., 19, 138–146. Kavanagh, T., Lonergan, P. E., and Lynch, M. A. (2004). Eicosapentaenoic acid and gamma-linolenic acid increase hippocampal concentrations of IL-4 and IL-10 and abrogate lipopolysaccharide-induced inhibition of long-term potentiation. Prostaglandins Leukot. Essent. Fatty Acids, 70, 391–397. Kawashima, N., and Kusnecov, A. W. (2002). Effects of staphylococcal enterotoxin A on pituitary-adrenal activation and neophobic behavior in the C57BL/6 mouse. J. Neuroimmunol., 123, 41–49. Kent, S., Bluthe, R. M., Dantzer, R., Hardwick, A. J., Kelley, K. W., Rothwell, N. J., and Vannice, J. L. (1992a). Different receptor mechanisms mediate the pyrogenic and behavioral effects of interleukin 1. Proc. Natl. Acad. Sci. USA, 89, 9117–9120. Kent, S., Bluthe, R. M., Kelley, K. W., and Dantzer, R. (1992b). Sickness behavior as a new target for drug development. Trends Pharmacol. Sci., 13, 24–28. Kent, S., Bret-Dibat, J. L., Kelley, K. W., and Dantzer, R. (1996). Mechanisms of sickness-induced decreases in food-motivated behavior. Neurosci. Biobehav. Rev., 20, 171–175. Kent, S., Kelley, K. W., and Dantzer, R. (1992c). Effects of lipopolysaccharide on food-motivated behavior in the rat are not blocked by an interleukin-1 receptor antagonist. Neurosci. Lett., 145, 83–86. Kent, S., Rodriguez, F., Kelley, K. W., and Dantzer, R. (1994). Reduction in food and water intake induced by microinjection of interleukin-1 beta in the ventromedial hypothalamus of the rat. Physiol. Behav., 56, 1031–1036. Kheir-Eldin, A. A., Motawi, T. K., Gad, M. Z., and Abd-ElGawad, H. M. (2001). Protective effect of vitamin E, beta-carotene and N-acetylcysteine from the brain oxidative stress induced in rats by lipopolysaccharide. Int. J. Biochem. Cell Biol., 33, 475–482. Klir, J. J., McClellan, J. L., and Kluger, M. J. (1994). Interleukin-1 beta causes the increase in anterior hypothalamic interleukin-6 during LPS-induced fever in rats. Am. J. Physiol., 266, R1845–1848. Kluger, M. J. (1991). Fever: role of pyrogens and cryogens. Physiol. Rev., 71, 93–127. Konsman, J. P., Kelley, K., and Dantzer, R. (1999). Temporal and spatial relationships between lipopolysaccharide-induced expression of Fos, interleukin-1beta and inducible nitric oxide synthase in rat brain. Neuroscience, 89, 535–548. Konsman, J. P., Luheshi, G. N., Bluthe, R. M., and Dantzer, R. (2000a). The vagus nerve mediates behavioural depression, but not fever, in response to peripheral immune signals; a functional anatomical analysis. Eur. J. Neurosci., 12, 4434–4446. Konsman, J. P., Parnet, P., and Dantzer, R. (2002). Cytokine-induced sickness behaviour: mechanisms and implications. Trends Neurosci., 25, 154–159. Konsman, J. P., Tridon, V., and Dantzer, R. (2000b). Diffusion and action of intracerebroventricularly injected interleukin-1 in the CNS. Neuroscience, 101, 957–967. Konsman, J. P., Vigues, S., Mackerlova, L., Bristow, A., and Blomqvist, A. (2004). Rat brain vascular distribution of interleukin-1 type-1 receptor immunoreactivity: relationship to patterns of inducible cyclooxygenase expression by peripheral inflammatory stimuli. J. Comp. Neurol., 472, 113–129. Kozak, W., Poli, V., Soszynski, D., Conn, C. A., Leon, L. R., and Kluger, M. J. (1997a). Sickness behavior in mice deficient in interleukin-6 during turpentine abscess and influenza pneumonitis. Am. J. Physiol., 272, R621–630. Kozak, W., Soszynski, D., Rudolph, K., Conn, C. A., and Kluger, M. J. (1997b). Dietary n-3 fatty acids differentially affect sickness behavior in mice during local and systemic inflammation. Am. J. Physiol., 272, R1298–1307.
Kubera, M., Basta-Kaim, A., Holan, V., Simbirtsev, A., Roman, A., Pigareva, N., et al. (1998). Effect of mild chronic stress, as a model of depression, on the immunoreactivity of C57BL/6 mice. Int. J. Immunopharmacol., 20, 781–789. Kubera, M., Maes, M., Holan, V., Basta-Kaim, A., Roman, A., and Shani, J. (2001). Prolonged desipramine treatment increases the production of interleukin-10, an anti-inflammatory cytokine, in C57BL/6 mice subjected to the chronic mild stress model of depression. J. Affect Disord., 63, 171–178. Kurumaji, A., Umino, A., Tanami, M., Ito, A., Asakawa, M., and Nishikawa, T. (2003). Distribution of anxiogenic-induced c-Fos in the forebrain regions of developing rats. J. Neural Transm., 110, 1161–1168. Kusnecov, A. W., and Goldfarb, Y. (2005). Neural and behavioral responses to systemic immunologic stimuli: a consideration of bacterial T cell superantigens. Curr. Pharm. Des., 11, 1039–1046. Kusnecov, A. W., Liang, R., and Shurin, G. (1999). T-lymphocyte activation increases hypothalamic and amygdaloid expression of CRH mRNA and emotional reactivity to novelty. J. Neurosci., 19, 4533–4543. Kwidzinski, E., Bunse, J., Aktas, O., Richter, D., Mutlu, L., Zipp, F., et al. (2005). Indolamine 2,3-dioxygenase is expressed in the CNS and down-regulates autoimmune inflammation. FASEB J., 19, 1347–1349. Lacroix, S., and Rivest, S. (1998). Effect of acute systemic inflammatory response and cytokines on the transcription of the genes encoding cyclooxygenase enzymes (COX-1 and COX-2) in the rat brain. J. Neurochem., 70, 452–466. Langhans, W., Harlacher, R., Balkowski, G., and Scharrer, E. (1990). Comparison of the effects of bacterial lipopolysaccharide and muramyl dipeptide on food intake. Physiol. Behav., 47, 805–813. Langhans, W., Harlacher, R., and Scharrer, E. (1989). Verapamil and indomethacin attenuate endotoxin-induced anorexia. Physiol. Behav., 46, 535–539. Larson, S. J., Romanoff, R. L., Dunn, A. J., and Glowa, J. R. (2002). Effects of interleukin-1beta on food-maintained behavior in the mouse. Brain Behav. Immun., 16, 398–410. Laye, S., Bluthe, R. M., Kent, S., Combe, C., Medina, C., Parnet, P., et al. (1995). Subdiaphragmatic vagotomy blocks induction of IL-1 beta mRNA in mice brain in response to peripheral LPS. Am. J. Physiol., 268, R1327–1331. Laye, S., Gheusi, G., Cremona, S., Combe, C., Kelley, K., Dantzer, R., and Parnet, P. (2000). Endogenous brain IL-1 mediates LPSinduced anorexia and hypothalamic cytokine expression. Am. J. Physiol. Regul. Integr. Comp. Physiol., 279, R93–98. Laye, S., Goujon, E., Combe, C., VanHoy, R., Kelley, K. W., Parnet, P., and Dantzer, R. (1996). Effects of lipopolysaccharide and glucocorticoids on expression of interleukin-1 beta converting enzyme in the pituitary and brain of mice. J. Neuroimmunol., 68, 61–66. Laye, S., Parnet, P., Goujon, E., and Dantzer, R. (1994). Peripheral administration of lipopolysaccharide induces the expression of cytokine transcripts in the brain and pituitary of mice. Brain Res. Mol. Brain Res., 27, 157–162. Lee, S. W., Tsou, A. P., Chan, H., Thomas, J., Petrie, K., Eugui, E. M., and Allison, A. C. (1988). Glucocorticoids selectively inhibit the transcription of the interleukin 1 beta gene and decrease the stability of interleukin 1 beta mRNA. Proc. Natl. Acad. Sci. USA, 85, 1204–1208. LeMay, L. G., Vander, A. J., and Kluger, M. J. (1990). The effects of psychological stress on plasma interleukin-6 activity in rats. Physiol. Behav., 47, 957–961. Lenczowski, M. J., Bluthe, R. M., Roth, J., Rees, G. S., Rushforth, D. A., van Dam, A. M., et al. (1999). Central administration of rat
14. Cytokines, Sickness Behavior, and Depression IL-6 induces HPA activation and fever but not sickness behavior in rats. Am. J. Physiol., 276, R652–658. Leon, L. R., Kozak, W., Rudolph, K., and Kluger, M. J. (1999). An antipyretic role for interleukin-10 in LPS fever in mice. Am. J. Physiol., 276, R81–89. Lestage, J., Verrier, D., Palin, K., and Dantzer, R. (2002). The enzyme indoleamine 2,3-dioxygenase is induced in the mouse brain in response to peripheral administration of lipopolysaccharide and superantigen. Brain. Behav. Immun., 16, 596–601. Linthorst, A. C., Flachskamm, C., Holsboer, F., and Reul, J. M. (1995a). Intraperitoneal administration of bacterial endotoxin enhances noradrenergic neurotransmission in the rat preoptic area: relationship with body temperature and hypothalamicpituitary-adrenocortical axis activity. Eur. J. Neurosci., 7, 2418–2430. Linthorst, A. C., Flachskamm, C., Holsboer, F., and Reul, J. M. (1996). Activation of serotonergic and noradrenergic neurotransmission in the rat hippocampus after peripheral administration of bacterial endotoxin: involvement of the cyclo-oxygenase pathway. Neuroscience, 72, 989–997. Linthorst, A. C., Flachskamm, C., Muller-Preuss, P., Holsboer, F., and Reul, J. M. (1995b). Effect of bacterial endotoxin and interleukin-1 beta on hippocampal serotonergic neurotransmission, behavioral activity, and free corticosterone levels: an in vivo microdialysis study. J. Neurosci., 15, 2920–2934. Linthorst, A. C., and Reul, J. M. (1999). Inflammation and brain function under basal conditions and during long-term elevation of brain corticotropin-releasing hormone levels. Adv. Exp. Med. Biol., 461, 129–152. Liu, C., Chalmers, D., Maki, R., and De Souza, E. B. (1996). Rat homolog of mouse interleukin-1 receptor accessory protein: cloning, localization and modulation studies. J. Neuroimmunol., 66, 41–48. Luheshi, G. N., Bluthe, R. M., Rushforth, D., Mulcahy, N., Konsman, J. P., Goldbach, M., and Dantzer, R. (2000). Vagotomy attenuates the behavioural but not the pyrogenic effects of interleukin-1 in rats. Auton. Neurosci., 85, 127–132. Luheshi, G. N., Gardner, J. D., Rushforth, D. A., Loudon, A. S., and Rothwell, N. J. (1999). Leptin actions on food intake and body temperature are mediated by IL-1. Proc. Natl. Acad. Sci. USA, 96, 7047–7052. Lyte, M., Varcoe, J. J., and Bailey, M. T. (1998). Anxiogenic effect of subclinical bacterial infection in mice in the absence of overt immune activation. Physiol. Behav., 65, 63–68. Marquette, C., van Dam, A. M., Ban, E., Laniece, P., CrumeyrolleArias, M., Fillion, G., et al. (1995). Rat interleukin-1 beta binding sites in rat hypothalamus and pituitary gland. Neuroendocrinology, 62, 362–369. Marvel, F. A., Chen, C. C., Badr, N., Gaykema, R. P., and Goehler, L. E. (2004). Reversible inactivation of the dorsal vagal complex blocks lipopolysaccharide-induced social withdrawal and c-Fos expression in central autonomic nuclei. Brain Behav. Immun., 18, 123–134. McClellan, J. L., Klir, J. J., Morrow, L. E., and Kluger, M. J. (1994). Central effects of glucocorticoid receptor antagonist RU-38486 on lipopolysaccharide and stress-induced fever. Am. J. Physiol., 267, R705–711. Merali, Z., Brennan, K., Brau, P., and Anisman, H. (2003). Dissociating anorexia and anhedonia elicited by interleukin-1beta: antidepressant and gender effects on responding for “free chow” and “earned” sucrose intake. Psychopharmacology (Berl), 165, 413–418. Miczek, K. A., Nikulina, E., Kream, R. M., Carter, G., and Espejo, E. F. (1999). Behavioral sensitization to cocaine after a brief social
315
defeat stress: c-fos expression in the PAG. Psychopharmacology (Berl), 141, 225–234. Miller, N. E. (1964). Some psychophysiological studies of motivation and of the behavioral effects of illness. Bulletin of the British Psychology Society, 17, 1–20. Minami, M., Kuraishi, Y., Yamaguchi, T., Nakai, S., Hirai, Y., and Satoh, M. (1991). Immobilization stress induces interleukin-1 beta mRNA in the rat hypothalamus. Neurosci. Lett., 123, 254–256. MohanKumar, S. M., MohanKumar, P. S., and Quadri, S. K. (1999). Lipopolysaccharide-induced changes in monoamines in specific areas of the brain: blockade by interleukin-1 receptor antagonist. Brain Res., 824, 232–237. Moore, P., Landolt, H. P., Seifritz, E., Clark, C., Bhatti, T., Kelsoe, J., et al. (2000). Clinical and physiological consequences of rapid tryptophan depletion. Neuropsychopharmacology, 23, 601–622. Moreau, M., Lestage, J., Verrier, D., Mormede, C., Kelley, K. W., Dantzer, R., and Castanon, N. (2005). Bacille Calmette-Guerin inoculation induces chronic activation of peripheral and brain indoleamine 2,3-dioxygenase in mice. J. Infect. Dis., 192, 537–544. Mormede, C., Palin, K., Kelley, K. W., Castanon, N., and Dantzer, R. (2004). Conditioned taste aversion with lipopolysaccharide and peptidoglycan does not activate cytokine gene expression in the spleen and hypothalamus of mice. Brain Behav. Immun., 18, 186–200. Morrow, L. E., McClellan, J. L., Conn, C. A., and Kluger, M. J. (1993). Glucocorticoids alter fever and IL-6 responses to psychological stress and to lipopolysaccharide. Am. J. Physiol., 264, R1010–1016. Nadeau, S., and Rivest, S. (2003). Glucocorticoids play a fundamental role in protecting the brain during innate immune response. J. Neurosci., 23, 5536–5544. Nadjar, A., Combe, C., Laye, S., Tridon, V., Dantzer, R., Amedee, T., and Parnet, P. (2003). Nuclear factor kappaB nuclear translocation as a crucial marker of brain response to interleukin-1. A study in rat and interleukin-1 type I deficient mouse. J. Neurochem., 87, 1024–1036. Nadjar, A., Tridon, V., May, M. J., Ghosh, S., Dantzer, R., Amedee, T., and Parnet, P. (2005). NFkappaB activates in vivo the synthesis of inducible COX-2 in the brain. J. Cereb. Blood Flow Metab., 25, 1047–1059. Nava, F., Calapai, G., Facciola, G., Cuzzocrea, S., Marciano, M. C., De Sarro, A., and Caputi, A. P. (1997). Effects of interleukin-10 on water intake, locomotory activity, and rectal temperature in rat treated with endotoxin. Int. J. Immunopharmacol., 19, 31–38. Nelson, R. J. (2004). Seasonal immune function and sickness responses. Trends Immunol., 25, 187–192. Nemeroff, C. B., and Vale, W. W. (2005). The neurobiology of depression: inroads to treatment and new drug discovery. J. Clin. Psychiatry, 66 (Suppl 7), 5–13. Nguyen, K. T., Deak, T., Will, M. J., Hansen, M. K., Hunsaker, B. N., Fleshner, M., et al. (2000). Timecourse and corticosterone sensitivity of the brain, pituitary, and serum interleukin-1beta protein response to acute stress. Brain Res., 859, 193–201. O’Connor, J. C., Satpathy, A., Hartman, M. E., Horvath, E. M., Kelley, K. W., Dantzer, R., et al. (2005). IL-1beta–mediated innate immunity is amplified in the db/db mouse model of type 2 diabetes. J. Immunol., 174, 4991–4997. Onodera, T., Watanabe, R., Tha, K. K., Hayashi, Y., Murayama, T., Okuma, Y., et al. (2000). Depressive behavior and alterations in receptors for dopamine and 5-hydroxytryptamine in the brain of the senescence accelerated mouse. (SAM)-P10. Jpn. J. Pharmacol., 83, 312–318.
316
II. Immune System Effects on Neural and Endocrine Processes and Behavior
Oprica, M., Zhu, S., Goiny, M., Pham, T. M., Mohammed, A. H., Winblad, B., et al. (2005). Transgenic overexpression of interleukin-1 receptor antagonist in the CNS influences behaviour, serum corticosterone and brain monoamines. Brain Behav. Immun., 19, 223–234. Owens, M. J., and Nemeroff, C. B. (1994). Role of serotonin in the pathophysiology of depression: focus on the serotonin transporter. Clin. Chem., 40, 288–295. Owens, T., Renno, T., Taupin, V., and Krakowski, M. (1994). Inflammatory cytokines in the brain: does the CNS shape immune responses? Immunol. Today, 15, 566–571. Parnet, P., Amindari, S., Wu, C., Brunke-Reese, D., Goujon, E., Weyhenmeyer, J. A., et al. (1994). Expression of type I and type II interleukin-1 receptors in mouse brain. Brain Res. Mol. Brain Res., 27, 63–70. Pauli, S., Linthorst, A. C., and Reul, J. M. (1998). Tumour necrosis factor-alpha and interleukin-2 differentially affect hippocampal serotonergic neurotransmission, behavioural activity, body temperature and hypothalamic-pituitary-adrenocortical axis activity in the rat. Eur. J. Neurosci., 10, 868–878. Perry, V. H. (2004). The influence of systemic inflammation on inflammation in the brain: implications for chronic neurodegenerative disease. Brain Behav. Immun., 18, 407–413. Perry, V. H., Newman, T. A., and Cunningham, C. (2003). The impact of systemic infection on the progression of neurodegenerative disease. Nat. Rev. Neurosci., 4, 103–112. Petitto, J. M., McCarthy, D. B., Rinker, C. M., Huang, Z., and Getty, T. (1997). Modulation of behavioral and neurochemical measures of forebrain dopamine function in mice by species-specific interleukin-2. J. Neuroimmunol., 73, 183–190. Phelps, E. A., and Ledoux, J. E. (2005). Contributions of the amygdala to emotion processing: from animal models to human behavior. Neuron, 48, 175–187. Plata-Salaman, C., and Turrin, N. (1999). Cytokine action in the brain. Mol. Psychiatry, 4, 302. Plata-Salaman, C. R. (1995). Cytokines and feeding suppression: an integrative view from neurologic to molecular levels. Nutrition, 11, 674–677. Plata-Salaman, C. R. (1998). Cytokines and anorexia: a brief overview. Semin. Oncol., 25, 64–72. Plata-Salaman, C. R. (1999). 1998 Curt P. Richter Award. Brain mechanisms in cytokine-induced anorexia. Psychoneuroendocrinology, 24, 25–41. Plata-Salaman, C. R., Oomura, Y., and Kai, Y. (1988). Tumor necrosis factor and interleukin-1 beta: suppression of food intake by direct action in the central nervous system. Brain Res., 448, 106–114. Plata-Salaman, C. R., Sonti, G., Borkoski, J. P., Wilson, C. D., and French-Mullen, J. M. B. (1996). Anorexia induced by chronic central administration of cytokines at estimated pathophysiological concentrations. Physiol. Behav., 60, 867–875. Porter, M. H., Hrupka, B. J., Langhans, W., and Schwartz, G. J. (1998). Vagal and splanchnic afferents are not necessary for the anorexia produced by peripheral IL-1beta, LPS, and MDP. Am. J. Physiol., 275, R384–389. Post, R. M., and Rose, H. (1976). Increasing effects of repetitive cocaine administration in the rat. Nature, 260, 731–732. Pousset, F., Cremona, S., Dantzer, R., Kelley, K. W., and Parnet, P. (2001). Dexamethasone up-regulates type II IL-1 receptor in mouse primary activated astrocytes. J. Neurochem. 76, 901–909. Pyter, L. M., Samuelsson, A. R., Quan, N., and Nelson, R. J. (2005). Photoperiod alters hypothalamic cytokine gene expression and sickness responses following immune challenge in female Siberian hamsters. (Phodopus sungorus). Neuroscience, 131, 779–784.
Quan, N., Avitsur, R., Stark, J. L., He, L., Shah, M., Caligiuri, M., et al. (2001). Social stress increases the susceptibility to endotoxic shock. J. Neuroimmunol., 115, 36–45. Quan, N., He, L., and Lai, W. (2003). Endothelial activation is an intermediate step for peripheral lipopolysaccharide induced activation of paraventricular nucleus. Brain Res. Bull., 59, 447–452. Quan, N., Whiteside, M., Kim, L., and Herkenham, M. (1997). Induction of inhibitory factor kappaBalpha mRNA in the central nervous system after peripheral lipopolysaccharide administration: an in situ hybridization histochemistry study in the rat. Proc. Natl. Acad. Sci. USA, 94, 10985–10990. Rady, P. L., Smith, E. M., Cadet, P., Opp, M. R., Tyring, S. K., and Hughes, T. K., Jr. (1995). Presence of interleukin-10 transcripts in human pituitary and hypothalamus. Cell. Mol. Neurobiol., 15, 289–296. Raison, C. L., Demetrashvili, M., Capuron, L., and Miller, A. H. (2005). Neuropsychiatric adverse effects of interferon-alpha: recognition and management. C.N.S. Drugs, 19, 105–123. Ramachandra, R. N., Sehon, A. H., and Berczi, I. (1992). Neurohormonal host defence in endotoxin shock. Brain Behav. Immun., 6, 157–169. Redei, E. E., Ahmadiyeh, N., Baum, A. E., Sasso, D. A., Slone, J. L., Solberg, L. C., et al. (2001). Novel animal models of affective disorders. Semin. Clin. Neuropsychiatry, 6, 43–67. Reichenberg, A., Yirmiya, R., Schuld, A., Kraus, T., Haack, M., Morag, A., and Pollmacher, T. (2001). Cytokine-associated emotional and cognitive disturbances in humans. Arch. Gen. Psychiatry, 58, 445–452. Reyes, T. M., and Sawchenko, P. E. (2002). Involvement of the arcuate nucleus of the hypothalamus in interleukin-1–induced anorexia. J. Neurosci., 22, 5091–5099. Rezvani, A. H., Parsian, A., and Overstreet, D. H. (2002). The FawnHooded (FH/Wjd) rat: a genetic animal model of comorbid depression and alcoholism. Psychiatr. Genet., 12, 1–16. Riedel, W. J., Klaassen, T., and Schmitt, J. A. (2002). Tryptophan, mood, and cognitive function. Brain Behav. Immun., 16, 581–589. Robinson, C. M., Shirey, K. A., and Carlin, J. M. (2003). Synergistic transcriptional activation of indoleamine dioxygenase by IFNgamma and tumor necrosis factor-alpha. J. Interferon Cytokine Res., 23, 413–421. Rohleder, N., Kudielka, B. M., Hellhammer, D. H., Wolf, J. M., and Kirschbaum, C. (2002). Age and sex steroid-related changes in glucocorticoid sensitivity of pro-inflammatory cytokine production after psychosocial stress. J. Neuroimmunol., 126, 69–77. Romanovsky, A. A. (2000). Thermoregulatory manifestations of systemic inflammation: lessons from vagotomy. Auton. Neurosci., 85, 39–48. Romeo, H. E., Tio, D. L., Rahman, S. U., Chiappelli, F., and Taylor, A. N. (2001). The glossopharyngeal nerve as a novel pathway in immune-to-brain communication: relevance to neuroimmune surveillance of the oral cavity. J. Neuroimmunol., 115, 91–100. Romeo, H. E., Tio, D. L., and Taylor, A. N. (2003). Effects of glossopharyngeal nerve transection on central and peripheral cytokines and serum corticosterone induced by localized inflammation. J. Neuroimmunol., 136, 104–111. Rossi-George, A., LeBlanc, F., Kaneta, T., Urbach, D., and Kusnecov, A. W. (2004). Effects of bacterial superantigens on behavior of mice in the elevated plus maze and light-dark box. Brain Behav. Immun., 18, 46–54. Rossi-George, A., Urbach, D., Colas, D., Goldfarb, Y., and Kusnecov, A. W. (2005). Neuronal, endocrine, and anorexic responses to the T-cell superantigen staphylococcal enterotoxin A: dependence on tumor necrosis factor-alpha. J. Neurosci., 25, 5314–5322.
14. Cytokines, Sickness Behavior, and Depression Roth, J., and De Souza, G. E. (2001). Fever induction pathways: evidence from responses to systemic or local cytokine formation. Braz. J. Med. Biol. Res., 34, 301–314. Sachot, C., Poole, S., and Luheshi, G. N. (2004). Circulating leptin mediates lipopolysaccharide-induced anorexia and fever in rats. J. Physiol., 561, 263–272. Santoso, D. I., Rogers, P., Wallace, E. M., Manuelpillai, U., Walker, D., and Subakir, S. B. (2002). Localization of indoleamine 2,3dioxygenase and 4-hydroxynonenal in normal and pre-eclamptic placentae. Placenta, 23, 373–379. Sarraf, P., Frederich, R. C., Turner, E. M., Ma, G., Jaskowiak, N. T., Rivet, D. J., 3rd, et al. (1997). Multiple cytokines and acute inflammation raise mouse leptin levels: potential role in inflammatory anorexia. J. Exp. Med., 185, 171–175. Satta, M. A., Jacobs, R. A., Kaltsas, G. A., and Grossman, A. B. (1998). Endotoxin induces interleukin-1beta and nitric oxide synthase mRNA in rat hypothalamus and pituitary. Neuroendocrinology, 67, 109–116. Schiepers, O. J., Wichers, M. C., and Maes, M. (2005). Cytokines and major depression. Prog. Neuropsychopharmacol. Biol. Psychiatry, 29, 201–217. Schiltz, J. C., and Sawchenko, P. E. (2002). Distinct brain vascular cell types manifest inducible cyclooxygenase expression as a function of the strength and nature of immune insults. J. Neurosci., 22, 5606–5618. Schmidt, E. D., Aguilera, G., Binnekade, R., and Tilders, F. J. (2003). Single administration of interleukin-1 increased corticotropin releasing hormone and corticotropin releasing hormone-receptor mRNA in the hypothalamic paraventricular nucleus which paralleled long-lasting (weeks) sensitization to emotional stressors. Neuroscience, 116, 275–283. Schmidt, E. D., Schoffelmeer, A. N., De Vries, T. J., Wardeh, G., Dogterom, G., Bol, J. G., et al. (2001). A single administration of interleukin-1 or amphetamine induces long-lasting increases in evoked noradrenaline release in the hypothalamus and sensitization of ACTH and corticosterone responses in rats. Eur. J. Neurosci., 13, 1923–1930. Schulz, D., Topic, B., De Souza Silva, M. A., and Huston, J. P. (2004). Extinction-induced immobility in the water maze and its neurochemical concomitants in aged and adult rats: a possible model for depression? Neurobiol. Learn. Mem., 82, 128–141. Schwartz, G. J., Plata-Salaman, C. R., and Langhans, W. (1997). Subdiaphragmatic vagal deafferentation fails to block feedingsuppressive effects of LPS and IL-1 beta in rats. Am. J. Physiol., 273, R1193–1198. Schwartz, M. W., Woods, S. C., Porte, D., Jr., Seeley, R. J., and Baskin, D. G. (2000). Central nervous system control of food intake. Nature, 404, 661–671. Segall, M. A., and Crnic, L. S. (1990). An animal model for the behavioral effects of interferon. Behav. Neurosci., 104, 612–618. Shuto, H., Kataoka, Y., Horikawa, T., Fujihara, N., and Oishi, R. (1997). Repeated interferon-alpha administration inhibits dopaminergic neural activity in the mouse brain. Brain Res., 747, 348–351. Simmons, D. A., and Broderick, P. A. (2005). Cytokines, stressors, and clinical depression: augmented adaptation responses underlie depression pathogenesis. Prog. Neuropsychopharmacol. Biol. Psychiatry, 29, 793–807. Slotkin, T. A., Miller, D. B., Fumagalli, F., McCook, E. C., Zhang, J., Bissette, G., and Seidler, F. J. (1999). Modeling geriatric depression in animals: biochemical and behavioral effects of olfactory bulbectomy in young versus aged rats. J. Pharmacol. Exp. Ther., 289, 334–345. Smoak, K. A., and Cidlowski, J. A. (2004). Mechanisms of glucocorticoid receptor signaling during inflammation. Mech. Aging Dev., 125, 697–706.
317
Sobczak, S., Honig, A., Nicolson, N. A., and Riedel, W. J. (2002). Effects of acute tryptophan depletion on mood and cortisol release in first-degree relatives of type I and type II bipolar patients and healthy matched controls. Neuropsychopharmacology, 27, 834–842. Song, C., Leonard, B. E., and Horrobin, D. F. (2004). Dietary ethyleicosapentaenoic acid but not soybean oil reverses central interleukin-1–induced changes in behavior, corticosterone and immune response in rats. Stress, 7, 43–54. Sonti, G., Ilyin, S. E., and Plata-Salaman, C. R. (1996). Neuropeptide Y blocks and reverses interleukin-1 beta-induced anorexia in rats. Peptides, 17, 517–520. Spurlock, M. E. (1997). Regulation of metabolism and growth during immune challenge: an overview of cytokine function. J. Anim. Sci., 75, 1773–1783. Stockmeier, C. A. (2003). Involvement of serotonin in depression: evidence from postmortem and imaging studies of serotonin receptors and the serotonin transporter. J. Psychiatr. Res., 37, 357–373. Strike, P. C., Wardle, J., and Steptoe, A. (2004). Mild acute inflammatory stimulation induces transient negative mood. J. Psychosom. Res., 57, 189–194. Swiergiel, A. H., and Dunn, A. J. (2001). Cyclooxygenase 1 is not essential for hypophagic responses to interleukin-1 and endotoxin in mice. Pharmacol. Biochem. Behav., 69, 659–663. Swiergiel, A. H., and Dunn, A. J. (2002). Distinct roles for cyclooxygenases 1 and 2 in interleukin-1–induced behavioral changes. J. Pharmacol. Exp. Ther., 302, 1031–1036. Swiergiel, A. H., Smagin, G. N., Johnson, L. J., and Dunn, A. J. (1997). The role of cytokines in the behavioral responses to endotoxin and influenza virus infection in mice: effects of acute and chronic administration of the interleukin-1–receptor antagonist (IL-1ra). Brain Res., 776, 96–104. Szekely, M., Balasko, M., Kulchitsky, V. A., Simons, C. T., Ivanov, A. I., and Romanovsky, A. A. (2000). Multiple neural mechanisms of fever. Auton. Neurosci., 85, 78–82. Takao, T., Tracey, D. E., Mitchell, W. M., and De Souza, E. B. (1990). Interleukin-1 receptors in mouse brain: characterization and neuronal localization. Endocrinology, 127, 3070–3078. Tazi, A., Dantzer, R., Crestani, F., and Le Moal, M. (1988). Interleukin-1 induces conditioned taste aversion in rats: a possible explanation for its pituitary-adrenal stimulating activity. Brain Res., 473, 369–371. Uehara, A., Ishikawa, Y., Okumura, T., Okamura, K., Sekiya, C., Takasugi, Y., and Namiki, M. (1989a). Indomethacin blocks the anorexic action of interleukin-1. Eur. J. Pharmacol., 170, 257–260. Uehara, A., Sekiya, C., Takasugi, Y., Namiki, M., and Arimura, A. (1989b). Anorexia induced by interleukin 1, involvement of corticotropin-releasing factor. Am. J. Physiol., 257, R613–617. Vallieres, L., and Rivest, S. (1997). Regulation of the genes encoding interleukin-6, its receptor, and gp130 in the rat brain in response to the immune activator lipopolysaccharide and the proinflammatory cytokine interleukin-1beta. J. Neurochem., 69, 1668–1683. van Dam, A. M., Bauer, J., Tilders, F. J., and Berkenbosch, F. (1995). Endotoxin-induced appearance of immunoreactive interleukin-1 beta in ramified microglia in rat brain: a light and electron microscopic study. Neuroscience, 65, 815–826. van Dam, A. M., Brouns, M., Louisse, S., and Berkenbosch, F. (1992). Appearance of interleukin-1 in macrophages and in ramified microglia in the brain of endotoxin-treated rats: a pathway for the induction of non-specific symptoms of sickness? Brain Res., 588, 291–296. van Dam, A. M., De Vries, H. E., Kuiper, J., Zijlstra, F. J., De Boer, A. G., Tilders, F. J., and Berkenbosch, F. (1996). Interleukin-1
318
II. Immune System Effects on Neural and Endocrine Processes and Behavior
receptors on rat brain endothelial cells: a role in neuroimmune interaction? FASEB J., 10, 351–356. van Dam, A. M., Poole, S., Schultzberg, M., Zavala, F., and Tilders, F. J. (1998). Effects of peripheral administration of LPS on the expression of immunoreactive interleukin-1 alpha, beta, and receptor antagonist in rat brain. Ann. N. Y. Acad. Sci., 840, 128–138. Van der Does, A. J. (2001). The effects of tryptophan depletion on mood and psychiatric symptoms. J. Affect. Disord., 64, 107–119. Vitkovic, L., Konsman, J. P., Bockaert, J., Dantzer, R., Homburger, V., and Jacque, C. (2000). Cytokine signals propagate through the brain. Mol. Psychiatry, 5, 604–615. Vitkovic, L., Maeda, S., and Sternberg, E. (2001). Anti-inflammatory cytokines: expression and action in the brain. Neuroimmunomodulation, 9, 295–312. Wan, W., Wetmore, L., Sorensen, C. M., Greenberg, A. H., and Nance, D. M. (1994). Neural and biochemical mediators of endotoxin and stress-induced c-fos expression in the rat brain. Brain Res. Bull., 34, 7–14. Watanabe, S., Kanada, S., Takenaka, M., and Hamazaki, T. (2004). Dietary n-3 fatty acids selectively attenuate LPS-induced behavioral depression in mice. Physiol. Behav., 81, 605–613. Watkins, L. R., and Maier, S. F. (2000). The pain of being sick: implications of immune-to-brain communication for understanding pain. Annu. Rev. Psychol., 51, 29–57. Watkins, L. R., Maier, S. F., and Goehler, L. E. (1995). Cytokine-tobrain communication: a review & analysis of alternative mechanisms. Life Sci., 57, 1011–1026. Widner, B., Ledochowski, M., and Fuchs, D. (2000). Interferongamma–induced tryptophan degradation: neuropsychiatric and immunological consequences. Curr. Drug Metab., 1, 193–204. Wieczorek, M., Swiergiel, A. H., Pournajafi-Nazarloo, H., and Dunn, A. J. (2005). Physiological and behavioral responses to interleukin-1beta and LPS in vagotomized mice. Physiol. Behav., 85, 500–511. Willner, P., and Mitchell, P. J. (2002). The validity of animal models of predisposition to depression. Behav. Pharmacol., 13, 169–188. Wisse, B. E., Ogimoto, K., Morton, G. J., Wilkinson, C. W., Frayo, R. S., Cummings, D. E., and Schwartz, M. W. (2004). Physiological regulation of hypothalamic IL-1beta gene expression by leptin and glucocorticoids: implications for energy homeostasis. Am. J. Physiol. Endocrinol. Metab., 287, E1107–1113. Wong, M. L., Bongiorno, P. B., Rettori, V., McCann, S. M., and Licinio, J. (1997). Interleukin (IL) 1beta, IL-1 receptor antagonist, IL-10, and IL-13 gene expression in the central nervous system and anterior pituitary during systemic inflammation: pathophysiological implications. Proc. Natl. Acad. Sci. USA, 94, 227–232. Wong, M. L., Rettori, V., al-Shekhlee, A., Bongiorno, P. B., Canteros, G., McCann, S. M., et al. (1996). Inducible nitric oxide synthase
gene expression in the brain during systemic inflammation. Nat. Med., 2, 581–584. Wright, C. E., Strike, P. C., Brydon, L., and Steptoe, A. (2005). Acute inflammation and negative mood: mediation by cytokine activation. Brain Behav. Immun., 19, 345–350. Wu, D., Yang, J., and Pardridge, W. M. (1997). Drug targeting of a peptide radiopharmaceutical through the primate blood-brain barrier in vivo with a monoclonal antibody to the human insulin receptor. J. Clin. Invest., 100, 1804–1812. Xu, B., Dube, M. G., Kalra, P. S., Farmerie, W. G., Kaibara, A., Moldawer, L. L., et al. (1998). Anorectic effects of the cytokine, ciliary neurotropic factor, are mediated by hypothalamic neuropeptide Y: comparison with leptin. Endocrinology, 139, 466–473. Yao, J., and Johnson, R. W. (1997). Induction of interleukin-1 betaconverting enzyme (ICE) in murine microglia by lipopolysaccharide. Brain Res. Mol. Brain. Res., 51, 170–178. Yirmiya, R., Weidenfeld, J., Pollak, Y., Morag, M., Morag, A., Avitsur, R., et al. (1999). Cytokines, “depression due to a general medical condition,” and antidepressant drugs. Adv. Exp. Med. Biol., 461, 283–316. Young, S. N., and Gauthier, S. (1981). Tryptophan availability and the control of 5-hydroxytryptamine and tryptamine synthesis in human CNS. Adv. Exp. Med. Biol., 133, 221–230. Zalcman, S., Murray, L., Dyck, D. G., Greenberg, A. H., and Nance, D. M. (1998). Interleukin-2 and -6 induce behavioral-activating effects in mice. Brain Res., 811, 111–121. Zalcman, S., Savina, I., and Wise, R. A. (1999). Interleukin-6 increases sensitivity to the locomotor-stimulating effects of amphetamine in rats. Brain Res., 847, 276–283. Zalcman, S. S. (2001). Interleukin-2 potentiates novelty- and GBR 12909–induced exploratory activity. Brain Res., 899, 1–9. Zalcman, S. S. (2002). Interleukin-2–induced increases in climbing behavior: inhibition by dopamine D-1 and D-2 receptor antagonists. Brain Res., 944, 157–164. Zhao, L., and Brinton, R. D. (2004). Suppression of proinflammatory cytokines interleukin-1beta and tumor necrosis factor-alpha in astrocytes by a V1 vasopressin receptor agonist: a cAMP response element-binding protein-dependent mechanism. J. Neurosci., 24, 2226–2235. Zhou, D., Kusnecov, A. W., Shurin, M. R., DePaoli, M., and Rabin, B. S. (1993). Exposure to physical and psychological stressors elevates plasma interleukin 6, relationship to the activation of hypothalamic-pituitary-adrenal axis. Endocrinology, 133, 2523–2530. Zuckerman, S. H., Shellhaas, J., and Butler, L. D. (1989). Differential regulation of lipopolysaccharide-induced interleukin 1 and tumor necrosis factor synthesis: effects of endogenous and exogenous glucocorticoids and the role of the pituitary-adrenal axis. Eur. J. Immunol., 19, 301–305.
C H A P T E R
15 The Differential Role of Prostaglandin E2 Receptors in the CNS Response to Systemic Immune Challenge MICHAEL LAZARUS AND CLIFFORD B. SAPER
nucleus and release of adrenal and pituitary hormones. EP1 and EP3 receptors on neurons in the preoptic area and in the ventromedial hypothalamus modulate activity of the descending pain inhibitory system and cause hyperalgesia or analgesia. EP3 receptors in the sleep-promoting ventrolateral preoptic area and EP4 receptors in the wake-promoting tuberomammillary nucleus might be involved in alteration of sleep behavior during a bacterial infection.
I. INTRODUCTION 319 II. SIGNALING MECHANISMS BETWEEN THE IMMUNE SYSTEM AND THE CNS 320 III. PATHWAYS ACTIVATED BY THE EP RECEPTORS 322 IV. CONCLUSION AND FUTURE STUDIES 331
ABSTRACT The innate immune system of mammals is able to detect bacteria when they infect local tissue or enter the bloodstream and initiate an immediate immune response, but the mechanism by which the innate immune system can activate CNS responses such as fever and sickness behavior is not well understood. Prostaglandin E2 (PGE2) is considered as the most important link between the peripheral immune system and the brain because drugs that block the synthesis of prostaglandins prevent fever and most components of sickness behavior. PGE2 mediates different or even counterposing components of the acute phase reaction via its action on four PGE2 receptors (EP receptors) and their differential expression in various areas of the hypothalamus and brain stem. A fever model is proposed in which EP1 and EP3 receptors in the preoptic area activate thermogenesis to cause fever, while counterpoised EP4 receptors promote hypothermia. The synergistic action of the EP1 and EP3 receptors is thought to be required for activation of the endocrine component of the paraventricular hypothalamic PSYCHONEUROIMMUNOLOGY, 4E VOLUME I
I. INTRODUCTION It is critical for mammals to be able to detect bacteria immediately when they infect local tissue and enter the bloodstream, and to mount a vigorous immune response. This response is mediated in mammals by an innate immune system, which can recognize components of bacterial cell walls even if it has not been previously exposed to them, and initiate an immediate immune response. This response is mediated, in turn, by a cascade of pro-inflammatory mediators, including the elaboration of a wide range of cytokines and prostaglandins. These mediators initiate an array of physiological responses, termed the acute phase reaction, among which is included a suite of CNS-mediated adaptive responses, sometimes called “sickness behavior” (fever, malaise, increased pain sensitivity, changes in wake-sleep cycles, and feeding) and changes in secretion of hormones such as corticosteroids.
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Although it has been known since the nineteenth century that aspirin could prevent many components of sickness behavior, and this compound was widely used clinically for this purpose, the mechanism of action was not understood until Sir John Vane in 1971 made the fundamental discovery that anti-inflammatory compounds such as aspirin act by blocking the formation of prostaglandins (PGs) (Vane, 1971). Originally, PGs were discovered independently by von Euler and Goldblatt in 1935 as a “vasodilatory substance” in seminal fluid and seminal vesicles from most animals including humans (Goldblatt, 1935; von Euler, 1935). They showed that PGs are involved in a large number of biochemical processes, often in extremely low concentrations. PGs are formed from unsaturated fatty acids, primarily arachidonic acid, which are metabolized to cyclic endoperoxides, which constitute an important branching point from which the stable prostaglandins as well as the more unstable thromboxanes and prostacyclin are formed. The task of these mediators is primarily to protect the integrity of the organism, and they are released when homeostasis is jeopardized by trauma, disease, or various stress factors and, thus, are also called the defense hormones. Prostaglandin E2 is now considered to be the most important link between the peripheral immune system and the brain. Produced at the boundaries between the bloodstream and brain tissue, PGE2 is thought to penetrate the blood-brain barrier and enter the CNS, and is therefore an ideal candidate to translate a peripheral immune signal into an acute phase response by modulating neural activity (Engblom et al., 2002b). The receptors for prostaglandins have now been identified and cloned, and there are four specific PGE receptors (EP receptors 1–4). In this chapter, we will summarize the differential role of prostaglandin E2 receptors in the CNS response to systemic immune challenge with major emphasis on our recent work on the regulation of fever by PGE2.
II. SIGNALING MECHANISMS BETWEEN THE IMMUNE SYSTEM AND THE CNS Although the interactions of the immune and the nervous system have been extensively studied in recent years, the mechanisms by which immune signals are transduced to influence the CNS remain controversial. The endotoxin lipopolysaccharide (LPS), a bacterial cell wall component, has been widely used as a model immune stimulant. LPS binds to the CD14 receptor on leukocytes and macrophages. By interac-
tion with the Toll-like receptor 4 (TLR4), this induces secretion of cytokines, including interleukin-1β (IL1β), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6), as well as prostaglandins (Fitzgerald and O’Neill, 2000; Rivest, 2003). In an effort to use a less complex immune stimulus, many studies have used systemically injected cytokines such as IL-1β and TNF-α to stimulate the immune system. However, circulating levels of IL-1β are not elevated in the bloodstream during systemic infection (Hopkins and Rothwell, 1995), and individual cytokines are rarely if ever elevated in isolation of other components of the pro-inflammatory response. Most cytokines are produced at the site of infection and act in a paracrine manner (Konsman et al., 2002), where they inevitably induce the secretion of the remaining pro-inflammatory cytokines and prostaglandins in any case. Hence, in the discussion that follows, we will concentrate on studies which have used LPS as a model of bacterial invasion and examine how it may act upon the CNS.
A. Stimulation of Peripheral Nerves Low levels of LPS, cytokines, or prostaglandins in the abdominal cavity can activate vagal afferents, mainly from the hepatic nerve, which can signal the brain and produce a CNS response (Blatteis et al., 1998; Romanovsky, 2004; Szekely et al., 2000). The role of the vagus nerves in transmission of immune signals to the brain has been assessed by experiments in which the vagus nerves were sectioned below the diaphragm. These studies suggest that vagal afferents can activate brain stem, hypothalamus, and limbic structures in response to peripherally administered LPS and IL-1β (Dantzer et al., 2000; Ek et al., 1998). Macrophages and dendritic cells of the abdominal cavity including Kupffer cells in the liver can produce IL-1β and PGE2 in response to LPS (Goehler et al., 1999; Lazarus et al., 2002; Sehic et al., 1997) and sensory neurons of the vagus nerves express receptors for IL1β and PGE2 that can activate afferent nerve fibers (Ek et al., 1998). In contrast, the abdominal vagus nerve does not seem to be necessary for causing the CNS response to intravenous or subcutaneous administration of LPS or IL-1β (Bluthe et al., 1996; Ericsson et al., 1997; Wan et al., 1994), nor does vagal transection block the CNS response to intraperitoneal administration of higher doses of LPS (Romanovsky et al., 2000), which may spill over into the systemic circulation. These observations suggest that the vagal sensory route may contribute mainly during low-grade peritonitis.
15. The Differential Role of Prostaglandin E2 Receptors in the CNS Response
B. Entry and Formation of Cytokines in the CNS Many early models of immune-CNS interactions hypothesized that the message might be carried by cytokines that would enter the CNS. However, cytokines are large proteins that cannot easily penetrate the BBB. It has been suggested that they may enter the CNS via carrier-mediated transport (for review, see Conti et al., 2004). However, the transport mechanisms that have been described are slow and saturable and, therefore, insufficient quantities of cytokines enter the brain following i.v. administration to explain the rapid responses of the CNS. During fever, brain IL-6 is largely increased, but this appears to be due to synthesis in the brain and not IL-6 crossing the BBB. IL-1β and TNF-α mRNA expression is not induced in the brain after systemic LPS (Breder et al., 1993; Breder and Saper, 1996). Thus, neither systemic cytokines that cross the BBB nor central synthesis of cytokines seems to play a major role in the brain response to systemic inflammation (Konsman et al., 2002).
C. Circumventricular Organs Another way in which cytokines or LPS might activate neurons in the CNS would be by action on circumventricular organs, such as the organum vasculosum of the lamina terminalis (OVLT), which lack a BBB (Blatteis et al., 1983; Saper and Breder, 1992; Stitt, 1985). Evidence showing IL-1β and TNF-α immunohistochemical staining in the brain suggested that PGE2 might act on cytokine-containing neurons in the preoptic and anterior hypothalamic areas and that these neurons might release cytokines from terminals at distal sites involved in producing the autonomic, endocrine, and behavioral components of the immune response of the CNS (Breder et al., 1988; Breder et al., 1993). Unfortunately, follow-up studies using in situ hybridization demonstrated that there is little if any synthesis of IL-1β and TNF-α by neurons in brain, either at baseline or after LPS stimulation. These studies, instead, showed that mRNA for these cytokines was confined to vascular-related cells along small penetrating blood vessels at the boundaries of the brain, and microglial cells in the circumventricular organs, at least during the first few hours after LPS administration (Breder et al., 1994; Nakamori et al., 1994; Quan et al., 1999). The CVOs are specialized neural regions in contact with the cerebroventricular system that have fenestrated capillaries and therefore lack a BBB. Many circulating hormones, such as angiotensin II, cholecystokinin, and leptin, act on neurons
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in the CVOs (Saper et al., 2002; Saper and Breder, 1994). The results of the immune response in CVOlesioned animals are contradictory (Blatteis, 1992; Ericsson et al., 1994; Ericsson et al., 1997; Katsuura et al., 1990; Takahashi et al., 1997). However, complete lesions inevitably damage structures surrounding the CVOs that might have a greater impact on the sickness behavior than the CVO itself. For example, large lesions that include the OVLT can prevent fever, but they also damage nearby preoptic regions that are crucial for thermoregulation (Blatteis, 1992). Animals with lesions of the OVLT and neighboring structures, such as the median preoptic area (MnPO), have high basal body temperature, which may make it difficult to identify fever (which may depend upon this same mechanism, i.e., inhibiting the cells in the MnPO; Romanovsky et al., 2003). As indicated by c-fos expression, neurons within the CVOs are activated by intravenous LPS or IL-1β, but only with substantially higher doses than those necessary to produce fever or corticotrophin responses (Elmquist et al., 1996; Ericsson et al., 1994). On the other hand, blockers of prostaglandin synthesis inhibit fever response in virtually all models, suggesting that prostaglandins are a necessary component of the fever response. Because prostaglandins may not require CVOs to cross the BBB, research in the last decade has turned from the CVOs as playing a primary role in fever, and instead has focused on the roles played by prostaglandins.
D. Central Production of PGE2 A hallmark of the CNS response to inflammation is that many of its manifestations, including fever and corticotropin activation, can be prevented by blocking the production of prostaglandins (Hashimoto et al., 1988; Johnson and von Borell, 1994; Stitt and Bernheim, 1985; Vane, 1971; Zhang et al., 2003). Both LPS and cytokines activate intracellular signaling cascades in endothelial cells in small blood vessels and in vascular-associated macrophages, termed perivascular cells, in the brain [for detailed review, see ref. (Matsumura and Kobayashi, 2004; Schiltz and Sawchenko, 2003)]. This cascade results in phospholipase A2 degrading phospholipids into arachidonic acid and increased expression of cyclooxygenase type 2 (COX-2) (Ivanov and Romanovsky, 2004; Schiltz and Sawchenko, 2002). COX-2 converts arachidonic acids to PGH2, from which specific prostaglandin synthases synthesize various prostaglandins (O’Banion, 1999; Smith and Dewitt, 1996). In the normal brain, COX-2 is present in certain neurons and meningeal cells but little is found in brain vascular cells (Beuckmann et al., 2000b; Breder
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et al., 1992; Breder et al., 1995; Elmquist et al., 1997; Yamagata et al., 1993). Following administration of LPS or IL-1β, there is little change in neuronal expression of COX-2, but intense induction of COX-2 is seen in vascular cells of the brain parenchyma and subarachnoidal space (Breder and Saper, 1996; Cao et al., 1995; Cao et al., 1996; Elmquist et al., 1997). Van Dam and colleagues (Van Dam et al., 1993) have reported PGE2 immunoreactivity in brain blood vessels of rats injected systemically with LPS, providing evidence that PGE2 is a mediator of the CNS response to immune challenge. Various enzymes have been characterized as prostaglandin E synthases (Beuckmann et al., 2000a; Tanioka et al., 2000), but it was not until 1999 that a membrane-bound prostaglandin E synthase (mPGES-1) was identified (Jakobsson et al., 1999) and its coordinate upregulation with COX-2 was shown (Lazarus et al., 2002; Thoren and Jakobsson, 2000). In the normal brain, mPGES-1 is expressed at very low levels in endothelial cells, but its expression is highly upregulated in response to systemic administration of LPS or IL-1β, and the distribution is very similar to that of COX-2 (Ek et al., 2001; Engblom et al., 2002a; Yamagata et al., 2001). A key role of both COX-2 and mPGES-1 in producing fever has been demonstrated in mouse strains lacking these key enzymes (Engblom et al., 2003; Li et al., 1999; Li et al., 2001). Animals lacking either COX-2 or mPGES-1 fail to produce a fever response when stimulated with LPS or IL-1β. Recent work (Kamei et al., 2004) also showed that mice lacking mPGES-1 have reduced pain hypersensitivity in response to LPS stimulation. Similarly, injections of specific COX-2 inhibitors prevent fever responses (Zhang et al., 2003), although COX-1 may also play a role in signaling the brain via the vagus nerve, as activation of c-fos expression in the nucleus of the solitary tract and other components of the visceral sensory system after LPS is blocked by COX-1 but not COX-2 inhibitors.
III. PATHWAYS ACTIVATED BY THE EP RECEPTORS PGE2 is transported or diffuses across the bloodbrain barrier in the CVOs or penetrating venules around the margins of the brain (Ivanov et al., 2003; Taogoshi et al., 2005), and as a result it can act in the adjacent brain on neurons expressing E type prostaglandin receptors (EPRs) differentially to activate various pathways in the CNS in response to systemic immune challenge. EP receptors are G-protein–coupled receptors and classified into four subtypes: EP1, EP2, EP3, and EP4. These receptors can be grouped into
three categories on the basis of their signal transduction: the EP1 receptor increases intracellular Ca2+. The EP2 and EP4 receptors mediate increases in intracellular cyclic adenosine monophosphate (cAMP). The EP3 receptor expressed in the brain is an inhibitory receptor that mediates decreases in intracellular cAMP, although other splicing variants of the EP3R have different signaling pathways. For a general review on prostanoid receptors, see ref. (Narumiya et al., 1999; Narumiya and FitzGerald, 2001).
A. Febrile Response and Hypothermia Fever is one of the most common symptoms of inflammatory disease and is a CNS-mediated component of the acute phase reaction, an adaptive suite of responses to systemic inflammatory stimuli. Fever represents a temporally complex but stereotyped set of physiological events, resulting in increased body temperature. Other responses are sickness behavior, which includes malaise, increased pain sensitivity, changes in wake-sleep cycles and feeding, and changes in secretion of hormones such as corticosteroids (reviewed below). In rodents, systemic administration of LPS is known to induce monophasic fever, multiphasic fever, or hypothermia depending on the species (and possibly strain of animals used), the dose, the route of administration, and the ambient temperature (Oka et al., 2003a; Romanovsky, 2004). We and others have used c-fos expression in the brain after intravenous or intraperitoneal LPS administration as a measure of the activation of specific brain pathways during fever responses. Of course, not all such activation is related to thermoregulation, and not all activated pathways will necessarily express c-fos protein. On the other hand, this method has given us a way to identify and test the importance of specific neuronal pathways in fever responses and allowed us to identify neurons in ventromedial preoptic nucleus (VMPO), paraventricular hypothalamic nucleus (PVH), parabrachial nucleus (PB), nucleus of the solitary tract (NTS), and ventrolateral medulla (VLM) that reliably show c-fos activation after LPS stimulation (Elmquist et al., 1996; Elmquist et al., 1997; Elmquist and Saper, 1996; Zhang et al., 2000). Cell-specific lesions of the VMPO, using ibotenic acid (Lu et al., 2001), had little if any effect on fever responses, although they did make baseline body temperature unstable. There was a much higher variance in body temperature across the day, as if fine control of thermoregulation had been disrupted. By contrast, lesions of the PVH unmasked a brief hypothermic response in the first hour after intravenous LPS, followed by a fever response that was about 0.5°C less than animals with an intact PVH.
15. The Differential Role of Prostaglandin E2 Receptors in the CNS Response
Pittman and colleagues observed similar results in rats that had a reduced febrile response to intracerebroventricular application of PGE2 and intraperitoneal injection of LPS after electrolytic lesion of the PVH, whereas the ablation of the PVH had no effect on maintenance of normal body temperature (Horn et al., 1994). E-type prostaglandins have been considered as principal mediators of fever since Milton and Wendlandt reported in 1970 that injection of prostaglandin E1 into the third ventricle of cats elevated body temperature (Milton and Wendlandt, 1970). LPSinduced c-fos expression can be replicated by injecting threshold doses (1–2 ng) of PGE2 into the preoptic area, but only within a radius of less than 1 mm from the anteroventral tip of the third ventricle (Scammell et al., 1996). Conversely, injecting a COX inhibitor into this same site attenuated fever dramatically after i.v. LPS (Scammell et al., 1998b), indicating that both the site of production of PGE2 and its neuronal targets for causing fever are located at the anterior tip of the third ventricle, a region containing the MnPO, OVLT, and VMPO. Recent work examining c-fos expression in the brains of rats that received intravenous LPS along with cyclooxygenase inhibitors confirmed that c-fos expres-
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sion patterns in rat brain can be dissociated from fever responses (Zhang et al., 2003). In fact, COX-1 inhibition, which did not prevent fever, eliminated LPSinduced c-fos expression in the brain stem and PVH, whereas COX-2 inhibition eliminated fever and c-fos expression in the VMPO and PVH, but left LPS-induced c-fos expression in the brain stem intact (Figure 1). One major clue to identifying the key circuitry involved in the CNS responses to systemic immune challenge is the location of EP receptors in the brain. Oka et al. (2000) mapped the distribution of all four EP receptors by using in situ hybridization (Figure 2). These studies and those by others demonstrated that EP3 receptors are highly localized to the MnPO appearing at rostral levels as an inverted Y-shaped structure, capping the OVLT. Lower levels of expression of the EP3 receptor were found in the medial part of the OVLT, the medial preoptic nucleus (MPO), and the caudal aspects of the VMPO (Ek et al., 2000; Nakamura et al., 1999; Nakamura et al., 2000; Yoshida et al., 2003). The localization of intense expression in the MnPO provides an important clue to the genesis of fever responses, as the EP3 receptor is probably the most critical for producing fever. EP1 receptors are much
FIGURE 1 A series of photomicrographs demonstrating the distribution of c-fos–like immunoreactivity (black nuclei) in the VMPO (A–C) and NTS (D–F) after intravenous LPS administration and intraperitoneal injection of COX-2 inhibitor (SC-236; A and D), or COX-1 inhibitor (SC-560; C and F), or vehicle (DMSO; B and E). Expression of c-fos protein is prevented in the VMPO by the COX-2 inhibitor, but expression of c-fos in the NTS is abolished by the COX-1 inhibitor, indicating that different forms of cyclooxygenase drive different CNS pathways. AVPV, anteroventral periventricular nucleus; dm, dorsomedial subnucleus; m, medial subnucleus; OX, optic chiasm; VMPO, ventral medial preoptic area; 3v, third ventricle; 4v, fourth ventricle; 10, dorsal motor nucleus of the vagus. [From (Zhang et al., 2003) with permission from John Wiley & Sons, Inc.].
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AC
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strand OC FIGURE 2 Distribution of EP receptor–bearing neurons within the PGE2-sensitive OVLTMnPO-VMPO region that showed c–fos expression after intravenous LPS administration. Gray areas represent the regions where EP4 (A–D), EP3 (E–H), and EP1 (I–L) receptor mRNA is predominantly expressed with darker areas indicating greater density of EP receptor expression. Circles represent c-fos immunoreactive neurons, and squares show neurons expressing EP4, EP3, and EP1 receptor mRNA as well as c–fos expression. [From (Oka et al., 2000) with permission from John Wiley & Sons, Inc.].
more widely distributed. In fact, EP1 receptors are found in each of the key anteroventral preoptic nuclei, including the MnPO, the VMPO, and the OVLT. By contrast, EP4 receptors are more highly localized. They
are found at highest levels in the VMPO and the lateral OVLT, but are also found at lower levels in the MnPO. LPS induces higher levels of EP4R expression in the PVH, although not in the preoptic area (Oka et al.,
15. The Differential Role of Prostaglandin E2 Receptors in the CNS Response
2000; Zhang and Rivest, 2000). Oka et al. (2000) did not identify EP2 receptors in rat hypothalamus, although Zhang and Rivest (1999) reported that EP2 receptor mRNA is expressed within the medial preoptic area (MPO). The combination of in situ hybridization for the EP receptors with c-fos staining during fever response revealed that c-fos expression was highly colocalized with EP4 receptor mRNA, especially in the OVLT and VMPO, whereas EP1 receptor mRNA was found diffusely colocalized with c-fos staining, particularly in the OVLT and VMPO (Oka et al., 2000). There was very little c-fos expression by neurons expressing EP3R mRNA. The EP3 receptor found in the rodent hypothalamus inhibits cells by reducing intracellular cAMP (Narumiya et al., 1999). Thus, patterns of c-fos expression may be misleading, because it is unlikely that EP3 receptor stimulation would cause c-fos expression, and it might suppress such expression. Previous studies that used relatively non-specific agonists for all four EP receptors produced conflicting results, suggesting the involvement of the EP1 and the EP2 receptors in producing fever in rats and pigs, respectively (Oka et al., 1997a; Oka et al., 1998; Oka
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and Hori, 1994; Parrott and Vellucci, 1996). In order to clarify which of the EP receptors might be involved in fever responses, Oka and colleagues (2003b) injected highly specific EP receptor agonists intracerebroventricular (i.c.v.) into awake rats and recorded body temperature telemetrically. In these experiments (Figures 3 and 4), it was found that the EP1 receptor agonist (ONODI-004) caused a brisk fever of about 1.5–2.0°C within 20 minutes of injection. The EP3 agonist (ONOAE-248) caused a slightly smaller fever, but there was a delay of about 40 minutes before it reached a maximum. This response was substantially delayed from PGE2, which caused a brisk fever response in about 20 minutes. The EP4 agonist (ONO-AE1-329) caused a 0.5°C hypothermia, whereas the EP2 receptor agonist (ONO-AE1-250-01) had no effect. The magnitude of these responses is difficult to compare, as all doses were limited by the solubility of the specific compounds to 20 nmol and the drugs may have activated their specific receptors to different degrees. However, these experiments demonstrated that the EP1 and EP3 receptors both are capable of producing hyperthermic responses, whereas the EP4 receptor is more likely to produce hypothermic responses.
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FIGURE 3 Effects of i.c.v. injection of EP receptor agonists on core temperature (T) in rats. Rats were injected with EP receptor agonists at 20 nmol (closed circle), i.e., ONO-DI-004 (A) and ONOAE-248 (B), or their vehicles (open circle) at time zero. The data are expressed as differences from the T at time zero, which is shown in the figure. Each point represents mean ±S.E. (n) = number of animals. Symbols adjacent to points represent level of significance when compared with vehicle-injected control. *P < 0.05; **P < 0.01. [From (Oka et al., 2003b) with permission from Elsevier Science B.V.].
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FIGURE 4 Dose-dependent effects of PGE2 and EP receptor agonists on core temperature (T) in rats. The maximal changes in T during 90 minutes after i.c.v. injection of the following drugs is shown: PGE2 at 0.03 and 0.3 nmol, ONO-DI-004 (EP1 agonist) at 2 and 20 nmol, ONO-AE1259-01 (EP2 agonist) at 20 nmol, ONO-AE-248 (EP3 agonist) at 2 and 20 nmol, and ONO-AE1-329 (EP4 agonist) at 2 and 20 nmol. The number in parentheses in each column represents the number of animals. In the parentheses below the compounds, doses (nmol) of drugs are shown. Each point represents mean ±S.E. Symbols adjacent to points represent level of significance when compared with the values of their corresponding vehicle-injected control rats at the same time point. *P < 0.05; **P < 0.01. [From (Oka et al., 2003b) with permission from Elsevier Science B.V.].
An early study of EP receptor knockout mice showed that only mice with EP3 (Ushikubi et al., 1998), but not EP1, EP2, or EP4 receptor gene deletion lacked a hyperthermic response to intracerebroventricular (i.c.v.) PGE2, suggesting a crucial role for EP3 receptors in producing fever in mice. However, in those experiments, body temperature was measured in restrained animals by using rectal robes, and only for one hour after LPS or PGE2 administration. As restraint causes stress that alters the body temperature, Oka et al. (2003a) telemetrically studied the fever response of the same strains of unrestrained EP1 and EP3 receptor knockout mice for up to 12 hours after intraperitoneal LPS administration at a variety of doses. Animals with EP4 receptor deletion were not studied because they rarely survive very long after birth; the ductus arteriosus remains patent, as it requires EP4 receptor stimulation to close (Nguyen et al., 1997; Segi et al., 1998). In the Oka et al. (2003a) study, different doses
of intraperitoneally injected LPS produced different temporal profiles of fever responses in C57BL/6 wild-type mice. A 1 μg/kg dose caused a brief, early hyperthermia (2–4 hours after LPS injection), which was eliminated in EP3 receptor knockout animals. At 10 μg/kg, the early hyperthermia was greater in wild-type mice. In EP1 receptor knockout animals, this response was reduced in magnitude, and in EP3 receptor null mice, only a brief hypothermia from 1–2 hours after LPS was noted. At 100 μg/kg, wild-type mice showed little early fever, but a 1°C hyperthermia from 4–9 hours after LPS administration (Figure 5). EP1 receptor null mice had no fever response, and EP3R knockout animals had a profound hypothermia of 2°C that lasted for 9 hours. At 1 mg/kg of LPS administration, the wild-type mice had a mild hypothermia of 0.5°C from 1 to 3 hours after the LPS injection, and then a more profound hypothermia of 4°C from 4–8 hours. EP1 receptor knockout animals had a similar response, which lasted at least 12 hours, whereas EP3 receptor knockout animals had an even more profound hypothermia, with body temperature dropping more than 6°C from 4–8 hours after the LPS injection. It appears that the EP3 receptor is necessary not only to produce fever responses, but also to prevent profound hypothermic responses, particularly at higher doses of LPS. The EP1 receptor, by contrast, does appear to play an important role in fever, particularly at intermediate (10–100 μg/kg) doses of LPS, where it is required to produce the hyperthermic responses seen in control animals. Thus, the fever curve at different time points and after different doses of LPS appears to reflect the interaction of both hyperthermic and hypothermic processes. EP3 receptors provide a strong hyperthermic drive; and EP1 receptors a substantial but less intense hyperthermic response. However, without these, the main effect of LPS is hypothermia, which appears from agonist studies (Oka et al., 2003b) to be due to EP4 receptors. Studies by Nakamura and colleagues (2000, 2004) have attempted to examine the neuronal pathways by which the EP3 receptor may cause fever. In agreement with other investigators (Oka et al., 2000), they showed that EP3 receptors are highly expressed by neurons in the MnPO, and went on to show that these cells demonstrate descending projections to the raphe pallidus nucleus (RP) in the brain stem. In addition, neurons in both the RP and the MnPO are retrogradely labeled by injection of the transneural tracer, pseudorabies virus, into the intrascapular brown adipose tissue (IBAT), and labeled neurons at both sites also contained EP3 receptors (Cano et al., 2003; Yoshida et al., 2003). On the other hand, blockade of PGE2 synthesis in the preoptic area prevented fever (Scammell et al., 1998b),
15. The Differential Role of Prostaglandin E2 Receptors in the CNS Response
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FIGURE 5 Effects of intraperitoneal injection of LPS at 100 μg/kg on core temperature (T) in WT, EP1 receptor KO, and EP3 receptor KO mice. Mice were injected with LPS (closed circle) or 0.9% saline (open circle) at time zero. The data are expressed as differences from the T at time zero, which is shown in the figure. Each point represents mean ±S.E. In the parentheses, the number of animals is shown. Bar shows dark period. Symbols represent level of significance when compared with 0.9% saline-injected control at each time point. *P < 0.05; **P < 0.01. [From (Oka et al., 2003a) with permission from The Physiological Society, UK].
and injection of PGE2 into the RP did not affect body temperature (Tanaka and McAllen, 2005). The RP has been shown in recent years to be a key site for integrating sympathetic responses important in producing increased body temperature, including both increased thermogenesis through activation of brown adipose tissue and reduced passive heat loss through the skin by tail artery vasoconstriction (Morrison, 2001; Morrison, 2004). Injection of a GABA agonist into the RP prevented febrile response to PGE2 injection i.c.v. (Morrison, 2003; Nakamura et al., 2002). Thus, a model for fever response was suggested in which EP3 receptor–bearing neurons in the MnPO are inhibited by PGE2, thus reducing their inhibition of the RP. This disinhibition of the RP would then lead to thermogenesis and heat conservation, resulting in fever. The model shown in Figure 6 is slightly more complex than the model described above, as it also incorporates the finding of Morrison and colleagues (2004) and our own observations. This model accounts for additional observations, such as the attenuation of fever response by lesion of the PVH or GABAergic inhibition of the dorsomedial hypothalamus (DMH), and that fever is attenuated by blocking excitatory amino acid neurotransmission in the RP, indicating that the RP receives both an augmented excitatory amino acid input and a reduced GABA input during fever responses (Lu et al., 2001; Madden and Morrison, 2003; Madden and Morrison, 2004). In our model, the preoptic area contains the mechanisms for both hyperthermic and hypothermic responses. Hyperthermia is
generated by a system of neurons including the paraventricular and dorsomedial nuclei of the hypothalamus and the RP, which activate thermogenic brown adipose tissue and heat conservation (vasoconstriction) responses. This thermogenic system is normally restrained by inhibitory neurons in the MnPO. Thus, inhibition of these MnPO neurons during fever disinhibits the thermogenic system and results in hyperthermia. Additionally, the MnPO neurons can be activated by excitatory neurons in the OVLT and VMPO, which paralyzes the thermogenic system. At ambient temperatures below thermoneutral, this results in hypothermia. Of course, both of these types of neurons in the MnPO and in the OVLT/VMPO whose activity causes hypothermia can be inhibited by local interneurons, whose activity is therefore hyperthermic. Although some MnPO neurons project to the RP, there are also inhibitory projections to neurons in the PVH and the DMH, which in turn provide excitatory inputs to the RP. Thus, inhibition of the MnPO during fever can disinhibit a wide range of descending thermogenic pathways. In this model, during fever, hyperthermic neurons in the MnPO and OVLT/VMPO are inhibited by EP3 receptors, thus disinhibiting, i.e., releasing, thermogenesis. The same neurons can contain EP4 receptors, which excite them and thereby limit thermogenesis, and in the absence of EP3 receptor action can produce hypothermia. At higher dosages of LPS, the EP4 receptors may predominate, resulting in predominantly
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- + nerve activity
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cAMP↓ FIGURE 6 A model for neuronal interactions with EP receptors in the fever response after systemic immune challenge. The action of PGE2 on EP1, EP3, and EP4 receptors surrounding the anteroventral tip of the third ventricle in the preoptic area, including the MnPO, OVLT, and VMPO, appears to be critical for producing fever. EP1 and EP3 receptors generate hyperthermia, and EP4 responses generate hypothermia. The body temperature of the animal represents the net effect of these counterpoised forces, which may vary at different time-points after immune stimuli start signaling the CNS.
hypothermic responses. We hypothesize that EP1 receptors, which are excitatory, are located on inhibitory interneurons in both the MnPO and the OVLT/ VMPO. These play an accessory role in permitting thermogenesis during fever, but in the absence of EP3 receptors, they cannot overcome the hypothermic effect of the EP4 receptors. On the other hand, in the absence of EP1 receptors, at doses of LPS from 10– 100 μg/kg the effects of the EP3 and EP4 receptors effects are nearly balanced, and little if any fever is seen (Oka et al., 2003a).
B. Alterations in the Secretion of Adrenal and Pituitary Hormones PGE2 also plays a key role in activating the hypothalamic-pituitary-adrenal (HPA) axis in response to inflammation. Activation of neurons that secrete corticotropin-releasing factor (CRF) in the parvocellular PVH is responsible for adrenocorticotropic hormone (ACTH) secretion during a stressful immune challenge. Subsequent increases in circulating ACTH drive synthesis and secretion of glucocorticoids by the adrenal glands. During stress, including systemic inflammation, catecholaminergic inputs from the NTS and VLM to the PVH are an essential component of the neuronal circuits, and their role in regulating the activity of CRF neurons is well recognized (Chan et al.,
1993; Ericsson et al., 1994; Sawchenko et al., 1996). The PVH neurons also receive direct inhibitory input from local hypothalamic circuits, including the preoptic area. These circuits might therefore modulate PVH output through disinhibition (Herman and Cullinan, 1997). The HPA axis response to systemic administration of IL-1β is attenuated by COX inhibitors, and intracerebroventricular or intra-preoptic injection of PGE2 triggers the transcription of CRF (Ericsson et al., 1997; Lacroix et al., 1996; Scammell et al., 1996; Zhang and Rivest, 2000). EP4 mRNA is upregulated in CRF neurons in the parvicellular PVH following intravenous LPS or IL-1β injection. EP4 receptors are also present in activated catecholaminergic neurons of the NTS and VLM, although only the A1 cell group of the VLM showed an increase in EP4 receptor transcription by circulating IL-1β (Zhang and Rivest, 1999). This pattern of EP4 expression suggested that EP4 receptors may play a leading role in the control of the corticotroph axis during acute phase reaction. In addition, EP4 receptors are expressed in the dorsal, ventral, and posterolateral parvicellular subnuclei of the PVH, which project to autonomic nuclei in the brain stem and spinal cord (Oka et al., 2000; Zhang et al., 2000). Although the increase in EP4 receptor expression might suggest that an enhanced effect of PGE2 on EP4 receptors in the PVH, in fact there is no evidence that
15. The Differential Role of Prostaglandin E2 Receptors in the CNS Response
PGE2 actually accesses the PVH during an inflammatory response. Thus, the function of the increased expression of EP4 receptor in this model remains a mystery. On the other hand, in situ hybridization studies of the EP1 receptor revealed a diffuse distribution in the PVH, suggesting a possible role for the EP1 receptor, too, in activation of the HPA axis (Batshake et al., 1995; Oka et al., 2000). The EP1 receptor is also expressed on neurons in the supraoptic nucleus (SON) and central nucleus of the amygdala (CeA), areas known to show c-fos expression in response to systemic LPS administration (Batshake et al., 1995; Matsuoka et al., 2003). Neural circuits that include the bed nucleus of the stria terminalis (BST) connect the CeA to the PVH (Herman and Cullinan, 1997) and, hence, might stimulate the secretion of glucocorticoids mediated by the EP1 receptor. The dominant expression of the EP3 receptors in the preoptic area, including the MnPO and MPO (cf. “Febrile Response and Hypothermia”), implicates this receptor in blocking GABAergic inputs to the PVH and, thus, triggering activation of the HPA axis. The MnPO is a major source of input to the PVH and SON to depress CRH, vasopressin, and oxytocin neurons in the PVH and SON. Using mice in which the genes for each individual EP receptor has been knocked out has been a useful approach to testing these hypotheses. Narumiya and colleagues showed that mice in which the EP1 or EP3 receptor had been deleted had defective release of ACTH from the pituitary gland in response to LPS challenge, whereas animals with EP2 or EP4 receptor deletion had a normal ACTH response (Matsuoka et al., 2003). Treatment with a highly selective EP1 antagonist, ONO-8713, suppressed LPS-induced ACTH release in wild-type mice (Matsuoka et al., 2003). A comparison of c-fos expression in brain areas of wildtype mice and EP1R- and EP3R-deficient mice after LPS administration highlighted areas that might be involved in activation of the HPA axis. Although the lack of either the EP1 or EP3 receptor did not reduce c-fos expression in PVH neurons after administration of LPS, the treatment of EP3 receptor knockout mice with ONO-8713 (a selective EP1 antagonist) reduced c-fos expression in CRF-containing neurons of the PVH after LPS administration to an extent comparable to that found in animals treated with the COX inhibitor indomethacin Thus, either the EP1 or the EP3 receptor can drive c–fos expression in the CRH cells, but both are needed to cause sufficient excitation to release excess CRH. The location of the neurons that activate the PVH CRH neurons in response to EP receptors remains to be determined. In EP1 receptor knockout mice, the
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expression of c-fos in response to LPS was reduced in the CeA (Matsuoka et al., 2003). CeA neurons were also found to be immunoreactive for EP1 receptors, suggesting that the EP1 receptors found on CeA neurons may play a major role in activating the HPA axis. On the other hand, Sawchenko and colleagues (Ericsson et al., 1994; Ericsson et al., 1997) have found that cutting the ascending noradrenergic input to the PVH from the VLM prevents CRH responses due to i.v. IL-1β. They can also block CRH responses by blocking PG synthesis locally in the VLM with indomethacin. As EP3 receptors are found in the VLM (Ek et al., 2000), they may play a role in activating local noradrenergic neurons. In summary, it may be necessary to activate both an EP1-dependent pathway involving the CeA and an EP3-dependent pathway involving the VLM to activate fully CRH responses to systemic immune challenge.
C. Global Changes in Nociceptive Thresholds Pain enhancement, also known as hyperalgesia, during a period of infection or illness would benefit the organism by minimizing activity, thus saving energetic resources for fighting infection, and for allowing recovery and healing to occur. Hyperalgesia is produced in animal models of acute inflammation that are induced by systemic administration of LPS or intravenous injection of IL-1β (Maier et al., 1993; Watkins et al., 1994; Wicrtelak et al., 1994). The analgesic effects of COX inhibitors such as indomethacin and aspirin confirm that prostaglandins participate in the processing of nociceptive stimuli (O’Banion, 1999; Vane, 1971; Vane and Botting, 2003). LPS-induced hyperalgesia can be abolished by microinjection of COX inhibitors into the preoptic area prior to LPS administration (Abe et al., 2001). The pain modulatory action of PGE2 during the course of acute systemic infection was previously reviewed in detail by Hori and colleagues (Hori et al., 2000). In brief, centrally administered PGE2 mediates nociception in a dose-dependent manner, causing hyperalgesia at low, non-pyrogenic doses (10 pg/kg– 10 ng/kg) and analgesia at high, pyrogenic ones (1 μg/ kg) (Oka et al., 1994; Oka et al., 1995). In order to clarify which of the EP receptors might mediate pain transmission responses, Hori and colleagues injected EP1, EP2, and EP3 receptor agonists i.c.v. into rats and recorded paw-withdrawal latency on a hot plate 15–60 minutes after injection or firing rate responses of the trigeminal wide dynamic range (WDR) neurons to noxious pinching (Oka et al., 1994; Oka et al., 1997b).
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In these experiments, only the EP3 receptor agonist (M&B28767) decreased the paw withdrawal latency and augmented the nociceptive responses of the trigeminal WDR neurons. In contrast, the EP1 agonist (17-phenyl-ω-trinor PGE2) caused a prolongation of the paw-withdrawal latency and inhibition of the nociceptive responses of the WDR neurons. Moreover, the EP1 receptor antagonist (SC19220) prevented the PGE2-induced analgesic effects on the nociceptive behavior and responses of WDR neurons. These experiments suggested that PGE2 produces hyperalgesia at lower levels through actions on the EP3 receptors and at higher levels causes analgesia through actions on the EP1 receptors. The most sensitive sites to microinjected PGE2 and EP3 receptor agonist for producing thermal hyperalgesia seem to be the preoptic area, including its medial and lateral parts, the MnPO, and the diagonal band of Broca (Hosoi et al., 1997). On the other hand, it was found that the PGE2 and EP1 receptor agonist was most effective for evoking analgesia when microinjected into the ventromedial hypothalamic nucleus (VMH; Hosoi et al., 1999). As described above, although the EP3 receptor is highly expressed on neurons in the preoptic area and the receptors can alter activity of those neurons, the expression of EP1 receptors in the VMH has not been reported and the action of this receptor in this area remained to be elucidated in future studies. In contrast, expression of the EP2 receptor has been described in the VMH (Zhang and Rivest, 1999), but butaprost (an EP2 receptor agonist) failed to modulate pain thresholds (Oka et al., 1994; Oka et al., 1997b). It is poorly understood how alteration of neuronal activity in the preoptic and ventromedial hypothalamus by PGE2 can produce hyperalgesia and analgesia, respectively. One hypothesis is that hypothalamic neurons that respond to PGE2 may send inputs to areas that modulate nociception, such as the periaqueductal gray matter (PAG) and the nucleus raphe magnus (NRM) (Jones, 1992; Vanegas and Schaible, 2004). Projections from hypothalamic structures to the PAG are extensive, and previous anatomic studies indicate that the preoptic area, including the MPO and MnPO, is a major source of afferent input to the PAG and that also the VMH sends a projection to this brain stem region (Canteras et al., 1994; Rizvi et al., 1992; Saper et al., 1976; Saper and Levisohn, 1983; Yoshida et al., 2005). Thus, inhibitory EP3 receptors reduce activity of neurons in the preoptic area that may activate anti-nociceptive systems in the PAG, and PGE2 may increase the activity of VMH neurons that activate the descending pain inhibitory system. It would be of interest to perform similar studies using the newer
generation of highly selective EP agonists, and in mice with EP receptor deletions.
D. Changes in the Sleep-Wake Cycle Sleep and wakefulness are induced by a flip-flop mechanism involving sleep-promoting neurons in the ventrolateral preoptic area (VLPO) and wake-promoting neurons in the brain stem and hypothalamus, including the tuberomammillary nucleus (TMN), locus coeruleus (LC), and dorsal raphe nucleus (DR) (Saper et al., 2001). Aminergic neurons in TMN, LC, and DR promote wakefulness by direct excitatory effects on arousal systems in the thalamus, hypothalamus, basal forebrain, and cerebral cortex, as well as by inhibition of sleep-promoting neurons of the VLPO. During sleep, the VLPO inhibits amine-mediated arousal regions through GABAergic and galaninergic projections. Although endogenous PGE2 levels in the hypothalamus were significantly higher during wakefulness than during non-rapid eye movement (NREM) sleep as determined by microdialysis and the simultaneous recording of electroencephalograms in freely moving rats (Gerozissis et al., 1995), PGE2 is known to have contrasting effects on sleep-wake regulation when infused in different areas of the brain. When PGE2 was infused into the subarachnoid space underlying the ventral surface area of the rostral basal forebrain, the sleeping time of rats was significantly increased (Ram et al., 1997). In a pharmacological study using selective agonists for the EP receptors, the EP4 receptor agonist (ONO-AE1329) exhibited a very potent, dosedependent effect on NREM sleep and showed at lower agonist concentrations (1 and 10 pmol/min) a statistically significant increase of rapid eye movement (REM) sleep during infusion into the subarachnoid space (Yoshida et al., 2000). The infusion site at the ventral surface zone of the rostral basal forebrain is topographically located adjacent to the preoptic area, including the sleep-promoting VLPO, an area known for its high expression of the EP4 receptor (Oka et al., 2000; Zhang et al., 2000). It is also noteworthy that either both NREM and REM sleep or only NREM sleep was increased during infusion of the EP2 (ONO-DI004) and EP3 (ONO-AE257) agonists, respectively, into the subarachnoid space surrounding the preoptic area. In contrast to the wide distribution of the EP3 receptor in the preoptic area, expression of the EP2 receptor in the VLPO has not been reported, and at best, low levels of this receptor can be found in adjacent nuclei of the preoptic area (Zhang and Rivest, 1999). Hayaishi and colleagues have intensively investigated the wake-promoting effect of PGE2 in the
15. The Differential Role of Prostaglandin E2 Receptors in the CNS Response
posterior hypothalamus (Huang et al., 2003; Matsumura et al., 1989a; Matsumura et al., 1989b). Recently, this group has shown by in situ hybridization that EP4 receptor mRNA was expressed in histaminergic neurons of the TMN (Huang et al., 2003). Moreover, only the EP4 receptor agonist (ONO-AE1329) mimicked the excitatory effect of PGE2 on histaminergic neurons in the TMN, and only perfusion of the EP4 receptor agonist into the TMN induced wakefulness. Investigations in animal research models and in humans have elucidated the role of cytokines in the physiological and inflammatory regulation of sleep (Krueger et al., 2001; Krueger and Majde, 2003; Mullington et al., 2001). Typically, there is a pronounced enhancement of NREM and an accompanied decrease of REM sleep in animals responding to proinflammatory cytokines, whereas the sleep patterns of humans in response to elevated level of cytokines are more complicated and dose-dependent, leading to increased or decreased NREM sleep. In addition, another PG, PGD2, has also been implicated in regulating sleep (Hayaishi and Urade, 2002). PGD2 is also produced by the action of COX-2, but PGD2 synthase is found only in the meninges surrounding the brain, not in the brain parenchyma (Beuckmann et al., 2000b). Focal infusion of PGD2 into the subarachnoid space ventral to the rostral basal forebrain causes profound enhancement of NREM sleep, and this also activates c-fos expression in the VLPO (Scammell et al., 1998a). Thus, Hayaishi and colleagues have hypothesized counterpoised PGE2 arousal and PGD2 soporific systems that may be activated during inflammation, and which may also play a role in daily regulation of sleep and wakefulness (Hayaishi and Huang, 2004). PGE2 evokes a number of physiological responses during systemic inflammation, though the alterations of sleep-wake patterns by PGE2 is poorly understood. The differential role of DP and EP receptors in sleep regulation during systemic inflammation remains to be clarified in pharmacological and physiological studies using DP and EP receptor agonists or knockout mice. These experiments are crucial to understand how elevated levels of PGE2 in the anterior and posterior hypothalamus in response to a peripheral infection may change sleep-wake cycles of the host, as for example, the excitatory EP4 receptor is expressed on neurons of the sleep-promoting VLPO and the wakepromoting TMN. Moreover, inhibitory EP3 receptors are expressed in the VLPO, thus PGE2 acting on those neurons would most likely decrease activity of the VLPO and induce wakefulness or changes between NREM and REM sleep stages.
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IV. CONCLUSION AND FUTURE STUDIES It is critical for mammals to be able to detect bacteria immediately when they infect local tissue or enter the bloodstream, and to mount a vigorous immune response. During a blood infection (septicemia), bacterial cell wall components such as LPS and cytokines would circulate in the blood, whereas if an infection were more localized, only circulating cytokines, such as IL-1β, TNF-α, and others, would reach the brain. Both LPS and cytokines act on specific receptors present on perivascular cells, and amplify the intracellular response that ultimately leads to elevated levels of PGE2 in the hypothalamus of the brain. Due to the variety of four EP receptors and their differential expression in various areas of the hypothalamus and brain stem, PGE2 mediates different or even counterposing components of the acute phase reaction. In the preoptic area, EP1 and EP3 receptors generate hyperthermia, and EP4 responses generate hypothermia. The body temperature of the animal represents the net effect of these opposing forces, which may vary at different time points after the infection. The synergistic action of the EP1 and EP3 receptor is required for activation of the endocrine component of the PVH in response to systemic LPS administration and release of adrenal and pituitary hormones. EP3 and EP1 receptors have opposing effects on neurons in the preoptic area and on VMH neurons that modulate activity of the descending pain inhibitory system and cause hyperalgesia or analgesia. EP receptors in the sleeppromoting VLPO and wake-promoting TMN might be involved in alteration of sleep behavior during a bacterial infection. Transgenic animals with constitutive gene disruptions of the EP receptors are very valuable for understanding the role played by the specific EP receptors for the mechanisms by which an immune stimulus, such as LPS or IL-1β, can cause a set of acute phase responses organized by the brain. However, the use of existing EP receptor knockout lines has several limitations. It is difficult to use EP4 receptor knockout animals because of the poor viability of the animals. Genetic disruption of the mouse EP4 receptor results in perinatal lethality associated with persistent patent ductus arteriosus. Moreover, because the gene knockout had been present for the entire life of the animals, including during development, there may have been some compensation for the lack of the specific receptors. Most importantly, constitutive knockout animals cannot be used to further localize individual brain areas or neurons involved in the acute phase responses.
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The neuron-specific modulation of EP receptors can be critically tested by using Cre- or Flp-recombinase– mediated DNA recombination in genetically engineered mice with conditional knockouts or knockins of the EP receptors (Lewandoski, 2001). Cre recombinase catalyzes deletion of DNA sequences flanked by 34 base pair LOX sites, while Flp recombinase works similarly on FRT sites. By transgenically directing Cre or Flp to discrete populations of neurons, and by crossing these transgenes with mice bearing LOX- or FRTmodified alleles, it is possible to modulate these genes in a neuron-specific fashion (Balthasar et al., 2004). Similarly, adeno-associated viral vectors (AAVs) expressing either Cre or Flp can be stereotaxically injected into specific nuclei in the brains of mice bearing LOX- or FRT-modified alleles to modulate the gene expression in patterns dictated by the site of AAV injection (Scammell et al., 2003). A mouse line with an EP4R gene amenable to conditional deletion using Cre recombinase was recently created by inserting LOX sites into introns flanking the second exon of the EP4R gene (Schneider et al., 2004). Moreover, our lab is currently producing mice with conditional expression of EP1 and EP3 receptors. The conditional knockout mice for the specific EP receptors will be useful to study the effect of focal gene manipulation in different areas of the hypothalamus, such as preoptic area, PVH, SON, TMN, and VMH, on LPSinduced acute phase responses of the CNS. Moreover, the focal deletion of EP receptors in conditional knockout mice would help to resolve the controversy that the EP receptors expressed in brain stem structures partly modulate autonomic or behavioral changes seen during systemic inflammation or that those changes are due to neural afferent signaling. For instance, the parabrachial nucleus projects to many forebrain structures and autonomic nuclei of the hypothalamus and reliably shows c-fos activation after LPS stimulation (Elmquist et al., 1996; Elmquist and Saper, 1996). Because the EP3 and EP4 receptors are expressed on LPSactivated PB neurons, it was speculated that PGE2 might mediate the signaling of PB neurons rather than the c-fos activation being caused by neural inputs from the NTS or the spinal cord (Engblom et al., 2001; Zhang et al., 2000). Animals with conditional expression of the EP receptor genes will help to test this and a wide range of hypotheses about the roles played by prostaglandins in the CNS response to systemic inflammation.
Acknowledgments We thank Takakazu Oka for his help and advice with this review and for permission to reuse figures from his papers in this review. This work was supported by USPHS grant NS33987.
References Abe, M., Oka, T., Hori, T., and Takahashi, S. (2001). Prostanoids in the preoptic hypothalamus mediate systemic lipopolysaccharide-induced hyperalgesia in rats. Brain Res., 916, 41–49. Balthasar, N., Coppari, R., McMinn, J., Liu, S. M., Lee, C. E., Tang, V., Kenny, C. D., McGovern, R. A., Chua, S. C. Jr., Elmquist, J. K., and Lowell, B. B. (2004). Leptin receptor signaling in POMC neurons is required for normal body weight homeostasis. Neuron, 42, 983–991. Batshake, B., Nilsson, C., and Sundelin, J. (1995). Molecular characterization of the mouse prostanoid EP1 receptor gene. Eur. J. Biochem., 231, 809–814. Beuckmann, C. T., Fujimori, K., Urade, Y., and Hayaishi, O. (2000a). Identification of mu-class glutathione transferases M2-2 and M3-3 as cytosolic prostaglandin E synthases in the human brain. Neurochem. Res., 25, 733–738. Beuckmann, C. T., Lazarus, M., Gerashchenko, D., Mizoguchi, A., Nomura, S., Mohri, I., Uesugi, A., Kaneko, T., Mizuno, N., Hayaishi, O., and Urade, Y. (2000b). Cellular localization of lipocalin-type prostaglandin D synthase β-trace in the central nervous system of the adult rat. J. Comp. Neurol., 428, 62–78. Blatteis, C. M. (1992). Role of the OVLT in the febrile response to circulating pyrogens. Prog. Brain Res., 91, 409–412. Blatteis, C. M., Bealer, S. L., Hunter, W. S., Llanos, Q. J., Ahokas, R. A., and Mashburn, T. A., Jr. (1983). Suppression of fever after lesions of the anteroventral third ventricle in guinea pigs. Brain Res. Bull., 11, 519–526. Blatteis, C. M., Sehic, E., and Li, S. (1998). Afferent pathways of pyrogen signaling. Ann. N. Y. Acad. Sci., 856, 95–107. Bluthe, R. M., Michaud, B., Kelley, K. W., and Dantzer, R. (1996). Vagotomy blocks behavioural effects of interleukin-1 injected via the intraperitoneal route but not via other systemic routes. Neuroreport, 7, 2823–2827. Breder, C. D., Dewitt, D., and Kraig, R. P. (1995). Characterization of inducible cyclooxygenase in rat brain. J. Comp. Neurol., 355, 296–315. Breder, C. D., Dinarello, C. A., and Saper, C. B. (1988). Interleukin-1 immunoreactive innervation of the human hypothalamus. Science, 240, 321–324. Breder, C. D., Hazuka, C., Ghayur, T., Klug, C., Huginin, M., Yasuda, K., Teng, M., and Saper, C. B. (1994). Regional induction of tumor necrosis factor alpha expression in the mouse brain after systemic lipopolysaccharide administration. Proc. Natl. Acad. Sci. U.S.A., 91, 11393–11397. Breder, C. D., and Saper, C. B. (1996). Expression of inducible cyclooxygenase mRNA in the mouse brain after systemic administration of bacterial lipopolysaccharide. Brain Res., 713, 64–69. Breder, C. D., Smith, W. L., Raz, A., Masferrer, J., Seibert, K., Needleman, P., and Saper, C. B. (1992). Distribution and characterization of cyclooxygenase immunoreactivity in the ovine brain. J. Comp. Neurol., 322, 409–438. Breder, C. D., Tsujimoto, M., Terano, Y., Scott, D. W., and Saper, C. B. (1993). Distribution and characterization of tumor necrosis factor-alpha–like immunoreactivity in the murine central nervous system. J. Comp. Neurol., 337, 543–567. Cano, G., Passerin, A. M., Schiltz, J. C., Card, J. P., Morrison, S. F., and Sved, A. F. (2003). Anatomical substrates for the central control of sympathetic outflow to interscapular adipose tissue during cold exposure. J. Comp. Neurol., 460, 303–326. Canteras, N. S., Simerly, R. B., and Swanson, L. W. (1994). Organization of projections from the ventromedial nucleus of the hypothalamus: a Phaseolus vulgaris-leucoagglutinin study in the rat. J. Comp. Neurol., 348, 41–79.
15. The Differential Role of Prostaglandin E2 Receptors in the CNS Response Cao, C., Matsumura, K., Yamagata, K., and Watanabe, Y. (1995). Induction by lipopolysaccharide of cyclooxygenase-2 mRNA in rat brain; its possible role in the febrile response. Brain Res., 697, 187–196. Cao, C., Matsumura, K., Yamagata, K., and Watanabe, Y. (1996). Endothelial cells of the rat brain vasculature express cyclooxygenase-2 mRNA in response to systemic interleukin-1 beta: a possible site of prostaglandin synthesis responsible for fever. Brain Res., 733, 263–272. Chan, R. K., Brown, E. R., Ericsson, A., Kovacs, K. J., and Sawchenko, P. E. (1993). A comparison of two immediate-early genes, c-fos and NGFI-B, as markers for functional activation in stress-related neuroendocrine circuitry. J. Neurosci., 13, 5126–5138. Conti, B., Tabarean, I., Andrei, C., and Bartfai, T. (2004). Cytokines and fever. Front. Biosci., 9, 1433–1449. Dantzer, R., Konsman, J. P., Bluthe, R. M., and Kelley, K. W. (2000). Neural and humoral pathways of communication from the immune system to the brain: parallel or convergent? Auton. Neurosci., 85, 60–65. Ek, M., Arias, C., Sawchenko, P., and Ericsson-Dahlstrand, A. (2000). Distribution of the EP3 prostaglandin E(2) receptor subtype in the rat brain: relationship to sites of interleukin-1–induced cellular responsiveness. J. Comp. Neurol., 428, 5–20. Ek, M., Engblom, D., Saha, S., Blomqvist, A., Jakobsson, P. J., and Ericsson-Dahlstrand, A. (2001). Inflammatory response: pathway across the blood-brain barrier. Nature, 410, 430–431. Ek, M., Kurosawa, M., Lundeberg, T., and Ericsson, A. (1998). Activation of vagal afferents after intravenous injection of interleukin-1beta: role of endogenous prostaglandins. J. Neurosci., 18, 9471–9479. Elmquist, J. K., Breder, C. D., Sherin, J. E., Scammell, T. E., Hickey, W. F., Dewitt, D., and Saper, C. B. (1997). Intravenous lipopolysaccharide induces cyclooxygenase 2–like immunoreactivity in rat brain perivascular microglia and meningeal macrophages. J. Comp. Neurol., 381, 119–129. Elmquist, J. K., and Saper, C. B. (1996). Activation of neurons projecting to the paraventricular hypothalamic nucleus by intravenous lipopolysaccharide. J. Comp. Neurol., 374, 315–331. Elmquist, J. K., Scammell, T. E., Jacobson, C. D., and Saper, C. B. (1996). Distribution of Fos-like immunoreactivity in the rat brain following intravenous lipopolysaccharide administration. J. Comp. Neurol., 371, 85–103. Engblom, D., Ek, M., Andersson, I. M., Saha, S., Dahlstrom, M., Jakobsson, P. J., Ericsson-Dahlstrand, A., and Blomqvist, A. (2002a). Induction of microsomal prostaglandin E synthase in the rat brain endothelium and parenchyma in adjuvant-induced arthritis. J. Comp. Neurol., 452, 205–214. Engblom, D., Ek, M., Ericsson-Dahlstrand, A., and Blomqvist, A. (2001). Activation of prostanoid EP(3) and EP(4) receptor mRNAexpressing neurons in the rat parabrachial nucleus by intravenous injection of bacterial wall lipopolysaccharide. J. Comp. Neurol., 440, 378–386. Engblom, D., Ek, M., Saha, S., Ericsson-Dahlstrand, A., Jakobsson, P. J., and Blomqvist, A. (2002b). Prostaglandins as inflammatory messengers across the blood-brain barrier. J. Mol. Med., 80, 5–15. Engblom, D., Saha, S., Engstrom, L., Westman, M., Audoly, L. P., Jakobsson, P. J., and Blomqvist, A. (2003). Microsomal prostaglandin E synthase-1 is the central switch during immuneinduced pyresis. Nat. Neurosci., 6, 1137–1138. Ericsson, A., Arias, C., and Sawchenko, P. E. (1997). Evidence for an intramedullary prostaglandin-dependent mechanism in the activation of stress-related neuroendocrine circuitry by intravenous interleukin-1. J. Neurosci., 17, 7166–7179.
333
Ericsson, A., Kovacs, K. J., and Sawchenko, P. E. (1994). A functional anatomical analysis of central pathways subserving the effects of interleukin-1 on stress-related neuroendocrine neurons. J. Neurosci., 14, 897–913. Fitzgerald, K. A., and O’Neill, L. A. J. (2000). The role of the interleukin-1/Toll-like receptor superfamily in inflammation and host defence. Microbes and Infection, 2, 933–943. Gerozissis, K., De Saint Hilaire, Z., Orosco, M., Rouch, C., and Nicolaidis, S. (1995). Changes in hypothalamic prostaglandin E2 may predict the occurrence of sleep or wakefulness as assessed by parallel EEG and microdialysis in the rat. Brain Res., 689, 239–244. Goehler, L. E., Gaykema, R. P., Nguyen, K. T., Lee, J. E., Tilders, F. J., Maier, S. F., and Watkins, L. R. (1999). Interleukin-1beta in immune cells of the abdominal vagus nerve: a link between the immune and nervous systems? J. Neurosci., 19, 2799–2806. Goldblatt, M. W. (1935). Properties of human seminal plasma. J. Physiol. (Lond), 84, 208–218. Hashimoto, M., Bando, T., Iriki, M., and Hashimoto, K. (1988). Effect of indomethacin on febrile response to recombinant human interleukin 1-alpha in rabbits. Am. J. Physiol., 255, R527–533. Hayaishi, O., and Huang, Z. L. (2004). Role of orexin and prostaglandin E2 in activating histaminergic neurotransmission. Drug News Perspect., 17, 105–109. Hayaishi, O., and Urade, Y. (2002). Prostaglandin D2 in sleep-wake regulation: recent progress and perspectives. Neuroscientist, 8, 12–15. Herman, J. P., and Cullinan, W. E. (1997). Neurocircuitry of stress: central control of the hypothalamo-pituitary-adrenocortical axis. Trends Neurosci., 20, 78–84. Hopkins, S. J., and Rothwell, N. J. (1995). Cytokines and the nervous system I: expression and recognition. Trends Neurosci., 18, 83–88. Hori, T., Oka, T., Hosoi, M., Abe, M., and Oka, K. (2000). Hypothalamic mechanisms of pain modulatory actions of cytokines and prostaglandin E2. Ann. N. Y. Acad. Sci., 917, 106–120. Horn, T., Wilkinson, M. F., Landgraf, R., and Pittman, Q. J. (1994). Reduced febrile responses to pyrogens after lesions of the hypothalamic paraventricular nucleus. Am. J. Physiol. Regul. Integr. Comp. Physiol., 267, R323–328. Hosoi, M., Oka, T., Abe, M., Hori, T., Yamamoto, H., Mine, K., and Kubo, C. (1999). Prostaglandin E(2) has antinociceptive effect through EP(1) receptor in the ventromedial hypothalamus in rats. Pain, 83, 221–227. Hosoi, M., Oka, T., and Hori, T. (1997). Prostaglandin E receptor EP3 subtype is involved in thermal hyperalgesia through its actions in the preoptic hypothalamus and the diagonal band of Broca in rats. Pain, 71, 303–311. Huang, Z.-L., Sato, Y., Mochizuki, T., Okada, T., Qu, W.-M., Yamatodani, A., Urade, Y., and Hayaishi, O. (2003). Prostaglandin E2 activates the histaminergic system via the EP4 receptor to induce wakefulness in rats. J. Neurosci., 23, 5975–5983. Ivanov, A. I., and Romanovsky, A. A. (2004). Prostaglandin E2 as a mediator of fever: synthesis and catabolism. Front. Biosci., 9, 1977–1993. Ivanov, A. I., Scheck, A. C., and Romanovsky, A. A. (2003). Expression of genes controlling transport and catabolism of prostaglandin E2 in lipopolysaccharide fever. Am. J. Physiol. Regul. Integr. Comp. Physiol., 284, R698–706. Jakobsson, P. J., Thoren, S., Morgenstern, R., and Samuelsson, B. (1999). Identification of human prostaglandin E synthase: a microsomal, glutathione-dependent, inducible enzyme, constituting a potential novel drug target. Proc. Natl. Acad. Sci. U.S.A., 96, 7220–7225.
334
II. Immune System Effects on Neural and Endocrine Processes and Behavior
Johnson, R. W., and von Borell, E. (1994). Lipopolysaccharideinduced sickness behavior in pigs is inhibited by pretreatment with indomethacin. J. Anim. Sci., 72, 309–314. Jones, S. L. (1992). Descending control of nociception. In P. L. Gildenberg (Ed.), Pain and headache (vol. 12, pp. 203–295). Basel: Karger. Kamei, D., Yamakawa, K., Takegoshi, Y., Mikami-Nakanishi, M., Nakatani, Y., Oh-Ishi, S., Yasui, H., Azuma, Y., Hirasawa, N., Ohuchi, K., Kawaguchi, H., Ishikawa, Y., Ishii, T., Uematsu, S., Akira, S., Murakami, M., and Kudo, I. (2004). Reduced pain hypersensitivity and inflammation in mice lacking microsomal prostaglandin E synthase-1. J. Biol. Chem., 279, 33684–33695. Katsuura, G., Arimura, A., Koves, K., and Gottschall, P. E. (1990). Involvement of organum vasculosum of lamina terminalis and preoptic area in interleukin 1 beta–induced ACTH release. Am. J. Physiol., 258, E163–171. Konsman, J. P., Parnet, P., and Dantzer, R. (2002). Cytokine-induced sickness behaviour: mechanisms and implications. Trends Neurosci., 25, 154–159. Krueger, J. M., and Majde, J. A. (2003). Humoral links between sleep and the immune system: research issues. Ann. N. Y. Acad. Sci., 992, 9–20. Krueger, J. M., Obal, F. Jr., Fang, J., Kubota, T., and Taishi, P. (2001). The role of cytokines in physiological sleep regulation. Ann. N. Y. Acad. Sci., 933, 211–221. Lacroix, S., Vallieres, L., and Rivest, S. (1996). C-fos mRNA pattern and corticotropin-releasing factor neuronal activity throughout the brain of rats injected centrally with a prostaglandin of E2 type. J. Neuroimmunol., 70, 163–179. Lazarus, M., Kubata, B. K., Eguchi, N., Fujitani, Y., Urade, Y., and Hayaishi, O. (2002). Biochemical characterization of mouse microsomal prostaglandin E synthase-1 and its colocalization with cyclooxygenase-2 in peritoneal macrophages. Arch. Biochem. Biophys., 397, 336–341. Lewandoski, M. (2001). Conditional control of gene expression in the mouse. Nat. Rev. Genet., 2, 743–755. Li, S., Ballou, L. R., Morham, S. G., and Blatteis, C. M. (2001). Cyclooxygenase-2 mediates the febrile response of mice to interleukin1beta. Brain Res., 910, 163–173. Li, S., Wang, Y., Matsumura, K., Ballou, L. R., Morham, S. G., and Blatteis, C. M. (1999). The febrile response to lipopolysaccharide is blocked in cyclooxygenase-2−/−, but not in cyclooxygenase1−/− mice. Brain Res., 825, 86–94. Lu, J., Zhang, Y. H., Chou, T. C., Gaus, S. E., Elmquist, J. K., Shiromani, P., and Saper, C. B. (2001). Contrasting effects of ibotenate lesions of the paraventricular nucleus and subparaventricular zone on sleep-wake cycle and temperature regulation. J. Neurosci., 21, 4864–4874. Madden, C. J., and Morrison, S. F. (2003). Excitatory amino acid receptor activation in the raphe pallidus area mediates prostaglandin-evoked thermogenesis. Neuroscience, 122, 5–15. Madden, C. J., and Morrison, S. F. (2004). Excitatory amino acid receptors in the dorsomedial hypothalamus mediate prostaglandin-evoked thermogenesis in brown adipose tissue. Am. J. Physiol. Regul. Integr. Comp. Physiol., 286, R320–325. Maier, S. F., Wiertelak, E. P., Martin, D., and Watkins, L. R. (1993). Interleukin-1 mediates the behavioral hyperalgesia produced by lithium chloride and endotoxin. Brain Res., 623, 321–324. Matsumura, H., Honda, K., Choi, W. S., Inoue, S., Sakai, T., and Hayaishi, O. (1989a). Evidence that brain prostaglandin E2 is involved in physiological sleep-wake regulation in rats. Proc. Natl. Acad. Sci. U.S.A., 86, 5666–5669. Matsumura, H., Honda, K., Goh, Y., Ueno, R., Sakai, T., Inoue, S., and Hayaishi, O. (1989b). Awaking effect of prostaglandin E2 in freely moving rats. Brain Res., 481, 242–249.
Matsumura, K., and Kobayashi, S. (2004). Signaling the brain in inflammation: the role of endothelial cells. Front. Biosci., 9, 2819–2826. Matsuoka, Y., Furuyashiki, T., Bito, H., Ushikubi, F., Tanaka, Y., Kobayashi, T., Muro, S., Satoh, N., Kayahara, T., Higashi, M., Mizoguchi, A., Shichi, H., Fukuda, Y., Nakao, K., and Narumiya, S. (2003). Impaired adrenocorticotropic hormone response to bacterial endotoxin in mice deficient in prostaglandin E receptor EP1 and EP3 subtypes. Proc. Natl. Acad. Sci. U.S.A., 100, 4132–4137. Milton, A. S., and Wendlandt, S. (1970). A possible role for prostaglandin E1 as a modulator for temperature regulation in the central nervous system of the cat. J. Physiol., 207, 76P–77P. Morrison, S. F. (2001). Differential regulation of sympathetic outflows to vasoconstrictor and thermoregulatory effectors. Ann. N. Y. Acad. Sci., 940, 286–298. Morrison, S. F. (2003). Raphe pallidus neurons mediate prostaglandin E2–evoked increases in brown adipose tissue thermogenesis. Neuroscience, 121, 17–24. Morrison, S. F. (2004). Central pathways controlling brown adipose tissue thermogenesis. News Physiol. Sci., 19, 67–74. Mullington, J. M., Hinze-Selch, D., and Pollmacher, T. (2001). Mediators of inflammation and their interaction with sleep: relevance for chronic fatigue syndrome and related conditions. Ann. N. Y. Acad. Sci., 933, 201–210. Nakamori, T., Morimoto, A., Yamaguchi, K., Watanabe, T., and Murakami, N. (1994). Interleukin-1 beta production in the rabbit brain during endotoxin-induced fever. J. Physiol., 476, 177–186. Nakamura, K., Kaneko, T., Yamashita, Y., Hasegawa, H., Katoh, H., Ichikawa, A., and Negishi, M. (1999). Immunocytochemical localization of prostaglandin EP3 receptor in the rat hypothalamus. Neuroscience Letters, 260, 117–120. Nakamura, K., Kaneko, T., Yamashita, Y., Hasegawa, H., Katoh, H., and Negishi, M. (2000). Immunohistochemical localization of prostaglandin EP3 receptor in the rat nervous system. J. Comp. Neurol., 421, 543–569. Nakamura, K., Matsumura, K., Hubschle, T., Nakamura, Y., Hioki, H., Fujiyama, F., Boldogkoi, Z., Konig, M., Thiel, H.-J., Gerstberger, R., Kobayashi, S., and Kaneko, T. (2004). Identification of sympathetic premotor neurons in medullary raphe regions mediating fever and other thermoregulatory functions. J. Neurosci., 24, 5370–5380. Nakamura, K., Matsumura, K., Kaneko, T., Kobayashi, S., Katoh, H., and Negishi, M. (2002). The rostral raphe pallidus nucleus mediates pyrogenic transmission from the preoptic area. J. Neurosci., 22, 4600–4610. Narumiya, S., and FitzGerald, G. A. (2001). Genetic and pharmacological analysis of prostanoid receptor function. J. Clin. Invest, 108, 25–30. Narumiya, S., Sugimoto, Y., and Ushikubi, F. (1999). Prostanoid receptors: structures, properties, and functions. Physiol. Rev., 79, 1193–1226. Nguyen, M., Camenisch, T., Snouwaert, J. N., Hicks, E., Coffman, T. M., Anderson, P. A., Malouf, N. N., and Koller, B. H. (1997). The prostaglandin receptor EP4 triggers remodelling of the cardiovascular system at birth. Nature, 390, 78–81. O’Banion, M. K. (1999). Cyclooxygenase-2: molecular biology, pharmacology, and neurobiology. Crit. Rev. Neurobiol., 13, 45–82. Oka, K., Oka, T., and Hori, T. (1997a). Prostaglandin E2 may induce hyperthermia through EP1 receptor in the anterior wall of the third ventricle and neighboring preoptic regions. Brain Res., 767, 92–99. Oka, K., Oka, T., and Hori, T. (1998). PGE2 receptor subtype EP1 antagonist may inhibit central interleukin-1beta–induced fever in rats. Am. J. Physiol., 275, R1762–1765.
15. The Differential Role of Prostaglandin E2 Receptors in the CNS Response Oka, T., Aou, S., and Hori, T. (1994). Intracerebroventricular injection of prostaglandin E2 induces thermal hyperalgesia in rats: the possible involvement of EP3 receptors. Brain Res., 663, 287–292. Oka, T., and Hori, T. (1994). EP1-receptor mediation of prostaglandin E2–induced hyperthermia in rats. Am. J. Physiol., 267, R289–294. Oka, T., Hori, T., Hosoi, M., Oka, K., Abe, M., and Kubo, C. (1997b). Biphasic modulation in the trigeminal nociceptive neuronal responses by the intracerebroventricular prostaglandin E2 may be mediated through different EP receptor subtypes in rats. Brain Res., 771, 278–284. Oka, T., Oka, K., Hosoi, M., Aou, S., and Hori, T. (1995). The opposing effects of interleukin-1 beta microinjected into the preoptic hypothalamus and the ventromedial hypothalamus on nociceptive behavior in rats. Brain Res., 700, 271–278. Oka, T., Oka, K., Kobayashi, T., Sugimoto, Y., Ichikawa, A., Ushikubi, F., Narumiya, S., and Saper, C. B. (2003a). Characteristics of thermoregulatory and febrile responses in mice deficient in prostaglandin EP1 and EP3 receptors. J. Physiol. (Lond), 551, 945–954. Oka, T., Oka, K., and Saper, C. B. (2003b). Contrasting effects of E type prostaglandin (EP) receptor agonists on core body temperature in rats. Brain Res., 968, 256–262. Oka, T., Oka, K., Scammell, T. E., Lee, C., Kelly, J. F., Nantel, F., Elmquist, J. K., and Saper, C. B. (2000). Relationship of EP(1–4) prostaglandin receptors with rat hypothalamic cell groups involved in lipopolysaccharide fever responses. J. Comp. Neurol., 428, 20–32. Parrott, R. F., and Vellucci, S. V. (1996). Effects of centrally administered prostaglandin EP receptor agonists on febrile and adrenocortical responses in the prepubertal pig. Brain Res. Bull., 41, 97–103. Quan, N., Stern, E. L., Whiteside, M. B., and Herkenham, M. (1999). Induction of pro-inflammatory cytokine mRNAs in the brain after peripheral injection of subseptic doses of lipopolysaccharide in the rat. J. Neuroimmunol., 93, 72–80. Ram, A., Pandey, H. P., Matsumura, H., Kasahara-Orita, K., Nakajima, T., Takahata, R., Satoh, S., Terao, A., and Hayaishi, O. (1997). CSF levels of prostaglandins, especially the level of prostaglandin D2, are correlated with increasing propensity towards sleep in rats. Brain Res., 751, 81–89. Rivest, S. (2003). Molecular insights on the cerebral innate immune system. Brain Behav. Immun., 17, 13–19. Rizvi, T. A., Ennis, M., and Shipley, M. T. (1992). Reciprocal connections between the medial preoptic area and the midbrain periaqueductal gray in rat: a WGA-HRP and PHA-L study. J. Comp. Neurol., 315, 1–15. Romanovsky, A. A. (2004). Signaling the brain in the early sickness syndrome: are sensory nerves involved? Front. Biosci., 9, 494–504. Romanovsky, A. A., Ivanov, A. I., Lenczowski, M. J. P., Kulchitsky, V. A., Van Dam, A.-M., Poole, S., Homer, L. D., and Tilders, F. J. H. (2000). Lipopolysaccharide transport from the peritoneal cavity to the blood: is it controlled by the vagus nerve? Autonomic Neuroscience, 85, 133–140. Romanovsky, A. A., Sugimoto, N., Simons, C. T., and Hunter, W. S. (2003). The organum vasculosum laminae terminalis in immuneto-brain febrigenic signaling: a reappraisal of lesion experiments. Am. J. Physiol. Regul. Integr. Comp. Physiol., 285, R420–428. Saper, C. B., and Breder, C. D. (1992). Endogenous pyrogens in the CNS: role in the febrile response. Prog. Brain Res., 93, 419–429. Saper, C. B., and Breder, C. D. (1994). The neurologic basis of fever. N. Engl. J. Med., 330, 1880–1886.
335
Saper, C. B., Chou, T. C., and Elmquist, J. K. (2002). The need to feed: homeostatic and hedonic control of eating. Neuron, 36, 199–211. Saper, C. B., Chou, T. C., and Scammell, T. E. (2001). The sleep switch: hypothalamic control of sleep and wakefulness. Trends Neurosci., 24, 726–731. Saper, C. B., and Levisohn, D. (1983). Afferent connections of the median preoptic nucleus in the rat: anatomical evidence for a cardiovascular integrative mechanism in the anteroventral third ventricular (AV3V) region. Brain Res., 288, 21–31. Saper, C. B., Swanson, L. W., and Cowan, W. M. (1976). The efferent connections of the ventromedial nucleus of the hypothalamus of the rat. J. Comp. Neurol., 169, 409–442. Sawchenko, P. E., Brown, E. R., Chan, R. K., Ericsson, A., Li, H. Y., Roland B. L., and Kovacs, K. J. (1996). The paraventricular nucleus of the hypothalamus and the functional neuroanatomy of visceromotor responses to stress. Prog. Brain Res., 107, 201–222. Scammell, T., Gerashchenko, D., Urade, Y., Onoe, H., Saper, C., and Hayaishi, O. (1998a). Activation of ventrolateral preoptic neurons by the somnogen prostaglandin D2. Proc. Natl. Acad. Sci. U.S.A., 95, 7754–7759. Scammell, T. E., Arrigoni, E., Thompson, M. A., Ronan, P. J., Saper, C. B., and Greene, R. W. (2003). Focal deletion of the adenosine A1 receptor in adult mice using an adeno-associated viral vector. J. Neurosci., 23, 5762–5770. Scammell, T. E., Elmquist, J. K., Griffin, J. D., and Saper, C. B. (1996). Ventromedial preoptic prostaglandin E2 activates fever-producing autonomic pathways. J. Neurosci., 16, 6246–6254. Scammell, T. E., Griffin, J. D., Elmquist, J. K., and Saper, C. B. (1998b). Microinjection of a cyclooxygenase inhibitor into the anteroventral preoptic region attenuates LPS fever. Am. J. Physiol., 274, R783–789. Schiltz, J. C., and Sawchenko, P. E. (2002). Distinct brain vascular cell types manifest inducible cyclooxygenase expression as a function of the strength and nature of immune insults. J. Neurosci., 22, 5606–5618. Schiltz, J. C., and Sawchenko, P. E. (2003). Signaling the brain in systemic inflammation: the role of perivascular cells. Front. Biosci., 8, S1321–1329. Schneider, A., Guan, Y., Zhang, Y., Magnuson, M. A., Pettepher, C., Loftin, C. D., Langenbach, R., Breyer, R. M., and Breyer, M. D. (2004). Generation of a conditional allele of the mouse prostaglandin EP(4) receptor. Genesis, 40, 7–14. Segi, E., Sugimoto, Y., Yamasaki, A., Aze, Y., Oida, H., Nishimura, T., Murata, T., Matsuoka, T., Ushikubi, F., and Hirose, M. (1998). Patent ductus arteriosus and neonatal death in prostaglandin receptor EP4-deficient mice. Biochem. Biophys. Res. Commun., 246, 7–12. Sehic, E., Hunter, W. S., Ungar, A. L., and Blatteis, C. M. (1997). Blockade of Kupffer cells prevents the febrile and preoptic prostaglandin E2 responses to intravenous lipopolysaccharide in guinea pigs. Ann. N. Y. Acad. Sci., 813, 448–452. Smith, W. L., and Dewitt, D. L. (1996). Prostaglandin endoperoxide H synthases-1 and -2. Adv. Immunol., 62, 167–215. Stitt, J. T. (1985). Evidence for the involvement of the organum vasculosum laminae terminalis in the febrile response of rabbits and rats. J. Physiol., 368, 501–511. Stitt, J. T., and Bernheim, H. A. (1985). Differences in endogenous pyrogen fevers induced by iv and icv routes in rabbits. J. Appl. Physiol., 59, 342–347. Szekely, M., Balasko, M., Kulchitsky, V. A., Simons, C. T., Ivanov, A. I., and Romanovsky, A. A. (2000). Multiple neural mechanisms of fever. Auton. Neurosci., 85, 78–82. Takahashi, Y., Smith, P., Ferguson, A., and Pittman, Q. J. (1997). Circumventricular organs and fever. Am. J. Physiol., 273, R1690–1695.
336
II. Immune System Effects on Neural and Endocrine Processes and Behavior
Tanaka, M., and McAllen, R. M. (2005). A subsidiary fever center in the medullary raphe? Am. J. Physiol. Regul. Integr. Comp. Physiol., 289, R1592–R1598. Tanioka, T., Nakatani, Y., Semmyo, N., Murakami, M., and Kudo, I. (2000). Molecular identification of cytosolic prostaglandin E2 synthase that is functionally coupled with cyclooxygenase-1 in immediate prostaglandin E2 biosynthesis. J. Biol. Chem., 275, 32775–32782. Taogoshi, T., Nomura, A., Murakami, T., Nagai, J., and Takano, M. (2005). Transport of prostaglandin E1 across the blood-brain barrier in rats. J. Pharm. Pharmacol., 57, 61–66. Thoren, S., and Jakobsson, P. J. (2000). Coordinate up- and downregulation of glutathione-dependent prostaglandin E synthase and cyclooxygenase-2 in A549 cells. Inhibition by NS-398 and leukotriene C4. Eur. J. Biochem., 267, 6428–6434. Ushikubi, F., Segi, E., Sugimoto, Y., Murata, T., Matsuoka, T., Kobayashi, T., Hizaki, H., Tuboi, K., Katsuyama, M., Ichikawa, A., Tanaka, T., Yoshida, N., and Narumiya, S. (1998). Impaired febrile response in mice lacking the prostaglandin E receptor subtype EP3. Nature, 395, 281–284. Van Dam, A. M., Brouns, M., Man, A. H. W., and Berkenbosch, F. (1993). Immunocytochemical detection of prostaglandin E2 in microvasculature and in neurons of rat brain after administration of bacterial endotoxin. Brain Res., 613, 331–336. Vane, J. R. (1971). Inhibition of prostaglandin synthesis as a mechanism of action for aspirin-like drugs. Nat. New Biol., 231, 232–235. Vane, J. R., and Botting, R. M. (2003). The mechanism of action of aspirin. Thromb. Res., 110, 255–258. Vanegas, H., and Schaible, H.-G. (2004). Descending control of persistent pain: inhibitory or facilitatory? Brain Res. Rev., 46, 295–309. von Euler, U. S. (1935). Über die spezifische blutdrucksenkende Substanz des menschlichen Prostata- und Samenblasensekretes. Klin. Wochenschrift., 14, 1182–1183. Wan, W., Wetmore, L., Sorensen, C. M., Greenberg, A. H., and Nance, D. M. (1994). Neural and biochemical mediators of endotoxin and stress-induced c-fos expression in the rat brain. Brain Res. Bull., 34, 7–14. Watkins, L. R., Wiertelak, E. P., Goehler, L. E., Mooney-Heiberger, K., Martinez, J., Furness, L., Smith, K. P., and Maier, S. F. (1994). Neurocircuitry of illness-induced hyperalgesia. Brain Res., 639, 283–299.
Wicrtelak, E. P., Smith, K. P., Furness, L., Mooney-Heiberger, K., Mayr, T., Maier, S. F., and Watkins, L. R. (1994). Acute and conditioned hyperalgesic responses to illness. Pain, 56, 227–234. Yamagata, K., Andreasson, K. I., Kaufmann, W. E., Barnes, C. A., and Worley, P. F. (1993). Expression of a mitogen-inducible cyclooxygenase in brain neurons: regulation by synaptic activity and glucocorticoids. Neuron, 11, 371–386. Yamagata, K., Matsumura, K., Inoue, W., Shiraki, T., Suzuki, K., Yasuda, S., Sugiura, H., Cao, C., Watanabe, Y., and Kobayashi, S. (2001). Coexpression of microsomal-type prostaglandin E synthase with cyclooxygenase-2 in brain endothelial cells of rats during endotoxin-induced fever. J. Neurosci., 21, 2669–2677. Yoshida, K., Konishi, M., Nagashima, K., Saper, C. B., and Kanosue, K. (2005). Fos activation in hypothalamic neurons during cold or warm exposure: projections to periaqueductal gray matter. Neuroscience, 133, 1039–1046. Yoshida, K., Nakamura, K., Matsumura, K., Kanosue, K., Konig, M., Thiel, H. J., Boldogkoi, Z., Toth, I., Roth, J., Gerstberger, R., and Hubschle, T. (2003). Neurons of the rat preoptic area and the raphe pallidus nucleus innervating the brown adipose tissue express the prostaglandin E receptor subtype EP3. Eur. J. Neurosci., 18, 1848–1860. Yoshida, Y., Matsumura, H., Nakajima, T., Mandai, M., Urakami, T., Kuroda, K., and Yoneda, H. (2000). Prostaglandin E (EP) receptor subtypes and sleep: promotion by EP4 and inhibition by EP1/ EP2. Neuroreport, 11, 2127–2131. Zhang, J., and Rivest, S. (1999). Distribution, regulation and colocalization of the genes encoding the EP2- and EP4-PGE2 receptors in the rat brain and neuronal responses to systemic inflammation. Eur. J. Neurosci., 11, 2651–2668. Zhang, J., and Rivest, S. (2000). A functional analysis of EP4 receptor-expressing neurons in mediating the action of prostaglandin E2 within specific nuclei of the brain in response to circulating interleukin-1beta. J. Neurochem., 74, 2134–2145. Zhang, Y. H., Lu, J., Elmquist, J. K., and Saper, C. B. (2003). Specific roles of cyclooxygenase-1 and cyclooxygenase-2 in lipopolysaccharide-induced fever and Fos expression in rat brain. J. Comp. Neurol., 463, 3–12. Zhang, Y.-H., Lu, J., Elmquist, J. K., and Saper, C. B. (2000). Lipopolysaccharide activates specific populations of hypothalamic and brainstem neurons that project to the spinal cord. J. Neurosci., 20, 6578–6586.
C H A P T E R
16 The Role of Pro-inflammatory Cytokines in Memory Processes and Neural Plasticity INBAL GOSHEN AND RAZ YIRMIYA
kines interleukin (IL)-1, IL-6, and tumor necrosis factor (TNF)-α, which coordinate subsequent immune, physiological, metabolic, and behavioral responses that are collectively termed the acute phase reaction (Dinarello, 2000). In addition to their role in immunoregulation of inflammatory processes, pro-inflammatory cytokines play a major role in modulation of neural, neuroendocrine, and behavioral systems during illness (Dantzer, 2004; Maier and Watkins, 1998; Rothwell et al., 1996; Yirmiya, 1997). For example, medical conditions that are associated with elevated brain levels of proinflammatory cytokines, or direct administration of these compounds into the brains of experimental animals, produce fever, activation of the hypothalamicpituitary-adrenal (HPA) axis, and many behavioral symptoms that are collectively termed sickness behavior (Dantzer, 2004; Kent et al., 1992; Maier, 2003; Yirmiya, 1997). Furthermore, recent studies suggest that brain cytokines may also have some physiological roles in neural, neuroendocrine, and behavioral regulation (Vitkovic et al., 2000). One of the most salient symptoms of the sickness behavior syndrome is alteration in learning and memory processes. The aim of this chapter is to summarize the results that have been obtained to date on the role of pro-inflammatory cytokines, particularly IL-1, IL-6, and TNF-α, in learning and memory, both during illness and in healthy individuals. In addition, we propose several mechanisms that can mediate the effects of cytokine-induced memory alterations.
I. INTRODUCTION 337 II. EFFECTS OF IL-1, IL-6, AND TNF-α ON LEARNING AND MEMORY IN RODENTS 342 III. MECHANISMS UNDERLYING THE EFFECTS OF PRO-INFLAMMATORY CYTOKINES ON LEARNING AND MEMORY 353 IV. PRO-INFLAMMATORY CYTOKINES AND MEMORY FUNCTIONING IN HUMANS 360 V. GENERAL SUMMARY AND CONCLUSIONS 366
I. INTRODUCTION In animals and in humans, infectious diseases pose one of the most serious challenges for survival and reproduction. This challenge constitutes a major selective force for the evolution of defense mechanisms against pathogen invaders. The first line of defense is the non-specific, innate immune response (Hoffmann et al., 1999). This response is triggered by conserved molecular patterns on infectious microorganisms, e.g., lipopolysaccharide (LPS—a major constituent of the cell wall of gram negative bacteria), which bind to specific receptors (e.g., the Toll-like receptors) expressed by cells of the innate immune system (e.g., macrophages) (Janeway and Medzhitov, 2002; Takeda et al., 2003). The resultant activation of these cells leads to the destruction of the pathogenic microorganisms, either by phagocytosis or by secreted compounds such as reactive oxygen species. Activated innate immune cells also secrete various compounds that induce inflammation, particularly the pro-inflammatory cytoPSYCHONEUROIMMUNOLOGY, 4E VOLUME I
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A. Pro-inflammatory Cytokines in the Brain Affect Behavioral Processes In order to modulate learning and memory, proinflammatory cytokines have to be able to reach the brain and to affect neural processes. The following section constitutes a short (and non-comprehensive) introduction to the signaling pathways via which proinflammatory cytokines exert their actions, the ways by which pro-inflammatory cytokines, secreted either by immune cells in the periphery or by glia cells and neurons within the central nervous system (CNS), influence neural processes, and the functional consequences of pro-inflammatory cytokines actions in the brain, i.e., their involvement in behavioral alterations during illness and in health. 1. The Signaling Pathways of Pro-inflammatory Cytokines IL-1 Signaling IL-1 signaling is mediated by a complex system, which includes several ligands and receptors. The cytokines IL-1α and IL-1β activate signaling, whereas IL-1 receptor antagonist (IL-1ra) serves to block the effects of IL-1 by binding to the same receptors without triggering signaling (Dinarello, 1996). Many types of IL-1 receptors have been identified (Loddick et al., 1998). In particular, the IL-1 receptor type I (IL-1rI) appears to mediate all of the known biological functions of IL-1, but in order to transmit a signal into the cell it has to form a complex with the IL-1 receptor accessory protein (IL-1rAcP). On the other hand, IL-1 receptor type II, which can be either soluble or membrane bound, is a decoy receptor, which antagonizes IL-1 signaling (Born et al., 2000; Smith et al., 2000). IL-6 Signaling IL-6 is a part of the IL-6–type cytokines family, which also includes IL-11 and ciliary neurotrophic factor (CNTF). In the first step of its signaling, IL-6 binds to the membrane-bound IL-6 receptor (IL-6R), and together they form a high-affinity complex with a homodimer of the signal transducer gp-130 (Heinrich et al., 2003; Naka et al., 2002). No specific endogenous inhibitor of IL-6 was identified. Rather, its signaling is suppressed by non-specific inhibitors, such as suppressor of cytokine signaling (SOCS) (Naka et al., 2002). Similar to IL-1, IL-6 also has a soluble receptor (sIL-6R). However, in contrast to IL-1RII, sIL-6R is an agonist of IL-6 signaling (Jones et al., 2005). Whereas gp-130 is ubiquitously expressed by all body cells, IL6R is differentially expressed in specific cell types. However, IL-6 can induce signaling in every cell that
expresses gp-130 by binding to sIL-6R, a process named transsignaling (Jones et al., 2005). For example, the influence of IL-6 on neuronal cells depends on sIL-6R (Marz et al., 1998; Marz et al., 1999). TNF Signaling TNF is a part of a large gene superfamily, comprising 18 known ligands, including TNF-α and β (Locksley et al., 2001). TNF is only stable as a homotrimer, either membrane-bound or soluble, and can bind to its receptors at either form. From the various proteins comprising the TNF receptor (TNF-R) family, TNF-R1 and TNF-R2 are the main mediators of its signaling (Tartaglia and Goeddel, 1992; Wajant et al., 2003). 2. Pro-inflammatory Cytokines Influence Neural Processes within the Brain Cytokines are produced by many types of cells, including immune cells in the periphery as well as glia and neurons within the brain, and their gene expression and protein production are elevated during various disease states. Peripheral IL-1, IL-6, and TNF-α orchestrate the inflammatory response to various immune stimuli, causing multiple physiological and behavioral responses. Many immune challenges also induce the production and secretion of cytokines in the brain, which directly produce changes in neurotransmitter and neuroendocrine systems, including monoaminergic systems and the HPA axis (Besedovsky and del Rey, 1996; Dunn and Wang, 1995; Turnbull and Rivier, 1999), as well as behavioral symptoms that will be specified below. To induce these effects, cytokines can directly influence the brain, as suggested by their presence and the expression of their receptors in various brain structures. For example, IL-1 and IL-6 receptors are present throughout the brain, specifically within the hippocampus (Cunningham and De Souza, 1993; Loddick et al., 1998; Parnet et al., 2002; Schobitz et al., 1992, 1993). TNF receptors are also expressed in various brain regions (Kinouchi et al., 1991). The fact that administration of IL-1ra into the brain blocks most of the effects of peripheral IL-1 administration (Kent et al., 1992; Rothwell and Luheshi, 2000) further supports the notion of its central influence. The source of cytokines in the brain can be either local synthesis by glia and neurons, or passage of peripherally produced IL-1, IL-6, and TNF-α through the blood-brain barrier (BBB) (Dantzer et al., 2000; Watkins et al., 1995). Because these cytokines are large proteins, such passage can be accomplished either passively in circumventricular organs, in which the BBB is weak, or via active transport in other areas (Banks, 2005). Alternatively, cytokines can induce the synthe-
16. The Role of Pro-inflammatory Cytokines in Memory Processes and Neural Plasticity
sis and secretion of smaller mediators that can easily cross the BBB, such as prostaglandins (Rivest, 2001). In addition, peripheral IL-1 and TNF-α can influence the brain via the activation of vagal afferent fibers. Indeed, vagotomy blocks many centrally mediated effects of peripheral immune activation (Dantzer, 2001; Goehler et al., 2000). 3. The Involvement of Pro-inflammatory Cytokines in Behavioral Alteration during Sickness and in Health Pro-inflammatory Cytokines Mediate Sickness Behavior During illness, IL-1, IL-6, and TNF-α mediate the collection of neurobehavioral symptoms that constitute the sickness behavior syndrome. It is fairly accepted that this syndrome is adaptive, at least under certain circumstances, helping the organism recuperate from the disease (Dantzer, 2004; Hart, 1988; Kent et al., 1992; Maier and Watkins, 1998; Yirmiya et al., 1999). The symptoms comprising the sickness behavior syndrome include anorexia, body weight loss, altered sleep patterns (characterized by an increase in slow-wave sleep and inhibition of rapid eye movement sleep), psychomotor retardation, fatigue, reduced exploratory behavior, impaired social behavior (e.g., reduction in the time spent by adult animals in social olfactory exploration of juvenile conspecifics), reduced libido (particularly in females), impaired sexual activity, altered pain perception, and anhedonia, defined as the diminished capacity to experience pleasure and gratification from activities that previously brought enjoyment. In animals, this parameter was mainly demonstrated by reduced consumption of and preference for sweet solutions, as well as by decreased responding to rewarding intracranial self-stimulation. Mediation of these symptoms by pro-inflammatory cytokines has been indicated by the findings that: (1) In both humans and animals there are correlations between the elevation in cytokine levels during various medical conditions and the prevalence and severity of the above-mentioned sickness behavior symptoms; (2) pharmacological administration (either peripherally, or directly into the brain) as well as geneticallyengineered transgenic overproduction of proinflammatory cytokines (particularly IL-1, IL-6, or TNF-α) produces sickness behavior symptoms; (3) inhibitors of pro-inflammatory cytokine signaling block the behavioral effects of sickness (Dantzer, 2004; Larson and Dunn, 2001; Maier and Watkins, 1998; Yirmiya et al., 1999). Together with the various behavioral alterations detailed above, cytokine-mediated sickness behavior
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is also accompanied by impairments in cognitive abilities, particularly learning and memory processes. The role of cytokines in this particular symptom will be the focus of this chapter. Pro-inflammatory Cytokines Regulate Behavior in Healthy Animals Recently, cytokines were implicated in the regulation of neurobehavioral processes not only during immune activation, but in healthy animals as well (Vitkovic et al., 2000). Most studies in this area rely on genetic mouse strains lacking normal cytokine signaling. For example, we demonstrated a regulatory role for IL-1 signaling in basal pain sensitivity and neuropathic pain, as well as in morphine-induced analgesia and the development of tolerance following repeated morphine administration, using strains of mice genetically impaired in IL-1 signaling (Shavit et al., 2005; Wolf et al., 2003; Wolf et al., 2006). Similarly, deficiencies in IL-6 and TNF signaling also resulted in behavioral modifications: IL-6 knockout mice differed from their wild-type (WT) controls in their sleep patterns (Morrow and Opp, 2005), and both IL-6 knockout and TNF-α knockout mice demonstrated altered emotional behavior (Armario et al., 1998; Yamada et al., 2000). 4. Interim Summary In conclusion, pro-inflammatory cytokines and their receptors are present in the brain, specifically in the areas that are known to be involved in memory formation, such as the hippocampus. Furthermore, pro-inflammatory cytokines mediate the behavioral alterations that accompany immune activation, and are also involved in the modulation of behavior in healthy animals. The combination of these findings, along with clinical and anecdotal reports about illness-associated cognitive impairments, encouraged many research groups to explore the role of proinflammatory cytokines in memory processes, either during sickness or under normal physiological conditions. Before reviewing the results of these studies in detail, we provide a brief introduction to the basic concepts of memory processes and the brain areas that underlie them. Furthermore, because most studies on pro-inflammatory cytokines and memory utilized rodents, and because proper interpretation of the results of these studies requires understanding of the memory testing paradigms, we describe the most common techniques to evaluate different memory types in rodents.
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B. Memory Processes and Their Assessment in Rodents 1. Memory Processes—Basic Concepts Memory is defined by Webster’s dictionary (1996) as “the mental capacity or faculty of retaining and reviving impressions, or of recalling or recognizing previous experiences.” Memories are acquired by the learning process, during which experiences cause lasting changes in the nervous system. The ability of all organisms to adapt to new situations and to react properly to previously encountered stimuli depends on their ability to remember. Memory can be divided into three stages: encoding, storage (which can last from seconds to years), and retrieval. Failure of any one of these processes will result in impaired memory functioning. One of the first to hypothesize that synaptic changes constitute the basis of memory formation was Donald Hebb, who suggested that the synapse between two neurons it amplified if they are active simultaneously (Hebb, 1949). This hypothesis received important empirical support by the studies of Bliss and Lomo (1973), who showed that brief high-frequency stimulation of hippocampal afferents resulted in persistent augmentation of their synaptic strength within the dentate gyrus (DG), a phenomenon termed long-term potentiation (LTP). Since then, synaptic plasticity was implicated in memory storage, in the hippocampus and other brain areas (e.g., Bliss and Collingridge, 1993; Eichenbaum, 1996). It should be noted, however, that although synaptic plasticity was proved in many studies to be necessary for learning and memory, it is not clear whether it is sufficient for memory formation (see Martin et al., 2000, for review). In addition to the biochemical and structural processes of synaptic plasticity, the brain is capable of plasticity in the whole neuronal level, i.e., via the formation of new neurons, a process termed neurogenesis (Gould et al., 2000; Gross, 2000; Kempermann et al., 2004; Rakic, 2002). In the last decade, the importance of neurogenesis in memory processes was demonstrated by showing that memory induces the generation of new neurons (Gould et al., 1999), and that changes in neurogenesis levels are accompanied by similar changes in memory performance (Gross, 2000). Much more research will be needed to fully understand the processes that underlie plasticity within the brain, and the connection between synaptic plasticity and neurogenesis to learning and memory processes. Various brain structures are involved in the modulation of different memory types, sometimes with a certain amount of redundancy (Zola-Morgan and
Squire, 1993). Among them are the amygdala, which modulates the consolidation of memories of emotionally arousing experiences (McGaugh, 2004), as well as the basal ganglia and the cerebellum (Packard and Knowlton, 2002; Thompson, 2005). This review, however, will focus on memory types that require the hippocampus, a brain region located within the medial temporal lobe. In humans, the hippocampus is responsible for conscience declarative memory—the facts and events we can recollect and report about (Squire et al., 2004). Whereas declarative memory can be easily assessed verbally in humans, it is more difficult to characterize in animals. However, the hippocampus also plays a critical role of spatial navigation and the association between discontinuous events (Eichenbaum, 2000; Squire, 1993; Wallenstein et al., 1998), and these functions can be readily assessed in animals, as will be discussed in the following section. 2. Paradigms for Memory Testing in Rodents During the many decades in which the cognitive behavior of laboratory animals has been investigated, many memory assessment techniques were developed, enabling researchers to examine various memory functions in different species (Cahill et al., 2001). These paradigms span from the simple Pavlovian classical conditioning to the complicated radial arm maze spatial task. Simple, elegant variations within some paradigms (the water maze and fear conditioning tests, for example) enable researchers to distinguish between hippocampal-dependent and hippocampalindependent memory performance. In the most prevalent paradigms, the incentive for learning is the avoidance of an aversive stimulus, whereas fewer paradigms utilize appetitive learning, in which the animal has to learn to perform in order to obtain a positive reward. The four paradigms that have been most frequently utilized in the research on the role of pro-inflammatory cytokines in memory will be described in this section. Less common paradigms will be described in the next section, in the context of the results obtained with these paradigms. The Water Maze The water maze paradigm for memory testing was devised by Morris et al. in 1982. Essentially, rodents are placed in a circular pool and trained to find a platform, located at a particular location within the pool. After reaching the platform and standing on it, the animal is taken out of the pool, dried, and given some rest (which can be considered as rewards) before the next trial. The latency to find the platform serves as an indicator for the learning process; the stronger the
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memory, the faster the animal will reach the platform. The experiments are usually conducted using a random protocol, in which the entrance point to the maze is varied randomly between trials, and the platform remains in a permanent position (Morris, 1981). This basic paradigm can be applied in several ways, which enable differentiation between hippocampaldependent spatial memory and hippocampalindependent memory. In the non-spatial memory paradigm, the platform is elevated above the water surface and therefore it is visible; thus, spatial learning is not required. The only thing to be learned is the escape opportunity, i.e., that climbing the platform results in extraction from the maze, and rodents acquire this learning rapidly (Morris, 1981). Hippocampal lesions have no effect on the performance level in this paradigm (Morris et al., 1982). In the spatial memory paradigm, animals are trained to find the location of a hidden platform, submerged below the opaque water surface, using extra maze visual cues. In this case, the animal has to learn both the procedure (climbing on the platform in order to stop swimming and be removed from the maze) and the spatial location of the invisible platform. The latter task depends on normal hippocampal functioning, as evident from the finding that hippocampal lesions abolish the ability of spatial navigation in the maze (Morris et al., 1982). Following acquisition of the spatial task, it is customary to perform a transfer test (also known as probe test), in which the platform is removed from the maze. The animal is placed in the maze for a short trial, in which the time it swims in the quadrant in which the platform was located or the number of times it crosses the former location of the platform is measured as another indicator of spatial memory (Morris, 1984). The basic paradigm described above can be modified in various ways and has been used since its invention to investigate the involvement of various pharmacological, genetic, and environmental factors in memory functioning (Brandeis et al., 1989; D’Hooge and De Deyn, 2001). Fear Conditioning Fear conditioning is the learning that a neutral stimulus predicts the appearance of an aversive event. The combination of a neutral (conditioned) stimulus and an aversive (unconditioned) stimulus renders the formerly neutral stimulus a frightful quality, so that even when it appears by itself, without the aversive stimulus, it will elicit a fearful conditioned response (Maren, 2001). Fear conditioning can be rapidly formed in humans and animals, even following a single conditioning trial, and is usually maintained for long periods (Maren, 2001). In rodents, the dominant behavioral fear response is freezing (complete immobility), and
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the most commonly used aversive stimulus is the delivery of a weak, short electrical shock (Fanselow, 2000). The conditioning process itself (i.e., the association between the neutral and aversive stimuli) is mediated primarily by the amygdala (Maren, 2001; Maren and Quirk, 2004), and by using different types of conditioned stimuli, the fear-conditioning paradigm enables differentiation between hippocampaldependent and -independent functions: When a simple perceptual conditioned stimulus (such as a light or an auditory cue) is used, the hippocampus is not required. However, when the conditioned stimulus is a new environment, a mental representation of this new context has to be created so that the amygdala can associate this representation with the aversive stimulus; this function depends on hippocampal functioning (Fanselow, 2000; Maren and Holt, 2000). In the most commonly used version of the fear-conditioning paradigm, animals are placed in a novel conditioning cage, in which they hear an auditory tone, followed by a brief foot-shock. Thus, the animal can associate the aversive stimulus with the new context as well as with the tone. To test contextual fear conditioning, animals are placed again in the original conditioning cage, and freezing is measured. This task is hippocampal dependent, as it cannot be performed following hippocampal lesions (Fanselow, 2000). To test the hippocampal-independent auditory-cued fear conditioning, freezing is measured when the tone is sounded in a differently shaped context (Fanselow, 2000; Maren and Holt, 2000). In this case, hippocampal lesions have no detrimental effect on performance level (Fanselow, 2000). The fear-conditioning paradigm has been employed extensively in research on the neural basis of memory in various pharmacological, genetic, and environmental studies (Fanselow and Poulos, 2005). Passive and Active Avoidance In the passive avoidance paradigm, animals learn to refrain from contacting a formerly desired stimulus, based on their experience that a previous contact with that stimulus resulted in an aversive incident. The aversive experience is usually a mild electrical shock, and the desired stimuli may be, for example, water for a thirsty animal, food for a hungry animal, or a small dark chamber for an animal placed in a spacious, brightly illuminated one (as rodents prefer narrow dark places). The paradigm is termed “passive” avoidance because the animal does not have to actively perform any action, but rather to refrain from performing an activity it desires (approaching drink, food, or a dark chamber, for example). Thus, the latency it takes the animal to perform the frightful activity serves as a measure for its memory of the aversive consequences
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of that action. Passive avoidance is hippocampal dependent, as hippocampal lesions impair learning in this task, as demonstrated by a diminished latency to enter a dark chamber in which an electric shock was administered in the past (Burwell et al., 2004). Induction of hippocampal lesion at different timings along the passive avoidance paradigm demonstrated a role for both the dorsal and ventral hippocampus in the acquisition, consolidation, and retrieval of passive avoidance (Ambrogi Lorenzini et al., 1996, 1997). Contrary to the passive avoidance paradigm, in active avoidance animals learn to perform a specific action in order to avoid an aversive stimulus. The aversive stimulus is usually a mild electrical shock, and the actions required to stop it can be lever press, entry to a protective area, etc. Thus, the latency to perform the avoidance action or the number of actions serves as an indicator of the learning strength. Active avoidance is also hippocampal dependent, as hippocampal lesions impair performance in this task (Cimadevilla et al., 2000; Munoz and Grossman, 1982).
II. EFFECTS OF IL-1, IL-6, AND TNF-a ON LEARNING AND MEMORY IN RODENTS Exposure to pathogens that stimulate the immune system results in altered memory performance, as part of the general sickness behavior syndrome. For example, viral, bacterial, and parasitic infections, as well as exposure to viral coat proteins or bacterial endotoxin, result in impaired memory performance in animals (e.g., Braithwaite et al., 1998; Gibertini et al., 1995a, b; Kamitani et al., 2003; Lee et al., 2000; Li et al., 2004a; Murray et al., 1992; Pugh et al., 1998; Pugh et al., 2000; Sparkman et al., 2005). Because the immune response to these factors and the sickness behavior that accompanies it are mediated by pro-inflammatory cytokines, many research groups sought to directly assess the involvement of pro-inflammatory cytokines in memory processes. The data collected in these studies, specifically regarding the cytokines IL-1, IL-6, and TNF, will be presented in this section.
A. IL-1 The role of IL-1 in memory processes has been extensively studied in the last decade by many research groups, using various models. Most of these studies showed a detrimental effect of IL-1 on memory formation; however, some studies reported no effect, and recent studies demonstrated an important role for IL-1 in normal memory functioning. These seemingly contradictory results will be presented in the following
sections, together with an attempt to accommodate all findings using a theoretical model. 1. Elevated IL-1 Levels Impair Memory Functioning The first attempt to evaluate the effect of IL-1 on memory was performed by Oitzl et al. in 1993 (Oitzl et al., 1993). In this study, IL-1β (100 ng/rat) injected intracerebroventricularly (i.c.v.) 1 hour before the beginning of spatial water maze training caused a transient memory impairment in the first trial of the following day. When the same dose was injected immediately before training, no effect was found, suggesting that IL-1β does not affect the acquisition of spatial memory but rather the retention of this learning and that the processes triggered by IL-1β require some time to exert their influence on memory (Oitzl et al., 1993). In another extensive set of experiments using the water maze procedure, Gibertini et al. (1995a) injected mice peripherally with IL-1β (100 ng/mouse, intraperitoneal—i.p.) on the first and second day of spatial water maze training and reported a complete blockade of spatial learning (Gibertini et al., 1995a). Gibertini then repeated the experiment, this time training mice in both the spatial (random entry) and non-spatial (fixed entry) versions of the water maze. IL-1β impaired learning in the spatial paradigm but had no effect on non-spatial memory (Gibertini, 1996). IL-1β–injected mice were also found to be less flexible in adapting to a change in the position of the hidden platform. This was demonstrated in an experiment in which after the mice were injected with IL-1β and learned to find the platform using the fixed-entry protocol, the position of the platform was changed. Although IL-1β did not interrupt the initial learning, when the platform position was changed, saline-injected mice quickly adjusted to the change, whereas IL-1β–injected mice continued to look for the platform in its former position (Gibertini, 1996). In a subsequent study, Gibertini (1998) further showed that the memory impairment caused by IL-1 is restricted to learning conditions of relatively low motivation: When mice were trained in the water maze using a water temperature of 23°C, the detrimental effect of IL-1β was observed as before. However, when the water temperature of the maze was reduced to 15°C, thus creating a greater motivation to escape, IL-1β injection had no effect (Gibertini, 1998). A recent study confirmed these early studies on the effects of IL-1β on spatial memory, demonstrating that the detrimental effect of i.c.v.-administered IL-1β on spatial memory could also be achieved using a lower dose (15 ng/rat) (Song and Horrobin, 2004). This study also repeated the finding that in contrast with the effect
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of IL-1β in the spatial hippocampal-dependent version of the water maze, no effect of IL-1β was found when the same rats were tested in the hippocampalindependent visually guided version (Song and Horrobin, 2004). In contrast with these findings, other studies, using somewhat different regimens of IL-1 administration and testing procedures, found no effect of IL-1 on spatial memory. Lacosta et al. (1999) injected mice daily with IL-1β (1 μg/mouse, i.p.) for a week before training in the water maze, as well as at the week of training itself, and found no effect on spatial learning (Lacosta et al., 1999). In another study, mice that were trained in the water maze using a spaced-learning protocol displayed normal latency to reach the platform following IL-1 injection (100 ng/mouse) (Gibertini, 1998). However, the IL-1β–injected mice used a different strategy to find the platform, as apparent from the fact that whereas saline-injected mice spent more and more time in the quadrant in which the platform was positioned, IL-1β–injected mice remained at a chance level (Gibertini, 1998). Taken together, the results of all the studies presented so far suggest that IL-1 interferes specifically with spatial learning in the water maze, which depends on normal hippocampal functioning. However, these effects are not demonstrated under all conditions and depend on various experimental parameters. The involvement of IL-1 in memory processes was also extensively examined using the fear-conditioning paradigm. Pugh et al. (1999) demonstrated that i.c.v. injection of IL-1β (either 10 or 20 ng/rat), immediately following conditioning, impaired contextual but not auditory-cued fear conditioning (Pugh et al., 1999; Pugh et al., 2001). These findings indicate that the impairment was restricted to the hippocampaldependent version of the fear-conditioning paradigm, without affecting the hippocampal-independent task. Further evidence for the specific localization of the effect of IL-1 was recently provided by demonstrating that bilateral intrahippocampal injection of IL-1β (10 ng/side) also impaired contextual fear conditioning (Barrientos et al., 2004). In another study, a different version of the contextual fear-conditioning paradigm was used. In that version, rats are preexposed to the context one day before the conditioning session, in which they receive an immediate shock when re-entering this context. The pre-exposure provides an opportunity to generate a mental representation of the context, and without it conditioning will not take place when an immediate shock is applied. This separation between the hippocampal-dependent memory of the context and the conditioning (associative) process itself (which is mediated by the amyg-
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dala) enables researchers to pinpoint the exact component of the learning process in which IL-1 is involved. Using this paradigm, Barrientos et al. (2002) bilaterally injected rats with IL-1β (1 ng/side) directly into the hippocampus after pre-exposure to the context. The animals were immediately shocked on the following day and tested for conditioned fear response one day following the shock. Rats that were injected with IL-1β, immediately or 3 hours following pre-exposure, demonstrated a 50% reduction in contextual fear conditioning. However, when rats were pre-exposed to the context and received the intra-hippocampal injection of IL-1β 24 hours later (at the time of conditioning), they demonstrated only a 20% decrease in fear response compared to controls. Finally, when IL-1β was injected at the time of testing (48 hours after preexposure to the context), no effect on the fear response was observed (Barrientos et al., 2002). These data suggest that the detrimental effect of IL-1 on contextual fear conditioning is caused by interference with the formation of the mental representation of the context by the hippocampus, rather than with the association of this representation with the shock. Another learning and memory task in which IL-1 is critically involved is spatial active avoidance: In a series of experiments, mice learned to avoid an electrical shock by entering a specific arm of a T-maze. IL-1 was injected after the learning phase, and retention was tested 1 week later (Banks et al., 2001). When administered intravenously (i.v.), both human IL-1α (0.3 and 1, but not 0.03 and 0.1 μg/mouse) and human IL-1β (1 μg/mouse) impaired memory; i.e., IL-1 injected mice required more trials in order to learn to perform the avoidance response. Much lower doses were needed to achieve this detrimental effect when human IL-1α (0.1, 0.3 and 1, but not 0.03 ng/side) and IL-1β (1 ng/side) were administered bilaterally into the posterior septum (PDS), connecting the hippocampus and the midbrain. Banks et al. (2001) further demonstrated that the effect of i.v.-injected human IL-1α stems from transport of this cytokine across the BBB as well as from endogenous stores of IL-1α, because the memory impairment was partially blocked by antibodies against either human or murine IL-1α injected into the PDS, and fully blocked by injecting the combination of these antibodies. Human IL-1β, however, did not cross the BBB, but induced the secretion of murine IL-1β, as shown by the findings that its influence on memory was blocked by murine anti–IL-1β injected into the PDS, but was unaffected by human anti–IL-1β (Banks et al., 2001, 2002–2003). This set of studies demonstrates again that IL-1 impairs hippocampal-dependent memory formation when administered either peripherally or centrally.
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IL-1β also impairs performance in several other memory-testing paradigms: three-panel runway, radial arm maze, autoshaping, and passive avoidance. In the three-panel runway task, rodents learn to open the correct doors between three consecutive chambers in order to receive a reward. In this task, a smaller number of errors (attempts to open incorrect doors) reflects better working memory performance (Furuya et al., 1988), which critically depends on normal hippocampal functioning (Kitajima et al., 1992; Ohno et al., 1992). Intrahippocampal IL-1β (32 and 100, but not 10 ng/ side) impaired working memory in the three-panel runway task, as shown by an increased number of errors (Matsumoto et al., 2001, 2004). The win-shift version of the radial arm maze is divided into a training session, in which the locations of the arms that will contain food in the future are marked by blocking them for entry, and a testing session in which the rats have to enter these arms in order to obtain a food reward. A smaller number of errors (entrees to empty arms) reflects better working memory functioning, which depends on normal hippocampal functioning (Floresco et al., 1997). I.c.v. IL1β (10 and 50 ng/rat) impaired working memory in the win-shift radial arm maze, as shown by an increased number of errors in the days in which IL-1 was injected 45 minutes before testing. The effect of the higher dose also remained for another day after the injections were terminated (Song et al., 2004). In the autoshaping task, rodents press a lever in order to hasten the appearance of a delayed food reward. The processing of temporal discontinuities (such as the delay between the lever press and the appearance of the reward) is performed by the hippocampus (Rawlins et al., 1985; Wallenstein et al., 1998), and septal lesions result in longer latencies to press the lever (Sagvolden and Holth, 1986). IL-1β (4 μg/rat, i.p.) delayed the acquisition of autoshaping in rats (Aubert et al., 1995). Furthermore, a positive correlation was found between the dose of IL-1β and the latency to press the lever; the higher the dose, the longer the latency, i.e., the greater the learning deficit (Aubert et al., 1995). A complementary approach to verify the detrimental effect of IL-1 administration on memory processes is to examine the possible beneficial effects of IL-1 blockade. Although most studies using this approach reported that such a blockade impairs rather than facilitates memory functioning (see below), one study demonstrated detrimental effects (Depino et al., 2004). In that study, the step-down passive avoidance test was used, in which rats are placed on an elevated platform in a new context, and an electrical shock is delivered upon stepping down from the platform. The latency to step
down from the platform on subsequent trials serves as a measure to memory (longer latencies indicate better memory). Depino et al. (2004) injected rats with an adenovector containing the rat IL-1ra gene to the hippocampi 1 week before passive avoidance training. The vector was expressed in neurons and glia cells, and blocked the activity of IL-1 within the hippocampus. This resulted in enhanced short- and long-term memory in these rats, as shown by longer latencies to step down from the platform compared to control rats 1.5 and 24 hours following training (Depino et al., 2004). Several studies examined the role of IL-1 in memory impairments caused by various inflammatory agents. Gibertini et al. (1995a, b) showed that inoculation with the bacterium Legionella pneumophila, which increases IL-1β levels in mice (Shinozawa et al., 2002), 24 hours before training in the spatial water maze task impaired learning. However, when mice were injected with anti–IL-1β antibodies 2 hours before training, this bacterial infection had no effect on spatial memory (Gibertini et al., 1995 a, b). Subsequently, Pugh et al. (1998) studied the influence of LPS on fear conditioning. They reported a detrimental effect of LPS, which was demonstrated to increase hippocampal IL-1β levels (Nguyen et al., 1998) on contextual fear conditioning, which requires normal hippocampal functioning. However, no effect on auditory-cued fear conditioning was observed. When the LPS injection was immediately followed by IL-1ra administration, the detrimental effect on contextual memory was abolished (Pugh et al., 1998). In an additional set of experiments, Pugh et al. (2000) demonstrated the potential role of IL-1 in AIDS-related memory impairments: They reported that i.c.v. injection of the HIV coat protein gp-120 increased IL-1β level in the hippocampus and impaired contextual, but not auditory-cued, fear conditioning. Moreover, they showed that IL-1 mediates this impairment, because when IL-1ra was administered i.c.v. immediately following HIV gp-120, the detrimental effect of this pathogen on contextual fear conditioning was abolished (Pugh et al., 2000). IL-1 was also found to mediate memory impairments during chronic brain inflammation. Palin et al. (2004) used a chronic neuroinflammation model based on delayed-type hypersensitivity (DTH) response to the bacterium Bacillus Calmette-Guerin in the hippocampus (Matyszak and Perry, 1995), and tested its influence on memory using the Y maze paradigm. In this paradigm, rats are exposed to two arms of a Y maze, and when they are re-introduced to the maze, a third arm is available as well. A rat that remembers the “old” arms will explore the novel arm more extensively (Dellu et al., 1992). Hippocampal DTH response resulted in memory impairment, as demonstrated by
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the finding that whereas control rats preferred to explore the novel arm, infected rats demonstrated no preference on day 16 of infection, suggesting that they did not remember the spatial position of the old arms. Additionally, DTH response produced elevated IL-1β levels in the infected hippocampus, compared to the non-infected hippocampus. Palin et al. (2004) showed that IL-1 mediated this DTH-induced memory impairment, evidenced by the finding that when IL-1ra was chronically administered for 10 days before the memory test, rats with hippocampal DTH response performed the task as well as controls. Interestingly, IL-1 mediates not only the effects of inflammatory agents on memory processes, but also the effect of psychological stress. Maier and Watkins (1995) were the first to demonstrate the role of IL-1 in stress-induced modulation of memory functioning. When rats are subjected to inescapable shock 24 hours before training in an active avoidance task, their performance is impaired, a phenomenon termed learned helplessness (Maier, 1990). I.c.v. administration of IL1ra (100 μg/rat) before inescapable shock administration blocked the learned helplessness induced by inescapable shock (Maier and Watkins, 1995). Pugh et al. (1999) further showed that when rats were isolated for 5 hours following fear conditioning, contextual memory was impaired, whereas auditory-cued memory remained intact. Furthermore, they showed that IL-1 mediates this effect, by demonstrating that hippocampal IL-1β levels were increased following social isolation, and that i.c.v. administration of IL-1ra before isolation blocked the effect of isolation on contextual memory (Pugh et al., 1999). To sum up, the data presented so far (summarized in Table 1) clearly demonstrate a detrimental effect of elevated IL-1 levels on memory processes. This negative influence was found in various studies to be specific to memory tasks that depend on normal hippocampal functioning, whereas the performance of hippocampal-independent tasks is spared. This finding was replicated using various doses (of either IL-1α or IL-1β), administration routes (i.p., i.v., i.c.v., intrahippocampal, and intraseptal), and species (rats and mice), thus strengthening the reliability, validity, and generalizability of these findings. 2. Impaired IL-1 Signaling Disrupts Memory Functioning Although most of the evidence presented so far indicates that IL-1’s effects on learning and memory processes are detrimental, accumulating recent evidence suggests that at least under some circumstances IL-1 may be required for the normal physiological
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regulation of memory processes within the hippocampus. The first example of IL-1–induced memory facilitation was published by Gibertini in 1998. He reported expedited acquisition of spatial memory in the water maze in mice that were injected with IL-1β (1 μg/ mouse, i.p.). In 2002, we further reported data supporting a beneficial role of IL-1 in spatial memory: Rats were trained to find a hidden platform in a water maze, and then injected with either IL-1β (10 ng/rat, i.c.v.) or IL-1ra (100 μg/rat, i.c.v.) at the end of the training day, and tested for retention 24 hours later (Yirmiya et al., 2002). We showed that whereas IL-1β had no effect on either spatial or visually guided memory in the water maze, IL-1ra specifically impaired spatial memory, as demonstrated by a longer latency to locate the hidden platform on the test day in IL1ra–injected rats. Visually guided performance was unaffected (Yirmiya et al., 2002), suggesting that basal IL-1 levels are specifically required for hippocampaldependent memory. We further illustrated the role of IL-1 in spatial memory by testing mice deficient in IL-1 receptor type I (IL-1rKO). In these mice, IL-1 signaling is completely abolished, as reflected by lack of responsiveness to exogenous IL-1α or IL-1β administration (Labow et al., 1997). IL-1rKO mice displayed a slower rate of learning in the spatial memory paradigm; i.e., their latencies to reach the platform were significantly longer (Avital et al., 2003). However, compared to controls, IL-1rKO mice also displayed a slower swimming speed, which may affect the latency to reach the platform. Nevertheless, these impairments cannot account for the slower rate of learning, because the learning deficit was also observed with respect to the path length to reach the platform, which provides a measurement of learning that is not dependent on speed. In contrast with these findings, in the non-spatial memory paradigm (visible platform) IL-1rKO mice showed no differences from controls in either the latency to reach the platform or the path length (Avital et al., 2003). Similar results were also observed in mice that overexpress the human IL-1ra gene specifically within the CNS (IL-1raTG), which demonstrate no response to exogenous IL-1 administration (Lundkvist et al., 1999). IL-1raTG mice displayed a slower rate of learning in the spatial memory paradigm; i.e., their latencies to reach the platform were significantly longer, although no differences in swimming speed were observed. However, in the non-spatial memory paradigm (visible platform) IL-1raTG mice showed no difference from controls (Goshen et al., 2003a). Taken together, the results of these studies suggest that IL-1 is specifically necessary for spatial learning in the water maze, which depends on normal hippocampal functioning.
346
II. Immune System Effects on Neural and Endocrine Processes and Behavior
Another task in which IL-1 was found to be critically involved is the fear-conditioning paradigm: IL-1rKO mice exhibited impaired contextual fear conditioning; i.e., they displayed a significantly shorter freezing time than their controls in the original conditioning context, 48 hours after the conditioning trial. In contrast, IL-1rKO mice displayed normal auditorycued fear conditioning (Avital et al., 2003). Similarly, IL-1raTG mice also displayed impaired contextual, but normal auditory-cued, fear conditioning (Goshen et al., 2003a). Again, the involvement of IL-1 in memory processes seems to be specific to hippocampaldependent performance. The involvement of IL-1 in memory processes was also examined using the passive and active avoidance paradigms: We examined the role of IL-1 in passive avoidance conditioning by injecting rats with either IL-1β (10 ng/rat, i.c.v.) or IL-1ra (100 μg/rat, i.c.v.) at the end of passive avoidance training, in which they were electrified when approaching a drinking spout. At different time-points afterwards, the latency to contact the water spout was measured, as an indicator for memory (longer latencies reflect better memory of the aversive nature of the spout). One day after conditioning, neither IL-1β nor IL-1ra had any effect on memory. However, at 5–8 days after conditioning, IL1β–injected rats exhibited facilitated memory, whereas IL-1ra–injected rats demonstrated impaired memory (Yirmiya et al., 2002). Another study replicated our results using the spatial form of the passive avoidance test. In this paradigm, the latency to enter a context in which an electric shock was administered serves as an indicator of memory (longer latencies reflect better memory). Rats that were i.c.v. injected with IL-1β (15 ng/rat) 50 minutes before the acquisition trial and then 50 minutes before the memory tests (24 and 48 hours later) demonstrated an improved memory of the context (Song et al., 2003). In contrast, Bianchi et al. (1998) reported that very low doses of IL-1α (0.125, 0.25, 0.5 and 1 μg/mouse, i.p.) had no effect on performance in a passive avoidance task. However, IL-1α (0.25 and 0.5 μg/mouse, i.p.) attenuated the amnesic effect of scopolamine (an anti-cholinergic drug) on memory in this test (Bianchi et al., 1998), again suggesting that under some circumstances IL-1 can have a beneficial effect on memory. Brennan et al. (2003) recently showed the importance of IL-1 in active avoidance, using the following paradigm: Rats were warned by a tone that a shock will be delivered 60 seconds afterwards and had a chance to prevent the occurrence of the shock by pressing a lever (avoidance response). Additionally, they could terminate the shock after it had begun by pressing the same lever (escape response). Injection of low
doses of IL-1β (1 and 3, but not 6 μg/kg, i.p.) 24 hours before training resulted in an increased number of avoidance responses, but did not affect the number of escape responses. In an additional study, this finding was replicated, using a 3 μg/kg dose of IL-1β, which improved avoidance, but not escape, responses (Brennan et al., 2004). As mentioned before, the processing of temporal discontinuities (such as the 1minute delay between the appearance of the tone and the electric shock) is performed by the hippocampus (Rawlins et al., 1985; Wallenstein et al., 1998). This learning is required in order to perform the avoidance response, but not the escape response, which is a direct reaction to the present appearance of the shock. To sum up, IL-1β administration, either peripherally or centrally, can improve performance in passive and active avoidance tasks, whereas IL-1ra administration impairs passive avoidance. As with the other paradigms presented above, these effects are restricted to hippocampal-dependent tests. In conclusion, the data presented in this section (summarized in Table 1) clearly demonstrate the role of low, “physiological” levels of IL-1 in memory processes. This role is further supported by the finding of increased IL-1α gene expression 4 hours after exposure to a single acquisition trial of a passive avoidance paradigm, compared to a control group that received only a shock, without performing the step-down action (Depino et al., 2004). The beneficial influence of IL-1 on memory processes was reported in various studies to be specific to hippocampal-dependent memory tasks, whereas the performance in hippocampalindependent tasks does not seem to require IL-1 signaling. These findings were replicated using either pharmacological approaches (over various species, doses, and administration routes), or the genetic approach (using different manipulations), thus strengthening the reliability, validity, and generalizability of these findings. 3. The Inverted U-shaped Model for the Influence of IL-1 on Memory Functioning The results of the studies presented above (summarized in Table 1) indicate that on the one hand elevated IL-1 levels have detrimental effects on memory, but on the other hand low IL-1 doses can facilitate memory and blockade of IL-1 signaling is associated with impaired memory functioning. Together, these findings suggest that the influence of IL-1 on memory follows an inverted U-shape pattern. According to this hypothesis, physiological levels of IL-1 are needed for memory formation; however, any deviation from the physiological range, either by
347
16. The Role of Pro-inflammatory Cytokines in Memory Processes and Neural Plasticity TABLE 1 Cytokine
Species
Summary of the Studies on the Effects of Interleukin-1 (IL-1) on Memory in Rodents
Dose
Administration route
Memory testing paradigm
Timing
Effect on memory
Reference
Experiments reporting detrimental effects of IL-1 on hippocampal-dependent memory IL-1β
Rat
100 ng/rat
i.c.v.
IL-1β
Rat
15 ng/rat
i.c.v.
IL-1β
Mouse
100 ng/mouse
i.p.
IL-1β
Mouse
100 ng/mouse
i.p.
IL-1β
Rat
10 ng/rat
i.c.v.
IL-1β
Rat
20 ng/rat
i.c.v.
IL-1β
Rat
10 ng/side
Intrahippocampal
IL-1β
Rat
1 ng/side
Intrahippocampal
IL-1α
Mouse
i.v.
IL-1α
Mouse
IL-1β IL-1β IL-1β
Mouse Mouse Rat
0.3 or 1 μg/mouse 0.1, 0.3, or 1 ng/side 1 μg/mouse 1 ng/side 32 ng/side
IL-1β
Rat
100 ng/side
Intrahippocampal
IL-1β
Rat
4 μg/rat
IL-1ra
Rat
Unknown
IL-1β
Rat
10 or 50 ng/rat
Water maze spatial Water maze spatial Water maze spatial Water maze spatial 23°C Fear-conditioning contextual Fear-conditioning contextual Fear-conditioning contextual Fear-conditioning contextual
1 hour before training
Impaired
Oitzl et al., 1993
During training
Impaired
Song and Horrobin, 2004
During training
Impaired
2 hours before training
Impaired
Gibertini et al., 1995; Gibertini, 1996 Gibertini, 1998
Impaired
Pugh et al., 1999
Impaired
Pugh et al., 1999
Impaired
Barrientos et al., 2004
Impaired
Barrientos et al., 2002
Active avoidance
Immediately following conditioning Immediately following conditioning Immediately following conditioning Immediately, 3 hours and 24 hours following preexposure to context Immediately after training
Impaired
Banks et al., 2001
Intraseptal
Active avoidance
Immediately after training
Impaired
Banks et al., 2001
i.v. Intraseptal Intrahippocampal
Immediately after training Immediately after training 10 minutes before training
Impaired Impaired Impaired
Banks et al., 2001 Banks et al., 2001 Matsumoto et al., 2001
10 minutes before training
Impaired
Matsumoto et al., 2001, 2004
i.p.
Active avoidance Active avoidance Three-panel runway Three-panel runway Autoshaping
Impaired
Aubert et al., 1995
Intrahippocampal adenovector i.c.v.
Passive avoidance, step down Radial arm maze
45 minutes before day 2 of training 1 week before training
Enhanced
Depino et al., 2004
45 minutes before testing (5 minutes after training)
Impaired
Song et al., 2004
No effect
Oitzl et al., 1993
No effect
Gibertini, 1998
No effect
Lacosta et al., 1999
No effect
Yirmiya et al., 2002
48 hours following preexposure to context Immediately after training
No effect
Barrientos et al., 2002
No effect
Banks et al., 2001
Immediately after training 24 hours before training 10 minutes before training
No effect No effect No effect
Banks et al., 2001 Brennan et al., 2003 Matsumoto et al., 2001
15 minutes before acquisition
No effect
Bianchi et al., 1998
2 hours before training
Enhanced
Gibertini, 1998
Immediately after training 50 minutes before acquisition and 50 minutes before test
Enhanced Enhanced
Yirmiya et al., 2002 Song et al., 2003
Experiments reporting no effects of IL-1β administration on hippocampal-dependent memory IL-1β
Rat
100 ng/rat
i.c.v.
IL-1β
Mouse
100 ng/mouse
i.p.
IL-1β
Mouse
1 μg/mouse
i.p.
IL-1β
Rat
10 ng/rat
i.c.v.
IL-1β
Rat
1 ng/side
Intrahippocampal
IL-1α
Mouse
i.v.
IL-1α IL-1β IL-1β
Mouse Rat Rat
0.03 or 0.1 μg/mouse 0.03 ng/side 6 μg/kg 10 ng/side
IL-1α
Mouse
0.125, 0.25, 0.5, or 1 μg/mouse
Intraseptal i.p. Intrahippocampal i.p.
Water maze spatial Water maze spatial 15°C Water maze spatial
Water maze spatial Fear-conditioning contextual Active avoidance Active avoidance Active avoidance Three-panel runway Passive avoidance
Immediately before training 2 hours before training Daily injections at the week preceding training, and at the week of training itself Immediately after training
Experiments reporting beneficial effects of IL-1β administration on hippocampal-dependent memory IL-1β
Mouse
1 μg/mouse
i.p.
IL-1β IL-1β
Rat Rat
10 ng/rat 15 ng/rat
i.c.v. i.c.v.
Water maze spatial Passive avoidance Passive avoidance
(Continues)
348
II. Immune System Effects on Neural and Endocrine Processes and Behavior TABLE 1 (Continued)
Cytokine
Species
IL-1β IL-1β
Rat Rat
Dose 1 μg/kg 3 μg/kg
Administration route i.p. i.p.
Memory testing paradigm
Timing
Effect on memory
Active avoidance Active avoidance
24 hours before training 24 hours before training
Enhanced Enhanced
Brennan et al., 2003 Brennan et al., 2003; Brennan et al., 2004
Impaired Impaired Impaired Impaired
Yirmiya et al., 2002 Yirmiya et al., 2002 Avital et al., 2003 Avital et al., 2003
Reference
Experiments reporting detrimental effects of IL-1 signaling blockade on hippocampal-dependent memory IL-1ra IL-1ra IL-1R IL-1R
Rat Rat Mouse Mouse
100 μg/rat 100 μg/rat No IL-1R1 No IL-1R1
i.c.v. i.c.v. Knockout Knockout
Water maze spatial Passive avoidance Water maze spatial Fear-conditioning contextual
Immediately after training Immediately after training Constant knockout Constant knockout
Experiments reporting no effect of IL-1 administration or IL-1 signaling blockade on hippocampal-independent memory IL-1β
Mouse
100 ng/mouse
i.p.
IL-1β
Rat
i.c.v.
IL-1β
Rat
10 or 20 ng/rat 10 ng/rat
i.c.v.
IL-1ra
Rat
100 μg/rat
i.c.v.
IL-1β
Rat
15 ng/rat
i.c.v.
IL-1R
Mouse
No IL-1R1
Knockout
IL-1R
Mouse
No IL-1R1
Knockout
Water maze fixed entry Fear-conditioning auditory-cued Water maze Visually guided Water maze Visually guided Water maze Visually cued Water maze Visually guided Fear-conditioning auditory-cued
During training
No effect
Gibertini, 1996
Immediately following conditioning Immediately after training
No effect
Pugh et al., 1999
No effect
Yirmiya et al., 2002
Immediately after training
No effect
Yirmiya et al., 2002
During training
No effect
Song and Horrobin, 2004
Constant knockout
No effect
Avital et al., 2003
Constant knockout
No effect
Avital et al., 2003
i.p.—Intraperitoneal; i.v.—Intravenous; i.c.v.—Intracerebroventricular.
excess elevation in IL-1 levels or by blockade of IL-1 signaling, results in impaired memory (Figure 1). This hypothetical model is based on: (A) The beneficial role of low-dose IL-1 administration on hippocampal-memory formation; (B) the detrimental effect of elevated IL-1 levels (induced by either exogenously administered IL-1 or by enhanced endogenous release of IL-1, stimulated by exposure to pathogens or stress) on hippocampal-dependent memory; and (C) the fact that blockade of IL-1 signaling either pharmacologically (by IL-1ra administration) or genetically (by deletion of the IL-1 receptor or overexpression of IL-1ra) impairs hippocampal-dependent memory. An inverted U-shape curve has been demonstrated for the effects of IL-1 on other processes, e.g., on the differentiation of mesencephalic progenitor cells into dopaminergic neurons (Ling et al., 1998), and for the influence of other substances on memory. For example, low doses of corticosterone are essential, whereas high doses are detrimental for spatial memory (Conrad et al., 1999). One weakness of this hypothesis is that, presently, no single study systematically assessed the dual role of IL-1 in memory under identical conditions. Rather, the hypothesis is based on data gathered by many groups, using various testing paradigms, experimental approaches (pharmacological or genetic),
species, doses, and administration routes. Future research should further substantiate the inverted Ushaped curve hypothesis by testing the detrimental effects on memory of both excess and absence of IL-1 signaling under similar experimental conditions.
B. IL-6 The effects of IL-6 on learning and memory have been studied by several approaches, including acute administration of IL-6, manipulations that produce chronic elevation of IL-6 levels, and testing the effects of IL-6 blockade. Many of these studies were conducted in the context of aging, because several studies demonstrated an age-dependent increase in brain IL-6 levels in mice (Prechel et al., 1996; Ye and Johnson, 1999, 2001), and a similar increase was also observed in human plasma (Wei et al., 1992). Additionally, IL-6 expression is higher in senescence-accelerated mice at the age of 10 months compared to controls (Tha et al., 2000). Because aging is accompanied by cognitive deterioration, these findings led to the hypothesis that IL-6 may mediate age-related memory impairments (e.g., Godbout and Johnson, 2004). Based on this hypothesis, the role of IL-6 in memory processes has been extensively investigated with an emphasis on
16. The Role of Pro-inflammatory Cytokines in Memory Processes and Neural Plasticity
349
B
0.6 0.4 0.2
t) /r a
t) ng 00 (1 -1 IL
-1
(1 ra
(1
00
0
m
ng
g/
/r a
ra
e ic m O IL
-1
IL
Brain IL-1 Level
t)
0.0
High rK
Basal -normal
0.8
-1
Low
1.0
IL
Latency to reach platform (Control group/Treated group)
Memory / Plasticity Level
A
FIGURE 1 The inverted U-shape model for the effects of IL-1 on memory functioning and neural plasticity. (A) According to this model, normal basal levels of IL-1, particularly within the hippocampus, promote memory consolidation and neural plasticity processes, whereas deviations from the physiological range, either by blockade of IL-1 signaling (induced by pharmacological or genetic manipulations) or excessive elevation in IL-1 levels (induced by infectious, autoimmune, or neurodegenerative diseases, trauma, stroke, or exposure to stress), impair memory and neural plasticity. (B) An example for experimental findings supporting the inverted U-shape model. The graph represents the results of several studies, examining the effects of manipulations in IL-1 signaling on spatial (hippocampal-dependent) learning and memory in the water maze. Each bar represents the latency to reach the platform, computed as the ratio between the latency of the control animals in that experiment to the latency of the manipulated animals. A low ratio means that control animals reached the platform faster; i.e., the manipulated animals displayed impaired memory compared to the controls. Specifically, animals with impaired IL-1 signaling (left two columns), induced by either a genetic manipulation (deletion of the IL-1 receptor type 1 in mice) or pharmacological manipulation (i.c.v. administration of IL-1ra [100 mg/kg] in rats), displayed impaired learning and memory (adopted from Avital et al., 2003 and Yirmiya et al., 2002, respectively). Animals injected with a relatively low dose of IL-1 (10 ng/rat, i.c.v.) displayed no impairment in spatial memory (adopted from Yirmiya et al., 2002), whereas animals injected with a high dose of IL-1 (100 ng/rat, i.c.v.) displayed reduced memory functioning (adopted from Oitzl et al., 1993).
progressive age-related processes. Whereas several studies found no effect of IL-6 on memory, all the studies that did find an involvement of IL-6 in learning and memory demonstrated a detrimental role, either by showing that excessive IL-6 levels impair memory, or by reporting improved memory when IL-6 is absent or when its signaling is blocked. The first study examining the role of IL-6 in memory processes was conducted in 1993 by Oitzl et al. In this study, i.c.v. injection of IL-6 (100 ng/rat), either immediately or 1 hour before the beginning of a 2-day spatial water maze training, had no effect on memory at any time-point, whereas IL-1β produced a memory impairment when it was administered 1 hour before training under similar conditions (Oitzl et al., 1993). Two other studies, using different testing paradigms, also reported that exogenous IL-6 administration did not influence hippocampal-dependent memory processes: Bianchi et al. (1997, 1998) reported that low doses of IL-6 (0.031, 0.125, 0.5, and 2 μg/mouse, i.p.), injected
15 minutes before passive avoidance acquisition had no effect on performance in that task. Furthermore, Brennan et al. (2004) reported no effect of IL-6 (3 μg/ kg, i.p.) when it was injected 24 hours before active avoidance training. The age-dependent involvement of IL-6 in memory processes was then extensively examined in mice that overexpress IL-6 using the active avoidance paradigm. The animals had a chance to prevent the occurrence of a shock by quickly entering a specific arm of a Y maze (avoidance response). Additionally, they could terminate the shock after it had begun by entering this arm (escape response). Heyser et al. (1997) employed this paradigm to test the memory of either homozygous or heterozygous transgenic mice overexpressing IL-6 specifically within the CNS (IL-6TG), at the ages of 3, 6, and 12 months. At 3 months of age, homozygous IL-6TG mice demonstrated impaired learning, as shown by a decreased number of avoidance responses, whereas heterozygous IL-6TG mice were able to learn
350
II. Immune System Effects on Neural and Endocrine Processes and Behavior
the avoidance task as well as control mice. At the age of 6 months, the same mice were re-tested, and once again homozygous IL-6TG mice demonstrated impaired learning, which worsened compared to their performance 3 months earlier. However, at that age, heterozygous IL-6TG mice also exhibited impaired memory, intermediate to that of the control and homozygous IL-6TG mice. By 12 months of age, the performance of both homozygous and heterozygous IL-6TG mice had declined further and became indistinguishable (Heyser et al., 1997). A similar progression was also found in the number of errors, first affecting homozygous IL-6TG mice (at 6 months of age), and later heterozygous IL-6TG mice as well (at 12 months of age). No differences in the latency of escape responses were observed at any time-point, suggesting no differences in the motivational properties of the shock (Heyser et al., 1997). Together, these findings imply progressive age-related deficits in spatial avoidance learning. Although the effects of IL-6 overproduction support a role for IL-6 in learning and memory, these findings should be interpreted in the context of other effects of IL-6 overproduction, particularly neurodegeneration and gliosis. However, a detrimental role of IL-6 in memory processes was also demonstrated using another approach, i.e., examination of the effects of IL-6 blockade on memory functioning. Braida et al. (2004) tested the performance of IL-6 knockout mice (IL-6KO), using different memory tests: In a passive avoidance task, in which the mice had to remember to avoid a chamber in which they were previously electrified, the performance of 4-month-old IL-6KO mice was similar to that of controls. However, IL-6KO mice were less susceptible to scopolamineinduced amnesia in this task. Furthermore, when IL6KO mice were tested in a more complex spatial task, the radial arm maze, their performance was found to be improved compared to age-matched WT controls; i.e., the percent of IL-6KO mice that fully acquired the task was higher compared to WT controls at both 4 and 12 months of age. This finding was also reflected in a smaller number of errors performed by IL-6KO mice at both 4 and 12 months of age. This increased precision can be explained by the fact that IL-6KO mice employed a more systematic exploration strategy, as shown by the finding that they demonstrated a higher tendency to visit neighboring arms. This difference in the pattern of entries was especially apparent at 12 months of age (Braida et al., 2004). Furthermore, Balschun et al. (2004) reported that even acute blockade of IL-6 signaling can enhance memory formation, using the forced alternation task. In this paradigm, rats are placed in complete darkness in a Y maze, at a different location in any trial, and have to alternately
choose the right or left arm in relation to the arm they were placed in. The forced alternation task is hippocampal dependent, as hippocampal lesions in rats prevent its acquisition (Aggleton et al., 1986). I.c.v. administration of neutralizing anti–IL-6 antibodies 90 minutes after acquisition resulted in enhanced retention 24 hours later. This was demonstrated by a lower percent of errors performed by anti–IL-6 injected rats, compared to controls (Balschun et al., 2004). The findings of improved performance in different memory tasks following blockade of IL-6 signaling, either by deletion of the IL-6 gene or by IL-6 immunoneutralization, suggest that IL-6 may have a physiological role in the inhibition of memory formation. Although the data on IL-6 overexpression and IL-6 blockade suggest a detrimental influence of IL-6 on memory formation, several studies demonstrated a protective role of IL-6 against memory impairments caused by either scopolamine or ischemia: In contrast to the finding of decreased susceptibility of IL-6KO mice to scopolamine-induced amnesia in the passive avoidance task (Braida et al., 2004), Binachi et al. (1997, 1998) reported that i.p. administration of IL-6 (0.125 and 0.5, but not 0.031 and 2 μg/mouse) partially blocked the effect of scopolamine in the same task. Moreover, chronic administration of IL-6 (450 but not 45 ng/day, via subcutaneous osmotic minipumps for a week), starting 2 hours before ischemia, resulted in improved memory in a passive avoidance task at the end of this week (Matsuda et al., 1996). It may be suggested that when brain homeostasis is maintained, IL6 has a detrimental effect on memory processes. However, when this balance is violated, IL-6 plays a protective role. This role is not necessarily directly connected to memory formation per se, but rather to the effort of recovering homeostasis. To sum up, the data presented above (summarized in Table 2) suggest a detrimental influence of IL-6 on memory processes, which is potentiated as the animals become older. This age-dependent effect is demonstrated by showing progressive memory deterioration in mice that overexpress IL-6, as well as a gradual memory improvement in mice lacking IL-6. However, the role of IL-6 in memory is quite complex, as acute administration of IL-6 did not produce any effect on memory in several studies, and in some situations IL-6 was found to have a protective role.
C. TNF-a The involvement of TNF-α in memory processes has been studied by several research groups, using various models. Most studies reported no involvement of TNF-α in memory functioning. However, a few
351
16. The Role of Pro-inflammatory Cytokines in Memory Processes and Neural Plasticity TABLE 2
Cytokine
Species
Summary of the Studies on the Effects of Interleukin-6 (IL-6) on Memory in Rodents
Dose
Effects of IL-6 administration IL-6 Rat 100 ng/rat
Administration route
i.c.v.
Memory testing paradigm
Hippocampal involvement
IL-6
Mouse
Unknown, homozygous
CNS-specific IL-6 transgene
Water maze spatial Active avoidance
Dependent
IL-6
Mouse
Unknown, heterozygous
CNS-specific IL-6 transgene
Active avoidance
Dependent
IL-6
Mouse
Unknown, homozygous
CNS-specific IL-6 transgene
Active avoidance
Dependent
IL-6
Mouse
Unknown, heterozygous
CNS-specific IL-6 transgene
Active avoidance
Dependent
IL-6
Rat
3 μg/kg
i.p.
Dependent
IL-6
Mouse
0.031, 0.125, 0.5 or 2 μg/mouse
i.p.
Active avoidance Passive avoidance
Dependent
Dependent
Effects of IL-6 signaling blockade IL-6 Mouse No IL-6
Knockout
Radial arm maze
Dependent
IL-6
Mouse
No IL-6
Knockout
Passive avoidance
Dependent
Anti-IL-6
Rat
—
i.c.v.
Forced alternation
Dependent
Timing
Effect on memory
Reference
1 hour before training 3 months of constant transgenic overexpression 3 months of constant transgenic overexpression 6 or 12 months of constant transgenic overexpression 6 or 12 months of constant transgenic overexpression 24 hours before training 15 minutes before acquisition
No effect
4 or 12 months of constant knockout 4 months of constant knockout Immediately following acquisition
Enhanced
Braida et al., 2004
No effect
Braida et al., 2004
Enhanced
Balschun et al., 2004
Impaired
Oitzl et al., 1993 Heyser et al., 1997
No effect
Heyser et al., 1997
Impaired
Heyser et al., 1997
Impaired
Heyser et al., 1997
No effect
Brennan et al., 2004 Bianchi et al., 1997; Bianchi et al., 1998
No effect
i.p.—Intraperitoneal; i.c.v.—Intracerebroventricular
studies demonstrated a detrimental effect of TNF-α on memory formation, and one study reported a beneficial role for TNF-α. These contradictory results will be presented, along with possible explanations for the discrepancies among them. The effect of TNF-α on memory was first investigated by Fiore et al. (1996), by testing the performance of adult mice (60 days old) that overexpress TNF-α within the CNS (TNFαTG). These mice were tested in the passive avoidance paradigm, in which they had to remember to avoid a chamber in which they were electrified (thus hesitating for a longer time before re-entering this chamber). TNFαTG mice exhibited
delayed acquisition of this task, reflected by the fact that they required a larger number of trials to reach the learning criterion and demonstrated lower latency in the first five trials. Bjugstad et al. (1998) explored the role of TNF-α in spatial memory by daily injecting rats with TNF-α (50 ng/rat, i.c.v.) for a week before water maze training. On day 8, the injections were terminated and a week-long water maze training started. TNF-α–injected rats demonstrated impaired spatial memory, reflected by longer escape latencies during water maze training, and no preference to the quadrant of the pool in which the platform was formerly positioned, in the probe trial (Bjugstad et al., 1998).
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II. Immune System Effects on Neural and Endocrine Processes and Behavior
A negative effect of TNF-α has also been reported following central administration (Matsumoto et al., 2002). In this study, the effect of TNF-α on working memory was examined using the three-panel runway task, a hippocampal-dependent task in which rodents learn to open the correct doors between three consecutive chambers in order to receive a reward (Furuya et al., 1988; Kitajima et al., 1992; Ohno et al., 1992). Intrahippocampal TNF-α (560 but not 10, 32, 100, or 320 ng/side) impaired working memory in this task, reflected by an increased number of errors and longer latencies to perform the task on days 1 and 2 postinjection (Matsumoto et al., 2002). Recently, Golan et al. (2004) further demonstrated the role of TNF-α in spatial memory by testing mice with targeted deletion of the TNF-α gene (TNFαKO) in the water maze. These mice exhibited enhanced spatial memory, reflected by their faster learning of the platform position and their better performance in the probe test compared to WT controls. However, TNFαKO mice demonstrated performance that was identical to WT controls in the hippocampalindependent, visually guided version of the water maze. Similarly, we recently found that mice lacking the TNF-R1 (TNF-R1KO) (Pfeffer et al., 1993) demonstrated enhanced contextual fear conditioning compared to their WT controls, as shown by increased freezing in this hippocampal-dependent task. These mice were similar to WT controls in the performance of auditory-cued fear conditioning, which does not require the hippocampus (Goshen and Yirmiya, unpublished observations). The results presented above suggest a detrimental role for TNF-α in memory processes. This role is independent of the species used or the memory-testing paradigm employed. However, it is restricted to the performance of tasks that depend on normal hippocampal functioning, such as the spatial version of the water maze and contextual fear conditioning, whereas hippocampal-independent tasks are spared. Additionally, the detrimental effect of TNF-α on memory seems to be dose dependent, as demonstrated in the study on intrahippocampal TNF-α administration (Matsumoto et al., 2002). In contrast with these findings, the studies presented in the following paragraphs reported no influence of either excess or absence of TNF-α expression on memory functioning. In two related studies, the influence of elevated TNFα levels on memory was studied using two different transgenic strains that overexpress TNF-α specifically within the CNS: TG6074 mice, with glial overexpression of the murine TNF-α gene, which display inflammatory demyelination and neurological abnormalities (Probert et al., 1995); and TGK3, with neuronal overexpression
of the uncleavable mutant human TNF-α gene, which display no neurological symptoms (Probert et al., 1997). Both of these transgenic strains had longer escape latencies compared to their WT controls at the age of 30 days, suggesting TNF-α–induced memory impairment (Aloe et al., 1999b; Fiore et al., 2000). However, compared to controls, these mice also displayed a slower swimming speed, which may affect the latency to reach the platform. Furthermore, the learning deficit was not observed with respect to the path length to reach the platform, which provides a measurement of learning that is not dependent on speed. Moreover, no difference was found in the preference of the quadrant in which the platform was positioned in the probe test, another memory parameter that is not influenced by swimming speed (Aloe et al., 1999b; Fiore et al., 2000). Together, these findings suggest no effect of excessive brain TNFα on spatial memory. The discrepancy between the results of these studies and the report of impaired spatial memory in TNFαTG6074 mice (Fiore et al., 1996) may be explained by differences in the age of the subjects. Because aging is accompanied by cognitive deterioration, and brain TNF-α expression is increased with age (Casolini et al., 2002; Sharman et al., 2002), it can be postulated that TNF-α may be involved in aging-related memory loss. Indeed, impaired spatial memory was observed in adult (60-day-old) mice, but not in young (30-day-old) mice. Fiore et al. (2000) also reported no difference between TNFαTG6074 and control mice in passive avoidance response in juvenile (15-day-old) mice. Thus, the detrimental effect of TNF-α transgenic overexpression in the brain on memory processes seems to be age dependent. Several studies report no effect of TNF-α deficiency on spatial memory. Both Scherbel et al. (1999) and Gerber et al. (2004), using two different lines of TNFαKO mice, reported normal performance in the water maze paradigm, compared to that of WT controls. We found similar results using TNF-R1KO mice, which demonstrated a similar performance to their WT controls in the water maze (Goshen and Yirmiya, unpublished observation). Nevertheless, TNFαKO mice were less susceptible to the memory impairment caused by brain injury, which was inflicted by controlled cortical impact (Scherbel et al., 1999), suggesting that in WT mice TNFα participates in the processes underlying this damage. Yamada et al. (2000) employed another spatial test, the water finding task, to examine the influence of TNF-α deficiency: In this task, mice are allowed to explore an open field, in which an alcove with a water spout is placed. The mice are then re-introduced to this context when they are thirsty, and the latency to find the water spout serves as an index to their spatial memory.
16. The Role of Pro-inflammatory Cytokines in Memory Processes and Neural Plasticity
TNFαKO mice performed this task as well as their WT controls (Yamada et al., 2000). A single study reported a beneficial effect of TNF-α administration on memory, using a passive avoidance task, in which rats could prevent the occurrence of a shock by pressing a lever (avoidance response) or terminate the shock after it had begun by pressing the lever (escape response). Brennan et al. (2004) reported that a single injection of TNF-α (6 μg/kg i.p.) 24 hours before training resulted in increased number of avoidance as well as escape responses. TNF-α also seems to have a positive effect on the recovery of memory functioning following infection: Gerber et al. (2004) reported that after surviving pneumococcal meningitis, TNFαKO mice demonstrated impaired water maze performance compared to surviving WT controls, suggesting a beneficial role for TNF-α in recovery. It may be suggested that, similar to IL-6, when brain homeostasis is maintained, TNF-α has a detrimental effect on memory processes, and when this balance is violated, TNF-α may play a protective role. To sum up, the data gathered so far (summarized in Table 3) do not provide definite conclusions regarding the role of TNF-α in memory processes. However, it can still be suggested that (A) basal levels of TNF-α are not required for memory, as TNF-α–deficient mice demonstrate no memory impairments, and one paper even reports improved memory in these mice; and (B) the negative influence of TNF-α appears to be both dose and age dependent. Further studies should clarify the nature of the involvement of TNF-α in learning and memory processes, both under basal conditions and following various inflammatory and noninflammatory challenges.
III. MECHANISMS UNDERLYING THE EFFECTS OF PRO-INFLAMMATORY CYTOKINES ON LEARNING AND MEMORY A. Neural Plasticity 1. Effects of IL-1 on Neural Plasticity Extensive research was performed to study the involvement of IL-1 in hippocampal plasticity (reviewed in Lynch, 2002; O’Connor and Coogan, 1999). Similar to the findings concerning the role of IL-1 in memory processes, this research also yielded seemingly contradictory results, as many studies demonstrated a detrimental effect of IL-1 on hippocampal plasticity, whereas other studies reported a beneficial role for IL-1 in normal hippocampal plasticity. These results will be presented together with an attempt to
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accommodate them into the inverted U-curve theoretical model, which was proposed for the involvement of IL-1 in memory processes. Detrimental Effects of IL-1 on Neural Plasticity Katsuki et al. (1990) were the first to examine the consequence of IL-1β application on LTP. They reported that IL-1β inhibited LTP in the CA3 region of mouse hippocampal slices in vitro. Additional studies then reported similar findings of IL-1–induced LTP inhibition in the rat CA1 area of the hippocampus (Bellinger et al., 1993) and the DG (Cunningham et al., 1996). This detrimental effect of IL-1 was accomplished by the inhibition of both N-methyl-D-aspartate (NMDA)-mediated and NMDA-independent synaptic potentiation (Coogan and O’Connor, 1997, 1999). Murray and Lynch (1998) reported that LTP maintenance is negatively correlated with IL-1 hippocampal levels; i.e., increased IL-1β levels in the hippocampus (caused by aging, stress, or exogenous application) are accompanied by reduced LTP maintenance. Additional studies shed light on the signal transduction mechanisms that underlie IL-1–induced LTP inhibition. One major mechanism that is affected by IL-1 is LTP-associated increase in glutamate release in the DG (Canevari et al., 1994), evidenced by several studies which demonstrated that IL-1β application resulted in inhibited KCl-induced glutamate release in the hippocampus (Kelly et al., 2003; O’Donnell et al., 2000; Vereker et al., 2000, 2001). A few studies showed that the inhibitory effect of IL-1 on LTP is accompanied by increased activity of stress-activated protein kinases. Concomitantly with LTP inhibition, i.c.v. IL-1β increased p38 mitogen-activated protein (MAP) kinase activity in DG synaptosomes (Kelly et al., 2003; Vereker et al., 2000). Co-administration of IL-1 together with the p38 inhibitor SB203580 attenuated the detrimental effect of IL-1 on LTP both in vivo (Kelly et al., 2003) and in vitro (Coogan et al., 1999), and restored KCl-induced glutamate release in IL-1–treated rats (Kelly at al., 2003). IL1β also increased NFκB activation in the hippocampus, and co-administration of the NFκB inhibitor SN50 attenuated the detrimental effect of IL-1 on LTP and restored KCl-induced glutamate release (Kelly et al., 2003). Similarly, IL-1 increased the activity of c-Jun N-terminal kinase (JNK) (Curran et al., 2003; Vereker et al., 2000), and the JNK inhibitor SP600125 blocked the inhibitory effect of IL-1 on LTP (Curran et al., 2003). Finally, IL-1β also enhanced the production of reactive oxygen species (ROS) (Vereker et al., 2000, 2001), and its inhibitory effect on LTP was blocked by application of the antioxidant phenylarsine oxide (Vereker et al., 2001) and even by a diet enriched in the antioxidant vitamins A and C (Vereker et al. 2000).
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II. Immune System Effects on Neural and Endocrine Processes and Behavior TABLE 3
Cytokine Species
Dose
Effects of TNF-α administration TNF-α Rat 50 ng/rat/ day
TNF-α
Summary of the Studies on the Effects of TNF-α on Memory in Rodents Administration route
Water maze spatial
Dependent
Unknown
Glia-specific overexpression
Water maze spatial
Dependent
Unknown
Neuron-specific overexpression
Water maze spatial
Unknown
Glia-specific overexpression
Unknown
Effect on memory
Reference
Bjugstad et al., 1998
Dependent
Constant No effect overexpression *
Aloe et al., 1999; Fiore et al., 2000
Passive avoidance
Dependent
Constant Impaired overexpression
Fiore et al., 1996
Glia-specific overexpression
Passive avoidance
Dependent
Constant No effect overexpression
Fiore et al., 2000
Three-panel runway Three-panel runway Active avoidance
Dependent
24 hours before training 24 hours before training 24 hours before training
Matsumoto et al., 2002 Matsumoto et al., 2002 Brennan et al., 2004
TNF-α
Rat
10, 32, 100, or Intrahippocampal 320 ng/side 560 ng/side Intrahippocampal
TNF-α
Rat
6 μg/kg
TNF-α
Timing
Daily injections Impaired at the week preceding training Constant No effect overexpression *
TNF-α
TNF-α
Hippocampal involvement
i.c.v.
Mouse 30 days old Mouse 30 days old Mouse 60 days old Mouse 15 days old Rat
TNF-α
Memory testing paradigm
i.p.
Effects of TNF-α signaling blockade TNF-α Mouse No TNFα Knockout TNF-α
Mouse
No TNFα
Knockout
TNF-α
Mouse
No TNFα
Knockout
TNF-α
Mouse
No TNFα
Knockout
TNF-α
Mouse
No TNFα
Knockout
Water maze spatial Water finding test Water maze spatial Water maze spatial Water maze Visually guided
Dependent Dependent
Dependent
Constant knockout Dependent Constant knockout Dependent Constant knockout Dependent Constant knockout Independent Constant knockout
No effect Impaired Enhanced
Aloe et al., 1999; Fiore et al., 2000
Enhanced
Scherbel et al., 1999 Yamada et al., 2000 Gerber et al., 2004 Golan et al., 2004
No effect
Golan et al., 2004
No effect No effect No effect
i.p.—Intraperitoneal; i.c.v.—Intracerebroventricular; *The transgenic mice had longer escape latencies, suggesting memory impairment. However, compared to controls, these mice also displayed a slower swimming speed, which may affect the latency to reach the platform. Furthermore, the learning deficit was not observed with respect to the path length to reach the platform, which provides a measurement of learning that is not dependent on speed, and no differences in preference for the quadrant in which the platform was positioned was found in the probe test.
In addition to its effects on LTP, IL-1 was also reported to affect basal synaptic activity: Bellinger et al. (1993) reported reduced postsynaptic potentials in the CA1 region of hippocampal slices, and Ikegaya et al. (2003) showed that incubation of hippocampal slices with IL-1β decreased basal CA1 synaptic transmission during that time, an effect that lasted for 30 minutes after IL-1 was washed out. This durable effect was dependent on increased GABA levels, as in the presence of the GABA receptor antagonist bicuculin, IL-1 decreased synaptic
transmission only when it was present in the experimental system, but not after it was washed out (Ikegaya et al., 2003). To sum up, the data presented above clearly demonstrate a detrimental effect of elevated IL-1 levels on hippocampal LTP. This negative influence was replicated in various studies, both in vivo and in vitro, using different doses of exogenously applied IL-1β, as well as endogenous IL-1β elevation caused by aging and stress. These adverse effects are mediated by stressactivated protein kinases and ROS.
16. The Role of Pro-inflammatory Cytokines in Memory Processes and Neural Plasticity
Beneficial Effects of IL-1 on Neural Plasticity In contrast to the data presented so far on the detrimental effect of increased IL-1 levels on LTP, recent studies suggest that IL-1 may actually be required for the normal regulation of hippocampal plasticity. The first evidence for the physiological involvement of IL-1 in plasticity was provided by Schneider et al. (1998), who reported that IL-1β gene expression is substantially increased during LTP, starting 15 minutes after stimulation in hippocampal slices and 8 hours after LTP induction in freely moving rats (Balschun et al., 2003; Schneider et al., 1998). Furthermore, the in vivo increase in IL-1β gene expression was long lasting, specific to potentiation (i.e., was observed only in the stimulated, but not contralateral, hippocampus) and could be prevented by blockade of potentiation with the NMDA receptor antagonist, (+/−)-2-amino-5phosphonopentanoic acid (AP-5) (Schneider et al., 1998). The elevation in IL-1β gene expression appears to have a physiological role in the maintenance of LTP, as blocking IL-1 receptors by i.c.v. administration of IL-1ra 90 minutes after the induction of LTP impaired its maintenance, whereas when IL-1ra was applied 30 minutes before or immediately after stimulation, it had no effect (Schneider et al., 1998). However, Loscher et al. (2003) reported that i.c.v. administration of IL-1ra 30 minutes before stimulation resulted in a smaller initial potentiation and no maintenance of LTP. The critical role of IL-1 in LTP was also demonstrated in hippocampal slices in vitro: Application of IL-1ra 30 minutes after the induction of LTP in the rat dentate gyrus in vitro reduced synaptic activity back to baseline levels (Coogan et al., 1999), and when IL-1ra was applied to hippocampal sliced in a physiological temperature for 40 minutes before stimulation, the initial small increase in synaptic activity subsided within 30 minutes (Ross et al., 2003). Loscher et al. (2003) investigated the mechanisms that underlie the detrimental effect of IL-1ra on LTP. They reported decreased glutamate release and increased JNK phosphorylation in hippocampal synaptosomes following exposure to IL-1ra. Interestingly, these effects are not mediated by the IL-1 receptor type I (IL-1RI), as they appear both in the presence of neutralizing antibodies against IL-1RI, and in synaptosomes prepared from IL-1rKO mice (Loscher et al., 2003). Lately, we further demonstrated the necessity of physiological IL-1 levels in hippocampal plasticity by reporting no potentiation following high-frequency stimulation in IL-1rKO mice and a complete absence of LTP in hippocampal slices prepared from these mice (Avital et al., 2003). Moreover, we reported, for
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the first time, an involvement of IL-1 in short-term plasticity as well, by showing enhanced paired-pulse inhibition in the DG of IL-1rKO mice in vivo, and decreased paired-pulse potentiation in vitro in hippocampal slices from IL-1rKO mice (Avital et al., 2003). It should be noted, however, that Ikegaya et al. (2003) reported normal LTP and LTD in IL-1α/βKO mice. To summarize, the data presented in the previous paragraphs demonstrate the requirement of physiological IL-1 levels in hippocampal LTP, both in vivo and in vitro. The importance of IL-1 in LTP is further supported by the findings of increased IL-1 gene expression following LTP. A Theoretical Model for the Effects of IL-1 on Neural Plasticity The data presented above suggest that, similar to the involvement of IL-1 in memory processes, an inverted U-curve pattern exists for its influence on hippocampal plasticity as well (Figure 1). Thus, whereas some studies report a detrimental effect of elevated IL-1 levels on LTP, others report that LTP is impaired when IL-1 signaling is blocked. Whereas the hypothesis of the dual role of IL-1 in memory is based on different results that were obtained under various conditions, Loscher et al. (2003) provide data on the effect of both IL-1 and IL-1ra on LTP under identical conditions. They report that i.c.v. administration of either IL-1β or IL-1ra 30 minutes before tetanic stimulation resulted in a decreased potentiation that did not sustain (Loscher et al., 2003). The combination of the data presented above suggests that physiological levels of IL-1 are needed for synaptic plasticity, and that any deviation from the physiological range, either by elevation in IL-1 levels or by blockade of IL-1 signaling, results in impaired hippocampal plasticity. This is postulated based on (A) the LTP-induced increase in hippocampal IL-1 gene expression; (B) the detrimental effect of elevated IL-1 levels (induced by exogenous application, stress, or aging) on hippocampal LTP both in vivo and in vitro; and (C) the fact that blockade of IL-1 signaling either pharmacologically by IL-1ra or genetically by deletion of the IL-1 receptor impairs synaptic plasticity both in vitro and in vivo. This model predicts that coapplication of IL-1 and IL-1ra, which both impair LTP independently, will not result in accumulated LTP impairment, but rather in a reduced inhibitory effect. Indeed, when IL-1β and IL-1ra are applied concomitantly, their detrimental effect on LTP is attenuated both in vivo (Loscher et al., 2003) and in vitro (Ross et al., 2003).
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Disruption in the balance of hippocampal IL-1 activity may be associated with the findings of agedependent decrease in LTP (Lynch, 1998a, b; O’Donnell et al., 2000). Aging is accompanied by an increase in basal hippocampal IL-1β levels together with reduced LTP (Murray and Lynch, 1998; O’Donnell et al., 2000). Furthermore, aged rats display a similar phenomenon to rats treated with IL-1; i.e., they display decreased KCl-induced glutamate release, increased activation of p38 and JNK, and increased ROS production (Murray and Lynch, 1998; O’Donnell et al., 2000). It should be noted, however, that these findings provide only circumstantial evidence, and no data that directly demonstrate a role for IL-1 in aging are available. Aging is also associated with a diminished increase in LTP-induced IL-1β gene expression. IL-1β expression is increased by 10-fold in young rats during LTP, but only by two-fold in mid-aged rats (Balschun et al., 2003). Together these findings suggest that deviations in either direction from the fine balance of hippocampal IL-1 levels may lead to LTP maintenance impairments in aging. 2. Effects of IL-6 on Neural Plasticity Corresponding to the reports of IL-6–induced memory loss, this cytokine was also found to impair hippocampal plasticity. Bellinger et al. (1995) were the first to demonstrate the detrimental effect of IL-6 on hippocampal plasticity in vitro by reporting reduced LTP in the DG of hippocampal slices prepared from transgenic mice with cerebral overexpression of IL-6. Li et al. (1997) further investigated the dose-dependent effect of IL-6 on the different phases of LTP in vitro by using four different concentrations of IL-6 (50, 200, 500, 2000 U/ml). One hour after tetanic stimulation, LTP in the CA1 region was reduced by all four concentrations. However, 10–15 minutes following stimulation only the three highest concentrations caused a decrease in potentiation, and only the two highest concentrations impaired even the initial post-tetanic potentiation (Li et al., 1997). All of these effects were mediated via the IL-6 receptor, as they were all blocked by antibodies against this receptor (Li et al., 1997). Tancredi et al. (2000) assessed the influence of IL-6 on LTP in the CA1 region in vitro, using three lower IL-6 concentrations (1, 5, 50 U/ml). However, they also reported that LTP was impaired in a dose-dependent manner (not affected by the lowest concentration, mildly repressed by the intermediate one, and strongly inhibited by the highest concentration), and that post-tetanic potentiation was also reduced by the two highest concentrations only (Tancredi et al., 2000). Although different IL-6 concentrations were used in the two studies, both suggest that IL-6 is involved mainly in the process of
the transformation between short- and long-term plasticity, but that at higher concentrations it can interrupt the potentiation process itself. No study reported a significant effect of IL-6 on basal synaptic transmission, and elevated IL-6 levels (either by transgenic overexpression or by external application) had no effect on paired-pulse response in vitro (Bellinger et al., 1995; Tancredi et al., 2000), indicating that this cytokine is not involved in short-term plasticity. Several mechanisms that may underlie the detrimental effect of IL-6 on LTP were investigated: IL-6 reduced glutamate release induced by AP-4 in a dosedependent way (D’Arcangelo et al., 2000). Additionally, IL-6 application to hippocampal slices resulted in increased STAT3 tyrosine phosphorylation and reduced activation of the MAP kinases ERK1 and ERK2 (D’Arcangelo et al., 2000; Tancredi et al., 2000), which play an important role in LTP maintenance (Kelleher et al., 2004). The finding that these effects were blocked by the tyrosine kinase inhibitor lavendustin A (D’Arcangelo et al., 2000; Tancredi et al., 2000) further implicates this signaling pathway in mediating the effects of IL-6 on LTP. All of the studies presented above demonstrate a detrimental effect of elevated IL-6 levels on long-term synaptic plasticity. However, recent studies suggest that endogenous IL-6 may actually have a physiological role in LTP inhibition. Jankowsky et al. (2000) reported a 20-fold increase in IL-6 gene expression 4 hours after LTP induction by high-frequency stimulation in vivo. Balschun et al. (2004) also found increased IL-6 gene expression 8 hours after high-frequency stimulation in freely moving rats. This increase was found only in rats in which LTP was robust and maintained for 8 hours, but not when it subsided within 3 hours following highfrequency stimulation (Balschun et al., 2004). Increased IL-6 gene expression was observed 1–3 hours following LTP induction in hippocampal slices in vitro as well (Balschun et al., 2004). Immunoneutralization of IL-6 by i.c.v. administration of anti–IL-6 antibodies 90 minutes following the induction of LTP resulted in longer maintenance of LTP; i.e., LTP was still preserved in anti–IL-6 injected rats after it subsided in control rats. In contrast, anti–IL-6 antibodies that were injected 30 minutes before or 5 minutes after the induction of LTP had no effect (Balschun et al., 2004), suggesting that IL-6 is selectively involved in a specific phase of LTP consolidation. No other endogenous protein is known to interfere with LTP maintenance in such a late phase, without influencing LTP induction. The findings of LTP-induced increase in IL-6 gene expression, together with longer preservation of LTP following IL-6 neutralization, suggest that IL-6 may have a physiological role in the termination of LTP.
16. The Role of Pro-inflammatory Cytokines in Memory Processes and Neural Plasticity
3. Effects of TNF-a on Neural Plasticity As reviewed above, TNF-α seems to have a negative effect on memory functioning, which is both dose- and age-dependent, although this effect is less robust than the effects of IL-1 and IL-6. Furthermore, in contrast to IL-1 and IL-6, basal levels of TNF-α are probably not involved in memory processes. The involvement of TNF-α in hippocampal plasticity was examined only in vitro, and the findings are in line with the behavioral conclusions. Tancredi et al. (1992) were the first to report a dosedependent inhibition of LTP in the CA1 region following TNF-α application in vitro. Many additional studies reported reduced potentiation and inhibited LTP maintenance following TNF-α application in vitro in the DG as well (Butler et al., 2002; Cunningham et al., 1996; Curran and O’Connor, 2001; Curran et al., 2003). However, Albensi and Mattson (2000) reported no change in LTP in the CA1 region of hippocampal slices from mice lacking both TNFR1 and TNFR2 (TNFrKO). This finding is in line with the behavioral reports of normal and even enhanced memory in TNFαKO and TNFR1KO mice. Furthermore, these TNFrKO mice demonstrated impaired LTD (Albensi and Mattson, 2000), suggesting a role for TNF-α in synaptic depression. The mechanisms underlying TNF-induced LTP impairment are quite similar to those that mediate the detrimental effect of IL-1 on LTP. Similar to IL-1β, TNF-α induced p38 MAP kinase activation in the DG (Butler et al., 2004). However, p38 MAP kinase seems to mediate primarily the initial inhibitory effect of TNF-α on LTP, as its inhibitor SB203580 completely blocked TNF-α–induced early-phase LTP impairment (1 hour following tetanic stimulation), but only partially blocked the negative effect of TNF-α 3 hours following tetanic stimulation (Butler et al., 2004; Pickering et al., 2005). Furthermore, like IL-1β, the inhibitory effect of TNF-α on LTP is attenuated by the JNK inhibitor SP600125 (Curran et al., 2003) and by nicotine (Curran and O’Connor, 2003), suggesting a role for JNK and acetylcholine (ACh) in TNF-α–induced LTP inhibition. Finally, TNF-α application was shown to increase surface expression of glutamate AMPA receptors, and TNF blockade resulted in decreased AMPA receptor expression (Beattie et al., 2002). However, these new receptors have abnormal stoichiometry, as they lack the GluR2 subunit; thus, they become Ca2+ permeable and may contribute to neurotoxicity (Stellwagen et al., 2005). To sum up, similar to the behavioral studies that imply a dose-dependent negative effect of TNF-α on memory, the electrophysiological studies presented
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above also suggest a detrimental effect of TNF-α on hippocampal plasticity, which is mediated by mechanisms similar to those mediating the effects of IL-1β.
B. Stress Responses and Glucocorticoids Secretion A broad range of aversive physiological and psychological stimuli can induce stress responses in both humans and animals. The most prominent physiological stress response is activation of the HPA axis: In response to stressful stimuli, hypothalamic neurons secrete corticotropin-releasing hormone (CRH), the major adrenocorticotropic hormone (ACTH) secretagoge, which induces the secretion of ACTH from the anterior pituitary into the systemic circulation, resulting in secretion of glucocorticoids (GC) from the adrenal cortex (Antoni, 1986). Many researchers examined the effects of stress on hippocampal-dependent memory and plasticity, finding seemingly contradictory results. In some studies, stress exposure or administration of stress hormones was found to produce detrimental effects on hippocampal-dependent memory and plasticity, in both humans and animal models. However, in other studies low levels of stress, accompanied by a mild increase in stress hormones, were found to be necessary for memory formation and LTP (reviewed in de Kloet et al., 1999; Kim and Diamond, 2002; McEwen and Sapolsky, 1995). Thus, similar to the finding on the involvement of IL-1 in hippocampal-dependent memory, corticosteroids also exert an inverted Ushaped influence on memory and plasticity (Conrad et al., 1999; Diamond et al., 1992). IL-1 is expressed throughout the components of the HPA axis (Besedovsky and del Rey, 1996; Turnbull and Rivier, 1999) and influences all of its levels: IL-1 induces the secretion of CRH from the hypothalamus and ACTH from the pituitary (Berkenbosch et al., 1987; Bernton et al., 1987; Sapolsky et al., 1987). Additionally, IL-1 stimulates GCs secretion from the adrenal, although no known IL-1 receptors were found in this gland (Besedovsky and del Rey, 1996; Turnbull and Rivier, 1999). The production, secretion, and influence of IL-1 on the HPA axis have been traditionally considered in the context of illness-associated immune activation (Besedovsky and del Rey, 1996; Turnbull and Rivier, 1999). However, over the last decade it became evident that psychological stressors activate the IL-1 system in the brain (Nguyen et al., 1998, 2000; O’Connor et al., 2003; Suzuki et al., 1997). Furthermore, it was demonstrated, by us and by others, that endogenous IL-1 activates the HPA axis not only during sickness, but also in response to various psy-
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chological stressors (Goshen et al., 2003b; Shintani et al., 1995). The findings that the influence of IL-1 and the influence of stress or corticosterone on memory follow the same inverted U shape and that stress can induce IL-1 production, which in turn activates the HPA axis, may lead to two hypotheses: First, IL-1 may mediate the detrimental effects of stress on memory. This hypothesis was confirmed by two studies (as detailed above in the section titled “IL-1”), which showed that i.c.v. administration of IL-1ra prior to stress exposure blocked its harmful effect on memory (Maier and Watkins, 1995; Pugh et al., 1999). Second, HPA axis activation may be involved in the influence of IL-1 on memory formation (both detrimental and beneficial), which is usually assessed in the context of stressful paradigms (e.g., the Morris water maze or fear conditioning). The studies that addressed the latter hypothesis will be discussed below. The possible involvement of HPA axis activation in IL-1–induced memory impairment was demonstrated by two studies (Song and Horrobin, 2004; Song et al., 2004), reporting a concomitant modulation of the effect of IL-1 on memory and corticosterone secretion. These studies found a detrimental effect of i.c.v. administered IL-1β on spatial memory in the water maze as well as on working memory in the win-shift radial arm maze. Eight weeks of feeding with a diet enriched in the antiinflammatory supplement ethyl-eicosapentaenoic acid (E-EPA, 1%) attenuated the IL-1–induced memory impairment and blocked the IL-1–induced increase in serum corticosterone concentration (Song and Horrobin, 2004; Song et al., 2004), suggesting that this increase mediated the effect of IL-1 on memory. The role of HPA axis activation in IL-1–induced memory improvement was directly assessed using GC receptor blockade: Song et al. (2003) reported improved contextual passive avoidance response concomitantly with increased corticosterone secretion in rats that were injected i.c.v. with IL-1β. However, when IL-1 was co-administered together with the GC receptor antagonist RU486, the beneficial effect on memory was abolished, and so was the increase in corticosterone levels (Song et al., 2003). Additionally, IL-1rKO mice, which demonstrated impaired memory performance (Avital et al., 2003), also showed diminished corticosterone secretion in response to mild stressors (Goshen et al., 2003b), suggesting that impaired HPA axis activation may mediate the poor memory performance of these mice. To conclude, the findings reported to date show that on the one hand IL-1 mediates the detrimental effects of stress on memory, and on the other hand HPA axis activation, which affects memory in an inverted U
pattern similar to IL-1, may be involved in both the detrimental and the beneficial effects of IL-1 on memory formation, which had been assessed using stressful paradigms. Based on all the data presented in this section, the following model may be proposed: Stressful stimuli induce an increase in brain IL-1 levels, which in turn contribute to the activation of the HPA axis. Subsequently, the secretion of corticosterone affects memory processes in an inverted U-shaped way.
C. Prostaglandins An increase in IL-1 levels is usually accompanied by the secretion of prostaglandins (PGs), the proinflammatory derivates of arachidonic acid. The first step of prostaglandin synthesis is performed by the enzyme cyclooxygenase (COX). The primary two COX isoforms are the constitutive COX-1 and the inducible COX-2, which are uniquely involved in different physiological processes (Smith and Langenbach, 2001). COX-1 and COX-2 are encoded by different genes and show only about 60% protein homology. The conformational variations between the two can account for their different sensitivities to specific inhibitors (Kurumbail et al., 1996). IL-1 is a strong inducer of COX-2 in brain glia cells (O’Banion et al., 1996), and both IL-1α and β increased the production of hippocampal prostaglandin E2 (PGE2) in a dose-dependent manner (Weidenfeld et al., 1995). Elevated PGE2 levels were shown in the past to mediate some of the physiological (e.g., fever) (Dinarello et al., 1999) and behavioral (e.g., pain perception and sexual behavior) (Avitsur and Yirmiya, 1999; Hori et al., 1998) effects of IL-1 administration; thus, they may also mediate its influence of memory processes. PGs were demonstrated to affect the cognitive state in many inflammatory and neurodegenerative brain diseases in humans (reviewed in Minghetti, 2004). Furthermore, PGs were repeatedly reported to be involved in memory processes in animals. Interestingly, PGs share the same inverted U-shape pattern of influence on memory as IL-1. On the one hand, high PG levels, e.g., following traumatic brain injury or LPS administration, impaired spatial memory, and COX inhibitors improved memory function (Gopez et al., 2005; Shaw et al., 2005). Moreover, mice with transgenic overexpression of COX-2 demonstrated elevated production of PGE2 in the brain, concomitantly with an agedependent spatial memory deficit in the water maze, as well as impaired passive and active avoidance (Andreasson et al., 2001). On the other hand, basal PGE2 levels may actually have a role in hippocampal memory and plasticity, because inhibition of COX
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activity in animals without inflammatory stimulation can negatively affect memory and plasticity. For example, the non-selective COX inhibitors indomethacin and ibuprofen and the COX-2 inhibitor NS-398 impaired spatial but not visually guided water maze performance (Shaw et al., 2003; Teather et al., 2002). COX inhibition by ibuprofen resulted in impaired hippocampal LTP as well (Shaw et al., 2003), and a similar finding was reported for specific COX-2 inhibition by NS398 and nimesulide (Chen et al., 2002), an effect that was reversed by PGE2 application (Chen et al., 2002). To date, PGs were found to mediate only the detrimental effect of IL-1 on memory: Intrahippocampal injection of IL-1, which increased hippocampal PGE2 secretion, impaired working memory performance in the three-panel runway task, similar to intrahippocampal injection of PGE2 itself. Furthermore, subcutaneous injection of the COX inhibitor diclofenac 30 minutes before IL-1 administration totally blocked the detrimental effect of IL-1 on working memory (Matsumoto et al., 2004). Another study showed that 8 weeks of feeding with a diet enriched in the antiinflammatory supplement E-EPA attenuated the spatial memory and working memory impairments induced by i.c.v.-administered IL-1β and blocked the IL-1– induced increase in hippocampal PGE2 concentration (Song and Horrobin, 2004; Song et al., 2004). Finally, chronic treatment with the COX-2 inhibitor cellecoxib for 4 months in aged rats diminished hippocampal protein levels of PGE2 and IL-1β, and blocked the agerelated memory impairment (Casolini et al., 2002). Inhibition of PG synthesis by indomethacin also blocked IL-1–induced LTP inhibition (Coogan et al., 1999). To conclude, PG synthesis, which affects memory and plasticity processes in an inverted U-shaped pattern similar to IL-1, seems to play a role in the detrimental effect of IL-1 on memory processes and plasticity. To date, the role of PGs in the beneficial role of IL-1 in memory processes has not been examined. However, the fact that IL-1 induces PG synthesis, which is necessary for normal memory functioning, suggests that PGs may also be involved in IL-1–induced memory facilitation.
D. Developmental Processes, Neurogenesis, and Neurotrophins Much of the data presented in “Effects of IL-1, IL-6, and TNF-α on Learning and Memory in Rodents,” demonstrating the role of pro-inflammatory cytokines in memory processes and plasticity, was obtained using genetically manipulated mice. Because in these animals the modified signaling is present throughout the life span of the animal, from conception to matu-
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rity, it may influence memory either by affecting brain development in a way that will alter memory functioning in adulthood, and/or by directly influencing ongoing memory processes in the adult brain at the time of learning. The ability of pro-inflammatory cytokines to affect memory processed in these ways will be further discussed in this section. Pro-inflammatory cytokines are expressed in human and mouse pre-implantation embryos and in the embryonic brain (De los-Santos et al., 1996; Gerwin et al., 1995; Kruessel et al., 1997; Mehler and Kessler, 1997; Pousset, 1994; Sharkey et al., 1995). Furthermore, IL-1β, IL-6, and TNF-α levels were reported to increase with time in embryonic human forebrain cells (Mousa et al., 1998), and they have a marked influence on neuronal differentiation and survival (Akaneya et al., 1995; Ling et al., 1998; Marz et al., 1999; Munoz-Fernandez and Fresno, 1998), as well as on neurite outgrowth (Edoff and Jerregard, 2002; Johanson and Stromberg, 2002; Neumann et al., 2002). Thus, pro-inflammatory cytokines may be involved in brain development, and interference with their signaling during the prenatal period may have behavioral effects in adulthood as well. The feasibility of this hypothesis was recently demonstrated in a study on TNFαKO mice. In the first postnatal week, these mice exhibited an accelerated maturation of the DG region of the hippocampus, which may have contributed to the improved memory that these mice displayed in adulthood (Golan et al., 2004). Pro-inflammatory cytokines may also influence ongoing memory processes in the adult brain either by one of the mechanisms that were suggested above (neural plasticity, stress hormones, and secretion of prostaglandins) or by altering neurogenesis, the formation of new neurons, which is considered a part of the biological substrate for memory formation (Gould et al., 2000; Gross, 2000; Kempermann et al., 2004). Recently, immune activation was demonstrated to have a detrimental influence on neurogenesis, suggesting a negative role for pro-inflammatory cytokines on this process. Specifically, microglia, the macrophage-like cells within the brain, were suggested as the mediators of this detrimental effect (e.g., Kempermann and Neumann, 2003). Ekdahl et al. (2003) demonstrated that intracortical LPS administration, which induced the activation of microglia, resulted in decreased neurogenesis. They also reported an inverse correlation between the amount of microglial activation and the generation of new neurons (Ekdahl et al., 2003). Moreover, in order to affect neurogenesis, the inflammatory stimulus does not have to be localized to the brain, as demonstrated by Monje et al. (2003), who reported that a single i.p. LPS
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injection increased the number of activated microglia and reduced hippocampal neurogenesis. Monje et al. (2003) further showed that in vitro, neuronal differentiation is decreased by co-culture with activated but not resting microglia, and that this effect is mediated by soluble factors, as conditioned medium (CM) from activated microglia produced the same effect. One of these factors may be IL-6, as IL-6 inhibited neuronal differentiation, and anti–IL-6 blocked the detrimental effect of IL-6 and of the CM from activated microglia on neuronal differentiation. Interestingly, IL-6 specifically blocked the generation of new neurons, without affecting the development of astrocytes or oligodendrocytes (Monje et al., 2003). Similarly, mice with transgenic overexpression of IL-6 displayed decreased proliferation and survival of neurons, with no effect on the number of glia cells (Vallieres et al., 2002). This finding corroborates the results of a previous study demonstrating that IL-6 promotes differentiation of cerebral cortical precursor cells into astrocytes and inhibits differentiation of cortical precursors along a neuronal lineage in vitro (Bonni et al., 1997). Liu et al. (2005) also showed that CM from LPS-activated microglia reduced neuronal differentiation, and that this effect was at least partly mediated by TNF-α: TNF-α secretion from activated, compared to resting, microglia, was increased, and pentoxifylline, a TNF-α inhibitor, reduced the detrimental effect on neuronal differentiation (Liu et al., 2005). The influence of pro-inflammatory cytokines on either brain development or adult neurogenesis, as well as their acute effects on memory in adulthood, may be mediated by neurotrophic factors. IL-1, IL-6, and TNF-α influence the expression and secretion of various neurotrophic factors, e.g., nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) (Frei et al., 1989; Gadient et al., 1990; Ishida et al., 1997; Murphy et al., 2000; Schulte-Herbruggen et al., 2005; Steiner et al., 1991). In addition to their role in the development of the CNS, NGF and BDNF have been implicated in hippocampal-dependent memory (e.g., Chen et al., 1997; Hall et al., 2000). A set of studies conducted by Barrientos et al. (2003, 2004) provides strong evidence that the detrimental effect of IL-1 on memory is mediated by interference with the increase in BDNF expression that accompanies contextual memory formation (Hall et al., 2000). Indeed, IL-1β reduced the increase in hippocampal BDNF mRNA following exposure to fear conditioning (Barrientos et al., 2004). Barrientos et al. (2003) also showed that social isolation stress impaired the acquisition of contextual fear conditioning and decreased BDNF mRNA in the hippocampus. Furthermore, intrahippocampal injection of IL-1ra before isolation prevented both the
memory impairment and the decrease in BDNF expression (Barrientos et al., 2003). Other studies suggest that NGF is involved in TNF-α–induced modulation of memory. Golan et al. (2004) reported that TNFαKO mice, which demonstrated enhanced memory performance, also exhibit increased expression of NGF following performance of the learning task. Moreover, TNFαTG mice, which showed impaired memory performance (Fiore et al., 1996), also demonstrated decreased hippocampal NGF secretion (Aloe et al., 1999a, b). To conclude, the ability of pro-inflammatory cytokines to influence neuronal proliferation and differentiation, as well as the secretion of neurotrophic factors both in the developing and the adult brain, may mediate their effect on memory processes. Future studies should elucidate further the role of specific cytokines in each of these processes.
IV. PRO-INFLAMMATORY CYTOKINES AND MEMORY FUNCTIONING IN HUMANS In humans, the relationships between proinflammatory cytokines and memory functioning were studied using three approaches: (1) examining the correlations between serum levels of these cytokines and cognitive functioning in various conditions that are associated with inflammatory processes (e.g., infectious, autoimmune, or neurodegenerative diseases, as well as aging); (2) directly assessing the effects of cytokine administration on memory; and recently (3) studying the relationships between polymorphisms in inflammatory cytokine genes and the risk and severity of neurodegenerative diseases and dementia.
A. Correlating Pro-inflammatory Cytokine Levels and Memory Functioning Cytokine levels and memory functioning were mainly examined in the context of normal and pathological aging. Ample evidence indicates that in normal aging, and particularly in aging-associated neurodegenerative diseases, the regulatory mechanisms responsible for inflammatory responses are ineffective or damaged, resulting in adverse pathological conditions (Bodles and Barger, 2004; Ferrucci et al., 2004; Krabbe et al., 2004). One of the most consistent findings in gerontological surveys of cytokines is an agedependent increase in IL-6 levels (Ershler et al., 1993; Forsey et al., 2003; Hager et al., 1994; Roubenoff et al., 1998; Wei et al., 1992). Some studies reported that plasma levels of TNF-α are also increased in elderly
16. The Role of Pro-inflammatory Cytokines in Memory Processes and Neural Plasticity
populations (Bruunsgaard et al., 1999; Paolisso et al., 1998), although other studies were not able to detect this effect (e.g., Peterson et al., 1994). Although the associations between inflammatory cytokines and aging are quite consistent, it is still not certain whether the increase in inflammatory markers results directly from the aging process per se, or whether it is mediated by indirect processes, particularly sub-clinical disorders like chronic infections and atherosclerosis. More clear and direct associations have been reported between inflammatory cytokines and aging-associated neurodegenerative diseases, particularly Alzheimer’s disease (AD). This condition is accompanied by elevated serum and cerebrospinal fluid (CSF) levels of TNF-α, IL-6, and IL-1 (Blum-Degen et al., 1995; Cacabelos et al., 1991; Licastro et al., 2000a, b; Tarkowski et al., 1999, but see Pirttila et al., 1994), and lower IL-1ra levels in the CSF (Tarkowski et al., 2001). Furthermore, several lines of evidence suggest that within the brain, inflammatory cytokines, particularly IL-1, are involved in the disease process itself (Griffin and Mrak, 2002; McGeer and McGeer, 2003): (1) IL-1 is involved in acute neurodegeneration, particularly by exacerbating various forms of brain injury (Rothwell, 2003). (2) Senile plaques, one of the hallmarks of AD, are surrounded by activated astrocytes and microglia, wherein levels of both IL-1α and IL-6 are elevated (Akiyama et al., 2000; Bauer et al., 1991; Griffin and Mrak, 2002; McGeer and McGeer, 2003; Mrak and Griffin, 2001). (3) IL-1 stimulates the expression of amyloid precursor protein (APP) (Griffin and Mrak, 2002). (4) IL-1 has been implicated in the hyperphosphorylation of tau (Li et al., 2003), another characteristic feature of AD. (5) IL-1 can elevate the levels of acetylcholine esterase (AChE), contributing to the reduction in cholinergic neurotransmission in AD patients (Li et al., 2000). (6) Recently, attention was allocated to the aggravating effect of systemic infections on the symptoms of AD, suggesting that infectioninduced production of peripheral pro-inflammatory cytokines, such as IL-1, is detrimental for AD progression (Perry et al., 2003). (7) Finally, anti-cholinesterases, which offer the only beneficial treatment for AD, were recently reported to reduce the levels of IL-1 within the hippocampus (Pollak et al., 2005). Ample evidence indicates that increases in proinflammatory cytokines, particularly IL-6, are associated with cognitive impairment in elderly people. Several longitudinal population-based studies showed that elderly subjects who had high levels of blood IL-6 (usually defined as being in the highest third for plasma IL-6) were also more likely to exhibit cognitive decline over 2.5–7-year follow-ups (Weaver et al., 2002; Yaffe et al., 2003). Interestingly, IL-6 levels as a risk factor for cognitive decline were particularly evident
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in subjects with apparent cognitive impairment at baseline (Dik et al., 2005). Consistently, in demented subjects with AD, higher levels of IL-6 were correlated with the severity of the dementia (Kalman et al., 1997). Serum levels of IL-1β may also be associated with cognitive decline, as AD subjects who had detectable serum levels of IL-1β at baseline had an increased rate of cognitive decline over a 2-month follow-up, compared with those with no detectable levels of IL-1β (Holmes et al., 2003). Together, these findings suggest that elevated pro-inflammatory cytokine levels, either in normal elderly people or in AD patients, play an important role in promoting cognitive decline. It should be noted that in all the studies mentioned above, cognitive functioning was measured by global neuropsychological rating scales (either the Mini Mental State Examination or a composite global score from various attention, memory, language, and executive function tests), and therefore these reports do not allow us to draw conclusions regarding specific impairments in memory. Contrary to IL-1 and IL-6, the increase in TNF-α seems to play a protective role in AD (Tarkowski et al., 2003b): AD is accompanied by elevated CSF levels of TNF-α (Tarkowski et al., 1999, 2000), and increased CSF TNF-α levels were detected in patients with mild cognitive impairment only if they developed AD 9 months later (Tarkowski et al., 2003a). However, CSF TNF-α levels were negatively correlated with protein levels of Tau, as well as with Fas/APO-1, a protein involved in apoptosis, and positively correlated with bcl-2, which inhibits apoptosis (Tarkowski et al., 1999). These correlations suggest a protective role for TNF-α in AD, although no causal relationship has been demonstrated yet. High levels of pro-inflammatory cytokines are also found in Down syndrome (DS) patients. Griffin et al. (1989) found a larger number of IL-1 immunoreactive cells in the brains of fetuses, neonates, and 3.5-monthold babies with DS compared to age-matched controls. Higher levels of IL-6 were found in the plasma of DS children compared to controls (Corsi et al., 2003; Licastro et al., 2001), and two groups also reported a positive correlation between IL-6 levels in the serum and the degree of mental retardation and dementia in DS patients (Carta et al., 2002; Kalman et al., 1997). Moreover, higher IL-6 levels in DS were already found before the appearance of dementia, suggesting that it may be an early sign of brain alterations leading many years later to cognitive deterioration and dementia (Licastro et al., 2005). Together, these findings suggest that elevated levels of the pro-inflammatory cytokines IL-6 and IL-1 may play an important role in promoting cognitive decline in DS patients.
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Further evidence for the involvement of IL-1 in mental retardation is offered by studies reporting that in humans, deletions in different parts of the encoding region of the IL-1 receptor accessory protein-like gene (IL-1RAPL), which result in premature translation termination, are responsible for a non-specific form of Xlinked mental retardation (Carrie et al., 1999; Jin et al., 2000). Although the function of the IL-1RAPL protein is presently unknown, the homologous mouse IL1RAPL gene is highly expressed in brain areas subserving memory processes, such as the hippocampus and entorhinal cortex (Carrie et al., 1999), further supporting a role for this gene in memory processes. Only a few studies examined the specific relationship between inflammatory markers and memory. In normal elderly subjects, IL-6 was not found to be associated with either immediate or delayed recall (Dik et al., 2005) in the hippocampal-dependent Auditory Verbal Learning Test. However, in another study, higher IL-6 levels were associated with poorer sensory memory, assessed by the intentional memory test (Elwan et al., 2003). It should be noted that in that study, IL-6 levels were not significantly associated with another measure of memory (incidental shortterm memory) and not related to several other cognitive measurements (Elwan et al., 2003), so this single finding should be interpreted cautiously. The importance of co-morbidity for the association between inflammation and memory was demonstrated in another study, in which a significant association was found between TNF-α/IL-10 ratio and memory functioning (including immediate and delayed verbal recall) in subjects above 85 years of age who also had cardiovascular disease. Interestingly, memory functioning did not depend on this inflammatory parameter when cardiovascular disease was absent (van Exel et al., 2003). Inflammatory cytokines are obviously elevated in many medical conditions other than neurodegenerative diseases, including acute and chronic infectious diseases, autoimmune diseases such as lupus and multiple sclerosis, as well as following stroke, surgery, or trauma. Although these conditions are also characterized by transient memory decline and in some conditions even by the development of dementia, the role of specific cytokines in illness-associated memory disturbances has not been elucidated. Interestingly, in one of the only studies in which the relationship between IL-6 levels and autoimmunity-induced memory impairments were investigated, patients with systemic lupus erythematosus, but not with rheumatoid arthritis, exhibited a significant impairment in learning of verbal and non-verbal information, and higher levels of IL-6 in the plasma were associated with higher learning
scores (reflecting better short-term memory functioning). This relationship was substantial, accounting uniquely (i.e., after adjustment for depression score and somatic symptoms) for 17% of the variance in learning scores (Kozora et al., 2001). We have recently found additional support for a possible protective effect of IL-6 in illness-associated memory disturbance (Shapira Lichter et al., 2004). In our study, 33 generally healthy volunteers, who went through moderate surgery, and 18 gender-, age- and education-matched controls completed a neuropsychological test battery at baseline and 24 hours post-surgery. Our preliminary results demonstrate that surgery stress produced impairments in verbal and visual declarative memory, but not in other cognitive parameters. Furthermore, the memory impairments were inversely correlated with the elevation in IL-6 following the surgery (accounting for 35% of the variance in memory decline). This finding suggests that post-surgery increases in IL-6 levels are associated with protection from surgeryinduced memory disturbances (Shapira Lichter et al., 2004). Together, these findings underscore the complexity of the associations between pro-inflammatory cytokines and memory, which is described in the sections on experimental animals, demonstrating that under some situations elevated levels of IL-6 may be associated with protective rather than detrimental effects on memory functioning. In another set of studies, we adapted a different approach for examining the relationship between cytokines and memory, using a double-blind, crossover study, in which healthy male volunteers completed psychological questionnaires and neuropsychological tests following endotoxin (LPS) administration. In one experiment, 20 volunteers were tested 1, 3, and 9 hours after intravenous injection of Salmonella abortus equi endotoxin (0.8 ng/kg) or saline in two experimental sessions (Reichenberg et al., 2001). Blood samples were collected hourly, and rectal temperature and heart rate were monitored continuously. Although endotoxin had no effects on physical sickness symptoms, blood pressure, or heart rate, it induced mild fever and markedly increased the circulating levels of IL-6, TNF-α, soluble TNF receptors, IL-1ra, and cortisol. Endotoxin administration produced a global decrease in memory functions, during all testing periods, reflected by decreased immediate recall of story items, reduced delayed story recall, a deficit in immediate and delayed recall of figure items, and decreased performance in Word List Learning. Furthermore, endotoxin-induced impairments in immediate and delayed story recall were significantly and positively correlated with the secretion of IL-6, TNF-α, and IL-1ra in the first and second testing periods, but not in the last period. Interestingly, using the same
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procedure we demonstrated that in contrast with the cytokine-associated deleterious effects of endotoxin on declarative memory, endotoxin administration induced a significant improvement in working memory performance, reflected by an increased score in the Digit Span Backward Test during all testing periods. This improvement was not associated with cytokine secretion (but it did associate with alterations in cholinergic neurotransmission) (Cohen et al., 2003). In another recent study (Krabbe et al., 2005), we also used a double-blind crossover design, in which 12 healthy young males completed neuropsychological tests before as well as 1.5, 6, and 24 hours after an intravenous injection of a very low dose of endotoxin (0.2 ng/kg) or saline in two experimental sessions. Endotoxin administration had no effect on body temperature, cortisol levels, blood pressure, or heart rate, but circulating levels of TNF-α, IL-6, TNFreceptors, and IL-1ra were markedly elevated. In this model, low-dose endotoxemia did not affect cognitive performance significantly, but declarative memory performance was inversely correlated with endotoxininduced increases in circulating IL-6 levels (Krabbe et al., 2005).
B. Assessment of the Direct Effects of Cytokine Administration on Memory Although in our studies on endotoxin-induced memory disturbances (Krabbe et al., 2005; Reichenberg et al., 2001), as well as in most of the literature reviewed above, higher levels of IL-6 were associated with poor memory functioning or memory decline over time; it should be noted that such a correlation does not prove causal relationship. A better approach for proving causality is to directly examine the effects of proinflammatory cytokine administration on memory. The effects of IL-6 on memory functioning were investigated only in one study, in which IL-6 (3 mg/kg) was administered to 19 chronic fatigue syndrome (CFS) patients and 10 control subjects, and memory (assessed by the Sternberg Memory Scanning Test, measuring speed of searching through short-term memory), as well as other neuropsychological functions, were assessed 6.5 hours later (Arnold et al., 2002). Surprisingly, IL-6 did not produce any memory disturbance. In fact, both CFS patients and controls demonstrated improved performance in this test (Arnold et al., 2002). Although the investigators ascribed this improvement to practice effect, it is possible that the improved cognitive functioning was induced by IL-6 (in the absence of a saline-administered control group, it is impossible to distinguish between these two possibilities). This study again demonstrates that IL-6 is not always associated with memory disturbance and that the conse-
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quences of elevated IL-6 levels are determined by many factors, including age and medical condition of the individual, the particular memory function that is assessed, as well as the magnitude and duration of IL-6 elevation.
C. The Influence of Polymorphisms in Inflammatory Cytokine Genes on Neurodegenerative Diseases, Dementia, and Memory In the last 15 years, extensive research efforts were invested in an attempt to link various gene polymorphisms to cognitive functioning in healthy people, as well as to the risk to develop neurodegenerative diseases, which are accompanied by cognitive deterioration. The evidence for the relationships between pro-inflammatory cytokine levels and dementia in AD and other medical conditions, which was reviewed above, suggests that polymorphisms in the genes encoding these cytokines may also play a role. Although the contribution of these gene polymorphisms to memory functioning has not been tested directly yet, recent genetic studies demonstrated a role for polymorphisms in the genes for IL-1, IL-6, and TNF-α in the risk to develop AD, as well as in the age of onset and the course of this disease. These studies are reviewed in the following section. 1. IL-1 Intensive research efforts were dedicated to the possible contribution of different polymorphisms in IL-1 family genes to AD. These studies were performed on thousands of patients from different ages, genders, and ethnic origins. Although the results of these studies are sometimes contradictory, the general conclusion is that several polymorphisms in IL-1 family genes play a role in the risk of developing AD, as well as in the severity of the disease. Most of the research focused on the relationship between IL-1α polymorphisms and AD. One polymorphism that was found to be associated with AD is a C (allele 1) to T (allele 2) transition at position −889 relative to the transcription start point, in the regulatory region of the IL-1α gene. Several studies reported that IL-1A −889 allele 2 (IL-1A −889 T) frequency is higher in AD patients compared to controls (Bosco et al., 2004; Du et al., 2000; Nicoll et al., 2000; Seripa et al., 2005). IL-1A −889 allele 2 serves as a risk factor in a dosedependent manner, as the risk of developing AD with two copies of the IL-1A allele 2 is higher than the risk with only one copy (Combarros et al., 2002; Du et al., 2000; Grimaldi et al., 2000).
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Some studies report that the IL-1A −889 T/T genotype frequency was significantly higher in early onset AD compared to late onset AD and to age-matched controls (Sciacca et al., 2003), and that the presence of the IL-1A −889 T allele was associated with increased risk of early onset AD (Du et al., 2000; Grimaldi et al., 2000; Rebeck, 2000), and with an earlier age of onset in general (Kolsch et al., 2001; Rebeck, 2000). However, a different study reported that the IL-1A −889 T/T genotype was associated with late onset AD but not with early onset AD (Hedley et al., 2002). Many other studies found no association between the presence of IL-1A −889 T allele and AD in different populations (Fidani et al., 2002; Green et al., 2002; Ki et al., 2001; Kolsch et al., 2001; Kuo et al., 2003; Li et al., 2004b; Minster et al., 2000; Pirskanen et al., 2002; Seripa et al., 2005; Tsai et al., 2003). However, two meta-analyses that were performed on this data set confirmed that the IL-1A −889 allele 2 is a risk factor for AD in an age-related pattern: One meta-analysis found that the IL-1A −889 T/T genotype is a risk factor for developing AD in general, and that the frequency of this genotype was increased only in patients with early-onset AD (Rainero et al., 2004). The second metaanalysis found that the IL-1A −889 T/T genotype contributes only to the risk of early-onset but not late-onset AD (Combarros et al., 2003). To conclude, polymorphisms in the regulatory region of the IL-1α gene are involved in the risk of developing AD. The effect of the IL-1A −889 T/T genotype may stem from overproduction of IL-1α in its carriers. Indeed, the IL-1A −889 T/T genotype significantly increased the transcriptional activity of the IL-1α . gene with respect to the IL-1A −889 C/C genotype, and this increase was accompanied by an increase of the IL-1α mRNA and protein levels in the plasma (Dominici et al., 2002a). Polymorphisms at different locations in the IL-1β gene were also found to be associated with AD. One polymorphism is a C to T transition at position −511 in the promoter region of the IL-1β gene. The IL-1B −511 T/T genotype was more frequently found in late onset AD than in healthy patients (Wang et al., 2005). The presence of this genotype was associated with increased risk for AD in general (Bosco et al., 2004), and specifically a risk for late-onset AD and delayed age of onset (Grimaldi et al., 2000). However, the concomitant presence of the IL-1B −511 T/T and alpha1antichymotrypsin T/T genotypes was associated with increased risk of AD and decreased age at disease onset (Licastro et al., 2000b). It should be noted that other studies found no association between the IL-1B −511 T allele and AD (Ehl et al., 2003; Green et al., 2002; Hedley et al., 2002; Li et al., 2004b; Licastro et al., 2004;
Ma et al., 2003; McCulley et al., 2004; Minster et al., 2000; Nishimura et al., 2004). However, in some of these studies, even though IL-1β −511 polymorphism did not influence the risk of AD, it was found to have a pathophysiological influence on the disease process. For example, Ehl et al. (2003) found that Aβ42 levels in the CSF were higher in carriers of the IL-1B −511 T allele, and Green et al. (2002) also reported an impact of IL-1B −511 on Aβ(40) load. The effect of the IL-1B −511 T polymorphism may be mediated by increased IL-1β levels in AD patients, which can contribute to the progression of the disease. Indeed, AD patients with the IL-1B −511 T/T genotype showed higher levels of plasma IL-1β compared to controls (Licastro et al., 2000b). The other polymorphism in the IL-1β gene is a C to T transition, located at position +3953 on exon 5. Hedley et al. (2002) found an increased prevalence of the IL-1B +3954 T/T genotype in late-onset AD patients compared to controls. Furthermore, patients carrying the IL-1B +3953 T allele had a decreased age of onset (Sciacca et al., 2003) and shorter survival (Licastro et al., 2004). These influences may be mediated by increased IL-1β secretion in homozygous carriers of the IL-1B +3953 T allele (Pociot et al., 1992, but see Dominici et al., 2002b). It should be noted, however, that three other studies found no association of the IL-1B +3953 polymorphism with AD (Ma et al., 2003; Rosenmann et al., 2004; Wang et al., 2005). To conclude, the findings presented in the last paragraphs suggest that IL-1β gene polymorphisms in two different loci may influence the age at onset, progression, and survival in AD. The polymorphisms in the IL-1α and IL-1β genes were also found to synergistically influence the risk for AD and the age of onset of the disease. As mentioned above, several studies reported that either IL-1A −889 T or IL-1B +3953 T frequencies were higher in AD patients compared to controls (e.g., Du et al., 2000; Hedley et al., 2002; Nicoll et al., 2000). Moreover, homozygosity for both IL-1A −889 T/T and IL-1B +3953 T/T genotypes conferred the greatest risk to develop AD (Hedley et al., 2002; Nicoll et al., 2000). Furthermore, whereas either IL-1A −889 T/T or IL-1B +3953 T/T genotypes are associated with an earlier onset of the disease (Kolsch et al., 2001; Rebeck, 2000; Sciacca et al., 2003), AD patients carrying both IL-1B +3953 T+ and IL-1A −889 T/T genotypes had the lowest age of onset (Sciacca et al., 2003). These data suggest a cumulative effect of the IL-1α and IL-1β gene polymorphisms in the risk to develop AD and the age of disease onset. The studies that examined the involvement of polymorphisms in the variable number of tandem repeat
16. The Role of Pro-inflammatory Cytokines in Memory Processes and Neural Plasticity
(VNTR) at intron 2 of the IL-1ra gene in AD yielded contradictory results. Two studies reported a protective role of IL1-RA allele 2 (2 repeats, instead of 4 in allele 1) on the onset and severity of AD: Grimaldi et al. (2000) reported a later age of onset in homozygous carriers of IL1-RA allele 2, and the presence of this allele was also protective for the severity of dementia, independent of age (Bosco et al., 2004). However, other studies found no association between IL-1-RA intron 2 VNTR and AD (Hedley et al., 2002; Li et al., 2004b; Minster et al., 2000; Wang et al., 2005). More research is needed in order to further clarify the involvement of polymorphisms in the VNTR at IL1RA intron 2 in AD. To conclude, different polymorphisms in the IL-1 gene family seem to be involved in the risk to develop AD, as well as in the progression of the disease. The strongest evidence is for the age-related contribution of the IL-1A −889 T allele to the risk of AD. Transitions in two different loci at the IL-1β gene (+3953 C → T and −511 C → T) also seem to be associated with the risk to develop AD. These polymorphisms in the IL-1α and IL-1β genes also appear to be involved in the age of onset and the progression of the disease. 2. IL-6 The research performed so far on the possible involvement of different IL-6 gene polymorphisms in AD focused on either a G to C transition in position −174 at the promoter region, or the four VNTR alleles (A–D) at the 3′ flanking area, of the IL-6 gene. These studies yielded somewhat ambiguous results, as will be described below. Two studies reported that the frequency of the IL-6 −174 C allele is increased in AD patients, and that carriers of this allele had a greater risk to develop AD (Arosio et al., 2004; Licastro et al., 2003). When the IL-6 −174 C allele appeared concomitantly with the IL-10 −1082 A allele, the risk of AD was even higher (Arosio et al., 2004). Carriers of the IL-6 −174 CC genotype have increased plasma and CSF levels of sIL-6R (Bagli et al., 2003), which can activate IL-6 signaling (Kishimoto et al., 1992). Furthermore, plasma IL-6 levels were higher in AD compared to controls, and the IL-6 −174 CC genotype was accompanied by the highest levels of IL-6 in the plasma and the brain (Licastro et al., 2003). However, other studies reported a lower frequency of the IL-6 −174 C allele in AD patients, and reduced risk of AD in carriers of this allele, suggesting a protective role, specifically for the IL-6 −174 CC genotype (Faltraco et al., 2003; Pola et al., 2002). Accordingly, the IL-6 −174 G allele was higher in AD patients, and the increase in IL-6 plasma levels
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in AD was higher in carriers of this allele (Pola et al., 2002; Shibata et al., 2002). This finding is in line with a report of lower IL-6 levels in healthy humans with the IL-6 −174 CC genotype (Fishman et al., 1998). It should be noted that additional studies found no differences in IL-6 −174 polymorphism distribution in AD patients (Bhojak et al., 2000; Capurso et al., 2004), and no effect on the age of disease onset (Bagli et al., 2000; Depboylu et al., 2004; Zhang et al., 2004). More consistent results were found in studies that examined the role of IL-6 VNTRs in AD. IL-6 VNTR C allele was found to be under-represented in AD patients, and its presence was associated with reduced risk and delayed age of onset of the disease (Licastro et al., 2003; Papassotiropoulos et al., 1999). Moreover, non-carriers of the IL-6 VNTR C allele demonstrated increased plasma levels of sIL-6R (Bagli et al., 2003), which activates IL-6 signaling (Kishimoto et al., 1992). In contrast, the IL-6 VNTR DD genotype is more frequent in AD patients (Licastro et al., 2003; and trend in Shibata et al., 2002). Furthermore, whereas plasma IL-6 levels are higher in all AD patients compared to controls, carriers of the IL-6 VNTR DD genotype had the highest levels (Licastro et al., 2003). It should be noted, however, that other studies found no involvement of IL-6 VNTRs in AD (Bagli et al., 2000). To conclude, although the nature of the role of IL-6 gene polymorphisms in AD is not clear yet, the findings gathered to date suggest that IL-6 gene VNTR polymorphisms play a role in the risk of developing AD, and that IL-6 −174 polymorphisms may also be involved in AD, possibly via interactions with other genes. 3. TNF-a Several polymorphisms in the TNF-α gene were found to be associated with AD, particularly G to A transitions at positions −308 and −238 and a C to T transition at position −850, all in the promoter region of the TNF-α gene, as well as different TNF-α microsatellite alleles. Some studies examined the effects of these specific polymorphisms on AD, whereas others examined the effect of the 2-1-2 TNF haplotype (TNFA −308 A, −238 G, and TNF-a2 microsatellite) on this disease. Polymorphisms in other locations, either in the TNF-α (position −1031) or in the TNF receptor type II genes, were not associated with AD (Nishimura et al., 2004; Shibata et al., 2004). Several studies reported no association between the frequency of different −308, −238, and TNF-α microsatellite alleles (Culpan et al., 2003; Laws et al., 2005; Perry et al., 2001). Two studies examined the involvement of the TNFA −308 A allele in AD age of onset and
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found contradictory results: Perry et al. (2001) reported increased age of onset in carriers of either the TNFA −308 A allele, which is associated with increased TNFα transcription (Wilson et al., 1997), or the TNFa2 microsatellite allele, whereas Alvarez et al. (2002) found an earlier age of onset in carriers of the TNFA −308 A allele. The research on the involvement of the 2-1-2 haplotype in AD also yielded conflicting results: Collins et al. (2000) reported that the presence of both the TNFa2 microsatellite allele and the TNF 2-1-2 haplotype was associated with increased risk of AD. However, Culpan et al. (2003) found that the absence of the 2-1-2 haplotype increased the risk of AD, suggesting that this haplotype plays a protective role, and this conclusion was substantiated by Perry et al. (2001), who reported that this haplotype is also associated with increased age of onset. Whereas one study reported that the TNFA −850 T allele was over-represented in AD patients and that carriers of this allele had an increased risk for AD (Laws et al., 2005), other studies found no association between the TNFA −850 T allele and either early- or late-onset AD (Infante et al., 2002; McCusker et al., 2001; Terreni et al., 2003). However, the TNFA −850 T allele seems to act in synergy with other genes to increase the risk of AD. In particular, the presence of this allele in conjunction with the APOE ε4 allele resulted in doubling the risk for AD (Laws et al., 2005; McCusker et al., 2001, but see Infante et al., 2002). Similarly, whereas individually the involvement of the TNFA −850 T and −308 G alleles in AD is questionable, −850 T/−308 G haplotype frequency is increased in AD patients, and carriers have a greater risk of developing this disease (Laws et al., 2005). To conclude, different TNF-α gene polymorphisms seem to be involved in the risk to develop AD. However, the exact nature of this involvement is not clear, and the data gathered so far suggest that the effects of these polymorphisms are achieved via interactions with polymorphisms in other genes. Further research may be able to resolve these ambiguous results. 4. Interim Summary The recent genetic studies that examined the involvement of the pro-inflammatory cytokines IL-1, IL-6, and TNF-α in AD suggest a role for these cytokines in the risk to develop AD, as well as in the age of onset and the course of this disease. To date, only a single research directly examined the connection between a specific polymorphism (in IL-1RA VNTR) and the degree of cognitive decline, and found an association between the genotype and the extent of demen-
tia (Bosco et al., 2004). Future studies should further elucidate the role of gene polymorphisms of proinflammatory cytokines in AD dementia. Furthermore, because specific polymorphisms result in changes in peripheral and central cytokine transcription levels, they may also be associated with memory performance in healthy people. Indeed, in a recent pilot study (Shapira Lichter et al., 2004), we found a role for IL-1B −511 polymorphism in stressinduced memory impairment in healthy patients going through a moderate surgical procedure: The IL-1B −511 C allele, which is associated with lower plasma IL-1β levels in AD patients (Licastro et al., 2000b), was found to be protective against the memory impairment that accompanied surgery stress (Shapira Lichter et al., 2004). This finding is in line with the reports of an association between the other allele, IL-1B −511 T, and AD (Bosco et al., 2004; Grimaldi et al., 2000; Wang et al., 2005), as described above. Due to the exceptional complexity of both memory processes and the interactions between different genes, it is unlikely that a single gene accounts for differences in normal memory functioning. However, in recent years, following the human genome sequencing many studies have found associations between gene polymorphisms and several cognitive processes, including memory (reviewed in Goldberg and Weinberger, 2004). For example, a BDNF polymorphism was repeatedly found to be associated with medial-temporalcortex–based declarative memory processes (Goldberg and Weinberger, 2004). Presently, the involvement of polymorphisms in pro-inflammatory cytokine genes in variations of normal memory functioning was not examined. Future studies may reveal if polymorphisms in pro-inflammatory cytokine genes may affect learning and memory processes, alone or in synergy with other gene polymorphisms, as found for the risk and severity of AD.
V. GENERAL SUMMARY AND CONCLUSIONS The present review shows clearly that proinflammatory cytokines are critically involved in several aspects of learning and memory. However, cytokine-induced modulation of memory processes is a complex phenomenon, including both detrimental and beneficial effects, depending on the specific pro-inflammatory cytokine, its levels (particularly within the brain), and the particular condition that elicits the cytokine secretion. Overall, several general conclusions can be drawn from the data:
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A. In general, elevations in IL-1, IL-6, and TNF-α levels, produced either by exogenous administration in experimental animals or by endogenous secretion during various diseases or exposure to stressful stimuli in both humans and experimental animals, result in impaired learning and memory. B. These impairments are fairly specific to memory tasks that involve the hippocampus, such as declarative memory in humans and spatial or contextual memory in animals. C. The effects of IL-6 and IL-1 seem to be particularly potentiated as humans and animals become older. This age-dependent effect is demonstrated by the high negative correlations between memory functioning and the levels of IL-6 and IL-1 in elderly people, as well as by the progressive memory deterioration in mice that overexpress IL-6, and the gradual memory improvement in mice lacking IL-6. D. Whereas high levels of IL-1 are consistently associated with memory disturbances, the findings on IL-6- or TNF-α–induced memory disturbances are less robust, and in many studies acute elevations in these cytokines, either in experimental animals or in humans, are associated with either no effect or even with protective effects. E. Pro-inflammatory cytokines seem to be involved in dementia, particularly of the Alzheimer type, in which memory loss is usually the first and most disturbing symptom. This involvement is reflected by altered serum levels of pro-inflammatory cytokines in AD patients; associations between polymorphisms of these cytokines and the incidence, age of onset, and severity of dementia; and evidence from studies in animal models for an involvement of cytokines in the mechanisms of AD. This evidence is particularly strong for IL-1 and IL-6, whereas TNF-α may actually play a protective role in AD. F. Pro-inflammatory cytokines, particularly IL-1, have a physiological role in memory processes. In particular, IL-1 within the hippocampus seems to be important for memory consolidation, reflected by the findings that administration of low doses of IL-1 specifically improves hippocampal-dependent memory functioning, whereas genetic or pharmacological impairments in IL-1 signaling produce memory disturbances. IL-6 may also be important physiologically, as a negative modulator of the consolidation process. G. Pro-inflammatory cytokines have marked effects on various neural and neuroendocrine processes
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that underlie learning and memory processes, including induction and maintenance of hippocampal LTP, alterations in intracellular signal transduction mechanisms, secretion of glucocorticoids and prostaglandins, production of neurotrophins, and neurogenesis. H. The influence of IL-1 on memory functioning and on the mechanisms that subserve it follows an inverted U-shape pattern; i.e., physiological levels of IL-1 are needed for optimal memory functioning, neural plasticity, and glucocorticoid secretion, whereas deviations from the physiological range, either by excess elevation in IL-1 levels or by blockade of IL-1 signaling, result in impaired memory and the associated physiological processes.
References Aggleton, J. P., Hunt, P. R., and Rawlins, J. N. (1986). The effects of hippocampal lesions upon spatial and non-spatial tests of working memory. Behav. Brain Res., 19 (2), 133–146. Akaneya, Y., Takahashi, M., and Hatanaka, H. (1995). Interleukin-1β enhances survival and interleukin-6 protects against MPP+ neurotoxicity in cultures of fetal rat dopaminergic neurons. Exp. Neurol., 136, 44–52. Akiyama, H., Arai, T., Kondo, H., Tanno, E., Haga, C., and Ikeda, K. (2000). Cell mediators of inflammation in the Alzheimer disease brain. Alzheimer Dis. Assoc. Disord., 14, S47–S53. Albensi, B. C., and Mattson, M. P. (2000). Evidence for the involvement of TNF and NF-kappaB in hippocampal synaptic plasticity. Synapse, 35 (2), 151–159. Aloe, L., Fiore, M., Probert L., Turrini P., and Tirassa P. (1999a). Overexpression of tumor necrosis factor alpha in the brain of transgenic mice differentially alters nerve growth factor levels and choline acetyltransferase activity. Cytokine, 11 (1), 45–54. Aloe, L., Properzi, F., Probert, L., Akassoglou, K., Kassiotis, G., Micera, A., and Fiore, M. (1999b). Learning abilities, NGF and BDNF brain levels in two lines of TNF-alpha transgenic mice, one characterized by neurological disorders, the other phenotypically normal. Brain Res., 840 (1–2), 125–137. Alvarez, V., Mata, I. F., Gonzalez, P., Lahoz, C. H., Martinez, C., Pena, J., Guisasola, L. M., and Coto, E. (2002). Association between the TNFalpha −308 A/G polymorphism and the onsetage of Alzheimer disease. Am. J. Med. Genet., 114 (5), 574–577. Ambrogi Lorenzini, C. G., Baldi, E., Bucherelli, C., Sacchetti, B., and Tassoni, G. (1996). Role of dorsal hippocampus in acquisition, consolidation and retrieval of rat’s passive avoidance response: a tetrodotoxin functional inactivation study. Brain Res., 730, 32–39. Ambrogi Lorenzini, C. G., Baldi, E., Bucherelli, C., Sacchetti, B., and Tassoni, G. (1997). Role of ventral hippocampus in acquisition, consolidation and retrieval of rat’s passive avoidance response memory trace. Brain Res., 768, 242–248. Andreasson, K. I., Savonenko, A., Vidensky, S., Goellner J. J., Zhang, Y., Shaffer, A., Kaufmann, W. E., Worley, P. F., Isakson, P., and Markowska, A. L. (2001). Age-dependent cognitive deficits and neuronal apoptosis in cyclooxygenase-2 transgenic mice. J. Neurosci., 21 (20), 8198–8209. Antoni, F. A. (1986). Hypothalamic control of adrenocorticotropin secretion: advances since the discovery of 41-residue corticotropin-releasing factor. Endocr. Rev., 7 (4), 351–378.
368
II. Immune System Effects on Neural and Endocrine Processes and Behavior
Armario, A., Hernandez, J., Bluethmann, H., and Hidalgo, J. (1998). IL-6 deficiency leads to increased emotionality in mice: evidence in transgenic mice carrying a null mutation for IL-6. J. Neuroimmunol., 92 (1–2), 160–169. Arnold, M. C., Papanicolaou, D. A., O’Grady, J. A., Lotsikas, A., Dale, J. K., Straus, S.E., and Grafman, J. (2002). Using an interleukin-6 challenge to evaluate neuropsychological performance in chronic fatigue syndrome. Psychol. Med., 32 (6), 1075–1089. Arosio, B., Trabattoni, D., Galimberti, L., Bucciarelli, P., Fasano, F., Calabresi, C., Cazzullo, C. L., Vergani, C., Annoni, G., and Clerici, M. (2004). Interleukin-10 and interleukin-6 gene polymorphisms as risk factors for Alzheimer’s disease. Neurobiol. Aging, 25 (8), 1009–1015. Aubert, A., Vega, C., Dantzer, R., and Goodall, G. (1995). Pyrogens specifically disrupt the acquisition of a task involving cognitive processing in the rat. Brain Behav. Immun., 9, 129–148. Avital, A., Goshen, I., Kamsler, A., Segal, M., Iverfeldt, K., RichterLevin, G., and Yirmiya, R. (2003). Impaired interleukin-1 (IL-1) signaling is associated with deficits in hippocampal memory processes and neural plasticity. Hippocampus, 13, 826–834. Avitsur, R., and Yirmiya, R. (1999). The immunobiology of sexual behavior: gender differences in the suppression of sexual activity during illness. Pharmacol. Biochem. Behav., 64 (4), 787–796. Bagli, M., Papassotiropoulos, A., Hampel, H., Becker, K., Jessen, F., Burger, K., Ptok, U., Rao, M. L., Moller, H. J., Maier, W., and Heun, R. (2003). Polymorphisms of the gene encoding the inflammatory cytokine interleukin-6 determine the magnitude of the increase in soluble interleukin-6 receptor levels in Alzheimer’s disease. Results of a pilot study. Eur. Arch. Psychiatry Clin. Neurosci., 253 (1), 44–48. Bagli, M., Papassotiropoulos, A., Knapp, M., Jessen, F., Luise Rao, M., Maier, W., and Heun, R. (2000). Association between an interleukin-6 promoter and 3′ flanking region haplotype and reduced Alzheimer’s disease risk in a German population. Neurosci. Lett., 283 (2), 109–112. Balschun, D., Randolf, A., Pitossi, F., Schneider, H., del Rey, A., and Besedovsky, H. O. (2003). Hippocampal interleukin-1 beta gene expression during long-term potentiation decays with age. Ann. N. Y. Acad. Sci., 992, 1–8. Balschun, D., Wetzel, W., del Rey, A., Pitossi, F., Schneider, H., Zuschratter, W., and Besedovsky, H. O. (2004). Interleukin-6: a cytokine to forget. FASEB J., 18 (14), 1788–1790. Banks, W. A. (2005). Blood-brain barrier transport of cytokines: a mechanism for neuropathology. Curr. Pharm. Des., 11 (8), 973–984. Banks, W. A., Farr, S. A., La Scola, M. E., and Morley, J. E. (2001). Intravenous human interleukin-1alpha impairs memory processing in mice: dependence on blood-brain barrier transport into posterior division of the septum. J. Pharmacol. Exp. Ther., 299 (2), 536–541. Banks, W. A., Farr, S. A., and Morley, J. E. (2002–2003). Entry of blood-borne cytokines into the central nervous system: effects on cognitive processes. Neuroimmunomodulation, 10 (6), 319–327. Barrientos, R. M., Higgins, E. A., Sprunger, D. B., Watkins, L. R., Rudy, J. W., and Maier, S. F. (2002). Memory for context is impaired by a post context exposure injection of interleukin-1 beta into dorsal hippocampus. Behav. Brain Res., 134 (1–2), 291–298. Barrientos, R. M., Sprunger, D. B., Campeau, S., Higgins, E. A., Watkins, L. R., Rudy, J. W., and Maier, S. F. (2003). Brain-derived neurotrophic factor mRNA downregulation produced by social isolation is blocked by intrahippocampal interleukin-1 receptor antagonist. Neuroscience, 121 (4), 847–853. Barrientos, R. M., Sprunger, D. B., Campeau, S., Watkins, L. R., Rudy, J. W., and Maier, S. F. (2004). BDNF mRNA expression in
rat hippocampus following contextual learning is blocked by intrahippocampal IL-1beta administration. J. Neuroimmunol., 155 (1–2), 119–126. Bauer, J., Strauss, S., Schreiter-Gasser, U., Ganter, U., Schlegel, P., Witt, I., Yolk, B., and Berger, M. (1991). Interleukin-6 and alpha2–macroglobulin indicate an acute-phase state in Alzheimer’s disease cortices. FEBS Lett., 285 (1), 111–114. Beattie, E. C., Stellwagen, D., Morishita, W., Bresnahan, J. C., Ha, B. K., Von Zastrow, M., Beattie, M. S., and Malenka, R. C. (2002). Control of synaptic strength by glial TNFalpha. Science, 295 (5563), 2282–2285. Bellinger, F. P., Madamba, S. G., Campbell, I. L., and Siggins, G. R. (1995). Reduced long-term potentiation in the dentate gyrus of transgenic mice with cerebral overexpression of interleukin-6. Neurosci. Lett., 198 (2), 95–98. Bellinger, F. P., Madamba, S., and Siggins, G. R. (1993). Interleukin1β inhibits synaptic strength and long-term potentiation in the rat CA1 hippocampus. Brain Res., 628, 227–234. Berkenbosch, F., van Oers, J., del Rey, A., Tilders, F., and Besedovsky, H. (1987). Corticotropin-releasing factor-producing neurons in the rat activated by interleukin-1. Science, 238 (4826), 524–526. Bernton, E. W., Beach, J. E., Holaday, J. W., Smallridge, R. C., and Fein, H. G. (1987). Release of multiple hormones by a direct action of interleukin-1 on pituitary cells. Science, 238 (4826), 519–521. Besedovsky, H. O., and del Rey, A. (1996). Immune-neuroendocrine interactions: facts and hypotheses. Endocr. Rev., 17 (1), 64–102. Bhojak, T. J., DeKosky, S. T., Ganguli, M., Kamboh, M. I. (2000). Genetic polymorphisms in the cathespin D and interleukin-6 genes and the risk of Alzheimer’s disease. Neurosci. Lett., 288 (1), 21–24. Bianchi, M., Ferrario, P., Clavenna, A., and Panerai, A. E. (1997). Interleukin-6 affects scopolamine-induced amnesia, but not brain amino acid levels in mice. Neuroreport, 8 (7), 1775–1778. Bianchi, M., Sacerdote, P., and Panerai, A. E. (1998). Cytokines and cognitive function in mice. Biol. Signals Recept., 7 (1), 45–54. Bjugstad, K. B, Flitter, W. D., Garland, W. A., Su, G. C., and Arendash, G. W. (1998). Preventive actions of a synthetic antioxidant in a novel animal model of AIDS dementia. Brain Res., 795 (1–2), 349–357. Bliss, T. V., and Lomo, T. (1973). Long-lasting potentiation of synaptic transmission in the dentate area of the anaesthetized rabbit following stimulation of the perforant path. J. Physiol., 232 (2), 331–356. Bliss, T. V .P., and Collingridge, G. L. (1993). A synaptic model of memory: long-term potentiation in the hippocampus. Nature, 361, 31–39. Blum-Degen, D., Muller, T., Kuhn, W., Gerlach, M., Przuntek, H., and Riederer, P. (1995). Interleukin-1 beta and interleukin-6 are elevated in the cerebrospinal fluid of Alzheimer’s and de novo Parkinson’s disease patients. Neurosci. Lett., 202 (1–2), 17–20. Bodles, A. M., and Barger, S. W. (2004). Cytokines and the aging brain—what we don’t know might help us. Trends Neurosci., 27 (10), 621–626. Bonni, A., Sun, Y., Nadal-Vicens, M., Bhatt, A., Frank, D. A., Rozovsky, I., Stahl, N., Yancopoulos, G. D., and Greenberg, M. E. (1997). Regulation of gliogenesis in the central nervous system by the JAK-STAT signaling pathway. Science, 278 (5337), 477–483. Born, T. L., Smith, D. E., Garka, K. E., Renshaw, B. R., Bertles, J. S., and Sims, J. E. (2000). Identification and characterization of two members of a novel class of the interleukin-1 receptor (IL-1R) family. J. Biol. Chem., 275 (39), 29946–29954.
16. The Role of Pro-inflammatory Cytokines in Memory Processes and Neural Plasticity Bosco, P., Gueant-Rodriguez, R. M., Anello, G., Romano, A., Namour, B., Spada, R. S., Caraci, F., Tringali, G., Ferri, R., and Gueant, J. L. (2004). Association of IL-1 RN*2 allele and methionine synthase, 2756 AA genotype with dementia severity of sporadic Alzheimer’s disease. J. Neurol. Neurosurg. Psychiatry., 75 (7), 1036–1038. Braida, D., Sacerdote, P., Panerai, A. E., Bianchi, M., Aloisi, A. M., Iosue, S., and Sala, M. (2004). Cognitive function in young and adult IL (interleukin)-6 deficient mice. Behav. Brain Res., 153 (2), 423–429. Braithwaite, V. A., Salkeld, D. J., McAdam, H. M., Hockings, C. G., Ludlow, A. M., and Read, A. F. (1998). Spatial and discrimination learning in rodents infected with the nematode Strongyloides ratti. Parasitology, 117 (2), 145–154. Brandeis, R., Brandys, Y., and Yehuda, S. (1989). The use of the Morris Water Maze in the study of memory and learning. Int. J. Neurosci., 48 (1–2), 29–69. Brennan, F. X., Beck, K. D., and Servatius, R. J. (2003). Low doses of interleukin-1beta improve the leverpress avoidance performance of Sprague-Dawley rats. Neurobiol. Learn. Mem., 80 (2), 168–171. Brennan, F. X., Beck, K. D., and Servatius, R. J. (2004). Proinflammatory cytokines differentially affect leverpress avoidance acquisition in rats. Behav. Brain Res., 153 (2), 351–355. Bruunsgaard, H., Andersen-Ranberg, K., Jeune, B., Pedersen, A. N., Skinhoj, P., and Pedersen B. K. (1999). A high plasma concentration of TNF-alpha is associated with dementia in centenarians. J. Gerontol. A Biol. Sci. Med. Sci., 54 (7), M357–M364. Burwell, R. D., Saddoris, M. P., Bucci, D. J., and Wiig, K. A. (2004). Corticohippocampal contributions to spatial and contextual learning. J. Neurosci., 24 (15), 3826–3836. Butler, M. P., Moynagh, P. N., and O’Connor, J. J. (2002). Methods of detection of the transcription factor NF-kappa B in rat hippocampal slices. J. Neurosci. Methods, 119 (2), 185–190. Butler, M. P., O’Connor, J. J., and Moynagh, P. N. (2004). Dissection of tumor-necrosis factor-alpha inhibition of long-term potentiation (LTP) reveals a p38 mitogen-activated protein kinase– dependent mechanism which maps to early- but not late-phase LTP. Neuroscience, 124 (2), 319–326. Cacabelos, R., Barquero, M., Garcia, P., Alvarez X. A., and Varela de Seijas, E. (1991). Cerebrospinal fluid interleukin-1 beta (IL-1 beta) in Alzheimer’s disease and neurological disorders. Methods Find. Exp. Clin. Pharmacol., 13 (7), 455–458. Cahill, L., McGaugh, J. L., and Weinberger, N. M. (2001). The neurobiology of learning and memory: some reminders to remember. Trends Neurosci., 24 (10), 578–581. Canevari, L., Richter-Levin, G., and Bliss, T. V. (1994). LTP in the dentate gyrus is associated with a persistent NMDA receptor– dependent enhancement of synaptosomal glutamate release. Brain Res., 667 (1), 115–117. Capurso, C., Solfrizzi, V., D’Introno, A., Colacicco, A. M., Capurso, S. A., Capurso, A., and Panza, F. (2004). Interleukin 6–174 G/C promoter gene polymorphism and sporadic Alzheimer’s disease: geographic allele and genotype variations in Europe. Exp. Gerontol., 39 (10), 1567–1573. Carrie, A., Jun, L., Bienvenu, T., Vinet, M., McDonell, N., Couvert, P., Zemni, R., Cardona, A., Van Buggenhout, G., Frints, S., Hamel, B., Moraine, C., Ropers, H. H., Storm, T., Howell, G. R., Whittaker, A., Ross, M. T., Kahn, A., Fryns, J., Beldjord, C., Marynen, P., and Chelly, J. (1999). A new member of the IL-1 receptor family highly expressed in hippocampus and involved in X-linked mental retardation. Nat. Genet., 23, 25–31. Carta, M. G., Serra, P., Ghiani, A., Manca, E., Hardoy, M. C., Del Giacco, G. S., Diaz, G., Carpiniello, B., and Manconi, P. E. (2002). Chemokines and pro-inflammatory cytokines in Down’s syn-
369
drome: an early marker for Alzheimer-type dementia? Psychother. Psychosom., 71 (4), 233–236. Casolini, P., Catalani, A., Zuena, A. R., and Angelucci, L. (2002). Inhibition of COX-2 reduces the age-dependent increase of hippocampal inflammatory markers, corticosterone secretion, and behavioral impairments in the rat. J. Neurosci. Res., 68 (3), 337–343. Chen, C., Magee, J. C., and Bazan, N. G. (2002). Cyclooxygenase-2 regulates prostaglandin E2 signaling in hippocampal long-term synaptic plasticity. J. Neurophysiol., 87 (6), 2851–2857. Chen, K. S., Nishimura, M. C., Armanini, M. P., Crowley, C., Spencer, S. D., and Phillips, H. S. (1997). Disruption of a single allele of the nerve growth factor gene results in atrophy of basal forebrain cholinergic neurons and memory deficits. J. Neurosci., 17 (19), 7288–7296. Cimadevilla, J. M., Fenton, A. A., and Bures, J. (2000). Functional inactivation of dorsal hippocampus impairs active place avoidance in rats. Neurosci. Lett., 285 (1), 53–56. Cohen, O., Reichenberg, A., Perry, C., Ginzberg, D., Pollmacher, T., Soreq, H., and Yirmiya, R. (2003). Endotoxin-induced changes in human working and declarative memory associate with cleavage of plasma “readthrough” acetylcholinesterase. J. Mol. Neurosci., 21 (3), 199–212. Collins, J. S., Perry, R. T., Watson, B. Jr, Harrell, L. E., Acton, R. T., Blacker, D., Albert, M. S., Tanzi, R. E., Bassett, S. S., McInnis, M. G., Campbell, R. D., and Go, R. C. (2000). Association of a haplotype for tumor necrosis factor in siblings with late-onset Alzheimer disease: the NIMH Alzheimer Disease Genetics Initiative. Am. J. Med. Genet., 96 (6), 823–830. Combarros, O., Llorca, J., Sanchez-Guerra, M., Infante, J., and Berciano J. (2003). Age-dependent association between interleukin-1A (−889) genetic polymorphism and sporadic Alzheimer’s disease. A meta-analysis. J. Neurol., 250 (8), 987–989. Combarros, O., Sanchez-Guerra, M., Infante, J., Llorca, J., and Berciano J. (2002). Gene dose-dependent association of interleukin-1A [−889] allele, 2 polymorphism with Alzheimer’s disease. J. Neurol., 249 (9), 1242–1245. Conrad, C. D., Lupien, S. J., and McEwen, B. S. (1999). Support for a bimodal role for type II adrenal steroid receptors in spatial memory. Neurobiol. Learn. Mem., 72, 39–46. Coogan, A., and O’Connor, J. J. (1997). Inhibition of NMDA receptor–mediated synaptic transmission in the rat dentate gyrus in vitro by IL-1β. Neuroreport, 8, 2107–2110. Coogan, A. N., and O’Connor, J. J. (1999). Interleukin-1beta inhibits a tetraethylammonium-induced synaptic potentiation in the rat dentate gyrus in vitro. Eur. J. Pharmacol., 374 (2), 197–206. Coogan, A. N., O’Neil, L. A. J., and O’Connor, J. J. (1999). The P38 mitogen-activated protein kinase inhibitor SB203580 antagonizes the inhibitory effects of interleukin-1b on long-term potentiation in the rat dentate gyrus in vitro. Neuroscience, 93, 57–69. Corsi, M. M., Ponti, W., Venditti, A., Ferrara, F., Baldo, C., Chiappelli, M., and Licastro F. (2003). Proapoptotic activated Tcells in the blood of children with Down’s syndrome: relationship with dietary antigens and intestinal alterations. Int. J. Tissue React., 25 (3), 117–125. Culpan, D., MacGowan, S. H., Ford, J. M., Nicoll, J. A., Griffin, W. S., Dewar, D., Cairns, N. J., Hughes, A., Kehoe, P. G., and Wilcock, G. K. (2003). Tumour necrosis factor-alpha gene polymorphisms and Alzheimer’s disease. Neurosci. Lett., 350 (1), 61–65. Cunningham, A. J., Murray, C. A., O’Neill, L. A. J., Lynch, M. A., and O’Connor, J. J. (1996). Interleukin-1β (IL-1β) and tumor necrosis factor (TNF) inhibit long-term potentiation in the rat dentate gyrus in vitro. Neurosci. Lett., 203, 17–20. Cunningham, E. T., and De Souza, E. B. (1993). Interleukin 1 receptors in the brain and endocrine tissues. Immunol. Today, 14, 171–176.
370
II. Immune System Effects on Neural and Endocrine Processes and Behavior
Curran, B., and O’Connor, J. J. (2001). The pro-inflammatory cytokine interleukin-18 impairs long-term potentiation and NMDA receptor–mediated transmission in the rat hippocampus in vitro. Neuroscience, 108 (1), 83–90. Curran, B. P., Murray, H. J., and O’Connor, J. J. (2003). A role for cJun N-terminal kinase in the inhibition of long-term potentiation by interleukin-1beta and long-term depression in the rat dentate gyrus in vitro. Neuroscience, 118 (2), 347–357. Curran, B. P., and O’Connor, J. J. (2003). The inhibition of long-term potentiation in the rat dentate gyrus by pro-inflammatory cytokines is attenuated in the presence of nicotine. Neurosci. Lett., 344 (2), 103–106. Dantzer, R. (2001). Cytokine-induced sickness behavior: mechanisms and implications. Ann. N. Y. Acad. Sci., 933, 222–234. Dantzer, R. (2004). Cytokine-induced sickness behaviour: a neuroimmune response to activation of innate immunity. Eur. J. Pharmacol., 500 (1–3), 399–411. Dantzer, R., Konsman, J. P., Bluthe, R. M., and Kelley, K. W. (2000). Neural and humoral pathways of communication from the immune system to the brain: parallel or convergent? Auton. Neurosci., 85 (1–3), 60–65. D’Arcangelo, G., Tancredi, V., Onofri, F., D’Antuono, M., Giovedi, S., and Benfenati F. (2000). Interleukin-6 inhibits neurotransmitter release and the spread of excitation in the rat cerebral cortex. Eur. J. Neurosci., 12 (4), 1241–1252. de Kloet, E. R., Oitzl, M. S., and Joels, M. (1999). Stress and cognition: are corticosteroids good or bad guys? Trends Neurosci., 22 (10), 422–426. Dellu, F., Mayo, W., Cherkaoui, J., Le Moal, M., and Simon, H. (1992). A two-trial memory task with automated recording: study in young and aged rats. Brain Res., 588 (1), 132–139. De los Santos, M. J., Mercader, A., Frances, A., Portoles, E., Remohi, J., Pellicer, A., and Simon, C. (1996). Role of endometrial factors in regulating secretion of components of the immunoreactive human embryonic interleukin-1 system during embryonic development. Biol. Reprod., 54 (3), 563–574. Depboylu, C., Lohmuller, F., Gocke, P., Du, Y., Zimmer, R., Gasser, T., Klockgether, T., and Dodel, R. C. (2004). An interleukin-6 promoter variant is not associated with an increased risk for Alzheimer’s disease. Dement. Geriatr. Cogn. Disord., 17 (3), 170–173. Depino, A. M., Alonso, M., Ferrari, C., del Rey, A., Anthony, D., Besedovsky H., Medina, J. H., and Pitossi, F. (2004). Learning modulation by endogenous hippocampal IL-1: blockade of endogenous IL-1 facilitates memory formation. Hippocampus, 14 (4), 526–535. D’Hooge, R., and De Deyn, P. P. (2001). Applications of the Morris water maze in the study of learning and memory. Brain. Res. Brain. Res. Rev., 36 (1), 60–90. Diamond, D. M., Bennet, M. C., Fleshner, M., and Rose, G. M. (1992). Inverted-U relationship between the level of peripheral corticosterone and the magnitude of hippocampal primed burst potentiation. Hippocampus, 2 (4), 421–430. Dik, M. G., Jonker, C., Hack, C. E., Smit, J. H., Comijs, H. C., and Eikelenboom, P. (2005). Serum inflammatory proteins and cognitive decline in older persons. Neurology, 64 (8), 1371–1377. Dinarello, C. A. (1996). Biologic basis for interleukin-1 in disease. Blood, 87, 2095–2147. Dinarello, C. A. (2000). Proinflammatory cytokines. Chest, 118 (2), 503–508. Dinarello, C. A., Gatti, S., and Bartfai, T. (1999). Fever: links with an ancient receptor. Curr. Biol., 9 (4), R147–R150. Dominici, R., Cattaneo, M., Malferrari, G., Archi, D., Mariani, C., Grimaldi, L. M., and Biunno, I. (2002a). Cloning and functional analysis of the allelic polymorphism in the transcription
regulatory region of interleukin-1 alpha. Immunogenetics, 54 (2), 82–86. Dominici, R., Malferrari, G., Mariani, C., Grimaldi, L., and Biunno, I. (2002b). The interleukin 1-beta exonic (+3953) polymorphism does not alter in vitro protein secretion. Exp. Mol. Pathol., 73 (2), 139–141. Du, Y., Dodel, R. C., Eastwood, B. J., Bales, K. R., Gao, F., Lohmuller, F., Muller, U., Kurz, A., Zimmer, R., Evans, R. M., Hake, A., Gasser, T., Oertel, W. H., Griffin, W. S., Paul, S. M., and Farlow, M. R. (2000). Association of an interleukin 1 alpha polymorphism with Alzheimer’s disease. Neurology, 55 (4), 480–483. Dunn, A. J., and Wang, J. (1995). Cytokine effects on CNS biogenic amines. Neuroimmunomodulation, 2 (6), 319–328. Edoff, K., and Jerregard, H. (2002). Effects of IL-1beta, IL-6 or LIF on rat sensory neurons co-cultured with fibroblast-like cells. J. Neurosci. Res., 67 (2), 255–263. Ehl, C., Kolsch, H., Ptok, U., Jessen, F., Schmitz, S., Frahnert, C., Schlosser, R., Rao, M. L., Maier, W., and Heun, R. (2003). Association of an interleukin-1beta gene polymorphism at position −511 with Alzheimer’s disease. Int. J. Mol. Med., 11 (2), 235–238. Eichenbaum, H. (1996). Learning from LTP: a comment on recent attempts to identify cellular and molecular mechanisms of memory. Learn. Mem., 3 (2–3), 61–73. Eichenbaum, H. (2000). A cortical-hippocampal system for declarative memory. Nat. Rev. Neurosci., 1 (1), 41–50. Ekdahl, C. T., Claasen, J. H., Bonde, S., Kokaia, Z., and Lindvall, O. (2003). Inflammation is detrimental for neurogenesis in adult brain. Proc. Natl. Acad. Sci. U.S.A., 100 (23), 13632–13637. Elwan, O., Madkour, O., Elwan, F., Mostafa, M., Abbas Helmy, A., Abdel-Naseer, M., Abdel Shafy, S., and El Faiuomy, N. (2003). Brain aging in normal Egyptians: cognition, education, personality, genetic and immunological study. J. Neurol. Sci., 211 (1–2), 15–22. Ershler, W. B., Sun, W. H., Binkley, N., Gravenstein, S., Volk, M. J., Kamoske, G., Klopp, R. G., Roecker, E. B., Daynes, R. A., and Weindruch R. (1993). Interleukin-6 and aging: blood levels and mononuclear cell production increase with advancing age and in vitro production is modifiable by dietary restriction. Lymphokine Cytokine Res., 12 (4), 225–230. Faltraco, F., Burger, K., Zill, P., Teipel, S. J., Moller, H. J., Hampel, H., Bondy, B., and Ackenheil, M. (2003). Interleukin-6-174 G/C promoter gene polymorphism C allele reduces Alzheimer’s disease risk. J. Am. Geriatr. Soc., 51 (4), 578–579. Fanselow, M. S. (2000). Contextual fear, gestalt memories, and the hippocampus. Behav. Brain Res., 110, 73–81. Fanselow, M. S., and Poulos, A. M. (2005). The neuroscience of mammalian associative learning. Annu. Rev. Psychol., 56, 207–234. Ferrucci, L., Ble, A., Bandinelli, S., Lauretani, F., Suthers, K., and Guralnik, J. M. (2004). A flame burning within. Aging Clin. Exp. Res., 16 (3), 240–243. Fidani, L., Goulas, A., Mirtsou, V., Petersen, R. C., Tangalos, E., Crook, R., and Hardy, J. (2002). Interleukin-1A polymorphism is not associated with late onset Alzheimer’s disease. Neurosci. Lett., 323 (1), 81–83. Fiore, M., Angelucci, F., Alleva, E., Branchi, I., Probert, L., and Aloe, L. (2000). Learning performances, brain NGF distribution and NPY levels in transgenic mice expressing TNF-alpha. Behav. Brain Res., 112 (1–2), 165–175. Fiore, M., Probert, L., Kollias, G., Akassoglou, K., Alleva, E., and Aloe, L. (1996). Neurobehavioral alterations in developing transgenic mice expressing TNF-alpha in the brain. Brain Behav. Immun., 10 (2), 126–138. Fishman, D., Faulds, G., Jeffery, R., Mohamed-Ali, V., Yudkin, J. S., Humphries, S., and Woo, P. (1998). The effect of novel polymorphisms in the interleukin-6 (IL-6) gene on IL-6 transcription and
16. The Role of Pro-inflammatory Cytokines in Memory Processes and Neural Plasticity plasma IL-6 levels, and an association with systemic-onset juvenile chronic arthritis. J. Clin. Invest., 102 (7), 1369–1376. Floresco, S. B., Seamans, J. K., and Phillips, A. G. (1997). Selective roles for hippocampal, prefrontal cortical, and ventral striatal circuits in radial-arm maze tasks with or without a delay. J. Neurosci., 17 (5), 1880–1890. Forsey, R. J., Thompson, J. M., Ernerudh, J., Hurst, T. L., Strindhall, J., Johansson, B., Nilsson, B. O., and Wikby, A. (2003). Plasma cytokine profiles in elderly humans. Mech. Aging Dev., 124 (4), 487–493. Frei, K., Malipiero, U. V., Leist, T. P., Zinkernagel, R. M., Schwab, M. E., and Fontana, A. (1989). On the cellular source and function of interleukin 6 produced in the central nervous system in viral diseases. Eur. J. Immunol., 19 (4), 689–694. Furuya, Y., Yamamoto, T., Yatsugi, S., and Ueki, S. (1988). A new method for studying working memory by using the three-panel runway apparatus in rats. Jpn. J. Pharmacol., 46 (2), 183–188. Gadient, R. A., Cron, K. C., and Otten, U. (1990). Interleukin-1 β and tumor necrosis factor-α synergistically stimulate nerve growth factor (NGF) release from cultured rat astrocytes. Neurosci. Lett., 117, 335–340. Gerber, J., Bottcher, T., Hahn, M., Siemer, A., Bunkowski, S., and Nau, R. (2004). Increased mortality and spatial memory deficits in TNF-alpha–deficient mice in ceftriaxone-treated experimental pneumococcal meningitis. Neurobiol. Dis., 16 (1), 133–138. Gerwin, N., Jia, G. Q., Kulbacki, R., and Gutierrez-Ramos, J. C. (1995). Interleukin gene expression in mouse preimplantation development. Dev. Immunol., 4 (3), 169–179. Gibertini, M. (1996). IL1 beta impairs relational but not procedural rodent learning in a water maze task. Adv. Exp. Med. Biol., 402, 207–217. Gibertini, M. (1998). Cytokines and cognitive behavior. Neuroimmunomodulation, 5, 160–165. Gibertini, M., Newton, C., Friedman, H., and Klein, T. W. (1995a). Spatial learning in mice infected with legionella pneumophila or administered exogenous interleukin-1β. Brain Behav. Immun., 9, 113–128. Gibertini, M., Newton, C., Klein, T. W., and Friedman, H. (1995b). Legionella pneumophila–induced visual learning impairment reversed by anti-interleukin-1 beta. Proc. Soc. Exp. Biol. Med., 210 (1), 7–11. Godbout, J. P., and Johnson, R. W. (2004). Interleukin-6 in the aging brain. J. Neuroimmunol., 147 (1–2), 141–144. Goehler, L. E., Gaykema, R. P., Hansen, M. K., Anderson, K., Maier, S. F., and Watkins, L. R. (2000). Vagal immune-to-brain communication: a visceral chemosensory pathway. Auton. Neurosci., 85 (1–3), 49–59. Golan, H., Levav, T., Mendelsohn, A., and Huleihel, M. (2004). Involvement of tumor necrosis factor alpha in hippocampal development and function. Cereb. Cortex, 14 (1), 97–105. Goldberg, T. E., and Weinberger, D. R. (2004). Genes and the parsing of cognitive processes. Trends Cogn. Sci., 8 (7), 325–335. Gopez. J. J., Yue, H., Vasudevan, R., Malik, A. S., Fogelsanger, L. N., Lewis, S., Panikashvili, D., Shohami, E., Jansen, S. A., Narayan, R. K., and Strauss, K. I. (2005). Cyclooxygenase-2–specific inhibitor improves functional outcomes, provides neuroprotection, and reduces inflammation in a rat model of traumatic brain injury. Neurosurgery, 56 (3), 590–604. Goshen, I., Avron, M., Kreisel, T., and Yirmiya, R. (2003a). Impaired IL-1 signaling during brain development induces memory deficits, which can be rescued by environmental enrichment. Brain Behav. Immun., 17 (3), 178. Goshen, I., Yirmiya, R., Iverfeldt, K., and Weidenfeld, J. (2003b). The role of endogenous interleukin-1 in stress-induced adrenal activation and adrenalectomy-induced adrenocorticotropic hormone hypersecretion. Endocrinology, 144 (10), 4453–4458.
371
Gould, E., Beylin, A., Tanapat, P., Reeves, A., and Shors, T. J. (1999). Learning enhances adult neurogenesis in the hippocampal formation. Nat. Neurosci., 2 (3), 260–265. Gould, E., Tanapat, P., Rydel, T., and Hastings, N. (2000). Regulation of hippocampal neurogenesis in adulthood. Biol. Psychiatry, 48, 715–720. Green, E. K., Harris, J. M., Lemmon, H., Lambert, J. C., ChartierHarlin, M. C., St Clair, D., Mann, D. M., Iwatsubo, T., and Lendon, C. L. (2002). Are interleukin-1 gene polymorphisms risk factors or disease modifiers in AD? Neurology, 58 (10), 1566–1568. Griffin, W. S., and Mrak, R. E. (2002). Interleukin-1 in the genesis and progression of and risk for development of neuronal degeneration in Alzheimer’s disease. L. Leukoc. Biol., 72, 233–238. Griffin, W. S., Stanley, L. C., Ling, C., White, L., MacLeod, V., Perrot, L. J., White, C. L., 3rd, and Araoz, C. (1989). Brain interleukin-1 and S-100 immunoreactivity are elevated in Down syndrome and Alzheimer disease. Proc. Natl. Acad. Sci. U.S.A., 86 (19), 7611–7615. Grimaldi, L. M., Casadei, V. M., Ferri, C., Veglia, F., Licastro, F., Annoni, G., Biunno, I., De-Bellis, G., Sorbi, S., Mariani, C., Canal, N., Griffin, W. S., and Franceschi, M. (2000). Association of earlyonset Alzheimer’s disease with an interleukin-1 alpha gene polymorphism. Ann. Neurol., 47 (3), 361–365. Gross, C. G. (2000). Neurogenesis in the adult brain: death of a dogma. Nat. Rev. Neurosci., 1, 67–73. Hager, K., Machein, U., Krieger, S., Platt, D., Seefried, G., and Bauer, J. (1994). Interleukin-6 and selected plasma proteins in healthy persons of different ages. Neurobiol. Aging, 15 (6), 771–772. Hall, J., Thomas, K. L., and Everitt, B. J. (2000). Rapid and selective induction of BDNF expression in the hippocampus during contextual learning. Nat. Neurosci., 3, 533–535. Hart, B. L. (1988). Biological basis of the behavior of sick animals. Neurosci. Biobehav. Rev., 12 (2), 123–137. Hebb, D. O. (1949). The organization of behavior: a neuropsychological theory. New York: Wiley. Hedley, R., Hallmayer, J., Groth, D. M., Brooks, W. S., Gandy, S. E., and Martins, R. N. (2002). Association of interleukin-1 polymorphisms with Alzheimer’s disease in Australia. Ann. Neurol., 51 (6), 795–797. Heinrich, P. C., Behrmann, I., Haan, S., Hermanns, H. M., MullerNewen, G., and Schaper, F. (2003). Principles of interleukin (IL)6–type cytokine signaling and its regulation. Biochem. J., 374 (1), 1–20. Heyser, C. J., Masliah, E., Samimi, A., Campbell, I. L., and Gold, L. H. (1997). Progressive decline in avoidance learning paralleled by inflammatory neurodegeneration in transgenic mice expressing interleukin 6 in the brain. Proc. Natl. Acad. Sci. U.S.A., 94 (4), 1500–1505. Hoffmann, J. A., Kafatos, F. C., Janeway, C. A. Jr., and Ezekowitz, R. A. B. (1999). Phylogenetic perspectives in innate immunity. Science, 284, 1313–1318. Holmes, C., El-Okl, M., Williams, A. L., Cunningham, C., Wilcockson, D., and Perry, V. H. (2003). Systemic infection, interleukin 1beta, and cognitive decline in Alzheimer’s disease. J. Neurol. Neurosurg. Psychiatry, 74 (6), 788–789. Hori, T., Oka, T., Hosoi, M., and Aou, S. (1998). Pain modulatory actions of cytokines and prostaglandin E2 in the brain. Ann. N.Y. Acad. Sci., 840, 269–281. Ikegaya, Y., Delcroix, I., Iwakura, Y., Matsuki, N., and Nishiyama, N. (2003). Interleukin-1beta abrogates long-term depression of hippocampal CA1 synaptic transmission. Synapse, 47 (1), 54–57. Infante, J., Llorca, J., Berciano, J., and Combarros, O. (2002). No synergistic effect between −850 tumor necrosis factor-alpha promoter polymorphism and apolipoprotein E epsilon, 4 allele in Alzheimer’s disease. Neurosci. Lett., 328 (1), 71–73.
372
II. Immune System Effects on Neural and Endocrine Processes and Behavior
Ishida, K., Yoshimura, N., Yoshida, M., Honda, Y., Murase, K., and Hayashi, K. (1997). Expression of neurotrophic factors in cultured human retinal pigment epithelial cells. Curr. Eye Res., 16 (2), 96–101. Janeway, C. A. Jr., and Medzhitov, R. (2002). Innate immune recognition. Annu. Rev. Immunol., 20, 197–216. Jankowsky, J. L., Derrick, B. E., and Patterson, P. H. (2000). Cytokine responses to LTP induction in the rat hippocampus: a comparison of in vitro and in vivo techniques. Learn. Mem., 7 (6), 400–412. Jin, H., Gardner, R. J., Viswesvaraiah, R., Muntoni, F. and Roberts, R. G. (2000). Two novel members of the interleukin-1 receptor gene family, one deleted in Xp22.1–Xp21.3 mental retardation. Eur. J. Hum. Genet., 8 (2), 87–94. Johanson, S., and Stromberg, I. (2002). Guidance of dopaminergic neuritic growth by immature astrocytes in organotypic cultures of rat fetal ventral mesencephalon. J. Comp. Neurol., 443, 237–249. Jones, S. A ., Richards, P. J., Scheller, J., and Rose-John, S. (2005). IL-6 transsignaling: the in vivo consequences. J. Interferon Cytokine Res., 25 (5), 241–253. Kalman, J., Juhasz, A., Laird, G., Dickens, P., Jardanhazy, T., Rimanoczy, A., Boncz, I., Parry-Jones, W. L., and Janka, Z. (1997). Serum interleukin-6 levels correlate with the severity of dementia in Down syndrome and in Alzheimer’s disease. Acta Neurol. Scand., 96 (4), 236–240. Kamitani, W., Ono, E., Yoshino, S., Kobayashi, T., Taharaguchi, S., Lee, B. J., Yamashita, M., Kobayashi, T., Okamoto, M., Taniyama, H., Tomonaga, K., and Ikuta, K. (2003). Glial expression of Borna disease virus phosphoprotein induces behavioral and neurological abnormalities in transgenic mice. Proc. Natl. Acad. Sci. U.S.A., 100 (15), 8969–8974. Katsuki, H., Nakai, S., Hirai, Y., Akaji, K., Kiso, Y., and Satoh, M. (1990). Interleukin-1 beta inhibits long-term potentiation in the CA3 region of mouse hippocampal slices. Eur. J. Pathol., 181, 323–326. Kelleher, R. J., 3rd, Govindarajan, A., and Tonegawa, S. (2004). Translational regulatory mechanisms in persistent forms of synaptic plasticity. Neuron, 44 (1), 59–73. Kelly, A., Vereker, E., Nolan, Y., Brady, M., Barry, C., Loscher, C. E., Mills, K. H., and Lynch, M. A. (2003). Activation of p38 plays a pivotal role in the inhibitory effect of lipopolysaccharide and interleukin-1 beta on long term potentiation in rat dentate gyrus. J. Biol. Chem., 278 (21), 19453–19462. Kempermann, G., and Neumann, H. (2003). Neuroscience. Microglia: the enemy within? Science, 302 (5651), 1689–1690. Kempermann, G., Wiskott, L., and Gage, F. H. (2004). Functional significance of adult neurogenesis. Curr. Opin. Neurobiol., 14 (2), 186–191. Kent, S., Bluthe, R. M., Kelley, K. W., and Dantzer, R. (1992). Sickness behavior as a new target for drug development. Trends. Pharmacol. Sci., 13 (1), 24–28. Ki, C. S., Na, D. L., Kim, D. K., Kim, H. J., and Kim, J. W. (2001). Lack of association of the interleukin-1alpha gene polymorphism with Alzheimer’s disease in a Korean population. Ann. Neurol., 49 (6), 817–818. Kim, J. J., and Diamond, D. M. (2002). The stressed hippocampus, synaptic plasticity and lost memories. Nat. Rev. Neurosci., 3 (6), 453–462. Kinouchi, K., Brown, G., Pasternak, G., and Donner, D. B. (1991). Identification and characterization of receptors for tumor necrosis factor-alpha in the brain. Biochem. Biophys. Res. Commun., 181 (3), 1532–1538. Kishimoto, T., Akira, S., and Taga, T. (1992). Interleukin-6 and its receptor: a paradigm for cytokines. Science, 258 (5082), 593–597.
Kitajima, I., Yamamoto, T., Ohno, M., and Ueki, S. (1992). Working and reference memory in rats in the three-panel runway task following dorsal hippocampal lesions. Jpn. J. Pharmacol., 58 (2), 175–183. Kolsch, H., Ptok, U., Bagli, M., Papassotiropoulos, A., Schmitz, S., Barkow, K., Kockler, M., Rao, M. L., Maier, W., and Heun R. (2001). Gene polymorphisms of interleukin-1alpha influence the course of Alzheimer’s disease. Ann. Neurol., 49 (6), 818–819. Kozora, E., Laudenslager, M., Lemieux, A., and West, S. G. (2001). Inflammatory and hormonal measures predict neuropsychological functioning in systemic lupus erythematosus and rheumatoid arthritis patients. J. Int. Neuropsychol. Soc., 7 (6), 745–754. Krabbe, K. S., Pedersen, M., and Bruunsgaard, H. (2004). Inflammatory mediators in the elderly. Exp. Gerontol., 39 (5), 687–699. Krabbe, K. S., Reichenberg, A., Yirmiya, R., Smed, A., Pedersen, B. K., and Bruunsgaard, H. (2005). Low-dose endotoxemia and human neuropsychological functions. Brain Behav. Immun., 19 (5), 453–460. Kruessel, J. S., Huang, H. Y., Wen, Y., Kloodt, A. R., Bielfeld, P., and Polan, M. L. (1997). Different pattern of interleukin-1 beta (IL-1 beta), interleukin-1 receptor antagonist (IL-1ra) and interleukin-1 receptor type I (IL-1R tI) mRNA-expression in single preimplantation mouse embryos at various developmental stages. J. Reprod. Immunol., 34 (2), 103–120. Kuo, Y. M., Liao, P. C., Lin C., Wu, C. W., Huang, H. M., Lin, C. C., and Chuo, L. J. (2003). Lack of association between interleukin1alpha polymorphism and Alzheimer disease or vascular dementia. Alzheimer Dis. Assoc. Disord., 17 (2), 94–97. Kurumbail, R. G., Stevens, A. M., Gierse, J. K., McDonald, J. J., Stegeman, R. A., Pak, J. Y., Gildehaus, D., Miyashiro, J. M., Penning, T. D., Seibert, K., Isakson, P. C., and Stallings, W. C. (1996). Structural basis for selective inhibition of cyclooxygenase2 by anti-inflammatory agents. Nature, 384 (6610), 644–648. Labow, M., Shuster, D., Zetterstorm, M., Nunes, P., Terry, R., Cullinan, E. B., Bartfei, T., Solorzano, C., Moldawer, L. L., Chizzonite, R., and McIntyre, K. W. (1997). Absence of IL-1 signaling and reduced inflammatory response in IL-1 type I receptor-deficient mice. J. Immunol., 159 (5), 2452–2461. Lacosta, S., Merali, Z., and Anisman, H. (1999). Influence of acute and repeated interleukin-2 administration on spatial learning, locomotor activity, exploratory behaviors, and anxiety. Behav. Neurosci., 113 (5), 1030–1041. Larson, S. J., and Dunn, A. J. (2001). Behavioral effects of cytokines. Brain Behav. Immun., 15 (4), 371–387. Laws, S. M., Perneczky, R., Wagenpfeil, S., Muller, U., Forstl, H., Martins, R. N., Kurz, A., and Riemenschneider, M. (2005). TNF polymorphisms in Alzheimer disease and functional implications on CSF beta-amyloid levels. Hum. Mutat., 26 (1), 29–35. Lee, B., English, J. A., and Paul, I. A. (2000). LP-BM5 infection impairs spatial working memory in C57BL/6 mice in the Morris water maze. Brain Res., 856 (1–2), 129–134. Li, A. J., Katafuchi, T., Oda, S., Hori, T., and Oomura, Y. (1997). Interleukin-6 inhibits long-term potentiation in rat hippocampal slices. Brain Res., 748 (1–2), 30–38. Li, S. T., Matsushita, M., Moriwaki, A., Saheki, Y., Lu, Y. F., Tomizawa, K., Wu, H. Y., Terada, H., and Matsui, H. (2004a). HIV-1 Tat inhibits long-term potentiation and attenuates spatial learning. Ann. Neurol., 55 (3), 362–371. Li, X. Q., Zhang, J. W., Zhang, Z. X., Chen, D., and Qu, Q. M. (2004b). Interleukin-1 gene cluster polymorphisms and risk of Alzheimer’s disease in Chinese Han population. J. Neural Transm., 111 (9), 1183–1190. Li, Y., Liu, L., Barger, S. W., and Griffin, W. S. (2003). Interleukin-1 mediates pathological effects of microglia on tau phosphoryla-
16. The Role of Pro-inflammatory Cytokines in Memory Processes and Neural Plasticity tion and on synaptophysin synthesis in cortical neurons through a p38-MAPK pathway. J. Neurosci., 23 (5), 1605–1611. Li, Y., Liu, L., Kang, J., Sheng, J. G., Barger, S. W., Mrak, R. E., and Griffin, W. S. T. (2000). Neuronal-glial interactions mediated by interleukin-1 enhance neuronal acetylcholinesterase activity and mRNA expression. J. Neurosci., 20, 149–155. Licastro, F., Chiappelli, M., Ruscica, M., Carnelli, V., and Corsi, M. M. (2005). Altered cytokine and acute phase response protein levels in the blood of children with Down’s syndrome: relationship with dementia of Alzheimer’s type. Int. J. Immunopathol. Pharmacol., 18 (1), 165–172. Licastro, F., Grimaldi, L. M., Bonafe, M., Martina, C., Olivieri, F., Cavallone, L., Giovanietti, S., Masliah, E., and Franceschi, C. (2003). Interleukin-6 gene alleles affect the risk of Alzheimer’s disease and levels of the cytokine in blood and brain. Neurobiol. Aging, 24 (7), 921–926. Licastro, F., Mariani, R. A., Faldella, G., Carpene, E., Guidicini, G., Rangoni, A., Grilli, T., and Bazzocchi, G. (2001). Immuneendocrine status and coeliac disease in children with Down’s syndrome: relationships with zinc and cognitive efficiency. Brain Res. Bull., 55 (2), 313–317. Licastro, F., Pedrini, S., Caputo, L., Annoni, G., Davis, L. J., Ferri, C., Casadei, V., and Grimaldi, L. M. (2000a). Increased plasma levels of interleukin-1, interleukin-6 and alpha-1–antichymotrypsin in patients with Alzheimer’s disease: peripheral inflammation or signals from the brain? J. Neuroimmunol., 103 (1), 97–102. Licastro, F., Pedrini, S., Ferri, C., Casadei, V., Govoni, M., Pession, A., Sciacca, F. L., Veglia, F., Annoni, G., Bonafe, M., Olivieri, F., Franceschi, C., and Grimaldi, L. M. (2000b). Gene polymorphism affecting alpha1-antichymotrypsin and interleukin-1 plasma levels increases Alzheimer’s disease risk. Ann. Neurol., 48 (3), 388–391. Licastro, F., Veglia, F., Chiappelli, M., Grimaldi, L. M., and Masliah, E. (2004). A polymorphism of the interleukin-1 beta gene at position +3953 influences progression and neuro-pathological hallmarks of Alzheimer’s disease. Neurobiol. Aging, 25 (8), 1017–1022. Ling, Z. D., Potter, E. D., Lipton, J. W., and Carvey, P. M. (1998). Differentiation of mesencephalic progenitor cells into dopaminergic neurons by cytokines. Exp. Neurol., 149, 411–423. Liu, Y. P., Lin, H. I., and Tzeng, S. F. (2005). Tumor necrosis factoralpha and interleukin-18 modulate neuronal cell fate in embryonic neural progenitor culture. Brain Res., 1054 (2), 152–158. Locksley, R. M., Killeen, N., and Lenardo, M. J. (2001). The TNF and TNF receptor superfamilies: integrating mammalian biology. Cell, 104 (4), 487–501. Loddick, S. A., Liu, C., Takao, T., Hashimoto, K., and De Souza, E. B. (1998). Interleukin-1 receptors: cloning studies and role in central nervous system disorders. Brain Res. Brain Res. Rev., 26, 306–319. Loscher, C. E., Mills, K. H., and Lynch, M. A. (2003). Interleukin-1 receptor antagonist exerts agonist activity in the hippocampus independent of the interleukin-1 type I receptor. J. Neuroimmunol., 137 (1–2), 117–124. Lundkvist, J., Sundgren-Andersson, A. K., Tingsborg, S., Ostlund, P., Engfors, C., Alheim, K., Bartfai, T., Iverfeldt, K., and Schultzberg, M. (1999). Acute-phase response in transgenic mice with CNS overexpression of IL-1 receptor antagonist. Am. J. Physiol., 276, R644–R651. Lynch, M. A. (1998a). Analysis of the mechanisms underlying the age-related impairment in long-term potentiation in the rat. Rev. Neurosci., 9 (3), 169–201. Lynch, M. A. (1998b). Age-related impairment in long-term potentiation in hippocampus: a role for the cytokine, interleukin-1 beta? Prog. Neurobiol., 56 (5), 571–589.
373
Lynch, M. A. (2002). Interleukin-1 beta exerts a myriad of effects in the brain and in particular in the hippocampus: analysis of some of these actions. Vitam. Horm., 64, 185–219. Ma, S. L., Tang, N. L., Lam, L. C., and Chiu, H. F. (2003). Lack of association of the interleukin-1beta gene polymorphism with Alzheimer’s disease in a Chinese population. Dement. Geriatr. Cogn. Disord., 16 (4), 265–268. Maier, S. F. (1990). Role of fear in mediating shuttle escape learning deficit produced by inescapable shock. J. Exp. Psychol. Anim. Behav. Process., 16 (2), 137–149. Maier, S. F. (2003). Bi-directional immune-brain communication: Implications for understanding stress, pain, and cognition. Brain Behav. Immun., 17 (2), 69–85. Maier, S. F., and Watkins L. R. (1995). Intracerebroventricular interleukin-1 receptor antagonist blocks the enhancement of fear conditioning and interference with escape produced by inescapable shock. Brain Res., 695, 279–282. Maier, S. F., and Watkins, L. R. (1998). Cytokines for psychologists: implications of bi-directional immune-to-brain communication for understanding behavior, mood and cognition. Psychol. Rev., 105, 83–107. Maren, S. (2001). Neurobiology of Pavlovian fear conditioning. Annu. Rev. Neurosci., 24, 897–931. Maren, S., and Holt, W. (2000). The hippocampus and contextual memory retrieval in Pavlovian conditioning. Behav. Brain Res., 110, 97–108. Maren, S., and Quirk, G. J. (2004). Neuronal signaling of fear memory. Nat. Rev. Neurosci., 5 (11), 844–852. Martin, S. J., Grimwood, P. D., and Morris, R. G. (2000). Synaptic plasticity and memory: an evaluation of the hypothesis. Annu. Rev. Neurosci., 23, 649–711. Marz, P., Cheng, J. G., Gadient, R. A., Patterson, P. H., Stoyan, T., Otten, U., and Rose-John, S. (1998). Sympathetic neurons can produce and respond to interleukin 6. Proc. Natl. Acad. Sci. U.S.A., 95 (6), 3251–3256. Marz, P., Otten, U., and Rose-John, S. (1999). Neural activities of IL6–type cytokines often depend on soluble cytokine receptors. Eur. J. Neurosci., 11 (9), 2995–3004. Matsuda, S., Wen, T. C., Morita, F., Otsuka, H., Igase, K., Yoshimura, H., and Sakanaka, M. (1996). Interleukin-6 prevents ischemiainduced learning disability and neuronal and synaptic loss in gerbils. Neurosci. Lett., 204 (1–2), 109–112. Matsumoto, Y., Watanabe, S., Suh, Y. H., and Yamamoto, T. (2002). Effects of intrahippocampal CT105, a carboxyl terminal fragment of beta-amyloid precursor protein, alone/with inflammatory cytokines on working memory in rats. J. Neurochem., 82 (2), 234–239. Matsumoto, Y., Yamaguchi, T., Watanabe, S., and Yamamoto, T. (2004). Involvement of arachidonic acid cascade in working memory impairment induced by interleukin-1 beta. Neuropharmacology, 46 (8), 1195–1200. Matsumoto, Y., Yoshida, M., Watanabe, S. and Yamamoto, T. (2001). Involvement of cholinergic and glutamatergic functions in working memory impairment induced by interleukin-1β in rats. Eur. J. Pharmacol., 430, 283–288. Matyszak, M. K., and Perry, V. H. (1995). Demyelination in the central nervous system following a delayed-type hypersensitivity response to bacillus Calmette-Guerin. Neuroscience, 64 (4), 967–977. McCulley, M. C., Day, I. N., and Holmes, C. (2004). Association between interleukin 1–beta promoter (−511) polymorphism and depressive symptoms in Alzheimer’s disease. Am. J. Med. Genet. B Neuropsychiatr. Genet., 124 (1), 50–53. McCusker, S. M., Curran, M. D., Dynan, K. B., McCullagh, C. D., Urquhart, D. D., Middleton, D., Patterson, C. C., McIlroy, S. P.,
374
II. Immune System Effects on Neural and Endocrine Processes and Behavior
and Passmore, A. P. (2001). Association between polymorphism in regulatory region of gene encoding tumour necrosis factor alpha and risk of Alzheimer’s disease and vascular dementia: a case-control study. Lancet, 357 (9254), 436–439. McEwen, B. S., and Sapolsky, R. M. (1995). Stress and cognitive function. Curr. Opin. Neurobiol., 5 (2), 205–216. McGaugh, J. L. (2004). The amygdala modulates the consolidation of memories of emotionally arousing experiences. Annu. Rev. Neurosci., 27, 1–28. McGeer, E. G., and McGeer, P. L. (2003). Inflammatory processes in Alzheimer’s disease. Prog. Neuropsychopharmacol. Biol. Psychiatry, 27 (5), 741–749. Mehler, M. F., and Kessler, J. A. (1997). Hematolymphopoietic and inflammatory cytokines in neural development. Trends Neurosci., 20 (8), 357–365. Minghetti, L. (2004). Cyclooxygenase-2 (COX-2) in inflammatory and degenerative brain diseases. J. Neuropathol. Exp. Neurol., 63 (9), 901–910. Minster, R. L., DeKosky, S. T., Ganguli, M., Belle, S., and Kamboh, M. I. (2000). Genetic association studies of interleukin-1 (IL-1A and IL-1B) and interleukin-1 receptor antagonist genes and the risk of Alzheimer’s disease. Ann. Neurol., 48 (5), 817–819. Monje, M. L., Toda, H., and Palmer, T. D. (2003). Inflammatory blockade restores adult hippocampal neurogenesis. Science, 302 (5651), 1760–1765. Morris, R. (1981). Spatial localization does not require the presence of local cues. Learn. Motiv., 12, 239–260. Morris, R. (1984). Developments of a water-maze procedure for studying spatial learning in the rat. J. Neurosci. Methods, 11, 47–60. Morris, R. G. M., Garrud, P., Rawlins, J. N. P., and O’Keefe, J. (1982). Place navigation impaired in rats with hippocampal lesions. Nature, 297, 681–683. Morrow, J. D., and Opp, M. R. (2005). Sleep-wake behavior and responses of interleukin-6–deficient mice to sleep deprivation. Brain Behav. Immun., 19 (1), 28–39. Mousa, A., Seiger, A., Kjaeldgaard, A., and Bakhiet, M. (1998). Human first trimester forebrain cells express genes for inflammatory and anti-inflammatory cytokines. Cytokine, 11, 55–60. Mrak, R. E., and Griffin, W. S. T. (2001). Interleukin-1, neuroinflammation, and Alzheimer’s disease. Neurobiol. Aging, 22, 903–908. Munoz, C., and Grossman, S. P. (1982). Spatial discrimination, reversal and active or passive avoidance learning in rats with KAinduced neuronal depletions in dorsal hippocampus. Brain Res. Bull., 6 (5), 399–406. Munoz-Fernandez, M. A., and Fresno, M. (1998). The role of tumour necrosis factor, interleukin 6, interferon-gamma and inducible nitric oxide synthase in the development and pathology of the nervous system. Prog. Neurobiol., 56 (3), 307–340. Murphy, P. G., Borthwick, L.A., Altares, M., Gauldie, J., Kaplan, D., and Richardson, P.M. (2000). Reciprocal actions of interleukin-6 and brain-derived neurotrophic factor on rat and mouse primary sensory neurons. Eur. J. Neurosci., 12 (6), 1891–1899. Murray, C. A., and Lynch, M. A. (1998). Evidence that increased hippocampal expression of the cytokine interleukin-1β is a common trigger for age- and stress-induced impairments in long-term potentiation. J. Neurosci., 18 (8), 2974–2981. Murray, E. A., Rausch, D. M., Lendvay, J., Sharer, L. R., and Eiden, L. E. (1992). Cognitive and motor impairments associated with SIV infection in rhesus monkeys. Science, 255 (5049), 1246–1249. Naka, T., Nishimoto, N., and Kishimoto, T. (2002). The paradigm of IL-6: from basic science to medicine. Arthritis Res., 4, S233–S242. Neumann, H., Schweigreiter, R., Yamashita, T., Rosenkranz, K., Wekerle, H., and Barde, Y. A. (2002). Tumor necrosis factor inhib-
its neurite outgrowth and branching of hippocampal neurons by a rho-dependent mechanism. J. Neurosci., 22 (3), 854–862. Nguyen, K. T., Deak, T., Owens, S. M., Kohno, T., Fleshner, M., Watkins, L. R., and Maier, S. F. (1998). Exposure to acute stress induces brain interleukin-1b protein in the rat. J. Neurosci., 18 (6), 2239–2246. Nguyen, K. T., Deak, T., Will, M. J., Hansen, M. K., Hunsaker, B. N., Fleshner, M., Watkins, L. R., and Maier, S. F. (2000). Timecourse and corticosterone sensitivity of the brain, pituitary, and serum interleukin-1 protein response to acute stress. Brain Res., 859, 193–201. Nicoll, J. A., Mrak, R. E., Graham, D. I., Stewart, J., Wilcock, G., MacGowan, S., Esiri, M. M., Murray, L. S., Dewar, D., Love, S., Moss, T., and Griffin, W. S. (2000). Association of interleukin-1 gene polymorphisms with Alzheimer’s disease. Ann. Neurol., 47 (3), 365–368. Nishimura, M., Sakamoto, T., Kaji, R., and Kawakami, H. (2004). Influence of polymorphisms in the genes for cytokines and glutathione S-transferase omega on sporadic Alzheimer’s disease. Neurosci. Lett., 368 (2), 140–143. O’Banion, M. K., Miller, J. C., Chang, J. W., Kaplan, M. D., and Coleman, P. D. (1996). Interleukin-1 beta induces prostaglandin G/H synthase-2 (cyclooxygenase-2) in primary murine astrocyte cultures. J. Neurochem., 66 (6), 2532–2540. O’Connor, J. J., and Coogan, A. N. (1999). Action of the pro-inflammatory cytokine IL-1β on central synaptic transmission. Exp. Physiol., 84, 601–614. O’Connor, K. A., Johnson, J. D., Hansen, M. K., Wieseler–Frank, J. L., Maksimova, E., Watkins, L. R., and Maier, S. F. (2003). Peripheral and central proinflammatory cytokine response to a severe acute stressor. Brain Res., 991, 123–132. O’Donnell, E., Vereker, E., and Lynch, M. A. (2000). Age-related impairment in LTP is accompanied by enhanced activity of stress-activated protein kinases: analysis of underlying mechanisms. Eur. J. Neurosci., 12 (1), 345–352. Ohno, M., Yamamoto, T., and Watanabe, S. (1992). Effects of intrahippocampal injections of N-methyl-D-aspartate receptor antagonists and scopolamine on working and reference memory assessed in rats by a three-panel runway task. J. Pharmacol. Exp. Ther., 263 (3), 943–950. Oitzl, M. S., van Oers, H., Schobitz, B., and de Kloet, E. R. (1993). Interleukin-1β, but not interleukin-6, impairs spatial navigation learning. Brain Res., 613, 160–163. Packard, M. G., and Knowlton, B. J. (2002). Learning and memory functions of the basal ganglia. Annu. Rev. Neurosci., 25, 563–593. Palin, K., Bluthe, R. M., Verrier, D., Tridon, V., Dantzer, R., and Lestage, J. (2004). Interleukin-1beta mediates the memory impairment associated with a delayed type hypersensitivity response to Bacillus Calmette-Guerin in the rat hippocampus. Brain Behav. Immun., 18 (3), 223–230. Paolisso, G., Rizzo, M. R., Mazziotti, G., Tagliamonte, M. R., Gambardella, A., Rotondi, M., Carella, C., Giugliano, D., Varricchio, M., and D’Onofrio, F. (1998). Advancing age and insulin resistance: role of plasma tumor necrosis factor-alpha. Am. J. Physiol., 275 (2 Pt, 1), E294–E299. Papassotiropoulos, A., Bagli, M., Jessen, F., Bayer, T. A., Maier, W., Rao, M. L., and Heun, R. (1999). A genetic variation of the inflammatory cytokine interleukin-6 delays the initial onset and reduces the risk for sporadic Alzheimer’s disease. Ann. Neurol., 45 (5), 666–668. Parnet, P., Kelley, K. W., Bluthe, R. M., and Dantzer, R. (2002). Expression and regulation of interleukin-1 receptors in the brain. Role in cytokines-induced sickness behavior. J. Neuroimmunol., 125 (1–2), 5–14.
16. The Role of Pro-inflammatory Cytokines in Memory Processes and Neural Plasticity Perry, R. T., Collins, J. S., Harrell, L. E., Acton, R. T., and Go, R. C. (2001). Investigation of association of 13 polymorphisms in eight genes in southeastern African American Alzheimer disease patients as compared to age-matched controls. Am. J. Med. Genet., 105 (4), 332–342. Perry, V. H., Newman, T. A., and Cunningham, C. (2003). The impact of systemic infection on the progression of neurodegenerative disease. Nat. Rev. Neurosci., 4 (2), 103–112. Peterson, P. K., Chao, C. C., Carson, P., Hu, S., Nichol, K., and Janoff, E. N. (1994). Levels of tumor necrosis factor alpha, interleukin 6, interleukin 10, and transforming growth factor beta are normal in the serum of the healthy elderly. Clin. Infect. Dis., 19 (6), 1158–1159. Pfeffer, K., Matsuyama, T., Kundig, T. M., Wakeham, A., Kishihara, K., Shahinian, A., Wiegmann, K., Ohashi, P. S., Kronke, M., and Mak, T. W. (1993). Mice deficient for the 55kd tumor necrosis factor receptor are resistant to endotoxic shock yet succumb to L. monocytogenes infection. Cell, 73, 457–467. Pickering, M., Cumiskey, D., and O’Connor, J. J. (2005). Actions of TNF-{alpha} on glutamatergic synaptic transmission in the central nervous system. Exp Physiol., 90 (5), 663–670. Pirskanen, M., Hiltunen, M., Mannermaa, A., Iivonen, S., Helisalmi, S., Lehtovirta, M., Koivisto, A. M., Laakso, M., Soininen, H., and Alafuzoff, I. (2002). Interleukin 1 alpha gene polymorphism as a susceptibility factor in Alzheimer’s disease and its influence on the extent of histopathological hallmark lesions of Alzheimer’s disease. Dement. Geriatr. Cogn. Disord., 14 (3), 123–127. Pirttila, T., Mehta, P. D., Frey, H., and Wisniewski, H. M. (1994). α1–antichymotrypsin and IL-1β are not increased in CSF or serum in Alzheimer’s disease. Neurobiol. Aging, 15, 313–317. Pociot, F., Molvig, J., Wogensen, L., Worsaae, H., and Nerup, J. (1992). A TaqI polymorphism in the human interleukin-1 beta (IL-1 beta) gene correlates with IL-1 beta secretion in vitro. Eur. J. Clin. Invest., 22 (6), 396–402. Pola, R., Flex, A., Gaetani, E., Lago, A. D., Gerardino, L., Pola, P., and Bernabei, R. (2002). The −174 G/C polymorphism of the interleukin-6 gene promoter is associated with Alzheimer’s disease in an Italian population. Neuroreport, 13 (13), 1645–1647. Pollak, Y., Gilboa, A., Ben-Menachem, O., Ben-Hur, T., Soreq, H., and Yirmiya, R. (2005). Acetylcholinesterase inhibitors reduce brain and blood interleukin-1beta production. Ann. Neurol., 57 (5), 741–745. Pousset, F. (1994). Developmental expression of cytokine genes in the cortex and hippocampus of the rat central nervous system. Brain Res. Dev. Brain Res., 81 (1), 143–146. Prechel, M. M., Halbur, L., Devata, S., Vaidya, A. M., and Young, M. R. (1996). Increased interleukin-6 production by cerebral cortical tissue of adult versus young mice. Mech. Aging Dev., 92 (2– 3), 185–194. Probert, L., Akassoglou, K., Kassiotis, G., Pasparakis, M., Alexopoulou, L., and Kollias, G. (1997). TNF-alpha transgenic and knockout models of CNS inflammation and degeneration. J. Neuroimmunol., 72 (2), 137–141. Probert, L., Akassoglou, K., Pasparakis, M., Kontogeorgos, G., and Kollias, G. (1995). Spontaneous inflammatory demyelinating disease in transgenic mice showing central nervous systemspecific expression of tumor necrosis factor alpha. Proc. Natl. Acad. Sci. U.S.A., 92 (24), 11294–11298. Pugh, C. R., Fleshner, M., Watkins, L. R., Maier, S. F., and Rudy, J. W. (2001). The immune system and memory consolidation: a role for the cytokine IL-1β. Neurosci. Biobehav. Rev., 25, 29–41. Pugh, C. R., Johnson, J. D., Martin, D., Rudy, J. W., Maier, S. F., and Watkins, L. R. (2000). Human immunodeficiency virus-1 coat protein gp120 impairs contextual fear conditioning: a potential
375
role in AIDS related learning and memory impairments. Brain Res., 861 (1), 8–15. Pugh, C. R., Kumagawa, K., Fleshner, M., Watkins L. R., Maier S. F., and Rudy, J. W. (1998). Selective effects of peripheral lipopolysaccharide administration on contextual and auditory-cue fear conditioning. Brain Behav. Immun., 12, 212–229. Pugh, C. R., Nguyen, K. T., Gonyea, J. L., Fleshner, M., Watkins, L. R., Maier, S. F., and Rudy, J. W. (1999). Role of interleukin-1 beta in impairment of contextual fear conditioning caused by social isolation. Behav. Brain Res., 106 (1–2), 109–118. Rainero, I., Bo, M., Ferrero, M., Valfre, W., Vaula, G., and Pinessi, L. (2004). Association between the interleukin-1alpha gene and Alzheimer’s disease: a meta-analysis. Neurobiol. Aging, 25 (10), 1293–1298. Rakic, P. (2002). Neurogenesis in the adult primate neocortex: an evaluation of the evidence. Nat. Rev. Neurosci., 3 (1), 65–71. Rawlins, J. N., Feldon, J., and Butt, S. (1985). The effects of delaying reward on choice preference in rats with hippocampal or selective septal lesions. Behav. Brain Res., 15 (3), 191–203. Rebeck, G. W. (2000). Confirmation of the genetic association of interleukin-1A with early onset sporadic Alzheimer’s disease. Neurosci. Lett., 293 (1), 75–77. Reichenberg, A., Yirmiya, R., Schuld, A., Kraus, T., Haack, M., and Pollmacher, T. (2001). Endotoxin-induced emotional and cognitive disturbances in healthy volunteers are associated with increased plasma levels of cytokines and cortisol. Arch. Gen. Psychiatry, 58, 445–452. Rivest, S. (2001). How circulating cytokines trigger the neural circuits that control the hypothalamic-pituitary-adrenal axis. Psychoneuroendocrinology, 26 (8), 761–788. Rosenmann, H., Meiner, Z., Dresner-Pollak, R., Kahana, E., Aladjem, Z., Grenader, T., Wertman, E., and Abramsky, O. (2004). Lack of association of interleukin-1beta polymorphism with Alzheimer’s disease in the Jewish population. Neurosci. Lett., 363 (2), 131–133. Ross, F. M., Allan, S. M., Rothwell, N. J., and Verkhratsky, A. (2003). A dual role for interleukin-1 in LTP in mouse hippocampal slices. J. Neuroimmunol., 144 (1–2), 61–67. Rothwell, N. J. (2003). Interleukin-1 and neuronal injury: mechanisms, modification, and therapeutic potential. Brain Behav. Immun., 17 (3), 152–157. Rothwell, N. J., and Luheshi, G. N. (2000). Interleukin 1 in the brain: biology, pathology and therapeutic target. Trends Neurosci., 23 (12), 618–625. Rothwell, N. J., Luheshi, G., and Toulmond, S. (1996). Cytokines and their receptors in the central nervous system: physiology, pharmacology, and pathology. Pharmacol. Ther., 69 (2), 85–95. Roubenoff, R., Harris, T. B., Abad, L. W., Wilson, P. W., Dallal, G. E., and Dinarello, C. A. (1998). Monocyte cytokine production in an elderly population: effect of age and inflammation. J. Gerontol. A Biol. Sci. Med. Sci., 53 (1), M20–M26. Sagvolden, T., and Holth, P. (1986). Slower acquisition of positively reinforced behavior following medial, but not dorsolateral, septal lesions in rats. Behav. Neurosci., 100 (3), 330–336. Sapolsky, R., Rivier, C., Yamamoto, G., Plotsky, P., and Vale, W. (1987). Interleukin-1 stimulates the secretion of hypothalamic corticotropin-releasing factor. Science, 238, 522–524. Scherbel, U., Raghupathi, R., Nakamura, M., Saatman, K. E., Trojanowski, J. Q., Neugebauer, E., Marino, M. W., and McIntosh, T. K. (1999). Differential acute and chronic responses of tumor necrosis factor-deficient mice to experimental brain injury. Proc. Natl. Acad. Sci. U.S.A., 96 (15), 8721–8726. Schneider, H., Pitossi, F., Balschun, D., Wagner, A., del Rey, A., and Besedovsky, H. O. (1998). A neuromodulatory role of interleukin1 in the hippocampus. Proc. Natl. Acad. Sci. U.S.A., 95, 7778–7783.
376
II. Immune System Effects on Neural and Endocrine Processes and Behavior
Schobitz, B., de Kloet, E. R., Sutanto, W., and Holsboer, F. (1993). Cellular localization of interleukin 6 mRNA and interleukin 6 receptor mRNA in rat brain. Eur. J. Neurosci., 5 (11), 1426–1435. Schobitz, B., Voorhuis, D. A., and de Kloet, E. R. (1992). Localization of interleukin 6 mRNA and interleukin 6 receptor mRNA in rat brain. Neurosci. Lett., 136 (2), 189–192. Schulte-Herbruggen, O., Nassenstein, C., Lommatzsch, M., Quarcoo, D., Renz, H., and Braun, A. (2005). Tumor necrosis factor-alpha and interleukin-6 regulate secretion of brain-derived neurotrophic factor in human monocytes. J. Neuroimmunol., 160 (1–2), 204–209. Sciacca, F. L., Ferri, C., Licastro, F., Veglia, F., Biunno, I., Gavazzi, A., Calabrese, E., Martinelli Boneschi, F., Sorbi, S., Mariani, C., Franceschi, M., and Grimaldi, L. M. (2003). Interleukin-1B polymorphism is associated with age at onset of Alzheimer’s disease. Neurobiol. Aging, 24 (7), 927–931. Seripa, D., Matera, M. G., Dal Forno, G., Gravina, C., Masullo, C., Daniele, A., Binetti, G., Bonvicini, C., Squitti, R., Palermo, M. T., Davis, D. G., Antuono, P., Wekstein, D. R., Dobrina, A., Gennarelli, M., and Fazio, V. M. (2005). Genotypes and haplotypes in the IL-1 gene cluster: analysis of two genetically and diagnostically distinct groups of Alzheimer patients. Neurobiol. Aging, 26 (4), 455–464. Shapira-Lichter, I., Beilin, B., Bessler, H., Ailon, K., Ballas, M., Shavit, Y., Seror, D., Grinevich, G., Posner, E., Soreq, H., and Yirmiya, R. (2004). Inflammatory cytokines and cholinergic signaling modulate stress-induced alterations in mood and cognition. Neural Plast., 12, 55–56. Sharkey, A. M., Dellow, K., Blayney, M., Macnamee, M., CharnockJones, S., and Smith, S. K. (1995). Stage-specific expression of cytokine and receptor messenger ribonucleic acids in human preimplantation embryos. Biol. Reprod., 53 (4), 974–981. Sharman, K. G., Sharman, E. H., Yang, E., and Bondy, S. C. (2002). Dietary melatonin selectively reverses age-related changes in cortical cytokine mRNA levels, and their responses to an inflammatory stimulus. Neurobiol. Aging, 23 (4), 633–638. Shavit, Y., Wolf, G., Goshen, I., Livshits, D., and Yirmiya, R. (2005). Interleukin-1 antagonizes morphine analgesia and underlies morphine tolerance. Pain, 115 (1–2), 50–59. Shaw, K. N., Commins, S., and O’Mara, S. M. (2003). Deficits in spatial learning and synaptic plasticity induced by the rapid and competitive broad-spectrum cyclooxygenase inhibitor ibuprofen are reversed by increasing endogenous brain-derived neurotrophic factor. Eur. J. Neurosci., 17 (11), 2438–2446. Shaw, K. N., Commins, S., and O’Mara, S. M. (2005). Cyclooxygenase inhibition attenuates endotoxin-induced spatial learning deficits, but not an endotoxin-induced blockade of long-term potentiation. Brain Res., 1038 (2), 231–237. Shibata, N., Ohnuma, T., Takahashi, T., Baba, H., Ishizuka, T., Ohtsuka, M., Ueki, A., Nagao, M., and Arai, H. (2002). Effect of IL-6 polymorphism on risk of Alzheimer disease: genotypephenotype association study in Japanese cases. Am. J. Med. Genet., 114 (4), 436–439. Shibata, N., Ohnuma, T., Takahashi, T., Matsubara, Y., Ueki, A., Nagao, M., and Arai, H. (2004). No genetic association between tumour necrosis factor receptor II, 196R polymorphism and Japanese sporadic Alzheimer’s disease. Psychiatr. Genet., 14 (1), 53–55. Shinozawa, Y., Matsumoto, T., Uchida, K., Tsujimoto, S., Iwakura, Y., and Yamaguchi, K. (2002). Role of interferon-gamma in inflammatory responses in murine respiratory infection with Legionella pneumophila. J. Med. Microbiol., 51 (3), 225–230. Shintani, F., Nakaki, T., Kanba, S., Sato, K., Yagi, G., Shiozawa, M., Aiso, S., Kato, R., and Asai, M. (1995). Involvement of interleukin-1 in immobilization stress-induced increase in plasma
adrenocorticotropic hormone and in release of hypothalamic monoamines in the rat. J. Neurosci., 15 (3), 1961–1970. Smith, D. E., Renshaw, B. R., Ketchem, R. R., Kubin, M., Garka, K. E., and Sims, J. E. (2000). Four new members expand the interleukin-1 superfamily. J. Biol. Chem., 275 (2), 1169–1175. Smith, W. L., and Langenbach, R. (2001). Why there are two cyclooxygenase isozymes. J. Clin. Invest., 107 (12), 1491–1495. Song, C., and Horrobin, D. (2004). Omega-3 fatty acid ethyleicosapentaenoate, but not soybean oil, attenuates memory impairment induced by central IL-1beta administration. J. Lipid. Res., 45 (6), 1112–1121. Song, C., Phillips, A. G., and Leonard, B. (2003). Interleukin 1 beta enhances conditioned fear memory in rats: possible involvement of glucocorticoids. Eur. J. Neurosci., 18, 1739–1743. Song, C., Phillips, A. G., Leonard, B. E., and Horrobin, D. F. (2004). Ethyl-eicosapentaenoic acid ingestion prevents corticosteronemediated memory impairment induced by central administration of interleukin-1beta in rats. Mol. Psychiatry, 9 (6), 630–638. Sparkman, N. L., Kohman, R. A., Garcia, A. K., and Boehm, G. W. (2005). Peripheral lipopolysaccharide administration impairs two-way active avoidance conditioning in C57BL/6J mice. Physiol. Behav., 85 (3), 278–288. Squire, L. R. (1993). The hippocampus and spatial memory. Trends Neurosci., 16 (2), 56–57. Squire, L. R., Stark, C. E., and Clark, R. E. (2004). The medial temporal lobe. Annu. Rev. Neurosci., 27, 279–306. Steiner, P., Pfeilschifter, J., Boeckh, C., Radeke, H., and Otten, U. (1991). Interleukin-1 beta and tumor necrosis factor-alpha synergistically stimulate nerve growth factor synthesis in rat mesangial cells. Am. J. Physiol., 261, F792–F798. Stellwagen, D., Beattie, E. C., Seo, J. Y., and Malenka, R. C. (2005). Differential regulation of AMPA receptor and GABA receptor trafficking by tumor necrosis factor-alpha. J. Neurosci., 25 (12), 3219–3228. Suzuki, E., Shintani, F, Kanba, S., Asai, M., and Nakaki, T. (1997). Immobilization stress increases mRNA levels of interleukin-1 receptor antagonist in various rat brain regions. Cell. Mol. Neurobiol., 17 (5), 557–561. Takeda, K., Kaisho, T., and Akira, S. (2003). Toll-like receptors. Annu. Rev. Immunol., 21, 335–376. Tancredi, V., D’Antuono, M., Café, C., Giovedi, S., Bue, M. C., D’Arcangelo, G., Onofri, F., and Benfenati, F. (2000). The inhibitory effects of interleukin-6 on synaptic plasticity in the rat hippocampus are associated with an inhibition of mitogen-activated protein kinase ERK. J. Neurochem., 75 (2), 634–643. Tancredi, V., D’Arcangelo, G., Grassi, F., Tarroni, P., Palmieri, G., Santoni, A., and Eusebi, F. (1992). Tumor necrosis factor alters synaptic transmission in rat hippocampal slices. Neurosci. Lett., 146 (2), 176–178. Tarkowski, E., Andreasen, N., Tarkowski, A., and Blennow, K. (2003a). Intrathecal inflammation precedes development of Alzheimer’s disease. J. Neurol. Neurosurg. Psychiatry, 74 (9), 1200–1205. Tarkowski, E., Blennow, K., Wallin, A., and Tarkowski, A. (1999). Intracerebral production of tumor necrosis factor-alpha, a local neuroprotective agent, in Alzheimer disease and vascular dementia. Clin. Immunol., 19 (4), 223–230. Tarkowski, E., Liljeroth, A. M., Minthon, L., Tarkowski, A., Wallin, A., and Blennow, K. (2003b). Cerebral pattern of pro- and antiinflammatory cytokines in dementias. Brain Res. Bull., 61 (3), 255–260. Tarkowski, E., Liljeroth, A. M., Nilsson, A., Minthon, L., and Blennow, K. (2001). Decreased levels of intrathecal interleukin 1 receptor antagonist in Alzheimer’s disease. Dement. Geriatr. Cogn. Disord., 12 (5), 314–317.
16. The Role of Pro-inflammatory Cytokines in Memory Processes and Neural Plasticity Tarkowski, E., Liljeroth, A. M., Nilsson, A., Ricksten, A., Davidsson, P., Minthon, L., and Blennow, K. (2000). TNF gene polymorphism and its relation to intracerebral production of TNFalpha and TNFbeta in AD. Neurology, 54 (11), 2077–2081. Tartaglia, L. A., and Goeddel, D. V. (1992). Two TNF receptors. Immunol. Today, 13 (5), 151–153. Teather, L. A., Packard, M. G., and Bazan, N. G. (2002) Post-training cyclooxygenase-2 (COX-2) inhibition impairs memory consolidation. Learn. Mem., 9 (1), 41–47. Terreni, L., Fogliarino, S., Quadri, P., Ruggieri, R. M., Piccoli, F., Tettamanti, M., Lucca, U., and Forloni, G. (2003). Tumor necrosis factor alpha polymorphism C–850T is not associated with Alzheimer’s disease and vascular dementia in an Italian population. Neurosci. Lett., 344 (2), 135–137. Tha, K. K., Okuma, Y., Miyazaki, H., Murayama, T., Uehara, T., Hatakeyama, R., Hayashi, Y., and Nomura, Y. (2000). Changes in expressions of proinflammatory cytokines IL-1beta, TNFalpha and IL-6 in the brain of senescence accelerated mouse (SAM) P8. Brain Res., 885 (1), 25–31. Thompson, R. F. (2005). In search of memory traces. Annu. Rev. Psychol., 56, 1–23. Tsai, S. J., Liu, H. C., Liu, T. Y., Wang, K. Y., and Hong, C. J. (2003). Lack of association between the interleukin-1alpha gene C(−889)T polymorphism and Alzheimer’s disease in a Chinese population. Neurosci. Lett., 343 (2), 93–96. Turnbull, A. V., and Rivier, C. L. (1999). Regulation of the hypothalamic-pituitary-adrenal axis by cytokines: actions and mechanisms of action. Physiol. Rev., 79, 1–71. Vallieres, L., Campbell, I. L., Gage, F. H., and Sawchenko, P. E. (2002). Reduced hippocampal neurogenesis in adult transgenic mice with chronic astrocytic production of interleukin-6. J. Neurosci., 22 (2), 486–492. van Exel, E., de Craen, A. J., Remarque, E. J., Gussekloo, J., Houx, P., Bootsma-van der Wiel, A., Frolich, M., Macfarlane, P. W., Blauw, G. J., and Westendorp, R. G. (2003). Interaction of atherosclerosis and inflammation in elderly subjects with poor cognitive function. Neurology, 61 (12), 1695–1701. Vereker, E., O’Donnell, E., and Lynch, M. A. (2000). The inhibitory effect of interleukin-1beta on long-term potentiation is coupled with increased activity of stress-activated protein kinases. J. Neurosci., 20 (18), 6811–6819. Vereker, E., O’Donnell, E., Lynch, A., Kelly, A., Nolan, Y., and Lynch, M. A. (2001). Evidence that interleukin-1beta and reactive oxygen species production play a pivotal role in stress-induced impairment of LTP in the rat dentate gyrus. Eur. J. Neurosci., 14 (11), 1809–1819. Vitkovic, L., Bockaert, J., and Jacque, C. (2000). “Inflammatory” cytokines: neuromodulators in normal brain? J. Neurochem., 74 (2), 457–471. Wajant, H., Pfizenmaier, K., and Scheurich, P. (2003). Tumor necrosis factor signaling. Cell Death Differ., 10 (1), 45–65. Wallenstein, G. V., Eichenbaum, H., and Hasselmo, M. E. (1998). The hippocampus as an associator of discontiguous events. Trends Neurosci., 21 (8), 317–323. Wang, W. F., Liao, Y. C., Wu, S. L., Tsai, F. J., Lee, C. C., and Hua, C. S. (2005). Association of interleukin-I beta and receptor antagonist gene polymorphisms with late onset Alzheimer’s disease in Taiwan Chinese. Eur. J. Neurol., 12 (8), 609–613. Watkins, L. R., Maier, S. F., and Goehler, L. E. (1995). Cytokine-tobrain communication: a review & analysis of alternative mechanisms. Life Sci., 57 (11), 1011–1026.
377
Weaver, J. D., Huang, M. H., Albert, M., Harris, T., Rowe, J. W., and Seeman, T. E. (2002). Interleukin-6 and risk of cognitive decline: MacArthur studies of successful aging. Neurology, 59 (3), 371–378. Webster’s encyclopedic unabridged dictionary of the English language. (1996). New York: Gramercy Books. Wei, J., Xu, H., Davies, J. L., and Hemmings, G. P. (1992). Increase of plasma IL-6 concentration with age in healthy subjects. Life Sci., 51 (25), 1953–1956. Weidenfeld, J., Crumeyrolle-Arias, M., and Haour, F. (1995). Effect of bacterial endotoxin and interleukin-1 on prostaglandin biosynthesis by the hippocampus of mouse brain: role of interleukin-1 receptors and glucocorticoids. Neuroendocrinology, 62 (1), 39–46. Wilson, A. G., Symons, J. A., McDowell, T. L., McDevitt, H. O., and Duff, G. W. (1997). Effects of a polymorphism in the human tumor necrosis factor alpha promoter on transcriptional activation. Proc. Natl. Acad. Sci. U.S.A., 94 (7), 3195–3199. Wolf, G., Gabay, E., Tal, M., Yirmiya, R., and Shavit, Y. (2006). Genetic impairment of interleukin-1 (IL-1) signaling attenuates neuropathic pain, autotomy, and spontaneous ectopic neuronal activity. Pain, 120 (3), 315–324. Wolf, G., Yirmiya, R., Goshen, I., Iverfeldt, K., Holmlund, L., Takeda, K., and Shavit, Y. (2003). Impairment of interleukin-1 (IL-1) signaling reduces basal pain sensitivity in mice: genetic, pharmacological and developmental aspects. Pain, 104 (3), 471–480. Yaffe K., Lindquist, K., Penninx, B. W., Simonsick, E. M., Pahor, M., Kritchevsky, S., Launer, L., Kuller, L., Rubin, S., and Harris, T. (2003). Inflammatory markers and cognition in wellfunctioning African–American and white elders. Neurology, 61, 76–80. Yamada, K., Iida, R., Miyamoto, Y., Saito, K., Sekikawa, K., Seishima, M., and Nabeshima, T. (2000). Neurobehavioral alterations in mice with a targeted deletion of the tumor necrosis factor-alpha gene: implications for emotional behavior. J. Neuroimmunol., 111 (1–2), 131–138. Ye, S. M., and Johnson, R. W. (1999). Increased interleukin-6 expression by microglia from brain of aged mice. J. Neuroimmunol., 93 (1–2), 139–148. Ye, S. M., and Johnson, R. W. (2001). Regulation of interleukin-6 gene expression in brain of aged mice by nuclear factor kappaB. J. Neuroimmunol., 117 (1–2), 87–96. Yirmiya, R. (1997). Behavioral and psychological effects of immune activation: implications for ‘depression due to a general medical condition.’ Curr. Opin. Psychiatry, 10, 470–476. Yirmiya, R., Weidenfeld, J., Pollak, Y., Morag, M., Morag, A., Avitsur, R., Barak, O., Reichenberg, A., Cohen, E., Shavit, Y., and Ovadia, H. (1999). Cytokines, ‘depression due to a general medical condition’ and antidepressants drugs. Adv. Exp. Med. Biol., 461, 283–316. Yirmiya, R., Winocur, G., and Goshen, I. (2002). Brain interleukin-1 (IL-1) is involved in spatial memory and passive avoidance conditioning. Neurobiol. Learn. Mem., 78, 379–389. Zhang, Y., Hayes, A., Pritchard, A., Thaker, U., Haque, M. S., Lemmon, H., Harris, J., Cumming, A., Lambert, J. C., ChartierHarlin, M. C., St Clair, D., Iwatsubo, T., Mann, D. M., and Lendon, C. L. (2004). Interleukin-6 promoter polymorphism: risk and pathology of Alzheimer’s disease. Neurosci. Lett., 362 (2), 99–102. Zola-Morgan, S., and Squire, L. R. (1993). Neuroanatomy of memory. Annu. Rev. Neurosci., 16, 547–563.
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17 Aging, Neuroinflammation, and Behavior RODNEY W. JOHNSON AND JONATHAN P. GODBOUT
neuroinflammatory response is accompanied by severe, longer-lasting behavioral deficits and may cause acute cognitive disorders that are often reported in elderly patients with peripheral infections. This chapter will provide a brief background on how the peripheral innate immune system communicates with the brain, discuss evidence that suggests the emergence of a neuroinflammatory state during normal aging, and present important new findings that suggest a peripheral infection induces an exaggerated neuroinflammatory response and severe behavioral deficits in the aged.
I. INTRODUCTION 379 II. BRAIN, MEET IMMUNE SYSTEM—IMMUNE SYSTEM, MEET BRAIN 380 III. IS NORMAL AGING ASSOCIATED WITH NEUROINFLAMMATION? 382 IV. ARE NEUROINFLAMMATION AND SICKNESS EXACERBATED IN THE AGED? 384 V. IF NEUROINFLAMMATION IS INCREASED, WHAT DOES IT MEAN? 385 VI. CODA 386
ABSTRACT Brain microglial cells are ordinarily quiescent but when stimulated can transition to a “primed” or activated state. Both primed and activated microglia are deramified and express markers that suggest activation, but only activated microglia produce appreciable levels of inflammatory cytokines. Primed microglia, however, are hyper-responsive to a secondary stimulus from the peripheral innate immune system and thus can produce an exaggerated cytokine response when provoked. The potential for primed microglia to mount an exaggerated response is important to psychoneuroimmunology because inflammatory cytokines mediate the sickness behavior syndrome and are involved in chronic neurodegenerative diseases. One physiological event that may prime microglial cells for an exaggerated response is aging. Signs of neuroinflammation emerge in healthy aged subjects, and new findings suggest that aged individuals suffer an exaggerated neuroinflammatory response when the peripheral innate immune system is activated. The exaggerated PSYCHONEUROIMMUNOLOGY, 4E VOLUME I
I. INTRODUCTION Aging is a process characterized by deterioration of a mature organism in the absence of detectable disease. The deterioration is time dependent but occurs at different rates in different individuals, so chronological age is not the same as biological age or senescence (Kirkwood et al., 2005). Nonetheless, aging gradually reduces an organism’s ability to cope with intrinsic and extrinsic factors that cause stress, and thus it increases the probability of disease and death. Because worldwide the segment of the population 60 years old and older is rapidly growing and is anticipated to number 2 billion by year 2050, more people than ever will encounter age-related physical and neurobehavioral deficits. Age-related deterioration of the brain produces a variety of behavioral deficits that are unrelated to disease. Cognitive aging, e.g., is a term used to describe
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a pattern of age-related impairments in cognitive functions including fluid reasoning, mental speed, memory, and spatial ability. Other changes such as decreased motivation for food and deficits in motor coordination are also common. Behavioral indications of brain aging are evident by middle age in clinically healthy individuals, so deterioration of the brain precedes the acceleration in mortality rate that is typical in old age. Individual differences in cognitive ability in late life are determined by the baseline of cognitive ability (e.g., intelligence in childhood) and the rate of cognitive aging (Whalley et al., 2004). The latter of these two is of particular interest to the interdisciplinary field of psychoneuroimmunology because the rate of brain aging is substantially influenced by environmental factors (e.g., chronic psychological stress and pathogenic agents) that elicit intrinsic responses that over time impair neural health (Kiecolt-Glaser et al., 2002; Porter and Landfield, 1998; Verkhratsky et al., 2004). One of the very important intrinsic factors that recently emerged as a leading detractor from successful aging is inflammation in the periphery and brain (Finch and Crimmins, 2004; Godbout and Johnson, 2004; Wilson et al., 2002). Thus, interest in the communication pathways between the immune system and brain and how aging influences these pathways has reached unprecedented heights in recent years. Individual differences not withstanding, the immune system deteriorates with age as well, so the elderly are more susceptible to peripheral infection (Armstrong et al., 1999; Castle, 2000; Pinner et al., 1996). This age-associated impairment of immune function is due to weakened defenses by cells involved in innate immunity (Plowden et al., 2004) and a reduction in naïve T-cells, which are critical for mounting both cell-mediated (T-cell) and humoral-mediated (Bcell) adaptive immune responses to novel antigens (Ginaldi et al., 2001; Ginaldi et al., 2005). Ageassociated changes in a number of key cytokines have been observed. For instance, lymphocytes taken from aged individuals secrete less interleukin (IL)-2, but more IL-4 and IL-10 in response to concanavalin A stimulation, indicating an intrinsic polarization of cells from aged individuals towards type-2 cytokine production, at the expense of type-1 cytokine production (Gorczynski et al., 1997). Interleukin-6 is another cytokine whose secretion changes with age, but what makes it unique is the rather dramatic age-related increase in spontaneous secretion. Lymphoid cells isolated from old but otherwise healthy humans and mice spontaneously secrete high levels of IL-6. Consequently, a positive correlation between age and plasma IL-6 concentration has been reported (Daynes et al., 1993; Wei et al., 1992).
In addition to inducing proliferation of activated B-cells, IL-6 is best known for inducing hepatic acute phase protein synthesis and causing metabolic changes that lead to frailty (Ershler and Keller, 2000). Given the cytokines’ metabolic effects and the once-held notion that the brain is an immunoprivileged site free of influence by the immune system, little consideration was given to the idea that an age-related change in a peripheral cytokine might either directly or indirectly hold influence over brain aging. However, dissecting the communication pathways connecting the peripheral immune system to the brain has led to new views on how peripheral inflammatory events influence brain function. Indeed, elevated serum levels of IL-6 were recently determined to be correlated to deficits in cognitive abilities (Weaver et al., 2002). Thus, how IL-6 and other inflammatory cytokines impinge upon the brain to affect brain aging is an important question. The purpose of this chapter is to provide a brief background on how the peripheral innate immune system communicates with the brain, discuss evidence that suggests the emergence of a neuroinflammatory state during normal aging, and present important new findings that suggest a peripheral infection induces an exaggerated neuroinflammatory response and severe behavioral deficits in the aged.
II. BRAIN, MEET IMMUNE SYSTEM— IMMUNE SYSTEM, MEET BRAIN Several working hypotheses on brain aging and inflammation are strongly influenced by research that has dissected the communication pathways that allow the immune system to induce the sickness behavior syndrome (e.g., anorexia, hypersomnia, lethargy, depression) during acute peripheral infection. Some of the first evidence that a cytokine caused sickness behavior came from studies of slow-wave sleep in rabbits (Krueger et al., 1984). Peritoneal macrophages from rabbits were stimulated in vitro with a muramyl peptide that had been shown to stimulate macrophages to secrete endogenous pyrogen—a protein previously shown to cause fever (Atkins, 1960) and activate the hypothalamic-pituitary-adrenal axis (Besedovsky et al., 1981). The cell-free supernatant was collected and later injected into rabbits. Animals injected with supernatant from stimulated macrophages showed an increase in slow-wave sleep compared to those receiving supernatant from unstimulated macrophages. The same behavior could be induced by injecting the supernatant into a lateral cerebral ventricle, indicating it acted at a central site. Thus, a protein (i.e., endogenous pyrogen) secreted by acti-
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vated macrophages that acted in the brain was responsible for the change in behavior. Endogenous pyrogen was later determined to be identical to another protein under investigation—IL-1β. It is now clear that mononuclear phagocytic cells secrete several other behaviorally active cytokines, including tumor necrosis factor α (TNF-α) and IL-6. Inflammatory cytokines appear necessary for the immune system to communicate with the brain (Figure 1). As a result of a mutation in a single gene, a certain strain of mice (C3H/HeJ) is resistant to the behavioral effects of lipopolysaccharide (LPS). When injected with LPS, this strain of mice does not become overtly ill like normal mice do (Johnson et al., 1997; Segreti et al., 1997). The mutation is in the Toll-like receptor 4 gene (Hoshino et al., 1999), a gene which encodes an extracellular receptor expressed on the surface of mononuclear phagocytic cells that specifically binds LPS to activate an innate immune response. Therefore, this mutation essentially prevents the animal’s mononuclear phagocytic cells from producing cytokines in response to LPS, so there is a complete breakdown in communication between the immune system and brain. The brain of these mice recognizes cytokines because if injected with recombinant IL-1β, they respond normally by reducing food intake, losing weight, and decreasing social behavior (Johnson et al., 1997).
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How do peripheral inflammatory cytokines instigate communication between the immune system and brain during infection? Although there is clear evidence that inflammatory cytokines (e.g., IL-1β, IL-6, and TNF-α) can be actively transported from the blood into the brain (Banks and Kastin, 1991; Banks et al., 1991; Banks et al., 1994; Banks et al., 1995; Gutierrez et al., 1993), peripheral cytokines need not enter the brain to elicit behavioral changes. It is now evident that inflammatory stimuli in the periphery (e.g., LPS and inflammatory cytokines) induce IL-1β, IL-6, and TNF-α in discrete brain areas of the mouse (Ban et al., 1992; Laye et al., 1994). For example, inflammatory stimuli in the periphery induce perivascular microglial cells to express cytokines (van Dam et al., 1992; van Dam et al., 1995). Furthermore, cytokines in the periphery can convey a message to the brain via the vagus nerve. After LPS challenge, dendritic cells and macrophages that are closely associated with the abdominal vagus have been shown to express IL-1β protein (Goehler et al., 1999). IL-1 binding sites have been identified in several regions of the vagus as well (Goehler et al., 1997). When activated by peripheral cytokines, the vagus, of course, can activate specific neural pathways that are involved in sickness behavior. However, activation of the vagus also appears to stimulate microglia in the brain to produce cytokines. If the vagus nerve is severed just below the diaphragm in rats, the
The strains are similar but C3H/HeJ mice have a mutated Toll-like receptor 4 (TLR4) gene. TLR4 on the surface of macrophages recognizes LPS and is involved in the innate immune response to Gram-negative bacteria.
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Macrophages of C3H/HeOuJ mice secrete inflammatory cytokines in response to LPS, but due to the mutation in the TLR4 gene macrophages of C3H/HeJ mice do not.
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C3H/HeOuJ mice show typical sickness behavior when challenged with LPS, but C3H/HeJ mice do not. If C3H/HeJ mice are administered recombinant IL-1β, they show typical sickness behavior, indicating inflammatory cytokines are needed for the immune system to convey a message to the brain.
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FIGURE 1 Overview of studies with C3H/HeJ mice, which show the importance of inflammatory cytokines for immune system–to–brain communication. Adapted from Segreti et al. (Segreti et al., 1997) and Johnson et al. (Johnson, 2002; Johnson et al., 1997).
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expression of cytokines in the brain and the sickness behavior that normally occurs after intraperitoneal injection of LPS or IL-1β can be inhibited (Bluthe et al., 1996a, b; Laye et al., 1995). Plasma levels of cytokines are elevated in LPS-injected vagotomized rats, indicating the neural signal is needed for the induction of sickness. The neural pathways activated in the brain by the vagus nerve for rapid immune-to-brain signaling have been described in some detail (Dantzer, 2001). These pathways appear to be responsible for activating the hypothalamic-pituitary-adrenal axis and depressing behavior in response to infection. Other mechanisms that involve induction of prostaglandin synthesis are also important for fever. Based on extensive mapping of the temporal and spatial expression of Fos (a marker for neural activity) and IL-1β, Konsman et al. (1999) proposed a slower immune-to-brain signaling mechanism based on volume transmission. In this method of immune-to-brain communication, production of IL-1β by the brain first occurs in the choroid plexus and circumventricular organs—brain areas devoid of an intact blood-brain barrier. The cytokines then slowly diffuse into the brain by volume transmission, along the way activating neurons and neural pathways relevant for expression of sickness behavior. This pathway may be more important for maintaining sickness behavior than inducing it. Regardless of the pathway(s) at work, it is evident that if inflammatory cytokines are increased in the periphery, they may be increased in the brain too.
III. IS NORMAL AGING ASSOCIATED WITH NEUROINFLAMMATION? Microglial cells are the most important cells of the innate immune system in the brain. Their phenotype is similar to macrophages; and like macrophages in the periphery, microglia in the brain serve as antigenpresenting cells and produce inflammatory cytokines. They are normally quiescent but are activated by factors such as brain trauma, ischemia, neurodegenerative disease, and infection. A critically important but less studied factor that may influence microglia is normal aging (Finch, 2003). In several age-sensitive areas of the hippocampal formation (dentate gyrus and CA1 region) of female mice, the number of microglia and astrocytes is increased about 20% (Mouton et al., 2002). Activated microglia express markers such as MHC class II antigens, which are increased in brains of aged but otherwise healthy humans, non-human primates, and rodents (Perry et al., 1993; Rogers et al., 1988; Sheffield and Berman, 1998; Streit and Sparks, 1997). Recently, morphological changes were charac-
terized in microglia from a healthy, cognitively normal (i.e., non-demented) elderly donor (Streit et al., 2004). Microglia in the aged brain had abnormalities in the cytoplasmic structure and were deramified, indicating a reactive state (i.e., primed but not activated). The morphological changes were distinct from those seen in neurodegenerative disease or brain trauma, where microglia are fully activated. The so-called “microglial dystrophy” has been interpreted to suggest microglial senescence. In aged brains dystrophic microglia were widespread and the number surpassed by nine-fold that seen in the young adult brain (Streit et al., 2004). Surprisingly, the change in microglial cells is reminiscent of the age-associated change in pyramidal neurons that was first reported 30 years ago (Scheibel et al., 1975). Thus, a change in microglial cells may affect neuronal morphology and ultimately function and cause cognitive impairment in the elderly. Very recently microglial senescence was proposed to result in functional defects that trigger an intracerebral inflammatory response that supports the development of age-associated neurodegenerative diseases such as Alzheimer’s disease (AD) (Blasko et al., 2004; Streit, 2004). In addition to signs of activated microglia, there also is good evidence that inflammatory cytokines are increased in brains of aged but otherwise healthy rodents. Much of this work has focused on IL-6, owing to the fact that it was the first inflammatory cytokine shown to be elevated in the periphery of healthy aged animals. For instance, the level of IL-6 in whole brain as well as in the hippocampus, cerebral cortex, and cerebellum was increased in aged mice compared to juvenile and adult mice (Ye and Johnson, 1999). Aging did not appear to increase IL-6 in the hypothalamus. Similarly, 10-month-old senescence-accelerated mice of the P8 strain—a murine model for accelerated aging—had increased IL-6 in the cerebral cortex and hippocampus compared to age-matched controls (Tha et al., 2000). Several studies indicate that the increased IL-6 in the aged brain is centrally produced and not simply a reflection of what is found in the peripheral circulation. Coronal sections of the cerebral cortex taken from aged rodents spontaneously secreted more IL-6 than sections taken from younger controls (Prechel et al., 1996; Ye and Johnson, 2001a). Furthermore, competitive quantitative RT-PCR showed a marked increase in steady-state IL-6 mRNA in whole brain of healthy aged mice compared to adults (Ye and Johnson, 2001b). Studies on glial cells cultured from aged mice also indicate an age-associated increase in IL-6 production. Ye and Johnson (1999) established glial cell cultures from neonate, adult, and aged mice that contained both astrocytes and microglia. The
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steady-state level of IL-6 mRNA and spontaneous secretion of IL-6 protein were higher in glial cells cultured from aged mice than in glia cultured from either adult or neonate mice (Ye and Johnson, 1999, 2001b). Two-color flow cytometric analysis of IL-6 and MAC-1 (a marker for microglia) staining showed an agerelated increase in IL-6–positive microglial cells (Ye and Johnson, 1999). Moreover, the IL-6 mean fluorescence intensity increased as a function of age, suggesting more IL-6 expression per cell. Brain endothelial cells, which form the blood-brain barrier, may also contribute IL-6 to the aged brain. Endothelial cells cultured from brains of very old rhesus monkeys spontaneously released more IL-6 than those isolated from adult and fetal/neonatal monkeys (Reyes et al., 1999). Collectively, these studies indicate that the transcription and expression of IL-6 is increased in the brain with age. The dysregulation of IL-6 secretion by microglia in the aged brain has been extended to include a description of how aging influences transcription factors that regulate the IL-6 gene. Interleukin-6 gene expression is regulated by a complex arrangement of several transcription factors including nuclear factor κ B (NFκB) (Libermann and Baltimore, 1990), multiple response element (MRE), C/EBPβ/NF-IL-6, and AP-1 (Li and Karin, 1999). The age-related increase in IL-6 gene expression in the brain, however, appears to be under control of NFκB. Relative to the adult brain, NFκB binding to the IL-6 gene promoter was increased in the brain of aged mice (Ye and Johnson, 2001b). The DNA binding activity of NF-IL-6, AP-1, and MRE was either unchanged or decreased in whole brains of aged mice. Moreover, intracerebroventricular injection of κB decoy—a molecule that competes with the DNAbinding sequences for NFκB—decreased NFκB DNAbinding activity and IL-6 mRNA in the brain of aged mice (Ye and Johnson, 2001b). Parallel studies with mixed glia cultures from aged mice also revealed increased NFκB binding to the IL-6 promoter. Incubating glia from aged mice with κB decoy decreased NFκB activity, IL-6 mRNA, and IL-6 protein secretion to levels similar to that in glia from adults (Ye and Johnson, 2001b). These findings are supported by other studies of age-related or disease-associated increases in NFκB transcriptional activity. For example, NFκB DNA-binding activity is increased in the aged rat forebrain and hippocampus (Korhonen et al., 1997; ToliverKinsky et al., 1997) and in hippocampal and cerebral cortical neurons of AD patients (Terai et al., 1996). Furthermore, in peripheral lymphoid organs of aged mice, NFκB activation is associated with chronic inflammation (Poynter and Daynes, 1999; Spencer et al., 1997).
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It is noteworthy that the concept of age-related neuroinflammation has begun to meld with another wellknown hypothesis on aging—namely, the “free radical hypothesis of aging” (Beckman and Ames, 1998). According to this hypothesis, damage to cell membranes and intracellular proteins increases due to either an increase in oxygen free radicals (i.e., reactive oxygen species, ROS), a decrease in the capacity of the antioxidant defense mechanisms to scavenge ROS, or some combination of these two (Beckman and Ames, 1998). The brain is particularly sensitive to oxidative damage because it is rich in polyunsaturated fatty acids, a principal target for lipid peroxidation. Bolstering the antioxidant defense mechanisms by feeding animals diets supplemented with antioxidant vitamins (e.g., vitamin E) or with fruits and vegetable extracts with high antioxidant activity has been shown to prevent and even reverse several age-related deficits in cognitive and motor function (Joseph et al., 1998). Likewise dietary restriction has been shown to protect neurons from oxidative insults and delay behavioral signs of brain aging (Guo et al., 2000). A recent study indicated that cognitive function in elderly people was related to vitamin E status (Ortega et al., 2002), and several epidemiological studies suggested that consuming an antioxidant-rich diet reduced the risk for age-associated neurodegenerative diseases that involve oxidative damage and impaired cognitive and motor function (Schapira and Olanow, 2004; Zandi et al., 2004). Although many potential mechanisms underlying the deleterious effects of oxidative stress on cognitive and motor behavior have been suggested, precisely how oxidative stress leads to neurobehavioral deficits is not known. The accumulated effects of oxidative stress appear to render neurons more susceptible to apoptosis, perhaps by reducing protein chaperones (e.g., heatshock protein-70; HSP-70) and neurotrophic factors (e.g., brain-derived neurotrophic factor; BDNF). Dietary restriction, which delays brain aging and increases life span, increased both HSP-70 and BDNF and protected neurons from oxidative insults (Mattson et al., 2003). Oxidative stress may also affect cognitive and motor behavior by activating intracellular signaling pathways that ultimately promote the expression of genes whose products cause inflammation and are behaviorally active. The inflammatory cytokines represent one such example. For instance, oxygen-free radicals can activate stress kinase pathways that activate NFκB (Flohe et al., 1997). α-tocopherol—an oxygen free radical scavenging agent—inhibits LPS-induced oxidative stress, NFκB DNA-binding activity, and IL-6 production in microglia and brains. For example, treating primary microglia with α-tocopherol prior to LPS reduced
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intracellular peroxides and IL-6 production (Godbout et al., 2004). Moreover, α-tocopherol was found to reduce NFκB DNA-binding activity, IL-1β, IL-6, and TNF-α in brains of mice challenged peripherally with LPS (Godbout, 2005a). Other studies showed that feeding mice diets high in antioxidants was effective at reducing LPS-induced sickness behavior in both adult and aged mice (Berg et al., 2004; Berg et al., 2005). Further support for melding of the two hypotheses comes from a recent study that investigated the relationship between brain oxidative stress, brain IL-6 production, and psychomotor deficits during aging. Mice reared in SPF conditions and ranging in age from 3–24 months were studied. There was a decline in motor function after 12 months of age and an increase in brain lipid peroxidation and IL-6 production by coronal brain slices ex vivo. Aging mice provided an antioxidant-rich diet for 6 months had improved psychomotor coordination compared to mice fed a diet adequate or low in antioxidants. Furthermore, when mice were tested on successive days, only those fed adequate and high antioxidants exhibited motor learning. Analysis of IL-6 production by coronal brain slices indicated that as dietary antioxidants increased, IL-6 production decreased (Richwine et al., 2005). That oxidative stress and inflammatory cytokines might both contribute to ageassociated deficits in cognition was previously suggested when long-term dietary supplementation with α-tocopherol prevented an age-associated increase in IL-1β and improved long-term potentiation in dentate gyrus of rats [O’Donnell and Lynch, 1998; Murray and Lynch, 1998]. The cytokine IL-1β may cause deficits in LTP by stimulating stress-activated kinases, which in turn inhibit glutamate release (Vereker et al., 2000) Other studies that examined gene expression in the brain on a global scale by microarray analysis also provide compelling evidence for an age-related shift towards a neuroinflammatory state. With an oligonucleotide-based array representing 6,347 genes, Lee et al. (2000) revealed a gene expression profile in the cortex and cerebellum of aged mice indicative of increased inflammation and oxidative stress. The effects of age on gene expression were annulled by caloric restriction—the only treatment known to slow aging and increase maximum life expectancy. Another microarray study that compared gene expression in brains of young adult and aged mice found 38 genes associated with inflammation that were differentially expressed—all but 4 were upregulated in the aged brain (Godbout, 2005b). And another study reported that an inflammatory profile was already evident in the hippocampus of middle-aged rats, and that the emergence of this profile preceded ageassociated cognitive deficits (Blalock et al., 2003).
IV. ARE NEUROINFLAMMATION AND SICKNESS EXACERBATED IN THE AGED? During peripheral infection, the inflammatory cytokines that are produced within the brain target neuronal substrates and elicit a behavioral response that is ordinarily adaptive (Dantzer, 2004; Johnson, 2002). However, excessive or prolonged release of inflammatory cytokines has been shown to produce severe behavioral deficits and promote neurotoxicity (Campbell et al., 1993; Finck and Johnson, 1997; Heyser et al., 1997). A number of studies involving intracerebroventricular administration of inflammatory cytokines or transgenic animal models that overexpress certain cytokines suggest that the magnitude and/or duration of sickness behavior is proportional to the quantity of inflammatory cytokines in the brain (Finck and Johnson, 1997; Heyser et al., 1997; Yao et al., 1999). Thus, circumstances that augment inflammatory cytokine production by microglial cells are likely to lead to pronounced and prolonged behavioral deficits and changes in neuronal circuitry that are counterproductive to recovery and rehabilitation after infection or injury. Several studies showed that coronal brain sections and primary mixed glia from aged rodents produced more IL-1β and IL-6 compared with adults when treated with LPS (Xie et al., 2003; Ye and Johnson, 2001a). The study by Ye et al. (Ye and Johnson, 2001a) also found that sections from aged brains secreted less IL-10 in both the absence and presence of LPS, and a decrease in IL-10 mRNA in the hippocampus of aged rats was recently reported (Frank et al., 2005). Therefore, deficits in important anti-inflammatory cytokines may contribute to the rise in inflammatory ones. Recent studies indicate that normal aging is associated with increased neuroinflammation and that an exaggerated inflammatory response occurs in the brain of healthy aged animals when the peripheral innate immune system is activated. The idea that systemic infection may result in an exaggerated inflammatory response in the aged brain emerged from several studies that suggested neurodegenerative diseases that involve primed or activated microglia are exacerbated by peripheral infection (Perry, 2004; Perry et al., 2003). In this situation, elements unique to the neurological disease provide a primary stimulus for microglial cell activation, and peripheral infection provides a secondary stimulus (Perry et al., 2003). In the ME-7 murine model of prion disease, microglia are activated throughout the limbic system, including the hippocampus where neuron loss occurs (Cunningham et al., 2003). In mice with pre-clinical ME-7–induced prion disease, a peripheral LPS challenge induced an exag-
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gerated depression in locomotor behavior and body temperature, and increased brain IL-1β compared to controls (Combrinck et al., 2002). In a transgenic murine model of amyotrophic lateral sclerosis (ALS), disease progression was exacerbated in presymptomatic mice given repeated i.p. injections of LPS (Nguyen et al., 2004). Toll-like receptor 2 and TNF-α were upregulated in discrete brain and spinal cord regions where degeneration occurred, and the average life span of ALS mice given LPS was decreased by 3 weeks (Nguyen et al., 2004). Finally, inflammatory cytokines produced by microglia are involved in chronic neurodegeneration in MS and AD. Systemic infection is a risk factor that can precipitate relapse in MS patients (Sibley et al., 1985) and trigger delirium in individuals with AD (Holmes et al., 2003). Deposition of β amyloid within senile plaques is a classical feature of AD, and conditions leading to the expression of inflammatory cytokines in the brain are associated with the rapid increase in β amyloid precursor protein (Brugg et al., 1995). In the Tg2576 murine model of AD, intravenous injection of LPS caused age-dependent increases in brain IL-1β and TNF-α levels and increased β amyloid deposition (Sly et al., 2001). This may provoke a positive feedback loop since β amyloid activates microglia (Giulian, 1999). Since activation of the peripheral innate immune system induces brain microglia to produce inflammatory cytokines that are responsible for behavioral deficits, it is reasonable to suspect that aging would exacerbate neuroinflammation and sickness behavior when the peripheral innate immune system is activated. Indeed, this important point has recently been found to be true in studies at the University of Illinois (Godbout, 2005b). Gene expression profiling demonstrated that aged mice had a unique gene expression profile in the brain both before and after an i.p. LPS injection. Moreover, the LPS-induced elevation in brain inflammatory cytokines and oxidative stress was both exaggerated and prolonged compared to adults. Aged mice were anorectic longer and lost more weight than adults following peripheral LPS administration. Remarkably, reductions in both locomotor and social behavior remained 24 hours later, when adults had fully recovered. We recently observed signs of depression in a forced swim test in aged mice 72 hours after LPS injection—a time when other signs of sickness had waned (unpublished data). Another group showed that aged rats suffered a similar exaggerated neuroinflammatory response during a peripheral infection and that the heightened neuroinflammation was associated with deficits in hippocampal-dependent learning and memory (Barrientos et al., 2005). Taken together, these studies show that peripheral infection
leads to exacerbated neuroinflammation in aged rodents. It is important to note that neither Godbout et al. (2005b) nor Barrientos et al. (2005) found peripheral inflammatory cytokines to be a reliable indicator of the exaggerated neuroinflammatory response. Thus, the dysregulated link between the peripheral and central innate immune system is likely to be involved in the severe behavioral deficits that frequently occur in older adults with systemic infections.
V. IF NEUROINFLAMMATION IS INCREASED, WHAT DOES IT MEAN? An exaggerated neuroinflammatory response may underlie the cognitive deficits that are highly prevalent in elderly patients (Figure 2). For example, acute cognitive impairment (i.e., delirium) is the most common psychiatric condition experienced by elderly emergency department patients (Chiovenda et al., 2002; Jackson et al., 2004; Wofford et al., 1996b) and most frequently results from infections that are unrelated to the CNS (Wofford et al., 1996a). In fact, the most striking characteristic of pneumonia (either viral or bacterial) in elderly patients is that it commonly presents clinically as delirium, even in the absence of classical pneumonia symptoms (Janssens and Krause, 2004). Overall, cognitive impairment results in a failure of self-care and is associated with increased hospitalization and delayed recovery (Johnston et al., 1987). The
(+) Infection Cognitive Impairment ↓ Self-Care
•Anorexia •Weight loss •Less likely to visit out-patient clinic
↑ Hospitalization ↑ Mortality Rate FIGURE 2 Elderly patients with a peripheral infection frequently experience cognitive disorders that reduce selfcare behaviors. Thus, cognitive impairment increases the likelihood of developing a new infection and can result in increased hospitalization and mortality.
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severity of dementia has been related to mortality of infectious disease, indicating an insidious relationship between infection and cognition, whereby in the elderly infection induces cognitive impairment and the cognitive impairment exacerbates the infection. In fact, peripheral infection has been found to enhance the risk of dementia in otherwise healthy individuals over the age of 84 (Dunn et al., 2005). Infection also is a risk factor for neurodegenerative diseases including multiple sclerosis (MS) (Sibley et al., 1985) and AD (Holmes et al., 2003). Because microglial cells and inflammatory cytokines are implicated in neurodegenerative diseases, an exaggerated inflammatory response in the aged brain may also underlie this well-documented but poorly understood phenomenon. In support of this hypothesis, a recent microarray study that allowed us to investigate gene expression on a global scale revealed that many inflammatory genes and a number of genes in the β-amyloid family are upregulated in the brains of aged mice but not adults after peripheral LPS challenge (Godbout, 2005b). Most studies concerning interactions between inflammatory cytokines and CNS neurons have focused on neurodegeneration, and more recently, inhibition of neurogenesis in the adult brain (Ekdahl et al., 2003; Monje et al., 2003). However, the transient increase in inflammatory cytokines in the brains of healthy aging subjects and the inflammatory cytokines produced in the brain when the peripheral innate immune system is activated are not likely to be acutely neurotoxic. For instance, although the decline in learning and memory in the aged was originally attributed to hippocampal cell loss (West, 1993), methodologically unbiased studies in rodents and primates, including humans, have now confirmed that in the absence of neurodegenerative disease cell number is preserved in this brain area (Calhoun et al., 1998; Rapp and Gallagher, 1996; Rasmussen et al., 1996). Serge Rivest’s group at Laval University has used in situ hybridization and immunohistochemical staining procedures to carefully examine the effects of peripheral LPS on microglial cell activation in young adult mice (Laflamme et al., 2001; Laflamme and Rivest, 2001). Despite robust activation of microglial cells, no indication of neuron loss under these conditions has been observed (Rivest, 2003). Although the effects of normal aging and systemic infection may conspire and produce an environment that is neurotoxic, it also is reasonable to suspect that changes in function and in existing structure, particularly synapse number and structure, underlie the profound behavioral changes evident in elderly adults with systemic infections. This is important because changes in dendrite morphology are of significant consequence to learning and memory: Treatments that
improve memory and learning, such as environmental enrichment, do so in part by increasing opportunities for synaptic inputs (Moser et al., 1994; Silva-Gomez et al., 2003). Thus, changes in dendrite morphology are likely to underlie the age-associated functional changes (de Brabander et al., 1998; Jacobs et al., 1997; Peters, 2002). A recent study examined the effects of conditioned supernatants from LPS-stimulated microglia on morphology and death of differentiated Neuro2a cells (a neuroblastoma cell line) (Munch et al., 2003). On the one hand, conditioned supernatants from microglia subjected to high concentrations of LPS caused neuronal cell death in a dose-dependent manner. On the other hand, supernatants from microglia exposed to low concentrations of LPS did not induce cell death but inhibited retinoic acid–induced neurite outgrowth and stimulated retraction of already-extended neurites. Another study showed TNF-α prevented neurite outgrowth and arborization in primary murine hippocampal neurons (Neumann et al., 2002). In demented AIDS patients, there is neuronal atrophy but no cell loss in the hippocampal formation (Sa et al., 2000). A recent Golgi impregnation study found diminished dendritic trees in all hippocampus neuron populations examined, including the dentate gyrus and CA1 and CA3 regions (Sa et al., 2004). These results are consistent with what was found in neocortical neurons of AIDS patients (Wiley et al., 1991), and suggest inflammatory cytokines as a common underlying mechanism responsible for the dendritic degeneration. Inflammatory cytokines, especially IL-1β, have been suggested to be involved in the pathogenesis of delirium, which is thought to be due to changes in cerebral metabolism that result in reduced synthesis of acetylcholine (Eikelenboom et al., 2002). IL-1β decreased extracellular acetylcholine in the hippocampus, and LPS administered into the forebrains of rats selectively decreased the number of choline acetyltransferase immunoreactive neurons (Willard et al., 1999). Thus, inflammatory cytokines have potential to influence both neuron structure and function.
VI. CODA Because the elderly are often immunosuppressed and susceptible to infection, the concept that aging may sensitize or prime the brain microglial compartment so that an exaggerated inflammatory response occurs when the peripheral immune system is activated is vitally important. As illustrated in Figure 3, a neuroinflammatory state emerges in the aged, and an exaggerated inflammatory response by primed microg-
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Brain Aging Neuroprotective Growth Factors
Inflammation
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(IL-1b, (IL-1β β, IL-6, TNFa) TNFα α) Innate immune system
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FIGURE 3 A heightened inflammatory state emerges in the aged brain, and microglial cells are primed. When a secondary stimulus from the peripheral innate immune system is experienced, primed microglia in the aged brain respond in an exaggerated fashion, producing more inflammatory cytokines than anticipated. The increase in inflammatory cytokines, coupled with age-associated reductions in neuroprotective factors, make neurons more susceptible to injury and exacerbate behavioral deficits. Adapted from Godbout et al. (2005b).
lia may further exacerbate conditions known to be driven in part by inflammatory cytokines. More severe behavioral deficits and delayed recovery are likely to contribute to disease and mortality in elderly patients whose ability to cope with intrinsic and extrinsic factors that cause stress is already diminished by the aging process. Thus, inhibiting neuroinflammation, especially in the presence of a peripheral infection, may be particularly important for enabling successful aging.
Acknowledgments This work was supported by NIH grants AG16710 and MH069148. J.P.G. was supported by a Ruth L. Kirchstein NRSA Postdoctoral Fellowship.
References Armstrong, G. L., Conn, L. A., and Pinner, R. W. (1999). Trends in infectious disease mortality in the United States during the 20th century. JAMA, 281, 61–66. Atkins, E. (1960). Pathogenesis of fever. Physiol. Rev., 40, 580–646.
Ban, E., Haour, F., and Lenstra, R. (1992). Brain interleukin 1 gene expression induced by peripheral lipopolysaccharide administration. Cytokine, 4, 48–54. Banks, W. A., and Kastin, A. J. (1991). Blood to brain transport of interleukin links the immune and central nervous systems. Life Sci., 48, PL117–121. Banks, W. A., Kastin, A. J., and Broadwell, R. D. (1995). Passage of cytokines across the blood-brain barrier. Neuroimmunomodulation, 2, 241–248. Banks, W. A., Kastin, A. J., and Gutierrez, E. G. (1994). Penetration of interleukin-6 across the murine blood-brain barrier. Neurosci. Lett, 179, 53–56. Banks, W. A., Ortiz, L., Plotkin, S. R., and Kastin, A. J. (1991). Human interleukin (IL) 1 alpha, murine IL-1 alpha and murine IL-1 beta are transported from blood to brain in the mouse by a shared saturable mechanism. J. Pharmacol. Exp. Ther., 259, 988–996. Barrientos, R. M., Higgins, E. A., Biedenkapp, J. C., Sprunger, D. B., Wright-Hardesty, K. J., Watkins, L. R., Rudy, J. W., and Maier, S. F. (2006). Peripheral infection and aging interact to impair hippocampal memory consolidation. Neurobiol. Aging. Beckman, K. B., and Ames, B. N. (1998). The free radical theory of aging matures. Physiol. Rev., 78, 547–581. Berg, B. M., Godbout, J. P., Chen, J., Kelley, K. W., and Johnson, R. W. (2005). Alpha-tocopherol and selenium facilitate recovery from lipopolysaccharide-induced sickness in aged mice. J. Nutr., 135, 1157–1163.
388
II. Immune System Effects on Neural and Endocrine Processes and Behavior
Berg, B. M., Godbout, J. P., Kelley, K. W., and Johnson, R. W. (2004). Alpha-tocopherol attenuates lipopolysaccharide-induced sickness behavior in mice. Brain Behav. Immun., 18, 149–157. Besedovsky, H. O., del Rey, A., and Sorkin, E. (1981). Lymphokinecontaining supernatants from con A-stimulated cells increase corticosterone blood levels. J. Immunol., 126, 385–387. Blalock, E. M., Chen, K. C., Sharrow, K., Herman, J. P., Porter, N. M., Foster, T. C., and Landfield, P. W. (2003). Gene microarrays in hippocampal aging: statistical profiling identifies novel processes correlated with cognitive impairment. J. Neurosci., 23, 3807–3819. Blasko, I., Stampfer-Kountchev, M., Robatscher, P., Veerhuis, R., Eikelenboom, P., and Grubeck-Loebenstein, B. (2004). How chronic inflammation can affect the brain and support the development of Alzheimer’s disease in old age: the role of microglia and astrocytes. Aging Cell, 3, 169–176. Bluthe, R. M., Michaud, B., Kelley, K. W., and Dantzer, R. (1996a). Vagotomy blocks behavioural effects of interleukin-1 injected via the intraperitoneal route but not via other systemic routes. Neuroreport, 7, 2823–2827. Bluthe, R. M., Michaud, B., Kelley, K. W., and Dantzer, R. (1996b). Vagotomy attenuates behavioural effects of interleukin-1 injected peripherally but not centrally. Neuroreport, 7, 1485–1488. Brugg, B., Dubreuil, Y. L., Huber, G., Wollman, E. E., DelhayeBouchaud, N., and Mariani, J. (1995). Inflammatory processes induce beta-amyloid precursor protein changes in mouse brain. Proc. Natl. Acad. Sci. USA, 92, 3032–3035. Calhoun, M. E., Kurth, D., Phinney, A. L., Long, J. M., Hengemihle, J., Mouton, P. R., Ingram, D. K., and Jucker, M. (1998). Hippocampal neuron and synaptophysin-positive bouton number in aging C57BL/6 mice. Neurobiol. Aging, 19, 599–606. Campbell, I. L., Abraham, C. R., Masliah, E., Kemper, P., Inglis, J. D., Oldstone, M. B., and Mucke, L. (1993). Neurologic disease induced in transgenic mice by cerebral overexpression of interleukin 6. Proc. Natl. Acad. Sci. USA, 90, 10061–10065. Castle, S. C. (2000). Clinical relevance of age-related immune dysfunction. Clin. Infect Dis., 31, 578–585. Chiovenda, P., Vincentelli, G. M., and Alegiani, F. (2002). Cognitive impairment in elderly ED patients: need for multidimensional assessment for better management after discharge. Am. J. Emerg. Med., 20, 332–335. Combrinck, M. I., Perry, V. H., and Cunningham, C. (2002). Peripheral infection evokes exaggerated sickness behaviour in preclinical murine prion disease. Neuroscience, 112, 7–11. Cunningham, C., Deacon, R., Wells, H., Boche, D., Waters, S., Diniz, C. P., Scott, H., Rawlins, J. N., and Perry, V. H. (2003). Synaptic changes characterize early behavioural signs in the ME7 model of murine prion disease. Eur. J. Neurosci., 17, 2147–2155. Dantzer, R. (2001). Cytokine-induced sickness behavior: mechanisms and implications. Ann. N. Y. Acad. Sci., 933, 222–234. Dantzer, R. (2004). Innate immunity at the forefront of psychoneuroimmunology. Brain Behav. Immun., 18, 1–6. Daynes, R. A., Araneo, B. A., Ershler, W. B., Maloney, C., Li, G. Z., and Ryu, S. Y. (1993). Altered regulation of IL-6 production with normal aging. Possible linkage to the age-associated decline in dehydroepiandrosterone and its sulfated derivative. J. Immunol., 150, 5219–5230. de Brabander, J. M., Kramers, R. J., and Uylings, H. B. (1998). Layerspecific dendritic regression of pyramidal cells with aging in the human prefrontal cortex. Eur. J. Neurosci., 10, 1261–1269. Dunn, N., Mullee, M., Perry, V. H., and Holmes, C. (2005). Association between dementia and infectious disease: evidence from a case-control study. Alzheimer Dis. Assoc. Disord., 19, 91–94. Eikelenboom, P., Hoogendijk, W. J., Jonker, C., and van Tilburg, W. (2002). Immunological mechanisms and the spectrum of psychi-
atric syndromes in Alzheimer’s disease. J. Psychiatr. Res., 36, 269–280. Ekdahl, C. T., Claasen, J. H., Bonde, S., Kokaia, Z., and Lindvall, O. (2003). Inflammation is detrimental for neurogenesis in adult brain. Proc. Natl. Acad. Sci. USA, 100, 13632–13637. Ershler, W. B., and Keller, E. T. (2000). Age-associated increased interleukin-6 gene expression, late-life diseases, and frailty. Annu. Rev. Med., 51, 245–270. Finch, C. E. (2003). Neurons, glia, and plasticity in normal brain aging. Neurobiol. Aging, 24 (Suppl 1), S123–127; discussion S131. Finch, C. E., and Crimmins, E. M. (2004). Inflammatory exposure and historical changes in human life-spans. Science, 305, 1736–1739. Finck, B. N., and Johnson, R. W. (1997). Anorexia, weight loss and increased plasma interleukin-6 caused by chronic intracerebroventricular infusion of interleukin-1beta in the rat. Brain Res., 761, 333–337. Flohe, L., Brigelius-Flohe, R., Saliou, C., Traber, M. G., and Packer, L. (1997). Redox regulation of NF-kappa B activation. Free Radic. Biol. Med., 22, 1115–1126. Frank, M. G., Barrientos, R. M., Biedenkapp, J. C., Rudy, J. W., Watkins, L. R., and Maier, S. F. (2006). mRNA up-regulation of MHC II and pivotal pro-inflammatory genes in normal brain aging. Neurobiol. Aging. Ginaldi, L., De Martinis, M., Monti, D., and Franceschi, C. (2005). Chronic antigenic load and apoptosis in immunosenescence. Trends Immunol., 26, 79–84. Ginaldi, L., Loreto, M. F., Corsi, M. P., Modesti, M., and De Martinis, M. (2001). Immunosenescence and infectious diseases. Microbes Infect., 3, 851–857. Giulian, D. (1999). Microglia and the immune pathology of Alzheimer disease. Am. J. Hum. Genet., 65, 13–18. Godbout, J. P., Berg, B. M., Kelley, K. W., and Johnson, R. W. (2004). Alpha-tocopherol reduces lipopolysaccharide-induced peroxide radical formation and interleukin-6 secretion in primary murine microglia and in brain. J. Neuroimmunol., 149, 101–109. Godbout, J. P., Berg, B. M., Krzyszton, C., and Johnson, R. W. (2005a). Alpha-tocopherol attenuates NF B activation and pro-inflammatory cytokine production in brain and improves recovery from lipopolysaccharide-induced sickness behavior. J. Neuroimmunol., 169, 97–105. Godbout, J. P., Chen, J., Abraham, J., Richwine, A. F., Berg, B. M., Kelley, K. W., and Johnson, R. W. (2005b). Exaggerated neuroinflammation and sickness in aged mice following activation of the peripheral innate immune system. FASEB J., 19, 1329–1331. Godbout, J. P., and Johnson, R. W. (2004). Interleukin-6 in the aging brain. J. Neuroimmunol., 147, 141–144. Goehler, L. E., Gaykema, R. P., Nguyen, K. T., Lee, J. E., Tilders, F. J., Maier, S. F., and Watkins, L. R. (1999). Interleukin-1beta in immune cells of the abdominal vagus nerve: a link between the immune and nervous systems? J. Neurosci., 19, 2799–2806. Goehler, L. E., Relton, J. K., Dripps, D., Kiechle, R., Tartaglia, N., Maier, S. F., and Watkins, L. R. (1997). Vagal paraganglia bind biotinylated interleukin-1 receptor antagonist: a possible mechanism for immune-to-brain communication. Brain Res. Bull., 43, 357–364. Gorczynski, R. M., Cinader, B., Ramakrishna, V., Terzioglu, E., Waelli, T., and Westphal, O. (1997). An antibody specific for interleukin-6 reverses age-associated changes in spontaneous and induced cytokine production in mice. Immunology, 92, 20–25. Guo, Z., Ersoz, A., Butterfield, D. A., and Mattson, M. P. (2000). Beneficial effects of dietary restriction on cerebral cortical synaptic terminals: preservation of glucose and glutamate transport and mitochondrial function after exposure to amyloid beta-
17. Aging, Neuroinflammation, and Behavior peptide, iron, and 3-nitropropionic acid. J. Neurochem., 75, 314–320. Gutierrez, E. G., Banks, W. A., and Kastin, A. J. (1993). Murine tumor necrosis factor alpha is transported from blood to brain in the mouse. J. Neuroimmunol., 47, 169–176. Heyser, C. J., Masliah, E., Samimi, A., Campbell, I. L., and Gold, L. H. (1997). Progressive decline in avoidance learning paralleled by inflammatory neurodegeneration in transgenic mice expressing interleukin 6 in the brain. Proc. Natl. Acad. Sci. USA, 94, 1500–1505. Holmes, C., El-Okl, M., Williams, A. L., Cunningham, C., Wilcockson, D., and Perry, V. H. (2003). Systemic infection, interleukin 1beta, and cognitive decline in Alzheimer’s disease. J. Neurol. Neurosurg. Psychiatry, 74, 788–789. Hoshino, K., Takeuchi, O., Kawai, T., Sanjo, H., Ogawa, T., Takeda, Y., Takeda, K., and Akira, S. (1999). Cutting edge: toll-like receptor 4 (TLR4)-deficient mice are hyporesponsive to lipopolysaccharide: evidence for TLR4 as the Lps gene product. J. Immunol., 162, 3749–3752. Jackson, J. C., Gordon, S. M., Hart, R. P., Hopkins, R. O., and Ely, E. W. (2004). The association between delirium and cognitive decline: a review of the empirical literature. Neuropsychol. Rev., 14, 87–98. Jacobs, B., Driscoll, L., and Schall, M. (1997). Life-span dendritic and spine changes in areas 10 and 18 of human cortex: a quantitative Golgi study. J. Comp. Neurol., 386, 661–680. Janssens, J. P., and Krause, K. H. (2004). Pneumonia in the very old. Lancet Infect. Dis., 4, 112–124. Johnson, R. W. (2002). The concept of sickness behavior: a brief chronological account of four key discoveries. Vet. Immunol. Immunopathol., 87, 443–450. Johnson, R. W., Gheusi, G., Segreti, S., Dantzer, R., and Kelley, K. W. (1997). C3H/HeJ mice are refractory to lipopolysaccharide in the brain. Brain Res., 752, 219–226. Johnston, M., Wakeling, A., Graham, N., and Stokes, F. (1987). Cognitive impairment, emotional disorder and length of stay of elderly patients in a district general hospital. Br. J. Med. Psychol., 60 (Pt 2), 133–139. Joseph, J. A., Shukitt-Hale, B., Denisova, N. A., Prior, R. L., Cao, G., Martin, A., Taglialatela, G., and Bickford, P. C. (1998). Long-term dietary strawberry, spinach, or vitamin E supplementation retards the onset of age-related neuronal signal-transduction and cognitive behavioral deficits. J. Neurosci., 18, 8047–8055. Kiecolt-Glaser, J. K., McGuire, L., Robles, T. F., and Glaser, R. (2002). Emotions, morbidity, and mortality: new perspectives from psychoneuroimmunology. Annu. Rev. Psychol., 53, 83–107. Kirkwood, T. B., Feder, M., Finch, C. E., Franceschi, C., Globerson, A., Klingenberg, C. P., LaMarco, K., Omholt, S., and Westendorp, R. G. (2005). What accounts for the wide variation in life span of genetically identical organisms reared in a constant environment? Mech. Aging Dev., 126, 439–443. Konsman, J. P., Kelley, K., and Dantzer, R. (1999). Temporal and spatial relationships between lipopolysaccharide-induced expression of Fos, interleukin-1beta and inducible nitric oxide synthase in rat brain. Neuroscience, 89, 535–548. Korhonen, P., Helenius, M., and Salminen, A. (1997). Age-related changes in the regulation of transcription factor NF-kappa B in rat brain. Neurosci. Lett., 225, 61–64. Krueger, J. M., Walter, J., Dinarello, C. A., Wolff, S. M., and Chedid, L. (1984). Sleep-promoting effects of endogenous pyrogen (interleukin-1). Am. J. Physiol., 246, R994–999. Laflamme, N., and Rivest, S. (2001). Toll-like receptor 4, the missing link of the cerebral innate immune response triggered by circulating gram-negative bacterial cell wall components. FASEB J., 15, 155–163.
389
Laflamme, N., Soucy, G., and Rivest, S. (2001). Circulating cell wall components derived from gram-negative, not gram-positive, bacteria cause a profound induction of the gene-encoding tolllike receptor 2 in the CNS. J. Neurochem., 79, 648–657. Laye, S., Bluthe, R. M., Kent, S., Combe, C., Medina, C., Parnet, P., Kelley, K., and Dantzer, R. (1995). Subdiaphragmatic vagotomy blocks induction of IL-1 beta mRNA in mice brain in response to peripheral LPS. Am. J. Physiol., 268, R1327–1331. Laye, S., Parnet, P., Goujon, E., and Dantzer, R. (1994). Peripheral administration of lipopolysaccharide induces the expression of cytokine transcripts in the brain and pituitary of mice. Brain Res. Mol. Brain Res., 27, 157–162. Lee, C. K., Weindruch, R., and Prolla, T. A. (2000). Gene-expression profile of the aging brain in mice. Nat. Genet., 25, 294–297. Li, N., and Karin, M. (1999). Is NF-kappaB the sensor of oxidative stress? FASEB J., 13, 1137–1143. Libermann, T. A., and Baltimore, D. (1990). Activation of interleukin-6 gene expression through the NF-kappa B transcription factor. Mol. Cell. Biol., 10, 2327–2334. Mattson, M. P., Duan, W., and Guo, Z. (2003). Meal size and frequency affect neuronal plasticity and vulnerability to disease: cellular and molecular mechanisms. J. Neurochem., 84, 417–431. Monje, M. L., Toda, H., and Palmer, T. D. (2003). Inflammatory blockade restores adult hippocampal neurogenesis. Science, 302, 1760–1765. Moser, M. B., Trommald, M., and Andersen, P. (1994). An increase in dendritic spine density on hippocampal CA1 pyramidal cells following spatial learning in adult rats suggests the formation of new synapses. Proc. Natl. Acad. Sci. USA, 91, 12673–12675. Mouton, P. R., Long, J. M., Lei, D. L., Howard, V., Jucker, M., Calhoun, M. E., and Ingram, D. K. (2002). Age and gender effects on microglia and astrocyte numbers in brains of mice. Brain Res., 956, 30–35. Munch, G., Gasic-Milenkovic. J., Dukic-Stefanovic, S., Kuhla, B., Heinrich, K., Riederer, P., Huttunen, H. J., Founds, H., and Sajithlal, G. (2003). Microglial activation induces cell death, inhibits neurite outgrowth and causes neurite retraction of differentiated neuroblastoma cells. Exp. Brain Res., 150, 1–8. Murray, C. A., and Lynch, M. A. (1998). Dietary supplementation with vitamin E reverses the age-related deficit in long term potentiation in dentate gyrus. J. Biol.Chem., 273, 12161–12168. Neumann, H., Schweigreiter, R., Yamashita, T., Rosenkranz, K., Wekerle, H., and Barde, Y. A. (2002). Tumor necrosis factor inhibits neurite outgrowth and branching of hippocampal neurons by a rho-dependent mechanism. J. Neurosci., 22, 854–862. Nguyen, M. D., D’Aigle, T., Gowing, G., Julien, J. P., and Rivest, S. (2004). Exacerbation of motor neuron disease by chronic stimulation of innate immunity in a mouse model of amyotrophic lateral sclerosis. J. Neurosci., 24, 1340–1349. O’Donnell, E., and Lynch, M. A. (1998). Dietary antioxidant supplementation reverses age-related neuronal changes. Neurobiol. Aging, 19, 461–467. Ortega, R. M., Requejo, A. M., Lopez-Sobaler, A. M., Andres, P., Navia, B., Perea, J. M., and Robles, F. (2002). Cognitive function in elderly people is influenced by vitamin E status. J. Nutr., 132, 2065–2068. Perry, V. H. (2004). The influence of systemic inflammation on inflammation in the brain: implications for chronic neurodegenerative disease. Brain Behav. Immun., 18, 407–413. Perry, V. H., Matyszak, M. K., and Fearn, S. (1993). Altered antigen expression of microglia in the aged rodent CNS. Glia, 7, 60–67. Perry, V. H., Newman, T. A., and Cunningham, C. (2003). The impact of systemic infection on the progression of neurodegenerative disease. Nat. Rev. Neurosci., 4, 103–112.
390
II. Immune System Effects on Neural and Endocrine Processes and Behavior
Peters, A. (2002). Structural changes in the normally aging cerebral cortex of primates. Prog. Brain Res., 136, 455–465. Pinner, R. W., Teutsch, S. M., Simonsen, L., Klug, L. A., Graber, J. M., Clarke, M. J., and Berkelman, R. L. (1996). Trends in infectious diseases mortality in the United States. JAMA, 275, 189–193. Plowden, J., Renshaw-Hoelscher, M., Engleman, C., Katz, J., and Sambhara, S. (2004). Innate immunity in aging: impact on macrophage function. Aging Cell, 3, 161–167. Porter, N. M., and Landfield, P. W. (1998). Stress hormones and brain aging: adding injury to insult? Nat. Neurosci., 1, 3–4. Poynter, M. E., and Daynes, R. A. (1999). Age-associated alterations in splenic iNOS regulation: influence of constitutively expressed IFN-gamma and correction following supplementation with PPARalpha activators or vitamin E. Cell. Immunol., 195, 127–136. Prechel, M. M., Halbur, L., Devata, S., Vaidya, A. M., and Young, M. R. (1996). Increased interleukin-6 production by cerebral cortical tissue of adult versus young mice. Mech. Aging Dev., 92, 185–194. Rapp, P. R., and Gallagher, M. (1996). Preserved neuron number in the hippocampus of aged rats with spatial learning deficits. Proc. Natl. Acad. Sci. USA, 93, 9926–9930. Rasmussen, T., Schliemann, T., Sorensen, J. C., Zimmer, J., and West, M. J. (1996). Memory impaired aged rats: no loss of principal hippocampal and subicular neurons. Neurobiol. Aging, 17, 143–147. Reyes, T. M., Fabry, Z., and Coe, C. L. (1999). Brain endothelial cell production of a neuroprotective cytokine, interleukin-6, in response to noxious stimuli. Brain Res., 851, 215–220. Richwine, A. F., Godbout, J. P., Chen, J., Berg, B. M., Escobar, J., Millard, D. K., and Johnson, R. W. (2005). An antioxidant-rich diet reduced brain interleukin-6 production and improved psychomotor performance in aged mice. Brain Behav. Immun., 19, 512–520. Rivest, S. (2003). Molecular insights on the cerebral innate immune system. Brain Behav. Immun., 17, 13–19. Rogers, J., Luber-Narod, J., Styren, S. D., and Civin, W. H. (1988). Expression of immune system–associated antigens by cells of the human central nervous system: relationship to the pathology of Alzheimer’s disease. Neurobiol. Aging, 9, 339–349. Sa, M. J., Madeira, M. D., Ruela, C., Volk, B., Mota-Miranda, A., Lecour, H., Goncalves, V., and Paula-Barbosa, M. M. (2000). AIDS does not alter the total number of neurons in the hippocampal formation but induces cell atrophy: a stereological study. Acta Neuropathol. (Berl), 99, 643–653. Sa, M. J., Madeira, M. D., Ruela, C., Volk, B., Mota-Miranda, A., and Paula-Barbosa, M. M. (2004). Dendritic changes in the hippocampal formation of AIDS patients: a quantitative Golgi study. Acta Neuropathol. (Berl), 107, 97–110. Schapira, A. H., and Olanow, C. W. (2004). Neuroprotection in Parkinson disease: mysteries, myths, and misconceptions. JAMA, 291, 358–364. Scheibel, M. E., Lindsay, R. D., Tomiyasu, U., and Scheibel, A. B. (1975). Progressive dendritic changes in aging human cortex. Exp. Neurol., 47, 392–403. Segreti, J., Gheusi, G., Dantzer, R., Kelley, K. W., and Johnson, R. W. (1997). Defect in interleukin-1beta secretion prevents sickness behavior in C3H/HeJ mice. Physiol. Behav., 61, 873–878. Sheffield, L. G., and Berman, N. E. (1998). Microglial expression of MHC class II increases in normal aging of nonhuman primates. Neurobiol. Aging, 19, 47–55. Sibley, W. A., Bamford, C. R., and Clark, K. (1985). Clinical viral infections and multiple sclerosis. Lancet, 1, 1313–1315. Silva-Gomez, A. B., Rojas, D., Juarez, I., and Flores, G. (2003). Decreased dendritic spine density on prefrontal cortical and hip-
pocampal pyramidal neurons in postweaning social isolation rats. Brain Res., 983, 128–136. Sly, L. M., Krzesicki, R. F., Brashler, J. R., Buhl, A. E., McKinley, D. D., Carter, D. B., and Chin, J. E. (2001). Endogenous brain cytokine mRNA and inflammatory responses to lipopolysaccharide are elevated in the Tg2576 transgenic mouse model of Alzheimer’s disease. Brain Res. Bull., 56, 581–588. Spencer, N. F., Poynter, M. E., Im, S. Y., and Daynes, R. A. (1997). Constitutive activation of NF-kappa B in an animal model of aging. Int. Immunol., 9, 1581–1588. Streit, W. J. (2004). Microglia and Alzheimer’s disease pathogenesis. J. Neurosci. Res., 77, 1–8. Streit, W. J., Sammons, N. W., Kuhns, A. J., and Sparks, D. L. (2004). Dystrophic microglia in the aging human brain. Glia, 45, 208–212. Streit, W. J., and Sparks, D. L. (1997). Activation of microglia in the brains of humans with heart disease and hypercholesterolemic rabbits. J. Mol. Med., 75, 130–138. Terai, K., Matsuo, A., and McGeer, P. L. (1996). Enhancement of immunoreactivity for NF-kappa B in the hippocampal formation and cerebral cortex of Alzheimer’s disease. Brain Res., 735, 159–168. Tha, K. K., Okuma, Y., Miyazaki, H., Murayama, T., Uehara, T., Hatakeyama, R., Hayashi, Y., and Nomura, Y. (2000). Changes in expressions of proinflammatory cytokines IL-1beta, TNFalpha and IL-6 in the brain of senescence accelerated mouse (SAM) P8. Brain Res., 885, 25–31. Toliver-Kinsky, T., Papaconstantinou, J., and Perez-Polo, J. R. (1997). Age-associated alterations in hippocampal and basal forebrain nuclear factor kappa B activity. J. Neurosci. Res., 48, 580–587. van Dam, A. M., Bauer, J., Tilders, F. J., and Berkenbosch, F. (1995). Endotoxin-induced appearance of immunoreactive interleukin-1 beta in ramified microglia in rat brain: a light and electron microscopic study. Neuroscience, 65, 815–826. van Dam, A. M., Brouns, M., Louisse, S., and Berkenbosch, F. (1992). Appearance of interleukin-1 in macrophages and in ramified microglia in the brain of endotoxin-treated rats: a pathway for the induction of non-specific symptoms of sickness? Brain Res., 588, 291–296. Vereker, E., O’Donnell, E., and Lynch, M. A. (2000). The inhibitory effect of interleukin-1beta on long-term potentiation is coupled with increased activity of stress-activated protein kinases. J. Neurosci., 20, 6811–6819. Verkhratsky, A., Mattson, M. P., and Toescu, E. C. (2004). Aging in the mind. Trends Neurosci., 27, 577–578. Weaver, J. D., Huang, M. H., Albert, M., Harris, T., Rowe, J. W., and Seeman, T. E. (2002). Interleukin-6 and risk of cognitive decline: MacArthur studies of successful aging. Neurology, 59, 371–378. Wei, J., Xu, H., Davies, J. L., and Hemmings, G. P. (1992). Increase of plasma IL-6 concentration with age in healthy subjects. Life Sci., 51, 1953–1956. West, M. J. (1993). Regionally specific loss of neurons in the aging human hippocampus. Neurobiol. Aging, 14, 287–293. Whalley, L. J., Deary, I. J., Appleton, C. L., and Starr, J. M. (2004). Cognitive reserve and the neurobiology of cognitive aging. Aging Res. Rev., 3, 369–382. Wiley, C. A., Masliah, E., Morey, M., Lemere, C., DeTeresa, R., Grafe, M., Hansen, L., and Terry, R. (1991). Neocortical damage during HIV infection. Ann. Neurol., 29, 651–657. Willard, L. B., Hauss-Wegrzyniak, B., and Wenk, G. L. (1999). Pathological and biochemical consequences of acute and chronic neuroinflammation within the basal forebrain cholinergic system of rats. Neuroscience, 88, 193–200. Wilson, C. J., Finch, C. E., and Cohen, H. J. (2002). Cytokines and cognition—the case for a head-to-toe inflammatory paradigm. J. Am. Geriatr. Soc., 50, 2041–2056.
17. Aging, Neuroinflammation, and Behavior Wofford, J. L., Loehr, L. R., and Schwartz, E. (1996a). Acute cognitive impairment in elderly ED patients: etiologies and outcomes. Am. J. Emerg. Med., 14, 649–653. Wofford, J. L., Schwartz, E., Timerding, B. L., Folmar, S., Ellis, S. D., and Messick, C. H. (1996b). Emergency department utilization by the elderly: analysis of the National Hospital Ambulatory Medical Care Survey. Acad. Emerg. Med., 3, 694–699. Xie, Z., Morgan, T. E., Rozovsky, I., and Finch, C. E. (2003). Aging and glial responses to lipopolysaccharide in vitro: greater induction of IL-1 and IL-6, but smaller induction of neurotoxicity. Exp. Neurol., 182, 135–141. Yao, J. H., Ye, S. M., Burgess, W., Zachary, J. F., Kelley, K. W., and Johnson, R. W. (1999). Mice deficient in interleukin-1beta converting enzyme resist anorexia induced by central lipopolysaccharide. Am. J. Physiol., 277, R1435–1443.
391
Ye, S. M., and Johnson, R. W. (1999). Increased interleukin-6 expression by microglia from brain of aged mice. J. Neuroimmunol., 93, 139–148. Ye, S. M., and Johnson, R. W. (2001a). An age-related decline in interleukin-10 may contribute to the increased expression of interleukin-6 in brain of aged mice. Neuroimmunomodulation, 9, 183–192. Ye, S. M., and Johnson, R. W. (2001b). Regulation of interleukin-6 gene expression in brain of aged mice by nuclear factor kappaB. J. Neuroimmunol., 117, 87–96. Zandi, P. P., Anthony, J. C., Khachaturian, A. S., Stone, S. V., Gustafson, D., Tschanz, J. T., Norton, M. C., Welsh-Bohmer, K. A., and Breitner, J. C. (2004). Reduced risk of Alzheimer disease in users of antioxidant vitamin supplements: the Cache County Study. Arch. Neurol., 61, 82–88.
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C H A P T E R
18 Neuroimmune Interactions and Pain: The Role of Immune and Glial Cells LINDA R. WATKINS, JULIE WIESELER-FRANK, MARK R. HUTCHINSON, ANNEMARIE LEDEBOER, LEAH SPATARO, ERIN D. MILLIGAN, EVAN M. SLOANE, AND STEVEN F. MAIER
phine is discussed, including the implications of these findings for clinical pain control.
I. PAIN BASICS 393 II. THE PROBLEM OF CHRONIC PAIN 396 III. HISTORICAL OVERVIEW: DISCOVERIES LEADING TO THE RECOGNITION OF IMMUNE/GLIAL INVOLVEMENT IN CHRONIC PAIN 396 IV. THE CONTRIBUTION OF PERIPHERAL IMMUNE CELLS TO CHRONIC PAIN 398 V. THE CONTRIBUTION OF CNS IMMUNE-LIKE GLIAL CELLS TO CHRONIC PAIN 401 VI. PHYSIOLOGY AND FUNCTION OF GLIA: GENERAL PRINCIPLES 401 VII. PAIN ENHANCEMENT BY ACTIVATED SPINAL CORD GLIA 405 VIII. BEYOND CHRONIC PAIN: GLIAL CELLS OPPOSE THE PAIN-SUPPRESSIVE EFFECTS OF OPIOIDS 408 IX. CONCLUSIONS AND IMPLICATIONS 409
I. PAIN BASICS Pain normally serves adaptive functions (Nash, 2005). First, pain is a sensory warning system. Pain signals relayed by sensory neurons to the spinal cord trigger the activation of protective reflexes. These reflexes rapidly remove endangered body parts from the potentially dangerous stimulus, thereby preventing or minimizing tissue damage. In turn, spinal cord neurons relay the pain message to the brain. Here, adaptive behaviors are organized, such as changing course so as not to continue walking on broken glass. Second, pain serves a recuperative function. After injury, pain motivates attention to the wound, as well as inactivity and behavior related to healing. Thus, normal pain promotes survival. Indeed, the survival value of pain is made all the more apparent by people born without the ability to feel pain (Nash, 2005). Such people lean on hot stoves and realize it only upon smelling their burning flesh, fail to avoid sharp objects, and are unaware of bone breaks or internal injuries which become life threatening as a result. They learn only with great difficulty how to survive in a world full of danger. The pain pathway from body to brain has classically been conceived of as a fairly simple chain of neurons. In skin, joints, muscle, and internal organs, sensory nerve terminals express receptors specialized to detect a wide range of potentially threatening
ABSTRACT This chapter explores how pain can be powerfully amplified by the activation of peripheral immune cells associated with peripheral nerves and by the activation of immune-like glial cells (microglia and astrocytes) within the central nervous system. After review of the basics of pain and pain modulation, the focus will shift to chronic pain, which is poorly if at all controlled by currently available drugs. The thesis will be developed that such pain arises as a consequence of immune and glial activation. The involvement of peripheral immune cells and glia in such pain states is explored. Finally, the very recent finding that glia also oppose the pain-suppressive effects of drugs like morPSYCHONEUROIMMUNOLOGY, 4E VOLUME I
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Copyright © 2007 by Elsevier, Inc. All rights of reproduction in any form reserved.
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(A)
(B)
Quiescent glia
Incoming A- /C fiber ‘pain’ signals Normal substance P release, EAA release
NK-1 receptor
PTN
AMPA receptor
Pain message to brain NMDA receptor
Pain stimulus
(C)
(D)
Viruses and bacteria
Non-existent glia
NK-1 receptor
AMPA receptor
PTN cNOS L-arginine
NO
Incoming A- /C fiber ‘pain’ signals Enhanced substance P release, EAA release
Ca2+ NMDA receptor
PTN – NO, PGs, Fractalkine
Primary afferent – Substance P, EAAs, ATP
Activated glia
IL-1, TNF, IL-6, ROS, NO, PGs, EAAs, ATP
Enhance PTN excitability
Enhance primary afferent, substance P and EAA release TRENDS in Neurosciences
stimuli, such as heat, cold, pressure, and various inflammatory mediators (acid, serotonin, proinflammatory cytokines, bradykinin, prostaglandins) (Julius and Basbaum, 2001). Upon activation, these nerve terminals create electrical signals that are relayed to the spinal cord dorsal horns (Figure 1A,B). Pain from the left side of the body is relayed to the left dorsal horn; pain from the right side of the body, to the right dorsal horn. The dorsal horns of the spinal cord are somatotopically organized, so, for example, pain from your abdomen and legs is relayed to the dorsal horns in the lumbar spinal cord. Even here, the neural patterning is exquisite, with a tiny map of the abdomen and legs intricately organized within each spinal cord slice (Clarke and Harris, 2004). At all levels of the spinal cord, the dorsal horns contain neurons that, upon receiving pain messages from sensory neurons, relay this information up to higher brain areas where the pain message is interpreted and acted upon.
However, pain is not simply, passively relayed from the body to the brain. Rather, pain is dynamically modulated. The spinal cord dorsal horns are the major site of pain modulation (Gebhart, 2004). When sensory neurons relay pain information to dorsal horn neurons, the pain message may be suppressed, relayed unaltered, or amplified. For example, if you have surgery and are given morphine for your pain, morphine acts at the spinal cord dorsal horns, preventing pain messages from being relayed to higher brain centers. Thus, you are unaware of the pain. Similarly, life-threatening events activate well-defined brain-to-spinal cord pathways, leading to the release of endogenous morphinelike neurotransmitters (enkephalins) within the spinal cord dorsal horns, again suppressing pain. Analgesia (“without pain”) under such fight/flight situations is adaptive, as being unaware of pain facilitates defense and escape (Gebhart, 2004). On the other hand, hyperalgesia (“exaggerated pain”) can also be adaptive. Hyperalgesia occurs as a
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FIGURE 1 Classical and non-classical views of pain transmission and pain modulation. Panel A: Classical pain transmission pathway. When a noxious (painful) stimulus is encountered, such as stepping on a nail as shown, peripheral “pain”-responsive A-delta and C nerve fibers are excited. These axons relay action potentials to the spinal cord dorsal horn. Here, neurotransmitters are released by the sensory neuron, and these chemicals bind to and activate postsynaptic receptors on pain transmission neurons (PTNs) whose cell bodies reside in the dorsal horn. Axons of the PTNs then ascend to the brain, carrying information about the noxious event to higher centers. The synapse interconnecting the peripheral sensory neuron and the dorsal horn PTN is shown in detail in panels B and C. Panel B: Normal pain. Under basal conditions, pain is not modulated by glia. Under these circumstances, glia are quiescent, and thus not releasing pain-modulatory levels of neuroexcitatory substances. Information about noxious stimuli arrives from the periphery along A-delta and C fibers, causing the release of substance P and excitatory amino acids (EAAs) in amounts appropriate to the intensity and duration of the initiating noxious stimulus. Activation of neurokinin-1 (NK-1) receptors by substance P and activation of AMPA receptors by EAAs cause transient depolarization of the PTNs, thereby generating action potentials that are relayed to the brain. NMDA-linked channels are silent as they are chronically “plugged” by magnesium ions. Panel C: Pathological pain: classical view. In response to intense and/or prolonged barrages of incoming “pain” signals, the PTNs become sensitized and over-respond to subsequent incoming signals The intense and/or prolonged barrage depolarizes the PTNs such that the magnesium ions exit the NMDA-linked channel. The resultant influx of calcium ion activates constitutively expressed nitric oxide synthase (cNOS), causing conversion of L-arginine to nitric oxide (NO). Because it is a gas, NO rapidly diffuses out of the PTNs. This NO acts presynaptically to cause exaggerated release of substance P and EAAs. Postsynaptically, NO causes the PTNs to become hyperexcitable. Glia have not been considered to have a role in creating pain facilitation in this neuronally driven model. Panel D: Pathological pain: new view. Here, glial activation is conceptualized as a driving force for creating and maintaining pathological pain states. The role of glia is superimposed on the NMDA-NO–driven neuronal changes detailed in panel C, so only the aspects added by including glia in the model are described here. Glia are activated (shown as hypertrophied relative to panel [B], as this reflects the remarkable anatomical changes that these cells undergo on activation) by three sources: bacteria and viruses which bind specific activation receptors expressed by microglia and astrocytes; substance P, EAAs, fractalkine, and ATP released by A-delta and/or C fiber presynaptic terminals (shown here) or by brain-to-spinal cord pain enhancement pathways (not shown); and NO, prostaglandins (PGs) and fractalkine released from PTNs. Following activation, microglia and astrocytes cause PTN hyperexcitability and the exaggerated release of substance P and EAAs from presynaptic terminals. These changes are created by the glial release of NO, EAAs, reactive oxygen species (ROS), PGs, pro-inflammatory cytokines (for example, IL-1, IL-6 or TNF), and nerve growth factor. From: Watkins, L. R., Milligan, E. D., and Maier, S. F. (2001). Glial activation: a driving force for pathological pain, Trends in Neuroscience, 24, 450–455. (Copyright permission being requested from TiNS.)
result of enhanced sensory neuron excitability, enhanced release of “pain” neurotransmitters from sensory neurons into the dorsal horn, and/or enhanced excitability of dorsal horn neurons that relay pain messages to the brain (Scholz and Woolf, 2002). Such enhancement of pain signaling in response to tissue damage or infection can be useful. It increases focus on the injury to ensure attention to the injury and can promote learning to avoid such injuries in the future. While many underlying mechanisms have been proposed to account for hyperalgesia (Gebhart, 2004; Scholz and Woolf, 2002), describing the most commonly accepted, classical view will provide the neces-
sary background for understanding sections that follow (Figures 1B,C). In this view, the key event is a change in function of neuronal NMDA receptors in the spinal cord dorsal horns (Petrenko et al., 2003). Pain-responsive neurons in the spinal cord express an array of receptors for transmitters that are released by sensory neurons upon their activation by painful stimuli. These transmitters include substance P and glutamate. Substance P is bound by neurokinin-1 (NK-1) receptors, while glutamate is bound by AMPA and NMDA receptors. Such binding to NK-1 and AMPA receptors always increases the excitability of neurons. In contrast, binding of glutamate to NMDA receptors is normally without effect, as the NMDA-
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associated ion channel is “plugged” by a magnesium ion so no current can pass. However, under conditions of strong and/or persistent pain stimulation, sufficient amounts of substance P and glutamate are released such that sustained depolarization of the spinal cord neurons occur. Under these conditions, the magnesium ions are removed from the NMDA channel, allowing calcium ions to now flow into the cell. This event is key as this influx of calcium causes the production of nitric oxide by calcium-activated neuronal nitric oxide synthase and the production of prostaglandins. These diffuse from the neurons and act to increase both the excitability of spinal cord neurons in response to incoming pain signals, and cause an exaggerated release of “pain” neurotransmitters from spinal cord presynaptic terminals in the spinal cord. Taken together, these downstream effects of NMDA receptor activation result in the amplification of pain messages being relayed to higher brain centers (Petrenko et al., 2003).
II. THE PROBLEM OF CHRONIC PAIN The problem with pain is that pain can become maladaptive, serving no survival advantage. Normally, in the absence of painful stimuli, you feel no pain. Normally, when your injury heals, pain stops. However, that is not the case with chronic pain. In this case, pain occurs spontaneously, in the absence of any identifiable persistent injury or obvious physical reason. In addition, hot, cold, and hard pressure pains are greatly amplified. Indeed, non-painful stimuli such as warm, cool, and light touch are now perceived as pain. Chronic pain occurs in epidemic proportions worldwide. One in four adults suffers from chronic pain that is unresolved by currently available therapies (Louis Harris and Associates, 1999). One or more members of the United States’ 44 million households is in chronic pain (Partners Against Pain, 2000). Such pain affects all aspects of their personal and professional lives. Two-thirds of people with chronic pain have been in pain for more than 5 years and one-third feel that they cannot function as normal people because of their pain (Roper Starch Worldwide, 1999). Many sufferers attempt suicide because of the pain (Partners Against Pain, 2000). A major focus of pain research has been to try to understand why pain goes wrong, and why drugs such as morphine are highly effective for suppressing normal pain yet fail to control chronic pain. Many changes in the functioning of neurons in the pain pathway have been identified in animal models of chronic pain (Woolf and Salter, 2000). For example,
sensory neurons can become spontaneously active, signaling pain when no such stimulus is present. Neurons that normally relay only light touch can change their neurochemistry under conditions of chronic pain. Under such conditions, for the first time, these neurons begin releasing neurotransmitters that signal “pain” in response to light touch. Neurons within the spinal cord dorsal horn have been shown to become spontaneously active and hyperexcitable to incoming pain signals, thus amplifying pain messages sent to the brain (Woolf and Salter, 2000). These, and many other, changes in neuronal functions have been identified, and drugs have been developed to control such neuronal changes. Yet, chronic pain remains unresolved. Indeed, the definition of a good drug for chronic pain is one that fails 80% of the time (McQuay et al., 1995; McQuay et al., 1996). What will become clear, in the sections to follow, is that a reason that chronic pain remains a problem may be the importance of non-neuronal cells in such pain states. Immune cells associated with peripheral nerves and immune-like glial cells within the spinal cord have long been ignored by pain researchers, as they were not thought to influence neuronal function. This view is dramatically changing. Recognition of the key role played by peripheral immune cells and glial cells suggests that development of drugs that target these cell populations may prove efficacious in the control of human chronic pain (Watkins and Maier, 2003).
III. HISTORICAL OVERVIEW: DISCOVERIES LEADING TO THE RECOGNITION OF IMMUNE/GLIAL INVOLVEMENT IN CHRONIC PAIN Three independent and distinct lines of research led to the recognition of the importance of nerve-associated immune cells and spinal cord glial cells in pain enhancement. Interestingly, none originally derived from studies of pain.
A. Sickness Behavior The first line of research, which flourished in the mid-1980s through 1990s, was focused on understanding immune-to-brain communication. These studies sought to understand how viral or bacterial challenge of the immune system could lead to the creation of a wide array of brain-mediated, survival-oriented responses (Hart, 1988). These evolutionarily old, phylogenetically ubiquitous “sickness responses” included physiological changes (e.g., increased sleep, alterations in the composition of blood, fever), endocrine changes
18. Neuroimmune Interactions and Pain: The Role of Immune and Glial Cells
(activation of the sympathetic nervous system and hypothalamo-pituitary response), as well as behavioral changes (e.g., decreased sexual activity, exploration, food/water intake, social dominance, etc.) (Maier and Watkins, 1998). The most recently recognized component of the sickness response was enhanced pain, which has come to be called “sickness-induced hyperalgesia.” This phenomenon was first characterized in the early 1990s (Maier et al., 1992; Watkins and Maier, 2000). The understanding of this enhanced pain state was greatly facilitated by prior studies of mechanisms underlying more classical components of the sickness response. By the early 1990s, it was becoming well accepted that pro-inflammatory cytokines (tumor necrosis factor [TNF], interleukin-1 [IL-1], and interleukin-6 [IL-6]) were key mediators of many sickness responses, both in the periphery and in the brain (Maier and Watkins, 1998; Parnet et al., 2002). In addition, glia were repeatedly implicated as a major source of these pro-inflammatory substances within the brain (Rothwell and Luheshi, 1994). Thus, based on this history, it was logical to explore whether glial pro-inflammatory cytokines within the spinal cord might be critically involved in the generation of sickness-induced hyperalgesia., and indeed, they were (Watkins and Maier, 2000; Watkins et al., 2001). This directly led to the exploration of whether peripheral inflammation/ trauma, more generally, could “tap into” this circuitry. In turn, it was discovered that there are many routes by which spinal cord glia can be activated, causing the release of pro-inflammatory cytokines, resulting in enhanced pain responses (Watkins et al., 2001; Watkins and Maier, 2000; Watkins and Maier, 2003).
B. Peripheral Nerve Damage The second line of research that led to the recognition of a central role of glia in pain regulation also arose independent of an interest in pain, per se. From the early 1970s (Sjostrand, 1971), literature has developed documenting the intriguing enigma that damage to nerve bundles in the periphery mysteriously led to the activation of microglia and astrocytes within the brain and spinal cord. This activation was not random, but rather occurred strictly within central nervous system (CNS) sites where damaged peripheral sensory neurons normally relayed their information to CNS neurons (for example, in the spinal cord dorsal horn). In addition, glial activation was found to occur surrounding CNS neuronal cell bodies (such as motor neurons) whose peripheral axons were damaged. It was not until the early 1990s that the first studies explored whether such glial activation might be poten-
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tially relevant to the understanding of pathological pain. At this time, Garrison and colleagues reported that a classic animal model of neuropathic pain (a form of pathological pain arising as a result of peripheral nerve injury) did indeed lead to marked glial activation within pain-related areas of the spinal cord dorsal horn (Figure 2). Importantly, the administration of a drug known to alleviate neuropathic pain (an NMDA receptor antagonist) also markedly attenuated dorsal horn glial activation (Garrison et al., 1991; Garrison et al., 1994). This finding provided the first evidence that, at minimum, dorsal horn glial activation was strongly correlated with neuropathic pain. As will be reviewed below, studies that followed from other laboratories proved that glial activation was not simply correlated with neuropathic pain, but rather was causal to such pain enhancement.
C. Immune Cells Associated with Peripheral Nerves The third line of research was not focused on spinal cord glia, but rather on immune cells associated with peripheral nerve bundles. It had been known that pain-sensitive peripheral nerves expressed receptors on their terminal endings in skin, for example, that were activated by pro-inflammatory products of nearby activated immune cells. This was not surprising, as it is the job of peripheral nerve endings to be aware of threats to the host. What was surprising was the discovery that immune and immune-like cells including macrophages, endothelial cells, fibroblasts, mast cells, and Schwann cells were resident within nerve bundles (Myers et al., 1999; Watkins and Maier, 2002). In addition, circulating immune cells were recruited to sites of damage within nerve bundles, just as in other bodily tissues (Myers et al., 1996). This led to investigations of the implications of such findings. Initially, these studies focused not on pain, but on nerve degeneration (Powell and Myers, 1986). In the course of the studies, it was documented that peripheral nerve damage led to the activation of resident immune and immune-like cells, leading to the release of chemoattractant factors and pro-inflammatory products. The activation of these resident cells, plus the recruitment and activation of macrophages from the general circulation, was found to be crucially involved in the degeneration of damaged peripheral nerves (Myers et al., 1999). As will be reviewed below, it soon became clear that these same nerve-associated immune and immune-like cells were also crucially involved in the creation of exaggerated pain responses that occur as a result of peripheral nerve damage (Watkins and Maier, 2002).
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IV. THE CONTRIBUTION OF PERIPHERAL IMMUNE CELLS TO CHRONIC PAIN
FIGURE 2 Example of microglial activation in spinal cord dorsal horns in response to a stimulus that creates exaggerated pain states. Peri-spinal administration of the HIV-1 envelope glycoprotein gp120 creates exaggerated responses to both thermal and touch/pressure stimuli (Milligan et al., 2001). Disruption of glial activation abolishes the pain changes. Furthermore, these pain changes are correlated with anatomical evidence of activation of both astrocytes and microglia. An example of such microglial activation is illustrated here. Panel A illustrates the dorsal horn of a rat injected peri-spinally with vehicle. Panel B is identical except that the rat received peri-spinal HIV-1 gp120 at a dose that creates exaggerated pain responses. These photomicrographs are from the tissues collected for analysis reported in Milligan et al. (Milligan et al., 2001). Activation of microglia induces these cells to upregulate their expression of complement type 3 receptors. Thus, enzyme-labeled antibodies directed against complement receptor type 3 (OX-42 monoclonal antibodies) can be used to detect microglial activation by light microscopy. By this method, activated microglia appear darker and more densely stained in accordance with their increased expression of OX-42 antibody-bound receptors. Modified from: Watkins, L. R., Milligan, E. D., and Maier, S. F. (2001). Glial activation: a driving force for pathological pain, Trends in Neuroscience, 24, 450–455. (Copyright permission being requested from TiNS).
Infection, inflammation, and trauma to peripheral nerves can result in pain enhancement perceived as arising from tissues normally innervated by the affected nerve. Thus, for example, insult to the sciatic nerve near the hip leads to the perception of pain radiating throughout the leg. Historically, immune cells were not considered to contribute to such pain phenomena. Rather, pain was thought to be created as a result of changes in neurons. An array of neuronally based mechanisms has been proposed, supported by data from animal studies. As noted above, these include nerve-injury–induced spontaneous electrical activity arising either at the site of injury or from the cell bodies of the injured nerves, and changes in what neurotransmitters are made such that neurons that normally relay touch sensations now, for the first time, begin releasing neurotransmitters that “mean” pain (Woolf and Salter, 2000; Scholz and Woolf, 2002). More recently, the contributions of immune cells to such pain states have been recognized (Marchand et al., 2005). While a thorough review is not possible here, interested readers are referred to one of our recent reviews (Watkins and Maier, 2002), which provides a comprehensive summary of the anatomy and immunology of healthy peripheral nerves, as well as discussion of a variety of ways that immune activation can lead to damage and dysfunction of peripheral nerves from both a basic science and clinical perspective. Here, discussion will focus on the involvement of immune cells to neuropathic pain arising as a result of peripheral nerve trauma, as this is the most common cause of neuropathic pain and the one that has been the focus of the most intense study. Evidence for pain amplification in response to immune activation has accrued through the study of the relatively simple sea slug Aplysia and the rat. From studies of Aplysia, it became clear as early as the mid1980s that sensory nerve damage induces prolonged, exaggerated responses to subsequent mechanical stimuli (Walters, 1994). In studies that followed, it was discovered that immunocytes (macrophage-like cells of Aplysia) migrate to the site of nerve damage (Clatworthy et al., 1994). This was an intriguing finding given that immunocytes, like their mammalian macrophage counterpart, release pro-inflammatory cytokine-like molecules (IL-1–like and TNF-like) upon activation. Indeed, IL-1 and TNF alter ion channels in Aplysia neurons, causing hyperexcitability (Clatworthy and Grose, 1999). Similarly, hyperexcitability of injured nerves is enhanced in the presence of activated immunocytes (Clatworthy and Grose, 1999).
18. Neuroimmune Interactions and Pain: The Role of Immune and Glial Cells
Strikingly parallel findings have been reported in rats. By the mid-1980s it was known that peripheral nerve injury causes enhanced pain states and axonal hyperexcitability, as well as axonal degeneration (called Wallerian degeneration). Both trauma-induced degeneration and enhanced pain are associated with the recruitment and activation of macrophages to the site of injury (Myers et al., 1999). Indeed, simply delaying the recruitment of macrophages to the site of nerve damage delays both the development of neuropathic pain and nerve degeneration (Myers et al., 1996). In contrast, neuropathic pain is increased if activated immune cells are attracted to the injury (Clatworthy et al., 1995). Of the various neuroactive substances released by activated macrophages, the most evidence implicates pro-inflammatory cytokines. These increase at sites of nerve injury, via production by Schwann cells, endothelial cells, and resident and recruited macrophages (Myers et al., 1999). Moreover, the blockade of IL-1, TNF, or IL-6 activity reduces neuropathic pain (Sommer et al., 1998; Sommer et al., 1999). In addition to pro-inflammatory cytokines, activation of the complement cascade and production of reactive oxygen species and nitric oxide have each been implicated in the development of neuropathic pain in animal models (Liu et al., 2000b). More recently, studies of immune involvement in neuropathic pain expanded from studies of traumatic injury of peripheral nerve to the consideration of how neuropathic pain may arise in the absence of frank trauma. Indeed, about half of human neuropathies are inflammatory rather than traumatic in origin (Said and Hontebeyrie-Joskowicz, 1992). How pain arises in such circumstances was a mystery. From early studies of Aplysia, it was clear that sensory neurons become hyperexcitable simply by the presence of immunologically activated immunocytes placed nearby (Clatworthy et al., 1994). In rats, simply exposing otherwise healthy rat peripheral nerves to killed bacteria, algae protein (carrageenan), yeast cell walls (zymosan), or the HIV-1 envelope glycoprotein gp120 increased pain responsivity (Chacur et al., 2001). Such pain changes are mimicked by pro-inflammatory cytokines. TNF and IL-1 injected into peripheral nerves increase pain responsivity, as well as induce nerve inflammation, demyelination, and axonal degeneration (Myers et al., 1999; Zelenka et al., 2005). Importantly, TNF applied to peripheral nerves generates action potentials at that site (Sorkin et al., 1997). Other inflammatory mediators, such as ATP, phospholipase A2, and reactive oxygen species, similarly increase pain responsivity after administration in close proximity to peripheral nerves (Chacur et al., 2004).
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Although it is clear that pro-inflammatory cytokines and other inflammatory mediators induce pain, how they can do this along large nerve bundles is controversial. This is understandable when it is realized that it is heretical to discuss activation of neurons at mid-axon. The classical view of how sensory neurons are activated revolves around the expression of specific receptors on nerve terminals within skin, muscle, or other tissues. It is only at nerve terminals, and certainly not along large nerve bundles, that sensory neurons were thought to be activated by pain-inducing stimuli. Only very recently has the notion been seriously considered that functional receptors may be expressed along the axon (Moalem, 2005), in addition to their expression at their terminations in skin and other tissues. In addition to the possibility of functional receptor expression along axons, inflammatory mediators may have other means for exciting peripheral nerves as well. Of the pro-inflammatory cytokines, TNF has received the most study to date. Studies of the structure of TNF indicate that it may insert into lipid membranes and form a central pore-like region due to its threedimensional configuration. Insertion is facilitated by a physiologically relevant lowering of pH (e.g., acidification), which naturally occurs at sites of inflammation (Kagan et al., 1992). It appears that the inserted TNF molecules form voltage-dependent sodium channels. Additional studies indicate that TNF can interact with sodium and calcium channels naturally expressed along peripheral nerves to increase their inward conductance, an effect that would increase neuronal excitability. Similar to TNF, IL-1 and IL-6 can also produce long-lasting increases in the conductance of voltage-sensitive sodium and calcium channels (Schettini et al., 1988; Wilkinson et al., 1996). In addition to enhancing pain responsivity by altering the function of peripheral nerves, immune activation can also enhance pain responsivity by altering the function of sensory nerve cells within dorsal root ganglia (DRG). There are left and right pairs of DRG in between successive vertebrae of the spinal column. The peripheral projections of these cell bodies innervate specific regions of the body, whereas their central projections innervate adjoining segments of the spinal cord. Each of these DRGs contains the cell bodies of neurons that sense what is occurring to a small “slice” of the body, called a dermatome (“skin slice”). In addition, DRGs contain glially derived satellite cells, dendritic cells, macrophages, and endothelial cells. Each neuronal cell body in the DRG is encapsulated by a layer of satellite cells (Olsson, 1990). Satellite cells are glia-like cells and as such share many of their regulatory and immune-like functions. Like glial cells (as will be described in more detail below), satellite cells regu-
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late the extracellular levels of neuroexcitatory substances such as excitatory amino acids, and can rapidly spread excitability to large regions of the DRG by gap junctional communication across inter-connected satellite cells (Huang and Hanini, 2005). Peripheral nerve injury leads to the activation of satellite cells and immune cells within the DRG, causing the release of pro-inflammatory cytokines and other neuroexcitatory substances (Zhou et al., 1999). Thus, satellite cells are well positioned to regulate neuronal excitability within the DRG. Herniated discs are but one example of the way immune activation can alter pain by actions at the level of the DRG. Herniated discs spontaneously release a variety of pain-producing substances including nitric oxide, pro-inflammatory cytokines, phospholipase A2, cyclooxygenase-2 (COX-2), thromboxanes, leutkotrienes, and prostaglandins (Ahn et al., 2002). These are created both by infiltrating immune cells as well as by histiocytes, fibroblasts, endothelial cells, and chondrocytes of the disc itself. Furthermore, herniated discs become hyperresponsive to inflammatory stimuli. As one example, they release enhanced amounts of nitric oxide, IL-6, and prostaglandins upon stimulation with IL-1 (Kang et al., 1997). Such findings suggest that discassociated pro-inflammatory substances may be a major factor in back pain (Burke et al., 2002). Indeed, there is now a substantial and striking literature accruing that the DRG is vulnerable to immunederived substances. Application of herniated disc tissue to DRG and its adjoining axons causes edema, spontaneous electrical activity in sensory nerves, and enhanced responsivity to pain (Olmarker and Rydevik, 2001). In addition, it causes increased production of pro-inflammatory cytokines, nitric oxide, and phospholipase A2 in DRG (Kawakami et al., 1999). Topical application of TNF to DRG likewise induces spontaneous electrical activity in sensory nerves, edema, and enhanced pain responsivity (Liu et al., 2000a). Other inflammatory mediators, such as bradykinin, chemokines, and phospholipase A2, have also been implicated in enhancing pain responsivity at the level of the DRG (Tang et al., 2004; Zhang et al., 2005). In addition, the meninges offer another means by which the peripheral immune system and the central nervous system (CNS) may interface, thereby potentially influencing pain responsivity. The meninges cover the CNS, creating a barrier between the CNS and the periphery. The meninges are composed of three layers: the pia mater, arachnoid, and dura mater (Patestas and Gartner, 2005). The pia mater lies closest to the parenchyma, which is the unique tissue (neurons and glia) that makes up the central nervous system. The pia mater is a thin, delicate covering that traces
the surface of the parenchyma, and it contains fine blood vessels that penetrate the parenchyma. The arachnoid layer has a spongy consistency and lies between the pia mater and the dura mater. The arachnoid layer does not have a blood supply. The cerebrospinal fluid (CSF) circulates in the subarachnoid space between the arachnoid layer and the pia mater. The dura mater is a tough, outer layer that rests on top of the arachnoid layer. The dura mater is heavily vascularized. At the level of the dura mater, the junctions of the vascular endothelial cells are tight, as this is a primary barrier between CNS vasculature and peripheral blood circulation. The main function of the meninges has previously been presented as one of protection. That is, the meninges, with the circulating CSF, serve to mechanically protect the parenchyma by absorbing shock as the organism moves about, and protects the CNS from bacteria or viruses circulating in the blood via the tight junctions in the dura mater. Of particular interest to those studying communication between the peripheral immune system and the CNS is the cellular composition of the meninges. The meninges are composed, in part, of large numbers of immune cells such as mast cells, dendritic cells, and macrophages (Braun et al., 1993; McMenamin, 1999 #140). Given the proximity of these cells to CSF and the CNS parenchyma, it seems likely that activation of these immune cells could influence neurons and glia in the region. Traditionally, the meninges have been thought of as functionally independent of the CNS parenchyma. However, it has been proposed that the meninges are able to significantly influence the activity of glia and neurons. Mercier and Hatton argue that signals released from the meninges, such as growth factors and cytokines, act on the parenchyma directly, and mediate glial and neuronal activity (Mercier and Hatton, 2004). It should be noted that neither the pia mater nor the basal lamina separating the parenchyma from the pia mater serves as a barrier to large molecules. In other words, any released signal or bacteria or virus able to gain access to the CSF is also able to gain access to the parenchyma as well. In light of the number of immune cells residing in the meninges, it seems possible that inflammation of the spinal cord meninges (meningitis) would lead to pain responses. Indeed, lumbar spinal arachnoiditis (inflammation of the arachnoid layer at the lumbar level of the spinal cord) is associated with back pain (Petty et al., 2000). Further, we have measured elevated IL-1 in the meninges following conditions leading to the exaggerated pain, including peri-spinal (intrathecal) administration of the HIV-1 envelope gp120 and peripheral nerve damage that produces neuropathic pain (Jekich et al., 2006; Wieseler-
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Frank et al., 2006). Administration of gp120 into the CSF space induces an inflammatory response by directly acting on immune cells in the meninges in addition to glial cells in the spinal cord. That we see increases in IL-1 following peripheral nerve injury that causes neuropathic pain is interesting, as it suggests that the inflammation of the damaged sciatic nerve at mid-thigh level leads to changes in the meninges as the nerve pierces through the meninges on its way to entering the spinal cord. This could be the result of signals released from the DRG, either inducing an inflammatory response in the meninges or signals from the DRG recruiting inflammatory cells to the meninges. In either case, the peripheral immune system is communicating with the central nervous system and is associated with exaggerated pain. In addition to surrounding the CNS parenchyma, the meninges also project into the brain and spinal cord. These projections are in the form of blood vessel ensheathments. Every blood vessel is ensheathed as it enters and leaves the meninges, and this ensheathment continues into the parenchyma. The cellular composition of these ensheathments differs from the meninges surrounding the parenchyma in that these are composed of fibroblasts and macrophages, which are coupled by gap junctions (Mercier et al., 2002; Mercier et al., 2003; Mercier and Hatton, 2001). The space between the ensheathment and the blood vessel is referred to as the perivascular space. Within the perivascular space are macrophages, termed perivascular macrophages. Perivascular macrophages are unique in that they constitutively express MHCII (Perry, 1998), possibly indicating a heightened state of responsivity. The perivascular macrophages, as well as the ensheathing meningeal macrophages, are well positioned to respond to blood-borne signals, and then release immune mediators that can act on other neurons and glia, and/or can be released back into the blood stream. Given this organization, it is possible that while some substances may not be able to cross the blood-brain barrier, they can still influence glial and neuronal activity by acting on vascular cells, inducing an immune response in the meninges resulting in the release of the neuroexcitatory substances into the CSF. For example, peripheral administration of lipopolysaccharide (LPS) induces cyclooxygenase-2 gene expression in perivascular monocytes/macrophages (Quan et al., 1998). The notion that resident meningeal immune cells may be communicating with glia and neurons in the parenchyma is a newer hypothesis. That it could be another pathway to consider when studying communication between the peripheral immune system and the CNS has not been previously considered.
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V. THE CONTRIBUTION OF CNS IMMUNELIKE GLIAL CELLS TO CHRONIC PAIN Astrocytes and microglia have been the focus of studies exploring the role of CNS immune-like cells in pain dysregulation (Marchand et al., 2005; Watkins et al., 2001; Watkins and Maier, 2003). While, as reviewed below, there are good reasons to implicate these two types of glia in pain facilitation, one must recognize that this focus on astrocytes and microglia is a simple accident of history. That is, astrocytes and microglia caught the attention of pain researchers because, when these cells are activated, they upregulate their expression of cell type-specific markers (e.g., glial fibrillary acidic protein by astrocytes, complement type 3 receptors by microglia). As simple immunohistochemistry can be used to detect increases in these so-called activation markers, microglia and astrocytes were favored for study over other immune and immune-like cells (fibroblasts, endothelial cells, oligodendrocytes, etc.) that do not express such markers. Thus, while it is likely that microglia and astrocytes are not alone in regulating pain, the contributions of other cells types have yet to be investigated. As glia are not yet commonly studied in the field of psychoneuroimmunology, a general overview will be provided prior to discussion of the evidence that these immune-like cells are involved in pain enhancement.
VI. PHYSIOLOGY AND FUNCTION OF GLIA: GENERAL PRINCIPLES A. Microglia Microglia constitute 5–10% of all glia and 5–12% of the total number of cells within the CNS (Cuadros and Navascues, 2001). The embryonic origin of microglia remains controversial, and they likely arise from multiple sources. Most evidence points to a mesodermal origin of these cells, likely of hematopoietic lineage (Cuadros and Navascues, 2001). In addition, peripheral blood monocytes are recruited in early development in response to chemoattractants released within the CNS during programmed cell death (Perry et al., 1985). While these recruited monocytes initially mature into tissue macrophages pursuant to their role in removing cells that die during CNS remodeling, they subsequently become indistinguishable from microglia (Perry et al., 1985). In the adult, resident microglia principally arise from two sources. The first is that resident microglia continue to divide throughout life, and in so doing continuously replenish their numbers. Second, periph-
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eral blood monocytes migrate into the healthy CNS and, once there, mature into resident microglia. These two sources are thought to equally contribute to the number of resident microglia in healthy adult CNS (Lawson et al., 1992). In injured CNS, additional recruitment occurs of circulating monocytes, which again are indistinguishable from microglia when matured (Kaur et al., 2001). Thus, both developmentally and throughout the life span, microglia arise from multiple sources. Regarding their function in healthy CNS, microglia are responsible for immune surveillance and host defense (Nimmerjahn et al., 2005). Logically, given such roles, they express receptors for viruses and bacteria, as well as indicators of cell damage such as heat shock proteins. When not stimulated by such stimuli, microglia actively monitor their microenvironment in their role as sentinels (Nimmerjahn et al., 2005). In this state, microglia express a highly ramified, stellate morphology 30–40 μm in diameter with little-to-no expression of receptors, activation markers, or functions characteristic of activate microglia (Raivich et al., 1999). As microglia are remarkably sensitive to their microenvironment, the shift from their sentinel state to an immune-reactive activated state can occur quite rapidly (Figure 3). Microglia can be activated by CNS trauma, ischemia, tumors, neurodegeneration, bacte-
ria, and viruses. Activation is not all-or-none, but rather is graded, reflected by alterations in morphology (retraction and thickening of processes, hypertrophy, membrane ruffling reflective of exploratory movements), proliferation, upregulated receptor expression (such as complement receptors and scavenger receptors), and changes in function (recruitment to sites of damage, phagocytosis, production of inflammatory mediators such as pro-inflammatory cytokines) (Raivich et al., 1999). Exactly what profile of changes occurs in microglia is defined by the type, intensity, and duration of the initiating stimulus and the prior history of microglial activation. Thus, stating that microglia are activated may not, per se, accurately reflect what form or function has changed. Upon resolution of the acute challenge (infection, damage, etc.), microglia may slowly revert to their basal state. However, microglia may also remain in a “primed,” hypervigilant state for prolonged periods of time (Perry et al., 1985). In such a primed state, microglia are not actively producing pro-inflammatory products but rather respond more rapidly and more vigorously to a new challenge. Thus, upon restimulation, an overproduction of pro-inflammatory products can occur (Perry et al., 1985). There are early indications that re-stimulation of spinal cord glia in such a “primed” state can result in exacerbation of pain (Cahill et al., 2003; Spataro et al., 2005).
FIGURE 3 Microglia under basal and activated states. Microglia in hippocampus were stained with FITC-IB4, which also labels blood vessels (arrowheads, Panels A and C). Microglia under basal conditions exhibit highly branched, ramified morphology (Panel A). A higher magnification of a single microglial cell is shown in Panel B; note the fine, finger-like extensions emanating from the major branches. By 12 hours after activation by isolation from the brain, microglia have lost most of their branches and appear amoeboid in form (Panel C). A comparison of representative microglia under basal versus strongly activated conditions, differences are evident by the reduction in number and length of branches within the first 12 hours after isolation from the brain (Panel D). Modified from: Stence, N., Waite, M., and Dailey, M. E. (2001). Dynamics of microglial activation: a confocal time-lapse analysis in hippocampal slices. Glia, 33, 256–266. (With permission from Wiley-Liss, Inc.)
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B. Astrocytes Astrocytes (also called astroglia) account for 40–50% of all glia and outnumber neurons (Figure 4) (Lee et al., 2000). Embryologically, astrocytes arise from the dorsal neural tube (Goldman and Vaysse, 1991). There are multiple precursor populations, which in turn lead to multiple subpopulations of astrocytes with varying receptor expressions and functions (Goldman and Vaysse, 1991). Mature astrocytes closely ensheath neuronal cell bodies as well as synapses. Thus astrocytes are physically well positioned to intimately detect and respond to neuronal signaling (Aldskogius and Kozlova, 1998). In their basal condition, astrocytes perform an array of functions. They contribute to the formation and structural integrity of the blood-brain barrier, provide neurons with energy sources and precursors for the synthesis of neurotransmitters (Tsacopoulos, 2002), release a variety of growth factors that support the development and maintenance of neurons, regulate extracellular concentrations of ions and neurotransmitters, regulate the formation of synapses, etc. (Perea and Araque, 2002) Beyond these functions, the concept of the “tripartite synapse” has recently been developed. This view redefines synapses as being composed of three, rather than the traditional two, elements: the presynaptic neuronal terminal, the postsynaptic neuronal terminal, and the enveloping astrocyte. Here, astrocytes are conceived of as active contributors to synaptic signaling.
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They receive signals from the neurons and, in turn, they signal back to the neurons and, in so doing, markedly alter neuronal activity and function (Araque et al., 1999; Haydon, 2001). Additionally, astrocytes communicate actively with other astrocytes. While astrocytes do not generate action potentials, as do neurons, they do create calcium waves in which intracellular calcium elevations are propagated in a non-decremental fashion from astrocyte to astrocyte over large distances (Porter and McCarthy, 1997). Such calcium waves, by activating distant astrocytes, lead to the release of glial products at sites distant from the origin of the astrocyte signal (Haydon, 2001). Thus, this can lead to an expansion of glial activation over time (Figure 5).
C. Glia and Glial Products Can Act in Synergy While this issue has just begun to be studied in the pain field, it is important to note that actions of glial pro-inflammatory cytokines can synergize, just as they do in the peripheral immune system. Pro-inflammatory cytokines can also synergize with neurotransmitters and neuromodulators. For example, IL-1 and TNF can synergize with a variety of neurotransmitters/ neuromodulators, resulting in the release of glial products, including pro-inflammatory cytokines (Crusazk et al., 1996). In terms of interactions within the spinal cord, what is known is that nitric oxide (which can be produced
FIGURE 4 Astrocytes under basal and activated states. Astrocytes in the spinal cord were labeled for their expression of glial fibrillary acidic protein (GFAP), an activation marker. Astrocytes in a healthy spinal cord (Panel A: Normal) are morphologically quite distinct from astrocytes strongly activated in response to spinal cord contusion (Panel B: Injured). Modified from: Peters, C. M., Rogers, S. D., Pomonis, J. D., Egnazyck, G. F., Keyser, C. P., Schmidt, J. A., Ghilardi, J. R., Maggio, J. E., and Mantyh, P. W. (2003). Endothelian receptor expression in the normal and injured spinal cord: potential involvement in injury-induced ischemia and gliosis. Experimental Neurology, 180, 1–13. (With permission from Academic Press)
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FIGURE 5 Gap junctions allow activated glia to create widespread excitation. To selectively activate glia in cell culture, one frequently used technique is the application of a mechanical stimulus, which triggers the release of intracellular calcium and, consequently, the stimulation of gap-junctional communication. Such gap-junctional spread of excitability also occurs in response to stimulation of glia with various excitatory substances such as ATP and glutamate. Panel A: A phase-contrast image of a field of cells in a 7-day-old mixed glial culture. A micropipette (P) is positioned over a single cell and is used to stimulate the cell mechanically. Panel B: A fluorescence image of the same field of cells loaded with fura-2 at an excitation wavelength of 380 nm. Panel C: Intracellular calcium ion concentration [Ca2+]in maps of the same field of cells at sequential time-points following mechanical stimulation of a single cell. Time (in seconds) after mechanical stimulation is indicated below each panel. A wave of increased [Ca2+]in is communicated cell by cell in all directions from the stimulated cell. The peak c increase in this example varies from 150–600 nM, as indicated by the pseudocolor scale bar. The wave is initiated at a specific point on each cell and spreads across the cell body and along its processes until it reaches the cell boundary. Scale bars, 100 um. From: Araque, A., Parpura, V., Sanzgiri, R. P., and Haydon, P. G. (1999). Tripartite synapses: glia, the unacknowledged partner. Trends in Neuroscience, 22, 208–215.
by activated glia as well as by activated neurons) potentiates IL-1—induced cyclooxygenase-2 (an inducible enzyme leading to prostaglandin synthesis) (Morioka et al., 2002). Nitric oxide also potentiates IL-1—induced release of substance P from painresponsive sensory neurons that send their presynaptic terminals into the spinal cord so to relay pain information there (Morioka et al., 2002). Also, human
spinal cord astrocytes enhance their release of IL-6 and PGE2 in response to substance P combined with IL-1 (Palma et al., 1997). Regarding microglia-astrocyte interactions, it is clear that astrocytes release substances that stimulate microglial activation, proliferation, and release of a wide array of neuroexcitatory products (Petrova et al., 2000). It is also clear that activation of microglia can
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lead, in turn, to the activation of nearby astrocytes (Ledeboer et al., 2005b; Raghavendra et al., 2003). Thus, each of these cell types impacts the functions of the other.
VII. PAIN ENHANCEMENT BY ACTIVATED SPINAL CORD GLIA Normally, glia appear to have little-to-no influence on pain (Marchand et al., 2005; Watkins et al., 2001). That is, if glial activation or their pro-inflammatory products are disrupted, no change in basal pain responsivity is detected. This has been interpreted to mean that, under normal pain states, spinal cord glial cells are simply performing their classical, regulatory functions, quite independently of pain processing. Under such basal conditions, glia are not releasing significant levels of pro-inflammatory products and so do not alter pain responsivity. In contrast, when glia become activated, the proinflammatory products they release do markedly enhance pain. Glial activation occurs under both physiological and pathological conditions. As noted above, peripheral immune challenge is one condition that leads to glial activation within the CNS (Watkins and Maier, 2000). Immune activation in the body can lead in turn to immune-to-brain communication. Such immune-to-brain communication results in sickness responses, including increases in pain. The recognition that many sickness responses are generated as a result of glial activation and consequent pro-inflammatory cytokine production predicted that glia and proinflammatory cytokines would mediate sicknessinduced pain facilitation as well. This did indeed turn out to be the case (Watkins and Maier, 2000). It is now known that glial and pro-inflammatory cytokine regulation of pain extends well beyond sickness responses (Figure 1D). Spinal cord glia are activated in response to a wide array of bodily challenges, including inflammation and damage to peripheral tissues, peripheral nerves, spinal nerves, and spinal cord. Indeed, the involvement of spinal cord glia in enhanced pain is so pervasive that in virtually every animal model of enhanced pain, pain is prevented and/or reversed by disrupting spinal cord glial activation or by disrupting the actions of pro-inflammatory products released by these cells (Marchand et al., 2005; Watkins et al., 2001; Watkins and Maier, 2003). Such disruption of glial effects can be produced by administration of various immunomodulatory drugs, glial metabolic inhibitors, pro-inflammatory cytokine antagonists, or anti-inflammatory cytokines such as interleukin-10 [IL-10] (Milligan et al., 2005a; Watkins
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and Maier, 2003). As one example, chronic exposure of the spinal cord to IL-10 can resolve neuropathic pain arising from peripheral nerve inflammation, traumatic injury, and chemotherapy-induced neurotoxicity (Ledeboer et al., 2005a; Milligan et al., 2005a; Milligan et al., 2005b; Sloane et al., 2005). Such studies are exciting due to the promise they hold for improved treatment of pain, as each model studied is reflective of major pain syndromes that are currently poorly, if at all, treatable in people. The mechanism or mechanisms by which glial proinflammatory products enhance neuronal excitability are still actively being investigated. Neurons within the pain-responsive regions of spinal cord express receptors for pro-inflammatory cytokines (Ohtori et al., 2004) and the excitability of pain-responsive neurons are rapidly increased upon exposure to these glial products, which suggests that a direct effect of these cytokines on neurons may be involved (Reeve et al., 2000). Intriguingly, IL-1 has recently been documented to increase the inward calcium conductance of neuronal NMDA receptors (Viviani et al., 2003), including those of pain-responsive neurons in the spinal cord (Samad et al., 2004). As reviewed in the “Pain Basics” section, such an increase in intracellular calcium would naturally lead to increased production of nitric oxide and prostaglandins, thereby amplifying pain. In addition, TNF has been documented to rapidly increase the number of AMPA receptors on the surface of neurons (Stellwagen et al., 2005), again consistent with increasing the excitability of neurons in a manner that could more easily lead to NMDA activation as a consequence. Lastly, pro-inflammatory cytokines can cause glia to release a variety of neuroexcitatory substances, including nitric oxide, prostaglandins, and a variety of reactive oxygen species (Samad et al., 2001) (Figure 1D). Thus, while pro-inflammatory cytokines can exert multiple effects, all are in the direction of amplifying pain by increasing the excitability of spinal cord neurons. Although, by far, the most focus in the pain literature has been on the role of glial pro-inflammatory cytokines in amplifying pain, it is important to recognize that these are by no means the only neuroexcitatory substances released by activated glia. For example, glia can release a variety of excitatory amino acids, including D-serine that potently enhances NMDA channel function (Snyder, 2004). Furthermore, activated glia can release ATP along with nitric oxide, reactive oxygen species, and prostaglandins, as noted above. Thus, glia are well endowed with releasable products that can enhance pain. Studies of such substances, as relates to how glia regulate pain, are hindered by the fact that neurons as well as glia release
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these. Thus, identifying the relative contribution of glia versus neurons to pain facilitation induced by these mediators is difficult to study in vivo. Also of note here is that glia have recently been implicated in the spread of pain beyond the site of injury. Chronic pain patients often report pain perceived as arising from regions well beyond the actual site of injury, a phenomenon known to be due to a spread of increased excitability within the spinal cord beyond the sensory inputs of the injured body site. Indeed, chronic pain patients may also report that pain is perceived not only in the region of the injury but also in the opposite, so-called mirror-image, body area. Spinal cord glia have been implicated in such spread of pain (Milligan et al., 2003; Spataro et al., 2004). It is intriguing that astrocytes are inter-connected into widespread networks via cell-to-cell connections, called gap junctions (Figure 5). These gap junctions allow for the spread of excitation from astrocyte to astrocyte over larger regions (Araque et al., 1999). As the newly excited, distant astrocytes can then begin releasing neuroexcitatory substances (Araque et al., 1999), this suggests that such spread of excitation by glia might be involved in the spread of pain as well. Indeed, disruption of spinal cord glial gap junctions has been found to abolish both mirror-image pain and pathological pain mediated by spinal immune activation in rats, an effect which may be due to attenuation
of the spread of glial activation and thus the absence of pro-inflammatory cytokine production by these distant glia (Spataro et al., 2004) (Figure 6). One last point that bears discussion here regards the relative role of microglia and astrocytes in pain amplification. As noted above, both astrocytes and microglia are thought to play key roles in pain enhancement. Recent studies have begun to examine the parameters that define which glial cell type or types) become activated. Evidence to date points to microglia as highly reactive, vigilant cells that rapidly respond to disruption of normal homeostasis (Nimmerjahn et al., 2005). While microglia, unlike astrocytes, do not enwrap synapses so have no direct “knowledge” of neuronal synaptic activity, they are rapidly responsive to alterations in the extracellular microenvironment. Microglia appear to be the first glial cell type activated under conditions leading to exaggerated pain responses. Blocking microglial activation with minocycline prevents the development of pathological pain in response to nerve injury (Ledeboer et al., 2005b; Raghavendra et al., 2003). Intriguingly, administration of minocycline after pathological pain has developed now fails to control such pain (Ledeboer et al., 2005b; Raghavendra et al., 2003). Data such as these have led to the current view that microglia are the first glial cell to respond, and they, in turn, lead to the recruitment of astrocytes. With astrocyte recruitment, microglial
FIGURE 6 Blocking spinal cord gap junctions with carbenoxolone blocks both astrocyte activation and interleukin-1 production. The gap junction decoupler carbenoxolone inhibits intrathecal HIV-1 gp120-induced spinal IL-1 production and glial activation (Panels A and B, respectively). Panel A: IL-1 protein in dorsal spinal cord 310 minutes after intrathecal (I.T.) injection of gp120 or vehicle (240 minutes after I.T. carbenoxolone or vehicle). Carbenoxolone (carbenoxolone + gp120) blocks increases in IL-1 typically seen following gp120 (vehicle + gp120). Panel B: Mean integrated density of GFAP immunoreactivity in dorsal spinal cord. Eight hours following I.T. gp120 (7 hours after I.T. carbenoxolone) rats were transcardially perfused with 4% paraformaldehyde, and lumbosacral spinal cords were collected for analysis of glial activation (GFAP) by immunohistochemistry. There is a strong trend even with small sample sizes for carbenoxolone to block gp120-induced GFAP increases.
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involvement decreases, and astrocytes maintain pain enhancement over time. The question of which glial cell type is activated first leads naturally to a consideration of the critical stimulus for such glial activation. Immunologically, glia (as noted above) become activated in response to bacteria and viruses. But here, the question is what substance or substances are released within the spinal cord as a consequence of peripheral nerve damage, such that glia become activated? Presumably, something has to be released in the spinal cord by incoming sensory neurons whose peripheral axons have been injured. Or, something could be released by spinal cord neurons upon receiving injury signals from those sensory neurons. In either case, it is presumed that neuron-toglia signals must exist. A number of neuron-to-glia signals have now been posited. Fractalkine is one such signal. Fractalkine is a unique protein (a chemokine) that, in the spinal cord, is expressed exclusively on the outside surface of neurons (Chapman et al., 2000). Fractalkine is released upon strong neuronal activation, thereby forming a diffusable signal. Our studies have shown that, in the spinal cord, only microglia express receptors for fractalkine under either basal or neuropathic pain states (Verge et al., 2004). In support of this conclusion, very strong fractalkine receptor gene expression is observed in enriched microglia cultures derived from rat dorsal spinal cord, while negligible expression is observed in comparable enriched astroglia cultures. Exposure of acutely isolated dorsal spinal cord to fractalkine causes the release of IL-1 (Johnston et al., 2004). As would be expected from this finding, intrathecal microinjection of fractalkine produces hyperalgesia (Milligan et al., 2004). This production of hyperalgesia occurs via activation of microglia, as these pain-enhancing effects are prevented by minocycline, a selective microglial inhibitor (Milligan et al., 2005c). Fractalkine-induced pain enhancement indeed results from the release of nitric oxide and pro-inflammatory cytokines, as these effects are prevented by a nitric oxide synthase inhibitor, an IL-1 receptor antagonist, and IL-6— neutralizing antibodies (Milligan et al., 2005c). Blockade of fractalkine effects, using a neutralizing antibody to the fractalkine receptor, delays the onset of neuropathic pain and also reverses established neuropathic pain for as long as the neutralizing antibody is administered (Milligan et al., 2004). This suggests that peripheral nerve injury causes the sustained release of fractalkine from damaged sensory afferents and/or intrinsic spinal cord neurons, leading to microglial activation and the release of painenhancing substances.
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Heat shock protein is a second putative neuron-toglia signal. This is a novel candidate that is only just beginning to be explored for its pain regulatory effects and effects on dorsal spinal cord glia. Heat shock proteins are best known as intracellular chaperones that protect cells in response to cellular stress. As intracellular signals, they are survival signals. However, when cells are damaged, dying, or dead, heat shock proteins are released and become extracellular signaling molecules to nearby glia. In this role, they can activate glia in their role as immune-like cells. Notably, remarkable upregulation of one member of the heat shock protein family, heat shock protein 27 (Hsp27), has been reported in damaged sensory fibers within spinal cord dorsal horn and surrounding white matter for months after peripheral nerve injury (Costigan et al., 1998). Thus, heat shock proteins may directly activate microglia and/or may synergize with fractalkine. Although speculative, synergy would be a logical mechanism for making glial activation “fail safe”; that is, a combination of “warning signals” may far more potently activate glial cells than any single signal. Synergy would be a logical solution for the regulation of glial activation that leads to pathological pain, as it would constrain the conditions under which such activation would be expected to occur. Notably, preliminary studies indicate that incubation of cultured dorsal spinal cord glia with fractalkine plus Hsp27 potentiates IL-1 gene expression (Wieseler-Frank et al., 2004). Adenosine triphosphate (ATP) is a third putative neuron-to-glia signal. ATP is considered a classical “pain” neurotransmitter, with many purinergic receptor subtypes found on neurons, astrocytes, and microglia. As regards the present proposal, Tsuda et al. (2003) recently demonstrated a key role of microglial P2X4 purinergic receptors in inducing pain enhancement. First, they documented that P2X4 receptors dramatically upregulate in spinal cord ipsilateral to peripheral nerve damage. Critically, these P2X4 receptors are expressed by microglia, but not neurons or astrocytes. Second, they administered a variety of purinergic receptor antagonists to reverse neuropathyinduced allodynia and found that the one specific to microglial P2X4 receptors was effective. Third, they stimulated microglia in vitro with ATP to activate them. Intrathecal microinjection of these in vitro— stimulated microglia was sufficient, in and of itself, to produce mechanical allodynia. While Tsuda et al. did not examine what neuron-to-glia signal so potently upregulates microglial P2X4 purinergic receptors in response to peripheral nerve injury, it may well be that the signal is, at minimum, fractalkine. Preliminary studies indicate that fractalkine upregulates P2X4 gene expression in cultured dorsal spinal cord
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microglia (Wieseler-Frank et al., 2003). Whether heat shock protein, alone or in combination with fractalkine, has similar effects is unknown.
VIII. BEYOND CHRONIC PAIN: GLIAL CELLS OPPOSE THE PAIN-SUPPRESSIVE EFFECTS OF OPIOIDS Up until this point, the discussion has focused on immune-derived and glia-derived enhancement of pain that occurs in response to inflammation, infection and/or injury. Here, the discussion extends to glial activation in response to opioids administered with the aim of relieving such pain (Watkins et al., 2005). The discussion below will develop the concept that spinal cord glia become progressively more activated over time when morphine is repeatedly administered, as would occur when delivered for relief of chronic pain (Watkins et al., 2005). Repeated administration of opioids such as morphine leads to the development of tolerance to the pain-relieving effects of such drugs. This, in turn, leads to progressive increases in drug dosage in an attempt to gain control over pain. Increases in drug dosage leads, in turn, to increases in side effects, such as constipation and respiratory depression (Raith and Hochhaus, 2004). In addition, prolonged opioid administration leads to pain amplification upon discontinuation of the drugs. Such abstinence-associated pain facilitation, like tolerance, is a clinically relevant problem (White, 2004). While tolerance is often thought to occur due to downregulation of opioid receptors, resulting in signaling failure, tolerance can also occur by a quite different process; that is, by the activation of endogenous pain facilitation systems such as those already discussed. The existence of both pain inhibitory and facilitatory systems means that the pain experienced by an individual reflects the summation of these two types of systems. Thus, tolerance could be produced by either a weakening of the pain suppressive system (the typical assumption) by repeated opioid administration, or by a progressive strengthening of pain facilitatory systems. In the latter scenario, the strengthening of the pain facilitatory system would counteract the pain-reducing effects of morphine. Spinal cord glia and the pro-inflammatory cytokine products they produce can be considered such a counteractive system (Watkins et al., 2005). Opioids such as morphine may directly, or indirectly, activate spinal cord glia. Glia elsewhere in the CNS express the full range of opioid receptor subtypes (Chao et al., 1996; Persson et al., 2000), so it is likely (but as yet unproven) that spinal cord glia do as well.
Opioids may also exert indirect effects. Dynorphin is one potential candidate for such indirect effects, as chronic morphine increases spinal dynorphin levels and dynorphin enhances pain, at least in part, via the release of pro-inflammatory cytokines, such as IL-1 (Laughlin et al., 2000; Rady and Fujimoto, 2001). There is also evidence that morphine can release soluble signals from neurons such as fractalkine that serve to induce pro-inflammatory responses from nearby glia (Johnston et al., 2004). Whatever the proximate cause of morphine-induced glial activation and pro-inflammatory cytokine release, it is clear that glial pro-inflammatory cytokines alter the analgesic effects of opioids, such as morphine. Spinal delivery of IL-1 receptor antagonist or the antiinflammatory cytokine IL-10 along with morphine enhances the magnitude and duration of analgesia (Johnston et al., 2004). Similarly, injecting IL-1 into the cerebrospinal fluid of mice, at a dose having no behavioral effect on its own, blocks the analgesic effect of systemic morphine (Shavit et al., 2005). Indeed, if morphine analgesia is allowed to be expressed and then dissipate, potent analgesia can be rapidly reinstated by injecting IL-1 receptor antagonist. This suggests that analgesia only appeared to disappear as a result of the release of pain-enhancing pro-inflammatory cytokines that drive pain-facilitatory effects that counterbalanced the pain-suppressive effects of morphine (Shavit et al., 2005). Such a conclusion is supported by studies of transgenic mice. For example, morphine analgesia is dramatically enhanced in mice with impairments of IL-1 signaling (Shavit et al., 2005). It is clear that chronic morphine activates spinal cord glia, as indicated by the upregulation of gliaspecific activation markers (Raghavendra et al., 2002; Song and Zhao, 2001). That such glial activation contributes to morphine tolerance is supported by the finding that co-administering glial inhibitors along with morphine disrupts the development of morphine tolerance (Song and Zhao, 2001). How glial activation disrupts the effects of morphine is still under investigation. At this point, all evidence points to pro-inflammatory cytokines. Morphine exposure increases spinal cord levels of mRNA, protein and protein release of pro-inflammatory cytokines (Johnston et al., 2004; Raghavendra et al., 2002). These morphine-induced increases in glial pro-inflammatory cytokines are causal to morphine tolerance as blocking pro-inflammatory cytokine function blocks, in turn, both tolerance- and abstinence-induced pain enhancement (Johnston et al., 2004; Raghavendra et al., 2004). Paralleling such findings, transgenic mice with impaired IL-1 signaling demonstrate dramatically reduced morphine tolerance (Shavit et al., 2005).
18. Neuroimmune Interactions and Pain: The Role of Immune and Glial Cells
Interestingly, spinal pro-inflammatory cytokine activation in neuropathic pain pathologies has been linked to the reduced morphine efficacy under neuropathic conditions (Raghavendra et al., 2003), producing a state of naive morphine tolerance. That is, ongoing glial activation in response to neuropathy may “prime” the glia so that they over-respond to morphine, compared to sham controls, rendering morphine ineffective in such pain pathologies. Therefore, spinal cord glia oppose the analgesic effects of morphine via the release of pro-inflammatory cytokines. In response to acute and chronic morphine, this is observed as a decrease in the magnitude and duration of analgesia. In response to cessation of chronic morphine, this is observed as abstinence-induced pain facilitation. Notably, it now appears that morphine will not be alone in having its efficacy undercut by glial activation. Preliminary studies now document that spinal cord glia and pro-inflammatory cytokines similarly compromise the analgesic effects of methadone, at least in part via non-classical opioid receptors (Hutchinson et al., 2005). These data also expand the clinical implications of spinal glial activation, as crosstolerance between opioids may be explained by the activation of the glial pain facilitatory system rendering all attempts to treat chronic pain ineffective. Once it is clear which clinically relevant opioids are affected by glial activation and whether classical opioid receptors or atypical receptors are involved, new therapies can be intelligently designed to separate the painrelieving effects of opioids from their glial-activating effects. Such an outcome would predict far-reaching improvements in the ability of opioids to resolve currently uncontrolled pathological pain states. The clinical implications of glial activation following opioid exposure have now extended to opioid addiction and dependence. Recent data suggest that systemic administration of the blood-brain barrier permeable glial inhibitor, AV-411, can blunt naloxoneprecipitated opioid withdrawal behaviors following chronic morphine administration (Figure 7). These data are supported by the work of Dafny et al. (Dafny et al., 1983; Dougherty and Dafny, 1990), who nearly 30 years ago demonstrated that non-selective immune suppression inhibited morphine-withdrawal behaviors. In light of these recent data, it would now appear Dafny et al. had non-selectively inhibited glial activity as well.
IX. CONCLUSIONS AND IMPLICATIONS Although the present chapter has focused on immune and glial modulation of pain, it should be clear that there is nothing a priori unique about the
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FIGURE 7 Total withdrawal behaviors recorded by a blinded observer, 41–50 minutes following naloxoneprecipitated withdrawal, in rats that had received an escalating dependence regimen of subcutaneous morphine for 5 days, and an intraperitoneal co-administration of vehicle or AV-411, a blood-brain permeable drug with glia suppressive actions. These data indicate that morphine activates glia within the brain, which create a hyperexcitable state expressed as withdrawal behaviors. Data modified from: Shumilla, J. A., Ledeboer, A., Liu, T., Hutchinson, M. R., Skyba, D., Pater, C., Watkins, L. R., and Johnson, K. W. (2005, In press). AV-411, a novel attenuator of neuropathic pain. In Proceedings of the 8th International Conference on the Mechanisms and Treatment of Neuropathic Pain.
nerves or neurons involved. All peripheral nerves, regardless of function, would be expected to be affected to some degree by immune activation in the ways described for pain. Similarly, all CNS neurons, regardless of function, would be expected to be affected by glial activation in the ways described for pain. Indeed, there is growing recognition that glia powerfully influence neuronal functions at all levels of the CNS. This chapter has surveyed immune interactions with pain systems at multiple non-classical sites. Whereas immune regulation of pain has long been recognized at sites in inflammation and damage in the skin, where peripheral nerve terminals have evolved explicitly to accurately sense what is happening to the body, immune regulation of pain along peripheral nerve bundles and within the spinal cord has not. There are several major points that bear reemphasis here. First and foremost is that immune activation and immune-like glial activation are important for pathological pain states, such as neuropathic pain. Classical immune cells (e.g., macrophages, dendritic cells), immunocompetent cells that can release factors thought of as immune cell products (e.g., endothelial cells, fibroblasts, Schwann cells, etc.), and immune-like
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spinal cord glial cells (astrocytes and microglia) can each contribute to pain enhancement. This has profound implications for the understanding of how such pain states occur and how such pain states can be effectively controlled via the development of drug therapies aimed at controlling these recently recognized sources of pain enhancement. The second major point is the pervasiveness of proinflammatory cytokine involvement in pain facilitation, including neuropathic pain. The pain-enhancing effects of pro-inflammatory cytokines at sites of skin or muscle injury have long been recognized. In contrast, pro-inflammatory cytokine enhancement of pain via actions along peripheral nerves, at the DRG, and in spinal cord has only recently been uncovered. These are striking in their implications as novel targets for pain control. The third major point is the breadth of impact that glia have on pain regulation. While most of this chapter reviewed direct effects of glial activation on pain, this topic has recently been expanded by the discovery that opioids such as morphine activate glia as well. The efficacy of opioids for pain relief is hampered by glial release of pro-inflammatory cytokines. Again, the implications of these findings are great. They predict that an understanding of how glia are activated by clinically relevant analgesic drugs will lead, in turn, to improvements in pain control by the development of therapeutics that avoid this unanticipated side effect. The last major point is that investigation of immune and glial involvement in pain is in its infancy. Many more immune cells and immune-derived substances are implicated in the etiology of pathological pain syndromes than have yet been studied for their potential involvement in the pain syndromes that follow, and lastly, very little is understood about the response repertoire and receptor expression of immune-like glial cells within the pain modulatory regions of the spinal cord. The reason is that it has only recently become recognized that glia residing in various sites within the CNS are not all the same. Rather, there can be striking regional heterogeneity in how these cells respond and to what they respond under basal or activated states. Glia are the product of their microenvironment and must be understood in this context. Given that brain glia have almost exclusively been the subject of study, much remains to be learned about the dynamics of dorsal spinal cord glial function under both basal and pathological pain conditions.
References Ahn, S. H., Cho, Y. W., Ahn, M. W., Jang, S. H., Sohn, Y. K., and Kim, H. S. (2002). mRNA expression of cytokines and chemo-
kines in nerniated lumbar intervertebral discs. Spine, 27, 911–917. Aldskogius, H., and Kozlova, E. N. (1998). Central neuron-glial and glial-glial interactions following axon injury. Prog. Neurobiol., 55, 1–26. Araque, A., Parpura, V., Sanzgiri, R. P., and Haydon, P. G. (1999). Tripartite synapses: glia, the unacknowledged partner. Trends in Neurosci., 22, 208–215. Braun, J. S., Kaissling, B., Le Hir, M., and Zenker, W. (1993). Cellular components of the immune barrier in the spinal meninges and dorsal root ganglia of the normal rat: immunohistochemical (MHC class II) and electron-microscopic observations. Cell Tissue Res., 273, 209–217. Burke, J. G., Watson, R. W., McCormack, D., Dowling, F. E., Walsh, M. G., and Fitzpatrick, J. M. (2002). Intervertebral discs which cause low back pain secrete high levels of proinflammatory mediators. J. Bone Joint Surg., 84, 196–201. Cahill, C. M., Dray, A., and Coderre, T. J. (2003). Enhanced thermal antinociceptive potency and anti-allodynic effects of morphine following spinal administration of endotoxin. Brain Res., 960, 209–218. Chacur, M., Milligan, E. D., Gazda, L., Armstrong, C. B., Wang, H., Tracey, K. J., Maier, S. F., and Watkins, L. R. (2001). A new model of sciatic inflammatory neuritis (SIN): induction of unilateral and bilateral mechanical allodynia following acute unilateral perisciatic immune activation in rats. Pain, 94, 231–244. Chacur, M., Milligan, E. D., Sloane, E. M., Wieseler-Frank, J., Barrientos, R., Martin, D., Poole, S., Gutierrez, J. M., Maier, S. F., Cury, Y., and Watkins, L. R. (2004). Snake venom phospholipase A2s (Asp49 and Lys49) induce mechanical allodynia upon perisciatic administration: involvement of spinal cord proinflammatory cytokines and nitric oxide. Pain, 108, 180–191. Chao, C. C., Gekker, G., Hu, S., Sheng, W. S., Shark, K. B., Bu, D. F., Archer, S., Bidlack, J. M., and Peterson, P. K. (1996). Kappa opioid receptors in human microglia downregulate human immunodeficiency virus 1 expression. Proc. Natl. Acad. Sci. USA, 93, 8051–8056. Chapman, G. A., Moores, K., Harrison, D., Campbell, C. A., Steward, B. R., and Strijbos, P. J. L. M. (2000). Fractalkine cleavage from neuronal membranes represents an acute event in the inflammatory response to excitotoxic brain damage. J. Neurosci., 20, RC87 (81–85). Clarke, R. W., and Harris, J. (2004). The organization of motor responses to noxious stimuli. Brain Res. Brain Res. Rev., 46, 163–172. Clatworthy, A. L., Castro, G. A., Budelmann, B. U., and Walters, E. T. (1994). Induction of a cellular defense reaction is accompanied by an increase in sensory neuron excitability in Aplysia. J. Neurosci., 14, 3263–3270. Clatworthy, A. L., and Grose, E. (1999). Immune-mediated alterations in nociceptive sensory function in Aplysia californica. J. Exp. Biol., 202, 623–630. Clatworthy, A. L., Illich, P. A., Castro, G. A., and Walters, E. T. (1995). Role of periaxonal inflammation in the development of thermal hyperalgesia and guarding behavior in a rat model of neuropathic pain. Neurosci. Letts., 184, 5–8. Costigan, M., Mannion, R. J., Kendall, G., Lewis, S. E., Campagna, J. A., Coggeshall, R. E., Meridith-Middleton, J., Tate, S., and Woolf, C. J. (1998). Heat shock protein 27: developmental regulation and expression after peripheral nerve injury. J. Neurosci., 18, 5891–5900. Crusazk, C. A., Sutherland, D. E., Billman, M. A., and Stein, S. H. (1996). Prostaglandin E2 potentiates interleukin-1beta induced interleukin-6 production by human gingival fibroblasts. Clin. Periodontol., 23, 635–640.
18. Neuroimmune Interactions and Pain: The Role of Immune and Glial Cells Cuadros, M. A., and Navascues, J. (2001). Early origin and colonization of the developing central nervous system by microglial precursors. In B. Castellano Lopez, and M. Nieto-Sampedro (Eds.), Prog. Brain Res. (pp. 51–59). Amsterdam: Elsevier. Dafny, N., Zielinksi, M., and Reyes-Vazquez, C. (1983). Alteration of morphine withdrawal to naloxone by interferon. Neuropeptides, 3, 453–463. Dougherty, P. M., and Dafny, N. (1990). Microiontophoretic application of muramyl-dipeptide upon single cortical, hippocampal and hypothalamic neurons in rats. Neuropharmacology, 29, 973–981. Garrison, C. J., Dougherty, P. M., and Carlton, S. M. (1994). GFAP expression in lumbar spinal cord of naive and neuropathic rats treated with MK-801. Exp. Neurol., 129, 237–243. Garrison, C. J., Dougherty, P. M., Kajander, K. C., and Carlton, S. M. (1991). Staining of glial fibrillary acidic protein (GFAP) in lumbar spinal cord increases following a sciatic nerve constriction injury. Brain Research, 565, 1–7. Gebhart, G. F. (2004). Descending modulation of pain. Neurosci. Biobehav. Rev., 27, 729–737. Goldman, J. E., and Vaysse, P. J. J. (1991). Tracing glial cell lineages in the mammalian forebrain. Glia., 4, 149–156. Hart, B. L. (1988). Biological basis of the behavior of sick animals. Neurosci. Biobehav. Rev., 12, 123–137. Haydon, P. G. (2001). Glia: Listening and talking to the synapse. Nature Rev. Neurosci., 2, 185–193. Huang, T.-Y., and Hanini, M. (2005, In press). Morphological and electrophysiological changes in mouse dorsal root ganglia after partial clonic obstruction. Am. J. Physiol. Gasrointest. Liver Physiol., 289, 670–678. Hutchinson, M. R., Milligan, E. D., Maier, S. F., and Watkins, L. R. (2005, In press). Interleukin-1 receptor antagonist (IL1ra) “unmasks” analgesia following both R- & S-methadone: evidence for induction of spinal proinflammatory cytokines (PICs) via non-classical opioid receptors. Proc. Soc. Neurosci. Jekich, B., Wieseler-Frank, J., Maier, S., and Watkins, L. (2006, In press). Meningeal immune cells produce proinflammatory cytokines in response to chronic constriction nerve injury. In Proceedings of the Psychoneuroimmunology Research Society. Johnston, I. N., Milligan, E. D., Wieseler-Frank, J., Frank, M. G., Zapata, V., Campisi, J., Langer, S., Martin, D., Green, P., Fleshner, M., Leinwand, L., Maier, S. F., and Watkins, L. R. (2004). A role for proinflammatory cytokines and fractalkine in analgesia, tolerance, and subsequent pain facilitation induced by chronic intrathecal morphine. J. Neurosci., 24, 7353–7365. Julius, D., and Basbaum, A. I. (2001). Molecular mechanisms of nociception. Nature, 413, 203–210. Kagan, B. L., Baldwin, R. L., Munoz, D., and Wisnieski, B. J. (1992). Formation of ion-permeable channels by tumor necrosis factoralpha. Science, 255, 1427–1430. Kang, J. D., Stepanovic-Racic, M., McIntyre, L. A., Georgescu, H. I., and Evans, C. H. (1997). Toward a biochemical understanding of a human intervertebral disc degeneration and herniation. Contributions of nitric oxide, interleukins, prostaglandin E2, and matrix metalloproteinases. Spine, 22, 1065–1073. Kaur, C., Hao, A. J., Wu, C. H., and Ling, E. A. (2001). Origin of microglia. Microscopy Res. Tech., 54, 2–9. Kawakami, M., Matsumoto, T., Kuribayashi, K., and Tamaki, T. (1999). mRNA expression of interleukins, phospholipase A2, and nitric oxide synthase in the nerve root and dorsal root ganglion induced by autologous nucleus pulposus in the rat. J. Orthop. Res., 17, 941–946. Laughlin, T. M., Bethea, J. R., Yezierski, R. P., and Wilcox, G. L. (2000). Cytokine involvement in dynorphin-induced allodynia. Pain, 84, 159–267.
411
Lawson, L. J., Perry, V. H., and Gordon, S. (1992). Turnover of resident microglia in the normal adult mouse brain. Neurosci., 48, 405–415. Ledeboer, A., Sloane, E. M., Milligan, E. D., Langer, S. J., Maier, S. F., Johnson, K. W., Leinwand, L. A., Chavez, R. A., Watkins, L. R. Paclitaxel-induced mechanical allodynia in rats is inhibited by spinal delivery of plasmid DNA encoding interleukin-10. In: H. Flor, E. Kalso, J. O. Dostrovsky (Eds.), Proceedings of the 11th World Congress on Pain, Progress in Pain Research and Management, Seattle: IASP Press, 2006, in press. Ledeboer, A., Sloane, E. M., Milligan, E. D., Frank, M. G., Mahony, J. H., Maier, S. F., and Watkins, L. R. (2005b). Minocycline attenuates mechanical allodynia and proinflammatory cytokine expression in rat models of pain facilitation. Pain, 115, 71–83. Lee, J. C., Mayer-Proschel, M., and Rao, M. S. (2000). Gliogenesis in the central nervous system. Glia, 30, 105–121. Liu, B.-G., Hastings, S. L., Li, H., Jia, Y.-P., Brull, S. J., and Zhang, J. M. (2000a). Tumor necrosis factor α enhances the excitability of dorsal root ganglion cells with unmyelinated axons. Soc. Neurosci. Abstr., 26, 1695. Liu, T., Knight, K. R., and Tracey, D. J. (2000b). Hyperalgesia due to nerve injury—role of peroxynitrite. Neuroscience, 97, 125–131. Liu, T., Ledeboer, A., Shumilla, J. A., Hutchinson, M. R., Skyba, D., Pater, C., Watkins, L. R. & Johnson, K. W., AV-411, a novel attenuator of neuropathic pain, Presented at the 8th International Conference on the Mechanisms and Treatment of neuropathicPain, San Francisco, CA, 2005. Louis Harris and Associates (1999). The 1999 National Pain Survey. On behalf of Ortho McNeil. Maier, S. F., and Watkins, L. R. (1998). Cytokines for psychologists: implications of bi-directional immune-to-brain communication for understanding behavior, mood, and cognition. Psych. Rev., 105, 83–107. Maier, S. F., Wiertelak, E. P., and Watkins, L. R. (1992). Endogenous pain facilitatory systems: anti-analgesia and hyperalgesia. American Pain Society Journal, 1, 191–198. Marchand, F., Perretti, M., and McMahon, S. B. (2005). Role of the immune system in chronic pain. Nat. Rev. Neurosci., 6, 521– 532. McMenamin, P. G. (1999). Distribution and phenotype of dendritic cells and resident tissue macrophages in the dura mater, leptomeninges, and choroid plexus of the rat brain as demonstrated in wholemount preparations, J. Comp. Neuro., 405, 553–562. McQuay, H., Carroll, D., Jadad, A. R., Wiffen, P., and Moore, A. (1995). Anticonvulsant drugs for management of pain: a systematic review. Brit. Med. J., 311, 1047–1052. McQuay, H. J., Tramer, M., Nye, B. A., Carroll, D., Wiffen, P. J., and Moore, R. A. (1996). A systematic review of antidepressants in neuropathic pain. Pain, 68, 217–227. Mercier, F., and Hatton, G. I. (2001). Connexin 26 and basic fibroblast growth factor are expressed primarily in the subpial and subependymal layers in adult brain parenchyma: roles in stem cell proliferation and morphological plasticity? J. Comp. Neurol., 431, 88–104. Mercier, F., and Hatton, G. I. (2004). Meninges and perivasculature as mediators of CNS plasticity. In L. Hertz (Ed.), Non-neuronal cells of the nervous system: Function and dysfunction (pp. 215–253). Amsterdam: Elsevier. Mercier, F., Kitasako, J. T., and Hatton, G. I. (2002). Anatomy of the brain neurogenic zones revisited: fractones and the fibroblast/ macrophage network. J. Comp. Neurol., 451, 170–188. Mercier, F., Kitasako, J. T., and Hatton, G. I. (2003). Fractones and other basal laminae in the hypothalamus. J. Comp. Neurol., 455, 324–340.
412
II. Immune System Effects on Neural and Endocrine Processes and Behavior
Milligan, E. D., Langer, S. J., Sloane, E. M., He, L., Wieseler-Frank, J., O’Connor, K., Martin, D., Forsayeth, J. R., Maier, S. F., Johnson, K., Chavez, R. A., Leinwand, L. A., and Watkins, L. R. (2005a). Controlling pathological pain by adenovirally driven spinal production of the anti-inflammatory cytokine, interleukin-10. Eur. J. Neurosci., 21, 2136–2148. Milligan, E. D., O’Connor, K. A., Nguyen, K. T., Armstrong, C. B., Twining, C., Gaykema, R. P., Holguin, A., Martin, D., Maier, S. F., and Watkins, L. R. (2001). Intrathecal HIV-1 envelope glycoprotein gp120 induces enhanced pain states mediated by spinal cord proinflammatory cytokines. J. Neurosci., 21, 2808–2819. Milligan, E. D., Sloane, E. M., Langer, S. J., Cruz, P. E., Chacur, M., Spataro, L., Wieseler-Frank, J., Hammack, S. E., Maier, S. F., Flotte, T. R., Forsayeth, J. R., Leinwand, L. A., Chavez, R., and Watkins, L. R. (2005b). Controlling neuropathic pain by adenoassociated virus driven production of the anti-inflammatory cytokine, interleukin-10. Molecular Pain, 1. Retrieved from http:// www.molecularpain.com/content/1/1/9. Milligan, E. D., Twining, C., Chacur, M., Biedenkapp, J., O’Connor, K., Poole, S., Tracey, K., Martin, D., Maier, S. F., and Watkins, L. R. (2003). Spinal glia and proinflammatory cytokines mediate mirror-image neuropathic pain in rats. J. Neurosci., 23, 1026–1040. Milligan, E. D., Zapata, V., Chacur, M., Schoeniger, D., Biedenkapp, J., O’Connor, K. A., Verge, G. M., Chapman, G., Green, P., Foster, A. C., Naeve, G. S., Maier, S. F., and Watkins, L. R. (2004). Evidence that exogenous and endogenous fractalkine can induce spinal nociceptive facilitation in rats. Eur. J. Neurosci., 20, 2294–2302. Milligan, E. D., Zapata, V., Schoeniger, D., Chacur, M., Green, P., Poole, S., Martin, D., Maier, S. F., and Watkins, L. R. (2005c, Submitted). An initial investigation of spinal mechanisms underlying pain enhancement induced by fractalkine, a neuronallyreleased chemokine. Moalem, G., Grafe, P., and Tracey, D. J. (2005, In press). Chemical mediators enhance the excitability of unmyelinated sensory axons in normal and injured peripheral nerve of the rat. Neuroscience., 134, 1399–1411. Morioka, N., Inoue, A., Hanada, T., Kumagai, K., Takeda, K., Ikoma, K., Hide, I., Tamura, Y., Shiomi, H., Dohi, T., and Nakata, Y. (2002). Nitric oxide synergistically potentiates interleukin-1 beta induced increase of cyclooxygenase-2 mRNA levels, resulting in the facilitation of substance P release from primary afferent neurons: involvement of cGMP-independent mechanisms. Neuropharmacology, 43, 868–876. Myers, R. R., Heckman, H. M., and Rodriguez, M. (1996). Reduced hyperalgesia in nerve-injured WLD mice: relationship to nerve fiber phagocytosis, axonal degeneration and regeneration in normal mice. Exp. Neurol., 141, 94–101. Myers, R. R., Wagner, R., and Sorkin, L. S. (1999). Hyperalgesic actions of cytokines on peripheral nerves. In L. R. Watkins and S. F. Maier (Eds.), Cytokines and pain (pp. 133–158). Basel: Birkause. Nash, T. P. (2005). What use is pain? Brit. J. ABrit. J. Anaesthesnaesthes, 94, 146–149. Nimmerjahn, A., Kirchhoff, F., and Helmchen, F. (2005). Resting microglial cells are highly dynamic surveillants of brain parenchyma in vivo. Science, 308, 1314–1318. Ohtori, S., Takahashi, K., Moriya, H., and Myers, R. R. (2004). TNFalpha and TNF-alpha receptor type 1 upregulation in glia and neurons after peripheral nerve injury: studies in murine DRG and spinal cord. Spine, 29, 1082–1088. Olmarker, K., and Rydevik, B. (2001). Selective inhibition of tumor necrosis factor-alpha prevents nucleus pulposus-induced
thrombus formation, intraneural edema, and reduction of nerve conduction velocity: possible implications for future pharmacologic treatment strategies of sciatica. Spine, 26, 863– 869. Olsson, Y. (1990). Microenvironment of the peripheral nervous system under normal and pathological conditions. Crit. Rev. Neurobiol., 5, 265–311. Palma, C., Minghetti, L., Atolfi, M., Ambrosini, E., Silberstein, F. C., Manzini, S., Levi, G., and Aloisi, F. (1997). Functional characterization of substance P receptors on cultured human spinal cord astrocytes: synergism of substance P with cytokines in inducing interleukin-6 and prostaglandin E2 production. Glia, 21, 183–193. Parnet, P., Kelley, K. W., Bluthe, R. M., and Dantzer, R. (2002). Expression and regulation of interleukin-1 receptors in the brain. Role in cytokine-induced sickness behavior. J. Neuroimmunol., 125, 5–14. Partners Against Pain (2000). A Survey of Pain in America. On behalf of Purdue Pharma. Patestas, M., and Gartner, L. (2006). A textbook of neuroanatomy. Oxford: Blackwell Publishing. Perea, G., and Araque, A. (2002). Communication between astrocytes and neurons: a complex language. J. Physiol., 96, 199–207. Perry, V. H. (1998). A revised view of the central nervous system microenvironment and major histocompatibility complex class II antigen presentation. J. Neuroimmunol., 90, 113–121. Perry, V. H., Hume, D. A., and Gordon, S. (1985). Immunohistochemical localisation of macrophages and microglia in the adult and developing mouse brain. Neurosci., 15, 313–326. Persson, P. A., Thorlin, T., Ronnback, L., Hansson, E., and Eriksson, P. S. (2000). Differential expression of delta opioid receptors and mRNA in proliferating astrocytes during the cell cycle. J. Neurosci. Res., 61, 371–375. Petrenko, A. B., Yamakura, T., Baba, H., and Shimoji, K. (2003). The role of N-methyl-D-aspartate (NMDA) receptors in pain: a review. Anesth. Analg., 97, 1108–1116. Petrova, T. V., Hu, J., and Van Eldik, L. J. (2000). Modulation of glial activation by astrocyte-derived protein S100B: differential responses of astrocyte and microglial cultures. Brain Res., 853, 74–80. Petty, P. G., Hudgson, P., and Hare, W. S. (2000). Symptomatic lumbar spinal arachnoiditis: fact or fallacy? J. Clin. Neurosci., 7, 395–399. Porter, J. T., and McCarthy, K. D. (1997). Astrocytic neurotransmitter receptors in situ and in vivo. Prog. Neurobiol., 51, 439–455. Powell, H. C., and Myers, R. R. (1986). Pathology of experimental nerve compression. Lab. Invest., 55, 91–100. Quan, N., Whiteside, M., and Herkenham, M. (1998). Cyclooxygenase 2 mRNA expression in rat brain after peripheral injection of lipopolysaccharide. Brain Res., 802, 189–197. Rady, J. J., and Fujimoto, J. M. (2001). Confluence of antianalgesic action of diverse agents through brain interleukin 1 beta in mice. J. Pharmacol. Exp. Ther., 299, 659–665. Raghavendra, V., Rutkowski, M. D., and DeLeo, J. A. (2002). The role of spinal neuroimmune activation in morphine tolerance/hyperalgesia in neuropathic and sham-operated rats. J. Neurosci., 22, 9980–9989. Raghavendra, V., Tanga, F., and DeLeo, J. A. (2003). Inhibition of microglial activation attenuates the development but not existing hypersensitivity in a rat model of neuropathy. J. Pharmacol. Exp. Ther., 306, 624–630. Raghavendra, V., Tanga, F. Y., and DeLeo, J. A. (2004). Attenuation of morphine tolerance, withdrawal-induced hyperalgesia, and
18. Neuroimmune Interactions and Pain: The Role of Immune and Glial Cells associated spinal inflammatory immune responses by propentofylline in rats. Neuropsychopharmacology, 29, 327–334. Raith, K., and Hochhaus, G. (2004). Drugs used in the treatment of opioid tolerance and physical dependence: a review. Int. J. Clin. Pharmacol. Ther., 42, 191–203. Raivich, G., Bohatschek, M., Kloss, C. U. A., Werner, A., Jones, L. L., and Kreutzberg, G. W. (1999). Neuroglial activation repertoire in the injured brain: graded response, molecular mechanisms and cures to physiological function. Brain Res. Rev., 30, 77–105. Reeve, A. J., Patel, S., Fox, A., Walker, K., and Urban, L. (2000). Intrathecally administered endotoxin or cytokines produce allodynia, hyperalgesia and changes in spinal cord neuronal responses to nociceptive stimuli in the rat. Eur. J. Pain, 4, 247–257. Roper Starch Worldwide, I. (1999). Chronic Pain in America: Roadblocks to Relief Survey. On behalf of the American Pain Society, American Academy of Pain Medicine and Janssen Pharmaceutica. Rothwell, N. J., and Luheshi, G. (1994). Pharmacology of interleukin1 actions in the brain. Adv. Pharmacol., 25, 1–20. Said, G., and Hontebeyrie-Joskowicz, M. (1992). Nerve lesions induced by macrophage activation. Res. Immunol., 143, 589–599. Samad, T. A., Moore, K. A., Sapirstein, A., Billet, S., Allchorne, A., Poole, S., Bonventre, J. V., and Woolf, C. J. (2001). Interleukin1beta mediated induction of COX-2 in the CNS contributes to inflammatory pain hypersensitivity. Nature, 410, 471–475. Samad, T. A., Wang, H., Broom, D. C., and Woolf, C. J. (2004). Central neuroimmune interactions after peripheral inflammation: interleukin-1b potentiates synaptic transmission in the spinal cord. Proc. Soc. Neurosci., 34, 511–517. Schettini, G. M., Florio, T., Scala, G., Landolfi, E., and Grimaldi, M. (1988). Effect of interleukin-1 beta on transducing mechanisms in 235-I clonal pituitary cells. Part II. Modulation of calcium fluxes. Biochem. Biophys. Res. Commun., 155, 1097–1104. Scholz, J., and Woolf, C. J. (2002). Can we conquer pain? Nature Neurosci., 5(Suppl.), 1062–1067. Shavit, Y., Wolf, G., Goshen, I., Livshits, D., and Yirmiya, R. (2005). Interleukin-1 antagonizes morphine analgesia and underlies morphine tolerance. Pain, 115, 50–59. Sjostrand, J. (1971). Neuroglial proliferation in the hypoglossal nucleus after nerve injury. Exp. Neurol., 30, 178–189. Sloane, E., Langer, S., Milligan, E., Jekich, B., Mahoney, J., Huberty, G., Hughes, T., Coates, B., Klinman, D., Poole, S., Maier, S., Johnson, K., Leinwand, L., Chavez, R., and Watkins, L. R. (2005, In press). Resolution of neuropathic pain by intrathecal (IT) gene therapy to drive the production of interleukin-10 (IL10): initial investigations into underlying mechanisms. Proceedings of the Eleventh World Congress of Pain, 217. Snyder, S. H. (2004). Opiate receptors and beyond: 30 years of neural signaling research. Neuropharmacology, 47(Supplement 271), 274–285. Sommer, C., Marziniak, M., and Myers, R. R. (1998). The effect of thalidomide treatment on vascular pathology and hyperalgesia caused by chronic constriction injury of rat nerve. Pain, 74, 83–91. Sommer, C., Petrausch, S., Lindenlaub, T., and Toyka, K. V. (1999). Neutralizing antibodies to interleukin 1-receptor reduce pain associated behavior in mice with experimental neuropathy. Neurosci. Lett., 270, 25–28. Song, P., and Zhao, Z. Q. (2001). The involvement of glial cells in the development of morphine tolerance. Neurosci. Res., 39, 281–286. Sorkin, L. S., Xiao, W. H., Wagner, R., and Myers, R. R. (1997). Tumor necrosis factor-alpha induces ectopic activity in nociceptive primary afferent fibers. Neuroscience, 81, 255–262.
413
Spataro, L., Sloane, E., Milligan, E. D., Wieseler-Frank, J., Schoeniger, D., Jekrich, B. M., Barrientos, R. M., Maier, S. F., and Watkins, L. R. (2004). Spinal gap junctions: potential involvement in pain facilitation. J. Pain, 5, 392–405. Spataro, L. E., Wieseler-Frank, J., Milligan, E. D., Jekich, B. M., Sprunger, D. B., Maier, S. F., and Watkins, L. R. (2005, In press). Prior peripheral immune/traumatic challenge may exacerbate later immune & pain responses. Proc. Soc. Neurosci. Stellwagen, D., Beattie, E. C., Seo, J. Y., and Malenka, R. C. (2005). Differential regulation of AMPA receptor and GABA receptor trafficking by tumor necrosis factor-alpha. J. Neurosci., 25, 3219–3228. Tang, H. B., Inoue, A., Oshita, K., and Nakata, Y. (2004). Sensitization of vanilloid receptor 1 induced by bradykinin via the activation of second messenger signaling cascades in rat primary afferents. Eur. J. Pharmacol., 498, 37–43. Tsacopoulos, M. (2002). Metabolic signaling between neurons and glial cells: a short review. J. Physiol., 96, 283–288. Tsuda, M., Shigemoto-Mogami, Y., Koizumi, S., Mizokoshi, A., Kohsaka, S., Salter, M. W., and Inoue, K. (2003). P2X4 receptors induced in spinal microglia gate tactile allodynia after nerve injury. Nature, 424, 778–783. Verge, G. M., Milligan, E. D., Maier, S. F., Watkins, L. R., Naeve, G. S., and Foster, A. C. (2004). Fractalkine (CX3CL1) and fractalkine receptor (CX3CR1) distribution in spinal cord and dorsal root ganglia under basal and neuropathic pain conditions. Eur. J. Neurosci., 20, 1150–1160. Viviani, B., Bartesaghi, S., Gardoni, F., Vezzani, A., Behrens, M. M., Bartfai, T., Binaglia, M., Corsini, E., DiLuca, M., Galli, C. L., and Marinovich, M. (2003). Interleukin-1beta enhances NMDA receptor-mediated intracellular calcium increase through activation of the Src family of kinases. J. Neurosci., 23, 8692–8700. Walters, E. T. (1994). Injury-related behavior and neuronal plasticity: an evolutionary perspective on sensitization, hyperalgesia, and analgesia. Int. Rev. Neurobiol., 36, 325–427. Watkins, L. R., Hutchinson, M. R., Johnston, I. N., and Maier, S. F. (2005, In press). Glia: novel counter-regulators of opioid analgesia. Trends in Neurosci., 28, 661–669. Watkins, L. R., and Maier, S. F. (2000). The pain of being sick: implications of immune-to-brain communication for understanding pain. Annu. Rev. Psychol., 51, 29–57. Watkins, L. R., and Maier, S. F. (2002). Evidence that immune and glial cells contribute to pathological pain states. Physiol. Rev., 82, 981–1011. Watkins, L. R., and Maier, S. F. (2003). Glia: a novel drug discovery target for clinical pain. Nat. Rev. Drug. Discov., 2, 973–985. Watkins, L. R., Milligan, E. D., and Maier, S. F. (2001). Glial activation: a driving force for pathological pain. Trends Neurosci., 24, 450–455. White, J. M. (2004). Pleasure into pain: the consequences of longterm opioid use. Addict. Behav., 29, 1311–1324. Wieseler-Frank, J., Jekich, B., Maier, S., and Watkins, L. (2006, In press) Meningeal immune cells produce proinflammatory cytokines in response to HIV glycoprotein, gp120. In Proceedings of the Psychoneuroimmunology Research Society. Wieseler-Frank, J., Kwiecien, O., Jekich, B. M., Maier, S. F., and Watkins, L. R. (2004). Putative neuron-to-glia signals synergize to enhance interleukin-1 production by rat dorsal spinal cord glial cells in vitro. Proc. Soc. Neurosci. Wieseler-Frank, J. L., Maskimova, E., Milligan, E. D., Campisi, J., Fleshner, M., Maier, S. F., and Watkins, L. R. (2003). Modulation of dorsal spinal cord glial function by the chronic pain mediator, fractalkine. Proc. Soc. Neurosci., 29, 587–589.
414
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Wilkinson, M. F., Earle, M. L., Triggle, C. R., and Barnes, S. (1996). Interleukin-1beta, tumor necrosis factor-alpha and LPS enhance calcium channel current in isolated vascular smooth muscle cells of rat tail artery. FASEB J., 10, 785–791. Woolf, C. J., and Salter, M. W. (2000). Neuronal plasticity: increasing the gain in pain. Science, 288, 1765–1769. Zelenka, M., Schafers, M., and Sommer, C. (2005). Intraneural injection of interleukin-1beta and tumor necrosis factor-alpha into rat sciatic nerve at physiological doses induces signs of neuropathic pain. Pain, 116, 257–263.
Zhang, N., Inan, S., Cowan, A., Sun, R., Wang, J. M., Rogers, T. J., Caterina, M., and Oppenheim, J. J. (2005). A proinflammatory cytokine, CC3, sensitizes the heat- and capsaicin-gated ion channel TRPV1. Proc. Natl. Acad. Sci. USA, 102, 4536–4541. Zhou, X. F., Deng, Y. S., Chie, E. T., Xue, Q., Zhong, J. H., McLachlan, E. M., Rush, R. A., and Xian, C. J. (1999). Satellitecell–derived nerve growth factor and neurotrophin-3 are involved in noradrenergic sprouting in the dorsal root ganglia following peripheral nerve injury in the rat. Eur. J. Neurosci., 11, 1711–1722.
C H A P T E R
19 Cytokines and Non-immune Brain Injury BARRY W. MCCOLL, CHRIS J. STOCK, AND NANCY J. ROTHWELL
effects of inflammation in the injured or diseased brain. This chapter will endeavor to provide an overview of the studies that have been integral to elucidating the putative involvement of cytokines in non-immune brain injury and disease.
I. INTRODUCTION 415 II. EVIDENCE OF CYTOKINE INVOLVEMENT IN CNS INJURY AND DISEASE 416 III. CYTOKINES IN REPAIR AND RECOVERY AFTER CNS INJURY 421 IV. MECHANISMS OF CYTOKINE ACTIONS 422 V. CONCLUSIONS AND THERAPEUTIC POTENTIAL 422
I. INTRODUCTION The importance of cytokine actions in the brain in regulating the host defense response is now well recognized, and described in detail elsewhere in this volume. Cytokines are classically recognized as local mediators of tissue responses to injury, infection, ischemia, and immune activation. Yet this local function was, for many years, largely ignored in the central nervous system. Infections of the brain, such as malaria, measles, and HIV have long been known to elicit local cytokine activation in the CNS and immune diseases, most notably multiple sclerosis has been linked to cytokines for well over a decade (Allan and Rothwell, 2003). However, the potential contribution of cytokines—both beneficial and detrimental to acute and chronic CNS diseases and insults is now well established. The most extensively studied cytokines in brain injury are the pro-inflammatory molecules IL-1, TNFα, and IL-6, but evidence, albeit often circumstantial, also implicates a range of other cytokines including IL-4, IL-10, IL-12, IL-18, interferons, and chemokines, as well as newer members of the IL-1 and TNF families. In many cases evidence is largely indirect and
ABSTRACT Emerging evidence, mainly derived from experimental studies, suggests that cytokines may play key roles in influencing the severity and evolution of acute tissue damage in response to ischemic and traumatic brain injury. Most convincing evidence has accumulated for IL-1, implicating the actions of this cytokine as detrimental to outcome after injury. In addition to their role in acute damage, there is growing interest regarding the involvement of cytokines in the postacute phase, notably in the resolution of acute inflammation and their impact on brain tissue repair and long-term functional recovery. The involvement of cytokines in chronic neurodegenerative disorders is also an area of expanding investigation in light of the discovery of cytokine gene polymorphisms which confer increased risk of developing Alzheimer’s disease. Further studies will be required to clarify the mechanisms by which cytokines can modulate the response to acute brain injury. It is conceivable that such studies may reveal novel targets for intervention that may prove useful in ameliorating the damaging PSYCHONEUROIMMUNOLOGY, 4E VOLUME I
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based predominantly on expression patterns. In others a clear role has been established, at least in experimental studies, as is the case for IL-1 in acute experimental brain injury. Some cytokines appear to have complex or even seemingly opposing actions, particularly during the acute phases of developing injury and later repair and recovery. There is less direct evidence to implicate cytokines in chronic CNS diseases associated with injury, but supportive data are now available or emerging for their likely contribution to Alzheimer’s disease, movement disorders, amyotrophic lateral sclerosis, injury resulting from epilepsy or tumors, and the transmissible spongiphorm encephalopathies.
II. EVIDENCE OF CYTOKINE INVOLVEMENT IN CNS INJURY AND DISEASE A. Evidence of Cytokine Overexpression after CNS Injury There exists substantial clinical and experimental evidence of increased local cytokine expression within the CNS in response to insults such as ischemic stroke and traumatic brain injury (TBI), although the spatiotemporal modulation of this expression is incompletely understood. Various anomalous observations, in combination with ample evidence of complex regulatory interactions between cytokines, suggest that the expres-
sion profile of CNS cytokines after injury is highly dynamic. While almost all CNS cell types are capable of expressing the majority of cytokines and their receptors, acute-phase transcription and immunoreactivity (ir) of “pro-inflammatory” cytokines such as IL-1β and TNF-α are localized to cells exhibiting monocytic or microglial morphologies and degenerating neurones (Buttini et al., 1994; Davies et al., 1999; Knoblach et al., 1999; Logan et al., 1994; Ohtaki et al., 2004; Sairanen et al., 2001; Wiessner et al., 1993). In contrast, postacute (days to weeks post-insult) immunoreactivity of “anti-inflammatory” cytokines (e.g., TGF-β and IL-10) is associated predominantly with astrocytes and large phagocytes (Lehrmann et al., 1995; Li et al., 2001; Logan et al., 1994; Wiessner et al., 1993) (Figure 1). There is also evidence of a significant delay (and in some cases a discrimination) between peak transcription and peak protein levels of some cytokines in response to injury, and a spatial transition of expression from pathologic foci to peri-infarct regions over the first 24–48 hours after injury. The majority of these data have been acquired from experimental models of cerebral ischemia in rodents, and it is primarily such studies that will be discussed here. 1. Pro-inflammatory Cytokines: IL-1b, TNF-a, and IL-6 IL-1β transcription is rapidly (1–3 hours) and transiently (up to 3 days, peak at 6–24 hours) upreg-
FIGURE 1 CNS cytokine expression after injury. Expression of several cytokines, including pro-inflammatory IL-1β, TNF-α, IL-6, and anti-inflammatory IL-10, is rapidly upregulated within injured brain tissue (in red). The primary source of this expression is microglia and infiltrating leukocytes, although TNF-α is strongly associated with neural processes. From 3 days onwards, resolution of energy deficits and reparative processes around the injury core (core in red, recovering tissue in green) coincide with significant production of both IL-1β and its endogenous antagonist IL-1RA, in parallel with elevated TGF-β expression within reactive astrocytes and large phagocytes.
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ulated within the ischemic rodent brain, accompanied by significant, but modest, increases in protein levels (Berti et al., 2002; Buttini et al., 1994; Legos et al., 2000; Liu et al., 1993; Zhai et al., 1997). Both in situ hybridization (ISH) and immunohistochemical (IHC) analyses have identified microglia and cells exhibiting a monocytic morphology as the source of this acute-phase expression (Buttini et al., 1994; Davies et al., 1999). Although IL-1 is believed to signal only through its type I receptor (IL-1RI), it is transcription of the “decoy” type II receptor that is acutely upregulated in response to injury, primarily in peripheral monocytes and endothelia (Docagne et al., 2005; Parker et al., 2000; Wang et al., 1997). In contrast, peak transcription of IL-1RI is not observed until 5 days after injury, which coincides with peaks in gross protein levels of both IL-1β (3–5 days) and its endogenous antagonist, IL-1RA (5 days), which is present in concentrations 20-fold higher than IL1β at these times (Legos et al., 2000; Wang et al., 1997). There is little clinical evidence of IL-1β upregulation, although elevated plasma concentrations of IL-1β are observed at 3 hours post-admission in stroke patients (Mazzotta et al., 2004). Both IL-6 and TNF-α exhibit similar upregulation to IL-1β after cerebral ischemia in the rat; mRNA levels are increased by 2–3 hours, peak at 6–12 hours, and decline to baseline by 3 days (Berti et al., 2002). Protein levels of IL-6 in the ischemic rat brain lag behind transcription, peaking at 24 hours, before declining by 3 days (Legos et al., 2000). Clinical data from stroke, TBI, and subarachnoid hemorrhage (SAH) patients demonstrate rapid (3 hours) increases in plasma and intrathecal IL-6 levels that peak at 2–4 days before declining to baseline, excepting stroke, after which CSF upregulation persists for up to 3 months (Hayakata et al., 2004; Mathiesen et al., 1993; Tarkowski et al., 1995; Vila et al., 2000). Higher cerebrospinal fluid (CSF) IL-6 concentrations cf plasma after such injuries and microdialysis assays of parenchymal IL-6 levels support the contention of significant local CNS production (Mathiesen et al., 1993; Tarkowski et al., 1995; Winter et al., 2004). IHC analysis of IL-6 immunoreactivity after focal ischemia in rodents suggests that it is primarily produced by microglia-like cells and neurones within the peri-infarct zone up to 14 days post-injury (Block et al., 2000). There are few reports of IL-6 receptor expression, although diffuse upregulation of IL-6R mRNA and immunoreactivity in neurones is observed up to 24 hours after striatal stab lesion in parallel with similar increases in IL-6, IL-1β, and IL-1R expression (Yan et al., 1992). Although comparable data are not available for TNF-α, immunohistochemical studies of acute isch-
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emic injury in the rat indicate strong TNF-α protein expression from 6 hours through to 24 hours (Liu et al., 1994; Ohtaki et al., 2004). Such studies demonstrate that this expression is associated with neuronal processes and oligodendrocytes, initially within the infarct zone and at a later time points in the peri-infarct zone. Similar investigations of human brain tissue, taken from severe ischemic stroke patients, indicate a biphasic expression profile of TNF-α with peaks at 1 and 3 days, localized to neuronal processes and microglia at 1 day and astrocytes from 3–8 days (Sairanen et al., 2001). This expression pattern is also exhibited by TNF-α type I receptor in ischemic mouse brain, localized to neurones and astrocytes within the infarct at 12–24 hours and peri-focal astrocytes at 4 days postinsult (Yin et al., 2004). 2. Anti-inflammatory Cytokines: IL-10 and TGF-b IL-10 mRNA production is upregulated rapidly after ischemia in the rat brain, with peak expression reported at either 6 or 24 hours according to two separate studies (Li et al., 2001; Zhai et al., 1997), while clinical data from the CSF of TBI patients support a putative acute-phase expression profile, with peak protein detection at 24 hours postadmission (Hayakata et al., 2004). Similar data are provided by observations from clinical stroke, which show increases in IL-10 levels up to 3 days (Tarkowski et al., 1997). Although TGF-β mRNA and immunoreactivity are seen 6–24 hours after ischemic (global and focal) and traumatic injury in rats, significant expression is not observed until 2–3 days later (Lehrmann et al., 1995). This expression is localized to microglia and macrophages in ischemic injury and astrocytes in mechanical trauma (Lehrmann et al., 1998; Logan et al., 1994). While TGF-β expression has dissipated by 7 days in global ischemic and traumatic insults, this represents the temporal peak after focal ischemia and TGF-β immunoreactivity persists in the infarct border of such injury for up to 3 months (Lehrmann et al., 1998). Interestingly, Vivien et al. (1998) demonstrate that while TGF-β mRNA production is elevated in the ischemic mouse cortex 1–3 days after the insult, expression of the TGF-β type II receptor (TβII) is significantly downregulated over the same time period, suggesting a negation of any increase in TGF-β levels. However, although Fee et al. (2004) report unchanged TβII ir 1 day after cryo-traumatic cortical injury in support of these data, this expression is significantly increased at 4–7 days, primarily in endothelial cells. Elevated intrathecal TGF-β levels are also a feature of clinical TBI (Morganti-Kossmann et al., 1999).
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B. Experimental Evidence of a Role for Cytokines in CNS Injury Alterations in cytokine expression as described above may simply reflect a response to the emerging tissue damage rather than a direct causative role. Accordingly, several approaches have been used to further elucidate a pathophysiological role in the brain for a number of cytokines. The majority of studies have employed animal models of acute brain injury, most notably focal cerebral ischemia induced by middle cerebral artery (MCA) occlusion, and as such, this section will focus on the findings which have emerged from these studies. 1. Pro-inflammatory Cytokines Administration of recombinant IL-1β by intracerebroventricular (i.c.v.) or intrastriatal infusion exacerbates ischemic brain damage induced by transient and permanent MCA occlusion in rodents (Loddick and Rothwell, 1996; Stroemer and Rothwell, 1998; Touzani et al., 2002; Yamasaki et al., 1995). Recently, we have further observed that peripheral (intraperitoneal) administration of IL-1β similarly exacerbates ischemic damage after transient MCA occlusion (our unpublished data), supporting an important role for periph-
eral inflammation in modulating outcome to ischemic brain injury (Figure 2). In contrast, administration of IL-1RA causes a marked reduction in ischemic brain damage when administered i.c.v. (Mulcahy et al., 2003; Loddick and Rothwell, 1996; Relton and Rothwell, 1992; Touzani et al., 2002), intrastriatally (Stroemer and Rothwell, 1997), or systemically (Garcia et al., 1995; Relton et al., 1996), suggesting a role for endogenous IL-1 in the development of ischemic brain damage. Furthermore, adenoviral-mediated overexpression of IL1RA also attenuates focal ischemic brain damage (Betz et al., 1995; Yang et al., 1998a). Interestingly, inconsistent effects of chronic (transgenic) overexpression of human IL-1RA in mice have been demonstrated. Tehranian et al. (2002) reported an improved neurological outcome after closed head injury, whereas Oprica et al. (2004) did not observe a neuroprotective effect after permanent MCA occlusion. This may reflect experimental differences or compensatory changes in IL-1 expression due to chronic blockade of IL-1 receptors. Simultaneous deletion of both the IL-1α and IL-1β genes results in a marked reduction in damage caused by transient MCA occlusion; however, deletion of IL1α or IL-1β alone does not have any impact, implying an important role for both IL-1 ligands and again suggesting that compensatory changes in the IL-1 system
FIGURE 2 Exacerbation of focal ischemic brain damage by peripheral IL-1β. Coronal brain sections stained with cresyl violet demonstrate areas of viable tissue (deep blue/purple) and infarcted tissue (pale blue/white). Images on the top row show typical damage 24 hours after transient MCA occlusion (30 minutes) from a mouse treated with vehicle (ip) at the onset of occlusion. Administration of IL-1β (4 μg/kg) markedly increases the extent of the infarct (bottom row), incorporating cortical tissue that is undamaged after vehicle treatment.
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may accompany its manipulation (Boutin et al., 2001). Indirect evidence of a role for endogenous IL-1 in acute brain injury has also emerged from studies in which the actions of IL-1β converting enzyme (ICE) have been inhibited. Administration of the ICE inhibitors z-VAD. FMK, YVAD.CMK, or z-DEVD.FMK reduces infarct volume after transient or permanent MCA occlusion (Hara et al., 1997b; Loddick et al., 1996). Similarly, mice expressing mutant, inactivating forms of the ICE gene demonstrate reduced infarct volumes (Hara et al., 1997a; Friedlander et al., 1997). It is tempting to speculate that the neuroprotective effects of ICE inhibition are due to a reduction in the production and release of mature IL-1; however, it cannot be excluded that attenuation of apoptotic cell death is the primary neuroprotective mechanism. Further indirect evidence for a pathogenic role for IL-1 in the brain was recently provided by Basu et al. (2005), who demonstrated that mice deficient in the IL-1 type I receptor (IL-1R1) showed an improved outcome after a hypoxic-ischemic insult. IL-18 shares several structural and functional similarities with IL-1 and is also cleaved by ICE to generate the mature, bioactive ligand (Ghayur et al., 1997; Gu et al., 1997). IL-18 deficient mice display reduced infarct volume and reduced white matter injury in response to neonatal hypoxic-ischemic injury (Hedtjarn et al., 2002, 2005). Furthermore, inhibition of IL-18 activity by a neutralizing binding protein improved neurological outcome after closed head injury (Yatsiv et al., 2002). However, deletion of the IL-18 gene was not associated with any difference in the extent of ischemic damage after transient MCA occlusion (Wheeler et al., 2003). Since brain damage was assessed later after neonatal injury (up to 7 days) compared to MCA occlusion (24 hours), the above discrepancies may reflect the delayed expression profile of IL-18, which was shown to begin at 48 hours and peak at 7–14 days after injury (Jander et al., 2002) and may therefore contribute to damage in the post-acute phase. Several strategies have been employed to investigate the role of TNF-α in acute brain injury. Administration (i.c.v.) of TNF-α produces a dose-dependent exacerbation of ischemic damage induced by permanent MCA occlusion in spontaneously hypertensive rats (Barone et al., 1997). In contrast, administration of compounds that suppress TNF-α synthesis have shown protective effects in models of focal ischemia and closed head injury (Leker et al., 1999; Meistrell et al., 1997; Shohami et al., 1996), although their actions may, in part, be mediated by their NMDA antagonist and antioxidant properties. Recently, Wang et al. (2004) achieved more selective suppression of TNF-α production by inhibiting TNF-α converting enzyme and dem-
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onstrated a marked reduction in focal ischemic damage. Numerous studies have inhibited endogenous TNF-α bioactivity by administration of TNF-α neutralizing antibodies (Barone et al., 1997; Hosomi et al., 2005; Lavine et al., 1998; Yang et al., 1998b) or TNF-α binding protein (TNFbp), a soluble fragment of the TNF-α cellsurface receptor (Dawson et al., 1996; Nawashiro et al., 1997; Shohami et al., 1996), which have shown consistent neuroprotection after focal ischemia and brain trauma. In contrast to the above studies showing deleterious effects of TNF-α in acute brain injury, studies in mice deficient in TNF-α receptors have produced conflicting findings. Bruce et al. (1996) reported that ischemic damage and oxidative stress were significantly greater in mice lacking the p55 and p75 receptors, suggesting acute protective effects of TNF-α. Deletion of the p55 receptor alone, but not the p75 receptor, also resulted in reduced ischemic brain damage (Gary et al., 1998), indicating that neuroprotective actions of TNF-α may be primarily p55 receptor-mediated. Scherbel et al. (1999) found that TNF-α knockout mice had a poorer chronic outcome after cortical contusion injury although acute recovery 24– 48 hours after injury was improved in the knockout mice, suggesting time-dependent biphasic effects of TNF-α. Thus, it appears that acute and chronic suppression of TNF-α activity results in divergent effects on the response to acute brain injury. Conflicting results have also been obtained regarding the role of IL-6 in acute brain injury. A protective role for IL-6 was suggested by Loddick et al. (1998), who demonstrated that administration of recombinant IL-6 (i.c.v.) significantly reduces infarct volume after permanent MCA occlusion. Astrocyte-targeted expression of IL-6 is also protective after a focal acute brain injury (Penkowa et al., 2003a, 2003b). Increased oxidative stress and neurodegeneration after excitotoxic lesion in IL-6 deficient mice further suggested a neuroprotective role for endogenous IL-6 (Penkowa et al., 2000, 2001). In contrast, infarct volume and neurological deficit induced by transient MCA occlusion were similar in IL-6 deficient and wild-type mice, suggesting that endogenous IL-6 is not directly involved in the development of focal ischemic brain damage (Clark et al., 2000). Similarly, neurological recovery after experimental traumatic brain injury was not affected in IL-6 deficient mice (Stahel et al., 2000) or by administration of a monoclonal neutralizing antibody to IL-6 (Marklund et al., 2005). 2. Anti-inflammatory Cytokines Consistent findings of a neuroprotective and antiinflammatory role for IL-10 have emerged. Adminis-
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tration and adenoviral-mediated overexpression of IL-10 ameliorated ischemic damage after both focal and global cerebral ischemia (Ooboshi et al., 2005; Spera et al., 1998), suggesting neuroprotective effects for this cytokine. Subcutaneous but not i.c.v. injection of IL-10 also improves neurological outcome after experimental TBI (Knoblach and Faden, 1998). Furthermore, infarct volume is smaller in IL-10 deficient mice compared to wild-type mice, indicating a neuroprotective function for endogenous IL-10 after ischemic brain injury (Grilli et al., 2000). Induction of IL-10 expression by CD4+ T-cells was also shown to be responsible for the anti-ischemic effects of myelin oligodendrocyte glycoprotein vaccination (Frenkel et al., 2003, 2005). Evidence has also emerged supporting TGF as an endogenous neuroprotectant. TGF-β1 deficient mice are more susceptible to excitotoxic injury in vivo and in vitro, and astrocytic overexpression of TGF-β1 protected against excitotoxic damage (Brionne et al., 2003). Administration of a TGF-β antagonist exacerbated excitotoxic injury and ischemic damage after transient MCA occlusion, further suggesting that TGF-β may limit the extent of acute brain damage (Ruocco et al., 1999). In addition, infarct volume is increased by 300% in mice deficient in persephin, a member of the TGF-β superfamily, and application of recombinant persephin markedly reduces ischemic damage (Tomac et al., 2002). Several studies have also shown that administration of exogenous TGF-β attenuates ischemic damage induced by global or focal cerebral ischemia, or excitotoxic damage (Boche et al., 2003; Henrich-Noack et al., 1996; Prehn et al., 1993). Similarly, exogenous TGF-α also reduces infarct volume after focal ischemia (Justicia et al., 2001). Thus, there is ample evidence to suggest that several cytokines are involved directly in the pathogenesis of brain damage after acute injury. Evidence indicates that IL-1 is detrimental to outcome and that IL-10 and TGF-β are neuroprotective. Inconsistent findings for other cytokines, notably IL-6 and TNF-α, allude to potential divergent effects of these mediators. Such discrepancies may reflect model-specific effects and associated differences in the spatial and temporal expression and sites of action of cytokines after brain injury. An inflammatory response is an integral component of regenerative processes in the periphery and, therefore, it will be important to further establish if some cytokines could have opposing acute and chronic actions in the aftermath of CNS injury as demonstrated by Scherbel et al. (1999). Such studies may also reconcile the neuroprotective effects of some cytokines (e.g., IL-1, TNF-α) observed in vitro with observations from
in vivo studies that generally indicate neurotoxic actions.
C. Clinical Evidence of a Role for Cytokines in CNS Injury and Disease Many experimental strategies to investigate the role of cytokines in brain injury and disease are evidently not feasible or ethical in humans. Therefore, clinical evidence for the involvement of cytokines in brain pathologies is more scarce and derived mostly from studies of expression (see “Evidence of Cytokine Overexpression after CNS Injury”). However, in a subset of these studies, associations between the level of expression and functional outcome have been investigated. In addition, there is emerging evidence that polymorphisms in some cytokine genes may be associated with increased susceptibility to neurodegenerative disease. 1. Stroke and Traumatic Brain Injury Numerous studies have consistently observed elevated plasma and CSF IL-6 levels after stroke and TBI in humans (see “Evidence of Cytokine Overexpression after CNS Injury”). Striking associations between IL-6 levels early after stroke and both infarct volume and long-term neurological outcome have been consistently shown (Fassbender et al., 1994; Mazzota et al., 2004; Tarkowski et al., 1995; Waje-Andreassen et al., 2005), suggesting that IL-6 may be an important factor in determining the pathological and neurological outcome after stroke. Conversely, such correlations may simply reflect that IL-6 is a marker of the severity of initial brain damage. A similar IL-6 response has also been observed consistently after traumatic brain injury. However, in contrast to the data from stroke patients, increased IL-6 levels appear to correlate with improved neurological outcome in traumatic brain injury, suggesting a possible neuroprotective effect for this cytokine (Singhal et al., 2002). There is little evidence of correlations between the levels of other cytokines after acute brain injury and acute damage or long-term outcome. There is little evidence showing that IL-1 levels are altered after acute brain injury, although it has been reported that plasma IL-1 levels following thrombolytic treatment of stroke patients correlate with clinical outcome at 3 months (Mazzota et al., 2004). The failure to correlate IL-1 with injury severity or outcome may reflect the fact that IL-1 expression is confined to local tissue injury but is rarely detected in extracellular fluids. Conflicting data also exist regarding the association between serum TNF-α levels after stroke and infarct size or neurological outcome (Intiso et al., 2004; Zaremba et al., 2001;
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Zaremba and Losy, 2001). Interestingly, reduced levels of the anti-inflammatory cytokine IL-10 after stroke correlates with early decline in neurological function (Vila et al., 2003), which is consistent with the neuroprotective effects of IL-10 observed in animal models (see “Anti-inflammatory Cytokines”). 2. Alzheimer’s Disease Genetic polymorphisms are now recognized as important elements in modulating susceptibility to and outcome from CNS injury and disease. Recently, polymorphisms in cytokine genes have been identified which may modulate the response to acute brain injury and also the risk of developing Alzheimer’s disease (AD), further implicating a pathogenic role for cytokines in neurological dysfunction (McGeer and McGeer, 2001; Waters and Nicoll, 2005). In a study assessing disability 3 months after ischemic stroke, patients with the -174G/G genotype in the IL-6 promoter region were more likely to be severely disabled (Greisenegger et al., 2003). IL-6 gene polymorphisms are also associated with risk of cerebrovascular disease (Chamorro et al., 2005; Flex et al., 2004; Pola et al., 2003; Revilla et al., 2002). Furthermore, there is growing evidence that polymorphisms in several cytokine genes, including IL-1 (Grimaldi et al., 2000; Kolsch et al., 2001; Nicoll et al., 2000; Rebeck et al., 2000), IL-1RA (Seripa et al., 2005), IL-6 (Arosio et al., 2004; Licastro et al., 2003; Papassotiropoulos et al., 1999; Pola et al., 2002), TNF-α (Alvarez et al., 2002; Culpan et al., 2003; Laws et al., 2005; Ma et al., 2004), and IL-10 (Arosio et al., 2004; Infante et al., 2004; Lio et al., 2003; Ma et al., 2005), modulate the risk of developing AD. Most of these polymorphisms reside within the promoter region of the gene, suggesting that cytokine expression levels may be a key factor in modulating risk of AD, and further supporting a role for cytokines in the pathophysiology of acute brain damage and chronic neurodegeneration.
III. CYTOKINES IN REPAIR AND RECOVERY AFTER CNS INJURY The repeated failure of putative neuroprotective strategies in recent years has led to growing attention to, and endorsement of, post-acute physical remodeling and neuromodulation as a route to improved clinical outcome. This shift in utilitarian goals has led to greater interest in the possibility that cytokines may exert significant influence upon such processes, a contention for which circumstantial evidence has existed for some time. Foremost among such evidence are the
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observations of chronic cytokine upregulation within peri-infarct regions of extensive physical reorganization, and their well-established involvement in psychopathological phenomena. Unfortunately, while several interventional studies have added weight to these arguments, the promiscuity of cytokines and the plurality of their observed effects limit the significance of such findings. Overall much of the data, reviewed here, indicate that cytokine coordination of physical remodeling would arise primarily indirectly via glial activation, while putative psychomodulatory effects would result from direct modulation of neural activity and synaptic plasticity.
D. Cytokines in Physical Reorganization and Reparative Processes Glial activation is a well-established response to pro-inflammatory cytokines such as IL-1, IL-6, and TNF-α, which stimulates cytotaxis towards injured tissue and the release of associated molecules such as matrix metalloproteinases, growth factors, and of course, cytokines themselves. The general view is that glial activation is a detrimental facet of CNS injury, based mainly on evidence that microglia may contribute to acute neurodegeneration and the long-held convention that astrocytic glial scarring, coordinated by TGF-β, impedes physical reorganization of neural connections (Fawcett and Asher, 1999). Yet such processes mimic the mobilization of macrophages and fibroblasts in peripheral tissues, mechanisms which, while imperfect, are a vital aspect of clearing and containing cytotoxic necrosing tissue, which may be of specific importance within the brain. Whatever the net contribution of these gross aspects of glial activation, IL-1, TNF-α, and IL-6 activated glia have been demonstrated to release multiple growth factors including vascular endothelial growth factor (VEGF), insulin-like growth factor-1 (IGF-1), and nerve growth factor (NGF) (Carman-Krzan et al., 1991; Fee et al., 2000; Juric and Carman-Krzan, 2001; Mason et al., 2001). VEGF is critical to the initiation and coordination of angio- and ateriogenesis in recovering tissue, while NGF and IGF1 promote neurite outgrowth, dendritic spiking, and mobilization of neural stem cells. Also, IL-1 and TNF-α induce activation and migration of oligodendrocyte precursor cells, which may reflect the need for concomitant neural regeneration and remyelination (Arnett et al., 2001; Mason et al., 2001). This last observation may also go some way to explain the paradoxical response of TNF-α KO mice to cerebral ischemia, characterized by reduced acute injury but improved long-term functional outcome.
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E. Psychopathological and Functional Influences of Cytokines The psychomodulatory effects of cytokines, especially IL-1, are now well established, with significant influences upon mood, learning, memory function, and sleep patterns in rodents reported, while clinically depressed patients exhibit gross perturbations of circulating cytokine levels (Capuron and Dantzer, 2003; Deboer et al., 2002; Hogan et al., 2003; Kenis and Maes, 2002; Manfridi et al., 2003). The contention that such mechanisms may have a significant role in functional recovery after CNS injury is supported by the conjunction of chronic disturbances in cytokine expression with clinical reports of psychological phenomena, consistent with neurochemical imbalance and the experimentally observed psychological effects of cytokines. In particular, clinical depression and impaired motivation, associated with worsened functional outcome, are common in stroke patients and mirror IL-1, IL-6, and TNF-α induced sickness behavior (adaptive behavioral quiescence), sleep disruption, and anhedonia seen in the rat (Kelley et al., 2003; Konsman et al., 2002; Kronfol and Remick, 2000; Parnet et al., 2002). Similarly, IL-1 dependent impairment of task acquisition and memory function, as observed in rodents, may have a significant influence upon the critical process of compensatory “re-wiring” of neural networks (Aubert et al., 1995). While there is much interest in these observations, the subject awaits a thorough analysis and direct evidence of a causative link between cytokine overexpression and functional outcome before any conclusions can be made.
IV. MECHANISMS OF CYTOKINE ACTIONS A full discussion of the known or potential mechanisms of action of each cytokine in neuronal injury and repair is outside the scope of this review. For some, the mechanisms of their contribution to acute injury are beginning to be unraveled (Allan and Rothwell, 2001), but appear complex. Cytokines can act on all neurons and brain cells and contribute to recruitment of peripheral immune cells, but their primary target appears to be glia. There are numerous examples by which glia can influence neuronal survival or death by modification of release of neurotoxins, such as glutamate; release of neuroprotective factors (e.g., growth factors or neurotrophins); and modification of cell matrix (Nedergaard et al., 2003). Cytokines can also exert potent influences on vascular endothelial cells to induce release of potential
neurotoxins (Grammas et al., 2004; Skopal et al., 1998), to compromise or damage the blood-brain barrier and to modify adhesion and invasion of immune cells (Blamire et al., 2000; Ferrari et al., 2004). As a further contribution, many cytokines influence physiological systems or systemic functions which are likely to influence neuronal injury and repair. Such effects include induction of fever, which exacerbates neuronal injury (IL-1), and modifications of neuroendocrine, cardiovascular, and immune function and behavioral changes (Rothwell, 2003). Another area of engaging interest is the relationship between CNS and peripheral inflammation and immune activation. Systemic infection is a key risk factor for poor outcome after stroke or brain injury (Grau et al., 1998; Syrjänen et al., 1988). The mechanism of this effect is unknown, but such infection induces expression of brain cytokines (Emsley and Tyrrell, 2002). Similarly, infectious events within the brain can have a profound effect on systemic inflammation.
V. CONCLUSIONS AND THERAPEUTIC POTENTIAL There is now extensive evidence to implicate cytokines in acute neuronal injury and chronic neurodegenerative disease and further indications of their contributions to repair, recovery, and plasticity. However, the precise role of many cytokines, their mechanisms of action, and indeed whether their effects are wholly beneficial or detrimental remain to be fully elucidated. This is not unexpected given the diversity of action of these proteins and the fact that their key actions as modulators of inflammation and immune activation have both good and bad impacts—these processes are critical in host defense responses but major contributors to disease and tissue injury when activated inappropriately. For several cytokines their impact on functional outcome may depend on dose or timing—with dual roles in early injury and later repair processes. The most extensive evidence for a direct contribution to CNS injury exists for IL-1, where numerous approaches by several independent groups indicate that IL-1 is a key mediator of acute experimental brain injury. At present the most attractive intervention to limit IL-1 actions is its endogenous antagonist, IL-1RA. This is quite a large protein (17 kDa), but it is effective in protecting against neuronal injury in rodents when administered peripherally and penetrates CSF in subarachnoid hemorrhage patients (our unpublished data). We have conducted a small Phase II random-
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ized, placebo controlled trial of IL-1RA in acute stroke patients (Emsley et al., 2005). The data indicate that IL-1RA is safe and inhibits the peripheral inflammatory response, and clinical outcomes in this small group were promising. It is likely that in the future IL-1RA and other cytokine-modulating strategies may prove beneficial in acute and chronic CNS injury and repair.
References Allan, S. M., and Rothwell, N. J. (2001). Cytokines and acute neurodegeneration. Nat. Rev. Neurosci., 2, 734–744. Allan, S. M., and Rothwell, N. J. (2003). Inflammation in central nervous system injury. Philos. Trans. R. Soc. Lond B Biol. Sci., 358, 1669–1677. Alvarez, V., Mata, I. F., Gonzalez, P., Lahoz, C. H., Martinez, C., Pena, J., Guisasola, L. M., and Coto, E. (2002). Association between the TNFalpha-308 A/G polymorphism and the onsetage of Alzheimer disease. Am. J. Med. Genet., 114, 574–577. Arnett, H. A., Mason, J., Marino, M., Suzuki, K., Matsushima, G. K., and Ting, J. P. (2001). TNF alpha promotes proliferation of oligodendrocyte progenitors and remyelination. Nat. Neurosci., 4, 1116–1122. Arosio, B., Trabattoni, D., Galimberti, L., Bucciarelli, P., Fasano, F., Calabresi, C., Cazzullo, C. L., Vergani, C., Annoni, G., and Clerici, M. (2004). Interleukin-10 and interleukin-6 gene polymorphisms as risk factors for Alzheimer’s disease. Neurobiol. Aging, 25, 1009–1015. Aubert, A., Vega, C., Dantzer, R., and Goodall, G. (1995). Pyrogens specifically disrupt the acquisition of a task involving cognitive processing in the rat. Brain Behav. Immun., 9, 129–148. Barone, F. C., Arvin, B., White, R. F., Miller, A., Webb, C. L., Willette, R. N., Lysko, P. G., and Feuerstein, G. Z. (1997). Tumor necrosis factor-alpha. A mediator of focal ischemic brain injury. Stroke, 28, 1233–1244. Basu, A., Lazovic, J., Krady, J. K., Mauger, D. T., Rothstein, R. P., Smith, M. B., and Levison, S. W. (2005). Interleukin-1 and the interleukin-1 type I receptor are essential for the progressive neurodegeneration that ensues subsequent to a mild hypoxic/ ischemic injury. J. Cereb. Blood Flow Metab., 25, 17–29. Berti, R., Williams, A. J., Moffett, J. R., Hale, S. L., Velarde, L. C., Elliott, P. J., Yao, C., Dave, J. R., and Tortella, F. C. (2002). Quantitative real-time RT-PCR analysis of inflammatory gene expression associated with ischemia-reperfusion brain injury. J. Cereb. Blood Flow Metab., 22, 1068–1079. Betz, A. L., Yang, G. Y., and Davidson, B. L. (1995). Attenuation of stroke size in rats using an adenoviral vector to induce overexpression of interleukin-1 receptor antagonist in brain. J. Cereb. Blood Flow Metab., 15, 547–551. Blamire, A. M., Anthony, D. C., Rajagopalan, B., Sibson, N. R., Perry, V. H., and Styles, P. (2000). Interleukin-1beta -induced changes in blood-brain barrier permeability, apparent diffusion coefficient, and cerebral blood volume in the rat brain: a magnetic resonance study. J. Neurosci., 20, 8153–8159. Block, F., Peters, M., and Nolden-Koch, M. (2000). Expression of IL-6 in the ischemic penumbra. Neuroreport, 11, 963–967. Boche, D., Cunningham, C., Gauldie, J., and Perry, V. H. (2003). Transforming growth factor-beta 1–mediated neuroprotection against excitotoxic injury in vivo. J. Cereb. Blood Flow Metab., 23, 1174–1182.
423
Boutin, H., LeFeuvre, R. A., Horai, R., Asano, M., Iwakura, Y., and Rothwell, N. J. (2001). Role of IL-1alpha and IL-1beta in ischemic brain damage. J. Neurosci., 21, 5528–5534. Brionne, T. C., Tesseur, I., Masliah, E., and Wyss-Coray, T. (2003). Loss of TGF-beta 1 leads to increased neuronal cell death and microgliosis in mouse brain. Neuron, 40, 1133–1145. Bruce, A. J., Boling, W., Kindy, M. S., Peschon, J., Kraemer, P. J., Carpenter, M. K., Holtsberg, F. W., and Mattson, M. P. (1996). Altered neuronal and microglial responses to excitotoxic and ischemic brain injury in mice lacking TNF receptors. Nat. Med., 2, 788–794. Buttini, M., Sauter, A., and Boddeke, H. W. (1994). Induction of interleukin-1 beta mRNA after focal cerebral ischaemia in the rat. Brain Res. Mol. Brain Res., 23, 126–134. Capuron, L., and Dantzer, R. (2003). Cytokines and depression: the need for a new paradigm. Brain Behav. Immun., 17(Suppl 1), S119–S124. Carman-Krzan, M., Vige, X., and Wise, B. C. (1991). Regulation by interleukin-1 of nerve growth factor secretion and nerve growth factor mRNA expression in rat primary astroglial cultures. J. Neurochem., 56, 636–643. Chamorro, A., Revilla, M., Obach, V., Vargas, M., and Planas, A. M. (2005). The −174 G/C polymorphism of the interleukin 6 gene is a hallmark of lacunar stroke and not other ischemic stroke phenotypes. Cerebrovasc. Dis., 19, 91–95. Clark, W. M., Rinker, L. G., Lessov, N. S., Hazel, K., Hill, J. K., Stenzel-Poore, M., and Eckenstein, F. (2000). Lack of interleukin6 expression is not protective against focal central nervous system ischemia. Stroke, 31, 1715–1720. Culpan, D., MacGowan, S. H., Ford, J. M., Nicoll, J. A., Griffin, W. S., Dewar, D., Cairns, N. J., Hughes, A., Kehoe, P. G., and Wilcock, G. K. (2003). Tumour necrosis factor-alpha gene polymorphisms and Alzheimer’s disease. Neurosci. Lett., 350, 61–65. Davies, C. A., Loddick, S. A., Toulmond, S., Stroemer, R. P., Hunt, J., and Rothwell, N. J. (1999). The progression and topographic distribution of interleukin-1beta expression after permanent middle cerebral artery occlusion in the rat. J. Cereb. Blood Flow Metab., 19, 87–98. Dawson, D. A., Martin, D., and Hallenbeck, J. M. (1996). Inhibition of tumor necrosis factor-alpha reduces focal cerebral ischemic injury in the spontaneously hypertensive rat. Neurosci. Lett., 218, 41–44. Deboer, T., Fontana, A., and Tobler, I. (2002). Tumor necrosis factor (TNF) ligand and TNF receptor deficiency affects sleep and the sleep EEG. J. Neurophysiol., 88, 839–846. Docagne, F., Campbell, S. J., Bristow, A. F., Poole, S., Vigues, S., Guaza, C., Perry, V. H., and Anthony, D. C. (2005). Differential regulation of type I and type II interleukin-1 receptors in focal brain inflammation. Eur. J. Neurosci., 21, 1205–1214. Emsley, H. C., and Tyrrell, P. J. (2002). Inflammation and infection in clinical stroke. J. Cereb. Blood Flow Metab., 22, 1399–1419. Emsley, H. C., Smith, C. J., Georgiou, R. F., Jail, A., Hopkins, S. J., Rothwell, N. J., and Tyrrell, P. J. (2005). A randomized phase II study of interleukin-1 receptor antagonist in acute stroke patients. J. Neurol. Neurosurg. Psychiatry, 76, 1366–1372. Fassbender, K., Rossol, S., Kammer, T., Daffertshofer, M., Wirth, S., Dollman, M., and Hennerici, M. (1994). Proinflammatory cytokines in serum of patients with acute cerebral ischemia: kinetics of secretion and relation to the extent of brain damage and outcome of disease. J. Neurol. Sci., 122, 135–139. Fawcett, J. W., and Asher, R. A. (1999). The glial scar and central nervous system repair. Brain Res. Bull., 49, 377–391. Fee, D. B., Sewell, D. L., Andresen, K., Jacques, T. J., Piaskowski, S., Barger, B. A., Hart, M. N., and Fabry, Z. (2004). Traumatic brain
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II. Immune System Effects on Neural and Endocrine Processes and Behavior
injury increases TGF beta RII expression on endothelial cells. Brain Res., 1012, 52–59. Ferrari, C. C., Depino, A. M., Prada, F., Muraro, N., Campbell, S., Podhajcer, O., Perry, V. H., Anthony, D. C., and Pitossi, F. J. (2004). Reversible demyelination, blood-brain barrier breakdown, and pronounced neutrophil recruitment induced by chronic IL-1 expression in the brain. Am. J. Pathol., 165, 1827–1837. Flex, A., Gaetani, E., Papaleo, P., Straface, G., Proia, A. S., Pecorini, G., Tondi, P., Pola, P., and Pola, R. (2004). Proinflammatory genetic profiles in subjects with history of ischemic stroke. Stroke, 35, 2270–2275. Frenkel, D., Huang, Z., Maron, R., Koldzic, D. N., Hancock, W. W., Moskowitz, M. A., and Weiner, H. L. (2003). Nasal vaccination with myelin oligodendrocyte glycoprotein reduces stroke size by inducing IL-10–producing CD4+ T cells. J. Immunol., 171, 6549–6555. Frenkel, D., Huang, Z., Maron, R., Koldzic, D. N., Moskowitz, M. A., and Weiner, H. L. (2005). Neuroprotection by IL-10–producing MOG CD4+ T cells following ischemic stroke. J. Neurol. Sci., 233, 125–132. Friedlander, R. M., Gagliardini, V., Hara, H., Fink, K. B., Li, W., MacDonald, G., Fishman, M. C., Greenberg, A. H., Moskowitz, M. A., and Yuan, J. (1997). Expression of a dominant negative mutant of interleukin-1 beta converting enzyme in transgenic mice prevents neuronal cell death induced by trophic factor withdrawal and ischemic brain injury. J. Exp. Med., 185, 933–940. Garcia, J. H., Liu, K. F., and Relton, J. K. (1995). Interleukin-1 receptor antagonist decreases the number of necrotic neurons in rats with middle cerebral artery occlusion. Am. J. Pathol., 147, 1477–1486. Gary, D. S., Bruce-Keller, A. J., Kindy, M. S., and Mattson, M. P. (1998). Ischemic and excitotoxic brain injury is enhanced in mice lacking the p55 tumor necrosis factor receptor. J. Cereb. Blood Flow Metab., 18, 1283–1287. Ghayur, T., Banerjee, S., Hugunin, M., Butler, D., Herzog, L., Carter, A., Quintal, L., Sekut, L., Talanian, R., Paskind, M., Wong, W., Kamen, R., Tracey, D., and Allen, H. (1997). Caspase-1 processes IFN-gamma–inducing factor and regulates LPS-induced IFNgamma production. Nature, 386, 619–623. Grammas, P., Ottman, T., Reimann-Philipp, U., Larabee, J., and Weigel, P. H. (2004). Injured brain endothelial cells release neurotoxic thrombin. J. Alzheimers Dis., 6, 275–281. Grau, A. J., Buggle, F., Becher, H., Zimmermann, E., Spiel, M., Fent, T., Maiwald, M., Werle, E., Zorn, M., Hengel, H., and Hacke, W. (1998). Recent bacterial and viral infection is a risk factor for cerebrovascular ischemia: clinical and biochemical studies. Neurology, 50, 196–203. Greisenegger, S., Endler, G., Haering, D., Schillinger, M., Lang, W., Lalouschek, W., and Mannhalter, C. (2003). The (−174) G/C polymorphism in the interleukin-6 gene is associated with the severity of acute cerebrovascular events. Thromb. Res., 110, 181–186. Grilli, M., Barbieri, I., Basudev, H., Brusa, R., Casati, C., Lozza, G., and Ongini, E. (2000). Interleukin-10 modulates neuronal threshold of vulnerability to ischaemic damage. Eur. J. Neurosci., 12, 2265–2272. Grimaldi, L. M., Casadei, V. M., Ferri, C., Veglia, F., Licastro, F., Annoni, G., Biunno, I., De, B. G., Sorbi, S., Mariani, C., Canal, N., Griffin, W. S., and Franceschi, M. (2000). Association of earlyonset Alzheimer’s disease with an interleukin-1alpha gene polymorphism. Ann. Neurol., 47, 361–365. Gu, Y., Kuida, K., Tsutsui, H., Ku, G., Hsiao, K., Fleming, M. A., Hayashi, N., Higashino, K., Okamura, H., Nakanishi, K., Kurimoto, M., Tanimoto, T., Flavell, R. A., Sato, V., Harding, M. W., Livingston, D. J., and Su, M. S. (1997). Activation of inter-
feron-gamma inducing factor mediated by interleukin-1beta converting enzyme. Science, 275, 206–209. Hara, H., Fink, K., Endres, M., Friedlander, R. M., Gagliardini, V., Yuan, J., and Moskowitz, M. A. (1997a). Attenuation of transient focal cerebral ischemic injury in transgenic mice expressing a mutant ICE inhibitory protein. J. Cereb. Blood Flow Metab., 17, 370–375. Hara, H., Friedlander, R. M., Gagliardini, V., Ayata, C., Fink, K., Huang, Z., Shimizu-Sasamata, M., Yuan, J., and Moskowitz, M. A. (1997b). Inhibition of interleukin 1beta converting enzyme family proteases reduces ischemic and excitotoxic neuronal damage. Proc. Natl. Acad. Sci. USA, 94, 2007–2012. Hayakata, T., Shiozaki, T., Tasaki, O., Ikegawa, H., Inoue, Y., Toshiyuki, F., Hosotubo, H., Kieko, F., Yamashita, T., Tanaka,, H., Shimazu, T., and Sugimoto, H. (2004). Changes in CSF S100B and cytokine concentrations in early-phase severe traumatic brain injury. Shock, 22, 102–107. Hedtjarn, M., Leverin, A. L., Eriksson, K., Blomgren, K., Mallard, C., and Hagberg, H. (2002). Interleukin-18 involvement in hypoxicischemic brain injury. J. Neurosci., 22, 5910–5919. Hedtjarn, M., Mallard, C., Arvidsson, P., and Hagberg, H. (2005). White matter injury in the immature brain: role of interleukin-18. Neurosci. Lett., 373, 16–20. Henrich-Noack, P., Prehn, J. H., and Krieglstein, J. (1996). TGF-beta 1 protects hippocampal neurons against degeneration caused by transient global ischemia. Dose-response relationship and potential neuroprotective mechanisms. Stroke, 27, 1609–1614. Hogan, D., Morrow, J. D., Smith, E. M., and Opp, M. R. (2003). Interleukin-6 alters sleep of rats. J. Neuroimmunol., 137, 59–66. Hosomi, N., Ban, C. R., Naya, T., Takahashi, T., Guo, P., Song, X. Y., and Kohno, M. (2005). Tumor necrosis factor-alpha neutralization reduced cerebral edema through inhibition of matrix metalloproteinase production after transient focal cerebral ischemia. J. Cereb. Blood Flow Metab., 25, 959–967. Infante, J., Sanz, C., Fernandez-Luna, J. L., Llorca, J., Berciano, J., and Combarros, O. (2004). Gene-gene interaction between interleukin-6 and interleukin-10 reduces AD risk. Neurology, 63, 1135–1136. Intiso, D., Zarrelli, M. M., Lagioia, G., Di, R. F., Checchia De, A. C., Simone, P., Tonali, P., and Cioffi Dagger, R. P. (2004). Tumor necrosis factor alpha serum levels and inflammatory response in acute ischemic stroke patients. Neurol. Sci., 24, 390–396. Jander, S., Schroeter, M., and Stoll, G. (2002). Interleukin-18 expression after focal ischemia of the rat brain: association with the late-stage inflammatory response. J. Cereb. Blood Flow Metab., 22, 62–70. Juric, D. M., and Carman-Krzan, M. (2001). Interleukin-1 beta, but not IL-1 alpha, mediates nerve growth factor secretion from rat astrocytes via type I IL-1 receptor. Int. J. Dev. Neurosci., 19, 675–683. Justicia, C., Perez-Asensio, F. J., Burguete, M. C., Salom, J. B., and Planas, A. M. (2001). Administration of transforming growth factor-alpha reduces infarct volume after transient focal cerebral ischemia in the rat. J. Cereb. Blood Flow Metab., 21, 1097–1104. Kelley, K. W., Bluthe, R. M., Dantzer, R., Zhou, J. H., Shen, W. H., Johnson, R. W., and Broussard, S. R. (2003). Cytokine-induced sickness behavior. Brain Behav. Immun., 17(Suppl 1), S112–S118. Kenis, G., and Maes, M. (2002). Effects of antidepressants on the production of cytokines. Int. J. Neuropsychopharmacol., 5, 401–412. Knoblach, S. M., and Faden, A. I. (1998). Interleukin-10 improves outcome and alters proinflammatory cytokine expression after experimental traumatic brain injury. Exp. Neurol., 153, 143–151. Knoblach, S. M., Fan, L., and Faden, A. I. (1999). Early neuronal expression of tumor necrosis factor-alpha after experimental
19. Cytokines and Non-immune Brain Injury brain injury contributes to neurological impairment. J. Neuroimmunol., 95, 115–125. Kolsch, H., Ptok, U., Bagli, M., Papassotiropoulos, A., Schmitz, S., Barkow, K., Kockler, M., Rao, M. L., Maier, W., and Heun, R. (2001). Gene polymorphisms of interleukin-1alpha influence the course of Alzheimer’s disease. Ann. Neurol., 49, 818–819. Konsman, J. P., Parnet, P., and Dantzer, R. (2002). Cytokine-induced sickness behaviour: mechanisms and implications. Trends Neurosci., 25, 154–159. Kronfol, Z., and Remick, D. G. (2000). Cytokines and the brain: implications for clinical psychiatry. Am. J. Psychiatry, 157, 683–694. Lavine, S. D., Hofman, F. M., and Zlokovic, B. V. (1998). Circulating antibody against tumor necrosis factor-alpha protects rat brain from reperfusion injury. J. Cereb. Blood Flow Metab., 18, 52–58. Laws, S. M., Perneczky, R., Wagenpfeil, S., Muller, U., Forstl, H., Martins, R. N., Kurz, A., and Riemenschneider, M. (2005). TNF polymorphisms in Alzheimer disease and functional implications on CSF beta-amyloid levels. Hum. Mutat., 26, 29–35. Legos, J. J., Whitmore, R. G., Erhardt, J. A., Parsons, A. A., Tuma, R. F., and Barone, F. C. (2000). Quantitative changes in interleukin proteins following focal stroke in the rat. Neurosci. Lett., 282, 189–192. Lehrmann, E., Kiefer, R., Christensen, T., Toyka, K. V., Zimmer, J., Diemer, N. H., Hartung, H. P., and Finsen, B. (1998). Microglia and macrophages are major sources of locally produced transforming growth factor-beta1 after transient middle cerebral artery occlusion in rats. Glia, 24, 437–448. Lehrmann, E., Kiefer, R., Finsen, B., Diemer, N. H., Zimmer, J., and Hartung, H. P. (1995). Cytokines in cerebral ischemia: expression of transforming growth factor beta-1 (TGF-beta 1) mRNA in the postischemic adult rat hippocampus. Exp. Neurol., 131, 114–123. Li, H. L., Kostulas, N., Huang, Y. M., Xiao, B. G., van der, M. P., Kostulas, V., Giedraitas, V., and Link, H. (2001). IL-17 and IFNgamma mRNA expression is increased in the brain and systemically after permanent middle cerebral artery occlusion in the rat. J. Neuroimmunol., 116, 5–14. Licastro, F., Grimaldi, L. M., Bonafe, M., Martina, C., Olivieri, F., Cavallone, L., Giovanietti, S., Masliah, E., and Franceschi, C. (2003). Interleukin-6 gene alleles affect the risk of Alzheimer’s disease and levels of the cytokine in blood and brain. Neurobiol. Aging, 24, 921–926. Lio, D., Licastro, F., Scola, L., Chiappelli, M., Grimaldi, L. M., Crivello, A., Colonna-Romano, G., Candore, G., Franceschi, C., and Caruso, C. (2003). Interleukin-10 promoter polymorphism in sporadic Alzheimer’s disease. Genes Immun., 4, 234–238. Liu, T., Clark, R. K., McDonnell, P. C., Young, P. R., White, R. F., Barone, F. C., and Feuerstein, G. Z. (1994). Tumor necrosis factoralpha expression in ischemic neurons. Stroke, 25, 1481–1488. Liu, T., McDonnell, P. C., Young, P. R., White, R. F., Siren, A. L., Hallenbeck, J. M., Barone, F. C., and Feurestein, G. Z. (1993). Interleukin-1 beta mRNA expression in ischemic rat cortex. Stroke, 24, 1746–1750. Leker, R. R., Shohami, E., Abramsky, O., and Oradia, H. (1999). Dexamabinol; a novel neuroprotective drug in experimental focal cerebral ischemia. J. Neurol. Sci., 162, 114–119. Loddick, S. A., MacKenzie, A., and Rothwell, N. J. (1996). An ICE inhibitor, z-VAD-DCB attenuates ischaemic brain damage in the rat. Neuroreport, 7, 1465–1468. Loddick, S. A., and Rothwell, N. J. (1996). Neuroprotective effects of human recombinant interleukin-1 receptor antagonist in focal cerebral ischaemia in the rat. J. Cereb. Blood Flow Metab., 16, 932–940. Loddick, S. A., Turnbull, A. V., and Rothwell, N. J. (1998). Cerebral interleukin-6 is neuroprotective during permanent focal cerebral ischemia in the rat. J. Cereb. Blood Flow Metab., 18, 176–179.
425
Logan, A., Berry, M., Gonzalez, A. M., Frautschy, S. A., Sporn, M. B., and Baird, A. (1994). Effects of transforming growth factor beta 1 on scar production in the injured central nervous system of the rat. Eur. J. Neurosci., 6, 355–363. Ma, S. L., Tang, N. L., Lam, L. C., and Chiu, H. F. (2004). Association between tumor necrosis factor-alpha promoter polymorphism and Alzheimer’s disease. Neurology, 62, 307–309. Ma, S. L., Tang, N. L., Lam, L. C., and Chiu, H. F. (2005). The association between promoter polymorphism of the interleukin-10 gene and Alzheimer’s disease. Neurobiol. Aging, 26, 1005–1010. Manfridi, A., Brambilla, D., Bianchi, S., Mariotti, M., Opp, M. R., and Imeri, L. (2003). Interleukin-1beta enhances non-rapid eye movement sleep when microinjected into the dorsal raphe nucleus and inhibits serotonergic neurons in vitro. Eur. J. Neurosci., 18, 1041–1049. Marklund, N., Keck, C., Hoover, R., Soltesz, K., Millard, M., LeBold, D., Spangler, Z., Banning, A., Benson, J., and McIntosh, T. K. (2005). Administration of monoclonal antibodies neutralizing the inflammatory mediators tumor necrosis factor alpha and interleukin-6 does not attenuate acute behavioral deficits following experimental traumatic brain injury in the rat. Restor. Neurol. Neurosci., 23, 31–42. Mason, J. L., Suzuki, K., Chaplin, D. D., and Matsushima, G. K. (2001). Interleukin-1beta promotes repair of the CNS. J. Neurosci., 21, 7046–7052. Mathiesen, T., Andersson, B., Loftenius, A., and von Holst, H. (1993). Increased interleukin-6 levels in cerebrospinal fluid following subarachnoid hemorrhage. J. Neurosurg., 78, 562–567. Mazzotta, G., Sarchielli, P., Caso, V., Paciaroni, M., Floridi, A., Floridi, A., and Gallai, V. (2004). Different cytokine levels in thrombolysis patients as predictors for clinical outcome. Eur. J. Neurol., 11, 377–381. McGeer, P. L., and McGeer, E. G. (2001). Polymorphisms in inflammatory genes and the risk of Alzheimer disease. Arch. Neurol., 58, 1790–1792. Meistrell, M. E., III, Botchkina, G. I., Wang, H., Di, S. E., Cockroft, K. M., Bloom, O., Vishnubhakat, J. M., Ghezzi, P., and Tracey, K. J. (1997). Tumor necrosis factor is a brain damaging cytokine in cerebral ischemia. Shock, 8, 341–348. Morganti-Kossmann, M. C., Hans, V. H., Lenzlinger, P. M., Dubs, R., Ludwig, E., Trentz, O., and Kossmann, T. (1999). TGF-beta is elevated in the CSF of patients with severe traumatic brain injuries and parallels blood-brain barrier function. J. Neurotrauma, 16, 617–628. Mulcahy, N. J., Ross, J., Rothwell, N. J., and Loddick, S. A. (2003). Delayed administration of interleukin-1 receptor antagonist protects against transient cerebral ischaemia in the rat. Br. J. Pharmacol., 140, 471–476. Nawashiro, H., Martin, D., and Hallenbeck, J. M. (1997). Inhibition of tumor necrosis factor and amelioration of brain infarction in mice. J. Cereb. Blood Flow Metab., 17, 229–232. Nedergaard, M., Ransom, B., and Goldman, S. A. (2003). New roles for astrocytes: redefining the functional architecture of the brain. Trends Neurosci., 26, 523–530. Nicoll, J. A., Mrak, R. E., Graham, D. I., Stewart, J., Wilcock, G., MacGowan, S., Esiri, M. M., Murray, L. S., Dewar, D., Love, S., Moss, T., and Griffin, W. S. (2000). Association of interleukin-1 gene polymorphisms with Alzheimer’s disease. Ann. Neurol., 47, 365–368. Ohtaki, H., Yin, L., Nakamachi, T., Dohi, K., Kudo, Y., Makino, R., and Shioda, S. (2004). Expression of tumor necrosis factor alpha in nerve fibers and oligodendrocytes after transient focal ischemia in mice. Neurosci. Lett., 368, 162–166. Ooboshi, H., Ibayashi, S., Shichita, T., Kumai, Y., Takada, J., Ago, T., Arakawa, S., Sugimori, H., Kamouchi, M., Kitazono, T., and Iida,
426
II. Immune System Effects on Neural and Endocrine Processes and Behavior
M. (2005). Postischemic gene transfer of interleukin-10 protects against both focal and global brain ischemia. Circulation, 111, 913–919. Oprica, M., Van Dam, A. M., Lundkvist, J., Iverfeldt, K., Winblad, B., Bartfai, T., and Schultzberg, M. (2004). Effects of chronic overexpression of interleukin-1 receptor antagonist in a model of permanent focal cerebral ischemia in mouse. Acta Neuropathol. (Berl), 108, 69–80. Papassotiropoulos, A., Bagli, M., Jessen, F., Bayer, T. A., Maier, W., Rao, M. L., and Heun, R. (1999). A genetic variation of the inflammatory cytokine interleukin-6 delays the initial onset and reduces the risk for sporadic Alzheimer’s disease. Ann. Neurol., 45, 666–668. Parker, L. C., Rushforth, D. A., Rothwell, N. J., and Luheshi, G. N. (2000). IL-1beta induced changes in hypothalamic IL-1R1 and IL-1R2 mRNA expression in the rat. Brain Res. Mol. Brain Res., 79, 156–158. Parnet, P., Kelley, K. W., Bluthe, R. M., and Dantzer, R. (2002). Expression and regulation of interleukin-1 receptors in the brain. Role in cytokines-induced sickness behavior. J. Neuroimmunol., 125, 5–14. Penkowa, M., Camats, J., Hadberg, H., Quintana, A., Rojas, S., Giralt, M., Molinero, A., Campbell, I. L., and Hidalgo, J. (2003a). Astrocyte-targeted expression of interleukin-6 protects the central nervous system during neuroglial degeneration induced by 6-aminonicotinamide. J. Neurosci. Res., 73, 481–496. Penkowa, M., Giralt, M., Carrasco, J., Hadberg, H., and Hidalgo, J. (2000). Impaired inflammatory response and increased oxidative stress and neurodegeneration after brain injury in interleukin6–deficient mice. Glia, 32, 271–285. Penkowa, M., Giralt, M., Lago, N., Camats, J., Carrasco, J., Hernandez, J., Molinero, A., Campbell, I. L., and Hidalgo, J. (2003b). Astrocyte-targeted expression of IL-6 protects the CNS against a focal brain injury. Exp. Neurol., 181, 130–148. Penkowa, M., Molinero, A., Carrasco, J., and Hidalgo, J. (2001). Interleukin-6 deficiency reduces the brain inflammatory response and increases oxidative stress and neurodegeneration after kainic acid-induced seizures. Neuroscience, 102, 805–818. Pola, R., Flex, A., Gaetani, E., Flore, R., Serricchio, M., and Pola, P. (2003). Synergistic effect of −174 G/C polymorphism of the interleukin-6 gene promoter and 469 E/K polymorphism of the intercellular adhesion molecule-1 gene in Italian patients with history of ischemic stroke. Stroke, 34, 881–885. Pola, R., Flex, A., Gaetani, E., Lago, A. D., Gerardino, L., Pola, P., and Bernabei, R. (2002). The −174 G/C polymorphism of the interleukin-6 gene promoter is associated with Alzheimer’s disease in an Italian population [corrected]. Neuroreport, 13, 1645–1647. Prehn, J. H., Backhauss, C., and Krieglstein, J. (1993). Transforming growth factor-beta 1 prevents glutamate neurotoxicity in rat neocortical cultures and protects mouse neocortex from ischemic injury in vivo. J. Cereb. Blood Flow Metab., 13, 521–525. Rebeck, G. W. (2000). Confirmation of the genetic association of interleukin-1A with early onset sporadic Alzheimer’s disease. Neurosci. Lett., 293, 75–77. Relton, J. K., Martin, D., Thompson, R. C., and Russell, D. A. (1996). Peripheral administration of interleukin-1 receptor antagonist inhibits brain damage after focal cerebral ischemia in the rat. Exp. Neurol., 138, 206–213. Relton, J. K., and Rothwell, N. J. (1992). Interleukin-1 receptor antagonist inhibits ischaemic and excitotoxic neuronal damage in the rat. Brain Res. Bull., 29, 243–246. Revilla, M., Obach, V., Cervera, A., Davalos, A., Castillo, J., and Chamorro, A. (2002). A −174 G/C polymorphism of the
interleukin-6 gene in patients with lacunar infarction. Neurosci. Lett., 324, 29–32. Rothwell, N. (2003). Interleukin-1 and neuronal injury: mechanisms, modification, and therapeutic potential. Brain Behav. Immun., 17, 152–157. Ruocco, A., Nicole, O., Docagne, F., Ali, C., Chazalviel, L., Komesli, S., Yablonsky, F., Roussel, S., MacKenzie, E. T., Vivien, D., and Buisson, A. (1999). A transforming growth factor-beta antagonist unmasks the neuroprotective role of this endogenous cytokine in excitotoxic and ischemic brain injury. J. Cereb. Blood Flow Metab., 19, 1345–1353. Sairanen, T., Carpen, O., Karjalainen-Lindsberg, M. L., Paetau, A., Turpeinen, U., Kaste, M., and Lindsberg, P. J. (2001). Evolution of cerebral tumor necrosis factor-alpha production during human ischemic stroke. Stroke, 32, 1750–1758. Scherbel, U., Raghupathi, R., Nakamura, M., Saatman, K. E., Trojanowski, J. Q., Neugebauer, E., Marino, M. W., and McIntosh, T. K. (1999). Differential acute and chronic responses of tumor necrosis factor-deficient mice to experimental brain injury. Proc. Natl. Acad. Sci. USA, 96, 8721–8726. Seripa, D., Matera, M. G., Dal, F. G., Gravina, C., Masullo, C., Daniele, A., Binetti, G., Bonvicini, C., Squitti, R., Palermo, M. T., Davis, D. G., Antuono, P., Wekstein, D. R., Dobrina, A., Gennarelli, M., and Fazio, V. M. (2005). Genotypes and haplotypes in the IL-1 gene cluster: analysis of two genetically and diagnostically distinct groups of Alzheimer patients. Neurobiol. Aging, 26, 455–464. Shohami, E., Bass, R., Wallach, D., Yamin, A., and Gallily, R. (1996). Inhibition of tumor necrosis factor alpha (TNFalpha) activity in rat brain is associated with cerebroprotection after closed head injury. J. Cereb. Blood Flow Metab, 16, 378–384. Singhal, A., Baker, A. J., Hare, G. M., Reinders, F. X., Schlichter, L. C., and Moulton, R. J. (2002). Association between cerebrospinal fluid interleukin-6 concentrations and outcome after severe human traumatic brain injury. J. Neurotrauma, 19, 929–937. Skopal, J., Turbucz, P., Vastag, M., Bori, Z., Pek, M., deChatel, R., Nagy, Z., Toth, M., and Karadi, I. (1998). Regulation of endothelin release from human brain microvessel endothelial cells. J. Cardiovasc. Pharmacol., 31(Suppl 1), S370–S372. Spera, P. A., Ellison, J. A., Feuerstein, G. Z., and Barone, F. C. (1998). IL-10 reduces rat brain injury following focal stroke. Neurosci. Lett., 251, 189–192. Stahel, P. F., Shohami, E., Younis, F. M., Kariya, K., Otto, V. I., Lenzlinger, P. M., Grosjean, M. B., Eugster, H. P., Trentz, O., Kossmann, T., and Morganti-Kossmann, M. C. (2000). Experimental closed head injury: analysis of neurological outcome, blood-brain barrier dysfunction, intracranial neutrophil infiltration, and neuronal cell death in mice deficient in genes for pro-inflammatory cytokines. J. Cereb. Blood Flow Metab., 20, 369–380. Stroemer, R. P., and Rothwell, N. J. (1997). Cortical protection by localized striatal injection of IL-1RA following cerebral ischemia in the rat. J. Cereb. Blood Flow Metab., 17, 597–604. Stroemer, R. P., and Rothwell, N. J. (1998). Exacerbation of ischemic brain damage by localized striatal injection of interleukin-1beta in the rat. J. Cereb. Blood Flow Metab., 18, 833–839. Syrjänen, J., Valtonen, V. V., Iivanainen, M., Kaste, M., and Huttunen, J. K. (1988). Preceding infection as an important risk factor for ischaemic brain infarction in young and middle aged patients. Br. Med. J. (Clin. Res. Ed), 296, 1156–1160. Tarkowski, E., Rosengren, L., Blomstrand, C., Wikkelso, C., Jensen, C., Ekholm, S., and Tarkowski, A. (1995). Early intrathecal production of interleukin-6 predicts the size of brain lesion in stroke. Stroke, 26, 1393–1398.
19. Cytokines and Non-immune Brain Injury Tarkowski, E., Rosengren, L., Blomstrand, C., Wikkelso, C., Jensen, C., Ekholm, S., and Tarkowski, A. (1997). Intrathecal release of pro- and anti-inflammatory cytokines during stroke. Clin. Exp. Immunol., 110, 492–499. Tehranian, R., Andell-Jonsson, S., Beni, S. M., Yatsiv, I., Shohami, E., Bartfai, T., Lundkvist, J., and Iverfeldt, K. (2002). Improved recovery and delayed cytokine induction after closed head injury in mice with central overexpression of the secreted isoform of the interleukin-1 receptor antagonist. J. Neurotrauma, 19, 939–951. Tomac, A. C., Agulnick, A. D., Haughey, N., Chang, C. F., Zhang, Y., Backman, C., Morales, M., Mattson, M. P., Wang, Y., Westphal, H., and Hoffer, B. J. (2002). Effects of cerebral ischemia in mice deficient in Persephin. Proc. Natl. Acad. Sci. USA, 99, 9521–9526. Touzani, O., Boutin, H., LeFeuvre, R., Parker, L., Miller, A., Luheshi, G., and Rothwell, N. (2002). Interleukin-1 influences ischemic brain damage in the mouse independently of the interleukin-1 type I receptor. J. Neurosci., 22, 38–43. Vila, N., Castillo, J., Davalos, A., and Chamorro, A. (2000). Proinflammatory cytokines and early neurological worsening in ischemic stroke. Stroke, 31, 2325–2329. Vila, N., Castillo, J., Davalos, A., Esteve, A., Planas, A. M., and Chamorro, A. (2003). Levels of anti-inflammatory cytokines and neurological worsening in acute ischemic stroke. Stroke, 34, 671–675. Waje-Andreassen, U., Krakenes, J., Ulvestad, E., Thomassen, L., Myhr, K. M., Aarseth, J., and Vedeler, C. A. (2005). IL-6: an early marker for outcome in acute ischemic stroke. Acta Neurol. Scand., 111, 360–365. Wang, X., Barone, F. C., Aiyar, N. V., and Feuerstein, G. Z. (1997). Interleukin-1 receptor and receptor antagonist gene expression after focal stroke in rats. Stroke, 28, 155–161. Wang, X., Feuerstein, G. Z., Xu, L., Wang, H., Schumacher, W. A., Ogletree, M. L., Taub, R., Duan, J. J., Decicco, C. P., and Liu, R. Q. (2004). Inhibition of tumor necrosis factor-alpha–converting enzyme by a selective antagonist protects brain from focal ischemic injury in rats. Mol. Pharmacol., 65, 890–896. Waters, R. J., and Nicoll, J. A. (2005). Genetic influences on outcome following acute neurological insults. Curr. Opin. Crit. Care, 11, 105–110. Wheeler, R. D., Boutin, H., Touzani, O., Luheshi, G. N., Takeda, K., and Rothwell, N. J. (2003). No role for interleukin-18 in acute murine stroke-induced brain injury. J. Cereb. Blood Flow Metab., 23, 531–535.
427
Wiessner, C., Gehrmann, J., Lindholm, D., Topper, R., Kreutzberg, G. W., and Hossmann, K. A. (1993). Expression of transforming growth factor-beta 1 and interleukin-1 beta mRNA in rat brain following transient forebrain ischemia. Acta Neuropathol. (Berl), 86, 439–446. Winter, C. D., Pringle, A. K., Clough, G. F., and Church, M. K. (2004). Raised parenchymal interleukin-6 levels correlate with improved outcome after traumatic brain injury. Brain, 127, 315–320. Yamasaki, Y., Matsuura, N., Shozuhara, H., Onodera, H., Itoyama, Y., and Kogure, K. (1995). Interleukin-1 as a pathogenetic mediator of ischemic brain damage in rats. Stroke, 26, 676–680. Yan, H. Q., Banos, M. A., Herregodts, P., Hooghe, R., and HooghePeters, E. L. (1992). Expression of interleukin (IL)-1 beta, IL-6 and their respective receptors in the normal rat brain and after injury. Eur. J. Immunol., 22, 2963–2971. Yang, G. Y., Gong, C., Qin, Z., Ye, W., Mao, Y., and Bertz, A. L. (1998). Inhibition of TNFalpha attenuates infarct volume and ICAM-1 expression in ischemic mouse brain. Neuroreport, 9, 2131–2134. Yang, G. Y., Liu, X. H., Kadoya, C., Zhao, Y. J., Mao, Y., Davidson, B. L., and Betz, A. L. (1998). Attenuation of ischemic inflammatory response in mouse brain using an adenoviral vector to induce overexpression of interleukin-1 receptor antagonist. J. Cereb. Blood Flow Metab, 18, 840–847. Yatsiv, I., Morganti-Kossmann, M. C., Perez, D., Dinarello, C. A., Novick, D., Rubinstein, M., Otto, V. I., Rancan, M., Kossmann, T., Redaelli, C. A., Trentz, O., Shohami, E., and Stahel, P. F. (2002). Elevated intracranial IL-18 in humans and mice after traumatic brain injury and evidence of neuroprotective effects of IL18–binding protein after experimental closed head injury. J. Cereb. Blood Flow Metab., 22, 971–978. Yin, L., Ohtaki, H., Nakamachi, T., Kudo, Y., Makino, R., and Shioda, S. (2004). Delayed expressed TNFR1 co-localize with ICAM-1 in astrocyte in mice brain after transient focal ischemia. Neurosci. Lett., 370, 30–35. Zaremba, J., and Losy, J. (2001). Early TNF-alpha levels correlate with ischaemic stroke severity. Acta Neurol. Scand., 104, 288–295. Zaremba, J., Skrobanski, P., and Losy, J. (2001). Tumour necrosis factor-alpha is increased in the cerebrospinal fluid and serum of ischaemic stroke patients and correlates with the volume of evolving brain infarct. Biomed. Pharmacother., 55, 258–263. Zhai, Q. H., Futrell, N., and Chen, F. J. (1997). Gene expression of IL-10 in relationship to TNF-alpha, IL-1beta and IL-2 in the rat brain following middle cerebral artery occlusion. J. Neurol. Sci., 152, 119–124.
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C H A P T E R
20 The Interaction between Brain Inflammation and Systemic Infection LEIGH M. FELTON AND V. HUGH PERRY
(prion diseases, Alzheimer’s disease). We also describe the impact of repeated systemic infection on the immunological status of the mammalian CNS, and summarize evidence demonstrating that priming of microglia, and other glia, by prolonged or repeated exposure to pro-inflammatory mediators can impact on the progression, severity, and clinical expression of subsequent CNS disease.
I. INTRODUCTION 429 II. NEUROENDOCRINE-IMMUNE INTERACTIONS IN HEALTH AND DISEASE: CYTOKINE EXPRESSION IN THE CNS 431 III. ACUTE INFLAMMATION OF THE CENTRAL NERVOUS SYSTEM 433 IV. IMMUNE-MEDIATED DISEASE OF THE CENTRAL NERVOUS SYSTEM: MULTIPLE SCLEROSIS 435 V. CHRONIC NEURODEGENERATION AND MICROGLIAL PRIMING 439 VI. SUMMARY 444
I. INTRODUCTION The immunological status of the central nervous system (CNS) is highly regulated in order to maintain the precise homeostasis that is required for its normal day-to-day functioning. Until recently, the parenchyma of the CNS, comprising in mammals the brain and the spinal cord, was considered to be an “immunologically privileged” site, being isolated from circulating leucocytes and potentially damaging soluble mediators by a highly impermeable bloodbrain barrier (BBB), and being devoid of cells capable of antigen presentation, such as macrophages and dendritic cells. However, we now know that the CNS is capable of mounting both acute and chronic inflammatory responses, albeit atypical, in response to tissue injury, infection, and disease (Perry et al., 1997). A key feature of inflammation is the expression and release of pro-inflammatory and anti-inflammatory mediators; these include cytokines, chemokines, eicosanoids, and acute phase proteins. The contribution of these mediators to inflammation and tissue repair
ABSTRACT In this chapter we consider the biological mechanisms underlying central cytokine expression, discuss their physiological relevance in the context of systemic inflammation, and contemplate the recent evidence demonstrating that pro-inflammatory cytokines can exacerbate neuronal death and inflammation in rodent models of CNS disease. We also describe the bi-directional nature of communication between the CNS and peripheral immune system, placing particular emphasis on the acute phase response to brain injury, and the complex role of the liver. In order to provide a comprehensive review, we have focused on a number of pro- and anti-inflammatory cytokines, chemokines, and lipophilic mediators of inflammation; and describe how their expression may exacerbate tissue injury in acute brain injury, multiple sclerosis (MS), and chronic neurodegenerative disease PSYCHONEUROIMMUNOLOGY, 4E VOLUME I
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Copyright © 2007 by Elsevier, Inc. All rights of reproduction in any form reserved.
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is complex and has been best characterized in models of peripheral infection. However, many of the inflammatory mediators that are synthesized and released by leucocytes in response to inflammatory stimuli in the periphery have also been detected in the CNS (Allan and Rothwell, 2003; Bajetto et al., 2001; Dantzer et al., 1998; Felton et al., 2005; Perry et al., 2002; Perry et al., 2003). The source of these mediators has yet to be fully determined, but the use of in vitro and in vivo models of CNS disease has confirmed that many cell types specific to the CNS are capable of their synthesis; these cell types include glia (such as microglia and astrocytes), perivascular macrophages, endothelial cells of the cerebral vasculature, and specific subpopulations of neurones. A number of these cell types, specifically cells of monocytic lineage, have been shown to upregulate their expression of MHC class antigens in response to inflammatory stimuli, and to actively participate in antigen presentation, thereby initiating both acute and chronic inflammatory responses within the brain and spinal cord, and contributing directly to the expression of inflammatory mediators (Aloisi, 2001). In a number of models of CNS disease, the expression of chemokines within the extracellular milieu of the CNS results in leucocyte recruitment to the parenchyma, which may further exacerbate the ongoing inflammation, and contribute to inflammatory mediator expression (Bajetto et al., 2001). The endogenous expression of pro-inflammatory cytokines within the CNS occurs in humans as a consequence of a wide range of disease states. Despite this, the precise roles and contributions of individual inflammatory species has remained elusive, possibly as a consequence of the extensive overlap and redundancy in their biological functions. Individual proinflammatory mediators have often been described as having deleterious effects in the acute stages of injury/disease, thereby exacerbating the ongoing pathology (Allan and Rothwell, 2003), but beneficial effects in the later stages of disease through promoting mechanisms of tissue repair (Kalehua et al., 2004). Furthermore, although many of the archetypal inflammatory diseases of the CNS, such as multiple sclerosis (MS), cerebral ischemia, and acute trauma, result in pro-inflammatory cytokine expression, there are a number of examples of acute injury and chronic neurodegenerative disease that are associated with a very low expression of proinflammatory mediators, and which demonstrate an almost exclusively anti-inflammatory profile (Perry et al., 2002). With the exception of a small number of cytokines and eicosanoids, constitutive expression of inflamma-
tory mediators within the healthy CNS is very low. However, it has been shown that the expression of some cytokines, and other downstream mediators of inflammation, can be elevated within the CNS in the absence of concurrent CNS pathology. For example, elevated expression of cytokine mRNA and protein has been demonstrated in well-defined regions of the brain and spinal cord as a result of systemic inflammation (for review, see Dantzer et al., 1998), and as a consequence of the natural course of aging (immunosenescence) (Felzien et al., 2001; Hacham et al., 2002). There is now a substantial body of evidence confirming that elevated levels of pro-inflammatory cytokines in peripheral tissues and the circulation can give rise to de novo synthesis of the same mediators within the CNS (Dantzer et al., 1998; Laye et al., 1994). This interaction between the peripheral immune system and CNS has been best characterized in rodent models of systemic infection, and it is now clear that this highly stereotyped physiological interaction forms an important part of the acute phase response to tissue injury and infection. Although such brief, intermittent, and tightly regulated increases in cytokine expression are unlikely to give rise to pathology in the healthy CNS, it is important for us to consider the consequences of such a response if brain tissue is already compromised by ongoing inflammatory disease or acute injury. In this chapter we will consider the biological mechanisms that underlie the expression of brain cytokines, discuss their physiological relevance in the context of systemic inflammation, and contemplate the recent evidence demonstrating that proinflammatory cytokines can exacerbate neuronal death and inflammation in rodent models of CNS disease. We will also describe the bi-directional nature of communication between the CNS and the peripheral immune system, placing particular emphasis on the acute phase response to brain injury and the complex role of the liver. In order to provide a comprehensive review, we will focus on a number of pro- and anti-inflammatory cytokines, chemokines, and lipophilic mediators of inflammation; and describe how their expression may contribute to tissue injury in acute brain injury, multiple sclerosis (MS) and chronic neurodegenerative diseases (Alzheimer’s disease). We will also describe the impact of repeated systemic infection on the immunological status of the mammalian CNS, and summarize evidence demonstrating that the “priming” of microglia, and other glia, caused by prolonged or repeated exposure to pro-inflammatory mediators, can impact on the progression, severity, and clinical expression of subsequent CNS disease.
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II. NEUROENDOCRINE-IMMUNE INTERACTIONS IN HEALTH AND DISEASE: CYTOKINE EXPRESSION IN THE CNS A. Infection and Inflammation When living tissue is attacked by physical, chemical, microbial, or viral agents, the body responds by mounting an inflammatory response. Inflammation is an all-encompassing term describing the complex responses mounted by a host organism that aim to protect tissue and promote healing and repair. In response to systemic infection, by either viral or bacterial pathogens, two arms of the host immune system are activated; these comprise a non-specific arm, driven by the innate immune system, and an adaptive arm, known as acquired immunity. Perhaps the simplest and most studied inflammatory response in humans and rodents is that mounted against infection by Gramnegative bacteria, which involves the innate immune system. The cell wall of Gram-negative bacteria is encompassed by an outer membrane, the outer leaflet of which includes a complex family of endotoxic macromolecules, the lipopolysaccharides (LPS). When these bacteria enter the body, the LPS of the outer membrane are recognized as non-self antigens by Toll-like receptors expressed by specialized phagocytic cells of the host (Beutler, 2002; Hajjar et al., 2002; Konsman et al., 2002). These cells, the tissue macrophages, are the first line of defense against infection by pathogenic organisms, and their activation results in the expression and local release of inflammatory mediators such as cytokines, chemokines, and prostaglandins. The main pro-inflammatory mediators that drive the initial host response to infection are the cytokines IL-1β, IL-6, and TNF-α (Dantzer et al., 1999). These small peptides are considered to be pro-inflammatory because they orchestrate the early immune response to infection and injury by communicating with cells of the host immune system, attracting them to the site of infection/injury and causing them to become activated and responsive. Pro-inflammatory cytokines also drive the expression of other inflammatory mediators, such as chemokines, eicosanoids, and acute phase proteins, which mediate other aspects of the inflammatory response, and which contribute to tissue repair and a return to homeostasis. An in-depth discussion of the biological actions of all of these cytokines is beyond the scope of this review, so we refer the reader to the following websites; http://www .copewithcytokines.de/cope.cgi and http://www .weizmann.ac.il/cytokine/.
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B. Neuroendocrine-immune Interactions and “Sickness Behavior” Much of the early research that was aimed at characterizing the biological mechanisms that underpin the host response to tissue injury and infection focused on identifying the contribution of individual inflammatory mediators to the cellular response mounted at the site of infection. However, in 1988, in his paper titled “The biological basis of sick animals,” the veterinary surgeon Benjamin Hart proposed that when mammals become infected by a pathogenic organism, in addition to mounting a cellular inflammatory response, they demonstrate a highly coordinated set of behavioral and metabolic changes, which he collectively termed “Sickness Behavior” (Hart, 1988). In his original hypothesis Hart stated that these changes in behavior and metabolism were not simply a detrimental consequence of the infection and associated inflammation per se, but that they represented a strategic reorganization of the host’s motivational priorities to aid the body’s immune system in fighting off infection, and in promoting tissue repair and recuperation. The behavioral and metabolic changes described in the original hypothesis of sickness behavior included the development of a febrile response, locomotor hypoactivity, and anorexia. Throughout the 1990s much research was subsequently undertaken to identify the spectrum of behavioral and metabolic changes that occur in humans and other mammals as a result of infection, and the list of nonspecific symptoms of ill health that fall under the umbrella of “sickness behavior” has grown significantly (Figure 1). Much of this research was also targeted at characterizing the mechanisms and routes of communication by which the peripheral immune system is able to communicate with the CNS to give rise to these complex changes in behavior, metabolism, mood, and motivation (neuroendocrine-immune interactions). A number of routes of communication have now been proposed and are described in detail in other chapters of this book. These include (1) passive diffusion of cytokines into the brain parenchyma at sites lacking a functional blood-brain barrier and/or active transport of cytokines across the cerebral vasculature and into the brain; (2) activation of neural afferents by cytokines; and (3) self-induction of cytokine synthesis within the brain, mainly by the resident macrophages of the brain and cerebral vasculature.
C. Central Cytokine Expression and Neuroendocrine-immune Interactions The contribution of neuroendocrine-immune interactions to the development of sickness behaviors in
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FIGURE 1 Summary of the metabolic, behavioral, and cognitive changes associated with sickness behavior.
mammals has received much interest over recent years, but a single unifying pathway has yet to be described; it appears that all of the proposed routes of communication described to date (see above) act in synergy to coordinate the complex neurophysiological changes that underpin the expression of sickness behavior. However, despite marked differences in their underlying biology, the actuation of each of these pathways is similar, being dependent on the de novo expression of pro-inflammatory cytokines and related inflammatory mediators in both the periphery and CNS. Peripheral challenges with LPS can induce the expression of pro-inflammatory cytokines within specific compartments of the CNS (Dantzer et al., 2000; Dantzer and Wollman, 1998; Laye et al., 1994). For example, intravenous (i.v.) and intraperitoneal (i.p.) challenges with LPS in rats have been reported to induce the expression of cytokines and their cognate receptors by many cell types throughout the brain (Breder et al., 1994; Gatti and Bartfai, 1993; Muramami et al., 1993) (for review, see Rothwell and Luheshi, 2000). In addition to cytokines, expression of other proinflammatory molecules, such as prostaglandins (PGs) and chemokines, has also been demonstrated in the CNS in response to models of systemic/peripheral infection. For example, upregulated expression of cyclooxygenase-2, the rate-limiting enzyme that metabolizes arachidonic acid to PGs and other eicosanoids, is reported in cells associated with the cerebral vasculature and glia (Lacroix and Rivest, 1998). Constitutive expression of pro-inflammatory cytokines, and other mediators of inflammation, is typically very low in healthy tissues. As discussed in
“Infection and Inflammation,” the acute expression of these mediators in peripheral tissues following infection or tissue injury gives rise to a robust cellular inflammatory response. Although the principal function of such a response is to remove pathogenic organisms, thereby protecting surrounding tissues from further infection, bystander damage to surrounding cells and tissues may occur as a consequence of cellular infiltration and the production of highly damaging superoxides (La et al., 2001; Matsuo et al., 1994; Matsuo et al., 1995). However, in contrast to the situation in peripheral tissues, there is no evidence to suggest that the expression of pro-inflammatory mediators within the healthy CNS parenchyma is damaging in the context of a physiological response to systemic infection/inflammation. This raises two important related questions: (1) What regulatory mechanisms exist within tissues of the CNS to limit the cellular response to the acute expression of pro-inflammatory mediators? (2) Are these mechanisms adequate to protect neurones when the CNS parenchyma is already compromised by ongoing inflammation, trauma, or other disease? In the rest of this chapter we will present and discuss evidence demonstrating that expression of proinflammatory cytokines within the CNS parenchyma can exacerbate tissue injury during acute brain trauma, immune-mediated disease, and chronic neurodegeneration. We will consider mechanisms by which peripheral inflammation and immunosenescence drive glial activation and de novo synthesis of cytokines within the CNS, and review evidence that systemic infection is a risk factor for relapse in immune-
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mediated disease, such as multiple sclerosis, and a stimulus for accelerated disease progression in rodent models of chronic neurodegeneration. In order to present a focused discussion, we will concentrate on in vivo models of CNS disease and bacterial infection, with brief reference to in vitro studies where necessary.
III. ACUTE INFLAMMATION OF THE CENTRAL NERVOUS SYSTEM A. Cytokines and Neuronal Death Physical trauma, ischemia, acute neurodegeneration, and infection of neuronal tissues all give rise to inflammation. Within the CNS, this response is mediated almost entirely by the innate immune system and is characterized by vascular and cellular changes including edema, vasodilation, glial activation, and recruitment of neutrophils and monocytes to the parenchymal tissue. In peripheral tissues, the first cells to respond to infection, tissue injury, and disease are the tissue macrophages. The macrophages of the CNS, the microglia, differ dramatically from those found in peripheral tissues, and in a healthy individual they adopt a quiescent phenotype with a highly ramified morphology. However, along with other glia, such as astrocytes, microglia respond rapidly to any changes in their microenvironment, becoming immunophenotypically and morphologically activated, upregulating their expression of cell surface antigens (Kreutzberg, 1996) and synthesizing and releasing a wide range of inflammatory mediators, including cytokines, chemokines, and prostanoids (Aloisi, 2001). Once released, these mediators act to further activate adjacent microglia, astrocytes, and neurones, amplifying the local glial response and driving leucocyte recruitment across the cerebral vasculature by inducing the expression of cell adhesion molecules (CAMs) on adjacent endothelia and by setting up chemotactic gradients. Interestingly, many of the pro-inflammatory cytokines expressed within the CNS in response to acute injury and infection are the same as those that dominate the inflammatory profile of acute injury and infection of peripheral tissues. However, in contrast to the periphery, delivery of the same inflammatory challenge to the brain parenchyma gives rise to only minimal leucocyte recruitment and inflammation (Andersson et al., 1992; Anthony et al., 1997). This relative insensitivity of the brain to acute inflammatory stimuli is important because tissues of the CNS have only a limited capacity to repair and regenerate. Despite this relative resistance of CNS tissues to acute inflammatory stimuli, there is now convincing
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evidence that pro-inflammatory cytokines, such as IL1β, IL-6, and TNF-α, contribute directly to tissue injury and neuronal death during acute trauma (for review, see Allan and Rothwell, 2003). Much of this work has come from studies using rodent models of focal cerebral ischemia and excitotoxic injury. Ischemic injury to the CNS occurs when tissue is deprived of oxygen and/or glucose for a protracted period of time, such as during a stroke. Under these circumstances, damage to tissue and neuronal death occurs in two distinct stages: (1) rapid loss of neuronal tissue in the ischemic core, where blood flow is reduced sufficiently to compromise energy metabolism; and (2) delayed loss of neuronal tissue in the area directly adjacent to the ischemic core (penumra), where blood flow is reduced, but not sufficiently to directly compromise neuronal survival (Dirnagl et al., 1999). Although the precise mechanisms of neuronal death in the penumra region have yet to be fully characterized, excessive glutamate release (excitotoxicity) from dying neurones and oxidative stress have been strongly implicated (Szatkowski and Attwell, 1994). Evidence for a role for inflammation is also convincing; marked leucocyte recruitment, pro-inflammatory cytokine expression, and glial activation occurs throughout the ischemic core and penumra region (Danton and Dietrich, 2003; Dirnagl et al., 1999). Direct evidence for a neurotoxic role of cytokines, such as IL-1β, has been provided by studies using rodent models of cerebral ischemia and experimentally induced excitotoxicity (Allan et al., 2000; Allan and Rothwell, 2003; Relton and Rothwell, 1992). For example, mice in which the genes encoding these cytokines, or their cognate receptors, have been disrupted (knockout mice) are significantly protected from the neuronal death in the striatum that results from occlusion of the middle cerebral artery (MCAo) (Boutin et al., 2001). Furthermore, administration of recombinant IL-1β to the CNS markedly exacerbates neuronal death resulting from MCAo and experimentally induced excitotoxicity. In support of this, abrogation of the activity of endogenous IL-1β by the administration of its endogenous antagonist, IL-1 receptor antagonist (IL-1RA), is protective in these models. Despite this convincing evidence for a neurotoxic action of pro-inflammatory cytokines in the acutely inflamed CNS, we still have only a limited understanding of the molecular mechanisms involved (Allan et al., 2005). To further complicate matters, deletion of certain pro-inflammatory cytokines from mice is detrimental to neuronal survival; for example, deletion from mice of the gene encoding IL-6 results in significantly larger regions of neuronal death in the CNS following MCAo (Loddick et al., 1998). Protection of CNS tissues following MCAo also occurs in mice in
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which expression of the chemokine, monocyte chemoattractant protein-1 (MCP-1), has been deleted (Hughes et al., 2002). In these mice, expression of pro-inflammatory cytokines during MCAo was significantly reduced prior to leucocyte recruitment to the CNS, suggesting that these inflammatory mediators may contribute to neuronal death by pleiotropic mechanisms that could be considered as distinct from their role in driving inflammation. Indeed, certain populations of neurones express receptors for cytokines and chemokines, although the physiological relevance of this has yet to be fully characterized (Cho and Miller, 2002). There are circumstances in which acute trauma and injury to the CNS results in neuronal death in the absence of pro-inflammatory cytokine expression. In our own laboratory, focal cerebral ischemia induced by the microinjection of endothelin-1 into the CNS of rats gave rise to focal neuronal death but in the absence of an acute inflammatory response (Hughes et al., 2003). Neuronal death was unaffected in this model by the administration of recombinant IL-1β and the induction of neutrophil recruitment to the CNS (Felton et al., manuscript in preparation). Thus, it seems that although pro-inflammatory cytokines do affect neuronal survival during acute trauma, this effect is highly dependent on the nature of the insult; the profile of inflammatory mediator expression; and complex interactions between cytokines, neurones, and recruited leucocytes. Of further interest is that acute delivery of cytokines to the healthy CNS, in the absence of concurrent pathology, does not lead to tissue damage despite inducing leucocyte recruitment to the parenchyma and the debilitating expression of sickness behaviors. For example, bolus injection of recombinant IL-1β and TNF-α into the brains of rats induces local glial activation and delayed leucocyte recruitment, but without injury to adjacent neurones or disruption of the BBB (Andersson et al., 1992; Anthony et al., 1997). Similar effects are observed during chronic cytokine expression; for example, adenoviral-mediated transfer of genes encoding human IL-1β into the rodent CNS results in chronic inflammation, lasting up to 2 weeks, but only mild reversible damage to myelin and no loss of neuronal cell bodies (Ferrari et al., 2004); only very high supraphysiological levels of transgene expression give rise to detectable tissue damage and neuronal loss (our unpublished observations). Thus, there is significant evidence that proinflammatory cytokine expression in the CNS compromises neuronal survival following acute trauma. Whether this is a direct consequence of the ensuing inflammatory response and associated bystander damage or a more direct interaction between cytokines,
neurones, and other components of the CNS is still unresolved. Furthermore, the demonstration that cytokine expression in the healthy CNS gives rise to inflammation in the absence of tissue injury and neuronal death suggests that only neurones compromised by concurrent or ongoing pathology are likely to be susceptible.
B. Bi-directional Communication between the CNS and the Peripheral Immune System Despite efforts to identify mechanisms by which peripheral inflammation can modify brain physiology, and vice versa, little consideration has been given to the contribution that the peripheral acute phase response makes to inflammation of CNS tissues following acute trauma or infection. Most studies of neuroendocrine-immune interactions have focused on “inflammatory reflexes” which function to downregulate and control inflammation following damage to or infection of peripheral tissues (for excellent reviews, see Pavlov and Tracey, 2005, and Tracey, 2002). The CNS has been considered as a privileged tissue in terms of its immune status, being relatively protected from the consequences of inflammatory mediator expression, and isolated from the general circulation by a highly impermeable BBB. This may explain to some extent why we are only now beginning to consider the impact on CNS pathologies of bi-directional communication between the peripheral immune system and brain. It is now recognized that inflammation and injury to CNS tissues gives rise to a peripheral inflammatory response, suggesting that descending pro-inflammatory pathways of brain-to-immune communication are activated in response to these pathologies. For example, elevated levels of acute phase proteins (APPs), cytokines, and chemokines have been reported in the circulation and liver after bolus injection of recombinant pro-inflammatory cytokines, such as IL-1β and TNF-α, into the brain parenchyma or cerebral ventricles (Campbell et al., 2003; Campbell et al., 2005; De Simoni et al., 1990; De Simoni et al., 1995; Di Santo et al., 1999; Wilcockson et al., 2002), and after spinal cord compression injury in rats (Campbell et al., 2005). They have also been reported in human patients following ischemic stroke; in these studies the extent of the peripheral inflammatory response was positively correlated with disease outcome in terms of infarct area and neurological deficit (Emsley et al., 2003; Smith et al., 2004). However, this observation should be considered with caution, as many of the patients investigated had concurrent peripheral infections which may have elevated circulating cytokines independently of the CNS pathology.
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We have investigated the contribution of the peripheral inflammatory response to leucocyte recruitment to the brain and spinal cord parenchyma following acute injury. We have shown that inflammation of these tissues induces rapid increases in hepatic and circulating concentrations of acute phase proteins (APPs), such as serum amyloid A protein (SAA) and serum amyloid P component, and chemokines, in addition to inducing local synthesis at the site of injury (Campbell et al., 2003; Campbell et al., 2005; Wilcockson et al., 2002). APPs have pleiotropic inflammatory actions, contributing to local inflammatory responses by driving processes such as pathogen opsinization, neutrophil activation, clotting, and tissue repair. Expression of these proteins, both at the site of injury and within the liver, occurs rapidly following acute injury or infection, and results in marked increases in their circulating concentrations within minutes to hours (Streetz et al., 2001). Chemokines also play a pivotal role during inflammation, driving leucocyte recruitment to injured tissues (chemotaxis), and activating resident cells of the immune system (Bajetto et al., 2001; Moser and Willimann, 2004). The traditional model of chemokine-driven leucocyte recruitment to injured/infected tissues is based on the generation of local chemotactic gradients which can be detected by circulating leucocytes through specific cell surface receptors. Chemokines are expressed by many cell types in CNS and peripheral tissues in response to inflammatory stimuli. On exposure to chemokines, circulating leucocytes take on an activated phenotype, allowing them to interact with endothelial CAMs, undergo diapedesis, and migrate into adjacent tissues along concentration gradients generated by passive diffusion of chemokine species from their site of synthesis (Rot and von Andrian, 2004). In general terms the CC chemokines are responsible for the selective recruitment of mononuclear cells to sites of inflammation and injury; examples of CC chemokines include CCL2 (Monocyte chemoattractant protein-1 [MCP-1]) and RANTES. The CXC chemokines, such as CXCL-1 (CINC-1 in the rat), drive the selective recruitment of neutrophils to inflamed tissues (Rot and von Andrian, 2004). We have previously reported that transient increases in levels of hepatic and circulating CC and CXC chemokines occur rapidly following acute injury to spinal cord tissue, or after the induction of inflammation in the brain parenchyma of rats. In the case of CINC-1, a CXC chemokine, this increase in expression peaks as early as 2 hours after an intracerebral (i.c.) injection of recombinant IL-1β, occurring earlier than the peak expression of a number of recognized APPs (Campbell et al., 2003; Campbell et al., 2005). The acute peripheral
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expression of these chemokines is also exquisitely sensitive to any injury of spinal cord tissue, and drives dramatic leucocyte mobilization from tissues such as the bone marrow. Moreover, we have recently demonstrated that this mobilization is essential for local leucocyte recruitment to the brain parenchyma induced by bolus injections of recombinant pro-inflammatory cytokines into the striatum of rats: delayed neutrophil and monocyte recruitment to the brain parenchyma that occurred after i.c. injections of recombinant IL-1β and TNF-α, respectively, was abolished by pharmacological neutralization of hepatic and circulating chemokines. Furthermore, artificial elevation of circulating CCL2 significantly increased local monocyte recruitment to the brain parenchyma. As a result of these investigations, we have proposed a novel mechanism by which hepatic chemokine synthesis contributes to local leucocyte recruitment and inflammation of CNS tissues. A summary of this mechanism is illustrated in Figure 2. The experiments described above provide convincing evidence that acute injury and/or infection of CNS tissues induces a peripheral inflammatory response, and that this is essential for leucocyte mobilization into the circulation, and local recruitment of neutrophils and monocytes during experimentally induced inflammation of the CNS parenchyma. The results of these studies point to the presence of rapid mechanisms of crosstalk between the brain and peripheral immune system that promote and amplify local inflammatory responses in tissues of the brain and spinal cord. Intriguingly, none of the inflammatory challenges administered to the CNS parenchyma in these studies led to detectable elevated levels of circulating cytokines (Campbell et al., 2003; Campbell et al., 2005), suggesting that the hepatic response to acute CNS injury may be mediated by an as yet unidentified pathway. Whether these routes of communication are essential for leucocyte recruitment to CNS tissues in response to all forms of acute injury, trauma, and infection warrants further investigation.
IV. IMMUNE-MEDIATED DISEASE OF THE CENTRAL NERVOUS SYSTEM: MULTIPLE SCLEROSIS A. Multiple Sclerosis as an Inflammatory Disease Multiple sclerosis (MS) is the archetypal immunemediated inflammatory disease of the human CNS, and although its etiology is currently unknown, it is widely believed to result from a complex interaction
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Rodent CNS 1
Inflammatory Stimulus Cytokines, chemokines
7 Periphery
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FIGURE 2 (A) Diagrammatic representation of bi-directional communication between the brain and periphery in response to acute CNS injury. (B) Changes in the levels of CC and CXC chemokines in the liver, circulation, and brain following acute CNS injury. Inflammatory stimuli such as acute trauma rapidly result in glial activation and inflammatory mediator expression within the CNS (1). As a result, descending routes of communication between the brain and peripheral immune system are activated (2, 3), giving rise to the rapid synthesis and release of liver acute phase proteins (APPs) (4) and chemokines (5) into the circulation. APPs exert pleiotropic inflammatory effects, driving processes such as opsinization, blood clotting, neutrophil activation, and tissue repair. The rapid but short-lived increases in CC and CXC chemokine levels within the circulation (B) drives leucocyte (neutrophil and monocyte) mobilization from bone marrow and other tissues (6), resulting in acute leucocytosis. Over the following hours, circulating levels of chemokines begin to fall, but expression within the brain parenchyma continues to increase (B). The resulting chemokine concentration gradient drives leucocyte recruitment across the blood-brain barrier and into the injured brain parenchyma (7), generating a focal inflammatory response.
of an individual’s genotype and environmental factors (Compston and Cole, 2002). MS affects both the brain and spinal cord and is characterized by the presence of focal lesions (or plaques) where macrophages and T-cells cross the BBB and invade the adjacent CNS parenchyma (Prat et al., 2002). In some of these lesions the BBB is damaged to the extent that its integrity is compromised; in the clinic these regions of pathology can be visualized by magnetic resonance imaging (MRI) as gadolinium-enhancing lesions. The classical key feature of MS lesions (or plaques) is an extensive loss of myelin, but recent evidence has highlighted that injury to axons occurs in the early stages of disease (Ferguson et al., 1997; Trapp et al., 1998). Although the molecular events underlying this demyelination and axon injury are unclear, the intensity of the inflammatory response in MS lesions correlates well with the extent of axon injury (Ferguson et al., 1997). Animal models that mimic aspects of MS pathology, such as experimental allergic encephalomyelitis (EAE), have proven extremely useful in developing hypotheses on the inflammatory mechanisms and pathways that underpin the development of an MS lesion (Kivisakk et al., 2001). These models have confirmed the involvement of T-cells and macrophages, and the expression of a wide range of inflammatory mediators, including cytokines and chemokines. Although a progressive loss of axonal integrity is a key feature of MS, the expression of neurological impairment often follows a relapsing-remitting course, particularly in the early stages of the disease (Compston and Coles, 2002). The expression of disease exacerbation (relapse) followed by near-complete recovery from neurological impairment (remission) is also reflected in the underlying pathology and inflammation (Figure 3). This relapsing-remitting feature of MS pathology also characterizes a number of inflammatory diseases of peripheral tissues, which include Crohn’s disease (Yang and Lichtenstein, 2002) and rheumatoid arthritis (Elkayam et al., 2002), affecting the bowel and synovial joints, respectively.
B. Systemic Infection as a Risk Factor for Relapse in Multiple Sclerosis The significance of systemic infection as a risk factor for disease relapse in MS was first described by Sibley et al. (1985). In this detailed study, the rate of symptomatic disease relapse in a 7-week “at risk” period was found to be about three times higher in MS patients that had suffered from a systemic infection. The majority of infections in the experimental cohort were upper respiratory tract infections, but it is now accepted that other infections also increase the risk of relapse.
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FIGURE 3 Disease progression in multiple sclerosis (MS). A graph showing the relationship between neurological impairment and axonal integrity. Neurological impairment in MS typically follows a relapsing-remitting course in the early stages of disease, despite a progressive loss of axonal integrity. In the later stages, when axonal integrity is markedly reduced, neurological function becomes progressively impaired (secondary progressive disease).
Further evidence that systemic infection is a risk factor for relapse in MS has been provided by studies of disease progression using MRI and positronemission tomography (PET) to visually assess the extent of CNS pathology. In MS, disruption of the BBB occurs in regions of inflammation and demyelination (plaques), and these pathologies can be visualized non-invasively in conscious patients using MRI to track the movement of normally impermeant molecules (such as gadolinium) from the general circulation and into the CNS parenchyma (Jeffery, 2000). In one such study, where relapse was defined by the onset of neurological impairment in combination with changes in the number and extent of gadolinium-enhancing lesions, the incidence of relapse in MS patients with systemic infections was up to 3.8-fold higher in a 7week “at risk” period than in control periods (Buljevac et al., 2002). Interestingly, when disease relapse was assessed in the same study using serial MRI scans around the time of infection, rather than by considering a protracted “at risk” period, there was no evidence of an increase in the number or extent of gadolinium-enhancing lesions. However, the results of such studies should be considered with caution, as they are likely to underestimate the real contribution of systemic infection to disease relapse. MS plaques visualized by MRI represent only a small proportion of the total inflammatory activity in the brains of MS
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patients. For example, PET scanning has revealed microglia activation throughout the brains of MS patients, including regions of the parenchyma in which the BBB is intact (Banati et al., 2000). Furthermore, animal models of immune-mediated disease have demonstrated that inflammation, BBB disruption, and tissue damage can occur independently in the CNS. It has been demonstrated by Newman et al. (2001) that focal delayed-type hypersensitivity (DTH) reactions in the rodent CNS, which are dominated by T-cell and macrophage infiltrates, have an extended phase in which inflammation, axonal injury, and other ongoing tissue damage can occur independently of BBB disruption, as assessed by MRI. To summarize, there is now substantial evidence that systemic inflammation following infection by bacterial or viral pathogens is a risk factor for relapse in MS. Although the majority of this work has focused on identifying risk factors for acute relapse in MS, it is also likely that systemic infection contributes to disease progression in the context of ongoing axonal injury. The nature of the transition from relapsing-remitting disease to secondary progressive disease in MS is currently unknown, but investigations of the impact of risk factors such as systemic infection would clearly be of great interest.
C. Mechanisms of Disease Exacerbation by Systemic Infection An understanding of the cellular and molecular mechanisms by which systemic infection, and the associated peripheral inflammatory response, may contribute to relapse in MS requires us to consider the role of pro-inflammatory mediators, activated glia, and infiltrating leucocytes in lesion pathogenesis. As discussed in “Multiple Sclerosis as an Inflammatory Disease,” recruitment of T-cells and macrophages across the BBB and into the CNS parenchyma is a key feature of the complex pathology associated with MS. Although the etiology of MS is largely unknown, a process of molecular mimicry of self-proteins by viral peptides is considered by some to be key to the resulting neuropathology (Edwards et al., 1998). Presentation of these peptides by the host’s immune system results in an inappropriate inflammatory response in which activated T-cells cross the BBB, target myelin peptides as non-self antigens, and generate a targeted chronic inflammatory response in the CNS. The contribution of systemic infection to disease progression and relapse in MS has therefore been largely interpreted in the context of further T-cell activation and recruitment that would result from elevated expression of pro-inflammatory cytokines in the periphery and CNS (Panitch, 1994)
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and activation of the T-cells by superantigens. For example, exposure of rodents to bacterial products such as LPS and Staphylococcal Enterotoxin A (SEA) and B (SEB), to mimic aspects of peripheral infection, has been shown to exacerbate clinical signs and induce relapse in models of immune-mediated disease such as EAE (Brocke et al., 1993; Schiffenbauer et al., 1993). However, similar responses to those seen with SEB challenges have also been reported after a single injection of TNF-α (Crisi et al., 1995), suggesting that peripheral innate inflammation, rather than antigendriven T-cell activation, is the stimulus for disease exacerbation. Although the mechanisms that result in clinical exacerbation have not been well studied, we do know that brain cytokine expression occurs as a result of systemic infection or inflammation (see “Neuroendocrine-Immune Interactions in Health and Disease: Cytokine Expression in the CNS”). We have studied how systemic inflammation impacts on an immune-mediated local DTH lesion in the brain parenchyma (Broom et al., 2005). A DTH lesion in the brain was evoked by depositing heatinactivated Bacillus Calmette-Guérin (BCG) into the brain parenchyma followed by systemic activation of the immune system with BCG (Matyszak and Perry, 1995). This results in a focal lesion in the brain parenchyma that is dominated by T-cells and macrophages with damage to the BBB, myelin, and axons. Over time the BBB damage resolves, but the inflammatory focus persists for many weeks. Using MRI and systemic administration of gadolinium, we have shown that peripheral challenge with bacterial endotoxin can give rise to a local transient breakdown of the BBB at the focus of the DTH lesion (Broom et al., 2005). Although the biological mechanisms underlying the reactivation of DTH lesions during systemic inflammation have yet to be characterized, the re-opening of the BBB observed in these rats clearly illustrates that systemic inflammation may impact on an immune lesion that is present behind an intact BBB. There is an extensive body of evidence to show that systemic inflammation can also give rise to the expression of pro-inflammatory mediators in regions of the CNS that have a fully functional BBB. When healthy rodents are exposed to very aggressive high-dose peripheral challenges with LPS, akin to levels associated with septic shock in man, expression of inflammatory cytokines has been observed throughout the CNS; studies using immunocytochemistry and in situ hybridization have demonstrated expression of cytokines by cells of the cerebral vasculature (endothelial cells and perivascular macrophages), meningeal macrophages, and parenchymal microglia. In related studies, the temporal and spatial expression pattern of
these cytokines within tissues of the CNS was also observed for other markers of inflammation, such as I-κβ, COX-2, CD-14, and cytokine receptors (for review, see Rivest, 2003, and Rivest et al., 2000). Although very aggressive challenges with LPS are required to induce detectable cytokine expression in the brains of healthy rats and mice, this may not be the case if tissue has already been compromised by a previous inflammatory reaction. Although some progress had been made by studies using immunocytochemistry and in situ hybridization, identification of the precise cellular sources of brain pro-inflammatory cytokines following systemic infection has proven difficult due to the limited spatial resolution of these approaches. In our laboratory, we have been particularly interested in the contribution that CD-163–positive macrophages make to brain cytokine synthesis during systemic infection. Although these are a minority population of brain macrophages, which comprises perivascular macrophages (PVMs) and meningeal macrophages (MMs), their strategic location might reflect a potentially important role in immune-to-brain signaling. PVMs are located throughout the cerebral vasculature and occupy a unique position at the BBB, lying between the glia limitans (formed by astrocytic end feet) and the basal lamina of cerebral endothelial cells (for review, see Schiltz and Sawchenko, 2003), whereas MMs are situated at the brain-cerebrospinal fluid interface (Figure 4). We now know that both PVMs (Elmquist et al., 1997; Schiltz and Sawchenko, 2002) and MMs (Garabedian et al., 2000) respond rapidly to elevated levels of circulating inflammatory mediators. Given the ideal locale of these cells to act as a relay mechanism between the circulation and brain parenchyma, we have been investigating whether they contribute to brain cytokine expression in a well-characterized model of peripheral infection. To do this, we have taken an in vivo approach in which CD-163–positive macrophages are depleted from the brains of rats using a selective toxin, sodium clodronate. Although not toxic at low concentrations, sodium clodronate induces apoptosis when actively concentrated in the cytoplasm of living cells (van Rooijen et al., 1996). In order to deplete CD-163–positive macrophages, sodium clodronate–filled liposomes were delivered into the cerebral ventricular system of anesthetized rats. These macrophages are the only cell type in the healthy CNS that is constitutively phagocytic, and as a result these are the only cells to take up the toxin and be depleted (van Rooijen et al., 1996). This approach has previously been utilized to demonstrate an important role for PVMs and MMs in driving leucocyte recruitment to the CNS during pneumococcal meningitis (Polfliet et al., 2001). However, our
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FIGURE 4 CD-163–positive macrophages in the rat brain. Photomicrographs of rat brain sections stained with a primary antibody (ED2) raised against the CD-163 antigen. (A) CD-163–positive perivascular macrophages (dark cells; arrows) lying between the glia limitans and the basal lamina of endothelial cells in the striatum of a healthy rat. (B) CD-163–positive meningeal macrophages (dark cells; arrows) lying at the braincerebrospinal fluid interface of a healthy rat. Scale bars = 50 μm.
investigations have failed to demonstrate a reduction in brain cytokine mRNA expression after an i.v. challenge with LPS in rats in which CD-163–positive macrophages had been depleted (Galea et al., manuscript in preparation). There are a number of possible explanations for this, but the most likely is that cerebral endothelial cells are capable of de novo cytokine synthesis in the absence of PVMs and MMs; endothelial cells outnumber PVMs throughout the CNS (25 : 1 in the striatum and 4 : 1 in the cortex), and have long been recognized as “brain sensors” of peripheral inflammation (Schiltz and Sawchenko, 2003). Thus, although there is a wealth of evidence showing that CD-163–positive PVMs and MMs do express cytokines (Garabedian et al., 2000; van Dam et al., 1992), their contribution to overall de novo brain cytokine synthesis is overshadowed by endothelial cells. However, whether endothelial-derived cytokines can cross the cerebral vasculature and penetrate the parenchyma remains to be demonstrated. Furthermore, our investigations to date have been limited to studies of brain cytokine expression in response to systemic infection in rats that are otherwise healthy. As observed for microglia, PVMs are reported to be upregulated in number and activation state in the CNS during and following immune-mediated disease (Fabriek et al., 2005). Thus, the contribution of these cells to brain cytokine synthesis may become significant if brain tissue is already compromised by ongoing pathology.
V. CHRONIC NEURODEGENERATION AND MICROGLIAL PRIMING Despite convincing evidence that inflammatory processes contribute to tissue pathology in acute CNS injury and disease, there are circumstances in which overt pathology of brain tissues can occur in the absence of a “typical” innate or acquired immune response. “Atypical” inflammatory responses are a characteristic feature of pathologies resulting from chronic neurodegenerative diseases, the archetypal example of which is Alzheimer’s disease (AD). AD is highly prevalent and the most common cause of cognitive decline in the elderly human population. The key features of AD pathology are non-specific deposition of Aβ-amyloid protein and the formation of neurofibrillary tangles within degenerating neurones. Although inflammatory mediator expression has been reported in postmortem brains of human AD patients and in some rodent models of chronic neurodegeneration, its contribution to disease progression has yet to be established (Akiyama et al., 2000). Much of the early research into the “inflammatory component” of AD was fueled by epidemiological studies demonstrating a significant protective effect of non-steroidal antiinflammatory drugs (NSAIDs) on disease onset and/ or progression (in t’ Veld et al., 2001; McGeer and Rogers, 1992; McGeer et al., 1996; Perry et al., 2003). It has been argued, however, that inflammation per se
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does not contribute to disease progression in AD. For example, AD pathology does not give rise to leucocyte recruitment to the brain parenchyma, as evidenced by the absence of immune cells in the perivascular space of blood vessels supplying CNS tissues; the cellular profile of AD is dominated instead by a process of microglial activation (Akiyama et al., 2000). Furthermore, clinical trials attempting to repeat the results of earlier NSAID studies using new and highly efficacious inhibitors of cyclooxygenase-2, a key enzyme in prostaglandin biosynthesis, or other antiinflammatory agents have proven unsuccessful (Aisen, 2002a; Aisen, 2002b; Aisen et al., 2002). Moreover, many patients with AD have systemic infections at the time of death (Beard et al., 1996), and we have to consider that this could significantly contribute to much of the pro-inflammatory mediator expression reported in postmortem brains. Interestingly, in our own studies, we have demonstrated that AD patients who have had a systemic infection, and/or elevated levels of circulating inflammatory cytokines, show a more rapid rate of cognitive decline over the following 2 months than patients that remain otherwise healthy (Holmes et al., 2003); these results were interpreted as evidence that peripheral inflammatory responses mounted against systemic infections have the potential to exacerbate or accelerate disease progression in AD. In related epidemiological studies, systemic infection has also been identified as a significant risk factor for the onset of dementia in the elderly, an important clinical symptom of AD (Dunn et al., 2005). In order to further investigate the contribution of inflammation to disease progression in AD, many research groups have turned to rodent models. However, although it is possible to induce aspects of AD-associated pathology in rodent brains, a reliable in vivo model has yet to be developed. As a result, we have turned our attentions to other models of chronic neurodegenerative disease. The transmissible spongiform encephalopathies (TSEs), or prion diseases, are a group of chronic fatal neurodegenerative diseases that share many pathological features with AD, and can be efficiently modeled in experimental rodents. Examples of prion disease include Creutzfeldt-Jakob disease (CJD) in humans, and bovine spongiform encephalopathy (BSE) in cattle. These diseases are either genetic, sporadic, or infectious in origin, and the causative agent is a protein (PrPSc) that is capable of inducing a conformational change in a normal host protein (PrPc), converting it into a protease-resistant likeness of itself (Prusiner, 1982). Despite the widespread expression of PrPc throughout the body (Aguzzi and Weissmann, 1997), and its conversion to PrPSc during disease, pathology
appears to be strictly isolated to the CNS. Much of our own research of the mechanisms underlying the pathology of prion disease has come from murine models in which mice have been intracranially inoculated into the hippocampus with brain homogenate of an infected animal. One example of this is the ME7 model (Betmouni et al., 1996; Williams et al., 1994), which has an incubation period of approximately 20 weeks (onset of clinical disease) and invariably results in death 2 to 3 weeks later. CNS pathology in this model reflects nearly all aspects of human prion disease. The first signs of disease appear within the hippocampus, well before the onset of clinical disease, and are characterized by synaptic loss, microglial activation, and deposition of PrPSc protein (Figure 5). Neuronal loss in this model typically occurs in the CA1 layer of the hippocampus and dorsal thalamic nuclei, but not until much later in the course of the disease (from week 18), when aspects of pathology have spread throughout the limbic system (Cunningham et al., 2003; Jeffrey et al., 2000). Interestingly, the inflammatory response to prion disease is highly atypical, being dominated by an immunophenotypical activation of microglia, but in the absence of marked pro-inflammatory cytokine expression. The pro-inflammatory cytokines that typically dominate acute inflammatory lesions, such as IL-1β, IL-6, and TNF-α, appear to be virtually undetectable in prioninfected brains (Cunningham et al., 2002; Walsh et al., 2001). The only mediators to have been shown to be consistently and significantly upregulated are acute phase proteins, transforming growth factor β1 (TGFβ1) (Cunningham et al., 2002), and the eicosanoid prostaglandin-E2 (PGE2) (Cunningham et al., 2005c; Minghetti et al., 2000; Walsh et al., 2000). TGFβ1 and PGE2 have well-defined anti-inflammatory properties in the CNS (McDonald et al., 1999; Zhang and Rivest, 2001), and are the principal mediators released by macrophages during phagocytosis of apoptotic cells (Fadok et al., 1998) (for review, see Perry et al., 2002). This has led to the suggestion that microglia in prion-infected brains are “primed” as a consequence of phagocytosing degenerating synapses and processes of neurons, which appear to degenerate in a manner akin to apoptosis (Cunningham et al., 2002; Perry et al., 2002). The nature of the triggers for microglial priming and neuronal apoptosis in prion-infected brains is still an area of much debate. Thus, taken together, the evidence suggests not only that the inflammatory response to prion disease is atypical, but that it may be relatively benign; in support of this, many manipulations of the immune system have failed to modify disease progression when prion agents are delivered directly into the CNS (Mabbott et al., 2000).
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FIGURE 5 Pathological changes in the brains of mice with prion disease. Microglia (FA11 staining) in the dorsal hippocampus of control mice (A; arrow), and mice inoculated with ME7 prion agent (B; arrows). Note the increase in the number of microglia in the brains of prion-diseased mice (B), and their activated morphology (B inset); microglia in the healthy CNS have a highly ramified morphology (A inset) characteristic of their quiescent phenotype. Synaptophysin staining in the dorsal hippocampus of control mice (C), and mice inoculated with ME7 scrapie (D); note the reduced synaptophysin staining, indicative of synaptic loss, across the hippocampus of prion-diseased mice (D). All prion-diseased tissue is taken from mice 19 weeks after inoculation with ME7 scrapie. Scale bars = 50 μm (A and B), 20 μm (A and B insets), 200 μm (C and D).
We have become interested in the contribution that “primed microglia” make to disease progression in the ME7 model of prion disease, particularly in the context of disease exacerbation during systemic infection. We have previously proposed that microglia primed by ongoing neuropathology may be more responsive to peripheral inflammatory responses than quiescent microglia, producing more potentially damaging inflammatory mediators in response to models of systemic infection (Figure 6) (Perry et al., 2003): Indeed, expression of the pro-inflammatory
cytokine, IL-1β, is much exaggerated in the brains of mice inoculated with ME7 after peripheral or intracerebral challenge with LPS (Combrinck et al., 2002). Similar elevated cytokine responses have also been reported in the brains of elderly (16 month) TgAPPsw mice, which display aspects of AD-associated pathology (Sly et al., 2001). Further evidence has come from studies of behavior in prion-diseased mice. Although clinical symptoms of disease, such as gross locomotor retardation, piloerection, and urinary incontinence, do not occur until late in the course of ME7 prion
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FIGURE 6 Microglial activation/priming responses. In a healthy CNS, microglia take on a quiescent phenotype with a highly ramified morphology and low expression of cell surface antigens (A). These quiescent cells respond rapidly to acute CNS injury or systemic infection, taking on an activated phenotype (B), upregulating their expression of cell surface antigens and pro-inflammatory mediators, thereby driving a local inflammatory response. In response to chronic neurodegeneration, or as a natural consequence of aging, quiescent microglia (A) do not become activated and are instead “primed” (C). Although primed microglia appear morphologically very similar to their fully activated counterparts, they express mediators that exert anti-inflammatory effects within the CNS; examples include TGF-β and PGE2. When these cells are exposed to a subsequent inflammatory stimulus, such as that which may occur during acute trauma or systemic infection, they switch to an activated phenotype (B), synthesizing and releasing pro-inflammatory mediators, such as IL-1β. In a CNS already compromised by pathology, such as that resulting from a chronic neurodegenerative condition, this expression of pro-inflammatory mediators may directly contribute to tissue injury and give rise to a heightened expression of sickness behaviors.
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disease (approximately week 18), formal behavioral testing has revealed a full battery of pre-clinical changes in species-stereotyped (“instinctive”), affective, locomotor, and nesting behaviors, and early changes in cognitive function (Cunningham et al., 2003; Felton et al., 2005). The onset of these subtle behavioral changes coincides with the first detectable loss of synapses from the dorsal hippocampus, and long before overt neuronal loss can be detected (Cunningham et al., 2003). The onset of these behavioral dysfunctions also coincides with the first signs of microglial activation/priming and PrPSc deposition in the dorsal hippocampus and adjacent thalamic and cortical tissue. The pathological mechanisms underlying these complex behavioral changes have been discussed at length elsewhere (Cunningham et al., 2005a). Interestingly, the temporal profile of these pre-clinical behavioral dysfunctions is highly ordered, their onset occurring in the same order even where different strains of prion agent that induce distinct pathologies have been compared (Bruce et al., 1991; Cunningham et al., 2005b). This has led to the suggestion that these distinct rodent models of prion disease share a common early neurodegenerative pattern that has yet to be fully identified. Furthermore, the highly ordered temporal profile of regional neuropathology, glial activation, and pre-clinical behavioral dysfunction in rodent prion disease has allowed us to use formal behavioral testing as a powerful non-invasive tool for following disease progression (Felton et al., 2005). This approach has many benefits over traditional studies that have investigated pathology alone; for example, using long-term assessment of behavioral dysfunction in a single prion-diseased mouse provides us with invaluable information about the temporal evolution of neuronal dysfunction and pathology, whereas immunocytochemical analysis of neuronal death and/or inflammation at a single time-point provides us with only a “snapshot” of the disease process. In addition to mounting exaggerated cytokine responses to systemic infection, prion-diseased mice demonstrate exaggerated sickness behavior in response to i.p. challenges with LPS (Combrinck et al., 2002): Mice challenged with LPS 19 weeks after i.c. inoculation with ME7 showed greater, more prolonged febrile responses and suppression of locomotor activity in a novel open-field, when compared to control mice that had been inoculated with a normal brain homogenate control. Both of these exaggerated sickness responses are consistent with elevated expression of brain pro-inflammatory cytokines, such as IL-1β, which are detrimental to neuronal survival in the many models of CNS pathology.
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In the terminal stages of disease, from weeks 18 onwards, mice infected with ME7 prion disease develop significant and debilitating clinical symptoms, including urinary incontinence and associated inflammation of the anogenital area and of the underbelly. In a recent series of experiments, we investigated differences in prion-induced pathology, inflammation, and behavioral dysfunction in mice in which the gene encoding the chemokine, monocyte chemoattractant protein-1 (MCP-1), had been ablated (Felton et al., 2005); this inflammatory mediator is an important monocyte chemoattractant and activator of microglia, and its expression is markedly upregulated in the brains of mice early in the course of prion disease. Interestingly, mice deficient in MCP-1 (MCP1−/− mice) lived significantly longer (10–15%) than their wild-type controls, and in most cases failed to develop typical clinical symptoms of disease, including anogenital and abdominal inflammation; most MCP-1−/− mice were terminated due to severe weight loss in the absence of any other clinical symptoms. However, despite these differences in the onset of clinical disease and survival, no protection against the usual neuronal death, microglial activation, synaptic loss, or PrPSc deposition was observed in the brains of these mice; neither was there protection against the early behavioral deficits in speciesspecific behaviors. It is possible that that the delay in transition to terminal disease observed in MCP-1−/− mice may be related to the absence of peripheral inflammation that is normally associated with prolonged urinary incontinence in wild-type mice. Although the absence of this chemokine did not protect against early pathological changes in the brains of MCP-1−/− mice, it is possible that it acted to downregulate inflammation at the site of incontinence. Whether the absence of a peripheral inflammatory response in MCP-1−/− mice contributes to the observed increase in survival time is under investigation. Despite the evidence from our behavior studies that peripheral inflammation/systemic infection may contribute to disease progression in rodent models of chronic neurodegeneration, it has proven difficult to demonstrate this at the level of pathology. One possible explanation for this is that inflammation resulting from acute challenges with LPS is very short-lived (12–24 hours); this is also reflected in the associated sickness behavior, which typically resolves within 24 hours (Combrinck et al., 2002). However, we now have evidence from our own laboratory that a secondary peripheral challenge with LPS can significantly increase the rate of neuronal death in the CA1 dorsal hippocampus in mice with late-stage prion
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disease (Cunningham et al., 2005). Furthermore, a recent study by Nguyen et al. (2004) has described exacerbation of a chronic neurodegenerative disease by repeat peripheral challenge with LPS: In a transgenic mouse model of amyotrophic lateral sclerosis (ALS), it was demonstrated that repeat i.p. injections of LPS in the presymptomatic stages of disease exacerbated CNS inflammation and motor neuron pathology, and reduced survival time. Thus, using approaches in which formal behavioral testing has been combined with studies of CNS pathology and inflammation, we have provided evidence that systemic infection may exacerbate clinical disease and/or pathology in rodent models of chronic neurodegeneration. The results of these investigations are consistent with the results of preliminary clinical studies of human AD patients, which have identified systemic infections and peripheral inflammation as a significant risk factor for accelerated disease progression (Dunn et al., 2005; Holmes et al., 2003). The mechanisms of neuronal death that underlie clinical disease in human neurodegenerative conditions are largely unclear. However, in the context of disease exacerbation during systemic infections, exaggerated cytokine expression by primed microglia has been strongly implicated. As discussed in previous sections, expression of pro-inflammatory cytokines within the brain parenchyma is deleterious to neuronal survival in a wide range of disease processes, although the precise mechanisms involved are unclear. This hypothesis has led to much concern recently with the demonstration that primed microglia, and other inflammatory markers such as cytokines and chemokines, can be found in the brains of healthy aged humans and rodents (Godbout et al., 2005; Perry et al., 1993; Perry et al., 2003; Sheng et al., 1998). Indeed, it is now well established that progressive microglial activation/priming forms a natural part of the aging process (immunosenescence), possibly resulting from repeated lifetime exposure to peripheral infections. In a recent paper by Godbout et al. (2005), it was demonstrated using behavioral analysis and gene expression profiling that aged healthy mice mount significantly greater brain inflammatory responses and sickness behaviors to peripheral challenges with LPS. That these responses would be even more exaggerated, and potentially damaging, if brain tissue was already primed by ongoing pathology seems most likely. Given the steady increases in life expectancy that we are now experiencing, the impact of immunosenescence on the progression of chronic neurodegenerative diseases, and on the clinical outcome of acute
brain injury and other pathologies, deserves further investigation.
VI. SUMMARY In this chapter we have discussed mechanisms by which peripheral inflammation resulting from systemic bacterial or viral infections can impact upon pathology and clinical progression of CNS diseases. An important physiological response to systemic infection is the expression of pro-inflammatory cytokines within the brain and the development of sickness behaviors, which help the body to fight off infection, recover, and recuperate. However, there is now substantial evidence that aging, perhaps as a result of repeated lifetime exposure to systemic infections or as a consequence of early subtle stages of neurodegeneration, can result in a “priming” of microglia within the brain parenchyma. Primed microglia are responsive to subsequent inflammatory challenges, switching their phenotype to a more activated state, and there is evidence that this may by deleterious to neuronal survival in chronic neurodegenerative diseases. There is also strong evidence from clinical and in vivo studies that brain cytokine expression resulting from systemic infection is detrimental to neuronal survival during acute trauma. Furthermore, systemic infections have been identified as an important risk factor for disease relapse and progression in MS patients, and there is circumstantial evidence that this is also associated with brain cytokine expression. Thus, it is clear that systemic infections have the potential to impact deleteriously on tissues of both the periphery and CNS, and that this may be more marked in individuals, such as the aged, where the immune system has been “primed” by previous inflammatory events. In terms of the underlying biological mechanisms, a role for pro-inflammatory cytokines appears promising. Given this, and the strong evidence for bi-directional communication between the peripheral immune system and brain tissues during systemic infections, it would appear that the “immunological privilege” once believed to be afforded to CNS tissues is far from absolute. These observations are clearly of great clinical significance.
Acknowledgments We should like to thank Dr. Ian Galea, Dr. Tracey Newman, and Dr. Colm Cunningham for their help with the preparation of this manuscript and for allowing the inclusion of preliminary results from their ongoing investigations. We should also like to thank Prof. C. Anthony for critical appraisal of this manuscript, and acknowledge the Wellcome Trust, MRC, BBSRC, MS Society, and Nurin Ltd. for funding much of the work described.
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References Aguzzi, A., and Weissmann, C. (1997). Prion research: the next frontiers. Nature, 389, 795–798. Aisen, P. S. (2002a). Evaluation of selective COX-2 inhibitors for the treatment of Alzheimer’s disease. J. Pain Symptom Manage., 23, S35–S40. Aisen, P. S. (2002b). The potential of anti-inflammatory drugs for the treatment of Alzheimer’s disease. Lancet Neurol., 1, 279–284. Aisen, P. S., Schmeidler, J., and Pasinetti, G. M. (2002). Randomized pilot study of nimesulide treatment in Alzheimer’s disease. Neurology, 58, 1050–1054. Akiyama, H., Barger, S., Barnum, S., Bradt, B., Bauer, J., Cole, G. M., Cooper, N. R., Eikelenboom, P., Emmerling, M., Fiebich, B. L., Finch, C. E., Frautschy, S., Griffin, W. S., Hampel, H., Hull, M., Landreth, G., Lue, L., Mrak, R., Mackenzie, I. R., McGeer, P. L., O’Banion, M. K., Pachter, J., Pasinetti, G., Plata-Salaman, C., Rogers, J., Rydel, R., Shen, Y., Streit, W., Strohmeyer, R., Tooyoma, I., Van Muiswinkel, F. L., Veerhuis, R., Walker, D., Webster, S., Wegrzyniak, B., Wenk, G., and Wyss-Coray, T. (2000). Inflammation and Alzheimer’s disease. Neurobiol. Aging, 21, 383–421. Allan, S. M., Parker, L. C., Collins, B., Davies, R., Luheshi, G. N., and Rothwell, N. J. (2000). Cortical cell death induced by IL-1 is mediated via actions in the hypothalamus of the rat. Proc. Natl. Acad. Sci. U.S.A., 97, 5580–5585. Allan, S. M., and Rothwell, N. J. (2003). Inflammation in central nervous system injury. Philos. Trans. R. Soc. Lond. B Biol. Sci., 358, 1669–1677. Allan, S. M., Tyrrell, P. J., and Rothwell, N. J. (2005). Interleukin-1 and neuronal injury. Nat. Rev. Immunol., 5, 629–640. Aloisi, F. (2001). Immune function of microglia. Glia., 36, 165–179. Andersson, P. B., Perry, V. H., and Gordon, S. (1992). Intracerebral injection of proinflammatory cytokines or leukocyte chemotaxins induces minimal myelomonocytic cell recruitment to the parenchyma of the central nervous system. J. Exp. Med., 176, 255–259. Anthony, D. C., Bolton, S. J., Fearn, S., and Perry, V. H. (1997). Agerelated effects of interleukin-1 beta on polymorphonuclear neutrophil-dependent increases in blood-brain barrier permeability in rats. Brain, 120 (Pt 3), 435–444. Bajetto, A., Bonavia, R., Barbero, S., Florio, T., and Schettini, G. (2001). Chemokines and their receptors in the central nervous system. Front. Neuroendocrinol., 22, 147–184. Banati, R. B., Newcombe, J., Gunn, R. N., Cagnin, A., Turkheimer, F., Heppner, F., Price, G., Wegner, F., Giovannoni, G., Miller, D. H., Perkin, G. D., Smith, T., Hewson, A. K., Bydder, G., Kreutzberg, G. W., Jones, T., Cuzner, M. L., and Myers, R. (2000). The peripheral benzodiazepine binding site in the brain in multiple sclerosis: quantitative in vivo imaging of microglia as a measure of disease activity. Brain, 123 (Pt 11), 2321–2337. Beard, C. M., Kokmen, E., Sigler, C., Smith, G. E., Petterson, T., and O’Brien, P. C. (1996). Cause of death in Alzheimer’s disease. Ann. Epidemiol., 6, 195–200. Betmouni, S., Perry, V. H., and Gordon, J. L. (1996). Evidence for an early inflammatory response in the central nervous system of mice with scrapie. Neuroscience, 74, 1–5. Beutler, B. (2002). TLR4 as the mammalian endotoxin sensor. Curr. Top. Microbiol. Immunol., 270, 109–120. Boutin, H., LeFeuvre, R. A., Horai, R., Asano, M., Iwakura, Y., and Rothwell, N. J. (2001). Role of IL-1alpha and IL-1beta in ischemic brain damage. J. Neurosci., 21, 5528–5534. Breder, C. D., Hazuka, C., Ghayur, T., Klug, C., Huginin, M., Yasuda, K., Teng, M., and Saper, C. B. (1994). Regional induction of tumor necrosis factor alpha expression in the mouse brain after systemic lipopolysaccharide administration. Proc. Natl. Acad. Sci. U.S.A., 91, 11393–11397.
445
Brocke, S., Gaur, A., Piercy, C., Gautam, A., Gijbels, K., Fathman, C. G., and Steinman, L. (1993). Induction of relapsing paralysis in experimental autoimmune encephalomyelitis by bacterial superantigen. Nature, 365, 642–644. Broom, K. A., Anthony, D. C., Blamire, A. M., Waters, S., Styles, P., Perry, V. H., and Sibson, N. R. (2005). MRI reveals that early changes in cerebral blood volume precede blood-brain barrier breakdown and overt pathology in MS-like lesions in rat brain. J. Cereb. Blood Flow Metab., 25, 204–216. Bruce, M. E., McConnell, I., Fraser, H., and Dickinson, A. G. (1991). The disease characteristics of different strains of scrapie in Sinc congenic mouse lines: implications for the nature of the agent and host control of pathogenesis. J. Gen. Virol., 72 (Pt 3), 595–603. Buljevac, D., Flach, H. Z., Hop, W. C., Hijdra, D., Laman, J. D., Savelkoul, H. F., van Der Meche, F. G., van Doorn, P. A., and Hintzen, R. Q. (2002). Prospective study on the relationship between infections and multiple sclerosis exacerbations. Brain, 125, 952–960. Campbell, S. J., Hughes, P. M., Iredale, J. P., Wilcockson, D. C., Waters, S., Docagne, F., Perry, V. H., and Anthony, D. C. (2003). CINC-1 is an acute-phase protein induced by focal brain injury causing leukocyte mobilization and liver injury. FASEB J., 17, 1168–1170. Campbell, S. J., Perry, V. H., Pitossi, F. J., Butchart, A. G., Chertoff, M., Waters, S., Dempster, R., and Anthony, D. C. (2005). Central nervous system injury triggers hepatic CC and CXC chemokine expression that is associated with leukocyte mobilization and recruitment to both the central nervous system and the liver. Am. J. Pathol., 166, 1487–1497. Cho, C., and Miller, R. J. (2002). Chemokine receptors and neural function. J. Neurovirol., 8, 573–584. Combrinck, M. I., Perry, V. H., and Cunningham, C. (2002). Peripheral infection evokes exaggerated sickness behaviour in preclinical murine prion disease. Neuroscience, 112, 7–11. Compston, A., and Coles, A. (2002). Multiple sclerosis. Lancet, 359, 1221–1231. Crisi, G. M., Santambrogio, L., Hochwald, G. M., Smith, S. R., Carlino, J. A., and Thorbecke, G. J. (1995). Staphylococcal enterotoxin B and tumor-necrosis factor-alpha–induced relapses of experimental allergic encephalomyelitis: protection by transforming growth factor-beta and interleukin-10. Eur. J. Immunol., 25, 3035–3040. Cunningham, C. (2005a). Mouse behavioural studies and what they can teach us about prion diseases. In D. R. Brown (Ed.), Neurodegeneration and prion disease (pp. 111–137). New York: Springer. Cunningham, C., Boche, D., and Perry, V. H. (2002). Transforming growth factor beta1, the dominant cytokine in murine prion disease: influence on inflammatory cytokine synthesis and alteration of vascular extracellular matrix. Neuropathol. Appl. Neurobiol., 28, 107–119. Cunningham, C., Deacon, R., Wells, H., Boche, D., Waters, S., Diniz, C. P., Scott, H., Rawlins, J. N., and Perry, V. H. (2003). Synaptic changes characterize early behavioural signs in the ME7 model of murine prion disease. Eur. J. Neurosci., 17, 2147–2155. Cunningham, C., Deacon, R. M., Chan, K., Boche, D., Rawlins, J. N., and Perry, V. H. (2005b). Neuropathologically distinct prion strains give rise to similar temporal profiles of behavioral deficits. Neurobiol. Dis., 18, 258–269. Cunningham, C., Wilcockson, D. C., Boche, D., and Perry, V. H. (2005c). Comparison of inflammatory and acute-phase responses in the brain and peripheral organs of the ME7 model of prion disease. J. Virol., 79, 5174–5184. Cunningham, C., Wilcockson, D. C., Campion, S., Lunnon, K., Perry, V. H. (2005). Central and systemic endotoxin challenges exacerbate the local inflammatory response and increase neuronal
446
II. Immune System Effects on Neural and Endocrine Processes and Behavior
death during chronic neurodegeneration. J. Neurosci., 25, 9275–9284. Danton, G. H., and Dietrich, W. D. (2003). Inflammatory mechanisms after ischemia and stroke. J. Neuropathol. Exp. Neurol., 62, 127–136. Dantzer, R., Aubert, A., Bluthe, R. M., Gheusi, G., Cremona, S., Laye, S., Konsman, J. P., Parnet, P., and Kelley, K. W. (1999). Mechanisms of the behavioural effects of cytokines. Adv. Exp. Med. Biol., 461, 83–105. Dantzer, R., Bluthe, R. M., Gheusi, G., Cremona, S., Laye, S., Parnet, P., and Kelley, K. W. (1998). Molecular basis of sickness behavior. Ann. N. Y. Acad. Sci., 856, 132–138. Dantzer, R., Konsman, J. P., Bluthe, R. M., and Kelley, K. W. (2000). Neural and humoral pathways of communication from the immune system to the brain: parallel or convergent? Auton. Neurosci., 85, 60–65. Dantzer, R., and Wollman, E. (1998). Molecular mechanisms of fever: the missing links. Eur. Cytokine Netw., 9, 27–31. De Simoni, M. G., Del Bo, R., De Luigi, A., Simard, S., and Forloni, G. (1995). Central endotoxin induces different patterns of interleukin (IL)-1 beta and IL-6 messenger ribonucleic acid expression and IL-6 secretion in the brain and periphery. Endocrinology, 136, 897–902. De Simoni, M. G., Sironi, M., De Luigi, A., Manfridi, A., Mantovani, A., and Ghezzi, P. (1990). Intracerebroventricular injection of interleukin 1 induces high circulating levels of interleukin 6. J. Exp. Med., 171, 1773–1778. Di Santo, E., Benigni, F., Agnello, D., Sipe, J. D., and Ghezzi, P. (1999). Peripheral effects of centrally administered interleukin1beta in mice in relation to its clearance from the brain into the blood and tissue distribution. Neuroimmunomodulation, 6, 300–304. Dirnagl, U., Iadecola, C., and Moskowitz, M. A. (1999). Pathobiology of ischaemic stroke: an integrated view. Trends Neurosci., 22, 391–397. Dunn, N., Mullee, M., Perry, V. H., and Holmes, C. (2005). Association between dementia and infectious disease: evidence from a case-control study. Alzheimer Dis. Assoc. Disord., 19, 91–94. Edwards, S., Zvartau, M., Clarke, H., Irving, W., and Blumhardt, L. D. (1998). Clinical relapses and disease activity on magnetic resonance imaging associated with viral upper respiratory tract infections in multiple sclerosis. J. Neurol. Neurosurg. Psychiatry, 64, 736–741. Elkayam, O., Yaron, M., and Caspi, D. (2002). Safety and efficacy of vaccination against hepatitis B in patients with rheumatoid arthritis. Ann. Rheum. Dis., 61, 623–625. Elmquist, J. K., Breder, C. D., Sherin, J. E., Scammell, T. E., Hickey, W. F., Dewitt, D., and Saper, C. B. (1997). Intravenous lipopolysaccharide induces cyclooxygenase 2–like immunoreactivity in rat brain perivascular microglia and meningeal macrophages. J. Comp. Neurol., 381, 119–129. Emsley, H. C., Smith, C. J., Gavin, C. M., Georgiou, R. F., Vail, A., Barberan, E. M., Hallenbeck, J. M., del Zoppo, G. J., Rothwell, N. J., Tyrrell, P. J., and Hopkins, S. J. (2003). An early and sustained peripheral inflammatory response in acute ischaemic stroke: relationships with infection and atherosclerosis. J. Neuroimmunol., 139, 93–101. Fabriek, B. O., Van Haastert, E. S., Galea, I., Polfliet, M. M., Dopp, E. D., Van Den Heuvel, M. M., Van Den Berg, T. K., De Groot, C. J., Van Der Valk, P., and Dijkstra, C. D. (2005). CD163–positive perivascular macrophages in the human CNS express molecules for antigen recognition and presentation. Glia., 51, 297–305. Fadok, V. A., Bratton, D. L., Konowal, A., Freed, P. W., Westcott, J. Y., and Henson, P. M. (1998). Macrophages that have ingested
apoptotic cells in vitro inhibit proinflammatory cytokine production through autocrine/paracrine mechanisms involving TGFbeta, PGE2, and PAF. J. Clin. Invest., 101, 890–898. Felton, L. M., Cunningham, C., Rankine, E. L., Waters, S., Boche, D., and Perry, V. H. (2005). MCP-1 and murine prion disease: separation of early behavioural dysfunction from overt clinical disease. Neurobiol. Dis., 20, 283–295. Felzien, L. K., McDonald, J. T., Gleason, S. M., Berman, N. E., and Klein, R. M. (2001). Increased chemokine gene expression during aging in the murine brain. Brain Res., 890, 137–146. Ferguson, B., Matyszak, M. K., Esiri, M. M., and Perry, V. H. (1997). Axonal damage in acute multiple sclerosis lesions. Brain, 120 (Pt 3), 393–399. Ferrari, C. C., Depino, A. M., Prada, F., Muraro, N., Campbell, S., Podhajcer, O., Perry, V. H., Anthony, D. C., and Pitossi, F. J. (2004). Reversible demyelination, blood-brain barrier breakdown, and pronounced neutrophil recruitment induced by chronic IL-1 expression in the brain. Am. J. Pathol., 165, 1827–1837. Garabedian, B. V., Lemaigre-Dubreuil, Y., and Mariani, J. (2000). Central origin of IL-1beta produced during peripheral inflammation: role of meninges. Brain Res. Mol. Brain Res., 75, 259–263. Gatti, S., and Bartfai, T. (1993). Induction of tumor necrosis factoralpha mRNA in the brain after peripheral endotoxin treatment: comparison with interleukin-1 family and interleukin-6. Brain Res., 624, 291–294. Godbout, J. P., Chen, J., Abraham, J., Richwine, A. F., Berg, B. M., Kelley, K. W., and Johnson, R. W. (2005). Exaggerated neuroinflammation and sickness behavior in aged mice after activation of the peripheral innate immune system. FASEB J., 19, 1329–1331. Guenther, K., Deacon, R. M., Perry, V. H., and Rawlins, J. N. (2001). Early behavioural changes in scrapie-affected mice and the influence of dapsone. Eur. J. Neurosci., 14, 401–409. Hacham, M., Argov, S., White, R. M., Segal, S., and Apte, R. N. (2002). Different patterns of interleukin-1alpha and interleukin1beta expression in organs of normal young and old mice. Eur. Cytokine Netw., 13, 55–65. Hajjar, A. M., Ernst, R. K., Tsai, J. H., Wilson, C. B., and Miller, S. I. (2002). Human toll-like receptor 4 recognizes host-specific LPS modifications. Nat. Immunol., 3, 354–359. Hart, B. L. (1988). Biological basis of the behavior of sick animals. Neurosci. Biobehav. Rev., 12, 123–137. Holmes, C., El-Okl, M., Williams, A. L., Cunningham, C., Wilcockson, D., and Perry, V. H. (2003). Systemic infection, interleukin 1beta, and cognitive decline in Alzheimer’s disease. J. Neurol. Neurosurg. Psychiatry, 74, 788–789. Hughes, P. M., Allegrini, P. R., Rudin, M., Perry, V. H., Mir, A. K., and Wiessner, C. (2002). Monocyte chemoattractant protein-1 deficiency is protective in a murine stroke model. J. Cereb. Blood Flow Metab., 22, 308–317. Hughes, P. M., Anthony, D. C., Ruddin, M., Botham, M. S., Rankine, E. L., Sablone, M., Baumann, D., Mir, A. K., and Perry, V. H. (2003). Focal lesions in the rat central nervous system induced by endothelin-1. J. Neuropathol. Exp. Neurol., 62, 1276–1286. Jeffery, D. R. (2000). Relationship between disease activity and doseresponse relationships with beta interferon therapies in the treatment of multiple sclerosis. J. Neurol. Sci., 178, 2–9. Jeffrey, M., Halliday, W. G., Bell, J., Johnston, A. R., MacLeod, N. K., Ingham, C., Sayers, A. R., Brown, D. A., and Fraser, J. R. (2000). Synapse loss associated with abnormal PrP precedes neuronal degeneration in the scrapie-infected murine hippocampus. Neuropathol. Appl. Neurobiol., 26, 41–54.
20. The Interaction between Brain Inflammation and Systemic Infection Kalehua, A. N., Nagel, J. E., Whelchel, L. M., Gides, J. J., Pyle, R. S., Smith, R. J., Kusiak, J. W., and Taub, D. D. (2004). Monocyte chemoattractant protein-1 and macrophage inflammatory protein-2 are involved in both excitotoxin-induced neurodegeneration and regeneration. Exp. Cell Res., 297, 197–211. Kivisakk, P., Trebst, C., Eckstein, D. J., Kerza-Kwiatecki, A. P., and Ransohoff, R. M. (2001). Chemokine-based therapies for MS: how do we get there from here? Trends Immunol., 22, 591–593. Konsman, J. P., Parnet, P., and Dantzer, R. (2002). Cytokine-induced sickness behaviour: mechanisms and implications. Trends Neurosci., 25, 154–159. Kreutzberg, G. W. (1996). Microglia: a sensor for pathological events in the CNS. Trends Neurosci., 19, 312–318. La, M., Tailor, A., D’Amico, M., Flower, R. J., and Perretti, M. (2001). Analysis of the protection afforded by annexin 1 in ischaemiareperfusion injury: focus on neutrophil recruitment. Eur. J. Pharmacol., 429, 263–278. Lacroix, S., and Rivest, S. (1998). Effect of acute systemic inflammatory response and cytokines on the transcription of the genes encoding cyclooxygenase enzymes (COX-1 and COX-2) in the rat brain. J. Neurochem., 70, 452–466. Laye, S., Parnet, P., Goujon, E., and Dantzer, R. (1994). Peripheral administration of lipopolysaccharide induces the expression of cytokine transcripts in the brain and pituitary of mice. Brain Res. Mol. Brain Res., 27, 157–162. Loddick, S. A., Turnbull, A. V., and Rothwell, N. J. (1998). Cerebral interleukin-6 is neuroprotective during permanent focal cerebral ischemia in the rat. J. Cereb. Blood Flow Metab., 18, 176–179. Mabbott, N. A., Williams, A., Farquhar, C. F., Pasparakis, M., Kollias, G., and Bruce, M. E. (2000). Tumor necrosis factor alphadeficient, but not interleukin-6–deficient, mice resist peripheral infection with scrapie. J. Virol., 74, 3338–3344. Matsuo, Y., Kihara, T., Ikeda, M., Ninomiya, M., Onodera, H., and Kogure, K. (1995). Role of neutrophils in radical production during ischemia and reperfusion of the rat brain: effect of neutrophil depletion on extracellular ascorbyl radical formation. J. Cereb. Blood Flow Metab., 15, 941–947. Matsuo, Y., Onodera, H., Shiga, Y., Nakamura, M., Ninomiya, M., Kihara, T., and Kogure, K. (1994). Correlation between myeloperoxidase-quantified neutrophil accumulation and ischemic brain injury in the rat. Effects of neutrophil depletion. Stroke, 25, 1469–1475. Matyszak, M. K., Perry, V. H. (1995). Demyelination in the central nervous system following a delayed-type hypersensitivity response to bacillus Calmette-Guerin. Neuroscience, 64, 967–977. McDonald, P. P., Fadok, V. A., Bratton, D., and Henson, P. M. (1999). Transcriptional and translational regulation of inflammatory mediator production by endogenous TGF-beta in macrophages that have ingested apoptotic cells. J. Immunol., 163, 6164–6172. McGeer, P. L., and Rogers, J. (1992). Anti-inflammatory agents as a therapeutic approach to Alzheimer’s disease. Neurology, 42, 447–449. McGeer, P. L., Schulzer, M., and McGeer, E. G. (1996). Arthritis and anti-inflammatory agents as possible protective factors for Alzheimer’s disease: a review of 17 epidemiologic studies. Neurology, 47, 425–432. Minghetti, L., Greco, A., Cardone, F., Puopolo, M., Ladogana, A., Almonti, S., Cunningham, C., Perry, V. H., Pocchiari, M., and Levi, G. (2000). Increased brain synthesis of prostaglandin E2 and F2-isoprostane in human and experimental transmissible spongiform encephalopathies. J. Neuropathol. Exp. Neurol., 59, 866–871.
447
Moser, B., and Willimann, K. (2004). Chemokines: role in inflammation and immune surveillance. Ann Rheum Dis, 63 (Suppl 2), ii84–ii89. Muramami, N., Fukata, J., Tsukada, T., Kobayashi, H., Ebisui, O., Segawa, H., Muro, S., Imura, H., and Nakao, K. (1993). Bacterial lipopolysaccharide-induced expression of interleukin-6 messenger ribonucleic acid in the rat hypothalamus, pituitary, adrenal gland, and spleen. Endocrinology, 133, 2574–2578. Newman, T. A., Woolley, S. T., Hughes, P. M., Sibson, N. R., Anthony, D. C., and Perry, V. H. (2001). T-cell- and macrophage-mediated axon damage in the absence of a CNSspecific immune response: involvement of metalloproteinases. Brain, 124, 2203–2214. Nguyen, M. D., D’Aigle, T., Gowing, G., Julien, J. P., and Rivest, S. (2004). Exacerbation of motor neuron disease by chronic stimulation of innate immunity in a mouse model of amyotrophic lateral sclerosis. J. Neurosci., 24, 1340–1349. Panitch, H. S. (1994). Influence of infection on exacerbations of multiple sclerosis. Ann Neurol, 36 (Suppl), S25–S28. Pavlov, V. A., and Tracey, K. J. (2005). The cholinergic antiinflammatory pathway. Brain Behav. Immun., 19, 493–499. Perry, V. H., Anthony, D. C., Bolton, S. J., and Brown, H. C. (1997). The blood-brain barrier and the inflammatory response. Mol. Med. Today, 3, 335–341. Perry, V. H., Cunningham, C., and Boche, D. (2002). Atypical inflammation in the central nervous system in prion disease. Curr. Opin. Neurol., 15, 349–354. Perry, V. H., Matyszak, M. K., and Fearn, S. (1993). Altered antigen expression of microglia in the aged rodent CNS. Glia., 7, 60–67. Perry, V. H., Newman, T. A., and Cunningham, C. (2003). The impact of systemic infection on the progression of neurodegenerative disease. Nat. Rev. Neurosci., 4, 103–112. Polfliet, M. M., Zwijnenburg, P. J., van Furth, A. M., van der Poll, T., Dopp, E. A., Renardel de Lavalette, C., van KesterenHendrikx, E. M., van Rooijen, N., Dijkstra, C. D., and van den Berg, T. K. (2001). Meningeal and perivascular macrophages of the central nervous system play a protective role during bacterial meningitis. J. Immunol., 167, 4644–4650. Prat, A., Biernacki, K., Lavoie, J. F., Poirier, J., Duquette, P., and Antel, J. P. (2002). Migration of multiple sclerosis lymphocytes through brain endothelium. Arch. Neurol., 59, 391–397. Prusiner, S. B. (1982). Novel proteinaceous infectious particles cause scrapie. Science, 216, 136–144. Relton, J. K., and Rothwell, N. J. (1992). Interleukin-1 receptor antagonist inhibits ischaemic and excitotoxic neuronal damage in the rat. Brain Res. Bull, 29, 243–246. Rivest, S. (2003). Molecular insights on the cerebral innate immune system. Brain Behav. Immun., 17, 13–19. Rivest, S., Lacroix, S., Vallieres, L., Nadeau, S., Zhang, J., and Laflamme, N. (2000). How the blood talks to the brain parenchyma and the paraventricular nucleus of the hypothalamus during systemic inflammatory and infectious stimuli. Proc. Soc. Exp. Biol. Med., 223, 22–38. Rot, A., and von Andrian, U. H. (2004). Chemokines in innate and adaptive host defense: basic chemokinese grammar for immune cells. Annu. Rev. Immunol., 22, 891–928. Rothwell, N. J., and Luheshi, G. N. (2000). Interleukin 1 in the brain: biology, pathology and therapeutic target. Trends Neurosci., 23, 618–625. Schiffenbauer, J., Johnson, H. M., Butfiloski, E. J., Wegrzyn, L., and Soos, J. M. (1993). Staphylococcal enterotoxins can reactivate experimental allergic encephalomyelitis. Proc. Natl. Acad. Sci. U.S.A., 90, 8543–8546.
448
II. Immune System Effects on Neural and Endocrine Processes and Behavior
Schiltz, J. C., and Sawchenko, P. E. (2002). Distinct brain vascular cell types manifest inducible cyclooxygenase expression as a function of the strength and nature of immune insults. J. Neurosci., 22, 5606–5618. Schiltz, J. C., and Sawchenko, P. E. (2003). Signaling the brain in systemic inflammation: the role of perivascular cells. Front. Biosci., 8, s1321–1329. Sheng, J. G., Mrak, R. E., and Griffin, W. S. (1998). Enlarged and phagocytic, but not primed, interleukin-1 alpha-immunoreactive microglia increase with age in normal human brain. Acta Neuropathol. (Berl), 95, 229–234. Sibley, W. A., Bamford, C. R., and Clark, K. (1985). Clinical viral infections and multiple sclerosis. Lancet, 1, 1313–1315. Sly, L. M., Krzesicki, R. F., Brashler, J. R., Buhl, A. E., McKinley, D. D., Carter, D. B., and Chin, J. E. (2001). Endogenous brain cytokine mRNA and inflammatory responses to lipopolysaccharide are elevated in the Tg2576 transgenic mouse model of Alzheimer’s disease. Brain Res. Bull., 56, 581–588. Smith, C. J., Emsley, H. C., Gavin, C. M., Georgiou, R. F., Vail, A., Barberan, E. M., del Zoppo, G. J., Hallenbeck, J. M., Rothwell, N. J., Hopkins, S. J., and Tyrrell, P. J. (2004). Peak plasma interleukin-6 and other peripheral markers of inflammation in the first week of ischaemic stroke correlate with brain infarct volume, stroke severity and long-term outcome. BMC Neurol., 4, 2. Streetz, K. L., Wustefeld, T., Klein, C., Manns, M. P., and Trautwein, C. (2001). Mediators of inflammation and acute phase response in the liver. Cell. Mol. Biol. (Noisy-le-grand), 47, 661–673. Szatkowski, M., and Attwell, D. (1994). Triggering and execution of neuronal death in brain ischaemia: two phases of glutamate release by different mechanisms. Trends Neurosci., 17, 359–365. t’ Veld, B. A., Ruitenberg, A., Hofman, A., Launer, L. J., van Duijn, C. M., Stijnen, T., Breteler, M. M., and Stricker, B. H. (2001). Nonsteroidal antiinflammatory drugs and the risk of Alzheimer’s disease. N. Engl. J. Med., 345, 1515–1521.
Tracey, K. J. (2002). The inflammatory reflex. Nature, 420, 853–859. Trapp, B. D., Peterson, J., Ransohoff, R. M., Rudick, R., Mork, S., and Bo, L. (1998). Axonal transection in the lesions of multiple sclerosis. N. Engl. J. Med., 338, 278–285. van Dam, A. M., Brouns, M., Louisse, S., and Berkenbosch, F. (1992). Appearance of interleukin-1 in macrophages and in ramified microglia in the brain of endotoxin-treated rats: a pathway for the induction of non-specific symptoms of sickness? Brain Res., 588, 291–296. van Rooijen, N., Sanders, A., and van den Berg, T. K. (1996). Apoptosis of macrophages induced by liposome-mediated intracellular delivery of clodronate and propamidine. J. Immunol. Methods, 193, 93–99. Walsh, D. T., Betmouni, S., and Perry, V. H. (2001). Absence of detectable IL-1beta production in murine prion disease: a model of chronic neurodegeneration. J. Neuropathol. Exp. Neurol., 60, 173–182. Walsh, D. T., Perry, V. H., and Minghetti, L. (2000). Cyclooxygenase2 is highly expressed in microglial-like cells in a murine model of prion disease. Glia, 29, 392–396. Wilcockson, D. C., Campbell, S. J., Anthony, D. C., and Perry, V. H. (2002). The systemic and local acute phase response following acute brain injury. J. Cereb. Blood Flow Metab., 22, 318–326. Williams, A. E., Lawson, L. J., Perry, V. H., and Fraser, H. (1994). Characterization of the microglial response in murine scrapie. Neuropathol. Appl. Neurobiol., 20, 47–55. Yang, Y. X., and Lichtenstein, G. R. (2002). Corticosteroids in Crohn’s disease. Am. J. Gastroenterol., 97, 803–823. Zhang, J., and Rivest, S. (2001). Anti-inflammatory effects of prostaglandin E2 in the central nervous system in response to brain injury and circulating lipopolysaccharide. J. Neurochem., 76, 855–864.
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III BEHAVIOR AND IMMUNITY MICHAEL R. IRWIN, LOS ANGELES, CA
INTRODUCTION Recent years have seen increasing public health attention to the contribution of psychosocial factors, behaviors, and behavioral disorders to chronic disease and health. In two separate reports from the Institute of Medicine, Health and Behavior (Institute of Medicine, 1982) and Health and Behavior (Institute of Medicine, 2001), a range of research aimed at understanding the interplay among biological, behavioral, and social factors in health and disease was identified and integrated. Indeed, this broad psychosomatic research has shown many reciprocal links among the central nervous system, which recognizes and records experiences; the endocrine system, which produces hormones that govern many bodily functions; and the immune system, which organizes responses to infections and other challenges. Similarly, it is recognized that specific behaviors are associated with increased risk of specific diseases and related conditions, which has led to an increasing acceptance of the fact that depression, for example, is linked to cardiovascular disease and to other health problems (Irwin, 2002). Recent research not only documents the importance of these behavioral factors, but also reveals some of the mechanisms involved. In other words, psychosocial factors influence health directly through biological mechanisms and indirectly through an array of behaviors. This Part addresses the myriad ways that behaviors and health are inter-related with an emphasis on the immunological mechanisms that underlie these interactions. As such, this series of chapters presents current knowledge about the influence of behaviors and behavioral disorders on the immune system, and about the impact of interventions on immune mechanisms with potential attendant improvements on health through modifying behaviors, emotions, or social relationships.
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The immune system is highly integrated with other physiological systems. It is sensitive to virtually every hormone, and sympathetic, parasympathetic, and sensory nerves innervate the organs of the immune system. In turn, the nervous, endocrine, and immune systems communicate bi-directionally through common hormones, neuropeptides, and cytokines. Hence, one conceptual theme for this collection of chapters is that behavioral responses are key in the activation of neuroendocrine and autonomic pathways, which in turn modulate the immune system with implications for increasing susceptibility to a variety of diseases. The importance of individual variability in disease susceptibility and health has been previously recognized (Ader, 2005), and this theme is similarly emphasized throughout this Part. People show large differences in resilience to and recovery from illness. Differences in behavioral responses are thought to mediate resilience, the ability to recover from adversity, by altering cellular processes that protect and build cells and tissues. A critical question raised by this research is whether positive emotions or behavioral interventions that target emotional processes or biological mechanisms including immunity might drive reserve capacity or resistance to the damaging effects of stressors on health. The generation of individual behaviors that influence morbidity and mortality occurs within a frame of development. Cumulative experience, adaptive plasticity, physical and social exchange with surrounding environments, and genetic predisposition interact to influence development and the biological and behavioral processes that preserve health or lead to human disease throughout life. Whereas developmental status is a continuing factor in health outcomes over life, in Chapter 21, Coe and Lubach aptly focus on the challenges faced during early infant development, given the heightened salience of this period for immediate and long-term health responses. These critical times of development from conception to weaning encompass extremely rapid biological and psychosocial changes, which have the potential to determine set points for homeostatic systems and the trajectories for subsequent biobehavioral functioning that can have long-term effects on health. For example, the handling of neonatal rats by experimenters leads to reduced emotionality and stress hormone reactivity throughout life, whereas prenatal stress increases emotionality and stress hormone reactivity throughout the life of the animal. Individuals develop and live in social systems, in which people influence and are influenced by their social networks. A full understanding of the interactions between health and behavior requires consideration of the separate levels of social interactions and the interplay among them. As articulated by Laudenslager and Kennedy in Chapter 22, social organization of many mammalian species creates dominance hierarchies, which alter behavioral responses, neuroendocrine activation, and immunity. Importantly, relational strengths among humans, such as positive ties with parents during childhood or intimate ties with a spouse during adulthood, can mitigate the negative consequences of social and environmental challenges. Most behaviors are not randomly distributed in the population, but are socially patterned and often occur together. Lower mortality, morbidity, and disability among
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socioeconomically advantaged people have been observed for hundreds of years, using various indicators of socioeconomic status and multiple disease outcomes. In Chapter 23, Chen and Miller provide a solid body of evidence that social integration, the quality of social ties, and extent of social support are critical in influencing disease processes and mortality, possibly via the cumulative effects of socioeconomic status on immune mechanisms relevant to inflammatory disorders. Behavioral disorders that encompass a constellation of abnormal behavioral processes along with changes in psychosocial factors and biological mechanisms yield some of the most compelling support for the contributions of behavior to health. Major depressive disorder, which exceeds a lifetime incidence of 10%, is a potent risk factor for disease morbidity, with depressed persons showing a mortality rate twice that found in non-depressed persons. As discussed by Capuron, Miller, and Irwin in Chapter 24, altered functioning of the immune system is implicated as a mechanism that might contribute to medical morbidity of major depressive disorder including risk of infectious disease as well as inflammatory disorders. Moreover, much evidence has shown that anxiety and depressive disorders are often a frequent mental health outcome of traumatic stress exposure, and it is also reasonable to ask whether the persistent behavioral sequelae of severe stress, as found with post-traumatic stress disorder (PTSD), contributes toward similar biologic dysregulation. The composite alterations of immune function, as found in major depression, PTSD, and chronic stress (as reviewed in Part II), are striking, which together raise the possibility of a single, common adaptive response among brain, behavior, and immunity. Less clear is whether these immunological effects are of clinical significance. Longitudinal research strategies that target vulnerable “at risk” populations and utilize immune biomarkers that are biologically relevant to specific disease processes need to be exploited in order to investigate the degree to which behavioral disorders influence the expression or progression of disease. Communication between the brain and the immune system does not flow only from the brain to the immune system, but also from the innate immune system to the brain. As discussed elsewhere in this book, immune-to-brain communication pathways induce a cascade of cellular and molecular events in the central nervous system, which have behavioral consequences. Capuron, Miller, and Irwin also discuss brain effects of proinflammatory cytokines due to the activation of the innate immune system that prevails in depressed subjects, and whether these mechanisms lead not only to functional changes in the brain but also to structural alterations. In addition, an exceedingly relevant extension of this hypothesis concerns the involvement of immunological and immunopathological mechanisms in the etiopathogenesis of schizophrenia. As reviewed by Rothermundt and Arolt in Chapter 27, three hypotheses are being critically examined—namely, the infectious hypothesis, autoimmune hypothesis, and the Th1/Th2 imbalance hypothesis. Future research directions are discussed to carry forward evidence that schizophrenia is associated with abnormalities in microglia, astroglia, antibodies against brain structures and neurotropic viruses, blood-brain barrier, humoral immunity, cellular immunity, and cytokines.
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Alterations in other behaviors such as increases in alcohol consumption, poor sleep, and inadequate physical activity frequently co-occur with behavioral disorders including depression and PTSD; and each of these adverse behaviors has been recognized as unhealthful. Indeed, excessive alcohol consumption, other substance abuse, unhealthy dietary habits, and sedentary lifestyles are among the most health-compromising behaviors identified and targeted for modification or prevention with consequent benefit to the public health. Further chapters in this Part focus on the influence of these behaviors on immune system responses. Alcohol abuse is one of the top contributors to death in the United States, after tobacco use and diet and activity patterns. Approximately 100,000 deaths are related to alcohol consumption in the United States each year, which translates into 15% of potential years of life lost before the age of 65. The relationship between mortality, alcohol-induced illnesses, and alcohol consumption is primarily attributable to differences in the amount, duration, and patterns of alcohol consumption, as well as to differences in genetic vulnerability to particular alcohol-related consequences. In Chapter 26, by Schleifer, there is focus on the consequences of alcohol on the immune system at the upper end of a U-shaped relationship, with much evidence indicating that the alcohol alters immunity in part by its effects on neuroendocrine and autonomic pathways and on behaviors including the induction of poor sleep. In 2004, the National Sleep Foundation in the United Stated specifically promoted the importance of sleep for good health, an emphasis that is well justified by the striking prevalence of sleep problems with about one quarter of the population of the United States reporting complaints of insomnia, as well as population-based data showing steady decreases in sleep amounts in the last century. Moreover, insomnia is increasingly implicated as a predictor of cardiovascular and other mortality, particularly in vulnerable older adults. Despite these robust epidemiologic data, little is known about the physiological consequences of poor sleep nor the reasons that sleep is necessary for maintenance of health. In Chapter 28, by Opp, Born, and Irwin, the bi-directional relationships between sleep and the immune system are examined. The action of the proinflammatory cytokine network on sleep and the consequences of sleep in the modulation of the immune system, particularly innate immunity, are discussed. The co-morbidity between insomnia and chronic inflammatory disorders illustrates an area that can be exploited to understand the reciprocal influence among inflammatory cytokines and sleep on disease progression. In Chapter 31, Nieman examines the role of physical activity on immunity. Only 11% of the United States adult population report regular, vigorous physical activity for 20 minutes or longer more than twice each week. The major decreases in physical activity over the last decade are thought to contribute to the explosion of obesity in the United Studies. Studies show that men and women who are physically active have, on the average, lower mortality than people who are inactive; in contrast, a sedentary lifestyle has been linked to 23% of deaths from major chronic diseases. However, physical activity does not need to be vigorous to be beneficial to health, and even small increases have been associated with measurable health benefits for people who are inactive.
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Against this backdrop, Nieman summarizes growing evidence that physical activity influences immune function and as a consequence, risk of certain types of infection including the most common of all, upper respiratory tract infections. However, emerging evidence also counters that prolonged and intensive exertion, in contrast to moderate physical activity, causes a downregulation of immunity, possibly by activation of stress response pathways. Variability in individual responses remains one of the common research themes linking behaviors and immunity (Ader, 2005), and the opportunities for research that exploits individual differences is further examined. In Chapter 29, Kemeny elegantly argues for a research strategy that is increasingly focused on psychological states and emotions that are posited to be the final links in brain regulation of physiological pathways and immune responses. Emotions, in contrast to longer-term affective states such as moods, are short, intensely felt, affects that are associated with distinctive facial expressions and behavioral predispositions. In other words, emotions serve to orchestrate the onset and coordination of a behavioral response to specific eliciting conditions (e.g., fear in response to threat of attack). Extensive research also documents that expression of emotions has beneficial effects on both emotional and physical well-being. Successful regulation of emotion appears to involve the controlled and modulated expression and release of feelings in ways that contribute to an increased understanding of those emotions and their meaning, which in turn can have immunologic consequences and even impacts on clinical outcomes of inflammatory disorders such as asthma and rheumatoid arthritis. As discussed by Kemeny, the specific mechanisms through which regulation of emotional expression affects immunity and possibly health are not fully understood and are the subject of continuing research. Nevertheless, the regulated expression of emotion is a potentially important component of interventions to change health. Behavior can be changed, and behavioral interventions can successfully teach new behaviors, alter behavioral response to stressors, and improve affective states (e.g., depressed mood). A critical challenge is to determine whether behavior changes can be maintained over time, and whether behavioral interventions can improve health outcomes and alter disease progression. Moreover, there are limited data on the influence of behavioral interventions on salient physiological pathways including immune responses, which may be relevant for infectious or inflammatory disease processes. Given this growing interest, the timely chapter by Antoni, Schneiderman, and Penedo (Chapter 32) provides insight into the empirical base demonstrating the influence of behavioral interventions on immune system functioning. Whereas relevant mechanisms have not been fully explored, it is thought that these approaches primarily act through proximal behavioral pathways in targeting emotional and affective responses with an emphasis on teaching new cognitive approaches to stress management. As a further extension and explicit test of the interplay between behavioral changes and the immune system, Pacheco-López, Niemi, Engler, and Schedlowski address whether immune response can be augmented by behavioral conditioning in Chapter 30. Building upon the seminal work by Ader and Cohen, this chapter provides a conceptual
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context for classical conditioning and presents empirical findings to demonstrate the adaptive capacity to associate specific stimuli (e.g., environmental cues) with certain immune responses. Given that both innate and adaptive immune responses can be enhanced by behavioral conditioning, potential clinical applications of this approach require investigation, with a focus on long duration efforts.
References Ader, R. (2005). Integrative summary. In K. Vedhara and R. IM (Eds.), Human psychoneuroimmunology (pp. 343–349). Oxford: Oxford University Press. Institute of Medicine. (1982). Health and behavior: frontiers of research in the biobehavioral sciences. Washington, D.C.: National Academy Press. Institute of Medicine. (2001). Health and behavior: the interplay of biological, behavioral, and societal influences. Washington, D.C.: National Academy Press. Irwin, M. (2002). Psychoneuroimmunology of depression: clinical implications (Presidential Address). Brain Behav., and Immun., 16, 1–16.
C H A P T E R
21 Mother-infant Interactions and the Development of Immunity from Conception through Weaning CHRISTOPHER L. COE AND GABRIELE R. LUBACH
I. INTRODUCTION 455 II. FETAL-INDUCED IMMUNE CHANGES IN THE MOTHER 457 III. PLACENTAL TRANSFER OF MATERNAL ANTIBODY TO THE FETUS 459 IV. ONTOGENY OF FETAL IMMUNITY 461 V. SOME IMPORTANT NUANCES OF IMMUNITY IN THE NEONATE 463 VI. SUSTAINED EFFECTS OF PRENATAL CONDITIONS ON LYMPHOCYTE FUNCTIONS 465 VII. INFLUENCES OF THE EARLY REARING ENVIRONMENT ON IMMUNITY 467 VIII. IMMUNE RESPONSES TO SOCIAL STRESSORS AND DISTURBANCE IN OLDER INFANTS 467 IX. CONCLUSIONS 469
processes are critically involved in the initiation and maintenance of pregnancy. Moreover, immune activation and disturbances of immune development are sometimes associated with cascading effects on brain and neuroendocrine physiology. As a consequence, the origins of health and immune-related disease can frequently be traced back to events that occurred in the womb and during early infancy.
I. INTRODUCTION Immune processes play a critical role in ensuring the survival and well-being of the developing baby. From the moment of implantation, the embryo must manipulate the mother’s immune responses to maintain the pregnancy. After birth the baby’s own immune responses then become essential for facilitating a successful adaptation to the rearing environment. Navigating this series of potentially treacherous hurdles requires a mixture of pre-programmed immune events, which appear to anticipate the baby’s needs, as well as some flexibility to accommodate unpredictable demands, including the variable level of pathogens in the postnatal world. It is the latter plasticity that is the subject of this chapter. Many studies have now documented that the developmental course followed by the immune system is not rigidly fixed in the immature host, but rather can be significantly affected by the antigens encountered by the young infant. In addition, the immune competence of the developing baby can
ABSTRACT The maturation of immunity in the developing infant highlights the complex interplay between intrinsic and external processes in shaping and regulating host defense. In addition to the programmed ontogeny of lymphoid tissue and cells, a capacity to adapt and learn from environmental priming is needed to provide optimal flexibility and resiliency. This malleability of immune responses during fetal life and infancy allows for a strong influence of pathogen exposure and early life events, including parental behavior. During development, the functions of leukocytes and cytokines also extend beyond protection against infection. Immune PSYCHONEUROIMMUNOLOGY, 4E VOLUME I
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be influenced by many other environmental and contextual factors. Exposure to environmental toxicants, maternal alcohol consumption, stress-related hormones, poor nutrition, and inadequate parental care have all been shown to influence the development of immune responses (Chandra, 1975; Weinberg and Jerrells, 1991; Wright et al., 2005). In a very real sense, the development of immunity in a young infant should be viewed as a malleable “learning” process, almost to the same degree as the developing brain. The basic building blocks of the immune system are set, such as the fact that a thymus will develop during the fetal stage. However, the amount and type of cellular activity are strongly influenced by the environmental priming, including the propensity toward a greater or lesser reliance on innate or adaptive immunity, and the set points at which the regulation of immune responses will become established in the mature host. For example, the resting number of B lymphocytes that will circulate in the healthy adult are strongly determined first by in utero processes and then affected further by the types of bacteria that are established in the gut (Cebra, 1999; Freitas and Rocha, 1993). Similarly, we have come to appreciate that early antigen exposure and infection can tilt the balance of immune processes toward or away from the development of allergies and asthma in the atropy-prone child (Warner et al., 2000). These findings are of importance for the field of psychoneuroimmunology (PNI) because they emphasize the significant influence of developmental and psychological processes on immunity (Ader, 1983). It is also of historical interest that a number of the pioneering findings in PNI were based on the observation that stressful events in infancy and disruptions of maternal care had a deleterious effect on later immune responses and resistance to disease (Ader and Friedman, 1965; Solomon et al., 1968). One challenge for the ongoing research today is to determine the full range of environmental events and stimuli that are salient enough to exert these longlasting effects on immunity. A second question of importance concerns the ways in which such persistent changes are mediated and sustained. In many cases, the immediate immune responses to the initiating event, such as a bacterial or viral infection during infancy, may have long subsided. Nevertheless, some lingering alterations remain because of changes that occurred in the infant’s developmental trajectory. Like a rocket on a new path, the altered course of maturation may extend and perhaps even magnify the consequences far beyond the initial responses. For example, injecting young mice and rats just once with endotoxin (lipopolysaccharide, LPS), or jolting it with a high dose
of a pro-inflammatory cytokine like interleukin-1 (IL-1), has been found to have life-long effects on the animal’s emotional reactivity, behavior, and adrenal responses to stress when tested in adulthood (Bilbo et al., 2005; Granger et al., 2001; Hodgson et al., 2001; Shanks et al., 1995). These concepts will be exemplified in this chapter mostly by reference to experiments conducted in our laboratory on the development of immune responses in young monkeys. However, the broader perspectives emanate from seminal papers on many other species, especially on rodents and domesticated farm animals, as well as from research on human infants (Kelley, 1980). The conclusions bear on our understanding of why some children grow up resilient and healthy, whereas others seem to succumb more readily to illness (Meyer and Haggerty, 1962). We have come to appreciate that the origins of cardiovascular and metabolic diseases can be traced back to the fetal period (Barker, 1994; Sayer et al., 1997). A similar viewpoint may also be appropriate for a number of immunerelated conditions, especially ones that involve inflammation like allergies and asthma (Devereux et al., 2001; Erb, 1999; Ferguson et al., 1997). The chapter begins with a brief review of immune processes required for implantation and the maintenance of pregnancy in the gravid female, which are essential to prevent rejection of the fetus. The next section provides a short summary of several formative immune events that occur during prenatal life, including the development of the thymus and the placental transfer of maternal antibody, critical for protecting the baby immediately at term. The rest of the chapter is devoted to a discussion of how events during the fetal and infant stages can elicit effects that continue to be evinced by the mature host. At least in animal models, including rats and nonhuman primates, many gestational stressors and perturbations of the rearing environment can exert a persistent influence on later immune responses (Klein and Rager, 1995). Investigations into the mediating processes often reveal that there were cascading effects that extend beyond immunity and involve parallel changes in both the brain and endocrine system. In many cases, animals that were disturbed during development also show alterations in hormones secreted by the hypothalamic-pituitaryadrenal (HPA) axis (Kay et al., 1998). Thus, understanding the basis for the immune sequelae of experimental manipulations in an immature animal often requires an analysis of multiple systems. Moreover, to say that one has an interest in learning about developmental PNI is analogous to stating a desire to delve more deeply into the numerous antecedents of health and the etiology of disease.
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II. FETAL-INDUCED IMMUNE CHANGES IN THE MOTHER Alterations in the immune biology of the gravid female become evident almost immediately after conception and must be sustained throughout pregnancy in order to allow the baby to reach term (Wegman et al., 1993). As illustrated in Figure 1, one of the embryo’s first tasks is to manipulate the intrinsic immunology of the uterine endometrium to promote engulfment of the implanting embryo and to prevent rejection. The invading edge of the trophoblasts that will become the mature placenta must actively inhibit certain types of maternal lymphocytes within the uterine tissue (e.g., the gamma/delta T-cells [γδ] and a CD56+ lymphocyte similar to a natural killer [NK] cell in blood) (Rai et al., 2005). This change is accomplished in part by activating uterine macrophages (Mφ) and CD8+ lymphocytes to constrain the other cells. The Mφ simultaneously stimulate the recruitment of maternal capillaries in order to provide a blood supply to the placenta, which they assist in sculpting (i.e., angiogenesis). Some of the mediating mechanisms have been resolved in exquisite detail, including the role of the non-classical human leukocyte antigen (HLA-G) on the trophoblast cells (Slukvin et al., 1998). Its involve-
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ment is intriguing because it must temper the response to the other paternal major histocompatibility complex (MHC) class 1 molecules on fetal cells, one of the primary factors against which the mother’s immune responses would have been directed. In addition, the maternal leukocytes are modulated further by the placentally induced increase in progesterone that is secreted from the ovary (i.e., via the stimulation of the corpus luteum with chorionic gonadotrophin). The complexity of getting these steps just right probably contributes to the high failure rate of early pregnancy. These are also immune pathways through which maternal stress could cause infertility, or affect fecundity in litter-bearing animals. Any physiological process or infectious pathogen that might stimulate the activity of the uterine NK cells could have an adverse effect on the viability of the conceptus. As shown in Figure 1, at this precarious stage, a promoter of the uterine NK response, such as increased interleukin-2 (IL-2), could become an abortifacient (Raghupathy, 1997). However, there has been relatively little systematic research on whether psychological factors do actually act at this level of reproductive immunology. Many more studies have been focused on how environmental and psychological factors may influence
FIGURE 1 Immune alterations induced in the uterine endometrium by the implanting embryo and trophoblast cells. Stimulation of macrophage and CD8+ cells helps to inhibit the responses γδ T- and NK cells and is required for successful implantation. The direction of facilitation (+) or inhibition (−) is shown.
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maternal and fetal immunity later in pregnancy. The conclusions from this large body of research are often erroneously simplified as just indicating that pregnancy is a time of immune suppression for the mother. Figure 2 illustrates that it is more appropriate to characterize pregnancy as a complex shift in immune balance (Makhsee et al., 2001). While some cellular responses in the mother do decline across pregnancy— such as how readily lymphocytes proliferate in culture or the inflammatory response in a test of cutaneous hypersensitivity—others may be enhanced (Sacks et al., 1999). For example, several components of innate immunity and inflammation may appear activated across pregnancy. Neutrophil and white cell counts are higher, and there is more granulocyte-macrophagecolony stimulating factor (GM-CSF) in the blood stream (Belo et al., 2005). The differential suppression or enhancement reflects the degree to which a particular immune reaction might participate in fetal rejection. It was once thought that fetal rejection was not initiated because the uterus is an “immune-privileged” site. Now it appears that the modulation of maternal immunity is really the primary factor. It is also reasonable to hypothesize that this immune modulation would have to be more pronounced in those species that have a hemachorial as compared to an epitheliochorial placenta. As some mammals, including the higher primates, evolved a more invasive placenta with less of a barrier between the maternal and fetal compartments, it would have increased maternal exposure to fetal cells and proteins. Thus, it became necessary to reduce the immune reaction to these fetal tissues exuding paternal antigens, which some have described as like a “tissue allograft” within the womb. Protection against infection must still be sustained. Cytokine production by maternal lymphocytes shifts increasingly away from a Th1 toward a Th2 profile, which enhances humoral immune responses (Veenstra van Nieuwenhoven et al., 2002) (Figure 2). Many studies of pregnant women indicate that a failure to appropriately make this transition, or a delay in its timing, could be a critical factor that contributes to miscarriage and other complications later in pregnancy, including eclampsia (Bates et al., 2002; Gervasi et al., 2001). The immune shift appears to be driven by a number of the key maternal and placental hormones that rise during pregnancy. It was once thought that the dramatic increase in progesterone was the major factor (Siiteri and Stites, 1982). Progesterone is secreted in large quantities from the placenta as pregnancy progresses, and does have immunomodulatory effects. However, other substances, such as alpha-fetoprotein (AFP), may be even more important. AFP is secreted
FIGURE 2 Changes in maternal immunity away from cellular and toward humoral responses, which is required for the maintenance of pregnancy and to prevent fetal rejection. Alpha fetoprotein and a number of hormones, including placental progesterone and CRH, may drive this shift in cytokine responses as pregnancy progresses. Used with permission of Blackwell Publishing.
in abundance from the fetal liver and crosses into maternal circulation, where it has many actions (Gabrant et al., 2002; Tomasi, 1977). The important take-home message for our review is that the immune changes in the mother (1) are substantial, (2) are essential for the viability of the pregnancy, and importantly (3) are driven by the fetus and placenta. Even though the immune changes are occurring within the mother and can be assessed by how her lymphocytes respond in culture—producing less Th1 cytokine (IFN-γ or IL-2) and more Th2 cytokine (IL-4 and IL-10)—the alterations were effected by the fetus for its own well-being. One other ramification of these immune changes for those interested in pregnancy outcomes and infant health is that they may be the vector explaining how the environment can influence the fetus. For example, bacterial infections during pregnancy, and the immune response to them, can be a cause of premature delivery. It doesn’t necessarily require a systemic infection. Women who have high levels of bacteria in their reproductive tract are at greater risk for delivering early (i.e., the gynecological condition of bacterial vaginosis, BV) (Hillier, 2005). High levels of maternal stress have been found to increase the prevalence of BV, perhaps by altering the protective levels of natural bacteria (Lactobacilli), and by inhibiting the ability of mucosal immune responses to contain the resulting bacteremia (Culhane et al., 2002). Increases in pro-inflammatory cytokines could then pose a problem for the maintenance of pregnancy. Research in animals has demonstrated that high levels of inflammatory cytokines, including interleu-
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kin-1 (IL-1) and tumor necrosis factor (TNF-α), can be a cause of pregnancy failure. Rising TNF-α levels in a woman’s blood are considered to be a valuable diagnostic marker of a pregnancy going awry and headed for an early termination (Bates et al., 2002; Makhsee et al., 2001). The placenta is extremely sensitive to the cytokines in maternal circulation, and in response may release its own cytokines and hormones. In the specific case of the monkey and human placenta, cytokines will also drive an increase in its secretion of corticotrophin-releasing hormone (CRH), another warning sign for a premature delivery (MacLean and Smith, 2001; Wadhwa et al., 2001). Some placental cytokines have been found to cross into the amniotic fluid and the fetal compartment. In fact, administering endotoxin (LPS) to a pregnant rat will result in a series of cytokine changes in the placenta and fetal blood, which in turn elevates cytokine production within the fetal brain (Gilmore et al., 2004; Urakubo et al., 2001). A similar type of cascading effect was seen after endotoxin administration to pregnant mice, because cardiovascular functioning in the fetuses was adversely impacted by impaired blood flow to the placenta (Rounioja et al., 2005). These types of findings have led many researchers to advocate that further study of cytokine biology during pregnancy is critical for our understanding of the relationships between stress, reproductive health, and infant development (Coussons-Read et al., 2003). In addition to the clinical significance of bacterial infections for explaining pregnancy complications, there is also a substantial literature on the risks posed by certain viral infections. Beyond viruses known to be teratogenic pathogens in the first trimester, causing fetal malformations and death (e.g., rubella and mumps), there are a number of others that may have more subtle effects on the fetus (Gonik, 1994). Of particular importance today are suspicions about the more virulent strains of influenza because of the new threat of avian flu. During the infamous 1918–19 flu pandemic, more than 50% of the infected pregnant women and babies died (Harris, 1919). But maternal infections with other strains of flu may also be of some concern, even for viable babies (O’Callaghan et al., 1991). A survey of antibody titers in 1,659 pregnant English women in 1993–94 indicated that approximately 11% had been infected with flu at some point during gestation (Irving et al., 2000). Prenatal flu infections have been implicated as a risk factor for a number of neurodevelopmental disorders as well as for later psychopathology, including schizophrenia (Brown et al., 2000; Dammann and Leviton, 1997). Animal models of flu infection have provided some support for this conjecture, even though the flu virus typically does not cross the placenta (Shi et al., 2003). In our research with
nonhuman primates, we are currently studying the consequences of maternal flu infections, with a particular focus on gestational timing because mid-trimester infections have been hypothesized to be of greatest concern. A greater fetal vulnerability at mid-pregnancy is thought to be due to the fact that a baby’s brain regions are still being organized and neurons are in the process of migrating, whereas later they proliferate and make connections in situ.
III. PLACENTAL TRANSFER OF MATERNAL ANTIBODY TO THE FETUS As pregnancy progresses, the maternal immune shift away from Th1- and toward Th2-driven humoral responses has a unique benefit for the developing fetuses of some species. For those mammals that transfer maternal antibody to the baby before term, the humoral bias may help to facilitate the transmission of maternal IgG across the placenta. Table 1 provides examples of species that transfer antibody prenatally as well as ones that do it postnatally in colostrum and breast milk. Higher primates have opted to provide antibody in two installments, transferring the G class primarily across the placenta, while maternal IgA is provided largely after birth in breast milk. About a decade ago, we became interested in how this placental function evolved in humans. Our species has a particularly active transport mechanism, because children are usually born with titers that exceed adult levels, typically between 100–200% of the maternal IgG level (Allansmith et al., 1968). These high antibody titers protect against pathogens previously encountered by the mother and afford an extended period of passive immunity. The availability of this antibody for binding and neutralizing pathogens reduces the need for as
TABLE 1 Representative Species that Provide Maternal Antibody (IgG) Before Birth via the Placenta or Postnatally in Colostrum and Breast Milk.
Kangaroo Pig, cow, horse Rabbit Rat, mouse Monkey, ape Human
Prenatal
Postnatal
yolk sac yolk sac placenta (IgG) placenta (IgG)
via ingestion colostrum, milk nursing nursing milk (sIgA) milk (sIgA)
Note: Humans acquire most IgG across the placenta and then receive sIgA via nursing to protect against enteric pathogens. Premature human babies are thus deficient in IgG; bottle-fed infants receive less sIgA.
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vigorous an immune response by the infant for the first 3–6 months of life. To better understand the transfer process, we conducted a comparative evaluation of representative species across the Primate Order (Coe et al., 1994). Blood samples were obtained from mothers and neonates in five taxonomic groups: prosimian, New World monkey, Old World monkey, ape, and human. Figure 3 shows the results, portraying the neonate’s IgG titer as a percentage of the mother’s level after birth. The galago, a prosimian more like the ancestral primate, is apparently still reliant on a postnatal transfer like that seen in camels, horses, and cows. Infants from the less advanced South American monkey had birth levels averaging between 35 and 40% of the mothers’ IgG. It was not until the rhesus monkey and the chimpanzee that IgG levels at birth began to approach equivalence between mother and baby. Humans go beyond attaining an equilibrium. With our active transport system, maternal IgG is avidly captured by the Fc receptors on the placenta and accumulated on the fetal side (Kohler and Farr, 1966). The importance of the placentally transferred antibody for the human neonate is that relatively little of the additional IgG acquired after birth by ingestion crosses the baby’s gut. Those animal species that provide IgG via colostrum or milk do so while the babies have a more permeable small intestine. Thus, in human and monkey babies, the maternal IgG declines
progressively over the next 3–6 months as the antibody slowly breaks down (Coe et al., 1988a). Infants born with low IgG levels will reach a nadir sooner and will experience a more marked period of hypogammaglobulinemia before they are capable of synthesizing substantial amounts of antibody by themselves (Hosking and Robertson, 1983). Children born premature are especially prone to this transient condition, because they typically have low IgG levels at the time of delivery (Berg, 1968). To track the temporal dynamics of the transfer process back into the fetal period, IgG levels were determined in cord blood samples collected from fetal rhesus monkeys delivered by caesarian-section (Coe et al., 1993). Sampling began at Day 125 postconception and continued through the end of pregnancy, which is typically 169 days. This evaluation revealed that there was a substantial increment in the amount of IgG transferred in the final 2 weeks of pregnancy (Figure 4). The late installment would make functional sense given the goal of extending the benefits as long as possible into the postpartum period. However, the lateness of the placental transfer would mean that any infant born more than a few weeks premature would be deficient. This observation provides one of the explanations for why premature babies are at greater risk for infection. The premature baby would also have to more quickly transition from a reliance on passive immunity to its own immature cellular immune
FIGURE 3 IgG levels at birth in neonates of representative species from five major taxonomic groups across the Order Primates (Coe et al., 1994). Neonate antibody values are portrayed as a percent of adult levels and reveal the progression toward an increased reliance on prenatal transfer. It coincided with the evolution of a more active transport of maternal antibody across the placenta.
FIGURE 4 Progressive increase in maternal antibody in fetal rhesus monkeys (n = 20) from Days 125 to 162 postconception (Coe et al., 1993). The marked increase in the last week demonstrates the lateness of the placental transfer as term approaches (Day 169). Premature infants would thus have low levels of maternal IgG.
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defenses. Such a necessity for an accelerated maturation could contribute to an immune predilection for the development of allergies. The immune responses of newborn human babies are usually Th2 dominant. It has been hypothesized that an inappropriate, early initiation of some cellular responses, including genetic biases toward certain cytokine responses (e.g., low IL12 production) might be one of the risk factors for emergence of asthma (Wright et al., 2005). For humans and the other higher primates that actively transfer IgG, this placenta transmission appears to be relatively resistant to gestational stress unless the pregnancy is foreshortened. Maternal stress was also found to not reduce the transfer of specific antibody to herpes simplex (HSV) in mice (Yorty and Bonneau, 2004). Moreover, in this study even low antibody titers were still sufficient to afford protection against HSV in the pups. Experiments on rats and pigs, however, have shown that maternal disturbance can sometimes impact IgG levels in the pups and piglets (Machado-Nedo et al., 1987; Sobrian et al., 1992). In addition, when the effects of gestational stress were investigated in squirrel monkeys—the primate species that transfers only 35% of maternal titers—we also found an effect of recurrent stress across pregnancy (Coe and Crispen, 2000). The finding was quite interesting because of a differential effect seen in the male and female babies. Pregnancy stress was induced by repeated disturbance of the mother’s social relations: moving the gravid monkeys to three different groups during early and mid-gestation. As expected, the male babies from stressed pregnancies had lower-thannormal IgG levels at birth. In contrast, the prenatally stressed female babies actually had higher antibody levels, both above the males as well as even higher than normal female infants from undisturbed pregnancies. It is intriguing to speculate that the placentas of female fetuses had engaged in a compensatory response, enhancing antibody transfer in seeming anticipation of an adverse postnatal world. We have also investigated the effects of antenatal corticosteroid treatments on IgG levels in the rhesus monkey, because it is known that drugs like dexamethasone (Dex) can catabolize antibody (Coe and Lubach, 2005). A 2-day regimen, which is the typical duration used for premature human babies in clinical practice, caused only a modest decline in maternal and fetal IgG levels. However, given that there was any effect of such an acute exposure, it is likely that longer corticosteroid treatments would result in a larger decrease in antibody over time. Repeated courses of Dex or betamethasone are sometimes employed when there is a recurrent threat of early delivery as well as in some premature babies (Cederqvist et al., 1978).
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IV. ONTOGENY OF FETAL IMMUNITY While the placental transfer of antibody is an interesting prenatal process that can affect postnatal immunity, many other aspects of the fetal immune system have already begun to develop in earnest before the third trimester. Moreover, this organogenesis and hematopoiesis within the fetus is likely to be of greater relevance for explaining how the extrinsic world first impinges upon the development of fetal immunity. Considerable information is available on when various components of the immune system become functional. The fetal thymus, for example, develops early in gestation, and in terms of its overall size is actually more prominent by birth than at later points in the life span. For over 100 years, it has been known that human babies are born with a relatively large thymus of about 25 grams, which is comparable to the size of a mature gland in adults, despite the vast differences in body weight (Hammar 1921; Kendall et al., 1980). The developmental course of the thymus postnatally is also predictable (Figure 5). Its size will peak at puberty, which led to some speculation that it was involved in determining age at puberty. In fact, the timing of pubertal maturation can be altered by thymectomy during infancy, and there is still much more to learn about the important life-long relationship between reproductive hormones and thymic function (Grossman, 1989; O’Grady and Hall, 1991). After puberty, the thymus begins a slow but progressive decrease in size, ultimately shrinking sufficiently to contribute to the onset of immune senescence in the aged host (George and Ritter, 1996; Mackall and Gress, 1997; Trainin, 1974). Whether early life events could actually shape the full trajectory of the thymus across the whole life span is
FIGURE 5 Developmental trajectory of the thymus across the human life span. The thymus is extremely large in the neonate, thymic size peaks at puberty, maintains its structure in adulthood and slowly regresses in old age.
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not well understood, but some studies have indicated a link between prenatal events and later thymusdependent functions in adolescence and adulthood (McDade et al., 2001). In addition, it is definitely well established that thymic size is extremely responsive to stress and challenge at all ages (Jeppesen, 2003; DiNaro et al., 2006). Thymo-lymphatic involution was one of the three cardinal signs that Hans Selye identified as indicative of the stressed state in the mature individual (Selye, 1956). Similarly, it has long been known that maternal stress and administration of corticosteroid and estrogenic drugs during pregnancy can cause a marked diminution of thymic size in the fetus (Selye and Marion, 1955). High levels of corticosteroids have a deleterious effect on the structural and lymphoid zones of the thymus, and can directly lyse or stimulate the apoptotic death of immature thymocytes (Godfrey et al., 2000; Hendrickx et al., 1975; Sawyer et al., 1977). Nevertheless, it appears that normal cortisol and corticosterone levels are actually beneficial, and may restrain the premature and inappropriate growth of certain cells. For example, the offspring of adrenalectomized female rats showed an accelerated development of thymic dendritic cells with a mature phenotype (Sacedon et al., 1999). Sex hormones also act on the thymus, and both estrogen and progesterone are very high during pregnancy (Bodey, 2002; Seiki and Sakabe, 1977). The fetus probably plays a major role in stimulating this type of feedback from hormones, because the dehydroepiandosterone (DHEA) from the fetal adrenal serves as the primary precursor for the estrogen made by the placenta. In addition, the androgenic hormones secreted by the male fetus during sexual differentiation may help to explain some of the gender differences in the propensity for autoimmune diseases later in adulthood (Savino and Dardenne, 2000). Androgens tend to have a dampening effect on the thymus (Olsen et al., 2001a, 2001b). Thus, a thymic enlargement is observed following castration of male rats. The development of the thymus during fetal life also coincides with the emergence of T-cells in utero and the initiation of some cellular functions before term. Hematopoietic stem cells migrate from the bone marrow and then grow and differentiate within the optimal microenvironment of the thymus (Bodey, 2002). At the same time, there has to be extensive intrathymic selection of the T-cell repertoires, in particular selecting against thymocytes that would respond inappropriately to self-antigens. This cellular pruning process is critical for preventing immune responses that might result in attacks on healthy tissue or be a cause of later autoimmune disease. In humans, func-
tioning T-cells can be found as early as 10 weeks after conception, based on the capacity to stimulate cord cells in vitro with mitogen (i.e., phytohemagglutinin, PHA) (Warner et al., 2000). Even so, T-cell responses and other aspects of cellular immunity are still not fully mature at birth. By mid-gestation, samples obtained from cord blood indicate that some cells may also have been activated already by allergens. This finding led to the hypothesis that prenatal exposure to certain proteins may be priming those babies who are genetically predisposed to atopic conditions (Devereux et al., 2001). An ex vivo modeling of protein diffusion across whole placentas demonstrated that small molecular weight substances can cross the placenta (especially if less than 500 Da) (Loibichler et al., 2002). Based on these analyses, consumption of eggs or milk by a pregnant woman could allow allergenic proteins like ovalbumin and lactoglobulin to reach the fetus as soon as 2 hours after ingestion. In keeping with this view, surveys of cord blood lymphocytes at term have documented a seasonal variation in the prevalence of babies born with cells activated against pollen (Piccinni et al., 1993; Van Duren Schmidt et al., 1997). These findings of cellular responses to grass and birch trees in the neonate suggested that there had been a prior in utero exposure. Further support for the idea of prenatal priming was garnered by showing that some cat dander can be pulled across the placenta as part of an IgG-bound complex along with the placental transfer of other maternal antibody (Casas et al., 2001). Nevertheless, from an overview perspective, Table 2 shows that it is still most correct to convey that the cellular immune responses of a newborn baby are immature and not yet fully functional. Lymphocytes obtained from cord blood do not proliferate as well as mature adult cells in culture, make less cytokine overall, and show a strong Th2 bias in their pattern of cytokine release (Adkins et al., 1999). Extensive TABLE 2
Distinguishing Features of Immunity in the Neonate
• Innate immunity more established than adaptive immune responses • Low lymphocyte proliferative responses in vitro compared to mature cells • Reduced ability of antigen-presenting cells (APC) • Low cytokine production and sensitivity; Th2 cytokine phenotype • Slower class switching in antibody responses to antigen (IgM to IgG) • Passive immunity from mother (IgG via placenta in monkeys and humans) • Unique CD4+ T-cell suppressor activity
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research has been directed to figure out the reasons for the deficient lymphocyte responses and the cells’ lower production of Th1 cytokines (e.g., IFN-γ). There appear to be many explanations, but an especially important factor is incompetent antigen presentation. When neonatal lymphocytes are incubated in culture along with professional antigen-presenting cells (APC) obtained from adults, a more mature response is elicited. These findings indicate the lymphocyte itself is not dysfunctional in the neonate. But under normal circumstances in vivo, the newborn infant would have to rely more on its innate immune responses, including the complement system, and also the passive immunity obtained via maternal antibody. When induced to produce antibody, the lymphocytes of developing infants are also more likely to make IgM and do not class switch as readily to IgG in the manner of adult cells.
V. SOME IMPORTANT NUANCES OF IMMUNITY IN THE NEONATE While it is essential for the newborn baby to have a sufficient armamentarium to respond to pathogens, an equally pressing need is to limit excessive overreactions. The young host is exposed to a myriad number of antigenic stimuli simultaneously, including a massive invasion of bacteria into the gut. So its immune responses must be tempered. Several decades ago, it was discovered that the young infant has a unique type of CD4+ T suppressor cell that can dampen immune reactions (Papadogianniakis et al., 1990). We took advantage of this observation to investigate whether a history of prenatal disturbance might alter how the newborn monkey responded to the world through a change in the activity of these T suppressor cells (Coe et al., 1996). Rhesus monkeys were generated from undisturbed, control pregnancies as well as from mothers that had been administered daily injections of adrenocorticotrophin hormone (ACTH). ACTH was used because it does not cross the placenta, but would raise the mother’s cortisol to high levels. For 2 weeks from Days 120–133 postconception, ACTH was administered to the gravid female either in the morning or afternoon. At 2 and 6 weeks postpartum, blood samples were then obtained from the babies, and their mononuclear cells (MNC) set up in a suppressor cell assay. Briefly, the infant’s MNC were stimulated with concanavalin A (Con A) for 2 days, after which they were treated with mitomycin C for 45 minutes. The primed cells were then added to heterologous cells from an adult male responding to Con A. Reduction in the proliferation of the responder cells was used as an index of suppressor activity. As can be
seen in Figure 6, monkeys generated from the ACTHtreated pregnancies showed significantly less cellular inhibition. It is also noteworthy that these babies as well as the control monkeys did show the typical agerelated decline. As a consequence, the ones from the ACTH-treated pregnancies had less suppressor activity at both age points. This maturational decrease by 2 months of age coincides with the developmental appearance of other immune responses. Our studies on maternal stress during pregnancy have documented effects on many other immune functions (Coe et al., 1999). One difference immediately apparent in the neonatal period is an impact on the types of bacteria that will become established as the commensal microbiota of the gut. This research conducted by Michael Bailey was especially insightful because it revealed how a seemingly innocuous change could set the stage for later disease (Bailey et al., 2004). It also documented how rapidly bacteria invade the gut as soon as the baby disembarks from the sterile environs of the womb. Within 1–2 days of birth, millions of bacteria were in evidence as determined by coprocultures. The main assessment then focused on the establishment of two bacterial populations known to be of benefit to the host: Lactobacilli and Bifidobacter. These natural constituents of the gut microbiota can help to suppress the growth of enteric pathogens (Cebra, 1999). Briefly, monkeys were generated either from undisturbed, control pregnancies or from females that had Infant Suppressor Activity
% Suppression
FIGURE 6 Suppressor cell activity in infant rhesus monkeys at 2 and 6 weeks of age (Coe et al., 1996). Some mothers were administered ACTH for 2 weeks during pregnancy (Days 120–133 postconception), which resulted in infants with lower suppressor responses. All infants showed the typical maturational change from 2 to 6 weeks of age. Used with permission of Elsevier.
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experienced daily periods of acute stress for 6 weeks of their 24-week gestation. The stress periods were scheduled to occur either Early or Late in pregnancy (Days 50–92, or 105–147 postconception, respectively). From Day 2 postpartum through 6 months of age, rectal swabs were obtained to determine the concentrations of Lactobacilli and Bifidobacter. As shown in Figure 7, babies from both the Early and Late Stress pregnancy conditions had significantly lower levels of Lactobacilli. When Bifidobacter levels were enumerated, a prenatal effect was seen primarily in the infants from the Late Stress pregnancies, indicating that the timing of the gestational disturbance also had a selective effect on certain gut bacteria. The altered bacterial profiles were found to have disease ramifications. All of the babies were screened for the presence of Shigella, a gram-negative enteric pathogen, which is endemic in most monkey colonies. Whereas none of the control babies evinced any Shigella across the first 6 months of life, it was found to be present without symptoms in 43% of Early Stress babies. Similarly, Shigella occurred periodically in the cultures from 38% of Late Stress monkeys, and two developed diarrhea symptoms requiring treatment with antibiotics. In summary, the prior occurrence of maternal stress altered how the young baby would interact with bacteria present in the rearing environment. The prenatal conditions influenced how bacteria became established as the gut microbiota, which was associated with the capacity to prevent enteric infection.
Log (10) CFU/g
Control
Early Stress
Late Stress
FIGURE 7 Levels of Lactobacilli in 24 infants quantified across the first 6 months of life by coproculture (Bailey et al., 2004). Prenatal disturbance resulted in lower levels of protective microbiota in the gut, which was associated with an increased risk for infection with Shigella, an enteric pathogen. Infants from the Late Stress condition also had lower levels of the protective Bifidobacter. Copyright 2002, The Endocrine Society.
These conclusions are not restricted to non-human primates. It has long been known that mice and rats reared in gnotobiotic environments will grow up to exhibit abnormal immune responses because the normal bacterial invasion of the gut did not occur (Cebra, 1999; Hooper and Gordon, 2001). Moreover, it has been shown that the gut microbiota are critical for the normal maturation of the gut-associated lymphoid tissue (GALT). Changes in GALT immunity would then affect other mucosal and systemic responses (Barreau et al., 2004). While these microbiological processes are not typically studied within the context of PNI research, they offer important outcome measures, which are known to be associated with long-term health. To reinforce this point, it is worth noting that the infant’s most exposed surface is the gut. In an adult human, the gastrointestinal tract spans 400 square meters as compared to the typical 2 square meters of skin. Ultimately, over 500 species of bacteria will become established as the resident microbiota of the intestines (Mazmanian et al., 2005). The significance of this symbiotic relationship can be highlighted further by the fact that their numbers will reach 1014, while the developing human host will be composed of just 1013 cells. In our study of stressed monkeys, we were not able to determine exactly what factors mediated the long-lasting change in these important gut bacteria. But among the suspects were alterations in gut motility and acidity, both of which are known to influence bacterial concentrations. In addition, we speculated about the possible effect of gestational stress on the composition of the mother’s breast milk. Our suspicions about milk were based on many papers reporting that several of its constituents can promote the growth of both Lactobacilli and Bifidobacter. Nursing by the mother also has other benefits for enhancing the baby’s immune competence (Hasselbalch et al., 1999; Labbok et al., 2004). As mentioned earlier, it is the primary source of sIgA, which helps to protect the epithelial surface of the gastrointestinal tract. Thus, it can directly assist in neutralizing pathogens that utilize this route of entry. Both the sIgA and gut bacteria likely contribute to the known differences in illness frequency between breastfed and bottle-fed babies, especially with regard to the risk for diarrheic conditions. A specific influence of maternal care and nursing on immunity in monkeys is discussed at greater length in a later section describing immune differences found between mother-reared infants and ones raised on formula by humans. However, before addressing those findings, it is important to summarize a few of the more long-term immune effects that occur in monkeys generated from prenatally disturbed pregnancies.
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VI. SUSTAINED EFFECTS OF PRENATAL CONDITIONS ON LYMPHOCYTE FUNCTIONS The immune effects of prenatal stress and hormone treatments have been found to extend beyond the infancy period. In one project, lymphocyte proliferative and cytokine responses were examined in prepubescent animals (Coe et al., 2002). Blood samples were collected from 2–3-year-old monkeys that had been generated from either undisturbed control or psychologically stressed mothers. The whole-blood cultures were stimulated overnight with LPS (with either 10 or 100 ng/ml), and the supernatants harvested the next day for quantification of interleukin-6 (IL-6) and TNFα levels. In response to both low and high concentrations of LPS, the monkeys from stressed pregnancies produced less IL-6 and TNF-α (Figure 8). This finding of a lower cytokine response to protein derived from the cell wall of E. coli concurred with a previous paper reporting smaller in vivo inflammatory responses in a different cohort of monkeys (Reyes and Coe, 1997). In that study circulating IL-6 levels were determined 1 hour after administration of IL-1 to 1–2-year-old monkeys that had been generated from control and hormone-treated pregnancies. If mothers had been administered ACTH for 2 weeks during pregnancy, their offspring had a reduced IL-6 response in both blood and cerebrospinal fluid (CSF). Delineating all the possible processes that account for such long-term effects, and distinguishing which ones are primary, is extremely difficult. In some instances, the immune alterations have been associated with parallel changes in the endocrine system (Figure 9). We, and others, were inclined to look for changes in the pituitary-adrenal axis (Weinberg and Jerrells, 1991; Weinstock, 1997). The main hypothesis is usually that the offspring from disturbed pregnancies will either have higher adrenal hormone levels all the time or be more stress-reactive. While the studies in rodents have sometimes reported the maintenance of higher basal levels of corticosterone, prenatally stressed monkeys do not usually manifest such a pervasive upregulation of HPA activity. Instead, they can be distinguished more readily by having prolonged cortisol responses when provoked, such as after being moved to an unfamiliar cage. In addition to a slower recovery, they may exhibit a differential response to a test of corticosteroid negative feedback, the dexamethasone suppression test (DST). Overnight probes of HPA suppression in monkeys from disturbed pregnancies indicate that they more likely to “break through” the Dex-induced inhibition by the next morning (Coe et al., 2003).
FIGURE 8 Levels of cytokine (tumor necrosis factor-alpha and interleukin-6) released after overnight stimulation of whole blood cultures with a low or high concentration of lipopolysaccharide (LPS) (Coe et al., 2002). A trait-like effect of Early and Late gestational stress on these pro-inflammatory responses was still evident in these 2-year-old juvenile monkeys. Used with permission of LW&W.
This type of linkage between hormone and immune alterations in the developing monkey is not restricted to the effects of gestational stress. In one experiment, the proliferative responses of MNC were examined in 1-year-old monkeys that had been exposed to Dex in utero a month before term (Coe and Lubach, 2005). Antenatal corticosteroid exposure on Days 143–144 postconception resulted in yearling animals with cells that proliferated less to mitogen. Their cells also reacted differentially when a gradation of cortisol was added to the cultures (10−5 to 10−9 M). The MNC seemed more insensitive to cortisol, with an overall shift in the doseresponse inhibition curve. We hypothesized that the corticosteroid receptors on the lymphocytes were downregulated, because of the frequent occurrence of higher in vivo hormone levels. The possibility that variation in the amount of adrenal hormone secretion had contributed to the long-term immune differences led us to examine a brain region critically involved in the regulation of the HPA axis. The hippocampus is the primary feedback center in the cortex for corticosteroids, and it exerts a tonic inhibition over the hypothalamic control of adrenal secretion. As found in studies of the brains of prenatally stressed rodents, our pregnancy manipulations had impacted the hippocampus (Coe et al., 2003; Lemaire et al., 2000; Takahashi, 1998). The monkeys generated from stressed pregnancies showed a substantial reduction in hippocampal volume when measured at 3 years of age (approximately 10% across its length). Smaller size was also associated with a lower growth rate of new neurons (neurogenesis), as measured by cells that had been labeled with bromodeoxyuridine (BrdU). While this did not definitively prove that these hippocampal changes accounted for
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FIGURE 9 Overview of physiological alterations induced by prenatal disturbance and some of the pathways likely to be involved in mediating the immune effects. In addition to changes in the neuroendocrine axis, an interference with the normal placental transfer of nutrients and an abnormal profile of gut bacteria may affect the development of immune responses.
the co-occurring hormone and immune changes, it seems reasonable to conclude that they were a contributing factor. Figure 9 summarizes the broad conceptual model that emerged from these primate studies. Given the range and duration of the immune changes, it is likely that they reflect a multi-factorial causation. Long-term alterations in neuroendocrine activity postnatally would presumably add to the immediate effects of prenatal stress on lymphoid tissue and cells that had occurred during gestation. Disturbances in the gut bacteria could increase the chance of infection in infancy, and recurrent illness would have its own effect on the development of immunity. Finally, we, and others, have some additional evidence that maternal stress during gestation may act through nutritional pathways (Beach et al., 1982; Caulfield et al., 1998). When similar studies were conducted on the offspring of stressed females fed a diet with just adequate iron but not the extra supplemented amounts recommended for pregnancy, larger effects on infant immunity were found. Iron stores and utilization in these infants were affected, and the prenatally stressed ones
developed an iron deficiency anemia as they grew after birth. This developmental impairment in red cell functioning provided a second hit to the immune system at 4–6 months postpartum. Even innate immune responses were now impacted. NK responses that had been solidly established earlier at 2 months of age deteriorated in the increasingly anemic infants from stressed pregnancies. The possible significance of stress-related changes in the prenatal transfer of micronutrients from mother-to-infant is not restricted to monkeys. Because mice and rats are litter-bearing species, the dams are even more taxed by the demands of providing iron to multiple offspring (Conner, 1994). Iron deficiency is also a serious concern in humans, occurring in between 60% and 80% of pregnant women in developing countries (Allen, 1997). As recently as 1980, 30% of infants in the United States became anemic before the advent of more widespread iron fortification in baby formulas and cereals (Beard, 1994; Lonnerdal and Dewey, 1995). So a possible link between stress, nutritional deficiencies, and the development of immune responses is an issue that may apply to both animals and humans (Lozoff et al., 1998). Even today,
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up to 10% of babies in low SES families of industrialized countries are destined to become anemic.
VII. INFLUENCES OF THE EARLY REARING ENVIRONMENT ON IMMUNITY In the introduction we stated that an influence of the postnatal rearing environment on the development of immune responses is at least equal to the effect of prenatal conditions. Adverse and stressful rearing may also further compound any vulnerability created by prior undernutrition or disturbance during gestation. Not too surprisingly, much of this research has focused on the influence of maternal care given that a period of nursing is a sine qua non for all mammals and essential for infant survival. Perhaps because it is such a predictable feature of the postnatal environment, the normal development of many biological systems including immunity appears to rely upon the infant’s receipt of maternal behavior. Developmental researchers have known for many decades that monkeys will show marked behavioral abnormalities if reared away from the mother. Even brief separations of rat pups from the mother can have deleterious effects on brain development. Thus, it may not be too surprising that the absence of maternal care will cause some immune responses to go awry. However, at the time our research was conducted two decades ago, no one had previously investigated the immune consequences of different types of rearing in monkeys (Coe et al., 1989). Specifically, the lymphocyte responses of rhesus monkeys normally reared by their mothers were compared to bottle-fed animals raised by humans in a nursery setting. Our first study took advantage of an opportunity to collect blood from yearling rhesus monkeys that were still with their mothers (MR) and to compare them to age-matched monkeys initially fed by humans and then raised in small peer groups (NR). Samples were collected from eight of each type, and their MNC were separated and stimulated in culture with mitogens (Con A, PHA, or PWM). To our surprise, the lymphocytes of the NR monkeys proliferated at dramatically higher levels. Because the findings differed from our expectation that the absence of maternal care would cause an immune inhibition, a second study was designed to assess other monkeys at a younger age (Coe et al., 1992). Again, it was found that the proliferative responses were exaggerated by a history of nursery rearing. But inclusion of some additional assays provided preliminary evidence that higher proliferation was not necessarily better. These NR infants
FIGURE 10 Monkey infants that are bottle-fed and reared by humans have different immune responses than do motherreared animals (Lubach et al., 1995). In addition to altered lymphocyte proliferation, nursery-reared infants (NR) have a skewed ratio of CD4+ and CD8+ T lymphocytes, due primarily to low CD8+ cells in circulation. This influence of early rearing continued to persist after an attempt to ameliorate the immune effects by housing all monkeys in similar social groups at 1 year of age (n = 8 and 8). Used by permission of Oxford University Press.
tended to have lower NK activity and smaller antibody responses to vaccinations. To explore the reason for the increased proliferation, a final study was conducted to prospectively examine a third set of monkeys at 6-month intervals from birth through 2 years of age (Lubach et al., 1995). This time the mitogen assays were accompanied by an enumeration of lymphocyte subsets. As can be seen in Figure 10, the higher proliferation proved to be associated with a different profile of CD4+ and CD8+ cells in circulation. Specifically, the NR infants had a relative abundance of CD4+ cells, due in large part to lower numbers of CD8+ cells. There is one other aspect of these results that is worthy of note because it highlighted the enduring nature of these rearing effects. When the MR and NR monkeys reached one year of age, all were re-housed so that they would be living in identical conditions. Eight monkeys from each background were combined into a small, stable social group that also included an elderly female monkey to serve as a supportive adult. Despite the comparable housing, the immune differences between MR and NR monkeys persisted for another year (see Figure 10). Later assessments of the NR monkeys at 3 years of age indicated that their cells still exhibited high proliferative activity.
VIII. IMMUNE RESPONSES TO SOCIAL STRESSORS AND DISTURBANCE IN OLDER INFANTS The long-lasting nature of the effects seen in nurseryreared monkeys suggested that the immune differ-
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ences would be perpetuated into adulthood. In those experiments, however, the disruption of normal rearing commenced when the infant’s immune system was still at a more vulnerable, formative stage. Conclusions about the duration of immune changes are quite different when the consequences of early life events are evaluated in older infants. Immune responses may still be affected by challenge and stress, but the effects are more transient if the events first occur in 6– 12-month-old infants, and they usually resolve within a few days to weeks. The experimental paradigm used most frequently by researchers for this type of study in older monkeys involved a several-day to 2-week period of separation from either the mother or familiar social group (Coe, 1993; Gust et al., 1992; Laudenslager et al., 1982). While the immune effects do subside over time, these pioneering papers on the acute dysregulation of immunity in young animals provided important insights into how stressful events can affect the immune system. Immediately after the social separation, a marked lymphocytopenia was evident for several days, which included a significant decline in T- and NK cell numbers. Studies of their cellular responses in vitro indicated that proliferative responses and cytolytic activity were also inhibited at this time (Figure 11). Depending upon the monkey species used in the study and how the separated infant was housed—either alone or in a familiar group after removal of the mother—the inhibition of lymphocyte functions might be sustained for several days to a few weeks (Laudenslager et al., 1990). If the lymphocyte responses of the stressed monkey were probed further with antigen, it was clear that the changes were sufficient to impair antibody responses. Levels of antibody produced in vivo in response to keyhole limpet hemocyanin (KLH) or to a bacteriophage (φX174) were reduced in the separated monkeys (Coe et al., 1988b). Nevertheless, most papers that followed these separated infants over a longer period of time reported that
the period of inhibition was delimited. Even if the mother and infant were not reunited, or the monkey was not returned to its original social group, there would be a re-establishment of immune responses similar to those seen before the stressful event. This recovery suggested that the older infant had already attained a better and more mature capacity to regulate its immune functions. Presumably, the resiliency also indicated that there were some regulatory set points established to guide the cellular return back to the normal numbers and reactions of the undisturbed state. When these social separation studies were conducted nearly 2–3 decades ago, they also made another novel contribution to the PNI literature. In addition to showing that stress could inhibit lymphocyte functions, the research revealed that some arms of the immune system might be activated simultaneously. A pronounced neutrophilia was frequently seen in the infant monkeys during the first few days after weaning from the mother or separation from the social group. In fact, the neutrophil numbers often increased to such a degree that the rise exceeded the decline in lymphocytes and resulted in higher overall leukocyte counts. Neutrophils and Mφ were also found to be in an activated state and would release more superoxides when stimulated with phorbol myrisate acetate (PMA) in an in vitro chemiluminescence assay (Coe et al., 1988b). This turning on of innate immunity by social stressors also extended to the complement system. Increases in
TABLE 3 Alterations in Immune Responses Observed Acutely after Young Monkeys Are Either Separated from Their Mothers or Removed from the Social Group • • • • •
Lymphocytopenia in association with marked neutrophilia Decreased T and NK cells in circulation Reduced in vitro proliferative and cytolytic activity Lower antibody responses to antigen challenge Enhanced innate immunity (complement activity and Mφ superoxide production) • Increased inflammatory responses (Delayed Type Hypersensitivity, DTH)
FIGURE 11 Cytolytic activity in infant squirrel monkeys (n = 11) before, and at 1 and 7 days after separation from the mother (Coe and Erickson, 1997). Note both the significant inhibition on Day 1, as well as the rapid recovery back to baseline in these older infants that were between 7 and 12 months of age. Assays were run at 5 Effector-to-Target cell ratios (100 : 1, 50 : 1, 25 : 1, 12.5 : 1, 6.25 : 1).
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hemolytic complement activity lasted for more than 2 weeks in the separated monkeys (Coe et al., 1988c). While the observation that stress can stimulate some innate and inflammatory processes is not surprising today, this formative research on young animals contributed to our awareness about the bi-directional nature of immune changes in the disturbed individual. Stressed infant monkeys also showed an enhancement of delayed hypersensitivity responses. When recall responses to dinitrochlorobenzene (DNCB) were elicited during the separation period, the erythema and induration were aggravated. This stress-related enhancement of inflammatory processes in young animals concurs with the more extensive and detailed investigations of cutaneous hypersensitivity in adult rats (Dhabhar and McEwen, 1999).
IX. CONCLUSIONS We now know that immune responses can be affected by environmental challenges and psychological disturbance at any point in the life span. However, the research on infant animals and children indicates that the effects may be more pronounced and long lasting in the immature individual. Disturbance of social relationships in monkeys of 6–12 months of age, which is developmentally equivalent to the 21-day-old rat and the 3–4-year-old child, has been found to impact a wide range of innate and adaptive immune responses (Coe, 1993). Nevertheless, there is already both a quantitative and qualitative difference in the reactions at this age when compared to immune alterations after perturbations that took place earlier during the fetal and neonatal stages. Immune changes in the older infant are more short-lived and usually resolve in a few weeks as the young animal adapts to the new situation. Thus, the recovery and resolution are more like that seen in the adult host. Any consequences of these transient immune changes for health would depend upon there being opportunistic infections or experimental probes at the maximal point of lymphocyte inhibition or enhanced inflammatory potential. The conclusions are quite different after disturbances of fetal or neonatal development. Permanent changes in immunity may then be observed if the perturbations were sufficiently salient. Even an abrupt, early weaning of the infant from the mother may cause long-lasting effects. This type of observation was first reported in a seminal paper 40 years ago when adult rats were found to respond poorly to a transplanted tumor if they had been removed from the mother on Day 14 rather than Day 21 (Ader and Friedman, 1965). The critical importance of maturational age at the time
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of insult generalizes from the rodent to the primate. For example, a retrospective examination of the reason for variation in how adult monkeys succumbed to infection with simian immunodeficiency virus (SIV) showed that it could be attributed to a history of disturbed early rearing and housing conditions (Capitanio and Lerche, 1991). Both maternal stress and hormone treatments during pregnancy can result in pervasive and lingering effects on the offspring. These developmental alterations in immunity are often associated with more widespread effects that span brain and neuroendocrine functions. As a consequence, it is difficult to designate just one pathway mediating the immune changes. Many investigators have pointed to the significance of increased adrenal activity during pregnancy and subsequently to the abnormal regulation of HPA activity in the offspring postpartum. Given the potent effects of adrenal hormones on the thymus and lymphoid cells, corticosteroids could undoubtedly play a role. However, in order to fully understand prenatal influences on the development of immunity, it is equally important to consider other mediators. This chapter highlighted a few other candidates, including prenatal and postnatal nutrition, the microbiota of the gut, and the infant’s early responses to viruses and bacterial infection. Relatively modest changes in the gut bacteria of prenatally stressed monkeys were found to set the stage for a vulnerability to enteric pathogens. We know that diarrheic disease is still the second largest killer of human babies worldwide. Adverse events postpartum can continue to disturb the gut microbiota and may even facilitate bacterial translocation through the gut wall into systemic circulation (Barreau et al., 2004; Wenzyl et al., 2003). This idea of accumulating risk, or a two-hit model of vulnerability after developmental insults, would concur with the views emerging in other disciplines. There is compelling evidence that a period of undernutrition or stunted growth in utero can alter the regulation of metabolism in such a way as to increase the risk for diabetes or cardiovascular disease in adulthood (Barker, 1994; Caulfield et al., 1998). Allergists have also started to take more seriously the idea that the origins of allergies and asthma may be found in fetal life (Herz et al., 2001; Warner et al., 2000). Some babies may already be born with an atopy-prone phenotype, which is then aggravated by allergens in the rearing environment, frequent upper respiratory infections, or inadequate medical and parental responses (Mrazek et al., 1991; Wright et al., 2005). Figure 12 illustrates how the developmental perspective on asthma has broadened to include more antecedent events. At the moment of birth, there may already be
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FIGURE 12 Developmental model of allergies and asthma highlighting the important influence of both prenatal and early rearing conditions. Some infants at birth may already show an immune predisposition toward atopic conditions, which can then be aggravated by exposure to allergens and recurrent upper respiratory infections.
elevated IgE levels in cord blood, cells activated against certain allergens, and lymphocytes more prone to produce Th2 cytokines (Karmaus et al., 2001). A premature birth presents a particular challenge for the immature immune system. Both prematurity and an extended gestation that goes past 40 weeks have been associated with an increased occurrence of allergies and asthma (Ferguson et al., 1997; Pekkanen et al., 2001). Given that an early activation of immunity is a risk factor, it may seem paradoxical that some bacterial infections and parasite infestations in young infants have been associated with a reduced risk for asthma. The latter observation has led to the so-called “hygiene hypothesis” (Yazdanbakhsh et al., 2002). This initially counterintuitive idea is in keeping with some of the findings discussed in this chapter. Aspects of the developing immune system are pre-programmed in anticipation of the infant’s needs to respond to antigens in the postnatal environment. This typical development and the “learning trajectory” of immunity could then become derailed in our modern, clean world, especially when common childhood infections are prevented by immunizations. The hygiene hypothesis proposes that the normal immunobiology could then be deflected and result in inappropriate reactions to innocuous antigens like pollen. Having highlighted how readily immune responses in young animals may be affected by disturbances of pregnancy or early rearing, a few caveats should also be acknowledged. For both scientific and ethical reasons, the experimental conditions in our primate studies were designed to ensure the viability of the
offspring. Thus, we did not study any extreme or noxious manipulations that caused fetal loss. In the real world, however, one clinical consequence of a maternal infection could be pregnancy failure or premature delivery. Similarly, our tests of antenatal corticosteroid treatments were limited to a 2-day course to emulate clinical practice. More prolonged dexamethasone regimens, at least in animals, can have devastating effects on fetal and infant immunity, as well as on brain development (for a review of primate studies, see Coe and Lubach, 2005). The elicitation of stress in the gravid females was also designed to approximate a level of disturbance that could occur naturally. Pregnant monkeys may experience periods of limited food availability, climatic challenges of drought and heat, a periodic threat of predation, and may be subjected to aggression from a more dominant animal. Thus, the natural demands and levels of arousal could exceed that evoked by the acute acoustical startle protocol pre-housing stress utilized in the laboratory. As a consequence, the immune alterations described for our monkey infants should be viewed as within the normal range of physiological variation. The offspring were not obviously sick or impaired to the same degree as a child with an immunodeficiency disorder or an autoimmune condition. Rather this research was designed to model how early life events can create developmental vulnerabilities in the infant. Our review also began with the important role that immune cells play in reproductive biology. This expanded function for the immune system goes beyond its traditional role in the response to infection. While the endocrine events associated with pregnancy usually receive more attention, immune processes are critical for the successful implantation and the maintenance of pregnancy. These early immune interactions between the mother and her developing baby foreshadow the equally vital functions that her maternal care will serve postpartum. Symbolically and concretely, the maternal facilitation of immune development begins prenatally via the placenta and then continues postnatally through breast milk and solicitous care giving. These contributions are critical for survival and for guiding the infant on the right trajectory to become an immune competent adult.
Acknowledgments This research was supported by grants from the National Institutes of Allergy and Infectious Disease as well as Child Health and Human Development (AI46521, HD39386). CLC has received partial salary support from MH61083 and AG20166. Special appreciation is due M. Bailey, H. Crispen, E. Fuchs, M. Kraemer, T. Reyes, M. Schneider, and A. Slukvina for invaluable help on specific studies reviewed in this chapter.
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References Ader, R. (1983). Developmental psychoneuroimmunology. Devel. Psychobiol., 16, 251–267. Ader, R., and Friedman, S. G. (1965). Social factors affecting emotionality and resistance to disease in animals: V. Early separation from the mother and response to transplanted tumor in the rat. Psychosomat. Med., 27, 119–122. Adkins, B. (1999). T-cell function in newborn mice and humans. Immunol. Today, 20(7), 330–335. Allansmith, M., McClellan, B. H., Butterworth, M., and Maloney, J. R. (1968). The development of immunoglobulin levels in man. J. Pediat., 72, 276–290. Allen, L. H. (1997). Pregnancy and iron deficiency: unresolved issues. Nutr. Rev., 55, 91–101. Bailey, M. T., Lubach, G. R., and Coe, C. L. (2004). Prenatal conditions alter the bacterial colonization of the gut in the infant monkey. J. Pediat. Clin. Gastroenterol., 17(7), 1704–1708. Barker, D. J. P. (1994). Mothers, babies, and disease in later life. London: BMJ Publishing. Barreau, F., Ferrier, L., Fioramonti, J., and Bueono, L. (2004). Neonatal maternal deprivation triggers long term alterations in epithelial barrier and mucosal immunity in rats. Gut, 53, 501–506. Bates, M. D., Quenby, S., Takakuwa, K., Johnson, P. M., and Vince, G. M. (2002). Aberrant cytokine production by peripheral blood mononuclear cells in recurrent pregnancy loss? Human Reprod., 17(9), 2439–2444. Beach, R. S., Gershwin, M. E., and Hurley, L. S. (1982). Gestational zinc deprivation in mice: persistence of immunodeficiency for three generations. Science, 218, 469–471. Beard, J. L. (1994). Iron deficiency: assessment during pregnancy and its importance in pregnant adolescents. Am. J. Clin. Nutr., 59(Supp), 502S–510S. Belo, L., Santos-Silva, A., Rocha, S., Caslake, M., Cooney, J., PereiraLeite, L., Quintanilha, A., and Rebelo, I. (2005). Fluctuations in C-reactive protein concentration and neutrophil activation during normal human pregnancy. Eur. J. Obstet. Gynecol. Reprod. Biol., 123, 46–51. Berg, T. (1968). Immunoglobulin levels in infants with low birth weights. Acta Pediat. Scand., 157, 367–376. Bilbo, S. D., Levkoff, L. H., Mahoney, J. H., Watkins, L. R., Rudy, J. W., and Maier, S. F. (2005). Neonatal infection induces memory impairments following an immune challenge in adulthood. Behav. Neurosci., 119(1), 293–301. Bodey, B. (2002). Neuroendocrine influence on thymic haematopoiesis via the reticulo-epithelial cellular network. Expert Opin. Therap. Targets, 6(1), 57–72. Brown, A. S., Schaefer, C. A., Wyatt, R. J., et al. (2000). Maternal exposure to respiratory infections and adult schizophrenia spectrum disorders: a prospective birth cohort study. Schizophr. Bull., 26, 287–295. Capitanio, J. P., and Lerche, N. W. (1991). Psychosocial factors and disease progression in simian AIDS: a preliminary report. AIDS, 5, 1103–1106. Casas, R., et al. (2001). Detection of Fel d-1–immunoglobulin G complexes in cord blood and sera from allergic and nonallergic mothers. Pediat. Allerg. Immun., 12(2), 59–64. Caulfield, L. E., Zavaleta, N., Shankar, A. H., and Merialdi, M. (1998). Potential contribution of maternal zinc supplementation during pregnancy to maternal and child survival. Am. J. Clin. Nutr., 68(Suppl), 499S–508S. Cebra, J. J. (1999). Influences of microbiota on intestinal immune system development. Am. J. Clin. Nutr., 69(Suppl), 1046S– 1051S.
471
Cederqvist, L. L., Ylikorkala, F. O., Ekelun, L., Tuimala, R., and Litwin, S. D. (1978). Fetal immunoglobulin production following prenatal glucocorticoid treatment. Obstet. Gyn., 52, 539–541. Chandra, R. K. (1975). Fetal undernutrition and postnatal immunocompetence. Am. J. Dis. Child, 129, 450–454. Coe, C. L. (1993). Psychosocial factors and immunity: a review. Psychosomat. Med., 55, 298–308. Coe, C. L., Cassayre, P., Levine, S., and Rosenberg, L. T. (1988a). Effects of age, sex, and psychological disturbance on immunoglobulin levels in the squirrel monkey. Devel. Psychobio., 21, 161–175. Coe, C. L., and Crispen, H. (2000). Social stress in pregnant monkeys differentially affects placental transfer of maternal antibody to male and female infants. Health Psych., 19(6), 1–6. Coe, C. L., and Erickson, C. (1997). Stress decreases natural killer cell activity in the young monkey even after blockade of steroid and opiate hormone receptors. Devel. Psychobio., 30(1), 1–10. Coe, C. L., Kemnitz, J. W., and Schneider, M. L. (1993). Vulnerability of placental antibody transfer and fetal complement synthesis to disturbance of the pregnant monkey. J. Med. Primat., 22, 294–300. Coe, C. L., Kramer, M., Czeh, B., Gould, E., Reeves, A. J., Kirschbaum, C., and Fuchs, E. (2003). Prenatal stress diminishes neurogenesis in the dentate gyrus of juvenile rhesus monkeys. Biol. Psychiat., 54(10), 1025–1034. Coe, C. L., Kramer, M., Kirschbaum, C., Netter, C., and Fuchs, E. (2002). Prenatal stress diminishes cytokine production after an endotoxin challenge and induces glucocorticoid resistance in juvenile rhesus monkeys. J. Clin. Endocr. Metab., 87, 675–681. Coe, C. L., and Lubach, G. R. (2005). Developmental consequences of antenatal dexamethasone treatments in nonhuman primates. Neurosci. BioBehav. Rev., 29, 227–235. Coe, C. L., Lubach, G. R., Ershler, W. B., and Klopp, R. G. (1989). Effect of early rearing on lymphocyte proliferation responses in rhesus monkeys. Brain Behav. Immun., 3, 47–60. Coe, C. L., Lubach, G. R., and Izard, K. M. (1994). Progressive improvement in the transfer of maternal antibody across the Order Primates. Am. J. Primat., 32(1), 51–55. Coe, C. L., Lubach, G. R., and Karaszewski, J. (1999). Prenatal stress and immune recognition of self and nonself in the primate neonate. Biol. Neonate, 76, 301–310. Coe, C. L., Lubach, G. R., Karaszewski, J., and Ershler, W. B. (1996). Prenatal endocrine activation influences the postnatal development of immunity in the infant monkey. Brain Behav. Immun., 10, 221–234. Coe, C. L., Lubach, G. R., Schneider, M. L., Dierschke, D. J., and Ershler, W. B. (1992). Early rearing conditions alter immune responses in the developing infant primate. Pediatrics, 90(3), 505–509. Coe, C. L., Rosenberg, L. T., and Levine, S. (1988b). Effect of maternal separation on the complement system and antibody responses in infant primates. Intern. J. Neurosci., 40, 289–302. Coe, C. L., Rosenberg, L. T., and Levine, S. (1988c). Prolonged effect of psychological disturbance on macrophage chemiluminesence in the squirrel monkey. Brain Behav. Immun., 2, 151–160. Conner, J. R. (1994). Iron acquisition and expression of iron regulatory proteins in the developing brain: manipulation by ethanol exposure, iron deprivation, and cellular dysfunction. Devel. Neurosci., 16, 233–247. Coussons-Read, M., Okun, M., and Simms, S. (2003). The psychoneuroimmunology of pregnancy. Brain Behav. Immun., 21(2), 103–112. Culhane, J. F., Rauh, V., McCollum, K. F., Elo, I. T., and Hogan, V. (2002). Exposure to chronic stress and ethnic differences in rates
472
III. Behavior and Immunity
of bacterial vaginosis among pregnant women. Am. J. Obstet. Gynecol., 187(5), 1272–1276. Dammann, O., and Leviton, A. (1997). Maternal intrauterine infection, cytokines and brain damage in the preterm newborn. Pediat. Res., 42, 1–8. Devereux, G., Seaton, A., and Barker, R. (2001). In utero priming of allergen specific helper T cells. Clin. Exp. Allerg., 31, 1686–1695. Dhabhar, F. S., and McEwen, B. S. (1999). Enhancing versus suppressive effects of stress hormones on skin immune function. Proc. Nat. Acad. Sci. USA, 96(3), 1059–1064. Di Naro, E., Cromi, A., Ghezzi, F., Raio, L., Uccella, S., D’Addario, V., and Loverra, G. (2006). Fetal thymic involution: A sonographic marker of the fetal inflammatory response syndrome. Am. J. Obstet. Gynelcol., 194, 153–159. Erb, K. J. (1999). Atopic disorders: a default pathway in the absence of infection. Immunol. Today, 20(7), 317–322. Ferguson, D. M., Crane, J., Beasely, R., and Horwood, N. (1997). Perinatal factors and atopic disease in childhood. Clin. Exp. Allerg., 27, 1394–1401. Freitas, A. A., and Rocha, B. B. (1993). Lymphocyte lifespans: homeostasis, selection, and competition. Immunol. Today, 14(1), 25–34. Gabant, P., Forrester, L., Nichols, J., Van Reeth, T., De Mees, C., Pajack, B., Watt, A., Smitz, J., Alexandre, H., and Szpirer, J. (2002). Alpha-fetoprotein, the major fetal serum protein, is not essential for embryonic development but is required for female fertility. Proc. Nat. Acad. Sci. USA, 99(20), 12865–12870. George, A. J. T., and Ritter, M. A. (1996). Thymic involution with aging: obsolescence or good housekeeping. Immunol. Today, 17, 267–272. Gervasi, M. T., Chaiworapongsa, T., Pacora, P., Naccasha, N., Yoon, B. H., Maymon, E., and Romero, R. (2001). Phenotypic and metabolic characteristics of monocytes and granulocytes in preeclampsia. Am. J. Obstet. Gynecol., 185(3), 792–797. Gilmore, J. H., Jarskog, L. F., Vadlamudi, S., Lauder, J. M. (2004). Prenatal infection and risk for schizophrenia: IL-1β, IL-6, and TNFα inhibit cortical neuron dendrite development. Neuropsychopharmacology, 29, 1221–1229. Gonik, B. (1994). Viral diseases in pregnancy. New York: Springer. Godfrey, D. I., Purton, J. F., Boyd, R. L., and Cole, T. J. (2000). Stress T cell development glucocorticoids are not obligatory. Immunol. Today, 21(12), 606–610. Granger, D. A., Hood, K. E., Dreschel, N. A., Sergeant, E., and Likos, A. (2001). Developmental effects of early immune stress on aggressive, socially reactive, and inhibited behaviors. Devel. Psychopath., 13, 599–601. Grossman, C. (1989). Possible underlying mechanisms of sexual dimorphism in the immune response, fact and hypothesis. J. Steroid Biochem., 34, 241–251. Gust, D. A., Gordon, T. P., and Wison, M. E. (1992). Removal from the natal social group to peer housing affects cortisol levels and absolute numbers of T cell subsets in juvenile rhesus monkeys. Brain Beh. Evol., 6(6), 189–199. Hammar, J. A. (1921). The new views as to the morphology of the thymus gland and their bearing on the problem of the function of the thymus. Endrocrinol., 5, 543–573. Harris, J. W. (1919). Influenza occurring in pregnant women. JAMA, 72(14), 978–980. Hasselbalch, H., Engelmann, M. D. M., Ersbool, A. K., Jeppesen, D. L., and Michaelsen, K. F. (1999). Breast feeding influences thymic size in late infancy. Eur. J Pediatr., 158, 964–967. Hendrickx, A. G., Sawyer, R. H., Terrell, T. G., Osburn, B. I., Henrickson, R. B., and Steffek, A. J. (1975). Teratogenic effects of triamcinolone on the skeletal and lymphoid systems in nonhuman primates. Fed. Proc., 34(8), 1661–1665.
Herz, U., Joachi, R., Ahrens, B., Scheffold, A., Radbruch, A., and Renz, H. (2001). Allergen sensitization and allergen exposure during pregnancy favor the development of atopy in the neonate. Intern. Arch. Allerg. Immunol., 124, 193–196. Hillier, S. L. (2005). The complexity of microbial diversity in bacterial vaginosis. N. Engl. J. Med., 353, 1886–1887. Hodgson, D. M., Knott, B., and Walker, F. R. (2001). Neonatal endotoxin exposure influences HPA responsivity and impairs tumor immunity in Fischer 344 rats in adulthood. Pediat. Res., 50, 750–755. Hooper, L. G., and Gordon, J. I. (2001). Commensal host-bacteria relationships in the gut. Science, 292, 1115–1118. Hosking, C. S., and Robertson, D. M. (1983). Epidemiology and treatment of hypogammaglobulinemia. Birth Defects, 19, 223–227. Irving, W. L., James, D. K., Stepheson, T., et al. (2000). Influenza virus infection in the second and third trimesters of pregnancy: a clinical and seroepidemiological study. B. J. Obset. Gynecol., 107, 1282–1289. Jeppesen, D. L. (2003). The size of the thymus: an important immunological diagnostic tool. Acta Paediat., 92(9), 994–996. Karmaus, W., Arshad, H., and Mattes, J. (2001). Does the sibling effect have its origin in utero? Investigating birth order, cord blood immunoglobulin E concentration and allergen sensitization at age 4 years. Am. J. Epidemiol., 154, 909–915. Kay, G., Tarcic, N., Polyrevt, T., and Weinstock, M. (1998). Prenatal stress depresses immune function in rats. Physiol. Behav., 63(3), 397–402. Kelley, K. W. (1980). Stress and immune function: a bibliographic review. Ann. Rech. Vet., 11, 445–478. Kendall, M. D., Johnson, H. R., and Singh, J. (1980). The weight of the human thymus at necropsy. J. Anat., 131, 483–497. Klein, S. L., and Rager, D. R. (1995). Prenatal stress alters immune function in the offspring of rats. Devel. Psychobiol., 28, 321– 326. Kohler, P. F., and Farr, R. S. (1966). Elevation of cord over maternal IgG immunoglobulin: evidence for an active placental IgG transport. Nature, 210, 1070–1071. Labbok, M. H., Clark, D., and Goldman, A. S. (2004). Breast-feeding: maintaining an irreplaceable immunological resource. Nature Rev., 4, 565–571. Laudenslager, M. L., Held, P. E., Boccia, M. L., Reite, M. L., and Cohen, J. J. (1990). Behavioral and immunological consequences of brief mother-infant separation. A species comparison. Devel. Psychobio., 23(3), 247–264. Laudenslager, M. L., Reite, M. R., and Harbeck, R. J. (1982). Suppressed immune response in infant monkeys associated with maternal separation. Behav. Neural Biol., 36, 40–48. Lemaire, V., Koehl, M., Le Moal, M., and Abrous, D. N. (2000). Prenatal stress produces learning deficits associated with an inhibition of neurogenesis in the hippocampus. Proc. Nat. Acad. Sci. USA, 97(20), 11032–11037. Loibichler, C., Pichler, J., Gerstmayr, M., Bohle, B., Kiss, H., Urbanke, R., and Szepfalusi, Z. (2002). Materno-fetal passage of nutritive and inhalant allergens across placentas of term and preterm deliveries infused in vitro. Clin. Exp. Allergy, 32, 1546–1551. Lonnerdal, B., and Dewey, K. G. (1995). Epidemiology of iron deficiency in infants and children. Ann. Nestle, 53, 11–17. Lozoff, B., Klein, N. K., Nelson, E. C., McClish, D. K., Manuel, M., and Chacon, M. E. (1998). Behavior of infants with irondeficiency anemia. Child Devel., 69, 24–36. Lubach, G. R., Coe, C. L., and Ershler, W. B. (1995). Effects of the early rearing environment on immune responses of infant rhesus monkeys. Brain Behav. Immun., 9, 31–46.
21. Developmental Antecedents of Immunity Machado-Neto, R., Graves, C. N., and Curtis, S. E. (1987). Immunoglobulins in piglets from sows heat-stressed prepartum. J. Anim. Sci., 65, 445–455. Mackall, C. L., and Gress, R. E. (1997). Thymic aging and T cell regeneration. Immunol. Rev., 160, 91–102. MacLean, M., and Smith, R. (2001). Corticotrophin releasing hormone and human parturition. Reprod., 121, 493–501. Makhsee, M., Raghupathy, R., Azizieh, F., Omu, A., Al-Shamli, E., and Ashkanani, L. (2001). Th1 and Ths cytokine profiles in recurrent aborters with successful pregnancy and with subsequent abortions. Hu. Reprod., 10, 2219–2226. Mazmanian, S. K., Lui, C. H., Tzianabos, A. O., and Kasper, D. L. (2005). An immunomodulatory molecule of symbiotic bacteria directs maturation of the host immune system. Cell, 122, 107–118. McDade, T. W., Beck, M. A., Kuzawa, C. W., and Adair, L. S. (2001). Prenatal undernutrition and postnatal growth are associated with adolescent thymic function. J. Nutr., 131, 1225–1235. Meyer, R. J., and Haggerty, R. J. (1962). Streptococcal infections in families. Factors altering individual susceptibility. Pediatrics, 29, 539–549. Mrazek, D. A., Klinnert, M. D., Mrazek, P., and Macey, T. (1991). Early asthma onset: consideration of parenting issues. J. Am. Acad. Child Adol. Psychiat., 30, 277–282. O’Callaghan, E., Sham, P., Takei, N., et al. (1991). Schizophrenia after prenatal exposure to 1957 A2 influenza epidemic. Lancet, 337, 1248–1250. O’Grady, M. P., and Hall, N. R. S. (1991). Long term effects of neuroendocrine-immune interactions during early development. In Psychoneuroimmunology (Ader and Cohen, Eds, 2nd ed., pp. 561–572). New York: Academic Press. Olsen, N. J., and Kovacs, W. J. (2001a). Effects of androgens on T and B lymphocyte development. Immunol. Res., 23, 281– 288. Olsen, N. J., Olson, G., Viselli, S. M., et al. (2001b). Androgen receptors in thymic epithelium modulate thymus size and thymocyte development. Endocrinology, 142, 1278–1283. Papadogianniakis, N., Svend-Aage, J., and Olding, L. B. (1990). Suppressor cell activity in cord blood. In G. Chaouat (Ed.), The immunology of the fetus (pp. 215–227). Boca Raton, FL: CRC Press. Pekkanen, J., Xu, B., and Jarvelin, M. R. (2001). Gestational age and occurrence of atopy at age 31—a prospective birth cohort study in Finland. Clin. Exp. Allerg., 31, 95–102. Piccinni, M. P., Mecacci, F., Sampognaro, S., et al. (1993). Aeroallergen sensitization can occur during fetal life. Int. Arch. Allergy Immun., 102, 301–303. Raghupathy, R. (1997). Th1-type immunity is incompatible with successful pregnancy. Immunol. Today, 18(10), 478–482. Rai, R., Sacks, G., and Trew, G. (2005). Natural killer cells and reproductive failure-theory, practice and prejudice. Hu. Reprod., 20(5), 1123–1126. Reyes, T. M., and Coe, C. L. (1997). Prenatal manipulations reduce the pro-inflammatory response to a cytokine challenge in juvenile monkeys. Brain Res., 769, 29–35. Rounioja, S., Rasanen, J., Ojaniemi, M., Glumoff, V., AutioHarmainen, H., and Hallman, M. (2005). Mechanism of acute fetal cardiovascular depression after maternal inflammatory challenge in mouse. Am. J. Pathol., 166(6), 1585–1592. Sacedon, R., Vicente, A., Varas, A., et al. (1999). Early differentiation of thymic dendritic cells in the absence of glucocorticoids. J. Neuroimmunol., 94, 103–108. Sacks, G., Sargent, I., and Redman, C. (1999). An innate view of human pregnancy. Immunol. Today, 2, 114–118.
473
Savino, W., and Dardenne, M. (2000). Neuroendocrine control of thymus physiology. Endocr. Rev., 21, 412–443. Sawyer, R, Hendrickx, A., Osburn, B., and Terrell, T. (1977). Abnormal morphology of the fetal monkey (Macaca mulatta). thymus exposed to a corticosteroid. J. Med. Primatol., 6, 145–150. Sayer, A. A., Cooper, C., and Barker, D. J. P. (1997). Is lifespan determined in utero? Arch. Dis. Childhood, 77(3), F162– F164. Seiki, K., and Sakabe, K. (1977). Sex hormones and the thymus in relation to thymocyte proliferation and maturation. Arch. Histol. Cytol., 60, 29–38. Selye, H. (1956). The stress of life. New York: McGraw Hill. Selye, H., and Marion, D. (1955). Direct thymolytic effect of hexestrol (oestrogen). Acta Anat., 23, 180–184. Shanks, N., Larocque, S., and Meaney, M. J. (1995). Neonatal endotoxin exposure alters the development of the hypothalamicpituitary-adrenal axis: early illness and later responsivity to stress. J. Neurosci., 15(1), 376–384. Shi, L., Fatemi, S. H., Sidwell, R. W., and Patterson, P. H. (2003). Maternal influenza infection causes marked behavioral and pharmacological changes in the offspring. J. Neurosci., 23(1), 297–302. Siiteri, P., and Stites, D. P. (1982). Immunologic and endocrine interrelationships in pregnancy. Biol. Reprod., 26, 1–14. Slukvin, I., Boyson, J. E., Watkins, D. I., and Golos, T. G. (1998). The rhesus monkey analogue of human lymphocyte-antigen-G is expressed primarily in villous syncytiotrophoblasts. Biol. Reprod., 58, 728–738. Sobrian, S. K, Vaughn, V. T., Bloch, E. F., and Burton, L. E. (1992). Influence of prenatal maternal stress on the immunocompetence of the offspring. Pharm. Biochem. Behav., 43, 537–547. Solomon, G. F., Levine, S., and Kraft, J. K. (1968). Early experience and immunity. Nature, 220, 821–822. Takahashi, L. K. (1998). Prenatal stress: consequences of glucocorticoids on hippocampal development and function. Int. J. Dev. Neurosci., 16(3–4), 199–207. Tomasi, T. B. (1977). Structure and function of alpha-fetoprotein. Ann. Rev. Med., 28, 453–465. Trainin, N. (1974). Thymic hormones and the immune response. Physiol. Rev., 54, 272–315. Urakubo, A., Jarskog, L. F., Lieberman, J. A., and Gilmore J. H. (2001). Prenatal exposure to maternal infection alters cytokine expression in the placenta, amniotic fluid, and fetal brain. Schizo. Res., 47, 27–36. Van Duren Schmidt, K., Pichler, J., Ebner, C., et al. (1997). Prenatal contact with inhalant allergens. Pediat. Res., 41, 128–131. Veenstra van Nieuwenhoven, A. L., Bouman, A., Moes, H., Heineman, M. J., de Leij, L. F., Santema, J., and Faas, M. M. (2002). Cytokine production in natural killer cells and lymphocytes in pregnant women compared with women in the follicular phase of the ovarian cycle. Fertil. Steril., 77(5), 1032–1037. Wadhwa, P. D., Sandman, C. A., and Garite, T. J. (2001). The neurobiology of stress in human pregnancy: implications for prematurity and development of the fetal central nervous system. Prog. Brain Res., 133, 131–142. Warner, J. A., Jones, C. A., Jones, A. C., and Warner, J. O. (2000). Prenatal origins of allergic disease. J. Allerg. Clin. Immunol., 105, 5493–5496. Wegmann, T. G., Lin, H., Guilbert, L., and Mosmann, T. R. (1993). Bidirectional cytokine interactions in the maternal-fetal relationship: is successful pregnancy a Th2 phenomenon? Immunol. Today, 14(7), 353–356.
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III. Behavior and Immunity
Weinberg, J., and Jerrells, T. (1991). Suppression of immune responsiveness: sex differences in prenatal ethanol effects. Alcoholism: Clin. Exp. Res., 15(3), 523–531. Weinstock, M. (1997). Does prenatal stress impair coping and regulation of hypothalamic-pituitary-adrenal axis? Neurosci. Biobehav. Rev., 21(1), 1–10. Wenzyl, H. H., Schimpl, G., Feierl, G., and Steinwender, G. (2003). Effect of prenatal corticosterone on spontaneous bacterial translocation from gastrointestinal tract in neonatal rat. Digest. Dis. Sci., 48, 1171–1176.
Wright, R., Cohen, R. T., and Cohen, S. (2005). The impact of stress on the development and expression of atopy. Current Opin. Allerg. Clin. Immunol., 5(1), 23–29. Yazdanbakhsh, M., Kremsner, P. G., and van Ree, R. (2002). Allergy, parasites, and the hygiene hypothesis. Science, 296, 490–494. Yorty, J. L., and Bonneau, R. H. (2004). Prenatal transfer of low amounts of herpes simplex virus (HSV)-specific antibody protects newborn mice against HSV infection during acute maternal stress. Brain Behav. Immun., 18, 15–23.
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22 Social Dominance and Immunity in Animals MARK L. LAUDENSLAGER AND SARAH KENNEDY
I. INTRODUCTION 475 II. ANIMAL MODELS 476 III. AN OVERVIEW OF AGGRESSION AND DOMINANCE RELATIONSHIPS 477 IV. DOMINANCE RELATIONSHIPS IN RODENTS 479 V. DOMINANCE RELATIONSHIPS IN NON-HUMAN PRIMATES 482 VI. DOES DOMINANCE MATTER? 491
tive social interaction in humans is observed as well among the non-human primates and can mitigate the negative consequences of social and environmental challenges. It is no longer possible to take simplistic approaches to behavior-immune relationships. A comprehensive view needs to include the underlying factors that contribute to observed error variance. The best victory is when the opponent surrenders of its own accord before there are any actual hostilities. . . . It is best to win without fighting. Sun-tzu “The Art of War” Chinese general and military strategist (∼400 B.C.)
ABSTRACT Similar stressors do not produce similar responses in an organism. The social organization of many mammalian species creates dominance hierarchies, which may or may not affect immunoregulation and neuroendocrine regulation, particularly for the glucocorticoids in response to environmental challenge. Not only can relative rank within a group affect these relationships, but individual differences in behavioral styles or personality also enter heavily into the equation. These relationships have been studied extensively in rodents and non-human primates for over a decade and are the focus of the present chapter. This chapter will review the nature of dominance relationships and aggressive behavior(s) across species and their relationships to glucocorticoids and immune measures. Although there is advantage to high rank such as priority of access to preferred or restricted resources (e.g., food and mates), it has the potential to carry with it occasional consequences. The essential role for posiPSYCHONEUROIMMUNOLOGY, 4E VOLUME I
I. INTRODUCTION Over a decade ago we noted that the reduction in specific antibody of an intruder rat was directly related to its behavior; e.g., did it fight back or show the residents a submissive response such as exposing highly vulnerable surfaces (Fleshner, Laudenslager, Simons, and Maier, 1989)? Signaling submission or defeat was associated with reduced specific antibody responses, whereas those intruders that fought back had antibody responses that were similar to controls exposed to the residents with a Plexiglas barrier between them, but without physical contact. The wisdom of Sun-tzu may have been lost among rodents as far as immune regulation of the defeated is concerned. If a number of individuals experience the same stressor or challenge under a common set of condi-
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tions, the observed impact of that event on the individual’s behavior and physiology is not necessarily consistent across individuals. The average response across a number of individuals is encompassed by a large confidence interval that most investigators would like to minimize. However, it is this variability in behavioral and physiological response patterns that will provide clues to the underlying organization of the system once the factors contributing to the variance are identified. There will always be factors out of our grasp, yet small steps in identifying any contribution to experimental variance are critical to the advancement of psychoneuroimmunology (PNI). In the present chapter, we will consider the influences of aggression and dominance or hierarchical relationships in rodents and non-human primates on endocrine and immune systems that are associated with individual and species survival. Although this chapter is not to be considered as comprehensive in coverage, we have attempted for the most part to focus on developments since the previous edition of Psychoneuroimmunology (Ader, Felten, and Cohen, 2001). The present chapter attempts to cover several areas. For example, is the dominant member of a dyad of a social group always in a more advantageous position compared to the lower-ranking member? High rank carries with it certain privileges. However noblesse oblige and higher social rank may be burdened with untoward side effects. The contributions of individual differences preclude simple descriptions of critical factors and their role in immunomodulation. We will focus on one of many potential endocrine mechanisms, the glucocorticoids, which may be related to immune modulation in association with dominance-related stressors that occur both acutely and chronically. Can animal models inform our understanding of brain-behaviorphysiology relationships in general and PNI more specifically?
II. ANIMAL MODELS A detailed empirical study of biological mechanisms underlying immune dysregulation in association with psychosocial stress, aging, affective disorders, cancer, autoimmune disorders, and many other medical conditions may not always be achievable in humans. The social situation of humans cannot be easily controlled; that is, we cannot experimentally introduce acute stressors (e.g., loss of a job) or set up situations of long-term stress in humans (e.g., poverty) for the study of underlying biological changes associated with immune dysregulation. Hence, animal models have an important place in biomedical research
when they are conducted in a careful and humane manner. One issue to consider in regard to an animal model is related to the concept of analogous and homologous phenotypes (Laudenslager and Worlein, 1999). Two analogous phenotypes may serve the same purpose but evolve via distinctly different paths such as flight in birds, bats, and flying squirrels. Consequently, the underlying structures, physiology, and regulation may differ substantially. Homologous phenotypes have similar etiologies from an evolutionary perspective and thus possess more common underlying mechanisms. Human and non-human primates share common evolutionary origins, and, as such, should reflect many homologous processes with regard to behavior-immune relationships. There are 320 identified primate species and perhaps as many as 600 subspecies. With regard to cross-species comparisons, it has been stated “. . . every living primate is literally more like a human than it is like any other living nonprimate animal. While humans share many conserved characteristics with the nonprimates, human characteristics that were derived during their evolution are homologous only with those of other primates . . .” (Erwin and Hof, 2002, p. viii). However, animal studies among the lower species do in fact inform the higher species by providing mechanistic clues when homologous processes might be involved. Some ethologists, notably Robert Hinde (1987), are quick to caution us that there are many examples wherein the non-human primate model may differ from the human condition and one must use “. . . humility . . .” in comparing non-human primates to humans, and to be careful not to focus on too narrow a perspective (e.g., a single species). According to Hinde, human/non-human primate comparisons must be drawn carefully with a full appreciation for the complexities of human emotions. When we speak of aggression in humans, we must address complex human emotions like jealousy, vengeance, and so on. Regardless, principles that generalize across several species are most likely to inform theory regarding their underlying mechanisms. The study of non-human primate social behavior began less than a century ago with studies of baboons in captivity (Zuckerman, 1932). Observations in captivity do not always mirror responses that might be noted under free-ranging situations. The semi–freeranging rhesus monkeys of Cayo Santiago, Puerto Rico, were introduced to this 17 hectare island as a research colony for the specific study of primate behavior by C.R. Carpenter in 1938 (Rawlins and Kessler, 1986). We will return to our studies on the Cayo Santiago population later in this chapter. The develop-
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ment of computer-assisted behavioral data collection techniques (Noldus, 1991) has not only improved the quality of data that can be collected, but it has also increased observational reliability. However, nonhuman primate models also have some limitations with regard to sample size and accessibility in naturalistic settings. Animal models permit a level of control in research not always possible in studies involving humans. The life span of many animals used as model systems is far shorter than that of humans. In non-human primates, this allows for longitudinal studies encompassing the prenatal period, early development, adolescence, adulthood, and old age within the same cohort. If one is focused on rodent models, their life span is much shorter, ranging from 24–36 months, compared to nonhuman primates that might span as much as two to three decades for macaque species maintained in captivity (Erwin and Hof, 2002). In contrast, the great apes practically match humans in terms of longevity. Four criteria specify the essentials of a valid animal model with regard to psychopathology (McKinney and Bunney, 1969). These criteria include similarities in etiology, phenomenology, pathophysiology, and treatment. Specific animal models serve different purposes. For example, rodent models allow for larger sample sizes and permit microanalysis of relevant neurochemical (CNS localization studies, receptor-binding studies, endocrine control) and immunological (trafficking patterns within immune compartments or challenge with infectious agents) systems generally not available for study in human or non-human primates. However, there are exceptions that we will discuss later. Animal models actually form bi-directional relationships with the human condition (McGuire, Brammer, and Raleigh, 1983) in that human observations can inform the animal model. Homology implies that one is studying similar processes that have a shared phylogenetic basis (McGuire et al., 1983). This will be reflected in similar underlying anatomy and physiology. As behavioral scientists, we ask if seemingly similar behaviors serve the same underlying function in rodents and non-human primates. Does subordinance for a rodent have the same implications as subordinance for a non-human primate? Is subordinance in laboratory settings a feature of rodent behavior that is commonly seen in nature? Rodents do not typically have repeated social interactions with the same dominant rodent (a typical laboratory model of social dominance); instead, they take appropriate measures to escape the situation and move to a safer but less appealing nesting location. These features should be kept in mind as we describe the impact of social interactions in both rodent and non-
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human primates. However, observations of speciesspecific social signals in rodents associated with dominance and submission suggest that these interactions do occur, and behavior plays an important role in modulating interactions between the members of the dyad. In the present chapter we attempt to draw parallels between social dominance hierarchies and dominancerelated behaviors across two orders, rodents and primates. The attention herein is not to focus specifically on models of psychiatric disorders but rather indicate the extent to which low social rank or subordinance contributes to long-term stress and increased risk for medical illness as mediated by immune dysregulation.
III. AN OVERVIEW OF AGGRESSION AND DOMINANCE RELATIONSHIPS We will begin by carefully specifying what we are referring to when we refer to aggression, dominance, and dominance hierarchies. Aggression is a term that is frequently used in the discussion of dominance and dominance relationships. Aggression represents a wide range of overlapping behaviors that serve one of two purposes: resource/territorial competition or defense. Aggression can be induced by a variety of conditions but generally by threat from an intruder/ aggressor. Examples of laboratory conditions that can elicit aggression include foot shock (painful stimulus) or schedule-induced aggression (frustration). Archer (1988) distinguishes three types of aggression: (1) Protective Aggression (attack by conspecific, attack by a predator, sudden pain, territorial intrusion), (2) Parental Aggression (protection of the offspring and a more neglected form of aggression as far as research is concerned), and (3) Competitive Aggression (to gain a territory, reproduction, resources; most studied aspect). Protective and competitive aggression are involved in situations reflecting dominance interactions and are the focus of this chapter. There are significant variations in aggressive displays. For example, across the primate order: lemurs “stink fight” by rubbing pheromonal secretions to their forearms; male squirrel monkeys display an erect penis and urinate on their forearms; baboons flash eyelids showing a white streak; macaques bear their teeth; and gorillas stand upright, beating their chest while charging (Walters and Seyfarth, 1987). None of these visual displays involve actual contact, and the subsequent behavior of the engaged parties is a function of each member’s response to the other’s display. Across species when contact actually occurs, behaviors
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are more similar in characteristics and include chasing, grabbing, and biting. Infants are relatively protected from aggressive interactions since infants of many primate species possess different coloration that distinguishes them from adolescents of the species. The age at which this “shield” ends varies across species. As the gender makeup of the group varies, the frequency of male–male interactions is affected; e.g., unimale group males will have more frequent aggressive encounters since the stakes are higher. For some species such as the squirrel money, males are outcasts from the social group until breeding season when the females “allow” them back in the troop to mate. Rodents differ from non-human primates in that physical contact is often a component of aggressive encounters. Rodent displays of aggression include offensive behaviors such as chasing (following a fleeing animal), sideways attacks, mounting attempts (distinguished from mating behavior by the absence of pelvic thrusts), and biting. In contrast, defensive behaviors include displaying a defensive upright posture, fleeing, boxing, and a decrease in time spent in open or vulnerable locations (for a review, see Blanchard, Wall, and Blanchard, 2003). Aggressivity in male rodents can be encouraged by housing with female rats, which increases territorial aggression, whereas male rats housed only with male rats appear to form more equitable social structures. Female rats and mice tend to be less aggressive toward other females, with some exceptions. Species differences are considerable. Female golden hamsters, which may be aggressive towards cohort members during adolescence, will subjugate younger females in adulthood (Taravosh-Lahn and Delville, 2004). In the common voles, adult females maintain dominance over their daughters (Heise and Van Acker, 2000). In many respects, dominance structures of rodents are limited by the number of possible interactions that occur in a short period of time. Dominance is a learned relationship (Bernstein, 1981), not an absolute attribute of an individual. It is always in reference to another individual. Thus, dominance is referred to as regularities in winning or losing fights (Archer, 1988; Bernstein, 1981). The history of the relationship is not the only factor that will determine dominance relationships among members of a social group. Factors such as size, age, matrilines (many primate species are organized along maternal or matrilineal ancestry), experience, and gender are all critical in the resolution of dominance interactions. A dominance relationship may change with time (e.g., age) or repeated encounters. Dominance is a dynamic process between individuals. Once a dominance relationship is established, there will be an energetic savings. Injuries are avoided, and the energy
required for a fight is minimized as well as a stress response. A dominance relationship develops between two animals during their first encounter, when both animals begin by evincing similar agonist behaviors, but ensuing responses of one animal may result in the termination of further agonistic behaviors by the other (see Bernstein, 1981). The termination might be signified by species-specific indications of subordinance or defeat. There are clear visual signals sent by dominant and subordinate animals. These signals are particularly important for non-human primates that live in social groups. These serve to reduce the number of actual fights in which an injury might occur. For example in male rhesus monkeys, an erect tail is a sign of a dominant male, as indicated in Figure 1. In a social group in which there was a previously established dominance hierarchy and a lower-ranking animal is threatening a rank reversal, escalated aggression might occur. In macaque monkeys, a dyadic interaction might begin as a facial gesture where the lower-ranking animal may simply lip smack and move away. A subsequent threat follows if the first gesture is not effective. Baring the teeth might indicate this, or one animal might lunge at the other without making contact. If neither animal backs down, the next lunge might be accompanied by actual contact and grabbing. If both contestants continue to hold firm, the grabbing will escalate to holding the opponent down and ultimately biting. Departures from the area or relinquish-
FIGURE 1 A high-ranking adult male rhesus monkey on Cayo Santiago, with its rank distinguished clearly by an erect vertical tail.
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ing the valued resource will ultimately terminate the agonistic interaction of the dyad. There are well-established neurochemical correlates (e.g., CNS serotonergic activity) associated with these aggressive challenges and how they are expressed (Mehlman et al., 1994). The animal remaining in the territory, the “winner,” is considered to be in control of a highly valued or preferred resource and is dominant to the departing, or “loser,” animal. Dominance relationships can be linear or transitive. In a linear relationship, A defeats B and B defeats C and C is always subordinate to A. A non-linear relationship occurs if C defeats A. Among primates, these contests are not always straightforward. Rank reversals frequently occur within the middle ranks where the distinctions are much less clear. Coalitions may form between two members of a troop that result in displacing a higher-ranking animal. Highly preferred resources are typically monopolized by the higherranking animals, particularly in times of scarcity. An interesting observation of displacement of a highranking animal from a preferred food resource was described by John Capitanio (personal communication) in which a lower-ranking macaque began a fight with two other monkeys while the high-ranking monkey was monopolizing a preferred resource in their field cage. The high-ranking animal left the resource to join in the fight at which point the lowerranking animal that started the fight moved to the preferred resource, while the higher-ranking animal continued to fight with the two animals remaining in the dispute. What starts an agonistic interaction has been intensively studied, although recent attention has turned to what terminates these interactions (De Waal, 2000). De Waal has argued that it is equally important to understand what modulates the intensity of these interactions and controls the end of these encounters. What happens between these two primates when they encounter each other again (which is highly probable in socially living species)? The subsequent encounters are often described in terms of conflict resolution and reconciliation. Other dimensions are added when the alpha male in a social group breaks up a fight between two females in the group. Socially grouped non-human primates provide a wealth of interactions not available to individually or even pair-housed monkeys. This was clearly recognized by researchers in the 1960s who formed social groups of macaque monkeys for the study of mother-infant relationships (Kaufman and Rosenblum, 1966), going beyond the earlier work of Harlow (Harlow, Harlow, Dodsworth, and Arling, 1966; Harlow and Zimmermann, 1958). The rich and complex connections existing in social species have
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been used as a means of understanding relationships between dominance status and various indications of immunoregulation. How do dominance relationships influence immune and health outcomes in rodents and non-human primates?
IV. DOMINANCE RELATIONSHIPS IN RODENTS Several models have been used to assess rodent social interactions and influence dominance interactions. One ethologically relevant model is the visible burrow system (Blanchard et al., 1995; Blanchard, McKittrick, and Blanchard, 2001; Tamashiro et al., 2004). The visible burrow apparatus consists of an open field connected to several smaller chambers by a series of tunnels. Typically, four male and two female rats are housed in the visible burrow; eventually, one male rat will become dominant over the other males. Dominant rats are distinguished behaviorally by increased time in open spaces, more aggressive behaviors, fewer wounds, and maintenance of body weight despite social stress (Blanchard et al., 1995; Blanchard, McKittrick et al., 2001). Dominant rodents are considered “proactive” in that they are more likely to attack and wound another rodent in an unstable social situation (Ebner, Wotjak, Landgraf, and Engelmann, 2005), and they will be the “winner” of these agonistic interactions (Stefanski, 1998; Stefanski, Knopf, and Schulz, 2001). The nature of this proactive activity can be used to measure the aggressive tendencies of an animal. For example, a proactive animal displays a shorter attack latency (SAL) (Koolhaas et al., 1999). Conversely, subordinate animals are “losers” of agonistic interactions and display a “reactive” coping style (Blanchard, Yudko, Dulloog, and Blanchard, 2001; Ebner et al., 2005; Koolhaas et al., 1999). Instead of instigating fights, subordinate animals will display more submissive/defensive upright postures, flee from aggressive animals, and show a lack of exploratory behavior. Defeat behaviors in rodents often include exposure of vulnerable surfaces (e.g., the dorsum) to the attacker, which signals defeat and often ends attack by the dominant animal. When they flee, bites and wounds occur predominantly on the back and neck. A delay in attack behavior denotes animals as having a long attack latency (LAL) (Koolhaas et al., 1999). Subordinates will have wound patterns targeted to their back and tail, and a rapid and sustained weight loss of up to 15% body weight over a 2-week period during establishment of a social hierarchy (Tamashiro et al., 2004). Subordinate rats will have basal corticosterone levels elevated in comparison to dominant rats.
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However, as has been noted in non-human primates, not all subordinate rodents are equivalent with regard to glucocorticoid modulation. Following an acute stressor, a smaller proportion of the subordinate animals will actually develop glucorticoid resistance, and fail to secrete a higher amount of corticosterone in response to an acute stressor, as seen in the dominant or control animals (Blanchard, Yudko et al., 2001; Tamashiro et al., 2004). Additional hormonal differences can be found after subdividing subordinate rodents into subdominant or submissive based on their behavior during the interaction. Using the social disruption model of social stress, an aggressive intruder rodent is introduced into a stable social environment; that is, a group that has a long history of living together. The animals are allowed to interact for a fixed period of time, during which time one animal is reliably defeated. The animal’s response to repeated defeat can either be passive (submissive) or active (subdominant). Submissive animals appear to have given up; they are more likely to hide or lie on their ventral side exposing their vulnerable surfaces and are generally more passive. Subdominant animals still fight, but they are repeatedly defeated by dominant and some subdominant animals. These behavioral differences affect the physiology of these animals depending on their initial status, e.g., resident or intruder. Subordinate animals that were original inhabitants of the housing show an increase in body weight, but the weight of intruder subordinate animals declines (Bartolomucci et al., 2004). Since food intake was equivalent, the difference in body weight was likely secondary to differences in activity levels and other factors. This divergence between reactions to subordinance may be due to stress inducing an increase in hypothalamic-pituitary-adrenal (HPA) activity or responding via activation of the sympathetic nervous system (Bartolomucci et al., 2005; Koolhaas et al., 1999). Submissive animals have an increased concentration of glucocorticoids in their blood, whereas subdominant animals have an increase in adrenal tyrosine hydroxylase (Koolhaas et al., 1999). This corresponds to greater weight loss in intruder submissive animals, secondary to increased corticosterone, but a continued readiness for fight in the subdominant animals, as suggested by an increase in epinephrine. Mice with the lowest levels of social investigation (passive behavior) were most likely to be submissive and develop corticosterone resistance following social disruption (Avitsur, Stark, and Sheridan, 2001). Physical contact appears to be a necessary component of this, as mice protected by a mesh screen did not develop corticosterone resistance (Bailey, Avitsur, Engler, Padgett, and
Sheridan, 2004). It has yet to be established if this state of resistance is advantageous, preventing the suppressive effects of corticosterone on wound healing, or a result of reaching a failure level in adaptation or allostatic load (McEwen and Wingfield, 2003). Considering the “learned helplessness” or passive component of human depression and its association with elevations in glucocorticoids (Patten, 1999), this phenomenon requires further study. Learned helplessness in rodents can be defined as the state wherein an animal fails to learn to escape from a controllable stressful situation (typically foot shock) after prior exposure to an uncontrollable stressor. This behavioral pattern has a U-shaped relationship to corticosterone levels, whereby intermediate corticosterone levels are actually protective against learned helplessness, but high or low levels of corticosterone levels lead to deleterious consequences (Kademian, Bignante, Lardone, McEwen, and Volosin, 2005). From an evolutionary perspective, depression, or this passive approach, may be adaptive in that suppression of environmental processing may prevent processing of further negative events (Patten, 1999). For rodents raised in a laboratory setting, the social challenge of establishing a dominance hierarchy or facing an aggressive intruder can be used as either acute or chronic stressors. Housing conditions affect reactions to challenges, which will vary according to strain of rodent (social or not) (Glasper and Devries, 2005) and the conditions under which the animals were raised (singly housed, pair or sibling group, or a stable social hierarchy) (Avitsur, Stark, Dhabhar, Kramer, and Sheridan, 2003; de Jong, van der Vegt, Buwalda, and Koolhaas, 2005). The hormonal profile and immune outcome are therefore somewhat dependent upon timing of measurement and challenge. Mice in stable social groups (3 weeks without disturbance) have differences in basal corticosterone, with lowestranking mice showing the lowest corticosterone levels (Bartolomucci et al., 2005). Social disruption induces the greatest increase in corticosterone after the first session compared to the seventh in animals of all social rank (Avitsur et al., 2001; Merlot, Moze, Dantzer, and Neveu, 2004a). The increase in corticosterone is greatest on the first day of disruption because attack intensity dissipates over 7 days of social disruption, perhaps reflecting an adaptation to the challenge and establishment of respective dominance relationships (Avitsur et al., 2001). It appears that subdominant animals have no change in corticosterone but a decrease in corticosteronebinding globulin (CBG), after 2 days of social conflict (Stefanski, 2001). A decrease in CBG is associated with an increase in free corticosterone, thus leading
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to a functional increase in bioactive corticosterone (Fleshner et al., 1995). Circulating epinephrine and norepinephrine are also elevated at this time-point. Adrenocorticotropic hormone (ACTH) increases in subordinate intruder rats and non-aggressive resident/dominant rats by 15 minutes after the initial social confrontation, but not in aggressive dominant residents (Ebner et al., 2005). The duration of time freezing was positively correlated with circulating ACTH. However, after 7 days of social disruption, with all animals losing to an aggressive intruder, regardless of rank, animals showed equivalent increase in corticosterone in BALB/c mice (Merlot, Moze et al., 2004a). Conversely, in Long-Evans rats, dominant males have a decrease in total corticosterone in comparison to control animals, with equivalent CBG, whereas subordinate animals in one study had equivalent corticosterone to controls, but a decrease in CBG (Stefanski, 2000). Seven days of social disruption also appeared insufficient to cause glucocorticoid resistance in all ranks of rats (Merlot, Moze et al., 2004a), as was seen in a subgroup of subordinate rats after 13 days in the visible burrow system (Blanchard et al., 1995; Tamashiro et al., 2004). Furthermore, housing for 2 weeks in a visible burrow system is insufficient to alter corticosterone receptor levels in the spleen (Spencer et al., 1996), hippocampus, hypothalamus, or pituitary (Blanchard et al., 1995), despite circulating corticosterone concentrations elevated in subordinate animals to twice those seen in dominant animals and 10 times higher than in control animals. The foregoing hormonal changes are likely to be involved in immunoregulation and immune balance, since increases in glucocorticoids are associated with a shift towards Th2 immunity (Iwakabe et al., 1998; Miyaura and Iwata, 2002). Lymphocyte profiles change in response to intruder challenges differentially based on social rank. Intruder mice that become subordinate have a decrease in white blood cell count and lymphocyte numbers, whereas granulocyte number increased in the blood by 2 hours after conflict onset. By 48 hours, only the increase in granulocytes persisted (Stefanski and Engler, 1998). When two malefemale rat pairs are housed together, a chronic, but stable, social stress situation develops with clear dominant and clear subordinate behavior patterns among the rats (Stefanski, 2000). CD4+ cells are decreased after 7 days in non-biting winners and both bitten and non-bitten losers, with no change in CD4+ count in biting winners, whereas only non-bitten losers showed a reliable decrease in CD8+ cells (Stefanski, 2000). Leukocyte numbers increased in losers that were bitten over both non-biting winners and control animals, whereas all groups except non-biting winners showed
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an increase in granulocytes. This difference in leukocyte counts may be related to hormonal changes, as wounded animals secrete higher levels of corticosterone and interleukin-6 than non-physically wounded animals (Merlot, Moze, Dantzer, and Neveu, 2003). The patterns of hormonal secretion varying with stressor type may be adaptive, as animals subjected to repeated social disruption stress, including wounding, are able to heal wounds faster than animals subjected to a similar number of the sessions of psychological stressor of restraint (Sheridan, Padgett, Avitsur, and Marucha, 2004). The nature of the stressor is quite important in the overall adaptive response of the organism. As these investigators have noted, burrow collapse (restraint) is likely a typical component of their evolutionary experience and for which adaptation might be quite different from wounding due to aggressive encounters. In vitro immune responses are affected by social interactions in rodents. Seven days of social disruption stress are associated with increases in both basal splenocyte proliferation and proliferative response to lipopolysaccharide (LPS), but proliferation in response to concanavalin A (Con A) is reduced (Merlot, Moze et al., 2004a). When subdivided by rank, only submissive animals show a decreased proliferative response to Con A, whereas subdominant animals’ response remains intact (Stefanski, 1998). This is supported by in vivo data showing that the amount of time in submissive posture correlates with suppression of antibody response to keyhole limpet hemocyanin (KLH) (Fleshner, Laudenslager et al., 1989). Following repeated social intrusion in the home environments, there were two characteristic behavior responses: fighting back and/or evincing defeat postures. Antibody titers to the KLH were lowest in the defeated animals, whereas those that fought back were similar to handled controls. A reduction in anti-KLH antibody is also evident in Syrian hamsters exposed to one or five sessions of social defeat (Jasnow, Drazen, Huhman, Nelson, and Demas, 2001). In contrast, 7 days of social disruption cause no difference in anti-KLH IgG response (Merlot, Moze et al., 2004a) or response to infection with BCG (Merlot, Moze, Dantzer, and Neveu, 2004b) compared to controls. The outcome was not divided by social rank within the stable housing groups; thus, it is unclear if mixing of social rank obscured a rank effect. Timing of social stress and immune challenge is also important, as submissive mice immunized after 2 weeks of daily 30-minute agonistic interactions show a decrease in primary antibody response to sheep red blood cells (SRBC), whereas after 3 weeks of daily antagonistic interactions, dominant mice showed an enhanced
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primary antibody response to SRBCs (Gasparotto, Ignacio, Lin, and Goncalves, 2002). Dominance in rodents may be seen as advantageous. For example, when a food competition task is used, the dominant animal repeatedly succeeds in securing the food, whereas low-ranking rats obtain the remnants or nothing at all (Merlot, Moze, Bartolomucci, Dantzer, and Neveu, 2004). However, the cost of aggressiveness may then limit resources available for other tasks such as reproduction. When animals were categorized as biting winners (most aggressive) versus non-biting winners or losers, the biting winners sexually approached females three times less often than non-biting winners, although still with greater frequency than the losing rats (Stefanski, 2000; see Sapolsky [1993] for similar observations in baboons). The role of female scent triggering aggressive behavior is well established, and exposure to female scent alone can overcome the decrease in aggressive behavior usually exhibited by mice treated with anti-thymocyte serum (Barnard, Behnke, Gage, Brown, and Smithurst, 1997). It is apparent that exposure to female scent modulates the stress response as well, as it both potentiates the heat-shock protein response to acute stress and prevents the acute-stress induced depletion in splenic norepinephrine (Kennedy and Fleshner, unpublished observations). The stimulus for becoming a hyper-aggressive animal, such as the biting winner, versus non-biting winners is yet unknown, but reinforces the idea that individual differences in personality, even in an inbred rodent model, influence reaction to stress and therefore immune outcome. Similar to observations among the rodent genera (Fleshner et al., 1989), other mammalian species show immunoregulatory changes after losing a social confrontation that are affected by individual responses to the challenge regardless of their outcome. For example, among the insectivores, when two male tree shrews (Tapaia belangeri) are housed together in a large cage for the first time, they will begin to fight immediately until one is clearly a winner of this initial fight (vonHolst, 1997). Submission after the fight may be characterized in one of two distinct patterns: (1) cowering in a corner of the cage or (2) active but alert to the location and actions of the winning tree shrew. HPA activation of the winning tree shrew returned to basal levels, while the cowering losing animal continued to show evidence of HPA activation for several weeks. In contrast, the active/alert losing subordinate showed a return to baseline within a few days. If following this initial social interaction, the two participants are housed in the same cage but with a screen between
them, the loser shows altered immune parameters including reduced lymphocyte activation by mitogens and lower interleukin-1 and interferon in the absence of further physical contact between the two animals. Across the primate order, there are clear indications of immune modulation in association with social group reorganization, but these in vitro measures may not provide the best insights into immune regulation of the intact organism (Maier and Laudenslager, 1988). In the following sections we will examine several hormonal and immune effects of social interactions driven by dominance rank that in many respects differ little from the preceding examples.
V. DOMINANCE RELATIONSHIPS IN NON-HUMAN PRIMATES The impact of dominance status for non-human primates has been investigated via several approaches in laboratory and naturalistic conditions. We will begin first with laboratory studies and move to the more difficult setting of free ranging non-human primate populations in natural or semi-naturalistic settings. These varied approaches may permit disentangling the relationship between dominance status and immune regulation and health in general. Social dominance status has been linked to reproductive maturation and regulation and HPA regulation. Focusing specifically on the HPA system, there are wide species variations in plasma cortisol levels under non-stressed basal conditions (Coe, Savage, and Bromley, 1992; Laudenslager, Bettinger, and Sackett, 2006). This makes cross-species comparisons of absolute levels a bit complicated. For example, New World primates tend to have higher steroid levels in general when compared to Old World species for total plasma cortisol levels. However, this is not always the case in that there are exceptions to this general observation: some New World species, like the titi monkey, have lower cortisol levels comparable to Old World species (Klosterman, Murai, and Siiteri, 1986; Mendoza and Moberg, 1985). One aspect affecting bio-available cortisol is the binding capacity and affinity of corticosteroid-binding globulin (CBG), both of which are lower in New World species, resulting in free levels higher than present in Old World species (Klosterman et al., 1986). In spite of these enormous differences, New World species show no physiological evidence of glucocorticoid excess (Chrousos et al., 1982; Chrousos et al., 1984). It turns out that the New World primates have a cytosolic-binding protein that inactivates the excess free cortisol (Fuller, Smith, and Rogerson, 2004; Scammell, Denny, Valentine, and Smith, 2001). In
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general, comparisons of glucocorticoid levels must remain within a species to avoid erroneous conclusions drawn across species with regard to absolute glucocorticoid levels. Another characteristic to be considered when making cross-species comparisons is the rather large differences in plasma/serum cortisol levels associated with body size. Smaller primates have higher cortisol levels than the larger apes (Coe et al., 1992). This variation associated with body mass extends to other non-primate species as well (Laudenslager et al., 2006). Stressful or challenging events have been associated with both up- and downregulation of in vitro immune measures (see Fleshner and Laudenslager, 2004). These opposite reactions are related to a variety of factors, including the duration of the stressor, its timing, and the exact immune parameter assessed. When one is considering dominance relationships, there are several levels to consider: (1) the immediate effects of brief dominance encounters that occur on a daily basis in social groups, (2) the impact of dominance status in modulating an individual’s response to an acute challenge that is unrelated to dominance status per se, and (3) the longer-term effects of high or low rank within a social structure. In the following sections, we will focus on both acute effects (social reorganization paradigms in the laboratory) and longer-term effects (in stable social groups where dominance status has been established). Immune and endocrine changes associated with the brief daily events in the context of typical dominance interactions in free-ranging non-human primates are difficult to capture (no pun intended). One might assume that the measures collected represent the summation of events occurring over the past hour or days. However, this is only a snapshot of the complicated interactions of these highly social organisms. The different players in each social situation will influence the nature of the changes noted in any biomarker or behavior, and thus generalities are difficult to make.
A. Primate Social Group Instability in Captive Settings Instability in primate social groups has been demonstrated to produce a number of pathophysiological changes that lead to immunomodulation and other medical risks. Instability in free-ranging conditions might be due to changes in the dominance structure of a group associated with attempts by a previously lower-ranking member to attain higher social status or the emigration of a new male into a troop and consequent rank changes. Social rank instability can be pro-
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duced in captive settings by rearranging membership in the group or by the introduction of an intruder to an established group as used in laboratory studies of rodents. Social group rearrangement of primates is associated with significant increases in aggressive behaviors. The social group rearrangement paradigm is created by taking four unfamiliar monkeys and placing them together in a common living area. Periodic reorganization may take place every 4–6 weeks, with monkeys encountering unfamiliar monkeys each time. This instability is associated with profound neuroendocrine changes, atherosclerotic disease, and ovarian dysfunction in cynomologous macaque monkeys (Macaca fascicularis) (Kaplan and Manuck, 1999; Kaplan and Manuck, 2004; Manuck, Kaplan, Adams, and Clarkson, 1988a; Manuck, Kaplan, Adams, and Clarkson, 1988b; Manuck, Marsland, Kaplan, and Williams, 1995; Mccabe et al., 2000). Social reorganization has been useful in the study of social challenges on immunoregulation including in vitro and in vivo markers and inoculation with benign protein antigens or replicating viruses. If cynomologous monkeys experiencing the reorganization paradigm were characterized as high or low with regard to behavioral measures of receiving and initiating aggression and affiliation during the reorganization, monkeys spending the greatest time performing social affiliation behaviors (grooming others, being groomed, or in passive contact or proximity to other monkeys) had the greatest response to mitogen stimulation and natural cytotoxicity of tumor targets (Kaplan et al., 1991). Although one might expect that significant relationships would exist with aggression, affiliation was positively associated with these immune measures during reorganization, and aggression was unrelated to immune outcomes. This is a subtle but important difference. Interestingly, relative rank in the reorganized groups did not influence these particular immune markers. Moreover, in stable social groups, relative affiliation and aggression were unrelated to in vitro immune parameters (Cohen, Kaplan, Cunnick, Manuck, and Rabin, 1992). We have also observed that relative dominance status does not affect natural cytotoxicity in stable social groups of bonnet (Macaca radiata) or pigtail (Macaca nemestrina) macaques (Boccia, Laudenslager, and Broussard, 1992; Boccia, Laudenslager, Broussard, and Hijazi, 1992). Enhanced natural cytotoxicity was observed when pigtail monkeys were contesting for a limited resource, but activation of the cytotoxic response was noted across group members independent of rank. These changes returned to basal levels within 48 hours.
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During social group reorganization of adolescent bonnet macaques, the presence of a “friend” in the new group mitigates acute changes of in vitro immune measure (Boccia et al., 1997). Friendship was determined, as suggested by Smuts for free-ranging baboons (Smuts, 1985), based on relative rates of reciprocal grooming and proximity. In the absence of an established social relationship with members of the new group, changes in natural cytotoxicity were noted as quickly as 2 hours following the reorganization. However, these parameters returned to baseline within a week. Reorganized group members with a pre-existing “friend” showed no change in immune parameters during the reorganization. One week after reorganization, all monkeys in the newly reorganized group had established new friendships in the group coincident with the return of immune parameters to baseline levels. Rates of relative affiliation were directly related to both lymphocyte activation and natural cytotoxicity as noted by others. We conclude from these observations among non-human primates that positive social relationships (e.g., associated with affiliative behaviors) promote these in vitro immune markers. Affiliation and agonism do not necessarily have opposite effects on immune modulation. Assessing the organisms’ specific antibody response to challenge with a benign novel protein antigen such as KLH or tetanus toxoid has been a particularly profitable means for observing immune modulation in the intact organism. Not surprisingly, social group reorganization of male cynomologous macaques immunized with tetanus toxoid (TT) affects primary and secondary responses (Cunnick et al., 1991). Immunization either 1 or 4 weeks prior to a single reorganization or at the time of reorganization did not have a significant effect on the primary response immunization with TT. However, across all groups regardless of the timing of immunization, dominance rank affected specific IgG levels; that is, subordinate monkeys demonstrated a greater primary IgG response to TT. These monkeys were followed and either experienced repeated monthly social reorganizations or were placed in a stable group. A secondary immunization with TT occurred after a tenth reorganization for the challenge group and 9 months after the last reorganization for the stable group. There was no effect on the booster response of social rank, but there was a significant effect of reorganization; that is, a significantly higher antibody titer was measured in the chronically reorganized group. Social rank affected the primary response to TT, and the social challenge independent of rank affected the secondary response. Thus, effects were dependent on whether memory or naive cells were involved.
B. Individual Characteristics Contributing to Immunomodulation As complex social organisms, non-human primates provide a unique opportunity to look at individual differences. Personality is an important aspect of the individual that contributes to immune modulation. It is not something that can be measured directly, but it appears as a general pattern of behavior(s) reflective of how the individual responds to different situations. Personality concepts drawn from the human literature have been successfully applied to macaque monkeys (Capitanio, 2004; Capitanio, Mendoza, and Bentson, 2004; Capitanio and Widaman, 2005; Clarke and Boinski, 1995; Laudenslager et al., 1999; Stevenson-Hinde and Zunz, 1978) and other species ranging from fish to dogs (Gosling, 2001). Several decades ago a list of adjectives was drawn together for describing impressions about their behavior that an observer might have after spending many hours watching monkeys (Stevenson-Hinde and Zunz, 1978). The 23-item adjective list included such items as Assertive, Aggressive, Confident, Dominant, Fearful, and so on. These adjectives were scored on a seven-point scale from 1 (extreme opposite of the behavior) to 7 (extreme manifestation) for each individual monkey. These investigators and others (Capitanio et al., 2004; Laudenslager et al., 1999) applied factor analytic techniques for clustering these behaviors into categories that reflect “personality” structure for the macaque monkey in much the same manner that was found useful for humans many years ago (Allport, 1937). The initial factor structure of these adjectives for rhesus monkeys revealed three main dimensional components: Confident/Fearful, Active/ Slow, and Sociable/Slow (Stevenson-Hinde and Zunz, 1978). Across studies the number of components has varied between two and four major factors. Variations in the number of these principal factors may be related to specific situations of the monkeys such as housing and the total amount of time the moneys were observed, to changes in the exact items included in the list to improve inter-observer reliability. There are, however, some consistencies that warrant attention as they are related to immune parameters, endocrine regulation, and viral illness following challenge in monkeys. The most recent application of the personality approach to individual differences comes from the work of Capitanio and colleagues (Capitanio, 2004; Capitanio and Widaman 2005). According to Capitanio, personality is mirrored in a number of traits or dispositions to respond in a given situation; that is, “. . . personality is manifested in a context . . .” (Capitanio, 2004, p. 16) much like dominance rank. It is difficult to discuss the concept of personality without
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commenting on the construct of “temperament,” which has been used frequently by both human (Kagan, 1994; Kagan and Snidman, 1991) and primate (Champoux, Suomi, and Schneider, 1994; Clarke and Boinski, 1995; Fairbanks, 2001; Fairbanks et al., 2004) researchers. Temperament may differ from the concept of personality somewhat in that it has been described as a biological predisposition to behave in a particular manner, whereas personality characteristics may be shaped more by experience. This is an arguable point (Capitanio, 2004), and it will not be addressed here. Temperament is personality and may simply be a reflection of personality at an early age (J. Capitanio and S. Suomi, personal communications, 2005). Neither temperament nor personality derives exclusively from genetic or environmental factors. For the purposes of this chapter, we will consider the two terms interchangeable, with both reflecting similar underlying processes derived from both genetic and environmental factors. Thus, temperamental dispositions, central neurochemical organization, and HPA reactivity have heritable (Williamson et al., 2003), physiological (Fairbanks et al., 1999; Fairbanks, Melega, Jorgensen, Kaplan, and McGuire, 2001; Manuck et al., 1995; Manuck, Kaplan, Adams, and Clarkson, 1989; Manuck, Kaplan, Rymeski, Fairbanks, and Wilson, 2003), and identified genetic aspects (Bethea et al., 2004; Bethea et al., 2005) which further interact with environmental events (Barr et al., 2003; Barr et al., 2004a; Barr et al., 2004b; Barr et al., 2004c) and gender (Barr et al., 2004b). The temperament of macaque monkeys may modulate responses to social and challenging situations. For example, cardiovascular responses to acute stressors vary in a striking manner across species in spite of close genetic relationships such as those that exist for the Macaque genus (Clarke and Lindburg, 1993; Clarke, Mason, and Mendoza, 1994). Rhesus (Macaca mulatta), bonnet, and long-tailed (Macaca silenus) macaques exposed to differing situations (their home cage, a novel environment, and restraint), while heart rate was collected via telemetry, showed species-specific heart rate responses. Average heart rate across all conditions indicated that heart rate of long-tailed > bonnet > rhesus macaques. Large behavioral/temperamental/personality differences exist both across species (Clarke and Boinski, 1995; Clarke and Lindburg, 1993) and within species (Capitanio, 2004). There appear to be temperamental differences in captive rhesus monkey infants dependent on their region of origin (Indian versus Chinese) and which influence enumerative blood parameters (Champoux, Kriete, Higley, and Suomi, 1996). Similar differences exist for regulation of the HPA axis as well.
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The study of species differences in bonnet and pigtail macaques has been the focus of our laboratory for many years (Laudenslager, 1988; Laudenslager et al., 1995; Laudenslager, Berger, Boccia, and Reite, 1996; Laudenslager, Held, Boccia, Reite, and Cohen, 1990). As a part of a longitudinal developmental study beginning shortly after birth until the monkeys reached 4 years, we collected blood samples every 6 months from a cohort of bonnet (n = 40) and pigtail (n = 34) monkeys housed in conspecific social groups. At approximately 42 months of age, we removed these monkeys from their peer groups and placed them in individual housing for a brief period of 72 hours, after which they were returned to their social group (Laudenslager, in preparation). Un-anesthetized blood samples were collected before and at the end of the individual housing experience. For both species, cortisol levels rose from baseline to post housing (p < .001). There were both species and gender differences in cortisol level (p < .001). Since female pigtail monkeys had higher cortisol levels than pigtail males at all timepoints (species by sex interaction, p = .04), they may be partially responsible for the overall effect of gender. Furthermore, CSF levels of corticotrophin-releasing hormone (CRH) are lower in bonnet relative to pigtail macaques (Rosenblum et al., 2002). These observations are consistent with established temperamental differences between bonnet and pigtailed monkeys (Boccia, Laudenslager, and Reite, 1994; Boccia, Laudenslager, and Reite, 1995; Kaufman and Rosenblum, 1966; Laudenslager and Boccia, 1996; Laudenslager, Boccia, and Reite, 1993). Compared to pigtail monkeys, bonnet monkeys are known to be more affiliative in social situations with group members, and care of the young is allomaternal (e.g., many members of the social group freely interact with the infants). Overall, these differences are consistent with differences noted between these species with regard to physiological responses to social challenge (Laudenslager and Boccia, 1996; Laudenslager, Boccia, and Reite, 1993; Reite, Kaemingk, and Boccia, 1989; Rosenblum et al., 2002). Yet intruder bonnet monkeys received far greater agonistic behavior from unfamiliar conspecific residents in a new social group (Figure 2, Laudenslager, unpublished observations). Thus, the expected pattern for greater affiliative behaviors among bonnets does not fit all circumstances, e.g., to conspecific intruders. Does personality variation within a species modulate the HPA axis along with immune responses? The answer is, not surprisingly, yes. Using the personality dimensions described earlier for the rhesus monkey, it was noted that adult male rhesus monkeys rated high on an excitability dimension (excitable, active, and
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monkeys. All monkeys were mid ranking prior to the move, and thus rank was not a variable in these studies. However, one might be concerned when drawing conclusions based on a grouping variable associated with subjective ratings of only three adjectives. Yet these general dimensions appear to be consistent across animal cohorts, varying only slightly with regard to the specific adjectives loading on a factor (Capitanio, 2004; Capitanio, 2005).
C. Social Reorganization and Response to Viral Challenges
FIGURE 2 Rates of agonistic behaviors during social group introductions in bonnet and pigtail monkeys. Although the bonnet monkey is typically considered to be more affiliative toward conspecifics, this does not hold for unfamiliar monkeys.
subordinate) and had lower plasma cortisol levels than monkeys rated as low on the same dimension during un-anesthetized blood draws (Capitanio, Mendoza, and Bentson, 2004). High scores on confidence (confident and aggressive) were associated with higher cortisol levels. The authors concluded that enhanced negative feedback among the excitable and low confidence monkeys was associated with lower plasma cortisol levels. These differences are not unlike what is noted in individuals diagnosed with post-traumatic stress disorder, that is, a lower cortisol level in the patient population compared to controls (Yehuda, 2002; Yehuda, 2003). Regardless of whether lower cortisol and/or disrupted diurnal rhythms are associated with a specific personality phenotype or environmental traumas (Nemeroff, 2004), identifying sources of these individual differences is central to a more complete understanding of brain behavior and immune relationships. Personality in the rhesus monkey affects responses to immunization that occur during relocation experiences in which monkeys were removed from large social groups to individual housing (Maninger, Capitanio, Mendoza, and Mason, 2003). The dimension of sociability, a trait that positively loaded on the adjectives of affiliative and warm and negatively on solitary, divided by a median split into high and low sociable monkeys was associated with greater secondary responses to TT boosters in the high sociable
What is the impact of social reorganization on response to a replicating viral challenge such as the common cold virus? Cohen has provided indications of the role of social factors in modulating viral susceptibility among primates (Cohen et al., 1997). These were crucial experiments for PNI as they challenged monkeys with an infectious agent, adenovirus SV17, not just a benign protein in a paradigm where the subjects could be behaviorally manipulated. Cohen had previously indicated in a series of elegant studies that susceptibility to the common cold was affected by self-reported psychological distress in humans (Cohen, Tyrrell, and Smith, 1991). Furthermore, the social environment had a significant impact to experimentally inoculated common cold viruses in humans (Cohen, Doyle, Skoner, Rabin, and Gwaltney, 1997). These studies in human populations were landmark experiments in PNI as they identified psychosocial risk factors for a medical illness which previous studies assessing immune parameters alone could not conclusively demonstrate. The social reorganization studies in primates (Cohen et al., 1997) showed that the social stress did not affect viral expression; however, social rank did. Lower social rank was associated with increased risk for infectious illness after viral inoculation. Risk was not associated with aggressive encounters among new social members, but rather where in the social dominance hierarchy a monkey fell. Although lowerranking animals had elevated cortisol levels, this did not account for risk for infection, nor did body weight or alterations in lymphocyte populations. In point of fact, more aggressive animals were at reduced risk for viral infection. These observations are consistent with observations of rodents who fought back in association with territorial intrusion and who had a more robust response to antigenic challenge (Fleshner et al., 1989) and similarly for the tree shrew (vonHolst, 1997). Important experiments have been carried out that followed the progression of simian immunodeficiency
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virus (SIV) after inoculation of rhesus monkeys. The viral response was studied as a function of prior stressor exposure, social reorganizations, or the personality dimension described previously. In an early pilot study based on a retrospective investigation of colony records (n = 22), it was noted that monkeys who experienced more frequent cage moves had shorter survival times (Capitanio and Lerche, 1991). Furthermore, post-inoculation weight loss was associated with the number of pre-inoculation cage moves. These effects were found after statistically controlling for viral strain, dose of virus, age at inoculation, and so on. Applying hazard analysis to a larger sample (n = 298), it was found that any social relocation occurring within 90 days prior to inoculation with SIV and up to 30 days following inoculation was associated with shorter survival (Capitanio and Lerche, 1998). Social housing (pair or group housing) after inoculation was associated with greater survival hazard. One must be cautious with regard to these observations, as the number of subjects was quite small (n = 17) and the housing was not part of a specific experimental design to investigate housing, but to look at the effects of horizontal and vertical transmission. The impact of unstable social grouping has been investigated systematically in SIV-inoculated rhesus monkeys (Capitanio, Mendoza, Lerche, and Mason, 1998). At 6 years of age, a group of 36 healthy male rhesus monkeys was removed from their natal social groups and transferred to individual housing. Three to 5 days a week, the monkeys were placed in either stable or unstable social groups for socialization for 100 minutes/day. In the stable groups, the individual animals were always the same. In the unstable groups, the group members during the socialization period varied for each exposure. After 3 weeks of these experiences, half of these monkeys in each group were inoculated with SIV, and half received control saline injections. Socialization continued following inoculation, but controls and SIV-inoculated animals remained separate. Animals in the unstable condition had a shorter median survival (420 days) compared to the stable group (589 days). Although the stable animals showed lower viral RNA levels and higher IgG response to SIV, these effects were not significant. However, aggression (receiving threats), independent of social stability, was positively associated with viral RNA levels and negatively associated with antibody titers to SIV. Animals in unstable compared to stable groups had a greater cortisol response to restraint stress and enhanced suppression by dexamethasone. The preceding results indicate that social stressors affect survival in monkeys inoculated with SIV. However, results indicated suppressed HPA activity
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following inoculation. In fact, this could be due to neurotrophic effects of the virus affecting CNS feedback mechanism although the authors suggest post-traumatic stress disorder–like phenomena. The well-known impact of pro-inflammatory cytokines on HPA regulation (Dunn, 1995) and the influence of SIV and HIV on HPA regulation (Clerici et al., 1997; Norbiato et al., 1992; Vago, Clerici, and Norbiato, 1994) together make it difficult to interpret HPA observations in SIV-infected monkeys. Not surprisingly, the aforementioned dimensions of personality affect responses to SIV inoculation in adult male rhesus monkeys as well (Capitanio, Mendoza, and Baroncelli, 1999). Low sociable (low subjective ratings on sociable, playful, and curious) monkeys had a higher viral load following inoculation. Viral load was directly related to survival in SIV (Watson et al., 1997) and in HIV as well (Mellors et al., 1995). These investigators have not determined the extent to which personality characteristics moderate social instability in disease progression. However, we will see below that personality characteristics moderate HPA activation in subordinate baboons in association with dominance status. Although laboratory settings allow control over many confounding variables, the field setting provides a far richer behavioral backdrop for the study of dominance, individual differences, and immune relationships.
D. Dominance Relationships in Naturalistic Settings When free-ranging animals are the subjects of study, a number of unforeseen factors can contribute to problems in research, as typified by a study that one of the authors (MLL) and Robert Sapolsky undertook. We were interested in individual differences in the response to antigenic challenge among a group of freeranging olive baboons that Sapolsky had studied extensively. We wanted to investigate the specific antibody response to a “novel” antigen, KLH, as it related to social dominance status. We first verified that we could in fact measure the IgG response to KLH in captive baboons. The captive baboon population showed a significant rise in specific IgG antibody titers following an intramuscular KLH challenge. Specific IgG levels rose from an absence of antibodies prior to immunization to significant levels measured from 7–28 days later. Sapolsky then spent a summer in Kenya, armed with KLH, tracking 20 male baboons, darting them for immunization, and re-darting them as close as possible 21 days later so we could assess their primary response to KLH. He succeeded in collecting plasma samples from the immunized baboons.
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Here, the realities of the field met the controlled conditions of the laboratory, or psychoneuroimmunology alfresco (paraphrased from Sapolsky, 1993). Every baboon we immunized had significant KLH-specific antibodies before immunization at the first darting. Antibody levels were higher for the second sample, but they were confounded by the differences that existed at baseline. We appeared to be measuring either background cross-reactivity or a booster response to KLH. It was highly unlikely that the animals had ever been exposed to keyhole limpets (a coastal tide pool mollusk) in their lifetime. We checked for crossreactivity to hemocyanin from the horseshoe crab in the baboons. We found antibodies to this protein as well at baseline in our baboon samples. We scratched our heads as to how they had acquired antibodies to this rather unique antigen until we realized that the free-ranging baboons fed on insects and land snails. Among invertebrates, the respiratory protein is represented by copper-based hemocyanin. The free-ranging baboon population appeared to have orally immunized themselves to hemocyanin by ingesting invertebrates as a part of their diet. Their immune system could not distinguish specifically between sources of hemocyanin. Thus, the study subjects did not have a controlled exposure to KLH. In seeking a novel antigen for the free-ranging baboons, we had been frustrated by their feeding habits. However, the study of free-ranging baboon populations can provide rich data with regard to endocrine regulation and its association with dominance status and personality characteristics in a variety of primate species. Sapolsky has focused much of his attention to dominance and personality/style influences on the male baboons free ranging in Kenya. Early studies indicated that male aggressiveness was associated with elevated testosterone but not mating success (Sapolsky, 1982; Sapolsky, 1991). Those successful in mating had lower initial cortisol levels but a greater rise in response to capture. In these studies dominance was based on the number of successful matings, assuming that mating success was reflective of dominance. During a period of social instability in the troop (dominance interactions were more frequent and less predictable), high-ranking males were more likely to participate in escalated aggression, but they showed endocrine levels quite different from lower-ranking males in the group (Sapolsky, 1983). During stable periods, there were no differences between high- and low-ranking male baboons, whereas when aggression was high and less predictable, low-ranking males had higher cortisol levels. During the period of instability, males’ testosterone levels were lower compared to the stable period, but most importantly, the greatest sup-
pression was among the low-ranking males. One of Sapolsky’s important contributions was the observation that aspects of social dominance in adult male baboons were modulated by individual characteristics of the baboons, e.g., their personality. Lower basal cortisol levels were most often noted among high-ranking males that recognized differences in social situations as either a threatening or neutral interaction with other males (Sapolsky, 2005a; Sapolsky, 2005b; Sapolsky, Alberts, and Altmann, 1997). Dominant males lacking this “skill” had cortisol levels as high as low-ranking members of the troop. This trait is quite similar to the adjective “understanding” in the Stevenson-Hinde and Zunz schema (1978). Overall, the hypercortisolism was related to disrupted feedback regulation at the CNS level in the subordinate baboons (Sapolsky, 2005a, 2005b). Another modifier of the impact of social instability is whether a baboon is rising or falling in rank. Ascending in dominance rank is associated with higher cortisol levels (Sapolsky, 1992). It is of note that rankrelated differences extend to cardiovascular reactivity as well (Sapolsky and Share, 1994), with high-ranking animals showing more rapid return to baseline following pharmacological challenge. The picture that emerges for the baboon is that rank is not the only determinant of hypercortisolism, but individual differences in personality contribute significantly to regulation of the HPA axis (Virgin and Sapolsky, 1997). Unfortunately, the nature and location of this field site have precluded in-depth assessment of immune regulation beyond changes in enumerative measures such as differential cell counts in this otherwise well-studied population. For this reason, we turned to a more accessible field setting. For over a decade, we have studied immune and neuroendocrine parameters in free-ranging rhesus monkeys (Macaca mulatta) on a provisioned island, Cayo Santiago, off the coast of Puerto Rico (Laudenslager, Rasmussen, Berman, Suomi, and Berger, 1993; Laudenslager et al., 1999). Macaque monkeys in large social troops are organized into smaller groups of related adult monkeys who are sisters, daughters, and granddaughters of a female, creating a matriline. Within the troop there are several matrilines, which have unique status relative to each other, that is, outranking others and having priority of access to valued resources. Recent analyses suggest that matrilineal dominance status affects hormones, in vitro immune parameters, and antibodies to a latent virus found in young macaque monkeys (Laudenslager, Rasmussen, and Suomi, in preparation). Unlike the aforementioned studies of the baboon, we have focused on earlier aspects of dominance status of the mother and its impact on her offspring. Among macaques,
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dominance status can be either along matrilines or based on a nepotistic hierarchy (Chapais, 2004). In a nepotistic hierarchy, individual attributes of the females are irrelevant to status, as rank is dependent on alliances formed by the females in agonistic and dominance-related encounters. In a matrilineal dominance hierarchy, a female’s rank is based on her kinship. Thus, in the rhesus macaque, our study subject, maternal rank is assumed by her female offspring. A macaque matriline might consist of an older female, her daughters, and their offspring, and so on. The principle of youngest ascendancy confers higher rank to a daughter over her aunts and cousins in the matriline. As you can imagine, these relationships are complicated for the casual observer, but the monkeys are clear in their ranking. In contrast to the role of matriline in determining rank of the female rhesus monkey, males are somewhat different, as the males typically emigrate from their natal troop around puberty or later and immigrate into a new troop or remain outside a troop as a peripheral male. Note that peripheral male status is unique to provisioned situations such as Cayo Santiago where predation is lacking. Until the males emigrate from their natal troop, their dominance status is that of the matriline. However, the dominance status of the male in a new troop is not predicted by its kinship and prior rank. Blood samples were obtained from these freeranging rhesus monkeys between the ages of 3 and 6 during the annual census and health checks that take place each January and February. The monkeys were trapped in provisioned field cages where they typically obtain their daily monkey chow. Blood samples were collected under light ketamine anesthesia exactly 30 minutes after the doors to the field cage were closed (base sample). This permitted control over time from trapping to blood draw not always possible at field sites (see Sapolsky, 1993). Subjects were then transported to a field laboratory, where they were held in individual housing over the next 24 hours. Prior to release the following day, they were anesthetized and blood was drawn a second time (challenge sample, e.g., being overnight in individual housing). Maternal dominance status within a troop was categorized as either high or low. Plasma cortisol levels assessed at the time of trapping (base) and prior to release (challenge) rose more in monkeys from low-ranking matrilines (p < .001), as shown in Figure 3. Collapsed across base and challenge conditions and years, plasma cortisol levels were greatest in the young males from low-ranking matrilines (p < .001). There was no difference in age of emigration based on matrilineal dominance status. Thus, matrilineal dominance status has a significant effect on
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FIGURE 3 Mean plasma cortisol level (μg/dl) ± 1 SEM noted following capture (Base) and 24 hours later after overnight housing in an individual cage (Challenge) in rhesus monkeys as a function of matrilineal dominance status. Note levels are comparable across ranks at Base, but the low-ranking animals showed a greater rise in association with the challenge.
glucocorticoid regulation of young males prior to emigration. It is of interest to note that peripheral or solitary males in this island setting have a number of indictors of greater fitness as measured by greater body weight and skin fold thickness (Rasmussen, Berard, and Suomi, 1995). Although these solitary males had a history of movement from group to group and spending more time as solitary peripheral animals, these animals were devoid of rank, as they were not a part of an established social structure or group. Sapolsky (2005a, 2005b) suggested that one feature lacking in studies of subordinate relationships are assessments that reflect transient immune activation (see Fleshner and Laudenslager, 2004, for a review of this phenomenon) and subsequent recovery functions. To some extent, this is difficult to accomplish under free-ranging conditions. However, we have noted significant effects of low matrilineal dominance status with regard to natural cytotoxicity. If we assume that the closure of the gates to the field cage described above initiates a stress response in the trapped monkeys, differences in relative levels of lysis of tumor targets may shed light on Sapolsky’s question. We noted that natural cytotoxicity of these tumor targets was higher on the day of trapping (base) for the young monkeys from subordinate matrilines, as indicated in Figure 4. That is, on the day of trapping (base), lysis of the tumor targets was significantly higher (p < .001) in the low-ranking group. This relationship was noted
III. Behavior and Immunity Estimated Marginal Mean B Virus Antibody Titer
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FIGURE 4 Percent lysis of K562 targets by isolated peripheral blood lymphocytes (30 : 1 effector-to-target ratio) of rhesus monkeys from high-and low-ranking matrilines. Overall, low-ranking animals displayed significantly higher lysis of targets, but both high- and low-ranking animals showed a decline between capture (Base) and release (Challenge) the following day.
across 3 consecutive years (from 3 to 6 years of age), during which we obtained blood samples for in vitro immune measures. Lysis declined from the first sample to the sample collected prior to release the following day in both groups. Lysis was consistently higher on both days in the low-ranking group. Gender did not influence these relationships, nor were these measures related to plasma cortisol at the time of blood sampling. We have noted increased natural cytotoxicity in previously challenged human populations such as combat veterans with PTSD (Laudenslager et al., 1998) and in monkeys throughout adolescence into adulthood after experiencing early social challenges (Laudenslager, Berger, et al., 1996). Increased numbers of activated NK cells were observed in a traumatized population among individuals who report no distress following the trauma but showed elevated cardiovascular activity, e.g., repressors (Benight et al., 2004). Since the NK cell is involved in viral defense (Shieh et al., 2001) and its relative activity might reflect immune activation in response to environmental challenges, these results suggest that there might be potential health implications for increased natural cytotoxicity associated with social subordination. Do the previous results suggest that the cells responsible for natural cytotoxicity in young monkeys from lower social ranks are actually activated? Does this in any way affect viral defense mechanisms in these free-ranging monkeys?
Age (Years)
FIGURE 5 Rhesus monkeys from low-ranking matrilines show elevated antibody titers to Simian B virus, a herpes virus found in macaque monkeys.
Simian B virus (Cercopithecine Herpesvirus 1) is a naturally occurring herpes virus found predominantly in macaque monkeys (Eberle and Hillard, 1995). B virus is passed vertically through mucosal exposure to oral and genital secretions from infected monkeys actively shedding virus. After an initial infection that includes mild symptoms, the B virus passes into a latent state (within sensory ganglia) as is typical of the herpes viruses (Favoreel, Nauwynck, and Pensaert, 2000). When the B virus is reactivated, it is observable as herpetic sores in the oral and genital regions. Following the same reasoning presented many years ago by Glaser and colleagues (2005), we screened our subject population between 2 and 5 years of age for specific antibodies to B virus. We observed significant effects of year (antibody titers rose, p < .001), gender (females greater than males, p < .001), and maternal dominance status (low-ranking titers exceeding highranking offspring, p < .001) on viral antibody titers to herpes B virus (Figure 5). If we assume that viral antibody level is a marker of the ability of cell-mediated responses to hold the virus in latency (Glaser, 2005), the low-ranking monkeys appear to be immune compromised, as reflected in the significantly higher antibody titers to B virus (Laudenslager, Rasmussen, and Suomi, in preparation). Across the years that samples were collected in this cohort, a number of changes occurred, including puberty, pregnancy for some females, and emigration from the natal troop for some of the males. However, the relationship of neuroendocrine and immune markers to matrilineal dominance status remained consistent. As has been suggested by other researchers
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(Coe, 1993; Coe, Lubach, Schneider, Dierschke, and Ershler, 1992), early events set the stage for immune regulation and its course throughout the life span. Certainly, early events affect regulation of the HPA axis, as has been shown repeatedly for the rodent (Liu et al., 1997; Meaney et al., 1993; Meaney, Aitken, Bodnoff, Iny, and Sapolsky, 1985). In the non-human primate, the early effects of matrilineal dominance may plant their seeds early in development. For the rhesus monkey, a female is stuck with the lot provided her via her mother—their matrilineal status. One might ask to what extent this will continue to direct the trajectory of the males who leave the social structure of their natal group. At present, these questions have not been addressed.
VI. DOES DOMINANCE MATTER? It is often customary to make comparisons between dominance rank in non-human species and socioeconomic status, with the assumption that a similar pathophysiology underlies both concepts with regard to lower social status (Goymann and Wingfield, 2004). Caste systems exist across nature from the social insects to higher primates, including humans. Dominance relationships confer a set of rules for the members of the group to follow in a situation in which resources might be limited. Dominance rank and signals associated with rank also provide individuals with predictability in their social interactions, regardless of social status. Living in social groups has clear advantages to the extent that groups provide protection from predation for the group that would be absent for the individual animal. Social grooming among group members assists in removal of parasites from the integument and also facilitates restoration of cardiovascular function following agonistic encounters (Boccia, Reite, and Laudenslager, 1989). Grooming is a reciprocal process wherein both the recipient and the groomer benefit, regardless of rank. However, for non-human primates, there are potential costs to low rank with regard to neuroendocrine regulation. For example, subordinates are frequently reproductively suppressed (Creel, 2001). One might pose the question, “Are the subordinate animals within a social group always stressed?” We indicated in stable social groups that immune differences are minimal between high- and low-ranking macaque monkeys (Boccia, Laudenslager, Broussard, and Hijazi, 1992; Boccia et al., 1992). Rank may not be stressful in stable groups. However, when the group is challenged as a whole, during a period of reduced resources, for example, then rank may have an impact. This relationship is far from simple.
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There are large species variations with regard to the impact of social status on physiology. Based on a metaanalytic study of cortisol in Old and New World monkeys, monkeys were ranked based on a relative cortisol level derived from basal cortisol levels of the subordinates expressed as a percentage of the dominants (Abbott et al., 2003). Surveyed investigators completed a series of 16 subjective questions regarding what it is like to be a male or female dominant or subordinate member of social groups corresponding to several New (n = 5) and Old (n = 5) World species. The social and breeding systems for each of these species were characterized. Group size and number of males in the group and cooperative versus polygamous breeding systems were considered. A number of interesting relationships were noted. Importantly, availability of social support to the subordinates was associated with lower relative cortisol among the subordinates. Our observations of higher cortisol levels in pigtail compared to bonnet macaques support this observation as well. Bonnet macaques have more affiliative relationships within their social group, and the presence of affiliative relationships after group introduction will significantly modulate immune responses during that transition (Boccia et al., 1997). Overall, the prior meta-analysis identified two factors that contribute to elevated cortisol levels in subordinate group members: the level of stress experience by the group and the availability of social support from other group members (Abbott et al., 2003). The presumed “stress” of low social rank has been compared to the concept of allostatic load (McEwen, 2003; McEwen, 2004). Briefly, allostatic load considers stress and challenges over a longer time frame than the original conceptualization of Hans Seyle. Allostatic load reflects a life span perspective (Seeman, Singer, Rowe, Horwitz, and McEwen, 1997). Allostasis and allostatic load are concepts that have elaborated on the old concepts of homeostasis, but extending them to life-long stressors and challenges on systems not immediately critical to survival such as pH or body temperature, which are prototypical homeostatic systems. The allostatic load model has been applied to non-human animal populations (McEwen and Wingfield, 2003), but the concept has been most frequently used for humans. It is beyond the scope of this chapter to discuss this concept in great detail but only to bring to the attention of the reader that variations in dominance status among social animals have been frequently used as models of allostatic load. Figure 6 summarizes the relationships observed between social factors such as rank or personality and in vivo and in vitro immune markers. This figure shows quite clearly that one cannot make broad-ranging
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FIGURE 6 The interrelationships of social aspects of behavior including sociability, aggression, and rank on various in vitro and in vivo measures of primate immunity.
summary statements regarding immune/social relationships based on single immune measures. Even simple in vivo responses such as response to antigenic challenge may provide different outcomes based on the observation of either a primary or secondary response. Responses to live viral challenge may not always reflect the same underlying mechanism(s) as responses to a simple non-replicating antigenic challenge. A life of challenges (e.g., low social rank under unstable conditions) is associated with increased risk for morbidity and mortality. However, even for nonhuman primates, social support moderates these effects in a significant manner, regardless of social status. Individual differences in behavior/personality contribute in a significant way to these relationships. We can no longer take simplistic approaches to behaviorimmune relationships but need to include these factors that contribute to larger error bars than we would often like to see in our data.
Acknowledgments Preparation of this manuscript and portions of the data present herein were supported in part by NIH grants MH37373 (MLL), AA13973 (MLL), and RR03640 (Caribbean Primate Research Center); funds from the Developmental Psychobiology Endowment Fund– University of Colorado Denver and Health Sciences Center; and intramural funding at NICHD (S. Suomi). We also acknowledge the expert assistance of Mark Goldstein and Anne Luckow in many aspects of this research and preparation of this manuscript.
References Abbott, D. H., Keverne, E. B., Bercovitch, F. B., Shively, C. A., Mendoza, S. P., Saltzman, W., et al. (2003). Are subordinates
always stressed? A comparative analysis of rank differences in cortisol levels among primates. Horm. Behav., 43, 67–82. Ader, R., Felten, D. L., and Cohen, N. (Eds.) (2001). Psychoneuroimmunology (3rd ed.). San Diego: Academic Press. Allport, G. W. (1937). Personality: a psychological interpretation. New York: Holt. Archer, J. (1988). The behavioural biology of aggression. New York: Press Syndicate of the University of Cambridge. Avitsur, R., Stark, J. L., Dhabhar, F. S., Kramer, K. A., and Sheridan, J. F. (2003). Social experience alters the response to social stress in mice. Brain Behav. Immun., 17 (6), 426–437. Avitsur, R., Stark, J. L., and Sheridan, J. F. (2001). Social stress induces glucocorticoid resistance in subordinate animals. Horm. Behav., 39 (4), 247–257. Bailey, M. T., Avitsur, R., Engler, H., Padgett, D. A., and Sheridan, J. F. (2004). Physical defeat reduces the sensitivity of murine splenocytes to the suppressive effects of corticosterone. Brain Behav. Immun., 18 (5), 416–424. Barnard, C. J., Behnke, J. M., Gage, A. R., Brown, H., and Smithurst, P. R. (1997). Immunity costs and behavioural modulation in male laboratory mice (Mus musculus) exposed to the odours of females. Physiol. Behav., 62 (4), 857–866. Barr, C. S., Newman, T. K., Becker, M. L., Champoux, M., Lesch, K. P., Suomi, S. J., et al. (2003). Serotonin transporter gene variation is associated with alcohol sensitivity in rhesus macaques exposed to early-life stress. Alcohol. Clin. Exp. Res., 27 (5), 812–817. Barr, C. S., Newman, T. K., Lindell, S., Becker, M. L., Shannon, C., Champoux, M., et al. (2004a). Early experience and sex interact to influence limbic-hypothalamic-pituitary-adrenalaxis function after acute alcohol administration in rhesus macaques (Macaca mulatta). Alcohol. Clin. Exp. Res., 28 (7), 1114–1119. Barr, C. S., Newman, T. K., Schwandt, M., Shannon, C., Dvoskin, R. L., Lindell, S. G., et al. (2004b). Sexual dichotomy of an interaction between early adversity and the serotonin transporter gene promoter variant in rhesus macaques. Proc. Natl. Acad. Sci. USA, 101 (33), 12358–12363. Barr, C. S., Newman, T. K., Shannon, C., Parker, C., Dvoskin, R. L., Becker, M. L., et al. (2004c). Rearing condition and rh5–HTTLPR interact to influence limbic-hypothalamic-pituitary-adrenal axis response to stress in infant macaques. Biol. Psychiatry, 55 (7), 733–738. Bartolomucci, A., Palanza, P., Sacerdote, P., Panerai, A. E., Sgoifo, A., Dantzer, R., et al. (2005). Social factors and individual vulnerability to chronic stress exposure. Neurosci. Biobehav. Rev., 29 (1), 67–81. Bartolomucci, A., Pederzani, T., Sacerdote, P., Panerai, A. E., Parmigiani, S., and Palanza, P. (2004). Behavioral and physiological characterization of male mice under chronic psychosocial stress. Psychoneuroendocrinology, 29 (7), 899–910. Benight, C., Harper, M., Zimmer, D., Lowery, M., Sanger, J., and Laudenslager, M. (2004). Repression following a series of natural disasters: immune and neuroendocrine correlates. Psychol. Health, 19, 337–352. Bernstein, I. S. (1981). Dominance: the baby and the bathwater. Behav. Brain Sci., 4, 419–457. Bethea, C. L., Streicher, J. M., Coleman, K., Pau, F. K. Y., Moessner, R., and Cameron, J. L. (2004). Anxious behavior and fenfluramine-induced prolactin secretion in young rhesus macaques with different alleles of the serotonin reuptake transporter polymorphism (5HTTLPR). Behav. Genet., 34, 295–307. Bethea, C. L., Streicher, J. M., Mirkes, S. J., Sanchez, R. L., Reddy, A. P., and Cameron, J. L. (2005). Serotonin-related gene expres-
22. Dominance and Immunity sion in female monkeys with individual sensitivity to stress. Neuroscience, 132, 151–166. Blanchard, D. C., Spencer, R. L., Weiss, S. M., Blanchard, R. J., McEwen, B., and Sakai, R. R. (1995). Visible burrow system as a model of chronic social stress: behavioral and neuroendocrine correlates. Psychoneuroendocrinology, 20 (2), 117–134. Blanchard, R. J., McKittrick, C. R., and Blanchard, D. C. (2001). Animal models of social stress: effects on behavior and brain neurochemical systems. Physiol. Behav., 73 (3), 261–271. Blanchard, R. J., Wall, P. M., and Blanchard, D. C. (2003). Problems in the study of rodent aggression. Horm. Behav., 44 (3), 161–170. Blanchard, R. J., Yudko, E., Dulloog, L., and Blanchard, D. C. (2001). Defense changes in stress nonresponsive subordinate males in a visible burrow system. Physiol. Behav., 72 (5), 635–642. Boccia, M. L., Laudenslager, M. L., and Broussard, C. L. (1992). Dominance effects on immune response to stressors in socially housed macaques. In N. Itogawa, Y. Sugiyama, G. P. Sackett, and K. R. Thompson (Eds.), Handbook of primatology (1st ed., pp. 127– 137). Tokyo: University of Tokyo Press. Boccia, M. L., Laudenslager, M. L., Broussard, C. L., and Hijazi, A. S. (1992). Immune responses following competitive dominance water tests in two species of macaques. Brain Behav. Immun., 6, 201–213. Boccia, M. L., Laudenslager, M. L., and Reite, M. L. (1994). Intrinsic and extrinsic factors affect infant responses to maternal separation. Psychiatry, 57, 43–50. Boccia, M. L., Laudenslager, M. L., and Reite, M. L. (1995). Individual differences in macaques’ responses to stressors based on social and physiological factors: implications for primate welfare and research outcomes. Lab. Anim., 29, 250–257. Boccia, M. L., Reite, M., and Laudenslager, M. (1989). On the physiology of grooming in a pigtail macaque. Physiol. Behav., 45, 667–670. Boccia, M. L., Scanlan, J. M., Laudenslager, M. L., Berger, C. L., Hijazi, A. S., and Reite, M. L. (1997). Juvenile friends, behavior, and immune responses to separation in bonnet macaque infants. Physiol. Behav., 61, 191–198. Capitanio, J. P. (2004). Personality factors between and within species. In B. Thierry, M. Singh, and W. Kaumanns (Eds.), Macaque societies: a model for the study of social organization (pp. 13–33). New York: Cambridge University Press. Capitanio, J. P., and Lerche, N. W. (1991). Psychosocial factors and disease progression in simian AIDS: a preliminary report. AIDS, 5 (9), 1103–1106. Capitanio, J. P., and Lerche, N. W. (1998). Social separation, housing relocation, and survival in simian AIDS: a retrospective analysis. [See comment]. Psychosom. Med., 60 (3), 235–244. Capitanio, J. P., Mendoza, S. P., and Baroncelli, S. (1999). The relationship of personality dimensions in adult male rhesus macaques to progression of simian immunodeficiency virus disease. Brain Behav. Immun., 13 (2), 138–154. Capitanio, J. P., Mendoza, S. P., and Bentson, K. L. (2004). Personality characteristics and basal cortisol concentrations in adult male rhesus macaques (Macaca mulatta). Psychoneuroendocrinology, 29 (10), 1300–1308. Capitanio, J. P., Mendoza, S. P., Lerche, N. W., and Mason, W. A. (1998). Social stress results in altered glucocorticoid regulation and shorter survival in simian acquired immune deficiency syndrome. Proc. Natl. Acad. Sci. USA., 95, 4714–4719. Capitanio, J. P., and Widaman, K. F. (2005). Confirmatory factor analysis of personality structure in adult male rhesus monkeys (Macaca mulatta). Am. J. Primatol., 65, 289–294. Champoux, M., Kriete, M. F., Higley, J. D., and Suomi, S. J. (1996). CBC and serum chemistry differences between Indian-derived
493
and Chinese-Indian hybrid rhesus monkey infants. Am. J. Primatol., 39 (1), 79–84. Champoux, M., Suomi, S. J., and Schneider, M. L. (1994). Temperament differences between captive Indian and Chinese-Indian hybrid rhesus macaque neonates. Lab. Anim. Sci., 44, 351–357. Chapais, B. (2004). How kinship generates dominance structures: a comparative perspective. In B. Thierry, M. Singh, and W. Kaumanns (Eds.), Macaque societies: A model for the study of social organization (pp. 186–208). New York: Cambridge University Press. Chrousos, G. P., Loriaux, D. L., Brandon, D., Shull, J., Renquist, D., Hogan, W., et al. (1984). Adaptation of the mineralocorticoid target tissues to the high circulating cortisol and progesterone plasma levels in the squirrel monkey. Endocrinology, 115 (1), 25–32. Chrousos, G. P., Renquist, D., Brandon, D., Eil, C., Pugeat, M., Vigersky, R., et al. (1982). Glucocorticoid hormone resistance during primate evolution: receptor-mediated mechanisms. Proc. Natl. Acad. Sci. USA, 79, 2036–2040. Clarke, A. S., and Boinski, S. (1995). Temperament in nonhuman primates. Am. J. Primatol., 37, 103–125. Clarke, A. S., and Lindburg, D. G. (1993). Behavioral contrasts between male cynomolgus and lion-tailed macaques. Am. J. Primatol., 29, 49–59. Clarke, A. S., Mason, W. A., and Mendoza, S. P. (1994). Heart rate patterns under stress in three species of macaques. Am. J. Primatol., 33, 133–148. Clerici, M., Trabattoni, D., Piconi, S., Fusi, M. L., Ruzzante, S., Clerici, C., et al. (1997). Possible role for the cortisol/anticortisols imbalance in the progression of human immunodeficiency virus. Psychoneuroendocrinology, 22, S27–S31. Coe, C. L. (1993). Psychosocial factors and immunity in nonhuman primates—a review. Psychosom. Med., 55, 298–308. Coe, C. L., Lubach, G. R., Schneider, M. L., Dierschke, D. J., and Ershler, W. B. (1992). Early rearing conditions alter immune responses in the developing infant primate. Pediatrics, 90, 505–509. Coe, C. L., Savage, A., and Bromley, L. J. (1992). Phylogenetic influences on hormone levels across the primate order. Am. J. Primatol., 28, 81–100. Cohen, S., Doyle, W. J., Skoner, D. P., Rabin, B. S., and Gwaltney, J. M. (1997). Social ties and susceptibility to the common cold. JAMA, 277, 1940–1944. Cohen, S., Kaplan, J. R., Cunnick, J. E., Manuck, S. B., and Rabin, B. S. (1992). Chronic social stress, affiliation and cellular immune response in nonhuman primates. Psychol. Sci., 3, 301–304. Cohen, S., Line, S., Manuck, S. B., Rabin, B. S., Heise, E. R., and Kaplan, J. R. (1997). Chronic social stress, social status, and susceptibility to upper respiratory infections in nonhuman primates. Psychosom. Med., 59 (3), 213–221. Cohen, S., Tyrrell, D. A. J., and Smith, A. P. (1991). Psychological stress and susceptibility to the common cold. N. Engl. J. Med., 325, 606–612. Creel, S. (2001). Social dominance and stress hormones. Trends Endocrinol. Metab., 16, 491–497. Cunnick, J. E., Cohen, S., Rabin, B. S., Carpenter, A. B., Manuck, S. B., and Kaplan, J. R. (1991). Alterations in specific antibody production due to rank and social instability. Brain Behav. Immun., 5, 357–369. de Jong, J. G., van der Vegt, B. J., Buwalda, B., and Koolhaas, J. M. (2005). Social environment determines the long-term effects of social defeat. Physiol. Behav., 84 (1), 87–95. De Waal, F. B. M. (2000). Primates—a natural heritage of conflict resolution. Science, 289, 586–590.
494
III. Behavior and Immunity
Dunn, A. J. (1995). Interactions between the nervous system and the immune system: implications for psychopharmacology. In F. E. Bloom and D. J. Kupfer (Eds.), Psychopharmacology: the fourth generation of progress (pp. 719–731). New York: Raven Press. Eberle, R., and Hillard, J. (1995). The simian herpesviruses. Infect. Agents Dis., 4, 55–70. Ebner, K., Wotjak, C. T., Landgraf, R., and Engelmann, M. (2005). Neuroendocrine and behavioral response to social confrontation: residents versus intruders, active versus passive coping styles. Horm. Behav., 47 (1), 14–21. Erwin, J. M., and Hof, P. R. (2002). Aging in nonhuman primates (vol. 31). New York: Karger. Fairbanks, L. A. (2001). Individual differences in response to a stranger: social impulsivity as a dimension of temperament in vervet monkeys (Cercopithecus aethiops sabaeus). J. Comp. Psychol., 115, 22–28. Fairbanks, L. A., Fontenot, M. B., Phillips-Conroy, J. E., Jolly, C. J., Kaplan, J. R., and Mann, J. J. (1999). CSF monoamines, age and impulsivity in wild grivet monkeys (Cercopithecus aethiops aethiops). Brain Behav. Evol., 53, 305–312. Fairbanks, L. A., Jorgensen, M. J., Huff, A., Blau, K., Hung, Y. Y., and Mann, J. J. (2004). Adolescent impulsivity predicts adult dominance attainment in male vervet monkeys. Am. J. Primatol., 64, 1–17. Fairbanks, L. A., Melega, W. P., Jorgensen, M. J., Kaplan, J. R., and McGuire, M. T. (2001). Social impulsivity inversely associated with CSF 5–HIAA and fluoxetine exposure in vervet monkeys. Neuropsychopharmacology, 24, 370–378. Favoreel, H. W., Nauwynck, H. J., and Pensaert, M. B. (2000). Immunological hiding of herpesvirus-infected cells—brief review. Arch. Virol., 145, 1269–1290. Fleshner, M., Deak, T., Spencer, R. L., Laudenslager, M. L., Watkins, L. R., and Maier, S. F. (1995). A long-term increase in basal levels of corticosterone and a decrease in corticosteroid-binding globulin after acute stressor exposure. Endocrinology, 136, 5336–5342. Fleshner, M., Laudenslager, M. L., Simons, L., and Maier, S. F. (1989). Reduced serum antibodies associated with social defeat in rats. Physiol. Behav., 45, 1183–1187. Fleshner, M. R., and Laudenslager, M. L. (2004). Psychoneuroimmunology: then and now. Behav. Cogn. Neurosci. Rev., 3, 114–130. Fuller, P. J., Smith, B. J., and Rogerson, F. M. (2004). Cortisol resistance in the new world revisited. Trends Endocrinol. Metab., 15, 296–299. Gasparotto, O. C., Ignacio, Z. M., Lin, K., and Goncalves, S. (2002). The effect of different psychological profiles and timings of stress exposure on humoral immune response. Physiol. Behav., 76 (2), 321–326. Glaser, R. (2005). Stress-associated immune dysregulation and its importance for human health: a personal history of psychoneuroimmunology. Brain Behav. Immun., 19 (1), 3–11. Glasper, E. R., and Devries, A. C. (2005). Social structure influences effects of pair-housing on wound healing. Brain Behav. Immun., 19 (1), 61–68. Gosling, S. D. (2001). From mice to men: what can we learn about personality from animal research? Psychol. Bull., 127, 45–86. Goymann, W., and Wingfield, J. C. (2004). Allostatic load, social status and stress hormones: the costs of social status matter. Anim. Behav., 67, 591–602. Harlow, H. F., Harlow, M. K., Dodsworth, R. O., and Arling, G. L. (1966). Maternal behavior of rhesus monkeys deprived of mothering and peer associations in infancy. Proc. Am. Philos. Soc., 110, 58–66.
Harlow, H. F., and Zimmermann, R. R. (1958). The development of affectional responses in infant monkeys. Proc. Am. Philos. Soc., 102, 501–509. Heise, S. R., and Van Acker, A. (2000). The effect of social environment on the immune response of female common voles in matriarchal laboratory groups. Physiol. Behav., 71 (3–4), 289–296. Hinde, R. A. (1987). Can nonhuman primates help us understand human behavior? In B. B. Smuts, D. L. Cheney, R. M. Seyfarth, R. W. Wrangham, and T. T. Struhsaker (Eds.), Primate societies (pp. 413–420). Chicago: The University of Chicago Press. Iwakabe, K., Shimada, M., Ohta, A., Yahata, T., Ohmi, Y., Habu, S., et al. (1998). The restraint stress drives a shift in Th1/Th2 balance toward Th2-dominant immunity in mice. Immunol. Lett., 62 (1), 39–43. Jasnow, A. M., Drazen, D. L., Huhman, K. L., Nelson, R. J., and Demas, G. E. (2001). Acute and chronic social defeat suppresses humoral immunity of male Syrian hamsters (Mesocricetus auratus). Horm. Behav., 40 (3), 428–433. Kademian, S. M., Bignante, A. E., Lardone, P., McEwen, B. S., and Volosin, M. (2005). Biphasic effects of adrenal steroids on learned helplessness behavior induced by inescapable shock. Neuropsychopharmacology, 30 (1), 58–66. Kagan, J. (1994). Galen’s prophecy: temperament in human nature. New York: Basic Books. Kagan, J., and Snidman, N. (1991). Temperament factors in human development. Am. Psychol., 46, 856–862. Kaplan, J. R., Heise, E. R., Manuck, S. B., Shively, C. A., Cohen, S., Rabin, B. S., et al. (1991). The relationship of agonistic and affiliative behavior patterns to cellular immune function among cynomolgus monkeys (Macaca fascicularis) living in unstable social groups. Am. J. Primatol., 25, 157–173. Kaplan, J. R., and Manuck, S. B. (1999). Status, stress, and atherosclerosis: the role of environment and individual behavior. Ann. N. Y. Acad. Sci., 896, 145–161. Kaplan, J. R., and Manuck, S. B. (2004). Ovarian dysfunction, stress, and disease: a primate continuum. ILAR J., 45 (2), 89–115. Kaufman, I. C., and Rosenblum, L. A. (1966). A behavioral taxonomy for Macaca nemestrina and Macaca radiata: based on longitudinal observation of family groups in the laboratory. Primates, 7, 205–258. Klosterman, L. L., Murai, J. T., and Siiteri, P. K. (1986). Cortisol levels, binding, and properties of corticosteroid-binding globulin in the serum of primates. Endocrinology, 118, 424–434. Koolhaas, J. M., Korte, S. M., De Boer, S. F., Van Der Vegt, B. J., Van Reenen, C. G., Hopster, H., et al. (1999). Coping styles in animals: current status in behavior and stress-physiology. Neurosci. Biobehav. Rev., 23 (7), 925–935. Laudenslager, M. L. (1988). The psychobiology of loss: lesson from humans and nonhuman primates. J. Soc. Issues, 44, 19–36. Laudenslager, M. L., Aasal, R., Adler, L., Berger, C. L., Montgomery, P. T., et al. (1998). Elevated cytotoxicity in combat veterans with long-term post-traumatic stress disorder: preliminary observations. Brain Behav. Immun., 12, 74–79. Laudenslager, M. L., Berger, C. L., Boccia, M. L., and Reite, M. L. (1996). Natural cytotoxicity toward K562 cells by macaque lymphocytes from infancy through puberty: effects of early social challenge. Brain Behav. Immun., 10, 275–287. Laudenslager, M. L., Bettinger, T., and Sackett, G. (2006). Saliva as a medium for assessing cortisol and other compounds in nonhuman primates: Collection, assays, and examples. In “Nursery Rearing of Nonhuman Primates in the 21st Century.” (G. P. Sackett, G. Ruppenthal, and K. Elias, Eds.), Plenum Publishers, New York, 403–427.
22. Dominance and Immunity Laudenslager, M. L., and Boccia, M. L. (1996). Some observations on psychosocial stressors, immunity, and individual differences in nonhuman primates. Am. J. Primatol., 39, 205–221. Laudenslager, M. L., Boccia, M. L., Berger, C. L., Gennaro-Ruggles, M. M., McFerran, B., and Reite, M. L. (1995). Total cortisol, free cortisol, and growth hormone associated with brief social separation experiences in young macaques. Dev. Psychobiol., 28 (4), 199–211. Laudenslager, M. L., Boccia, M. L., and Reite, M. L. (1993). Biobehavioral consequences of loss in nonhuman primates: individual differences. In W. Stroebe, M. Stroebe, and R. Hansson (Eds.), Handbook of bereavement: theory, research, and intervention (1st ed., pp. 129–142). New York: Cambridge University Press. Laudenslager, M. L., Held, P. E., Boccia, M. L., Reite, M. L., and Cohen, J. J. (1990). Behavioral and immunological consequences of brief maternal separation: a species comparison. Dev. Psychobiol., 23, 247–264. Laudenslager, M. L., Rasmussen, K. L., Berman, C. M., Lilly, A. A., Shelton, S. E., Kalin, N. H., et al. (1999). A preliminary description of responses of free-ranging rhesus monkeys to brief capture experiences: behavior, endocrine, immune, and health relationships. Brain Behav. Immun., 13, 124–137. Laudenslager, M. L., Rasmussen, K. L., Berman, C. M., Suomi, S. J., and Berger, C. B. (1993). Specific antibody levels in free-ranging rhesus monkeys: relationships to plasma hormones, cardiac parameters, and early behavior. Dev. Psychobiol., 26, 407– 420. Laudenslager, M. L., and Worlein, J. M. (1999). Behavior/immune relationships in nonhuman primates. In M. Schedlowski and U. Tewes (Eds.), Psychoneuroimmunology: an interdisciplinary introduction (pp. 277–291). New York: Kluwer Academic/Plenum Publishers. Liu, D., Diorio, J., Tannenbaum, B., Caldji, C., Francis, D., Freedman, A., et al. (1997). Maternal care, hippocampal glucocorticoid receptors, and hypothalamic-pituitary-adrenal responses to stress. Science, 277 (5332), 1659–1662. Maier, S. F., and Laudenslager, M. L. (1988). Commentary: inescapable shock, controllability, and mitogen-stimulated lymphocyte proliferation. Brain Behav. Immun., 2, 87–91. Maninger, N., Capitanio, J. P., Mendoza, S. P., and Mason, W. A. (2003). Personality influences tetanus-specific antibody response in adult male rhesus macaques after removal from natal group and housing relocation. Am. J. Primatol., 61, 73–83. Manuck, S. B., Kaplan, J. R., Adams, M. R., and Clarkson, T. B. (1988a). Effects of stress and the sympathetic nervous system on coronary artery atherosclerosis in the cynomolgus macaque. Am. Heart J., 116 (1, Pt 2), 328–333. Manuck, S. B., Kaplan, J. R., Adams, M. R., and Clarkson, T. B. (1988b). Studies of psychosocial influences on coronary artery atherogenesis in cynomolgus monkeys. Health Psychol., 7 (2), 113–124. Manuck, S. B., Kaplan, J. R., Adams, M. R., and Clarkson, T. B. (1989). Behaviorally elicited heart rate reactivity and atherosclerosis in female cynomolgus monkeys (Macaca fascicularis). Psychosom. Med., 51, 306–318. Manuck, S. B., Kaplan, J. R., Rymeski, B. A., Fairbanks, L. A., and Wilson, M. E. (2003). Approach to a social stranger is associated with low central nervous system serotonergic responsivity in female cynomolgus monkeys (Macaca fascicularis). Am. J. Primatol., 61 (4), 187–194. Manuck, S. B., Marsland, A. L., Kaplan, J. R., and Williams, J. K. (1995). The pathogenicity of behavior and its neuroendocrine mediation: an example from coronary artery disease. Psychosom. Med., 57, 275–283.
495
Mccabe, P. M., Sheridan, J. F., Weiss, J. M., Kaplan, J. P., Natelson, B. H., and Pare, W. P. (2000). Animal models of disease. Physiol. Behav., 68, 501–507. McEwen, B. S. (2003). Interacting mediators of allostasis and allostatic load: towards an understanding of resilience in aging. Metab. Clin. Exp., 52 (10, Suppl 2), 10–16. McEwen, B. S. (2004). Protection and damage from acute and chronic stress: allostasis and allostatic overload and relevance to the pathophysiology of psychiatric disorders. Ann. N. Y. Acad. Sci., 1032, 1–7. McEwen, B. S., and Wingfield, J. C. (2003). The concept of allostasis in biology and biomedicine. Horm. Behav., 43 (1), 2–15. McGuire, M. T., Brammer, G. L., and Raleigh, M. J. (1983). Animal models: Are they useful in the study of psychiatric disorders? In “Ethopharmacology: Primate Models of Neuropsychiatric Disorders.” (R. F. Schlemmer, J. M. Davis, and K. A. Miczek, Eds), Alan Liss Publisher, New York, 313–328. McKinney, W. T., Jr., and Bunney, W. E., Jr. (1969). Animal model of depression. Arch. Gen. Psychiatry., 21, 240– 248. Meaney, M. J., Aitken, D. H., Bodnoff, S. R., Iny, L. J., and Sapolsky, R. M. (1985). The effects of postnatal handling on the development of the glucocorticoid receptor systems and stress recovery in the rat. Prog. Neuropsychopharmacol. Biol. Psychiatry., 9, 731–734. Meaney, M. J., Bhatnagar, S., Larocque, S., Mccormick, C., Shanks, N., Sharma, S., et al. (1993). Individual differences in the hypothalamic-pituitary-adrenal stress response and the hypothalamic CRF system. Ann. N. Y. Acad. Sci., 697, 70–85. Mehlman, P. T., Higley, J. D., Faucher, I., Lilly, A. A., Taub, D. M., Vickers, J., et al. (1994). Low CSF 5-HIAA concentrations and severe aggression and impaired impulse control in nonhuman primates. Am. J. Psychiatry, 151, 1485–1491. Mellors, J. W., Kingsley, L. A., Rinaldo, C. R. Jr., Todd, J. A., Hoo, B. S., Kokka, R. P., et al. (1995). Quantitation of HIV-1 RNA in plasma predicts outcome after seroconversion. Ann. Intern. Med., 122, 573–579. Mendoza, S. P., and Moberg, G. P. (1985). Species differences in adrenocortical activity of new world primates: response to dexamethasone suppression. Am. J. Primatol., 8, 215– 224. Merlot, E., Moze, E., Bartolomucci, A., Dantzer, R., and Neveu, P. J. (2004). The rank assessed in a food competition test influences subsequent reactivity to immune and social challenges in mice. Brain Behav. Immun., 18 (5), 468–475. Merlot, E., Moze, E., Dantzer, R., and Neveu, P. J. (2003). Importance of fighting in the immune effects of social defeat. Physiol. Behav., 80 (2–3), 351–357. Merlot, E., Moze, E., Dantzer, R., and Neveu, P. J. (2004a). Cytokine production by spleen cells after social defeat in mice: activation of T cells and reduced inhibition by glucocorticoids. Stress, 7 (1), 55–61. Merlot, E., Moze, E., Dantzer, R., and Neveu, P. J. (2004b). Immune alterations induced by social defeat do not alter the course of an on-going BCG infection in mice. Neuroimmunomodulation, 11 (6), 414–418. Miyaura, H., and Iwata, M. (2002). Direct and indirect inhibition of Th1 development by progesterone and glucocorticoids. J. Immunol., 168 (3), 1087–1094. Nemeroff, C. B. (2004). Neurobiological consequences of childhood trauma. J. Clin. Psychol., 65 (Suppl 1), 18–28. Noldus, L. P. J. J. (1991). The observer: a software system for collection and analysis of observational data. Behav. Res. Methods, 23, 415–429.
496
III. Behavior and Immunity
Norbiato, G., Bevilacqua, M., Vago, T., Baldi, G., Chebat, E., Bertora, P., et al. (1992). Cortisol resistance in acquired immunodeficiency syndrome. J. Clin. Endocrinol. Metab., 74, 608–613. Patten, S. B. (1999). Depressive symptoms and disorders, levels of functioning and psychosocial stress: an integrative hypothesis. Med. Hypotheses, 53 (3), 210–216. Rasmussen, K. L. R., Berard, J. D., and Suomi, S. J. (1995). Extremes of social integration: Biobehavioral patterns of solitary vs. social males in Cayo Santiago rhesus macaques. Am. J. Primatol., 36, 150. Rawlins, R. G., and Kessler, M. J. (1986). The Cayo Santiago macaques: history, behavior, and biology. Albany: State University of New York Press. Reite, M., Kaemingk, K., and Boccia, M. L. (1989). Maternal separation in bonnet monkey infants: altered attachment and social support. Child Dev., 60, 473–480. Rosenblum, L. A., Smith, E. L. P., Altemus, M., Scharf, B. A., Owens, M. J., Nemeroff, C. B., et al. (2002). Differing concentrations of corticotropin-releasing factor and oxytocin in the cerebrospinal fluid of bonnet and pigtail macaques. Psychoneuroendocrinology, 27, 651–660. Sapolsky, R. M. (1982). The endocrine stress-response and social status in the wild baboon. Horm. Behav., 16, 279–292. Sapolsky, R. M. (1983). Endocrine aspects of social instability in the olive baboon (Papio anubis). Am. J. Primatol., 5, 365–379. Sapolsky, R. M. (1991). Testicular function, social rank and personality among wild baboons. Psychoneuroendocrinology, 16, 281–293. Sapolsky, R. M. (1992). Cortisol concentrations and the social significance of rank instability among wild baboons. Psychoneuroendocrinology, 17, 701–709. Sapolsky, R. M. (1993). Endocrinology alfresco: psychoneuroendocrine studies of wild baboons. Recent Prog. Horm. Res., 48, 437–468. Sapolsky, R. M. (2005a). Social status and health in humans and other animals. Annu. Rev. Anthropol., 33, 393–418. Sapolsky, R. M. (2005b). The influence of social hierarchy on primate health. Science, 308 (5722), 648–652. Sapolsky, R. M., Alberts, S. C., and Altmann, J. (1997). Hypercortisolism associated with social subordinance or social isolation among wild baboons. Arch. Gen. Psychiatry, 54 (12), 1137–1143. Sapolsky, R. M., and Share, L. J. (1994). Rank-related differences in cardiovascular function among wild baboons: role of sensitivity to glucocorticoids. Am. J. Primatol., 32, 261–275. Scammell, J. G., Denny, W. B., Valentine, D. L., and Smith, D. F. (2001). Overexpression of the FK506-binding immunophilin FKBP51 is the common cause of glucocorticoid resistance in three new world primates. Gen. Comp. Endocrinol., 124, 152–165. Seeman, T. E., Singer, B. H., Rowe, J. W., Horwitz, R. I., and McEwen, B. S. (1997). Price of adaptation—allostatic load and its health consequences: MacArthur studies of successful aging. Arch. Intern. Med., 157 (19), 2259–2268. Sheridan, J. F., Padgett, D. A., Avitsur, R., and Marucha, P. T. (2004). Experimental models of stress and wound healing. World J. Surg., 28 (3), 327–330. Shieh, T. M., Carter, D. L., Blosser, R. L., Mankowski, J. L., Zink, M. C., and Clements, J. E. (2001). Functional analyses of natural killer cells in macaques infected with neurovirulent simian immunodeficiency virus. J. Neurovirol., 7 (1), 11–24.
Smuts, B. B. (1985). Sex and friendship in baboons. New York: Aldine de Gruyter. Spencer, R. L., Miller, A. H., Moday, H., McEwen, B. S., Blanchard, R. J., Blanchard, D. C., et al. (1996). Chronic social stress produces reductions in available splenic type II corticosteroid receptor binding and plasma corticosteroid binding globulin levels. Psychoneuroendocrinology, 21 (1), 95–109. Stefanski, V. (1998). Social stress in loser rats: opposite immunological effects in submissive and subdominant males. Physiol. Behav., 63 (4), 605–613. Stefanski, V. (2000). Social stress in laboratory rats: hormonal responses and immune cell distribution. Psychoneuroendocrinology, 25 (4), 389–406. Stefanski, V. (2001). Social stress in laboratory rats: behavior, immune function, and tumor metastasis. Physiol. Behav., 73 (3), 385–391. Stefanski, V., and Engler, H. (1998). Effects of acute and chronic social stress on blood cellular immunity in rats. Physiol. Behav., 64 (5), 733–741. Stefanski, V., Knopf, G., and Schulz, S. (2001). Long-term colony housing in Long Evans rats: immunological, hormonal, and behavioral consequences. J. Neuroimmunol., 114 (1–2), 122–130. Stevenson-Hinde, J., and Zunz, M. (1978). Subjective assessment of individual rhesus monkeys. Primates, 19, 473–482. Tamashiro, K. L., Nguyen, M. M., Fujikawa, T., Xu, T., Yun Ma, L., Woods, S. C., et al. (2004). Metabolic and endocrine consequences of social stress in a visible burrow system. Physiol. Behav., 80 (5), 683–693. Taravosh-Lahn, K., and Delville, Y. (2004). Aggressive behavior in female golden hamsters: development and the effect of repeated social stress. Horm. Behav., 46 (4), 428–435. Vago, T., Clerici, M., and Norbiato, G. (1994). Glucocorticoids and the immune system in AIDS. Baillieres Clin. Endocrinol. Met., 8, 789–802. Virgin, C. E., and Sapolsky, R. M. (1997). Styles of male social behavior and their endocrine correlates among low-ranking baboons. Am. J. Primatol., 42 (1), 25–39. vonHolst, D. (1997). Social relations and their health impact in tree shrews. Acta Physiol. Scand., 161, 77–82. Walters, J. R., and Seyfarth, R. M. (1987). Conflict and cooperation. In B. B. Smuts, D. L. Cheney, R. M. Seyfarth, R. W. Wrangham, and T. T. Struhsaker (Eds.), Primate societies (pp. 306–317). Chicago: The University of Chicago Press. Watson, A., Ranchalis, J., Travis, B., McClure, J., Sutton, W., Johnson, P. R., et al. (1997). Plasma viremia in macaques infected with simian immunodeficiency virus: plasma load early in infection predicts survival. J. Virol., 71, 284–290. Williamson, D. E., Coleman, K., Bacanu, S. A., Devlin, B. J., Rogers, J., Ryan, N. D., et al. (2003). Heritability of fearful-anxious endophenotypes in infant rhesus macaques: a preliminary report. Biol. Psychiatry, 53, 284–291. Yehuda, R. (2002). Current status of cortisol findings in posttraumatic stress disorder. Psychiatr. Clin. N. Am., 25, 341–368. Yehuda, R. (2003). Hypothalamic-pituitary-adrenal alterations in PTSD: are they relevant to understanding cortisol alterations in cancer? Brain Behav. Immun., 17 (Suppl 1), S73–83. Zuckerman, S. (1932). The social life of monkeys and apes. London: Kegan.
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23 Social Context as an Individual Difference in Psychoneuroimmunology EDITH CHEN AND GREGORY E. MILLER
I. INTRODUCTION 497 II. SOCIOECONOMIC STATUS AND HEALTH 498 III. PATHWAYS LINKING SOCIOECONOMIC STATUS AND IMMUNE FUNCTIONS 498 IV. DEFINING AND MEASURING SOCIOECONOMIC STATUS 500 V. EVIDENCE OF SOCIOECONOMIC STATUS ASSOCIATIONS WITH IMMUNE FUNCTIONS 501 VI. CONCLUSIONS 505
Weitzman, Schoen, & Anton, 1999; Davidson, Coe, Dolski, & Donzella, 1999; Denollet et al., 2003; Marsland, Cohen, Rabin, & Manuck, 2001; Miller, Cohen, Rabin, Skoner, & Doyle, 1999; Miller, Dopp, Myers, Felten, & Fahey, 1999; Segerstrom, Taylor, Kemeny, & Fahey, 1998; Strauman, Lemieux, & Coe, 1993; Suarez, 2003; Suarez, Lewis, & Kuhn, 2003). Because several excellent reviews of this area of research have been published recently (Segerstrom, 2000; Segerstrom, 2003; Segerstrom, Kemeny, & Laudenslager, 2001), the goal of this chapter will be to introduce an alternative approach to conceptualizing individual differences, and discuss its implications for conducting and interpreting research in PNI. Though research on individual differences in PNI has been very fruitful, it has consistently overlooked questions about the origins of cognitive, affective, and behavioral characteristics. In this chapter we will argue that the larger social context is a critical factor in shaping individual differences and needs to be considered more thoroughly in PNI. The term social context refers to neighborhood, community, and family influences on an individual. In contrast, much of the individual differences literature isolates the individual and focuses on defining his/her characteristics, without much emphasis on how the larger social context may shape the development of these characteristics. As one representative indicator of this larger social context, we focus here on the role of socioeconomic status (SES). By SES, we refer to an individual’s position within a larger social hierarchy, as typically indicated
I. INTRODUCTION Individual differences refer to enduring characteristics that distinguish one organism from another and that are stable over time and across situations. Traditionally, these characteristics have included cognitive, affective, behavioral, and/or genetic traits ascribed to persons or animals. In humans, a large body of work has documented associations between individual differences and morbidity and mortality (Cohen, Doyle, Skoner, Rabin, & Gwaltney, Jr., 1997; Cohen et al., 1995; Cole, Kemeny, & Taylor, 1997; Cole, Kemeny, Taylor, Visscher, & Fahey, 1996; Cole et al., 2001; Kubzansky, Sparrow, Vokonas, & Kawachi, 2001; Miller, Smith, Turner, Guijarro, & Hallet, 1996; Reed, Kemeny, Taylor, & Visscher, 1999; Reed, Kemeny, Taylor, Wang, & Visscher, 1994; Scheier & Bridges, 1995; Scheier et al., 1999), and this work has given rise to mechanistic questions regarding the immunologic correlates of personality characteristics (Cole, Kemeny, PSYCHONEUROIMMUNOLOGY, 4E VOLUME I
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by social status (e.g., occupation, educational attainment) or material resources (e.g., income, savings). Focusing on the role of SES in PNI is important for several reasons. First, SES is a construct that simultaneously reflects neighborhood, community, and family influences. At the broadest level, markers of SES can be derived from community characteristics (e.g., the gap between the rich and the poor across a community). At a more proximal level, indicators of SES can be derived from features of a person’s neighborhood (e.g., the median home price or rates of violent crime), or the family that he/she is part of (e.g., annual family income or educational attainment). Second, SES is often considered to reflect a stable, enduring characteristic, a necessary quality for an individual difference variable. Although some SES characteristics can change from year to year (e.g., family income), many are fairly consistent across time (e.g., educational attainment). Finally, there is robust evidence that SES at one point in time can have long-lasting impacts on health. For example, early childhood SES has been found to predict health outcomes decades later in adult life, such as cardiovascular disease, stomach cancer, and hemorrhagic stroke (Barker, 1992; Galobardes, Lynch, & Smith, 2004). These observations suggest that SES is an important social context variable that contributes to the development of enduring individual differences across people.
II. SOCIOECONOMIC STATUS AND HEALTH SES has a profound influence on physical and mental health outcomes. Of all the social and psychological factors studied to date, SES exhibits the strongest and most consistent associations with morbidity and mortality. Individuals lower in SES are more likely to develop illnesses in the first place, to have difficulties managing them, and to die from them, compared with their higher-status peers. This “social gradient” exists for nearly all acute and chronic medical conditions. It also emerges in nearly all countries of the world, regardless of whether their citizens have universal access to care. Lastly, the social gradient persists across the life span, from early childhood to older adulthood (see Adler, Boyce, Chesney, Folkman, & Syme, 1993; Chen, Matthews, & Boyce, 2002; Marmot, Kogevinas, & Elston, 1987; Townsend & Davidson, 1982; Williams & Collins, 1995, for reviews). SES also is associated with a wide variety of psychological variables. These include traditional individual difference variables, such as hostility, optimism, depression, and anxiety (Adler et al., 1994; Barefoot et
al., 1991; Gallo & Matthews, 2003; Kubzansky, Sparrow, Vokonas, & Kawachi, 2001). Furthermore, low SES is associated with poor health behaviors, such as increased risk of smoking and decreased physical activity (Adler et al., 1994; Cohen, Kaplan, & Salonen, 1999; Lynch, Kaplan, & Salonen, 1997). Finally, evidence suggests that individuals from different SES backgrounds have different types of life experiences. For example, lower SES individuals are more likely to be exposed to stressful life events and are more likely to perceive stress in their lives (Brady & Matthews, 2002; Chen, Langer, Raphaelson, & Matthews, 2004; Cohen et al., 1999). Taken together, these findings suggest that SES is an individual difference variable that has profound effects on health and well-being. This highlights the importance of studying SES from a PNI perspective in order to understand mechanisms for how SES “gets under the skin” to influence health outcomes. Furthermore, SES clearly has psychosocial influences, underscoring the importance of considering SES as a psychologically relevant individual difference variable in PNI studies. In the next section, we briefly discuss possible pathways between SES and immune functions.
III. PATHWAYS LINKING SOCIOECONOMIC STATUS AND IMMUNE FUNCTIONS Why would a person’s SES influence the functions of his/her immune system? Although there are many potential answers to this question, they can usually be placed into one of two categories of explanation, depending on whether they emphasize SES’s role in fostering exposure versus vulnerability. Exposure hypotheses maintain that a person’s SES influences his/her chances of coming into contact with stimuli (exposures) that modify the immune response. These stimuli can range from micro-organisms that give rise to infectious disease, to environmental pollutants that set off inflammatory processes in the lung, to psychosocial stressors such as negative life events and community violence. Although these stimuli differ from one another in many respects, and influence immune functions through disparate mechanisms, what they share in common is a robust social gradient. For example, sanitation, environmental pollution, and violence vary by SES (Evans, 2004; Selner-O’Hagan, Kindlon, Buka, Raudenbush, & Earls, 1998). In addition, robust SES differences exist in the frequency of stressor exposure (Attar, Guerra, & Tolan, 1994; Brady et al., 2002; Garbarino, Kostelny, & Dubrow, 1991) and
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in the way that stressors are appraised (Chen et al., 2004; Cohen et al., 1999). This cumulative stressor burden is expected to give rise to immune system dysregulation among low SES individuals, rendering them vulnerable to diseases that are immunologically resisted or mediated (Herbert & Cohen, 1993; Segerstrom & Miller, 2004). See Figure 1 for a graphical depiction of the exposure model. There are several mechanisms through which stressful experiences could “get inside the body” to modify immunity. They include activation of autonomic fibers descending from the brain to lymphoid organs, stressrelated secretion of hormones and neuropeptides that regulate leukocyte function, or changes in coping behaviors such as smoking or sleeping (Ader, Cohen, & Felten, 1995; Cohen & Williamson, 1991). Behaviors such as cigarette smoking, alcohol consumption, and a sedentary lifestyle also can be viewed as potential mechanisms of exposure. These behaviors are more frequently observed among low SES individuals (Adler et al., 1994; Cohen et al., 1999; Lynch et al., 1997), and they are known to modify various immune functions (Cohen, Miller, & Rabin, 2001; Kiecolt-Glaser & Glaser, 1988). However, social disparities in morbidity and mortality persist after statistical adjustment for health practices, suggesting that behavior is not likely to be the primary mechanism of action for SES (Lantz et al., 1998; Lantz et al., 2001). In contrast to exposure hypotheses, vulnerability hypotheses maintain that low SES makes individuals more vulnerable when an exposure occurs. That is, among low SES individuals, higher levels of exposure will relate to greater dysregulation of immune function. In contrast, high SES will buffer individuals from the effects of exposure, such that greater exposure will be only weakly or not associated with immune dysregulation. Thus, this hypothesis argues that low SES individuals have a more pronounced response to an equivalent exposure (stimulus) compared to high SES individuals. See Figure 2. Much of this work has been
conducted with testing stress as a type of exposure. In this context, the vulnerability hypothesis predicts that low SES individuals would exhibit heightened immunologic dysregulation during times of high stress compared to low stress; in contrast, high SES individuals will be buffered and show few immune differences during high stress versus low stress times. Why would low and high SES individuals differ in their response to an identical stressor? One hypothesis is that people continuously appraise ongoing stressful circumstances along dimensions of threat and manageability (Lazarus & Folkman, 1984). To the extent that circumstances are evaluated as posing significant threat and exceeding coping resources, they elicit a cascade of emotional, behavioral, and hormonal responses, which ultimately result in dysregulation of various immune system functions (Cohen & Williamson, 1991; Segerstrom & Miller, 2004). Moreover, a person’s tendency to appraise stressors as threatening is shaped by his/her SES (Chen & Matthews, 2001; Chen & Matthews, 2003). By virtue of living and working in settings that are unpredictable and sometime dangerous, lower SES persons develop a tendency to interpret situations as potentially threatening, even when the extent of danger is ambiguous. This vigilant cognitive style results in interpretations of an equivalent stressor as more threatening among lower SES individuals. This response strategy in turn may activate stress-response systems unnecessarily, and over time this may contribute to cumulative wearand-tear on the endocrine and immune systems ( Chen et al., 2004; McEwen, 1998).
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FIGURE 1 Exposure model. Low SES individuals receive higher levels of exposure to micro-organisms, pollutants, and stressors, and in turn, higher levels of exposure are associated with greater immune dysregulation.
↑ SES: 0 relation Exposure – Immune Change FIGURE 2 Vulnerability model. The relationship between exposure and immune function depends on SES. Among low SES individuals, high levels of exposure are related to greater immune dysregulation. In contrast, high SES buffers individuals from the effects of exposures, such that there is no relationship between exposure and immune dysregulation in this group.
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A second aspect of the vulnerability hypothesis suggests that a person’s SES governs the types of coping resources he/she has available and can utilize during stressful encounters. Persons of lower SES by definition have fewer economic and educational resources than their high-SES peers; these disparities are likely to accentuate the impact of life stressors like job loss or chronic illness in the family. In support of this hypothesis, previous research has documented that providing individuals with resources reduces cardiovascular reactivity during an acute laboratory stressor among low SES, but not high SES, individuals (Chen, 2005). Thus, these theories suggest that the reasons why low SES individuals may show heightened biological responses compared to high SES individuals to equivalent exposures have to do with psychological processes such as threat appraisals and coping.
IV. DEFINING AND MEASURING SOCIOECONOMIC STATUS SES is a multi-dimensional construct, and the measures one chooses of SES can reflect different underlying conceptualizations about what SES means (Winkleby, Jatulis, Frank, & Fortmann, 1992). One traditional approach to conceptualizing SES is as an indicator of a person’s status or standing within society. Researchers have termed these “prestige-based measures of SES,” as they indicate how a person is regarded within the community. Commonly used prestigebased indicators include education and occupation (Krieger, Williams, & Moss, 1997; Winkleby et al., 1992), with more advanced training and more prestigious jobs viewed as higher status. Others have argued for a resource-based model of SES, which suggests that the critical component of SES is the material resources a person possesses. These assets, including family income, assets, and wealth, are hypothesized to play a role in determining both health status and health trajectories over time in a family (Krieger et al., 1997; Lynch, Smith, Kaplan, & House, 2000). In contrast to these two more objective approaches, other researchers have argued for a more subjective, or relative, approach to measuring SES. This approach is based on the notion that most individuals do not understand SES in terms of absolute dollars, but rather in terms of where they stand relative to their peers, and that an individual’s perception of his/her SES or social standing will be more important to health outcomes than objective measures (Adler, Epel, Castellazzo, & Ickovics, 2000).
In addition, SES can be measured at multiple levels (Krieger et al., 1997). For example, one could measure characteristics of the community, neighborhood, family, or individual. Community measures include factors such as the level of income inequality in a society, or the level of social capital (community norms for cooperation and behavior) (Kawachi, Kennedy, Lochner, & Prothrow-Stith, 1997; Wilkinson, 1992). Neighborhood SES measures are narrower than community measures, and represent an aggregate measure of the group of individuals living in a neighborhood. These include indicators such as the percentage of adults with less than high school education in the neighborhood, median family income of the neighborhood, and percentage of people who own their own homes in the neighborhood. These characteristics describe the larger context that an individual lives in. At the family and individual levels, SES measures include direct assessments of the individual participant or the household that the participant lives in. Family measures include those described above, such as the income and savings of all family members living in a household. In contrast, individual SES measures focus on just the study participant, and could include either objective indicators, such as the individual’s occupation or educational attainment, or the subjective indicators described above, such as perceived social status. These various approaches highlight the importance of understanding the measurement approach when interpreting findings on SES and PNI. In addition, it also indicates the importance for future researchers in this area to consider the ways in which SES might exert effects on their immune outcomes of interest, and to choose theoretically meaningful approaches to measuring SES when designing PNI studies. For example, stronger associations with resource-based SES measures such as income and savings might suggest that more money allows families to afford higher quality medical care, which would presumably have effects on disease processes. In contrast, stronger associations with prestige-based SES measures such as educational attainment might suggest that higher SES families have better knowledge about healthy lifestyles, which in turn may lead to better health behaviors with immunological consequences. Finally, stronger associations with subjective SES measures might suggest that perceptions of social standing are related to the control one perceives over one’s life, or the degree to which one utilizes proactive coping strategies for dealing with stress, both of which may have implications for activation of stress-response systems.
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V. EVIDENCE OF SOCIOECONOMIC STATUS ASSOCIATIONS WITH IMMUNE FUNCTIONS This section describes existing research on SES and immunity in humans. Following the conceptual distinction introduced earlier, studies are grouped according to whether they emphasize exposure versus vulnerability, and also according to kinds of immune system outcomes they include. Because this is a new area of inquiry, most research focuses on the simple question of whether SES and immune outcomes are related, without attempting to identify mechanisms that might be responsible for such an association. As we note, this will be an important direction for later research.
A. Exposure Hypothesis Studies guided by the exposure hypothesis examine associations between SES indicators and immune functions. The better research in this area goes a step further and seeks to identify potential underlying mechanisms, such as SES-related disparities in pathogen exposure, environmental pollutants, health practices, or stressful experience.
B. Studies in Community Populations A number of these studies have shown associations of SES with inflammatory molecules involved in the pathogenesis of coronary heart disease (CHD). For example, healthy adults from lower SES groups (as defined by a combination of education and income) had higher levels of CRP, IL-6, TNR-α, fibrinogen, and homocysteine (Panagiotakos et al., 2005). Adults from lower occupation groups had higher levels of CRP, IL-6, and serum amyloid A (though no differences were found for adhesion molecules that reflect endothelial activation) (Hemingway et al., 2003), and higher levels of fibrinogen (Brunner et al., 1993). Being unemployed also was associated with higher levels of CRP, although no differences in CRP were found for other SES markers such as education, car and home ownership (Danesh et al., 1999). Finally, adults from a low income group had higher levels of heat shock protein 60 compared to those from a high income group (Lewthwaite, Owen, Coates, Henderson, & Steptoe, 2002). Heat shock protein 60 is a protein released by cells that have faced trauma, such as heat, injury, or infection, and high levels have been related to CHD (Zhu et al., 2001). Other studies have examined immune markers different from those implicated in CHD. For example, one
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study measured the presence of the immunoglobulin secretory IgA (or sIgA) in maternal breast milk. Lower household income was associated with higher sIgA (Groer, Davis, & Steele, 2004). These findings suggest that low SES mothers may have been exposed to infectious micro-organisms to a greater extent than high SES mothers. At the same time, however, higher concentrations of sIgA may be beneficial for breastfeeding infants, who receive most of their mucosal immune protection through maternal transfer of antibody in milk.
C. Studies with Relative SES Measures Another study utilized a novel approach of measuring SES to investigate associations with immune variables. All of the above studies have relied on objective indicators of SES, such as education or occupation. However, families vary greatly in the extent to which they spend money on material possessions, regardless of their objective status. Dressler (Dressler, 1990; Dressler, Bindon, & Neggers, 1998) has argued that the discrepancy between outward displays of prestige (via material possessions) and actual objective circumstances (via education or occupation) is an indicator of “lifestyle incongruity,” and that higher levels of lifestyle incongruity are detrimental because they create stresses on the family. Consistent with this line of reasoning, one study found that in adolescents greater lifestyle incongruity (greater material possessions relative to objective circumstances) was associated with more antibody to the latent Epstein-Barr virus (EBV) (McDade, 2001). Higher levels of antibodies suggest that latent EBV may have been reactivated, either by stress hormones, poor immune control, or other mechanisms (Glaser & Gottlieb-Stematsky, 1982). Given that EBV plays a role in the pathogenesis of infectious mononucleosis, these findings could have implications for explaining some of the SES gradient in infectious disease.
D. Studies in Chronically Ill Populations Finally, one study examined associations of SES with immune markers in the context of a chronic inflammatory disease. Adolescents diagnosed with persistent asthma were recruited from either low SES or high SES neighborhoods (based on the percentage of people living below poverty in each neighborhood). Blood was drawn, and cells were stimulated with a combination of phorbol myristate acetate and ionomycin to induce the production of cytokines. Researchers have hypothesized that certain cytokines are impor-
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tant for the orchestration of cellular events related to airway inflammation and hyper-responsiveness (Chung & Barnes, 1999). For example, Th-2 cell secretion of IL-4 induces B-cells to produce IgE antibodies, which initiate an inflammatory cascade leading to airway constriction and mucus production (Bacharier & Geha, 2000). Th-2 cell secretion of the cytokine IL-5 has been found to increase eosinophil production, which also promotes airway inflammation and obstruction (Kamfar, Koshak, & Milaat, 1999; Ying et al., 1997). More recently, some researchers have argued that the cytokines that Th-1 cells produce (e.g., IFN-γ) also are elevated in patients with asthma, and can induce airway inflammation (Busse & Lemanske, 2001; Hansen, Berry, DeKruyff, & Umetsu, 1999; Holtzman, Sampath, Castro, Look, & Jayaraman, 1996; Marguet, Dean, & Warner, 2000). Thus, this study investigated stimulated production of IL-4, IL-5, and IFN-γ. Adolescents with asthma from low SES neighborhoods displayed significantly greater production of IL-5, IFN-γ, and marginally greater production of IL-4 compared to adolescents with asthma from high SES neighborhoods (Chen, Fisher, Jr., Bacharier, & Strunk, 2003). See Figure 3. These findings suggest that within the context of a chronic disease, low SES adolescents may exhibit heightened inflammatory responses to pathogens, and that the specific nature of these responses is consistent with pathways to more severe exacerbations of asthma.
E. Vulnerability Hypothesis
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Studies examining the vulnerability hypothesis often utilize the acute-stress paradigm. This entails bringing participants into the laboratory and collecting blood from them during a resting baseline. Participants then engage in a brief stressor, such as impromptu public speaking or pressured mental arithmetic, and additional blood is collected after the stressor. The vulnerability hypothesis is supported when low SES participants exhibit greater stressor-induced immune dysregulation compared with high SES participants.
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FIGURE 3 Evidence for exposure model: Low SES adolescents with asthma have higher levels of stimulated production of IL-5 and IFN-γ compared to high SES adolescents with asthma.
Importantly, under this hypothesis SES differences are predicted to emerge during stressful circumstances, rather than during the baseline period.
F. Laboratory Stress Paradigms A number of studies have examined the vulnerability hypothesis in relation to inflammatory molecules implicated in CHD. These studies have been conducted by one research group and have all used a similar paradigm. Healthy adults underwent two acute stress tasks. One involved tracing an image that could only be seen in a mirror, as quickly and accurately as possible. The second involved identifying as quickly as possible the colors of color words that were printed in incongruent colors (e.g., the word red printed in blue. This is also known as the Stroop task). These tasks typically lasted 5 minutes each. Blood was drawn at baseline, in some studies immediately after the acute stressors, and then during a recovery period (ranging from 30–120 minutes post-stressor across the various studies). SES was defined by participants’ occupational status, for example, higher status jobs being managerial positions, and lower status jobs being clerical positions. One of these studies found partial support for the vulnerability hypothesis. Lower SES participants had higher circulating concentrations of the inflammatory cytokine interleukin-6 (IL-6) 120 minutes after the stressor ended compared with higher SES participants (Brydon, Edwards, Mohamed-Ali, & Steptoe, 2004). No SES differences in IL-6 were evident at baseline, or at 30 or 75 minutes after the stressor. Given that protein synthesis requires a minimum of 1–2 hours to occur, 30–75 minutes may have been too soon to detect stressrelated boosts in IL-6 expression. Regardless, if the findings at 120 minutes prove to be robust, they could help to explain the SES gradient in cardiovascular disease, as inflammatory processes have a key role in the development, progression, and clinical expression of atherosclerosis (Libby, Ridker, & Maseri, 2002; Ross, 1999). In contrast, several of this group’s other studies have found SES differences in inflammatory molecules during resting periods, but this difference did not change during or after participants were exposed to a stressor. For example, adults who are low in SES by virtue of having a low-prestige occupation (or lower education or income) showed elevated concentrations of the inflammatory molecule C-reactive protein during a resting baseline (Owen, Poulton, Hay, Mohamed-Ali, & Steptoe, 2003). CRP is a marker of systemic inflammation, and high levels are associated with CHD risk (Ridker, 2003; Ridker, Hennekens,
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G. Life Experiences with Stress It is important to remember that these studies focused on acute stressors in the laboratory, and the artificial nature of these tasks raises questions about their generalizability to the real world. A project conducted by a different research group found support for the vulnerability hypothesis when low and high SES persons were compared in the midst of a real-life chronic stressor. In this study, healthy adults were recruited who were either undergoing a major life chronic stressor (having a child being treated for pediatric cancer) or were under no chronic stress (having medically healthy children and no other major life
stressors). Parents underwent blood draw, and their cells were co-incubated in vitro with lipopolysaccharide (a bacterial product that stimulates cytokine production) and dexamethasone (a synthetic form of the hormone cortisol, which is a potent inhibitor of inflammation), and subsequent production of IL-6 was measured. This assay tests leukocyte sensitivity to the inhibitory properties of glucocorticoid hormones, which in vivo play a key role in regulating the magnitude and duration of inflammation. Interestingly, chronic stress-related alterations in the immune system were evident only among low SES participants. That is, parents of cancer patients showed reduced sensitivity to the anti-inflammatory properties of dexamethasone compared to parents of healthy children, but this was true only if they had lower levels of education (defined as a high school diploma or less). In parents of cancer patients who had some college education, there were no detectable alterations in glucocorticoid sensitivity relative to controls (Miller, 2002). See Figure 4. These findings suggest that low SES individuals facing chronic stressors may have disrupted mechanisms for regulating inflammation, which if sustained could place them at risk for conditions involving excessive inflammation, such as cardiac, allergic, and autoimmune diseases (Miller, Cohen, & Ritchey, 2002). More generally, these findings provide support for a vulnerability hypothesis of SES, at least in the context of real-world stressors that are severe and chronic.
H. Vulnerability to Viral Challenge A handful of studies have examined a modified version of the vulnerability hypothesis. In this view
IL-6 (percent resistance)
Buring, & Rifai, 2000). They also showed higher numbers of total lymphocytes, T lymphocytes, and natural killer cells at baseline compared with higher SES adults, but SES disparities did not increase in magnitude 1 or 45 minutes after the stressor ended, as the vulnerability hypothesis would predict (Owen et al., 2003). In another study by this group, women with lower occupational status had higher IL-6 at baseline, but again SES differences did not change in magnitude after the stressor. There also were no SES disparities for men (Steptoe, Owen, Kunz-Ebrecht, & MohamedAli, 2002). Other studies from this group have focused on coagulation processes involved in CHD progression. This work has yielded a similar pattern of findings. Participants with lower SES showed higher levels of coagulation markers such as fibrinogen (Steptoe et al., 2003a), leukocyte-platelet aggregate, and monocyte-platelet aggregate (Steptoe et al., 2003b) during resting-baseline periods. However, the SES disparities did not change in magnitude from the resting baseline to after the stressor. Finally, one study found quadratic effects of SES on inflammatory molecules linked to CHD. Adults in the intermediate SES group had the highest levels of the inflammatory cytokines tumor necrosis factor-α (TNF-α and interleukin-1 receptor antagonist (IL-1ra) compared to those in the low or high SES groups at baseline. Again, these disparities did not diverge further during or after the stressor (Steptoe et al., 2002). Collectively, these findings suggest that SES differences primarily exist under basal conditions, supporting the exposure hypotheses (SES differences in immune markers evident across different conditions). These studies on the whole did not find evidence suggesting that among low SES individuals, there is a stronger relationship between exposure to stress and immune function compared to among high SES individuals (as the vulnerability hypothesis would suggest).
1
CANCER CONTROL
0.75 0.5 0.25 0 HIGH SCHOOL DIPLOMA
SOME COLLEGE
COLLEGE DEGREE
FIGURE 4 Evidence for vulnerability model: Among low SES individuals, high exposure to chronic stress (being a parent of a child with cancer) is associated with reduced sensitivity to the anti-inflammatory properties of dexamethasone compared to low exposure to chronic stress (being a parent of a healthy child). In contrast, among higher SES individuals, exposure to chronic stress is not related to sensitivity to dexamethasone.
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SES determines the efficacy of a person’s immune response to infectious challenge rather than (or perhaps in addition to) his/her response to stressful experience. The idea here is that SES influences the immune system’s capacity to eradicate invading pathogens, or modifies the nature and severity of clinical symptoms a person experiences once infected. This paradigm usually involves assessing healthy participants on a variety of SES variables and then exposing participants to a rhinovirus that causes upper respiratory infection. Participants are quarantined and monitored for signs of objective infection (viral shedding and antibody production) and clinical illness (mucus production and nasal congestion). Participants are considered to have a “cold” if they meet criteria for both infection and illness. One group of researchers has documented several SES-related findings using this paradigm. For example, adults who were unemployed (or underemployed) were three to four times more likely to develop a cold after rhinovirus exposure compared with adults who had sufficient work (Cohen et al., 1998). In another study, this group showed that SES during early periods of life has important consequences for disease susceptibility. Adults who had lower SES when they were children—as indicated by their parents not owning a home—were more likely to develop a cold following viral exposure (Cohen, Doyle, Turner, Alper, & Skoner, 2004). This was a dose-response association, such that the more years a family did not own a home, the more likely the participant was to develop a cold. Interestingly, owning a home later in life—either during adolescence or adulthood—did not attenuate these associations. This suggests that early childhood may be a critical period during which SES shapes the immune system in a fashion that cannot be “undone” by later improvements in a person’s social status. Finally, in addition to objective indicators of SES, these researchers also investigated the role of subjective indicators of status. Before exposure to the virus, participants were asked to rate where they stood in their own community relative to others. Adults who perceived themselves to be lower in social status were more likely to develop infection following exposure to a rhinovirus (Cohen, 1999).
I. Response to Vaccination Lastly, one study from another research group utilized a slightly different paradigm for examining SES differences in vulnerability to immune challenge. Rather than exposing participants to viruses that cause the common cold, these investigators tested the associations of SES with responses to vaccination for rubella
in adolescent girls. After vaccination, adolescents were classified as either infected with the rubella virus (being seronegative at the start of the study, then showing at least a four-fold increase in rubella antibody titers), or as showing no change in antibody titers (due to being seropositive at the start of the study). These researchers found that antibody response was associated with different behavioral effects, depending on the SES of the adolescents. Among low SES girls, those who showed an antibody response to vaccination reported more depression, attention problems, and delinquent behaviors 2–10 weeks after vaccination compared to those who did not respond to vaccination (Morag, Yirmiya, Lerer, & Morag, 1998). In contrast, among middle and high SES girls, there were no behavioral differences between those who did and did not show antibody response to vaccination. Research indicates that inflammation following pathogen exposure can produce a constellation of adjustments known as sickness behavior (Maier & Watkins, 1998; Yirmiya, 1996). These behaviors are thought to be similar to depression and can include negative mood, difficulty concentrating, and anhedonia. Thus, the findings from the above study suggest that low SES individuals may be particularly vulnerable to sickness behaviors that result from infectious challenges.
J. Potential Pathways between SES and the Immune System In addition to investigating associations of SES with immune markers, several of the above studies have also tested whether different mechanisms may account for relationships between SES and immune markers. These mechanisms include ones described earlier, such as stress and health behaviors, as well as other pathways such as social support and the endocrine system. Typically, these studies statistically control for possible mechanistic pathways, and compare the relationship of SES and immune markers prior to and after controlling for these variables. In their study on production of cytokines implicated in asthma, Chen et al. (2003) found that adolescents with asthma from low SES neighborhoods had heightened production of IL-5 and IFN-γ compared to adolescents with asthma from high SES neighborhoods. Stress was measured in this study both in terms of life stress exposure and perceptions of stress. When stress was included as a control variable, the relationship between SES and cytokine production decreased by 38–76%, and was no longer significant (Chen et al., 2003), suggesting that stress is a critical pathway linking SES and cytokine production in adolescents with asthma.
23. Social Context as an Individual Difference in Psychoneuroimmunology
With respect to health behaviors, a number of studies have tested the effects of controlling for health behaviors. Some studies have found that controlling for health behaviors somewhat reduces the association between SES and immune markers. For example, controlling for smoking, alcohol, exercise, and diet reduced the relationship between low SES and high fibrinogen levels to non-significant in women (but not men) (Brunner et al., 1993). On the other hand, controlling only for smoking did not reduce the association between SES and fibrinogen to non-significant in another study (Steptoe et al., 2003a). This may be because the constellation of health behaviors as a whole best accounts for the SES-fibrinogen relationship, or because factors such as alcohol use or exercise are more important to the SES-fibrinogen relationship than smoking. In contrast, the association between SES and other inflammatory markers, including CRP, IL-6, TNF-α, fibrinogen, and homocysteine remained significant after controlling for smoking, diet, physical activity, and medication compliance (Panagiotakos et al., 2005). Similarly, in the viral cold studies described above, controlling for smoking, alcohol, exercise, sleep, and vitamin C consumption slightly reduced the magnitude of the relationship between unemployment and risk of cold; however, the risk of cold for those facing unemployment was still significant (Cohen et al., 1998). In addition, controlling for smoking, alcohol, exercise, and sleep did not diminish the relationship between perceived social status and likelihood of developing a cold (Cohen, 1999). Taken together, these findings suggest that as they have been assessed to date, there is not much evidence that health behaviors play a major role in relationships between SES and inflammatory processes. However future studies that conduct more thorough and objective assessments of factors such as sleep, exercise, and diet may reveal greater support for the role of health behaviors in SES-immune relationships. Other pathways that have been tested include social support and endocrine measures. No evidence has been found for either of these processes as pathways. For example, the relationship between lower income and higher heat shock protein 60 remained significant after controlling for social isolation (Lewthwaite et al., 2002). The relationship between unemployment and colds remained significant after controlling for the diversity of a person’s social network (Cohen et al., 1998). With respect to endocrine measures, the association between unemployment and colds, as well as between perceived social status and colds, remained significant after controlling for epinephrine and norepinephrine (Cohen et al., 1998; Cohen, 1999).
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Taken together, these findings suggest that additional research is needed to uncover the mechanisms by which SES exerts effects on the inflammatory processes. Perhaps the most promising mediator is stress; however, only one study has tested the role of stress on SES and immune markers (Chen et al., 2003). Thus far, health behaviors, social support, and endocrine measures do not have much evidence supporting their mediational role. Future studies should explore the role of stress in greater depth, as well as test other possible mediators psychosocially (e.g., trait variables such as locus of control) and biologically (e.g., cortisol).
VI. CONCLUSIONS Though it has received scant attention in the PNI literature thus far, SES is emerging as an important individual difference characteristic. Persons of low SES exhibit various indicators of immune dysregulation when they are at rest, including heightened expression of inflammatory and coagulation molecules involved in CHD, and greater production of cytokines that are responsible for the symptoms of asthma. Although low SES does not seem to render people especially vulnerable to immune dysregulation following acute lab stress, there is preliminary evidence that it amplifies the biological consequences of severe and chronic stressors in real-life settings. Perhaps most compelling are the influences of SES following infectious challenge; persons of lower status exhibit heightened susceptibility to respiratory infection and sickness behavior. The mechanisms underlying these findings have not yet been elucidated. However, with further efforts in this exciting new area of PNI research, we will soon have a better understanding of how social context “gets under the skin” to influence well-being and health outcomes in such a profound fashion.
Acknowledgments Support for this chapter was provided by National Institutes of Health grant HL073975, the Canadian Institutes of Health Research, and the Michael Smith Foundation for Health Research.
References Ader, R., Cohen, N., and Felten, D. (1995). Psychoneuroimmunology: Interactions between the nervous system and the immune system. Lancet, 345, 99–103. Adler, N. E., Boyce, T., Chesney, M. A., Cohen, S., Folkman, S., Kahn, R. L., et al. (1994). Socioeconomic status and health: The challenge of the gradient. American Psychologist, 49, 15–24.
506
III. Behavior and Immunity
Adler, N. E., Boyce, W. T., Chesney, M. A., Folkman, S., and Syme, S. L. (1993). Socioeconomic inequalities in health: No easy solution. Journal of the American Medical Association, 269, 3140–3145. Adler, N. E., Epel, E. S., Castellazzo, G., and Ickovics, J. R. (2000). Relationship of subjective and objective social status with psychological and physiological functioning: preliminary data in healthy white women. Health Psychology, 19, 586–592. Attar, B. K., Guerra, N. G., and Tolan, P. H. (1994). Neighborhood disadvantage, stressful life events, and adjustment in urban elementary-school children. Journal of Clinical Child Psychology, 23, 391–400. Bacharier, L. B., and Geha, R. S. (2000). Molecular mechanisms of IgE regulation. Journal of Allergy and Clinical Immunology, 105, S547–S548. Barefoot, J. C., Peterson, B. L., Dahlstrom, W. G., Siegler, I. C., Anderson, N. B., and Williams, R. B. (1991). Hostility patterns and health implications: correlates of Cook-Medley Hostility scale scores in a national survey. Health Psychology, 10, 18–24. Barker, D. J. P. (1992). Fetal and infant origins of adult disease. London, England: British Medical Journal. Brady, S. S., and Matthews, K. A. (2002). The effect of socioeconomic status and ethnicity on adolescents’ exposure to stressful life events. Journal of Pediatric Psychology, 27, 575–583. Brunner, E. J., Marmot, M. G., White, I. R., O’Brien, J. R., Etherington, M. D., Slavin, B. M., et al. (1993). Gender and employment grade differences in blood cholesterol, apolipoproteins and haemostatic factors in the Whitehall II study. Atherosclerosis, 102, 195–207. Brydon, L., Edwards, S., Mohamed-Ali, V., and Steptoe, A. (2004). Socioeconomic status and stress-induced increases in interleukin-6. Brain Behavior and Immunity, 18, 281–290. Busse, W. W., and Lemanske, R. F. (2001). Advances in immunology: Asthma. New England Journal of Medicine, 344, 350–362. Chen, E. (2005). Socioeconomic status and physiological health in adolescents: The role of control versus resources. Presented at the Society of Behavioral Medicine annual meeting, Boston, MA. Chen, E., Fisher, E. B., Jr., Bacharier, L. B., and Strunk, R. C. (2003). Socioeconomic status, stress, and immune markers in adolescents with asthma. Psychosomatic Medicine, 65, 984–992. Chen, E., Langer, D. A., Raphaelson, Y. E., and Matthews, K. A. (2004). Socioeconomic status and health in adolescents: the role of stress interpretations. Child Development, 75, 1039– 1052. Chen, E., and Matthews, K. A. (2001). Cognitive appraisal biases: an approach to understanding the relation between socioeconomic status and cardiovascular reactivity in children. Annals of Behavioral Medicine, 23, 101–111. Chen, E., and Matthews, K. A. (2003). Development of the Cognitive Appraisal and Understanding of Social Events (CAUSE) videos. Health Psychology, 22, 106–110. Chen, E., Matthews, K. A., and Boyce, W. T. (2002). Socioeconomic differences in children’s health: how and why do these relationships change with age? Psychological Bulletin, 128, 295–329. Chung, K. F., and Barnes, P. J. (1999). Cytokines in asthma. Thorax, 54, 825–857. Cohen, S., (1999). Social status and susceptibility to respiratory infections. Annals of the New York Academy of Sciences, 896, 246–253. Cohen, S., Doyle, W. J., Skoner, D. P., Fireman, P., Gwaltney, J. M., Jr., and Newsom, J. T. (1995). State and trait negative affect as predictors of objective and subjective symptoms of respiratory viral infections. Journal of Personality and Social Psychology, 68, 159–169.
Cohen, S., Doyle, W. J., Skoner, D. P., Rabin, B. S., and Gwaltney, J. M., Jr. (1997). Social ties and susceptibility to the common cold. Journal of the American Medical Association, 277, 1940–1944. Cohen, S., Doyle, W. J., Turner, R. B., Alper, C. M., and Skoner, D. P. (2004). Childhood socioeconomic status and host resistance to infectious illness in adulthood. Psychosomatic Medicine, 66, 553–558. Cohen, S., Frank, E., Doyle, W. J., Skoner, D. P., Rabin, B. S., and Gwaltney, J. M., Jr. (1998). Types of stressors that increase susceptibility to the common cold in healthy adults. Health Psychology, 17, 214–223. Cohen, S., Kaplan, G. A., and Salonen, J. T. (1999). The role of psychological characteristics in the relation between socioeconomic status and perceived health. Journal of Applied Social Psychology, 29, 445–468. Cohen, S., Miller, G. E., and Rabin, B. S. (2001). Psychological stress and antibody response to immunization: a critical review of the human literature. Psychosomatic Medicine, 63, 7–18. Cohen, S., and Williamson, G. M. (1991). Stress and infectious disease in humans. Psychological Bulletin, 109, 5–24. Cole, S. W., Kemeny, M. E., and Taylor, S. E. (1997). Social identity and physical health: accelerated HIV progression in rejectionsensitive gay men. Journal of Personality and Social Psychology, 72, 320–335. Cole, S. W., Kemeny, M. E., Taylor, S. E., Visscher, B. R., and Fahey, J. L. (1996). Accelerated course of human immunodeficiency virus infection in gay men who conceal their homosexual identity. Psychosomatic Medicine, 58, 219–231. Cole, S. W., Kemeny, M. E., Weitzman, O. B., Schoen, M., and Anton, P. A. (1999). Socially inhibited individuals show heightened DTH response during intense social engagement. Brain Behavior and Immunity, 13, 187–200. Cole, S. W., Naliboff, B. D., Kemeny, M. E., Griswold, M. P., Fahey, J. L., and Zack, J. A. (2001). Impaired response to HAART in HIV-infected individuals with high autonomic nervous system activity. Proceedings of the National Academy of Sciences of the United States of America, 98, 12695–12700. Danesh, J., Muir, J., Wong, Y. K., Ward, M., Gallimore, J. R., and Pepys, M. B. (1999). Risk factors for coronary heart disease and acute-phase proteins. European Heart Journal, 20, 954–959. Davidson, R. J., Coe, C. L., Dolski, I., and Donzella, B. (1999). Individual differences in prefrontal activation asymmetry predict natural killer cell activity at rest and in response to challenge. Brain Behavior and Immunity, 13, 93–108. Denollet, J., Conraads, V. M., Brutsaert, D. L., De Clerck, L. S., Stevens, W. J., and Vrints, C. J. (2003). Cytokines and immune activation in systolic heart failure: the role of Type D personality. Brain Behavior and Immunity, 17, 304–309. Dressler, W. W., (1990). Lifestyle, stress, and blood pressure in a southern black community. Psychosomatic Medicine, 52, 182–198. Dressler, W. W., Bindon, J. R., and Neggers, Y. H. (1998). Culture, socioeconomic status, and coronary heart disease risk factors in an African American community. Journal of Behavioral Medicine, 21, 527–544. Evans, G. W. (2004). The environment of childhood poverty. American Psychologist, 59, 77–92. Gallo, L. C., and Matthews, K. A. (2003). Understanding the association between socioeconomic status and physical health: do negative emotions play a role? Psychological Bulletin, 129, 10–51. Galobardes, B., Lynch, J. W., and Smith, G. D. (2004). Childhood socioeconomic circumstances and cause-specific mortality in adulthood: systematic review and interpretation. Epidemiologic Reviews, 26, 7–21.
23. Social Context as an Individual Difference in Psychoneuroimmunology Garbarino, J., Kostelny, K., and Dubrow, N. (1991). What children can tell us about living in danger. American Psychologist, 46, 376–383. Glaser, R., and Gottlieb-Stematsky, T. E. (1982). Human herpesvirus infections: clinical aspects. New York: Marcel Dekker. Groer, M., Davis, M., and Steele, K. (2004). Associations between human milk SIgA and maternal immune, infectious, endocrine, and stress variables. Journal of Human Lactation, 20, 153–158. Hansen, G., Berry, G., DeKruyff, R. H., and Umetsu, D. T. (1999). Allergen-specific Th1 cells fail to counterbalance Th2 cell–induced airway hyperreactivity but causes severe airway inflammation. Journal of Clinical Investigation, 103, 175–183. Hemingway, H., Shipley, M., Mullen, M. J., Kumari, M., Brunner, E., Taylor, M., et al. (2003). Social and psychosocial influences on inflammatory markers and vascular function in civil servants (The Whitehall II study). American Journal of Cardiology, 92, 984–987. Herbert, T. B., and Cohen, S. (1993). Stress and immunity in humans: a meta-analytic review. Psychosomatic Medicine, 55, 364–379. Holtzman, M. J., Sampath, D., Castro, M., Look, D. C., and Jayaraman, S. (1996). The one-two of T helper cells: does interferon-γ knock out the Th2 hypothesis for asthma. American Journal of Respiratory Cell and Molecular Biology, 14, 316–318. Kamfar, H. Z., Koshak, E. E., and Milaat, W. A. (1999). Is there a role for automated eosinophil count in asthma severity assessment? Journal of Asthma, 36, 153–158. Kawachi, I., Kennedy, B. P., Lochner, K., and Prothrow-Stith, D. (1997). Social capital, income inequality, and mortality. American Journal of Public Health, 87, 1491–1498. Kiecolt-Glaser, J. K., and Glaser, R. (1988). Methodological issues in behavioral immunology research with humans. Brain Behavior and Immunity, 2, 67–78. Krieger, N., Williams, D. R., and Moss, N. E. (1997). Measuring social class in US public health research: concepts, methodologies, and guidelines. Annual Review of Public Health, 18, 341–378. Kubzansky, L. D., Sparrow, D., Vokonas, P., and Kawachi, I. (2001). Is the glass half empty or half full? A prospective study of optimism and coronary heart disease in the normative aging study. Psychosomatic Medicine, 63, 910–916. Lantz, P. M., House, J. S., Lepkowski, J. M., Williams, D. R., Mero, R. P., and Chen, J. (1998). Socioeconomic factors, health behaviors, and mortality: results from a nationally representative prospective study of US adults. Journal of the American Medical Association, 279, 1703–1708. Lantz, P. M., Lynch, J. W., House, J. S., Lepkowski, J. M., Mero, R. P., Musick, M. A., et al. (2001). Socioeconomic disparities in health change in a longitudinal study of US adults: the role of health-risk behaviors. Social Science and Medicine, 53, 29–40. Lazarus, R. S., and Folkman, S. (1984). Stress, appraisal, and coping. New York: Springer. Lewthwaite, J., Owen, N., Coates, A., Henderson, B., and Steptoe, A. (2002). Circulating human heat shock protein 60 in the plasma of British civil servants: relationship to physiological and psychosocial stress. Circulation, 106, 196–201. Libby, P., Ridker, P. M., and Maseri, A. (2002). Inflammation and atherosclerosis. Circulation, 105, 1135–1143. Lynch, J. W., Kaplan, G. A., and Salonen, J. T. (1997). Why do poor people behave poorly? Variation in adult health behaviors and psychosocial characteristics by stages of the socioeconomic lifecourse. Social Science and Medicine, 44, 809–819. Lynch, J. W., Smith, G. D., Kaplan, G. A., and House, J. S. (2000). Income inequality and mortality: importance to health of individual income, psychosocial environment, or material conditions. British Medical Journal, 320, 1200–1204.
507
Maier, S. F., and Watkins, L. R. (1998). Cytokines for psychologists: implications of bidirectional immune-to-brain communication for understanding behavior, mood, and cognition. Psychological Review, 105, 83–107. Marguet, C., Dean, T. P., and Warner, J. O. (2000). Soluble intercellular adhesion molecule 1 (sICAM-1) and IFN-γ in bronchoalveolar lavage fluid from children with airway diseases. American Journal of Respiratory and Critical Care Medicine, 162, 1016–1022. Marmot, M. G., Kogevinas, M., and Elston, M. A. (1987). Social/economic status and disease. Annual Review of Public Health, 8, 111–135. Marsland, A. L., Cohen, S., Rabin, B. S., and Manuck, S. B. (2001). Associations between stress, trait negative affect, acute immune reactivity, and antibody response to hepatitis B vaccination. Health Psychology, 20, 4–11. McDade, T. W. (2001). Lifestyle incongruity, social integration, and immune function in Samoan adolescents. Social Science and Medicine, 53, 1351–1362. McEwen, B. S. (1998). Protective and damaging effects of stress mediators. New England Journal of Medicine, 338, 171–179. Miller, G. E. (2002). All those years of school do pay off: education as a buffer against the biological sequelae of chronic stress. Presented at the MacArthur Symposium on Education and Health, Washington, DC. Miller, G. E., Cohen, S., Rabin, B. S., Skoner, D. P., and Doyle, W. J. (1999). Personality and tonic cardiovascular, neuroendocrine, and immune parameters. Brain Behavior and Immunity, 13, 109–123. Miller, G. E., Cohen, S., and Ritchey, A. K. (2002). Chronic psychological stress and the regulation of pro-inflammatory cytokines: a glucocorticoid resistance model. Health Psychology, 21, 531–541. Miller, G. E., Dopp, J. M., Myers, H. F., Felten, S. Y., and Fahey, J. L. (1999). Psychosocial predictors of natural killer mobilization during marital conflict. Health Psychology, 18, 262–271. Miller, T. Q., Smith, T. W., Turner, C. W., Guijarro, M. L., and Hallet, A. J. (1996). A meta-analytic review of research on hostility and physical health. Psychological Bulletin, 119, 322–348. Morag, M., Yirmiya, R., Lerer, B., and Morag, A. (1998). Influence of socioeconomic status on behavioral, emotional and cognitive effects of rubella vaccination: a prospective, double blind study. Psychoneuroendocrinology, 23, 337–351. Owen, N., Poulton, T., Hay, F., Mohamed-Ali, V., and Steptoe, A. (2003). Socioeconomic status, C-reactive protein, immune factors, and responses to acute mental stress. Brain Behavior and Immunity, 17, 286–295. Panagiotakos, D. B., Pitsavos, C., Manios, Y., Polychronopoulos, E., Chrysohoou, C. A., and Stefanadis, C. (2005). Socio-economic status in relation to risk factors associated with cardiovascular disease, in healthy individuals from the ATTICA study. European Journal of Cardiovascular Prevention and Rehabilitation, 12, 68–74. Reed, G. M., Kemeny, M. E., Taylor, S. E., and Visscher, B. R. (1999). Negative HIV-specific expectancies and AIDS-related bereavement as predictors of symptom onset in asymptomatic HIVpositive gay men. Health Psychology, 18, 354–363. Reed, G. M., Kemeny, M. E., Taylor, S. E., Wang, H. Y., and Visscher, B. R. (1994). Realistic acceptance as a predictor of decreased survival time in gay men with AIDS. Health Psychology, 13, 299–307. Ridker, P. M. (2003). Clinical application of C-reactive protein for cardiovascular disease detection and prevention. Circulation, 107, 363–369.
508
III. Behavior and Immunity
Ridker, P. M., Hennekens, C. H., Buring, J. E., and Rifai, N. (2000). C-reactive protein and other markers of inflammation in the prediction of cardiovascular disease in women. New England Journal of Medicine, 342, 836–843. Ross, R. (1999). Atherosclerosis—an inflammatory disease. New England Journal of Medicine, 340, 115–126. Scheier, M. F., and Bridges, M. W. (1995). Person variables and health: personality predispositions and acute psychological states as shared determinants for disease. Psychosomatic Medicine, 57, 255–268. Scheier, M. F., Matthews, K. A., Owens, J. F., Schulz, R., Bridges, M. W., Magovern, G. J., Sr., et al. (1999). Optimism and rehospitalization after coronary artery bypass graft surgery. Archives of Internal Medicine, 159, 829–835. Segerstrom, S. C. (2000). Personality and the immune system: Models, methods, and mechanisms. Annals of Behavioral Medicine, 22, 180–190. Segerstrom, S. C. (2003). Individual differences, immunity, and cancer: Lessons from personality psychology. Brain Behavior and Immunity, 17, 92–97. Segerstrom, S. C., Kemeny, M. E., and Laudenslager, M. L. (2001). Individual differences and psychoneuroimmunology. In R. Ader, D. Felten, and N. Cohen (Eds.), Psychoneuroimmunology (third ed., pp. 87–109). New York: Academic Press. Segerstrom, S. C., and Miller, G. E. (2004). Psychological stress and the immune system: a meta-analytic study of 30 years of inquiry. Psychological Bulletin, 130, 601–630. Segerstrom, S. C., Taylor, S. E., Kemeny, M. E., and Fahey, J. L. (1998). Optimism is associated with mood, coping, and immune change in response to stress. Journal of Personality and Social Psychology, 74, 1646–1655. Selner-O’Hagan, M. B., Kindlon, D. J., Buka, S. L., Raudenbush, S. W., and Earls, F. J. (1998). Assessing exposure to violence in urban youth. Journal of Child Psychology and Psychiatry, 19, 215–224. Steptoe, A., Kunz-Ebrecht, S., Owen, N., Feldman, P. J., Rumley, A., Lowe, G. D. O., et al. (2003a). Influence of socioeconomic status and job control on plasma fibrinogen responses to acute mental stress. Psychosomatic Medicine, 65, 137–144. Steptoe, A., Magid, K., Edwards, S., Brydon, L., Hong, Y., and Erusalimsky, J. (2003b). The influence of psychological stress and
socioeconomic status on platelet activation in men. Atherosclerosis, 168, 57–63. Steptoe, A., Owen, N., Kunz-Ebrecht, S., and Mohamed-Ali, V. (2002). Inflammatory cytokines, socioeconomic status, and acute stress responsivity. Brain Behavior and Immunity, 16, 774–784. Strauman, T. J., Lemieux, A. M., and Coe, C. L. (1993). Selfdiscrepancy and natural killer cell activity: immunological consequences of negative self-evaluation. Journal of Personality and Social Psychology, 64, 1042–1052. Suarez, E. C. (2003). Joint effect of hostility and severity of depressive symptoms on plasma interleukin-6 concentration. Psychosomatic Medicine, 65, 523–527. Suarez, E. C., Lewis, J. G., and Kuhn, C. M. (2003). The relation of aggression, hostility, and anger to lipopolysaccharide-stimulated tumor necrosis factor-α by blood monocytes from healthy men. Brain Behavior and Immunity, 16, 675–684. Townsend, P., and Davidson, N. (1982). Inequalities in health: the Black Report. Harmondsworth, England: Penguin. Wilkinson, R. G. (1992). Income distribution and life expectancy. British Medical Journal, 304, 165–168. Williams, D. R., and Collins, C. (1995). US socioeconomic and racial differences in health: patterns and explanations. Annual Review of Sociology, 21, 349–386. Winkleby, M. A., Jatulis, D. E., Frank, E., and Fortmann, S. P. (1992). Socioeconomic status and health: how education, income, and occupation contribute to risk factors for cardiovascular disease. American Journal of Public Health, 82, 816–820. Ying, S., Humbert, M., Barkans, J., Corrigan, C. J., Pfister, R., Menz, G., et al. (1997). Expression of IL-4 and IL-5 mRNA and protein product by CD4+ and CD8+ T cells, eosinophils, and mast cells in bronchial biopsies obtained from atopic and nonatopic (intrinsic) asthmatics. Journal of Immunology, 158, 3539–3544. Yirmiya, R. (1996). Endotoxin produces a depressive-like episode in rats. Brain Research, 711, 163–174. Zhu, J., Quyyumi, A. A., Rott, D., Csako, G., Wu, H., Halcox, J., et al. (2001). Antibodies to human heat-shock protein 60 are associated with the presence and severity of coronary artery disease. Circulation, 103, 1071–1075.
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24 Psychoneuroimmunology of Depressive Disorder: Mechanisms and Clinical Implications LUCILE CAPURON, ANDREW MILLER, AND MICHAEL R. IRWIN
I. INTRODUCTION 509 II. IMMUNOLOGICAL ALTERATIONS IN DEPRESSION 509 III. CLINICAL MODERATING FACTORS OF IMMUNE ALTERATIONS IN DEPRESSION 512 IV. BIOLOGICAL MEDIATORS OF IMMUNE ALTERATIONS IN DEPRESSION 515 V. BEHAVIORAL MECHANISMS OF IMMUNE ALTERATIONS IN DEPRESSION 516 VI. FROM CYTOKINES TO DEPRESSION 518 VII. PATHWAYS LINKING IMMUNITY TO DEPRESSION 520 VIII. CYTOKINE ABNORMALITIES IN DEPRESSION: TREATMENT IMPLICATIONS 523 IX. CONCLUSION 524
and innate immune responses that are associated with infectious disease susceptibility (Cohen and Miller, 2000; Leserman 2003), whereas other studies have found that depression is linked to immune activation in patients with inflammatory disorders such as rheumatoid arthritis (Zautra et al., 2004), cardiovascular disease (Lesperance et al., 2004; Miller et al., 2002c), or undergoing cytokine therapy (Capuron and Miller, 2004). In this chapter, we examine evidence linking major depressive disorder to reductions of innate and acquired immunity, as well as the associations between depression and alterations in the capacity of immune cell to express pro-inflammatory cytokines. Finally, we consider the hypothesis that the cytokine abnormalities found in depressed patients may have reciprocal influences on the central nervous system and contribute in part to the pathophysiology of the disorder.
I. INTRODUCTION Major depressive disorder, which exceeds a lifetime incidence of 10% (Irwin, 2002; Michaud et al., 2001), is a potent risk factor for disease morbidity, with depressed persons showing a mortality rate twice that found in non-depressed persons (Cuijpers and Smit, 2002; Penninx et al., 1999; Rudisch and Nemeroff, 2003; Wulsin et al., 1999). Altered functioning of the immune system is implicated as a mechanism that might contribute to medical morbidity of major depressive disorder, including risk of infectious disease (Evans et al., 2002) as well as inflammatory disorders (Zautra et al., 2004). Depressed persons show reductions of cellular PSYCHONEUROIMMUNOLOGY, 4E VOLUME I
II. IMMUNOLOGICAL ALTERATIONS IN DEPRESSION Many immunological changes reliably occur in patients with major depressive disorder, as described in a comprehensive meta-analyses of over 180 studies with more than 40 immune measures (Zorrilla et al., 2001). This section provides a review of the psychoneuroimmunological research being conducted on the relationship between depression and immunity, with a detailed review of various immune findings that
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occur in major depression. In addition, the behavioral correlates and biological mechanisms that might contribute to immune changes in major depression are discussed.
A. Enumerative Measures Evidence for increases in the total number of white blood cells and in the numbers and percentages of neutrophils and lymphocytes was among the first immunological changes identified in depressed persons (Herbert and Cohen, 1993; Kronfol et al., 1984; Zorrilla et al., 2001). In contrast, changes in monocyte counts have not been consistently reported (Irwin et al., 1990c; Maes et al., 1992). Further evaluation of lymphocyte numbers in depression has used phenotype-specific cell surface markers to enumerate lymphocyte subsets, and found that depression is negatively related to the number and percentage of lymphocytes (B-cells, Tcells, T helper cells, and T suppressor/cytotoxic cells) (Herbert and Cohen, 1993). In addition, a decrease in the circulating number of cells that express the NK cell phenotype occurs, which appears to be moderated in part by gender, with a decline in NK cell numbers found in male but not female depressed subjects compared with gender-matched controls (Evans et al., 1992). However, in one of the largest study samples of depressed subjects, no difference in the number of peripheral blood lymphocytes or T-lymphocyte subsets was found between depressed patients and controls (Schleifer et al., 1989). Indeed, with the recent accumulation of studies and the results of comprehensive meta-analyses, it is questionable as to whether there are consistent changes in the number of circulating B-, T-, or NK cells in depression (Zorrilla et al., 2001).
B. Functional Measures For the evaluation of the function of the immune system in depressed patients, a majority of studies have relied on results from assays of non-specific mitogen-induced lymphocyte proliferation, mitogenstimulated cytokine production, and NK cytotoxicity. Among the first few studies, it was found that mitogen proliferation responses were reduced in depressed subjects compared with controls (Kronfol et al., 1983; Schleifer et al., 1984). Whereas subsequent studies failed to replicate these observations, raising questions about the reliability of this immune alteration in depression (Schleifer et al., 1989), more than a dozen studies have now been conducted on lymphocyte proliferation in depression, and a reliable association between depression and lower proliferative responses to the three non-specific mitogens including phytohem-
aglutinin (PHA), concanavalin-A (Con A), and pokeweed (PWM) has been found (Herbert and Cohen, 1993; Zorrilla et al., 2001). Attention has also been given to the assessment of natural killer (NK) cell activity in depressed patients. Following the initial observations by Irwin and colleagues (Irwin and Gillin, 1987), over a dozen subsequent independent samples have replicated the finding of reduced NK activity in major depression (Herbert and Cohen, 1993; Zorrilla et al., 2001). Nevertheless, several caveats must be considered when reviewing the associations between NK activity, NK numbers, and depression. Compared with controls, decreases in NK counts and NK activity have been primarily found in male but not female depressed subjects (Evans et al., 1992; Irwin, 2002), and other studies have found no difference of NK activity in depression (Schleifer et al., 1989). Additional factors that might moderate or mediate the effects of depression on NK activity are discussed later in this chapter. Importantly, the declines of NK activity in depression may be relevant for certain infectious disease outcomes. Evans and colleagues found that major depression in women with HIV infection was associated with lower NK activity, as well as increases in the numbers of activated CD8 lymphocytes and viral load, and suggested that declines of killer lymphocytes in association with depression may increase risk of HIV disease progression in women (Evans et al., 2002).
C. Stimulated Cytokine Production Studies of stimulated cytokine production have not yielded consistent findings. For example, in whole blood assays, Kronfol et al. (2003) found increased lipopolysaccharide-stimulated production of IL-1 and IL-6, but no change in the expression of tumor necrosis factor-α. Other studies have suggested a shift in the relative balance of T helper 1 versus T helper 2 cytokine production with increases in the capacity of lymphocytes to produce interferon in depression (Seidel et al., 1995), yet no difference in the stimulated production of IL-2 has been found (Irwin et al., 2003a; Seidel et al., 1995). These negative findings cannot be ascribed to differences in depressed samples, as depressed patients who show no difference in IL-2 production evidence declines of NK activity (Irwin et al., 2003a). Recent attention has focused on evaluating different patterns of cytokine activation in subtypes of depression. Whereas one study found no differences in the capacity of lymphocytes to produce IL-2 between melancholic and non-melancholic depression (Schlatter et al., 2004), another study suggested
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that peripheral blood mononuclear cells of nonmelancholic depressed patients showed a greater stimulated capacity to produce interleukin-1β and interleukin-1 receptor antagonist as compared to responses from controls and melancholic depressed patients (Kaestner et al., 2005), although earlier work by this group of investigators did not identify such increases in IL-1 production (Rothermundt et al., 2001). Nevertheless, further observations suggest that the melancholic but not non-melancholic depressed patients showed evidence of HPA axis, which is thought to inhibit immune activation and the expression of inflammatory markers; this might account for the reported differences in these two groups of diagnostic depression (Kaestner et al., 2005).
D. Inflammation and Circulating Levels of Inflammatory Markers The presence of immune activation in major depression has also been evaluated by examining circulating levels of inflammatory markers. In contrast to the inconsistent findings regarding association between depression and production of inflammatory cytokines, meta-analyses indicate that depression is associated with increases in circulating levels of the proinflammatory cytokine, interleukin-6 (IL-6) (Zorrilla et al., 2001). Importantly, as compared to controls, elevated levels of IL-6 have been found in adults with major depression (Frommberger et al., 1997; Irwin and Pike, In press; Motivala et al., 2005), as well as in depressed elderly populations (Penninx et al., 2003) and in those with chronic medical disorders such as rheumatoid arthritis (Zautra et al., 2004), cancer (Musselman et al., 2001b), and cardiovascular disease (Empana et al., 2005). It is hypothesized that increases in circulating levels of pro-inflammatory cytokine are due to activation of monocyte populations, and increases in circulating levels of other pro-inflammatory cytokines such as tumor necrosis factor-α (TNF) and interleukin-1β (IL-1) have been reported in depressed patients (Anisman et al., 1999; Maes et al., 1993), including late-life depressive disorder (Thomas et al., 2005), although the numbers of studies that have examined these additional cytokines are too few to make firm conclusions. One study also reported increases of plasma levels of IL-12 in a large cohort of depressed patients (Kim et al., 2002); IL-12 is a hertodimeric cytokine that is produced primarily by monocytes and macrophages and plays a central role in the early phases of inflammation. Given evidence that depression is associated with immune activation with increases primarily of monocyte-derived cytokines, additional studies have
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extended these observations and assayed markers of systemic inflammation such as acute phase proteins and/or levels of sIL-2r. Although early reports suggested increases in haptoglobin and other acute phase proteins in depressed patients (Zorrilla et al., 2001), these data were primarily limited to reports from one laboratory, and recent efforts have failed to identify abnormal increases in acute phase proteins (Irwin and Pike, In press) consistent with the preliminary conclusions from meta-analyses (Zorrilla et al., 2001). Nevertheless, increases in c-reactive protein have been found in association with depression, with elevated levels in healthy-depressed adults (Miller et al., 2002c), as well as in those depressed patients with acute coronary syndrome (Lesperance et al., 2004; Miller et al., 2005). In turn, systemic immune activation is thought to lead to endothelial activation in depression with increases in the expression of soluble intercellular adhesion molecule (sICAM) (Lesperance et al., 2004; Motivala et al., 2005); elevated levels of c-reactive protein and sICAM are associated with cardiovascular disease and are prospectively linked to myocardial infarction risk (Ridker, 2001).
E. Dissociation between Declines of Innate Immunity and Inflammatory Markers As reviewed above, a number of studies have evaluated different cellular immunity and inflammation of immunity in depression, yet little attention has been given to the potential relationship between measures of innate immunity, such as NK activity, and levels of inflammatory markers in the context of major depression (Raison and Miller, 2003; Segerstrom and Miller, 2004). Rather, these immune differences have been generated in separate samples of depressed patients. In a recent study, Irwin and Pike measured levels of NK activity, circulating levels of interleukin-6 (IL-6), soluble interleukin-2 receptor (sIL-2r), and acute phase proteins in patients with current major depressive disorder (Irwin and Pike, In press). Consistent with prior observations, patients with major depressive disorder showed lower NK activity and higher circulating levels of IL-6 as compared to age-, gender-, and body-weight– matched controls, yet levels of NK activity were not correlated with IL-6 or with other markers of immune activation including acute phase proteins or IL-2r. The independent effect of depression on inflammatory markers as compared to NK responses has implications for understanding individual differences in the adverse health effects of major depressive disorder. Altered functioning of the immune system is thought to contribute to medical morbidity of major depressive
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disorder, including risk of infectious disease (Evans et al., 2002) as well as inflammatory disorders (Zautra et al., 2004). Some depressed persons show reductions of cellular and innate immune responses that are associated with infectious disease susceptibility (Cohen and Miller, 2000; Leserman, 2003). As noted above, other studies report that depression is linked to immune activation in patients with inflammatory disorders such as rheumatoid arthritis (Zautra et al., 2004) and cardiovascular disease (Lesperance et al., 2004; Miller et al., 2002c). It is not known what mechanisms might account for increases of IL-6 levels in some depressed patients and for decreases of NK activity in other patients with depression. Raison and Miller (2003) have proposed that depressed patients show inadequate glucocorticoid-mediated feedback inhibition of immune activation (Raison and Miller, 2003); for example, increased concentrations of plasma IL-6 positively correlate with post-dexamethasome suppression test (DST) cortisol levels in depression (Lowy et al., 1988). In contrast, several studies of patients with major depression have failed to show a relationship between altered NK activity and plasma or urinary concentrations of free cortisol (Irwin et al., 1988; Kronfol et al., 1986; Miller et al., 1991). Together, these data suggest that glucocorticoid resistance in depression is associated with immune activation (Miller et al., 2002b; Raison and Miller, 2003), yet not with declines of NK activity. Hence, it is speculated that insufficiency in glucocorticoid signaling of inflammation might identify a group of depressed patients at risk for exacerbations of inflammatory disorders such as rheumatoid arthritis (Raison and Miller, 2003). Genetic and metabolic variation in the expression of pro-inflammatory cytokines may also operate independently of processes that regulate NK activity. Whereas chronic psychological stress is found to induce increases in the expression of the proinflammatory cytokines (Kiecolt-Glaser et al., 2003) as well as decreases of NK activity (Pike, 1996), stressinduced increases of plasma C-reactive protein are reported to occur only in stressed persons who have the A allele of tumor necrosis factor-α −308 G/A polymorphism (Jeanmonod et al., 2004). Likewise, polymorphism of the 174 bp upstream of the transcription initiation site of the IL-6 gene, the −174 G/C allele, correlates with plasma IL-6 levels (Fishman et al., 1998), although the relationship of this polymorphism with major depression or with NK immune responses is not known. Finally, one-third of total IL-6 in the circulation is estimated to originate from adipose tissue (Mohamed-Ali et al., 1998). Even in depressed patients and controls who are similar in body weight and/or adiposity, metabolic alterations in adipose tissue sig-
naling might contribute to increases of IL-6 in depression independent of immune cell production of this pro-inflammatory cytokine.
F. Viral-specific Immune Measures Extension of these non-specific measures of immunity to viral-specific immune response has begun to yield promising findings relevant to the increased risk of infectious disease in depression and psychological stress. For example, major depression is associated with a functional decline in memory T-cells that respond to varicella zoster virus (Irwin et al., 1998), and this immune response is thought to be a surrogate marker for herpes zoster risk (Oxman et al., 2005). Such findings are consistent with a broader literature which has demonstrated that psychological stress is associated with decline in specific immune responses to immunization against viral infections (Miller et al., 2004; Vedhara et al., 1999), although extension of this work to major depression has not yet been conducted.
G. Assays of in vivo Responses Basic observations in animals have raised the possibility that depression can alter in vivo immune responses, as administration of chronic stress in animals suppresses the delayed type hypersensitivity (DTH) response (Dhabhar, 2000). Indeed, in depressed patients, suppression of the DTH response to a panel of antigenic challenges has been found (Hickie et al., 1993). In contrast, Shinkawa et al. (2002) found that older depressed patients were more likely to show positive tuberculin responses than non-depressed patients. To our knowledge, no study has investigated whether depression alters immunological response to vaccination, although several studies have revealed that psychological stress is associated with declines of hepatitis B antibody responses as well as antibody response to influenza immunization (Glaser et al., 1992; Miller et al., 2004; Vedhara et al., 1999).
III. CLINICAL MODERATING FACTORS OF IMMUNE ALTERATIONS IN DEPRESSION A. Demographic and Clinical Factors Alterations in the immune system during major depressive disorder may be influenced by the severity of depressive symptoms and other factors such as age, gender, ethnicity, body mass, and hospitalization stress (Stein et al., 1991) (see Figure 1). Whereas many
24. Psychoneuroimmunology of Depressive Disorder: Mechanisms and Clinical Implications
Depression
- Age - Gender - Ethnicity - Body mass
- Sleep disturbance - Physical activity - Tobacco smoking - Alcohol abuse
Corticotropinreleasing hormone
Adrenocortiocotropic hormone
Adrenal g land
Cortex
Autonomic innervation
Noradrenaline
Lymphoid organs
Medulla Immune cell activity Cortisol NK cell Adrenaline
Th2
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Cytokines IFN IL-10 IL-6, TNF-α, IL-1
Monocyte Inhibitory
APC
Stimulatory Increase Decrease
FIGURE 1 Model of depression-associated modulation of immune cell activity. The effects of depression on immune cell activity are moderated by clinical variables such as age, gender, ethnicity, and body mass. Behavioral mechanisms such as sleep disturbance, physical inactivity, and substance dependence co-occur in depression, have independent effects on immune cell function, and alter the magnitude of depression-related immune changes. Depression results in the central release of corticotrophin-releasing hormone that activates the hypothalamic-pituitaryadrenal (HPA) axis and the sympathetic-adrenal-medullary axis. The production of adrenocorticotropic hormone by the pituitary gland results in the production of glucocorticoid hormones. Autonomic activation leads to the production of adrenal medulla adrenaline, and the sympathetic neural release of noradrenaline in lymphoid organs. Immune cells have receptors for cortisol and catecholamines; receptor binding of cortisol, adrenaline, or noradrenaline induces a downregulation of natural killer (NK) cell function; a shift in the stimulated production of cytokines with decreases of the Th1 cytokine interferon γ (IFN) and increases of the Th2 cytokine interleukin-10 (IL-10); and increases in the production of pro-inflammatory cytokines such as interleukin-6 (IL-6), tumor necrosis factor-α (TNF), and interleukin-1 (IL-1). These cytokines can also have bi-directional effects and can modulate the activity of the hypothalamus and also induce behavioral symptoms.
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studies have controlled for the influence of these factors in the selection of controls who are comparable to the depressed patients on demographic and clinical characteristics, some evidence suggests that these factors may interact with depression status in altering immune variables. For example, older adults show declines in cellular immunity; the presence of comorbid depression may further exacerbate age-related immune alterations (Schleifer et al., 1989). Gender also exerts differential effects on pituitary, adrenal, and immune systems by modulating the sensitivity of target tissues, and one study, for example, showed that women have an exaggerated expression of pro-inflammatory cytokines in response to psychological stress (Rohleder et al., 2001), which is thought to place women at increased risk for autoimmune disorders. Other data indicate that declines of T-cell and NK cell response appear to be more prominent in depressed men than depressed women (Evans et al., 1992). In regards to ethnicity, African American ethnicity interacts with a history of alcohol consumption to exacerbate immune abnormalities (Irwin and Miller, 2000), but the influence of ethnicity on depression-related changes of immunity is not known. Increases in body mass index and the presence of obesity are associated with increases in markers of inflammation such as circulating levels of c-reactive protein and IL-6 (Yudkin et al., 2000). In healthy adult depressed patients, Miller and colleagues showed that adiposity and great body mass partially mediated the increase of these inflammatory markers (Miller et al., 2002c). However, other studies have found increases of IL-6 and of c-reactive protein in healthy non-obese depressed persons that is independent of the contribution of body mass (Lesperance et al., 2004; Motivala et al., 2005), suggesting that the effects of adiposity on depression-related increases of inflammatory markers may only occur above a threshold or in those with obesity. Psychological stress may also impact measures of cellular immunity (Kiecolt-Glaser et al., 2002), and depressed patients show elevated rates of life stress and adverse events as compared to nondepressed persons (Kendler et al., 2000). Indeed, depressed patients who evidence greater life stress show greater declines of NK activity than depressed patients who are not stressed, although depression alone is associated with significant declines of NK activity (Irwin et al., 1990c). Finally, specific diagnostic comorbidity such as anxiety disorder (Andreoli et al., 1992) and sleep disturbance (Motivala et al., 2005) might moderate immune system functioning in depression. As discussed below, a number of studies have identified sleep in the regulation of some aspects of immune function (Irwin et al., 1992b; Irwin et al., 1994; Irwin et al., 1996), and depressed individuals with
somatic symptoms of depression such as insomnia are more likely to show immune changes (Cover and Irwin, 1994), which for markers of inflammation may be mediated by increases in the latency for sleep onset and rapid eye movement (REM) sleep (Motivala et al., 2005).
B. Depression Treatment: Effects of Antidepressant Medications Only a limited number of studies have investigated the clinical course of depression and changes of cellular immunity in relation to antidepressant medication treatment and symptom resolution. In one longitudinal case-control study, Irwin and co-workers (1992a) found that depressed patients showed an increase in NK activity during a 6-month course of tricyclic antidepressant medication treatment and symptom resolution, although the improvements of NK activity were correlated declines of symptom severity and not treatment status at the time of follow-up. In another longitudinal follow-up study (Schleifer et al., 1999) of young adults with unipolar depression involving 6 weeks of treatment with nortriptyline and alprazolam, clinical improvements in the severity of depressive symptoms were associated with decreased numbers of circulating lymphocytes and decreased responses to PHA and Con A but not PWM. In addition, decreases in T-cells, CD4+, and CD29 were found although there were no changes in B-cell numbers or CD8+ cells. None of these changes were related to nortriptyline blood levels (Schleifer et al., 1999). In addition, Frank et al. (1999) found that in vivo and in vitro treatment with fluoxetine, a selective serotonin reuptake inhibitor, resulted in enhanced NK activity, along with changes in depressive symptoms, consistent with the finding of Ravidran et al. (1995) in which a number of different antidepressants were used, including nafazodone, paroxetine, sertraline, and venlafaxine. In regards to pro-inflammatory cytokine expression and inflammation, Castanon et al. (2002) recently reviewed animal research that focused on the immunological effects of antidepressant medications and concluded that antidepressants decrease proinflammatory cytokine (e.g., IL-β, TNF, and IL-6) expression, with similar findings generated using in vitro and in vivo experimental approaches. Although the specific mechanism or mechanisms involved have not yet been identified, antidepressants modify the expression of glucocorticoids and their receptors (Barden ,1999; Goujon et al., 1995); limit the synthesis of prostaglandin and nitric oxide, which contribute to
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pro-inflammatory effects (Yaron et al., 1999; Yirmiya et al., 1999); and act on intracellular messenger pathways with downstream effects on pro-inflammatory cytokines (Hindmarch, 2001). A few studies have extended these pre-clinical data and examined the effects of antidepressants on pro-inflammatory cytokine levels and productin in depressed patients. Increased levels of IL-6 during acute depression were normalized after 8 weeks of fluoxetine treatment (Sluzewska et al., 1995). Similarly, production of IL-6 and TNF was decreased in depressed patients treated with amitriptyline, although this decrease was confined to those depressed patients who responded to treatment, suggesting that symptom resolution is an important predictor of cytokine changes (Sluzewska et al., 1995). In contrast, 4-week treatment with clomipramine was found to be associated with increases in the mononuclear cell production of IL-1 in depressed patients (Weizman et al., 1994). A few studies have also examined the effects of antidepressant treatment on Th1 versus Th2 cytokine production in depression. Treatments in vivo and in vitro with imipramine, venlafaxine, or fluoxetine increased stimulated cellular production of IL-10, with a decrease in the ratio of interferon (IFN) to IL-10 (Kubera et al., 1996). In hospitalized psychiatric patients (with either schizophrenia, depression, or bipolar disorder), one study found that treatment with psychotropic medications reduced IL-12 expression as compared to controls (Kim et al., 2002), consistent with the view held by Kenis and Maes (2002) that antidepressants decrease pro-inflammatory cytokine expression and induce a shift toward Th2 cytokine expression.
IV. BIOLOGICAL MEDIATORS OF IMMUNE ALTERATIONS IN DEPRESSION A. Central Modulation of Immunity: Effects of Corticotropinreleasing Hormone Depressed patients show elevated levels of corticotropin-releasing hormone (CRH) (Owens and Nemeroff, 1991), and this key peptide is involved in integrating neural neuroendocrine as well as immune responses to stress. Release of this peptide in the brain alters a variety of immune processes including aspects of innate immunity, cellular immunity, and in vivo measures of antibody production (Friedman and Irwin, 1995; Friedman and Irwin, 1997). Peripheral immune measures also change following lesioning of the brain (e.g., hypothalamus) or in response to the stimulation
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of certain brain regions which ultimately impact CRH systems. The brain controls immune cells in lymphoid tissue in the same manner it controls other visceral organs, namely by coordinating autonomic and neuroendocrine pathways; when these pathways are blocked by specific factors that bind to sympathetic or hormone receptors, the effects of CRH on immune function are also blocked (Irwin et al., 1990b; Irwin et al., 1990d).
B. Autonomic Nervous System (ANS) At rest and in response to acute physical and/or psychological challenge, depressed patients show elevated levels of circulating catecholamines and neuropeptide Y (Irwin et al., 1991), consistent with the notion that depression is associated with activation of the peripheral sympathetic nervous system (SNS). The SNS regulates multiple aspects of the immune system and is thought to mediate changes of immunity in depression. It is known, for example, that sympathetic nerve terminals are juxtaposed with immune cells in organs where the immune system cells develop and respond to pathogens (e.g., bone marrow, thymus, spleen, and lymph nodes) (Friedman and Irwin, 1997; Sanders and Straub, 2002). When sympathetic release of norepinephrine and neuropeptide Y occurs, receptor binding serves as a signal in this “hard-wire” connection between the brain and the immune system. In addition, sympathetic nerves penetrate into the adrenal gland and cause the release of epinephrine into the bloodstream, which circulates to immune cells as another sympathetic regulatory signal. In depressed patients, excretion of 3-methoxy-4-hydroxy-phenylglycol (MHPG), a metabolic breakdown product of catecholamines, has been used as an index of total body noradrenergic turnover, or sympathetic activity, and MHPG excretion was inversely related with lymphocyte proliferative responses in depressed patients (Maes et al., 1989). Under both laboratory and naturalistic conditions including depression, sympathetic activation has been shown to suppress the activity of diverse populations of immune cells, including NK cells and T lymphocytes (Friedman and Irwin, 1997; Sanders and Straub, 2002). In contrast, other aspects of the immune response can be enhanced. For example, catecholamines can increase the production of antibodies by B-cells and the ability of macrophages to release cytokines and thereby signal the presence of a pathogen. Additional studies indicate that sympathetic activation can also shunt some immune system cells out of circulating blood and into the lymphoid organs (e.g., spleen, lymph nodes, thymus) while recruiting other types of
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immune cells into circulation (e.g., NK cells). It is thought that sympathetic activation reduces the immune system’s ability to destroy pathogens that live inside cells (e.g., viruses) via decreases of the cellular immune response, while enhancing the humoral immune response to pathogens that live outside cells (e.g., bacteria) (Sanders and Straub, 2002).
C. Neuroendocrine Axis A hallmark of major depression is dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis and the overexpression of cortisol. Cortisol exerts diverse effects on a wide variety of physiological systems and also coordinates the actions of various cells involved in an immune response by altering the production of cytokines or immune messengers (Moynihan and Stevens, 2001). Similar to sympathetic activation, cortisol can suppress the cellular immune response critical to defending the body against viral infections. Cortisol can also prompt some immune cells to move out from circulating blood into lymphoid organs or peripheral tissues such as the skin (Dhabhar et al., 1996). The relationship between HPA axis activation and immune alterations in depression has not been compellingly demonstrated. For example, in depressed patients, decreased lymphocyte responses to mitogens are not associated with dexamethasone nonsuppression (Kronfol and House, 1985) or with increased excretion rates of urinary-free cortisol (Kronfol et al., 1986). Dexamethasone non-suppression refers to the diminished feedback inhibition of the HPA axis and is associated with HPA overactivity. Furthermore, in bereavement which is complicated by depressive symptoms, changes of NK activity are not associated with plasma cortisol levels (Irwin et al., 1988). Nevertheless, disruption of one’s physiological homeostasis is implicated in depression, and neuroendocrine-immune interactions are thought to contribute to this dysregulation. As noted above, major depression is associated with the increased expression of pro-inflammatory cytokines, which in turn leads to the progression of the immune response and activation of the HPA axis (Besedovsky and del Rey, 1996; McEwen et al., 1997; Schobitz et al., 1994; Turnbull and Rivier, 1999). In a study of 28 inpatients with major depression, Maes and colleagues (Maes et al., 1993) found a significant positive correlation between mitogen-induced IL-1β production and postdexamethasone cortisol values, which suggested to the authors that IL-1β oversecretion may contribute to HPA axis overactivity in depression.
V. BEHAVIORAL MECHANISMS OF IMMUNE ALTERATIONS IN DEPRESSION In addition to the biological mediators of immune changes in depression, several behavioral factors associated with depression might contribute to immune dysfunction. Indeed, as reviewed by Cohen and Miller (Miller et al., 1999b), examination of health status and behavioral factors is needed in clinical psychoneuroimmunology. For example, alcohol and tobacco have well-recognized effects on immunity. Yet, there is limited empirical information on the processes by which these substances alter immune function in depressed subjects, despite their high rates of use in depressed patients. In the following sections, four of the more pertinent behavioral factors linking depression and immune dysfunction are discussed, namely, tobacco smoking, alcohol/substance abuse, activity/ exercise, and sleep disturbance.
A. Smoking: Prevalence and Immune Effects Cigarette smoking has long been considered a health risk, with effects on immunity via direct actions or possibly endocrine-mediated mechanisms (Sopori and Kozak, 1998). Nicotine is reported to affect the HPA axis (Rosecrans and Karin, 1998) and to alter measures of humoral and cellular immunity (McAllister-Sistilli et al., 1998) and markers of immune activation (Mendall et al., 1997). For example, specific immunological alterations occur in adult smokers affecting a variety of parameters, including increases of WBC counts, declines of NK activity, and increases of markers of immune activation such as IL-6. Hence, several studies of depressed patients have begun to evaluate the contribution of cigarette smoking to depression-related declines of NK activity and increases of IL-6 and other inflammatory markers (Andreoli et al., 1993; Irwin et al., 1990b; Lesperance et al., 2004; Miller et al., 2002c; Motivala et al., 2005). In a large study of 245 depressed and comparison controls stratified by smoking status, Jung and Irwin (1999) reported that depression and smoking status interact to produce greater declines of NK activity than those found in depressed or smoking groups alone. In addition, smoking status was associated with increases of IL-6 and sICAM in depression (Lesperance et al., 2004; Miller et al., 2002c; Motivala et al., 2005), although evidence of immune activation occurs in depression independent of smoking status (Irwin and Pike, In press; Lesperance et al., 2004; Miller et al., 2002c; Motivala et al., 2005). Nevertheless, epidemiologic evidence suggests that depression interacts
24. Psychoneuroimmunology of Depressive Disorder: Mechanisms and Clinical Implications
with cigarette smoking to impact health, rather than the presence of a unitary link between depression and cancer. In a 12-year follow-up of 2,264 adult men and women, depressed mood together with cigarette smoking were associated with a marked increase in the relative risk of cancer (Linkins and Comstock, 1990), as compared to the risk associated with smoking or depression status alone.
B. Alcohol Dependence: Prevalence and Immune Effects in Depression According to Cadoret (Cadoret, 1981), nearly 30% of individuals with depression also suffer from alcohol dependence, and over 30% of depressives escalate their drinking during the depressive episode. Whereas alcohol/substance dependence and depression each have a significant negative impact on the immune system, the interaction of alcohol/substance abuse with affective disorders may result in significantly more immune impairment than either condition alone. In a study by Irwin et al. (1990a), individuals with a dual diagnosis of alcoholism and depression had further decreases of NK activity compared with individuals diagnosed with only alcoholism or depression. Furthermore, these researchers found that depressed subjects with histories of alcoholism had lower NK activity compared with depressed subjects without such histories. Alcoholics with secondary depression showed a further decrease in cytotoxicity compared with alcoholics who were not clinically depressed (Irwin et al., 1990a). Strikingly, this result reflects the effects of past consumption of alcohol. Depressed and alcoholic subjects were free of alcohol for a minimum of 2 weeks, and thus the decline of NK activity was not due to a direct pharmacological effect of alcohol. More systematic assessment of current alcohol use along with dependence histories is needed.
C. Activity and Exercise: Immune Consequences in Depression Activity, or a lack thereof, can have negative consequences on the immune system, and some data suggest that older adults with depression may be especially vulnerable to the harmful effects of sedentary lifestyles. Conversely, exercise has been shown to have potent salutary effects on immune measures and has even been found to promote a remission of depressive symptoms in older adults. In the meta-analysis from Herbert and Cohen (Herbert and Cohen, 1993), melancholic depression correlated with greater impairments
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of cellular immunity, which may be due, at least in part, to an increased predominance of neurovegetative symptoms. Cover and Irwin (1994) found that severity of psychomotor retardation uniquely predicted declines of NK activity, similar to the effects of insomnia. Given that behavioral interventions that include a component of physical activity have been found to boost antibody response to a novel antigen (Smith et al., 2004), antibody production in response to influenza vaccination (Kohut et al., 2005), and viral-specific T-cell memory response to the varicella zoster virus (Irwin et al., 2003b), future studies are needed to determine whether interventions that increase physical activity and/or exercise capacity will yield improvements in immunity in depression. The administration of aerobic exercise has been found to alleviate depressive symptoms and to decrease the risk of relapse in major depressive disorder (Babyak et al., 2000; Blumenthal et al., 2005).
D. Disordered Sleep and Immunity: Relevance to Depression Disordered sleep and loss of sleep are thought to adversely affect resistance to infectious disease, increase cancer risk, and alter inflammatory disease progression. Animal studies show that sleep deprivation impairs influenza viral clearance and increases rates of bacteremia. In humans, normal sleep is associated with a redistribution of circulating lymphocyte subsets, increases of NK activity, increases of certain cytokines (e.g., IL-2, IL-6), and a relative shift toward Th1 cytokine expression that is independent of circadian processes. Conversely, sleep deprivation suppresses NK activity and IL-2 production, although prolonged sleep loss has been found to enhance measures of innate immunity and pro-inflammatory cytokine expression. Insomnia is one of the most common complaints of depressed subjects, but its role in moderating and/or mediating immune alterations in depression has been relatively unexplored. However, with evidence that subjective insomnia correlates with NK activity in depression, but not with other depressive symptoms, including somatization, weight loss, cognitive disturbance, or diurnal variation, the hypothesis has emerged that disordered sleep may be a distinct factor accounting for some of the observed immune alterations found in depression. In depressed samples who are at risk for disordered sleep, alterations of natural and cellular immune function among depressed patients correlate with disturbances of EEG sleep (Cover and Irwin, 1994; Irwin
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et al., 1992b). Recent studies in bereaved subjects have replicated this correlation, and studies have shown by way of causal statistical analyses that disordered sleep also mediates the relationship between severe life stress and a decline of NK responses (Hall et al., 1998). Further studies involving subjects with primary insomnia (e.g., no depression, other psychiatric disorder, and medical disorder) have found that prolonged sleep latency and fragmentation of sleep are associated with nocturnal elevations of sympathetic catecholamines and declines in daytime levels of NK cell responses (Irwin et al., 2003a; Savard et al., 2003). A more extensive line of research has focused on alcohol-dependent patient populations who have profound disturbances of sleep continuity and sleep architecture (Irwin et al., 2002; Irwin et al., 2000); decreases of total sleep time, declines of delta sleep, and increases of REM are associated with increases in the nocturnal and daytime expression of IL-6, possibly with consequences for daytime fatigue (Redwine et al., 2003). Finally, studies of depressed patients have found the prolonged sleep latency and increases of REM density are associated with elevated levels of IL-6 and sICAM in depression, and these EEG sleep measures fully account for the association between depression and IL-6 in healthy adults (Motivala et al., 2005). Findings linking sleep and IL-6 and sICAM may have important health implications. Recent epidemiological data show that self-reported difficulty initiating sleep is a predictor of cardiovascular disease mortality (Mallon et al., 2002). Similarly, objective measures of difficulty initiating sleep (i.e., prolonged sleep latency) yields a two-fold elevated risk of death in a healthy older adult population (Dew et al., 2003). Prospective data further indicate that sICAM and IL-6, directly implicated in atherosclerotic disease processes, predict risk for myocardial infarction independent of cholesterol levels, smoking status, and obesity (Ridker et al., 1998; Ridker et al., 2000). Likewise, in patients recovering from an acute coronary artery event, comorbidity for depression is associated with elevated levels of sICAM independent of smoking status, obesity, and other traditional risk markers (Lesperance et al., 2004). Thus, further examination of disordered sleep along with inflammation and endothelial activation may prove to be a key biobehavioral mechanism contributing to excess cardiovascular mortality in persons with depression.
VI. FROM CYTOKINES TO DEPRESSION There are many reasons to believe that the immunologic changes found in depressed patients described
above may in part contribute to the pathophysiology of the disorder. First, medically ill patients, who exhibit evidence of immune activation and/or inflammation secondary to tissue damage and destruction, infection, autoimmunity, or neoplastic disease, exhibit high rates of depression. Second, cytokine therapies for infectious diseases and cancer are notorious for causing behavioral alterations. Finally, there are many pathways known to be involved in the pathophysiology of depression that are influenced by cytokines, including neuroendocrine function, neurotransmitter function, and information processing.
A. Depression in the Medically Ill Major depression is frequent in the medically ill. Whereas the prevalence rate of depression in the general population ranges from 2–5%, patients with medical illnesses exhibit rates up to 50% and higher, depending on the type and severity of disease (Evans et al., 1999). Relevant illnesses include neurologic disorders (e.g., Parkinson’s disease), cancer, infectious diseases, autoimmune disorders, and cardiovascular disease (Evans et al., 1999). While there has been substantial focus on the psychosocial factors that may contribute to depression in medically ill patients, new developments in the biology of mood disorders have raised novel considerations regarding the pathophysiology and treatment of depression in the medically ill (Maier and Watkins, 1998). Specifically, recent theories have proposed that pro-inflammatory cytokines, released as a function of disease-related inflammatory processes, participate in the pathophysiology of depression, given their potent effect on neurotransmitter function, neuroendocrine function, and behavior (Besedovsky and del Rey, 1996; Dunn and Wang, 1995; Yirmiya, 1996). Behavioral changes induced by cytokines include the induction of a syndrome referred to as “sickness behavior” that has many overlapping features with major depression (Kent et al., 1992). (See Table 1.) Thus, cytokine-induced sickness behavior may account in part for the high rate of major depression found in the medically ill. Sickness behavior is typically associated with the behavioral changes seen in humans and laboratory animals suffering from microbial infections and includes symptoms of cognitive dysfunction, fatigue/anergia, psychomotor slowing, anorexia, anhedonia, sleep alterations, and increased sensitivity to pain (Kent et al., 1992). Relevant to its mediation by pro-inflammatory cytokines, sickness behavior can be reliably reproduced by administration of each of the pro-inflammatory cytokines in isolation or by administering agents (e.g., endotoxin or lipopolysaccharide
24. Psychoneuroimmunology of Depressive Disorder: Mechanisms and Clinical Implications
[LPS]) that induce the pro-inflammatory cytokine cascade (TNF-α to IL-1 to IL-6) (Yirmiya et al., 1999). Relevant to the role of cytokines in behavioral pathology in medically ill patients, depressed patients with cancer were found to exhibit significantly higher plasma IL-6 concentrations compared to non-depressed cancer patients and healthy controls (Musselman et al., 2001b). In addition, elevated plasma concentrations of cytokines have been found in association with specific symptoms of depression, including elevated plasma concentrations of IL-1ra and soluble TNF receptor type II in cancer patients with significant fatigue (Bower et al., 2002) and elevated IL-6 concentrations in cancer patients with impaired executive function (Meyers et al., 2005).
B. Model of Cytokine Therapy The model of cytokine therapy has been recently used to better investigate the physiopathology of cytokine-induced depression. Because of their immunomodulatory, anti-viral and anti-proliferative properties, cytokines—principally interferon (IFN)-alpha and interleukin (IL)-2—are currently used for the treatTABLE 1
Overlapping Symptoms of Sickness Behavior and Major Depression
Sickness behavior
Major depression
Anhedonia Anorexiaa Decreased libido Cognitive disturbance Psychomotor retardationa Fatiguea Weight lossa Sleep disturbance Hyperalgesia Social isolation Sad mood Worthlessness/guilt Suicidal ideation
Anhedonia Anorexia Decreased libido Cognitive disturbance Psychomotor retardation Fatigue Weight loss Sleep disturbance Increased pain complaints Social isolation Sad moodb Worthlessness/guiltb Suicidal ideationb
a
More frequent in sickness behavior than depression. More frequent in depression than sickness behavior. Reproduced with permission from Miller et al., Clinical Neuroscience Research, 2005. b
TABLE 2
Symptoms Time course Responsiveness to antidepressant
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ment of immune-mediated medical illnesses, including cancer and viral infections (e.g., chronic hepatitis C, AIDS). Despite their therapeutic efficacy, cytokine therapies are, however, notorious for causing neurobehavioral symptoms, including major depression, in a large number of patients. Indeed, data indicate that approximately 30–50% of patients undergoing treatment with the cytokine IFN-alpha develop major depression during the course of their treatment, depending on the dose, route, and duration of treatment (Capuron et al., 2002a; Miyaoka et al., 1999; Musselman et al., 2001a). Similar rates of depression have been reported in patients treated with the cytokine IL-2 for renal cell carcinoma (Buter et al., 1993; Capuron et al., 2004; Denicoff et al., 1987). It is important to note that in the context of cytokine administration in medically ill patients, major depression refers in the classification of the DSM-IV to a substanceinduced affective disorder (American Psychiatric Association, 1994). Recent advances made using the model of cytokine therapy have revealed that cytokine-induced neuropsychiatric symptoms in patients treated with IFNalpha therapy represent two distinct behavioral syndromes with different phenomenology and responsiveness to antidepressants (Capuron et al., 2002a). (See Table 2.) The mood and cognitive syndrome, characterized by the typical symptoms of depression such as depressed mood, anxiety, irritability, memory, and attentional disturbance, develops usually between the first and third month of IFN-alpha therapy in vulnerable patients (Capuron and Miller, 2004; Capuron et al., 2002a; Capuron et al., 2004; Musselman et al., 2001a). In contrast, the neurovegetative syndrome, characterized by symptoms of fatigue, psychomotor slowing, anorexia, and altered sleep patterns, develops earlier (within 2 weeks of IFN-alpha therapy) in a large proportion of patients and persists at later stages of therapy. For instance, fatigue, the symptom most common during cytokine therapy, has been shown to occur in up to 80% of patients undergoing IFN-alpha therapy (Capuron et al., 2002a). In terms of their responsiveness to antidepressants, the mood and cognitive syndrome was found to be highly responsive to pre-treatment with the antidepressant paroxetine (a
Neurobehavioral Effects of Interferon-Alpha Therapy Mood/Cognitive syndrome
Neurovegetative syndrome
Depressed mood, anxiety cognitive dysfunction Appears later (mean onset: week 8) Responsive
Psychomotor slowing Fatigue, sleep disturbance, anorexia Appears early and persists (onset: 1st 4 weeks of treatment) Minimally responsive
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selective serotonin inhibitor), whereas the neurovegetative syndrome was antidepressant non-responsive (Capuron et al., 2002a). This differentiation between mood versus neurovegetative symptoms has been also found in cancer patients undergoing chemotherapy, where it was also noted that depression was responsive to paroxetine treatment, whereas fatigue was treatment resistant (Morrow et al., 2003). Moreover, in a factor analysis of behavioral symptoms in a large number of cancer patients (N = 527) with a variety of different types of cancers in different stages of treatment, neurovegetative symptoms including weakness/fatigue, anorexia, and inability to get things done were found to be a distinct factor versus mood/cognitive symptoms, which clustered in a factor that included symptoms of worrying, irritability, sadness, nervousness, and problems with attention and memory (Cleeland, 2000). Taken together, these data suggest that differential pathophysiological pathways may be involved in the development of specific symptom dimensions including mood/cognitive versus neurovegetative symptoms in the context of cytokine system activation.
VII. PATHWAYS LINKING IMMUNITY TO DEPRESSION A. Do Cytokines Produced Peripherally Reach the Brain? As previously noted, evidence of increased inflammatory markers, including plasma concentrations of pro-inflammatory cytokines, has been found in patients with major depression. Given that pro-inflammatory cytokines are relatively large molecules that do not freely cross the blood-brain barrier, research has focused on how cytokine signals reach the brain. At least three pathways have been described (discussed in more detail in Chapter 13) including (1) passage through leaky regions in the blood-brain barrier; (2) active transport via cytokine-specific transport molecules; and (3) activation of vagal afferent nerves, which signal relevant brain nuclei such as the nucleus of the solitary tract. Once cytokine signals reach the brain, there is a cytokine network within the brain that can amplify and transpose relevant signals into those that interact with pathophysiologic pathways that are known to be involved in the development of depression.
B. Cytokines in the Brain: Pathophysiological Effects There are several potential mechanisms by which cytokines may contribute to the pathophysiology of
depression. These mechanisms, which are not mutually exclusive, involve (1) neuroendocrine effects, (2) alterations in neurotransmitter function, and (3) effects on neuronal activity/function. 1. Neuroendocrine Effects Cytokines have profound effects on neuroendocrine function. The HPA axis and immune system axis interact via a complicated circuitry composed of both feed-forward excitatory and feedback inhibitory loops. Under normal conditions, inhibitory elements such as glucocorticoids and anti-inflammatory cytokines limit the activation of the immune system to levels that are appropriate for clearing the initial antigenic stimulus (Maier and Watkins, 1998). However, it is becoming increasingly recognized that in certain conditions these inhibitory feedback loops become impaired, allowing for chronic immune activation and the persistence of sickness symptoms that follow from this activation. Depression may correspond to one of these conditions where inhibitory feedback loops are altered and both neuroendocrine and immune systems become persistently activated (Raison and Miller, 2003). As described in more detail elsewhere (see Chapter 13), a number of inflammatory and immunoregulatory cytokines have been found to have potent effects on the HPA axis (Besedovsky and del Rey, 1996). One consistent finding is the capacity of the cytokines that mediate innate immune responses (e.g., IFN-alpha, IL-1, IL-6, and TNF-alpha) to increase the release of corticotrophin-releasing factor (CRF) (Besedovsky and del Rey, 1996; Gisslinger et al., 1993; Raber et al., 1997). CRF is a key neuropeptide in the regulation of the response to stress, orchestrating stress-induced activation of the HPA axis (and the release of ACTH and cortisol) and the sympathetic nervous system (and the release of catecholamines) (Owens and Nemeroff, 1993). Activation of CRF pathways by inflammatory cytokines represents one of the primary mechanisms by which cytokines may contribute to the development of depression (Owens and Nemeroff, 1993). Indeed, hypersecretion of CRF is a reliable finding in patients with major depression as manifested by increased csf concentrations of CRF and increased CRF mRNA and protein in the hypothalamus of postmortem samples from depressed patients (Owens and Nemeroff, 1993; Pariante and Miller, 2001). In addition, administration of CRF to laboratory animals leads to behavioral symptoms that overlap with those seen in both major depression and sickness behavior, including alterations in food intake, locomotor activity, and sleep (Owens and Nemeroff, 1993).
24. Psychoneuroimmunology of Depressive Disorder: Mechanisms and Clinical Implications
Recent studies in humans have indicated that cytokine-induced activation of the HPA axis may represent a risk factor for the development of depression. Indeed, cancer patients who developed major depression while undergoing treatment with the cytokine IFN-alpha exhibited significantly higher ACTH and cortisol responses to the first injection of IFN-alpha compared to cancer patients who remained free of depression during IFN-alpha therapy (Capuron et al., 2003b). Moreover, a significant correlation was found between the degree of the initial ACTH and cortisol response to IFN-alpha and the development of depression, anxiety, and cognitive dysfunction after 8 weeks of IFN-alpha treatment (Capuron et al., 2003b). Interestingly, IL-6 responses to the initial injection of IFNalpha were no different in patients who became depressed versus those who did not, suggesting that the vulnerability to depression is a function of the interaction of cytokines with stress responsive pathways (Capuron et al., 2003b). Thus, individual differences in stress responsivity including hyperactive CRF pathways, such as has been described following early life stress (Heim et al., 2000), may lead to increased vulnerability to cytokine-induced behavioral alterations. Indeed, the oft-replicated finding of a correlation between baseline mood state and subsequent development of depression during cytokine therapy indicates that baseline mood status may be a behavioral marker of this neuroendocrine vulnerability (Capuron and Ravaud, 1999; Raison et al., 2005). Another pathway by which cytokines may influence the neuroendocrine system and thereby contribute to depression is through disruption of the functioning of the glucocorticoid receptor (GR) (Miller et al., 1999a; Pariante and Miller, 2001). Patients with major depression have reliably been shown to exhibit alterations in GR function as manifested both in vivo (as reflected by an abnormal dexamethasone suppression test and/or dexamethasone-CRF test) and in vitro (as reflected by reduced sensitivity of PBMCs to dexamethasone-induced inhibition of immune cell function) (Pariante and Miller, 2001). Of specific relevance to the GR, inflammatory and immunoregulatory cytokines have been shown to alter virtually every aspect of GR function, including GR expression, GR phosphorylation state, GR translocation, GR protein-protein interactions, and ultimately GR binding to DNA (Goleva et al., 2002; Miller et al., 1999a; Pariante et al., 1999; Smoak and Cidlowski, 2004). The signal transduction pathways by which cytokines affect GR function also have been described and include NFκB, p38 MAPK, JNK, and STAT5 (Goleva et al., 2002; Smoak and Cidlowski, 2004; Wang et al., 2004; Wang et al., 2005). Finally, cytokines (e.g., IL-2 and IL-4) have been
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shown to induce the beta isoform of the GR, which is inactive and thereby serves to compete for ligand and reduce activation of the GR alpha isoform, the primary mediator of GR effects (Leung et al., 1998). Given the role of glucocorticoids in regulating immune activation and inflammation, cytokine-induced disruption of GR function may lead to a feed-forward cascade in which increasing inflammation leads to increased glucocorticoid resistance, which in turn leads to reduced glucocorticoid-mediated feedback inhibition of inflammatory responses (Raison and Miller, 2003). 2. Effects on Neurotransmitter Function Both in animals and humans, cytokines have been shown to have profound effects on the metabolism of brain neurotransmitters. Special emphasis will be placed on the effects of cytokines on serotonin and dopamine neurotransmission. Serotonin There is abundant evidence for abnormalities of serotonin (5HT) function in depression (Delgado et al., 1994; Owens and Nemeroff, 1994; Price et al., 1991; Ressler and Nemeroff, 2000). In many studies, cytokines have been shown to interfere with 5HT metabolism and activity, a mechanism that may account for the depressogenic effects of cytokines. Indeed, significant and consistent decreases in serum/plasma concentrations of tryptophan, the primary precursor of 5HT, have been reported in patients undergoing IL-2 and/or IFN-alpha therapy (Bonaccorso et al., 2002; Brown et al., 1989; Brown et al., 1991; Capuron et al., 2003a; Capuron et al., 2002c). Interestingly, in some of these studies, decreases in blood tryptophan concentrations were found to correlate with depressive symptoms (Bonaccorso et al., 2002; Capuron et al., 2003a; Capuron et al., 2002c). More specifically, it has been recently shown that tryptophan degradation during IFN-alpha therapy was associated with the development of mood and cognitive symptoms (e.g., depressed mood, anxiety, memory/attention disturbance) but not with neurovegetative and somatic symptoms (e.g., fatigue, psychomotor slowing, pain) (Capuron et al., 2003a). At the experimental level, treatments with IFNalpha and IL-1-beta were found to significantly upregulate the expression of the 5HT transporter mRNA, both in human cells, an effect which is opposite the activity of certain antidepressants (Morikawa et al., 1998; Ramamoorthy et al., 1995). In contrast to findings obtained in humans, several data in animals have shown stimulating effects of acute treatment with proinflammatory cytokines on 5HT metabolism (Dunn
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et al., 1999b; Linthorst et al., 1994). Nevertheless, recent data have indicated that cytokine effects on 5HT release in the nucleus accumbens were cytokine-dependent (Song et al., 1999). For instance, IL-1 and IL-6 were found to modestly increase extracellular 5-hydroxyindoleacetic acid (5-HIAA), the major metabolite of 5HT, from the nucleus accumbens in the rat, whereas IL-2 did not. Other data have shown that IFN-alpha reduced concentrations of 5HT and 5-HIAA in the midbrain and striatum of rats and in the frontal cortex in a dosedependent manner (Kamata et al., 2000). In addition, TNF-alpha has been found to enhance 5HT uptake, whereas IL-4, which acts as an anti-inflammatory cytokine within the central nervous system, induced a dose-dependent reduction of 5HT uptake (Mossner et al., 2001; Mossner et al., 1998). Finally, chronic administration of IFN-alpha was found to affect the low-affinity 5-HT1A receptors in the rat brain (Abe et al., 1999) and to increase the levels of 5HT transporter mRNA both in the midbrain and adrenal gland in rats (Morikawa et al., 1998). Strong support for a role of 5HT alterations in cytokine-induced depression is the involvement of cytokines in the induction of the enzyme indoleamine 2,3 dioxygenase (IDO). IDO is induced by cytokines, especially IFN-gamma, in a variety of immune cells including monocyte-derived macrophage and microglia, upon the immune system activation (Konan and Taylor, 1996; Mellor and Munn, 1999; Taylor and Feng, 1991; Widner et al., 2000). (See Figure 2.) IDO catalyzes the rate-limiting step of tryptophan conversion into kynurenine and then quinolinic acid (Byrne et al., 1986), thereby reducing the availability of tryptophan for conversion into 5-HT, the primary mediator of serotonin effects in the brain. In vivo, the activity of IDO is reflected by the ratio of kynurenine/tryptophan (Widner et al., 2000). Findings in experimental animals have shown that IDO is induced in the brain in response to peripheral immune stimulation by LPS and Bacille Calmette-Guerin (BCG) inoculation in mice (Lestage et al., 2002; Moreau et al., 2005). In addition, it has been recently shown in vitro, using IFN-gamma–stimulated purified cultures of neurons, astrocytes, microglia, and macrophages, that all these cellular types expressed IDO, but only microglia were able to produce detectable amounts of quinolinic acid. However, astrocytes and neurons were found to have the ability to catabolize quinolinic acid (Guillemin et al., 2005). Of relevance to depressed patients, TRP depletion in patients who became depressed during IFN-alpha therapy was associated with marked increases in kynurenine, suggesting that increased IDO activity contributed to the TRP decreases observed in depressed patients (Capuron et al., 2003a). Taken together, these data support the
Immune Stimulus
Cytokines (e.g., IFN-°)
Tryptophan
IDO
Kynurenine
Qu in olinic Acid
TPH
5-Hydroxytryptophan
Serotonin
FIGURE 2 Effects of immune activation on tryptophan metabolism. The induction by cytokines (e.g., interferongamma) of the enzyme, indoleamine-2, 3-dioxygenase (IDO), upon immune activation leads to tryptophan catabolism into kynurenine and quinolinic acid, thereby reducing the availability of tryptophan for serotonin synthesis via the enzyme tryptophan hydroxylase (TPH).
notion that IDO may represent a key player in the pathophysiology of cytokine-induced depression. Dopamine Dopamine is a neurotransmitter that is involved in multiple brain functions, including motor activity regulation, addictive behavior, and certain psychiatric disorders, including schizophrenia and depression (Bedard, 1995; Koob, 1996; van Praag et al., 1990). Consistent with the effects of cytokines on motor/movement activity, hedonic tone, and fatigue, several clinical and pre-clinical studies have shown that cytokines are able to modulate dopamine function. In clinical studies, symptoms characteristic of dopamine dysfunction (e.g., Parkinson-like symptoms) have been reported in patients treated with the cytokine IFN-alpha (Horikawa et al., 1999; Mizoi et al., 1997). In that regard, intravenous administration of levodopa significantly ameliorated a refractory case of akathisia induced by
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IFN-alpha (Sunami et al., 2000). Consistent with these clinical observations, alterations in basal ganglia activity, suggestive of decreased/impaired dopamine function, have been reported using positron emission tomography (PET) in medically ill patients undergoing treatment with IFN-alpha and exhibiting the neurovegetative symptoms of psychomotor slowing, fatigue, and anhedonia (Capuron et al., 2002b). Interestingly, dopamine uptake, as assessed by PET with 18 18 [ F]fluorodopa ([ F]DOPA), has also been found to be significantly lower in the left caudate of depressed patients with marked psychomotor retardation and affective flattening compared with depressed patients with high impulsivity and healthy controls (Martinot et al., 2001). These findings support the hypothesis that psychomotor retardation as well as anhedonia, which constitute two core neurovegetative symptoms induced by IFN-alpha, may be caused by diminished presynaptic striatal dopamine function. Regarding the symptom of fatigue, alterations in dopamine pathways may also participate to fatigue induction in patients undergoing treatment with cytokines. In support of this notion, treatments with levodopa or other pharmacologic agents increasing dopamine release (e.g. stimulants) have been shown to improve physical fatigue in patients with Parkinson’s disease as well as IFN-alpha–treated patients (Lou et al., 2003; Schwartz et al., 2002). In animals, chronic treatment with IFN-alpha was found to induce a dosing-schedule–dependent alteration of rhythmicity in locomotor activity (Ohdo et al., 2001) and a robust depression of motor activity (De Sarro et al., 1990; Dunn and Crnic, 1993). In addition, this cytokine was shown to decrease dopamine activity in the mouse brain (Kamata et al., 2000; Shuto et al., 1997). More recently, treatment with chronic IFN-alpha in rats was found to potentiate latent inhibition, a phenomenon believed to rely mainly on mesolimbic dopamine system (Bethus et al., 2003). In addition, chronic infusion of lipopolysaccharide into rat brain leads to delayed and selective degeneration of nigral dopaminergic neurons through microglial activation (Gao et al., 2002). Finally, recent data have indicated that nitric oxide induced by intramuscular injection of IFNalpha in rats was able to cross the blood-brain barrier and suppress both tetrahydrobiopterin biosynthesis (a co-factor for monoaminergic neurotransmitter biosynthesis) and dopamine production in the amygdala and raphe areas (Kitagami et al., 2003). Other cytokines, such as IL-2, were found to reduce dopamine turnover in the caudate and substantia nigra in mice when administered repeatedly (Lacosta et al., 2000). Consistent with the effects of cytokines on dopamine function, receptors for pro-inflammatory cytokines are
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abundantly expressed in the basal ganglia (Haas and Schauenstein, 1997), and basal ganglia and relevant dopamine pathways during cytokine activation appear involved in infectious diseases associated with neuropsychiatric alterations similar to those seen during cytokine treatment, including human immunodeficiency virus (Berger and Arendt, 2000). Effects on Brain Functions Aside from effects on neurotransmitter and neuroendocrine function, recent data suggest that cytokines are able to alter higher cognitive brain functions including fundamental information processing. Indeed, in a recent brain functional magnetic resonance imaging (fMRI) study, patients with chronic hepatitis C (HCV) treated with IFN-alpha for 12 weeks were found to exhibit significant activation in the dorsal part of the anterior cingulate cortex (Capuron et al., 2005), a brain region that has been involved in conflict monitoring and cognitive control during cognitive tasks with high demand (Botvinick et al., 2001; Bush et al., 2000; Carter et al., 1998; Carter et al., 1999; Paus 2001). Interestingly, in IFN-alpha–treated HCV patients, activation of the cingulate cortex highly correlated with errors made in a visuo-spatial attention task administered during the fMRI session (Capuron et al., 2005). This activation of the anterior cingulate cortex was not apparent in untreated HCV patients, although these patients exhibited a similar error rate and similar task-related performance compared to IFN-alpha–treated subjects. Similar to IFN-alpha–treated patients, activation of the dorsal anterior cingulate cortex in the context of a lowerror rate has been found in individuals with personality characteristics (e.g., high-trait anxiety, neuroticism) known to be risk factors for the development of mood and anxiety disorders (Paulus et al., 2004). These data suggest that cytokines (IFN-alpha) induce alterations in information processing (as revealed by increased activity in the anterior cingulate cortex) that may manifest by an increased sensitivity to processing conflicts and events perceived as potentially threatening (Capuron et al., 2005), possibly reflecting a so-called “danger” signal in the brain. Such changes in brain activity and relevant cognitive processes may in turn impart an increased vulnerability to negative effects and more generally to psychopathology (e.g., mood disorders).
VIII. CYTOKINE ABNORMALITIES IN DEPRESSION: TREATMENT IMPLICATIONS Based on the potential role of cytokines in the pathophysiology of depression, opportunities exist for
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“translational” research strategies that focus on the management of sickness/depressive symptoms using novel therapies targeted at the pathways by which cytokines may contribute to depression. Probably the most obvious targets are the pro-inflammatory cytokines themselves, including the use of interleukin (IL)1 receptor antagonist (e.g., anakinra) to target IL-1; the soluble TNF receptor (e.g., etanercept) or antibodies to TNF (e.g., infliximab) to target TNF; and the antiinflammatory cytokine, IL-10, to target multiple inflammatory cytokines. Such cytokine “antagonists” may find both systemic usefulness as well as local applications, such as the treatment of peripheral nerve pathological pain syndromes (Watkins et al., 2003). Of note, etanercept, infliximab, and anakinra are all available commercially for the treatment of rheumatoid arthritis, and therefore are available for preliminary analyses of efficacy in patients with altered mood status. Other promising approaches include the targeting of corticotropin-releasing factor (CRF), which, as noted above, is induced by pro-inflammatory cytokines and has been shown to cause many of the same symptoms as sickness behavior when administered to laboratory animals (Owens and Nemeroff, 1993). Antidepressants targeting CRH and novel CRH antagonists are being developed by several pharmaceutical companies (Stout et al., 2002). Other targets include inflammatory mediators such as the prostaglandins as well as the CNS monoamines such as serotonin, norepinephrine, and dopamine. Given the capacity of cytokine exposure to influence brain monoamines (Dunn et al., 1999a), therapies targeted at influencing monoamine neurotransmission (including selected antidepressants as well inhibitors of IDO) might be especially useful. Finally, because glucocorticoids serve to potently inhibit inflammatory signaling pathways, pharmacologic agents that enhance glucocorticoid signaling and/or inhibit inflammatory signaling, including type 4 phospodiesterase inhibitors, may be worthy of consideration (McKay and Cidlowski, 1999; Miller et al., 1999a; Miller et al., 2002a).
IX. CONCLUSION In conclusion, there is strong evidence that depression involves alterations in multiple aspects of immunity that may not only contribute to the development or exacerbation of a number of medical disorders, but also may contribute to the pathophysiology of the disease itself. Accordingly, aggressive management of depressive disorders in medically ill populations or individuals at risk for disease may improve disease outcome or prevent disease development. On the other
hand, in light of data suggesting that immune processes may interact with the pathophysiologic pathways known to contribute to depression, novel approaches to the treatment of depression may target relevant aspects of the immune response. Taken together, the data provide compelling evidence that a psychoimmunologic frame of reference may have profound implications regarding the consequences and treatment of depression.
References Abe S., Hori T., Suzuki T., Baba A., Shiraishi H., and Yamamoto T. (1999). Effects of chronic administration of interferon alpha A/D on serotonergic receptors in rat brain. Neurochem. Res., 24, 359–363. American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders (4th ed.). Washington, DC: Author. Andreoli A., Keller S. E., Rabaeus M., Zaugg L., Garrone G., and Taban C. (1992). Immunity, major depression, and panic disorder comorbidity. Biol. Psychiatry, 31, 896–908. Andreoli A. V., Keller S. E., Rabaeus M., Marin P., Bartlett J. A., and Taban C. (1993). Depression and immunity: age, severity, and clinical course. Brain Behav. Immun., 7, 279–292. Anisman H., Ravindran A. V., Griffiths J., and Merali Z. (1999). Endocrine and cytokine correlates of major depression and dysthymia with typical or atypical features. Mol. Psychiatry, 4, 182–188. Babyak M. A., Blumenthal J. A., Herman S., et al. (2000). Exercise treatment for major depression: maintenance of therapeutic benefit at 10 months. Psychosom. Med., 62, 633–638. Barden N. (1999). Regulation of corticosteroid receptor gene expression in depression and antidepressant action. J. Psychiatry Neurosci., 24, 25–39. Bedard P. J. (1995). D-1 receptors in neurology and psychiatry: an overview. Prog. Neuropsychopharmacol. Biol. Psychiatry, 19, 713–726. Berger J. R., and Arendt G. (2000). HIV dementia: the role of the basal ganglia and dopaminergic systems. J. Psychopharmacol., 14, 214–221. Besedovsky H. O., and del Rey A. (1996). Immune-neuro-endocrine interactions: facts and hypotheses. Endocri. Rev., 17, 64– 102. Bethus I., Stinus L., and Goodall G. (2003). Chronic interferon-alpha potentiates latent inhibition in rats. Behav. Brain Res., 144, 167–174. Blumenthal J. A., Sherwood A., Babyak M. A., et al. (2005). Effects of exercise and stress management training on markers of cardiovascular risk in patients with ischemic heart disease: a randomized controlled trial. JAMA, 293, 1626–1634. Bonaccorso S., Marino V., Puzella A., et al. (2002). Increased depressive ratings in patients with hepatitis C receiving interferon-alpha–based immunotherapy are related to interferonalpha–induced changes in the serotonergic system. J. Clin. Psychopharmacol., 22, 86–90. Botvinick M. M., Braver T. S., Barch D. M., Carter C. S., and Cohen J. D. (2001). Conflict monitoring and cognitive control. Psychol. Rev., 108, 624–652. Bower J. E., Ganz P. A., Aziz N., and Fahey J. L. (2002). Fatigue and proinflammatory cytokine activity in breast cancer survivors. Psychosom. Med., 64, 604–611.
24. Psychoneuroimmunology of Depressive Disorder: Mechanisms and Clinical Implications Brown R. R., Lee C. M., Kohler P. C., Hank J. A., Storer B. E., and Sondel P. M. (1989). Altered tryptophan and neopterin metabolism in cancer patients treated with recombinant interleukin 2. Cancer Res., 49, 4941–4944. Brown R. R., Ozaki Y., Datta S. P., Borden E. C., Sondel P. M., and Malone D. G. (1991). Implications of interferon-induced tryptophan catabolism in cancer, auto-immune diseases and AIDS. Adv. Exp. Med. Biol., 294, 425–435. Bush G., Luu P., and Posner M. I. (2000). Cognitive and emotional influences in anterior cingulate cortex. Trends Cogn. Sci., 4, 215–222. Buter J., de Vries E. G., Sleijfer D. T., Willemse P. H., and Mulder N. H. (1993). Neuropsychiatric symptoms during treatment with interleukin-2. Lancet, 341, 628. Byrne G. I., Lehmann L. K., Kirschbaum J. G., Borden E. C., Lee C. M., and Brown R. R. (1986). Induction of tryptophan degradation in vitro and in vivo: a gamma-interferon-stimulated activity. J. Interferon Res., 6, 389–396. Cadoret R. J. (1981). Depression and alcoholism. In J. E. OBrien (Ed.), Evaluation of the alcoholic (1st ed.). Rockville, MD: National Institute on Alcohol Abuse and Alcoholism. 55–85. Capuron L., Gumnick J. F., Musselman D. L., et al. (2002a). Neurobehavioral effects of interferon-alpha in cancer patients: phenomenology and paroxetine responsiveness of symptom dimensions. Neuropsychopharmacology, 26, 643–652. Capuron L., and Miller A. H. (2004). Cytokines and psychopathology: lessons from interferon-alpha. Biol. Psychiatry, 56, 819– 824. Capuron L., Neurauter G., Musselman D. L., et al. (2003a). Interferon-alpha–induced changes in tryptophan metabolism. Relationship to depression and paroxetine treatment. Biol. Psychiatry, 54, 906–914. Capuron L., Pagnoni G., Demetrashvili M., et al. (2005). Anterior cingulate activation and error processing during interferon-alpha treatment. Biol. Psychiatry, 58, 190–196. Capuron L., Pagnoni G., Lawson D. H., et al. (2002b). Altered frontopallidal activity during high-dose interferon-alpha treatment as determined by PET. Society for Neuroscience, Abstract 498.5. Capuron L., Raison C. L., Musselman D. L., Lawson D. H., Nemeroff C. B., and Miller A. H. (2003b). Association of exaggerated HPA axis response to the initial injection of interferon-alpha with development of depression during interferon-alpha therapy. Am. J. Psychiatry, 160, 1342–1345. Capuron L., and Ravaud A. (1999). Prediction of the depressive effects of interferon alfa therapy by the patient’s initial affective state. N. Engl. J. Med., 340, 1370. Capuron L., Ravaud A., Miller A. H., and Dantzer R. (2004). Baseline mood and psychosocial characteristics of patients developing depressive symptoms during interleukin-2 and/or interferonalpha cancer therapy. Brain Behav. Immun., 18, 205–213. Capuron L., Ravaud A., Neveu P. J., Miller A. H., Maes M., and Dantzer R. (2002c). Association between decreased serum tryptophan concentrations and depressive symptoms in cancer patients undergoing cytokine therapy. Mol. Psychiatry, 7, 468–473. Carter C. S., Botvinick M. M., and Cohen J. D. (1999). The contribution of the anterior cingulate cortex to executive processes in cognition. Rev. Neurosci., 10, 49–57. Carter C. S., Braver T. S., Barch D. M., Botvinick M. M., Noll D., and Cohen J. D. (1998). Anterior cingulate cortex, error detection, and the online monitoring of performance. Science, 280, 747–749. Castanon N., Leonard B. E., Neveu P. J., and Yirmiya R. (2002). Effects of antidepressants on cytokine production and actions. Brain Behav., Immun., 16, 569–574.
525
Cleeland C. S. (2000). Cancer-related symptoms. Semin. Radiat. Oncol., 10, 175–190. Cohen S., and Miller G. (2000). Stress, immunity and susceptibility to upper respiratory infection. In N. Cohen (Ed.), Psychoneuroimmunology (3rd ed., pp. 499–509). San Diego: Academic Press. Cover H., and Irwin M. (1994). Immunity and depression: insomnia, retardation, and reduction of natural killer cell activity. J. Behav. Med., 17, 217–223. Cuijpers P., and Smit F. (2002). Excess mortality in depression: a meta-analysis of community studies. J. Affect. Disord., 72, 227–236. De Sarro G. B., Masuda Y., Ascioti C., Audino M. G., and Nistico G. (1990). Behavioural and ECoG spectrum changes induced by intracerebral infusion of interferons and interleukin 2 in rats are antagonized by naloxone. Neuropharmacology, 29, 167–179. Delgado P. L., Price L. H., Miller H. L., et al. (1994). Serotonin and the neurobiology of depression. Effects of tryptophan depletion in drug-free depressed patients. Arch. Gen. Psychiatry, 51, 865–874. Denicoff K. D., Rubinow D. R., Papa M. Z., et al. (1987). The neuropsychiatric effects of treatment with interleukin-2 and lymphokine-activated killer cells. Ann. Intern. Med., 107, 293–300. Dew M. A., Hoch C. C., Buysse D. J., et al. (2003). Healthy older adults’ sleep predicts all-cause mortality at 4 to 19 years of follow-up. Psychosom. Med., 65, 63–73. Dhabhar F. S. (2000). Acute stress enhances while chronic stress suppresses skin immunity. The role of stress hormones and leukocyte trafficking. Ann. N. Y. Acad. Sci., 917, 876–893. Dhabhar F. S., Miller A. H., McEwen B. S., and Spencer R. L. (1996). Stress-induced changes in blood leukocyte distribution. Role of adrenal steroid hormones. J. Immunol., 157, 1638–1644. Dunn A. J., and Wang J. (1995). Cytokine effects on CNS biogenic amines. Neuroimmunomodulation, 2, 319–328. Dunn A. J., Wang J., and Ando T. (1999a). Effects of cytokines on cerebral neurotransmission. Comparison with the effects of stress. Adv. Exp. Med. Biol., 461, 117–127. Dunn A. J., Wang J., and Ando T. (1999b). Effects of cytokines on cerebral neurotransmission: comparison with the effects of stress. In R. Dantzer, E. E. Wollman, and R. Yirmiya (Eds.), Cytokines, stress, and depression (pp. 117–127). New York: Plenum, Kluwer Academic. Dunn A. L., and Crnic L. S. (1993). Repeated injections of interferonalpha A/D in BALB/c mice: behavioral effects. Brain Behav. Immun., 7, 104–111. Empana J. P., Sykes D. H., Luc G., et al. (2005). Contributions of depressive mood and circulating inflammatory markers to coronary heart disease in healthy European men: the Prospective Epidemiological Study of Myocardial Infarction (PRIME). Circulation, 111, 2299–2305. Evans D. L., Folds J. D., Petitto J. M., et al. (1992). Circulating natural killer cell phenotypes in men and women with major depression. Arch. Gen. Psychiatry, 49, 388–395. Evans D. L., Staab J. P., Petitto J. M., et al. (1999). Depression in the medical setting: biopsychological interactions and treatment considerations. J. Clin. Psychiatry, 60 (Suppl 4), 40–55; discussion, 56. Evans D. L., Ten Have T. R., Douglas S. D., et al. (2002). Association of depression with viral load, CD8 T lymphocytes, and natural killer cells in women with HIV infection. Am. J. Psychiatry, 159, 1752–1759. Fishman D., Faulds G., Jeffery R., et al. (1998). The effect of novel polymorphisms in the interleukin-6 (IL-6) gene on IL-6 transcription and plasma IL-6 levels, and an association with
526
III. Behavior and Immunity
systemic-onset juvenile chronic arthritis. J. Clin. Invest., 102, 1369–1376. Frank M. G., Hendricks S. E., Johnson D. R., Wieseler J. L., and Burke W. J. (1999). Antidepressants augment natural killer cell activity: in vivo and in vitro. Neuropsychobiology, 39, 18–24. Friedman E. M., and Irwin M. (1995). A role for CRH and the sympathetic nervous system in stress-induced immunosuppression. Ann. N. Y. Acad. Sci., 771, 396–418. Friedman E. M., and Irwin M. R. (1997). Modulation of immune cell function by the autonomic nervous system. Pharmacol. Ther., 74, 27–38. Frommberger U. H., Bauer J., Haselbauer P., Fraulin A., Riemann D., and Berger M. (1997). Interleukin-6 (IL-6)–plasma levels in depression and schizophrenia: comparison between the acute state and after remission. Eur. Arch. Psychiatry Clin. Neurosci., 247, 228–233. Gao H. M., Jiang J., Wilson B., Zhang W., Hong J. S., and Liu B. (2002). Microglial activation-mediated delayed and progressive degeneration of rat nigral dopaminergic neurons: relevance to Parkinson’s disease. J. Neurochem., 81, 1285–1297. Gisslinger H., Svoboda T., Clodi M., et al. (1993). Interferon-alpha stimulates the hypothalamic-pituitary-adrenal axis in vivo and in vitro. Neuroendocrinology, 57, 489–495. Glaser R., Kiecolt-Glaser J. K., Bonneau R. H., Malarkey W., Kennedy S., and Hughes J. (1992). Stress-induced modulation of the immune response to recombinant hepatitis B vaccine. Psychosom. Med., 54, 22–29. Goleva E., Kisich K. O., and Leung D. Y. (2002). A role for STAT5 in the pathogenesis of IL-2–induced glucocorticoid resistance. J. Immunol., 169, 5934–5940. Goujon E., Parnet P., Aubert A., Goodall G., and Dantzer R. (1995). Corticosterone regulates behavioral effects of lipopolysaccharide and interleukin-1b in mice. American Journal of Physiology, 269, R154–R159. Guillemin G. J., Smythe G., Takikawa O., and Brew B. J. (2005). Expression of indoleamine 2,3–dioxygenase and production of quinolinic acid by human microglia, astrocytes, and neurons. Glia, 49, 15–23. Haas H. S., and Schauenstein K. (1997). Neuroimmunomodulation via limbic structures—the neuroanatomy of psychoimmunology. Prog. Neurobiol., 51, 195–222. Hall M., Baum A., Buysse D. J., Prigerson H. G., Kupfer D. J., and Reynolds C. F. (1998). Sleep as a mediator of the stress-immune relationship. Psychosom. Med., 60, 48–51. Heim C., Newport D. J., Heit S., et al. (2000). Pituitary-adrenal and autonomic responses to stress in women after sexual and physical abuse in childhood. JAMA, 284, 592–597. Herbert T. B., and Cohen S. (1993). Depression and immunity—a meta-analytic review. Psychol. Bull., 113, 472–486. Hickie I., Hickie C., Lloyd A., Silove D., and Wakefield D. (1993). Impaired in vivo immune responses in patients with melancholia. Br. J. Psychiatry, 162, 651–657. Hindmarch F. (2001). Expanding the horizons of depression: beyond the monoamine hypothesis. Hum. Psychopharmacol., 16, 203– 218. Horikawa N., Yamazaki T., Sagawa M., and Nagata T. (1999). A case of akathisia during interferon-alpha therapy for chronic hepatitis type C. Gen. Hosp. Psychiatry, 21, 134–135. Irwin M. (2002). Psychoneuroimmunology of depression: clinical implications (Presidential Address). Brain Behav., Immun., 16, 1–16. Irwin M., Brown M., Patterson T., Hauger R., Mascovich A., and Grant I. (1991). Neuropeptide Y and natural killer cell activity: findings in depression and Alzheimer caregiver stress. FASEB J, 5, 3100–3107.
Irwin M., Caldwell C., Smith T. L., Brown S., Schuckit M. A., and Gillin J. C. (1990a). Major depressive disorder, alcoholism, and reduced natural killer cell cytotoxicity: role of severity of depressive symptoms and alcohol consumption. Arch. Gen. Psychiatry, 47, 713–719. Irwin M., Clark C., Kennedy B., Gillin, J. C., and Ziegler M. (2003a). Nocturnal catecholamines and immune function in insomniacs, depressed patients, and control subjects. Brain Behav. Immun., 17, 365–372. Irwin M., Costlow C., Williams H., et al. (1998). Cellular immunity to varicella-zoster virus in patients with major depression. J. Infect. Dis., 178 (Suppl 1), S104–108. Irwin M., Daniels M., Risch S. C., Bloom E., and Weiner H. (1988). Plasma cortisol and natural killer cell activity during bereavement. Biol. Psychiatry, 24, 173–178. Irwin M., Gillin J. C., Dang J., Weissman J., Phillips E., and Ehlers C. L. (2002). Sleep deprivation as a probe of homeostatic sleep regulation in primary alcoholics. Biol. Psychiatry, 51, 632–641. Irwin M., Hauger R. L., Jones L., Provencio M., and Britton K. T. (1990b). Sympathetic nervous system mediates central corticotropin-releasing factor induced suppression of natural killer cytotoxicity. J. Pharmacol. Exp. Ther., 255 (1), 101–107. Irwin M., Lacher U., and Caldwell C. (1992a). Depression and reduced natural killer cytotoxicity: a longitudinal study of depressed patients and control subjects. Psychol. Med., 22, 1045–1050. Irwin M., Mascovich A., Gillin J. C., Willoughby R., Pike J. L., and Smith T. L. (1994). Partial sleep deprivation reduces natural killer cell activity in humans. Psychosom. Med., 56, 493–498. Irwin M., McClintick J., Costlow C., Fortner M., White J., and Gillin J. C. (1996). Partial night sleep deprivation reduces natural killer and cellular immune responses in humans. FASEB J, 10, 643–653. Irwin M., and Miller C. (2000). Decreased natural killer cell responses and altered interleukin-6 and interleukin-10 production in alcoholism: an interaction between alcohol dependence and African-American ethnicity. Alcohol. Clin. Exp. Res., 24, 560– 569. Irwin M., Miller C., Gillin J. C., Demodena A., and Ehlers C. L. (2000). Polysomnographic and spectral sleep EEG in primary alcoholics: an interaction between alcohol dependence and African-American ethnicity. Alcohol. Clin. Exp. Res., 24, 1376–1384. Irwin M., Patterson T. L., Smith T. L., et al. (1990c). Reduction of immune function in life stress and depression. Biol. Psychiatry, 27, 22–30. Irwin M., Smith T. L., and Gillin J. C. (1992b). Electroencephalographic sleep and natural killer activity in depressed patients and control subjects. Psychosom. Med., 54, 107–126. Irwin M., Vale W., and Rivier C. (1990d). Central corticotropinreleasing factor mediates the suppressive effect of stress on natural killer cytotoxicity. Endocrinology, 126, 2837–2844. Irwin M. R., and Gillin J. C. (1987). Impaired natural killer cell activity among depressed patients. Psychiatry Res., 20, 181–182. Irwin M. R., and Pike J. L. (2006). Dissociation between natural killer cell activity and inflammatory markers in major depression. Brain Behav. Immun., 20, 169–174. Irwin M. R., Pike J. L., Cole J. C., and Oxman M. N. (2003b). Effects of a behavioral intervention, Tai Chi Chih, on varicella-zoster virus specific immunity and health functioning in older adults. Psychosom. Med., 65, 824–830. Jeanmonod P., von Kanel R., Maly F. E., and Fischer J. E. (2004). Elevated plasma C-reactive protein in chronically distressed subjects who carry the A allele of the TNF-alpha −308 G/A polymorphism. Psychosom. Med., 66, 501–506.
24. Psychoneuroimmunology of Depressive Disorder: Mechanisms and Clinical Implications Jung W., and Irwin M. (1999). Reduction of natural killer cytotoxic activity in major depression: interaction between depression and cigarette smoking. Psychosom. Med., 61, 263–270. Kaestner F., Hettich M., Peters M., et al. (2005). Different activation patterns of proinflammatory cytokines in melancholic and nonmelancholic major depression are associated with HPA axis activity. J. Affect. Disord., 87, 305–311. Kamata M., Higuchi H., Yoshimoto M., Yoshida K., and Shimizu T. (2000). Effect of single intracerebroventricular injection of alphainterferon on monoamine concentrations in the rat brain. Eur. Neuropsychopharmacol., 10, 129–132. Kendler K. S., Thornton L. M., and Gardner C. O. (2000). Stressful life events and previous episodes in the etiology of major depression in women: an evaluation of the “kindling” hypothesis. Am. J. Psychiatry, 157, 1243–1251. Kenis G., and Maes M. (2002). Effects of antidepressants on the production of cytokines. Int. J. Neuropsychopharmacol., 5, 401–412. Kent S., Bluthe R. M., Kelley K. W., and Dantzer R. (1992). Sickness behavior as a new target for drug development. Trends Pharmacol. Sci., 13, 24–28. Kiecolt-Glaser J. K., McGuire L., Robles T. F., and Glaser R. (2002). Psychoneuroimmunology and psychosomatic medicine: back to the future. Psychosom. Med., 64, 15–28. Kiecolt-Glaser J. K., Preacher K. J., MacCallum R. C., Atkinson C., Malarkey W. B., and Glaser R. (2003). Chronic stress and age-related increases in the proinflammatory cytokine IL-6. Proc. Nat. Acad. Sci. U.S.A., 100, 9090–9095. Kim Y. K., Suh I. B., Kim H., et al. (2002). The plasma levels of interleukin-12 in schizophrenia, major depression, and bipolar mania: effects of psychotropic drugs. Mol. Psychiatry, 7, 1107–1114. Kitagami T., Yamada K., Miura H., Hashimoto R., Nabeshima T., and Ohta T. (2003). Mechanism of systemically injected interferon-alpha impeding monoamine biosynthesis in rats: role of nitric oxide as a signal crossing the blood-brain barrier. Brain Res., 978, 104–114. Kohut M. L., Lee W., Martin A., et al. (2005). The exercise-induced enhancement of influenza immunity is mediated in part by improvements in psychosocial factors in older adults. Brain Behav. Immun., 19, 357–366. Konan K. V., and Taylor M. W. (1996). Importance of the two interferon-stimulated response element (ISRE) sequences in the regulation of the human indoleamine 2,3-dioxygenase gene. J. Biol. Chem., 271, 19140–19145. Koob G. F. (1996). Hedonic valence, dopamine and motivation. Mol. Psychiatry, 1, 186–189. Kronfol Z. (2003). Cytokine regulation in major depression. In Z. Kronfol (Ed.), Cytokines and mental health (pp. 259–280). Boston: Kluwer Academic Publishers. Kronfol Z., and House J. D. (1985). Depression, hypothalamicpituitary-adrenocortical activity and lymphocyte function. Psychopharmacol. Bull., 21, 476–478. Kronfol Z., House J. D., Silva J., Greden J., and Carroll B. J. (1986). Depression, urinary free cortisol excretion, and lymphocyte function. Br. J. Psychiatry, 148, 70–73. Kronfol Z., Silva J., Greden J., Dembinski S., Gardner R., and Carroll B. (1983). Impaired lymphocyte function in depressive illness. Life Sci., 33, 241–247. Kronfol Z., Turner R., Nasrallah H., and Winokur G. (1984). Leukocyte regulation in depression and schizophrenia. Psychiatry Res., 13, 13–18. Kubera M., Symbirtsev A., Basta-Kaim A., et al. (1996). Effect of chronic treatment with imipramine on interleukin-1 and interleukin-2 production by splenocytes obtained from rats subjected
527
to a chronic mild stress model of depression. Pol. J. Pharmacol., 48, 503–506. Lacosta S., Merali Z., and Anisman H. (2000). Central monoamine activity following acute and repeated systemic interleukin-2 administration. Neuroimmunomodulation, 8, 83–90. Leserman J. (2003). HIV disease progression: depression, stress, and possible mechanisms. Biol. Psychiatry, 54, 295–306. Lesperance F., Frasure-Smith N., Theroux P., and Irwin M. (2004). The association between major depression and levels of soluble intercellular adhesion molecule 1, interleukin-6, and C-reactive protein in patients with recent acute coronary syndromes. Am. J. Psychiatry, 161, 271–277. Lestage J., Verrier D., Palin K., and Dantzer R. (2002). The enzyme indoleamine 2,3-dioxygenase is induced in the mouse brain in response to peripheral administration of lipopolysaccharide and superantigen. Brain Behav. Immun., 16, 596–601. Leung D. Y., de Castro M., Szefler S. J., and Chrousos G. P. (1998). Mechanisms of glucocorticoid-resistant asthma. Ann. N. Y. Acad. Sci., 840, 735–746. Linkins R. W., and Comstock G. W. (1990). Depressed mood and development of cancer. Am. J. Epidemiol., 132 (5), 962– 972. Linthorst A. C., Flachskamm C., Holsboer F., and Reul J. M. (1994). Local administration of recombinant human interleukin-1 beta in the rat hippocampus increases serotonergic neurotransmission, hypothalamic-pituitary-adrenocortical axis activity, and body temperature. Endocrinology, 135, 520–532. Lou J. S., Kearns G., Benice T., Oken B., Sexton G., and Nutt J. (2003). Levodopa improves physical fatigue in Parkinson’s disease: a double-blind, placebo-controlled, crossover study. Mov. Disord., 18, 1108–1114. Lowy M. T., Reder A. T., Gormley G. J., and Meltzer H. Y. (1988). Comparison of in vivo and in vitro glucocorticoid sensitivity in depression: relationship to the dexamethasone suppression test. Biol. Psychiatry, 24, 619–630. Maes M., Bosmans E., Suy E., Minner B., and Raus J. (1989). Impaired lymphocyte stimulation by mitogens in severely depressed patients. A complex interface with HPA-axis hyperfunction, noradrenergic activity and the aging process. Br. J. Psych., 155, 793–798. Maes M., Lambrechts J., Bosmans E., et al. (1992). Evidence for a systemic immune activation during depression: results of leukocyte enumeration by flow cytometry in conjunction with monoclonal antibody staining. Psychol. Med., 22, 45–53. Maes M., Scharpe S., Meltzer H. Y., et al. (1993). Relationships between interleukin-6 activity, acute phase proteins, and function of the hypothalamic-pituitary-adrenal axis in severe depression. Psychiatry Res., 49, 11–27. Maier S. F., and Watkins L. R. (1998). Cytokines for psychologists: implications of bidirectional immune-to-brain communication for understanding behavior, mood, and cognition. Psychol. Rev., 105, 83–107. Mallon L., Broman J. E., and Hetta J. (2002). Sleep complaints predict coronary artery disease mortality in males: a 12-year follow-up study of a middle-aged Swedish population. J. Intern. Med., 251, 207–216. Martinot M., Bragulat V., Artiges E., et al. (2001). Decreased presynaptic dopamine function in the left caudate of depressed patients with affective flattening and psychomotor retardation. Am. J. Psychiatry, 158, 314–316. McAllister-Sistilli C. G., Caggiula A. R., Knopf S., Rose C. A., Miller A. L., and Donney E. C. (1998). The effects of nicotine on the immune system. Psychoneuroendocrinology, 23, 175–187. McEwen B. S., Biron C. A., Brunson K. W., et al. (1997). The role of adrenocorticoids as modulators of immune function in health
528
III. Behavior and Immunity
and disease: neural, endocrine and immune interactions. Brain Res.: Brain Res. Rev., 23, 79–133. McKay L. I., and Cidlowski J. A. (1999). Molecular control of immune/inflammatory responses: interactions between nuclear factor-kappa B and steroid receptor-signaling pathways. Endocr. Rev., 20, 435–459. Mellor A. L., and Munn D. H. (1999). Tryptophan catabolism and T-cell tolerance: immunosuppression by starvation? Immunol. Today, 20, 469–473. Mendall M. A., Patel P., Asante M., et al. (1997). Relation of serum cytokine concentrations to cardiovascular risk factors and coronary heart disease. Heart, 78, 273–277. Meyers C. A., Albitar M., and Estey E. (2005). Cognitive impairment, fatigue, and cytokine levels in patients with acute myelogenous leukemia or myelodysplastic syndrome. Cancer, 104, 788–793. Michaud C. M., Murray C. J., and Bloom B. R. (2001). Burden of disease—implications for future research. JAMA, 285, 535–539. Miller A. H., Asnis G. M., Lackner C., Halbreich U., and Norin A. J. (1991). Depression, natural killer cell activity, and cortisol secretion. Biol. Psychiatry, 29, 878–886. Miller A. H., Pariante C. M., and Pearce B. D. (1999a). Effects of cytokines on glucocorticoid receptor expression and function. Glucocorticoid resistance and relevance to depression. Adv. Exp. Med. Biol., 461, 107–116. Miller A. H., Vogt G. J., and Pearce B. D. (2002a). The phosphodiesterase type 4 inhibitor, rolipram, enhances glucocorticoid receptor function. Neuropsychopharmacology, 27, 939–948. Miller G. E., Cohen S., and Herbert T. B. (1999b). Pathways linking major depression and immunity in ambulatory female patients. Psychosom. Med., 61, 850–860. Miller G. E., Cohen S., Pressman S., Barkin A., Rabin B. S., and Treanor J. J. (2004). Psychological stress and antibody response to influenza vaccination: when is the critical period for stress, and how does it get inside the body? Psychosom. Med., 66, 215–223. Miller G. E., Cohen S., and Ritchey A. K. (2002b). Chronic psychological stress and the regulation of pro-inflammatory cytokines: a glucocorticoid-resistance model. Health Psychol., 21, 531–541. Miller G. E., Freedland K. E., Duntley S., and Carney R. M. (2005). Relation of depressive symptoms to C-reactive protein and pathogen burden (cytomegalovirus, herpes simplex virus, Epstein-Barr Virus) in patients with earlier acute coronary syndromes. Am. J. Cardiol., 95, 317–321. Miller G. E., Stetler C. A., Carney R. M., Freedland K. E., and Banks W. A. (2002c). Clinical depression and inflammatory risk markers for coronary heart disease. Am. J. Cardiol., 90, 1279–1283. Miyaoka H., Otsubo T., Kamijima K., Ishii M., Onuki M., and Mitamura K. (1999). Depression from interferon therapy in patients with hepatitis C. Am. J. Psychiatry, 156, 1120. Mizoi Y., Kaneko H., Oharazawa A., and Kuroiwa H. (1997). Parkinsonism in a patient receiving interferon alpha therapy for chronic hepatitis C. Rinsho Shinkeigaku, 37, 54–56. Mohamed-Ali V., Pinkney J. H., and Coppack S. W. (1998). Adipose tissue as an endocrine and paracrine organ. Int. J. Obes. Relat. Metab. Disord., 22, 1145–1158. Moreau M., Lestage J., Verrier D., et al. (2005). Bacille CalmetteGuerin inoculation induces chronic activation of peripheral and brain indoleamine 2,3-dioxygenase in mice. J. Infect. Dis., 192, 537–544. Morikawa O., Sakai N., Obara H., and Saito N. (1998). Effects of interferon-alpha, interferon-gamma and cAMP on the transcriptional regulation of the serotonin transporter. Eur. J. Pharmacol., 349, 317–324.
Morrow G. R., Hickok J. T., Roscoe J. A., et al. (2003). Differential effects of paroxetine on fatigue and depression: a randomized, double-blind trial from the University of Rochester Cancer Center Community Clinical Oncology Program. J. Clin. Oncol., 21, 4635–4641. Mossner R., Daniel S., Schmitt A., Albert D., and Lesch K. P. (2001). Modulation of serotonin transporter function by interleukin-4. Life Sci., 68, 873–880. Mossner R., Heils A., Stober G., Okladnova O., Daniel S., and Lesch K. P. (1998). Enhancement of serotonin transporter function by tumor necrosis factor alpha but not by interleukin-6. Neurochem. Int., 33, 251–254. Motivala S. J., Sarfatti A., Olmos L., and Irwin M. R. (2005). Inflammatory markers and sleep disturbance in major depression. Psychosom. Med., 67, 187–194. Moynihan J. A., and Stevens S. Y. (2001). Mechanisms of stressinduced modulation of immunity in animals. In N. Cohen (Ed.), Psychoneuroimmunology (vol 2., pp. 227–250). San Diego: Academic Press. Musselman D. L., Lawson D. H., Gumnick J. F., et al. (2001a). Paroxetine for the prevention of depression induced by high-dose interferon alpha. N. Engl. J. Med., 344, 961–966. Musselman D. L., Miller A. H., Porter M. R., et al. (2001b). Higher than normal plasma interleukin-6 concentrations in cancer patients with depression: preliminary findings. Am. J. Psychiatry, 158, 1252–1257. Ohdo S., Koyanagi S., Suyama H., Higuchi S., and Aramaki H. (2001). Changing the dosing schedule minimizes the disruptive effects of interferon on clock function. Nat. Med., 7, 356–360. Owens M. J., and Nemeroff C. B. (1991). Physiology and pharmacology of corticotropin-releasing factor. Pharmacol. Rev., 91, 425–473. Owens M. J., and Nemeroff C. B. (1993). The role of corticotropinreleasing factor in the pathophysiology of affective and anxiety disorders: laboratory and clinical studies. Ciba Found Symp, 172, 296–308; discussion, 308–316. Owens M. J., and Nemeroff C. B. (1994). Role of serotonin in the pathophysiology of depression: focus on the serotonin transporter. Clin. Chem., 40, 288–295. Oxman M. N., Levin M. J., Johnson G. R., et al. (2005). A vaccine to prevent herpes zoster and postherapetic neuralgia in older adults. N. Engl. J. Med., 352, 2271–2284. Pariante C. M., and Miller A. H. (2001). Glucocorticoid receptors in major depression: relevance to pathophysiology and treatment. Biol. Psychiatry, 49, 391–404. Pariante C. M., Pearce B. D., Pisell T. L., et al. (1999). The proinflammatory cytokine, interleukin-1alpha, reduces glucocorticoid receptor translocation and function. Endocrinology, 140, 4359–4366. Paulus M. P., Feinstein J. S., Simmons A., and Stein M. B. (2004). Anterior cingulate activation in high trait anxious subjects is related to altered error processing during decision making. Biol. Psychiatry, 55, 1179–1187. Paus T. (2001). Primate anterior cingulate cortex: where motor control, drive and cognition interface. Nat. Rev. Neurosci., 2, 417–424. Penninx B. W., Geerlings S. W., Deeg D. J., van Eijk J. T., van Tilburg W., and Beekman A. T. (1999). Minor and major depression and the risk of death in older persons. Arch. Gen. Psychiatry, 56, 889–895. Penninx B. W., Kritchevsky S. B., Yaffe K., et al. (2003). Inflammatory markers and depressed mood in older persons: results from the Health, Aging and Body Composition study. Biol. Psychiatry, 54, 566–572.
24. Psychoneuroimmunology of Depressive Disorder: Mechanisms and Clinical Implications Pike J. L., Smith T. L., Hauger R., Nicassio P. M., Patterson T. L., McClintick J., Costlow C., and Irwin M. R. (1996). Chronic life stress alters sympathetic neuroendocrine and immune responsivity to an acute psychological stressor in humans. Psychosom. Med., 59, 447–457. Price L. H., Charney D. S., Delgado P. L., and Heninger G. R. (1991). Serotonin function and depression: neuroendocrine and mood responses to intravenous L-tryptophan in depressed patients and healthy comparison subjects. Am. J. Psychiatry, 148, 1518–1525. Raber J., Koob G. F., and Bloom F. E. (1997). Interferon-alpha and transforming growth factor-beta 1 regulate corticotropinreleasing factor release from the amygdala: comparison with the hypothalamic response. Neurochem. Int., 30, 455–463. Raison C. L., Borisov A. S., Broadwell S. D., et al. (2005). Depression during pegylated interferon-alpha plus ribavirin therapy: prevalence and prediction. J. Clin. Psychiatry, 66, 41–48. Raison C. L., and Miller A. H. (2003). When not enough is too much: the role of insufficient glucocorticoid signaling in the pathophysiology of stress-related disorders. Am. J. Psychiatry, 160, 1554–1565. Ramamoorthy S., Ramamoorthy J. D., Prasad P. D., et al. (1995). Regulation of the human serotonin transporter by interleukin-1 beta. Biochem. Biophys. Res. Commun., 216, 560–567. Ravindran A. V., Griffiths J., Merali Z., and Anisman H. (1995). Lymphocyte subsets associated with major depression and dysthymiai modification by antidepressant treatment Psychsom. Med., 57, 555–563. Redwine L., Dang J., Hall M., and Irwin M. (2003). Disordered sleep, nocturnal cytokines, and immunity in alcoholics. Psychosom. Med., 65, 75–85. Ressler K. J., and Nemeroff C. B. (2000). Role of serotonergic and noradrenergic systems in the pathophysiology of depression and anxiety disorders. Depress. Anxiety, 12 (Suppl 1), 2–19. Ridker P. M. (2001). Role of inflammatory biomarkers in prediction of coronary heart disease. Lancet, 358, 946–948; Comment on: 971–976. Ridker P. M., Hennekens C. H., Roitman-Johnson B., Stampfer M. J., and Allen J. (1998). Plasma concentration of soluble intercellular adhesion molecule 1 and risks of future myocardial infarction in apparently healthy men [see comments]. Lancet, 351, 88–92. Ridker P. M., Rifai N., Stampfer M. J., and Hennekens C. H. (2000). Plasma concentration of interleukin-6 and the risk of future myocardial infarction among apparently healthy men. Circulation, 101, 1767–1772. Rohleder N., Schommer N. C., Hellhammer D. H., Engel R., and Kirschbaum C. (2001). Sex differences in glucocorticoid sensitivity of proinflammatory cytokine production after psychosocial stress. Psychosom. Med., 63, 966–972. Rosecrans J. A., and Karin L. D. (1998). Effects of nicotine on the hypothalamic-pituitary-axis (HPA) and immune function: introduction to the Sixth Nicotine Round Table Satellite, American Society of Addiction Medicine Nicotine Dependence Meeting. Psychoneuroendocrinology, 23, 95–102. Rothermundt M., Arolt V., Peters M., et al. (2001). Inflammatory markers in major depression and melancholia. J. Affect. Disord., 63, 93–102. Rudisch B., and Nemeroff C. B. (2003). Epidemiology of comorbid coronary artery disease and depression. Biol. Psychiatry, 54, 227–240. Sanders V. M., and Straub R. H. (2002). Norepinephrine, the betaadrenergic receptor, and immunity. Brain Behav. Immun., 16, 290–332.
529
Savard J., Laroche L., Simard S., Ivers H., and Morin C. M. (2003). Chronic insomnia and immune functioning. Psychosom. Med., 65, 211–221. Schlatter J., Ortuno F., and Cervera-Enguix S. (2004). Lymphocyte subsets and lymphokine production in patients with melancholic versus nonmelancholic depression. Psychiatry Res., 128, 259–265. Schleifer S. J., Keller S. E., and Bartlett J. A. (1999). Depression and immunity: clinical factors and therapeutic course. Psychiatry Res., 85, 63–69. Schleifer S. J., Keller S. E., Bond R. N., Cohen J., and Stein M. (1989). Major depressive disorder and immunity: role of age, sex, severity, and hospitalization. Arch. Gen. Psychiatry, 46, 81–87. Schleifer S. J., Keller S. E., Meyerson A. T., Raskin M. J., Davis K. L., and Stein M. (1984). Lymphocyte function in major depressive disorder. Arch. Gen. Psychiatry, 41, 484–486. Schobitz B., Reul J. M., and Holsboer F. (1994). The role of the hypothalamic-pituitary-adrenocortical system during inflammatory conditions. Crit. Rev. Immunol., 8, 263–291. Schwartz A. L., Thompson J. A., and Masood N. (2002). Interferoninduced fatigue in patients with melanoma: a pilot study of exercise and methylphenidate. Oncol. Nurs. Forum, 29, E85– E90. Segerstrom S. C., and Miller G. E. (2004). Psychological stress and the human immune system: a meta-analytic study of 30 years of inquiry. Psychol. Bull., 130, 601–630. Seidel A., Arolt V., Hunstiger M., Rink L., Behnisch A., and Kirchner H. (1995). Cytokine production and serum proteins in depression. Scand. J. Immunol., 41, 534–538. Shinkawa M., Nakayama K., Hirai H., Monma M., and Sasaki H. (2002). Depression and immunoreactivity in disabled older patients. J. Am. Geriatr. Soc., 50, 198–199. Shuto H., Kataoka Y., Horikawa T., Fujihara N., and Oishi R. (1997). Repeated interferon-alpha administration inhibits dopaminergic neural activity in the mouse brain. Brain Res., 747, 348–351. Sluzewska A., Rybakowski J. K., Laciak M., Mackiewicz A., Sobieska M., and Wiktorowicz K. (1995). Interleukin-6 serum levels in depressed patients before and after treatment with fluoxetine. Ann. N. Y. Acad. Sci., 762, 474–476. Smith T. P., Kennedy S. L., and Fleshner M. (2004). Influence of age and physical activity on the primary in vivo antibody and T cell–mediated responses in men. J. App. Physiol., 97, 491– 498. Smoak K. A., and Cidlowski J. A. (2004). Mechanisms of glucocorticoid receptor signaling during inflammation. Mech. Ageing Dev., 125, 697–706. Song C., Merali Z., and Anisman H. (1999). Variations of nucleus accumbens dopamine and serotonin following systemic interleukin-1, interleukin-2 or interleukin-6 treatment. Neuroscience, 88, 823–836. Sopori M. L., and Kozak W. (1998). Immunomodulatory effects of cigarette smoke. J. Neuroimmunol., 83, 148–156. Stein M., Miller A. H., and Trestman R. L. (1991). Depression, the immune system, and health and illness. Arch. Gen. Psychiatry, 48, 171–177. Stout S. C., Owens M. J., and Nemeroff C. B. (2002). Regulation of corticotropin-releasing factor neuronal systems and hypothalamic-pituitary-adrenal axis activity by stress and chronic antidepressant treatment. J. Pharmacol. Exp. Ther., 300, 1085–1092. Sunami M., Nishikawa T., Yorogi A., and Shimoda M. (2000). Intravenous administration of levodopa ameliorated a refractory akathisia case induced by interferon-alpha. Clin. Neuropharmacol., 23, 59–61.
530
III. Behavior and Immunity
Taylor M. W., and Feng G. S. (1991). Relationship between interferon-gamma, indoleamine 2,3-dioxygenase, and tryptophan catabolism. FASEB J, 5, 2516–2522. Thomas A. J., Davis S., Morris C., Jackson E., Harrison R., and O’Brien J. T. (2005). Increase in interleukin-1beta in late-life depression. Am. J. Psychiatry, 162, 175–177. Turnbull A. V., and Rivier C. L. (1999). Regulation of the hypothalamic-pituitary-adrenal axis by cytokines: actions and mechanisms of action. Physiol. Rev., 79, 1–71. van Praag H. M., Asnis G. M., Kahn R. S., et al. (1990). Monoamines and abnormal behaviour. A multi-aminergic perspective. Br. J. Psychiatry, 157, 723–734. Vedhara K., Cox N. K., Wilcock G. K., et al. (1999). Chronic stress in elderly carers of dementia patients and antibody response to influenza vaccination [see comments]. Lancet, 353, 627–631. Wang X., Wu H., Lakdawala V. S., Hu F., Hanson N. D., and Miller A. H. (2005). Inhibition of Jun N-terminal kinase (JNK) enhances glucocorticoid receptor-mediated function in mouse hippocampal HT22 cells. Neuropsychopharmacology, 30, 242–249. Wang X., Wu H., and Miller A. H. (2004). Interleukin 1alpha (IL1alpha) induced activation of p38 mitogen-activated protein kinase inhibits glucocorticoid receptor function. Mol. Psychiatry, 9, 65–75. Watkins L. R., Milligan E. D., and Maier S. F. (2003). Glial proinflammatory cytokines mediate exaggerated pain states: implications for clinical pain. Adv. Exp. Med. Biol., 521, 1–21. Weizman R., Laor N., Podliszewski E., Notti I., Djaldetti M., and Bessler H. (1994). Cytokine production in major depressed
patients before and after clomipramine treatment. Biol. Psychiatry, 35, 42–47. Widner B., Ledochowski M., and Fuchs D. (2000). Interferongamma–induced tryptophan degradation: neuropsychiatric and immunological consequences. Curr. Drug Metab., 1, 193–204. Wulsin L. R., Vailant G. E., and Wells V. E. (1999). A systematic review of the mortality of depression. Psychosom. Med., 61, 6–17. Yaron I., Shirazi L., Judovich R., Levatrovsky D., Caspi D., and Yaron M. (1999). Fluoxetine and amitriptyline inhibit nitric oxide, prostaglandin E2, and hyaluronic acid production in human synovial cells and synovial tissue cultures. Arthritis Rheuma., 42, 2561–2568. Yirmiya R. (1996). Endotoxin produces a depressive-like episode in rats. Brain Res., 711, 163–174. Yirmiya R., Weidenfeld J., Pollak Y., et al. (1999). Cytokines, “depression due to a general medical condition,” and antidepressant drugs. Adv. Exp. Med. Biol., 461, 283–316. Yudkin J. S., Kumari M., Humphries S. E., and Mohamed-Ali V. (2000). Inflammation, obesity, stress and coronary heart disease: is interleukin-6 the link? Atherosclerosis, 148, 209–214. Zautra A. J., Yocum D. C., Villanueva I., et al. (2004). Immune activation and depression in women with rheumatoid arthritis. J. Rheumatol., 31, 457–463. Zorrilla E. P., Luborsky L., McKay J. R., et al. (2001). The relationship of depression and stressors to immunological assays: a metaanalytic review. Brain Behav. Immun., 15, 199–226.
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25 Immune and Neuroendocrine Alterations in Post-traumatic Stress Disorder GAIL IRONSON, DEAN CRUESS, AND MAHENDRA KUMAR
I. PSYCHOLOGICAL TRAUMA, PTSD, AND IMMUNE FUNCTION 531 II. PTSD: ENDOCRINE 539 III. ENDOCRINE-IMMUNE INTERACTIONS IN PTSD 542 IV. CONCLUSION 543
diabetes, and thyroid disease (Boscarino, 2004); musculoskeletal problems (Boscarino, 1997); and asthma and other respiratory problems (Dobie et al., 2004; Green and Kimmerling, 2004; McFarlane et al., 1994; Walker et al., 1999). However, the mechanisms linking PTSD to these conditions have yet to be elucidated. One possibility is the immune system.
I. PSYCHOLOGICAL TRAUMA, PTSD, AND IMMUNE FUNCTION
2. Overview The purpose of this chapter is to review the immune findings in trauma and PTSD. Since it is impossible to interpret the immune findings without reference to the endocrine system, that literature is covered as well. Thus, the chapter is divided into three primary sections. After the introduction and review of symptoms comprising the PTSD diagnosis, the first primary section deals with immune alterations in PTSD. Next, the endocrine findings in PTSD are covered, followed by a discussion of immune endocrine interactions in the third major section. A concluding section summarizing the main points completes the chapter.
A. Introduction and Overview 1. Interest in PTSD: PTSD and Health Interest in studying post-traumatic stress disorder (PTSD) and its associated physiological states has risen dramatically in recent years. One reason for this is the association of PTSD and severe trauma with increased morbidity and mortality (Friedman and McEwen, 2004; Green and Kimmerling, 2004). For example, a 50-year longitudinal study found those with combat exposure had a greater chance of early death and more chronic illnesses by age 65 (Lee et al., 1995). In another study exposure to severe stress was associated with more diseases over a 20-year follow-up (Boscarino, 1997). More specifically, studies have found severe trauma/PTSD to be associated with increased rates of coronary heart disease (Boscarino and Chang, 1999b); gastrointestinal disorders (Schnurr et al., 2000), including irritable bowel syndrome (Dobie et al., 2004; Irwin et al., 1996); autoimmune diseases such as rheumatoid arthritis (Boscarino, 2004; Grady et al., 1991), psoriasis, PSYCHONEUROIMMUNOLOGY, 4E VOLUME I
3. Types of Trauma Studies Trauma studies can be differentiated in many ways. A few obvious ones are the type of stressor (natural disaster vs. war), the duration of the trauma (time limited vs. an extended period of time), age at which the trauma occurred (i.e., as an adult vs. as a child), the time between the trauma and assessment, and the severity of the trauma (did people think they might die, damage/loss). Tables 1, 2, and 3 summarize these
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studies. Table 1 covers studies involving traumas in which a diagnosis of PTSD is not explicitly made, in which the traumatic event has usually been time limited, and assessments have primarily been done in closer proximity to the trauma than traumas such as combat or childhood abuse. Tables 2 and 3 cover studies where the diagnosis of PTSD has been explicitly made. In recognition of the potential importance of the time elapsed between the trauma and assessment, Table 2 covers studies in which the diagnosis of PTSD has been made, but the time frame between the trauma and assessment is shorter than in Table 3, or is not explicitly stated in the article. Table 3 covers studies in which the diagnosis of PTSD has been made, and the time frame between the trauma and assessment is long. The traumas in Table 3 include such traumas as being a combat veteran or a victim of childhood sexual abuse. These types of traumatic events usually (but not always) have occurred over an extended period of time, and assessment is usually, but not always, long after the trauma has occurred. For the traumas covered in Table 1, which are primarily studies of time-limited TABLE 1 Investigator McKinnon et al., 1989
Dekaris et al., 1993
traumas in which the diagnosis of PTSD is usually not explicitly made, many of the people may have PTSD or develop it. For example, in the Ironson et al. (1997) study after Hurricane Andrew, symptoms of PTSD were assessed, but the diagnosis of PTSD was not. Using high scores on the impact of event scale (measured 1 to 4 months after the event), 44% could be estimated to have PTSD. Subsequent assessment of 46 people from this sample, augmented with 15 people living in the same damaged areas, showed that 36% met the criteria for PTSD several months later (6 to 12 months after the storm) (David et al., 1996). Additionally the diagnosis of PTSD requires at least 1 month’s time to have elapsed since the trauma. These studies of trauma were included as they are relevant to PTSD even if they do not directly diagnose PTSD. 4. Diagnosis of PTSD The diagnosis of PTSD requires several criteria to be met. First and foremost, a person must have been exposed to a traumatic event that involved a threat
Time-Limited Traumas, No PTSD Diagnosis, Measurement Time Frame Mostly <2 Years Patient/Design 20 subjects that were among the participants in a longitudinal study of TMI (Three Mile Island); 12 of them from within 5 miles of TMI; 8 of them in the control city 80 miles away from the TMI. Study done 6 years past TMI. 29 men (27 civilians) liberated after 4 to 7 months from war prisoner camp; 15 healthy controls and pre-war historical control subjects.
Weiss et al., 1996
22 male Israeli civilians who were subject to SCUD missile attacks (Persian Gulf War) were assessed during and after hostilities (beginning 2nd week of SCUD attacks).
Delahanty et al., 1997
159 plane crash site workers (some exposed to remains, some not exposed); vs. 41 controls (ER workers not at crash site). Assessed 2 and 6 months after crash. 180 people who experienced Hurricane Andrew vs. laboratory controls. 1 to 4 months post Andrew. 68 workers at medical center at earthquake. Examined beginning 11 days post-earthquake until 4 months.
Ironson et al., 1997 Solomon et al., 1997 Aurer et al., 1999
Sabioncello et al., 2000
20 active soldiers with rapidly progressive periodontitis (RPP); Non-combat control subjects with adult periodontitis (AP). 20 female civilians displaced by the Croatian War; 14 control women residents of Zagreb, Croatia, not directly exposed to major trauma.
Key immune findings Residents who lived near TMI had lower NK #, lower T suppressor/cytotoxic, B-cell #; Increased neutrophils, higher Ab to HSV, CMV. No diffs lymphocytes, WBC, Ab to Rubella, IgG, or IgM. Detainees had low NKCC, IFN, phagocytic function, hematocrit, hemoglobin, serum proteins and albumin level, % naïve T-cells. High activated T and B lymphocytes, total HLA-DR, TNF. No diff NK#, total T, IL-2. Natural killer cell activity and CML were significantly elevated during war. Decreased incorporation of thymidine by PBMC unstimulated cultures. No diff mitogen response to PHA, IL-1β, IL-4, IFNgamma in supernatants of stimulated cells. IL-2 marginally increased. Non-morgue workers exposed to bodies had elevated NKCC vs. other groups at time 1. Normalized at time 2. Lower NKCC, high NK, low CD4, low CD8 vs. controls. NKCC least in people with greatest damage, loss, and post-traumatic stress symptoms. Total T, NK #, T blastogenesis, NKCC, went down over time as did distress. Low distress Ss had higher CD3+, CD8+ cells. Higher basal salivary IL-6 in combat Ss with RPP versus decreased CRP, C3, alpha-2-macroglobulin in AP control. Incr NK#; activated phenotypes for T, B, and NK cells. Increased % of proliferating lymphocytes, decreased CD8%, PHA-stimulated proliferation.
25. Immune and Neuroendocrine Alterations in Post-traumatic Stress Disorder TABLE 2
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Diagnosed PTSD with Shorter Time Frame from Trauma to Study Assessment, or Time Frame from Trauma to Assessment for Study Not Explicitly Given
Investigator
Patients/Design
Key immune findings
Maes et al., 1999
13 patients with PTSD, victims of two accidental traumatic events (a fire in a hotel and a multiple collision car crash) and 32 healthy volunteers. 7–9 months after event.
Inoue-Sakurai et al., 2000
155 male workers about 1 to 11/3 years after an earthquake that they experienced. Subjects divided into four groups by lifestyle and PTSD symptoms. 15 mixed trauma survivors with chronic PTSD; 8 control subjects without PTSD (time frame not explicit)
Serum IL-6 and soluble IL-6R receptor (sIL-6R but not sgp 130, sIL-RA, CC16, or sCD8 were significantly higher in PTSD patients versus normal volunteers. Serum sIL-6R concentration was higher in PTSD patients with concurrent major depression than in PTSD patients without major depression and controls. Subjects with PTSD symptoms showed lower NK cell activity than those without symptoms. Subjects with positive lifestyle and few or no PTSD symptoms showed highest NK cell activity. No difference basal IL-6 between PTSD and comparison subjects; Decreased whole blood IL-6 response to LPS in PTSD subjects; Low basal levels of sIL-2R; sIL-2R DST response associated with LGR number in PTSD subjects; High basal IL-10 in PTSD subjects associated with increased cortisol DST suppression. # of lymphocytes, number of T-cells, NK cell activity, and production of IFN and IL-4 lower in men with past PTSD history.
Wong et al., 2000
Kawamura et al., 2001
Miller et al., 2001
12 Japanese male workers identified with a past history of PTSD and 48 men who had had similar stressful life experiences but no PTSD (time frame not explicit) Study to examine the inflammatory response to PTSD; 15 patients with diagnosed PTSD and 8 controls with musculoskeletal injuries studied >3 months after their index trauma.
Baker et al., 2001
11 combat veterans with PTSD vs. 8 healthy control subjects. (time frame not explicit)
Tucker et al., 2004
58 PTSD and 21 controls. PTSD subjects participated in a 10-week double-blind treatment with citalopram (n = 19), sertraline (n = 18), or placebo (n = 7) (time frame not explicit)
of death or serious injury, and the person’s response involved intense fear, helplessness, or horror (American Psychiatric Association, 1994). Three symptom clusters must be present: re-experiencing, avoidance and numbing, and increased arousal. Symptoms described by people from the re-experiencing cluster include flashbacks, recurrent distressing dreams of the trauma, intense distress at exposure to things reminding one of the trauma, intrusive and recurrent thoughts of the event, and physiologic reactivity to reminders of the event. Examples from the avoidance/ numbing cluster include avoidance of thoughts of the event and avoidance of activities, places, or people that remind one of the event; an inability to recall significant aspects of the event; withdrawal from activities, feeling of detachment from others, and inability to
Positive relationship between sIL-6r and the RevisedIES(RIES) intrusion score. Positive relationship also between CRP and DTS intrusion scores, GHQ depression, and RIES intrusion in PTSDdiagnosed patients. Increased CSF levels of IL-6; no group differences in plasma IL-6. Plasma IL-6 and norepinephrine levels positively correlated in the PTSD but not control groups. At baseline, PTSD patients had higher levels of depression and IL-1β, and lower IL-2R levels than controls. Both treatment groups had lower PTSD, depression, and IL-1β levels and increased IL-2R similar to control levels post treatment.
have loving feelings; and lowered expectations about having a future. The third cluster, increased arousal, is exemplified by such symptoms as difficulty concentrating, hypervigilance, an exaggerated startle response, problems sleeping, and increased irritability. As noted above, the three symptom clusters must be present at least 1 month for PTSD to be diagnosed. In addition, the symptoms must have caused significant distress or impairment in ability to function in social or occupational roles.
B. Studies of PTSD and the Immune System There are several reasons why one might expect an association between PTSD and the immune system.
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Investigator Mosnaim et al., 1993
Burges-Watson et al., 1993, 1995
Diagnosed PTSD, Assessment Distant (>2 Years after Trauma) Patients/Design
Key immune findings
Vietnam combat veterans with chronic PTSD: 13 with comorbid alcoholism, 11 with drug use disorders, 8 with both alcohol and drug use disorder, 8 healthy control subjects with no psychiatric or substance abuse disorders. 25 Vietnam combat veterans with PTSD clinical treatment. 28 civilians (no military service) and 20 non-combat vets. Controls had no diagnosed psychiatric disorders. All males.
Low NKCC with MET challenge in PTSD subjects with comorbid drug use but not alcohol use disorders.
Spivak et al., 1997
19 male patients with combat-related PTSD and 19 age- and sex-matched controls. 3 had served in the Yom Kippur War, 6 in the war with Lebanon, and 10 during the Intifada.
Laudenslager et al., 1998
10 male veterans of the Vietnam War diagnosed with long-term PTSD and 9 controls (combat veterans without PTSD). Male Vietnam veterans were analyzed and divided into groups. Males with current partial posttraumatic stress = 286, anxiety = 274, depression disorders = 192. They were compared to 2,179– 2,272 veterans without these symptoms 20 years after military service.
Boscarino and Chang, 1999a
Wilson et al., 1999
10 female subjects with childhood sexual trauma, diagnosed with PTSD, and 10 controls.
Altemus et al., 2003
16 women with PTSD due to childhood sexual or physical abuse and 15 women with no history of abuse, trauma, or psychiatric disorder. Chronic PTSD in a sample of 2,490 Vietnam veterans
Boscarino, 2004
First, the description of PTSD above, which includes re-experiencing of a stressful traumatic event and the occurrence of autonomic arousal, suggests the involvement of biological stress response systems such as the sympathetic nervous system. In addition, established interconnections between the brain and immune systems have been made, both by showing the existence of hardwiring (Felten and Felten, 1994), and endocrine mediators (such as cortisol, epinephrine, and norepinephrine, which interact with receptors on immune cells). There are several different effector cells of the immune system as well as indicators of their functioning that may be measured. Thus, this review will cover both functional measures and enumerative measures, and will review each in turn. Functional measures are covered first, as studies of chronic stress have been found to have a stronger relationship with those (Segerstrom and Miller, 2004).
The arousal/hyper vigilance were more important than depression or anxiety correspondence. Need to control for medication, alcohol, or smoking. Veterans with PTSD had enhanced CMI compared with civilians. Serum IL-1β but not sIL-2R were higher in the PTSD patients. IL-1β did not correlate with cortisol levels, severity of PTSD, depressive symptoms, or alexithymia scores, but they did correlate with duration of the PTSD symptoms. NK activity was higher in the PTSD sample than in the controls. No difference hormone levels or CD4, CD8, or NK cells between groups. Veterans with PTSD had higher adjusted leukocyte, lymphocyte, and T-cell counts (including CD4’s) compared with vets without PTSD, but no difference in DTH response to CMI skin multi-test. Veterans with anxiety disorders had adjusted lymphocyte and T-cell counts above range and highly reactive CMI. Depressed veterans were less likely to have B-cell counts above reference range. Ratio of CD45R0-positive to CD45RA-positive lymphocytes (an index of lymphocyte activation) was higher in PTSD subjects. No differences in the number of PBL or any major T, B, or NK lymphocyte subsets. PTSD patients had higher DTH.
Those with PTSD had clinically higher T-cell counts, hyper-reactive DTH, clinically higher IgM.
1. Overview of Immune System There are two main arms of the immune system: innate or natural, and adaptive or specific. The innate arm does not require specific recognition of an invader and can function quickly after an invader appears. Some of the cell types in this arm of the immune system are neutrophils, macrophages (monocytes), and natural killer (NK) cells. Neutrophils and macrophages (monocytes) are phagocytic; that is, they digest the foreign invader. Macrophages (monocytes), particularly when activated by non-self substances, also secrete cytokines (IL-1, IL-6, TNF-alpha), which serve a communication function and are pro-inflammatory. Natural killer cells are particularly important in fighting off viruses and tumor cells, as they can recognize cells that are not self or that have become malignant. They kill by secreting toxic substances. The major cell types in the adap-
25. Immune and Neuroendocrine Alterations in Post-traumatic Stress Disorder
tive or specific arm are T helper, T cytotoxic, and B-cells. T helper cells secrete cytokines that are chemical messengers which direct and “help” increase the immune response. Two types of cytokines are produced: Th1 and Th2 (see paragraph below on cytokines). Th1 cytokines are involved in cellular immunity and activate T cytotoxic and NK cells. Th2 cytokines are involved in humoral immunity and activate Bcells. B-cells, in turn, produce antibodies that are particularly important in helping to fight off bacteria and parasites and in increasing the effectiveness of innate immunity. 2. PTSD and Functional Measures of Immunity The functioning of natural killer cells is one of the measures included most often in studies of stress and trauma. As noted, natural killer cells are part of the innate arm of the immune system and can thus fight against invaders without specific recognition of a particular invader. They are particularly important not only because they fight off viruses and tumors, but because they are effective before specific immunity engages. NKCC measures the effectiveness of NK cells at killing tumor cells (typically, the K562 target cell line). NKCC was decreased in people (n = 180) with post-traumatic stress symptoms 1 to 4 months after Hurricane Andrew (Ironson et al., 1997), in 155 male workers with PTSD symptoms 14 to 18 months after an earthquake (Inoue-Sakurai et al., 2000), in 29 men detained in a prisoner of war camp in Bosnia (Dekaris et al., 1993), and in 12 Japanese male workers with a past history of PTSD (Kawamura et al., 2001). Finally, NKCC response to stimulation with methionineenkephalin (MET) was decreased in Vietnam War veterans with PTSD and comorbid drug use (Mosnaim et al., 1993) 10 days or more into a drug detoxification program, although unstimulated NKCC showed no difference. In contrast, NKCC was elevated in workers exposed to bodies and body parts at a plane crash site 2 months after the crash (Delahanty et al., 1997) but normalized at the 6-month follow-up. Higher levels of NKCC were correlated with intrusive thoughts of the disaster. NKCC was also elevated in 68 people experiencing an earthquake but returned to normal within 4 months (Solomon et al., 1997) and in Israelis experiencing SCUD missile attacks during the Persian Gulf War (Weiss et al., 1996). Finally, NKCC was increased in a sample of 10 male veterans of the Vietnam War with PTSD and substance abuse problems compared to 9 controls who had only substance abuse problems (Laudenslager et al., 1998). Thus, the picture for NKCC is inconsistent, with some studies showing more of an acute stressor response (with initial increases), fol-
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lowed by decrements when the stressor persists over time, but other studies fitting more of a chronic stress pattern of decreased NKCC (Segerstrom and Miller, 2004). The delayed-type hypersensitivity (DTH) response measured by the cell-mediated immunity (CMI) multitest was among the first immune measures studied in PTSD and is thought to involve primarily T-cell responses. The earliest study (Burges-Watson et al., 1993) found enhanced cutaneous CMI multi-test compound scores in 25 Vietnam combat veterans with PTSD versus 28 civilians (and although the compound score on the CMI multi-test was greater for the combat veterans vs. non-combat servicemen, the number of positive reactions on the CMI was not). Consistent with this, Altemus et al. (2003) compared 16 women with PTSD due to childhood sexual or physical abuse to 15 women without any history of trauma or psychiatric disorders and found the PTSD patients had higher DTH. However, in the largest study to date, Boscarino and Chang (1999a) found no differences on the DTH response to the CMI multi-test between 286 Vietnam combat veterans with PTSD and 2,179 veteran control subjects with no PTSD (see Table 3). However, the same author (Boscarino, 2004) found hyper-reactive immune responses to standardized cutaneous hypersensitivity tests in a national sample of 2,490 Vietnam veterans. Thus, findings suggest either an enhancement or no difference. A few studies have examined lymphocyte proliferative responses to mitogens. Proliferation to the mitogen PHA measures primarily T-cell proliferation. Sabioncello et al. (2000) found decreased proliferative capacity (ratio of cells in stimulated to non-stimulated cultures) to PHA in 20 female civilians displaced by the Croatian War, which is consistent with both the acute stress literature and the chronic stress literature (Segerstrom and Miller, 2004). Solomon et al. (1997) found that people who had recently experienced an earthquake and reported less distress had higher proliferation to PHA, suggesting a psychologyimmune connection. However, Weiss et al., (1996) found no difference between war and post-war periods in thymidine uptake of PBMCs under PHA stimulation. 3. PTSD and Cytokines The next set of immune-related measures that have been included in studies of trauma and PTSD are cytokines. Cytokines, mediators of the immune response produced by immune cells, fall into a few major classes: Pro-inflammatory cytokines (produced predominantly by macrophages), monocytes, and T-cells have been
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examined in the largest number of studies (IL-1, IL-6, TNF-alpha). Th1 cytokines such as IL-2, IL-12, and IFN-gamma are thought to be involved in cellular immunity. T cytotoxic cells and natural killer cells are activated by these cytokines. They are particularly useful in fighting off viruses and tumors. Th2 cytokines include IL-4, IL-5, IL-6, and IL-10. These cytokines help to direct and coordinate humoral immunity which involves antibodies, specific recognition of extracellular pathogens, and fighting against bacteria and parasites. Cytokines are most commonly measured in plasma/serum, or in culture supernatants before and after stimulation with an appropriate antigen or with a more general stimulant such as the T-cell stimulant PHA. Pro-inflammatory cytokines: Higher salivary IL-6 was found in 20 combat veterans with PTSD and rapidly progressive periodontitis (RPP) compared with non-combat controls with adult periodontitis (Aurer et al., 1999). Maes et al. (1999) found elevated serum IL-6 and soluble interleukin-6 receptor (sIL-6R) to be significantly higher in 13 PTSD victims of a fire or car crash. Interestingly, Miller et al. (2001) found that higher serum levels of the receptor to IL-6 (sIL-6R) were positively correlated with revised IES intrusion scores. Baker et al. (2001) found increased levels of IL-6 in cerebrospinal fluid, although they did not find any differences in plasma IL-6 between 11 combat veterans to 8 healthy controls. Interestingly, plasma IL-6 correlated with NE levels in the PTSD group. Another study finding no differences in basal plasma levels of IL-6 between PTSD and control groups was Wong et al. (2000), who compared 15 mixed trauma survivors with chronic PTSD to 8 control subjects without PTSD. Interestingly, Wong et al. (2000) found IL-6 response to LPS was lower in 15 people with PTSD from mixed traumas than 8 control subjects without PTSD. While IL-6 is the most studied pro-inflammatory cytokine, other pro-inflammatory cytokines have been studied. Tucker et al. (2004) found higher levels of another proinflammatory cytokine, IL-1β, in 58 PTSD patients versus 21 controls. Serum interleukin-1β was also higher in 19 Israeli soldiers with combat-related PTSD (Spivak et al., 1997) than healthy controls, and it correlated with duration of PTSD symptoms (but not severity). This suggests higher activity of the mononuclear phagocytes that produce this cytokine. A related cytokine, IL-1 receptor antagonist, was no different between trauma victims (fire, car crash) as compared with healthy controls. Furthermore, IL-1β produced by PBMC after stimulation by PHA was no different between Israeli civilians undergoing SCUD missile attacks pre- to post-war (Weiss and Hirt, 1996). Thus, IL-6 has the most studies, and several of these
studies have shown elevations of basal levels in PTSD. This result is consistent with the significant increase in IL-6 production seen in acute stress (Segerstrom and Miller, 2004), although there are not many PTSD studies of IL-6 production in cultured supernatants. IL-6 has also not been studied enough in chronic stress to compare it to the stress literature. (The only cytokine whose production has been studied enough in chronic stress is IL-2, whose production has been found to decrease [Segerstrom and Miller, 2004.]) It may further be pointed out that among these inflammatory cytokines, TNF-alpha appears first and is followed by tandem secretion of IL-1 and IL-6. Also, all three of these cytokines stimulate their own secretion. In addition, TNF-alpha and IL-1 stimulate secretion of IL-6, and conversely IL-6 inhibits secretion of TNF-alpha and IL-1 (Chrousos, 2000). It may be therefore inferred that pro-inflammatory cytokines should be investigated as a group, and there is a scarcity of such studies in PTSD. Moreover, in addition to studying the secretion of cytokines, it is highly desirable to rule out changes in the rate of catabolism of these cytokines, and their specific mRNA activity should also be investigated to understand the mechanisms involved. The next cytokines are those referred to as Th1, which are involved with cell-mediated immunity (CMI). Tucker et al. (2004) found lower levels of IL-2 receptors in 44 PTSD patients as compared with 21 controls. Wong et al. (2000) found decreased soluble interleukin-2 receptor (sIL-2R) in 15 people with mixed traumas with chronic PTSD in comparison with 8 control subjects without PTSD. In contrast, Spivak et al. (1997) found no difference in sIL-2R between 19 male PTSD combat-related PTSD subjects and 19 ageand sex-matched controls. Tucker et al. (2004) showed that these differences in results may be due to gender differences in the sample, as their study had predominantly females with abuse histories, and Wong’s study had predominantly females with mixed traumas. This is consistent with Dekaris et al. (1993), who found no difference in IL-2 in detainees from a war camp who were primarily male civilians. One study that found marginally higher levels of IL-2 (in supernatants of PHA-stimulated cells) was that of Weiss et al. (1996), who measured Israeli civilians during and after the SCUD missile attacks of the Persian Gulf War. Of additional interest, in Tucker’s study (2004) after treatment of PTSD and depression, the IL-2R levels increased for the PTSD patients. Thus, the most evidence is available for IL-2 receptors, and they appear to be decreased or unchanged. Only a few studies have been done on IFN. Kawamura et al. (2001) found lower IFN in 12 Japanese volunteers with PTSD. Weiss et al. (1996) found no differences between those experiencing
25. Immune and Neuroendocrine Alterations in Post-traumatic Stress Disorder
SCUD missile attacks pre- and post-war in IFN-gamma in supernatants of CML cultures. Only two studies have looked at Th2 cytokines. Wong et al. (2001) found higher levels of basal plasma and whole blood IL-10 in 15 mixed trauma survivors with chronic PTSD versus 8 control subjects without PTSD. In contrast, Kawamura et al. (2001) found lower levels of IL-4 in 12 Japanese men compared to 48 men with similar life experiences but no PTSD. Weiss et al. (1996) found no differences in IL-4 production in 22 Israeli men experiencing missile attacks pre- to postwar. While there are gender differences in these samples, results are too preliminary and samples too small to reach any conclusions. Finally, one study looked at treatment effects on the cytokine levels in people with PTSD (Tucker et al., 2004). Patients with PTSD were randomized in a double-blind fashion (2 : 2 : 1) to treatment with citalopram (n = 19), sertraline (n = 18), or placebo (n = 7). Treatment was successful in lowering PTSD, depression, and IL-1β levels, and increased IL-2R compared to controls. 4. PTSD and Enumerative Immune Measures Studies have also investigated numbers of different phenotypes of immune system cells. Abnormally high leukocyte and lymphocyte counts (including higher T-cell/CD4 cells) were found by Boscarino and Chang (1999a) in a large study of 286 Vietnam combat vets with current partial chronic PTSD compared to 2,190 veteran controls without symptoms of PTSD, depression, or anxiety. Consistent with this, Ironson et al. (1997) found significantly higher white blood cell counts in people who had recently experienced Hurricane Andrew compared to laboratory controls. Boscarino also found that in a national sample of 2,490 Vietnam veterans, those with PTSD were more likely to have clinically higher T-cell counts. In contrast, Kawamura et al. (2001), who had much smaller samples (12 with PTSD and 48 without, matched on similar life experiences), found lower lymphocytes and T-cell counts in the group with PTSD, and Solomon et al. (1997) found a decrease in T-cell numbers over 4 months after an earthquake. Lower T-cells were associated with greater distress and disruption at the initial assessment. Ironson et al. (1997) found lower CD4 and CD8 cells 1 to 4 months after Hurricane Andrew compared to laboratory controls. McKinnon and Weisse (1989) also found lower CD8 T-cells in residents living in the vicinity of the Three Mile Island nuclear reactor disaster 6 years after the incident. In contrast, Maes et al. (1999) found no differences in CD8 cells between 13 people with PTSD from accidents (car crash or fire) and 32 healthy volunteers, as did a study by Wilson
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et al. (1999), which found that 10 women with PTSD and a history of childhood trauma did not show differences in numbers of peripheral blood lymphocytes or T, B, or NK subsets. However, it should be noted that the latter study was on women, and both Wilson et al. (1999) and Maes et al. (1999) had much smaller sample sizes than the three studies showing differences. Another interesting finding of the Wilson et al. (1999) study was that although there were no differences in the number of PBL or major subsets (T, B, or NK), people with PTSD had a higher ratio of CD45R0 cells to CD45RA cells, an indication of lymphocyte activation. This ratio of increased memory to naïve Tcells is not only an indication of T lymphocyte activation, but is increased with aging. In one of the few other studies investigating the naïve T-cell subset (CD4+/CD45RA), Dekaris et al. (1993) found the percentage of these cells was decreased in men just released from a prisoner of war camp. Dekaris et al. (1993) also reported high levels of activated T and B lymphocytes in 29 men liberated from a war prisoner camp in the Croatian War, as did Sabioncello et al. (2000) in 20 female civilians displaced by the Croatian War. The latter study also found a higher level of activated NK phenotypes in the displaced women versus 14 control female residents of Zagreb, Croatia, not directly exposed to trauma. Thus, weighing the studies by the sample sizes, it appears that trends are there for increased lymphocytes and leukocytes, alterations in cell phenotypes, especially T-cells, and with activation a distinct possibility. In a summary of the acute stress literature (Segerstrom and Miller, 2004), significant increases have been found for leukocytes, natural killer cells, lymphocytes, and T cytotoxic lymphocytes (CD8). A review of the chronic stress literature showed no significant changes in any of the subsets studied (Segerstrom and Miller, 2004). A few studies have also looked at NK cells. Wilson et al. (1999) found no differences; the large Boscarino and Chang study did not look at this subset. Two studies in trauma (without PTSD diagnosis) found increased NK cell numbers (Ironson et al., 1997; Sabioncello et al., 2000), but two others found lower NK cells (Solomon et al., 1997; McKinnon and Weisse, 1989). Solomon et al. (1997) found a decrease in NK cell numbers over 4 months after an earthquake. A re-examination of this study showed that those in a high worry group had lower NK cell numbers than those in the low worry group or laboratory controls (Segerstrom et al., 1998). McKinnon and Weisse (1989) found that residents who lived near the Three Mile Island nuclear reactor disaster had lower NK cells as compared to control people 80 miles away, even 6 years after the disaster.
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5. Other Measures A few other immune-related measures were included in other studies. Residents living near the Three Mile Island nuclear reactor had higher antibody titers to herpes simplex virus and cytomegalovirus (McKinnon and Weisse, 1989) compared to people living in control cities 80 miles away, suggesting worse control over these latent viruses. They further determined that the results were not just due to immune activation, as there were no differences of the TMI and control groups on antibodies to rubella virus, IgG, and IgM. Plasma antinuclear antibodies were examined in one study in which girls who had been sexually abused for an average of 23 months were compared to healthy adult women (DeBellis et al., 1996). The abused girls were found to have higher levels of plasma antinuclear antibodies, which is suggestive of B-cell dysfunction. One study (Miller et al., 2001) found a measure of inflammation (C-reactive protein or CRP) to be correlated with intrusion scores, thus lending support to the notion that PTSD symptoms may be associated with increases in inflammatory substances. Weiss et al. (1996) found higher cell-mediated lympholysis (CML) in 22 men who experienced the SCUD missile attacks in Israel during the 1991 Persian Gulf War versus postwar, thus indicating enhanced T-cell lytic capacity of PBMCs. Finally, Dekaris et al. (1993) investigated phagocytic functioning of polymorphonuclear neutrophilic leukocytes (ingestion, digestion, and antibodydependent cellular cytotoxic [ADCC] abilities toward oopsonized sheep red blood cells) and found that ingestion and digestion (but not ADCC) were significantly depressed in 29 liberated detainees for a prisoner of war camp compared to 15 healthy controls and pre-war historical controls. 6. Some Methodological Issues Before concluding this section, some important methodological issues need to be raised in interpreting PTSD immune interactions. First, many of these studies were done with very small sample sizes. The larger samples were only able to measure a limited number of variables. Second, as noted above, characteristics of the trauma need to be taken into account, such as duration of the trauma, age at which trauma occurred, time from trauma to measurement, etc. Third, there are many potential confounders that occur with PTSD and are known to affect the immune system. For example, psychiatric disorders are comorbid with PTSD. Prominent among these are major depression and generalized anxiety disorder (David et al., 1996; Kessler et al., 1995). These disorders have been known to affect the
immune systems in their own right (Irwin et al., 1990) and may impact the immune system above the effects of PTSD alone. For example, Maes et al. (1999) found that PTSD patients with concomitant major depression have a distinct immune inflammatory profile. Serum IL-6R was higher in patients with PTSD and depression than in those with PTSD alone. In one of the few other studies that tried to disentangle these effects, Boscarino and Chang (1999a) attempted to compare veterans with and without PTSD as well as with and without an anxiety disorder (presumably excluding PTSD), and with and without depression. Differences were found only between the PTSD and no PTSD groups after controlling for sociodemographic and health behaviors (drug use and alcohol consumption). As noted above, those veterans with PTSD had higher WBC’s lymphocytes and T-cell counts than those without PTSD but did not differ on the CMI multi-test. Another comorbid condition found in PTSD that affects the immune system is alcohol and drug use (Irwin et al., 1990). It is interesting to note that in a study by Mosnaim et al. (1993), which looked at NKCC (after 10 days or more of detox), there were no differences between a group of veterans with PTSD (all of whom had a history of substance abuse), several control groups from the hospital’s Substance Abuse Unit (a control group with drug use, another control with alcohol use, and a third with drug and alcohol use), and drug-free, healthy controls. Note, however, NKCC response to stimulation with methionine-enkephalin (MET) was decreased in Vietnam War veterans with PTSD and comorbid drug use (Mosnaim et al., 1993) 10 days or more into a drug detox program. Thus, confounds such as psychopathology and alcohol and substance use need to be accounted for before being able to interpret associations with PTSD as being due to the stress of PTSD. In addition to psychiatric conditions comorbid with PTSD, another variable that may have a confounding effect is sleep. Sleep has been found to be disrupted in trauma (Davidson et al., 1987) and is an important immunomodulator (Irwin et al., 1994). In fact, Ironson et al. (1997) found that sleep disturbance mediated the effect of post-traumatic stress symptoms on NKCC in a community sample of people experiencing Hurricane Andrew. Finally, nutritional status is another potential confounder, especially, for example, when comparing prisoners of war to non-combat veterans (Dekaris et al., 1993). In addition to nutritional status as an immune modulator and potential confounder, Kiecolt-Glaser and Glaser (1988) described other important confounders to consider when doing human PNI work.
25. Immune and Neuroendocrine Alterations in Post-traumatic Stress Disorder
II. PTSD: ENDOCRINE A. Hypothalamic-Pituitary-Adrenal (HPA) Axis and PTSD There is a substantial body of evidence demonstrating altered functioning of the hypothalamic-pituitaryadrenal (HPA) axis among individuals diagnosed with post-traumatic stress disorder. HPA axis functioning has been assessed within a variety of PTSD populations through various methods, such as determining the levels of specific HPA axis hormones (e.g., cortisol), examining the response of the negative feedback mechanism of the HPA axis to a number of challenge and stimulation tests, and also evaluating the number and sensitivity of glucocorticoid receptors. Following is a summary of some of the main findings in this area. It is important to note that the complex nature of PTSD, including a wide range of traumatic events and responses to trauma; a diversity of symptoms and possible co-occurrence of depression, substance use, and sleep disruption; and also a broad array of demographic and individual difference (e.g., personality, coping, support) variables among subjects and comparison groups, poses a challenge in fully discerning HPA axis functioning among individuals diagnosed with PTSD. 1. Cortisol Levels Because cortisol is one of the major stress hormones produced by the HPA axis, the vast majority of studies have assessed the cortisol levels of PTSD patients as a general indicator of HPA axis activity. In early studies of male Vietnam veterans, lower 24-hour urinary cortisol output was observed among combat veterans with PTSD compared to psychiatric patients without combat experience, combat veterans without PTSD, and also normal control subjects (Kosten et al., 1990; Mason et al., 1986; Yehuda et al., 1990; Yehuda et al., 1993b). Reductions in urinary cortisol output have also been reported among other PTSD populations as well, such as Holocaust survivors and the adult children of Holocaust survivors (Yehuda et al., 1995b; Yehuda et al., 2000). However, some studies have reported higher levels of urinary cortisol output among combat veterans with PTSD compared with combat veterans without PTSD (Pittman and Orr, 1990), among women with PTSD resulting from sexual abuse compared to women victims of sexual abuse without PTSD and normal control subjects (Lemieux and Coe, 1995), among people living in the areas damaged by Hurricane Andrew (Ironson et al., 1996), among people living in areas close to the Three Mile Island damaged
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nuclear plant compared to control sites (Schaeffer and Baum, 1984), and among victims of flash fires and multiple car crashes with PTSD compared to psychiatric patients and normal control subjects (Maes et al., 1998). In fact, in the Ironson et al. (1996) study, reductions in cortisol over the course of a year were significantly correlated with the decrease in psychological symptoms of trauma (re-experiencing, intrusive thoughts, and avoidant thoughts). It is important to note that the bulk of the studies conducted in this topic area, regardless of whether cortisol increases or decreases, report fluctuations in cortisol levels that remain within the normal range. Studies assessing the cortisol levels of PTSD patients assayed from either plasma or saliva samples have also shown similarly mixed results. Lower morning cortisol levels have been observed among Vietnam veterans with PTSD (Boscarino, 1996), adult women traumatized by childhood sexual abuse (Stein et al., 1997), and also adolescents with PTSD as a result of the 1988 Armenian earthquake (Goenjian et al., 1996). However, some other studies have shown elevated levels of cortisol among PTSD patients compared to various comparison groups (Hoffman et al., 1989; Liberzon et al., 1999). Some studies have also examined the circadian rhythms of cortisol secretion in PTSD patients as well. An increased dynamic range in plasma cortisol levels (primarily due to lower levels in the late evening and early morning hours) has been observed among combat veterans with PTSD as compared to combat veterans with depression or nonpsychiatric comparison subjects (Yehuda et al., 1996b). However, it was recently reported that salivary cortisol levels were significantly lower at awakening, at 8:00 a.m., and at 8:00 p.m. in Holocaust survivors with PTSD than in non-survivors, which resulted in a flattening of the circadian rhythm (Yehuda et al., 2005). These results run contrary to those reported in younger combat veterans and may be particular to HPA axis alterations seen in aging as opposed to PTSD. Although there are conflicting findings, the majority of studies conducted to date seem to point to reductions in cortisol output among PTSD patients. Rachel Yehuda, one of the prominent researchers in this area, has noted that there are a number of methodological issues that may have led to these differing results across studies regardless of whether urine, plasma, or saliva samples were studied, including variability in the selection of subjects and comparison groups, different methods of collecting and assaying biological samples, and in some cases inadequate sample sizes and dissimilar inclusion/exclusion criteria (Yehuda, 2002). In addition, PTSD patients often vary in the
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degree of severity, duration, proximity, and type of traumatic event, and also gender (i.e., many of the early studies were of male Vietnam veterans), as well as the degree of certain coping strategies (i.e., dissociation) employed and availability of social support to deal with the traumatic event and its aftermath. Furthermore, PTSD, by definition, is composed of multiple symptoms with many patients also often contending with depression, substance-related issues, and sleep problems that can substantially disrupt the HPA axis and add to the complexity of quantifying a distinct hormonal profile of PTSD. Thus, while the majority of controlled studies conducted over the past 20 years seem to show hypocortisolism among PTSD patients (which runs contrary to what might be expected in a stress-related condition), there are notable exceptions. The circumstances under which trauma is associated with low or high cortisol are not currently clear. In addition, the role of cortisol in PTSD is not clear. It is not understood whether cortisol has any causal relationship (to PTSD symptoms) or is an outcome. Studies suggest that people with PTSD may have smaller hippocampal regions (Gurvitis et al., 1993). A smaller hippocampus in PTSD may be a result of neuronal loss, as has been reported using magnetic resonance imaging (MRI) with high resolution that is capable of distinguishing the amygdala from the hippocampus (Gurvitis et al., 1993). Could the smaller hippocampal area leave people susceptible to PTSD, or does PTSD result in a smaller hippocampal area? Sapolsky (1996) observed that among individuals with PTSD, there is no information as to the extent of the glucocorticoid levels during the trauma. Glucocorticoids are known to cause neural destruction in the brain (Sapolsky, 1996, 1997), especially in the hippocampal area, leading to a decrease in the size of the hippocampus. Alternately, given the cognitive role of the hippocampus and the association of a smaller hippocampus with both PTSD and depression (Steffens et al., 2000), could a smaller hippocampus lead to a greater disposition towards depression as well as PTSD? One possibility is that a smaller hippocampus may be associated with lack of signaling to the HPAC system, leading to lower levels of glucocorticoids. At any rate, this is an intriguing area that awaits further study. 2. Challenge and Stimulation Tests Researchers have also examined the HPA axis functioning of PTSD patients through evaluating how the negative feedback mechanism of the HPA axis responds to various challenge or stimulation tests. Because dexamethasone mimics the biological activity of cortisol,
the dexamethasone suppression test (DST) is commonly employed to assess the relative strength of this negative feedback mechanism, with elevated cortisol levels following DST indicative of a weaker negative feedback mechanism and diminished levels indicative of a stronger negative feedback mechanism. A number of DST studies using low doses of dexamethasone have shown an enhanced suppression of cortisol (i.e., lower cortisol levels) among combat veterans with PTSD compared to combat veterans without PTSD (Yehuda et al., 1993b; Yehuda et al., 1995a) and among adult female survivors of childhood sexual abuse compared to non-victimized women (Stein et al., 1997). Another study reported similar results among activeduty Gulf War soldiers (Kellner et al., 2000). In addition to the DST, several other challenge and stimulation tests have also shown an increase in the negative feedback mechanism among PTSD patients. For example, an exaggerated ACTH response to the metyrapone stimulation test (Yehuda et al., 1996a) and a blunted ACTH response to the CRH challenge test (Smith et al., 1989) have also been observed among PTSD patients. Overall, the challenge and stimulation tests have provided fairly consistent evidence of an increased negative feedback inhibition of the HPA axis among various PTSD populations. 3. Glucocorticoid Receptors To better understand HPA axis functioning in PTSD, researchers have also studied the number and sensitivity of Type II glucocorticoid receptors, because an increased number of these receptors is likely associated with both lower cortisol output and an increased sensitivity of the negative feedback loop of the HPA axis. In an early study, Vietnam veterans showed an increase in lymphocyte glucocorticoid receptor numbers compared to a normal control group (Yehuda et al., 1991). Recently, hypocortisolism among Bosnian refugees with PTSD was associated with increased glucocorticoid sensitivity of interleukin-6 (IL-6) production (Rohleder et al., 2004). These findings further support the notion of enhanced negative feedback inhibition and hypocortisolism in PTSD. 4. Conclusion: HPAC Section Overall, the majority of studies conducted over the past 20 years seem to show significant alterations in HPA axis functioning among a variety of PTSD populations. HPA axis dysregulation among PTSD patients seems to point primarily to hypocortisolism, enhanced negative feedback inhibition, and an increase in lymphocyte Type II glucocorticoid receptor number and sensitivity. It appears that the HPA axis may become
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hypersensitive during and after exposure to trauma, which then perhaps leads to an increase in the negative feedback loop, resulting in lower cortisol levels and an increase in glucocorticoid receptors. However, the exact temporal mechanism involved in this process is unclear at this time. Some studies have also reported altered circadian rhythms of both cortisol secretion and glucocorticoid receptor levels as well. Because PTSD patients often report difficulties with sleep and thus may have altered sleep-wake cycles, studies of circadian rhythms may help further elucidate the HPA axis alterations associated with PTSD. There is also evidence that altered HPA axis functioning developing either before or in response to a traumatic event may be associated with the risk of developing PTSD or PTSD symptoms (Delahanty et al., 2005; Resnick et al., 1995; Yehuda et al., 1998). Some researchers have also hypothesized that the HPA axis alterations described above may also play a role in memory disturbances commonly reported by PTSD patients (Golier and Yehuda, 1998a). In summary, HPA alterations are often evidenced among PTSD patients, although exactly how this process unfolds and the extent of its impact are currently unclear.
B. Sympathetic-Adrenal-Medullary (SAM) System and PTSD PTSD often manifests with multiple symptoms of anxiety, and thus an increase in sympathetic-adrenalmedullary (SAM) system activation is commonly observed among PTSD patients. Among various PTSD populations, an increase in heart rate, blood pressure, startle response, and skin conductance have all been reported, especially in response to loud noises or from exposure to reminders of the traumatic event (Blanchard et al., 1996; Orr et al., 1997a, 1997b; Pitman et al., 1990). Similar to studies of the HPA axis discussed above, researchers have assessed the SAM system functioning of a variety of PTSD populations through a number of methods, such as determining the levels of sympathetic nervous system hormones (e.g., the catecholamines epinephrine and norepinephrine), examining catecholamine levels in response to stimulation tests, and also evaluating the number and sensitivity of noradrenergic receptors. Following is a summary of some of the main findings in this area. 1. Catecholamine Levels Because the release of catecholamines, such as epinephrine and norepinephrine, represents sympathetic activation and triggering of the fight/flight stress response, the vast majority of studies have assessed
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the catecholamine levels of PTSD patients in either urine or plasma samples as a general indicator of sympathetic nervous system functioning. An increase in both 24-hour urinary and plasma catecholamine output has been observed among combat veterans with PTSD compared to combat veterans without PTSD and normal controls (Kosten et al., 1987; Yehuda et al., 1998b), although not in all studies (Pittman and Orr, 1990). Plasma catecholamine levels have also been shown to be elevated in combat veterans with PTSD in response to stress as well (Blanchard et al., 1991; McFall et al., 1990). In a recent examination of urinary catecholamines among a community sample of PTSD patients over a 10-year period, individuals with lifetime PTSD had significantly higher catecholamine levels than the group exposed to trauma without PTSD and also a non-exposed group (Young and Breslau, 2004). In an interesting study, Mellman et al. (1995) collected 24-hour urine in three 8-hour collections from combat related PTSD patients and analyzed these samples for 3-methoxy-4-hydroxyphenylglycol (MHPG), the main metabolite of norepinephrine. They observed a higher level of MHPG in the nocturnal urine sample. In addition, nocturnal MHPG correlated negatively with the total sleep time in the PTSD patients. These findings are important, since awakening from sleep, exhibiting an exaggerated startle response, and having increased vigilance are among the characteristics of PTSD. All these symptoms might be a result of higher levels of nocturnal catecholamines. Elevated urinary norepinephrine had also been observed among maltreated children with PTSD (DeBellis et al., 1997) and among people living in areas of high damage after Hurricane Andrew (Ironson et al., 1996). Overall, the vast majority of studies conducted show significant sympathetic activation and increased catecholamine output among a variety of PTSD populations. 2. Stimulation Tests Researchers have utilized stimulation tests, such as the administration of agents (e.g., yohimbine) that induce SAM system activation, to help fully understand sympathetic nervous system response in PTSD. Yohimbine is an antagonist that blocks alpha-2– adrenergic receptor sites and thus exacerbates the sympathetic nervous system. The use of yohimbine results in panic or anxiety attacks in 70% of combat veterans with PTSD and flashbacks in 40% of this population, which points to a heightened response of the SAM system in PTSD patients (Southwick et al., 1993). This also may indicate that an increased level of catecholamines may be associated with expression of spe-
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cific symptoms and that perhaps at least some PTSD patients are hypersensitive to noradrenergic stimulation. 3. Noradrenergic Receptors Researchers have also examined SAM system functioning of PTSD patients through evaluation of the number of binding sites and sensitivity of noradrenergic receptors. Both combat veterans and children with PTSD have shown fewer alpha-2–adrenergic receptor binding sites per platelet than controls (Perry, 1994; Perry et al., 1987). The reduction in number of receptors in PTSD is likely due to an increased degradation caused by elevated catecholamine levels. Thus, compared to normal control subjects, patients with PTSD may have receptors that are hypersensitive to circulating catecholamines. 4. Conclusion: SAM Section In summary, the vast majority of studies conducted seem to show heightened activation of the SAM system among a variety of PTSD populations. Sympathetic activation, including increased heart rate, blood pressure, startle response, and skin conductance, are consistently reported among PTSD patients. In addition, higher catecholamine output, a supersensitivity to noradrenergic stimulation with yohimbine, and a degradation of alpha-2–adrenergic receptors are also evidence of SAM system activation in PTSD. As expected in a condition commonly characterized by heightened anxiety, fear, and exaggerated startle response, the SAM system appears to be chronically activated and hypersensitive to stress states, including reminders of the initial trauma. Heightened SAM system activation, particularly increased heart rate or catecholamine level, either before or in response to a traumatic event, may be associated with the risk of developing PTSD or PTSD symptoms (Blanchard et al., 1996; Bryant et al., 2000; Delahanty et al., 2003; Hawk et al., 2000; Shalev et al., 1998). Some researchers have also hypothesized that the sympathetic activation described above may reflect an increase in arousal, fear conditioning, and perhaps even problems in memory formation often reported by PTSD patients (O’Donnell et al., 2004). Overall, SAM system activation is commonly observed among PTSD patients, although the extent of its impact is currently unclear.
III. ENDOCRINE-IMMUNE INTERACTIONS IN PTSD Although many studies have examined the connection between the endocrine system and immune func-
tion across a number of psychiatric and medical conditions and also among healthy individuals, relatively few studies have done so among PTSD populations. However, data have started to emerge linking the alterations in the HPA axis and the SAM system noted above with a number of autoimmune and inflammatory diseases regulated by the immune system. A recent study in a national sample of 2,490 Vietnam veterans reported an association with PTSD and the prevalence of common autoimmune diseases, including rheumatoid arthritis, psoriasis, insulindependent diabetes, and thyroid disease (Boscarino et al., 2004). The author of this study also found evidence of endocrine and immune alterations in the sample as well as both cardiovascular and autoimmune diseases. There is also evidence that pro-inflammatory cytokines may play a role in the association between the endocrine-immune interactions (Chrousos, 1998) and perhaps subsequent health status in PTSD. Alterations in cytokines have been implicated in many disorders including rheumatoid arthritis (Feldmann et al., 1996), inflammatory bowel disease (McClane and Rombeau, 1999), and coronary heart disease (Yudkin et al., 2000). HPA axis dysfunction in PTSD, including insufficient glucocorticoid signaling and impaired feedback regulation, resulting in immune activation/inflammation, may in turn contribute to stress-related pathology, including alterations in behavior, insulin sensitivity, bone metabolism, and acquired immune responses (Raison and Miller, 2003). For example, in Bosnian War refugees with PTSD, hypocortisolism was associated with increased glucocorticoid sensitivity of pro-inflammatory cytokine (i.e., interleukin-6, IL-6) production (Rohleder et al., 2004). The relationship between cortisol, norepinephrine, and elevated pro-inflammatory cytokines is an intriguing area to be explored. Despite high NE levels, a measure of central nervous system activation, the HPA axis appears to remain unstimulated, as evidenced by low levels of cortisol. Despite this, there is an elevation of the secretion of TNF-alpha, suggesting possible mechanisms could be either elevated catecholamine or reduced glucocorticoids. There is a good deal of evidence that glucocorticoids suppress production of the IL-1β and TNF-α (Knudson et al., 1987; Lee et al., 1988; Waage and Bakke, 1988; Zuckerman, 1989), so the increase in pro-inflammatory cytokines could potentially be a function of low glucocorticoids. With respect to catecholamines, high catecholamines have been associated with elevated IL-6 in heart failure (MullerWerden and Werden, 2000), and catecholamines stimulate IL-6 production in rat cardiac fibroblasts (Burger et al., 2001). Altered IL-6 production has also been associated with norepinephrine levels among combat
25. Immune and Neuroendocrine Alterations in Post-traumatic Stress Disorder
veterans with PTSD as well (Baker et al., 2001), although the sample size for that was very small (n = 11). In addition, Severn et al. (1992) found that preexposure to adrenaline and B-adrenergic agonists increased TNF-alpha production. However, to further complicate matters, a recent study (Rontgen et al., 2004) showed the effects of epinephrine and norepinephrine on monocytes stimulated with LPS were associated acutely with inhibition of IL-6 and TNFalpha. As this was an acute in vitro study, the relevance for PTSD may be limited. Future studies might help to unravel the precise mechanism. Stress-induced changes in hormones (such as cortisol and catecholamines) and also cytokines in Gulf War veterans have been linked to specific immunerelated illnesses reported by these veterans, such as skin and joint problems (Everson et al., 1999). Overall, there appears to be an association between HPA axis and SAM system alterations and changes in immune functioning linked to certain illnesses in PTSD patients, but the work is preliminary, and many of the studies have been done on small sample sizes. Future work is need to help further clarify the mechanisms linking endocrine and immune changes observed in PTSD and physical and medical health status of these individuals.
IV. CONCLUSION It is clear that there are immune and endocrine alterations associated with PTSD. For most of the findings, there are some studies showing a trend in one direction with others showing no difference. Thus, trends are found for an increase in pro-inflammatory cytokines, enhanced DTH, decreased proliferation to PHA, and increased antibody titers to latent viruses. Some of these findings are consistent with enhanced immunity, such as enhanced DTH, an indication of cell-mediated immunity. Others are consistent with poorer immunity, such as decreased proliferation to PHA or increased antibody titers to latent viruses, suggesting poorer control of latent viruses. Alterations in enumerative immune measures have also been found, the most notable of which are increases in leukocytes, lymphocytes, and T-cells. Activation is also a distinct possibility, as indicated by the presence of particular cell surface markers. Finally, alterations of the immune system in PTSD are sometimes consistent with what is found in acute stress, while others are consistent with what is found in chronic stress (Segerstrom and Miller, 2004). The endocrine findings are intriguing as well. Alterations in both HPAC and SAM systems have been found in PTSD. Perhaps the most consistent is elevated
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catecholamines, which is associated with sympathetic activation. A product of another major stress hormonal system (the HPAC system), cortisol, shows less consistent results, although the majority have shown low cortisol. This stands in contrast to the stress literature in which cortisol tends to be elevated. The elucidation of why and when low versus high cortisol is present remains to be discovered. Studies of linkages of immune alterations in PTSD with specific diseases are few. However, there is a potential link between altered cytokines and diseases that are more prevalent in PTSD, such as inflammatory and autoimmune disorders. The relationship between cortisol, norepinephrine, epinephrine, and proinflammatory cytokines is an area that holds potential promise. Much of the above needs to be regarded as preliminary, as many studies with immune measures have been done with very small sample sizes. Some of the larger studies have often been limited to a few immune measures, such as DTH, leukocyte, and lymphocyte counts. It is difficult to make conclusions from much of this literature, as the findings are somewhat inconsistent. At a minimum a few suggestions for future research can be made: First, larger sample sizes are needed. Second, major confounders need to be taken into account in studies of PTSD. These include, at a minimum, psychiatric disorders such as depression, anxiety, and drug and alcohol use/abuse/dependence, all of which are known to be comorbid with PTSD and are known to impact the immune system. While some researchers have attempted to sort this out, more needs to be done. Other confounders impacting on the immune system and particularly relevant to PTSD studies include impaired sleep, poor nutrition (e.g., such as in being a prisoner of war), and age at assessment. In addition, future studies of PTSD need to determine the possible impact of elapsed time between the assessment of the immune system in relation to the original trauma, the duration of the trauma, and the severity of the trauma. Furthermore, it would be useful to have assessments before and after the trauma. While this is not feasible in most traumatic situations, it may be feasible in some (i.e., combat). Choice of immune measures in studies of PTSD should be guided both by the measures of interest for the disease one is studying (i.e., cancer, rheumatoid arthritis, cardiovascular disease), as well as the measures that are likely to be altered in acute or chronic stress (Segerstrom and Miller, 2004). Studies treating trauma and determining the impact on immune measures would also be helpful. This field is really in its early development, and there lies much promise ahead, especially because there are good treatments available for PTSD (Chard and Gilman, 2005; Ironson et al.,
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2002) and the potential impact on illness remains a possibility for exploration.
Acknowledgments The authors wish to thank Grisell Hernandez and Elizabeth Balbin for their help in compiling the literature and constructing the table, and Joe Paroulo for checking references. We also thank NIMH for their support (R01MH066697) to Gail Ironson, P. I.
References Altemus, M., Cloitre, M., and Dhabhar, F. S. (2003). Enhanced cellular response in women with PTSD related to childhood abuse. Am. J. Psychiatry, 160 (9), 1705–1706. American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders (4th ed.). Washington DC: Author. Aurer, A., Aurer-Kozelj, J., Stavljenic-Rukavina, A., Kalenic, S., Ivic-Kardum, M., and Haban, V. (1999). Inflammatory mediators in saliva of patients with rapidly progressive periodontitis during war stress induced incidence increase. Colleguim Anthropologicum, 23 (1), 117–124. Baker, D. G., Ekhator, N. N., Kasckow, J. W., Hill, K. K., Zoumakis, E., Dashevsky, B. A., Chrousos, G. P., and Geracioti, T. D. (2001). Plasma and cerebrospinal fluid interleukin-6 concentrations in posttraumatic stress disorder. Neuroimmunomodulation, 9, 209–217. Blanchard, E. B., Hickling, E. J., Buckley, T. C., Taylor, A. E., Vollmer, A., and Loos, W. R. (1996). Psychophysiology of posttraumatic stress disorder related to motor vehicle accidents: replication and extension. J. Consult. Clin. Psychol., 64, 742–751. Blanchard, E. B., Kolb, L. C., Prins, A., Gates, S., and McCoy, G. C. (1991). Changes in plasma norepinephrine to combat-related stimuli among Vietnam veterans with posttraumatic stress disorder. J. Nerv. Ment. Dis., 179, 371–373. Boscarino, J. A. (1996). Posttraumatic stress disorder, exposure to combat, and lower plasma cortisol among Vietnam veterans: findings and clinical implications. J. Consult. Clin. Psychol., 64, 191–201. Boscarino, J. A. (1997). Diseases among men 20 years after exposure to severe stress: implications for clinical research and medical care. Psychosom. Med., 59, 605–614. Boscarino, J. A. (2004). Posttraumatic stress disorder and physical illness: Results from clinical and epidemiologic studies. Ann. NY. Acad. Sci., 1032, 141–153. Boscarino, J. A., and Chang, J. (1999a). Higher abnormal leukocyte and lymphocyte counts 20 years after exposure to severe stress: research and clinical implications. Psychosom. Med., 61, 378–386. Boscarino, J. A., and Chang, J. (1999b). Electrocardiogram abnormalities among men with stress-related psychiatric disorders: implications for coronary heart disease and clinical research. Ann. Behav. Med., 21, 227–234. Bryant, R. A., Guthrie, R. M., Moulds, M. L., et al. (2000). A prospective study of psychophysiological arousal, acute stress disorder, and posttraumatic stress disorder. J. Abnorm. Psychol., 109, 341–344. Burger, A., Benicke, M., Deten, A., and Zimmer, H. G. (2001). Catecholamines stimulate interleukin-6 synthesis in rat cardiac fibroblasts. Am. J. Physiol. Heart. Circ. Physiol., 281, H14–H21. Burges-Watson, I. P., Muller, H. K., Jones, I. H., and Bradley, A. J. (1993). Cell-mediated immunity in combat veterans with posttraumatic stress disorder. Med. J. Aust., 159 (8), 513–516.
Burges-Watson, I. P., Muller, H. K., Hoffman, L., Wilson, G., and Jones, I. H. (1995). Cell-mediated immunity in combat veterans with post-traumatic stress disorder. Med. J. Aust, 162, 55. Chard, K. M., and Gilman, R. (2005). Counseling trauma victims: 4 brief therapies meet the test. Current Psychiatry, 4 (8), 50–63. Chrousos, G. P. (1998). Stressors, stress, and neuroendocrine integration of the adaptive immune response. Ann. N. Y. Acad. Sci., 851, 311–335. Chrousos, G. P. (2000). The stress response and immune function: clinical implications. Ann. N. Y. Acad. Sci., 917, 38–67. David, D., Mellman, T. A., Mandoza, L. M., Kulick-Bell, R., Ironson, G., and Schneiderman, N. (1996). Psychiatric morbidity following Hurricane Andrew. J. Trauma. Stress, 9 (3), 607–611. Davidson, L. M., Fleming, R., and Baum, A. (1987). Chronic stress, catecholamines, and sleep disturbance at the Three Mile Island. J. Hum. Stress, 13 (2), 75–83. DeBellis, M. D., Baum, A. S., Birmaher, B., and Ryan, N. D. (1997). Urinary catecholamine excretion in childhood overanxious and posttraumatic stress disorders. Ann. N. Y. Acad. Sci., 821, 451–455. DeBellis, M. D., Burke, L., Trickett, P. K., and Putnam, F. W. (1996). Antinuclear antibodies and the thyroid function in sexually abused girls. J. Trauma. Stress, 9 (2), 369–378. Dekaris, D., Sabioncelo, A., Mazuran, R., Rabatic, S., SvobodaBeusan, N. L., and Tomasic, J. (1993). Multiple changes of immunologic parameters in prisoners of war. Assessments after release from a camp in Manjaca, Bosnia. JAMA, 270 (5), 595–599. Delahanty, D. L., Dougall, A. L., Craig, K. J., Jenkins, F. J., and Baum, A. (1997). Chronic stress and natural killer cell activity after exposure to traumatic death. Psychosom. Med., 59 (5), 467–476. Delahanty, D. L., Nugent, N. R., Christopher, N. C., and Walsh, M. (2005). Initial urinary epinephrine and cortisol levels predict acute PTSD symptoms in child trauma victims. Psychoneuroendocrinology, 30, 121–128. Delahanty, D. L., Royer, D. K., Raimonde, A. J., and Spoonster, E. (2003). Peritraumatic dissociation is inversely related to catecholamine levels in initial urine samples of motor vehicle accident victims. J. Trauma Dissociation, 4, 65–80. Dobie, D. J., Kivlahan, D. R., Maynard, C., Bush, K. R., Davis, T. M., and Bradley, K. A. (2004). Posttraumatic stress disorder in female veterans. Arch. Intern. Med., 164, 394–400. Everson, M. P., Kotler, S., and Blackburn, W. D. (1999). Stress and immune dysfunction in Gulf War veterans. Ann. N. Y. Acad. Sci., 876, 413–418. Feldmann, M., Brennan, F. M., and Maini, R. N. (1996). Role of cytokines in rheumatoid arthritis. Annu. Rev. Immunol., 14, 397–440. Felten, S. Y., and Felten, D. (1994). Neural-immune interaction. Prog. Brain Res., 100, 157–162. Friedman, M. J., and McEwen, B. S. (2004). Posttraumatic stress disorder, allostatic load, and medical illness. In P. P. Schnurr and B. L. Green (Eds.), Trauma and health (pp. 157–188). Washington, DC: American Psychological Association. Goenjian, A. K., Yehuda, R., Pynoos, R. S., Steinberg, A. M., Tashjian, M., Yang, R. K., et al. (1996). Basal cortisol, dexamethasone suppression of cortisol and MHPG in adolescent after the 1988 earthquake in Armenia. Am. J. Psychiatry, 153, 929–934. Golier, J., and Yehuda, R. (1998). Neuroendocrine activity and memory-related impairments in posttraumatic stress disorder. Dev. Psychopathol., 10, 857–869. Grady, K. E., Reisine, S. T., Fifield, J., Lee, N. R., McVay, J., and Kelsey, M. E. (1991). The impact of Hurricane Hugo and the San Francisco earthquake on a sample of people with rheumatoid arthritis. Arthritis Care Res., 4, 106–110.
25. Immune and Neuroendocrine Alterations in Post-traumatic Stress Disorder Green, B. L., and Kimmerling, R. (2004). Trauma, posttraumatic stress disorder, and health status. In P. P. Schnurr and B. L. Green (Eds.), Trauma and health (13– 42). Washington, DC: American Psychological Association. Gurvitis, T. V., Lasko, N. B., Schachter, S. C., Kuhne, A. A., Orr, S. P., and Pitman, R. K. (1993). Neurological status of Vietnam veterans with chronic posttraumatic stress disorder. J. Neuropsy. Clin. Neurosci., 5, 183–188. Hawk, L. W., Dougall, A. L., Ursano, R. J., and Baum, A. (2000). Urinary catecholamines and cortisol in recent-onset posttraumatic stress disorder after motor vehicle accidents. Psychosom. Med., 62, 423–434. Hoffman, L., Burges-Watson, P., Wilson, G., and Montgomery, J. (1989). Low plasma b-endorphin posttraumatic stress disorder. Aust. N. Z. Psychiatry, 23, 269–273. Inoue-Sakurai, C., Maruyama, S., and Morimoto, K. (2000). Posttraumatic stress and lifestyles are associated with natural killer cell activity in victims of the Hansin-Awaji earthquake in Japan. Prev. Med., 31, 467–473. Ironson, G., Cruess, D., Kumar, M., Wynings, C., Benight, C., Greenwood, D., Baum, A., and Schneiderman, N. (1996, August). Neuroendocrine and immune correlates of intrusive and avoidant thoughts. Paper presented at the annual meeting of the American Psychological Association, Toronto. Ironson, G., Freund, B., Strauss, J., and Williams, J. (2002). A comparison of two treatments for traumatic stress: A community based study of EMDR and prolonged exposure. J. Clin. Psychol. (Special issue on treating trauma victims), 58, 113–128. Ironson, G., Wynings, C., Schneiderman, N., Baum, A., Rodriguez, M., Greenwood, D., Benight, C., Antoni, M., La Perriere, A., Huang, H., Klimas, N., and Fletcher, M. N. (1997). Posttraumatic stress symptoms, intrusive thoughts, loss, immune function after Hurricane Andrew. Psychosom. Med., 59, 128– 141. Irwin, C., Falsetti, S. A., Lydiard, R. B., Ballanger, J. C., Brock, C. D., and Brener, W. (1996). Comorbidity of posttraumatic stress disorder and irritable bowel syndrome. J. Clin. Psychiatry, 57, 576–578. Irwin, M., Caldwell, C., Smith, T., Brown, S., Schuckit, M., and Gillin, C. (1990). Major depressive disorder, alcoholism, and reduced natural killer cell cytotoxicity. Arch. Gen. Psychol., 47, 713–719. Irwin, M., Mascovich, A., Gillin, J., Willoughby, R., Pike, J., and Smith, T. (1994). Partial sleep deprivation reduces natural killer cell activity in humans. Psychosom. Med., 56, 493–498. Kawamura, N., Kim, Y., and Asuaki, N. (2001). Suppression of cellular immunity in men with a past history of posttraumatic stress disorder. Am. J. Psychiatry, 158, 484–486. Kellner, M., Wiedemann, K., Yassouridis, A., Levengood, R., Guo, L. S., Holsboer, F., et al. (2000). Behavioral and endocrine response to cholecystokinin tetrapeptide in patients with posttraumatic stress disorder. Biol. Psychiatry, 47, 107–111. Kessler, R. C., Sonnega, A., Bromet, E., Hughes, M., and Nelson, C. B. (1995). Posttraumatic stress disorder in the National Comorbidity Survey. Arch. Gen. Psychiatry, 52, 1048–1060. Kiecolt-Glaser, J. K., and Glaser, R. (1988). Methodological issues in behavioral immunology research with humans. Brain, Behavior, Immunity, 2, 67–78. Knudsen, P. J., Dinarello, C. A., and Strom, T. B. (1987). Glucocorticoids inhibit transcriptional and post-transcriptional expression of interleukin 1 in U937 cells. J. Immunol., 139, 4129–4134. Kosten, T. R., Mason, J. W., Giller, E. L., Ostroff, R. B., and Harkness, L. (1987). Sustained urinary norepinephrine and epinephrine in post-traumatic stress disorder. Psychoneuroendocrinology, 12, 13–20.
545
Kosten, T. R., Wahby, V., Giller, E., and Mason, J. (1990). The dexamethasone suppression test and thyrotropin-releasing hormone stimulation test in posttraumatic stress disorder. Biol. Psychiatry, 28, 657–664. Laudenslager, M. L., Assal, R., Adler, L., Berger, C. L., Montgomery, P. T., Sandberg, E., Wahlberg, L. J., Wilkins, R. T., Zweig, L., and Reite, M. L. (1998). Elevated cytotoxicity in combat veterans with long term posttraumatic stress disorder: preliminary observations. Brain, Behav. Immun., 12, 74–79. Lee, K. A., Vaillant, G. E., Torrey, W. C., and Elder, G. H. (1995). A 50 year prospective study of the psychological sequelae of the World War II combat. Am. J. Psychiatry, 152, 516–522. Lee, S. W., Tsou, A. P., Chan, H., Thomas, J., Petrie, K., Eugui, E. M., and Allison, A. C. (1988). Glucocorticoids selectively inhibit the transcription of the interleukin-1β gene and decrease the stability of interleukin-1β mRNA. Proc. Natl. Acad. Sci. USA, 85, 1204–1208. Lemieux, A. M., and Coe, C. L. (1995). Abuse-related posttraumatic stress disorder: evidence for chronic neuroendocrine activation in women. Psychosom. Med., 57, 105–115. Liberzon, I., Abelson, J. L., Flagel, S. B., Raz, J., and Young, E. A. (1999). Neuroendocrine and psychophysiological responses in PTSD: a symptom provocation study. Neuropsychopharmacology, 21, 40–50. Maes, M., Lin, A., Bonaccorso, S., van Hunsel, F., van Gastel, A., Delmiere, L., et al. (1998). Increased 24-hour urinary cortisol excretion in patients with post-traumatic stress disorder and patients with major depression, but not in patients with fibromyalgia. Acta. Psychiatr. Scand., 98, 328–335. Maes, M., Lin, A., Delmeire, L., Gastel, A. V., Kenis, G., Jongh, R. D., and Bosmans, E. (1999). Elevated serum interleukin-6 (IL-6) and IL-6 receptor concentrations in posttraumatic stress disorder following accidental man-made traumatic events. Soc. Biol. Psychiatry, 45, 833–839. Mason, J. W., Giller, E. L., Kosten, T. R., Ostroff, R. B., and Podd, L. (1986). Urinary free-cortisol levels in posttraumatic stress disorder patients. J. Nerv. Ment. Dis., 174, 145–159. McClane, S. J., and Rombeau, J. L. (1999). Cytokines and inflammatory bowel disease: a review. J. Parenter. Enteral. Nutr., 23 (Suppl 5), S20–24. McFall, M. E., Murburg, M. M., Ko, G. N., and Veith, R. C. (1990). Autonomic responses to stress in Vietnam combat veterans with posttraumatic stress disorder. Biol. Psychiatry, 27, 1165–1175. McFarlane, A. C., Atchison, M., Rafalowicz, E., and Papay, P. (1994). Physical symptoms in posttraumatic stress disorder. J. Psychosom. Res., 38, 715–726. McKinnon, W., and Weisse, C. S. (1989). Chronic stress, leukocyte subpopulations, and humoral response to latent viruses. Health Psychol., 8 (4), 389–402. Mellman, T. A., Kumar, A., Kulick-Bell, R., Kumar, M., and Nolan, B. (1995). Nocturnal/daytime urine noradrenergic measures and sleep combat-related PTSD. Biol. Psychiatry, 38, 174–179. Miller, R. J., Sutherland, A. G., Hutchinson, D., and Alexander, D. A. (2001). C-reactive protein and interleukin 6 receptor in the post-traumatic stress disorder: a pilot study. Cytokine, 13 (4), 253–255. Mosnaim, A. D., Wolf, M. E., Maturana, P., Mosnaim, G., Puente, J., Kucuk, O., and Gilman-Sachs, A. (1993). In vitro studies of natural killer cell activity in post traumatic stress disorder patients. Response to methionine-enkephalin challenge. Immunophamacology, 25, 107–116. Muller-Werden, U., and Werden, K. (2000). Immune modulation by catecholamines—a potential mechanism of cytokine release in heart failure. HERZ, 25 (3), 271–273.
546
III. Behavior and Immunity
O’Donnell, T., Hegadoren, K. M., and Coupland, N. C. (2004). Noradrenergic mechanisms in the pathophysiology of post-traumatic stress disorder. Neuropsychobiology, 50, 273–283. Orr, S. P., Lasko, N. B., Metzger, L. J., and Pitman, R. K. (1997a). Physiologic responses to non-startling tones in Vietnam veterans with post-traumatic stress disorder. Psychiatry Res., 73, 103–107. Orr, S. P., Solomon, Z., Peri, T., Pitman, R. K., and Shalev, A. Y. (1997b). Physiologic responses to loud tones in Israeli veterans of the 1973 Yom Kippur War. Biol. Psychiatry, 41, 319–326. Perry, B. D. (1994). Neurobiological sequelae of childhood trauma: PTSD in children. In M. M. Murburg (Ed.), Catecholamine function in PTSD (pp. 253–276). Washington, DC: American Psychiatric Press. Perry, B. D., Giller, E. L., and Southwick, S. M. (1987). Altered platelet alpha 2–adrenergic binding sites in posttraumatic stress disorder. Am. J. Psychiatry, 144, 1511–1512. Pittman, R. K., and Orr, S. P. (1990). Twenty-four hour urinary cortisol and catecholamine excretion in combat-related posttraumatic stress disorder. Biol. Psychiatry, 27, 245–247. Pitman, R. K., Orr, S. P., Forgue, D. F., Altman, B., de Jong, J. B., and Herz, L. R. (1990). Psychophysiologic responses to combat imagery in Vietnam veterans with posttraumatic stress disorder other anxiety disorders. J. Abnorm. Psychol., 99, 49–54. Raison, C. L., and Miller, A. H. (2003). When not enough is too much: the role of insufficient glucocorticoid signaling in the pathophysiology of stress-related disorders. Am. J. Psychiatry, 160, 1554–1565. Resnick, H. S., Yehuda, R., Pitman, R. K., and Foy, D. W. (1995). Effect of previous trauma on acute plasma cortisol levels following rape. Am. J. Psychiatry, 152, 1675–1677. Rohleder, N., Joksimovic, L., Wolf, J. M., and Kirschbaum, C. (2004). Hypocortisolism and increased glucocorticoid sensitivity of proinflammatory cytokine production in Bosnian war refugees with posttraumatic stress disorder. Biol. Psychiatry, 55, 745–751. Rontgen, P., Sablotzki, A., Simm, A., Silber, R. E., and Czeslick, E. (2004). Effect of catecholamines on intracellular cytokine synthesis in human monocytes. Eur. Cytokine Netw., 15 (1), 14–23. Sabioncello, A., Kocijan-Hergigonja, D., Rabatic, S., Tomasic, J., Jeren, T., Matijevic, L., Rijavec, M., and Dekaris, D. (2000). Immune, endocrine, and psychological responses in civilians displaced by war. Psychosom. Med., 62, 502–508. Sapolsky, R. M. (1996). Why stress is bad for your brain. Science, 273, 749–750. Sapolsky, R. M. (1997) Stress and glucocorticoids (letters to the editor). Science, 275, 1663. Schaeffer, M. A., and Baum, A. (1984). Adrenal cortical response to stress at the Three Mile Island. Psychosom. Med., 46 (3), 227–237. Schnurr, P. P., Spiro, A. III, and Paris, A. H. (2000). Physiciandiagnosed medical disorders in relation to PTSD symptoms in older male military veterans. Health Psychol., 19, 91–97. Segerstrom, S. C., and Miller, G. E. (2004). Psychological stress and the human immune system: a meta-analytic study of 30 years of inquiry. Psychological Bulletin, 130 (4), 601–630. Segerstrom, S. C., Solomon, G. F., Kemeny, M. E., and Fahey, J. L. (1998). Relationship of worry to immune sequelae of the Northridge earthquake. J. Behav. Med., 21, 433–450. Severn, A., Rapson N. T., Hunter C. A., et al. (1992). Regulation of tumor necrosis factor production by adrenaline and B-adrenergic agonists. J. Immunol., 148, 3441–3445. Shalev, A. Y., Sahar, T., Freedman, S., et al. (1998). Prospective study of physiological response to trauma and subsequent PTSD. Arch. Gen. Psychiatry, 55, 553–559.
Smith, M. A., Davidson, J., Ritchie, J. C., Kudler, H., Lipper, S., Chappell, P., et al. (1989). The corticotropin-releasing hormone test in patients with posttraumatic stress disorder. Biol. Psychiatry, 26, 349–355. Solomon, G. F., Sergerstrom, S. C., Grohr, P., Kemeny, M., and Fahey, J. (1997). Shaking up immunity: psychological and immunologic changes after a natural disaster. Psychosom. Med., 59, 114–127. Southwick, S. M., Krystal, J. H., Morgan, C. A., Johnson, D., Nagy, L. M., Nicolaou, A., Heninger, G. R., and Charney, D. S. (1993). Abnormal noradrenergic function in posttraumatic stress disorder. Arch. Gen. Psychiatry, 50, 266–274. Spivak, B., Shohat, B., Mester, R., Avraham, S., Gil-Ad, I., Bleich, A., Valevski, A., and Weizman, A. (1997). Elevated levels of serum interleukin-1β in combat-related posttraumatic stress disorder. Biological Psychiatry, 42, 345–348. Steffens, D. C., Byrum, C. E., McQuid, D. R., Greensburg, D. L., Payne, M. E., Blichington, T. F., McFall, J. R., and Krishnan, K. R. (2000). Hippocampal volume in geriatric depression. Biol. Psychiatry, 48, 301–309. Stein, M. B., Yehuda, R., Koverola, C., and Hanna, C. (1997). Enhanced dexamethasone suppression of plasma cortisol in adult women traumatized by childhood sexual abuse. Biol. Psychiatry, 42, 680–686. Tucker, P., Ruwe, W. D., Masters, B., Parker, D. E., Hossain, A., Trautman, R. P., and Wyatt, D. B. (2004). Neuroimmune and cortisol changes in selective serotonin reuptake inhibitor and placebo treatment of chronic posttraumatic stress disorder. Biol. Psychiatry, 56, 121–128. Waage, A., and Bakke, O. (1988). Glucocorticoids suppress the production of tumor necrosis factor by LPS stimulated human monocytes. Immunology, 63, 299–302. Walker, E. A., Gelfand, A. N., Katon, W. J., Koss, M. P., Von Korff, M., Bernstein, D. E., et al. (1999). Adult health status of women with histories of childhood abuse and neglect. Am. J. Med., 107, 332–339. Weiss, D. W., Hirt, R., Tarcic, N., Nerzon, Y., Benzur, H., Breznitz, S., Glaser, B., Grover, N. B., Baras, M., and O’Dorisio, T. M. (1996). Studies in psychoneuroimmunology: psychological, immunological, and neuroendocrinological parameters in Israeli civilians during and after a period of SCUD missile attacks. Behav. Med., 22 (1), 5–14. Wilson, S. N., Van der Kolk, B., Burbridge, J., Fisler, R., and Kradin, R. (1999). Phenotype of blood lymphocytes in PTSD suggests chronic immune activation. Psychosomatics, 40, 222–225. Wong, C. M. (2002). Post-traumatic stress disorder: Advances in psychoneuroimmunology. Psychiatr. Clin. North Am., 25 (2), 369–383. Wong, C. M., Rapaport, M. H., Golier, J. A., Grossman, R., and Yehuda, R. (2000). Cytokine function in PTSD: serum and LPS whole blood responses to the DST. Presented at the 39th annual meeting of the American College of Neuropsychopharmacology, San Juan. Cited in Wong, 2002. Wong, C. M., Rapaport, M. H., Yang, R. K., Golier, J. A., Grossman, R., and Yehuda, R. (2001). Interleukin-10 and trauma type in post-traumatic stress disorder. Presented at the 21st national conference of the Anxiety Disorders Association of America, Atlanta. Poster abstract NR-057, p. 78. Cited in Wong, 2002. Yehuda, R. (2002). Current status of cortisol findings in posttraumatic stress disorder. Psychiatr. Clin. North Am., 25, 341–368. Yehuda, R., Bierer, L. M., Schmeidler, J., Aferiat, D. H., Breslau, I., and Dolan, S. (2000). Low cortisol and risk for PTSD in adult offspring of Holocaust survivors. Am. J. Psychiatry, 157, 1252–1259.
25. Immune and Neuroendocrine Alterations in Post-traumatic Stress Disorder Yehuda, R., Boisoneau, D., Lowy, M. T., and Giller, E. L. (1995a). Dose-response changes in plasma cortisol and lymphocyte glucocorticoid receptors following dexamethasone administration I combat veterans with and without posttraumatic stress disorder. Arch. Gen. Psychiatry, 52, 583–593. Yehuda, R., Boisoneau, D., Mason, J. W., and Giller, E. L. (1993a). Glucocorticoid receptor number and cortisol excretion in mood, anxiety, and psychotic disorders. Biol. Psychiatry, 34, 18–25. Yehuda, R., Golier, J. A., and Kaufman, S. (2005). Circadian rhythm of salivary cortisol in Holocaust survivors with and without PTSD. Am. J. Psychiatry, 162, 998–1000. Yehuda, R., Kahana, B., Binder-Brynes, K., Southwick, S. M., Mason, J. W., and Giller, E. L. (1995b). Low urinary cortisol excretion in Holocaust survivors with posttraumatic stress disorder. Am. J. Psychiatry, 152, 982–986. Yehuda, R., Levengood, R. A., Schmeidler, J., Wilson, S., Guo, L. S., and Gerber, D. (1996a). Increased pituitary activation following metyrapone administration in post-traumatic stress disorder. Psychoneuroendocrinology, 21, 1–16. Yehuda, R., Lowy, M. T., Southwick, S., Shaffer, D., and Giller, E. L. (1991). Lymphocyte glucocorticoid receptor number in posttraumatic stress disorder. Am. J. Psychiatry, 148, 499–504. Yehuda, R., McFarlane, A. C., and Shalev, A. Y. (1998a). Predicting the development of posttraumatic stress disorder from the acute response to a traumatic event. Biol. Psychiatry, 44, 1305–1313. Yehuda, R., Siever, L. J., Teicher, M. H., Levengood, R. A., Gerber, D. K., Schmeidler, J., and Yang, R. K. (1998b). Plasma norepi-
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nephrine and 3-methoxy-4-hydroxyphenylglycol concentrations and severity of depression in combat posttraumatic stress disorder and major depressive disorder. Biol. Psychiatry, 44, 56–63. Yehuda, R., Southwick, S. M., Krystal, J. H., Bremner, D., Carney, D. S., and Mason, J. W. (1993b). Enhanced suppression of cortisol following dexamethasone administration in posttraumatic stress disorder. Am. J. Psychiatry, 150, 83–86. Yehuda, R., Southwick, S. M., Nussbaum, G., Wahby, V., Giller, E. L., and Mason, J. W. (1990). Low urinary cortisol excretion in patients with posttraumatic stress disorder. J. Nerv. Ment. Dis., 178, 366–369. Yehuda, R., Teicher, M. H., Trestman, R. L., Levengood, R. A., and Siever, L. J. (1996b). Cortisol regulation in posttraumatic stress disorder and major depression: A chronobiological analysis. Biol. Psychiatry, 40, 79–88. Young, E. A., and Breslau, N. (2004). Cortisol and catecholamines in posttraumatic stress disorder: An epidemiologic community study. Arch. Gen. Psychiatry, 61, 394–401. Yudkin, J. S., Kumari, M., Humphries, S. E., and Mohamed-Ali, V. (2000). Inflammation, obesity, stress and coronary heart disease: Is interleukin-6 the link? Atherosclerosis, 148, 209–214. Zuckerman, S. H., Shellhaas, J., and Butler, L. D. (1989). Differential regulation of lipopolysaccharide induced interleukin-1 and TNF synthesis: Effects of endogenous and exogenous glucocorticoids and the role of the pituitary-adrenal axis. Eur. J. Immunol., 19, 301–305.
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C H A P T E R
26 Psychoneuroimmunologic Aspects of Alcohol and Substance Abuse STEVEN J. SCHLEIFER
I. INTRODUCTION 549 II. ALCOHOL, ALCOHOLISM, AND IMMUNITY 550 III. ALCOHOL, ALCOHOLISM, AND IMMUNITY: MEDIATING AND MODULATING FACTORS 552 IV. ALCOHOL, ALCOHOLISM, AND IMMUNITY: MECHANISMS 553 V. ALCOHOLISM AND IMMUNITY: CONSEQUENCES FOR DISEASE 554 VI. STIMULANTS AND IMMUNITY 555 VII. NICOTINE AND IMMUNITY 556 VIII. OPIATES AND IMMUNITY 556 IX. MARIJUANA AND OTHER SUBSTANCES 557 X. CONCLUDING COMMENTS 557
while acute exposure to alcohol has demonstrable immune effects, chronic alcohol abusers tend to show immune alterations of only modest scope in the absence of liver disease or other comorbid medical conditions (Cook et al., 1997; Kronfol et al., 1993; Schleifer et al., 1999; Stefanini et al., 1989; Watson et al., 1985). Direct effects of alcohol include those resulting from acute exposure of immune tissues to alcohol as well as cumulative effects of chronic exposure. Some substances (e.g., opioids) are most potent in naive subjects, while others (e.g., nicotine) may show immune cell effects only after extended exposure (Sharp, 1998). Effects of acute or subacute substance withdrawal may actually be more pronounced than that of drug exposure itself. Drug exposure and withdrawal may operate centrally (CNS) as well as at the immune-cell level. Chronic exposure may, similarly, lead to immune tolerance through central as well as direct immune-cell processes. Still other categories of indirect immune effects of alcohol and other substances are associated with toxicity to somatic tissues (e.g., liver, hematopoietic system), substance-induced nutritional or hormonal changes, or somatic consequences of druginduced high-risk behavior (resulting in physical trauma or exposure to infection, such as HIV). The immune effects of a substance may be additive or synergistic with those of other drugs used in combination with the index agent (e.g., alcohol plus cocaine) or be additive or interact with immune effects of co-occurring clinical conditions (e.g., depressive disorders).
I. INTRODUCTION Substance use, abuse, and dependence have long been associated with increased risk of disease, some of which (e.g., alcoholic hepatitis, cirrhosis) may be directly attributable to toxic effects of the abused substance. Increased prevalence of medical disorders such as infectious diseases is also associated with alcoholism or other substance abuse, and has been attributed, in part, to altered immunity in substance abusers (Arria et al., 1991; Cook, 1998; Irwin, 2002). Alcohol abuse, the main focus of this chapter, is among the more intensively studied paradigms and is a major public health issue worldwide. Changes in the immune system and in immunerelated medical disorders in alcoholics are associated with complex direct and indirect effects. For example, PSYCHONEUROIMMUNOLOGY, 4E VOLUME I
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For alcohol, and possibly other drugs, it may be essential to distinguish effects of alcohol exposure from those associated with alcoholism as a syndrome. Such syndromal states may have genetic and constitutional (e.g., CNS) characteristics with immune correlates independent of the drug exposure. Some syndromes, such as alcoholism, appear to have clinical/biological subtypes, with potentially distinct immune consequences. One clinically important subgrouping distinguishes early- from late-onset alcoholism, early-onset disorders showing distinct cognitive, behavioral, and affective patterns and more prominent CNS and familial effects (Cloninger, 1987). The various clinical dimensions of substance use provide a context for interpreting discordant observations in the psychoimmunologic literature. They also dictate a need for caution in generalizing across clinical settings, especially if the index study assesses acute substance exposure in non-abusing subjects. Selection bias in clinical samples, most notably with crosssectional designs, must also be considered. For example, the only modest immune effects found in studies of otherwise healthy chronic alcoholics would appear to result from adaptation of immune tissues to drug exposure. They may also, however, reflect differential resistance to toxic drug effects, resulting in sustained good health (hence, study eligibility) for chronic abusers with more robust baseline immune function. The current chapter will consider primarily those PNI effects that appear to be a consequence of substance exposure or syndromal substance abuse rather than secondary consequences of medical conditions such as alcoholic liver disease. Immune-related clinical consequences of drug abuse will be reviewed in brief.
II. ALCOHOL, ALCOHOLISM, AND IMMUNITY A. Lymphocytes and Adaptive Immunity Increased circulating immunoglobulins were among the earliest described immune abnormalities in alcoholics. As with many other reported immune changes, these appeared to be largely associated with alcoholic liver disease (Cook, 1998), although increased IgE levels independent of liver dysfunction have been described (Dominguez-Santalla et al., 2001). There are many reports of altered lymphocyte distribution in patients with moderate to advanced alcoholic liver disease (ALD). Roselle and colleagues (1988) found decreased CD4+, CD8+, and CD3+ cells in hospitalized patients with alcoholic hepatitis. In a mixed
sample of alcoholics with and without liver disease, Cook and colleagues (1995) found decreased CD3+ cell subsets (L-selectin CD8+, CD45RA+) compared with non-alcoholic volunteers. Laso and colleagues (1996) found increased HLA DR expression, increased circulating (CD56+) NK cells, and decreased (CD19+) Bcells in persons with alcoholic cirrhosis. In contrast to the changes in persons with alcoholic liver disease or other comorbid disorders, there is only modest evidence for altered peripheral blood lymphocytes and lymphocyte subsets in alcoholic patients without liver disease (AWLDs) (Cook, 1998). Some studies suggest a shift toward an inflammatory state in alcoholics, possibly with “incomplete activation” of T-cells and moderately reduced B-cells. Chronic AWLDs from an ambulatory clinic in Barcelona (Sacanella et al., 1998) showed decreased B-cell markers and increased markers of T-cell activation, including CD69, CD25, sIL-2R, and HLA-DR. Other markers of functional immune activation were not elevated (IL-6, CD71). Cook and co-workers, at a rural U.S. Veterans Hospital, studied AWLDs admitted for inpatient detoxification and similarly found evidence for activated T-cells (Cook et al., 1991) and a reduction in some CD45RA+ markers representing suppressor inducer or naive cells (Cook et al., 1994). Our group examined in vitro immune measures in alcoholdependent persons, without liver or other medical disorders and free of other substance abuse, who were seeking treatment at an inner-city alcohol treatment center. No differences between alcohol-dependent and community control subjects were found in circulating leukocyte and lymphocyte subsets (Schleifer et al., 1999). In contrast, alcohol-dependent persons from the same clinic with evidence of even mild medical disorder (mostly mild liver abnormalities) showed evidence of immune activation, including increased HLA-DR+ cells and decreased total CD45RA+ cells (Schleifer et al., 2002). These subjects, however, also consumed more alcohol than the alcoholics with no evidence of liver disease. (Absolute levels of activation markers intermediate between those of the healthy non-abusers and alcoholics with mild medical abnormalities were found for the AWLDs; however, those differences were not statistically significant.) Adhesion markers in peripheral blood mononuclear cells, which are associated with cellular interactions and passage into the periphery, may also differ in alcoholics. In AWLDs, Cook and co-workers (1995) described changes in the distribution of L-selectin, CD11b, CD31, and CD57 cells, and Sacanella et al. (1998) found increased CD29+ cells and VLA proteins. These observations, together with the increased CD45RO+ (memory) cells found by both groups, are
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consistent with increased immune activation even in the absence of liver disease. Mitogen responses have been among the commonly studied non-specific measures of immune activation in PNI research. Lower mitogen response has been reported in alcoholic patients but appears to be a consequence of liver or other organ dysfunction (Lundy et al., 1975; Mutchnick and Lee, 1988; Stefanini et al., 1989; Watson et al., 1985). In our study, AWLDs did not differ from a healthy community comparison sample in PHA, ConA, or PWM responses (Schleifer et al., 1999), nor were effects seen in the alcoholdependent sample with mild liver dysfunction and greater alcohol consumption (Schleifer et al., 2002). Studies of cytokine levels and expression in relation to alcohol exposure and alcoholism, consistent with studies of other immune parameters, suggest that alcoholic patients with liver disease have substantially altered circulating cytokines, with only modest effects in AWLDs. Khoruts and co-workers (1991), in a Midwestern U.S. Veterans Hospital, found that chronic alcoholic patients, 1–2 weeks after admission to a drug dependency unit, did not differ from healthy nonabusers in circulating TNF-α, IL1-α, and IL-6 levels. Patients with alcoholic and other liver diseases, however, showed dramatic increases in these cytokines. A study in Athens of hospitalized AWLDs after about 24 hours of abstinence (Nicolaou et al., 2004) showed no changes in TNF-α, IL-8, IL-10, or IL-12. Moderate increases were found in IL-6, possibly related to the much briefer period of abstinence compared with the earlier study. Accordingly, the subjects in Athens were likely to be experiencing early acute withdrawal, a powerful stressor that may have induced IL-6. Another study of hospitalized AWLDs, in Antwerp (Song et al., 1999), however, found increases in both pro-inflammatory (IL-6, TNF-α) and negative immunomodulators (IL-10, IL-1RA) as long as 1 month after alcohol detoxification (increased circulating neutrophils were also found). In that study, the authors speculated that comorbid depressive disorders contributed to the observations (see below). Finally, studies of actively drinking AWLDs, in Salamanca, showed increased serum IL-12 (Laso et al., 1998) and increased intracellular IFN-γ and IL-2 (Laso et al., 1999). In sum, while both clinical conditions and immune assays are not directly comparable across studies (e.g., Cook, 2000), and the data are still limited in scope, the studies suggest that there is modestly increased Th1 activation in alcoholism even in the absence of liver disease. Experimental studies demonstrating different effects of acute alcohol exposure on Th1–Th2 balance as a function of immunoregulatory status at the time
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of exposure (Girouard et al., 1998) emphasize the need to explore the role of chronic alcohol use from a dynamic perspective.
B. Innate Immunity 1. Natural Killer Cell Activity NK cell activity is among the most sensitive immune components to stress, depression, and other behavioral factors (Herbert and Cohen, 1993a, 1993b). As with other immune measures, decreased NKCA is readily demonstrable in advanced liver disease (Charpentier et al., 1984), with variable findings in alcoholics without liver or other medical disorders. Irwin and co-workers (1990) found decreased NKCA in hospitalized alcoholic men, while Cook and co-workers (1997) found no changes in hospitalized AWLDs in either NKCA or the number of (CD56+) NK cells. In a study of actively drinking ambulatory AWLDs, our group also found no differences from community controls in NKCA and circulating CD56+ cells (Schleifer et al., 1999). Kronfol and co-workers (1993), studying a more medically heterogeneous but mostly healthy alcoholic sample, similarly found no differences in NKCA compared with non-alcoholics. Laso and co-workers (1997), however, found increased NKCA and circulating NK cells in actively drinking AWLDs. In that study, the differences persisted 3 months after alcohol withdrawal, suggesting that effects were unrelated to acute or ongoing alcohol exposure or to acute withdrawal. As with other immune measures, the influence of acute versus chronic alcohol exposure, drug withdrawal, intercurrent medical conditions, and syndromal alcoholism is likely of importance. These and other modulating factors such as age, gender, and genetic factors are reviewed below. 2. Phagocytic Function The studies reviewed have emphasized the modest impact of alcohol use and alcoholism per se on most immune functions. In contrast, alcohol may have a more substantial influence on phagocytic functions (phagocytosis and intracellular killing by phagocytic cells, but not antigen processing by phagocytic cells), granulocytes playing a key role in protecting against the bacterial infections to which alcohol abusers are especially susceptible (Adams and Jordan, 1984; MacGregor, 1986). Alcohol effects on granulocyte function have been reported in vitro, including in human cells (Jareo et al., 1996; MacGregor, 1986; MacGregor et al., 1978; Patel et al., 1996), but there is still limited research data on such functions in alcohol-dependent persons. One study found alterations in chemotaxis but not
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phagocytosis in a small, uncontrolled alcoholic sample (MacGregor et al., 1978). In our study of ambulatory alcohol-dependent persons, decreased phagocytosis was found in alcohol-dependent males, but not females, with no changes in intracellular bacterial killing (Schleifer et al., 1999). Such gender-specific effects are of note considering the differences in alcohol-related behavior in men and women (Schuckit et al., 1995) and gender differences in the immune system itself (Tollerud et al., 1989). There is some evidence that alcohol effects may differ among the phagocytic cells. A recent study of mostly male alcoholics, assessing phagocytosis and the release of reactive oxygen species (necessary for microbial killing), found that alcoholism affected PMNs preferentially (Parlesak et al., 2003). PMN, but not monocyte, phagocytosis was decreased in AWLDs (and ALDs), and chemiluminescence was increased in resting PMNs from AWLDs (and ALDs). Under resting conditions, monocytes from alcoholics showed no differences from healthy controls. Following LPS stimulation, however, monocytes as well as PMNs showed functional changes in the release of reactive oxygen species. Evidence for adaptation to alcohol effects on phagocytes was also found, with acute suppression following drug exposure in non-alcoholic but not alcoholic subjects.
III. ALCOHOL, ALCOHOLISM, AND IMMUNITY: MEDIATING AND MODULATING FACTORS The studies described have identified a number of factors associated with immune effects in patients with alcoholism. These include substantial influences for concurrent medical disorders and organ (e.g., hepatic) dysfunction and important effects associated with the chronicity and volume of alcohol exposure. The role of gender in the immune effects of alcohol and alcoholism in humans has occasioned some discussion, with limited systematic data. Studies of women have been few due to the overwhelming prevalence of males in most clinical patient samples (many U.S. studies from Veterans Administration Hospitals have been largely restricted to males). There is reason to expect different immune effects in women due to baseline gender differences in immunity (e.g., related to estrogen and testosterone levels) and increased susceptibility of women to alcohol-related liver injury (Kovacs and Messingham, 2002). Women also tend to show greater immune activation and inflammation than do men (Kovacs and Messingham, 2002). In rats, acute ethanol administration resulted in increased
PMN phagocytosis in female but not male rats (Spitzer and Zhang, 1996). This may provide a model for exploring the reported decreased phagocytosis in male but not female AWLDs (Schleifer et al., 1999). More research is required concerning the effects of age and aging on immunity in alcoholics. Studies of AWLDs have focused largely on subjects in the 35–50 year age range. Since age may play an important interacting role in PNI processes (Schleifer et al., 1989), studies of alcoholism and immunity across the life span are needed. The design of such research will be challenging since clinical longitudinal studies of aging per se are likely to be confounded by increasing cumulative exposure to alcohol with advancing age. Crosssectional studies are further confounded by sampling procedures that will select for those increasingly atypical subjects who have remained in good health with increasing age. A cohort effect may also complicate such research since, in recent decades, fewer persons abuse alcohol exclusively (e.g., without additional substances such as cocaine). Age-related alcoholism effects may also interact with alcoholism subtypes, some of which are age related (Cloninger, 1987), although we found no association between age of alcoholism onset and several immune measures (Schleifer et al., 1999). Other genetic predisposing factors, whether in relation to the immune system or alcoholism, may influence interactions between alcoholism and immunity. Animal studies have found reciprocal correlations between alcohol sensitivity and immune activity (Morato and Morato, 1993; Petitto et al., 1990). In humans, genetic polymorphisms have been associated with cytokine (TNF and IL-8) changes following alcohol exposure (Gonzalez-Quintela et al., 2004). Allelic differences in the IL-1 receptor have been associated with increased risk of alcoholism (Pastor et al., 2000). Genetic polymorphisms are of additional interest in relation to racial/ethnic background. AfricanAmericans tend to differ from Caucasians in circulating leukocytes (Tollerud et al., 1989) and Irwin and Miller (2000), studying detoxified alcoholics, found decreased NKCA and IL-6 in relation to African American background and alcoholism. The two effects were additive. African American alcoholics also had the highest IL-10 production compared with other groups. These data suggest that health risks may be greater for African Americans compared with Caucasians who become alcohol dependent. Behavioral factors such as stress and depression can also mediate or modulate the association between alcoholism and immunity. Some of these effects may be related to associated somatic symptoms and signs such as sleep disturbance, nutritional change, exercise, and activity level. There is much evidence that stress,
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depressive disorders, and altered sleep (especially deprivation) influence the immune system (reviewed elsewhere in this volume), and the increased prevalence of such behavioral conditions in alcoholics may contribute to immune change. Nutritional deprivation in alcoholism may serve as a mediator and modulator of alcohol effects on immunity, as extensively considered in animal studies (e.g., Blank et al., 1991; Watzl and Watson, 1993). Sleep patterns are associated, bidirectionally, with cytokine production and other immune processes, and disordered sleep in alcoholics, a common phenomenon, is associated with altered cytokine levels and NKCA (Redwine et al., 2003). Further interactions result from the frequent experience of physical trauma in intoxicated states, with alcoholics shown to have increased morbidity and mortality following trauma such as burns (McGill et al., 1995). The clinical effects may be associated with additive, possibly synergistic, immunosuppressive effects of the trauma itself and alcohol exposure, and may be gender related (Kovacs et al., 2004; Messingham et al., 2000; Szabo et al., 1994). Approximately one-third of alcoholics suffer from major depression (Kessler et al., 1997; Penick et al., 1994), itself associated with immune system changes including increased circulating leukocytes, monocytes, and neutrophils; increased markers of immune activation and inflammation; and decreased NKCA and mitogen responses (Herbert and Cohen, 1993a; Zorrilla et al., 2001). Some of these effects may be mediated by clinical characteristics such as sleep disturbance that are common in depression (and in alcoholism) (Irwin, 2002). Irwin and co-workers (1990), comparing alcoholics with and without major depression, nonalcoholic depressed patients, and non-depressed non-alcoholics, found independent additive effects for depression and alcoholism in relation to decreased NKCA. Alcoholic and depressed patients also had increased circulating leukocytes and neutrophils, and alcoholics showed increased monocytes and lymphocytes. In our study of ambulatory alcohol-dependent persons, we found similar effects for depression, but more limited differences associated with alcoholism (Schleifer et al., 2006). Depression was associated independently with decreased PHA and possibly NKCA, and increased circulating monocytes. Independent effects of alcohol dependence included decreased Bcells, possibly decreased CD56+ (NK) cells, and increased monocytes, but no effects for NKCA or mitogen response. The immune correlates of alcoholism were largely attributable to recent alcohol exposure. Drug withdrawal is a clinical dimension of considerable importance (Laso et al., 1997). Withdrawal from
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alcohol is a state of extreme physiologic activation and substantial hormonal imbalance. In addition to periodic episodes of acute withdrawal, the day-to-day experience of the alcoholic, especially when access to the agent is variable, may involve continuing shifts in and out of mild to extreme states of withdrawal. These may have substantial immune consequences (Jerrels et al., 1989). Even the mild “hangover” associated with acute exposure in non-alcoholic subjects has been associated with immune alterations (increased IL-10, IL-12, IFN-γ) (Kim et al., 2003).
IV. ALCOHOL, ALCOHOLISM, AND IMMUNITY: MECHANISMS Biological mechanisms associating alcoholism and immunity are likely to vary in relation to the “clinical” dimensions already described (e.g., alcohol exposure, hepatic and hematologic pathology). Mediating and modulating physiologic processes may involve interactions at the systemic/central as well as the cellular level. Studies of direct cellular effects of alcohol exposure suggest that specific receptors are not involved, with drug effects associated with altered membrane fluidity (see, however, below). Ethanol exposure has been associated with decreased adenylyl cyclase activity in lymphocyte membranes (Pauly et al., 1999), altered erythrocyte membrane fatty acid composition, and decreased intracellular free calcium and inositol phosphates following lymphocyte stimulation (Stefanini et al., 1996). Jerrells and co-workers (1989), using an animal model, suggested, however, that the direct cellular effects of alcohol exposure are of limited importance under most conditions and that the most prominent immune effects relate to induction of stress hormones (e.g., corticosteroids) following alcohol withdrawal. Of further note is a report that decreased adenylyl cyclase activity itself is found primarily during acute alcohol withdrawal, with little change in actively drinking alcoholics or persons completely detoxified from the drug (Szegedi et al., 1998). An interesting other model suggests that hormonal effects, such as of opioids, both locally and centrally acting, are key to altered immune activity following chronic alcohol exposure. Rosenberger and colleagues (2003) demonstrated increased lymphocyte POMC mRNA in chronic alcoholics, together with increased LPS-stimulated IL-1RA. Following CRF injection, POMC mRNA increased in non-alcoholics but decreased in alcoholics. Chronic ethanol exposure inhibits hypothalamic CRF terminals, which recover after extended withdrawal from the drug, and both CRF and IL-1 induce the release of POMC-derived
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hormones (Schafer et al., 1996). Another intriguing interaction is suggested by altered levels of the cytokine-like peptide leptin in chronic alcoholics (possibly contributing to malnutrition and varying in relation to alcohol exposure and withdrawal), with a possible association of leptins with altered NKCA and other immune changes (Motivala et al., 2003; Nicolas et al., 2001). Some direct intracellular effects have also been described. Alcohol has been reported to induce suppression of NF-κb mediated production of inflammatory cytokines (Mandrekar et al., 2002). It was also found to augment glucocorticoid receptors (GR) while decreasing transactivation as a result of suppressed nuclear binding (Mandrekar et al., 2002).
V. ALCOHOLISM AND IMMUNITY: CONSEQUENCES FOR DISEASE The psychoneuroimmunology of alcoholism is often linked to its association with immune-related medical disorders. These include infectious diseases (bacterial pneumonia, tuberculosis, hepatitis C, possibly HIV), neoplasia, and autoimmune disorders (Cook, 1998). Autoimmune processes have been implicated in the development of alcoholic hepatitis and cirrhosis (Cook, 1998; Purohit et al., 2005), in turn associated, in a cruel irony, with impaired immunity. The association of alcoholism with morbidity and mortality, however, is not straightforward. There has been some (impassioned) debate concerning the relative health benefits and hazards of light to moderate alcohol use. There is little doubt, however, that alcohol-dependent persons have increased all-cause mortality (Dawson, 2000), including both “unnatural” deaths (traffic accidents, falls, suicide, homicide), of which one-third or more may be alcohol-associated (Sjogren et al., 2000), and death from disease. Mortality among alcoholdependent persons is three to five times higher than that of the general population, and longitudinal studies have found a broad array of (immunologically relevant) factors, from liver disease to divorced/separated status, to be predictive of mortality in alcoholics (Lewis et al., 1995). Although alcoholism is more prevalent in males, female alcoholics seem to be more susceptible to adverse medical outcomes, due in part to higher blood levels per unit ethanol consumed; alcohol-dependent women also face the prospect of inducing fetal alcohol syndromes in offspring (Schenker, 1997). Immune changes in alcoholism most often represent an exacerbating, rather than primary, element in the pathophysiology of infectious diseases (and other
medical conditions), and studies clearly linking alcoholism, immunity, and disease are few. For example, the prominent association between alcoholism and pneumonia relates mostly to the sedative effects of alcohol resulting in diminished clearance of respiratory tract pathogens. Immunologic factors are likely to exacerbate the process, impairing neutrophil migration to the lung. Recognized for many decades, alcohol’s effect on neutrophil migration is now considered not to result from direct cytotoxic effects, but rather from suppressed pulmonary chemokine production and impaired neutrophil adhesion (Boe et al., 2003). Other local immunologic effects, such as impaired alveolar macrophage cytokine production, contribute additionally to reduced host resistance (Omidvari et al., 1998). Alcohol-associated immune changes, including suppressed inflammatory cytokine responses, are especially important in magnifying the risk associated with other co-existing factors. For example, alcohol exacerbates the risk of infection following burns and other physical trauma (Faunce et al., 2003) as well as after elective surgery (Sander et al., 2002; Spies et al., 2004). The role of alcoholism in HIV disease has occasioned much speculation; however, there is only limited specific data concerning this disorder. Alcohol potentiates HIV infection of human monocyte-derived macrophages (Wang et al., 2002), and there is clinical data associating alcohol use with less effective response to anti-retroviral therapy. The latter, however, is likely to be a consequence of less reliable medication adherence rather than alcohol-impaired immune processes (Samet et al., 2003). Alcohol-associated immune alterations contribute to infections of the liver. In hepatitis C virus (HCV)infected patients, alcohol is associated with suppressed antigen-presenting cells, in which viral factors and alcohol interact to impair immune processing (Szabo et al., 2004). Alcohol use can reduce the efficacy of interferon therapy for HCV (Mochida et al., 1996) and of hepatitis B vaccines (Nalpas et al., 1993). Complex immune dysregulation associated with alcohol and alcoholism also appears to contribute to the pathogenesis of alcoholic hepatitis, which has been linked to autoimmune processes since the 1970s (Kakumu and Leevy, 1977). TNF-α and other cytokines are implicated in alcoholic as well as other chronic liver diseases, suggesting directions for therapeutic interventions (Neuman et al., 2001; Tilg and Diehl, 2000). A general exacerbating effect of alcoholism and alcohol use on allergic disorders has been reported, as well as increased IgE levels (Vidal et al., 2002). The association of alcohol and alcoholism with cancer risk is well described, especially for primary neoplasias of the upper gastrointestinal tract. Alcohol-
26. Psychoneuroimmunologic Aspects of Alcohol and Substance Abuse
associated immune changes, however, have received little attention in relation to the pathogenesis of these disorders (Purohit et al., 2005). In contrast, there is intriguing data linking alcohol-induced immune changes with the course of established cancers. Studies in animals have found direct links between alcohol consumption, suppressed NKCA, and increased metastases for NK-sensitive tumors (Ben-Eliyahu et al., 1996; Hebert and Pruett, 2003). Such observations may have substantial clinical implications and call for systematic clinical study. In sum, theoretical and empirical considerations suggest that most immune changes in chronic alcoholics are attributable to clinical factors such as medical disorders, drug withdrawal, depression, sleep disturbances, nutritional state, and level of recent alcohol exposure. To the extent that alcohol-associated immune deficits are not intrinsic to the chronic alcoholic, (guarded) optimism concerning the health benefits of reducing alcohol use, and thereby its comorbidities (e.g., hepatitis), may be warranted.
VI. STIMULANTS AND IMMUNITY Substances with stimulant properties, especially cocaine and amphetamine, are among the more commonly abused recreational drugs. These drugs are associated with dramatic changes in the levels of catecholamines, with both central and peripheral effects and both neurotransmitter and neurohormonal properties. The immunoregulatory effects of catecholamines have been a focus of attention for many decades due to their association with sympathetic nervous system activation, making them important potential mediators of the immune effects of stress. Effects of norepinephrine on the immune system are readily demonstrated; however, they are complex, associated with increases or decreases in Th1 and Th2 responses as a function of exposure condition (Moynihan et al., 2004). Altered leukocyte trafficking is also involved (Dhabhar, 2002). Dopamine has important immunomodulatory effects comparable to those of norepinephrine (Torres et al., 2005). Stimulant exposure is also associated with activation of the HPA axis, which has well-characterized immune effects that interact with the direct immune effects of the catecholamines (Torres et al., 2005). A clinical rationale for studies of stimulants is provided by the increased incidence of HIV infection in cocaine abusers. Experimental studies, however, have failed to demonstrate cocaine effects at non-toxic levels on a number of immune-related medical disorders (Pellegrino and Bayer, 1998).
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Pellegrino and Bayer (1998) reviewed studies of cocaine effects on the immune system, which are not extensive and almost all using animal models. They suggest that cocaine is associated with decreased lymphocyte numbers but increased NK cells. Cocaine can suppress lymphocyte proliferation acutely, but tolerance is induced with repeated administration. The latter is of further interest since chronic cocaine administration induces cross-tolerance to the proliferationsuppressive effects of morphine (Bayer et al., 1996). Effects on cytokine production, even with acute exposure, are still more complex, with increased followed by decreased Th1 cytokines reported (Pellegrino and Bayer, 1998). A recent experimental study in cocaine users suggests that the net effect of acute cocaine exposure is suppressive of Th1 responses, with IL-6 release during acute inflammation substantially blocked by intravenous cocaine injection (Halpern et al., 2003). In contrast to these functions, NKCA does not appear very sensitive to cocaine (Pellegrino and Bayer, 1998). Cocaine effects on immunity are primarily centrally mediated, with shared mechanisms (hence, perhaps, cross-tolerance) with morphine effects, and are related to serotonergic activity (Bayer et al., 1996; Halpern et al., 2003). Nevertheless, in at least one model, cocaine effects on lymphocyte proliferation appeared to be a consequence of peripheral rather than central effects (Pellegrino et al., 2001). While few in number, immune observations in human cocaine abusers have been similar to those with alcoholics, showing little evidence of altered distribution of peripheral blood lymphocytes or lymphocyte responses (Ruiz et al., 1998), but some impairment of phagocytic function (alveolar macrophages) (Baldwin et al., 1997). Studies of amphetamine effects on immunity have also largely been confined to animals, generally as a model of stress. Acute administration is associated with decreased circulating lymphocytes and suppressed mitogen response, effects largely attributable to noradrenergic rather than corticosteroid mechanisms (Pezzone et al., 1992). NKCA was suppressed by amphetamines in some studies, most with acute exposure, and enhanced in others (Wrona et al., 2005). Enhancement is associated with chronic exposure and is more readily found in animals with greater motoric activity and aggressiveness. Amphetamine effects also relate to catecholamine activity, with lesser and indirect corticosteroid effects (Swerdlow et al., 1991; Wrona et al., 2005). Overall, the limited immune studies with stimulants support the pattern seen with alcohol, acute exposure having the clearest effects. The most important mechanisms appear to be associated with cate-
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cholamine release. It is unclear whether the immune effects of stimulant exposure are of substantial clinical relevance.
VII. NICOTINE AND IMMUNITY The recreational use of tobacco is a major risk factor for a host of diseases ranging from lung and other neoplasias to cardiovascular diseases, microbial infections, chronic obstructive pulmonary disease, and diseases of the fetus (Sopori, 2002). In addition to toxic effects on end organs such as the lung, tobacco has also been thought to have suppressive effects on immunity, and to contribute to reduced risk among smokers for some autoimmune disorders (Sopori, 2002). Decreased immune function is often found together with increased numbers of immune cells, possibly reflecting compensatory mechanisms. Since the earliest reports, cigarette smoking has been linked to leukocytosis (Corre et al., 1971). Smoking induces a shift in the balance of T-cell subsets (modulated by factors such as racial background) (Tollerud et al., 1991). It is associated with decreased lymphocyte proliferation (Petersen et al., 1983) and decreased immunoglobulin levels and specific antibody responses (McAllister-Sistilli et al., 1998). Increased numbers and decreased function have been found for alveolar macrophages (Sopori, 2002). Decreased NK cell activity, linked to increased risk for some cancers, has been reported in smokers, although findings have not been uniform (Ferson et al., 1979; Jung and Irwin, 1999). A provocative study by Jung and Irwin (1999), with depressed and non-depressed smokers and non-smokers, found that both leukocytosis and decreased NK activity were a function of the interaction of depression and smoking. Depressed persons have considerably increased rates of tobacco use, adding to the clinical concerns. The nature of the association between cigarette smoke and the immune system requires further study. Nicotine, an important component of cigarette smoke, has been associated with its immune effects; however, the importance of this link is not well established and many other potentially immunoactive substances are contained in cigarettes (McAllister-Sistilli et al., 1998; Sopori, 2002). Effects of nicotine on the immune system may be mediated by both peripheral and central mechanisms (Sopori et al., 1998), analogous to observations with most substances of abuse. Finally, most of the above studies have focused on chronic smokers, and acute exposure to cigarette smoke yields even more variable results (McAllister-Sistilli et al., 1998). As with many of the substances considered in this chapter, the association between tobacco use and
immunity cannot be considered in isolation but must consider the pattern of substance exposure, characteristics of persons who consume cigarettes (as modulating and confounding factors—e.g., depression, genetic/ethnic factors), and the role of direct versus indirect immune effects.
VIII. OPIATES AND IMMUNITY A large literature of more than 25 years (Vallejo et al., 2004; Wybran et al., 1979), with antecedent reports more than a century old (Vallejo et al., 2004), has emphasized the relationship between opioids and immunity. Similarities as well as (bi-directional) interactions between the opioid and immune systems have been noted (Vallejo et al., 2004). As with other substances, the association is complex and mediated by multiple mechanisms. Exogenous opiates, such as morphine, administered in vivo in both acute and chronic schedules, inhibit T- and B-cell and NK activity as well as phagocytic functions (both macrophage and PMN) (Eisenstein and Hilburger, 1998; Vallejo et al., 2004). In contrast, endogenous opioids, such as β-endorphin, appear to enhance immune cell functions, including those of NK cells and phagocytes (Eisenstein and Hilburger, 1998; Vallejo et al., 2004). Important differences can also be demonstrated between in vitro and in vivo conditions, which select for direct versus CNS-mediated processes. Phagocytic functions appear to be directly sensitive to opioids (Eisenstein and Hilburger, 1998), while effects on lymphoid cells, especially NK activity, appear to be indirectly mediated by effects on the CNS (Shavit et al., 1986; Weber and Pert, 1989). The latter involve both sympathetic and HPA axis mechanisms (Eisenstein and Hilburger, 1998; Mellon and Bayer, 1998). The opioid effects, both direct and indirect, also differ in relation to the three primary opioid receptors (Nelson et al., 2000; Vallejo et al., 2004). Reciprocal effects of immune activity on opioid systems result in further interactions that modulate both neural and immune processes. For example, inflammation facilitates pain (through peripheral and central mechanisms) and the induction of morphine tolerance may be influenced by immunologic processes (Shavit et al., 2005; Watkins and Maier, 2002). Immunologic studies in opiate abusers are limited and subject to a host of confounding factors relating to lifestyle (e.g., nutritional effects and infections introduced by contaminated needles). There is, nevertheless, evidence of a general impairment of immune functions in this population. This includes decreased CD4+/CD8+ ratios and other shifts in T-cell subsets,
26. Psychoneuroimmunologic Aspects of Alcohol and Substance Abuse
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decreased mitogen-induced lymphocyte proliferation, and decreased NK activity (Brown et al., 1974; Donahoe et al., 1987; Novick et al., 1989). As with other substances of abuse, the immune changes may also relate to acute and chronic withdrawal and variable schedules of drug exposure/availability and quality with dramatic stress effects (Govitrapong et al., 1998; Rahim et al., 2002; Weber et al., 2004).
kine production, and PMN phagocytic activity (Connor, 2004). Such effects are demonstrable with acute-controlled exposure as well as in habitual users (Connor, 2004; Pacifici et al., 2002). As with many other substances of abuse, the immune effects of MDMA appear largely mediated through the CNS effects of the drug, although PMN phagocytosis (once again) is directly sensitive to this drug (Connor, 2004).
IX. MARIJUANA AND OTHER SUBSTANCES
X. CONCLUDING COMMENTS
While marijuana is among the most commonly used recreational substances and traditionally considered to have only modest medical risk, the medical consequences of marijuana, such as adverse effects on pulmonary function, have become a focus of much attention (Watson et al., 2000). The possibility of cannabinoid effects on the immune system were supported by identification of CB2 receptors on leukocytes (Galiegue et al., 1995). Marijuana has been shown to impair aspects of innate immunity including several alveolar macrophage functions. Such changes may be more extensive than those found following either tobacco or cocaine exposure (Baldwin et al., 1997). Effects on PMNs, however, are not prominent (Deusch et al., 2003). In addition to using the traditional substances already noted, people demonstrate a remarkable ability to adapt naturally occurring and synthetic substances, including those found in the medical pharmacopoeia, to recreational use. Especially when used in combination, some of these are likely to have immune effects (not to mention “dietary” substances such as caffeine). Two substances of abuse will be mentioned as examples of evolving social practice. Anabolic steroids have been popular in recent years, although only indirectly for their CNS effects. Recreational use of these drugs is likely to have immune consequences considering the effects of sex hormones on immunity and the substantial deleterious health effects of these agents (Hughes et al., 1998). Another popular substance of abuse, MDMA (“Ecstasy”), has been studied more extensively, and demonstrates again the multiple mechanisms of immune effects in substance abusers (Connor, 2004). Being related to amphetamine, MDMA is likely to share some immune effects with that agent (see above), and provide insights concerning amphetamine’s immune effects. Numerous immune changes can be demonstrated for MDMA under conditions of controlled exposure, including suppressed CD4+ cells, mitogen-induced lymphocyte proliferation, Th1 cyto-
The nearly ubiquitous use of alcohol and other substances for their CNS-altering properties suggests that all clinical psychoneuroimmunology studies should consider the contribution of such behavior to immunity and health. Immune system effects on substancerelated CNS systems (e.g., opioid) should also be noted. Substance abuse is a major risk factor for many long-standing and emerging threats to public health, including infections and neoplasia, and the present review suggests that psychoneuroimmune processes play some role in these effects. While some immune changes are directly related to immune cell exposure, it appears that the most important immune effects relate to indirect CNS effects shared by most substances of abuse. Many of these drug effects on the immune system are identical to those of stress. Among stressors, drug withdrawal is one of the most powerful experienced by humans under non-traumatic conditions.
References Adams, H. G., and Jordan, C. (1984). Infections in the alcoholic. Med. Clin. North Am., 68, 179–200. Arria, A. M., Tarter, R. E., and Van Thiel, D. H. (1991). Vulnerability to alcoholic liver disease. Recent Dev. Alcohol., 9, 185–204. Baldwin, G. C., Tashkin, D. P., Buckley, D. M., Park, A. N., Dubinett, S. M., and Roth, M. D. (1997). Marijuana and cocaine impair alveolar macrophage function and cytokine production. Am. J. Respir. Crit. Care Med., 156, 1606–1613. Bayer, B. M., Hernandez, Mc., Dunn, K. L., Mellon, R. D., and Pellegrino, T. (1996). Central pathways are involved in morphine and cocaine modulation of the immune system. J. Neuroimmunol., 69, 33–34. Ben-Eliyahu, S., Page, G. G., Yirmiya, R., and Taylor, A. N. (1996). Acute alcohol intoxication suppresses natural killer cell activity and promotes tumor metastasis. Nat. Med., 2, 457–460. Blank, S. E., Duncan, D. A., and Meadows, G. G. (1991). Suppression of natural killer cell activity by ethanol consumption and food restriction. Alcohol. Clin. Exp. Res., 15, 16–22. Boe, D. M., Nelson, S., Zhang, P., Quinton, L., and Bagby, G. J. (2003). Alcohol-induced suppression of lung chemokine production and the host defense response to Streptococcus pneumoniae. Alcohol. Clin. Exp. Res., 27, 1838–1845.
558
III. Behavior and Immunity
Brown, S. M., Stimmel, B., Taub, R. N., Kochwa, S., and Rosenfield, R. E. (1974). Immunologic dysfunction in heroin addicts. Arch. Intern. Med., 134, 1001–1006. Charpentier, B., Franco, D., Paci, L., Charra, M., Martin, B., Vuitton, D., and Fries, D. (1984). Deficient natural killer cell activity in alcoholic cirrhosis. Clin. Exp. Immunol., 58, 107–115. Cloninger, C. R. (1987). Neurogenetic adaptive mechanisms in alcoholism. Science, 236, 410–416. Connor, T. J. (2004). Methylenedioxymethamphetamine (MDMA, “Ecstasy”): a stressor on the immune system. Immunology, 111, 357–367. Cook, R. T. (1998). Alcohol abuse, alcoholism, and damage to the immune system—a review. Alcohol. Clin. Exp. Res., 22, 1927–1942. Cook, R. T. (2000). Cytoplasmic cytokines in the T cells of chronic alcoholics. Alcohol. Clin. Exp. Res., 24, 241–243. Cook, R. T., Ballas, Z. K., Waldschmidt, T. J., Vandersteen, D., LaBrecque, D. R., and Cook, B. L. (1995). Modulation of T-cell adhesion markers, and the CD45R and CD57 antigens in human alcoholics. Alcohol. Clin. Exp. Res., 19, 555–563. Cook, R. T., Garvey, M. J., Booth, B. M., Goeken, J. A., Stewart, B., and Noel, M. (1991). Activated CD-8 cells and HLA DR expression in alcoholics without liver disease. J. Clin. Immunol., 11, 246–253. Cook, R. T., Li, F., Vandersteen, D., Ballas, Z. K., Cook, B. L., and LaBrecque, D. R. (1997). Ethanol and natural killer cells. I. Activity and immunophenotype in alcoholic humans. Alcohol. Clin. Exp. Res., 21, 974–980. Cook, R. T., Waldschmidt, T. J., Ballas, Z. K., Cook, B. L., Booth, B. M., Stewart, B. C., and Garvey, M. J. (1994). Fine T-cell subsets in alcoholics as determined by the expression of L-selectin, leukocyte common antigen, and beta-integrin. Alcohol. Clin. Exp. Res., 18, 71–80. Corre, F., Lellouch, J., and Schwartz, D. (1971). Smoking and leucocyte-counts. Results of an epidemiological survey. Lancet, 2, 632–634. Dawson, D. A. (2000). Alcohol consumption, alcohol dependence, and all-cause mortality. Alcohol. Clin. Exp. Res., 24, 72–81. Erratum in: Alcohol. Clin. Exp. Res., 24, 395. Deusch, E., Kraft, B., Nahlik, G., Weigl, L., Hohenegger, M., and Kress, H. G. (2003). No evidence for direct modulatory effects of delta 9-tetrahydrocannabinol on human polymorphonuclear leukocytes. J. Neuroimmunol., 141, 99–103. Dhabhar, F. S. (2002). Stress-induced augmentation of immune function—the role of stress hormones, leukocyte trafficking, and cytokines. Brain Behav. Immun., 16, 785–798. Dominguez-Santalla, M. J., Vidal, C., Vinuela, J., Perez, L. F., and Gonzalez-Quintela, A. (2001). Increased serum IgE in alcoholics: relationship with Th1/Th2 cytokine production by stimulated blood mononuclear cells. Alcohol. Clin. Exp. Res., 25, 1198–1205. Donahoe, R. M., Bueso-Ramos, C., Donahoe, F., Madden, J. J., Falek, A., Nicholson, J. K., and Bokos, P. (1987). Mechanistic implications of the findings that opiates and other drugs of abuse moderate T-cell surface receptors and antigenic markers. Ann. N. Y. Acad. Sci., 496, 711–721. Eisenstein, T. K., and Hilburger, M. E. (1998). Opioid modulation of immune responses: effects on phagocyte and lymphoid cell populations. J. Neuroimmunol., 83, 36–44. Faunce, D. E., Garner, J. L., Llanas, J. N., Patel, P. J., Gregory, M. S., Duffner, L. A., Gamelli, R. L., and Kovacs, E. J. (2003). Effect of acute ethanol exposure on the dermal inflammatory response after burn injury. Alcohol. Clin. Exp. Res., 27, 1199–1206.
Ferson, M., Edwards, A., Lind, A., Milton, G. W., and Hersey, P. (1979). Low natural killer-cell activity and immunoglobulin levels associated with smoking in human subjects. Int. J. Cancer, 23, 603–609. Galiegue, S., Mary, S., Marchand, J., Dussossoy, D., Carriere, D., Carayon, P., Bouaboula, M., Shire, D., Le Fur, G., and Casellas, P. (1995). Expression of central and peripheral cannabinoid receptors in human immune tissues and leukocyte subpopulations. Eur. J. Biochem., 232, 54–61. Girouard, L., Mandrekar, P., Catalano, D., and Szabo, G. (1998). Regulation of monocyte interleukin-12 production by acute alcohol: a role for inhibition by interleukin-10. Alcohol. Clin. Exp. Res., 22, 211–216. Gonzalez-Quintela, A., Dominguez-Santalla, M. J., Loidi, L., Quinteiro, C., and Perez, L. F. (2004). Relation of tumor necrosis factor (TNF) gene polymorphisms with serum concentrations and in vitro production of TNF-alpha and interleukin-8 in heavy drinkers. Alcohol., 34, 273–277. Govitrapong, P., Suttitum, T., Kotchabhakdi, N., and Uneklabh, T. (1998). Alterations of immune functions in heroin addicts and heroin withdrawal subjects. J. Pharmacol. Exp. Ther., 286, 883–889. Halpern, J. H., Sholar, M. B., Glowacki, J., Mello, N. K., Mendelson, J. H., and Siegel, A. J. (2003). Diminished interleukin-6 response to proinflammatory challenge in men and women after intravenous cocaine administration. J. Clin. Endocrinol. Metab., 88, 1188–1193. Hebert, P., and Pruett, S. B. (2003). Ethanol decreases natural killer cell activation but only minimally affects anatomical distribution after administration of polyinosinic:polycytidylic acid: role in resistance to B16F10 melanoma. Alcohol. Clin. Exp. Res., 27, 1622–1631. Herbert, T. B., and Cohen, S. (1993a). Depression and immunity: a meta-analytic review. Psychol. Bull., 113, 472–486. Herbert, T. B., and Cohen, S. (1993b). Stress and immunity in humans: a meta-analytic review. Psychosom. Med., 55, 364–379. Hughes, T. K. Jr., Rady, P. L., and Smith, E. M. (1998). Potential for the effects of anabolic steroid abuse in the immune and neuroendocrine axis. J. Neuroimmunol., 83, 162–167. Irwin, M. (2002). Effects of sleep and sleep loss on immunity and cytokines. Brain Behav. Immun., 16, 503–512. Irwin, M., Caldwell, C., Smith, T. L., Brown, S., Shuckit, M. A., and Gillin, J. C. (1990). Major depressive disorder, alcoholism and reduced natural killer cell cytotoxicity. Arch. Gen. Psychiatry, 47, 713–719. Irwin, M., and Miller, C. (2000). Decreased natural killer cell responses and altered interleukin-6 and interleukin-10 production in alcoholism: an interaction between alcohol dependence and African American ethnicity. Alcohol. Clin. Exp. Res., 24, 560–569. Jareo, P. W., Preheim, L. C., and Gentry, M. J. (1996). Ethanol ingestion impairs neutrophil bactericidal mechanisms against streptococcus pneumoniae. Alcohol., Clin. Exp. Res., 20, 1646–1652. Jerrells, T. R., Peritt, D., Marietta, C., and Eckhardt, M. J. (1989). Mechanisms of suppression of cellular immunity induced by ethanol. Alcohol., Clin. Exp. Res., 13, 490–493. Jung, W., and Irwin, M. (1999). Reduction of natural killer cytotoxic activity in major depression: interaction between depression and cigarette smoking. Psychosom. Med., 61, 263–270. Kakumu, S., and Leevy, C. M. (1977). Lymphocyte cytotoxicity in alcoholic hepatitis. Gastroenterology, 72, 594–597. Kessler, R. C., Crum, R. M., Warner, L. A., Nelson, C. B., Schulenbe, J., and Anthony, J. C. (1997). Lifetime co-occurrence of DSM-III-R
26. Psychoneuroimmunologic Aspects of Alcohol and Substance Abuse alcohol abuse and dependence with other psychiatric disorders in the National Comorbidity Survey. Arch. Gen. Psychiatry, 54, 313–321. Khoruts, A., Stahnke, L., McClain, C. J., Logan, G., and Allen, J. I. (1991). Circulating tumor necrosis factor, interleukin-1 and interleukin-6 concentrations in chronic alcoholic patients. Hepatology, 13, 267–276. Kim, D. J., Kim, W., Yoon, S. J., Choi, B. M., Kim, J. S., Go, H. J., Kim, Y. K., and Jeong, J. (2003). Effects of alcohol hangover on cytokine production in healthy subjects. Alcohol, 31, 167–170. Kovacs, E. J., Faunce, D. E., and Messingham, K. A. (2004). Ethanol and burn injury: estrogen modulation of immunity. Alcohol, 33, 209–216. Kovacs, E. J., and Messingham, K. A. (2002). Influence of alcohol and gender on immune response. Alcohol Health Res., 26, 257–263. Kronfol, Z., Madhavan, N., Hill, E., Kroll, P., Brower, K., and Greden, J. (1993). Immune function in alcoholism: A controlled study. Alcohol. Clin. Exp. Res., 17, 279–283. Laso, F. J., Iglesias, M. C., Lopez, A., Ciudad, J., San Miguel, J. F., and Orfao, A. (1998). Increased interleukin-12 serum levels in chronic alcoholism. J. Hepatol., 28, 771–777. Laso, F. J., Iglesias-Osma, C., Ciudad, J., Lopez, A., Pastor, I., and Orfao, A. (1999). Chronic alcoholism is associated with an imbalanced production of Th-1/Th-2 cytokines by peripheral blood T cells. Alcohol. Clin. Exp. Res., 23, 1306–1311. Laso, F. J., Madruga, J. I., Giron, J. A., Lopez, A., Ciudad, J., San Miguel, J. F., Alvarez-Mon, M., and Orfao, A. (1997). Decreased natural killer cytotoxic activity in chronic alcoholism is associated with alcohol liver disease but not active ethanol consumption. [Erratum appears in Hepatology Dec. 26 (6), 1694]. Hepatology, 25, 1096–1100. Laso, F. J., Madruga, J. I., Lopez, A., Ciudad, J., Alvarez-Mon, M., San Miguel, J., and Orfao, A. (1996). Distribution of peripheral blood lymphoid subsets in alcoholic liver cirrhosis: influence of ethanol intake. Alcohol. Clin. Exp. Res., 20, 1564–1568. Lewis, C. E., Smith, E., Kercher, C., and Spitznagel, E. (1995). Predictors of mortality in alcoholic men: a 20-year follow-up study. Alcohol. Clin. Exp. Res., 19, 984–991. Lundy, J., Raaf, J. H., Deakins, S., Wanebo, H. J., Jacobs, D. A., Lee, T., Jacobowitz, D., Spear, C., and Oettgen, H. F. (1975). The acute and chronic effects of alcohol on the immune system. Surg. Gyn. Obst., 141, 212–218. MacGregor, R. R. (1986). Alcohol and immune defense. JAMA, 256, 1474–1479. MacGregor, R. R., Gluckman, S. J., and Senior, J. R. (1978). Granulocyte function and levels of immunoglobulins and complement in patients admitted for withdrawal from alcohol. J. Infect. Dis., 138, 747–753. Mandrekar, P., Dolganiuc, A., Bellerose, G., Kodys, K., Romics, L., Nizamani, R., and Szabo, G. (2002). Acute alcohol inhibits the induction of nuclear regulatory factor kappa B activation through CD14/toll-like receptor 4, interleukin-1, and tumor necrosis factor receptors: a common mechanism independent of inhibitory kappa B alpha degradation? Alcohol. Clin. Exp. Res., 26, 1609–1614. McAllister-Sistilli, C. G., Caggiula, A. R., Knopf, S., Rose, C. A., Miller, A. L., and Donny, E. C. (1998). The effects of nicotine on the immune system. Psychoneuroendocrinology, 23, 175–187. McGill, V., Kowal-Vern, A., Fisher, S. G., Kahn, S., and Gamelli, R. L. (1995). The impact of substance use on mortality and morbidity from thermal injury. J. Trauma, 38, 931–934. Mellon, R. D., and Bayer, B. M. (1998). Evidence for central opioid receptors in the immunomodulatory effects of morphine: review of potential mechanism(s) of action. J. Neuroimmunol., 83, 19–28.
559
Messingham, K. A., Fontanilla, C. V., Colantoni, A., Duffner, L. A., and Kovacs, E. J. (2000). Cellular immunity after ethanol exposure and burn injury: dose and time dependence. Alcohol, 22, 35–44. Mochida, S., Ohnishi, K., Matsuo, S., Kakihara, K., and Fujiwara, K. (1996). Effect of alcohol intake on the efficacy of interferon therapy in patients with chronic hepatitis C as evaluated by multivariate logistic regression analysis. Alcohol. Clin. Exp. Res., 20 (9 Suppl.), 371A–377A. Morato, G. S., and Morato, E. F. (1993). Differential effects of ethanol in mouse lines genetically selected for high and low antibody production. Brain Behav. Immun., 7, 224–230. Motivala, S. J., Dang, J., Obradovic, T., Meadows, G. G., Butch, A. W., and Irwin, M. R. (2003). Leptin and cellular and innate immunity in abstinent alcoholics and controls. Alcohol. Clin. Exp. Res., 27, 1819–1824. Moynihan, J., Kruszewska, B., Madden, K., and Callahan, T. (2004). Sympathetic nervous system regulation of immunity. J. Neuroimmunol., 147, 87–90. Mutchnick, M. G., and Lee, H. H. (1998). Impaired lymphocyte proliferative response to mitogen in alcoholic patients. Absence of a relation to liver disease activity. Alcohol. Clin. Exp. Res., 12, 155–158. Nalpas, B., Thepot, V., Driss, F., Pol, S., Courouce, A. M., Saliou, P., and Berthelot, P. (1993). Secondary immune response to hepatitis B virus vaccine in alcoholics. Alcohol. Clin. Exp. Res., 17, 295–298. Nelson, C. J., Schneider, G. M., and Lysle, D. T. (2000). Involvement of central mu- but not delta- or kappa-opioid receptors in immunomodulation. Brain Behav. Immun., 14, 170–184. Neuman, M. G., Brenner, D. A., Rehermann, B., Taieb, J., CholletMartin, S., Cohard, M., Garaud, J. J., Poynard, T., Katz, G. G., Cameron, R. G., Shear, N. H., Gao, B., Takamatsu, M., Yamauchi, M., Ohata, M., Saito, S., Maeyama, S., Uchikoshi, T., Toda, G., Kumagi, T., Akbar, S. M., Abe, M., Michitaka, K., Horiike, N., and Onji, M. (2001). Mechanisms of alcoholic liver disease: cytokines. Alcohol. Clin. Exp. Res., 25, 251S–253S. Nicolaou, C., Chatzipanagiotou, S., Tzivos, D., Tzavellas, E. O., Boufidou, F., and Liappas, I. A. (2004). Serum cytokine concentrations in alcohol-dependent individuals without liver disease. Alcohol, 32, 243–247. Nicolas, J. M., Fernandez-Sola, J., Fatjo, F., Casamitjana, R., Bataller, R., Sacanella, E., Tobias, E., Badia, E., and Estruch, R. (2001). Increased circulating leptin levels in chronic alcoholism. Alcohol. Clin. Exp. Res., 25, 83–88. Novick, D. M., Ochshorn, M., Ghali, V., Croxson, T. S., Mercer, W. D., Chiorazzi, N., and Kreek, M. J. (1989). Natural killer cell activity and lymphocyte subsets in parenteral heroin abusers and long-term methadone maintenance patients. J. Pharmacol. Exp. Ther., 250, 606–610. Omidvari, K., Casey, R., Nelson, S., Olariu, R., and Shellito, J. E. (1998). Alveolar macrophage release of tumor necrosis factoralpha in chronic alcoholics without liver disease. Alcohol. Clin. Exp. Res., 22, 567–572. Pacifici, R., Zuccaro, P., Farre, M., Pichini, S., Di Carlo, S., Roset, P. N., Palmi, I., Ortuno, J., Menoyo, E., Segura, J., and de la Torre, R. (2002). Cell-mediated immune response in MDMA users after repeated dose administration: studies in controlled versus noncontrolled settings. Ann. N. Y. Acad. Sci., 965, 421–433. Parlesak, A., Schafer, C., Paulus, S. B., Hammes, S., Diedrich, J. P., and Bode, C. (2003). Phagocytosis and production of reactive oxygen species by peripheral blood phagocytes in patients with different stages of alcohol-induced liver disease: effect of acute
560
III. Behavior and Immunity
exposure to low ethanol concentrations. Alcohol. Clin. Exp. Res., 27, 503–508. Pastor, I. J., Laso, F. J., Avila, J. J., Rodriguez, R. E., and GonzalezSarmiento, R. (2000). Polymorphism in the interleukin-1 receptor antagonist gene is associated with alcoholism in Spanish men. Alcohol. Clin. Exp. Res., 24, 1479–1482. Patel, M., Keshavarzian, A., Kottapalli, V., Badie, B., Winship, D., and Fields, J. Z. (1996). Human neutrophil functions are inhibited in vitro by clinically relevant ethanol concentrations. Alcohol, Clin. Exp. Res., 20, 275–283. Pauly, T., Dahmen, N., Szegedi, A., Wetzel, H., Bol, G. F., Ferdinand, K., and Hiemke, C. (1999). Blood ethanol levels and adenylyl cyclase activity in lymphocytes of alcoholic patients. Biol. Psychiatry, 45, 489–493. Pellegrino, T., and Bayer, B. M. (1998). In vivo effects of cocaine on immune cell function. J. Neuroimmunol., 83, 139–147. Pellegrino, T. C., Dunn, K. L., and Bayer, B. M. (2001). Mechanisms of cocaine-induced decreases in immune cell function. Int. Immunopharmacol., 1, 665–675. Penick, E. C., Powell, B. J., Nickel, E. J., Bingham, S. F., Riesenny, K. R., Reod, M. R., and Campbell, J. (1994). Co-morbidity of lifetime psychiatric disorder among male alcoholic patients. Alcohol. Clin. Exp. Res., 18, 1289–1293. Petersen, B. H., Steimel, L. F., and Callaghan, J. T. (1983). Suppression of mitogen-induced lymphocyte transformation in cigarette smokers. Clin. Immunol. Immunopathol., 27, 135–140. Petitto, J. M., McIntyre, T. D., McRae, B. L., Skolnick, P., and Arora, P. K. (1990). Differential immune responsiveness in mouse lines selectively bred for high and low sensitivity to ethanol. Brain Behav. Immun., 4, 39–49. Pezzone, M. A., Rush, K. A., Kusnecov, A. W., Wood, P. G., and Rabin, B. S. (1992). Corticosterone-independent alteration of lymphocyte mitogenic function by amphetamine. Brain Behav. Immun., 6, 293–299. Purohit, V., Khalsa, J., and Serrano, J. (2005). Mechanisms of alcoholassociated cancers: introduction and summary of the symposium. Alcohol, 35, 155–160. Rahim, R. T., Adler, M. W., Meissler J. J. Jr., Cowan, A., Rogers, T. J., Geller, E. B., and Eisenstein, T. K. (2002). Abrupt or precipitated withdrawal from morphine induces immunosuppression. J. Neuroimmunol., 127, 88–95. Redwine, L., Dang, J., Hall, M., and Irwin, M. (2003). Disordered sleep, nocturnal cytokines, and immunity in alcoholics. Psychosom. Med., 65, 75–85. Roselle, G. A., Mendenhall, C. L., Grossman, C. J., and Weesner, R. E. (1988). Lymphocyte subset alterations in patients with alcoholic hepatitis. J. Clin. Lab. Immunol., 26, 169–173. Rosenberger, P., Muhlbauer, E., Weissmuller, T., Rommelspacher, H., Sinha, P., Wernecke, K. D., Finckh, U., Rettig, J., Kox, W. J., and Spies, C. D. (2003). Decreased proopiomelanocortin mRNA in lymphocytes of chronic alcoholics after intravenous human corticotropin releasing factor injection. Alcohol. Clin. Exp. Res., 27, 1693–700. Ruiz, P., Berho, M., Steele, B. W., and Hao, L. (1998). Peripheral human T lymphocyte maintenance of immune functional capacity and phenotypic characteristics following in vivo cocaine exposure. Clin. Immunol. Immunopathol., 88, 271–276. Sander, M., Irwin, M., Sinha, P., Naumann, E., Kox, W. J., and Spies, C. D. (2002). Suppression of interleukin-6 to interleukin-10 ratio in chronic alcoholics: association with postoperative infections. Inten. Care Med., 28, 285–292. Sacanella, E., Estruch, R., Gaya, A., Fernandez-Sola, J., Antunez, E., and Urbano-Marquez, A. (1998). Activated lymphocytes [CD25-
super(+)] cells in well-nourished chronic alcoholics without ethanol-related diseases. Alcohol. Clin. Exp. Res., 22, 897–901. Samet, J. H., Horton, N. J., Traphagen, E. T., Lyon, S. M., and Freedberg, K. A. (2003). Alcohol consumption and HIV disease progression: are they related? Alcohol. Clin. Exp. Res., 27, 862–867. Schafer, M., Mousa, S. A., Zhang, Q., Carter, L., and Stein, C. (1996). Expression of corticotropin-releasing factor in inflamed tissue is required for intrinsic peripheral opioid analgesia. Proc. Natl. Acad. Sci. USA, 93, 6096–6100. Schenker, S. (1997). Medical consequences of alcohol abuse: is gender a factor? Alcohol. Clin. Exp. Res., 21, 179–181. Schleifer, S. J., Benton, T. S., Keller, S. E., and Dhaibar, Y. (2002). Immune measures in alcohol-dependent persons with minor health abnormalities. Alcohol, 26, 35–41. Schleifer, S. J., Keller, S. E., Bond, R. N., Cohen, J., and Stein, M. (1989). Depression and immunity: role of age, sex, and severity. Arch. Gen. Psychiatry, 46, 81–87. Schleifer, S. J., Keller, S. E., and Czaja, S. (2006). Major depression and immunity in alcohol dependent persons. Brain Behav. Immun., 20, 80–91. Schleifer, S. J., Keller, S. E., Shiflett, S. C., Benton, T., and Eckholdt, H. M. (1999). Immune changes in alcohol-dependent patients without medical disorders. Alcohol. Clin. Exp. Res., 23, 1199–1206. Schuckit, M. A., Anthenelli, R. M., Bucholz, K. K., Hesselbrock, V. M., and Tipp, J. (1995). The time course of development of alcohol-related problems in men and women. J. Stud. Alcohol, 56, 218–225. Sharp, C. W. (1998). Perspectives of neuroimmune issues and substances of abuse. J. Neuroimmunol, 83, 1–3. Shavit, Y., Depaulis, A., Martin, F. C., Terman, G. W., Pechnick, R. N., Zane, C. J., Gale, R. P., and Liebeskind, J. C. (1986). Involvement of brain opiate receptors in the immune-suppressive effect of morphine. Proc. Natl. Acad. Sci. USA, 83, 7114–7117. Shavit, Y., Wolf, G., Goshen, I., Livshits, D., and Yirmiya, R. (2005). Interleukin-1 antagonizes morphine analgesia and underlies morphine tolerance. Pain, 115, 50–59. Sjogren, H., Eriksson, A., and Ahlm, K. (2000). Role of alcohol in unnatural deaths: a study of all deaths in Sweden. Alcohol. Clin. Exp. Res., 24, 1050–1056. Song, C., Lin, A., De Jong, R., Vandoolaeghe, E., Kenis, G., Bosmans, E., Whelan, A., Scharpe, S., and Maes, M. (1999). Cytokines in detoxified patients with chronic alcoholism without liver disease: increased monocytic cytokine production. Biol. Psychiatry, 45, 1212–1216. Sopori, M. (2002). Effects of cigarette smoke on the immune system. Nat. Rev. Immunol., 2, 372–377. Sopori, M. L., Kozak, W., Savage, S. M., Geng, Y., Soszynski, D., Kluger, M. J., Perryman, E. K., and Snow, G. E. (1998). Effect of nicotine on the immune system: possible regulation of immune responses by central and peripheral mechanisms. Psychoneuroendocrinology, 23, 189–204. Spies, C. D., von Dossow, V., Eggers, V., Jetschmann, G., El-Hilali, R., Egert, J., Fischer, M., Schroder, T., Hoflich, C., Sinha, P., Paschen, C., Mirsalim, P., Brunsch, R., Hopf, J., Marks, C., Wernecke, K. D., Pragst, F., Ehrenreich, H., Muller, C., Tonnesen, H., Oelkers, W., Rohde, W., Stein, C., and Kox, W. J. (2004). Altered cell-mediated immunity and increased postoperative infection rate in long-term alcoholic patients. Anesthesiology, 100, 1088–1100. Spitzer, J. A., and Zhang, P. (1996). Gender differences in phagocytic responses in the blood and liver, and the generation of cytokine-
26. Psychoneuroimmunologic Aspects of Alcohol and Substance Abuse induced neutrophil chemoattractant in the liver of acutely ethanol-intoxicated rats. Alcohol. Clin. Exp. Res., 20, 914–920. Stefanini, G. F., Castelli, E., Foschi, F. G., Terzi, A., Biagi, P. L., Bordoni, A., Celadon, M., and Hrelia, S. (1996). Defective calcium increase and inositol phosphate production in anti-CD3– stimulated lymphocytes of alcoholics without progressive liver disease. Alcohol. Clin. Exp. Res., 20, 523–527. Stefanini, G. F., Mazzetti, M., Zunarelli, P., Piccinini, G., Amorati, P., Capelli, S., Cicognani, G., and Gasbarrini, G. (1989). In vivo effect of chronic ethanol abuse on membrane 1-glycoprotein of lymphocytes and immune response to various stimulating agents. Alcohol. Clin. Exp. Res., 13, 444–448. Swerdlow, N. R., Hauger, R., Irwin, M., Koob, G. F., Britton, K. T., and Pulvirenti, L. (1991). Endocrine, immune, and neurochemical changes in rats during withdrawal from chronic amphetamine intoxication. Neuropsychopharmacology, 5, 23–31. Szabo, G., Dolganiuc, A., Mandrekar, P., and White, B. (2004). Inhibition of antigen-presenting cell functions by alcohol: implications for hepatitis C virus infection. Alcohol, 33, 241–249. Szabo, G., Mandrekar, P., Verma, B., Isaac, A., and Catalano, D. (1994). Acute ethanol consumption synergizes with trauma to increase monocyte tumor necrosis factor alpha production late postinjury. J. Clin. Immunol., 14, 340–352. Szegedi, A., Anghelescu, I., Pauly, T., Dahmen, N., Muller, M. J., Wetzel, H., and Hiemke, C. (1998). Activity of the adenylyl cyclase in lymphocytes of male alcoholic patients is state dependent. Alcohol. Clin. Exp. Res., 22, 2073–2079. Tilg, H., and Diehl, A. M. (2000). Cytokines in alcoholic and nonalcoholic steatohepatitis. N. Engl. J. Med., 343, 1467–1476. Tollerud, D. J., Brown, L. M., Blattner, W. A., Mann, D. L., Pankiw-Trost, L., and Hoover, R. N. (1991). T cell subsets in healthy black smokers and nonsmokers. Evidence for ethnic group as an important response modifier. Am. Rev. Respir. Dis., 144, 612–616. Tollerud, D. J., Clark, J. W., Brown, L. M., Neuland, C. Y., PankiwTrost, L. K., Blattner, W. A., and Hoover, R. N. (1989). The influence of age, race, and gender on peripheral blood mononuclearcell subsets in healthy nonsmokers. J. Clin. Immunol., 9, 214–222. Torres, K. C., Antonelli, L. R., Souza, A. L., Teixeira, M. M., Dutra, W. O., and Gollob, K. J. (2005). Norepinephrine, dopamine and dexamethasone modulate discrete leukocyte subpopulations and cytokine profiles from human PBMC. J. Neuroimmunol., 166, 144–157.
561
Vallejo, R., de Leon-Casasola, O., and Benyamin, R. (2004). Opioid therapy and immunosuppression: a review. Am. J. Ther., 11, 354–365. Vidal, C., Armisen, M., Dominguez-Santalla, M. J., Gude, F., Lojo, S., and Gonzalez-Quintela, A. (2002). Influence of alcohol consumption on serum immunoglobulin E levels in atopic and nonatopic adults. Alcohol. Clin. Exp. Res., 26, 59–64. Wang, X., Douglas, S. D., Metzger, D. S., Guo, C. J., Li, Y., O’Brien, C. P., Song, L., Davis-Vogal, A., and Ho, W. Z. (2002). Alcohol potentiates HIV-1 infection of human blood mononuclear phagocytes. Alcohol. Clin. Exp. Res., 26, 1880–1886. Watkins, L. R., and Maier, S. F. (2002). Beyond neurons: evidence that immune and glial cells contribute to pathological pain states. Physiol. Rev., 82, 981–1011. Watson, R. R., Jackson, J. C., Hartmann, B., Sampliner, R., Mobley, D., and Eskelson, C. (1985). Cellular immune functions, endorphins, and alcohol consumption in males. Alcohol. Clin. Exp. Res., 9, 248–254. Watson, S. J., Benson J. A. Jr., and Joy, J. E. (2000). Marijuana and medicine: assessing the science base: a summary of the 1999 Institute of Medicine report. Arch. Gen. Psychiatry, 57, 547–552. Watzl, B., and Watson, R. R. (1993). Role of nutrients in alcoholinduced immunomodulation. Alcohol Alcohol., 28, 89–95. Weber, R. J., Gomez-Flores, R., Smith, J. E., and Martin, T. J. (2004). Immune, neuroendocrine, and somatic alterations in animal models of human heroin abuse. J. Neuroimmunol., 147, 134–137. Weber, R. J., and Pert, A. (1989). The periaqueductal gray matter mediates opiate-induced immunosuppression. Science, 245, 188–190. Wrona, D., Sukiennik, L., Jurkowski, M. K., Jurkowlaniec, E., Glac, W., and Tokarski, J. (2005). Effects of amphetamine on NKrelated cytotoxicity in rats differing in locomotor reactivity and social position. Brain Behav. Immun., 19, 69–77. Wybran, J., Appelboom, T., Famaey, J. P., and Govaerts, A. (1979). Suggestive evidence for receptors for morphine and methionineenkephalin on normal human blood T lymphocytes. J. Immunol., 123, 1068–1070. Zorrilla, E. P., Luborsky, L., McKay, J. R., Rosenthal, R., Houldin, A., Tax, A., McCorkle, R., Seligman, D. A., and Schmidt, K. (2001). The relationship of depression and stressors to immunological assays: a meta-analytic review. Brain Behav. Immun., 15, 199–226.
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C H A P T E R
27 Schizophrenia and Immunity MATTHIAS ROTHERMUNDT AND VOLKER AROLT
I. II. III. IV. V. VI. VII. VIII. IX.
INTRODUCTION 563 MICROGLIA 564 ASTROGLIA 565 ANTIBODIES 566 BLOOD-BRAIN BARRIER (BBB) 568 HUMORAL IMMUNITY 568 CELLULAR IMMUNITY 569 CYTOKINES 569 HYPOTHESES AND PERSPECTIVES 571
quently involves young adults and can produce severe psychological, social, and vocational disability during the potentially most creative and productive years of a person’s life. Not only is the suicide rate in schizophrenia high, but the deaths tend to occur at a relatively young age. This results in an enormous loss of total years of expected life. Cost-of-illness studies have estimated that approximately 1.5% to 3% of national health expenditures in developed countries and 22% of the costs of mental illness are related to schizophrenia. The National Institute of Mental Health has estimated that schizophrenia costs the United States about $32.5 billion each year for about 2 million patients with the diagnosis. For comparison, the estimated cost of depression is about $30 billion each year for about 19 million patients with that diagnosis (Thieda et al., 2003). About two-thirds of this cost is a consequence of the relative lack of productive employment. In human suffering the social and psychological costs cannot be expressed monetarily. Despite major research efforts, the etiology and pathogenesis have yet to be defined. Two major hypotheses on the pathogenesis of schizophrenia have been discussed. (1) The neurodevelopmental hypothesis suggests that schizophrenia is a disorder based on disturbances in the early development of neurons and glial cells starting in the second trimenon of intrauterine life. It is supported by several pieces of evidence: (a) the presence of minor physical anomalies; (b) the presence of neurological, cognitive, and behavioral dysfunction long before illness onset; (c) a course and outcome of the illness itself that is predominantly incompatible with a classical degenerative disorder; (d) the presence of ventricular
ABSTRACT The involvement of immunological and immunopathological mechanisms in the etiopathogenesis of schizophrenia has been a matter of research with recently increasing effort. This chapter reviews the findings focusing on microglia, astroglia, antibodies against brain structures and neurotropic viruses, blood-brain barrier, humoral immunity, cellular immunity, and cytokines. Evidence for the three primarily postulated hypotheses (infectious hypothesis, autoimmune hypothesis, Th1/Th2 imbalance) is critically discussed. On the basis of the findings, perspectives for future research are outlined, aiming at a precise and consequent strategy to elucidate a potential involvement of immune mechanisms in the etiopathogenesis of schizophrenia.
I. INTRODUCTION Schizophrenia is a severe psychiatric disorder with a worldwide prevalence of about 1%. The illness frePSYCHONEUROIMMUNOLOGY, 4E VOLUME I
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Copyright © 2007 by Elsevier, Inc. All rights of reproduction in any form reserved.
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enlargement and decreased cortical volume at onset of symptoms, if not earlier; (e) the presence and nature of cytoarchitectural abnormalities (such as neuron density, number and morphology, dendritic arbors and spines, synapse-related proteins); and (f) the absence of postmortem evidence of neurodegeneration comprising gliosis as a sequelae of a classic degenerative mechanism (Arnold, 1999; Harrison, 1999; Marenco and Weinberger, 2000). The second (2) and, for a long time, opposing approach was called the neurodegenerative hypothesis. More than 100 years ago Kraepelin and Alzheimer were convinced that schizophrenia was an organic disease involving destruction of neural tissue. This hypothesis fell behind when researchers failed to consistently demonstrate a destruction of neurons and glial cells or gliosis as a consequence of a passed neurodegenerative process. The implementation of imaging techniques such as CT and MRI as well as improved methodologies and new techniques in postmortem studies, however, has confirmed that neurodegeneration is present in at least a subgroup of schizophrenic patients. There are convincing data showing (a) progression of cerebral volume reduction during the course of disease (DeLisi et al., 1999; Gur et al., 1998; Lieberman et al., 2001; Pearlson and Marsh, 1999; Shenton et al., 2001). A classic neurodegenerative mechanism involving loss of neurons and development of gliosis, however, appears unlikely to be relevant for schizophrenia. Brains from patients who had suffered from schizophrenia mostly show (b) unchanged numbers of neurons but a reduction of neuronal cell size and neuropil that accounts for the loss of brain volume (Harrison, 1999; McGlashan and Hoffman, 2000; Powers, 1999; Selemon and GoldmanRakic, 1999). A reduction of neuropil involves compromised cell structure and decrease of neuronal connectivity, resulting in a presumed loss of functional communication between neurons. Beyond that, several studies reported (c) changes in synaptic proteins and their gene expression (Glantz and Lewis, 2000; Harrison and Eastwood, 2001; Karson et al., 1999; Kung et al., 1998; Mirnics et al., 2001). These findings support a diminution or dysfunction of dendrites, neurites, and synapses in schizophrenia (Jones et al., 2002). Recently, several authors endeavored to integrate the neurodevelopmental and the neurodegenerative aspects into a comprehensive pathogenetic hypothesis of schizophrenia (Bartzokis et al., 2002; Lieberman et al., 1997; Mirnics et al., 2001; Woods et al., 1998). Immune factors play an important role in neurodevelopmental as well as neurodegenerative processes. Inflammatory and immune reactions directly influence
neuronal proliferation, differentiation, migration, and apoptosis. Therefore, it is obvious that immune mechanisms have to be considered as potential pathogenic factors of schizophrenia. This has been a matter of scientific discussion since Esquirol described an “epidemic” appearance of psychotic disorders in 1845. The review summarizes the current knowledge of altered immunity in schizophrenia and evaluates the contribution of immune factors to the pathogenesis of schizophrenia (Figure 1).
II. MICROGLIA Microglial cells represent a major part of the cerebral immune system and are located within the brain parenchyme behind the blood-brain barrier. They originate from mesodermal hemapoietic precursors and are slowly turned over and replenished by proliferation in the adult central nervous system. In the healthy brain resting, ramified microglia function as supportive glia cells, and their activation status is regulated by neurons through soluble mediators and cell-cell contact. However, in response to brain pathology, microglia become activated: acquisition of innate immune cell functions render microglia competent to react toward brain injury through tissue repair or induction of immune responses. They are capable of phagocytosis, secretion of cytokines and neural growth Lymphocytes NK Cells Cytokines
Astroglia
Microglia Monocytes
B R A I N
Neurons
Antibodies
Viruses
Blood-Brain Barrier Immunoglobulins
BLOOD
FIGURE 1 Interaction between various immune subsystems in schizophrenia.
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factors, and antigen presentation. In addition, microglia are involved in central nervous system development and remodeling. In certain pathological conditions, however, microglia activation may sustain a chronic inflammation of the brain, leading to neuronal dysfunction and cell death. This might be mediated by the microglial release of extracellular toxic reactive oxygen and nitrogen species (Vilhardt, 2005). Despite the important role of microglia in inflammation of the brain, only a few studies focused on these cells in schizophrenia. Recently, it was demonstrated in two postmortem studies (Bayer et al., 1999; Radewicz et al., 2000) that activated microglia cells can be observed in a subset of patients with schizophrenia. Hirsch (2004) undertook a PET study using (R)PK11195 to label activated microglia cells. Patients with schizophrenia showed increased isotope binding throughout the cortex with some regional accentuation in the frontal lobes. A significant correlation was found between the reduction in the amplitude of mismatch negativity and increased (R)-PK11195 binding. Solov’eva and Orlovskaia (1979) reported that embryos of schizophrenic mothers show signs of increased microglia activity. In elderly schizophrenic patients, Falke et al. (2000) found no signs of microgliosis, while Wierzba-Bobrowicz and colleagues (2004) described signs of microglia degeneration (cytoplasm shrinkage, thinning, shortening, and fragmentation of their processes). The evidence for an activation of microglia cells in schizophrenia is not sufficient so far. However, the application of advanced techniques such as (R)PK11195 PET is promising, especially since it can be performed in various states of disease and correlated with functional aspects.
III. ASTROGLIA Astrocytes (macroglia) are the major glial cells within the central nervous system (CNS) and have a number of important physiological properties related to CNS homeostasis. Besides regulating the extracellular ionic and chemical environment, they serve as immunocompetent cells within the brain. They are able to express class II major histocompatibility complex (MHC) antigens and co-stimulatory molecules (B7 and CD40) that are critical for antigen presentation and T-cell activation. As immune effector cells, they influence aspects of inflammation and immune reactivity within the brain, e.g., by promoting Th2 responses. In addition, astrocytes produce a wide array of chemokines and cytokines (Dong and Benveniste, 2001).
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Early studies focusing on astrocytes in schizophrenia were initiated to search for astrogliosis as a sign of neurodegeneration supporting the neurodegenerative hypothesis (Arnold et al., 1996, 1998; Falkai et al., 1999). None of these studies could demonstrate an increase of astrocyte numbers. Quite contrary, Webster et al. (2001) reported a reduction of glial fibrillary acidic protein (GFAP)-immunoreactive astroglia adjacent to blood vessels of the prefrontal cortex. Rajkowska et al. (2002) also found decreased GFAP-positive astrocytes, but in layer V of the dorsolateral prefrontal cortex. In the serum of schizophrenic patients, antibodies against astrocyte muscarinic cholinoceptors were reported (Borda et al., 2004). A DNA microarray study revealed that the highest frequency of mRNA expression alterations occurred in astrocyte- and oligodendrocyte-related genes in the prefrontal cortex of schizophrenic patients (Sugai et al., 2004). Matute and colleagues (2005) discovered a 2.5-fold increase in astrocytic glutamate transporter (GLT-1) mRNA in the prefrontal cortex of schizophrenics. Protein concentration and function of the transporter were also elevated. A different approach to assess the functionality of astrocytes in patients suffering from schizophrenia is to measure astrocytic markers that can be detected in CSF and serum. This offers the opportunity to investigate patients in various stages of disease, including drug-naïve first-episode patients. S100B can serve as such a marker. S100B–-a small, Ca2+-binding, astrocytic protein–plays an important role modulating the proliferation and differentiation of neurons and glia cells. It is involved in the regulation of the cellular energy metabolism and interacts with many immunological functions of the brain (Adami et al., 2001; Vives et al., 2003). It is highly brain specific and easily passes the bloodbrain barrier. Just recently, Liu and colleagues (2005) reported an association between a certain haplotype of the S100B-gene (four SNPs examined) and schizophrenia, making the S100B-gene a susceptibility gene. For S100B protein concentrations in schizophrenia, the data base is quite consistent. Rothermundt et al. (2004a) showed that S100B is increased in the CSF and serum of schizophrenic patients. CSF and serum levels are in high correlation, and the S100B concentration is correlated with the severity of symptoms. Several other studies focused solely on serum concentrations. Wiesmann and co-workers (1999) presented a significantly increased serum concentration of S100B in schizophrenic subjects under neuroleptic medication. S100B levels tended to be higher in patients with residual symptomatology and long-term continuous psychotic symptoms. The study by Gattaz et al. (2000)
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showing decreased S100B levels in chronic schizophrenic patients has to be cautiously interpreted since the samples used (citrate plasma) were not adequate for the assays used. In 2001 the same group published data on medication-free schizophrenic patients (Lara et al., 2001). The serum of the patients contained significantly higher concentrations of S100B than that of the matched healthy controls and was negatively correlated with illness duration. Schroeter and colleagues (2003) reported increased S100B serum concentrations in schizophrenic patients treated with anti-psychotic drugs, while untreated patients showed normal values. Patients with deficit schizophrenia had higher S100B concentrations than non-deficit subtypes. In a longitudinal study paranoid schizophrenics were examined in acute stage of disease without medication and after 6 weeks of anti-psychotic treatment (Rothermundt et al., 2001b). Upon admission, the S100B serum level was significantly higher compared to the matched healthy controls. After 6 weeks of treatment, the level of significance was no longer reached. However, S100B levels after treatment were positively correlated with severity of negative symptoms after 6 weeks, indicating that little change or even deterioration of the negative symptomatology was associated with high S100B levels (Rothermundt et al., 2001b). Another longitudinal study focusing on chronic schizophrenic patients with primarily negative symptoms supported these findings. In a large sample, serum S100B concentrations were increased at the beginning of the study as well as after 12 and 24 weeks of standardized treatment. Patients with high S100B concentration at intake showed a slower improvement of symptoms than patients with normal S100B levels (Rothermundt et al., 2004b). In summarizing the evidence, it is likely that a dysfunction of astrocytes might be a pathogenic factor for schizophrenia. However, replication studies in independent samples are needed, and the character of the astrocytic dysfunction remains to be concretized.
IV. ANTIBODIES In 1937 the German neuropsychiatrist LehmannFacius (1937) pointed to the possible role of an autoimmune process in the etiology of schizophrenia. This assumption is supported by certain clinical features that can be observed in both schizophrenia and autoimmune diseases. Both categories of diseases have onset in late adolescence or early adulthood, often triggered by psychosocial distress, drug abuse, and physical injury. In both cases, variability, of course, often with acute disease episodes and subsequent deficit
remittance, is regularly observed. Such clinical features can also be observed in acute and chronic (viral) infections. Menninger (1919, 1926, 1928) reported the occurrence of schizophrenia-like psychoses in victims of the influenza pandemic which occurred after the end of World War I. Furthermore, there is an ongoing discussion on the association between viral infections (influenza) during pregnancy (second trimester) and the birth of a child who later developed schizophrenia (Torrey et al., 1997). If this were the case, a line of evidence would point to the possibility that a viral contact with an extremely immature immune system would have taken place, leading to enduring immunological abnormalities. These observations have resulted in different forms of infectious/autoimmune hypotheses of schizophrenia. One hypothesis states that a virus, possibly a retrovirus, causes direct structural or functional damage to the brain, eventually leading to schizophrenic psychosis (for review, see Kirch, 1993). Another hypothesis suggests that an early viral contact of the fetal brain induces a dysfunctional reaction of the immature immune system, leading to autoimmune pathology (for review, see Kirch, 1993).
A. Antibodies against Neurotropic Viruses Antibodies against several neurotropic viruses have been the subject of research throughout the years. Most studies have focused on the family of herpes viruses. Bartova et al. (1987) reported antibodies against herpes simplex virus (HSV) in the CSF of 16% of studied patients with schizophrenia. Pelonero et al. (1990) found increased HSV antibody levels in the serum of 32% of investigated schizophrenics. An increased CSF/serum antibody ratio suggesting local antibody production in the brain was found in 4% of studied schizophrenic subjects (Albrecht et al., 1980). Pandurangi et al. (1994) reported an association between high HSV antibody titers and left frontal cortical atrophy. Dickerson and colleagues (2003) demonstrated an association between serologic evidence of HSV infection and cognitive impairment in schizophrenia. The offspring of mothers with antibodies to HSV appear to be at increased risk for the development of schizophrenia in adulthood (Buka et al., 2001). On the other hand, many researchers have failed to demonstrate increased serum HSV antibody titers in schizophrenia (review: Rothermundt et al., 2001a). Cytomegalovirus (CMV) antibodies were discovered in the CSF of 11% of schizophrenics (Torrey et al., 1982), and Albrecht et al. (1980) reported signs of local CMV antibody production in the brains of 68% of
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patients. In the serum of schizophrenic subjects, no changes in antibody titers were observed (review: Rothermundt et al., 2001a). DeLisi et al. (1986) found increased quantities of Epstein Barr Virus (EBV) antibodies in the serum of schizophrenics. Decreased titers against mumps virus and unchanged titers against rubella and measles were reported. Measles antibodies in the CSF were increased in 35% of patients (review: Rothermundt et al., 2001a). Fukuda et al. (1999) discovered no changes in antibody titers against HSV, CMV, VZV, EBV, measles, rubella, mumps, influenza, and Japanese encephalitis virus between an acutely psychotic state and after 8 weeks of treatment in schizophrenic patients. More recent studies have focused on Borna Disease Virus (BDV), a neurotropic, single-stranded RNA virus. Between 3% and 45% of schizophrenic patients were reported to have BDV serum antibodies compared to 0–5% in various samples of controls without psychiatric disorder (review: Rothermundt et al., 2001a; Terayama et al., 2003; Yang et al., 2003). Waltrip et al. (1997) observed higher BDV antibody levels in schizophrenic patients with deficit syndrome, whereas Richt et al. (1997) discovered no BDV antibodies in patients suffering from psychosis. Antibodies against retroviral antigens were reported in 52% of studied psychotic patients (Hart et al., 1999). Karlsson et al. (2001) demonstrated sequences homologous to retroviral pol genes in the CSF of 28.6% of patients with recent onset of schizophrenia. Antibodies against non-human primate retroviruses (MasonPfizer monkey virus [MPMV], baboon endogenous virus [BaEV], simian retrovirus type 5 [SRV-5]) were observed to be more frequent in schizophrenic patients than healthy controls (Lillehoj et al., 2000), e.g., MPMV antibodies in 28.9% first-episode schizophrenia patients as compared to 3.7% of the unaffected controls. Serum antibodies against the viruses of the herpes family are very common in the general population worldwide. Most of the antibody carriers are asymptomatic, and the assumption of active disease in individuals should be based on increasing specific antibody titers in the same individual over a defined period of time. Changes in antibody production at local sites are helpful in substantiating an ongoing infectious pathology in the brains of tested individuals. Only a few of the above-mentioned studies adhered to these criteria. This fact might be primarily responsible for the inconsistency of the findings. In addition, inconsistent laboratory methods used and differing definitions of antibody reactivity contribute to the diversity of findings. However, it is a promising strategy to associate antibody titers or virus load with various phenotypes such
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as cognitive impairment (Dickerson et al., 2003) or electrophysiological abnormalities. This strategy will help to identify a subgroup of patients which is more likely to have an infectious pathogenesis for their disorder.
B. Autoantibodies against Brain Structures Several studies have focused on specific antibodies against brain structures. Serum anti-brain antibodies were positive in 28–95% of studied schizophrenics, while in several other investigations this finding could not be reproduced (review: Rothermundt et al., 2001a). Pandey et al. (1981) reported anti-brain antibodies in serum and CSF of 48% of studied schizophrenic patients. More recent studies have investigated specific brain regions, with serum antibodies against the following regions being reported: hippocampus, septum, cingulate gyrus, amygdala, and frontal cortex (review: Rothermundt et al., 2001a). Another approach to specifying the early finding was to study specific structures of cells in the brain. Most of these findings have not been reproduced so far: antibodies against membrane antigen, ganglioside, nicotinic acetylcholine receptor, GFAP, S100, neuronspecific enolase, p80–85 protein of a human neuroblastoma cell line, myelin basic protein (review: Rothermundt et al., 2001a), cholinergic muscarinic receptor (Borda et al., 2002), and nerve growth factor (NGF) (Shcherbakova et al., 2003, 2004). Anti-neuronal cell antibodies (review: Rothermundt et al., 2001a) and antibodies against astrocytes (Borda et al., 2004) were also reported. The search for antibodies against specific neuronal, glial, or microglial structures represents a fundamentally interesting scientific approach in the search for etiopathogenetic factors of schizophrenia. An antigenantibody interaction might be responsible for functional changes in the brains of a subgroup of patients suffering from schizophrenia. This hypothesis is compatible with the fact that the brains of schizophrenics usually show no glial scars or major defects but rather cellular pruning, a diminution of dendrites, and synaptic contacts. Unfortunately, the search for antibodies has not yet gone beyond the screening stage. Most findings have not been replicated in independent samples, and possible pathophysiological consequences of antigen-antibody-interactions in the brains of schizophrenic patients have not been explored. Cross-reactivity of each tested antibody has to be considered to prevent false positive results and to document the specificity of the antibody. Until now
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researchers have not been successful in identifying clinical or biological subtypes of schizophrenic patients by means of specific antibodies. It appears reasonable to correlate specific phenotypes identified by imaging, electrophysiology, or neuropsychology with antibodies against specific brain regions, cell types, or molecular structures. Subtyping merely according to psychopathology obviously is not promising.
V. BLOOD-BRAIN BARRIER (BBB) In several studies an impairment of the blood-brain barrier in schizophrenia has been discussed. Between 18% and 31% of studied subjects showed signs of increased permeability of the BBB (review: Rothermundt et al., 2001a). In these patients reduced concentrations of the soluble intercellular adhesion molecule-1 (sICAM-1) (Krönig et al., 2005; Schwarz et al., 2000) and the very late antigen-4 (VLA-4) positive CD4+ and CD8+ cells were reported (Müller et al., 1999). Krönig and co-workers tried to find a correlation between sICAM-1 concentrations and a polymorphism of the respective gene. This could be seen in healthy controls but not in schizophrenic patients (Krönig et al., 2005). Furthermore, endogenous CNS IgG-production was detected (review: Rothermundt et al., 2001a). Heat shock protein 60 (hsp60) antibodies were discovered in 10–62% of subjects suffering from schizophrenia (review: Rothermundt et al., 2001a); antibodies against hsp70 and hsp90 were detected in 31% or 20%, respectively (Kim et al., 2001). Autoantibodies against a 60 kDa protein were demonstrated by Wang et al. (2003). Potential target proteins include hsp60 and protein associated with MYC (PAM). These findings might indicate that an increased permeability of the BBB could play an important role in the understanding of possible immunopathogenic mechanisms in schizophrenia. It facilitates the penetration of T-cells to fight an inflammatory CNS process. Interleukin-2 (IL-2) is also known to modify the permeability of the BBB. An increased permeability of the TABLE 1 IgA
IgE
IgG
Increased Normal Decreased
Number of studies reporting evidence.
IgM
BBB facilitates the spread of a primarily local CNS process into the periphery or the invasion of infectious pathogens, causing damage to the CNS.
VI. HUMORAL IMMUNITY Several studies have focused on serum immunoglobulins and acute phase proteins in schizophrenic patients. Immunoglobulin M (IgM) may be an index of acute infection, while immunoglobulin G (IgG) titers are more persistently elevated after infection. The results of immunoglobulins are inconsistent (Table 1). IgG, IgM, and IgA concentrations in the serum of patients were reported to be increased, normal, or decreased (review: Rothermundt et al., 2001a). IgE levels were reported to be increased (Ramchand et al., 1994; Sugerman et al., 1982) in patients with poor therapeutic response or normal (Cazzullo et al., 1998). The producers of immunoglobulins, the B-lymphocytes, were shown to be increased at least in subgroups of studied patients, while others found no differences between patients and healthy controls (review: Rothermundt et al., 2001a). Maes et al. (1993, 1995) reported increased transferrin receptor serum levels. Neopterin was normal in urine, normal, or increased in serum (review: Rothermundt et al., 2001a). Overall complement activity (review: Rothermundt et al., 2001a) was normal although certain parts of the complement were up(C1, C3, C4) or downregulated (C2) (Hakobyan et al., 2005). C-reactive protein was increased (Mazzarello et al., 2004) or normal (Wilke et al., 1996). Acute phase proteins and immunoglobulins are non-specific markers of changes in the immune system of the body. Their concentrations can be changed under many different conditions such as infection, inflammation, and stress. As separate parameters, they cannot be specifically related to the development of schizophrenic psychosis but might be helpful as additional parameters in characterizing the role of specific immune subsystems.
Humoral Immunity
B-lymphocytes
C-reactive protein
Neopterin
Transferrin receptor
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VII. CELLULAR IMMUNITY Leukocytes and especially lymphocytes have been a matter of research interest in schizophrenic psychosis for quite some time. In one of the first immunopathological studies on schizophrenia ever published, Bruce and Peebles (1903) observed increased leukocyte counts especially during the acute phase of the illness. This finding was reproduced by Zorilla et al. (1996), while Rothermundt et al. (1998) found no leukocytosis in schizophrenia. Lymphocytes were extensively studied but with conflicting results (Table 2). The contradictions could not be solved as yet, not even by lymphocyte subtyping. Lymphocytes were reported to be unchanged or increased (review: Rothermundt et al., 2001a). Tlymphocytes were shown to be increased, decreased, or unchanged. The determination of T-helper cells (CD4) also resulted in conflicting results showing increased as well as decreased or unchanged numbers. The same holds true for T-suppressor cells (CD8) (review: Rothermundt et al., 2001a). Nikkilä et al. (1995) saw increased CD4 and CD8 cells in the CSF of some patients, while others showed decreased numbers. Monocytes were reported to be increased in blood (Zorilla et al., 1996) and CSF (Nikkilä et al., 1999). Natural killer (NK) cells were found to be increased (Sasaki et al., 1994) or decreased (Sperner-Unterweger et al., 1999). Counting absolute or relative numbers of immunocompetent cells in the blood of patients obviously does not help to unravel whether there is an immunopathology that might be linked to the etiopathogenesis of schizophrenia. This method is too non-specific and may be too sensitive concerning confounding variables. It is unlikely that a defect in the immune system reflected by the counts of defined groups of immunocompetent cells is relevant in the pathogenesis of schizophrenia. Furthermore, minor infections not involving the central nervous system as well as stress or medication largely influence the numbers and composition of immunocompetent cells without any releTABLE 2 Lymphocytes
T-lymphocytes
Increased Normal Decreased
Number of studies reporting evidence.
vance regarding the pathophysiology of schizophrenia. Focusing on the functional capacity and the degree of activation of certain specific subsystems appears to be more promising (see the next section, titled “Cytokines”). Changes in the counts of immunocompetent cells in CSF indicate ongoing pathology in the central nervous system (CNS). The potential confounding effect of infections outside the CNS is minimized by focusing on CSF measurements. However, these findings do not indicate specificity regarding the pathophysiology of schizophrenia but rather show unspecific signs of CNS infection.
VIII. CYTOKINES The function of T-lymphocytes as a major part of the adaptive immune system has become a focus of interest for immunological research in schizophrenia during the last 15 years. Technical advances have permitted different cytokines and activation markers to be studied. Cytokines represent a class of signaling proteins produced by immunocompetent cells with numerous important functions in immune regulation. In various animal experiments, intrauterine or perinatal inflammatory exposure was shown to cause changes in cytokine concentrations and produce similar behavioral changes in the offspring as seen in schizophrenia. Maternal infection increases TNF-α and decreases BDNF and NGF (Gilmore et al., 2005). A disruption of prepulse inhibition in the offspring (Borell et al., 2002; Tohmi et al., 2004) could be shown, which was reversed by application of anti-psychotic medication. In humans, Brown et al. (2004) reported increased IL-8 serum concentrations in the second trimester of pregnancy in mothers whose offspring later developed schizophrenia. The cytokines interleukin-2 (IL-2) and interferongamma (IFN-γ) are produced by T-helper cells and are functionally closely related. They play a major role in the regulation of T-cell–mediated immunity. In CSF,
Cellular Immunity T-helper cells
T-suppressor cells
Monocytes
NK cells
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three studies demonstrated unchanged IL-2 levels (Barak et al., 1995; El-Mallakh et al., 1993; Rapaport et al., 1997), while two studies reported increased concentrations of IL-2 (Licinio et al., 1993; McAllister et al., 1995); in one study an increase in IL-2 predicted the recurrence of psychotic symptoms in relapse-prone schizophrenics (McAllister et al., 1995). The measurement of serum concentrations of these cytokines was not a promising method, showing mostly normal values (Barak et al., 1995; Becker et al., 1990; Gattaz et al., 1992; Xu et al., 1994) with two exceptions (Theodoropoulou et al., 2001; Zhang et al., 2003: IL-2 increased). Several groups then started to investigate the capacity of T-cells to produce cytokines upon mitogen stimulation. In many studies it was shown that schizophrenic patients have a reduced capacity to produce IL-2 (review: Kaminska et al., 2001; Koliaskina et al., 2004; Mahendran et al., 2004; Rothermundt et al., 2001a; Zhang et al., 2002) and IFN-g (review: Kaminska et al., 2001; Koliaskina et al., 2004; Rothermundt et al., 2001a). However, O’Donnell (1996) and Cazzullo et al. (1998, 2001, 2002) were unable to reproduce these findings (Table 3). The serum concentration of the soluble IL-2 receptor (sIL-2R) indicating the degree of activation of T-helper cells was reported by most groups to be increased (review: Rothermundt et al., 2001a). However, some studies reported normal sIL-2R concentrations (Erbagci et al., 2001; Haack et al., 1999; Naudin et al., 1997; O’Donnell et al., 1996; Villemain et al., 1989); one
TABLE 3 IL-2 CSF
IL-2 serum
IL-2 production
Increased
Normal
Decreased
Number of studies reporting evidence.
IFN-g production
study reported decreased levels (Kowalski et al., 2000). It was discussed whether the increase of sIL-2R might be a medication artifact since unmedicated patients had normal levels but medicated patients had increased concentrations in some studies (Maes et al., 1996; Müller et al., 1997b). Gaughran and colleagues (2002) found elevated sIL-2R levels in first-degree relatives of patients with schizophrenia. T-helper cells are subdivided into functionally different subgroups. Type 1 helper cells (Th1) evolve mainly from pro-inflammatory action, producing IL-2 and IFN-γ among others. The products of the type 2 helper cells (Th2) such as interleukin-10 (IL-10) are antagonists of the type 1 cytokines. The production of IL-10 was reported to be increased (Cazzullo et al., 1998), unchanged (Kaminska et al., 2001), or decreased (Koliaskina et al., 2004; Rothermundt et al., 1996); serum concentration was increased (Maes et al., 2002). The serum concentration of interleukin-6 (IL-6), a cytokine produced by several different immunocompetent cells, was reported to be increased (review: Rothermundt et al., 2001a; Kaminska et al., 2001; Zhang et al., 2003) or normal (review: Erbagci et al., 2001; Rothermundt et al., 2001a). Frommberger et al. (1997) showed increased levels of IL-6 in acutely psychotic patients with normalization in remission. The soluble IL-6 receptor (sIL-6R) was shown to be increased (Lin et al., 1998) or decreased (Maes et al., 1994), while Müller et al. (1997a, 1997b) reported normal concentra-
Cytokines sIL-2R
IL-10 production
IL-6
sIL-6R
IL-1
TNF-a
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tions in unmedicated and decreased levels in medicated schizophrenics. Conflicting results were reported concerning serum concentrations of the fast-acting monokines (produced by monocytes), interleukin-1 (IL-1), and tumor necrosis factor-alpha (TNF-a) (review: Rothermundt et al., 2001a). Various other cytokines were investigated, showing increased (Kaminska et al., 2001; Maes et al., 2002; Zhang et al., 2002) or normal (Erbagci et al., 2001) concentrations of IL-8, normal IL-12 (Kim et al., 2002), and elevated IL-18 (Tanaka et al., 2000). Measuring the plasma cytokine response to surgical stress, Kudoh et al. (2001) found decreased levels of IL-6 and IL-8 in schizophrenic patients, while TNF-α did not change. Genetic studies investigating polymorphisms of genes encoding cytokines or cytokine receptors have recently been started. For IL-1 (Chowdari et al., 2001) and IL-4 (Jun et al., 2003a), no associations were found, while a polymorphism of the IL-1 receptor antagonist (IL-1RA) was identified in a Korean population with an odds ratio of 2.24 (Kim et al., 2004). For IL-10, significant findings were reported by Chiavetto et al. (2002) and Yu et al. (2004), while Jun and co-workers (2003b) failed to reproduce this finding. In the light of these findings, up to now two subsystems show convincing results to strengthen the hypothesis that an immunopathology might be involved in the etiopathogenesis of schizophrenia: the IL-6 system and even more so the IL-2/IFN-γ system (Table 3). The inconsistencies in the IL-6 system might be clarified by studying schizophrenic phenotypes characterized by imaging, electrophysiology, and neuropsychology. The IL-2/IFN-γ system offers fairly consistent findings in schizophrenic patients and compatible data from CSF, serum, and cell culture stimulation experiments. There is, to date, considerable evidence that an altered regulation of the IL-2/IFN-γ system plays a role in the development of autoimmune disorders. An in vivo activation of T-cells in autoimmune disorders is typically reflected in increased serum levels of their products, namely interleukin-2 (IL-2) and the soluble interleukin-2 receptor (sIL-2R). Paradoxically, a decreased in vitro production of IL-2 upon IFN mitogen stimulation is found in these patients. These common features of autoimmune disorders (Ganguli et al., 1993; Kroemer and Martinez, 1991) have been supplemented by the demonstration of a decreased in vitro production of interferon-gamma (IFN-γ) upon mitogen stimulation (Ruschen et al., 1992). Genetic studies need to be amended, and a phenotypic subclassification of schizophrenia appears helpful, since most likely only in a subgroup of patients, cytokine dysfunction represents a pathogenic factor.
IX. HYPOTHESES AND PERSPECTIVES Compiling the findings of immunological and immunopathological research in schizophrenia reveals several lines of evidence that an infectious or autoimmune process might play a role in the etiopathogenesis of a subgroup of schizophrenic disorders. Specific dysfunctions of immunological subsystems have been demonstrated repeatedly and coherently, as well as some non-specific markers of immune activation. Signs of inflammation, microglia and astroglia activation in postmortem brains and in the CSF with a dysfunctional BBB, increased retroviral activity, proof of antibodies against brain structures and neurotropic viruses, enhanced cytokine levels in the CSF preceding psychotic episodes, signs of T-cell system activation, and decreased cytokine production capacity in the peripheral blood point to impressive parallels between schizophrenia and autoimmune/infectious disorders. However, although some striking findings cannot be overlooked, there is as yet no direct proof of an immune pathogenesis of schizophrenia. On the basis of the findings, various hypotheses have been formulated and are currently discussed.
A. Infection Hypothesis In the event of an infection being responsible for the development of a schizophrenic psychosis, it seems important to identify the infectious agent. The search for antibodies as well as for antigens should be included to find this agent. So far no virus or bacterium could be identified as a causative agent in the development of schizophrenia. If an infectious agent with widespread occurrence is suspected to be involved in the pathology, increases in antibody levels over time are essential to prove an ongoing infection. Findings in CSF appear more reliable since peripheral signs of infection do not necessarily imply CNS involvement. The majority of published studies did not consider these criteria and are therefore not able to prove an infectious pathology. A CNS infection is usually associated with microglia and/or astroglia activation as presented for schizophrenia directly or indirectly in various studies. An impairment of the BBB is to be expected in case of a relevant CNS infection, as has been shown in several studies which indeed need reproduction. However, more subtle infections might not necessarily cause a detectable change in the permeability of the BBB. If the infection is limited to the CNS, changes in acute phase proteins are not to be expected. Therefore, serum measurements of these proteins are helpful only as additional markers to complete the knowledge of
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the actual immune situation. Immunocompetent cells and markers of pro-inflammatory immune cell activation such as cytokines can be expected to be increased in the CSF in case of a CNS infection, as has been shown by several studies in schizophrenia. The functional capacity of the peripheral immunocompetent cells reflected by cytokine production experiments gives important indications concerning the individual’s potential to fight an infection.
B. Autoimmune Hypothesis It has been hypothesized that an autoimmune process might be involved in the etiopathogenesis of schizophrenia. The microglia activation reported in two studies might be due to an autoimmune pathology, although microglia activation is an unspecific inflammation marker. Signs of BBB impairment with increased permeability are also seen in autoimmune diseases of the brain. So far it is unknown how an individual develops an autoimmune disorder. One hypothesis suggests that a foreign protein induces an immune reaction. Subsequently, the produced antibodies cross-react with specific proteins of the individual. In schizophrenia, cross-reacting antibodies are assumed to target specific brain structures. Therefore, the search for autoantibodies against specific brain structures represents an important approach. However, the reported findings on antibodies against specific structures of brain cells have not yet been reliably reproduced. It appears to be more relevant to focus on cellular structures rather than on topographic regions. As soon as antibodies against certain cell structures have been repeatedly found in schizophrenic individuals, it will be essential to elucidate their functional role. If the autoimmune reaction is limited to the CNS, changes in acute phase proteins are not inevitably to be expected. Counting immunocompetent cells does not help to identify autoimmune pathology, but it is rather the characterization of the functional capacity of those cells that is relevant. A decreased production capacity of Th1 cytokines in the periphery associated with increased cytokine levels on the inflammatory site, as has been repeatedly reported in schizophrenia, can be understood as a typical feature of an autoimmune pathology (Ganguli et al., 1993; Kroemer and Martinez, 1991; Ruschen et al., 1992).
C. Th1/Th2 Hypothesis Schwarz and colleagues (2001) formulated the Th1/ Th2 hypothesis in schizophrenia. This hypothesis is
based on the fact that T-lymphocytes can be divided in subclasses with at least partially antagonistic functions. Th1-like action is mainly pro-inflammatory; Th2like activity, predominantly anti-inflammatory. There is evidence for a downregulation of Th1-like (decreased IFN-γ and IL-2 production ex vivo, elevated sIL-2R serum levels) and an upregulation of Th2-like immune parameters (increased serum concentrations of IgE, IL6, antibodies against several antigens, elevated IgG and IL-4 CSF levels) in psychosis patients. They suggested that there might be a Th2 shift in schizophrenia, especially in patients with predominant negative symptoms and treatment resistance. However, inconsistent data or even controversial results question the hypothesis. It is necessary and trendsetting to formulate wellfounded hypotheses to enable a hypothesis-driven approach. This method appears much more promising than remaining in a screening stage. Utilizing advanced techniques in cell cultures and animal models will be helpful in studying immune subsystems under welldefined conditions. What mechanisms generate the pattern of microglial and astroglial activation found in the brains of schizophrenics? How does a specific antibrain antibody interfere with the function of neurons or glia cells? Is there a specific retroviral activity in the brains of schizophrenic patients? How do increased CSF cytokine concentrations influence neurons and glia cells? What are the molecular mechanisms underlying the decreased peripheral cytokine production in schizophrenic patients? Increasing our knowledge about functional interactions on a molecular basis and the application of appropriate animal models will enable us to interpret the indirect parameters available from CSF, blood, or functional MRI studies in schizophrenic patients. Clinical studies should focus on the identification of a subgroup of patients with schizophrenia showing immunological abnormalities. It is obvious that many reported studies did not include sophisticated psychopathological examinations. Acute and chronic, psychotic and residual, paranoid and disorganized, schizophrenic and schizoaffective patients were often compiled into one sample. Associations of psychopathological and immunological findings have not been sufficiently reproduced. A psychopathological characterization may well not be enough to permit subtyping. Advanced neuropsychological and electrophysiological methodology, structural and functional MRI techniques, evaluation of the course of disease and treatment response should be included to identify specific phenotypes of schizophrenic patients showing immunopathology. Investigation of gene polymorphisms of immune modulators in connection with
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their transcription and translation products might provide further insight in specific subtypes and the functional relevance for the pathogenesis of schizophrenia. First-episode or even prodromal patients appear to be promising for study purposes, as an active immunopathology would be expected in the early stage of the disease, probably even before the manifestation of overt clinical symptoms. Focusing on patients with a recent onset of disease also helps in reducing confounding variables such as medication, diet, or exposure to a hospital environment. However, since schizophrenia is often a chronic disorder, mechanisms causing the progressive deterioration of several brain functions and maintaining inflammatory pathology throughout the course of disease need to be investigated. Applying novel methods and technologies in basic and clinical sciences will eventually enable researchers to characterize immunopathological mechanisms involved in the etiopathogenesis of schizophrenic psychoses and to delineate a subtype of schizophrenia in which infectious or autoimmune pathology is relevant.
References Adami, C., Sorci, G., Blasi, E., Agneletti, A. L., Bistoni, F., and Donato, R. (2001). S100B expression in and effects on microglia. Glia, 33, 131–142. Albrecht, P., Torrey E. F., Boone, E., Hicks, J. T., and Daniel, N. (1980). Raised cytomegalovirus-antibody level in cerebrospinal fluid of schizophrenic patients. Lancet, 2 (8198), 769–772. Arnold, S. E. (1999). Neurodevelopmental abnormalities in schizophrenia: insights from neuropathology. Dev. Psychopathol., 11, 439–456. Arnold, S. E., Franz, B. R., Trojanowski, I. Q., Moberg, P. J., and Gur, R. E. (1996). Glial fibrillary acidic protein-immunoreactive astrocytis in elderly patients with schizophrenia and dementia. Acta Neuropathol. (Berl.), 91, 269–277. Arnold, S. E., Trojanowski, I. Q., Gur, R. E., Blackwell, P., Han, L. Y., and Choi, C. (1998). Absence of neurodegeneration and neural injury in the cerebral cortex in a sample of elderly patients with schizophrenia. Arch. Gen. Psychiatry, 55, 225–232. Barak, V., Barak, Y., Levine, J., Nisman, B., and Roisman, I. (1995). Changes in interleukin-1β and soluble interleukin-2 receptor levels in CSF and serum of schizophrenic patients. J. Bas. Clin. Physiol. & Pharmacol., 6, 61–69. Bartova, L., Rajcani, J., and Pogady, J. (1987). Herpes simplex antibodies in the cerebrospinal fluid of schizophrenic patients. Acta Virol., 31, 443–446. Bartzokis, G. (2002). Schizophrenia: breakdown in the wellregulated lifelong process of brain development and maturation. Neuropsychopharmacology, 27, 672–683. Bayer, T. A., Buslei, R., Havas, L., and Falkai, P. (1999). Evidence for activation of microglia in patients with psychiatric illnesses. Neurosci. Lett., 271, 126–128.
573
Becker, D., Kritschmann, E., Floru, S., Shlomo-David, Y., and GotliebStematsky, T. (1990). Serum interferon in first psychotic attack. Br. J. Psychiatry, 157, 136–138. Borda, T., Gomez, R., Berria, M. I., and Sterin-Borda, L. (2004). Antibodies against astrocyte M1 and M2 muscarinic cholinoceptor from schizophrenic patients’ sera. Glia, 45, 144–154. Borda, T., Perez Rivera, R., Joensen, L., Gomez, R. M., and SterinBorda, L. (2002). Antibodies against cerebral M1 cholinergic muscarinic receptor from schizophrenic patients: molecular interaction. J. Immunol., 168, 3667–3674. Borrell, J., Vela, J. M., Arevalo-Martin, A., Molina-Holgado, E., and Guaza, C. (2002). Prenatal immune challenge disrupts sensorimotor gating in adult rats. Implications for the etiopathogenesis of schizophrenia. Neuropsychopharmacology, 26, 204–215. Brown, A. S., Hooton, J., Schaefer, C. A., Zhang, H., Petkova, E., Babulas, V., Perrin, M., Gorman, J. M., and Susser, E. S. (2004). Elevated maternal interleukin-8 levels and risk of schizophrenia in adult offspring. Am. J. Psychiatry, 161, 889–895. Bruce, L. C., and Peebles, A. M. S. (1903). Clinical and experimental observations on catatonia. J. Ment. Science, 49, 614–628. Buka, S. L., Zsuang, M. T., Torrey, E. F., Klebanoff, M. A., Bernstein, D., and Yolken, R. H. (2001). Maternal infections and subsequent psychosis among offspring. Arch. Gen. Psychiatry, 58, 1032–1037. Cazzullo, C. L., Sacchetti, E., Galluzzo, A., Panariello, A, Adorni, A., Pegoraro, M., Bosis, S., Colombo, F., Trabattoni, D., Zagliani, A., and Clerici, M. (2002). Cytokine profiles in schizophrenic patients treated with risperidone. A 3-month follow-up study. Prog. Neuropsychopharmacol. Biol. Psychiatry, 26, 33–39. Cazzullo, C. L., Sacchetti, E., Galluzzo, A., Panariello, A., Colombo, F., Zagliani, A., and Clerici, M. (2001). Cytokine profiles in drugnaive schizophrenic patients. Schizophr. Res., 1, 293–298. Cazzullo, C. L., Scarone, S., Grassi, B., Vismara, C., Trabattoni, D., Clerici, M., and Clerici, M. (1998). Cytokines production in chronic schizophrenia patients with or without paranoid behavior. Neuropsychopharmacol. Biol. Psychiatry, 22, 947–957. Chiavetto, L. B., Boin, F., Zanardini, R., Popoli, M., Michelato, A., Bignotti, S., Tura, G. B., and Gennarelli, M. (2002). Association between promoter polymorphic haplotypes of interleukin-10 gene and schizophrenia. Biol. Psychiatry, 51, 480–484. Chowdari, K. V., Xu, K., Zhang, F., Ma, C., Li, T., Xie, B. Y., Wood, J., Trucco, M., Tsoi, W. F., Saha, N., Rudert, W. A., and Nimgaonkar, V. L. (2001). Immune related genetic polymorphisms and schizophrenia among the Chinese. Hum. Immunol., 62, 714–724. DeLisi, L. E. (1999). Defining the course of brain structural change and plasticity in schizophrenia. Psychiatry Res. Neuroimaging, 92, 1–9. DeLisi, L. E., Smith, S. B., Hamovit, J. R., Maxwell, M E., Goldin, L. R., Dingman, C. W., and Gershon, E. S. (1986). Herpes simplex virus, cytomegalovirus and Epstein-Barr virus antibody titres in sera from schizophrenic patients. Psychol. Med., 16, 757–763. Dickerson, F. B., Boronow, J. J., Stallings, C., Origoni, A. E., Ruslanova, I., and Yolken, R. H. (2003). Association of serum antibodies to herpes simplex virus 1 with cognitive deficits in individuals with schizophrenia. Arch. Gen. Psychiatry, 60, 466–472. Dong, Y., and Benveniste, E. N. (2001). Immune function of astrocytes. Glia, 36, 180–190. El-Mallakh, R. S., Suddath, R. L., and Wyatt, R. J. (1993). Interleukin1α and interleukin-2 in cerebrospinal fluid of schizophrenic subjects. Proc. Neuropsychopharmacol. Biol. Psychiatry, 17, 383–391. Erbagci, A. B., Herken, H., Koyluoglu, O., Yilmaz, N., and Tarakcioglu, M. (2001). Serum-IL-1beta, sIL-2R, IL-6, IL-8 and
574
III. Behavior and Immunity
TNF-alpha in schizophrenic patients, relation with symptomatolog and responsiveness to risperidone treatment. Mediators Inflamm., 10, 109–115. Falkai, P., Honer, W. G., David, S., Bogerts, B., Majtenyi, C., and Bayer, T. A. (1999). No evidence for astrogliosis in brains of schizophrenic patients. A post-mortem study. Neuropathol. Appl. Neurobiol., 25, 48–53. Falke, E., Han, L. Y., and Arnold, S. E. (2000). Absence of neurodegeneration in the thalamus and caudate of elderly patients with schizophrenia. Psychiatry Res., 6, 103–110. Frommberger, U. H., Bauer, J., Haselbauer, P., Fräulin, A., Riemann, D., and Berger, M. (1997). Interleukin-6–(IL-6) plasma levels in depression and schizophrenia: comparison between the acute state and after remission. Eur. Arch. Psychiatry Clin. Neurosci., 247, 228–233. Fukuda, R., Sasaki, T., Kunugi, H., and Nanko, S. (1999). No changes in paired viral antibody titers during the course of acute schizophrenia. Neuropsychobiology, 40, 57–62. Ganguli, R., Brar, J. S., Chengappa, K. N. R., Yang, Z. W., Nimgaonkar, V. L., and Rabin, B. S. (1993). Autoimmunity in schizophrenia: A review of recent findings. Ann. Med., 25, 489–496. Gattaz, W. F., Dalgalarrondo, P., and Schröder, H. C. (1992). Abnormalities in serum concentrations of interleukin-2 interferon-α and interferon-γ in schizophrenia not detected. Schizophr. Res., 6, 237–241. Gattaz, W. F., Lara, D. R., Elkis, H., Portel, L. V., Goncalves, C. A., Tort, A. B., Henna, J., and Souza, D. O. (2000). Decreased S100beta protein in schizophrenia: preliminary evidence. Schizophr. Res., 43, 91–95. Gaughran, F., O’Neill, E., Sham, P., Daly, R. J., and Shanahan, F. (2002). Soluble interleukin 2 receptor levels in families of people with schizophrenia. Schizophr. Res., 56, 235– 239. Gilmore, H. J., Jarskog, L. F., and Vadlamudi, S. (2005). Maternal pol I:C exposure during pregnancy regulates TNmF alpha, BDNF, and NGF expression in neonatal brain and the maternal-fetal unit of the rat. J. Neuroimmunol., 159, 106–112. Glantz, L. A., and Lewis, D. A. (2000). Decreased dendritic spine density on prefrontal cortical pyramidal neurons in schizophrenia. Arch. Gen. Psychiatry, 57, 65–73. Gur, R. E., Cowell, P., Turetsky, B. I., Gallacher, F., Cannon, T., Bilker, W., and Gur, R. C. (1998). A follow-up magnetic resonance imaging study of schizophrenia. Arch. Gen. Psychiatry, 55, 145–152. Haack, M., Hinze-Selch, D., Fenzel, T., Kraus, T., Kühn, M., Schuld, A., and Pollmächer, T. (1999). Plasma levels of cytokines and soluble cytokine receptors in psychiatric patients upon hospital admission: effects of confounding factors and diagnosis. J. Psychiatr. Res., 33, 407–418. Hakobyan, S., Boyajyan, A., and Sim, R. B. (2005). Classical pathway complement activity in schizophrenia. Neurosci. Lett., 374, 35–37. Harrison, P. J. (1999). The neuropathology of schizophrenia. A critical review of the data and their interpretation. Brain, 122, 593–624. Harrison, P. J., and Eastwood, S. L. (2001). Neuropathological studies of synaptic connectivity in the hippocampal formation in schizophrenia. Hippocampus, 11, 508–519. Hart, D. J., Heath, R. G., Sautter, F. J. Jr., Schwartz, B. D., Garry, R. F., Choi, B., Beilke, M. A., and Hart, L. K. (1999). Antiretroviral antibodies: implications for schizophrenia, schizophrenia spectrum disorders and bipolar disorder. Biol. Psychiatry, 45, 704–714.
Hirsch, S. (2004). Glial changes measured by [11C](R)-PK11195 PET in patients with psychosis and cognitive decline are associated with impaired event related potential mismatch negativity. Schizophrenia Res., 67 (1 Suppl), 103. Jones, L. B., Johnson, N., and Byne, W. (2002). Alterations in MAP2 immunocytochemistry in areas 9 and 32 of schizophrenic prefrontal cortex. Psychiatry Res., 114, 137–148. Jun, T. Y., Lee, K. U., Pae, C. U., Chae, J. H., Bahk, W. M., Kim, K. S., and Han, H. (2003a). Polymorphisms of interleukin-4 promoter and receptor gene for schizophrenia in the Korean population. Psychiatry Clin. Neurosci., 57, 283–288. Jun, T. Y., Pae, C. U., Kim, K. S., Han, H., and Serretti, A. (2003b). Interleukin-10 gene promoter polymorphism is not associated with schizophrenia in the Korean population. Psychiatry Clin. Neurosci., 57, 153–159. Kaminska, T., Wysocka, A., Marmurowska-Michalowska, H., Dubas-Slemp, H., and Kandefer-Szerszen, M. (2001). Investigation of serum cytokine levels and cytokine production in whole blood cultures of paranoid schizophrenic patients. Arch. Immunol. Ther. Exp., 49, 439–445. Karlsson, H., Bachmann, S., Schröder, J., McArthur, J., Torrey, E. F., and Yolken, R. H. (2001). Retroviral RNA identified in the cerebrospinal fluids and brains of individuals with schizophrenia. Proc. Natl. Acad. Sci., 98, 4634–4639. Karson, C. N., Mrak, R. E., Schluterman, K. O., Sturner, W. Q., Sheng, J. G., and Griffin, W. S. T. (1999). Alterations in synaptic proteins and their encoding mRNAs in prefrontal cortex in schizophrenia: a possible neurochemical basis for “hypofrontality.” Mol. Psychiatry, 4, 39–45. Kim, J. J., Lee, S. J., Toh, K. Y., Lee, C. U., Lee, C., and Paik, I. H. (2001). Identification of antibodies to heat shock proteins 90 kDa and 70 kDa in patients with schizophrenia. Schizophr. Res., 52, 127–135. Kim, S. J., Lee, H. J., Koo, H. G., Kim, J. W., Song, J. Y., Kim, M. K., Shin, D. H., Jin, S. Y., Hong, M. S., Park, H. J., Yoon, S. H., Park, H. K., and Chung, J. H. (2004). Impact of IL-1 receptor antagonist gene polymorphism on schizophrenia and bipolar disorder. Psychiatr. Genet., 14, 165–167. Kim, Y. K., Suh, I. B., Kim, H., Han, C. S., Lim, C. S., Choi, S. H., and Licinio, J. (2002). The plasma levels of interleukin-12 in schizophrenia, major depression, and bipolar mania: effects of psychotropic drugs. Mol. Psychiatry, 7, 1107–1114. Kirch, D. G. (1993). Infection and autoimmunity as etiologic factors in schizophrenia: a review and reappraisal. Schizophr. Bull., 19, 355–370. Koliaskina, G. I., Sekirina, T. P., Androsova, L. V., Kushner, S. G., Vasil’eva, E. F., Burbaeva, O. A., and Morozova, M. A. (2004). A change of immune profile of patients with schizophrenia during treatment. Zh. Nevrol. Psikhiatr: Im. S. S. Korsakova, 104, 39–45. Kowalski, J., Blada, P., Kucia, K., Lawniczek, T., Madej, A., Belowski, D., and Herman, Z. S. (2000). In-vitro immunomodulatory effects of haloperidol and perazine in schizophrenia. World J. Biol. Psychiatry, 1, 190–196. Kroemer, G., and Martinez, C. (1991). Cytokines and autoimmune disease. Clin. Immunol. Immunopathol., 61, 275–295. Krönig, H., Riedel, M., Schwarz, M. J., Strassnig, M., Möller, H. J., Ackenheil, M., and Müller, N. (2005). ICAM G241A polymorphism and soluble ICAM-1 serum levels: evidence for an active immune process in schizophrenia. Neuroimmunomodulation, 12, 54–59. Kudoh, A., Sakai, T., Ishihara, H., and Matsuki, A. (2001). Plasma cytokine response to surgical stress in schizophrenic patients. Clin. Exp. Immunol., 125, 89–93.
27. Schizophrenia and Immunity Kung, L., Conley, R., Chute, D. J., Smialik, J., and Roberts, R. C. (1998). Synaptic changes in the striatum of schizophrenic cases: a controlled postmortem ultrastructural study. Synapse, 28, 125–139. Lara, D. R., Gama, C. S., Belmonte-de-Abreu, P., Portela, L. V. C., Goncalves, C. A., Fonseca, M., Hauck, S., and Souza, D. O. (2001). Increased serum S100B protein in schizophrenia: a study in medication-free patients. J. Psychiatr. Res., 35, 11–14. Lehmann-Facius, H. (1937). Über die Liquordiagnose der Schizophrenien. Klin. Wochenschr, 16, 1646–1648. Licinio, J., Seibyl, J. P., Altemus, M., Charney, D. S., and Krystal, J. H. (1993). Elevated CSF levels of interleukin-2 in neurolepticfree schizophrenic patients. Am. J. Psychiatry, 150, 1408– 1410. Lieberman, J. A., Sheitman, B. B., and Kinon, B. J. (1997). Neurochemical sensitization in the pathophysiology of schizophrenia: deficits and dysfunction in neuronal regulation and plasticity. Neuropsychopharmacology, 17, 205–229. Liebermann, J., Chakos, M., Wu, H., Alvir, J., Hoffmann, E., Robinson, D., and Bilder, R. (2001). Longitudinal study of brain morphology in first episode schizophrenia. Biol. Psychiatry, 49, 487–499. Lillehoj, E. P., Ford, G. M., Bachmann, S., Schroder, J., Torrey, E. F., and Yolken, R. H. (2000). Serum antibodies reactive with nonhuman primate retroviruses identified in acute onset schizophrenia. J. Neurovirol., 6, 492–497. Lin, A., Kenis, G., Bignotti, S., Tura, G. J. B., De Jong, R., Bosmans, E., Pioli, R., Altamura, C., Scharpe, S., and Maes, M. (1998). The inflammatory response system in treatment-resistant schizophrenia: increased serum interleukin-6. Schizophr. Res., 32, 9–15. Liu, J., Shi, Y., Tang, J., Guo, T., Li, X., Yang, Y., Chen, Q., Zhao, X., He, G., Feng, G., Gu, N., Zhu, S., Liu, H., and He, L. (2005). SNPs and haplotypes in the S100B gene reveal association with schizophrenia. Biochem. Biophys. Res. Commun., 328, 335–341. Maes, M., Bocchio Chiavetto, L., Bignotti, S., Battisa Tura, G. J., Pioli, R., Boin, R., Kenis, G., Bosmans, E., de Jongh, R., and Atamura, C. A. (2002). Increased serum interleukin-8 and interleukin-10 in schizophrenic patients resistant to treatment with neuroleptics and the stimulatory effects of clozapine on serum leukemia inhibitory factor receptor. Schizophr. Res., 54, 281–291. Maes, M., Bosmans, E., Ranjan, R., Vandoolaeghe, E., Meltzer, H. Y., De Ley, M., Berghmans, R., Stans, G., and Desnyder, R. (1996). Lower plasma CC16, a natural anti-inflammatory protein, and increased plasma interleukin-1 receptor antagonist in schizophrenia: effects of antipsychotic drugs. Schizophr. Res., 21, 39–50. Maes, M., Meltzer, H. Y., and Bosmans, E. (1994). Immuneinflammatory markers in schizophrenia: comparison to normal controls and effects of clozapine. Acta Psychiatr. Scand., 89, 346–351. Maes, M., Meltzer, H. Y., Buckley, P., and Bosmans, E. (1995). Plasma-soluble interleukin-2 and transferrin receptor in schizophrenia and major depression. Eur. Arch. Psychiatry Clin. Neurosci., 244, 325–329. Maes, M. B., Meltzer, H. Y., Scharpe, S., and Suy, E. (1993). Interleukin-1beta: a putative mediator of HPA axis hyperactivity in major depression? Am. J. Psychiatry, 150, 1189–1193. Mahendran, R., Mahendran, R., and Chang, Y. H. (2004). Interleukin-2 levels in chronic schizophrenia patients. Ann. Acad. Med. Singapore, 33, 320–323. Marenco, S., and Weinberger, D. R. (2000). The neurodevelopmental hypothesis of schizophrenia: Following a trail of evidence from cradle to grave. Dev. Psychopathol., 12, 501–527.
575
Matute, C., Melone, M., Vallejo-Illarramendi, A., and Conti, F. (2005). Increased expression of the astrocytic glutamate transporter GLT-1 in the prefrontal cortex of schizophrenics. Glia, 49, 451–455. Mazzarello, V., Cecchini, A., Fenu, G., Rassu, M., Dessy, L. A., Lorettu, L., and Montella, A. (2004). Lymphocytes in schizophrenic patients under therapy: serological, morphological and cell subset findings. Ital. J. Anat. Embryol., 109, 177–188. McAllister, C. G., van Kammen, D. P., Rehn, T. J., Miller, A. L., Gurklis, B. S. J., Kelley, M. E., Yao, B. S. J., and Peters, J. L. (1995). Increases in CSF levels of interleukin-2 in schizophrenia: effects of recurrence of psychosis and medication status. Am. J. Psychiatry, 152, 1291–1297. McGlashan, T. H., and Hoffman, R. E. (2000). Schizophrenia as a disorder of developmentally reduced synaptic connectivity. Arch. Gen. Psychiatry, 57, 637–648. Menninger, K. A. (1919). Psychoses associated with influenza. JAMA, 72, 235–241. Menninger, K. A. (1926). Influenza and schizophrenia. An analysis of postinfluenza “dementia praecox” as of 1918 and five years later. Am. J. Psychiatry, 5, 469–529. Menninger, K. A. (1928). The schizophrenia syndrome as a product of acute infectious disease. Arch. Neurol. Psychiatry, 20, 464– 481. Mirnics, K., Middleton, F. A., Lewis, D. A., and Levitt, P. (2001). Analysis of complex brain disorders with gene expression microarrays: schizophrenia as a disease of the synapse. Trends Neurosci., 24, 479–486. Müller, N., Dobmeier, P., Empl, M., Riedel, M., Schwarz, M., and Ackenheil, M. (1997a). Soluble IL-6 receptors in the serum and cerebrospinal fluid of paranoid schizophrenic patients. Eur. Psychiatry, 12, 294–299. Müller, N., Empl, M., Riedel, M., Schwarz, M., and Ackenheil, M. (1997b). Neuroleptic treatment increases soluble IL-2 receptors and decreases soluble IL-6 receptors in schizophrenia. Eur. Arch. Psychiatry Clin. Neurosci., 247, 308–313. Müller, N., Riedel, M., Hadjamu, M., Schwarz, M. J., Ackenheil, M., and Gruber, R. (1999). Increase in expression of adhesion molecule receptors on T helper cells during antipsychotic treatment and relationship to blood-brain barrier permeability in schizophrenia. Am. J. Psychiatry, 156, 634–636. Naudin, J., Capo, C., Giusano, B., Mege, J. L., and Azorin, J. M. (1997). A differential role for interleukin-6 and tumor necrosis factor-alpha in schizophrenia. Schizophr. Res., 26, 227–233. Nikkilä, H., Müller, K., Ahokas, A., Miettinen, K., Andersson, L. C., and Rimón, R. (1995). Abnormal distributions of T-lymphocyte subsets in the cerebrospinal fluid of patients with acute schizophrenia. Schizophr. Res., 14, 215–221. Nikkilä, H., Müller, K., Ahokas, A., Miettinen, K., Rimón, R., and Andersson, L. C. (1999). Accumulation of macrophages in the CSF of schizophrenic patients during acute psychotic episodes. Am. J. Psychiatry, 156, 1725–1729. O’Donnell, M. C., Catts, S. V., Ward, P. B., Liebert, B., Liebert, B., Lloyd, A., Wakefield, D., and McConaghy, N. (1996). Increased production of interleukin-2 (IL-2) but not soluble interleukin-2 receptors (sIL-2R) in unmedicated patients with schizophrenia and schizophreniform disorder. Psychiatry Res., 65, 171–178. Pandey, R. S., Gupta, A. K., and Chaturvede, U. C. (1981). Autoimmune model of schizophrenia with special reference to antibrain antibodies. Biol. Psychiatry, 16, 1123–1136. Pandurangi, A. K., Pelonero, A. L., Nadel, L., and Calabrese, V. P. (1994). Brain structure changes in schizophrenics with high serum titers of antibodies to herpes virus. Schizophr. Res., 11, 245–250.
576
III. Behavior and Immunity
Pearlson, G. D., and Marsh, L. (1999). Structural brain imaging in schizophrenia: a selective review. Biol. Psychiatry, 46, 627–649. Pelonero, A. L., Pandurangi, A. K., and Calabrese, V. P. (1990). Autoantibodies to brain lipids in schizophrenia. Am. J. Psychiatry, 147, 661–662. Powers, R. E. (1999). The neuropathology of schizophrenia. J. Neuropathol. Exp. Neurol., 58, 679–690. Radewicz, K., Garey, L. J., Gentleman, S. M., and Reynolds, R. (2000). Increase in HLA-DR immunoreactive microglia in frontal and temporal cortex of chronic schizophrenics. J. Neuropathol. Exp. Neurol., 59, 137–150. Rajkowska, G., Miguel-Hidalgo, J. J., Makkos, Z., Meltzer, H., Overholser, J., and Stockmeier, C. (2002). Layer-specific reductions in GFAP-reactive astroglia in the dorsolateral prefrontal cortex in schizophrenia. Schizophr. Res., 57, 127–138. Ramchand, R., Wei, J., Ramchand, C. N., and Hemmings, G. P. (1994). Increased serum IgE in schizophrenic patients who responded poorly to neuroleptic treatment. Life Sci., 54, 1579–1584. Rapaport, M. H., McAllister, C. G., Pickar, D., Tamarkin, L., Kirch, D. G., and Paul, S. M. (1997). CSF IL-1 and IL-2 in medicated schizophrenic patients and normal volunteers. Schizophr. Res., 25, 123–129. Richt, J. A., Alexander, R. C., Herzog, S., Hooper, D. C., Kean, R., Spitsin, S., Bechter, K., Schuttler, R., Feldmann, H., Heiske, A., Fu, Z. F., Dietzschold, B., Rott, R., and Koprowski, H. (1997). Failure to detect Borna Disease Virus infection in peripheral blood leukocytes from humans with psychiatric disorders. J. Neurovirol., 3, 174–178. Rothermundt, M., Arolt, V., and Bayer, T. A. (2001a). Review of immunological and immunopathological findings in schizophrenia. Brain Behav. Immun., 15, 319–339. Rothermundt, M., Arolt, V., Weitzsch, C., Eckhoff, D., and Kirchner, H. (1996). Production of cytokines in acute schizophrenic psychosis. Biol. Psychiatry, 40, 1294–1297. Rothermundt, M., Arolt, V., Weitzsch, C., Eckhoff, D., and Kirchner, H. (1998). Immunological dysfunction in schizophrenia: a systematic approach. Neuropsychobiology, 37, 186–193. Rothermundt, M., Falkai, P., Ponath, G., Abel, S., Bürkle, H., Diedrich, M., Hetzel, G., Peters, M., Siegmund, A., Pedersen, A., Maier, W., Schramm, J., Suslow, T., Ohrmann, P., and Arolt, V. (2004a). Glial cell dysfunction in schizophrenia indicated by increased S100B in the CSF. Mol. Psychiatry, 9, 897–899. Rothermundt, M., Missler, U., Arolt, V., Peters, M., Leadbeater, J., Wiesmann, M., Rudolf, S., Wandinger, K. P., and Kirchner, H. (2001b). Increased S100B blood levels in unmedicated and treated schizophrenic patients are correlated with negative symptomatology. Mol. Psychiatry, 6, 445–449. Rothermundt, M., Ponath, G., Glaser, T., Hetzel, G., and Arolt, V. (2004b). S100B serum levels and long-term improvement of negative symptoms in patients with schizophrenia. Neuropsychopharmacology, 29, 1004–1011. Ruschen, S., Stellberg, W., and Warnatz, H. (1992). Kinetics of cytokine secretion by mononuclear cells of the blood in rheumatoid arthritis patients are different from those of healthy controls. Clin. Exp. Immunol., 89, 32–37. Sasaki, T., Nanko, S., Fukuda, R., Kawate, T., Kunugi, H., and Kazamatsuri, H. (1994). Changes of immunological functions after acute exacerbation in schizophrenia. Biol. Psychiatry, 35, 173–178. Schroeter, M. L., Abdul-Khaliq, H., Fruhauf, S., Hohne, R., Schick, G., Diefenbacher, A., and Blasig, I. E. (2003). Serum S100B is increased during early treatment with antipsychotics and in deficit schizophrenia. Schizophr. Res., 62, 231–236.
Schwarz, M. J., Chiang, S., Muller, N., and Ackenheil, M. (2001). Thelper-1 and T-helper-2 responses in psychiatric disorders. Brain Behav. Immun., 15, 340–370. Schwarz, M. J., Riedel, M., Ackenheil, M., and Muller, N. (2000). Decreased levels of soluble intercellular adhesion molecule-1 (sICAM-1) in unmedicated and medicated schizophrenic patients. Biol. Psychiatry, 47, 29–33. Selemon, L. D., and Goldman-Rakic, P. S. (1999). The reduced neuropil hypothesis: a circuit based model of schizophrenia. Biol. Psychiatry, 45, 17–25. Shcherbakova, I. V., Siriachonko, T. M., Mazaeva, N. A., Krasnolobova, S. A., Lideman, R. R., and Kliushnik, T. P. (2003). A comparison of some indices of innate and adaptive immunity in different types of schizophrenia. Zh. Nevrol. Psikhiatr. Im. S. S. Korsakova, 103, 69–72. Shcherbakova, I. V., Siryachenko, T. M., Mazaeva, N. A., Kaleda, V. G., Krasnolobova, S. A., and Klyushnik, T. P. (2004). Leukocyte elastase and autoantibodies to nerve growth factor in the acute phase of schizophrenia and their relationship to symptomatology. World J. Biol. Psychiatry, 5, 143–148. Shenton, M. E., Dickey, C. C., Frumin, M., and McCarley, R. W. (2001). A review of MRI findings in schizophrenia. Schizophr. Res., 49, 1–52. Solov’eva, Z. V., and Orlovskaia, D. D. (1979). Microglia-type cells in normal and pathologic human embryonic brains. Zh. Nevropatol. Psikhiatr. Im. S. S. Korsakova, 79, 852–857. Sperner-Unterweger, B., Whitworth, A., Kemmler, G., Hilbe, W., Thaler, J., Weiss, G., and Fleischhacker, W. W. (1999). T-cell subsets in schizophrenia: a comparison between drug-naive first episode patients and chronic schizophrenic patients. Schizophr. Res., 38, 61–70. Sugai, T., Kawamura, M., Iritani, S., Araki, K., Makifuchi, T., Imai, C., Nakamura, R., Kakita, A., Takahashi, H., and Nawa, H. (2004). Profrontal abnormality of schizophrenia revealed by DnA microarray: impact on glial and neurotrophic gene expression. Ann. N. Y. Acad. Sci., 1025, 84–91. Sugerman, A. A., Southern, D. L., and Curran, J. F. (1982). A study of antibody levels in alcoholic, depressive and schizophrenic patients. Ann. Allergy, 48, 166–171. Tanaka, K. F., Shintani, F., Fujii, Y., Yagi, G., and Asai, M. (2000). Serum interleukin-18 levels are elevated in schizophrenia. Psychiatry Res., 96, 75–80. Terayama, H., Nishino, Y., Kishi, M., Ikuta, K., Itoh, M., and Iwahashi, K. (2003). Detection of anti-Borna Disease Virus (BDV) antibodies from patients with schizophrenia and mood disorders in Japan. Psychiatry Res., 120, 201–206. Theodoropoulou, S., Spanakos, G., Baxevanis, C. N., Economou, M., Gritzapis, A. D., Papamichail, M. P., and Stefanis, C. N. (2001). Cytokine serum levels, autologous mixed lymphocyte reaction and surface marker analysis in never medicated and chronically medicated schizophrenic patients. Schizophr. Res., 47, 13–25. Thieda, P., Beard, S., Richter, A., and Kane, J. (2003). An economic review of compliance with medication therapy in the treatment of schizophrenia. Psychiatr. Serv., 54, 508–516. Tohmi, M., Tsuda, N., Watanabe, Y., Kakita, A., and Nawa, H. (2004). Perinatal inflammatory cytokine challenge results in distinct neurobehavioral alterations in rats: implication in psychiatric disorders of developmental origin. Neurosci. Res., 50, 67–75. Torrey, E. F., Miller, J., Rawlings, R., and Yolken, R. H. (1997). Seasonality of births in schizophrenia and bipolar disorder: a review of the literature. Schizophr. Res., 28, 1–38. Torrey, E. F., Yolken, R. H., and Winfrey, C. J. (1982). Cytomegalovirus antibody in cerebrospinal fluid of schizophrenic patients detected by enzyme immunoassay. Science, 216, 892–894.
27. Schizophrenia and Immunity Vilhardt, F. (2005). Microglia: phagocyte and glial cell. Int. J. Biochem. Cell Biol., 37, 17–21. Villemain, F., Chatenoud, L., Galinowski A., Homo-Delarche, F., Ginestet, D., Loo, H., Zarifan, E., and Bach, J. F. (1989). Aberrant T-cell mediated immunity in untreated schizophrenic patients: deficient interleukin-2 production. Am. J. Psychiatry, 146, 609–616. Vives, V., Alonso, G., Solal, A. C., Joubert, D., and Legraverend, C. (2003). Visualization of S100B-positive neurons and glia in the central nervous system of EGFP transgenic mice. J. Comp. Neurol., 457, 404–419. Waltrip, R. W., Buchanan, R. W., Carpenter, W. T., Kirkpatrick, B., Summerfelt, A., Breier, A., Rubin, S. A., and Carbone, K. M. (1997). Borna Disease Virus antibodies and the deficit syndrome of schizophrenia. Schizophr. Res., 23, 253–257. Wang, X. F., Wang, D., Zhu, W., Delrahim, K. K., Dolnak, D., and Rapaport, M. H. (2003). Studies characterizing 60 kDa autoantibodies in subjects with schizophrenia. Biol. Psychiatry, 53, 361–375. Webster, M. J., Knable, M. B., Johnston-Wilson, N., Nagata, K., Inagaki, M., and Yolken, R. H. (2001). Immunohistochemical localization of phosphorylated glial fibrillar acid protein in the prefrontal cortex and hippocampus from patients with schizophrenia, bipolar disorder, and depression. Brain Behav. Immun., 15, 388–400. Wierzba-Bobrowicz, T., Lewandowska E., Kosno-Kruszewska, E., Lechowicz, W., Pasennik, E., and Schmidt-Sidor, B. (2004). Degeneration of microglial cells in frontal and temporal lobes of chronic schizophrenics. Folia Neuropathol., 42, 157–165. Wiesmann, M., Wandinger, K. P., Missler, U., Eckhoff, D., Rothermundt, M., Arolt, V., and Kirchner, H. (1999). Elevated plasma levels of S-100b protein in schizophrenic patients. Biol. Psychiatry, 45, 1508–1511.
577
Wilke, I., Arolt, V., Homberg, M., and Kirchner, H. (1996). Investigations of cytokine production in whole blood cultures of paranoid and residual schizophrenics. Eur. Arch. Psych. & Clin. Neurosci., 246, 279–284. Woods, B. T. (1998). Is schizophrenia a progressive neurodevelopmental disorder? Toward a unitary pathogenetic mechanism. Am. J. Psychiatry, 155, 1661–1670. Xu, H. M., Wei, J., and Hemmings, C. P. (1994). Changes of plasma concentrations of interleukin-1α and interleukin-6 with neuroleptic treatment of schizophrenia. Br. J. Psychiatry, 164, 251–253. Yang, A. Y., Zhang, F. M., Li, J. H., Li, G. M., Gu, H. X., and Ikuta, K. (2003). Detection of Borna Disease Virus-p24 specific antibody in the sera of schizophrenic patients of China by means of Western-blot. Zhonghua Shi Yan He Lin Chuang Bing Du Yue Za Zhi., 17, 85–87. Yu, L., Yang, M. S., Zaho, J., Shi, Y. Y., Zhao, X. Z., Yang, J. D., Liu, Z. J., Gu, N. F., Feng, G. Y., and He, L. (2004). An association between polymorphisms of the interleukin-10 gene promoter and schizophrenia in the Chinese population. Schizophr. Res., 71, 179–183. Zhang, X. Y., Zhou, D. F., Cao, L. Y., Zhang, P. Y., and Wu, G. Y. (2002). Decreased production of interleukin-2 (IL-2), IL-2 secreting cells and CD4+ cells in medication-free patients with schizophrenia. J. Psychiatr. Res., 36, 331–336. Zhang, X. Y., Zhou, D. F., Zhang, P. Y., Wu, G. Y., Cao, L. Y., and Shen, Y. C. (2003). Elevated interleukin-2, interleukin-6 and interleukin-8 serum levels in neuroleptic-free schizophrenia: association with psychopathology. Schizophr. Res., 57, 247–258. Zorilla, E. P., Cannon, T. D., Gur, R. E., and Kessler, J. (1996). Leukocytes and organ-nonspecific autoantibodies in schizophrenics and their siblings: markers of vulnerability or disease? Biol. Psychiatry, 40, 825–833.
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C H A P T E R
28 Sleep and the Immune System MARK R. OPP, JAN BORN, AND MICHAEL R. IRWIN
I. INTRODUCTION 579 II. OVERVIEW OF SLEEP AND ITS CHARACTERISTICS 580 III. EFFECTS OF INFECTIONS ON SLEEP 584 IV. CYTOKINE REGULATION OF SLEEP 586 V. SLEEP MODULATION OF IMMUNITY 591 VI. DISORDERED SLEEP AND IMMUNITY: CLINICAL POPULATIONS 606 VII. SUMMARY 609
possibly disease risk (Ancoli-Israel and Cooke, 2005; Lager, 1994). Epidemiological data increasingly implicate insomnia as a predictor of cardiovascular and non-cardiovascular disease mortality, particularly in community elderly populations (Bryant et al., 2004; Foley et al., 1995; Kripke et al., 2002; Mallon et al., 2000; Mallon et al., 2002; Pollak et al., 1990). Furthermore, objective electroencephalographic (EEG) measures of sleep amounts and quality show that prolonged sleep latency (i.e., a difficulty falling asleep) predicts a nearly twofold increase in all-cause mortality over and above the contribution of demographic confounds and medical factors in healthy older adults (Dew et al., 2003). In 2004, the National Sleep Foundation in the United Stated specifically promoted the importance of sleep for good health. Hence, it is increasingly important to consider the possible physiological effects of sleep and the consequences of sleep loss for homeostatic regulation of systemic processes including the immune system. It is commonly thought that persons are more susceptible to infections when deprived of sleep, and that infections seem to increase somnolence (Bryant et al., 2004). However, the evidence to support these anecdotal observations has only recently begun to emerge. In this chapter, we consider the reciprocal influences of sleep and the immune system. Specifically, this review addresses whether the immune system causes changes in sleep, and whether sleep has a role in the modulation of the immune system with possible consequences for disease risk. Finally, we consider clinical conditions in which disordered sleep and disordered
I. INTRODUCTION About one-quarter of the population of the United States experiences sleep problems, with the prevalence of at least one insomnia complaint occurring in up to one-third of the population (Ohayon, 1996; Ohayon, 2002). Nearly 10% of all persons fulfill diagnostic criteria for chronic syndromal insomnia characterized by symptoms of insomnia of greater than 6 months duration with difficulties in sleep initiation or maintenance (e.g., greater than 30 minutes awake per night), frequent sleep problems (e.g., greater than three times per week), and associated distress and clinical significant impairments in daytime functioning (e.g., fatigue) (Ancoli-Israel and Cooke, 2005; Ohayon, 2002; Savard and Morin, 2001). Moreover, during the past 90 years the amount of time that we spend sleeping has steadily decreased (Jean-Louis et al., 2000), and average nightly sleep has declined from 9 hours in 1910 to 7 hours in 2002. Together, the high prevalence of insomnia and the curtailment of sleep amounts pose a large economic burden to society with reduced productivity, accidents, behavioral and cognitive consequences, and PSYCHONEUROIMMUNOLOGY, 4E VOLUME I
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Copyright © 2007 by Elsevier, Inc. All rights of reproduction in any form reserved.
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immune function co-occur, as such disorders provide naturalistic evidence for a role of sleep in the regulation of the immune system and possibly in mediating increases in the risk infectious disease and inflammatory disorders in these populations.
II. OVERVIEW OF SLEEP AND ITS CHARACTERISTICS
human SWS the slow waves predominate for less than half of a 30-second period, that period is defined as stage 3. If slow waves predominate for more than half of a 30-second period, the period is considered stage 4. The arbitrary criteria that are used to define phases and stages of sleep give the impression that sleep consists of discrete units that are quantal in nature. This is not the case. In healthy humans and laboratory
A. Sleep Characteristics Arousal states compose a continuum from fully awake and alert to deep sleep. Until 1953, sleep was thought to result passively from withdrawal of wakefulness-promoting stimuli. The discovery of rapid eye movement (REM) sleep by Aserinsky and Kleitman (1953) demonstrated that sleep is not a passive process; during REM sleep several brain regions are as active, or more so, than during wakefulness. The fact that REM sleep was only recently discovered (1953) is remarkable considering that brain electrical activity [the electroencephalogram (EEG)] was recorded as early as 1875. By the 1920s, the Austrian psychiatrist Hans Berger was recording human EEG. During the 1930s several seminal papers were published, notably by Loomis and colleagues (Davis et al., 1938; Loomis et al., 1938) and Blake, Gerard, and Kleitman (Blake and Gerard, 1937; Blake et al., 1939) demonstrating changes in the EEG through the course of a night’s sleep. In none of these early works was the possibility of distinct phases of sleep acknowledged. We now consider sleep to consist of two major phases: REM sleep and non-rapid eye movement (NREM) sleep. Most investigators conducting preclinical studies using laboratory animals find it sufficient to define only two phases of sleep. In sleep research using human subjects and in sleep disorders medicine, the phase of NREM sleep is further subdivided into four stages: stages 1, 2, 3, and 4. The four stages of NREM sleep may generally be considered to parallel a continuum of sleep depth with stage 2 being lighter sleep than stage 4. Stage 1 is the transition between wakefulness and sleep, whereas sleep onset is generally considered to occur when two EEG features characteristic of stage 2 appear—spindles and K-complexes. Spindles are bursts of sinusoidal waves of about 12–14 cycles/second (Hz), whereas K-complexes are transient high-voltage biphasic waves. Sleep spindles and K-complexes are superimposed on a background of low voltage EEG (Figure 1). Human stages 3 and 4 NREM sleep are referred to as slowwave sleep (SWS) due to the preponderance of highamplitude low-frequency components characteristic of the EEG. Differentiating between stages of human sleep is done on the basis of arbitrary criteria. If during
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FIGURE 1 Stages of sleep in humans. The relationship between human sleep, level of consciousness, and electroencephalogram (EEG) patterns. Stages of sleep are characterized by differences in the frequency and amplitude of EEG waves. Stage 1 comprises light sleep with lowamplitude waveforms. Stage 2 is characterized by sleep spindles (the higher frequency waves) and K-complexes (not shown). Stages 3 and 4 comprise slow-wave sleep (SWS) with high-amplitude waves and a deeper level of unconsciousness. These four stages comprise non–rapid eye movement (NREM) sleep. The final stage is rapid eye movement (REM) sleep, which is associated with θ-activity (all waves shown) and, in some individuals, with lowamplitude sawtooth waves (not shown) and a higher level of consciousness. [From Horne, J. A. Why We Sleep: The Functions of Sleep in Humans and Other Mammals. Oxford University Press, Oxford. 1988. Reproduced by permission of Oxford University Press.]
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animals, there is an orderly progression from wakefulness to NREM sleep and REM sleep. Healthy animals and humans enter NREM sleep from wakefulness. From NREM sleep there is a transition to REM sleep. After a period of REM sleep, there may or may not be a brief arousal or awakening (Figure 2). These progressions from wakefulness through stages of sleep repeat to form cycles. The number and duration of cycles that occur during a period of sleep are species-specific; healthy human adults will have four to six NREM– REM cycles of about 80–110 minutes duration, whereas rats will have many NREM–REM cycles, each lasting about 8–10 minutes. In addition to species-specific features with respect to the number and duration of cycles that occur during a sleep period, there are species-specific aspects to the timing and distribution of sleep across the 24-hour day (Campbell and Tobler, 1984; Tobler, 1989; Tobler, 1995). Sleep distributions of vertebrates may generally be considered to be either monophasic or polyphasic. If all sleep across a 24-hour day occurs during a single period, an animal is said to be monophasic with respect to sleep. Sleep distributed during multiple periods across the 24-hour day constitutes a polyphasic sleep pattern (Tobler, 1989). Humans are generally thought to be monophasic, with sleep normally occurring only at night, but the monophasic patterning of human sleep may be a societal artifact and not necessarily a manifestation of fundamental physiological processes. Laboratory rodents (rats, mice), the subjects of most pre-clinical sleep studies, are polyphasic, sleeping during both the light and dark periods of a 24-hour
light:dark cycle. However, though rats and mice sleep during both the light and dark periods, their sleepwake behavior is strongly influenced by circadian factors, and they are generally considered to be nocturnal; rats and mice sleep more during the light period of a light:dark cycle than they do during the dark period. As will be detailed later, the differences in the distribution of sleep across the 24-hour period is an important consideration when conducting studies on the relationship between sleep-wake behavior and immunomodulators.
B. Assessment of Sleep Sleep is first and foremost a behavior, and can be defined by behavioral criteria. Body posture and eye state are primary indicators that may be used to differentiate between sleep and wakefulness. It is also possible to differentiate between NREM sleep and REM sleep of mammals and birds on the basis of changes in muscle tone; during REM sleep postural muscle tone is lost. The most observable consequence of loss of postural muscle tone is a drooping of the head. The use of behavioral criteria as the only determinants of arousal state, however, has little utility for exploration of underlying physiological processes. To systematically determine those neuroanatomical and neurochemical substrates involved in the regulation of arousal state, it is necessary to instrument the subject, whether human or animal, so that multiple physiological parameters may be recorded for relatively long periods.
FIGURE 2 The progression of sleep stages across a single night in a normal young adult. The hypnogram is based on a continuous overnight recording from a 19-year-old man as assessed in 30-second epochs. [From Carskadon, M. A., and W. C. Dement. Normal human sleep: an overview. Chapter 2, in: Principles and Practices of Sleep Medicine, Fourth Edition. (eds. Kryger, Roth, Dement). W. B. Saunders, Philadephia. 2005. Reproduced by permission of W. B. Saunders].
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Every physiological parameter studied to date has been demonstrated to differ depending on whether the animal is awake or asleep. As such, there are numerous parameters that could be recorded that would allow instantaneous assessment of arousal state, and there are now well-defined associations between multiple physiological parameters and arousal state. Some parameters, however, are easier to record and require less instrumentation. The most frequently recorded parameters include the EEG and one or more of the following: muscle tone [electromyogram (EMG)], eye movements [electrooculogram (EOG)], respiration, body movements, and body or brain temperature. In human studies, whether for research purposes or for diagnostic assessment of sleep disorders, multiple surface electrodes are used to record the EEG over several regions of the cerebral cortex. Pre-clinical studies using laboratory animals generally employ surgically implanted electrodes, and only one or two channels of EEG are recorded. For most pre-clinical studies using laboratory animals, recording the EEG and either the EMG or body movements provides information sufficient to allow determination of phases of sleep or wakefulness. The determination of arousal state in laboratory rodents is readily done on the basis of the relationship between specific amplitude and frequency characteristics of the EEG and the EMG or body movements. When awake and active, the EEG of a laboratory rodent is characterized by a low amplitude (voltage) waveform composed of mixed frequencies, while the EMG recorded from the neck muscles of these animals will be activated due to use of postural muscles and movement. During wakefulness, generalized activity (feeding, locomotion, grooming) of the animal within the recording cage will also be detected. Upon a transition from wakefulness to NREM sleep, generalized activity and the amplitude of the EMG in the neck muscles will begin to diminish. Spectral analyses of several types may be used to characterize amplitude and/or frequency components of the EEG waveform. Spectral analyses of the EEG of a rodent that is awake reveal mixed frequency components. During the transition from wakefulness to NREM sleep, the amplitude of the EEG will increase, and spectral analyses reveal shifts from mixed EEG frequencies to predominately lower EEG frequencies (<5 Hz). The low EEG frequency band, from 0.5 Hz to approximately 5 Hz, is referred to as the delta frequency band. As such, a highvoltage, low-frequency EEG characterizes NREM sleep of rodents; spectral analyses will detect increases in the delta frequency band, and there will be reduced EMG activity in the absence of generalized body movements. At the transition from NREM sleep to REM sleep, the
amplitude of the EEG is reduced relative to that observed during NREM sleep. During the transition from NREM sleep to REM sleep, there is a shift in the major frequency components of the EEG from the lowfrequency delta band to a higher-frequency band. Spectral analyses of the EEG during REM sleep reveal an increase in the theta frequency band, generally defined as between 6 Hz and 9 Hz. During REM sleep, EMG activity of the neck muscles is reduced to its lowest level. Generalized activity is absent during REM sleep, but phasic twitches may be detected in the EMG. Therefore, REM sleep of rodents is characterized by a low-voltage EEG with predominant theta frequency, reduced generalized activity, and diminished EMG activity with occasional body twitches. A fundamental feature of sleep is that the longer we are awake, the sleepier we become. When we obtain a good night’s sleep, we wake up feeling refreshed. In response to prolonged wakefulness (sleep deprivation), humans and animals sleep longer, but not so long as to make up, or recover, all the sleep lost. For example, a college student staying up all night to study for an exam may be expected to lose about 6–7 hours of sleep. Assuming the individual is not chronically sleep deprived, upon going to bed the next night, this individual will not sleep for 12–14 hours; i.e., there is not a one-to-one correspondence to the amount of sleep lost and the amount of sleep recovered. The most extreme case demonstrating that sleep loss is not recovered on a one-for-one time basis is that of Randy Gardiner. As part of a high school science project, Randy Gardiner decided to set a new Guinness World Book of Records for prolonged wakefulness. With the help of two friends, he remained awake for 264 consecutive hours (11 days). During the first three nights of sleep after this sleep deprivation period, Randy slept slightly more than 13 hours longer than his normal sleep time (Gulevich et al., 1966). That is, he lost approximately 78 hours of sleep, but recovered slightly more than 13 hours. However, prolonged sleep loss results in a deeper sleep, as it is more difficult to arouse humans or animals from sleep after they have been sleep deprived. The observation that sleep loss is not regained on a one-for-one time basis and that arousal thresholds are higher after sleep deprivation suggests there may be an intensity component to sleep. On the basis of a model first proposed by Borbély (1982), it is now accepted that power in the delta frequency band during NREM sleep (sometimes referred to as delta power, or slow wave activity) is a measure of sleep depth or intensity. Therefore, sleep lost during prolonged wakefulness may be functionally recovered by sleeping longer and with deeper intensity.
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C. Humoral/Peptide Regulation of Sleep The notion that sleep is regulated by humoral mechanisms (sleep factors) was postulated in antiquity. The concept that “vapors” were responsible for sleep induction were prevalent in ancient times, and persisted for thousands of years. During the latter part of the nineteenth century, there was renewed interest in “fatigue substances” (Rosenbaum, 1892). The identification of “secretin” by Baylis and Starling (1902) heralded the modern age of endocrinology and provided the basis upon which much of the modern discipline of neuroimmunology is founded. Early in the twentieth century, two laboratories published independent studies that indicated humoral factors modulate sleep. The groups of Ishimori (1909) in Japan and Piéron (Legendre and Piéron, 1910) in France studied sleep-deprived dogs and extracted cerebrospinal fluid from these animals. The cerebrospinal fluid from the sleep-deprived dogs was then injected into rested recipient dogs; i.e., they had not been sleep deprived. The recipient dogs in both studies then fell into a deep sleep that resembled a narcosis. Speaking of these studies, Ishimori wrote “that the cerebral matter of sleep-deprived animals contains a potent hypnogenic substance which cannot be detected in the brain of normally sleeping animals leads to clarify the cause of induction of our normal sleep. . . . A special substance . . . is gradually produced [during waking] . . . and induces the so-called state of drowsiness, and finally causes natural sleep.” These studies were largely forgotten, and it was not until the 1960s that research once again focused on humoral mechanisms for sleep regulation. The CNS utilizes numerous transmitter substances for communication among neurons. These transmitter substances may be small or large molecules, may be stored in vesicles or produced de novo upon neuronal stimulation, and act locally (neurotransmitters released into a synaptic cleft and binding to post-synaptic receptors) or on more distant targets (peptides and hormones). Given the multitude of characteristics of substances used as transmitters in the CNS, it is necessary to establish criteria by which a chemical substance may be said to be involved in the regulation of sleep, i.e., may be considered a sleep factor. Several authors have developed relatively extensive lists of such criteria (e.g., Borbély, 1990; Krueger et al., 1999). An abbreviated list of the criteria by which a substance may be considered a sleep factor includes the following: (1) the substance and its receptors must be found in brain, (2) the substance should induce sleep when administered or when produced endogenously, and (3) inhibition or inactivation of the substance or blocking its receptors
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should reduce sleep. In addition, (4) concentrations or turnover of the substance (or its receptor) should vary with the sleep-wake cycle, (5) the substance (or its receptor) should increase with prior wakefulness, and (6) increased sleep that occurs after sleep deprivation, during infection, or mild increases in ambient temperature should be diminished if the substance or its receptor is antagonized. The neurochemical substrates that act in brain to regulate and or modulate arousal state include the classical neurotransmitters acetylcholine, dopamine, gamma-aminobutyric acid, glutamate, histamine, norepinephrine, and serotonin. There are criteria that differentiate neurotransmitters from peptides and hormones, though peptides and hormones may be considered transmitter substances. In a broader sense, any endogenous substance that promotes sleep may be considered a sleep factor, but in the context of sleep factor research, peptides and hormones are generally the focus of study, not neurotransmitters. There are several peptides and hormones that fulfill some of the criteria listed above for sleep factors. Examples of peptides and hormones implicated in the regulation/modulation of NREM sleep include, but are not limited to, delta-sleep–inducing peptide (a peptide produced by stimulation of the thalamus), growth hormone-releasing hormone, growth hormone, insulin-like growth factor-1, neuropeptide Y, oleamide, cortistatin, cholecystokinin, and insulin (reviewed Obál, Jr. and Krueger, 2003). Though nitric oxide is not a peptide or hormone, it is considered a sleep factor involved in the modulation of NREM sleep. Peptides and hormones that play a role in the modulation of REM sleep include vasoactive intestinal polypeptide, prolactin, and peptide histidine-isoleucine/methionine, whereas corticotropin-releasing hormone and somatostatin have been implicated as wakefulness-inducing factors (reviewed Chang and Opp, 2001; Obál et al., 1990; Steiger, 2003). With respect to the aforementioned criteria by which endogenous substances may be considered sleep factors, only growth hormone-releasing hormone from this list of peptides and hormones has been studied extensively enough to have met all criteria as being a sleep factor. This is not to say that additional peptides and hormones would not meet criteria, but at this time data are not available that would allow such a classification. Finally, the synthesis and secretion of most of the peptides and hormones listed in this paragraph are altered during immune challenge. As such, the changes in sleep and other complex behavior that are induced by immune challenge may be mediated, in large part, by downstream actions of multiple peptide and hormone systems (see Krueger et al., 2001).
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D. Potential Role of Immune Factors The work of Ishimori and Piéron remained largely ignored for many years. During the early 1960s, several groups [Kornmüller (Kornmüller et al., 1961), Monnier (Monnier and Hoesli, 1964), and Uchizono (Nagasaki et al., 1974)] focused their attention on humoral regulatory mechanisms for sleep and conducted independent investigations aimed at elucidating such mechanisms. These groups used conceptually similar approaches to those of Ishimori and Piéron; samples extracted from manipulated animals were transferred into recipient animals and the impact on subsequent sleep-wake behavior was determined. It was the studies of John Pappenheimer at Harvard, however, that had the most impact on our current understanding of interactions between sleep and the immune system. Pappenheimer et al. (1967) demonstrated that cerebrospinal fluid extracted from sleep-deprived goats induced sleep when injected into rats. It took 15 years for this unknown substance, termed Factor S (Fencl et al., 1971), to be extracted (Pappenheimer et al., 1975), purified (Krueger et al., 1978), characterized (Krueger et al., 1982b), and determined to be muramyl peptide (Krueger et al., 1982a; Martin et al., 1984). The identification and characterization of Factor S as muramyl peptide led directly to studies of immune factors and sleep. Immunologists had demonstrated that muramyl peptide, and synthetic muramyl dipeptide, induced the synthesis and secretion of lymphocyte-activating factor/endogenous pyrogen, which is now known as interleukin-1 (IL-1). Fontana et al. (1982) demonstrated that astrocytes produce IL-1, which provided the impetus to determine if IL-1 exerted effects on the CNS in addition to the already-documented ability of this substance to induce fever. Abstracts and papers published in 1983 and 1984 demonstrated that IL-1 injected ICV into rabbits and rats increased the amount of time spent in NREM sleep, suppressed REM sleep, and altered the properties of the EEG (Krueger et al., 1983; Krueger et al., 1984; Tobler et al., 1984). Most studies of a role for immunomodulators as regulators/modulators of arousal state have focused on a few select cytokines (IL-1, TNF-α, IL-6; see later). However, over the last 20 years, numerous other cytokines, chemokines, and growth factors have been reported to modulate sleep-wake behavior. Cytokines, chemokines, and growth factors that have been shown to alter sleep when administered to laboratory animals (and in some cases human volunteers) include IL-1α, IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-13, IL-15, IL-18, interferon-γ, interferon-α/β, TNF-α, TNF-β, MIP-1β, GM-CSF, FGF, NGF, BDNF, GDNF, and TGF-β1. With the exception of IL-1β, TNF-α, IL-6, and interferons
(IFN), each of these immunomodulators has been the subject of one or two studies, and generally speaking no systematic attempts have been made to target these systems for intervention.
III. EFFECTS OF INFECTIONS ON SLEEP A. Basic Studies Feelings of malaise and lethargy are common symptoms during colds or “the flu.” Systematic studies of the impact of infections on sleep were not conducted until the 1920s, when neurologist Baron Constantin von Economo published observations of patients with central nervous system (CNS) lesions produced during viral infections resulting from the encephalitis lethargica pandemic. During the past 20 years, several animal models have been used to determine the impact of infections on sleep, including infection with viral, bacterial, and fungal pathogens; prion-related diseases; and responses to the protozoan parasite Trypanosoma. The extent to which viral infections alter sleep has been determined using mouse-adapted strains of influenza virus. Mice infected with influenza virus exhibit increased NREM sleep primarily during the dark period when they are normally most active (Fang et al., 1994; Fang et al., 1995; Toth, 1994). There is a genetic component to the responses of mice to influenza infection, C57BL/6J mice exhibit robust increases in NREM sleep, whereas BALB/c mice do not (Toth, 1994). The changes in NREM sleep of mice during infection with influenza may be mediated by their capability to produce IFN. IFNs are well known for their antiviral properties (Refinetti, 1999). Type I IFN production is under control of the If1gene. C57BL/6 mice possess the If1 high allele and produce relatively high levels of IFN-α/β in response to influenza (Refinetti, 1999); they exhibit increases in NREM sleep during influenza infection (Toth, 1996; Toth et al., 1995b). In contrast, BALB/c mice possess the If1 low allele, produce low levels of IFN-α/β in response to influenza and do not increase NREM sleep in response to influenza (Toth, 1996). However, because the If1 gene also influences the production of TNF-α and IL-6, cytokines that also modulate NREM sleep, the precise mediators of influenza-induced alterations in NREM sleep remain to be elucidated. The impact of bacterial infections on sleep has been most fully characterized in rabbit models (reviewed Toth, 1999; Toth and Opp, 2002). Infection of rabbits with Staphylococcus aureus or Escherichia coli results in a biphasic change in NREM sleep; there is an initial increase followed by a reduction in NREM sleep, such
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that infected animals sleep less than they normally would at the same circadian time (Toth and Krueger, 1988; Toth and Krueger, 1989). REM sleep is suppressed for the duration of the infection. During bacterial infection, delta power during NREM sleep changes in parallel with changes in NREM sleep. As such, responses of rabbits to bacterial infection include changes in both the amount and intensity of NREM sleep. The increase in NREM sleep of rabbits during infection with bacteria is generally concurrent with the development of fever. However, the febrile response under these conditions is protracted and persists during periods when NREM sleep is suppressed, indicating that fever and increased NREM sleep may be dissociated. Bacterial replication in the host is not necessary to elicit alterations in sleep of rabbits. Inoculation with killed bacteria or isolated bacterial components also alters sleep-wake behavior, though higher doses may be necessary. Structure/function studies indicate that the precise nature of infection-induced alterations in sleep depend on particular properties of the pathogen. For example, NREM sleep of rabbits increases more rapidly, but for a shorter duration, in response to gram-negative bacteria than in response to grampositive bacteria. Lipid A, a component of endotoxin from gram-negative bacteria, elicits increases in NREM sleep of rabbits within an hour of administration, whereas NREM sleep increases after a longer latency when muramyl dipeptide, a synthetic analogue of the monomeric muramyl peptide component of bacterial cell wall peptidoglycan, is injected. Microbial pathogens other than virus and bacteria also alter sleep-wake behavior. For example, the fungus Candida albicans alters sleep of rabbits in a manner similar to that of gram-positive bacteria (Toth and Krueger, 1989). Pathologies in which prions are the etiologic agent also disrupt sleep. Rats and cats develop chronic alterations in EEG parameters and sleep-wake behavior following inoculation with brain homogenates from scrapie-infected animals or from human postmortem tissue, respectively (Bassant et al., 1984; Gourmelon et al., 1987; Gourmelon et al., 1991). Mice in which the prion protein gene has been ablated have alterations in circadian rhythms and sleep (Tobler et al., 1996; Tobler et al., 1997). Humans suffering from fatal familial insomnia, a prion disease in which there is degeneration of the thalamus, exhibit profound alterations in sleep (Montagna et al., 1995). Perhaps the most notorious of infection-induced alterations in sleep are those that accompany infection with trypanosomes. The protozoan Trypanosoma brucei is the causative agent for “sleeping sickness.” During infection with this parasite, nighttime sleep is severely disrupted, there are numerous short bouts of sleep
during daytime, and there is a disappearance of the normal distribution of sleep and wakefulness across the 24-hour day (Buguet et al., 2001; Lundkvist et al., 2004). During the advanced stages of the disease, there are also profound alterations in the secretory patterns of rhythmic hormones, particularly cortisol (Brandenberger et al., 1996), and in the release of sleep-related hormones such as growth hormone (Radomski et al., 1996). Rabbits and rats have been used as experimental models to determine the impact of Trypanosomiasis on sleep-wake behavior (Berge et al., 2005; Darsaud et al., 2004; Lundkvist et al., 2002; Toth et al., 1994). Infection of rabbits induces an increase in NREM sleep after several days that is concurrent with fever and other signs of clinical illness. This initial period of NREM sleep subsides, but there are episodes of increased NREM sleep that occur in association with recrudescence of the parasite (Toth et al., 1994). As in humans (see next section), rats and rabbits lose the circadian rhythms of sleep and body temperature.
B. Human Studies As early as the fourth century B.C., Aristotle documented in his writings about “Sleep and Waking” the basic human experience that fever is commonly accompanied with feelings of tiredness and fatigue. However, with the exception of infections with human immunodeficiency virus (HIV), few studies have systematically examined the influence of spontaneous infection on sleep in humans in a scientific context. There have been in recent years some studies employing vaccinations in humans as an experimental model of infection. These recent studies focused on the effects of sleep loss on responses to immunization rather than on the effects of infection on sleep (Lange et al., 2003; Spiegel et al., 2002). Nevertheless, Smith (1992) investigated sleep time during a rhinoviral influenza infection in otherwise healthy subjects. Sleep time was reported to be shortened during the incubation period but to be prolonged during the symptomatic period of the infection. This result contrasts with another study, in which an experimental infection with rhinovirus led to a decrease in sleep time during the symptomatic period (Drake et al., 2000). Children with mild upper respiratory tract infection did not show any substantial changes in the sleep rate or total sleep time (Gould et al., 1980). Studies investigating changes in sleep following experimental administration of Salmonella abortus equi endotoxin, which mimics some aspects of a bacterial infection, revealed likewise equivocal results [(Pollmächer et al., 2000), reported in detail in the subsection titled “Human Studies,” in Part IV]. Patients infected with Epstein Barr Virus (EBV) typically report
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a strong feeling of tiredness. Polysomnographic recordings of these patients indicate an increase in sleep time and a shorter sleep latency when assessed during daytime (Pollmächer et al., 1995). A basic question in the study of spontaneous infections is whether observed changes in sleep are due to a specific direct central nervous system involvement or reflect changes originating from the systemic immune response to the infection. Most obvious are symptoms of sleepiness in patients with human African trypanosomiasis (sleeping sickness), a disease due to the transmission of Trypanosoma brucei by the tsetse fly and which may develop into meningo-encephalitis. Polysomnographic recordings do not show increased sleep time in these patients but indicate primarily a disruption of the circadian distribution of the sleep-wake rhythm, which usually disappears after successful treatment (Buguet et al., 1993; Buguet et al., 1999; Buguet et al., 2005). Characteristic changes in sleep structure occur also in patients infected with HIV. Sleep disruptions are apparent in healthy subjects that are seropositive, but asymptomatic for the disease. These disruptions to sleep are characterized by increased daytime fatigue and alterations in nighttime sleep. Polysomnographic recordings reveal increased proportions of SWS in combination with enhanced plasma TNF-α concentrations (Darko et al., 1995; Norman et al., 1990; White et al., 1995). Studies in rats show that central nervous administration of HIV glycoproteins 120, 160, and 41 increase NREM sleep, implicating an immediate viral action on the brain (Gemma and Opp, 1999; Opp et al., 1996; SanchezAlavez et al., 2000). However, there are also reports of decreased amounts of SWS in asymptomatic HIVinfected patients (Ferini-Strambi et al., 1995; Reid and Dwyer, 2005). As the infection progresses to AIDS, sleep deteriorates in association with a shift in the type 1/type 2 balance toward type 2 cytokine activity (DiPiro, 1997; Toth, 1995). The differences in sleep reported among studies of HIV-infected humans are likely due to many factors, including the variable lengths of time subjects were infected at the time they visited the sleep laboratory and differences in rates of progression of the disease process. Chronic fatigue syndrome and fibromyalgia are two additional conditions characterized by sleep-related changes. Both conditions can develop after major infections and are associated with distinctly increased subjective daytime sleepiness and fatigue (e.g., Fischler, 1999; Mease, 2005). These syndromes may also be associated with disturbances to nighttime sleep, as determined polysomnographically, as well as with alterations in endocrine and immune function (Farrar et al., 1995; Krupp and Pollina, 1996; Moldofsky, 1995).
However, the role of infectious processes and disruptions to sleep in the etiology of these conditions is obscure. In summary, while subjective fatigue is a very common symptomatic response to infection, the few human subjects studies of spontaneous or experimentally induced infection do not support the view that increased or deeper sleep represents a similar basic and general component of the acute phase response to infection. However, enhanced sleep of humans, although not consistently observed immediately upon infection, may occur with some delay. While the factors determining this response are unknown, enhanced sleep may in turn be beneficial for immune defense. Rabbits responding with distinctly increased SWS to experimental infections with different bacteria showed a more favorable prognosis and less severe clinical signs than rabbits showing minor sleep changes (see later Toth et al., 1993). A similar relationship between poor sleep quality and morbidity/mortality may be evidenced in humans as well (Bryant et al., 2004; Kripke et al., 2002).
IV. CYTOKINE REGULATION OF SLEEP A. Basic Studies 1. Pro-inflammatory, Th1/Th2 Cytokines Most information with respect to the role of cytokines in the regulation and/or modulation of sleep has been derived from studies of three cytokines: IL-1β, TNF-α, and IL-6 (reviewed Krueger and Majde, 2003; Krueger et al., 2001; Opp, 2005; Opp and Toth, 2003). Of these, IL-1β and TNF-α are involved in physiological sleep regulation, whereas IL-6 is likely a modulator of sleep during chronic pathology. These three proinflammatory cytokines are also likely to play a key role as mediators of alterations in sleep during infection, but studies to test directly this hypothesis are generally lacking. Data derived from electrophysiological, biochemical, and molecular genetic studies indicate a role for IL-1β and TNF-α in the regulation of spontaneously occurring, physiological NREM sleep (Opp, 2005). IL-1 perfused via microdialysis into the preoptic area of the hypothalamus of freely behaving rats increases NREM sleep. These increases in NREM sleep are associated with decreases in the discharge rates of wake-active neurons and increases in the discharge rates of at least a subset of sleep-active neurons (Alam et al., 2004). IL-1 microinjected into the dorsal raphe nucleus of the brain stem increases NREM sleep of rats; firing rates of serotonergic neurons in the dorsal raphe nucleus of
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slice preparations are reduced when IL-1 is introduced into the bath (Manfridi et al., 2003). Most studies to date on the role of cytokines as regulators of NREM sleep have used biochemical or molecular genetic approaches (reviewed Krueger and Majde, 2003; Krueger et al., 2001; Opp, 2005; Opp and Toth, 2003). Central or peripheral administration of IL-1 (Figure 3) or TNF into laboratory animals increases the amount of time spent in NREM sleep. Although low doses of cytokines need not affect REM sleep, doses that are generally effective in laboratory studies reduce REM sleep. Neurons immunoreactive for IL-1 and TNF and their receptors are located in brain regions implicated in the regulation of sleep-wake behavior, notably the hypothalamus, hippocampus, and brain stem. There are diurnal changes in IL-1 and TNF mRNA and protein within laboratory rodent brain, and these changes parallel the diurnal changes in sleep-wake behavior. Studies by Moldofsky and colleagues indicate that IL-1–like activity detected in the
Time Post-injection (h)
cerebrospinal fluid of cats is in phase with sleep-wake activity, and that human plasma concentrations of IL-1 peak at sleep onset (Lue et al., 1988; Moldofsky et al., 1986). The amount of time mice in which IL-1 or TNF signaling receptors have been genetically ablated spend in NREM sleep is less than that of genetically intact control animals (Fang et al., 1997; Fang et al., 1998). Substances or manipulations that increase endogenous IL-1 or TNF increase NREM sleep. For example, IL-1 and TNF increase during the course of prolonged wakefulness (sleep deprivation) or in response to mild elevations of ambient temperature; sleep deprivationand temperature-induced increases in NREM sleep are blocked when IL-1 or TNF receptors are antagonized (Opp and Krueger, 1994a; Opp and Krueger, 1994b; Takahashi and Krueger, 1997; Takahashi et al., 1997). Recent clinical and pre-clinical studies suggest IL-6 may be a modulator of sleep during some pathologies that are characterized by excessive daytime sleepiness,
Time Post-injection (h)
Time Post-injection (h)
FIGURE 3 Effects of IL-1β on slow-wave sleep (SWS), rapid eye movement (REM) sleep, and brain temperature of three genetically related strains. Each Sprague-Dawley (n = 7), Fischer 344 (n = 8), and Lewis (n = 7) rat was injected before dark onset with either vehicle (3 μl PFS; open symbols, thin lines) or 5.0 ng IL-1β (in 3 μl vehicle; closed symbols, thick lines). Values are the hourly means ± SEM. The dark bars on the x-axis indicate the dark portion of the light : dark cycle. * p ≥ 0.05 vs. vehicle. [From Opp and Imeri, 2001. Reproduced by permission of Blackwell Publishing].
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such as narcolepsy, sleep apnea, and obesity (Alberti et al., 2003; Okun et al., 2004; Vgontzas et al., 1997). The first study to determine a role for IL-6 as a modulator of sleep indicated that ICV administration of IL-6 into laboratory rabbits induces a febrile response but does not alter sleep (Opp et al., 1989a). However, in that study human recombinant IL-6 was used, leaving open the possibility that species differences in the binding of IL-6 to its receptor complex may have been responsible for the lack of effects on sleep. When rat IL-6 became commercially available, subsequent studies demonstrated that rat recombinant IL-6 when administered ICV increases NREM sleep and induces fever in rats (Hogan et al., 2003). In contrast to IL-1 or TNF, ICV administration of IL-6 does not alter REM sleep of rats. Neither monoclonal nor polyclonal antirat IL-6 antibodies alter any aspect of rat sleep (Hogan et al., 2003), suggesting that this cytokine may not be involved in the regulation of physiological sleep but may modulate sleep under conditions when IL-6 is elevated. The conclusion that IL-6 may not be involved in the regulation of physiological NREM sleep is further supported by studies using IL-6–deficient (knockout, KO) mice. The rhythms of body temperature and NREM and REM sleep are normal in IL-6 KO mice, and the amount of time spent in NREM sleep does not differ from C57BL/6J control mice (Morrow and Opp, 2005b). However, IL-6 KO mice do spend more time in REM sleep across the 24-hour light:dark cycle and have slightly elevated body temperatures during the light period. The recovery of sleep when deprived of sleep for 6 hours at the beginning of the light period is the same in both IL-6 KO mice and C57BL/6J, though the time course of this recovery differs: IL-6 KO mice take 18 hours to obtain this recovery sleep, whereas C57BL/6J mice require only 12 hours (Morrow and Opp, 2005b). These data suggest IL-6 is not necessary for normal timing of sleep and body temperature rhythms, although there may be subtle contributions of IL-6 to responses to sleep deprivation. In contrast to a subtle role in spontaneous sleep or in responses to sleep deprivation, IL-6 does appear necessary for the full manifestation of alterations of sleep during immune challenge. Peripheral administration of 10 μg lipopolysaccharide (LPS) into C57BL/6J mice induces a transient hypothermic response, which is followed by fever (Morrow and Opp, 2005a). NREM sleep is increased and REM sleep suppressed. The magnitude and duration of these responses depends upon timing of administration. In contrast to the febrile response of C57BL/6J mice, IL-6 KO mice become profoundly hypothermic. NREM sleep increases in IL-6 KO mice after LPS, but this increase is about 50–85%
less than that observed in C57BL/6J mice, depending on time of day the LPS is administered (Morrow and Opp, 2005a). LPS suppresses REM sleep of IL-6 KO mice to the same extent as in C57BL/6J mice. Therefore, sleep of mice lacking IL-6 is normal in many respects, but responses to immune challenge are impaired. The three cytokines studied most extensively with respect to sleep-wake behavior—IL-1β, TNF-α, and IL-6—are pro-inflammatory cytokines. Antiinflammatory cytokines take their name from their actions in antagonizing many effects of proinflammatory cytokines. Therefore, it stands to reason that anti-inflammatory cytokines would have the opposite effect on sleep-wake behavior than proinflammatory cytokines. This appears to be the case, at least with respect to IL-4 and IL-10. Central administration of IL-10 into rats or rabbits reduces the amount of time these animals spend in NREM sleep (Kushikata et al., 1999; Opp et al., 1995), whereas IL-4 reduces the amount of spontaneous NREM sleep of rabbits (Kushikata et al., 1998). In addition, mice lacking a functional IL-10 gene spend more time in NREM sleep during the dark period of the light:dark cycle than do genetically intact mice (Toth and Opp, 2001). The increase in the amount of time mice lacking IL-10 spend in NREM sleep during the dark period is presumably due to reduction of the inhibition by IL-10 on IL-1 synthesis. 2. Cytokine Antagonists In addition to genetic ablation of cytokine receptors, several methods have been used to antagonize cytokine systems and determine the impact on spontaneous sleep-wake behavior. These methods include the use of cytokine receptor antagonists, soluble receptors, and antibodies. Each of these methods has proven effective in reducing the amount of time laboratory animals spend in spontaneous NREM sleep. The impact of antagonizing cytokine systems on spontaneous sleep-wake behavior depends on the manner in which the systems are targeted. For example, ICV administration of the IL-1ra reduces NREM sleep of rabbits for less than 1 hour, irrespective of dose (Opp and Krueger, 1991). The relatively transient nature of the reduction in NREM sleep after the IL-1ra is likely due to the short half-life of this antagonist. Targeting cytokines with antibodies or soluble receptors has a greater impact on spontaneous NREM sleep. For example, antibodies directed against IL-1β when administered ICV into rabbits (Opp and Krueger, 1994b) or rats (Opp and Krueger, 1994a) reduce spontaneous NREM sleep for periods of 4 to 12 hours. Antibodies directed against TNF similarly reduce
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spontaneous NREM sleep of rabbits and rats (Takahashi et al., 1995a). Soluble TNF receptors at high doses reduce spontaneous NREM sleep of rabbits by more than 30% in the 6 hours after administration (Takahashi et al., 1995b). Receptor antagonists, soluble receptors, and antibodies target cytokine systems directly. There are numerous mechanisms that provide regulatory feedback control of cytokine actions, which may indirectly modulate sleep-wake behavior. For example, the hypothalamic-pituitary-adrenocortical (HPA) axis, via actions of glucocorticoids, inhibits the synthesis of multiple cytokines in brain. Components of the HPA axis, such as corticotropin-releasing hormone (Opp et al., 1989b) and α-melanocyte–stimulating hormone [α-MSH; (Opp and Krueger, 1988)], when administered into laboratory animals increase wakefulness and reduce spontaneous NREM sleep (reviewed Chang and Opp, 2001). In addition, CRH and α-MSH antagonize effects of IL-1 on sleep and temperature regulation (Opp and Krueger, 1988; Opp et al., 1989b). Rat strains that differ in production of CRH exhibit different responses to IL-1 administration (Opp and Imeri, 2001). Fischer 344 rats respond to IL-1 with a CRH surge that is larger than that observed in Lewis rats. As such, these genetically related rat strains diverge with respect to HPA axis responses to immune challenge, with Fischer 344 being hypersecretory and Lewis rats being hyposecretory. Responses to IL-1 differ among these rat strains (see Figure 3); Lewis rats (deficient in CRH production) respond to IL-1 with rapid increases in NREM sleep, whereas Fischer 344 rats (hypersecretory with respect to CRH production) respond to the same dose of IL-1 with enhanced wakefulness, after which NREM sleep increases (Opp and Imeri, 2001). These difference in responses to IL-1 are attributed to differences in CRH secretion, as pre-treatment of Fischer 344 rats with the CRH receptor antagonist α-hCRH blocks the IL-1–induced wakefulness normally observed in this rat strain (Opp and Imeri, 2001). Because the HPA axis provides negative feedback inhibition for cytokine synthesis in the brain via actions of corticosteroids, cytokine mRNA and protein in brain are out of phase with HPA axis activity. That is, when HPA axis activity is high, cytokine mRNA and protein in rodent brain are low. As such, modulating HPA axis activity impacts cytokine mRNA and protein in brain (Goujon et al., 1996; Mustafa et al., 1999). This relationship between HPA axis activity and cytokine mRNA and protein in brain is of functional consequence to the regulation of physiological sleep. When HPA axis activity is reduced by ICV administration of the CRH receptor antagonist astressin prior to the dark period,
the time when HPA axis activity would normally be at its highest and when laboratory rodents are awake the most, there are increases in NREM sleep of rats and of IL-1 mRNA in rat brain (Chang and Opp, 2000). Pretreating rats ICV with antibodies directed against IL-1 blocks this increase in NREM sleep after HPA axis antagonism (Chang and Opp, 2000).
B. Human Studies As described in the preceding section, basic animal studies have provided considerable evidence that pro-inflammatory cytokines such as IL-1β and TNF-α promote NREM sleep and suppress REM sleep. In addition to direct actions on neurons in brain regions implicated in the regulation of sleep, effects of cytokines may be mediated, in part, by two major cascades of reactions, i.e., via activation of GHRH and/or via activation of nuclear factor-κB (NF-κB) followed by induction of nitric oxide (NO), prostaglandin D2, or IL-2 (e.g., Krueger and Majde, 2003). In humans, the view of a facilitatory influence of cytokines on sleep, especially of those involved in acute innate immune responses, is supported by clinical observations of increased tiredness and sleepiness in the course of infections. However, in comparison with the available data from laboratory animals, human subjects data supporting a role for cytokines in sleep are less direct. It is still not clear which cytokines at what stage in the cascade of immune reactions convey somnogenic influences to the human brain, although in light of recent studies TNF-α appears to be a most likely candidate for such a function (Vgontzas et al., 2004b). In contrast to pre-clinical studies in laboratory animals, human studies are equivocal with respect to whether the cytokines of interest induce sleep or merely increase feelings of tiredness and sleepiness. It is also not clear from human studies whether cytokines serve these functions only during infection or also under normal physiological conditions. As an experimental model of acute infection, in an extended series of studies the group of Pollmächer administered to healthy humans Salmonella abortus endotoxin, an LPS selectively stimulating activity of monocytes and macrophages (Hermann et al., 1998; Korth et al., 1996; Mullington et al., 2000; Pollmächer et al., 1993; Pollmächer et al., 1995). As depicted in Figure 4, this endotoxin induces acute increases in plasma concentrations of TNF-α, IL-6, and the IL-1 receptor antagonist, accompanied by an enhanced release of stress hormones such as ACTH and cortisol. After doses of 0.8 and 0.4 ng/kg body weight of endotoxin, there was a significant increase in time spent in NREM sleep stage 2 sleep, whereas SWS (stages 3 and
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FIGURE 4 Dose-dependent changes in (A) sleep architecture and (B) immune parameters, plasma cortisol concentration, and body temperature in healthy subjects following administration of endotoxin (23:00 h) at doses of 0.2 (n = 7), 0.4 (n = 6), and 0.8 ng/kg body weight (n = 5). Average changes after endotoxin (endotoxin minus placebo) in the time in sleep stages (Wake + Stage 1, non-REM and REM sleep) are plotted through the night. Dashed vertical lines indicate time of endotoxin or placebo administration. Immediately after intravenous injection of the substances, lights were turned off and the subjects were permitted to sleep. Immune parameters measured were plasma levels of TNF-α, soluble TNF-α receptors (sTNFRp55, sTNFRp75), IL-6, and IL-1 receptor antagonist (IL-1-ra) ** and * indicate p < 0.05 in A and B, respectively. Note increase in non-REM sleep (mainly due to increased slow wave activity) immediately after the lowest dose of endotoxin, which did not induce a significant increase in body temperature, and a delayed increase in non-REM sleep after the high dose of endotoxin once body temperature had recovered placebo levels. [Adapted from Mullington et al., 2000. Reproduced by permission of American Physiological Society].
4) remained unaffected. The higher dose of 0.8 ng/kg body weight when given during the daytime even reduced total sleep time and stage 2 sleep during a subsequent nap, although sleepiness was increased in this condition (Hermann et al., 1998). Also, REM sleep was generally reduced following higher doses of endotoxin, which can be attributed to the associated increase in the release of cortisol known to acutely suppress REM sleep (Born et al., 1989). By contrast, an acute enhancement in the amount of NREM sleep and inten-
sity of slow wave activity was observed in these studies when a very low dose of 0.2 ng/kg body weight of endotoxin was administered, which unlike the higher doses did not induce fever or cortisol release (Mullington et al., 2000). These observations confirm that some factor activated early during the acute innate immune response conveys a somnogenic influence to the human brain, although full development of the response (fever, elevated cortisol) with increasing magnitude of challenge interferes with sleep.
28. Sleep and the Immune System
Endotoxin stimulates a diversity of pro-inflammatory cytokines. Hence, the evaluation of changes in sleep after endotoxin does not allow the identification of signal substances mediating such infection-related changes. For this purpose, a number of studies concentrated on some specific cytokines to assess their somnogenic potency. Two studies investigated changes in sleep following administration of IL-6 and IFN-α, representative of key mediators of acute innate immunity to bacterial and viral infection, respectively (SpäthSchwalbe et al., 1998; Späth-Schwalbe et al., 2000). The substances were injected subcutaneously in the evening (19.00 h) before sleep at doses (IL-6: 0.5 μg/kg body weight; IFN-α: 1000 and 10,000 U/kg body weight) inducing systemic concentrations that are clearly beyond those observed normally in healthy humans, but within ranges detected during pathological conditions. Both cytokines enhanced the release of cortisol and significantly increased body temperature, although the thermoregulatory response to IFN-α was on average marginal. Effects on sleep were rather similar for these cytokines. IL-6 as well as IFN-α acutely suppressed SWS during the early part of nocturnal sleep. Moreover, there were also signs of reduced REM sleep after both cytokines. In the case of IL-6, the acute suppression of SWS by IL-6 was followed by increased SWS during the later part of the night, suggesting that via secondary mechanisms IL-6 might enhance SWS after a delay. Interestingly, the suppression of SWS following both cytokines was associated with substantially increased feelings of tiredness measured before sleep, a pattern similar to that observed in many depressed patients who complain of fatigue but simultaneously show reduced SWS (Born and SpäthSchwalbe, 1999). Overall, these results complement the findings after administration of endotoxin in healthy humans, indicating that high concentrations of proinflammatory cytokines like IL-6 and IFN-α, which increase body temperature and stress hormone release, disrupt rather than promote sleep. Similar observations of sleep-disruptive effects of high concentrations of cytokines have been made in pre-clinical animal studies (Opp et al., 1991). This does not exclude that fluctuations in these substances within the normal physiological range as observed in healthy subjects may promote sleep processes. Such an influence could be effectively probed in human subjects by administering substances under normal conditions that suppress the ongoing release of cytokines. So far effects on sleep of IL-1β and TNF-α, or of direct receptor antagonists of these substances, have not been examined in healthy humans. Nevertheless, there is indirect evidence that at least TNF-α could mediate an enhancing influence on SWS in humans.
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Schuld et al. (1999) observed a distinctly reduced time spent in SWS in healthy subjects within the first 2 hours following subcutaneous administration of granulocyte-colony stimulating factor (G-CSF) before sleep. The decrease occurred in parallel to steep increases in the plasma levels of IL-1 receptor antagonist (IL-1ra) and soluble TNF-α receptors (p55, p75) known to antagonize effects of IL-1β and TNF-α, respectively. Moreover, an increase in TNF-α during the late night after G-CSF was paralleled by an increase in SWS in this study. The view of a facilitating influence of TNFα on human sleepiness, but not EEG-staged sleep, was suggested by recent findings in obese men with sleep apnea in which the prolonged administration of etanercept, a selective TNF-α antagonist, reduced daytime sleepiness (Vgontzas et al., 2004b). This antagonist also reduced IL-6 concentrations. In light of the preponderance of sleep-disrupting effects following endotoxin administration as well as following administration of pro-inflammatory cytokines of the early innate immune response, it has been suggested that a somnogenic effect occurs with some delay during the course of the immune response and could be mediated by T-cell–derived cytokines of the adaptive response. However, there has been only one study testing the effects of IL-2, a central regulator of T-cell function, on sleep in healthy humans (Lange et al., 2002). IL-2 was administered subcutaneously before nocturnal sleep at very low doses (1,000 and 10,000 IU/kg body weight) enabling a selective activation of high affinity IL-2 receptors. The cytokine induced various immunological changes, including an increased release of IL-4 and a reduction in the number of circulating lymphocytes and NK cells. However, there was no effect of IL-2 on sleep architecture. Overall, the data from human studies indicate that an early innate immune response and the administration of pro-inflammatory cytokines at concentrations inducing fever disrupt rather than promote sleep. Simultaneously, this response is accompanied by enhanced feelings of tiredness. However, very slight increases in plasma concentrations of proinflammatory cytokines, as they may occur as part of non-pathological fluctuations during the day, could support the expression of sleep.
V. SLEEP MODULATION OF IMMUNITY A. Circadian Influences on Immunity Although there is diurnal variation of IL-1β and TNF-α mRNA and protein in rodent brain, few preclinical studies have focused on the relationships
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among sleep, immune function, and circadian rhythms. There have been numerous studies examining variations in multiple facets of human immune function across normal 24-hour cycles that include a period of regular, undisturbed nocturnal sleep. The changes in immune function observed in these studies could represent an influence of sleep per se, but alternatively could also reflect influences of circadian oscillators. Thus, strict separation of the influences of sleep and circadian oscillators on immune function requires a comparison of the immune parameters of interest during a regular sleep-wake cycle and during 24 hours of continuous wakefulness. Few such studies have been performed. Moreover the exact determination of circadian rhythms requires multiple measurements across the entire 24-hour period, which have also rarely been performed. Facing these methodological obstacles, we will here shortly summarize available evidence that many immune functions, indeed, show variations across a regular 24-hour period, although for some of these variations the contribution of sleep and circadian oscillators has not been dissociated. To assess different aspects of the acute innate and adaptive immune function, these studies employed different measures, including white blood cell differential counts, cytokine activity, proliferative capabilities of lymphocyte and antibody responses. The number of circulating white blood cells shows prominent variations during the regular sleep-wake cycle but also during continuous, 24-hour wakefulness conditions. Roughly similar temporal patterns are evidenced across studies, although the exact timing of the reported diurnal maxima and minima for certain parameters differs considerably among studies (Figure 5). Numbers of leukocytes, granulocytes, and monocytes as well as the major lymphocyte subsets, including T-helper cells (CD4+), cytotoxic T-cells (CD8+), activated T-cells (HLA-DR+) and B-cells (CD19+), all appear to reach a maximum in the evening or early night and then decline throughout the night to reach a minimum in the morning hours (Born et al., 1997; Haus, 1992; Haus and Smolensky, 1999; Miyawaki et al., 1984; Palm et al., 1996; Ritchie et al., 1983). In contrast, NK cell counts reach a minimum during the early part of the night and thereafter increase to reach a maximum in the late morning hours. Cytotoxic activity of NK cells appears to follow a similar time course, at least during regular sleep-wake conditions (Haus, 1992; Ritchie et al., 1983). Though this pattern suggests a differential regulation of cell counts within the different leukocyte subsets, the physiological meaning of such changes remains unclear. A decrease in subset counts could reflect increased migration of respective cells into extravascular and lymphoid tissues. This
view is supported by data from human and animal studies indicating that regular rest periods are associated with an accumulation of lymphocytes in lymphatic tissues (Dickstein et al., 2000; Engeset et al., 1977). However, alternative explanations that decreasing leukocyte counts during the night reflect a marginalization of the cells sticking to the walls of blood vessels or an accumulation in the spleen cannot be entirely ruled out. The variations in the blood cell counts across the 24-hour period generally are rather similar during regular sleep-wake conditions and during continuous waking. However, sleep during the night may generally reinforce the decrease in the number of circulating lymphocytes during this period, thereby slightly advancing the phase of their circadian rhythm with the maximum count reached at an earlier time (Born et al., 1997). With respect to changes in blood cytokine activity across the 24-hour cycle, overall results are less consistent. This may be partly due to the fact that, with the exception of IL-6, many of the cytokines of interest do not serve hormone-like functions, i.e., do not convey signals directly via the circulation. Thus, under normal non-pathological conditions the endogenous levels of these cytokines in blood are close to the lower detection limit of most assays. On this background, rather than determining cytokine levels in serum, some more recent studies measured the production of cytokines after stimulating blood cells in vitro with mitogens (i.e., the capability of cells to release a cytokine in response to a stimulus), and with this approach appeared to reveal more consistent effects of sleep. Several reports suggest that the production of IL-1β and TNF-α reaches a maximum during the afternoon and evening hours and then decreases during undisturbed nocturnal sleep (Hohagen et al., 1993; Petrovsky and Harrison, 1998; Petrovsky et al., 1998; Zabel et al., 1990). However, these findings were based on absolute level of cytokine activity determined in the blood samples. When the production of IL-1β and TNF-α is standardized with respect to monocyte numbers, the main cellular source of these cytokines in blood, the sleep-related temporal dynamics of cytokine activity disappear (Born et al., 1997). Since blood monocyte counts also decrease during nighttime, the diurnal variations in IL-1β and TNF-α observed in some studies most likely do not reflect changes in cytokine production per se, but rather a decrease in the number of circulating cells producing the cytokines. Moreover, the production of IL-1β and TNF-α per number of monocytes under conditions of sustained wakefulness does not reveal systematic circadian variations (Born et al., 1997). Nevertheless, this issue is in need of further exploration, perhaps by focusing on
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Neutrophils
B-Cells
6.0 /nL
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5.0
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**
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*
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*
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**
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/nL Activated T-Cells (HLA-DR)
**
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FIGURE 5 Mean (±SEM) numbers of (left) circulating neutrophils, monocytes, natural killer cells, and total lymphocytes, and (right) of B-cells, CD4+ T (helper) cells, CD8+ T (cytotoxic) cells, and activated T-cells (HLA-DR+) during two 51hour sessions (WS-WS and WW-WS). The WS-WS condition (open circles, dashed lines) included two regular wake-sleep cycles. During the WW-WS condition (black squares, solid lines) subjects remained awake the first night and recovered sleep during the second night. Time in bed (horizontal bars) started at 23:00 h, and on the first night ended at 7:00 h. On the second night, subjects were allowed to sleep ad libitum, and stayed in bed until 11:00 h. n = 10. ** p < 0.01, * p < 0.05, for pairwise comparisons between the effects of both conditions. Note, during sleep numbers of NK cells, CD4+ and CD8+ T-cells are acutely reduced in comparison with nocturnal wakefulness, whereas after sleep this relationship is reversed, indicating that the effects of sleep and nocturnal sleep deprivation essentially depend on the time of measurement. [From Born et al., 1997. Reproduced by permission of The Journal of Immunology].
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the intracellular production of these cytokines in specific monocyte subtypes using multi-parametric flow cytometry. Though cytokine production per se may not be modulated in a diurnal fashion, the signals conveyed by IL-1β and TNF-α may be subjected to a diurnal regulation because their receptors exhibit substantial variation across the 24-hour cycle. Haack et al. (2004) serially sampled blood at 2-hour intervals and determined concentrations of soluble TNF receptors (sTNFR) during normal sleep and wakefulness as well as during a 24-hour vigil. The soluble receptors act as functional agonists of TNF-α. Levels of sTNFRp55 and sTNFRp75 do not differ significantly between nocturnal sleep and nocturnal wakefulness. However, concentrations of both soluble receptors showed a distinct circadian rhythm with peak levels around 0600 h. The inverse relation of the rhythm of soluble receptors to that of body temperature led those authors to suggest an involvement of the TNF signal in the circadian regulation of body temperature. If so, increasing TNFR concentrations during nighttime could facilitate sleep via decreasing body temperature during this period (Gilbert et al., 2004). IL-6 is critically involved in the regulation of various aspects of the acute phase response, and it is also an important stimulus of pituitary-adrenal secretion (Späth-Schwalbe et al., 1996; Späth-Schwalbe et al., 1998). Its concentration in blood is distinctly higher than that of other pro-inflammatory cytokines. However, regarding diurnal variations or a possible association of variations in IL-6 concentrations with nocturnal sleep, reports vary largely. Some studies failed to find any systematic changes in IL-6 concentrations across the 24-hour cycle (Born et al., 1997; Lissoni et al., 1998), whereas others suggested significant maxima at different times of the day (Bauer et al., 1994; Gudewill et al., 1992; Sothern et al., 1995; Vgontzas et al., 1999; Vgontzas et al., 2005; Zabel et al., 1993). Haack et al. (2002) have provided evidence that these discrepancies might be attributed to the procedures of blood drawing used in these studies. These authors found that placement of an indwelling intravenous catheter used for frequent blood sampling over an extended period of time can produce spurious increases of IL-6 but not TNF, most likely due to local proinflammatory activity resulting from mechanical irritation of venous walls by the catheter or by the presence of contamination of blood sample by low levels of heparin used in the collection procedures. Whereas this observation has been replicated in some laboratories (see Figure 7D), other controlled studies have not confirmed a confounding effect of catheter placement (Vgontzas, Papanicolaou et al., 1999; Redwine, Hauger
et al., 2000). Nevertheless, in one study where sampling was conducted using a needle stick for each blood sample (Sothern et al., 1995), a distinct circadian rhythm of serum IL-6 concentration in healthy men, with peak concentrations at 0100 h during the night and nadir concentrations around 1000 h in the morning, was revealed. Similarly, Redwine et al., who used serial sampling procedures, found a nocturnal peak of IL-6 at around 0100 h, which was delayed by nocturnal wakefulness (Figure 6). Overall, IL-6 concentrations were higher during nighttime than daytime in this study. This pattern of diurnal variation in IL-6 activity was confirmed in a recent study assessing the intracellular production of IL-6 in monocytes as the main source of this cytokine in blood (Dimitrov et al., 2005). IL-6 was determined by multi-parametric flow cytometry after stimulating the cells with LPS. With reference to the total number of monocytes, the percentage of monocytes producing IL-6 showed a clear 24-hour rhythm peaking during nighttime around 0250 h, independently of whether the subject slept or remained awake during the night. The particular focus of this study, however, was on the regulation of IL-6 receptors (IL6R). Membrane-bound IL-6R densities, assessed in terms of the number of IL-6R on granulocytes, monocytes, and T-cells during sustained wakefulness, also showed distinct circadian rhythms with peak densities, respectively, around 0600 h (T-cells), 0800 h (monocytes), and 1000 h (granulocytes). During regular sleep-wake conditions the peaks occurred slightly earlier in time, but the patterns were otherwise similar. Soluble receptor compounds binding IL-6 (sIL-6R, sgp130) were also assessed but did not show any systematic variation when subjects remained awake throughout the 24-hour study period. Production of the T-cell–derived cytokine IL-2 also exhibits distinct diurnal variation, characterized by increases during nocturnal sleep (Lissoni et al., 1998). T-cell production of IFN-γ is likewise enhanced during nighttime sleep (Hohagen et al., 1993; Petrovsky and Harrison, 1998; Petrovsky et al., 1994; Petrovsky et al., 1998). The increase in production of the T-cell–derived cytokines may start prior to the sleep period. However, significant diurnal variations or nocturnal increases in the activity of these cytokines are not observed during conditions of sustained wakefulness, arguing against a primary influence of circadian oscillators on these cytokines (Born et al., 1997). Petrovsky and Harrison (1997) examined 24-hour variations during regular sleep-wake conditions in the ratio of IFN-γ to IL-10 production. The ratio of IFN-γ to IL-10 production is an indicator of the balance between type 1 and type 2 cytokine activity, and is
28. Sleep and the Immune System
A.
B.
C.
D.
FIGURE 6 Averaged change scores from the awake period (±SEM) for circulating levels of IL-6 (A), GH (B), cortisol (C), and melatonin (D) in subjects during baseline (f) and PSD-E nights. The vertical dashed line after 23:00 h indicates the average time that the subjects were asleep on the baseline night; the vertical dashed line at 03:00 h indicates the time that the subjects were asleep on the PSD-E night. [From Redwine et al., 2000. Reproducted by permission of The Endocrine Society].
considered an essential determinant for the selection of the effector mechanisms of immune defense. T helper 1 (Th1) cells releasing mainly IFN-γ, aside from other cytokines such as IL-2, become activated in response to intracellular viral and bacterial challenges and support various cellular responses (so-called type 1), including macrophage activation and antigen pre-
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sentation. In contrast, the cytokines characteristic of T helper 2 (Th2) cell-mediated immunity, such as IL-4, IL-5, and IL-10, tend to drive humoral defense (type 2) via stimulating mast cells, eosinophils, and B-cells against extracellular pathogens. Predominance of type 2 cytokines, as observed, for example, in aged humans, is associated with reduced responses to vaccination (Ginaldi et al., 1999a). Studies by Petrovsky and Harrison (1997, 1998) and Redwine et al. (Redwine, Dang et al., 2003) show that nocturnal sleep favors a shift toward Th1-(predominance of IFN-γ) mediated immune defense peaking between 0300 h and 0630 h (e.g., Figure 7). Notably, the shift towards Th1 activity is completely blocked by administering glucocorticoids prior to sleep. In addition, as will be discussed below, a nocturnal shift toward Th1 predominance fails to occur in persons with clinically disordered sleep (Redwine, Dang et al., 2003). In summary, studies in healthy humans indicate a distinct and differential influence of circadian oscillators on the number of circulating white blood cell subpopulations, which is revealed under conditions of sustained 24-hour wakefulness. The most prominent feature of this circadian influence represents a decrease in circulating lymphocytes during nighttime, which may well reflect an enhanced extravasation of these cells to lymphatic tissues during the nocturnal rest period. Diurnal variations observed for cytokine activity can be considered secondary to circadian influences on the cells producing the respective cytokines, although further consideration of this question requires assessment of cytokine production at the cellular level. The diurnal variations in cytokine activity in blood may in principle originate from a differential migratory behavior of the cytokine-producing cells, as appears to be the case for the variations in IL-1β and TNF-α production, which is not observed when cytokine production is standardized with respect to numbers of circulating monocytes. However, diurnal variations could also reflect an acute regulation of cytokine expression by blood-borne factors. A distinct nocturnal increase in IL-6 activity independent of the number of circulating monocytes has been demonstrated. Of interest are findings of distinct circadian rhythms in sTNFR and membrane-bound IL-6R, indicating that the circadian regulation of the cytokine signals may also be conveyed via an influence on respective cytokine receptors.
B. Sleep Effects on Immunity 1. Basic Studies Animal studies indicate that long-term sleep deprivation is detrimental, and if prolonged, sleep
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A
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sIL-6R ng/ml
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FIGURE 7 Mean (±SEM) concentrations of (A) sIL-6R, (B) sgp130, and (C) percentage (of total monocyte counts) of IL6–producing monocytes during a regular sleep-wake cycle (black circles) and during 24 hours of continuous wakefulness (white circles).The shaded area indicates bed time. Parameters were measured in 15 healthy men. sIL-6R concentrations distinctly increased during late sleep (after 2:00 h) when REM sleep is predominant. Analysis of data during 24 hours of wakefulness did not reveal any circadian rhythm. Concentrations of sgp130 (serving as functional antagonist of the sIL-6R) were not influenced by sleep or circadian rhythm. Percent of IL-6–producing monocytes (determined after LPS stimulation with flow cytometry) were not changed by sleep but showed a pronounced circadian rhythm with peak numbers around 3:30 h. In (D) IL-6 concentrations in plasma are indicated, which continuously increased across the 24-hour interval regardless of whether subjects slept or remained awake. The insert depicts IL-6 concentrations before and after replacement of the intravenous catheter, which, due to difficulties in blood sampling, was done in four cases. The distinct fall in IL-6 plasma concentration after catheter replacement suggests that the increasing IL-6 over the 24-hour interval reflects contamination of the measurement by local IL-6 release due to catheterization. [Adapted from Dimitrov et al., 2005]
30 20
*
35 30 25 20 15 10 5 0 before
after
10 0
deprivation results in death. Long-term sleep deprivation studies were conducted in the late nineteenth and early twentieth century, before the discovery of REM sleep, and as such constituted total sleep deprivation. Several of these studies were conducted on puppies or adult dogs, and all resulted in death over periods of 3
to 77 days (reviewed Rechtschaffen et al., 1989). These studies report various pathologies, including hypothermia, weight loss, and a reduction in red blood cell counts. It was the pioneering studies of Alan Rechtschaffen, however, that provided the basis for the statement that prolonged sleep deprivation of laboratory rats results in death. Rechtschaffen and his students at the University of Chicago advanced pre-clinical sleep deprivation research by designing an apparatus that subjected an experimental animal and a control animal to the same stimulus. This apparatus is composed of a flat disk that is separated into halves. One rat is placed on each half of the disk and has food and water available ad lib. One of the animals is designated the experimental animal, and when the computer algorithm detects entry into sleep by the experimental animal, the disk is slowly rotated until the rat wakes up. If the rotation of the disk does not awake the rat, it is eventually forced by the partition wall off the disk and into a shallow pan of water. The rat must then wake up and get back onto the disk, or remain in the water. Because of this feature, this apparatus is now known as the disk-over-water method of sleep deprivation. The control animal may also be partially sleep deprived, but is able to sleep whenever the experimental animal is awake. The initial study (Rechtschaffen et al., 1983) demonstrated total sleep deprivation by this method resulted in death with survival times ranging from 5
28. Sleep and the Immune System
to 33 days; no control rats died. Many subsequent studies using this apparatus (summarized in Rechtschaffen et al., 1989) determined survival times to range from 11 to 32 days when rats were deprived of all sleep, and from 16 to 54 days when selectively deprived of REM sleep. The variability in survival times eventually led Rechtschaffen’s group to divide survival into quartiles, and to define a characteristic syndrome that progressed through the course of deprivation. This syndrome included scrawny and debilitated appearance, severe ulcerative skin lesions on the tail and plantar regions of paws, and increased food intake, which during the final quartile of survival reached 80 and 100% above baseline levels for total sleep-deprived rats and REM sleep-deprived rats, respectively. This increase in food intake was concurrent with weight loss (about 18 and 22% for total sleep deprivation and REM sleep deprivation, respectively), increased energy expenditure, and decreased body temperature during the mid-to-late stages of deprivation. Plasma norepinephrine increased and plasma thyroxine decreased. Of these effects, the increase in energy expenditure was most predictive of death. Though the sleep deprivation syndrome indicated severe disruption to multiple organ systems, the proximal cause of death remained unknown until Carole Everson demonstrated that rats subjected to sleep deprivation until death became septicemic (Everson, 1993; Everson and Toth, 2000). The septicemia is evidenced by infection of mesenteric lymph nodes by viable bacteria, which presumably translocated from the intestine. Using the same model, Everson has shown that long-term total sleep deprivation of rats results in a pro-inflammatory state as indicated by elevated serum IL-1β and endotoxin (Everson, 2005). These increases in serum IL-1β and endotoxin are apparent within 10 days of sleep deprivation, long before the expected time of death of 21 days (Everson, 2005). In addition to this progressive inflammatory state, several serum Ig classes (IgM, IgG, IgA) increase during the course of the deprivation protocol, though no experimental antigens had been administered. Immune activation does not result in eradication of invading bacteria and toxins, suggesting impaired immune function. 2. Human Studies As with animal studies, the demonstration of a causative role of human sleep for the modulation of immune function requires the experimental manipulation of sleep and wakefulness. To rule out confound-
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ing influences of circadian rhythms, wake periods in these experiments usually cover the same phase of the 24-hour cycle as the sleep period, i.e., nighttime in humans. Asking a human subject, or forcing a nonhuman animal, to stay awake when he/she would normally be asleep induces a state of deprivation accompanied by some more-or-less non-specific stress responses. There is no doubt that sleep deprivation of humans, if extended for more than one night, represents a stressful experience that via activation of the major stress hormonal systems per se influences immune function. Accordingly, changes in immune function found after such extended periods of wakefulness are to be considered consequences of the deprivation of sleep, but should not be used to directly infer functions of normal sleep. However, stress-related effects appear to be limited when subjects voluntarily stay awake during the night for only a couple of hours (as during partial sleep deprivation) or a single night. In fact, in humans the plasma levels of the stress hormones (cortisol, catecholamines) during a night of quiet wakefulness, although significantly enhanced in comparison with those observed during nocturnal sleep, do not reach the levels seen during normal daytime wakefulness or in response to experimental stressors (e.g., Dodt et al., 1997; Lange et al., 2003). Accordingly, it is justified to assume that differences between waking and sleeping subjects occurring in the course of a single night, and often only during the first few hours of the night, are only marginally confounded by non-specific stress responses. As such, these differences in cortisol and catecholamines under these conditions primarily reflect differential influences of sleep and wakefulness. In fact, based on this rationale, a widely used approach to dissociate the effects of sleep from those of circadian oscillators compares time courses of parameters of interest between a regular sleep-wake cycle and a condition of sustained 24-hour wakefulness. Here, we discuss separately results from studies investigating immune functions during short periods of sleep deprivation (partial sleep restriction or total sleep deprivation of up to a single night) and prolonged periods of sleep deprivation. As described in the subsection titled “Human Studies” in Part IV, numbers of almost all white blood cell subpopulations show marked diurnal rhythms, manifest as decreased counts of these cells in blood during nighttime during conditions of sustained wakefulness. Sleep appears to add synergistically to this circadian influence. Thus, compared with a night awake or partial sleep deprivation, nocturnal sleep reduces the numbers of granulocytes, monocytes, and
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the major lymphocyte subsets (Born et al., 1997; Irwin et al., 1996). Regarding NK cells, some studies report increased NK cell numbers and also increased NK cell activity after sleep in comparison with wake periods (Irwin et al., 1994; Irwin et al., 1996), suggesting that the loss of sleep reduces morning levels of NK cell numbers and NK cell activity. In contrast, when NK cell numbers are measured during sleep, there is an immediate reducing influence of sleep in comparison with waking NK cell numbers (Born et al., 1997). However after the sleep period, there was a reboundlike increase in circulating NK cells exceeding the numbers during the wake condition, indicating that discrepancies among the studies may be a result of whether NK cell counts are determined during sleep or after awakening. Investigations of cellular adhesion molecule expression suggest that the overall decrease in circulating lymphocytes seen during regular sleep reflects an increase in trafficking of these cells to extravascular tissues (Redwine et al., 2004). These experiments show that the percentage of Mac-1 positive lymphocytes increases during a night of regular sleep, as compared to conditions of partial sleep deprivation (between 2300 and 0300 h). Simultaneously, regular sleep tends to reduce percentages of L-selectin–positive lymphocytes and monocytes. The increase in the proportion of lymphocytes expressing Mac-1 may derive from cleavage of L-selectin in the process of immune activation (Tohya and Kimura, 1998), and is thought to indicate an increased ability of lymphocyte subpopulations to migrate to lymphoid tissue. Presently, there is no substantial evidence that pro-inflammatory cytokine activity is also subject to a differential regulation/modulation by sleep in humans. Decreases in the production of IL-1β and TNF-α observed during sleep as compared to short wake periods are related to diurnal changes in the number of monocytes in blood (Born et al., 1997; Born and Hansen, 1997; Dinges et al., 1995; Uthgenannt et al., 1995). Reported diurnal variation in plasma IL-6 concentrations may be confounded, in part, by the use of indwelling intravenous catheters (Haack et al., 2002). Redwine et al. (2000) report increases in IL-6 plasma concentrations during early nocturnal sleep (2200 and 0300 h) as compared to levels during partial sleep deprivation between (see Figure 6), whereas others failed to find such a difference between sleeping and waking subjects (e.g., Born et al., 1997). Intracellular production of IL-6 in monocytes as determined by multi-parametric flow cytometry did not reveal any modulating effect of sleep on this cytokine, though the percentage of IL-6–producing monocytes, with respect to total monocyte counts,
showed a marked circadian rhythm (Dimitrov et al., 2005). Nevertheless, consistent with the view of an increased IL-6 signaling during sleep (Redwine et al., 2000), this latter study revealed pronounced influences of nocturnal sleep, in comparison with wakefulness, on the regulation of soluble IL-6R (sIL-6R; Figure 7). Different from other cytokine signals, sIL-6Rs mediate agonistic actions of IL-6. IL-6, by forming a complex with sIL6-R, is able to influence a great variety of cells that express only membrane-bound gp130 (e.g., Jones and Rose-John, 2002). The process by which IL-6 is able to stimulate cells lacking the membrane-bound IL-6R is termed trans-signaling, and is thought to be responsible also for the effects of IL-6 on neural functions and the brain (Schobitz et al., 1995). Nocturnal sleep increases sIL-6R blood concentrations on average by 70% over levels during wakefulness (Dimitrov et al., 2005) (see Figure 7). The effect of sleep on sIL-6R is most pronounced during the late part of the night, when REM sleep prevails. Similarly, Redwine and colleagues (Redwine et al., 2000) found that circulating levels of IL-6 were higher during REM sleep as compared to periods of SWS. Analyses of subtypes of sIL6R indicate that the sleep-dependent increase in IL-6R results primarily from an increase in shedding of membrane receptors, i.e., to the proteolytic cleavagevariant of the IL-6R. Thus, by enforcing trans-signaling, sleep appears to widen the profile of IL-6 actions, thereby integrating signaling to both the immune and central nervous system. Sleep also exerts a distinct effect on T-cell–derived cytokines. IL-2 activity is enhanced during regular nocturnal sleep as compared to conditions of partial or total sleep deprivation, and this effect is independent of the total number of circulating T-cells (Born et al., 1997; Irwin et al., 1996; Uthgenannt et al., 1995). Moreover, studies of T helper cells indicated a shift in the type 1/type 2 cytokine balance toward increased type 1 cytokine activity during sleep (Dimitrov et al., 2004a). This shift is evidenced as an increased ratio of IFN-γ to IL-4–producing T helper cells during the early part of sleep that in humans is dominated by SWS. However, this shift toward type 1 cytokine activity is only of moderate size and is replaced by type 2 cytokine dominance during sleep late in the night. Nevertheless, data from a recent study concentrating on type 1 and type 2 cytokine activity in monocytes corroborate the view of sleep-induced increases in type 1 activity (Lange et al., 2005). Multi-parametric flow cytometry reveals a distinct increase during nocturnal sleep in the percentage of monocytes producing IL-12 (i.e., a cytokine supporting type 1 responses) and a concurrent decrease in the percentage of monocytes producing the type 2
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↓ ↓ ↔ ↔ 96 h↑ ↓ 72 h↓ 63 h↑ ↓ ↔ ↑ >39 h↑ ↑ ↔ ↑ 63 h↑ ↑ >24 h↑
24 h/every 3 h 120–168 h/6:30 h 64 h/22:00 h 40 h/7:00 h 72–126 h/variable 40 h/every 30–120 min 48 h/8:00 h 77 h/12:30 h 88 h/every 6 h 24 h/every 30–60 min 40 h/every 60 min 8 d partial SD/every 30 min Born et al., 1997 [1,2] Boyum et al., 1996 [3] Dinges et al., 1994, 1995 Heiser et al., 2000 Kuhn et al., 1969 Moldofsky et al., 1989 Öztürk et al., 1999 Palmblad et al., 1976 [2] Shearer et al., 2001 Späth-Schwalbe et al., 1992 [2] Vgontzas et al., 1999 Vgontzas et al., 2004a [4]
IFN-g IL-2 TNF-a IL-6 IL-1b Lymphocytes NK cells Monocytes Granulocytes (neutr.) Duration of SD/ time of blood sampling
Effects of Sleep Deprivation (SD) of More Than 10 hours on White Blood Cell Counts and Cytokines TABLE 1
cytokine IL-10, as compared to wakefulness. These results are similar to those of Redwine et al. (Redwine, Dang et al., 2003), who found a nocturnal shift in the ratio of stimulated production of IFN-γ/IL-10 using mixed mononuclear cell populations. Taken together, these observations suggest a preferential facilitation of type 1 cytokine activity and point to a general supportive influence of sleep on launching a cellular adaptive immune response. A considerable number of studies in healthy humans have examined effects of prolonged periods of sleep deprivation, lasting between 24 hours and 168 hours, on immune functions (Table 1). Numbers of circulating granulocytes and monocytes increase after extended periods of total or partial sleep deprivation (e.g., Boyum et al., 1996; Dinges et al., 1994; Heiser et al., 2000; Kuhn et al., 1969). The effects of sleep loss on granulocytes and monocytes appear to take some time to develop. In the study by Dinges et al., monocytes did differ until 39 hours of sleep deprivation, and the increase in granulocyte counts required 63 hours of deprivation to be altered. These long-term sleep deprivation studies also rather consistently indicate a more or less pronounced decrease in the number of NK cells, in NK activity, and in the number of the major lymphocyte subpopulations that gradually develops during the sleep-deprivation period (Boyum et al., 1996; Dinges et al., 1994; Öztürk et al., 1999). Examination of cytokine activity likewise suggests an activation of innate immune functions after extended sleep deprivation. Thus, an early study by Moldofsky et al. (1989) reported increases in IL-1–like and IL-2– like activity in plasma after 40 hours of wakefulness. Another study examining effects of 4 days of partial sleep deprivation (allowing 2-hour naps each day) and of total sleep deprivation revealed an increase in soluble TNF-α RI (p55) and in IL-6 plasma concentration following total sleep deprivation (Shearer et al., 2001). Levels of TNF-α, TNF-α RII (p75), and of IL-10 and sIL-2R remained unaffected by prolonged sleep deprivation in this study. Plasma concentrations of IL-6 increase after 1 week of sleep restriction to 6 hours a night (Vgontzas et al., 2004a). In contrast, Boyum et al. (1996) reported decreased plasma IL-6 concentrations after 96 hours of sleep deprivation in young men participating in a military training course. However, in addition to being sleep deprived, these men were also subjected to physical exercise and reduced food intake. No consistent changes in T-cell–derived cytokines such as IL-2, IL-4, and IFN-γ were found after prolonged sleep deprivation (Boyum et al., 1996; Dinges et al., 1995). In summary, in comparison with sleep restriction or short periods of sleep deprivation (one night),
Significant effects of SD in comparison with regular sleep-wake conditions are indicated. [1] Note, only effects after the first night (i.e., >10 hours of SD) are shown. Effects occurring during the first night are partly opposite and not shown (see text). [2] Production of cytokines was measured after in vitro mitogen stimulation of whole blood or PBMC. [3] Most of the effects in this study were observed after 24 hours of sleep deprivation. [4] Measures were taken before and after sleep restriction to 6 hours for 1 week.
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nocturnal sleep promotes a decrease in circulating lymphocytes presumably reflecting an enhanced accumulation of these cells into extravascular lymphoid tissues. Moreover, apart from some studies indicating increased IL-6 concentrations during sleep, sleep has been found to increase sIL-6R concentrations, enabling an integration of IL-6 actions on brain and other nonimmune functions, aside from its effects on immune cells through the membrane-bound IL-6R. Finally, distinct sleep-dependent increases in some type 1–related cytokines such as IL-2 and IL-12 have been demonstrated. Overall, these changes point toward a supportive influence of sleep on the initial steps of an adaptive cellular immune response, i.e., on the priming of naive lymphocytes by antigen presenting cells in secondary lymphatic tissues. Extended periods of sleep deprivation, on the other hand, primarily manifest themselves in a distinct granulocytosis, decreased NK cell numbers and activity, and other signs of disturbed innate immunity.
C. Sleep Effects on Infectious Processes The profound alterations in sleep that occur during an infection have led to the hypothesis that sleep promotes recovery. Though such an hypothesis has high face validity and is the basis of folklore, there is little empirical evidence to support such an hypothesis. Most studies of interactions between sleep and the immune system have used one of two approaches: Animals or human volunteers are subjected to immune challenge and the impact on sleep determined, or subjects are sleep deprived and impact on immune function determined. As reviewed in the previous section, most studies of immune function and sleep have documented changes in cytokine levels or profiles, changes in numbers or cytotoxic activity of NK cells, or changes in numbers of cell types associated with specific aspects of immunity. While determination of these parameters provides information about many aspects of the immune system, they do not necessarily indicate there are functional consequences of infection-induced alterations in sleep. That is, do the changes in these immune parameters during the course of infection facilitate recovery? To determine if there are functional consequences to infection-induced alterations in sleep, it is necessary to alter sleep during the course of infection and determine if there are effects on outcome. An early pre-clinical study by Brown et al. (Brown, Pang et al., 1989) evaluated the effects of sleep deprivation of mice on responses to influenza virus challenge. Mice that were sleep deprived before inoculation with influenza virus did not clear the virus as efficiently as non–sleep-deprived animals (Brown, Pang et al., 1989). However, subsequent studies failed to replicate these
provocative results (Renegar et al., 1998a; Renegar et al., 1998b; Renegar et al., 2000), and it is not clear whether sleep loss alters influenza risk in animals. In another pre-clinical study, Toth and Opp (Toth et al., 1995a) sleep deprived rabbits for 4 hours either before or immediately after inoculation with Escherichia coli. Rabbits sleep deprived before infection demonstrated increases in NREM sleep, delta power during NREM sleep, and NREM sleep bout lengths that were greater than observed after sleep deprivation alone or E. coli alone. Animals that were sleep deprived after infection with E. coli exhibited only transient increases in NREM sleep and delta power during NREM sleep, suggesting these rabbits maintained a sleep deficit. Rabbits inoculated with E. coli and then sleep deprived developed fevers that were greater in magnitude than either the hyperthermia elicited by sleep deprivation or the fever elicited by infection alone. Other clinical symptoms of E. coli infection (plasma IL-1β, corticosterone, cortisol, and triglycerides; total white blood cell counts; nucleated red blood cells; lymphocytes; neutrophils) were not dramatically altered by the combination of sleep deprivation and infection. As such, under the conditions of this pre-clinical study, sleep deprivation of rabbits alters changes in sleep that occur during bacterial infection but does not alter clinical illness. Two recent studies of human subjects also examined the question of whether sleep loss is of consequence with respect to immune function. Spiegel et al. invited healthy subjects into the sleep laboratory, where they were either allowed 8 hours sleep each night for 14 days or were subjected to 14 days of sleep restriction to 4 hours per night. After 4 days of this protocol, individuals of both groups were immunized against infection to influenza A virus; that is, they received their flu shots (Spiegel, Sheridan et al., 2002). In those persons who underwent sleep restriction, virus-specific antibody titers were less than 50% of those in non–sleep-deprived persons. In a similar study, Lange et al. found that total sleep deprivation for one night after vaccination lead to low virusspecific antibody titers after immunization against hepatitis A virus (Lange, Perras et al., 2003). These two studies are intriguing because they demonstrate impairment of immune function by short-term sleep loss that is of functional consequence to public health. It may be that prior sleep history is a factor to be considered in vaccination programs, in that sleep loss prior to immunization may reduce the effectiveness of antibody production against the vaccine and result in individuals being at risk for these viral diseases. As sleep loss appears to impact at least some aspects of responses to true infections of viral vaccinations, the converse, that changes in sleep during the course of
28. Sleep and the Immune System
infection aid in the recovery process, may also be true. Though few studies have focused on this aspect of the relationship between sleep and immune function, there is tantalizing evidence this may indeed be the case. Toth et al. (1993) retrospectively analyzed data obtained from rabbits that had been infected with E. coli, Staphylococcus aureus, or Candida albicans and calculated a sleep quality score for each animal. The sleep quality score incorporated both the amount of time spent in NREM sleep and delta power during NREM sleep. Using the sleep quality score, the animals were classified as exhibiting minimal sleep changes during infection, enhanced sleep during infection, or suppressed sleep during infection. Enhanced sleep during infection was associated with more favorable prognosis (survival) and less severe clinical illness, whereas suppressed sleep was associated with increased mortality and more severe clinical illness. The results of these analyses support the hypothesis that changes in sleep through the course of an infectious challenge facilitate recuperation.
D. Mechanisms Linking Sleep and Immunity Humoral and neural influences are the principal mediators of bi-directional sleep-immune interactions (Besedovsky and delRey, 1996). Both the endocrine and autonomic nervous systems convey efferent information from the brain to the periphery. The endocrine and autonomic nervous systems also convey afferent information from peripheral systems to the brain. Accordingly, these systems mediate the brain’s control over immune processes during sleep and also mediate influences of systemic immune responses on the central nervous sleep process. There may be additional mechanisms linking sleep and immunity. For example, it has been suggested that sleep-promoting actions of TNF-α signaling are conveyed via an influence on hypothalamic thermoregulation (Haack et al., 2004). The disturbance of sleep observed after administration of endotoxin and proinflammatory cytokines in humans could well be a consequence of increased body temperature in response to these agents. Likewise, increases in NREM sleep of laboratory animals after administration of various cytokines (IL-1, IL-2, IL-6, IL-8, IL-15, IL-18, TNF-α) are associated with distinct febrile responses (reviewed Krueger et al., 2001; Opp, 2005; Opp and Toth, 2003). However, the NREM sleep-promoting effects of IL-1β and TNF-α are not a byproduct of changes in body or brain temperature (Krueger and Takahashi, 1997). For example, CNS inhibition of IL-1β and TNF-α reduces cytokine-induced increases in NREM sleep but does not alter febrile responses (Takahashi et al., 1999). Low
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doses of IL-1 administered to laboratory animals and of endotoxin injected into human volunteers increase NREM sleep and SWS, respectively, without affecting brain or body temperature (Mullington et al., 2000; Opp et al., 1991). Though sleep and thermoregulation are closely linked, the role of pro-inflammatory cytokines in the regulation of sleep can indeed be separated from their actions on body temperature (Krueger and Takahashi, 1997). In the following section we will focus on neuroendocrine and vegetative mechanisms linking sleep and immune function. 1. Neuroendocrine Nocturnal sleep in humans is characterized by a unique orchestration in the neuroendocrine activity of a number of hormones well known for their immunomodulatory properties (Born and Fehm, 1998; Steiger, 2003). The most relevant of these hormones and their temporal secretory patterns during human sleep are briefly described (Figure 8). There is a strong surge in secretory activity of the somatotropic system during the early period of sleep, which in humans is typically dominated by SWS (stages 3 and 4). Activity of this system, i.e., hypothalamic release of growth hormonereleasing hormone (GHRH) and, in turn, pituitary release of growth hormone (GH), decreases to a minimum during the late part of nocturnal sleep, during which REM sleep is predominant. This pattern is primarily determined by sleep processes, and independent of circadian oscillators; a surge in GH in the early period of sleep occurs also during daytime sleep. Like somatotropic activity, release of prolactin is also enhanced during sleep and particularly so during periods of SWS (Spiegel et al., 1995). Activity of the hypothalamic-pituitary-adrenal (HPA) system shows a reversed temporal pattern. The release of hypothalamic corticotropin-releasing hormone (CRH), of pituitary corticotropin (ACTH), and of adrenal corticosteroids reaches an absolute minimum during the early SWS-rich part of nocturnal sleep, and increases during the late, REM sleep-rich part of sleep, reaching a maximum at about the time of morning awakening. HPA secretory activity during nocturnal sleep is determined both by circadian and sleep-dependent mechanisms. SWS inhibits HPA secretory activity, as can be demonstrated by experimental stimulation of the system during SWS (Bierwolf et al., 1997; SpäthSchwalbe et al., 1993). However, normally sleep and circadian oscillators act synergistically so that sleep deprivation during a single night does not induce a substantial increase in cortisol release during the early night. Release of epinephrine and norepineprhine is generally greatly reduced during sleep as compared to levels during waking (Dodt et al., 1997). Minimum
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FIGURE 8 (Top) Representative profiles of nocturnal sleep and (Bottom) associated plasma concentrations of immunoactive hormones (cortisol, growth hormone [GH], epinephrine, and norepinephrine) in a healthy young man. Abscissa indicates time of day, ordinate indicates sleep stage (W, wake; REM, rapid eye movement sleep; S1, S2, S3, S4, sleep stages 1–4; M, movements). S3 + S4 represents the time in slow-wave sleep (SWS). Note that the first half of sleep is dominated by SWS; the second half, by extended epochs of REM sleep. Minimum plasma concentrations of cortisol and maximum concentrations of GH occur during early sleep. Catecholamine concentrations are reduced during sleep and, in particular, during REM sleep. [From Marshall and Born. Brain-immune interactions in sleep. Int’l. Rev. Neurobiol. 52: 93–131, 2002. Reproduced by permission of Elsevier].
28. Sleep and the Immune System
plasma catecholamine concentrations were found during periods of SWS in some studies (Irwin et al., 1999) and during REM sleep in others (Dodt et al., 1997), although single sympathetic nerve fiber activity decreases during SWS, but not REM sleep (Somers et al., 1993). Plasma concentrations of thyroid stimulating hormone (TSH) normally are increased in the evening hours before sleep. Subsequent sleep decreases TSH levels, in comparison with persistent wakefulness (Allan and Czeisler, 1994; Goichot et al., 1992). Melatonin, a pineal hormone that has attracted much interest in sleep research, is controlled by the dark:light cycle, with light inhibiting its release. Accordingly, melatonin concentrations show strong circadian rhythm with peak concentrations around midnight (Arendt, 2000). Melatonin facilitates sleep. However, the effect of sleep per se on melatonin seems negligible. Immune cells express specific receptors for all of these steroid and peptide hormones (Blalock, 1994). Effects of the hormones on immune function have been mostly studied in vitro and often with pharmacological doses far beyond the normal physiological range of variation. Hence, conclusions with regard to the role of these hormones in mediating effects of sleep on immune function under normal conditions must be tempered with caution. The effects of GH, prolactin, and melatonin appear to be generally immunosupportive, whereas ACTH, cortisol, and catecholamines are considered immunosuppressive hormones (Besedovsky and delRey, 1996; Brzezinski, 1997; Chikanza, 1999; Gala, 1991). In general, during the early, SWSrich part of sleep, enhanced release of GH and prolactin in combination with the suppression of HPA secretory activity may convey primarily immunosupportive influences. During nocturnal sleep late in the night, characterized by strongly enhanced release of glucocorticoids and distinctly lowered release of GH and, to a lesser degree, reduced prolactin, these influences on immune function become reversed. Among the hormones modulated by sleep, the corticosteroids are the best-studied regulators of immune functions. Cortisol affects the distribution of white blood cells by inducing a pronounced decrease in the numbers of circulating lymphocytes due to an enhanced trafficking of the cells to the bone marrow (Fauci et al., 1976; Ottaway and Husband, 1992; Sackstein and Borenstein, 1995). The effect of cortisol on lymphocyte distribution occurs with some delay; the nadir in the number of lymphocytes circulating in blood follows by 2–4 hours the maximum cortisol concentration (Gatti et al., 1992; Kronfol et al., 1997). While these temporal relationships indicate a strong contribution of cortisol to circadian rhythms in lymphocyte counts, they
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cannot explain sleep-dependent reductions in lymphocyte and monocyte counts, since, as mentioned earlier, differences in nocturnal plasma cortisol concentrations between awake and sleeping subjects are normally marginal, and not altered by such experimental strategies as partial-night sleep deprivation (Redwine et al., 2000). GH, prolactin, and the reduced concentrations of catecholamines possibly contribute to these changes during sleep. However, with the exception of catecholamines (see the subsection titled “Autonomic” in Part V), the influence of these hormones on cell trafficking has so far not been thoroughly investigated. Glucocorticoids, even at relatively low concentrations, suppress the production of pro-inflammatory cytokines, including IL-1β, TNF-α, and IL-6 (Besedovsky and delRey, 1996; Petrovsky and Harrison, 1998). In contrast, melatonin is reported to stimulate pro-inflammatory cytokine activity (e.g., Sutherland et al., 2002) and to decrease the production of the Th2 cytokine IL-10 (Kuhlwein and Irwin, 2001). In combination, reduced glucocorticoid levels and increased melatonin levels during the night may well account for the circadian increase in IL-6 activity, and the shift toward Th1 cytokine dominance that is consistently observed during the night. There are also reports of a stimulating influence of GH on monocyte/ macrophage activity (Edwards, III et al., 1992; Kelley et al., 1992) and of increased IL-1β and TNF-α activity after repeated GH administration in children (Bozzola et al., 2003). However, since sleep-dependent increases in the activity of these cytokines have so far not consistently been demonstrated in humans, the relationship of the sleep-associated surge in GH concentrations to the systemic regulation of these cytokines remains to be fully elucidated. However, in combination with reduced catecholamine levels during sleep (see the subsection titled “Autonomic” in Part V), GH might contribute to an enhancement in NK cell activity observed upon awakening (Bidlingmaier et al., 1997). Sleep-dependent alterations in T-cell function have been primarily linked to the enhanced release of GH and prolactin during sleep. GH and prolactin, which act via receptors of the same cytokine/hemopoietin receptor superfamily and have similar binding affinities and intracellular signal transduction (Matera et al., 2000; Yu-Lee, 2002), have enhanced T-cell proliferation and type 1 cytokine activity (Chikanza, 1999; Dimitrov et al., 2004b; Mellado et al., 1998; Postel-Vinay et al., 1997; Rook et al., 1994; Takagi et al., 1998). Concurrently, type 2 cytokine activity may be reduced by GH and prolactin. Both hormones stimulate the differentiation of T-cells and enhance the primary antibody response when given within a short period after
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vaccination (Chikanza, 1999; Spangelo et al., 1987; Stephenson et al., 1991). Accordingly, the distinctly enhanced release of these hormones may not only account for the immediate sleep-dependent shift toward a predominance of type 1 cytokine activity, but also for a supportive effect of sleep on longer-lasting adaptive immune defense and memory. The sleep-dependent effects of GH and prolactin on T-cell function arise on a background of circadian modulation that appears to reflect, in part, effects of glucocorticoids and melatonin on these functions. At higher concentrations, glucocorticoids also suppress the production of T-cell–derived cytokines such as IL-2 and IFN-γ. In contrast, at low nanomolar concentrations, glucocorticoids may enhance the in vitro production of IL-2 (Snijdewint et al., 1995). Petrovsky and Harrison (1997) showed in healthy humans that the circadian shift in the type1/type 2 cytokine balance towards increased type 1 cytokine activity during early nocturnal sleep can be effectively inhibited by prior administration of a high dose of cortisone. Apart from the inhibition of adrenal corticosteroid release during the early night, the nocturnal rise in melatonin has been considered another factor that contributes to the nocturnal predominance of type 1 cytokines like IL-2 (Lissoni et al., 1998). In vitro, melatonin stimulates lymphocyte proliferation and reduces production of IL-10, a cytokine with strong inhibitory actions on the synthesis of type 1–related cytokines, whereas IFN-γ activity remains unaffected by melatonin application (Kuhlwein and Irwin, 2001). Two recent studies directly addressed the issue of the extent to which the hormonal milieu established during nocturnal sleep, particularly the early SWS-rich sleep of humans, controls T-cell–derived cytokine activity (Dimitrov et al., 2004b; Lange et al., 2005). The first study analyzed intracellular cytokine production in morning blood samples from awake healthy humans by multi-parametric flow cytometry. Sleep-like hormonal conditions were established by adding GH and prolactin at concentrations mimicking levels present during normal SWS. High glucocorticoid activity present in these morning samples was suppressed by adding corticosteroid receptor blockers. Under these conditions, prolactin and GH increase the percentage of IFN-γ producing CD4+ T-cells. Moreover, prolactin increases the percentage of CD4+ T-cells producing IL-2 and TNF-α, as well as the percentage of CD8+ Tcells producing IFN-γ and IL-2. In the second of these studies, blood samples were collected during the early night while subjects were in a period of SWS. Intracellular cytokine production was determined after a 6hour incubation of the samples with GH-neutralizing
antibody and with cortisol at concentrations typical for blood levels in awake subjects in the morning. Incubation with GH antibody led to a clear reduction in CD4+ T-cells producing IFN-γ. However, other cytokines, like IL-2 and IL-4, were not influenced. Collectively, results of these two studies provide supporting evidence for the view that during normal SWS, prolactin and GH release by increasing type 1 cytokine activity contributes to a sleep-dependent shift in the type 1/ type 2 cytokine balance. Noteworthy are the results of these studies with regard to the function of cortisol, which suggest actions of this hormone are mediated not only via glucocorticoid receptors (GR) but also via mineralocorticoid receptors (MR). Binding affinity of the major endogenous corticosteroids, i.e., cortisol in humans and corticosterone in the rat, is about 10-fold higher for MR than GR (De Kloet et al., 1998). Accordingly, about 70–80% of MR are continuously occupied throughout the 24-hour cycle, whereas GR become predominantly occupied during periods of distinctly increased corticosteroid concentrations, i.e., during stress and around the maximum of the circadian oscillation. The blockade of MR in blood from awake subjects (characterized by high cortisol concentrations) markedly enhances CD4+ and CD8+ T-cells producing IL-2, IFN-γ, and TNF-α, and thereby also induces a shift toward increased type 1 cytokine activity as measured by the ratio of IFN-γ/IL-4 producing CD4+ T-cells. The effects of MR blockade are stronger than those of the selective GR blockade (with RU-486), suggesting that the suppressing effects of cortisol on T-cell–derived cytokines are to a substantial extent mediated via MR activation. Adding cortisol to blood sampled during SWS (characterized by minimum cortisol concentrations) confirmed a decrease in the percentage of CD4+ and CD8+ T-cells producing IFN-γ, IL-2, and TNF-α, as well as a decrease in CD4+ T-cells producing the type 2 cytokine IL-4. Collectively, data from these two ex vivo studies in humans indicate a specific role of sleepassociated GH and prolactin release for inducing a shift toward type 1 cytokine activity, whereas the simultaneous suppression of endogenous cortisol release during the early night appears to serve a general facilitation of both production of type 1 and type 2 cytokines. Hormones are also involved in signaling infection to the brain. The acute response to infection includes an activation of different hormonal systems, primarily the hypothalamic-pituitary-adrenal (HPA) stress system and the adrenal release of catecholamines. Experimental administration of endotoxin in humans and animals increases plasma concentrations of ACTH,
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cortisol, and GH (e.g., Daniel et al., 2005; Lang et al., 1997; Mullington et al., 2000). Administration of proinflammatory cytokines such as IL-1β, TNF-α, and IL-6 also stimulates activity of the HPA system at its different levels (Turnbull and Rivier, 1999). Simultaneously, these cytokines appear to suppress somatotropic activity, although this action is complex (e.g., Jones and Kennedy, 1993). In rats, ICV injection of IL-1β increases expression of GHRH receptors but does not change GHRH expression (Taishi et al., 2004). Whereas low doses of IL-1β administered ICV into rats increase GH release, high ICV doses suppress GH release. In humans, administration of IL-6 does not alter plasma GH concentrations but does increase plasma ACTH and cortisol concentrations (Späth-Schwalbe et al., 1996). 2. Autonomic Lymphoid tissues are densely enervated by nerve endings of the autonomic nervous system, and leukocytes express adrenergic and cholinergic receptors. These conditions enable an efferent control of lymphocyte function via paracrine release of neurotransmitters and peptidergic neuromodulators. These efferent neuronal pathways appear to convey predominantly influences of the sympathetic nervous system (Elenkov et al., 2000; Ottaway and Husband, 1992; Straub et al., 1998). A parasympathetic enervation of lymphoid tissues has been demonstrated in some studies (Madden and Felten, 1995) but questioned by others (e.g., Qiu et al., 2005). However, there is also some evidence suggesting that lymphocytes express cholinergic receptors to a greater extent than adrenergic receptors, which are prevalent in granulocytes (Abo and Kawamura, 2002). Analyses of various physiological functions (e.g., heart rate variability), which allow the separation of parasympathetic and sympathetic activation, have indicated that sympathetic tone is synergistically controlled both by circadian oscillators and sleep, whereas parasympathetic tone appears to be controlled mainly by circadian factors (e.g., Burgess et al., 1997). Moreover, these studies show that nocturnal sleep in humans is characterized by a general reduction in sympathetic activity and a relatively enhanced parasympathetic tone. The sympathetic nervous system exerts a great variety of influences on the immune system, which globally manifest themselves in an enhancing effect on innate immune functions. Responses to experimental administration of agonists and antagonists of adrenergic receptors have consistently supported the view that sympathetic activation, among others, induces
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leukocytosis and transient lymphocytosis, enforcing primarily a mobilization of NK cells and granulocytes to the circulation (Benschop et al., 1996; Ottaway and Husband, 1992; Ottaway and Husband, 1994). Administration of β-adrenergic blockers increases the emigration of lymphocytes to extravascular tissues. Moreover, β-adrenergic blockers enhance, and catecholamines reduce, the in vitro production of T-cell–derived IL-2 and IFN-γ (Maisel et al., 1991; Malec et al., 1990; Sanders, 1995). There have been also a number of reports on effects of cholinergic agonists and antagonists on immune cell function, reflecting possible contributions of parasympathetic activity. Thus, an early study showed that over several days in healthy humans administration of the muscarinic cholinergic blocker atropine left the number of circulating lymphocytes unaffected but impaired in vitro PHA-stimulated lymphocyte proliferation (Pluzanska and Mazurowa, 1977). On the other hand, stimulation of (muscarinic) acetylcholine receptors increases mitogen-stimulated proliferation of T-cells and the production of IL-2 (Fujino et al., 1997; Nomura et al., 2003; Qiu et al., 2005). Acetylcholinergic agonists attenuate the production of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6, IL-18) in human macrophages (Borovikova et al., 2000). In vivo electrical stimulation of the vagus in rats during endotoxinemia likewise inhibits production and reduces circulating TNF-α. Moreover, animal studies suggest that parasympathomimetic treatment improves the antibody immune response to vaccination (Besedovsky and delRey, 1992). Collectively, these observations support the view that parasympathetic activity globally acts to attenuate systemic pro-inflammatory responses of innate immunity and supports aspects of T-cell–mediated adaptive immune functions. The regulatory influence of sympathetic and parasympathetic activity on immune functions has so far been rarely studied in the context of sleep. However, from the available evidence, it can be hypothesized that the profound sleep-associated reduction in sympathetic tone, together with a circadian increase in parasympathetic tone during the night, affects adaptive T-cell function by increasing type 1 cytokines and decreases aspects of innate immunity (Besedovsky and delRey, 1996; Petrovsky, 2001; Sanders, 1995). In addition, this constellation of changes may permit an enhanced homing of lymphocytes in secondary lymphatic tissues, which is probably controlled cooperatively via endocrine factors (Abo and Kawamura, 2002; Ottaway and Husband, 1994). Considering the size of the hypothesized effects, more thorough investigations to elucidate the influences of the autonomous
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nervous system on immune functions directly in the context of sleep appear promising.
VI. DISORDERED SLEEP AND IMMUNITY: CLINICAL POPULATIONS To determine whether the experimental associations between sleep disturbance, sleep loss, and immunity translate to a naturalistic or “real life” setting, evidence has been sought from clinical conditions in which disturbances of sleep are found along with alterations in immunity. Such work is important, as it carries forward the acute effects of sleep disturbances and especially partial sleep loss, and evaluates whether chronic loss of sleep as found in many clinical disorders impacts the immune system, which might play a role in the increased incidence of infectious diseases and inflammatory disorders in at-risk populations such as depressed persons or older adults. In addition, such studies have the potential to provide insights into the reciprocal influence of cytokines on sleep, and whether increases in inflammatory markers in many of these disorders (e.g., major depression, aging, rheumatoid arthritis) might contribute to abnormalities in sleep continuity or sleep depth in these populations.
A. Primary Insomnia Chronic primary insomnia is characterized by the presence of difficulties in sleep initiation or maintenance and frequent sleep problems with associated distress and clinical significant impairments in daytime functioning that persist for greater than 6 months. Importantly, primary insomnia, by definition, cannot be accounted for by the confounding presence of another psychiatric disorder, such as depression, or underlying medical conditions. Hence, evaluation of immune alterations in primary insomnia patients lends compelling evidence that chronic sleep disturbances lead to changes in immune responses. Consistent with the acute effects of partial-night sleep deprivation, patients with chronic insomnia show significant decreases in the numbers of CD3+, CD4+, and CD8+ T-cells (Savard et al., 2003) along with decreases in NK cell responses (Irwin et al., 2003). In the latter study, primary insomnia patients also showed nocturnal elevations of circulating levels of norepinephrine, which correlated with difficulties with sleep maintenance. Together with evidence that β-adrenergic activation mediates a suppression of NK activity in humans (Friedman and Irwin, 1997), these data suggest that abnormalities in sleep continuity might mediate declines in NK responses via sympathetic nervous system activation. In animals, substantial evidence
suggests that NK cell responses are an important marker of immunological defenses against tumors (Ben-Eliyahu et al., 2000; Shakhar and Ben-Eliyahu, 1998). The present data show that insomnia is associated with declines of NK activity, suggesting a possible pathway in the link between insomnia and cancer morbidity (Savard et al., 1999) and mortality (Kripke et al., 1979). Vitaliano and colleagues have also found declines of NK activity in individuals with cancer histories which are exacerbated by the presence of sleep problems (Vitaliano et al., 1999). Cytokine abnormalities have also been reported in association with chronic insomnia. Consistent with the effects of sleep deprivation to shift the Th1/Th2 cytokine balance, insomnia correlates with low levels of IFN-γ and a low IFN-γ to IL-4 ratio. There is also evidence that primary insomnia may lead to increases in circulating levels of inflammatory cytokines. Vgontzas et al. (2002) reported increases in daytime circulating levels of IL-6, and Burgos et al. (2005) extended these findings to show that IL-6 levels are prominently elevated during the nocturnal period. Furthermore, nocturnal IL-6 amounts negatively correlated with perceived subjective sleep quality. In another study of healthy persons, sleep quality also negatively correlated with morning IL-6 levels (Hong et al., 2005). Further temporal characterization of profile of IL-6 secretion in relationship to sleep and/or the use of experimental administration of cytokine antagonists is needed to evaluate whether sleep impairments activate IL-6 analogous to sleep deprivation, or whether increases of IL-6 have sleep-disturbing effects in this population, as has been described following the infusion of IL-6 (Späth-Schwalbe et al., 1998). However, consistent with the effects of acute IL-6 infusion, the amount of SWS in primary insomnia patients was negatively correlated with nocturnal IL-6 levels (Burgos et al., 2005). Given that immune activation is implicated in atherosclerosis and the progression of cardiovascular disease (Ridker, 2001), these findings have implications for understanding the mechanisms that might underlie the association between insomnia and cardiovascular disease mortality. For example in a 12year follow-up of 1,870 middle-aged men and women, sleep complaints (e.g., difficulty maintaining sleep) predicted coronary artery disease mortality (Mallon et al., 2002).
B. Aging Poor sleep is one of the most common complaints in older adults. Even in healthy seniors, populations with prevalence rates of diagnostic insomnia exceed 20–30%, greater in frequency and severity than any
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other age group (Ancoli-Israel, 2000; Foley et al., 1995; Petit et al., 2003). Independent of medical and psychiatric illness, medication use, circadian rhythm changes, and psychosocial factors, which can all contribute to complaints of insomnia, primary insomnia is highly prevalent in older adults (Ancoli-Israel, 2000). Indeed, normal aging is associated with declines in subjective sleep quality, sleep fragmentation, increases of light (stages 1 and 2) sleep, and decreases of deep slowwave sleep (Benca et al., 1992; Ehlers and Kupfer, 1989; Ehlers and Kupfer, 1997; Van Cauter et al., 2000), and these sleep abnormalities are thought to contribute to daytime fatigue, depression, and impairments in health functioning. Elderly persons exhibit many of the prominent immune changes observed after acute or prolonged sleep deprivation in younger persons, i.e., an impaired adaptive immune response conjoined with signs of disturbed innate immune function. Like acute sleep deprivation, aging is associated with reduced T-cell function that includes a shift in the type 1/type 2 balance toward enhanced type 2 cytokine activity, and in some studies has been found also to be associated with decreased production of IL-2 and IFN-γ (e.g., Ginaldi et al., 1999b; Ginaldi et al., 1999c; Perras and Born, 2005; Shearer, 1997). Regarding innate immune functions, aging, like sleep deprivation, leads to diminished NK cell activity when considered on a per cell basis (Irwin et al., 1994; Solana and Mariani, 2000). Blood counts of activated T-cells (HLA-DR) have likewise been found to be increased after short periods of sleep deprivation as well as in the aged, and there are also hints at increased activity of pro-inflammatory cytokines like IL-6, IL-1β, and TNF-α in both conditions. Poor sleep in the aged may in fact contribute to these alterations. For example, in one study, healthy elderly in comparison with young subjects showed an increased production of IL-1β and TNF-α, which appeared to be particularly pronounced during nocturnal sleep (Born et al., 1995). In addition, nocturnal levels of IL-6 are lower during SWS as compared to Stages 1–2 sleep, and the deficits of SWS in older adults may be associated with overall increases in circulating levels of this pro-inflammatory cytokine. However, other changes in the aged, like the reduced number of circulating lymphocytes thought to originate from a thymic involution, are clearly opposite to what is observed following sleep deprivation. Accordingly, it should be cautioned against considering alterations in immune function in the aged as a consequence of a “chronic sleep deprivation,” since the effects of poor sleep in elderly persons interact with a number of other physiological conditions not related to sleep.
C. Major Depressive Disorder Insomnia is also one of the most common complaints of depressed subjects, and emerging evidence indicates that disturbances of sleep in depression moderate and/or mediate immune alterations in these patients. For example, as with primary insomnia, subjective sleep quality and insomnia complaints negatively correlate with NK activity in depression, whereas other depressive symptoms including somatization, weight loss, cognitive disturbance, or diurnal variation do not show a similar relationship (Irwin et al., 2003). Likewise, EEG studies reveal that disturbances of sleep continuity (e.g., prolonged sleep latency, declines of total sleep time) correlated with alterations of natural and cellular immune function among depressed patients (Cover and Irwin, 1994; Irwin et al., 1992). Moreover, in bereaved subjects, causal statistical analyses have shown that disordered sleep mediates the relationship between severe life stress and a decline of NK responses (Hall et al., 1998). Recent attention has focused on the links between sleep, IL-6, and sICAM in depression, as these markers of immune activation have important implications for cardiovascular disease in depression. For example, in patients recovering from an acute coronary artery event, comorbidity for depression is associated with elevated levels of sICAM independent of smoking status, obesity, and other traditional risk markers (Lesperance et al., 2004). Motivala and colleagues (Motivala et al., 2005) found that prolonged sleep latency and increases of REM density are associated with elevated levels of IL-6 and sICAM in depression. Moreover, these EEG sleep measures fully account for the association between depression and IL-6, indicating that sleep disturbances have a key role in alterations of inflammatory markers in depression.
D. Alcohol Dependence A more extensive line of research has focused on alcohol-dependent patient populations, who have profound disturbances of sleep continuity and sleep architecture, including decreases of total sleep time, declines of delta sleep, and increases of REM (Irwin et al., 2000; Irwin et al., 2002). To determine the consequences of disordered sleep on immunity and to explore whether abnormal cytokine expression is associated with alterations in sleep continuity or sleep depth in alcohol dependence, the relationships between EEG-defined sleep and NK cell responses and nocturnal cytokine expression have been investigated in alcoholdependent persons as compared to controls. In addition, by blood sampling across the nocturnal period
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before sleep onset and during sleep, these studies have evaluated the hypothesized bi-directional relationships between sleep and cytokines. In alcohol-dependent men who have profound disturbances of sleep depth, there is a differential change in the nocturnal expression of IFN-γ/IL-10 ratio in which alcohol-dependent persons showed a shift toward a Th2 cytokine response after the onset of sleep and a predominance of this Th2 response throughout the night (Figure 9). In contrast, controls showed an increase in the relative expression of Th1 cytokines during the later half of the nocturnal period. The nocturnal production of IL-6 also changed differently in the alcohol-dependent persons versus controls; during the early part of the night, alcohol-dependent subjects showed lower amounts of IL-6 expression, but then higher amounts during the second half of the night as compared to controls. Finally, alcohol-dependent persons showed low levels of NK activity across the night as compared to controls, with increases of NK activity occurring across the night in the controls but not in the alcohol-dependent persons. Taken together, this pattern of abnormal immune responses in alcoholdependent persons is similar to the immune changes during sleep deprivation. Abnormalities of sleep architecture were also associated with measures of nocturnal immunity, and REM sleep amounts predicted morning increases in stimulated IL-6 production and decreases of NK activity. These data, along with evidence that IL-6 is elevated during REM sleep (Redwine et al., 2000), raise the possibility that greater amounts of REM sleep during the
FIGURE 9 The TH1/TH2 ratio increased from 03:00 to 06:30 hours (p < 0.01) in the controls, whereas the IFN-γ/IL10 ratio decreased from 23:00 to 03:00 hours (p < 0.05) and remained low from 03:00 to 06:30 hours in the alcoholics. [From Redwine et al., 2003. Reproduced by permission of Lippincott, Williams and Wilkins].
late part of the night contribute to the nocturnal rise of IL-6 in alcohol-dependent persons. Deficits in SWS in alcohol dependence may also lead to abnormal elevations of IL-6 and TNF. For example, experimental sleep deprivation typically induces a rebound increase in SWS, as described above. However, alcoholics evidence a defect in SWS recovery (Irwin et al., 2002), which is coupled with an exaggerated recovery night increase in circulating levels of IL-6 and TNF in alcoholics as compared to controls (Irwin et al., 2004). Finally, given that daytime elevations of IL-6 correlate with fatigue (Vgontzas et al., 1997), such increases in the production or circulating levels of IL-6 may have implications for daytime fatigue in alcohol-dependent persons. Studies in alcohol-dependent patients have also provided insights into the possible influence of cytokine abnormalities on occurrence of disordered sleep in this population. In studies in which measures of circulating levels of pro-inflammatory cytokines and stimulated cytokine production were taken prior to the onset of sleep onset as well as during sleep, tests were conducted to determine whether levels at evening awake, as opposed to nocturnal sleep or morning awake, predicted measures of sleep continuity or sleep architecture. Using a regression model, evening awake levels of circulating IL-6 were associated with prolonged sleep latency in alcohol-dependent persons independent of confounding influences and other times of cytokine assessment (Irwin et al., 2004) (Figure 10). In addition, IL-6 is associated with increases in REM sleep during the later half of the night. In contrast, expression of the anti-inflammatory cytokine, IL10, before sleep predicted increases in delta sleep, accounting for over 23% of the variance in delta sleep independent of age and alcohol consumption (Redwine et al., 2003). Further experimental studies are needed to determine whether anti-inflammatory cytokines augment delta sleep and whether pro-inflammatory cytokines inhibit delta sleep in human beings. Nevertheless, these observations suggest that cytokine abnormalities temporally predict changes in sleep in clinical populations such as alcohol-dependent persons, and that these immune abnormalities are not merely a consequence of disordered sleep. As reviewed elsewhere in this text, peripheral pro-inflammatory cytokines are capable of exerting direct effects on central nervous system function. Bower et al. (2002) found that immune activation is associated with severity of fatigue symptoms in women recovering from breast cancer, and Capuron et al. (Capuron et al., 2002) suggest that immune activation is associated with cognitive impairments. Likewise, experimental immune activation
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FIGURE 10 Associations between IL-6 at 23:00 h prior to sleep onset and sleep latency in the baseline night (r = 0.37, p = 0.08), PSD-E night (r = 0.56, p < 0.01), and recovery night (r = 0.53, p < 0.01) in alcoholics and controls . [From Irwin et al., 2004. Reproduced by permission of Elsevier].
results in increases of anxiety and depressed mood, which are coupled with declines of memory functions (Reichenberg et al., 2001). Whether disordered sleep and daytime elevations of pro-inflammatory cytokines contribute to depressive symptom severity and cognitive disturbances in recovering alcoholics is not known. Importantly, the contribution of cytokines in the regulation of sleep suggests that cytokine mechanisms are a possible target for interventions to optimize sleep initiation and sleep quality in alcoholic and other atrisk populations.
E. Rheumatoid Arthritis The prevalence of self-reported sleep disturbances in the inflammatory disorder rheumatoid arthritis (RA) is very high, with 50–75% of patients complaining of difficulties initiating or maintaining sleep (Drewes, 1999). In one study, RA patients had significantly longer sleep latency and poorer sleep efficiency with more awakenings during the night as compared to controls (Hirsch et al., 1994). Two other studies similarly found fragmented sleep in RA patients with evidence of alpha-EEG arousals during slow-wave sleep (Drewes et al., 1998; Mahowald et al., 1989). In this population, sleep disturbance is also hypothesized to contribute to complaints of pain, fatigue, and depressed mood in patients with RA, and a number of studies show that subjective sleep complaints correlate with fatigue, functional disability, greater joint pain, and more depressive symptoms in rheumatic patients (Moldofsky, 2001). Indeed, sleep difficulties, pain, depressed mood, and fatigue appear to cluster together in RA; depression is associated with greater pain (Frank et al., 1988; Murphy et al., 1988), whereas sleep difficulties are associated with fatigue, depression, and
pain (Drewes et al., 1998; Nicassio and Wallston, 1992). There is a striking absence of studies examining the role of inflammatory processes in mediating these links between sleep and disease symptoms in RA patients. Prospective and/or experimental studies are needed which simultaneously assess multiple symptoms and inflammatory mechanisms in order to advance our understanding of sleep and its association with other RA symptoms. One study measured sleep disturbance and found that sleep loss was associated with an overnight increase in tenderness in the peripheral joints in RA patients who are experiencing an acute flare (Moldofsky et al., 1983); no assessment of cytokines was completed. In a non-clinical sample of healthy men, experimental disruption of NREM sleep over 3 nights induced increases in objective and subjective measures of pain sensitivity and muscle tenderness (Moldofsky et al., 1975), a finding replicated in healthy middle-aged women (Lentz et al., 1999). Again, studies have not examined the biological mechanisms that underlie the link between sleep loss and/or sleep recovery deficits and increases of pain and fatigue, although elevations in pro-inflammatory cytokine activity are implicated (Moldofsky, 2001).
VII. SUMMARY In this chapter, we have reviewed evidence of a reciprocal relationship between sleep and immunity, and that sleep loss influences immune responses with potential impacts on infectious and inflammatory disease processes. Some evidence in humans suggests sleep preferentially supports aspects of adaptive immune function. Given the association between
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insomnia and mortality, sleep disturbance that is suffered by those with chronic disease, depression, or other disorders may have substantial heath implications due to the effects of sleep on the regulation of the immune system, although the underlying reasons linking insomnia and morbidity remain unclear. The possible effect of sleep disruption has tremendous import because of the pervasiveness of insomnia complaints, with up to 69% of adults reporting having sleep problems on a few nights a week or more. Moreover, in recent decades, decreases in the mean duration of sleep and an increase in shift work have occurred, which might pose substantial public health burden that has not yet been evaluated. Together, these data indicate that sleep is a new “vital sign” that should be more carefully characterized in the management of patients, particularly in vulnerable populations such as the elderly or the immune compromised. To this end, medical environments are needed which will minimize the likelihood of sleep disruption as patients recover from infections or surgery and other medical procedures. Ongoing basic and clinical research aims to provide insight into the molecular and cellular pathways by which sleep and the immune system are interrelated, which will ultimately lead to novel interventions and therapies for insomnia which have the potential to promote health.
References Abo, T., and Kawamura, T. (2002). Immunomodulation by the autonomic nervous system: therapeutic approach for cancer, collagen diseases, and inflammatory bowel diseases. Ther. Apher., 6, 348–357. Alam, M. N., McGinty, D., Bashir, T., Kumar, S., Imeri, L., Opp, M. R., and Szymusiak, R. (2004). Interleukin-1β modulates state-dependent discharge activity of preoptic area and basal forebrain neurons: role in sleep regulation. Eur. J. Neurosci., 20, 207–216. Alberti, A., Sarchielli, P., Gallinella, E., Floridi, A., Floridi, A., Mazzotta, G., and Gallai, V. (2003). Plasma cytokine levels in patients with obstructive sleep apnea syndrome: a preliminary study. J. Sleep Res., 12, 305–311. Allan, J. S., and Czeisler, C. A. (1994). Persistence of the circadian thyrotropin rhythm under constant conditions and after lightinduced shifts of circadian phase. J. Clin. Endocrinol. Metab., 79, 508–512. Ancoli-Israel, S. (2000). Insomnia in the elderly: a review for the primary care practitioner. Sleep, 23(Suppl 1), 23–30. Ancoli-Israel, S., and Cooke, J. R. (2005). Prevalence and comorbidity of insomnia and effect on functioning in elderly populations. J. Am. Geriatr. Soc., 53, 264–271. Arendt, J. (2000). Melatonin, circadian rhythms, and sleep. N. Engl. J. Med., 343, 1114–1116. Aserinsky, E., and Kleitman, N. (1953). Regularly occurring periods of eye motility, and concomitant phenomena, during sleep. Science, 118, 273–274.
Bassant, M. H., Cathala, F., Court, L., Gourmelon, P., and Hauw, J. J. (1984). Experimental scrapie in rats: first electrophysiological observations. Electroencephalogr. Clin. Neurophysiol., 57, 541–547. Bauer, J., Hohagen, F., Ebert, T., Timmer, J., Ganter, U., Krieger, S., Lis, S., Postler, E., Voderholzer, U., and Berger, M. (1994). Interleukin-6 serum levels in healthy persons correspond to the sleep-wake cycle. Clin. Invest., 72, 315. Baylis, W., and Starling, E. (1902). The mechanism of pancreatic secretion. J. Physiol., 28, 325–353. Ben-Eliyahu, S., Shakhar, G., Page, G. G., Stefanski, V., and Shakhar, K. (2000). Suppression of NK cell activity and of resistance to metastasis by stress: a role for adrenal catecholamines and betaadrenoceptors. Neuroimmunomodulation, 8, 154–164. Benca, R. M., Obermeyer, W. H., Thisted, R. A., and Gillin, J. C. (1992). Sleep and psychiatric disorders. A meta-analysis. Arch. Gen. Psychiatry, 49, 651–668. Benschop, R. J., Rodriguez-Feuerhahn, M., and Schedlowski, M. (1996). Catecholamine-induced leukocytosis: early observations, current research, and future directions. Brain Behav. Immun., 10, 77–91. Berge, B., Chevrier, C., Blanc, A., Rehailia, M., Buguet, A., and Bourdon, L. (2005). Disruptions of ultradian and circadian organization of core temperature in a rat model of African trypanosomiasis using periodogram techniques on detrended data. Chronobiol. Int., 22, 237–251. Besedovsky, H. O., and delRey, A. (1992). Immune-neuroendocrine circuits: integrative role of cytokines. Front. Neuroendocrinol., 13, 61–94. Besedovsky, H. O., and delRey, A. (1996). Immune-neuro-endocrine interactions: facts and hypotheses. Endocr. Rev., 17, 64–102. Bidlingmaier, M., Auernhammer, C. J., Feldmeier, H., and Strasburger, C. J. (1997). Effects of growth hormone and insulinlike growth factor I binding to natural killer cells. Acta Paediatr. Suppl., 423, 80–81. Bierwolf, C., Struve, K., Marshall, L., Born, J., and Fehm, H. L. (1997). Slow wave sleep drives inhibition of pituitary-adrenal secretion in humans. J. Neuroendocrinol., 9, 479–484. Blake, H., and Gerard, R. W. (1937). Brain potentials during sleep. Am. J. Physiol., 119, 692–703. Blake, H., Gerard, R. W., and Kleitman, N. (1939). Factors influencing brain potentials during sleep. J. Neurophysiol., 2, 48–60. Blalock, J. E. (1994). The syntax of immune-neuroendocrine communication. Immunol. Today, 15, 504–511. Borbély, A. A. (1982). A two process model of sleep regulation. Hum. Neurobiol., 1, 195–204. Borbély, A. A. (1990). “Sleep substances”: criteria and physiological basis. In S. Inoué and J. M. Krueger (Eds.), Endogenous sleep factors (pp. 31–38). The Hague, The Netherlands: SPB Academic Publishing. Born, J., and Fehm, H. L. (1998). Hypothalamus-pituitary-adrenal activity during human sleep: a coordinating role for the limbic hippocampal system. Exp. Clin. Endocrinol. Diabetes, 106, 153– 163. Born, J., and Hansen, K. (1997). Dependence of human cytokine production and mononuclear cell subset counts on circadian rhythm and sleep. In A. E. Henneberg and W. P. Kaschka (Eds.), Immunological alterations in psychiatric diseases (pp. 18–31). Basel: Karger. Born, J., Lange, T., Hansen, K., Molle, M., and Fehm, H. L. (1997). Effects of sleep and circadian rhythm on human circulating immune cells. J. Immunol., 158, 4454–4464. Born, J., and Späth-Schwalbe, E. (1999). The role of interferon-alpha in the regulation of sleep. In N. Müller (Ed.), Psychiatry, psychoimmunology, and viruses (pp. 131–144). Wien: Springer-Verlag.
28. Sleep and the Immune System Born, J., Späth-Schwalbe, E., Schwakenhofer, H., Kern, W., and Fehm, H. L. (1989). Influences of corticotropin-releasing hormone, adrenocorticotropin, and cortisol on sleep in normal man. J. Clin. Endocrinol. Metab., 68, 904–911. Born, J., Uthgenannt, D., Dodt, C., Nunninghoff, D., Ringvolt, E., Wagner, T., and Fehm, H. L. (1995). Cytokine production and lymphocyte subpopulations in aged humans. An assessment during nocturnal sleep. Mech. Aging Dev., 84, 113–126. Borovikova, L. V., Ivanova, S., Zhang, M., Yang, H., Botchkina, G. I., Watkins, L. R., Wang, H., Abumrad, N., Eaton, J. W., and Tracey, K. J. (2000). Vagus nerve stimulation attenuates the systemic inflammatory response to endotoxin. Nature, 405, 458–462. Bower, J. E., Ganz, P. A., Aziz, N., and Fahey, J. L. (2002). Fatigue and proinflammatory cytokine activity in breast cancer survivors. Psychosom. Med., 64, 604–611. Boyum, A., Wiik, P., Gustavsson, E., Veiby, O. P., Reseland, J., Haugen, A. H., and Opstad, P. K. (1996). The effect of strenuous exercise, calorie deficiency and sleep deprivation on white blood cells, plasma immunoglobulins and cytokines. Scand. J. Immunol., 43, 228–235. Bozzola, M., De, B. F., De, A. M., Jouret, B., Travaglino, P., Pagani, S., Conte, F., and Tauber, M. (2003). Stimulating effect of growth hormone on cytokine release in children. Eur. J. Endocrinol., 149, 397–401. Brandenberger, G., Buguet, A., Spiegel, K., Stanghellini, A., Muanga, G., Bogui, P., and Dumas, M. (1996). Disruption of endocrine rhythms in sleeping sickness with preserved relationship between hormonal pulsatility and the REM-NREM sleep cycles. J. Biol. Rhythms, 11, 258–267. Brown, R., Pang, G., Husband, A. J., and King, M. G. (1989). Suppression of immunity to influenza virus infection in the respiratory tract following sleep disturbance, Regional Immunology, vol. 2, pp. 321–325. Bryant, P. A., Trinder, J., and Curtis, N. (2004). Sick and tired: does sleep have a vital role in the immune system. Nature Immunology, 4, 457–467. Brzezinski, A. (1997). Melatonin in humans. N. Engl. J. Med., 336, 186–195. Buguet, A., Bert, J., Tapie, P., Tabaraud, F., Doua, F., Lonsdorfer, J., Bogui, P., and Dumas, M. (1993). Sleep-wake cycle in human African trypanosomiasis. J. Clin. Neurophysiol., 10, 190–196. Buguet, A., Bisser, S., Josenando, T., Chapotot, F., and Cespuglio, R. (2005). Sleep structure: a new diagnostic tool for stage determination in sleeping sickness. Acta Trop., 93, 107–117. Buguet, A., Bourdon, L., Bouteille, B., Cespuglio, R., Vincendeau, P., Radomski, M. W., and Dumas, M. (2001). The duality of sleeping sickness: focusing on sleep. Sleep Med. Rev., 5, 139–153. Buguet, A., Tapie, P., and Bert, J. (1999). Reversal of the sleep/wake cycle disorder of sleeping sickness after trypanosomicide treatment. J. Sleep Res., 8, 225–235. Burgess, H. J., Trinder, J., Kim, Y., and Luke, D. (1997). Sleep and circadian influences on cardiac autonomic nervous system activity. Am. J. Physiol., 273, H1761–H1768. Burgos, I., Richter, L., Klein, T., Fiebich, B., Feige, B., Lieb, K., Voderholzer, U., and Riemann, D. (2006). Increased nocturnal interleukin-6 excretion in patients with primary insomnia: a pilot study. Brain Behav. Immun., 20, 246–253. Campbell, S. S., and Tobler, I. (1984). Animal sleep: a review of sleep duration across phylogeny. Neurosci. Biobehav. Rev., 8, 269–300. Capuron, L., Gumnick, J. F., Musselman, D. L., Lawson, D. H., Reemsnyder, A., Nemeroff, C. B., and Miller, A. H. (2002). Neurobehavioral effects of interferon-alpha in cancer patients:
611
phenomenology and paroxetine responsiveness of symptom dimensions. Neuropsychopharmacology, 26, 643–652. Chang, F. C., and Opp, M. R. (2000). IL-1 is a mediator of increases in slow-wave sleep induced by CRH receptor blockade. Am. J. Physiol., 279, R793–R802. Chang, F. C., and Opp, M. R. (2001). Corticotropin-releasing hormone (CRH) as a regulator of waking. Neurosci. Biobehav. Rev., 25, 445–453. Chikanza, I. C. (1999). Prolactin and neuroimmunomodulation: in vitro and in vivo observations. Ann. N. Y. Acad. Sci., 876, 119–130. Cover, H., and Irwin, M. (1994). Immunity and depression: insomnia, retardation, and reduction of natural killer cell activity. Journal of Behavioral Medicine, 17, 217–223. Daniel, J. A., Elsasser, T. H., Martinez, A., Steele, B., Whitlock, B. K., and Sartin, J. L. (2005). Interleukin-1{beta} and tumor necrosis factor-{alpha} mediation of endotoxin action on growth hormone. Am. J. Physiol. Endocrinol. Metab. epub doi: 10.1152/ajpendo. 00489.2004. Darko, D. F., Mitler, M. M., and Henriksen, S. J. (1995). Lentiviral infection, immune response peptides and sleep. Adv. Neuroimmunol., 5, 57–77. Darsaud, A., Bourdon, L., Mercier, S., Chapotot, F., Bouteille, B., Cespuglio, R., and Buguet, A. (2004). Twenty-four–hour disruption of the sleep-wake cycle and sleep-onset REM-like episodes in a rat model of African trypanosomiasis. Sleep, 27, 42–46. Davis, H., Davis, P. A., Loomis, A. L., Harvey, E. N., and Hobart, G. (1938). Human brain potentials during the onset of sleep. J. Neurophysiol., 1, 24–38. De Kloet, E. R., Vreugdenhil, E., Oitzl, M. S., and Joels, M. (1998). Brain corticosteroid receptor balance in health and disease. Endocr. Rev., 19, 269–301. Dew, M. A., Hoch, C. C., Buysse, D. J., Monk, T. H., Begely, A. E., Houck, P. R., Hall, M., Kupper, D. J., and Reynold, C. F. (2003). Healthy older adults’ sleep predicts all-cause mortality at 4 to 19 years of follow-up. Psychosom. Med., 65, 63–73. Dickstein, J. B., Hay, J. B., Lue, F. A., and Moldofsky, H. (2000). The relationship of lymphocytes in blood and in lymph to sleep/ wake states in sheep. Sleep, 23, 185–190. Dimitrov, S., Lange, T., Benedict, C., Nowell, M. A., Jones, S. A., Scheller, J., Rose-John, S., and Born, J. (submitted). Sleep enhances IL-6 trans-signaling in humans. Dimitrov, S., Lange, T., Fehm, H. L., and Born, J. (2004a). A regulatory role of prolactin, growth hormone, and corticosteroids for human T-cell production of cytokines. Brain Behav. Immun., 18, 368–374. Dimitrov, S., Lange, T., Tieken, S., Fehm, H. L., and Born, J. (2004b). Sleep associated regulation of T helper 1/T helper 2 cytokine balance in humans. Brain Behav. Immun., 18, 341–348. Dinges, D. F., Douglas, S. D., Hamarman, S., Zaugg, L., and Kapoor, S. (1995). Sleep deprivation and human immune function. Adv. Neuroimmunol., 5, 97–110. Dinges, D. F., Douglas, S. D., Zaugg, L., Campbell, D. E., McMann, J. M., Whitehouse, W. G., Orne, E. C., Kapoor, S. C., Icaza, E., and Orne, M. T. (1994). Leukocytosis and natural killer cell function parallel neurobehavioral fatigue induced by 64 hours of sleep deprivation. J. Clin. Invest., 93, 1930–1939. DiPiro, J. T. (1997). Cytokine networks with infection: mycobacterial infections, leishmaniasis, human immunodeficiency virus infection, and sepsis. Pharmacotherapy, 17, 205–223. Dodt, C., Breckling, U., Derad, I., Fehm, H. L., and Born, J. (1997). Plasma epinephrine and norepinephrine concentrations of healthy humans associated with nighttime sleep and morning arousal. Hypertension, 30, 71–76.
612
III. Behavior and Immunity
Drake, C. L., Roehrs, T. A., Royer, H., Koshorek, G., Turner, R. B., and Roth, T. (2000). Effects of an experimentally induced rhinovirus cold on sleep, performance, and daytime alertness. Physiol. Behav., 71, 75–81. Drewes, A. M. (1999). Pain and sleep disturbances with special reference to fibromyalgia and rheumatoid arthritis. Rheumatology (Oxford), 38, 1035–1038. Drewes, A. M., Svendsen, L., Taagholt, S. J., Bjerregard, K., Nielsen, K. D., and Hansen, B. (1998). Sleep in rheumatoid arthritis: a comparison with healthy subjects and studies of sleep/wake interactions. British Journal of Rheumatology, 37, 71–81. Edwards, C. K., III, Ghiasuddin, S. M., Yunger, L. M., Lorence, R. M., Arkins, S., Dantzer, R., and Kelley, K. W. (1992). In vivo administration of recombinant growth hormone or gamma interferon activities macrophages: enhanced resistance to experimental Salmonella typhimurium infection is correlated with generation of reactive oxygen intermediates. Infect. Immun., 60, 2514–2521. Ehlers, C. L., and Kupfer, D. J. (1989). Effects of age on delta and REM sleep parameters. Electroencephalogr. Clin. Neurophysiol., 72, 118–125. Ehlers, C. L., and Kupfer, D. J. (1997). Slow-wave sleep: do young adult men and women age differently? J. Sleep Res., 6, 211–215. Elenkov, I. J., Wilder, R. L., Chrousos, G. P., and Vizi, E. S. (2000). The sympathetic nerve—an integrative interface between two supersystems: the brain and the immune system. Pharmacol. Rev., 52, 595–638. Engeset, A., Sokolowski, J., and Olszewski, W. L. (1977). Variation in output of leukocytes and erythrocytes in human peripheral lymph during rest and activity. Lymphology, 10, 198–203. Everson, C. A. (1993). Sustained sleep deprivation impairs host defense. Am. J. Physiol., 265, R1148–R1154. Everson, C. A. (2005). Clinical assessment of blood leukocytes, serum cytokines, and serum immunoglobulins as responses to sleep deprivation in laboratory rats. Am. J. Physiol. Regul. Integr. Comp. Physiol., 289, R1054–R1063. Everson, C. A., and Toth, L. A. (2000). Systemic bacterial invasion induced by sleep deprivation. Am. J. Physiol., 278, R916. Fang, J., Sanborn, C. K., Majde, J. A., and Krueger, J. M. (1994). Sleep changes induced by influenza virus infection in mice. Sleep Res., 23, 358. Fang, J., Sanborn, C. K., Renegar, K. B., Majde, J. A., and Krueger, J. M. (1995). Influenza viral infections enhance sleep in mice. P. S. E. B. M., 210, 242–252. Fang, J., Wang, Y., and Krueger, J. M. (1997). Mice lacking the TNF 55 kDa receptor fail to sleep more after TNFα treatment. J. Neurosci., 17, 5949–5955. Fang, J., Wang, Y., and Krueger, J. M. (1998). Effects of interleukin-1 beta on sleep are mediated by the type I receptor. Am. J. Physiol., 274, R655–R660. Farrar, D. J., Locke, S. E., and Kantrowitz, F. G. (1995). Chronic fatigue syndrome. 1: Etiology and pathogenesis. Behav. Med., 21, 5–16. Fauci, A. S., Dale, D. C., and Balow, J. E. (1976). Glucocorticosteroid therapy: mechanisms of action and clinical considerations. Ann. Intern. Med., 84, 304–315. Fencl, V., Koski, G., and Pappenheimer, J. R. (1971). Factors in cerebrospinal fluid from goats that affect sleep and activity in rats. J. Physiol., 216, 565–589. Ferini-Strambi, L., Oldani, A., Tirloni, G., Zucconi, M., Castagna, A., Lazzarin, A., and Smirne, S. (1995). Slow wave sleep and cyclic alternating pattern (CAP) in HIV-infected asymptomatic men. Sleep, 18, 446–450. Fischler, B. (1999). Review of clinical and psychobiological dimensions of the chronic fatigue syndrome: differentiation from
depression and contribution of sleep dysfunctions. Sleep Med. Rev., 3, 131–146. Foley, D. J., Monjan, A. A., Brown, S. L., Simonsick, E. M., Wallace, R. B., and Blazer, D. G. (1995). Sleep complaints among elderly persons: an epidemiologic study of three communities. Sleep, 18, 425–432. Fontana, A., Kristensen, F., Dubs, R., Gemsa, D., and Weber, E. (1982). Production of prostaglandin E and an interleukin-1 like factor by cultured astrocytes and C6 glioma cells. J. Immunol., 129, 2413–2419. Frank, R. G., Beck, N. C., Parker, J. C., Kashani, J. H., Elliott, T. R., Haut, A. E., Smith, E., Atwood, C., Brownlee-Duffeck, M., and Kay, D. R. (1988). Depression in rheumatoid arthritis. J. Rheumatol., 15, 920–925. Friedman, E. M., and Irwin, M. (1997). Modulation of immune cell function by the autonomic nervous system. Pharmacol. Ther., 74, 27–38. Fujino, H., Kitamura, Y., Yada, T., Uehara, T., and Nomura, Y. (1997). Stimulatory roles of muscarinic acetylcholine receptors on T cell antigen receptor/CD3 complex-mediated interleukin-2 production in human peripheral blood lymphocytes. Mol. Pharmacol., 51, 1007–1014. Gala, R. R. (1991). Prolactin and growth hormone in the regulation of the immune system. Proc. Soc. Exp. Biol. Med., 198, 513– 527. Gatti, G., Angeli, A., and Carignola, R. (1992). Chronobiology of endocrine-immune interactions. In Y. Touitou and E. Haus (Eds.), Biologic rhythms in clinical and laboratory medicine (pp. 361–374). New York: Springer. Gemma, C., and Opp, M. R. (1999). Human immunodeficiency virus glycoproteins 160 and 41 alter sleep and brain temperature of rats. J. Neuroimmunol., 97, 94–101. Gilbert, S. S., van den Heuvel, C. J., Ferguson, S. A., and Dawson, D. (2004). Thermoregulation as a sleep signalling system. Sleep Med. Rev., 8, 81–93. Ginaldi, L., De, M. M., D’Ostilio, A., Marini, L., Loreto, M. F., Corsi, M. P., and Quaglino, D. (1999a). The immune system in the elderly: I. Specific humoral immunity. Immunol. Res., 20, 101–108. Ginaldi, L., De, M. M., D’Ostilio, A., Marini, L., Loreto, M. F., Martorelli, V., and Quaglino, D. (1999b). The immune system in the elderly: II. Specific cellular immunity. Immunol. Res., 20, 109–115. Ginaldi, L., De, M. M., D’Ostilio, A., Marini, L., Loreto, M. F., and Quaglino, D. (1999c). The immune system in the elderly: III. Innate immunity. Immunol. Res., 20, 117–126. Goichot, B., Brandenberger, G., Saini, J., Wittersheim, G., and Follenius, M. (1992). Nocturnal plasma thyrotropin variations are related to slow-wave sleep. J. Sleep Res., 1, 186–190. Goujon, E., Parnet, P., Layé, S., Combe, C., and Dantzer, R. (1996). Adrenalectomy enhances pro-inflammatory cytokines gene expression, in the spleen, pituitary and brain of mice in response to lipopolysaccharide. Mol. Brain Res., 36, 53–62. Gould, J. B., Lee, A. F., Cook, P., and Morelock, S. (1980). Apnea and sleep state in infants with nasopharyngitis. Pediatrics, 65, 713–717. Gourmelon, P., Amyx, H. L., Baron, H., Lemercier, G., Court, L., and Gibbs, C. J., Jr. (1987). Sleep abnormalities with REM disorder in experimental Creutzfeldt-Jakob disease in cats: a new pathological feature. Brain Res., 411, 391–396. Gourmelon, P., Briet, D., Clarencon, D., Court, L., and Tsiang, H. (1991). Sleep alterations in experimental street rabies virus infection occur in the absence of major EEG abnormalities. Brain Res., 554, 159–165.
28. Sleep and the Immune System Gudewill, S., Pollmächer, T., Vedder, H., Schreiber, W., Fassbender, K., and Holsboer, F. (1992). Nocturnal plasma levels of cytokines in healthy men. Eur. Arch. Psychiatry Clin. Neurosci., 242, 53–56. Gulevich, G., Dement, W., and Johnson, L. (1966). Psychiatric and EEG observations on a case of prolonged (264 hours) wakefulness. Arch. Gen. Psychiatry, 15, 29–35. Haack, M., Kraus, T., Schuld, A., Dalal, M., Koethe, D., and Pollmächer, T. (2002). Diurnal variations of interleukin-6 plasma levels are confounded by blood drawing procedures. Psychoneuroendocrinology, 27, 921–931. Haack, M., Pollmächer, T., and Mullington, J. M. (2004). Diurnal and sleep-wake dependent variations of soluble TNF- and IL-2 receptors in healthy volunteers. Brain Behav. Immun., 18, 361–367. Hall, M., Baum, A., Buysse, D. J., Prigerson, H. G., Kupfer, D. J., and Reynolds, C. F. (1998). Sleep as a mediator of the stress-immune relationship. Psychosom. Med., 60, 48–51. Haus, E. (1992). Chronobiology of circulation blood cells and platelets. In Y. Touitou and E. Haus (Eds.), Biologic rhythms in clinical and laboratory medicine (pp. 504–526). New York: Springer. Haus, E., and Smolensky, M. H. (1999). Biologic rhythms in the immune system. Chronobiol. Int., 16, 581–622. Heiser, P., Dickhaus, B., Schreiber, W., Clement, H. W., Hasse, C., Hennig, J., Remschmidt, H., Krieg, J. C., Wesemann, W., and Opper, C. (2000). White blood cells and cortisol after sleep deprivation and recovery sleep in humans. Eur. Arch. Psychiatry Clin. Neurosci., 250, 16–23. Hermann, D. M., Mullington, J., Hinze-Selch, D., Schreiber, W., Galanos, C., and Pollmächer, T. (1998). Endotoxin-induced changes in sleep and sleepiness during the day. Psychoneuroendocrinology, 23, 427–437. Hirsch, M., Carlander, B., Verge, M., Tafti, M., Anaya, J. M., Billiard, M., and Sany, J. (1994). Objective and subjective sleep disturbances in patients with rheumatoid arthritis. A reappraisal. Arthritis Rheum., 37, 41–49. Hogan, D., Morrow, J. D., Smith, E. M., and Opp, M. R. (2003). Interleukin-6 alters sleep of rats. J. Neuroimmunol., 137, 59– 66. Hohagen, F., Timmer, J., Weyerbrock, A., Fritsch-Montero, R., Ganter, U., Krieger, S., Berger, M., and Bauer, J. (1993). Cytokine production during sleep and wakefulness and its relationship to cortisol in healthy humans. Neuropsychobiology, 28, 9–16. Hong, S., Mills, P. J., Loredo, J. S., Adler, K. A., and Dimsdale, J. E. (2005). The association between interleukin-6, sleep, and demographic characteristics. Brain Behav. Immun., 19, 165–172. Irwin, M., Clark, C., Kennedy, B., Christian, G. J., and Ziegler, M. (2003). Nocturnal catecholamines and immune function in insomniacs, depressed patients, and control subjects. Brain Behav. Immun., 17, 365–372. Irwin, M., Gillin, J. C., Dang, J., Weissman, J., Phillips, E., and Ehlers, C. L. (2002). Sleep deprivation as a probe of homeostatic sleep regulation in primary alcoholics. Biol. Psychiatry, 51, 632–641. Irwin, M., Mascovich, A., Gillin, J. C., Willoughby, R., Pike, J., and Smith, T. L. (1994). Partial sleep deprivation reduces natural killer cell activity in humans. Psychosom. Med., 56, 493–498. Irwin, M., McClintick, J., Costlow, C., Fortner, M., White, J., and Gillin, J. C. (1996). Partial night sleep deprivation reduces natural killer and cellular immune responses in humans. FASEB J., 10, 643–653. Irwin, M., Miller, C., Gillin, J. C., Demodena, A., and Ehlers, C. L. (2000). Polysomnographic and spectral sleep EEG in primary alcoholics: an interaction between alcohol dependence and
613
African-American ethnicity. Alcohol Clin. Exp. Res., 24, 1376– 1384. Irwin, M., Rinetti, G., Redwine, L., Motivala, S., Dang, J., and Ehlers, C. (2004). Nocturnal proinflammatory cytokine-associated sleep disturbances in abstinent African American alcoholics. Brain Behav. Immun., 18, 349–360. Irwin, M., Smith, T. L., and Gillin, J. C. (1992). Electroencephalographic sleep and natural killer activity in depressed patients and control subjects. Psychosom. Med., 54, 107–126. Irwin, M., Thompson, J., Miller, C., Gillin, J. C., and Ziegler, M. (1999). Effects of sleep and sleep deprivation on catecholamine and interleukin-2 levels in humans: clinical implications, J. Clin. Endocrinol. Metab., vol. 84, no. 6, pp. 1979–1985. Ishimori, K. (1909). True cause of sleep: a hypnogenic substance as evidenced in the brain of sleep-deprived animals. Tokyo Igakkai Zasshi, 23, 429–459. Jean-Louis, G., Kripke, D. F., Ancoli-Israel, S., Klauber, M. R., and Sepulveda, R. S. (2000). Sleep duration, illumination, and activity patterns in a population sample: effects of gender and ethnicity. Biol. Psychiatry, 47, 921–927. Jones, S. A., and Rose-John, S. (2002). The role of soluble receptors in cytokine biology: the agonistic properties of the sIL-6R/IL-6 complex. Biochim. Biophys. Acta, 1592, 251–263. Jones, T. H., and Kennedy, R. L. (1993). Cytokines and hypothalamic-pituitary function. Cytokine, 5, 531–538. Kelley, K. W., Arkins, S., and Li, Y. M. (1992). Growth hormone, prolactin, and insulin-like growth factors: new jobs for old players. Brain Behav. Immun., 6, 317–326. Kornmüller, A., Lux, H., Winkel, K., and Klee, M. (1961). Neurohumoral ausgelöste schlafzustände an tieren mit gekreuztem kreislfau unter kontrolle von EEG-Ableitiungen. Naturwissenschaften, 14, 503–505. Korth, C., Mullington, J., Schreiber, W., and Pollmächer, T. (1996). Influence of endotoxin on daytime sleep in humans. Infect. Immun., 64, 1110–1115. Kripke, D. F., Garfinkel, L., Wingard, D. L., Klauber, M. R., and Marler, M. R. (2002). Mortality associated with sleep duration and insomnia. Arch. Gen. Psychiatry, 59, 131–136. Kripke, D. F., Simons, R. N., Garfinkel, L., and Hammond, E. C. (1979). Short and long sleep and sleeping pills. Is increased mortality associated? Arch. Gen. Psychiatry, 36, 103–116. Kronfol, Z., Nair, M., Zhang, Q., Hill, E. E., and Brown, M. B. (1997). Circadian immune measures in healthy volunteers: relationship to hypothalamic-pituitary-adrenal axis hormones and sympathetic neurotransmitters. Psychosom. Med., 59, 42–50. Krueger, J. M., Dinarello, C. A., and Chedid, L. (1983). Promotion of slow-wave sleep (SWS) by a purified interleukin-1 (IL-1) preparation. Federation Proc., 42, 356. Krueger, J. M., and Majde, J. A. (2003). Humoral links between sleep and the immune system: research issues. Ann. N. Y. Acad. Sci., 992, 9–20. Krueger, J. M., Obal, F., Jr., and Fang, J. (1999). Humoral regulation of physiological sleep: cytokines and GHRH. J. Sleep Res., 8(Suppl 1), 53–59. Krueger, J. M., Obal, F. J., Fang, J., Kubota, T., and Taishi, P. (2001). The role of cytokines in physiological sleep regulation. Ann. N. Y. Acad. Sci., 933, 211–221. Krueger, J. M., Pappenheimer, J. R., and Karnovsky, M. L. (1978). Sleep-promoting factor S: purification and properties. Proc. Natl. Acad. Sci. USA, 75, 5235–5238. Krueger, J. M., Pappenheimer, J. R., and Karnovsky, M. L. (1982a). Sleep-promoting effects of muramyl peptides. Proc. Natl. Acad. Sci. USA, 79, 6102–6106.
614
III. Behavior and Immunity
Krueger, J. M., Pappenheimer, J. R., and Karnovsky, M. L. (1982b). The composition of sleep-promoting factor isolated from human urine. J. Biol. Chem., 257, 1664. Krueger, J. M., and Takahashi, S. (1997). Thermoregulation and sleep: closely linked but separable. In C. M. Blatteis (Ed.), Annals of the New York Academy of Sciences, vol., 813; Thermoregulation: proceedings of the 10th international symposium on the pharmacology of thermoregulation (pp. 281–286). New York: New York Academy of Sciences. Krueger, J. M., Walter, J., Dinarello, C. A., Wolff, S. M., and Chedid, L. (1984). Sleep-promoting effects of endogenous pyrogen (interleukin-1). Am. J. Physiol., 246, R994–R999. Krupp, L. B., and Pollina, D. A. (1996). Mechanisms and management of fatigue in progressive neurological disorders. Curr. Opin. Neurol., 9, 456–460. Kuhlwein, E., and Irwin, M. (2001). Melatonin modulation of lymphocyte proliferation and Th1/Th2 cytokine expression. J. Neuroimmunol., 117, 51–57. Kuhn, E., Brodan, V., Brodanova, M., and Rysanek, K. (1969). Metabolic reflection of sleep deprivation. Act. Nerv. Super. (Praha), 11, 165–174. Kushikata, T., Fang, J., and Krueger, J. M. (1999). Interleukin-10 inhibits spontaneous sleep in rabbits. J. Interferon Cytokine Res., 19, 1025–1030. Kushikata, T., Fang, J., Wang, Y., and Krueger, J. M. (1998). Interleukin-4 inhibits spontaneous sleep in rabbits. Am. J. Physiol., 275, R1185–R1191. Lager, D. (1994). The cost of sleep-related accidents: a report of the National Commission on Sleep Disorders Research. Sleep, 17, 84–93. Lang, C. H., Pollard, V., Fan, J., Traber, L. D., Traber, D. L., Frost, R. A., Gelato, M. C., and Prough, D. S. (1997). Acute alterations in growth hormone-insulin–like growth factor axis in humans injected with endotoxin. Am. J. Physiol., 273, R371–R378. Lange, T., Dimitrov, S., Fehm, H. L., and Born, J. (2006). Sleep-like concentrations of growth hormone and cortisol modulate type 1 and type 2 in vitro cytokine production in human T cells. Int. Immunopharmacol., 6, 216–225. Lange, T., Marshall, L., Späth-Schwalbe, E., Fehm, H. L., and Born, J. (2002). Systemic immune parameters and sleep after ultra-low dose administration of IL-2 in healthy men. Brain Behav. Immun., 16, 663–674. Lange, T., Perras, B., Fehm, H. L., and Born, J. (2003). Sleep enhances the human antibody response to hepatitis A vaccination. Psychosom. Med., 65, 831–835. Legendre, R., and Piéron, H. (1910). Le problème des facteurs du sommeil. Résultats d’injections vasculaires et intracérébrales de liquides insomniques. C. R. Soc. Biol., 68, 1077–1079. Lentz, M. J., Landis, C. A., Rothermel, J., and Shaver, J. L. (1999). Effects of selective slow wave sleep disruption on musculoskeletal pain and fatigue in middle aged women. J. Rheumatol., 26, 1586–1592. Lesperance, F., Frasure-Smith, N., Theroux, P., and Irwin, M. (2004). The association between major depression and levels of soluble intercellular adhesion molecule 1, interleukin-6, and C-reactive protein in patients with recent acute coronary syndromes. Am. J. Psychiatry, 161, 271–277. Lissoni, P., Rovelli, F., Brivio, F., Brivio, O., and Fumagalli, L. (1998). Circadian secretions of IL-2, IL-12, IL-6 and IL-10 in relation to the light/dark rhythm of the pineal hormone melatonin in healthy humans. Nat. Immun., 16, 1–5. Loomis, A. L., Harvey, E. N., and Hobart, G. A., III (1938). Distribution of disturbance-patterns in the human electroencephalogram, with special reference to sleep. J. Neurophysiol., 1, 413–430.
Lue, F. A., Bail, M., Jephthah-Ochola, J., Carayanniotis, K., Gorczynski, R., and Moldofsky, H. (1988). Sleep and cerebrospinal fluid interleukin-1–like activity in the cat. Int. J. Neurosci., 42, 179–183. Lundkvist, G. B., Hill, R. H., and Kristensson, K. (2002). Disruption of circadian rhythms in synaptic activity of the suprachiasmatic nuclei by African trypanosomes and cytokines. Neurobiol. Dis., 11, 20–27. Lundkvist, G. B., Kristensson, K., and Bentivoglio, M. (2004). Why trypanosomes cause sleeping sickness. Physiology (Bethesda), 19, 198–206. Madden, K. S., and Felten, D. L. (1995). Experimental basis for neural-immune interactions. Physiol. Rev., 75, 77–106. Mahowald, M. W., Mahowald, M. L., Bundlie, S. R., and Ytterberg, S. R. (1989). Sleep fragmentation in rheumatoid arthritis. Arthritis Rheum., 32, 974–983. Maisel, A. S., Murray, D., Lotz, M., Rearden, A., Irwin, M., and Michel, M. C. (1991). Propranolol treatment affects parameters of human immunity. Immunopharmacology, 22, 157–164. Malec, P. H., Zeman, K., Markiewicz, K., and Tchorzewski, H. (1990). Chronic beta-adrenergic antagonist treatment affects human T lymphocyte responsiveness “in vitro.” Allergol. Immunopathol. (Madr.), 18, 83–85. Mallon, L., Broman, J. E., and Hetta, J. (2000). Relationship between insomnia, depression, and mortality: a 12-year follow-up of older adults in the community. Int. Psychogeriatr., 12, 295–306. Mallon, L., Broman, J. E., and Hetta, J. (2002). Sleep complaints predict coronary artery disease mortality in males: a 12-year follow-up study of a middle-aged Swedish population. J. Intern. Med., 251, 207–216. Manfridi, A., Brambilla, D., Bianchi, S., Mariotti, M., Opp, M. R., and Imeri, L. (2003). Interleukin-1β enhances non-rapid eye movement sleep when microinjected into the dorsal raphe nucleus and inhibits serotonergic neurons in vitro. Eur. J. Neurosci., 18, 1041–1049. Martin, S. A., Karnovsky, M. L., Krueger, J. M., Pappenheimer, J. R., and Biemann, K. (1984). Peptidoglycans as promoters of slowwave sleep. I. Structure of the sleep-promoting factor isolated from human urine. J. Biol. Chem., 259, 12652–12658. Matera, L., Mori, M., Geuna, M., Buttiglieri, S., and Palestro, G. (2000). Prolactin in autoimmunity and antitumor defence. J. Neuroimmunol., 109, 47–55. Mease, P. (2005). Fibromyalgia syndrome: review of clinical presentation, pathogenesis, outcome measures, and treatment. J. Rheumatol., Suppl. 75, 6–21. Mellado, M., Llorente, M., Rodriguez-Frade, J. M., Lucas, P., Martinez, C., and Del, R. G. (1998). HIV-1 envelope protein gp120 triggers a Th2 response in mice that shifts to Th1 in the presence of human growth hormone. Vaccine, 16, 1111–1115. Miyawaki, T., Taga, K., Nagaoki, T., Seki, H., Suzuki, Y., and Taniguchi, N. (1984). Circadian changes of T lymphocyte subsets in human peripheral blood. Clin. Exp. Immunol., 55, 618–622. Moldofsky, H. (1995). Sleep, neuroimmune and neuroendocrine functions in fibromyalgia and chronic fatigue syndrome. Adv. Neuroimmunol., 5, 39–56. Moldofsky, H. (2001). Sleep and pain. Sleep Med. Rev., 5, 385– 396. Moldofsky, H., Lue, F. A., Davidson, J. R., and Gorczynski, R. (1989). Effects of sleep deprivation on human immune functions. FASEB J., 3, 1972–1977. Moldofsky, H., Lue, F. A., Eisen, J., Keystone, E., Gorczynski, R. M. (1986). The relationship of interleukin-1 and immune functions to sleep in humans. Psychosom. Med., 48, 309–318.
28. Sleep and the Immune System Moldofsky, H., Lue, F. A., and Smythe, H. A. (1983). Alpha EEG sleep and morning symptoms in rheumatoid arthritis. J. Rheumatol., 10, 373–379. Moldofsky, H., Scarisbrick, P., England, R., and Smythe, H. (1975). Musculosketal symptoms and non-REM sleep disturbance in patients with “fibrositis syndrome” and healthy subjects. Psychosom. Med., 37, 341–351. Monnier, M., and Hoesli, L. (1964). Dialysis of sleep and waking factors in blood of the rabbit. Science, 146, 796–798. Montagna, P., Cortelli, P., Gambetti, P., and Lugaresi, E. (1995). Fatal familial insomnia: sleep, neuroendocrine and vegetative alterations. Advan. Neuroimmunol., 5, 13. Morrow, J. D., and Opp, M. R. (2005a). Diurnal variation of lipopolysaccharide-induced alterations in sleep and body temperature of interleukin-6–deficient mice. Brain Behav. Immun., 19, 40– 51. Morrow, J. D., and Opp, M. R. (2005b). Sleep-wake behavior and responses of interleukin-6–deficient mice to sleep deprivation. Brain Behav. Immun., 19, 28–39. Motivala, S. J., Sarfatti, A., Olmos, L., and Irwin, M. R. (2005). Inflammatory markers and sleep disturbance in major depression. Psychosom. Med., 67, 187–194. Mullington, J., Korth, C., Hermann, D. M., Orth, A., Galanos, C., Holsboer, F., and Pollmächer, T. (2000). Dose-dependent effects of endotoxin on human sleep. Am. J. Physiol. Regul. Integr. Comp. Physiol., 278, R947–R955. Murphy, S., Creed, F., and Jayson, M. I. (1988). Psychiatric disorder and illness behaviour in rheumatoid arthritis. Br. J. Rheumatol., 27, 357–363. Mustafa, M., Mustafa, A., Nyberg, F., Mangat, H., Elhassan, A., and Adem, R. (1999). Hypophysectomy enhances interleukin-1β, tumor necrosis factor-a, and interleukin-10 mRNA expression in the rat brain. J. Interferon Cytokine Res., 19, 583–587. Nagasaki, H., Iriki, M., Inoue, S., and Uchizono, K. (1974). Proceedings: sleep promoting substances in the brain stem of rats. Nippon Seirigaku Sazzhi, 36, 293. Nicassio, P. M., and Wallston, K. A. (1992). Longitudinal relationships among pain, sleep problems, and depression in rheumatoid arthritis. J. Abnorm. Psychol., 101, 514–520. Nomura, J., Hosoi, T., Okuma, Y., and Nomura, Y. (2003). The presence and functions of muscarinic receptors in human T cells: the involvement in IL-2 and IL-2 receptor system. Life Sci., 72, 2121–2126. Norman, S. E., Chediak, A. D., Kiel, M., and Cohn, M. A. (1990). Sleep disturbances in HIV-infected homosexual men. AIDS, 4, 775–781. Obál, F., Jr., and Krueger, J. M. (2003). Biochemical regulation of non–rapid-eye-movement sleep. Front. Biosci., 8, d520–d550. Obál, F., Jr., Opp, M. R., Sary, G., and Krueger, J. M. (1990). Endocrine mechanisms in sleep regulation. In S. Inoué and J. M. Krueger (Eds.), Endogenous sleep factors (pp. 109–120). The Hague, The Netherlands: SPB Academic Publishing. Ohayon, M. (1996). Epidemiological study on insomnia in the general population. Sleep, 19, 7–15. Ohayon, M. M. (2002). Epidemiology of insomnia: what we know and what we still need to learn. Sleep Med. Rev., 6, 97–111. Okun, M. L., Giese, S., Lin, L., Einen, M., Mignot, E., and CoussonsRead, M. E. (2004). Exploring the cytokine and endocrine involvement in narcolepsy. Brain Behav. Immun., 18, 326–332. Opp, M. R. (2005). Cytokines and sleep. Sleep Med. Rev., 9, 355–364. Opp, M. R., Cady, A. B., Johannsen, L., and Krueger, J. M. (1989a). Interleukin-6 is pyrogenic but not somnogenic. Physiol. Behav., 45, 1069–1072.
615
Opp, M. R., and Imeri, L. (2001). Rat strains that differ in corticotropin-releasing hormone production exhibit different sleep-wake responses to interleukin 1. Neuroendocrinology, 73, 272–284. Opp, M. R., and Krueger, J. M. (1988). Effects of α-MSH on sleep, behavior, and brain temperature: interactions with IL-1. Am. J. Physiol., 255, R914–R922. Opp, M. R., and Krueger, J. M. (1991). Interleukin 1–receptor antagonist blocks interleukin 1–induced sleep and fever. Am. J. Physiol., 260, R453–R457. Opp, M. R., and Krueger, J. M. (1994a). Anti-interleukin-1β reduces sleep and sleep rebound after sleep deprivation in rats. Am. J. Physiol., 266, R688–R695. Opp, M. R., and Krueger, J. M. (1994b). Interleukin-1 is involved in responses to sleep deprivation in the rabbit. Brain Res., 639, 57–65. Opp, M. R., Obál, F., and Krueger, J. M. (1991). Interleukin-1 alters rat sleep: temporal and dose-related effects. Am. J. Physiol., 260, R52–R58. Opp, M. R., Obál, F., Jr., and Krueger, J. M. (1989b). Corticotropinreleasing factor attenuates interleukin-1 induced sleep and fever in rabbits. Am. J. Physiol., 257, R528–R535. Opp, M. R., Rady, P. L., Hughes, T. K., Jr., Cadet, P., Tyring, S. K., and Smith, E. M. (1996). Human immunodeficiency virus envelope glycoprotein 120 alters sleep and induces cytokine mRNA expression in rats. Am. J. Physiol., 270, R963–R970. Opp, M. R., Smith, E. M., and Hughes, T. K., Jr. (1995). IL-10 (cytokine synthesis inhibitory factor) acts in the central nervous system of rats to reduce sleep. J. Neuroimmunol., 60, 165– 168. Opp, M. R., and Toth, L. A. (2003). Neural-immune interactions in the regulation of sleep. Front. Biosci., 8, d768–d779. Ottaway, C. A., and Husband, A. J. (1992). Central nervous system influences on lymphocyte migration. Brain Behav. Immun., 6, 97–116. Ottaway, C. A., and Husband, A. J. (1994). The influence of neuroendocrine pathways on lymphocyte migration. Immunol. Today, 15, 511–517. Öztürk, L., Pelin, Z., Karadeniz, D., Kaynak, H., Cakar, L., and Gozukirmizi, E. (1999). Effects of 48 hours’ sleep deprivation on human immune profile. Sleep Res. Online, 2, 107–111. Palm, S., Postler, E., Hinrichsen, H., Maier, H., Zabel, P., and Kirch, W. (1996). Twenty-four–hour analysis of lymphocyte subpopulations and cytokines in healthy subjects. Chronobiol. Int., 13, 423–434. Pappenheimer, J. R., Koski, G., Fencl, V., Karnovsky, M. L., and Krueger, J. (1975). Extraction of sleep-promoting factor S from cerebrospinal fluid and from brains of sleep-deprived animals. J. Neurophysiol., 38, 1299–1311. Pappenheimer, J. R., Miller, T. B., and Goodrich, C. A. (1967). Sleeppromoting effects of cerebrospinal fluid from sleep-deprived goats. Proc. Natl. Acad. Sci. USA, 58, 513–517. Perras, B., and Born, J. (2005). Sleep associated endocrine and immune changes in the elderly. In M. P. Mattson (Ed.), Sleep and aging (pp. 113–154). Baltimore: Elsevier. Petit, L., Azad, N., Byszewski, A., Sarazan, F. F., and Power, B. (2003). Non-pharmacological management of primary and secondary insomnia among older people: review of assessment tools and treatments. Age Aging, 32, 19–25. Petrovsky, N. (2001). Towards a unified model of neuroendocrineimmune interaction. Immunol. Cell Biol., 79, 350–357. Petrovsky, N., and Harrison, L. C. (1997). Diurnal rhythmicity of human cytokine production: a dynamic disequilibrium in T helper cell type 1/T helper cell type 2 balance? J. Immunol., 158, 5163–5168.
616
III. Behavior and Immunity
Petrovsky, N., and Harrison, L. C. (1998). The chronobiology of human cytokine production. Int. Rev. Immunol., 16, 635–649. Petrovsky, N., McNair, P., and Harrison, L. C. (1994). Circadian rhythmicity of interferon-gamma production in antigenstimulated whole blood. Chronobiologia, 21, 293–300. Petrovsky, N., McNair, P., and Harrison, L. C. (1998). Diurnal rhythms of pro-inflammatory cytokines: regulation by plasma cortisol and therapeutic implications. Cytokine, 10, 307–312. Pluzanska, A., and Mazurowa, A. (1977). T and B lymphocytes in peripheral blood of subjects receiving atropine. Acta Haematol. Pol., 8, 39–43. Pollak, C. P., Perlick, D., Linsner, J. P., Wenston, J., and Hsieh, F. (1990). Sleep problems in the community elderly as predictors of death and nursing home placement. J. Community Health, 15, 123–135. Pollmächer, T., Mullington, J., Korth, C., and Hinze-Selch, D. (1995). Influence of host defense activation on sleep in humans. Adv. Neuroimmunol., 5, 155–169. Pollmächer, T., Schreiber, W., Gudewill, S., Vedder, H., Fassbender, K., Wiedemann, K., Trachsel, L., Galanos, C., and Holsboer, F. (1993). Influence of endotoxin on nocturnal sleep in humans. Am. J. Physiol., 264, R1077–R1083. Pollmächer, T., Schuld, A., Kraus, T., Haack, M., Hinze-Selch, D., and Mullington, J. (2000). Experimental immunomodulation, sleep, and sleepiness in humans. Ann. N. Y. Acad. Sci., 917, 488–499. Postel-Vinay, M. C., De, M. C., V, Gagnerault, M. C., and Dardenne, M. (1997). Growth hormone stimulates the proliferation of activated mouse T lymphocytes. Endocrinology, 138, 1816–1820. Qiu, P., Wang, Z. J., and Liu, K. J. (2005). Ensemble dependence model for classification and prediction of cancer and normal gene expression data. Bioinformatics, 21, 3114–3121. Radomski, M. W., Buguet, A., Doua, F., Bogui, P., and Tapie, P. (1996). Relationship of plasma growth hormone to slow-wave sleep in African sleeping sickness. Neuroendocrinology, 63, 393– 396. Rechtschaffen, A., Bergmann, B. M., Everson, C. A., Kushida, C. A., and Gilliland, M. A. (1989). Sleep deprivation in the rat: X. Integration and discussion of the findings. Sleep, 12, 68–87. Rechtschaffen, A., Gilliland, M. A., Bergmann, B. M., and Winter, J. B. (1983). Physiological correlates of prolonged sleep deprivation in rats. Science, 221, 182–184. Redwine, L., Dang, J., Hall, M., and Irwin, M. (2003). Disordered sleep, nocturnal cytokines, and immunity in alcoholics. Psychosom. Med., 65, 75–85. Redwine, L., Dang, J., and Irwin, M. (2004). Cellular adhesion molecule expression, nocturnal sleep, and partial night sleep deprivation. Brain Behav. Immun., 18, 333–340. Redwine, L., Hauger, R. L., Gillin, J. C., and Irwin, M. (2000). Effects of sleep and sleep deprivation on interleukin-6, growth hormone, cortisol, and melatonin levels in humans. J. Clin. Endocrinol. Metab., 85, 3597–3603. Refinetti, R. (1999). Relationship between the daily rhythms of loco motor activity and body temperature in eight mammalian species. Am. J. Physiol., 277, R1493–R1500. Reichenberg, A., Yirmiya, R., Schuld, A., Kraus, T., Haack, M., Morag, A., and Pollmächer, T. (2001). Cytokine-associated emotional and cognitive disturbances in humans. Arch. Gen. Psychiatry, 58, 445–452. Reid, S., and Dwyer, J. (2005). Insomnia in HIV infection: a systematic review of prevalence, correlates, and management. Psychosom. Med., 67, 260–269. Renegar, K. B., Crouse, D., Floyd, R. A., and Krueger, J. (2000). Progression of influenza viral infection through the murine respira-
tory tract: the protective role of sleep deprivation. Sleep, 23, 859–863. Renegar, K. B., Floyd, R., and Krueger, J. M. (1998a). Effect of sleep deprivation on serum influenza-specific IgG. Sleep, 21, 19–24. Renegar, K. B., Floyd, R. A., and Krueger, J. M. (1998b). Effects of short-term sleep deprivation on murine immunity to influenza virus in young adult and senescent mice. Sleep, 21, 241–248. Ridker, P. M. (2001). Role of inflammatory biomarkers in prediction of coronary heart disease. Lancet, 358, 946–948; Comment On: 971–976. Ritchie, A. W., Oswald, I., Micklem, H. S., Boyd, J. E., Elton, R. A., Jazwinska, E., and James, K. (1983). Circadian variation of lymphocyte subpopulations: a study with monoclonal antibodies. Br. Med. J. (Clin. Res. Ed.), 286, 1773–1775. Rook, G. A., Hernandez-Pando, R., and Lightman, S. L. (1994). Hormones, peripherally activated prohormones and regulation of the Th1/Th2 balance. Immunol. Today, 15, 301–303. Rosenbaum, E. (1892). Warum müssen wir schlafen? Eine neue theorie des schlafes. Berlin: Verlag von August Hirschwald. Sackstein, R., and Borenstein, M. (1995). The effects of corticosteroids on lymphocyte recirculation in humans: analysis of the mechanism of impaired lymphocyte migration to lymph node following methylprednisolone administration. J. Invest. Med., 43, 68–77. Sanchez-Alavez, M., Criado, J., Gomez-Chavarin, M., JimenezAnguiano, A., Navarro, L., az-Ruiz, O., Galicia, O., SanchezNarvaez, F., Murillo-Rodriguez, E., Henriksen, S. J., Elder, J. H., and Prospero-Garcia, O. (2000). HIV- and FIV-derived gp120 alter spatial memory, LTP, and sleep in rats. Neurobiol. Dis., 7, 384–394. Sanders, V. M. (1995). The role of adrenoceptor-mediated signals in the modulation of lymphocyte function. Adv. Neuroimmunol., 5, 283–298. Savard, J., Laroche, L., Simard, S., Ivers, H., and Morin, C. M. (2003). Chronic insomnia and immune functioning. Psychosom. Med., 65, 211–221. Savard, J., Miller, S. M., Mills, M., O’Leary, A., Harding, H., Douglas, S. D., Mangan, C. E., Belch, R., and Winokur, A. (1999). Association between subjective sleep quality and depression on immunocompetence in low-income women at risk for cervical cancer. Psychosom. Med., 61, 496–507. Savard, J., and Morin, C. M. (2001). Insomnia in the context of cancer: a review of a neglected problem. J. Clin. Oncol., 19, 895–908. Schobitz, B., Pezeshki, G., Pohl, T., Hemmann, U., Heinrich, P. C., Holsboer, F., and Reul, J. M. (1995). Soluble interleukin-6 (IL-6) receptor augments central effects of IL-6 in vivo. FASEB J., 9, 659–664. Schuld, A., Mullington, J., Hermann, D., Hinze-Selch, D., Fenzel, T., Holsboer, F., and Pollmächer, T. (1999). Effects of granulocyte colony-stimulating factor on night sleep in humans. Am. J. Physiol., 276, R1149–R1155. Shakhar, G., and Ben-Eliyahu, S. (1998). In vivo beta-adrenergic stimulation suppresses natural killer activity and compromises resistance to tumor metastasis in rats. J. Immunol., 160, 3251– 3258. Shearer, G. M. (1997). Th1/Th2 changes in aging. Mech. Aging Dev., 94, 1–5. Shearer, W. T., Reuben, J. M., Mullington, J. M., Price, N. J., Lee, B. N., Smith, E. O., Szuba, M. P., Van Dongen, H. P., and Dinges, D. F. (2001). Soluble TNF-alpha receptor 1 and IL-6 plasma levels in humans subjected to the sleep deprivation model of spaceflight. J. Allergy Clin. Immunol., 107, 165–170.
28. Sleep and the Immune System Smith, A. (1992). Sleep, colds, and performance. In R. J. Broughton, and R. D. Ogilvie (Eds.), Sleep, arousal and performance (pp. 233– 242). Boston: Birkhauser. Snijdewint, F. G., Kapsenberg, M. L., Wauben-Penris, P. J., and Bos, J. D. (1995). Corticosteroids class-dependently inhibit in vitro Th1- and Th2-type cytokine production. Immunopharmacology, 29, 93–101. Solana, R., and Mariani, E. (2000). NK and NK/T cells in human senescence. Vaccine, 18, 1613–1620. Somers, V. K., Dyken, M. E., Mark, A. L., and Abboud, F. M. (1993). Sympathetic-nerve activity during sleep in normal subjects. N. Engl. J. Med., 328, 303–307. Sothern, R. B., Roitman-Johnson, B., Kanabrocki, E. L., Yager, J. G., Roodell, M. M., Weatherbee, J. A., Young, M. R., Nenchausky, B. M., and Scheving, L. E. (1995). Circadian characteristics of circulating interleukin-6 in men. J. Allergy Clin. Immunol., 95, 1029–1035. Spangelo, B. L., Hall, N. R., Ross, P. C., and Goldstein, A. L. (1987). Stimulation of in vivo antibody production and concanavalinA–induced mouse spleen cell mitogenesis by prolactin. Immunopharmacology, 14, 11–20. Späth-Schwalbe, E., Hansen, K., Schmidt, F., Schrezenmeier, H., Marshall, L., Burger, K., Fehm, H. L., and Born, J. (1998). Acute effects of recombinant human interleukin-6 on endocrine and central nervous sleep functions in healthy men. J. Clin. Endocrinol. Metab., 83, 1573–1579. Späth-Schwalbe, E., Lange, T., Perras, B., Fehm, H. L., and Born, J. (2000). Interferon-alpha acutely impairs sleep in healthy humans. Cytokine, 12, 518–521. Späth-Schwalbe, E., Schrezenmeier, H., Bornstein, S., Burger, K., Porzsolt, F., and Born, J. (1996). Endocrine effects of recombinant interleukin 6 in man. Neuroendocrinology, 63, 237–243. Späth-Schwalbe, E., Uthgenannt, D., Voget, G., Kern, W., Born, J., and Fehm, H. L. (1993). Corticotropin-releasing hormoneinduced adrenocorticotropin and cortisol secretion depends on sleep and wakefulness. J. Clin. Endocrinol. Metab., 77, 1170–1173. Spiegel, K., Luthringer, R., Follenius, M., Schaltenbrand, N., Macher, J. P., Muzet, A., and Brandenberger, G. (1995). Temporal relationship between prolactin secretion and slow-wave electroencephalic activity during sleep. Sleep, 18, 543–548. Spiegel, K., Sheridan, J. F., and Van, C. E. (2002). Effect of sleep deprivation on response to immunization. JAMA, 288, 1471–1472. Steiger, A. (2003). Sleep and endocrinology. J. Intern. Med., 254, 13–22. Stephenson, J. R., Lee, J. M., Bailey, N., Shepherd, A. G., and Melling, J. (1991). Adjuvant effect of human growth hormone with an inactivated flavivirus vaccine. J. Infect. Dis., 164, 188–191. Straub, R. H., Westermann, J., Scholmerich, J., and Falk, W. (1998). Dialogue between the CNS and the immune system in lymphoid organs. Immunol. Today, 19, 409–413. Sutherland, E. R., Martin, R. J., Ellison, M. C., and Kraft, M. (2002). Immunomodulatory effects of melatonin in asthma. Am. J. Respir. Crit. Care Med., 166, 1055–1061. Taishi, P., De, A., Alt, J., Gardi, J., Obal, F., Jr., and Krueger, J. M. (2004). Interleukin-1beta stimulates growth hormone-releasing hormone receptor mRNA expression in the rat hypothalamus in vitro and in vivo. J. Neuroendocrinol., 16, 113–118. Takagi, K., Suzuki, F., Barrow, R. E., Wolf, S. E., and Herndon, D. N. (1998). Recombinant human growth hormone modulates Th1 and Th2 cytokine response in burned mice. Ann. Surg., 228, 106–111.
617
Takahashi, S., Fang, J., Kapás, L., Wang, Y., and Krueger, J. M. (1997). Inhibition of brain interleukin-1 attenuates sleep rebound after sleep deprivation in rabbits. Am. J. Physiol., 273, R677–R682. Takahashi, S., Kapás, L., Fang, J., and Krueger, J. M. (1995a). An anti-tumor necrosis factor antibody suppresses sleep in rats and rabbits. Brain Res., 690, 241–244. Takahashi, S., Kapas, L., Fang, J., and Krueger, J. M. (1999). Somnogenic relationships between tumor necrosis factor and interleukin-1. Am. J. Physiol., 276, R1132–R1140. Takahashi, S., and Krueger, J. M. (1997). Inhibition of tumor necrosis factor prevents warming-induced sleep responses in rabbits. Am. J. Physiol., 272, R1325–R1329. Takahashi, S., Tooley, D. D., Kapás, L., Fang, J., Seyer, J. M., and Krueger, J. M. (1995b). Inhibition of tumor necrosis factor in the brain suppresses rabbit sleep. Pflügers Arch., 431, 155–160. Tobler, I. (1989). Napping and polyphasic sleep in mammals. In D. F. Dinges and R. J. Broughton (Eds.), Sleep and alertness: chronobiological, behavioral, and medical aspects of napping (pp. 9–30). New York: Raven Press, Ltd. Tobler, I. (1995). Is sleep fundamentally different between mammalian species? Behav. Brain Res., 69, 35–41. Tobler, I., Borbély, A. A., Schwyzer, M., and Fontana, A. (1984). Interleukin-1 derived from astrocytes enhances slow wave activity in sleep EEG of the rat. Eur. J. Pharmacol., 104, 191–192. Tobler, I., Deboer, T., and Fischer, M. (1997). Sleep and sleep regulation in normal and prion protein-deficient mice. J. Neurosci., 17, 1869–1879. Tobler, I., Gaus, S. E., Deboer, T., Achermann, P., Fischer, M., Rülicke, T., Moser, M., Oesch, B., McBrides, P. A., and Manson, J. C. (1996). Altered circadian activity rhythms and sleep in mice devoid of prion protein. Nature, 380, 639–642. Tohya, K., and Kimura, M. (1998). Ultrastructural evidence of distinctive behavior of L-selectin and LFA-1 (alphaLbeta2 integrin) on lymphocytes adhering to the endothelial surface of high endothelial venules in peripheral lymph nodes. Histochem. Cell Biol., 110, 407–416. Toth, L. A. (1994). Sleep patterns in healthy and influenza-infected mice are correlated with alleles of the If-1 gene. Physiologist, 37, A-49. Toth, L. A. (1995). Sleep, sleep deprivation and infectious disease: studies in animals. Adv. Neuroimmunol., 5, 79–92. Toth, L. A. (1996). Strain differences in the somnogenic effects of interferon inducers in mice. J. Interferon Cytokine Res., 16, 1065–1072. Toth, L. A. (1999). Microbial modulation of sleep. In R. Lydic and H. A. Baghdoyan (Eds.), Handbook of behavioral state control: cellular and molecular mechanisms (pp. 641–657). Boca Raton: CRC Press. Toth, L. A., and Krueger, J. M. (1988). Alterations of sleep in rabbits by Staphylococcus aureus infection. Infect. Immun., 56, 1785–1791. Toth, L. A., and Krueger, J. M. (1989). Effects of microbial challenge on sleep in rabbits. FASEB J., 3, 2062–2066. Toth, L. A., and Opp, M. R. (2001). Cytokine- and microbiallyinduced sleep responses of interleukin-10 deficient mice. Am. J. Physiol., 280, R1806–R1814. Toth, L. A., and Opp, M. R. (2002). Infection and sleep. In T. LeeChiong, M. A. Carskadon, and M. Sateia (Eds.), Sleep medicine (pp. 77–84). Philadelphia: Hanley & Belfus, Inc. Toth, L. A., Opp, M. R., and Mao, L. (1995a). Somnogenic effects of sleep deprivation and Escherichia coli inoculation in rabbits. J. Sleep Res., 4, 30–40. Toth, L. A., Rehg, J. E., and Webster, R. G. (1995b). Strain differences in sleep and other pathophysiological sequelae of influenza virus
618
III. Behavior and Immunity
infection in naive and immunized mice. J. Neuroimmunol., 58, 89–99. Toth, L. A., Tolley, E. A., Broady, R., Blakely, B., and Krueger, J. M. (1994). Sleep during experimental trypanosomiasis in rabbits. P. S. E. B. M., 205, 174–181. Toth, L. A., Tolley, E. A., and Krueger, J. M. (1993). Sleep as a prognostic indicator during infectious disease in rabbits. P. S. E. B. M., 203, 179–192. Turnbull, A. V., and Rivier, C. (1999). Regulation of the hypothalamic-pituitary-adrenal axis by cytokines: actions and mechanisms of action. Physiol. Rev., 79, 1–71. Uthgenannt, D., Schoolmann, D., Pietrowsky, R., Fehm, H. L., and Born, J. (1995). Effects of sleep on the production of cytokines in humans. Psychosom. Med., 57, 97–104. Van Cauter, E., Leproult, R., and Plat, L. (2000). Age-related changes in slow wave sleep and REM sleep and relationship with growth hormone and cortisol levels in healthy men. JAMA, 284, 861–868. Vgontzas, A. N., Bixler, E. O., Lin, H. M., Prolo, P., Trakada, G., and Chrousos, G. P. (2005). IL-6 and its circadian secretion in humans. Neuroimmunomodulation, 12, 131–140. Vgontzas, A. N., Papanicolaou, D. A., Bixler, E. O., Kales, A., Tyson, K., and Chrousos, G. P. (1997). Elevation of plasma cytokines in disorders of excessive daytime sleepiness: role of sleep disturbance and obesity. J. Clin. Endocrinol. Metab., 82, 1313–1316. Vgontzas, A. N., Papanicolaou, D. A., Bixler, E. O., Lotsikas, A., Zachman, K., Kales, A., Prolo, P., Wong, M. L., Licinio, J., Gold, P. W., Hermida, R. C., Mastorakos, G., and Chrousos, G. P. (1999). Circadian interleukin-6 secretion and quantity and depth of sleep. J. Clin. Endocrinol. Metab., 84, 2603–2607.
Vgontzas, A. N., Zoumakis, E., Bixler, E. O., Lin, H. M., Follett, H., Kales, A., and Chrousos, G. P. (2004a). Adverse effects of modest sleep restriction on sleepiness, performance, and inflammatory cytokines. J. Clin. Endocrinol. Metab., 89, 2119–2126. Vgontzas, A. N., Zoumakis, E., Lin, H. M., Bixler, E. O., Trakada, G., and Chrousos, G. P. (2004b). Marked decrease in sleepiness in patients with sleep apnea by etanercept, a tumor necrosis factoralpha antagonist. J. Clin. Endocrinol. Metab., 89, 4409–4413. Vgontzas, A. N., Zoumakis, M., Papanicolaou, D. A., Bixler, E. O., Prolo, P., Lin, H. M., Vela-Bueno, A., Kales, A., and Chrousos, G. P. (2002). Chronic insomnia is associated with a shift of interleukin-6 and tumor necrosis factor secretion from nighttime to daytime. Metabolism, 51, 887–892. Vitaliano, P. P., Scanlan, J. M., Ochs, H. D., Syrjala, K., Siegler, I. C., and Snyder, E. A. (1998). Psychosocial stress moderates the relationship of cancer history with natural killer cell activity. Ann. Behav. Med. (Summer), 20(3), 199–308. White, J. L., Darko, D. F., Brown, S. J., Miller, J. C., Hayduk, R., Kelly, T., and Mitler, M. M. (1995). Early central nervous system response to HIV infection: sleep distortion and cognitive-motor decrements. AIDS, 9, 1043–1050. Yu-Lee, L. Y. (2002). Prolactin modulation of immune and inflammatory responses. Recent Prog. Horm. Res., 57, 435–455. Zabel, P., Horst, H. J., Kreiker, C., and Schlaak, M. (1990). Circadian rhythm of interleukin-1 production of monocytes and the influence of endogenous and exogenous glucocorticoids in man. Klin. Wochenschr., 68, 1217–1221. Zabel, P., Linnemann, K., and Schlaak, M. (1993). Circadian rhythm in cytokines. Immun. Infekt., 21(Suppl 1), 38–40.
C H A P T E R
29 Emotions and the Immune System MARGARET E. KEMENY
I. INTRODUCTION 619 II. IMPORTANCE OF STUDYING AFFECT IN PNI 619 III. CAN THE IMMUNE SYSTEM PLAY A ROLE IN SUPPORTING THE ADAPTIVE BEHAVIORAL CHANGES ORCHESTRATED BY EMOTIONS? 620 IV. NEGATIVE AFFECTIVE STATES AND THE IMMUNE SYSTEM 621 V. DEPRESSION AND THE IMMUNE SYSTEM 622 VI. ANXIETY AND THE IMMUNE SYSTEM 622 VII. ANGER, HOSTILITY, AND THE IMMUNE SYSTEM 623 VIII. SELF-CONSCIOUS EMOTIONS AND THE IMMUNE SYSTEM 624 IX. POSITIVE AFFECT AND THE IMMUNE SYSTEM 624 X. DIFFERENTIAL IMMUNE CORRELATES OF AFFECTIVE STATES 625 XI. SUMMARY 625 XII. FUTURE DIRECTIONS 626
extensive over the past 30 years. The majority of this research focuses on the immunological effects of exposure to naturalistic or laboratory-induced stressors (Segerstrom and Miller, 2004). A limitation in this literature is the lack of a consistent theoretical framework for understanding the psychological mediators of the effects of stressors on the immune system (Kemeny and Laudenslager, 1999; Segerstrom et al., 2001). While the stress and coping model is often invoked (Lazarus and Folkman, 1984), adoption of this model has tended to result in studies which measure one or more of a long list of potential psychological variables consistent with the model (e.g., anxiety, depression, active coping, passive coping, denial, social support, support seeking, threat appraisal) and one or more of a long list of indices of enumerative or functional immunity, resulting in a very large matrix of findings. From this matrix, it is difficult to discern the critical psychological variables that have reliable links to specific immune pathways.
I. INTRODUCTION II. IMPORTANCE OF STUDYING AFFECT IN PNI
This chapter will discuss the importance of studying affect in the field of psychoneuroimmunology, consider the possible adaptive nature of immunologic changes that have been associated with specific affective or motivational responses, and review the literature linking specific affective states to immune changes, including potential mediators of these relations. Finally, future directions in this area of research will be considered. Research on the relationship between psychological factors and the immune system has become quite PSYCHONEUROIMMUNOLOGY, 4E VOLUME I
One strategy for grappling with the heterogeneity in psychological variables that could be examined in this area is to focus on the most proximal end of the psychological continuum. Research could focus on those psychological states that are posited to be the final links in the pathway from psychological response to the CNS orchestration of the neuroendocrine and immune effects of that response. Many stress and coping theorists consider affective states to be the final
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link in the chain from the environmental perturbation to the biological response (Lazarus and Folkman, 1984). In other words, coping processes and social support, for example, are posited to act on physiology by modifying the affective response to a given context. A greater understanding of the links between affect and peripheral systems might help to organize and focus this complex literature. This chapter will discuss frameworks for considering the relationship between affect and the immune system and review the literature linking affective experience to indicators of immune status. Affective experience includes a number of categories of experience. Emotions are short, intensely felt, affective states that are associated with distinctive facial expressions and behavioral predispositions; emotions have evolved to coordinate response to specific eliciting conditions (e.g., fear in response to threat of attack) (Ekman, 1994; Levenson, 1992; Segerstrom et al., 2001). Moods are longer-term affective states that do not necessarily have a specific trigger, may involve a blend of different affective experiences, do not have unique facial expressions (Ekman, 1994), and often are accompanied by persistent and distinctive cognitions (e.g., negative thoughts about the self and the future with depressed mood; cynicism with hostility). Affective traits involve the dispositional tendency to experience specific emotions and moods across situations and over time. Affective disorders, such as major depressive disorder and generalized anxiety disorder, are pathological forms of affective experience that can interfere with daily life and may require intervention. Affect has been categorized in a variety of ways, for example, along the dimension of valence (positive and negative) and arousal (high or low). While there is a great deal of research on the link between depressive disorders and immune parameters (see Chapter 24, this volume), research on immune correlates of affective responses outside the context of a psychiatric illness is limited.
III. CAN THE IMMUNE SYSTEM PLAY A ROLE IN SUPPORTING THE ADAPTIVE BEHAVIORAL CHANGES ORCHESTRATED BY EMOTIONS? Currently, it is presumed by most investigators that all negative affective experiences would have the same peripheral physiological effects. However, there is increasing evidence that distinct emotions have different physiological correlates. For example, specific emotions are associated with distinct patterns of activation in the central nervous system (Canli et al., 2001;
Damasio et al., 2000; Lane et al., 1997) and in the autonomic nervous system (although the findings in this area are sometimes inconsistent) (Ekman et al., 1983; Herrald and Tomaka, 2002). Given these distinctions in neural systems, it is possible that peripheral physiological systems such as the immune system that are impacted by these neural systems could also respond with different patterns of activation depending on the affect experienced. In considering what physiological changes would be predicted to correlate with an affective response to a given context, it may be useful to consider what the adaptive psychological/behavioral and physiological responses to that context may be. Fleeing from a predator, grieving a loss, or demonstrating one’s social status require different kinds of psychological, physiological, and behavioral changes to respond adaptively to the situation (Weiner, 1992). Emotions may play a central role in orchestrating these coordinated psychobiological responses. For example, fear in response to a threat to survival is associated with specific behavioral and physiological changes that facilitate flight. It would be expected that these behavioral and physiological changes would differ from those associated with sadness, for example (Ekman, 1999; Levenson, 1994). There are at least three adaptive affective/motivational response patterns that become activated in response to specific eliciting conditions that may involve the immune system: the fight/flight response, the recuperative response, and the behavioral disengagement response (Kemeny, in press). The fight/flight response involves recognition of a threat that requires physical action and the mobilization of physiological resources to promote such activity, while at the same time downregulating other systems, for example, resource building or restorative systems, that are not central in the context of a threat (Sapolsky, 1993). This shift from resource building to resource utilization during a threat has been shown to activate the sympathetic nervous system (SNS), the hypothalamicpituitary-adrenal (HPA) axis, and other physiological systems. Immune changes that have been observed during fight/flight responses have mostly been conceived of as negative side effects of the adaptive activation of mobilization systems such as the SNS. However, Dhabhar and McEwen (2001) argue that some of these immune changes are actually an integrated part of the physiological response to such threats. Specifically, they argue that leukocytes are shunted from the bloodstream to immune organs in the context of this type of threat and that this redistribution is an integral part of the fight-flight response, preparing the animal for pos-
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sible wounding or infection as a result of activities related to fighting or fleeing (Dhabhar, 2003; Dhabhar and McEwen, 2001). In addition, “first line of defense” cells such as natural killer cells are increased in number in the bloodstream with these forms of acute threat, and a rapid increase in these first line of defense cells has been argued to allow for quick, non-specific killing of organisms that puncture the skin via wounds or other injuries (Kemeny and Gruenewald, 2000). This acute increase in NK cells is mediated by activation of the SNS; products of the SNS increase heart rate, cause this redistribution of white blood cells including NK cells, and modulate the expression of immune molecules that control trafficking (Ottaway and Husband, 1992). Fear, which is a central component of the fight/ flight response, plays an important role in coordinating the SNS activation that occurs with such a threat. These SNS changes then modulate the activity and distribution of immunologic cells, possibly in the service of promoting adaptation in the context of this particular type of threat. The immune system also supports another adaptive behavioral response called behavioral recuperation following infection or injury. Pro-inflammatory cytokines are proteins that are released during an infection or injury and play an important role in facilitating the destruction of the pathogen and tissue repair. These cytokines also act on the brain and cause “sickness behavior,” which includes an increase in sleep and a decrease in social, sexual, aggressive, exploratory, and other behaviors, and leads to a withdrawal from normal activities. Overall, these behavioral changes are an adaptive mechanism for supporting recuperation from injury or illness by lowering energy utilization so that energy-related systems can support the physiological response to infection (e.g., fever) and also facilitate other restorative processes (Maier and Watkins, 1998). Researchers have argued that disengagement-related affective responses, in particular depression, share a number of features with sickness behavior, as will be described below, and may be a central part of this response. Pro-inflammatory cytokines may play a role in other forms of behavioral disengagement as well. There are a variety of physiological changes that occur with goal disengagement in animals, such as increases in ACTH and cortisol, opioid-mediated analgesia, release of dopamine from the prefrontal cortex, and lowered cellular immune function (Fleshner et al., 1989; Miczek et al., 1982; Stefanski and Ben-Eliyahu, 1996). More recently, evidence suggests a link between goal disengagement and pro-inflammatory cytokine levels. It appears that elevated levels of these cytokines are more likely to be occur when the animal is confronted
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with a stressor that is uncontrollable—a context in which behavioral disengagement would be adaptive (Kemeny et al., 2006; Dickerson et al., 2004). For example, in an encounter with a dominant and aggressive male, cytokine-induced behavioral withdrawal and reduction in aggressive and social behavior would be adaptive because it would reduce the chances of attack. This link between behavioral disengagement and pro-inflammatory production has been demonstrated using a social reorganization model, which involves the introduction of a dominant animal into the home cage of other animals. The subordinate animals show glucocorticoid resistance (GCR), a condition in which the glucocorticoid receptor on immune cells is downregulated and the cells become unresponsive to glucocorticoids, resulting in unrestrained production of pro-inflammatory cytokines. The level of GCR is correlated with the frequency of submissive behavior (Avitsur et al., 2001). Also, animals injected with a pro-inflammatory cytokine display no offensive behavior in an aggressive encounter but only defensive elements, such as upright defensive posture and submissive posture, a pattern of behavior that is usually exhibited in uncontrollable contests with other animals in which they are likely to lose (Cirulli et al., 1998). Thus, increases in pro-inflammatory cytokines may be an adaptive response to an uncontrollable social status threat because an increase in these cytokines can induce or maintain behavioral disengagement, which would reduce the likelihood that the animal would provoke an attack by the dominant animal (Dickerson et al., 2004a). Also, the release of these molecules during such an encounter would promote wound healing, since subordinates are more likely to be wounded in such encounters. Acute social threats in humans have also been shown to increase levels of these cytokines (Ackerman et al., 1998; Dickerson et al., in press). Overall, uncontrollable social and other threats may be capable of increasing levels of pro-inflammatory cytokines and eliciting behavioral disengagement in animals and humans. These immunological changes may be orchestrated by the disengagement-related affective/motivational states that are elicited in these conditions (as described below).
IV. NEGATIVE AFFECTIVE STATES AND THE IMMUNE SYSTEM There is a growing literature linking negative affective states to various immune parameters. Stable individual differences in negative affect, called negative affectivity, have been studied in psychoneuroimmunology. Negative affectivity is strongly associated with
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the personality dimension of neuroticism (Watson and Clark, 1992). Negative affectivity and/or neuroticism has been associated with decrements in functional immune measures (Segerstrom, Kemency, and Laudenslager, 2001). More recently, task-based neurophysiological measures of negative affectivity have been used to understand the link between this construct and peripheral physiological systems. For example, using an EEG measure of cortical asymmetries, Davidson (1998) found that higher levels of right-prefrontal activation is associated with less positive and more negative affect and that individual differences in this pattern of asymmetry predict responses to negative emotion tasks. This pattern of cerebral activation has been associated with lower antibody titers after vaccination for influenza (Davidson et al., 2003). Greater relative right-sided prefrontal activation has also been found to be associated with lower natural killer cell activity (Davidson et al., 1999; Kang et al., 1991). These are important studies because they utilized non-self report measures of negative affect and suggest potential CNS mediators of the link between affect and peripheral physiological response patterns.
V. DEPRESSION AND THE IMMUNE SYSTEM The most commonly and carefully studied affective state in the field of PNI is depression. Studies have examined correlations between major depressive episodes and immune status as well the associations between immune processes and other forms of psychiatric depression and depressed mood. In addition, because depression has been associated with risk of mortality from cardiovascular disease (Glassman and Shapiro, 1998) as well as the onset and course of other illnesses and all cause mortality in some studies (Wulsin et al., 1999), the potential immunologic mediators of these effects are a new area of investigation. Major depression has been associated with a variety of functional and phenotypic immune alterations, in some cases mirroring the changes observed with exposure to major life events, such as bereavement (Irwin et al., 1986; Schleifer et al., 1984). Depression has been associated with reliable increases in immune subsets including neutrophils and decreases in B- and T-cells, as well as deficiencies in the proliferative response to mitogenic stimulation and natural killer cell activity, based on a meta-analytic review in this area (Herbert and Cohen, 1993). In some cases, these changes can resolve with psychiatric treatment (Irwin et al., 1992).
Depressed individuals most likely to show immune impairment are those who are older, with a more severe form of depression (for example, melancholia), and those who also have a sleep disorder or alcoholism (Irwin, 2001). See Chapter 24, this volume for a full discussion of immune correlates of depression. In addition to the function decrements described above, there is increasing evidence that depression is associated with increased levels and/or production of pro-inflammatory cytokines. Maes and his colleagues (1994) found that patients with depressive symptoms or those with a depression syndrome showed elevated levels of these cytokines, although the findings across studies have not always been consistent. Other researchers have demonstrated this pattern of inflammatory activity in patients with clinical depression compared to demographically matched controls, controlling for other medical conditions, medications, and health behaviors (Miller et al., 2002). Researchers have proposed the intriguing hypothesis that pro-inflammatory cytokines may play an etiologic role in depression (Dantzer et al., 2001; Yirmiya, 1996; Yirmiya et al., 1999). In addition to the findings linking depression with higher levels of these cytokines as described above, there are three other sources of evidence for this hypothesis. First, patients with inflammatory diseases often experience depressed affect, which could be due, in part, to the inflammatory cytokines that play a role in the pathophysiology of their condition. Second, individuals injected with these cytokines, as part of cancer treatment, for example, show psychological and behavioral changes that are similar to depression, such as dysphoria, anhedonia, fatigue, apathy, and helplessness, which disappear when treatment has ended. Third, animals injected with these cytokines show the behavioral changes called sickness behavior, including locomotor retardation; immobility; anorexia; sleep disorders; decreased sexual, social, and aggressive behavior; and anhedonia. It is interesting that the behavioral changes observed with sickness behavior bear a striking resemblance to the vegetative signs and symptoms of some forms of depression and, in many cases, are part of the diagnostic criteria for a clinical depression. Work is ongoing that attempts to link pro-inflammatory cytokines causally to depression in humans.
VI. ANXIETY AND THE IMMUNE SYSTEM Anxiety is a reaction to a real or perceived threat that can include fear and apprehension about current and future circumstances, and includes actions that relate to escape or avoidance of the threat. There is
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evidence that anxiety is associated with risk for cardiovascular endpoints, including morbidity and mortality, although the findings are not as strong as they are for depression (Kubzansky et al., 1998). There is as yet no clear pattern of association between immune system alterations and anxiety disorders. In one study of panic disorder (PD) patients, changes in anxiety levels from pre to post-intervention were associated with changes in proliferative responses to mitogens and IL-2 cytokine production (Koh and Lee, 2004), suggesting that anxiety may have mediated effects of the intervention on immune functions. However, overall, for each study that has shown an immune difference in PD versus controls, another study has failed to replicate the finding. In a carefully conducted study of a range of phenotypic and functional immune parameters in medication-free patients with PD compared to a carefully matched control group without psychiatric illness, there were no significant differences in proliferative response to different mitogens or NKCA and no differences in the numbers of most lymphocyte subsets (Schleifer et al., 2002). However, these studies are conducted in patients who are not undergoing a panic attack and do not provide evidence for or against the possibility of immune effects of the experience of panic during an actual episode. A variety of studies have correlated anxiety levels with immune parameters in individuals without a psychiatric disorder. Again, the studies do not present a cohesive picture of the relationship between anxiety and the immune system. In some studies, increased levels of anxiety are associated with a similar pattern of immune changes seen with exposure to an acute laboratory stressor. In other studies, the opposite pattern is observed. When individuals in an actively anxiety-producing naturalistic situation are studied, there is an increased likelihood of finding immune effects. For example, patients at their first visit to an outpatient clinic were asked about their anxiety about having cancer. Those reporting higher levels of anxiety about cancer had significantly lower levels of NKCA, which suggests that new and acute anxiety may have immunological correlates (Koga et al., 2001). In addition, some intervention studies that have demonstrated reductions in anxiety have also shown increases in functional measures of the immune system (Anderson et al., 2004). Worry can be differentiated from anxiety. Trait worriers are those who are more likely to anticipate and imagine potential future negative events. Individuals with trait worry (controlling for anxiety) have demonstrated distinct immune changes (e.g., fewer NK cells) in response to naturalistic stressors such as the after-
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math of an earthquake (Segerstrom et al., 1998) as well as immune alterations in response to acute laboratoryinduced stressors (Segerstrom et al., 1999).
VII. ANGER, HOSTILITY, AND THE IMMUNE SYSTEM The anger family of affective experience includes anger, hostility, and aggression (Spielberger et al., 1995). Anger is an emotion that often results from exposure to a situation that interferes with one’s goals, particularly if the interference is experienced as deliberate (Ekman, 2003). It can also be elicited from the perception that one has been treated unfairly; it is associated with the tendency toward aggressive behavior. Hostility has been considered both a mood state and an affective trait and often includes specific cognitions about others, in particular cynical mistrust. Both anger and hostility can lead to aggressive behavior, which involves the intention to harm. There is now an extensive literature suggesting that hostility is as an independent risk factor for coronary heart disease (Miller et al., 1996). Outcomes in these studies have included measures of blood pressure, atherosclerosis, coronary artery calcification, mortality, and other endpoints (Suinn, 2001). Anger, particularly trait anger, has also been linked to cardiovascular endpoints, such as the incidence of cardiac events, but the relationship has been studied less often (Kubzansky and Kawachi, 2000). Evidence is beginning to suggest that immune factors may play a role in these relationships (Murasko et al., 1988). For example, it is now recognized that inflammation can play a key role in plaque formation, and studies are beginning to provide the links between hostility, inflammatory processes, and cardiovascular disease. In a related literature, anger has been associated with greater cardiovascular reactivity, and cardiovascular reactivity has been related to declines in cellular immunity (Matthews et al., 1995). In an excellent model for understanding the relationship between acute real-world anger and the immune system, Kiecolt-Glaser and colleagues (1993) asked married couples to engage in a standardized marital interaction task which involved attempting to resolve a conflict in their marriage for 20 minutes. They found that hostility coded from verbal and nonverbal indicators during the conflict task predicted decreases in a number of functional immune parameters (NKCA, proliferative response to mitogen stimulation), and increases in antibody titers to latent viruses (an indicator of failure of immune control over this latent virus) over a 24-hour period.
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One intervention study suggests the possibility that anger experience may have some beneficial physiological effects. In a cognitive behavioral intervention in cancer patients, results indicated that those assigned to the intervention, compared to the control condition, showed a decrease in negative mood over a 6-month follow-up period as well as an increase in the percent of NK cells and an increase in the ability of the NK cell activity to be augmented with the addition of IFNα. In other words, the cells were more responsive to cytokine signals following the intervention (Fawzy et al., 1990). In addition, patients assigned to the intervention showed a greater disease-free interval and greater survival over a 6-year follow-up (Fawzy et al., 1993). With regards to psychological mediators of NK effects, the patients most likely to show increases in NK cell percent or function following the intervention were those who showed a decrease in depressed and anxious mood over the 6-month period and an increase in anger. Thus, it may be that interventions of this kind help those with difficulty acknowledging, experiencing, or expressing anger, and that changes in their response to their own anger experience are associated with physiological benefits.
et al., 2004; Dickerson and Kemeny, 2004; Dickerson et al., 2004b). Chronic or repeated exposure to social evaluative or rejecting contexts, a sensitivity to evaluation or rejection, or a vulnerability to experience shame might result in persistent activations of these systems with potential health consequences. In partial support of this hypothesis, rejection sensitivity around homosexuality predicted CD4 T-cell decline, time to the onset of AIDS, and mortality in a 9-year follow-up of HIV positive gay and bisexual men (Cole et al., 1997). Moreover, rejection sensitivity also predicted elevated levels of HIV viral load following antiretroviral treatment (Cole et al., 2003), controlling for demographic, behavioral, and medical confounds. Persistent HIV-related shame over a 1-year period predicted CD4 decline over 7 years in an HIV positive sample (Weitzman et al., 2005). Thus, shame, as a disengagement-related emotion, is related to a physiological system that supports disengagement and may also be associated with health effects when experienced persistently.
VIII. SELF-CONSCIOUS EMOTIONS AND THE IMMUNE SYSTEM
A growing but still limited literature suggests that positive affective states may also be associated with immune system changes (Pressman and Cohen, 2005). Older literature suggests that positive affect is associated with increases in secretory Immunoglobulin A (SIgA), an antibody found in the mucosal immune system (e.g., in saliva) (Hucklebridge et al., 2000; Lambert and Lambert, 1995; McClelland and Cheriff, 1997). These findings are difficult to interpret. In most cases, total salivary protein levels were not controlled for and increases in salivary rate could explain some of these findings (decreases in salivation are associated with anxiety). A much stronger approach involves the administration of an antigen and the examination of SIgA specific to that antigen. In two studies, daily positive affect was associated with elevated levels of SIgA to a specific antigen measured on a daily basis (Stone et al., 1987; Stone et al., 1994); one study did not find this association (Evans et al., 1993). Inducing positive affect has been associated with increases in the number of certain subsets of white blood cells, although the results are not entirely consistent. It is interesting that the direction of relationships is similar to that seen with exposure to an acute stressor (Segerstrom and Miller, 2004). Studies of immune function are rare in this area, but evidence thus far suggests that laboratory induction of
More recently, a set of studies has examined the physiological correlates of shame and other selfconscious emotions and the possible health consequences of persistent shame-related affective experience. Shame is a self-conscious emotion, like guilt and embarrassment, that is elicited in social evaluative or rejecting contexts, in response to appraisals of a loss of social esteem (evaluations of how others view the self), social status, or social acceptance (Dickerson et al., 2004a; Gruenewald et al., 2004). “Social Self Preservation Theory” argues that threats to one’s social self are associated with the experience of shame-related emotions and a coordinated set of behavioral and physiological responses that relate to the motivation to withdraw, appease, or submit (Dickerson et al., 2004a). A key component of the physiological response is an increase in pro-inflammatory cytokines. An increase in pro-inflammatory cytokines would support the behavioral disengagement that occurs in this context (as described above). In a number of studies of acute laboratory-induced social evaluative threat, increases in social evaluation and shame have been associated with increases in cortisol and/or pro-inflammatory cytokines (Gruenewald
IX. POSITIVE AFFECT AND THE IMMUNE SYSTEM
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positive affect may result in increases in lymphocyte proliferative response to mitogenic stimulation (Futterman et al., 1992). These effects were not mediated by changes in cortisol in response to the manipulation. Positive mood induction may also result in increased levels of certain cytokines (interleukin [IL]-2, IL-3) while resulting in decreases in others (i.e., interferon-γ and tumor necrosis factor-α (Mittwoch-Jaffe et al., 1995). However, some studies have found no correlates (Pressman and Cohen, 2005; Ryff et al., 2004). In studies of a whole ex vivo immune responses—type I hypersensitivity to an allergen—positive states of mind have been associated with reductions in response in some studies (Kimata, 2001; Laidlaw et al., 1996) but not in others (Zachariae et al., 2001). There is a consistent increase in the number of NK cells and often in NKCA in laboratory studies of stress induction (Segerstrom and Miller, 2004). It is interesting that induction of positive affect can also result in an increase in NK function. One study found such an increase in NKCA with both positive and negative affect induction; both appeared to be mediated by sympathetic nervous system arousal (Futterman et al., 1994). It is possible that changes in patterns of activation of the HPA, sympathetic nervous system, and/ or parasympathetic nervous system could mediate some of the associations found above. A number of studies have shown decreases in cortisol levels following positive mood induction or correlated with trait positive affect in naturalistic studies (Berk et al., 1989; Buchanan et al., 1999; Zachariae et al., 1991), and some of the immune parameters described above can be affected by the HPA (e.g., cytokine production). However, others have found increases in cortisol with induced positive affect, which may result from the arousal that is experienced (Pressman and Cohen, 2005). Positive affect induction has been shown to increase heart rate and blood pressure in a number of studies (Ekman et al., 1983; Futterman et al., 1994; Schwartz et al., 1981) particularly in tasks that involve active rather than passive involvement of participants (Pressman and Cohen, 2005). This pattern of changes is consistent with ANS effects of stress or negative affect manipulations. However, in studies that attempted to test for endocrine or autonomic mediation of the relationship between positive affect and the immune system, the results are mixed. For example, in the study comparing positive and negative affect induction, cellular proliferation indices were reduced with positive affect, but cortisol levels and SNS arousal were increased (Futterman et al., 1994).
X. DIFFERENTIAL IMMUNE CORRELATES OF AFFECTIVE STATES Very few studies have directly tested the premise that different affective states may have different immunological effects. There is, however, some evidence that induced positive and negative affect result in different acute immunological changes. Futterman and colleagues (1994) found an increase in NKCA with both positive and negative affect induction over a 25minute period. However, positive affect was associated with an increase in the proliferative response to mitogens, while negative affect was associated with a decrease in this immune function. These data are consistent with a larger literature indicating that the number of NK cells and, in some cases, their activity increase in response to a wide variety of emotionally evocative stimuli. However, these data suggest that proliferative capacity may depend on the valence of the emotions experienced. Also, studies of daily mood ratings and measures of antigen-specific IgA antibody response have shown increases in this antibody response with positive affect and decreases with negative (Stone et al., 1987). There is initial evidence of different immune correlates of bereavement exposure depending on whether an individual responds with depression and/or grief (Irwin et al., 1987; Kemeny et al., 1995; Kemeny et al., 1994). And, in one study designed to induce shame and guilt by asking individuals to write about a situation in which they blamed themselves on three different days in one week or to write about a neutral topic, the self-blame condition elicited increases in TNF-α receptor levels in oral mucosal transudate—a marker of pro-inflammatory cytokine activity—and the increases were correlated with increases in shame but not guilt (or other negative emotions) (Dickerson et al., 2004b).
XI. SUMMARY Evidence suggests that immune system changes are associated with affective states, including depression, anxiety, anger/hostility, shame, and positive affect. As yet, studies have not been able to determine whether the nature of the changes depend on the nature of the affective experience or are a function, for example, of the arousal that occurs across many forms of emotional experience. There is also not sufficient evidence to support the hypothesis that adaptive immunologic changes occur in the context of certain emotional/ motivational states, namely the fight/flight response, the recuperative responses, and the behavioral disen-
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gagement response. While initial evidence suggests adaptive trafficking effects of white blood cells with fight/flight responses and increases in the production of pro-inflammatory cytokines with disengagement responses, this area requires further study to fully test these hypotheses.
XII. FUTURE DIRECTIONS Research on emotion and the immune system to date has suffered from significant limitations that hinder development in this important area. For example, many studies have relied on self-report of emotion and mood. Self-reports suffer from a number of methodological problems. Most such scales require individuals to describe their emotional response over an extended time period, e.g., level of sadness over the past week on a scale from 1 to 7. It is unclear how individuals do this and what cognitive processes are utilized to make this determination. Do people rely on their current state of mind or try to count up the number of sad episodes over the time frame? Kahneman and colleagues (Kahneman and Riis, 2005) argue that there are three “selves” that can be tapped by a given measurement tool: the experiencing self, the evaluative self, and the anticipating self. Self-reports of mood capture the evaluative self—i.e., how we evaluate our experience and summarize it—but do not capture the experiencing self—what we actually experience at a given moment in time. And there are a number of biases that have been demonstrated when individuals attempt to evaluate their subjective states over a period of time. For example, after a medical procedure, pain ratings of the procedure reflect the most recent level of pain experienced and the most intense pain experienced during the procedure but do not capture duration and other dynamics. This pattern has been called the “peak end theory” of bias in reports of emotional experience (Kahneman et al., 1993). Thus, it may be very difficult to link changes in self-reported affect and changes in physiological parameters when the affect reports do not capture the actual affect experienced over the time frame of interest. To capture something closer to the actual emotional experience over a given period, all moments in a given episode would be assessed. The closest approximation to this approach is experience sampling, where online assessments of emotion are captured at specific moments throughout the day, with various collection methods like diaries or PDAs. There are a few studies in the emotion and immunity literature that utilize this technique; rather, the vast majority use scales that require evaluation and summarization and do not
adequately represent the emotional experience. This limitation may explain some of the difficulty investigators have found in correlating changes in affective state with changes in peripheral physiological indicators. Second, there are individual difference factors that complicate these self-report affect assessments. For example, many people are not psychologically minded and do not differentiate their feelings in the way questionnaires require. Some individuals have rarely reflected on what they are feeling and may not be able to make the emotional distinctions required in a mood measure. Emotion reporting is confounded by emotional styles; e.g., those with a repressive style will under-report their emotional experience in contrast to those with a sensitizer style. Other biases, such as the motive to respond in a socially desirable way or to please the investigator, complicate self-reports in this area. There are now a number of alternatives to selfreports that may increase the chances of detecting relationships between emotion and immune parameters. Tools used in other fields of psychology, for example, cognitive psychology and affective neuroscience, are beginning to be employed by investigators interested in predicting patterns of peripheral physiological responding. Examples of more behavioral measures of emotional responding include emotion-induction techniques such as emotion films or other tasks that generate emotion and involve ratings of facial expressions of emotion, tasks that prime emotion, implicit measures that capture “non-conscious” emotional experience, and startle eye blink tasks to measure anxiety-related experience. Despite the fact that human research in PNI began to flourish in the 1980s, it is difficult to paint a coherent picture of the primary psychological processes that can affect the immune system, outside the work on depression and “stress.” Studies of affective experience, including affective pathologies, individual differences in affectivity, and emotional responses, could play a critical role in bringing clarity to this important area. Such research could help to link other important psychological factors such as personality, coping processes, social context, and appraisals to peripheral physiological responses, including the immune system.
References Ackerman, K. D., Martino, M., Heyman, R., Moyna, N. M., and Rabin, B. S. (1998). Stressor-induced alteration of cytokine production in multiple sclerosis patients and controls. Psychosomatic Medicine, 60, 484–491.
29. Emotions and the Immune System Anderson, N. B., Kaplan, R. M., Kumanyika, S., Salovey, P., Kawachi, I., Dunbar-Jacob, J., and Kemeny, M. E. (2004). Encyclopedia of health and behavior. Thousand Oaks, CA: Sage Publications. Avitsur, R., Stark, J. L., and Sheridan, J. F. (2001). Social stress induces glucocorticoid resistance in subordinate animals. Hormones and Behavior, 39, 247–257. Berk, L. S., Tan, S. A., Fry, W. F., Napier, B. J., Lee, J. W., Hubbard, R. W., Lewis, J. E., and Eby, W. C. (1989). Neuroendocrine and stress hormone changes during mirthful laughter. American Journal of the Medical Sciences, 298, 390–396. Buchanan, T. W., al’Absi, M., and Lovallo, W. R. (1999). Cortisol fluctuates with increases and decreases in negative affect. Psychoneuroendocrinology, 24, 227–241. Canli, T., Zhao, Z., Desmond, J. E., Kang, E., Gross, J., and Gabrieli, J. D. (2001). An fMRI study of personality influences on brain reactivity to emotional stimuli. Behavioral Neuroscience, 115, 33–42. Cirulli, F., De Acetis, L., and Alleva, E. (1998). Behavioral effects of peripheral interleukin-1 administration in adult CD-1 mice: specific inhibition of the offensive components of intermale agonistic behavior. Brain Res, 791, 308–312. Cole, S. W., Kemeny, M. E., Fahey, J. L., Zack, J. A., and Naliboff, B. D. (2003). Psychological risk factors for HIV pathogenesis: mediation by the autonomic nervous system. Biological Psychiatry, 54, 1444–1456. Cole, S. W., Kemeny, M. E., and Taylor, S. E. (1997). Social identity and physical health: accelerated HIV progression in rejectionsensitive gay men. Journal of Personality and Social Psychology, 72, 320–335. Damasio, A. R., Grabowski, T. J., Bechara, A., Damasio, H., Ponto, L. L., Parvizi, J., and Hichwa, R. D. (2000). Subcortical and cortical brain activity during the feeling of self-generated emotions. Nature Neuroscience, 3, 1049–1056. Dantzer, R., Bluthe, R., Castanon, N., Cauvet, N., Capuron, L., Goodall, G., Kelley, K. W., Konsman, J., Laye, S., Parnet, P., and Pousset, F. (2001). Cytokine effects on behavior. In R. Ader, D. L. Felten, and N. Cohen (Eds.), Psychoneuroimmunology (vol. 1, pp. 703–727). New York: Academic Press. Davidson, R. I. (1998). Affective style and affective disorders: perspectives from affective neuroscience. Cognition and Emotion, 12, 307–330. Davidson, R. J., Coe, C. C., Dolski, I., and Donzella, B. (1999). Individual differences in prefrontal activation asymmetry predict natural killer cell activity at rest and in response to challenge. Brain, Behavior, and Immunity, 13, 93–108. Davidson, R. J., Kabat-Zinn, J., Schumacher, J., Rosenkranz, M., Muller, D., Santorelli, S. F., Urbanowski, F., Harrington, A., Bonus, K., and Sheridan, J. F. (2003). Alterations in brain and immune function produced by mindfulness meditation. Psychosomatic Medicine, 65, 564–570. Dhabhar, F. S. (2003). Stress, leukocyte trafficking, and the augmentation of skin immune function. Ann N Y Acad Sci, 992, 205–217. Dhabhar, F. S., and McEwen, B. S. (2001). Bidirectional effects of stress and glucocorticoid hormones on immune function: possible explanations for paradoxical observations. In R. Ader, D. L. Felten, and N. Cohen (Eds.), Psychoneuroimmunology (vol. 1, pp. 301–338). New York: Academic Press. Dickerson, S. S., Gruenewald, T. L., and Kemeny, M. E. (2004a). When the social self is threatened: shame, physiology, and health. Journal of Personality, 72, 1191–1216. Dickerson, S. S., and Kemeny, M. E. (2004). Acute stressors and cortisol responses: a theoretical integration and synthesis of laboratory research. Psychological Bulletin, 130, 355–391.
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Dickerson, S. S., Kemeny, M. E., Aziz, N., Kim, K. H., and Fahey, J. L. (2004b). Immunological effects of induced shame and guilt. Psychosomatic Medicine, 66, 124–131. Ekman, P. (1994). Moods, emotions, and traits. In R. I. Davidson, P. Ekrnan, and K. Scherer (Eds.), The nature of emotion: fundamental questions (pp. 56–58). New York: Oxford University Press. Ekman, P. (1999). Basic emotions. In T. Dalgleish and M. Powers (Eds.), Handbook of cognition and emotion. (pp. 45–60) Sussex, U.K.: John Wiley and Sons, Ltd. Ekman, P. (2003). Emotions revealed: recognizing faces and feelings to improve communications and emotional life. New York: Henry Holt and Company. Ekman, P., Levenson, R. W., and Friesen, W. V. (1983). Autonomic nervous system activity distinguishes among emotions. Science, 221, 1208–1210. Evans, P., Bristow, M., Hucklebridge, F., Clow, A., and Walters, N. (1993). The relationship between secretory immunity, mood and life-events. British Journal of Clinical Psychology, 32, 227–236. Fawzy, F. I., Fawzy, N. W., Hyun, C. S., Elashoff, R., Guthrie, D., Fahey, J. L., and Morton, D. L. (1993). Malignant melanoma. Effects of an early structured psychiatric intervention, coping, and affective state on recurrence and survival 6 years later. Archives of General Psychiatry, 50, 681–689. Fawzy, F. I., Kemeny, M. E., Fawzy, N. W., Elashoff, R., Morton, D., Cousins, N., and Fahey, J. L. (1990). A structured psychiatric intervention for cancer patients: II. Changes over time in immunological measures. Archives of General Psychiatry, 47, 729–735. Fleshner, M., Laudenslager, M. L., Simons, L., and Maier, S. F. (1989). Reduced serum antibodies associated with social defeat in rats. Physiol Behav, 45, 1183–1187. Futterman, A. D., Kemeny, M. E., Shapiro, D., and Fahey, J. L. (1994). Immunological and physiological changes associated with induced positive and negative mood. Psychosomatic Medicine, 56, 499–511. Futterman, A. D., Kemeny, M. E., Shapiro, D., Polonsky, W., and Fahey, J. L. (1992). Immunological variability associated with experimentally-induced positive and negative affective states. Psychol Med, 22, 231–238. Glassman, A. H., and Shapiro, P. A. (1998). Depression and the course of coronary artery disease. Am J Psychiatry, 155, 4–11. Gruenewald, T. L., Kemeny, M. E., Aziz, N., and Fahey, J. L. (2004). Acute threat to the social self: shame, social self-esteem and cortisol activity. Psychosomatic Medicine, 66, 915–924. Herbert, T. B., and Cohen, S. (1993). Depression and immunity: a meta-analytic review. Psychological Bulletin, 113, 472–486. Herrald, M. M., and Tomaka, J. (2002). Patterns of emotion-specific appraisal, coping, and cardiovascular reactivity during an ongoing emotional episode. J Pers Soc Psychol, 83, 434–450. Hucklebridge, F., Lambert, S., Clow, A., Warburton, D. M., Evans, P. D., and Sherwood, N. (2000). Modulation of secretory Immunoglobulin A in saliva; response to manipulation of mood. Biological Psychology, 53, 25–35. Irwin, M. (2001). Depression and immunity. In R. Ader, D. L. Felten, and N. Cohen (Eds.), Psychoneuroimmunology (vol. 2, pp. 383– 398). New York: Academic Press. Irwin, M., Daniels, M., Bloom, E., Smith, T. L., and Weiner, H. (1987). Life events, depressive symptoms, and immune function. American Journal of Psychiatry, 144, 437. Irwin, M., Daniels, M., Bloom, E. T., and Weiner, H. (1986). Life events, depression, and natural killer cell activity. Psychopharmacol Bull, 22, 1093–1096. Irwin, M. R., Lacher, U., and Caldwell, C. (1992). Depression and reduced natural killer cytotoxicity: a longitudinal study of
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III. Behavior and Immunity
depressed patients and control subjects. Psychological Medicine, 22, 1045–1050. Kahneman, D., Fredrickson, B. L., Schreiber, C. A., and Redelmeier, D. A. (1993). When more pain is preferred to less: adding a better end. Psychological Science, 4, 401–405. Kahneman, D. (2000). Experienced utility and objective happiness: A moment-based approach. In D. K. A. Tversky (Ed.), Choices, Values, and Frames (pp. 673–692). Cambridge: Cambridge University Press. Kang, D. H., Davidson, R. I., Coe, C. L., Wheeler, R. W., Tomarken, A. J., and Ershler, W. B. (1991). Frontal brain asymmetry and immune function. Behavioral Neuroscience, 105, 860–869. Kemeny, M. E. (in press). Psychoneuroimmunology. In H. Friedman and R. Silver (Eds.), Foundations of Health Psychology. New York: Oxford University Press. Kemeny, M. E., and Gruenewald, T. L. (2000). Affect, cognition, the immune system and health. In E. A. Mayer and C. B. Saper (Eds.), The biological basis for mind body interactions (vol. 122, pp. 291–308). New York: Elsevier Science. Kemeny, M. E., Gruenewald, T. L., and Dickerson, S. S. (2006). Social-self preservation system: The interface of social threats, self-evaluation, and health. Manuscript in preparation. Kemeny, M. E., and Laudenslager, M. (1999). Beyond stress: The role of individual differences factors in psychoneuroimmunologic relationships. Brain, Behavior, and Immunity, 13, 73–75. Kemeny, M. E., Weiner, H., Duran, R., Taylor, S. E., Visscher, B., and Fahey, J. L. (1995). Immune system changes after the death of a partner in HIV-positive gay men. Psychosomatic Medicine, 57, 547–554. Kemeny, M. E., Weiner, H., Taylor, S. E., Schneider, S., Visscher, B., and Fahey, J. L. (1994). Repeated bereavement, depressed mood, and immune parameters in HIV seropositive and seronegative gay men. Health Psychol, 13, 14–24. Kiecolt-Glaser, J. K., Malarkey, W. B., Chee, M., Newton, T., Cacioppo, J. T., Mao, H. Y., and Glaser, R. (1993). Negative behavior during marital conflict is associated with immunological down-regulation. Psychosomatic Medicine, 55, 410–412. Kimata, H. (2001). Effect of humor on allergen-induced wheal reactions. Journal of the American Medical Association, 285, 738. Koga, C., Itoh, K., Aoki, M., Suefuji, Y., Yoshida, M., Asosina, S., Esaki, K., and Kameyama, T. (2001). Anxiety and pain suppress the natural killer cell activity in oral surgery outpatients. Oral Surg Oral Med Oral Pathol Oral Radiol Endod, 91, 654–658. Koh, K. B., and Lee, Y. (2004). Reduced anxiety level by therapeutic interventions and cell-mediated immunity in panic disorder patients. Psychother Psychosom, 73, 286–292. Kubzansky, L. D., and Kawachi, I. (2000). Going to the heart of the matter: do negative emotions cause coronary heart disease? J Psychosom Res, 48, 323–337. Kubzansky, L. D., Kawachi, I., Weiss, S. T., and Sparrow, D. (1998). Anxiety and coronary heart disease: a synthesis of epidemiological, psychological, and experimental evidence. Ann Behav Med, 20, 47–58. Laidlaw, T. M., Booth, R. J., and Large, R. G. (1996). Reduction in skin reactions to histamine after a hypnotic procedure. Psychosomatic Medicine, 58, 242–248. Lambert, R. B., and Lambert, N. K. (1995). The effects of humor on secretory Immunoglobulin A levels in school-aged children. Pediatric Nursing, 21, 16–19. Lane, R. D., Reiman, E. M., Ahern, G. L., Schwartz, G. E., and Davidson, R. J. (1997). Neuroanatomical correlates of happiness, sadness, and disgust. American Journal of Psychiatry, 154, 926–933.
Lazarus, R. S., and Folkman, S. (1984). Stress, appraisal, and coping. New York: Springer Publishing Company. Levenson, R. W. (1992). Autonomic nervous system differences among emotions. Psychological Science, 3, 23–27. Levenson, R. W. (1994). The search for autonomic specificity. In P. Ekman and R. Davidson (Eds.), The nature of emotion: fundamental questions (pp. 252–257). New York: Oxford University Press. Maes, M., Scharpe, S., Meltzer, H. Y., Okayli, G., Bosmans, E., D’Hondt, P., Bossche, B. V., and Cosyns, P. (1994). Increased neopterin and interferon-gamma secretion and lower availability of L-tryptophan in major depression: further evidence for an immune response. Psychiatry Research, 54, 143–160. Maier, S. F., and Watkins, L. R. (1998). Cytokines for psychologists: Implications of bidirectional immune-to-brain communication for understanding behavior, mood, and cognition. Psychological Review, 105, 83–107. Matthews, K. A., Caggiula, A. R., McAllister, C. G., Berga, S. L., Owens, J. F., Flory, J. D., and Miller, A. L. (1995). Sympathetic reactivity to acute stress and immune response in women. Psychosomatic Medicine, 57, 564–571. McClelland, D. C., and Cheriff, A. D. (1997). The immunoenhancing effects of humor on secretory IgA and resistance to respiratory infections. Psychology & Health, 12, 329–344. Miczek, K. A., Thompson, M. L., and Shuster, L. (1982). Opioid-like analgesia in defeated mice. Science, 215, 1520–1522. Miller, G. E., Stetler, C. A., Carney, R. M., Freedland, K. E., and Banks, W. A. (2002). Clinical depression and inflammatory risk markers for coronary heart disease. American Journal of Cardiology, 90, 1279–1283. Miller, T. Q., Smith, T. W., Turner, C. W., Guijarro, M. L., and Hallet, A. J. (1996). A meta-analytic review of research on hostility and physical health. Psychol Bull, 119, 322–348. Mittwoch-Jaffe, T., Shalit, F., Srendi, B., and Yehuda, S. (1995). Modification of cytokine secretion following mild emotional stimuli. Neuroreport, 6, 789–792. Murasko, D., Weiner, P., and Kaye, D. (1988). Association of lack of mitogen-induced lymphocyte proliferation with increased mortality in the elderly. Aging: Immunology and Infectious Disease, 1, 1–6. Ottaway, C. A., and Husband, A. J. (1992). Central nervous system influences on lymphocyte migration. Brain, Behavior, and Immunity, 6, 97–116. Pressman, S. D. and Cohen, S. (2005). Does Positive Affect Influence Health? Psychological Bulletin, 131(6), 925–971. Ryff, C. D., Singer, B. H., and Dienberg Love, G. (2004). Positive health: Connecting well-being with biology. Philosophical transactions of the Royal Society of London. Series B, Biological Sciences, 359, 1383–1394. Sapolsky, R. M. (1993). Endocrinology alfresco: psychoendocrine studies of wild baboons. Recent Progress in Hormone Research, 48, 437–468. Schleifer, S. J., Keller, S. E., and Bartlett, J. A. (2002). Panic disorder and immunity: few effects on circulating lymphocytes, mitogen response, and NK cell activity. Brain Behav Immun, 16, 698–705. Schleifer, S. J., Keller, S. E., Meyerson, A. T., Raskin, M. J., Davis, K. L., and Stein, M. (1984). Lymphocyte function in major depressive disorder. Archives of General Psychiatry, 41, 484. Schwartz, G. E., Weinberger, D. A., and Singer, J. A. (1981). Cardiovascular differentiation of happiness, sadness, anger, and fear following imagery and exercise. Psychosomatic Medicine, 43, 343–364. Segerstrom, S. C., Glover, D. A., Craske, M. G., and Fahey, J. L. (1999). Worry affects the immune response to phobic fear. Brain, Behavior, and Immunity, 13, 80–92.
29. Emotions and the Immune System Segerstrom, S. C., Kemeny, M. E., and Laudenslager, M. (2001). Individual difference in psychoneuroimmunology. In R. Ader, D. L. Felten, and N. Cohen (Eds.), Psychoneuroimmunology (vol. 2, pp. 87–109). New York: Academic Press. Segerstrom, S. C., and Miller, G. E. (2004). Psychological stress and the human immune system: a meta-analytic study of, 30 years of inquiry. Psychological Bulletin, 130, 601–630. Segerstrom, S. C., Solomon, G. F., Kemeny, M. E., and Fahey, J. L. (1998). Relationship of worry to immune sequelae of the Northridge earthquake. J Behav Med, 21, 433–450. Spielberger, C. D., Reheiser, E. C., and Sydeman, S. J. (1995). Measuring the experience, expression, and control of anger. Issues Compr Pediatr Nurs, 18, 207–232. Stefanski, V., and Ben-Eliyahu, S. (1996). Social confrontation and tumor metastasis in rats: defeat and beta-adrenergic mechanisms. Physiology and Behavior, 60, 277–282. Stone, A. A., Cox, D. S., Valdlmarsdottir, H., Jandorf, L., and Neale, J. M. (1987). Evidence that secretory IgA antibody is associated with daily mood. Journal of Personality and Social Psychology, 52, 988–993. Stone, A. A., Neale, J. M., Cox, D. S., Napoli, A., Valdimarsdottir, H., and Kennedy-Moore, E. (1994). Daily events are associated with a secretory immune response to an oral antigen in men. Health Psychol, 13, 440–446. Suinn, R. M. (2001). The terrible twos—anger and anxiety. Hazardous to your health. Am Psychol, 56, 27–36. Watson, D. and Clark, L. A. (1992). On traits and temperament: General and specific factors of emotional experience and their
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relation to the five-factor model. Journal of Personality, 60(2), 441–476. Weiner, H. (1992). Perturbing the organism: the biology of stressful experiences. Chicago: The University of Chicago Press. Weitzman, O., Kemeny, M. E., and Fahey, J. L. (2005). HIV-related shame and guilt predict CD4 decline. Manuscript submitted for publication. Wulsin, L. R., Vaillant, G. E., and Wells, V. E. (1999). A systematic review of the mortality of depression. Psychosomatic Medicine, 61, 6–17. Yirmiya, R. (1996). Endotoxin produces a depressive-like episode in rats. Brain Research, 711, 163–174. Yirmiya, R., Weidenfeld, J., Pollak, U., Morag, M., Morag, A., and Avitsur, R., et al. (1999). Cytokines, “depression due to a general medical condition,” and antidepressant drugs. In R. Dantzer, E. Wollman, and R. Yirmiya (Eds.), Cytokines, stress and depression (pp. 283–316). New York: Kluwer Academic. Zachariae, R., Bjerring, P., Zachariae, C., Arendt-Nielsen, L., Nielsen, T., Eldrup, E., Larsen, C. S., and Gotliebsen, K. (1991). Monocyte chemotactic activity in sera after hypnotically induced emotional states. Scandinavian Journal of Immunology, 34, 71–79. Zachariae, R., Jorgensen, M. M., Egekvist, H., and Bjerring, P. (2001). Skin reactions to histamine of healthy subjects after hypnotically induced emotions of sadness, anger, and happiness. Allergy, 56, 734–740.
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C H A P T E R
30 Behaviorally Conditioned Enhancement of Immune Responses GUSTAVO PACHECO-LÓPEZ, MAJ-BRITT NIEMI, HARALD ENGLER, AND MANFRED SCHEDLOWSKI
I. INTRODUCTION WITH A HISTORICAL OVERVIEW 631 II. THE PHENOMENON OF BEHAVIORALLY CONDITIONED ENHANCEMENT OF IMMUNE RESPONSES 636 III. CLINICAL AND ADAPTIVE RELEVANCE OF CONDITIONED IMMUNE ENHANCEMENT 652 IV. SUMMARY 654
is beginning to emerge, with potential clinical applications.
I. INTRODUCTION WITH A HISTORICAL OVERVIEW Ambulatory organisms evolved to face a rapidly changing environment, thus acquiring the ability to learn. Most learning situations comprise one or more initially neutral stimuli (later becoming the conditioned stimulus, CS), the animal’s responses (behavioral and others), and a biologically significant stimulus (unconditioned stimulus, US). Classical or Pavlovian conditioning is often described as the transfer of the response-eliciting property of a biologically significant stimulus (US) to another stimulus (CS) without that property (Carew and Sahley, 1986; Domjan, 2005; Fanselow and Poulos, 2005; Hawkins et al., 1983; Pavlov, 1927). This transfer is thought to occur only if the CS serves as a predictor of the US (Pearce, 1987; Rescorla, 1988; Rescorla and Wagner, 1972). Thus, classical conditioning can be understood as learning about the temporal or causal relationships between external and internal stimuli to allow for the appropriate preparatory set of responses before biologically significant events occur. Much progress has been made in eluci-
ABSTRACT Classical conditioning can be understood as learning about the temporal or causal relationships between external and internal stimuli to allow for the appropriate preparatory set of responses before biologically significant events occur. In this regard, the capacity to associate a certain immune response or status (e.g., allergens, toxins, antigens) with a specific stimulus (e.g., environments or flavors) is of high adaptive value; we consider that it was acquired during evolution as an adaptive strategy in order to protect the organism and/or prepare it for danger. In this chapter current data are reviewed and summarized to indicate that both innate and adaptive immune responses can be enhanced by behavioral conditioning protocols. An understanding of the effects of behavioral conditioning on immune functions PSYCHONEUROIMMUNOLOGY, 4E VOLUME I
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dating the neuronal and molecular events that take place during association and consolidation of the memory trace in classical conditioning paradigms (Berman and Dudai, 2001; Bermúdez-Rattoni, 2004; Glanzman, 1995; Kandel et al., 1983; Menzel and Muller, 1996; Tully et al., 1990).
A. Definition of Behavioral Immunoconditioning An immunomodulatory stimulus (e.g., antigen, immunostimulating, or immunosuppressive drug) is used as a US and paired with a neutral stimulus. After this phase, the neutral stimulus becomes a conditioned stimulus (CS), which modifies the immune response (conditioned response, CR), as the US did before conditioning. The influences of behavioral conditioning on immune responses have been reviewed several times before (Ader and Cohen, 1991; Ader and Cohen, 2001; Brittain and Wiener, 1985; Hucklebridge, 2002; Markovic et al., 1993). In this chapter we will focus on conditioning protocols eliciting an enhancement of immune responses.
B. Associative Learning Rules Two basic steps compose any conditioning protocol: an association phase in which one or more CS-US pairings occur inducing an associative learning process, and a recall phase in which the memory of such an association is retrieved after exposure to the CS. In order to successfully acquire a typical Pavlovian CR (e.g., salivation, eye blink, nictitating membrane, freezing behavior), many CS-US pairings or trials are necessary, occurring in a contingent manner, with a fixed order (forward association: CS precedes US), and with a short inter-stimuli interval (seconds or even shorter intervals). Typically, a backward association scheme where the US precedes the CS will not induce an associative learning process. The features of CS-US timing and predictability affecting classical conditioning have been reviewed elsewhere (Rescorla, 1988). Regarding the CS, it is important to mention that features such as novelty, intensity, duration, and naturalistic relation to the US may explain the feasibility of associating the CS with the US, and the stability and strength of such an association. The rest interval between association and recall is another key factor explaining the CR magnitude: Typically, the longer the rest interval, the weaker the CR (passive forgetting). Moreover, extinction of the CR is a classical feature of behavioral conditioning. This phenomenon occurs at recall time if the CS is repeatedly presented without the US (active forgetting), reducing the CR magnitude, and finally extin-
guishing it. Pre-exposure to the CS before the association phase usually induces a reduction in the CR, which is called latent inhibition. Additionally, it is important to mention that the CR and the response elicited by the US (unconditioned response, UR) are not necessarily of a similar magnitude nor of the same direction, and the kinetics of each response may also differ (Rescorla, 1988).
C. Experimental Design in Immunoconditioning When I. P. Pavlov (1849–1936) studied the conditioned salivary response in dogs, it was sufficient to note that before conditioning a dog would not salivate after the sound of a bell, but that after conditioning the dog would do so. All that was needed as a control was this before-after comparison with another dog not exposed to the conditioning protocol. The emphasis was on observing conditioning in the individual animal, and it was noted that some animals conditioned better than others (Pavlov, 1927). Dealing with immune functions involves further challenges for the researcher attempting to demonstrate a behaviorally conditioned immune response. The immune system itself shows “memory” to be independent of neural activity. This means that the experimenter not only has to control for psychological sensitization and habituation, but also for immune memory and tolerance. In addition, immunoconditioning protocols involving taste/odor-visceral associative learning may require more consideration than standard conditioning protocols. The fact that flavor trace memory lasts for a number of hours should be taken into account in the experimental design of immunoconditioning protocols as well as in the analysis of the results (Garcia et al., 1966; Schafe et al., 1995). Considering all these particularities with regard to the behavioral conditioning of immune functions, R. Ader and N. Cohen provided the following guidelines for the experimental design of such protocols (Ader, 2003; Ader and Cohen, 2001): • Conditioned group: The primary experimental group
that is conditioned by pairing CS and US, and at recall time is exposed to the CS. • Conditioned not evoked group: At association time this group is treated identically to the conditioned group, but not exposed to the CS at recall phase. This group serves as a control for any direct or indirect immunomodulating effects of the association procedure per se, as well as for possible residual effects of the US at recall phase upon re-exposure to the CS.
30. Conditioned Immune Enhancement • Unconditioned response group: At association time
this group is exposed to the US and CS at the same times as the conditioned group. At recall time it should be exposed to the US in the absence of the CS. This control group defines the magnitude and direction of the UR. • Latent inhibition group: In order to assure an associative learning process, this group is pre-exposed to the CS at least once before being submitted to the same association and recall regimen as the conditioned group, since pre-exposure to the CS before the association phase usually induces a reduction in the CR. • Non-conditioned but evoked group: At association time this group is exposed to the CS and US as many times as the conditioned group, but in a non-contingent manner. At recall time, the subjects in this group are exposed to the CS. This group is mainly intended to control for non-associative factors, and also certifies the immunological neutrality of the CS during association and recall phases as well. • Placebo group: In the association and recall phases this group is exposed to the CS, which is paired with an immunological neutral stimulus (e.g., sterile saline or phosphate-buffered saline) as a placebo. This group controls for residual effects of the CS and possible artifacts due to the procedure (e.g., handling, injection, etc.). It should be noted that there may be experimental situations in which it is not possible to include certain control conditions, in particular in human studies. However, we recommend that future studies on immunoconditioning include all necessary control groups, since omissions will be detrimental to the interpretation and validation of the resulting data.
D. Theoretical Framework for Behavioral Immunoconditioning Before the existing data about conditioned enhancement of immune responses can be analyzed in detail, it is important to draw up some guidelines for the general mechanisms underlying behavioral immunoconditioning (summarized in Figure 1). Part of this conceptualization has already been elaborated (Bovbjerg, 2003; Eikelboom and Stewart, 1982). According to this theory, in the terminology of behavioral conditioning, both the CS (i.e., changes in the external environment) and the US (i.e., changes in the internal environment) must be inputs to the central nervous system (CNS), which in turn processes and associates
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this information. Thus, at association time only a change in the immune system that is sensed by the CNS can serve as a US. Furthermore, both the CR and the UR must be outputs of the CNS. Thus, only an immune parameter that can be modulated by the CNS can serve as a UR for conditioning, and at recall time the CR will resemble such a UR. Association: There are two possible unconditioned stimuli employed to acquire a behaviorally conditioned immune response. The US that is directly detected by the CNS is defined as a genuine US, whereas the one that needs one or more intermediary molecules, released by another system, in order to be detected by the CNS, is called a sham US. For any US, genuine or sham, there are two possible afferent pathways to the CNS: (a) a neural afferent pathway and (b) a humoral afferent pathway. The neural afferent pathway may detect the US and translate this information into neural activity. This sensory process implies the CNS’s interoceptive capacities including immunoception (Blalock, 2005; Goehler et al., 2000). Theoretically, this afferent pathway may also be able to codify the location of stimulation (local vs. systemic). The humoral afferent pathway is required for any US that is not detected locally or for the molecules induced by sham US that reach the CNS via blood stream. If a sham US has effects on several cell types, it is reasonable to assume that several molecules are candidates for the genuine US perceived by the CNS. Figure 1 indicates that for the sham US the pathway to the CNS is complex and longer than for the genuine US. In this regard, we hypothesize that it takes longer for the CNS to detect the sham US after administration. This feature can be employed in the experimental design to elucidate the nature of the US. For instance, backward conditioning should not be possible in the case of the genuine US, whereas the sham US could induce a CR under such conditions. For those sham USs that affect immune functions, it is necessary to consider that the immune history (tolerance and memory) of the subject may interfere with the response to such USs, resulting in a different immune reaction and different signal intensity to the CNS. For example, the immune response to a given antigen differs completely between the first and the second exposure, since an immune memory process takes place after the first exposure to an antigen. Another example is the phenomenon of immune tolerance developed after repeated exposition to the same drug. Therefore, applying the same conditioning protocol to two subjects with varying immune histories may result in quite different associative learning processes, which in turn may affect the conditioned immune responses in diverse ways.
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FIGURE 1 Theoretical framework for immunoconditioning. At association time there are two possible unconditioned stimuli (US) to be associated with a conditioned stimulus (CS). The US that is directly detected by the central nervous system (CNS) is defined as a genuine US, whereas the one that needs one or more intermediary molecules, released by another system, in order to be detected by the CNS is called a sham US. For any US, genuine or sham, there are two possible afferent pathways to the CNS: a neural afferent pathway and a humoral afferent pathway. At recall time there are two possible pathways by which the CNS can modulate immune functions: the humoral efferent pathway and the neural efferent pathway. The humoral efferent pathway may imply changes in neurohormones that directly or indirectly modify the immune response. The neural efferent pathway is supported by the direct innervations of primary and secondary lymphoid organs. Regarding the CS, it is important to mention that features such as novelty, intensity, duration, and naturalistic relation to the US may explain the feasibility of associating the CS with the US, as well as the stability and strength of such an association. In addition, it is necessary to consider that the immune history (tolerance and memory) of the subject may vary the response to the US, and from the CNS, resulting in a different associative learning at association time and/or in a different conditioned response at recall time.
In Pavlovian conditioning, the strength of the association between the CS and the US is affected by the temporal relation between these stimuli, the interstimulus interval. The orthodox theory predicts that when the US precedes the presentation of the CS (backward conditioning) learning is poor. In addition, when the CS precedes the US by increasing intervals, the probability of a CR declines (Rescorla, 1988). The specific inter-stimulus interval that yields the most pronounced CR varies with the organism and responses studied. For behavioral immunoconditioning, this associative feature could be employed to delineate the nature of the US (genuine vs. sham) by systematically
varying the inter-stimulus interval between the CS and US and describing the UR kinetics. Regarding the CS, it is important to mention that features such as novelty, intensity, duration, and naturalistic relation to the US may explain the feasibility of associating the CS with the US, as well as the stability and strength of such an association. For instance, it is well documented that gustatory or olfactory stimuli are strongly and easily associated with visceral US, in contrast to tactile, visual, or auditory stimuli (Domjan, 1973; Domjan, 2005). The strength and lastingness of flavor-visceral associations are reflected in several features of the CR, such as the high magnitude and the
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low forgetting rate. Additionally, the neutrality of the CS on the immune system needs to be assured for each experimental setting. Recall: The CR is the tacit and unique proof that an associative learning process has occurred at association time. In several immunoconditioning protocols the experimental subjects display a complex CR, with behavioral and neuroendocrine components in addition to the conditioned effects observed in the immune system. Furthermore, it is necessary to consider that the immune system itself displays sensitization (memory) and habituation (tolerance) responses to specific stimuli and that, in addition, many immune parameters underlie a circadian rhythm. Thus, the specific time-points for association and recall, as well as the immunological history of each experimental subject, may be important variables for the final outcome of the conditioned immune response. The portrait of some of the conditioned immune responses reported, therefore, might be the bizarre reflection of neural activity, which cannot be explained by the established learning and memory rules. For example, in a given conditioning protocol, the neural activity responsible for the conditioned immune response may follow a normal extinction process during consecutive recall trials, whereas the conditioned immune response itself may not display the same extinction slope, or may even be enhanced. Such peculiar results might be explained in two ways: It is possible that the interval between the recall trials is not long enough for the specific immune measure to return to its baseline, resulting in an additive effect of the conditioned immune response during consecutive, near-recall trials. Another possibility is related to immune processes that may be modulated by neural activity; however, once such a process has started, it is basically independent of neural modulation (e.g., hematopoiesis, immune memory, anaphylactic response). Thus, some changes in the immune response cannot strictly be called a CR (Eikelboom and Stewart, 1982). In summary, immune responses can be affected by behavioral conditioning protocols, but this does not necessarily imply that such immune responses were behaviorally conditioned. Regarding the conditioned immune response, there are specific features that may give important clues to its nature, and should be considered in the experimental design in order to differentiate the underlying mechanisms. There are two possible pathways by which the CNS can modulate immune functions: (a) the humoral efferent pathway and (b) the neural efferent pathway. The humoral efferent pathway may imply changes in neurohormones that directly or indirectly modify the immune response at recall time. The peripheral effects evoked after activation of this pathway would be diffuse
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and long-lasting like any neuroendocrine response. The neural efferent pathway is supported by the direct innervations of primary and secondary lymphoid organs (Elenkov et al., 2000; Mignini et al., 2003). There are several immune parameters that are subject to neural modulation, e.g., T-cell differentiation (Sanders and Kohm, 2002; Sanders and Straub, 2002), hematopoiesis (Artico et al., 2002; Maestroni, 1998; Miyan et al., 1998), T-cell activity, B-cell activity (Downing and Miyan, 2000), NK cell activity (Hori et al., 1995; Katafuchi et al., 1993a; Katafuchi et al., 1993b), and inflammatory response (Czura and Tracey, 2005; Pavlov and Tracey, 2005; Tracey, 2002). We hypothesize that many of these neuroimmune interactions may be affected by behavioral conditioning protocols, but few have been investigated experimentally so far. The extinction of the conditioned immune response is another feature that may give some hints about the underlying mechanisms. It has been demonstrated that for behavioral conditioning, in which the nervous system directly modulates the CR (e.g., nictitating membrane, gastric secretion, aversive behavior), an extinction process occurs when the CS is repeatedly presented without the US (active forgetting). However, if the CR observed is the reflection of neural activity on different types of cells, like immune cells that exhibit tolerance and memory processes, then CR extinction will not necessarily be elicited in an orthodox Pavlovian manner. Moreover, if the CR observed reflects the neural activity on two or more cellular types, then the picture may be more abnormal (e.g., neuroendocrine efferent pathway affecting immune functions). Further consideration is required since the life span of immune cells is short. Thus, each recall trial might affect a different cellular set.
E. Historical Development of Immunoconditioning S. Metalnikov and V. Chorine are generally credited with having conducted the first studies on behaviorally conditioned immune effects (Metalnikov and Chorine, 1926). However, V. I. Luk’ianenko cites observations in the dissertation of I. I. Makukhin (1911) at the University of St. Petersburg, and the report by A. Voronov and I. Riskin (1925) as perhaps the first ones demonstrating “conditioned leukocytic reaction” (Luk’ianenko, 1961). From the beginning, behavioral immunoconditioning has had an interdisciplinary history. The enzymatic-immunologist Sergey Metalnikov was born in 1870 in St. Petersburg, Russia. After finishing his studies at the University of St. Petersburg, he worked for many years with the embryologist A. Kowalevsky. In 1897 he moved to the University of
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Heidelberg, with the zoologist O. Bütschli, and then in 1901 he went to work with the famous immunologist E. Metchnikov at the Pasteur Institute in Paris. In 1907 he was appointed professor at the University of St. Petersburg, and in 1910 he became director of the Institute of Biology. At that time I. P. Pavlov was already a famous physiologist, who had been awarded the Nobel Prize in 1904, and certainly S. Metalnikov would have been aware of the conditioning paradigms. During the Bolshevistic revolution in 1919, he decided to leave Russia and returned to continue his work at the Pasteur Institute in Paris. Due to the importance of these visionary findings, it is worthwhile taking a closer look at the first reports on conditioned enhancement of immune responses. In their pioneer experiments, increases in peritoneal leukocytes similar to those observed after an antigenic challenge were reported as a result of behavioral conditioning (Metalnikov and Chorine, 1926; Metalnikov and Chorine, 1928). Guinea pigs were given daily association trials with contingent pairing of scratching or heating of the skin as a CS, and with an immune challenge as US (i.p. injection of a small dose of tapioca, Bacillus anthrax, or a Staphylococcus filtrate). The conditioning protocols consisted of 15 to 20 association trials, and after 12 to 15 days recall took place. The CR was an increase in peritoneal leukocyte numbers that was weaker and more transitory than the UR. Followup experiments examined the survival of guinea pigs after a normally lethal injection of Vibrio cholera bacteria. Conditioning was essentially carried out as before. Association was performed by a daily presentation of the CS (scratch) contingently paired with a US (injection of either Staphylococcus filtrate or B. anthrax). The number of association trials varied greatly among these experiments, and different resting intervals between association and recall were reported. In each experiment, there were two conditioned animals and two control animals, which received neither the CS nor the US in the association phase. One day post-recall, all animals were given an injection of V. cholera. The unconditioned control animals died after 7–8 hours, whereas the conditioned animals died after 36 hours. Some conditioned “survivors” were tested once more a month later, receiving an injection of Streptococcus. One animal was evoked (CS exposure) before such injection, whereas another was not. The re-evoked individual survived, whereas the non–re-evoked and two controls died. These initial results were rapidly replicated (Nicolau and Antinescu-Dimitriu, 1929a; Nicolau and Antinescu-Dimitriu, 1929b; Ostravskaya, 1930), and in the following years considerable attention was given to the question of conditioned immune effects by
Soviet investigators (Ader, 1981; Luk’ianenko, 1961). Many of these experiments were basically similar to those performed by Metalnikov and Chorine (1926, 1928), and apparently there was some controversy over the reproducibility of some experiments. In parallel to the Soviet experiments, but not as well known, investigations were performed in Romania by I. Baciu (Baciu et al., 1965; Benetato, 1955; Benetato et al., 1952) demonstrating that the phagocytic activity of polymorphonuclear cells in the peripheral blood of dogs could be markedly increased by behavioral conditioning. In 1975, a new interest in the behavioral conditioning of immunity was generated by the publication of R. Ader and N. Cohen on conditioned immunosuppression (Ader and Cohen, 1975), which formally is the beginning of psychoneuroimmunology as a modern (inter)discipline.
II. THE PHENOMENON OF BEHAVIORALLY CONDITIONED ENHANCEMENT OF IMMUNE RESPONSES There are several ways to arrange the data reporting on the behavioral conditioning of immune functions. One possibility is to organize the data according to the nature of the CS (e.g., gustatory, olfactory, visual, auditory, touch) or the type of US (e.g., stress, immunosuppressive, or immunoenhancing drugs; antigens; cytokines). However, regardless of the experimental protocol, we decided to classify the existing data according to the conditioned immune response, with the aim of giving relevance to the possible biological and clinical significance of immunoconditioning. In general, the conditioned enhancement of immune responses can be classified into two main categories: (a) the innate immune responses and (b) the adaptive immune responses. Furthermore, a nomenclature will specify the conditioning protocol employed in each experiment. For example, a putative conditioning protocol with 5 association and 11 recall trials will be described as 5/11 conditioning.
A. Innate vs. Adaptive Immune Responses The immune system can be roughly classified into two subsystems: the innate and the adaptive immune system. In general, innate immunity is considered a non-specific response, whereas the adaptive immune system is thought to be very specific. The main distinctive features of both innate and adaptive immune responses are depicted in Table 1 and have been reviewed elsewhere (Janeway et al., 2005).
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30. Conditioned Immune Enhancement TABLE 1
Summary of Innate and Adaptive Immune Responses
Innate immune responses
Adaptive immune responses
Receptors
Germline-encoded
Distribution Repertoire
Subset-specific but non-clonal Limited Selected in groups of individuals within a given species No Phagocytic cells (e.g., Neutrophils, Macrophages, Monocytes), as well as NK cells, eosinophils, dendritic cells Complement, certain cytokines (e.g., IFN, TNF-α), enzymes (e.g., lyzozime), nitric oxide There is immediate maximal response
Immune memory Cellular component Humoral component Speed of the response
B. Stress Induces Enhancement of Immune and Cognitive Functions The impact of stress on both immune and cognitive functions (e.g., learning and memory) has already been documented (Dhabhar and Viswanathan, 2005; Engler et al., 2004; Shors, 2004). For example, acute stressors have been shown to enhance certain immune functions such as mitogen-induced cell proliferation, phagocytosis, and NK cell activity (Lyte et al., 1990; Millar et al., 1993; Shurin et al., 1994a; Shurin et al., 1994b). In addition, it has been reported that acute stress also enhances associative neural capacities (Shors et al., 2000). In several immunoconditioning protocols, either at association or at recall time, the experimental subjects experienced stressful conditions, thus affecting the immune and/or cognitive functions. In particular, activation of the HPA axis is often conditioned as a result of the behavioral protocols that also produce a CR in the immune system (Buske-Kirschbaum et al., 1996; Pacheco-López et al., 2004; Shurin et al., 1995). The signaling of an unconditioned immune stimulus to the CNS at association time can differ considerably between animals that are stressed and those that are not. Thus, the associative strength between the CS and the US may differ, and the CR magnitude as well. Moreover, the fact that different strains of animals displayed diverse CR magnitude, in corticosterone plasma levels, for example, in the same conditioning protocol (Shurin et al., 1995) may further complicate this issue.
C. Conditioned Enhancement of Innate Immune Responses An overview of studies reporting the conditioned enhancement of innate immune responses is shown in
Antigen receptors are products of site-specific somatic recombination Antigen receptors are clonally distributed Immense Selected in each individual within a given species Yes Lymphocytes (e.g., T- and B-cells, NK cells) Immunoglobulins, certain cytokines There is a lag time between exposure and maximal response
Table 2. In order to be able to objectively compare such data, important methodological details are included, such as the nature, duration, and intensity of CS and US; the specific conditioning protocol (number of association trials, rest interval, number of recall trials); the type of experimental subjects (species, strain, and gender); and the conditioned responses (immune and others). 1. Natural Killer Cell Activity Natural killer (NK) cells are important in innate immunity with regard to viruses and other intracellular pathogens. In addition, NK cells have a significant role within antibody-dependent cellular toxicity, which is an adaptive immune response (Janeway et al., 2005). One of the best-described immune response that can be enhanced by behavioral conditioning is the cytotoxic activity of NK cells. The US employed is polyinosinic : polycytidylic acid (poly I : C), a doublestranded synthetic RNA that mimics a viral infection. The advantages of using poly I : C over live viruses include safety, convenience, and, more importantly, reproducibility and control over dose and time of administration of the immunological challenge. Systemic administration of poly I : C elicits an acute-phase reaction, fever, and sickness behavior in a variety of species including mice, rabbits, guinea pigs, and rhesus monkeys. Poly I : C is also a potent inducer of alpha and beta-interferon (IFN) which, in turn, stimulate NK-cell–mediated cytotoxicity (Magee and Griffith, 1972; Manetti et al., 1995). Conditioning protocol: It is necessary to indicate some key features of the conditioned enhancement of NK cell activity. All experiments were performed in colonyhoused BALB/c mice, mostly in females and just once in males (Spector et al., 1994), and with the condition-
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TABLE 2 Conditioned stimulus Nature Duration Description
Unconditioned stimulus Nature Dose Administration route
Overview of the Conditioning Protocols Enhancing Innate Immune Responses Conditioning protocol Association # trials
Rest interval # days
Recall # trials
Subjects Species Strain Gender
Conditioned responses Immune Others
Ref.
poly I : C 20 μg/mouse i.p.
9
3
1
Mouse BALB/c Female
Increased NK-cell activity 1 day after each evocation trial NR
(Ghanta et al., 1985; Ghanta et al., 1987)
Odor 60–90 min Camphor
poly I : C 40 μg/mouse i.p.
9
3
2
Mouse BALB/c Male
Increased NK-cell activity 1 day after each evocation trial NR
(Spector et al., 1994)
Taste & Visceral 60 min 0.1% saccharin + i.p. LiCl 125 mg/kg
poly I : C 20 μg/mouse i.p.
1
2 or 5 or 6
1&2
Mouse BALB/c Female
Increased NK-cell activity 1 day after each evocation trial. Additive CR: i.e., CR after 2nd evocation trial >1st evocation trial. Rest interval of 6 days induces stronger CR than rest interval of 2 days NR
(Ghanta et al., 1987; Hiramoto et al., 1987)
Odor 60 min Camphor
LPS 100 μg/mouse i.p.
1
2
1
Mouse BALB/c Female
Increased splenic NK cells activity 1 day post evocation (in which a low-dose activating injection of 2.5 μg of poly I : C was i.p. administered) NR
(Demissie et al., 1997)
Odor 60 min Camphor
poly I : C 1.5 mg/kg i.p.
1
2
1
Mouse BALB/c Female
Increased splenic NK cells activity 1 day post evocation NR
(Hsueh et al., 1995; Hsueh et al., 1996; Kuo et al., 2001; Hsueh et al., 2002)
Odor 60 min Camphor
poly I : C 1.5 mg/kg i.p.
1
2
1
Mouse BALB/c Female
Increased splenic neutrophil activity 1 day post evocation NR
(Chao et al., 2005)
NR: Not reported; Poly I : C: polyinosinic : polycytidylic acid; LPS: lipopoly saccblaride
III. Behavior and Immunity
Odor 240 min (after US) Camphor
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ing procedure taking place at the beginning of the inactive phase (light phase). The conditioned immune response occurred during one or more association trials (Ghanta et al., 1985; Solvason et al., 1992). Solvason et al. (1988) reported that, using camphor odor (240 minutes) as the CS and poly I : C as the US, more than six association trials were required to elicit a statistically significant enhancement of NK cell activity. For conditioning protocols in which either camphor odor (60 minutes), citronella odor (60 minutes), or saccharin + LiCl were employed as conditioned stimuli, the effect of increasing the number of association trials on the magnitude of the CR has not been systematically analyzed. CS neutrality: Using saccharin + LiCl as CS induced a significant decrease in NK cell activity (Solvason et al., 1988); therefore, this CS cannot be considered as neutral. In contrast, the neutrality of camphor odor as CS for the conditioned enhancement of NK cell activity has been proved (Hiramoto et al., 1992). The neutrality of citronella odor on NK cell activity has been suggested but not completely proved (Solvason et al., 1991). The CS duration varied from 4 hours to 30 minutes of odor exposure; however, the number of association trials (9 to 1) was modified at the same time, which makes a systematic analysis of which of these two factors is responsible for the CR magnitude impossible. The most common CS exposition length is 1 hour for camphor odor. In the first reports on conditioned enhancement of NK cell activity, the exact procedure for preparing the camphor odor (CS) was not clearly reported (Ghanta et al., 1985; Ghanta et al., 1987a; Hiramoto et al., 1987). However, in order to optimize the experimental protocol there is a citation from a later report by the same group “. . . we modified our earlier experiments using camphor odor as the CS to a onetrial conditioning event by intensifying the camphor smell during the CS exposure” (Solvason et al., 1988). The inter-stimuli interval at association time has been systematically tested within the 1/1 conditioning protocol, and it is documented that the optimum CR is achieved when the CS precedes the US by 24 hours. Intervals of 15 minutes and 48 hours yielded a CR of similar magnitude. In the backward association scheme (US→CS), intervals of 96 hours and 24 hours resulted in a similar CR magnitude (Hiramoto et al., 1992; Solvason et al., 1992). However, the fact that the association between the CS and US is still possible with intervals as long as 48 hours is striking. The rapid habituation to neural (cortical and mitral) responses seems to allow filtering of background odors, enhancing the ability of the subject to discriminate new odors (Wilson and Stevenson, 2003). This neurobiological
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feature of the olfactory sense itself rules out the possibility that such long inter-stimuli intervals are related to a possible residual camphor odor on the fur of the mice that is still present at US administration. The authors mention that the CS trace memory (camphor odor) must be latent for such a long time in order to be able to make an association with the US. This seems to be supported by the long latency (maximum 12 hours) reported for the association of the stimuli in conditioned taste aversion paradigms (Schafe et al., 1995). However, to our knowledge there is no other paradigm showing such long inter-stimulus interval. Actually, conditioned odor aversion in rats occurs only if the time interval separating the odor (CS) from the subsequent intoxication (US) is very short (less than 30 minutes), suggesting that the memory trace of the odor is subject to rapid decay (faster than taste), at least for associative processes (Ferry et al., 1999). Since it has been reported that the inter-stimulus interval (for conditioned taste aversion avoidance) is modulated by the US intensity, subject’s age, and body temperature (Hinderliter et al., 2002; Misanin et al., 2002), it will be necessary to systematically analyze such unusually long inter-stimuli intervals under more specific conditions (i.e., gender, age, temperature), before discarding this possibility. The rest interval before recall phase varied within the 9/1 conditioning paradigm from 1 to 6 days, producing unexpected results, since the longer intervals resulted in a stronger CR (Hiramoto et al., 1987). When saccharin + LiCl was used as a CS, varying the rest interval from 3 to 7 days did not influence the magnitude of the CR (Solvason et al., 1988). For the 1/1 conditioning protocols where camphor or citronella odor were employed as a CS, the rest interval reported was always 2 days. However, a systematic approach testing several rest intervals is necessary to elucidate how this factor affects the CR. Recall: The conditioned enhancement of NK cell activity has repeatedly been demonstrated 24 hours after a single recall trial and the extinction of the CR has partly been tested. The data of a report where a second recall trial was implemented (9/2 conditioning) indicate an additive effect for the CR; i.e., the magnitude of the CR after the second recall trial was larger than after the first (Hiramoto et al., 1987). In parallel, 1/2 conditioning produced a stronger CR than a 1/1 conditioning protocol (Solvason et al., 1991). Here, the authors argue that due to the kinetics of the augmentation of NK cell activity, they believe that each recall trial boosts NK cell activity in an additive manner. The fact that the same experimental subjects cannot be tested during extinction processes complicates the experimental design. Consequently, more
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recall trials should be included in future experimental designs to evaluate this unexpected result. The specificity of the CS to recall the CR has already been demonstrated (Solvason et al., 1991). Conditioned animals displayed an increase in NK cell activity only in response to the specific CS (camphor or citronella) employed at association time. No CR was evoked in animals conditioned with one CS (e.g., citronella) but evoked with another stimulus (e.g., camphor). The CR kinetics have been described for 1/1 conditioning, showing that adrenocorticotropic hormone (ACTH) was elevated in the serum within 30 minutes post-recall, followed by an increase in IFN-α mRNA expression (4–6 hours) and NK cell activity (24 hours) (Hsueh et al., 1994a). However, in a previous report IFN levels were not detectable when assayed at 6 hours post-recall in a 9/1 conditioning protocol (Ghanta et al., 1987a). In order to be able to compare the CR and the UR, it is necessary to assay the NK cell activity at other time-points after recall (e.g., 2 hours, 12 hours, 48 hours) for each conditioning protocol (1/1 vs. 9/1), and to determine the expression and production of several cytokines at different time-points post-recall. In addition to the conditioned immune effects, fever response has been reported as an additional CR elicited by 1/1 conditioning (Hiramoto et al., 1991a; Rogers et al., 1992). And, it is possible that a broader repertory of physiological and behavioral responses, not tested, have been as well conditioned, e.g., aversive/avoidance behaviors. The impact of aging on the conditioned enhancement of NK cell activity has also been suggested (Spector et al., 1994). Three-month-old and 24-monthold BALB/c male mice were submitted to a 9/2 conditioning protocol with camphor odor paired with poly I : C. Although young animals displayed a stronger immune response to poly I : C than older ones, both displayed a conditioned immune response (enhanced NK cell activity), indicating that even old animals are able to associate olfactory and immune stimuli, and evoke such association. However, old animals showed a lower CR magnitude than young ones. This is in parallel with a report showing that aged mice have diminished conditioned immunosuppression (Gorczynski, 1987; Gorczynski, 1991). Underlying mechanism: Regarding the CS (camphor odor), the neurobiology of olfactory perceptual learning has been reviewed elsewhere (Wilson and Stevenson, 2003) and is out of the scope of the present chapter. We shall, therefore, concentrate on analyzing the US within this conditioning paradigm. There is experimental evidence that one important genuine US for this conditioning protocol is the cytokine IFN-β. Interferon-β, but not IFN-α, can replace poly I : C as the US in order
to acquire a CR with enhancing effects on NK cell activity (Solvason et al., 1988). In this regard, several doses of the US (poly I : C or IFN-β) were tested, indicating that 0.5 mg/kg of poly I:C is the threshold which induces sufficient signaling as a US (Hiramoto et al., 1993a). Interestingly, lower doses of poly I : C can still raise the NK cell activity in the periphery, but apparently do not induce sufficient signaling to reach the CNS. This indicates that the level of IFN-β produced in the periphery is important, as this mediator may penetrate the CNS. It has been reported that association can be achieved by i.v. administration of IFN-β at a dose of 10,000 IU, but not at 1,000 IU. However, if IFN-β was directly delivered into the CNS via the cisterna magna, a smaller dose of IFN-β (100 IU) was enough to be associated with the CS. Supportive evidence about the preponderant role of IFN-β as a genuine US also comes from experiments in which anti–IFN-β (100 neutralizing units) was injected into the cisterna magna 24 hours before association, blocking the CR when poly I : C (1 mg/kg) was used as a US (Solvason et al., 1993). The afferent mechanism responsible for the associative learning process supporting the CR that enhances NK activity seems to be distinguishable from that by which conditioned fever is induced. Intraperitoneal injection of sodium carbonate blocked the CS-US association responsible for the enhancement of NK cell activity, but left the fever response intact. In contrast, indomethacin treatment, which blocks prostaglandin synthesis, abolished the fever response but had no adverse effect on the association of NK cell response (Rogers et al., 1992). Recently, it has been shown that interleukin (IL)-1 is the main peripheral messenger responsible for fever induction after injecting poly I : C (Fortier et al., 2004). Central processing: In order to differentiate learning from memory processes, a series of experiments was designed in which the 1/1 conditioning protocol was analyzed using a neuropharmacological approach. In these experiments different drugs were administered peripherally or centrally before association (learning) or before recall (memory). Moreover, since a long inter-stimuli interval at association time had been demonstrated for this conditioning protocol (Hiramoto et al., 1992), it was possible to administer the drugs (peripherally or centrally) after the CS but shortly before the US exposure, with the aim of distinguishing the sensory processes of the CS from those of the US. In summary, central but not peripheral lidocaine administration blocked the association as well as the recall of the CR (Rogers et al., 1994a). Additionally, it has been reported that central administration of lidocaine blocked the CNS sensory processes of the CS, but not those of the US. Following the same rationale,
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peripheral or central administration of monosodium glutamate (Ghanta et al., 1994) or sodium carbonate (Rogers et al., 1994b) seems to block the US association with the CS, without affecting the CS perception. Furthermore, some data demonstrated that the hypothalamic arcuate nucleus is needed at association but not at recall time (Ghanta et al., 1994). Recall of the conditioned enhancement of NK cell activity seems to be dependent on opioid signaling. Central but not peripheral opioid pathways are thought to be involved in this associative learning process, since injection of the less potent opioid receptor antagonist quaternary naltrexone, which does not penetrate the CNS, did not affect the CR. In contrast, the association process does not seem to require central opioid pathways, since naltrexone given prior to association did not interfere with the formation of this conditioning (Solvason et al., 1989). In an initial attempt to determine the role of catecholamines within this model, reserpine treatment was administered before recall. Results showed that this treatment, unspecifically depleting central and peripheral catecholamine contents, blocked the CR (Hiramoto et al., 1990). More recently a relevant role for central catecholamines at recall time has been confirmed. α- and β-adrenoceptor antagonists or dopamine (DA)1– and DA-2–receptor antagonists administered immediately before recall also blocked the effects on the conditioned immune response (Hsueh et al., 1999). In addition, glutamate but not gamma-aminobutyric acid (GABA) was required at recall time (Kuo et al., 2001). In the last of this series of experiments, the role of cholinergic and serotonergic central systems at both association and recall times was assessed. At association, acetylcholine seems to act through the nicotinic, M2-, and M3-muscarinic receptors, whereas at recall neither the latter receptors nor the M1 receptors appear to affect the CR. In both association and recall phases, serotonin acts through the 5-HT1 and 5-HT2 receptors to modulate the CR (Hsueh et al., 2002). Determining neurotransmitter contents in brain structures during recall has produced a set of interesting results. Immediately after recall the contents of several neurotransmitters in the cerebellum, hippocampus, striatum, cortex, and amygdala were determined. Results showed that the norepinephrine content in the cerebellum and dopamine contents in the striatum and hippocampus were significantly higher in conditioned animals than in controls (Hsueh et al., 1999). In contrast, glutamate contents did not differ among the groups in any of the analyzed brain structures at recall time (Kuo et al., 2001). Neural efferent pathway: The possibility that the sympathetic innervation of the spleen is responsible for the
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conditioned increase in NK cell activity has been partially discarded. Peripheral sympathectomy (using 6OHDA) performed after association but before recall did not prevent the expression of the conditioned immune response (Hiramoto et al., 1990). However, conclusive evidence can only be obtained after splenic denervation. The humoral efferent pathway was also explored within this conditioning protocol. In conditioned animals, plasma ACTH and β-endorphin levels and splenic IFN-α expression were determined at recall time (Hsueh et al., 1994a) showing that plasma ACTH and splenic IFN-α expression were elevated after recall. These data indicate a sequence in the appearance of each signal: plasma ACTH (30 minutes) → IFN-α mRNA expression (4–6 hours) → NK cell activity (24 hours). Peripheral administration of the synthetic glucocorticoid dexamethasone blocked the recall but not the association of the CR, presumably by negative feedback inhibition of HPA axis activity (Hsueh et al., 1994b). However, control experiments are needed in which the effects of blocking the proposed signals on NK cell activity are analyzed. Recently, it has been shown that the CR may be independent of the nature of the US and that it is basically directed by the immune status of the individual at recall time (Demissie et al., 2000). In a set of experiments, two different US (poly I : C or arecoline) were paired with camphor odor as CS. At recall time, it was observed that both NK cell activity and cytotoxic T lymphocyte (CTL) activity were enhanced. Pairing only one of the two US (arecoline or poly I : C) with the CS (camphor odor) at association time resulted in similar associative learning, as shown by a similar CR at recall time. However, when the conditioned animals received an antigen challenge before association, thereby priming the CTL immune response, the resulting CR was enhanced CTL activity. More importantly, it was possible to induce both conditioned immune responses, the CTL and the NK cell activity, in animals receiving the antigen challenge before association and a suboptimal poly I : C dose immediately post-recall. It is also the case that lipopolysaccharide employed as US induces enhanced NK cell activity as CR when a suboptimal poly I : C dose was applied post-recall (Demissie et al., 1997). These data indicate that following the same conditioning protocol the immune response observed as a CR may vary among subjects, depending on their immune history and/or status at association and recall time. This phenomenon should be characterized in more detail with a view to the possible application of conditioning protocols to human subjects, who may show larger variability in their immune history and immune status at a given time-point.
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2. Neutrophil Activity Neutrophils play a key role in the cellular defense against various pathogens. The functions of neutrophils include phagocytosis, chemotaxis, and the release of inflammatory factors such as granzyme, perforin, chemokines, reactive oxygen species, and reactive nitrogen substance (Segal, 2005). Conditioning protocol: In a 1/1 conditioning protocol, using camphor odor as a CS and poly I : C as a US, splenic neutrophil activity was enhanced 24 hours after recall (Chao et al., 2005). The main control group chosen for comparison with conditioned animals was a group of animals that received association trials in a backward scheme, in which the US preceded the CS by some minutes (personal communication, C.-H. Hsueh). It has been argued that poly I : C by itself does not directly signal to the CNS. Thus, the immune consequences (e.g., cytokine production) are thought to be the genuine US that in fact reaches the CNS (Solvason et al., 1993). This process may take some minutes to be induced; therefore, it is surprising that animals submitted to a backward association scheme did not associate the CS (camphor odor) with the genuine US (cytokines) which may occur in parallel. In order to better control for conditioning, it will be necessary in future experiments to include a group of animals conditioned but not evoked, or to increase the inter-stimuli interval in the backward association. CS neutrality was analyzed in this paradigm by testing the effects of a single exposure to camphor on neutrophil activity. Nitrite levels remained the same at 0, 4, 12, 24, 48, and 72 hours after a single camphor exposure. Additionally, data from animals exposed twice to the CS but not conditioned further support the neutrality of the camphor stimulus on neutrophil activity. Chao et al. (2005) also reported the UR kinetics. Animals receiving a poly I : C injection showed that splenic neutrophil activity was significantly increased 4 hours post-stimulation. In another set of experiments, neutrophil activation markers, such as myeloperoxidase activity and adherence activity, were also determined in the splenic neutrophils isolated 4 hours after poly I : C treatment. Results showed that in addition to the release of nitrite, myeloperoxidase activity and cellular adhesiveness of the splenic neutrophils were also significantly increased. Regarding the CR kinetics, the only time-point in which the neutrophil activity was measured was 24 hours post-recall. Thus, it would be interesting to delineate the kinetics of this CR. Underlying mechanisms: Since the association protocol is identical to that used for the conditioned enhance-
ment of NK cell activity, it is likely that the afferent pathway is similar (see Section II in this chapter). However, this does not mean that the neural principles apply equally to every conditioned immune response at recall time. Central catecholamines seem to be relevant for evoking the conditioned enhancement of neutrophil activity (Chao et al., 2005). With the aim of localizing the action sites of catecholamines, the same authors analyzed the expression levels of tyrosine hydroxylase (TH) in various brain structures 24 hours post-recall. Although the results showed that conditioned animals had significantly more neurons expressing tyrosine hydroxylase in the locus coeruleus, hypothalamus, and cortex than control animals, this result does not necessarily indicate a neural memory process. It is unlikely that the memory trace lasts for 24 hours after presentation of the CS. Appropriate controls are needed in order to refute the view that a possible immunoception process (feedback) at recall phase might be responsible for the observed effects. Additionally, it is not clear whether the enhanced expression of tyrosine hydroxylase in the brain is linked to the memory process. Regarding the efferent pathway responsible for this CR (neutrophil activity), the data are different from that reported for NK cell conditioning. Peripheral sympathectomy before recall completely blocked the CR, indicating that sympathetic innervation of the spleen might be one efferent pathway. However, the main efferent pathway for the conditioned enhancement of NK cell activity seems to be independent of the peripheral sympathetic nervous system (see above). Dexamethasone treatment before recall resulted in higher neutrophil activity in conditioned animals than in controls, indicating that this specific CR is basically independent of hypothalamicpituitary-adrenocortical activity. NK cells vs. neutrophils vs. CTL activity as CR: The published data indicate that the immune consequences of poly I : C and an olfactory stimulus can be rapidly associated. The recall of such associative learning may modulate several immune functions by activation of neural and humoral (neuroendocrine) efferent pathways. However, these facts do not prove that NK cell, neutrophil, and CTL activity are truly behaviorally conditioned. Moreover, the data indicate that some immune responses are enhanced at recall time depending on the immunological history of the particular subject (Demissie et al., 1997; Demissie et al., 2000). 3. Humoral Innate Immunity Little attention has been given to humoral defense in the context of behavioral immunoconditioning,
30. Conditioned Immune Enhancement
However, several experiments indicated conditioned changes in complement activity (Dolin et al., 1960; Reidler, 1956) and lysozyme (Gasanov, 1953, cited in Ader, 1981). It is likely that humoral factors in immunity become enhanced as a CR, but to our knowledge no research program has attempted to continue this research line, nor even to confirm initial reports.
D. Conditioned Enhancement of Adaptive Immune Responses Tables 3, 4, and 5 summarize data reporting the conditioned enhancement of adaptive immune responses. In addition, they include important methodological details such as the nature, duration, and intensity of the CS and US; the conditioning protocol (i.e., number of associations trials, rest interval days, and recalls trials); the experimental subjects (species, strain, and gender); and the conditioned responses (immune and others) observed. 1. Antibody Production A central question is whether the immune response to a specific antigen can be sensed by the CNS, enabling a US to induce an associative learning process within behavioral conditioning settings. In this case, the CNS should be capable of inducing antibody production at recall time. During association, a complex cascade of immune responses (e.g., phagocytosis → antigen processing-presentation process → cytokines release → recognition of antigen by T- and/or B-cells → clonal expansion) is induced after the exposure to the US (immunization), ultimately resulting in the production of immunoglobulins (UR). The genuine US that signals to the CNS is a key feature in this process. Thus, the research reports are grouped according to the specific antigen (US) that was employed to elicit conditioned antibody production (see Table 3). In the mid-1950s Soviet researchers reported the first controlled conditioning studies in which antibody production was elicited as a CR (Zeitlenok and Bychkova, 1954). Albino rats were submitted to daily association trials, pairing a short tactile stimulus (CS) with either simultaneous or subsequent injection of influenza A virus (US). After 30–45 days, animals were exposed to the CS, and daily blood samples were taken over the next 10–12 days. When antibody titers had again stabilized at a sufficiently low level, recall was repeated for a second and a third time. Conditioned animals elicited an antibody production as a CR. However, the CR magnitude and kinetics differ to those from the UR. Interestingly, the conditioned increase in antibody production was not extinguished
643
over the three recall trials and was even more pronounced after the second and the third recall trial. Several other studies followed this initial attempt to demonstrate the capabilities of the CNS to elicit antibody production as a CR. A detailed review of these pioneer reports can be found elsewhere (Ader, 1981; Luk’ianenko, 1961). Jenkins and colleagues reported elicited antibody production as a CR following a 1/2 conditioning protocol (Jenkins et al., 1983). In this report intraperitoneal immunization with sheep red blood cells (SRBC) was employed as the US, and was paired with a complex visceral-gustatory CS (LiCl intraperitoneally and saccharin orally). Seven days later, the animals were exposed to the CS and for the second time 2 days later. Anti-SRBC antibody titers were significantly elevated in conditioned animals compared to control groups 4 days after the second recall trial. A third recall trial took place 16 days postassociation, and antibodies were determined 4 days later. However, a meta-analysis of the original data reported that there was no conditioned effect (Ader and Cohen, 1991). Keyhole limpet hemocyanin (KLH): Conditioned antibody production employing KLH as the US was reported by Ader et al. (1993). In a 3/1 conditioning protocol, male BALB/c mice were repeatedly injected with a low dose of KLH as US. By its nature this protein is highly immunogenic, inducing a strong antibody response with high and long-lasting immune memory. Association was initially implemented by three trials (at 3-week intervals), in each of which a complex gustatory stimulus (chocolate milk drinking solution) as a CS was followed by an immunization with KLH (100 ng). A single recall trial was conducted 3 weeks after the last association trial, and serum antibody titers were determined at 5-day intervals. The conditioned animals showed no conditioned taste avoidance at recall time. However, the same animals, boosted with a small dose of antigen (2.5 ng) at recall phase, elicited a relatively modest but significant enhancement of anti–KLH-IgG antibody production (observed at day 10 post-recall). In order to increase the CR magnitude, a 5/1 conditioning protocol with lower US intensity (50 ng of KLH) and higher booster antigen dose (5 ng) was implemented. Results showed that the magnitude of the CR was increased, almost reaching the same magnitude and kinetics as the UR. However, with these data it is not possible to distinguish which of the parameters (i.e., number of association trials, US intensity, or antigen booster dose) mainly affects CR magnitude. In order to narrow down the genuine US, a backward association scheme was implemented in which the inter-stimuli interval was systematically varied in a backward association manner. In
TABLE 3 Unconditioned stimulus Nature Dose Administration route
Taste & Visceral 60 min 0.1% saccharin + i.p LiCl 128 mg/kg
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Conditioned stimulus Nature Duration Description
Overview of the Conditioning Protocols Enhancing Antibody Production Conditioning protocol Subjects Species Strain Gender
Conditioned responses Immune Others
2
Rats Hooded & CD Male
Increased anti-SRBC antibody titers 4 days post last evocation NR
(Jenkins et al., 1983)
21
1
Mouse BALB/c Male
Increased anti-KLH IgG antibody titers, peaking at 10 days post evocation (in which a low-dose booster injection of 2.5 ng of KLH was i.p. administered) NR
(Ader et al., 1993)
1
14
1
Rat Wistar NR
Increased anti-OVA antibody titers and OVA-induced T-cell proliferative response in vitro at 4 days post evocation Conditioned taste aversion
(Husband et al., 1993)
Ovalbumin (OVA) 80 μg i.p.
1
30
1
Rats Wistar Male
Increased anti-Ova −IgG antibody titers, peaking at 25 days post evocation NR
(Chen et al., 2004)
“Touch” 15 min Electro-stimulation (2 ms/2 Hz/2 or 4 V)
Ovalbumin (OVA) 80 μg i.p.
1
30
1
Rats Wistar Male
Increased anti-Ova −IgG antibody titers, peaking at 17 days post evocation. This CR was also obtained when acquisition was performed under anesthesia NR
(Huang et al., 2004)
Taste 10 min 0.1% saccharin
Hen egg-white lisozyme (HEL) 0.5 mg/Rat i.p.
1
30
1
Rat Wistar Male
Increased anti HEL −IgG and −IgM antibody titers, peaking at 8 days post evocation NR
(Alvarez-Borda et al., 1995; Ramérez-Amaya & Bermúdez-Rattoni, 1999)
Odor 10 min Almond essence
Hen egg-white lisozyme (HEL) 0.5 mg i.p.
1
30
1
Rat Wistar Male
Increased anti HEL −IgG antibody titers, peaking at 8 days post evocation NR
(Ramírez-Amaya & Bermúdez-Rattoni, 1999)
Taste 10 min 0.1% saccharin
Hen egg-white lisozyme (HEL) 0.5 mg i.p.
1
45
1
Rat Wistar Male
Increased anti-HEL −IgG antibody titers, peaking at 8 days post evocation NR
(Madden et al., 2001)
Taste 10 min 0.1% saccharin
Hen egg-white lisozyme (HEL) 0.5 mg i.p.
1
37
1
Rat Wistar Male
Increased anti-HEL −IgG antibody titers, peaking at 8 days post evocation NR
(Espinosa et al., 2004)
Rest interval # days
Recall # trials
Sheep red blood cells (SRBC) 2 ml/kg (1% thrice washed SRBC suspension) i.p.
1
7
Taste & Odor 60 min Chocolate milk
Keyhole limpet hemocyanin (KLH) 100 ng/Mouse i.p.
3
Taste 15 min 0.25% saccharin
Ovalbumin (OVA) 200 μg i.p.
Taste 15 min 0.25% saccharin
NR: Not Reported
Ref.
III. Behavior and Immunity
Association # trials
30. Conditioned Immune Enhancement
this experiment, the CS was presented 3, 6, 9, or 15 days after the US during the five association trials. After a single recall trial, no conditioned effects were found at any time. These results suggest that the genuine US is one or more of the relatively early events in the sequence of immune responses that are triggered by the antigen. Recently, it has been reported that following immunization with KLH, rapid and transient neural activity (c-Fos expression) can be detected within specific brain structures (PachecoLópez et al., 2002). These data support the hypothesis that early immune effects of KLH are sensed by the CNS, possibly resulting in associative learning when conditioning is applied. However, no investigations have been undertaken so far to elucidate the mechanisms behind this specific behavioral conditioning of antibody production. Ovalbumin (OVA): In the early 1990s an Australian group reported conditioned enhancement of antibody production following a 1/1 conditioning protocol (Husband et al., 1993). During the association trial, male rats received an intraperitoneal injection of OVA (200 μg) as a US, after presenting saccharin solution as a CS. Recall was implemented 14 days later, in which the conditioned animals were exposed to the CS, and 4 days later the conditioned immune response was assayed. Since a further US exposition may induce a different UR (secondary antibody immune response; IgM), the positive control group was not exposed to the US at recall. Results indicated that anti-OVA IgG antibody titers (CR) were higher in conditioned animals than in controls. Importantly, this CR was achieved without the necessity of booster antigen administration at recall time. Additionally, the conditioned animals displayed a conditioned taste avoidance at recall time which might have been induced by the administration of Freund’s adjuvant with OVA at association. Although the attempt to exactly replicate these results failed (Boehm et al., 1998) unless a booster non-immunogenic antigen was administered at recall (Li et al., 1997), a recent follow-up report successfully reproduced the original 1/1 conditioning protocol (Chen et al., 2004). Importantly, in this follow-up report most appropriate controls were included to assure the associative learning process and CS neutrality on the CR. The major variations in the conditioning protocol were a lower antigen dose (80 μg) and a longer rest interval between association and recall (30 days); this may have resulted in a lower primary antibody response, which hence increased the CR. The anti-OVA IgG antibody titers were measured in 5-day intervals after the recall trial. Although anti-OVA IgG antibody titers were still above baseline values, the results showed a
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clear increment of antibody production as a CR, compared to the appropriate control groups. Interestingly, the CR kinetics differed from the UR, showing a smooth slope and peaking at 25 days post-recall. In addition, pre-exposure to saccharin prevented the conditioned antibody response (i.e., latent inhibition), suggesting that the conditioned immune response was neither due to the effect of stress from the aversive behavioral re-sponse nor to the physiological effects of saccharin. In order to further investigate the neural mechanisms underlying this specific conditioning protocol, neural activity was quantified within the insular cortex after recall (Chen et al., 2004). The study revealed that reexposure to the CS resulted in a significant increase in c-Fos immunoreactivity in all insular areas (granular, dysgranular, and agranular) 120 minutes postrecall. Accordingly, several studies have demonstrated that the insular cortex subserves the association, retrieval, retention, and extinction of long-term visceral-gustatory memory (Bermúdez-Rattoni, 2004; Bermúdez-Rattoni et al., 1997; Nerad et al., 1996). Additionally, recent data support the idea that immune-gustatory associative learning may be stored in this neo-cortex (Pacheco-López et al., 2005; RamírezAmaya and Bermúdez-Rattoni, 1999; Ramírez-Amaya et al., 1996). In an interesting follow-up report, it was demonstrated that antibody response can be conditioned using electro-acupuncture as a CS (Huang et al., 2004). Following a 1/1 conditioning protocol, OVA (80 μg) was employed as a US, paired with electroacupuncture (at acupoint Zusanli = ST36) as a CS. Thirty days after conditioning, animals were reexposed to the CS and anti-OVA IgG antibody titers were analyzed on days 10, 17, 24, and 31 post-recall. On days 10 and 17 post-recall, a significant augmentation of antibody production was observed as a CR. In order to minimize background responses during conditioning, e.g., stress due to the restraint procedure as a part of the CS, a second experiment was implemented in which association and recall trials were performed under anesthesia. The neutrality of the CS on the CR was assured by a non-contingent conditioned but evoked group. Results clearly indicated that electroacupuncture (CS) and OVA (US) can be associated and recalled under anesthesia. Furthermore, the exclusion of a stress response and other possible associative factors blocked by the anesthesia resulted in a clearer conditioned effect. In this regard, electro-acupuncture effects have also been behaviorally conditioned in humans using imagery as the CS (Ulett, 1996). It is tempting to speculate whether some of the documented effects of acupuncture on the immune system (Joos
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et al., 2000; Karst et al., 2003; Kou et al., 2005; Ye et al., 2002) could be behaviorally conditioned. Hen egg lysozyme (HEL): A Mexican research group developed a 1/1 conditioning protocol in male Wistar rats, pairing saccharin solution (CS) with an intraperitoneal injection of HEL (0.5 mg) as a US (AlvarezBorda et al., 1995). Recall was implemented on day 39 post-association, and blood samples were collected on days 4, 8, 12, and 16 after recall. The rats did not show avoidance behavior to the saccharin. However, the levels of anti-HEL IgM and IgG were significantly enhanced as the CR. Importantly, these conditioned effects did not require further antigen immunization at recall time. Surprisingly, the magnitude of the CR for both IgM and IgG was comparable to the UR after the second antigen administration at peaking timepoints, but the CR kinetics differed from those of the UR. A conditioned but not evoked group was implemented to assure for associative learning and another group to assure CS neutrality. These findings were confirmed by an independent group. However, a much lower magnitude of the conditioned immune response (antibody production) was found, and significant effects were observed for IgG, but not IgM (Madden et al., 2001). With the aim of investigating the neural mechanisms behind this immunoconditioning, brain lesions were performed in the insular cortex, the amygdala, or the dorsal hippocampus before association (RamírezAmaya and Bermúdez-Rattoni, 1999). Results indicate that the insular cortex and the amygdala are brain structures indispensable for associating the CS with the US. Although the hippocampus plasticity is modulated by neuroimmune interactions (Avital et al., 2003; Balschun et al., 2004; Ikegaya et al., 2003), this limbic structure does not seem to be necessary for this associative learning process. Additionally, it was demonstrated that an odor (almond odor) can be successfully employed as a CS and paired with HEL as a US, resulting in a conditioned immune response of similar magnitude at recall time (Ramírez-Amaya and Bermúdez-Rattoni, 1999). The insular cortex lesion blocked the association of this odor-antigen conditioning. Furthermore, data showing that this neo-cortex is not necessary for the development of odor-conditioned avoidance behavior (Kiefer et al., 1982) indicate that this brain structure may be more related to an immune associative process, or at least to immune-visceral sensory processes, rather than to pure aversive/avoidance learning, as has traditionally been assumed. Conversely, a number of studies have demonstrated that amygdala lesion disrupts conditioning when using an odor, but not when using a taste as a CS (Ferry et al., 1995; Hatfield and
Gallagher, 1995). However, conditioned antibody production was blocked in animals with amygdala lesions when using either taste or odor as a CS, indicating that the amygdala may be related to an immune sensory process. Common mechanism for conditioned enhancement of antibody production: Although it has been demonstrated that the CNS is able to detect or sense certain immune signals, such as cytokines or neurotransmitters released by immune cells, it is unlikely that the CNS is able to distinguish specific antigens or epitopes. Rather, the current data indicate that the CNS may be able to codify the immune responses according to their profile, i.e., inflammatory versus non-inflammatory reactions, T-dependent versus B-dependent antigens, as well as the magnitude and localization of the immune response occurring in the periphery (Blalock, 2005; Goehler et al., 2000). However, at recall time the efferent pathways (endocrine/neural) that are involved in the conditioned enhancement of antibody production have not been investigated. Surgical denervations or pharmacological blockades in the periphery may result in a basic delineation of the efferent pathway used by the CNS to promote antibody production. In addition, the specificity of the CR has not been tested yet. It is not known whether the CNS enhances antibody production of all clones activated at recall time, or whether it is able to specify which clone will proliferate. The use of different antigens at association time has been tested in order to analyze the generality of conditioning of antibody production (Espinosa et al., 2004). Two different antigens (KLH or HEL) were employed as a US in a 1/1 conditioning protocol in rats. It seems that one-trial association to induce conditioned enhancement of antibody production is not a general protocol that produces the optimum response for all antigens. For instance, KLH-immunized animals did not show enhancement of KLH-antibody production at recall time, whereas HEL-immunized animals did, indicating that the immune signaling to the CNS might differ from antigen to antigen, resulting in different associative strengths. In fact, Soviet researchers in the early 1960s already reported more rapid association with SRBC as a US than with influenza virus (Il’enko and Kovaleva, 1960). Thus, for some antigens at certain doses, it may be necessary to carry out more association trials in order to induce a stable association with the CS. 2. Anaphylactic Response First indications about the role of associative learning in allergic reactions date back to the nineteenth century (MacKenzie, 1886). An overview of condition-
30. Conditioned Immune Enhancement
ing protocols eliciting an anaphylactic response is shown in Table 4. The first experiments demonstrating an asthma-like response after behavioral conditioning were performed in guinea pigs, when an allergic attack was paired with an auditory stimulus (Noelpp and Noelpp-Eschenhagen, 1951a; Noelpp and NoelppEschenhagen, 1951b; Noelpp and Noelpp-Eschenhagen, 1951c; Noelpp and Noelpp-Eschenhagen, 1952a; Noelpp and Noelpp-Eschenhagen, 1952b; Noelpp and Noelpp-Eschenhagen, 1952c). After five association trials, one out of eight animals displayed the CR, i.e., asthmatic respiration in response to the CS. Additional association trials resulted in a conditioned asthmatic response in three more animals. These initial findings were extrapolated to humans in the mid-1950s, suggesting behavioral conditioning as one of the causes of asthmatic attacks (Dekker et al., 1957). In this case report, two asthmatic patients suffering from skin sensitivities to house-dust extract and grass pollen were exposed to these allergens by inhalation. After a series of conditioning trials, they experienced allergic attacks after inhalation of the neutral solvent used to deliver the allergens. This work showed not only fast conditioning of the asthmatic attack, but also tenacious retention, i.e., low rate extinction. Ottenberg and colleagues demonstrated that administration of a sprayed egg-white solution (US) in a certain context (CS) to immune-sensitized guinea pigs on several daily association trials provoked a UR consisting of respiratory distress (Ottenberg et al., 1958). When the animals were returned to the environmental chamber in which the association had occurred and sprayed with vehicle rather than antigen, a similar response was observed. Furthermore, the CR was completely extinguished in all animals after 13 daily recall trials, supporting the concept of associative learning. These data resulted in the early hypothesis that asthma could be conceived of as a learned response (Turnbull, 1962). Few attempts to elucidate the principles and underlying mechanisms behind this phenomenon were performed until the beginning of the 1980s. Several experiments demonstrated that a conditioned anaphylactic response can be obtained using olfactory stimuli as a CS (Dark et al., 1987; Peeke et al., 1987a; Peeke et al., 1987b; Russell et al., 1984). The UR measured in these studies was an antigen-induced increase in blood histamine levels in animals immunized with bovine serum albumin. A classical discrimination conditioning protocol was employed, in which two distinct olfactory stimuli were used: a positive olfactory stimulus (CS+), which signaled the administration of antigen (US); and a negative olfactory stimulus (CS−), which was not paired with the presentation of the antigen. In this specific protocol, each animal served as its own control,
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since at recall time it was possible to determine the CR elicited after CS+ or CS− presentation. An increase in blood histamine levels in the absence of antigen was observed after presentation of the CS+, but not after the CS−. Importantly, the conditioned histamine release showed a typical extinction process, since the CR magnitude was lower after the second recall trial than after the first. Additionally, it has been shown that mild stress, induced by handling, administered weeks prior to association, predisposes animals to learn the association between the antigen (US) and the odor (CS) (Dark et al., 1987; Peeke et al., 1987b). Furthermore, HPA axis activity also seems to be conditioned during this paradigm; and similar enhancing effects of prior stress were found with circulating cortisol levels as a CR (Peeke et al., 1987a). Interestingly, the conditioning of a cough response in awake guinea pigs was demonstrated following a similar discriminative conditioning protocol (CS+: camphor odor/US: capsaicin), indicating that the CR elicited by the CNS is a complex repertoire of physiological responses orchestrated to protect the organism (Pinto et al., 1995). These results have been replicated employing a 5/1 conditioning protocol, also demonstrating that the release of histamine cannot be recalled under anesthesia (Irie et al., 2001). Furthermore, it has been shown that stress (fasting) immediately after association exacerbates the CR at recall time (Irie et al., 2002). This indicates the sensitivity of this specific CR to stress before and/or after association. Finally, it has been reported that diazepam treatment before recall prevented the conditioned histamine release (Irie et al., 2004), which indicates that this sedative treatment prevents the recall or at least the manifestation of the associative learning process. This finding may have important clinical implications in the management of allergic disease, particularly bronchial asthma, by helping to prevent the stress-anxiety–related airway responses. It has been demonstrated that auditory and visual stimuli (CS) can be associated with the presentation of a specific antigen (US). For instance, MacQueen and colleagues showed that rats were sensitized with a subcutaneous injection of aluminium precipitated ovalbumin (OVA) and an intraperitoneal injection of Bordetella pertussis (MacQueen et al., 1989). Two weeks later, the animals additionally received a larval infection with the nematode Nippostrongylus brasiliensis, in order to produce higher levels of IgE after subsequent antigen injections and to increase the number of mast cells in their intestine. Subsequently, subcutaneous injections of OVA (US) were paired with an auditory/ visual clue (CS) in three association trials. One hour after a single recall trial (CS alone), rat mast cell protease (RMCP) II levels in the serum were enhanced,
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TABLE 4 Unconditioned stimulus Nature Dose Administration route
Odor 3 sec 1% dimethylsulfide or triethylamine
Conditioning protocol Subjects Species Strain Gender
Conditioned responses Immune Others
Association # trials
Rest interval # days
Recall # trials
Bovine serum albumin 0.5 mg inhalated
5
14
1&2
Guinea pig Hartley Male
Increased plasma histamine concentration. Extinguishable CR: i.e., CR after 1st evocation trial > 2nd evocation trial Conditioned increases in plasma cortisol. Additive CR: i.e., CR after 2nd evocation trial > 1st evocation trial
(Russell et al., 1984; Dark et al., 1987; Peeke et al., 1987)
Odor ≈6 min 1% dimethylsulfide
Bovine serum albumin 1.0–3.0 mg/ml inhalated
5
7
1
Guinea pig Hartley Male
Increased plasma histamine concentration 8–10 min post evocation. This CR could not be evoked under anesthesia NR
(Irie et al., 2001; Irie et al., 2002, 2004)
Audio-visual 15 min Light flash (300 ms alternation rate) and continuous sound (ventilation fan)
Ovalbumin (OVA) 300 mg s.c.
3
11
1
Rat SpragueDawley Male
Increased levels of rat mast cell protease II in plasma 1 h after evocation NR
(MacQueen et al., 1989)
Audio-visual 15 min Light flash (10 W green lamp) and continuous sound (ventilation fan)
Ovalbumin (OVA) 40 mg/kg inhalated
3
7
1
Rat Wistar Male
High levels of lung anaphylactic response immediately post evocation Conditioned increases in plasma corticosterone
(Palermo-Neto & Guimarães, 2000)
NR: Not Reported
Ref.
III. Behavior and Immunity
Conditioned stimulus Nature Duration Description
Overview of the Conditioning Protocols Enhancing Anaphylactic Response
30. Conditioned Immune Enhancement
suggesting that the degranulation of mucosal mast cells was the conditioned immune response. Five hours after recall, serum RMCP II levels did not significantly differ from control groups. A strong anaphylactic response in the lung as conditioned response was recently reported following the same conditioning protocol (Palermo-Neto and Guimarães, 2000). In addition, they reported high levels of stress and anxiety post-recall, and demonstrated that the audio-visual stimulus (CS) was stressful and anxiogenic, per se. Another set of animal studies supports the associability of environmental stimuli (CS) with anaphylactic shock reaction (Djuric et al., 1987; Djuric et al., 1988; Markovic et al., 1988; Markovic et al., 1992). Rats sensitized with OVA were given an injection of the same antigen to elicit a second anaphylactic shock response in a context different from that in which the first anaphylactic shock was induced. Animals experiencing both anaphylactic shocks in the same context displayed a much smaller shock than rats subjected to the second shock in a different context. Repeated, unreinforced presentation of the antigen in the new context prior to the CS and the induction of the first anaphylactic shock prevented the increased resistance to the induction of a second anaphylactic shock reaction. These findings were ascribed to the CR which attenuated the UR (anaphylactic shock). Additionally, it has been demonstrated that rats immunized with a shock-inducing dose of OVA exhibit a conditioned aversion to the taste (CS) with which it was previously associated (Djuric et al., 1987). Conditioned taste avoidance was found 8 weeks after the association trial, and pre-exposure to the CS weakened the CR (i.e., latent inhibition). Interestingly, this avoidance behavioral CR was obtained following three different modes of CS-US presentation at association time: (1) CS orally/US i.v., (2) CS orally/ US i.p., and (3) CS i.v./US i.v. (Markovic et al., 1988). Furthermore, a dose-response relationship between the amount of antigen used for the induction of anaphylactic shock and the conditioned taste avoidance was demonstrated: the higher the antigen dose, the more pronounced the conditioned taste avoidance (Djuric et al., 1988). Accordingly, it has recently been shown that OVA-immunized mice avoid the context previously associated with presentation of the allergen against which they have been immunized (Costa-Pinto et al., 2005). In a modified classical passive avoidance test, OVA aerosol was employed as an aversive stimulus (US); albeit attracted by the supposedly safer, dark compartment of the apparatus (CS), OVA-immunized mice avoided entering the dark side, preferring the bright (usually aversive) side of the box. When CNS activity was tracked using c-Fos expression as a neuronal metabolic marker, allergic animals showed
649
enhanced c-Fos immunoreactivity in the hypothalamic paraventricular nucleus and central nucleus of the amygdala after airway OVA challenge. These brain structures are commonly linked to emotional and affective behavioral patterns that are important components in the development of learned aversive behavior, such as conditioned taste aversion/ avoidance (Bermúdez-Rattoni, 2004). Allergic asthma proceeds through two distinct phases: an immediate response mediated by IgE and mast cells; and a late phase, during which the presence of Th2 cells, eosinophils, and other immune cells is evident (Maddox and Schwartz, 2002). It will, therefore, be relevant to determine the messenger(s) and afferent pathway(s) by which the immune system signals the CNS. Since activation of the hypothalamic paraventricular nucleus and central nucleus of the amygdala has been detected 90 minutes after nasal OVA challenge, it is likely that the immediate hypersensitivity reaction, which is dependent on IgE-mediated mastcell deregulation with the concomitant histamine release, plays a major role in the brain activation reported (Costa-Pinto et al., 2005). However, both the early and late phases of the allergic responses may mediate the learned avoidance behavior to the dark side of the cage. This behavioral CR was displayed in animals receiving multiple aerosol OVA challenges, and consequently there was an ongoing inflammatory lung reaction, as well as high levels of IgE. 3. Delayed-type Hypersensitivity Cell-mediated immunity is defined as a beneficial host response characterized by an expanded population of specific T-cells, which, in the presence of antigens, produce cytokines locally. The activation and recruitment of cells into an area of inflammation are a crucial step in the development of certain cellular immune responses, e.g., delayed-type hypersensitivity (DTH). The data summarizing these conditioning protocols are shown in Table 5. It has been demonstrated that, depending on the concentration and the timing, cyclophosphamide (CY) can suppress an initial DTH response and enhance the response to subsequent antigenic challenge (Bovbjerg et al., 1986). Based on such a phenomenon, DTH response has been reported to be enhanced as a CR, when CY is employed as US (Bovbjerg et al., 1987). In this conditioning paradigm, three daily association trials were employed in which a saccharin solution (CS) was paired with an intraperitoneal injection of CY (50 mg/kg) as the US. Three weeks later, all animals were sensitized to SRBC, and 2 days later, conditioned animals were re-exposed to the CS (sac-
650
TABLE 5 Conditioned stimulus Nature Duration Description
Overview of the Conditioning Protocols Enhancing Adaptive Cellular Immune Responses
Unconditioned stimulus Nature Dose Administration route
Conditioning protocol Association # trials
Rest interval # days
Recall # trials
Subjects Species Strain Gender
Conditioned responses Immune Others
Ref.
Alloantigen (skin graft) from C57BL/6 mice 1.0 cm2 Abdominal dermis
3
40
1, 2, 3 &4
Mouse CBA/J Male
Increased in cytotoxic T lymphocyte precursors in blood 2 days post evocation. Extinguishable CR: i.e., CR after 1st evocation trial > 2nd evocation trial > 3rd evocation trial NR
(Gorczynski et al., 1982)
Odor 60 min Camphor
Alloantigen (spleen cells) from C57BL/6 mice 1.5 × 107 i.p.
1
5
1
Mouse BALB/c Female
Increased splenic CTL cells activity 1 day post evocation NR
(Hiramoto et al., 1993)
Taste 60 min + 0.1–0.2 ml 0.1% saccharin
Cyclophosphamide 50 mg/kg i.p.
3
23
3
Mouse CD-1 Male
Increased in delayed-type hypersensitivity peaking at 7 days post last evocation Conditioned taste aversion
(Bovbjerg et al., 1987)
Taste 10 min 0.1% saccharin
Levamisole 3 mg/rat s.c.
1
14
1
Rat Wistar NR
Increased T helper: T suppressor subset ratio 24 h post evocation Conditioned taste aversion
(Husband et al., 1987)
Taste 15 min 0.2% saccharin
Staphylococcal enterotoxin B (SEB) 2.0 mg/kg i.p.
1
6
1
Rat Dark agouti Male
Increased IL-2 and INF-γ plasma levels at 2 h post evocation Conditioned taste aversion and corticosterone plasma increments
(Pacheco-López et al., 2004)
NR: Not Reported
III. Behavior and Immunity
Multi-sensory ≈91/2 days Grafting procedure
30. Conditioned Immune Enhancement
charin), alone, on 3 consecutive days. On the second recall trial, conditioned animals and controls received another CY injection. Later, three SRBC-challenges were employed to detect the DTH response. The results indicate that the DTH response was enhanced in conditioned animals after the second and third challenges. However, this specific CR may actually represent a conditioned immunosuppressive effect (Ader and Cohen, 2001), since CY applied on the second recall trial may depress suppressor cell function (Gill and Liew, 1978). 4. T-Cell Function Cytotoxic T lymphocyte (CTL) numbers were reported to be increased as a result of a 3/3 conditioning protocol (Gorczynski et al., 1982). CBA/J mice were repeatedly grafted with skin from C57BL/6 mice. Association was achieved by pairing the CS (the surgical procedure: shaving, anesthetizing, grafting, banding) and the US (the skin graft). This procedure was repeated three times at an interval of 40 days. At recall, all groups received a sham graft, i.e., the CS without the US, and conditioned animals displayed an increase in CTL precursor numbers as a CR. However, only 50–60% of the conditioned animals showed this conditioned immune response. Those animals that displayed the CR (responders) were subdivided into two groups that were subsequently given two further recall trials in order to develop extinction, or two further association trials in order to reinforce the CR. After 40 days of rest, both groups were submitted to a further recall trial. The results showed that the CR was either extinguished or reinforced after repeated extinction or reinforcement trials, respectively, clearly indicating an associative learning phenomenon. Following a 1/1 conditioning protocol, CTL activity has been reported to be enhanced as a CR (Demissie et al., 2000; Hiramoto et al., 1993b). At association, BALB/c mice were immunized with splenocytes from C57BL/6 mice (US), and this procedure was paired with an exposure to camphor odor (CS). A recall trial was implemented 6 days later, in which conditioned animals were exposed to the CS. Enhanced CTL activity was observed 24 hours post-recall. In a next step, naltrexone, a central and peripheral opioid receptor blocker, was administered before recall. This treatment blocked the recall of the CR (CTL activity) due to a central opioid blockade, since quaternary naltrexone, a peripheral opioid receptor blocker, did not affect the conditioned increase in CTL activity. In rats, levamisole injection results in an elevation of the T helper : T suppressor subset ratio due to a selective depression in the cytotoxic/suppressor
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subset. This response was shown to be elicited as a CR through a 1/1 conditioning protocol (Husband et al., 1987). Saccharin solution (CS) was paired with levamisole (3 mg) administration (US), and 14 days later a single recall trial (CS only) was employed to recall this associative learning. One day after recall, T-cell subsets were assessed, indicating that the T helper : T suppressor ratio was enhanced. 5. Cytokines Cytokines are soluble glycoproteins released by cells of the immune system, which act non-enzymatically through specific receptors to regulate immune responses. Cytokines resemble hormones in that they act at low concentrations bound with high affinity to a specific receptor. Pro-inflammatory cytokines such as IL-1, IL-6, and tumor necrosis factor (TNF)-α are produced predominantly by activated immune cells, such as macrophages, and are involved in the amplification of inflammatory reactions. Anti-inflammatory cytokines such as IL-10, IL-4, and IL-12 are involved in the reduction of inflammatory reactions (Janeway et al., 2005). Due to the immunoregulatory properties of cytokines, the possibility of enhancing the production of cytokines by behavioral conditioning has been repeatedly addressed but mainly without success (Goebel et al., 2005; Mormède et al., 2003). It is likely that one of the major issues in those experiments was the nature of the US. If the immune response induced by the US is weak, slow, and long-lasting, then the CNS may not be able to detect these changes in the periphery, resulting in a weak association with the CS. Another key factor may be the number of association trials employed. The use of superantigens as the US in a conditioning paradigm has several advantages, since it induces strong, rapid, and transient immune stimulation (Proft and Fraser, 2003). It has been demonstrated that, when superantigen administration was preceded by exposure to a novel taste, the animals were able to associate those stimuli and later elicit a complex CR (PachecoLópez et al., 2004). At association time, the taste of saccharin (CS) was paired with an intraperitoneal injection of staphylococcal enterotoxin B (SEB) as the US. SEB is a superantigen that induces strong and transient T-cell activation, followed by increased cytokine production, mainly IL-2, IFN-γ, and TNF-α. In addition to these immune effects, SEB immunization induces significant changes in endocrine, neurobiological, and behavioral functions (Gonzalo et al., 1993; Kusnecov and Goldfarb, 2005; Shurin et al., 1997). At recall time, conditioned animals were exposed to the
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CS, resulting in enhanced IL-2 plasma levels as a conditioned immune response. The HPA axis also seemed to be conditioned, since plasma corticosterone levels were enhanced as well after recall (conditioned endocrine response). Furthermore, conditioned animals demonstrated a behavioral CR, since a strong taste avoidance to the CS was observed. The mechanisms of behavioral conditioning using SEB as the US are still not known. However, at association, it may involve T-cell–derived cytokines signaling to the brain. This hypothesis is supported by previous work demonstrating that central monoamine activity is modified by systemic IL-2 administration (Lacosta et al., 2000). Similar results were reported after SEB immunization, since striatum catecholamine levels followed a dose-response curve in reaction to increased amounts of peripheral SEB immunization (PachecoLópez et al., 2004). At recall time the efferent pathway has not been investigated, and the cellular origin of the IL-2 is not known.
III. CLINICAL AND ADAPTIVE RELEVANCE OF CONDITIONED IMMUNE ENHANCEMENT Conditioning experiments performed in humans have revealed the possibility of enhancing immune activity, indicating the feasibility of modulating immune reactivity through behavioral approaches. One study has shown that NK cell activity may be enhanced by behavioral conditioning, after pairing a subcutaneous injection of epinephrine as a US with a novel taste as a CS (Buske-Kirschbaum et al., 1992). However, the results could not be confirmed in a follow-up study (Kirschbaum et al., 1992). Although not conclusive—and still controversial (see Ader and Cohen, 2001), interesting results suggest that behavioral conditioning regulates tumor growth (Ghanta et al., 1987b; Ghanta et al., 1988; Ghanta et al., 1990; Hiramoto et al., 1991b), as well as reverses the immune senescence process (Spector, 1996; Spector, 1999; Spector et al., 1994).
A. Conditioned Immune Enhancement as Supportive Therapy It may be advisable to treat several idiopathic illnesses or syndromes with various therapeutic approaches in order to optimize the outcome. In this context, behavioral conditioning regimens should be employed as complementary therapy supporting the pharmacological treatment and ameliorating undesired pharmacological side effects.
1. Cancer: Tumor Progression Behavioral conditioning as supportive therapy has been delineated in the context of cancer treatment (Bovbjerg, 2003; Hiramoto et al., 1991b; Spector, 1996). Pioneer experiments performed at the University of Alabama reported that female BALB/c mice inoculated with a transplanted MOPC 104E myeloma were able to reverse the growth of the tumor and enhance survival as a function of the conditioned immune response (Ghanta et al., 1987a). The conditioning protocol was composed of 10 association trials (CS: camphor, US: poly I : C) at 3-day intervals. One day after the last association trial, animals were inoculated with the tumor. One day post-inoculation, animals were re-exposed to the camphor odor and subsequently every third day. The findings indicate that for the conditioned group there was an increase in median survival on day 43, compared to days 34, 37, and 38 of various control groups. Actually, two of these conditioned mice lived more than 120 days; they had shown early tumor growth but were free of disease on day 97. Although the group differences could be explained by the differences due to the outliers, an alternative hypothesis is that through behavioral conditioning, immune tolerance was induced in some animals by unknown mechanisms. The neutrality of 1-hour (Ghanta et al., 1988) and 4hours (Ghanta et al., 1987a) exposure to camphor odor (CS) on the tumor growth was documented. In summary, these results indicate that conditioning has beneficial effects on tumor control. However, tumor inoculation took place after the association phase, complicating further applications in clinical settings. A second series of experiments was performed in the following order: tumor inoculation → conditioning. Results showed conditioned resistance against the YC8 lymphoma in female BALB/c mice (Ghanta et al., 1990). YC8-specific resistance seems to be conferred by immunizing BALB/c mice with DBA/2 splenocytes (Parmiani et al., 1982; Sensi et al., 1986); therefore, DBA/2 spleen cells were used as a US (alloantigen) paired with a CS (camphor odor 1 h). Several conditioning protocols were implemented (2/6, 3/5, 4/4), with the first association trial always taking place 5 days after tumor implantation. Association trials were separated by 2 or 3 days, and recall trials by 2 or 7 days. The rest interval between association and recall varied from 2 days (3/5 conditioning) or 3 days (2/6 conditioning), to 7 days (4/4 conditioning). The tumor size was measured, and the mortality rate was recorded to evaluate the effects of conditioning and immunotherapy. Results indicate that tumor growth and sur-
30. Conditioned Immune Enhancement
vival are improved by conditioning protocols in the following odd order: 3/5 > 4/4 > 2/6. Astonishingly, the results also indicated that regulation of tumor growth (as measured by growth delay) through behavioral conditioning was more effective than the immunotherapy treatment itself. Finally, it was shown that camphor odor exposure by itself does not trigger tumoricidal activity (i.e. CS neutrality). In a follow-up report, similar results were observed following a 4/4 conditioning protocol, pairing camphor odor (CS) with DBA/2 splenocytes (US) (Hiramoto et al., 1991b). Mice were then subcutaneously injected with YC8 tumor cells. Five days post-implantation, the animals were submitted to the association phase (four trials, each separated by 2 or 3 days), and 14 days afterwards the animals were evoked. Three further recall trials were employed on days 26, 33, and 40 post-tumor implantation. Results indicate that the conditioned group which was re-exposed to the CS at weekly intervals appeared to resist tumor growth, as evidenced by the slower growth of the tumor and by an increase in the survival of this group versus controls. Although these studies suggest that behavioral conditioning improves the survival rate of experimental animals after tumor inoculation, this effect seems to be modest. Moreover, a number of questions must be addressed in order to improve the conditioning process and the effects on immune functions. For instance, it is not known how long the CR can be maintained in each animal after recall. Since it may be necessary to apply reinforcement at appropriate intervals, is reconditioning possible? As tumors appear frequently in elderly life stages, how do gender and age affect this conditioned immune response?
B. Conditioned Immune Enhancement as an Adaptive Process Neuroimmune interactions appear to bring several adaptive advantages to those organisms that acquired and further developed during ontogeny and phylogeny (Ottaviani et al., 1998; Tada, 1997). A complex repertoire of physiological responses, including immune, endocrine, neural, and behavioral responses, may be orchestrated to achieve a better adaptation of the organism to a constantly challenging environment. For example, one interesting hypothesis regarding psychoneuroimmunological interactions has been delineated: It associates the adolescent’s acne, timed to cortical development of the brain, as an adaptive evolutionary strategy of Homo sapiens; delaying the mate choice (although reproductively mature) until the indi-
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viduals are emotionally, intellectually, and physically fit to be parents (Bloom, 2004). In vertebrates, it is well established that there are many intricate interactions between the immune and nervous systems, and vice versa (Ottaviani and Franceschi, 1996; Salzet et al., 2000; Straub and Besedovsky, 2003; Vishwanath, 1996). Recently, it has been demonstrated that invertebrate biology has also evolved around acquiring and developing complex neuroimmune communication. For example, interaction between neurons and immune cells has been demonstrated in the mollusk Aplysia californica (Clatworthy, 1998). Furthermore, invertebrates also express neuropeptides (e.g., opioids) in the neural and immune tissues, which play a key role as neuroimmune messengers during their evolution (Salzet et al., 2000). Neuroimmune complexity appears as well in the behavior of insects, for example, in the linkage between the immune system and the nervous system of the bee (Mallon et al., 2003; Schedlowski, 2006). Non-infected honey bees whose immune systems were challenged by a non-pathogenic immunogenic elicitor (lipopolysaccharide) displayed a reduced ability to associate an odor with sugar reward in a classical conditioning paradigm. Classical conditioning can be understood as learning about the temporal or causal relationships between external and internal stimuli to allow for the appropriate preparatory set of responses before biologically significant events occur (Rescorla, 1988; Rescorla, 2003). In this regard, the capacity to associate a certain immune response or status (e.g., allergens, toxins, antigens) with a specific stimulus (e.g., environments or flavors) is of high adaptive value; we consider that it was acquired during evolution as an adaptive strategy in order to protect the organism and/or prepare it for danger. Furthermore, such associative learning is typically acquired under certain stressful conditions. For example, the exposure to a specific antigen (and its categorization as an allergen) might be associated (learning) with a specific environment or food. An adaptive response is then elicited (memory), consisting first of a behavioral modification, in order to avoid the place or food associated with the antigen (Costa-Pinto et al., 2005; Djuric et al., 1987). If this is not possible, the organism will try to reduce the contact with the allergen, i.e., by coughing or sneezing (Pinto et al., 1995), and, at the same time, its immune system may prepare the body for interaction with the antigen, for instance: mast cell degranulation (Irie et al., 2001; MacQueen et al., 1989; Palermo-Neto and Guimarães, 2000; Russell et al., 1984) or antibody production (Ader et al., 1993; Alvarez-Borda et al., 1995; Chen et al., 2004; Husband et al., 1993). Although under experimental conditions such associative learning can be extin-
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guished, it is likely that it will last for a long time, since, in natural situations, the organism will try to avoid contact with the environmental clues that signal the CS. 1. Perspectives and Summary Conceptualizing Pavlovian conditioning as a mechanism by which an organism anticipates the onset of a biologically important event (the US) and initiates preparatory responses (CR) to allow the organism to deal better with the US effects invites the hypothesis that one reason for the neural control of immunity lies in accommodating the adaptive value of classical conditioning. In its natural environment, an animal with a cut or a scratch has to build up immunological defense against micro-organisms. In the laboratory or a clinical setting, an antigen is reliably preceded by an injection. Therefore, conditioned immune effects may, in fact, be very common. The difficulty for the investigator lies not so much in inducing such responses, but in employing the proper controls, both immunological and psychological, in order to demonstrate that these responses exist and to expose the underlying mechanism.
C. Expectations Regarding Immunoconditioning Due to the physiological basis of the conditioned effects, the magnitude of the conditioned immune response should not be expected to override the homeostatic balance of the organism. However, this does not mean that conditioned effects on immune functions are not of biological/clinical significance, as has been reviewed here and in previous work (Ader, 2003). A very small increase in the potential of the immune system may be of great value in the fight against pathogens when the system reaches an allostatic load (McEwen, 1998; McEwen and Lasley, 2003), but it may increase the occurrence and severity of allergies and autoimmune disorders in other conditions. It is important to emphasize that several immune responses may be affected by behavioral conditioning protocols, but this does not necessarily imply that such immune responses were conditioned. Due to the complexity of neuroimmune interaction, such differentiation is not easy to establish. As has been reviewed in this chapter, the use of a US with immune consequences, such as immunomodulating drugs or antigens, is not the only requirement for genuinely conditioning an immune response through a behavioral protocol. Experimental data reflect a dichotomy
that is possibly supported by different mechanisms and therefore might follow different rules. In our own experience and after reviewing the available literature, we conclude that a key feature for associative learning is when the direction of the CR is maintained during conditioning; i.e., the direction of this response should be independent of the immune, endocrine, and circadian status of the subject at association and recall time. Before behavioral immunoconditioning is implemented as supportive therapy together with traditional pharmacological regimens, it is essential to describe some of its features. For example, it is not known how long conditioned immune responses last and how immune specific they are. Since it may be necessary to apply reinforcement at appropriate intervals, the question arises as to whether re-conditioning is possible. Since at some time the therapy will stop, what is the forgetting pattern of conditioned immune responses? How predictable is the conditioned immune response in a human population with different immune and psychological histories? What is the impact of age and gender on immunoconditioning? When using immunomodulating drugs as the US, are some side effects also conditioned? To date, experimental evidence indicates that behavioral conditioning may have practical implications in a clinical setting and be of use as supportive therapy, with the aim of reducing undesired side effects and maximizing the effects of pharmacological therapies. For instance, immunosuppressive status in humans could be achieved by combining the pharmacological effects of cyclosporine A with intermittent recall trials of its association with a specific exteroceptive clue (e.g., gustative stimulus) (Goebel et al., 2002).
IV. SUMMARY In this chapter we have reviewed and summarized the current data indicating that both innate and adaptive immune responses are affected by behavioral conditioning protocols. An understanding of the effects of behavioral conditioning on immune functions is beginning to emerge, with potential clinical applications. In future studies it will be essential to analyze the afferent and efferent pathways in brain-to-immune communication before behavioral conditioning paradigms can be employed as beneficial tools in a clinical setting. Finally, the research on behavioral immunoconditioning has revealed that the organism has important adaptive psychoneuroimmune strategies, acquired to deal with the constantly changing and challenging environment in a better way.
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References Ader, R. (1981). A historical account of conditioned immunobiologic responses. In R. Ader (Ed.), Psychoneuroimmunology (pp. 321– 352): New York: Academic Press. Ader, R. (2003). Conditioned immunomodulation: research needs and directions. Brain Behav. Immun., 17 (Suppl 1), S51–57. Ader, R., and Cohen, N. (1975). Behaviorally conditioned immunosuppression. Psychosom. Med., 37, 333–340. Ader, R., and Cohen, N. (1991). The influence of conditioning on immune responses. In R. Ader, D. Felten, and N. Cohen (Eds.), Psychoneuroimmunology (pp. 611–646). New York: Academic Press. Ader, R., and Cohen, N. (2001). Conditioning and immunity. In R. Ader, D. Felten, and N. Cohen (Eds.), Psychoneuroimmunology (vol. 2, pp. 3–34). New York: Academic Press. Ader, R., Kelly, K., Moynihan, J., Grota, L., and Cohen, N. (1993). Conditioned enhancement of antibody production using antigen as the unconditioned stimulus. Brain Behav. Immun., 7, 334–343. Alvarez-Borda, B., Ramírez-Amaya, V., Pérez-Montfort, R., and Bermúdez-Rattoni, F. (1995). Enhancement of antibody production by a learning paradigm. Neurobiol. Learn. Mem., 64, 103–105. Artico, M., Bosco, S., Cavallotti, C., Agostinelli, E., Giuliani-Piccari, G., Sciorio, S., Cocco, L., and Vitale, M. (2002). Noradrenergic and cholinergic innervation of the bone marrow. Int. J. Mol. Med., 10, 77–80. Avital, A., Goshen, I., Kamsler, A., Segal, M., Iverfeldt, K., RichterLevin, G., and Yirmiya, R. (2003). Impaired interleukin-1 signaling is associated with deficits in hippocampal memory processes and neural plasticity. Hippocampus, 13, 826–834. Baciu, I., Sotuz, V., Stoica, N., and Raducanu, N. (1965). Sur les centres nerveux régulateurs de l’erythropoièse. Rev. Roum. Physiol., 2, 123–133. Balschun, D., Wetzel, W., Del Rey, A., Pitossi, F., Schneider, H., Zuschratter, W., and Besedovsky, H. (2004). Interleukin-6: a cytokine to forget. FASEB J., 18, 1788–1790. Benetato, G. (1955). Central nervous mechanism of the leukocytic and phagocytic reaction. J. Physiol. (Paris), 47, 391–403. Benetato, G., Baciu, I., Vitebski, V., Derevenco, V., and Telia, M. (1952). Despre rolul scoartie cerebrale in activarea sistemului fagocitar si mobilizarea anticorpilor. Studii si. cercetari ale Fil. Acad. R.P.R. Chij., 8, 264–270. Berman, D., and Dudai, Y. (2001). Memory extinction, learning anew, and learning the new: dissociations in the molecular machinery of learning in cortex. Science, 291, 2417–2419. Bermúdez-Rattoni, F. (2004). Molecular mechanisms of tasterecognition memory. Nat. Rev. Neurosci., 5, 209–217. Bermúdez-Rattoni, F., Introini-Collison, I., Coleman-Mesches, K., and McGaugh, J. (1997). Insular cortex and amygdala lesions induced after aversive training impair retention: effects of degree of training. Neurobiol. Learn. Mem., 67, 57–63. Blalock, J. (2005). The immune system as the sixth sense. J. Intern. Med., 257, 126–138. Bloom, D. (2004). Is acne really a disease?: a theory of acne as an evolutionarily significant, high-order psychoneuroimmune interaction timed to cortical development with a crucial role in mate choice. Med. Hypotheses, 62, 462–469. Boehm, G., Karp, J., Grota, L., Moynihan, J., Cohen, N., and Ader, R. (1998). Failure to replicate conditioned enhancement of antibody production following single-trial learning paradigms using antigen as the unconditioned stimulus. Neuroimmunomodulation, 5, 67.
655
Bovbjerg, D. (2003). Conditioning, cancer, and immune regulation. Brain Behav. Immun., 17 (Suppl 1), S58–61. Bovbjerg, D., Ader, R., and Cohen, N. (1986). Long-lasting enhancement of the delayed-type hypersensitivity response to heterologous erythrocytes in mice after a single injection of cyclophosphamide. Clin. Exp. Immunol., 66, 539–550. Bovbjerg, D., Cohen, N., and Ader, R. (1987). Behaviorally conditioned enhancement of delayed-type hypersensitivity in the mouse. Brain Behav. Immun., 1, 64–71. Brittain, R., and Wiener, N. (1985). Neural and Pavlovian influences on immunity. Pavlov J. Biol. Sci., 20, 181–194. Buske-Kirschbaum, A., Grota, L., Kirschbaum, C., Bienen, T., Moynihan, J., Ader, R., Blair, M., Hellhammer, D., and Felten, D. (1996). Conditioned increase in peripheral blood mononuclear cell (PBMC) number and corticosterone secretion in the rat. Pharmacol. Biochem. Behav., 55, 27–32. Buske-Kirschbaum, A., Kirschbaum, C., Stierle, H., Lehnert, H., and Hellhammer, D. (1992). Conditioned increase of natural killer cell activity (NKCA) in humans. Psychosom. Med., 54, 123–132. Carew, T., and Sahley, C. (1986). Invertebrate learning and memory: from behavior to molecules. Annu. Rev. Neurosci., 9, 435–487. Chao, H., Hsu, Y., Yuan, H., Jiang, H., and Hsueh, C. (2005). The conditioned enhancement of neutrophil activity is catecholamine dependent. J. Neuroimmunol., 158, 159–169. Chen, J., Lin, W., Wang, W., Shao, F., Yang, J., Wang, B., Kuang, F., Duan, X., and Ju, G. (2004). Enhancement of antibody production and expression of c-Fos in the insular cortex in response to a conditioned stimulus after a single-trial learning paradigm. Behav. Brain Res., 154, 557–565. Clatworthy, A. (1998). Neural-immune interactions—an evolutionary perspective. Neuroimmunomodulation, 5, 136–142. Cohen, N. (2006). The uses and abuses of psychoneuroimmunology: a global overview. Brain Behav. Immun., 20, 99–112. Costa-Pinto, F. A., Basso, A. S., Britto, L. R. G., Malucelli, B. E., and Russo, M. (2005). Avoidance behavior and neural correlates of allergen exposure in a murine model of asthma. Brain Behav. Immun., 19, 52–60. Czura, C., and Tracey, K. (2005). Autonomic neural regulation of immunity. J. Intern. Med., 257, 156–166. Dark, K., Peeke, H., Ellman, G., and Salfi, M. (1987). Behaviorally conditioned histamine release. Prior stress and conditionability and extinction of the response. Ann. N.Y. Acad. Sci., 496, 578–582. Dekker, E., Pelser, H., and Groen, J. (1957). Conditioning as a cause of asthmatic attacks; a laboratory study. J. Psychosom. Res., 2, 97–108. Demissie, S., Ban, E., Rogers, C., Hiramoto, N., Ghanta, V., and Hiramoto, R. (1997). Afferent signals to the CNS appear not to condition the modulation of interleukin-1 receptors in the hippocampus. Neuroimmunomodulation, 4, 298–304. Demissie, S., Ghanta, V., Hiramoto, N., and Hiramoto, R. (2000). NK cell and CTL activities can be raised via conditioning of the CNS with unrelated unconditioned stimuli. Int. J. Neurosci., 103, 79–89. Dhabhar, F., and Viswanathan, K. (2005). Stress and the augmentation of immune function. In C. Schütt and H. Hannich (Eds.), Stress, behavior and immune response (pp. 53–65). Lengerich: Pabst Science Publishers. Djuric, V., Markovic, B., Lazarevic, M., and Jankovic, B. (1987). Conditioned taste aversion in rats subjected to anaphylactic shock. Ann. N.Y. Acad. Sci., 496, 561–568. Djuric, V., Markovic, B., Lazarevic, M., and Jankovic, B. (1988). Anaphylactic shock-induced conditioned taste aversion. II. Correla-
656
III. Behavior and Immunity
tion between taste aversion and indicators of anaphylactic shock. Brain Behav. Immun., 2, 24–31. Dolin, A., Krylov, V., Luk’ianenko, V., and Flerov, B. (1960). Recent experimental data on conditioned reflex production and inhibition of immune and allergic reactions. Zh. Vyssh. Nerv. Deiat. Im. I. P. Pavlova, 10, 832–841. Domjan, M. (1973). Role of ingestion in odor-toxicosis learning in the rat. J. Comp. Physiol. Psychol., 84, 507–521. Domjan, M. (2005). Pavlovian conditioning: a functional perspective. Annu. Rev. Psychol., 56, 179–206. Downing, J., and Miyan, J. (2000). Neural immunoregulation: emerging roles for nerves in immune homeostasis and disease. Immunol. Today, 21, 281–289. Eikelboom, R., and Stewart, J. (1982). Conditioning of drug-induced physiological responses. Psychol. Rev., 89, 507–528. Elenkov, I., Wilder, R., Chrousos, G., and Vizi, E. (2000). The sympathetic nerve—an integrative interface between two supersystems: the brain and the immune system. Pharmacol. Rev., 52, 595–638. Engler, H., Bailey, M., Engler, A., and Sheridan, J. (2004). Effects of repeated social stress on leukocyte distribution in bone marrow, peripheral blood and spleen. J. Neuroimmunol., 148, 106–115. Espinosa, E., Calderas, T., Flores-Muciño, O., Pérez-García, G., Vázquez-Camacho, A., and Bermúdez-Rattoni, F. (2004). Enhancement of antibody response by one-trial conditioning: contrasting results using different antigens. Brain Behav. Immun., 18, 76–80. Fanselow, M., and Poulos, A. (2005). The neuroscience of mammalian associative learning. Annu. Rev. Psychol., 56, 207–234. Ferry, B., Sandner, G., and Di Scala, G. (1995). Neuroanatomical and functional specificity of the basolateral amygdaloid nucleus in taste-potentiated odor aversion. Neurobiol. Learn. Mem., 64, 169–180. Ferry, B., Wirth, S., and Di Scala, G. (1999). Functional interaction between entorhinal cortex and basolateral amygdala during trace conditioning of odor aversion in the rat. Behav. Neurosci., 113, 118–125. Fortier, M., Kent S., Ashdown, H., Poole, S., Boksa, P., and Luheshi, G. (2004). The viral mimic, polyinosinic : polycytidylic acid, induces fever in rats via an interleukin-1-dependent mechanism. Am. J. Physiol. Regal. Integr. Comp. Physiol., 287, R759–766. Garcia, J., Ervin, E., and Koelling, R. (1966). Learning with prolonged delay of reinforcement. Psychon. Sci., 5, 121–122. Ghanta, V., Hiramoto, N., Solvason, H., Soong, S., and Hiramoto, R. (1990). Conditioning: a new approach to immunotherapy. Cancer Res., 50, 4295–4299. Ghanta, V., Hiramoto, N., Solvason, H., Tyring, S., Spector, N., and Hiramoto, R. (1987a). Conditioned enhancement of natural killer cell activity, but not interferon, with camphor or saccharin-LiCl conditioned stimulus. J. Neurosci. Res., 18, 10–15. Ghanta, V., Hiramoto, R., Solvason, B., and Spector, N. (1987b). Influence of conditioned natural immunity on tumor growth. Ann. N.Y. Acad. Sci., 496, 637–646. Ghanta, V., Hiramoto, R., Solvason, H., and Spector, N. (1985). Neural and environmental influences on neoplasia and conditioning of NK activity. J. Immunol., 135, 848s–852s. Ghanta, V., Miura, T., Hiramoto, N., and Hiramoto, R. (1988). Augmentation of natural immunity and regulation of tumor growth by conditioning. Ann. N.Y. Acad. Sci., 521, 29–42. Ghanta, V., Rogers, C., Hsueh, C., Demissie, S., Lorden, J., Hiramoto, N., and Hiramoto, R. (1994). Role of arcuate nucleus of the hypothalamus in the acquisition of association memory between the CS and US. J. Neuroimmunol., 50, 109–114. Gill, H., and Liew, F. (1978). Regulation of delayed-type hypersensitivity. III. Effect of cyclophosphamide on the suppressor cells
for delayed-type hypersensitivity to sheep erythrocytes in mice. Eur. J. Immunol., 8, 172–176. Glanzman, D. (1995). The cellular basis of classical conditioning in Aplysia californica—it’s less simple than you think. Trends. Neurosci., 18, 30–36. Goebel, M. U., Trebst, A. E., Steiner, J., Xie, Y. F., Exton, M. S., Frede, S., Canbay, A. E., Michel, M. C., Heemann, U., and Schedlowski, M. (2002). Behavioral conditioning of immunosuppression is possible in humans. FASEB J, 16, 1869–1873. Goebel, M., Hübell, D., Kou, W., Janssen, O., Katsarava, Z., Limmroth, V., and Schedlowski, M. (2005). Behavioral conditioning with interferon beta-1a in humans. Physiol. Behav., 84, 807–814. Goehler, L., Gaykema, R., Hansen, M., Anderson, K., Maier, S., and Watkins, L. (2000). Vagal immune-to-brain communication: a visceral chemosensory pathway. Auton. Neurosci., 85, 49–59. Gonzalo, J., González-García, A., Martínez, C., and Kroemer, G. (1993). Glucocorticoid-mediated control of the activation and clonal deletion of peripheral T cells in vivo. J. Exp. Med., 177, 1239–1246. Gorczynski, R. (1987). Conditioned immunosuppression in young versus aged mice: differences in cells and responses to environmental stimuli lead to altered conditioning in aged animals. Brain Behav. Immun., 1, 306–317. Gorczynski, R. (1991). Toward an understanding of the mechanisms of classical conditioning of antibody responses. J. Gerontol., 46, P152–156. Gorczynski, R., Macrae, S., and Kennedy, M. (1982). Conditioned immune response associated with allogeneic skin grafts in mice. J. Immunol., 129, 704–709. Hatfield, T., and Gallagher, M. (1995). Taste-potentiated odor conditioning: impairment produced by infusion of an N-methyl-Daspartate antagonist into basolateral amygdala. Behav. Neurosci., 109, 663–668. Hawkins, R., Abrams, T., Carew, T., and Kandel, E. (1983). A cellular mechanism of classical conditioning in Aplysia: activitydependent amplification of presynaptic facilitation. Science, 219, 400–405. Hinderliter, C., Goodhart, M., Anderson, M., and Misanin, J. (2002). Extended lowered body temperature increases the effective CSUS interval in conditioned taste aversion for adult rats. Psychol. Rep., 90, 800–802. Hiramoto, R., Ghanta, V., Lorden, J., Solvason, H., Soong, S.-J., Rogers, C., Hsueh, C.-M., and Hiramoto, N. (1992). Conditioning of enhanced natural killer cell activity: effects of changing interstimulus intervals and evidence for long-delayed learning. Prog. Neuroendocrinimmunology, 5, 13–20. Hiramoto, R., Ghanta, V., Rogers, C., and Hiramoto, N. (1991a). Conditioning the elevation of body temperature, a host defensive reflex response. Life Sci., 49, 93–99. Hiramoto, R., Ghanta, V., Solvason, B., Lorden, J., Hsueh, C., Rogers, C., Demissie, S., and Hiramoto, N. (1993a). Identification of specific pathways of communication between the CNS and NK cell system. Life Sci., 53, 527–540. Hiramoto, R., Hiramoto, N., Rish, M., Soong, S., Miller, D., and Ghanta, V. (1991b). Role of immune cells in the Pavlovian conditioning of specific resistance to cancer. Int. J. Neurosci., 59, 101–117. Hiramoto, R., Hiramoto, N., Solvason, H., and Ghanta, V. (1987). Regulation of natural immunity (NK activity) by conditioning. Ann. N.Y. Acad. Sci., 496, 545–552. Hiramoto, R., Solvason, B., Ghanta, V., Lorden, J., and Hiramoto, N. (1990). Effect of reserpine on retention of the conditioned NK cell response. Pharmacol. Biochem. Behav., 36, 51–56. Hiramoto, R. N., Chi-Mei Hsueh, Rogers, C. F., Demissie, S., Hiramoto, N. S., Seng-Jaw Soong, and Ghanta, V. K. (1993b).
30. Conditioned Immune Enhancement Conditioning of the allogeneic cytotoxic lymphocyte response. Pharmacol. Biochem. Behav., 44, 275–280. Hori, T., Katafuchi, T., Take, S., Shimizu, N., and Niijima, A. (1995). The autonomic nervous system as a communication channel between the brain and the immune system. Neuroimmunomodulation, 2, 203–215. Hsueh, C., Chen, S., Lin, R., and Chao, H. (2002). Cholinergic and serotonergic activities are required in triggering conditioned NK cell response. J. Neuroimmunol., 123, 102–111. Hsueh, C., Hiramoto, R. N., and Ghanta, V. K. (1994a). Efferent signal(s) responsible for the conditioned augmentation of NK cell activity. Neuroimmunomodulation, 1, 74–81. Hsueh, C., Kuo, J., Chen, S., Huang, H., Cheng, F., Chung, L., and Lin, R. (1999). Involvement of catecholamines in recall of the conditioned NK cell response. J. Neuroimmunol., 94, 172–181. Hsueh, C., Rogers, C., Hiramoto, R., and Ghanta, V. (1994b). Effect of dexamethasone on conditioned enhancement of natural killer cell activity. Neuroimmunomodulation, 1, 370–376. Huang, J., Lin, W., and Chen, J. (2004). Antibody response can be conditioned using electroacupuncture as conditioned stimulus. Neuroreport, 15, 1475–1478. Hucklebridge, F. (2002). Behavioral conditioning of the immune system. Int. Rev. Neurobiol., 52, 325–351. Husband, A., King, M., and Brown, R. (1987). Behaviourally conditioned modification of T cell subset ratios in rats. Immunol. Lett., 14, 91–94. Husband, A. J., Lin, W., Madsen, G., and King, M. G. (1993). A conditioning model for immunostimulation: Enhancement of the antibody responses to ovalbumin by behavioral conditioning in rats. In A. J. Husband (Ed.), Psychoimmunology (pp. 139–148). Boca Raton, FL: CRC Press. Ikegaya, Y., Delcroix, I., Iwakura, Y., Matsuki, N., and Nishiyama, N. (2003). Interleukin-1beta abrogates long-term depression of hippocampal CA1 synaptic transmission. Synapse, 47, 54–57. Il’enko, V., and Kovaleva, G. (1960). On conditioned reflex regulation of immunological reactions. Zh. Mikrobiol. Epidemiol. Immunobiol., 31, 108–113. Irie, M., Maeda, M., and Nagata, S. (2001). Can conditioned histamine release occur under urethane anesthesia in guinea pigs? Physiol. Behav., 72, 567–573. Irie, M., Nagata, S., and Endo, Y. (2002). Fasting stress exacerbates classical conditioned histamine release in guinea pigs. Life Sci., 72, 689–698. Irie, M., Nagata, S., and Endo, Y. (2004). Diazepam attenuates conditioned histamine release in guinea pigs. International J. Psychophysiol., 51, 231–238. Janeway, C., Travers, P., Walport, M., and Shlomchik, M. (2005). Immunobiology (6th ed). New York: Garland Sciences Publishing. Jenkins, P., Chadwick, R., and Nevin, J. (1983). Classically conditioned enhancement of antibody production. Bull. Psychonom. Soc., 21, 485–487. Joos, S., Schott, C., Zou, H., Daniel, V., and Martin, E. (2000). Immunomodulatory effects of acupuncture in the treatment of allergic asthma: a randomized controlled study. J. Altern. Complement. Med., 6, 519–525. Kandel, E., Abrams, T., Bernier, L., Carew, T., Hawkins, R., and Schwartz, J. (1983). Classical conditioning and sensitization share aspects of the same molecular cascade in Aplysia. Cold Spring Harb. Symp. Quant. Biol., 48 (Pt 2), 821–830. Karst, M., Scheinichen, D., Rueckert, T., Wagner, T., Wiese, B., Piepenbrock, S., and Fink, M. (2003). Effect of acupuncture on the neutrophil respiratory burst: a placebo-controlled singleblinded study. Complement Ther. Med., 11, 4–10.
657
Katafuchi, T., Ichijo, T., Take, S., and Hori, T. (1993a). Hypothalamic modulation of splenic natural killer cell activity in rats. J. Physiol., 471, 209–221. Katafuchi, T., Take, S., and Hori, T. (1993b). Roles of sympathetic nervous system in the suppression of cytotoxicity of splenic natural killer cells in the rat. J. Physiol., 465, 343–357. Kiefer, S., Rusiniak, K., and Garcia, J. (1982). Flavor-illness aversions: gustatory neocortex ablations disrupt taste but not tastepotentiated odor cues. J. Comp. Physiol. Psychol., 96, 540–548. Kirschbaum, C., Jabaaij, L., Buske-Kirschbaum, A., Hennig, J., Blom, M., Dorst, K., Bauch, J., DiPauli, R., Schmitz, G., and Ballieux, R. (1992). Conditioning of drug-induced immunomodulation in human volunteers: a European collaborative study. Br. J. Clin. Psychol., 31 (Pt 4), 459–472. Kou, W., Bell, J., Gareus, I., Pacheco-López, G., Goebel, M., Spahn, G., Stratmann, M., Janssen, O., Schedlowski, M., and Dobos, G. (2005). Repeated acupuncture treatment affects leukocyte circulation in healthy young male subjects: a randomized singleblind two-period crossover study. Brain Behav. Immun., 19, 318–324. Kuo, J., Chen, S., Huang, H., Yang, C., Tsai, P., and Hsueh, C. (2001). The involvement of glutamate in recall of the conditioned NK cell response. J. Neuroimmunol., 118, 245–255. Kusnecov, A., and Goldfarb, Y. (2005). Neural and behavioral responses to systemic immunologic stimuli: a consideration of bacterial T cell superantigens. Curr. Pharm. Des., 11, 1039–1046. Lacosta, S., Merali, Z., and Anisman, H. (2000). Central monoamine activity following acute and repeated systemic interleukin-2 administration. Neuroimmunomodulation, 8, 83–90. Li, B., Lin, W., Wei, X., Tang, C., and Guo, Y. (1997). Conditioned immunomodulation using antigen as the unconditioned stimulus. Acta Psychologica Sinica, 29, 34–38. Luk’ianenko, V. (1961). The problem of conditioned reflex regulation of immunobiologic reactions. USP Sovrem. Biol., 51, 170–187. Lyte, M., Nelson, S., and Baissa, B. (1990). Examination of the neuroendocrine basis for the social conflict-induced enhancement of immunity in mice. Physiol. Behav., 48, 685–691. MacKenzie, J. (1886). The production of the so-called rose effect by means of an artificial rose, with remarks and historical notes. Am. J. Med. Sci., 91, 45–57. MacQueen, G., Marshall, J., Perdue, M., Siegel, S., and Bienenstock, J. (1989). Pavlovian conditioning of rat mucosal mast cells to secrete rat mast cell protease II. Science, 243, 83–85. Madden, K., Boehm, G., Lee, S., Grota, L., Cohen, N., and Ader, R. (2001). One-trial conditioning of the antibody response to hen egg lysozyme in rats. J. Neuroimmunol., 113, 236–239. Maddox, L., and Schwartz, D. (2002). The pathophysiology of asthma. Annu. Rev. Med., 53, 477–498. Maestroni, G. (1998). Catecholaminergic regulation of hematopoiesis in mice. Blood, 92, 2971; author reply 2972–2973. Magee, W., and Griffith, M. (1972). The liver as a site for interferon production in response to poly I : poly C. Life Sci. II, 11, 1081–1086. Mallon, E., Brockmann, A., and Schmid-Hempel, P. (2003). Immune response inhibits associative learning in insects. Proc. Biol. Sci., 270, 2471–2473. Manetti, R., Annunziato, F., Tomasevic, L., Giannò, V., Parronchi, P., Romagnani, S., and Maggi, E. (1995). Polyinosinic acid : polycytidylic acid promotes T helper type 1-specific immune responses by stimulating macrophage production of interferon-alpha and interleukin-12. Eur. J. Immunol., 25, 2656–2660. Markovic, B., Dimitrijevic, M., and Jankovic, B. (1992). Anaphylactic shock in neuropsychoimmunological research. Int. J. Neurosci., 67, 271–284.
658
III. Behavior and Immunity
Markovic, B., Dimitrijevic, M., and Jankovic, B. (1993). Immunomodulation by conditioning: recent developments. Int. J. Neurosci., 71, 231–249. Markovic, B., Djuric, V., Lazarevic, M., and Jankovic, B. (1988). Anaphylactic shock-induced conditioned taste aversion. I. Demonstration of the phenomenon by means of three modes of CS-US presentation. Brain Behav. Immun., 2, 11–23. McEwen, B. (1998). Stress, adaptation, and disease. Allostasis and allostatic load. Ann. N.Y. Acad. Sci., 840, 33–44. McEwen, B., and Lasley, E. (2003). Allostatic load: when protection gives way to damage. Adv. Mind. Body Med., 19, 28–33. Menzel, R., and Muller, U. (1996). Learning and memory in honeybees: from behavior to neural substrates. Annu. Rev. Neurosci., 19, 379–404. Metalnikov, S., and Chorine, V. (1926). Role des réflexes conditionnels dans l’immunité. Ann. Institut Pasteur, Paris, 11, 893–900. Metalnikov, S., and Chorine, V. (1928). Role des réflexes conditionnels dans la formation des anticorps. C. R. Seances Soc. Biol. Des. Fil., 99, 142–144. Mignini, F., Streccioni, V., and Amenta, F. (2003). Autonomic innervation of immune organs and neuroimmune modulation. Auton. Autacoid. Pharmacol., 23, 1–25. Millar, D., Thomas, J., Pacheco, N., and Rollwagen, F. (1993). Natural killer cell cytotoxicity and T-cell proliferation is enhanced by avoidance behavior. Brain Behav. Immun., 7, 144–153. Misanin, J., Collins, M., Rushanan, S., Anderson, M., Goodhart, M., and Hinderliter, C. (2002). Aging facilitates long-trace tasteaversion conditioning in rats. Physiol. Behav., 75, 759–764. Miyan, J., Broome, C., and Whetton, A. (1998). Neural regulation of bone marrow. Blood, 92, 2971–2973. Mormède, C., Castanon, N., Médina, C., and Dantzer, R. (2003). Conditioned place aversion with interleukin-1beta in mice is not associated with activation of the cytokine network. Brain Behav. Immun., 17, 110–120. Nerad, L., Ramírez-Amaya, V., Ormsby, C., and Bermúdez-Rattoni, F. (1996). Differential effects of anterior and posterior insular cortex lesions on the acquisition of conditioned taste aversion and spatial learning. Neurobiol. Learn. Mem., 66, 44–50. Nicolau, I., and Antinescu-Dimitriu, O. (1929a). L’influence des réflexes conditionnels sur l’exsudat peritonéal. C. R. Seances Soc. Biol. Ses. Fil., 102, 144–145. Nicolau, I., and Antinescu-Dimitriu, O. (1929b). Rôle des réflexes conditionnels dans la formation des anticorps. C. R. Seances Soc. Biol. Ses. Fil., 102, 133–134. Noelpp, B., and Noelpp-Eschenhagen, I. (1951a). Experimental bronchial asthma in guinea pigs, Part I. Methods for objective registration of asthma attacks. Int. Arch. Allergy Appl. Immunol., 2, 308–320. Noelpp, B., and Noelpp-Eschenhagen, I. (1951b). Experimental bronchial asthma in guinea pigs. Part II. The role of conditioned reflexes in the pathogenesis of bronchial asthma. Int. Arch. Allergy Appl. Immunol., 2, 321–329. Noelpp, B., and Noelpp-Eschenhagen, I. (1951c). Role of conditioned reflex in bronchial asthma: experimental investigation on the pathogenesis of bronchial asthma. Helv. Med. Acta, 18, 142–158. Noelpp, B., and Noelpp-Eschenhagen, I. (1952a). Experimental bronchial asthma in the guinea pig. IV. Experimental asthma in the guinea pig as an experimental model. Int. Arch. Allergy Appl. Immunol., 3, 207–217. Noelpp, B., and Noelpp-Eschenhagen, I. (1952b). Experimental bronchial asthma of guinea-pigs. III. Studies on the significance of conditioned reflexes; ability to develop conditioned reflexes and their duration under stress. Int. Arch. Allergy Appl. Immunol., 3, 108–136.
Noelpp, B., and Noelpp-Eschenhagen, I. (1952c). The experimental bronchial asthma of the guinea pig. V. Experimental pathophysiological studies. Int. Arch. Allergy Appl. Immunol., 3, 302–323. Ostravskaya, O. (1930). Le réflex conditionnel et les réactions de l’immunité. Ann. Inst. Pasteur Paris, 44, 340–345. Ottaviani, E., and Franceschi, C. (1996). The neuroimmunology of stress from invertebrates to man. Prog. Neurobiol., 48, 421–440. Ottaviani, E., Valensin, S., and Franceschi, C. (1998). The neuroimmunological interface in an evolutionary perspective: the dynamic relationship between effector and recognition systems. Front. Biosci., 3, d431–435. Ottenberg, P., Stein, M., Lewis, J., and Hamilton, C. (1958). Learned asthma in the guinea pig. Psychosom. Med., 20, 395–400. Pacheco-López, G., Espinosa, E., Zamorano-Rojas, H., RamírezAmaya, V., and Bermúdez-Rattoni, F. (2002). Peripheral protein immunization induces rapid activation of the CNS, as measured by c-Fos expression. J. Neuroimmunol., 131, 50–59. Pacheco-López, G., Niemi, M., Kou, W., Härting, M., Del Rey, A., Besedovsky, H., and Schedlowski, M. (2004). Behavioural endocrine immune-conditioned response is induced by taste and superantigen pairing. Neuroscience, 129, 555–562. Pacheco-López, G., Niemi, M., Kou, W., Härting, M., Fandrey, J., and Schedlowski, M. (2005). Neural substrates for behaviorally conditioned immunosuppression in the rat. J. Neurosci., 25, 2330–2337. Palermo-Neto, J., and Guimarães, R. (2000). Pavlovian conditioning of lung anaphylactic response in rats. Life Sci., 68, 611–623. Parmiani, G., Sensi, M., Carbone, G., Colombo, M., Pierotti, M., Ballinari, D., Hilgers, J., and Hilkens, J. (1982). Cross-reactions between tumor cells and allogeneic normal tissues. Inhibition of a syngeneic lymphoma outgrowth in H-2 and non–H-2 alloimmune BALB/c mice. Int. J. Cancer, 29, 323–332. Pavlov, I. (1927). Conditioned reflexes: an investigation of the physiological activity of the cerebral cortex. Cambridge: Oxford University Press. Pavlov, V., and Tracey, K. (2005). The cholinergic anti-inflammatory pathway. Brain Behav. Immun., 19, 493– 499. Pearce, J. (1987). A model for stimulus generalization in Pavlovian conditioning. Psychol. Rev., 94, 61–73. Peeke, H., Ellman, G., Dark, K., Salfi, M., and Reus, V. (1987a). Cortisol and behaviorally conditioned histamine release. Ann. N.Y. Acad. Sci., 496, 583–587. Peeke, H. V. S., Dark, K., Ellman, G., McCurry, C., and Salfi, M. (1987b). Prior stress and behaviorally conditioned histamine release. Physiol. Behav., 39, 89–93. Pinto, A., Yanai, M., Sekizawa, K., Aikawa, T., and Sasaki, H. (1995). Conditioned enhancement of cough response in awake guinea pigs. Int. Arch. Allergy. Immunol., 108, 95–98. Proft, T., and Fraser, J. (2003). Bacterial superantigens. Clin. Exp. Immunol., 133, 299–306. Ramírez-Amaya, V., Alvarez-Borda, B., Ormsby, C., Martínez, R., Pérez-Montfort, R., and Bermúdez-Rattoni, F. (1996). Insular cortex lesions impair the acquisition of conditioned immunosuppression. Brain Behav. Immun., 10, 103–114. Ramírez-Amaya, V., and Bermúdez-Rattoni, F. (1999). Conditioned enhancement of antibody production is disrupted by insular cortex and amygdala but not hippocampal lesions. Brain Behav. Immun., 13, 46–60. Reidler, M. (1956). Effect of complex conditioned and unconditioned (pain) stimulus on antibody formation in the blood in normal conditions and following excision of the cerebellum. Fiziol. Zh. SSSR. Im. I. M. Sechenova, 42, 398–405.
30. Conditioned Immune Enhancement Rescorla, R. (1988). Behavioral studies of Pavlovian conditioning. Annu. Rev. Neurosci., 11, 329–352. Rescorla, R. (2003). Contemporary study of Pavlovian conditioning. Span. J. Psychol., 6, 185–195. Rescorla, R., and Wagner, A. (1972). A theory of Pavlovian conditioning: variations in the effectiveness of reinforcement and nonreinforcement. In A. Black and W. Prokasy (Eds.), Classical conditioning II: current research and theory (pp. 64–99). New York: Appleton-Century-Crofts. Rogers, C., Ghanta, V., Demissie, S., Hiramoto, N., and Hiramoto, R. (1994a). Lidocaine interrupts the conditioned natural killer cell response by interfering with the conditioned stimulus. Neuroimmunomodulation, 1, 278–283. Rogers, C., Ghanta, V., Demissie, S., Hiramoto, N., and Hiramoto, R. (1994b). Sodium carbonate prevents NK cell conditioning by interfering with the US signal. Int. J. Neurosci., 77, 277–286. Rogers, C., Ghanta, V., Hsueh, C., Hiramoto, N., and Hiramoto, R. (1992). Indomethacin and sodium carbonate effects on conditioned fever and NK cell activity. Pharmacol. Biochem. Behav., 43, 417–422. Russell, M., Dark, K. A., Cummins, R. W., Ellman, G., Callaway, E., and Peeke, H. V. (1984). Learned histamine release. Science, 225, 733–734. Salzet, M., Vieau, D., and Day, R. (2000). Crosstalk between nervous and immune systems through the animal kingdom: focus on opioids. Trends Neurosci., 23, 550–555. Sanders, V., and Kohm, A. (2002). Sympathetic nervous system interaction with the immune system. Int. Rev. Neurobiol., 52, 17–41. Sanders, V., and Straub, R. (2002). Norepinephrine, the betaadrenergic receptor, and immunity. Brain Behav. Immun., 16, 290–332. Schafe, G., Sollars, S., and Bernstein, I. (1995). The CS-US interval and taste aversion learning: a brief look. Behav. Neurosci., 109, 799–802. Schedlowski, M. (2006). Insecta immune-cognitive interactions. Brain Behav. Immun., 20, 133–134. Segal, A. (2005). How neutrophils kill microbes. Annu. Rev. Immunol., 23, 197–223. Sensi, M., Grazioli, L., and Parmiani, G. (1986). Analysis of the cellular immune response to and adoptive immunotherapy of a BALB/c lymphoma that cross-reacts with normal DBA/2 cells. Cancer Immunol. Immunother., 21, 199–204. Shors, T. (2004). Learning during stressful times. Learn. Mem., 11, 137–144. Shors, T., Beylin, A., Wood, G., and Gould, E. (2000). The modulation of Pavlovian memory. Behav. Brain Res., 110, 39–52. Shurin, G., Shanks, N., Nelson, L., Hoffman, G., Huang, L., and Kusnecov, A. (1997). Hypothalamic-pituitary-adrenal activation by the bacterial superantigen staphylococcal enterotoxin B: role of macrophages and T cells. Neuroendocrinol., 65, 18–28. Shurin, M., Kusnecov, A., Hamill, E., Kaplan, S., and Rabin, B. (1994a). Stress-induced alteration of polymorphonuclear leukocyte function in rats. Brain Behav. Immun., 8, 163–169. Shurin, M., Kusnecov, A., Riechman, S., and Rabin, B. (1995). Effect of a conditioned aversive stimulus on the immune response in three strains of rats. Psychoneuroendocrinology, 20, 837–849. Shurin, M., Zhou, D., Kusnecov, A., Rassnick, S., and Rabin, B. (1994b). Effect of one or more footshocks on spleen and blood lymphocyte proliferation in rats. Brain Behav. Immun., 8, 57–65.
659
Solvason, H., Ghanta, V., and Hiramoto, R. (1988). Conditioned augmentation of natural killer cell activity. Independence from nociceptive effects and dependence on interferon-beta. J. Immunol., 140, 661–665. Solvason, H., Ghanta, V., and Hiramoto, R. (1993). The identity of the unconditioned stimulus to the central nervous system is interferon-beta. J. Neuroimmunol., 45, 75–81. Solvason, H., Ghanta, V., Lorden, J., Soong, S., and Hiramoto, R. (1991). A behavioral augmentation of natural immunity: odor specificity supports a Pavlovian conditioning model. Int. J. Neurosci., 61, 277–288. Solvason, H., Ghanta, V., Soong, S., Rogers, C., Hsueh, C., Hiramoto, N., and Hiramoto, R. (1992). A simple, single, trial-learning paradigm for conditioned increase in natural killer cell activity. Proc. Soc. Exp. Biol. Med., 199, 199–203. Solvason, H., Hiramoto, R., and Ghanta, V. (1989). Naltrexone blocks the expression of the conditioned elevation of natural killer cell activity in BALB/c mice. Brain Behav. Immun., 3, 247–262. Spector, N. (1996). Neuroimmunomodulation: a brief review. Can conditioning of natural killer cell activity reverse cancer and/or aging? Regul. Toxicol. Pharmacol., 24, S32–38. Spector, N. (1999). The NIM revolution. Rom. J. Physiol., 36, 127–143. Spector, N., Provinciali, M., di Stefano, G., Muzzioli, M., Bulian, D., Viticchi, C., Rossano, F., and Fabris, N. (1994). Immune enhancement by conditioning of senescent mice. Comparison of old and young mice in learning ability and in ability to increase natural killer cell activity and other host defense reactions in response to a conditioned stimulus. Ann. N.Y. Acad. Sci., 741, 283–291. Straub, R., and Besedovsky, H. (2003). Integrated evolutionary, immunological, and neuroendocrine framework for the pathogenesis of chronic disabling inflammatory diseases. FASEB J., 17, 2176–2183. Tada, T. (1997). The immune system as a supersystem. Annu. Rev. Immunol., 15, 1–13. Tracey, K. (2002). The inflammatory reflex. Nature, 420, 853–859. Tully, T., Boynton, S., Brandes, C., Dura, J., Mihalek, R., Preat, T., and Villella, A. (1990). Genetic dissection of memory formation in Drosophila melanogaster. Cold Spring Harb. Symp. Quant. Biol., 55, 203–211. Turnbull, J. (1962). Asthma conceived as a learned response. J. Psychosom. Res., 6, 59–70. Ulett, G. (1996). Conditioned healing with electroacupuncture. Altern. Ther. Health Med., 2, 56–60. Vishwanath, R. (1996). The psychoneuroimmunological system: a recently evolved networking organ system. Med. Hypotheses, 47, 265–268. Wilson, D., and Stevenson, R. (2003). Olfactory perceptual learning: the critical role of memory in odor discrimination. Neurosci. Biobehav. Rev., 27, 307–328. Ye, F., Chen, S., and Liu, W. (2002). Effects of electro-acupuncture on immune function after chemotherapy in 28 cases. J. Tradit. Chin. Med., 22, 21–23. Zeitlenok, N., and Bychkova, E. (1954). Role of the higher nervous function in infection and immunity. Zh. Vyssh. Nerv. Deiat. Im. I. P. Pavlova, 4, 267–281.
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C H A P T E R
31 Exercise and Immunity: Clinical Studies DAVID C. NIEMAN
I. II. III. IV.
I. INTRODUCTION
INTRODUCTION 661 EXERCISE, IMMUNITY, AND URTI RISK 662 ATHLETIC ENDEAVOR AND URTI 668 CONCLUSIONS 670
Exercise immunology is a relatively new area of scientific endeavor, with 80% of articles published during the past decade (Nieman, 2003). Growing evidence indicates that physical activity does influence immune function and as a consequence risk of certain types of infection, in particular the most common of all, upper respiratory tract infections (URTI). This chapter will summarize recent investigations showing that in contrast to moderate physical activity, prolonged and intensive exertion causes numerous negative changes in immunity and an increased risk of URTI.
ABSTRACT Moderate to heavy exercise workloads have contrasting influences on immune function. Moderate exercise training has been associated with favorable perturbations in immunity and a reduction in incidence of upper respiratory tract infection (URTI). More research is needed to establish whether or not a link exists between moderate exercise-induced perturbations in immunity and improvements in other clinical outcomes such as cancer, heart disease, type 2 diabetes, arthritis, and aging. Epidemiological data indicate that endurance athletes are at increased URTI risk during periods of heavy training and the 1–2 week period following race events. For several hours subsequent to heavy exertion, components of both the innate (e.g., natural killer cell activity and neutrophil oxidative burst activity) and adaptive (e.g., T- and B-cell function) immune system exhibit suppressed function. Some attempts have been made through nutritional means (e.g., glutamine, vitamins C and E, and carbohydrate supplementation) to attenuate immune changes following intensive exercise and thus lower URTI risk. Carbohydrate supplementation during heavy exercise has emerged as the most effective countermeasure, and attenuates increases in blood neutrophil counts, stress hormones, and inflammatory cytokines. PSYCHONEUROIMMUNOLOGY, 4E VOLUME I
A. Exercise, Immune Changes, and Clinical Outcomes The link between exercise-induced perturbations in immunity and improvements in other clinical outcomes such as cancer, heart disease, type 2 diabetes, arthritis, and aging has not been investigated as thoroughly as with URTI. More research is needed to determine if immune alterations during exercise training help explain the lowered risk of chronic disease. For example, although epidemiological and experimental studies with animal models suggest that physical activity may protect against several forms of cancer, evidence linking this to enhanced immunity is limited and controversial (Fairey et al., 2005). Hoffman-Goetz and Husted (1995) more than a decade ago proposed that although various exercise-induced mechanical and hormonal changes best explain the relationship to reduced risk of colon, breast, and prostate cancer in
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physically active individuals, several potential immunological effects may be contributing factors. These include exercise-induced immune modulation of cytokines; activation and changes in signal transduction of natural killer (NK) cells, macrophages, neutrophils, and tumor-infiltrating lymphocytes; changes in the expression of cell adhesion molecules; and alterations in prostaglandins. Accumulating evidence indicates that exercise training causes changes in pro- and antiinflammatory cytokine levels and activity that may influence both the prevention and treatment of certain types of carcinomas (Allgayer et al., 2004). This area of research endeavor is highly complex, and more research is needed. Immune senescence or age-associated immune deficiency appears to be partly responsible for the afflictions of old age. Elderly persons are more susceptible to many infections, autoimmune disorders, and cancers when compared with younger adults. A new and growing area of research endeavor is the study of the relationship between physical activity and immune senescence. One study of adults over the age of 65 years showed that a 10-month exercise program enhanced the antibody titer response to an influenza immunization (Kohut et al., 2004), thus showing that exercise can have some immediate benefits for the elderly. Regular physical activity may also attenuate the age-related decrease in T lymphocyte function (Smith et al., 2004). Very few studies have been conducted in this area, but the available data taken together suggest that exercise training may need to be long term and of sufficient volume to induce changes in body weight and fitness before any change in immunity can be expected in old age (Kohut and Senchina, 2004; Nieman et al., 1993). In other words, because the aging process is so dominant in old age, long-term physical activity combined with leanness and other positive lifestyle habits may be necessary before immune function is enhanced. Type 2 diabetes and cardiovascular disease are associated with chronic low-grade systemic inflammation. During exercise, IL-6 is produced by muscle fibers and stimulates the appearance in the circulation of other anti-inflammatory cytokines such as IL-1ra and IL-10 (Petersen and Pedersen, 2005). IL-6 also inhibits the production of the pro-inflammatory cytokine TNF-alpha and stimulates lipolysis and fat oxidation. With weight loss from energy restriction and exercise, plasma levels of IL-6 fall, skeletal muscle TNF-alpha decreases, and insulin sensitivity improves (Ferrier et al., 2004; Ryan and Nicklas, 2004). Thus, IL-6 release from the exercising muscle may help mediate some of the health benefits of exercise including metabolic control of type 2 diabetes (Petersen and Pedersen,
2005). The exercise-induced cytokine links between adipose and muscle tissues clearly warrant further study (Tomas et al., 2004).
II. EXERCISE, IMMUNITY, AND URTI RISK Upper respiratory tract infections are the most frequently occurring illnesses in humans worldwide. More than 200 different viruses cause the common cold, and rhinoviruses and coronaviruses are the culprits 25–60% of the time. The U.S. Centers for Disease Control and Prevention has estimated that more than one billion URTIs occur annually in the United States, a leading cause of lost school and work days. The average person has two or three respiratory infections each year, with young children suffering six to seven. Among elite athletes and their coaches, a common perception is that heavy exertion lowers resistance and is a predisposing factor to URTI. In a 1996 survey by the Gatorade Sports Science Institute of 2,700 high school and college coaches and athletic trainers, 89% checked “yes” to the question, “Do you believe overtraining can compromise the immune system and make athletes sick?” (personal communication, Gatorade Sports Science Institute, Barrington, IL). Conversely, there is also a common belief among fitness enthusiasts that regular exercise confers resistance against infection. In a survey of 170 non-elite marathon runners (personal best time, average of 3 hours 25 minutes) who had been training for and participating in marathons for an average of 12 years, 90% reported that they definitely or mostly agreed with the statement that they “rarely get sick” (unpublished observations). A survey of 750 masters athletes (ranging in age from 40 to 81 years) showed that 76% perceived themselves as less vulnerable to viral illnesses than their sedentary peers (Shephard et al., 1995). Although the relationship between exercise and URTI and other types of infections has been explored since early in the twentieth century (Baetjer, 1932), the number of well-designed epidemiological and exercise training experimental trials on humans is still small, limiting our understanding of this important topic (Nieman, 1997a, 2003). Data from animal studies have been difficult to apply to the human condition but in general have supported the finding that one or two periods of exhaustive exercise following inoculation lead to a more frequent appearance of infection and a higher fatality rate (but results differ depending on the pathogen, with some more affected by exercise than others) (Friman et al., 1995; Pedersen and Bruunsgaard, 1995).
31. Exercise and Immunity: Clinical Studies
Davis et al. (1997), for example, exposed mice to rest, 30 minutes of moderate exercise, or 2.5–3 hours of exhaustive exercise following intranasal infection with the herpes simplex virus (HSV-1). Mice exercised to fatigue had a greater overall mortality during a 21-day period than did controls or moderately exercised mice. In humans, it is well established that various measures of physical performance capability are reduced during an infectious episode (Friman et al., 1995). Several case histories have been published demonstrating that sudden and unexplained deterioration in athletic performance can be traced to either recent URTI or subclinical viral infections that run a protracted course. In some athletes, a viral infection may lead to a debilitating state known as “post-viral fatigue syndrome” (Maffulli et al., 1993; Parker et al., 1996). The symptoms include lethargy, easy fatigability, and myalgia, and can persist for several months.
A. Exercise-Induced Changes in Immune Function Together, these data imply that there is a relationship between exercise and infection, and that heavy exertion may suppress various components of immunity. Research data on the resting immunity of athletes and non-athletes, however, are limited and present a confusing picture at present (Nieman, 1997b). For example, the few studies available suggest that the innate immune system responds differentially to the chronic stress of intensive exercise, with natural killer cell activity tending to be enhanced while neutrophil function is suppressed (Nieman et al., 1995b, 1999; Pyne et al., 1995; Smith and Pyne, 1997). The adaptive immune system (resting state) in general seems to be largely unaffected by athletic endeavor. Each acute bout of cardiorespiratory endurance exercise leads to transient but significant changes in immunity and host defense (Gabriel and Kindermann, 1997; Hoffman-Goetz and Pedersen, 1994; Nieman et al., 1997b, 2002a, 2003a, 2004; Pedersen and Brunsgaard, 1995). Natural killer cell activity, various measures of T- and B-cell function, upper airway neutrophil function, and salivary IgA concentration have all been reported to be suppressed for at least several hours during recovery from prolonged, intense endurance exercise (Bruunsgaard et al., 1997; Gabriel and Kindermann, 1997; Mackinnon and Hooper, 1994; Müns, 1993; Nieman et al., 1995a, 1995c, 2001, 2003b; Shinkai et al., 1993). During this “open window” of decreased host protection, viruses and bacteria may gain a foothold, increasing the risk of subclinical and clinical infection (Figure 1).
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FIGURE 1 The “open window theory”: Moderate exercise causes mild immune changes; in contrast, prolonged, intensive exercise (90 minutes or longer) leads to a downturn in immunosurveillance that increases the likelihood for opportunistic upper respiratory tract infections.
Although this is an attractive hypothesis, no one has yet demonstrated conclusively that athletes showing the most extreme immunosuppression are those that contract an infection (Lee et al., 1992; Mackinnon et al., 1993). In one study, salivary IgA secretion rate decreased by nearly half in a group of 155 ultramarathon runners following a 160 km race (Nieman et al., 2006). Nearly one in four runners reported an URTI episode during the 2-week period following the race, and the decrease in sIgA secretion rate was significantly greater in these runners (54%) compared to those not reporting URTI (31%). It is doubtful, however, that sIgA output alone can be used to predict URTI at the individual athlete level. In this study, the overall predictive value for URTI was 55%, indicating that sIgA output was more useful at the group compared to the individual level, and that other factors need to be discovered and combined with sIgA before URTI risk can be predicted for individual athletes.
B. Heavy Exertion and URTI: Epidemiological Evidence Understanding the relationship between exercise and infection has potential implications for public health, and for the athlete, it may mean the difference between being able to compete or performing at a subpar level or missing the event altogether because of illness. It has been proposed that the relationship between exercise and URTI may be modeled in the form of a “J” curve (Nieman, 1997a) (Figure 2). This model suggests that although the risk of URTI may decrease below that of a sedentary individual when
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FIGURE 2 Model on the relationship between exercise workload, risk of upper respiratory tract infection (URTI), and immunosurveillance.
one engages in moderate exercise training, risk may rise above average during periods of excessive amounts of high-intensity exercise. The model in Figure 2 also suggests that immunosurveillance mirrors that relationship between infection risk and exercise workload. In other words, it makes sense that if regular moderate exercise lowers infection risk, it should be accompanied by enhanced immunosurveillance. On the other hand, when an athlete engages in unusually heavy exercise workloads (e.g., overtraining or a competitive endurance race event), infection risk should be related to diminished immunosurveillance. At present, there is more evidence, primarily epidemiological in nature, exploring the relationship between heavy exertion and infection, and these data will be reviewed first followed by a section on moderate exercise training and infection (Table 1). Much more research using larger subject pools and improved research designs is necessary before this model can be wholly accepted or rejected. The epidemiological studies summarized in Table 1 all used self-reported URTI data (primarily retrospective, with two studies using 1-year daily logs). None have attempted to verify symptomatology using viral identification or verification by physicians. There is some concern that the symptoms reported by endurance athletes following competitive race events may reflect those associated with an inflammatory response rather than URTI (Castell et al., 1997; Drenth et al., 1995; NehlsenCannarella et al., 1997). Nonetheless, the data are consistent in supporting the viewpoint that heavy exertion increases the risk of URTI, while moderate exercise training is associated with a decreased risk.
Several epidemiological reports suggest that athletes engaging in marathon-type events and/or very heavy training are at increased risk of URTI (Table 1). Nieman et al. (1990a) researched the incidence of URTI in a group of 2,311 marathon runners who varied widely in running ability and training habits. Runners retrospectively self-reported demographic, training, and URTI episode and symptom data for the 2-month period (January, February) prior to and the 1-week period immediately following the 1987 Los Angeles Marathon race. During the week following the race, 12.9% of the marathoners reported an URTI compared to only 2.2% of control runners who did not participate (odds ratio, 5.9, using a logistic regression model that controlled for various training and demographic variables). Forty percent of the runners reported at least one URTI episode during the 2-month winter period prior to the marathon race. Controlling for various confounders, it was determined that runners training more than 96 km/wk doubled their odds for sickness compared to those training less than 32 km/wk. Linde (1987) studied URTI in a group of 44 elite orienteers and 44 non-athletes of the same age, sex, and occupational distribution during a 1-year period. Athletes and controls recorded symptoms of sickness using daily logs for 1 year. The orienteers experienced significantly more URTI episodes during the year in comparison to the control group (2.5 vs. 1.7 episodes, respectively). While one-third of the controls reported no URTI during the year-long study period, this applied to only 10% of the orienteers. The average duration of symptoms in the group of orienteers was 7.9 days compared to 6.4 days in the control group (NS). The control group had the expected seasonal variation with the peak incidence in winter and relatively few cases in summer, while the orienteers tended to show a more even distribution. Heath et al. (1991) also followed a cohort of runners (N = 530) who self-reported URTI symptoms daily for 1 year. The average runner in the study was about 40 years of age, ran 32 km/wk, and experienced a rate of 1.2 URTI per year. Controlling for various confounding variables using logistic regression, the lowest odds ratio for URTI was found in those running less than 16 km/wk. The odds ratio more than doubled for those running more than 27 km/wk. This study demonstrated that total running distance for a year is a significant risk factor for URTI, with risk increasing as the running distance rises. Peters and Bateman (1983) studied the incidence of URTI in 150 randomly selected runners who took part in a 56 km Cape Town race in comparison to matched controls who did not run. Symptoms of URTI occurred in 33.3% of runners compared with 15.3% of controls
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31. Exercise and Immunity: Clinical Studies TABLE 1
Epidemiological Research on the Relationship Between Intense, Prolonged Exercise and Upper Respiratory Tract Infection (URTI)
Investigators Peters and Bateman (1982) Linde (1987) Nieman et al. (1989)
Peters (1990)
Nieman et al. (1990a)
Subjects
Method of determining URTI
141 South African marathon runners vs. 124 live-in controls 44 Danish elite orienteers vs. 44 matched non-athletes 294 California runners training for race
2-week recall of URTI incidence and duration after 56 km race URTI symptoms self-recorded in daily log for 1 year 2-month recall of URTI incidence; 1 week recall after winter 5, 10, 21 km races 2-week recall of URTI incidence and duration after 56 km race 2-month recall of URTI incidence during training for marathon; 1-week recall after winter race 1-year daily log using selfreported, pre-coded, symptoms 2-week recall of URTI incidence and duration after 90 km race
108 South African marathon runners vs. 108 live-in controls 2,311 Los Angeles marathon runners
Heath et al. (1991)
530 runners, South Carolina
Peters et al. (1993)
84 South African marathon runners vs. 73 non-runner controls
Nieman (1993) (unpublished data)
170 North Carolina marathon runners
Peters et al. (1996)
178 South African runners vs. 162 controls
Castell et al. (1996)
151 endurance athletes in the United Kingdom
1-week recall of URTI incidence after heavy exertion
Nieman et al. (2002a)
91 marathon runners, North Carolina
15-day recall of URTI incidence after marathon race event
Nieman et al. (2006)
155 ultramarathoners, Western U.S. 160 km
2-week recall of URTI incidence after 160 km race event
1-week recall of URTI incidence after summer marathon race 2-week recall of URTI incidence and duration after 90 km race
during the 2-week period following the race, and were most common in those who achieved the faster race times. The most prevalent symptoms after the race were reported to be sore throats and nasal symptoms. Of the total number of symptoms reported by the runners, 80% lasted for longer than 3 days, suggesting an infective origin. Several subsequent studies from this group of researchers have confirmed this finding (Peters, 1990; Peters et al., 1993, 1996). During the 2-week period following the 56 km Milo Korkie Ultramarathon in Pretoria, South Africa, 28.7% of the 108 subjects who completed the race reported non-allergy–derived URTI symptoms as compared to 12.9% of controls (Peters, 1990). In another study, 68% of runners reported the
Major finding URTI incidence twice as high in runners after 56 km race vs. controls (33.3% vs. 15.3%) Orienteers vs. controls had 2.5 vs. 1.7 URTIs during year Training 42 vs. 12 km/wk associated with lower URTI; no effect of race participation on URTI URTI incidence 28.7% in runners vs. 12.9% in controls after 56 km race Runners training ≥97 vs. <32 km/wk at higher URTI risk; odds ratio 5.9 for participants vs. non-participants 1 week after 42.2 km race Increase in running distance positively related to increased URTI risk URTI incidence 68% in runners vs. 45% in controls after 56 km race; 33% in runners using vitamin C vs. 53% of controls URTI reported by only 3% of marathoners during week after summer race URTI incidence 40.4% in placebo runners vs. 15.9% using vitamin C (500 mg/d for 3 weeks). Vitamin A and E had no additional effect URTI reported by 81% of athletes using placebo vs. 49% using a glutamine-based beverage URTI reported by 17% of marathoners; post-race sIgA: protein lower in URTI vs. non-URTI group URTI reported by 24% of athletes; sIgA decrease was 54% in URTI vs. 31% in nonURTI group
development of symptoms of URTI within 2 weeks after the 90 km Comrades Ultramarathon (Peters et al., 1993). Using a double-blind placebo research design, it was determined that only 33% of runners taking a 600 mg vitamin C supplement daily for 3 weeks prior to the race developed URTI symptoms. The incidence of URTI was greatest among the runners who trained the hardest coming into the race (85% vs. 45% of the low- or medium-training status runners). In subsequent research, vitamin C, but not vitamin A and E, supplements have not been found to alter URTI rates following ultramarathon competitions (Peters et al., 1996; Peters-Futre, 1997). As summarized in Table 1, 15.9% of runners using vitamin C supplements (500 mg/day) reported URTI during the 2-week
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period following the 1993 90 km Comarades ultramarathon in comparison to 40.4% of runners using placebo, 20–26% of runners using vitamin C with vitamin E and beta carotene, and 24.4% of controls on placebo. The authors suggested that because heavy exertion enhances the production of free oxygen radicals, vitamin C, which has antioxidant properties, may be required in increased quantities (Peters et al., 1993; Peters-Futre, 1997). Other researchers have reported reduced URTI rates following marathon race events in runners consuming beverages containing glutamine, an amino acid used by various cells of the immune system (Castell et al., 1996, 1997). Predicting what runners will obtain URTI following an endurance race event from demographic and immune function parameters has proven to be a difficult task. Table 1 summarizes two studies that showed that URTI was more likely in runners experiencing low salivary IgA output during and after competing in a 160 km race event (Nieman et al., 2002a; 2006). URTI risk following a race event may depend on the distance, with an increased incidence conspicuous only following marathon or ultramarathon events. For example, Nieman et al. (1989) were unable to establish any increase in prevalence of URTI in 273 runners during the week following 5 km, 10 km, and 21.1 km events as compared to the week before. URTI incidence was also measured during the 2 winter-month period prior to the three races, and in this group of recreational runners, 25% of those running 25 or more km/wk (average of 42 km/wk) reported at least one URTI episode, as opposed to 34% training less than 25 km/wk (average of 12 km/wk) (p = 0.09). These findings suggest that, in recreational running, an average weekly distance of 42 versus 12 km is associated with either no change in or even a slight reduction of URTI incidence. Further, they suggest, that racing 5 km to 21.1 km is not related to an increased risk of sickness during the ensuing week. URTI rates after endurance races may also vary depending on the season. As summarized in Table 1, only 3% of marathon runners reported URTI symptoms during the week after the July 1993 Grandfather Mountain Marathon (Boone, NC). Together, these epidemiological studies imply that heavy acute or chronic exercise is associated with an increased risk of URTI. The risk appears to be especially high during the 1- or 2-week period following marathon-type race events. Among runners varying widely in training habits, the risk for URTI is slightly elevated for the highest distance runners, but only when several confounding factors are controlled. Thus, it makes sense that URTI risk may be increased when the endurance athlete goes through repeated
cycles of unusually heavy exertion; has been exposed to novel pathogens; and has experienced other stressors to the immune system including lack of sleep, severe mental stress, malnutrition, or weight loss. A 1-year retrospective study of 852 German athletes showed that risk of URTI was highest in endurance athletes who also reported significant stress and sleep deprivation (Konig et al., 2000). In other words, URTI risk is related to many factors, and when brought together during travel to important competitive events, the athletes may be unusually susceptible. The majority of endurance athletes, however, do not report URTI after competitive race events. For example, only 1 in 7 marathon runners reported an episode of URTI during the week following the March 1987 Los Angeles Marathon, compared to 2 in 100 who did not compete (Nieman et al., 1990a). When athletes train hard, but avoid overreaching and overtraining, URTI risk is typically unaltered. For example, during a 2.5month period (winter/spring) in which elite female rowers trained 2–3 hours daily (rowing drills, resistance training), incidence of URTI did not vary significantly from that of non-athletic controls (Nieman et al., 2000a).
C. Moderate Exertion, URTI, and Immune Function What about the common belief that moderate physical activity is beneficial in decreasing URTI risk? Very few studies have been carried out in this area, and more research is certainly warranted to investigate this interesting question. At present, there are few published epidemiological reports that have retrospectively or prospectively compared incidence of URTI in large groups of moderately active and sedentary individuals. A 1-year epidemiological study of 547 adults demonstrated a 23% reduction in risk of URTI in those engaging in regular versus irregular moderate-to-vigorous physical activity (Matthews et al., 2002). In healthy elderly subjects, URTI symptomatology during a 1-year period was inversely related to energy expended during moderate physical activity (Kostka et al., 2000). In Project PRIME, a randomized clinical trial that investigated interventions to increase physical activity, the odds ratio for reporting URTI symptoms was 0.50 (95% C.I., 0.28 to 0.91) among participants who engaged in a minimum of 150 minutes per week of moderate and vigorous activity compared with less active participants (Strasner et al., 2001). Three randomized experimental trials have provided important data in support of the viewpoint that moderate physical activity may reduce URTI symptomatology (Table 2). In one randomized, controlled
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31. Exercise and Immunity: Clinical Studies TABLE 2
Exercise Training Studies on the Relationship Between Moderate Exercise and Upper Respiratory Tract Infection (URTI) Subjects
Method of determining URTI
Major finding
Nieman et al. (1990b)
36 mildly obese, inactive women, California
Nieman et al. (1993)
42 elderly women (30 inactive, 12 athletes), North Carolina
Daily logs using self-reported, pre-coded, URTI symptoms for 15 weeks during winter season Daily logs using self-reported, pre-coded, URTI symptoms for 12 weeks during fall season
Nieman et al. (1998a)
90 overweight and 30 normal-weight women
Walking group reported fewer days with URTI symptoms than controls (5.1 vs. 10.8) Incidence of URTI 8% in athletes; inactives randomized to 12 weeks walking vs. controls, 21% in walkers, 50% in sedentary controls Number of days with URTI symptoms, 9.4 ± 1.1, 5.6 ± 0.9, and 4.8 ± 0.9 in overweight walkers, overweight controls, and normal-weight controls
Daily logs using self-reported, pre-coded URTI symptoms for 12 weeks during winter season
study of 36 women (mean age 35 years), exercise subjects walked briskly for 45 minutes, 5 days a week, and experienced one-half the days with URTI symptoms during the 15-week period compared to that of the sedentary control group (5.1 ± 1.2 vs. 10.8 ± 2.3 days, p = 0.039) (Nieman et al., 1990b). The effect of exercise training (five 45-minute walking sessions/week at 60–75% maximum heart rate) and/or moderate energy restriction (4.19–5.44 MJ or 1,200–1,300 kcal per day) on URTI was studied in non-obese, physically active women (N = 30) and obese women (N = 91, body mass index 33.1 ± 0.6 kg/m2) randomized to one of four groups: control, exercise, diet, exercise and diet (Nieman et al., 1998a). All subjects self-reported symptoms of sickness in health logs using a pre-coded checklist. Energy restriction had no significant effect on URTI incidence, and subjects from the two exercise groups were contrasted with subjects from the two non-exercise groups. The number of days with symptoms of URTI for subjects in the exercise groups was reduced relative to the non-exercise groups (5.6 ± 0.9 and 9.4 ± 1.1 sickness days, respectively), similar to that of the non-obese controls (4.8 ± 0.9). Figure 3 summarizes the combined data set from these two training studies. In a study of elderly women, the incidence of the common cold during a 12-week period in the fall was measured to be lowest in highly conditioned, lean subjects who exercised moderately each day for about 1.5 hours (8%) (Nieman et al., 1993). Elderly subjects who walked 40 minutes, 5 times/week had an incidence of 21%, as compared to 50% for the sedentary control group (X = 6.36, p = 0.042). These data suggest that elderly women not engaging in cardiorespiratory exercise are more likely than those who do exercise regularly to experience an URTI during the fall season. During moderate exercise or vigorous exercise that incorporates rest intervals, several positive changes
Number of Days in 12 Weeks with URTI Symptoms
Investigators
FIGURE 3 The number of URTI symptom days was decreased by approximately half through a walking program (5 days per week, 45 minutes per session, for 15 weeks).
occur in the immune system (Nehlsen-Cannarella et al., 1991; Nieman, 2000; Nieman and NehlsenCannarella, 1994; Nieman et al., 2005a). Stress hormones, which can suppress immunity, and pro- and anti-inflammatory cytokines, indicative of intense metabolic activity, are not elevated during moderate exercise. Although the immune system returns to preexercise levels very quickly after the exercise session is over, each session represents a boost in immune surveillance that appears to reduce the risk of infection over the long term. Although public health recommendations must be considered tentative, the data on the relationship between moderate exercise, enhanced immunity, and lowered risk of sickness are consistent with guidelines
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urging the general public to engage in near-daily brisk walking.
III. ATHLETIC ENDEAVOR AND URTI Endurance athletes are often uncertain of whether they should exercise or rest during an infectious episode. There are few data available in humans to provide definitive answers. Most clinical authorities in this area recommend that if the athlete has symptoms of a common cold with no constitutional involvement, then regular training may be safely resumed a few days after the resolution of symptoms. Mild exercise during sickness with a common cold does not appear to be contraindicated. Weidner et al. (1997), for example, have shown that rhinovirus-caused upper respiratory illness does not impair short duration submaximal or maximal exercise performance. In addition, moderate exercise training did not influence URTI symptomatology (Weidner et al., 1998; Weidner and Schurr, 2003). However, it should be cautioned that rhinoviruses account for only 40% of URTI, and further research is needed with other pathogens to determine their relationship to exercise. Some clinicians feel that if there are symptoms or signs of systemic involvement (fever, extreme tiredness, muscle aches, swollen lymph glands, etc.), then 2–4 weeks should probably be allowed before resumption of intensive training (Friman et al., 1995; Nieman, 1997a). For elite athletes who may be undergoing heavy exercise stress in preparation for competition, several precautions may help them reduce their risk of URTI. Considerable evidence indicates that two other environmental factors—improper nutrition and psychological stress—can compound the negative influence that heavy exertion has on the immune system (Nieman, 1997a; Shephard and Shek, 1995). Based on current understanding, the athlete is urged to eat a well-balanced diet, keep other life stresses to a minimum, avoid overtraining and chronic fatigue, obtain adequate sleep, and space vigorous workouts and race events as far apart as possible. Immune system function may be suppressed during periods of rapid weight loss, so when necessary, the athlete is advised to lose weight slowly during noncompetitive training phases (Nieman et al., 1998a; Shade et al., 2004). Cold viruses are spread by both personal contact and breathing the air near sick people. Therefore, if at all possible, athletes should avoid being around sick people before and after important events. If the athlete is competing during the winter months, a flu shot is recommended.
A. Nutritional Strategies Nutrition impacts the development of the immune system, both in the growing fetus and in the early months of life. Nutrients are also necessary for the immune response to pathogens so that cells can divide and produce antibodies and cytokines. Many enzymes in immune cells require the presence of micronutrients, and critical roles have been defined for zinc; iron; copper; selenium; and vitamins A, B6, C, and E in the maintenance of optimum immune function. Although endurance athletes may be at increased infection risk during heavy training or competitive cycles, they must exercise intensively to contend successfully. Athletes appear less interested in reducing training workloads, and more receptive to ingesting nutrient supplements that have the potential to counter exercise-induced inflammation and immune alterations (Nieman, 2001; Shephard and Shek, 1995). The influence of a growing list of nutritional supplements on the immune and infection response to intense and prolonged exercise has been assessed. Supplements studied thus far include zinc, dietary fat, plant sterols, antioxidants (e.g., vitamins C and E, betacarotene, N-acetylcysteine, and butylated hydroxyanisole), glutamine, and carbohydrate. Except for carbohydrate beverages, none of these supplements has emerged as an effective countermeasure to exercise-induced immune suppression. Antioxidants and glutamine have received much attention, but the data thus far do not support their role in negating immune changes after heavy exertion. At this point, athletes should eat a varied and balanced diet in accordance with the Food Guide Pyramid and energy needs, and be assured that vitamin and mineral intake is adequate for both health and immune function. 1. Carbohydrate Supplements Research during the 1980s and early 1990s established that a reduction in blood glucose levels was linked to hypothalamic-pituitary-adrenal activation, an increased release of adrenocorticotrophic hormone and cortisol, increased plasma growth hormone, and increased plasma epinephrine levels (Murray et al., 1991). Stress hormones have an intimate link with some aspects of immune function (Figure 4). Several studies with runners and cyclists have shown that carbohydrate beverage ingestion plays a role in attenuating changes in immunity when the athlete experiences physiologic stress and depletion of carbohydrate stores in response to high intensity (∼75–80% VO2max) exercise bouts lasting longer than 90 minutes (Nehlsen-Cannarella et al., 1997; Nieman et al., 1997a, 1997c, 1998b, 2003a). In particular, carbo-
31. Exercise and Immunity: Clinical Studies
FIGURE 4 Carbohydrate supplementation during exercise attenuates plasma stress hormone, blood neutrophil count, and plasma cytokine responses.
hydrate ingestion (about one liter per hour of a typical sports drink) compared to a placebo has been linked to reduced change in blood immune cell counts, and lower pro- and anti-inflammatory cytokines. However, carbohydrate ingestion during intense and prolonged exercise is largely ineffective in countering postexercise decrements in NK and T-cell function, and salivary IgA output. Overall, these data indicate that physiological stress to some aspects of the immune system is reduced when endurance athletes use carbohydrate during intense exertion lasting 90 minutes or more. Does this mean that endurance athletes using carbohydrate beverages during marathon-type race events will lower their risk of sickness afterwards? One study suggests this is so, but more research is needed (Nieman et al., 2002a). 2. Antioxidants Heavy exertion increases the generation of free radicals and reactive oxygen species (ROS) through several pathways including oxidative phosphorylation, increase in catecholamines, prostanoid metabolism, xanthine oxidase, and NAD(P)H oxidase (Urso and Clarkson, 2003). Neutrophils and macrophages migrate to the site of contraction-induced muscle damage, infiltrate the muscle tissue, activate the release of cytokines, and produce additional ROS. Most ROS are neutralized by a sophisticated antioxidant defense system consisting of a variety of enzymes and nonenzymatic antioxidants including vitamin A, E, and C; glutathione; ubiquinone; and flavonoids. Intensive and sustained exercise, however, can create an imbalance between ROS and antioxidants, leading to oxida-
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tive stress that not only causes lipid peroxidation and protein oxidation, but may also impact immune function. Can antioxidant supplements attenuate exerciseinduced changes in immune function and infection risk? Several double-blind placebo studies of South African ultramarathon runners demonstrated that vitamin C (but not E or beta-carotene) supplementation (about 600 mg/day for 3 weeks) was related to fewer reports of URTI symptoms (Peters, 1990; Peters et al., 1993, 1996; Peters and Bateman, 1983; PetersFutre, 1997). This has not been replicated, however, by other research teams. Himmelstein et al. (1998), for example, reported no alteration in URTI incidence among 44 marathon runners and 48 sedentary subjects randomly assigned to a 2-month regimen of 1,000 mg/ day of vitamin C or placebo. Most randomized, placebo-controlled studies have been unable to demonstrate that vitamin C supplements modulate immune responses following heavy exertion (Nieman et al., 1997b; Nieman et al., 2000b, 2002b). Vitamin E functions primarily as a non-specific, chain-breaking antioxidant that prevents the propagation of lipid peroxidation. The vitamin is a peroxyl radical scavenger and protects polyunsaturated fatty acids within membrane phospholipids and in plasma lipoproteins. The effect of vitamin E supplementation on the inflammatory and immune response to intensive and prolonged exercise is largely unstudied and equivocal. Cannon et al. (1991) found that vitamin E supplementation of 800 IU/day for 48 days attenuated endotoxin-induced IL-6 secretion from mononuclear cells for 12 days after running downhill on an inclined treadmill. Singh et al. (1999) showed no effect of vitamin E supplementation (4 days, 800 IU/day) on the increase in plasma IL-6 following a 98-minute treadmill run at 65–70% VO2max to exhaustion. Petersen et al. (2002) reported no influence of vitamin E and C supplementation (500 mg and 400 mg, respectively, for 14 days before and 7 days after) on the plasma cytokine response to a 5% downhill 90-minute treadmill run at 75% VO2max. Two months of vitamin E supplementation at a dose of 800 IU/day α-tocopherol did not effect increases in plasma cytokines, perturbations in other measures of immunity, or oxidative stress in triathletes competing in the Triathlon World Championship race event (Nieman et al., 2004). To the contrary, athletes in the vitamin E compared to placebo group experienced greater lipid peroxidation and increases in plasma levels of several cytokines following the triathlon. Despite these indications that vitamin E exerted prooxidant and pro-inflammatory effects, race performance did not differ between athletes in the vitamin E
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and placebo groups. In general, vitamin E supplementation to counter immune suppression and oxidative stress in endurance athletes cannot be recommended. 3. Glutamine Glutamine, a non-essential amino acid, has attracted much attention by investigators (Mackinnon and Hooper, 1996; Rhode et al., 1995, 1998). Glutamine is the most abundant amino acid in the body, and is synthesized by skeletal muscle and other tissues. Glutamine is an important fuel for lymphocytes and monocytes, and decreased amounts in vitro have a direct effect in lowering proliferation rates of lymphocytes. Reduced plasma glutamine levels have been observed in response to various stressors, including prolonged exercise. Since skeletal muscle is the major tissue involved in glutamine production and is known to release glutamine into the blood compartment at a high rate, it has been hypothesized that muscle activity may directly influence the immune system by altering the availability of this immune cell fuel substrate. Whether exercise-induced reductions in plasma glutamine levels are linked to impaired immunity and host protection against viruses in athletes is still unsettled, but the majority of studies have not favored such a relationship (Nieman and Pedersen, 2000). For example, in a crossover, placebo-controlled study of eight males, glutamine supplementation abolished the post-exercise decrease in plasma glutamine concentration but still had no influence relative to placebo on exercise-induced decreases in T- and natural killer cell function (Rhode et al., 1998). One problem with the glutamine hypothesis is that plasma concentrations following exercise do not decrease below threshold levels that are detrimental to lymphocyte function as demarcated by in vitro experiments. In other words, even marathon-type exertion does not deplete the large body stores of glutamine enough to diminish lymphocyte function. In summary, there is growing evidence that prolonged intensive exercise is associated with an increased risk of URTI, in contrast to a decreased risk with moderate exercise training. Attempts have been made to alter the elevated URTI risk and suppressed immunity that have been associated with heavy exertion through chemical and nutritional means, with the most promising results thus far reported for carbohydrate supplementation. Further research is needed to establish the relationship of other nutrient supplements to changes in both immune function and host protection against URTI pathogens.
IV. CONCLUSIONS By far, the most important finding that has emerged from exercise immunology studies during the past 2 decades is that positive immune changes take place during each bout of moderate physical activity. Over time, this translates to fewer days of sickness with the common cold and other upper respiratory tract infections. This is consistent with public health guidelines urging individuals to engage in near-daily physical activity of 30 minutes or greater. The future of exercise immunology is determining whether or not exercise-induced perturbations in immunity help explain improvements in other clinical outcomes such as cancer, heart disease, type 2 diabetes, arthritis, and aging. This is an exciting new area of scientific endeavor, and preliminary data suggest that immune changes during exercise training are one of multiple mechanistic factors. Risk of upper respiratory tract infections can increase when athletes push beyond normal limits. The infection risk is amplified when other factors related to immune function are present, including exposure to novel pathogens during travel, lack of sleep, severe mental stress, malnutrition, or weight loss. Should the athlete exercise when sick? In general, if the symptoms are from the neck up (e.g., the common cold), moderate exercise is probably acceptable and some researchers would argue even beneficial, while bedrest and a gradual progression to normal training are recommended when the illness is systemic (e.g., the flu). If in doubt as to the type of infectious illness, individuals should consult a physician. Many components of the immune system exhibit adverse change after prolonged, heavy exertion lasting longer than 90 minutes. These immune changes occur in several compartments of the immune system and body (e.g., the skin, upper respiratory tract mucosal tissue, lung, blood, and muscle). During this “open window” of impaired immunity (which may last between 3 and 72 hours, depending on the immune measure), viruses and bacteria may gain a foothold, increasing the risk of subclinical and clinical infection. Of the various nutritional countermeasures that have been evaluated thus far, ingestion of carbohydrate beverages during intense and prolonged exercise has emerged as the most effective. However, carbohydrate supplementation during exercise decreases exerciseinduced increases in plasma cytokines and stress hormones, but is largely ineffective against other immune components including natural killer and T-cell function.
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References Allgayer, H., Nicolaus, S., and Schrieber, S. (2004). Decreased interleukin-1 receptor antagonist response following moderate exercise in patients with colorectal carcinoma after primary treatment. Cancer Detect. Prev., 28, 208–213. Baetjer, A. M. (1932). The effect of muscular fatigue upon resistance. Physiol. Rev., 12, 453–468. Bruunsgaard, H., Hartkopp, A., Mohr, T., Konradsen, H., Heron, I., Mordhorst, C. H., and Pedersen, B. K. (1997). In vivo cellmediated immunity and vaccination response following prolonged, intense exercise. Med. Sci. Sports Exerc., 29, 1176–1181. Cannon, J. G., Meydani, S. N., Fiedling, R. A., Fiatarone, M. A., Meydani, M., Farhangmehr, M., Orencole, S. F., Blumberg, J. B., and Evans, W. J. (1991). Acute phase response to exercise. II. Associations between vitamin E, cytokines, and muscle proteolysis. Am. J. Physiol., 260, R1235–R1240. Castell, L. M., Poortmans, J. R., Leclercq, R., Brasseur, M., Duchateau, J., and Newsholme, E. A. (1997). Some aspects of the acute phase response after a marathon race, and the effects of glutamine supplementation. Eur. J. Appl. Physiol., 75, 47–53. Castell, L. M., Poortmans, J. R., and Newsholme, E. A. (1996). Does glutamine have a role in reducing infections in athletes? Eur. J. Appl. Physiol., 73, 488–490. Davis, J. M., Kohut, M. L., Colbert, L. H., Jackson, D. A., Ghaffar, A., and Mayer, E. P. (1997). Exercise, alveolar macrophage function, and susceptibility to respiratory infection. J. Appl. Physiol., 83, 1461–1466. Drenth, J. P., Van Uum, S. H. M., Van Deuren, M., Pesman, G. J., Van Der VenJongekrijg, J., and Van Der Meer, J. W. M. (1995). Endurance run increases circulating IL-6 and IL-1ra but down regulates ex vivo TNF-α and IL-1β production. J. Appl. Physiol., 79, 1497–1503. Fairey, A. S., Courneya, K. S., Field, C. J., Bell, G. J., Jones, L. W., and Mackey, J. R. (2005). Randomized controlled trial of exercise and blood immune function in postmenopausal breast cancer survivors. J. Appl. Physiol., 98, 1534–1540. Ferrier, K. E., Nestel, P., Taylor, A., Drew, B. C., and Kingwell, B. A. (2004). Diet but not aerobic exercise training reduces skeletal muscle TNF-alpha in overweight humans. Diabetologia, 47, 630–637. Friman, G., Wesslen, L., Karjalainen, J., and Rolf, C. (1995). Infectious and lymphocytic myocarditis: epidemiology and factors relevant to sports medicine. Scand. J. Med. Sci. Sports, 5, 169–278. Gabriel, H., and Kindermann, W. (1997). The acute immune response to exercise: what does it mean? Int. J. Sports Med., 18 (Suppl. 1), S28–S45. Heath, G. W., Ford, E. S., Craven, T. E., Macera, C. A., Jackson, K. L., and Pate, R. R. (1991). Exercise and the incidence of upper respiratory tract infections. Med. Sci. Sports Exerc., 23, 152–157. Himmelstein, S. A., Robergs, R. A., Koehler, K. M., Lewis, S. L., and Qualls, C. R. (1998). Vitamin C supplementation and upper respiratory tract infections in marathon runners. J. Exerc. Physiol. Online, 1 (2), 1–17. Hoffman-Goetz, L., and Husted, J. (1995). Exercise and cancer: do the biology and epidemiology correspond? Exerc. Immunol. Rev., 1, 81–96. Hoffman-Goetz, L., and Pedersen, B. K. (1994). Exercise and the immune system: a model of the stress response? Immunol. Today, 15, 382–387. Kohut, M. L., Arntson, B. A., Lee, W., Rozeboom, K., Yoon, K. J., Cunnick, J. E., and McElhaney, J. (2004). Vaccine, 22, 2298–2306.
671
Kohut, M. L., and Senchina, D. S. (2004). Reversing age-associated immunosenescence via exercise. Exerc. Immunol. Rev., 10, 6–41. Konig, D., Grathwohl, D., Weinstock, C., Northoff, H., and Berg, A. (2000). Upper respiratory tract infection in athletes: influence of lifestyle, type of sport, training effort, and immunostimulant intake. Exerc. Immunol. Rev., 6, 102–120. Kostka, T., Berthouze, S. E., Lacour, J., and Bonnefoy, M. (2000). The symptomatology of upper respiratory tract infections and exercise in elderly people. Med. Sci. Sports Exerc., 32, 46–51. Lee, D. J., Meehan, R. T., Robinson, C., Mabry, T. R., and Smith, M. L. (1992). Immune responsiveness and risk of illness in U. S. Air Force Academy cadets during basic cadet training. Aviat. Space Environ. Med., 63, 517–523. Linde, F. (1987). Running and upper respiratory tract infections. Scand. J. Sports Sci., 9, 21–23. Mackinnon, L. T., Ginn, E. M., and Seymour, G. J. (1993). Temporal relationship between decreased salivary IgA and upper respiratory tract infection in elite athletes. Aust. J. Sci. Med. Sport, 25, 94–99. Mackinnon, L. T., and Hooper, S. (1994). Mucosal (secretory) immune system responses to exercise of varying intensity and during overtraining. Int. J. Sports Med., 15, S179–S183. Mackinnon, L. T., and Hooper, S. L. (1996). Plasma glutamine and upper respiratory tract infection during intensified training in swimmers. Med. Sci. Sports Exerc., 28, 285–290. Maffulli, N., Testa, V., and Capasso, G. (1993). Post-viral fatigue syndrome. A longitudinal assessment in varsity athletes. J. Sports Med. Phys. Fit., 33, 392–399. Matthews, C. E., Ockene, I. S., Freedson, P. S., Rosal, M. C., Merriam, P. A., and Hebert, J. R. (2002). Moderate to vigorous physical activity and risk of upper-respiratory tract infection. Med. Sci. Sports Exerc., 34, 1242–1248. Müns, G. (1993). Effect of long-distance running on polymorphonuclear neutrophil phagocytic function of the upper airways. Int. J. Sports Med., 15, 96–99. Murray, R., Paul, G. L., Seifert, G. J., and Eddy, D. E. (1991). Responses to varying rates of carbohydrate ingestion during exercise. Med. Sci. Sports Exerc., 23, 713–718. Nehlsen-Cannarella, S. L., Fagoaga, O. R., Nieman, D. C., Henson, D. A., Butterworth, D. E., Schmitt, R. L., Bailey, E. M., Warren, B. J., and Davis, J. M. (1997). Carbohydrate and the cytokine response to 2.5 hours of running. J. Appl. Physiol., 82, 1662–1667. Nehlsen-Cannarella, S. L., Nieman, D. C., Jessen, J., Chang, L., Gusewitch, G., Blix, G. G., and Ashley, E. (1991). The effects of acute moderate exercise on lymphocyte function and serum immunoglobulins. Int. J. Sports Med., 12, 391–398. Nieman, D. C. (1997a). Exercise immunology: practical applications. Int. J. Sports Med., 18 (Suppl. 1), S91–S100. Nieman, D. C. (1997b). Immune response to heavy exertion. J. Appl. Physiol., 82, 1385–1394. Nieman, D. C. (2000). Exercise effects on systemic immunity. Immunol. Cell Biol., 78, 496–501. Nieman, D. C. (2001). Exercise immunology: nutritional countermeasures. Can. J. Appl. Physiol., 26 (Suppl), S45–S55. Nieman, D. C. (2003). Current perspective on exercise immunology. Curr. Sports Med. Rep., 2, 239–242. Nieman, D. C., Ahle, J. C., Henson, D. A., Warren, B. J., Suttles, J., Davis, J. M., Buckley, K. S., Simandle, S., Butterworth, D. E., Fagoaga, O. R., and Nehlsen-Cannarella, S. L. (1995a). Indomethacin does not alter the natural killer cell response to 2.5 hours of running. J. Appl. Physiol., 79, 748–755.
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Nieman, D. C., Buckley, K. S., Henson, D. A., Warren, B. J., Suttles, J., Ahle, J. C., Simandle, S., Fagoaga, O. R., and NehlsenCannarella, S. L. (1995b). Immune function in marathon runners versus sedentary controls. Med. Sci. Sports Exerc., 27, 986–992. Nieman, D. C., Davis, J. M., Henson, D. A., Walberg-Rankin, J., Shute, M., Dumke, C. L., Utter, A. C., Vinci, D. M., Carson, J., Brown, A., Lee, W. J., McAnulty, S. R., and McAnulty, L. S. (2003a). Carbohydrate ingestion influences skeletal muscle cytokine mRNA and plasma cytokine levels after a 3–h run. J. Appl. Physiol., 94, 1917–1925. Nieman, D. C., Dumke, C. L., Henson, D. A., McAnulty, S. R., McAnulty, L. S., Lind, R. H., and Morrow, J. D. (2003b). Immune and oxidative changes during and following the Western States Endurance Run. Int. J. Sports Med., 24, 541–547. Nieman, D. C., Fagoaga, O. R., Butterworth, D. E., Warren, B. J., Utter, A., Davis, J. M., Henson, D. A., Nehlsen-Cannarella, S. L. (1997a). Carbohydrate supplementation affects blood granulocyte and monocyte trafficking but not function following 2.5 hours of running. Am. J. Clin. Nutr., 66, 153–159. Nieman, D. C., Henson, D. A., Austin, M. D., and Brown, V. A. (2005a). The immune response to a 30-minute walk. Med. Sci. Sports Exerc., 37, 57–62. Nieman, D. C., Henson, D. A., Butterworth, D. E., Warren, B. J., Davis, J. M., Fagoaga, O. R., and Nehlsen-Cannarella, S. L. (1997b). Vitamin C supplementation does not alter the immune response to 2.5 hours of running. Int. J. Sports Nutr., 7, 174– 184. Nieman, D. C., Henson, D. A., Dumke, C. L., Lind, R. H., Shooter, L. R., and Gross, S. J. (2006). Relationship between salivary IgA secretion and upper respiratory tract infection following a 160-km race. J. Sports Med. Phys. Fit., 46, 158–162. Nieman, D. C., Henson, D. A., Fagoaga, O. R., Utter, A. C., Vinci, D. M., Davis, J. M., and Nehlsen-Cannarella, S. L. (2002a). Change in salivary IgA following a competitive marathon race. Int. J. Sports Med., 23, 69–75. Nieman, D. C., Henson, D. A., Garner, E. B., Butterworth, D. E., Warren, B. J., Utter, A., Davis, J. M., Fagoaga, O. R., and NehlsenCannarella, S. L. (1997c). Carbohydrate affects natural killer cell redistribution but not activity after running. Med. Sci. Sports Exerc., 29, 1318–1324. Nieman, D. C., Henson, D. A., Gusewitch, G., Warren, B. J., Dotson, R. C., Butterworth, D. E., and Nehlsen-Cannarella, S. L. (1993). Physical activity and immune function in elderly women. Med. Sci. Sports Exerc., 25, 823–831. Nieman, D. C., Henson, D. A., McAnulty, S. R., McAnulty, L. S., Morrow, J. D., Ahmed, A., and Heward, C. B. (2004). Vitamin E and immunity after the Kona Triathlon World Championship. Med. Sci. Sports Exerc., 36, 1328–1335. Nieman, D. C., Henson, D. A., McAnulty, S. R., McAnulty, L., Swick, N. S., Utter, A. C., Vinci, D. M., Opiela, S. J., and Morrow, J. D. (2002b). Influence of vitamin C supplementation on oxidative and immune changes following an ultramarathon. J. Appl. Physiol., 92, 1970–1977. Nieman, D. C., Henson, D. A., Smith, L. L., Utter, A. C., Vinci, D. M., Davis, J. M., Kaminsky, D. E., and Shute, M. (2001). Cytokine changes after a marathon race. J. Appl. Physiol., 91, 109–114. Nieman, D. C., Johanssen, L. M., and Lee, J. W. (1989). Infectious episodes in runners before and after a roadrace. J. Sports Med. Phys. Fit., 29, 289–296. Nieman, D. C., Johanssen, L. M., Lee, J. W., Cermak, J., and Arabatzis, K. (1990a). Infectious episodes in runners before and after the Los Angeles Marathon. J. Sports Med. Phys. Fit., 30, 316–328.
Nieman, D. C., and Nehlsen-Cannarella, S. L. (1994). The immune response to exercise. Sem. Hematol., 31, 166–179. Nieman, D. C., Nehlsen-Cannarella, S. L., Fagoaga, O. R., Henson, D. A., Shannon, M., Davis, J. M., Austin, M. D., Hisey, C. L., Holbeck, J. C., Hjertman, J. M. E., Bolton, M. R., and Schilling, B. K. (1999). Immune response to two hours of rowing in female elite rowers. Int. J. Sports Med., 20, 476–481. Nieman, D. C., Nehlsen-Cannarella, S. L., Fagoaga, O. R., Henson, D. A., Shannon, M., Hjertman, J. M. E., Schmitt, R. L., Bolton, M. R., Austin, M. D., Schilling, B. K., and Thorpe, R. (2000a). Immune function in female elite rowers and nonathletes. Br. J. Sports Med., 34, 181–187. Nieman, D. C., Nehlsen-Cannarella, S. L., Henson, D. A., Butterworth, D. E., Fagoaga, O. R., and Utter, A. (1998a). Immune response to exercise training and/or energy restriction in obese women. Med. Sci. Sports Exerc., 30, 679–686. Nieman, D. C., Nehlsen-Cannarella, S. L., Henson, D. A., Butterworth, D. E., Fagoaga, O. R., and Utter, A. (1998b). Influence of carbohydrate ingestion and mode on the granulocyte and monocyte response to heavy exertion in triathletes. J. Appl. Physiol., 84, 1252–1259. Nieman, D. C., Nehlsen-Cannarella, S. L., Markoff, P. A., BalkLamberton, A. J., Yang, H., Chritton, D. B. W., Lee, J. W., and Arabatzis, K. (1990b). The effects of moderate exercise training on natural killer cells and acute upper respiratory tract infections. Int. J. Sports Med., 11, 467–473. Nieman, D. C., and Pedersen, B. K. (2000). Nutrition and exercise immunology. Boca Raton, FL: CRC Press. Nieman, D. C., Peters, E. M., Henson, D. A., Nevines, E., and Thompson, M. M. (2000b). Influence of vitamin C supplementation on cytokine changes following an ultramarathon. J. Interferon Cytokine Res., 20, 1029–1035. Nieman, D. C., Simandle, S., Henson, D. A., Warren, B. J., Suttles, J., Davis, J. M., Buckley, K. S., Ahle, J. C., Butterworth, D. E., Fagoaga, O. R., and Nehlsen-Cannarella, S. L. (1995c). Lymphocyte proliferation response to 2.5 hours of running. Int. J. Sports Med., 16, 406–410. Parker, S., Brukner, P., and Rosier, M. (1996). Chronic fatigue syndrome and the athlete. Sports Med. Train. Rehab., 6, 269– 278. Pedersen, B. K., and Bruunsgaard, H. (1995). How physical exercise influences the establishment of infections. Sports Med., 19, 393–400. Peters, E. M. (1990). Altitude fails to increase susceptibility of ultramarathon runners to post-race upper respiratory tract infections. S. Afr. J. Sports Med., 5, 4–8. Peters, E. M., and Bateman, E. D. (1983). Respiratory tract infections: an epidemiological survey. S. Afr. Med. J., 64, 582–584. Peters, E. M., Goetzsche, J. M., Grobbelaar, B., and Noakes, T. D. (1993). Vitamin C supplementation reduces the incidence of postrace symptoms of upper-respiratory-tract infection in ultramarathon runners. Am. J. Clin. Nutr., 57, 170–174. Peters, E. M., Goetzsche, J. M., Joseph, L. E., and Noakes, T. D. (1996). Vitamin C as effective as combinations of anti-oxidant nutrients in reducing symptoms of upper respiratory tract infection in ultramarathon runners. S. Afr. J. Sports Med., 11 (3), 23–27. Peters-Futre, E. M. (1997). Vitamin C, neutrophil function, and upper respiratory tract infection risk in distance runners: the missing link. Exerc. Immunol. Rev., 3, 32–52. Petersen, E. W., Ostrowski, K., Ibfelt, T., Richelle, M., Offord, E., Halkjaer-Kristensen, J., and Pedersen, B. K. (2002). Effect of vitamin supplementation on cytokine response and on muscle damage after strenuous exercise. Am. J. Physiol. Cell Physiol., 280, C1570–C1575.
31. Exercise and Immunity: Clinical Studies Petersen, A. M., and Pedersen, B. K. (2005). The anti-inflammatory effect of exercise. J. Appl. Physiol., 98, 1154–1162. Pyne, D. B., Baker, M. S., Fricker, P. A., McDonald, W. A., and Nelson, W. J. (1995). Effects of an intensive 12–wk training program by elite swimmers on neutrophil oxidative activity. Med. Sci. Sports Exerc., 27, 536–542. Rhode, T., MacLean, D. A., and Pedersen, B. K. (1998). Effect of glutamine supplementation on changes in the immune system induced by repeated exercise. Med. Sci. Sports Exerc., 30, 856–862. Rhode, T., Ullum, H., Rasmussen, J. P., Kristensen, J. H., Newsholme, E., and Pedersen, B. K. (1995). Effects of glutamine on the immune system: influence of muscular exercise and HIV infection. J. Appl. Physiol., 79, 146–150. Ryan, A. S., and Nicklas, B. J. (2004). Reductions in plasma cytokine levels with weight loss improve insulin sensitivity in overweight and obese postmenopausal women. Diabetes Care, 27, 1699– 1705. Shade, E. D., Ulrich, C. M., Wener, M. H., Wood, B., Yasui, Y., Lacroix, K., Potter, J. D., and McTiernan, A. (2004). Frequent intentional weight loss is associated with lower natural killer cell cytotoxicity in postmenopausal women: possible long-term immune effects. J. Am. Diet. Assoc., 104, 903–912. Shephard, R. J., Kavanagh, T., Mertens, D. J., Qureshi, S., and Clark, M. (1995). Personal health benefits of Masters athletics competition. Br. J. Sports Med., 29, 35–40. Shephard, R. J., and Shek, P. N. (1995). Heavy exercise, nutrition and immune function: Is there a connection? Int. J. Sports Med., 16, 491–497. Shinkai, S., Kurokawa, Y., Hino, S., Hirose, M., Torii, J., Watanabe, S., Watanabe, S., Shiraishi, S., Oka, K., and Watanabe. T. (1993).
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Triathlon competition induced a transient immunosuppressive change in the peripheral blood of athletes. J. Sports Med. Phys. Fit., 33, 70–78. Singh, A., Papanicolaou, D. A., Lawrence, L. L., Howell, E. A., Chrousos, G. P., and Deuster, P. A. (1999). Neuroendocrine responses to running in women after zinc and vitamin E supplementation. Med. Sci. Sports Exerc., 31, 536–542. Smith, J. A., and Pyne, D. B. (1997). Exercise, training, and neutrophil function. Exerc. Immunol. Rev., 3, 96–117. Smith, T. P., Kennedy, S. L., and Fleshner, M. (2004). Influence of age and physical activity on the primary in vivo antibody and T cell-mediated responses in men. J. Appl. Physiol., 97, 491–498. Strasner, A., Barlow, C. E., Kampert, J. B., and Dunn, A. L. (2001). Impact of physical activity on URTI symptoms in Project PRIME participants. Med. Sci. Sports Exerc., 33 (Suppl), S304. Tomas, E., Kelly, M., Xiang, X., Tsao, T. S., Keller, C., Keller, P., Luo, Z., Lodish, H., Saha, A. K., Unger, R., and Ruderman, N. B. (2004). Metabolic and hormonal interactions between muscle and adipose tissue. Proc. Nutr. Soc., 63, 381–385. Urso, M. L., and Clarkson, P. M. (2003). Oxidative stress, exercise, and antioxidant supplementation. Toxicol., 189, 41–54. Weidner, T. G., Anderson, B. N., Kaminsky, L. A., Dick, E. C., and Schurr, T. (1997). Effect of a rhinovirus-caused upper respiratory illness on pulmonary function test and exercise responses. Med. Sci. Sport Exerc., 29, 604–609. Weidner, T., Cranston, T., Schurr, T., and Kaminsky, L. (1998). The effect of exercise training on the severity and duration of a viral upper respiratory illness. Med. Sci. Sports Exerc., 30, 1578–1583. Weidner, T., and Schurr, T. (2003). Effect of exercise on upper respiratory tract infection in sedentary subjects. Br. J. Sports Med., 37, 304–306.
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C H A P T E R
32 Behavioral Interventions: Immunologic Mediators and Disease Outcomes MICHAEL H. ANTONI, NEIL SCHNEIDERMAN, AND FRANK PENEDO
I. INTRODUCTION 675 II. STRESSORS, AFFECT, ENDOCRINES, AND THE IMMUNE SYSTEM IN HUMANS 676 III. BEHAVIORAL INTERVENTIONS, STRESS RESPONSES, AND THE IMMUNE SYSTEM 683 IV. CLINICAL APPLICATIONS OF BEHAVIORAL INTERVENTION-PNI PARADIGMS IN HEALTH AND DISEASE 688 V. CONCLUSION 695
directed toward disease management are those designed to reduce anxiety, depressed affect, hostility, and stress/distress; modify cognitive appraisals about stress and disease; teach new behavioral and interpersonal coping skills; and provide social support. Several recent surveys polling physician opinions about the effectiveness of alternative medical interventions such as exercise, biofeedback, acupuncture, massage, and hypnosis have suggested that the majority of practitioners now view these techniques as at least moderately effective and comparable with other medical practices (Fontanaros and Lundberg, 1997). While solid empirical tests of the efficacy and underlying mechanisms of action of many of these practices are still lacking, the extensive body of PNI research documenting interactions of behavioral, neural, endocrine, and immune systems across a wide variety of species and situations is often used to justify their existence. The PNI research that is most relevant to rationalizing the use of behavioral interventions to improve health outcomes derives from studies relating immune parameters to acute and chronic stressors, as well as central nervous system and endocrine-mediated “stress responses,” mood states, and a variety of stressmoderating variables such as personality and social factors. This evidence has evolved from correlational studies to animal models and experimental trials in healthy humans focusing on human disease models. Contemporary human disease models of PNI that are of greatest interest are those examining pathological processes such as tumorogenesis, immunopathology,
I. INTRODUCTION Behavioral interventions are the mainstay of the biobehavioral arsenal used to prevent the development of disease, and to foster adaptation to the stress of diagnosis and treatment for major conditions including cancers, cardiovascular disease, and immunologic disorders such as Acquired Immune Deficiency Syndrome (AIDS). There is growing interest in the question of whether the effects of these interventions in diagnosed patients may extend beyond improving adjustment and quality of life (QOL) to the possibility of improving health outcomes including decreased risk of recurrence and slowed disease progression. In the interest of exploring the mechanisms underlying these effects, there has accumulated a small but important empirical base demonstrating that behavioral interventions may also modulate immune system functioning by modifying stress responses and negative mood states. The major behavioral interventions PSYCHONEUROIMMUNOLOGY, 4E VOLUME I
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Copyright © 2007 by Elsevier, Inc. All rights of reproduction in any form reserved.
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and inflammation, which are most clearly demonstrated in conditions such as cancers, AIDS, and cardiovascular disease. This chapter will review the basic and clinical PNI evidence supporting the use of behavioral interventions to modify psychosocial and physiological processes relevant to the pathological processes underlying these three major disease groups.
II. STRESSORS, AFFECT, ENDOCRINES, AND THE IMMUNE SYSTEM IN HUMANS A. Stress-Endocrine-Immune Responses 1. Stressors and the Immune System Early PNI studies used cross-sectional designs to relate a series of field stressors (Herbert and Cohen, 1993b) and mood disturbances such as clinical depression (Herbert and Cohen, 1993a) to various immunologic indices including lymphocyte proliferative responses to mitogens; natural killer (NK) cell cytotoxicity (NKCC); neutrophil phagocytosis; antibody titers to herpesviruses such as Epstein Barr Virus (EBV) and Herpes Simplex Virus (HSV); interferon (IFN) production; salivary immunoglobulin-A (IgA) production; and changes in the numbers of circulating immune cells such as T-lymphocytes, B-lymphocytes, NK cells, and macrophages. Stressful experiences associated with decrements in the immune system in humans range from the more commonplace experiences such as medical school examinations (Glaser, Rice, Sheridan et al., 1987), sleep disruption (Hall et al., 1998), and care giving (Kiecolt-Glaser, Dura, Speicher et al., 1991), to more dramatic events such as death of a spouse (Bartrop, Lazurus, Luckhurst et al., 1977), marital separation and divorce (Kiecolt-Glaser, Fisher, Ogrocki et al., 1987), nuclear reactor accidents (McKinnon et al., 1989), earthquakes (Solomon, Segerstrom, Grohr et al., 1997), and hurricanes (Ironson, Wynings, Schneiderman et al., 1997). Major reviews of the stress-immune literature found that in 38 studies, stressors were associated with changes in 23 different immune system measures (Herbert and Cohen, 1993b). The most consistent of these measures were lymphoproliferative response to mitogens, NKCC, immunoglobulin levels, herpesvirus antibody titers, and circulating white blood cells. Among these indices, effect sizes ranged from low to moderate for lymphocyte proliferation and NKCC, to quite large for antibody titers to HSV and EBV. Two functional immune measures, lymphocyte proliferation and NKCC, were the focus of the majority of human PNI studies conducted in the 1980s and 1990s. For instance, decrements in NKCC have been associ-
ated with bereavement (Irwin, Daniels, Smith et al., 1987), anxiety-related symptoms following a major hurricane (Ironson et al., 1997), the chronic stress of being a caregiver for a dependent relative (Esterling, Kiecolt-Glaser, Bodnar et al., 1994), lack of social support (Baron, Cutrona, Hicklin et al., 1990), and marital distress (Kiecolt-Glaser et al., 1987). The fact that cellular immune function indicators are among the immune measures most consistently associated with a similar set of psychosocial variables suggests that these relations could be mediated by a few common mechanisms, possibly involving neuroendocrine-cytokine interactions. Interleukin-2 (IL-2), one cytokine involved directly in determining the magnitude of lymphocyte proliferation and NKCC functions, is particularly sensitive to stress hormones such as catecholamines and corticosteroids (Sheridan, 1996). It is therefore quite relevant that more recent work has moved in the direction of relating stressors to the production of IL-2 (Glaser, Kenedy, Lafuse et al., 1990) and the effects of IL-2 stimulation on functions such as NKCC (Esterling, Kiecolt-Glaser, and Glaser, 1996). Stressors appear to be more strongly associated with decrements in IL-2–stimulated NKCC than they are with unstimulated NKCC (Esterling, KiecoltGlaser, and Glaser, 1996), suggesting that efforts to develop assays more reflective of in vivo conditions may be fruitful in PNI research. With regard to the clinical significance of stressimmune relations, it is worth noting that lymphocyte proliferative responses to specific viral antigens (e.g., Herpes Simplex Virus, HSV) have been shown to be suppressed among caregivers of ill relatives (Glaser and Kiecolt-Glaser, 1997). We know that elevated HSV antibody titers (reflecting re-infection or latent virus reactivation) have also been related to marital separation and divorce (Kiecolt-Glaser, Kenedy, Malkoff et al., 1988), being a caregiver (Glaser and KiecoltGlaser, 1997), and being a resident of Three Mile Island during the period following the nuclear reactor accident (McKinnon et al., 1989). These associations are responsible for some of the highest stress-immune correlations (Herbert and Cohen, 1993b) documented in healthy humans to date. Because these antibody titers are specific to a certain pathogen and build slowly over predictable periods on the order of days or weeks, these types of indices may be more reliably tied to cumulative stressor load than would relatively transient fluctuations in cell numbers. Virus-specific T-cell response to other herpesviruses is decreased during medical school examinations (Glaser, Pearson, Bonneau et al., 1993), suggesting some of the cellmediated immune pathways by which stressors relate to infectious disease processes. This supports the
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notion that stressors may relate to indicators of immune responses to pathogens that may contribute directly to disease. 2. Mood-Immune Associations Other work has focused on immune associations with persons experiencing clinical depression as well as those reporting negative mood states. The most commonly used immune system index in studies of clinical depression is lymphocyte proliferation to mitogens such as phytohemagglutinin (PHA), concanavalin A (Con-A), or pokeweed mitogen (PWM). A quantitative (meta-analytic) review of studies relating depression and immunity found a reliable relationship between depression and decrements in a variety of immune measures including related lymphocyte populations, especially in older individuals and those with greater depression severity (Herbert and Cohen, 1993a). Even in individuals not meeting criteria for a diagnosis of depression, a linear relationship was found between depressed mood and impairments in measures of cell-mediated immunity (Herbert and Cohen, 1993a). Another review of this literature noted that patients with a diagnosis of depression also show lower percentages and numbers of total lymphocytes, and less NKCC and neutrophil activity (Weisse, 1992). Despite the relative success of pharmacotherapy and cognitive therapy in treating depression in humans, there were until only recently very few studies demonstrating parallel remission of depression symptoms and immunologic deficits in patients undergoing such treatments. In one of these studies, treatment with a serotonin antagonist decreased depressive symptoms and restored neutrophil activity to levels similar to controls over a 6-week trial (O’Neill and Leonard, 1986). 3. Stress Moderators and Immune Parameters Implicit in much human PNI research is the notion that psychosocial factors relate to immune system changes by way of stress- or mood-induced changes in hormonal regulatory systems, resulting in neuroendocrine elevations and imbalances (Maier, Watkins, and Fleshner, 1994). Neuroendocrine system responses are known to be altered as a function of an individual’s appraisal (i.e., controllable vs. uncontrollable) and coping response (i.e., active vs. passive) to stressful stimuli. Immunologic decrements and elevations in adrenocortical hormones have also been observed in those reporting significant degrees of loneliness (Kiecolt-Glaser, Ricker, George et al., 1984), suggesting that the degree of disruption in personal ties and social support may contribute significantly to the degree of
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immune system decrements observed during stressful periods. Given that perceived loss of control and social losses (e.g., divorce and bereavement) have been related to alterations in some of these immunomodulatory hormones (Calabrese, Kling, and Gold, 1987), it can be reasoned that many PNI relationships might be mediated, in part, by neurohormonal changes that are linked to an individual’s appraisals of, coping responses to, and resources available for dealing with environmental stimuli (Antoni and Schneiderman, 1998). In people undergoing stressful circumstances, perceptions of a loss of personal control, helplessness/hopelessness, and low self-efficacy have all been associated with immunologic decrements (Wiedenfeld, O’Leary, Bandura et al., 1990). Passive coping strategies (Goodkin et al., 1992) and insufficient emotional expression about traumatic or highly stressful events (Lutgendorf et al., 1994; Pennebaker et al., 1988) have been associated with decreased lymphoproliferative responses to mitogens and elevated antibody titers (reflecting poorer cell-mediated immune control) to Epstein Barr Virus (EBV). Finally, interpersonal processes such as social support (Baron et al., 1990), marital distress (Kiecolt-Glaser et al., 1987), and hostile interactions between marital partners (Kiecolt-Glaser, Malarkey, Cacioppo, and Glaser, 1994) have also been related to decrements in several cellular immune function measures. It is generally agreed that efforts to characterize the mechanisms underlying stressor-immune interactions in humans must take into account these appraisal, coping, and interpersonal processes since they can moderate the nature, degree, and duration of neuroendocrine responses. Recent theoretical models proposing stress-associated neuroanatomical changes involving structures critical for hypothalamicpituitary-adrenal (HPA) (McEwen, 1998) and sympatho-adreno-medullary (SAM) (Felten, 1996) hormonal regulation and efficient neuroimmune interactions have laid the groundwork for contemporary investigations designed to identify the mechanisms underlying the negative health consequences of chronic and repeated stressor exposure. 4. Stress Response Mechanisms: Endocrine-Immune Interactions For most of the twentieth century, the immune system was viewed as an autonomous set of tissues, individual cells, and soluble agents capable of both protecting the body from foreign antigens and its own mutating cells, as well as turning on itself in the form of anaphylactic and autoimmune reactions capable of
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killing or seriously crippling its host. The idea that these processes were capable of being influenced by environmental stimuli, perceptual processes and hormonal responses, and by the central nervous system (CNS) was completely foreign to mainstream thinking until the 1970s. At that time the convergence of many different lines of evidence established functional relationships among behavior, neural structures and processes, endocrine changes, and immune system components (Ader, 1996). A set of well-known behavioral conditioning studies (for review see Ader, 1996) provided empirical support for the notion that neural-immune system interactions might be plausible. Evidence of adrenergic receptors on lymphocytes and subsequent changes in lymphocyte proliferation to mitogens and cyclic AMP within lymphocytes after β-adrenergic stimulation provided a signaling mechanism for CNS-immune interaction (Hadden, Hadden, and Middleton, 1970). These effects were found to be mediated by changes in lymphocyte membrane enzymes that direct second messenger processes (e.g., ATPases) (Coffey, Hadden, and Hadden, 1975). Conversely, cholinergic stimulation of lymphocytes resulted in increased lymphoproliferative responses to PHA, and these effects appeared to be mediated by cyclic GMP (Hadden, Hadden, Meetz et al., 1973). Sympathetic noradrenergic fibers terminate in the thymus, bone marrow, spleen, and lymph nodes and appear to form synaptic connections with areas rich in lymphocytes and monocytes (Felten, Felten, Bellinger et al., 1987), establishing a “hard-wired” anatomical basis for neural-immune interactions in lymphoid organs. These connections may play a critical role in the early development of the immune system (Ackerman, Felten, Dijkstra et al., 1989) and in agerelated declines in sympathetic neurons projecting to lymphoid organs such as the spleen and lymph nodes (Bellinger, Ackerman, Felten, and Felten, 1992)— changes that might mediate the diminished cell-mediated immune functions and poorer resistance to certain infectious pathogens that occur later in life (Felten, 1996). This work was critical in establishing a physical medium (adrenergic and cholinergic receptors) through which both arms of the autonomic nervous system could signal cells of the immune system, and the second messenger mechanisms that could mediate their effects on lymphocyte physiology (Ader, 1996). Immunologic activities are also communicated “back” to the CNS by producing changes in neurotransmitters and endocrine substances subsequent to cytokine production (Besedovsky, del Rey, Sorkin et al., 1983). Increases in electrical activity in hypothalamic neurons, increases in plasma corticosterone, and decreases in brain NE follow injection of cytokine-rich
supernatants from stimulated lymphocytes (Besedovsky, del Rey, and Sorkin, 1981) and purified cytokines such as interleukin-1 (IL-1) (Berkenbosch, VanOers, del Rey et al., 1987). There is good evidence that the paraventricular nucleus of the hypothalamus is a key depot for immunoneural feedback control of the HPA axis (Carlson, Felten, Livnat, and Felten, 1987). Stress-related noradrenergic depletion disinhibits corticotrophin-releasing hormone (CRH) production with resulting increases in ACTH and peripheral cortisol, setting the stage for corticosteroid-induced inhibition of immune functioning. Peripherally produced cytokines such as IL-1 may also feed back to the CNS by way of IL-1 receptors on the paraganglia of the vagus nerve (Watkins, Wiertelak, Goehler et al., 1994). Much of the work in basic PNI that is used to explain psycho-immunologic associations in humans is focused on hormonal substances that are liberated into the circulation where they are free to interact with cells in the bloodstream, lymphatic fluid, and lymphoid organs (e.g., spleen and lymph nodes). The most commonly studied of these in field research is the adrenal hormone, cortisol. This empirical base is often cited as providing a potential mechanism for associations between stressful stimuli and immunologic changes. For years it has been known that adrenal cortical hormones directly impair or modify several components of cellular immunity directed by T-lymphocytes (Cupps and Fauci, 1982), macrophages (Pavlidis and Chirigos, 1980), and NK cells (Herberman and Holden, 1978). Corticosteroids can also modulate production of “upstream” cytokines (those related to initial encounters with pathogens) such as chemotaxic factor, macrophage migration inhibitory factor, and other cytokines such as IL-1 and plasminogen activator by monocytes, and IFN-γ and tumor necrosis factor-beta (TNF-β) by lymphocytes (Cupps and Fauci, 1982; Duncan, Sadlik, and Hadden, 1982; Stites et al., 1982). Intracytoplasmic glucocorticoid receptors characterized in lymphocytes mediate many of these effects (Freedman et al., 1989). Another commonly studied set of neurohormones in humans are catecholamines. Elevations in peripheral catecholamines and β-adrenergic agonists decrease human NKCC and T-lymphocyte proliferation to mitogens (Crary, Borysenko, Sutherland et al., 1983). Some work suggests that elevated catecholamines may promote a predominance of Th2 over Th1 cytokines, thus downregulating cytotoxic responses and other cellular immune functions. These changes may compound the pathogenic processes already evident in conditions such as human immunodeficiency virus (HIV) infection (Cole et al., 1996, 2001). Interestingly,
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β-adrenergic stimulation may also facilitate the production of pro-angiogenic substances such as vascular endothelial growth factor (VEGF) in cancer patients, opening up the possibility that a “stress hormone” could facilitate the vascularization of new tumor cells, thereby promoting their growth (Lutgendorf, Cole et al., 2003). It is plausible that corticosteroids and catecholamines may interact in producing immune changes. Patients treated with glucocorticoids show an increased β-adrenergic responsiveness due to an increased receptor number and enhanced receptor-adenyl cyclase coupling (Davies and Leflowitz, 1984), evidencing a synergy between these two classes of stress hormones. The hypothalamus and various limbic structures (e.g., amygdala) are capable of synthesizing both catecholamines and CRH (Masek, Petroviky, and Seifert, 1992). Adding corticosteroids to ovarian cancer cultures appears to amplify the VEGF-enhancing properties of β-adrenergic agents (Lutgendorf, Cole et al., 2003). In sum, at least two stress-related pathways are capable of orchestrating behavioral-immune interactions: the HPA axis by way of CRH, ACTH, and corticosteroids; and the SAM system, by way of peripheral catecholamine production (Chroussos and Gold, 1992; McEwen, 1998). Since these systems may synergize in bringing about their effects on certain immune parameters, it follows that stress responses or psychological states that are characterized by HPA and SAM activation may have the greatest effects on certain immune system functions. Another possible endocrine-immune mechanism involves the effects of hypothalamic-pituitary-gonadal (HPG) hormones such as estrogens, progesterone, and testosterone on the immune system (or directly on tumors themselves in the cases of hormone-responsive cancers such as breast and prostate cancer) (van der Pompe et al., 1994). Estradiol and testosterone administration causes NKCC reductions (Hou and Zheng, 1988); estrogen increases during the menstrual cycle (Sulke et al., 1985) and pregnancy (Pope, 1990) are associated with NKCC declines. Progesterone appears to suppress NKCC and may additively suppress NKCC when combined with estrogens (Feinberg et al., 1991), which could be due to a downregulation of IFN-γ production. There is some evidence that behavioral interventions focused on stress management can modulate HPG hormone levels (e.g., testosterone) in men with HIV infection (Cruess et al., 2000) and women with breast cancer (Cruess et al., 2000). Interestingly, in each of these studies the magnitude of the hormonal changes was associated with the improvement in psychosocial functioning. Whether these hormonal changes are associated with immune parameters during stress
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management intervention remains to be determined. A large research literature demonstrates that other hormones such as met-enkephalin, β-endorphin, substance P, growth hormone, thyroid hormones, androgens and estrogens, prolactin, arginine vasopressin, and neuropeptide-Y can modulate immune functioning, though this work is not reviewed here. No studies have tested the effects of behavioral interventions on these substances in humans; thus, their utility in justifying the use of behavioral interventions to modulate immune parameters is unclear at present. For most of the 1990s the majority of PNI studies were designed to elucidate mechanisms underlying associations between stressors and affect on the one hand and infectious and neoplastic disease on the other. Accordingly the downregulation of immune parameters associated with these disease processes received the greatest attention. In the past 10 years there has been an increasing focus on examining relations between behavioral factors and inflammatory processes in an effort to better understand the role of stressors, stress responses, and negative mood states on other major diseases such as cardiovascular disease (Steptoe and Brydon, 2005) and rheumatoid arthritis (Heijnen and Kavelaars, 2005).
B. Inflammation in Biological Processes There is growing evidence that acute and chronic stress as well as negative mood states may contribute to inflammatory responses, and this forms the basis for emerging PNI models applied to conditions such as coronary heart disease and other conditions where dysfunctions in inflammation are the key pathophysiological feature. 1. Biological Processes The cardinal signs of inflammation (literally meaning “in flame”) in tissue are heat, redness, swelling, and pain. These reflect underlying biologic processes designed to ward off infection in the presence of microbial invaders. Briefly, after sensing rightly or wrongly that a microbial invasion has begun, leukocytes convene in the apparently threatened tissue and secrete oxidants that damage microbes, and cytokines whose signals help to organize immune defenses. In some instances such as atherosclerosis (Ross, 1999), inflammatory processes prove to be harmful. As pointed out by Libby, Ridker, and Maseri (2002), the clearest picture of inflammation’s role in atherosclerosis has been shown in studies involving lowdensity lipoprotein (LDL) cholesterol. At reasonable blood concentrations, LDLs pass back and forth
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between the arterial lumen (i.e., blood-carrying channel) and the intima of the vessel. This intima consists of a single layer of endothelial cells that line the arterial vessel lumen, an underlying extracellular matrix of connective tissue, and smooth muscle cells that serve as matrix producers. When LDLs begin to accumulate in excess, they become stuck in the matrix. This leads to a cascade that produces inflammation. The initial stage of atherosclerosis, leading to the original excess accumulation of LDLs, is characterized by functional alterations of the endothelium. Normally, the endothelium protects cardiovascular function by producing fibrinolytic, anti-clotting, and anti-platelet factors. These prevent cells from adhering to the endothelial surface and regulate vascular tone through the production of molecules such as nitric oxide. However, endothelial dysfunction, secondary to endothelial injury, can occur due to elevated concentrations of LDL-cholesterol, free radicals, homocysteine, vasoactive amines, and even infectious micro-organisms (e.g., herpes viruses). Once the endothelium is breached through injury, LDL cholesterol begins to accumulate in the subendothelial matrix. The trapped LDLs then undergo oxidation due to exposure to the wastes of vascular cells. This produces minimally oxidized LDL species with pro-inflammatory activity. The modified LDLs spur endothelial and smooth muscle cells to secrete chemokines (chemoattractant molecules) that attract monocytes. These monocytes are normally quiescent inflammatory cells that circulate in blood. The process of attracting monocytes to the endothelium involves cell adhesion molecules (CAM) that latch on to the monocytes. The monocytes squeeze between endothelial cells and follow a chemical trail to the intima. Chemokines then induce the monocytes to multiply and mature into active macrophages. A number of pro-inflammatory cytokines produced by the endothelium, smooth muscle cells, and leukocytes also stimulate CAM upregulation, thereby facilitating leukocyte recruitment and adhesion. These cytokines include IFN-α, IL-1, IL-6, IL-8, and TNF-α. Firm adhesion of leukocytes to the vessel wall and transmigration to the intima is controlled by the interaction of vascular cell adhesion molecule-1 (VCAM-1) and immunoglobulin-related adhesion molecule-1 (ICAM-1). Monocytes, T-cells, and platelet-leukocyte aggregates continue to transmigrate into the intima and produce a pro-inflammatory response that helps form a lesion. Upon entering the intima of the vessel, the monocytes differentiate into macrophages, which ingest highly oxidized LDL (ox-LDL), leading to the formation of foam cells. The foam cells eventually die
but contribute their lipid-filled contents to the necrotic core of the lesion. When activated by macrophages, pro-inflammatory cytokines, ox-LDL, or viral infections (e.g., herpes viruses), T-cells also contribute to the progression of atherosclerosis. Activated T-cells produce inflammatory cytokines (TNF-α, IL-1, IL-6, IFN-α) that stimulate macrophages and vascular endothelial cells, thereby amplifying the inflammatory process. Together with T-cells, macrophages, endothelial cells, and smooth muscle cells secrete factors that induce smooth muscle cells to migrate to the surface of the intima and synthesize components of the extracellular matrix. The cells and matrix coalesce into a fibrous cap. This cap and the lipid or necrotic core under it are referred to as a fibrous plaque. During their early stages, atherosclerotic plaques tend to expand outward rather than impinging in on the blood-carrying lumen. Subsequently, the plaques may push inward causing stenosis, which is a restriction of blood flow. Most myocardial infarctions occur after a plaque’s fibrous cap breaks open. This causes a thrombus (blood clot) to develop over the ruptured plaque. In general, plaques likely to rupture possess a thin cap and large lipid pool. As in earlier stages of atherosclerosis, vulnerability stems from a large number of macrophages and long, intense periods of inflammation. 2. Acute Stress and Inflammation Acute psychological stressors can set the stage for inflammatory responses. Thus, for example, a stressful speech task has been shown to induce transient endothelial dysfunction in healthy men (Ghiadoni, Donald, Cropley et al., 2000). Similarly, a stressful interview elicited increases in IL-1β, IL-10, TNF-α, cortisol, and NE in healthy women (Altemus, Rao, Dhabhar et al., 2001). Other acute mental stressors have been shown to increase plasma levels of the inflammatory cytokines IL-1Ra and IL-6 as well as heart rate and blood pressure in healthy individuals (Steptoe et al., 2001). Several studies have demonstrated that acute psychological stressors can lead to a rapid redistribution of total number of lymphocytes, CD4+, CD8+, and NK in the peripheral circulation (Starr, Antoni, Hurwitz et al., 1996). This redistribution appears to be mediated by altered adhesions of CAMs and by chemotaxis. Thus, there appears to be an increase in peripheral leukocyte adhesion molecule expression and density after acute psychological laboratory stress (Goebel and Mills, 2000) as well as increased chemotaxis of peripheral blood mononuclear cells (Redwine, Snow, Mills, and Irwin, 2003). The findings by Redwine et al. (2003)
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that acute stress-induced increases in catecholamine levels were positively associated with lymphocyte expression of Mac-1 and negatively associated with L-selectin expression suggests that the expression of these adhesion molecules is mediated by adrenergic receptors. 3. Chronic Stress and Inflammation Chronic stress and inflammation have been associated with exacerbations of autoimmune (Harbuz, Chover-Gonzalez, and Jessop, 2003) and coronary heart disease (Appels et al., 2000). As previously mentioned, pro-inflammatory cytokines mediate the migration of leukocytes during acute stress. During chronic stress in normally healthy people, cortisol eventually suppresses this pro-inflammatory cytokine production. However, in individuals with autoimmune disease or severe atherosclerosis, prolonged stress appears to cause pro-inflammatory cytokine production to remain chronically activated, leading to an exacerbation of pathophysiology and symptomatology. Miller, Cohen, and Ritchey (2002) have hypothesized that a downregulation in the number of cortisol receptors in immune cells reduces the effects of cortisol. With cortisol unable to suppress inflammation, the chronic stress continues to promote pro-inflammatory cytokines at a high level, thereby exacerbating disease processes. Although there is only limited empirical support for the Miller et al. (2002) hypothesis, it is consistent with available data. Thus, for example, in rheumatoid arthritis, excessive inflammation is responsible for joint damage, swelling, pain, and reduced mobility. Research has found that in such patients, stress is associated with increased swelling and reduced mobility (Affleck et al., 1997). Similarly, in multiple sclerosis, in which an overactive immune system targets and destroys the myelin sheath contributing to multiple symptoms, chronic stress has been associated with an exacerbation of disease (Mohr et al., 2004). And in coronary heart disease, elevated levels of inflammatory markers, such as C-reactive protein (CRP), are predictive of myocardial infarction, even when controlling for other traditional risk factors such as cholesterol, blood pressure, and smoking (Morrow and Ridker, 2000). To the extent that the hypothesis proposed by Miller et al. (2002) is plausible, it would appear that behavioral interventions that reduce chronic stress and cortisol production in dysregulated systems may lead to an upregulation of cortisol receptors on immune cells, thereby eventually decreasing inflammation.
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4. Depression, Inflammation, and Heart Disease The positive association between depression and cardiovascular disease has been consistently found for initially healthy people as well as for those suffering myocardial infarction (Rugulies, 2002). This relationship remains after controlling for traditional risk factors (e.g., hypertension, cholesterol, age) and disease severity. Nearly 20% of heart attack patients meet criteria for major (Carney et al., 1987) and 27% for minor depression (Schleifer et al., 1989), whereas the point prevalence of major depression for patients of comparable age and gender without cardiovascular disease is only 3% (Myers et al., 1984). Depressed patients with cardiovascular disease are at elevated risk of heart attack (Lésperance et al., 2002). The mechanisms linking depression in cardiac patients to poor prognosis are not known, but autonomic nervous system dysfunction is widely suspected (Carney, Freedland, Miller, and Jaffe, 2002). Another hypothesis that deserves consideration is that depression may exacerbate vascular inflammation, adversely affecting the cardiovascular system (Broadley, Korszun, Jones, and Frenneaux, 2002). Depressed people have higher IL-6 and CRP levels than non-depressed individuals (Miller et al., 2002). Elevated levels of serum IL-1β, TNF-α, and IL-6 were observed in cardiac patients with increased vital exhaustion (a syndrome similar to depression) (Appels et al., 2000). And in cardiac patients with major depression, elevations were observed in soluble ICAM-1 and CRP levels although not in IL-6 (Lésperance, Frasure-Smith, Theroux, and Irwin, 2004). Although depression has been proposed to be related to poor coronary outcomes in terms of behavioral (e.g., increased smoking and poorer eating habits) and physiological pathways (Rozanski, Blumenthal, and Kaplan, 1999), Appels et al. (2000) have proposed that depression, vital exhaustion, or fatigue may simply be due to inflammation associated with cardiovascular disease (CVD). Research in other situations (e.g., influenza) has shown that inflammation can induce a number of behavioral and motivational changes, including fatigue and depressed affect (Larson and Dunn, 2001). The mechanisms by which inflammation induces these changes involve the CNS. Pro-inflammatory cytokines initiate behavioral, affective, and motivational changes by binding to receptors in the hypothalamus and other limbic structures (Dantzer, 2001). However, pro-inflammatory cytokines are large, lipophobic molecules that have difficulty crossing the blood-brain barrier (Maier and Watkins, 1998). One alternative pathway taken by
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pro-inflammatory cytokines (e.g., IL-1) is through the afferent limb of the vagus nerve. The proinflammatory cytokines IL-1, IL-6, and TNF-α also gain entry into the CNS by diffusing across relatively permeable portions of the blood-brain barrier (i.e., circumventricular organs) and engaging active transport mechanisms (Rivest, 2001). The pro-inflammatory cytokines that influence the CNS produce a set of behavioral changes collectively known as “sickness behavior.” This refers to the subjective feelings of fatigue, weakness, malaise, and listlessness characteristic of sick individuals. Sick individuals also commonly experience changes in appetite and weight, altered sleeping patterns, diminished interest in their surroundings, and difficulty concentrating. There is considerable overlap between the symptoms of depression and sickness behavior. An important link between inflammation, vital exhaustion (or depression or sickness behavior), and viral infections was made by Appels et al. (2000). CVD patients with vital exhaustion (compared to nonexhausted CVD patients) had higher levels of IL-1β and TNF-α and a trend towards higher levels of IL-6. The exhausted patients also had elevated antibody titers against chlamydia pneumoniae and cytomegalovirus. Van Der Ven et al. (2003) found that exhausted CVD patients had greater “pathogen burden” (i.e., number of seropositive tests) to herpes simplex virus, varicella-zoster virus, EBV, and cytomegalovirus than non-exhausted CVD patients. Patients with the most vital exhaustion and greatest pathogen burden also had increased levels of IL-6. According to the investigators, increased pathogen burden may contribute to inflammation and may be a biological correlate of vital exhaustion. There is some evidence that measures of depression and exhaustion are assessing the same construct (Wojciechowski et al., 2000). This suggests that depression may be a key correlate of both pathogen burden and inflammatory responses. Previous research has shown that depression can be associated with changes in the HPA axis, resulting in increased production of corticotrophin-releasing factor, dysregulated negative feedback, and an overall increase in cortisol production (e.g., Carroll et al., 1981). This could lead to a downregulation in the number of cortisol receptors in immune cells, thereby reducing the effects of cortisol (Miller et al., 2002). According to Miller et al., if cortisol is unable to suppress inflammation, chronic stress may continue to promote pro-inflammatory cytokines, exacerbating atherosclerosis. In this regard it is interesting to note that major depression is also associated with increased SNS activity (Veith et al., 1994). To the extent that the HPA and SAM axes are involved, psychosocial
(e.g., stress management) or pharmacological (selective serotonin reuptake inhibitors, SSRIs) interventions may be useful in decreasing chronic stress and depression, thereby decreasing inflammation and cardiac risk. Given this emerging evidence, the relationships among depression, inflammation, and CVD will likely represent a major focus of PNI research in coming years.
C. Opportunistic Infectious Disease in Vulnerable Persons: Carcinogenic Viral Infections A number of reviews have addressed the possible role of the immune system and PNI processes in the incidence and progression of different types of cancers and neoplastic changes (Andersen, Kiecolt-Glaser, and Glaser, 1994; Antoni, 2003a; Bovjberg, 1991; Goodkin, Antoni, Fox, and Sevin, 1993; Kiecolt-Glaser, Robles et al., 2002; Antoni, Lutgendorf, Cole et al., 2006). Despite the fact that this area has been of some interest for nearly 30 years, definitive PNI work linking stressendocrine-immune processes to cancer outcomes is only now emerging. For instance, there is exciting work demonstrating that psychosocial variables and immune parameters are associated with a greater likelihood of developing pre-cancerous changes in persons with cancers that have a viral etiology. Viral-associated cancers are likely to have greater immunogenicity than other cancers due to the presence of viral antigens; thus, the role of immune surveillance in disease development is more likely. One neoplastic disease that has been the focus of some biobehavioral research is human papillomavirus (HPV)-associated cervical intraepithelial neoplasia (CIN), a process that pre-dates invasive cervical carcinoma (Antoni, 2003c). There is evidence that elevated negative life events are associated with evidence of greater severity of CIN (Goodkin, Antoni, and Blaney, 1986; Antoni et al., 1988) as measured on biopsy (results unknown to patient at time of psychological testing). Follow-up studies showed that greater pessimism interacted with elevated life events such that the stress-CIN association was present only in the more pessimistic women (Antoni et al., 1989). The incidence rate for HPV-associated CIN and cervical cancer is elevated in persons who are immunocompromised due to receiving immune suppressants after organ transplant and women who have HIV infection (Maiman and Fruchter, 1996; Periera et al., 2003b). Accordingly, programmatic research has studied PNI influences on development of CIN in women who are immunocompromised due to co-infection with HIV as well as oncogenic HPV types such as Type 16 or 18. Among women co-infected with HIV and HPV, greater
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pessimism was cross-sectionally associated with lower NKCC and lower CD8+ cell counts (Byrnes, Antoni, Goodkin et al., 1998). In a separate sample, greater negative life events prospectively predicted greater declines in NK cell number (Pereira et al., 2000), greater risk of a genital herpesvirus outbreak (Pereira et al., 2003a), and a greater likelihood of developing or persisting CIN over a 1-year follow-up in HIV+HPV+ women (Pereira et al., 2003b). Interestingly, glucocorticoids have been associated with promotion of HPVassociated neoplastic changes (Bartholomew et al., 1997), suggesting that stress-related cortisol elevations may promote neoplasias in HPV-infected persons (Antoni, Lutgendorf, Cole et al., 2006). If stressors and individual psychosocial factors related to stress appraisals (e.g., pessimism) predict a greater risk of the development of CIN among HIV+ HPV co-infected women, then it is plausible that stress management interventions may retard CIN promotion and other opportunistic pathogens over time (Pereira, 2002). Ongoing work is examining the psychological, immune, and health effects of behavioral intervention in HIV+HPV+ women, and preliminary analyses show promise (Pereira et al., 2005). Other viral-associated cancers may present plausible PNI models. Some of these include HPV-associated anal carcinoma, human herpesvirus type 8 (HHV-8)-associated Kaposi’s sarcoma, and EBV-associated Burkitt’s lymphoma (Huang et al., 2001; Killibrew et al., 2004; Suligoi, Dorrucci, Uccella, Andreoni, and Rezza, 2003). One place to begin this line of work may be in persons with a background of immunosuppression secondary to HIV infection or medical treatments such as surgery, radiation, or chemotherapy.
D. PNI Rationale for Using Behavioral Interventions to Affect Disease Processes Using a PNI rationale, one could reason that the most effective behavioral interventions for helping stressed and distressed individuals handle the challenges in their lives while optimizing physical health need to consider the role of psychosocial, neuroendocrine, and immunologic mechanisms. It is reasonable that those interventions that are of greatest value are the ones that are found to be effective in individuals whose immune systems are compromised due to a medical disease (e.g., HIV/AIDS), a medical treatment (e.g., adjuvant therapy for cancer), or other conditions (e.g., aging, malnutrition, inflammation) known to be associated with immunologic alterations. The following sections focus on some of the empirical evidence that has been gathered for the effects of behavioral interventions on immunologic parameters in healthy
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persons. This is followed by examples of work applying these interventions to a number of chronic disease populations, with a major focus on persons dealing with viral, neoplastic, or inflammatory diseases.
III. BEHAVIORAL INTERVENTIONS, STRESS RESPONSES, AND THE IMMUNE SYSTEM Over the past 15 years a number of experimental studies have tested the effects of several different behavioral interventions on assorted immune parameters. The most commonly used behavioral interventions in the PNI research included relaxation and imagery techniques, cognitive behavioral stress management, and exercise training, but there is a growing body of work examining the effects of other techniques such as massage, biofeedback, hypnosis, and expressive writing, and other forms of psychotherapeutic approaches such as supportive expressive group therapy. Each of these intervention techniques is now briefly described along with a summary of the PNI studies that have evaluated their immunologic effects.
A. Relaxation and Imagery Techniques Relaxation techniques teach participants ways to reduce anxiety, bodily tension, and other forms of stress responses. The primary relaxation strategies taught in most stress management programs are progressive muscle relaxation (PMR) (Bernstein and Borkovec, 1973) and some form of mental imagery. Some of these exercises teach participants systematically to reduce tension throughout all of their major muscle groups, while others teach the participants ways to use mental imagery to bring about a total state of relaxation. Often they are combined with other techniques such as deep breathing and meditation techniques (Antoni, 1997). Stress responses are often characterized by SAM activation, with concomitant activity in the HPA axis. Affective processes such as anxiety often accompany these responses and may manifest themselves in physical symptoms of tension. Empirical evidence for the influence of relaxation training on SNS-related indices includes reported decreases in hypertensives’ blood pressure and significant decreases in urinary and plasma cortisol levels (relative to controls’) using relaxation training with biofeedback (McGrady et al., 1987). Biofeedback combined with PMR also significantly improved glucose tolerance in a group of non– insulin-dependent diabetics relative to a no-treatment control group (Surwit and Feinglos, 1983). Since neither insulin secretion nor action changed as a result of
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treatment, it is plausible that hepatic glucose uptake was increased, suggesting that relaxation training effects may have been mediated by decreased SNS activity. This technique is particularly relevant for PNI research as the effects of stressors on the immune system are believed to be mediated in part by elevations or dysregulation of neuroendocrine systems that are affected by anxiety and tension (Maier, Watkins, and Fleshner, 1994). Relaxation and guided imagery increased lymphocyte proliferative response to mitogens and NKCC in healthy subjects (Kiecolt-Glaser, Glaser, Williger et al., 1985; Kiecolt-Glaser et al., 1986; Zachariae et al., 1994). Relaxation techniques have also been shown to modulate similar immune system indices in cancer patients (Hidderley and Holt, 2004; Schedlowski et al., 1994; Walker et al., 1999) and those dealing with HIV infection (Antoni, 2003b). Many of these studies had small samples, a lack of randomization, short follow-ups, non-standardized relaxation techniques, and an absence of systematic controls for biological measures. The clinical significance of these immunologic changes in both healthy and disease populations remains unclear.
B. Massage It has been pointed out that techniques such as massage therapy provide a useful paradigm for studying relaxation because it does not require effort on the part of the participant, and because it is easy to monitor objectively (i.e., one knows how much massage a participant is receiving) (Ironson et al., 2002). One group examined the effects of daily massage among HIVinfected men (Ironson et al., 1996). This massage intervention included a full body massage with the application of several types of strokes provided in 45minute sessions, 5 days per week over a 4-week period. Significant interactions (increase during the massage period; no change or decrease during the control period) were found for NK cell number, NKCC, soluble CD8, and the cytotoxic subset of CD8 cells. However, no changes in disease progression markers (CD4, CD4/CD8 ratio, Beta-2 microglobulin, neopterin) were observed over the course of the massage period. The massages were also associated with significant decreases in anxiety and significant increases in relaxation reported, and these changes were significantly correlated with increases in NK cell number. Finally, there was a significant reduction in 24-hour urinaryfree cortisol. Despite this pattern of results, it is important to note that this was a small sample and that participants were not randomized. This study needs to be replicated with a larger group in a randomized
design. One recently completed randomized trial reported that breast cancer patients receiving daily massage also show beneficial changes in endocrine and immunologic parameters (Hernandez-Reif, Ironson et al., 2004).
C. Biofeedback, Imagery, and Hypnosis There have been a few studies combining relaxation with other techniques such as biofeedback and hypnosis to examine mood and immune effects in various populations. Taylor (1995) examined the effect of an intervention combining PMR, biofeedback, meditation, and hypnosis in 20 one-hour sessions on mood, self-esteem, and CD4 cell counts in HIV+ men. Subjects in the intervention group showed decreases in anxiety, increases in self-esteem, and increases in CD4 cell counts. These immune changes should be interpreted with caution as there is no information provided on anti-retroviral drug therapy, and the CD4 cell count data was taken from subject medical records rather than being coordinated with the collection of psychosocial data. Another intervention consisting of 8 weeks of training in thermal biofeedback, guided imagery, and hypnosis was associated with reduced selfreported symptoms of HIV (fever, fatigue, pain, headache, nausea, and insomnia) and increased vigor and hardiness, relative to controls (Auerbach et al., 1992). However, there was no change in anxiety, depression, or CD4+ cell number. Combining techniques like biofeedback, guided imagery, and hypnosis may have clinical utility, though the evidence that any one of these strategies can reliably modulate immune parameters remains unclear.
D. Physical Exercise Exercise training is one of the most commonly employed behavioral interventions and has been shown to decrease distress, depressed mood, and anxiety and to modulate immune measures in a variety of populations including healthy persons (Morgan, 1982), and those with chronic diseases such as HIV infection (LaPerriere et al., 1990). One form of aerobic exercise training that has been examined for immune effects in HIV+ persons consists of stationary bicycle ergometry interval aerobic exercise training for 45 minutes 3 days per week, with a maximum intensity of 80% of predicted maximum heart rate (LaPerriere et al., 1990). This form of aerobic training was shown to buffer anxiety and depressed mood increases after HIV+ serostatus notification in gay men (LaPerriere et al., 1990). Men who learned they were HIV+ who had been assigned to the exercise
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group also maintained their CD4 cell number, NK cell number, or NKCC, while those in an assessment-only control group showed significant decreases in NK cell counts and a non-significant decrease in CD4 cell counts. This suggested that exercise may buffer the effects of stress on immune status in HIV+ persons. These HIV+ exercisers showed significant decreases in antibody titers to EBV (suggesting better immunologic control of these latent viruses), whereas the HIV+ controls showed no change (Esterling et al., 1992). Importantly, men who attended more exercise sessions were less likely to have progressed to AIDS up to 2 years later—even after controlling for CD4 count at entry to the study (Ironson et al., 1994). Other studies examined the immune effects of other forms of exercise in HIV-infected persons. These programs ranged from 8–12 weeks and were composed of activities such as supervised sports games designed to develop cardiovascular endurance, gymnastics, games, and relaxation (Florijn et al., 1991; Schlenzig et al., 1989). Effects of these interventions include reductions in anxiety and depression (Florijn et al., 1991; Schlenzig et al., 1989), decreased fatigue and anger, and an increase in vigor and quality of life (Florijn et al., 1991). Only one of these studies reported a significant effect on immune parameters in the form of buffering the decline in CD4 and CD8 cell counts that was observed in a control group (Florijn et al., 1991). These studies did not explore longer-term effects of exercise and fitness training on immune parameters or health outcomes. The effects of these programs on immune status are not totally clear and likely depend to a large degree on participants’ ability to maintain excellent adherence (LaPerriere et al., 1997). The largest sustained immune effects of exercise may only be achieved by those individuals who are able to train at the level necessary to modulate stress hormone levels (e.g., cortisol) on a more continuous basis. Although it is beyond the scope of this chapter to review the entire exercise PNI literature, it is plausible that exercise may be capable of modulating endocrine and immune functioning in medical patients who are dealing with emotionally and physically stressful periods surrounding diagnosis and treatment for conditions such as cancer and myocardial infarction. While most of the behavioral interventions reviewed to this point appear capable of addressing anxiety and physical tension, they do not attempt to address many other emotional and interpersonal aspects of stressful situations that may affect physiological functioning. In the next three sections we focus on sets of techniques that address some of these psychosocial processes and provide a summary of their effects on immune parameters.
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E. Expressive Writing The act of writing about one’s stressful, traumatic, or emotional experiences has also been associated with immunologic changes and some indicators of health or health behaviors (Smyth, 1998). Expressive writing interventions often require individuals to participate in one to four 15–30-minute writing sessions over a period of time ranging from 1–30 days. The idea behind this intervention is that expressing one’s thoughts and feelings surrounding a previously unexpressed event may pave the way for resolving the stressfulness of the event, increasing one’s understanding and insights into the cause and consequences of the event, and allowing one to move on from the event so that it does not negatively affect the ability to process new events or experiences. Persons participating in these writing sessions have shown changes in some immunologic parameters including both primary and secondary humoral immune measures. Primary IgG responses to hepatitis B vaccine were enhanced among those assigned to expressive writing (Petrie et al., 1995), while another group found that IgG levels against latent herpesviruses such as EBV were decreased (reflecting better immunologic control over latent virus reactivation) among persons assigned to a similar writing intervention (Esterling et al., 1994). Others have also shown that persons assigned to an expressive writing intervention show increases in cellular immunity as measured by increases in lymphocyte proliferative responses to mitogen (Pennebaker, Kiecolt-Glaser, and Glaser, 1988). For the most part these early studies have explored the effects of expressive writing in healthy individuals; hence, the clinical implications of these immunologic changes are unclear. Ongoing work is applying this paradigm to persons who have medical conditions in which the immune system may contribute to health outcomes (e.g., HIV infection, breast cancer). To date, such interventions have been shown to improve psychosocial adjustment in breast cancer patients (Stanton et al., 2002) though there is no published work indicating immune effects. In contrast, one study did report that HIV+ persons randomized to a 4-day emotional disclosure intervention revealed a drop in HIV viral load and increases in CD4 cell counts compared to those in a neutral writing condition (Petrie, Fonanilla, Thomas, Booth, and Pennebaker, 2004). Effects on clinical disease progression remain unknown. Another group found that expressive writing resulted in clinical improvements in two populations dealing with autoimmune disease: arthritis and asthma (Smyth, Stone, Hurewitz, and Kaell, 1999). However, there
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were no immunologic parameters collected in that study. If expressive writing is shown to have effects on immune parameters that contribute to physical health improvements, this form of intervention has the potential to make an impact in clinical practice, as it is possible to train patients to “journal” in virtually any location; thus, continued practice after the completion of the training period is more likely. Despite all the expressive writing studies conducted to date, the mechanism underlying their effects on immune parameters remains unknown.
F. Cognitive Behavioral Stress Management (CBSM) Other behavioral interventions focus more on modifying the cognitive appraisals that precede an individual’s response to stressful situations. Theorists have argued that the amount of stress an individual experiences when encountering a stressor is determined by both appraisal of the stimulus and perception of available resources (Turk, Holzman, and Kerns, 1986). Since thoughts, feelings, behaviors, and social factors are continually interacting, cognitive appraisals of stressors can affect emotional and interpersonal responses. Importantly, individuals can be taught to change their cognitive, emotional, and behavioral responses to stressors to help them achieve a sense of mastery and self-efficacy, and decrease negative affect and maladaptive behaviors (Antoni, 2003c). The changes brought about by CBSM may be brought about with techniques designed to modify appraisals of stressors (cognitive restructuring) (Beck and Emory, 1979), teach new cognitive coping strategies (coping effectiveness training) (Folkman et al., 1991), and promote the use of efficient interpersonal skills (anger management and assertiveness training) (Antoni, 1997). These interventions are believed to work by challenging maladaptive or “distorted” stressor-appraisals (Simons, Garfield, and Murphy, 1984), furnishing the person with an appropriate coping response (Folkman et al., 1991), and decreasing hopeless thoughts (Rush, Beck, Kovacs et al., 1982). The techniques are often used in sequence with cognitive restructuring used to build awareness of stressor appraisals as a means for altering cognitions early on in training. Coping skills training is the next logical step after one has clarified appraisal of the stressful situation as accurate. Rather than simply teaching people to avoid using obviously destructive coping responses (e.g., denial, violence, substance use), more sophisticated approaches attempt to improve the “efficiency” of the coping response using Coping Effectiveness Training (Folkman et al., 1991). Here,
individuals are taught to choose problem-focused coping strategies (e.g., active coping, planning) for dealing with the controllable aspects of stressful situations and emotion-focused strategies (e.g., venting, relaxation, seeking emotional support) for dealing with the uncontrollable or unchangeable aspects of stressful situations. After cognitive and behavioral coping skills are addressed, many programs teach skills such as assertiveness and anger management to address sources of interpersonal stress (Antoni, 2003c). The rationale for including assertion training and anger management in stress management programs is as follows. If one cannot communicate his/her emotional reactions and behavioral intentions to others in his/her social network, then interpersonal conflict may persist, resulting in hostile reactions and resentment. These conflicts may be accompanied by physiological changes characterizing protracted “stress responses” (elevated SNS activation), which in turn may affect aspects of immune system functioning (Kiecolt-Glaser, Malarkey, Chee et al., 1993) that may have health relevance in certain populations. Responding assertively and managing angry reactions may minimize these conflicts and their accompanying affective, interpersonal, and physiological effects. Moreover, it may be that the more active components of social support (e.g., engaging and interacting with supportive others), as opposed to mere distraction from troubles and avoidance of conflict, have the strongest stressbuffering effects (Kobasa, Maddi, Puccetti et al., 1985). Thus, the beneficial effects of these interventions may also be mediated by improvements in social support, a well-researched correlate of psychosocial and physiological functioning over the past 20 years (e.g., Esterling et al., 1996; Kiecolt-Glaser, Ricker, George et al., 1984; Levy and Herberman, 1990; Lutgendorf, Antoni, Ironson et al., 1998; Lutgendorf et al., 2002). This argues for a role of social support improvement in explaining the effects of behavioral interventions on immune system functioning—a role that has been demonstrated in a number of studies (e.g., Antoni et al., 1996; Cruess, Antoni, Cruess, Fletcher, Ironson, Kumar, Hayes et al., 2000). The changes in cognitive, behavioral, emotional, and interpersonal processes elicited by these interventions are hypothesized to result in an increased sense of self-efficacy, personal control, and mastery as well as decreases in anxiety and depressed mood (Antoni, 1997). Altering stressor appraisals and building coping skills are thought to diminish the likelihood of extreme cognitive and behavioral reactions (e.g., catastrophizing and giving up prematurely), improve health behaviors (e.g., diet, exercise, and medication adher-
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ence), and may also affect neuroendocrine responses and immunologic parameters in vulnerable populations (e.g., persons diagnosed with HIV infection, patients undergoing treatment for cancer) (Antoni, 2003a; Antoni, 2003b). Often used in combination with anxiety-reducing techniques such as muscle relaxation and guided imagery, these interventions can be referred to as cognitive-based stress management (CBSM) approaches. Most PNI studies examining the effects of these interventions have used group formats; thus, social support was “built into” these interventions as a component beyond specific cognitive or interpersonal techniques that were taught. Social support may be experienced from the persons sharing the same diagnosis or similar challenges in these groups, through the use of role-playing exercises that involve group members to facilitate cohesiveness, and by learning new techniques for expanding social support networks to include persons who meet one’s current needs (Antoni, 2003b; Zuckerman and Antoni, 1995). Over the past 2 decades CBSM interventions have been shown to be effective in improving psychosocial functioning in a wide range of medical conditions. These include hypertension (Crowther, 1983), rheumatoid arthritis (Parker, Frank, Beck et al., 1987), peptic ulcer (Brooks and Richardson, 1980), breast cancer (Andersen et al., 2004; Antoni, 2003c), and prostate cancer (Lepore et al., 2003; Penedo et al., 2004) and in patients dealing with acute, chronic, and cancer pain (Fishman and Loscalzo, 1987). These interventions have also been shown to modulate a wide range of physiological indices including endocrine indicators such as urinary and serum cortisol (e.g., Antoni et al., 2000a; Cruess et al., 2000a), urinary norepinephrine (e.g., Antoni et al., 2000b), and serum testosterone (e.g., Cruess et al., 2001; Cruess, Antoni, Cruess, Fletcher, Ironson, Kumar, Lutgendorf et al., 2000). CBSM interventions have also been shown to modulate a variety of immune parameters including T-lymphocytes and NK cells (e.g., Antoni et al., 1991; Antoni et al., 2000b; Antoni et al., 2002), antibody titers to herpesviruses (e.g., Esterling et al., 1992; Lutgendorf et al., 1997), and lymphocyte proliferative responses (Andersen et al., 2004; McGregor et al., 2004). These physiological changes have been demonstrated in HIV-infected men and in women under treatment for breast cancer. The CBSM techniques discussed thus far are likely to be most powerful if taught as an integrated set of strategies that can be employed in a variety of situations. By using treatment manuals including explanation of terminology, flow diagrams, and exercises, interventionists may help participants to see how to sequence the use of these new tools as they encounter and work
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through different situations. Research that seeks to compare the psychosocial and physiological effects of these integrated interventions across different populations would benefit greatly from the availability of empirically supported treatment “packages” that could be employed in large-scale clinical trials (Schneiderman, Antoni, Ironson, and Saab, 2001).
G. Supportive-Expressive Therapy Some forms of psychosocial intervention that have been examined for their effects on physiological functioning come closer to what might be referred to as psychotherapy. The major technique studied in this fashion is existential/experiential group psychotherapy, also referred to as Supportive Expressive Therapy (SET) (Classen et al., 1998). SET interventions have been shown to improve emotional functioning in persons dealing with life-threatening diseases such as metastatic breast cancer (Spiegel et al., 1989), AIDS (Lechner et al., 2003), or disease-related losses such as bereavement (Goodkin et al., 2001). SET is believed to work by helping individuals express and work through anxieties, ventilate negative feelings, provide emotional support, and encourage positive goals and activities (Spiegel and Glafkides, 1983). At the same time these interventions, because of the group format, allow participants to share strategies for coping with disease-related stressors, experience a sense of universality, engage in altruistic behaviors, and minimize the sense of isolation that many persons with life-threatening diseases face (Spiegel, Bloom, and Yalom, 1981). By addressing social isolation, emotional suppression, self-esteem loss, and hopelessness, SET interventions appear to target many of the areas that are addressed in the behavioral interventions reviewed so far in this chapter. In one of the most wellknown behavioral intervention studies published to date, it was demonstrated that women with metastatic breast cancer who were assigned to a 1-year weekly SET intervention lived, on average, twice as long as those randomized to a no-treatment control condition (Spiegel et al., 1989). Efforts to replicate these survival effects in women with metastatic breast cancer have not been successful to date (Goodwin et al., 2001), though other trials are underway. Despite the appeal of SET interventions for persons with life-threatening diseases, and these findings in cancer patients, little is known about their effects on neuroendocrine or immune system parameters that might contribute to health outcomes. On the other hand, one group has demonstrated that a time-limited 10-week SET program that incorporated elements of coping skills training was associated with decreases in plasma cortisol,
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increases in CD4 cell counts, decreases in HIV viral load, and decreased visits to their physician in recently bereaved HIV-infected gay men (Goodkin et al., 2001).
H. Other Approaches It is plausible that behavioral interventions such as yoga, sleep hygiene treatments, music therapy (e.g., guided imagery in music), healing touch, and other forms of energy manipulation, and spiritual counseling, and prayer-based interventions may modulate immune parameters in healthy and diseased populations. At present, however, there is little clear evidence from experimental studies to suggest that these interventions can affect psychosocial and endocrine variables that could in turn influence immune functions. One exception is a technique called Guided Imagery in Music (GIM), wherein different musical passages are used to accelerate the process of recalling past traumatic stressors and emotional reactions (McKinney et al., 1997). This technique has been shown in randomized studies to decrease depressed mood and serum cortisol levels (McKinney et al., 1997). Randomized trials testing the effects of complementary and alternative medicine (CAM) techniques such as healing touch on endocrine and immune parameters are underway. The 1980s brought some of the first systematic studies of the effects of behavioral intervention on immune parameters in young and older but healthy samples. During the 1990s this work and related studies of relaxation, guided imagery, physical exercise, and hypnosis in healthy and medical populations paved the way for full-scale PNI studies of behavioral interventions in medical populations for whom immune system modulation might have clinical benefits. The bulk of this applied work has for the last decade focused on persons dealing with HIV infection and different types of cancer, and this will be the focus of the next section.
IV. CLINICAL APPLICATIONS OF BEHAVIORAL INTERVENTION-PNI PARADIGMS IN HEALTH AND DISEASE A. HIV/AIDS 1. Behavioral Intervention Effects on Stress-associated Endocrine and Immune Changes As mentioned previously, persons infected with HIV suffer from profound decrements in cellmediated immune functioning. Because T-helper
(CD4) lymphocytes are depleted in persons with HIV infection (Klimas, Caralis, LaPerriere et al., 1991), qualitative decrements in lymphocyte functioning (e.g., proliferation and cytotoxicity) might be important in predicting those HIV-infected individuals who do and do not develop opportunistic infections quickly. There is some evidence that NKCC may compensate for CD4 cell depletions in HIV-infected persons (Ironson et al., 2001), perhaps by conferring protection against extant viral infections. Since herpesviruses such as EBV or HSV are prevalent and often poorly controlled in HIVinfected persons (Biron, Byron, and Sullivan, 1989), it is plausible that NKCC could help to control these and other infections in the HIV-infected host. It follows that stress-induced impairments in NKCC may permit reactivation of these herpesviruses and other pathogenic challenges to go unchecked in HIV-infected individuals (Kiecolt-Glaser and Glaser, 1988) with the subsequent effects of increased HIV replication (Carbonari, Fiorilli, Mezzaroma et al., 1989). Given existing evidence for stress-immune relations in healthy persons, it has been reasoned that psychosocial and behavioral factors might influence immunologic status and, possibly, disease course in HIV-infected individuals (Kemeny, 1994). Similarly, stress management interventions that target these factors might provide both psychological and physical benefits for infected people, especially for those in the early stages of this chronic disease (Antoni, 2003b; Antoni, Schneiderman, Fletcher et al., 1990). Research over the past 20 years has examined how individual differences in stressors and other psychosocial factors relate to the rate of immunologic decline and disease progression in persons who are HIV+ (Kopinsky, Stoff, and Rausch, 2004). Much of this work has been motivated by an underlying PNI model. Accordingly, it has been hypothesized that stressful events interpreted by HIV-infected individuals as beyond their control might lead to social isolation, loneliness, anxiety, and depressed affect, which might accompany alterations in some neurohormones (e.g., peripheral catecholamine and cortisol elevations) due to SNS/HPA axis activation (Antoni et al., 1990). These neuroendocrine changes may contribute to changes in the immune system via neuroendocrine signals to immune cell receptors and altered production of cytokines. In the case of HIV infection in particular, it can be further hypothesized that superimposing stressorinduced changes in the functioning of the immune system on extant suppression of immune functions may increase the rate at which infected people develop opportunistic infections and neoplasias (Antoni et al., 1990).
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Psychosocial factors that have been related to the rate of decline of CD4 cells over time in HIV-infected gay men include stressful life events (Leserman, Pettito, Perkins et al., 1997), depressive symptoms (Burack, Barrett, Stall et al., 1993), fatalistic appraisals (Reed, Kemeny, Taylor et al., 1994), denial coping (Ironson et al., 1994; Leserman et al., 2003), and less social support (Theorell, Blomkvist, Jonsson et al., 1995). On the other hand, the ability to preserve functions such as NKCC may predict longer survival (Ironson et al., 2001) and might be more likely in persons who use more active coping (Goodkin, Blaney, Feaster et al., 1992) and who remain engaged in life, able to find meaning, and maintain adequate social support (Ironson, Solomon, Cruess et al., 1995). Some work suggests that excessive rumination (Mulder et al., 1999) may predict faster disease progression, while active confrontation of stressors predicts slower disease progression (Mulder, Antoni, Duivenvoorden et al., 1995) in HIV-infected men. Together, this work suggests that use of active, expressive means of dealing with stressors may be beneficial, while more passive, avoiding, and detached methods of coping may be detrimental. This work has paved the way for exploration of the biobehavioral effects of behavioral interventions in HIV-infected persons. Interventions such as group-based CBSM have been shown in HIV+ men to (a) buffer the emotional distress and immunologic decrements (CD4 cells and NK cells) occurring after the stress of HIV seropositivity notification (Antoni et al., 1991), and (b) lower IgG antibody titers to herpesviruses such as EBV and Human Herpesvirus Type-6 (HHV-6) (Esterling, Antoni, Schneiderman et al., 1992) and genital herpes (HSV-2) (Lutgendorf, Antoni, Ironson, et al., 1997) in conjunction with anxiety and dysphoria reductions. HIV+ men assigned to CBSM also show decreases in 24-hour urinary cortisol in association with decreases in depression levels (Antoni, Wagner, Cruess et al., 2000). In another study HIV+ men showed decreases in 24-hour urinary NE association with reductions in anxiety levels (Antoni, Cruess, Wagner et al., 2000). This work suggests that behavioral interventions that can modulate emotional and neuroendocrine responses to stressors may affect immune parameters relevant to health outcomes in HIV-infected persons. Other work has observed that HIV-infected men receiving another form of stress reduction, massage therapy, showed increases in CD8 cytotoxic cells, NK cell number, and NKCC in parallel with decreased anxiety and 24-hour urinary cortisol output (Ironson et al., 1996). Two studies following participants over the post-intervention period revealed that greater distress reductions
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during these types of interventions appeared to predict slower rates of immunologic decline up to 2 years later (Ironson et al., 1994; Mulder, Antoni, Emmelkamp et al., 1995). These studies point to the potential efficacy of stress management interventions for increasing psychological adjustment, improving neuroendocrine regulation, normalizing immune functioning, and improving health status in HIV-infected people (Antoni, 2003b). Individuals participating in the majority of the initial biobehavioral studies of HIV/AIDS were all gay or bisexual men, congruent with the predominant incidence patterns occurring in the 1980s. Women now make up nearly 20% of all AIDS cases, and most of these women are low-income ethnic minority group members (Centers for Disease Control, 1997). Thus, it is imperative to develop techniques to help women of color and other HIV-infected populations manage their disease. Preliminary data indicate that CBSM techniques may impact both the psychological and immune functioning of HIV+ women of color, though results of larger-scale studies are still pending (Lechner et al., 2003). 2. Reconstituting Immune Function in Conjunction with Anti-viral Treatment Longer-term follow-up of HIV+ persons who were enrolled in behavioral interventions in the 1990s have begun to show some interesting effects in follow-up studies reported in the past few years. HIV+ men who had received CBSM intervention revealed greater numbers of CD8+ cytotoxic-suppressor cells (Antoni, Cruess, Wagner et al., 2000) and CD4+CD45RA+CD29+ transitional naïve T-cells (Antoni et al., 2002) at 6–12 months after the intervention. In support of a PNI model, men with the greatest decreases in urinary NE during the 10-week CBSM intervention showed the greatest CD8+ cell counts at follow-up (Antoni, Cruess, Wagner et al., 2000). Those showing the greatest reductions in cortisol during the intervention showed the greatest transitional naïve T-cell counts at follow-up (Antoni et al., 2005). Importantly, prior work had indicated that NE decreases during this intervention paralleled anxiety reductions, whereas cortisol decreases paralleled decreases in depressed mood. Thus, a behavioral intervention may contribute to the recovery or “reconstitution” of important immune parameters over time by decreasing anxiety and depressed mood and thereby regulating the output of neuroendocrine substances such as NE and cortisol. This work, however, did not have the means to adequately control for the viral progression of the disease or medication
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changes that could explain variability in recovery of immune parameters in this population. 3. Behavioral Intervention in Conjunction with Anti-retroviral Therapy Research has now evolved to the point of testing the effects of behavioral intervention in the context of well-characterized anti-viral therapy with regular monitoring of medication adherence and plasma HIV viral load in order to examine the effects of such intervention on disease progression. The development of highly active anti-retroviral therapy (HAART) including the use of protease inhibitors was key in providing this opportunity. The arrival of protease inhibitors and triple combination therapies brought about important improvements in the health care of HIV-infected patients and brought attention to the fact that HIV infection is a chronic disease where patient management is critical (Schneiderman, Antoni, and Ironson, 1997). The reason is that HAART treatment requires consistent adherence to a demanding medication schedule in the context of an already stressful daily existence. Failure to rigidly adhere to specific guidelines can compromise the effects of the particular regimen being used and also reduce the efficacy of other related compounds to which cross-resistance has developed (Lewin, 1996). It is also possible that persons who do not adhere to these medication schedules may harbor highly resistant strains of HIV that can then be transmitted through unprotected sex and IV drug use; hence, there is a potential public health crisis brewing. We reasoned that interventions such as CBSM, which can decrease anxiety and tension levels as well as denial and depressed affect, might facilitate adherence to medical treatment regimens. The improvements in immune function that have been associated with these psychosocial interventions in the preHAART era also suggest that CBSM might help reconstitute the compromised immune system once HAART regimens have contained the virus (Schneiderman, Antoni, and Ironson, 1997). Thus, CBSM and other behavioral interventions may be particularly efficient means to manage this chronic disease. These latter questions constitute the focus of the ongoing work using stress management interventions to address medical treatment issues in the growing populations of HIV-infected persons. PNI research in the context of HIV infection may offer new insights about the role of stress responses, neuorendocrines, and immune parameters in moderating the effects of powerful antiviral therapies, in reconstituting the immune system, and in contributing to the opportunistic infections and
neoplasms that these individuals will still be susceptible to for years to come. Antoni et al. (2006) compared the effects of adherence training alone versus adherence training plus CBSM on HIV viral load in gay men treated with HAART. In men with detectable viral load at entry into the study, those who received both adherence training and CBSM had significantly lower viral load after the intervention than men who received only adherence training. The effect lasted throughout 15 months of study. This reduction appeared to be mediated by a decrease in depressed affect. To the extent that self-reported medication adherence was nearly identical in the two groups, and the intervention effects were mediated by a decrease in depressed affect, it appears likely that depression-endocrine-immuneviral load interactions may have been involved and should be followed up in future studies. In summary, it seems that intervention studies in HIV spectrum disease provide an excellent model for studying the clinical relevance of PNI in disease processes.
B. Cancer Psychoneuroimmunologic research that may be relevant once invasive cancer has been diagnosed has been focused in two separate areas: the effects of psychosocial factors on psychological and physiological “recovery” after stressful cancer treatments and the effects of PNI processes on the physical course of disease in cancer patients. A third area of growing interest concerns the effects of immunologic changes during medical treatment on mood and other psychological states/processes (i.e., sickness behavior). Behavioral intervention work has been concentrated in the first two areas. 1. Immunologic “Complications” of Medical Treatment for Cancer One of the points within the experience of cancer where PNI research is particularly relevant is the period surrounding initial curative and adjuvant treatments. During the treatment phase, people’s predominant emotional reactions include feelings of fear and grief (Fawzy et al., 1997). Adjuvant therapy for cancers (including chemotherapy, radiation, and endocrine therapy) can also negatively affect immune parameters (Brenner et al., 1991; Chuang, Lotzova, Cook et al., 1993; Tichatschek et al., 1988). Theoretically, adjuvant therapy-associated changes in immune cell numbers associated with cytotoxic responses (NK cells and CD3+CD8+ cells), lymphocyte proliferation and NKCC may make treated cancer patients more vulnerable to
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poorer surveillance of cancer-related antigens over the recovery period and possibly to recurrence of disease over the longer term. It is also plausible that stressors and negative mood states may compound the immunologic deficits during and after these treatments, thus paving the way for negative health effects. It follows that behavioral intervention at this critical juncture may act to mitigate some of these immunomodulatory changes and facilitate faster recovery of pre-adjuvant levels of immune system functioning (Antoni, 2003a). Several studies have evaluated behavioral interventions with cancer patients, including techniques such as progressive muscle relaxation, imagery, and biofeedback (Gruber, Hall, Hirsch et al., 1993); group-based multimodal CBSM and other cognitivebehavioral group interventions (Andersen et al., 1998; Antoni, Lehman, Kilbourn et al., 2001); and structured problem-oriented cognitive therapy (Greer, Moorey, Barach et al., 1992). Other studies have tested the effects of hypnosis, autogenic training, guided imagery, and stress inoculation training on quality of life in cancer patients (Jacobsen and Hann, 1998). Since stressors, surgery, and adjuvant therapy have been associated with decrements in immune functioning (van der Pompe et al., 1998), stress-reducing psychosocial interventions administered in cancer patients under treatment might optimize post-surgical immune status. This might reduce the risk of the growth of cancer cells (e.g., micrometastases) mechanically “spread” through the surgical procedure (Andersen et al., 1998; Kiecolt-Glaser and Glaser, 1994). Behavioral intervention studies that randomized cancer patients undergoing active medical treatment showed increases in immune parameters such as NKCC, lymphocyte proliferative responses, increases in lymphocyte counts, and less decline in IFN-γ production as compared to controls. In studies that measured neuroendocrine changes, intervention group participants showed reductions in plasma cortisol levels. Studies examining the effects of behavioral interventions on immune parameters have been done in patients being treated for breast cancer and malignant melanoma (for review see Antoni, 2003c). The most consistent findings from breast cancer studies is that behavioral interventions, ranging from 10–14 weeks in duration, can increase lymphocyte proliferative responses (Andersen et al., 2004; Gruber, Hersh, Hall et al., 1993; McGregor et al., 2004; van der Pompe et al., 1996) and decrease serum cortisol levels (Cruess et al., 2000; Schedlowski, Jungk, Schimanski et al., 1994; van der Pompe, Duivenvoorden, Antoni et al., 1997). Some studies have shown that women receiving behavioral interventions show increases in lymphocyte counts (Schedlowski et al., 1994) and less decline in INF-γ
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production (Larson, Duberstein, Talbot et al., 2000). Among melanoma patients recruited after surgery, a 6-week behavioral intervention group (focused on stress reduction) showed increases in active coping and reductions in distress over the first 6 weeks and increases in IFN-α–stimulated NKCC 6 months later (Fawzy, Kemeny, Fawzy, and Elashoff, 1990). A major issue in examining immune effects of behavioral interventions with cancer patients under treatment concerns the timing of behavioral intervention and immune assessments. Surgery and anesthesia as well as adjuvant therapies such as chemotherapy and radiation may have large and variable downregulatory effects on cellular immune functions that must be taken into account (van der Pompe et al., 1998). If the study is well controlled and carefully plans the measurements of blood samples to minimize the effects of these medical treatments, it may be possible to evaluate whether stress management helps to mitigate the stress-induced immune decrements in cancer patients receiving immunosuppressive treatments like chemotherapy. Such studies need to use randomized experimental designs to test the effects of a standardized intervention, homogeneous samples of patients with specific cancer types and stages, controls for medical treatment (e.g., surgery only, surgery plus radiation, surgery plus chemotherapy), and clinicopathological prognostic factors (e.g., estrogen receptor status). Most behavioral intervention studies in cancer patients have focused on relating distress reduction to physiological changes. One set of studies looked instead at relations between intervention-associated increases in positive states (e.g., finding benefit in the cancer experience) and physiological changes. This work involved a randomized trial of a 10-week CBSM intervention among women diagnosed with breast cancer recruited 4–8 weeks after surgery but before the onset of chemotherapy or radiation therapy. Postintervention blood draws for immune testing were conducted 3 months after the intervention, at a point when adjuvant therapy had been completed. Women assigned to CBSM showed increases in lymphocyte proliferative responses to anti-CD3 (T-cell receptor) challenge after the end of adjuvant therapy (McGregor et al., 2004). The immunologic effects of the intervention at 3-month follow-up appeared to be greatest in the women who had made the largest positive psychological changes during the initial 10 weeks of training (McGregor et al., 2004). These immunological effects may provide preliminary evidence for a “recovery” from adjuvant therapy that is facilitated by positive psychological changes that result from stress management. Such work may ultimately show that the primary
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health value of behavioral interventions conducted during active medical treatment for cancer are that they enhance immune defenses against infectious disease during the post-adjuvant period (Bovjsberg and Valdimarsdottir, 1996) as well as to longer-term delayed effects related to enhanced surveillance of “micrometastases” after surgery. The relevance of these short-term changes in the immune system for longer-term QOL and health outcomes in these cancer patients is central to work testing the effects of behavioral interventions on survival time and disease-free interval in cancer “survivors.” 2. Immune Surveillance and Preventing Cancer Recurrence and Metastasis Some cancers where psychosocial factors have been shown to be associated with survival are also those in which the immune system may be involved in disease progression. These include malignant melanoma (Fonteneau, LeDrean, LeGuiner et al., 1997) and breast cancer (Baxevanis, Reclos, Gritzapis et al., 1993). Psychosocial factors such as active coping have been shown to predict greater survival time (Fawzy, Fawzy, Hyun et al., 1993), while repressive coping has been related to poorer survival in melanoma patients (Rogentine, Van Krammen, Fox et al., 1979). Breast cancer patients experiencing elevated life stressors may be at risk for a relapse or shortened survival time after treatment (Ramirez, Craig, Watson et al., 1989; Watson et al., 1999), though other work refutes this (Barraclough, Pinder, Cruddas et al., 1992). Breast cancer patients’ reactions to the stress of diagnosis (e.g., distress, depression, poor expression of anger, stoicism, repressiveness, maintaining a “fighting spirit”) may also predict the course of disease (e.g., Greer, 1991; Greer, Morris, Pettingale et al., 1990; Jensen, 1987; Pettingale, Morris, Greer, and Haybittle, 1985). A couple of studies have provided evidence that a behavioral intervention may affect survival time in cancer patients. One study showed that metastatic breast cancer patients assigned to a long-term supportive expressive therapy (SET) group lived twice as long as similar women assigned to standard care (Spiegel, Bloom, Kramer et al., 1989). Unfortunately, these researchers did not collect information on immunologic effects of the intervention. The one study showing positive effects on coping, mood, immunology, and survival for a behavioral intervention was done in patients with early stage malignant melanoma (Fawzy et al., 1990, 1993, 2003). Those patients assigned to the intervention group showed a greater diseasefree interval and survival rate at 6-year follow-up as compared to those in the standard-care control (Fawzy,
Fawzy, Hyun et al., 1993). Intervention-related increases in active coping predicted greater survival time (Fawzy et al., 1993). This group has since reported that the effects of this intervention on survival persist at 10-year follow-up (Fawzy et al., 2003). Several other behavioral interventions have been unable to demonstrate effects on survival in cancer patients (for review, see Spiegel, 2002). In order to study the biobehavioral mechanisms underlying survival effects of behavioral interventions, one needs large samples of similarly treated patients for whom adequate controls are in place for medical treatments, clinicopathological prognostic risk factors, and behavioral risk factors for recurrence and relevant immune indices (e.g., sun exposure in melanoma survivors). Contemporary PNI research in cancer should include antigen-specific functional assays (e.g., cytotoxicity tests that use breast-cancer–associated cell lines), tests of cytokine production from specific immune cell types (e.g., inducing cytokine production by stimulating the CD3 or T-cell receptor on lymphocytes), and tests designed to reflect in-vivo conditions (e.g., cytokineenhanced cytotoxicity, also known as lymphokineactivated killing [LAK] assays using recombinant interleukin-2 or IFN-γ). In the end it is unlikely that a single immune measure will be found that is an indicator of long-term health in patients with specific cancers; thus, patterns of changes in several indicators are used. It also remains possible that health effects are independent of immunological changes occurring during or after behavioral interventions, though they may be tied to neuroendocrine changes. Emerging work suggests that some tumor-promoting processes might be directly affected by neuroendocrines shown to be modulated by behavioral interventions in cancer patients (for review see Antoni, Lutgendorf, Cole et al., 2006). A major limitation in biobehavioral research in cancer is the near absence of any studies relating psychosocial factors and interventions to changes in subclinical markers of tumor activity, before the point at which clinical disease relapse, metastasis, or death occurs. It is important in “survival” studies to monitor disease activity markers that are relevant to the growth of the specific cancer being studied. Some measures related to tumor growth focus on quantifying agents that promote tumor growth. Vascular endothelial growth factor (VEGF) is a cytokine that promotes tumor angiogenesis, the process by which tumor cells develop a blood supply that is critical for their survival (Beck et al., 1997; Bergers and Benjamin, 2003). Research conducted in ovarian cancer shows that VEGF levels are elevated in women who perceive lower social support (Lutgendorf et al., 2002). This same group
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used an in vitro model to show that HPA (cortisol) and SNS (norepinephrine) hormones may interact to promote greater production of VEGF from stimulated ovarian cancer cells (Lutgendorf, Cole et al., 2003). This suggests a possible mechanism whereby stress and social isolation might promote carcinogenesis in patients with ovarian cancer. Similar studies have yet to be done in patients with cancers for which angiogenesis may also play a key role (e.g., melanoma) (Hendrix, Seftor, Hess, and Seftor, 2003). Future research should monitor levels of VEGF in cancer survivors after behavioral interventions and correlate VEGF levels with measures of QOL, endocrine function and survival, and disease-free interval. There is no study to date that has attempted to relate immune and neuroendocrine changes during a behavioral intervention to changes in tumor-promoting agents or tumor antigen levels over time. Limitations that have precluded the initiation of such work are the lack of specificity in some of these tumor markers and the practical issues involved in collecting tumor tissues samples that may be necessary to quantify pro-angiogenic activities. Organ-specific disease markers may be sensitive measures of health-related effects of behavioral interventions in cancer patients. Prostate-specific antigen (PSA) is thought to be highly specific for prostate tissue and may be increased in prostate cancer, benign prostatic hyperplasia, and prostatitis (Oesterling and Oesterling, 1991). There is growing evidence that behavioral interventions can improve quality of life and physical functioning in men treated for prostate cancer (Lepore et al., 2003; Penedo et al., 2004). It may be useful to examine effects of behavioral interventions on PSA levels in men treated for prostate cancer and to correlate PSA levels with psychosocial, immune, neuroendocrine, and physical status indicators. Such studies seem plausible given a growing literature documenting a significant association between immune and neuroendocrine measures and prostate cancer pathogenesis on the one hand, and psychosocial modulation of immune and neuroendocrine parameters, on the other. For instance, among men treated with radical prostatectomy for early stage prostate cancer, greater levels of illness-related marital disruption, less emotional expression, less optimism, and negative personality traits are associated with suppressed NKCC (Penedo et al., 2002a, 2002b; 2006). In regard to neuroendocrine function, it has been shown in animal studies that psychological stress reduces blood flow and raises lymphocytic infiltration of the rat prostate (Gatenbeck, 1986). Neuropeptide Y, which is elevated during stress (Irwin et al., 1992), is localized and coreleased with catecholamines in response to stress, and
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is the most abundant neuropeptide in prostatic autonomic nerves. This suggests a possible biobehavioral mechanism for the association between psychosocial factors and disease activity in prostate cancer. Because behavioral interventions such as CBSM have been shown to impact immune and neuroendocrine parameters in other disease populations, it is reasonable to examine behavioral intervention effects among prostate cancer survivors. Biobehavioral research in cancer needs to address several methodological issues that are critical for evaluating the efficacy of behavioral interventions for improving outcomes. Some of these include the need for (a) well-timed and standardized, valid, and reliable assessments to monitor changes in psychosocial, endocrine, immunologic, and disease activity parameters over time; and (b) information on individual difference variables such as genetic factors, disease type/stage, treatment type and duration, sociodemographic characteristics, spiritual beliefs, and personality and contextual factors that could moderate intervention effects. Importantly, because of the large role played by these individual difference factors, PNI-disease research will likely require large-scale clinical trials in order to arrive at definitive answers in cancer research (Schneiderman, Antoni, Saab, and Ironson, 2001). Although the role of the immune system as a surveillance system for human cancers is controversial, tumor-specific immune responses related to prognosis in certain cancers (e.g., cervical carcinoma and malignant melanoma) and related treatments are being elucidated (Osanto, Brouwenstyn, Vessen et al., 1993). Immune system processes controlling programmed cell death or apoptosis (e.g., Hahne, Rimoldi, Schroter et al., 1996) and angiogenesis (Kurtzman, Miller, Anderson et al., 1997) may be a major focus of biobehavioral research in coming years. 3. Examining the Role of Sickness Behavior in Cancer Patients Undergoing Treatment Many of the quality of life challenges faced by cancer patients involve negative mood (Payne et al., 1999), persistent fatigue (Portenoy and Miaskowski, 1998), sleep disorders, lack of exercise, and chronic pain (Engstrom, Strohl, Rose, Lewandowski, and Stefanek, 1999). Certain treatments for medical conditions such as cancer (e.g., chemotherapy) may induce cytokine dysregulations associated with a constellation of symptoms collectively referred to as “sickness behavior” (Dantzer, 2001). These symptoms, including fatigue, memory problems, sleep problems, pain, and general malaise, can have a huge effect on the quality of life of cancer patients. Since behavioral interven-
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tions have been shown to decrease fatigue levels (Jacobsen and Hann, 1998), improve sleep quality (Cruess et al., 2002), and decrease pain perceptions (e.g., Breitbart and Payne, 1998), it is possible that these interventions work by modulating pro-inflammatory cytokine regulation. PNI processes underlying sickness behaviors may be helpful in identifying the mechanisms through which behavioral (and pharmacological) interventions work on these physical symptoms in order to make them more targeted for specific treatment-related conditions in cancer patients and other populations.
C. Behavioral Interventions and PNI Applications to Other Immunoregulatory Health Problems Four sets of PNI findings appear to be relevant to the question of applying behavioral interventions to prevent disease complications and facilitate recovery after medical treatments in different medical populations. These sets of studies have related stressors, stress responses, or distress/negative mood states to (a) increased susceptibility to viral infections such as upper respiratory infections (URIs) associated with the common cold (Cohen, Tyrrell, and Smith, 1991); (b) poorer responses to vaccinations for hepatitis B (Glaser, Kiecolt-Glaser, Bonneau et al., 1992); (c) slower rates of wound healing (Kiecolt-Glaser, Marucha, Malarkey et al., 1995); and (d) increases in cytokines that promote inflammatory processes (Miller et al., 2002; Steptoe et al., 2001). This work provides a rationale to study the health relevance of behavioral interventions in populations who are likely to show clinical benefits of immune system modulation. In terms of infectious disease processes, behavioral interventions may be helpful in accelerating the recovery of immune system functioning after patients have undergone surgery or successfully completed their course of adjuvant therapy. Understanding the specific viral, bacterial, and fungal infections that these persons are most likely to contract during this period and how stressors and other psychosocial factors relate to this risk is a necessary first step before choosing end points for study in randomized trials of behavioral interventions. One study has tested behavioral intervention effects on vaccination responses. Subjects with greater emotional expression during repeated disclosure sessions showed a more vigorous primary response to hepatitis B vaccination (Petrie, Booth, Pennebaker et al., 1995). Although this work was conducted with healthy persons, it is plausible that particularly vulnerable populations (geriatric patients) may benefit from “adjuvant” stress management intervention at the time
of their vaccinations, in order to maximize the effects on the primary immune response. As noted, chronic stress has been associated with poorer wound healing using a variety of paradigms in healthy populations (Kiecolt-Glaser, Marucha, Malarkey, Mercado, and Glaser, 1995). It is plausible that chronic stress superimposed on surgeryassociated changes in immune system functioning (van der Pompe et al., 1998) may slow post-surgical wound healing (Yang and Glaser, 2005). The risk of such complications might be particularly high in older persons, or those manifesting pre-existing diseaserelated immunosuppression. Other populations known to be vulnerable to difficulties with wound healing (e.g., persons with diabetes mellitus) might also be at added risk if they are unable to manage stressors, with an increased possibility of limb loss. It is yet to be determined whether behavioral interventions such as stress management, and possibly physical exercise, might bring about clinically meaningful improvements in wound healing in these vulnerable populations. Stressors, stress responses, and negative mood states have been related to amplified proinflammatory cytokine responses (Altemus, Rao, Dhabhar et al., 2001; Ghiadoni, Donald, Cropley et al., 2000; Lésperance, Frasure-Smith, Theroux, and Irwin, 2004; Miller et al., 2002; Steptoe et al., 2001) that could affect disease processes such as atherosclerosis (Appels et al., 2000; Ross, 1999) and physical symptoms defining the sickness behavior complex (Dantzer, 2001). Well-established risk factors for myocardial infarction such as depression, social isolation, and hostility (Case, Moss, Case et al., 1992; Frasure-Smith, Lésperance, and Talajic, 1995; Williams, Barefoot, Califf et al., 1992) may contribute to disease pathophysiology via alterations in immunoregulation. Alternatively, cytokines and psychosocial factors might operate through a common set of events orchestrated by neuroendocrines. Given this evidence, it is plausible that behavioral and pharmacological interventions capable of modifying stress responses and negative mood states may be used to mitigate inflammatory processes contributing to diseases such as CVD. Meta-analyses conducted upon studies with post-myocardial infarction patients have indicated that psychosocial interventions significantly decrease mortality above and beyond decreases associated with usual care (Dusseldorp et al., 1999; Linden et al., 1996; Mullen et al., 1992). The major study reporting positive results was the Recurrent Coronary Prevention Project, which used group-based CBSM, and decreased hostility and depressed affect (Mendes de Leon et al., 1991) as well as the composite
32. Behavioral Interventions: Immunologic Mediators and Disease Outcomes
medical end point of cardiac death and non-fatal myocardial infarction (Friedman et al., 1986). Another large, randomized clinical trial, the Enhancing Recovery in Coronary Heart Disease (ENRICHD) study, specifically assessed whether mortality or recurrent infarction are reduced by treatment of depression and/or low perceived social support with CBSM, supplemented with an SSRI when indicated (Berkman et al., 2003). The ENRICHD intervention did not increase eventfree survival, but it did decrease depression more than in the control group. It is conceivable that some portion of the decrease in depression observed in the ENRICHD groups was primarily due to a decrease in inflammation as part of the recovery process that was not associated with the ENRICHD treatment. However, the trial did not look at markers of inflammation and therefore could not assess this possibility. A secondary analysis indicated that the intervention may have decreased both mortality and recurrent heart attack in patients taking SSRIs compared with those not taking the drugs (Taylor et al., 2005). This finding needs to be interpreted with caution, because the antidepressant was not administered in a randomized manner. It should be noted that in addition to decreasing depression, SSRIs block platelet aggregation and possess antiinflammatory properties (de Beaurepaire, 2002). Relationships among depression, inflammation, CVD, and behavioral and pharmacological treatments deserve further attention.
V. CONCLUSION While a number of PNI studies using patients with HIV infection and different types of cancer have been published in the past decade, only recently have investigators attempted to test PNI hypotheses in the context of other diseases and syndromes that are likely mediated by the immune system. Briefly, some of these include atherosclerosis (Libby, Ridker, and Maseri, 2002), allergies and asthmatic conditions (Busse, Kiecolt-Glaser, and Coe, 1995), tuberculosis (Zwilling, 1996), rheumatoid arthritis (Sternberg, 1996), multiple sclerosis (Mohr et al., 2004), and systemic lupus erythematosus (Whitacre, Cunnings, and Griffin, 1994). In addition to these diseases, poorly understood conditions such as chronic fatigue syndrome (CFS) have been studied from a PNI perspective, a notion that is plausible in light of the known association between CFS symptom exacerbation and both stressors (Lutgendorf, Antoni, Ironson et al., 1995) and immune system abnormalities (Antoni and Weiss, 2003; Buchwald, Cheny, Peterson et al., 1992). One interest-
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ing theory holds that CFS symptoms derive from disturbances in cytokine regulation due to alterations in HPA functioning, including inadequate production of cortisol (Demitrack, Dale, Straus et al., 1991). Finally, diseases previously thought to be independent of immune system activities, such as cardiovascular disease, are now known to be associated with inflammation and infectious disease. These are now beginning to receive attention from PNI researchers. This may be a fruitful venture, given that myocardial infarction and the underlying atherosclerotic process have been linked to stress, depression, and negative affect on the one hand and cytokine dysregulation on the other. All of this contemporary PNI work will be facilitated by carefully coordinated field and laboratory stress research, and the development of animal models that allow investigators to manipulate biological processes governing the control of infections, neoplasms, and inflammatory-induced pathological changes. This work may in the future lead to the development of behavioral interventions to modify relevant biobehavioral processes so as to help manage or ameliorate the most prevalent chronic diseases of our time.
References Ackerman, K., Felten, S., Dijkstra, C., Livnat, S., and Felten, D. (1989). Parallel development of noradrenergic innervation and cellular compartmentation in the rat spleen. Exp. Neurol., 103, 239. Ader, R. (1996). Role of conditioning in the pharmacotherapy of autoimmune diseases. In N. Hall, F. Altman, and S. Blumenthal (Eds.), Mind-body interactions and disease and psychoneuroimmunological aspects of health and disease (pp. 295–300). Washington, DC: Heath Dateline Press. Ader, R., Felten, D., and Cohen, N. (1991). Psychoneuroimmunology (2nd ed.). New York: Academic Press. Affleck, G., Urrows, S., Tennen, H., Higgins, P., Pav, D., and Aloisi, R. (1997). A dual pathway model of daily stressor effects on rheumatoid arthritis. Ann. Behav. Med., 19, 161–170. Altemus, M., Rao, B., Dhabhar, F., Ding, W., and Granstein, R. (2001). Stress-induced changes in skin barrier function in healthy women. J. Invest. Dermatol., 117, 309–317. Andersen, B., Farrar, W., Golden-Kreutz, D., Kutz, L., MacCallum, R., Courtney, M., and Glaser, R. (1998). Stress and immune responses after surgical treatment for regional breast cancer. J. NCI, 90, 30–36. Andersen, B., Farrar, W., Golden-Kreutz, D., Glaser, R., Emery, C., Crespin, T., Shapiro, C., and Carlson, W. (2004). Psychological, behavioral, and immune changes after a psychosocial intervention: a clinical trial. J. Clin. Oncol., 22, 3570–3580. Andersen, B., Kiecolt-Glaser, J., and Glaser, R. (1994). A biobehavioral model of cancer stress and disease course. Am. Psychol., 49, 389–404. Antoni, M. H., Lutgendorf, S., Ironson, G., Fletcher, M. A., and Schneiderman, N. (March, 1996). CBSM intervention effects on social support, coping, depression and immune function in symptomatic HIV-infected men. Paper presented at the American Psychosomatic Society. Williamsburg, VA. Antoni, M. H. (1997). Cognitive behavioral stress management for gay men learning of their HIV-1 antibody test results. In J. Spira
696
III. Behavior and Immunity
(Ed.), Group therapy for patients with chronic medical diseases. New York: Guilford Press. (pp. 55–91). Antoni, M. H., Lufgendorf, S., Cole, S. W., Dhabhar, F. S., Sephton, S. E., McDonald, P. G., Stefanek, M., and Sood, A. (2006). The influence of biobehavioral factors on tumor biology: pathways and mechanisms. Nature Reviews Cancer, 6, 240–248. Antoni, M. H. (2003a). Psychoneuroendocrinology and psychoneuroimmunology of cancer: plausible mechanisms worth pursuing? Brain Behav. Immun., 17, S84–S91. Antoni, M. H. (2003b). Stress management effects on psychological, endocrinological and immune function in men with HIV: empirical support for a psychoneuroimmunological model. Stress, 6, 173–188. Antoni, M. H. (2003c). Stress management intervention for women with breast cancer. Washington, DC: American Psychological Association Press. Antoni, M. H., Baggett, L., Ironson, G., August, S., LaPerriere, A., Klimas, N., Schneiderman, N., and Fletcher, M. A. (1991). Cognitive-behavioral stress management intervention buffers distress responses and immunologic changes following notification of HIV-1 seropositivity. J. Consult. Clin. Psychol., 6, 906–915. Antoni, M. H., Caricco, A., Duran, R., Spitzer, S., Penedo, F., Ironson, G., Fletcher, M. A., Klimas, N., and Schneiderman, N. (2006). Randomized Clinical Trial of Cognitive Behavioral Stress Management on HIV Viral Load in Gay Men Treated with HAART. Psychosom. Med., 68 (1), 143–151. Antoni, M. H., Cruess, S., Cruess, D., Kumar, M., Lutgendorf, S., Ironson, G., Dettmer, E., Williams, J., Klimas, N., Fletcher, M. A., and Schneiderman, N. (2000). Cognitive behavioral stress management reduces distress and 24-hour urinary free cortisol among symptomatic HIV-infected gay men. Ann. Behav. Med., 22, 1–11. Antoni, M. H., Cruess, D., Klimas, N., Maher, K., Cruess, S., Kumar, M., Lutgendorf, S., Ironson, G., Schneiderman, N., and Fletcher, M. A. (2002). Stress management and immune system reconstitution in symptomatic HIV-infected gay men over time: effects on transitional naïve T-cells (CD4+CD45RA+CD29+). Am. J. Psychiatry, 159, 143–145. Antoni, M. H., Cruess, D., Klimas, N., Maher, K., Cruess, S., Lechner, S., Carrico, A., Kumar, M., Lutgendorf, S., Ironson, G., Fletcher, M. A., and Schneiderman, N. (2005). Increases in a marker of immune system reconstitution are predated by decreases in 24hour urinary cortisol output and depressed mood during a 10week stress management intervention in symptomatic gay men. J. Psychosom. Res., 58, 3–13. Antoni, M. H., Cruess, D., Wagner, S., Lutgendorf, S., Kumar, M., Ironson, G., Klimas, N., Fletcher, M. A., and Schneiderman, N. (2000). Cognitive behavioral stress management effects on anxiety, 24-hour urinary catecholamine output, and T-cytotoxic/ suppressor cells over time among symptomatic HIV-infected gay men. J. Consult. Clin. Psychol., 68, 31–45. Antoni, M. H., and Goodkin, K. (1988). Life stress and moderator variables in the promotion of cervical neoplasia. I: Personality facets. J. Psychosom. Research, 32 (3), 327–338. Antoni, M. H., and Goodkin, K. (1989). Life stress and moderator variables in the promotion of cervical neoplasia. II: Life event dimensions. J. Psychosom. Res., 33 (4), 457–467. Antoni, M. H., Lehman, J., Kilbourn, K., Boyers, A., Yount, S., Culver, J., Alferi, S., McGregor, B., Arena, P., Harris, S., Price, A., and Carver, C. S. (2001). Cognitive-behavioral stress management intervention decreases the prevalence of depression and enhances benefit finding among women under treatment for early-stage breast cancer. Health Psychol., 20, 20–32.
Antoni, M. H., and Schneiderman, N. (1998). HIV/AIDS. In A. Bellack and M. Hersen (Eds.), Comprehensive clinical psychology (pp. 237–275). New York: Elsevier Science. Antoni, M. H., Schneiderman, N., Fletcher, M., Goldstein, D., LaPerriere, A., and Ironson, G. (1990). Psychoneuroimmunology and HIV-1. J. Consult. Clin. Psychol., 58 (1), 38–49. Antoni, M. H., Wagner, S., Cruess, D., Kumar, M., Lutgendorf, S., Ironson, G., Dettmer, E., Williams, J., Klimas, N., Fletcher, M. A., and Schneiderman, N. (2000). Cognitive behavioral stress management reduces distress and 24-hour urinary free cortisol among symptomatic HIV-infected gay men. Ann. Behav. Med., 22, 29–37. Antoni, M. H., and Weiss, D. (2003). Stress, immunity, and chronic fatigue syndrome: a conceptual model to guide the development of treatment and research. In L. Jason, P. Fenell, and R. Taylor (pp. 527–545) (Eds.), Handbook of chronic fatigue syndrome and fatiguing illnesses. New York: John Wiley and Sons. Appels, A., Bar, F. W., Bar, J., Bruggeman, C., and de Bates, M. (2000). Inflammation, depressive symptomatology, and coronary artery disease. Psychosom. Med., 62, 601–605. Auerbach, J. E., Oleson, T. D., and Solomon, G. F. (1992). A behavioral medicine intervention as an adjunctive treatment for HIVrelated illness. Psychol. Health, 6, 325–334. Baron, R., Cutrona, C., Hicklin, D., Russel, D., and Lubaroff, D. (1990). Social support and immune function among spouses of cancer patients. J. Pers. Soc. Psychol., 59, 344–352. Barraclough, J., Pinder, P., Cruddas, M., Osmond, C., Taylor, I., and Perry, M. (1992). Life events and breast cancer prognosis. Br. Med. J., 304, 1078–1081. Bartholomew, J. S., et al. (1997). Integration of high-risk human papillomavirus DNA is linked to the down-regulation of class I human leukocyte antigens by steroid hormones in cervical tumor cells. Cancer Res., 57, 937–942. Bartrop, R., Lazarus, L., Luckhurst, E., Kiloh, L., and Penny, R. (1977). Depressed lymphocyte function after bereavement. Lancet, 1, 834–836. Baxevanis, C., Reclos, G., Gritzapis, A., Dedousis, G., Missitzis, I., and Papamichail, M. (1993). Elevated prostaglandin E2 production by monocytes is responsible for the depressed levels of natural killer and lymphokine-activated killer cell function in patients with breast cancer. Cancer, 72, 491–501. Beck, L. Jr., and D’Amore, P. A. (1997). Angiogenesis and markers. FASEB J. 5, 365–373. Beck, A., and Emery, G. (1979). Cognitive therapy of anxiety and phobic disorders. Philadelphia, PA: Center for Cognitive Therapy. Bellinger, D., Ackerman, K., Felten, S., and Felten, D. (1992). A longitudinal study of age-related loss of noradrenergic nerves and lymphoid cells in the aged rat spleen. Exp. Neurol., 116, 295–311. Bergers, G., and Benjamin, L. (2003). Tumorigenesis and the angiogenic switch. Nat. Rev. Cancer, 3, 401–410. Berkenbosch, F., Van Oers, J., del Rey, A., Tilders, F., and Besedovsky, H. (1987). Corticotropin-releasing factor-producing neurons in the rat activated by interleukin-1. Science, 238, 524. Berkman, L. F., Blumenthal, J., Burg, M., Carney, R. M., Catellier, D., Cowan, M. J., Czajkowski, S. M., DeBusk, R., Hosking, J., Jaffe, A., Kaufmann, P. G., Mitchell, P., Norman, J., Powell, L. H., Raczynski, J. M., and Schneiderman, N. (2003). Effects of treating depression and low perceived social support on clinical events after myocardial infarction: the enhancing recovery in coronary heart disease patients (ENRICHD) randomized trial. JAMA, 289, 3106–3116.
32. Behavioral Interventions: Immunologic Mediators and Disease Outcomes Bernstein, B., and Borkovec, T. (1973). Progressive muscle relaxation training: a manual for the helping professions. Champaign, IL: Research Press. Besedovsky, H., del Rey, A., and Sorkin, E. (1981). Lymphokine containing supernatants from Con A–stimulated cells increase corticosterone blood levels. J. Immunol., 126, 385. Besedovsky, H., del Rey, A., Sorkin, E., DaPrada, M., Burri, R., and Honegger, C. (1983). The immune response evokes changes in brain noradrenergic neurons. Science, 221, 564. Biron, G., Byron, K., and Sullivan, J. (1989). Severe herpes virus infections in an adolescent without natural killer cells. N. Engl. J. Med., 320, 1731–1735. Bovjberg, D. (1991). Psychoneuroimmunology: implications for oncology? Cancer, 67, 828–832. Bovbjerg, D., and Valdimarsdottir, H. (1996). Stress, immune modulation, and infectious disease during chemotherapy for breast cancer. Ann. Behav. Med., 18, S63. Breitbart, W., and Payne, D. (1998). Pain. In J. Holland (Ed.), Textbook of psycho-oncology (pp. 450–467). New York: Oxford. Brenner, B., and Margolese, R. (1991). The relationship of chemotherapeutic and endocrine intervention on natural killer cell activity in human breast cancer. Cancer, 68, 482–488. Broadley, A. J., Korszun, A., Jones, C. J., and Frenneaux, M. P. (2002). Arterial endothelial function is impaired in treated depression. Heart, 88, 521–523. Brooks, G. R., and Richardson, F. C. (1980). Emotional skills training: a treatment program for duodenal ulcer. Behav. Ther., 11, 198–207. Buchwald, D., Cheney, D., Peterson et al. (1992). A chronic illness characterized by fatigue, neurologic and immunologic disorders, and active human herpesvirus-type 6 infection. Ann. Int. Med., 116, 103–113. Burack, J. H., Barrett, D. C., Stall, R. D., Chesney, M. A., Ekstrand, M. L., and Coates, T. J. (1993). Depressive symptoms and CD4 lymphocyte decline among HIV-infected men. JAMA, 270, 2567–2573. Busse, W., Kiecolt-Glaser, J., and Coe, C. (January, 1995). Stress and asthma: NHLBI workshop report. Am. J. Crit. Care Med., 248–252. Byrnes, D., Antoni, M. H., Goodkin, K., Efantis-Potter, J., Simon, T., Munajj, J., Ironson, G., and Fletcher, M. A. (1998). Stressful events, pessimism, natural killer cell cytotoxicity, and cytotoxic/ suppressor T-cells in HIV+ Black women at risk for cervical cancer. Psychosomat. Med., 60, 714–722. Calabrese, J., Kling, M., and Gold, P. (1987). Alterations in immunocompetence during stress, bereavement, and depression: focus on neuroendocrine regulation. Am. J. Psychiatry, 144 (9), 1123–1134. Carbonari, M., Fiorilli, M., Mezzaroma, I., Cherichi, M., and Aiuti, F. (1989). CD4 as the receptor for retroviruses of the HTLV family: immunopathogenetic implications. Adv. Exp. Med. Biol., 257, 3–7. Carlson, S., Felten, D., Livnat, S., and Felten, S. (1987). Noradrenergic sympathetic innervation of the spleen. V. Acute drug-induced depletion of lymphocytes in the target fields of innervation results in redistribution of noradrenergic fibers but maintenance of compartmentation. J. Neurosci. Res., 18, 64–69. Carney, R. M., Freedland, K. E., Miller, G. E., and Jaffe, A. S. (2002). Depression as a risk factor for cardiac mortality and morbidity: a review of potential mechanisms. J. Psychosom. Res., 53, 897–902. Carney, R. M., Rich, M. W., Tevelde, A., Saini, J., Clark, K., and Jaffe, A. S. (1987). Major depressive disorder in coronary artery disease. Am. J. Cardiol., 60, 1273–1275.
697
Carroll, B. J., Reinberg, M., Greden, J. F., et al. (1981). A specific laboratory test for the diagnosis of melancholia: standardization, validation, and clinical utility. Arch. Gen. Psych., 38, 15–22. Case, R. B., Moss, A. J., Case, N., McDermott, M., and Eberly, S. (1992). Living alone after myocardial infarction. J. Am. Med. Assoc., 267, 515–519. Centers for Disease Control. (1997). HIV/AIDS surveillance report. 9 (1), 1–39. Chrousos, G., and Gold, P. (1992). The concepts of stress and stress system disorders: overview of physical and behavioral homeostasis. JAMA, 267, 1244–1252. Chuang, L., Lotzova, E., Cook, K., Cristoforoni, P., Morris, M., and Wharton, J. (1993). Effect of new investigational drug taxol on oncolytic activity and stimulation of human lymphocytes. Gynecol. Oncol., 49, 291–298. Classen, C., Sephton, E., Diamond, S., and Spiegel, D. (1998). Studies of life-extending psychosocial interventions. In J. Holland (Ed.), Textbook of psycho-oncology (pp. 730–742). New York: Oxford. Coffey, R., Hadden, E., and Hadden, J. (1975). Norepinephrine stimulation of membrane ATPase in human lymphocytes. Endocrinol. Res. Comm., 12, 179. Cohen, S., Tyrrell, D. A., and Smith, A. P. (1991). Psychological stress in humans and susceptibility to the common cold. N. Engl. J. Med., 325, 606–612. Cole, S., Kemeny, M., Naliboff, B., Fahey, J., and Zack, J. (2001). ANS enhancement of HIV pathogenesis. Brain Behav. Immun., 15, 121. Cole, S., Kemeny, M., Taylor, S., Visscher, B., and Fahey, J. (1996). Accelerated course of HIV infection in gay men who conceal their homosexuality. Psychosom. Med., 58, 219–231. Crary, B., Borysenko, M., Sutherland, D., Kutz, I., Borysenko, J., and Benson, H. (1983). Decrease in mitogen responsiveness of mononuclear cells from peripheral blood after epinephrine administration in humans. J. Immunol., 130, 694–697. Crowther, J. H. (1983). Stress management training and relaxation imagery in the treatment of essential hypertension. J. Behav. Med., 6, 169–187. Cruess, D. (2002). Improving sleep quality in patients with chronic illness. In M. Chesney and M. Antoni (Eds.), Innovative approaches to health psychology: prevention and treatment lessons from AIDS. (pp. 235–252) Washington, DC: American Psychological Association Press. Cruess, D., Antoni, M., Cruess, S., Fletcher, M., Ironson, G., Kumar, M., Hayes, A., Klimas, N., and Schneiderman, N. (2000). Cognitive-behavioral stress management increases free testosterone and decreases psychological distress in HIV-seropositive men. Health Psychol., 19 (1), 12–20. Cruess, S., Antoni, M. H., Cruess, D., Fletcher, M. A., Ironson, G., Kumar, M., Lutgendorf, S., Hayes, A., Klimas, N., and Schneiderman, N. (2000a). Reductions in HSV-2 antibody titers after cognitive behavioral stress management and relationships with neuroendocrine function, relaxation skills, and social support in HIV+ gay men. Psychosom. Med., 62, 828–837. Cruess, D. G., Antoni, M. H., McGregor, B. A., Boyers, A., Kumar, M., Kilbourn, K., and Carver, C. S. (2000). Cognitive-behavioral stress management reduces serum cortisol by enhancing positive contributions among women being treated for early stage breast cancer. Psychosom. Med., 62, 304–308. Cruess, D., Antoni, M. H., McGregor, B., Kilbourn, K., Boyers, A., Alferi, S., Carver, C. S., Duran, R., and Kumar, M. (2001). Cognitive behavioral stress management effects on testosterone and positive growth in women with early-stage breast cancer. Int. J. Behavl. Med., 8, 194–207.
698
III. Behavior and Immunity
Cupps, T., and Fauci, A. (1982). Corticosteroid-mediated immunoregulation in man. Immunol. Rev., 65, 133–155. Dantzer, R. (2001). Cytokine-induced sickness behavior: where do we stand? Brain Behav. Immun., 15, 7–24. Davies, A., and Lefkowitz, R. (1984). Regulation of β-adrenergic receptors by steroid hormones. Ann. Rev. Physiol., 46, 119–130. De Beaurepaire, R. (2002). Questions raised by the cytokine hypothesis of depression. Brain, Behav. Immun., 16, 610–617. Demitrack, M., Dale, J., Straus, S., Loue, L., Listwak, S., Kruesi, M., Chrousos, G., and Gold, P. (1991). Evidence for impaired activation of the hypothalamic-pituitary-adrenal axis in patients with chronic fatigue syndrome. J. Clin. Endocrinol. Metab., 73, 1224–1234. Duncan, M., Sadlik, J., and Hadden, J. (1982). Glucocorticoid modulation of lymphokine-induced macrophage proliferation. Cell. Immunol., 67, 23–36. Dusseldorp, E., van Elderen, T., Maes, S., Meulman, J., and Kraaij, V. (1999). A meta-analysis of phychoeducational programs for coronary heart disease patients. Health Psychol., 18, 506–519. Engstrom, C., Strohl, R., Rose, L., Lewandowski, L., and Stefanek, M. (1999). Sleep alterations in cancer patients. Cancer Nurs., 22, 143–148. Esterling, B., Antoni, M. H., Fletcher, M. A., Margulies, S., and Schneiderman, N. (1994). Emotional disclosure through writing or speaking modulates latent Epstein-Barr Virus antibody titers. J. Consult. Clin. Psychol., 62, 130–140. Esterling, B., Antoni, M. H., Kumar, M., and Schneiderman, N. (1990). Emotional repression, stress disclosure responses, and EpsteinBarr viral capsid antigen titers. Psychosom. Med., 52, 397– 410. Esterling, B., Antoni, M. H., Schneiderman, N., Carver, C., LaPerriere, A., Ironson, G., Klimas, N., and Fletcher, M. (1992). Psychosocial modulation of antibody to Epstein-Barr viral capsid antigen and Human Herpes Virus-Type 6 in HIV-1 infected and at-risk gay men. Psychosom. Med., 54, 354–371. Esterling, B., Kiecolt-Glaser, J., Bodnar, J., and Glaser, R. (1994). Chronic stress, social support, and persistent alterations in the natural killer cell response to cytokines in older adults. Health Psychol., 13, 291–298. Esterling, B., Kiecolt-Glaser, J., and Glaser, R. (1996). Psychosocial modulation of cytokine-induced natural killer cell activity in older adults. Psychosom. Med., 58, 264–272. Fawzy, F., Canada, A., and Fawzy, N. (2003). Malignant melanoma: effects of a brief, structured psychiatric intervention on survival and recurrence at 10-year follow-up. Arch. Gen. Psychiatry, 60, 100–103. Fawzy, F., Fawzy, N., Hyun, C., Elashoff, R., Guthrie, D., Fahey, J., and Morton, D. (1993). Malignant melanoma. Effects of an early structured psychiatric intervention, coping, and affective state on recurrence and survival 6 years later. Arch. Gen. Psychiatry, 50, 681–689. Fawzy, F., Fawzy, N., Hyun, C., and Wheeler, J. (1997). Brief, copingoriented therapy for patients with malignant melanoma. In J. Spria (Ed.), Group therapy for medically ill patients (pp. 133–164). New York: Guilford. Fawzy, F., Kemeny, M., Fawzy, N., Elashoff, R., Morton, D., Cousins, N., and Fawzy, S. (1990). A structured psychiatric intervention for cancer patients. II. Changes over time in immunological measures. Arch. Gen. Psychiatry, 47, 729–735. Feinberg, B. B., Tan, N. S., Gonik, B., Brath, P. C., and Walsh, S. W. (1991). Increased progesterone concentrations are necessary to suppress interleukin mediated cell cytotoxicity. Am. J. Obstet. Gynecol., 165, 1872–1876. Felten, D. (1996). Changes in the neural innervation of lymphoid tissues with age. In N. Hall, F. Altman, and S. Blumenthal (Eds.),
Mind-body interactions and disease and psychoneuroimmunological aspects of health and disease. Proceedings of conference on Stress, Immunity and Health. National Institutes of Health (pp. 157–164). Washington, DC: Heath Dateline Press. Felten, D., Felten, S., Bellinger, D., Carlson, S., Ackerman, K., Madden, K., Olscowka, J., and Livnat, S. (1987). Noradrenergic sympathetic neural interactions with the immune system: structure and function. Immunol. Rev., 100, 225–260. Fishman, B., and Loscalzo, M. (1987). Cognitive-behavioral interventions in management of cancer pain: principles and applications. Med. Clin. North Am., 71 (2), 271–287. Florijn, Y., and Geiger, A. (1991). Community based physical activity program for HIV-1 infected persons. Proceedings of the Biological Aspects of HIV Infection Conference. Folkman, S., Chesney, M., McKusick, L., Ironson, G., Johnson, D., and Coates, T. (1991). Translating coping theory into intervention. In J. Eckenrode (Ed.), The social context of coping (pp. 239– 259). New York: Plenum. Fontanarosa, P., and Lundberg, G. (1997). Complementary, alternative, unconventional, and integrative medicine. JAMA, 278, 2111–2112. Fonteneau, J. F., Le Drean, E., Le Guiner, S., Gervois, N., Diez, E., and Jotereau, F. (1997). Heterogeneity of biologic responses of melanoma-specific CTL. J. Immunol., 15, 2831–2839. Frasure-Smith, N., Lésperance, F., and Talajic, M. (1995). Depression and 18-month prognosis after myocardial infarction. Circulation, 91, 999–1005. Freedman, L., Yoshinaga, S., Vanderbilt, J., and Yamamoto, K. (1989). In vitro transcription enhancement by purified derivatives of glucocorticoid receptor. Science, 245, 298–301. Friedman, M., Thoresen, C. E., Gill, J., Ulmer, D., Powell, L. H., et al. (1986). Alteration of Type A behavior and its effect on cardiac recurrences in postmyocardial infarction patients: summary results of the Recurrent Coronary Prevention Project. Am. Heart J., 112, 653–665. Gatenbeck, L. (1986). Stress stimuli and the prostatic gland: An experimental study in the rat. Scandinavian Journal of Urology and Nephrology, 99, 1–11. Ghiadoni, L., Donald, A. E., Cropley, M., et al. (2000). Mental stress induces transient endothelial dysfunction in humans. Circulation, 102, 2473–2478. Glaser, R., Kennedy, S., Lafuse, W. P., Bonneau, R. H., Speicher, C. E., and Kiecolt-Glaser, J. K. (1990). Psychological stressinduced modulation of IL-2 receptor gene expression and IL-2 production in peripheral blood leukocytes. Arch. Gen. Psychiatry, 47, 707–712. Glaser, R., and Kiecolt-Glaser, J. (1997). Chronic stress modulates the virus-specific immune response to latent herpes simplex virus type 1. Ann. Behav. Med., 19, 78–82. Glaser, R., Kiecolt-Glaser, J. K., Bonneau, R., Malarkey, W., and Hughes, J. (1992). Stress-induced modulation of the immune response to recombinant hepatitis B vaccine. Psychosom. Med., 54, 22–29. Glaser, R., Pearson, G., Bonneau, R., et al. (1993). Stress and the memory T-cell response to the Epstein-Barr Virus in healthy medical students. Health Psychol., 12, 435–442. Glaser, R., Rice, J., Sheridan, J., Fertel, R., Stout, J., Speicher, C., Pinsky, D., Kotur, M., Post, A., Beck, M., and Kiecolt-Glaser, J. (1987). Stress-related immune suppression: health implications. Brain Behav. Immun., 1, 7–20. Goebel, M. U., and Mills, P. J. (2000). Acute psychological stress and exercise and changes in peripheral leukocyte adhesion molecule expression and density. Psychosom. Med., 62, 664– 670.
32. Behavioral Interventions: Immunologic Mediators and Disease Outcomes Goodkin, K., Antoni, M. H., and Blaney, P. (1986). Stress and hopelessness in the promotion of cervical intraepithelial neoplasia to invasive squamous cell carcinoma of the cervix. J. Psychosom. Res., 30 (1), 67–76. Goodkin, K., Antoni, M. H., Fox, B. H., and Sevin, B. (1993). A partially testable model of psychosocial factors in the etiology of cervical cancer. II. Psychoneuroimmunological aspects, critique and prospective integration. Psycho-oncology, 2 (2), 99–121. Goodkin, K., Baldewicz, T., Asthana, D., Khanis, I., Blaney, N., Kumar, M., Burkhalter, J., Leads, B., and Shapshak, P. (2001). A bereavement support group intervention affects plasma burden of HIV-1. J. Hum. Virol., 4 (1), 44–54. Goodkin, K., Blaney, N., Feaster, D., and Fletcher, M. A. (1992). Active coping is associated with natural killer cell cytotoxicity in asymptomatic HIV-1 seropositive homosexual men. J. Psychosom. Res., 36 (7), 635–650. Goodwin, P., Leszcz, M., and Ennis, M. (2001). The effect of group psychosocial support on survival in metastatic breast cancer. N. Engl. J. Med., 345, 1719–1726. Greer, S. (1991). Psychological responses to cancer and survival. Psychol. Med., 21, 43–49. Greer, S., Moorey, S., Baruch, J., Watson, M., Robertson, B., Mason, A., Rowden, L., Law, M., and Bliss, J. (1992). Adjuvant psychological therapy for patients with cancer: a prospective randomised trial. Br. Med. J., 304, 675–680. Greer, S., Morris, T., Pettingale, K., and Haybittle, J. (1990). Psychological response to breast cancer and 15-year outcome. Lancet, i, 49–50. Gruber, B., Hersh, S., Hall, N., Waletzky, L., Kunz, J., Carpenter, J., Kverno, K., and Weiss, S. (1993). Immunologic responses of breast cancer patients to behavioral interventions. Biofeedback and Self-Regulation, 18, 1–22. Hadden, J., Hadden, E., Meetz, G., Good, R., Haddox, M., and Goldberg, N. (1973). Cyclic GMP in cholinergic and mitogenic modulation of lymphocyte metabolism and proliferation. Fed. Proc., 32, 1022. Hadden, J., Hadden, E., and Middleton, E. (1970). Lymphocyte blast transformation. I. Demonstration of adrenergic receptors in human peripheral lymphocytes. J. Cell. Immunol., 1, 583. Hahne, M., Rimoldi, D., Schroter, M., Romero, P., Schreier, M., French, L., Schneider, P., Bornand, T., Fontana, A., and Lienard, D. (1996). Melanoma cell expression of fas (Apo-1/ CD95) ligand: implications for tumor immune escape. Science, 274, 1363–1366. Hall, M., Baum, A., Buysse, D., Prigerson, G., Kupfer, D., and Reynolds, C. (1998). Sleep as a mediator of the stress-immune relationship. Psychosom. Med., 60, 48–51. Harbuz, M. S., Chover-Gonzalez, A. J., and Jessop, D. S. (2003). Hypothalamo-pituitary-adrenal axis and chronic immune activation. Ann. NY Acad. Sci., 992, 99–106. Heijnen, C., and Kavelaars, A. (2005). Psychoneuroimmunology and chronic autoimmune disease: rheumatoid arthritis. In K. Vedhara and M. Irwin (Eds.), Human psychoneuroimmunology (pp. 195– 218). Oxford: Oxford University Press. Hendrix, M., Seftor, E., Hess, A., and Seftor, R. (2003). Vasculogenic mimicry and tumour-cell plasticity: lessons from melanoma. Nat. Rev.: Cancer, 3, 411–421. Herberman, R., and Holden, H. (1978). Natural cell-mediated immunity. Adv. Cancer Res., 27, 305–377. Herbert, T., and Cohen, S. (1993a). Depression and immunity: A meta-analytic review. Psychol. Bull., 113, 472–486. Herbert, T., and Cohen, S. (1993b). Stress and immunity in humans: A meta-analytic review. Psychosom. Med., 55, 364–379.
699
Hernandez-Reif, M., Ironson, G., et al. (2004). Breast cancer patients have improved immune and neuroendocrine functions following massage therapy. J. Psychosom. Res., 57 (1), 45–52. Hidderley, M., and Holt, M. (2004). A pilot randomized trial assessing the effects of autogenic training in early stage cancer patients in relation to psychological status and immune system responses. Eur. J. Oncol. Nurs., 8, 61–65. Hou, J., and Zheng, W. F. (1988). Effect of sex hormones on NK and ADCC activity of mice. Int. J. Immunopharmacol., 10 (1), 15–22. Huang, L. M., Chao, M. F., Chen, M. Y., Shih, H. M., Chiang, Y. P., Chuang, C. Y., et al. (2001). Reciprocal regulatory interaction between Human Herpesvirus 8 and Human Immunodeficiency Virus Type 1. J. Biol. Chem., 276, 13427–13432. Ironson, G., Antoni, M. H., and Lutgendorf, S. (2002). Coping: interventions for optimal disease management. In M. Chesney and M. H. Antoni (Eds.), Innovative approaches to health psychology: prevention and treatment lessons from AIDS. Washington, DC: American Psychological Association Press. Ironson, G., Balbin, E., Solomon, G., Fahey, J., Klimas, N., Schneiderman, N., and Fletcher, M. A. (2001). Relative preservation of natural killer cell cytotoxicity and number in healthy AIDS patients with low CD4 counts. AIDS, 15, 2065–2073. Ironson, G., Field, T., Scafidi, F., Hashimoto, M., Kumar, M., Kumar, A., Price, A., Goncalves, A., Burman, R., Tetenman, C., Patarca, R., and Fletcher, M. A. (1996). Massage therapy is associated with enhancement of the immune system’s cytotoxic capacity. Int. J. Neurosci., 84, 205–217. Ironson, G., Friedman, A., Klimas, N., et al. (1994). Distress, denial, and low adherence to behavioral intervention predict factor disease progression in gay men infected with HIV. Int. J. Beh. Med., 1994, 1 (1), 90–105. Ironson, G., Solomon, G., Cruess, D., Barroso, J., and Stivers, M. (1995). Psychosocial factors related to long-term survival in HIV/ AIDS. Clin. Psychol. Psychother., 2, 249–266. Ironson, G., Wynings, C., Schneiderman, N., Baum, A., Rodriquez, M., Greenwood, D., Benight, C., Antoni, M. H., LaPerriere, A., Huang, H., Klimas, N., and Fletcher, M. (1997). Post traumatic stress symptoms, intrusive thoughts, loss and immune function after Hurricane Andrew. Psychosom. Med., 59, 128–141. Irwin, M., Brown, M., Patterson, T., Hauger, R., Mascovich, A., and Grant, I. (1992). Neuropeptide Y and natural killer activity. Findings in depression and Alzheimer caregiver stress. FASEB J., 5, 3100–3107. Irwin, M., Daniels, M., Smith, T., Bloom, E., and Weiner, H. (1987). Impaired natural killer cell activity during bereavement. Brain Behav. Immun., 1, 98–104. Jacobsen, P., and Hann, D. (1998). Cognitive-behavioral interventions. In J. Holland (Ed.), Textbook of psycho-oncology (pp. 717– 729). New York: Oxford Press. Jensen, M. (1987). Psychobiological factors predicting the course of breast cancer. J. Pers., 55, 317–342. Kemeny, M. E. (1994). Stressful events, psychological responses and progression of HIV infection. In R. Glaser and J. Kiecolt-Glaser (Eds.), Handbook on stress and immunity. (pp. 245–266). New York: Academic Press. Kiecolt-Glaser, J., Dura, J. R., Speicher, C. E., Trask, O. J., and Glaser, R. (1991). Spousal caregivers of dementia victims: longitudinal changes in immunity and health. Psychosom. Med., 53, 345–362. Kiecolt-Glaser, J., Fisher, L., Ogrocki, P., Stout, J., Speicher, C., and Glaser, R. (1987). Marital quality, marital disruption, and immune function. Psychosom. Med., 49, 13–34. Kiecolt-Glaser, J., and Glaser, R. (1988). Psychological influences on immunity: implications for AIDS. Am. Psychol, 43, 892–898.
700
III. Behavior and Immunity
Kiecolt-Glaser, J., Glaser, R., and Williger, D. (1985). Psychosocial enhancement of immunocompetence in a geriatric population. Health Psychol., 4, 25–41. Kiecolt-Glaser, J., Glaser, R., Strain, E., Stout, J., Tarr, K., Holliday, J., and Speicher, C. (1986). Modulation of cellular immunity in medical students. J. Behav. Med., 9, 311–320. Kiecolt-Glaser, J. K., Kennedy, S., Malkoff, S., Fisher, L., Speicher, C. E., and Glaser, R. (1988). Marital discord and immunity in males. Psychosom. Med., 50, 213–229. Kiecolt-Glaser, J., Malarkey, W., Cacioppo, J., and Glaser, R. (1994). Stressful personal relationships: endocrine and immune function. In R. Glaser and J. Kiecolt-Glaser (Eds.), Handbook of human stress and immunity (pp. 321–339). San Diego, CA: Academic Press. Kiecolt-Glaser, J., Malarkey, W., Chee, M., et al. (1993). Negative behavior during marital conflict is associated with immunological down regulation. Psychosom. Med., 55, 395–409. Kiecolt-Glaser, J., Marucha, P., Malarkey, W., Mercado, A., and Glaser, R. (1995). Slowing of wound healing by psychological stress. Lancet, 346, 1194–1196. Kiecolt-Glaser, J., Ricker, D., George, J., Messick, G., Speicher, C., Garner, W., and Glaser, R. (1984). Urinary cortisol levels, cellular immunocompetency, and loneliness in psychiatric inpatients. Psychosom. Med., 46 (1), 15–23. Kiecolt-Glaser, J. K., Robles, T. F., et al. (2002). Psycho-oncology and cancer: psychoneuroimmunology and cancer. Ann. Oncol., 13 (Suppl 4), 165–169. Killebrew, D., and Shiramizu, B. (2004). Pathogenesis of HIVassociated non-Hodgkin lymphoma. Curr. HIV Res., 2, 215– 221. Klimas, N., Caralis, P., LaPerriere, A., Antoni, M., Ironson, G., Simoneau, J., Schneiderman, N., and Fletcher, M. A. (1991). Immunologic function in a cohort of HIV Type-1 seropositive and negative healthy homosexual men. J. Clin. Microbiol., 29, 1413–1421. Kobasa, S., Maddi, S., Puccetti, M., and Zola, M. (1985). Effectiveness of hardiness, exercise, and social support as resources against illness. J. Psychosom. Res., 29 (5), 525–533. Kopinsky, K. L., Stoff, D. M., and Rausch, D. M. (2004). Workshop report: the effects of psychological variables on the progression of HIV-1 disease. Brain Behav. Immun., 18, 246–261. Kurtzman, S., Miller, L., Anderson, K., Wang, P., and Kreutzer, D. (1997). Cytokine regulation of angiogenesis in human breast cancer. Proceedings of the Dept. of Defense Breast Cancer Research Program Meeting “Era of Hope,” 341–342. LaPerriere, A., Antoni, M. H., Schneiderman, N., Ironson, G., et al. (1990). Exercise intervention attenuates emotional distress and natural killer cell decrements following notification of positive serologic status for HIV-1. Biofeedback and Self-Regulation, 15 (3), 229–242. LaPerriere, A., Goldstein, A., Klimas, N., Ironson, G., Major, P., Maik, G., Talluto, C., Fletcher, M. A., and Schneiderman, N. (April, 1997). Non compliant exercise decreases CD4 cells in early symptomatic HIV-1 infection. Paper presented at the Society of Behavioral Medicine, San Francisco, CA. Larson, M., Duberstein, P., Talbot, N., Caldwell, C., and Moynihan, J. (2000). A pre-surgical psychosocial intervention for breast cancer patients: psychological distress and the immune response. J. Psychosom. Res., 48, 187–194. Larson, S. J., and Dunn, A. J. (2001). Behavioral effects of cytokines. Brain Behav. Immun., 15, 371–387. Lechner, S., Antoni, M. H., Lydston, D., LaPerriere, A., Ishii, M., Stanley, H., Ironson, G., Schneiderman, N., Brondolo, E., Tobin, J., and Weiss, S. (2003). Cognitive-behavioral interventions
improve quality of life in women with AIDS. J. Psychosom. Res., 54, 253–261. Lepore, S. J., Eton, D. V., Helgeson, V. S., and Schulz, R. (2003). Improving quality of life in men with prostate cancer: a randomized controlled trial of group education interventions. Health Psychol., 22 (5), 443–452. Leserman, J. (2003). HIV disease progression: depression, stress, and possible mechanisms. Biol. Psychiatry, 54, 295–306. Leserman, J., Petitto, J., Perkins, D., Folds, J., Golden, R., and Evans, D. (1997). Severe stress, depressive symptoms, and changes in lymphocyte subsets in human immunodeficiency virus-infected men. Arch. Gen. Psychiatry, 54, 279–285. Lésperance, F., Frasure-Smith, N., Talajic, M., and Bourassa, M. G. (2002). Five-year risk of cardiac mortality in relation to initial severity and one-year change in depression symptoms after myocardial infarction. Circulation, 105, 1049–1053. Lésperance, F., Frasure-Smith, N., Theroux, P., and Irwin, M. (2004). The association between major depression and levels of soluble intercellular adhesion molecule 1, interleukin-6 and c-reactive protein in patients with recent acute coronary syndromes. Am. J. Psychiatry, 161, 271–277. Levy, S., Herberman, R., Lippman, M., D’Angelo, T., and Lee, J. (1991). Immunological and psychosocial predictors of disease recurrence in patients with early-stage breast cancer. Beh. Med., 17, 67–75. Levy, S., Herberman, R., Whiteside, T., et al. (1990). Perceived social support and tumor estrogen/progesterone receptor status as predictors of natural killer cell activity in breast cancer patients. Psychosom. Med., 52, 73–85. Lewin, D. (1996). Protease inhibitors: HIV-1 summons a Darwinian defense. J. NIH Res., 8, 33–35. Libby, P., Ridker, P. M., and Maseri, A. (2002). Inflammation and atherosclerosis. Circulation, 105, 1135–1143. Linden, W., Stossel, C., and Maurice, J. (1996). Psychosocial interventions for patients with coronary artery disease. Arch. Intern. Med., 156, 745–752. Lutgendorf, S., Antoni, M. H., Ironson, G., Fletcher, M. A., Penedo, F., VanRiel, F., Baum, A., Schneiderman, N., and Klimas, N. (1995). Physical symptoms of chronic fatigue syndrome are exacerbated by the stress of Hurricane Andrew. Psychosom. Med., 57, 310–323. Lutgendorf, S., Antoni, M., Ironson, G., Klimas, N., Kumar, M., Starr, K., McCabe, P., Cleven, K., Fletcher, M., and Schneiderman, N. (1997). Cognitive-behavioral stress management decreases dysphoric mood and herpes simplex virus-Type 2 antibody titers in symptomatic HIV-seropositive gay men. J. Consult. Clin. Psychol., 64, 31– 43. Lutgendorf, S., Antoni, M., Ironson, G., Starr, K., Costello, N., Zuckerman, M., Klimas, N., Fletcher, M., and Schneiderman, N. (1998). Changes in cognitive coping skills and social support during cognitive behavioral stress management intervention and distress outcomes in symptomatic human immunodeficiency virus (HIV)-seropositive gay men. Psychosom. Med., 60 (2), 204–214. Lutgendorf, S., Antoni, M., Kumar, M., and Schneiderman, N. (1994). Changes in cognitive coping strategies predict EBV-antibody titre change following a stressor disclosure induction. J. Psychosom. Res., 38 (1), 63–78. Lutgendorf, S., Cole, S., Costanzo, E., et al. (2003). Stress-related mediators stimulate vascular endothelial growth factor secretion by two ovarian cancer cell lines. Clin. Cancer Res., 9, 4514– 4521. Lutgendorf, S., Johnsen, E., Holmes, R., Anderson, B., Sorosky, J., Buller, R., and Sood, A. (2002). Social relationships and tumor
32. Behavioral Interventions: Immunologic Mediators and Disease Outcomes angiogenesis factors in ovarian cancer patients. Cancer, 95, 808–815. Maier, S. F., and Watkins, L. R. (1998). Cytokines for psychologists: implications of bidirectional immune-to-brain communication for understanding behavior, mood, and cognition. Psychol. Rev., 105, 83–107. Maier, S. F., Watkins, L., and Fleshner, M. (1994). Psychoneuroimmunology: the interface between behavior, brain, and immunity. Am. Psychol., 49, 1004–1017. Maiman, M., and Fruchter, R. (1996). Cervical neoplasia and the human immunodeficiency virus. In S. Rubino and W. Hoskins (Eds.), Cervical cancer and preinvasive neoplasia (pp. 405–416). Philadelphia: Lippincott-Raven. Masek, K., Petrovicky, P., and Seifert, J. (1992). An introduction to the possible role of central nervous system structures in neuroendocrine-immune systems interaction. Int. J. Immunopharmacol., 14, 317–322. McEwen, B. (1998). Protective and damaging effects of stress mediators. N. Engl. J. Med., 338, 171–179. McGrady, A., Woerner, M., Bernal, G. A. A., and Higgins, J. T. (1987). Effect of biofeedback-assisted relaxation on blood pressure and cortisol levels in normotensives and hypertensives. J. Behav. Med., 10, 301–310. McGregor, B., Antoni, M. H., Boyers, A., Alferi, S., Cruess, D., Blomberg, B., and Carver, C. S. (2004). Effects of cognitive behavioral stress management on immune function and positive contributions in women with early-stage breast cancer. J. Psychosom. Res., 54, 1–8. McKinney, C., Antoni, M. H., Kumar, M., Tims, F., and McCabe, P. (1997). Effects of guided imagery and music (GIM) therapy on mood and cortisol in healthy adults. Health Psychol., 16 (4), 1–12. McKinnon, W., Weisse, C. S., Reynolds, C. P., Bowles, C. A., and Baum, A. (1989). Chronic stress, leukocyte subpopulations, and humoral response to latent viruses. Health Psychol., 8, 399–402. Mendes de Leon, C. F., Powell, L. H., and Kaplan, B. H. (1991). Change in coronary-prone behaviors in the recurrent coronary prevention project. Psychosom. Med., 53, 407–419. Miller, G. E., Cohen, S., and Ritchey, A. K. (2002). Chronic psychological stress and the regulation of pro-inflammatory cytokines: a glucocorticoid-resistance model. Health Psychol., 21, 531–541. Mohr, D. C., Hart, S. L., Julian, L., Cox, D., and Pelletier, D. (2004). Association between stressful life events and exacerbation in multiple sclerosis: a meta-analysis. Br. Med. J., 328, 731. Morgan, W. (1982). Psychological effects of exercise. Behav. Med. Update, 4, 25–30. Morrow, D. A., and Ridker, P. M. (2000). C-reactive protein, inflammation, and coronary disease. Med. Clin. North Am., 81, 149–161. Mulder, C., Antoni, M. H., Duivenvoorden, H., Kauffmann, R., and Goodkin, K. (1995). Active confrontational coping predicts decreased clinical progression over a one-year period in HIV-infected homosexual men. J. Psychosom. Res., 39, 957– 965. Mulder, C., de Vroome, E., van Griensven, G., Antoni, M. H., and Sandfort, T. (1999). Distraction as a predictor of the virological course of HIV-1 infection over a 7-year period in gay men. Health Psychol., 18, 107–113. Mulder, N., Antoni, M., Emmelkamp, P., Veugelers, P., Sandfort, T., van der Vijver, F., and de vries, M. (1995). Psychosocial group intervention and the rate of decline of immunologic parameters in asymptomatic HIV-infected homosexual men. J. Psychother. Psychosom., 63, 185–192.
701
Mullen, P. D., Mains, D. A., and Velez, R. (1992). A meta-analysis of controlled trials of cardiac patient education. Patient Educ. Couns., 19, 143–162. Myers, J. K., Weissman, M. M., Tischler, G. L., et al. (1984). Six month prevalence of psychiatric disorders in three communities, 1980 to 1982. Arch. Gen. Psychiatry, 41, 959–967. Oesterling, E., and Oesterling, J. E. (1991). Prostate specific antigen: a critical assessment of the most useful tumor marker for adenocarcinoma of the prostate. J. Urol., 143, 907–923. O’Neill, B., and Leonard, B. (1986). Is there an abnormality in neutrophil phagocytosis in depression? IRCS Med. Sci., 14, 802–803. Osanto, S., Brouwenstyn, N., Vessen, N., Figdor, C., Melief, C., and Schrier, P. (1993). Clinical protocol. Immunization with interleukin-2–transfected melanoma cells. A phase I-II study of patients with metastatic melanoma. Hum. Gene Ther., 4, 323–330. Parker, J., Frank, R., Beck, N., Smarr, K., Beuscher, K., Phillips, L., Smith, E., and Anderson, S. (1987). Pain management in rheumatoid arthritis: a cognitive-behavioral approach. Unpublished manuscript, Washington University. Pavlidis, N., and Chirigos, M. (1980). Stress-induced impairment of macrophage tumoricidal function. Psychosom. Med., 42 (1), 47–54. Payne, D., Hoffman, R., Theodoulou, M., Dosik, M., and Massie, M. (1999). Screening for anxiety and depression in women with breast cancer. Psychosomatics, 40, 64–69. Penedo, F. J., Dahn, J., Gonzalez, J. S., Molton, I., Schneiderman, N., and Antoni, M. H. (2002a). Personality relates to mood states, quality of life and immune function in men who underwent prostate cancer surgery. Ann. Beh. Med., 24, S186 [Abstract]. Penedo, F. J., Dahn, J., Kinsinger, D., Antoni, M. H., Molton, I., Gonzalez, J. S., Fletcher, M. A., Roos, B., Carver, C., and Schneiderman, N. (2006). Anger suppression mediates the relationship between optimism and natural killer cell cytotoxicity in men treated for localized prostate cancer. J. Psychosom Res., 60, 423– 427. Penedo, F. J., Dahn, J. R., Molton, I., Gonzalez, J., Roos, B., Schneiderman, N., and Antoni, M. (2004). Cognitive-behavioral stress management improves quality of life and stress management skill in men treated for localized prostate cancer. Cancer, 100, 192–200. Penedo, F. J., Gonzalez, J. S., Duran, R., Dahn, J. R., Mendiola, M., Thomas, E., Antoni, M. H., and Schneiderman, N. (2002b). Illnessrelated spousal/marital disruption relates to psychological distress and immune function in men treated with radical prostatectomy for prostate cancer. Psychosom. Med., 64 (1), 158. Pennebaker, J. W., Kiecolt-Glaser, J. K., and Glaser, R. (1988). Disclosure of traumas and immune function: health implications for psychotherapy. J. Consult. Clin. Psychol., 56, 239–245. Pereira, D. (2002). Interventions for mothers during pregnancy and postpartum: behavioral and pharmacological approaches. In M. Chesney and M. H. Antoni (Eds.), Innovative approaches to health psychology: prevention and treatment lessons from AIDS (pp. 141–166). Washington, DC: American Psychological Association Press. Pereira, D., Antoni, M. H., Danielson, A., Simon, T., Munajj, J., Efantis-Potter, J., and O’Sullivan, M. J. (2000). Declines in natural killer cell percentages mediate the effects of high life stress on the incidence of cervical dysplasia in HIV+ black women at risk for cervical cancer. Psychosom. Med., 62, 105. Pereira, D., Antoni, M. H., Simon, T., Efantis-Potter, J., Carver, C., Duran, R., Ironson, G., Klimas, N., and O’Sullivan, M. J. (2003a). Stress as a predictor of symptomatic genital herpes virus recur-
702
III. Behavior and Immunity
rence in women with human immunodeficiency virus. J. Psychosom. Res., 54, 237–244. Pereira, D., Antoni, M. H., Simon, T., Efantis-Potter, J., Carver, C. S., Duran, R., Ironson, G., Klimas, N., and O’Sullivan, M. J. (2003b). Stress and squamous intraepithelial lesions in women with human papillomavirus and human immunodeficiency virus. Psychosom. Med., 65, 427–434. Pereira, D., Antoni, M. H., Simon, T., Potter, J., and O’Sullivan, M. J. (March, 2005). Cognitive behavioral stress management effects on regression of cervical dysplasia among HIV+ women. Paper presented at the American Psychosomatic Society meeting, Washington, DC. Petrie, K., Fonanilla, I., Thomas, M. G., Booth, R. J., and Pennebaker, J. (2004). Effect of written emotional expression on immune function in patients with human immunodeficiency virus infection: a randomized trial. Psychosom. Med., 66, 272–275. Petrie, K. J., Booth, R. J., Pennebaker, J. W., Davidson, K. P., and Thomas, M. G. (1995). Disclosure of trauma and immune response to a hepatitis B vaccination program. J. Consult. Clin. Psychol., 63 (5), 787–792. Pettingale, K. W., Morris, T., Greer, S., and Haybittle, J. L. (1985). Mental attitudes to cancer: an additional prognostic factor. Lancet, 1, 750. Pope, R. (1990). Immunoregulatory mechanisms present in the maternal circulation during pregnancy. Baillieres Clin. Rheumatol., 4, 33–52. Portenoy, R., and Miaskowski, C. (1998). Assessment and management of cancer-related fatigue. In A. Berger (Ed.), Principles and practice of supportive oncology (pp. 109–1180). New York: Lippincott-Raven. Ramirez, A., Craig, T., Watson, J., Fentiman, I., North, W., and Rubens, R. (1989). Stress and relapse of breast cancer. Br. Med. J., 298, 291–293. Redwine, L., Snow, S., Mills, P., and Irwin, M. (2003). Acute psychological stress: effects on chemotaxis and cellular adhesion molecule expression. Psychosom. Med., 65, 598–603. Reed, G., Kemeny, M., Taylor, S. E., Wang, H. J., and Visscher, B. (1994). Realistic acceptance as a predictor of decreased survival time in gay men with AIDS. Health Psychol., 13, 299–307. Rivest, S. (2001). How circulating cytokines trigger the neural circuits that control the hypothalamic-pituitary-adrenal axis. Psychoneuroendocrinology, 26, 761–788. Rogentine, G., Van Krammen, D., Fox, B., Docherty, J., Rosenblatt, J., Boyd, S., and Bunney, W. (1979). Psychological factors in the prognosis of malignant melanoma: a prospective study. Psychosom. Med., 4, 647–655. Ross, R. (1999). Atherosclerosis—an inflammatory disease. N. Engl. J. Med., 340, 115–126. Rozanski, A., Blumenthal, J. A., and Kaplan, J. (1999). Impact of psychological factors on the pathogenesis of cardiovascular disease and implications for therapy. Circulation, 99, 2192–2217. Rugulies, R. (2002). Depression as a predictor for coronary heart disease. Am. J. Preven. Med., 23, 51–61. Rush, A. J., Beck, A. T., Kovacs, M., Weissenburger, J., and Hollon, S. D. (1982). Comparison of the effects of cognitive therapy and pharmacotherapy on hopelessness and self-concept. Am. J. Psychiatry, 139, 862–866. Schedlowski, M., Jungk, C., Schimanski, G., Tewes, U., and Schmoll, H. (1994). Effects of behavioral intervention on plasma cortisol and lymphocytes in breast cancer patients: an exploratory study. Psycho-oncology, 3, 181–187. Schleifer, S. J., Macari-Hinson, M. M., Coyle, D. A., et al. (1989). The nature and course of depression following myocardial infarction. Arch. Intern. Med., 149, 1785–1789.
Schlenzig, C., Jager, H., Rieder, H., et al. (June, 1989). Supervised physical exercise leads to psychological and immunological improvement in pre-AIDS patients. Proceedings of the 5th International AIDS Conference. Schneiderman, N., Antoni, M., Saab, P., and Ironson, G. (2001). Health psychology: psychosocial and biobehavioral aspects of chronic disease management. Ann. Rev. Psychol., 52, 555–580. Schneiderman, N., Antoni, M. H., and Ironson, G. (1997). Cognitive behavioral stress management and secondary prevention in HIV/AIDS. Psychol. AIDS Exchange, 22, 1–8. Sheridan, J. Viral models of neuroendocrine/immune interactions. In N. Hall, F. Altman, and S. Blumenthal (Eds.), Mind-Body interactions and disease and psychoneuroimmunological aspects of health and disease. Proceedings of conference on Stress, Immunity and Health. National Institutes of Health (pp. 199–204). Washington, DC: Heath Dateline Press, 1996. Simons, A. D., Garfield, S., and Murphy, G. E. (1984). The process of change in cognitive therapy and pharmacotherapy for depression. Changes in mood and cognition. Arch. Gen. Psych., 41, 45–51. Smyth, J. M. (1998). Written emotional expression: effect sizes, outcome types, and moderating effects. J. Consult. Clin. Psychol., 66, 174–184. Smyth, J. M., Stone, A. A., Hurewitz, A., and Kaell, A. (1999). Effects of writing about stressful experiences on symptom reduction in patients with asthma or rheumatoid arthritis: a randomized trial. JAMA, 281, 1304–1309. Solomon, G., Segerstrom, S., Grohr, P., Kemeny, M., and Fahey, J. (1997). Shaking up immunity: psychological and immunologic changes after a natural disaster. Psychosom. Med., 59, 114–127. Spiegel, D. (2002). Effects of psychotherapy on cancer survival. Nat. Rev. Cancer, 2 (5), 383–389. Spiegel, D., Bloom, J., Kraemer, H. C., and Gottheil, E. (1989). Effect of psychosocial treatment on survival of patients with metastatic breast cancer. Lancet, 2, 888–891. Spiegel, D., Bloom, J., and Yalom, I. (1981). Group support for patients with metastatic cancer: A randomized prospective outcome study. Arch. Gen. Psychiatry, 38 (5), 527–533. Spiegel, D., and Glafkides, M. (1983). Effects of group confrontation with death and dying. Int. J. Group Psychother., 33 (4), 433–447. Stanton, A., Danoff-Burg, S., Sworowski, L. A., et al. (2002). Randomized, controlled trial of written emotional expression and benefit finding in breast cancer patients. J. Clin. Oncol., 20, 4160–4168. Starr, K., Antoni, M. H., Hurwitz, B., Rodriguez, M., Ironson, G., Fletcher, M. A., Kumar, M., Patarca, R., Lutgendorf, S., Quillian, R., Klimas, N., and Schneiderman, N. (1996). Patterns of immune, neuroendocrine, and cardiovascular stress responses in HIV seropositive and seronegative men. Int. J. Behav. Med., 3, 135–162. Steptoe, A., and Brydon, L. (2005). Psychoneuroimmunology and coronary heart disease. In K. Vedhara and M. Irwin (Eds.), Human psychoneuroimmunology (pp. 107–136). Oxford: Oxford University Press. Steptoe, A., Willemsen, G., Owen, N., Flower, L., and Mohamed-Ali, V. (2001). Acute mental stress elicits delayed increases in circulating inflammatory cytokine levels. Clin. Sci., 101, 185–192. Sternberg, E. (1996). Inflammatory disease and rheumatoid arthritis. In N. Hall, F. Altman, and S. Blumenthal (Eds.), Mind-body interactions and disease and psychoneuroimmunological aspects of health and disease. Proceedings of conference on Stress, Immunity and Health. National Institutes of Health (pp. 105–115). Washington, DC: Heath Dateline Press.
32. Behavioral Interventions: Immunologic Mediators and Disease Outcomes Stites, D., Stobo, J., Fudenberg, H., and Wells, J. (1982). Basic and clinical immunology (4th ed.). Los Altos, CA: Lange. Sulke, A. N., Jones, D. B., and Wood, P. J. (1985). Variation in natural killer activity in peripheral blood during the menstrual cycle. Brit. Med. J. (Clinical Research Ed.), 290, 884–886. Suligoi, B., Dorrucci, M., Uccella, I., Andreoni, M., Rezza, G., and the Italian Seroconversion Study. (2003). Effect of multiple herpesvirus infections on the progression of HIV disease in a cohort of HIV seroconverters. J. Med. Virol., 69, 182–187. Surwit, R. S., and Feinglos, M. N. (1983). The effects of relaxation on glucose tolerance in non–insulin-dependent diabetes. Diabetes Care, 6, 176–179. Taylor, C. B., Youngblood, M. E., Catellier, D., Veith, R. C., Carney, R. M., Burg, M. M., Kaufmann, P. G., Shuster, J., Mellman, T., Blumenthal, J. A., Krishnan, R., and Jaffe, A. S. for the ENRICHD Investigators. (2005). Effects of antidepressant medication on morbidity and mortality in depressed patients after myocardial infarction. Arch. Gen. Psychiatry, 62, 792–798. Taylor, D. N. (1995). Effects of a behavioral stress management program on anxiety, mood, self-esteem, and T-cell count in HIVpositive men. Psychol. Rep., 76, 451–457. Theorell, T., Blomkvist, V., Jonsson, H., Schulman, S., Berntorp, E., and Stigendal, L. (1995). Social support and the development of immune function in human immunodeficiency virus infection. Psychosom. Med., 57, 32–36. Tichatschek, E., Zielinski, C., Muller, C., Sevelda, P., Kubista, E., Czerwenka, K., Spona, J., Wolf, H., and Eibl, M. (1988). Longterm influence of adjuvant therapy on natural killer cell activity in breast cancer. Immunotherapy, 27, 278–282. Turk, D., Holzman, A., and Kerns, R. (1986). Chronic pain. In K. Holroyd and T. Creer (Eds.), Self management of chronic disease: handbook of clinical interventions and research. Orlando, FL: Academic Press, Inc. Van der Pompe, G., Antoni, M., and Heijnen, C. (1998). The effects of surgical stress and psychological stress on the immune function of operative cancer patients. Psychol. Health, 13, 1015–1026. Van der Pompe, G., Antoni, M. H., Mulder, N., Heijnen, C., Goodkin, K., de Graeff, A., Garssen, B., and de Vries, M. (1994). Psychoneuroimmunology and the course of breast cancer, an overview: the impact of psychosocial factors on progression of breast cancer through immune and endocrine mechanisms. Psycho-oncology, 3, 271–288. Van der Pompe, G., Antoni, M. H., Visser, A., Heijnen, C., and deVries, M. (1996). Psychological and immunological effects of psychotherapy for breast cancer patients: a reactivity study. Psychosom. Med., 58, 97 (abstract). Van der Pompe, G., Duivenvoorden, H., Antoni, M. H., Visser, A., and Heijnen, C. (1997). Effectiveness of a short-term group psychotherapy program on endocrine and immune function in breast cancer patients: an exploratory study. J. Psychosom. Res., 42, 453–466. Van Der Ven, A., Van Diest, R., Hamulyak, K., Maes, M., Bruggeman, C., and Appels, A. (2003). Herpes viruses, cytokines, and altered hemostasis in vital exhaustion. Psychosom. Med., 65, 194–200.
703
Veith, R. C., Lewis, N., Linares, O. A., Barnes, R. F., Raskind, M. A., Villacres, E. C., Murburg, M. M., Ashleigh, E. A., Castillo, S., Peskind, E. R., and Halter, J. B. (1994). Sympathetic nervous system activity in major depression: basal and desipramineinduced alterations in plasma norepinephrine kinetics. Arch. Gen. Psychiatry, 51, 411–422. Walker, L. G., Walker, M., Ogston, K., Heys, S., Ah-See, A., Miller, I., et al. (1999). Psychological, clinical and pathological effects of relaxation training and guided imagery during primary chemotherapy. Brit. J. Cancer, 80, 262–268. Watkins, L., Wiertelak, E., Goehler, L., Mooney-Heiberger, K., Martinez, J., Furness, L., Smith, K., and Maier, S. (1994). Neurocircuitry of illness-induced hyperalgesia. Brain Res., 639, 283–299. Watson, M., Haviland, J., Greer, S., Davidson, J., and Bliss, J. (1999). Influence of psychological response on survival in breast cancer: a population-based cohort study. Lancet, 354, 1331–1336. Weisse, C. (1992). Depression and immunocompetence: a review of the literature. Psychol Bull., 111, 475–489. Whitacre, C., Cummings, S., and Griffin, A. (1994). The effects of stress on autoimmune disease. In R. Glaser and J. Kiecolt-Glaser (Eds.), Handbook of human stress and immunity (pp. 77–100). New York: Academic Press. Wiedenfeld, S., O’Leary, A., Bandura, A., Brown, S., Levine, S., and Raska, K. (1990). Impact of perceived self-efficacy in coping with stressors on components of the immune system. J. Pers. Soc. Psy, 59, 1082–1094. Williams, R. B., Barefoot, J. C., Califf, R. M., Haney, T. L., Saunders, W. B., Pryor, D. B., Hlatky, M. A., Siegler, I. C., and Mark, D. B. (1992). Prognostic importance of social and economic resources among medically treated patients with angiographically documented coronary artery disease. J. Am. Med. Assoc., 267, 520–524. Wojciechowski, F. L., Strik, J. J. M. H., Falger, P., Lousberg, R., and Honig, A. (2000). The relationship between depressive and vital exhaustion symptomatology post-myocardial infarction. Acta Psychiatr. Scand., 102, 359–365. Yang, E., and Glaser, R. (2005). Wound healing and psychoneuroimmunology. In K. Vedhara and M. Irwin (Eds.), Human psychoneuroimmunology (pp. 265–284). Oxford: Oxford University Press. Zachariae, R., Hansen, J. B., and Andersen, M. (1994). Changes in cellular immune function after immune specific guided imagery and relaxation in high and low hypnotizable healthy subjects. Psychother. Psychosom., 61, 74–92. Zuckerman, M., and Antoni, M. H. (1995). Social support and its relationship to psychological, physical and immune variables in HIV infection. Clin. Psychol. Psychother., 2 (4), 210–219. Zwilling, B. (1996). Effects of stress on the course of mycobacterial infections including tuberculosis. In N. Hall, F. Altman, and S. Blumenthal (Eds.), Mind-body interactions and disease and psychoneuroimmunological aspects of health and disease. National Institutes of Health (pp. 211–216). Washington, DC: Heath Dateline Press.
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P A R T
IV STRESS AND IMMUNITY RONALD GLASER
INTRODUCTION Psychoneuroimmunology (PNI) is a good example of a multidisciplinary/interdisciplinary field of research. It deals with the interactions among the central nervous system, the endocrine system, and the immune system and how psychological stressors modulate these interactions. For those of us who work in the field of PNI, studying these complex interactions is one of the attractions; we do “systems biology.” Psychoneuroimmunology attracts basic scientists to work with psychologists and psychiatrists and clinicians in other specialties. Several years ago, the leadership of the NIH came to the conclusion that behavioral medicine/mind body medicine, including PNI, should be an important aspect of what NIH does within its institutes. There has been some effort to add behavioral medicine to many programs in the NIH institutes to explore the role that behavior/stress may play in a variety of diseases. Dr. Elias Zerhouni, the Director of the NIH, proposed a blueprint for the NIH that reflects his view that multidisciplinary/interdisciplinary approaches to understanding disease processes are what the NIH should be about. One of several examples that he uses in his blueprint is PNI. This reflects how far the field of PNI has come and recognizes the contributions that have been made. Animal models have been developed allowing us to do experiments that confirm results obtained from studies with human subjects and have helped us to understand how stress-induced immune dysregulation can impact health outcomes. My own interest in PNI has focused on the interactions among the endocrine system, the immune system, and the central nervous system, concentrating primarily on human stress studies conducted with Janice Kiecolt-Glaser and other collaborators. After
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spending about 10 years doing studies on the impact of academic stress on medical students to understand how an everyday type of stressor, taking examinations, could influence cellular immunity, we thought it was important to explore this question: Are statistically significant differences in the immune response associated with psychological stressors large enough to produce biologically significant outcomes that have a risk for health? We and others have found that psychological stressors can affect how people respond to viral and bacterial vaccines (antibody and T-cell responses); re-activate latent herpesviruses such as Epstein-Barr virus (EBV), herpes simplex virus (HSV), and cytomegalovirus (CMV), and affect the early phase of the wound-healing process, resulting in significant delays in healing. The animal modelers in our group confirmed virtually all of the human studies and are providing data that will help us understand the mechanisms underlying the stress-associated outcomes. In selecting the contributors for this Part, I wanted to emphasize the clinical implications of stress-induced immune dysregulation. However, there were certain key issues that I also wanted to include because I felt that they were timely and relevant to behavior and illness. I believe that the chapters in this Part will provide the reader with a current summary of the field of PNI as it pertains to stress and illness outcomes. The Part starts, in Chapter 33, with an overview of the impact of stress on the immune system by Bruce Rabin, who writes these kinds of overviews so well and provides a historical prospective for both human studies and animal models. A chapter on the bi-directional effects of stress on immune function, by Firdaus Dhabhar and Bruce McEwen, follows. There is a literature which suggests that different kinds of stressors produce different kinds of physiological changes and, therefore, different health outcome possibilities. Understanding the physiological mechanisms associated with different kinds of stressors is important in designing studies and interpreting the results. Chapter 34 will provide the reader with the most up-to-date information on differences between acute versus chronic stressors and the implications of different kinds of stressors on immune function and health outcomes, written by two distinguished researchers who have pioneered this particular area. Chapter 35, on positive affect and immune function, by Anna Marsland, Sarah Pressman, and Sheldon Cohen, provides the reader with an overview of how psychological/behavioral influences play important roles in immune function/dysregulation. This chapter, by a very well-known team of investigators, reviews the literature and presents data from their laboratory that may be used by the reader as a primer on the influence of positive affect on immune function. Jennifer Graham, Lisa Christian, and Janice Kiecolt-Glaser provide an overview of pertinent literature as well as seminal data from the authors’ laboratory exploring the importance of social support and close relationships on immunity and health. The focus of Chapter 36 is important physiological and behavioral pathways by which relationships may affect immune function in response to acute and chronic stress and, ultimately, health.
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A shift in focus to the clinical implications of stress-induced immune dysregulation begins with a chapter on stress and allergic diseases, by Gailen Marshall and Sitesh R. Roy. Historically, stress-associated immune changes focused primarily on immune suppression. Early studies supported those outcomes. It is now clear, however, that other aspects of the immune system were being upregulated and enhanced by some psychological stressors affecting, for example, allergies and asthma. These complex interactions are discussed earlier in this Part. Gailen Marshall, a clinical immunologist/allergist, is one of the leading experts on the impact of stress on the allergic response and allergic diseases. Chapter 37 will provide the reader with an up-to-date survey on this subject. The emphasis on clinical implications continues with a series of chapters that review the literature on stress-induced immune dysregulation that results in a downregulation of, for example, pro-inflammatory cytokines, and models that have been used to study these interactions. Chapter 38, by Philip Marucha and Christopher Engeland, provides an overview of human studies focused on the early stages of wound healing in which pro-inflammatory cytokines play a very important role. It was Philip Marucha who originally proposed studying the effects of stress on wound healing. Chapter 39, prepared by David Padgett, Philip Marucha, and John Sheridan, addresses stress and wound healing in animal models. This trio has provided a solid literature describing animal models that demonstrate how stress influences wound healing. The clinical implication for the data surveyed in both of these chapters on wound healing clearly show the impact that stress-induced immune dysregulation can have on the early phases of wound healing as mediated by stress hormones and pro-inflammatory cytokines. These studies have important implications for both major and minor surgeries that undoubtedly have implications for morbidity and mortality in a hospital setting. By selecting Chapter 40, “Reactivation of Latent Herpes Viruses in Astronauts,” by Duane Pierson, Satish Mehta, and Raymond Stowe, I was indulging myself. As already mentioned, I have a personal interest in studying different kinds of stressors and their impact on re-activation of latent herpesviruses, particularly EBV. I became aware of a series of very interesting studies being performed by this group at NASA. I was delighted to see that their work confirmed and extended the work that we had done by expanding the knowledge base of latent viruses affected by stress to other herpesviruses, like CMV and Herpes Zoster virus. These authors have done an excellent job in reviewing the literature in an exciting area of research that has implications for future interplanetary space flight. Chapter 41, on psychosocial influences in oncology, by Susan Lutgendorf, Erin Costanzo, and Scott Siegel, was selected because I thought it important to include at least one chapter that surveyed what is known about the role that psychological stress might play in malignant disease. EBV is a human tumor virus, and the work that we, the NASA group, and others have done on stress and viral latency all clearly points to possible implications for EBV-associated lymphomas. What about other possibilities linking stress with tumorigenesis? Susan Lutgendorf, a distinguished researcher known
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for her innovative studies in PNI, surveys the literature on both the initiation and progression aspects of tumorigenesis. Chapter 42, “Vaccination Studies in Psychoneuroimmunology,” by Mark Wetherall and Kavita Vedhara, provides one more example of pioneering work that shows an association between stress-induced immune dysregulation and the immune response to both viruses and bacteria. There is a growing literature that clearly supports the hypothesis that the production of both antibody and virus-specific T-cell immunity to vaccines can be modulated by psychological stress. If stress can influence how a person responds to a vaccine, it is a reasonable conclusion that stress may affect the degree of protection to a pathogen. Using vaccines as a surrogate for an infectious agent, the studies suggest that stress could reduce the protective immune response to a pathogen, resulting in an increased risk for morbidity and mortality. Since new cancer vaccines are now being developed, it is reasonable to assume that the effectiveness of such vaccines would be affected by stress as well. These are public health issues that should be considered in a clinical setting. It is my hope that the reader will be as pleased as I was by the efforts made by my colleagues by providing these reviews. The take-home message is that stress-induced immune dysregulation is not good for your health.
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33 Stress: A System of the Whole BRUCE RABIN
I. INTRODUCTION 709 II. SYSTEM 1: THE IN UTERO ENVIRONMENT 711 III. SYSTEM 2: THE STRESS SYSTEM INFLUENCES EARLY STAGES OF LIFE 713 IV. SYSTEM 3: PERSONALITY AND PSYCHOLOGICAL CHARACTERISTICS AND HEALTH 713 V. THE INFLUENCE OF STRESS ON PARAMETERS OF HEALTH 715 VI. STRESS IN THE WORKPLACE 717 VII. CAN A SYSTEM BE DEVELOPED THAT WILL REDUCE THE NEGATIVE IMPACT OF STRESS ON HEALTH? 717 VIII. CONCLUSIONS 718
function of the whole affected. Proper integrated and stable function of all systems is homeostasis. The respiratory system exemplifies this. Components of the respiratory system include the systems of the nose and mouth, the trachea, the lungs, and the oxygen-carrying red cells. The primary purpose of the respiratory system is to deliver oxygen to cells throughout the body to support tissue viability. If the systems that comprise the respiratory system are not working properly, other systems dependent on adequate oxygenation will not work properly. Interestingly, exemplifying the theme of this chapter of stress having an effect on many systems, changes in the function of the stress system may contribute to dysregulation of the respiratory system (Han et al., 1998; Wientjes and Grossman 1994).
I. INTRODUCTION Psychoneuroimmunologists direct their attention to understanding the mechanisms of stressor-induced alterations of immune system function and subsequent health alterations. However, stressor-induced health alterations involve many components of health and affect many tissues of the body that are independent of immune system alterations. Although the theme of this book is directed to the immune system, this chapter will consider stress as a system that alters the function of other systems that are not part of the immune system, an area of particular interest to the chapter author. A system can be defined as a group of interdependent components that form a larger complex. The human body represents a large, complex system composed of many interdependent systems. When one system is altered, others may also be altered and the PSYCHONEUROIMMUNOLOGY, 4E VOLUME II
A. System Function Characteristics Proper function of the total human system is a highly complex and variable process. An example is provided by obstruction of the blood supply to the heart muscle which can have minimal or catastrophic effects. A partial obstruction can produce pain (angina). Total obstruction of blood flow to a small amount of muscle may go unnoticed or cause death, depending on which portion of the cardiac muscle is deprived of oxygen. Total obstruction to a large critical area of muscle may produce rapid death. An obstruction developing slowly may allow time for compensation to occur as collateral blood vessels form with no resultant clinical effects. Thus, the site, amount, and rate of onset of the obstruction will have varying health
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effects. Similar issues may relate to the effect of stress on health (acute vs. chronic, mild vs. extreme, coping skills present or lacking). Baseline function is also important. For example, if a heart has a congenital malformation, its susceptibility to demand may be compromised, and insults that may not have an effect on a normal heart may cause problems in the compromised heart. If a heart has increased musculature and vascularity through the individual engaging in behaviors of physical activity, the heart will be hardier with more collateral circulation and able to tolerate insults (ischemia) better. The brain should be viewed in a similar manner. All too often when we report our psychoneuroimmunolgy studies, we assume a brain is a brain. However, as will be described in this chapter, the responsivity of the brain is influenced by in utero and early life experiences. To continue to advance the contribution of PNI to health care and wellness, we will need to be more cognizant of the baseline characteristics of the particular brain that is responding to stress. What are the characteristics of the stress responder and stress nonresponder brains? What lifestyle behaviors will contribute to the development of a brain that is resistant to inducing health-altering hormonal alterations when a stressor is encountered?
B. Activation of the Brain An event in one’s environment that is perceived by the brain as stress and that does not involve physical contact must be processed by the brain if it is going to disturb hormonal homeostasis. Obviously, the brain is constantly processing information that comes in through the visual, olfactory, tactile, and auditory systems. Processing of the inputs that the brain does not perceive to be stress is usually not associated with health alterations and, indeed, often provides safety from harm. We don’t walk into walls (visual system), we question the reason for the presence of noxious odors (olfactory system), and we leave when someone yells, “Fire!” (auditory system). Inputs to the brain are also associated with pleasure, which may have an enhancing effect on health. For example, seeing a painting one considers beautiful, smelling the aroma of flowers, or listening to music one enjoys is calming. Thus, activity of the brain contributes to well-being as well as health impairment. An example of functional changes related to the responsivity of the brain to perceived stimuli is provided from the pioneering conditioning work of Dr. Robert Ader. His studies established the ability of the brain to respond to a perceived event and produce changes in the function of the immune system. Such
brain activation does not require physical events but can occur solely through mental processes. Many of the stressors used in human research studies involve only mental processes. It is likely that multiple brain areas are activated by the perception of a stressor and that the final outcome of hormonal alteration represents a summation of those brain areas that activate and suppress blood hormone concentrations. The technology of functional MRI and PET scanning has not progressed where meaningful studies can be done in humans, but there is considerable experimental animal data available for evaluation. At a minimum, the stress-reactive brain areas include the paraventricular nucleus of the hypothalamus and the locus coeruleus (Pezzone et al., 1992; Pezzone et al., 1993; Rassnick et al., 1994; Rassnick et al., 1995; Rassnick et al., 1998; Valentino et al., 1998). Importantly, modalities other than stress that can activate functionally important brain areas are being identified and may have potential for helping to regulate hormonal responses that have an impact on health. One such modality is a placebo. A placebo is an inert substance that is provided to a patient in place of a medication. Often, a placebo will have clinical effects and, in addition, effects on the central nervous system that are similar to those produced by an actual medication (Mayberg et al., 2002). The perception of pain is also susceptible to placebos (Levine et al., 1978; Petrovic et al., 2002), and placebo-associated alterations of brain activity are detected in pain-responsive brain areas (Wager et al., 2004). In a study of the effect of transplantation of human mesencephalic (midbrain) tissue into the brain of patients with Parkinson’s disease, the patients’ belief of whether they had an actual treatment or a sham treatment was the principal factor in changes in motor function and quality of life (Freed et al., 2001; McRae et al., 2004). Placebos can also alter the rate of firing and pattern of firing of neurons (Benedetti et al., 2004). The effect of a placebo rather than analgesic medication on altering functional parameters of the brain related to pain has been reported using computergenerated virtual reality (Hoffman et al., 2004). The subjective rating of experimentally induced pain was reduced as was activity on pain-reactive areas of the brain. As there is an analgesic-related alteration of immune function (Beilin et al., 2003), techniques that can decrease the response of the brain to pain will provide a means to reduce the amount of analgesic medication utilized in patients experiencing pain and help to preserve immune function with the associated clinical benefits. At first thought, it may be surprising to find placeboinduced functional alterations in the brain. However,
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that is exactly what a conditioned stress response can do. If a placebo is considered to be the antithesis of a stressor and a stressor produces functional alterations in the brain (Pezzone et al., 1992), a placebo that produces health-enhancing effects can be viewed as an anti-stressor. As such it would be expected to produce functional brain alterations that can have positive health effects. How is the baseline brain established, and how do differences in baseline function influence the characteristics of a brain’s response to stress? What contributes to the uniqueness of an individual’s response to stress? To answer this question, we will first review some of the research that suggests that the in utero environment influences the formation and function of the brain. Early life experiences will then be discussed, as will personality factors.
II. SYSTEM 1: THE IN UTERO ENVIRONMENT Animal and human studies suggest a link between stress experienced by a pregnant woman and the mental and physical health of the offspring. Thus, along with the widely recognized deleterious effects of smoking and inadequate nutrition during pregnancy, it is equally important to recognize that maternal stress responsiveness is a factor in determining the baseline characteristics of the brain. The duration of stress during pregnancy is reported to be important (Lobel, 1994; Rondo et al., 2003). There may be critical points during pregnancy when experiencing stress is more capable of altering fetal development, specifically between 18 and 33 weeks, during which the elevation of stress hormones may have a strong influence on fetal development (Hobel et al., 1999; Sandman et al., 1997; Wadhwa et al., 2004). It is also likely that the intensity of the stressor and the resulting level of hormonal elevation would be an important concern. Chronic stress is anticipated to be associated with sustained and higher levels of cortisol than acute stress (van Eck et al., 1996). It is likely that stress during pregnancy will have an effect only on the health of a subpopulation of fetuses. We postulate that this is likely related to the effectiveness of stress-coping mechanisms utilized by some pregnant women when high levels of stress are experienced prior to or during pregnancy. Pregnant women who are high in social connectedness, physical fitness, optimism, a sense of humor, religiosity, and use behaviors to cope with stress may be less likely to have a stressor-induced elevation of stress hormones than women who lack these coping mechanisms.
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A. Mediators of the Association between Maternal Stress and Fetal Development Stressor-induced hypothalamic-pituitary-adrenal (HPA) activation may contribute to the interrelationship between stress, duration of pregnancy, and birth weight. During a normal pregnancy, cortisol levels gradually increase, especially during the third trimester, to 2–3 times normal (Mastorakos and Illias, 2003). Further elevation of maternal plasma corticotrophinreleasing hormone (CRH) and cortisol concentrations have been associated with spontaneous pre-term delivery and decreased fetal growth (Hobel and Culhane, 2003; Mancuso et al., 2004; Mulder et al., 2002; Wadhwa et al., 2004). Prenatal maternal anxiety and a resultant elevation of CRH in mid-pregnancy have been negatively associated with gestational age at delivery (Mancuso et al., 2004). Thus, stress during pregnancy may produce an additive effect on the normal elevation of cortisol concentrations during pregnancy. There is also a cytokine-mediated pathway that increases CRH and AVP production and elevates cortisol (Tsigos and Chrousos, 2002). Thus, infection in a pregnant individual may be associated with cortisol elevation beyond the normal physiologic elevation. Intra-amniotic infection is a well-accepted and significant risk factor for pre-term labor. Infection and inflammation of the gestational tissues may trigger labor by activating monocytes and macrophages, which result in increased inflammatory cytokines that can elevate CRH concentrations (Goldenberg et al., 2000; Hillier et al., 1993; Wadhwa et al., 2001). Stress-associated decreased immunity during pregnancy may increase a pregnant woman’s susceptibility to infection. Alteration of the HPA axis in adult offspring of rodent mothers who were stressed by repeated restraint during pregnancy has been shown to be related to corticosterone elevation in the mother (Barbazanges et al., 1996). Adrenalectomized mothers who were stressed did not produce offspring who had altered HPA responses to stress. Thus, it is likely that transplacental passage of corticosterone is the mediator of the change in the rodent fetus and suggests this as a pathway in the human.
B. The Association between Maternal Stress and Brain Receptors and Hormones As there are no human studies to discuss, relevant studies in animals will be discussed. The offspring of rats stressed at different times of gestation had decreased opioid receptor concentration in several areas of the brain (Sanchez et al., 1996; Sanchez et al., 2000). Thus, there may be a critical period of
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development for alteration of receptors, and this may or may not be identical for each type of hormone receptor. Alterations in the concentration of glucocorticoid receptors in the brains of offspring of stressed rodent mothers have also been reported (McCormick et al., 1995). The content and release of CRH from the amygdala of adult rats born to mothers who had been stressed during pregnancy were significantly greater in comparison to matched control rats (Hack et al., 2004). Even structural alterations in the newborn brain of the anterior division of the anterior commissure and the amygdala have been reported to be induced by prenatal stress (Jones et al., 1997; Salm et al., 2004). Techniques currently available to pursue hormone receptor quantitation in the human brain should be applied to determining the influence of maternal stress on quantitative receptor alteration. It is anticipated that alteration of receptor numbers and hormone production will be associated with altered biological functions.
C. Health Concerns Associated with Altered Fetal Development Maternal stress and/or low birth weight has been associated with the following physical health alterations in humans: • Characteristics of the metabolic syndrome (Body Mass Index, waist-hip-ratio, diastolic blood pressure, insulin plasma insulin, triglycerides, HDL and LDL cholesterol) (Kanaka-Gantenbein et al., 2003; Fagerberg et al., 2004). • Higher total cholesterol in men (Davies et al., 2004) • Hypertension (Barker, 1996) • Insulin resistance and Type 2 diabetes (Eriksson et al., 2002) Maternal stress and/or low birth weight has been associated with the following central nervous system and mental health alterations in humans: • Elevated activity of the sympathetic nervous system (Phillips and Barker, 1997) • Elevated cortisol levels (Essex et al., 2002; Phillips et al., 2000) • Increased risk of psychopathology, including anxiety and depression (Hack et al., 2004) • Increased risk of schizophrenia and suicide (Huttunen and Niskanen, 1978; Mittendorfer-Rutz et al., 2004) • Performance in school at age 6 (Niederhofer and Reiter, 2004) • Motor and social developmental delay (Hediger et al., 2002)
• Increased risk for lower cognitive performance and schooling achievements (Paz et al., 1995) • Significant decreases in academic attainment but no significant differences in the rate of employment, marriage, or satisfaction with life in adults who were born small of gestational age (Strauss, 2000) Relevant information from non-human studies include the following: • Prenatal stress in non-human primates results in a reduction of the volume of the hippocampus and decreased neurogenesis in the dentate gyrus (Coe et al., 2003). • High anxiety behaviors were found in the adult offspring of stressed mothers who were stressed during the last week of gestation compared to a control group (Poltyrev et al., 1996; Vallee et al., 1997). • Adult rats born to mothers who had been stressed during pregnancy responded differently to an electric shock stressor than rats born to mothers not stressed during pregnancy. Although HPA axis activity was the same in both groups, there was significantly increased catecholamine metabolism in the cerebral cortex and locus coeruleus in the offspring of stressed mothers (Takahashi et al., 1992). • Studies of non-human primates have indicated that the endocrine response to stress, behavior, and immune function of monkeys born to mothers who were stressed during pregnancy is altered as a consequence of the maternal stress (Clarke and Schneider, 1993; Coe et al., 1996; Schneider et al., 1992; Schneider and Coe, 1993). The same effects are obtained if, as a means of mimicking the hormonal response to stress, monkeys were injected with ACTH to elevate plasma cortisol. It is important to recognize that the quality of the mental and physical health of a woman who becomes pregnant has been influenced by factors experienced from gestation to adulthood. Women who are high stress reactors (Manuck et al., 1992) may not easily be able to buffer their stressor-induced elevation of stress hormones. Thus, easily obtained positive results achieved by reducing the effects of maternal stress on fetal development should not be anticipated. If future studies determine that a child born to a prenatally stressed mother has an impaired ability to cope with stress, interventions to help the pregnant woman and child in coping with aversive situations may be found to be beneficial to themselves and their progeny. If the quality of mental and physical health of an individual can be modified by the course of fetal devel-
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opment, an understanding of the mechanisms responsible will deserve to receive increased research attention. A central goal of this research will be the identification of critical periods during gestation when developmental process can be modified and elucidation of the hormones responsible for this alteration. The development of effective countermeasures would then be appropriate.
III. SYSTEM 2: THE STRESS SYSTEM INFLUENCES EARLY STAGES OF LIFE The influence of the environment during early ages on later adult health has been studied. A large study of 9,500 adults found an association between childhood emotional, physical, sexual abuse, and household dysfunction to increased health risks for alcoholism, drug abuse, depression, suicide attempts, smoking, ischemic heart disease, cancer, chronic lung disease, skeletal fractures, and liver disease (Felitti et al., 1998). The more categories of aversive childhood experiences, the greater the likelihood of adult health impairment. Mothers who are depressed while raising children have an effect of elevated salivary cortisol levels in the children (Essex et al., 2002). The children were at an increased risk for mental health symptoms when they were evaluated in first grade (approximately 6–7 years old). Whether this is due to the influence of hormones of depressed individuals crossing the placenta or to the effects of the mother on the quality of raising the child could not be determined. The quality of relationships with classmates can also influence health (Gadin and Hammarstrom, 2000). Behavioral problems of a child at 4 years of age may be influenced by the level of reported parental stress at ages of 1, 2, and 3 years (Goldberg et al., 1997). A significant stressor that occurs in the lives of children is being bullied. Both behavioral and health problems have been associated with being bullied in early life (Wolke et al., 2001; Wolke and Samara, 2004). Thus, the systems regulating the environment during the early years of life are additional important determinants of the quality of health through determining the baseline characteristics of the stressor-induced responsiveness of the brain.
IV. SYSTEM 3: PERSONALITY AND PSYCHOLOGICAL CHARACTERISTICS AND HEALTH Personality involves behavior, temperament, emotion, and mental processes. There is a strong literature
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associating different types of personality with different qualities of health. Why? Can different central nervous system processes define personality? Are they part of a molecular and hormonal system where the concentration of hormones and hormone receptors in different brain locations contribute to defining personality? Baseline cortisol concentrations have been reported to differ in individuals with different personality characteristics. Individuals who experience more anxiety and distress have higher baseline cortisol levels than individuals who do not have these traits (Bell et al., 1993; Kagan et al., 1988). Individuals who repress anxiety or experience high levels of anxiety have higher baseline cortisol levels than individuals who experience low levels of anxiety (Brown et al., 1996). Is personality a system that is determined by central nervous system processes modified by behavioral interaction with parents and other children when a young child? Are there identifiable patterns of plasma hormones associated with different personality types that increase the risk of the development of disease? Are they state or trait? Are there neuroanatomical projections in the brain that regulate activity of discrete brain areas, and do they have consequences related to personality (DeBruin, 1990; Ongur et al., 1998)? Do behaviors associated with different personalities predispose to different diseases? Do different personalities have different stress-buffering capabilities? Although the answers to what shapes personality are not yet fully defined, there are known associations between personality characteristics and health which suggest that the quality of health does not operate outside the reach of psychosocial influences. For example, individuals who are well adjusted, socially stable, and well integrated into their communities are at significantly lower risk for disease than those who are more unstable, impulsive, isolated, and alienated (Friedman, 2000). Individuals who are high in optimism are at a reduced risk of developing heart disease and following coronary bypass surgery are likely to recover faster than are pessimists (Kubzansky et al., 2001; Scheier et al., 1999) and are at reduced risk of having a stroke (Ostir et al., 2001; Sesso et al., 1998). An optimist has the belief that there will be positive outcomes to life events. Indeed, the effect of optimism on health has been repeatedly documented and is becoming an area of increasing research interest. The course of HIV infection is influenced by optimism (Taylor et al., 2000; Tomakowsky et al., 2001), although an optimistic explanatory style differed from dispositional optimism in their effects. Dispositional optimism may also function as a buffer of immune alterations when individuals experience moderate but not high levels of stress (Cohen et al., 1999; Segerstrom et al.,
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1998). Whether there are different functional brain alterations in those high or low in optimism when experiencing a stressor would be of interest, and based on the effect of optimism buffering, immune alterations would be expected. Individuals who are high in anger or hostility are at an increased risk of developing heart disease (Chang et al., 2002; Kawachi et al., 1996). Following an initial stroke, more rapid recovery and better post-stroke function are present in subjects with more social support (Glass et al., 1993; Reifman, 1995). What are the differences in the hormonal milieu of those high or low in interpersonal support? Having interactions with family members, friends, religious organizations, and community activities reduced the extent of functional impairment after a stroke (Colantonio et al., 1993). Is it because those with social support have someone to turn to for emotional or intellectual support find aversive events less burdensome, less painful, and less frightening when they have someone to share it with and have less of an elevation of stress hormones? Other relationships suggesting ties between psychology and physiology are found in increased susceptibility to diseases such as asthma, allergies, and autoimmune diseases, in subjects with depression (Vogt et al., 1994), and individuals who are high in perceived stress being at an increased risk of developing upper respiratory viral infections, and the onset or exacerbation of autoimmune disease (Rabin, 1999). Individuals who are high in intrinsic religiosity in which their faith is internalized rather than being used for external reasons, such as social acceptability, have a better quality of health than individuals who are low in religiosity (Levin and Chatters, 1998). Affiliation and participation with a religious community are associated with lower use of hospital services by medically ill individuals age 60 or greater (Koenig and Larson, 1998). Mental and physical health-related benefits found to be associated with religious factors include reduced depression, alcohol and drug use, hostility, anxiety, blood pressure, and improved life satisfaction, marital satisfaction, well-being, and quality of life (Matthews et al., 1998). There are interesting indications that personality characteristics can be a factor in health care utilization. For example, individuals with borderline personality symptoms, as defined by the Personality Diagnostic Questionnaire\Revised (PDQ-R), have significantly higher utilization of primary care resources than those without borderline personality symptoms (Sansone et al., 1996). A database of 46,026 individuals who had completed a 78-item health risk appraisal assessment and their medical claims data were analyzed for the
period 1990–1995 (Goetzel et al., 1998). Individuals who had 3 years of available data were included. The likelihood of having any medical expenditures was highest for employees with self-reported depression and high stress. Relevant data are as follows: • 997 individuals self-reported persistent depression and had annual health care expenditures 70% greater than those not reporting being depressed • 8,641 individuals self-reported high stress and had annual health care expenditures 46% greater than those not reporting high stress Further analysis of the same data set (Wasserman et al., 2000) evaluated 2,459 individuals diagnosed with coronary heart disease (CHD) through CPT and ICD-9-CM codes. In males, smoking was the major predictor of heart disease. In females, profound obesity and uncontrolled stress were the major predictors. In the male subjects, depression was associated with health care costs 91% greater than those not depressed. There was no association between depression and health care costs in the females. The studies reported above suggest that individuals with psychological characteristics of anger, hostility, and low optimism have an increased risk of disease development and that health care costs are elevated in subjects with self-reported depression and stress. It is also suggested that there may be personality characteristics that attenuate the use of health care resources. If biochemical, hormonal, immune, and physiological responses are related to the characteristics of an individual’s personality, it is not surprising that different personalities have different responses to stress and different health consequences of their response. Social support may be effective by supporting a hormonal milieu that enhances beneficial physiologic processes. However, social support may also promote other beneficial health practices such as • Earlier seeking out of appropriate medical treatment • Involvement in a program of exercise • Less use of alcohol and cigarettes • A better diet • A better sleep pattern Social support has been shown to have physiological effects in experimental situations. Subjects given a stress-eliciting task to perform had less heart rate elevation and blood pressure elevation when a friend was present in comparison to subjects who performed the task without a friend being present (Kamarck et al., 1990). The presence of a stranger is not as effective as having a friend present in buffering cardiovascular
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reactivity to a stressor (Christenfeld et al., 1997). This suggests that there must be an element of familiarity or comfort associated with the presence of the other person. It is not merely the presence of a warm body. This is not surprising. We select other individuals for friendship based on some aspect of central nervous system activity that promotes pleasure with the sharing of events and activities with the other person. Possibly, pheromones contribute to how we perceive someone. We generally do not become friends with someone whom we find annoying. This study (Kamarck et al., 1990) suggests that those elements within the brain that are activated and motivate the desire for friendship are capable of buffering stress effects on physiological reactivity.
V. THE INFLUENCE OF STRESS ON PARAMETERS OF HEALTH A. Stress and Weight Management Results from the 1999–2000 National Health and Nutrition Examination Survey using measured heights and weights indicate that an estimated 15% of children and adolescents ages 6–19 years are overweight in the United States. This represents a 4% increase from the overweight estimates of a prevalence of 11% obtained from 1988–94 and represents approximately 9 million children. The economic impact of obesity-related health care costs is estimated at $75 billion in 2003 dollars, and approximately one-half of these expenditures are financed by Medicare and Medicaid (http:// www.cdc.gov/nchs/products/pubs/pubd/hestats/ overwght99.htm). Approximately 70–80% of overweight children will be overweight as adults (Finkelstein et al., 2004). Thus, the diseases associated with being overweight—hypertension, heart disease, type 2 diabetes, respiratory ailments, osteoarthritis, and depression—will likely continue to be major health problems of increased prevalence. If an interaction exists between stress and compliance with a healthy diet, stress-coping skills may have a role as a component of weight management programs (Bradshaw et al., 2004; Brehm et al., 2003; Guo and Chumlea, 1999; Laitinen et al., 2002; Toobert et al., 2002). As cortisol can contribute to central obesity, impaired glucose regulation, hypertension, depression, and atherosclerotic heart disease, stress coping becomes an issue for the diseases that are associated with obesity. If parents are having difficulty coping with the stressors in their own lives, they may not be able to direct the proper and needed guidance and role modeling that will be of benefit to their children.
B. Stress and Diabetes An example of the interrelationship between the onset of an endocrine disease and the clinical course of an endocrine disease is provided by type 2 diabetes. Type 2 diabetes is the most common form of diabetes, accounting for 90% of cases. The pathogenesis of type 2 diabetes may involve “insulin resistance” wherein insulin is unable to move glucose into the cells where it can be used. Over time, the pancreas becomes unable to produce enough insulin to overcome resistance. In type 2 diabetes the initial effect of this stage is usually an abnormal rise in blood sugar right after a meal. Eventually, the cycle of elevated glucose further impairs and possibly destroys the insulin-producing pancreatic beta cells, thereby stopping insulin production completely and causing full-blown diabetes. The stressor-induced elevation of cortisol induces glucose release from tissue into the blood and contributes to difficulty in regulating blood glucose concentrations. Chronic stressor-induced cortisol elevation may contribute to the onset of type 2 diabetes in individuals who are at a genetic risk of disease development and who also develop an elevated body mass index (BMI) and elevated waist : hip ratio (as a reflection of increased abdominal fat) (Rosmond and Bjorntorp, 2000; Westenhoefer et al., 2004). A study of the predictive value of BMI and waist : hip ratio for the development of type 2 diabetes in Pima Indians found a significant association of these measures as predictors of type 2 diabetes risk (Tulloch-Reid et al., 2003). In addition to chronic psychological stress, low education, unemployment, problems at work, poor economic status, divorce, and loneliness are associated with abdominal obesity and the risk of type 2 diabetes (McEwen, 2002). If the stressor-induced elevation of cortisol is associated with glucose dysregulation, modalities that ameliorate the stressor-induced cortisol elevation should contribute to an enhanced control of glucose concentrations. The clinical advantages may be a reduction in some of the complications of diabetes: blindness, limb amputation, and loss of renal function. Indeed, enhanced stress coping is likely to accomplish this. A study of individuals at risk of developing clinical diabetes based on elevated fasting and postload plasma glucose concentrations found that over 2.8 years of follow-up the incidence (the number of new cases during 2.8 years of follow-up) of type 2 diabetes in 1,082 control individuals was 11.0%, while the incidence was 4.8% in 1,079 individuals in a lifestyle modification program (Diabetes Prevention Research Group, 2002). Lifestyle modification consisted of weight loss, a low fat diet, and physical activity.
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Stress-coping programs have been found to be effective having significant clinical benefits, as determined by a reduction in hemoglobin A1c (Diabetes Prevention Research Group, 2002; Ismail et al., 2004; Surwit et al., 2002). To be effective in reducing the risk of developing diabetes and ameliorating the level of hemoglobin A1c, stress-coping programs must be acceptable to individuals of diverse demographic situations, easily accessible, socially interactive, fun, and doable with a facilitator that stimulates participation.
C. Stress and Hypertension Blood pressure is determined by the amount of blood that the heart pumps and the resistance to the flow of blood in the arteries. Hypertension increases the risk of stroke, myocardial infarction, vascular disease, kidney disease, and heart failure. Treatment of hypertension reduces the risk of these diseases. Although medications can reduce blood pressure by reducing the volume of blood pumped by the heart or reducing the resistance of arteries to the flow of blood, there are also behavioral interventions that can be utilized. The side effects of many of the pharmacologic approaches to management of hypertension have side effects that range from being uncomfortable (such as frequent urination) to an increased risk of death. Behavioral interventions may make a significant contribution to patients with hypertension. However, as with all behavioral interventions, unless they are used, they are ineffective. Behavioral interventions for hypertension include dietary modification, physical activity, relaxation, and stress coping. Dietary modification can reduce the volume of blood and mass of tissue that the heart has to pump blood through. Physical activity programs can produce a reduction of blood pressure in some individuals, but the types of programs, the importance of social interaction in physical fitness programs, the expectations of the participants, and the degree and duration of hypertension are factors that may influence the outcome (Karlsen et al., 2004). Increasing physical activity may have its effect by decreasing heart rate and the activity of the sympathetic nervous system (which would decrease arterial resistance to blood flow). Decreasing stress responsiveness and producing an enhanced state of relaxation may operate through the same mechanisms as does physical activity (Blumenthal et al., 2002). Of course, increasing physical activity and stress coping techniques will also decrease the stressor-induced alteration of immune system function. Thus, it is expected that the clinical application of behavioral interventions that enhance
immune function will also have beneficial effects on blood pressure. The behavioral management of hypertension may best be achieved by utilizing several modalities rather than a single intervention (Linden et al., 2001). The combination of Yoga and biofeedback has been reported to be effective (Spence et al., 1999) with the effectiveness maintained for many months (Patel and North, 1975). This approach has been found to be effective when utilized by general practitioners (Patel, 1975), although its application may be better achieved utilizing trained facilitators who have the time and skills to engage individuals in the intervention. If stress-coping procedures are effective in lowering blood pressure, it would be anticipated that they also have other positive effects. Evidence for a reduction in the risk of developing cardiovascular disease; reduced risk of myocardial infarction; and enhanced quality of life as determined by enjoyment of life, general health, interpersonal relationships, mental well-being, and social interactions has been reported (Patel and Marmot, 1988; Patel et al., 1985). Recently, the Food and Drug Administration approved use of a non-pharmacological device as an adjunct for the management of hypertension. The device promotes the slowing of the rate of breathing as a means of achieving relaxation and reducing stress (Patel and Marmot, 1987). Slow and regular breathing provides the beneficial effect of increased heart rate variability and blood pressure reduction (Novak et al., 1994; Viskoper et al., 2003). This may be effective in reducing blood pressure through decreased sympathetic nervous system activation induced by regular slow breathing (Pitzalis et al., 1998). Whether this approach will also have beneficial effects of immune system function, cardiovascular disease, glycemic control in diabetics, and mild and moderate depression needs to be determined.
D. Stress and Depression The etiology of clinical depression is undergoing re-evaluation based on new studies indicating that elevated levels of glucocorticoids can damage neurons, which are important to the etiology of depression (Claes, 2004). Thus, depression may be a disease in which neurodegeneration is a critical component. Studies in experimental animals have established that stress early in life can influence the magnitude of the hormonal response to stress (Sapolsky, 2004) and possibly an association with increased susceptibility to stressor-induced depression. A possible mechanism of the action of antidepressant medication is stimula-
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tion of the regeneration of neurons damaged by glucocorticoids. Pathways of the neurocircuitry of the brain associated with depression still need to be carefully defined. A possible pathway involves defective activity of the prefrontal cortex, which allows the amygdala to increase the cognition of negative emotions. Another possible pathway for depression involves altered production of brain-derived neurotrophic factor (BDNF), which promotes survival of neurons. Reduced production of BDNF by stressor-induced elevation of glucocorticoids may contribute to the development of depression (Russo-Neustadt and Chen, 2005; TapiaArancibia et al., 2004; Yang et al., 2004).
VI. STRESS IN THE WORKPLACE There is evidence to suggest that an important component of the environment that influences health is where an individual works (Shannon et al., 2001). For example, 900 hospital employees were questioned about their jobs and emotional well-being. The general health of the employees worsened over 3 years. Variables such as the work interference with family life, the amount of influence employees had over their jobs, the hours worked, and an increase in psychological demand, rather than personal characteristics, were predictors of the health changes. The workforce’s decline in health was mirrored by increases in burnout, emotional exhaustion, depression, and anxiety. The Whitehall study of male British Civil Servants aged 20–64 found an inverse association between grade (level) of employment and mortality from coronary heart disease (CHD). Men in the lowest grade (messengers, doorkeepers, etc.) had a three-fold higher mortality rate than men in the highest grade (administrators) (Marmot et al., 1984). While low status was associated with obesity, smoking, less leisure time physical activity, more baseline illness, higher blood pressure, and shorter height, controlling for all of these risk factors accounted for no more than 40% of the grade difference in CHD mortality (Marmot et al., 1984; Marmot et al., 1987). After controlling for standard risk factors, the lowest grade still had a relative risk of 2.1 for CHD mortality compared to the highest grade. Employee depression has an impact on productivity losses, employee turnover, and suboptimal work performance (Goetzel et al., 2002). Again, the workplace would be an ideal environment for health education if, during the hours that one is an employee, he/she accepts the concept and potential extra hours’ time commitment.
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As would be anticipated, psychosocial factors are related to health care costs. One study of subjects with coronary artery disease found health care expenditures were 42% higher in depressed versus nondepressed individuals and 27% higher for individuals with high levels of stress versus those without high levels of stress (Wasserman et al., 2000). Another study found that individuals with self-reported persistent depression had annual health care expenditures 70% greater than those not reporting being depressed. Individuals with self-reported high stress had annual health care expenditures 46% greater than those not reporting high stress (Goetzel et al., 1998). Employees who participate in a comprehensive health promotion program have moderation of health care costs (Musich et al., 2000). Only using education regarding health risk awareness was not effective at moderating health care costs. Thus, programs that provide the opportunity for employee involvement are required. Reducing the perception of work-related stress through a reward system and increasing employee involvement in decisions regarding the worksite may be of benefit (Kivimaki et al., 2002; Kuper et al., 2002; Zavala et al., 2002). One such reward may be as simple as attention to the amount of light in the workplace (Avery et al., 2001), which can have a significant effect on mood, energy, alertness, and productivity. Epidemiologic investigations have shown that low socioeconomic status is related to ischemic coronary heart disease mortality in men and women, as well as to major risk factors for coronary heart disease predominantly in men. A study of women found the less education the women reported, the more atherogenic was their risk factor profile. These types of data suggest many biologic and behavioral factors that can elevate the risk for coronary heart disease and suggest that education regarding health may be an appropriate intervention (Matthews et al., 1989). The workplace would be an ideal environment for such education and, if successful, would contribute to lowering health care costs for the employer.
VII. CAN A SYSTEM BE DEVELOPED THAT WILL REDUCE THE NEGATIVE IMPACT OF STRESS ON HEALTH? The most obvious way to reduce the influence of stress on health is to reduce the amount of stress one encounters. This may be possible for some, but they would be the exceptions. A pharmacological approach may work if side effects, such as lethargy, could be
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eliminated. Unfortunately, more people are willing to take medications than to change behavior. The most feasible approach is to reduce the influence of stress on activating the stress-reactive areas of the brain (Rabin, 1999). A system of stress coping involves behaviors that are associated with lower reactivity of the brain to the perception of stress with an associated lowered production of the health-altering hormones cortisol and norepinephrine. Behaviors including being socially interactive, being high in optimism, being physically active, having a sense of humor, and enjoying participation in religious activities have been associated with an increased ability to cope with stress. Thus, the incorporation of behaviors that contribute to a healthy lifestyle into the educational process, starting with young children, may have significant effects on the quality of mental and physical health of future generations. Ideally, these behaviors would be incorporated into daily life routines so that they would be utilized as routine behaviors. However, in adults it is not easy to change behavior from one that is less likely to promote health to one that is more likely. If it were, obesity and smoking should be less prevalent than they currently are. Thus, the importance of routinely incorporating healthy lifestyle behaviors into the lives of young children is emphasized. To successfully incorporate healthy lifestyle behaviors into life, they should not be taught as a schoolbased class. It is possible that relegating health education to an academic class segregates it from being a part of a lifestyle. To achieve this goal, the school health curriculum needs to be embedded/integrated throughout the day and into many of the courses that are being taken. By including health in courses of writing, math, history, and science, as well as physical education classes, young individuals will grow in an atmosphere where health is indeed a routine part of lifestyle. The goal would be a measurable improvement in health outcomes, starting at infancy and continuing throughout the life span. The influence of parents, caretakers, faith-based institutions, governments/ municipalities, merchants, and schools would be required to help children grow up using healthy behaviors. However, many parents have difficulty coping with stress and may not be good role models. Yet, the home and parents and grandparents need to become role models of healthy lifestyle behaviors. For the community to be successful in addressing issues of lifestyle, the community must recognize that there is a condition that needs to be addressed (such as 50% of children being overweight) and that there is
a desired outcome (90% of children having the ideal body mass index [BMI]) that is the antithesis of the initial condition. The community must accept an intervention that transforms the initial condition into the desired outcome (increased facilities for physical fitness, physical fitness classes in school, removal of soda and candy vending machines from schools, parents becoming involved in preparing healthier foods at home, merchants decreasing emphasis on selling foods that have minimal nutritional value).
VIII. CONCLUSIONS The stress system involves the brain, hormone receptors, and hormones. Normal function of this system is associated with homeostasis and normal mental and physical health. Abnormal function of this system is associated with altered homeostasis and abnormal mental and physical health. For example, when the stress system affects blood pressure, many other systems are affected, including the heart, cerebral blood vessels, the eyes, and the kidneys. The stress system that alters immune function through the alteration of concentrations of various hormones will simultaneously affect many other health systems. The number of chapters in this book is an indication of how much knowledge has been accumulated in this scientific area and is a tribute to Drs. George Solomon and Robert Ader for their pioneering work. To continue to evolve the significance of their contributions to having an influence on the quality of life, it will be important to develop interventions that are acceptable, effective, and utilized. As described in this chapter, such interventions will have an effect on many aspects of health, not only immune function. The mental and physical health of future generations depends on healthy adults utilizing healthy lifestyle behaviors over their life span, not only for their benefit but also to serve as meaningful role models for those who look to them for guidance. The health of our future population and the costs of our health treatment system depend on healthy adults in whom healthy behaviors are ingrained and who do not have to be asked to change behavior. One strategy for providing this is to provide a culture in which children grow up using healthy behaviors throughout their lives. This can be accomplished through a system of healthy lifestyle education and teaching and modeling healthy behaviors to improve nutrition and physical activity. The result can be the reduction of the incidence and prevalence of preventable diseases and a significant improvement in the quality of life.
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References Avery, D. H., Kizer, D., Bolte, M. A., and Hellekson, C. (2001). Bright light therapy of subsyndromal seasonal affective disorder in the workplace, morning vs afternoon exposure. Acta Psychiatr. Scand., 103, 267–274. Barbazanges, A., Piazza, P. V., Le Moal M., and Maccari, S. (1996). Maternal glucocorticoid secretion mediates long-term effects of prenatal stress. Journal of Neuroscience, 16, 3943–3949. Barker, D. J. (1996). The fetal origins of hypertension. J. Hypertens. Suppl., 14, S117–120. Beilin, B., Shavit, Y., Trabekin, E., Mordashev, B., Mayburd, E., Zeidel, A., and Bessle, H. (2003). The effects of postoperative pain management on immune response to surgery. Anesth. Analg., 97, 822–827. Bell, J., Adler, M. W., Greenstein, J. I., and Liu-Chen, L. Y. (1993). Identification and characterization of I125 arginine vasopressin binding sites on human peripheral blood mononuclear cells. Life Sciences, 52, 95–105. Benedetti, F., Colloca, L., Torre, E., Lanotte, M., Melcarne, A., Pesare, M., Bergamasco, B., and Lopiano, L. (2004). Placebo responsive Parkinson patients show decreased activity ion single neurons of subthalamic nucleus. Nature Neurosci, 7, 587–588. Blumenthal, J. A., Sherwood, A., Gullette, E. C. D., Georgiades, A., and Tweedy, D. (2002). Biobehavioral approaches to the treatment of essential hypertension. J. Consulting and Clinical Psychology, 70, 569–589. Bradshaw, A., Katzer, L., Horwath, C. C., Gray, A., O’Brien, S., Joyce, and Jabs, J. (2004). A randomised trial of three non-dieting programs for overweight women. Asia. Pac. J. Clin. Nutr., 13 (Suppl), S43. Brehm, B. J., Rourke, K. M., Cassell, C., and Sethuraman, G. (2003). Psychosocial outcomes of a pilot multidisciplinary program for weight management. Am. J. Health. Behav., 27, 348–354. Brown, L. L., Tomarken, A. J., Orth, D. N., Loosen, P. T, Kalin, N. H., and Davidson, R. J. (1996). Individual differences in repressive-defensiveness predict basal salivary cortisol levels. Journal of Personality and Social Psychology, 70, 362–371. Chang, P. P., Ford, D. E., Meoni, L. A., Wang, N. Y., and Klag, M. J. (2002). Anger in young men and subsequent premature cardiovascular disease, the Precursors study. Archives of Internal Medicine, 162, 901–906. Christenfeld, N., Gerin, W., Linden, W., Sanders, M., Mathur, J., Seich, J. D., and Pickering, T. G. (1997). Social support effects on cardiovascular reactivity—is a stranger as effective as a friend? Psychosom Med., 59, 388–398. Claes, S. J. (2004). CRH, stress, and major depression, a psychobiological interplay. Vitam. Horm., 69, 117–150. Clarke, A. S., and Schneider, M. L. (1993). Prenatal stress has longterm effects on behavioral responses to stress in juvenile rhesus monkeys. Developmental Psychobiology, 26, 293–304. Coe, C. L., Kramer, M., Czeh, B., Gould, E., Reeves, A. J., Kirschbaum, C., and Fuchs, E. (2003). Prenatal stress diminishes neurogenesis in the dentate gyrus of juvenile monkeys. Biol. Psychiatry, 54, 1025–1034. Coe, C. L., Lubach, G. R., Karaszewski, J. W., and Erschler, W. B. (1996). Prenatal endocrine activation alters postnatal cellular immunity in infant monkeys. Brain, Behavior and Immunity, 10, 221–234. Cohen, F., Kearney, K. A., Zagans, L. S., Kemeny, M. E., Neuhaus, J. M., and Stites, D. P. (1999). Differential immune system changes with acute and persistent stress for optimists vs pessimists. Brain, Behavior and Immunity, 13, 155–174.
719
Colantonio, A., Kasl, S. V., Ostfeld, A. M., and Berkman, L. F. (1993). Psychosocial predictors of stroke outcomes in an elderly population. Journal of Gerontology, Social Sciences, 48, S261–S268. Davies, A. A., Smith, G. D., Ben-Shlomo, Y., and Litchfield, P. (2004). Low birth weight is associated with higher adult total cholesterol concentration in men, findings from an occupational cohort of 25,843 employees. Circulation, 110, 1258–1262. DeBruin, J. P. C. (1990). Social behavior and the prefrontal cortex. Prog. Brain. Res., 85, 485–496. Diabetes Prevention Research Group. (2002). Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. New England Journal of Medicine, 346, 393–403. Eriksson, J. G., Forsen, T., Tuomilehto, J., Jaddoe, V. W., Osmond, C., and Barker, D. J. (2002). Effects of size at birth and childhood growth on the insulin resistance syndrome in elderly individuals. Diabetologia, 45, 342–348. Essex, M. J., Klein, M. H., Cho, E., and Kalin, N. H. (2002). Maternal stress beginning in infancy may sensitize children to later stress exposure, effects on cortisol and behavior. Biol. Psychiatry, 52, 776–784. Fagerberg, B., Bondjers, L., and Nilsson, P. (2004). Low birth weight in combination with catch-up growth predicts the occurrence of the metabolic syndrome in men at late middle age, the Atherosclerosis and Insulin Resistance study. J. Int. Med., 256, 254–259. Felitti, V. J., Anda, R. F., Nordenberg, D., Williamson, D. F., Spitz, A. M., Edwards, V., Koss, M. P., and Marks J. S. (1998). Relationship of childhood abuse and household dysfunction to many of the leading causes of death in adults. The Adverse Childhood Experiences (ACE) study. Am. J. Prev. Med., 14, 245–258. Finkelstein, E. A., Fiebelkorn, I. C., and Wang, G. (2004). State-level estimates of annual medical expenditures attributable to obesity. Obesity Research, 12, 18–24. Freed, C. R., Greene, P. E., Breeze, R. E., Tsai, W. Y., DuMouchel, W., Kao, R., Dillon, S., Winfield, H., Culver, S., Trojanowski, J. Q., Eidelberg, D., and Fahn, S. (2001). Transplantation of embryonic dopamine neurons for severe Parkinson’s disease. New England Journal of Medicine, 344, 710–719. Friedman, H. S. (2000). Long-term relations of personality and health, dynamisms, mechanisms, tropisms. Journal of Personality, 68, 1089–1108. Gadin, K. G., and Hammarstrom, A. (2000). School-related health—a cross-sectional study among young boys and girls. Int. J. Health Serv., 30, 797–820. Glass, T. A., Matchar, D. B., Belyea, M., and Feussner, J. R. (1993). Impact of social support on outcome in first stroke. Stroke, 24, 64–70. Goetzel, R. Z., Anderson, D. R., Whitmer, R. W., Ozminkowski, R. J., Dunn, R. L., and Wasserman, J. (1998). The relationship between modifiable health risks and health care expenditures. An analysis of the multi-employer HERO risk and cost database. J. Occup. Environ. Med., 40, 843–854. Goetzel, R. Z., Ozminkowski, R. J., Sederer, L. I., and Mark, T. L. (2002). The business case for quality mental health services. Why employers should care about the mental health and well-being of their employees. J. Occup. Environ. Med., 44, 320–330. Goldberg, S., Janus, M., Washington, J., Simmons, R. J., MacLusky, I., and Fowler, R. S. (1997). Prediction of preschool behavioral problems in healthy and pediatric samples. Dev. Behav. Pediatr., 18, 304–313. Goldenberg, R. L., Hauth, J. C., and Andrews, W. W. (2000). Intrauterine infection and premature delivery. New England Journal of Medicine, 342, 1500–1507.
720
IV. Stress and Immunity
Guo, S. S., and Chumlea, W. C. (1999). Tracking of body mass index in children in relation to overweight in adulthood. Am. J. Clin. Nutr., 70, 145S–148S. Hack, M., Youngstrom, E. A., Cartar, L., Schluchterm, M., Taylor, H. G., Flannery, D., Klein, N., and Borawski, E. (2004). Behavioral outcomes and evidence of psychopathology among very low birth weight infants at age 20 years. Pediatrics, 114, 932–940. Han, J. N., Stegen, K., Schepers, R., Van den Bergh, O., and Van de Woestijne, K. P. (1998). Subjective symptoms and breathing pattern at rest and following hyperventilation in anxiety and somatoform disorders. J. Psychosom. Res., 45, 519–532. Hediger, M. L., Overpeck, M. D., Ruan, W. J., and Troendle, J. F. (2002). Birthweight and gestational age effects on motor and social development. Paediatric and Perinatal Epidemiology, 16, 33–46. Hillier, S., Witkin, S., Krohn, M., Watts, D. H., Kiviat, N. B., and Eschenbach, D. A. (1993). The relationship of amniotic fluid cytokines and preterm delivery, amniotic fluid infection, histologic chorioamnionitis and chorioamnion infection. Obstetrics and Gynecology, 81, 941–948. Hobel, C., and Culhane, J. (2003). Role of psychosocial and nutritional stress on poor pregnancy outcome. J. Nutr., 133, 1709S–1717S. Hobel, C. J., Dunkel-Schetter, C., Roesch, S. C., Castro, L. C., and Arora, C. P. (1999). Maternal plasma corticotrophin-releasing hormone associated with stress at 20 weeks gestation in pregnancies ending in preterm delivery. American Journal of Obstetrics and Gynecology, 180, S257–S263. Hoffman, H. G., Richards, T. L., Coda, B., Bills, A. R., Blough, D., Richards, A. L., and Sharar, S. R. (2004). Modulation of thermal pain-related brain activity with virtual reality, evidence from fMRI. Neuroreport, 15, 1245–1248. http://www.cdc.gov/nchs/ products/pubs/pubd/hestats/overwght99.htm Huttunen, M. O., and Niskanen, P. (1978). Prenatal loss of father and psychiatric disorders. Arch. Gen. Psychiat., 35, 429–431. Ismail, K., Winkley, K., and Rabe-Hesketh, S. (2004). Systematic review and meta-analysis of randomized controlled trials of psychological interventions to improve glycemic control in patients with type 2 diabetes. Lancet, 363, 1589–1597. Jones, H. E., Ruscio, M. A., Keyser, L. A., Gonzalez, C., Billack, B., Rowe, R., Hancock, C., Lambert, K. G., and Kinsley, C. H. (1997). Prenatal stress alters the size of the rostral anterior commissure in rats. Brain Research Bulletin, 42, 341–346. Kagan, J., Reznick, J. S., and Snidman, N. (1988). Biological basis of childhood shyness. Science, 240, 167–171. Kamarck, T. W., Manuck, S. B., and Jennings, J. R. (1990). Social support reduces cardiovascular reactivity to psychological challenge, a laboratory model. Psychosom. Med., 52, 42–58. Kanaka-Gantenbein, C., Mastorakos, G., and Chrousos, G. P. (2003). Endocrine related causes and consequences of intrauterine growth retardation. Ann. N. Y. Acad. Sci., 997, 150–157. Karlsen, B., Idsoe, T., Dirdal, I., Rokne Hanestad, B., and Bru, E. (2004). Effects of a group-based counselling programme on diabetes-related stress, coping, psychological well-being and metabolic control in adults with type 1 or type 2 diabetes. Pat. Edu. Counsel., 53, 299–308. Kawachi, I., Sparrow, D., Spiro, A. 3rd., Vokonas, P., and Weiss, S. T. (1996). A prospective study of anger and coronary heart disease. The Normative Aging study. Circulation, 94, 2090– 2095. Kivimaki, M., Leino-Arjas, P., Luukkonen, R., Riihimaki, H., Vahtera, J., and Kirjonen, J. (2002). Work stress and risk of cardiovascular mortality, prospective cohort study of industrial employees. BMJ, 325, 857–862.
Koenig, H. G., and Larson, D. B. (1998). Use of hospital services, religious attendance, and religious affiliation. Southern Medical Journal, 91, 925–932. Kubzansky, L. D., Sparrow, D., Vokonas, P., and Kawachi, I. (2001). Is the glass half empty or half full? A prospective study of optimism and coronary heart disease in the normative aging study. Psychosom. Med., 63, 910–916. Kuper, H., Singh-Manoux, A., Siegrist, J., and Marmot, M. (2002). When reciprocity fails, effort-reward imbalance in relation to coronary heart disease and health functioning within the Whitehall II study. Occup. Environ. Med., 59, 777–784. Laitinen, J., Ek, E., and Sovio, U. (2002). Stress-related eating and drinking behavior and body mass index and predictors of this behavior. Prev. Med., 34, 29–39. Levin, J. S., and Chatters, L. M. (1998). Religion, health, and psychological well-being in older adults. Findings from three national surveys. J. Aging Health, 10, 504–531. Levine, J. D., Gordon, N. C., and Fields, H. L. (1978). The mechanism of placebo analgesia. Lancet, 2, 654–657. Linden, W., Lenz, J. W., and Con, A. H. (2001). Individualized stress management for primary hypertension. Arch. Int. Med., 161, 1071–1080. Lobel, M. (1994). Conceptualizations, measurement and effects of prenatal maternal stress on birth outcomes. Journal of Behavioral Medicine, 17, 225–273. Mancuso, R. A., Schetter, C. D., Rini, C. M., Roesch, S. C., and Hobel, C. J. (2004). Maternal prenatal anxiety and corticotropinreleasing hormone associated with timing of delivery. Psychosom. Med., 66, 762–769. Manuck, S. B., Olsson, G., Hjemdahl, P., and Rehnqvist, N. (1992). Does cardiovascular reactivity to mental stress have prognostic value in postinfarction patients? A pilot study. Psychosom. Med., 54, 102–108. Marmot, M. G., Kogevinas, M., and Elston, M. A. (1987). Social/ economic status and disease. Annu. Rev. Public Health, 8, 111–135. Marmot, M. G., Shipley, M. J., and Rose, G. (1984). Inequalities in death-specific explanations of a general pattern? Lancet, 1, 1003–1006. Mastorakos, G., and Illias, I. (2003). Maternal and fetal hypothalamic-pituitary-adrenal axes during pregnancy and postpartum. Ann. N. Y. Acad. Sci., 997, 136–149. Matthews, D. A., Larson, D. B., and Barry, C. P. (1998). The faith factor, an annotated bibliography of clinical research on spiritual subjects (vol 1). West Conshohocken, PA: John Templeton Foundation. Matthews, K. A., Kelsey, S. F., Meilahn, E. N., Kuller, L. H., and Wing, R. R. (1989). Educational attainment and behavioral and biologic risk factors for coronary heart disease in middle-aged women. Am. J. Epidemiol., 129, 1132–1144. Mayberg, H. S., Silva, A., Brannan, S. K., Tekell, J. L., Mahurin, R. K., McGinnis, S., and Jerabek, P. A. (2002). The functional neuroanatomy of the placebo effect. Am. J. Psychiatry, 159, 728–737. McCormick, C. M., Smythe, J. W., Sharma, S., and Meaney, M. J. (1995). Sex-specific effects of prenatal stress on hypothalamicpituitary-adrenal responses to stress and brain glucocorticoid receptor density in adult rats. Developmental Brain Research, 84, 55–61. McEwen, B. S. (2002). Protective and damaging effects of stress mediators. The good and the bad sides of the response to stress. Metabolism, 51, 2–4. McRae, C., Cherin, E., Yamazaki, T. G., Diem, G., Vo, A. H., Ellgring, J. H., Fahn, S., Greene, P., Dillon, S., Winfield, H., Bjugstad,
33. Stress: A System of the Whole K. B., and Freed, C. R. (2004). Effects of perceived environment on quality of life and medical outcomes in a double-blind placebo surgery trial. Arch. Gen. Psychiatry, 61, 412–420. Mittendorfer-Rutz, E., Rasmussen, F., and Wasserman, D. (2004). Restricted fetal growth and adverse maternal psychosocial and socioeconomic conditions as risk factors for suicidal behaviour of offspring, a cohort study. Lancet, 364, 1135–1140. Mulder, E. J., Robles, de Medina, P. G., Huizink, A. C., Huizink, A. C., Van den Berg, B. R., Buitelaar, J. K., and Visser, G. H. (2002). Prenatal maternal stress, effects on pregnancy and the (unborn) child. Early Hum. Dev., 70, 3–14. Musich, S. A., Adams, L., and Edington, D. W. (2000). Effectiveness of health promotion programs in moderating medical costs in the USA. Health Promotion Int., 15, 5–15. Niederhofer, H., and Reiter, A. (2004). Prenatal maternal stress, prenatal fetal movements and perinatal temperament factors influence behavior and school marks at the age of 6 years. Fetal. Diagn. Ther., 19, 160–162. Novak, V., Novak, P., de Champlain, J., and Nadeau, R. (1994). Altered cardiorespiratory transfer in hypertension. Hypertension, 23, 104–113. Ongur, D., An, X., and Price, J. L. (1998). Prefrontal cortical projections to the hypothalamus in Macaque monkeys. J. Comp. Neurol., 401, 480–505. Ostir, G. V., Markides, K. S., Peek, M. K., and Goodwin, J. S. (2001). The association between emotional well-being and the incidence of stroke in older adults. Psychosom. Med., 63, 210–215. Patel, C. (1975). 12-month follow-up of yoga and bio-feedback in the management of hypertension. Lancet, 305, 62–64. Patel, C., and Marmot, M. G. (1987). Stress management, blood pressure and quality of life. J. Hypertens-Suppl., 5, S21–28. Patel, C., and Marmot, M. G. (1988). Can general practitioners use training in relaxation and management of stress to reduce mild hypertension? Brit. Med. J. Clin. Res. Ed., 296, 21–24. Patel, C., Marmot, M. G., Terry, D. J., Carruthers, M., Hunt, B., and Patel, M. (1985). Trial of relaxation in reducing coronary risk, four year follow-up. Brit. Med. J. Clin. Res. Ed., 290, 1103–1106. Patel, C., and North, W. R. S. (1975). Randomized controlled trial of yoga and bio-feedback in management of hypertension. Lancet, 306, 93–95. Paz, I., Gale, R., Laor, A., Danon, Y. L., Stevenson, D. K., and Seidman, D. S. (1995). The cognitive outcome of full-term small for gestational age infants at late adolescence. Obstetrics and Gynecology, 85, 452–456. Petrovic, P., Kalso, E., Petersson, K. M., and Ingvar, M. (2002). Placebo and opioid analgesia—imaging a shared neuronal network. Science, 295, 1737–1740. Pezzone, M. A., Lee, W-S., Hoffman, G., and Rabin, B. S. (1992). Induction of c-Fos immunoreactivity in the rat forebrain by conditioned and unconditioned aversive stimuli. Brain Research, 597, 41–50. Pezzone, M. A., Lee, W-S., Hoffman, G. E., Pezzone, K. M., and Rabin, B. S. (1993). Activation of brainstem catecholaminergic neurons by conditioned and unconditioned aversive stimuli as revealed by c-Fos immunoreactivity. Brain Research, 608, 310–318. Phillips, D. I., and Barker, D. J. (1997). Association between low birthweight and high resting pulse in adult life. Is the sympathetic nervous system involved in programming the insulin resistance syndrome? Diabet. Med., 14, 673–677. Phillips, D. I., Walker, B. R., Reynolds, R. M., Flanagan, D. E., Wood, P. J., Osmond, C., Barker, D. J., and Whorwood, C. B. (2000). Low birth weight predicts elevated plasma cortisol concentrations in adults from 3 populations. Hypertension, 35, 1301–1306.
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Pitzalis, M. V., Mastropasqua, F., Massari, F., Passantino, A., Colombo, R., Mannarini, A., Forleo, C., and Rizzon, P. (1998). Effect of respiratory rate on the relationships between RR interval and systolic blood pressure fluctuations, a frequencydependent phenomenon. Cardiovasc. Res., 38, 332–339. Poltyrev, T., Keshet, G. I., Kay, G., and Weinstock, M. (1996). Role of experimental conditions in determining differences in exploratory behavior of prenatally stressed rats. Developmental Psychobiology, 29, 453–462. Rabin, B. S. (1999). Stress, immune function, and health, the connection. New York: John Wiley and Sons. Rassnick, S., Hoffman, G. E., Rabin, B. S., and Sved, A. F. (1998). Injection of corticotropin-releasing hormone into the locus coeruleus or foot shock increases neuronal Fos expression. Neuroscience, 85, 259–268. Rassnick, S., Sved, A. F., and Rabin, B. S. (1994). Locus coeruleus stimulation by corticotropin-releasing hormone suppresses in vitro cellular immune responses. J. Neuroscience, 14, 6033–6040. Rassnick, S., Zhou, D., and Rabin, B. S. (1995). Central administration of prostaglandin E2 suppresses in vitro cellular immune responses. Am. J. Physiol., 269, R92–R97. Reifman, A. (1995). Social relationships, recovery from illness, and survival, a literature review. Annals of Behavioral Medicine, 17, 124–131. Rondo, P. H., Ferreira, R. F., Nogueira, F., Ribeiro, M. C., Lobert, H., and Artes, R. (2003). Maternal psychological stress and distress as predictors of low birth weight, prematurity and intrauterine growth retardation. Eur. J. Clin. Nutr., 57, 266–272. Rosmond, R., and Bjorntorp, P. (2000). The hypothalamic-pituitaryadrenal axis activity as a predictor of cardiovascular disease, type 2 diabetes and stroke. J. Int. Med., 247, 188–197. Russo-Neustadt, A. A., and Chen, M. J. (2005). Brain-derived neurotrophic factor and antidepressant activity. Curr. Pharm. Des., 11, 1495–1510. Salm, A. K., Pavelko, M., Krouse, E. M., Webster, W., Kraszpulski, M., and Birkle, D. L. (2004). Lateral amygdaloid nucleus expansion in adult rats is associated with exposure to prenatal stress. Develop Brain Res., 148, 159–167. Sanchez, M. D., Milanes, M. V., Pazos, A., Diaz, A., and Laorden, M. L. (1996). Autoradiographic evidence of mu opioid receptor down-regulation after prenatal stress in offspring rat brain. Develop Brain Res., 94, 14–21. Sanchez, M. D., Milanes, M. V., Pazos, A., Diaz, A., and Laorden, M. L. (2000). Autoradiographic evidence of delta opioid receptor down-regulation after prenatal stress in offspring rat brain. Pharmacology, 60, 13–18. Sandman, C. A., Wadhwa, P. D., Chicz-DeMet, A., Dunkel-Schetter, C., and Porto, M. (1997). Maternal stress, HPA activity, and fetal/ infant outcome. Ann. N. Y. Acad. Sci., 814, 266–275. Sansone, R. A., Sansone, L. A., and Wiederman, M. W. (1996). Borderline personality disorder and health care utilization in a primary care setting. Southern Medical J., 89, 1162–1165. Sapolsky, R. M. (2004). Is impaired neurogenesis relevant to the affective symptoms of depression? Biol. Psychiatry, 56, 137–139. Scheier, M. F., Matthews, K. A., Owens, J. F., Schulz, R., Bridges, M. W., Magovern, G. J., and Carver, C. S. (1999). Optimism and rehospitalization after coronary artery bypass graft surgery. Arch. Intern. Med., 159, 829–835. Schneider, M. L., and Coe, C. L. (1993). Repeated social stress during pregnancy impairs neuromotor development of the primate infant. J. Develop. Behav. Pediat., 14, 81–87. Schneider, M. L., Coe, C. L., and Lubach, G. R. (1992). Endocrine activation mimics the adverse effects of prenatal stress on
722
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neuromotor development of the infant primate. Developmental Psychobiology, 25, 427–439. Segerstrom, S. C., Taylor, S. E., Kemeny, M. E., and Fahey, J. L. (1998). Optimism is associated with mood, coping, and immune change in response to stress. J. Pers. Soc. Psychol., 74, 1646–1655. Sesso, H. D., Kawachi, I., Vokonas, P. S., and Sparrow, D. (1998). Depression and the risk of coronary heart disease in the Normative Aging study. Am. J. Cardiol., 82, 851–856. Shannon, H. S., Woodward, C. A., Cunningham, C. E., McIntosh, J., Lendrum, B., Brown, J., and Rosenbloom, D. (2001). Changes in general health and musculoskeletal outcomes in the workforce of a hospital undergoing rapid change: a longitudinal study. J. Occupat Health Psychol, 6, 3–14. Spence, J. D., Barnett, P. A., Linden, W., Ramsden, V., and Taenzer, P. (1999). Lifestyle modifications to prevent and control hypertension. 7. Recommendations on stress management. Canad. Assoc. Med. J., 160, S46–50. Strauss, R. S. (2000). Adult functional outcome of those born small for gestational age, twenty-six year follow-up of the 1970 British Birth Cohort. JAMA, 283, 625–632. Surwit, R. S., Van Tilburg, M. A. L., Zucker, N., McCaskill, C. C., Parekh, P., Feinglos, M. N., Edwards, C. L., Williams, P., and Lane, J. D. (2002). Stress management improves long-term glycemic control in type 2 diabetes. Diabetes Care, 25, 30–34. Takahashi, L. K., Turner, J. G., and Kalin, N. H. (1992). Prenatal stress alters brain catecholaminergic activity and potentiates stress-induced behavior in adult rats. Brain Research, 574, 131–137. Tapia-Arancibia, L., Rage, F., Givalois, L., and Arancibia, S. (2004). Physiology of BDNF: focus on hypothalamic function. Front Neuroendocrinol, 25, 77–107. Taylor, S. E., Kemeny, M. E., Reed, G. M., Bower, J. E., and Gruenewald, T. L. (2000). Psychological resources, positive illusions, and health. Am. Psycholog., 55, 99–109. Tomakowsky, J., Lumley, M. A., Markowitz, N., and Frank, C. (2001). Optimistic explanatory style and dispositional optimism in HIV-infected men. J. Psychosom. Res., 5, 577–587. Toobert, D. J., Strycker, L. A., Glasgow R. E., Barrera M., and Bagdade J. D. (2002). Enhancing support for health behavior change among women at risk for heart disease, the Mediterranean Lifestyle Trial. Health Edu. Res., 17, 574–585. Tsigos, C., and Chrousos, G. P. (2002). Hypothalamic-pituitaryadrenal axis, neuroendocrine factors and stress. J. Psychosom. Res., 53, 865–871. Tulloch-Reid, M. K., Williams, D. E., Looker, H. C., Hanson, R. L., and Knowler, W. C. (2003). Do measures of body fat distribution provide information on the risk of type 2 diabetes in addition to measures of general obesity? Diabetes Care, 26, 2556–2561. Valentino, R. J., Curtis, A. L., Page, M. E., Pavcovich, L. A., and Florin-Lechner, S. M. (1998). Activation of the locus ceruleus brain noradrenergic system during stress, circuitry, consequences, and regulation. Adv. Pharm., 42, 781–784. Vallee, M., Mayo, W., Dellu, F., Le Moal, M., Simon, H., and Maccari, S. (1997). Prenatal stress induces high anxiety and postnatal handling induces low anxiety in adult offspring. Correlation with
stress induced corticosterone secretion. J. Neurosci., 17, 2626– 2636. van Eck, M., Berkhof, H., Nicolson, N., and Sulon, J. (1996). The effects of perceived stress, traits, mood states, and stressful daily events on salivary cortisol. Psychosom. Med., 58, 447–458. Viskoper, R., Shapira, I., Priluck, R., Mindlin, R., Chornia, L., Laszt, A., Dicker, D., Gavish, B., and Alter, A. (2003). Nonpharmacologic treatment of resistant hypertensives by device-guided slow breathing exercises. Am. J. Hypertension, 16, 484–487. Vogt, T., Pope, C., Mullooly, J., and Hollis, J. (1994). Mental health status as a predictor of morbidity and mortality. A 15 year follow-up of members of a health maintenance organization. Am. J. Publ. Health, 84, 227–231. Wadhwa, P. D., Culhane, J. F., Rauh, V., Barve, S. S., Hogan, V., Sandman, C. A., Hobel, C. J., Chicz-DeMet, A., Dunkel-Schetter, C., Garite, T. J., and Glynn, L. (2001). Stress, infection and preterm birth, a biobehavioral perspective. Pediatr Perinat Epidemiol, 15 (Suppl 2), 17–29. Wadhwa, P. D., Garite, T. J., Porto, M., Glynn, L., Chicz-DeMet, A., Dunkel-Schetter, C., Sandman, C. A. (2004). Placental corticotropin-releasing hormone (CRH), spontaneous preterm birth, and fetal growth restriction, a prospective investigation. Am. J. Obstet. Gynecol., 191, 1063–1069. Wager, T. D., Rilling, J. K., Smith, E. E., Sokolik, A., Casey, K. L., Davidson, R. J., Kosslyn, S. M., Rose, R. M., and Cohen, J. D. (2004). Placebo-induced changes in fMRI in the anticipation and experience of pain. Science, 303, 1162–1167. Wasserman, J., Whitmer, R. W., Bazzarre, T. L., Kennedy, S. T., Merrick, N., Goetzel, R. Z., Dunn, R. L., and Ozminkowski, R. J. (2000). Gender-specific effects of modifiable health risk factors on coronary heart disease and related expenditures. J. Occup. Environ. Med., 42, 1060–1069. Westenhoefer, J., von Falck, B., Stellfeldt, A., and Fintelmann, S. (2004). Behavioural correlates of successful weight reduction over 3 y. Results from the Lean Habits study. Int. J. Obesity. Rel. Metab. Disord., 28, 334–335. Wientjes, C. J., and Grossman, P. (1994). Overreactivity of the psyche or the soma? Interindividual associations between psychosomatic symptoms, anxiety, heart rate, and end-tidal partial carbon dioxide pressure. Psychosom. Med., 56, 533–540. Wolke, D., and Samara, M. M. (2004). Bullied by siblings, association with peer victimization and behavior problems in Israeli lower secondary school children. J. Child Psychol. and Psychiatry, 45, 1015–1029. Wolke, D., Woods, S., Bloomfield, L., and Karstadt, L. (2001). Bullying in primary school and common health problems. Arch. Dis. Child, 85, 197–201. Yang, C. H., Huang, C. C., and Hsu, K. S. (2004). Behavioral stress modifies hippocampal synaptic plasticity through corticosterone-induced sustained extracellular signal-regulated kinase/mitogen-activated protein kinase activation. J. Neurosci., 24, 11029–11034. Zavala, S. K., French, M. T., Zarkin, G. A., and Omachonu, V. K. (2002). Decision latitude and workload demand, implications for full and partial absenteeism. J. Public Health Policy, 23, 344–361.
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34 Bi-directional Effects of Stress on Immune Function: Possible Explanations for Salubrious as Well as Harmful Effects FIRDAUS S. DHABHAR AND BRUCE S. McEWEN
I. INTRODUCTION 723 II. ACUTE STRESS-INDUCED ENHANCEMENT OF IMMUNE FUNCTION: AN ADAPTIVE RESPONSE 724 III. PARADOXICAL OBSERVATIONS REGARDING THE EFFECTS OF STRESS ON IMMUNE FUNCTION 726 IV. STRESS-INDUCED REDISTRIBUTION OF IMMUNE CELLS 726 V. STRESS-INDUCED ENHANCEMENT OF IMMUNE FUNCTION 731 VI. STRESS-INDUCED SUPPRESSION OF IMMUNE FUNCTION 733 VII. IMMUNOENHANCING EFFECTS OF GLUCOCORTICOID HORMONES 734 VIII. IMMUNOSUPPRESSIVE EFFECTS OF GLUCOCORTICOID HORMONES 737 IX. INDIVIDUAL DIFFERENCES IN HPA-AXIS REACTIVITY—EFFECTS ON RESISTANCE TO AUTOIMMUNE DISEASE, INFECTION, AND CANCER 741 X. FACTORS THAT DETERMINE WHETHER STRESS WILL ENHANCE OR SUPPRESS IMMUNE FUNCTION 742 XI. THE STRESS SPECTRUM 747 XII. CONCLUSIONS 748
stimulant for some individuals, but a burden for many others. We proposed a definition of stress as a constellation of events, consisting of a stimulus (stressor) that precipitates a reaction in the brain (stress perception), which activates physiologic fight-or-flight systems in the body (stress response) (Dhabhar & McEwen, 1997). It is often overlooked that a stress response has salubrious adaptive effects in the short run (Dhabhar, 1996; Dhabhar & McEwen, 1999b; Dhabhar, Miller, McEwen & Spencer, 1995; Dhabhar, Miller, Stein, McEwen & Spencer 1994; Dhabhar & Viswanathan, 2005; Sapolsky, Romero & Munck, 2000) although stress can be harmful when it is long lasting (Dhabhar & McEwen, 1997; Glaser & Kiecolt-Glaser, 2005; Kiecolt-Glaser, 1999; McEwen, 1998). This chapter discusses the bidirectional effects of stress and glucocorticoid hormones on immune function. Important distinguishing characteristics of stress include its duration and intensity. We define acute stress as stress that lasts for a period of minutes to hours, and chronic stress as stress that persists for several hours a day for an extended period of time (generally months to years). The magnitude of stress may be gauged by the peak levels of stress hormones, neurotransmitters, and other physiological changes such as increases in heart rate and blood pressure, and by the amount of time these changes persist during and following stressor exposure. An important marker for deleterious amounts of chronic stress may be a dysregulation of the circadian corticosterone rhythm in rodents (Dhabhar & McEwen, 1997) and cortisol
I. INTRODUCTION Stress is a term that means different things to different people but generally has a negative connotation. Yet, stress is a familiar aspect of modern life, being a PSYCHONEUROIMMUNOLOGY, 4E VOLUME II
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rhythm in humans (Sephton, Sapolsky, Kraemer & Spiegel, 1998). Stress has long been suspected to play a role in the etiology of many diseases, and numerous studies have shown that stress can be immunosuppressive and hence may be detrimental to health (Ader, Felten & Cohen, 2001; Borysenko & Borysenko, 1982; Cohen & Herbert, 1996; Herbert & Cohen, 1993; Irwin, Patterson, Smith, Caldwell, Brown, Gillin & Grant, 1990; Khansari, Murgo & Faith, 1990; Kiecolt-Glaser, Glaser, Gravenstein, Malarkey & Sheridan, 1996; Kort, 1994; Maier, Watkins & Fleshner, 1994; Marucha, Kiecolt-Glaser & Favagehi, 1998; Munck, Guyre & Holbrook, 1984; Sheridan, 1998; Straub & Schedlowski, 2002). Moreover, glucocorticoid stress hormones are regarded widely as being immunosuppressive (Munck et al., 1984), and are used clinically as antiinflammatory agents (Schleimer, Claman & Oronsky, 1989). Numerous excellent articles have reviewed the literature examining the effects of stress (Ader et al., 2001; Glaser & Kiecolt-Glaser, 2005; Herbert & Cohen, 1993; Maier et al., 1994; Riley, 1981; Straub & Schedlowski, 2002) and glucocorticoid hormones (Boumpas, Paliogianni, Anastassiou & Balow, 1991; Claman, 1972; Cupps & Fauci, 1982; Dougherty, 1952; Fauci, 1979; McEwen, Biron, Brunson, Bulloch, Chambers, et al., 1997; Munck et al., 1984; Parillo & Fauci, 1979; Sapolsky et al., 2000; Schleimer et al., 1989; Schobitz, Reul & Holsboer, 1994; Spencer, Kalman & Dhabhar, 2001) on immune function. In addition to the generally accepted idea that stress and stress mediators are harmful, this chapter examines the potentially beneficial effects of stress and stress hormones in preparing the immune system for dealing with immunologic challenges (e.g., wounding or infection), which may be imposed by the actions of a stressor (e.g., a predator).
II. ACUTE STRESS-INDUCED ENHANCEMENT OF IMMUNE FUNCTION: AN ADAPTIVE RESPONSE Dhabhar et al. initially suggested that an acute stress-induced enhancement of immune function may be an adaptive psychophysiological mechanism that confers increased immune protection during times of stress (Dhabhar, 1996; Dhabhar et al., 1994; Dhabhar et al., 1995b). When viewed from an evolutionary perspective, immunosuppression under all stress conditions would not be adaptive because stress is an intrinsic part of life for most organisms, and dealing successfully with stressors enables survival. Most selection pressures, the chisels of evolution, are stressors that are psychological (threat, aggression), physical
(wounding, infection), or physiological (scarcity of food, salt, or water). The brain perceives stressors, warns the body of danger, and promotes survival (e.g., when a gazelle sees a charging lion, the gazelle’s brain detects a threat and orchestrates a physiological response that enables the gazelle to flee). Therefore, since stressful experiences often result in wounding or infection, immunoenhancement rather than immunosuppression would be adaptive during acute stress since it is unlikely that eons of evolution would select for a system exquisitely designed to escape the jaws and claws of a lion only to succumb to wounds and pathogens (Dhabhar, 1996; Dhabhar et al., 1994; Dhabhar et al., 1995b). In other words, just as an acute stress response prepares the cardiovascular, musculoskeletal, and neuroendocrine systems for fight or flight, it should also prepare the immune system for challenges (wounding or infection) that are likely to result from stressful encounters (attack by a predator). In contrast to the above discussion, it was previously believed that stress-induced suppression of immune function may be adaptive because immunosuppression may conserve energy which is required to deal with the immediate demands imposed by the stressor. However, immunosuppression does not necessarily conserve energy, and some of the proposed mechanisms for immunosuppression, such as apoptosis of leukocytes, are indeed likely to expend energy. Moreover, the immune system may often be critically needed for responding immediately to the actions of the stress-inducing agent (e.g., wounding by a predator). Thus, while ovulation, copulation, or digestion can wait for the cessation of stress, the immune response may not be dispensable in terms of meeting the immediate demands of stress. Furthermore, the time course for many proposed mechanisms for stress-induced immunosuppression such as inhibition of prostaglandin synthesis, cytokine production, or leukocyte proliferation (Schleimer et al., 1989) is significantly longer than that seen during acute stress. Thus, while energy conservation may play a role in stress-induced immunosuppression under some conditions, it would not do so under all stress conditions. The energy conservation hypothesis has also been invoked to suggest that adaptive immunity is suppressed and that only innate immunity is enhanced during acute stress (Dopp, Miller, Myers & Fahey, 2000; Segerstrom & Miller, 2004). The underlying assumption for this hypothesis is that only innate immune responses are required for and are capable of effective immunoprotection on a short time scale and that suppressing adaptive immune function would make more energy available to the innate immune
34. Possible Explanations for Salubrious as Well as Harmful Effects
system. There are several reasons for considering a revision to these assumptions and hypothesis: First, while classifications such as “innate” and “adaptive” are useful for conceptualization of different types of immune responses, it is now increasingly apparent that in vivo immune responses consist of intricate and synchronous interactions between numerous proteins, cytokines, and cell types that include components of what were traditionally thought to be separate “innate” versus “adaptive” systems (Vivier & Malissen, 2005). In general, most if not all components of an immune response are galvanized following immune activation although different components may predominate during different phases of the response. Second, it must be appreciated that suppressing an immune response does not necessarily conserve energy and, in fact, may even require additional energy expenditure (e.g., energy is consumed during synthesis and/or release of immunosuppressive factors or during apoptosis). Third, the “adaptive” immune system is not designed solely to fight challenges that the “innate” system fails to overcome. An important function of adaptive immunity is to “memorize” previously encountered antigens/pathogens and to increase the overall efficiency with which a total, in vivo immune response is mounted against the antigen/pathogen upon subsequent exposure. In many instances, antigens and pathogens that activate an immune response may be those that the organism has previously encountered. In such cases, surveillance memory T-cells may play a critical role in conferring protection by initiating the immune response cascade, and the sooner they are activated, the more efficient the protection. It would make no sense from an evolutionary standpoint to specifically waste precious energy during stress to suppress memory T-cell–driven immune responses that the organism has invested considerable amounts of energy to build up in the first place. We suggest that the acute stress response prepares the immune system for most naturally occurring immune challenges (Dhabhar et al., 1995b; Dhabhar & McEwen, 1996). Multiple components of an immune response have the potential to be enhanced by acute stress. The antigen, pathogen, chemoattractants, and initially responding cells and leukocytes at the site of immune activation determine which specific components are recruited in greater numbers and respond more vigorously (Dhabhar & McEwen, 1996; Dhabhar & Viswanathan, 2005; Viswanathan, Daugherty & Dhabhar, 2005; Viswanathan & Dhabhar, 2005). Exposure to novel antigens during or following acute stress will enhance innate immune mechanisms that initially respond to first-time antigen encounters (Dhabhar & Viswanathan, 2005; Saint-Mezard, Chavagnac, Bosset,
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Ionescu, Peyron, Kaiserlian, Nicolas & Berard, 2003; Viswanathan et al., 2005; Viswanathan & Dhabhar, 2005). Such immunoenhancement during primary antigen exposure can also induce long-lasting increases in immunological memory (Dhabhar & Viswanathan, 2005). Similarly, exposure to previously encountered antigens during or following stress is likely to enhance adaptive immune mechanisms (Dhabhar & McEwen, 1996; Dhabhar, Satoskar, Bluethmann, David & McEwen, 2000). Both Type-1 cytokine-driven cellmediated immunity (Dhabhar & McEwen, 1996; Dhabhar & McEwen, 1999b; Dhabhar & Viswanathan, 2005; Dhabhar et al., 2000; Saint-Mezard et al., 2003; Viswanathan et al., 2005) and Type-2 cytokine-driven humoral immunity (Carr, Woolley & Blalock, 1992; Cocke, Moynihan, Cohen, Grota & Ader, 1993; Persoons, Berkenbosch, Schornagel, Thepen & Kraal, 1995; Wood, Karol, Kusnecov & Rabin, 1993) cytokine can be enhanced by acute stress. The predominance of one type of response over the other is determined once again by the antigen/pathogen and the antigen presentation milieu that initialize the immune response cascades. Importantly, it appears that acute stress significantly enhances dendritic cell and macrophage trafficking, maturation, and function (Viswanathan et al., 2005; Viswanathan & Dhabhar, 2005). Therefore, macrophages and dendritic cells, which form the nexus between innate and adaptive immune responses, may be critical mediators of acute stress-induced enhancement of in vivo immune responses. Other cells such as keratinocytes, endothelial cells, and mast cells may also be important, and their roles need to be investigated further. It is important to bear in mind that experimentally, one is likely to observe acute stress-induced immunoenhancement if the antigen/pathogen is administered to the natural site of antigen/pathogen exposure, and the appropriate immune parameter is measured in the relevant immune compartment at the relevant time. It is also important to recognize that a stressinduced enhancement of immune function is likely to be beneficial in the context of wound healing, vaccination, or resistance to infection (Dhabhar & McEwen, 1996; Dhabhar & McEwen, 2001; Dhabhar & Viswanathan, 2005; Viswanathan et al., 2005; Viswanathan & Dhabhar, 2005). However, such immunoenhancement is likely to be harmful if it exacerbates inflammatory (cardiovascular disease, gingivitis) or autoimmune (psoriasis, arthritis, multiple sclerosis) diseases (Ackerman, Heyman, Rabin, Anderson, Houck, Frank & Baum, 2002; Al’Abadie, Kent & Gawkrodger, 1994; Amkraut, Solomon & Kraemer, 1971; Buske-Kirschbaum, Geiben & Hellhammer, 2001; Folks & Kinney, 1992; Mei-Tal, Meyerowitz & Engel,
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1970; Pawlak, Heiker, Witte, Wiese, Heijnen, Schmidt & Schedlowski, 1999; Solomon & Moos, 1964; Thomason, Brantley, Jones, Dyer & Morris, 1992; Weigl, 2000). Therefore, the focus of our research has been the elucidation of cellular and molecular mechanisms mediating the beneficial versus harmful effects of stress on the health of an organism.
III. PARADOXICAL OBSERVATIONS REGARDING THE EFFECTS OF STRESS ON IMMUNE FUNCTION Three paradoxes present themselves when one reviews the literature examining the relationship between stress, immune function, and health: First, as the preceding discussion suggests, it is paradoxical that organisms would have evolved to suppress immune function at a time when an active immune response may be critical for survival, for example, under conditions of stress when an organism may be injured or infected by the actions of the stress-inducing agent (e.g., an attacking predator). Second, on the one hand stress is thought to suppress immunity and increase susceptibility to infections and cancer (Ben Eliyahu, Yirmiya, Liebeskind, Taylor & Gale, 1991; Cohen, Tyrrell & Smith, 1991; Glaser & Kiecolt-Glaser 2005; Kiecolt-Glaser et al., 1996; Sheridan, 1998), while on the other, it is thought to exacerbate inflammatory (cardiovascular disease, gingivitis, dermatitis) or autoimmune (psoriasis, arthritis, multiple sclerosis) diseases (Ackerman et al., 2002; Al’Abadie et al., 1994; Amkraut et al., 1971; Buske-Kirschbaum et al., 2001; Folks & Kinney, 1992; Mei-Tal et al., 1970; Pawlak et al., 1999; Solomon & Moos, 1964; Thomason et al., 1992; Weigl, 2000) which should be ameliorated by a suppression of immune function. Third, stress is known to exacerbate autoimmune and inflammatory diseases; however, stress hormones (glucocorticoids) are used clinically to treat these diseases (Schleimer et al., 1989). In this chapter we will present data and propose a model to describe interactions between stress, stress hormones, and immune function, which provides possible explanations for these paradoxical observations. This chapter will focus on glucocorticoid hormones since the immunomodulatory effects of catecholamines and other stress-responsive hormones are covered elsewhere in this volume. We propose that four key parameters may influence the direction (enhancing vs. suppressive) of the effects of stress or glucocorticoid hormones on a given immune measure: (1) the effects of stress or glucocorticoids on leukocyte distribution; (2) the differential effects of acute versus chronic stress (or acute vs.
chronic exposure to glucocorticoid hormones) on immune function; (3) the differential effects of physiologic versus pharmacologic concentrations of glucocorticoids, and the differential effects of endogenous (e.g., cortisol, corticosterone) versus synthetic (e.g., dexamethasone) glucocorticoids; (4) the timing of stressor or glucocorticoid hormone exposure relative to the time course of the immune response. It is important to recognize that factors such as gender, genetics, age, route of administration, nature, dose of the immunizing antigen, and time of day may also significantly affect the relationship between stress and immune function.
IV. STRESS-INDUCED REDISTRIBUTION OF IMMUNE CELLS Stress and stress hormones induce significant changes in the distribution of leukocytes within the body. An important function of the psychophysiological stress response may be to ensure that appropriate leukocytes are present in the right place and at the right time to respond to an immune challenge which might be initiated by the stress-inducing agent (e.g., attack by a predator, invasion by a pathogen, etc.) (Dhabhar et al., 1994; Dhabhar et al., 1995b; Dhabhar, Miller, McEwen & Spencer, 1996). Thus, the modulation of immune cell distribution by acute stress may be an adaptive response designed to enhance immune surveillance and increase immune preparedness for potential (or ongoing) immune challenge. Such changes in immune cell distribution may also have significant implications for the way in which data regarding the effects of stress on immune function in a specific body compartment are interpreted.
A. Effects of Stress on Blood Leukocytes Immune cells or leukocytes circulate continuously from the blood, into various organs, and back into the blood. This circulation is essential for the maintenance of an effective immune defense network (Sprent & Tough, 1994). The numbers and proportions of leukocytes in the blood provide an important representation of the state of distribution of leukocytes in the body and of the state of activation of the immune system. Since the blood is the most accessible and commonly used compartment for human studies, it is important to carefully evaluate how changes in blood immune parameters might reflect in vivo immune function in the context of the specific experiments or studies at hand. Moreover, since most blood collection procedures involve a certain amount of stress, since all patients or subjects will have experienced stress in some manner, and since many studies of psychophysi-
34. Possible Explanations for Salubrious as Well as Harmful Effects
ological effects on immune function focus on stress, it is important to keep in mind the effects of stress on blood leukocyte distribution. Numerous studies have shown that stress and stress hormones induce significant changes in absolute numbers and relative proportions of leukocytes in the blood. In fact, decreases in blood leukocyte numbers were used as an indirect measure for increases in plasma corticosterone before methods were available to directly assay the hormone (Hoagland, Elmadjian & Pincus, 1946). Stress-induced decreases in blood leukocyte numbers have been reported in fish (Pickford, Srivastava, Slicher & Pang, 1971), mice (Jensen, 1969), rats (Dhabhar et al., 1994; Dhabhar et al., 1995b; Johns, 1967; Rinner, Schauenstein, Mangge, Porta & Kvetnansky, 1992; Stefanski, Solomon, Kling, Thomas & Plaeger, 1996), rabbits (Toft, Svendsen, Tonnesen, Rasmussen & Christensen, 1993), horses (Snow, Ricketts & Mason, 1983), non-human primates (Morrow-Tesch, McGlone & Norman, 1993), and humans (Altemus, Rao, Dhabhar, Ding & Granstein, 2001; Herbert & Cohen, 1993; Schedlowski, Jacobs, Stratman, Richter, Hädike, Tewes, Wagner & Schmidt, 1993). This suggests that the phenomenon of stressinduced leukocyte distribution has been conserved through evolution and that perhaps this redistribution has an important adaptive and functional significance. Studies have shown that stress-induced increases in plasma corticosterone are accompanied by a significant decrease in numbers and percentages of lymphocytes, and by an increase in numbers and percentages of neutrophils. Dhabhar et al. have shown that stressinduced changes in blood leukocyte distribution are apparent within 30 minutes of applying the stressor (Dhabhar et al., 1995b). These authors reported a large decrease (45–60% lower than baseline) in total blood leukocyte numbers. FACS analyses revealed that absolute numbers of peripheral blood helper T-cell (Th), cytolytic T-cell (CTL), B-cells, natural killer (NK) cells, and monocytes all show a rapid and significant decrease (40–70% lower than baseline) during stress (Dhabhar et al., 1995b). Further experiments revealed that stress-induced decreases in blood leukocyte numbers are rapidly reversed with leukocyte numbers returning to pre-stress baseline levels within 3 hours after the cessation of stress (Dhabhar et al., 1995b).
B. Adrenal Stress Hormones Mediate Stress-Induced Changes in Blood Leukocyte Numbers Stress-induced changes in leukocyte distribution are largely mediated by hormones released by the adrenal gland (Dhabhar et al., 1996; Dhabhar &
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McEwen, 1999b). Thus, the magnitude of the stressinduced changes in blood leukocyte numbers is significantly reduced in adrenalectomized animals (Dhabhar et al., 1995b; Dhabhar et al., 1996). Cyanoketone treatment, which virtually eliminates the corticosterone stress response, also virtually eliminates the stress-induced decrease in blood lymphocyte numbers and significantly enhances the stress-induced increase in blood neutrophil numbers (Dhabhar et al., 1996). Studies have shown that glucocorticoid treatment induces changes in leukocyte distribution in mice (Cohen, 1972; Dougherty & White, 1945; Spain & Thalhimer, 1951; Zatz, 1975), guinea pigs (Fauci, 1975), rats (Dhabhar et al., 1996; Miller, Spencer, Hasset, Kim, Rhee, Cira, Dhabhar, McEwen & Stein, 1994; Ulich, Keys, Ni, del Castillo & Dakay, 1988), rabbits (Van Den Broek, Keuning, Soeharto & Prop, 1983), and humans (Fauci, 1976; Fauci & Dale, 1974; Onsrud & Thorsby, 1981). It has been shown in rats that both adrenalectomy (which eliminates the corticosterone and epinephrine stress response) (Dhabhar et al., 1995b; Dhabhar et al., 1996; Jensen, 1969; Keller, Weiss, Schleifer, Miller & Stein, 1983) and cyanoketone treatment (which eliminates only the corticosterone stress response) virtually eliminate the stress-induced redistribution of blood leukocytes (Dhabhar et al., 1996). Since adrenal steroids act at two distinct receptor subtypes which show a heterogeneity of expression in immune cells and tissues (Dhabhar, McEwen & Spencer, 1993; Dhabhar, Miller, McEwen & Spencer, 1995; Miller, Spencer, Pearce, Pisell, Azrieli, Tanapat, Moday, Rhee & McEwen, 1998; Spencer et al., 2001), Dhabhar et al. investigated the role played by each receptor subtype in mediating changes in leukocyte distribution (Dhabhar et al., 1996). Acute administration of aldosterone (a specific type I adrenal steroid receptor agonist) to adrenalectomized animals did not have a significant effect on blood leukocyte numbers. In contrast, acute administration of corticosterone (the endogenous type I and type II receptor agonist) or RU28362 (a specific type II receptor agonist) to adrenalectomized animals induced changes in leukocyte distribution which were similar to those observed in intact animals during stress. These results suggest that corticosterone, acting at the type II adrenal steroid receptor, is a major mediator of the stress-induced decreases in blood lymphocyte and monocyte distribution. Taken together, these studies show that stress and glucocorticoid hormones induce a significant decrease in blood lymphocyte numbers when administered under acute or chronic conditions. In contrast to glucocorticoid hormones, catecholamine hormones have been shown to increase blood leukocyte numbers in rats (Harris, Waltman, Carter & Maisel, 1995) and humans (Landmann, Muller, Perini,
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Wesp, Erne & Buhler, 1984). On closer examination it is observed that following adrenaline or noradrenaline administration, neutrophil and NK cell numbers increase rapidly and dramatically, whereas T- and B-cell numbers decrease (Benschop, RodriguezFeuerhahn & Schedlowski, 1996; Landmann, 1992; Schedlowski, Falk, Rohne, Wagner, Jacobs, Tewes & Schmidt, 1993; Tonnesen, Christensen & Brinklov, 1987). Carlson et al. have shown that catecholamine pre-treatment results in increased accumulation of lymphocytes in the spleen and lymph nodes (Carlson, Fox & Abell, 1997), which would be in agreement with a catecholamine-induced decrease in lymphocytes in the blood. By acutely administering epinephrine, norepinephrine, selective α and β adrenergic receptor agonists, or corticosterone to adrenalectomized animals, Dhabhar and McEwen have shown that increases in blood granulocyte numbers may be mediated by the α1 and β adrenergic receptors and are counteracted by corticosterone acting at the type II adrenal steroid receptor (Dhabhar & McEwen, 1999a). Increases in lymphocytes may be mediated by the α2 receptor, while decreases in lymphocytes may be mediated by β adrenergic and type II adrenal steroid receptors (Dhabhar & McEwen, 1999a). Therefore, the absolute number of specific blood leukocyte subpopulations is affected by the ambient concentrations of epinephrine, norepinephrine, and corticosterone. Differences in concentrations and combinations of these hormones may explain reported differences in blood leukocyte numbers during different stress conditions (e.g., shortvs. long-duration acute stress, acute vs. chronic stress) and during exercise.
C. A Stress-induced Decrease in Blood Leukocyte Numbers Represents a Redistribution Rather Than a Destruction or Net Loss of Blood Leukocytes From the above discussion, it is clear that stress and glucocorticoid hormones induce a rapid and significant decrease in blood lymphocyte, monocyte, and NK cell numbers. This decrease in blood leukocyte numbers may be interpreted in two ways. It could reflect a large-scale destruction of circulating leukocytes, or it could reflect a redistribution of leukocytes from the blood to other organs in the body. Several studies have shown that glucocorticoid-induced decrease in blood leukocytes reflects a redistribution rather than a destruction of immune cells (Cohen, 1972; Cox & Ford, 1982; Dougherty & White, 1945; Lundin & Hedman, 1978; Spain & Thalhimer, 1951; Zatz, 1975). Dhabhar et al. conducted experiments to test the hypothesis that acute stress induces a redistribution of
leukocytes from the blood to other compartments in the body (Dhabhar, 1998; Dhabhar et al., 1995b). The first series of experiments examined the kinetics of recovery of the stress-induced reduction in blood leukocyte numbers. It was hypothesized that if the observed effects of stress represented a redistribution rather than a destruction of leukocytes, one would see a relatively rapid return of leukocyte numbers back to baseline upon the cessation of stress. Results showed that all leukocyte subpopulations which showed a decrease in absolute numbers during stress showed a complete recovery, with numbers reaching pre-stress baseline levels within 3 hours after the cessation of stress (Dhabhar et al., 1995b). Plasma levels of lactate dehydrogenase (LDH), which is a marker for cell damage, were also monitored in the same experiment. If the stress-induced decrease in leukocyte numbers was the result of a destruction of leukocytes, one would expect to observe an increase in plasma levels of LDH during or following stress. However, no significant changes in plasma LDH were observed, further suggesting that a redistribution rather than a destruction of leukocytes was primarily responsible for the stressinduced decrease in blood leukocyte numbers (Dhabhar et al., 1995b). It is important to bear in mind that glucocorticoids induce changes in various immune parameters (Callewaert, Moudgil, Radcliff & Waite, 1991; Munck et al., 1984), including immune cell distribution (Cohen, 1972; Dhabhar et al., 1994; Dhabhar et al., 1995b; Fauci, 1975; Fauci & Dale, 1974; Lundin & Hedman, 1978; Spry, 1972; Zatz, 1975), in the absence of cell death even though these hormones are also known to induce leukocyte apoptosis (Cohen, 1992). It has been suggested that some species may be “steroid-resistant” and others may be “steroid-sensitive,” and that glucocorticoid-induced changes in blood leukocyte numbers represent changes in leukocyte redistribution in “steroid-resistant” species (humans and guinea pig), and leukocyte lysis in “steroid-sensitive” species (mouse and rat) (Claman, 1972). However, evidence now indicates that even in species previously thought to be “steroid-sensitive,” adrenal steroids induce leukocyte redistribution rather than leukocyte destruction (Cohen, 1972; Hedman & Lundin, 1977; Moorhead & Claman, 1972; Thompson & Van Furth, 1973).
D. Target Organs of a Stress-induced Redistribution of Blood Leukocytes Based on the above discussion, the obvious question one might ask is: “Where do blood leukocytes go during or following stress?” Numerous studies using stress or stress hormone treatments have investigated
34. Possible Explanations for Salubrious as Well as Harmful Effects
this issue. Using gamma imaging to follow the distribution of adoptively transferred radio-labeled leukocytes in rabbits, Toft et al. showed that stress induces a redistribution of leukocytes from the blood to lymphatic tissues (Toft et al., 1993). It has been reported that anesthesia stress, as well as the infusion of adrenocorticotropic hormone (ACTH) and prednisolone in rats results in decreased numbers of labeled lymphocytes in the thoracic duct, while the cessation of drug infusion results in normal circulation (Spry, 1972). This suggests that hormonal changes similar to those observed during stress induce the retention of circulating lymphocytes in different body compartments, thus resulting in a decrease in lymphocyte numbers in the thoracic duct and a concomitant decrease in numbers in the peripheral blood (Spry, 1972). Fleshner et al. have shown that acute stress results in an increase in CD4% and a decrease in CD8% in the mesenteric lymph nodes and have suggested that these changes in lymphocyte composition may mediate changes in antibody production by the affected lymph nodes (Fleshner, Watkins, Lockwood, Laudenslager & Maier, 1992). It has also been reported that a single injection of hydrocortisone, prednisolone, or ACTH results in increased numbers of lymphocytes in the bone marrow of mice (Cohen, 1972), guinea pigs (Fauci, 1975), and rats (Cox & Ford, 1982). Fauci et al. have suggested that glucocorticoid-induced decreases in blood leukocyte numbers in humans may also reflect a redistribution of immune cells to other organs in the body (Fauci & Dale, 1974; Fauci & Dale, 1975; Yu, Clements, Paulus, Peter, Levy & Barnett, 1974). Finally, corticosteroids have been shown to induce the accumulation of lymphocytes in mucosal sites (Walzer, LaBine, Redington & Cushion, 1984), and the skin has been identified as a target organ to which leukocytes traffic during stress (Dhabhar & McEwen, 1996; Viswanathan & Dhabhar, 2005). It is important to note that in these studies, a return to resting glucocorticoid levels is almost always followed by a rapid return to baseline numbers of blood lymphocytes, further supporting the hypothesis that the decrease in blood leukocyte numbers is the result of a glucocorticoid-induced redistribution rather than a glucocorticoid-induced destruction of blood leukocytes.
E. Stress-induced Changes in Blood Leukocyte Numbers: Contradicting Results or a Biphasic Response? As stated above, stress has been shown to induce a significant decrease in blood leukocyte numbers in fish (Pickford et al., 1971), mice (Jensen, 1969), rats (Dhabhar et al., 1994; Dhabhar et al., 1995b; Rinner et al., 1992),
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rabbits (Toft et al., 1993), horses (Snow et al., 1983), non-human primates (Morrow-Tesch et al., 1993), and humans (Herbert & Cohen, 1993; Schedlowski et al., 1993). However, studies have shown that acute stress increases rather than decreases blood leukocyte numbers in humans. In fact, stress-induced increases (rather than decreases) in blood leukocyte numbers are more commonly reported in human studies (Brosschot, Benschop, Godaert, Olff, De Smet, Heijnen & Ballieux, 1994; Mills, Berry, Dimsdale, Ziegler, Nelesen & Kennedy, 1995; Hong, Farag, Nelesen, Ziegler & Mills, 2004; Naliboff, Benton, Solomon, Morley, Fahey, Bloom, Makinodan & Gilmore, 1991; Schedlowski et al., 1993). This apparent contradiction is resolved when three important factors are taken into account: First, stress-induced increases in blood leukocyte numbers are observed following stress conditions which primarily result in the activation of the sympathetic nervous system. These stressors are often of a short duration (order of a few minutes) or are relatively mild (e.g., public speaking) (Altemus et al., 2001; Brosschot et al., 1994; Mills et al., 1995; Naliboff et al., 1991; Schedlowski et al., 1993). Second, the increase in leukocyte numbers may be accounted for by stress- or catecholamine-induced increases in granulocytes and NK cells (Brosschot et al., 1994; Mills et al., 1995; Benschop et al., 1996; Naliboff et al., 1991; Schedlowski et al., 1993). Since granulocytes form a large proportion of circulating leukocytes in humans (60–80% granulocytes), an increase in granulocyte numbers is reflected as an increase in total leukocyte numbers in contrast to rats and mice (10–20% granulocytes). Third, stress or pharmacologically induced increases in glucocorticoid hormones induce a significant decrease in blood lymphocyte and monocyte numbers (Dhabhar et al., 1995b; Dhabhar et al., 1996; Hoagland et al., 1946; Stein, Ronzoni & Gildea, 1951; Schedlowski et al., 1993). Thus, stress conditions which result in a significant and sustained activation of the HPA axis are likely to result in a decrease in blood leukocyte numbers. We propose that acute stress induces an initial increase followed by a decrease in blood leukocyte numbers according to the following pattern: Stress conditions which result in activation of the sympathetic nervous system, especially conditions which induce high levels of norepinephrine, may induce an increase in circulating leukocyte numbers. These conditions may occur during the very beginning of a stress response, very short duration stress (order of minutes), mild psychological stress, or during exercise. In contrast, conditions that result in the activation of the hypothalamic-pituitary-adrenal (HPA) axis induce a decrease in circulating leukocyte numbers which does not reflect a net loss of leukocytes but a redistribution
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from the blood to other organs (e.g., skin and sentinel lymph nodes). These conditions often occur during the later stages of a stress response, long duration acute stressors (order of hours), or during severe psychological, physical, or physiological stress. An elegant and interesting example in support of this hypothesis comes from Schedlowski et al., who measured changes in blood T-cell and NK cell numbers as well as plasma catecholamine and cortisol levels in parachutists (Schedlowski et al., 1993). Measurements were made 2 hours before, immediately after, and 1 hour after the parachute jump. Results showed a significant increase in blood T-cell and NK cell numbers immediately (minutes) after the jump that was followed by a significant decrease 1 hour after the jump. An early increase in plasma catecholamines preceded early increases in lymphocyte numbers, whereas the more delayed rise in plasma cortisol preceded the late decrease in lymphocyte numbers (Schedlowski et al., 1993). Importantly, changes in NK cell activity and antibody-dependent cell-mediated cytotoxicity (ADCC) closely paralleled changes in blood NK cell numbers, thus suggesting that changes in leukocyte numbers may be an important mediator of apparent changes in leukocyte “activity.” Similarly, Rinner et al. have shown that a short stressor (1-minute handling) induced an increase in mitogen-induced proliferation of T- and B-cells obtained from peripheral blood, while a longer stressor (2-hour immobilization) induced a decrease in the same proliferative responses (Rinner et al., 1992). In another example, Manuck et al. showed that acute psychological stress induced a significant increase in blood CTL numbers only in those subjects who showed heightened catecholamine and cardiovascular reactions to stress (Manuck, Cohen, Rabin, Muldoon & Bachen, 1991). Thus, we propose that an acute stress response induces biphasic changes in blood leukocyte numbers. Soon after the beginning of stress (order of minutes) or during mild acute stress, or exercise, catecholamine hormones and neurotransmitters induce the body’s “soldiers” (leukocytes) to exit their “barracks” (spleen, lung, marginated pool, and other organs) and enter the “boulevards” (blood vessels and lymphatics). This results in an increase in blood leukocyte numbers, the effect being most prominent for NK cells and granulocytes. As the stress response continues, activation of the HPA axis results in the release of glucocorticoid hormones, which induce leukocytes to exit the blood and take position at potential “battle stations” (skin, mucosal lining of gastro-intestinal and urinary-genital tracts, lung, liver, and lymph nodes) in preparation for immune challenges which may be imposed by the actions of the stressor (Dhabhar et al., 1994; Dhabhar
et al., 1996; Dhabhar & McEwen, 1996; Dhabhar & McEwen, 1997). Such a redistribution of leukocytes results in a decrease in blood leukocyte numbers. Thus, acute stress may result in a redistribution of leukocytes from the barracks, through the boulevards, and to potential battle stations within the body.
F. Stress-induced Redistribution of Blood Leukocytes—Mechanisms It is likely that stress-induced changes in leukocyte distribution are mediated by changes in either the expression, or affinity, of adhesion molecules on leukocytes and/or endothelial cells. It has been suggested that following stress or glucocorticoid-treatment, specific leukocyte subpopulations (being transported by blood and lymph through different body compartments) may be selectively retained in those compartments in which they encounter a stress- or glucocorticoid-induced “adhesion match” (Dhabhar, 1996; Dhabhar & McEwen, 1999b). As a result of this selective retention, the proportion of some leukocyte subpopulations would decrease in the blood, while it increases in the organ in which the leukocytes are retained (e.g., the skin) (Dhabhar & McEwen, 1996; Viswanathan & Dhabhar, 2005). Support for the “selective retention” hypothesis comes from studies which show that prednisolone induces the retention of circulating lymphocytes within the bone marrow, spleen, and some lymph nodes, thus resulting in a decrease in lymphocyte numbers in the thoracic duct and a concomitant decrease in peripheral blood (Cox & Ford, 1982; Spry, 1972). Adhesion molecules such as the selectins, integrins, ICAMS, and their ligands are likely mediators of a stress-induced retention of blood leukocytes within the vasculature of target organs such as the skin and lymph nodes. Stress has been shown to upregulate lymphocyte function-associated-antigen 1 (LFA-1), downregulate L selectin (CD62L) expression on peripheral blood leukocytes (Goebel & Mills, 2000; Mills & Dimsdale, 1996; Shephard, 2003), enhance integrin CD11b expression on lymphocytes, and enhance blood PBMC chemotaxis to FMLP and SDF-1, factors usually expressed at sites of infection or inflammation (Redwine, Snow, Mills & Irwin, 2003). Studies have also shown that CD11a and CD11b adhesion molecules may be involved in stress-induced alterations of T-cell distribution, as their expression was upregulated in rats subjected to acute stress, and the level of expression correlated to circulating levels of glucocorticoids (Bauer, Perks, Lightman & Shanks, 2001). Taken together, these studies suggest that stress hormoneinduced changes in activity or expression of adhesion
34. Possible Explanations for Salubrious as Well as Harmful Effects
molecules on immune cells and/or endothelial cells may mediate stress-induced changes in leukocyte distribution within the body and infiltration into tissues. Moreover, stress hormones also influence the production of cytokines (Daynes & Araneo, 1989; Munck & Guyre, 1989), and lipocortins (Hirata, 1989) which in turn can affect the surface adhesion properties of leukocytes and endothelial cells (Issekutz, 1990). Further investigation of the effects of endogenous glucocorticoids (administered in physiologic doses, and examined under physiologic kinetic conditions) on changes in expression/activity of cell surface adhesion molecules and on leukocyte-endothelial cell adhesion is necessary.
G. Stress-induced Redistribution of Blood Leukocytes—Functional Consequences Dhabhar et al. were the first to propose that a stressinduced decrease in blood leukocyte numbers may represent an adaptive response (Dhabhar et al., 1994; Dhabhar et al., 1995b; Dhabhar et al., 1996; Dhabhar & McEwen, 1996; Dhabhar & McEwen, 1997; Dhabhar & McEwen, 1999b). These authors suggested that such a decrease in blood leukocyte numbers represents a redistribution of leukocytes from the blood to other organs such as the skin, mucosal lining of gastrointestinal and urinary-genital tracts, lung, liver, and lymph nodes, which may serve as “battle stations” should the body’s defenses be breached during or following the stressful experience (e.g., wounding or infection following a fight). Such a leukocyte redistribution may enhance immune function in compartments into which leukocytes traffic during stress. Thus, an acute stress response may direct the body’s “soldiers” (leukocytes) to exit their “barracks” (spleen and bone marrow), travel the “boulevards” (blood vessels), and take position at potential “battle stations” (skin, lining of gastro-intestinal and urinary-genital tracts, lung, liver, and lymph nodes) in preparation for immune challenge (Dhabhar et al., 1994; Dhabhar et al., 1995a; Dhabhar et al., 1996; Dhabhar & McEwen, 1996; Dhabhar & McEwen, 1997). In addition to “redeploying” leukocytes to potential “battle stations,” stress hormones may also better equip them for “battle” by enhancing processes like antigen presentation (Viswanathan et al., 2005), phagocytosis (Lyte, Nelson & Thompson, 1990), and antibody production (Cocke et al., 1993). Thus, a hormonal alarm signal released by the brain upon detecting a stressor may “prepare” the immune system for potential challenges (wounding or infection) which may arise due to the actions of the stress-inducing agent (e.g., a predator or attacker).
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An important but underappreciated function of endocrine mediators released under conditions of acute stress may be to ensure that appropriate leukocytes are present in the right place and at the right time to respond to an immune challenge that might be initiated by the stress-inducing agent (e.g., attack by a predator, invasion by a pathogen, etc.). The modulation of immune cell distribution by acute stress may be an adaptive response designed to enhance immune surveillance and increase the capacity of the immune system to respond to challenge in immune compartments (such as the skin and epithelia of lung, gastrointestinal, and urinary-genital tracts) which serve as major defense barriers for the body. Thus, endocrine mediators released during stress may serve to enhance immune preparedness for potential (or ongoing) immune challenge.
V. STRESS-INDUCED ENHANCEMENT OF IMMUNE FUNCTION While a majority of studies in the field of psychoneuroimmunology have focused on the immunosuppressive effects of stress, several studies have also revealed that stress can augment immune function. In general acute stress is found to be immunoenhancing, whereas chronic stress is found to be immunosuppressive (as discussed in the previous section, the effects of stress on leukocyte numbers and proportions in the compartment being assayed need to be taken into consideration). Dhabhar et al. have suggested that a stressinduced enhancement of immune function may be an important adaptive response which prepares an organism for potential immunologic challenges (e.g., a wound or infection inflicted by an attacker) for which stress perception by the brain and subsequent stress hormone and neurotransmitter release may serve as an early warning. Studies showing stress-induced enhancements in immune parameters in vivo and in vitro are reviewed below.
A. Stress-induced Enhancement of Cell-Mediated Immunity Acute stress induces a significant redistribution of leukocytes from the blood to other organs (e.g., skin and lymph nodes) in the body, and adrenal stress hormones are major mediators of this leukocyte redistribution (Dhabhar et al., 1996). Since the skin is one of the targets to which leukocytes traffic during stress (Dhabhar & McEwen, 1996; Viswanathan & Dhabhar, 2005), Dhabhar and McEwen hypothesized that a stress-induced leukocyte redistribution may increase
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immune surveillance in the skin and consequently enhance immune function should the skin be exposed to antigen following acute stress (Dhabhar & McEwen, 1996). To test this hypothesis, they examined the effects of acute stress on skin immunity, using a rodent model for a skin cell-mediated immunity (CMI) involving the delayed type hypersensitivity (DTH) response (Dhabhar & McEwen, 1996). In order to induce CMI, animals were initially sensitized with hapten (2,4dinitro-1-fluorobenzene [DNFB] or oxazalone) or protein (keyhole limpet hemocyanin [KLH]) antigens. The immunization or sensitization phase of a CMI reaction is one in which the organism develops an immunologic memory (through the generation of memory T-cells) for antigen. Following sensitization, the ability of the animals to mount a CMI response was examined by re-administering antigen to a novel site (often the pinna). The CMI response was subsequently measured as an increase in pinna thickness, which is proportional to the intensity of the ongoing immune reaction (Kimber & Dearman, 1993; Phanuphak, Moorhead & Claman, 1974). This phase, also known as the elicitation phase, involves recruitment of memory T-cells and effector cells such as macrophages, CTLs, and NK cells that mount an immune response against the antigen to which the animal was previously sensitized. Acute restraint stress administered immediately before immunization (Dhabhar & Viswanathan, 2005; Viswanathan et al., 2005) or challenge (Dhabhar & McEwen, 1996; Dhabhar et al., 2000) resulted in a large and long-lasting enhancement of skin CMI (Dhabhar & Viswanathan, 2005). Histological analysis identified significantly higher numbers of leukocytes in the skin of stressed animals both before and after exposure to antigen, and suggested that a stress-induced redistribution of leukocytes was one of the factors mediating the stress-induced enhancement of skin immunity (Dhabhar & McEwen, 1996). Other investigators have reported a similar enhancement of skin CMI following acute stress (Bilbo, Dhabhar, Viswanathan, Saul, Yellon & Nelson, 2002; Blecha, Barry & Kelley, 1982; SaintMezard et al., 2003).
B. Stress-induced Enhancement of Humoral Immunity Wood et al. (1993) have shown that exposure to foot shock stress enhances humoral as well as cellmediated immunity to keyhole limpet hemocyanin (KLH). These investigators administered a single acute foot shock session on days −1, 0, 1, and 3 relative to sensitization (day 0). They observed that compared to non-stressed controls, animals stressed on days 0 or 1 showed enhanced immune responses with respect to
serum anti-KLH IgG levels, splenocyte proliferation, and skin cell-mediated immunity to KLH antigen. Interestingly, non-stressed animals failed to show a significant increase in serum antibody titers and in KLH-stimulated splenocyte proliferation relative to non-immunized animals (Wood et al., 1993). Similarly, Cocke et al. have shown enhancement of IgM and IgG titers following olfactory stressor exposure, and Persoons et al. have shown that acute stress administered prior to intrathecal immunization with trinitrophenyl keyhole limpet hemocyanin (TNP-KLH) significantly enhanced the primary humoral response (Cocke et al., 1993; Persoons et al., 1995). They also showed that acute stress administered prior to antigen re-administration resulted in a significant enhancement of a secondary humoral response (Persoons et al., 1995). In another study, Carr et al. reported that cold stress enhanced IgG and IgM production by splenocytes and that this enhancement was mediated by the alpha adrenergic receptor (Carr et al., 1992). Several other studies have reported stress-induced enhancement of humoral immune responses. For example, cold stress has been shown to accelerate antigen removal in mice (Sabiston, Ste Rose & Cinader, 1978). Other stressors have been shown to increase antigen-specific antibody titers in rats, mice, and pigs (Berkenbosch, Wolvers & Derijk, 1991; Blecha & Kelley, 1981; Cocke et al., 1993; Persoons et al., 1995; Solomon, 1969; Wood et al., 1993). Importantly, it been proposed that glucocorticoids shift the balance of an ongoing immune response in favor of humoral immunity driven by type 2 cytokines (Daynes & Araneo, 1989; Elenkov, 2004; Gajewski, Schell, Nau & Fitch, 1989; Mason, 1991; Mosmann & Coffman, 1989), and physiological doses of glucorticoids have been shown to enhance immunoglobulin production by mitogen– (Grayson, Dooley, Koski & Blaese, 1981) and IL-4– (Wu, Sarfati, Heusser, Forunier, Rubio-Trujillo, Peleman & Delespesse, 1991) stimulated human lymphocytes in culture.
C. Stress-induced Enhancement of Innate Immune Parameters Acute stress has been shown to enhance spleen macrophage phagocytic function (Lyte, Nelson & Baissa, 1990; Lyte, Nelson, & Thompson, 1990), blood polymorphonuclear leukocyte phagocytosis (Shurin, Kusnecov, Hamill, Kaplan & Rabin, 1994), clearance of subcutaneously injected bacteria (Deak, Nguyen, Fleshner, Watkins & Maier, 1999), and blood NK cell activity (Jain & Stevenson, 1991; Millar, Thomas, Pacheco & Rollwagen, 1993). Acute stressors such as handling (Rinner et al., 1992), restraint (Jain &
34. Possible Explanations for Salubrious as Well as Harmful Effects
Stevenson, 1991), and foot shock (Lysle, Cunnick & Rabin, 1990; Shurin, Zhou, Kusnecov, Rassnick & Rabin, 1994) have also been shown to enhance proliferation of blood and spleen leukocytes. Several studies have shown that in vitro administration of stress hormones to immune cells can enhance different aspects of immune function. Low physiological concentrations of corticosterone have been shown to stimulate mitogen– (Wiegers, Reul, Holsboer & De Kloet, 1994) and anti-T-cell receptor– (Wiegers, Labeur, Stec, Klinkert, Holsboe & Reul, 1995) induced proliferation of splenocytes. Similarly, glucocorticoid hormones have been shown to enhance nitric oxide and IL-1β (Broug-Holub & Kraal, 1996) and TNF-α secretion by macrophages (Renz, Henke, Hofmann, Wolff, Schmidt, Rüschoff & Gemsa, 1992). Finally, acute stress has been shown to induce acute phase proteins in vivo (Deak, Meriwether, Fleshner, Spencer, Abouhamze, Moldawer, Grahn, Watkins & Maier, 1997).
D. Stress-induced Enhancement of Immune Function: Clinical Implications We have introduced the novel concept that a psychophysiological stress response is nature’s fundamental survival mechanism that could be therapeutically harnessed to augment immune function during vaccination, wound healing, or infection (Dhabhar & McEwen, 1996; Dhabhar & McEwen, 2001). The phenomenon of a stress-induced increase in resistance to infections or cancer needs to be rigorously investigated. Recent studies have suggested that a stressinduced enhancement of a primary immune response following exposure to novel antigen results in increased numbers of memory T-cells and a long-lasting increase in anti-gen-specific immunological memory (Dhabhar & Viswanathan, 2005). This suggests that harnessing acute stress physiology during the process of vaccination may significantly increase the efficacy of vaccineinduced immunoprotection. One would hypothesize that a stress-induced enhancement of immune function may be beneficial in case of infections or cancer, but could be harmful in case of autoimmune or inflammatory disorders. Numerous studies have reported stress-induced exacerbation of autoimmune and inflammatory diseases (Straub & Besedovsky, 2003; Straub, Dhabhar, Bijlsma & Cutolo, 2005; Straub & Schedlowski, 2002). Over 40 years ago, Solomon and Moos described an association between stress and autoimmune disorders (Solomon & Moos, 1964). Rimon and Laakso (1985) have classified two categories of rheumatoid arthritis, a disease form more associated with genetic factors, and another more associated with psychodynamic factors such as stress.
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Thomason et al. found that minor stress events such as day-to-day irritants were associated with exacerbations of rheumatoid arthritis (Thomason et al., 1992). Similarly, stress has been associated with the onset and exacerbation of psoriasis (Al’Abadie et al., 1994). Stress has also been reported to precede the onset and exacerbation of multiple sclerosis (Ackerman et al., 2002; Mei-Tal et al., 1970); in some cases, however, it was chronic but not acute stress that was reported to precipitate disease (Philippopoulos, Wittkower & Cousineau, 1958). Some studies have also failed to discover consistent relationships between life stress and autoimmune disease (Hendrie, Parasekvas, Baragar & Adamson, 1971; Zautra, Okun, Robinson, Lee, Roth & Emmanual, 1989). Further studies are needed to rigorously examine both—stress-induced enhancement in resistance to infections and cancer and stress-induced exacerbation of autoimmune and inflammatory disorders.
VI. STRESS-INDUCED SUPPRESSION OF IMMUNE FUNCTION Numerous studies have shown that stress can be immunosuppressive and hence may be detrimental to health (for review, see Black, 1994; Borysenko & Borysenko, 1982; Glaser & Kiecolt-Glaser, 2005; Irwin, 1994; Khansari et al., 1990; Kort, 1994; Sklar & Anisman, 1981; Zwilling, 1992). Since these studies have been reviewed and discussed extensively, here we present only a few relevant examples of a stress-induced suppression of immune function and refer the reader to these excellent reviews and other chapters in this volume for a more detailed account of the subject. It may be worth noting that most stress conditions which are found to be immunoenhancing involve acute stress, and those which are found to be immunosuppressive involve chronic stress (with the effects of stress on leukocyte distribution being an important factor to be taken into account as discussed later in this chapter). It has been shown that in contrast to acute stress, chronic stress suppresses the skin CMI response (Basso, Depiante-Depaoli, Cancela & Molina, 1993; Dhabhar & McEwen, 1997). A chronic stress-induced decrease in leukocyte mobilization from the blood to other body compartments is thought to be one of the mediators of this stress-induced suppression of skin CMI (Dhabhar & McEwen, 1997). Similarly, in human and animal studies, chronic stress has also been shown to suppress different immune parameters, examples of which include CMI (Basso et al., 1993; Kelley, Greenfield, Evermann, Parish & Perryman, 1982), antibody
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production (Edwards & Dean, 1977; Fleshner, Laudenslager, Simons & Maier, 1989), NK activity (Bartrop, Lazarus, Luckhurst, Kiloh & Penny, 1977; Cheng, Morrow-Tesch, Beller, Levy & Black, 1990; Irwin et al., 1990; Kiecolt-Glaser, Garner, Speicher, Penn, Holliday & Glaser, 1984), leukocyte proliferation (Bartrop et al., 1977; Cheng et al., 1990; Regnier & Kelley, 1981), skin homograft rejection (Wistar & Hildemann, 1960), virus-specific T-cell and NK cell activity (Bonneau, Sheridan, Feng & Glaser, 1991), and anti-mycobacterial activity of macrophages from susceptible mouse strains (Brown & Zwilling, 1994). Interestingly, recent studies have shown accelerated blood leukocyte telomere shortening in response to life stress, indicating that chronic stress may accelerate leukocyte aging (Epel, Blackburn, Lin, Dhabhar, Adler, Morrow & Cawthon, 2004).
A. Stress-induced Increase in Susceptibility to Infections or Cancer In addition to suppressing different immune parameters, human as well as animal studies have shown that chronic stress increases susceptibility to the common cold (Cohen et al., 1991) and to infection with viruses such as influenza (Sheridan, 1998), and bacteria such as Toxoplasma (Chao, Peterson, Filice, Pomeroy & Sharp, 1990) and Salmonella (Edwards & Dean, 1977). It has been suggested that stress may also increase susceptibility to cancer (Andersen, Farrar, GoldenKreutz, Kutz, MacCallum, Courtney & Glaser, 1998; Ben Eliyahu et al., 1991; Brenner, Cohen, Ader & Moynihan, 1990). Similarly, chronic stress has been shown to delay wound healing (Marucha et al., 1998) and to impair the immune response to vaccination (Glaser, Kiecolt-Glaser, Bonneau, Malarkey, Kennedy & Hughes, 1991; Kiecolt-Glaser et al., 1996).
B. Stress-induced Amelioration of Autoimmune Disease If chronic stress suppresses immune function and increases susceptibility to infectious disease and cancer, it may also be hypothesized that under these conditions, stress should ameliorate autoimmune or inflammatory diseases. Numerous studies have investigated the effects of environmental or psychological stress on autoimmune reactions. Levine, Strebel, Wenk, and Harman (1962) have demonstrated that the administration of prolonged restraint stress to rats before the induction of experimental allergic encephalomyelitis (EAE) resulted in a suppression of the incidence and severity of disease (Levine & Saltzman, 1987). Rogers et al. (1980) have shown that exposure of rats to a
variety of stressors results in a marked suppression of the clinical and histological manifestations of type II collagen-induced arthritis. Similarly, Griffin et al. have demonstrated suppression of EAE by chronic stress (Griffin, Warren, Wolny & Whitacre, 1993). Thus, it is evident that under certain conditions, stress suppresses different immune parameters. While this increases susceptibility to infectious disease and cancer, it may also confer protection against autoimmune and pro-inflammatory diseases.
VII. IMMUNOENHANCING EFFECTS OF GLUCOCORTICOID HORMONES In contrast to the well-known immunosuppressive effects of glucocorticoids, several studies have revealed that glucocorticoid hormones also exert immunomodulating (for review, see Apolsky et al., 2000; Wilckens, 1995; Wilckens & DeRijk, 1997) and immunoenhancing effects (for review, see Jefferies, 1991; Spencer et al., 2001). In general, pharmacological concentrations of glucocorticoids exert immunosuppressive effects, whereas under different conditions, physiologic concentrations may exert immunomodulatory, immunoenhancing, or immunosuppressive effects. It is important to recognize that the source (natural vs. synthetic) and concentration (physiologic vs. pharmacologic) of glucocorticoid hormones, the effects of other physiologic factors (hormones, cytokines, and neurotransmitters), and the state of activation of an immune parameter (naive vs. activated leukocyte, early vs. late activation, etc.) are all important factors which ultimately determine the nature of the effects of glucocorticoids on a given immune response. Immunoenhancing effects of glucocorticoids are discussed below, whereas immunosuppressive effects are discussed in the following section.
A. Glucocorticoid-induced Enhancement of Cell-Mediated Immunity Acute stress-induced enhancement of skin CMI is mediated by adrenal stress hormones (Dhabhar & McEwen, 1999b). Adrenalectomy, which eliminates the glucocorticoid and epinephrine stress response, eliminated the stress-induced enhancement of skin CMI. Low dose corticosterone or epinephrine administration significantly enhanced skin CMI and produced a significant increase in T-cell numbers in lymph nodes draining the site of the CMI reaction (Dhabhar & McEwen, 1999b). Moreover, simultaneous administration of these two stress hormones produced an additive increase in the skin CMI response. These
34. Possible Explanations for Salubrious as Well as Harmful Effects
results showed that hormones released during an acute stress response may help prepare the immune system for potential challenges (e.g., wounding or infection) for which stress perception by the brain may serve as an early warning signal (Dhabhar & McEwen, 1999a).
B. Glucocorticoid-induced Enhancement of Humoral Immunity A permissive role for glucocorticoids in antibody production was described over 40 years ago. Several investigators reported that low levels of cortisol were a necessary factor in cell culture media in order to obtain in vitro antibody production (Ambrose, 1964; Halliday & Garvey, 1964). Moreover, glucocorticoids were determined to be the critical permissive component present in serum supplements of culture media, and it was suggested that variability in antibody production assays may be the result of variability of glucocorticoid content in different batches of serum (Halliday & Garvey, 1964). Under some conditions, glucocorticoids have been shown to shift the balance of an immune response towards humoral immunity (Daynes & Araneo, 1989; Gajewski et al., 1989; Mason, 1991; Mosmann & Coffman, 1989). Physiological doses of glucocorticoids have been shown to enhance immunoglobulin production by mitogen– (Grayson et al., 1981) and IL-4– (Wu et al., 1991) stimulated human lymphocytes in culture, and glucocorticoids have been shown to stimulate Bcell number and antibody production in vitro and in vivo (Fauci, Pratt & Whalen, 1977; Rusu & Cooper, 1975; Tuchinda, Newcomb & DeVald, 1972; for review, see Plaut, 1987). One possible mechanism by which glucocorticoids may enhance humoral immunity is by shifting the balance of an ongoing immune response towards a Th2 cytokine profile (Elenkov, 2004). Dexamethasone has been found to reduce IL-2 production and increase IL-4 production by mouse T-cells both in vitro and in vivo (Daynes & Araneo, 1989; Daynes, Dudley & Araneo, 1990). Low doses of cortisol have also been shown to stimulate IL-4 production by human peripheral blood mononuclear cells and human T-cell lines (Snijdewint, Kapsenberg, Wauben-Penris & Bos, 1995). Interestingly, the ubiquitous transcription factor Oct-1 and the B-cell-selective transcription factor Oct-2 are thought to be important for immunoglobulin gene expression, and activated glucocorticoid receptors have been found to interact with both of these factors in vitro (Wieland, Dobbeling & Rusconi, 1991). It is possible that glucocorticoids enhance antibody production by selectively inhibiting B-cells which are less
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efficient at producing antibody. Thus, high concentrations of glucocorticoids present in vitro during the early stages of B-cell stimulation can significantly suppress antibody production; however, even extremely high concentrations of glucocorticoids are not able to suppress antibody production once it has begun (Fauci et al., 1977). Similarly, B-cells that differentiate to produce antibody following in vitro mitogenic stimulation are more resistant to the lethal effects of high levels of glucocorticoids than are B-cells that do not produce antibody (Roess, Bellone, Ruh, Nadel & Ruh, 1982). It has also been proposed that glucocorticoidinduced enhancement of humoral immunity may be induced by glucocorticoid actions on monocytes and subsequently on T-cells rather than a direct effect on B-cells (Orson, Grayson, Pike, de Seau & Blaese, 1983).
C. Glucocorticoid-induced Enhancement of T-Cell Activation Studies examining the effects of corticosterone on T lymphocyte proliferation in vitro demonstrate an important mechanism by which corticosterone may mediate the enhancement of immune function (Wiegers et al., 1995). These studies have shown that during the early stages of T-cell activation, low levels of corticosterone potently enhance anti–T-cell receptor (TCR)– induced lymphocyte proliferation. Furthermore, they showed that corticosterone had to be present during the process of TCR activation in order to enhance the proliferative response. Other studies have suggested that low concentration corticosterone-induced enhancement of concanavalin A-stimulated mitogenesis of splenocytes from ADX animals may be mediated by the Type 1 or mineralocorticoid receptor (Wiegers et al., 1994). It has also been shown that low doses of corticosterone stimulate DNA synthesis in thymic lymphoblasts (Whitfield, MacManus & Gillan, 1973). Finally, it was shown that corticosterone increases Tcell responsiveness to IL-2 and proliferation under conditions of high cell densities in vitro, which mimic conditions that are likely to be found in lymph nodes in vivo (Wiegers, Stec, Klinkert, Linthorst & Reul, 2001). Thus, these in vitro studies indicate a possible mechanism by which stress and stress hormones may enhance immune function in vivo.
D. Glucocorticoid-induced Potentiation of Cytokine Function Several lines of evidence indicate that glucocorticoid stress hormones may act synergistically with cytokines to enhance specific immune reactions. Thus, while
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glucocorticoids inhibit the synthesis of cytokines under some conditions, they have also been shown to induce the release and potentiate the actions of cytokines under other conditions. For example, acute psychological stress has been shown to increase circulating TNF-α, IL-1β, and IL-10 levels in human subjects (Altemus et al., 2001), and acute stress increases circulating IL-1β and IL-6 in rodents (Mekaouche, Givalois, Barbanel, Siaud, Maurel, Malaval, Bristow, Boissin, Assenmacher & Ixart, 1994; Takaki, Huang, Somogyvari-Vigh & Arimura, 1994). Acute stress has also been shown to induce IL-18 mRNA (Conti, Jahng, Tinti, Son & Joh, 1997). Glucocorticoids have been shown to induce the production of migration inhibitory factor (MIF) (Calandra, Bernhagen, Metz, Spiegel, Bacher, Donnelley, Cerami & Bucala, 1995). Moreover, glucocorticoids synergistically enhance the induction of acute phase proteins by IL-1 and IL-6 (Baumann & Gauldie, 1994). Glucocorticoids similarly enhance the biological responses of other cytokines such as IL-2, gamma-interferon (IFN-γ), granulocyte colonystimulating factor (G-CSF), granulocyte macrophage colony-stimulating factor (GM-CSF), and oncostatin M (for review, see Wiegers & Reul, 1998). Using a liver perfusion model, Liao et al. have shown that direct administration of corticosterone at physiological doses stimulates the production of IL-6 and TNF-α (Liao, Keiser, Scales, Kunkel & Kluger, 1995). Synergistic interactions between glucocorticoids and cytokines may be mediated by glucocorticoidinduced upregulation of cytokine receptors on target cells as determined by increased cytokine binding or cytokine receptor mRNA expression. For example, glucocorticoid-induced TNF receptor (GITR) has been shown to promote survival and serve as a costimulatory receptor for T-cells (Esparza & Arch, 2005; Tone, Tone, Adams, Yates, Frewin, Cobbold & Waldmann, 2003), and glucocorticoids increase IL-1 binding to human peripheral blood B-cells (Akahoshi, Oppenheim & Matsushima, 1988) and to a glioblastoma cell line (Gottschall, Koves, Mizuno, Tatsuno & Arimura, 1991). Glucocorticoids also act synergistically with IFN-γ to induce high-affinity Fcγ receptors on human monocytic cell lines (Girard, Hjaltadottir, Fejes-Toth & Guyre, 1987; Warren & Vogel, 1985), and stress-induced increases in endogenous glucocorticoids also appear to facilitate the expression of low affinity Fcγ receptors on peritoneal macrophages (Kizaki, Oh-Ishi, Ookawara, Yamamoto, Izawa & Ohno, 1996). Similarly, glucocorticoids potentiate granulocyte macrophage-colony stimulating factorinduced expression of MHC class II molecules on human monocytes (Sadeghi, Hawrylowicz, Chernajovsky & Feldmann, 1992). Glucocorticoids also
increase GM-CSF binding to human monocytes (Hawrylowicz, Guida & Paleolog, 1994). This increased cytokine binding may mediate the potentiation of GM-CSF-induced expression of MHC class II molecules on human monocytes (Sadeghi et al., 1992). While some studies have reported that glucocorticoids inhibit IL-2 receptor expression in leukocytes (Arya, Wong-Staal & Gallo, 1984; Reed, Abidi, Alpers, Hoover, Robb & Nowell, 1986), one study indicates that the reduced IL-2 receptor expression is secondary to glucocorticoid suppression of IL-2 (Boumpas et al., 1991). In contrast, studies have found a stimulating effect of glucocorticoids on IL-2 induction of IL-2 receptor mRNA levels in several T-cell lines (Lamas, Sanz, Martin-Parras, Espel, Sperisen, Collins & Silva, 1993). Glucocorticoids have also been shown to upregulate IL-6 receptor binding and mRNA levels in epithelial and hepatoma cell lines (Snyers, DeWit & Content, 1990), and this may be a mechanism for the glucocorticoid potentiation of IL-6 induction of acute phase proteins in liver (Baumann & Gauldie, 1994).
E. Glucocorticoid-induced Increase in Resistance to Infection Administration of physiologic doses of glucocorticoids has been reported to enhance immunity and reduce the number of respiratory infections observed in patients with adrenocortical insufficiency (Jefferies, 1981). Interestingly, an increase in glucocorticoid dosage at the onset of symptoms of respiratory illness induced a disappearance of symptoms, which did not reappear upon return to normal maintenance doses (Jefferies, 1981). It has also been reported that resistance to infection with influenza virus was lower in patients with adrenal insufficiency and that glucocorticoid replacement increased resistance to disease (Skanse & Miorner, 1959). A similar increase in resistance to influenza has also been reported in patients without adrenal insufficiency (Jefferies, 1981; Mickerson, 1959), and it has been suggested that viral infection might temporarily impair ACTH secretion and thus necessitate glucocorticoid replacement (Mickerson, 1959). Beneficial effects of cortisone replacement in cases of mononucleosis have also been reported (Bender, 1967; Chappel, 1962). These studies show that in addition to enhancing specific immune parameters, glucocorticoid hormones may also enhance resistance to infectious agents in vivo. Importantly, there are numerous reports of local (Alani & Alani, 1972; Reitamo, Lauerma, Stubb, Kayhko, Visa & Forstrom, 1986; Wilkinson, 1994) or systemic (Murrieta-Aguttes, Michelen, Leynadier, Duarte-Risselin, Halpern & Dry, 1991; Peller & Bardana,
34. Possible Explanations for Salubrious as Well as Harmful Effects
1985; Rosenblum, 1982; Vidal, Tome, FernandexRedondo & Tato, 1994; Whitmore, 1995) reactions to corticosteroids. Given the above discussion, it is tempting to speculate that cases of exacerbation of inflammatory responses following glucocorticoid administration, which are often characterized as “corticosteroid hypersensitivity” (Wilkinson, 1994) or “pseudoallergic reactions” (Peller & Bardana, 1985), may occur because the ambient conditions (dosage and timing) favor a glucocorticoid-induced immunoenhancement rather than the desired immunosuppression.
VIII. IMMUNOSUPPRESSIVE EFFECTS OF GLUCOCORTICOID HORMONES It was the immunosuppressive effects of glucocorticoid hormones that led Philip Hench and Edward Kendall to the Nobel Prize in 1950, which was awarded for their discovery of the use of corticosteroids in the treatment of autoimmune disease (Hench, 1952; Hench, Kendall, Slocumb & Polley, 1949). Hench observed that patients suffering from autoimmune diseases showed recovery from these diseases during periods of other illnesses such as hepatitis. He postulated that the inflammatory response accompanying the nonautoimmune disease was stimulating the production of an endogenous immunosuppressive mediator that was responsible for inhibiting the autoimmune disease. Together with Kendall, he determined that the cortisol was that endogenous mediator, and their finding revolutionized the treatment of autoimmune disease and a host of other inflammatory disorders. Since that time, glucocorticoid hormones have been widely used as immunosuppressive agents in various clinical and experimental situations (for review, see Fauci, 1979; Goldstein, Bowen & Fauci, 1992; Marx, 1995; Schleimer et al., 1989). As stated previously, pharmacological concentrations of glucocorticoids exert immunosuppressive effects, whereas under different conditions, physiologic concentrations may exert modulatory, enhancing, or suppressive effects on immune function (Dhabhar & McEwen, 2001; Pruett, 2001; Sapolsky et al., 2000; Schwab, Fan, Zheng, Myers, Hebert & Pruett, 2005; Straub & Besedovsky, 2003; Straub et al., 2005). It is important to recognize that the source (natural vs. synthetic) and concentration (physiologic vs. pharmacologic) of glucocorticoid hormones, the effects of other physiologic factors (hormones, cytokines, and neurotransmitters), and the state of activation of an immune parameter (naive vs. activated leukocyte, early vs. late activation, etc.) are all important factors
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which may ultimately determine the nature of the effects of glucocorticoids on a given immune response (Dhabhar & McEwen, 2001). For example, as discussed previously, Dhabhar and McEwen have shown that ADX eliminated the stress-induced enhancement of skin CMI (Dhabhar & McEwen, 1999b). Low-dose corticosterone or epinephrine administration to ADX animals significantly enhanced skin CMI and produced a significant increase in T-cell numbers in lymph nodes, draining the site of the CMI reaction. In contrast, high-dose corticosterone, chronic corticosterone, or low-dose dexamethasone administration significantly suppressed skin CMI (Dhabhar & McEwen, 1999b).
A. Immunosuppression by Pharmacologic Doses of Glucocorticoids Several books and articles have extensively reviewed the anti-inflammatory or immunosuppressive effects of glucocorticoid hormones (Cupps & Fauci, 1982; Fauci, 1979; Goldstein et al., 1992; Haynes, 1990; Marx, 1995; Munck et al., 1984; Munck & Guyre, 1989; Sapolsky et al., 2000; Schleimer et al., 1989). It is apparent from these reviews that under specific conditions glucocorticoids have been shown to suppress immunoglobulin, prostaglandin, leukotriene, histamine, and cytokine production; neutrophil superoxide production; macrophage function; mitogen- and antigen-induced lymphocyte proliferation; lymphocyte differentiation; NK cell activity; and leukocyte migration and activation. Due to their potently immunosuppressive actions, glucorticoids are widely used in the clinic as anti-inflammatory agents (Haynes, 1990; Schleimer et al., 1989). Given that the immunosuppressive actions of pharmacologic treatments with glucocorticoids have been reviewed extensively in the literature, here we will focus mainly on immunosuppressive actions of physiologic changes in glucocorticoid hormones.
B. Physiological Changes in Glucocorticoid Levels Have Protective Immunosuppressive Effects It has been hypothesized that an important physiologic role of endogenous glucocorticoids might be to suppress an ongoing immune response so as to prevent it from reaching levels of reactivity, which might cause damage to self (Munck et al., 1984; Sternberg, Hill, Chrousos, Kamilaris, Listwak, Gold & Wilder, 1989; Sternberg & Wilder, 1989; Webster, Tonelli & Sternberg, 2002). Strong support for this hypothesis comes from studies which show that adrenalectomized
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rats die within 24–48 hours after being immunized with horse serum or Freund’s complete adjuvant (FCA), but they can be rescued by corticosterone replacement therapy (Dougherty, 1949; Dougherty, 1950). A number of studies involving animal models of inflammatory disorders and autoimmune disease also lend support for this hypothesis (Mason, 1991). These studies have demonstrated the existence of a negative feedback loop between the immune system and the HPA axis, such that pro-inflammatory mediators arising from an ongoing immune reaction stimulate the HPA axis (Besedovsky, Del Ray, Sorkin & Dinarello, 1986; Kroemer, Brezinschek, Faessler, Schauenstein & Wick, 1988; Munck et al., 1984; Sapolsky, Rivier, Yamamoto, Plotsky & Vale, 1987), which in turn results in the secretion of corticosterone which suppresses the immune response and prevents it from potentially damaging the host. The protective effects of immunosuppression by endogenous glucocorticoids are discussed below.
C. Glucocorticoid-induced Immunosuppression: Protection against Sepsis Studies have shown that endogenous glucocorticoids play a crucial role in containing an inflammatory response and preventing it from becoming systemic and leading to septic shock. It has been known for over 75 years that adrenalectomized animals are sensitive to the lethal effects of various inflammatory agents, such as diphtheria toxin, typhoid vaccine, bacterial infection, foreign cells, and foreign serum (for review, see Swingle & Remington, 1944). Moreover, it has been shown that the protective factor present in the adrenals is corticosterone. Thus, glucocorticoid administration to adrenalectomized animals protects them from inflammatory shock induced by endotoxin (LPS), cytokines such as IL-1 and TNF, carrageenin, superantigen (SEB), or cobra venom factor (Bertini, Bianchi & Ghezzi, 1988; Gonzalo, Gonzalez-Garcia, Martinez & Kroemer, 1993; Nakano, Suzuki & Oh, 1987; Nakano, Suzuki, Oh & Yamashita, 1986). Moreover, treatment of animals with the glucocorticoid receptor antagonist, RU486, induces susceptibility to these inflammatory agents to nearly the same extent as adrenalectomy (Fan, Gong, Wu, Zhang & Xu, 1994; Gonzalo et al., 1993; Laue, Kawai, Brandon, Brightwell, Barnes, Knazek, Loriaux & Chrousos, 1988; Lazar Jr., Duda & Lazar, 1992). Importantly, high doses of glucocorticoids are used to treat septic shock in humans, although their beneficial effects are controversial since sepsis may require glucocorticoid administration too early in the disease process to be practically useful (Cohen & Glauser,
1991). Glucocorticoids are thought to protect against sepsis by inhibiting toxin-induced increases in cytokines such as IL-1 and TNF (Beutler, Krochin, Milsark, Luedke & Cerami, 1986; Lee, Tsou, Chan, Thomas, Petrie, Eugui & Allison, 1988), which are known to mediate early events leading to sepsis (Dinarello & Wolff, 1993). Interestingly, endotoxin treatment also induces a rise in plasma corticosterone (Nakano et al., 1987), which coincides with a decrease in plasma TNF (Zuckerman, Shelhaas & Butler, 1989). Moreover, adrenalectomy or RU486 treatment increases the amount and duration of TNF induction in response to LPS, further supporting a role for corticosterone in suppressing the endogenous production of proinflammatory cytokines following endotoxin exposure (Lazar Jr. et al., 1992; Zuckerman et al., 1989). In addition to suppressing the production of proinflammatory cytokines, glucocorticoids are also thought to protect against septic shock by inhibiting the actions of these cytokines by inhibiting the production of factors such as eicosanoids, histamine, plateletactivating factor, and nitric oxide (Bertini et al., 1988; Radomski, Palmer & Moncada, 1990; Williams & Yarwood, 1990).
D. Glucocorticoid-induced Immunosuppression: Protection against Autoimmune Disease Evidence suggests that three contributing factors result in susceptibility to inflammatory and autoimmune disorders (Mason, 1991; Sternberg, 1995; Tsigos & Chrousos, 1994; Wick, Sgonc & Lechner, 1998): First is the presence of host immune response genes, which carry the potential for contributing to autoimmunity. Second is exposure to a pro-inflammatory or antigenic challenge that initiates the cascade of immune reactions which ultimately result in autoimmunity. Third, there is a deficiency in the hypothalamicpituitary-adrenal (HPA) axis such that it is not capable of mounting an appropriate immunosuppressive corticosterone response in reaction to an ongoing immune reaction. Numerous studies have elegantly investigated the role played by the HPA axis in protecting the host from autoimmune reactions, and some of these studies are discussed below. Interestingly, while most studies examining the effects of stress on immune function have shown stress to be immunosuppressive, an impressive body of work has clearly laid out the yin-yang relationships between physiological stress responses and regulation of immune function. These studies have shown that dysregulated stress reactivity can also have harmful consequences, resulting in increased susceptibility to
34. Possible Explanations for Salubrious as Well as Harmful Effects
autoimmune and pro-inflammatory disorders (Harbuz, Chover-Gonzalez & Jessop, 2003; Harbuz, Conde, Marti, Lightman & Jessop, 1997; Mason, MacPhee & Antoni, 1990; Sternberg, 2001; Sternberg, Chrousos, Wilder & Gold, 1992; Tonelli, Webster, Rapp & Sternberg, 2001; Webster et al., 2002). In a series of seminal studies, Sternberg, Hill et al. (1989) showed that decreased HPA axis reactivity to inflammatory stimuli results in increased susceptibility to experimental arthritis (Sternberg, Glowa, Smith, Calogero, Listwak, Aksentijevich, Chrousos, Wilder & Gold, 1992; Sternberg, Hill et al., 1989; Sternberg, Young, Bernadini, Calogero, Chrousos, Gold & Wilder, 1989). A similar role for HPA axis-mediated endogenous immunoregulation has been shown for development of autoimmune thyroiditis, lupus erythematosus, and avian scleroderma in Obese strain (OS) chickens (Wick et al., 1998) and experimental autoimmune encephalomyelitis in rats (Whitacre, Dowdell & Griffin, 1998). Sternberg et al. have investigated the influence of the HPA axis on the development of streptococcal cell wall (SCW)-induced arthritis in female rats belonging to the genetically related Lewis/N (LEW/N) and Fischer 344/N (F344/N) strains (Sternberg, Hill et al., 1989; Sternberg, Young et al., 1989; Sternberg & Wilder, 1989; Webster et al., 2002). The F344/N strain is resistant to the development of SCW-induced arthritis, whereas the LEW/N strain is susceptible. Interestingly, the F344/N strain mounts a significantly greater corticosterone and adrenocorticotropin (ACTH) response than the LEW/N strain when challenged with a variety of stressors or with inflammatory mediators like SCW peptidoglycan polysaccharide or interleukin-1α (IL-1α) (Sternberg, Hill et al., 1989; Sternberg, Young et al., 1989; Dhabhar et al., 1993; Dhabhar et al., 1995a); and compared to the F344 strain, the Lewis strain shows a significantly greater habituation or adaptation to an acute or chronic stressor (Dhabhar, McEwen & Spencer, 1997). F344/N rats treated with the glucocorticoid receptor antagonist, RU486, are rendered susceptible to SCW-induced arthritis, indicating that they do carry the immune response genes with potential for triggering autoimmunity (Sternberg, Hill et al., 1989; Sternberg, Young et al., 1989). Conversely, LEW rats treated with pharmacologic doses of dexamethasone become completely resistant to the development of SCW-induced arthritis (Sternberg, Hill et al., 1989; Sternberg, Young et al., 1989). Furthermore, compared to Fischer 344 (F344) rats, adrenal steroid receptors in neural and immune tissues of Lewis (LEW) rats show a significantly lower magnitude of activation in response to stress-induced increases in plasma corticosterone (Dhabhar et al., 1993; Dhabhar et al., 1995a). Thus, strain differences in
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plasma corticosterone levels are also manifest as significant differences in the extent of activation of corticosterone receptors in target tissues. Experimental allergic encephalomyelitis (EAE) is another animal model of an autoimmune disease in which a similar immunosuppressive role for the HPA axis has been proposed (for review, see Mason et al., 1990; Mason, 1991; Whitacre et al., 1998). The Lewis strain shows a greater susceptibility to EAE (Mason, 1991). MacKenzie et al. (1989) have suggested that during the pre-clinical phase of EAE, elevations in plasma corticosterone may regulate the lymphoproliferative stage of the disease, and that during the clinical phase of the disease, elevations in plasma corticosterone as well as splenic norepinephrine may regulate other recovery-oriented immune mechanisms (MacKenzie, Leonard & Cuzner, 1989). Similar correlations between HPA axis hyporeactivity and susceptibility to autoimmune disease have been observed for autoimmune conditions in chickens (Wick et al., 1998) and mice (Lechner, Hu, Jafarian-Tehrani, Dietrich, Schwarz, Herold, Haour & Wick, 1996). Complementing these pre-clinical studies, a series of elegantly conducted clinical studies (BuskeKirschbaum & Hellhammer, 2003; Torpy & Chrousos, 1996) has shown that patients with atopic dermatitis (Buske-Kirschbaum, Geiben & Hellhammer, 2001; Buske-Kirschbaum, Jobst & Hellhammer, 1998; BuskeKirschbaum, Jobst, Psych, Wustmans, Kirschbaum, Rauh & Hellhammer, 1997) and asthma (BuskeKirschbaum, von Auer, Krieger, Weis, Rauh & Hellhammer, 2003) show decreased reactivity of their HPA axes. Studies of pediatric rheumatic diseases suggest a similar HPA axis deficiency coupled with other pro-inflammatory hormonal biases (Chikanza, Kuis & Heijnen, 2000). Differences in NK cell stress reactivity and beta(2)-adrenorecptor upregulation on PBMC have been observed in patients with systemic lupus erythematosus (Pawlak, Jacobs, Mikeska, Ochsmann, Lombardi, Kavelaars, Heijnen, Schmidt & Schedlowski, 1999). A more complex role for sympathetic nervous system involvement in autoimmune disease has also been proposed (Kavelaars, de Jong-de Vos van Steenwijk, Kuis & Heijnen, 1998; Kuis, de Jong-de Vos van Steenwijk, Sinnema, Kavelaars, Prakken, Helders & Heijnen, 1996).
E. Glucocorticoid-induced Suppression of Pro-inflammatory and Autoimmune Reactions Glucocorticoid hormones may exert their protective immunosuppressive effects by inhibiting the production or actions of pro-inflammatory molecules, as
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discussed previously. In addition, it has been hypothesized that glucocorticoids may suppress certain autoimmune reactions by inducing a shift towards a Th2 or humoral immune response (Chrousos, 2000; Elenkov, 2004; Mason, 1991; Mason et al., 1990). For example, stimulation of the HPA axis by inflammatory mediators released during the initiation of an autoimmune response results in increased plasma corticosterone. Increased corticosterone levels may shift the balance of the ongoing immune reaction from a Th1directed (cell-mediated) response towards a Th2directed (antibody-mediated) response, by promoting the production of IL-4 and suppressing the production of IL-2 (Daynes & Araneo, 1989). Since the pathology associated with EAE is thought to be the result of activation of T-cells auto-reactive with peptide fragments of myelin basic protein (Steinman, 1991), the net result of this shift from cell-mediated to humoral immunity could be the suppression of EAE. Griffin et al. have shown that chronic stress administered to Lewis rats before MBP challenge resulted in suppression of the clinical and histopathologic changes associated with EAE. However, the same stress regimen had no effect on the clinical course of EAE in rats challenged with MBP peptide fragment 68–88 (MBP 68–88), suggesting that the stress-induced increase in corticosterone could be affecting mechanisms involved in processing and/ or presentation of the encephalitogen. Importantly, a decrease in frequency of MBP-reactive cells and a decrease in production of IL-2 and IFN-γ (i.e., a condition which would favor a humoral immune response) was observed in stressed animals relative to controls. Antibodies directed against the encephalitogen, MBP, may be involved in the suppression of EAE since it has been reported that anti-MBP antibodies are first detected at the beginning of the refractory phase after plasma corticosterone levels rise in response to the initial phase of EAE (MacPhee, Day & Mason, 1990). Further, it has been observed that symptoms in the initial phase of the disease are minimal if an animal makes an anti-peptide antibody response during the early stages of EAE. If Lewis rats are immunized with different doses of MBP peptide linked to bovine serum albumin (BSA), recipients of low doses make fewer anti-peptide antibodies and show severe clinical symptoms, the converse being true for recipients of high doses (Mason, 1991). It is also possible that part of the mechanism of suppression may involve the generation of anti-idiotypic antibodies directed against variable regions of autoreactive T-cell receptors. Interestingly, in the case of myasthenia gravis, an autoantibody-mediated disease in humans, early investigators found that intensive treatment of patients with steroids exacerbated the symptoms. Therefore,
the current treatment regimen involves a short initial intensive treatment followed by alternate-day steroid therapy. Improvement is observed 10–15 days after the beginning of therapy (Claman, 1989). It may be hypothesized that during the initial period of steroid treatment, the promotion of an antibody-biased response by steroid treatment might exacerbate the disease by stimulating autoantibody production. However later during steroid treatment, the production of inhibitory antibodies or the activation of other immunosuppressive mechanisms might result in suppression of the disease. Alternatively, as discussed earlier in this chapter, glucocorticoid treatment may under certain conditions stimulate other immune parameters such as innate immunity, antigen presentation, cell-mediated immunity, or effector cell function. This may in turn exacerbate an autoimmune disease if the enhanced response were directed against self-antigens. Wilder et al. (1986) have demonstrated an increase in expression of class II major histocompatibility antigen (Ia) in synovial tissues, which parallels the development of SCW-induced arthritis. This increase is observed in the susceptible Lewis strain, but not in the resistant F344 strain (Wilder, Allen & Hansen, 1986). Doeberitz et al. (1990) have shown that longterm treatment with dexamethasone reduces surface expression, membrane-bound protein, and mRNA of class I major histocompatibility antigen on human epithelial cells (Doeberitz, Koch, Drzonek & Hausen, 1990). Since strain differences in the ability to mount a corticosterone response to immune challenge are thought to be responsible for the strain differences in resistance to SCW-induced arthritis, it may be hypothesized that glucocorticoids may play a role in preventing the immunostimulatory upregulation of Ia expression. A role for HPA axis interactions with macrophage differentiation has also been proposed as a mediator of susceptibility to autoimmune disease (Damoiseaux, Huitinga, Dopp & Dijkstra, 1992). Recent evidence suggests that corticotropinreleasing hormone (CRH) produced in peripheral inflammatory sites might stimulate inflammatory reactions at these sites (Karalis, Sano, Redwine, Listwak, Wilder & Chrousos, 1991). CRH has been shown to stimulate numerous immune functions. Stephanou et al. (1990) have demonstrated CRH mRNA and immunoreactivity in human leukocytes, and CRHbinding sites have also been observed on leukocytes (Singh & Fudenberg, 1988; Stephanou, Jessop, Knight & Lightman, 1990). Importantly, Karalis et al. (1991) have shown that administration of antiserum to CRH significantly suppresses inflammatory exudate volume and cell concentration in a model involving carrageenin-induced aseptic inflammation. Further, the
34. Possible Explanations for Salubrious as Well as Harmful Effects
same authors have shown that glucocorticoids inhibit the production of immune CRH. Thus, it might be hypothesized that part of the immunosuppressive actions of glucocorticoids may involve suppression of CRH production at sites of inflammation. One of the best known effects of glucocorticoids on the immune system is their ability to kill leukocytes. Glucocorticoids have been shown to mediate this effect through two mechanisms: apoptosis or programmed cell death, and cell lysis. While there is a considerable amount of evidence showing that apoptosis is induced by physiological concentrations of glucocorticoids in vivo, non-specific leukocyte lysis is thought to be the result of exposure to pharmacologic concentrations of glucocorticoids (Godlowski, 1952; Muehrcke, Lewis & Kark, 1952; Padawer & Gordon, 1952). Glucocorticoidinduced apoptosis of immune cells is thought to occur through the activation of genes which specifically regulate programmed cell death. It has been shown that mRNA and protein synthesis are both required in order for the apoptotic program to be executed since agents like actinomycin D, emetine, and cyclohexamide significantly inhibit glucocorticoid-induced apoptosis (Cohen & Duke, 1984; Thomas, Edwards & Bell, 1981; Wyllie, Morris, Smith & Dunlop, 1984). It is believed that glucocorticoids stimulate the expression of a protein or a group of proteins, which in turn execute the apoptotic program (Cohen, 1989). The proteins induced by glucocorticoids are not thought to be directly lethal to the cell but are thought to act through other intermediaries to effect cell death (Cohen, 1989). Other molecular mechanisms have been proposed for glucocorticoid-mediated immunosuppression (Barnes & Adcock, 1993; Sapolsky et al., 2000). Glucocorticoids are thought to inhibit the actions of nuclear factor kappa B (NF-κB), a transcription factor which activates a number of genes coding for various immunoregulatory molecules, cytokines, and adhesion molecules (May & Ghosh, 1998). Glucocorticoid inhibition of NF-κB is achieved through glucocorticoid induction of a negative regulator of NF-κB, IκBα, which by binding NF-κB prevents the induction of genes for pro-inflammatory molecules (Auphan, DiDonato, Rosette, Helmberg & Karin, 1995; Scheinman, Cogswell, Lofquist & Baldwin, 1995). AP-1 (e.g., FosJun heterodimer) is another transcription factor which stimulates a variety of pro-inflammatory molecules (Park, Kaushansky & Levitt, 1993; Serfling, Barthelmas, Pfeuffer, Schenk, Zarius, Swoboda, Mercurio & Karin, 1989). Activated glucocorticoid receptors have been shown to directly bind and interfere with the function of both AP-1 (Schule & Evans, 1991) and NF-κB (Caldenhoven, Liden, Wissink, Van de Stolpe, Raaijmakers, Koenderman, Okret, Gustafsson & Van
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der Saag, 1995; Mukaida, Morita, Ishikawa, Rice, Okamoto, Kasahara & Matsushima, 1994; Scheinman et al., 1995). Thus, glucocorticoids may exert their immunosuppressive effects by directly inhibiting the actions of activational transcription factors and by indirect inhibition through the induction of negative modulators of these transcription factors. Glucocorticoids may also directly regulate genes for certain immune mediators. For example, DNA regions with moderate homology to the consensus glucocorticoid response element (GRE) have been identified in the promoter region of the IL-6 gene, and footprinting studies suggest that activated glucocorticoid receptors bind to regulatory regions of this gene (Ray, LaForge & Seghal, 1990). Glucocorticoids may also inhibit certain immune molecules by reducing mRNA stability. This has been demonstrated for IL-1β mRNA levels following in vitro dexamethasone administration (Amano, Lee & Allison, 1993; Lee et al., 1988).
IX. INDIVIDUAL DIFFERENCES IN HPA-AXIS REACTIVITY—EFFECTS ON RESISTANCE TO AUTOIMMUNE DISEASE, INFECTION, AND CANCER The discussion above illustrates that HPA axisinduced immunosuppression can provide beneficial protection from autoimmune reactions. Strains of animals that show a robust HPA axis response to environmental stress and immune challenge are relatively resistant to autoimmune disease even if they carry potentially autoreactive immune response genes and are exposed to antigens capable of inducing an autoimmune reaction. However, one might hypothesize that a robust HPA axis response that confers protection against autoimmune disease via immunosuppression might result in greater susceptibility to infectious diseases and cancer, which require a strong and active immune response for their elimination. The significantly lower corticosterone response to stress and immune challenge observed in LEW rats compared to F344 rats (Dhabhar et al., 1993; Sternberg, Hill, et al., 1989; Sternberg et al., 1992; Sternberg & Wilder, 1989), the significantly greater adaptation to acute or chronic stress observed in LEW rats (Dhabhar et al., 1997), and the significantly lower activation of adrenal steroid receptors seen in immune tissues of Lewis rats (Dhabhar et al., 1993; Dhabhar et al., 1995a) may contribute to the increased susceptibility of the Lewis strain to autoimmune diseases. However, these conditions might also serve to protect this strain from diseases like viral or bacterial infections and cancer, which require an active immune response for their
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elimination. In contrast, the substantially higher levels of corticosterone (which result in greater activation of adrenal steroid receptors in immune tissues) of F344 rats may protect them from autoimmune diseases but may also be responsible for the reported susceptibility of this strain to diseases like cancer. A similar example is seen in differences between BALB/c and C57/BL mice in their ability to resist Leishmania major (Mason, 1991). The BALB/c strain is susceptible to infection, whereas the C57/BL strain is resistant. Compared to C57/BL mice, BALB/c mice show a more robust corticosterone response to stress. It has been hypothesized that the stronger corticosterone response induced by infection in BALB/c mice results in a bias towards a Th2-directed, humoral immune response, which results in susceptibility to infection (Mason, 1991). In contrast, the lower corticosterone response of C57/BL mice favors a Th1-directed, cell-mediated response, which confers resistance to the parasite. Importantly, administration of anti–IL-4 antibody to L. major–infected BALB/c mice confers resistance to further infection, suggesting that IL-4–mediated suppression may be responsible for susceptibility of the BALB/c strain to the parasite. Thus, intrinsic differences in the ability of the HPA axis to respond to stressful stimuli and immunologic challenge may translate into differences in the ability to resist autoimmune or infectious diseases and cancer. These differences are clearly observed as species or strain differences, but they may also contribute significantly to individual differences within strains in relative susceptibility or resistance to disease. Such individual differences are especially relevant for outbred populations like those of humans. It may be hypothesized that individuals who show a low HPA axis responsivity may be relatively susceptible to autoimmune diseases but resistant to infectious diseases and cancer. For example, Buske-Kirschbaum et al. have conducted a series of elegantly clinical studies (Buske-Kirschbaum & Hellhammer, 2003) showing that patients with atopic dermatitis (BuskeKirschbaum et al., 1997; Buske-Kirschbaum et al., 1998; Buske-Kirschbaum et al., 2001) and asthma (BuskeKirschbaum et al., 2003) show decreased reactivity of their HPA axes. Similarly, individuals who show a high HPA axis responsivity may be relatively resistant to autoimmune diseases but susceptible to infectious diseases and cancer. Thus, while genetic factors acting at the level of the immune system may render an individual susceptible to a certain disease, genetic and/or environmental factors acting at the level of the neuroendocrine system may be able to compensate for the immune defect and confer protection upon susceptible individuals.
X. FACTORS THAT DETERMINE WHETHER STRESS WILL ENHANCE OR SUPPRESS IMMUNE FUNCTION Based on the above discussion, we suggest that four key parameters may influence the direction (enhancing vs. suppressive) of the effects of stress or glucocorticoid hormones on a given immune measure: (1) the effects of stress or glucocorticoids on leukocyte distribution in the body; (2) the differential effects of acute versus chronic stress (or acute vs. chronic exposure to glucocorticoids) on immune function; (3) the differential effects of physiologic versus pharmacologic doses of glucocorticoids and the differential effects of endogenous (e.g., cortisol, corticosterone) versus synthetic (e.g., dexamethasone) glucocorticoids; (4) the timing of stressor or glucocorticoid hormone exposure relative to the time course of the immune response. It is important to recognize that factors such as gender, genetics, age, route of administration, nature of the immunizing antigen, and time of day may also affect the relationship between stress and immune function.
A. Stress or Glucocorticoid-induced Redistribution of Leukocytes May Determine Immunoenhancement versus Immunosuppression Numerous studies examining the effects of stress or glucocorticoid hormones on immune function have focused on the effects of these factors on immune function measured in in vitro cytotoxicity and proliferation assays. However, one of the most underappreciated aspects of the interaction between stress, glucocorticoid hormones, and the immune system is the effect of glucocorticoids on leukocyte distribution. It is important to note that such changes in leukocyte distribution may mediate many of the effects of stress and glucocorticoids on immune function. 1. A Redistribution of Blood Leukocytes May Represent an Adaptive Response Dhabhar et al. were the first to propose that a stressinduced decrease in blood leukocyte numbers may represent an adaptive response (Dhabhar, 1998; Dhabhar et al., 1994; Dhabhar et al., 1996; Dhabhar & McEwen, 1996; Dhabhar & McEwen, 1997; Dhabhar & McEwen, 1999b). These authors suggested that such a decrease in blood leukocyte numbers may represent a redistribution of leukocytes from the blood to other organs such as the skin, mucosal lining of gastrointestinal and urinary-genital tracts, lung, liver, and lymph nodes, which may serve as potential “battle
34. Possible Explanations for Salubrious as Well as Harmful Effects
stations” should the body’s defenses be breached. They have also suggested that such a leukocyte redistribution may enhance immune function in those compartments to which leukocytes traffic during stress (Dhabhar et al., 1994; Dhabhar et al., 1996; Dhabhar & McEwen, 1996; Dhabhar & McEwen, 1997; Dhabhar & McEwen, 1999b). Thus, an acute stress response may direct the body’s “soldiers” (leukocytes) to exit their “barracks” (spleen, lung, other organs), travel the “boulevards” (blood vessels), and take position at potential “battle stations” (skin, lining of gastro-intestinal and urinary-genital tracts, lymph nodes) in preparation for immune challenge (Dhabhar et al., 1994; Dhabhar et al., 1996; Dhabhar & McEwen, 1996; Dhabhar & McEwen, 1997). In addition to “redeploying” leukocytes to potential “battle stations,” stress hormones may also better equip them for “battle” by enhancing processes like antigen presentation, phagocytosis, and antibody production. Thus, a hormonal alarm signal released by the brain upon detecting a stressor may “prepare” the immune system for potential challenges (wounding or infection) which may arise due to the actions of the stress-inducing agent (e.g., a predator or attacker). The cellular and molecular mechanisms mediating these effects of stress and stress hormones on immune function merit further investigation. 2. Leukocyte Redistribution and the Interpretation of Experimental Data When one interprets data showing stress-induced changes in functional assays such as lymphocyte proliferation or NK activity, it may be important to bear in mind the effects of stress on the leukocyte composition of the compartment in which an immune parameter is being measured. For example, it has been shown that acute stress induces a redistribution of leukocytes from the blood to the skin and that this redistribution is accompanied by a significant enhancement of a skin CMI response (Dhabhar & McEwen, 1996; Dhabhar & Viswanathan, 2005; Viswanathan et al., 2005; Viswanathan & Dhabhar, 2005). In what might appear to be contradicting results, acute stress has been shown to suppress splenic and peripheral blood responses to Tcell mitogens (Cunnick, Lysle, Kucinski & Rabin, 1990; Monjan & Collector, 1977; Shurin et al., 1994; Weiss, Schleifer, Miller & Stein, 1981) and splenic IgM production (Zalcman & Anisman, 1993). However, it is important to note that in contrast to the skin, which is enriched in leukocytes during acute stress, peripheral blood and spleen are relatively depleted of leukocytes during acute stress (Dhabhar, 1996; Dhabhar, 1998; Keller, Schleifer, Liotta, Bond, Farhoody & Stein, 1988);
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this stress-induced decrease in blood and spleen leukocyte numbers may contribute to the acute stressinduced suppression of immune function in these compartments. In contrast to acute stress, chronic stress has been shown to suppress skin CMI, and a chronic stress-induced suppression of blood leukocyte redistribution is thought to be one of the factors mediating the immunosuppressive effect of chronic stress (Dhabhar & McEwen, 1997). Again, in what might appear to be contradicting results, chronic stress has been shown to enhance mitogen-induced proliferation of splenocytes (Monjan & Collector, 1977) and splenic IgM production (Zalcman & Anisman, 1993). However, the spleen is relatively enriched in T-cells during chronic glucocorticoid administration, suggesting that it may also be relatively enriched in T-cells during chronic stress (Miller et al., 1994), and this increase in spleen leukocyte numbers may contribute to the chronic stress-induced enhancement of immune parameters measured in the spleen. Similarly, the issue of leukocyte distribution and of the immune compartment being assayed may be important to bear in mind while interpreting data from other experimental or pharmacological treatments, such as nicotine administration, that have been shown to suppress immune responses. Caggiula et al. have shown that nicotine administration suppresses blood proliferative responses (Caggiula, McAllister, Epstein, Antelman, Knopf, Saylor & Perkins, 1992). An examination of their data reveals that nicotine administration induces a large magnitude corticosterone response (Caggiula et al., 1992). Thus, it is possible that the observed immunosuppressive effects of nicotine administration are mediated through a nicotineinduced rise in corticosterone, which induces a significant decrease in blood leukocyte numbers. 3. Leukocyte Redistribution: Functional Consequences It is also important to bear in mind that the heterogeneity of the stress-induced changes in leukocyte distribution implies that using equal numbers of leukocytes in a functional assay may not account for stressinduced changes in relative percentages of different leukocyte subpopulations in the cell suspension being assayed. For example, samples that have been equalized for absolute numbers of total blood leukocytes from control versus stressed animals may still contain significantly different numbers of specific leukocyte subpopulations (e.g., stress may alter the ratio between antigen-presenting cells or helper T-cells and effector T, B, and NK cells). Such changes in leukocyte composition may mediate the effects of stress even in
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functional assays using equalized numbers of leukocytes from different treatment groups. This possibility needs to be taken into account before concluding that a given treatment changes an immune parameter on a “per cell” rather than a “population” basis. Moreover, as discussed previously, a stress-induced redistribution of leukocytes from the blood to other compartments such as the skin may have significant consequences for immune function, with a decrease in functional parameters in the blood coinciding with an increase in the skin (Dhabhar & McEwen, 1996; Dhabhar & McEwen, 1997). 4. Circadian Changes in Blood Leukocyte Distribution: Similarity with the Effects of Stress Numerous investigators have reported that the circadian peak in blood corticosterone levels coincides with a circadian trough in peripheral blood lymphocyte numbers, and that the circadian trough in corticosterone levels coincides with a circadian peak in peripheral blood lymphocyte numbers. This rhythmicity has been shown in humans (Abo, Kawate, Itoh & Kumagai, 1981; Bartter, Delea & Halberg, 1962; Tavadia, Fleming, Hume & Simpson, 1975; Thompson, McMahon & Nugent, 1980), non-human primates (Morrow-Tesch et al., 1993), mice (Kawate, Abo, Hinuma & Kumagai, 1981), and rats (Dhabhar et al., 1994; Griffin & Whitacre, 1991). Furthermore, Thompson, McMahon, and Nugent (1980) have reported circadian variations in peripheral blood lymphocytes in healthy adults and have shown that patients with adrenal insufficiency lack this circadian pattern, and that administration of cortisol to these patients causes a dose-dependent lowering of lymphocyte levels in the blood (Thompson et al., 1980). In addition, Kawate et al. (1981) have demonstrated in mice that adrenalectomy abolishes the circadian rhythm in lymphocyte numbers and that a single injection of prednisolone produces a reversible depression of circulating lymphocyte number soon after drug administration (Kawate et al., 1981). Circadian changes in blood leukocyte distribution are similar in magnitude and in leukocyte subpopulation specificity to stress-induced changes, and they may have similar functional consequences (Dhabhar et al., 1994). For example, a study examining human T lymphocyte antigen responsivity to tetanus toxoid found that the T-cell proliferative response was lowest when corticosterone levels were at their circadian peak (Hiemke, Brunner, Hammes, Müller, Meyer Zum Büschenfelde & Lohse, 1995). These authors concluded that their studies, as well as other studies showing similar results (Eskola, Frey, Molnar & Soppi, 1976;
Kaplan, Byers, Levin, German, Fudenberg & Lecam, 1976), reflected a corticosteroid-induced circadian suppression of blood T lymphocytes. However, an alternate interpretation of their results could be proposed: The decrease in antigen-stimulated blood T-cell proliferation at the beginning of the active phase of the human circadian cycle may reflect the fact that those T-cells which were most capable of responding to the antigen had migrated from the bloodstream, redistributed to other compartments in the body, and hence were not available for assay. Normalizing total leukocyte numbers from different time-points in such a study still would not account for heterogeneity in the subpopulation composition of blood samples from different time-points (Dhabhar et al., 1994). Thus, while leukocyte emigration from the blood might result in an apparent immunosuppression in the blood, its overall effects might in fact be immunoenhancing, because the T-cells may have relocated to organs in the body where they might be more likely to encounter, and effectively deal with, the injected antigen. Moreover, as with stress, the organs to which leukocytes traffic at the beginning of the active period (glucocorticoid peak) may be areas such as the skin, certain lymph nodes, and the lining of the urinary-genital and gastro-intestinal tracts—organs which may serve as potential battle stations should the body’s defenses be breached. 5. Stress or Glucocorticoid-induced Redistribution of Leukocytes: An Important Mediator of Neuroendocrine-Immune Effects The above discussion is not intended to discount the fact that stress and stress hormones affect different immune parameters or susceptibility to infections and cancer independently of leukocyte trafficking. Such effects of stress and glucocorticoids are discussed below. However, the aim of the preceding discussion is to highlight the role of stress- and glucocorticoidinduced changes in leukocyte distribution as being important and underappreciated factors mediating the effects of stress on immune function and on the overall health of an organism.
B. Acute Stress Enhances While Chronic Stress Suppresses Immune Function (In Some Instances Stress-induced Changes in Leukocyte Distribution Need to Be Taken into Consideration) The studies described in this chapter show that acute stress can be immunoenhancing, while chronic stress can be immunosuppressive. These studies may help reconcile the apparent contradiction between
34. Possible Explanations for Salubrious as Well as Harmful Effects
reports showing that on the one hand stress suppresses immunity and increases susceptibility to infections and cancer, while on the other it exacerbates autoimmune diseases which should be ameliorated by a suppression of immune function. Under normal conditions, acute stress may serve a protective role by enhancing an immune response directed towards a wound, infection, or cancer. For example, acute stress significantly enhances a skin immune response (Dhabhar & McEwen, 1996; Dhabhar & McEwen, 1999b; Dhabhar & Viswanathan, 2005; Viswanathan et al., 2005; Viswanathan & Dhabhar, 2005). Moreover, administration of physiologic doses of glucocorticoids has been reported to enhance immunity and reduce the number of respiratory infections observed in patients with adrenocortical insufficiency (Skanse & Miorner, 1959; Jefferies, 1981). Interestingly, an increase in glucocorticoid dosage at the onset of symptoms of respiratory illness induced a disappearance of symptoms which did not reappear upon return to normal maintenance doses (Jefferies, 1981). It is important to note that while a stress-induced enhancement of immune function is beneficial in the case of infections or cancer, such an enhancement could also be detrimental if the immune response were directed against an innocuous (poison ivy, nickel in jewelry, latex, etc.) or autoimmunogenic antigen, and this could explain the wellknown stress-induced exacerbations of autoimmune and inflammatory disorders (Ackerman et al., 2002; Al’Abadie et al., 1994; Mei-Tal et al., 1970; Rimon & Laakso, 1985; Solomon & Moos, 1964; Thomason et al., 1992). In contrast to acute stress, chronic stress suppresses immune function. This may explain stressinduced exacerbation of infections and cancer (Ben Eliyahu et al., 1991; Cohen et al., 1991; Glaser, Pearl, Kiecolt-Glaser & Malarkey, 1994; Sheridan, 1998), and stress-induced suppression of wound healing (Marucha et al., 1998), and autoimmune reactions (Griffin et al., 1993; Levine, Strebel, Wenk & Harman, 1962; Rogers, Trentham, McCune, Ginsberg, Reich & David, 1979).
C. Bi-directional Effects of Glucocorticoid Hormones on Immune Function Studies of several physiologic systems have revealed a bi-directional regulatory role for glucocorticoids that consists of enhancing versus suppressive effects on key physiologic parameters (Korte, Koolhaas, Wingfield & McEwen, 2005; McEwen, 1998; Pruett, 2001; Sapolsky et al., 2000; Schwab et al., 2005). Low levels of glucocorticoids are generally permissive or stimulatory for a physiological process, whereas higher levels of glucocorticoids are inhibitory (Sapolsky et al.,
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2000). For example, low concentrations of glucocorticoids are permissive for normal growth and body weight gain, whereas high levels of glucocorticoids are catabolic and suppress feeding (Devenport, Thomas, Knehans & Sundstrom, 1990). In the central nervous system, low glucocorticoid levels positively regulate tryptophan hydroxylase function and thereby are a necessary permissive factor for the synthesis of serotonin (for review, see McEwen, de Kloet & Rostene, 1986). However, high levels of glucocorticoids suppress tryptophan hydroxylase function and may dampen the effects of serotonin secretion by downregulating serotonin receptor levels (Mendelson & McEwen, 1992). Similarly, low levels of glucocorticoids increase hippocampal neuronal excitability and enhance long-term potentiation, whereas higher levels of glucocorticoids inhibit these electrophysiological measures (Diamond, Bennett, Fleshner & Rose, 1992; Joels & de Kloet, 1992; Pavlides, Watanabe, Magarinos & McEwen, 1995). Low levels of glucocorticoids are also required for the survival of granule cell neurons in the adult rat dentate gyrus (Sloviter, Valiquette, Abrams, Ronk, Sollas, Paul & Nuebort, 1989; Woolley, Gould, Sakai, Spencer & McEwen, 1991); however, high levels of glucocorticoids can lead to atrophy and neuronal loss of nearby hippocampal pyramidal neurons (Sapolsky, 1987; Woolley, Gould & McEwen, 1990). A modulatory role for glucocorticoid hormones with respect to immune system function has been suggested (for review, see Jefferies, 1991; McEwen et al., 1997; McEwen, 1998; Munck & Naray-Fejes-Toth, 1992; Sapolsky et al., 2000; Spencer et al., 2001; Wilckens, 1995; Wilckens & DeRijk, 1997). This chapter has specifically discussed the bi-directional effects of glucocorticoid hormones on different immune parameters. We suggest that the stimulatory effects of glucocorticoids occur with relatively low levels of circulating hormone as is seen with other physiological systems, whereas the inhibitory effects predominate in the presence of high glucocorticoid levels. Such dose-response relationships have been described for bi-directional effects of corticosterone on skin CMI responses in vivo (Dhabhar & McEwen, 1999b), for bi-directional effects of glucocorticoids on immunoglobulin synthesis and secretion by human peripheral lymphocytes (Smith, Sherman & Middleton, 1972; Levo, Harbeck & Kirkpatrick, 1985), for the effects of hydrocortisone on human peripheral blood B-cell activation (Fauci et al., 1977), for glucocorticoid-induced proliferation versus apoptosis of thymocytes (Whitfield, MacManus & Rixon, 1970), and for bi-directional effects of corticosterone on T-cell mitogenesis (Wiegers et al., 1994) and macrophage phagocytosis (Forner, Barriga, Rodriquez
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& Ortega, 1995; Rhinehart, Sagone, Balcerzak, Ackerman & LoBuglio, 1975). We suggest that in general physiological changes in endogenous glucocorticoid hormones may help to enhance immune function and prepare the immune system to deal with challenges which may arise under conditions of stress. In contrast, physiological changes in glucocorticoids which involve prolonged HPA axis activation by an immune response may lead to prolonged exposure to endogenous glucocorticoids and exert an inhibitory effect on immune function, and even in those cases counter-regulation may preferentially spare the effector phase of specific immune responses.
D. Immunomodulatory Effects of Timing of Stress or Stress Hormone Administration Relative to the Course of an Immune Response Under certain conditions, physiological levels of endogenous glucocorticoids have immunoenhancing effects, while under other conditions similar hormone levels suppress autoimmune and inflammatory reactions. We hypothesize that these differential effects are achieved by differences in the glucocorticoid sensitivity or receptivity of the immune response being affected. At the very beginning of an immune response, certain components such as leukocyte trafficking, antigen presentation, helper T-cell function, leukocyte proliferation, cytokine and chemokine function, and effector cell function may all be receptive to glucocorticoid-mediated immunoenhancement. In contrast, at a later, more advanced stage of an immune response, these components may be more receptive to glucocorticoid-mediated immunosuppression. While this hypothesis needs to be tested through further experiments, examples from studies showing temporal differences in the sensitivity of immune reactions to the effects of physiologic concentrations of glucocorticoid hormones are presented below. 1. Bi-directional Effects of Glucocorticoids on Early versus Late Stages of T Lymphocyte Proliferation Studies examining the effects of corticosterone on T lymphocyte proliferation in vitro support the hypothesis that there may be temporal differences in the receptivity of an immune response to the enhancing versus suppressive effects of endogenous glucocorticoid hormones (Wiegers et al., 1995). These studies have shown that during the early stages of T-cell activation, low levels of corticosterone potently enhance anti-TCR–induced lymphocyte proliferation. However, during later stages of culture, the same
levels of corticosterone suppress T lymphocyte proliferation (Wiegers et al., 1995). Furthermore, Wiegers et al. showed that corticosterone had to be present during the process of TCR activation in order to enhance the proliferative response. If corticosterone was added to the culture system more than 2 hours after the initiation of TCR activation, the enhancement of lymphoproliferation was not observed. Interestingly, Weigers et al. have shown that these bi-directional effects of corticosterone on different stages of T lymphocyte proliferation are mediated by opposing effects of corticosterone on IL-2 receptor (IL2R) versus the cytokine itself (for review, see Wiegers & Reul, 1998). Thus, during the early stages of lymphocyte proliferation, corticosterone induces an increase in IL-2Rα expression. This increases the IL-2 receptivity of lymphocytes and is reflected by an increase in lymphocyte proliferation (Wiegers et al., 1995). Although corticosterone reduces the production of IL2 under these conditions, this decrease is not rate limiting at this stage since exogenously added IL-2 fails to increase proliferation. However, if corticosterone is administered at later stages, the enhancement in IL-2R expression is absent, while the suppression of IL-2 production is still present. Under these conditions, the availability of IL-2 does become rate-limiting, and hence corticosterone suppresses the lymphoproliferative response. Thus, these studies indicate an important mechanism mediating an endogenous glucocorticoid-induced immunoenhancement during the early stages and an endogenous glucocorticoidinduced immunosuppression during the later stages of an immune response. 2. The Immune Response, Corticosteroid-Binding Globulin (CBG), 11-BetaHydroxysteroiddehydrogenase (11beta-HSD), and Local Glucocorticoid Levels Factors such as CBG and 11beta-HSD, which can locally regulate glucocorticoid bioavailability at sites of immune reactions, may alter the concentrations and immunological effects of circulating hormones. CBG is a plasma-binding protein to which both cortisol and corticosterone bind with a high affinity. In humans and rats, under basal conditions, the majority of circulating glucocorticoid hormones (greater than 80%) is bound by CBG (Brien, 1980; Henning, 1978; Siiteri, Murai, Hammond, Nisker, Raymoure & Kuhn, 1982). Only stress or peak circadian levels of glucocorticoids saturate the binding capacity of CBG enough to result in a significant proportion (greater than 50%) of free hormone in the bloodstream. Most studies of
34. Possible Explanations for Salubrious as Well as Harmful Effects
glucocorticoid action suggest that only the free hormone is capable of producing a cellular effect (Mendel, 1989). Thus, regulation of CBG levels (that in turn regulate the level of free glucocorticoid hormones) is critical in terms of the hormones being able to exert their cellular effects. An ongoing immune response may help increase free circulating levels of glucocorticoid hormones by three main mechanisms by (1) stimulating HPA axis activity and resulting in greater adrenal secretion of glucocorticoids (discussed previously, for review, see Munck et al., 1984; Munck & Guyre, 1989); (2) inducing a decrease in circulating CBG levels, presumably by decreasing CBG production in the liver (Savu, Lombart & Nunez, 1980); (3) decreasing CBG levels locally at the site of an immune reaction (Hammond, Smith, Paterson & Sibbald, 1990). For example, it has been determined that the CBG molecule can be cleaved by elastase, a serine protease, thus resulting in the release of bound corticosterone (Hammond, 1990). High levels of elastase secreted by activated neutrophils have been shown to induce the cleavage of CBG molecules and release high levels of free glucocorticoids in close proximity to the site of the inflammatory reaction (Hammond, Smith, Underhill & Nguyen, 1990). This immune response–induced increase in availability of free systemic or local glucocorticoid hormones may occur towards the later stages of an immune response. The resultant increased levels of endogenous glucocorticoids may mediate the protective immunosuppression which prevents the ongoing immune response from going out of control and damaging self. Similarly, an elegant series of studies has highlighted the importance of 11beta-HSD for immune regulation by glucocorticoids (Hennebold & Daynes, 1998) and shown that increased activity of the enzyme that results in lower glucocorticoid concentrations results in Th1-type immune responses, whereas decreased activity promotes Th2-type responses (Hennebold, Ryu, Mu, Galbraith & Daynes, 1996). Studies have also shown that 11beta-HSD is expressed upon macrophage differentiation (Thieringer, Le Grand, Carbin, Cai, Wong, Wright & Hermanowski-Vosatka, 2001).
XI. THE STRESS SPECTRUM We have proposed a definition of stress as a constellation of events (Figure 1), consisting of a stimulus (STRESSOR) that precipitates a reaction in the brain (STRESS PERCEPTION & PROCESSING) that activates physiologic fight-or-flight systems in the body (STRESS RESPONSE) (Dhabhar & McEwen, 1997). It is often overlooked that a stress response has salubrious
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adaptive effects in the short run (Dhabhar et al., 1995b; Dhabhar & McEwen, 1996; Dhabhar & McEwen, 1999b; Dhabhar & Viswanathan, 2005; Sapolsky et al., 2000; Viswanathan & Dhabhar, 2005) although stress can be harmful when it is long lasting (Dhabhar & McEwen, 1997; Glaser & Kiecolt-Glaser, 2005; McEwen, 1998; Sapolsky et al., 2000). In order to reconcile these seemingly contradictory effects of stress, we proposed that a stress response and its effects on immune function be viewed in the context of a STRESS SPECTRUM (Dhabhar & McEwen, 1997; Dhabhar & McEwen, 2001) (Figure 1). One region of this spectrum is characterized by ACUTE STRESS or EUSTRESS, i.e., conditions of short-duration stress that may result in immunopreparatory or immunoenhancing physiological conditions. An important characteristic of acute stress is a rapid physiological stress response mounted in the presence of the stressor, followed by a rapid shutdown of the response upon cessation of the stressor. The other region of the stress spectrum is characterized by CHRONIC STRESS or DISTRESS, i.e., repeated or prolonged stress, which may result in dysregulation or suppression of immune function. An important characteristic of chronic stress is that the physiological response either persists long after the stressor has ceased or is activated repeatedly to result in an overall integrated increase in exposure of the organism to stress hormones. The concept of “allostatic load” has been proposed to define the “psychophysiological wear and tear” that takes place while different biological systems work to stay within a range of equilibrium (allostasis) in response to demands placed by internal or external chronic stressors (for review, see McEwen, 1998; McEwen, 2002). We suggest that conditions of high allostatic load would result in dysregulation or suppression of immune function. Importantly, a disruption of the circadian corticosterone/cortisol rhythm may be an indicator and/or mediator of distress or high allostatic load (Dhabhar & McEwen, 1997; Sephton et al., 1998). The Stress Spectrum also proposes that acute or chronic stress are generally superimposed on a psycho-physiological HEALTH MAINTENANCE EQUILIBRIUM (Figure 1). The extent and efficiency with which an organism returns to its health maintenance equilibrium after stress depends on RESILIENCE, which we define as reserve capacity of psychophysiological systems to recover from challenging conditions (Figure 1). Factors such as coping mechanisms, sense of control, optimism, social support, early life experiences, learning, genetics, and sleep may be important mediators of PSYCHOLOGICAL RESILIENCE (Figure 1). Factors such as neuro-endocrine reactivity, genetics, environment, nutrition, and sleep may be important mediators
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of PHYSIOLOGICAL RESILIENCE (Figure 1). The psychophysiological basis of resilience (Charney, 2004) and reserve capacity are underinvestigated and provide an important area for future research. The Stress Spectrum, taken together with the preceding discussion, shows that the duration, intensity/ concentration, and timing of exposure to stressor-induced physiological activation (neurotransmitters; hormones; and their molecular, cellular, organ-level, and systemic effects) are critical for determining whether stress will enhance or suppress/dysregulate immune function. The model shows that the stressor itself can be acute or chronic (Figure 1). Stress perception and processing by the brain and mechanisms mediating psychological and physiological resilience are critical for determining the duration and magnitude of the physiological stress response (Figure 1). Psychological resilience mechanisms are especially important in humans because they can limit the duration and magnitude of chronic stress responses. Psychogenic stressors are also very important in human subjects because they can generate stress responses long after stressor exposure (e.g., posttraumatic stress disorder following a severe traumatic experience or, in a milder form, lingering anger/mood disturbance following a social altercation) or even in the absence of a physical stressor or salient threat (e.g., worrying about whether one’s romantic feelings will
be reciprocated). Therefore, following stressor exposure and its processing by the brain, there ensues a PHYSIOLOGICAL STRESS RESPONSE. This response may consist of acute or chronic physiological activation (neurotransmitters; hormones; and their molecular, cellular, organ-level, and systemic effects), which results in PSYCHO-PHYSIOLOGICAL STATES that have different effects on overall health and immune function, as shown in Figure 1.
XII. CONCLUSIONS Stress has long been suspected to play a role in the etiology of many diseases, and numerous studies have shown that stress can be immunosuppressive and hence may be detrimental to health. Moreover, glucocorticoid stress hormones are widely regarded as being immunosuppressive and are used clinically as antiinflammatory agents. However, this chapter shows that under certain conditions, stress and glucocorticoid hormones exert immunoenhancing effects. Dhabhar et al. have suggested that the acute stress response may play a critical adaptive and protective role, with stress hormones and neurotransmitters serving as messengers from the brain that prepare the immune system for potential challenges (e.g.,
FIGURE 1 The Stress Spectrum. We have proposed a definition of stress as a constellation of events, consisting of a stimulus (STRESSOR) that precipitates a reaction in the brain (STRESS PERCEPTION & PROCESSING) that activates physiologic fight-or-flight systems in the body (PHYSIOLOGICAL STRESS RESPONSE) (Dhabhar & McEwen, 1997). The duration of a physiological stress response is the critical determinant of its effects on immune function and health. The STRESSOR itself may be ACUTE (e.g., narrowly missing being hit by a car) or CHRONIC (e.g., caring for a chronically ill child or adult). STRESS PERCEPTION and PROCESSING by the brain are critical for determining the duration and magnitude of the PHYSIOLOGICAL STRESS RESPONSE stimulated by any given stressor. Acute or chronic stress are generally superimposed on a psycho-physiological HEALTH MAINTENANCE EQUILIBRIUM or SET POINT. The extent and efficiency with which an organism returns to its health maintenance set point after stress depends on RESILIENCE, which we define as reserve capacity of psychological and interacting physiological systems to recover from challenging conditions. Factors such as coping mechanisms, sense of control, optimism, social support, early life experiences, learning, genetics, and sleep are important mediators of PSYCHOLOGICAL RESILIENCE. Factors such as neuro-endocrine reactivity, genetics, environment, nutrition, and sleep are important mediators of PHYSIOLOGICAL RESILIENCE. Psychological resilience mechanisms are especially important in humans because they can limit the duration and magnitude of chronic stress responses. Psychogenic stressors are also important in human subjects because they may generate stress responses long after stressor exposure or even in the absence of physical stressors or salient threats. The PHYSIOLOGICAL STRESS RESPONSE is the ultimate effector arm of the stress spectrum. It may consist of acute or chronic physiological activation (neurotransmitters; hormones; and their molecular, cellular, organ-level, and systemic effects), which results in PSYCHO-PHYSIOLOGICAL STATES that have different effects on health. Acute stress generally results in activation of protective mechanisms that include enhancement of immune function, while chronic stress results in healthaversive conditions that result in dysregulation or suppression of immune function. The molecular mechanisms mediating conversion from positive to negative effects of stress on immune function are only now beginning to emerge and need further investigation.
34. Possible Explanations for Salubrious as Well as Harmful Effects
STRESS SPECTRUM ACUTE (minutes to hours)
CHRONIC (months to years)
STRESSOR MAINTENANCE EQUILIBRIUM STRESS PERCEPTION & PROCESSING
PSYCHOLOGICAL RESILIENCE coping, control, optimism, support, early experiences, learning, sleep, genetics
PHYSIOLOGICAL STRESS RESPONSE PHYSIOLOGICAL RESILIENCE physiological health, genetics, habituation, environment, nutrition, sleep
PSYCHOPHYSIOLOGICAL STATE
ACTIVE PROTECTIVE
IMMUNE ENHANCEMENT ↑ leukocyte mobilization ↑ innate response ↑ adaptive response ↑ Th1 or Th2 response ↑ immunoprotection
HEALTHMAINTENANCE
IMMUNE EQUILIBRIUM normal/resting surveillance, & leukocyte turnover
HEALTHAVERSIVE
IMMUNE DYSREGULATION ↓ leukocyte mobilization ↓ innate response ↓ adaptive response ↑ Th2 response ↓ immunoprotection
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wounding or infection) that are perceived by the brain (e.g., the detection of predator or attacker) (Dhabhar et al., 1994; Dhabhar & McEwen, 1996; Dhabhar & McEwen, 1997; Dhabhar & Viswanathan, 2005; Viswanathan & Dhabhar, 2005). It is important to recognize that humans as well as animals experience stress as an intrinsic part of life, and in conjunction with many standard diagnostic, clinical, and experimental manipulations. Unintended stressors may significantly affect these measures and overall health outcomes. Thus, when conducting clinical, diagnostic, or experimental procedures, it may be important to account for the effects of stress on the specific physiologic parameter or health outcome being measured. For example, it is critical to elucidate and account for the effects of stress and/or stress hormones on changes in leukocyte distribution within different body compartments. Where possible, redistribution needs to be monitored in terms of changes in absolute numbers of specific sub-populations of leukocytes. Stress-induced changes in immune cell numbers and/ or function could significantly affect results (in the case of experiments), diagnosis (in the case of medical tests), or outcome (in the case of treatment procedures and surgery). This chapter illustrates the complex role that stress and stress hormones play as modulators and regulators of an immune response. There is evidence to show that under certain conditions stress and/or glucocorticoid hormones are immunoenhancing, while under other conditions they are immunosuppressive. The following factors determine whether stress or stress hormones will enhance or suppress immune function: (1) changes in leukocyte distribution within the body; (2) the duration (acute vs. chronic) of stress; (3) the concentration (physiologic vs. pharmacologic), duration (acute vs. chronic), and nature (endogenous vs. synthetic) of glucocorticoid hormone exposure; (4) the timing of stress or stress hormone exposure relative to the stage (early vs. late) of an immune response. Further elucidation of the interactions between the above-mentioned factors and other nervous, endocrine, and genetic factors in mediating the effects of stress on immune function is necessary. Due to a host of psycho-socio-political factors, stress has unfortunately become an increasing and inevitable part of people’s lives. Stress is also a major factor during the diagnosis, treatment, and follow-up for most diseases. Chronic stress has been shown to suppress immune function and is thought to play a role in the etiology of many diseases. In contrast, it has been shown relatively recently that activation of acute stress physiology may enhance protective immune responses (Dhabhar et al., 1995b; Dhabhar & McEwen, 1996;
Dhabhar & Viswanathan, 2005; Viswanathan, Daugherty & Dhabhar, 2005). Therefore, a determination of the physiologic mechanisms through which stress and stress hormones enhance or suppress immune responses is critically important for elucidating risk, developing preventative and therapeutic interventions, and optimizing a patient’s response to treatment. The elucidation of such mechanisms would help in the development of biomedical treatments designed to harness an individual’s physiology to selectively enhance (during vaccination, wounding, infections, or cancer) or suppress (during autoimmune or inflammatory disorders) the immune response, depending on what would be most beneficial for the patient.
Acknowledgments Portions of the work described in this chapter were supported by grants from The Dana Foundation Clinical Hypotheses Program in Brain Body Interaction, NIH RO1 AI48995, and the John D. and Catherine T. MacArthur Foundation. We thank Kavitha Viswanathan, Jean Tillie, Christine Daugherty, Alison Saul, and Kanika Ghai for conducting and assisting with some of the described studies.
References Abo, T., Kawate, T., Itoh, K., and Kumagai, K. (1981). Studies on the bioperiodicity of the immune response I. Circadian rhythms of human T, B, and K cell traffic in the peripheral blood. Journal of Immunology, 126, 1360–1363. Ackerman, K. D., Heyman, R., Rabin, B. S., Anderson, B. P., Houck, P. R., Frank, E., and Baum, A. (2002). Stressful life events precede exacerbations of multiple sclerosis. Psychosomatic Medicine, 64, 916–920. Ader, R., Felten, D. L., and Cohen, N. (Eds.) (2001). Psychoneuroimmunology. San Diego: Academic Press. Akahoshi, T., Oppenheim, J. J., and Matsushima, K. (1988). Induction of high-affinity interleukin 1 receptor on human peripheral blood lymphocytes by glucocorticoid hormones. Journal of Experimental Medicine, 167, 924–936. Al’Abadie, M. S., Kent, G. G., and Gawkrodger, D. J. (1994). The relationship between stress and the onset and exacerbation of psoriasis and other skin conditions. British Journal of Dermatology, 130, 199–203. Alani, M. D., and Alani, S. D. (1972). Allergic contact dermatitis to corticosteroids. Annals of Allergy, 30, 181–185. Altemus, M., Rao, B., Dhabhar, F. S., Ding, W., and Granstein, R. (2001). Stress-induced changes in skin barrier function in healthy women. J Investigative Dermatology, 117, 309–317. Amano, Y., Lee, S. W., and Allison, A. C. (1993). Inhibition by glucocorticoids of the formation of interleukin-1α, interleukin-1β, and interleukin-6: mediation by decreased mRNA stability. Molecular Pharmacology, 43, 176–182. Ambrose, C. T. (1964). The requirement for hydrocortisone in antibody-forming tissue cultivated in serum-free medium. Journal of Experimental Medicine, 119, 1027–1049. Amkraut, A. A., Solomon, C. F., and Kraemer, H. C. (1971). Stress, early experience and adjuvant-induced arthritis in the rat. Psychosomatic Medicine, 33, 203–214.
34. Possible Explanations for Salubrious as Well as Harmful Effects Andersen, B. L., Farrar, W. B., Golden-Kreutz, D., Kutz, L. A., MacCallum, R., Courtney, M. E., and Glaser, R. (1998). Stress and immune responses after surgical treatment for regional breast cancer. Journal of the National Cancer Institute, 90, 30–36. Arya, S. K., Wong-Staal, F., and Gallo, R. C. (1984). Dexamethasonemediated inhibition of human T cell growth factor and γinterferon messenger RNA. Journal of Immunology, 133, 273–276. Auphan, N., DiDonato, J. A., Rosette, C., Helmberg, A., and Karin, M. (1995). Immunosuppression by glucocorticoids: inhibition of NF-κB activity through induction of IκB synthesis. Science, 270, 286–290. Barnes, P. J., and Adcock, I. (1993). Anti-inflammatory actions of steroids: molecular mechanisms. Trends in Pharmacological Sciences, 14, 436–441. Bartrop, R., Lazarus, L., Luckhurst, E., Kiloh, L. G., and Penny, R. (1977). Depressed lymphocyte function after bereavement. Lancet, 8016, 834–836. Bartter, F. C., Delea, C. S., and Halberg, F. (1962). A map of blood and urinary changes related to circadian variations in adrenal cortical function in normal subjects. Annals of the New York Academy of Sciences, 98, 969–983. Basso, A. M., Depiante-Depaoli, M., Cancela, L., and Molina, V. (1993). Seven-day variable-stress regime alters cortical βadrenoreceptor binding and immunologic responses: reversal by imipramine. Pharmacology, Biochemistry & Behavior, 45, 665–672. Bauer, M. E., Perks, P., Lightman, S. L., and Shanks, N. (2001). Are adhesion molecules involved in stress-induced changes in lymphocyte distribution? Life Sciences, 69, 1167–1179. Baumann, H., and Gauldie, J. (1994). The acute phase response. Immunology Today, 15, 74–80. Ben Eliyahu, S., Yirmiya, R., Liebeskind, J. C., Taylor, A. N., and Gale, R. P. (1991). Stress increases metastatic spread of a mammary tumor in rats: evidence for mediation by the immune system. Brain, Behavior and Immunity, 5, 193–205. Bender, C. E. (1967). The value of corticosteroids in the treatment of infectious mononucleosis. Journal of the American Medical Association, 199, 529–532. Benschop, R. J., Rodriguez-Feuerhahn, M., and Schedlowski, M. (1996). Catecholamine-induced leukocytosis: early observations, current research, and future directions. Brain, Behavior and Immunity, 10, 77–91. Berkenbosch, F., Wolvers, D. A., and Derijk, R. (1991). Neuroendocrine and immunological mechanisms in stress-induced immunomodulation. Journal of Steroid Biochemistry & Molecular Biology, 40, 639–647. Bertini, R., Bianchi, M., and Ghezzi, P. (1988). Adrenalectomy sensitizes mice to the lethal effects of interleukin 1 and tumor necrosis factor. Journal of Experimental Medicine, 167, 1708–1712. Besedovsky, H., Del Ray, A., Sorkin, E., and Dinarello, C. A. (1986). Immunoregulatory feedback between interleukin-1 and glucocorticoid hormones. Science, 233, 652–655. Beutler, B., Krochin, N., Milsark, I. W., Luedke, C., and Cerami, A. (1986). Control of cachectin (tumor necrosis factor) synthesis: mechanisms of endotoxin resistance. Science, 232, 977–980. Bilbo, S. D., Dhabhar, F. S., Viswanathan, K., Saul, A., Yellon, S. M., and Nelson, R. J. (2002). Short day lengths augment stressinduced leukocyte trafficking and stress-induced enhancement of skin immune function. Proceedings of the National Academy of Sciences USA, 99, 4067–4072. Black, P. H. (1994). Immune system-central nervous system interactions: effect and immunomodulatory consequences of immune system mediators on the brain. Antimicrobial Agents & Chemotherapy, 38, 7–12.
751
Blecha, F., Barry, R. A., and Kelley, K. W. (1982). Stress-induced alterations in delayed-type hypersensitivity to SRBC and contact sensitivity to DNFB in mice. Proceedings of the Society for Experimental Biology, 169, 239–246. Blecha, F., and Kelley, K. W. (1981). Effects of cold and weaning stressors on the antibody-mediated immune response of pigs. Journal of Animal Science, 53, 439–447. Bonneau, R. H., Sheridan, J. F., Feng, N., and Glaser, R. (1991). Stressinduced effects on cell-mediated innate and adaptive memory components of the murine immune response to herpes simplex virus infection. Brain, Behavior and Immunity, 5, 274–295. Borysenko, M., and Borysenko, J. (1982). Stress, behavior, and immunity: animal models and mediating mechanisms. General Hospital Psychiatry, 4, 59–67. Boumpas, D. T., Paliogianni, F., Anastassiou, E. D., and Balow, J. E. (1991). Glucocorticosteroid action on the immune system: molecular and cellular aspects. Clinical & Experimental Rheumatism, 9, 413–423. Brenner, G. J., Cohen, N., Ader, R., and Moynihan, J. A. (1990). Increased pulmonary metastases and natural killer cell activity in mice following handling. Life Sciences, 47, 1813–1819. Brien, T. G. (1980). Free cortisol in human plasma. Hormone & Metabolic Research, 12, 643–650. Brosschot, J. F., Benschop, R. J., Godaert, G. L., Olff, M., De Smet, M., Heijnen, C. J., and Ballieux, R. E. (1994). Influence of life stress on immunological reactivity to mild psychological stress. Psychosomatic Medicine, 56, 216–224. Broug-Holub, E., and Kraal, G. (1996). Dose- and time-dependent activation of rat alveolar macrophages by glucocorticoids. Clinical & Experimental Immunology, 104, 332–336. Brown, D. H., and Zwilling, B. S. (1994). Activation of the hypothalamic-pituitary-adrenal axis differentially affects the antimycobacterial activity of macrophages from BCG-resistant and susceptible mice. Journal of Neuroimmunology, 53, 181–187. Buske-Kirschbaum, A., Geiben, A., and Hellhammer, D. (2001). Psychobiological aspects of atopic dermatitis: an overview. Psychother Psychosom, 70, 6–16. Buske-Kirschbaum, A., and Hellhammer, D. H. (2003). Endocrine and immune responses to stress in chronic inflammatory skin disorders. Annals of the New York Academy of Sciences, 992, 231–240. Buske-Kirschbaum, A., Jobst, S., and Hellhammer, D. H. (1998). Altered reactivity of the hypothalamus-pituitary-adrenal axis in patients with atopic dermatitis: pathologic factor or symptom? Annals of the New York Academy of Sciences, 840, 747–754. Buske-Kirschbaum, A., Jobst, S., Psych, D., Wustmans, A., Kirschbaum, C., Rauh, W., and Hellhammer, D. (1997). Attenuated free cortisol response to psychosocial stress in children with atopic dermatitis. Psychosomatic Medicine, 59, 419–426. Buske-Kirschbaum, A., von Auer, K., Krieger, S., Weis, S., Rauh, W., and Hellhammer, D. (2003). Blunted cortisol responses to psychosocial stress in asthmatic children: a general feature of atopic disease? Psychosomatic Medicine, 65, 806–810. Caggiula, A. R., McAllister, C. G., Epstein, L. H., Antelman, S. M., Knopf, S., Saylor, S., and Perkins, K. (1992). Nicotine suppresses the proliferative response of peripheral blood lymphocytes in rats. Drug Development Research, 26, 473–479. Calandra, T., Bernhagen, J., Metz, C. N., Spiegel, L. A., Bacher, M., Donnelley, T., Cerami, A., and Bucala, R. (1995). MIF as a glucocorticoid-induced modulator of cytokine production. Nature, 377, 68–71. Caldenhoven, E., Liden, J., Wissink, S., Van de Stolpe, A., Raaijmakers, J., Koenderman, L., Okret, S., Gustafsson, J.-A., and Van der Saag, P. T. (1995). Negative cross-talk between RelA and
752
IV. Stress and Immunity
the glucocorticoid receptor: a possible mechanism for the antiinflammatory action of glucocorticoids. Molecular Endocrinology, 9, 401–412. Callewaert, D. M., Moudgil, V. K., Radcliff, G., and Waite, R. (1991). Hormone specific regulation of natural killer cells by cortisol— direct inactivation of the cytotoxic function of cloned human NK cells without an effect on cellular proliferation. FEBS, 285, 108–110. Carlson, S. L., Fox, S., and Abell, K. M. (1997). Catecholamine modulation of lymphocyte homing to lymphoid tissues. Brain, Behavior and Immunity, 11, 307–320. Carr, D. J., Woolley, T. W., and Blalock, J. E. (1992). Phentolamine but not propranolol blocks the immunopotentiating effect of cold stress on antigen-specific IgM production in mice orally immunized with sheep red blood cells. Brain, Behavior and Immunity, 6, 50–63. Chao, C. C., Peterson, P. K., Filice, G. A., Pomeroy, C., and Sharp, B. M. (1990). Effects of immobilization stress on the pathogenesis of acute murine toxoplasmosis. Brain, Behavior and Immunity, 4, 162–169. Chappel, M. R. (1962). Infectious mononucleosis. Southwest Med, 43, 253–256. Charney, D. S. (2004). Psychobiological mechanisms of resilience and vulnerability: implications for successful adaptation to extreme stress. American Journal of Psychiatry, 161, 195–216. Cheng, G. J., Morrow-Tesch, J. L., Beller, D. I., Levy, E. M., and Black, P. H. (1990). Immunosuppression in mice induced by cold water stress. Brain, Behavior and Immunity, 4, 278–291. Chikanza, I. C., Kuis, W., and Heijnen, C. J. (2000). The influence of the hormonal system on pediatric rheumatic diseases. Rheum. Dis. Clin. North Am., 26, 911–925. Chrousos, G. P. (2000). Stress, chronic inflammation, and emotional and physical well-being: concurrent effects and chronic sequelae. Journal of Allergy & Clinical Immunology 106, S275–S291. Claman, H. N. (1972). Corticosteroids and lymphoid cells. New England Journal of Medicine, 287, 388–397. Claman, H. N. (1989). Glucocorticoids and autoimmune disorders. In R. P. Schleimer, H. N. Claman, and A. Oronsky (Eds.), Antiinflammatory steroid action: basic and clinical aspects (pp. 409–422). San Diego: Academic Press. Cocke, R., Moynihan, J. A., Cohen, N., Grota, L. J., and Ader, R. (1993). Exposure to conspecific alarm chemosignals alters immune responses in BALB/c mice. Brain, Behavior and Immunity, 7, 36–46. Cohen, J., and Glauser, M. P. (1991). Septic shock: treatment. Lancet, 338, 736–739. Cohen, J. J. (1972). Thymus-derived lymphocytes sequestered in the bone marrow of hydrocortisone-treated mice. Journal of Immunology, 108, 841–844. Cohen, J. J. (1989). Lymphocyte death induced by glucocorticoids. In R. P. Schleimer, H. N. Claman, and A. Oronsky (Eds.), Antiinflammatory steroid action: basic and clinical aspects (pp. 110–131). San Diego: Academic Press. Cohen, J. J. (1992). Glucocorticoid-induced apoptosis in the thymus. Seminars in Immunology, 4, 363–369. Cohen, J. J., and Duke, R. C. (1984). Glucocorticoid activation of a calcium-dependent endonuclease in thymocyte nuclei leads to cell death. Journal of Immunology, 132, 38–42. Cohen, S., and Herbert, R. B. (1996). Health psychology: psychological factors and physical disease from the perspective of human psychoneuroimmunology. Annual Reviews Psychology, 47, 113–142. Cohen, S., Tyrrell, D. A. J., and Smith, A. P. (1991). Psychological stress and susceptibility to the common cold. New England Journal of Medicine, 325, 606–612.
Conti, B., Jahng, J. W., Tinti, C., Son, J. H., and Joh, T. H. (1997). Induction of interferon-γ inducing factor in the adrenal cortex. Journal of Biological Chemistry, 272, 2035–2037. Cox, J. H., and Ford, W. L. (1982). The migration of lymphocytes across specialized vascular endothelium. IV. Prednisolone acts at several points on the recirculation pathway of lymphocytes. Cellular Immunology, 66, 407–422. Cunnick, J. E., Lysle, D. T., Kucinski, B. J., and Rabin, B. S. (1990). Evidence that shock-induced immune suppression is mediated by adrenal hormones and peripheral beta-adrenergic receptors. Pharmacology, Biochemistry & Behavior, 36, 645–651. Cupps, T. R., and Fauci, A. S. (1982). Corticosteroid-mediated immunoregulation in man. Immunological Reviews, 65, 133–155. Damoiseaux, J. G., Huitinga, I., Dopp, E. A., and Dijkstra, C. D. (1992). Expression of the ED3 antigen on rat macrophages in relation to experimental autoimmune diseases. Immunobiology, 184, 311–320. Daynes, R. A., and Araneo, B. A. (1989). Contrasting effects of glucocorticoids on the capacity of T cells to produce the growth factors interleukin 2 and interleukin 4. European Journal of Immunology, 19, 2319–2325. Daynes, R. A., Dudley, D. J., and Araneo, B. A. (1990). Regulation of murine lymphokine production in vivo. II. Dehydroepiandrosterone is a natural enhancer of interleukin 2 synthesis by helper T cells. European Journal of Immunology, 20, 793–802. Deak, T., Meriwether, J. L., Fleshner, M., Spencer, R. L., Abouhamze, A., Moldawer, L. L., Grahn, R. E., Watkins, L. R., and Maier, S. F. (1997). Evidence that brief stress may induce the acute phase response in rats. American Journal of Physiology, 273, R1998–2004. Deak, T., Nguyen, K. T., Fleshner, M., Watkins, L. R., and Maier, S. F. (1999). Acute stress may facilitate recovery from a subcutaneous bacterial challenge. Neuroimmunomodulation, 6, 344–354. Devenport, L., Thomas, T., Knehans, A., and Sundstrom, A. (1990). Acute, chronic, and interactive effects of type I and II corticosteroid receptor stimulation on feeding and weight gain. Physiology & Behavior, 47, 1221–1228. Dhabhar, F. S. (1996). Stress-induced enhancement of antigenspecific, cell-mediated immunity: the role of hormones and leukocyte trafficking (Doctoral dissertation, Laboratory of Neuroendocrinology, The Rockefeller University, New York, 1996). Dhabhar, F. S. (1998). Stress-induced enhancement of cell-mediated immunity. In S. M. McCann, J. M. Lipton, E. M. Sternberg et al. (Eds.), Neuroimmunomodulation: molecular, integrative systems, and clinical advances (pp. 359–372). New York: New York Academy of Sciences. Dhabhar, F. S., and McEwen, B. S. (1996). Stress-induced enhancement of antigen-specific cell-mediated immunity. Journal of Immunology, 156, 2608–2615. Dhabhar, F. S., and McEwen, B. S. (1997). Acute stress enhances while chronic stress suppresses immune function in vivo: a potential role for leukocyte trafficking. Brain, Behavior and Immunity, 11, 286–306. Dhabhar, F. S., and McEwen, B. S. (1999a). Changes in blood leukocyte distribution: interactions between catecholamine & glucocorticoid hormones. Neuroimmunomodulation, 6, 213. Dhabhar, F. S., and McEwen, B. S. (1999b). Enhancing versus suppressive effects of stress hormones on skin immune function. Proceedings of the National Academy of Sciences USA, 96, 1059–1064. Dhabhar, F. S., and McEwen, B. S. (2001). Bidirectional effects of stress & glucocorticoid hormones on immune function: possible explanations for paradoxical observations. In R. Ader, D. L. Felten, and N. Cohen (Eds.), Psychoneuroimmunology (3rd ed., pp. 301–338). San Diego: Academic Press.
34. Possible Explanations for Salubrious as Well as Harmful Effects Dhabhar, F. S., McEwen, B. S., and Spencer, R. L. (1993). Stress response, adrenal steroid receptor levels, and corticosteroidbinding globulin levels—a comparison between Sprague Dawley, Fischer 344, and Lewis rats. Brain Research, 616, 89–98. Dhabhar, F. S., McEwen, B. S., and Spencer, R. L. (1997). Adaptation to prolonged or repeated stress—comparison between rat strains showing intrinsic differences in reactivity to acute stress. Neuroendocrinology, 65, 360–368. Dhabhar, F. S., Miller, A. H., McEwen, B. S., and Spencer, R. L. (1995a). Differential activation of adrenal steroid receptors in neural and immune tissues of Sprague Dawley, Fischer 344, and Lewis rats. Journal of Neuroimmunology, 56, 77–90. Dhabhar, F. S., Miller, A. H., McEwen, B. S., and Spencer, R. L. (1995b). Effects of stress on immune cell distribution—dynamics and hormonal mechanisms. Journal of Immunology, 154, 5511–5527. Dhabhar, F. S., Miller, A. H., McEwen, B. S., and Spencer, R. L. (1996). Stress-induced changes in blood leukocyte distribution— role of adrenal steroid hormones. Journal of Immunology, 157, 1638–1644. Dhabhar, F. S., Miller, A. H., Stein, M., McEwen, B. S., and Spencer, R. L. (1994). Diurnal and stress-induced changes in distribution of peripheral blood leukocyte subpopulations. Brain, Behavior and Immunity, 8, 66–79. Dhabhar, F. S., Satoskar, A. R., Bluethmann, H., David, J. R., and McEwen, B. S. (2000). Stress-induced enhancement of skin immune function: a role for IFNγ. Proceedings of the National Academy of Sciences USA, 97, 2846–2851. Dhabhar, F. S., and Viswanathan, K. (2005). Short-term stress experienced at the time of immunization induces a long-lasting increase in immunological memory. AJP: Regulatory, Integrative, & Comparative Physiology 289, R738–744. Available on the Web at DOI, 10. 1152/ajpregu. 00145. Diamond, D. M., Bennett, M. C., Fleshner, M., and Rose, G. M. (1992). Inverted-U relationship between the level of peripheral corticosterone and the magnitude of hippocampal primed burst potentiation. Hippocampus, 2, 421–430. Dinarello, C. A., and Wolff, S. M. (1993). The role of interleukin-1 in disease. New England Journal of Medicine, 328, 106–113. Doeberitz, M. V. K., Koch, S., Drzonek, H., and Hausen, H. Z. (1990). Glucocorticoid hormones reduce the expression of major histocompatibility class I antigen on human epithelial cells. European Journal of Immunology, 20, 35–40. Dopp, J. M., Miller, G. E., Myers, H. F., and Fahey, J. L. (2000). Increased natural killer-cell mobilization and cytotoxicity during marital conflict. Brain, Behavior and Immunity, 14, 10– 26. Dougherty, R. F., and White, A. (1945). Functional alterations in lymphoid tissue induced by adrenal cortical secretion. American Journal of Anatomy, 77, 81–116. Dougherty, T. F. (1949). Role of the adrenal gland in the protection against anaphylactic shock. Anatomical Records, 103, 24. Dougherty, T. F. (1950). The protective role of adrenal cortical secretion in the hypersensitive state. In R. C. Christman (Ed.), Pituitary-adrenal function (pp. 79–87). Washington, DC: American Association for the Advancement of Science. Dougherty, T. F. (1952). Effect of hormones on lymphatic tissue. Physiological Review, 32, 379–401. Edwards, E. A., and Dean, L. M. (1977). Effects of crowding of mice on humoral antibody formation and protection to lethal antigenic challenge. Psychosomatic Medicine, 39, 19–24. Elenkov, I. J. (2004). Glucocorticoids and the Th1/Th2 balance. Annals of the New York Academy of Sciences, 1024, 138–146. Epel, E., Blackburn, E. H., Lin, J., Dhabhar, F. S., Adler, N. E., Morrow, J. D., and Cawthon, R. M. (2004). Accelerated telomere
753
shortening in response to life stress. Proceedings of the National Academy of Sciences USA, 101, 17312–17315. Eskola, J., Frey, H., Molnar, G., and Soppi, E. (1976). Biological rhythm of cell-mediated immunity in man. Clinical & Experimental Immunology, 26, 253–257. Esparza, E. M., and Arch, R. H. (2005). Glucocorticoid-induced TNF receptor functions as a costimulatory receptor that promotes survival in early phases of T cell activation. Journal of Immunology, 174, 7869–7874. Fan, J., Gong, X. Q., Wu, J., Zhang, Y.-F., and Xu, R.-B. (1994). Effect of glucocorticoid receptor (GR) blockage on endotoxemia in rats. Circulatory Shock, 42, 76–82. Fauci, A. S. (1975). Mechanisms of corticosteroid action on lymphocyte subpopulations. I. Redistribution of circulating T and B lymphocytes to the bone marrow. Immunology, 28, 669–680. Fauci, A. S. (1976). Mechanisms of corticosteroid action on lymphocyte subpopulations. II. Differential effects of in vivo hydrocortisone, prednisone, and dexamethasone on in vitro expression of lymphocyte function. Clinical & Experimental Immunology, 24, 54–62. Fauci, A. S. (1979). Immunosuppressive and anti-inflammatory effects of glucocorticoids. In J. D. Baxter and G. G. Rousseau (Eds.), Glucocorticoid hormone action (pp. 449–465). Berlin: Springer-Verlag. Fauci, A. S., and Dale, D. C. (1974). The effect of in vivo hydrocortisone on subpopulations of human lymphocytes. Journal of Clinical Investigation, 53, 240–246. Fauci, A. S., and Dale, D. C. (1975). Alternate-day prednisone therapy and human lymphocyte subpopulations. Journal of Clinical Investigation, 55, 22–32. Fauci, A. S., Pratt, K. R., and Whalen, G. (1977). Activation of human B lymphocytes. IV. Regulatory effects of corticosteroids on the triggering signal in the plaque-forming cell response of human peripheral blood B lymphocytes to polyclonal activation. Journal of Immunology, 119, 598–603. Fleshner, M., Laudenslager, M. L., Simons, L., and Maier, S. F. (1989). Reduced serum antibodies associated with social defeat in rats. Physiology & Behavior, 45, 1183–1187. Fleshner, M., Watkins, L. R., Lockwood, L. L., Laudenslager, M. L., and Maier, S. F. (1992). Specific changes in lymphocyte subpopulations: a potential mechanism for stress-induced immunomodulation. Journal of Neuroimmunology, 41, 131–142. Folks, D. G., and Kinney, F. C. (1992). The role of psychological factors in dermatologic conditions. Psychosomatics, 33, 45–54. Forner, M. A., Barriga, C., Rodriquez, A. B., and Ortega, E. (1995). A study of the role of corticosterone as a mediator in exerciseinduced stimulation of murine macrophage phagocytosis. Journal of Physiology, 488, 789–794. Gajewski, T. F., Schell, S. R., Nau, G., and Fitch, F. W. (1989). Regulation of T-cell activation: differences among T-cell subsets. Immunological Reviews, 111, 79–110. Girard, M. T., Hjaltadottir, S., Fejes-Toth, A. N., and Guyre, P. M. (1987). Glucocorticoids enhance the γ-interferon augmentation of human monocyte IgG Fc receptor expression. Journal of Immunology, 138, 3235–3241. Glaser, R., and Kiecolt-Glaser, J. K. (2005). Stress-induced immune dysfunction: implications for health. Nat. Rev. Immunol, 5, 243–251. Glaser, R., Kiecolt-Glaser, J. K., Bonneau, R. H., Malarkey, W., Kennedy, S., and Hughes, J. (1991). Stress-induced modulation of the immune response to recombinant hepatitis B vaccine. Psychosomatic Medicine, 54, 22–29. Glaser, R., Pearl, D. K., Kiecolt-Glaser, J. K., and Malarkey, W. B. (1994). Plasma cortisol levels and reactivation of latent Epstein-
754
IV. Stress and Immunity
Barr virus in response to examination stress. Psychoneuroendocrinology, 19, 765–772. Godlowski, Z. Z. (1952). The fate of eosinophils in hormonally induced eosinopenia and its significance. Journal of Endocrinology, 8, 102–125. Goebel, M. U., and Mills, P. J. (2000). Acute psychological stress and exercise and changes in peripheral leukocyte adhesion molecule expression and density. Psychosomatic Medicine, 62, 664–670. Goldstein, R. A., Bowen, D. L., and Fauci, A. S. (1992). Adrenal corticosteroids. In J. I. Gallin, I. M. Goldstein, and R. Snyderman (Eds.), Inflammation: basic principles and clinical correlates (pp. 1061–1081). New York: Raven Press. Gonzalo, J. A., Gonzalez-Garcia, A., Martinez, A. C., and Kroemer, G. (1993). Glucocorticoid-mediated control of the activation and clonal deletion of peripheral T cells in vivo. Journal of Experimental Medicine, 177, 1239–1246. Gottschall, P. E., Koves, K., Mizuno, K., Tatsuno, I., and Arimura, A. (1991). Glucocorticoid upregulation of interleukin 1 receptor expression in a glioblastoma cell line. American Journal of Physiology, 261, E362–E368. Grayson, J., Dooley, N. J., Koski, I. R., and Blaese, R. M. (1981). Immunoglobulin production induced in vitro by glucocorticoid hormones: T cell-dependent stimulation of immunoglobulin production without B cell proliferation in cultures of human peripheral blood lymphocytes. Journal of Clinical Investigation, 68, 1539–1547. Griffin, A. C., Warren, D. L., Wolny, A. C., and Whitacre, C. C. (1993). Suppression of experimental autoimmune encephalomyelitis by restraint stress. Journal of Neuroimmunology, 44, 103–116. Griffin, A. C., and Whitacre, C. C. (1991). Sex and strain differences in the circadian rhythm fluctuation of endocrine and immune function in the rat: implications for rodent models of autoimmune disease. Journal of Neuroimmunology, 35, 53–64. Halliday, W. J., and Garvey, J. S. (1964). Some factors affecting the secondary immune response in tissue cultures containing hydrocortisone. Journal of Immunology, 93, 757–762. Hammond, G. L. (1990). Molecular properties of corticosteroid binding globulin and the sex-steroid binding proteins. Endocrine Reviews, 11, 65–79. Hammond, G. L., Smith, C. L., Paterson, N. A. M., and Sibbald, W. J. (1990). A role for corticosteroid-binding globulin in delivery of cortisol to activated neutrophils. Journal of Clinical Endocrinology & Metabolism, 71, 34–39. Hammond, G. L., Smith, C. L., Underhill, C. M., and Nguyen, V. T. (1990). Interaction between corticosteroid binding globulin and activated leukocytes in vitro. Biochemical & Biophysical Research Communications, 172, 172–177. Harbuz, M. S., Chover-Gonzalez, A. J., and Jessop, D. S. (2003). Hypothalamo-pituitary-adrenal axis and chronic immune activation. Annals of the New York Academy of Sciences, 992, 99–106. Harbuz, M. S., Conde, G. L., Marti, O., Lightman, S. L., and Jessop, D. S. (1997). The hypothalamic-pituitary-adrenal axis in autoimmunity. Annals of the New York Academy of Sciences, 823, 214–224. Harris, T. J., Waltman, T. J., Carter, S. M., and Maisel, A. S. (1995). Effect of prolonged catecholamine infusion on immunoregulatory function: implications in congestive heart failure. Journal of the American College of Cardiology, 26, 102–109. Hawrylowicz, C. M., Guida, L., and Paleolog, E. (1994). Dexamethasone up-regulates granulocyte-macrophage colony-stimulating factor receptor expression on human monocytes. Immunology, 83, 274–280.
Haynes, R. C. J. (1990). Adrenocorticotropic hormone; adrenocortical steroids and their structural analogs; inhibitors of the synthesis and actions of adrenocortical hormones. In A. G. Gilman, T. W. Rall, A. S. Nies, and P. Taylor (Eds.), The pharmacological basis of experimental therapeutics (pp. 1431–1462). New York: Pergamon. Hedman, L. A., and Lundin, P. M. (1977). The effect of steroids on the circulating lymphocyte population. II. Studies of the thoracic duct lymphocyte population of the guinea pig after neonatal thymectomy and prednisolone treatment. Lymphology, 10, 192–198. Hench, P. S. (1952). The reversibility of certain rheumatic and nonrheumatic conditions by the use of cortisone or of the pituitary adrenocorticotropic hormone. Annals of Internal Medicine, 36, 1–25. Hench, P. S., Kendall, E. C., Slocumb, C. H., and Polley, H. (1949). The effect of a hormone of the adrenal cortex (17-hydroxy-11dehydrocorticosterone: Compound E) and of pituitary adrenocorticotropic hormone on rheumatoid arthritis. Proceedings Staff Meeting Mayo Clinic, 24, 181–197. Hendrie, H. C., Parasekvas, R., Baragar, F. D., and Adamson, J. D. (1971). Stress, immunoglobulin levels, and early polyarthritis. Journal of Psychosomatic Research, 15, 337–342. Hennebold, J., and Daynes, R. (1998). Inhibition of skin 11betahydroxysteroid dehydrogenase activity in vivo potentiates the anti-inflammatory actions of glucocorticoids. Arch Dermatol Res, 290, 413–419. Hennebold, J. D., Ryu, S. Y., Mu, H. H., Galbraith, A., and Daynes, R. A. (1996). 11 beta-hydroxysteroid dehydrogenase modulation of glucocorticoid activities in lymphoid organs. Am J Physiol Regulatory Integrative Comp Physiol, 270, R1296–1306. Henning, S. J. (1978). Plasma concentrations of total and free corticosterone during development in the rat. American Journal of Physiology, 235, E451–E456. Herbert, T. B., and Cohen, S. (1993). Stress and immunity in humans: a meta-analytic review. Psychosomatic Medicine, 55, 364–379. Hiemke, C., Brunner, R., Hammes, E., Müller, H., Meyer Zum Büschenfelde, K.-H., and Lohse, A. W. (1995). Circadian variations in antigenic-specific proliferation of human T lymphocytes and correlation to cortisol production. Psychoneuroendocrinology, 20, 335–342. Hirata, F. (1989). The role of lipocortins in cellular function as a second messenger of glucocorticoids. In R. P. Schleimer, H. N. Claman, and A. Oronsky (Eds.), Anti-inflammatory steroid action— basic and clinical aspects (pp. 67–95). San Diego: Academic Press. Hoagland, H., Elmadjian, F., and Pincus, G. (1946). Stressful psychomotor performance and adrenal cortical function as indicated by the lymphocyte response. Journal of Clinical Endocrinology & Metabolism, 6, 301–311. Hong, S., Farag, N. H., Nelesen, R. A., Ziegler, M. G., and Mills, P. J. (2004). Effects of regular exercise on lymphocyte subsets and CD62L after psychological vs. physical stress. Journal of Psychosomatic Research, 56, 363–370. Irwin, M. (1994). Stress-induced immune suppression: role of brain corticotropin releasing hormone and autonomic nervous system mechanisms. Advances in Neuroimmunology, 4, 29–47. Irwin, M., Patterson, T., Smith, T. L., Caldwell, C., Brown, S. A., Gillin, C. J., and Grant, I. (1990). Reduction of immune function in life stress and depression. Biological Psychiatry, 27, 22–30. Issekutz, T. B. (1990). Effects of six different cytokines on lymphocyte adherence to microvascular endothelium and in vivo lymphocyte migration in the rat. Journal of Immunology, 144, 2140–2146.
34. Possible Explanations for Salubrious as Well as Harmful Effects Jain, S., and Stevenson, J. R. (1991). Enhancement by restraint stress of natural killer cell activity and splenocyte responsiveness to concanavalin A in Fischer 344 rats. Immunological Investigations, 20, 365–376. Jefferies, W. M. (1981). Safe uses of cortisone. Springfield: Thomas. Jefferies, W. M. (1991). Cortisol and immunity. Medical Hypotheses, 34, 198–208. Jensen, M. M. (1969). Changes in leukocyte counts associated with various stressors. Journal of the Reticuloendothelial Society, 8, 457–465. Joels, M., and de Kloet, E. R. (1992). Control of neuronal excitability by corticosteroid hormones. Trends in Neuroscience, 15, 25–30. Johns, M. W. (1967). Leukocyte response to sound stress in rats: role of the adrenal gland. Journal of Pathology & Bacteriology, 93, 681–685. Kaplan, M. S., Byers, V. S., Levin, A. S., German, D. F., Fudenberg, H. H., and Lecam, L. N. (1976). Circadian rhythm of stimulated lymphocyte blastogenesis. Journal of Allergy & Clinical Immunology, 58, 180–189. Karalis, K., Sano, H., Redwine, J., Listwak, S., Wilder, R. L., and Chrousos, G. P. (1991). Autocrine or paracrine inflammatory actions of corticotropin-releasing hormone in vivo. Science, 254, 421–423. Kavelaars, A., de Jong-de Vos van Steenwijk, T., Kuis, W., and Heijnen, C. J. (1998). The reactivity of the cardiovascular system and immunomodulation by catecholamines in juvenile chronic arthritis. Annals of the New York Academy of Sciences, 840, 698–704. Kawate, T., Abo, T., Hinuma, S., and Kumagai, K. (1981). Studies on the bioperiodicity of the immune response II. Co-variations of murine T and B cells and a role for corticosteroid. Journal of Immunology, 126, 1364–1367. Keller, S. E., Schleifer, S. J., Liotta, A. S., Bond, R. N., Farhoody, N., and Stein, M. (1988). Stress-induced alterations of immunity in hypophysectomized rats. Proceedings of the National Academy of Sciences USA, 85, 9297–9301. Keller, S. E., Weiss, J. M., Schleifer, S. J., Miller, N. E., and Stein, M. (1983). Stress-induced suppression of immunity in adrenalectomized rats. Science, 221, 1301–1304. Kelley, K. W., Greenfield, R. E., Evermann, J. F., Parish, S. M., and Perryman, L. E. (1982). Delayed-type hypersensitivity, contact sensitivity, and PHA skin-test responses of heat- and coldstressed calves. American Journal of Veterinary Research, 43, 775–779. Khansari, D. N., Murgo, A. J., and Faith, R. E. (1990). Effects of stress on the immune system. Immunology Today, 11, 170–175. Kiecolt-Glaser, J. K. (1999). Norman Cousins Memorial Lecture 1998. Stress, personal relationships, and immune function: health implications. Brain, Behavior and Immunity, 13, 61–72. Kiecolt-Glaser, J. K., Garner, W., Speicher, C., Penn, G. M., Holliday, J., and Glaser, R. (1984). Psychosocial modifiers of immunocompetence in medical students. Psychosomatic Medicine, 46, 7–14. Kiecolt-Glaser, J. K., Glaser, R., Gravenstein, S., Malarkey, W. B., and Sheridan, J. (1996). Chronic stress alters the immune response to influenza virus vaccine in older adults. Proceedings of the National Academy of Sciences USA, 93, 3043–3047. Kimber, I., and Dearman, R. (1993). Approaches to the identification and classification of chemical allergens in mice. Journal of Pharmacology & Toxicology Methods, 29, 11–16. Kizaki, T., Oh-Ishi, S., Ookawara, T., Yamamoto, M., Izawa, T., and Ohno, H. (1996). Glucocorticoid-mediated generation of suppressor macrophages with high density FcγRII during acute cold stress. Endocrinology, 137, 4260–4267.
755
Kort, W. J. (1994). The effect of chronic stress on the immune system. Advances in Neuroimmunology, 4, 1–11. Korte, S., Koolhaas, J., Wingfield, J., and McEwen, B. (2005). The Darwinian concept of stress: benefits of allostasis and costs of allostatic load and the trade-offs in health and disease. Neurosci Biobehav Rev, 29, 3–38. Kroemer, G., Brezinschek, H. P., Faessler, R., Schauenstein, K., and Wick, G. (1988). Physiology and pathology of an immunoendocrine feedback loop. Immunology Today, 9, 163–165. Kuis, W., de Jong-de Vos van Steenwijk, C., Sinnema, G., Kavelaars, A., Prakken, B., Helders, P. J., and Heijnen, C. J. (1996). The autonomic nervous system and the immune system in juvenile rheumatoid arthritis. Brain, Behavior and Immunity, 10, 387–398. Lamas, M., Sanz, E., Martin-Parras, L., Espel, E., Sperisen, P., Collins, M., and Silva, A. G. (1993). Glucocorticoid hormones upregulate interleukin 2 receptor A gene expression. Cellular Immunology, 151, 437–450. Landmann, R. (1992). Beta-adrenergic receptors in human leukocyte subpopulations. European Journal of Clinical Investigation, 22(Suppl. 1), 30–36. Landmann, R., Muller, F. B., Perini, C. H., Wesp, M., Erne, P., and Buhler, F. R. (1984). Changes of immunoregulatory cells induced by psychological and physical stress: relationship to plasma catecholamines. Clinical & Experimental Immunology, 58, 127–135. Laue, L., Kawai, S., Brandon, D. D., Brightwell, D., Barnes, K., Knazek, R. A., Loriaux, D. L., and Chrousos, G. P. (1988). Receptor-mediated effects of glucocorticoids on inflammation: enhancement of the inflammatory response with a glucocorticoid antagonist. Journal of Steroid Biochemistry, 29, 591–598. Lazar Jr., G., Duda, E., and Lazar, G. (1992). Effect of RU38486 on TNF production and toxicity. FEBS, 308, 137–140. Lechner, O., Hu, Y., Jafarian-Tehrani, M., Dietrich, H., Schwarz, S., Herold, M., Haour, F., and Wick, G. (1996). Disturbed immunoendocrine communication via the hypothalamo-pituitaryadrenal axis in murine lupus. Brain, Behavior and Immunity, 10, 337–350. Lee, S. W., Tsou, A.-P., Chan, H., Thomas, J., Petrie, K., Eugui, E. M., and Allison, A. C. (1988). Glucocorticoids selectively inhibit the transcription of the interleukin 1β gene and decrease the stability of interleukin 1β mRNA. Proceedings of the National Academy of Sciences USA, 85, 1204–1208. Levine, S., and Saltzman, A. (1987). Nonspecific stress prevents relapses of experimental allergic encephalomyelitis in rats. Brain, Behavior and Immunity, 1, 336–341. Levine, S., Strebel, R., Wenk, E., and Harman, P. (1962). Suppression of experimental allergic encephalomyelitis by stress. Proceedings of the Society for Experimental Biology, 109, 294–298. Levo, Y., Harbeck, R. J., and Kirkpatrick, C. H. (1985). Regulatory effect of hydrocortisone on the in vitro synthesis of IgE by human lymphocytes. International Archives of Allergy & Applied Immunology, 77, 413–424. Liao, J., Keiser, J. A., Scales, W. E., Kunkel, S. L., and Kluger, M. J. (1995). Role of corticosterone in TNF and IL-6 production in isolated perfused rat liver. American Journal of Physiology, 268, R699–706. Lundin, P. M., and Hedman, L. A. (1978). Influence of corticosterone on lymphocyte recirculation. Lymphology, 11, 216–221. Lysle, D. T., Cunnick, J. E., and Rabin, B. S. (1990). Stressor-induced alteration of lymphocyte proliferation in mice: evidence for enhancement of mitogenic responsiveness. Brain, Behavior and Immunity, 4, 269–277. Lyte, M., Nelson, S. G., and Baissa, B. (1990). Examination of the neuroendocrine basis for the social conflict-induced enhancement of immunity in mice. Physiology & Behavior, 48, 685–691.
756
IV. Stress and Immunity
Lyte, M., Nelson, S. G., and Thompson, M. L. (1990). Innate and adaptive immune responses in a social conflict paradigm. Clinical Immunology & Immunopathology, 57, 137–147. MacKenzie, F. J., Leonard, J. P., and Cuzner, M. L. (1989). Changes in lymphocyte B-adrenergic receptor density and noradrenaline content of the spleen are early indicators of immune reactivity in acute experimental allergic encephalomyelitis in the Lewis rat. Journal of Neuroimmunology, 23, 93–100. MacPhee, I. A. M., Day, M. J., and Mason, D. W. (1990). The role of serum factors in the suppression of experimental allergic encephalomyelitis: evidence for immunoregulation by antibody to the encephalitogenic peptide. Immunology, 70, 527–534. Maier, S. F., Watkins, L. R., and Fleshner, M. (1994). Psychoneuroimmunology—the interface between behavior, brain, and immunity. American Psychologist, 49, 1004–1017. Manuck, S. B., Cohen, S., Rabin, B. S., Muldoon, M. F., and Bachen, E. A. (1991). Individual differences in cellular immune response to stress. Psychological Science, 2, 111–115. Marucha, P. T., Kiecolt-Glaser, J. K., and Favagehi, M. (1998). Mucosal wound healing is impaired by examination stress. Psychosomatic Medicine, 60, 362–365. Marx, J. (1995). How the glucocorticoids suppress immunity. Science, 270, 232–233. Mason, D. (1991). Genetic variation in the stress response: susceptibility to experimental allergic encephalomyelitis and implications for human inflammatory disease. Immunology Today, 12, 57–60. Mason, D., MacPhee, I., and Antoni, F. (1990). The role of the neuroendocrine system in determining genetic susceptibility to experimental allergic encephalomyelitis in the rat. Immunology, 70, 1–5. May, M. J., and Ghosh, S. (1998). Signal transduction through NF-kB. Immunology Today, 19, 80–88. McEwen, B. S. (1998). Protective and damaging effects of stress mediators: allostasis and allostatic load. New England Journal of Medicine, 338, 171–179. McEwen, B. S. (2002). The end of stress as we know it. Washington, DC: Dana Press. McEwen, B. S., Biron, C. A., Brunson, K. W., Bulloch, K., Chambers, W. H., Dhabhar, F. S., Goldfarb, R. H., Kitson, R. P., Miller, A. H., Spencer, R. L., et al. (1997). Neural-endocrine-immune interactions: The role of adrenalcorticoids as modulators of immune function in health and disease. Brain Research Reviews, 23, 79–133. McEwen, B. S., de Kloet, E. R., and Rostene, W. (1986). Adrenal steroid receptors and actions in the nervous system. Physiological Review, 66, 1121–1188. Mei-Tal, V., Meyerowitz, S., and Engel, G. (1970). Role of psychological process in a somatic disorder: multiple sclerosis. Psychosomatic Medicine, 32, 67–86. Mekaouche, M., Givalois, L., Barbanel, G., Siaud, P., Maurel, D., Malaval, F., Bristow, A. F., Boissin, J., Assenmacher, I., and Ixart, G. (1994). Chronic restraint enhances interleukin-1–beta release in the basal state and after endotoxin challenge, independently of adrenocorticotropin and corticosterone release. Neuroimmunomodulation, 1, 292–299. Mendel, C. M. (1989). The free hormone hypothesis: a physiologically based mathematical model. Endocrine Reviews, 10, 232–274. Mendelson, S. C., and McEwen, B. S. (1992). Autoradiographic analyses of the effects of adrenalectomy and corticosterone on 5HT1A and 5-HT1B receptors in the dorsal hippocampus and cortex of the rat. Neuroendocrinology, 55, 444–450. Mickerson, J. N. (1959). Influenzal pituitary suppression. Lancet, 1, 1118–1120.
Millar, D. B., Thomas, J. R., Pacheco, N. D., and Rollwagen, F. M. (1993). Natural killer cell cytotoxicity and T-cell proliferation is enhanced by avoidance behavior. Brain, Behavior and Immunity, 7, 144–153. Miller, A. H., Spencer, R. L., Hasset, J., Kim, C., Rhee, R., Cira, D., Dhabhar, F. S., McEwen, B. S., and Stein, M. (1994). Effects of selective type I and type II adrenal steroid receptor agonists on immune cell distribution. Endocrinology, 135, 1934–1944. Miller, A. H., Spencer, R. L., Pearce, B. D., Pisell, T. L., Azrieli, Y., Tanapat, P., Moday, H., Rhee, R., and McEwen, B. S. (1998). Glucocorticoid receptors are differentially expressed in the cells and tissues of the immune system. Cellular Immunology, 186, 45–54. Mills, P. J., Berry, C. C., Dimsdale, J. E., Ziegler, M. G., Nelesen, R. A., and Kennedy, B. P. (1995). Lymphocyte subset redistribution in response to acute experimental stress: effects of gender, ethnicity, hypertension, and the sympathetic nervous system. Brain, Behavior and Immunity, 9, 61–69. Mills, P. J., and Dimsdale, J. E. (1996). The effects of acute psychologic stress on cellular adhesion molecules. Journal of Psychosomatic Research, 41, 49–53. Monjan, A. A., and Collector, M. I. (1977). Stress-induced modulation of the immune response. Science, 196, 307–308. Moorhead, J. W., and Claman, H. N. (1972). Thymus-derived lymphocytes and hydrocortisone: identification of subsets of theta-bearing cells and redistribution to bone marrow. Cellular Immunology, 5, 74–86. Morrow-Tesch, J. L., McGlone, J. J., and Norman, R. L. (1993). Consequences of restraint stress on natural killer cell activity, behavior, and hormone levels in rhesus macaques (Macaca mulatta). Psychoneuroendocrinology, 18, 383–395. Mosmann, T. R., and Coffman, R. L. (1989). TH1 and TH2 cells: different patterns of lymphokine secretion lead to different functional properties. Annual Reviews Immunology, 7, 145– 173. Muehrcke, R. C., Lewis, J. L., and Kark, R. M. (1952). The effects of cortisone and heparin on eosinophils in defibrinated human blood. Science, 115, 377–378. Mukaida, N., Morita, M., Ishikawa, Y., Rice, N., Okamoto, S., Kasahara, T., and Matsushima, K. (1994). Novel mechanism of glucocorticoid-mediated gene repression. Journal of Biological Chemistry, 269, 13289–13295. Munck, A., and Guyre, P. M. (1989). Glucocorticoid physiology and homeostasis in relation to anti-inflammatory actions. In R. P. Schleimer, H. N. Claman, and A. Oronsky (Eds.), Anti-inflammatory steroid action—basic and clinical aspects (pp. 30–47). San Diego: Academic Press. Munck, A., Guyre, P. M., and Holbrook, N. J. (1984). Physiological functions of glucocorticoids in stress and their relation to pharmacological actions. Endocrine Reviews, 5, 25–44. Munck, A., and Naray-Fejes-Toth, A. (1992). The ups and downs of glucocorticoid physiology. Permissive and suppressive effects revisited. Molecular & Cellular Endocrinology, 90, C1–C4. Murrieta-Aguttes, M., Michelen, V., Leynadier, F., Duarte-Risselin, C., Halpern, G. M., and Dry, J. (1991). Systemic allergic reactions to corticosteroids. Journal of Asthma, 28, 329–339. Nakano, K., Suzuki, S., and Oh, C. (1987). Significance of increased secretion of glucocorticoids in mice and rats injected with bacterial endotoxin. Brain, Behavior and Immunity, 1, 159–172. Nakano, K., Suzuki, S., Oh, C., and Yamashita, K. (1986). Possible role of glucocorticoids in a complement-activated state induced by cobra venom factor in rats. Acta Endocrinologica, 112, 122–129. Naliboff, B. D., Benton, D., Solomon, G. F., Morley, J. E., Fahey, J. L., Bloom, E. T., Makinodan, T., and Gilmore, S. L. (1991). Immuno-
34. Possible Explanations for Salubrious as Well as Harmful Effects logical changes in young and old adults during brief laboratory stress. Psychosomatic Medicine, 53, 121–132. Onsrud, M., and Thorsby, E. (1981). Influence of in vivo hydrocortisone on some human blood lymphocyte subpopulations. Scandinavian Journal of Immunology, 13, 573–579. Orson, F. M., Grayson, J., Pike, S., de Seau, V., and Blaese, R. M. (1983). T cell-replacing factor for glucocorticosteroid-induced immunoglobulin production. A unique steroid-dependent cytokine. Journal of Experimental Medicine, 158, 1473–1482. Padawer, J., and Gordon, A. S. (1952). A mechanism for the eosinopenia induced by cortisone and epinephrine. Endocrinology, 51, 52–88. Parillo, J. E., and Fauci, A. S. (1979). Mechanisms of glucocorticoid action and immune processes. Annual Review of Pharmacology & Toxicology, 19, 179–201. Park, J. H., Kaushansky, K., and Levitt, L. (1993). Transcriptional regulation of interleukin 3 (IL3) in primary human T lymphocytes. Role of AP-1-and octamer-binding proteins in control of IL3 gene expression. Journal of Biological Chemistry, 268, 6299–6308. Pavlides, C., Watanabe, Y., Magarinos, A. M., and McEwen, B. S. (1995). Opposing roles of type I and type II adrenal steroid receptors in hippocampal long-term potentiation. Neuroscience, 68, 387–394. Pawlak, C., Heiker, H., Witte, T., Wiese, B., Heijnen, C. J., Schmidt, R. E., and Schedlowski, M. (1999). A prospective study of daily stress and disease activity in patients with systemic lupus erythematosus. Neuroimmunomodulation, 6, 241. Pawlak, C. R., Jacobs, R., Mikeska, E., Ochsmann, S., Lombardi, M. S., Kavelaars, A., Heijnen, C. J., Schmidt, R. E., and Schedlowski, M. (1999). Patients with systemic lupus erythematosus differ from healthy controls in their immunological response to acute psychological stress. Brain, Behavior and Immunity, 13, 287–302. Peller, J. S., and Bardana, E. J. J. (1985). Anaphylactoid reaction to corticosteroid: case report and review of the literature. Annals of Allergy, 54, 302–305. Persoons, J. H. A., Berkenbosch, F., Schornagel, K., Thepen, T., and Kraal, G. (1995). Increased specific IgE production in lungs after the induction of acute stress in rats. Journal of Allergy & Clinical Immunology, 95, 765–770. Phanuphak, P., Moorhead, J. W., and Claman, H. N. (1974). Tolerance and contact sensitivity to DNFB in mice. I. In vivo detection by ear swelling and correlation with in vitro cell stimulation. Journal of Immunology, 112, 115–123. Philippopoulos, G. S., Wittkower, E. D., and Cousineau, A. (1958). The etiologic significance of emotional factors in onset and exacerbation of multiple sclerosis. Psychosomatic Medicine, 20, 458–474. Pickford, G. E., Srivastava, A. K., Slicher, A. M., and Pang, P. K. T. (1971). The stress response in the abundance of circulating leukocytes in the killifish, Fundulus heteroclitus. I. The cold-shock sequence and the effects of hypophysectomy. Journal of Zoology, 177, 89–96. Plaut, M. (1987). Lymphocyte hormone receptors. Annual Reviews Immunology, 5, 621–669. Pruett, S. B. (2001). Quantitative aspects of stress-induced immunomodulation. Int. Immunopharmacol, 1, 507–520. Radomski, M. W., Palmer, R. M. J., and Moncada, S. (1990). Glucocorticoids inhibit the expression of an inducible, but not the constitutive, nitric oxide synthase in vascular endothelial cells. Proceedings of the National Academy of Sciences USA, 87, 10043–10047. Ray, A., LaForge, K. S., and Seghal, P. B. (1990). On the mechanism of efficient repression of the interleukin-6 promoter by glucocor-
757
ticoids: Enhancer, TATA bod, and RNA start site (Inr Motif) occlusion. Molecular & Cellular Biology, 10, 5736–5746. Redwine, L., Snow, S., Mills, P., and Irwin, M. (2003). Acute psychological stress: effects on chemotaxis and cellular adhesion molecule expression. Psychosomatic Medicine, 65, 598–603. Reed, J., Abidi, A., Alpers, J., Hoover, R., Robb, R., and Nowell, P. (1986). Effect of cyclosporin A and dexamethasone on interleukin 2 receptor gene expression. Journal of Immunology, 137, 150–154. Regnier, J. A., and Kelley, K. W. (1981). Heat- and cold-stress suppresses in vivo and in vitro cellular immune response of chickens. American Journal of Veterinary Research, 42, 294–299. Reitamo, S., Lauerma, A., Stubb, S., Kayhko, K., Visa, K., and Forstrom, L. (1986). Delayed hypersensitivity to topical corticosteroids. Journal of the American Academy of Dermatology, 14, 582–589. Renz, H., Henke, A., Hofmann, P., Wolff, L. J., Schmidt, A., Rüschoff, J., and Gemsa, D. (1992). Sensitization of rat alveolar macrophages to enhanced TNF-α release by in vivo treatment with dexamethasone. Cellular Immunology, 144, 249–257. Rhinehart, J. J., Sagone, A. L., Balcerzak, S. P., Ackerman, G. A., and LoBuglio, A. F. (1975). Effects of corticosteroid therapy on human monocyte function. New England Journal of Medicine, 292, 236–241. Riley, V. (1981). Psychoneuroendocrine influences on immunocompetence and neoplasia. Science, 212, 1100–1109. Rimon, R., and Laakso, R.-L. (1985). Life stress and rheumatoid arthritis. Psychotherapy & Psychosomatics, 43, 38–43. Rinner, I., Schauenstein, K., Mangge, H., Porta, S., and Kvetnansky, R. (1992). Opposite effects of mild and severe stress on in vitro activation of rat peripheral blood lymphocytes. Brain, Behavior and Immunity, 6, 130–140. Roess, D. A., Bellone, C. J., Ruh, M. F., Nadel, E. M., and Ruh, T. S. (1982). The effect of glucocorticoids on mitogen-stimulated Blymphocytes: thymidine incorporation and antibody secretion. Endocrinology, 110, 169–175. Rogers, M. P., Trentham, D. E., McCune, W. J., Ginsberg, B. I., Reich, P., and David, J. R. (1979). Abrogation of type II collagen-induced arthritis in rats by psychological stress. Transactions of the Association of American Physicians, 92, 218–228. Rogers, M. P., Trentham, D. E., McCune, W. J., Ginsberg, B. I., Rennke, H. G., Reich, P., et al. (1980). Effect of psychological stress on the induction of arthritis in rats. Arthritis & Rheumatism, 23(12), 1337–1342. Rosenblum, G. A. (1982). Selective allergy to systemic and topical corticosteroids. Ariz Med, 39, 780–781. Rusu, V. M., and Cooper, M. D. (1975). In vivo effects of cortisone on the B cell line in chickens. Journal of Immunology, 115, 1370–1374. Sabiston, B. H., Ste Rose, J. E. M., and Cinader, B. (1978). Temperature stress and immunity in mice. Journal of Immunogenetics, 5, 197–212. Sadeghi, R., Hawrylowicz, C. M., Chernajovsky, Y., and Feldmann, M. (1992). Synergism of glucocorticoids with granulocyte macrophage colony stimulating factor (GM-CSF) but not interferon gamma or interleukin-4 on induction of HLA class II expression on human monocytes. Cytokine, 4, 287–297. Saint-Mezard, P., Chavagnac, C., Bosset, S., Ionescu, M., Peyron, E., Kaiserlian, D., Nicolas, J. F., and Berard, F. (2003). Psychological stress exerts an adjuvant effect on skin dendritic cell functions in vivo. Journal of Immunology, 171 (8), 4073–4080. Sapolsky, R., Rivier, C., Yamamoto, G., Plotsky, P., and Vale, W. (1987). Interleukin-1 stimulates the secretion of hypothalamic corticotropin releasing factor. Science, 238, 522–525. Sapolsky, R. M. (1987). Glucocorticoids and hippocampal damage. Trends in Neuroscience, 10, 346–349.
758
IV. Stress and Immunity
Sapolsky, R. M., Romero, L. M., and Munck, A. U. (2000). How do glucocorticoids influence stress responses? Integrating permissive, suppressive, stimulatory, and preparative actions. Endocr Rev, 21 (1), 55–89. Savu, L., Lombart, C., and Nunez, E. A. (1980). Corticosterone binding globulin: an acute phase “negative” protein in the rat. FEBS Letters, 113, 102–106. Schedlowski, M., Falk, A., Rohne, A., Wagner, T. O. F., Jacobs, R., Tewes, U., and Schmidt, R. E. (1993). Catecholamines induce alterations of distribution and activity of human natural killer (NK) cells. Journal of Clinical Immunology, 13, 344–351. Schedlowski, M., Jacobs, R., Stratman, G., Richter, S., Hädike, A., Tewes, U., Wagner, T. O. F., and Schmidt, R. E. (1993). Changes of natural killer cells during acute psychological stress. Journal of Clinical Immunology, 13, 119–126. Scheinman, R. I., Cogswell, P. C., Lofquist, A. K., and Baldwin, A. S. J. (1995). Role of transcriptional activation of IκBα in mediation of immunosuppression by glucocorticoids. Science, 270, 283–286. Schleimer, R. P., Claman, H. N., and Oronsky, A. (Eds.). (1989). Antiinflammatory steroid action: basic and clinical aspects. San Diego: Academic Press. Schobitz, B., Reul, J. H. M., and Holsboer, F. (1994). The role of the hypothalamic-pituitary-adrenocortical system during inflammatory conditions. Critical Reviews in Neurobiology, 8, 263–291. Schule, R., and Evans, R. M. (1991). Cross-coupling of signal transduction pathways: zinc finger meets leucine zipper. Trends in Genetics, 7, 377–381. Schwab, C. L., Fan, R., Zheng, Q., Myers, L. P., Hebert, P., and Pruett, S. B. (2005). Modeling and predicting stress-induced immunosuppression in mice using blood parameters. Toxicol Sci., 83, 101–113. Segerstrom, S. C., and Miller, G. E. (2004). Psychological stress and the human immune system: a meta-analytic study of 30 years of inquiry. Psychology Bulletin, 130, 601–630. Sephton, S. E., Sapolsky, R. M., Kraemer, H. C., and Spiegel, D. (1998). Absence of diurnal cortisol variation predicts early breast cancer mortality. Preprint Neuroimmunomodulation, 5, 45. Serfling, E., Barthelmas, R., Pfeuffer, I., Schenk, B., Zarius, S., Swoboda, R., Mercurio, F., and Karin, M. (1989). Ubiquitous and lymphocyte-specific factors are involved in the induction of the mouse interleukin 2 gene in T lymphocytes. EMBO Journal, 8, 465–473. Shephard, R. J. (2003). Adhesion molecules, catecholamines and leukocyte redistribution during and following exercise. Sports Med., 33, 261–284. Sheridan, J. F. (1998). Stress-induced modulation of anti-viral immunity—Normal Cousins Memorial Lecture 1997. Brain, Behavior and Immunity, 12, 1–6. Shurin, M. R., Kusnecov, A., Hamill, E., Kaplan, S., and Rabin, B. S. (1994). Stress-induced alteration of polymorphonuclear leukocyte function in rats. Brain, Behavior and Immunity, 8, 163–169. Shurin, M. R., Zhou, D., Kusnecov, A., Rassnick, S., and Rabin, B. S. (1994). Effect of one or more footshocks on spleen and blood lymphocyte proliferation in rats. Brain, Behavior and Immunity, 8, 57–65. Siiteri, P. K., Murai, J. T., Hammond, G. L., Nisker, J. A., Raymoure, W. J., and Kuhn, R. W. (1982). The serum transport of steroid hormones. Recent Progress in Hormone Research, 38, 457–503. Singh, V. K., and Fudenberg, H. H. (1988). Binding of [125I] corticotropin-releasing factor to blood immunocytes and its reduction in Alzheimer’s disease. Immunological Letters, 18, 5–8. Skanse, B., and Miorner, G. (1959). Asian influenza with adrenocortical insufficiency. Lancet, 1, 1121–1123.
Sklar, L. S., and Anisman, H. (1981). Stress and cancer. Psychology Bulletin, 89, 369–406. Sloviter, R. S., Valiquette, G., Abrams, G. M., Ronk, E. C., Sollas, A. I., Paul, L. A., and Nuebort, A. S. L. (1989). Selective loss of hippocampal granule cells in the mature rat brain after adrenalectomy. Science, 243, 535–538. Smith, R. S., Sherman, N. A., and Middleton, E. (1972). Effect of hydrocortisone on immunoglobulin synthesis and secretion by human peripheral blood lymphocytes in vitro. International Archives of Allergy, 43, 859–870. Snijdewint, F. G., Kapsenberg, M. L., Wauben-Penris, P. J. J., and Bos, J. D. (1995). Corticosteroids class-dependently inhibit in vitro Th1- and Th2-type cytokine production. Immunopharmacology, 39, 93–101. Snow, D. H., Ricketts, S. W., and Mason, D. K. (1983). Hematological responses to racing and training exercise in thoroughbred horses, with particular reference to the leukocyte response. Equine Veterinary Journal, 15, 149–154. Snyers, L., DeWit, L., and Content, J. (1990). Glucocorticoid upregulation of high-affinity IL-6 receptors on human epithelial cells. Proceedings of the National Academy of Sciences USA, 87, 2838–2842. Solomon, G. F. (1969). Stress and antibody response in rats. International Archives of Allergy, 35, 97–104. Solomon, G. F., and Moos, R. H. (1964). Emotions, immunity and disease. Archives of General Psychiatry, 11, 657–669. Spain, D. M., and Thalhimer, W. (1951). Temporary accumulation of eosinophilic leucocytes in spleen on mice following administration of cortisone. Proceedings of the Society for Experimental Biology, 76, 320–322. Spencer, R. L., Kalman, B. A., and Dhabhar, F. S. (2001). Role of endogenous glucocorticoids in immune system function: regulation and counterregulation. In B. S. McEwen (Ed.), Handbook of physiology (p. 562). New York: Oxford. Sprent, J., and Tough, D. F. (1994). Lymphocyte life-span and memory. Science, 265, 1395–1400. Spry, C. J. F. (1972). Inhibition of lymphocyte recirculation by stress and corticotropin. Cellular Immunology, 4, 86–92. Stefanski, V., Solomon, G. F., Kling, A. S., Thomas, J., and Plaeger, S. (1996). Impact of social confrontation on rat CD4 T cells bearing different CD45R isoforms. Brain, Behavior and Immunity, 10, 364–379. Stein, M., Ronzoni, E., and Gildea, E. F. (1951). Physiological responses to heat stress and ACTH of normal and schizophrenic subjects. American Journal of Psychiatry, 6, 450–455. Steinman, L. (1991). The development of rational strategies for selective immunotherapy against autoimmune demyelinating disease. Advances in Immunology, 49, 357–379. Stephanou, A., Jessop, D. S., Knight, R. A., and Lightman, S. L. (1990). Corticotropin-releasing factor-like immunoreactivity and mRNA in human leukocytes. Brain, Behavior and Immunity, 4, 67–73. Sternberg, E. M. (1995). Neuroendocrine factors in susceptibility to inflammatory disease: focus on the hypothalamic-pituitaryadrenal axis. Hormone Research, 43, 159–161. Sternberg, E. M. (2001). Neuroendocrine regulation of autoimmune/ inflammatory disease. Journal of Endocrinology, 169, 429– 435. Sternberg, E. M., Chrousos, G. P., Wilder, R. L., and Gold, P. W. (1992). The stress response and the regulation of inflammatory disease. Annals of Internal Medicine, 117, 854–866. Sternberg, E. M., Glowa, J., Smith, M., Calogero, A. E., Listwak, S. J., Aksentijevich, S., Chrousos, G. P., Wilder, R. L., and Gold, P. W. (1992). Corticotropin releasing hormone related behav-
34. Possible Explanations for Salubrious as Well as Harmful Effects ioural and neuroendocrine responses to stress in Lewis and Fischer rats. Brain Research, 570, 54–60. Sternberg, E. M., Hill, J. M., Chrousos, G. P., Kamilaris, T., Listwak, S. J., Gold, P. W., and Wilder, R. L. (1989). Inflammatory mediator-induced hypothalamic-pituitary-adrenal axis activation is defective in streptococcal cell wall arthritis-susceptible Lewis rats. Proceedings of the National Academy of Sciences USA, 86, 2374–2378. Sternberg, E. M., and Wilder, R. L. (1989). The role of the hypothalamic-pituitary-adrenal axis in an experimental model of arthritis. Progress in Neuroendocrinimmunology, 2, 102–108. Sternberg, E. M., Young, W. S., Bernadini, R., Calogero, A. E., Chrousos, G. P., Gold, P. W., and Wilder, R. L. (1989). A central nervous system defect in biosynthesis of corticotropin releasing hormone is associated with susceptibility to streptococcal cell wall-induced arthritis in Lewis rats. Proceedings of the National Academy of Sciences USA, 86, 4771–4775. Straub, R. H., and Besedovsky, H. O. (2003). Integrated evolutionary, immunological, and neuroendocrine framework for the pathogenesis of chronic disabling inflammatory diseases. FASEB J., 17, 2176–2183. Straub, R. H., Dhabhar, F. S., Bijlsma, J. W. J., and Cutolo, M. (2005). How psychological stress via hormones and nerve fibers may exacerbate rheumatoid arthritis. Arthritis & Rheumatism, 52, 16–26. Straub, R. H., and Schedlowski, M. (2002). Immunology and multimodal system interactions in health and disease. Trends Immunol, 23, 118–120. Swingle, W. W., and Remington, J. W. (1944). The role of the adrenal cortex in physiological processes. Physiological Review, 24, 89–127. Takaki, A., Huang, Q.-H., Somogyvari-Vigh, A., and Arimura, A. (1994). Immobilization stress may increase plasma interleukin-6 via central and peripheral catecholamines. Neuroimmunomodulation, 1, 335–342. Tavadia, H. B., Fleming, K. A., Hume, P. D., and Simpson, H. W. (1975). Circadian rhythmicity of human plasma cortisol and PHA-induced lymphocyte transformation. Clinical & Experimental Immunology, 22, 190–193. Thieringer, R., Le Grand, C. B., Carbin, L., Cai, T.-Q., Wong, B., Wright, S. D., and Hermanowski-Vosatka, A. (2001). 11{{beta}}hydroxysteroid dehydrogenase type 1 is induced in human monocytes upon differentiation to macrophages. Journal of Immunology, 167, 30–35. Thomas, N., Edwards, J. L., and Bell, P. A. (1981). Studies of the mechanism of glucocorticoid-induced pyknosis in isolated rat thymocytes. Journal of Steroid Biochemistry, 18, 519–524. Thomason, B. T., Brantley, P. J., Jones, G. N., Dyer, H. R., and Morris, J. L. (1992). The relations between stress and disease activity in rheumatoid arthritis. Journal of Behavioral Medicine, 15, 215–220. Thompson, J., and Van Furth, R. (1973). The effect of glucocorticoids on the kinetics of promonocytes and monocytes of the bone marrow. Journal of Experimental Medicine, 137, 10–21. Thompson, S. P., McMahon, L. J., and Nugent, C. C. (1980). Endogenous cortisol: a regulator of the number of lymphocytes in peripheral blood. Clinical Immunology & Immunopathology, 17, 506–514. Toft, P., Svendsen, P., Tonnesen, E., Rasmussen, J. W., and Christensen, N. J. (1993). Redistribution of lymphocytes after major surgical stress. Acta Anesthesiologica Scandinavica, 37, 245–249. Tone, M., Tone, Y., Adams, E., Yates, S. F., Frewin, M. R., Cobbold, S. P., and Waldmann, H. (2003). From the cover: mouse gluco-
759
corticoid-induced tumor necrosis factor receptor ligand is costimulatory for T cells. Proceedings of the National Academy of Sciences USA, 100, 15059–15064. Tonelli, L., Webster, J. I., Rapp, K. L., and Sternberg, E. (2001). Neuroendocrine responses regulating susceptibility and resistance to autoimmune/inflammatory disease in inbred rat strains. Immunol Rev., 184, 203–211. Tonnesen, E., Christensen, N. J., and Brinklov, M. M. (1987). Natural killer cell activity during cortisol and adrenaline infusion in healthy volunteers. European Journal of Clinical Investigation, 17, 497–503. Torpy, D. J., and Chrousos, G. P. (1996). The three-way interactions between the hypothalamic-pituitary-adrenal and gonadal axes and the immune system. Baillieres Clinical Rheumatology, 10, 181–198. Tsigos, C., and Chrousos, G. P. (1994). Physiology of the hypothalamic-pituitary-adrenal axis in health and dysregulation in psychiatric and autoimmune disorders. Endocrinology & Metabolism Clinics of North America, 23, 451–466. Tuchinda, M., Newcomb, R. W., and DeVald, B. L. (1972). Effect of prednisone treatment on the human immune response to keyhole limpet hemocyanin. International Archives of Allergy, 42, 533–544. Ulich, T. R., Keys, M., Ni, R. X., del Castillo, J., and Dakay, E. B. (1988). The contributions of adrenal hormones, hemodynamic factors, and the endotoxin-related stress reaction to stable prostaglandin analog-induced peripheral lymphopenia and neutrophilia. Journal of Leukocyte Biology, 43, 5–10. Van Den Broek, A. A., Keuning, F. J., Soeharto, R., and Prop, N. (1983). Immune suppression and histophysiology of the immune response I. Cortisone acetate and lymphoid cell migration. Virchows Archiv [Cell Pathol], 43, 43–54. Vidal, C., Tome, S., Fernandez-Redondo, V., and Tato, F. (1994). Systemic allergic reaction to corticosteroids. Contact Dermatitis, 31, 273–274. Viswanathan, K., Daugherty, C., and Dhabhar, F. S. (2005). Stress as an endogenous adjuvant: augmentation of the immunization phase of cell-mediated immunity. International Immunology, 17, 1059–1069. Viswanathan, K., and Dhabhar, F. S. (2005). Stress-induced enhancement of leukocyte trafficking into sites of surgery or immune activation. Proceedings of the National Academy of Sciences USA, 102, 5808–5813. Vivier, E., and Malissen, B. (2005). Innate and adaptive immunity: specificities and signaling hierarchies revisited. Nat. Immunol, 6, 17–21. Walzer, P. D., LaBine, M., Redington, T. J., and Cushion, M. T. (1984). Lymphocyte changes during chronic administration of and withdrawal from corticosteroids: relation to pneumocystis carinii pneumonia. Journal of Immunology, 133, 2502– 2508. Warren, M. K., and Vogel, S. N. (1985). Opposing effects of glucocorticoids on interferon-γ–induced murine macrophage Fc receptor and Ia antigen expression. Journal of Immunology, 134, 2462–2469. Webster, J. I., Tonelli, L., and Sternberg, E. M. (2002). Neuroendocrine regulation of immunity. Annual Reviews Immunology, 20, 125–163. Weigl, B. A. (2000). The significance of stress hormones (glucocorticoids, catecholamines) for eruptions and spontaneous remission phases in psoriasis. Int J Dermatol, 39, 678–688. Weiss, J. M., Schleifer, S. J., Miller, N. E., and Stein, M. (1981). Suppression of immunity by stress: effect of a graded series of stressors. Science, 213, 1397–1400.
760
IV. Stress and Immunity
Whitacre, C. C., Dowdell, K., and Griffin, A. C. (1998). Neuroendocrine influences on experimental autoimmune encephalomyelitis. Annals of the New York Academy of Sciences, 840, 705–716. Whitfield, J. F., MacManus, J. P., and Gillan, D. J. (1973). The calciumdependent stimulation of thymic lymphoblast DNA synthesis and proliferation by a low concentration of cortisol. Hormone & Metabolic Research, 5, 200–204. Whitfield, J. F., MacManus, J. P., and Rixon, R. H. (1970). Cyclic AMP-mediated stimulation of thymocyte proliferation by low concentrations of cortisol. Proceedings of the Society for Experimental Biology, 134, 1170–1174. Whitmore, S. E. (1995). Delayed systemic allergic reactions to corticosteroids. Contact Dermatitis, 32, 193–198. Wick, G., Sgonc, R., and Lechner, O. (1998). Neuroendocrine-immune disturbances in animal models with spontaneous autoimmune diseases. Annals of the New York Academy of Sciences, 840, 591–598. Wiegers, G. J., Labeur, M. S., Stec, I. E., Klinkert, W. E., Holsboe, R. F., and Reul, J. M. (1995). Glucocorticoids accelerate anti-T cell receptor-induced T cell growth. Journal of Immunology, 155, 1893–1902. Wiegers, G. J. Reul, J. M. H. M. (1998). Induction of cytokine receptors by glucocorticoids: functional and pathological significance. Trends in Pharmacological Sciences, 19, 317–321. Wiegers, G. J., Reul, J. M. H. M., Holsboer, F., and De Kloet, E. R. (1994). Enhancement of rat splenic lymphocyte mitogenesis after short term exposure to corticosteroids in vitro. Endocrinology, 135, 2351–2357. Wiegers, G. J., Stec, I. E., Klinkert, W. E., Linthorst, A. C., and Reul, J. M. (2001). Bidirectional effects of corticosterone on splenic Tcell activation: critical role of cell density and culture time. Neuroendocrinology, 73, 139–148. Wieland, S., Dobbeling, U., and Rusconi, S. (1991). Interference and synergism of glucocorticoid receptor and octamer factors. EMBO Journal, 10, 2513–2521. Wilckens, T. (1995). Glucocorticoids and immune function: physiological relevance and pathogenic potential of hormonal dysfunction. Trends in Pharmacological Sciences, 16, 193–197. Wilckens, T., and DeRijk, R. (1997). Glucocorticoids and immune function: unknown dimensions and new frontiers. Immunology Today, 18, 418–424. Wilder, R. L., Allen, J. B., and Hansen, C. (1986). Thymus-dependent and -independent regulation of Ia antigen expression in situ by cells in the synovium of rats with streptococcal cell wall-induced arthritis. Journal of Clinical Investigation, 79, 1160–1171. Wilkinson, S. M. (1994). Hypersensitivity to topical corticosteroids. Clinical & Experimental Dermatology, 19, 1–11.
Williams, T. J., and Yarwood, H. (1990). Effect of glucocorticoids on microvascular permeability. American Review of Respiratory Diseases, 141, S39–S43. Wistar, R., and Hildemann, W. H. (1960). Effect of stress on skin transplantation immunity in mice. Science, 131, 159–160. Wood, P. G., Karol, M. H., Kusnecov, A. W., and Rabin, B. S. (1993). Enhancement of antigen-specific humoral and cell-mediated immunity by electric footshock stress in rats. Brain, Behavior and Immunity, 7, 121–134. Woolley, C. S., Gould, E., and McEwen, B. S. (1990). Exposure to excess glucocorticoids alters dendritic morphology of adult hippocampal pyramidal neurons. Brain Research, 531, 225–231. Woolley, C. S., Gould, E., Sakai, R. R., Spencer, R. L., and McEwen, B. S. (1991). Effects of aldosterone or RU28362 treatment on adrenalectomy-induced cell death in the dentate gyrus of the adult rat. Brain Research, 554, 312–315. Wu, C. Y., Sarfati, M., Heusser, C., Forunier, S., Rubio-Trujillo, M., Peleman, R., and Delespesse, G. (1991). Glucocorticoids increase the synthesis of immunoglobulin E by interleukin 4–stimulated human lymphocytes. Journal of Clinical Investigation, 87, 870–877. Wyllie, A. H., Morris, R. G., Smith, A. L., and Dunlop, D. (1984). Chromatin cleavage in apoptosis: association with condensed chromatin morphology and dependence on macromolecular synthesis. Journal of Pathology, 142, 67–77. Yu, D. T. Y., Clements, P. J., Paulus, H. E., Peter, J. B., Levy, J., and Barnett, E. V. (1974). Human lymphocyte subpopulations. Effects of corticosteroids. Journal of Clinical Investigation, 53, 565–571. Zalcman, S., and Anisman, H. (1993). Acute and chronic stressor effects on the antibody response to sheep red blood cells. Pharmacology, Biochemistry & Behavior, 46, 445–452. Zatz, M. M. (1975). Effects of cortisone on lymphocyte homing. Israel Journal of Medical Sciences, 11, 1368–1372. Zautra, A. J., Okun, M. A., Robinson, S. E., Lee, D., Roth, S. H., and Emmanual, J. (1989). Life stress and lymphocyte alterations among patients with rheumatoid arthritis. Health Psychology, 8, 1–14. Zuckerman, S. H., Shelhaas, J., and Butler, L. D. (1989). Differential regulation of lipopolysaccharide-induced interleukin 1 and tumor necrosis factor synthesis: effects of endogenous and exogenous glucocorticoids and the role of the pituitary-adrenal axis. European Journal of Immunology, 19, 301–305. Zwilling, B. (1992). Stress affects disease outcomes. Confronted with infectious disease agents, the nervous and immune systems interact in complex ways. ASM News, 58, 23–25.
C H A P T E R
35 Positive Affect and Immune Function ANNA L. MARSLAND, SARAH PRESSMAN, AND SHELDON COHEN
II. POSITIVE AFFECT
I. INTRODUCTION 761 II. POSITIVE AFFECT 761 III. THE EMPIRICAL EVIDENCE FOR AN ASSOCIATION BETWEEN PA AND IMMUNE FUNCTION 762 IV. CLINICAL CONTEXT: POSITIVE AFFECT AND HEALTH 769 V. POTENTIAL PATHWAYS LINKING PA AND IMMUNE FUNCTION 771 VI. TRAIT PA AND OTHER RELATED PERSONALITY CONSTRUCTS 773 VII. PSYCHOLOGICAL INTERVENTIONS 773 VIII. SUMMARY 774
Although the literature examining positive psychological constructs and health is growing rapidly, there is little consensus in the field regarding a single definition of positive affect (PA). In this chapter, we define PA as the feelings that reflect a level of pleasurable engagement with the environment such as happiness, joy, excitement, enthusiasm, and contentment (Clark et al., 1989). There are other “positive” psychological constructs used in studies of immunity and health that have similarities to PA. Some are cognitive and motivational constructs such as self-esteem, optimism, extraversion, purpose, and mastery (DeNeve and Cooper, 1998; Lyubomirsky et al., 2005; Ryff, 2003; Salovey et al., 2000; Zautra, 2003), while others are complex measures like quality of life and subjective well-being (e.g., Diener, 1984; McDowell and Newell, 1996; Weisman, 1979) that combine PA in an undifferentiated manner with other constructs. Because our focus is on the influence of affect, we limit this review to studies using scales or experimental manipulations that primarily or solely address emotional response. PA can be brief, longer lasting, or more stable traitlike feelings. Although some use the terms affect, mood, and emotion to distinguish duration, these uses are not applied consistently in the literature, and thus we use these terms interchangeably. We, however, distinguish between studies using measures that assess more stable disposition-like PA, which we refer to as trait PA, and those measuring or manipulating relatively
I. INTRODUCTION It is now over 40 years since it was first hypothesized that emotions could influence immunity and disease (Ader et al., 1987; Solomon and Moos, 1964). Since then, reliable associations have been found between immune function and depression, stress, and anxiety (see reviews by Herbert and Cohen, 1993a, 1993b; Segerstrom and Miller, 2004). In contrast, there has been little work on the effects of positive emotions on immunity and immune-mediated disease (Pressman and Cohen, 2005). Indeed, a search of PsycINFO revealed almost 100 times more studies on “depression and immunity” than there are on “happiness and immunity.” The goal of this chapter is to review evidence for a relationship between positive emotions and immune function, and to explore the implications of this connection for health. PSYCHONEUROIMMUNOLOGY, 4E VOLUME II
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Copyright © 2007 by Elsevier, Inc. All rights of reproduction in any form reserved.
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short-term bouts of positive emotions, which we refer to as state PA. For the purpose of this chapter, we consider state a measurement of moment-to-moment affect lasting up to a day in duration and trait a measure of affect assessed over at least 1 week and often evaluated as how people “typically” feel. The status of measures reflecting the experience of emotion over a few days is less clear, and they are generally thought of as longerlasting state appraisals. An important consideration for immunology researchers interested in studying emotion is the debate regarding the structure of affect (e.g., Ekman, 1992; Izard, 1977; Larsen and Diener, 1992; Russell, 1980; Watson and Tellegen, 1985). There is a growing consensus that positive and negative affect (NA) are broad, underlying dimensions of basic emotions that consistently emerge across studies (Watson and Tellegen, 1985). However, whether they represent two ends of a continuum or are independent concepts is controversial. Should positive and negative affect lie on opposite ends of a bipolar scale, then any effect of PA may merely reflect the absence of NA and vice versa. On the other hand, should they reflect relatively independent constructs, they may have distinctive influences on physiology. Given the strong evidence for the relation between NA and immunity, the magnitude of the correlation between NA and PA is key to understanding the importance of PA. To date, it appears that short-term (minutes, day) measures of PA and NA are strongly negatively correlated, while the longer the period that the measure covers (weeks, months, years, typically), the more independent they become (e.g., Diener and Emmons, 1985; Diener et al., 1985; Watson, 1988). In addition to a positive versus negative valence dimension (e.g., happy versus sad), emotions are often categorized along a second dimension, high versus low activation (aroused versus unaroused), according to a circumplex model (e.g., Russell, 1980). Thus, emotions can be categorized by where they fall on these two dimensions. For example, excitement is positive valence/high activation, and sad is negative valence/ low activation. While there are other ways of distinguishing between emotions, this system appeals to health researchers who equate emotional activation with physiological arousal, which is thought to be a primary pathway through which emotions may influence immunity and health (Cohen et al., 1997b; Krantz et al., 1981). The majority of naturalistic studies examining relations between PA and immune function employ selfreport measures of affect, using adjective checklists such as the Positive and Negative Affect Schedule (PANAS) (Watson et al., 1988) or the vigor subscale
from the Profile of Mood States (POMS) (McNair et al., 1971). Both of these scales have been demonstrated to provide valid and reliable assessments of affect, with a bias towards positive valence/high activation emotions. Depending on the time frame employed when considering the experience of affect, these (and similar) scales are used to measure state (current mood) or trait (typical mood) PA. There are also a number of experimental studies examining associations between PA and immunity utilizing mood manipulation paradigms to determine the impact of transient emotional experiences (states) on immune function. Mood inductions include a number of methods, for example, imagining previous positive events, listening to positive music, making facial expressions, reading emotional statements, and watching films. These procedures are effective in inducing changes in mood that typically last for 10 to 15 minutes (e.g., Frost and Green, 1982).
III. THE EMPIRICAL EVIDENCE FOR AN ASSOCIATION BETWEEN PA AND IMMUNE FUNCTION A recent survey of Medline and PsycINFO and a review of the reference sections of identified papers revealed 25 studies examining the relationship between state or trait PA and immune function (Pressman and Cohen, 2005) (see Tables 1 and 2). The majority of these studies focus on the impact of the experimental induction of state positive moods, while the remainder involve naturalistic assessments of PA and immunity.
A. Mood Induction Studies Of the 15 studies that examined mood induction, 8 assessed the effects of state PA on levels of secretory immunoglobulin A (sIgA) measured in saliva. SIgA is an antibody that provides the main immunological defense of mucosal surfaces and plays an important role in primary defense against viral and bacterial infection. Early studies measured the absolute concentration of total sIgA in saliva samples and were criticized because of the possibility that mood might alter saliva flow rate (Stone et al., 1987a). However, later studies controlling for saliva flow (using secretion rate or adjusting sIgA concentration for flow rate) have found similar results. In short, various forms of positive mood induction, including watching films, listening to positive music, or reflecting on positive personal experiences increase total sIgA levels in saliva. (Dillon et al., 1985; Harrison et al., 2000; Hucklebridge et al.,
TABLE 1 Summary of Mood Induction and Immune Function Studies (From Pressman and Cohen, Psychological Bulletin, 2005. Copyright 2005 by the American Psychological Association. Adapted with permission). Study
Participants
Dependent measure
Mood induction
Berk et al., 2001
52 healthy men (M = 27)
Humorous film (No control condition)
NKCC; Plasma Ig A, G, M; # T- and Bcells; IFN gamma
Dillon et al., 1985
10 students (M = 23)
Humorous film and control condition
SIgA
Futterman et al., 1992
5 actors (ages 25–38)
Monologue based on personal happy, sad, or neutral experience
NKCC; Cell subtype numbers (CD56, CD57, T-cell subgroups)
Futterman et al., 1994
14 male actors (M = 35)
NKCC; lymphocyte proliferation to PHA; Cell subtype numbers (CD57, NK, and T-cells)
Harrison et al., 2000
30 students (M = 21)
Hucklebridge et al., 2000 (2 studies)
Knapp et al., 1992
Study 1: 19 female students Study 2: 41 male and female students (M = 20) 20 volunteers (ages 19–30)
Labott et al., 1990 Lambert and Lambert, 1995
39 women (M = 22) 39 5th grade students
Five mood inductions on separate days; induced high/low arousal PA and NA by reading scenarios and using personal memories (No control) Humor and excitement inducing films and control condition Study 1: Self-reflection on happy versus guilty life experience Study 2: Happy versus sad music No control condition Two 2.5 hour sessions on different days. Recall of positive or negative personal event and reenactment Humorous and sad films and control condition Humorous program and control condition
McCraty et al., 1996
10 healthy volunteers (M = 41)
Mittwoch-Jaffe, 1995
123 students (M = 23)
Njus et al., 1996
50 students
Perera et al., 1998 Yoshino et al., 1996
Zachariae et al., 1991
16 students (M = 25) 26 women with rheumatoid arthritis and 31 healthy controls 11 hypnotizable students
Zachariae et al., 2001
15 hypnotizable students
Music inducing calm with energetic alertness and self-induced positive emotional states of appreciation versus non-appreciation. No control condition Positive (humorous) and negative films. No control condition Writing about humorous or negative film or neutral control topic Humorous or neutral film 3 hour performance of “Rakugo” (Japanese comedy). No control condition Hypnotized to feel happiness and well-being versus anger and depression. No control condition Hypnotized to feel sadness, happiness, and anger. No control condition
SIgA (measured 2 months after each film) SIgA
Lymphocyte proliferation to PHA, ConA, and PWM; NKCC; T-cell subsets SIgA SIgA
SIgA
IL-1beta, IL-2, IL-3, IL-6, TNF-alpha SIgA
SIgA and salivary lysozyme Substance P, CD4 : CD8 ration, NKCC, IL-6 and IFN-gamma Monocyte chemotaxis
Hypersensitivity response to histamine
Findings Increased NKCC; IgG, A, & M; activated T, cytotoxic T, helper- T, B, and NK cell numbers; total leukocytes, and IFN gamma. SIgA increased from baseline in mood induction, but not during control condition. More immune fluctuation (combined) for affect inductions versus neutral condition and for aroused conditions (happy, anxious) than unaroused (depression, neutral). All mood states were associated with NKCC and NK cell percent. Response to PHA increased after positive moods and decreased after negative moods. SIgA increased in response to all 3 films. SIgA increased with both manipulations regardless of valence. More pronounced elevation for happy mood.
PHA stimulated proliferation decreased for PA and NA inductions (Con A decreased with NA only).
Humorous film associated with increased SIgA. SIgA increased in response to the humorous, but not the nonhumorous, film. SIgA increased by 55% with calm/alert music and by 50% with appreciation induction. Simultaneous calm/alert music and appreciation produced a 141% increase.
Positive mood induction associated with decreased TNF and increased IL-2 and IL-3. Writing about positive or negative films associated with increased SIgA when compared with writing about neutral topic. Both lysozyme and SIgA increased with humorous versus neutral film. Comedy associated with decreased IL-6 in arthritic patients, and a decrease in IFN-gamma in both groups. Chemotactic index was higher after happy-relaxed induction versus baseline and NA states.
No effect of induced emotion was found on the size of the wheal reaction.
TABLE 2 Study
Summary of Naturalistic Mood Studies and Immune Function (adapted from Pressman and Cohen, 2005)
Participants
Design/Independent measure
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Costanzo et al., 2004
18 older males and females (M = 84)
Cross-sectional. PA and NA measured using short form of POMS based on how they felt during the past week and optimism
Evans et al., 1993
12 students (Age approx. 20)
Logan et al., 1998
9 healthy subject with history of cold sores (ages 20–40)
Longitudinal—2 weeks ambulatory monitoring of mood (Nowlis Mood Adjective Checklist) Longitudinal—3 months daily mood report on bipolar mood continuums (e.g., happy-unhappy) also Affect Intensity Scale
Lutgendorf et al., 2001
30 older adults moving to assisted living and 28 non-moving controls (M = 78)
Marsland et al., 2006
84 healthy graduate students (M = 24)
Moss et al., 1989
10 healthy subjects (M = 24)
Ryff et al., 2004
135 older women (ages 61–91)
Stone et al., 1987
30 graduate students (M = 24.5)
Stone et al., 1994
96 adults (M = 42)
Valdimarsdottir and Bovbjerg, 1997
48 healthy women (M = 39)
Longitudinal (1 month before move and 2 weeks and 3 months post-move). PA and NA measured using short form of POMS based on how they felt during the past week. Cross-sectional. PA assessed with adjective checklist based on how they usually are as compared to peers and measured after first 2 vaccinations in 3-vaccine sequence Longitudinal—4 weeks of weekly mood questionnaires and blood draws. PA assessed with POMS Cross-sectional—4 days of mood report on PANAS, short form of Watson MASQ (happy, cheerful, fun over past week) and Ryff eudaimonic well-being scale and 1 blood draw Longitudinal—4 weeks ambulatory monitoring of daily mood (Nowlis Mood Adjectives) Longitudinal—12 weeks ambulatory monitoring of daily mood with PANAS Cross-sectional—2 days of mood report on subject of POMS adjectives from factor analysis
Dependent measure
Findings
Production of IL-2, IFNgamma, and IL-10 by PBMCs stimulated with live influenza virus and vaccine SIgA
PA and optimism positively associated with T-helper type 1 cytokine responses to live virus and vaccine. Higher NA associated with lower cytokine responses.
Weekly blood draw to measure T lymphocytes and NK cell number
NKCC, IL-6, and IgG antibody titers to EBV
Within subject analysis showed higher SIgA levels on days with negative mood. More contentment correlated with lower NK level and elevated CD8+ cells the week before cold sore outbreak. Greater depression (combination of low happiness, low hopefulness) associated with lower CD8+ numbers. Across both groups and all time-points, higher PA was associated with greater NKCC. At the 2-week post-move time-point, higher PA associated with lower EBV titers across both groups.
Antibody response to hepatitis B vaccination
Trait PA was associated with higher levels of antibody production, independently of NA and closely related constructs such as optimism and extraversion.
NKCC
No correlation between any mood item (NA or PA) and NKCC.
IL-6
No association between mood and IL-6, but eudaimonic factors (high life purpose) correlated with lower IL-6.
Antigen-specific SIgA in response to novel antigen-rabbit albumin Antigen-specific SIgA in response to novel antigen-rabbit albumin NKCA
SIgA higher on days with high PA and lower on days with high NA. SIgA higher on days with high PA and lower on days with high NA. PA associated with higher NKCA, NA associated with lower. Significant interaction where PA is only beneficial when some NA present.
35. Positive Affect and Immune Function
2000; Labott et al., 1990; Lambert and Lambert, 1995; McClelland and Cheriff, 1997; McCraty et al., 1996; Njus et al., 1996; Perera et al., 1998). All of these studies examined healthy, young adults except the study by Lambert and Lambert (1995), which demonstrated the same effect in a sample of fifth grade children. All but two (Lambert and Lambert, 1995; McCraty et al., 1996) studies confirmed that the mood induction was successful. Furthermore, the majority of the studies included an emotionally neutral condition to control for diurnal variation, passage of time, and other contextual factors. Plasma levels of immunoglobulins G, A, and M have also been shown to increase in response to a film designed to stimulate mirthful laughter (Berk et al., 2001). Two studies in this literature have examined whether mood-induced increases in sIgA are valence specific (Hucklebridge et al., 2000; Njus et al., 1996). Njus and colleagues (1996) examined the impact of writing about films designed to arouse positive or negative moods (a Bill Cosby performance or a documentary about the death of a child) on salivary sIgA levels among 50 healthy, undergraduate volunteers. After watching one of the two films, subjects were instructed to write about either the film or a mundane topic (their shoes). Saliva samples were obtained before and immediately after the writing exercise and again 24 and 48 hours later. Manipulation checks (selfreported moods) confirmed that the films were effective at inducing positive and negative affect, respectively. Moreover, subjects who wrote about either film had higher concentrations of salivary sIgA than the control groups who wrote about their shoes. There was no differential effect of positive versus negative mood states on sIgA. Similarly, Hucklebridge et al. (2000) reported on two separate experiments examining the impact of positive and negative mood induction on sIgA concentration. In the first, 19 healthy female subjects attended two laboratory sessions and were asked to write for 10 minutes about a past situation in which they had been either “very happy” or “very guilty.” Mood ratings validated the efficacy of the manipulation. In the second study, 41 healthy male and female undergraduates listened to music that had previously been demonstrated to induce sad and happy mood states. Both experiments showed a significant elevation in sIgA concentration and secretion rate in response to mood manipulations regardless of the valence of the induced emotion. Thus, although there is consistent evidence for mood-induced increases in total sIgA concentration, it appears to be the activation dimension of the emotion, rather than the valence, that is associated with increased antibody levels. This conclusion is consistent with the studies showing an
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increase in total salivary sIgA levels in response to acute laboratory stress tasks that typically induce negative mood states (e.g., Bristow et al., 1997; Willemson et al., 1998). Induced positive emotions have also been shown to affect a handful of other immunologic parameters, although these findings are more difficult to interpret. A few studies have examined positive mood-induced changes in the numbers of immune cells in peripheral circulation. Here, findings are mixed, with some studies showing increases in the percentage of NK cells and in absolute numbers of circulating B-cells, Tcells, T-helper cells, cytotoxic T-cells, and total leukocytes (Berk et al., 2001; Futterman et al., 1992, 1994), and another showing no change (Knapp et al., 1992). The effect of induced PA on measures of cellular immune function has also received little attention. A few studies have examined NK cell cytotoxicity (NKCC), and initial findings suggest a mood-induced increase in this measure (Berk et al., 2001; Futterman et al., 1994), but it is not clear that this is specific to moods of positive valence (Futterman et al., 1994). Findings from the two studies examining phytohemagglutinin (PHA)-induced proliferation of lymphocytes are also mixed. Futterman et al. (1994) found that induced positive moods were associated with increases and induced negative moods with decreases in this measure. In contrast, Knapp et al. (1992) found decreases in PHA-elicited proliferation with both positive and negative mood inductions. Overall, interpretation of these few mixed findings is limited by small sample sizes and a general failure to include an emotionally neutral control condition or to differentiate between high and low activated positive states, making it premature to form any conclusions. More recent attention in the field of psychoneuroimmunology has turned to relationships between emotions and the concentration of cytokines in peripheral circulation. The health significance of circulating levels of cytokines is difficult to interpret, as it reflects regulation of levels in response to specific demands. Nevertheless, the few studies that have examined cytokine levels in response to positive mood induction provide some evidence that state PA is associated with increases in interleukin (IL)-2, IL-3, and decreases in tumor necrosis factor-alpha (Berk et al., 2001; MittwochJaffe et al., 1995). Findings are less consistent for interferon gamma, with one study showing PA-related increases (Berk et al., 2001) and another showing decreases (Yoshino et al., 1996). Finally, a study examining circulating levels of IL-6 among patients with rheumatoid arthritis demonstrated that watching a comedy performance was associated with a decrease in levels of this pro-inflammatory cytokine (Yoshino
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et al., 1996) that may be a marker of a short-term beneficial health effect. A few studies have examined whether induced PA is associated with a more clinically meaningful measure of cellular immune function, allergic hypersensitivity reactions in response to allergen, or histamine exposure in allergic subjects. In support of a health benefit of state PA, a reduction in allergic response (wheal size) was found when pleasantness and relaxation were induced by hypnotic suggestion (Laidlaw et al., 1996) and when humor was induced by watching a film (Kimata, 2001). In contrast, Zachariae and colleagues (2001) did not find an effect of hypnotically induced positive or negative moods on magnitude of hypersensitivity response. In sum, the most consistent findings from studies examining the effects of brief positive mood induction on immune function in healthy individuals support PA-related increases in sIgA levels, numbers of immune cells in peripheral circulation, and possibly NK cell activity, suggesting an upregulation of parameters of innate immunity. These findings are consistent with those found in response to acute laboratory stress tasks designed to elicit negative moods, such as speech and mental arithmetic tasks (for review, see Segerstrom and Miller, 2004). Similar immune responses to positive and negative mood states suggest that it is the increase in affective arousal, rather than the positive or negative valence of the emotion, that contributes to immunological variability. Further evidence for this is derived from the few studies that have induced both positive and negative moods in the laboratory and show similar immune effects (Futterman et al., 1992; Knapp et al., 1992; Hucklebridge et al., 2000; Njus et al., 1996). To date, the majority of positive mood induction protocols have induced activated positive states, such as humor and excitement. It remains to be determined whether low activation positive mood states such as calm and pleasure are associated with similar immune responses. There is now a large body of literature demonstrating that immune changes in response to acute laboratory stress are largely mediated by activation of the SNS (Marsland et al., 2001a). For example, it has been demonstrated that immune outcomes assessed after a laboratory stressor covary with the magnitude of sympathetic activation elicited under the same stimulus conditions (e.g., Manuck et al., 1991). Pharmacological studies provide further support for this pathway, with the administration of physiological doses of sympathetic stimulants (e.g., exogenous catecholamines) invoking functional modulation of innate immunity that is similar to that seen during mental stress (van
Tits et al., 1990). Furthermore, acute stress-related immune responses are blocked by adrenergic receptor inhibition (Bachen et al., 1995). Given the similarity in immune responses to both positive and negative mood induction, it is possible that the arousal dimension of these mood states induces activation of the SNS and an upregulation of innate immunity. It has been proposed that brief increases in innate immune function in response to acute challenge are adaptive, reducing risk of infection and aiding in wound healing (Segerstrom and Miller, 2004).
B. Naturalistic Studies of Positive Emotional States Others have studied self-reports of PA and their relations with immune outcomes in naturalistic settings. These studies utilize daily diary measures of mood states and examine mood-related immune function. A well-designed study by Stone and colleagues (1987) had volunteers ingest a capsule containing an innocuous novel antigen (rabbit albumin) daily for 10 weeks so that the researchers could determine the specific sIgA response to the novel antigen, unlike other studies that look at more general total (non-specific) levels of this marker. For the latter 8 weeks of this period, volunteers also completed daily diaries, recording positive and negative mood states, and gave daily saliva samples to assess specific sIgA to the novel antigen. Within subjects, analyses revealed that antigen-specific sIgA was higher on days with higher positive mood relative to days with lower positive mood. Conversely, sIgA was lower on days with high negative mood relative to days with lower negative mood (Stone et al., 1987). These results were replicated in a subsequent study by the same group that monitored mood and antibody levels over a 12-week period (Stone et al., 1994). Evans et al. (1993) examined relationships between daily mood and non-specific sIgA over a 2-week measurement period. Although they found no associations between positive mood and total sIgA, negative mood was associated with higher total sIgA concentration and secretion rate. It may be that these results differ from the studies discussed above because the specific marker of immune activity in response to an antigenic challenge used in Stone’s work better gauges immune function than the non-specific and unstimulated marker used here. Further naturalistic studies are indicated to aid in better understanding relationships between acute mood states and immune function and disentangling the differential roles of emotional valence and arousal.
35. Positive Affect and Immune Function
C. Naturalistic Studies of Positive Emotional Traits 1. General Findings Other naturalistic research has explored the relationship between longer-lasting PA and NKCC. For example, Lutgendorf et al. (2001) employed a sample of 58 older adults (65–89 years), 30 of whom were moving to an assisted living facility. They measured mood over the past week using the POMS and assessed NKCC on three occasions, 1 month before the move, and 2 weeks and 3 months after the move. Across the whole sample and study period, higher levels of vigor were associated with greater NKCC. Higher vigor was also associated with lower IgG antibody titers to Epstein-Barr Virus (EBV), as measured at the 2-week post-move assessment. These results suggest that a trait PA measure is associated with increased cellular immune competence, including more effective immune control of latent EBV. Valdimarsdottir and Bovbjerg (1997) also found a relationship between PA (averaged over a 2-day period) and NKCC. In this study, 48 healthy female volunteers completed a positive and negative adjective checklist derived from the POMS on 2 consecutive days. Overall, higher levels of PA were associated with greater NKCC. Conversely, when compared with women who endorsed no NA, the 26 women who endorsed some NA had lower NKCC. Interestingly, there was also an interaction between PA and NA scores in predicting NKCC, with individuals who endorsed both lower levels of PA and the presence of some NA showing lower NKCC than individuals with either higher PA or no negative mood. Thus, it is possible that PA is protective for individuals who also experience negative mood traits. In contrast to the above two studies, Moss et al. (1989) tracked relationships between weekly positive moods and NKCC for 4 weeks during summer vacation among 10 healthy professional students and found no consistent effects of mood on NKCC. These findings are more difficult to interpret as a consequence of a large interindividual variability in NKCC (Moss et al., 1989). Evidence suggesting that trait PA is associated with more effective cellular immune function is provided by a recent study examining in vitro cytokine responses to live influenza virus and to influenza vaccine among 18 healthy older adults (75–91 years) who had previously received the influenza vaccine (Costanzo et al., 2004). The POMS was employed here as a measure of affect over the course of the past week. Higher levels of PA (and optimism) were associated with greater Thelper type 1 (TH1) cytokine (IL-2 and IFN-gamma) responses to in vitro stimulation of peripheral blood
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mononuclear cells with live influenza virus or vaccine. Conversely, higher NA was associated with lower TH1 cytokine responses, indicating a potential influence of affect on cell memory. TH2 cytokine responses were largely unaffected by mood. It is unclear whether these findings reflect independent effects of PA and NA. Two other studies have examined associations between trait affect and immune responses among individuals with immune-related diseases. For example, Logan et al. (1998) followed 10 individuals with a history of herpes labialis (cold sores) over a 3month period, recorded daily state measures of PA and NA, and drew blood each week for the determination of numbers of circulating T lymphocytes and NK cells. In the week prior to a cold sore outbreak, individuals who endorsed being more content demonstrated higher numbers of NK cells and cytotoxic T-cells than individuals who were discontent. Conversely, individuals who reported low happiness/ hopefulness showed lower CD8+ cell numbers than those at the other end of the happiness continuum. Similarly, Laidlaw et al. (1994) found that individuals with allergies who endorsed greater liveliness on a bipolar continuum from liveliness to listless and more vigor on the POMS, as averaged over a 2-week period, had smaller mean hypersensitivity skin responses to allergens than their more listless and lower vigor counterparts. Because positive and negative affect were assessed in these studies on a single continuum, it is impossible to know whether one or both valences contributed to the reported associations. In sum, available evidence from the few naturalistic studies examining mood across periods ranging from a few days to a couple of weeks suggests that PA is associated with markers of immune function, including higher NK cell number and activity, greater control of latent EBV, and increased TH1 cytokine responses to in vitro stimulation with live influenza virus. Of greater potential clinical relevance are studies linking PA to an increasing number of circulating CD8+ and NK cells among individuals with herpes and a reduction in allergic response in individuals with allergies. Although this literature is not yet convincing, these findings raise the possibility that PA-related changes in immune function confer a health benefit. However, because these studies used scales that included adjectives that primarily tapped vigor (for example, energetic, peppy, and vigorous), it is possible that the association of PA with immunity reported here merely occurs because the PA measures that were used assessed underlying health status. To date, the majority of studies examining relationships between trait affect and immunity have focused on mood averaged across relatively short periods
IV. Stress and Immunity
(days to a couple of weeks). In contrast, the literature examining relationships between emotions and health has focused on stable, dispositional characteristics, which may be associated with more stable immune differences of greater potential health significance. There is no single accepted method of measuring stable dispositions; however, one method that is widely employed is to ask people to characterize themselves as they typically are. Using this method, a large literature has demonstrated a reliable association between self-endorsed NA and immune function (for reviews, see Herbert and Cohen, 1993a; Kiecolt-Glaser et al., 2002). In contrast, relations between dispositional PA and immunity have received little attention. 2. Trait PA and Vaccination Response: The Pittsburgh Hepatitis B Study We recently reported results of one of the first studies to explore relationships between a dispositional measure of PA and immune function, examining whether individuals’ perceptions of their positive affective style were associated with antibody response to hepatitis B vaccination (Marsland et al., 2006). In this study, 84 healthy male and female graduate students (ages 20–35) who tested negative for prior exposure to hepatitis B virus were administered the standard series of three hepatitis B vaccinations. The first two vaccinations were given 6 weeks apart, with a follow-up booster dose administered 6 months following the first shot. Five months following the initial vaccination, each subject completed a battery of psychosocial measures, assessing trait positive and negative affect, extraversion, optimism, depression, and health behaviors, and a blood sample was drawn to assess hepatitis B surface antibody levels. Our measure of trait PA was derived from a factor analysis of the POMS affect scale (Usala and Hertzog, 1989) and included nine positive (lively, full-of-pep, energetic, happy, pleased, cheerful, atease, calm, and relaxed) and nine negative (sad, depressed, unhappy, on-edge, nervous, tense, hostile, resentful, and angry) mood adjectives. For each item, subjects were required to rate how accurately the trait described them as they typically are, as compared with other persons of the same sex. Cohen et al. (2003) found that this measure of dispositional affect correlated highly with an aggregate measure of mood averaged across a 7-day period and that it predicted vulnerability to upper respiratory infections equivalently to the aggregated measure. Our decision to focus on the influence of affective style on antibody response after the second vaccination in the sequence was based on (1) an existing literature suggesting that trait negative affect has its greatest impact on secondary as opposed to primary immune
response to vaccination (as reviewed by Cohen et al., 2001); (2) evidence that psychosocial factors are associated with magnitude of antibody response at this time (e.g., Jabaaij et al., 1993; Marsland et al., 2001b); and (3) evidence that there is widespread interindividual variability in the magnitude of antibody response following the second vaccination in the sequence (Szmuness et al., 1980), enabling us to explore emotional factors associated with individual difference in response. The primary question of interest in this study was whether individual differences in trait PA were related to subjects’ ability to mount an antibody response to the vaccine. In this regard, we found that, when compared with low antibody responders, subjects who mounted higher antibody responses to hepatitis B vaccination following the first two doses displayed higher levels of trait PA (b = .54, p < .03), with the odds of an individual with high trait PA belonging to the high antibody response group being 1.73 times that of an individual with low trait PA. These findings are displayed in Figure 1. A large number of control factors (including age, sex, body mass, smoking, alcohol use, and exercise) failed to explain the higher antibody responses among individuals high in trait PA. We next took a closer look at the activation level of the positive emotions to determine whether the relationship between PA and antibody response was specific to emotions of low or high activation/arousal. The relationship between PA and higher antibody response was similar for three subgroups of positive emotions: (1) well-being (happy, pleased, cheerful); (2) calm (atease, calm, relaxed: low arousal); and (3) vigor (lively, full-of-pep, energetic: high arousal), suggesting that the associations between trait PA and antibody
0.4 0.3 0.2 Standard Affect Scores
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0.1 PA
0
NA
-0.1 -0.2 -0.3 -0.4 Low Ab
High Ab
FIGURE 1 Standardized positive and negative affect scores among individuals high and low in antibody response. (From Marsland et al., 2006. Brain, Behavior and Immunity.)
35. Positive Affect and Immune Function
response are equivalent irrespective of activation/ arousal dimension. We previously reported that trait NA is significantly related to lower antibody responses to hepatitis B vaccination (Marsland et al., 2001b), raising the possibility that the findings we reported above reflect the absence of NA rather than the presence of positive emotional styles. Thus, we next examined whether the relationship between trait PA and antibody response was independent of the influences of trait NA. When the two affect measures were entered into the regression model simultaneously to test the independent contribution of each factor, PA remained the dominant factor predicting antibody group. In contrast, no independent influence of trait NA was observed. To date, the literature has focused on the relationships between trait NA and immune function and health, with little consideration of the role of trait PA. Our findings suggest that, in the presence of PA, there is no independent effect of trait NA on antibody response. Furthermore, previous studies, including our own, that find a relationship between trait NA and immune response may reflect the absence of PA, rather than the presence of distinct negative feelings. This interpretation is consistent with findings of Cohen et al. (2003) that positive, but not negative, emotional styles predict the incidence of upper respiratory infections.
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line medical conditions, body mass index, smoking, drinking, sociodemographic characteristics (including age), and levels of negative affect (NA), individuals who scored higher PA were half as likely to die during the follow-up than those who endorsed lower levels of PA. Other prospective studies have similarly demonstrated that PA is associated with lower mortality among community-residing elderly samples (e.g., Kawamoto and Doi, 2002; Levy et al., 2002; Maier and Smith, 1999; Parker et al., 1992). However, the evidence from two studies of seniors institutionalized in nursing homes looks quite different from that found for those residing in the community. In these cases, higher levels of PA were associated with increased risk for mortality (Janoff-Bulman and Marshall, 1982; Stones et al., 1989). Moreover, the few studies of other populations are inconsistent and include evidence that PA is not associated with mortality (Kaplan and Camacho, 1983), is associated with a decreased risk (Koivumaa-Honkanen et al., 2000, 2001), and is associated with an increased risk (Friedman et al., 1993). In sum, existing evidence suggests that trait PA is associated with greater longevity in the relatively healthy community-residing elderly. Work with other populations is limited to date but suggests the possibility that PA may not always be beneficial.
B. Positive Affect and Morbidity IV. CLINICAL CONTEXT: POSITIVE AFFECT AND HEALTH In general, the literature examining the association between PA and health has not focused on the role of PA in specific immune-mediated diseases. Instead, it primarily includes studies with unspecified pathologies (e.g., total mortality) and studies of a broad range of diseases, some with obvious (e.g., infection) or possible (e.g., coronary heart disease) immune etiology. Because the literature is small, and because immune function could play a role in many of the pathological processes involved, we provide an overview of the entire literature examining objective health outcomes, rather than focusing on only those studies that are obviously immune mediated.
A. Positive Affect and Mortality A recent review provides evidence for an association between PA and decreased mortality rates in the community-residing elderly (Pressman and Cohen, 2005). For example, Ostir and colleagues (2000) followed 2,282 older Mexican Americans (65–99 years) for 2 years and found that, after controlling for base-
1. General Findings A large cross-sectional literature has examined PA among people with chronic disease. Not surprisingly, they find lower levels of PA among individuals with physical health problems than among healthy controls and declines in PA with increasing severity of disease. For example, patients with lupus (Pfeiffer and Wetstone, 1988), gastrointestinal cancer (Hornquist et al., 1992), hypertension (Knox et al., 1988), fibromyalgia (Celiker and Borman, 2001), arthritis (Celiker and Borman, 2001), and increasing numbers of chronic medical conditions (Jelicic and Kempen, 1999) report lower PA than healthy controls. It is likely that this reflects the influence of the disease on PA, rather than the influence of PA on disease. Interestingly, however, there is some recent evidence that individuals with chronic illness adapt over time, with PA levels eventually returning to similar levels to those reported by healthy controls (e.g., Riis et al., 2005). The more conservative prospective studies of PA provide stronger support for the hypothesis that PA contributes to better health (Pressman and Cohen, 2005). Here, trait PA is assessed in people who are healthy at baseline and correlated with later (months to years) disease onset. In these studies, trait PA has
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been associated with lower rates of stroke among noninstitutionalized elderly (Ostir et al., 2001), lower rates of re-hospitalization for coronary problems (Middleton and Byrd, 1996), fewer injuries (KoivumaaHonkanen et al., 2000; Smith et al., 1997), and improved pregnancy outcomes among women undergoing assisted fertilization (Klonoff-Cohen et al., 2001). These community studies are often limited by a lack of control for factors that may influence both PA and disease susceptibility, and many do not rule out the possibility that PA itself (e.g., endorsing of items such as energetic, full-of-pep, and vigorous) is merely a marker of sub-clinical disease processes. 2. PA and Susceptibility to Upper Respiratory Infection: The Pittsburgh Cold Study Viral challenge studies resolve some of the limitations of community studies by selecting disease- and symptom-free volunteers and experimentally exposing them to a virus after assessment of PA and other factors that may influence susceptibility to upper respiratory infection. A recent viral challenge study from our group provides initial evidence to corroborate prospective findings from community studies by demonstrating that individuals who characterize themselves by moods such as happy, pleased, relaxed, and lively are less susceptible to upper respiratory infections (Cohen et al., 2003). In this study, 334 healthy male and female volunteers (18–54 years) were interviewed by telephone three times per week for 2 weeks to assess daily levels of PA and NA using an adjective checklist derived from the POMS (Usala and Hertzog, 1989). Adjective ratings were averaged over the 2 weeks to obtain an estimate of trait PA and NA. Subjects were then quarantined, and a baseline assessment of respiratory symptoms (including self-reported symptoms, two objective indicators of illness: nasal mucociliary clearance and nasal mucus production, and pre-challenge antibody titer) was performed before they were experimentally inoculated with one of two rhinoviruses. Quarantine continued for 5 days after exposure. On each day, subjects completed a respiratory symptoms questionnaire and were tested for the two objective markers of illness. Presence of an infection was biologically verified by viral isolation in nasal secretion samples and four-fold increases in virus-specific antibody in serum. Volunteers were considered to have a cold if they were both infected and met illness criteria. Finally, on the day before viralchallenge, 12 saliva samples were obtained for the measurement of salivary cortisol. Figure 2 depicts the study’s major finding. For both viruses, higher trait PA was associated (in a dose-
response manner) with lower risk of developing a cold. In contrast, there was no relationship between trait NA and susceptibility to colds, and the association of PA and colds was independent of NA. A large number of control factors (including age, sex, education, race, body mass, season, and pre-challenge virus-specific antibody) were not able to explain the decreased risk for colds among persons reporting higher dispositional PA. Consistent with findings from other studies (reviewed in Pressman and Cohen, 2005), individuals high in trait PA also reported fewer and less severe symptoms in response to verified upper respiratory infection (Cohen et al., 2003). Although trait PA was associated with lower levels of epinephrine, norepinephrine, and cortisol and better health practices, including better sleep quality and efficiency and more exercise, none of these accounted for the PA association with colds. However, higher PA was also associated with less production of IL-6 (in nasal secretions) in response to infection, and the data were consistent with IL-6 partly mediating the association of PA and upper respiratory disease (Doyle et al., 2006).
C. Positive Affect and Disease Course 1. Survival Comparatively few studies have examined whether PA predicts survival among people with chronic disease, and available findings are mixed. Based on their review of the literature, Pressman and Cohen (2005) concluded that higher levels of trait PA may be
FIGURE 2 Positive emotional style and incidence of clinical colds using objective and subjective criteria for illness. (From Cohen et al., 2003. Psychosomatic Medicine, 65, 652–657.)
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35. Positive Affect and Immune Function
detrimental to the health of individuals who have advanced disease with a poor short-term prognosis, such as patients with melanoma (Brown et al., 2000), metastatic breast cancer (Derogatis et al., 1979), and end-stage renal disease (Devins et al., 1990), possibly as a consequence of underreporting of symptoms or a lack of adherence to treatment. In contrast, individuals with diseases that have better prospects for longerterm survival, such as AIDS (Moskowitz, 2003), breast cancer (Levy et al., 1988), and coronary heart disease (van Domburg et al., 2001), were generally benefited by PA. 2. Asthma Severity In contrast, there is a growing literature on the role of state PA in triggering asthma attacks (see review in Pressman and Cohen, 2005). In laboratory studies of asthmatics, acute states of arousal (either induced PA or NA) appear to worsen pulmonary outcomes (e.g., Ritz et al., 2000a; Ritz et al., 2000b; Ritz et al., 2001; Florin et al., 1985). In contrast, naturalistic studies typically found that state PA was associated with improved lung function (e.g., Apter et al., 1997). The reason may be that most laboratory inductions are associated with more intense and arousing emotions as compared to the day-to-day fluctuations that occur in naturalistic follow-ups. In fact, Ritz and Steptoe (2000) found that there was a decrease in pulmonary function in a naturalistic study on the occasions that adult asthmatic subjects reported their most extreme levels of positive and negative moods. Hence, the association between state PA and lung function outcomes may be curvilinear, with small to moderate changes in mood improving function but truly intense emotions having detrimental effects associated with arousal. This is consistent with findings that strong emotional arousal, irrespective of valence, activates the immune system, increasing the likelihood of an inflammatory response and associated airway constriction in the lungs of asthmatics.
V. POTENTIAL PATHWAYS LINKING PA AND IMMUNE FUNCTION The pathways through which PA influences immune function are not entirely clear. To help provide a theoretical framework to guide future research, we propose two models linking trait PA to immune function: a main (direct) effect model and a stress-buffering model (Figures 3 and 4; adapted from Pressman and Cohen, 2005). In the first case, PA has a direct effect on behavioral and biological mechanisms that influence immune
Positive Affect Endogenous Opioids
ANS & HPA Activity
Social Ties
Health Practices
Immune Function FIGURE 3 The Direct Effect Model: Direct pathways through which PA might influence onset and progression of immune system-mediated disease. (From Figure 1, Pressman and Cohen, 2005. Psychological Bulletin. Copyright (c) 2005 by the American Psychological Association. Adapted with permission.)
function. In the second model, PA acts as a buffer of behavioral and physiological responses to stress. We realize that these models represent oversimplifications, considering pathways in only one direction from PA to immune function. No lack of alternative paths is implied.
A. The Direct Effect Model A number of direct pathways link psychological variables to immune function, including behavioral, neurological, and endocrine mechanisms. In the first case, positive emotional styles could directly influence immunity through favorable health habits (Myers and Diener, 1995). For example, better sleep quality, more exercise, and more and higher quality social relationships have been associated with more positive dispositional styles (Bardwell et al., 1999; Berry et al., 2000; Cohen et al., 2003; Ryff et al., 2004; Watson et al., 1992; but not Diener and Seligman, 2002). Better health practices, including nutritional status, not smoking, exercise, social support, and sleep, have also been associated with more positive immune status and lower risk for morbidity and mortality (e.g., Berkman and Breslow, 1983; Cohen et al., 1993; Kiecolt-Glaser and Glaser, 1988; Kronfol et al., 1989; Luoto et al., 1998; Uchino et al., 1996; Wingard et al., 1994). PA may also directly alter immune function through the activation of neurological and neuroendocrine pathways and the release of hormones and neurotransmitters, such as cortisol and catecholamines. Here, there is extensive evidence for direct anatomical and functional links between the central nervous and immune systems, as indicated by the sympathetic
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and parasympathetic innervation of lymphoid organs (Felten and Olschowka, 1987; Livnat et al., 1985) and the presence of receptors on immune cells for a variety of hormones and neurotransmitters that are released in response to emotional stimuli, including catecholamines (epinephrine and norepinephrine), corticosteroids, and opiates (Rabin, 1999). Aroused positive and negative emotional states are associated with activation of the sympathetic branch of the autonomic nervous system (e.g., Futterman et al., 1994; Knapp et al., 1992; Neumann and Waldstein, 2001). It is well accepted that activation of this pathway drives the upregulation of innate immune function that follows acute stress (Marsland et al., 2001a), making it likely that it also accounts for the similar immune responses that accompany the induction of activated positive moods. In contrast, less activated positive emotional states (e.g., calm) have been associated with decreases in SNS activation and possible activation of the parasympathetic branch (PNS) of the autonomic system (e.g., Bacon et al., 2004, but not Frazier et al., 2004). Interestingly, recent findings demonstrate that PNS activation is associated with a downregulation of inflammation (Borovikova et al., 2000; Tracey, 2002). Thus, relationships between low arousal positive moods and immune function warrant investigation. In addition to autonomic pathways, it is widely accepted that psychological factors can regulate immune function by direct activation of the hypothalamic-pituitary-adrenal (HPA) axis and release of hormones, including cortisol, from the adrenal cortex. A number of studies have demonstrated that higher levels of trait PA are associated with lower levels of cortisol (Buchanan et al., 1999; Cohen et al., 2003; Smyth et al., 1998; Steptoe et al., 2005). However, not all findings are consistent (Ryff et al., 2004; van Eck et al., 1996). Other studies have demonstrated that low levels of trait PA are associated with dysregulated cortisol rhythms, with higher cortisol levels in the afternoon and evening (Polk et al., 2005). Glucocorticoid receptors are expressed on a variety of immune cells, and ligand binding to these receptors has a number of immune inhibitory effects (e.g., Almawi et al., 1996; Cato and Wade, 1996). Other hormones are also found to increase in response to positive emotions, including growth hormone (Berk et al., 1989), prolactin (Codispoti et al., 2003), and endogenous opioids (Gerra et al., 1996, 1998), which might also play a role in the regulation of immune function.
B. The Stress-Buffering Model PA may also act as a buffer of the immune influences of stressful life events. Although there is a sub-
Stress Positive Affect
Endogenous Opioids
Social Support
ANS & HPA Activity
Health Practices
Immune Function FIGURE 4 The Stress-Buffering Model: Pathways through which PA might influence onset and progression of immune system-mediated disease though the buffering of stress effects. (From Figure 2, Pressman and Cohen, 2005. Psychological Bulletin. Copyright (c) 2005 by the American Psychological Association. Adapted with permission.)
stantial literature demonstrating that psychological stress dysregulates immune function, not all individuals display immune changes following stressful life events. Variability among individuals in the magnitude of their immune responses to stress is attributed to their level of perceived stress. A psychological stress response composed of negative cognitive and emotional states is proposed to be the consequence of perceptions that demands imposed by events exceed individuals’ abilities to cope (Lazarus and Folkman, 1984). It is these stress responses that are thought to influence immune function through their effects on health behaviors and neuroendocrine responses. Trait PA may act as a buffer of stress responses, acting to reduce negative appraisals of events and to facilitate adaptive coping. In this way, PA may ameliorate stress-related ANS and HPA activation. PA may also encourage restorative coping activities such as sleep, exercise, relaxation, social support, and vacation (Smith and Baum, 2003). These hypotheses are consistent with Fredrickson’s proposal that positive emotions broaden and diversify individuals’ thoughts and actions, which enable them to build “enduring personal resources,” including social contacts that can be drawn on when facing environmental threats (Fredrickson, 1998). In addition to buffering the effects of stress, PA may also facilitate faster recovery from stress-related psychological and physiological activation. In support of this possibility, Fredrickson and associates (2000) demonstrated that inducing PA following a stressful stimulus resulted in faster recovery to baseline levels of heart rate and blood pressure.
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VI. TRAIT PA AND OTHER RELATED PERSONALITY CONSTRUCTS A. Optimism and Extraversion An issue that requires clarification in the literature linking trait PA to immunity and disease is the role of psychological concepts that are related to trait PA, such as optimism and extraversion. These constructs are typically moderately correlated with PA (e.g., Roysamb et al., 2002). Indeed, a recent meta-analysis of 137 studies examining the relationship between current conceptualizations of personality and positive emotional traits found that trait positive affect was correlated with extraversion (r = .20) and agreeableness (r = .17) (DeNeve and Cooper, 1998). Optimism and extraversion have also been related to improved objective health outcomes (e.g., Cohen et al., 1997a; Scheier and Carver, 1987), including decreased susceptibility to upper respiratory infections (Broadbent et al., 1984; Cohen et al., 1997a; Totman et al., 1980) and improved immune function (Miller et al., 1999; Segerstrom et al., 1998). Thus, it is possible that these dispositional characteristics account for associations between PA and immune function. To date, the majority of studies examining relations between PA and immune function or health have failed to assess and evaluate the role of these overlapping cognitive and motivational concepts, making it difficult to parse out the unique effects of PA. In our recent vaccination study (Marsland et al., 2006), trait PA was related to optimism (r = .52) and extraversion (r = .51). However, high and low antibody responders did not differ on these constructs. Furthermore, trait PA predicted greater production of antibody after controlling for both constructs, suggesting that the association between trait PA and antibody response is largely independent of the related constructs of optimism and extraversion. However, it remains likely that personality and coping styles predispose individuals to stable affective dispositions, which, in turn, mediate physiological responses, including regulation of immune function.
B. Relationships between Trait PA and NA Although there is growing acceptance that positive and negative affect are broad, underlying dimensions of basic emotions that consistently emerge across studies (Watson and Tellegen, 1985), the relationship between them remains unclear. Rather than being opposite extremes of the same underlying construct, trait measures of emotional style are thought to be
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mutually independent, with PA conferring health benefits independently of NA levels (Diener and Emmons, 1985). The few studies that have examined both constructs generally support their independent influence on immune function (Marsland et al., 2006) and susceptibility to disease (Cohen et al., 2003; Ostir et al., 2001; Smith et al., 1997). Further evidence for trait PA and NA as separate constructs is derived from their asymmetrical activation of regions of the prefrontal cortex in the brain (Davidson et al., 1999). Individuals who show high levels of left-sided prefrontal activation endorse higher levels of dispositional positive affect and also show improved immune function as measured by increased natural killer cell activity, when compared with their right-frontally activated counterparts who endorse more dispositional negative affect (Davidson et al., 1999; Davidson et al., 2000). Neurotransmitters may also respond differently to PA than NA. For example, trait PA was associated with increased serotonergic function after controlling for NA (Flory et al., 2004). Taken together, these findings suggest that trait PA is not simply the absence of trait NA or vice versa, and the independent influences of both emotional traits on immunity warrants further investigation.
VII. PSYCHOLOGICAL INTERVENTIONS If there is a link between PA and regulation of immune function, interventions designed to increase PA might bring about positive health outcomes by improving immunocompetence. To our knowledge, no studies to date have directly examined the health benefit of interventions designed to increase PA. However, a number of studies have investigated whether psychological interventions designed to decrease NA can alleviate the immune dysregulation that accompanies stress. A meta-analysis of this literature concluded that there is only modest evidence that interventions can reliably alter immune parameters (Miller and Cohen, 2001). The many null findings were attributed to theoretical and methodological limitations of existing studies, including a general failure to focus on individuals with high levels of NA, to use interventions demonstrated to be effective at reducing NA, or to measure immune parameters that are typically dysregulated by NA (Miller and Cohen, 2001). In fact, if you focus on the few studies that have recruited populations experiencing high levels of NA, results are more consistent and document intervention-related improvements in immune function (Antoni et al., 1991; Fawzy et al., 1990; Goodkin et al., 1998; Lutgendorf et al., 1994). To date, these interventions have employed
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stress management techniques, including coping skills training, cognitive restructuring, relaxation training, and social support, and the extent of immune system change has been shown to covary with reductions in NA (Antoni et al., 1991; Fawzy et al., 1990). The possibility that these interventions might also influence immunity by increasing PA remains to be explored. Further evaluation and development of psychological interventions designed to increase PA may shed light on causal relationships between PA and immune function, and have valuable clinical implications. It is advisable, however, to proceed with caution. Given that it is trait PA that is most consistently associated with immune and health outcomes, to see any longterm health benefit, the improvement in PA will need to be long lasting. It is, however, controversial whether one can alter trait PA. Historically, it has been considered a stable characteristic of the individual that is relatively impervious to manipulation. However, more recently it has been argued that powerful positive events can alter trait affect (Diener et al., unpublished).
VIII. SUMMARY Recent attention has turned to the potential immune benefits of positive emotions. In contrast to the large established literature showing associations between NA and immune function (for review, see KiecoltGlaser et al., 2002), the literature examining PA and immune function is in its infancy. In this chapter, we review findings from 25 studies examining relationships between state or trait PA and immune function. The majority of these studies (15/25) have examined the impact of the experimental induction of state positive moods in the laboratory, with the remainder examining concomitants of naturalistic state and trait mood. Overall, findings from studies examining transient mood states suggest that activated positive moods (e.g., excitement, humor, joy) are associated with an upregulation of components of the innate immune system among healthy volunteers, including increases in total and antigen-specific salivary sIgA levels, numbers of immune cells in peripheral circulation, and possibly NK cell activity. Induced positive mood states have also been associated with a reduction in allergic responses among allergy sufferers. In general, these findings are consistent with immune responses to activated negative mood states, as induced by laboratory stress tasks, suggesting that it may be the increase in affective arousal, rather than the positive or negative valence of the emotion, that is responsible for immune modulation. Future work is needed to disentangle the
valence and arousal dimensions of mood states in a more sophisticated manner. Other limitations of the current mood induction literature necessitate caution in interpreting findings and drawing definitive conclusions. To date, many of the studies employ insufficient sample sizes to provide enough power, so it is important to weigh results accordingly. Furthermore, a number of studies fail to include either an emotionally neutral but interesting condition to control for diurnal variations, passage of time, and factors associated with the manipulation itself (e.g., distraction) or conditions examining the induction of other types of emotion (e.g., NA or differing types of PA). Without these controls interpretation of the true effect of PA is difficult, and it becomes impossible to address the valence/arousal question raised earlier. If one is interested in specific emotions, it is also important to understand the precise nature of the induced state. For example, humor is often used to induce PA, so without measuring, it is impossible to know whether a change in physiology is due to increases in humor or PA (see Martin, 2001, for a review of humor and health). More problematic for interpretation purposes is that these studies employ manipulations that result in only momentary mood changes. Aside from studies that have demonstrated associations between highly activated emotional states and poorer lung function among asthmatics, the majority of studies demonstrating associations between PA and health have focused on trait affect, leaving the influence of induced state PA on actual health unclear. Of greater potential relevance for heath are the small number of naturalistic studies that examine relationships between longer-lasting PA and immune function. Here, findings are promising and provide initial support for a relationship between trait PA and more effective cellular immune function, including higher NK cell numbers and activity, increased TH1 cytokine responses to in vitro stimulation of mononuclear cells with influenza virus or vaccine, higher antibody responses to hepatitis B vaccination, and decreased hypersensitivity skin responses to allergens among allergy sufferers. These findings raise the possibility that PA-related immune function is one mediator of observed associations between positive emotional styles and better general health. However, again, caution is warranted in interpreting these early findings. Before firm conclusions can be drawn, more studies are necessary to replicate initial findings and address gaps in our knowledge of PA-immune-disease relationships. Indeed, it remains to be determined whether the nature and magnitude of immunologic alterations associated with PA bear relevance to decreased disease susceptibility, especially in light of
35. Positive Affect and Immune Function
the fact that immune responses that accompany psychosocial parameters typically fall within normal ranges (Rabin et al., 1989). To date, few studies have examined immune function as a mediator of associations between trait PA and immune-mediated disease susceptibility, and other possible pathways exist, including the likely role of health behaviors. Additional studies that employ longitudinal designs, measure dispositional PA, adequately control for both objective and perceived health at baseline, predict immune mediators relevant for disease, control for health behavior, and document related health outcomes are needed. These studies will need to examine the independent contributions of closely related constructs, including trait NA, optimism, and extraversion, and begin to explore behavioral, psychological, and biological mechanisms that may link positive affective styles to immune function. In sum, initial evidence suggests the possibility of a relationship between PA and immune parameters of relevance to health. This is clearly a potential pathway through which PA may modulate host resistance to disease onset or progression and provides one of the most exciting recent developments in the field of PNI. It is time for researchers interested in psychological influences on health to move beyond the role of situational stress and negative affect to further explore the impact of positive emotions on health-related immune function.
Acknowledgments Dr. Marsland was supported during the preparation of this work by grant R01 NR008237 from the National Institute of Nursing Research (ALM), Ms. Pressman by a Post-Graduate Scholarship from the Natural Science & Engineering Research Council of Canada, and Dr. Cohen by a grant to the Pittsburgh NIH Mind-Body Center (HL65111 and HL65112). The authors thank Jeffrey Horn for helpful comments on an earlier version of the manuscript and Ellen Conser for assistance with manuscript preparation.
References Ader, R., Cohen, N., and Felten, D. L. (1987). Brain, behavior, and immunity. Brain Beh. Imm., 1, 1–6. Almawi, W. Y., Beyhum, H. N., Rahme, A. A., and Rieder, M. J. (1996). Regulation of cytokine and cytokine receptor expression by glucocorticoids. J. Leukoc. Biol., 60, 563–572. Antoni, M. H., Baggett, L., Ironson, G., LaPerriere, A., Sugust, S., Klimas, N. G., Schneiderman, N., and Fletcher, M. A. (1991). Cognitive-behavioral stress management intervention buffers distress responses and immunologic changes following notification of HIV-1 seropositivity. J. Consult. Clin. Psychol., 59, 906–915. Apter, A. J., Affleck, G., Reisine, S. T., Tennen, H. A., Barrows, E., Wells, M., Willard, A., and ZuWallack, R. L. (1997). Perception of airway obstruction in asthma: sequential daily analyses of
775
symptoms, peak expiratory flow rate, and mood. J. Allergy Clin. Immun., 99, 605–612. Bachen, E. A., Manuck, S. B., Cohen, S., Muldoon, M. F., Raible, R., Herbert, T. B., and Rabin, B. S. (1995). Adrenergic blockade ameliorates cellular immune responses to stress in humans. Psychosom. Med., 57, 366–372. Bacon, S. L., Watkins, L. L., Babyak, M., Sherwood, A., Hayano, J., Hinderliter, A. L., Waugh, R., and Blumenthal, J. A. (2004). Effects of daily stress on autonomic cardiac control in patients with coronary artery disease. Am. J. Cardiol., 93, 1292–1294. Bardwell, W. A., Berry, C. C., Ancoli-Israel, S., and Dimsdale, J. E. (1999). Psychological correlates of sleep apnea. J. Psychosom. Res., 47, 583–596. Berk, L. S., Felten, D. L., Tan, S. A., Bittman, B. B., and Westengard, J. (2001). Modulation of neuroimmune parameters during the eustress of humor-associated mirthful laughter. Altern. Ther. Health. Med., 7, 62–76. Berk, L. S., Tan, S. A., Fry, W. F., Napier, B. J., Lee, J. W., Hubbard, R. W., Lewis, J. E., and Eby, W. C. (1989). Neuroendocrine and stress hormone changes during mirthful laughter. Am. J. Med. Sci., 298, 390–396. Berkman, L., and Breslow, L. (1983). Health and ways of living: the Alameda County study. New York: Oxford University Press. Berry, D. S., Willingham, J. K., and Thayer, C. A. (2000). Affect and personality as predictors of conflict and closeness in young adults’ friendships. J. Res. Pers., 34, 84–107. Borovikova, L. V., Ivanova, S., Zhang, M., Yang, H., Botchkina, G. I., and Watkins, L. R. (2000). Vagus nerve stimulation attenuates the systemic inflammatory response to endotoxin. Nature, 405, 458–461. Bristow, M., Hucklebridge, F., Clow, A., and Evans, P. (1997). Modulation of secretory immunoglobulin A in relation to an acute episode of stress and arousal. J. Psychophys., 11, 248–255. Broadbent, D. E., Broadbent, M. H. P., Phillpotts, R. J., and Wallace, J. (1984). Some further studies on the prediction of experimental colds in volunteers by psychological factors. J. Psychosom. Res., 28, 511–523. Brown, J. E., Butow, P. N., Culjak, G., Coates, A. S., and Dunn, S. M. (2000). Psychosocial predictors of outcome: time to relapse and survival in patients with early stage melanoma. Br. J. Cancer, 83, 1448–1453. Buchanan, T. W., al’Absi, M., and Lovallo, W. R. (1999). Cortisol fluctuates with increases and decreases in negative affect. Psychoneuroendocrinology, 24, 227–241. Cato, A. C. B., and Wade, E. (1996). Molecular mechanisms of anti-inflammatory action of glucocorticoids. Bioessays, 18, 371–378. Celiker, R., and Borman, P. (2001). Fibromyalgia versus rheumatoid arthritis: a comparison of psychological disturbance and life satisfaction. J. Musculoskel. Pain, 9, 35–45. Clark, L. A., Watson, D., and Leeka, J. (1989). Diurnal variation in the positive affects. Motiv. Emot., 13, 205–234. Codispoti, M., Gerra, G., Montebarocci, O., Zaimovic, A., Raggi, M. A., and Baldaro, B. (2003). Emotional perception and neuroendocrine changes. Psychophysiology, 40, 863–868. Cohen, S., Doyle, W. J., Skoner, D. P., Rabin, B. S., and Gwaltney, J. M. (1997a). Social ties and susceptibility to the common cold. JAMA, 277, 1940–1944. Cohen, S., Doyle, W. J., Turner, R. B., Alper, C. M., and Skoner, D. P. (2003). Emotional style and susceptibility to the common cold. Psychosom. Med., 65, 652–657. Cohen, S., Kessler, R. C., and Underwood Gordon, L., Eds. (1997b). Measuring stress: a guide for health and social scientists. London: Oxford University Press.
776
IV. Stress and Immunity
Cohen, S., Miller, G. E., and Rabin, B. S. (2001). Psychological stress and antibody response to immunization: a critical review of the human literature. Psychosom. Med., 63, 7–18. Cohen, S., Tyrrell, D. A., Russell, M. A., Jarvis, M. J., and Smith, A. P. (1993). Smoking, alcohol consumption, and susceptibility to the common cold. Am. J. Pub. Health, 83, 1277–1283. Costanzo, E. S., Lutgendorf, S. K., Kohut, M. L., Nisly, N., Roseboom, K., Spooner, S., Benda, J., and McElhaney, J. E. (2004). Mood and cytokine response to influenza virus in older adults. J. Gerontol., 12, 1328–1333. Davidson, R. J., Coe, C. C., Dolski, I., and Donzella, B. (1999). Individual differences in prefrontal activation asymmetry predict natural killer cell activity at rest and in response to challenge. Brain Behav. Imm., 13, 93–108. Davidson, R. J., Jackson, D. C., and Kalin, N. H. (2000). Emotion, plasticity, context, and regulation: perspectives from affective neuroscience. Psychol. Bull., 126, 890–909. DeNeve, K. M., and Cooper, H. (1998). The happy personality: a meta-analysis of 137 personality traits and subjective well-being. Psychol. Bull., 124, 197–229. Derogatis, L. R., Abeloff, M. D., and Melisaratos, N. (1979). Psychological coping mechanisms and survival time in metastatic breast cancer. JAMA, 242, 1504–1508. Devins, G. M., Mann, J., Mandin, H., Paul, L. C., Hons, R. B., Burgess, E. D., Taub, K., Schorr, S., Letourneau, P. K., and Buckle, S. (1990). Psychosocial predictors of survival in end-stage renal disease. J. Nerv. Ment. Dis., 178, 127–133. Diener, E. (1984). Subjective well-being. Psychol. Bull., 95, 542–575. Diener, E., and Emmons, R. A. (1985). The independence of positive and negative affect. J. Pers. Soc. Psychol., 47, 1105–1117. Diener, E., Larsen, R. J., Levine, S., and Emmons, R. A. (1985). Intensity and frequency: dimensions underlying positive and negative affect. J. Pers. Soc. Psychol., 48, 1253–1265. Diener, E., Lucas, R. E., and Scollon, C. N. (2005). Beyond the Hedonic treadmill: revisions to the adaptation theory of wellbeing. Unpublished. Diener, E., and Seligman, M. E. (2002). Very happy people. Psychol. Sci., 13, 81–84. Dillon, K. M., Minchoff, B., and Baker, K. H. (1985). Positive emotional states and enhancement of the immune system. Int. J. Psychiatry Med., 15, 13–18. Doyle, W. J., Gentile, D. A., and Cohen, S. (2006). Emotional style, nasal cytokines, and illness expression after experimental rhinovirus exposure. Brain Beh. Imm., 20, 175–181. Ekman, P. (1992). Are there basic emotions? Psychol. Rev., 99, 550–553. Evans, P., Bristow, M., Hucklebridge, F., Clow, A., and Walters, N. (1993). The relationship between secretory immunity, mood and life-events. Brit. J. Clin. Psychol., 32, 227–236. Fawzy, F. I., Kemeny, M. E., Fawzy, N. W., Elashoff, R., Morton, D., Cousins, N., and Fahey, J. L. (1990). A structured psychiatric intervention for cancer patients: changes over time in immunological measures. Arch. Gen. Psychiatry, 47, 729–735. Felten, S. Y., and Olschowka, J. (1987). Noradrenergic sympathetic innervation of the spleen. II. Tyrosine hydroxylase (TH)-positive nerve terminals for synaptic like contacts on lymphocytes in the splenic white pulp. J. Neurosci. Res., 18, 37–48. Florin, I., Freudenberg, G., and Hollaender, J. (1985). Facial expressions of emotion and physiologic reactions in children with bronchial asthma. Psychosom. Med., 47, 382–393. Flory, J. D., Manuck, S. B., Matthews, K. A., and Muldoon, M. F. (2004). Serotonergic function in the central nervous system is associated with daily ratings of positive mood. Psychiatry Res., 129, 11–19.
Frazier, T. W., Strauss, M. E., and Steinhauer, S. R. (2004). Respiratory sinus arrhythmia as an index of emotional response in young adults. Psychophysiology, 41, 75–83. Fredrickson, B. L. (1998). What good are positive emotions? Rev. Gen. Psychol., 2, 300–319. Fredrickson, B. L., Mancuso, R. A., Branigan, C., and Tugade, M. M. (2000). The undoing effect of positive emotions. Motiv. Emot., 24, 237–258. Friedman, H. S., Tucker, J. S., Tomlinson-Keasey, C., Schwartz, J. E., Wingard, D. L., and Criqui, M. H. (1993). Does childhood personality predict longevity? J. Pers. Soc. Psychol., 65, 176–185. Frost, R. O., and Green, M. L. (1982). Duration and postexperimental removal of Velten mood induction procedure effects. Pers. Soc. Psychol. Bull., 8, 341–347. Futterman, A. D., Kemeny, M. E., Shapiro, D., and Fahey, J. L. (1994). Immunological and physiological changes associated with induced positive and negative mood. Psychosom. Med., 56, 499–511. Futterman, A. D., Kemeny, M. E., Shapiro, D., Polonsky, W., and Fahey, J. L. (1992). Immunological variability associated with experimentally-induced positive and negative affective states. Psychol. Med., 22, 231–238. Gerra, G., Fertomani, G., Zaimovic, A., Caccavari, R., Reali, N., Maestri, D., Avanzini, P., Monica, C., Delsignore, R., and Brambilla, F. (1996). Neuroendocrine responses to emotional arousal in normal women. Neuropsychobiology, 33, 173–181. Gerra, G., Zaimovic, A., Franchini, D., Palladino, M., Giucastro, G., Reali, N., Maestri, D., Caccavari, R., Delsignore, R., and Brambilla, F. (1998). Neuroendocrine responses of healthy volunteers to ‘techno-music’: Relationships with personality traits and emotional state. Int. J. Psychophysiol., 28, 99–111. Goodkin, K., Feaster, D. J., Asthana, D., Blaney, N. T., Kumar, M., Baldewicz, T., Tuttle, R. S., Maher, K. G., Baum, M. K., Shapshak, P., and Fletcher, M. A. (1998). A bereavement support group intervention is longitudinally associated with salutary effects of CD4 cell count and number of physician visits. Clin. Diagn. Lab. Immunol., 5, 382–390. Harrison, L. K., Carroll, D., Burns, V. E., Corkill, A. R., Harrison, C. M., Ring, C., and Drayson, M. (2000). Cardiovascular and secretory immunoglobulin A reactions to humorous, exciting, and didactic film presentations. Biol. Psychol., 52, 113–126. Herbert, T. B., and Cohen, S. (1993a). Depression and immunity: a meta-analytic review. Psychol. Bull., 113, 472–486. Herbert, T. B., and Cohen, S. (1993b). Stress and immunity in humans: a meta-analytic review. Psychosom. Med., 55, 364–379. Hornquist, J. O., Hansson, B., Akerlind, I., and Larsson, J. (1992). Severity of disease and quality of life: a comparison in patients with cancer and benign disease. Qual. Life Res., 1, 135–141. Hucklebridge, F., Lambert, S., Clow, A., Warburton, D. M., Evans, P. D., and Sherwood, N. (2000). Modulation of secretory immunoglobulin A in saliva: response to manipulation of mood. Biol. Psychol., 53, 25–35. Izard, C. E., Ed. (1977). Human emotions. New York: Plenum Press. Jabaaij, L., Grosheide, P. M., Heijtink, R. A., Duivenvoorden, H. J., Ballieux, R. E., and Vingerhoets, A. J. J. M. (1993). Influence of perceived psychological stress and distress on antibody response to low dose rDNA hepatitis B vaccine. J. Psychosom. Res., 37, 361–369. Janoff-Bulman, R., and Marshall, G. (1982). Mortality, well-being, and control: a study of a population of institutionalized aged. Person. Soc. Psych. Bull., 8, 691–698. Jelicic, M., and Kempen, G. I. J. M. (1999). Chronic medical conditions and life satisfaction in the elderly. Psychol. Health, 14, 65–70.
35. Positive Affect and Immune Function Kaplan, G. A., and Camacho, T. (1983). Perceived health and mortality: a nine-year follow-up of the human population laboratory cohort. Am. J. Epi., 117, 292–304. Kawamoto, R., and Doi, T. (2002). Self-reported functional ability predicts three-year mobility and mortality in communitydwelling older persons. Geriatrics & Gerontology International, 2, 68–74. Kiecolt-Glaser, J. K., and Glaser, R. (1988). Methodological issues in behavioral immunology research with humans. Brain Beh. Imm., 2, 67–78. Kiecolt-Glaser, J. K., McGuire, L., Robles, T. F., and Glaser, R. (2002). Emotions, morbidity, and mortality: new perspectives from psychoneuroimmunology. Ann. Rev. Psychol., 53, 83–107. Kimata, H. (2001). Effect of humor on allergen-induced wheal reactions. JAMA, 285, 738. Klonoff-Cohen, H., Chu, E., Natarajan, L., and Sieber, W. (2001). A prospective study of stress among women undergoing in vitro fertilization or gamete intrafallopian transfer. Fertil. Steril., 76, 675–687. Knapp, P. H., Levy, E. M., Giorgi, R. G., Black, P. H., Fox, B. H., and Heeren, T. C. (1992). Short-term immunological effects of induced emotion. Psychosom. Med., 54, 133–148. Knox, S., Svensson, J., Waller, D., and Theorell, T. (1988). Emotional coping and the psychophysiological substrates of elevated blood pressure. Beh. Med., 14, 52–58. Koivumaa-Honkanen, H., Honkanen, R., Viinamaeki, H., Heikkilae, K., Kaprio, J., and Koskenvuo, M. (2001). Life satisfaction and suicide: a 20-year follow-up study. Am. J. Psychiatry, 158, 433–439. Koivumaa-Honkanen, H., Honkanen, R., Viinamaki, H., Heikkila, K., Kaprio, J., and Koskenvuo, M. (2000). Self-reported life satisfaction and 20-year mortality in healthy Finnish adults. Am. J. Epi., 152, 983–991. Krantz, D. S., Glass, D. C., Contrada, R., and Miller, N. E. (1981). Behavior and health: mechanisms and research issues. Soc. Sci. Res. Council: ITEMS., 35, 1–6. Kronfol, Z., Nair, M., Goodson, J., Goel, K., Haskett, R., and Schwartz, S. (1989). Natural killer cell activity in depressive illness: a preliminary report. Biol. Psychiatry, 26, 753–756. Labott, S. M., Ahleman, S., Wolever, M. E., and Martin, R. B. (1990). The physiological and psychological effects of the expression and inhibition of emotion. Behav. Med., 16, 182–189. Laidlaw, T. M., Booth, R. J., and Large, R. G. (1994). The variability of type I hypersensitivity reactions: the importance of mood. J. Psychosom. Res., 38, 51–61. Laidlaw, T. M., Booth, R. J., and Large, R. G. (1996). Reduction in skin reactions to histamine after a hypnotic procedure. Psychosom. Med., 58, 242–248. Lambert, R. B., and Lambert, N. K. (1995). The effects of humor on secretory immunoglobulin A levels in school-aged children. Pediatr. Nurs., 21, 16–19. Larsen, R. J., and Diener, E. (1992). Promises and problems with the circumplex model of emotion. In M. S. Clark (Ed.), Emotion (pp. 25–59). Thousand Oaks, CA: Sage Publications. Lazarus, R. S., and Folkman, S. (1984). Stress, appraisal, and coping. New York: Springer. Levy, B. R., Slade, M. D., Kunkel, S. R., and Kasl, S. V. (2002). Longevity increased by positive self-perceptions of aging. J. Pers. Soc. Psychol., 83, 261–270. Levy, S. M., Lee, J., Bagley, C., and Lippman, M. (1988). Survival hazards analysis in first recurrent breast cancer patients: sevenyear follow-up. Psychosom. Med., 50, 520–528. Livnat, S., Felten, S. Y., Carlson, S. L., Bellinger, D. L., and Felten, D. L. (1985). Involvement of peripheral and central catechol-
777
amine systems in neural-immune interactions. J. Neuroimm., 10, 5–30. Logan, H. L., Lutgendorf, S., Hartwig, A., Lilly, J., and Berberich, S. L. (1998). Immune, stress, and mood markers related to recurrent oral herpes outbreaks. Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endod., 86, 48–54. Luoto, R., Prattala, R., Uutela, A., and Puska, P. (1998). Impact of unhealthy behaviors on cardiovascular mortality in Finland, 1978–1993. Prev. Med: Int. J. Devoted Practice and Theory, 27, 93–100. Lutgendorf, S. K., Antoni, M. H., Kumar, M., and Schneiderman, N. (1994). Changes in cognitive coping strategies predict EBVantibody titer change following a stress disclosure induction. J. Psychosom. Res., 38, 63–78. Lutgendorf, S. K., Tripp Reimer, T., Harvey, J. H., Marks, G., Hong, S-Y., Hillis, S. L., and Lubaroff, D. M. (2001). Effects of housing relocation on immunocompetence and psychosocial functioning in older adults. J. Geront., 56A, M97–105. Lyubomirsky, S., King, L., and Diener, E. (2005). The benefits of frequent positive affect: does happiness lead to success? Psychol. Bull., 131, 803–855. Maier, H., and Smith, J. (1999). Psychological predictors of mortality in old age. J. Gerontol. B Psychol. Sci. Soc. Sci., 54, P44–P54. Manuck, S. B., Cohen, S., Rabin, B. S., Muldoon, M. F., and Bachen, E. A. (1991). Individual differences in cellular immune response to stress. Psychol. Sci., 2, 111–115. Marsland, A. L., Bachen, E. A., Cohen, S., and Manuck, S. B. (2001a). Stress, immunity and susceptibility to infectious illness. In A. Baum, T. A. Revenson, and J. E. Singer (Eds.), Handbook of health psychology (pp. 683–695). New Jersey: Lawrence Erlbaum Associates. Marsland, A. L., Cohen, S., Rabin, B. S., and Manuck, S. B. (2006). Trait positive affect and antibody response to hepatitis B vaccination. Brain. Beh. Imm., 20, 261–269. Marsland, A. L., Cohen, S., Rabin, B. S., and Manuck, S. B. (2001b). Associations between stress, trait negative affect, acute immune reactivity, and antibody response to hepatitis B injection in healthy young adults. Health Psychol., 20, 1–8. Martin, R. A. (2001). Humor, laughter, and physical health: methodological issues and research findings. Psychol. Bull., 127, 504–519. McClelland, D. C., and Cheriff, A. D. (1997). The immunoenhancing effects of humor on secretory IgA and resistance to respiratory infections. Psychol. Health, 12, 329–344. McCraty, R., Atkinson, M., Rein, G., and Watkins, A. D. (1996). Music enhances the effect of positive emotional states on salivary IgA. Stress Med., 12, 167–175. McDowell, I., and Newell, C. (1996). Measuring health: a guide to rating scales and questionnaires (2nd ed.). New York: Oxford University Press. McNair, D. M., Lorr, M., and Droppleman, L. F. (1971). Profile of mood states manual. San Diego: Educational and Industrial Testing Service. Middleton, R. A., and Byrd, E. K. (1996). Psychosocial factors and hospital readmission status of older persons with cardiovascular disease. J. App. Rehab. Counsel., 27, 3–10. Miller, G. E., and Cohen, S. (2001). Psychological interventions and the immune system: a meta-analytic review and critique. Health Psychol., 20, 47–63. Miller, G. E., Cohen, S., Rabin, B. S., Skoner, D. P., and Doyle, W. J. (1999). Personality and tonic cardiovascular, neuroendocrine, and immune parameters. Brain Beh. Imm., 13, 109– 123.
778
IV. Stress and Immunity
Mittwoch-Jaffe, T., Shalit, F., Srendi, B., and Yehuda, S. (1995). Modification of cytokine secretion following mild emotional stimuli. Neuroreport, 6, 789–792. Moskowitz, J. T. (2003). Positive affect predicts lower risk of AIDS mortality. Psychosom. Med., 65, 620–626. Moss, R. B., Moss, H. B., and Peterson, R. (1989). Microstress, mood, and natural killer-cell activity. Psychosom., 30, 279–283. Myers, D. G., and Diener, E. (1995). Who is happy? Psychol. Sci., 6, 10–19. Neumann, S. A., and Waldstein, S. R. (2001). Similar patterns of cardiovascular response during emotional activation as a function of affective valence and arousal and gender. J. Psychosom. Res., 50, 245–253. Njus, D. M., Nitschke, W., and Bryant, F. B. (1996). Positive affect, negative affect, and the moderating effect of writing on sIgA antibody levels. Psychol. Health, 12, 135–148. Ostir, G. V., Markides, K. S., Black, S. A., and Goodwin, J. S. (2000). Emotional well-being predicts subsequent functional independence and survival. J. Am. Geriatr. Soc., 48, 473–478. Ostir, G. V., Markides, K. S., Peek, M. K., and Goodwin, J. S. (2001). The association between emotional well-being and the incidence of stroke in older adults. Psychosom. Med., 63, 210–215. Parker, M. G., Thorslund, M., and Nordstrom, M. L. (1992). Predictors of mortality for the oldest old: a 4-year follow-up of community-based elderly in Sweden. Arch. Gerontol. Geriatr., 14, 227–237. Perera, S., Sabin, E., Nelson, P., and Lowe, D. (1998). Increases in salivary lysozyme and IgA concentrations and secretory rates independent of salivary flow rates following viewing of a humorous video. Int. J. Beh. Med., 5, 118–228. Pfeiffer, C. A., and Wetstone, S. L. (1988). Health locus of control and well-being in systemic lupus erythematosus. Arthritis Care Res., 1, 131–138. Polk, D. E., Cohen, S., Doyle, W. J., Skoner, D. P., and Kirschbaum, C. (2005). State and trait affect as predictors of salivary cortisol in healthy adults. Psychoneuroendocrinology, 30, 261–272. Pressman, S., and Cohen, S. (2005). Does positive affect influence health? Psychol. Bull., 131, 925–971. Rabin, B. S. (1999). Stress, immune function, and health: the connection. New York: Wiley-Liss. Rabin, B. S., Cohen, S., Ganguli, R., Lusle, D. T., and Cunnick, J. E. (1989). Bidirectional interaction between the central nervous and the immune system. Crit. Rev. Imm., 9, 279–312. Riis, J., Loewenstein, G., Baron, J., Jepson, C., Fagerlin, A., and Ubel, P. A. (2005). Ignorance of hedonic adaptation to hemodialysis: a study using ecological momentary assessment. J. Exp. Psychol. Gen., 134, 3–9. Ritz, T., Claussen, C., and Dahme, B. (2001). Experimentally induced emotions, facial muscle activity, and respiratory resistance in asthmatic and non-asthmatic individuals. Brit. J. Med. Psychol., 74, 167–182. Ritz, T., George, C., and Dahme, B. (2000a). Respiratory resistance during emotional stimulation: evidence for a nonspecific effect of experienced arousal? Biol. Psychol., 52, 143–160. Ritz, T., and Steptoe, A. (2000). Emotion and pulmonary function in asthma: reactivity in the field and relationship with laboratory induction of emotion. Psychosom. Med., 62 (6), 808–815. Ritz, T., Steptoe, A., DeWilde, S., and Costa, M. (2000b). Emotions and stress increase respiratory resistance in asthma. Psychosom. Med., 62, 401–412. Roysamb, E., Harris, J. R., Magnus, P., Vitterso, J., and Tambs, K. (2002). Subjective well-being: sex-specific effects of genetic and environmental factors. Personal. Indiv. Diff., 32, 211–223.
Russell, J. A. (1980). A circumplex model of affect. J. Personal. Soc. Psychol., 39, 1161–1178. Ryff, C. D. (2003). The role of emotion on pathways to positive health. In R. Davidson (Ed.), Handbook of affective sciences (pp. 1083–1104). London: Oxford University Press. Ryff, C. D., Singer, B. H., and Dienberg Love, G. (2004). Positive health: connecting well-being with biology. Philos. Trans. R. Soc. Lond. B. Biol. Sci., 359, 1383–1394. Salovey, P., Rothman, A. J., Detweiler, J. B., and Steward, W. T. (2000). Emotional states and physical health. Am. Psychol., 55, 110–121. Scheier, M. F., and Carver, C. S. (1987). Dispositional optimism and physical well-being: the influence of generalized outcome expectancies on health. J. Personal., 55, 169–210. Segerstrom, S. C., and Miller, G. E. (2004). Psychological stress and the human immune system: a meta-analytic study of 30 years of inquiry. Psychol. Bull., 130, 601–630. Segerstrom, S. C., Taylor, S. E., Kemeny, M. E., and Fahey, J. L. (1998). Optimism is associated with mood, coping, and immune change in response to stress. J. Personal. Soc. Psychol., 74, 1646–1655. Smith, A. M., Stuart, M. J., Wiese-Bjornstal, D. M., and Gunnon, C. (1997). Predictors of injury in ice hockey players. A multivariate, multidisciplinary approach. Am. J. Sports Med., 25, 500–507. Smith, A. W., and Baum, A. (2003). The influence of psychological factors on restorative function in health and illness. In J. Suls and K. A. Wallston (Eds.), Social psychological foundations of health and illness (pp. 431–457). Malden, MA: Blackwell Publishers. Smyth, J., Ockenfels, M. C., Porter, L., Kirschbaum, C., Hellhammer, D. H., and Stone, A. A. (1998). Stressors and mood measured on a momentary basis are associated with salivary cortisol secretion. Psychoneuroendocrinology, 23, 353–370. Solomon, G. F., and Moos, R. (1964). Emotions immunity, and disease. Arch. Gen. Psychiatry, 11, 657–674. Steptoe, A., Wardle, J., and Marmot, M. (2005). Positive affect and health-related neuroendocrine, cardiovascular, and inflammatory processes. Proc. Natl. Acad. Sci. USA, 102, 6508–6512. Stone, A. A., Cox, D. S., Valdimarsdottir, H., Jandorf, L., and Neale, J. M. (1987). Evidence that secretory IgA antibody is associated with daily mood. J. Personal. Soc. Psychol., 52, 988–993. Stone, A. A., Neale, J. M., Cox, D. S., Napoli, A., Valdimarsdottir, H., and Kennedy-Moore, E. (1994). Daily events are associated with a secretory immune response to an oral antigen in men. Health Psychol., 13, 440–446. Stones, M. J., Dornan, B., and Kozma, A. (1989). The prediction of mortality in elderly institution residents. J. Gerontology, 44 (3), P72–P79. Szmuness, W., Stevens, C. E., Harley, E. J., Zang, E. A., Oleszko, W. R., William, D. C., Sadovsky, R., Morrison, J. M., and Kellner, A. (1980). Hepatitis B vaccine: demonstration of efficacy in a controlled clinical trial in a high-risk population in the United States. N. Engl. J. Med., 303, 833–841. Totman, R., Kiff, J., Reed, S. E., and Craig, J. W. (1980). Predicting experimental colds in volunteers from different measures of recent life stress. J. Psychosom. Res., 24, 155–163. Tracey, K. J. (2002). The inflammatory reflex. Nature, 420, 853–859. Uchino, B. N., Cacioppo, J. T., and Kiecolt-Glaser, J. K. (1996). The relationship between social support and physiological processes: a review with emphasis on underlying mechanisms and implications for health. Psychol. Bull., 119, 488–531. Usala, P. D., and Hertzog, C. (1989). Measurement of affective states in adults: evaluation of an adjective rating scale instrument. Res. Aging, 11, 403–426.
35. Positive Affect and Immune Function Valdimarsdottir, H. B., and Bovbjerg, D. H. (1997). Positive and negative mood: association with natural killer cell activity. Psychol. Health, 12, 319–327. van Domburg, R. T., Pedersen, S. S., van den Brand, M. J. B. M., and Erdman, R. A. M. (2001). Feelings of being disabled as a predictor of mortality in men 10 years after percutaneous coronary transluminal angioplasty. J. Psychosom. Res., 51, 469–477. van Eck, M., Berkhof, H., Nicolson, N., and Sulon, J. (1996). The effects of perceived stress, traits, mood states, and stressful daily events on salivary cortisol. Psychosom. Med., 58, 447–458. van Tits, L. J. H., Michel, M. C., Grosse-Wide, H., Happel, M., Eigler, F. W., Soliman, A., and Brodde, O. E. (1990). Catecholamines increase lymphocyte beta-2 adrenergic receptors via a beta adrenergic, spleen-dependent process. Am. J. Physiol., 258, E191–202. Watson, D. (1988). The vicissitudes of mood measurement: effects of varying descriptors, time frames, and response formats on measures of positive and negative affect. J. Personal. Soc. Psychol., 55, 128–141. Watson, D., Clark, L. A., McIntyre, C. W., and Hamaker, S. (1992). Affect, personality, and social activity. J. Personal. Soc. Psychol., 63, 1011–1025. Watson, D., Clark, L. A., and Tellegen, A. (1988). Development and validation of brief measures of positive and negative affect: the PANAS scales. J. Personal. Soc. Psychol., 54, 1063–1070. Watson, D., and Tellegen, A. (1985). Toward a consensual structure of mood. Psychol. Bull., 98, 219–235.
779
Weisman, A. D. (1979). Coping with cancer. New York: McGraw-Hill. Willemson, G., Ring, C., Carroll, D., Evans, P., Clow, A., and Hucklebridge, F. (1998). Secretory immunoglobulin A and cardiovascular reactions to mental arithmetic and cold pressor. Psychophysiology, 35, 252–259. Wingard, D. L., Berkman, L. F., and Brand, R. J. (1994). A multivariate analysis of health-related practices: a nine-year mortality follow up of the Alameda county study. In A. Steptoe and J. Wardle (Eds.), Psychosocial processes and health: a reader (pp. 273–289). New York: Cambridge University Press. Yoshino, S., Fujimori, J., and Kohda, M. (1996). Effects of mirthful laughter on neuroendocrine and immune systems in patients with rheumatoid arthritis. J. Rheumatol., 23, 793– 794. Zachariae, R., Jorgensen, M. M., Egekvist, H., and Bjerring, P. (2001). Skin reactions to histamine of healthy subjects after hypnotically induced emotions of sadness, anger, and happiness. Allergy, 56, 734–740. Zachariae, R., Bjerring, P., Zachariae, C., Arendt-Nielsen, L., Nielsen, T., Eldrup, E., Larsen, C. S., and Gotliebsen, K. (1991). Monocyte chemotactic activity in sera after hypnotically induced emotional states. Scand. J. Imm., 34, 71–79. Zautra, A. J. (2003). Emotions, stress, and health. London: Oxford University Press.
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C H A P T E R
36 Close Relationships and Immunity JENNIFER E. GRAHAM, LISA M. CHRISTIAN, AND JANICE K. KIECOLT-GLASER
I. INTRODUCTION 781 II. KEY FINDINGS IN CLOSE RELATIONSHIPS AND IMMUNE FUNCTION 782 III. INTERVENTIONS 791 IV. CONCLUSIONS AND FUTURE DIRECTIONS 792
The current review is organized around three aspects of close relationships: social integration, social support, and negative aspects of social ties. These topics map relatively well onto three models by which social relationships can affect health in relation to psychological stress: the main effects model, the stressbuffering model, and the social strain model (Cohen, 2004; Orth-Gomer, 2000; Rook, 1990). In this literature, psychological stress is most often determined by selfreported perceived stress, as well as by objective indicators of life stress and reports of life events. We first present work on social integration, including in this category broad measures of network size as well as studies focused on marital status, a key social tie. In line with the main effects model (Lazarus and Folkman, 1984), measures of social integration are typically associated with health benefits independent of stress (Cohen, 1988; Cohen, 2004). Next, we review literature focused on social support. In contrast to quantitative measures of network size, social support is typically defined as the perception that assistance would be available if and when it is needed, as well as the receipt of assistance during such times. Such assistance can include, but is not limited to, the provision of material aid, assistance with tasks, information, or emotional support. In line with the stress-buffering model, the benefits of perceived social support are frequently seen only (or primarily) when a person encounters stress of a sufficient magnitude (Cohen, 1988). Relevant work on the related constructs of loneliness and intimacy is also covered briefly in this section. Finally, we review work that best fits with the social strain model, which holds that relationships can sometimes serve as a source of stress
I. INTRODUCTION Our lives tend to be centered around close relationships with significant others, family, and friends. It is increasingly apparent that the existence and quality of such relationships and the support they provide have a strong impact not only on our psychological wellbeing (Glenn and Weaver, 1981) but also our physical health. A number of prospective studies have reported remarkably similar patterns of increasing risk for allcause mortality with a decreasing number of social ties, even after controlling for sociodemographic characteristics and health (e.g.. Berkman and Syme, 1979; House et al., 1982; Kaplan et al., 1988). The existence and quality of key close relationships, such as marriage, are also predictive of morbidity and mortality from a range of chronic and acute conditions (Johnson et al., 2000; Kiecolt-Glaser and Newton, 2001; Verbrugge, 1979). One key pathway underlying the association between social relationships and health outcomes appears to be changes in immune function (Kiecolt-Glaser, 1999), an area of research which holds great promise for further clarifying the role of close relationships and health and which will be the focus of this chapter. PSYCHONEUROIMMUNOLOGY, 4E VOLUME II
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themselves (Coyne and Bolger, 1990), with accompanying negative implications for health and immunity. This section includes a brief review of the relatively large body of work on marital conflict, in addition to evidence that other social ties and some forms of social support can be problematic. Experimental designs and clinical interventions provide some of the best evidence that aspects of close relationships are causally related to immunity in both healthy and clinical populations. Such studies are briefly reviewed in a subsequent section. The topics covered in this intervention section and, indeed, throughout the review, sometimes have overlapping content. In a concluding section, we address more broadly what is currently known about the mechanisms common to reviewed findings. As other chapters in this volume cover the relevance of physiological responses and phenomena, such as hypothalamicpituitary-adrenal (HPA) axis reactivity and glucocorticoid responsiveness, our focus is on the major psychological and behavioral pathways by which relationship factors may affect health and immune function in relation to acute and chronic stress. In that context, we discuss how relationships may affect immunity indirectly by impacting cognitions, affect, manners of coping, and health behaviors. We conclude by suggesting promising future research directions.
II. KEY FINDINGS IN CLOSE RELATIONSHIPS AND IMMUNE FUNCTION A. Social Integration Social integration refers to the degree to which a person is linked to or involved with his/her social environment at different levels, including community, individual network of social ties, and intimate relationships. The converse of social integration would be isolation, or the lack of regular contact with friends, neighbors, co-workers, family members, and social groups. 1. Network Size A key aspect of social integration, network size can be measured by assessing the number of different types of relationships (e.g., a spouse, a parent, a friend, a co-worker), the total number of individuals in one’s social network, and the frequency of contact with network members. Such quantitative measures are associated with mortality and morbidity from a range of conditions, including certain cancers and respira-
tory diseases with a clear immunological component (for a review, see Berkman and Glass, 2000). In addition, larger social network size predicts better functional and perceived health 30 years later, even after controlling for age and previous health (Moen et al., 1992). The relationship between network size and health outcomes rivals that of well-established health risk factors, such as smoking, blood pressure, blood lipids, obesity, and physical activity (House et al., 1988). Strong evidence of an impact of network size on immune function comes from work on virus susceptibility by Cohen and colleagues, in which healthy individuals were experimentally exposed to the common cold virus and subsequently observed under controlled conditions. One such study showed that increasing social network size was associated with decreased susceptibility to infection (Cohen et al., 1997), although this association has not been found consistently (e.g., Cohen et al., 2003). A link between network size and cold susceptibility raises the question of whether these effects may be explained by personality variables. For example, sociability, the trait tendency to seek out and maintain social ties, is also associated with greater resistance to the cold virus (Cohen et al., 2003). However, preliminary findings suggest that the effects of sociability and network size are somewhat independent (Cohen, 2004). In addition, smaller social network size was associated with a lower antibody response among healthy undergraduate students; this effect was also independent of personality traits sometimes associated with loneliness, such as self-esteem, hostility, and extraversion, as well as perceived stress, health behaviors, and mood (Pressman et al., 2005). Of note, having more diverse social contacts also increases exposure to infectious agents, potentially increasing the risk of illness (Hamrick et al., 2002). However, in a naturalistic setting where potential of exposure to viruses varies, individuals with more diverse networks show fewer upper respiratory infections only when they also report low stress (Hamrick et al., 2002). Regular attendance of religious services is one component of many measures of social network size, as many individuals derive close social ties and a feeling of social integration from religious groups. Religious participation is associated with perceptions of a more supportive social network (Ellison and George, 1994) and is associated with lower mortality rates (McCullough et al., 2000; Strawbridge et al., 1997) and with lower levels of interleukin-6 (IL-6), a proinflammatory cytokine (Koenig et al., 1997; Lutgendorf et al., 2004). Although the pathways between religious participation and mortality are not well understood,
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researchers speculate that increased social integration and immune function play a role. However, some studies indicate that social network size does not account for the relationship between religious participation and immune outcomes, suggesting that the effects of religious participation are explained primarily by other factors (e.g., Lutgendorf et al., 2004). Evidence for association between social network size and health supports the main effects model of social support: Social network size appears to confer health benefits regardless of the experience of psychosocial stress (Cohen, 2004). However at least one study supports the stress-buffering model—the proposition that social relationships confer benefits especially to those who experience more psychosocial stress. A study of patients with disseminated cancer found that greater social network size related to greater responses to delayed-type hypersensitivity (DTH) tests only for those reporting a high level of life stress (Turner-Cobb et al., 2004). However, among individuals with less life stress, the relationship was reversed: Individuals with smaller network size showed more robust immune responses. One interpretation of these findings is that under conditions of low stress, a greater number of social contacts may have been experienced as stressful due to obligations of the sick individual to those network members or because of unhelpful attempts at support by those network members; in contrast, under conditions of high stress, perhaps social contacts were either able to provide better support or their perceived availability and support were more appreciated. As will be discussed in greater detail later, situations of chronic illness may potentiate problems with social support when they exist. Much of the literature on social network size has been interpreted in terms of positive benefits that result from social integration. This interpretation is supported by the graduated increases in health that have repeatedly been found with increasing integration (e.g., Berkman and Syme, 1979; Cohen et al., 1997). However, as noted by Cohen (2004), it appears that the most isolated individuals are at “greater risk than one would expect if the relation between social integration and health was linear” (p. 680); that is, it appears that the greatest differences in health are seen between the very isolated as compared to their less isolated counterparts. In concordance with this observation, there is evidence that being able to identify even just one person who functions as a confidante, someone who can be trusted to listen to personal events and feelings, is predictive of better health. For a majority of adults in the United States, the marital relationship serves as a primary source of support (Glenn and Weaver, 1981; Simmons and O’Connell, 2003) and, correspondingly,
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a majority of research on specific close relationships has focused on marriage. 2. Marital Status and Divorce Married individuals consistently experience better health than unmarried and divorced individuals and are at lower risk of mortality from a range of acute and chronic conditions over and above effects of age, income, and other biomedical risk factors (Gordon and Rosenthal, 1995; Johnson et al., 2000; Verbrugge, 1979). Interestingly, older individuals who become divorced appear to be at greater risk of both mortality and morbidity than younger people, perhaps in part because they typically lack a support network sympathetic to such concerns (Schulz and Rau, 1985). The association between physical health and marriage remains after controlling for selection effects, (i.e., the tendency for healthy individuals to marry and stay married) (Wu et al., 2003). Although other factors undoubtedly contribute to the association, the support provided by marriage and the stress of marital transitions are widely acknowledged to account for much of the predictive power of marital status on health outcomes (Burman and Margolin, 1992). In interpreting studies more specifically relevant to immune function, it is important to note that the effect of marital status on both mortality and morbidity is substantially stronger for men than for women (KiecoltGlaser and Newton, 2001); non-married women have a 50% greater risk of mortality than their married counterparts, compared to a 250% greater risk for nonmarried compared to married men (Ross et al., 1990). In fact, men show greater benefit from social integration in general (House et al., 1988). There are several plausible explanations for why marriage confers greater health benefits to men than women (Johnson et al., 2000; Kiecolt-Glaser and Newton, 2001), most of which involve differences in actual supportive functions and which are described in the section titled “Perceived Marital Support.” Research focused on marital status and immune function is limited, with a greater body of work focusing on marital quality. However, one study suggests that married women may have more adaptive immune function than comparable recently separated or divorced women (Kiecolt-Glaser et al., 1987), with the latter showing lower percentages of natural killer (NK) cells (Kiecolt-Glaser et al., 1987) and higher antibody titers to latent Epstein-Barr virus (EBV), indicating poorer cellular immune function control over the steady state expression of the latent virus. These effects were not explained by differences in drug or alcohol use, diet, or sleep. Similar results were found with
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men, with divorced or separated men showing higher antibody titers to two herpes viruses—EBV and herpes simplex type 1 (HSV-1) (Kiecolt-Glaser et al., 1988). Individual variation in responses to divorce, which can include acute as well as long-lasting depression in addition to other stress responses, are likely to play a role in these immune changes (Kiecolt-Glaser et al., 1987). The potential impact of depression on immune function (for a review, see Irwin, 2001) is discussed in the following section, as well as in our conclusion section. Rheumatoid arthritis (RA), a systemic autoimmune disease, provides other immune-relevant data relevant to marital status. Among this population, increases in aspects of immune function are maladaptive because they are associated with disease flare-ups (Zautra et al., 1994). In both men and women with this disease, married individuals demonstrate slower progression of functional disability than the unmarried (Ward and Leigh, 1993). No one category of unmarried individuals (e.g., never married, separated, and widowed) appeared to drive the effect in this study (Ward and Leigh, 1993). 3. Bereavement The emotional and physical health consequences of surviving a close other can be profound. As with divorce, there any many complicated issues surrounding bereavement other than the loss of social connectedness and social support. Sadness, anxiety, and rumination are common and often long lasting (Weiss, 2001). Some studies have focused on bereavement in general. For example, Gerra and colleagues (2003) found that individuals experiencing unexpected bereavement from a close other (parent, child, spouse) demonstrated alterations in functional (as opposed to quantitative) immune measures post-bereavement as compared to non-bereaved matched controls. However, the majority of health-relevant work on bereavement focuses on sequelae subsequent to the death of a spouse. Spousal bereavement is associated with an increased risk for inflammatory disorders (Sternberg et al., 1992) and increased all-cause morbidity and mortality. Similar to gender differences in social integration described earlier, men appear to be at a greater risk of mortality following spousal bereavement (Kiecolt-Glaser and Newton, 2001). A particularly well-controlled and comprehensive study found that surviving one’s spouse led to increased risk of mortality among men but not women over a 10-year period (Helsing et al., 1981). Interestingly, older individuals tend to be at less risk for both mortality and morbidity from spousal bereavement than younger people (for a
review, see Schulz and Rau, 1985), perhaps because of their expectations and a tendency to have social networks prepared and able to provide support following this event. As the majority of studies of bereavement have been of older women, the association between bereavement and health in younger individuals may be underestimated. A number of studies have demonstrated dysregulation of immune function following the death of a spouse. The first such study demonstrated that bereaved women had significantly lower lymphocyte responses to two mitogens (Concanavalin A [Con-A] and phytohemogglutin-A [PHA]) two months after the death of their spouse (Bartrop et al., 1977), followed by a study of men which found such effects after the death of a spouse from breast cancer (Schleifer et al., 1983). While the former study was not able to control for baseline levels, in the latter study lymphocyte responses were not suppressed in the men prior to their spouses’ death, despite their reported increase in life stress due to coping with the disease. More recent studies have shown that bereavement is associated with a decrease in NK cell activity (e.g., Hall and Irwin, 2001; Irwin et al., 1987b). Although the clinical relevance of such dysregulation of immune function is not clear, the potential importance of these findings is highlighted by the morbidity and mortality rates associated with bereavement. Clinically relevant changes in immune function are more clearly demonstrable in HIV seropositive (HIV+) individuals for whom subtle changes in CD4+ T-cell numbers and proliferative responses of T-cells to mitogens are associated with morbidity and mortality. HIV+ men who had lost their partner to AIDS in the previous year evidenced greater serum neopterin levels (produced by activated macrophages and linked to progressive HIV infection) and a decreased T-cell proliferative response as compared to seropositive non-bereaved, seronegative bereaved, and seronegative non-bereaved men (Kemeny et al., 1995). Bereavement status in this population predicts decreases in CD4+ cells across a 4-year period, and NK cell cytotoxicity between 6 to 12 months post-bereavement (Kemeny and Dean, 1995; Goodkin et al., 1996). Limited research has compared bereavement from different types of close relationships. Data from HIV+ populations indicate that close romantic partnership is particularly significant: Although loss of a partner predicts immune changes in HIV+ men in the following year (Kemeny et al., 1995), loss of a close friend to AIDS does not predict immune changes (Kemeny et al., 2004). Factors including depression, elevated cortisol levels, and sleep may account for the association
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between bereavement and immunity (Hall and Irwin, 2001; Herbert and Cohen, 1993). Although the direction of causality has not yet been established, depression appears to play a particularly prominent role. A large longitudinal study of older adults found a ninefold increase in major depression and a four-fold increase in depressive symptoms among the recently bereaved as compared to married individuals (Turvey et al., 1999). A rise in depressive symptoms following bereavement is particularly common among those for whom the loss of spouse was unexpected (Carnalley et al., 1999) and for whom social support is lacking (Wortman et al., 2004). More severe depressive symptoms among bereaved women are associated with lower lymphocyte proliferative responses to mitogens, less adaptive NK cell activity, a decrease in the number of T-cells, and an increase in the ratio of CD4+ to CD8+ cells (Irwin et al., 1987a).
B. Social Support One reason that the existence of social ties is related so strongly to health outcomes is that they provide many forms of positive social support. The term social support refers to support from a variety of domains: instrumental support (including both financial and assistance with tasks), emotional (appraisal) support, information, companionship, and self-esteem support (Cohen and Hoberman, 1983; Cohen et al., 1985). A distinction is frequently made between perceived and received support, with perceived support referring to the degree to which an individual believes that support would be available if and when necessary, and received support referring to the actual amount of support that has been recently provided. Because measures of social support tap into the quality of social ties, they are often but not always correlated with social network size. For example, an individual with only one close relationship may feel that all of his/her needs are met, while another individual with 10 relationships may report low perceived social support. While higher levels of social integration (e.g., social network size) are typically beneficial regardless of stress level, measures of perceived support appear to operate in tandem with psychological stress (Uchino et al., 1996). Furthermore, the stress-buffering effects of social support may depend on the degree to which the functions provided by the social network match the specific needs elicited by the stressful event (Cohen and Wills, 1985). An important consideration is that these measures may correlate with and possibly interact with socioeconomic status (SES); individuals with higher SES may be better able to provide a variety of types of support due to a variety of factors, including greater
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time, money, and health. Individuals with higher annual earnings report providing more support to others than do those in middle or lower income categories (Krause and Borawski-Clark, 1995). Individuals with higher incomes also report greater satisfaction with the support they receive from others (Krause and Borawski-Clark, 1995). While individuals in lower social classes tend to provide support to others less frequently, they simultaneously rely more heavily on support provision; older low-SES adults tend to turn to others for assistance at relatively low levels of stress, while older high-SES individuals tend to rely on their own personal resources, turning to others only in times of greater need (Krause, 1997). Thus, not only is social class an important construct to consider in studies of social support, but social support interventions may be especially beneficial to individuals of lower social class. 1. Perceived Social Support As compared to other measures of social support (e.g., received support), perceived social support is most reliably and strongly associated with well-being (Wills and Shinar, 2000) and most research relevant to immunity has employed such measures. Although there have been null findings, a meta-analytic review of studies predominantly based on perceived support concluded that higher support is associated with better immune system function overall (Uchino et al., 1996). For example, higher perceived support has been associated with a robust antibody response to a hepatitis B vaccine among medical students (Glaser et al., 1992). Among healthy men, perceived support, but not network size or actual utilization of support, is positively correlated with NK cell numbers (Miyazaki et al., 2003). Similarly, among spouses of those with cancer, higher perceived support on a variety of dimensions was associated with higher NK cell activity as well as better proliferative responses to one of two tested mitogens over and above any effect of depressed mood (Baron et al., 1990). In one of few studies to examine gender differences, however, the perceived availability of a confidante was associated with a stronger proliferative response for women but not men (Thomas et al., 1985). Finally, low perceived support has also been correlated with an increase in self-reported episodes of upper respiratory infection (for a review, see Biondi, 2001). A broader view of the health-promoting effects of social support suggests that perceived support largely operates via a stress-buffering model, with the greatest and most reliable benefits of support found under conditions of psychological stress, when the support is
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most needed (Cohen, 2004). The majority of data with immune relevance appears to follow the same pattern. Supporting the stress-buffering model, social support buffered the negative effects of minor daily stressors on total lymphocyte counts and mitogen-induced proliferative responses of lymphocytes in an elderly sample (Thomas et al., 1985). Additionally, examination stress effects on NK cell activity were also ameliorated by high perceived support (Kang et al., 1998). In a population representing chronically stressed individuals, caregivers of spouses with dementia who reported low perceived support and less closeness with others demonstrated poorer augmentation of NK cell activity to two cytokines (Esterling et al., 1994b; Esterling et al., 1996). Caregivers who reported lower levels of perceived support demonstrated more negative changes in immunity 1 year later if they were distressed by their spouse’s dementia-related behavior (Kiecolt-Glaser et al., 1991), indicating again that social support may be particularly important for those experiencing greater subjective distress. Among cancer patients, lack of social support is associated with increased mood disturbance, decreased life expectancy, and decreased NK cell activity (Ell et al., 1992; Jensen, 1991; Levy et al., 1992; WaxlerMorrison et al., 1992). Among ovarian cancer patients there is a negative correlation between social wellbeing and vascular endothelial growth factor (VEGF) levels, a cytokine associated with tumor angiogenesis and poorer survival (Lutgendorf et al., 2002). As noted earlier, social integration tends to benefit men in terms of health significantly more than it does women. While gender disparities related to supportive functions provided by men versus women have been posited as explanations for these effects, in most cases these disparities have not been directly linked to health or immune outcomes and represent an area ripe for future research. In terms of general social integration, women tend to provide support more to others in general. In addition, most caregivers of both children and older adults are women (for a review, see Mancini and Blieszner, 1989). As will be addressed later, providing long-term care to others, even loved ones, can be a considerable source of stress. 2. Perceived Marital Support The marital relationship represents a relatively stable resource for all of the supportive functions one may derive from a support network. However, little research has focused on the relationship between support functions provided by one’s spouse and immune parameters. Among breast cancer patients, NK cell activity was associated with the perceived
quality of emotional support provided by a spouse or intimate partner (Levy et al., 1990a). Another study found that, averaging across support domains, newlywed wives who reported greater satisfaction with the support provided by their spouses demonstrated smaller increases in negative affect, blood pressure, and cortisol in response to a conflict interaction with their spouses (Heffner et al., 2004). These data suggest that satisfaction with spousal support may be a unique predictor of physiological outcomes, above and beyond support from an overall social network. Gender disparities in the supportive functions spouses provide have been posited as explanations for noted gender differences in the health benefits of being married. Although no data are available to support the contention that such gender disparities relate to immune-relevant outcomes, this represents an important area to target future research. For example, wives tend to influence their spouses to improve health behaviors to a greater extent than do husbands (Umberson, 1992), which can be interpreted as a form of informational support (the conferring of advice, recommendations, and feedback). In addition, married women do a greater percent of housework and child care than their spouses (Bittman et al., 2003), an aspect of the marital relationship that can be interpreted as disparity in provision of instrumental support. Evidence suggests that this disparity is more stressful for women who hold egalitarian ideals; these women report less satisfaction with their marriages and demonstrate more adverse cardiovascular and catecholamine responses than others (Kiecolt-Glaser and Newton, 2001). Finally, men tend to rely more heavily on their wives for emotional support. For example, one study found that although men and women were equally likely to confide their main concerns with others in the weeks following cancer diagnosis, 40% of men reported confiding only to their partner, as compared to 15% of women who reported this pattern (Harrison et al., 1995). Because women tend to have broader support networks in whom they confide personal problems or difficulties, husbands may receive greater relative benefits from receiving emotional support from their spouses. Future research focused on the relative benefits of specific support functions from the spouse may provide a way of determining what elements of social support are key to health and immune benefits. Other types of close relationships provide many of the same supportive functions as do married relationships. Of note, the number of individuals living as if married (which includes but is not limited to same-sex couples) has increased dramatically in recent years (Simmons and O’Connell, 2003). Recent evidence sug-
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gests that such unmarried romantic partners share many of the physical and psychological benefits of married individuals, after controlling for income and age (Wu et al., 2003). Non-romantic close relationships (e.g., parents, children, friends) certainly also provide key aspects of support. However, family relations tend to provide for different supportive functions than do friendships, and the relative importance of family versus friends depends on age. Although relatives provide more instrumental support than do friends, friendships are central to emotional support and reducing feelings of loneliness (Lee and Ishii-Kuntz, 1987). Relatives, rather than friends or neighbors, are more likely to provide long-term assistance (Greenblatt et al., 1982); it is estimated that 80–90% of care of older persons is provided by family members (Brody, 1981). Additional comparisons of the marital relationship to other types of close relationships would be helpful in determining the underlying mechanisms behind health correlates of marriage. 3. Received Support In humans, received support can be measured by assessing the degree to which certain types of support were provided to an individual over a given time period, such as the previous 4 weeks (Wills and Shinar, 2000). Literature on received support is much more limited than that on perceived support, in part because there are some limitations of utilizing received support as a measure that make results difficult to interpret. Received support reflects not only the availability of support and willingness to access available support but also the need for support. Perhaps because individuals experiencing greater need tend to receive more assistance, received support is sometimes correlated positively with functional disability and mortality (Dunkel-Schetter and Bennett, 1990; Krause, 1997). However, self-reports of receiving support when one is ill have been associated with health benefits. Social support provided by volunteers is associated with increased survival time in terminally ill patients by 80 days (Herbst-Damm and Kulik, 2005). Additionally, breast cancer patients who actively seek social support as a coping strategy show greater NK cell activity than those who do not (Levy et al., 1990a). Seeking instrumental support at diagnosis of ovarian cancer is associated with lower concurrent IL-6 as well as better clinical status and less disability 1 year later (Lutgendorf et al., 2000). However, in this study IL-6 did not mediate the effects of social support on these health outcomes. Another reason the human literature on received support is limited is that interventions involving
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received support are unethical and direct observations of support are difficult. Primate studies provide perhaps the strongest evidence that received support is adaptive for immune function. Rhesus monkeys housed with familiar peers during maternal separation show a smaller decrease in CD4+ and CD8+ cell numbers as compared to those housed alone (Coe, 1993). Primates exposed to the social stress of rehousing had poorer mitogen responses than those that were not re-housed. Further, among those who were re-housed, those demonstrating higher levels of naturally occurring affiliative behavior had better immunological responses (Cohen et al., 1992). 4. Loneliness and Intimacy One reason social integration and social support may be beneficial is their association with the more specific constructs of loneliness and intimacy (Reis and Franks, 1994). Indeed, loneliness can be interpreted as a perceived lack of support. However, although loneliness is often related to social network size, the association is by no means perfect. One can feel isolated from others despite having a large number of social contacts, or feel very socially connected due to a particularly good social contact. There is some evidence that feelings of loneliness can be immune dysregulating (Cacioppo et al., 2003). In a population of psychiatric patients, loneliness was related to lower NK cell and PHA responses (Kiecolt-Glaser et al., 1984b). In addition, loneliness in medical students is associated with lower NK cell activity (Kiecolt-Glaser et al., 1984a). More recently, feelings of loneliness among college freshmen were associated with poorer antibody responses to one of three tested vaccines (Pressman et al., 2005). The effect of loneliness on antibody responses was not mediated by cortisol, increases of which correlated with reports of loneliness close in time to the cortisol measures, but was partially attributable to the higher perceived stress of lonely individuals (Pressman et al., 2005). In contrast to loneliness, intimacy refers to the perceptions of closeness with a social partner. Evidence suggests that the majority of the health-promoting benefits of intimacy are accounted for by differences in social support, while benefits of social support are not mediated by intimacy (Reis and Franks, 1994). However, studies of more specific constructs like intimacy in the context of health are valuable in that they can illuminate more specific mechanisms by which social support is beneficial (Prager and Roberts, 2004). There is very little immune-relevant research on intimacy. Perhaps the most relevant research in this area comes from a prospective study of married rheumatoid
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arthritis patients in which self-reported perceptions of positive spousal interaction patterns were associated with less severe increases in disease activity in response to interpersonal stress (Zautra et al., 1998). Thus, as with the bulk of the social support literature, this study supports the contention that the self-reported receipt of support from close relationships serves a protective function in the face of difficulties.
C. Social Strain Although for most people supportive social contacts outnumber troublesome ones (Rook, 1984), close relationships are often marked by both positives and negatives (Major et al., 1997), and overall networks may be characterized by both support and rejection (Finch et al., 1989). As described by social exchange theory, relationships can be a source of stress due to demands of time, money, and emotional resources (Cook and Rice, 2003). Finally, support may be well intended but provided in a manner that is not helpful. In the current section, we review evidence that negative aspects of social relationships can themselves serve as stressors, with a resulting impact on immune function. 1. Negative or Ambivalent Characterizations of Social Ties There is substantial evidence that interactions marked by acute conflict and negative emotions have direct physiological consequences. Because close ties tend to be relatively stable (Weihs et al., 1999), conflict within relationships can function as both an acute and a chronic stressor, and may thus dramatically impact health over an extensive time period (Rook, 1992). Conflictive social interactions consistently result in heightened blood pressure and heart rate (Kamarck and Lovallo, 2003), especially for those high in trait hostility (Suls and Wan, 1993). Work with populations suffering from diseases related to immune dysregulation and inflammation supports a link between interpersonal stress and health outcomes. For example, among those with rheumatoid arthritis, interpersonal stress has been linked to both endocrine and immune alterations, changes which were associated with clinician-rated disease activity as well as self-reported joint tenderness in well-designed prospective studies (Zautra et al., 1994; Zautra et al., 1998). People’s negative characterizations of particular social ties or interactions are relatively independent (Ruehlman and Karoly, 1991): One can view someone as being an important and positive member of his/her social network while also acknowledging negative
aspects of the relationship (e.g., a family member who provides valued financial support but who is difficult socially). In fact, almost half of an individual’s important social ties can be characterized as ambivalent (Uchino et al., 2001), which means they are perceived to be high in both positive and negative aspects. Recent studies indicate that relationships characterized as ambivalent may be just as toxic as those characterized as predominantly negative, in part because people tend to avoid contact with individuals they consider negative but have greater contact with ambivalent ties. Uchino and colleagues found that high numbers of ambivalent relationships in the networks of older adults predicted increased sympathetic reactivity during stress (Uchino et al., 2001). Similarly, compared to interacting with someone characterized as predominantly supportive or aversive, interacting with individuals characterized as ambivalent is related to larger increases in ambulatory systolic blood pressure (HoltLunstad et al., 2003). To our knowledge, research with specific immune measures has not yet explored the possible interactive contributions of positive and negative perceptions toward social network members, which is clearly an important avenue for future research. Ambivalence in the marital relationship may be particularly important, as this is a relationship requiring a great deal of interaction and cooperation. 2. Marital Conflict and Dissatisfaction Although, on average, being married confers health benefits, the mere existence of a close relationship is not enough to be protective. A particularly strong and reliable association is found between poor marital quality and poor health (Kiecolt-Glaser and Newton, 2001). One commonly used indicator of the quality of marital relationships is satisfaction with marriage, which is typically assessed with self-report scales. In the studies described previously that compared married men and women with separated or divorced individuals, lower marital satisfaction was associated with several indicators of poorer immune function, including levels of EBV antibody titers for women and men and the percentage of CD4+ and CD8+ cells for men (Kiecolt-Glaser et al., 1987; Kiecolt-Glaser et al., 1988). Immune data from these studies were consistent with the epidemiological observation that recently separated individuals have greater incidence of health impairment than individuals who have been divorced for many years (Dohrenwend et al., 1978). Studies with chronically ill populations support a correlation between marital satisfaction and immune function. For example, among wives with chronic fatigue and
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immune dysfunction syndrome (CFIDS), marital satisfaction is correlated with health symptoms related to the disease (Goodwin, 1997). In addition to self-report measures of marital satisfaction, marital quality has increasingly been assessed using observations of behavior during couple interactions. Hostile behaviors, such as interrupting and criticizing, appear to be particularly predictive of physiological outcomes. Hostile behaviors during marital discussions are associated with adverse changes in blood pressure and endocrine levels (Ewart et al., 1991; Kiecolt-Glaser et al., 1993; Malarkey et al., 1994). Moreover, research utilizing a variety of populations provides substantial evidence for immune dysregulation resulting from marital conflict. For example, using a sample of healthy newlywed couples with high marital satisfaction overall, subjects who exhibited more negative or hostile behavior during a 30-minute discussion of marital problems showed greater decrements over 24 hours as compared to other subjects on functional immunological assays (Ewart et al., 1991; Kiecolt-Glaser et al., 1993; Malarkey et al., 1994). Older couples also evidence endocrine and immune dysregulation following marital conflict discussion (Kiecolt-Glaser et al., 1997), with both men and women who demonstrated more negative behavior evidencing the poorest immunological responses across three assays. In another marital interaction study, wives responded to a 45minute conflictive discussion task with greater increases in depression, hostility, and systolic blood pressure than husbands (Mayne et al., 1997); women’s lymphocyte proliferative responses decreased following conflict, while men’s increased (Mayne et al., 1997). Several studies of individuals provide evidence that changes in immune parameters as a response to marital strain have clinical relevance. For example, in a population of predominantly female rheumatoid arthritis patients, negative spouse behavior (e.g., critical remarks) was predictive of poorer pain outcomes, even after controlling for baseline pain (Waltz et al., 1998). Marital strain is also associated prospectively with the development of mouth ulcers (Levenstein et al., 1999; Medalie et al., 1992), an area where the immune system is important; endocrine and immune dysregulation appear to play a role in these effects, in addition to gastrointestinal stress responses and adverse health behaviors. In addition, recent research on the effects of marital interactions has assessed healing of experimentally induced wounds, a clinically important outcome measure. Couples who demonstrated consistently higher levels of hostile behavior during across both conflictive and supportive interactions healed wounds at 60% of the rate of low hostile couples (Kiecolt-Glaser et al., in press).
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Some consistent effects of individual differences have emerged from the literature on physiological responses to marital conflict. Notably, trait hostility—a dispositional tendency characterized by aggression, anger, and cynicism—may interact with marital conflict to produce even greater immune dysregulation. Individuals high in trait hostility show greater endocrine and immune responses to marital conflict, but only in part because they demonstrate more negative conflict behaviors during marital interactions (Mayne et al., 1997; Newton et al., 1995). Another study found a significant association between behaviorally coded affect during conflict and cardiovascular, immune, or cortisol data only among husbands who were high on cynical hostility (Miller et al., 1999). The weight of evidence suggests that women suffer more from poor relationship quality and conflict (e.g., Hibbard and Pope, 1993; Kiecolt-Glaser et al., 1996; Malarkey et al., 1994; Mayne et al., 1997). For example, women who reported that they had considerable conflicts with their husbands and who also reported work conflict had a 2.54-fold risk of work-related disability related to a variety of health problems in the ensuing 6 years; neither work nor marital conflict was a risk factor for men (Appelberg et al., 1996). These differences between wives and husbands do not seem to be a function of gender differences in broader physiological patterns of responding to acute stress (KiecoltGlaser and Newton, 2001). One possible explanation for gender differences related to marriage is that conflict may dampen the benefits of being married more for women than men, perhaps because women’s selfrepresentations tend to be characterized by greater relational interdependence (Cross and Madson, 1997) and women tend to spend more time thinking about marital events than do men (Burnett, 1987; Ross and Holmberg, 1990). 3. Relationship Burden Even relationships construed as predominantly positive can function as a source of stress when one individual in the relationship requires substantial care, such as a sick child or a spouse with Alzheimer’s disease. In addition to direct demands on time, emotional, financial, and physical resources, care giving often requires dramatic restructuring of the family environment (Ell, 1996). Individuals care giving for a spouse with dementia have higher rates of depression and anxiety, and continue to show these higher levels even years after the loss of spouse for whom they were providing care (Bodnar and Kiecolt-Glaser, 1994). One reason why caregiving may be so emotionally and physically difficult is that caregivers often experience
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social isolation, with accompanying reductions in access to social support (Ell, 1996). Converging evidence from a variety of immune markers and outcomes demonstrates that caregiving is consistently associated with immune dysregulation. As compared to well-matched controls, caregivers report more days of infectious illness (Kiecolt-Glaser et al., 1991) and evidence poorer immune responses to virus and vaccine challenges (Glaser et al., 2000; Vedhara et al., 1999). Caregivers also demonstrate slower healing of laboratory-induced wounds, an outcome with clear clinical relevance (Kiecolt-Glaser et al., 1995). In addition, both current and former caregivers had poorer enhancement of NK cell activity in response to recombinant IL-2 and interferon-gamma (INF-γ) in vitro (Esterling et al., 1994b; Esterling et al., 1996) and showed a substantially greater increase in IL-6 over a 6-year period as compared to non-caregivers (KiecoltGlaser et al., 2003). Caregivers with less positive social support and less emotional closeness among social contacts showed greater dysregulation, suggesting that the stress of caregiving is partially buffered by strong support networks (Esterling et al., 1996). Caregiving for a chronically ill child is also related to important health outcomes. Telomerase activity and telomere length, two cellular markers associated with aging, were measured in peripheral blood mononuclear cells taken from healthy mothers, a subset of whom were caregivers for a chronically ill child (Epel et al., 2004). Regardless of whether the mother’s child was healthy or sick, both perceived stress and chronicity of stress were significantly associated with lower telomerase activity and shorter telomere length (Epel et al., 2004). High stress levels were also associated with higher oxidative stress (Epel et al., 2004). In conjunction with immune dysregulation found among caregivers of spouses, these results provide substantial evidence that chronic stress is associated with premature aging (Glaser and Kiecolt-Glaser, 2005). An important caveat to the caregiver literature is that providing support is not necessarily detrimental to one’s health. Indeed, providing social support to others is associated with reduced mortality over a 5-year time period, after controlling for age and gender (Brown et al., 2003). Providing support to others may provide a source of self-esteem and connectedness with others. However, in situations such as caregiving for an individual with chronic illness, stress associated with the provision of support may override the potential benefits. Relationship burden may help explain some unexpected findings in the HIV literature. While some research has shown that low support is associated with acceleration of the progress of HIV infection (e.g., Leserman et al., 1999; Solano et al., 1993), substantial
evidence suggests HIV+ men who report more loneliness (Miller et al., 1997), less attachment to others (Persson et al., 1994b), or less social support (Persson et al., 1994a) show better immune function, although the immune outcomes are not always related to disease progression or mortality (e.g., Miller et al., 1997). There are several possible explanations for why these latter findings are discordant with the bulk of research reviewed in this chapter showing benefits of social integration and social support. Individuals with HIV and Acquired Immune Deficiency Syndrome (AIDS) are more likely to have social contacts who also have the disease. For this reason, HIV+ individuals are more likely to take on the burden of providing care to their close social ties (Cole and Kemeny, 2001). Those with HIV/AIDS are also more likely to experience bereavement than are members of the general population and report a related increase in depression, anxiety, and general distress (Gluhoski et al., 1997). In addition, gay men in the United States, on whom the majority of research has focused, may suffer strain in their social contacts due to prejudice about homosexuality and AIDS. HIV+ gay men who conceal their homosexuality and who also have high levels of social support have lower CD4+ cell counts than those who do not, suggesting that the strain of concealment is magnified for these individuals (Ullrich et al., 2003). 4. Problematic Received Support While social support is generally considered to be beneficial, some attempts to provide support may be misguided, potentially causing additional stress. For example, when someone becomes critically ill or loses a loved one, friends and family may avoid discussing the issue (Lichtman et al., 1988), criticize one’s responses (Koopman et al., 1998), or be overprotective (Hagedoorn et al., 2000). Among rheumatoid arthritis patients, evidence suggests that responses to pain that are overly accommodating may inadvertently reinforce pain behaviors and encourage less adaptive health behavior (Turk et al., 1992). Rheumatoid arthritis patients who report that their spouses engaged in more solicitous, distracting, and punishing responses reported greater pain intensity and demonstrated more pain behavior during a standardized battery of physical tasks (Williamson et al., 1997). Similarly, in a study of chronic back pain patients, higher spousal ratings of solicitousness were associated with less time spent walking on a treadmill in the partner’s presence than when alone (Lousberg et al., 1992). In addition, regardless of how skillfully support is provided, receiving high levels of support may reduce the recipient’s self-esteem, perceived competence, and
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perceived control (Matire et al., 2002). The effects of received support may depend on individual differences in the degree to which people desire support and how they adjust to support provision. For example, one study demonstrated that the effects of instrumental support (i.e., physical assistance) from spouses of women with osteoarthritis depended on the centrality of functional independence to the woman. Women who rated physical independence as highly important and who received high levels of support reacted negatively to this support, experienced greater depressive symptoms, and showed fewer self-care behaviors (Matire et al., 2002). This suggests that support interventions need to account for individual difference in how one responds to support provision.
III. INTERVENTIONS Interventions provide some of the best evidence that social support and key aspects of close relationships are causally related to immune changes and that these changes can be clinically relevant. Here, we highlight findings related to psychosocial interventions aimed at improving aspects of close relationships and which have relevance to immune function. As described earlier, one way in which close relationships buffer stress is by allowing for the disclosure of negative emotions. Emotional disclosure through journaling and/or verbal accounting of stressful events may allow individuals without sufficient close ties to reap some of the benefits of emotional expression and may augment the effects of supportive ties for others. In both clinical and non-clinical populations, dramatic physical and psychological health improvements result from emotional disclosure interventions (Pennebaker, 1997; Smyth et al., 1999), including objective health outcomes among rheumatoid arthritis patients (Smyth et al., 1999). Changes in immune function appear to play a role in the health benefits of emotional disclosure. For example, among healthy medical students, those assigned to write about a traumatic experience once per day for 4 days prior to receiving a hepatitis B vaccine had higher antibody titers to the vaccine at 4 and 6 months post-vaccination than controls (Petrie et al., 1995). In addition, undergraduate students whose essays about stressful life events evidenced a lot of emotion had lower levels of antibody to EBV, suggesting greater cellular immune control over this latent virus (Esterling et al., 1990). In general, interventions focused on emotional disclosure appear to be more effective if the individual has not already disclosed or come to terms with the circumstances giving rise to their emotions (Pennebaker et al., 2001).
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Of course, writing about an event is different from actually expressing emotions to someone else who can respond and provide support. To our knowledge, no study has compared emotional disclosure while alone to disclosure to a close friend or significant other, which would be particularly meaningful to the impact of disclosure in close relationships. However, verbal disclosure of stressful life events may be even more effective than written disclosure. As compared to those assigned to write non-emotionally, healthy undergraduates assigned to express their emotions about stressful events showed lower EBV titers; those assigned to verbally disclose their emotions (alone into a tape-recorder) showed even lower EBV titers than those assigned to write about them (Esterling et al., 1994a). In addition, preliminary evidence with chronic pain patients suggests that writing letters in a directed way about angry feelings can be beneficial in terms of pain severity, control over pain, and depression (Graham et al., 2006). A number of psychosocial interventions have focused on chronically ill populations. While not entirely consistent, research targeting cancer distress generally demonstrates that psychosocial interventions have strong effects on psychological function. In fact, it has been argued that evidence is strong enough to justify the integration of psychosocial treatment into standard care (Carlson and Bultz, 2004). Data regarding the impact of psychosocial interventions on health outcomes in cancer populations is mixed, and beneficial findings in terms of longevity have not withstood replication (Goodwin, 2004). An important note is that interventions with cancer patients showing beneficial effects have encouraged discussion of negative thoughts and emotions such as fear of dying, hopelessness, and guilt, suggesting that emotional disclosure may be a key mechanism underlying successful interventions in this area as well. Most support interventions are based on peer support from other individuals with the same disease. However, it may be more effective to focus support interventions on improving utilization of a more naturalistic, existing support network (Cohen, 2004). Given the reviewed data on the particular importance of the marital relationship, it may also be beneficial to target the marital relationship as a source of support. One unique intervention related to marriage, the CanCOPE intervention, was developed specifically for couples in which the women had either early stage breast or gynecological cancer (Scott et al., 2004). The intervention emphasized mutual support and effective communication. The intervention for couples produced significantly greater improvements in couples’ supportive communication, greater reduction in
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psychological distress, improved sexual adjustment, and improved coping strategies compared to standard care and a similar cognitive behavioral intervention for the women alone. As noted earlier, bereavement is associated with immune dysregulation. Disclosure of emotion is common after bereavement, but may be constrained if the death was traumatic or stigmatized (e.g., from AIDS or suicide) (Pennebaker et al., 2001). In a correlational study, those who talked about the traumatic death of their spouse reported being in better health than those who had not (Pennebaker and O’Heeron, 1984). In an emotional disclosure intervention, those assigned to write about the recent death of their spouse showed improvement on hopelessness and depression (Pennebaker and Seagal, 1999). More comprehensive interventions with bereaved individuals also result in improved health. For example, bereavement support groups have been demonstrated to result in greater improvements of health-related quality of life in HIV+ individuals than comparable individual therapy (Sikkema et al., 2005). Literature on immune outcomes of such interventions has overwhelmingly focused on HIV+ men, primarily because they are particularly likely to experience bereavement (Gluhoski et al., 1997). In a sample of HIV-1 positive homosexual men, a bereavement support group was demonstrated to buffer against the decrement in CD4+ cell count and the increment in plasma viral burden typically seen as a response to bereavement (Goodkin et al., 1998). Research on the immune effects of support groups for HIV+ women is needed, particularly as they report greater distress, anxiety, and a suicidal ideation in response to bereavement compared to HIV+ men (Summers et al., 2004). In addition, following psychosocial interventions, psychological and quality-of-life improvements appear to be greater for HIV+ women than for men (Sikkema et al., 2005). The bulk of the evidence indicates that support interventions have beneficial effects. However, support interventions are not always necessary, and may do harm to individuals who are experiencing little distress or who already have adequate support. One study (Helgeson et al., 2000) found that women who began a supportive group intervention with high levels of social support demonstrated decreases in physical function over the course of the intervention. Negative interactions in the group increased over time, so this may not be typical of support groups in general. However, other studies have similarly found that support interventions may result in deleterious effects (Frasure-Smith et al., 1997). In addition, for those who are experiencing support deficiencies, interventions may be most effective if they are tailored to address
the individual’s particular support problem (Hogan et al., 2002). For example, while some individuals may benefit from increasing their number of social ties, other individuals may have access to adequate support but difficulty asking for assistance. There are many other promising areas for interventions focused on close relationships that are not reviewed here. For example, training providers to provide better support (e.g., in a medical setting) may be helpful; one study of cancer patients showed that positive ratings of emotional support from a spouse were related to NK cell function as well as better ratings of emotional support from a physician (Levy et al., 1990b). Also, given the substantial data linking marital conflict to immune dysregulation, another promising avenue is interventions targeting marital distress. Based on emerging data, interventions to reduce interaction conflict and improve interpersonal support and communication may improve wound healing and aid in surgical recovery (Kiecolt-Glaser et al., 1998).
IV. CONCLUSIONS AND FUTURE DIRECTIONS The research reviewed in this chapter, predominately based on work from the past 20 years, provides powerful evidence that social relationships are associated with immune function. In work focused on the existence and status of close relationships, a small social network, loneliness, divorce, and bereavement are associated with adverse alterations in immune function and related health (e.g., Gerra et al., 2003; Kiecolt-Glaser et al., 1984b; Kiecolt-Glaser et al., 1987; Pressman et al., 2005; Ward and Leigh, 1993). Similarly, considerable work suggests that problematic social relationships can function as a source of stress and be immune dysregulating (e.g., Glaser et al., 2000; Kiecolt-Glaser et al., 1988; Malarkey et al., 1994). In contrast, positive aspects of social support are associated with more adaptive immune function (e.g., Cohen et al., 1992; Uchino et al., 1996), often apparently by buffering the effects of stress. Several lines of work suggest that such changes have a corresponding impact on health. For example, wound healing is affected by both marital strain and the stress of care giving (Kiecolt-Glaser et al., 1995; Kiecolt-Glaser et al., in press). Research on vaccine responses and infectious illness risk also suggest clinical relevance (Kiecolt-Glaser et al., 2002). Moreover, although the effects of social support interventions have been mixed, some studies have shown clinically meaningful improvements (e.g., Goodkin et al., 1998). Although longitudinal data are available with chroni-
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cally ill populations, additional work is needed to link relationship-driven immune changes to longitudinal health outcomes in healthy populations. In addition, greater delineation of the psychological mechanisms by which relationships affect immune function is needed. Although beyond the scope of this chapter, cognition, affect, and behavior are interrelated domains that are believed to underlie the association between social ties and health outcomes. For example, the degree to which a person perceives a given stressor as challenging or threatening depends on his/her assessment of the difficulty of the task and his/her ability to meet its demands (Blascovich and Mendes, 2001). These appraisals, which can be affected by the degree to which social support is available, in turn influence affective responses and coping behaviors. In terms of health behavior, the influence of close social ties is typically positive; however, relationships marked by conflict or negative social influence can result in detriments to health behaviors with clear relevance to immune function (Kiecolt-Glaser and Glaser, 1988). In the affective domain, there is substantial evidence that emotional responses, such anxiety, anger, and depression, are associated with immune function. For example, hostility, which clearly affects social interactions, is uniquely associated with C-reactive protein (Graham et al., in press; Suarez, 2004) and IL-6 for certain individuals (Suarez, 2003). Depression is also associated with production of pro-inflammatory cytokines (for a review, see Kiecolt-Glaser and Glaser, 2002) as well as with both enumerative and, more reliably, functional measures of immune function (Herbert and Cohen, 1993). As depression is associated with social integration, perceived adequacy of social support, and relationship conflict, it may be a particularly important psychological mechanism by which close relationships affect immune function. Moreover, clinical depression involves changes not only in affect, but also in behavior and cognition. Clearer delineation of the degree to which cognition, emotional responses, and behavior interact with each other and ultimately mediate the relationship between social ties and immune function is needed. Research often treats emotion and behavior as well as biomedical risk factors and demographics (e.g., gender, ethnicity, socioeconomic status) as “spurious” variables that need to be controlled to determine the independent impact of a particular variable of interest. Such attempts are often successful and valuable. However, these factors clearly play an important role in determining health and immune function. Additional research is needed to examine not only the unique effects of these factors, but their interactive effects as well. To that end, we predict that multi-
variate statistical techniques, particularly structural equation modeling, will be become increasingly valuable in the field of psychoneuroimmunology. Although use of these methods may be impeded by unfamiliarity as well as difficulty in obtaining adequate sample sizes, they are valuable in that they enable the specification of the multiple converging pathways that exist in reality. Other areas of research that deserve further investigation include positive aspects of relationship interactions (Robles and Kiecolt-Glaser, 2003) and the impact of ambivalent social ties (those characterized as both positive and negative). Relatedly, the immune relevance of other measures of partner closeness, such as those assessed with pictorial diagrams and unobtrusive reaction time tests (Aron et al., 1992), has not been studied to our knowledge. Interestingly, the activation of feelings of romantic love toward an intimate partner has recently been associated with brain activity in specific regions as determined by fMRI (Aron et al., 2005). As novel methods of assessing social relationships are developed, our ability to conceptualize the association between immune outcomes and social ties will gain even more sophistication. Even after controlling for potentially confounding factors that make work in this area challenging, there is substantial evidence that key aspects of close relationships are associated with immune function. We are not yet at a point where we can claim that immune changes account for a proportion of the morbidity and mortality risk associated with social integration, social support, and relationship discord. However, it should be clear that psychosocial and behavioral interventions targeted at close relationships should be included in the arsenal of methods we consider as we strive to improve physical as well as psychological well-being.
Acknowledgments Work on this chapter was supported by grants T32AI55411, AG16321, DE13749, M01-RR-0034, and CA16058 from the National Institutes of Health.
References Appelberg, K., Romanov, K., Heikkila, K., Honkasaol, M. L., and Koskenvuo, M. (1996). Interpersonal conflict as a predictor of work disability: a follow-up study of 15,348 Finnish employees. J. Psychosom. Res., 40, 157–167. Aron, A., Aron, E. N., and Smollan, D. (1992). Inclusion of other in the self scale and the structure of interpersonal closeness. J. Pers. Soc. Psychol., 63, 596–612. Aron, A., Fisher, H., Mashek, D. J., Strong, G., Haifang, L., and Brown, L. L. (2005). Reward, motivation, and emotion systems associated with early-state intense romantic love. J. Neurophysiol., 94, 327–337.
794
IV. Stress and Immunity
Baron, R. S., Cutrona, C. E., Hicklin, D., Russell, D. W., and Lubaroff, D. M. (1990). Social support and immune function among spouses of cancer patients. J. Pers. Soc. Psychol., 59, 344–352. Bartrop, R., Luckhurst, E., Lazarus, L., Kiloh, L. G., and Penny, R. (1977). Depressed lymphocyte function after bereavement. Lancet., 1, 374–377. Berkman, L. F., and Glass, T. (2000). Social integration, social networks, social support, and health. In L. F. Berkman and I. Kawachi (Eds.), Social epidemiology (pp. 137–173). New York: Oxford Press. Berkman, L. F., and Syme, L. (1979). Social networks, host resistance, and mortality: a nine-year follow-up study of Alameda county residents. Am. J. Epidemiol., 109, 186–203. Biondi, M. (2001). Effects of stress on immune functions: an overview. In R. Ader, D. L. Felten, and N. Cohen (Eds.), Psychoneuroimmunology (pp. 189–226). San Diego: Academic Press. Bittman, M., and Bittman, M. E., Paula; Sayer, Liana; Folbre, Nancy; Matheson, George (2003). When does gender trump money? Bargaining and time in household work. American Journal of Sociology, 109, 186–214. Blascovich, J., and Mendes, W. B. (2001). Challenge and threat appraisals: the role of affective cues. In J. P. Forgas (Ed.), Feeling and thinking: the role of affect in social cognition (pp. 59–82). Cambridge: Cambridge University Press. Bodnar, J., and Kiecolt-Glaser, J. K. (1994). Caregiver depression after bereavement: chronic stress isn’t over when it’s over. Psychol. Aging, 9, 372–380. Brody, E. (1981). “Women in the middle” and family help to older people. Gerontologist, 21, 471–480. Brown, S. L., Nesse, R. M., Vinokur, A. D., and Smith, D. M. (2003). Providing social support may be more beneficial than receiving it: results from a prospective study of mortality. Psychol. Sci., 14, 320–327. Burman, B., and Margolin, G. (1992). Analysis of the association between marital relationships and health problems: an interactional perspective. Psychol. Bull., 112, 39–63. Burnett, R. (1987). Reflections in personal relationships. In R. Burnett, P. McGhee, and D. Clarke (Eds.), Accounting for relationships: explanation, representation, consciousness (pp. 102–110). New York: Methuen. Cacioppo, J. T., Hawkley, L. C., and Berntson, G. G. (2003). The anatomy of loneliness. Curr. Dir. Psychol. Sci., 12, 71–74. Carlson, L. E., and Bultz, B. D. (2004). Efficacy and medical cost offset of psychosocial interventions in cancer care: making the case for economic analyses. Psychooncology, 13, 837–849. Carnalley, K. B., Wortman, C. B., and Kessler, R. C. (1999). The impact of widowhood on depression: findings from a prospective study. Psychol. Med., 29, 1111–1123. Coe, C. L. (1993). Psychosocial factors and immunity in nonhuman primates: a review. Psychosom. Med., 55, 298–308. Cohen, S. (1988). Psychosocial models of the role of social support in the etiology of physical disease. Health Psychol., 7, 269–297. Cohen, S. (2004). Social relationships and health. Am. Psychol., 59, 676–684. Cohen, S., Doyle, W. J., Skoner, D. P., Rabin, B. S., and Gwaltney, J. M. (1997). Social ties and susceptibility to the common cold. JAMA, 277, 1940–1944. Cohen, S., Doyle, W. J., Turner, R. B., Alper, C. M., and Skoner, D. P. (2003). Sociability and susceptibility to the common cold. Psychological Science, 14, 389–395. Cohen, S., and Hoberman, H. M. (1983). Positive events and social supports as buffers of life change stress. J. Appl. Soc. Psychol., 13, 99–125.
Cohen, S., Kaplan, J. R., Cunnick, J. E., Manuck, S. B., and Rabin, B. S. (1992). Chronic social stress, affiliation, and cellular immune response in nonhuman primates. Psychological Science, 3, 301–304. Cohen, S., Mermelstein, R., Camrack, T., and Hoberman, H. (1985). Measuring the functional components of social support. In I. G. Sarason and B. R. Sarason (Eds.), Social Support: theory, research, and applications (pp. 73–94). The Hague, Netherlands: Martinus Nijhoff Publishers. Cohen, S., and Wills, T. A. (1985). Stress, social support, and the buffering hypothesis. Psychol. Bull, 98, 310–357. Cole, S. W., and Kemeny, M. E. (2001). Psychosocial influences on the progression of HIV infection. In R. Ader, D. L. Felten, and N. Cohen (Eds.), Psychoneuroimmunology (pp. 583–612). San Diego: Academic Press. Cook, K. S., and Rice, E. (2003). Social exchange theory. In J. Delamater (Ed.), Handbook of social psychology (pp. 53–76). New York: Kluwer Academic/Plenum Publishers. Coyne, J. C., and Bolger, N. (1990). Doing without social support as an explanatory concept. J. Soc. Clin. Psychol., 9, 148–158. Cross, S. E., and Madson, L. (1997). Models of the self: self-construals and gender. Psychol. Bull., 122, 5–37. Dohrenwend, B. S., Krasnoff, L., Askenasy, A. R., and Dohrenwend, B. P. (1978). Exemplification of a method for scaling life events: The PERI Life Events scale. J. Health Soc. Behav., 19, 205–229. Dunkel-Schetter, C., and Bennett, T. L. (1990). Differentiating the cognitive and behavioral aspects of social support. In B. R. Sarason, I. G. Sarason, and G. R. Pierce (Eds.), Social support: an interactional view (pp. 267–296). Oxford: John Wiley & Sons. Ell, K. (1996). Social networks, social support and coping with serious illness: the family connection. Social Science Medicine, 42, 173–183. Ell, K., Nishimoto, R., Mediansky, L., Mantell, J., and Hamovitch, M. (1992). Social relations, social support and survival among patients with cancer. J. Psychosom. Res., 36, 531–541. Ellison, C., and George, L. (1994). Religious involvement, social ties, and social support in a southeastern community. Journal for the Scientific Study of Religion, 33, 46–61. Epel, E. S., Blackburn, E. H., Lin, J., Dhabhar, F. S., Adler, N. E., Morrow, J. D., and Cawthon, R. M. (2004). Accelerated telomere shortening in response to life stress. Proc. Natl. Acad. Sci. USA, 101, 17312–17315. Esterling, B. A., Antoni, M., Kumar, M., and Schneiderman, N. (1990). Emotional repression, stress disclosure responses, and EpsteinBarr viral capsid antigen titers. Psychosom. Med., 52, 397–410. Esterling, B. A., Antoni, M. H., Fletcher, M. A., Margulies, S., and Schneiderman, N. (1994a). Emotional disclosure through writing or speaking modulates latent Epstein-Barr virus antibody titers. J. Consult. Clin. Psychol., 62, 130–140. Esterling, B. A., Kiecolt-Glaser, J. K., Bodnar, J., and Glaser, R. (1994b). Chronic stress, social support, and persistent alterations in the natural killer cell response to cytokines in older adults. Health Psychol., 13, 291–299. Esterling, B. A., Kiecolt-Glaser, J. K., and Glaser, R. (1996). Psychosocial modulation of cytokine-induced natural killer cell activity in older adults. Psychosom. Med., 58, 264–272. Ewart, C. K., Taylor, C. B., Kraemer, H. C., and Agras, W. S. (1991). High blood pressure and marital discord: not being nasty matters more than being nice. Health Psychol., 10, 155–163. Finch, J. F., Okun, M. A., Barrera, M., Zautra, A. J., and Reich, J. W. (1989). Positive and negative social ties among older adults: Measurement models and the prediction of psychological distress and well-being. Am. J. Community Psychol., 17, 585– 605.
36. Close Relationships and Immunity Frasure-Smith, N., Lesperance, F., Prince, R., Verrier, P., Garber, R. A., Juneau, M., Wolfson, C., and Bourassa, M. G. (1997). Randomised trial of home-based psychological nursing intervention for patients recovering from myocardial infarction. Lancet, 350, 473–479. Gerra, G., Monti, D., Panerai, A. E., Sacerdote, P., Anderlini, R., Avanzini, P., Zaimovic, A., Brambilla, F., and Franceschi, C. (2003). Long-term immune-endocrine effects of bereavement: relationships with anxiety levels and mood. Psychiatry Res., 121, 145–158. Glaser, R., and Kiecolt-Glaser, J. K. (2005). Stress-induced immune dysfunction: implications for health. Nature Reviews Immunology, 5, 243–251. Glaser, R., Kiecolt-Glaser, J. K., Bonneau, R. H., Malarkey, W., Kennedy, S., and Hughes, J. (1992). Stress-induced modulation of the immune response to recombinant hepatitis B vaccine. Psychosom. Med., 54, 22–29. Glaser, R., Sheridan, J. F., Malarkey, W. B., MacCallum, R. C., and Kiecolt-Glaser, J. K. (2000). Chronic stress modulates the immune response to a pneumococcal pneumonia vaccine. Psychosom. Med., 62, 804–807. Glenn, N. D., and Weaver, C. N. (1981). The contribution of marital happiness to global happiness. J. Marriage Fam., 43, 161–168. Gluhoski, V. L., Fishman, B., and Perry, S. W. (1997). The impact of multiple bereavement in a gay male sample. AIDS Education & Prevention, 9, 521–531. Goodkin, K., Feaster, D. J., Asthana, D., Blaney, N. T., Kumar, M., Baldewicz, T., Tuttle, R. S., Maher, K. J., Baum, M. K., Shapshak, P., and Fletcher, M. A. (1998). A bereavement support group intervention is longitudinally associated with salutary effects on the CD4 cell count and number of physician visits. Clin. Diagn. Lab. Immunol., 5, 382–391. Goodkin, K., Feaster, D. J., Tuttle, R., Blaney, N. T., Kumar, M., Baum, M. K., Shapshak, P., and Fletcher, M. A. (1996). Bereavement is associated with time-dependent decrements in cellular immune function in asymptomatic human immunodeficiency virus type 1-seropositive homosexual men. Clin. Diagn. Lab. Immunol., 3, 109–118. Goodwin, P. J. (2004). Support groups in breast cancer: When a negative result is positive. J. Clin. Oncol., 22, 4244–4246. Goodwin, S. (1997). The marital relationship and health in women with chronic fatigue and immune dysfunction syndrome: Views of wives and husbands. Nurs. Res., 46, 138–146. Gordon, H. S., and Rosenthal, G. E. (1995). Impact of marital status on outcomes in hospitalized patients. Arch. Intern. Med., 155, 2465–2471. Graham, J. E., Lobel, M., Glass, P., and Lokshina, I. (2006). Effects of written constructive anger expression in chronic pain patients: a randomized trial. Manuscript submitted for publication. Graham, J. E., Robles, T. F., Kiecolt-Glaser, J. K., Malarkey, W. B., Bissell, M. G., and Glaser, R. (In press). Hostility and pain are related to serum CRP levels in older adults. Brain Behav. Immun. Greenblatt, M. Y., Becerra, R. M., and Serafetinides, E. A. (1982). Social networks and mental health: an overview. American Journal of Psychiatry, 139, 977–984. Hagedoorn, M., Kuijer, R. G., Buunk, B. P., DeJong, G. M., Wobbes, T., and Sanderman, R. (2000). Marital satisfaction in patients with cancer: does support from intimate partners benefit those who need it most? Health Psychol., 19, 274–282. Hall, M., and Irwin, M. (2001). Physiological indices of functioning in bereavement. In M. S. Stroebe, R. O. Hansson, W. Stroebe et al. (Eds.), Handbook of bereavement research (pp. 473–492). Washington, DC: American Psychological Association.
795
Hamrick, N., Cohen, S., and Rodriguez, M. (2002). Being popular can be healthy or unhealthy: stress, social network diversity, and incidence of upper respiratory infection. Health Psychol., 21, 294–298. Harrison, J., Maguire, P., and Pitceathly, C. (1995). Confiding in crisis: gender differences in pattern of confiding among cancer patients. Social Science & Medicine, 41, 1255–1260. Heffner, K. L., Kiecolt-Glaser, J. K., Loving, T. J., Glaser, R., and Malarkey, W. B. (2004). Spousal support satisfaction as a modifier of physiological responses to marital conflict in younger and older couples. J. Behav. Med., 27, 233–254. Helgeson, V. S., Cohen, S., Schulz, R., and Yasko, J. (2000). Group support interventions for women with breast cancer: who benefits from what? Health Psychol., 19, 107–114. Helsing, K., Szklo, M., and Comstock, G. (1981). Factors associated with mortality after widowhood. American Journal of Public Health, 71, 802–809. Herbert, T. B., and Cohen, S. (1993). Depression and immunity: a meta-analytic review. Psychol. Bull., 113, 472–486. Herbst-Damm, K. L., and Kulik, J. A. (2005). Volunteer support, marital status, and survival times of terminally ill patients. Health Psychol., 24, 225–229. Hibbard, J. H., and Pope, C. R. (1993). The quality of social roles as predictors of morbidity and mortality. Soc. Sci. Med., 36, 217–225. Hogan, B. E., Linden, W., and Najarian, B. (2002). Social support interventions: do they work? Clin. Psychol. Rev., 22, 381–440. Holt-Lunstad, J., Uchino, B. N., Smith, T. W., Olson-Cerny, C., and Nealey-Moore, J. B. (2003). Social relationships and ambulatory blood pressure: structural and qualitative predictors of cardiovascular function during everyday social interactions. Health Psychol., 22, 388–397. House, J. S., Landis, K. R., and Umberson, D. (1988). Social relationships and health. Science, 241, 540–545. House, J. S., Robbins, C., and Metzner, H. L. (1982). The association of social relationships and activities with mortality: prospective evidence from the Tecumseh Community Health Study. Am. J. Epidemiol., 116, 123–140. Irwin, M. (2001). Depression and immunity. In R. Ader, D. L. Felten, and N. Cohen (Eds.), Psychoneuroimmunology (3rd ed., pp. 383– 398). San Diego: Academic Press. Irwin, M., Daniels, M., Bloom, E. T., Smith, T. L., and Weiner, H. (1987a). Life events, depressive symptoms, and immune function. Am. J. Psychiatry, 144, 437–441. Irwin, M., Daniels, M., Smith, T. L., Bloom, E., and Weiner, H. (1987b). Impaired natural killer cell activity during bereavement. Brain Behav. Immun., 1, 98–104. Jensen, A. B. (1991). Psychological factors in breast cancer and their possible impact upon prognosis. Cancer Treat Rev., 18, 191–210. Johnson, N. J., Backlund, E., Sorlie, P. D., and Loveless, C. A. (2000). Marital status and mortality: the National Longitudinal Mortality study. Ann. Epidemiol., 10, 224–238. Kamarck, T. W., and Lovallo, W. R. (2003). Cardiovascular reactivity to psychological challenge: conceptual and measurement considerations. Psychosom. Med., 65, 9–21. Kang, D.-H., Coe, C., Karaszweski, J., and McCarthy, D. O. (1998). Relationship of social support to stress responses and immune function in healthy and asthmatic adolescents. Res. Nurs. Health, 21, 117–128. Kaplan, G. A., Salomen, J. T., Cohen, R. D., Brand, R. J., Syme, S. L., and Puska, P. (1988). Social connections and mortality from all causes and from cardiovascular disease: prospective evidence from eastern Finland. Am. J. Epidemiol., 128, 370–380.
796
IV. Stress and Immunity
Kemeny, M., and Dean, L. (1995). Effects of AIDS-related bereavement of HIV progression among New York City gay men. AIDS Education & Prevention, 7, 36–47. Kemeny, M., Weiner, H., Taylor, S. E., Schneider, S., Visscher, B., and Fahey, J. (2004). Repeated bereavement, depressed mood, and immune parameters in HIV seropositive and seronegative gay men. Health Psychol., 13, 14–24. Kemeny, M. E., Weiner, H., Duran, R., Taylor, S. E., Visscher, B., and Fahey, J. L. (1995). Immune system changes after the death of a partner in HIV-positive gay men. Psychosom. Med., 57, 547–554. Kiecolt-Glaser, J. K. (1999). Norman Cousins Memorial Lecture 1998. Stress, personal relationships, and immune function: health implications. Brain Behav. Immun., 13, 61–72. Kiecolt-Glaser, J. K., Dura, J. R., Speicher, C. E., Trask, O. J., and Glaser, R. (1991). Spousal caregivers of dementia victims: longitudinal changes in immunity and health. Psychosom. Med., 53, 345–362. Kiecolt-Glaser, J. K., Fisher, L. D., Ogrocki, P., Stout, J. C., Speicher, C. E., and Glaser, R. (1987). Marital quality, marital disruption, and immune function. Psychosom. Med., 49, 31–34. Kiecolt-Glaser, J. K., Garner, W., Speicher, C., Penn, G. M., Holliday, J., and Glaser, R. (1984a). Psychosocial modifiers of immunocompetence in medical students. Psychosom. Med., 46, 7–14. Kiecolt-Glaser, J. K., and Glaser, R. (1988). Methodological issues in behavioral immunology research with humans. Brain Behav. Immun., 2, 67–78. Kiecolt-Glaser, J. K., and Glaser, R. (2002). Depression and immune function: central pathways to morbidity and mortality. J. Psychosom. Res., 53, 873–876. Kiecolt-Glaser, J. K., Glaser, R., Cacioppo, J. T., MacCallum, R. C., Snydersmith, M., Kim, C., and Malarkey, W. B. (1997). Marital conflict in older adults: endocrinological and immunological correlates. Psychosom. Med., 59, 339–349. Kiecolt-Glaser, J. K., Kennedy, S., Malkoff, S., Fisher, L., Speicher, C. E., and Glaser, R. (1988). Marital discord and immunity in males. Psychosom. Med., 50, 213–229. Kiecolt-Glaser, J. K., Loving, T. J., Stowell, J. R., Malarkey, W. B., Lemeshow, S., Dickinson, S. L., and Glaser, R. (2005). Hostile marital interactions, proinflammatory cytokine production, ad wound healing. Arch. Gen. Psychiatry, 62, 1377–1384. Kiecolt-Glaser, J. K., Malarkey, W. B., Chee, M., Newton, T., Cacioppo, J. T., Mao, H., and Glaser, R. (1993). Negative behavior during marital conflict is associated with immunological downregulation. Psychosom. Med., 55, 395–409. Kiecolt-Glaser, J. K., Marucha, P. T., Malarkey, W. B., Mercado, A. M., and Glaser, R. (1995). Slowing of wound healing by psychological stress. Lancet, 346, 1194–1196. Kiecolt-Glaser, J. K., McGuire, L., Robles, T. F., and Glaser, R. (2002). Psychoneuroimmunolgy: psychological influences on immune function and health. J. Consult. Clin. Psychol., 70, 537–547. Kiecolt-Glaser, J. K., and Newton, T. (2001). Marriage and health: his and hers. Psychol. Bull., 127, 472–503. Kiecolt-Glaser, J. K., Newton, T., Cacioppo, J. T., MacCallum, R. C., Glaser, R., and Malarkey, W. B. (1996). Marital conflict and endocrine function: are men really more physiologically affected than women? J. Consult. Clin. Psychol., 64, 324–332. Kiecolt-Glaser, J. K., Page, G. G., Marucha, P. T., MacCallum, R. C., and Glaser, R. (1998). Psychological influences on surgical recovery: perspectives from psychoneuroimmunology. Am. Psychol., 53, 1209–1218. Kiecolt-Glaser, J. K., Preacher, K. J., MacCallum, R. C., Atkinson, C., Malarkey, W. B., and Glaser, R. (2003). Chronic stress and agerelated increases in the proinflammatory cytokine IL-6. Proc. Natl. Acad. Sci. USA, 100, 9090–9095.
Kiecolt-Glaser, J. K., Ricker, D., George, J., Messick, G., Speicher, C. E., Garner, W., and Glaser, R. (1984b). Urinary cortisol levels, cellular immunocompetency, and loneliness in psychiatric inpatients. Psychosom. Med., 46, 15–24. Koenig, H. G., Cohen, H. J., George, L. K., Hays, J. C., Larson, D. B., and Blazer, D. G. (1997). Attendance at religious services, interleukin-6, and other biological parameters of immune function in older adults. Int. J. Psychiatry Med., 27, 233–250. Koopman, C., Hermanson, K., Diamond, S., Angell, K., and Spiegel, D. (1998). Social support, life stress, pain and emotional adjustment to advanced breast cancer. Psychooncology, 7, 101–111. Krause, N. (1997). Received support, anticipated support, social class, and mortality. Res. Aging, 19, 387–422. Krause, N., and Borawski-Clark, E. A. (1995). Social class differences in social support among older adults. Gerontologist, 35, 498–508. Lazarus, R. S., and Folkman, S. (1984). Stress, appraisal, and coping. New York: Springer. Lee, G. R., and Ishii-Kuntz, M. (1987). Social interaction, loneliness, and emotional well-being among the elderly. Res. Aging, 9, 459–482. Leserman, J., Jackson, E. D., Petitto, J. M., Golden, R. N., Silva, S. G., Perkins, D. O., Cai, J., Folds, J. D., and Evans, D. L. (1999). Progression to AIDS: the effects of stress, depressive symptoms, and social support. Psychosom. Med., 61, 397–406. Levenstein, S., Ackerman, S., Kiecolt-Glaser, J. K., and Dubois, A. (1999). Stress and peptic ulcer disease. JAMA, 281, 10–11. Levy, S. M., Haynes, L. T., Herberman, R. B., Lee, J., McFeeley, S., and Kirkwood, J. (1992). Mastectomy versus breast conservation surgery: mental health effects at long-term follow-up. Health Psychol., 11, 347–348. Levy, S. M., Herberman, R. B., Lee, J., Whiteside, T., Kirkwood, J., and McFeeley, S. (1990a). Estrogen receptor concentration and social factors as predictors of natural killer cell activity in earlystage breast cancer patients. Nat. Immun. Cell Growth Regul., 9, 313–324. Levy, S. M., Herberman, R. B., Whiteside, T., Sanzo, K., Lee, J., and Kirkwood, J. (1990b). Perceived social support and tumor estrogen/progesterone receptor status as predictors of natural killer cell activity in breast cancer patients. Psychosom. Med., 52, 73–85. Lichtman, R. R., Taylor, S. E., and Wood, J. V. (1988). Social support and marital adjustment after breast cancer. J. Psychosoc. Oncol., 5, 47–74. Lousberg, R., Schmidt, A. J., and Groenman, N. H. (1992). The relationship between spouse solicitousness and pain behavior: searching for more experimental evidence. Pain, 51, 75–79. Lutgendorf, S., Johnsen, E. L., Cooper, B., Andersen, B., Sorosky, J. I., Buller, R. E., and Sood, A. K. (2002). Vascular endothelial growth factor and social support in patients with ovarian carcinoma. Cancer, 95, 808–815. Lutgendorf, S., Russell, D., Ullrich, P., Harris, T. B., and Wallace, R. (2004). Religious participation, interleukin-6, and mortality in older adults. Health Psychol., 23, 465–475. Lutgendorf, S. K., Anderson, B., Sorosky, J. I., Buller, R. E., and Lubaroff, D. M. (2000). Interleukin-6 and use of social support in gynecologic cancer patients. Int. J. Behav. Med., 7, 127–142. Major, B., Zubek, J. M., Cooper, M. L., Cozzarelli, C., and Richards, C. (1997). Mixed messages: implications of social conflict and social support within close relationships for adjustment to a stressful life event. J. Pers. Soc. Psychol., 72, 1349–1363. Malarkey, W., Kiecolt-Glaser, J. K., Pearl, D., and Glaser, R. (1994). Hostile behavior during marital conflict alters pituitary and adrenal hormones. Psychosom. Med., 56, 41–51.
36. Close Relationships and Immunity Mancini, J. A., and Blieszner, R. (1989). Aging parents and adult children: research themes in intergenerational relationships. J. Marriage Fam., 51, 275–290. Matire, L. M., Stephens, M. A. P., Druley, J. A., and Wojno, W. C. (2002). Negative reactions to received spousal care: predictors and consequences of miscarried support. Health Psychol., 21, 167–176. Mayne, T. J., O’Leary, A., McCrady, B., Contrada, R., and Labouvie, E. (1997). The differential effects of acute marital distress on emotional, physiological and immune functions in maritally distressed men and women. Psychol. Health, 12, 277–288. McCullough, M. E., Hoyt, W. T., Larson, D. B., Koenig, H. G., and Thoresen, C. (2000). Religious involvement and mortality: a meta-analytic review. Health Psychol., 19, 211–222. Medalie, J. H., Stange, K. C., Zyanski, S. J., and Goldbourt, U. (1992). The importance of biopsychosocial factors in the development of duodenal ulcer in a cohort of middle-aged men. Am. J. Epidemiol., 136, 1280–1287. Miller, G., Kemeny, M., Taylor, S., Cole, S., and Visscher, B. (1997). Social relationships and immune processes in HIV seropositive gay and bisexual men. Ann. Behav. Med., 19, 139–151. Miller, G. E., Dopp, J. M., Myers, H. F., Felten, S. Y., and Fahey, J. L. (1999). Psychosocial predictors of natural killer cell mobilization during marital conflict. Health Psychol., 18, 262–271. Miyazaki, T., Ishikawa, T., Hirofumi, I., Akiko, M., Wenner, M., Fukunishi, I., and Kawamura, N. (2003). Relationship between perceived social support and immune function. Stress and Health, 19, 3–7. Moen, P., Dempster-McClain, D., and Williams, Jr., R. M. (1992). Social integration and longevity: An event history analysis of women’s roles and resilience. Am. Sociol. Rev., 54, 635–647. Newton, T. L., Kiecolt-Glaser, J. K., Glaser, R., and Malarkey, W. B. (1995). Conflict and withdrawal during marital interaction: The roles of hostility and defensiveness. Personal Soc. Psychol. Bulletin, 21, 512–524. Orth-Gomer, K. (2000). Stress and social support in relation to cardiovascular health. In P. M. McCabe, N. Schneiderman, T. Field et al. (Eds.), Stress, coping and cardiovascular disease (pp. 229–240). Mahwah, NJ: Lawrence Erlbaum Associates, Inc. Pennebaker, J. W. (1997). Writing about emotional experience as a therapeutic process. Psychol. Sci., 8, 162–166. Pennebaker, J. W., and O’Heeron, R. C. (1984). Confiding in others and illness rate among spouses of suicide and accidental death victims. J. Abnorm. Psychol., 93, 473–476. Pennebaker, J. W., and Seagal, J. D. (1999). Forming a story: The health benefits of narrative. J. Clin. Psychol., 55, 1243–1254. Pennebaker, J. W., Zech, E., and Rime, B. (2001). Disclosing and sharing emotion: psychological, social, and health consequences. In M. S. Stroebe, R. O. Hansson, et al. (Eds.), Handbook of bereavement research: consequences, coping, and care (pp. 517–543). Washington, DC: American Psychological Association. Persson, L., Gullberg, B., Hanson, B. S., Moestrup, T., and Ostergren, P. O. (1994a). HIV infection: social network, social support, and CD4 lymphocyte values in infected homosexual men in Malmo, Sweden. J. Epidemiol. Community Health, 48, 580–585. Persson, L., Gullberg, B., Hanson, B. S., Moestrup, T., and Ostergren, P. O. (1994b). Influences of social network and social support on the development of the CD4-lymphocyte level—a prospective population study of HIV-infected homo- and bi-sexual men in Malmo, Sweden. Second International Conference on Psychosocial Aspects of AIDS, Brighton, UK. Petrie, K. J., Booth, R. J., Pennebaker, J. W., Davison, K. P., and Thomas, M. G. (1995). Disclosure of trauma and immune response to a hepatitis B vaccination program. J. Consult. Clin. Psychol., 63, 787–792.
797
Prager, K. J., and Roberts, L. J. (2004). Deep intimate connection: self and intimacy in couple relationships. In D. J. Mashek and A. Aron (Eds.), Handbook of closeness and intimacy (pp. 43–60). Mahwah, NJ: Lawrence Erlbaum Associates, Inc. Pressman, S., Cohen, S., Miller, G., Barkin, A., Rabin, B. S., and Treanor, J. (2005). Loneliness, social network size, and immune response to influenza vaccination in college freshmen. Health Psychol., 24, 297–306. Reis, H. T., and Franks, P. (1994). The role of intimacy and social support in health outcomes: Two processes or one? Personal Rel., 1, 185–197. Robles, T. F., and Kiecolt-Glaser, J. K. (2003). The physiology of marriage: pathways to health. Physiology and Behavior, 79, 409–416. Rook, K. S. (1984). The negative side of social interaction: Impact on psychological well-being. J. Pers. Soc. Psychol., 46, 1097– 1108. Rook, K. S. (1990). Parallels in the study of social support and social strain. J. Soc. Clin. Psychol., 9, 118–132. Rook, K. S. (1992). Detrimental aspects of social relationships: taking stock of an emerging literature. In H. O. F. Veiel and U. Baumann (Eds.), The meaning and measurement of social support (pp. 157–169). New York: Hemisphere Publishing. Ross, C. E., Mirowsky, J., and Goldsteen, K. (1990). The impact of the family on health: the decade in review. J. Marriage Fam., 52, 1059–1078. Ross, M., and Holmberg, D. (1990). Recounting the past: gender differences in the recall of events in the history of a close relationship. In J. M. Olson and M. P. Zanna (Eds.), Self-influence processes (pp. 135–152). Hillsdale, NJ: Erlbaum. Ruehlman, L. S., and Karoly, P. (1991). With a little flak from my friends: development and preliminary validation of the Test of Negative Social Exchange (TENSE). Psychol. Assess., 3, 97–104. Schleifer, S., Keller, S., Camerino, M., Thorton, J. C., and Stein, M. (1983). Suppression of lymphocyte stimulation following bereavement. JAMA, 250, 374–377. Schulz, R., and Rau, M. T. (1985). Social support through the life course. In S. Cohen and S. L. Syme (Eds.), Social support and health (pp. 129–149). San Diego: Academic Press. Scott, J. L., Halford, K. W., and Ward, B. G. (2004). United we stand? The effects of a couple-coping intervention on adjustment to early stage breast or gynecological cancer. J. Consult. Clin. Psychol., 72, 1122–1135. Sikkema, K. J., Hansen, N. B., Meade, C. S., Kochman, A., and Lee, R. S. (2005). Improvements in health-related quality of life following a support group intervention with AIDS-bereavement among HIV-infected men and women. Qual. Life Res., 14, 991–1005. Simmons, T., and O’Conell, M. (2003). Married-couple and unmarriedpartner households: 2000. Washington, D.C.: U.S. Census Bureau. Smyth, J. M., Stone, A. A., Hurewitz, A., and Kaell, A. (1999). Effects of writing about stressful experiences on symptom reduction in patients with asthma or rheumatoid arthritis: A randomized trial. JAMA, 281, 1304–1309. Solano, L., Costa, M., Salvati, S., Coda, R., Aiuti, F., Mezzaroma, I., and Bertini, M. (1993). Psychosocial factors and clinical evolution in HIV-1 infection: a longitudinal study. J. Psychosom. Res., 37, 39–51. Sternberg, E. M., Chrousos, G. P., Wilder, R. L., and Gold, P. W. (1992). The stress response and the regulation of inflammatory disease. Ann. Intern. Med., 117, 854–866. Strawbridge, W. J., Cohen, R. D., Shema, S. J., and Kaplan, G. A. (1997). Frequent attendance at religious services and mortality over 28 years. Am. J. Public Health, 87, 957–961.
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IV. Stress and Immunity
Suarez, E. C. (2003). Plasma interleukin-6 is associated with psychological coronary risk factors: moderation by use of multivitamin supplements. Brain Behav. Immun., 17, 296–303. Suarez, E. C. (2004). C-reactive protein is associated with psychological risk factors of cardiovascular diseases in apparently healthy adults. Psychosom. Med., 66, 684–691. Suls, J., and Wan, C. K. (1993). The relationship between trait hostility and cardiovascular reactivity: a quantitative review and analysis. Psychophys., 30, 615–626. Summers, J., Zisook, S., Sciolla, A. D., Patterson, T., and Atkinson, J. H. (2004). Gender, AIDS, and bereavement: a comparison of women and men living with HIV. Death Stud., 28, 225–241. Thomas, P. D., Goodwin, J. M., and Goodwin, J. S. (1985). Effect of social support on stress-related changes in cholesterol level, uric acid level, and immune function in an elderly sample. Am. J. Psychiatry, 142, 735–737. Turk, D. C., Kerns, R. D., and Rosenberg, R. (1992). Effects of marital interaction on chronic pain and disability: examining the down side of social support. Rehab. Psychol., 37, 259–274. Turner-Cobb, J. M., Koopman, C., Rabinowitz, J., Terr, A. I., Sephton, S. E., and Spiegel, D. (2004). The interaction of social network size and stressful life events predict delayed-type hypersensitivity among women with metastatic breast cancer. Int. J. Psychophysiol., 54, 241–249. Turvey, C., Carney, C., Arndt, S., Wallace, R. B., and Herzog, R. (1999). Conjugal loss and syndromal depression in a sample of elders aged 70 years or older. Am. J. Psychiatry, 156, 1596–1601. Uchino, B. N., Cacioppo, J. T., and Kiecolt-Glaser, J. K. (1996). The relationship between social support and physiological processes: a review with emphasis on underlying mechanisms. Psychol. Bull., 119, 488–531. Uchino, B. N., Holt-Lunstad, J., Uno, D., and Flinders, J. B. (2001). Heterogeneity in the social networks of young and older adults: prediction of mental health and cardiovascular reactivity during acute stress. J. Behav. Med., 24, 361–382. Ullrich, P. M., Lutgendorf, S. K., and Stapleton, J. T. (2003). Concealment of homosexual identity, social support and CD4 cell count among HIV-seropositive gay men. J. Psychosom. Res., 54, 205– 212. Umberson, D. (1992). Gender, marital status and the social control of health behavior. Soc. Sci. Med., 24, 907–917. Vedhara, K., Cox, N. K. M., Wilcock, G. K., Perks, P., Hunt, M., Anderson, S., Lightman, S. L., and Shanks, N. M. (1999). Chronic
stress in elderly carers of dementia patients and antibody response to influenza vaccination. Lancet, 353, 627–631. Verbrugge, L. M. (1979). Marital status and health. J. Marriage Fam., 41, 267–285. Waltz, M., Kriegel, W., and Bosch, P. V. (1998). The social environment and health in rheumatoid arthritis: marital quality predicts individual variability in pain severity. Arthritis Care Res., 11, 356–374. Ward, M. M., and Leigh, J. P. (1993). Marital status and the progression of functional disability in patients with rheumatoid arthritis. Arthritis Rheum., 36, 581–588. Waxler-Morrison, N., Hislop, T. G., Mears, B., and Kan, L. (1992). Effects of social relationships on survival for women with breast cancer: a prospective study. Soc. Sci. & Med., 33, 177–183. Weihs, K., Enright, T., Howe, G., and Simmens, S. (1999). Marital satisfaction and emotional adjustment after breast cancer. J. Psychosoc. Oncol., 17, 33–49. Weiss, R. S. (2001). Grief, bonds, and relationships. In M. S. Stroebe, R. O. Hansson, and W. Stroebe et al. (Eds.), Handbook of bereavement research: consequences, coping, and care (pp. 47–62). Washington, DC: American Psychological Association. Williamson, D., Robinson, M. E., and Melamed, B. (1997). Pain behavior, spouse responsiveness, and marital satisfaction in patients with rheumatoid arthritis. Behav. Modific., 21, 97–118. Wills, T. A., and Shinar, O. (2000). Measuring perceived and received social support. In S. Cohen, L. G. Underwood, and B. H. Gottlieb (Eds.), Social support measurement and intervention: a guide for health and social scientists (pp. 86–135). Oxford: Oxford Press. Wortman, C. B., Wolff, K., and Bonanno, G. A. (2004). Loss of an intimate partner through death. In D. J. Mashek and A. P. Aron (Eds.), Handbook of closeness and intimacy (pp. 305–320). Mahwah, NJ: Lawrence Erlbaum Associates, Inc. Wu, Z., Penning, M. J., Pollard, M. S., and Hart, R. (2003). In sickness and in health: does cohabitation count. J. Fam. Issues, 24, 811–838. Zautra, A. J., Burleson, M. H., Matt, K. S., Roth, S., and Burrows, L. (1994). Interpersonal stress, depression, and disease activity in rheumatoid arthritis and osteoarthritis patients. Health Psychol., 13, 139–148. Zautra, A. J., Hoffman, J. M., Matt, K. S., Yocum, D., Potter, P. T., Castro, W. L., and Roth, S. (1998). An examination of individual differences in the relationship between interpersonal stress and disease activity among women with rheumatoid arthritis. Arthritis Care Res., 11, 271–279.
C H A P T E R
37 Stress and Allergic Diseases GAILEN D. MARSHALL AND SITESH R. ROY
I. INTRODUCTION 799 II. HISTORICAL PERSPECTIVES OF ALLERGIC DISEASES 801 III. PATHOPHYSIOLOGY OF ALLERGIC DISEASES 802 IV. CLINICAL MANIFESTATIONS OF ALLERGIC DISEASES 805 V. CURRENT THERAPEUTIC APPROACHES TO ALLERGIC DISEASES 806 VI. GENE-ENVIRONMENT INTERACTION IN THE EXPRESSION OF ALLERGIC PHENOTYPE 807 VII. NEURAL CONTROL OF THE AIRWAYS 809 VIII. IMMUNE DYSREGULATION IN ALLERGIC DISEASE 810 IX. EFFECTS OF ACUTE AND CHRONIC STRESS ON TH1/TH2 BALANCE 811 X. EVIDENCE FOR STRESS TRIGGERING EXACERBATION OF ALLERGIC DISEASES 812 XI. POTENTIAL FOR INTERVENTION IN STRESS-RELATED ALLERGIC DISEASES 813 XII. CONCLUDING REMARKS 815 XIII. FUTURE DIRECTIONS FOR RESEARCH IN STRESS AND ALLERGIC DISEASES 816
been appreciated among clinicians for centuries (Solomon, Amkraut et al. 1974; O’Leary 1990; Chrousos and Gold 1992). However, the bi-directional anatomical and physiological connections between the immune, central nervous, and neuroendocrine systems have only recently been discovered and are currently being characterized (Reichlin 1993; Stratakis and Chrousos 1995; Cacioppo, Berntson et al. 1998; Yang and Glaser 2002). Various stressors, including both psychological and physiological, have been demonstrated to influence immune function via various direct and indirect mechanisms. In addition to anecdotal evidence, there are published reports that demonstrate an effect of psychological and physiological stress on immune-based diseases such as allergic and infectious diseases. This chapter will discuss the effect of psychological stress on immune function, the relationships between allergic diseases and stress including the impact of psychological stress on immune-based pathology, and future directions of research to determine the mechanisms and clinical importance of this exciting area of translational research. The prevalence of allergy and asthma continues to escalate in Western society. As many as 1 in 3 individuals suffer from some form of allergic disorder (Peroni, Piacentini et al. 2003). The etiology involves genetic susceptibility since the number one risk factor is a strong family history of allergic disease (Klinnert, Nelson et al. 2001; Lin, Wen et al. 2004). Yet, environmental factors clearly play a major role as well, since the prevalence of allergy was 1 in 10 in 1970, and it has
I. INTRODUCTION The immune system is composed of a network of cells producing various humoral factors that function together to maintain a state of homeostasis for the host in the face of persistent attacks from external and altered internal challenges. The effects of emotions on clinical manifestations of immune dysfunction have PSYCHONEUROIMMUNOLOGY, 4E VOLUME II
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Copyright © 2007 by Elsevier, Inc. All rights of reproduction in any form reserved.
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tripled in less than 40 years (Marshall 2004; Nelson 2005). The external environment with air pollution and changes in indoor antigen exposure likely contribute. However, in parallel with the increase in allergy prevalence is a documented increase in many life stressors in various socioeconomic populations (Helmert and Shea 1994; Evans, Der et al. 2000; Lapidus 2001; McDade 2001). Indeed, populations with the highest documented stress levels are also those who show a high rate of allergy and asthma (Chen, Fisher et al. 2003), suggesting a causal relationship between the two. In order to better explore the mechanisms that could account for the biological relationships between the two, an explanation must begin with an understanding of the immune response.
A. Normal Host Immunity In the normal host, presentation of antigen for a specific protective immune response elicits a complex series of events that result in a mixed cellular and humoral protective response, the intensity and nature of which depend upon the specific inciting antigen. Extracellular parasites (i.e., bacteria) incite primarily a humoral response, while intracellular parasites (i.e., virus, fungi, mycobacteria, etc.) elicit a cell-mediated response. The host immune response has a variety of mechanisms to direct the immune response into the humoral versus cellular direction—nature of antigenpresenting cells (Robson, Beacock-Sharp et al. 2003; Koh, Choi et al. 2004), major histocompatibility complex (MHC) restriction (Parkhurst, Riley et al. 2004), and availability of specific T- and B-cell components (O’Garra and Vieira 2004). However, the central control of the cellular versus humoral response to an antigenic challenge appears to be via production of specific cytokine milieu (Lanzavecchia and Sallusto 2000). A central source of these cytokines comes from CD4+ helper T-cell subpopulations, often referred to as Th1 and Th2 cells (Romagnani, Annunziato et al. 2000). Human Th1 cells secrete a specific cytokine profile including interferon-gamma (IFN-γ) and tumor necrosis factor-beta (TNF-β). These cytokines are important helper factors in the generation of cellular immune responses, including antigen-specific cytotoxic T lymphocytes (CTL) and natural killer (NK) cells (Trinchieri, Wysocka et al. 1992; Mustafa and Oftung 1995). Additionally, IFN-γ in particular has an antagonistic activity against Th2 cytokines (Parronchi, De Carli et al. 1992). Interleukin-12 (IL-12), produced primarily by activated macrophages, plays a central role in inducing IFN-γ production. In contrast, Th2 cells secrete IL-4, IL-5, IL-9, IL-10, and IL-13, which are involved in isotype switching of B-cells as well as pro-
liferation and differentiation into antibody-secreting plasma cells (DeKruyff, Rizzo et al. 1993). In particular, IL-4 and IL-13 are involved in the isotype switch from IgM to IgE, the antibody responsible for classical allergic disease (Akbari and Umetsu 2005). IL-4 and IL-10 are also regulatory cytokines, antagonizing the activities of Th1 cytokines (Romagnani 2000). In humans, helper T-cells can have a third cytokine secretory pattern. Th0 cells (Bendelac and Schwartz 1991) are capable of secreting all of the above-mentioned cytokines and are often thought of as precursors. Whether this represents a differentiation pathway for Th cells remains to be determined. Thus, it can be said that the nature, intensity, and duration of a specific immune response depends upon the delicate balance between Th1 and Th2 numbers and/or activities. Since it is now appreciated that many other cell types besides Th cells produce IFN-γ, IL-4, IL-5, IL-9, and IL-10, many scientists now refer to these as type 1 and type 2 cytokines, supporting cellular and humoral immune responses, respectively. More recently, specific regulatory pathways have been described to control the overall immune balance and thus effector responses (O’Garra and Vieira 2004). The best described involve regulatory T-cells that are variably characterized by phenotype as well as cytokine production. T-cells that are CD4+ CD25+ and produce varying amounts of transforming growth factor-β (TGF-β) and/or IL-10 are able to regulate Th1/Th2 activity (Sakaguchi 2004) as well as effector cell function including T-cell proliferation, cytotoxic T-cell killing, and helper T-cell–dependent antibody production (Trzonkowski, Szmit et al. 2004). Indeed, Treg deficiency (either in number or function) has been implicated in a variety of immunopathological states including multiple sclerosis, systemic lupus erythematosus, and various allergic states (Rook, Adams et al. 2004; Ostroukhova and Ray 2005).
B. Altered Host Immunity in Allergy Allergic reactions are clinically referred to as hypersensitivity diseases in that the immune response intended to protect the host actually provokes disease in its mistaken vigor against otherwise innocuous stimuli. Allergy describes a series of immune-based reactions occurring as a result of the induction of allergen-specific IgE that binds to mast cells via highaffinity FcεR1 receptors. Subsequent re-exposure of the individual to the inciting allergen causes a crosslinking of the mast cell-bound IgE with activation and release of mast cell contents such as histamine, leukotrienes, and tryptase. These mediators contribute to the molecular milieu that causes the signs and symptoms of allergic airway disease, typically beginning
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within 1 hour of allergen exposure. Some 6–24 hours later, a second round of symptoms (called late phase reactions) develops from the recruited inflammatory cells that move to the target tissues (nose, lung, skin, gastrointestinal tract, and/or blood vessels), resulting in a renewed and more persistent symptom complex.
C. Psycho-Neuro-Humoral Interactions and Allergic Disease Hypercortisolemia is associated with depression (Gillespie and Nemeroff 2005) Indeed, pharmacological and physiological levels of glucocorticoids seen in plasma of depressed patients can simultaneously increase production of IL-4 and suppress interferon-γ (IFN-γ) in vivo and in vitro (Agarwal and Marshall 1998a; Marshall, Agarwal et al. 1998; Agarwal and Marshall 2001). These data may help explain why allergy patients can have increased serum IgE levels when treated with glucocorticoids (Settipane, Pudupakkam et al. 1978; Zieg, Lack et al. 1994). Catecholamines, at levels noted in stressed individuals, can also influence allergic and asthmatic diseases. Norepinephrine acts through β-adrenoceptors to inhibit IL-2, interferon-γ, and IL-12, while stimulating production of IL-6 and IL-10 (Elenkov, Papanicolaou et al. 1996; Agarwal and Marshall 2000). Norepinephrine also enhances IL-4–stimulated IgE production (Mencia-Huerta, Paul-Eugene et al. 1991; Paul-Eugene, Dugas et al. 1993). Many mast cells have a close anatomic relationship with post-ganglionic sympathetic nerve fibers that release norepinephrine (Basbaum and Levine 1991; Black 2002). Furthermore, cortisol can heighten catecholamine production from sympathetic nerve terminals and the adrenal medulla (Vizi and Elenkov 2002). It should also be considered that other mechanisms could be involved in the common immune dysregulation seen in allergy and stress. Wright, Cohen et al. (2005) recently postulated alternate mechanisms based upon common influences of other stimuli on immune circuits that could impact upon the development of allergic diseases. These include increased chromosomal damage, oxidative stress pathways, glucocorticoid resistance, nerve-mast cell interactions, and intestinal dysbiosis. Each of these has been postulated to increase risk for allergic diseases (Preynat-Seauve, Coudurier et al. 2003) due to their presumed immune effects. Stress may have an additive effect on some of these environmental influences by enhancing oxidative damage (Kiecolt-Glaser, Stephens et al. 1985; Preynat-Seauve, Coudurier et al. 2003); increasing DNA repair rates (a marker for chromosomal damage) (Kiecolt-Glaser, Stephens et al. 1985; Cohen, Marshall et al. 2000); downregulating glucocorticoid receptor
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number and/or function (Lowy 1991) and altered population dynamics of enteric bacteria, possibly resulting in dysfunctional mucosal antigen processing, a proposed mechanism for acquiring allergic sensitization (Noverr, Noggle et al. 2004). The presence of these influences along with the concomitant immune effects of various stress states or mood disorders may actually more definitively drive the development of the allergic response. Although there are few definitive studies to date, current data increasingly support modulation of allergic responses by mood and psychological stressors. For example, atopic dermatitis is a chronic inflammatory skin disease that affects 10 to 15% of the population (Williams 2005). One study demonstrated significant positive correlations between a number of Minnesota Multiphasic Personality Inventory distressrelated scales and enhanced skin reactivity in response to allergens (Gauci, King et al. 1993). Older literature reported that allergic skin disorders could be substantially reduced by administration of anti-anxiety medications. However, it is now appreciated that many of these medications (such as doxepin) also have antihistaminic properties. A recent study (Liu, Coe et al. 2002) provided excellent evidence that stress can enhance allergic inflammatory responses. Sputum eosinophils collected from 20 asthmatic college students were evaluated before and after an allergen challenge. Although there were no baseline differences in eosinophil counts before antigen challenge at low- and high-stress periods (midsemester and during final examinations), counts rose significantly higher in response to allergen challenge during examinations, and this elevation also persisted longer. Furthermore, the percentage of blood eosinophils was significantly higher both before and after challenge during examinations compared with midsemester. These data are particularly notable because they show clear interactions between stress and allergen challenge. Collectively, these data provide evidence for a significant association between stress, immune dysfunction, and clinical activity of allergic and asthmatic diseases. They also support the notion of an association between the presence of excessive psychological stress and the pathogenesis of allergy and asthma in genetically susceptible individuals.
II. HISTORICAL PERSPECTIVES OF ALLERGIC DISEASES Allergic diseases such as asthma, allergic rhinitis, food allergies, and insect sting allergies were described in ancient literature. Asthma-like symptoms were first
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recorded 3,500 years ago in an Egyptian manuscript called Ebers Papyrus (Ebers 1875). Hippocrates (460– 357 B.C.) was able to recognize the spasmodic nature of asthma and believed its onset to be caused by moisture, occupation, and climate (Adams 1939). He suspected that asthma was comparable to epilepsy and had “its own nature” arising from external causes. Hippocrates’ descriptions of asthma in tailors, fishermen, and metal workers are some of the earliest reported cases of what is now considered occupational asthma. The word asthma was also used in Homer’s Iliad, with the meaning of a short-drawn breath. The actual term asthma is a Greek word that is derived from the verb aazein, meaning to exhale with an open mouth or to pant. Accurate clinical description of asthma in later antiquity is offered by the master clinician Aretaeus of Cappadocia (1st century A.D.), who emphasized the wheezing, dry productive cough, and difficulty sleeping in bed as characteristics of asthma (Adams 1856). The numerous mentions of “asthma” in the extensive writings of Galen of Pergamus (130–200 A.D.) appear to be in general agreement with the Hippocratic texts and to some extent with the statements of Aretaeus. Galen believed asthma was caused by thick viscid humors in the lungs that caused lack of room in the lungs (Daremberg CH 1856). The first book specifically about asthma was written in A.D. 1190 by a Jewish doctor from Spain, Moses Maimonides (Muntner 1963). He was physician to the Sultan Saladin, whose son had “asthma and melancholia.” This may be one of the earliest reported associations between asthma and depression. Maimonides wrote that asthma was characterized by sudden bouts of breathlessness; his treatments included copious amounts of chicken soup or sweetened barley porridge and sexual abstinence. He also advocated the holistic approach with a rational conduct of life and had the humility to admit that he lacked a magical cure. Physicians during the seventeenth and eighteenth centuries realized that asthma was due to constrictions of the bronchi. One doctor called asthma “Epilepsy of the lungs,” reflecting the sudden and unpredictable nature of asthma “attacks” or “fits.” It was not until the 1960s that physicians discovered that asthma is an inflammatory disease. The earliest report of an allergic disease is that of King Menses of Egypt, who was killed by the sting of a wasp sometime between 3640 and 3300 B.C. Another report from ancient history is that of Britannicus, the son of the Roman Emperor Claudius. He was allergic to horses and would develop a rash and his eyes would swell to the extent that he could not see where he was going. The modern era of allergy started in the 1800s with the description of hay fever in 1819 by Dr. John
Bostock, who first accurately described hay fever as a disease that affected the upper respiratory tract. It was originally so named due to the belief that the effluvium from new hay caused symptoms of allergies during summer (Finn 1992). In 1869, to investigate his own hay fever, Charles Blakely performed the first skin test by applying pollen through an abrasion in his skin. His experiment introduced the concept that pollen sensitivity caused hay fever. In 1902, Charles Robert Richet and Paul Portier coined the term anaphylaxis when, in the course of immunizing dogs to jellyfish toxins, they discovered this life-threatening response (Cohen SG 2002). In 1906, Austrian pediatrician Clemens von Pirquet first used the word allergy to describe the strange, non–disease-related symptoms that some diphtheria patients developed when treated with a horse serum antitoxin (Bukantz 2002). The word comes from the Greek word allos’ meaning, “deviation from the original state or altered response.” Indeed, an allergic reaction is the result of the body’s change when it adversely responds to a harmless substance. The term atopy is derived from the Greek word atopos, meaning out of place, and describes IgE-mediated diseases. Between 1911 and 1914, Leonard Noon and John Freeman helped establish the basis for immunotherapy or allergy shots (Noon 1911). In 1953, researchers James F. Riley and Geoffrey B. West discovered the mast cell granule to be the major source of histamine, an essential mediator in allergic reactions (Riley 1953). In 1967, Kimishige and Teruko Ishizaka further explained the allergic process by discovering the role of IgE antibodies, the principal mediator in allergic reactions (Kirkpatrick 2005). Samuelsson received the Nobel Prize in Medicine/Physiology for identifying leukotrienes as the elusive “slowing reacting substance of anaphylaxis” which has been implicated in many aspects of allergic inflammation (Dahlen SE 1980). Thus, our understanding of asthma and allergic diseases continues to evolve from mostly astute clinical descriptions in ancient times to the recognition of elaborate molecular pathways of inflammation and immune dysregulation in genetically predisposed individuals exposed to variety of environmental catalysts.
III. PATHOPHYSIOLOGY OF ALLERGIC DISEASES The pathophysiology of allergic diseases will be discussed in the context of three most common prototypic allergic disorders: namely, atopic dermatitis, allergic rhinitis, and asthma. It has been well recognized that
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atopic dermatitis and food allergies are often the earliest manifestation of atopic predisposition in a young child. Given the fact that nearly 80% of children with atopic dermatitis develop allergic rhinitis or asthma, “atopic march” is a sequential and sometimes simultaneous expression of two or three of the above-mentioned allergic disorders in an individual as he/she goes from infancy to adolescence and adulthood (Hahn and Bacharier 2005).
A. Atopic Dermatitis Atopic dermatitis (AD) is a chronic, relapsing, extremely pruritic inflammatory skin disorder that often manifests before age 5 years in about 10–20% of children in developed countries (Williams, Robertson et al. 1999). Increased transepithelial water losses, defective skin barrier function, allergen- and infectioninduced inflammation, and abnormal regeneration of damaged skin are some of the characteristics of AD (Leung, Jain et al. 2003). An imbalance between Thelper cell type 2 (Th2) immune response, which drives allergic responses, and T-helper cell type 1 (Th1) immune responses, which are essentially triggered during infections, is evident in AD. An increased number of skin-homing T-cells producing typical Th2 cytokines—namely, IL-4, IL-5, and IL-13—and little interferon-gamma (IFN-γ)—a classic Th1 cytokine— has been found in peripheral blood of patients with AD (Akdis, Simon et al. 1999). IL-4 and IL-13 promote B-cell immunoglobulin isotype switching to IgE production, and they share the same intracellular signal transducer and transactivator, STAT-6. IL-5 is essential for the development, activation, and survival of eosinophils. Cross-linking of specific IgE molecules on mast cells and basophils followed by mediator release from these cells, as well as eosinophilic infiltration of affected tissues, are hallmarks of allergic reactions in a variety of target organs. Indeed, elevated serum IgE levels and peripheral eosinophilia are found in most patients with AD (Leung 2000). Clinically unaffected skin of AD patients demonstrates mild epidermal hyperplasia and a sparse perivascular T-cell infiltrate. Marked intercellular edema (spongiosis) of the epidermis is seen in acute eczematous lesions. Marked perivenular T-cell infiltrates with occasional monocyte-macrophages, and normal numbers of mast cells in various stages of degranulation are found in the dermis. Antigen presenting cells (APC) such as Langerhans cells and macrophages in the skin of patients with AD have surface-bound IgE molecules. These cells could orchestrate a rapid response to a variety of triggering antigens, initiating an allergic cascade. Chronic lichenified lesions of AD
are characterized by hyperplastic epidermis, prominent hyperkeratosis, and minimal spongiosis. Within these chronic lesions of AD, mast cells are increased in number as are eosinophils. Increased IL-12 expression in chronic AD lesions implies a role for IFN-γ in perpetuation of skin inflammation. Thus, besides the typical Th2 cytokines, Th1 cytokines also seem to contribute to disease pathology in established AD. Tumor necrosis factor (TNF)-α produced by macrophages, antigen-stimulated T-cells, and mast cells might also play an important role in chronic eczema. In response to different pharmacological stimuli, a substantial proportion of patients with AD show a decreased β-adrenergic and an increased α-adrenergic or cholinergic reactivity. Chronic scratching, a hallmark of AD, causes kertinocytes to release TNF-α and several other proinflammatory cytokines, and such behavior is also greatly influenced by acute stressors, which will be discussed later in the chapter. Various food allergens including cow’s milk, eggs, wheat, soy, nuts, and seafood can worsen AD via IgEmediated reactions (Sicherer and Sampson 1999). Similarly, aeroallergens such as house dust mites, animal dander, pollen, and molds have been directly and indirectly implicated as inciting allergens in AD. A nonallergic phenotype of chronic eczematous skin diseases that fit the description of classic AD has also been recognized as a separate subset, hence prompting the World Allergy Organization to suggest atopic eczema/ dermatitis syndrome to encompass all patients with the classic clinical presentation of AD. A ubiquitous pathogenic bacterium, Staphyloccocus aureus, colonizes the skin of 95% of patients with AD. This bacterium releases toxins that can act as superantigens and stimulate marked inflammatory skin responses as well as induce specific IgE production. Patients with atopic dermatitis are prone to recurrent impetigo as well as recurrent fungal (tinea) and viral (herpes simplex, molluscum contagiosum) infections of the skin.
B. Allergic Rhinitis Allergic rhinitis is an inflammatory condition of the nasal mucosa characterized by symptoms of pruritus, sneezing, rhinorrhea, and stuffiness, induced by an IgE-mediated response to allergens. Allergic rhinitis affects almost 20–40 million people in the United States (Meltzer 1997). In individuals with an atopic diathesis, exposure to threshold concentrations of ubiquitous environmental antigens such as house dust mite fecal proteins, cockroach allergen, animal dander/salivary proteins, pollens, and molds for prolonged periods of time leads to generation of a Th2-type pro-allergic response, resulting in specific IgE production during
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the sensitization phase. Subsequent exposure to these antigens elicits early- and late-phase allergic reactions. Repeated exposure to allergens primes the nasal mucosa for a more rapid reaction to smaller doses of allergen (Connell 1969). Excitability of the local neural circuits and reflexes also contributes to the priming effect seen in allergic rhinitis. Early-phase response is initiated when allergen deposited on nasal mucosa cross-links specific IgE molecules on mast cells, initiating an intracellular cascade resulting in degranulation of pre-formed mediators from mast cell granules—namely, histamine, tryptase, chymase, kininogenase, heparin, and other enzymes. Subsequently, within minutes, prostaglandin D2 and sulfidopeptidyl leukotrienes (LT) LTC4, LTD4, and LTE4 are released. These mediators induce vascular leaks, causing mucosal edema and watery rhinorrhea. Mucosal gland secretions and blood vessel dilatation contribute to nasal congestion and occlusion. Stimulation of sensory nerves triggers nasal itch and systemic reflexes such as sneezing and possibly coughing. Late-phase allergic response begins with increased expression of vascular adhesion molecules and Eselectin, which facilitate circulating leukocyte adhesion to vascular endothelium. Cytokines such as IL-5 and chemokines such as RANTES then promote infiltration and migration of eosinophils, basophils, neutrophils, T lymphocytes, and macrophages to the nasal submucosa. This cellular infiltrate releases inflammatory mediators in the 3–9 hours following an early phase response and can regenerate all the above symptoms as well as prominent nasal congestion. Th2 cytokines again play a critical role in orchestrating ongoing inflammation. Cytokines such as TNF-α, IL-1, and others enter systemic circulation; reach the hypothalamus; and result in fatigue, malaise, irritability, and neurocognitive deficits commonly noted in allergic rhinitis patients who are in the midst of an exacerbation of their disease (Marshall, O’Hara et al. 2002).
C. Asthma Asthma is a complex, multi-factorial clinical disease characterized by variable airflow obstruction, airway hyperresponsiveness, and inflammation. It is estimated that asthma affects approximately 15 million persons, including 5 million children in the United States alone (Adams and Marano 1995). Asthma begins before age 4 in a large majority of these patients and is the most common chronic respiratory condition of the pediatric population (Wainwright, Isles et al. 1997). The direct and indirect costs from asthma in the United States run
into billions of dollars, while the immense psychosocial impact of this chronic disease may be hard to quantify. Allergic asthma is the most common form of asthma in both children and adults although non-allergic asthma has been recognized to inflict a sub-group of asthmatics, both children and adults. Airway inflammation in asthma can be incited by a variety of triggers alone or in combination, including allergens, viral infections (i.e., respiratory syncytial virus, parainfluenza, rhinovirus), environmental pollutants (diesel exhaust particles, ozone, sulfur dioxide, nitrogen dioxide), and environmental tobacco smoke (ETS), to name a few. Early- and late-phase allergic reactions in the lower airways similar to that seen in the upper airways result in erythema, denudation of the epithelium, edema, increased mucus production, and vascular congestion. Epithelial damage is a result of mediator release from esoinophils, neutrophils, and mast cells, but epithelial cells can be active participants in release of cytokines and propagation of airway inflammation once disease has been established. Infiltration of the airway lining with eosinophils, lymphocytes, mast cells, and neutrophils, which can survive in a pro-inflammatory cytokine milieu and perpetuate the damage to the airways, has been well characterized in asthma. Interestingly, predominance of eosinophilic inflammation is seen in some asthmatics and neutrophilic inflammation in others (Wenzel 2004). Chronic changes seen in airways of asthmatics include smooth muscle hypertrophy and hyperplasia, goblet cell hyperplasia, submucosal gland hypertrophy, neovascularization, thickening of reticular basement membrane, and fibrotic changes with collagen deposition (James 2005). Aberrant repair after repeated airway injury is believed to underlie these changes. Airway remodeling, which implies irreversible or only partially reversible changes to the airway wall anatomy, can be seen even in infancy and progresses with longer duration of asthma. Airway smooth muscle hyperresponsiveness to experimental agents such as methacholine, histamine, and natural triggers such as allergens, exercise, cold air, and extremes of emotions (laughing hard or crying) is another hallmark of asthma. Smooth muscle hyperresponsiveness might precede, accompany, and sometimes be independent of airway inflammation, suggesting heterogeneity of asthma phenotypes. Airway smooth muscle cells can also be actively involved in the release of cytokines, suggesting more than just a passive role for these cells in asthma (Hirst 2003). The importance of the epithelial-mesenchymal unit in asthma pathophysiology is being recognized now (Davies and Holgate 2002). Evolving knowledge
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of an intricate network of neural pathways and mediators that play an essential role in the pro- and antiinflammatory responses in the lung as well as airflow dynamics will be discussed later in the chapter. The impact of stress and emotions on airway smooth muscle reactivity and airway inflammation is an area in need of further research, since many patients historically report exacerbation of asthma symptoms during periods of acute stress or extremes of emotions. Airway inflammation and hyperresponsiveness in asthma manifest as variable airflow obstruction, which reverses spontaneously or with bronchodilator (beta 2-agonist) therapy and can be measured by spirometry and peak flow recordings. With prolonged or severe disease, restrictive changes in airflow can also appear. It is this airflow limitation that elicits symptoms of asthma in most patients. It has been noted in prospective, longitudinal studies that adult asthmatic subjects have greater progressive decline in lung function compared to healthy non-asthmatic individuals, regardless of smoking status (Lange, Parner et al. 1998). Thus, early recognition of this chronic disease with institution of anti-inflammatory therapies, along with environmental modifications, might alter the natural history of this disease. Prevention, however, would be the ultimate goal.
IV. CLINICAL MANIFESTATIONS OF ALLERGIC DISEASES A. Atopic Dermatitis The earliest descriptions of AD have referred to it as “neurodermatitis” due to the belief that the itch and scratch cycle, which results in a rash, was related to nerves and emotions. Though a lot more has been learned about immunopathogenesis of AD, recognition of itching and scratching as hallmarks of this disease remains true. Itching is often worse at night. Chronic sleep disturbance due to frequent scratching can have adverse effects on the patient and his/her immediate family members and is a source of significant stress. When subjects with AD get upset, they tend to itch even more, probably secondary to flushing of the skin due to vasodilatation induced by neurogenic peptides, followed by histamine and prostaglandin E2 (Ostlere, Cowen et al. 1995). Papules, lichenification, and eczematous lesions result from repeated skin trauma. Vesicles and erythema with excoriation of the skin are seen in acute eczema. Crusted lesions and pustules are seen in infected eczema. Allergens, irritants (wool, soap, detergents,
heat and humidity with sweating), infections, and certain foods can worsen eczema, and such history helps establish the right diagnosis. Distribution of rash on the face and extensor surfaces in infants and young children, changing to mostly flexural involvement in older ages, is a classic finding of AD and one of the essential features required to make this diagnosis. Dry skin (xerosis), personal and family history of allergic diseases, palmar hyperlinearity, nipple eczema, keratosis pilaris, pityriasis alba, and non-specific hand or foot dermatitis are some of the other clinical manifestations of this condition (Leung and Bieber 2003; Leung, Jain et al. 2003). The impact of AD on selfesteem and social interactions of kids or adults with this condition cannot be underestimated (Lapidus and Kerr 2001).
B. Allergic Rhinitis Most patients with AR have some symptoms all year round (perennial AR) with or without seasonal worsening of symptoms due to increases in allergen exposure. A smaller subset of patients tend to have only seasonal AR with no symptoms at other times of the year. Hence, historically, AR has been classified as seasonal or perennial. The World Health Organization has suggested classifying AR based on duration and severity of symptoms as mild intermittent, mild persistent, moderate or severe intermittent, and moderate or severe persistent to aid with choice of therapy; however, this classification has not yet been widely accepted (Johansson, Bieber et al. 2004). Typical symptoms of AR include profuse watery rhinorrhea, sneezing, itchy nose (also ears and throat in some), and congestion. Postnasal drip might be present and could incite cough or throat clearing. Pallor of the nasal mucosa, edema and hypertrophy of turbinates, clear nasal discharge, reduced nasal airflow, infraorbital hyperemia (allergic shiners), and increased linear markings below the eyes (Dennie Morgan lines) can be found on examination. Non-allergic triggers such as strong odors, tobacco smoke, and temperature changes can stimulate the above symptoms in allergic individuals too, suggesting hyperresponsiveness similar to that seen with the lower airways. Reflexes from the upper airways, when challenged with allergens, can stimulate bronchospasm, implying neural connections and providing one of the bases for the “one airway hypothesis,” which suggests a close relationship between allergic rhinitis and asthma (Blaiss 2005). Patients with allergic rhinitis can have sleep impairment due to nasal obstruction that seems to get worse at night. Fatigue, malaise, and impairment of work or school
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performance are not uncommon when symptoms are worse (Meltzer 2001). Patients with allergic rhinitis might be more prone to upper respiratory infections especially during periods of acute stress (Jaber 2002).
C. Asthma Asthma symptoms most commonly described by patients include cough, wheezing, chest tightness, dyspnea, and occasionally chest pain. Some patients might present exclusively with persistent dry cough as their primary complaint, the so-called cough-variant asthma. Episodic nature of symptoms implies that some patients may go weeks or months without any symptoms, and a few others have debilitating daily symptoms. Nocturnal awakening due to worsening of asthma symptoms is not uncommon in untreated or uncontrolled asthma patients. Exercise-induced bronchospasm resulting from rapid fluctuation of airway temperatures with increased tidal volumes and mouth breathing during periods of exercise is present in more than 90% of all asthmatics. Presently, the most widely accepted classification of asthma includes mild intermittent, mild persistent, moderate persistent, and severe persistent based on frequency of daytime and nighttime symptoms, percent predicted peak expiratory flow rates, and forced expiratory volume in 1 second during spirometry as well as variability of peak flows between early morning and late afternoons. Asthma is a dynamic disease, and any given patient can be classified differently at different time-points based on any of the above criteria. Acute exacerbations of asthma can be triggered by upper and lower respiratory tract infections (especially viruses such as rhinovirus, influenza, parainfluenza, respiratory syncytial viruses), changes in weather, significant allergen exposure in sensitized individuals, cold air, exercise, stressful situations, and hormonal changes related to menses in some women. Progression of acute asthma episodes might be gradual in some and rapid in others, requiring emergency room/ urgent care visits, sometimes hospitalization, and rarely intubation in the intensive care unit. Interestingly, vocal cord dysfunction, which results from spasmodic narrowing of the vocal cords during inspiration and expiration, may co-exist in a sizeable population of asthmatics and further implicate stressful situations in addition to chemical sensitivities in such individuals (Gavin, Wamboldt et al. 1998). Approximately 5,000 deaths occur due to asthma each year in the United States, the majority of which should be completely avoidable with appropriate preventive controller therapy and careful follow-up.
V. CURRENT THERAPEUTIC APPROACHES TO ALLERGIC DISEASES The general therapeutic approach to managing allergic diseases can be broadly divided into avoidance of known allergic/non-allergic triggers, pharmacotherapy to treat or prevent allergic inflammation, and immunotherapy, all in conjunction with ongoing patient education. Prick or intradermal skin testing, along with careful history, helps identify allergens that an individual is sensitized to and needs to avoid. Sometimes in vitro blood testing for allergen-specific IgE antibodies by standardized radioallergosorbent testing (CAP-RAST) helps direct avoidance efforts. Complete and total avoidance of pollen or dust mite or cat allergens, for example, is impossible; hence, benefits/success of avoidance measures in reducing allergic symptoms are modest at best. Pharmacotherapy relies on anti-inflammatory medications to reduce symptoms and prevent flare-ups of disease, specific antagonists or blocking agents of mediators released in the course of allergic reactions, as well as acute relief agents. Immunomodulatory therapies are beginning to become available, with many more still under development. Anti-inflammatory therapies with inhaled corticosteroids for asthma, nasal corticosteroids for allergic rhinitis, and topical steroid preparations for atopic dermatitis represent standard of care for persistent disease. These agents have the ability to affect many cell types when delivered topically to the affected areas via suppression of harmful (pro-allergic) cytokine gene expression, transactivation of anti-inflammatory genes, as well as induction of apoptosis of eosinophils, among a myriad of other effects (Schleimer, Spahn et al. 2003). While mostly safe within recommended doses, the potential for side effects in some individuals, especially on high inhaled doses of these drugs or prolonged oral and topical steroid use, is real. Rarely, severe asthmatics require oral glucocorticoids in a daily or every-other-day regimen to control their disease. Also, short courses of oral glucocorticoids are invaluable in management of significant acute exacerbations of asthma or allergic rhinitis and other allergic diseases. Antihistamines (H-1 receptor antagonists), especially second-generation antihistamines with reduced sedation potential such as fexofenadine, cetirizine, loratidine, and desloratadine, are invaluable in controlling allergic manifestations resulting from histamine release. Routine daily administration is often necessary for optimal control of allergic manifestations. A nasal antihistamine, namely, azelastine, is useful in AR and non-AR man-
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agement. Leukotriene receptor antagonists such as montelukast and zafirlukast as well as 5-lipoxygenase pathway modifiers such as zileuton add another dimension to the armamentarium of anti-allergic drugs by preventing or blocking some of the harmful consequences of leukotriene release during allergic reactions. Non-specific phosphodiesterase (PD) inhibitors such as theophylline and other specific PDE4 inhibitors that are in development can be valuable in managing some patients with asthma. Inhaled sodium cromoglycate, though very safe, has little efficacy when compared to most other available drugs for asthma therapy. Most pharmacotherapeutic agents only control symptomatology without affecting the underlying immunologic disease processes (i.e., they do not cure the problem); hence, long-term therapy is essential for optimal control. Immunomodulatory therapy with anti-IgE (omalizumab), a monoclonal humanized antibody that is capable of binding free-circulating IgE molecules when given subcutaneously every 2–4 weeks, is truly a major advancement in the field of allergy and immunology. Once IgE molecules are removed from circulation, fewer are available to coat mast cells and basophils, thus reducing the likelihood of initiation of allergic cascades. Profound reduction in tissue eosinophilia and reductions in submucosal T-cell and B-cell numbers has been seen in airways of patients with mild allergic asthma (Holgate, Casale et al. 2005). In selected moderate and severe asthma patients, anti-IgE therapy results in reduced steroid dosing, improved lung functions, and fewer asthma exacerbations. Decreasing FcεRI, the high-affinity receptor for IgE, on circulating dendritic cells might also lead to reduction in antigen presentation, Th2 cell activation, and proliferation. Other anti-cytokine and anti-chemokine agents are in various stages of development and could revolutionize the way we manage allergic diseases in the future. True immunomodulation in allergic disease is best achieved by allergen immunotherapy (IT), which is the practice of subcutaneously (SQ) injecting gradually increasing doses with subsequent maintenance therapy using allergens that a given patient is sensitized to and has history of problems when exposed to. During ongoing IT, the patient’s immune system develops blocking (IgG) antibodies to these specific allergens, shifts its response to these allergens from Th2-type cytokine production to Th1-type cytokine production, and generates specific T-regulatory cells that can dampen harmful allergic responses to the allergens, thus providing long-lasting improvement in anywhere from 50–70% of patients who undergo treatment for
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3–5 years or longer (Durham, Walker et al. 1999). The benefits of IT have been found to last 5–10 years and even longer in the case of venom IT. Risks of serious allergic reactions to these IT injections are very low but not zero. Sublingual IT, which is safer than SQ IT, utilizes much higher doses of allergens placed under the tongue, and is practiced in Europe and other parts of the world, but not in the United States. Modified allergens with altered epitopes might provide safer options for therapy in the future. Research is being conducted into CpG DNA motifs attached to certain allergens (e.g., ragweed) for use in IT, which might allow administration of lower doses with greater efficacy in the future (Jain, Kitagaki et al. 2003). The preventive role of allergen immunotherapy was highlighted in a study of young allergen-sensitized children who were placed on IT and had significantly reduced risk of developing additional allergies in a very interesting pilot study by Bousquet et al. (Des Roches, Paradis et al. 1997). Some data exist mostly from non-randomized trials without adequate patient numbers or control groups to lend support to the usefulness of stress reduction/management techniques and psychotherapeutic approaches in the management of allergic diseases. This is despite the recognition by clinicians for centuries that many of the manifestations of allergic disease have a strong psychoneurologic component. Further research into this area is very essential if we are to devise preventive approaches and provide our patients optimal control of these conditions.
VI. GENE-ENVIRONMENT INTERACTION IN THE EXPRESSION OF ALLERGIC PHENOTYPE There is known genetic risk associated with various allergic diseases including asthma (Bener, Abdulrazzaq et al. 1996; Marshall 2004a) Clinically, this is identified by a family history of allergic disease, which is a powerful predictor of allergy and asthma risk for a specific individual patient (Arshad, Stevens et al. 1993). A similar risk has been postulated for stress-susceptible individuals as well (Gillaspy, Hoff et al. 2002; Kilpelainen, Koskenvuo et al. 2002; Wright, Cohen et al. 2005). We now recognize that allergic diseases are complex, multi-factorial, exaggerated immune responses to ubiquitous glycoproteins resulting from an interplay of genetic susceptibility and environmental influences. Hippocrates noted the possibility that asthma could be an inherited condition. Clearly, increased risk of
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allergic diseases above that of the general population risk in children whose parents or siblings have asthma, AR, or AD has long been recognized. The concordance rate for monozygous twin pairs for increased IgE levels or positive skin prick tests is about 70%, whereas that for asthma or AR is 30–40% (Hanson, McGue et al. 1991). Obviously, not every individual with familial risk of developing allergies does so, implying that additional risk factors are provided by the environment. Parental psychopathology—namely, parental depression and panic attacks—was associated with increased risk for childhood atopic disorders in biological parent-child dyads with added risk, if the parent was also atopic (Mojtabhai 2005). Genetic mechanisms alone cannot explain the sudden and dramatic rise in allergic disorders worldwide in the past 3–4 decades, especially in the highly developed Westernized societies (Beasley, Crane et al. 2000). The hygiene hypothesis purports that our changing lifestyle with reduced interaction with infectious agents via inhaled, ingested, or other routes impairs the development of immune tolerance via T-regulatory cells and production of cytokines such as IL-10 and TGF-β, leading to Th1/Th2 imbalance and allergic diseases (Holla, Roy et al. 2002; Liu and Murphy 2003). Indeed, in a German study, children raised in farming environments with
FIGURE 1
Gene—environment interactions.
likely exposure to high levels of endotoxin from farm barns and history of drinking unpasteurized milk had reduced asthma and atopy when older (Von Ehrenstein, Von Mutius et al. 2000). Similarly some of the underdeveloped countries of the world with traditional lifestyles seem to have very low prevalence of allergic diseases. No one has studied the influence of acute and chronic stressors associated with urban living in highly developed nations as a potential contributing factor to this model. Altered gut microflora, severe lower respiratory viral infections, environmental tobacco smoke exposure, increased allergens exposure, diesel exhaust particulates, air pollutants, and maternal prenatal influences can all potentially impact the expression of the allergic phenotype in genetically susceptible individuals (Figure 1). Advances in molecular genetics have provided tools for unraveling some of the mysteries regarding inheritance of risk factors for allergic disease. Two different strategies have been used to identify susceptibility genes for asthma, including positional cloning and the candidate gene approach. Once narrowed, genetic linkage studies and genetic association studies have detected genetic variations utilizing variable number of tandem repeats (VNTRs) and single-nucleotide polymorphisms (SNPs) in high-probability loci that
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promote atopy, asthma, or both. Loci on chromosomes 5, 6, 11, 12, 13, 16, and 20 have so far been identified to potentially have significant effects on atopy or asthma development (Blumenthal 2005). Genetic variants in Th2 immune signaling pathways such as IL-13 (chromosome 5), IL-4Rα (chromosome 16), and STAT6 (chromosome 12), as well as variants of a metalloprotease and disintegrin ADAM33 (chromosome 20), which could be involved in airway remodeling after allergic inflammation, have been found. Also, loci controlling nitric oxide (NO) synthesis and metabolism as well as TNF and other pro-inflammatory cytokines and chemokines have been looked at as possible candidates influencing asthma risk. Variants of neuronal NO synthase (NOS1) gene have been associated with asthma, and neuronal NO synthase is also an important neuromodulator in the areas of the brain that are related to stress and depression (Grasemann H 2000; McLeod TM 2001). In a classic example of geneenvironment interactions, polymorphisms in genes coding for receptors to bacterial components can alter the immune responsiveness of the host to microbial agents and may indicate the development of aberrant immune responses that are associated with immunemediated diseases such as atopic diseases. Indeed, certain polymorphisms in the Toll-like receptor 4 and CD 14 genes, essential for signaling from bacterial endotoxin, have been associated with increased atopy/ asthma and lower Th1 immune responses and others with reduced risks of atopy/asthma (Williams LK 2005). New loci on additional chromosomes influencing risk factors for atopy are very likely to be discovered, since atopic diseases are genetically heterogeneous conditions with marked racial and ethnic differences. Gene-gene interactions are critical in addition to the gene-environment interactions for expression of various allergic diseases.
VII. NEURAL CONTROL OF THE AIRWAYS A. Architecture of Airways Innervation The nervous system coordinates protective reflexes such as sneezing, coughing, mucus secretion, and bronchospasm in our airways to keep noxious stimuli out. The lungs and airways are innervated by the vagus nerves, the majority of which are afferent (sensory) fibers that feed into the integrative centers of the brain stem (nucleus tractus solitarius), and the remainder are pre-ganglionic parasympathetic nerve fibers innervating parasympathetic ganglia from the brain stem nuclei (dorsal motor nucleus of the vagus
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nerve) and motor nerve fibers (from the nucleus ambiguous) to the striated muscle of the larynx, upper airways, and esophagus (Jordan 2001). The functional role of the post-ganglionic sympathetic nerves projecting to the airways from the superior cervical and stellate ganglia is poorly understood. Afferent and efferent nerves form multiple nerve plexuses in the airway wall such as the epithelial nerve plexuses, plexus of lamina propria, and serosal nerve plexuses. These can be found from the larynx to the terminal bronchioles. Airway afferent nerves innervate the epithelium, glands, smooth muscle, blood vessels and airway parasympathetic ganglia. Post-ganglionic autonomic nerves innervate all the above except the epithelium. A few parasympathetic ganglia are found throughout the airways. Acetylcholine is the primary neurotransmitter between the pre- and post-ganglionic parasympathetic fibers in the bronchi (Kajekar, Rhode et al. 2001). Several different afferent nerves innervate the airways, including low-threshold mechanoreceptors (rapidly adapting receptors and slowly adapting receptors) as well as nociceptors. The airway mechanoreceptors help maintain baseline autonomic tone and respiratory pattern and can also be indirectly activated by bronchoconstrictors such as histamine, acetylcholine, and leukotrienes (Bergren, Myers et al. 1985). These agents initiate both cough and reflex bronchospasm. The nociceptors, another important set of afferent nerves, are mostly unmyelinated C fibers, which are activated by inflammatory mediators such as bradykinin, 5-hydroxytryptamine, low pH, capsaicin, and hypertonic saline. Nociceptor stimulation triggers reflex bronchospasm and reflex dilation of bronchial vasculature. Esophageal afferent nerve stimulation can also cause reflex bronchospasm and might explain effects of gastroesophageal reflux in triggering bronchospasm in some asthmatic individuals (Canning and Mazzone 2003). Similarly, upper airway afferent nerve stimulation can trigger reflex bronchospasm too, which is very relevant since allergen challenges of the upper airways can trigger bronchospasm in some sensitized individuals, and emphasizes the importance of the “one airway hypothesis” (Wang, Goh et al. 2003). Physical exercise likely initiates reflex bronchodilation through withdrawal of baseline cholinergic tone. Vagal afferents, both mechanoceptors and nociceptors, regulate cough reflex in humans. The sympathetic nerves primarily innervate bronchial vasculature, and parasympathetic nerves innervate airway smooth muscle, glands, and vasculature (Barnes 1992). Although human airway smooth muscles have plenty of beta adrenoreceptors, direct evidence of adrenergic innervation of human airway
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smooth muscle is lacking, suggesting that hormonal catecholamines from the circulation are primarily responsible for binding to these receptors. Circulating catecholamine levels vary widely with acute and chronic stresses; hence, they could represent one of the likely many links between stress and airway physiology/pathology. Cholinergic innervation is primarily responsible for bronchomotor tone in human airways (Canning and Fischer 2001). Parasympathetic nerves provide functional relaxant innervation of airway smooth muscles in humans mediated by vasoactive intestinal peptide (VIP), pituitary adenylate cyclaseactivating peptide (PACAP), polypeptide with histidine at N-terminal and methionine at C-terminal (PHM), and nitric oxide synthesized from arginine by neuronal NO synthase. These non-adrenergic, noncholinergic (NANC) relaxant responses can be stimulated anywhere from the trachea to the small bronchi (Ellis and Undem 1994).
B. Axonal Reflexes and Inflammation Axonal reflexes involve the peripheral release of neurotransmitters from sensory nerves, resulting in end-organ effects. Neurogenic inflammation due to release of pro-inflammatory transmitters such as substance P after nociceptor stimulation is one such example of an axonal reflex. Various potent pro-inflammatory peptides such as substance P, neurokinin A, and calcitonin gene-related peptide (CGRP) are present in these afferent nerve endings. These peptides have the potential to initiate bronchospasm, mucus secretion, vasodilatation, and plasma exudation and cause inflammatory cell recruitment, potentially contributing to airway inflammation. Interestingly, CGRP, which is found in the neuroendocrine epithelial cells of normal lungs and sensory C fibers, can also have bronchoprotective, anti-inflammatory, and tissue repair roles (Dakhama, Larsen et al. 2004). Due to the widespread distribution and potent biological effects of tachykinins (e.g., substance P and neurokinin A) released from excitatory NANC fibers, the tachykinin receptors NK1 and NK2 are attractive biological targets for asthma therapy (Joos 2001). Thus, the central, peripheral, and autonomic nervous systems form a complex network, with the airways maintaining a fine balance that can be tipped in disease states.
C. Impact of Allergic Inflammation on the Nerves Many clinical manifestations of allergic diseases such as itch, sneeze, cough, bronchospasm with dyspnea, and rhinorrhea are the result of neuronal
activity triggered by allergic inflammation. Mediators involved in allergic reactions such as histamine, leukotrienes, neurotrophins, chemokines, and cytokines can all potentially stimulate receptors on sensory and autonomic nerves. Heightened excitability of neural reflex arcs by allergic inflammatory mediators such as histamine and bradykinin (Sheahan, Walsh et al. 2005) as well as enhanced neuropeptide secretion by histamine and cysteinyl leukotrienes (Ellis and Undem 1991) are some examples of the ways allergen-induced mediator release can recruit neural effector pathways. Indeed, upregulation of reflex physiology has been demonstrated by studies in the human nose. For example, the sensory nerve irritant, bradykinin, when applied to the nostril of allergic subjects outside their allergen season did not cause any symptoms, but when the process was repeated during the allergy season, it led to excessive sneezing and nasal secretions (Riccio and Proud 1996). Airway inflammation can also alter the afferent input into the CNS and cause electrophysiologic changes that result in increased efficacy of synaptic transmission within the CNS where different afferent nerves may converge. Similarly, an increased autonomic tone by increased efficacy of synaptic transmission within autonomic ganglia might be caused by allergic inflammation (Myers 2001). Autonomic synaptic efficacy can also be induced directly by sensitizing antigens (Cavalcantede Albuquerque, Leal-Cardose et al. 1996). Allergic eosinophilic inflammation via major basic protein released by activated eosinophils might augment acetylcholine release from postganglionic nerve fibers by inhibiting the function of muscarinic M2 receptors, which provide negative feedback in this loop (Evans, Fryer et al. 1997). Eosinophil-derived superoxide, released after allergen exposure, might also counteract the relaxant responses mediated by neuronal nitric oxide (Miura, Yamauchi et al. 1997). Also, mast cell tryptase and other peptidases may attenuate relaxant responses mediated by VIP and, possibly, other relaxant neuropeptides (Lilly, Kobzik et al. 1994). Thus, neuromodulatory effects of allergic reactions are quite widespread and can be the target of therapeutic approaches in the future as pathways and mediators become better characterized.
VIII. IMMUNE DYSREGULATION IN ALLERGIC DISEASE The production of the IgE is under the direct control of type 2 cytokine production with IL-4 and IL-13 being responsible for the isotype switch from IgM to IgE (Lebman and Coffman 1988). IL-4 is also a mast cell growth factor, and IL-5 is a major chemotactic,
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growth, and activation factor for eosinophils, which are a central component of allergic inflammation (Weltman and Karim 2000). Thus, clinical allergic diseases can be viewed as immunoregulatory imbalances where type 2 cytokines predominate (Ngoc, Gold et al. 2005). Dysregulation of the type 1 and type 2 cytokine balance is believed to play a central role in the immunopathology of asthma and atopy. Antigen-specific Tcell clones from atopic and allergic patients tend to be more of the Th2 or Th0 type compared with healthy individuals, which tend to be Th1 (Romagnani, Maggi et al. 1991). Finally, treatment of allergic rhinitis with allergen immunotherapy has been demonstrated to result in a shifting of the overall type 1 and type 2 cytokine balance back toward a type 1 response, which correlates with clinical response (Schmidt-Weber and Blaser 2004). These mechanism studies would support the theory that physiological states associated with a type 2 cytokine environment could exacerbate asthmatic and allergic diseases.
IX. EFFECTS OF ACUTE AND CHRONIC STRESS ON TH1/TH2 BALANCE A. Impact of Stress on Immune Responses Stress is best thought of as a psychophysiological process, usually experienced as a negative emotional state, that is the product of (a) the appraisal of situational and psychological factors, and (b) the resulting impetus for coping. Stressors, defined as events posing threat, harm, or challenge, are judged in the context of dispositional and environmental factors and, if appraised as menacing or challenging, produce specific responses directed at reducing the stress. A common clinical observation is the adverse relationship between stress and human disease (Ray 2004). Indeed, various sources have estimated that up to 75% of all visits to physicians’ offices are stress-related. This appears to be particularly true in relationship to immune-based dysfunctions such as increased susceptibility to infections (Sheridan, Dobbs et al. 1994; Glaser 2005), allergic diseases (Marshall 2004a; Marshall 2004b; Wright, Cohen et al. 2005), and asthma (Marshall 2004b; Bloomberg and Chen 2005). Stress is also suspected to play a role in morbidity and mortality in other immune-based diseases such as cancer (KiecoltGlaser, Robles et al. 2002; Reiche, Nunes et al. 2004), HIV disease (Kopnisky, Stoff et al. 2004), inflammatory bowel diseases (Garrett, Brantley et al. 1991; Levenstein, Pratera et al. 1994), and even immune senescence (Burleson, Poehlmann et al. 2002; Kiecolt-Glaser,
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Preacher et al. 2003). Stress may also cause persistent increases in sympathetic nervous system activity, including increased blood pressure, heart rate, and catecholamine secretion, as well as platelet aggregation (Wu, de Groot et al. 1997; Benschop, Geenen et al. 1998), which may explain, at least in part, the known association between stress, immune alterations, and cardiovascular disease. The immune dysfunctions induced by various stressors have previously been thought of primarily as immunosuppressive (Glaser, Rice et al. 1987). While increased susceptibility to various infectious agents has been described with chronic stress (Cohen, Tyrell et al. 1991; Wilson, Megel et al. 2003), recent data indicate that dysfunctions of immunoregulatory pathways play a more central role in stress-induced immune alterations; (Sheridan, Dobbs et al. 1998; Elenkov 2004; Marshall 2004b; Glaser and Kiecolt-Glaser 2005). Thus, because of an inappropriate rather than deficient immune response, otherwise healthy individuals may, at times of significant stress, have increased incidence, severity, and/or duration of multiple distinct conditions such as allergic rhinitis (AR) (Marshall 2004b). This would likely affect performance, stamina, and/or durability of these individuals. The psychological and behavioral consequences of stress may have additional, albeit indirect, effects on health by increasing incidence and/or severity of negative affect, post-traumatic stress disorder, healthimpairing behaviors (e.g., poor diet, lack of exercise, substance abuse), and poor sleep; narrowing attention; and decreasing quality of life (Satterwhite 1978; Pruessner, Hellhammer et al. 1999; Adams, Wilson et al. 2004). These research studies suggest that stressinduced changes in psychological, behavioral, and/or physiological functioning can be harmful and may result in negative health consequences through both direct and indirect mechanisms. The clinical significance of these sympathetic nervous system (SNS) and immune system changes must still be defined for specific patient populations, although it is reasonable to conclude that such stress-induced changes would adversely affect health in many individuals. Recent studies from our group and others have shown similar immune dysregulation occurring with experimental stress and/or exposure to stress hormones in vitro (Agarwal and Marshall 1999; Agarwal and Marshall 2001; Marshall 2004b). Medical student examination stress models have been used to investigate the effects of acute psychological stress superimposed upon chronic physical and psychological stress on immune function in healthy, young individuals (Kiecolt-Glaser, Garner et al. 1984; Marshall, Agarwal et al. 1998; Uchakin, Tobin et al. 2001). Medical stu-
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dents already experience the day-to-day chronic stress of classes, including anxiety, sleep deprivation, and even physical deconditioning from decreased exercise. Initially, stress-induced immunosuppression was thought to account for the laboratory findings (Glaser, Kiecolt-Glaser et al. 1985). More recent data have suggested that dysregulation of the type 1 and type 2 cytokine network plays a significant role in the observed immune responses (Marshall, Agarwal et al. 1998; Cohen, Baile et al. 1999). Such data have significant implications in investigating the role of stress in diseases, such as atopy and asthma, characterized by immune dysregulation rather than immunosuppression. Thus, it is not unreasonable to speculate that the biological as well as clinical aspects of allergies and stress are influenced by one another.
X. EVIDENCE FOR STRESS TRIGGERING EXACERBATION OF ALLERGIC DISEASES A. Relationships between Stress and Allergic Diseases Psychoneuroimmunology as a translational scientific discipline has been focused on providing information to explain the long-held clinical belief that stress can make people sick. Stress has been postulated to be a contributing factor in up to 75% of medical office visits in the United States. Observations supporting the relationships between stress and disease extend back into antiquity and are commonly associated with many illnesses including allergies and asthma (Marshall and Agarwal 2000). A number of researchers have documented an association between higher rates of allergic disorders and stress-related conditions such as depression (Cuffel, Wamboldt et al. 1999; Hurwitz and Morgenstern 1999) and anxiety disorders (Michel 1994; Strine, Ford et al. 2004). Both psychology and immunology researchers have suggested that individuals prone to affective disorders are more likely to have allergic diseases (Bussing, Burket et al. 1996; Huovinen, Kaprio et al. 2001; Bloomberg and Chen 2005). This association, if accurate, poses several interesting mechanistic questions that could have significant clinical implications including (1) Does depression predispose individuals to allergic disorders? (2) Does atopy predispose people to depression? (3) Is there a common genotype and/or phenotype that would enhance the risk for both depressive disorders and atopy? There are data for each of these questions posed from the allergy-depression association. First, there is reason to believe that depression pre-
disposes individuals to allergic disorders through endocrine and immune dysregulation. Importantly, depression and stress can augment humoral immunity at the expense of cell-mediated immunity (Leonard 2000), thus providing a clear mechanism through which stress and depression favor the increased production of IgE (Wright, Finn et al. 2004). The immunological changes associated with depressive disorders, particularly the shift from T helper 1 (Th1) to T helper 2 (Th2), promote allergic responses (Marshall and Agarwal 2000; Elenkov 2004). Hypercortisolemia is associated with depression (Gillespie and Nemeroff 2005). Glucocorticoids suppress some Th1 activities— e.g., IL-12, IFN-γ production (Elenkov, Chrousos et al. 2000; Elenkov 2004)—while enhancing Th2 activity (Agarwal and Marshall 1999; Agarwal and Marshall 2001) and thus amplify IL-4 and IgE antibody synthesis (Buske-Kirschbaum, Gierens et al. 2002). Indeed, pharmacologic as well as physiologic levels of glucocorticoids can simultaneously increase production of IL-4 and suppress IL-2 in vivo; these data help explain why allergy patients can actually demonstrate increased IgE production when treated with glucocorticoids (Wu, Sarfati et al. 1991).
B. Common Mechanisms between Stress-induced and Allergic Immunopathology Because of diversity of presentations and responses to therapy, allergic conditions (including asthma) are no longer considered single diseases but rather clinical syndromes reflecting a common systemic immune imbalance with differing phenotypes at end organs, such as the nose, lung, skin, and gut (Braunstahl and Hellings 2003; Togias 2003). Although certain aspects of therapy have commonalties, current research emphasis is focused on identifying at-risk populations, including specific genes (Blumenthal 2005), and the interactive environmental influences that increase risks for specific clinical manifestations of allergic diseases (Marshall 2004; Romagnani 2004). The adverse effects of psychological stress on asthma have been well documented (Oh, Kim et al. 2004; Bloomberg and Chen 2005; Wright, Cohen et al. 2005). Initially, the mechanism was presumed to operate via increased cholinergic reactivity that can accompany the increased sympathetic activity of various stressors. This increased vagal activity would result in bronchial hyperreactivity, thereby worsening asthma symptoms. However, more recent studies observed that psychosocial influences that adversely affect the severity of allergic rhinitis could lead to increased incidence and/
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or severity of asthma as well (Romagnani 2004; Blaiss 2005). Such influences may include differences in type, amount, and/or duration of psychological stress, incidence of depression and/or anxiety disorders, and/or restricted capacity to deal with psychosocial stressors faced in everyday life (Brook and Tepper 1997; Roder, Kroonenberg et al. 2003). Thus, the relationships between stress and allergic diseases represent a potentially comprehensive model for understanding pathogenic as well as pathophysiological mechanisms. However, even when at-risk individuals can be identified, there is typically a prolonged time (years to decades) before the allergic condition becomes clinically manifested. Thus, most studies have focused on demonstrating harmful effects of stress on established allergic diseases. In subjects with AD, many patients (or family members) report that stressful or frustrating situations trigger episodes of severe itching and lead to significant scratching. High technology such as video games, frequently ringing cell phones, and computer-induced stress has been found to enhance allergic responses with concomitant elevations of substance P, vasoactive intestinal peptide, and nerve growth factor in children with AD compared to those with allergic rhinitis or normal controls (Kimata 2003; Kimata 2003). In AD subjects with higher baseline total IgE , increased CLA+ CD8+ T-lymphocytes expressing Th2 cytokines were found with high psychological stress. Choi reported that increased psychological stress due to insomnia could alter skin permeability-barrier homeostasis (Choi, Brown et al. 2005). Subjects with AD who had history of stress-related exacerbations had increased numbers of skin-associated mast cells, VIP+ nerve fibers, and decreased CGRP fibers (Lonne-Rahm, Berg et al. 2004). Attenuated cortisol responses have been found in adolescents with clinically active allergic diseases compared to sensitized and healthy controls (Wamboldt, Laudenslager et al. 2003). A blunted cortisol response to laboratory stressors has been documented in children with AD compared to normal controls, which might highlight the importance of the HPA axis in stress-induced exacerbation of atopic diseases (Buske-Kirschbaum, Jobst et al. 1997; BuskeKirschbaum and Hellhammer 2003). Asthma exacerbations have also been causally related to stressful situations and events. Stressful life events not only elevate the risk of a new asthma attack within the first few days after the event, but a delayed risk up to 5–7 weeks later has also been reported (Sandberg, Jarvenpaa et al. 2004). Severely negative life events have been associated with increased risk of asthma exacerbation, especially when occurring
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against a backdrop of chronic high stress. Children whose caregivers have significant levels of mental health problems tend be hospitalized more often, and children with clinically significant behavioral problems tend to wheeze more often and have poorer functional status (Weil, Wade et al. 1999). Exposure to violence via stress-induced and possibly other unknown mechanisms has also been associated with asthma morbidity (Wright and Steinbach 2001). Indeed, a murine model of asthma and stress has confirmed the potential of stress to exacerbate airway hyperreactivity and airway inflammation in allergic asthma (Joachim, Sagach et al. 2004). Chronic idiopathic urticaria (CIU) is characterized by recurrent hives, with episodes lasting greater than 6–8 weeks. It is a frustrating problem for patient and clinician due to lack of obvious pathophysiologic explanation for the hives in a significant proportion of these individuals. Various studies have associated stress, anxiety, or depression to CIU (Sperber, Shaw et al. 1989). It has also been suggested that depression might reduce the threshold for pruritus in variety of dermatologic disorders (Gupta, Gupta et al. 1994). Thus, through known and unknown pathways, stress can trigger symptoms in atopic subjects with established disease. Stress reduction/management techniques should be considered an important adjunct to other therapeutic interventions for these allergic patients.
XI. POTENTIAL FOR INTERVENTION IN STRESS-RELATED ALLERGIC DISEASES Although many think that allergic diseases are easily cared for, it is clear that with the high prevalence in our society, the economic impact is extraordinary. It is estimated that over $6 billion was expended for the care of allergic rhinitis in 2000 (Fineman 2002). This does not count the impact of 2 million lost work days, 3 million lost school days, and 28 million days of decreased productivity on students and workers from the side effects of their illness. Additionally, allergic rhinitis can lead to asthma in as many as 50% over a 5–10-year period in both children and adults. (Guerra, Sherrill et al. 2002; Bousquet, Vignola et al. 2003; Koh and Kim 2003). The direct and indirect costs from asthma in the United States are estimated to be around $11 billion annually (Thomas, Kocevar et al. 2005). Finally , the same inflammatory mechanisms active in allergic/asthmatic diseases are the same ones implicated in other immune-based diseases such as coronary artery disease (Langer, Criqui et al. 1996), diabetes mellitus (Simpson, Anderson et al. 2002), HIV progres-
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sion (Agarwal and Marshall 1998a), and certain malignancies (Reiche, Nunes et al. 2004). Disease progression for each of these clinical entities has also been suggested for high-stress populations (Kiecolt-Glaser, Preacher et al. 2003), implying that interventional strategies could have far greater applicability beyond simple hay fever. Interventional strategies involve identifying at-risk individuals for both allergic and stress-related diseases and searching for commonalities in mechanisms to provide rationale for the development of specific therapies. Such searches would involve identifying populations at risk for allergic diseases (i.e., family history, specific genetic patterns) and determining the prevalence of AR, asthma, and/or AD in high- versus low-stressed populations. Alternatively, naturally high- and low-stressed populations can be identified and the incidence of allergic conditions compared between groups. Finally, specific genetic profiles associated with allergic and asthmatic diseases such as single nucleotide polymorphisms at sites coding for β2 adrenergic receptors (Johnson 1998), glucocorticoid receptors (Hawkins, Amelung et al. 2004; Wust, Van Rossum et al. 2004), IL-4 promoter (Song, Casolaro et al. 1996), IL-4 receptor (Zhu, Chan-Yeung et al. 2000; Wjst, Kruse et al. 2002), and immunoregulatory molecules such as CTLA4 (CD152) (Hizawa, Yamaguchi et al. 2001) could be important targets for study. Individuals with these or other phenotypes may have increased risk for allergic diseases while under significant stress. Once the at-risk individual is identified, interventional strategies would be based upon one of two major approaches. If identified before allergic diseases were clinically present, interventions would be prophylactic in nature, aimed at preventing the immune changes associated with allergy. If allergic disease was already present, then interventions would be therapeutic, with the intent to minimize the immunoregulatory imbalance that characterizes chronic stress-induced immune changes. This would conceptually lower the risk of stress-induced disease exacerbation in patients experiencing stressful situations. The most obvious intervention would be stress avoidance or reduction. Interpersonal relationships (Kiecolt-Glaser, Bane et al. 2003), job situations (Spurgeon, Gompertz et al. 1997), and socioeconomic conditions (Evans, Der et al. 2000) are all known sources of chronically stressful situations for many individuals. The long-standing question as to whether repeated acute stressors (such as soldiers in combat, police officers in high crime areas vs. desk jobs, etc.) can collectively cause the same immune changes as chronic stressors (caring for chronically ill family member,
low socioeconomic status, etc.) must be addressed and answered. Although stress reduction/elimination options can be available, they are often limited by practical life situations. Thus, stress management aimed at improving coping abilities is more likely to be clinically useful as a basis for interventional strategies (Barton, Clarke et al. 2003). Approaches to stress management can be categorized into psychological, physiological, or pharmacological, interventions with various combinations of the three.
A. Psychological Interventions It has been well described that psychological interventions can have positive effects on clinical outcomes in immune-based diseases (Biondi and Zannino 1997; Wright 2004). Support groups have been studied for their effects on survival in breast cancer patients (Edwards, Hailey et al. 2004), CD4 counts in HIV+ patients (Birk, McGrady et al. 2000), and asthma disease activity (Ritz, Steptoe et al. 2000). Expressive writing about stressful life events was studied and shown to improve FEV1, a measure of airway obstruction in asthma patients in some (Smyth, Stone et al. 1999; Warner, Lumley et al. 2005) but not all studies (Harris, Thoresen et al. 2005). Biofeedback has been used with some success in asthma management (Lehrer, Vaschillo et al. 2004), as has mental imagery techniques (Epstein, Halper et al. 2004; Freeman and Welton 2005). Relaxation therapy has a positive effect on asthma outcomes, including hospitalization, airway function, and exacerbation rates (Huntley, White et al. 2002). Psychotherapy in depressed asthma patients was shown to be beneficial in disease activity, including trips to the ER and numbers of exacerbations (Lehrer, Feldman et al. 2002). All of these techniques have corresponding studies demonstrating an “anti-allergic” immune balance produced by the intervention. But the direct correlation of clinical improvement with immune changes in allergic diseases including asthma await, further study.
B. Physiological Interventions Physiological interventions for allergy/asthma management have been studied largely within the context of complementary and alternative medicine. Modalities such as therapeutic back massage have been shown to have positive effects comparable to relaxation training on asthma and allergic disease activity (Long, Huntley et al. 2001). The same techniques have shown an improvement in immune functions that would be considered anti-allergic as
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well (Markham and Wilkinson 2004). Published studies suggest that acupuncture, chiropractic, and applied kinesiology have all been advanced as valuable in the management of allergic disorders, especially asthma (Miller 2001). However, carefully controlled studies have failed to show clear clinical benefit, perhaps due to the strong placebo effect that occurred in these studies—a strong psychophysiological influence on immunity (Jamison 1996; Rossi 2002) and thus allergic diseases as well (Markham and Wilkinson 2004). Various forms of physical exercise have been shown to have positive effects on stress management. Exercise training done in a conditioning manner can actually have a protective or salutary effect on immunity (Pyne and Gleeson 1998; Nieman 2000). However, overtraining or exhaustion can be detrimental to the immune response, resulting in immunosuppression (Fitzgerald 1991; Shephard and Shek 1998) or altered immunoregulation (Lakier Smith 2003), which could enhance hypersensitivity conditions such as allergy and asthma. A controlled exercise training program is often recommended for asthma patients to enhance their pulmonary function and improve clinical control (Cochrane and Clark 1990; Counil, Varray et al. 2003). But exercise during periods of poorly controlled asthma can cause exacerbations that have an inflammatory basis (Crowther and Rees 2000; Smith, Mahony et al. 2002).
C. Pharmacological Interventions Until recently, psychoactive agents have been the mainstay of therapeutic intervention for “stressinduced asthma.” Antidepressants (both tricyclics and SSRI) have documented value in certain populations with asthma—especially those with defined depressive disorders (Krommydas, Gourgoulianis et al. 2005). There are also studies which suggest that asthma patients with depressive episodes but no formal diagnosis may also benefit from antidepressive therapy. This may occur, at least in part, due to the depressive effects of many cytokines that are prominent in allergic diseases (Watkins 1995; Maier and Watkins 1998). If correct, this would suggest that managing the clinical allergic disease could itself be antidepressive by altering the cytokine milieu that crosses the blood-brain barrier resulting in depressive episodes (Maier and Watkins 1998; Frieri 2003). In such cases, the need for concomitant antidepressants could be minimized or even supplanted by anti-inflammatory therapy for the specific allergic condition. Patients with anxiety disorders have an increased incidence of allergy and asthma symptoms (Goodwin, Fergusson et al. 2004; Katon, Richardson et al. 2004).
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Allergic and asthmatic patients often report increased frequency and severity of symptoms during times of high anxiety (Stauder and Kovacs 2003). Anxiolytic drugs (especially the benzodiazepines) have been demonstrated to improve the immune milieu in situ in a fashion that could, at least in part, explain their positive clinical effects in asthma management (DeVane, Hill et al. 1998). This is of particular interest since the use of these agents has been relatively contraindicated in the most acutely stressed of all asthma patient populations—those with acute exacerbations—because of concerns over the respiratory-depressant properties of benzodiazepines (Clergue, Desmonts et al. 1981). Recent studies have shown that increased superoxide formation occurs in times of high stress (Kang and McCarthy 1994). Thus, agents that have antioxidant properties, such as vitamins C and E, could potentially have prophylactic properties against stress-induced immune changes. Studies from our group and others have shown that vitamin C and vitamin E (Wakikawa, Utsuyama et al. 1999; Ritter and Marshall 2004) can reduce immunoregulatory imbalances noted in stressed individuals. Additionally, vitamin C has been noted to have direct impact on plasma cortisol and blood pressure levels as well as direct anti-anxiety properties (Brody, Preut et al. 2002; Currie, Lee et al. 2005). Similarly, both vitamin C and vitamin E (Miller 2001) have been reported to reduce the symptoms of allergy and asthma. Further, at-risk children of nursing mothers who took large amounts of vitamin C subsequently detected in their milk had a decreased incidence of atopy compared to controls (Hoppu, Rinne et al. 2005). These data suggest a strong association between immune dysfunctions responsible for allergic diseases, and those induced by stressful situations may respond to both therapeutic and prophylactic antioxidant ingestion.
XII. CONCLUDING REMARKS The use of patients with allergic diseases such as rhinitis, asthma, and even skin diseases as models for clinically relevant stress-induced immune changes is particularly attractive for a variety of reasons. First, based upon multiple studies by many different investigators, there are many commonalities between the mechanisms of immunopathology in allergic diseases and the immune changes associated with acute and chronic stress (Sandberg, Paton et al. 2000; Rohleder, Wolf et al. 2003). Next, there is always a significant challenge in studying any human disease population because of significant confounding factors such as comorbid conditions, side effects of medications and/
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or therapies, and prolonged course of disease, requiring months to years to see either the natural history of the disease (including mortality) or the results of a therapeutic intervention. While some patients with allergic diseases have other conditions, the typical patient with allergic rhinitis, for example, is young and otherwise healthy. Thus, he/she usually is not taking other medications that could impact immune assessments in stress-related studies. Also, since allergic disease is described as immediate hypersensitivity, evaluations of exacerbating factors such as an acute stressor or an intervention can be evaluated clinically in a matter of minutes to hours rather than months to years. Finally, since this model involves human subjects, results and conclusions can be more directly translatable to other immune-based diseases.
XIII. FUTURE DIRECTIONS FOR RESEARCH IN STRESS AND ALLERGIC DISEASES A. Identifying the At-Risk Patients As in other areas of human research, the molecular epidemiology of stress and allergic disease is an area that needs intensive investigation. Identifying people “at risk” for developing allergic diseases continues to be an area of active investigation (Devereux and Seaton 2005; Upham and Holt 2005; Wright, Cohen et al. 2005). Current data strongly indicate that allergic diseases are actually syndromes (i.e., multiple pathophysiologies that alter immune responses to cause similar clinical presentations). Thus, it is not surprising to know that multiple genes have been implicated in the pathophysiology of allergy and asthma (Blumenthal 2005) More recently, SNP for such gene products as β2 adrenergic receptors (Leineweber, Buscher et al. 2004), IL-4 promoters (Kabesch, Tzotcheva et al. 2003), IL-4 receptors (Woitsch, Carr et al. 2004), and co-stimulatory molecules including CTLA4 (CD152) (Hizawa, Yamaguchi et al. 2001) have been increasingly associated with certain asthma populations. As previously described, atopic diseases are immunologically characterized as primary Th2 diseases, and psychological stress-induced immunoregulatory dysfunctions are also largely characterized by decreased Th1 cytokines (i.e., IFN-γ) and increased Th2 cytokines (i.e., IL-4, IL10). Thus, it is provocative to speculate how such patient populations with these various SNP phenotypes would respond to stressful situations. Such a genetic link could be useful to prepare prophylactic or, in established disease, therapeutic protocols that
involve specific forms of stress prevention, reduction, and/or management.
B. Role of Specific Stressors in Allergic Disease Another area for further research is evaluating the relative roles of specific stressors—acute versus chronic, psychological versus physiological versus pharmacological—in allergic diseases. There is a paucity of human data that examine acute versus chronic stress effects in human disease models. Additionally, acute stressors superimposed upon chronic stress may have a distinctly different immune and/or clinical effect than either one alone. The psychological stressors including anxiety and depression have been the most studied and described in allergy. However, physiological stressors such as exercise, pain, and fatigue/exhaustion have all been implicated in allergy/ asthma exacerbations (Papiris, Kotanidou et al. 2002) and immune effects in stress studies (Kiecolt-Glaser, Page et al. 1998). Fatigue has been implicated in poor asthma control as well as worsening symptoms of allergic rhinitis (Blaiss 2004). Overtraining of athletes who have allergic or asthmatic diseases to the point of exhaustion has been demonstrated to have adverse effects on immunity (Pedersen, Rohde et al. 1996). Whether these conditions represent direct effects of the physiological stressors or whether they exacerbate anxiety and/or depression episodes is unclear—but both mechanisms may contribute (Graham-Bermann and Seng 2005). There is also a known association between allergic disease exacerbations and the improper use of certain pharmacological agents, including β2 adrenergic receptor agonists, both long and short acting (Abramson, Walters et al. 2003; Alvarez, Schulzer et al. 2005); and even irregular use of corticosteroids, both inhaled and systemically administered (Milgrom, Bender et al. 1996; Schatz, Cook et al. 2003). Adding these observations to the results of studies from our group and others demonstrating that both catecholamines and corticosteroids in so-called stress concentrations can alter immunoregulatory networks (Elenkov, Papanicolaou et al. 1996; Agarwal and Marshall 2000; Agarwal and Marshall 2001; Elenkov 2004), it is tempting to speculate that certain individuals may be more likely to experience the adverse effects of these therapeutic agents at specific concentrations. Determining to whom and by what mechanisms this might happen is an area of specific research interest.
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C. Animal Models Although human models may offer the most rapid translation to clinical settings, practical and ethical considerations make animal models a useful tool, particularly for looking at mechanistic associations between various forms of stress and allergy. Wellestablished murine allergy and asthma models have highly characterized immune alterations that correlate with physiological airway obstructions which are accepted models for human asthma (Gleich and Kita 1997; Wills-Karp 2000; Joachim, Quarcoo et al. 2003). The same murine strains have been used to study the effects of various stressors on immune responses as well. Thus, studies could readily be done that examined the effects of acute versus chronic stress versus both on allergic sensitization and/or allergenchallenged airway obstruction in previously sensitized mice. Another major use of animal models is to study the relative contribution of immune cells (both innate and adaptive) derived from various lymphoid organs to the overall airway restriction. Such data can help to determine local organ versus general immune responses in stress-related allergy exacerbations.
D. Interventional Studies While understanding the mechanisms of stressassociated immune changes in allergy and asthma patients is interesting in itself, it is the translational studies that will ultimately provide the greatest clinical benefit. The task of developing effective interventions is clearly multifaceted. If specific high-risk individuals can be reliably identified, the effectiveness of stress prophylaxis interventions can be more readily addressed in allergy and asthma. Such interventions may be immediate, such as the use of vitamin C prior to known stressful situations, or more complex, such as socioeconomic interventions through altered public policy in at-risk inner city children who have an extraordinarily high incidence of allergy and asthma. Specific stress prevention versus reduction versus management protocols can be directly compared for their relative value in preventing versus treating allergy and asthma symptoms in susceptible populations. While any person could have an immune alteration associated with a specific stressor, studying the highest risk populations is useful from an epidemiological standpoint, allowing stronger mechanistic correlations in populations with both documented increased stress exposure and increased allergic disease prevalence.
E. Applications to Other Inflammatory Disease States As stated earlier, the allergic patient is a classical model for inflammatory disease in humans. It is increasingly appreciated that many, if not most, human diseases from cardiovascular (Kofler, Nickel et al. 2005) to endocrine (Wellen and Hotamisligil 2005) to psychiatric diseases (Melamed, Shirom et al. 2004) have an inflammatory component to their pathophysiology. There are certainly commonalities but also differences in immunological abnormalities that have been described in association with these diseases. For example, allergy and asthma are considered Th2 diseases, while other diseases such as multiple sclerosis, diabetes mellitus, and rheumatoid arthritis are all conditions dominated by abnormal Th1 activity (Romagnani 1995; Christen and von Herrath 2004). Yet, stress has demonstrated adverse effects in both Th1 and Th2 immune-based conditions (Frieri 2003; Lorton, Lubahn et al. 2003). A unifying immunopathophysiology that could satisfy the apparent mechanistic paradox may be the effects of stress in altering immunoregulatory circuits, particularly involving regulatory T-cells in susceptible patients (von Herrath and Harrison 2003; Hawrylowicz and O’Garra 2005). Stress has not been extensively studied for its effects on regulatory T-cells (Treg). However, if Treg circuits with their characteristic cytokines (TGF-β, IL-10) are adversely affected by various stressors (Glaser, MacCallum et al. 2001), this could possibly explain the common adverse effects of stress on these distinct disease entities. Finally, if the specifics of the relationship between stress and allergic diseases can be established, this will ultimately result in an individualization of treatment for the stress-afflicted patient—regardless of his/her specific disease. The future is bright for the realization of that clinical goal first espoused so many centuries ago by King Solomon who wrote “a merry heart doeth well like a medicine but a broken spirit drieth the bones” (Proverbs 17:12). It is significant that even in ancient civilization it was understood that stressors could have adverse impact on the bone marrow, the ultimate source of immune cells.
References Abramson, M., Walters, J. A. et al. (2003). “Adverse effects of beta agonists: are they clinically relevant?” Am. J. Respir. Med., 2, 287– 297. Adams, F. (1856). The extant works of Areateus, the Cappodocain. London, Sydenham Society. Adams, F. (1939). The genuine works of Hippocrates. Baltimore, Williams and Wilkins.
818
IV. Stress and Immunity
Adams, P., and Marano, M. (1995). “Current estimates from the National Health Interview Survey 1994.” Vital Health Stat., 10, 94. Adams, R. J., Wilson, D. H. et al. (2004). “Psychological factors and asthma quality of life: a population based study.” Thorax, 59 (11), 930–935. Agarwal, S., and Marshall, G. D. (1998a). “In Vivo Alteration in Type-1 and Type-2 Cytokine Balance: A Possible Mechanism for Elevated Total IgE in HIV-infected Patients.” J. Allergy Clin. Immunol., 101, S56. Agarwal, S. K., and Marshall, G. D. (1999). “Dexamethasone differentially regulates human IL-4 and IL-5 production in vitro.” J. Allergy Clin. Immunol., 103 (1 Pt 2), S86. Agarwal, S. K., and Marshall, G. D. Jr. (1998b). “Glucocorticoidinduced type 1/type 2 cytokine alterations in humans: a model for stress-related immune dysfunction.” J. Interferon Cytokine Res., 18 (12), 1059–1068. Agarwal, S. K., and Marshall, G. D. Jr. (2000). “Beta-adrenergic modulation of human type-1/type-2 cytokine balance.” J. Allergy Clin. Immunol., 105 (1 Pt 1), 91–98. Agarwal, S. K., and Marshall, G. D. Jr. (2001). “Dexamethasone promotes type 2 cytokine production primarily through inhibition of type 1 cytokines.” J. Interferon Cytokine Res., 21 (3), 147–155. Akbari, O., and Umetsu, D. T. (2005). “Role of regulatory dendritic cells in allergy and asthma.” Curr. Allergy Asthma Rep., 5 (1), 56–61. Akdis, M., Simon, H. et al. (1999). “Skin homing (cutaneous lymphocyte-associated antigen-positive) CD8+ T cells respond to superantigen and contribute to superantigen and contribute to eosinophilia and IgE production in atopic dermatitis.” J. Immunol., 162, 466–475. Alvarez, G., Schulzer, M. et al. (2005). “A systematic review of risk factrors associated with near fatal or fatal asthma.” Can. Respir. J., 12, 265–270. Arshad, S. H., Stevens, M. et al. (1993). “The effect of genetic and environmental factors on the prevalence of allergic disorders at the age of two years.” Clin. Exp. Allergy, 23 (6), 504–511. Barnes, P. J. (1992). “Modulation of neurotransmission in airways.” Physio. Rev., 72, 699–729. Barton, C., Clarke, D. et al. (2003). “Coping as a mediator of psychosocial impediments to optimal management and control of asthma.” Respir. Med., 97 (7), 747–761. Basbaum, A. I., and Levine, J. D. (1991). “The contribution of the nervous system to inflammation and inflammatory disease.” Can. J. Physiol. Pharmacol., 69 (5), 647–651. Beasley, R., Crane, J. et al. (2000). “Prevalence and etiology of asthma.” J. Allergy Clin. Immunol., 105, S466–S472. Bendelac, A., and Schwartz, R. H. (1991). “Th0 cells in the thymus: the question of T-helper lineages.” Immunol. Rev., 123, 169–188. Bener, A., Abdulrazzaq, Y. M. et al. (1996). “Genetic and environmental factors associated with asthma.” Hum. Biol., 68 (3), 405–414. Benschop, R. J., Geenen, R. et al. (1998). “Cardiovascular and immune responses to acute psychological stress in young and old women: a meta-analysis.” Psychosom. Med., 60 (3), 290–296. Bergren, D., Myers, D. et al. (1985). “Activity of rapidly-adapting receptors to histamine and antigen challenge before and after sodium cromoglycate.” Arch. Int. Pharmacodyn. Ther., 273, 88– 99. Biondi, M., and Zannino, L. G. (1997). “Psychological stress, neuroimmunomodulation, and susceptibility to infectious diseases in animals and man: a review.” Psychother. Psychosom., 66 (1), 3–26. Birk, T. J., McGrady, A. et al. (2000). “The effects of massage therapy alone and in combination with other complementary therapies
on immune system measures and quality of life in human immunodeficiency virus.” J. Altern. Complement. Med., 6 (5), 405–414. Black, P. H. (2002). “Stress and the inflammatory response: a review of neurogenic inflammation.” Brain Behav. Immun., 16 (6), 622–653. Blaiss, M. (2004). “Current concepts and therapeutic strategies for allergic rhinitis in school-age children.” Clin. Ther., 26 (11), 1876–1889. Blaiss, M. S. (2005). “Rhinitis-asthma connection: epidemiologic and pathophysiologic basis.” Allergy Asthma Proc., 26, 35–40. Bloomberg, G. R., and Chen, E. (2005). “The relationship of psychologic stress with childhood asthma.” Immunol. Allergy Clin. North Am., 25 (1), 83–105. Blumenthal, M. (2005). “The role of genetics in the development of atopy and asthma.” Curr. Opin. Allergy Clin. Immunol., 5, 141–145. Bousquet, J., Vignola, A. M. et al. (2003). “Links between rhinitis and asthma.” Allergy, 58 (8), 691–706. Braunstahl, G. J., and Hellings, P. W. (2003). “Allergic rhinitis and asthma: the link further unraveled.” Curr. Opin. Pulm. Med., 9 (1), 46–51. Brody, S., Preut, R. et al. (2002). “A randomized controlled trial of high dose ascorbic acid for reduction of blood pressure, cortisol, and subjective responses to psychological stress.” Psychopharmacology Berl., 159 (3), 319–324. Brook, U., and Tepper, I. (1997). “Self image, coping and familial interaction among asthmatic children and adolescents in Israel.” Patient Educ. Couns., 30 (2), 187–192. Bukantz, S. (2002). “Clemens von Pirquet and the concept of allergie.” J. Allergy Clin. Immunol., 109, 724–726. Burleson, M. H., Poehlmann, K. M. et al. (2002). “Stress-related immune changes in middle-aged and older women: 1-year consistency of individual differences.” Health Psychol., 21 (4), 321–331. Buske-Kirschbaum, A., Gierens, A. et al. (2002). “Stress-induced immunomodulation is altered in patients with atopic dermatitis.” J. Neuroimmunol., 129 (1–2), 161–167. Buske-Kirschbaum, A., and Hellhammer, D. H. (2003). “Endocrine and immune responses to stress in chronic inflammatory skin disorders.” Ann. N. Y. Acad. Sci., 992, 231–240. Buske-Kirschbaum, A., Jobst, S. et al. (1997). “Attenuated free cortisol response to psychosocial stress in children with atopic dermatitis.” Psychosom. Med., 59 (4), 419–426. Bussing, R., Burket, R. C. et al. (1996). “Prevalence of anxiety disorders in a clinic-based sample of pediatric asthma patients.” Psychosomatics, 37 (2), 108–115. Cacioppo, J. T., Berntson, G. G. et al. (1998). “Autonomic, neuroendocrine, and immune responses to psychological stress: the reactivity hypothesis.” Ann. N. Y. Acad. Sci., 840, 664–673. Canning, B., and Fischer, A. (2001). “Neural regulation of airway smooth muscle tone.” Respir. Physiol., 125, 113–127. Canning, B. J., and Mazzone, S. B. (2003). “Reflex mechanisms in gastroesophageal reflux diseases and asthma.” Am. J. Med., 115, 45S–48S. Cavalcantede Albuquerque, A., Leal-Cardose, J. et al. (1996). “Antigen-induced synaptic plasticity in sympathetic ganglia from actively and passively sensitized guinea-pigs.” J. Auton. Nerve Syst., 61, 139–144. Chen, E., Fisher, E. B. et al. (2003). “Socioeconomic status, stress, and immune markers in adolescents with asthma.” Psychosom. Med., 65 (6), 984–992. Choi, E. H., Brown, B. E. et al. (2005). “Mechanisms by which psychologic stress alters cutaneous permeability barrier homeostasis and stratum corneum integrity.” J. Invest. Dermatol., 124 (3), 587–595.
37. Stress and Allergic Diseases Christen, U., and von Herrath, M. G. (2004). “Manipulating the type 1 vs type 2 balance in type 1 diabetes.” Immunol. Res., 30 (3), 309–325. Chrousos, G. P., and Gold, P. W. (1992). “The concepts of stress and stress system disorders. Overview of physical and behavioral homeostasis.” JAMA, 267 (9), 1244–1252. Clergue, F., Desmonts, J. M. et al. (1981). “Depression of respiratory drive by diazepam as premedication.” Br. J. Anaesth., 53 (10), 1059–1063. Cochrane, L. M., and Clark, C. J. (1990). “Benefits and problems of a physical training programme for asthmatic patients.” Thorax, 45 (5), 345–351. Cohen, L., Baile, W. F. et al. (1999). “Immune dysregulation in healthy medical students during exposure to acute and chronic stressors.” Psychosom. Med., 61, 83–130. Cohen, L., Marshall, G. D. Jr., et al. (2000). “DNA repair capacity in healthy medical students during and after exam stress.” J. Behav. Med., 23 (6), 531–544. Cohen, S., Tyrell, D. et al. (1991). “Psychological stress and susceptibility to the common cold.” N. Engl. J. Med., 325, 606– 612. Cohen SG, Z.-Q. M. (2002). “Portier, Richet and the discovery of anaphylaxis: acentennial.” J. Allergy Clin. Immunol., 110, 331–336. Connell, J. (1969). “Quantitative intranasal pollen challenges, III: The priming effect in allergic rhinitis.” J. Allergy, 43, 34–44. Counil, F. P., Varray, A. et al. (2003). “Training of aerobic and anaerobic fitness in children with asthma.” J. Pediatr., 142 (2), 179–184. Crowther, S. D., and Rees, P. J. (2000). “Current treatment of asthma—focus on leukotrienes.” Expert Opin. Pharmacother., 1 (5), 1021–1040. Cuffel, B., Wamboldt, M. et al. (1999). “Economic Consequences of Comorbid Depression, Anxiety, and Allergic Rhinitis.” Psychosomatics, 40 (6), 491–496. Currie, G. P., Lee, D. K. et al. (2005). “Vitamin E supplements in asthma.” Thorax, 60 (2), 171–172; author reply 172. Dahlen SE, H. P., Hammarstrom S., and Samuelsson, B. (1980). “Leukotrienes as potent constrictors of the human bronchi.” Nature, 288, 484–486. Dakhama, A., Larsen, G. L. et al. (2004). “Calcitonin gene-related peptide: role in airway homeostasis.” Curr. Opin. Pharmacol., 4, 215–220. Daremberg CH, G. C. (1856). Oeuvres anatomiques physiologiques et medicales de Galien. Paris, Baillière. Davies, D., and Holgate, S. (2002). “Asthma the importance of the epithelial mesenchymal communication in pathogenesis. Inflammation and the airway epithelium in asthma.” Int. J. Biochem. Cell Biol., 34, 1520–1526. DeKruyff, R. H., Rizzo, L. V. et al. (1993). “Induction of immunoglobulin synthesis by CD4+ T cell clones.” Semin. Immunol., 5 (6), 421–430. Des Roches, A., Paradis, L. et al. (1997). “Immunotherapy with a standardized Dermatophagoides pteronyssinus extract VI. Specific immunotherapy prevents the onset of new sensitizations in children.” J. Allergy Clin. Immunol., 99, 450–453. DeVane, C. L., Hill, M. et al. (1998). “Therapeutic drug monitoring of alprazolam in adolescents with asthma.” Ther. Drug. Monit., 20 (3), 257–260. Devereux, G., and Seaton, A. (2005). “Diet as a risk factor for atopy and asthma.” J. Allergy Clin. Immunol., 115 (6), 1109–1117; quiz 1118. Durham, S. R., Walker, S. M. et al. (1999). “Long-term clinical efficacy of grass-pollen immunotherapy.” N. Engl. J. Med., 341, 468–475.
819
Ebers, G. (1875). Das hermetische buch uber die arzneimittel der alten aegypter. Leipzig, Henrichs. Edwards, A. G., Hailey, S. et al. (2004). “Psychological interventions for women with metastatic breast cancer.” Cochrane Database Syst. Rev., 2, CD004253. Elenkov, I. J. (2004). “Glucocorticoids and the Th1/Th2 balance.” Ann. N. Y. Acad. Sci., 1024, 138–146. Elenkov, I. J., Chrousos, G. P. et al. (2000). “Neuroendocrine regulation of IL-12 and TNF-alpha/IL-10 balance. Clinical implications.” Ann. N. Y. Acad. Sci., 917, 94–105. Elenkov, I. J., Papanicolaou, D. A. et al. (1996). “Modulatory effects of glucocorticoids and catecholamines on human interleukin-12 and interleukin-10 production: clinical implications.” Proc. Assoc. Am. Physicians, 108 (5), 374–381. Ellis, J., and Undem, B. (1991). “Role of peptidoleukotrienes in capsaicin-sensitive sensory fiber-mediated responses in guinea-pig airways.” J. Physiol., 436, 469–484. Ellis, J., and Undem, B. (1994). “Phamacology of non-adrenergic, non-cholinergic nerves in airways smooth muscle.” Pulm. Pharmacol., 7, 205–223. Epstein, G. N., Halper, J. P. et al. (2004). “A pilot study of mind-body changes in adults with asthma who practice mental imagery.” Altern. Ther. Health Med., 10 (4), 66–71. Evans, C. C., Fryer, A. D. et al. (1997). “Pretreatment with anitbody to eosinophil major basic protein prevents hyperresponsiveness by protecting neuronal M2 muscarinic receptors in antigenchallenged guinea pigs.” J. Clin. Invest., 100, 2254–2262. Evans, P., Der, G. et al. (2000). “Social class, sex, and age differences in mucosal immunity in a large community sample.” Brain Behav. Immun., 14 (1), 41–48. Fineman, S. M. (2002). “The burden of allergic rhinitis: beyond dollars and cents.” Ann. Allergy Asthma Immunol., 88 (4 Suppl 1), 2–7. Finn, R. (1992). “John Bostock, hay fever and the mechanism ofallergy.” Lancet, 12, 1453–1455. Fitzgerald, L. (1991). “Overtraining increases the susceptibility to infection.” Int. J. Sports Med., 12 (Suppl 1), S5–S8. Freeman, L. W., and Welton, D. (2005). “Effects of imagery, critical thinking, and asthma education on symptoms and mood state in adult asthma patients: a pilot study.” J. Altern. Complement. Med., 11 (1), 57–68. Frieri, M. (2003). “Neuroimmunology and inflammation: implications for therapy of allergic and autoimmune diseases.” Ann. Allergy Asthma Immunol., 90 (6 Suppl 3), 34–40. Garrett, V., Brantley, P. et al. (1991). “The relationship betweeen daily stress and Crohn’s disease.” J. Behav. Med., 14, 87–96. Gauci, M., King, M. G. et al. (1993). “A Minnesota Multiphasic Personality Inventory profile of women with allergic rhinitis.” Psychosom. Med., 55 (6), 533–540. Gavin, L., Wamboldt, M. et al. (1998). “Psychological and family characteristics of adolescents with vocal cord dysfunction.” J. Asthma, 35, 409–417. Gillaspy, S. R., Hoff, A. L. et al. (2002). “Psychological distress in high-risk youth with asthma.” J. Pediatr. Psychol., 27 (4), 363– 371. Gillespie, C. F., and Nemeroff, C. B. (2005). “Hypercortisolemia and depression.” Psychosom. Med., 67 (Suppl 1), S26–S28. Glaser, R. (2005). “Stress-associated immune dysregulation and its importance for human health: a personal history of psychoneuroimmunology.” Brain Behav. Immun., 19 (1), 3–11. Glaser, R., Kiecolt-Glaser, J. K. et al. (1985). “Stress-related impairments in cellular immunity.” Psychiatry Res., 16 (3), 233–239. Glaser, R., MacCallum, R. C. et al. (2001). “Evidence for a shift in the Th-1 to Th-2 cytokine response associated with chronic stress and aging.” J. Gerontol. A. Biol. Sci. Med. Sci., 56 (8), M477–M482.
820
IV. Stress and Immunity
Glaser, R., Rice, J. et al. (1987). “Stress-related immune suppression: health implications.” Brain Behav. Immun., 1 (1), 7–20. Gleich, G. J., and Kita, H. (1997). “Bronchial asthma: lessons from murine models.” Proc. Natl. Acad. Sci. U.S.A., 94, 2101–2102. Goodwin, R. D., Fergusson, D. M. et al. (2004). “Asthma and depressive and anxiety disorders among young persons in the community.” Psychol. Med., 34 (8), 1465–1474. Graham-Bermann, S., and Seng, J. (2005). “Violence exposure and traumatic stress symptoms as additional predictors of health problems in high-risk children.” J. Pediatr., 146, 349–354. Grasemann H, Y. C., Storm Van’s Gravesande K., and Deykin, A. (2000). “A neuronal NO synthase (NOS1) gene polymorphism is associated with asthma.” Biochem. Biophys. Res. Commun., 272, 391–394. Guerra, S., Sherrill, D. L. et al. (2002). “Rhinitis as an independent risk factor for adult-onset asthma.” J. Allergy Clin. Immunol., 109 (3), 419–425. Gupta, M. A., Gupta, A. K. et al. (1994). “Depression modulates pruritus perception: a study of pruritus in psoriasis, atopic dermatitis, and chronic idiopathic urticaria.” Psychosom. Med., 56 (1), 36–40. Hahn, E., and Bacharier, L. (2005). “The atopic march: the pattern of allergic disease development in childhood.” Immunol. Allergy Clin. North Am., 25, 231–246. Hanson, B., McGue, M. et al. (1991). “Atopic disease and IgE in twins reared apart and together.” Am. J. Hum Genet., 48, 873–879. Harris, A. H., Thoresen, C. E. et al. (2005). “Does writing affect asthma? A randomized trial.” Psychosom. Med., 67 (1), 130– 136. Hawkins, G. A., Amelung, P. J. et al. (2004). “Identification of polymorphisms in the human glucocorticoid receptor gene (NR3C1) in a multi-racial asthma case and control screening panel.” DNA Seq., 15 (3), 167–173. Hawrylowicz, C. M., and O’Garra, A. (2005). “Potential role of interleukin-10-secreting regulatory T cells in allergy and asthma.” Nat. Rev. Immunol., 5 (4), 271–283. Helmert, U., and Shea, S. (1994). “Social inequalities and health status in western Germany.” Public Health, 108 (5), 341–356. Hirst, S. (2003). “Regulation of airway smooth muscle cell immunomodulatory function: role in asthma.” Respir. Physiol. Neurobiol., 137, 309–326. Hizawa, N., Yamaguchi, E. et al. (2001). “Increased total serum IgE levels in patients with asthma and promoter polymorphisms at CTLA4 and FCER1B.” J. Allergy Clin. Immunol., 108 (1), 74– 79. Holgate, S., Casale, T. et al. (2005). “The anti-inflammatory effects of omalizumab confirm the central role of IgE in allergic inflammation.” J. Allergy Clin. Immunol., 115, 459–465. Holla, A., Roy, S. et al. (2002). “Endotoxin, atopy and asthma.” Curr. Opin. Allergy Clin. Immunol., 2, 141–145. Hoppu, U., Rinne, M. et al. (2005). “Vitamin C in breast milk may reduce the risk of atopy in the infant.” Eur. J. Clin. Nutr., 59 (1), 123–128. Huntley, A., White, A. R. et al. (2002). “Relaxation therapies for asthma: a systematic review.” Thorax, 57 (2), 127–131. Huovinen, E., Kaprio, J. et al. (2001). “Asthma in relation to personality traits, life satisfaction, and stress: a prospective study among 11,000 adults.” Allergy, 56 (10), 971–977. Hurwitz, E. L., and Morgenstern, H. (1999). “Cross-sectional associations of asthma, hay fever, and other allergies with major depression and low-back pain among adults aged 20–39 years in the United States.” Am. J. Epidemiol., 150 (10), 1107–1116. Jaber, R. (2002). “Respiratory and allergic diseases: from upper respiratory tract infections to asthma.” Prim. Care, 29 (2), 231–261.
Jain, V. V., Kitagaki, K. et al. (2003). “CpG DNA and immunotherapy of allergic airway diseases.” Clin. Exp. Allergy, 33 (10), 1330– 1335. James, A. (2005). “Airway remodeling in asthma.” Curr. Opin. Pulm. Med., 11, 1–6. Jamison, J. R. (1996). “Psychoneuroendoimmunology: the biological basis of the placebo phenomenon?” J. Manipulative Physiol. Ther., 19 (7), 484–487. Joachim, R. A., Quarcoo, D. et al. (2003). “Stress enhances airway reactivity and airway inflammation in an animal model of allergic bronchial asthma.” Psychosom. Med., 65 (5), 811–815. Joachim, R. A., Sagach, V. et al. (2004). “Neurokinin-1 receptor mediates stress-exacerbated allergic airway inflammation and airway hyperresponsiveness in mice.” Psychosom. Med., 66 (4), 564–571. Johansson, S. G., Bieber, T. et al. (2004). “Rivised nomenclature for allergy for global use: Report of the Nomenclature Review Committee of the World Allergy Oranization, October 2003.” J. Allergy Clin. Immunol., 113, 832–836. Johnson, M. (1998). “The beta-adrenoceptor.” Am. J. Respir. Crit. Care Med., 158 (5 Pt 3), S146–S153. Joos, G. (2001). “The role of neuroeffector mechanisms in the pathogenesis of asthma.” Curr. Allergy Asthma Rep., 1, 134–143. Jordan, D. (2001). “Central nervous pathways and control of the airways.” Respir. Physiol., 125, 67. Kabesch, M., Tzotcheva, I. et al. (2003). “A complete screening of the IL4 gene: novel polymorphisms and their association with asthma and IgE in childhood.” J. Allergy Clin. Immunol., 112 (5), 893–898. Kajekar, R., Rhode, H. K. et al. (2001). “The integrative membrane properties of human parasympathetic ganglia neuron.” Am. J. Respir. Crit. Care Med., 164, 1927–1932. Kang, D. H., and McCarthy, D. O. (1994). “The effect of psychological stress on neutrophil superoxide release.” Res. Nurs. Health, 17 (5), 363–370. Katon, W. J., Richardson, L. et al. (2004). “The relationship of asthma and anxiety disorders.” Psychosom. Med., 66 (3), 349–355. Kiecolt-Glaser, J. K., Bane, C. et al. (2003). “Love, marriage, and divorce: newlyweds’ stress hormones foreshadow relationship changes.” J. Consult. Clin. Psychol., 71 (1), 176–188. Kiecolt-Glaser, J. K., Garner, W. et al. (1984). “Psychosocial modifiers of immunocompetence in medical students.” Psychosom. Med., 46 (1), 7–14. Kiecolt-Glaser, J. K., Page, G. G. et al. (1998). “Psychological influences on surgical recovery. Perspectives from psychoneuroimmunology.” Am. Psychol., 53 (11), 1209–1218. Kiecolt-Glaser, J. K., Preacher, K. J. et al. (2003). “Chronic stress and age-related increases in the proinflammatory cytokine IL-6.” Proc. Natl. Acad. Sci. U.S.A., 100 (15), 9090–9095. Kiecolt-Glaser, J. K., Robles, T. F. et al. (2002). “Psycho-oncology and cancer: psychoneuroimmunology and cancer.” Ann. Oncol., 13 (Suppl 4), 165–169. Kiecolt-Glaser, J. K., Stephens, R. E. et al. (1985). “Distress and DNA repair in human lymphocytes.” J. Behav. Med., 8 (4), 311–320. Kilpelainen, M., Koskenvuo, M. et al. (2002). “Stressful life events promote the manifestation of asthma and atopic diseases.” Clin. Exp. Allergy, 32 (2), 256–263. Kimata, H. (2003). “Enhancement of allergic skin wheal responses and in vitro allergen-specific IgE production by computerinduced stress in patients with atopic dermatitis.” Brain Behav. Immun., 17 (2), 134–138. Kimata, H. (2003). “Enhancement of allergic skin wheal responses in patients with atopic eczema/dermatitis syndrome by playing video games or by a frequently ringing mobile phone.” Eur. J. Clin. Invest., 33 (6), 513–517.
37. Stress and Allergic Diseases Kirkpatrick, C. (2005). “The Ishizakas and the search for reaginic antibodies.” J. Allergy Clin. Immunol., 115, 642–644. Klinnert, M. D., Nelson, H. S. et al. (2001). “Onset and persistence of childhood asthma: predictors from infancy.” Pediatrics, 108 (4), E69. Kofler, S., Nickel, T. et al. (2005). “Role of cytokines in cardiovascular diseases: a focus on endothelial responses to inflammation.” Clin. Sci. Lond., 108 (3), 205–213. Koh, Y. I., Choi, I. S. et al. (2004). “Effects of cytokine milieu secreted by BCG-treated dendritic cells on allergen-specific Th immune response.” J. Korean Med. Sci., 19 (5), 640–646. Koh, Y. Y., and Kim, C. K. (2003). “The development of asthma in patients with allergic rhinitis.” Curr. Opin. Allergy Clin. Immunol., 3 (3), 159–164. Kopnisky, K. L., Stoff, D. M. et al. (2004). Workshop report: The effects of psychological variables on the progression of HIV-1 disease. Krommydas, G., Gourgoulianis, K. I. et al. (2005). “Therapeutic value of antidepressants in asthma.” Med. Hypotheses., 64 (5), 938–940. Lakier Smith, L. (2003). “Overtraining, excessive exercise, and altered immunity: is this a T helper-1 versus T helper-2 lymphocyte response?” Sports Med., 33 (5), 347–364. Lange, P., Parner, J. et al. (1998). “A 15-year follow-up study of ventilatory function in adults with asthma.” N. Engl. J. Med., 339, 1194–1200. Langer, R. D., Criqui, M. H. et al. (1996). “IgE predicts future nonfatal myocardial infarction in men.” J. Clin. Epidemiol., 49 (2), 203–209. Lanzavecchia, A., and Sallusto, F. (2000). “Dynamics of T lymphocyte responses: intermediates, effectors, and memory cells.” Science, 290 (5489), 92–97. Lapidus, C. S. (2001). “Role of social factors in atopic dermatitis: the US perspective.” J. Am. Acad. Dermatol., 45 (Suppl 1), S41– S43. Lapidus, C. S., and Kerr, P. E. (2001). “Social impact of atopic dermatitis “ Med. Health R. I., 84, 294–295. Lebman, D. A., and Coffman, R. L. (1988). “Interleukin 4 causes isotype switching to IgE in T cell-stimulated clonal B cell cultures.” J. Exp. Med., 168 (3), 853–862. Lehrer, P., Feldman, J. et al. (2002). “Psychological aspects of asthma.” J. Consult Clin. Psychol., 70 (3), 691–711. Lehrer, P. M., Vaschillo, E. et al. (2004). “Biofeedback treatment for asthma.” Chest, 126 (2), 352–361. Leineweber, K., Buscher, R. et al. (2004). “Beta-adrenoceptor polymorphisms.” Naunyn Schmiedebergs Arch. Pharmacol., 369 (1), 1–22. Leonard, B. (2000). “Stress, depression and the activation of the immune system.” World J. Biol. Psychiatry, 1 (1), 17–25. Leung, D. Y. (2000). “Atopic dermatitis: new insights and opportunities for therapeutic intervention.” J. Allergy Clin. Immunol., 105, 860–876. Leung, D. Y., and Bieber, T. (2003). “Atopic dermatitis.” Lancet, 361, 151–160. Leung, D. Y., Jain, N. et al. (2003). “New concepts in the pathogenesis of atopic dematitis.” Curr. Opin. Immunol., 15, 634–638. Levenstein, S., Pratera, C. et al. (1994). “Psychological stress and disease activity in ulcerative colitis: a multidimensional crosssectional study.” Am. J. Gastroenterol., 89, 1219–1225. Lilly, C. M., Kobzik, L. et al. (1994). “Effects of chronic airway inflammation on the activity and enzymatic inactivation of neuropeptides in guinea pig lungs.” J. Clin. Invest., 93, 2667–2674. Lin, Y. C., Wen, H. J. et al. (2004). “Are maternal psychosocial factors associated with cord immunoglobulin E in addition to family atopic history and mother immunoglobulin E?” Clin. Exp. Allergy, 34 (4), 548–554.
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Liu, A., and Murphy, J. (2003). “Hygeine hypothesis: Fact of fiction?” J. Allergy Clin. Immunol., 111, 471–478. Liu, L. Y., Coe, C. L. et al. (2002). “School examinations enhance airway inflammation to antigen challenge.” Am. J. Respir. Crit. Care Med., 165 (8), 1062–1067. Long, L., Huntley, A. et al. (2001). “Which complementary and alternative therapies benefit which conditions? A survey of the opinions of 223 professional organizations.” Complement. Ther. Med., 9 (3), 178–185. Lonne-Rahm, S., Berg, M. et al. (2004). “Atopic dermatitis, stinging, and effects of chronic stress: a pathocausal study.” J. Am. Acad. Dermatol., 51 (6), 899–905. Lorton, D., Lubahn, C. et al. (2003). “Potential use of drugs that target neural-immune pathways in the treatment of rheumatoid arthritis and other autoimmune diseases.” Curr. Drug. Targets Inflamm. Allergy, 2 (1), 1–30. Lowy, M. T. (1991). “Corticosterone regulation of brain and lymphoid corticosteroid receptors.” J. Steroid Biochem. Mol. Biol., 39 (2), 147–154. Maier, S., and Watkins, L. R. (1998). “Cytokines for psychologists: implications of bidirectional immune-to-brain communication for understanding behavior, mood, and cognition.” Psychol. Rev., 105 (1), 83–107. Markham, A. W., and Wilkinson, J. M. (2004). “Complementary and alternative medicines (CAM) in the management of asthma: an examination of the evidence.” J. Asthma, 41 (2), 131–139. Marshall, G. D. (2004a). “Internal and external environmental influences in allergic diseases.” J. Am. Osteopath. Assoc., 104 (5 Suppl 5), S1–S6. Marshall, G. D. (2004b). “Neuroendocrine mechanisms of immune dysregulation: applications to allergy and asthma.” Ann. Allergy Asthma Immunol., 93 (2 Suppl 1), S11–S17. Marshall, G. D., Jr., and Agarwal, S. K. (2000). “Stress, immune regulation, and immunity: applications for asthma.” Allergy Asthma Proc., 21 (4), 241–246. Marshall, G. D., Jr., Agarwal, S. K. et al. (1998). “Cytokine dysregulation associated with exam stress in healthy medical students.” Brain Behav. Immun., 12 (4), 297–307. Marshall, P., O’Hara, C. et al. (2002). “Effects of seasonal allergic rhinitis on fatigue levels and mood.” Psychosom. Med., 64, 684–691. McDade, T. W. (2001). “Lifestyle incongruity, social integration, and immune function in Samoan adolescents.” Soc. Sci. Med., 53 (10), 1351–1362. McLeod TM, L.-F. A., and Lopez-Figueroa, MO. (2001). “Nitric oxide, stress, and depression.” Psychopharmacol. Bull., 35, 24– 41. Melamed, S., Shirom, A. et al. (2004). “Association of fear of terror with low grade inflammation among appparently healthy employed adults.” Psychosom. Med., 66, 484–491. Meltzer, E. O. (1997). “The prevalence and medical and economic impact of allergic rhinitis in the United States.” J. Allergy Clin. Immunol., 99, SA805–SA828. Meltzer, E. O. (2001). “Quality of life in adults and children with allergic rhinitis.” J. Allergy Clin. Immunol., 108, S45–S53. Mencia-Huerta, J. M., Paul-Eugene, N. et al. (1991). “Beta-2-adrenoceptor agonists up-regulate the in vitro Fc epsilon receptor II/ CD23 expression on, and release from, the promonocytic cell line U937 and human blood monocytes.” Int. Arch. Allergy Appl. Immunol., 94 (1–4), 91–92. Michel, F. B. (1994). “Psychology of the allergic patient.” Allergy, 49 (18 Suppl), 28–30. Milgrom, H., Bender, B. et al. (1996). “Noncompliance and treatment failure in children with asthma.” J. Allergy Clin. Immunol., 98, 1051–1057.
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Miller, A. L. (2001). “The etiologies, pathophysiology, and alternative/complementary treatment of asthma.” Altern. Med. Rev., 6 (1), 20–47. Miura, M., Yamauchi, H. et al. (1997). “Impairment of neural nitric oxide-mediated relaxation after antigen exposure in guinea pigs airways in vitro.” Am. J. Crit. Care Med., 156, 217–222. Mojtabhai, R. (2005). “Parental psychopathology and childhood atopic disorders in the community.” Psychosom. Med., 67, 448–453. Muntner, S. E. (1963). The medical writings of Moses Maimonides: treatise on asthma. Philadelphia, JB Lippincott. Mustafa, A. S., and Oftung, F. (1995). “Cytokine production and cytotoxicity mediated by CD4+ T cells from healthy subjects vaccinated with Mycobacterium bovis BCG and from pulmonary tuberculosis patients.” Nutrition, 11 (Suppl 5), 698–701. Myers, A. (2001). “Transmission in autonomic ganglia.” Respir. Physiol., 125, 99–111. Nelson, H. S. (2005). “Advances in upper airway diseases and allergen immunotherapy.” J. Allergy Clin. Immunol., 115 (4), 676–684. Ngoc, L. P., Gold, D. R. et al. (2005). “Cytokines, allergy, and asthma.” Curr. Opin. Allergy Clin. Immunol., 5 (2), 161–166. Nieman, D. C. (2000). “Special feature for the Olympics: effects of exercise on the immune system: exercise effects on systemic immunity.” Immunol. Cell Biol., 78 (5), 496–501. Noon, L. (1911). “Prophylactic innoculation against hay fever.” Lancet, 1, 1572–1573. Noverr, M. C., Noggle, R. M. et al. (2004). “Role of antibiotics and fungal microbiota in driving pulmonary allergic responses.” Infect. Immun., 72 (9), 4996–5003. O’Garra, A., and Vieira, P. (2004). “Regulatory T cells and mechanisms of immune system control.” Nat. Med., 10 (8), 801– 805. O’Leary, A. (1990). “Stress, emotion, and human immune function.” Psychol. Bull., 108 (3), 363–382. Oh, Y. M., Kim, Y. S. et al. (2004). “Association between stress and asthma symptoms: a population-based study.” Respirology, 9 (3), 363–368. Ostlere, L., Cowen, T. et al. (1995). “Neuropeptides in the skin of patients with atopic dermatitis.” Clin. Exp. Dermatol., 20, 462–467. Ostroukhova, M., and Ray, A. (2005). “CD25+ T cells and regulation of allergen-induced responses.” Curr. Allergy Asthma Rep., 5 (1), 35–41. Papiris, S., Kotanidou, A. et al. (2002). “Clinical review: severe asthma.” Crit. Care, 6 (1), 30–44. Parkhurst, M. R., Riley, J. P. et al. (2004). “Induction of CD4+ Th1 lymphocytes that recognize known and novel class II MHC restricted epitopes from the melanoma antigen gp100 by stimulation with recombinant protein.” J. Immunother., 27 (2), 79–91. Parronchi, P., De Carli, M. et al. (1992). “IL-4 and IFN (alpha and gamma) exert opposite regulatory effects on the development of cytolytic potential by Th1 or Th2 human T cell clones.” J. Immunol., 149 (9), 2977–2983. Paul-Eugene, N., Dugas, B. et al. (1993). “Beta 2-adrenoceptor stimulation augments the IL-4-induced CD23 expression and release and the expression of differentiation markers (CD14, CD18) by the human monocytic cell line, U 937.” Clin. Exp. Allergy, 23 (4), 317–325. Pedersen, B. K., Rohde, T. et al. (1996). “Immunity in athletes.” J. Sports Med. Phys. Fitness, 36 (4), 236–245. Peroni, D. G., Piacentini, G. L. et al. (2003). “Rhinitis in pre-school children: prevalence, association with allergic diseases and risk factors.” Clin. Exp. Allergy, 33 (10), 1349–1354.
Preynat-Seauve, O., Coudurier, S. et al. (2003). “Oxidative stress impairs intracellular events involved in antigen processing and presentation to T cells.” Cell Stress Chaperones, 8 (2), 162–171. Pruessner, J. C., Hellhammer, D. H. et al. (1999). “Burnout, perceived stress, and cortisol responses to awakening.” Psychosom. Med., 61 (2), 197–204. Pyne, D. B., and Gleeson, M. (1998). “Effects of intensive exercise training on immunity in athletes.” Int. J. Sports Med., 19 (Suppl 3), S183–S191; discussion S191–S194. Ray, O. (2004). “The revolutionary health science of psychoendoneuroimmunology: a new paradigm for understanding health and treating illness.” Ann. N. Y. Acad. Sci., 1032, 35–51. Reiche, E. M., Nunes, S. O. et al. (2004). “Stress, depression, the immune system, and cancer.” Lancet Oncol., 5 (10), 617–625. Reichlin, S. (1993). “Neuroendocrine-immune interactions.” N. Engl. J. Med., 329 (17), 1246–1253. Riccio, M., and Proud, D. (1996). “Evidence that enhanced nasal reactivity to bradykinin in patients with symptomatic allergy is mediated by neural reflexes.” J. Allergy Clin. Immunol., 97, 1252– 1263. Riley, J., and West, G. B. (1953). “Histamine and tissue mast cells.” J. Physiology, 120 (120), 528. Ritter, S. Y., and Marshall, G. D. (2004). “Immunomodulation by Vitamin C in an Exam Stress Model.” FASEB J., 18, A457. Ritz, T., Steptoe, A. et al. (2000). “Emotions and stress increase respiratory resistance in asthma.” Psychosom. Med., 62 (3), 401– 412. Robson, N. C., Beacock-Sharp, H. et al. (2003). “The role of antigenpresenting cells and interleukin-12 in the priming of antigenspecific CD4+ T cells by immune stimulating complexes.” Immunology, 110 (1), 95–104. Roder, I., Kroonenberg, P. M. et al. (2003). “Psychosocial functioning and stress-processing of children with asthma in the school context: differences and similarities with children without asthma.” J. Asthma, 40 (7), 777–787. Rohleder, N., Wolf, J. M. et al. (2003). “Glucocorticoid sensitivity in humans—interindividual differences and acute stress effects.” Stress, 6 (3), 207–222. Romagnani, P., Annunziato, F. et al. (2000). “Th1/Th2 cells, their associated molecules and role in pathophysiology.” Eur. Cytokine Netw., 11 (3), 510–511. Romagnani, S. (1995). “Biology of human TH1 and TH2 cells.” J. Clin. Immunol., 15 (3), 121–129. Romagnani, S. (2000). “T-cell subsets (Th1 versus Th2).” Ann. Allergy Asthma Immunol., 85 (1), 9–18; quiz 18, 21. Romagnani, S. (2004). “The increased prevalence of allergy and the hygiene hypothesis: missing immune deviation, reduced immune suppression, or both?” Immunology, 112 (3), 352–363. Romagnani, S., Maggi, E. et al. (1991). “Increased numbers of Th2like CD4+ T cells in target organs and in the allergen-specific repertoire of allergic patients. Possible role of IL-4 produced by non-T cells.” Int. Arch. Allergy Appl. Immunol., 94 (1–4), 133–136. Rook, G. A., Adams, V. et al. (2004). “Mycobacteria and other environmental organisms as immunomodulators for immunoregulatory disorders.” Springer Semin. Immunopathol., 25 (3–4), 237–255. Rossi, E. L. (2002). “Psychosocial genomics: gene expression, neurogenesis, and human experience in mind-body medicine.” Adv. Mind Body Med., 18 (2), 22–30. Sakaguchi, S. (2004). “Naturally Arising CD4+ Regulatory T Cells for Immunologic Self-Tolerance and Negative Control of Immune Responses.” Annual Review of Immunology, 22 (1), 531–562. Sandberg, S., Jarvenpaa, S. et al. (2004). “Asthma exacerbations in children immediately following stressful life events: a Cox’s hierarchical regression.” Thorax, 59 (12), 1046–1051.
37. Stress and Allergic Diseases Sandberg, S., Paton, J. Y. et al. (2000). “The role of acute and chronic stress in asthma attacks in children.” Lancet, 356 (9234), 982–987. Satterwhite, B. B. (1978). “Impact of chronic illness on child and family: an overview based on five surveys with implications for management.” Int. J. Rehabil. Res., 1 (1), 7–17. Schatz, M., Cook, E. et al. (2003). “Risk factors for asthma hospitalizations in a managed care organization: development of a clinical prediction rule.” Am. J. Manag. Care, 9, 538–547. Schleimer, R. P., Spahn, J. D. et al. (2003). Glucocorticoids. Philadelphia, Mosby. Schmidt-Weber, C. B., and Blaser, K. (2004). “Immunological mechanisms in specific immunotherapy.” Springer Semin. Immunopathol., 25 (3–4), 377–390. Settipane, G. A., Pudupakkam, R. K. et al. (1978). “Corticosteroid effect on immunoglobulins.” J. Allergy Clin. Immunol., 62 (3), 162–166. Sheahan, P., Walsh, R. M. et al. (2005). “Induction of nasal hyperresponsiveness by allergen challenge in allergic rhinitis: the role of afferent and efferent nerves.” Clin. Exp. Allergy, 35, 45–51. Shephard, R. J., and Shek, P. N. (1998). “Acute and chronic over-exertion: do depressed immune responses provide useful markers?” Int. J. Sports Med., 19 (3), 159–171. Sheridan, J., Dobbs, C. et al. (1994). “Psychoneuroimmunology: stress effects on pathogenesis and immunity during infection.” Clin. Microbiol. Rev., 7, 200–212. Sheridan, J. F., Dobbs, C. et al. (1998). “Stress-induced neuroendocrine modulation of viral pathogenesis and immunity.” Ann. N. Y. Acad. Sci., 840, 803–808. Sicherer, S., and Sampson, H. (1999). “Food hypersensitivity and atopic dermatitis: pathophysiology, epidemiology, diagnosis and management.” J. Allergy Clin. Immunol., 104, S114–S122. Simpson, C. R., Anderson, W. J. et al. (2002). “Coincidence of immune-mediated diseases driven by Th1 and Th2 subsets suggests a common aetiology. A population-based study using computerized general practice data.” Clin. Exp. Allergy, 32 (1), 37–42. Smith, E., Mahony, N. et al. (2002). “Prevalence of obstructive airflow limitation in Irish collegiate athletes.” Ir. J. Med. Sci., 171 (4), 202–205. Smyth, J. M., Stone, A. A. et al. (1999). “Effects of writing about stressful experiences on symptom reduction in patients with asthma or rheumatoid arthritis: a randomized trial.” JAMA, 281 (14), 1304–1309. Solomon, G. F., Amkraut, A. A. et al. (1974). “Immunity, emotions and stress. With special reference to the mechanisms of stress effects on the immune system.” Ann. Clin. Res., 6 (6), 313–322. Song, Z., Casolaro, V. et al. (1996). “Polymorphic nucleotides within the human IL-4 promoter that mediate overexpression of the gene.” J. Immunol., 156 (2), 424–429. Sperber, J., Shaw, J. et al. (1989). “Psychological components and the role of adjunct interventions in chronic idiopathic urticaria.” Psychother. Psychosom., 51 (3), 135–141. Spurgeon, A., Gompertz, D. et al. (1997). “Non-specific symptoms in response to hazard exposure in the workplace.” J. Psychosom. Res., 43 (1), 43–49. Stauder, A., and Kovacs, M. (2003). “Anxiety symptoms in allergic patients: identification and risk factors.” Psychosom. Med., 65 (5), 816–823. Stratakis, C. A., and Chrousos, G. P. (1995). “Neuroendocrinology and pathophysiology of the stress system.” Ann. N. Y. Acad. Sci., 771, 1–18. Strine, T. W., Ford, E. S. et al. (2004). “Risk behaviors and healthrelated quality of life among adults with asthma: the role of mental health status.” Chest., 126 (6), 1849–1854.
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Thomas, M., Kocevar, V. S. et al. (2005). “Asthma-related health care resource use among asthmatic children with and without concomitant allergic rhinitis.” Pediatrics, 115 (1), 129–134. Togias, A. (2003). “Rhinitis and asthma: evidence for respiratory system integration.” J. Allergy Clin. Immunol., 111 (6), 1171–1183; quiz 1184. Trinchieri, G., Wysocka, M. et al. (1992). “Natural killer cell stimulatory factor (NKSF) or interleukin-12 is a key regulator of immune response and inflammation.” Prog. Growth Factor Res., 4 (4), 355–368. Trzonkowski, P., Szmit, E. et al. (2004). “CD4+CD25+ T regulatory cells inhibit cytotoxic activity of T CD8+ and NK lymphocytes in the direct cell-to-cell interaction.” Clinical Immunology, 112 (3), 258–267. Uchakin, P. N., Tobin, B. et al. (2001). “Immune responsiveness following academic stress in first-year medical students.” J. Interferon Cytokine Res., 21 (9), 687–694. Upham, J. W., and Holt, P. G. (2005). “Environment and development of atopy.” Curr. Opin. Allergy Clin. Immunol., 5 (2), 167– 172. Vizi, E. S., and Elenkov, I. J. (2002). “Nonsynaptic noradrenaline release in neuro-immune responses.” Acta Biol. Hung., 53 (1–2), 229–244. Von Ehrenstein, O. S., Von Mutius, E. et al. (2000). “Reduced risk of hay fever and asthma among children of farmers.” Clin. Exp. Allergy, 30 (2), 187–193. Von Herrath, M. G., and Harrison, L. C. (2003). “Antigen-induced regulatory T cells in autoimmunity.” Nat. Rev. Immunol., 3 (3), 223–232. Wainwright, C., Isles, A. et al. (1997). “Asthma in children.” Medical Journal of Australia Practice Essentials, 167, 218–223. Wakikawa, A., Utsuyama, M. et al. (1999). “Vitamin E enhances the immune functions of young but not old mice under restraint stress.” Exp. Gerontol., 34 (7), 853–862. Wamboldt, M. Z., Laudenslager, M. et al. (2003). “Adolescents with atopic disorders have an attenuated cortisol response to laboratory stress.” J. Allergy Clin. Immunol., 111 (3), 509–514. Wang, D. Y., Goh, D. Y. et al. (2003). “The upper and lower airway reponses to nasal challenge with house dust mite Blomia tropicalis.” Allergy, 58, 78–82. Warner, L. J., Lumley, M. A. et al. (2005). “Health Effects of Written Emotional Disclosure in Adolescents with Asthma: A Randomized, Controlled Trial.” J. Pediatr. Psychol. Watkins, A. D. (1995). “Perceptions, emotions and immunity: an integrated homeostatic network.” QJM, 88 (4), 283–294. Weil, C. M., Wade, S. L. et al. (1999). “The relationship between psychosocial factors and asthma morbidity in inner-city children with asthma.” Pediatrics, 104 (6), 1274–1280. Wellen, K., and Hotamisligil, G. (2005). “Inflammation, stress and diabetes.” J. Clin. Invest., 115, 1111–1119. Weltman, J. K., and Karim, A. S. (2000). “IL-5: biology and potential therapeutic applications.” Expert Opin. Investig. Drugs, 9 (3), 491–496. Wenzel, S. E. (2004). “Phenotypes in asthma useful guides to therapy, distinct biological processes or both.” Am. J. Respir. Crit. Care Med., 170, 579–580. Williams, H., Robertson, C. et al. (1999). “Worldwide variations in the prevalence of symptoms of atopic eczema in the International Study of Asthma and Allergies in Childhood.” J. Allergy Clin. Immunol., 103, 125–138. Williams, H. C. (2005). “Clinical practice. Atopic dermatitis.” N. Engl. J. Med., 352 (22), 2314–2324. Williams LK, O. D., Maliarik M. J., and Johnson, C. C. (2005). “The role of endotoxin and its receptors in allergic disease.” Ann. Allergy Asthma Immunol., 94, 323–332.
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IV. Stress and Immunity
Wills-Karp, M. (2000). “Murine models of asthma in understanding immune dysregulation in human asthma.” Immunopharmacology, 48, 263–268. Wilson, M. E., Megel, M. E. et al. (2003). “Physiologic and behavioral responses to stress, temperament, and incidence of infection and atopic disorders in the first year of life: a pilot study.” J. Pediatr. Nurs., 18 (4), 257–266. Wjst, M., Kruse, S. et al. (2002). “Asthma and IL-4 receptor alpha gene variants.” Eur. J. Immunogenet., 29 (3), 263–268. Woitsch, B., Carr, D. et al. (2004). “A comprehensive analysis of interleukin-4 receptor polymorphisms and their association with atopy and IgE regulation in childhood.” Int. Arch. Allergy Immunol., 135 (4), 319–324. Wright, R. J. (2004). “Alternative modalities for asthma that reduce stress and modify mood states: evidence for underlying psychobiologic mechanisms.” Ann. Allergy Asthma Immunol., 93 (2 Suppl 1), S18–S23. Wright, R. J., Cohen, R. T. et al. (2005). “The impact of stress on the development and expression of atopy.” Curr. Opin. Allergy Clin. Immunol., 5 (1), 23–29. Wright, R. J., Finn, P. et al. (2004). “Chronic caregiver stress and IgE expression, allergen-induced proliferation, and cytokine profiles in a birth cohort predisposed to atopy.” J. Allergy Clin. Immunol., 113 (6), 1051–1057.
Wright, R. J., and Steinbach, S. F. (2001). “Violence: an unrecognized environmental exposure that may contribute to greater asthma morbidity in high risk inner-city populations.” Environ. Health Perspect., 109 (10), 1085–1089. Wu, C., Sarfati, M. et al. (1991). “Glucocorticoids increase the synthesis of immunoglobulin E by interleukin 4-stimulated human lymphocytes.” Journal of Clinical Investigation, 87, 870– 877. Wu, Y. P., de Groot, P. G. et al. (1997). “Shear-stress-induced detachment of blood platelets from various surfaces.” Arterioscler. Thromb. Vasc. Biol., 17 (11), 3202–3207. Wust, S., Van Rossum, E. F. et al. (2004). “Common polymorphisms in the glucocorticoid receptor gene are associated with adrenocortical responses to psychosocial stress.” J. Clin. Endocrinol. Metab., 89 (2), 565–573. Yang, E. V., and Glaser, R. (2002). “Stress-induced immunomodulation and the implications for health.” Int. Immunopharmacol., 2 (2–3), 315–324. Zhu, S., Chan-Yeung, M. et al. (2000). “Polymorphisms of the IL-4, TNF-α, and Fc-ε RI-β genes and the risk of allergic disorders in at-risk infants.” Am. J. Respir. Crit. Care Med., 161 (5), 1655–1659. Zieg, G., Lack, G. et al. (1994). “In vivo effects of glucocorticoids on IgE production.” J. Allergy Clin. Immunol., 94 (2 Pt 1), 222–230.
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38 Stress, Neuroendocrine Hormones, and Wound Healing: Human Models PHILLIP T. MARUCHA AND CHRISTOPHER G. ENGELAND
I. OVERVIEW 825 II. STRESS AND NEUROENDOCRINE ACTIVATION 825 III. EFFECT OF GLUCOCORTICOIDS ON WOUND HEALING 826 IV. EFFECTS OF CATECHOLAMINES ON WOUND HEALING 826 V. STRESS AND WOUND HEALING 827 VI. STRESS, PHAGOCYTE FUNCTION, AND MICROBIAL INFECTION 828 VII. ROLE OF SEX HORMONES ON WOUND HEALING 828 VIII. GENDER DIFFERENCES IN WOUND HEALING 830 IX. THE HEALING OF DERMAL VERSUS MUCOSAL WOUNDS 830 X. WOUND HEALING IN THE AGED 831 XI. SUMMARY AND FUTURE DIRECTIONS 832
“perfection” of wound healing is essential. In this chapter, the impact of neuroendocrine factors on wound healing will be reviewed. A central focus will be the role of stress and neuroendocrine factors released in response to stress in humans. Aging and gender effects will also be addressed. The basic biology of wound repair is presented elsewhere in this text and will not be reviewed here in detail. Instead, this chapter will focus upon the neuroendocrine pathways and how they may impact clinical outcomes such as wound closure, infection, and potential interventions. Stress could affect wound healing through a number of pathways: (1) stress-induced hormones are immunosuppressive, which could reduce the expression of pro-inflammatory cytokines and growth factors required for healing; (2) stress hormones and activation of the sympathetic nervous system could reduce blood flow to the wound site, which would impede the delivery of oxygen, cells, and nutrients to the site; (3) stress could alter health behaviors including compliance to post-operative care; (4) stress could increase the perception of pain and, therefore, increase required pain medication post-operatively; and (5) through a combination of the mechanisms above, stress could increase the rate of infection, which in itself delays healing.
I. OVERVIEW Wound healing is the process of re-establishing the normal structure and function of a tissue after injury. Abnormal healing can result in increased rates of infection, scarring, altered integrity of the injured tissue, and impaired function. Impaired healing occurs commonly in the United States, and its treatment costs U.S. Health Services more than $9 billion per year (Ashcroft and Mills, 2002). Much of this cost has been associated with delays in wound closure, which in turn relate to higher rates of infection and medical complications. With an aging population and increases in the number of remedial and elective surgeries, the PSYCHONEUROIMMUNOLOGY, 4E VOLUME II
II. STRESS AND NEUROENDOCRINE ACTIVATION Many of the somatic effects of stress are mediated by two major neuroendocrine systems: the
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sympathetic nervous system (SNS) and the hypothalamic-pituitary-adrenal (HPA) axis. Activation of the SNS results in the production of catecholamines. Activation of the HPA axis results in production of glucocorticoids (GCs) and epinephrine. Stress disrupts the normal circadian rhythms of GC production throughout the day. When stress is perceived by the integrative cortex, it causes a release of corticotropinreleasing factor, which induces the anterior pituitary to secrete adrenocorticotropic hormone (ACTH). ACTH then acts on the adrenals to produce GCs. GCs act as hormones to reduce inflammation and also feed back to the hypothalamus to inhibit the production of CRF. Immune cells have GC receptors, and thus, GCs have effects on all immune cells. As a result, GCs have been extensively studied for their anti-inflammatory as well as immunosuppressive actions, whereas much less is known about catecholamine effects on immune cells.
III. EFFECT OF GLUCOCORTICOIDS ON WOUND HEALING It is the potent anti-inflammatory effects of GCs that account for their inhibitory effect on wound healing. After administration of exogenous GCs, neutrophil (Clark et al., 1979) and monocyte (Norris et al., 1982) recruitment is decreased, and macrophage phagocytosis and bacterial killing are suppressed (Fauci et al., 1976). This results in delayed wound debridement, including foreign body and bacterial elimination. In the epidermis, keratinocyte proliferation is inhibited (Edwards and Dunphy, 1958) producing a thinned, abnormal epidermis. Wound strength is impaired, as well as epithelialization and closure of open wounds. Brauchle et al. (1995) found a dramatically delayed re-epithelialization in histological wound sections of dexamethasone-treated mice and impaired induction of epidermal keratinocyte growth factor (KGF) mRNA after injury. Chedid et al. (1996) showed that addition of dexamethasone significantly reduces the level of constitutively produced KGF mRNA, protein, and bioactivity in medium from human dermal fibroblasts. These results suggest that downregulation of KGF expression by GCs may be due to a direct effect on mesenchymal cells. However, it may also be explained by an inhibition of KGF-inducing factors in the wound, such as IL-1 and TNF, which are known to be downregulated by GCs. Indeed, addition of TNF-α or IL-1β to dexamethasone-treated fibroblasts reversed the inhibitory effect of GCs on KGF expression. Furthermore, Hubner et al. (1996) demonstrated that GCtreatment of mice reduced induction of IL-1α, IL-1β,
and TNF-α mRNA and protein after injury. This was associated with a reduced infiltration of inflammatory cells, delayed wound re-epithelialization, and impaired granulation tissue formation. Therefore, elevated levels of exogenous GCs can dysregulate the profile of proinflammatory cytokines and growth factors that interact locally for a rapid and effective restoration of skin integrity.
IV. EFFECTS OF CATECHOLAMINES ON WOUND HEALING Stress-induced activation of the sympathetic nervous system results in the release of potent hormones such as catecholamines, which can alter cell function and blood flow. Catecholamines are known for their contribution to local tissue edema, increasing endothelial cell wall adhesion (Koopman, 1995). Catecholamines have also been shown to have an inhibitory effect on epidermal cell migration (Donaldson and Mahan, 1984). This suggests that increased levels of catecholamines at the wound site, either arising from the peripheral circulation or released from local sympathetic nerve endings, may impact upon wound-healing processes by increasing edema and retarding reepithelialization. Stress-induced catecholamines can also have potent effects on peripheral blood flow. For example, psychological stress has been associated with impaired vascular function in Raynaud’s phenomenon (O’Connor, 2001). The sympathetic alpha-adrenergic receptors predominate in the skin, and their activation evokes a potent vaso-constrictive response (Ahlquist, 1976). The peripheral vasoconstriction restricts oxygen delivery to the healing tissues. Alpha 1A and alpha 1D adrenergic receptors are predominantly found on the vasculature, with the former seen on the smaller vasculature, while the latter is seen on the larger blood vessels like the aortic, iliac, and femoral arteries. Moreover, norepinephrine binding to the beta-adrenergic receptor increases C-AMP levels. An increase in C-AMP is associated with decreased pro-inflammatory cytokines (Sanders and Straub, 2002). Cell signaling through the alpha-adrenergic receptors activates PLC and PLA2. This results in an increase of intracellular calcium. These receptors also activate calcium influx through voltage-gated calcium channels (Piascik and Perez, 2001). The increase in calcium results in smooth muscle contraction. Catecholamine-mediated vasoconstriction is mediated by this increase in cytosolic calcium. Increase in calcium binds to calmodulin to cause changes in calmodulin structure. This activates the myosin light chain kinase and, therefore, increases the
38. Stress, Neuroendocrine Hormones, and Wound Healing: Human Models
tone in the smooth muscle cells (Salomonsson et al., 2001). Vasoconstriction, as a result of the activation of the SNS, may have profound effects on wound healing by altering the delivery of oxygen. Oxygen available to the cells of a healing wound has been shown to play a significant role in several aspects of the tissue repair process (Whitney, 1989). Several decades ago, it was very difficult for the scientific community to accept that any component of the healing process could be greatly varied by merely changing the oxygen supply to the wound (Hunt and Pai, 1972). Continuing research in the field showed that oxygen tension does significantly influence revascularization and epithelialization in wounds in a variety of animal models (Pai and Hunt, 1972). Oxygen influences a plethora of healing processes including collagen synthesis, angiogenesis, epithelialization, and metabolic reactions for leukocyte bactericidal action (Whitney, 1989). In a study by Knighton et al. (1981), during neovascularization in healing tissue, greater capillary density was observed with greater concentrations of oxygen. Patients showed significantly lower tissue pO2 in surgical wounds when compared to non-operated control tissue through the first 5 days after surgery. Overall, the disruption of blood supply and the accumulation of a large population of oxygen-consuming cells in the wound make the availability of oxygen a vital requisite for physiologic healing (Chang et al., 1983). Decreased oxygen in wounds has been shown to predict wound infection in surgical patients (Hopf et al., 1997) and also in animal models (Jonsson et al., 1988). Infusion of epinephrine decreases wound oxygen by around 45% (Jensen et al., 1985). Discontinuation of epinephrine perfusion resulted in rebound of oxygen levels in the wounds. Furthermore, England et al. (1983) has shown that local injection of epinephrine during vaginal hysterectomies has been associated with increased rates of infections in patients. Therefore, catecholamines released during stress appear to mediate vascular changes that play a key role in the dysregulation of oxygenation and ultimately wound infection.
V. STRESS AND WOUND HEALING Psychological stress has been shown to impair human wound healing in a number of well-controlled studies. Kiecolt-Glaser, Marucha et al. (1995) placed 3.5 mm punch biopsy experimental wounds on the arms of 13 chronically stressed Alzheimer caregivers and 13 well-matched controls to study dermal wound healing. Chronically stressed Alzheimer caregivers took an average of 9 days more than controls (over a
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4–7 week period), or 24% longer to heal standardized wounds. Group differences in wound size appeared within the first week of healing, reaching statistical significance within the second week. Furthermore, the ability to mount an inflammatory response was tested using an ex vivo endotoxin-stimulated IL-1β gene expression assay in whole blood. Alzheimer caregivers produced significantly less IL-1β than controls. These results suggest that stress begins to have an impact in the early phases of wound repair, specifically the inflammatory phase, resulting in delayed wound closure. In an oral wound model, with wounds placed 3 days before examinations, dental students healed an average of 40% slower than wounds made in the same students during summer vacation, and the differences were quite reliable. No student healed as rapidly during examinations as during vacation (Marucha et al., 1998). These data show that something as transient, predictable, and relatively benign as examination stress may have significant consequences for wound healing, even in young adults. A third experimental study used a cross-sectional approach to further generalize the effects of stress on healing. Ebrecht et al. (2003) demonstrated that perceived stress and cortisol predicted the rate of healing in a cross-sectional study of healthy young males. The subjects had 4 mm punch biopsies placed and healing was assessed using a novel ultrasound scanning method. Salivary cortisol was measured 2 weeks prior, directly after, and 2 weeks after wounding. A strong negative correlation (r = −.59) was found between the Perceived Stress Score (Cohen, 1988) and wound closure. Furthermore, when a median split was done between slow healers and fast healers, slow healers had significantly higher stress levels, lower trait optimism, and higher cortisol during awakening. This study further confirms links among stress, stress hormones known to suppress the inflammatory response, and impaired healing. All three of these studies used experimental wounds, and great care was taken to account for potential confounding effects, e.g., alterations in health behaviors or compliance with post-operative care. Furthermore, the wounds were small, and pain was not a likely confound. In fact, in the first two studies, no significant pain was reported by the subjects. Therefore, these studies indicate a strong effect of stressors activating neuroendocrine pathways that impact on physiologic outcomes. Several studies have investigated the role of stress in altering cytokines in wound fluids. Glaser et al. (1999) used an experimental blister model to investigate the role of stress in the development of an inflammatory exudate in wounded skin. They found that women with higher perceived stress scores had lower
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levels of IL-1α and IL-8 in the experimental blisters 5 hours after blister induction. After 24 hours, subjects with lower levels of both cytokines reported more stress and negative affect at the wound sites. They also had higher levels of salivary cortisol compared to those subjects that had high levels of the cytokines. Broadbent et al. (2003) investigated the role of pre-operative stress on IL-1 and MMP-9 in wound fluid from 36 inguinal surgery patients. Both IL-1 and MMP-9 were negatively correlated with stress; i.e., stress was again associated with decreased cytokine and inflammatory protease production in early wounds, suggesting immunosuppression. This is consistent with human and animal experimental studies suggesting links among stress, immunosuppressive hormones, proinflammatory cytokine responses, and impaired healing. Since stress impairs wound healing, an essential issue is whether interventions that reduce stress also ameliorate wound healing. Devine (1992) used a meta analysis to show that a variety of interventions, including providing education to the patient, can reduce anxiety and stress to patients, ultimately leading to reduced pain and hospital stays. In a recent study, Holden-Lund (1998) showed that patients undergoing cholecystectomy and utilizing Relaxation with Guided Imagery had lower state anxiety, lower urinary cortisol, and less wound erythema as compared to randomly selected controls. Field et al. (1998) also demonstrated that burn patients undergoing debridement and receiving massage therapy had decreased anxiety, pain, depression, and cortisol. Two biological interventions have been used in a murine model of stress-impaired healing. Blockade of the GC pathway with RU486 (Padgett et al., 1998) restores wound closure to near control levels, but only partially restores microbial clearance. Hyperbaric oxygen therapy (Gajendrareddy et al., 2005) also ameliorates wound closure, suggesting oxygen as an important mediator of stress-impaired healing. Interventions have the potential for a high impact on surgical outcomes, and additional research on effective interventions are warranted.
VI. STRESS, PHAGOCYTE FUNCTION, AND MICROBIAL INFECTION Wounds, regardless of their origin, are colonized by bacteria (Bikowsky, 1999; Robson, 1997). Infected wounds heal slower and have an increased incidence of scarring (Robson, 1997). Infected wounds can lead to systemic infection and mortality. Therefore, if the mechanisms of antibacterial protection are compro-
mised, infection and tissue damage increase and healing rates decrease. Neutrophils and macrophages provide primary defense against microbial infection. The process of phagocyte recruitment can be altered at several levels, and disruption of neuroendocrine homeostasis by psychological stress can lead to critical alterations of the leukocyte-endothelial interactions at the molecular level. Glucocorticoids inhibit the production of pro-inflammatory cytokines and chemokines that are essential for the activation of both leukocytes and endothelial cells (Almawi et al., 1996), leading to altered surface expression of adhesion molecules and their ligands. Stress has been shown to modulate the effectiveness of the immune response. Stress can impact the immune system by impairing macrophage and neutrophil activities. Impairment of the phagocytic activity of macrophages interferes with the efficient clearance of bacteria and cellular debris (Okimura, 1986; Palermo-Neto, 2003). Mice subjected to repeated restraint-stress exhibit a 2- to 5-log increase of opportunistic bacteria (e.g., Staphylococcus aureus) in a punch-biopsy wound despite an excessive recruitment of neutrophils, suggesting that the antimicrobial activity of these neutrophils is impaired (Rojas et al., 2002). When mice were treated with the glucocorticoid blocker, RU486, there was only a partial restoration of microbial clearance. These findings suggest a second mechanistic pathway is involved in stress-impaired wound healing. Since oxygen and its metabolites play an essential role in microbial clearance, the sympathetic nervous system is a likely candidate.
VII. ROLE OF SEX HORMONES ON WOUND HEALING A sexual dimorphism in immune functioning exists. Compared to males, females typically exhibit enhanced functioning of both arms of immunity (Giglio et al., 1994; Miller and Hunt, 1996; Schuurs and Verheul, 1990; Zuk and McKean, 1996), have higher levels of circulating antibodies (Giglio et al., 1994; Miller et al., 1996), and have a greater ability to overcome bacterial infection (Engeland et al., 2003; Krzych et al., 1981; Miller et al., 1996). This dimorphism has primarily been attributed to differences in the levels of circulating sex hormones (Gaillard and Spinedi, 1998; Lahita, 2000). Both estrogen and androgen receptors are found on a large number of immune cells critical to the healing process (Ashcroft and Ashworth, 2003; Gilliver et al., 2003). Estrogen receptors are found on macrophages, fibroblasts, and endothelial and epidermal cells (Ashcroft and Ashworth, 2003). Moreover, estrogens
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have been shown to modulate IL-1 synthesis by macrophages, the expression of platelet-derived growth factor (PDGF) by monocytes and macrophages, and neutrophil chemotaxis to the wound site (Ashcroft and Ashworth, 2003). Estrogens appear beneficial to wound healing, and studies of specific oral diseases, such as gingivitis, have found that inflammatory levels are inversely correlated to levels of circulating estrogen (Ashcroft et al., 1999). In dermal wounds, estrogens decrease inflammation, increase matrix deposition, increase the rate of epithelialization (through mitogenic effects on keratinocytes), stimulate angiogenesis, regulate proteolysis, and increase the oxidative metabolism of neutrophils, thereby increasing phagocytosis (Ashcroft et al., 2003b; Ashcroft and Ashworth, 2003; Mascarenhas et al., 2003). All of these events promote faster wound reepithelialization and healing. Most of the studies concerning sex hormones and wound healing have focused on the effects of estrogens in relation to menopause. During menopause, skin becomes reduced in thickness, primarily due to collagen loss, and capillary blood flow is decreased (Ashcroft et al., 1997a; Ashcroft et al., 2003b; Ashcroft and Ashworth, 2003; Raine-Fenning et al., 2003). This reduces both the elasticity and the strength of the skin. Dermal wounds in post-menopausal women are characterized with excessive inflammation, increases in neutrophil influx and protease production, decreased phagocytosis (Ashcroft and Ashworth, 2003), and delayed healing (Ashcroft et al., 1997a), characterized by reduced collagen content and slower re-epithelialization (Ashcroft et al., 1997a). The duration of estrogen deficiency is also important. Matrix deposition and wound contraction are both reduced following estrogen deficiency, but only after 1 and 4 months, respectively (Ashcroft et al., 1997a; Calvin et al., 1998). Hormone replacement therapy for as little as 3 months reverses all of the above changes (Ashcroft and Ashworth, 2003), indicating that female sex hormones play a key role in dermal wound healing. In animal studies, ovariectomized mice healed dermal wounds slower than controls, and their wound healing deficits were qualitatively similar to those described above in post-menopausal women (Ashcroft and Ashworth, 2003). This healing delay was associated with greater inflammation, as macrophage migration inhibitory factor (MIF) and tumor necrosis factor (TNF-α) were both increased in the wound site (Ashcroft and Ashworth, 2003). Estrogens have also been shown to have beneficial effects on wound healing in males. In castrated male rats, estradiol, administered via a subcutaneous pellet (3.2 μg/kg/day), increased re-epithelialization rates in
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dermal wounds. This appeared dependent on vascular endothelial growth factor (VEGF), as antibodies against VEGF obliterated this effect (Concina et al., 2000). In humans, topical or systemic estrogen treatment accelerates dermal healing in both women and men (Ashcroft et al., 1999). These effects were associated with decreased levels of elastase, as a result of a reduced number of neutrophils in the wound site, which resulted in increased collagen deposition and wound strength (Ashcroft et al., 1999). The role of progestins on wound healing has seldom been reported. Progesterone increases levels of prostaglandins (Leslie and Dubey, 1994) as well as IL-1, and may at certain concentrations augment TNF secretion (Cannon, 1998; Cannon and St Pierre, 1997). Progesterone also downregulates GC receptors (Viau and Meaney, 1991) and subsequently reduces the anti-inflammatory effects of GCs (Mascarenhas et al., 2003). These findings suggest that progesterone modulates inflammation and may be proinflammatory in nature. Similar to estrogen receptors, androgen receptors are located on many cell types important to wound healing including keratinocytes, fibroblasts, vascular endothelial cells, macrophages, neutrophils, platelets, and B-cells (Gilliver et al., 2003). This suggests that, like estrogens, androgens should impact upon woundhealing parameters. Indeed, androgens have been shown to influence all stages of wound healing, from initial clot formation to eventual wound re-modeling (Gilliver et al., 2003). The androgen testosterone has been examined the most. Studies have found that testosterone reduces IL6 levels. IL-6 is mitogenic to keratinocytes and appears necessary for normal healing. For instance, IL-6 knockout mice healed dermal wounds three times slower than wild-type controls due to delayed re-epithelialization of the wound site. Testosterone also increases TNF-α levels in wounded tissue, which in turn increases inflammation and can hinder the healing process (Ashcroft and Mills, 2002). Animal studies of dermal wounds further suggest that androgens are detrimental to dermal wound healing. Male castration is associated with decreased inflammation, a reduced number of macrophages being recruited to the wound site, and increased collagen content in the extracellular matrix (Gilliver et al., 2003). In addition, castrated male mice heal faster than non-castrated mice, and androgen treatment reverses this effect (Ashcroft et al., 2003a). These findings indicate that sex hormones impact upon many facets of dermal wound healing and likely underlie the gender differences, which have been reported in healing rates (see below). Overall,
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estrogens appear to improve (Ashcroft et al., 1997a; Ashcroft et al., 1999; Ashcroft et al., 2003b; Ashcroft and Ashworth, 2003; Concina et al., 2000; Mascarenhas et al., 2003) and androgens hinder (Ashcroft and Mills, 2002; Gilliver et al., 2003; Mascarenhas et al., 2003) the wound-healing process in skin. These ameliorative effects of estrogen on dermal healing are partly due to decreased inflammation in wound tissue (Ashcroft et al., 1999; Ashcroft and Ashworth, 2003; Mascarenhas et al., 2003), whereas androgens have been associated with increased inflammatory responses (Ashcroft and Mills, 2002; Gilliver et al., 2003).
VIII. GENDER DIFFERENCES IN WOUND HEALING Gender has been implicated as a factor in wound healing, and a number of studies have shown a female advantage in healing rates (Ashcroft et al., 1997a; Ashcroft et al., 2003b; Ashcroft and Ashworth, 2003; Jorgensen et al., 2002). Moreover, the male genotype is considered to be a strong positive risk factor for impaired healing in the elderly (Ashcroft and Mills, 2002). For instance, in the elderly, men exhibit higher levels of TNF-α and lower levels of collagen than women, both of which are correlated to the observed delay in dermal wound-healing rates in aged men (Ashcroft et al., 1999; Ashcroft and Mills, 2002). Similarly, younger men exhibit lower levels of collagen and heal dermal wounds slower than younger women (Jorgensen et al., 2002). Sex hormones play a role in periodontal disease (Mascarenhas et al., 2003), suggesting they are similarly involved in oral mucosal healing. However, the literature does not indicate an evident female advantage in the healing of the oral mucosa, as some studies have reported no sex difference in healing rates in this region (Heard et al., 2000; Lopez et al., 2002; Yumiba et al., 2003). Other studies which examined healing after third molar surgery found that women healed significantly slower (Conrad et al., 1999; Phillips et al., 2003), and needed additional post-surgery treatment (Benediktsdottir et al., 2004; Phillips et al., 2003) compared to men. Recently, we placed experimental wounds on the oral hard palate of 212 adult volunteers and assessed wound sizes for 7 days post-wounding. The wounds (3.5 mm in diameter) were standardized for size, depth, site, and time of placement. We observed a robust gender difference in favor of males (Engeland et al.; in press). Although wounds were originally the same size, by 24 hours post-wounding men had significantly smaller-sized wounds than women, and this was
evident up to 6 days post-wounding. As a result, significantly more men than women were considered healed by days 5 and 6 post-wounding. On day 5, the wounds of women were 27% larger than those of men, and men were 2.5 times more likely to be considered healed than women. This gender difference was apparent regardless of age group (18–35 years or 50–88 years), and these results were independent of common demographic factors, such as ethnicity, education, alcohol/nicotine use, exercise, or body-mass index (Engeland et al., in press). We have recently replicated this finding of a male advantage in mucosal wound healing in a second clinical study using undergraduate university students (n = 193; 18–31 years of age). These results are contrary to the large amount of data that show a distinct female advantage in dermal wound healing (Ashcroft et al., 2003b; Ashcroft and Ashworth, 2003; Jorgensen et al., 2002; Shimizu et al., 2004). Dermal and mucosal wounds are often equated, and direct comparisons are commonly made between their underlying healing processes. However, these findings suggest that healing is modulated by different mechanisms depending upon tissue type (dermal vs. mucosal), and direct comparisons between dermal and mucosal tissues may be inappropriate. We hypothesize that sex hormones modulate both mucosal and dermal wound healing, but do so differentially, perhaps driving healing in opposite directions.
IX. THE HEALING OF DERMAL VERSUS MUCOSAL WOUNDS Mucosal wounds occur frequently, and mucosal healing is necessary in most surgical outcomes. A number of studies have compared the healing of dermal versus mucosal wounds. Overall, it is well accepted that mucosal wounds heal significantly faster than dermal wounds (Lee and Eun, 1999; Szpaderska et al., 2003). This is logical because compared to skin, the oral mucosa is prone to a higher incidence of damage and has a higher bacterial load. These factors increase the chance of infection once wounded, so faster wound healing is needed. The higher bacterial load in mucosal wounds appears to alter the wound-healing process. Mice with targeted deletions of the interleukin-1 type 1 receptor (IL-1R1-/-) healed dermal scalp wounds at normal rates but showed delayed healing of oral mucosal wounds compared to wild-type controls. The administration of antibiotics to these mice largely reversed this delay in mucosal wound healing (Graves et al., 2001). These findings indicate that normal IL-1 activity is more important in oral mucosal wounds than in
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dermal wounds due to the higher bacterial load found in the mouth (Graves et al., 2001). Other intrinsic differences help to explain why mucosal tissue heals faster than skin. Compared to skin, mucosal epithelial turnover is more rapid and its tissue is more vascularized. Due to increased vascularization, it takes less time to recruit inflammatory cells to a mucosal wound site. Furthermore, in the oral mucosa, immunomodulating compounds, such as growth factors, are more readily supplied to the site via saliva. Oral mucosal and dermal tissue cells also possess different characteristics (Szpaderska et al., 2003; Yamada et al., 2004). Previous studies have found that, compared to dermal fibroblasts, oral mucosal fibroblasts proliferate more, contract earlier, and in the presence of TGF-β1, synthesize more collagen (Lee et al., 1999). Likely, these differences in cellular behavior contribute to the divergent healing rates seen in these tissues. Studies in mice have reported lower levels of neutrophil, macrophage, and T-cell infiltration in oral mucosal wounds versus dermal wounds. Associated with this, levels of IL-6, KC (a murine homolog of human IL-8), and TGF-β1 were all lower in oral mucosal than in dermal wounds (Szpaderska et al., 2003). Taken together, oral mucosal tissue expresses lower levels of inflammation when in a reparative state than dermal tissue (Lee et al., 1999; Szpaderska et al., 2003). As reduced inflammation in dermal wounds has been associated with faster healing times (Dovi et al., 2003; Dovi et al., 2004), this may help to explain why oral mucosal wounds heal faster than dermal wounds. This also suggests that the amount of inflammation needed for optimal healing is lower in mucosal than in dermal tissue. Given that testosterone is abundant in saliva and other mucosal fluids, and has potent antiinflammatory properties, higher testosterone levels in males may then explain the faster mucosal healing that we have observed in men compared to women (Engeland et al., in press). Many of the changes which occur in aged skin are due to extrinsic factors, such as sun exposure (Gosain and DiPietro, 2004; Thomas, 2001). As mucosal tissue is not exposed to the sun, it provides a good assessment of intrinsic aging on wound healing. Given that mucosal tissue heals quickly with little inflammation, rarely scars, and appears similar to the idealized healing seen in fetal tissue, a mucosal model of wound healing may also provide unique insights into perfecting the healing process in various tissue types.
X. WOUND HEALING IN THE AGED It is well accepted that aging alters skin morphology (Ashcroft et al., 2002). Older adult skin has been shown
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to have reductions in vascularization (van de Kerkhof et al., 1994), collagen content (Cook and Dzubow, 1997; Gosain et al., 2004; van de Kerkhof et al., 1994), granulation tissue (van de Kerkhof et al., 1994), and elastin (Ashcroft et al., 1997c; Thomas, 2001). But do these deficits necessarily result in healing rate alterations? Dating back to World War I, there have been reports of age-associated delays in wound healing. DuNuoy (1916) observed that older soldiers wounded in battle exhibited slower wound closure in comparison to the wounds of younger soldiers. These findings are difficult to interpret, however, as the soldiers were relatively young (20–40 years), and factors such as wound type, depth, and incidence of infection were not accounted for. Numerous studies involving the elderly (65+ years) have since reported age-associated delays in wound healing (Fenske and Lober, 1986; Gerstein et al., 1993; Goodson III and Hunt, 1979). Chief criticisms of such findings, however, are that confounding factors more common in the elderly, such as comorbidity and medication use, have not been adequately controlled (Ashcroft et al., 1995; Ashcroft et al., 1997b; Ashcroft et al., 2002; Thomas, 2001). In addition, as these have been mostly clinical reports, wounds were not standardized between individuals. Thus, although it is generally accepted that aging slows wound healing in animal models (Ashcroft et al., 1997b; Quirinia and Viidik, 1991; Swift et al., 1999), it remains unclear that aging per se delays wound healing in humans. Using a standardized model of mucosal wound healing, in which a 3.5 mm diameter wound was placed upon the oral hard palate, our laboratory assessed the effects of aging on wound healing. Wound sizes were assessed daily for 7 days post-wounding. Older individuals (50–88 years; n = 93) healed these wounds significantly slower than younger adults (18– 35 years; n = 119), regardless of gender. Compared to older adults, wounds were significantly smaller in younger adults from days 2–7 post-wounding, resulting in a greater number of younger subjects being considered healed on days 5 through 7. On day 5, wounds were 56% larger in older versus younger subjects, and older individuals were 3.7 times less likely to be considered healed than younger individuals. Additional analyses were performed which excluded individuals that were on any type of medication (excluding allergy medication, birth control or nutritional supplements), and/or ever had a serious medical condition (e.g., diabetes, cancer, stroke, heart disease, hypertension, hypothyroidism, arthritis, other inflammatory disease, psychopathology). Even with these individuals excluded from the analyses, older
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individuals were found to heal slower than younger subjects. Surprisingly, the exclusion of individuals on medication strengthened the above findings of an age-associated deficit in wound healing. Thus, ageassociated delays were not exaggerated by medication use. This suggests the detrimental effects of aging on wound healing may be even stronger than previously suspected (Engeland et al., in press). The mechanisms by which aging impairs wound healing are not fully understood. Clearly, there are intrinsic differences in skin from older adults related to exposure to the sun, cell turnover, availability of stems cells, etc. Aging is also known to influence the HPA axis. It is generally accepted that peak levels of GCs are not substantially different in older adults compared to younger adults, but that termination of the stress response is impaired (McEwen et al., 1993; Sapolsky et al., 1986). Thus, GCs are expressed for a longer period of time. During healing, an extended period of GC secretion would result in lower cell recruitment and inhibition of growth factors for fibroblasts and endothelial cells. This may account for, in part, the tissue differences found in older adults or may increase the variability of healing among older adults.
XI. SUMMARY AND FUTURE DIRECTIONS The mechanisms by which stress modulates wound healing remain to be fully elucidated. Two major pathways appear to be involved, the HPA axis and the sympathetic nervous system (SNS). HPA axis activation results in adrenal production of glucocorticoids and epinephrine. Glucocorticoids can regulate the production of pro-inflammatory cytokines, chemokines, and growth factors required for phagocyte recruitment/activation and tissue repair. Limited data in human models presented in this review suggest that cortisol and cytokines are involved in stressimpaired healing. Animal studies further suggest a role for glucocorticoids. Mice subjected to restraint stress have lower levels of pro-inflammatory cytokines and growth factors, including IL-1β, in their wounds (Padgett et al., 1998; Mercado et al., 2002). Importantly, treatment of stressed mice with RU486, a glucocorticoid antagonist, restores normal expression of IL-1β, but only partially ameliorates normal healing and to a lesser extent microbial clearance (Rojas et al., 2002). Although cytokines play a key role in phagocyte activation and recruitment, these findings are indicative of a second pathway important in stress-impaired healing. This other important pathway activated by
stress is the SNS. The SNS can cause peripheral vasoconstriction, impairing blood flow to the wound and resulting in tissue hypoxia. This limits oxygen availability for both tissue repair and microbial clearance. Reactive oxygen species (ROS, e.g., superoxide anion, H2O2, and NO) are known to be critical components of signaling during healing and antimicrobial defense systems in phagocytic cells. Human studies have demonstrated the importance of tissue oxygen during healing (Hunt and Pai, 1972). Additionally, oxygenmodulated genes are dysregulated by stress in wounds. For example, iNOS gene expression is upregulated three-fold in wound tissue from stressed mice. Treatment of stressed mice with hyperbaric oxygen (HBO) restores normal healing and normal iNOS gene expression (Gajendrareddy et al., 2005). Therefore, these two pathways and downstream mediators provide potential targets for “perfecting” wound healing in stressed humans. The demand for perfected wound healing has never been greater. Increasingly, surgical interventions are done not only for therapeutic outcomes, but also for esthetic reasons. An esthetic outcome requires idealized healing. With an aging population, the demand and the needs will only increase. This will become an even greater challenge as we start to engineer tissues to replace body parts and tissues. A thorough understanding of how to “perfect” wound healing is essential for optimum results. It has been shown that neuroendocrine hormones as modified by stress, gender, or aging can alter the course of wound healing. The effects of stress are as robust as other known risk factors for impaired healing, e.g., diabetes or cigarette smoking. These studies have generally been done in relatively healthy populations. It is likely that an even greater impact may be seen in compromised patients. There are many unanswered questions that will require additional studies in both human and animal models. Do the effects of stress equally impact both males and females? Does the source or size of injury matter? Can we identify populations at increased risk? What is the role of genetics? What are the relative roles of the HPA axis and sympathetic nervous system? What are the critical targets for biological interventions? What is the basis for tissue-specific differences in healing? How can we exploit differences in healing between mucosal and dermal tissues? The answers to these questions will help to individualize perfected wound healing, taking into account the type of injury, the tissues involved, the gender and age of the patient, as well as the psychological states and traits of the individual. Clearly, a biological intervention would be ideal, since changing behavior has been a difficult task in our society.
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References Ahlquist, R. P. (1976). Present state of alpha- and beta-adrenergic drugs I. The adrenergic receptor. Am. Heart J., 92 (5), 661–664. Almawi, W. Y., Beyhum, H. N., Rahme, A. A., and Rieder, M. J. (1996). Regulation of cytokine and cytokine receptor expression by glucocorticoids. Journal of Leukocyte Biology, 60, 563–572. Ashcroft, G. S., and Ashworth, J. J. (2003). Potential role of estrogens in wound healing. Am. J. Clin. Dermatol., 4 (11), 737–743. Ashcroft, G. S., Dodsworth, J., van Boxtel, E., Tarnuzzer, R. W., Horan, M. A., Schultz, G. S., et al. (1997a). Estrogen accelerates cutaneous wound healing associated with an increase in TGF-beta1 levels. Nat. Med., 3 (11), 1209–1215. Ashcroft, G. S., Greenwell-Wild, T., Horan, M. A., Wahl, S. M., and Ferguson, M. W. (1999). Topical estrogen accelerates cutaneous wound healing in aged humans associated with an altered inflammatory response. Am. J. Pathol., 155 (4), 1137–1146. Ashcroft, G. S., Horan, M. A., and Ferguson, M. W. (1995). The effects of aging on cutaneous wound healing in mammals. J. Anat., 187 (Pt 1), 1–26. Ashcroft, G. S., Horan, M. A., and Ferguson, M. W. (1997b). Aging is associated with reduced deposition of specific extracellular matrix components, an upregulation of angiogenesis, and an altered inflammatory response in a murine incisional wound healing model. J. Invest. Dermatol., 108 (4), 430–437. Ashcroft, G. S., Kielty, C. M., Horan, M. A., and Ferguson, M. W. (1997c). Age-related changes in the temporal and spatial distributions of fibrillin and elastin mRNAs and proteins in acute cutaneous wounds of healthy humans. J. Pathol., 183 (1), 80–89. Ashcroft, G. S., and Mills, S. J. (2002). Androgen receptor-mediated inhibition of cutaneous wound healing. J. Clin. Invest., 110 (5), 615–624. Ashcroft, G. S., Mills, S. J., and Ashworth, J. J. (2002). Aging and wound healing. Biogerontology, 3 (6), 337–345. Ashcroft, G. S., Mills, S. J., Flanders, K. C., Lyakh, L. A., Anzano, M. A., Gilliver, S. C., et al. (2003a). Role of Smad3 in the hormonal modulation of in vivo wound healing responses. Wound Repair Regen., 11 (6), 468–473. Ashcroft, G. S., Mills, S. J., Lei, K., Gibbons, L., Jeong, M. J., Taniguchi, M., et al. (2003b). Estrogen modulates cutaneous wound healing by downregulating macrophage migration inhibitory factor. J. Clin. Invest., 111 (9), 1309–1318. Benediktsdottir, I. S., Wenzel, A., Petersen, J. K., and Hintze, H. (2004). Mandibular third molar removal: risk indicators for extended operation time, postoperative pain, and complications. Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endod., 97 (4), 438–446. Bikowsky, J. (1999). Secondarily infected wounds and dermatoses: a diagnosis and treatment guide. J. Emerg. Med., 17, 4793–4800. Brauchle, M., Fässler, R., and Werner, S. (1995). Suppression of keratinocyte growth factor expression by glucocorticoids in vitro and during wound healing. J. Invest. Dermatol., 105, 579–584. Broadbent, E., Petrie, K. J., Alley, P. G., and Booth, R. J. (2003). Psychological stress impairs early wound repair following surgery. Psychosom. Med., 65 (5), 865–869. Calvin, M., Dyson, M., Rymer, J., and Young, S. R. (1998). The effects of ovarian hormone deficiency on wound contraction in a rat model. Br. J. Obstet. Gynaecol., 105 (2), 223–227. Cannon, J. G. (1998). Adaptive interactions between cytokines and the hypothalamic-pituitary-gonadal axis. Ann. N.Y. Acad. Sci., 856, 234–242. Cannon, J. G., and St Pierre, B. A. (1997). Gender differences in host defense mechanisms. J. Psychiatr. Res., 31 (1), 99–113.
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Chang, N., Goodson III, W. H., et al. (1983). Direct measurement of wound and tissue oxygen tension in postoperative patients. Ann. Surg., 197 (4), 470–478. Chedid, M., Hoyle, J. R., Csaky, K. G., and Rubin, J. S. (1996). Glucocorticoids inhibit keratinocyte growth factor production in primary dermal fibroblasts. Endocrinol., 137, 2232–2237. Clark, R. A. F., Gallin, J. I., and Fauci, A. S. (1979). Effect of in vivo prednisone on in vitro eosinophil and neutrophil adherence and chemotaxis. Blood, 53, 633–641. Cohen, S. (1988). Psychosocial models of the role of social support in the etiology of physical disease. Health Psychology, 7, 269–297. Concina, P., Sordello, S., Barbacanne, M. A., Elhage, R., Pieraggi, M. T., Fournial, G., et al. (2000). The mitogenic effect of 17betaestradiol on in vitro endothelial cell proliferation and on in vivo reendothelialization are both dependent on vascular endothelial growth factor. J. Vasc. Res., 37 (3), 202–208. Conrad, S. M., Blakey, G. H., Shugars, D. A., Marciani, R. D., Phillips, C., and White Jr., R. P. (1999). Patients’ perception of recovery after third molar surgery. J. Oral Maxillofac. Surg., 57 (11), 1288–1294. Cook, J. L., and Dzubow, L. M. (1997). Aging of the skin: implications for cutaneous surgery. Arch. Dermatol., 133 (10), 1273–1277. Devine, E. C. (1992). Effects of psychoeducational care for adult surgical patients: a meta-analysis of 191 studies. Patient Educ. Couns., 19 (2), 129–142. Donaldson, D. J., and Mahan, J. T. (1984). Influence of catecholamine on epidermal cell migration during wound closure in adults newts. Comp. Biochem. Physiol. C., 78 (2), 267–270. Dovi, J. V., He, L. K., and DiPietro, L. A. (2003). Accelerated wound closure in neutrophil-depleted mice. J. Leukoc. Biol., 73 (4), 448–455. Dovi, J. V., Szpaderska, A. M., and DiPietro, L. A. (2004). Neutrophil function in the healing wound: adding insult to injury? Thromb. Haemost., 92 (2), 275–280. DuNuoy, P. L. (1916). Cicatrization of wounds. J. Exp. Med., 24, 461–470. Ebrecht, M., Hextall, J., Kirtley, L. G., Taylor, A., et al. (2004). Perceived stress and cortisol levels predict speed of wound healing in healthy male adults. Psychoneuroendocrinology, 29, 798–809. Engeland, C. G., Bosch, J. A., Cacioppo, J. T., and Marucha, P. T. (In press). Mucosal Wound Healing: The Roles of Age and Gender. Archives of Surgery. Engeland, C. G., Kavaliers, M., and Ossenkopp, K. P. (2003). Sex differences in the effects of muramyl dipeptide and lipopolysaccharide on locomotor activity and the development of behavioral tolerance in rats. Pharmacol. Biochem. Behav., 74 (2), 433–447. England, G. T., Randal, H. W., and Graves, W. L. (1983). Impairment of tissue defenses by vasoconstriction in vaginal hysterectomies. Obstet. Gynecol., 61 (3), 271–274. Edwards, J. C., and Dunphy, J. E. (1958). Wound healing. II. Injury and abnormal repair. N. Engl. J. Med., 259, 275–285. Fauci, A. S., Dale, D. C., and Balow, J. E. (1976). Glucocorticoid therapy: mechanisms of action and clinical considerations. Ann. Intern. Med., 84, 304–315. Fenske, N. A., and Lober, C. W. (1986). Structural and functional changes of normal aging skin. J. Am. Acad. Dermatol., 15 (4, Pt. 1), 571–585. Field, T., Peck, M., Krugman, S., Tuchel, T., et al. (1998). Burn injuries benefit from massage therapy. J. Burn Care Rehabil., 19 (3), 241–244. Gaillard, R. C., and Spinedi, E. (1998). Sex- and stress-steroids interactions and the immune system: evidence for a neuroendocrine-
834
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immunological sexual dimorphism. Domest. Anim. Endocrinol., 15 (5), 345–352. Gajendrareddy, P. K., Sen, C. K., Horan, M. P., and Marucha, P. T. (2005). Hyperbaric oxygen therapy ameliorates stress-impaired dermal wound healing. Brain Behav. Immun., 19 (3), 201–202. Gerstein, A. D., Phillips, T. J., Rogers, G. S., and Gilchrest, B. A. (1993). Wound healing and aging. Dermatol. Clin., 11 (4), 749–757. Giglio, T., Imro, M., Filaci, G., Scudeletti, M., Puppo, F., De Cecco, L., et al. (1994). Immune cell circulating subsets are affected by gonadal function. Life Sciences, 54 (18), 1305–1312. Gilliver, S. C., Wu, F., Ashcroft, G. S. (2003). Regulatory roles of androgens in cutaneous wound healing. Thromb. Haemost., 90 (6), 978–985. Glaser, R., Kiecolt-Glaser, J. K., Marucha, P. T., et al. (1999). Stressrelated changes in proinflammatory cytokine production in wounds. Arch. Gen. Psychiatry, 56, 450–456. Goodson III, W. H., and Hunt, T. K. (1979). Wound healing and aging. J. Invest. Dermatol., 73 (1), 88–91. Gosain, A., and DiPietro, L. A. (2004). Aging and wound healing. World J. Surg., 28 (3), 321–326. Graves, D. T., Nooh, N., Gillen, T., Davey, M., Patel, S., Cottrell, D., et al. (2001). IL-1 plays a critical role in oral, but not dermal, wound healing. J. Immunol., 167 (9), 5316–5320. Heard, R. H, Mellonig, J. T., Brunsvold, M. A, Lasho, D. J, Meffert, R. M, and Cochran, D. L. (2000). Clinical evaluation of wound healing following multiple exposures to enamel matrix protein derivative in the treatment of intra-bony periodontal defects. J. Periodontol., 71 (11), 1715–1721. Holden-Lund, C. (1998). Effects of relaxation with guided imagery on surgical stress and wound healing. Res. Nurs. Health, 11 (4), 235–244. Hopf, H. W., Hunt, T. K., West, J. M., Blomquist, P., Goodson, W. H., Jensen, J. A., Jonsson, K., Paty, P. B., Rabkin, J. M., Upton, R. A., von Smitten, K., and Whitney, J. D. (1997). Wound tissue oxygen tension predicts the risk of wound infection in surgical patients. Arch. Surg., 132, 997–1005. Hübner, G., Brauchle, M., Smola, H., Madlener, M., Fässler, R., and Werner, S. (1996). Differential regulation of pro-inflammatory cytokines during wound healing in normal and glucocorticoidtreated mice. Cytokine, 8 (7), 548–556. Hunt, T. K., and Pai, M. P. (1972). The effect of varying ambient oxygen tensions on wound metabolism and collagen synthesis. Surg. Gynecol. Obstet., 135 (4), 561–567. Jensen, J. A., Jonsson, K., Goodson, W. H., Hunt, T. K., and Roizen, M. F. (1985). Epinephrine lowers subcutaneous wound oxygen tension. Curr. Surg., 42 (6), 472–474. Jonsson, K., Hunt, T. K., and Mathes, S. J. (1988). Oxygen as an isolated variable influences resistance to infection. Ann. Sur., 208 (6), 783–787. Jorgensen, L. N., Sorensen, L. T., Kallehave, F., Vange, J., and Gottrup, F. (2002). Premenopausal women deposit more collagen than men during healing of an experimental wound. Surgery, 131 (3), 338–343. Kiecolt-Glaser, J. K., Marucha, P. T., et al. (1995). Slowing of wound healing by psychological stress. Lancet, 346 (8984), 1194–1196. Knighton, D. R., Silver, I. A., et al. (1981). Regulation of woundhealing angiogenesis-effect of oxygen gradients and inspired oxygen concentration. Surgery, 90 (2), 262–270. Koopman, C. F. (1995). Cutaneous wound healing, an overview. Otolaryngol. Clin. North Am., 28 (5), 835–845. Krzych, U., Strausser, H. R., Bressler, J. P., and Goldstein, A. L. (1981). Effects of sex hormones on some T and B cell functions, evidenced by differential immune expression between male and
female mice and cyclic pattern of immune responsiveness during the estrous cycle in female mice. Am. J. Reprod. Immunol., 1 (2), 73–77. Lahita, R. (2000). Gender and the immune system. The Journal of Gender-Specific Medicine, 3 (7), 19–22. Lee, H. G., and Eun, H. C. (1999). Differences between fibroblasts cultured from oral mucosa and normal skin: implication to wound healing. J. Dermatol. Sci., 21 (3), 176–182. Leslie, C. A., and Dubey, D. P. (1994). Increased PGE2 from human monocytes isolated in the luteal phase of the menstrual cycle. Implications for immunity? Prostaglandins, 47 (1), 41–54. Lopez, R., Fernandez, O., Jara, G., and Baelum, V. (2002). Epidemiology of necrotizing ulcerative gingival lesions in adolescents. J. Periodontal Res., 37 (6), 439–444. Marucha, P. T., Kiecolt-Glaser, J. K., et al. (1998). Mucosal wound healing is impaired by examination stress. Psychosom. Med., 60 (3), 362–365. Mascarenhas, P., Gapski, R., Al Shammari, K., and Wang, H. L. (2003). Influence of sex hormones on the periodontium. J. Clin. Periodontol., 30 (8), 671–681. McEwen, B. S., and Stellar, E. (1993). Stress and the individual: mechanisms leading to disease. Arch. Intern. Med., 153, 2093–2101. Mercado, A. M., Padgett, D. A., et al. (2002). Altered kinetics of IL-1 alpha, IL-1 beta, and KGF-1 gene expression in early wounds of restrained mice. Brain Behav. Immun., 16 (2), 150–162. Miller, L., and Hunt, J. S. (1996). Sex steroid hormones and macrophage function. Life Sci., 59 (1), 1–14. Norris, D. A., Capin, L., and Weston, W. L. (1982). The effect of epicutaneous glucocorticosteroids on human monocyte and neutrophil migration in vivo. J. Invest. Dermatol., 78, 386–390. O’Connor, C. M. (2001). Raynaud’s phenomenon. J. Vasc. Nurs., 19 (3), 87–92; quiz, 93–94. Okimura, T., Ogawa, M., and Yamauchi, T. (1986). Stress and immune responses. III. Effect of restraint stress on delayed type hypersensitivity (DTH) response, natural killer (NK) activity and phagocytosis in mice. Jpn. J. Pharmacol., 41 (2), 229–235. Padgett, D. A., Marucha, P. T., and Sheridan, J. F. (1998). Restraint stress slows cutaneous wound healing in mice. Brain Behav. Immun., 12 (1), 64–73. Pai, M. P., and Hunt, T. K. (1972). Effect of varying oxygen tensions on healing of open wounds. Surg. Gynecol. Obstet., 135 (5), 756–758. Palermo-Neto, J., de Oliveira Massoco, C., et al. (2003). Effects of physical and psychological stressors on behavior, macrophage activity, and Ehrlich tumor growth. Brain Behav. Immun., 17 (1), 43–54. Plante, G. E. (2002). Vascular responses to stress in health and disease. Metabolism, 51 (6 Suppl), 25–30. Phillips, C., White, R. P., Shugars Jr., D. A., and Zhou, X. (2003). Risk factors associated with prolonged recovery and delayed healing after third molar surgery. J. Oral Maxillofac. Surg., 61 (12), 1436–1448. Piascik, M. T., and Perez, D. M. (2001). Alphal-adrenergic receptors: new insights and directions. J. Pharmacol. Exp. Ther., 298 (2), 403–410. Quirinia, A., and Viidik, A. (1991). The influence of age on the healing of normal and ischemic incisional skin wounds. Mech. Aging Dev., 58 (2–3), 221–232. Raine-Fenning, N. J., Brincat, M. P., and Muscat-Baron, Y. (2003). Skin aging and menopause: implications for treatment. Am. J. Clin. Dermatol., 4 (6), 371–378. Robson, M. C. (1997). Wound infection: a failure of wound healing caused by an imbalance of bacteria. Surg. Clin. North Amer., 77, 637–650.
38. Stress, Neuroendocrine Hormones, and Wound Healing: Human Models Rojas, I. G., Padgett, D. A., et al. (2002). Stress-induced susceptibility to bacterial infection during cutaneous wound healing. Brain Behav. Immun., 16 (1), 74–84. Salomonsson, M., Oker, M., et al. (2001). Alpha1-adrenoceptor subtypes on rat afferent arterioles assessed by radioligand binding and RT-PCR. Am. J. Physiol. Renal Physiol., 281 (1), F172– 178. Sanders, V. M., and Straub, R. H. (2002). Norepinephrine, the betaadrenergic receptor, and immunity. Brain Behav. Immun., 16 (4), 290–332. Sapolsky, R. M., Krey, L. C., and McEwen, B. S. (1986). The neuroendocrinology of stress and aging: the glucocorticoid cascade hypothesis. Endocr. Rev., 7, 284–301. Schuurs, A. H. W. M., and Verheul, H. A. M. (1990). Effects of gender and sex steroids on the immune response. Journal of Steroid Biochemistry, 35, 157–172. Shimizu, T., Nishihira, J., Watanabe, H., Abe, R., Honda, A., Ishibashi, T., et al. (2004). Macrophage migration inhibitory factor (MIF) is induced by thrombin and factor Xa in endothelial cells. J. Biol. Chem., 279 (14), 13729–13737. Swift, M. E., Kleinman, H. K., and DiPietro, L. A. (1999). Impaired wound repair and delayed angiogenesis in aged mice. Lab. Invest., 79 (12), 1479–1487. Szpaderska, A. M., Zuckerman, J. D., and DiPietro, L. A. (2003). Differential injury responses in oral mucosal and cutaneous wounds. J. Dent. Res., 82 (8), 621–626.
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Thomas, D. R. (2001). Age-related changes in wound healing. Drugs Aging, 18 (8), 607–620. van de Kerkhof, P. C., Van Bergen, B., Spruijt, K., and Kuiper, J. P. (1994). Age-related changes in wound healing. Clin. Exp. Dermatol., 19 (5), 369–374. Viau, V., and Meaney, M. J. (1991). Variations in the hypothalamicpituitary-adrenal response to stress during the estrous cycle in the rat. Endocrinology, 129 (5), 2503–2511. Whitney, J. D. (1989). Physiologic effects of tissue oxygenation on wound healing. Heart Lung, 18 (5), 466–474. Yamada, Y., Itano, N., Hata, K., Ueda, M., and Kimata, K. (2004). Differential regulation by IL-1beta and EGF of expression of three different hyaluronan synthases in oral mucosal epithelial cells and fibroblasts and dermal fibroblasts: quantitative analysis using real-time RT-PCR. J. Invest. Dermatol., 122 (3), 631– 639. Yumiba, T., Ito, T., Ikushima, H., Taniguchi, E., Inoue, Y., Nishida, T., et al. (2003). Effect of mucosal suture on the healing of mucosal defect in laparoscopic intragastric surgery. Gastric Cancer, 6 (2), 96–99. Zuk, M., and McKean, K. A. (1996). Sex differences in parasite infections: patterns and processes. Int. J. Parasitol., 26 (10), 1009–1023.
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C H A P T E R
39 Stress and Wound Healing: Animal Models DAVID A. PADGETT, PHILLIP T. MARUCHA, AND JOHN F. SHERIDAN
I. INTRODUCTION 837 II. THE INFLAMMATORY PHASE OF WOUND REPAIR 837 III. THE PROLIFERATIVE PHASE OF WOUND REPAIR 844 IV. THE REMODELING PHASE OF WOUND REPAIR 846 V. CONCLUSIONS 847
factors including the location of the wound, the size and depth of the injured area, the presence of bacteria, and the age and overall health of the host (Robins et al., 1984; Ashcroft et al., 2002). The impact that the overall “health of the host” has on wound healing is the focal point for this review. More specifically, we will delineate how stress’s influence on the health of an animal can influence the wound-healing cascade. First, we will provide a basic outline of the woundhealing process. Then, where data exist, we provide an understanding of how stress influences wound healing.
I. INTRODUCTION Tissue injury causes cell death, which can impair the structure and function of that particular tissue. If the injury is substantial, the overall health of the individual can be compromised. Therefore, a healing cascade is set in motion at the time of injury in an attempt to restore the original properties to the tissue (Singer and Clark, 1999; Waldorf and Fewkes, 1995). Without regard to the type of tissue (whether it be skin, bone, or internal soft organ), injury initiates a set of biological events that attempt to fix damage. These events have been separated into three overlapping phases including: (a) an inflammatory phase composed of hemostasis or blood clotting and migration of inflammatory cells to the wound; (b) a proliferative phase involving migration and proliferation of keratinocytes, fibroblasts, and endothelial cells, leading to re-epithelialization, neovascularization, and granulation tissue formation; and (c) a long remodeling phase involving extracellular matrix maturation aimed at restoring tissue structure and function (see Figure 1). Although most wounds heal in a similar fashion, the rate of healing is dependent upon a number of PSYCHONEUROIMMUNOLOGY, 4E VOLUME II
II. THE INFLAMMATORY PHASE OF WOUND REPAIR If a tissue injury is substantial, the overall health of the individual can be compromised. Therefore, the healing cascade is set in motion at the time of injury in an attempt to restore the original properties to the tissue. Coincident with the initial damage, the inflammatory phase of repair begins. It is initiated by factors released by resident cells after their mechanical disruption and also by the immediate response of platelets to “damage” signals in injured blood vessels (King and Reed, 2002). This initial inflammatory response serves to jump-start healing. First, inflammation stabilizes the wound by removing contaminating debris and controlling microbial invasion, and second, it creates an environment conducive to tissue repair. During this inflammatory phase, at least three different cell types are recruited from circulation: (a) platelets are retained in the area for hemostasis, (b) neutrophils
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FIGURE 1 Wound healing is a cascade of events. At the time of wounding, a coordinated series of events begins in an attempt to heal the injury. Coordinated by chemokines, cytokines, and growth factors, the three main phases work in concert to create a replacement tissue that approximates the original in both structure and function. Although the inflammatory phase begins at the time of injury, the subsequent overlapping phases of healing may take months to years to complete.
flood into the wound margin to control infection, and (c) resident macrophages are activated and circulating monocytes are recruited to prepare the wound for repair (Hart, 2002; Henry and Garner, 2003). Platelets and Hemostasis: With any type of injury there is vascular damage. To limit the flow and loss of blood at the injury site, blood vessels immediately constrict. Soon thereafter, with the aid of the von Willebrand factor and thrombin, platelets become sticky and adhere to collagen that is exposed when the endothelial lining of vessels is ruptured at the time of injury. As platelets aggregate, they bind soluble fibrinogen and release the contents of their granules, driving the conversion of fibrinogen into an insoluble network of fibrin. This fibrin clot stabilizes the initial platelet plug and entraps additional cells to form a more solid barrier to prevent blood loss (for review of platelet function, see references Ofosu, 2002; Wagner and Burger, 2003). The fibrin clot is not inert. It serves as a rudimentary scaffold (or provisional matrix) for repair and also plays an important role in the ensuing inflammatory process. The platelets entrapped in the clot release an
array of biologically active substances that serve to initiate healing by promoting cell migration and ingrowth to the site of injury (Anitua et al., 2004). The clot itself functions as a reservoir for cytokines and growth factors, amplifying chemotaxis by increasing the local cytokine/chemokine concentrations and thus directing cellular trafficking toward the damaged site (Clark, 2001a). In principle, the formation of the blood clot is the first step in the inflammatory phase of repair as platelets, in concert with the injured parenchyma, produce factors that increase blood flow and increase blood vessel permeability (Clark, 2001b; Mannaioni et al., 1997). Likewise, bradykinin from the kinin system, fibrinopeptides released during fibrinogen cleavage, and histamine released from mast cells all increase blood flow to the site (Artuc et al., 1999; Francel, 1992; Weisel, 2005). The resulting increased movement of plasma and the “leaky” blood vessels near the site of injury help produce an environment rich in recruitment factors. Equally important, the platelets that become entrapped in the fibrin clot release their stores of chemotactic and growth factors, which include
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platelet-derived growth factor (PDGF) and transforming growth factors (TGF) alpha and beta (Anitua, 2004). Thus, shortly after clot formation, inflammatory cells are initially recruited to the wound because of the formation of the blood clot. Neutrophils and infection control: Repair of significant tissue injury requires protection against infection by opportunistic microorganisms. For such protection, neutrophils and monocytes/macrophages are attracted into injured tissues. Neutrophils dominate the early infiltrate due to their abundance in circulation. In fact, the hallmark of the inflammatory stage is the infiltration of massive numbers of neutrophils into the wound margin (Hart, 2002; Steed, 2003). As neutrophils circulate, they continually survey the endothelial lining of blood vessels. Where the neutrophils stick and leave the circulation is determined by leukocyte-endothelial interactions. These interactions are substantially increased by a cascade of molecular events which are dependent upon the inflammatory signals produced by the injured tissue. Locally produced chemoattractants (e.g., C5a, fMLP), inflammatory cytokines (e.g., interleukin-1 [IL-1], tumor necrosis factor [TNF-α]) and the C-X-C chemokines (e.g., IL-8, MIP-2α) concentrated in the fibrin clot enhance E and P selectin molecule expression on the luminal side of the blood vessels proximal to the damaged areas (Tsang et al., 1997; Wan et al., 2003). This reactive endothelium slows the movement of neutrophils through blood vessels, thus promoting attachment. Although selectins only contribute to low affinity binding, the decreased movement enables the neutrophil to establish additional and stronger attachments through its integrin molecules (Tsang et al., 1997). The integrins recognize and bind to adhesion molecules selectively expressed on endothelial cells lining the blood vessels near sites of injury. These integrinmediated attachments, which can occur only during conditions of low flow, promote firm attachment and allow for diapedesis of the neutrophil through vascular basement membrane and into the wound site (Stein et al., 2003). Once in the wound area, the neutrophil plays the lead role in controlling microbial contamination. The most common anti-microbial defense attributed to the neutrophil is phagocytosis, and it is ably prepared for this role, as it contains multiple cytolytic mechanisms that enable it to kill a wide variety of ingested microorganisms (see Burg and Pillinger, 2001; Karlsson and Dahlgren, 2002, for review of neutrophil-killing mechanisms). If substantial wound contamination does not occur, neutrophil infiltration usually ceases within a few days, and effete neutrophils become entrapped within the wound clot, which sloughs during tissue
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repair. Neutrophils within viable tissue undergo programmed cell death within a few days and are phagocytosed by tissue macrophages (whose numbers progressively grow during the first few days after healing) (Fadeel and Kagan, 2003; Sylvia, 2003). However, the neutrophil does not give its life simply to control microbial contamination. In addition to phagocytosis, the neutrophil plays an important role in further promoting the inflammatory phase of healing. For example, neutrophils produce numerous pro-inflammatory molecules and enzymes that help recruit additional cells and degrade the matrix of the wound bed, thus facilitating subsequent cell recruitment and movement into the wound (TheilbaardMonch et al., 2004). For example, while in the wound, neutrophils express a number of pro-inflammatory cytokine genes (e.g., TNF-α, interleukin [IL]-1β) and chemokine genes (e.g., IL-8, MIP-1α, and MIP-1β) that aid in the recruitment of macrophages to the wound (Scapini et al., 2000; Theilbaard-Monch et al., 2004). In other words, the neutrophil does not simply travel to the wound to control bacterial contamination; it begins to prepare the tissue environment for subsequent aspects of tissue repair. Macrophages and Initiation of Repair: In the absence of infection, wounds can heal without the involvement of neutrophils (Torkvist et al., 2001). On the other hand, as early as 1975, the infiltrating monocyte/macrophage was thought to be necessary for repair, as macrophagedeficient mice were shown to heal slower, and the healed wounds on such mice had reduced strength compared to those on wild-type animals (Leibovich and Ross, 1975). However, recent observations cast some doubt on the necessity of the macrophage in healing. For example, Martin et al. (2003) showed that wounds on the PU.1 null mouse, which is incapable of raising an inflammatory response due to a lack of both neutrophils and macrophages, showed no delay in the repair process. In addition, these authors claimed that the healed wound on the macrophage-less mouse showed fewer signs of scar formation (i.e., fibrosis). This single publication casts some doubt on the “dogma” that the macrophage is the key to successful wound healing. Until this recent publication, most wound-healing biologists agreed that without the macrophage, wound healing would not proceed correctly. The debate still continues, and this chapter will not attempt to reconcile the issue. However, even if the macrophage is not the lynchpin to healing as once thought, it is still one of the most abundant cell types recruited to the wound during the inflammatory phase of repair. Furthermore, the extant literature clearly illustrates that the chemokines, cytokines, and growth factors produced by the
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macrophage play an important role in coordinating the wound-healing process. For example, DiPietro showed that MCP-1–deficient animals, which are impaired in their ability to recruit macrophages to their wounds, have delayed re-epithelialization, angiogenesis, and collagen deposition (Low et al., 2001). In addition, many of the cytokines and growth factors that are produced by the macrophage during the inflammatory phase of healing play an important role in coordinating the subsequent proliferative and re-modeling phases of repair. Thus, the cytokines and growth factors that the macrophage produces are among the most important in coordinating the wound-healing process. As it was for the neutrophil, diapedesis of monocytes through vessel endothelium is the first step required for their recruitment into the wound area. The main difference in the recruitment of neutrophils and monocytes is manifest in the different chemokines involved in their recruitment. Due to differential distribution of chemokine receptors on these two cell types, the C-X-C chemokines recruit neutrophils, whereas the C-C chemokines are chemoattractant for macrophages (Gillitzer and Goebeler, 2001). In addition, because they precede macrophages at the inflammatory site, neutrophils in the wound contribute to the signals that call in the macrophage. Once the circulating monocytes have crossed the endothelial barrier, they differentiate into macrophages and migrate to the wound. Activated macrophages complement the neutrophil in its efforts to control microbial contamination and kill much the same way as neutrophils. In addition to the processes that they share with neutrophils, macrophages also use antibody-dependent cell-mediated cytotoxicity to kill or damage larger extracellular targets (Dasgupta et al., 2000). Furthermore, the macrophage not only phagocytoses microbial contaminants but also ingests damaged cells in the wound margin and effete neutrophils in healing tissues by recognition of phosphatidylserine expressed on apoptotic cells (Li, Sarkisian et al., 2003; Kurosaka et al., 2003). Although the initial responsibility of the macrophage is control of contamination, their overall role is much broader than that of the neutrophil. While wound macrophages continue to eliminate deleterious materials and generate chemotactic factors that recruit additional inflammatory cells to the injury site, the macrophage also begins to initiate tissue repair. It produces many products involved in the preparation of the tissue for healing. For example, macrophages produce enzymes such as hyaluronidase, elastase, and collagenase, which degrade hyaluronic acid, elastin, and collagen in connective tissue (Hieta et al., 2003;
Madlener et al., 1998). In doing so, the macrophage weakens the extracellular matrix to allow for easier migration and in-growth of fibroblasts, keratinocytes, and endothelial cells that build the new tissue. Not only do the macrophages prepare the extracellular matrix for tissue growth, they also synthesize and release multiple growth and regulatory factors, critical to the coordination of granulation tissue formation (the second broad phase of healing). Once the macrophage begins to produce these growth factors, the repair part of healing actually begins. For example, the formation of new capillaries from pre-existing blood vessels (angiogenesis) is a key element in the proliferative phase of repair (see the section titled “The Proliferative Phase of Wound Repair”). Macrophages are highly angiogenic when exposed to hypoxic conditions found in the microenvironment of the wound (Bingle et al., 2002). In response to such conditions, the macrophage secretes several growth factors (e.g., VEGF) that induce proliferation of capillary endothelium. In addition, as the macrophage digests and weakens the connective tissue matrix in the wound bed, it releases reserves of growth factors that are concentrated in the extracellular matrix (Ortega et al., 1998). Such activity allows the macrophage to target the wound bed for the in-growth of new blood vessels. Therefore, it is believed that the growth factors and chemotactic factors released by macrophages are important in the transition from the inflammatory phase to the proliferative phase of wound repair. Furthermore, the final remodeling phase of wound repair (see the section titled “The Remodeling Phase of Wound Repair”), which is necessary for restoration of tissue structure and function, is dependent upon the proliferation of fibroblasts and the deposition of new extracellular matrix during the proliferative phase. Thus, although the primary responsibility of inflammation is to ensure that the appropriate cells and effector functions are activated to control infection before the deposition of new tissue proceeds, the cytokines, chemokines, and growth factors involved in the inflammatory phase of healing appear equally important to the overall healing process.
A. The Chemokines, Cytokines, and Growth Factors of the Inflammatory Phase of Wound Repair 1. Chemokines Chemokines are a family of small chemotactic cytokines that regulate the movement of many different leukocytes into sites of inflammation (for review, see
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Rossi and Slotnik, 2000). They exert their effects through G-protein–linked receptors on the surface of their target cells. As such, they induce the rearrangement of the leading edge of the target cell and actually stimulate them to crawl toward the source of the chemokine—in this case, the wound. Members of the CX-C subclass of chemokines are generally specific for neutrophils, whereas the C-C subclass members are specific for macrophages (Gillitzer and Goebeler, 2001). Interleukin-8 (IL-8) and GRO-α (which is also called CXCL1) are potent regulators of neutrophil chemotaxis. Both are produced by surviving epidermal cells near the wound edge and by cells entrapped within the blood clot. Gene expression of IL-8 can be detected within 4 hours of wounding (Engelhardt et al., 1998). Likewise, CXCL1 mRNA is highly expressed within a day of wounding (Engelhardt et al., 1998). These C-X-C chemokines induce a wide range of responses in neutrophils, including activation of the motile apparatus and directional migration, expression of surface adhesion molecules, release of lysosomal enzymes, and production of reactive oxygen intermediates. Within hours of wounding, the expression of both Macrophage Chemoattractant Protein (MCP-1), or CCL2, and Macrophage Inflammatory Protein-1α (MIP-1α), or CCL3, is induced in surviving keratinocytes. Expression of each reaches peak levels within 24–36 hours of wounding (DiPietro et al., 1998; Engelhardt et al., 1998; Gillitzer and Goebeler, 2001). These C-C chemokines are necessary for macrophage recruitment as neutralizing antibodies to either MCP-1 or MIP-1α reduce the number of macrophages recruited to the wound. (DiPietro et al., 1998). In addition, resolution of the acute neutrophil-rich inflammatory response is linked to the secretion of MIP-1α from the neutrophils themselves (Sato et al., 1999). The action of these C-C chemokines is not limited to cellular movement, as illustrated by delayed wound reepithelialization, angiogenesis, and collagen synthesis in MCP-1 or MIP-1α deficient mice (DiPietro et al., 1998; Low et al., 2001). 2. Pro-inflammatory Cytokines As they arrive in the wound, neutrophils and macrophages begin to synthesize and secrete small amounts of IL-1α, IL-1β, IL-6, TNF-α, and GM-CSF (for detailed review, see Hart, 2002; Henry and Garner, 2003; Werner and Grose, 2003). Although neutrophils and macrophages are the major sources, resident cells, such as keratinocytes, are also capable of cytokine production. In concert with the chemokines, pro-inflammatory
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cytokines aid in the recruitment of cells into the wound by inducing the expression of adhesion molecules on the luminal side of vessel endothelium proximal to the inflammatory site. Expression of many of the pro-inflammatory cytokine genes is turned on within the first 24–48 hours of wounding (Theilbaard-Monch et al., 2004). Many of the activities of the proinflammatory cytokines are shared. For example, IL-1α and TNF-α both contribute to the activation of NADPH oxidase, thereby enhancing the microbicidal activity of neutrophils and macrophages (Dusi et al., 2001). In addition, pro-inflammatory cytokines can also prolong neutrophil survival in the wound (Chitnis et al., 1996), and their continued presence can be a sign of continuing bacterial contamination. In addition to enhancing inflammation, IL-1α, IL-1β, IL-6, TNF-α, and GM-CSF play important roles in subsequent aspects of healing, including keratinocyte and fibroblast chemotaxis and proliferation, extracellular matrix protein deposition, and tissue remodeling. 3. Growth Factors Re-epithelialization and granulation tissue formation during repair are mediated by a wide variety of growth and differentiation factors. Many of those factors are produced early in the healing process during the inflammatory phase. The macrophage produces many chemotactic and mitogenic factors that attract fibroblasts, keratinocytes, and endothelial cells into the wound site and then stimulates them to proliferate. Thus, the cells involved in inflammation have an important role in driving the transition from inflammation to the proliferative phase of repair and eventually in the initiation of remodeling of new tissue. Among the most important growth factors produced during the inflammatory phase that influence the generation of the new tissue are the following: • Platelet-Derived Growth Factor (PDGF): PDGF is released from a variety of cells involved in healing, but degranulating platelets that accumulate at disrupted capillaries serve as the earliest sources of PDGF. It is the principal inducer of matrix proteins that are important for creating the provisional matrix that initially fills the void created by tissue damage (Beer et al., 1997). • Transforming Growth Factor-b (TGF-b1, -b2, and -b3): TGFs help to drive the chemotaxis of macrophages to the wound bed. As macrophages accumulate in the wound, concentrations of TGF-β escalate and correspond with the induction of angiogenesis. TGF-β also contributes to new tissue deposition as it regulates the production of
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collagen, proteoglycans, and fibronectin (Ferrara, 2001; Gruss et al., 2003; Takehara, 2000). In fact, its role in new tissue deposition is characterized by its contribution to scar formation. In contrast to adult tissues, fetal tissues heal without scarring and contain substantially less TGF-β (Liu et al., 2004). • Fibroblast Growth Factors (FGF): FGFs are a family of growth factors that are mitogenic for a variety of cells involved in the proliferative phase of healing. Some FGFs drive fibroblast proliferation and new tissue deposition. Other FGFs stimulate endothelial cell proliferation and thus contribute to angiogenesis. Still other FGFs drive keratinocyte proliferation and help drive re-epithelialization (Giavazzi et al., 2003; Takehara, 2000). • Vascular Endothelial Growth Factor (VEGF): VEGF is known to promote angiogenesis. Its expression is enhanced by PDGF and TNF-α, which are produced by the macrophage during the inflammatory stage of repair. In the presence of VEGF, neovascularization of the wound margins begins almost immediately (Diegelmann and Evans, 2004; Ferrara, 2001; Jacobi et al., 2004). • Anti-inflammatory Cytokines: Some cytokines, although present in wounds, do not have direct effects on the process. For example, IL-10 is important for controlling inflammation during the latter stages of healing so that repair can proceed after infection has been controlled (Furudoi et al., 2003). IL-10 inhibits the continued infiltration of neutrophils and macrophages into the wound site, by turning off the expression of chemokine and pro-inflammatory cytokine genes (Liechty et al., 2000; Sato et al., 1999). IL-10 is not produced in quantity until several days into the wound-healing process. As such, inflammation continues unabated for several days until regulatory cytokines such as IL-10 are expressed. This check on inflammation is important because prolonged inflammation may delay closure and increase scarring (Liechty et al., 2000).
B. The Effects of “Stress” on the Inflammatory Phase of Repair When the stages of repair proceed normally, wounds heal without serious consequences. However, the timing of each event during the phases of healing is important, as each component is dependent on the one that came before. Therefore, influences at any of these stages could impact the healing process and delay wound closure. Until recently, most wound-healing biologists agreed that without the macrophage, wound healing
would not proceed correctly. This dogma was based on a 1975 manuscript by Leibovich and Ross (1975) in which a “macrophage-less” animal was created with anti-macrophage serum and hydrocortisone treatment. That animal from 1975 was much more than macrophage deficient. Because glucocorticoids depress inflammatory gene expression by interfering with NFκB– and AP-1–mediated transcription (Caramori and Adcock, 2005; Gougat et al., 2002; Hayashi et al., 2004), treatment of mice with hydrocortisone undoubtedly diminished the expression of many chemokines, cytokines, growth factors, and extracellular matrix proteins involved in healing. Although Leibovich and Ross did not solidify the macrophage as essential to wound healing, they inadvertently showed that inflammatory gene expression was a critical feature of healing. Thus, any influence on inflammatory gene expression could impact healing and potentially affect the rate of closure. Behavioral stress is one of those influences that alter healing. Studies in both animals and humans have shown that psychological stress (e.g., emotional distress, depression, anxiety, helplessness) can delay the closure of small cutaneous wounds by several days (Broadbent et al., 2003; Derr, 1981; Detillion et al., 2004; Ebrecht et al., 2004; Glaser et al., 1999; Glasper and Devries, 2005; Horan et al., 2005; Kiecolt-Glaser et al., 1995; Kiecolt-Glaser et al., 1998; Marucha et al., 1998; Mercado et al., 2002a; Mercado et al., 2002b; Padgett et al., 1998; Rojas et al., 2002; Sheridan et al., 2004). Presumably, psychological and behavioral stressors reduce the onset and magnitude of the inflammatory phase of healing as the production of proinflammatory factors is diminished in stressed subjects. Thus, the recruitment of neutrophils and macrophages is diminished as well as their ability to kill and remove microorganisms. This results in impaired bacterial elimination and delayed wound debridement (i.e., removal of dead, devitalized, or contaminated tissue). For example, in 1995, observations were published showing that the stress of chronic caregiving to Alzheimer’s patients resulted in substantial changes in healing—taking significantly longer in caregivers than in controls (Kiecolt-Glaser et al., 1995). Also, peripheral-blood leukocytes from caregivers also produced significantly less IL-1β mRNA in response to lipopolysaccharide stimulation than did controls’ cells. In addition, in students reporting high levels of psychological stress associated with examination and competency testing, the kinetics of wound repair were slowed in an oral mucosal biopsy model (Marucha et al., 1998). Furthermore, experiments in a murine model showed that the immunosuppressive influences of restraint stress mimicked the delay in wound healing reported
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in the human studies (Mercado et al., 2002a; Padgett et al., 1998). In the animal model, the delay in healing correlated with an increased susceptibility to infection with opportunistic skin microorganisms such as Staphylococcus aureus (Rojas et al., 2002). The data from these experiments suggested that early events in wound healing, particularly during the inflammatory response, represent a critical period in the overall healing process. Again, any influence on inflammatory gene expression could impact healing and potentially affect the rate of closure. How does stress influence the inflammatory phase of wound healing? Psychological stressors activate a body-wide set of physiologic adaptations mediated in part by the hypothalamic-pituitary-adrenal axis. The hypothalamus coordinates responses to environmental stressors through nerves and hormones (for review, see Buijs and Van Eden, 2000; Sawchenko et al., 1996). Visual information, smell, hearing, temperature sensation, and pain alert the hypothalamus to emergencies or environmental hazards. The emotional portions of the brain also relay information to the hypothalamus. From this integrative center, the brain controls hormone secretion from the pituitary gland and other tissues such as the adrenal glands. For example, corticotrophin-releasing hormone is secreted from the paraventricular nucleus of the hypothalamus into the hypophyseal portal blood supply and subsequently stimulates the expression of adrenocorticotrophic hormone (ACTH) in the anterior pituitary gland. ACTH then circulates in the bloodstream to the adrenal glands where it induces the expression and release of glucocorticoid hormones (Tsigos and Chrousos, 2002; Webster and Sternberg, 2004). These hormones affect cardiovascular, renal function, and metabolism and act together with the nervous system to adjust our responses to the environment. As one of the “core stress responses” originally described by Selye in 1936 (Selye, 1936), the acute production of glucocorticoid hormones from the adrenal cortex stimulates the metabolism of glucose to provide for energy to flee or combat an immediate threat. However, when chronically activated, the HPA axis can cause deterioration in general health and worsen existing diseases. Glucocorticoids can regulate a wide variety of immune cell functions. For example, they modulate cytokine expression, chemoattractant expression, adhesion molecule expression and trafficking, proliferation, differentiation, and effector function of many cells of the immune system (reviewed in Ashwell et al., 2000; Elenkov and Chrousos, 2002; Russo-Marie, 1982). Their anti-inflammatory activity is so powerful that glucocorticoids have been used clinically for this
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purpose since the middle of the last century. However, the use of exogenous glucocorticoids has been associated with increased risk of wound contamination and delayed healing of open wounds. Glucocorticoids produce these effects by interfering, not only with inflammation, but also with fibroblast proliferation, collagen synthesis and degradation, angiogenesis, wound contraction, re-epithelialization, and remodeling (Beer et al., 2000; Lee et al., 2005). Glucocorticoids, whether exogenously administered by a physician or endogenously elevated due to psychological stress, regulate the expression of various genes at the wound site that encode key players in each of these wound repair processes. For example, pro-inflammatory cytokines (IL-1 and TNF-α), growth factors (keratinocyte growth factor, TGF-β and PDGF), and re-modeling enzymes (macrophage- and fibroblast-derived matrix metalloproteinases) are targets of glucocorticoid action in wounded skin (Brauchle et al., 1995; Lee et al., 2005). More specifically, from in vitro studies, Snyder and Unanue (1982) demonstrated that hydrocortisone reduced the production of IL-1 by phorbol myristate acetate (PMA)-stimulated murine peritoneal macrophages. Similarly, dexamethasone has also been shown to diminish the rate of TNF-α gene transcription in ex vivo murine macrophages (Beutler et al., 1986). In vivo, and paralleling these findings, Hubner et al. (1996) demonstrated that glucocorticoid-treatment of mice reduced induction of IL-1 and TNF after injury. This effect was associated with reduced infiltration of inflammatory cells into a wound. As a consequence, re-epithelialization was delayed and granulation tissue formation was impaired. It is not just the pro-inflammatory cytokines that are affected by glucocorticoids. Beer, Fassler, and Werner (2000) demonstrated that keratinocyte growth factor; TGF-β1, TGF-β2, and TGF-β3 and their receptors; PDGFs and their receptors; tenascin-C; stromelysin-2; macrophage metalloelastase; and enzymes involved in the generation of nitric oxide are targets of glucocorticoid action in wounded skin. Together, these findings show that the anti-inflammatory steroids inhibit wound repair at least in part by influencing the expression of these key regulatory molecules. To bring this back full circle, multiple experiments suggest that it is the stress-induced glucocorticoids that bear the responsibility for impaired wound healing. For example, experimentally, the circadian pattern of corticosterone synthesis can be disrupted by restraint stress of mice (Hermann et al., 1994). Disruption of the circadian pattern by restraint results in significantly elevated circulating corticosterone in mice. Using this model, it was demonstrated that wounds on mice subjected to restraint stress healed slower than
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those on control animals (Padgett et al., 1998). In addition, the production of inflammatory cytokines, the infiltration of inflammatory cells, and the production of various growth factors were depressed by restraint (Mercado et al., 2002a, 2002b). Owing to the importance of glucocorticoids, in animals treated with various glucocorticoid receptor antagonists such as RU486 and RU40555, many of the influences of stress could be prevented or reversed. For example, in restraint-stressed mice treated with RU486, wound IL1β mRNA levels were restored to normal control levels (Mercado et al., 2002a), and this restoration of inflammatory gene expression correlated with restoration of overall healing kinetics (Padgett et al., 1998). Thus, when the stages of repair proceed without substantive disruption, wound healing progresses without significant negative consequences. However, because the coordination of the wound-healing cascade begins with inflammatory gene expression, a negative event at this stage can potentially impact the overall healing process and delay wound closure. Psychological or behavioral stressors have been shown to mediate such an undesirable effect, in part, through the antiinflammatory influences of glucocorticoid hormones.
III. THE PROLIFERATIVE PHASE OF WOUND REPAIR Once neutrophils have controlled microbial contamination and macrophages have arrived and begun to prepare the wound for repair, the second or proliferative phase of healing can proceed. The goal of this phase is to replace the void with viable but temporary tissue. In doing so, the epidermal barrier is recreated and a functional provisional tissue is created. In cutaneous wounds, this proliferative phase is characterized by re-epithelialization and granulation tissue formation (for review, see Steed 2003). Re-epithelialization is the reconstitution of the cells of the epidermis in order to cover the injured site and restore barrier function. Concomitant with the inflammatory stage of repair, re-epithelialization begins within hours after injury. Epithelial cells from the margin of the wound, and also from residual epithelial structures such as hair follicles, migrate quickly to divide the damaged stroma from the wound space and re-cover the surface of viable tissue. Closure of the wound surface is not solely the responsibility of re-epithelialization; it is the summation of re-epithelialization and wound contraction (Nedelec et al., 2000). Wound contraction is mediated by specialized fibroblasts called myofibroblasts (Darby et al., 1990; Desmouliere et al., 2005). They develop
increased levels of smooth muscle actin. These contractile proteins help the myofibroblasts to line up along the wound margins and essentially pull the edges together toward the center of the wound. By cinching in the edges of the tissue margins through contraction, the amount of tissue required to resurface, or reepithelialize, the wound is minimized. IL-1 is known to stimulate the differentiation of fibroblasts into myofibroblasts (Irwin et al., 1998) and thus, alterations in IL-1 may alter wound contraction and the size of the wound to be re-covered (Dinarello, 1989). Regardless of the size of the void to be filled, new tissue, or granulation tissue, is deposited. Granulation tissue formation consists of fibroplasia and angiogenesis. Fibroplasia is the process of fibroblast recruitment into the wound site, their proliferation, and the ensuing synthesis and secretion of a temporary extracellular matrix of structural collagens and space-filling sugars (i.e., glycosaminoglycans and proteoglycans) (Metz, 2003). The provisional and immature matrix produced during the proliferative phase provides for temporary scaffolding upon which the wound heals. The second aspect of granulation tissue formation is angiogenesis, which is the process of new blood vessel formation. It occurs simultaneously with fibroplasia, commencing within days of injury. The assembly of a dense network of capillaries in the healing scar helps provide the energy and nutrients necessary for the proliferation of fibroblasts, the production of large quantities of provisional matrix, and the secretion of growth factors by macrophages (for review, see Neal, 2001). Fibroblasts play a critical role in the repair and production of connective tissue. In other words, the fibroblast deposits the replacement tissue to fill the void left by injury. The cytokines and growth factors produced by the macrophage recruit and stimulate fibroblasts to proliferate (a.k.a. fibroplasia). In fact, almost as soon as the macrophage arrives in the area of the wound, fibroblasts begin to migrate to the margin of the wound and begin to proliferate. Much like macrophages during the previous inflammatory phase of repair, the fibroblasts have several varied functions to accomplish during the proliferative phase of repair. They synthesize the extracellular matrix components (collagens, fibronectins, glycosaminoglycans) and additional growth factors necessary for subsequent aspects of healing. The first product of the fibroblasts is an appreciable quantity of a glycosaminoglycan called hyaluronic acid (HA) (Croce et al., 2001). HA has a very large negative charge, attracts water into the wound, and forms a provisional “gel” that fills the wound. HA enables the newly deposited tissue to resist compressive forces. Concomitantly, the fibroblast secretes
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extensive amounts of type III collagen (Carlson and Longaker, 2004). The abundance of collagen gives the newly deposited tissue an ability to resist tensile or tearing forces. Together, the network of type III collagen and gel-like HA provide structural support for the newly forming tissue and a scaffold for the migration of the many cell types involved in the repair process. As the new tissue begins to take shape, endothelial cells migrate in response to angiogenic stimuli and form new replacement capillaries (Duraisamy et al., 2001; Tonnesen et al., 2000). The newly formed capillaries are not just to replace the ones that were damaged upon injury. Because of the extensive energy required for new tissue construction, many additional capillaries are created to meet the needs of the dynamic tissue. In fact, healing tissues take on a characteristic granular appearance because of the vast network of newly created blood vessels; new tissue is sometimes referred to as granulation tissue because of this. As new tissue is formed, re-epithelialization begins in earnest. Epithelial cells from the margin of the wound and also from residual epithelial structures such as hair follicles try to recover the injured tissue with a protective barrier (Regauer and Compton, 1990). In an attempt to divide the damaged viable tissue from the non-viable scab, the epithelial cells are stimulated to proliferate and migrate across the wound surface but below the blood clot. The stimulus for angiogenesis and for re-epithelialization originated during the previous inflammatory phase of repair. Growth factors for angiogenesis include VEGF, basic fibroblast growth factor (bFGF), and TGF-beta (Li, Zhang et al., 2003; Neal, 2001). Growth factors for re-epithelialization include keratinocyte growth factor (KGF) and epidermal growth factor (EGF) (Li et al., 2004). During wound healing, the production of all of these growth factors is attributed, at least in part, to the macrophage. Thus, the coordinated expression of many cytokines and growth factors during the early inflammatory phase of repair appears quite important to fibroplasia, angiogenesis, and re-epithelialization, which occur during this later proliferative phase of repair.
A. The Effects of “Stress” on the Proliferative Phase of Repair Stress has the potential to negatively affect three major aspects of the proliferative phase of healing: reepithelialization, wound contraction, and angiogenesis. As stated earlier, glucocorticoids are known to decrease expression of a number of growth factors important during the proliferative phase of healing, e.g., VEGF, KGF, FGF, and TGF-β. Furthermore,
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disruption of the inflammatory phase of healing would also likely disrupt the proliferative phase. Yet, there are a limited number of studies demonstrating stress effects on the proliferative phase of healing. Mercado et al. (2002a; 2002b) showed in two related studies the impact of stress on wound epithelialization. Restrained mice had a reduced expression of an important growth factor for re-epithelialization, KGF1, one day after wounding. Furthermore, in a related study, Mercado demonstrated that stressed mice did not show a normal hyperproliferative epithelium at the margins of their wounds (Mercado, 2002b). The histological appearance showed a thinned atrophic epithelium in stressed mice. In situ analysis demonstrated a substantial reduction in the number of fibroblasts producing KGF-1. Granulation tissue was also reduced in the tissue of restrained mice with focal areas of intense inflammation, suggesting infection. The relative paucity of granulation tissue suggests a potential for decreased production of endothelial cell growth factors although they were not measured in those studies. Epithelial cells are known to be major producers of these growth factors. The overall picture presented is that stress decreased re-epithelialization and reduced granulation tissue at the wound site. Interestingly, the glucocorticoid antagonist, RU486, did not restore normal KGF-1 production, suggesting an alternative pathway for stress impairment of epithelialization. Yet, glucocortioids have been shown to have similar effects on growth factor gene expression (Brauchle et al., 1995; Lee et al., 2005; Werner and Grose, 2003). Recent studies by Horan et al. (2005) showed that stressed mice were impaired in wound contraction. Impaired wound contraction was first apparent one day after wounding and followed the delayed time course seen with overall impaired wound closure. These studies also demonstrated a delay in the differentiation of fibroblasts into myofibroblasts and a failure for fibroblasts to line up along the wound margins. Although TGF-β is thought to play a major role in wound contraction and TGF-β is potentially regulated by glucocorticoids, no difference was found in TGF-β expression. A likely pathway in impaired contraction is through IL-1. IL-1 is known to modulate fibroblast differentiation and migration (Dinarello, 1990, Irwin et al., 1998). As shown previously, stress is known to decrease early IL-1 expression after wounding, and this may be glucocorticoid-mediated (Mercado, 2002a). In summary, stress has been shown to affect several activities during the proliferative phase of healing, including impaired wound contraction, reepithelialization, and the generation of granulation tissue. Although the mechanisms of these effects have
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yet to be fully elucidated, it is likely that glucocorticoids are partly responsible.
IV. THE REMODELING PHASE OF WOUND REPAIR Initial wound closure represents a complex and masterfully orchestrated interaction of cells, the extracellular matrix, cytokines, and growth factors. However, the tissue that is initially deposited during the proliferative phase of repair is temporary. Neither its structure nor its function closely approximates that of the original tissue. The initial type III collagen deposited during construction of the new tissue is poorly organized and does not provide sufficient resistance against tensile forces to which mature tissues are subjected. This unfortunate reality is illustrated by the ease at which healing wounds can be re-injured. In addition, the HA, which was highly capable of resisting compressive forces while new blood vessels and epithelium were created during the proliferative phase of repair, is quite unsatisfactory for mature tissues. HA is poorly organized, and as such, it does not facilitate alignment of the extracellular matrix in parallel with tensile forces. Thus, the large quantity of HA in the provisional matrix further limits the ability of the tissue to resist tensile forces. Over a long period of time that can stretch on for months or years, this provisional tissue is re-crafted. It is during this third and final phase of wound healing when remodeling occurs. In fact, remodeling begins soon after the first molecules of connective tissue are produced by the fibroblast (Steed, 2003). During remodeling, there is a rapid synthesis and degradation of extracellular matrix proteins. The nature of the matrix components in healing tissues changes over time. In an attempt to regenerate the characteristics of the original tissue, provisional matrix molecules are progressively replaced by mature forms of collagens and proteoglycans. For example, fibers of type I collagen, which are characteristic of pre-injury tissues, progressively replace type III collagen (Ballas and Davidson, 2001; Diegelman and Evans, 2004). Similarly, dermatan sulfate and chondroitin sulfate take the place of HA (Raghow, 1994). Through re-modeling, the highly cellular and highly vascular granulation tissue is gradually replaced, forming scar tissue, which is less cellular and less vascular than the temporary granulation tissue (Diegelman and Evans, 2004). Although repaired tissues will not be identical to the original, the resultant remodeled matrix should resemble it in both strength and function whether it is bone, skin, liver, or
any other type of tissue. This remodeling of immature tissues is dependent upon the digestion of the provisional matrix. Matrix metalloproteinases, hyaluronidase, elastase, and collagenases fill this role, and the production of these enzymes is attributed, at least in part, to the macrophage. Thus, the coordinated process of tissue maturation appears to be influenced by the activity of the tissue macrophage that was originally activated during the inflammatory phase of repair.
A. The Effects of “Stress” on the Remodeling Phase of Repair Little data exists regarding the effects of stress on the remodeling phase of healing. Clearly, this phase is dependent upon the previous stages of healing. Protracted inflammation, infection, and poor development of granulation tissue are known to impact the final outcome of healing (Baum and Arpey, 2005; Robson, 1997). As discussed above, several findings during the early phases of healing would suggest a potential for a negative result in the remodeling phase. First, stress has been shown to delay healing (Kiecolt-Glaser, 1995; Kiecolt-Glaser et al., 1998; Marucha et al., 1998; Padgett et al., 1998). Slower healing has been shown to result in increased fibrosis and a weaker final result (Baum and Arpey, 2005). Second, Mercado et al. (2002b) showed that mice subjected to restraint stress exhibited an extended inflammatory response during healing. Control mice reduced pro-inflammatory cytokine gene expression by day 5 after a 3.5 mm wound was placed, while stressed mice still had significant expression of IL-1α and IL-1β 5 days after wounding. In the same model, it was shown that focal areas of intense inflammation occurred, suggesting infection. Indeed, Rojas et al. (2002) demonstrated 4 logs more bacteria in wounds of stressed mice. As bacteria accumulate in the wounded tissue, increased neutrophils are recruited, and increased tissue injury ensues from direct microbial damage and the release of noxious products by neutrophils. All of these findings would suggest an altered remodeling phase of healing. For example, an extended neutrophil response associated with infection is known to lead to increased scarring (Dovi et al., 2004; Robson, 1997). In addition, whereas the deposition of granulation tissue is required for adequate wound strength, exogenous glucocorticoids diminish new tissue synthesis, thereby decreasing wound integrity (Bitar et al., 1999). Furthermore, during the remodeling phase, proliferation of cells and deposition of new tissue must be discontinued, and eventually the hypercellularity of wound tissue must be resolved. This is done through a combination of
39. Stress and Wound Healing: Animal Models
apoptosis and reduced growth factor gene expression. When inflammation continues through later stages of healing, proliferation continues. Again, glucocorticoids are known to alter apoptosis. For example, glucocorticoids extend neutrophils’ life span in tissues and prevent epithelial differentiation (Chang et al., 2004; Sheu et al., 1991). Therefore, there is high potential for stress to alter the remodeling phase of healing, leading to a higher likelihood for scarring and resulting in diminished wound integrity. However, this hypothesis needs to be tested for its validity.
V. CONCLUSIONS There are quite a few growth factors and cytokines present at a wound site during the healing process. Their coordinated expression forms the microenvironment in which the inflammatory cells perform their functions, which include controlling infection, depositing extracellular matrix, migrating across the surface of the damaged region, forming new blood vessels, or remodeling the matrix to approach the original structure and function of the tissue. As wound healing cascades along toward repair, the cytokines expressed earlier stimulate the growth factors that are important to coordinate subsequent processes. What does this mean for wound healing? Understanding the contribution of a chemokine, cytokine, or growth factor will enable manipulation of the wound-healing process to affect a desired outcome. Stress is known to alter the expression of many of these factors in vitro and in vivo. The understanding of their roles in stress-impaired healing is just beginning. Several important questions need to be answered. What are the effects of stress on the whole of the pro-inflammatory phase of wound healing? Are the effects of stress totally directed at the inflammatory phase of healing and the other changes part of that cascade? Does stress alter wound strength and scarring? Are there any other long-term effects to wound tissue biology at the site? Can stressors other than restraint stress give comparable results? Do the other components of the stress response play a role in stress-impaired healing (e.g., opioids, catecholamines, and the sympathetic nervous system)? As these questions are answered, targeted therapies that ameliorate the effects of stress can be developed.
References Anitua, E., Andia, I., Ardanza, B., Nurden, P., and Nurden, A. T. (2004). Autologous platelets as a source of proteins for healing and tissue regeneration. Thromb. Haemost., 91 (1), 4–15. Artuc, M., Hermes, B., Steckelings, U. M., Grutzkau, A., and Henz, B. M. (1999). Mast cells and their mediators in cutaneous wound
847
healing—active participants or innocent bystanders? Exp. Dermatol., 8 (1), 1–16. Ashcroft, G. S., Mills, S. J., and Ashworth, J. J. (2002). Aging and wound healing. Biogerontology, 3 (6), 337–345. Ashwell, J. D., Lu, F. W., and Vacchio, M. S. (2000). Glucocorticoids in T cell development and function. Annu. Rev. Immunol., 18, 309–345. Ballas, C. B., and Davidson, J. M. (2001). Delayed wound healing in aged rats is associated with increased collagen gel remodeling and contraction by skin fibroblasts, not with differences in apoptotic or myofibroblast cell populations. Wound Repair Regen., 9 (3), 223–237. Baum, C. L., and Arpey, C. J. (2005). Normal cutaneous wound healing: clinical correlation with cellular and molecular events. Dermatol. Surg., 31 (6), 674–686. Beer, H. D., Fassler, R., and Werner, S. (2000). Glucocorticoidregulated gene expression during cutaneous wound repair. Vitam. Horm., 59, 217–239. Beer, H. D., Longaker, M. T., and Werner, S. (1997). Reduced expression of PDGF and PDGF receptors during impaired wound healing. J. Invest. Dermatol., 109 (2), 132–138 . Beutler, B., Krochin, N., Milsark, I. W., Luedke, C., and Cerami, A. (1986). Control of cachectin (tumor necrosis factor) synthesis: mechanisms of endotoxin resistance. Science, 232 (4753), 977–980. Bingle, L., Brown, N. J., and Lewis, C. E. (2002). The role of tumourassociated macrophages in tumour progression: implications for new anticancer therapies. J. Pathol., 196 (3), 254–265. Bitar, M. S., Farook, T., Wahid, S., and Francis, I. M. (1999). Glucocorticoid-dependent impairment of wound healing in experimental diabetes: amelioration by adrenalectomy and RU 486. J. Surg. Res., 82 (2), 234–243. Brauchle, M., Fassler, R., and Werner, S. (1995). Suppression of keratinocyte growth factor expression by glucocorticoids in vitro and during wound healing. J. Invest. Dermatol., 105 (4), 579–584. Broadbent, E., Petrie, K. J., Alley, P. G., and Booth, R. J. (2003). Psychological stress impairs early wound repair following surgery. Psychosom. Med., 65 (5), 865–869. Buijs, R. M., and Van Eden, C. G. (2000). The integration of stress by the hypothalamus, amygdala and prefrontal cortex: balance between the autonomic nervous system and the neuroendocrine system. Prog. Brain Res., 126, 117–132. Burg, N. D., and Pillinger, M. H. (2001). The neutrophil: function and regulation in innate and humoral immunity. Clin. Immunol., 99 (1), 7–17. Caramori, G., and Adcock, I. (2005). Anti-inflammatory mechanisms of glucocorticoids targeting granulocytes. Curr. Drug Targets Inflamm. Allergy, 4 (4), 455–463. Carlson, M. A., and Longaker, M. T. (2004). The fibroblast-populated collagen matrix as a model of wound healing: a review of the evidence. Wound Repair Regen., 12 (2), 134–147. Chang, L. C., Madsen, S. A., Toelboell, T., Weber, P. S., and Burton, J. L. (2004). Effects of glucocorticoids on Fas gene expression in bovine blood neutrophils. J. Endocrinol., 183 (3), 569–583. Chitnis, D., Dickerson, C., Munster, A. M., and Winchurch, R. A. (1996). Inhibition of apoptosis in polymorphonuclear neutrophils from burn patients. J. Leukoc. Biol., 59 (6), 835–839. Clark, R. A. (2001a). Fibrin and wound healing. Ann. N. Y. Acad. Sci., 936, 355–367. Clark, R. A. (2001b). Growth factors and wound repair. J. Cell Biochem., 46 (1), 1–2. Croce, M. A., Dyne, K., Boraldi, F., Quaglino, D. Jr, Cetta, G., Tiozzo, R., and Pasquali Ronchetti, I. (2001). Hyaluronan affects protein and collagen synthesis by in vitro human skin fibroblasts. Tissue Cell, 33 (4), 326–331.
848
IV. Stress and Immunity
Darby, I., Skalli, O., and Gabbiani, G. (1990). Alpha-smooth muscle actin is transiently expressed by myofibroblasts during experimental wound healing. Lab. Invest., 63 (1), 21–29. Dasgupta, D., Chakraborty, P., and Basu, M. K. (2000). Ligation of Fc receptor of macrophages stimulates protein kinase C and antileishmanial activity. Mol. Cell Biochem., 209 (1–2), 1–8. Derr, R. F. (1981). Restraint stress inhibited healing in rats. Physiol. Behav., 27 (5), 941–942. Desmouliere, A., Chaponnier, C., and Gabbiani, G. (2005). Tissue repair, contraction, and the myofibroblast. Wound Repair Regen., 13 (1), 7–12. Detillion, C. E., Craft, T. K., Glasper, E. R., Prendergast, B. J., and DeVries, A. C. (2004). Social facilitation of wound healing. Psychoneuroendocrinology, 29 (8), 1004–1011. Diegelmann, R. F., and Evans, M. C. (2004). Wound healing: an overview of acute, fibrotic and delayed healing. Front. Biosci., 9, 283–289. Dinarello, C. A. (1989). Interleukin-1 and its biologically related cytokines. Adv. Immunol., 44, 153–205. DiPietro, L. A., Burdick, M., Low, Q. E., Kunkel, S. L., and Strieter, R. M. (1998). MIP-1alpha as a critical macrophage chemoattractant in murine wound repair. J. Clin. Invest., 101 (8), 1693–1698. Dovi, J. V., Szpaderska, A. M., and DiPietro, L. A. (2004). Neutrophil function in the healing wound: adding insult to injury? Thromb. Haemost., 92, 275–280. Duraisamy, Y., Slevin, M., Smith, N., Bailey, J., Zweit, J., Smith, C., Ahmed, N., and Gaffney, J. (2001). Effect of glycation on basic fibroblast growth factor induced angiogenesis and activation of associated signal transduction pathways in vascular endothelial cells: possible relevance to wound healing in diabetes. Angiogenesis, 4 (4), 277–288. Dusi, S., Donini, M., Lissandrini, D., Mazzi, P., Bianca, V. D., and Rossi, F. (2001). Mechanisms of expression of NADPH oxidase components in human cultured monocytes: role of cytokines and transcriptional regulators involved. Eur. J. Immunol., 31 (3), 929–938. Ebrecht, M., Hextall, J., Kirtley, L. G., Taylor, A., Dyson, M., and Weinman, J. (2004). Perceived stress and cortisol levels predict speed of wound healing in healthy male adults. Psychoneuroendocrinology, 29 (6), 798–809. Elenkov, I. J., and Chrousos, G. P. (2002). Stress hormones, proinflammatory and antiinflammatory cytokines, and autoimmunity. Ann. N. Y. Acad. Sci., 966, 290–303. Engelhardt, E., Toksoy, A., Goebeler, M., Debus, S., Brocker, E. B., and Gillitzer, R. (1998). Chemokines IL-8, GROalpha, MCP-1, IP-10, and Mig are sequentially and differentially expressed during phase-specific infiltration of leukocyte subsets in human wound healing. Am. J. Pathol., 153 (6), 1849–1860. Fadeel, B., and Kagan, V. E. (2003). Apoptosis and macrophage clearance of neutrophils: regulation by reactive oxygen species. Redox. Rep., 8 (3), 143–150. Ferrara, N. (2001). Role of vascular endothelial growth factor in regulation of physiological angiogenesis. Am. J. Physiol. Cell Physiol., 280 (6), C1358–C1366. Francel, P. C. (1992). Bradykinin and neuronal injury. J. Neurotrauma, 9 (Suppl 1), S27–S45. Furudoi, S., Yoshii, T., and Komori, T. (2003). Balance of tumor necrosis factor alpha and interleukin-10 in a buccal infection in a streptozotocin-induced diabetic rat model. Cytokine, 24 (4), 143–149. Giavazzi, R., Sennino, B., Coltrini, D., Garofalo, A., Dossi, R., Ronca, R., Tosatti, M. P., and Presta, M. (2003). Distinct role of fibroblast growth factor-2 and vascular endothelial growth factor on tumor growth and angiogenesis. Am. J. Pathol., 162 (6), 1913–1926.
Gillitzer, R., and Goebeler, M. (2001). Chemokines in cutaneous wound healing. J. Leukoc. Biol., 69 (4), 513–521. Glaser, R., Kiecolt-Glaser, J. K., Marucha, P. T., MacCallum, R. C., Laskowski, B. F., and Malarkey, W. B. (1999). Stress-related changes in proinflammatory cytokine production in wounds. Arch. Gen. Psychiatry, 56 (5), 450–456. Glasper, E. R., and Devries, A. C. (2005). Social structure influences effects of pair-housing on wound healing. Brain Behav. Immun., 19 (1), 61–68. Gougat, C., Jaffuel. D., Gagliardo, R., Henriquet, C., Bousquet, J., Demoly, P., and Mathieu, M. (2002). Overexpression of the human glucocorticoid receptor alpha and beta isoforms inhibits AP-1 and NF-kappaB activities hormone independently. J. Mol. Med., 80 (5), 309–318. Gruss, C. J., Satyamoorthy, K., Berking, C., Lininger, J., Nesbit, M., Schaider, H., Liu, Z. J., Oka, M., Hsu, M. Y., Shirakawa, T., Li, G., Bogenrieder, T., Carmeliet, P., El-Deiry, W. S., Eck, S. L., Rao, J. S., Baker, A. H., Bennet, J. T., Crombleholme, T. M., Velazquez, O., Karmacharya, J., Margolis, D. J., Wilson, J. M., Detmar, M., Skobe, M., Robbins, P. D., Buck, C., and Herlyn, M. (2003). Stroma formation and angiogenesis by overexpression of growth factors, cytokines, and proteolytic enzymes in human skin grafted to SCID mice. J. Invest. Dermatol., 120 (4), 683–692. Hart, J. (2002). Inflammation. 1: Its role in the healing of acute wounds. J. Wound Care, 11 (6), 205–209. Hayashi, R., Wada, H., Ito, K., and Adcock, I. M. (2004). Effects of glucocorticoids on gene transcription. Eur. J. Pharmacol., 500 (1–3), 51–62. Henry, G., and Garner, W. L. (2003). Inflammatory mediators in wound healing. Surg. Clin. North Am., 83 (3), 483–507. Hermann, G., Tovar, C. A., Beck, F. M., and Sheridan, J. F. (1994). Kinetics of glucocorticoid response to restraint stress and/or experimental influenza viral infection in two inbred strains of mice. J. Neuroimmunol., 49 (1–2), 25–33. Hieta, N., Impola, U., Lopez-Otin, C., Saarialho-Kere, U., and Kahari, V. M. (2003). Matrix metalloproteinase-19 expression in dermal wounds and by fibroblasts in culture. J. Invest. Dermatol., 121 (5), 997–1004. Horan, M. P., Quan, N., Subramanian, S. V., Strauch, A. R., Gajendrareddy, P. K., and Marucha, P. T. (2005). Impaired wound contraction and delayed myofibroblast differentiation in restraintstressed mice. Brain Behav. Immun., 19 (3), 207–216. Hubner, G., Brauchle, M., Smola, H., Madlener, M., Fassler, R., and Werner, S. (1996). Differential regulation of pro-inflammatory cytokines during wound healing in normal and glucocorticoidtreated mice. Cytokine, 8 (7), 548–556. Irwin, C. R., Myrillas, T., Smyth, M., Doogan, J., Rice, C., and Schor, S. L. (1998). Regulation of fibroblast-induced collagen gel contraction by interleukin-1beta. J. Oral. Pathol. Med., 27 (6), 255–259. Jacobi, J., Tam, B. Y., Sundram, U., von Degenfeld, G., Blau, H. M., Kuo, C. J., and Cooke, J. P. (2004). Discordant effects of a soluble VEGF receptor on wound healing and angiogenesis. Gene Ther., 11 (3), 302–309. Karlsson, A., and Dahlgren, C. (2002). Assembly and activation of the neutrophil NADPH oxidase in granule membranes. Antioxid. Redox. Signal., 4 (1), 49–60. Kiecolt-Glaser, J. K., Marucha, P. T., Malarky, W. B., Mercado, A. M., and Glaser, R. (1995). Slowing of wound healing by psychological stress. Lancet, 346, 1194–1196. Kiecolt-Glaser, J. K., Page, G. G., Marucha, P. T., MacCallum, R. C., and Glaser, R. (1998). Psychological influences on surgical recovery. Perspectives from psychoneuroimmunology. Am. Psychol., 53, 1209–1218.
39. Stress and Wound Healing: Animal Models King, S. M., and Reed, G. L. (2002). Development of platelet secretory granules. Semin. Cell Dev. Biol., 13 (4), 293–302. Kurosaka, K., Takahashi, M., Watanabe, N., and Kobayashi, Y. (2003). Silent cleanup of very early apoptotic cells by macrophages. J. Immunol., 171 (9), 4672–4679. Lee, B., Vouthounis, C., Stojadinovic, O., Brem, H., Im, M., and Tomic-Canic, M. (2005). From an enhanceosome to a repressosome: molecular antagonism between glucocorticoids and EGF leads to inhibition of wound healing. J. Mol. Biol., 345 (5), 1083–1097. Leibovich, S. J., and Ross, R. (1975). The role of the macrophage in wound repair. A study with hydrocortisone and antimacrophage serum. Am. J. Pathol., 78 (1), 71–100. Li, J., Zhang, Y. P., and Kirsner, R. S. (2003). Angiogenesis in wound repair: angiogenic growth factors and the extracellular matrix. Microsc. Res. Tech., 60 (1), 107–114. Li, M. O., Sarkisian, M. R., Mehal, W. Z., Rakic, P., and Flavell, R. A. (2003). Phosphatidylserine receptor is required for clearance of apoptotic cells. Science, 302 (5650), 1560–1563. Li, W., Henry, G., Fan, J., Bandyopadhyay, B., Pang, K., Garner, W., Chen, M., and Woodley, D. T. (2004). Signals that initiate, augment, and provide directionality for human keratinocyte motility. J. Invest. Dermatol., 123 (4), 622–633. Liechty, K. W., Kim. H. B., Adzick, N. S., and Crombleholme, T. M. (2000). Fetal wound repair results in scar formation in interleukin-10–deficient mice in a syngeneic murine model of scarless fetal wound repair. J. Pediatr. Surg., 35 (6), 866–872. Liu, W., Wang, D. R., and Cao, Y. L. (2004). TGF-beta: a fibrotic factor in wound scarring and a potential target for anti-scarring gene therapy. Curr. Gene Ther., 4 (1), 123–136. Low, Q. E., Drugea, I. A., Duffner, L. A., Quinn, D. G., Cook, D. N., Rollins, B. J., Kovacs, E. J., and DiPietro, L. A. (2001). Wound healing in MIP-1alpha(−/−) and MCP-1(−/−) mice. Am. J. Pathol., 159 (2), 457–634. Madlener, M., Parks, W. C., and Werner, S. (1998). Matrix metalloproteinases (MMPs) and their physiological inhibitors (TIMPs) are differentially expressed during excisional skin wound repair. Exp. Cell Res., 242 (1), 201–210. Mannaioni, P. F., Di Bello, M. G., and Masini, E. (1997). Platelets and inflammation: role of platelet-derived growth factor, adhesion molecules and histamine. Inflamm. Res., 46 (1), 4–18. Martin, P., D’Souza, D., Martin, J., Grose, R., Cooper, L., Maki, R., and McKercher, S. R. (2003). Wound healing in the PU. 1 null mouse—tissue repair is not dependent on inflammatory cells. Curr. Biol., 13 (13), 1122–1128. Marucha, P. T., Kiecolt-Glaser, J. K., and Favagehi, M. (1998). Mucosal wound healing is impaired by examination stress. Psychosom. Med., 60, 362–365. Mercado, A. M., Padgett, D. A., Sheridan, J. F., and Marucha, P. T. (2002a). Altered kinetics of IL-1 alpha, IL-1 beta, and KGF-1 gene expression in early wounds of restrained mice. Brain Behav. Immun., 16 (2), 150–162. Mercado, A. M., Quan, N., Padgett, D. A., Sheridan, J. F., and Marucha, P. T. (2002b). Restraint stress alters the expression of interleukin-1 and keratinocyte growth factor at the wound site: an in situ hybridization study. J. Neuroimmunol., 129 (1–2), 74–83. Metz, C. N. (2003). Fibrocytes: a unique cell population implicated in wound healing. Cell Mol. Life Sci., 60 (7), 1342–1350. Neal, M. S. (2001). Angiogenesis: is it the key to controlling the healing process? J. Wound Care, 10 (7), 281–287. Nedelec, B., Ghahary, A., Scott, P. G., and Tredget, E. E. (2000). Control of wound contraction. Basic and clinical features. Hand Clin., 16 (2), 289–302.
849
Ofosu, F. A. (2002). The blood platelet as a model for regulating blood coagulation on cell surfaces and its consequences. Biochemistry (Mosc.), 67 (1), 47–55. Ortega, N., L’Faqihi, F. E., and Plouet, J. (1998). Control of vascular endothelial growth factor angiogenic activity by the extracellular matrix. Biol. Cell, 90 (5), 381–390. Padgett, D. A., Marucha, P. T., and Sheridan, J. F. (1998). Restraint stress slows cutaneous wound healing in mice. Brain Behav. Immun., 12 (1), 64–73. Raghow, R. (1994). The role of extracellular matrix in postinflammatory wound healing and fibrosis. FASEB J., 8 (11), 823–831. Regauer, S., and Compton, C. C. (1990). Cultured keratinocyte sheets enhance spontaneous re-epithelialization in a dermal explant model of partial-thickness wound healing. J. Invest. Dermatol., 95 (3), 341–346. Robins, P., Day, C. L. Jr, and Lew, R. A. (1984). A multivariate analysis of factors affecting wound-healing time. J. Dermatol. Surg. Oncol., 10 (3), 219–221. Robson, M. C. (1997). Wound infection: a failure of wound healing caused by an imbalance of bacteria. Surg. Clin. of North Amer., 77, 637–650. Rojas, I. G., Padgett, D. A., Sheridan, J. F., and Marucha, P. T. (2002). Stress-induced susceptibility to bacterial infection during cutaneous wound healing. Brain Behav. Immun., 16 (1), 74–84. Rossi, D., and Slotnik, A. (2000). The biology of chemokines and their receptors. Annual Rev. Immunol., 18, 217–242. Russo-Marie, F. (1992). Macrophages and the glucocorticoids. J. Neuroimmunol., 40 (2–3), 281–286. Sato, Y., Ohshima, T., and Kondo, T. (1999). Regulatory role of endogenous interleukin-10 in cutaneous inflammatory response of murine wound healing. Biochem. Biophys. Res. Commun., 265 (1), 194–199. Sawchenko, P. E., Brown, E. R., Chan, R. K., Ericsson, A., Li, H. Y., Roland, B. L., and Kovacs, K. J. (1996). The paraventricular nucleus of the hypothalamus and the functional neuroanatomy of visceromotor responses to stress. Prog. Brain Res., 107, 201–222. Scapini, P., Lapinet-Vera, J. A., Gasperini, S., Calzetti, F., Bazzoni, F., and Cassatella, M. A. (2000). The neutrophil as a cellular source of chemokines. Immunol. Rev., 177, 195–203. Selye, H. (1936). A syndrome produced by diverse nocuous agents. Nature, (Lond.). 138, 32. Sheridan, J. F., Padgett, D. A., Avitsur, R., and Marucha, P. T. (2004). Experimental models of stress and wound healing. World J. Surg., 28 (3), 327–330. Sheu, H. M., Tai, C. L., Kuo, K. W., Yu, H. S., and Chai, C. Y. (1991). Modulation of epidermal terminal differentiation in patients after long-term topical corticosteroids. J. Dermatol., 18 (8), 454–464. Singer, A. J., and Clark, R. A. (1999). Cutaneous wound healing. New England Journal of Medicine, 341 (10), 738–746. Snyder, D. S., and Unanue, E. R. (1982). Corticosteroids inhibit murine macrophage Ia expression and interleukin 1 production. J. Immunol., 129 (5), 1803–1805. Steed, D. L. (2003). Wound-healing trajectories. Surg. Clin. North Am., 83 (3), 547–555. Stein, B. N., Gamble, J. R., Pitson, S. M., Vadas, M. A., and KhewGoodall, Y. (2003). Activation of endothelial extracellular signalregulated kinase is essential for neutrophil transmigration: potential involvement of a soluble neutrophil factor in endothelial activation. J. Immunol., 171 (11), 6097–6104. Sylvia, C. J. (2003). The role of neutrophil apoptosis in influencing tissue repair. J. Wound Care, 12 (1), 13–16. Takehara, K. (2000). Growth regulation of skin fibroblasts. J. Dermatol. Sci., 24 (Suppl 1), S70–S77.
850
IV. Stress and Immunity
Theilbaard-Monch, K., Knudsen, S., Follin, P., and Borregaard, N. (2004). The transcriptional activation program of human neutrophils in skin lesions supports their important role in wound healing. J. Immunol., 172, 7684–7693. Tonnesen, M. G., Feng, X., and Clark, R. A. (2000). Angiogenesis in wound healing. J. Investig. Dermatol. Symp. Proc., 5 (1), 40–46. Torkvist, L., Mansson, P., Raud, J., Larsson, J., and Thorlacius, H. (2001). Role of CD18-dependent neutrophil recruitment in skin and intestinal wound healing. Eur. Surg. Res., 33 (4), 249–254. Tsang, Y. T., Neelamegham, S., Hu, Y., Berg, E. L., Burns, A. R., Smith, C. W., and Simon, S. I. (1997). Synergy between L-selectin signaling and chemotactic activation during neutrophil adhesion and transmigration. J. Immunol., 159 (9), 4566–4577. Tsigos, C., and Chrousos, G. P. (2002). Hypothalamic-pituitaryadrenal axis, neuroendocrine factors and stress. J. Psychosom. Res., 53 (4), 865–871.
Wagner, D. D., and Burger, P. C. (2003). Platelets in inflammation and thrombosis. Arterioscler. Thromb. Vasc. Biol., 23 (12), 2131– 2137. Waldorf, H., and Fewkes, J. (1995). Wound healing. Advances in Dermatology, 10, 77–96. Wan, M. X., Wang, Y., Liu, Q., Schramm, R., and Thorlacius, H. (2003). CC chemokines induce P-selectin–dependent neutrophil rolling and recruitment in vivo: intermediary role of mast cells. Br. J. Pharmacol., 138 (4), 698–706. Webster, J. I., and Sternberg, E. M. (2004). Role of the hypothalamicpituitary-adrenal axis, glucocorticoids and glucocorticoid receptors in toxic sequelae of exposure to bacterial and viral products. J. Endocrinol., 181 (2), 207–221. Weisel, J. W. (2005). Fibrinogen and fibrin. Adv. Protein Chem., 70, 247–299. Werner, S., and Grose, R. (2003). Regulation of wound healing by growth factors and cytokines. Physiol. Rev., 83 (3), 835–870.
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40 Reactivation of Latent Herpes Viruses in Astronauts DUANE L. PIERSON, SATISH K. MEHTA, AND RAYMOND P. STOWE
I. II. III. IV. V. VI. VII. VIII. IX. X.
INTRODUCTION 851 HUMAN SPACE FLIGHT 851 SPACECRAFT ENVIRONMENT 852 LIMITATIONS OF SPACE FLIGHT INVESTIGATIONS 852 STRESS ASSOCIATED WITH SPACE FLIGHT 853 NEUROENDOCRINE AND IMMUNE RESPONSES 853 SPACE FLIGHT STUDIES OF REACTIVATION OF LATENT HERPES VIRUSES 856 MEDICAL SIGNIFICANCE OF LATENT VIRUS REACTIVATION IN SPACE FLIGHT 863 SUMMARY 864 FUTURE DIRECTIONS 864
changes in astronauts. Astronauts are in excellent health and in superb physical condition. Illnesses in astronauts during space flight are not common, are generally mild, and rarely affect mission objectives. In an attempt to clarify this issue, we identified the latent herpes viruses as medically important indicators of the effects of space flight on immunity. This chapter demonstrates that space flight leads to asymptomatic reactivation of latent herpes viruses and proposes that this results from marked changes in neuroendocrine function and immunity caused by the inherent stressfulness of human space flight.
II. HUMAN SPACE FLIGHT I. INTRODUCTION The Apollo Program culminated in the first human venture away from planet Earth. In the more than 30 years since the Apollo Program was completed, spacefaring humans have been restricted to low Earth orbit within the Earth’s magnetic field. Human physiology investigations have been conducted on the space shuttle (mission durations ≤16 days), Skylab (28, 56, and 84 days), the International Space Station (180 days), and the Russian Space Station Mir (≤366 days). The National Aeronautics and Space Administration (NASA) is actively planning ambitious human exploration missions to the moon and Mars. The exploration program will unfold in phases over many years and will be subject to substantial changes, as it is only in the planning stages now. Development of a new crew exploration vehicle is essential for the exploration missions. After verification of the new vehicle in Earth and
Space flight has many adverse effects on human physiology. Changes in multiple systems, including the cardiovascular, musculoskeletal, neurovestibular, endocrine, and immune systems, have occurred (Graebe et al., 2004; White and Averner, 2001; Williams, 2003). Alterations in drug pharmacokinetics and pharmacodynamics (Graebe et al., 2004), nutritional needs (Smith et al., 2005), renal stone formation (Zerwekh, 2002), and microbial flora (Castro et al., 2004) have also been reported. Evidence suggests that the magnitude of some changes may increase with time in space. A variety of changes in immunity have been reported during both short (≤16 days) and long (>30 days) space missions. However, it is difficult to determine the medical significance of these immunological PSYCHONEUROIMMUNOLOGY, 4E VOLUME II
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lunar orbits, exploration will begin with a return to the moon for stays on the surface of approximately 180 days. An exploratory mission to Mars will follow this phase. The first human exploration mission to Mars will probably consist of a detailed study of the surface from orbit. This approximately 400-day Mars orbital mission will be followed by missions in which astronauts will descend to the Martian surface for closer study. The transit time for a round trip of nearly 90 million miles to Mars with current propulsion systems is expected to be about 12 months, and astronauts will explore the surface for about 12 to 18 months, making the total mission duration 24 to 30 months. The estimated date for the beginning of the Mars missions is no earlier than 2025. Exploration of Mars will be a singular accomplishment in human history.
efficiency particulate air (HEPA) filters to remove microbial contaminants and particulates. The levels of bacterial and fungal contaminants in the air and on surfaces of the ISS are lower than in most homes and offices. The most commonly isolated bacterial species found in air and on surfaces of the ISS, Mir, and space shuttle are Staphylococcus spp., Micrococcus spp., and Bacillus spp. The fungal species most commonly isolated are Aspergillus spp. and Penicillium spp. The microbiological risks associated with space flight and characterization of microbial content of spacecraft have been reported (Castro et al., 2004; Pierson, 2001). Mars exploration spacecraft will provide similar internal environments for crew habitation. However, because of vast distances, the Mars spacecraft must be much less dependent upon Earth for resupplies (e.g., water and food) and technical support.
III. SPACECRAFT ENVIRONMENT The environment typically provided by spacecraft for astronauts to live and work in is relatively small, confined, and closed, yet complex with respect to technology and contaminants. Major challenges for exploration missions will include maintenance of basic environmental parameters. The spacecraft environment must provide appropriate temperature, humidity, and breathing air with generally low levels of chemical and biological contaminants. Biologically and chemically safe drinking water and a nutritious and varied food supply are also essential. For exploration missions, the environmental systems providing and maintaining the air and water must function without failure for about 3 years in a space environment. The environment on board the space shuttle, the Russian Soyuz spacecraft, and the International Space Station (ISS) includes an atmosphere of 20% oxygen and 80% nitrogen at 14.7 psi. A temperature range from 70 to 75°F (21 to 24°C) and a relative humidity of 35 to 45% provide a shirt-sleeve environment. Drinking water on board the ISS is currently provided by a Russian system that reclaims humidity condensate (and in the future will reclaim urine). It provides drinking water and hot and warm water for rehydration of foods and drinks. The U.S. will provide a waterprocessing assembly that will produce additional potable water. Ground-supplied water is also transported to the ISS and, along with shuttle-produced water, is distributed for use. Gram-negative bacteria of low pathogenic potential are the major microbiological contaminants of water on the ISS (Pierson, 2001). Breathing air is reconditioned by removal of trace chemical contaminants and recycled through high-
IV. LIMITATIONS OF SPACE FLIGHT INVESTIGATIONS The space flight environment puts many constraints on science investigations, and performing experiments can itself be a source of stress for astronauts. All human space flight investigations require approval from the Johnson Space Center Committee for the Protection of Human Subjects, and astronauts may select investigations in which to participate as a human subject. Access of researchers to astronauts is always limited, but is more likely to be available before and after space flight than during flight. The earliest time that post-flight samples can be obtained is several hours after landing. During space shuttle missions, collection of blood, urine, saliva, and other specimens is very limited because of the great demands on astronauts’ time and the limited equipment available. Equipment needed to support the in-flight phase of science investigations must meet stringent limitations on its volume, mass, power requirements, calibration needs, maintenance, consumables (shelf life must be considered), waste products, and expertise required for operation. In addition, many instruments commonly used in biomedical experiments do not operate properly in microgravity. Few shuttle flights are dedicated to life sciences investigations. Typically, a crew of seven astronauts is divided into two teams. Work proceeds throughout a 24-hour period; one team is working while the other team sleeps. The workload is very heavy for the flight crew, who conduct many science investigations and carry out other spacecraft duties. An investigation that meets all of the science requirements and equipment
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constraints, and in which crew members are willing to participate, may still not be included because space available for stowing the investigation’s support equipment is insufficient. Most studies are limited to small numbers of human or animal subjects.
V. STRESS ASSOCIATED WITH SPACE FLIGHT Astronauts experience uniquely stressful environments during space flight. Potential stressors include confinement in an unfamiliar, crowded environment, isolation, separation from family, anxiety, fear, sleep deprivation, psychosocial issues, physical exertion, noise, variable acceleration forces, increased radiation, and others. Many of these are intermittent and variable in duration and intensity, but variable gravity forces (including transitions from launch acceleration to microgravity and from microgravity to planetary gravity) and variable radiation levels are part of each mission and contribute to a stressful environment that cannot be duplicated on Earth. Radiation outside the Earth’s magnetosphere is particularly worrisome because it includes ionizing radiation from cosmic galactic radiation. Increased stress levels appear even before flight, presumably from the rigors of pre-flight training and the anticipation of the mission.
VI. NEUROENDOCRINE AND IMMUNE RESPONSES A. Stress Hormones The main neuroendocrine responses to stress are mediated through the hypothalamic-pituitaryadrenocortical (HPA) and sympathetic-adrenalmedullary axes. Both of these systems are active in the human response to space flight, but they seem to be activated by different stresses. Because of constraints on sampling and stowage during space flight, most of the data pertaining to changes in stress hormones and immune studies have been derived from samples taken before launch and after landing. Cortisol is the stress hormone that has been measured most often in samples from astronauts. Even before launch, stress-related changes in cortisol concentrations can occur. Serum cortisol levels of two cosmonauts was greater 15 days before launch than at 2 months before launch (Caillot-Augusseau et al., 1998). Plasma cortisol levels of shuttle astronauts was also greater before flight (10 days before launch) than at their annual medical exams, a period well removed
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from launch and generally considered to be a period of low stress (Stowe et al., 2000). These results indicate that the time when pre-flight samples are obtained must be considered in interpreting results for analytes that could be affected by stress. For example, L − 10 (10 days before launch) has been used in many studies as a baseline value. More recent studies have demonstrated that most astronauts are experiencing considerable stress by L − 10, leading to the conclusion that the annual medical exam is a more suitable baseline than a time shortly before flight (Mehta et al., 2000b; Mehta et al., 2001; Pierson et al., 2005). Although in-flight data are very limited, a pattern has emerged for the early phase of flight. One astronaut had a significant elevation in urinary cortisol immediately after launch (Leach, 1987). For both crews of the Spacelab Life Sciences (SLS) missions, urinary cortisol was also significantly increased immediately after launch, 128% in the SLS-1 crew and 146% in the SLS-2 crew (Leach et al., 1996). During flight days 2–9 of SLS-1, urinary cortisol returned to pre-flight levels, whereas during SLS-2 it was significantly elevated throughout most of the flight. In the STS-95 mission, plasma cortisol of both participating crew members was significantly elevated after launch (Stowe et al., 2001a). In the later “adaptive” phase of space flight, cortisol levels have been reported to either not change or increase. Throughout the Skylab missions (28 to 84 days duration), plasma and urinary cortisol concentrations were generally greater than they were before flight (Leach and Rambaut, 1977). During the Salyut-7 mission, on flight days 43–45 urinary excretion of cortisol was less than before flight, but on flight day 88 it was greater than pre-flight values (Vorobyev et al., 1986). On days 216–219 of the 237-day Salyut flight, plasma cortisol was increased; urinary cortisol was not observed to change (Gazenko et al., 1988). Toward the end of a 241-day Mir mission, plasma cortisol was unchanged from pre-flight levels (Grigoriev et al., 1990). Urinary cortisol levels of two subjects on a later Mir mission were greater between flight days 88 and 186 than before flight, but urinary cortisol of four other subjects was less during flight (Stein et al., 1999). It has been proposed that the variability in cortisol levels during long-duration missions may be caused by mission-specific stress (Stein et al., 1999), changes in the steroidogenesis pathway (Vorobyev et al., 1986), disruption of circadian rhythms (Leach Huntoon and Cintron, 1996), and the operation of negative feedback loops (Gauquelin et al., 1990; Leach Huntoon and Cintron, 1996). Plasma cortisol concentrations have generally been lower after short-term space flight than before flight:
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They were 27% less in 30 Apollo astronauts at landing than before flight (Leach et al., 1975), and 3% less in 133 Shuttle astronauts at landing (Leach, 1992). In contrast, measurement of 24-hour urine pools has generally revealed a greater concentration of cortisol after landing than before flight (Crucian, 2000; Mehta et al., 2000b; Stowe et al., 1999; Stowe et al., 2000). Plasma cortisol has a short half-life in the circulation (<90 minutes). Its concentration may have been greater at landing than before flight, but may have dropped below pre-flight values by the time post-flight samples were taken (3 to 4 hours after landing) (Mehta et al., 2001). Mission duration may also affect the magnitude of the stress response at landing. After missions of 9 or fewer days, plasma cortisol levels were significantly lower than before flight and urinary cortisol was unchanged, but after 16-day missions, both plasma and urinary cortisol were significantly greater than before flight (Figure 1) (Stowe et al., 2003). Plasma and urinary cortisol have also increased at landing after the longer International Space Station (ISS) missions (R. P. Stowe, unpublished data). Catecholamine levels have usually been measured in urine rather than blood. After short-term space flights, urinary catecholamines have been elevated (Crucian, 2000; Meehan et al., 1993; Mehta et al., 2000b; Stowe et al., 1999; Stowe et al., 2000; Stowe et al., 2001a), but after missions of 16 days, they were not elevated (Stowe et al., 2003). During space flight, catecholamines generally are not elevated, indicating that little or no sympathetic adrenal activation occurs.
Two 16-Day Flights (n = 12)
400
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Percent change in stress hormones
Three 9-Day Flights (n = 16)
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100
0
-100
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Plasma ACTH
Plasma Cortisol
U r i na r y Cortisol
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U r in a r y Cortisol
FIGURE 1 Changes in plasma adrenocorticotropic hormone (ACTH) and plasma and urinary cortisol after 9- and 16-day space flights. Percent change in stress hormones at landing (R + 0) is expressed as the difference between the values at landing and before flight, as a percentage of the preflight (L – 10) value, for each individual. * indicates P < 0.05. From Stowe et al. (2003, Fig. 1, p. 1282), with permission.
Landing stresses, however, result in significant elevations in plasma and urinary catecholamine concentrations (Mehta et al., 2000b; Smith et al., 1997). Some of the discrepancies between the results of different space-flight studies may be explained by differences between type and time of sample, and by the small number of subjects for whom in-flight data are available. In the bloodstream, about 85% of total cortisol is bound to corticosteroid-binding globulin (CBG). Urinary cortisol is reported as unbound cortisol. Only the unbound form is biologically active (Granger et al., 1999; Kirschbaum and Hellhammer, 1989; Kirschbaum and Hellhammer, 1994; Laudenslager et al., In press). Acute stress suppresses the binding of cortisol to CBG (Fleshner et al., 1995). Stress associated with space missions may suppress cortisol binding to CBG and thus elevate urinary (unbound) cortisol without changing plasma total cortisol. Another difference between plasma and urine samples is that the concentration of cortisol in a plasma sample represents a “snapshot” of cortisol at a single time-point, whereas cortisol in a urine sample (whether it is a single void or a 24-hour pool) represents from several hours to 24 hours of urinary excretion. Unbound cortisol has a circadian rhythm, and the time at which a sample is obtained can greatly affect cortisol concentration in that sample. The number of crew members on a space mission who participate in a given experiment is usually fewer than 7, and even if subjects from several similar missions participate, the number of subjects (n) may be too low to detect small changes. Measuring cortisol in saliva may help to resolve some of the discrepancies caused by timing of samples and inclusion of bound cortisol in measurements. The circadian rhythm of cortisol can be followed in saliva (Smyth et al., 1997), and salivary concentrations of cortisol (which are 5 to 15% of plasma levels) include only the unbound hormone. Thus, saliva sampling permits the measurement of biologically active levels of cortisol rather than total levels. Salivary concentrations of cortisol are not influenced by saliva flow rate (Kirschbaum and Hellhammer, 1989). Collecting saliva samples during space flight requires no new technology development. It is noninvasive, unlike collecting blood samples, and it is more convenient than collecting urine samples. Collection of saliva samples during flight should capture the diurnal variation of cortisol with greater fidelity than collection of urine samples, because of the potential for increased sampling frequency.
B. Immune System Space flight causes significant changes in human immune function (Sonnenfeld et al., 2001), but the
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means by which these changes come about have been difficult to discern. Consistent indicators of stress associated with space flight include increased production of stress hormones and certain changes in cells of the immune system. These changes include elevated white blood cell (WBC) and neutrophil counts at landing (Kaur et al., 2004; Kaur et al., 2005; Stowe et al., 1999; Taylor et al., 1997). Activation of generalized stress responses before, during, and after space flight probably affects the function of the immune system. Space flight has been shown to decrease many aspects of immune function, including natural killer (NK) cell activity, interferon production, the blastogenic response of leukocytes to mitogens, cell-mediated immunity, and neutrophil function (Crucian et al., 2001; Kaur et al., 2004; Konstantinova et al., 1993; Mehta et al., 2001; Stowe et al., 1999; Stowe et al., 2003; Taylor et al., 1997). The results of recent investigations of the effects of mission duration on neuroendocrine responses have suggested that it is mainly catecholamines that are responsible for the changes in WBC and lymphocyte populations observed after shorter flights (<9 days). Mills and co-workers (Mills et al., 2001) found an association between catecholamine levels and increases in counts of WBCs and CD4+ T lymphocytes. The number of band neutrophils has been found to increase during and after flight (Leach et al., 1988; Stowe et al., 1999). A 10-fold increase in band neutrophils in Spacelab 1 crew members after launch (Leach et al., 1988) was consistent with a spike in cortisol and serves as a biological indicator of the stress response. Cortisol could have achieved this effect by releasing immature neutrophils from the bone marrow. Even stress-related changes that occur before launch may alter the immune responses of space travelers. The findings of greater blood concentrations of cortisol at sampling times closer to launch than at other pre-flight times are consistent with observations of decreased immune function before launch. In the Skylab program, lymphocyte blastogenesis decreased before flight (Kimzey, 1977). Collectively, these results indicate that a link exists between stressors (such as anticipation and acceleration) before and during launch, acute elevations in cortisol, and subsequent alterations in the immune system. Cortisol influences the immune system through its effects on patterns of cytokine release from lymphocytes. A Type 1 cytokine pattern is the release of IFN-γ, TNF-β, IL-2, IL-3, and IL-12 by a subgroup of helper T-cells called Th1 cells. A Type 2 pattern is the release of IL-4, IL-5, IL-6, IL-10, and IL-13 (Daynes et al., 1995; Del Prete, 1998; Lucey, 1999; Morel and Oriss, 1998; Rook et al., 1994) by a different subgroup of helper
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T-cells called Th2 cells. [Th1 and Th2 cells are not the only sources of Type 1 and 2 cytokines (Lucey, 1999).] The Type 1 pattern promotes cell-mediated immune responses (resistance to viruses and possibly control of latent virus reactivation), whereas the Type 2 pattern is hypothesized to support production of specific antibodies and other humoral immune processes. Type 1 and Type 2 cytokine releases control immunoglobulin class switching. Diminished Type 1 releases are associated with impaired cell-mediated immune (CMI) responses (cytotoxic activity) (Wasik et al., 1997) and elevated IgE levels in plasma (De Martino et al., 1999a; De Martino et al., 1999b). Glucocorticoids are primarily anti-inflammatory in that they inhibit IL-12 production and increase IL-4 and IL-10 production by monocytes, which drives the immune response toward a Type 2 cytokine profile and away from a Type 1 profile (Elenkov et al., 1996), resulting in increased circulating IgE levels in vivo (Ramierz et al., 1996; Zieg et al., 1994). Neuropeptides can also influence cytokine production. Incubation of naive T-cells with substance P (SP) induced cytokine production that was associated with activity of Th2 cells (Levite, 1998). Increased concentrations of SP, calcitonin gene-related peptide (CGRP), and vasoactive intestinal peptide (VIP) have been associated with decreased CMI (Ferrandez et al., 1996; Morley et al., 1987). Recently, increased levels of SP have been observed after space flight (Pierson et al., 2005). It has been proposed that a shift from the Type 1 to the Type 2 cytokine pattern may increase susceptibility to opportunistic infections such as those caused by pathogenic viruses (Elenkov et al., 1996). The CMI component of the immune system controls localized Epstein-Barr virus (EBV) infections after reactivation of the latent virus and prevents further systemic disease (Rand et al., 1990; Tosato et al., 1984). Evidence that space flight and associated stressors result in a shift toward the Type 2 cytokine profile is increasing. Decreased production of Type 1 cytokines has been documented repeatedly in astronauts (reviewed by Taylor et al., 1997). Previous studies have shown that the CMI responses, in the form of delayedtype hypersensitivity (DTH), decrease during shortterm (Taylor and Janney, 1992) and long-term (Konstantinova et al., 1993) missions. Similar decreases in the CMI response have also been reported in people staying in the Antarctic during the long winter, in a stressful environment that is analogous in some ways to that of space flight (Mehta et al., 2000a; Muller et al., 1995b). The hypothesis that space flight shifts the cytokine profile toward Type 2 is also supported by data from Stein et al. (1996), who showed that IL-10 levels spike immediately after launch and correlate with
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increased urinary levels of cortisol. Moreover, we have recently noted increased IgE levels after short-term space flights (Stowe et al., 2001a; Stowe et al., 2001b; Stowe et al., 2003). The mechanisms of the immune changes observed remain an enigma; the medical significance is also unclear.
VII. SPACE FLIGHT STUDIES OF REACTIVATION OF LATENT HERPES VIRUSES To better understand the medical significance of the immune changes associated with space flight, we studied the relationship between astronauts and the latent herpes viruses they harbor. Astronauts experience various stressors that may result in inhibition of their cell-mediated immunity and increased reactivation of latent viruses during space flight, potentially increasing the risk of disease among crew members. Risks associated with many infectious agents are reduced by restricting pre-flight contact of the flight crews with high-risk populations. However, the risk of latent virus reactivation is unaffected by such precautions. Virus reactivation could pose an important health risk for astronauts, as well as for people living and working in other extreme environments. Our laboratories and collaborators have found evidence for latent virus reactivation in astronauts by examining the shedding of viral DNA and the titer of antibodies to the same viruses, and in many of the same experiments we have determined the concentration of stress hormones. In this section we summarize the results from our studies of reactivation of three latent herpes viruses in astronauts and discuss our interpretation of these results.
A. Epstein-Barr Virus Latent virus infections are ubiquitous, and EpsteinBarr virus (EBV), a DNA virus, infects over 90% of the population (Cohen, 2000; Lennette, 1991; Oxman, 1986). EBV is highly infectious and can be transmitted by microdroplets and by direct contact with saliva. When the acute infectious phase subsides, EBV can become latent in B lymphocytes. EBV is the causative agent of infectious mononucleosis and is associated with several malignancies, including Burkitt’s lymphoma, nasopharyngeal carcinoma, and diffuse oligoclonal B-cell lymphoma (Brandwein et al., 1996; Henle and Henle, 1974; Jordan, 1986; Lennette, 1991; Niedobitek et al., 1997; Simon, 1997). Latent EBV may be reactivated by a range of physical and psychosocial stress factors and shed in saliva (Glaser et al., 1985b; Glaser et al., 1995).
1. EBV DNA In our first study of latent virus reactivation, saliva samples were collected from 11 EBV-seropositive astronauts before, during, and after space flight (Payne et al., 1999). EBV DNA was detected by polymerase chain reaction (PCR) with greater frequency before space shuttle missions than during (P < 0.001) or after (P < 0.01) missions. No significant difference in the frequency of occurrence of EBV DNA was detected between the in-flight and post-flight periods (Payne et al., 1999). In a subsequent study, EBV reactivation in 32 astronauts and 18 healthy age-matched control subjects was characterized by quantifying EBV shedding in their saliva samples (Pierson et al., 2005). The frequency of EBV shedding in astronauts was 29% before and 16% both during and after space flight. The mean number of EBV copies from samples taken during 10 space shuttle flights was 417, significantly greater (10-fold, P < 0.05) than the copies from the pre-flight (40) and post-flight (44) phases (Figure 2). In contrast, the control subjects shed EBV DNA with a frequency of 3.7% and a mean number of EBV copies of 40 per mL of saliva. We found no correlation between shedding frequency and amount of EBV DNA in astronauts’ saliva. The quantitative EBV DNA data (number of viral copies) indicated that the amount of EBV DNA shed in the saliva of astronauts during space flight increased as the number of days in space increased. Similar data from 2 cosmonauts aboard the Russian space station Mir showed that EBV shedding in saliva occurred throughout the nearly 3-month mission, a much longer time than the relatively short (≤14 days) duration of the space shuttle missions. However, the number of EBV copies shed by cosmonauts aboard Mir did not increase as a function of days in flight, as observed with astronauts on the space shuttle. The maximum number of EBV copies shed by cosmonauts on Mir was 1130/mL of saliva, and the maximum number of copies shed by astronauts on the shorter shuttle flights was 738/mL of saliva. 2. Anti-EBV Antibody Levels In addition to viral DNA, the titers of antibodies to EBV antigens virus capsid antigen (VCA) and early antigen (EA) were measured in blood samples taken from astronauts at their annual medical exams (baseline), 10 days before launch (L − 10), about 3 hours after landing (R + 0), and 3 days after landing (R + 3). All 32 astronauts tested were seropositive. At L − 10, the titer of anti-VCA antibodies was greater than the baseline value (Figure 3) (Pierson et al., 2005; Stowe et al.,
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EBV copies/mL saliva
EBV frequency: 16% EBV copies: 417 ± + 31/ml
800
600
400 EBV frequency: 29% EBV copies: 4 40 ± 2/ml
EBV frequency: 16% EBV copies: 44 4 ± 5/ml
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0 200–140 139–60
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5–7
8–14
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FIGURE 2 Distribution of the number of EBV DNA copies per mL of saliva in EBV-positive samples from 32 astronauts during sampling periods before, during, and after 10 space shuttle missions. Though each dot represents an EBV-positive sample, some dots overlap. Therefore, the number of dots should not be used to calculate the number of positive samples. From Pierson et al. (2005, Fig. 1, p. 238), with permission.
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11
**
**
11
**
10 VC A
9
EA Measles
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L - 10
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FIGURE 3 Astronaut titers (mean log2 ± SE) of IgG antibodies to EBV antigens viral capsid antigen (VCA) and early antigen (EA). Blood samples were obtained from 32 astronauts at their annual medical examination (baseline, BL; low-stress period), 10 days before launch (L – 10), at landing (R + 0), and 3 days after landing (R + 3). The titer of antibody to EA was not available at BL. From Pierson et al. (2005, Fig. 2, p. 239), with permission.
Anti-viral IgG antibody titers (log2 )
Viral antibody titer (log2)
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VCA EBNA Measles
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*
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R+3
4 3
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2000; Stowe et al., 2001a), but at L − 10 as well as after landing, the titer of anti-EBV nuclear antigen (EBNA) antibodies was less than its titer at the baseline (Figure 4) (Stowe et al., 2001b). Increases in the number of EBV DNA copies and in the amount of anti-VCA antibody were consistent with EBV reactivation before, during, and after space flight.
**
L-10
Collection Time
FIGURE 4 Change in anti-viral capsid antigen (VCA), anti–Epstein-Barr Virus nuclear antigen (EBNA), and antimeasles virus IgG antibody titers before and after space flight. Annual medical exam, Baseline (BL); 10 days before launch (L – 10); return/landing day (R + 0); 3 days after landing (R + 3). *P < 0.05 and **P < 0.01. From Stowe et al. (2001, Fig. 1, p. 892), with permission.
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B. Cytomegalovirus Another latent herpes virus, human cytomegalovirus (CMV), may pose a similar kind of risk to astronauts’ health during space flight (Mehta et al., 2000b). CMV infection is usually acquired asymptomatically during childhood. However, in individuals whose immune system is either immature or compromised (as by HIV infection), CMV can cause a number of serious diseases such as encephalitis, gastroenteritis, pneumonia, and chorioretinitis (Fiala, 1975). Moreover, several studies have suggested that CMV infection may contribute to pre-existing immunosuppression by directly infecting leukocytes as well as hematopoietic cells (Carney, 1981; Rice et al., 1984; Simmons et al., 1990). We therefore examined the effect of space flight on CMV reactivation and shedding. 1. CMV DNA CMV reactivation and shedding were examined in urine samples collected from 71 crew members on 12 separate short-term space missions (Mehta et al., 2000b). Samples were collected 10 and 3 days before flight and within 2–3 hours after landing of the space
shuttle. Of the 71 crew members, 55 (77%) were seropositive. The frequency of CMV DNA shedding in either pre- or post-flight urine samples from astronauts was significantly higher than that of the control population (P < 0.05). CMV DNA was detected in 27% of the crew members studied during the mission monitoring period. By contrast, only 1 of the 61 control subjects shed CMV during 1 sampling period (Figure 5). We had an opportunity to sample both blood and urine from 4 astronauts during a subsequent flight. Consistent with the earlier study (Mehta et al., 2000b), CMV was shed in urine of 1 crew member before, during, and after flight, and in urine of the other crew members only during flight (on 2 days) (Stowe et al., 2001a). No evidence of CMV shedding was found in remaining two crew members. 2. Anti-CMV Antibody Titers No significant changes in anti-CMV antibody titers occurred before or after flight within the group of 55 seropositive astronauts. However, when these subjects were divided into 40 non-shedders and 15 CMV shedders, an interesting difference was found. No significant change in CMV IgG antibody titer of non-shedders was found at any time-point compared to the baseline values (Figure 6). In contrast, the anti-CMV antibody titer of the 15 shedders was significantly increased at all time-points compared to their baseline values. In addition, antibody was significantly increased at R + 3 compared to L − 10. The non-latent measles IgG antibody titer at R + 0 or R + 3 was not significantly different from the titer at L − 10 (data not shown), and no changes in anti-CMV IgG antibody titer from 11 CMVseropositive control subjects were found across three sampling times. The anti-CMV antibody titers of the
Percent of subjects shedding CMV
VCA is the structural antigen complex of proteins produced most abundantly during virus replication. Elevated amounts of antibodies to VCA and decreased or absent antibodies against EBNA are thought to reflect decreased cellular immunity against EBV (McDade et al., 2000; Preiksaitis et al., 1992). Kusunoki et al. (1993) demonstrated a positive correlation between antiEBNA antibody levels and precursor frequency of EBV-specific cytotoxic T-cells. We hypothesize that the increase in anti-VCA antibodies before flight (L − 10) was a result of stressinduced decreases in immunity to EBV. Glaser (Glaser and Kiecolt-Glaser, 1998; Glaser et al., 1985a; Glaser et al., 1985b) and others have found increased reactivation of latent EBV, as measured by increases in the titer of antibody to VCA, in several stress models. However, reactivation of EBV occurred only with certain types of stress (Glaser et al., 1991; Glaser et al., 1994). For example, physical stress associated with basic training of West Point cadets did not result in EBV reactivation. However, stress associated with final examinations resulted in substantial viral reactivation, with decreased virus-specific cytotoxic T-cell function and increased titer of antibodies to latent EBV (Glaser et al., 1987; Glaser et al., 1991; Glaser et al., 1993). The psychological stress of training for a space flight and anticipation of it may be a type of stress that is similar to examination stress.
35 30 25 20 15 10 5 0
Controls Astronauts FIGURE 5 Percentage of subjects (55 astronauts, 61 controls) who shed CMV DNA in urine samples collected before, during, and after short-duration space flights.
40. Reactivation of Latent Herpes Viruses in Astronauts
control subjects did not differ significantly from the baseline levels of astronauts (Mehta et al., 2000b). In addition, anti-CMV antibody titers of the two astronauts in the subsequent study (Stowe et al., 2001a) were significantly greater during flight than before flight. No change occurred in anti-measles virus antibodies, confirming the specificity of CMV reactivation. The results of our CMV studies demonstrated that CMV reactivation occurred in astronauts before flight and indicated that CMV may further reactivate during space flight.
C. Varicella-Zoster Virus Varicella-zoster virus (VZV) is an exclusively human neurotropic herpes virus that causes about 4 million cases of chickenpox annually. Varicella (chickenpox) is characterized by malaise, fever, and an extensive vesicular rash (Abendroth and Arvin, 2000; Gilden et al., 2000). It is not always a mild disease. In 1994, an epidemic of chickenpox resulted in 292 cases and 3 deaths (Balraj and John, 1994). In England, where VZV vaccination is not mandatory, about 25 people die from chickenpox every year (Rawson et al., 2001). Although VZV vaccine effectively prevents varicella (Arvin and Gershon, 1996; Gershon and Steinberg, 1990; Gershon et al., 1988; Gershon et al., 1992; Weibel et al., 1984) and reduces the severity of virus reactivation (Trannoy et al., 2000), breakthrough varicella (Takayama et al., 1997) and virus reactivation still occur (Krause and Klinman, 2000; LaRussa et al., 2000).
CMV IgG antibody titers log2
8
7
55 astronauts 15 CMV shedders 40 non-shedders
†*
* 6
*
5
4
3
2
L-10 R+0 R+3 BL FIGURE 6 Cytomegalovirus (CMV) IgG antibody titer (mean log2 ± SE) in astronaut blood samples at baseline (BL), 10 days before launch (L – 10), and at landing (R + 3). *Significant increase from BL (P < 0.001); †significant increase from L – 10 (P < 0.001). From Mehta et al. (2000, Fig. 1, p. 1763), with permission.
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After chickenpox symptoms subside, VZV becomes latent in cranial nerve, dorsal root, and autonomic nervous system ganglia. Virus reactivation, which occurs mostly in elderly and immunocompromised individuals, produces zoster (shingles), characterized by severe sharp, lancinating, radicular pain and rash restricted to 1–3 dermatomes. In affected dermatomes, sensation is decreased, yet the skin is exquisitely sensitive to touch (allodynia). In the United States, more than 500,000 cases of zoster occur annually. Although varicella occurs mostly in spring, zoster develops at any time of year. The incidence of recurrent zoster in immunocompetent individuals is less than 5%. Thoracic zoster is most common, followed by facial lesions, usually in the ophthalmic division of the trigeminal nerve and frequently accompanied by zoster keratitis, a potential cause of blindness if not recognized and treated promptly. Recently, VZV was identified as the causal agent in 29% of 3,231 encephalitis, meningitis, and myelitis cases (Koskiniemi et al., 2001). In another study of 322 patients with acute encephalitis, VZV was shown to be the leading cause in patients aged 65 years or more (Rantalaiho et al., 2001). VZV is ubiquitous. A serologic study of 1,201 U.S. military basic trainees indicated that 95.8% had been exposed to VZV (Jerant et al., 1998). A study of siblings in pre-vaccine Japan showed a 100% secondary attack rate (Asano et al., 1977). Reactivation of VZV results in shedding of infectious virus, which ensures its continual transmission. Reactivation of VZV and herpes simplex virus-1 (HSV-1) can result from dental treatment and orofacial surgery, which are examples of acute physical stress (Furuta et al., 2000; Kameyama et al., 1988). This is generally explained as resulting from local damage to nerve endings. Patients who have delayed facial palsy after orofacial surgery may have VZV DNA in their saliva and increased titers of antibody to VZV antigens in their blood. 1. VZV DNA The unexpected occurrence of thoracic zoster in an astronaut 2 days before space flight prompted our search for VZV reactivation in astronauts before, during, and after space flight. Using nested PCR and real-time PCR by Taqman 7700, we found that 312 saliva samples collected from 8 astronauts more than 6 months before space flight, during flight, and shortly after flight were positive for VZV DNA (Figure 7). Before space flight, only one of the 112 saliva samples was positive for VZV DNA. In contrast, during and after space flight, 61 of 200 (30%) saliva samples were positive for VZV. All 8 astronauts shed VZV in their
Number of positive saliva samples
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IV. Stress and Immunity 25
20
Taqman 7700 Nested PCR
15
10
5
HFL 0
Pre-flight In-flight Post-flight FIGURE 7 Number of astronaut saliva samples positive for VZV DNA before, during, and after three space flights, detected by real-time PCR with Taqman 7700 and by nested PCR. A total of 312 saliva samples were collected from 8 astronauts more than 6 months before space flight, during flight, and shortly after flight.
saliva at least once. VZV DNA was detected in 1% of pre-flight, 28% of in-flight, and 31% of post-flight samples. The number of copies of the VZV gene 63A was in the range of 10 to 4000/ml in the positive samples. No VZV DNA was detected in any of 88 saliva samples from 10 healthy control subjects. These results indicate that VZV, like CMV and EBV, reactivates during acute non-surgical stress in healthy individuals—astronauts—after they are exposed to the stress or environmental factors associated with space flight (Mehta et al., 2004). 2. Survival of VZV in Human Saliva Having shown that either stress or environmental factors associated with space flight can trigger VZV reactivation detected as viral DNA in saliva, we refocused our research to determine if VZV reactivation constitutes a health risk to astronauts. Our approach was to demonstrate the propagation of infectious VZV from astronauts’ saliva after space flight. First, however, we asked if VZV can remain infectious after being exposed to human saliva. A known amount of cell-free VZV was mixed with human saliva or phosphate-buffered saline (PBS), and the plaque reduction assay with human malignant melanoma (MeWo) cells was used to determine the loss of infectious virus in terms of plaque-forming units (pfu). In addition, an aliquot of each sample was used to determine the number of VZV DNA copies by real-time PCR. For 4 out of 5 subjects, survival of cellfree VZV plaque-forming units was about 33% after exposure to human saliva. This experiment showed
MeWo FIGURE 8 Plaque morphology as an indicator of the susceptibility to VZV infection of two types of indicator cells, primary human lung fibroblast (HLF, upper panel) and human malignant melanoma (MeWo, lower panel) cells. Sub-confluent monolayers of MeWo and HLF cells were infected with identical amounts of cell-free VZV. After 5 days of incubation, the cultures were fixed and stained to reveal VZV cytopathology (open arrows).
that infectious VZV can be detected in human saliva, albeit at a 1/3 survival rate, but VZV plaque assay of astronaut saliva is not sensitive enough to detect low levels of shedding of infectious VZV. As an alternative to using direct plaque assay to determine shedding of infectious VZV, two types of indicator cells (MeWo and HLF [primary human lung fibroblast]) were infected with healthy human saliva and the inoculated culture was blind-passaged to allow the in vivo amplification of low levels of infectious VZV. Figure 8 compares the susceptibility to infection of the two cell types. Although VZV plaques (open arrows in Figure 8) were always smaller in HLF monolayers, the virus was more prolific in these cells than in MeWo cultures, indicating that HLF cells are better than MeWo cultures for retrieving infectious virus from clinical samples. 3. Anti-VZV Antibody Titers IgG antibody against VZV was determined by enzyme immunoassay (EIA) (Forghani, 1986; Forghani,
861
40. Reactivation of Latent Herpes Viruses in Astronauts 25 L-10 R+0 Mean + SE—Control Mean + SE—Astronaut
Antibody titer index
20
* 15
10
A3
A4
A5
A6
A7
A8
Astronaut
C1
C2
C3 Control
C4
C5
Astronaut
0
Control
5
FIGURE 9 Antibody titer index of anti-VZV antibody in astronauts before and after space flight and in control subjects. IgG antibody against VZV was determined by enzyme immunoassay (EIA). Serum titer of anti-VZV IgG was determined in 5 control subjects and in 6 astronauts 10 days before flight (L – 10) and again 2 to 3 hours after landing (R + 0) P < 0.001.
2000). Serum titers of anti-VZV IgG were determined in 5 control subjects and in 6 astronauts 10 days before flight and again 2–3 hours after landing (Figure 9). Each serum sample was tested at a 1 : 200 dilution against viral antigen, a lysate prepared from VZVinfected human diploid lung cells, and against control antigen, a lysate prepared from uninfected cells at the same passage level. Data generated by EIA were expressed as antibody titer index (ATI), defined as the absorbance value of viral antigen minus the absorbance value of control antigen divided by the cut-off value (mean absorbance of a large number of VZVseronegative samples). An ATI of ≥1.0 was considered positive for the presence of VZV-specific IgG, and an ATI of <1.0 was considered negative for the presence of VZV-specific IgG, suggesting no previous exposure to the virus. The average ATI of anti-VZV IgG from the 6 astronauts (14.9 ± 1.1, mean ± SD) was significantly higher (P = 0.01) than the average ATI of IgG from the 4 control subjects (5.8 ± 0.5). The mean titer of anti-VZV IgG 10 days before flight was not significantly different from the mean titer after landing. We also found two- to threefold greater levels of circulating anti-VZV IgG in astronauts than in control subjects. Because we were unable to obtain baseline serum samples before flight or a second serum sample from astronauts weeks to months after flight, it was not possible to demonstrate a significant change in antibody to VZV. For example, a fourfold rise and fall in the level of antibody to VZV has been used as evi-
dence of sub-clinical VZV reactivation in both immunocompromised and immunocompetent individuals (Arvin et al., 1983; Gershon et al., 1984; Schunemann et al., 1998). However, the combination of VZV DNA in saliva and a larger specific antibody response in serum from astronauts than in serum from control subjects further indicates sub-clinical reactivation of VZV. This study adds VZV to the list of human herpes viruses capable of reactivation in response to acute non-surgical stress. HSV types 1 and 2 were detected in 2–3% of preand post-flight and in 8% of in-flight saliva samples collected from space shuttle crew members. HHV-6 was detected in 29% of pre-flight, 2% of in-flight, and 15% of post-flight samples (Pierson et al., unpublished data).
D. Virus Reactivation, Immune Function, and Stress Hormones Latent herpes virus replication and reactivation can result from the activation of stress response systems by increased stress levels. The stress hormones released by activation of these systems can directly affect virus reactivation (Cacioppo et al., 2002; Glaser et al., 1995) and can indirectly affect reactivation by impairing cellmediated immunity, which normally helps control the steady-state expression of latent herpes viruses. Because glucocorticoids have been shown to directly reactivate latent EBV (Cacioppo et al., 2002; Glaser et al., 1995), in one study (Stowe et al., 2001b) stress
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hormone data were grouped according to whether the subjects did or did not show evidence of EBV reactivation. EBV reactivation occurred in 35% of the male and 60% of the female astronauts (Stowe et al., 2000). No significant differences in plasma or urinary levels of cortisol were found in the two groups (reactivation/ non-reactivation of EBV). Urinary cortisol excretion by astronauts with EBV reactivation was not significantly different from cortisol excretion of those without EBV reactivation. Changes in urinary epinephrine and norepinephrine were greater in the EBV-reactivating group (220% and 100%, respectively) than in the non-reactivating group (−1% and 1%, respectively); these differences were statistically significant (Figure 10). In the EBVreactivating group, 9 of 12 astronauts had >70% increase in epinephrine, compared with 3 of 17 astronauts in the non-reactivating group (P = 0.006). In addition, the number (10 of 12) of EBV-reactivating astronauts with a 50% or more increase in norepinephrine was greater than the number (2 of 17) in the nonreactivating group (P = 0.001). These results suggest that catecholamines, which have been shown to suppress T-cell cytotoxicity (Dobbs et al., 1993), were a critical factor in EBV reactivation.
400 350
The increased CMV shedding found during flight in 2 of 4 astronauts was also presumably linked to increased stress levels, possibly a result of launch stress. Glucocorticoids have been shown to directly reactivate CMV in vitro (Lathey and Spector, 1991; Tanaka et al., 1984a; Tanaka et al., 1984b). Increased urinary cortisol has been found previously in astronauts during the “early phase” of flight (Leach, 1987; Leach et al., 1996), and it was found concomitant with CMV shedding in urine (Mehta et al., 2000b). Levels of cortisol, adrenocorticotropic hormone, and catecholamines in urine of the astronauts in this study were significantly greater at landing than before flight (P < 0.005) (Mehta et al., 2000b). Concentrations of stressassociated hormones were not determined in our VZV studies. Selected neuropeptides, including SP, CGRP, neuropeptide Y, and VIP, were also measured in plasma from 5 astronauts before and after space flight. They were elevated immediately after landing (Figure 11). This is consistent with the decrease in cell-mediated immunity (CMI) reported earlier in astronauts (Taylor et al., 1997) and Antarctic expeditioners (Mehta et al., 2000a; Muller et al., 1995a), and therefore is consistent with an increase in viral reactivation (Pierson et al., 2005). However, until neuropeptide data can be obtained from a larger number of astronauts, the significance of changes in astronaut neuropeptide levels cannot be adequately assessed.
Non-EBV Reactivation EBV Reactivation *
250
250 200 150
**
125 100 75
Neuropeptides (pg/ml)
Percent increase
300
SP
200
150
CGRP 100
NY VIP
50
50 25 0 Cortisol EPI NE FIGURE 10 Post-flight changes in urinary excretion of stress hormones in astronauts with or without evidence of EBV reactivation after space flight. EPI, epinephrine; NE, norepinephrine. *P < 0.05, **P < 0.025. From Stowe et al. (2001, Fig. 3, p. 893), with permission.
0
L - 10
R+0
R+3
FIGURE 11 Plasma concentration (mean ± SE) of neuropeptides in blood samples from 5 astronauts at 3 times before and after a 5-day mission: 10 days before launch (L – 10), at landing (R + 0), and 3 days after landing (R + 3). SP, substance P; CGRP, calcitonin gene-related peptide; NY, neuropeptide Y; VIP, vasoactive intestinal peptide. From Pierson et al. (2005, Fig. 4, p. 239), with permission.
40. Reactivation of Latent Herpes Viruses in Astronauts
In a student stress model, the level of antibody to EBV VCA increased with downregulation of the cellular immune response (Glaser et al., 1985a). We observed similar increases in anti-CMV antibodies in astronauts, beginning before the flight and continuing during the flight, and even during the first few days after landing (Mehta et al., 2000b). The anti-VZV IgG levels for astronauts were significantly greater (P = 0.01) than the control subjects’ (Pierson, unpublished observations). When CMI was assessed along with latent virus reactivation in Antarctic expeditioners, the findings (Mehta et al., 2000a) indicated that the stress associated with the extreme environment of Antarctica caused a decline in CMI, resulting in increased production of infectious viral particles and a greater risk of disease. Reactivation of VZV is thought to result from a decline in VZV-specific T-cell–mediated immunity. This view is based on observing cohorts of elderly people who are likely to develop zoster, and on the frequency of zoster in patients with depressed T-cell– mediated immunity (Levin, 2003). Sub-clinical reactivation of VZV (as manifested by sub-clinical viremia or by shedding in the saliva) may stimulate these specific immune responses. The increased frequency of shedding of EBV DNA and elevated level of antibody to the virus before flight suggested that stress levels may be greater before launch than during or after space flight. These findings (Payne et al., 1999; Stowe et al., 2000) are consistent with observations of decreased immune function before launch and greater plasma concentrations of cortisol at sampling times closer to launch than at other pre-flight times (Caillot-Augusseau et al., 1998; Stowe et al., 2000). Astronaut findings mirror results from psychological stress studies of medical students during exam periods (Glaser et al., 1985a; Glaser et al., 1987; Glaser et al., 1991). The increased amount of herpes virus replication was thought to result, in part, from decreased T-cell immunity (Glaser et al., 1993; Stowe et al., 2001a). Acute elevations in glucocorticoids resulting from launch stress may directly reactivate viruses as well as decrease cellular immunity, resulting in increased viral shedding (viral load) as mission duration increases. At landing, continued activation of both the HPA and sympathetic-adrenalmedullary axes could result in profound changes in immune function (Glaser et al., 1993; Stowe et al., 2001a), which could lead to further virus replication and reactivation. This scenario is also very similar to the chronic stress models (such as academic examination stress) mentioned above, which show decreased cellular immunity and later increased latent herpes virus reactivation (Glaser et al., 1985a; Glaser et al., 1987; Glaser et al., 1991). The differences between types
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of stress in different phases of a mission (including before and after the mission) may explain the differences we found in the patterns of different measures of viral reactivation. Reactivation of each of these three herpes viruses seems to have its own unique timing (e.g., before, during, and after space flight), and their shedding was independent of each other. We found no differences in latent EBV reactivation between military and non-military astronauts or between first-time and experienced flyers. Initially, males and females showed similar results (Payne et al., 1999; Pierson et al., 2005). However, in a subsequent study, female astronauts had greater plasma concentrations of cortisol than male astronauts (R. P. Stowe, unpublished observations). The female astronaut group also had a higher incidence of EBV reactivation. This finding, together with the cortisol data, agrees with findings of other studies on gender differences (Kiecolt-Glaser et al., 1993; Kiecolt-Glaser et al., 1996; Malarkey et al., 1994). The number of female astronauts to date has not been large enough to conduct many studies on astronaut gender differences, and additional work must be done to resolve the gender questions.
VIII. MEDICAL SIGNIFICANCE OF LATENT VIRUS REACTIVATION IN SPACE FLIGHT The medical significance of asymptomatic viral shedding in astronauts remains unknown. During the flight phase, the mean number of EBV DNA copies shed by astronauts was 417/mL, with a maximum of 738/mL. In the saliva of acquired immunodeficiency syndrome (AIDS) patients, we found 3700 copies/mL (mean value) of EBV DNA. However, some AIDS patients had levels as low as 600 copies. Kimura et al. (1999), who used a similar PCR assay, reported that a group of patients with infectious mononucleosis had a mean number of 158 copies of EBV DNA per mL of saliva. In renal transplant recipients with active CMV infection, Stagno et al. (1975) found that the number of CMV genomes per mL of urine was 100-fold greater in symptomatic patients than in asymptomatic patients. The number of EBV copies found in astronaut saliva indicated that the diminishment of immune response is very mild on short shuttle flights and cannot be compared to that of patients with severely impaired immunity (such as AIDS patients). However, lengthy stays in space may result in substantial reductions in immunity, and the number of EBV copies in saliva of
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cosmonauts aboard the Mir space station is consistent with this scenario. The increased amount of EBV DNA in saliva, coupled with the propensity of large and small saliva droplets to float in the microgravity environment of the crew compartment, may lead to increased risk of cross-infection among crew members. One would expect minimal medical effects of such events in healthy individuals, but viral reactivation is more likely to have clinical significance (Cohen, 2000) for astronauts if their immune responses are impaired.
IX. SUMMARY Space flight subjects astronauts to a uniquely stressful environment, resulting in adverse physiological effects. Astronauts experience various stressors while they are preparing for space flight, during flight, and immediately after landing. The effects of these space flight–associated stressors are mediated through the HPA and sympathetic-adrenal-medullary axes, resulting in increased circulating concentrations of cortisol, catecholamines, and neuropeptides. These neuroendocrine changes and perhaps other factors associated with space flight initiate changes in immunity. The stress hormones cortisol and the catecholamines have generally been found to increase in response to space flight. However, notable inconsistencies, thought to result from small numbers of subjects and from flightspecific variables, are common. For astronauts, the annual medical examination provides baseline values for physiological variables affected by stress. For most parameters, the baseline values from annual medical examination are far superior to the sampling times historically used (such as 10 days before launch). Many immune functions are consistently diminished in astronauts immediately after space flight, and a space flight–induced shift to a Type 2 cytokine pattern is becoming evident. Alterations in immunity and stress hormone levels may promote asymptomatic reactivation of latent herpes viruses. EBV, CMV, and VZV reactivate in astronauts, and the magnitude of the reactivation of EBV tends to increase as a function of time in space. Evidence for reactivation includes the presence of specific viral DNA in saliva (EBV and VZV) or urine (CMV). Further evidence is provided by physiologically significant increases in virus-specific antibodies. EBV reactivation occurs during all three mission phases (before, during, and after flight) but peaks with a 10fold increase during the in-flight phase. CMV reactivates and is shed in urine during all three phases, but further studies are needed to determine if shedding
peaks during flight. VZV appearance in saliva peaks during the flight phase and extends into the post-flight period. The medical significance of altered immunity and increased, but asymptomatic, viral reactivation in astronauts is unknown, but it is possible that space flight–induced changes in immunity may increase during the exploration missions, some of which will have much longer durations than current International Space Station missions. Further decreases in immunity may result in greater risks of active infection by opportunistic pathogens, including latent herpes viruses. Studies addressing these issues, and including virusspecific changes in T-cells, are currently underway on ISS astronauts participating in missions up to 6 months. These studies of asymptomatic reactivation of latent herpes viruses in a very healthy, superbly conditioned study group may provide new insight into stress, immunity, and viral disease in the general population.
X. FUTURE DIRECTIONS Latent viruses and their reactivation patterns may prove to be a valuable tool for assessing the medical significance of space flight-associated changes in the human immune response. Determining the mechanism(s) of space flight–associated changes in immunity is a high priority for the lengthy exploration missions to the moon and Mars being planned. Unfortunately, flight opportunities for human research in the near future are expected to be highly limited. High fidelity ground-based models of space flight are needed to supplement the limited flight studies of human immunity and viral reactivation. Ground-based models such as bedrest, chambers, Antarctic science stations, undersea habitat, animals, and cellular studies have provided valuable information on the immune response during space flight. If countermeasures are needed, they can be tested in the same ground-based model. Countermeasures may include exercise or stress management regimens, nutritional or pharmacological measures, or combinations of these or other preventive or therapeutic measures.
Acknowledgments The authors extend a special thanks to the astronauts who participated in the studies described in this chapter. We express our appreciation to Donald Gilden and Randall Cohrs, University of Colorado Health Center in Denver, for their active participation in some of the studies described and in hours of discussion about
40. Reactivation of Latent Herpes Viruses in Astronauts them. We sincerely thank Ronald Glaser, Ohio State University, for his guidance, encouragement, and countless discussions of stressinduced psychological effects. We gratefully acknowledge Mark Laudenslager, University of Colorado Health Center in Denver, and Bagher Forghani, California Department of Health Services CA, and the staff members of our respective laboratories for their dedication and skill in the conduct of studies described in this manuscript. The statistical analyses were performed by Alan Feiveson, Johnson Space Center, NASA. We thank Jane Krauhs of Wyle Laboratories Life Sciences Group for her very capable editing and many helpful suggestions in the preparation of the manuscript. This work was supported by NASA grants 111-30-10-03 and 111-30-10-06 to DLP, and NGT-51666, NAS 9-01006, and NNJ04HD75G to RPS.
References Abendroth, A., and Arvin, A. M. (2000). Host response to primary infection. New York: Cambridge University Press. Arvin, A. M., and Gershon, A. A. (1996). Live attenuated varicella vaccine. Annu. Rev. Microbiol., 50, 59–100. Arvin, A. M., Koropchak, C. M., and Wittek, A. E. (1983). Immunologic evidence of reinfection with varicella-zoster virus. Journal of Infectious Diseases, 148, 200–205. Asano, Y., Nakayama, H., Yazaki, T., Kato, R., and Hirose, S. (1977). Protection against varicella in family contacts by immediate inoculation with live varicella vaccine. Pediatrics, 59, 3–7. Balraj, V., and John, T. J. (1994). An epidemic of varicella in rural southern India. Journal of Tropical Medicine and Hygiene, 97, 113–116. Brandwein, M., Nuovo, G., Ramer, M., Orlowski, W., and Miller, L. (1996). Epstein-Barr virus reactivation in hairy leukoplakia. Mod. Pathol., 9, 298–303. Cacioppo, J. T., Kiecolt-Glaser, J. K., Malarkey, W. B., Laskowski, B. F., Rozlog, L. A., Poehlmann, K. M., Burleson, M. H., and Glaser, R. (2002). Autonomic and glucocorticoid associations with the steady-state expression of latent Epstein-Barr virus. Horm. Behav, 42, 32–41. Caillot-Augusseau, A., Lafage-Proust, M.-H., Soler, C., Pernod, J., Dubois, F., and Alexandre, C. (1998). Bone formation and resorption biological markers in cosmonauts during and after a 180-day space flight (Euromir 95). Clin. Chem., 44, 578–585. Carney, W. P. (1981). Mechanisms of immunosuppression in cytomegalovirus mononucleosis. J. Infect. Dis., 144, 47–54. Castro, V. A., Thrasher, A. N., Healy, M., Ott, C. M., and Pierson, D. L. (2004). Microbial characterization during the early habitation of the International Space Station. Microb. Ecol., 47, 119–126. Cohen, J. I. (2000). Epstein-Barr virus infection. New England Journal of Medicine, 343, 481–492. Crucian, B. E. (2000). Altered cytokine production by specific human peripheral blood cell subsets immediately following space flight. J. Interferon Cytokine Res., 20, 547–556. Crucian, B. E., Stowe, R. P., Pierson, D. L., and Sams, C. F. (2001). Routine detection of Epstein-Barr virus specific T-cells in the peripheral blood by flow cytometry. J. Immunol. Methods, 247, 35–47. Daynes, R. A., Araneo, B. A., Hennebold, J., Enioutina, E., and Mu, H. H. (1995). Steroids as regulators of the mammalian immune response. Endogenous Immune Regulators, 105, 14S–19S. Del Prete, G. (1998). The concept of type-1 and type-2 helper T cells and their cytokines in humans. International Reviews of Immunology, 16, 427–455.
865
De Martino, M., Rossi, M., Azzari, C., Chiarelli, F., Galli, L., and Vierucci, A. (1999a). Low IgG3 and high IgG4 subclass levels in children with advanced human immunodeficiency virus-type 1 infection and elevated IgE levels. Annals of Allergy, Asthma, and Immunology, 83, 160–164. De Martino, M., Rossi, M., Azzari, C., Chiarelli, F., Galli, L., and Vierucci, A. (1999b). Interleukin-6 synthesis and IgE overproduction in children with perinatal human immunodeficiency virustype 1 infection. Annals of Allergy, Asthma, and Immunology, 82, 212–216. Dobbs, C. M., Vasquez, M., Glaser, R., and Sheridan, J. F. (1993). Mechanisms of stress-induced modulation of viral pathogenesis and immunity. J. Neuroimmunol., 48, 151–160. Elenkov, I. J., Papanicolaou, D. A., Wilder, R. L., and Chrousos, G. P. (1996). Modulatory effects of glucocorticoids and catecholamines on human interleukin-12 and interleukin-10 production: clinical implications. Proceedings of the Association of American Physicians, 108, 374–381. Ferrandez, M. D., Maynar, M., and De la Fuente, M. (1996). Effects of a long-term training program of increasing intensity on the immune function of indoor Olympic cyclists. International Journal of Sports Medicine, 17, 592–596. Fiala, M. (1975). Epidemiology of cytomegalovirus infection after transplantation and immunosuppression. J. Infect. Dis., 132, 421–433. Fleshner, M., Deak, T., Spencer, R. L., Laudenslager, M. L., Watkins, L. R., and Maier, S. F. (1995). A long term increase in basal levels of corticosterone and a decrease in corticotrophin-binding globulin following acute stressor exposure. Endocrinology, 136, 5336–5342. Forghani, B. (1986). Varicella-zoster virus antibodies. In H. Bergmeyer (Ed.), Methods of enzymatic analysis (3rd ed., vol. 10, pp. 267–284). Weinheim, Germany: Verlag Chemie. Forghani, B. (2000). Laboratory diagnosis of varicella-zoster virus infection. In A. M. Arvin and A. A. Gershon (Eds.), Varicellazoster virus: virology and clinical management (pp. 351–382). New York: Cambridge University Press. Furuta, Y., Ohtani, F., Fukuda, S., Inuyama, Y., and Nagashima, K. (2000). Reactivation of varicella-zoster virus in delayed facial palsy after dental treatment and oro-facial surgery. J. Med. Virol., 62, 42–45. Gauquelin, G., Geelen, G., Gharib, C., Grigoriev, A., Guell, A., Kvetnansky, R., Macho, L., Noskov, V., Pasi, P., Soukanov, J., Patricot, M., Raffin, J., Wang, X. G., Poliakov, V., and Chretien, J. L. (1990). Volume regulating hormones, fluid and electrolyte modifications during the Aragatz mission (MIR station). In Proceedings of the Fourth European Symposium on Life Sciences Research in Space, held in Trieste, Italy, from 28 May to 1 June 1990 (ESA SP307 ed., pp. 603–608). Paris: European Space Agency. Gazenko, O. G., Schulzhenko, E. B., Grigoriev, A. I., Atkov, O., and Egorov, A. D. (1988). Review of basic medical results of the Salyut-7-Soyuz-T 8-month manned flight. Acta Astronaut., 17, 155–160. Gershon, A. A., LaRussa, P., Hardy, I., Steinberg, S., and Silverstein, S. (1992). Varicella vaccine: the American experience. Journal of Infectious Diseases, 166 (Suppl 1), S63–S68. Gershon, A. A., and Steinberg, S. P. (1990). Live attenuated varicella vaccine: protection in healthy adults compared with leukemic children. National Institute of Allergy and Infectious Diseases Varicella Vaccine Collaborative Study Group. Journal of Infectious Diseases, 161, 661–666. Gershon, A. A., Steinberg, S. P., and Gelb, L. (1984). Clinical reinfection with varicella-zoster virus. Journal of Infectious Diseases, 149, 137–142.
866
IV. Stress and Immunity
Gershon, A. A., Steinberg, S. P., LaRussa, P., Ferrara, A., Hammerschlag, M., and Gelb, L. (1988). Immunization of healthy adults with live attenuated varicella vaccine. Journal of Infectious Diseases, 158, 132–137. Gilden, D. H., Kleinschmidt-DeMasters, B. K., LaGuardia, J. J., Mahalingam, R., and Cohrs, R. J. (2000). Neurologic complications of the reactivation of varicella-zoster virus. New England Journal of Medicine, 342, 635–645. Glaser, R., and Kiecolt-Glaser, J. K. (1998). Stress-associated immune modulation: relevance to viral infections and chronic fatigue syndrome. Am. J. Med., 105, 35S–42S. Glaser, R., Kiecolt-Glaser, J. K., Speicher, C. E., and Holliday, J. E. (1985a). Stress, loneliness, and changes in herpesvirus latency. J. Behav. Med., 8, 249–260. Glaser, R., Kiecolt-Glaser, J. K., Stout, J. C., Tarr, K. L., Speicher, C. E., and Holliday, J. E. (1985b). Stress-related impairments in cellular immunity. Psychiatry Research, 16, 233–239. Glaser, R., Kutz, L. A., MacCallum, R. C., and Malarkey, W. B. (1995). Hormonal modulation of Epstein-Barr virus replication. Neuroendocrinology, 62, 356–361. Glaser, R., Pearl, D. K., Kiecolt-Glaser, J. K., and Malarkey, W. B. (1994). Plasma cortisol levels and reactivation of latent EpsteinBarr virus in response to examination stress. Psychoneuroendocrinology, 19, 765–772. Glaser, R., Pearson, G. R., Bonneau, R. H., Esterling, B. A., Atkinson, C., and Kiecolt-Glaser, J. K. (1993). Stress and the memory T-cell response to the Epstein-Barr virus in healthy medical students. Health Psychology, 12, 435–442. Glaser, R., Pearson, G. R., Jones, J. F., Hillhouse, J., Kennedy, S., Mao, H. Y., and Kiecolt-Glaser, J. K. (1991). Stress-related activation of Epstein-Barr virus. Brain, Behavior and Immunity, 5, 219–232. Glaser, R., Rice, J., Sheridan, J., Fertel, R., Stout, J., Speicher, C., Pinsky, D., Kotur, M., Post, A., Beck, M., et al. (1987). Stressrelated immune suppression: health implications. Brain, Behavior and Immunity, 1, 7–20. Graebe, A., Schuck, E. L., Lensing, P., Putcha, L., and Derendorf, H. (2004). Physiological, pharmacokinetic, and pharmacodynamic changes in space. Journal of Clinical Pharmacology, 44, 837–853. Granger, D. A., Schwartz, E. B., Booth, A., Curran, M., and Zakaria, D. (1999). Assessing dehydroepiandrosterone in saliva: a simple radioimmunoassay for use in studies of children, adolescents and adults. Psychoneuroendocrinology, 24, 567–579. Grigoriev, A. I., Polyakov, V. V., Bogomolov, V. V., Egorov, A. D., Pestov, I. D., and Kozlovskaya, I. B. (1990). Medical results of the fourth prime expedition on the orbital station Mir. In Proceedings of the Fourth European Symposium on Life Sciences Research in Space, held in Trieste, Italy, from 28 May to 1 June 1990 (ESA SP-307 ed., pp. 19–22). Paris: European Space Agency. Henle, W., and Henle, G. (1974). Epstein-Barr virus and human malignancies. Cancer, 43, 1368–1374. Jerant, A. F., DeGaetano, J. S., Epperly, T. D., Hannapel, A. C., Miller, D. R., and Lloyd, A. J. (1998). Varicella susceptibility and vaccination strategies in young adults. Journal of the American Board of Family Practice, 11, 296–306. Jordan, M. C. (1986). Infectious mononucleosis due to Epstein-Barr virus and cytomegalovirus. In A. I. Braude, C. E. Davis, and J. Fierer (Eds.), Infectious diseases and medical microbiology (pp. 1311). Philadelphia: W. B. Saunders Company. Kameyama, T., Sujaku, C., Yamamoto, S., Hwang, C. B., and Shillitoe, E. J. (1988). Shedding of herpes simplex virus type 1 into saliva. J. Oral Pathol., 17, 478–481. Kaur, I., Simons, E. R., Castro, V. A., Ott, C. M., and Pierson, D. L. (2004). Changes in neutrophil functions in astronauts. Brain, Behavior and Immunity, 18, 443–450.
Kaur, I., Simons, E. R., Castro, V. A., Ott, C. M., and Pierson, D. L. (2005). Changes in monocyte functions of astronauts. Brain, Behavior and Immunity, 547–554. Kiecolt-Glaser, J. K., Malarkey, W. B., Chee, M., Newton, T., Cacioppo, J. T., Mao, H. Y., and Glaser, R. (1993). Negative behavior during marital conflict is associated with immunological down-regulation [see comments]. Psychosom. Med., 55, 395–409. Kiecolt-Glaser, J. K., Newton, T., Cacioppo, J. T., MacCallum, R. C., Glaser, R., and Malarkey, W. B. (1996). Marital conflict and endocrine function: are men really more physiologically affected than women? Journal of Consulting and Clinical Psychology, 64, 324–332. Kimura, H., Morita, M., Yabuta, Y., Kuzushima, K., Kato, K., Kojima, S., Matsuyama, T., and Morishima, T. (1999). Quantitative analysis of Epstein-Barr virus load by using a real-time PCR assay. J. Clin. Microbiol., 37, 132–136. Kimzey, S. L. (1977). Hematology and immunology studies. In R. S. Johnston and L. F. Dietlein (Eds.), Biomedical results from Skylab (NASA SP-377 ed. pp. 249–282). Washington, DC: National Aeronautics and Space Administration. Kirschbaum, C., and Hellhammer, D. H. (1989). Salivary cortisol in psychobiological research: an overview. Neuropsychobiology, 22, 150–169. Kirschbaum, C., and Hellhammer, D. H. (1994). Salivary cortisol in psychoneuroendocrine research—recent developments and applications. Psychoneuroendocrinology, 19, 313–333. Konstantinova, I. V., Rykova, M. P., Lesnyak, A. T., and Antropova, E. A. (1993). Immune changes during long-duration missions. J. Leukoc. Biol., 54, 189–201. Koskiniemi, M., Rantalaiho, T., Piiparinen, H., von Bonsdorff, C. H., Farkkila, M., Jarvinen, A., Kinnunen, E., Koskiniemi, S., Mannonen, L., Muttilainen, M., Linnavuori, K., Porras, J., Puolakkainen, M., Raiha, K., Salonen, E. M., Ukkonen, P., Vaheri, A., and Valtonen, V. (2001). Infections of the central nervous system of suspected viral origin: a collaborative study from Finland. J. Neurovirol., 7, 400–408. Krause, P. R., and Klinman, D. M. (2000). Varicella vaccination: evidence for frequent reactivation of the vaccine strain in healthy children. Nat. Med., 6, 451–454. Kusunoki, Y., Huang, H., Fukuda, Y., Ozaki, K., Saito, M., Hirai, Y., and Akiyama, M. (1993). A positive correlation between the precursor frequency of cytotoxic lymphocytes to autologous EpsteinBarr virus-transformed B cells and antibody titer level against Epstein-Barr virus-associated nuclear antigen in healthy seropositive individuals. Microbiol. Immunol., 37, 461–469. LaRussa, P., Steinberg, S. P., Shapiro, E., Vazquez, M., and Gershon, A. A. (2000). Viral strain identification in varicella vaccinees with disseminated rashes. Pediatric Infectious Disease Journal, 19, 1037–1039. Lathey, J. L., and Spector, S. A. (1991). Unrestricted replication of human cytomegalovirus in hydrocortisone-treated macrophages. J. Virol., 65, 6371–6375. Laudenslager, M. L., Bettinger, T., and Sackett, G. (In press). Saliva as a medium for assessing cortisol and other compound in nonhuman primates: collection, assay, and examples. In G. Sackett and G. Ruppenthal (Eds.), Nursery rearing of nonhuman primates in the 21st century. New York: Plenum Publishers. Leach, C. S. (1987). Fluid control mechanisms in weightlessness. Aviat., Space Environ. Med., 58, A74–79. Leach, C. S. (1992). Biochemical and hematologic changes after short-term space flight. Microgravity Quarterly, 2, 69–75. Leach, C. S., Alexander, W. C., and Johnson, P. C. (1975). Endocrine, electrolyte, and fluid volume changes associated with Apollo
40. Reactivation of Latent Herpes Viruses in Astronauts missions. In R. S. Johnston, L. F. Dietlein, and C. A. Berry (Eds.), Biomedical results of Apollo (NASA SP-368, pp. 163–184). Washington, DC: National Aeronautics and Space Administration. Leach, C. S., Alfrey, C. P., Suki, W. N., Leonard, J. I., Rambaut, P. C., Inners, L. D., Smith, S. M., Lane, H. W., and Krauhs, J. M. (1996). Regulation of body fluid compartments during short-term spaceflight. J. Appl. Physiol., 81, 105–116. Leach, C. S., Chen, J. P., Crosby, W., Johnson, P. C., Lange, R. D., Larkin, E., and Tavassoli, M. (1988). Hematology and biochemical findings of Spacelab 1 flight. In E. D. Zanjani, M. Tavassoli, and J. L. Ascensao (Eds.), Regulation of erythropoiesis (pp. 415– 453). New York: PMA Publishing Corp. Leach, C. S., and Rambaut, P. C. (1977). Biochemical responses of the Skylab crewmen: an overview. In R. S. Johnston and L. F. Dietlein (Eds.), Biomedical results from Skylab (NASA SP-377, pp. 204– 216). Washington, DC: National Aeronautics and Space Administration. Leach Huntoon, C. S., and Cintron, N. M. (1996). Endocrine system and fluid and electrolyte balance. In C. S. Leach Huntoon, V. V. Antipov, and A. I. Grigoriev (Eds.), Humans in spaceflight (vol. III, book 1, pp. 89–104). Reston, VA: American Institute of Aeronautics and Astronautics. Lennette, E. T. (1991). Epstein Barr virus. In A. Balows, W. J. Hausler, K. L. Herrmann, H. D. Isenberg, and H. J. Shadomy (Eds.), Manual of clinical microbiology (pp. 847–852). Washington, DC: American Society for Microbiology. Levin, M. J., Smith, J. G., Kaufhold, R. M., Barber, D., Hayward, A. R., Chan, C., Y., Chan I., Li, D. J., J. S. F. Wang, W., Keller, P. M., Shaw A., Silber, J. L., Schleinger, K., Chalikonda, I., Vessey, S. J. R., and Caulfield, M. J. (2003). Decline in varicella-zoster virus (VZV)-specific cell-mediated immunity with increasing age and boosting with a high-dose VZV vaccine. J. Infect. Dis., 188, 1336–1344. Levite, M. (1998). Neuropeptides, by direct interaction with T cells, induce cytokine secretion and break the commitment to a distinct T helper phenotype. Proc. Natl. Acad. Sci. USA, 95, 12544–12549. Lucey, D. R. (1999). Evolution of the type-1 (Th1)-type-2 (Th2) cytokine paradigm. Infectious Disease Clinics of North America, 13, 1–9. Malarkey, W. B., Kiecolt-Glaser, J. K., Pearl, D., and Glaser, R. (1994). Hostile behavior during marital conflict alters pituitary and adrenal hormones. Psychosom. Med., 56, 41–51. McDade, T. W., Stallings, J. F., Angold, A., Costello, E. J., Burleson, M., Cacioppo, J. T., Glaser, R., and Worthman, C. M. (2000). Epstein-Barr virus antibodies in whole blood spots: a minimally invasive method for assessing an aspect of cell-mediated immunity. Psychosom. Med., 62, 560–567. Meehan, R., Whitson, P., and Sams, C. (1993). The role of psychoneuroendocrine factors on spaceflight-induced immunological alterations. J. Leukocyte Biol., 54, 236–244. Mehta, S. K., Cohrs, R. J., Forghani, B., Zerbe, G., Gilden, D. H., and Pierson, D. L. (2004). Stress-induced subclinical reactivation of varicella zoster virus in astronauts. J. Med. Virol., 72, 174–179. Mehta, S. K., Kaur, I., Grimm, E. A., Smid, C., Feeback, D. L., and Pierson, D. L. (2001). Decreased non-MHC–restricted (CD56+) killer cell cytotoxicity after spaceflight. J. Appl. Physiol., 91, 1814–1818. Mehta, S. K., Pierson, D. L., Cooley, H., Dubow, R., and Lugg, D. (2000a). Epstein-Barr virus reactivation associated with diminished cell-mediated immunity in Antarctic expeditioners. J. Med. Virol., 61, 235–240. Mehta, S. K., Stowe, R. P., Feiveson, A. H., Tyring, S. K., and Pierson, D. L. (2000b). Reactivation and shedding of cytomegalovirus in
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astronauts during spaceflight. Journal of Infectious Diseases, 182, 1761–1764. Mills, P. J., Meck, J. V., Waters, W. W., D’Aunno, D., and Zeigler, M. G. (2001). Peripheral leukocyte subpopulations and catecholamine levels in astronauts as a function of mission duration. Psychosom. Med., 63, 886–890. Morel, P. A., and Oriss, T. B. (1998). Cross regulation between Th1 and Th2 cells. Critical Reviews in Immunology, 18, 275–303. Morley, J. E., Kay, N. E., Solomon, G. F., and Plotnikoff, N. P. (1987). Neuropeptides: conductors of the immune orchestra. Life Sci., 41, 527–544. Muller, H. K., Lugg, D. J., and Quinn, D. (1995a). Cell mediated immunity in Antarctic wintering personnel; 1984–1992. Immunol. Cell Biol., 73, 316–320. Muller, H. K., Lugg, D. J., Ursin, H., Quinn, D., and Donovan, K. (1995b). Immune responses during an Antarctic summer. Pathology, 27, 186–190. Niedobitek, G., Agathanggelou, A., Herbst, H., Whitehead, L., Wright, D. H., and Young, L. S. (1997). Epstein-Barr virus (EBV) infection in infectious mononucleosis: virus latency, replication and phenotype of EBV-infected cells. J. Pathol., 182, 151–159. Oxman, M. N. (1986). Herpes stomatitis. In A. I. Braude, C. E. Davis, and J. Fierer (Eds.), Infectious diseases and medical microbiology (pp. 752–769). Philadelphia: W. B. Saunders Company. Payne, D. A., Mehta, S. K., Tyring, S. K., Stowe, R. P., and Pierson, D. L. (1999). Incidence of Epstein-Barr virus in astronaut saliva during spaceflight. Aviat., Space Environ. Med., 70, 1211–1213. Pierson, D. L. (2001). Microbial contamination of spacecraft. Gravit. Space Biol. Bull., 14, 1–6. Pierson, D. L., Stowe, R. P., Phillips, T. M., Lugg, D. J., and Mehta, S. K. (2005). Epstein-Barr virus shedding by astronauts during space flight. Brain, Behavior and Immunity, 19, 235–242. Preiksaitis, J. K., Diaz-Mitoma, F., Mirzayans, F., Roberts, S., and Tyrrell, D. L. (1992). Quantitative oropharyngeal Epstein-Barr virus shedding in renal and cardiac transplant recipients: relationship to immunosuppressive therapy, serologic responses, and the risk of posttransplant lymphoproliferative disorder. J. Infect. Dis., 166, 986–994. Ramirez, F., Fowell, D. J., Puklavec, M., Simmonds, S., and Mason, D. (1996). Glucocorticoids promote a TH2 cytokine response by CD4+ T cells in vitro. J. Immunol., 156, 2406–2412. Rand, K. H., Hoon, E. F., Massey, J. K., and Johnson, J. H. (1990). Daily stress and recurrence of genital herpes simplex. Arch. Intern. Med., 150, 1889–1893. Rantalaiho, T., Farkkila, M., Vaheri, A., and Koskiniemi, M. (2001). Acute encephalitis from 1967 to 1991. Journal of the Neurological Sciences, 184, 169–177. Rawson, H., Crampin, A., and Noah, N. (2001). Deaths from chickenpox in England and Wales 1995–7: analysis of routine mortality data. Br. Med. J., 323, 1091–1093. Rice, G. P. A., Schrier, R. D., and Oldstone, M. B. A. (1984). Cytomegalovirus infects human lymphocytes and monocytes: virus expression is restricted to immediate-early gene products. Proc. Natl. Acad. Sci. USA, 81, 6134–6138. Rook, G. A., Hernandez-Pando, R., and Lightman, S. L. (1994). Hormones, peripherally activated prohormones and regulation of the Th1/Th2 balance. Immunology Today, 15, 301–303. Schunemann, S., Mainka, C., and Wolff, M. H. (1998). Subclinical reactivation of varicella-zoster virus in immunocompromised and immunocompetent individuals. Intervirology, 41, 98–102. Simmons, P., Kaushansky, K., and Torok-Storb, B. (1990). Mechanisms of cytomegalovirus-mediated myelosuppression: perturbation of stromal cell function versus direct infection of myeloid cells. Proc. Natl. Acad. Sci. USA, 87, 1386–1390.
868
IV. Stress and Immunity
Simon, M. W. (1997). Manifestations of relapsing Epstein-Barr virus illness. Journal of the Kentucky Medical Association, 95, 240–243. Smith, S. M., Krauhs, J. M., and Leach, C. S. (1997). Regulation of body fluid volume and electrolyte concentrations in spaceflight. Adv. Space Biol. Med., 6, 123–165. Smith, S. M., Zwart, S. R., Block, G., Rice, B. L., and Davis-Street, J. E. (2005). The nutritional status of astronauts is altered after long-term space flight aboard the International Space Station. Journal of Nutrition, 135, 437–443. Smyth, J. M., Ockenfels, M. C., Gorin, A. A., Catley, D., Porter, L. S., Kirschbaum, C., Hellhammer, D. H., and Stone, A. A. (1997). Individual differences in the diurnal cycle of cortisol. Psychoneuroendocrinology, 22, 89–105. Sonnenfeld, G., Taylor, G. R., and Kinney, K. S. (2001). Acute and chronic effects of space flight on immune functions. In R. Ader, D. L. Felten, and N. Cohen (Eds.), Psychoneuroimmunology (3rd ed., vol. 2, pp. 279–289). San Diego: Academic Press. Stagno, S., Reynolds, D. W., Tsiantos, A., Fuccillo, D. A., Long, W., and Alford, C. A. (1975). Comparative serial virologic and serologic studies of symptomatic and subclinical congenitally and natally acquired cytomegalovirus infections. Journal of Infectious Diseases, 132, 568–577. Stein, T. P., Leskiw, M. J., and Schluter, M. D. (1996). Diet and nitrogen metabolism during spaceflight on the shuttle. J. Appl. Physiol., 81, 82–97. Stein, T. P., Leskiw, M. J., Schluter, M. D., Donaldson, M. R., and Larina, I. (1999). Protein kinetics during and after longduration spaceflight on Mir. Am. J. Physiol., 276, E1014– 1021. Stowe, R. P., Mehta, S. K., Ferrando, A. A., Feeback, D. L., and Pierson, D. L. (2001a). Immune responses and latent herpesvirus reactivation in spaceflight. Aviat., Space Environ. Med., 72, 884–891. Stowe, R. P., Pierson, D. L., and Barrett, A. D. T. (2001b). Elevated stress hormone levels relate to Epstein-Barr virus reactivation in astronauts. Psychosom. Med., 63, 891–895. Stowe, R. P., Pierson, D. L., Feeback, D. L., and Barrett, A. D. (2000). Stress-induced reactivation of Epstein-Barr virus in astronauts. Neuroimmunomodulation, 8, 51–58. Stowe, R. P., Sams, C. F., Mehta, S. K., Kaur, I., Jones, M. L., Feeback, D. L., and Pierson, D. L. (1999). Leukocyte subsets and neutrophil function after short-term spaceflight. J. Leukocyte Biol., 65, 179–186. Stowe, R. P., Sams, C. F., and Pierson, D. L. (2003). Effects of mission duration on neuroimmune responses in astronauts. Aviat., Space Environ. Med., 74, 1281–1284. Takayama, N., Minamitani, M., and Takayama, M. (1997). High incidence of breakthrough varicella observed in healthy Japanese children immunized with live attenuated varicella vaccine (Oka strain). Acta Paediatrica Japonica, 39, 663–668.
Tanaka, J., Ogura, T., Kamiya, S., Sato, H., Yoshie, T., Ogura, H., and Hatano, M. (1984a). Enhanced replication of human cytomegalovirus in human fibroblasts treated with dexamethasone. J. Gen. Virol., 65, 1759–1767. Tanaka, J., Ogura, T., Kamiya, S., Yoshie, T., Yabuki, Y., and Hatano, M. (1984b). Dexamethasone enhances human cytomegalovirus replication in human epithelial cell cultures. Virology, 136, 448–452. Taylor, G. R., and Janney, R. P. (1992). In vivo testing confirms a blunting of the human cell-mediated immune mechanism during space flight. J. Leukocyte Biol., 51, 129–132. Taylor, G. R., Konstantinova, I., Sonnenfeld, G., and Jennings, R. (1997). Changes in the immune system during and after spaceflight. Adv. Space Biol. Med., 6, 1–32. Tosato, G., Steinberg, A. D., Yarchoan, R., Heilman, C. A., Pike, S. E., De Seau, V., and Blaese, R. M. (1984). Abnormally elevated frequency of Epstein-Barr virus-infected B cells in the blood of patients with rheumatoid arthritis. J. Clin. Invest., 73, 1789–1795. Trannoy, E., Berger, R., Hollander, G., Bailleux, F., Heimendinger, P., Vuillier, D., and Creusvaux, H. (2000). Vaccination of immunocompetent elderly subjects with a live attenuated Oka strain of varicella zoster virus: a randomized, controlled, dose- response trial. Vaccine, 18, 1700–1706. Vorobyev, Y. I., Gazenko, O. G., Shulzhenko, Y. B., Grigoryev, A. I., Barer, A. S., Yegorov, A. D., and Skiba, I. A. (1986). Preliminary results of medical investigations during 5-month spaceflight aboard Salyut-7-Soyuz-T orbital complex. Kosmicheskaya Biologiya i Aviakosmicheskaya Meditsina, 20, 27–34. Wasik, T. J., Jagodzinski, P. P., Hyjek, E. M., Wustner, J., Trinchieri, G., Lischner, H. W., and Kozbor, D. (1997). Diminished HIVspecific CTL activity is associated with lower type 1 and enhanced type 2 responses to HIV-specific peptides during perinatal HIV infection. Journal of Immunology, 158, 6029–6036. Weibel, R. E., Neff, B. J., Kuter, B. J., Guess, H. A., Rothenberger, C. A., Fitzgerald, A. J., Connor, K. A., McLean, A. A., Hilleman, M. R., and Buynak, E. B. (1984). Live attenuated varicella virus vaccine. Efficacy trial in healthy children. New England Journal of Medicine, 310, 1409–1415. White, R. J., and Averner, M. (2001). Humans in space. Nature, 409, 1115–1118. Williams, D. R. (2003). The biomedical challenges of space flight. Annual Review of Medicine, 54, 245–256. Zerwekh, J. E. (2002). Nutrition and renal stone disease in space. Nutrition, 18, 857–863. Zieg, G., Lack, G., Harbeck, R. J., Gelfand, E. W., and Leung, D. Y. (1994). In vivo effects of glucocorticoids on IgE production. J. Allergy Clin. Immunol., 94, 222–230.
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41 Psychosocial Influences in Oncology: An Expanded Model of Biobehavioral Mechanisms SUSAN K. LUTGENDORF, ERIN S. COSTANZO, AND SCOTT D. SIEGEL
I. BIOBEHAVIORAL INFLUENCES ON DISEASE PROGRESSION 869 II. PSYCHOSOCIAL FACTORS IN CANCER INITIATION AND PROGRESSION 870 III. PSYCHOSOCIAL FACTORS AND THE IMMUNE RESPONSE IN THE CONTEXT OF CANCER 874 IV. IMMUNOLOGIC MECHANISMS AND TUMOR CONTROL 878 V. PSYCHOSOCIAL FACTORS AND TUMOR ANGIOGENESIS 881 VI. STRESS AND VIRAL ACTIVATION 883 VII. STRESS, DNA REPAIR AND APOPTOSIS, AND IMPLICATIONS FOR CANCER 883 VIII. NEUROENDOCRINE REGULATION AND CANCER PROGRESSION 884 IX. IMMUNE ACTIVATION AND QUALITY OF LIFE IN CANCER PATIENTS: BI-DIRECTIONAL PATHWAYS 885 X. SUMMARY AND FUTURE DIRECTIONS 886
progression (Antoni & Goodkin, 1988; Greer & Watson, 1985; Levy, Herberman, Lippman, D’Angelo, & Lee, 1991; Pettingale, Burge, & Greer, 1988; Price et al., 2001; Stommel, Given, & Given, 2002). For many years an immunosuppression model has guided much of the thinking regarding mechanisms underlying the relationship between stress and cancer. The underlying assumption of this model is that stress, depression, and other negative psychosocial factors elevate the risk for cancer progression by suppressing elements of the immune response that might otherwise be able to aggressively fight the tumor (Andersen, Kiecolt-Glaser, & Glaser, 1994). Relationships between stress and the immune response and the putative mechanisms linking these systems have been well characterized and are well represented in this volume. Linkages between the immune response and cancer progression have been observed, as have associations between psychosocial factors and cancer progression. However, all of these factors have not yet been demonstrated in the same model of human cancer, and the inconsistent nature of the findings has left controversy surrounding the strength of these relationships (Cassileth, 1996; McGee, Williams, & Elwood, 1996; McKenna, Zevon, Corn, & Rounds, 1999). Although much work has focused on the immune response as a likely mediator between psychosocial factors and cancer progression, emerging findings link psychosocial factors to other putative mechanisms involved in cancer growth including angiogenesis, DNA repair, activity of matrix metalloproteinases
I. BIOBEHAVIORAL INFLUENCES ON DISEASE PROGRESSION Epidemiologically established risk factors for carcinogenesis include endocrine, environmental, socioeconomic, and genetic factors (Daly & Obrams, 1998). However, recognized risk factors explain only a modest percentage of the chance for cancer development. In addition, a substantial body of research has emerged over the last 30 years documenting relationships between psychological factors, cancer risk, and disease PSYCHONEUROIMMUNOLOGY, 4E VOLUME II
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(MMPs), and inflammation. Moreover, our emerging understanding of interrelationships between neuroendocrine hormones, angiogenic cytokines, and immune and inflammatory mediators provides a much more complex picture of how psychosocial factors may influence tumor growth and survival, particularly within the tumor microenvironment. This chapter presents the current state of the literature regarding relationships between psychosocial factors and cancer initiation and progression, followed by an examination of the existing literature on psychosocial-immune relationships in cancer patients in light of the limitations of the immunosurveillance theory. Evidence supporting direct effects of psychosocial factors on a variety of other fundamental physiological processes associated with cancer development will be presented. Finally, effects of the immune response on quality-of-life factors such as fatigue will be examined, and suggestions will be presented for broadening conceptualizations of PNI models in oncology. Although health behaviors may make an important contribution to the immune response and other processes discussed herein (e.g., Andersen et al., 1994), discussion of their influence is beyond the scope of this chapter.
II. PSYCHOSOCIAL FACTORS IN CANCER INITIATION AND PROGRESSION The role of psychological factors in the development of cancer has been an area of intense interest: A recent review found 108 studies over the past 40 years that have examined the role of psychological factors in the development and progression of cancer (Garssen, 2004). Although the evidence for the role of psychosocial factors in cancer initiation is limited, psychosocial factors appear to play a larger role following cancer initiation.
A. Stressful Life Events Much research has focused on the question of whether stressful life events might be a risk factor for the development of cancer (Chen et al., 1995; Protheroe et al., 1999). Recent meta-analyses and a review paper have concluded that there is no convincing overall link between stressful life events and cancer risk (Butow et al., 2000; Duijts, Zeegers, & Borne, 2003; Petticrew, Fraser, & Regan, 1999). However, the evidence is more compelling for severe life events associated with loss, such as death of a child or spouse (Geyer, 1991, 1993; Lillberg et al., 2003). In a recent meta-analysis, death of a spouse was associated with increased risk for breast cancer (Duijts et al., 2003), while events such as
health difficulties, change in marital status, and change in financial status were not. Links between bereavement and development of cancer may vary by cancer site. For example, although death of a child or spouse was not related to increased risk for cancer overall in several studies (Kvikstad & Vatten, 1996; Levav et al., 2000), stratification of cancer by site has revealed links between such events and increased risk for melanoma and lymphatic, hematopoietic, uterine, ovarian, and lung cancers (Levav et al., 2000; Martikainen & Valkonen, 1996). There is also evidence that stressful life events occurring both before and after diagnosis are linked to cancer recurrence and death among breast cancer patients (Forsen, 1991; Ramirez et al. 1989). However, the majority of studies, particularly those with larger sample sizes, have not demonstrated a relationship between stressful events and cancer relapse (Barraclough et al., 1992; Forsen, 1991; Geyer, 1991, 1993; Kvikstad & Vatten, 1996; Levav et al., 2000; Lillberg et al., 2003; Martikainen & Valkonen, 1996; Maunsell, Brisson, Mondor, Verreault, & Deschenes, 2001; Ramirez et al., 1989).
B. Depression There is minimal evidence that depression alone is a risk factor for the development of cancer. A recent review of the role of psychosocial factors in the development of breast cancer found null results in all nine studies examining this link (Butow et al., 2000), and a meta-analysis of prospective longitudinal studies of the link between depression and later incidence of cancer found only marginally significant relationships that were not thought to be of any clinical significance (McGee, Williams, & Elwood, 1994). However, depression may be linked to the development of cancer in certain at-risk populations, such as older adults or smokers. A large, well-designed prospective study found that older adults who reported significantly elevated depressive symptomatology for at least 6 years were at greater risk for cancer, after controlling for a variety of other risk factors (Penninx et al., 1998). This study was noteworthy for including repeated assessments of depression, thus capturing chronic depression. In another large-scale prospective study, risk of lung cancer was greater among depressed individuals, even after controlling for other risk factors including smoking. Importantly, depression interacted with smoking status such that when both risk factors were present the risk of lung cancer was much greater than when either risk factor was present alone (Knekt et al., 1996). A second study found similar results; presence of both smoking and depressed mood resulted in elevated risk for all cancer sites, and risk
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was even more elevated for cancer sites associated with smoking (Linkins & Comstock, 1990). Evidence for the relationship between depression and cancer recurrence or survival is mixed. Depressed mood has been associated with poorer survival in studies of breast cancer, lung cancer, and bone marrow transplant patients (Buccheri, 1998; Rodrigue, Pearman, & Moreb, 1999; Watson, Haviland, Greer, Davidson, & Bliss, 1999). However, others have found no links between depression and survival in similar populations (Andrykowski, Brady, & Henslee-Downey, 1994; Faller, Bulzebruck, Drings, & Lang, 1999). In a recent review, only about one-third of prospective, longitudinal studies examining links between negative emotions and course of cancer found that negative emotions were associated with poorer clinical outcomes (Garssen, 2004). Several factors might account for such inconsistent results. It may be that individuals who suffer chronic depression or those who are depressed prior to their diagnosis are at greater risk for adverse outcomes than individuals who become acutely depressed following diagnosis. Consistent with this idea, a large-scale epidemiologic study reported cancer patients with emotional difficulties prior to the diagnosis of cancer were more likely to die over a 15-month period than patients without previous difficulties. In contrast, patients experiencing depression for the first time after diagnosis had no poorer survival than those without depression (Stommel et al., 2002). Inconsistent findings may also be due to lack of specificity regarding type of depression. Gold and Chrousos (2002) distinguish between hyperactive and hypoactive hypothalamicpituitary-adrenal (HPA) and sympatho-adrenomedullary (SAM) profiles associated with different types of depression. One would expect quite different downstream effects of these very different depressive HPA profiles on immune, tumor growth, and inflammatory pathways.
C. Personality and Coping Style 1. Emotional Suppression Long-standing traits or characteristics that influence how individuals relate to their environment may play a greater role than the occurrence of stressful events or acute depression in the development and progression of cancer. Although links between development of cancer and well-known personality traits such as extraversion, neuroticism, hostility, and dependence have not been found (Chen et al., 1995; Greer & Morris, 1975, 1978; Schapiro et al., 2001), some have characterized cancer patients as appeasing, self-sacrificing, and
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outwardly calm as a result of suppressing emotions, especially anger. This constellation of characteristics has been termed by Temoshok (1987) the “cancerprone” or “Type C” personality. An early study demonstrated that veterans diagnosed with cancer had higher scores on a measure of emotional repression at least 2 years prior to diagnosis (Dattore, Shontz, & Coyne, 1980). However, a subsequent large-scale study of male electrical company employees did not find that the same measure of repression predicted cancer incidence over a 20-year follow-up period (Persky, Kempthorne-Rawson, & Shekelle, 1987). The literature to date continues to be inconclusive with both positive (Fox, Harper, Hyner, & Lyle, 1994; Grassi & Cappellari, 1988) and null findings (Hahn & Petitti, 1988; Price et al., 2001). There is some evidence that relationships may vary by age: Two studies have found a link between emotional suppression and breast cancer development only in women less than 50 years of age (Greer & Morris, 1975, 1978; Scherg, Cramer, & Blohmke, 1981). Low expression or high suppression of emotions has been associated with a variety of important clinical outcomes, including poorer outcomes on a prognostic indicator (tumor thickness) in malignant melanoma (Temoshok et al., 1985), greater progression of breast cancer (Jensen, 1987), and poorer survival among breast cancer and lymphoma patients (Reynolds et al., 2000; Weihs, Enright, Simmens, & Reiss, 2000). However, not all findings have been consistent (Giraldi et al., 1997; Watson et al., 1999). 2. Fighting Spirit An early and well-publicized study demonstrated that early-stage breast cancer patients who exhibited a “fighting spirit” 3 months after surgery had fewer recurrences and better survival 5, 10, and 15 years later (Greer, Morris, & Pettingale, 1979; Greer, Morris, Pettingale, & Haybittle, 1990; Pettingale, 1984; Pettingale, Morris, Greer, & Haybittle, 1985). A similar link was found among leukemia patients undergoing bone marrow transplantation (Tschuschke et al., 2001). Despite these provocative findings, both studies have been criticized for small sample sizes. Furthermore, the findings have not been replicated in other samples of bone marrow transplant patients (Andrykowski et al., 1994; Murphy, Jenkins, & Whittaker, 1996) or breast cancer patients (Giraldi et al., 1997; Watson et al., 1999). 3. Hopelessness/Pessimism Data are more consistent for the detrimental effects of a hopeless or pessimistic coping style. Helplessness
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and hopelessness among newly diagnosed breast cancer patients were associated with greater likelihood of relapse and poorer survival 5 years post-diagnosis in two studies, one with a very large sample (Greer et al., 1979; Watson et al., 1999). Similarly, patients who reported less hopefulness at the time of a bone marrow transplant did not live as long following the transplant (Molassiotis, Van den Akker, Milligan, & Goldman, 1997), and pessimism among patients undergoing palliative radiation treatment was associated with greater mortality for participants younger than 60 (Schulz, Bookwala, Knapp, Scheier, & Williamson, 1996). The majority of these studies adjusted for important confounding variables, suggesting that hopelessness does not simply represent patients’ assessment of a poorer prognosis. While findings are more robust for hopelessness as compared to other personality variables, other studies have not replicated relationships between hopelessness and clinical outcomes among cancer patients (Andrykowski et al., 1994; Cassileth, Walsh, & Lusk, 1988; Giraldi et al., 1997). 4. Active Coping versus Avoidance A meta-analysis of coping techniques found that active, attentional strategies are more effective for coping with serious, long-term stressors requiring readjustment, such as a cancer diagnosis, while avoidant strategies work best for coping with less serious, brief stressful life events (Suls & Fletcher, 1985). Survival outcomes appear to follow this pattern. Among melanoma patients enrolled in a psychosocial intervention trial, active coping at baseline and positive changes in active coping were associated with lower recurrence and death 6 years later (Fawzy et al., 1993). In contrast, measures of avoidance have been related to poorer survival (J. E. Brown, Butow, Culjak, Coates, & Dunn, 2000; Epping-Jordan, Compas, & Howell, 1994; Morris, Pettingale, & Haybittle, 1992). However, most studies of active and avoidant coping strategies have not found significant relationships with recurrence (Buddeberg et al., 1997; Butow, Coates, & Dunn, 1999; Butow et al., 2000); this is true of diverse cancer sites and for follow-up periods as long as 10 years. 5. Denial/Minimization Denial or minimizing the impact of cancer was associated with positive clinical outcomes in several samples. Among breast cancer patients, denial assessed in the months following surgery was associated with lower likelihood of recurrence and greater likelihood of survival between 5 and 15 years later (Greer et al., 1979; Greer et al., 1990; Pettingale, 1984; Pettingale et al., 1985). Patients with metastatic breast and lung
cancers who minimized the impact of their cancer also survived longer (Butow et al., 1999; Butow et al., 2000), although this effect was not found among earlystage melanoma patients (Brown et al., 2000). The relatively consistent positive findings are somewhat perplexing because denial is generally considered to be maladaptive. However, the denial measures used in these studies may have tapped into optimism or hopefulness. 6. Summary of Coping and Personality Research A recent review of the literature exploring links between coping and cancer survival or recurrence concluded that coping had little effect on recurrence and survival (Petticrew, Bell, & Hunter, 2002). In particular, there appears to be little evidence that avoidance, active problem-focused coping, or maintaining a “fighting spirit” is associated with important clinical outcomes among cancer patients. Often links were found only in studies with small sample sizes and other design problems. The evidence is stronger for the effects of hopelessness and denial on recurrence and survival. These findings converge on the idea that a hopeless outlook, as opposed to a more optimistic view, may be detrimental to survival.
D. Social Support Social support is defined as the degree of perceived satisfaction with social relationships (Cohen & Wills, 1985). In epidemiological studies, the relationship between social support and diminished morbidity and mortality risk has been quite robust (House, Landis, & Umberson, 1988). Although most studies have not found relationships between measures of social support and cancer risk (Bleiker, Van der Ploeg, Hendriks, & Ader, 1996; Edwards et al., 1990), there is some indication that lack of social support may interact with sex and other risk factors in the development of cancer. For example, social isolation was associated with greater incidence of all types of cancer but only among women (Reynolds & Kaplan, 1990). Social support may also interact with stressful life events in predicting cancer development. In a large sample of older women with suspicious mammograms, those who had experienced highly threatening life stressors and had little emotional support were nine times more likely to be diagnosed with breast cancer than those who did not have these risk factors, but neither stressors nor lack of support alone was associated with increased risk of breast cancer (Price et al., 2001). Moreover, there is relatively consistent evidence that social support is associated with clinical outcomes
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among individuals who have already been diagnosed with cancer, at least among breast cancer patients. Although some studies have not found a link between social support and survival (Butow et al., 1999; Butow et al., 2000; Giraldi et al., 1997), several large-scale studies of breast cancer patients have found that social support is related to longer survival (Funch & Marshall, 1983; Marshall & Funch, 1983; Maunsell, Brisson, & Deschenes, 1995; Reynolds et al., 1994; Reynolds et al., 2000). In these samples, both perceived social and emotional support and a more extensive social network (greater number of social ties, more confidants, greater social involvement) were associated with greater likelihood of survival.
E. Psychosocial Interventions and Cancer Survival Intervention studies that use a randomized controlled design allow for experimental investigation of effects of psychosocial factors on disease course. Research in this area was mobilized by a study reporting that metastatic breast cancer patients assigned to a year-long weekly support group survived an average of 18 months longer than patients randomized to a control group (Spiegel, Bloom, Kramer, & Gottheil, 1989). However, further analyses of the data suggested that the control group may have been composed of patients with poorer prognoses, more lung and bone metastases, and shorter survival than the general population of metastatic breast cancer patients (Fox, 1998; Kogon, Biswas, Pearl, Carson, & Spiegel, 1997). Moreover, two replications of Spiegel’s study have not found a survival effect (Cunningham et al., 1998; Goodwin, Leszcz, & Ennix, 2001), although Goodwin and colleagues (2001) were effective in improving mood and decreasing pain among women with more severe symptoms. Similarly, a cognitive-behavioral intervention for metastatic breast cancer patients showed no survival effects (Edelman, Lemon, Bell, & Kidman, 1999). Randomized trials of psychosocial interventions among other cancer patient populations have shown some promising results. A group coping intervention was effective in improving mood, positive coping strategies, and immune functioning among malignant melanoma patients, and participants randomized to the intervention were less likely to experience a recurrence and more likely to be alive 6 and 10 years later (Fawzy et al., 1993; 2003). The intervention appeared to be particularly effective among patients with the poorest prognoses. Among 271 patients undergoing surgery for gastrointestinal cancers and randomized to in-patient counseling versus standard care, inter-
vention participants were more likely to be alive 2 years later, and survival differences between control and intervention groups were particularly striking among female patients (Kuchler et al., 1999).
F. Summary Evidence for a role of psychosocial factors in the development or initiation of cancer is inconsistent and inconclusive. Evidence is most consistent for the role of death of a close family member and some types of emotional suppression, but these findings are far from robust. The literature is suggestive of a more nuanced and complex role of psychosocial factors in the development of cancer than may have been previously thought. It is likely that the role of psychosocial factors in the development of cancer varies by cancer site. The literature also suggests the importance of examining interactions between psychosocial factors and other host factors such as age (Greer & Morris, 1975, 1978; Penninx et al., 1998; Scherg et al., 1981). Older adults with normal age-related changes in immune functioning may be especially susceptible to the detrimental effects of distress and depression. Similarly, individuals with other vulnerabilities, such as smokers, may be more at risk for an impact of psychosocial factors in the development of cancer. Suppression of negative emotions, hopelessness and pessimism, denial and minimization of cancer’s impact, and social support are the psychosocial constructs that demonstrate the most consistent relationships with clinical outcomes following diagnosis. Cancer patients who are hopeful and minimize the threat of cancer, but are willing to express their negative emotions, and those who have extensive social networks and emotional support appear to have decreased risk of recurrence and death. These qualities appear to reflect more trait-like individual differences than factors for which the evidence is more inconsistent. The evidence is less convincing for the effects of stressful life events, acute depressed mood, fighting spirit, or use of active versus avoidant coping techniques on recurrence and survival. The evidence for the effects of psychosocial interventions on survival is mixed but cannot be discounted. These findings coupled with the strong animal literature supporting relationships between stress and social factors and tumor growth (Ben-Eliyahu, 2003; Riley, 1975; Wu, 2000) have given rise to research examining potential mechanisms for these relationships. In the next sections of the chapter, evidence supporting physiological mechanisms that may mediate the relationships noted above is described. Evidence consistent with a stress-induced immunosuppression
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model of cancer is presented, followed by a discussion of potential limitations of this model. The model is then extended to other physiological processes, including inflammation, angiogenesis, DNA repair, and neuroendocrine influences on tumor progression.
III. PSYCHOSOCIAL FACTORS AND THE IMMUNE RESPONSE IN THE CONTEXT OF CANCER In examining potential mechanisms underlying findings such as those outlined above, the immune response has been the main focus of much PNI oncology research. The immune response is thought to function in several roles in cancer. Among these is immunosurveillance, the process by which immune cells (a) recognize and eliminate cells in which tumor promotion events have occurred and (b) block subsequent growth and development of cells that have escaped detection (Dunn, Bruce, Ikeda, Old, & Schreiber, 2002). It has generally been thought that psychosocial factors influence cancer via the cellular immune response, and stress-mediated immunosuppression has been thought to impair the body’s ability to control cancer. Evidence examining the role of immunosurveillance in cancer control will be examined later in the chapter. First, data relating psychosocial factors and the immune response in cancer patients will be reviewed.
A. Individuals at Risk for Cancer One strategy for examination of interactions between psychosocial factors and potential for developing cancer has been to examine immune activity in individuals who may be at higher risk for developing cancer, such as women with family histories of breast cancer. In one comprehensive study, 80 daughters of breast cancer patients reported greater emotional distress accompanied by higher levels of urinary cortisol and catecholamines, and lower in vitro secretion of the TH-1 cytokines IL-2, IL-12, and IFN-γ compared to age- and education-matched healthy women with no family history of breast cancer. Furthermore, compared to controls, daughters of breast cancer patients demonstrated significantly lower NK cell activity against both NK resistant (MCF-7, COLO-205, U937) and NK sensitive (K562) cell lines, as well as lower IL-2– or IL-12–augmented NK activity. Greater emotional distress was correlated with lower NK activity and TH-1 cytokine secretion, which in turn were correlated with higher levels of stress hormones (Cohen et al., 2002). Similar findings of reduced NK cell activ-
ity, independent of distress, have been found in an independent sample of women with familial breast cancer risk (Bovbjerg & Valdimarsdottir, 1993). Women with familial breast cancer risk have demonstrated greater neuroendocrine reactivity responses to stressful laboratory tasks (Valdimarsdottir et al., 2002). Compared to women at low risk, these women also have a higher level of epinephrine excretion while at work and a greater percentage increase in epinephrine levels between sleep and work, suggesting a heightened neuroendocrine response to stress (James, Berge-Landry, Valdimarsdottir, Montgomery, & Bovbjerg, 2004). Taken together, these findings suggest that the combination of a genetic vulnerability along with chronic emotional distress and greater physiological reactivity to stress may create conditions consistent with impaired immune surveillance in daughters of breast cancer patients and thus put them at a greater vulnerability to develop breast cancer.
B. Distress, Depression, and Immunity among Cancer Patients Substantial evidence (elaborated elsewhere in this volume) indicates that cellular immunologic activities relevant to cancer such as number and function of T lymphocyte subsets and NK cells are modulated by negative psychological states such as stress, depression, loneliness, and hopelessness (Irwin, 2002; KiecoltGlaser et al., 1987; Zorilla, Luborsky, & McKay, 2001). Similar relationships have been found among individuals with cancer. In a series of prospective studies among Stage I and II breast cancer patients, psychosocial factors contributed 51% of the variance in NK cell activity prior to adjuvant treatment, with greater distress associated with poorer NK function (Levy, Herberman, Maluish, Schlein, & Lippman, 1985). Furthermore, elevated distress after surgery predicted lower NK cell activity at a 15-month follow-up, and patients with lower NK activity 15 months post-surgery had a shorter time to recurrence over a 5–8-year followup (Levy, Herberman, Lippman, & D’Angelo, 1987). NK cell activity at diagnosis and at repeated assessments predicted probability of recurrence, and both emotional distress and social support predicted the rate of progression, but a model including psychosocial factors, NK cell activity and progression was not supported (Levy et al., 1991). Several recent studies have also documented relationships between psychosocial factors and immune functioning among women with breast cancer. In a study of 116 early-stage breast cancer patients assessed between surgery and adjuvant therapy, patients reporting greater stress demonstrated lower levels of NK cell
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activity, diminished response of NK cells to recombinant IFN-γ, and decreased lymphoproliferative response to mitogens, after controlling for variables that could potentially affect the immune response, such as age, disease stage, and days since surgery (Andersen et al., 1998). These findings indicate that distress is related to decrements in a broad range of markers of cellular immunity in breast cancer patients following surgery and suggest that distressed patients may be more vulnerable to secondary infections during chemotherapy. Consistent with these results, Garland and colleagues (2004) found that among 55 early breast cancer patients assessed pre-surgically, those who reported past or current psychiatric illness had lower NK cell activity, as compared to those with no previous mental health history. These effects were not mediated by early morning cortisol levels. Surprisingly, higher scores on the trait of “fighting spirit” on the Mental Adjustment to Cancer scale were related to significantly greater tumor size. These findings are in contrast to Greer’s (1979) report of a link between “fighting spirit” and better survival outcomes in breast cancer patients. This paradoxical finding remains to be more clearly understood. However, in contrast to Garland’s findings, Osborne and colleagues (2004) found that “fighting spirit” was related to more prolonged survival in an Australian sample of 61 early-stage breast cancer patients initially assessed at least 4 weeks following chemotherapy and followed up for almost 8 years. In this sample, lower NK cell activity also predicted longer survival, with both models adjusting for lymph node status. The authors concluded that their data provided little support for a PNI model in breast cancer survival (Osborne et al., 2004). However, as will be discussed below, these findings may point to limitations in looking at one measure of immune function as the sole physiological mediator of survival in a biobehavioral study of cancer. Tjemsland and colleagues (1997) found pre-operative distress, depression, intrusive anxiety, and anxious preoccupation associated with lower numbers of total lymphocytes, B-cells, and CD4+ lymphocytes in 106 women newly diagnosed with Stage I or II breast cancer assessed pre-surgically. Furthermore, depression predicted a decrease in blood lymphocytes, and intrusion predicted an increase in lymphocyte numbers from pre- to post-surgery (Tjemsland, Soreide, Matre, & Malt, 1997). There is also some evidence for relationships between distress and immune functioning in other cancer populations. A cross-sectional study of cervical and endometrial cancer patients assessed at two timepoints prior to surgical treatment found that psycho-
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social distress was significantly associated with decreased NK cell number but not with decreased NK cytotoxicity. In addition, adjusting for clinical stage and NK cell activity, examiner-rated distress predicted number of nodes positive for cancer infiltration (Roberts, Anderson, & Lubaroff, 1994). In a study of 108 patients with digestive tract cancers, depression was related to lower numbers of NK cells (CD56+) and total lymphocytes, but not to numbers of CD4+ or CD8+ cells. These findings did not control for stage or type of digestive cancer (Nan et al., 2004).
C. Distress and Conditioned Immunosuppression during Chemotherapy There is evidence from several studies that cancer patients exhibit conditioned immunosuppression to chemotherapy. In one study, proliferative responses to T-cell mitogens were lower for cells isolated from hospital blood samples than from home samples obtained several days earlier (Bovbjerg et al., 1990). A second study found impaired NK cell function and lower numbers of CD4+ cells in pre-chemotherapy blood samples obtained in the hospital compared to those obtained at home 2 days earlier, suggesting conditioned anticipatory immunosuppression in the hospital at the time of receiving chemotherapy (Fredrikson, Furst, Lekander, Rotstein, & Blomgren, 1993). This type of anticipatory immune suppression may leave patients more vulnerable to secondary infections during chemotherapy. Furthermore, Fredrikson and colleagues (1993) found that impaired NK cell function prior to chemotherapy was found only among patients with high levels of trait anxiety, suggesting that psychosocial factors may moderate this response. Psychosocial factors may also impact immune recovery following chemotherapy. Three months following completion of adjuvant chemotherapy, patients with high social attachment had higher counts and percentages of granulocytes and lower proportions of lymphocytes and monocytes. These alterations were not seen during chemotherapy, however, suggesting to the authors that these relationships may be dwarfed by the biological effects of chemotherapy on hematopoiesis (Lekander, Furst, Rotstein, Blomgren, & Fredrikson, 1996).
D. Protective Psychosocial Factors 1. Social Support Although much work has focused on downregulation of the immune response with psychological
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distress, some psychosocial factors may protect against decrements in immune functioning or may promote better immune activity. For example, Levy and colleagues found that among women with Stage I and II breast cancer following surgery, those women who perceived greater social support from their spouse or significant other and from their physician, women with estrogen receptor negative status, and women who sought social support as an important coping strategy were more likely to have higher concurrent NK cell activity (Levy et al., 1987; Levy et al., 1985). A follow-up report on the same sample reported that perceived support and use of social support as a coping strategy under stress continued to be related to higher levels of NK cell activity at 3 months post-surgery (Levy et al., 1990). The studies reviewed so far have all assessed immune functioning in peripheral blood. However, in many cancers the immune response in the tumor microenvironment is known to be impaired. For example, in ovarian cancer, decrements in NK cell activity and in the lymphoproliferative response to autologous tumor cells have been demonstrated in ascites (the fluid around the tumor) and in TIL as compared to peripheral blood lymphocytes (Lotzova, Savary, Freedman, & Bowen, 1986; Schondorf et al., 1997). Decreased expression and function of signaling molecules has been observed in T- and NK cells found in ascites, and these signaling deficiencies have been associated with decreased ability to produce IL-2 and IFN-γ (Lai et al., 1996). Recent data suggest that psychosocial factors may also be associated with immune activity at the tumor site. Lutgendorf and colleagues examined NK cell activity in peripheral blood, ascites, and TIL in a sample of ovarian cancer patients. NK cell activity in TIL was significantly impaired compared to that in ascites or in peripheral blood mononuclear cell (PBMC), and as compared to that of women undergoing surgery for suspected ovarian cancer that was ultimately diagnosed as benign disease. Adjusting for disease stage, patients with higher levels of social support had higher NK cell activity both in peripheral blood and in lymphocytes isolated from the tumor. In contrast, patients with higher levels of distress demonstrated lower levels of NK cell activity in tumor-infiltrating lymphocytes isolated from ovarian tumors (Lutgendorf et al., 2005). Distress-associated suppression of the immune response combined with the already-impaired immune response in TIL suggests a high vulnerability in these patients. One final study examined social support and antigen-specific cell-mediated immunity among metastatic beast cancer patients using the delayed hyper-
sensitivity (DTH) response to seven recall antigens in the Multi-test CMI. In general, reduced DTH responses were seen in this population. Interestingly, size of social network was not associated with DTH response. However, DTH responsivity was predicted by an interaction between size of the social network and life stress, with the highest DTH responses found in two groups: those patients with high social support and high life stress and those patients with low social support and low life stress. These results do suggest a relationship of DTH with psychosocial factors in cancer, but because of the counter-intuitive nature of the findings (e.g., low DTH in patients with high social support and low stress), the authors recommend caution in interpreting these findings (Turner-Cobb et al., 2004). 2. Benefit Finding The ability to find benefit in the experience of cancer may include an enhanced sense of meaning or purpose in life, improved interpersonal relationships, a renewed sense of spirituality, and an overall greater appreciation for life. Among women with early-stage breast cancer 1–2 months post-surgery, positive factors such as perceived social support, use of positive reframing, and optimism were associated with a greater lymphoproliferative response (LPR) to the T-cell monocolonal antibody (CD3) (McGregor et al., 2004). Along these same lines, among 112 women with metastatic breast cancer, those reporting spiritual expression as more important had greater numbers of peripheral white blood cells, total lymphocytes, and CD4+ and CD8+ cells, controlling for demographics, disease status, and treatment variables. There was no association between spiritual expression and NK cell activity or the DTH response to seven commonly encountered antigens. In contrast, religious attendance was negatively correlated with the DTH responses but not to other measures (Sephton, Koopman, Schaal, Thoresen, & Spiegel, 2001). Emotional expression may also be adaptive with respect to immune functioning among cancer patients. For example, in a sample of 119 cutaneous malignant melanoma patients, greater expression of sadness and anger was related to higher numbers of lymphocytes at the tumor site, an increase in the length of the cell cycle of tumor cells, and greater desmoplasia (a positive late-stage host response in melanoma patients in which the tumor is enclosed by fibrosis, thereby inhibiting spread) (Temoshok et al., 1985). This study is noteworthy for observations of relationship between emotional expression and clinically significant indicators at the tumor site. In a second study assessing
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emotional expression, Roberts and colleagues found that cervical and endometrial cancer patients with greater emotional expression showed higher levels of concurrent NK activity before surgery (Roberts et al., 1994).
E. Psychosocial Interventions, the Immune Response, and Disease Progression in Cancer Patients The utility of psychosocial interventions as an experimental strategy for determining relationships between psychological factors and disease outcomes in cancer was previously described. Such experimental designs can also help elucidate relationships between psychological and immune factors in cancer patients. There is consistent evidence that stress management interventions may be effective in improving immune functioning or protecting immunity against declines associated with cancer and its treatment. For example, Fawzy and colleagues’ intervention for malignant melanoma patients described previously measured several aspects of the immune response. Patients assigned to the intervention group demonstrated increased IFNγ–augmented NK cell activity at the 6-month followup. Moreover, those reporting reduced anxiety and depression showed increased NK cell activity at this time point (Fawzy, Kemeny et al., 1990). However NK cell activity was not related to survival (Fawzy et al., 1993). In one large-scale study, 227 early-stage breast cancer patients were randomized to a 4-month, weekly stress management intervention or a control group. Among those assigned to the intervention, anxiety decreased and improvements in social support, diet, and smoking cessation were seen. The lymphoproliferative T-cell response to PHA and ConA either maintained a constant level or increased among intervention patients while decreasing among the controls. Differences between the groups over time in NK cytotoxicity or number were not noted (Andersen et al., 2004). In another recent large intervention study, early-stage breast cancer patients participating in a 10-week cognitive behavioral stress management intervention showed significantly increased benefit-finding and lymphoproliferative response to a CD3 monoclonal antibody to the T-cell receptor compared to wait-list controls between study entry and a 3-month postintervention follow-up. Furthermore, extent of benefit finding was positively correlated with the T-cell lymphoproliferative response (McGregor et al., 2004). The latter study was noteworthy for detecting sustained alterations in the immune response 3 months after the intervention had actually ended.
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A recent study points to the effectiveness of intensive lifestyle changes in markers related to prostate cancer progression. Ninety-three prostate cancer patients who had chosen not to undergo any conventional treatment (watchful waiting) were randomized to an intervention group that was asked to make comprehensive lifestyle changes versus a standard care control group. The intervention included adherence to a vegan diet with specific supplements, moderate aerobic exercise, stress management (including yoga, meditation, imagery, and visualization), and participation in an hour-long weekly support group to enhance adherence to the intervention. Men in the intervention group showed an average decrease of 4% in Prostate Specific Antigen (PSA), whereas this marker of cancer progression increased 6% in the control group. Moreover, serum from the experimental group inhibited the growth of LNCaP prostate cancer cells almost eight times more than serum from the control group. Furthermore, extent of adherence to diet and lifestyle changes was associated with extent of changes in serum PSA and in LNCaP cell growth. This study indicates the potential impact of comprehensive lifestyle changes on markers of progression of prostate cancer (Ornish et al., 2005). Breast cancer patients participating in an intensive intervention including relaxation, biofeedback, and imagery demonstrated better NK cell activity, circulating peripheral lymphocytes, and lymphocyte response to ConA as compared to a control group (Gruber et al., 1993), and a second similar intervention showed decreased plasma cortisol levels as well as increased lymphocyte numbers (Schedlowski, Jung, Schimanski, Tewes, & Schmoll, 1994). Consistent with these findings, 22 ovarian cancer patients who were randomized to receive relaxation training during chemotherapy showed higher lymphocyte counts and a trend to higher white blood cell counts prior to chemotherapy as compared to the control group, but there were no group differences in functional assays such as NK cell activity or T-cell proliferative responses to ConA (Lekander, Furst, Rotstein, Hursti, & Fredrikson, 1997). Finally, a mindfulness-based stress reduction intervention for breast and prostate cancer patients who had completed primary treatment increased T-cell production of IL-4, decreased T-cell production of IFN-γ, and decreased NK cell production of IL-10 over the course of the intervention. Although these findings were interpreted by the authors as a positive change because of a shift away from a pro-inflammatory (TH1) profile (Carlson, Speca, Patel, & Goodey, 2003), this shift is also indicative of decreased cellular immune capabilities, and thus these findings are equivocal until there is a clearer understanding of the health
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implications of pro- versus anti-inflammatory cytokine profiles in this population. Moreover, the study did not include a control group, and thus findings could not be compared with the natural course of these changes over time. Not all interventions have shown physiological effects. A small-scale randomized 5-week psychosocial intervention had no effect on the immune response (CD4+, CD8+ lymphocytes, and NK cell activity) in a sample of 34 Japanese breast cancer patients (Hosaka, Tokuda, Sugiyama, Hirai, & Okuyama, 2000). However, it is possible that only extended interventions can have measurable effects on the immune response in cancer patients.
F. Summary of Research on Psychosocial Factors and the Immune Response in Cancer Patients Taken together, these findings suggest the following types of psychosocial-immune relationships in cancer patients: (1) impairment of several aspects of the cellular immune response associated with the psychological stress that accompanies the diagnosis and initial treatment of cancer, (2) a positive relationship between social support and several measures of immunity, and (3) psychological interventions that increase social support and assist participants with managing stress are able to positively modulate immune function. The demonstration of these relationships in the tumor microenvironment highlights the potential relevance of these findings to cancer control. Although studies vary in the strength of their designs, findings in general support the possibility that the stress of cancer adjustment may have biological as well as psychological effects, and that interventions aimed at decreasing stress and increasing social supports may have biological as well as psychological relevance.
IV. IMMUNOLOGIC MECHANISMS AND TUMOR CONTROL To date the majority of studies examining psychoneuroimmunological processes in cancer have been predicated on the assumption of immunosurveillance, the hypothesis that the immune system surveys the body for developing malignancies. The status of the immunosurveillance hypothesis has shifted over time, and recent revisions have important implications for the possible role of stress as a co-factor for cancer. In this section, we provide a brief background on immunosurveillance and the related concepts of immunoselection and tumor escape.
A. Immunosurveillance First introduced in 1909 by Paul Ehrlich, immunosurveillance was largely ignored until the 1960s when it was shown that mice could be immunized against transplanted tumors (Ehrlich, 1909). It was also documented that individuals with immunodeficiencies had increased rates of malignancies (Penn, 1999). Although the theory fell into disfavor in the 1970s, the cancer immunosurveillance hypothesis has been described as being in a period of “renaissance” (Dunn et al., 2002), with new evidence suggesting that the immune system responds to both viral and non-viral cancers. For example, a series of animal studies in the 1990s (Dighe, Richards, Old, & Schreiber, 1994) demonstrated that the cytokine IFN-γ protected against the growth of both transplanted and spontaneous tumors, and recent studies have shown that genetically modified mice that completely lacked T-, B-, and natural killer T (NKT) cells develop more spontaneous tumors than wild-type mice (Shankaran et al., 2001). There is also evidence for increased incidence of viral cancers among immunocompromised humans. Several recent reviews of the relative risk ratios of non-viral cancers in organ transplant patients document increased incidence and prevalence rates of melanoma; non-Kaposi’s sarcoma; and tumors of the lung, colon, pancreas, bladder, kidney, and ureter (Dunn et al., 2002). Moreover, NK cells and cytotoxic T lymphocytes have been shown to lyse various types of tumor cells, and measures of the activity of these cells have been associated with cancer progression and survival. NK cells have been shown to play a role in inhibition and surveillance related to tumor metastases, and are able to spontaneously kill tumor- or virus-infected cells without prior sensitization, independent of major histocompatibility complex (MHC) expression. Impairments in NK activity or number have been associated with the development of cancer as well as its progression (Hirte & Clark, 1991; Whiteside & Herberman, 1989). NK cell activity has also demonstrated prognostic value in predicting relapse, responses to treatment, and survival time without metastasis in cancers including breast, colorectal, and head and neck cancers (Garner, Minton, James, & Hoffman, 1983; Schantz & Goephert, 1987; Tartter, Martinelli, Steinberg, & Barron, 1986). Furthermore, animal studies have shown that NK cells play a critical role in controlling progression and metastases of various cancers (Barlozzari, Leonhardt, Wiltrout, Herbreman, & Reynolds, 1985; BenEliyahu & Page, 1992; Ben-Eliyahu, Shakhar, Page, Stefanski, & Shakhar, 2000). Cytotoxic T lymphocytes (CTL) can recognize an antigen(s) on the surface of tumor cells that express them and can kill such cells (Goedegebuure et al., 1997; Melief & Kast, 1991). In
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murine models, CTLs have been identified as the predominant effector T-cell population responsible for tumor protection and destruction (Hamaoka & Fujiwara, 1987; Melief, 1992). For example, CTLs recognize multiple antigens on ovarian tumors (Ioannides, Freedman, Platsoucas, Rashed, & Kim, 1991) and mediate lysis of ovarian tumor cells (Heo, Whiteside, Kanbour, & Herberman, 1988). Several studies have reported a correlation between the infiltration of NK, CTL, or dendritic cells into tumor tissue and survival time in patients with melanoma or cancer of the breast, bladder, colon, prostate, ovary, or rectum (Dunn et al., 2002). CTL counts have recently been shown to be prognostic for survival in women with metastatic or recurrent breast cancer, with higher counts of CD3+CD8+ lymphocytes predicting longer survival, independent of medical treatment, and performance status (Blake-Mortimer, Sephton, Carlson, Stites, & Spiegel, 2004).
B. Immunosurveillance: An “Evolving” Hypothesis The original immunosurveillance hypothesis failed to account for some clinical observations including the fact that immunocompetent individuals develop cancer; in fact, immunocompromised individuals represent only a minority of cancer patients (Seymour, Pettit, O’Flaherty, Charnley, & Kirby, 1999). It also failed to account for the failure of immunotherapy to produce much clinical benefit for cancer patients (Khong & Restifo, 2002). The revised immunosurveillance hypothesis has reconciled these clinical findings by drawing on the principles of Darwinian natural selection, using a new concept known as immunoselection (Phillips, 2002). Neoplasms are composed of heterogeneous cells with varying phenotypes that vary with respect to morphology, growth rate, cell surface proteins, hormone receptors, chemotherapy sensitivity, and the potential for metastasis (Fidler, 1997). Some of these properties may be related to the immunogenic potential of the cell; that is, how readily the immune system is able to identify and destroy the neoplastic cell. Cancer cells that show high immunogenic potential are readily eliminated by the immune system; those with low immunogenic potential may evade immunosurveillance. The net result of immunoselection is that the immune system selects for the very cancerous cells it cannot detect and eliminate.
C. Tumor Escape Mechanisms The specific ways by which a particular cancer cell evades immunosurveillance are known as tumor escape mechanisms (Khong & Restifo, 2002). These specific
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adaptations allow malignant cells to survive and replicate in the microenvironment of the host. Tumor cells acquire tumor escape mechanisms through genetic mutation. In recent years, researchers have identified a growing list of tumor escape mechanisms that help cancerous cells evade not only immunosurveillance, but also develop resistance to chemotherapy, radiation, hormone-deprivation treatments, and immunotherapy. Two frequently observed tumor escape mechanisms include the downregulation of class I major histocompatibility complex (MHC I) and tumor-associated antigen expression (Garcia-Lora, Algarra, & Garrido, 2003). Because cytotoxic T-cells can only recognize antigen in the context of the MHC I molecule, cancer cells that downregulate either antigen or MHC I can escape T-cell recognition. The ability to downregulate tumor-associated antigens may explain why cancer vaccinations show only short-term benefit (Lee et al., 1998). In addition to downregulating primary stimulation, tumor cells can interfere with co-stimulatory signals. Without co-stimulation, T-cells and other lymphocytes develop tolerance to tumor cells (Kowalczyk, 2002; Matzinger, 1994). For example, there are reports of neoplastic cells producing type 2 cytokine profiles in the tumor microenvironment of patients with several cancers (Coussens & Werb, 2002; Hsu, Meier, & Meenhard, 2002; Li, Ruttinger, Li, Si, & Wang, 2003). So-called type 2 cytokines, such as Interleukin-10 (IL-10), are anti-inflammatory and suppress anti-cancer immunological processes (e.g., NK cell activity). Thus, tumors can “pro-actively” alter their local microenvironment in ways that inhibit immunological responses. Apoptosis is the process by which a cell undergoes programmed cell death. Cytotoxic T-cells and NK cells induce apoptosis in virally infected and neoplastic cells (Khong & Restifo, 2002) by initiating a cascade of processes that eventually culminate in cell death. In certain cancerous cells, disrupted apoptosis signaling prevents the cell from receiving the final signal to selfdestruct. Disrupted apoptosis signaling has been described in several cancers, including multiple myeloma, non-Hodgkin’s lymphoma, and melanoma (Khong & Restifo, 2002). Interestingly, certain tumor cells not only disregard apoptosis signaling, but they induce apoptosis in T-cells (Rivoltini et al., 2002).
D. Immunosurveillance, Immunoselection, and Tumor Escape: Implications for PNI 1. Methodology The revised immunosurveillance hypothesis has implications for the PNI immunosuppression model.
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First, only limited conclusions can be drawn by focusing on the potency of the immune response without considering other factors such as downregulation of tumor antigen, tolerance, apoptosis, and cytokine profiles in the tumor microenvironment. The degree that a tumor type induces an immune response involving innate and tumor-specific immune responses would be important to examine when possible. For example, NK cell activity is typically assayed in vitro with K562 cells as the target. K562 cells are used precisely because NK cells can easily detect and kill them. However, K562 cells do not acquire escape mechanisms, induce tolerance, ignore apoptosis, or modify local cytokine profiles. Therefore, the K562 NK cell activity assay may not be a completely representative measure of in vivo immune-tumor interactions. Future research may benefit from using a variety of targets for NK cell (and CTL) assays such as those used by Cohen et al. (2002). Ideally, these would include autologous tissue. This would allow for testing of relationships not only between psychosocial factors and the potency of the immune response, but also between psychosocial factors and tumor recognition. Although there are obvious logistical and ethical challenges inherent in this kind of work, findings can be extrapolated more closely to clinical models. 2. “Windows of Opportunity” During the growth and progression of a tumor, there are specific periods when the immune response has a window of “maximum opportunity” for tumor detection and destruction. The life of a cancer cell begins with the genetic mutations in a normal cell, which in some cases leads to neoplastic transformation. After this transformation from benign to malignant, neoplastic cells initially survive via the nutrients supplied by the local microenvironment. As the tumor approaches 1 to 2 mm in diameter, the nutrients supplied by the local microenvironment are no longer sufficient, and to survive, the tumor must promote angiogenesis (Fidler, 1997). Presumably, the force of immunoselection is operating during this period of proliferation and early angiogenesis, particularly when the tumor invades surrounding tissue and incites a local inflammatory response. “Successful” tumors will progressively become less and less immunogenic through the acquisition of escape mechanisms. Eventually successful tumors become fully capable of evading all immunological responses (Zhou, Zhengbin, McCadden, Levitsky, & Marson, 2004). Thus, early in tumor development, before the development of a full array of tumor escape mechanisms, the immune response has a “window of opportunity” to
detect and respond to the tumor. This “window of opportunity” would also extend back to the pre-malignant period when a neoplasm is abnormal but not yet cancerous. The peri-surgical period represents another “window of opportunity” for the immune response. Anesthesia, pain, blood transfusions, hypothermia, and psychological distress all suppress cell-mediated immunity (Ben-Eliyahu, 2003). Furthermore, the surgical procedure invariably disrupts the tumor, leading to the release of tumor cells into circulation. Following surgery, there is a release of growth factors and a disinhibition of angiogenesis that may promote tumor growth. Another “window of opportunity” may occur following primary or adjuvant treatment as the patient is re-establishing his/her immune response and while the tumor burden is very small. Yet another “window of opportunity” may occur during the process of metastasis, just following the extravasation of tumor cells into new tissue sites, but just prior to the tumor cells developing the ability to modify the local microenvironment in ways that impair immunosurveillance (Ben-Eliyahu, 2003). These time-points illustrate some of the major “windows of opportunity” but are not meant to be complete. Should the immune response be suppressed (e.g., by stress-associated immune dysfunction) or enhanced (e.g., by relaxation, social support) during a “window of opportunity,” there may be implications for tumor progression. In sum, PNI research is likely to uncover the most robust relationships between stress, immune functioning, and cancer during these windows; studies examining PNI relationships outside a window of opportunity (e.g., in established metastatic disease) may represent less than fully optimal tests of the PNI immunosuppression model of cancer. Moreover, stable psychosocial variables such as personality or socioeconomic status (Segerstrom, 2003) as well as distress may place individuals at risk for immunosuppression during a “window of opportunity”.
E. Does the Immune Response Mediate the Relationship between Psychosocial Factors and Survival? Tests of the Full Model There have been few published attempts to fully test the model that psychosocial factors predict disease progression via their putative effects on immunological or neuroendocrine factors. Levy’s work, as noted above, fell short of being able to predict survival from psychosocial factors via the mediation of immunologic factors. As noted above, melanoma patients participating in Fawzy and colleagues’ intervention demonstrated increased use of active coping strategies,
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decreased distress, and increased IFN-γ–augmented NK cell activity at the 6-month follow-up, and a lower death rate over a 5–6 year and a 10-year follow-up as compared to a control group (Fawzy, Canada, & Fawzy, 2003). Although decreased anxiety and depression during the intervention were significantly correlated with increases in augmented NK cell activity at 6 months, the changes in NK activity did not account for the survival effects (Fawzy, Cousins et al., 1990; Fawzy et al., 1993; Fawzy, Kemeny et al., 1990). Other ongoing PNI-cancer research has not yet reported survival findings (Andersen et al., 2004; McGregor et al., 2004). Taken together, these findings suggest consistent relationships between distress and compromised immune function in patients with several types of cancer as well as less impaired immune function among patients with higher levels of social support or positive coping. Both Levy’s and Fawzy’s findings support a relationship between psychosocial factors and cancer progression. However, these studies do not provide strong evidence that cellular immune factors account for this relationship. Whereas cellular immune mechanisms are important in control of tumors, as discussed above, immune surveillance alone may be an incomplete explanation for the associations that exist between biobehavioral factors and cancer progression. The lack of strong mediation by immune factors of the relationship between biobehavioral factors and disease progression suggests that other mechanisms may underlie these relationships.
F. Inflammation Whereas cellular immune processes have traditionally been seen as important for tumor control and the stress-induced shift from TH-1 to TH-2 cytokines has been thought to be inimical to tumor control because it reflects poorer cellular immunity (Elenkov, Chrousos, & Wilder, 2000; Kiecolt-Glaser & Glaser, 1999), a more complex view is emerging. Thus, proinflammatory TH-1 cytokines in the vicinity of the tumor may actually serve to promote inflammation, angiogenesis, and tumor growth (Coussens & Werb, 2002). These tumor-enhancing inflammatory processes may be seen in light of the well-documented relationship between stress and chronic inflammation. There is ample evidence that chronic stress or repeated episodes of acute stress can promote conditions of chronic inflammation (Black, 2002; Elenkov & Chrousos, 2002). Chronic stress appears to support the development of the inflammatory response by stimulating secretion of pro-inflammatory cytokines and by dysregulating HPA processes that are designed to inhibit inflammation (Chrousos, 1992; Miller, Cohen, & Ritchey, 2002).
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Although speculative, in the context of cancer, chronic stress may favor inflammatory conditions that would support the development and progression of transformed cells. Studies of distress and inflammation in cancer are relatively rare. In a study of 35 women undergoing biopsy for suspicion of breast cancer, the relationships between mood and the inflammatory cytokines tumor growth factor-beta (TGF-β) and tumor necrosis factoralpha (TNF-α) were examined. Although no difference was found in cytokine levels between women ultimately diagnosed with benign versus malignant tumors, greater psychological distress was related to higher levels of TNF-α 7 to 10 days after biopsy in both groups (DeKeyser, Wainstock, Rose, Converse, & Dooley, 1998). Thus, post-biopsy distress was related to an inflammatory cytokine that may support tumor growth (Coussens & Werb, 2002). The findings of Costanzo and colleagues (2005), cited below, of associations between social support and IL-6 in peripheral blood and ascites in ovarian cancer patients also support the hypothesis that psychosocial factors may contribute to (or inhibit) an inflammatory milieu in the tumor microenvironment.
V. PSYCHOSOCIAL FACTORS AND TUMOR ANGIOGENESIS Angiogenesis is the process by which new blood vessels are formed from a pre-existing vascular network, a process critical for the growth and metastatic spread of solid tumors such as ovarian cancer (Folkman, 1990). As mentioned above, most primary solid tumors go through a prolonged state of avascular growth in which the maximum size attainable is 1–2 mm in diameter (Folkman, 1990). The molecular mechanisms leading to the acquisition of the angio-stimulatory phenotype, also called “the angiogenic switch,” have not been fully characterized but are thought to result from a local imbalance between pro- and anti-angiogenic factors (Brown, Blanchette, & Kohn, 2000). When angiogenesis is switched on, surrounding blood vessels are recruited for tumor perfusion, resulting in tumor growth and metastases (Folkman, 1990). Extent of tumor angiogenesis has been associated with early recurrence (Zhang et al., 2003) and survival in a variety of solid cancers (Abulafia, Triest, & Sherer, 1999; Bando et al., 2005; Smith, Smith, Carter, Sasaki, & Haffty, 2000).
A. Regulation of Angiogenesis Angiogenesis is tightly controlled by a number of factors. One of the most potent regulators appears to
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be vascular endothelial growth factor (VEGF) (Folkman, 1995), a multi-functional cytokine produced by a variety of cells, including tumor cells, endothelial cells, tumor-associated inflammatory cells, neutrophils, platelets, and mononuclear cells (Inoue et al., 2001; Lewin et al., 1999). VEGF stimulates endothelial cells in microvessels to proliferate, migrate, and alter their pattern of gene expression. It also makes cells hyperpermeable, resulting in conditions that favor angiogenesis in the extracellular matrix (Brown et al., 1997). VEGF is a prognostic marker in ovarian, breast, and nasopharyngeal carcinomas (Bando et al., 2005; Cooper et al., 2002; Smith et al., 2000). VEGF is also immunosuppressive; for example, it interferes with the maturation of T-cells and dendritic cells (Gabrilovich, Chen, & Girgis, 1996; Ohm, Gabrilovich, & Sempowski, 2003). Lutgendorf and colleagues have demonstrated a link between psychosocial factors and VEGF in ovarian cancer patients (Lutgendorf et al., 2002). Twenty-four patients with epithelial ovarian cancer completed psychosocial assessments and had blood drawn preoperatively. Those patients reporting higher levels of social well-being had significantly lower levels of VEGF, adjusting for cancer stage. Although depressed mood as a whole was not significantly related to VEGF, patients reporting greater helplessness and worthlessness had higher levels of VEGF. Additionally, patients reporting a history of treatment for depression or anxiety had a trend toward higher VEGF. Although the sample size was small, relationships were robust. Moreover, in an in vitro model, Lutgendorf and colleagues (2003) have observed that stress hormones, including norepinephrine and epinephrine, as well as a beta-adrenergic agonist (isoproterenol) are able to stimulate production of VEGF by two ovarian cell lines (SKOV3 and EG). Both of these cell lines express β-adrenergic receptors, making such signal transduction possible, and these effects were completely blocked by propranolol, a non-specific beta antagonist (Lutgendorf et al., 2003). These findings indicate that neuroendocrine factors implicated in the stress response may directly influence tumor growth and angiogenesis. Effects of neuroendocrine factors on angiogenesis, tumor invasion, and on matrix metalloproteinases are discussed at length in Chapter 11 in Volume I. A second cytokine that regulates angiogenesis and plays an important role in cancer progression is Interleukin-6 (IL-6). For example, IL-6 stimulates proliferation, migration, attachment, and invasion of ovarian cancer cells in vitro (Obata, Tamakoshi, Shibata, Kikkawa, & Tomoda, 1997; S. Wu et al., 1992) and serves as an indirect promoter of angiogenesis as it
induces expression of VEGF, which in turn induces expression of IL-6 in a positive feedback loop (Dankbar et al., 2000). Elevated IL-6 has been associated with faster tumor progression in ovarian and cervical cancers (Berek et al., 1991; Chopra, Dinh, & Hannigan, 1998) and with shorter disease-free intervals and poorer overall survival in ovarian cancer (Scambia et al., 1995). IL-6 becomes elevated with chronic stress and depression (Dentino et al., 1999; Kiecolt-Glaser et al., 2003; Lutgendorf et al., 1999). Lutgendorf and colleagues (2000) have examined relationships between psychosocial factors and IL-6 in heterogeneous gynecologic cancer patients. In a sample of 21 early-stage and regionally advanced gynecologic cancer patients assessed prior to surgery, the coping strategy of seeking instrumental social support was related to lower levels of IL-6. Analyses adjusted for extent of disease, age, and smoking (Lutgendorf, Anderson, Buller, Sorosky, & Lubaroff, 2000). In a second study of 61 ovarian cancer patients, greater social support was associated with lower levels of IL-6 pre-surgically, both in plasma and in ascites, adjusting for age and disease stage (Costanzo et al., 2005). The presence of a relationship between a psychosocial factor and this pro-inflammatory and pro-angiogenic cytokine in the compartment adjacent to the tumor supports the contention that psychosocial factors may contribute to enhanced (or inhibited) tumor growth via angiogenic pathways.
B. Matrix Metalloproteinases The process of angiogenesis is assisted by a group of enzymes called matrix metalloproteinases (MMPs). These enzymes degrade components of the extracellular matrix and thereby facilitate migration of endothelial cells to form new blood vessels (Henney et al., 2000). In the course of this activity, angiogenic signaling molecules are released from the extracellular matrix (Bergers et al., 2000). Human ovarian cancer cells produce both MMP-2 and MMP-9 (Naylor, Stamp, Davies, & Balkwill, 1994), and levels of these MMPs are directly proportional to the invasive and metastatic potentials of ovarian tumor cells (Huang et al., 2002). Stress hormones such as norepinephrine and cortisol have been shown to modulate MMP expression (Yang et al., 2002). Moreover, social isolation stress induced elevations in MMP-2 and MMP-9 in tumor and liver tissues as compared to levels in nonisolated mice (W. Wu et al., 1999). Recent findings indicate that MMP-2 and MMP-9 production by two ovarian cancer cell lines can be directly enhanced by doses of norepinephrine and epinephrine that approximate levels in the body during chronic stress (Sood,
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Landen, Bhatty, Thaker, & Lutgendorf, 2004; Thaker et al., 2005). Taken together, these findings suggest the possibility that stress hormones may be able to influence MMPs in a way that could directly contribute to tumor progression. Research in this area is still in the early stages, but very promising, and suggests the importance of examination of stress-based inflammatory and angiogenic processes in studies of PNI and cancer.
VI. STRESS AND VIRAL ACTIVATION Viral activation can also support the production of pro-inflammatory cytokines and dysregulation of the immune response, and may contribute to conditions favoring cancer initiation or progression. For example, Epstein-Barr Virus (EBV), the etiologic agent for infectious mononucleosis, is strongly associated with nasopharyngeal carcinoma, chronic lymphocytic leukemia, Hodgkin’s lymphoma, and various B-cell malignancies, including Burkitt’s lymphoma and post-transplant Bcell lymphomas (Ansell, Li, Lloyd, & Phyliksy, 1999). EBV can be partially reactivated, in which case viral replication subsequently ceases. Even though the virus may not completely reactivate, these viral proteins can have substantial effects. Several viral proteins are associated with the early activation of EBV, including EBV deoxyuridine triphosphate nucleotidohydrolase (dUTPase). In a series of experiments, Glaser and colleagues showed that dUTPase can induce production of the pro-inflammatory cytokines IL-6, TNF-α, IL-8, IL-1β, and IL-10. Monocytes/macrophages are the primary cell type responsible for this cytokine production (Glaser et al., 2005). It is therefore possible that activation of viral proteins such as dUTPase could contribute to a pro-inflammatory microenvironment, producing conditions that would support the progression of pre-existing tumors or enhance the development of tumors in vulnerable tissue. As stress is one factor that contributes to the reactivation of latent EBV and other latent herpes viruses (Glaser, Pearl, Kiecolt-Glaser, & Malarkey, 1994), stress may promote conditions leading to viral activation, with subsequent downstream effects. A unique line of work has examined psychosocial factors in the context of mechanisms associated with development of a virally implicated cancer. Antoni and colleagues have studied the pre-clinical processes associated with cervical cancer (Antoni, 2003). The Human Papilloma Virus (HPV) places women at risk for cervical cancer, particularly HPV types 16 or 18. Antoni and colleagues have used a model of cervical intraepithelial neoplasia (CIN), a pre-cancerous condi-
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tion that can progress to invasive cervical cancer in some women. Progression of CIN to invasive cancer is known to be influenced by both specific and nonspecific immune responses (Goodkin, Antoni, Helder, & Sevin, 1993). Interactions between life stress and a pessimistic, hopeless, and avoidant coping style as well as somatic anxiety have been associated the promotion of CIN to invasive cervical cancer (Antoni & Goodkin, 1989; Goodkin, Antoni, & Blaney, 1986; Goodkin et al., 1993). The effects of stress on women co-infected with HPV and the Human Immunodeficiency Virus (HIV) have also been investigated. Women with HPV and suppressed immune systems are at a much greater risk for progression of CIN to cervical cancer. Among women who are seropositive for both HIV and HPV, those patients reporting greater pessimism had lower NK cell activity and lower numbers of CD3+CD8+ cells, even after adjusting for presence or absence of HPV types 16 or 18, lifestyle factors, and self-reports of the impact of negative life events (Byrnes et al., 1998). Thus, stress factors appear to modulate activation of viral proteins and are related to progression of viral cancers.
VII. STRESS, DNA REPAIR AND APOPTOSIS, AND IMPLICATIONS FOR CANCER Psychosocial stressors and distress have been shown to have direct effects on intracellular processes that are implicated in cancer initiation. Following damage to cellular DNA by carcinogens, a number of cellular DNA repair processes may be initiated, and immune cells recognize and destroy abnormal cells. When DNA repair processes are not working optimally, production and survival of abnormal cells is increased (Stetlow, 1978). Glaser and colleagues, in a series of studies, showed that stress is related to both increased DNA damage and alterations in DNA repair. In animal models, stressors such as swim stress and foot shock induced an increase in the frequency of sister chromatid exchange (SCE) in bone marrow cells. Sister chromatid exchange is an indicator of DNA damage and genomic instability and is thought to be related to increased cancer risk (Li, Yao, & Glaser, 1989). In another animal model, following ingestion of a carcinogen, stressed rats had lower levels of spleen methyltransferase, an important DNA repair enzyme, as compared to non-stressed control rats (Glaser, Thorn, Tarr, Kiecolt-Glaser, & D’Ambrosio, 1985). Several human studies have demonstrated that stress modulates DNA repair abilities. Following X-irradiation, lymphocytes from non-medicated
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psychiatric patients demonstrated a decreased ability for DNA repair as compared to lymphocytes from ageand gender-matched controls. Additionally, extent of depression was related to degree of reduction in DNA repair abilities following radiation (Kiecolt-Glaser, Stephens, Lipetz, Speicher, & Glaser, 1985). Another study found that academic stress enhanced the ability of the carcinogen phorbol ester to block apoptosis (programmed cell death) of cells damaged by irradiation. Furthermore, an increase in levels of total cellular DNA was noted in surviving lymphocytes. These findings suggest that the combination of genetic damage from irradiation and stress in the presence of a carcinogen may create conditions that are more favorable to survival of cells with abnormal DNA, and may therefore increase the risk of cancer (Tomei, Kiecolt-Glaser, Kennedy, & Glaser, 1990). Contrasting findings have been reported in two stressed student populations in which academic stress was related to enhanced DNA repair (Cohen, Marshall, Cheng, Agarwal, & Wei, 2000; Forlenza, Latimer, & Baum, 2000). However, differences in methodology, duration of stress, and resilience of student versus chronic psychiatric populations may underlie the disparate findings. Taken together, these findings indicate that stress may alter cellular DNA repair abilities, may increase the likelihood of retention of damaged DNA, and therefore increase the likelihood of development of malignant cells (Yang & Glaser, 2003).
VIII. NEUROENDOCRINE REGULATION AND CANCER PROGRESSION Hormones of the hypothalamic-pituitary-adrenal (HPA) axis have been associated with cancer incidence and progression. In animal models and in vitro, hormones of the HPA axis have been found to enhance tumor growth (Rowse, Weinberg, Bellward, & Emerman, 1992; Sapolsky & Donnelly, 1985), and neuroendocrine hormones such as CRH are thought to promote the expression of breast cancer oncogenes (Licinio, Gold, & Wong, 1995). Alterations in cortisol levels and in diurnal cortisol rhythms in cancer patients have been observed, particularly in the later stages of cancer (Mormont & Levi, 1997). For example, ovarian cancer patients with poor prognoses showed elevated cortisol levels at all times in the diurnal cycle compared to patients with good prognoses. In addition, the diurnal cortisol cycle was markedly altered in patients with poor performance status, large residual tumor size, or metastases (Mormont & Levi, 1997). Significantly flatter cortisol rhythms have been reported among women with metastatic breast cancer as com-
pared to healthy controls (Abercrombie et al., 2004). Abnormal circadian rhythms appear to have prognostic significance as well. Sephton and colleagues reported a strong relationship between abnormal cortisol circadian rhythms and survival among 104 patients with metastatic breast cancer. The cortisol slope predicted subsequent survival up to 6 years later, with flattened or abnormal diurnal cortisol rhythms related to earlier mortality. Flattened cortisol rhythms were also associated with low NK cell counts, which was a secondary predictor of survival time (Sephton, Sapolsky, Kraemer, & Speigel, 1999). The nature of the relationship between cancer and abnormal circadian rhythms is not yet clear. It has been suggested that abnormal rhythms promote cancer incidence and progression; alternatively, the tumor itself may influence systemic rhythms (Sephton & Spiegel, 2003). Psychological stress could potentially contribute to or augment disease-related dysregulations in cortisol and circadian rhythms. There is evidence that chronic stressors, depression, and loneliness are associated with cortisol dysregulation, often resulting in flattened cortisol slopes (Cacioppo et al., 2000; Deuschle et al., 1997; Pruessner, Hellhammer, & Kirschbaum, 1999). In contrast, positive psychological factors, such as religiosity, have been associated with more normal cortisol profiles in women with chronic illness (Dedert et al., 2004). A study of women with metastatic breast cancer found that those classified as highly anxious or repressors demonstrated significantly flatter cortisol slopes than less anxious, selfassured women (Giese-Davis, Sephton, Abercrombie, Duran, & Spiegel, 2004). In contrast, women with metastatic breast cancer reporting higher levels of social support had lower levels of mean diurnal salivary cortisol over a 3-day period, suggesting more normalized neuroendocrine function (Turner-Cobb, Sephton, Koopman, Blake-Mortimer, & Spiegel, 2000). Along similar lines, a 10-week randomized stress management intervention among early-stage breast cancer patients was able to reduce serum cortisol levels compared to a control group in whom there was no cortisol change. Post hoc analyses suggest that increases in benefit finding mediated the relationship between treatment and cortisol reductions (Cruess, Antoni, Kumar, & Schneiderman, 2000). Thus, there is ample evidence that psychological stress influences cortisol rhythms in cancer patients and that positive factors such as social support, benefit finding, and stress reduction are associated with lower cortisol levels. Sephton & Spiegel (2003) argue that preliminary evidence points to multiple pathways by which psychologically mediated abnormal circadian rhythms may influence cancer outcomes. First, HPA activation
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may directly enhance tumor growth by altering glucose uptake rates. Cortisol reduces glucose uptake in normal tissue. Tumor cells, however, may become resistant to cortisol and maintain glucose uptake levels. Tumor cells would remain active while local normal cells suspend growth and other activities. Second, as neuroendocrine factors have been shown to modulate angiogenic mechanisms, they may be directly implicated in modulation of tumor growth (Lutgendorf et al., 2003; Machein et al., 1999). Third, cortisol may impair immunosurveillance through direct suppression of NK cells or CTLs. Altered circadian rhythms have also been associated with disrupted immune cell trafficking (Mormont & Levi, 1997; Sephton & Spiegel, 2003), raising the possibility that insufficient numbers of immune cells infiltrate the tumor microenvironment. Finally, altered circadian rhythms may directly modulate the genes that control cancer initiation (Fu, Palican, Liu, Huang, & Lee, 2002).
IX. IMMUNE ACTIVATION AND QUALITY OF LIFE IN CANCER PATIENTS: BI-DIRECTIONAL PATHWAYS Whereas there is strong evidence that psychosocial factors can influence the immune response among cancer patients, immune activation may also impact psychosocial functioning (Maier & Watkins, 1998). Peripheral pro-inflammatory cytokines such as IL-1, IL-6, and TNF-α are able to activate central nervous system pathways and initiate a series of behavioral responses associated with withdrawal and conservation of energy, including fatigue, depression, inhibited appetite and exploration, fever, somnolence, difficulty with concentration, and inhibited social interaction (Maier & Watkins, 1998). Pro-inflammatory cytokines may also disrupt sleep patterns, thus contributing to poorer sleep and fatigue (Redwine, Hauger, Gillin, & Irwin, 2000). Although the profile of behavioral responses to cytokine activation may be adaptive for conservation of energy in the event of an infectious illness such as influenza, such responses may be detrimental to quality of life among cancer patients. Recent reviews have suggested that pro-inflammatory cytokines may play a key role in a host of clinical symptoms associated with decrements in cancer patients’ quality of life, including depression, fatigue, fever, anemia, and weight loss (Illman et al., 2005; Kurcrock, 2001). Compelling evidence for the impact of immune activation on quality of life among cancer patients comes from studies of patients undergoing treatment with exogenous pro-inflammatory cytokines. Biobehavioral
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changes, including intense fatigue, depressive symptomatology, and anxiety, as well as declines in cognitive functioning, occur among cancer patients treated with interferon, IL-2, and lymphokine-activated killer cells (Capuron et al., 2002). Endogenous pro-inflammatory cytokines also impact quality of life. Cytokines are produced by some types of tumors and are released by immune cells in response to the tumor itself or in response to tissue damage associated with cancer treatment such as radiotherapy (Dranoff, 2004; Vujaskovic et al., 2002). A recent study found that serum IL-6 levels were associated with greater fatigue, as well as poorer physical and functional well-being among advanced-stage ovarian cancer patients. These associations were found after adjusting for age and disease severity (Costanzo et al., 2005). Consistent with these results, several studies have found relationships between proinflammatory cytokines and fatigue among patients during radiation or chemotherapy. For example, higher levels of IL-6 and IL-1β were associated with fatigue among both breast and prostate cancer patients undergoing radiation therapy (Bower, Ganz, Fahey, Belin, & Tao, 2005). Over the course of treatment, fatigue increased along with increases in cumulative levels of pro-inflammatory cytokines. IL-6 was also positively associated with fatigue among lung cancer patients receiving both radiotherapy and chemotherapy (Rigas et al., 1998); and IL-1 levels rose with fatigue scores among prostate cancer patients undergoing radiation therapy (Greenberg, Gray, Mannix, Eisenthal, & Carey, 1993). In contrast, Geinitz found no changes in levels of IL-1β, TNF-α, or IL-6 levels in breast cancer patients during radiotherapy. However, at least 50% of the TNF-α levels were undetectable in this study (Geinitz, Zimmermann, & Stoll, 2001). Bower and colleagues have also found elevations of markers associated with immune activation, including soluble tumor necrosis factor receptor Type II (sTNFRII), neopterin, and IL-1 receptor antagorist, in fatigued breast cancer survivors as compared to survivors who did not report fatigue. Fatigued breast cancer survivors also had significantly lower levels of serum cortisol, a significantly lower percentage of NK cells, a higher percentage of CD45RO+ (memory T) cells, and a lower percentage of CD4+CD45RA+ cells than the nonfatigued group. Although patients with greater fatigue reported higher levels of depressed mood, none of the immune parameters were correlated with self-reports of depression; thus, the association between fatigue and markers of immune activation was likely not due to depression (Bower, Ganz, Aziz, & Fahey, 2002). These data suggest that the relationship between psychosocial factors and immune functioning may be
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more complex than previously thought, utilizing bidirectional pathways between the brain and immune system. In particular, inflammation related to tumor progression or cancer treatment is associated with behavioral changes, including declines in mood, and symptoms such as fatigue, which may impair quality of life. Recent reviews have proposed that cytokine antagonists or other therapies targeting cytokines may help ameliorate fatigue and depression and improve quality of life in cancer patients (Illman et al., 2005; Kurcrock, 2001).
X. SUMMARY AND FUTURE DIRECTIONS The findings reviewed here highlight the complex interrelationships between psychosocial factors and physiological factors implicated in tumor progression. Although not all findings are consistent, there are relatively strong data supporting a relationship between psychosocial factors such as social support and slower cancer progression. Findings relating psychosocial factors to cancer initiation and progression have been discussed in light of a number of mechanisms that may mediate these relationships, including the immune response; factors involved in tumor growth, such as angiogenic factors and MMPs; DNA repair mechanisms; and neuroendocrine hormones. There are relatively strong data supporting relationships between psychosocial factors such as distress and social support and the immune response among cancer patients. Recent findings indicate that these relationships exist not only at the peripheral blood level, but in the area of the tumor, suggesting that psychosocial modulation of the immune response may be highly relevant for interactions in the tumor microenvironment. Data supporting direct relationships between psychosocial factors and mechanisms of tumor growth including angiogenic cytokines and MMPs are also emerging. Thus, psychosocial factors may have effects on tumor growth and survival, via both immune and nonimmune mechanisms. Interactions between mechanisms make these relationships even more complex. For example, stress may result in direct suppression of cellular immunity via adrenergic or neuroendocrine pathways. Additionally, catecholamines can induce elevations of VEGF within the tumor; VEGF in turn downregulates various immune mechanisms, including the maturation of Tcells and dendritic cells, thus contributing to immunosuppression. Therefore, psychosocial factors may have direct and indirect influences on immunosuppression. Importantly, psychosocial factors simultaneously contribute to enhancement of tumor growth while com-
promising relevant cellular immunity in the tumor microenvironment. This could profoundly affect the growth potential of the tumor. We therefore propose a model of biobehavioral oncology that encompasses many possible mechanisms and their interactions, and we suggest that future research in the psychoneuroimmunology of cancer extend to the various mechanisms that are modulated by neuroendocrine and autonomic influences. Although not discussed in detail above, in light of the possible role of “stress hormones” in the progression of the disease, consideration of the expression of hormone receptors on the surface of tumor cells may also be important. (For further discussion, see Chapter 11 in Volume I). These pathways are illustrated in Figure 1.
A. Future Directions In light of these findings, several recommendations can be offered for future work. 1. Biological Relevance It is recommended that future work move beyond examination of numbers of lymphocyte subsets and extend to markers and functional assays that are as specific as possible, and assessment of cytokines and other factors discussed above that may be implicated in tumor growth. Understanding relationships of psychosocial factors with tumor growth factors and the relevance of these findings for invasion and progression versus inhibition of disease is still at an early stage. Much more research is needed in clinical, in vitro, and animal models to understand the mechanisms and pathways involved. Markers should be chosen carefully in terms of biological relevance. For example, in a cancer in which there has been complete excision of the tumor, examination of angiogenic markers or MMPs may not be very relevant, but examination of immune, inflammatory, or viral markers may be important. 2. Compartment of Measurement Most studies examining PNI relationships in cancer have examined the activities or numbers of immune cells in peripheral blood. However, as noted above, tumors have multiple mechanisms for downregulating the immune response in the tumor microenvironment. Thus, the peripheral immune response of PBLs may be quite different than that of lymphocytes found in the tumor microenvironment. Along with other tumor mechanisms of immune escape, these findings suggest that examination of the immune response in peripheral blood may not provide an accurate understanding
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Psychosocial Factors Stress, depression, personality, social support, benefit finding, optimism, etc.
Neuroendocrine and Sympathetic influences, Circadian Rhythms
41. Stress and Cancer in Humans
Biological Factors Genetics, age, sex, environment, toxins, diet, tumor stage, grade, aggressiveness, comorbid diseases,
Physiological Mediators Immune, Angiogenic factors, MMPs Inflammation DNA repair Tumor Viruses, etc.
Clinical Outcomes: Cancer Initiation, Progression, Recurrence Free Interval, Survival
FIGURE 1 Biobehavioral Influences on Clinical Outcomes in Cancer—Putative Pathways. Psychosocial factors interact with biological factors, resulting in alterations in the HPA axis, other neuroendocrine mediators, and the autonomic nervous system. Neuroendocrine and autonomic factors influence the immune response, angiogenic factors, matrix metalloproteinases, etc., which have downstream effects on cancer initiation, progression, and survival. The tumor can also have effects on upstream processes, e.g., downregulating the immune response, upregulating augiogenesis, and modulating neuroendocrine pathways.
of the effectiveness of immune response in the tumor microenvironment. Because of differential immune response in peripheral blood and in the area of the tumor, use of models, such as surgical models or skin cancers, that allow for examination of the immune response in the vicinity of the tumor can be highly informative when logistically feasible.
metastasized are less than optimal. In contrast, examination of relationships between psychosocial factors and angiogenic factors such as VEGF may be quite appropriate in patients with advanced or metastatic disease, where vascularity is highly relevant. Thus, the biology of the processes underlying the markers examined should be carefully taken into account.
3. Windows of Opportunity
4. Cancer and Aging
As discussed above, psychosocial effects on the immune response may have the greatest implications for survival during specific periods of cancer development and progression. These include (but are not limited to) the period early in tumor development before tumor escape mechanisms become established, peri-surgically, following adjuvant treatment, and at the time of recurrence. It may be that attempts to establish relationships between psychosocial factors and the immune response in cancer when the cancer has fully
Age, sex, and other biological or demographic characteristics may interact with psychosocial factors in predicting clinical outcomes. This has been the case in several studies that have examined such interactions (Kuchler et al., 1999; Morris et al., 1992; Schulz et al., 1996), and it is important for future work to determine the likely complex relationships among these “host” factors. Aging is associated with alterations in the immune response (e.g., review by Miller, 1996), neuroendocrine regulation (Deuschle, Weber, Colla,
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Depner, & Heuser, 1998), autonomic innervation of secondary lymphoid organs (Bellinger, Lorton, Lubahn, & Felten, 2001), and control of inflammation (Schwartsburd, 2004). Psychosocial stress appears to exacerbate many of these age-related alterations (Kiecolt-Glaser et al., 2003) and thus may promote additional vulnerability for cancer initiation and progression. Little is known about age-related effects of psychosocial factors on immune and other mechanisms among cancer patients; as cancer patients are predominantly over 55 (American Cancer Society, 2005), this represents an important domain to be explored in future research. 5. Interventions and Models Greater understanding is needed of the extent to which psychosocial interventions are able to modulate physiological factors related to cancer progression and whether this modulation confers survival benefits. Can stress management affect DNA repair enzymes, pro-angiogenic or pro-inflammatory milieus in the tumor microenvironment, along with immune function? To the extent that inflammatory cytokines are related to fatigue, can psychosocial interventions ameliorate both the fatigue and the cytokine profile? Will complementary and alternative medicine (CAM) interventions and antidepressant medications have similar effects? For example, Irwin has shown benefits of a Tai Chi intervention on the immune response to a novel antibody in older adults (Irwin, Pike, & Oxman, 2003). Would this sort of intervention be useful for slowing tumor progression in older cancer patients? Innovative research examining a variety of interventions and cancer-specific biological mediators is needed. Moreover, little is known at this point as to whether certain types of cancers are more responsive to psychological factors. In a proposed model of cancer stress and disease course, Andersen et al. (1994) noted that cancers sensitive to changes in immune functioning, such as leukemias and lymphomas, or those sensitive to hormonal factors, such as breast, ovarian, and prostate cancers, might be particularly important to examine. Finally, an examination of the clinical relevance of the models being tested is critically needed. Cohen and Rabin (1998) raised a fundamental question in their 1998 editorial as to whether the type and magnitude of the physiological changes influenced by psychosocial factors are sufficient to influence cancer progression and survival. Furthermore, do psychosocial interventions that support immune function and other physiological mediators offer survival benefit? These remain the fundamental questions for future research.
Acknowledgments We gratefully acknowledge Erin Johnson for editorial assistance. Preparation of this chapter was supported in part by grants #RO1CA1048-25 and #R21CA102515 to Dr. Lutgendorf from the National Cancer Institute, and grant #P20 AT-756 from the National Center for Complementary and Alternative Medicine.
References Abercrombie, H. C., Giese-Davis, J., Sephton, S., Epel, E. S., TurnerCobb, J. M., and Spiegel, D. (2004). Flattened cortisol rhythms in metastatic breast cancer patients. Psychoneuroendocrinology, 29, 1082–1092. Abulafia, O., Triest, W., and Sherer, D. (1999). Angiogenesis in malignancies of the female genital tract. Gyn. Oncol., 72, 220–231. American Cancer Society. (2005). Cancer Facts and Figures, Atlanta, GA: Author. Andersen, B., Farrar, W. B., Golden-Kreutz, D., Kutz, L. A., MacCallum, R., Courtney, M. E., et al. (1998). Stress and immune responses after surgical treatment for regional breast cancer. J. Natl. Cancer Inst., 90, 30–36. Andersen, B., Farrar, W. B., Golden-Kreutz, D. M., Glaser, R., Emery, C. F., Crespin, T. R., et al. (2004). Psychological, behavioral, and immune changes after a psychological intervention: a clinical trial. J. Clin. Oncol., 22, 3570–3580. Andersen, B., Kiecolt-Glaser, J., and Glaser, R. (1994). A biobehavioral model of cancer stress and disease course. Am. Psychol., 49, 389–404. Andrykowski, M. A., Brady, M. J., and Henslee-Downey, P. J. (1994). Psychosocial factors predictive of survival after allogeneic bone marrow transplantation for leukemia. Psychosom. Med., 56, 432–439. Ansell, S. M., Li, C.-Y., Lloyd, R. V., and Phyliksy, R. L. (1999). Epstein-Barr virus infection in Richter’s transformation. Am. J. Hematol., 60, 99–104. Antoni, M. H. (2003). Psychoneuroendocrinology and psychoneuroimmunology of cancer. Plausible mechanisms worth pursuing? Brain Behav. Immun., 17, 84–91. Antoni, M. H., and Goodkin, K. (1988). Host moderator variables in the promotion of cervical neoplasia—I. Personality facets. J. Psychosom. Res., 33, 327–338. Antoni, M. H., and Goodkin, K. (1989). Host moderator variables in the promotion of cervical neoplasia—II. Dimensions of life stress. J. Psychosom. Res., 33, 457–467. Bando, H., Weich, H. A., Brokelmann, M., Horiguchi, S., Funata, N., Ogawa, T., et al. (2005). Association between intratumoral free and total VEGF, soluble VEGFR-1, VEGFR-2 and prognosis in breast cancer. Br. J. Cancer, 92 (3), 553–561. Barlozzari, T., Leonhardt, J., Wiltrout, R., Herbreman, R., and Reynolds, C. (1985). Direct evidence for the role of LGL in the inhibition of experimental tumor metastases. J. Immunol., 134, 2783–2789. Barraclough, J., Pinder, P., Cruddas, M., Osmond, C., Taylor, I., and Perry, M. (1992). Life events and breast cancer prognosis. British Medical Journal, 304, 1078–1081. Bellinger, D., Lorton, D., Lubahn, C., and Felten, D. (2001). Innervation of lymphoid organs—association of nerves with cells of the immune system and their implications in disease. In R. Ader, D. Felten, & N. Cohen (Eds.), Psychoneuroimmunology (3rd ed., vol. 1, pp. 55–111). San Diego: Academic Press. Ben-Eliyahu, S. (2003). The promotion of tumor metastasis by surgery and stress: immunological basis and implications for psychoneuroimmunology. Brain Behav. Immun., 17, 27–36.
41. Stress and Cancer in Humans Ben-Eliyahu, S., and Page, G. (1992). In vivo assessment of natural killer cell activity in rats. Prog. Neuroendocrine Immunol., 5, 199–214. Ben-Eliyahu, S., Shakhar, G., Page, G. G., Stefanski, V., and Shakhar, K. (2000). Suppression of NK cell activity and of resistance to metastasis by stress: a role for adrenal catecholamines and betaadrenoceptors. Neuroimmunomodulation, 8, 154–164. Berek, J. S., Chung, C., Kaldi, K., Watson, H. M., Knox, R. M., and Martinez-Maza, O. (1991). Serum interleukin-6 levels correlate with disease status in patients with epithelial ovarian cancer. Am. J. Obstet. Gynecol., 164, 1038–1042. Bergers, G., Brekken, R., McMahon, G., Vu, T. H., Itoh, T., Tamaki, K., Tanzawa, K., Thorpe, P., Itohara, S., Werb, Z., and Hanahan D. Matrix metallo-proteinase-9 triggers the angiogenic switch during carcinogenesis. Nat. Cell Biol., 2, 737–744. Black, P. H. (2002). Stress and the inflammatory response: a review of neurogenic inflammation. Brain Behav. Immun., 16, 622–653. Blake-Mortimer, J. S., Sephton, S. E., Carlson, R. W., Stites, D., and Spiegel, D. (2004). Cytotoxic T lymphocyte count and survival time in women with metastatic breast cancer. Breast J., 10, 195– 199. Bleiker, E. M., Van der Ploeg, H. M., Hendriks, J. H., and Ader, H. J. (1996). Personality factors and breast cancer development: a prospective longitudinal study. J. Natl. Cancer Inst., 88, 1478– 1482. Bovbjerg, D., Redd, W. H., Maier, L. A., Holland, J. C., Lesko, L. M., Niedzwiecki, D., et al. (1990). Anticipatory immune suppression and nausea in women receiving cyclic chemotherapy for ovarian cancer. J. Consut. Clin. Psychol., 58, 153–157. Bovbjerg, D., and Valdimarsdottir, H. (1993). Familial cancer, emotional distress, and low natural cytotoxic activity in healthy women. Ann. Oncol., 4, 745–752. Bower, J. E., Ganz, P. A., Aziz, N., and Fahey, J. L. (2002). Fatigue and proinflammatory cytokine activity in breast cancer survivors. Psychosom. Med., 64, 604–611. Bower, J. E., Ganz, P. A., Fahey, J. L., Belin, T. R., and Tao, M. L. (2005). Mechanisms of fatigue during radiation therapy for breast and prostate cancer. Paper presented at the American Psychosomatic Society Annual Meeting, Vancouver, BC. Brown, J. E., Butow, P. N., Culjak, G., Coates, A. S., and Dunn, S. M. (2000). Psychosocial predictors of outcome; time to relapse and survival in patients with early stage melanoma. Brit. J. Cancer, 83, 1448–1453. Brown, L., Detmar, M., Claffey, K., Nagy, J. A., Feng, D., Dvorak, A. M., et al. (1997). Vascular permeability factor/vascular endothelial growth factor: a multifunctional angiogenic cytokine. EXS, 79, 233–269. Brown, M. R., Blanchette, J. O., and Kohn, E. C. (2000). Angiogenesis in ovarian cancer. Balliere’s Clin. Obstet. Gyn., 14, 901–918. Buccheri, G. (1998). Depressive reactions to lung cancer are common and often followed by a poor outcome. Eur. Resp. J., 11, 173–178. Buddeberg, C., Sieber, M., Wolf, C., Landolt-Ritter, C., Richter, D., and Steiner, R. (1997). Coping strategies and 10-year outcome in early breast cancer. J. Psychosom. Res., 43, 625–626. Butow, P. N., Coates, A. S., and Dunn, S. M. (1999). Psychosocial predictors of survival in metastatic melanoma. J. Clin. Oncol., 17, 2256–2263. Butow, P. N., Hiller, J. E., Price, M. A., Thackway, S. V., Kricker, A., and Tennant, C. C. (2000). Epidemiological evidence for a relationship between life events, coping style, and personality factors in the development of breast cancer. J. Psychosom. Res., 49, 169–181. Byrnes, D., Antoni, M., Goodkin, K., Efantis-Potter, J., Asthana, D., Simon, T., et al. (1998). Stressful events, pessimism, natural
889
killer cell cytotoxicity, and cytotoxic/suppressor T cells in HIV+ black women at risk for cervical cancer. Psychosom. Med., 60, 714–722. Cacioppo, J., Ernst, J., Burleson, M., McClintock, M., Malarkey, W., Hawkley, L., et al. (2000). Lonely traits and concomitant physiological processes: the MacArthur social neuroscience studies. Int. J. Psychophysiol., 35, 143–154. Capuron, L., Gumnick, J. F., Musselman, D. L., Lawson, D. H., Reemsnyder, A., Nemeroff, C. B., et al. (2002). Neurobehavioral effects of interferon-A in cancer patients: phenomenology and paroxetine responsiveness of symptom dimensions. Neuropsychopharmacol., 26, 643–662. Carlson, L. E., Speca, M., Patel, K. D., and Goodey, E. (2003). Mindfulness-based stress reduction in relation to quality of life, mood, symptoms of stress, and immune parameters in breast and prostate cancer outpatients. Psychosom. Med., 65, 571–581. Cassileth, B. R. (1996). Stress and the development of breast cancer: a persistent and popular link despite contrary evidence. Cancer, 77, 1015–1016. Cassileth, B. R., Walsh, W. P., and Lusk, E. J. (1988). Psychosocial correlates of cancer survival: subsequent report 3 to 8 years after cancer diagnosis. J. Clin. Oncol., 6, 1753–1759. Chen, C. C., David, A. S., Nunnerleym, H., Michell, M., Dawson, J. L., Berry, H., et al. (1995). Adverse life events and breast cancer: case-control study. Brit. Med. J., 311, 1527–1530. Chopra, V., Dinh, T. V., and Hannigan, E. (1998). Circulating serum levels of cytokines and angiogenic factors in patients with cervical cancer. Cancer Invest., 16, 152–159. Chrousos, G. (1992). The concepts of stress and stress system disorders. JAMA, 267, 1244–1252. Cohen, L., Marshall, G. D. J., Cheng, L., Agarwal, S. K., and Wei, Q. (2000). DNA repair capacity in healthy medical students during and after exam stress. J. Behav. Med., 23, 531–544. Cohen, M., Klein, E., Kuten, A., Fried, G., Zinder, O., and Pollack, S. (2002). Increased emotional distress in daughters of breast cancer patients is associated with decreased natural cytotoxic activity, elevated levels of stress hormones and decreased secretion of Th1 cytokines. Int. J. Cancer, 100, 347–354. Cohen, S., and Rabin, B. (1998). Psychological stress, immunity, and cancer. J. Natl. Cancer Inst., 90, 3–4. Cohen, S., and Wills, T. (1985). Stress, social support, and the buffering hypothesis. Psychol. Bull., 98, 310–357. Cooper, B. C., Ritchie, J. M., Broghammer, C. L. W., Coffin, J., Sorosky, J. I., Buller, R. E., et al. (2002). Preoperative serum vascular endothelial growth factor (VEGF) levels: significance in ovarian cancer. Clin. Cancer Res., 8, 3193–3197. Costanzo, E. S., Lutgendorf, S. K., Sood, A. K., Anderson, B., Sorosky, J., and Lubaroff, D. M. (2005). Psychosocial factors and interleukin-6 among women with advanced ovarian cancer. Cancer, 104, 305–313. Coussens, L. M., and Werb, Z. (2002). Inflammation and cancer. Nature, 420, 860–867. Cruess, D., Antoni, M., Kumar, M., and Schneiderman, N. (2000). Reductions in salivary cortisol are associated with mood improvement during relaxation training among HIV-seropositive men. J. Behav. Med., 23, 107–122. Cunningham, A. J., Edmonds, C. V., Jenkins, G. P., Pollack, H., Lockwood, G. A., and Warr, D. (1998). A randomized controlled trial of the effects of group psychological therapy on survival in women with metastatic breast cancer. Psychooncology, 7, 508– 517. Daly, M., and Obrams, G. I. (1998). Epidemiology and risk assessment for ovarian cancer. Sem. Oncol., 25, 255–264. Dankbar, B., Padro, T., Leo, R., Feldmann, B., Kropff, M., Mesters, R., et al. (2000). Vascular endothelial growth factor and interleu-
890
IV. Stress and Immunity
kin-6 in paracrine tumor-stromal cells interactions in multiple myeloma. Blood, 95 (8), 2630–2636. Dattore, P. J., Shontz, F. C., and Coyne, L. (1980). Premorbid personality differentiation of cancer and noncancer groups: a test of the hypothesis of cancer proneness. J. Consult. Clin. Psychol., 48, 388–394. Dedert, E. A., Studts, J. L., Weissbecker, I., Salmon, P. G., Banis, P. L., and Sephton, S. E. (2004). Religiosity may help preserve the cortisol rhythm in women with stress-related illness. Int. J. Psychiatry Med., 34, 61–77. DeKeyser, F. G., Wainstock, J. M., Rose, L., Converse, P. J., and Dooley, W. (1998). Distress, symptom distress, and immune function in women with suspected breast cancer. Onc. Nurs. Forum, 25, 1415–1422. Dentino, A. N., Pieper, C. F., Rao, M. K., Currie, M. S., Harris, T., Blazer, D. G., et al. (1999). Association of interleukin-6 and other biologic variables with depression in older people living in the community. J. Am. Ger. Soc., 47, 6–11. Deuschle, M., Schweiger, U., Weber, B., Gotthardt, U., Korner, A., Schmider, J., et al. (1997). Diurnal activity and pulsatility of the hypothalamus-pituitary-adrenal system in male depressed patients and healthy controls. J. Clin. Endocrinol. Metab., 82, 234–238. Deuschle, M., Weber, B., Colla, M., Depner, M., and Heuser, I. (1998). Effects of major depression, aging and gender upon calculated diurnal free plasma cortisol concentrations: a re-evaluation study. Stress, 2, 281–287. Dighe, A. S., Richards, E., Old, L. J., and Schreiber, R. D. (1994). Enhanced in vivo growth and resistance to rejection of tumor cells expressing dominant negative IFN-g receptors. Immunity, 1, 447–456. Dranoff, G. (2004). Cytokines in cancer pathogenesis and cancer therapy. Nature Rev. Cancer, 4, 11–22. Duijts, S. F. A., Zeegers, M. P. A., and Borne, B. V. (2003). The association between stressful life events and breast cancer risk: a meta-analysis. Intl. J. Cancer, 107, 1023–1029. Dunn, G. P., Bruce, A. T., Ikeda, H., Old, L. J., and Schreiber, R. D. (2002). Cancer immunoediting: from immunosurveillance to tumor escape. Nat. Immunol., 3, 991–998. Edelman, S., Lemon, J., Bell, D. R., and Kidman, A. D. (1999). Effects of group CBT on the survival time of patients with metastatic breast cancer. Psychooncology, 8, 474–481. Edwards, J. R., Cooper, C. L., Pearl, S. G., De Paredes, E. S. O., Leary, T., and Wilhelm, M. C. (1990). The relationship between psychosocial factors and breast cancer: some unexpected results. Behav. Med., 16, 5–14. Ehrlich, P. (1909). Ueber den jetzigen stand der Karzinomforschung. Ned Tijdechr Geneeskd, 5, 273–290. Elenkov, I. J., and Chrousos, G. P. (2002). Stress hormones, proinflammatory and antiinflammatory cytokines, and autoimmunity. Ann. N.Y. Acad. Sci., 966, 290–303. Elenkov, I. J., Chrousos, G. P., and Wilder, R. L. (2000). Neuroendocrine regulation of IL-12 and TNF-alpha/IL-10 balance. Clinical implications. Ann. N. Y. Acad. Sci., 917, 94– 105. Epping-Jordan, J., Compas, B., and Howell, D. (1994). Predictors of cancer progression in young adult men and women: avoidance, intrusive thoughts, and psychological symptoms. Health Psychol., 13, 539–547. Faller, H., Bulzebruck, H., Drings, P., and Lang, H. (1999). Coping, distress, and survival among patients with lung cancer. Arch. Gen. Psychiatry, 56, 756–762. Fawzy, F. I., Canada, A. L., and Fawzy, R. N. (2003). Malignant melanoma: effects of a brief, structured psychiatric intervention
on survival and recurrence at 10-year follow-up. Arch. Gen. Psychiatry, 60, 100–103. Fawzy, F. I., Cousins, N., Fawzy, N. W., Kemeny, M. E., Elashoff, R., and Morton, D. (1990). A structured psychiatric intervention for cancer patients. I. Changes over time in methods of coping and affective disturbance. Arch. Gen. Psychiatry, 47, 720–725. Fawzy, F. I., Fawzy, N. W., Hyun, C. S., Elashoff, R., Guthrie, D., Fahey, J. L., et al. (1993). Malignant melanoma: effects of an early structured psychiatric intervention, coping, and affective state on recurrence and survival 6 years later. Arch. Gen. Psychiatry, 50, 681–689. Fawzy, F. I., Kemeny, M. E., Fawzy, N. W., Elashoff, R., Morton, D., Cousins, N., et al. (1990). A structured psychiatric intervention for cancer patients. II. Changes over time in immunological measures. Arch. Gen. Psychiatry, 47, 729–735. Fidler, I. J. (1997). Mol. biol. cancer: invasion and metastasis. Philadelphia: Lippincott-Raven. Folkman, J. (1990). What is the evidence that tumors are angiogenesis dependant? J. Natl. Cancer Inst., 82, 4–6. Folkman, J. (1995). Tumor angiogenesis. In: J. Mendelsohn, P. M. Howley, M. A. Israel, and L. A. Liotta (eds.), The Molecular Basis of Cancer, pp. 206–232. Philadelphia: W.B. Saunders. Forlenza, M. J., Latimer, J. J., and Baum, A. (2000). The effects of stress on DNA repair capacity. Psychol. Health, 15, 881–891. Forsen, A. (1991). Psychosocial stress as a risk for breast cancer. Psychotherapy & Psychosomatics, 55, 176–185. Fox, B. H. (1998). A hypothesis about Spiegel et al.’s 1989 paper on psychosocial intervention and breast cancer survival. Psychooncology, 7, 361–370. Fox, C. M., Harper, A. P., Hyner, G. C., and Lyle, R. M. (1994). Loneliness, emotional repression, marital quality, and major life events in women who develop breast cancer. J. Community Health, 19, 467–482. Fredrikson, M., Furst, C. J., Lekander, M., Rotstein, S., and Blomgren, H. (1993). Trait anxiety and anticipatory immune reactions in women receiving adjuvant chemotherapy for breast cancer. Brain Behav. Immun., 7, 79–90. Fu, L., Palican, H., Liu, J., Huang, P., and Lee, C. (2002). The circadian gene Period2 plays an important role in tumor suppression and DNA damage response in vivo. Cell, 111, 41–50. Funch, D. P., and Marshall, J. (1983). The role of stress, social support and age in survival from breast cancer. J. Psychosom. Res., 27, 77–83. Gabrilovich, D. I., Chen, H. L., and Girgis, K. R. (1996). Production of vascular endothelial growth factor by human tumors inhibits the functional maturation of dendritic cells. Nat. Med., 2, 1096–1103. Garcia-Lora, A., Algarra, I., and Garrido, F. (2003). MHC class I antigens, immune surveillance, and tumor escape. J. Cell. Physiol., 195, 346–355. Garland, M. R., Lavelle, E., Doherty, D., Golden-Mason, L., Fitzpatrick, P., Hill, A., et al. (2004). Cortisol does not mediate the suppressive effects of psychiatric morbidity on natural killer cell activity: a cross-sectional study of patients with early breast cancer. Psychol. Med., 34, 481–490. Garner, W., Minton, J., James, A., and Hoffman, C. (1983). Human breast cancer and impaired NK cell function. J. Surg. Oncol., 24, 64–66. Garssen, B. (2004). Psychological factors and cancer development: evidence after 30 years of research. Clin. Psychol. Rev., 24, 315–338. Geinitz, H., Zimmermann, F., and Stoll, P. (2001). Fatigue, serum cytokine levels, and blood cell counts during radiotherapy of
41. Stress and Cancer in Humans patients with breast cancer. Intl. J. Radiat. Oncol. Biol. Phys., 51, 691–698. Geyer, S. (1991). Life events prior to manifestation of breast cancer: a limited prospective study covering eight years before diagnosis. Journal of Psychosomatic Research, 35, 355–363. Geyer, S. (1993). Life events, chronic difficulties and vulnerability factors preceding breast cancer. Social Science & Medicine, 37, 1545–1555. Giese-Davis, J., Sephton, S., Abercrombie, H., Duran, R., and Spiegel, D. (2004). Repression and high anxiety are associated with aberrant diurnal cortisol rhythms in women with metastatic breast cancer. Health Psychol., 23, 645–650. Giraldi, T., Rodani, M. G., Cartei, G., and Grassi, L. (1997). Psychosocial factors and breast cancer: a 6-year Italian follow-up study. Psychother. Psychosom., 66, 229–236. Glaser, R., Padgett, D., Litsky, M., Baiocchi, R., Yang, E., Chen, M., et al. (2005). Stress-associated changes in the steady-state expression of latent Epstein-Barr virus: implications for chronic fatigue syndrome and cancer. Brain Behav. Immun., 19, 91– 103. Glaser, R., Pearl, D. K., Kiecolt-Glaser, J. K., and Malarkey, W. B. (1994). Plasma cortisol levels and reactivation of latent EpsteinBarr virus in response to examination stress. Psychoneuroendocrinology, 19, 765–772. Glaser, R., Thorn, B., Tarr, K., Kiecolt-Glaser, J., and D’Ambrosio, S. (1985). Effects of stress on methyl-transferase synthesis: an important DNA repair enzyme. Health Psychol., 4, 403–412. Goedegebuure, P. S., Douville, C. C., Doherty, J. M., Linehan, D. C., Lee, K. Y., Ganguly, E. K., et al. (1997). Simultaneous production of T helper-1–like cytokines and cytolytic activity by tumor-specific T cells in ovarian and breast cancer. Cell. Immunol., 175, 150–156. Gold, P. W., and Chrousos, G. P. (2002). Organization of the stress system and its dysregulation in melancholic and atypical depression: high vs low CRH/NE states. Mol. Psychiatry, 7, 254– 275. Goodkin, K., Antoni, M., and Blaney, P. (1986). Stress and hopelessness in the promotion of cervical intraepithelial neoplasia to invasive squamous cell carcinoma of the cervix. J. Psychosom. Res., 30, 67–76. Goodkin, K., Antoni, M., Helder, L., and Sevin, B. (1993). Psychosocial factors in the progression of cervical intraepithelial neoplasia—CIN. J. Psychosom. Res., 37, 554–557. Goodwin, P. J., Leszcz, M., and Ennix, M. E. A. (2001). The effect of group psychosocial support on survival in metastatic breast cancer. N. Engl. J. Med., 345, 1719–1726. Grassi, L., and Cappellari, L. (1988). State and trait psychological characteristics of breast cancer patients. New Trends Exp. Clin. Psychiatry, 4, 99–109. Greenberg, D., Gray, J., Mannix, C., Eisenthal, S., and Carey, M. (1993). Treatment-related fatigue and serum interleukin-1 levels in patients during external beam irradiation for prostate cancer. J. Pain Symptom Manage., 8, 196–200. Greer, S., and Morris, T. (1975). Psychological attributes of women who develop breast cancer: a controlled study. J. Psychosom. Res., 19, 147–153. Greer, S., and Morris, T. (1978). The study of psychological factors in breast cancer: problems of method. Soc. Sci. Med., 12, 129–134. Greer, S., Morris, T., and Pettingale, K. (1979). Psychological response to breast cancer: effect on outcome. Lancet, 335, 49–50. Greer, S., Morris, T., Pettingale, K., and Haybittle, J. (1990). Psychological response to breast cancer and 15 year outcome. Lancet, 335, 49–50.
891
Greer, S., and Watson, M. (1985). Towards a psychobiological model of cancer: psychological considerations. Soc. Sci. Med., 20, 773–777. Gruber, B., Hersh, S., Hall, N., Waletzky, L., Kunz, J., Carpenter, J., et al. (1993). Immunologic responses of breast cancer patients to behavioral interventions. Biofeedback Self-Regul., 18, 1–22. Hahn, R. C., and Petitti, D. B. (1988). Minnesota multiphasic personality inventory-rated depression and the incidence of breast cancer. Cancer, 61, 845–848. Hamaoka, T., and Fujiwara, H. (1987). Phenotypically and functionally distinct T-cell subsets in anti-tumor responses. Immunol. Today, 8, 267–269. Henney, A., Ye, S., Zhang, B., Jormsjo, S., Whatling, C., Eriksson, P., et al. (2000). Genetic diversity in the matrix metalloproteinase family. Effects on function and disease progression. Ann. N.Y. Acad. Sci., 902, 27–37. Heo, D., Whiteside, T., Kanbour, A., and Herberman, R. (1988). Lymphocytes infiltrating human ovarian tumors. I. Role of Leu19 (NKH1)-positive recombinant IL-2–activated cultures of lymphocytes infiltrating human ovarian tumors. J. Immunol., 140, 4042–4049. Hirte, H., and Clark, D. (1991). Factors determining the ability of cytokine-activated killer cells to lyse human ovarian carcinoma targets. Cell. Immunol., 136, 122–132. Hosaka, T., Tokuda, Y., Sugiyama, Y., Hirai, K., and Okuyama, T. (2000). Effects of a structured psychiatric intervention on immune function of cancer patients. Tokai J. Exp. Clin. Med., 25, 183–188. House, J. S., Landis, K. R., and Umberson, D. (1988). Social relationships and health. Science, 241, 540–545. Hsu, M. Y., Meier, F., and Meenhard, H. (2002). Melanoma development and progression: a conspiracy between tumor and host. Differentiation, 70, 522–536. Huang, S., Van Arsdall, M., Tedjarati, S., McCarty, M., Wu, W., Langley, R., et al. (2002). Contributions of stromal metalloproteinase-9 to angiogenesis and growth of human ovarian carcinoma in mice. J. Nat. Cancer Inst., 94, 1134–1142. Illman, J., Corringham, R., Robinson, D. J., Davis, H. M., Rossi, J. F., Cella, D., et al. (2005). Are inflammatory cytokines the common link between cancer-associated cachexia and depression. J. Supportive Oncol., 3, 37–50. Inoue, M., Itoh, H., Tanaka, T., Chun, T., Doi, K., Fukunaga, Y., et al. (2001). Oxidized LDL regulates vascular endothelial growth factor expression in human macrophages and endothelial cells through activation of peroxisome proliferator-activated receptorgamma. Arterioscler. Thromb. Vasc. Biol., 21, 560–566. Ioannides, C., Freedman, R., Platsoucas, C., Rashed, S., and Kim, Y. (1991). Cytotoxic T cell clones isolated from ovarian tumor-infiltrating lymphocytes recognize multiple antigenic epitopes on autologous tumor cells. J. Immunol., 146, 1700–1707. Irwin, M. (2002). Psychoneuroimmunology of depression: clinical implications. Brain Behav. Immun., 16 (1), 1–16. Irwin, M., Pike, J., and Oxman, M. N. (2003). Effects of a behavioral intervention, Tai Chi Chih, on varicella-zoster virus specific immunity and health functioning in older adults. Psychosom. Med., 65, 824–830. James, G. D., Berge-Landry H., Valdimarsdottir, H. B., Montgomery, G., and Bovbjerg, D. H. (2004). Urinary catecholamine levels in daily life are elevated in women at familial risk of breast cancer. Psychoneuroendocrinology, 29, 831–838. Jensen, M. R. (1987). Psychobiological factors predicting the course of breast cancer. J. Pers., 55, 317–342. Khong, H. T., and Restifo, N. P. (2002). Natural selection of tumor variants in the generation of “tumor escape” phenotypes. Nat. Immunol., 3, 999–1005.
892
IV. Stress and Immunity
Kiecolt-Glaser, J., Fisher, L., Ogrocki, P., Stout, J., Speicher, C., and Glaser, R. (1987). Marital quality, marital disruption, and immune function. Psychosom. Med., 49, 13–34. Kiecolt-Glaser, J. K., and Glaser, R. (1999). Psychoneuroimmunology and cancer: fact or fiction? Eur. J. Cancer, 35, 1603–1607. Kiecolt-Glaser, J. K., Preacher, K. J., MacCallum, R. C., Atkinson, C., Malarkey, W. B., and Glaser, R. (2003). Chronic stress and agerelated increases in the proinflammatory cytokine IL-6. Proc. Natl. Acad. Sci. USA, 100, 9090–9095. Kiecolt-Glaser, J. K., Stephens, R. E., Lipetz, P. D., Speicher, C. E., and Glaser, R. (1985). Distress and DNA repair in human lymphocytes. J. Behav. Med., 8, 311. Knekt, P., Raitasalo, R., Heliovaara, M., Lehtinen, V., Pukkala, E., Teppo, L., et al. (1996). Elevated lung cancer risk among persons with depressed mood. Am. J. Epidemiol., 144, 1096–1103. Kogon, M. M., Biswas, A., Pearl, D., Carson, R. W., and Spiegel, D. (1997). Effects of medical and psychotherapeutic treatment on the survival of women with metastatic breast carcinoma. Cancer, 80, 225–230. Kowalczyk, D. W. (2002). Tumors and the danger model. Acta Biochimica Polonica, 49, 295–302. Kuchler, T., Henne-Bruns, D., Rappat, S., Graul, J., Holst, K., Williams, J. I., et al. (1999). Impact of psychotherapeutic support on gastrointestinal cancer patients undergoing surgery: survival results of a trial. Hepato Gastroenterol., 46, 322–335. Kurcrock, R. (2001). The role of cytokines in cancer-related fatigue. Cancer, 92, 1684–1688. Kvikstad, A., and Vatten, L. J. (1996). Risk and prognosis of cancer in middle-aged women who have experienced the death of a child. International Journal of Cancer, 67, 165–169. Lai, P., Rabinowich, H., Crowley-Nowick, P., Bell, M., Mantovani, G., and Whiteside, T. (1996). Alteration in expression and function of signal-transducing proteins in tumor-associated T and natural killer cells in patients with ovarian carcinoma. Clin. Cancer Res., 2, 161–173. Lee, K. H., Panelli, M. C., Kim, C. J., Riker, A. I., Bettinotti, M. P., and Roden, M. M. (1998). Functional dissociation between local and systemic immune response during anti-melanoma peptide vaccination. J. Immunol., 161, 4183–4194. Lekander, M., Furst, C., Rotstein, S., Blomgren, H., and Fredrikson, M. (1996). Social support and immune status during and after chemotherapy for breast cancer. Acta Oncologica, 35, 31–37. Lekander, M., Furst, C. J., Rotstein, S., Hursti, T. J., and Fredrikson, M. (1997). Immune effects of relaxation during chemotherapy for ovarian cancer. Psychother. Psychosom., 66, 185–191. Levav, I., Kohn, R., Iscovich, J., Abramson, J. H., Tsai, W. Y., and Vigdorovich, D. (2000). Cancer incidence and survival following bereavement. American Journal of Public Health, 90, 1601–1607. Levy, S., Herberman, R., Lee, J., Whiteside, T., Kirkwood, J., and McFeeley, S. (1990). Estrogen receptor concentration and social factors as predictors of natural killer cell activity in early-stage breast cancer patients. Nat. Immun. Cell. Growth Regul., 9, 313–324. Levy, S., Herberman, R., Lippman, M., and D’Angelo, T. (1987). Correlation of stress factors with sustained depression of natural killer cell activity and predicted prognosis in patients with breast cancer. J. Clin. Oncol., 5, 348–353. Levy, S., Herberman, R., Lippman, M., D’Angelo, T., and Lee, J. (1991). Immunological and psychosocial predictors of disease recurrence in patients with early-stage breast cancer. Behav. Med., 17, 67–75. Levy, S., Herberman, R., Maluish, A., Schlein, B., and Lippman, M. (1985). Prognostic risk assessment in primary breast cancer by behavioral and immunological parameters. Health Psychol., 4, 99–113.
Lewin, M., Bredow, S., Sergeyev, N., Marecos, E., Bogdanov, A., and Weissleder, R. (1999). In vivo assessment of vascular endothelial growth factor-induced angiogenesis. Int. J. Cancer, 83, 798–802. Li, G. Y., Yao, K. T., and Glaser, R. (1989). Sister chromatid exchange and nasopharyngeal carcinoma. Int. J. Cancer, 43, 613–618. Li, R., Ruttinger, D., Li, R., Si, L. S., and Wang, Y. L. (2003). Analysis of the immunological microenvironment at the tumor site in patients with non-small cell lung cancer. Langenbeck’s Arch. Surg., 388, 406–412. Licinio, J., Gold, P. W., and Wong, M. L. (1995). A molecular mechanism for stress-induced alterations in susceptibility to disease. Lancet, 346, 104–106. Lillberg, K., Verkasalo, P. K., Kaprio, J., Teppo, L., Helenius, H., and Koskenvuo, M. S. (2003). Stressful life events and risk of breast cancer in 10,808 women: a cohort study. American Journal of Epidemiology, 157, 415–423. Linkins, R. W., and Comstock, G. W. (1990). Depressed mood and development of cancer. Am. J. Epidemiol., 132, 962–972. Lotzova, E., Savary, C., Freedman, R., and Bowen, J. (1986). Natural immunity against ovarian tumors. Comp. Immunol. Microbio. Infect. Dis., 9, 269–275. Lutgendorf, S., Anderson, B., Buller, R., Sorosky, J., and Lubaroff, D. (2000). Interleukin-6 and social support in gynecologic cancer patients. Int. J. Behav. Med., 7, 127–142. Lutgendorf, S., Garand, L., Buckwalter, K., Tripp-Reimer, T., Hong, S., and Lubaroff, D. (1999). Life stress, mood disturbance, and elevated IL-6 in healthy older women. J. Gerontol. A. Biol. Sci. Med. Sci., 54, M434–439. Lutgendorf, S. K., Sood, A. K., Anderson, B., McGinn, S., Maiseri, H., Dao, M., et al. (2005). Social support, psychological distress, and natural killer cell activity in ovarian cancer. J. Clin Oncol., 23, 7106–7113. Lutgendorf, S. K., Cole, S., Costanzo, E., Bradley, S., Coffin, J., Jabbari, S., et al. (2003). Stress-related mediators stimulate vascular endothelial growth factor secretion by two ovarian cancer cell lines. Clin. Cancer Res., 9, 4514–4521. Lutgendorf, S. K., Johnsen, E., Cooper B., Anderson, B., Sorosky, J. I., Buller, R. E., et al. (2002). Vascular endothelial growth factor and social support in patients with ovarian carcinoma. Cancer, 95, 808–815. Machein, M., Kullmer, J., Ronicke, V., Machein, U., Krieg, M., Damert, A., et al. (1999). Differential downregulation of vascular endothelial growth factor by dexamethasone in normoxic and hypoxic rat glioma cells. Neuropathol. Appl. Neurobiol., 25, 104–112. Maier, S., and Watkins, L. (1998). Cytokines for psychologists: implications of bidirectional immune to brain communication for understanding behavior, mood, and cognition. Psychol. Rev., 105, 83–107. Marshall, J., and Funch, D. P. (1983). Social environment and breast cancer: a cohort analysis of patient survival. Cancer, 52, 1546– 1550. Martikainen, P., and Valkonen, T. (1996). Mortality after death of a spouse: rates and causes of death in a large Finnish cohort. American Journal of Public Health, 86, 1087–1093. Matzinger, P. (1994). Tolerance, danger, and the extended family. Ann. Rev. Immunol., 12, 991–1045. Maunsell, E., Brisson, J., and Deschenes, L. (1995). Social support and survival among women with breast cancer. Cancer, 76, 631– 637. Maunsell, E., Brisson, J., Mondor, M., Verreault, R., and Deschenes, L. (2001). Stressful life event and survival after breast cancer. Psychosomatic Medicine, 63, 306–315.
41. Stress and Cancer in Humans McGee, R., Williams, S., and Elwood, M. (1994). Depression and the development of cancer: a meta-analysis. Soc. Sci. Med., 38, 187–192. McGee, R., Williams, S., and Elwood, M. (1996). Are life events related to the onset of breast cancer? Psychol. Med., 26, 441–447. McGregor, B., Antoni, M., Boyers, A., Alferi, S., Blomberg, B., and Carver, C. (2004). Cognitive-behavioral stress management increases benefit finding and immune function among women with early-stage breast cancer. J. Psychosom. Res., 56, 1–8. McKenna, M., Zevon, M., Corn, B., and Rounds, J. (1999). Psychological factors and the development of breast cancer: a metaanalysis. Health Psychol., 18, 520–531. Melief, C. (1992). Tumor eradication by adoptive transfer of cytotoxic T lymphocytes. Adv. Cancer Res., 58, 143–175. Melief, C., and Kast, W. (1991). Cytotoxic T lymphocyte therapy of cancer and tumor escape mechanisms. Cancer Biol., 2, 347–353. Miller, G. E., Cohen, S., and Ritchey, A. K. (2002). Chronic psychological stress and the regulation of pro-inflammatory cytokines: a glucocorticoid-resistance model. Health Psychol., 21, 531–541. Miller, R. A. (1996). The aging immune system: primer and prospectus. Science, 273, 70–74. Molassiotis, A., Van den Akker, O. B. A., Milligan, D. W., and Goldman, J. M. (1997). Symptom distress, coping style and biological variables as predictors of survival after bone marrow transplantation. J. Psychosom. Res., 42, 275–285. Mormont, M., and Levi, F. (1997). Circadian system alterations during cancer processes: a review. Int. J. Cancer, 70, 241–247. Morris, T., Pettingale, K. W., and Haybittle, J. L. (1992). Psychological response to cancer diagnosis and disease outcome in patients with breast cancer and lymphoma. Psychooncology, 1, 105–114. Murphy, K. C., Jenkins, P. L., and Whittaker, J. A. (1996). Psychosocial morbidity and survival in adult bone marrow transplant recipients—a follow-up study. Bone Marrow Transplant., 18, 199–201. Nan, K., Wei, Y., Zhou, F. L., Li, C. L., Sui, C. G., Hui, L. Y., et al. (2004). Effects of depression on parameters of cell-mediated immunity in patients with digestive tract cancers. World J. Gastroenterol., 10, 268–272. Naylor, M. S., Stamp, G. W., Davies, B. D., and Balkwill, F. R. (1994). Expression and activity of MMPS and their regulators in ovarian cancer. Intl. J. Cancer, 58, 50–56. Obata, N. H., Tamakoshi, K., Shibata, K., Kikkawa, F., and Tomoda, Y. (1997). Effects of interleukin-6 on in vitro cell attachment, migration, and invasion of human ovarian carcinoma. Anticancer Res., 17, 337–342. Ohm, J. E., Gabrilovich, D. I., and Sempowski, G. D. (2003). VEGF inhibits T-cell development and may contribute to tumor-induced immune suppression. Blood, 101, 4878–4886. Ornish, D., Weidner, G., Fair, W. R., Marlin, R., Pettengill, E. B., Raisin, C. J., et al. (2005). Intensive lifestyle changes may affect the progression of prostate cancer. Journal of Urology, 174, 1065–1070. Osborne, R. H., Sali, A., Aaronson, N. K., Elsworth, G. R., Mdzewski, B., and Sinclair, A. J. (2004). Immune function and adjustment style: do they predict survival in breast cancer? Psychooncology, 13, 199–210. Penn, I. (1999). Posttransplant malignancies. Transplant Proc., 31, 1260–1262. Penninx, B. W., Guralnik, J. M., Pahor, M., Ferrucci, L., Cerhan, J. R., et al. (1998). Chronically depressed mood and cancer risk in older persons. J. Natl. Cancer Inst., 90, 1888–1893. Persky, V. W., Kempthorne-Rawson, J., and Shekelle, R. B. (1987). Personality and risk of cancer: 20-year follow-up of the Western Electric study. Psychosom. Med., 49, 435–449.
893
Petticrew, M., Bell, R., and Hunter, D. (2002). Influence of psychological coping on survival and recurrence in people with cancer: systematic review. Br. Med. J., 325, 1066–1076. Petticrew, M., Fraser, J. M., and Regan, M. F. (1999). Adverse lifeevents and risk of breast cancer: a meta-analysis. Br. J. Health Psychol., 4, 1–17. Pettingale, K. W. (1984). Coping and cancer prognosis. J. Psychosom. Res., 28, 363–364. Pettingale, K. W., Burge, C., and Greer, S. (1988). Psychological response to cancer diagnosis: I. Correlations with prognostic variables. J. Psychosom. Res., 32, 255–261. Pettingale, K. W., Morris, T., Greer, S., and Haybittle, J. (1985). Mental attitudes to cancer: an additional prognostic factor. Lancet, 1, 750. Phillips, R. E. (2002). Immunology taught by Darwin. Nat. Immunol., 3, 987–989. Price, M., Tennant, C., Smith, R., Butow, P., Kennedy, S., Kossoff, M. (2001). The role of psychosocial factors in the development of breast carcinoma: part 1. Cancer, 91, 679–685. Protheroe, D., Turvey, K., Horgan, K., Benson, E., Bowers, D., and House, A. (1999). Stressful life events and difficulties and onset of breast cancer: case-control study. Br. Med. J., 319, 1027–1030. Pruessner, J. C., Hellhammer, D. H., and Kirschbaum, C. (1999). Burnout, perceived stress, and cortisol responses to awakening. Psychosom. Med., 61, 197–204. Ramirez, A. J., Craig, T. K., Watson, J. P., Fentiman, I. S., North, W. R., and Rubens, R. D. (1989). Stress and relapse of breast cancer. British Medical Journal, 298, 291–293. Redwine, L., Hauger, R. L., Gillin, J. C., and Irwin, M. (2000). Effects of sleep and sleep deprivation on interleukin-6, growth hormone, cortisol, and melatonin levels in humans. J. Clin. Endocrinol. Metab., 85, 3597–3603. Reynolds, P., Boyd, P. T., Blacklow, R. S., Jackson, J. S., Greenberg, R. S., Austin, D. F., et al. (1994). The relationship between social ties and survival among black and white breast cancer patients. Cancer Epidemiol. Biomarkers Prev., 3, 253–259. Reynolds, P., Hurley, S., Torres, M., Jackson, J., Boyd, P. T., Chen, V. W., et al. (2000). Use of coping strategies and breast cancer survival: results from the Black/White Cancer Survival study. Am. J. Epidemiol., 152, 940–949. Reynolds, P., and Kaplan, G. A. (1990). Social connections and risk for cancer: prospective evidence from the Alameda County study. Behav. Med., 16, 101–110. Rigas, J., Hoopes, P., Meyer, L., Smith, E., Hammond, S., Leopold, K., et al. (1998). Fatigue linked to plasma cytokines in patients with lung cancer undergoing combined modality therapy. Proc. ASCO, 17, 68A. Riley, V. (1975). Mouse mammary tumors: alteration of incidence as apparent function of stress. Science, 189, 465–467. Rivoltini, L., Carrabba, M., Huber, V., Castelli, C., Novellino, L., Dalerba, P., et al. (2002). Immunity to cancer: attack and escape in T lymphocyte-tumor cell interaction. Immunol. Rev., 188, 97– 113. Roberts, D., Anderson, B., and Lubaroff, D. (1994). Stress and immunity at cancer diagnosis. University of Iowa. Unpublished doctoral dissertation. Rodrigue, J. R., Pearman, T. P., and Moreb, J. (1999). Morbidity and mortality following bone marrow transplantation: predictive utility of pre-BMT affective functioning, compliance, and social support stability. Intl. J. Behav. Med., 6, 241–254. Rowse, D. L., Weinberg, J., Bellward, G. D., and Emerman, J. T. (1992). Endocrine mediation of psychosocial stressor effects on mouse mammary tumor growth. Cancer Lett., 65, 85–93.
894
IV. Stress and Immunity
Sapolsky, R. M., and Donnelly, T. M. (1985). Vulnerability to stressinduced tumor growth increases with age in rats: role of glucocorticoids. Endocrinol., 117, 662–666. Scambia, G., Testa, U., Benedetti, P., Foti, E., Nartucci, R., Gadducci, A., et al. (1995). Prognostic significance of IL-6 serum levels in patients with ovarian cancer. Br. J. Cancer, 71, 352–356. Schantz, S., and Goephert, H. (1987). Multimodal therapy and distant metastasis: the impact of NK cell activity. Arch. Otolaryngol. Head Neck Surg., 113, 1207–1213. Schapiro, I. R., Ross-Petersen, L., Saelan, H., Garde, K., Olsen, J. H., and Johansen, C. (2001). Extraversion and neuroticism and the associated risk of cancer: a Danish cohort study. Am. J. Epidemiol., 153, 757–763. Schedlowski, M., Jung, C., Schimanski, G., Tewes, U., and Schmoll, H. J. (1994). Effects of behavioral intervention on plasma cortisol and lymphocytes in breast cancer patients: an exploratory study. Psychooncology, 3, 181–187. Scherg, H., Cramer, I., and Blohmke, M. (1981). Psychosocial factors and breast cancer: a critical reevaluation of established hypotheses. Cancer Detect. Prev., 4, 165–171. Schondorf, T., Engel, H., Lindemann, C., Kolhagen, H., Von Rucker, A., and Mallmann, P. (1997). Cellular characteristics of peripheral blood lymphocytes and tumour-infiltrating lymphocytes in patients with gynecological tumours. Cancer Immunol. Immunother., 44, 88–96. Schulz, R., Bookwala, J., Knapp, J. E., Scheier, M., and Williamson, G. M. (1996). Pessimism, age, and cancer mortality. Psychol. Aging, 11, 304–309. Schwartsburd, P. M. (2004). Age-promoted creation of a pro-cancer microenvironment by inflammation: pathogenesis of dyscoordinated feedback control. Mech. Aging Dev., 125, 581–590. Segerstrom, S. C. (2003). Individual differences, immunity, and cancer: lessons from personality psychology. Brain Behav. Immun., 17 (Suppl 1), 92–97. Sephton, S., Koopman, C., Schaal, M., Thoresen, C., and Spiegel, D. (2001). Spiritual expression and immune status in women with metastatic breast cancer: an exploratory study. Breast J., 7, 345– 353. Sephton, S., Sapolsky, R. M., Kraemer, H. C., and Speigel, D. (1999). Early mortality in metastatic breast cancer patients absent of abnormal diurnal cortisol rhythms. J. Natl. Cancer Inst., 92, 994–1000. Sephton, S., and Spiegel, D. (2003). Circadian disruption in cancer: a neuroendocrine-immune pathway from stress to disease? Brain Behav. Immun., 17, 321–328. Seymour, K., Pettit, S., O’Flaherty, E., Charnley, R. M., and Kirby, J. A. (1999). Selection of metastatic tumor phenotypes by host immune system. Lancet, 353, 1989–1991. Shankaran, V., Ikeda, H., Bruce, A. T., White, J. M., Swanson, P. E., Old, L. J., et al. (2001). IFNgamma and lymphocytes prevent primary tumour development and shape tumour immunogenicity. Nature, 410, 1107–1111. Smith, B. D., Smith, G. L., Carter, D., Sasaki, C. T., and Haffty, B. G. (2000). Prognostic significance of vascular endothelial growth factor protein levels in oral and oropharyngeal squamous cell carcinoma. J. Clin. Oncol. 1, 18, 2046–2052. Sood, A., Landen, C., Bhatty, R., Thaker, P., and Lutgendorf, S. (2004). Stress hormone mediated invasion of ovarian cancer cells. Psychosom. Med., 65, A14. Spiegel, D., Bloom, G., Kramer, J., and Gottheil, E. (1989). Effect of psychosocial treatment on survival of patients with metastatic breast cancer. Lancet, 2, 888–891. Stetlow, R. B. (1978). Repair deficient human disorders and human cancer. Nature, 271, 713–717.
Stommel, M., Given, B. A., and Given, C. W. (2002). Depression and functional status as predictors of death among cancer patients. Cancer, 94, 2719–2727. Suls, J., and Fletcher, B. (1985). The relative efficacy of avoidant and nonavoidant coping strategies: a meta-analysis. Health Psychol., 4, 249–288. Tartter, P., Martinelli, G., Steinberg, B., and Barron, D. (1986). Changes in peripheral T cell subsets and natural killer cytotoxicity in relation to colon rectal cancer surgery. Cancer Detect. Prev., 89, 359–364. Temoshok, L. (1987). Personality, coping style, emotion and cancer: towards an integrative model. Cancer Surv., 6, 545– 567. Temoshok, L., Heller, B., Sagebiel, R. W., Blois, M. S., Sweet, D. M., DiClemente, R. J., et al. (1985). The relationship of psychosocial factors to prognostic indicators in cutaneous malignant melanoma. J. Psychosom. Res., 29, 139–153. Thaker, P., Lloyd, M., Jennings, N., Felix, E., Gershenson, D., Newman, R., et al. (2005). Chronic stress promotes tumor growth and metastasis in ovarian carcinoma. Paper presented at Society of Gynecological Oncology 36th Annual Meeting, Miami Beach, FL. Tjemsland, L., Soreide, J. A., Matre, R., and Malt, U., F. (1997). Preoperative psychological variables predict immunological status in patients with operable breast cancer. Psychooncology, 6, 311–320. Tomei, L. D., Kiecolt-Glaser, J. K., Kennedy, S., and Glaser, R. (1990). Psychological stress and phorbol ester inhibition of radiationinduced apoptosis in human peripheral blood leukocytes. Psychiatry Res., 33, 59–71. Tschuschke, V., Hertenstein, B., Arnold, R., Bunjes, D., Denzinger, R., and Kaechele, H. (2001). Associations between coping and survival time of adult leukemia patients receiving allogenic bone marrow transplantation: results of a prospective study. J. Psychosom. Res., 50, 277–285. Turner-Cobb, J., Koopman, C., Rabinowitz, J., Terr, A., Sephton, S. E., and Spiegel, D. (2004). The interaction of social network size and stressful life events predict delayed-type hyper-sensitivity among women with metastatic breast cancer. Int. J. Psychophysiol., 54, 241–249. Turner-Cobb, J. M., Sephton, S. E., Koopman, C., Blake-Mortimer, J., and Spiegel, D. (2000). Social support and salivary cortisol in women with metastatic breast cancer. Psychosom. Med., 62, 337–345. Valdimarsdottir, H., Zakowski, S. G., Gerin, W., Mamakos, J., Pickering, T., and Bovbjerg, D. H. (2002). Heightened psychobiological reactivity to laboratory stressors in healthy women at familial risk for breast cancer. J. Behav. Med., 25, 51–65. Vujaskovic, Z., Feng, Q. F., Rabbani, Z. N., Anscher, M. S., Samulski, T. V., and Brizel, D. M. (2002). Radioprotection of lungs by amifostine is associated with reduction in profibrogenic cytokine activity. Radiat. Res., 157, 656–660. Watson, M., Haviland, J. S., Greer, S., Davidson, J., and Bliss, J. M. (1999). Influence of psychological response on survival in breast cancer: a population-based cohort study. Lancet, 354, 1331–1336. Weihs, K. L., Enright, T. M., Simmens, S. J., and Reiss, D. (2000). Negative affectivity, restriction of emotions, and site of metastases predict mortality in recurrent breast cancer. J. Psychosom. Res., 49, 59–68. Whiteside, T., and Herberman, R. (1989). The role of natural killer cells in human disease. Clin. Immun. Immunopathol., 53, 1–23. Wu, S., Rodabaugh, K., Martinez-Maza, O., Watson, J. M., Silberstein, D. S., Boyer, C. M., et al. (1992). Stimulation of ovarian
41. Stress and Cancer in Humans tumor cell proliferation with monocyte products including interleukin-1, interleukin-6, and tumor necrosis factor-alpha. Am. J. Obstet. Gynecol., 166, 997–1007. Wu, W. (2000). Social isolation stress enhanced liver metastasis of murine colon 26-L5 carcinoma cells by suppressing immune responses in mice. Life Sci., 66, 1827–1838. Wu, W., Yamura, T., Murakami, K., Ogasawara, M., Hayashi, K., Murata, J., et al. (1999). Involvement of TNFα in enhancement of invasion and metastasis of colon 26-L5 carcinoma cells in mice by social isolation stress. Oncol. Res., 11, 461–469. Yang, E., Bane, C. M., MacCallum, R. C., Kiecolt-Glaser, J. K., Malarkey, W. B., and Glaser, R. (2002). Stress-related modulation of matrix metalloproteinase expression. J. Neuroimmunol., 133, 144–150.
895
Yang, E., and Glaser, R. (2003). Stress-induced immunomodulation: implications for tumorigenesis. Brain Behav. Immun., 17, S37–S40. Zhang, L., Conejo-Garcia, J. R., Katsaros, D., Gimotty, P. A., Massobrio, M., Regnani, G., et al. (2003). Intratumoral T cells, recurrence, and survival in epithelial ovarian cancer. N. Engl. J. Med., 348, 203–213. Zhou, G., Zhengbin, L., McCadden, J. D., Levitsky, H. I., and Marson, A. L. (2004). Reciprocal changes in tumor antigenicity and antigen-specific T cell function during tumor progression. J. Exper. Med., 200, 1581–1592. Zorilla, E. P., Luborsky, L., and McKay, J. R. (2001). The relationship of depression and stressors to immunological assays: a metaanalytic review. Brain Behav. Immun., 15, 199–226.
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C H A P T E R
42 Stress-associated Immune Dysregulation Can Affect Antibody and T-cell Responses to Vaccines MARK A. WETHERELL AND KAVITA VEDHARA
I. INTRODUCTION 897 II. THE VACCINE RESPONSE 897 III. AN OVERVIEW OF VACCINATION STUDIES IN PNI 914
may influence immune responses to vaccination. The review has been subdivided into three parts based on the methods used and/or focuses of the work. The first part deals with observational studies. The majority of studies in this field are observational in nature; that is, they take advantage of naturally occurring variations in psychological factors (e.g., distress) and assess individual differences in these factors in relation to immune responses to vaccination. The second part focuses on the few studies that have attempted to improve vaccination efficacy through some form of intervention. In the third part we review studies in which immune outcomes have not been the principal focus. That is, vaccinations have been used as a model in which to explore other questions regarding the relationship between psychological and physiological processes. Third, several studies have attempted to explore the mechanisms by which psychological factors lead to dysregulated immune responses following vaccination. We will therefore present a discussion of these studies that have examined potential mechanisms. We will then conclude the chapter by summarizing the findings and suggesting potential directions and considerations for future studies assessing vaccination responses.
I. INTRODUCTION A vast literature now exists which suggests that psychological factors can influence physiological, and therefore, health outcomes. Psychological distress, in particular, has been shown to have deleterious effects on a multitude of immune system outcomes. One model for assessing the effects of distress on immunological outcomes is the use of vaccinations. Vaccinations provide a clinically relevant, in vivo model in which to study how an individual responds to an antigen and therefore how other factors (e.g., distress) may influence this immune response. Vaccination studies can also provide information regarding the most appropriate administration of routine vaccinations. This information can therefore be utilized to maximize responses to vaccinations in order to achieve maximal protection. This chapter will be divided into several sections. First, we will start with a brief overview of the immune system. This section will focus on how the immune system responds to vaccination and will present some of the immune measures typically used in vaccination studies. Second, we will provide a critical review of the literature examining how psychological factors PSYCHONEUROIMMUNOLOGY, 4E VOLUME II
II. THE VACCINE RESPONSE The immune system is responsible for the continual surveillance and subsequent protection of the body
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Copyright © 2007 by Elsevier, Inc. All rights of reproduction in any form reserved.
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from foreign organisms that may compromise the health of the host (for a detailed overview of the immune system, see Rabin, 2005). The most important aspect of the immune response in relation to the efficacy of vaccinations is the creation of memory cells. That is, following infection, or stimulation of the immune system via vaccination, T and B memory cells are produced. These cells circulate throughout the body, enabling a faster and more effective immune response should that antigen, or antigens of similar structure, be encountered again. Thus, the antigen can be eliminated before symptoms related to the infection can be produced.
A. Different Types of Vaccines Pathogens can attack the host in a variety of ways and, accordingly, the immune system has a broad repertoire of responses at its disposal. Several different vaccination paradigms have been developed to reflect this diversity. The following section gives a brief summary of the four most commonly used vaccination “types” used in vaccination studies: attenuated, inactivated, subunit, and conjugated. The most effective way of eliciting an immune response to an antigen would be to administer that antigen. This technique was developed by Edward Jenner in the late 1700s. Jenner observed that milkmaids, who were exposed to cowpox, did not contract the more lethal human version, smallpox. In the first demonstration of what we now know as a vaccine, Jenner administered a live cowpox virus to a child who had never had either the cowpox or smallpox viruses. Six weeks later Jenner injected the child with the smallpox virus. The immune response elicited by the cowpox virus protected the child against the genetically similar smallpox virus, and the child did not become infected. Cowpox has no serious, long-term consequences if contracted by humans; immunity to the disease can, therefore, be built up without compromising the health of the host. There are, however, very few diseases in which similar, but non-harmful, alternatives are available to administer as vaccines. As a result, alternative methods for administering antigens as vaccines have been developed. Live, attenuated vaccines (e.g., measles, mumps, rubella) are prepared from attenuated, or weakened, strains of the virus. These vaccines mimic the exact action of the pathogen without the antigenic salience to induce an infection. These vaccines may result in symptoms of infection, but ideally (depending upon the level of attenuation) they are only mild. These vaccines typically produce a strong immune response, so life-long immunity can usually be provided with one or two doses. Possible draw-
backs of live attenuated vaccines are that they may cause disease in immuno-compromised individuals and could genetically mutate to become more virulent. As attenuated vaccines usually elicit weaker immune responses, booster doses are often needed to maintain the desired level of immunity. A second approach involves vaccines containing the entire virus where the virus has been inactivated or killed in some way (e.g., influenza). If, however, the virus has been insufficiently deactivated, subsequent infection may occur, although such events are rare. A third approach seen in subunit vaccines involves the vaccine containing only the active component of the pathogen (e.g., isolated proteins). For example, the hepatitis B vaccine is a recombinant subunit vaccine genetically engineered from the hepatitis B protein. The vaccine is highly antigenic but not infectious. These vaccines can take a long time to develop (i.e., the antigenic components must be correctly identified), but they do provide a safe, effective method of immunization. A fourth common approach is to use conjugated vaccines. Some bacteria have a polysaccharide outer coating (e.g., pneumococcal and meningitis), which prevents detection of the antigen by the immune system. Thus, in order to aid recognition of these otherwise invisible antigens, vaccines against these antigens are conjugated to a carrier protein. This carrier protein subsequently binds to the polysaccharide coat of the bacteria. Conjugated vaccines are therefore recognized via the carrier protein, not the actual pathogen.
B. Immune Outcome Measures Following Vaccination Like antigens, vaccinations elicit both cellular and humoral responses. These responses complement one another, leading to an efficient immune response. A variety of cellular and humoral immune parameters are, therefore, likely to change following vaccination, and these can be used to quantify the immune response. Two techniques are typically used to measure the presence and concentration of antibodies, thus providing a measure of the humoral immune response. The first technique is known as the Hemagglutination Inhibition (HI/HAI) test and utilizes the properties of many viruses (e.g., influenza). The protein (hemagglutin) found on the surface of some RNA viruses has the ability to cause clumping of red blood cells. However, the presence of hemagglutin-specific antibody prevents this clumping. The presence, or not, of clumping can therefore be used as an inverse marker
42. Stress-associated Immune Dysregulation Can Effect Antibody and T-cell Responses to Vaccines
for the presence antibody. That is, a positive reaction occurs when no clumping is observed; i.e., the antibody is present and prevents red blood cells clumping together. Furthermore, the extent to which red blood cells clump or do not clump together can be used as a marker of antibody concentration (titer). That is, less clumping is indicative of greater antibody titers. The second technique, enzyme-linked immunosorbant assay (ELISA), uses a color reactive enzyme to measure the binding of antigen-specific antibodies. The optical density (OD) of the reaction can be used as a marker for antibody concentration; the greater the concentration of antibodies bound to the antigen, the more intense the enzyme-induced color reaction. This technique is more sensitive than HAI tests (Cohen et al., 2001) and can be used to detect much lower antibody concentrations. Such a technique may, therefore, be preferable when dealing with immuno-compromised individuals who may not show a sizable response. Both of these techniques can be used to report levels of antibody in two ways. The first refers to the presence, or not, of antibody, that is, whether an individual seroconverted (produced antibody) in response to the vaccination. Seroconverters can then be compared with those individuals who have not demonstrated an antibody response. This distinction, however, rarely refers to the complete absence of antibodies. Instead, pre-defined cut-offs are often used to indicate whether an individual has mounted a clinically significant response. For example, a four-fold increase in antibody titers is considered a sufficient response to an influenza virus vaccination. An alternative method uses levels of antibody as a continuous variable. That is, variations in the concentration or titer of the antibody are assessed in relation to other variables (e.g., distress). A variety of other parameters can also be measured in response to vaccination. Levels of T Helper 1 (Th1) cytokines; e.g., interleukin-2 (IL-2) and interferongamma (IFN-γ) provide an indication of the cellular immune response to vaccination. In contrast, levels of Th2 cytokines (e.g., IL-4, IL-5, and IL-6) produced by peripheral blood lymphocytes (PBLs) provide an indication of the antibody or humoral response. These assays are usually conducted to examine the potential mechanisms by which psychological factors may regulate the immune response to vaccination.
III. AN OVERVIEW OF VACCINATION STUDIES IN PNI The number of studies using vaccinations has steadily increased in the last decade. The studies can, in general, be classified in one of three ways: observa-
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tional, intervention, or experimental. Within each of these areas, several studies have also examined the mechanisms by which psychological factors may influence immune responses to vaccination. Thus, these “mechanism” studies will be examined in a fourth section. The following sections provide an overview of studies in each of these areas. These studies are also summarized in Table 1.
A. Observational Studies The majority of studies that have assessed psychological factors and responses to vaccination can be classified as observational; that is, they take advantage of naturally occurring differences in psychological factors such as stress. Such studies typically utilize standard vaccination programs and assess vaccination responses in relation to individual differences in psychological factors (e.g., levels of actual and perceived stress, coping style, stressor appraisal). These studies have been further classified in terms of their main findings: (1) studies showing the expected relationship between psychological factors and immune outcomes (i.e., negative characteristics are associated with downregulated immunity, and positive characteristics are associated with upregulated immunity); (2) studies reporting apparently contradictory findings (i.e., negative characteristics are associated with upregulated immunity); and (3) studies that have found no relationships between psychological factors and immune responses to vaccination.
1. Studies Reporting the Expected Relationship between Psychological Factors and Immune Responses to Vaccination The studies in this area vary in terms of the administered vaccine and also the time course of the effects. Several studies report an immediate effect, that is, within weeks following vaccination, whereas other studies report effects several months after vaccination. Thus, it is possible to examine the effects of psychological factors on both the formation of antibodies in response to the vaccine, as well as the maintenance of this response over time. Short-term Effects/Antibody Formation One of the first studies to assess potential relationships between psychological factors and vaccination responses was conducted by Glaser et al. (1992). In this study, the authors attempted to observe the effect of stress, induced by examinations, upon responses to a
TABLE 1 Type of study Obs Exp Int Expected Effects Glaser et al., (1992)
Participants
Psychological factors
Vaccine type
×
Healthy students
Self-reported examination stress
Hep B
Hayney et al., (2003)
×
Healthy adults
Psychological well-being & relationship quality
Flu
Kiecolt-Glaser et al., (1996)
×
Elderly spousal caregivers
Self-reported caregiver stress
Flu
Vedhara et al., (1999)
×
Elderly spousal caregivers
Self-reported caregiver stress
Flu
Glaser et al., (1998)
×
Former & current elderly caregivers
Self-reported caregiver stress
Flu
Bovberg et al., (1990)
×
Healthy students
Examination stress
Flu
Moynihan et al., (2004)
×
Healthy older adults
Perceived stress & social support
Flu
Miller et al., (2004)
×
Healthy students
Daily stress levels
Flu
Jabaaij et al., (1993)
×
Healthy students
Self-reported stress
Hep B
Burns et al., (2002a)
×
Healthy students
Stressful life events in previous 12 month
Hep B
Burns et al., (2002b)
×
Healthy students
Life events & perceived stress
Flu
Glaser et al., (2000)
× ×
Self-reported caregiver stress Life stress, mood and optimism
Pneumococcal
Costanzo et al., (2004)
Former & current elderly caregivers Healthy older adults
Contradictory Effects Petry et al., (1992)
×
Healthy students
Hep B
Larson et al., (2002)
×
Healthy adults
Positive, negative or neutral ratings of life events Life events
Humoral response
Sero-converters after 1st dose reported less stress and anxiety, but no relationship between stress and secondary Ab response
Fewer caregivers demonstrated clinically significant Ab response 1 month post-vaccine Fewer caregivers demonstrated clinically significant Ab response 1 month post-vaccine Fewer caregivers & former caregivers demonstrated clinically significant Ab response 1 month post-vaccine Smaller Ab responses 3 weeks post-vaccine in students reporting greatest examination-related distress Low perceived stress & high social support related to increased titers to NC & HK strains. Inverse relationships observed with Pan strain Individuals with highest levels of daily stress demonstrated lowest Ab responses at 1 and 4 months post-vaccine Levels of Ab at 7 months inversely related to self-reported stress at 2 months Increased stress exposures and coping by substance abuse related to poorer antibody level in Ps vaccinated >12 months previously Adequate response related to higher life events at week 2, greatest protection at month 5 in Ps with lower life events & perceived stress Current caregivers demonstrate faster Ab decline over time
Flu
Flu
Cellular response
Greater T-cell responses seen in those with greater social support Greater well-being associated with greater IFN-y & IL-10 levels Suppressed IL-2 levels in caregivers
Lower levels of IL-2 in current & former caregivers
Greater IL-2 and IL-10 levels related to greater optimism and lower anger, fatigue and mood disturbance
Greatest Ab responses in Ps reporting greatest life stressors Positive relationship between life events and Ab response 2 weeks post-vaccine
Burns et al., (2002c)
×
Healthy students
Life events & perceived stress
Meningitis C
High perceived stress & low well-being, but not life events associated with reduced Ab response, but not bactericidal titers
No Effects Locke et al., (1979)
×
Healthy volunteers
Life change stress, anxiety, depression & hostility
Flu
Jabaaij et al., (1996) Boyce et al., (1995)
× ×
Healthy students Healthy children
Hep B Pneumococcal
Vedhara et al., (2002)
×
Younger spousal caregivers
Self-reported stress Incidences of problem behaviour after starting kindergarten Self-reported caregiver stress
No relationships between any psychological variable and AB responses 2 weeks after vaccination No relationships between stress and Ab levels No relationships between incidences of problem behavior and Ab responses
Flu
No differences in Ab response between caregivers & controls
×
Healthy students
Inhibited trauma
Hep B
×
Healthy workers
General work stress
Flu
×
Elderly spousal caregivers
Self-reported caregiver stress
Flu
Greater Ab response at 2nd booster in intervention Ps Greater Ab response between 4–8 weeks in intervention Ps Greater % of intervention Ps demonstrated clinically significant response to vaccine
Travel vaccinations Typhoid
None
None
None
None
Flu
No differences in depressive symptoms between Ab responders and non-responders No differences in specific Ab responses between CFS patients & controls
Increased depressive symptoms associated with higher pre and post vaccine IL-6 levels Earlier peak responses in T-cells in CFS patients, but no differences in magnitude of response
Intervention Studies Petrie et al., (1995) Davidson et al., (2003) Vedhara et al., (2003) Experimental Studies Petrie et al., (2004)
×
Healthy young adults
Trait negative affect
Strike et al., (2004)
×
Healthy young adults
Glaser et al., (2003)
×
Older adults (including caregivers)
State mood & chronic stress (financial strain & work demands) Depressive symptoms
Vedhara et al., (1997)
×
CFS patients & healthy controls
Morag et al., (1999)
×
Healthy teenaged females
Self-esteem & neuroticism
Rubella
Marsland et al., (2001)
×
Healthy students
Trait negative affect
Hep B
Live poliovirus
Obs = Observational, Exp = Experimental, Int = Intervention, NC = New Caledonian, HK = Hong Kong, Pan = Panama, Ps = Participants, Ab = Antibody, CFS = Chronic Fatigue Syndrome.
Low self-esteem & neuroticism related to lower Ab titers in Ps seronegative at baseline Lower Ab responses associated with increases in trait negative affect
Increases in CD4 after starting school
Lower Ab responses associated with reduced T-cell proliferation to PHA
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series of routine hepatitis B (Hep B) vaccinations. A series of three hepatitis injections were administered at baseline, 1 and 6 months later to a group of 48 healthy medical students with no prior exposure to Hep B. Each of these injections coincided with the final day of a 3-day examination period, and levels of perceived stress and anxiety were averaged across the vaccination/examination period. One month after the initial immunization (i.e., at the time of the second vaccination) a quarter of the sample had seroconverted, that is, developed antibody to the Hep B antigen. There were no differences in levels of stress and anxiety reported at the first vaccination between those who did and did not mount a primary response. However, those who seroconverted were more likely to report lower levels of stress and anxiety throughout the series of examinations. In addition, individuals with greater levels of social support and lower anxiety also demonstrated the greatest T-cell responses to the antigen following the final exam. This study provided preliminary evidence that levels of stress—in this case, self-reported stress—can impair the ability to mount adequate cellular and antibody immune responses following vaccination. Furthermore, the inability to mount a response was only associated with cumulative stress measures, not with the individual measurements taken alongside each vaccination. It can be assumed, therefore, that this cumulative stress measure represents a trait-like perception of stress across the study period. This study also demonstrated that positive psychological factors can have beneficial effects on immune parameters following vaccination. That is, individuals who reported the greatest levels of social support also demonstrated higher antibody titers and a more vigorous T-cell response following vaccination. Other studies have observed greater immune responses in individuals with higher levels of positive traits, following an influenza virus vaccination. Hayney et al. (2003) evaluated the relationships between positive factors and responses to an influenza virus vaccine in a sample of 18 healthy adults. Although humoral immune responses were not assessed, positive correlations were observed between antigen-specific cytokine levels (IFN-γ and IL-10), psychological well-being, and quality of relationships 28 days after vaccination. Short-term effects on vaccination responses have also been observed in groups of individuals experiencing enduring periods of chronic stress, for example, informal caregivers. Caring for an elderly spouse or a spouse with chronic illness is a source of prolonged and chronic stress (Wallsten, 1993). The effects of chronic stress on immune responses can, therefore, be examined through comparisons between caregivers and non-caregiving control participants.
In the first of the seminal studies by Kiecolt-Glaser et al. (1996), influenza virus vaccines were administered to a group of elderly caregivers of spouses with progressive dementia. Given the increased susceptibility to and subsequent morbidity from upper respiratory infections, such as influenza and pneumonia, the choice of vaccine provided an appropriate and clinically relevant model of immune system efficacy. A group of 32 caregivers were recruited, and their responses to an influenza virus vaccination were compared with the same number of controls who were carefully matched for age, sex, and other socioeconomic factors. In addition, all participants had received an influenza virus vaccination in the previous year and so were also similar in terms of previous exposure to the influenza virus. As might be expected, caregivers reported greater levels of depression than control participants. In addition, when compared with controls, fewer caregivers demonstrated a clinically significant antibody response (a four-fold increase in antibody titers) 1 month post-vaccination. That is, while approximately two-thirds of the control group demonstrated an adequate response, such a response was seen only in approximately one-third of the caregivers. These findings were also consistent across two assay techniques (ELISA and HAI assay). Further analyses, conducted on only those individuals who had demonstrated a clinically significant vaccination response, revealed further differences between the groups. That is, PBLs from caregivers had suppressed levels of IL-2 after stimulation with the same vaccine (antigens) over a subsequent 6-month period compared with controls. This study clearly demonstrated that the chronic stress associated with caregiving can suppress aspects of both humoral and cellular immunity. These findings were supported by a subsequent study. Vedhara et al. (1999) assessed the responses of 50 carers of patients with dementia and 67 healthy, matched controls to an influenza virus vaccine containing three influenza virus strains: Harbin, Johannesburg, and Nanchang. Like the previously presented study, carers exhibited significantly greater levels of distress when compared with controls. There were no differences in antibody levels between carers and controls prior to vaccination. However, significantly fewer caregivers demonstrated a clinically significant response to the vaccine over the 28 days following vaccination. This reduction in response was not, however, common to all three of the component strains of the trivalent vaccine. That is, while both carers and controls showed significant increases in response to the Harbin and Johannesburg strains, carers had a weaker response to the Nanchang. The authors suggested that more recent exposure to the Harbin and
42. Stress-associated Immune Dysregulation Can Effect Antibody and T-cell Responses to Vaccines
Johannesburg strains (either through natural exposure or through the previous year’s vaccination) may have accounted for the more robust responses across groups to these strains and the absence of between-group differences. Other studies, while failing to find differences related to the ability to seroconvert, have observed relationships between self-reported stress and antibody titers in the weeks immediately following vaccination. For example, Bovberg et al. (1990) examined responses to a standard influenza virus vaccination in healthy students during a period of examinations. Three weeks following the vaccination, the smallest influenza virus antibody responses were observed in those individuals who reported the highest levels of stress. In contrast, positive characteristics have been shown to have beneficial effects on vaccination responses in older adults over the same time period. Moynihan et al. (2004) assessed responses to influenza virus vaccine in a group of 37 older adults (mean age = 84) living in residential nursing homes. HAI assays were conducted on blood samples drawn immediately before and 3 weeks after vaccination with a trivalent vaccination containing Panama, New Caledonian, and Hong Kong influenza virus strains. Psychological questionnaires assessing perceived stress and social support were administered between the two sampling points. Social support and perceived stress were independently related to pre-vaccination titers, with higher social support and lower perceived stress associated with higher pre-vaccination titers for the New Caledonian and Hong Kong strains. No associations, however, were observed with post-vaccination levels. Conversely, a different pattern emerged with the preand post-vaccination levels of the Panama strain, higher levels of which were associated with lower social support. This latter finding obviously contradicts the notion that positive psychological factors may buffer or protect against deteriorations in immunity. However, the apparent differences observed between the strains may be accounted for by previous natural exposures. That is, the majority of naturally occurring influenza virus cases in the preceding flu season were similar to the Panama strain administered in this study. The authors therefore suggested that this natural exposure may differentially affect Panama titers and may therefore account for the negative associations observed with psychosocial variables. This study provided evidence that positive psychosocial factors (i.e., greater social support) are related to increased influenza virus antibody titers. The authors hypothesized that these factors may also protect the host by delaying the decline in titers over time. That is, while higher social support and lower perceived stress seemed to have no
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impact on post-vaccination levels, they may help with the longer-term maintenance of antibody levels, as evidenced by the positive associations observed with antibody titers prior to vaccination. Thus far, the findings indicate that both chronic (e.g., care giving) and acute (e.g., examinations) stress can have deleterious effects on vaccine responses in the weeks and months immediately following vaccination. Indeed, Jabaaij and colleagues (1993) have suggested that the process of antibody formation may be particularly vulnerable to the effects of stress. A more detailed exploration of when and how stress may affect vaccine responses was conducted by Miller et al. (2004). In this study, healthy participants (N = 83) were asked to record their levels of stress four times daily using a palm computer. These scores were then aggregated to produce daily ratings of stress for 2 days prior to and 11 days after an influenza virus vaccination containing three viral strains: New Caledonian, Panama, and Victoria/Yamanashi. Antibody titers were measured at the time of vaccination, and subsequently at 1 and 4 months post-vaccination. Relationships between psychological factors and immune responses were observed only in relation to the New Caledonian viral strain. There was no effect of stress level on antibody status prior to vaccination. However, individuals who reported the highest levels of daily stress demonstrated the poorest antibody responses to the vaccine at both 1 and 4 months. The measurement of daily stress prior to, on the day of, and following vaccination also allowed for detailed analyses regarding the precise timing of this deficit. In other words, is there a critical period during which the effects of stress have the most deleterious effects on the vaccine response? Reports of stress prior to and on the day of vaccination were unrelated to antibody responses. However, higher levels of self-reported stress on the 10 days following vaccination were indicative of slower antibody responses and poorer maintenance over the follow-up period. Specifically, the greatest inverse relationships between stress and antibody response were observed on the eighth day following vaccination. This study provided further evidence that levels of stress are inversely related to a vaccine response. Specifically, higher levels of daily stress were related to slower and less well-maintained antibody responses to the New Caledonian viral strain. More importantly, levels of stress were recorded during the period of time when the initiation of the antibody response occurred and thus allowed for more precise conclusions to be drawn regarding the period of time when stress can be most harmful. This study also provided novel information regarding the timing of
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vaccinations. That is, self-reported stress was seen to be most influential on antibody responses in the days following vaccination, i.e., in the few days toward the end of the follow-up period. It may, therefore, be the case that stress-induced deficits in antibody status may extend beyond the 10 days post-vaccine assessed in the current study. This information has practical implications for the administration of vaccinations. That is, if individuals were most at risk during the period immediately following a vaccination, then methods of reducing stress during this period may have beneficial effects on antibody status and subsequent protection from infection. Future studies should, therefore, evaluate the potential protective role of stress-reducing interventions during this critical period. Pressman et al. (2005) report further data from the sample assessed by Miller et al. (2004). At the beginning of the study, participants completed questionnaires regarding social network sizes, loneliness, and state and trait characteristics. They were also asked to record their current level of loneliness and affect four times per day on a palm computer. As with Miller et al. (2004), these ambulatory data were collected for 2 days prior and 11 days after an influenza virus vaccination, and antibody titers were measured at the time of vaccination and subsequently at 1 and 4 months post-vaccination. Loneliness and social network size were independently associated with antibody titers to the New Caledonian strain. That is, individuals who reported smaller social networks at baseline had reduced antibody levels at 1 and 4 months postvaccination. In addition, higher levels of total loneliness were also associated with lower levels of antibodies 1 and 4 months after vaccination. There is some evidence, however, that the association between loneliness and antibody levels is not direct. That is, as previously reported in this cohort (Miller et al., 2004), self-reported stress was also associated with reduced antibody responses. Furthermore, tests of mediation demonstrate that stress, in part, mediated the relationship between loneliness and reduced antibody responses. However, the effects of other factors, e.g., network size, were not mediated stress. The ability to continually monitor psychological characteristics clearly allows for more detailed examinations of the relationships between characteristics such as stress and vaccine responses. The methodology adopted by Miller et al., for example, made it possible to explore the effects of stress experienced in the days immediately following vaccination on subsequent antibody levels. Such an approach can therefore provide evidence regarding those periods in the vaccination response that may be most susceptible to the adverse effects of psychological factors such as stress.
It should also be noted that the sample utilized by Pressman et al. (2005) and Miller et al. (2004) comprised healthy young adults with no age-related deterioration in immune system efficacy. As the majority of young, healthy adults would be expected to produce clinically significant responses to influenza virus vaccination, this would have reduced the chances of observing distress or other psychological effects on vaccine responses. The consistency of the observed relationships between psychological factors and vaccine responses in this sample suggest, therefore, a robust phenomenon, whereby psychological factors can lead to immune dysregulation. Finally, Morag et al. (1999) assessed whether a range of psychological factors could predict antibody responses to a viral infection in a sample of healthy young females receiving a routine rubella virus vaccination. Pre-vaccination measurements revealed two distinct groups: those who were not immune to the virus prior to vaccination (seronegative group) and those who were immune (seropositive group). These groups therefore differed in their baseline antibody levels and would therefore differ in their responses to the vaccine. That is, the seronegative group would be infected by the virus, whereas the seropositive group were already immune to the virus, and, as such, would not become infected. Levels of rubella virus– specific antibodies were assessed again 10.5 weeks post-vaccination. Separate analyses for these groups revealed a range of associations between antibody responses and psychological variables in the seronegative group, but not in those who were already immune to the virus. Specifically, lower self-esteem and higher neuroticism were associated with reduced antibody responses in the seronegative group only. Longer Term Effects/Antibody Maintenance The studies presented so far have assessed changes occurring in the weeks and months immediately following a vaccination. However, relationships have also been observed many months after the vaccination. These studies will be examined here. Jabaaij et al. (1993) assessed relationships between self-reported stress during examinations and Hep B vaccination responses using a different dose of the vaccine than the dose used in the Glaser et al. 1992 study. A sample of 95 healthy students, who had tested negative for the presence of anti-Hep B antibodies, were administered a series of reduced dose Hep B vaccinations. Levels of self-reported stress (a composite measure of stressful events and negative affect) 2 and 6 months after the initial vaccine dose were then compared with levels of anti-Hep B antibodies measured 7 months after the initial vaccination. No differ-
42. Stress-associated Immune Dysregulation Can Effect Antibody and T-cell Responses to Vaccines
ences were observed between those who did and did not mount a response. However, a significant relationship was observed between self-reported stress at 2 months and antibody levels 7 months post-vaccine. This relationship was also evident, although not significant, in relation to self-reported stress at 6 months. This pattern of results clearly does not conform to those observed by Glaser and colleagues (1992). One explanation for the differences may be related to the dose of the vaccine used. The inconsistency may also be due to differences between the studies regarding the assessment of immune outcomes (Glaser et al. measured antibody responses at 1 month post-vaccine, while Jabaaij et al. measured responses at 7 months post-vaccine). As such, individuals seroconverting in the Jabaaij et al. study may have done so at any point during the vaccination series. Stress levels were, however, recorded at two time-points during the study. Relationships between stress and antibody levels varied between these time-points. The authors suggested that the reduced salience of the relationship with stress reported at 6 months indicates that the effects of stress were most influential during the earlier stages of vaccine response, that is, prior to booster vaccinations (i.e., 2 months post-vaccine). This implies, therefore, that stress may have differential effects on different aspects of the vaccination response. However, this issue can only be explored fully if antibody levels are examined repeatedly in the weeks and months following vaccination. Two large-scale correlational studies have also assessed antibody status many months after initial vaccination. The first study (Burns et al., 2002c) examined responses to a bacterial vaccine, the meningitis C vaccine. Unlike previously discussed viral vaccines, responses to the meningitis C antigen occur independently of the thymus. In order to create a more effective immune response, the antigen is therefore conjugated to a protein molecule. This protein is recognized, and a thymus-dependent antibody response is mounted. The study involved 60 healthy students who had recently (within 16 months) received the meningitis C vaccine. At one testing session, a blood sample was taken for measurement of specific antibody levels (IgG) and serum bactericidal titers (a measure of antibody function). In addition, questionnaires were administered to measure perceived stress, life events, and psychological well-being. Although the two immune measures were correlated, different associations between these measures and the psychological factors were observed. Stress, as measured by life events, was not related to antibody responses, but individuals who reported high levels of perceived stress were more likely to have reduced antibody
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levels. These associations were not observed in relation to bactericidal titers. This may suggest that stress, or a perception of stress, is detrimental to enumerative, but not functional, aspects of the vaccine response. The authors suggested, however, that while the measured antibody levels were specific to the antigen, measurements of bactericidal titers comprised all antibodies with a capacity to destroy the antigen, and as such, this assay was less specific to the administered vaccine. Given the length of time since vaccination, this study also suggested that increases in levels of perceived stress may impact upon the maintenance of the antibody response. The second study of this kind took advantage of a large student population (N = 260) undergoing routine vaccination against Hep B (Burns et al., 2002b). All participants had received a series of 3 Hep B vaccinations prior to recruitment to the study. Participants then returned for a single assessment, where a blood sample was taken for quantification of antibodies and questionnaires regarding psychological stress (stressful life events in the previous 12 months), coping style, and health behaviors were completed. As might be expected in a large cohort of this kind, there was considerable variation in the time since the participants had received their vaccination course. Accordingly, there was a relationship between length of time since last vaccination and antibody status at follow-up; the greater time since vaccination, the greater the likelihood that participants would have an inadequate antibody level. As a result, the sample was divided into two separate cohorts: those who had commenced the vaccination series within the last 12 months (N = 102) and those who had started the vaccination series more than 13 months previously (N = 147). None of the study variables predicted antibody levels in the recently vaccinated cohort. However, both stress and coping style were independently associated with antibody levels in those participants who had been vaccinated more than 12 months prior to assessment. That is, participants who reported a greater than average number of life events in the previous 12 months were twice as likely to be at risk of having an inadequate antibody level. Furthermore, while acceptance coping appeared to have a protective effect over antibody levels, those who coped by substance abuse were at greater risk of demonstrating an inadequate antibody response. These two large-scale correlational studies illustrate that it is not stressors per se, but how much stress an individual feels, that can be detrimental to immune system efficacy. That is, individuals can experience a greater than average number of stressful life events without showing suppressed immunity. However, if
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they interpret these events as stressful, this increases the likelihood of dysregulated immune responses. Such data do, of course, underscore the importance of individual differences in perceptions of stress and, thus, the stress process. The authors also suggested that the data from the latter study provide evidence that stress can exert different effects on different parts of the humoral immune response. No relationships were observed between psychological variables and immune responses in those individuals who had been vaccinated recently, only in those who had been vaccinated more than 13 months previously. It has been suggested that these data may indicate that stress exerts affects the maintenance rather than the initiation of humoral protection. However, two aspects of the methodology in this study make it difficult to distinguish between stress effects on antibody formation versus antibody maintenance. The first concerns the fact that antibody levels were not assessed soon after vaccination. Thus, it is not clear whether the lower levels observed at follow-up were driven by lower levels of antibody immediately postvaccination (which would reflect impairments in the initiation of antibody production, which, in turn, may have affected antibody maintenance) or reflected genuine stress effects on antibody maintenance. The second concerns the distinction between the two cohorts (i.e., individuals vaccinated in the previous 12 months and individuals vaccinated >13 months previously). Clearly, data from some of the individuals in the former cohort are likely to have reflected antibody maintenance rather than formation. It is evident that prospective studies, in which repeated assessments of both stress and immune outcomes are required if the impact of stress on antibody formation versus maintenance is to be disentangled. One study to have clearly distinguished between stress effects on antibody maintenance and formation was conducted by Glaser and colleagues (2000). This group assessed the responses of 11 current and 13 former caregivers to a pneumococcal pneumonia vaccination, in relation to 28 healthy controls. Unlike the previously discussed vaccines, pneumococcal is a bacterial vaccine that elicits a thymus-independent response, and therefore no T-helper cells are generated. Although not significant, current caregivers reported greater levels of stress than did former caregivers or controls. Furthermore, current caregivers reported significantly less social support than both former caregivers and control participants. Unlike their previous studies of caregivers, however, there were no differences in pneumococcal antibody titers between the groups for several weeks post-inoculation. However, the groups did differ in the maintenance of their
response over a 6-month period. That is, while antibody levels in controls and former caregivers were stable over 6 months, current caregivers demonstrated reduced antibody levels over the same time period. This study therefore provided preliminary evidence that the ongoing chronic stress associated with caregiving impacts differently on the antibody response to a bacterial vaccine than a viral vaccine and may be related to the requirement for a thymus-dependent role in processing the antigen in the case of a viral vaccine. The data suggest that chronic stress may impact on the maintenance of the response and, therefore, on ongoing levels of protection. Finally, other factors have been suggested to have a buffering effect on the deterioration of immune protection over time. Costanzo et al. (2004) assessed the influence of mood and optimism on the in vitro cellular immune response to an influenza virus vaccine using cells from 18 healthy older adults reporting low to moderate levels of life stress. Greater cytokine responses were observed in those individuals who reported greater levels of vigor and optimism. However, the relationships between these factors and humoral responses are unknown. As immune outcomes were assessed 1 year after vaccination, Costanzo and colleagues suggest that the observed beneficial effects on cytokine levels may reflect a buffering by “vigor” and “optimism” of the deterioration of memory T-cells. Such a proposal further supports the view that psychological factors can also affect the maintenance of immune responses as well as initial responses. 2. Studies Reporting Contradictory Relationships between Psychological Factors and Immune Responses to Vaccination Despite the presence of a large body of evidence suggesting that stress and other psychological factors can have deleterious effects on vaccination responses, three studies report findings to the contrary. That is, these studies have observed greater antibody responses in individuals reporting higher levels of stress. Petry et al. (1991) assessed relationships between life stress and responses to Hep B vaccination in a sample of 85 healthy students. Vaccinations were administered at 0, 1, and 6 months to those individuals who had no previous exposure to hepatitis B. All participants completed questionnaires regarding their perceptions (either positive, negative, or neutral) of life experiences on the final day of vaccinations and again 3 months post-vaccine, at which time a final assessment of antibody levels was obtained. Individuals with higher levels of perceived stress, as measured at 6 months, demonstrated the highest peak responses to
42. Stress-associated Immune Dysregulation Can Effect Antibody and T-cell Responses to Vaccines
the vaccine 3 months later. That is, high stress in the 6 months of the vaccination program was indicative of greater antibody responses. Similar findings have also been reported following influenza virus vaccination. Larson et al. (2002) reported that greater numbers of stressful life events were related to increased antibody titers 2 weeks postvaccination in 149 healthy young adults. Similarly, in a study of healthy students, Burns et al. (2002c) observed better rates of protection 5 weeks postvaccination in those individuals reporting higher life events stress. Although positive relationships were observed in the short term, the latter study also reported that reduced protection was associated with increased life events and perceived stress 5 months following vaccination. This subsequent finding is, therefore, more in line with the majority of studies demonstrating relationships between lowered immunity and negative psychological factors. Furthermore, this finding indicates that, in the longer term, negative factors (e.g., increased life stress) can have deleterious effects on the maintenance of antibody responses, supporting previously reported findings (e.g., Burns et al., 2002b; Glaser et al., 2000). While these results may initially appear to be anomalous, there is some support for relationships in this direction in the literature. For example, previous work has demonstrated that modest levels of stress can actually result in enhancements in immunity (e.g., Jemmott and Locke, 1984). However, as there are no recognized thresholds according to which we can distinguish between levels of stress that may have neutral or beneficial effects (sometimes referred to as “eustress”) (Selye, 1976) and those that may have harmful consequences, such an explanation can provide only a limited account of these data. Instead, we must consider that methodological differences in the choice of population, the measurement of stress, etc., may have contributed to these apparently contradictory findings. 3. No Relationships between Psychological Factors and Immune Responses to Vaccination Several studies have failed to find any significant relationships between psychological factors and vaccine responses. One of the earliest studies in this area (Locke et al., 1979) assessed responses to an influenza virus vaccination in 124 healthy individuals. Antibody titers were assessed before and 2 weeks after receiving an influenza virus vaccination and compared with measures of anxiety, depression, hostility, and immediate and long-term changes in life stress. Postvaccination HAI titers were unrelated to any of the
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psychological variables. Although these findings suggest that the chosen psychological parameters have no relationship to vaccination responses, it is possible that the 2-week follow-up period was not long enough for a relationship to be observed. Indeed, most studies in this area have observed relationships between psychological factors and vaccination responses approximately 1 month following vaccination (e.g., Kiecolt-Glaser et al., 1996, Vedhara et al., 1999). In another study by Jabaaij et al. (1996), the effects of self-reported stress on a standard Hep B vaccination were explored in a sample of 68 healthy students, with extreme stress scores (i.e., low or high). In keeping with the Hep B vaccine schedule, students were administered the vaccine at 0, 1, and 6 months, and antibody levels were determined at 0, 2, 6, and 7 months. In addition, levels of self-reported psychological stress were recorded prior to the first vaccine and again at the 6-month follow-up. Unlike their previous study, no relationships were observed between psychological stress at 0 and 6 months and antibody levels at any of the follow-ups. The authors suggested that the antigenic doses of the vaccines used in the two studies may have accounted for the differences in their results (they had adopted a reduced dose vaccine in their earlier study). However, the studies also differed in other aspects of their methodology. In particular, the first study observed relationships between stress at 2 months and antibody levels at 7 months. However, there was no 2-month assessment of stress in the second study. If, as the authors suggested, stress is most damaging during this 2-month period, the absence of a stress measurement at 2 months may account for the reported null effects. A third study assessed whether a naturally occurring stressful event could disrupt vaccination responses. Boyce et al. (1995) administered a pneumococcal vaccination to a group of 39 pre-school children (aged 5 years) 1 week before the stressful experience of commencing kindergarten. Subsequent antibody responses were assessed 1 week later and related to reported incidences of problem behavior, an indirect measure of stress. The authors speculated that if stress had adverse effects on vaccine responses, the children for whom starting school was the most stressful would demonstrate the poorest vaccination responses. Although aspects of cellular immunity (e.g., CD4 counts) increased in response to the vaccine, no relationships between problem behavior and antibody responses were observed. There are at least two possible explanations for these findings. First, the chosen measure of stress (reports of problem behavior) was not sufficiently sensitive to measure the stress of starting kindergarten. Thus, any stress effects on immunity
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may have been overlooked by this methodology. Second, as has been suggested by Glaser and colleagues (2000), stress may exert effects on the maintenance of pneumococcal vaccine responses, not the initial formation of antibodies. Although this suggestion was based on data from older adults, who are already immuno-compromised, subsequent assessments of antibody responses in the months following the starting of kindergarten may have revealed differences in the maintenance of antibody responses to the vaccine. Finally, Vedhara et al. (2002) observed no relationships between distress and responses to an influenza virus vaccination in younger caregivers of patients with multiple sclerosis. The caregivers assessed in previous studies of this kind were all elderly (e.g., KiecoltGlaser et al., 1996, mean age = 73.1). It is possible, therefore, that the immune deficits observed in these studies were exacerbated by a natural age-related decline in their immune defenses and/or a chronic stress/aging interaction. To examine this issue, Vedhara et al. (2002) compared influenza virus vaccine responses in a younger population (mean age = 45.7 years) with age-matched controls. Unlike previous studies, no differences in vaccine responses were observed between caregivers and healthy controls. Furthermore, these younger caregivers did not differ from healthy controls in terms of psychological morbidity (e.g., anxiety and depression). This finding suggests that age-related decline in immune system efficacy might be responsible for the stress-related reductions in vaccine responses observed in previous caregiver studies. However, other differences between younger and older caregivers might account for the differences in vaccine response. For example, younger caregivers differ in terms of their levels of psychological morbidity. That is, despite providing continual care for a spouse, younger carers were considerably less distressed than their elderly counterparts. This may be socially mediated—e.g., younger carers have better social networks and therefore greater levels of support—or financial—i.e., the younger carers were more likely to be employed and therefore more financially secure. Further, these differences may be related to the illness of the spouse; e.g., caregivers of dementia patients report a greater burden of care giving than other caregiver groups (Ory et al., 1999). The differences in levels of distress between the older and younger cohorts obviously hinder any definitive conclusions regarding the effects of age-related decline on vaccine responses. Taken together, these studies suggest that there is no simple association between psychological factors and vaccination responses. However, clear method-
ological differences do differentiate between studies that have observed detrimental effects of stress on vaccine responses and studies that have not, and these differences are likely to account for many of the apparently contradictory findings. Trying to define the complex interactions that are taking place in the HPA and SAM axes with immune response to various types of vaccines is a complex challenge to the investigator interested in this area of research.
B. Intervention Studies Observational studies can provide information regarding how individuals respond to vaccination in “normal” compared with “stressed” conditions and how “stressed” individuals respond in relation to “normal, non-stressed” controls. It therefore follows that if stress leads to a reduced vaccination response, it should be possible to maximize immune responses to vaccinations if levels of stress are reduced. Relatively few studies have assessed the impact of interventions on responses to vaccine. This section details three such studies. The first study assessed the effects of an emotional disclosure intervention on responses to a Hep B vaccination program (Petrie et al., 1995). Emotional disclosure involves writing about a personally traumatic or stressful event for short periods of time (e.g., 20 minutes) over several consecutive days (e.g., 3–4 days). It is suggested that inhibition of stress or trauma can cause states of psychological and biological tension leading to a compromised immune system and subsequent ill health (Pennebaker, 1986). A controlled release of this tension, through written emotional disclosure can, therefore, lead to a reduction in stress and a subsequent improvement in immune function. Petrie and colleagues assessed potential improvements on immune function through responses to a Hep B vaccination program. Potential participants were screened for previous exposure to Hep B. Only those who demonstrated a negative Hep B antibody response were recruited into the study, and as such, it could be assumed that only primary immune responses to the vaccine were subsequently observed. A group of 40 healthy students were randomly assigned to either the emotional disclosure condition (i.e., writing about a traumatic or upsetting experience for 4 consecutive days) or a control condition in which they were asked to write in a descriptive manner about how they had spent the previous day, what they were intending to do the following day, week, and year. The Hep B vaccination was then administered to both groups on the final day of the writing task, and subsequent booster shots were given 1 and 4 months later. Blood samples
42. Stress-associated Immune Dysregulation Can Effect Antibody and T-cell Responses to Vaccines
were obtained for the measurement of Hep B antibody and a measure of cellular immunity (NK cells) immediately before each of the vaccinations and again 6 months after the initial vaccination. Although there was very little difference between the groups 1 month post-vaccination, levels of Hep B antibody in disclosure participants were greater than those in control participants 4 and 6 months later. However, as there were no assessments of mood at each of the follow-up sessions in this study, it is not possible to determine whether the intervention resulted in a longer-term reduction in stress and whether this “stress-reduction” was responsible for the beneficial immune outcomes in the disclosure group. An important caveat to this study involved the measurement of primary and secondary antibody responses. Initial screening of potential participants resulted in only those participants with no Hep B antibody at baseline being entered into the study. However, more sensitive immune assays of the samples obtained immediately pre-vaccine revealed Hep B antibody to be present in five participants. Although the levels of antibody were low, detection indicated that these individuals had, at some stage, been previously exposed to the Hep B virus. The authors therefore employed specific statistical techniques to account for the presence of individuals who were expressing a secondary rather than primary antibody response. Although the presence of these individuals seemed to have very little impact on the overall findings, the subsequent identification of seropositive individuals highlights the importance of rigorous assay techniques. As previously demonstrated (Vedhara et al., 1999), elderly caregivers report greater levels of stress and have reduced responses to vaccination compared with controls. Vedhara et al. (2003) therefore implemented an intervention aimed at reducing the levels of distress in this population. Of a sample of 43 spousal caregivers of dementia patients, 16 were allocated to a stress-management intervention (SMI) and 27 to a control group. These groups were subsequently compared with 27 sociodemographically matched noncarer controls. Levels of distress (combined levels of anxiety, depression, and perceived stress) were measured at the baseline, halfway through, and at the end of the SMI. The SMI consisted of 8 weeks of 1-hour group cognitive-behavioral sessions facilitated by a clinical psychologist. The sessions focused on dealing with stressors specific to the role of being a caregiver, as well as the development of relaxation and cognitive restructuring techniques aimed at reducing the overall distress levels associated with care giving. At the end of the SMI, IgG antibody levels were assessed immediately prior to receiving a standard influenza virus
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vaccination. Subsequent IgG levels were then assessed 2, 4, and 6 weeks after vaccination. The results revealed that both carer groups reported significantly higher levels of distress than control participants before, during, and after the SMI. However, despite the absence of significant changes in distress, significantly more of the carers in the SMI group (50%) generated a clinically appropriate (four-fold increase in antibody levels) response to the vaccine compared with carers not in the intervention (7%). Indeed, the proportion of intervention carers achieving this fourfold increase in antibody levels exceeded that observed in the control group (29%), although this difference between the intervention carers and the control groups was not statistically significant. This study provided clear evidence that participation in an intervention aimed at reducing levels of stress can have remarkable effects on immune system efficacy, as measured by responses to an influenza virus vaccination. However, there were no changes in levels of distress following the intervention. That is, despite the intervention having a substantial effect on immune system efficacy, the intervention had no apparent effect on self-reported levels of distress. The authors suggested that a response shift could account for the absence of change in levels of stress. That is, the SMI encouraged participants to evaluate their lives in terms of stressors and responses to these stressors. This process of cognitive restructuring allowed participants to deal more effectively with the stressors in their lives; however, it may also have resulted in an increasing number of factors being relabeled as stressful. Finally, Davidson and colleagues assessed the effects of a meditation intervention on responses to an influenza virus vaccination (Davidson et al., 2003). Forty-eight healthy adults were randomly assigned to either a mindful meditation intervention or a waitinglist control group. The intervention lasted for a period of 8 weeks and involved weekly meditation meetings, home practice of the meditation techniques, and a single meditation retreat in the sixth week of the intervention. At the end of the 8-week period, all participants were administered an influenza virus vaccine and assessed for antibody levels 3–5 and 8–9 weeks post-vaccine. Those individuals who had participated in the meditation intervention demonstrated the greatest increases in influenza virus antibodies between the two follow-up periods. In addition, at the end of the intervention period, these individuals also demonstrated significant reductions in state anxiety when compared with controls. This study demonstrated that a psychological intervention—in this case, meditation—resulted in reduced levels of distress
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and increased antibody responses to an influenza virus vaccine. The efficacy of this intervention has, however, been brought into question. It has been suggested that the observed enhancement in immune response may not be unique to the implemented intervention (Smith, 2004), and that any prolonged activity that involves periods of quiet and pleasurable activity could evoke changes in affect and brain and immune system activity. This, of course, is not a criticism of the mindful meditation intervention in particular, but moreover, an important consideration for any studies using an intervention that involves activities that would not ordinarily be encountered. This is especially important when the implementation of an intervention involves the removal of an individual from the source of the stress (e.g., time away from work or time away from his/her caregiving responsibilities). Vedhara et al. (2003) attempted to control for this effect through the provision of respite to non-intervention carers. However, a reluctance of the carers to accept this offer led the authors to suggest that respite from the chronic stressor could also account for immune enhancement in elderly caregivers. Further, Davidson et al. (2003) acknowledged that the observed effects on immunity are probably not unique to their chosen intervention. Conclusions regarding the “active ingredients” of these interventions can, therefore, only be drawn following simultaneous comparison of the components of the interventions alongside respite controls. Despite potential methodological flaws, the implications of studies that assess the impact of stressreduction interventions on vaccination responses are far reaching. Such studies demonstrate that interventions can improve responses to vaccinations; however, it remains unclear as to whether these increases occur as a direct result of a reduction or removal of stress. These studies also provide essential information that could aid the effectiveness of vaccination programs. Further intervention work is clearly needed in this area, including studies which explore whether postintervention improvements in immune response are related to clinical improvements in health.
C. Experimental Studies The previously described observational and intervention studies have in common that the vaccine challenge is central to the aims of the study, and subsequent immune responses to the vaccine are the primary outcome. There is, however, another group of studies evident in the literature in which the vaccination and immune responses are incidental to the main aims of the study. Indeed, in many of these studies the immune
response data are not measured or reported. We describe these studies as being “experimental,” and although they are diverse in their design and objectives, they will all be reviewed here. One unique study assessed psychological, but not immune, responses to a vaccination. In order to assess the effects of trait negative affect on symptom attribution, Petrie et al. (2004) recorded a range of physiological symptoms 20 minutes and 7 days following a range of vaccinations typically offered prior to overseas travel (e.g., typhoid, hepatitis, and yellow fever). Individuals with higher levels of negative affect were more likely to attribute their symptoms to the vaccination despite the fact that they were not directly related to vaccination. Negative mood has also been assessed in relation to responses to a typhoid vaccination. Strike et al. (2004) were interested in sickness behavior, that is, common symptoms exhibited by individuals during times of infection or inflammation (e.g., lethargy and malaise). In a double-blind study, a sample of 26 healthy participants was administered either a placebo or typhoid injection. Mood and body temperature were assessed for 8 hours post-vaccination. No measures of humoral or cellular immune responses were reported; instead, the vaccination was used to model the physiological responses associated with sickness behavior. No differences were observed between the vaccination and placebo group in relation to reported symptoms or bodily temperature post-vaccination; however, significant differences in mood did occur between the groups. That is, while facets of negative mood generally improved in those who had received the placebo injection, negative mood deteriorated in the vaccination group. Furthermore, post-vaccination changes in negative mood were greater in those individuals who reported higher levels of chronic stress. In addition, the time course of the changes in negative mood in the current study was consistent with the changes that might be expected in cytokine levels following challenge (e.g., within 8 hours). It is therefore suggested that the changes in mood may represent changes in cytokine levels elicited by the vaccination. While cytokine activity does provide a plausible pathway through which infection and inflammation lead to sickness behaviors, the direct role of cellular responses was not assessed in this study. Further support for this hypothesis is provided by Glaser et al. (2003). They examined levels of depression and cytokines (IL-6) in a sample of 119 older adults before and 2 weeks after an annual influenza virus vaccination. As predicted, individuals with higher levels of depressive symptoms demonstrated greater IL-6 levels both before and after vaccination.
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Increased depressive symptoms were also associated with the greatest post-vaccination increase in IL-6. Although increased depression is also associated with increases in health-compromising behaviors (e.g., smoking), controlling for these factors did not alter the relationship between depression and levels of IL-6. Cytokines, in part, are responsible for alerting other immune cells to the site of infection or the presence of an antigen and for regulating the immune response. Increased sensitivity of cytokines, such as that observed in individuals with higher levels of depression, may therefore lead to dysregulation of the immune system as a whole. Another study utilized a vaccine in an attempt to understand the possible etiology of chronic fatigue syndrome (CFS) (Vedhara et al., 1997). Viral infection has been implicated as one potential cause of CFS. In order to assess this assertion, 14 CFS patients were administered either a placebo or a live poliovirus, and aspects of their immune responses were compared with the responses of matched controls who had also received the vaccine. The vaccine did not significantly increase the incidence of CFS-related symptoms, psychological symptoms (e.g., anxiety), or affect aspects of cognitive performance. However, peak responses in T-cell proliferation were found to be greater in CFS patients than controls, although there was no difference between the groups in terms of the magnitude of these responses. Similarly, no significant differences were observed between the groups with regard to cytokine activity, mucosal immunity, or specific antibody responses to the vaccine. There were, however, some emerging differences in the rate of virus shedding, with some CFS patients demonstrating increased shedding compared with controls. Given the absence of consistent differences between the groups, the authors concluded that it was unlikely that enterovirus responses could be implicated in the etiology of CFS. Marsland et al. (2001) adopted an experimental design to assess whether responses to Hep B vaccination were related to immune reactivity to an acute stressor. A sample of 84 healthy students with no previous exposure to Hep B were administered a routine course of three Hep B vaccinations at 0, 6 weeks, and a final booster at 6 months. Following the second vaccination, participants were classified as either low or high responders on the basis of their antibody responses to the vaccine. These groups did not differ in terms of age, sex, alcohol, or tobacco use, but lower antibody responders reported greater levels of trait negative affect. Participants were then administered a laboratory-based stressor 2 to 4 months following their final vaccination. The stressor comprised a 2-minute preparation period followed by a 3-minute period of
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simulated public speaking in which participants were asked to defend themselves against a hypothetical shoplifting charge while being videotaped. Blood samples were taken immediately before and after the stressor task for measurement of Hep B antibody levels and various aspects of cellular immunity (e.g., lymphocyte proliferation, number of circulating T-cells and NK cells). Individuals classified as low antibody responders also demonstrated reduced T-cell proliferative responses following the stressor. This study supported previous findings suggesting that adverse psychological factors can have deleterious effects on vaccination responses. Furthermore, this study demonstrated that reactivity to a vaccine may be analogous to acute stress reactivity. That is, individuals classified as mounting a low antibody response to vaccination also demonstrated reduced cellular responses to an acute stress task.
D. Studies Examining Mechanisms The preceding sections have sought to distinguish vaccination studies into three main categories according to their objectives. However, many of the studies reviewed here have also sought to address the issue of potential mechanisms as part of their inquiry. Mechanisms implicated include both direct biological pathways linking stress and immune responses to vaccinations and indirect pathways whereby stress alters behavior, which in turn affects the response. In this section, we review the evidence on the mechanisms underlying psychological factors and immune responses to vaccination. 1. Biological Mechanisms There now exists a considerable literature indicating that stress can lead to dysregulation of the HPA axis, resulting in blunted immune responses (Sapolsky, 1996). Several studies have, therefore, examined the role of cortisol as a mediating mechanism between stress and vaccination responses. Two different assessments of HPA functioning have been assessed in relation to vaccination responses: Several studies have examined basal levels of cortisol, whereas other studies have assessed cortisol responses to a stressor (i.e., HPA reactivity). Vedhara et al. (1999) observed inverse relationships between basal levels of cortisol and antibody responses to influenza virus vaccine in elderly caregivers. However, this finding was not replicated in their later study assessing the efficacy of a stress management intervention in reducing stress levels in spousal care (Vedhara et al., 2003). That is, there were no
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differences in cortisol levels between those carers who did and did not partake in a stress management intervention and, furthermore, no differences between these groups and healthy controls. Other studies have also failed to find a relationship between levels of cortisol and vaccination responses. For example, Miller et al. (2004) and Pressman et al. (2005) observed negative associations between stress and loneliness and vaccine responses, respectively. However, no associations were observed between aggregated levels of stress or loneliness and cortisol. Moreover, no associations were observed between levels of cortisol and vaccine responses. The potential mediating role of cortisol cannot be discounted, however. Miller et al. (2004) suggest that an absence of a relationship may be due to the timing of the cortisol samples in relation to the self-report measures of stress. That is, the strongest associations between stress and antibody responses were only observed after the saliva-sampling period was completed. Other studies have assessed the relationship between vaccination responses and activation of the HPA through the measurement of cortisol in response to a stressor. Boyce et al. (1995) assessed cortisol responses in children following the stress of starting kindergarten. The lowest antibody responses to the pneumococcal vaccine were observed in those children who demonstrated the greatest cortisol increases to the stress of starting kindergarten. Other studies have assessed vaccination responses in relation to HPA reactivity following an acute laboratory stressor. Cacciopo (1994) assessed cellular immune responses (IL-2) in healthy older adults 3 months following an influenza virus vaccine in response to an evaluative speech task. Individuals who demonstrated the greatest cortisol reactivity to the task had lower levels of IL-2. Contrasting effects on immune outcomes have been observed in healthy young adults (Burns et al., 2002d). A sample of 30 healthy students completed an evaluative mental arithmetic stressor following completion of a routine series of Hep B vaccinations. Although there was some evidence that antibody titers were lower in individuals who demonstrated a diminished post-task reduction in cortisol, in the main, relationships between cortisol and antibody levels were not in the expected direction. That is, individuals with the highest antibody levels consistently demonstrated higher levels of cortisol (i.e., prior to and following the stressor). The findings regarding the role of cortisol as a mediating mechanism between stress and responses to vaccination are, therefore, mixed. However, the role of the HPA axis in immune dysregulation should not be discounted. Activation of the HPA axis in humans is typi-
cally assessed using salivary cortisol. Although there are obvious methodological benefits in utilizing noninvasive measurements of HPA activation, there are some limitations associated with the measurement of cortisol in saliva. For example, as there is considerable inter-individual variation in salivary cortisol, large sample sizes are required in order to observe intergroup differences. Yet, many of the studies published in this area have relatively small sample sizes. This variation may also lead to differences between studies. For example, Burns et al. (2002d) reported mean cortisol levels in their cohort that were lower than those observed in other similar studies (e.g., Clow et al., 1997). Individuals with low or high levels of cortisol may not, therefore, be comparable between studies, which can, as a consequence, influence the direction of relationships with other psychological variables and vaccination responses. Second, as human cortisol secretion is subject to diurnal variation, specific aspects of the diurnal cycle may be more sensitive to the effects of stress than others, for example, the waking response (Kunz-ebrecht et al., 2004). Finally, studies that have examined the role of cortisol as a mediating mechanism all differ in terms of their methodology—with differences evident not only in approaches to the quantification of cortisol (e.g., area under the curve, early morning peak, slopes, etc.), but also in the aspects of immunity under investigation (e.g., cellular and humoral) in response to a variety of vaccinations, over different time periods, in populations differing in terms of age and stressor type, duration, and frequency. Careful consideration must be given to these methodological variations when attempting to elucidate the role of the HPA axis as a mediating mechanism between stress and the immune system. Another key system involved in the human stress response is the SAM system. Activation of the SAM system is typically measured through cardiovascular parameters (e.g., blood pressure and heart rate) and levels of catecholamines. Cacioppo (1994) assessed the relationships between the reactivity of these parameters to acute stress and in response to cellular immune responses (IL-2) to influenza virus vaccination. Individuals who demonstrated the greatest sympathetic cardiac reactivity, as measured by pre-ejection period (PEP), to the stressor exhibited the greatest decline in immune responses 3 months after vaccination. Catecholamine levels (epinephrine) and heart rate were, however, unrelated to immune responses during the same period. Burns et al. (2002d) have reported similar findings following Hep B vaccination. Greater sympathetic activation (cardiac output and cardiac contractility) following an acute stressor task was observed in those individuals with low antibody titers. Marsland
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et al. (2001) observed a relationship between another marker of sympathetic activation (increased heart rate in response to acute stress) and decreases in lymphocyte proliferative responses. However, no relationships were observed between heart rate reactivity and antibody responses to influenza virus vaccination. Like the studies assessing HPA reactivity, studies assessing the potential role of sympathetic activation and vaccination responses are mixed. Furthermore, like the HPA studies, these studies differ in their methodologies. Taken together, however, these studies indicate that it is cellular rather than humoral immune responses that are most associated with sympathetic parameters. This may reflect the greater individual differences in HPA reactivity. That is, while most stressors elicit a sympathetic response of some kind, HPA responses have a higher threshold for activation. Furthermore, HPA responses may be more determined by individual differences in the interpretation of a stressor than the more immediate, fight-flight responses elicited via the SAM system. The stress response is characterized by the activation of both the HPA and SAM systems, and as such, poor vaccine response may not occur as a direct result of dysregulation of either system but, moreover, an interaction of the two. Further studies attempting to elucidate these mechanisms could, therefore, usefully employ assessment of both HPA and sympathetic responses (e.g., Burns et al., 2002d). Specific brain areas have also been implicated as potential pathways by which psychological factors can influence immune system efficacy. Davidson et al. (2003) assessed activity in the left anterior regions of the brain following periods of meditation. This area is associated with emotion (Davidson and Irwin, 1999) and also enhanced cellular immunity (Kang et al., 1991), and as such may mediate between stress and immune dysregulation. Meditation resulted in increased activation of these brain areas and was also related to the greatest antibody responses. Although the authors suggested that their measures of brain activity were crude, this study provided further evidence that a stress-reduction intervention can increase immune system efficacy. In addition, this intervention also reduced perceived reports of distress and highlighted a potential mediating pathway. Evidence also implicates the prefrontal cortex as a potential pathway. Rosenkranz et al. (2003) assessed activation of the prefrontal cortex via EEG and eyeblink magnitude during an emotional recall task. These neurobehavioral responses were subsequently compared with influenza virus antibody titers. Increased activation of the right prefrontal cortex and larger eyeblink magnitude were associated with lower antibody
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titers. This brain region has been previously associated with higher levels of depression (Henriques and Davidson, 1991) and therefore provides a potential pathway by which negative emotions can lead to suppressed immunity. 2. Psychosocial and Behavioral Mechanisms Stress not only influences biological systems, but also can affect behavior. For example, periods of examination stress have been associated with increases in smoking and reductions in exercise and food intake (Ogden and Mtandabari, 1997). In turn, these behaviors can directly or indirectly compromise the immune system, for example, disruption of antibody formation (Kiecolt-Glaser and Glaser, 1988). One study reported earlier (Burns et al., 2002b) suggests that the way an individual copes with stressful situations can affect immune responses. That is, coping with a stressful situation by acceptance was associated with better responses to Hep B vaccination. In contrast, coping by substance abuse was related to a reduced antibody response. Coping by substance abuse implies engaging in health behaviors that may independently compromise immunity (e.g., alcohol consumption); however, controlling for alcohol intake did not reduce the strength of the observed association. Like alcohol, a whole range of other health behaviors could affect immune status; however, very few studies have provided significant evidence of the mediating role of health behaviors. Two studies have suggested that sleep may mediate between levels of stress and antibody responses. Miller et al. (2004) observed no mediating effect of a range of health behaviors, for example, smoking behavior, alcohol consumption, and levels of physical activity. However, sleep quality was associated with both levels of stress and antibody responses to influenza virus vaccination. That is, individuals with higher levels of cumulative stress reported fewer hours sleep, levels of which were subsequently associated with poorer antibody responses. Further evidence regarding the role of sleep comes from an experimental study. Lange et al. (2003) compared two groups of healthy young adults following a primary Hep A vaccination. All participants were vaccinated in the morning and then allocated to either a normal-sleep or a sleep-deprived group. Individuals who had a normal night of sleep following vaccination demonstrated a two-fold higher increase in Hep A antibody titers 1 month following vaccination. Interestingly, apart from increased tiredness the following morning, the sleepdeprived individuals did not report greater incidences of other negative states, suggesting that it is lack of sleep rather than a state of stress created by lack of
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sleep that is responsible for the observed immune suppression. Although this study provided support for the role of sleep as a unique mediating variable, the authors also reported differences between the groups with regard to endocrine responses following vaccination. Specifically, individuals in the normal sleep group demonstrated higher levels of prolactin and growth hormone. These hormones have been previously demonstrated to exert stimulatory effects on several aspects of the immune system (Gala, 1991). This study highlighted the complexity of the interactions between these proposed mediators. That is, the precise impact of behavioral factors on vaccination responses is unclear and could also be mediated by other pathways (e.g., the endocrine system). The observed associations, therefore, indicate that, at the very least, behavioral factors should be controlled in future studies evaluating the effects of psychological factors on immune responses. It would, however, be beneficial not only to control these factors, but also to examine them as potential mediating mechanisms. Furthermore, the inter-relationships observed between behavioral and biological pathways highlight the importance of their simultaneous measurement.
IV. CONCLUSIONS AND FUTURE DIRECTIONS Several issues are apparent from this overview of the literature regarding the use of vaccinations in PNI studies. These issues can be broadly distinguished into those concerning methodology and those concerning research findings. With regard to methodology, two main observations can be made. First, a variety of vaccines have been assessed in this body of literature. These vaccines all vary in terms of the expected time course of responses and also in the likelihood of previous exposure. This is especially pertinent for studies that have examined responses to influenza virus vaccines, where previous exposure seems to influence subsequent relationships between psychological variables and vaccination response. For example, Miller et al. (2004), Vedhara et al. (1999), and Moynihan et al. (2004) all observed differential effects on each of the strains; that is, increases in stress were associated with one strain but not the other. Although there appears to be no consistent explanation regarding the causes of the differential effects of stress on differing viral strains, prior exposure to these strains is likely to alter the relationship between psychological variables and antibody responses to vaccination. These vaccines do, however, have one thing in common. With the excep-
tion of Jabaaij et al. (1993), all the studies described in this overview utilized standardized vaccinations. These vaccines are not intended for experimental use but instead are designed to create maximal responses in a maximum number of people, thus creating widespread immunity to infectious diseases. For example, most Hep B vaccinations elicit responses in 90% of individuals (Petrie et al., 1995). This issue may account for the fact that the most consistent results are observed in elderly individuals, who, as a result of age-related declines in immune system efficacy, are less likely to mount an adequate response to vaccination. The second methodological issue concerns the considerable variation in the psychological factors under investigation. For example, stress has been defined and measured in many ways. Studies have assessed the absence or presence of stress (e.g., Vedhara et al., 1999), individual perceptions of stress (e.g., Miller et al., 2004), numbers of life events (Burns et al., 2002c), and even proxy measures of stress (incidences of problem behavior, e.g., Boyce et al., 1995). With such a range of definitions and, therefore, assessment tools, it is unsurprising that a mixed pattern of results has been observed. The predominant theme, however, is that adverse psychological events can lead to poorer vaccine responses, whereas other factors (e.g., positive mood, increased social support) can have a protective role, resulting in enhanced cellular responses and maintenance of humoral immune responses to vaccination. These studies do suggest, therefore, that increasing positive factors (e.g., well-being, optimism, quality of relationships and social support), possibly through interventions, can enhance immune responses to vaccination. Among the salient issues regarding research findings, perhaps one of the most prominent concerns the fact that, upon initial inspection, the findings regarding the effects of psychological factors upon vaccination responses appear to be mixed. Some of these inconsistencies may be due to the methodological issues described earlier. However, lack of clarity regarding whether the study is designed to explore antibody formation or antibody maintenance may also contribute to this inconsistent literature as psychological factors may affect each of these processes differently. Future research may benefit from longitudinal designs in which both antibody formation and maintenance are explored. A second issue concerns the fact that, while several studies have attempted to examine potential mechanisms, few have explored these mechanisms directly, as they are inherently correlational in their design. Thus, while a factor may be statistically correlated, a full examination of its influence as a moderator or
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mediator would require some degree of manipulation. For example, if the HPA axis is believed to moderate responses to influenza virus vaccines as suggested by Vedhara et al. (1999), then one test of that mediating relationship would be to modify levels of the hormone cortisol (e.g., pharmacologically) and examine the effects on immune responses to vaccination. This may prove to be a fruitful area for future enquiry. A third, and related, issue concerns the fact that only three studies have examined the effects of interventions upon vaccination responses. Although they consistently demonstrated post-intervention improvements in vaccination responses, the underlying mechanisms of this process remain unclear. That is, is it respite from the source of stress or a specific element of these interventions that is responsible for improvements in immunity? A fourth issue concerns the studies described in the experimental section. The range and diversity of these studies indicate that the vaccination paradigm can be usefully employed to examine a range of research questions, other than those that explicitly focus on psychoneuroimmunological pathways between stress and disease. This may prove to a fruitful area of inquiry. In conclusion, despite differences in methods and, on occasion, contradictory findings, in the main these studies demonstrate that adverse psychological factors have deleterious effects on vaccination responses. However, what remains unclear is whether these deficits result in increased susceptibility to disease. That is, if an individual fails to mount a clinically significant antibody response to a vaccine, is that individual more likely to experience disease or illness at a later date? Furthermore, intervention studies demonstrate that reducing adverse psychological factors can improve responses to vaccination. Yet it remains unclear as to whether observed improvements in immunity have actual implications for the health status of the individual. Future studies should, therefore, focus on clinical indications of health and disease in order to examine whether the levels of immune deficits and enhancements observed in experimental studies increase or decrease the likelihood of subsequent episodes of illness or disease.
References Bovberg, D. H., Manne, S. L., and Gross, P. A. (1990). Immune responses to influenza vaccine is related to psychological state following exams. Psychosomatic Medicine, 52, 229 [Abstract]. Boyce, W. T., Adams, S., Tschann, J. M., Cohen, F., Wara, D., and Gunnar, M. R. (1995). Adrenocortical and behavioural predictors of immune responses to starting school. Pediatric Research, 38, 1009–1016.
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Burns, V. E., Carroll, D., Drayson, M., Whitham, M., and Ring, C. (2002a). Psychological stress, cortisol and antibody response to influenza vaccination in a young, healthy cohort. Brain, Behavior and Immunity, 16, 173 [Abstract]. Burns, V. E., Carroll, D., Ring, C., Harrison, L. K., and Drayson, M. (2002b). Stress, coping and hepatitis B antibody status. Psychosomatic Medicine, 64, 287–293. Burns, V. E., Drayson, M., Ring, C., and Carroll, D. (2002c). Perceived stress and psychological well-being are associated with antibody status after meningitis C conjugate vaccination. Psychosomatic Medicine, 64, 963–970. Burns, V. E., Ring, C., Drayson, M., and Carroll, D. (2002d). Cortisol and cardiovascular reactions to mental stress and antibody status following hepatitis B vaccination: a preliminary study. Psychophysiology, 39, 361–368. Cacioppo, J. T. (1994). Social neuroscience: autonomic, neuroendocrine and immune responses to stress. Psychophysiology, 31, 113–128. Clow, A., Patel, S., Najafi, M., Evans, P. D., and Hucklebridge, F. (1997). The cortisol response to psychological challenge is preceded by a transient rise in endogenous inhibitor of monoamine oxidase. Life Sciences, 61, 567–575. Cohen, S., Miller, G. E., Rabin, B. S. (2001). Psychological stress and antibody response to immunization: a critical review of the human literature. Psychosomatic Medicine, 63, 7–18. Costanzo, E. S., Lutgendorf, S. K., Kohut, M. L., Nisly, N., Rozeboom, K., Spooner, S., Benda, J., and McElhaney, J. E. (2004). Mood and cytokine responses to influenza virus in older adults. Journal of Gerontology: Medical Sciences, 59, 1328–1333. Davidson, R. J., and Irwin, W. (1999). The functional neuroanatomy of emotion and affective style. Trends in Cognitive Science, 3, 25–39. Davidson, R. J., Kabat-Zinn, J., Schumacher, J., Rosenkranz, M., Muller, D., Santorelli, S. K., Urbanowski, F., Harrington, A., Bonus, K., and Sheridan, J. F. (2003). Alterations in brain and immune function produced by mindfulness meditation. Psychosomatic Medicine, 65, 564–570. Gala, R. R. (1991). Prolactin and growth hormone in the regulation of the immune system. Proceedings of the Society of Experimental Biology and Medicine, 198, 513–527. Glaser, R., Kiecolt-Glaser, J. K., Bonneau, R. H., Malarkey, W., Kennedy, S., and Hughes, J. (1992). Stress-induced modulation of the immune response to recombinant hepatitis B vaccine. Psychosomatic Medicine, 54, 22–29. Glaser, R., Kiecolt-Glaser, J. K., Malarkey, W., and Sheridan, J. F. (1998). The influence of psychological stress on the immune response to vaccines. Annals of the New York Academy of Science, 840, 649–655. Glaser, R., Robles, T. F., Sheridan, J., Malarkey, W. B., and KiecoltGlaser, J. K. (2003). Mild depressive symptoms are associated with amplified and prolonged inflammatory responses after influenza virus vaccination in older adults. Archives of General Psychiatry, 60, 1009–1014. Glaser, R., Sheridan, J., Malarkey, W. B., MacCallum, R. C., and Kiecolt-Glaser, J. K. (2000). Chronic stress modulates the immune response to a pneumococcal pneumonia vaccine. Psychosomatic Medicine, 62, 804–807. Hayney, M. S., Dienberg Love, G., Buck, J. M., Ryff, C. D., Singer, B., and Muller, D. (2003). The association between psychosocial factors and vaccine-induced cytokine production. Vaccine, 21, 2428–2432. Henriques, J. B., and Davidson, R. J. (1991). Left frontal hypoactivation in depression. Journal of Abnormal Psychology, 100, 535–545.
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Jabaaij, L., Grosheide, P. M., Heijtink, R. A., Duivenvoorden, H. J., Ballieux, R. E., and Vingerhoets, A. J. J. M. (1993). Influence of perceived psychological stress and distress on antibody response to low dose rDNA hepatitis B vaccine. Journal of Psychosomatic Research, 37, 361–369. Jabaaij, L., vanHattum, J., Vingerhoets, A. J. J. M., Oostveen, F. G., Duivenvoorden, H. J., and Ballieux, R. E. (1996). Modulation of immune response to rDNA hepatitis B vaccination by psychological stress. Journal of Psychosomatic Research, 41, 129–137. Jemmott, J. B. III, and Locke, S. E. (1984). Psychosocial factors, immunologic mediation and human susceptibility to infectious disease: how much do we know? Psychological Bulletin, 95, 78–108. Kang, D. H., Davidson, R. J., Coe, C. C., Wheeler, R. E., Tomarken, A. J., and Ershler, W. B. (1991). Frontal brain asymmetry and immune function. Behavioral Neuroscience, 105, 860–869. Kiecolt-Glaser, J. K., and Glaser, R. (1988). Methodological issues in behavioural immunology research with humans. Brain, Behavior and Immunity, 2, 67–78. Kiecolt-Glaser, J. K., Glaser, R., Gravenstein, S., Malarkey, W. B., and Sheridan, J. (1996). Chronic stress alters the immune response to influenza virus vaccine in older adults. Proceedings of the National Academy of Sciences of the United States of America, 93, 3043–3047. Kunz-ebrecht, S. R., Kirschboum, C., Marued, M., Steptoe, A. (2004). Differences in cortrsol certaining response on work days and weekends in women and men from Whitehall II cohort. Psychoneuroendocrinology, 29, 516–528. Lange, T., Perras, B., Fehm, H. L., and Born, J. (2003). Sleep enhances the human antibody response to hepatitis A vaccination. Psychosomatic Medicine, 65, 831–835. Larson, M. R., Treanor, J. J., and Ader, R. (2002). Psychosocial influences on responses to reduced and full-dose trivalent inactivated influenza vaccine. Psychosomatic Medicine, 64, 113 [Abstract]. Locke, S. E., Hurst, M. W., Heisel, S. J., Kraus, L., and Williams, M. (1979). The influence of stress and other psychosocial factors on human immunity. In Proceedings of the 36th Annual Meeting of the Psychosomatic Society. Marsland, A. L., Cohen, S., Rabin, B. S., and Manuck, S. B. (2001). Associations between stress, trait negative affect, acute immune reactivity, and antibody response to hepatitis B injection in healthy young adults. Health Psychology, 20, 4–11. Miller, G. E., Cohen, S., Pressman, S., Barkin, A., Rabin, B. S., and Traenor, J. J. (2004). Psychological stress and antibody response to influenza vaccination: when is the critical period for stress, and how does it get inside the body? Psychosomatic Medicine, 66, 215–223. Morag, M., Morag, A., Reichenberg, A., Lerer, B., and Yirmiya, R. (1999). Psychological variables as predictors of rubella antibody titers and fatigue—a prospective double blind study. Journal of Psychiatric Research, 33, 389–395. Moynihan, J. A., Larson, M. R., Treanor, J., Duberstein, P. R., Power, A., Shore, B., and Ader, R. (2004). Psychosocial factors and the response to influenza vaccination in older adults. Psychosomatic Medicine, 66, 950–953. Ogden, J., and Mtandabari, T. (1997). Examination stress and changes in mood and health related behaviours. Psychology and Health, 12, 289–299. Ory, M., Hoffman, R. R., Yee, J. L., Tennstedt, S., and Schulz, R. (1999). Prevalence and impact of caregiving: a detailed comparison between dementia and non-dementia caregivers. Gerontologist, 39, 177–185. Pennebaker, J. W., and Beall, S. (1986). Confronting a traumatic event: toward an understanding of inhibition and disease. Journal of Abnormal Psychology, 95, 274–281.
Petrie, K. J., Booth, R. J., Pennebaker, J. W., Davison, K. P., and Thomas, M. G. (1995). Disclosure of trauma and immune responses to a hepatitis B vaccination programme. Journal of Consulting and Clinical Psychology, 63, 787–792. Petrie, K. J., Moss-Moriss, R., Grey, C., and Shaw, M. (2004). The relationship of negative affect and perceived sensitivity to symptom reporting following vaccination. British Journal of Health Psychology, 9, 101–111. Petry, J., Weems, L. B., and Livingstone, J. N. (1991). Relationship of stress, distress and the immunologic response to a recombinant hepatitis B vaccine. Journal of Family Practice, 32, 481–486. Pressman, S. D., Cohen, S., Miller, G. E., Barkin, A., Rabin, B. S., Treanor, J. J. (2005). Loneliness, social network size, and immune responses to influenza vaccination in college freshmen. Health Psychology, 24 (3), 297–306. Rabin, B. S. (2005). Introduction to immunology and immuneendocrine interactions. In K. Vedhara and M. E. Irwin (Eds.), Human psychoneuroimmunology. (pp. 1–25) Oxford: Oxford University Press. Rosenkranz, M. A., Jackson, D. C., Dalton, K. M., Dolski, I., Ryff, C. D., Singer, B. H., Muller, D., Kalin, N. H., and Davidson, R. J. (2003). Affective style and in vivo immune response: neurobehavioral mechanisms. Proceedings of the National Academy of Sciences of the United States of America, 100, 11148–11152. Sapolsky, R. M. (1996). Why stress is bad for your brain. Science, 273, 749–750. Selye, H. (1976). The stress of life (rev. ed.). New York: McGraw-Hill. Smith, J. C. (2004). Alterations in brain immune function produced by mindfulness meditation: three caveats. Psychosomatic Medicine, 66, 148–152. Strike, P. C., Wardle, J., and Steptoe, A. (2004). Mild acute inflammatory stimulation induces transient negative mood. Journal of Psychosomatic Research, 57, 189–194. Vedhara, K., Bennett, P. D., Clark, S., Lightman, S. L., Shaw, S., Perks, P., Hunt, M. A., Philip, J. M. D., Tallon, D., Murphy, P. J., Jones, R. W., Wilcock, G. K., and Shanks, N. M. (2003). Enhancement of antibody responses to influenza vaccination in the elderly following a cognitive-behavioural stress management intervention. Psychotherapy and Psychosomatics, 72, 245–252. Vedhara, K., Cox, N. K. M., Wilcock, G. K., Perks, P., Hunt, M., Anderson, S., Lightman, S. L., and Shanks, N. M. (1999). Chronic stress in elderly carers of dementia patients and antibody response to influenza vaccination. Lancet, 353 (9153), 627–631. Vedhara, K., Llewelyn, M. B., Fox, J. D., Jones, M., Jones, R., Clements, G. B., Wang, E. C. Y., Smith, A. P., and Borysiewicz, L. K. (1997). Consequences of live poliovirus vaccine administration in chronic fatigue syndrome. Journal of Neuroimmunology, 75, 183–195. Vedhara, K., McDermott, M. P., Evans, T. G., Treanor, J. J., Plummer, S., Tallon, D., Cruttenden, K. A., and Schifitto, G. (2002). Chronic stress in non-elderly caregivers—Psychological, endocrine and immune implications. Journal of Psychosomatic Research, 53, 1153–1161. Vedhara, K., Miles, J., Bennett, P. D., Plummer, S., Tallon, D., Brooks, E., Munnoch, K., Schreiber-Kounine, C., Fowler, C., Lightman, S. L., Sammon, A., Rayter, Z., and Fardon, J. (2003). Salivary cortisol, stress, anxiety and depression. Biological Psychology, 62, 89–96. Wallsten, S. M. (1993). Comparing patterns of stress in daily experiences of elderly caregivers and non-caregivers. International Journal of Aging and Human Development, 37, 55–68.
P A R T
V PSYCHONEUROIMMUNOLOGY AND PATHOPHYSIOLOGY DAVID A. PADGETT AND JOHN F. SHERIDAN
MIND BODY INTERACTIONS AND THEIR INFLUENCE ON THE PATHOPHYSIOLOGY OF DISEASE Now that we have made it to the fourth edition of Psychoneuroimmunology, many of us who work in the field take for granted that mind-body interactions influence immune function. As the previous Parts in this compendium have noted, we toil with the understanding that cells of the immune system have receptors for neurotransmitters, neuropeptides, and hormones, and we embrace the notion that primary and secondary lymphoid tissues are innervated by the sympathetic nervous system. Today, in 2006, we have a solid working knowledge of how stressors activate the hypothalamicpituitary-adrenal axis and the sympathetic nervous system; we also have an appreciable grasp of how products of these systems affect molecular and cellular changes in the immune system. In an attempt to capture the breadth of the extant literature in PNI and disease pathophysiology, the chapters included in this Part were solicited to provide an in-depth understanding of psychoneuroimmunological influences on disease. As far back as the early twentieth century, investigators who were undertaking hypothesis-driven research in psychosomatic medicine demonstrated the importance of mind-body interactions in the pathophysiology of disease. In the 1930s Walter Cannon was one of the first to note that fear and stress contributed to the development of physical symptoms akin to heart disease (Cannon, 1939). In the first chapter in this Part, Kop and Cohen discuss how mind-body interactions directly and indirectly influence the development of cardiovascular disease. They note multiple psychological risk factors for heart disease. These can be categorized as chronic personality traits, such as
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hostility; they can be episodic factors, which can include depression and exhaustion; or risk factors can manifest in the form of something like anger, which they classify as an acute psychological trigger. As the years passed since Cannon’s observations, the results of an increasing number of studies suggest that the immune system plays an important role in the relationship between these psychological risk factors and future coronary syndromes. In Chapter 43, Kop and Cohen review the potential interrelationships between the myriad of psychological factors and immune system mediators and their influence on pathophysiology of coronary artery disease progression. The role of psychoneuroimmunological processes in coronary heart disease is continued in the second chapter, prepared by Steptoe and Brydon. According to the authors, “the role of psychoneuroimmunology in coronary heart disease (CHD) has only become widely recognized in the last decade, and research is rapidly evolving as the contribution of immunological processes to disease becomes better understood (Steptoe and Brydon, 2005)”. Chapter 44 summarizes current understanding of this field and addresses two major issues. The first is whether emotional and behavioral factors stimulate the inflammatory and immunological processes that contribute to coronary atherosclerosis and CHD morbidity, while the second asks whether psychoneuroimmunological pathways mediate links between psychosocial risk factors and CHD. Psychological factors have been implicated in the onset and exacerbation of various skin disorders. Chapter 45, by Buske-Kirschbaum, addresses the influence of immunological and psychological factors on various skin diseases with a focus on atopic dermatitis (AD). Dysregulation of the hypothalamic-pituitary-adrenal axis and sympathetic-adreno-medullary system are proposed to aggravate the allergic inflammatory process in atopic dermatitis. Buske-Kirschbaum states . . . “although it is well accepted that exacerbation of skin condition in AD is closely linked to emotional stress, the underlying mechanisms of stress-induced exacerbation of AD are rarely understood.” She goes on to propose a psycho-neuro-endocrine-immunological model of AD in an attempt to integrate the existing data and to highlight potential future research strategies in the field. While the influence of stress on the development of cardiovascular and inflammatory diseases was among the first areas in psychoneuroimmunology to receive attention, the field has broadened significantly as the role of inflammation in numerous central and peripheral processes became evident. The next chapter in this Part, by Guest et al., summarizes evidence relating obesity and immunity with an emphasis on the mechanism associated with the underlying pathologies. Obesity has become a significant health problem in the United States, and the view of adipose tissue as an inert depot for excess energy has shifted. In Chapter 46, the authors state that “adipose tissue is now recognized as a dynamic organ with important roles in modulating satiety, reproduction, immunity and metabolism.” And importantly, it has been reported that the obese exhibit increased markers of inflammation including macrophage infiltration. Studies on the relationship between inflammation and obesity may provide information on the pathologies associated with obesity.
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The remaining chapters in this Part focus on psychoneuroimmunology and host defense. Pathogen recognition has been a major focus of immunological research for the past decade. Studies on innate resistance and the mechanism by which a mammal initially recognizes a viral or bacterial challenge have provided insight into basic host resistance. The long-held dogma of “self versus non-self” discrimination as the capstone of the immune response has been modified to include the concept of “danger signals” (Matzinger, 1994). Danger signals are elicited in damaged tissues in response to insult/ injury, and they provide information through primitive receptor–ligand interactions as part of innate resistance. In Chapter 47, by Fleshner et al., the authors address the concept that exposure to mental or physical stressors stimulates a cascade of behavioral and physiological responses that are directed at improving an organism’s chance of survival. They put a novel twist on this idea and focus on danger signals. Fleshner and colleagues review a collection of data showing that, at the cellular level, the induction of heat shock proteins—specifically heat-shock protein 72 (Hsp72)—may be a previously unrecognized feature of an acute stress response. Their chapter advances the hypothesis that Hsp72 may function as an endogenous “danger signal,” leading to the facilitation of immune responses during times of acute stress. In sum, their chapter focuses on how even the sub-cellular response to a stressor is not intended to be immunosuppressive, but instead is aimed at improving an organism’s survival opportunities. Various infectious diseases commonly befall the average person, and diseases caused by bacteria and viruses continue to be a significant cause of morbidity and mortality worldwide. The remaining chapters in this Part focus upon the underlying mechanisms of psychoneuroimmune interactions that influence microbial pathogenesis and individual susceptibility to infection. Chapter 48, by Emeny and Lawrence, focuses on the consequences of short-term restraint or cold-restraint treatment on the pathophysiology of infection with the bacterium Listeria monocytogenes (LM). The authors initially focus attention on host defense mechanisms that are known to contribute to a successful anti-LM response. This is followed by an in-depth analysis of the neuroimmune interactions that likely influence the host’s immune response during LM infection. In Chapter 49, Sloan et al. point out that a “large body of research has linked psychosocial factors to variations in HIV disease progression. . . . However, the biological processes mediating those effects remain poorly understood.” The chapter reviews the biological signaling pathways that “convey the effects of psychosocial factors to the cellular and molecular processes involved in HIV pathogenesis.” The chapter concludes with a consideration of the broader relationship between psychosocial characteristics and clinical disease outcomes in an effort to understand the behavioral ecology of those relationships. The next chapter, written by Bonneau and Hunzeker, examines another latent viral infection (herpes simplex virus, HSV) that is associated with stress-induced reactivation. A review of HSV biology is followed by studies that probe the relationship between psychological stress and the immune response to, and pathogenesis of, an HSV
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infection. Studies are included that examine the stress-immune-HSV relationship at both the cellular and molecular levels. Chapter 50 concludes with a discussion of “. . . how stress-induced modulation of immunity alters the pathogenesis of HSV infection and possibly plays a role in current and yet-to-be-developed strategies to prevent HSV infection. . . .” The next chapter in this Part, by Bailey et al., delineates the influence of experimental laboratory stressors on the immune response to viral infection. The authors focus attention on the immune response to influenza virus starting with innate immunity and continuing through the development of immunological memory. In sum, Chapter 51 outlines the delicate balance that occurs between nervous, endocrine, and immune system functioning during stressful and quiescent periods. They suggest that if that balance is disturbed by a stressor, the implications for the health of the host can be dire. The final chapter in this Part of Psychoneuroimmunology, Chapter 52, looks at how stress-induced neuroendocrine interactions influence the immune system during a viral infection that leads to an autoimmune disease. Meagher et al., address the effects of stress on the pathophysiology of a Theiler’s virus infection of the central nervous system. Using this experimental model for multiple sclerosis (MS), the authors review the basic pathology of the disease and present evidence supporting a role for viral infection in the etiology of MS. Meagher and colleagues conclude with a review of the extant literature and focus on the influences of stress on the development of MS, paying particular regard to anti-viral immune responses in the development of disease. The chapters in this Part are not intended to be an exhaustive review of the influence of psychoneuroimmune interactions on the pathophysiology of disease. These chapters were solicited to provide a broad overview of PNI and disease. The goal is to provide an idea of where the field is and where work needs to be done to define the mechanisms linking social and behavioral processes to peripheral physiological responses.
References Cannon, W. B. (1939). The wisdom of the body (2nd ed.). New York: WW Norton and Company. Matzinger, P. (1994). Tolerance, danger, and the extended family. Annu. Rev. Immunol., 12, 991–1045. Steptoe, A., and Brydon, L. (2005). Psychoneuroimmunology and coronary heart disease. In K. Vedhara and M. R. Irwin (Eds.), Human psychoneuroimmunology (pp. 107–135). Oxford: Oxford University Press.
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43 Psychoneuroimmunological Pathways Involved in Acute Coronary Syndromes WILLEM J. KOP, AND NICHOLAS COHEN
I. IMMUNE SYSTEM INVOLVEMENT IN CORONARY DISEASE PROGRESSION 921 II. PSYCHOLOGICAL RISK FACTORS FOR CORONARY ARTERY DISEASE 928 III. CONCLUSIONS AND FUTURE DIRECTIONS 936
be followed by a summary of research on psychological CAD risk factors and potential neuroimmunological pathways by which these psychological factors may promote CAD progression (see “Psychological Risk Factors for Coronary Artery Disease”). This chapter concludes with possible clinical implications and directions for future research.
Inflammatory processes play an important role in the progression of coronary atherosclerosis (Danesh et al., 1997; Fahdi et al., 2003; Hansson, 2005; Libby and Theroux, 2005; Ross, 1999). Evidence also suggests that both chronic and acute psychological factors increase the risk of coronary artery disease (CAD) (Kop, 1999; Krantz et al., 1996; Rozanski et al., 1999; Suls and Bunde, 2005). These psychological risk factors can be categorized as chronic personality traits (e.g., hostility), episodic factors (e.g., depression and exhaustion), and acute psychological triggers (e.g., anger). Of direct relevance to psychoneuroimmunology are the results of an increasing number of studies suggesting that the immune system plays an important role in the relationship between these psychological risk factors and future coronary syndromes (Fricchione et al., 1996; Kop, 1994; Kop, 2003; Kop and Cohen, 2001). This review describes potential interactions of psychological factors and immune system mediators in the pathophysiology of CAD progression. We will distinguish between CAD and its clinical manifestations as acute coronary syndromes, namely myocardial infarction and sudden cardiac death. A brief overview of immune system involvement in CAD (see “Immune System Involvement in Coronary Disease Progression”) will PSYCHONEUROIMMUNOLOGY, 4E VOLUME II
I. IMMUNE SYSTEM INVOLVEMENT IN CORONARY DISEASE PROGRESSION Risk for acute coronary syndromes is based on plaque, blood, and myocardial vulnerability markers (Naghavi et al., 2003a). These vulnerability markers are part of the atherosclerotic disease process and are influenced by the immune system. Immune system parameters also affect gradual CAD progression indirectly by their association with known CAD risk factors (e.g., hypertension, smoking, dyslipidemia, obesity). Clinical manifestations of CAD may be symptomatic without damage to the myocardium (i.e., angina pectoris and its equivalents). In addition, clinical manifestations of CAD may present as acute coronary syndromes such as myocardial infarction (MI) and sudden cardiac death (Alonzo et al., 1975; Braunwald, 1988; Naghavi et al., 2003a; Naghavi et al., 2003b). In most instances, acute coronary syndromes occur in the presence of underlying coronary atherosclerotic disease. In this section, we will first describe the characteristics of vascular injury in stages of CAD progression and then discuss the association between the
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severity of atherosclerotic disease and the onset of acute coronary syndromes (see “Stages of Coronary Atherosclerosis and the Onset of Acute Coronary Syndromes”). The atherosclerotic consequences of inflammation and infections will then be reviewed (see “Immunological Processes in Coronary Disease” and “Bacterial and Viral Infection”).
A. Stages of Coronary Atherosclerosis and the Onset of Acute Coronary Syndromes Given that atherosclerosis causes damage to the coronary vessel wall, the gradual progression of atherosclerotic plaques can be viewed as a “response to injury” (Ross, 1986; Ross, 1999). Several pathophysiological classifications of coronary vascular injury have been formulated based on the extent of damage to the arterial wall (Falk et al., 1995; Fuster et al., 1992a; Fuster et al., 1992b). The severity of coronary disease will be used here to clarify effects of immunological and psychosocial factors on CAD progression and its clinical manifestations as acute coronary syndromes. The initial stages of coronary atherosclerosis, characterized by fatty streaks, are associated with functional alterations of the endothelium (the lining cells of the vessel wall) without substantial morphological changes in the vessel. Mild endothelial damage is promoted by several factors including hypercholesterolemia, circulating vasoactive amines, chemical irritants such as tobacco smoke, and inflammatory processes (Fuster et al., 1992a; Fuster et al., 1992b). These early lesions promote the accumulation of lipids, macrophages, and T lymphocytes in the vascular wall (Hansson, 2005; Ross, 1999). Fatty streaks are never associated with cardiac symptoms and may either disappear or develop into atheromata (i.e., atherosclerotic lesions) (Hansson, 2005). Platelets, endothelial cells, and macrophages may secrete several growth factors that initiate migration of smooth muscle cells to other layers of the vessel wall and proliferation (growth) of these cells. Endothelial dysfunction and smooth muscle cell proliferation may result in lesions of more inward layers of the coronary vascular wall. When atherosclerosis progresses to established atheromata, vessel damage involves the endothelium and the intima. These coronary lesions are characterized by fibrin deposits in the intima and/or the development of lesions composed of lipid-laden phagocytes (i.e., foam cells). LDL cholesterol modification by oxidation results in release of phospholipids that can activate endothelial cells. Platelets are the first cells that respond to activated endothelium and may further increase endothelial activation by their glycoproteins (Ib and
IIb/IIIa). The lipid-laden lesion is then coated by a capsule-like fibrous layer of smooth muscle cells and a matrix primarily consisting of collagen. The atherosclerotic lesion is also infiltrated by T-cells, macrophages, and mast cells, particularly at sites where the atheroma grows. These activated immune cells produce inflammatory cytokines. As a result of compensatory vessel dilatation (remodeling) and an inward growth of the lesion, the arterial luminal narrowing is generally minimal at this stage. However, because of its thin layer, lipid-laden lesions can easily rupture, causing blood-clot formation and development of severe vascular lesions. Atherosclerotic plaques at the advanced stage of CAD (formerly referred to as Type III lesions) are characterized by severe damage to all three layers of the vessel wall, including the elastic lamina. Platelets may activate several growth factors that cause the smooth muscle cells to proliferate and migrate from the medial vascular layer to the intima. Following the formation of the initial platelet clot, an extracellular matrix may develop which includes fibrotic organization of the clot. Platelet adhesion and aggregation, as well as coagulation and fibrinolytic processes, are involved in the formation and stabilization of the blood clot (thrombus). The nature and speed of the processes causing progression from moderate to severe lesions are mediated by immunological processes and are associated with major clinical consequences, including unstable anginal complaints and acute coronary syndromes. Anginal symptoms such as chest pain and shortness of breath are indicative of CAD. Such symptoms occur when coronary artery disease has progressed to become flow-limiting (i.e., >50% stenosis of luminal diameter). The ischemia caused by increased cardiac demand in the setting of reduced coronary supply accounts for the symptoms of chest pain and other angina equivalents. Acute coronary syndromes are often the first clinical manifestations of CAD and occur in vulnerable individuals with advanced lesions (Fuster et al., 1992a; Muller et al., 1994). Acute coronary syndromes commonly occur in the setting of relatively stable but nonobstructive (<75% stenosis) atherosclerotic plaques as a result of plaque rupture or endothelial erosion. Myocardial infarction develops as a consequence of acute sustained cardiac ischemia, which results from an imbalance between the supply of oxygenated blood to the heart muscle and cardiac demand (Fuster et al., 1992a; Muller et al., 1994). Sudden cardiac death is often preceded by acute myocardial ischemia (Davies and Thomas, 1984) and, therefore, may be triggered by the same pathophysiological factors as those involved in myocardial ischemia and infarction. Evidence indi-
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cates that advanced coronary lesions progress to total occlusion three times as often as less severe lesions (Ambrose et al., 1988; Giroud et al., 1992). In most instances, however, these advanced lesions do not significantly impair coronary blood flow (<75% luminal stenosis). Furthermore, coronary disease pathology does not progress in a constant manner; rather, lesions undergo periodic spurts of growth (Bruschke et al., 1989; Yokoya et al., 1999). Physical disruption of the atherosclerotic plaque accounts for virtually all acute coronary syndromes (Libby et al., 2005). In addition to rupture of relatively stable coronary lesions, sudden progression of a non-obstructive lesion to a large and occlusive thrombus may result in acute coronary occlusion and subsequent myocardial infarction (Falk et al., 1995). It is estimated that plaque rupture and thrombus formation account for approximately 50% of acute coronary syndromes (Ross, 1999). In summary, atherosclerosis progresses from minor endothelial injury (fatty streaks) via intimal damage (atheromata) to thrombus formation. Initially, platelet adhesion and aggregation, arterial engulfment of lipids, macrophages and T-cells, as well as smooth muscle cell proliferation, play a crucial role. At later stages of coronary artery disease, thrombosis and impaired fibrinolysis contribute to the development of severe coronary lesions. Prolonged coronary disease often results in gradual vessel narrowing, which may be accompanied by anginal complaints. In this situation of gradual progressive CAD, acute coronary syndromes may not occur at all as a consequence of the protective effects of well-developed collateral coronary blood supply. In contrast, the disruption of relatively small atherosclerotic plaques plays a crucial role in the pathogenesis of acute myocardial infarction. Thus, it is important to differentiate between the stage of anatomical CAD progression and its clinical manifestation as an acute coronary syndrome. The immunological aspects of CAD progression are likely to parallel the non-linear progression of coronary disease; the next two sections review the associations of immune system mediators and microorganisms with the severity of CAD and acute coronary syndromes.
B. Immunological Processes in Coronary Disease Immune system parameters are involved in all stages of CAD. Reference to immune system involvement in atherosclerosis can be found in the nineteenth century literature, including those by European pioneers von Rokitansky and Virchow. In early atherosclerotic lesions, immune system mediators act as effector molecules that accelerate lesion progression,
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whereas acute coronary syndromes are promoted by inflammation-related plaque activation. The role of the immune system in CAD is supported by various clinical observations, including the increased risk of myocardial infarction among individuals with splenectomy (Robinette and Fraumeni, Jr., 1977), the adverse cardiovascular consequences in patients with rheumatic arthritis (Wolfe et al., 1994), and the beneficial effects of influenza vaccination among post-MI patients (Gurfinkel et al., 2002). In addition to these clinical studies, advances in monoclonal antibody as well as DNA technology have provided insights into the different types and functions of endothelial cells and smooth muscle cells in the progression of coronary atherosclerosis. It is now well established that immunological and growth-mediating factors play significant roles at various stages of CAD progression, in addition to the known contributions of thrombogenic and fibrinolytic factors. At the initial stages of atherosclerosis, immune system parameters mediate arterial lipid deposition as well as in the proliferation and migration of smooth muscle cells. In addition, immune factors affect CAD progression indirectly by their association with known risk factors for CAD progression (e.g., lipids and obesity). Both mechanisms may initiate a vicious cycle of inflammation, lipid modification, and further inflammation that is maintained in the arterial segment as a consequence of the presence of these lipids (Ross, 1999; White, 1997). In general, the initial inflammatory response to arterial injury is beneficial. However, if the damaging agent is not removed by the inflammatory response and inflammation persists, this protective response then becomes injurious. As in other chronic inflammatory diseases, the subsequent walling off of the damaged area may ultimately diminish the function of the artery, and inflammation becomes part of the atherosclerotic disease process (Ross, 1999). At advanced stages of CAD, immunological processes can precipitate acute coronary syndromes by playing a role in plaque activation and promoting thrombus formation. The role of immune system involvement in coronary disease is supported by multiple prospective epidemiological studies. This research has indicated that non-specific markers of systemic inflammation are associated with an increased risk for cardiovascular events (Kuller et al., 1996; Liuzzo et al., 1994; Ridker et al., 1997; Thompson et al., 1995; Tracy et al., 1997). Among the wide range of immune system mediators, prospective epidemiological data are most consistent for the predictive value of C-reactive protein (CRP), interleukin 6 (IL-6), and tumor necrosis factor-alpha (TNF-α) (Danesh et al., 1997). A recent meta-analysis
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of 22 studies (7,068 cardiac events) supports a significant role of CRP as predictor of incident and recurrent myocardial infarction and cardiac death (OR = 1.5) (Danesh et al., 2004). CRP is a non-specific marker of systemic inflammation which activates coronary endothelium and accumulates in plaques. Levels of CRP, IL-6, and TNF-α tend to be correlated within patients, and the combined presence of elevated CRP, IL-6, and TNF-α in the upper tertile is associated with elevated risks of clinical manifestations of CAD (RR = 2.3; 95%; CI = 1.5–3.5) and congestive heart failure (RR = 4.2; CI = 2.5–7.0), exceeding the risks of the separate inflammatory markers (Cesari et al., 2003). CRP measures are relatively stable over time (e.g., the within person correlation coefficient of CRP over 12 years = 0.59) (Danesh et al., 2004) and, therefore, may reflect subclinical CAD or other pathogenic factors involved in sustained lowgrade inflammation. The immune system components of atherosclerosis are not completely understood, but a complex array of immunological factors including multiple feedback loops is involved. In this section, we will selectively review research supporting the cascade of inflamma-
tory processes in CAD progression; the potential importance of immune system responses to infectious microorganisms will be discussed afterwards (see “Bacterial and Viral Infection”). We will review components of the immune system relevant to CAD progression (macrophages, lymphocytes, cytokines, acute phase proteins, adhesion molecules) including the clinical and experimental evidence supporting associations between these immune parameters and coronary disease (Figure 1). 1. Macrophages Macrophages play multiple functions in CAD progression. The initial stages of atherosclerosis are characterized by formation of layers of lipid-laden foam cells, i.e., macrophages that have ingested circulating lipids. Macrophageous foam cells originate from circulating monocytes that penetrate the vascular wall, lipid-laden smooth muscle cells, and extracellular lipids. The differentiation of monocytes into macrophages is essential to atherosclerosis and is associated with upregulation of scavenger receptors and Toll-
Risk factors Genetic Environmental Behavioral Comorbidity
Atherosclerotic Plaque Macrophage
Lipid T-cell modification activation
Cytokine release
SMC proliferation migration
Adhesion molecule expression
Plaque Instability
Blood Stream Leukocyte Activation Adhesion
Lipids Pathogens
Thrombus Formation
General Host response
FIGURE 1 Immune system parameters involved in the progression of coronary artery disease and its clinical manifestations as acute coronary syndromes. Arterial lipid and leukocyte deposition characterize early stages of coronary disease and include involvement of adhesion molecules. At the advanced disease stage, several immune parameters may increase the risk of acute coronary syndromes by promoting plaque instability and thrombus formation (see text for details).
43. Psychoneuroimmunological Pathways Involved in Acute Coronary Syndromes
like receptors (TLRs), both of which are patternrecognizing receptors in innate immunity. TLRs bind molecules with pathogen-like molecular patterns leading to cell activation. Activated macrophages then release cytokines and proteases, potentially leading to inflammation and tissue damage (Hansson, 2005). Macrophages play multiple roles in atherosclerosis, including (1) the uptake and metabolism of lipids, (2) promotion of the transportation and oxidation of lowdensity lipoprotein (LDL) cholesterol, (3) contribution to the release of several growth factors involved in lesion progression by inducing smooth muscle cell proliferation, and (4) generation of toxic products (products of lipid oxidation; free radicals) that increase atherosclerosis as a consequence of intimal damage. Oxidized lipids purportedly interfere with the normal phagocytic/scavenger function of macrophages that would prevent progressive CAD under normal circumstances (Adams, 1994; Libby and Hansson, 1991). At the advanced stages of atherosclerosis, macrophages have been reported to produce protein- and/or peptide-dissolving enzymes (proteases) that may result in disruption of the organized extracellular matrix leading to formation of unstable advanced lesions. In addition, macrophages can promote thrombus formation by secreting tissue factor and plasminogen activator inhibitor (Libby et al., 1991). 2. Lymphocytes Damage of the vessel wall activates the endothelium leading to adhesion of leukocytes. These leukocytes also migrate into the sub-endothelial layers, further promoting secretion of growth factors and cytokines. T lymphocytes may be deposited passively in the developing atherosclerotic plaque but become important contributors to the progression of atherosclerosis when activated immunologically. B-cells are not very prevalent in atherosclerotic lesions and may have anti-atherosclerotic properties. Natural killer (NK) cells have been documented in early lesions but are not common in the atherosclerotic plaque (Hansson, 2005). T-cell infiltrates in atherosclerotic plaques are primarily Th1 (CD4+) cells involved in macrophage activation and inflammation in the defense against intracellular pathogens and, to a lesser extent, Th2 (CD8+) cells. T-cell activity in areas of smooth muscle cells and endothelial cells is marked by gammainterferon (IFN-γ) production, which increases TNF-α and IL-1 secretion as well as efficiency of antigen presentation. Although IFN-γ is also secreted by NK cells, IFN-γ in atherosclerotic plaques primarily reflects the presence of activated T-cells since NK cells are virtu-
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ally absent in advanced atherosclerotic plaques. A clear demonstration of T-cell involvement in atherosclerosis has been provided by Hansson and colleagues using the arterial intimal growth response to experimentally induced vascular damage (Hansson et al., 1991). Depletion of T-cells by monoclonal antibody or removal of the thymus was associated with decreased atherosclerotic plaque formation, and infusion with IFN-γ resulted in a significant reduction of intimal thickening, suggesting T-cell involvement in response to injury. Additional evidence for T-cell activity comes from the observation that T-cells in atherosclerotic plaques exhibit interleukin-2 (IL-2) receptors. Several factors may result in T-cell activation in atherogenesis, such as oxidized lipoproteins, especially apolipoprotein-B fragments, antigens exposed to blood resulting from necrosis, and viral infection (herpestypes and cytomegalovirus; see “Bacterial and Viral Infection”). T-cell activation leads to secretion of cytokines, and elevated levels of IL-6 and CRP can be detected in the peripheral circulation. At the local plaque, activated T-cells intensify plaque inflammation and stimulate metalloproteinase production by macrophages. The latter effect may result in instability of the atherosclerotic plaque, potentially leading to acute coronary syndromes. Furthermore, activation of T lymphocytes is promoted, in turn, by several cytokines. T-cell activation is higher in unstable than stable angina (Caligiuri et al., 1998). As in the case of activated macrophages, activated T-cells promote acute coronary syndromes by producing molecules involved in plaque destabilization (cytokines, proteases, coagulation factors, and radicals) and inhibition of the formation of a stable fibrous cap. 3. Cytokines Cytokines are low molecular weight peptides that affect the behavior of a variety of cell types. Cytokines, released in response to microorganisms or other challenges, result in a characteristic response of the organism referred to as inflammation. In addition, cytokines increase the adhesive function of the vascular endothelium such that leukocytes and other substances adhere to the vessel wall. Cytokines were originally thought to be solely produced by and affect leukocytes, hence the generic name interleukin (IL). However, proinflammatory cytokines (primarily IL-1, IL-6, and TNF-α) are also released by endothelial cells, smooth muscle cells, and other cell types. Pro-inflammatory cytokines, as well as cellular adhesion molecules, are involved in binding of monocytes to the vascular endothelium and, therefore, are important factors in CAD.
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When coronary atherosclerosis is present, blood cells in the vessel wall express not only immunoactive substances, but may also react to immunological stimulation. IL-6 contributes primarily to the stimulation of T- and B-cell activity, whereas IL-1 appears to be more important in cell-cell contact (Libby et al., 1991). For example, IL-1 is generally not present in unstimulated vascular cells, but its production is known to increase in response to bacterial endotoxin. IL-8 may both promote and inhibit leukocyte accumulation in the atherosclerotic plaque. Atherosclerosis is further promoted when TNF-α is produced by smooth muscle cells. Moreover, following bacterial endotoxin stimulation, higher levels of IL-1 and TNF-α levels are found in atherosclerotic rabbit arteries than in normal arteries. Loppnow and Libby (1992) found that the low basal level of IL-1 in isolated human atherosclerotic plaques was markedly increased after exposure to endotoxin. Based on a super-perfusion model, it has also been shown that myocardial IL-6 is modulated by neurohormones (corticosterone and angiotensin II) (Jeron et al., 2003). These data are consistent with the notion that the central nervous system may influence CAD via immunological pathways. At advanced stages of atherosclerosis, cytokines may promote activation of unstable plaques, leading to acute coronary syndromes. In addition to their important local effects, cytokines have “long-range” effects that contribute to the general host defense. Several prospective studies have documented that elevated IL-6 and TNF-α are associated with increased risk of cardiac events (Ridker et al., 2000a; Ridker et al., 2000b) Increasing evidence also supports the role of chemokines and stem cell/muscle progenitor cell homing and chemotaxis in ischemic cardiac tissue (Wojakowski et al., 2004); this should lead to important further investigations in the pathophysiology and treatment of acute coronary syndromes. In summary, several pro-inflammatory cytokines are involved in the early stages of atherosclerosis, and cytokines probably play an important role in the adverse effects of low-grade inflammation on acute coronary syndromes. 4. Acute Phase Proteins The acute phase response is part of the initial reaction to infection and involves secretion of several proteins from the liver, including CRP, serum amyloid A, and fibrinogen. The release of these acute phase proteins (part of the non-specific innate immune system) is initiated by cytokines (primarily IL-6, but also IL-1 and TNF-α), shifting the production from so-called
housekeeping proteins (e.g., albumin) to acute phase reactants. Levels of acute phase proteins rise dramatically within 24–48 hours after an acute inflammatory stimulus, but the regulation of these proteins in lowlevel diseases is not well understood. Evidence suggests that elevated CRP levels reflect coronary inflammation rather than ischemic myocardium per se (Liuzzo et al., 1996). C-reactive protein is associated with elevated risk for cardiac events (Cesari et al., 2003; Danesh et al., 2004; Kol and Libby, 1998; Kuller et al., 1996; Liuzzo et al., 1994; Ridker, 1998; Ridker et al., 1997; Thompson et al., 1995; Tracy et al., 1997). Some reports indicate that the magnitude of adverse risk associated with CRP is more pronounced within 1 year of assessment and decreases with longer follow-up durations (Tracy et al., 1997), whereas other reports have documented long-term effects of inflammatory markers (Engstrom et al., 2004). Currently, the extent to which the association between acute phase reactants and adverse cardiovascular risk is mediated by a generalized systemic inflammatory condition is not well established; neither is the extent to which these proteins directly affect vascular thrombus formation. The importance of the acute phase protein fibrinogen in CAD progression is well documented, but because its purported action primarily involves coagulation, the role of fibrinogen will not be discussed in detail. The elevated risk associated with increased levels of CRP is independent of other risk factors such as fibrinogen (Ridker et al., 1997), and CRP displays synergism with elevated lipid levels as a risk factor of acute coronary syndromes (Ridker et al., 1998a). 5. Adhesion Molecules Adhesion molecules, including the integrins and selectins, are involved in binding cells to one another. Adhesion of leukocytes to the endothelium is stimulated by IL-1 and TNF-α; these two cytokines also regulate the interaction between the endothelium and platelet adhesion, as well as clotting and fibrinolytic factors, thereby promoting stabilized clot formation (Bevilacqua et al., 1986; Stern et al., 1985). The function of adhesion molecules is primarily local, but circulating levels of adhesion molecules can be used as markers of ongoing inflammatory processes because they may reflect “shedding” from the sites of inflammation. For example, the adhesion molecules L-selectin can be detached from leukocytes (e.g., by a metalloproteinase), enabling assessment of these molecules in plasma (Ross, 1999). During the initial stages of atherosclerosis, the binding of leukocytes to the endothelium involves
43. Psychoneuroimmunological Pathways Involved in Acute Coronary Syndromes
mediation by adhesion molecules. Leukocyte migration is activated by cytokines (IFN-γ, IL-1, IL-6, IL-8, and TNF-α), oxidized lipoproteins, and chemotactic complement activation product. P-selectin, an important adhesion molecule stored in platelets and the endothelium, is released by thrombin. Until integrin activation occurs, neutrophil adhesion to the endothelium is very sensitive to shear stress. Shear stress is generally high (±12 dyn/cm2) in arterial vessels, but can be substantially lower in areas immediately distal of a coronary lesion or in the microcirculation. T-cells and monocytes may “stick” at the sites of low shear as a result of upregulation of the adhesion molecules on both the endothelium and leukocytes (Ross, 1999). Adhesion molecules (e.g., intercellular adhesion molecule-1, ICAM-1) have a long-term prognostic value for incident myocardial infarction (Ridker et al., 1998b). Moreover, ICAM-1 levels are correlated with C-reactive protein levels. In the case of sudden (stressinduced) changes in coronary diameter, activated neutrophils and monocytes may injure the coronary vessel distal to the obstruction, promote platelet activation and coagulation, and activate cytokines, resulting in a net vasoconstriction distal to the obstruction (Entman and Ballantyne, 1993). A cell-surface signaling system has been identified (CD154) which binds to its leukocyte receptor (CD40) and promotes coagulation by inducing tissue factor (Libby and Simon, 2001). Thus, adhesion molecules affect hemostasis and thrombus formation, which may be one of the mechanisms by which these molecules contribute to the transition from chronic CAD to acute coronary syndromes (Libby et al., 1991; Libby et al., 1997).
C. Bacterial and Viral Infection Research starting in the 1950s indicates that avian herpesvirus (Marek) can induce atherosclerosis in chickens (Hinderliter et al., 1996; Paterson and Cottral, 1950). The role of chronic infection in coronary disease progression is supported by seroepidemiological studies demonstrating elevated levels of antibodies to various pathogens in patients with CAD. Beck et al. (1996) demonstrated that individuals with gingivitis were at increased risk of developing future acute coronary syndromes (myocardial infarction) and cerebrovascular events (Beck et al., 1996). Some evidence also suggests that Helicobacter pylori is a risk indicator of MI, especially the more virulent H. pylori strain (cytotoxinassociated gene-A), which is found in 43% of the patients with cardiovascular disease compared to 17% in controls (Pasceri et al., 1998). However, the association between H. pylori and coronary syndromes may reflect common background factors, primarily low
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socioeconomic status (Danesh et al., 1997). Additional research has focused on circulating antibodies to Chlamydia pneumoniae and cytomegalovirus (CMV) in patients with CAD. For example, significantly higher antibody titers to C. pneumoniae have been reported in CAD patients than in healthy controls (27/40 in myocardial infarction patients, 15/30 in patients with established CAD, 7/41 in controls) (Saikku et al., 1988; see also Melnick et al., 1993). An overall assessment of the literature on C. pneumoniae and CMV reveals that these pathogenic microorganisms are associated with a two-fold risk of coronary syndromes (Danesh et al., 1997). Because several types of pathogens may potentially contribute to CAD, it is not likely that a single microorganism causes atherosclerosis. It has been suggested, therefore, that the total number of infections (pathogen burden) may be a risk indicator for acute coronary syndromes (Prasad et al., 2002; Zhu et al., 2001). In concordance with these epidemiological data, certain pathogens are frequently observed in atherosclerotic plaques. Muhlestein and colleagues observed Chlamydia antigens in 79% of the atherosclerotic plaques of 90 CAD patients, compared to 4% in arteries of healthy controls (Muhlestein et al., 1996). Further animal research by Muhlestein et al. indicates that infecting rabbits with Chlamydia promotes plaque formation, especially in hyperlipidemic animals, and that this effect can be neutralized by antibiotic treatment with azithromyzin. Research has identified potential direct as well as indirect pathophysiological mechanisms (Danesh et al., 1997; Kol et al., 1998; Libby et al., 1997). Direct effects of microorganisms include (1) promotion of a pro-thrombotic state of the endothelium, including coagulation and fibrinolytic factors; (2) increased expression of several endothelial-leukocyte contact adhesion molecules (e.g., ICAM-1 by C. pneumoniae, and P-selectin by CMV); (3) cytokine production by endothelial and smooth muscle cells; and (4) lytic cytopathic changes leading to leukocyte migration and vascular inflammation. The effects of these microorganisms do not necessarily require a productive infection. Viruses have additional direct effects on smooth muscle cells such as increased cell proliferation, decreased cell apoptosis, cholesterol esterification, and cytokine production. Such vascular effects have not been demonstrable for bacteria. Indirect effects of microorganisms involve injury and activation of the endothelium and smooth muscle cells. These indirect effects are mediated via lymphocytes and macrophages. In addition to the potential chronic atherogenic consequences of infection, other factors may play a role in the onset of acute coronary syndromes. Cytokines
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released during a systemic infection may “activate” leukocytes and smooth muscle cells of an existing atherosclerotic plaque that may trigger plaque rupture. Furthermore, infections may cause increased cardiac demand because of tachycardia and increased cardiac contractility (Libby et al., 1997). During gram-negative bacterial sepsis, circulating endotoxins provoke substantial alterations in physiology, including hypotension and decreased systemic vascular resistance. Furthermore, endotoxin diffusely activates the endothelium, thereby promoting the development of disseminated intravascular coagulation often accompanying gram-negative sepsis. Finally, febrile illnesses are known to increase the wall-stress challenge to the atheromatous lesion, which may lead to acute coronary syndromes in individuals with vulnerable plaques (Libby et al., 1997). Several theories explaining the presence of bacteria and viruses in atherosclerotic plaques have been advanced. (1) Microorganisms in atherosclerotic plaques may reflect the consequences of an inflammatory response initiated by these infectious organisms. This “low-grade” inflammation hypothesis postulates that infectious sites release toxins and activate surface molecules initiating an inflammatory response of the vascular endothelial cells. This hypothesis is supported by the observation that increased levels of exposure to H. pylori are associated with increasing levels of Creactive protein (Mendall et al., 1996). In addition, systemic endotoxemia or cytokinemia may evoke an “echo” effect—namely an increased local cytokine production in the atherosclerotic lesion by resident cells such as macrophages. (2) An alternative theory states that microorganisms adversely affect the local coagulation-fibrinolysis balance. In support of this notion are numerous studies demonstrating direct viral effects on the anti-coagulatory function of the vascular endothelium (for review, see Libby et al., 1997). (3) Another theory is that microorganisms play an accelerating role rather than act as the pathogenic stimulus per se. A “stronger” version of this theory is that microorganisms are merely innocent bystanders. The facts that only microbial DNA and RNA are found in atherosclerotic arteries, and that efforts to culture microorganisms from atherosclerotic tissue have generally failed, may suggest that infections are not a primary cause of coronary disease progression. Additional factors cast further doubt on a primary role of infections in CAD. The clinical epidemiological observations in support of microorganisms may, in part, reflect common causal factors (e.g., smoking status, age, access to health care, low socioeconomic status, adverse environmental exposures and pollution, and possibly chronic psycho-
logical distress) because these factors may promote the onset of infectious diseases as well as CAD progression. Prospective studies that have controlled for these factors have generally not supported an independent contribution of microorganisms to the progression of CAD (Wald et al., 1997). Finally, intervention trials using antibiotics targeting C. pneumoniae have not been successful in reducing risk for recurrent cardiac events (Cercek et al., 2003; Grayston et al., 2005). Further research is needed to document the association between C. pneumoniae and cytomegalovirus with CAD progression. In summary, microorganisms may cause atherosclerotic vascular changes that do not depend on an active infection. Acute infections may trigger acute coronary syndromes by increased hemodynamic stress and by inducing a pro-thrombotic state (Kol et al., 1998). Although several studies suggest a potential role of infection in coronary atherosclerosis, both clinical and experimental studies are far from conclusive in this regard. Several factors may explain why an existing association between infection and CAD progression is not consistently found. First, analogous to other conditions in which microbial infections play a crucial role (e.g., peptic ulcers), it is conceivable that a subgroup of individuals exists with a genetically determined elevated susceptibility to certain pathogens. Second, it is possible that viruses trigger the onset of atherosclerotic disease without persisting in the infected tissue. Third, the measurement procedures used to detect microorganisms may substantially influence the research findings, and techniques such as microimmunofluorescence require expertise and often produce variable results (Libby et al., 1997). Thus, although the involvement of inflammatory processes in coronary disease is well documented (see “Immunological Processes in Coronary Disease”), further research is needed to determine whether inflammation is a primary trigger or a secondary response to the ongoing atherosclerotic disease process.
II. PSYCHOLOGICAL RISK FACTORS FOR CORONARY ARTERY DISEASE An extensive literature addresses the role of psychological factors in the progression of CAD and acute coronary syndromes (Kop, 1999; Rozanski et al., 1999; Suls et al., 2005). The severity of underlying CAD influences the nature and magnitude of the associations between psychological factors with the onset of acute coronary syndromes. Analogous to the traditional CAD risk factors, it has proven useful to distin-
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guish between chronic and acute psychological factors in the progression of CAD (Kop, 1997; Krantz et al., 1996). Chronic psychological risk factors may promote the onset of initial stages of atherosclerosis by their sympathetic nervous system-mediated pathophysiological consequences (e.g., lipid deposition and inflammatory processes) and/or as a result of their association with known CAD risk factors (e.g., hypertension, smoking, lipids, and obesity). At advanced stages of CAD, acute psychological risk factors may trigger cardiac ischemia or malignant arrhythmias, leading to acute coronary syndromes. Psychological risk factors for CAD can be classified into three categories, based on their duration and temporal proximity to coronary syndromes: (1) chronic factors, such as negative personality traits (e.g., hostility) and low socioeconomic status; (2) episodic factors with a duration of several weeks up to 2 years, among which are depression and exhaustion; and (3) acute triggers, including acute mental distress and outburst of anger (Kop, 1999) (see Table 1). It is also known that the exposure duration of psychological distress influences the nature of its immune system correlates (Benschop et al., 1996; Herbert and Cohen, 1993b; Segerstrom and Miller, 2004). In the following sections, we will briefly review evidence for the adverse cardiovascular risk associated with each of these three categories of psychological factors. We will also describe the potential immune system mediators involved as possible pathophysiological mechanisms (see Table 1).
TABLE 1
A. Chronic Psychological Risk Factors 1. Relationship with Coronary Disease Psychological studies in cardiovascular disease have extensively investigated hostility and, previously, the Type A behavior pattern. The influential studies by Friedman and Rosenman in the late 1950s on Type A behavior documented that this antagonistic personality trait is associated with incident myocardial infarction as well as with relevant cardiovascular risk factors (Friedman and Rosenman, 1959; Suarez et al., 1991; Welin et al., 1985). Later studies have indicated that hostility is the toxic component of Type A behavior. Hostility is assumed to be a stable personality trait characterized by cynical mistrust, aggressive responding, and an overall antagonistic attitude (Barefoot et al., 1983; Engebretson and Matthews, 1992). Most studies report an association between hostility/Type A behavior and severity of underlying coronary disease (Siegman et al., 1987; Williams et al., 1988) as well as first myocardial infarction (Barefoot et al., 1983; Meesters and Smulders, 1994; Shekelle et al., 1983). Research with primates supports a relationship between hostile behavior and severity of CAD (Manuck et al., 1995). In contrast, recurrent coronary syndromes are less consistently predicted by hostility/Type A behavior (Ragland, 1989; Shekelle et al., 1985). Moreover, the association between hostility and MI is more pronounced in younger (<55 years of age) than older men (Meesters et al., 1994; Siegman et al., 1987;
Classification of Psychological Risk Factors for Myocardial Infarction and Sudden Cardiac Death
Psychological risk factor
Chronic
Episodic
Acute
Example
Hostility Low SES
Depression Exhaustion
Anger Mental Activity
Temporal relation to coronary syndrome
>10 years
<2 years
<1 hour
Associated CV risk
Hyperlipidemia Hypertension Prolonged sympathetic activation
↑ Blood clotting ↓ Fibrinolysis Shift of sympatho/vagal balance ↑ Platelet activation
↑ ↑ ↓ ↓
Immune response
↓ Macrophage function ↑ Infections (latent)
Immunosuppression ↑ Infections (active) ↑ Cytokines
Partial immune activation
Primary pathological result
Atherosclerosis
Altered homeostasis
Plaque rupture Ischemia Arrhythmia
Catecholamines Cardiac demand Coronary supply Plasma volume
Primary pathophysiological pathways are presented only; not shown are the multiple associations within and between cardiovascular (CV) risk factors and pathophysiological consequences. SES = Socioeconomic status.
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Williams et al., 1988), suggesting a role of hostility at early stages of CAD progression.
The purported pathophysiological mechanisms accounting for the relationship between chronic psychological factors and CAD involve increased sympathetic nervous system tone and reactivity resulting in accelerated CAD progression. Direct adverse effects of elevated sympathetic activity include damage of vasculature as a result of arterial lipid deposition and elevated intra-arterial pressure that promote early stages of CAD. In addition to the consequences of sympathetic hyperactivity, chronic psychological risk factors affect CAD progression indirectly by their association with persistent cardiovascular risk factors such as hypertension, circulating lipids, and blood clotting factors (for reviews, see Suarez et al., 1991; Williams et al., 1991). Another potential mechanism explaining increased risk of CAD progression and its clinical manifestations involves elevated responsiveness to acute environmental challenges (e.g., mental distress) of catecholamines and hemodynamic measures among hostile individuals. This so-called “hyperreactivity,” which plays a crucial role at the advanced stage of coronary atherosclerosis, may also promote early CAD processes. Increased catecholamine reactivity to challenging conditions in hostile individuals may specifically effect acute physiological responses leading to increased cardiac demand, as well as coronary constriction (Muller et al., 1994) and increased clotting tendency (Markovitz and Matthews, 1991). These acute challenge-induced (patho)physiological changes may increase the risk of ischemia and subsequent acute coronary syndromes.
phages (Adams, 1994). Gidron et al. (2003) have demonstrated that hostility is positively correlated with the percentage of monocytes among patients with acute coronary syndromes. Some evidence also supports associations between hostility and hyperlipidemia or elevated levels of oxidized lipids. Other evidence indicates that plasma IL-6 is independently associated with anger and hostility in otherwise healthy individuals (Suarez, 2003). Relevant to the aforementioned reactivity hypothesis, Mills and colleagues have demonstrated that the hostility trait is related to a laboratory speech task– induced immune response, such that hostility is associated with elevated levels of NK cells during the task (Mills et al., 1996). However, the pattern of results was rather complex, because the overall task-response was in the direction of suppressed immunocompetence, and furthermore, other indicators of hostility (e.g., anger expression) were related to lower NK cell levels and higher B-cell responses. Christensen et al. (1996) have observed that in response to a self-disclosure task, high-hostile participants exhibited a significantly greater increase in NK cell cytotoxicity than low-hostile individuals. The authors conclude that the elevated short-term increase in NK cell activity observed in hostile persons reflects an exaggerated acute arousal response. Lee and colleagues investigated the predictive value of hostility to a distressing condition in a setting of basic cadet training in first-year Air Force Academy cadets (Lee et al., 1995). Hostility measures assessed prior to arrival at the academy did not predict either the level of PHA-, PMA-, and anti-CD3stimulated thymidine uptake by lymphocytes or the risk of illness. However, hostility levels reported during the training predicted risk of illness in the 4 weeks following psychosocial assessment (odds ratio = 7.1; 95% confidence interval: 1.4–36.1).
3. Immune System Correlates
4. Summary and Interpretation
Relatively little is known about the relationship between psychological traits and immune system functioning among CAD patients. It has been argued that atherosclerosis may initially be promoted by immunosuppressive effects of persistent psychological distress, whereas at later stages of atherosclerosis, the reduced immunocompetence will become ineffective because of the silencing effects of the atherosclerotic process itself (Fricchione et al., 1996). Since the early 1940s, it has been well documented that macrophages and lipids interact at the early stages of CAD (Leary, 1941). One potential mechanism would be that hostility promotes early CAD progression by adversely affecting the normal phagocytic function of macro-
Clinical investigations examining hostility and other chronic psychological factors are limited by their essentially observational study designs. Some evidence suggests that chronic psychological traits are associated with persistent alterations in immunological parameters that are known to be associated with gradual CAD progression. The elevated risk factors associated with chronic psychological risk factors (e.g., hyperlipidemia) may also interact with inflammatory or infectious processes, thereby indirectly promoting CAD progression. In addition to these indirect effects, some evidence suggests elevated immune responses to acute challenging conditions in hostile individuals. It is well documented that sympathetic nervous
2. Pathophysiological Mechanisms
43. Psychoneuroimmunological Pathways Involved in Acute Coronary Syndromes
system tone and reactivity are elevated among hostile individuals. The direct consequences of increased sympathetic nervous system activity for the psychoimmunological component of gradual CAD progression require further investigation. In addition to hostility, other psychological traits such as trait anxiety as well as sociological factors— particularly low socioeconomic status—may act as additional sources of persistent exposure to psychological distress. Low socioeconomic status is associated with adverse cardiovascular health outcome (Marmot et al., 1984), which is mediated, in part, by increased cardiovascular risk factors and adverse health behaviors (Kraus et al., 1980; Winkleby et al., 1992), including measures of chronic low-grade inflammation (Owen et al., 2003). Thus, both hostility and low socioeconomic status can be construed as chronic risk indicators that promote atherosclerosis and affect cardiovascular risk (Table 1). These chronic factors may also increase the likelihood of developing proximate psychological risk factors such as episodes of exhaustion and frequent occurrences of acute psychological arousal (see “Interaction between Psychological Factors and Immune System Parameters as Risk Indicators for Acute Coronary Syndromes”; Figure 2).
B. Episodic Psychological Risk Factors 1. Relationship with Coronary Disease Episodic psychological risk factors are transient and recurring, with a duration ranging from several weeks to 2 years (Appels et al., 1994; Kop, 1999). Episodic risk factors are associated with a two- to three-fold elevated risk for incident or recurrent coronary syndromes (Appels, 1997; Carney et al., 1995; Lesperance and Frasure-Smith, 2000; Wulsin and Singal, 2003). Despite the significant predictive value for adverse cardiovascular health outcome, episodic risk factors are not consistently associated with elevated CAD severity (Kop et al., 1993; Kop et al., 1996), suggesting that gradual CAD progression is not the primary pathway by which these factors increase risk for acute coronary syndromes. Instead, factors involved in the transition from stable to vulnerable atherosclerotic plaques may be involved in the elevated risk of episodic risk factors for acute coronary syndromes. Depression is considered to be the core episodic risk factor in behavioral cardiology. Numerous studies indicate that depression is predictive of first and recurrent myocardial infarction and sudden cardiac death (for reviews, see Appels, 1997; Carney et al., 1995; Lesperance et al., 2000; Wulsin et al., 2003). It is still
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debated whether depression reflects one single underlying pathologic process, or whether depression represents a group of distinct disorders with overlapping characteristics (Gold et al., 1988). Independent of the research on depression and CAD, clinical and experimental studies have shown that extreme fatigue is among the most common premonitory symptoms of acute coronary syndromes (Appels and Otten, 1992; Kuller et al., 1972; McSweeney et al., 2003). This state has been referred to as “vital exhaustion” (i.e., lack of energy, increased irritability, and demoralization). The term “vital” will not be used in the remainder of this text and was originally included to reflect the far-reaching consequences of this condition on daily life functioning (similar to vital depression). The predictive value of exhaustion for adverse cardiovascular events has been demonstrated in prospective studies examining healthy and CAD populations (Appels and Mulder, 1988; Kop et al., 1994; Prescott et al., 2003). The extent to which exhaustion reflects the same construct as depression is not fully understood, but some evidence suggests that depression and exhaustion are not entirely overlapping constructs (Appels, 1997; Kopp et al., 1998) with different biological concomitants (Gold et al., 1988; Kop, 1997; Raikkonen et al., 1996). 2. Pathophysiological Mechanisms The most common finding is that depression, especially melancholia, is associated with increased activation of the corticotropin-releasing hormone (CRH) system and, hence, elevated cortisol levels. Both norepinephrine released from the locus ceruleus as well as hypothalamic CRH are the main effectors of the general adaptation response (Selye, 1977). One neurohormonal theory of depression postulates that the inhibiting effect of glucocorticoids on CRH secretion is deteriorated in depressed individuals. In addition to neuroendocrine correlates, episodic risk factors are related to hemostatic cardiovascular risk factors, including impaired fibrinolysis (Kop et al., 1998; Pietraszek et al., 1991; Raikkonen et al., 1996), increased platelet adhesion and aggregation (Bruce and Musselman, 2005), as well as sympathetic overactivity and decreased parasympathetic activity (Carney et al., 2005). An overall imbalance of normal homeostatic function may be characteristic of episodic risk factors. Research has also demonstrated that episodic factors are related to a range of blood clotting factors, including fibrinogen, factor VII, and PAI-1 (Von et al., 2001). Studies have found moderately elevated hemodynamic responsiveness among individuals with episodic risk factors (Kibler and Ma, 2004), but this has
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not been consistently documented in CAD patients (Carney et al., 1995; Kop et al., 1997). It is not known whether the variability in reactivity finding reflects a blunted hyperresponsiveness in a subgroup of individuals exposed to prolonged psychological challenges, as a result of what has been described as increased allostatic load (McEwen, 1998; Seeman et al., 1997). Evidence indicates that atypical forms of depression, characterized by hyperphagia and hypersomnia and mood reactivity (transient elevations of negative affect in response to positive events), are characterized by inactivation of the CRH system and reduced NE levels (Gold et al., 1988). Weight gain and hypersomnia often occur in exhaustion and other conditions in which fatigue is a primary symptom. Therefore, evidence suggests that typical melancholic depression is associated with different neurohormonal concomitants than those observed in exhaustion and atypical forms of depression. One study showed that exhaustion was associated with increased markers of impaired fibrinolysis (elevated PAI-1 levels), whereas no effects on blood coagulation factors were found (e.g., factor VII and VIII) (Kop et al., 1998). Thus, episodic risk factors may elevate the risk of acute coronary syndromes in the setting of advanced CAD by their association with thrombotic factors and plaque rupture. 3. Immune System Correlates The main outflow pathways by which the central nervous system affects the immune system are the hypothalamic-pituitary-adrenal (HPA) axis and the autonomic nervous system. Corticotropin-releasing hormone is elevated in typical depression and acts as the main regulatory hormone in the acute stress response, resulting in the release of pro-inflammatory cytokines, as well as a wide range of other immune system responses. The autonomic nervous system also plays an important role in the acute phase reaction, and parasympathetic outflow inhibits macrophage activation via the “cholinergic anti-inflammatory pathway” (Tracey, 2002). Depression is associated with decreased parasympathetic nervous system activity in CAD patients, which may thus contribute to elevations in pro-inflammatory cytokines. Immune system correlates of depression have been reviewed in detail elsewhere (Herbert and Cohen, 1993a; Kop and Gottdiener, 2005; Maes, 1995; Stein et al., 1991; Weisse, 1992; Zorrilla et al., 2001). In brief, depression is associated with several immune parameters, including increased numbers of peripheral leukocytes (particularly neutrophils and monocytes), decreased lymphocytes, and elevated cytokine production. In addition to numeric
measures of immune function, depression is also associated with reduced functional measures, including lower NK cell activity and a decreased proliferative response of lymphocytes to mitogenic stimulation (Herbert et al., 1993a; Weisse, 1992; Segerstrom et al., 2004). Evidence suggests that inflammation-related parameters are not necessarily inter-related among depressed individuals (Pike and Irwin, 2005), suggesting multiple pathway involvement in the immune system correlates of depression. The psychoneuroimmunology literature generally categorizes the immunosuppressive correlates of depression along with the long-term immunological consequences of distressing behavioral or emotional states (e.g., bereavement, separation, and daily hassles) (Segerstrom et al., 2004). As reviewed by Black (2003), the inflammatory response is contained within the stress response, and the stress, inflammatory, and immune systems evolved in parallel throughout evolution (Black, 2003). Our group (Kop et al., 2002) and others (e.g., Empana et al., 2005; Ladwig et al., 2003; Lesperance et al., 2004; Miller et al., 2002; Panagiotakos et al., 2004) have consistently found elevated CRP levels among individuals with depressive symptoms. These associations may be mediated, in part, by being overweight and other adverse health behaviors (Douglas et al., 2004) (see “Conclusions and Future Directions”). The association between exhaustion and CRP remains significant after adjusting for potentially confounding variables (age, gender, race, diabetes mellitus, smoking status, systolic blood pressure), whereas the association between depressed mood and CRP is reduced when adjusting for the same variables (Kop et al., 2002). Thus, the clinical nature of depression (i.e., melancholic atypical versus depression) may influence the association between depressive symptoms and immune system parameters. Patients with clinical depression also have increased levels of antibody to several herpesviruses, including CMV. An elevated pathogen burden has been documented by Appels and colleagues (2000) in patients undergoing coronary angioplasty and by Miller et al. (2005) in post-myocardial infarction patients. It could be argued, therefore, that increased antibody titers to pathogens such as CMV among depressed individuals result from an overall immunosuppressed state of the specific adaptive immunity including suppressed T-helper cells that normally suppress pathogens; this compromised specific immunity is accompanied by a compensatory increase in components of the innate immune system (see also Goodkin and Appels, 1997). Some evidence suggests that inflammatory processes may cause central nervous system responses as
43. Psychoneuroimmunological Pathways Involved in Acute Coronary Syndromes
well as psychological states similar to depression and exhaustion (Dantzer and Kelley, 1989; Goodkin et al., 1997). Animal models of sickness behavior, induced by administration of cytokines, may provide new insights into the bi-directional relationships between immune system parameters and depressive symptomatology. The immune system (e.g., IL-1 and TNF-α) can indeed activate the HPA axis (Dantzer et al., 1989; Sapolsky et al., 1987). This negative feedback loop may account for the immunosuppressive state in episodic risk factors. Evidence of immunological influences on the central nervous system is supported by observations that cytokines mediate non-specific responses to infection, such as malaise, fatigue, fever, slow wave sleep, apathy, and irritability. Fatigue and malaise are common side effects of the parenteral administration of certain cytokines. For example, systemic administration of IL-1 increases plasma levels of glucocorticoids and ACTH (Dantzer et al., 1989). Because elevated glucocorticoids inhibit the synthesis of cytokines (IL-1 and IL-2), a negative feedback loop may exist between cytokines and the neuroendocrine system. Under normal circumstances, this feedback loop downregulates the inflammatory response and reduces proliferation of lymphocytes (Dantzer et al., 1989). Sickness behavior shares common characteristics with depression and exhaustion, and is characterized by reduced social and sexual behaviors, increased pain sensitivity, reduced activity levels, depressed mood, cognitive alterations, and decreased food and liquid intake. Thus, sickness behavior may have an adaptive function by conserving energy resources. More research is needed to establish the clinical importance of the bi-directional relationship between immune system parameters and brain function, particularly in vulnerable populations with depressive symptoms (Tracey, 2002). 4. Summary and Interpretation The relationship between depression and immune system parameters is bi-directional, such that central nervous system correlates of depressive symptoms result in immune system changes, and vice versa. Immunosuppression of the specific adaptive immune system is well documented in episodic psychological factors, particularly depression. Some of the correlates of depression (e.g., increased levels of leukocytes, cytokines, and antibodies to viruses) are also associated with elevated risk for acute coronary syndromes. These markers of a pro-inflammatory state in depression may promote CAD progression by enhancing macrophage and lipid deposition processes at early stages of atherosclerosis. More importantly, low-grade inflammation may alter the stability of atherosclerotic
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plaques and increase the risk of plaque rupture, leading to acute coronary syndromes. The latter mechanism is probably more important since the duration of episodic risk factors may not be long enough to initiate and sustain an atherosclerotic process. This notion is further supported by the finding that although depression may have long-term predictive values for adverse CAD outcomes, no consistent associations have been found between episodic risk factors and CAD severity. In addition, the predictive value of episodic risk factors decreases when the follow-up exceeds 2 years. These factors indicate that plaque activation, rather than gradual CAD progression, may be involved in the adverse risk associated with episodic psychological risk factors. Studies relating depression and other episodic risk factors to biological measures relevant to the pathophysiology of CAD are limited in the sense that no inferences regarding causality can be made because of the correlational nature of the study designs. Because of the recurring nature of episodic risk factors, longitudinal studies may further our understanding of the time-trajectory of immunological and psychological factors in patients at risk for acute coronary syndromes.
C. Acute Psychological Risk Factors 1. Relationship with Coronary Disease Epidemiological studies suggest that acute outbursts of anger as well as natural disasters can provoke acute coronary syndromes (Dobson et al., 1991; Meisel et al., 1991; Mittleman et al., 1995; Trichopoulos et al., 1983). As described in “Stages of Coronary Atherosclerosis and the Onset of Acute Coronary Syndromes,” coronary syndromes often result from cardiac ischemia and/or arrhythmias. Laboratory and field studies have demonstrated that mental activities and emotions are potent triggers of myocardial ischemia (Krantz et al., 1996) and life-threatening arrhythmias (Verrier, 1987). Specifically, 30–60% of patients with stable CAD develop ischemic responses to laboratory tasks such as public speech, anger recall, mental arithmetic with harassment, and the Stroop color word test (Krantz et al., 1996). Moreover, transient ambulatory ischemia is triggered by both mental and physical activities and is more prevalent among patients who demonstrate mental stress-induced ischemia in the laboratory (Blumenthal et al., 1995). 2. Pathophysiological Mechanisms Acute mental arousal is associated with a shift toward increased activity of the sympathetic nervous system and a decreased parasympathetic (vagal)
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activity, accompanied by elevated circulating catecholamines and increased cardiac demand (i.e., elevated blood pressure, heart rate, and cardiac contractility). The exact pattern of physiological and biological responses to acute emotional and mental challenges is determined by multiple factors, including demographic characteristics, task characteristics, presence of comorbidity, and cardiovascular risk factors. Clinical consequences of these acute psychological risk factors in patients with cardiac disease may result from increased cardiac demand and decreased coronary supply (Krantz et al., 1996). Markers of decreased coronary supply in response to mental challenge tasks include impaired dilation of the coronary vessels ( Kop et al., 2001; Yeung et al., 1991), decreases in plasma volume (Patterson et al., 1993), and increased platelet activity and blood clotting tendency (Jern et al., 1989; Patterson et al., 1995). The resulting imbalance between increased cardiac demand and decreased coronary blood supply may potentially lead to cardiac ischemia. The mechanisms accounting for cardiac arrhythmias induced by mental arousal have been reviewed elsewhere (Verrier, 1987) and include the autonomic nervous system, particularly vagal withdrawal. Furthermore, hemodynamic responses to acute mental and physical challenges can lead to plaque rupture, and increased platelet aggregation may promote acute coronary thrombus formation. 3. Immune System Correlates Lymphocytes have receptors for neurohormones associated with the sympathetic-adreno-medullary and hypothalamic-pituitary-adrenal (HPA) axes. The effects of acute mental arousal on the immune system are complex (Ader et al., 1995), and both increased and decreased numbers of lymphocytes and NK cells have been reported. Most studies show increases in B-cells and CD8+ T-cells and decreases in CD4+ T-cells in response to acute challenge tasks. Cytokines (IL-1α and IL-2) are reported to increase with psychological challenge (e.g., undergoing coronary angioplasty Schulte et al., 1994), suggesting at least a partial activation of the immune system (see also Dantzer et al., 1989). However, both task characteristics (e.g., predictability of the stimulus, social interaction component) and subject characteristics (e.g., concomitant chronic psychological disorder, disease status, and health behaviors) affect the direction and magnitude of the acute immune response to mental challenges. Consistent with the notion of immune activation is that acute phase proteins (CRP and fibrinogen) (Dugue et al., 1993; Jern et al., 1989; Kop et al., 2004), as well as adhesion molecules (Mills and Dimsdale, 1996), increase
during mental challenge tasks. Modulation of autonomic nervous system activity by surgical or pharmacological procedures elicits disparate responses of the immune system. The effects of acute laboratory challenge tasks on immune parameters are also mediated in part by the increased hemoconcentration following laboratory tasks (Marsland et al., 1997). It has been demonstrated that the acute immune system response may be exaggerated among individuals with cardiovascular risk factors, such as hypertension. Patients with hypertension display larger numbers of circulating white blood cells compared with normotensives (Mills et al., 2003). Hypertensives also show a greater increase in the number of circulating CD3+CD8+, CD8+CD62L T-cells, as well as increased expression of the endothelial CD11a ligand, ICAM-1, suggesting that patients with hypertension exhibit increased leukocyte adhesion (Mills et al., 2003). Further support of endothelial activation in the acute stress response is provided by a study by Bosch et al. indicating a selective increase in T-cell expression of chemokines (CXCR2, CXCR3, and CCR5), independent of the total number of T lymphocytes expressed (Bosch et al., 2003). Analyses of individual differences have further demonstrated sympathetic cardiac reactivity involvement in T-cell, but not monocyte, activation. Thus, acute mental challenges may promote the recruitment of circulating immune cells into the endothelium and, therefore, accelerate atherosclerotic plaque formation and potentially contribute to the onset of acute coronary syndromes. Inflammation and coagulation are related processes, but the mechanisms by which inflammatory factors promote atherosclerosis do not necessarily involve thrombotic processes. Some evidence suggests that the immune system changes that follow sympathetic activation precede the HPA response (Landmann et al., 1984). In general, the magnitude of the immunosuppressive response is correlated with the hemodynamic increase (Benschop et al., 1995; Benschop et al., 1998; Herbert et al., 1994; Zakowski et al., 1992) which probably reflects increased sympathetic nervous system activation as a common factor in the triggers of acute coronary syndromes. 4. Summary and Interpretation Acute psychological challenges induce a partial activation of the immune system. Although the overall acute challenge response is quite complex, increased levels in response to mental challenge tasks have been documented for CD8+ T-cells, cytokines, acute phase proteins (e.g., C-reactive protein and fibrinogen), and circulating adhesion molecules. These immune system
43. Psychoneuroimmunological Pathways Involved in Acute Coronary Syndromes
changes may be relevant with respect to the triggering of acute coronary syndromes because increased immune activation may lead to activation and subsequent rupture of vulnerable atherosclerotic plaques (Libby et al., 1997). Moreover, immune activation may directly interact with several blood clotting factors and indirectly promote thrombus formation and coronary vasoconstriction by interfering with normal endothelial function. Recent evidence suggests that short-term activation of the immune system by Salmonella typhi vaccine results in negative mood, which was correlated with the magnitude of IL-6 increase (Wright et al., 2005). Thus, as in episodic risk factors, bidirectional pathways may also be involved in the acute psychological triggers of acute coronary syndromes. Acute immune system activation may further result in reduced perfusion of coronary arteries distal to the culprit lesion and decrease perfusion of the microcirculation (Entman et al., 1993). The immune activation component of the acute response to challenges, therefore, may be more important than the immunosuppressive component in the pathophysiology of acute coronary syndromes.
D. Interaction between Psychological Factors and Immune System Parameters as Risk Indicators for Acute Coronary Syndromes The reviewed evidence regarding chronic, episodic, and acute psychological risk factors for coronary syndromes may have distinct consequences for the immunological components of CAD progression and its clinical manifestations as acute coronary syndromes. Figure 2 presents a simplified diagram that distinguishes among (1) psychological factors, (2) physiological and immunological correlates, and (3) the atherosclerotic consequences. It is hypothesized that physiological and immunological correlates of psychological risk factors are involved in the progression of CAD as well as the transition from advanced atherosclerotic lesions into acute coronary syndromes (lower part of Figure 2). At the psychological level, chronic factors increase the likelihood of developing episodic and acute risk factors. For example, exhaustion is considered to be the end-stage of prolonged uncontrollable psychological distress (Appels, 1990; Selye, 1977). Consequently, exhaustion is more prevalent among hostile individuals. Several studies have found additive adverse cardiovascular effects of exhaustion superimposed on these chronic sources of psychological distress (Falger and Schouten, 1992; Kop, 1997; Mendes de Leon et al., 1996). Furthermore, chronic psychological risk factors
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for coronary syndromes are associated with elevated responsiveness to acute challenges (Suarez et al., 1991). These inter-relations of psychological risk factors provide a framework to conceptualize the “clustering” of psychological risk factors as they relate to acute coronary syndromes (Rozanski et al., 1999; Suls et al., 2005). 1. Chronic Psychological Risk Factors Chronic psychological risk factors are involved in CAD progression and its clinical manifestations by two main pathways: elevations of adverse cardiovascular background factors and exaggerated responsiveness to acute challenges. The effects of chronic psychological risk factors on background factors are primarily mediated by increased sympathetic tone (Williams et al., 1991) and adverse health behaviors (Suarez et al., 1991). An important result is development of an adverse lipid profile and lipid oxidation. The immunological correlates of chronic psychological factors may be related to CAD progression by way of decreased phagocytic function of macrophages, higher incidence of infectious disease, and elevated proinflammatory markers. These immunological consequences may promote the onset of early atherosclerotic lesions and their progression into more severe vascular damage. Furthermore, hyperreactivity may promote early atherosclerosis by increasing vessel damage but is primarily relevant to the onset of acute coronary syndromes. Increased responsiveness of immune system parameters may be one mechanism by which chronic psychological risk factors elevate risk of plaque rupture, thrombus formation and, consequently, acute coronary syndromes. Latent infections may play a role in this two-way involvement of chronic psychological factors. 2. Episodic Psychological Risk Factors Episodic psychological risk factors are associated with a sympathetic/parasympathetic imbalance. Among the episodic risk factors, research has focused primarily on depression and exhaustion. The onset of initial depressive episodes is often triggered by psychological stressful situations, but some evidence suggests that these precipitating events are less apparent at later episodes of the depressive disorder (Gold et al., 1988). Assuming an immunosuppressed state in episodic risk factors, it could be argued that activation of latent viruses in atherosclerotic plaques is facilitated by systemic factors. An example of such a process is that glucocorticoids enhance transcription (reactivation) of latent herpesvirus (Libby et al., 1997). Dantzer et al. (1989) have postulated a bi-directional relationship between immune system and psychological
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Psychological Risk Factors Acute Anger Mental activity
Immune System Parameters
Partial immune activation
Coronary Disease Outcome
Coronary Artery Pathology
Acute Coronary Syndromes Myocardial Infarction Sudden Cardiac Death
thrombus
thinning cap
Episodic Depression Exhaustion
Immune suppression Activation of infections Pro-inflammatory cytokines
Severe CAD luminal narrowing
plaque activation
SMC over plaque
macrophages
Intermediate CAD foam cells, minimal stenosis Chronic Low SES Personality (Hostility)
Macrophage phagocytosis Exposure to infections
Early CAD T-cell and macrophage recruitment
endothelial dysfunction cytokine activation
lumen
monocyte deposition
FIGURE 2 Pathophysiological model of the relationships among chronic, episodic, and acute psychological risk factors for coronary syndromes. Acute psychological factors result in physiological responses leading to cardiac effects (increased cardiac demand, decreased coronary supply) as well as partial immune activation that may cause plaque instability. In vulnerable patients, these cardiac effects may have pathophysiological results, including myocardial ischemia, thrombus formation, and plaque rupture. Episodic psychological factors have physiological correlates that are involved in the progression of severe coronary disease to acute coronary syndromes. Chronic psychological factors promote the onset of early atherosclerosis, especially in the setting of genetic vulnerability, adverse health behaviors, and other environmental risk factors. In addition, chronic psychological factors are related to increased frequency and elevated responsiveness to acute psychological factors and promote the risk of developing episodic factors. (HR = heart rate; BP = blood pressure). (Modified from Kop and Cohen, 2001).
characteristics (Dantzer et al., 1989). Moreover, infections can cause characteristics of a classical stress response, including increased glucocorticoid levels and enhanced catecholamine turnover (Dantzer et al., 1989). Thus, episodic factors may promote cardiac disease progression by their immunosuppressive correlates, which are important primarily at the early stages of CAD, and by their associated elevated cytokines, which are crucial at later disease stages in the transition from advanced coronary lesions to acute coronary syndromes. The hypothesis that proinflammatory cytokines primarily affect fatigue and energy depletion and that depression will primarily develop among individuals in whom the immune response coincides with elevated HPA axis activity requires further investigation. 3. Acute Psychological Risk Factors Acute psychological risk factors trigger acute coronary syndromes primarily by the ischemic and/or
arrhythmic consequences of increased autonomic nervous system activity, including cardiac demand (increased blood pressure, heart rate, and cardiac contractility) and decreased coronary supply (coronary vasoconstriction, decreased plasma volume). The immediate immune system response to acute psychological factors includes a partial immune activation. Immune activation plays a direct and amplifying role in plaque disruption and thrombus formation. Immune activation may also promote cardiac ischemia by effecting endothelial function and promoting vasoconstriction. Moreover, active infectious states may be related to increased cardiac demand and promote the onset of ischemia.
III. CONCLUSIONS AND FUTURE DIRECTIONS This chapter provides support for an integrative model of psychoneuroimmunological risk factors for
43. Psychoneuroimmunological Pathways Involved in Acute Coronary Syndromes
acute coronary syndromes. Future research and clinical applications of these biobehavioral pathways may develop in the following areas: (1) the importance of obesity, adipose tissue, and the metabolic syndrome in the association of psychological and immune systemrelated risk factors for acute coronary syndromes; (2) immune system correlates of cardiovascular pharmacological interventions; and (3) the importance of psychoneuroimmunological processes in non-pharmacological psychological and behavioral interventions. Recent evidence supports the role of obesity in the relationship between depression and inflammatory markers. In a population-based study of 3,204 men, a significant association between increased CRP among obese (body mass index >30 kg/m2) versus non-obese individuals was primarily observed among depressed individuals (obesity × depression interaction p = .021) (Ladwig et al., 2003). Another study demonstrates that controlling for weight substantially attenuates the relationship between depressive symptoms and inflammatory markers (Douglas et al., 2004). It is important, therefore, to consider weight status when examining psychoneuroimmunological processes in coronary disease. Adipose tissue produces IL-6 and TNF-α in obese individuals and those with metabolic syndrome. Adipokines are cytokines of adipose tissue (including leptin, adiponectin, and resistin) that may increase systemic inflammatory responses. Using statistical structural equation analysis, Miller et al. found support for a model in which depressive symptoms promote weight accumulation, which in turn activates an inflammatory response through increased adipose tissue release of IL-6 and leptin-induced upregulation of IL-6 release by leukocytes (Miller et al., 2003). More research is needed to clarify the importance of obesity and other related adverse health behaviors (e.g., physical inactivity, smoking status) in the psychoneuroimmunological mechanisms involved in acute coronary syndromes. Pharmacological intervention strategies aimed at the immune system component of recurrent cardiac events have focused on reducing immune activation in patients with established atherosclerosis, primarily in the setting of preventing coronary artery re-narrowing after percutaneous coronary interventions (coronary angioplasty). The effects of corticosteroids (i.e., methylprednisolone) and angiopeptin have been examined because angioplasty induces vessel injury resulting in immune activation and subsequent intimal cell growth. Glucocorticoids have diminishing effects on monocyte influx and decreasing leukocyte activity. However, corticosteroid interventions have been ineffective in preventing restenosis (Pepine et al., 1990; Stone et al.,
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1989). Furthermore, corticosteroid administration shortly after myocardial infarction results in adverse clinical outcomes, including a larger infarct size (Roberts et al., 1976). Simple antibiotics, in addition to lipid-lowering drugs and anti-hypertensive medication, may be effective in reducing recurrent cardiac events (Gupta et al., 1997). However, azithromyzin trials have been largely unsuccessful in reducing cardiac events among CAD patients. The benefits of pharmacological interventions targeted at the immune system components of atherosclerosis in secondary events have at best statistically significant results but the clinical success (i.e., effect size) is relatively limited. Recent developments in percutaneous coronary interventions have demonstrated substantial clinical benefits from intra-coronary stents coated with immunosuppressive agents (for review, see Fattori and Piva, 2003). These agents reduce intimal hyperplasia by inhibiting growth factors and are associated with substantial reduced coronary restenosis and recurrent event rates. The role of psychological factors and health behaviors has not been examined systematically in this context. Pharmacological interventions with primary targets other than the immune system (e.g., lipid-lowering statins and aspirin) may have beneficial effects that are partly mediated via immunological processes (Ikonomidis et al., 1999; Ridker et al., 2005). Some evidence indicates that the beneficial effects of anti-oxidant therapy (e.g., probucol and vitamin E) are meditated by their anti-inflammatory effects, possibly by reducing the upregulation of adhesion molecules and smooth muscle cell proliferation (Yokoi et al., 1997). Suarez (2003) has demonstrated that use of multi-vitamins attenuates the association between negative affect and IL-6 (Suarez, 2003). Future studies may shed further light on the interaction between psychological factors and immune system components of pharmacotherapy outcome. Several non-pharmacological psychological intervention studies in patients with CAD indicate positive effects of relaxation (Appels et al., 1997; van Dixhoorn et al., 1987), stress management (Blumenthal et al., 1997), Type A behavior/hostility intervention (Friedman et al., 1986), and social support (FrasureSmith and Prince, 1985; for review, see Linden et al., 1996). The overall pattern of results suggests a twofold higher incidence of cardiac events among patients who do not receive psychosocial intervention, but negative studies are reported as well (e.g., Appels et al., 2005; Berkman et al., 2003; Frasure-Smith et al., 1997). Intervention studies in cardiac patients generally result in improved health behaviors and reduced cardiovascular risk profiles (e.g., lipid profile and
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blood pressure). However, because of the multiple levels of intervention, the mechanisms underlying these positive effects are not well understood. Theoretically, it is possible that part of the beneficial effects of behavioral treatment programs in coronary disease patients is mediated by immunological consequences of such interventions. These psychoneuroimmunological pathways may be of particular importance in chronic cardiac conditions such as heart failure in which the burden of disease is high and multiple immunological, neurohormonal, and psychosocial processes are interrelated in the prediction of adverse outcomes (Denollet et al., 2003; Pasic et al., 2003). Given the role of inflammatory processes at all stages of coronary disease progression and the known relationships between psychological factors and immune system function, future research in this area is likely to provide intriguing new information that may improve the development of targeted behavioral interventions.
Ascknowledgments The opinions and assertions expressed herein are those of the authors and are not to be construed as reflecting the views of the USUHS or the U.S. Department of Defense. Preparation of this manuscript is supported by a grant from the NIH (HL66149).
References Adams, D. O. (1994). Molecular biology of macrophage activation: a pathway whereby psychosocial factors can potentially affect health. Psychosom. Med., 56, 316–327. Ader, R., Cohen, N., and Felten, D. (1995). Psychoneuroimmunology: interactions between the nervous system and the immune system. Lancet, 345, 99–103. Alonzo, A. A., Simon, A. B., and Feinleib, M. (1975). Prodromata of myocardial infarction and sudden death. Circulation, 52, 1056–1062. Ambrose, J. A., Tannenbaum, M. A., Alexopoulos, D., HjemdahlMonsen, C. E., Leavy, J., Weiss, M. et al. (1988). Angiographic progression of coronary artery disease and the development of myocardial infarction. J. Am. Coll. Cardiol., 12, 56–62. Appels, A. (1990). Mental precursors of myocardial infarction. British Journal of Psychiatry, 156, 465–471. Appels, A. (1997). Depression and coronary heart disease: observations and questions. Journal of Psychosomatic Research, 43, 443–452. Appels, A., Bar, F., Lasker, J., Flamm, U., and Kop, W. (1997). The effect of a psychological intervention program on the risk of a new coronary event after angioplasty: a feasibility study. Journal of Psychosomatic Research, 43, 209–217. Appels, A., Bar, F., Van Der, P. G., Erdman, R., Assman, M., Trijsburg, W. et al. (2005). Effects of treating exhaustion in angioplasty patients on new coronary events: results of the randomized exhaustion intervention trial (exit). Psychosom. Med., 67, 217–223. Appels, A., Bar, F. W., Bar, J., Bruggeman, C., and De Baets, M. (2000). Inflammation, depressive symptomatology, and coronary artery disease. Psychosom. Med., 62, 601–605.
Appels, A., Kop, W. J., Meesters, C. M., Markusse, R., Golombeck, B., and Falger, P. R. (1994). Vital exhaustion and the acute coronary syndromes. In S. Maes, H. Leventhal, and M. Johnston (Eds.), International review of health psychology (pp. 65–95). New York: John Wiley and Sons, Ltd. Appels, A., and Mulder, P. (1988). Excess fatigue as a precursor of myocardial infarction. Eur. Heart J., 9, 758–764. Appels, A., and Otten, F. (1992). Exhaustion as precursor of cardiac death. British Journal of Clinical Psychology, 31, 351–356. Barefoot, J. C., Dahlstrom, W. G., and Williams, R. B. (1983). Hostility, Chd incidence, and total mortality: a 25-year follow-up study of 255 physicians. Psychosom. Med., 45, 59–63. Beck, J., Garcia, R., Heiss, G., Vokonas, P. S., and Offenbacher, S. (1996). Periodontal disease and cardiovascular disease. Journal of Periodontology, 67, 1123–1137. Benschop, R. J., Geenen, R., Mills, P. J., Naliboff, B. D., Kiecolt-Glaser, J. K., Herbert, T. B. et al. (1998). Cardiovascular and immune responses to acute psychological stress in young and old women: a meta-analysis. Psychosom. Med., 60, 290–296. Benschop, R. J., Godaert, G. L., Geenen, R., Brosschot, J. F., De Smet, M. B., Olff, M. et al. (1995). Relationships between cardiovascular and immunological changes in an experimental stress model. Psychological Medicine, 25, 323–327. Benschop, R. J., Rodriguez-Feuerhahn, M., and Schedlowski, M. (1996). Catecholamine-induced leukocytosis: early observations, current research, and future directions. Brain Behav. Immun., 10, 77–91. Berkman, L. F., Blumenthal, J., Burg, M., Carney, R. M., Catellier, D., Cowan, M. J. et al. (2003). Effects of treating depression and low perceived social support on clinical events after myocardial infarction: the Enhancing Recovery In Coronary Heart Disease Patients (ENRICHD) randomized trial. JAMA, 289, 3106–3116. Bevilacqua, M. P., Schleef, R. R., Gimbrone, M. A., Jr., and Loskutoff, D. J. (1986). Regulation of the fibrinolytic system of cultured human vascular endothelium by interleukin 1. J. Clin. Invest., 78, 587–591. Black, P. H. (2003). The inflammatory response is an integral part of the stress response: implications for atherosclerosis, insulin resistance, type II diabetes and metabolic syndrome X. Brain Behav. Immun., 17, 350–364. Blumenthal, J. A., Jiang, W., Babyak, M. A., Krantz, D. S., Frid, D. J., Coleman, R. E. et al. (1997). Stress management and exercise training in cardiac patients with myocardial ischemia. Effects on prognosis and evaluation of mechanisms. Archives of Internal Medicine, 157, 2213–2223. Blumenthal, J. A., Jiang, W., Waugh, R. A., Frid, D. J., Morris, J. J., Coleman, R. E. et al. (1995). Mental stress-induced ischemia in the laboratory and ambulatory ischemia during daily life. Association and hemodynamic features. Circulation, 92, 2102–2108. Bosch, J. A., Berntson, G. G., Cacioppo, J. T., Dhabhar, F. S., and Marucha, P. T. (2003). Acute stress evokes selective mobilization of T cells that differ in chemokine receptor expression: a potential pathway linking immunologic reactivity to cardiovascular disease. Brain Behav. Immun., 17, 251–259. Braunwald, E. (1988). Heart disease (3d ed.). Philadelphia: WB Saunders. Bruce, E. C., and Musselman, D. L. (2005). Depression, alterations in platelet function, and ischemic heart disease. Psychosom. Med., 67 (Suppl 1), S34–S36. Bruschke, A. V., Kramer, J. R., Jr., Bal, E. T., Haque, I. U., Detrano, R. C., and Goormastic, M. (1989). The dynamics of progression of coronary atherosclerosis studied in 168 medically treated patients who underwent coronary arteriography three times. Am. Heart J., 117, 296–305.
43. Psychoneuroimmunological Pathways Involved in Acute Coronary Syndromes Caligiuri, G., Liuzzo, G., Biasucci, L. M., and Maseri, A. (1998). Immune system activation follows inflammation in unstable angina: pathogenetic implications. J. Am. Coll. Cardiol., 32, 1295–1304. Carney, R. M., Freedland, K. E., Rich, M. W., and Jaffe, A. S. (1995). Depression as a risk factor for cardiac events in established coronary heart disease: a review of possible mechanisms. Ann. Behav. Med., 17, 142–149. Carney, R. M., Freedland, K. E., and Veith, R. C. (2005). Depression, the autonomic nervous system, and coronary heart disease. Psychosom. Med., 67 (Suppl 1), S29–S33. Cercek, B., Shah, P. K., Noc, M., Zahger, D., Zeymer, U., Matetzky, S. et al. (2003). Effect of short-term treatment with azithromycin on recurrent ischaemic events in patients with acute coronary syndrome in the Azithromycin in Acute Coronary Syndrome (AZACS) trial: a randomised controlled trial. Lancet, 361, 809–813. Cesari, M., Penninx, B. W., Newman, A. B., Kritchevsky, S. B., Nicklas, B. J., Sutton-Tyrrell, K. et al. (2003). Inflammatory markers and onset of cardiovascular events: results from the health ABC study. Circulation, 108, 2317–2322. Christensen, A. J., Edwards, D. L., Wiebe, J. S., Benotsch, E. G., McKelvey, L., Andrews, M. et al. (1996). Effect of verbal selfdisclosure on natural killer cell activity: moderating influence of cynical hostility. Psychosom. Med., 58, 150–155. Danesh, J., Collins, R., and Peto, R. (1997). Chronic infections and coronary heart disease: is there a link? Lancet, 350, 430–436. Danesh, J., Wheeler, J. G., Hirschfield, G. M., Eda, S., Eiriksdottir, G., Rumley, A. et al. (2004). C-reactive protein and other circulating markers of inflammation in the prediction of coronary heart disease. New England Journal of Medicine, 350, 1387–1397. Dantzer, R., and Kelley, K. W. (1989). Stress and immunity: an integrated view of relationships between the brain and the immune system. Life Sciences, 44, 1995–2008. Davies, M. J., and Thomas, A. (1984). Thrombosis and acute coronary-artery lesions in sudden cardiac ischemic death. New England Journal of Medicine, 310, 1137–1140. Denollet, J., Conraads, V. M., Brutsaert, D. L., De Clerck, L. S., Stevens, W. J., and Vrints, C. J. (2003). Cytokines and immune activation in systolic heart failure: the role of type D personality. Brain Behav. Immun., 17, 304–309. Dobson, A. J., Alexander, H. M., Malcolm, J. A., Steele, P. L., and Miles, T. A. (1991). Heart attacks and the Newcastle earthquake. Med. J Aust., 155, 757–761. Douglas, K. M., Taylor, A. J., and O’Malley, P. G. (2004). Relationship between depression and C-reactive protein in a screening population. Psychosom. Med., 66, 679–683. Dugue, B., Leppanen, E. A., Teppo, A. M., Fyhrquist, F., and Grasbeck, R. (1993). Effects of psychological stress on plasma interleukins-1 beta and 6, C-reactive protein, tumour necrosis factor alpha, anti-diuretic hormone and serum cortisol. Scandinavian Journal of Clinical and Laboratory Investigation, 53, 555–561. Empana, J. P., Sykes, D. H., Luc, G., Juhan-Vague, I., Arveiler, D., Ferrieres, J. et al. (2005). Contributions of depressive mood and circulating inflammatory markers to coronary heart disease in healthy European men: the prospective epidemiological study of myocardial infarction (prime). Circulation, 111, 2299–2305. Engebretson, T. O., and Matthews, K. A. (1992). Dimensions of hostility in men, women, and boys: relationships to personality and cardiovascular responses to stress. Psychosom. Med., 54, 311–323. Engstrom, G., Hedblad, B., Stavenow, L., Tyden, P., Lind, P., Janzon, L. et al. (2004). Fatality of future coronary events is related to
939
inflammation-sensitive plasma proteins: a population-based prospective cohort study. Circulation, 110, 27–31. Entman, M. L., and Ballantyne, C. M. (1993). Inflammation in acute coronary syndromes. Circulation, 88, 800–803. Fahdi, I. E., Gaddam, V., Garza, L., Romeo, F., and Mehta, J. L. (2003). Inflammation, infection, and atherosclerosis. Brain Behav. Immun., 17, 238–244. Falger, P. R., and Schouten, E. G. (1992). Exhaustion, psychological stressors in the work environment, and acute myocardial infarction in adult men. Journal of Psychosomatic Research, 36, 777–786. Falk, E., Shah, P. K., and Fuster, V. (1995). Coronary plaque disruption. Circulation, 92, 657–671. Fattori, R., and Piva, T. (2003). Drug-eluting stents in vascular intervention. Lancet, 361, 247–249. Frasure-Smith, N., Lesperance, F., Prince, R. H., Verrier, P., Garber, R. A., Juneau, M. et al. (1997). Randomised trial of home-based psychosocial nursing intervention for patients recovering from myocardial infarction. Lancet, 350, 473–479. Frasure-Smith, N., and Prince, R. (1985). The ischemic heart disease life stress monitoring program: impact on mortality. Psychosom. Med., 47, 431–445. Fricchione, G. L., Bilfinger, T. V., Hartman, A., Liu, Y., and Stefano, G. B. (1996). Neuroimmunologic implications in coronary artery disease. Advances in Neuroimmunology, 6, 131–142. Friedman, M., and Rosenman, R. (1959). Association of specific overt behavior pattern with blood and cardiovascular findings: blood cholesterol level, blood clotting time, incidence of Arcis senilis and clinical coronary artery disease. JAMA, 169, 1286–1296. Friedman, M., Thoresen, C. E., Gill, J. J., Ulmer, D., Powell, L. H., Price, V. A. et al. (1986). Alteration of type A behavior and its effect on cardiac recurrences in post myocardial infarction patients: summary results of the recurrent coronary prevention project. Am. Heart J., 112, 653–665. Fuster, V., Badimon, L., Badimon, J. J., and Chesebro, J. H. (1992a). The pathogenesis of coronary artery disease and the acute coronary syndromes (1). New England Journal of Medicine, 326, 242–250. Fuster, V., Badimon, L., Badimon, J. J., and Chesebro, J. H. (1992b). The pathogenesis of coronary artery disease and the acute coronary syndromes (2). New England Journal of Medicine, 326, 310–318. Gidron, Y., Armon, T., Gilutz, H., and Huleihel, M. (2003). Psychological factors correlate meaningfully with percent-monocytes among acute coronary syndrome patients. Brain Behav. Immun., 17, 310–315. Giroud, D., Li, J. M., Urban, P., Meier, B., and Rutishauer, W. (1992). Relation of the site of acute myocardial infarction to the most severe coronary arterial stenosis at prior angiography. Am. J. Cardiol., 69, 729–732. Gold, P. W., Goodwin, F. K., and Chrousos, G. P. (1988). Clinical and biochemical manifestations of depression. relation to the neurobiology of stress (1). New England Journal of Medicine, 319, 348–353. Goodkin, K., and Appels, A. (1997). Behavioral-neuroendocrineimmunologic interactions in myocardial infarction. Med. Hypotheses, 48, 209–214. Grayston, J. T., Kronmal, R. A., Jackson, L. A., Parisi, A. F., Muhlestein, J. B., Cohen, J. D. et al. (2005). Azithromycin for the secondary prevention of coronary events. New England Journal of Medicine, 352, 1637–1645. Gupta, S., Leatham, E. W., Carrington, D., Mendall, M. A., Kaski, J. C., and Camm, A. J. (1997). Elevated Chlamydia pneumoniae antibodies, cardiovascular events, and azithromycin in male survivors of myocardial infarction. Circulation, 96, 404–407.
940
V. Psychoneuroimmunology and Pathophysiology
Gurfinkel, E. P., De La Fuente, R. L., Mendiz, O., and Mautner, B. (2002). Influenza vaccine pilot study in acute coronary syndromes and planned percutaneous coronary interventions: the Flu Vaccination Acute Coronary Syndromes (FLUVACS) study. Circulation, 105, 2143–2147. Hansson, G. K. (2005). Inflammation, atherosclerosis, and coronary artery disease. New England Journal of Medicine, 352, 1685–1695. Hansson, G. K., Holm, J., Holm, S., Fotev, Z., Hedrich, H. J., and Fingerle, J. (1991). T lymphocytes inhibit the vascular response to injury. Proc. Natl. Acad. Sci. USA, 88, 10530–10534. Herbert, T. B., and Cohen, S. (1993a). Depression and immunity: a meta-analytic review. Psychological Bulletin, 113, 472–486. Herbert, T. B., and Cohen, S. (1993b). Stress and immunity in humans: a meta-analytic review. Psychosom. Med., 55, 364–379. Herbert, T. B., Cohen, S., Marsland, A. L., Bachen, E. A., Rabin, B. S., Muldoon, M. F. et al. (1994). Cardiovascular reactivity and the course of immune response to an acute psychological stressor. Psychosom. Med., 56, 337–344. Hinderliter, A. L., Light, K. C., Girdler, S. S., Willis, P. W., and Sherwood, A. (1996). Blood pressure responses to stress: relation to left ventricular structure and function. Ann. Behav. Med., 18, 61–66. Ikonomidis, I., Andreotti, F., Economou, E., Stefanadis, C., Toutouzas, P., and Nihoyannopoulos, P. (1999). Increased proinflammatory cytokines in patients with chronic stable angina and their reduction by aspirin. Circulation, 100, 793–798. Jern, C., Eriksson, E., Tengborn, L., Risberg, B., Wadenvik, H., and Jern, S. (1989). Changes of plasma coagulation and fibrinolysis in response to mental stress. Thrombosis and Haemostasis, 62, 761–771. Jeron, A., Kaiser, T., Straub, R. H., Weil, J., Riegger, G. A., and Muders, F. (2003). Myocardial Il-6 regulation by neurohormones—an in vitro superfusion study. Brain Behav. Immun., 17, 245–250. Kibler, J. L., and Ma, M. (2004). Depressive symptoms and cardiovascular reactivity to laboratory behavioral stress. Int. J. Behav. Med., 11, 81–87. Kol, A., and Libby, P. (1998). The mechanisms by which infectious agents may contribute to atherosclerosis and its clinical manifestations. Trends Cardiovasc. Med., 8, 191–199. Kop, W. J. (1994). The predictive value of vital exhaustion in the clinical course after coronary angioplasty. Maastricht: Datawyse. Kop, W. J. (1997). Acute and chronic psychological risk factors for coronary syndromes: moderating effects of coronary artery disease severity. Journal Psychosom. Res., 43, 167–181. Kop, W. J. (1999). Chronic and acute psychological risk factors for clinical manifestations of coronary artery disease. Psychosom. Med., 61, 476–487. Kop, W. J. (2003). The integration of cardiovascular behavioral medicine and psychoneuroimmunology: new developments based on converging research fields. Brain Behav. Immun., 17, 233–237. Kop, W. J., Appels, A., Howell, R. H., Krantz, D. S., Bairey Merz, C. N., Caravalho, J. Jr. et al. (1997). Relationship between vital exhaustion and stress-induced myocardial ischemia. Ann. Behav. Med., 19, 159. Kop, W. J., Appels, A., Mendes De Leon, C. F., and Bar, F. W. (1996). The relationship between severity of coronary artery disease and vital exhaustion. Journal of Psychosomatic Research, 40, 397–405. Kop, W. J., Appels, A. P., Mendes De Leon, C. F., De Swart, H., and Bar, F. W. (1993). The effect of successful coronary angioplasty on feelings of exhaustion. Int. J. Cardiol., 42, 269–276. Kop, W. J., Appels, A. P., Mendes De Leon, C. F., De Swart, H. B., and Bar, F. W. (1994). Vital exhaustion predicts new cardiac
events after successful coronary angioplasty. Psychosom. Med., 56, 281–287. Kop, W. J., and Cohen, N. (2001). Psychological risk factors and immune system involvement in cardiovascular disease. In R. Ader, D. L. Felten, and N. Cohen (Eds.), Psychoneuroimmunology (3rd ed., pp. 525–544). San Diego: Academic Press. Kop, W. J., and Gottdiener, J. S. (2005). The role of immune system parameters in the relationship between depression and coronary artery disease. Psychosom. Med., 67, 537–541. Kop, W. J., Gottdiener, J. S., Tangen, C. M., Fried, L. P., McBurnie, M. A., Walston, J. et al. (2002). Inflammation and coagulation factors in persons >65 years of age with symptoms of depression but without evidence of myocardial ischemia. Am. J. Cardiol., 89, 419–424. Kop, W. J., Hamulyak, K., Pernot, K., and Appels, A. (1998). Relationship between blood coagulation and fibrinolysis to vital exhaustion. Psychosom. Med., 60, 352–358. Kop, W. J., Krantz, D. S., Howell, R. H., Ferguson, M. A., Papademetriou, V., Lu, D. et al. (2001). Effects of mental stress on coronary epicardial vasomotion and flow velocity in coronary artery disease: relationship with hemodynamic stress responses. J. Am. Coll. Cardiol., 37, 1359–1366. Kop, W. J., Zhu, J., Doyle, M. P., Tracy, R. P., Gottdiener, J. S., Asch, F. et al. (2004). Mental stress and exercise effects on immune system and blood coagulation parameters in patients with coronary artery disease following coronary angioplasty (abstract). Ann. Behav. Med., S069. Kopp, M. S., Falger, P. R., Appels, A., and Szedmak, S. (1998). Depressive symptomatology and vital exhaustion are differentially related to behavioral risk factors for coronary artery disease. Psychosom. Med., 60, 752–758. Krantz, D. S., Kop, W. J., Santiago, H. T., and Gottdiener, J. S. (1996). Mental stress as a trigger of myocardial ischemia and infarction. Cardiology Clinics, 14, 271–287. Kraus, J. F., Borhani, N. O., and Franti, C. E. (1980). Socioeconomic status, ethnicity, and risk of coronary heart disease. Am. J. Epidemiol., 111, 407–414. Kuller, L., Cooper, M., and Perper, J. (1972). Epidemiology of sudden death. Archives of Internal Medicine, 129, 714–719. Kuller, L. H., Tracy, R. P., Shaten, J., and Meilahn, E. N. (1996). Relation of C-reactive protein and coronary heart disease in the MRFIT nested case-control study. Multiple Risk Factor Intervention Trial. Am. J. Epidemiol., 144, 537–547. Ladwig, K. H., Marten-Mittag, B., Lowel, H., Doring, A., and Koenig, W. (2003). Influence of depressive mood on the association of CRP and obesity in 3205 middle aged healthy men. Brain Behav. Immun., 17, 268–275. Landmann, R. M., Muller, F. B., Perini, C., Wesp, M., Erne, P., and Buhler, F. R. (1984). Changes of immunoregulatory cells induced by psychological and physical stress: relationship to plasma catecholamines. Clinical and Experimental Immunology, 58, 127–135. Leary, T. (1941). The genesis of atherosclerosis. Archives of Pathology, 32, 507–555. Lee, D. J., Meehan, R. T., Robinson, C., Smith, M. L., and Mabry, T. R. (1995). Psychosocial correlates of immune responsiveness and illness episodes in US Air Force Academy cadets undergoing basic cadet training. Journal of Psychosomatic Research, 39, 445–457. Lesperance, F., and Frasure-Smith, N. (2000). Depression in patients with cardiac disease: a practical review. Journal of Psychosomatic Research, 48, 379–391. Lesperance, F., Frasure-Smith, N., Theroux, P., and Irwin, M. (2004). The association between major depression and levels of soluble intercellular adhesion molecule 1, interleukin-6, and C-reactive
43. Psychoneuroimmunological Pathways Involved in Acute Coronary Syndromes protein in patients with recent acute coronary syndromes. American Journal of Psychiatry, 161, 271–277. Libby, P., Egan, D., and Skarlatos, S. (1997). Roles of infectious agents in atherosclerosis and restenosis: an assessment of the evidence and need for future research. Circulation, 96, 4095–4103. Libby, P., and Hansson, G. K. (1991). Involvement of the immune system in human atherogenesis: current knowledge and unanswered questions. Laboratory Investigation, 64, 5–15. Libby, P., and Simon, D. I. (2001). Inflammation and thrombosis: the clot thickens. Circulation, 103, 1718–1720. Libby, P., and Theroux, P. (2005). Pathophysiology of coronary artery disease. Circulation, 111, 3481–3488. Linden, W., Stossel, C., and Maurice, J. (1996). Psychosocial interventions for patients with coronary artery disease: a meta-analysis. Archives of Internal Medicine, 156, 745–752. Liuzzo, G., Biasucci, L. M., Gallimore, J. R., Grillo, R. L., Rebuzzi, A. G., Pepys, M. B. et al. (1994). The prognostic value of Creactive protein and serum amyloid, a protein in severe unstable angina. New England Journal of Medicine, 331, 417–424. Liuzzo, G., Biasucci, L. M., Rebuzzi, A. G., Gallimore, J. R., Caligiuri, G., Lanza, G. A. et al. (1996). Plasma protein acute-phase response in unstable angina is not induced by ischemic injury. Circulation, 94, 2373–2380. Loppnow, H., and Libby, P. (1992). Functional significance of human vascular smooth muscle cell-derived interleukin 1 in paracrine and autocrine regulation pathways. Experimental Cell Research, 198, 283–290. Maes, M. (1995). Evidence for an immune response in major depression: a review and hypothesis. Progress in Neuro-Psychopharmacology and Biological Psychiatry, 19, 11–38. Manuck, S. B., Marsland, A. L., Kaplan, J. R., and Williams, J. K. (1995). The pathogenicity of behavior and its neuroendocrine mediation: an example from coronary artery disease. Psychosom. Med., 57, 275–283. Markovitz, J. H., and Matthews, K. A. (1991). Platelets and coronary heart disease: potential psychophysiologic mechanisms. Psychosom. Med., 53, 643–668. Marmot, M. G., Shipley, M. J., and Rose, G. (1984). Inequalities in death—specific explanations of a general pattern? Lancet, 1003–1006. Marsland, A. L., Herbert, T. B., Muldoon, M. F., Bachen, E. A., Patterson, S., Cohen, S. et al. (1997). Lymphocyte subset redistribution during acute laboratory stress in young adults: mediating effects of hemoconcentration. Health Psychol., 16, 341–348. McEwen, B. S. (1998). Protective and damaging effects of stress mediators. New England Journal of Medicine, 338, 171–179. McSweeney, J. C., Cody, M., O’Sullivan, P., Elberson, K., Moser, D. K., and Garvin, B. J. (2003). Women’s early warning symptoms of acute myocardial infarction. Circulation, 108, 2619–2623. Meesters, C. M., and Smulders, J. (1994). Hostility and myocardial infarction in men. J. Psychosom. Res., 38, 727–734. Meisel, S. R., Kutz, I., Dayan, K. I., Pauzner, H., Chetboun, I., Arbel, Y. et al. (1991). Effect of Iraqi missile war on incidence of acute myocardial infarction and sudden death in Israeli civilians. Lancet, 338, 660–661. Melnick, J. L., Adam, E., and Debakey, M. E. (1993). Cytomegalovirus and atherosclerosis. Eur. Heart J., 14 (Suppl K), 30–38. Mendall, M. A., Patel, P., Ballam, L., Strachan, D., and Northfield, T. C. (1996). C reactive protein and its relation to cardiovascular risk factors: a population based cross sectional study. BMJ., 312, 1061–1065. Mendes De Leon, C. F., Kop, W. J., De Swart, H. B., Bar, F. W., and Appels, A. P. (1996). Psychosocial characteristics and recurrent
941
events after percutaneous transluminal coronary angioplasty. Am. J. Cardiol., 77, 252–255. Miller, G. E., Freedland, K. E., Carney, R. M., Stetler, C. A., and Banks, W. A. (2003). Pathways linking depression, adiposity, and inflammatory markers in healthy young adults. Brain Behav. Immun., 17, 276–285. Miller, G. E., Freedland, K. E., Duntley, S., and Carney, R. M. (2005). Relation of depressive symptoms to C-reactive protein and pathogen burden (cytomegalovirus, herpes simplex virus, Epstein-Barr virus) in patients with earlier acute coronary syndromes. American Journal of Cardiology, 95, 317–321. Miller, G. E., Stetler, C. A., Carney, R. M., Freedland, K. E., and Banks, W. A. (2002). Clinical depression and inflammatory risk markers for coronary heart disease. Am. J. Cardiol., 90, 1279–1283. Mills, P. J., and Dimsdale, J. E. (1996). The effects of acute psychologic stress on cellular adhesion molecules. Journal of Psychosomatic Research, 41, 49–53. Mills, P. J., Dimsdale, J. E., Nelesen, R. A., and Dillon, E. (1996). Psychologic characteristics associated with acute stressorinduced leukocyte subset redistribution. Journal of Psychosomatic Research, 40, 417–423. Mills, P. J., Farag, N. H., Hong, S., Kennedy, B. P., Berry, C. C., and Ziegler, M. G. (2003). Immune cell CD62L and CD11a expression in response to a psychological stressor in human hypertension. Brain Behav. Immun., 17, 260–267. Mittleman, M. A., Maclure, M., Sherwood, J. B., Mulry, R. P., Tofler, G. H., Jacobs, S. C. et al. (1995). Triggering of acute myocardial infarction onset by episodes of anger. Determinants of myocardial infarction onset study investigators. Circulation, 92, 1720–1725. Muhlestein, J. B., Hammond, E. H., Carlquist, J. F., Radicke, E., Thomson, M. J., Karagounis, L. A. et al. (1996). Increased incidence of Chlamydia species within the coronary arteries of patients with symptomatic atherosclerotic versus other forms of cardiovascular disease. J. Am. Coll. Cardiol., 27, 1555–1561. Muller, J. E., Abela, G. S., Nesto, R. W., and Tofler, G. H. (1994). Triggers, acute risk factors and vulnerable plaques: the lexicon of a new frontier. J. Am. Coll. Cardiol., 23, 809–813. Naghavi, M., Libby, P., Falk, E., Casscells, S. W., Litovsky, S., Rumberger, J. et al. (2003a). From vulnerable plaque to vulnerable patient: a call for new definitions and risk assessment strategies: part I. Circulation, 108, 1664–1672. Naghavi, M., Libby, P., Falk, E., Casscells, S. W., Litovsky, S., Rumberger, J. et al. (2003b). From vulnerable plaque to vulnerable patient: a call for new definitions and risk assessment strategies: part II. Circulation, 108, 1772–1778. Owen, N., Poulton, T., Hay, F. C., Mohamed-Ali, V., and Steptoe, A. (2003). Socioeconomic status, C-reactive protein, immune factors, and responses to acute mental stress. Brain Behav. Immun., 17, 286–295. Panagiotakos, D. B., Pitsavos, C., Chrysohoou, C., Tsetsekou, E., Papageorgiou, C., Christodoulou, G. et al. (2004). Inflammation, coagulation, and depressive symptomatology in cardiovascular disease-free people; the Attica study. Eur. Heart J., 25, 492–499. Pasceri, V., Cammarota, G., Patti, G., Cuoco, L., Gasbarrini, A., Grillo, R. L. et al. (1998). Association of virulent Helicobacter pylori strains with ischemic heart disease. Circulation, 97, 1675–1679. Pasic, J., Levy, W. C., and Sullivan, M. D. (2003). Cytokines in depression and heart failure. Psychosom. Med., 65, 181–193. Paterson, J., and Cottral, G. E. (1950). Experimental coronary sclerosis III. Lymphomatosis as a cause of coronary sclerosis in chickens. Archives of Pathology, 49, 699.
942
V. Psychoneuroimmunology and Pathophysiology
Patterson, S. M., Gottdiener, J. S., Hecht, G., Vargot, S., and Krantz, D. S. (1993). Effects of acute mental stress on serum lipids: mediating effects of plasma volume. Psychosom. Med., 55, 525–532. Patterson, S. M., Krantz, D. S., Gottdiener, J. S., Hecht, G., Vargot, S., and Goldstein, D. S. (1995). Prothrombotic effects of environmental stress: changes in platelet function, hematocrit, and total plasma protein. Psychosom. Med., 57, 592–599. Pepine, C. J., Hirshfeld, J. W., MacDonald, R. G., Henderson, M. A., Bass, T. A., Goldberg, S. et al. (1990). A controlled trial of corticosteroids to prevent restenosis after coronary angioplasty. MHeart Group. Circulation, 81, 1753–1761. Pietraszek, M. H., Takada, Y., Nishimoto, M., Ohara, K., and Takada, A. (1991). Fibrinolytic activity in depression and neurosis. Thrombosis Research, 63, 661–666. Pike, J. L., and Irwin, M. R. (2005). Dissociation of inflammatory markers and natural killer cell activity in major depressive disorder. Brain Behav. Immun. Prasad, A., Zhu, J., Halcox, J. P., Waclawiw, M. A., Epstein, S. E., and Quyyumi, A. A. (2002). Predisposition to atherosclerosis by infections: role of endothelial dysfunction. Circulation, 106, 184–190. Prescott, E., Holst, C., Gronbaek, M., Schnohr, P., Jensen, G., and Barefoot, J. (2003). Vital exhaustion as a risk factor for ischaemic heart disease and all-cause mortality in a community sample. A prospective study of 4084 men and 5479 women in the Copenhagen City Heart study. International Journal of Epidemiology, 32, 990–997. Ragland, D. R. (1989). Type A behavior and outcome of coronary disease. New England Journal of Medicine, 319, 1480–1481. Raikkonen, K., Lassila, R., Keltikangas-Jarvinen, L., and Hautanen, A. (1996). Association of chronic stress with plasminogen activator inhibitor-1 in healthy middle-aged men. Arteriosclerosis, Thrombosis, and Vascular Biology, 16, 363–367. Ridker, P. M. (1998). Inflammation, infection, and cardiovascular risk: how good is the clinical evidence? Circulation, 97, 1671–1674. Ridker, P. M., Cannon, C. P., Morrow, D., Rifai, N., Rose, L. M., McCabe, C. H. et al. (2005). C-reactive protein levels and outcomes after statin therapy. New England Journal of Medicine, 352, 20–28. Ridker, P. M., Cushman, M., Stampfer, M. J., Tracy, R. P., and Hennekens, C. H. (1997). Inflammation, aspirin, and the risk of cardiovascular disease in apparently healthy men. New England Journal of Medicine, 336, 973–979. Ridker, P. M., Glynn, R. J., and Hennekens, C. H. (1998a). C-reactive protein adds to the predictive value of total and HDL cholesterol in determining risk of first myocardial infarction. Circulation, 97, 2007–2011. Ridker, P. M., Hennekens, C. H., Roitman-Johnson, B., Stampfer, M. J., and Allen, J. (1998b). Plasma concentration of soluble intercellular adhesion molecule 1 and risks of future myocardial infarction in apparently healthy men. Lancet, 351, 88–92. Ridker, P. M., Rifai, N., Pfeffer, M., Sacks, F., Lepage, S., and Braunwald, E. (2000a). Elevation of tumor necrosis factor-alpha and increased risk of recurrent coronary events after myocardial infarction. Circulation, 101, 2149–2153. Ridker, P. M., Rifai, N., Stampfer, M. J., and Hennekens, C. H. (2000b). Plasma concentration of interleukin-6 and the risk of future myocardial infarction among apparently healthy men. Circulation, 101, 1767–1772. Roberts, R., De Mello, V., and Sobel, B. E. (1976). Deleterious effects of methylprednisolone in patients with myocardial infarction. Circulation, 53, I204–206.
Robinette, C. D., and Fraumeni, J. F., Jr. (1977). Splenectomy and subsequent mortality in veterans of the 1939–45 war. Lancet, 2, 127–129. Ross, R. (1986). The pathogenesis of atherosclerosis: an update. New England Journal of Medicine, 314, 488–500. Ross, R. (1999). Atherosclerosis—an inflammatory disease. New England Journal of Medicine, 340, 115–126. Rozanski, A., Blumenthal, J. A., and Kaplan, J. (1999). Impact of psychological factors on the pathogenesis of cardiovascular disease and implications for therapy. Circulation, 99, 2192– 2217. Saikku, P., Leinonen, M., Mattila, K., Ekman, M. R., Nieminen, M. S., Makela, P. H. et al. (1988). Serological evidence of an association of a novel Chlamydia, Twar, with chronic coronary heart disease and acute myocardial infarction. Lancet, 2, 983–986. Sapolsky, R., Rivier, C., Yamamoto, G., Plotsky, P., and Vale, W. (1987). Interleukin-1 stimulates the secretion of hypothalamic corticotropin-releasing factor. Science, 238, 522–524. Schulte, H. M., Bamberger, C. M., Elsen, H., Herrmann, G., Bamberger, A. M., and Barth, J. (1994). Systemic interleukin-1 alpha and interleukin-2 secretion in response to acute stress and to corticotropin-releasing hormone in humans. European Journal of Clinical Investigation, 24, 773–777. Seeman, T. E., Singer, B. H., Rowe, J. W., Horwitz, R. I., and McEwen, B. S. (1997). Price of adaptation—allostatic load and its health consequences. MacArthur studies of successful aging. Archives of Internal Medicine, 157, 2259–2268. Segerstrom, S. C., and Miller, G. E. (2004). Psychological stress and the human immune system: a meta-analytic study of 30 years of inquiry. Psychological Bulletin, 130, 601–630. Selye, H. (1977). The stress of life. New York: McGraw Hill. Shekelle, R. B., Gale, M., and Norusis, M. (1985). Type A score (Jenkins Activity Survey) and risk of recurrent coronary heart disease in the Aspirin Myocardial Infarction study. Am. J Cardiol., 56, 221–225. Shekelle, R. B., Gale, M., Ostfeld, A. M., and Paul, O. (1983). Hostility, risk of coronary heart disease, and mortality. Psychosom. Med., 45, 109–114. Siegman, A. W., Dembroski, T. M., and Ringel, N. (1987). Components of hostility and the severity of coronary artery disease. Psychosom. Med., 49, 127–135. Stein, M., Miller, A. H., and Trestman, R. L. (1991). Depression, the immune system, and health and illness: findings in search of meaning. Archives of General Psychiatry, 48, 171–177. Stern, D., Nawroth, P., Handley, D., and Kisiel, W. (1985). An endothelial cell-dependent pathway of coagulation. Proc. Natl. Acad. Sci USA, 82, 2523–2527. Stone, G. W., Rutherford, B. D., McConahay, D. R., Johnson, W. L., Giorgi, L. V., Ligon, R. W. et al. (1989). A randomized trial of corticosteroids for the prevention of restenosis in 102 patients undergoing repeat coronary angioplasty. Catheterization and Cardiovascular Diagnosis, 18, 227–231. Suarez, E. C. (2003). Plasma interleukin-6 is associated with psychological coronary risk factors: moderation by use of multivitamin supplements. Brain Behav. Immun., 17, 296–303. Suarez, E. C., Williams, R. B., Kuhn, C. M., Zimmerman, E. H., and Schanberg, S. M. (1991). Biobehavioral basis of coronary-prone behavior in middle-age men. Part II: Serum cholesterol, the type A behavior pattern, and hostility as interactive modulators of physiological reactivity. Psychosom. Med., 53, 528–537. Suls, J., and Bunde, J. (2005). Anger, anxiety, and depression as risk factors for cardiovascular disease: the problems and implications of overlapping affective dispositions. Psychological Bulletin, 131, 260–300.
43. Psychoneuroimmunological Pathways Involved in Acute Coronary Syndromes Thompson, S. G., Kienast, J., Pyke, S. D., Haverkate, F., and Van De Loo, J. C. (1995). Hemostatic factors and the risk of myocardial infarction or sudden death in patients with angina pectoris. European Concerted Action on Thrombosis and Disabilities Angina Pectoris Study Group. New England Journal of Medicine, 332, 635–641. Tracey, K. J. (2002). The inflammatory reflex. Nature, 420, 853–859. Tracy, R. P., Lemaitre, R. N., Psaty, B. M., Ives, D. G., Evans, R. W., Cushman, M. et al. (1997). Relationship of C-reactive protein to risk of cardiovascular disease in the elderly. Results from the Cardiovascular Health Study and the Rural Health Promotion Project. Arteriosclerosis, Thrombosis, and Vascular Biology, 17, 1121–1127. Trichopoulos, D., Katsouyanni, K., Zavitsanos, X., Tzonou, A., and Dalla-Vorgia, P. (1983). Psychological stress and fatal heart attack: The Athens (1981) Earthquake Natural Experiment. Lancet, 1, 441–443. Van Dixhoorn, J., Duivenvoorden, H. J., Staal, J. A., Pool, J., and Verhage, F. (1987). Cardiac events after myocardial infarction: possible effect of relaxation therapy. Eur. Heart J., 8, 1210–1214. Verrier, R. L. (1987). Mechanisms of behaviorally induced arrhythmias. Circulation, 76, I48–I56. Von, K. R., Mills, P. J., Fainman, C., and Dimsdale, J. E. (2001). Effects of psychological stress and psychiatric disorders on blood coagulation and fibrinolysis: a biobehavioral pathway to coronary artery disease? Psychosom. Med., 63, 531–544. Wald, N. J., Law, M. R., Morris, J. K., and Bagnall, A. M. (1997). Helicobacter pylori infection and mortality from ischaemic heart disease: negative result from a large, prospective study. BMJ., 315, 1199–1201. Weisse, C. S. (1992). Depression and immunocompetence: a review of the literature. Psychological Bulletin, 111, 475–489. Welin, L., Tibblin, G., Svardsudd, K., Tibblin, B., Ander-Peciva, S., Larsson, B. et al. (1985). Prospective study of social influences on mortality. The study of men born in 1913 and 1923. Lancet, 915–918. White, P. D. (1997). The relationship between infection and fatigue. Journal of Psychosomatic Research, 43, 345–350. Williams, R. B., Barefoot, J. C., Haney, T. L., Harrell, F. E., Jr., Blumenthal, J. A., Pryor, D. B. et al. (1988). Type A behavior and angiographically documented coronary atherosclerosis in a sample of 2,289 patients. Psychosom. Med., 50, 139–152. Williams, R. B., Suarez, E. C., Kuhn, C. M., Zimmerman, E. A., and Schanberg, S. M. (1991). Biobehavioral basis of coronary-prone behavior in middle-aged men. Part I: evidence for chronic SNS activation in type As. Psychosom. Med., 53, 517–527.
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Winkleby, M. A., Jatulis, D. E., Frank, E., and Fortmann, S. P. (1992). Socioeconomic status and health: how education, income, and occupation contribute to risk factors for cardiovascular disease. Am. J. Public Health, 82, 816–820. Wojakowski, W., Tendera, M., Michalowska, A., Majka, M., Kucia, M., Maslankiewicz, K. et al. (2004). Mobilization of CD34/ CXCR4+, CD34/CD117+, C-Met+ stem cells, and mononuclear cells expressing early cardiac, muscle, and endothelial markers into peripheral blood in patients with acute myocardial infarction. Circulation, 110, 3213–3220. Wolfe, F., Mitchell, D. M., Sibley, J. T., Fries, J. F., Bloch, D. A., Williams, C. A. et al. (1994). The mortality of rheumatoid arthritis. Arthritis and Rheumatism, 37, 481–494. Wright, C. E., Strike, P. C., Brydon, L., and Steptoe, A. (2005). Acute inflammation and negative mood: mediation by cytokine activation. Brain Behav. Immun., 19, 345–350. Wulsin, L. R., and Singal, B. M. (2003). Do depressive symptoms increase the risk for the onset of coronary disease? A systematic quantitative review. Psychosom. Med., 65, 201–210. Yeung, A. C., Vekshtein, V. I., Krantz, D. S., Vita, J. A., Ryan, T. J., Jr., Ganz, P. et al. (1991). The effect of atherosclerosis on the vasomotor response of coronary arteries to mental stress. New England Journal of Medicine, 325, 1551–1556. Yokoi, H., Daida, H., Kuwabara, Y., Nishikawa, H., Takatsu, F., Tomihara, H. et al. (1997). Effectiveness of an antioxidant in preventing restenosis after percutaneous transluminal coronary angioplasty: the Probucol Angioplasty Restenosis trial. J. Am. Coll. Cardiol., 30, 855–862. Yokoya, K., Takatsu, H., Suzuki, T., Hosokawa, H., Ojio, S., Matsubara, T. et al. (1999). Process of progression of coronary artery lesions from mild or moderate stenosis to moderate or severe stenosis: a study based on four serial coronary arteriograms per year. Circulation, 100, 903–909. Zakowski, S. G., McAllister, C. G., Deal, M., and Baum, A. (1992). Stress, reactivity, and immune function in healthy men. Health Psychol., 11, 223–232. Zhu, J., Nieto, F. J., Horne, B. D., Anderson, J. L., Muhlestein, J. B., and Epstein, S. E. (2001). Prospective study of pathogen burden and risk of myocardial infarction or death. Circulation, 103, 45–51. Zorrilla, E. P., Luborsky, L., McKay, J. R., Rosenthal, R., Houldin, A., Tax, A. et al. (2001). The relationship of depression and stressors to immunological assays: a meta-analytic review. Brain Behav. Immun., 15, 199–226.
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C H A P T E R
44 Psychosocial Factors and Coronary Heart Disease: The Role of Psychoneuroimmunological Processes ANDREW STEPTOE AND LENA BRYDON
I. THE PROBLEM OF CORONARY HEART DISEASE 945 II. PSYCHOSOCIAL FACTORS IN CHD 946 III. PATHOPHYSIOLOGY OF CHD 950 IV. PSYCHOBIOLOGICAL STUDIES 960 V. CONCLUSIONS 970
and developing progressively through adult life. As described in more detail in the section titled “Pathophysiology of CHD,” coronary atherosclerosis involves inflammation of the arterial vessel walls and the proliferation of cells in the intima-medial layer, followed at later stages by flow-limiting stenosis (narrowing), plaque disruption, and thrombus formation. The disease typically comes to clinical attention in one of three forms: angina pectoris, an acute coronary syndrome (ACS), or sudden cardiac death. Angina pectoris is chest pain or discomfort due to insufficient blood flow to the heart muscle, when the capacity of the coronary arteries does not match the energy demands of the working heart. It is most commonly stimulated by physical exertion, though may be also be elicited by emotional stress. The prevalence of angina pectoris in the adult U.S. population is thought to be around 3.8%. Acute coronary syndrome is the term increasingly used to describe either an acute myocardial infarction (MI) or unstable angina. The reason for using this broader term is that this cluster of problems shares common pathological processes, and they are all serious conditions that may lead to admission to acute coronary care. ACS can be fatal, though prognosis has improved dramatically over recent years with prompt thrombolysis (clot busting) and early revascularization procedures. Sudden cardiac death is usually defined as a natural death resulting from an abrupt loss of heart function (cardiac arrest) occurring within a short time of symptom onset. The mechanism involves disturbance in the electrical stability of the heart, leading to
I. THE PROBLEM OF CORONARY HEART DISEASE Coronary heart disease (CHD) is the single largest cause of death in men and women in the USA, Western Europe, and many other countries. In the USA, 38% of fatalities in 2002 were caused by cardiovascular diseases, of which 53% were CHD deaths (American Heart Association, 2005). The estimated prevalence of CHD is 8.4% in men and 5.6% in women. Although CHD is a disease of older age, it also affects many younger people, and approximately one-third of cardiovascular deaths occur in people under age 75. In 2002, CHD accounted for 22% of male and 13% of female deaths in people under age 75 in the UK (British Heart Foundation, 2004). The direct and indirect costs of CHD in 2005 have been estimated by the American Heart Association as $142 billion. Fortunately, mortality rates have declined over recent decades. In the Framingham Heart Study, for example, overall CHD death rates decreased by 59% between 1950 and 1999 (Fox et al., 2004). The disease process underlying clinical CHD is coronary atherosclerosis, a condition starting early in life PSYCHONEUROIMMUNOLOGY, 4E VOLUME II
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a fatal arrhythmia such as ventricular fibrillation, but the underlying cause is CHD. More than 50% of people who die suddenly of CHD have had no previous symptoms. Coronary heart disease is also a major determinant of congestive heart failure, a serious condition in which the pumping action of the heart is impaired, leading to increased mortality risk and poor quality of life. The major risk factors for CHD are well established, and include high blood pressure (hypertension), high cholesterol (hyperlipidemia), smoking, diabetes, and a positive family history. Other factors that contribute to the risk profile include obesity and physical inactivity. A relatively new construct that is important both to CHD and type 2 diabetes is the metabolic syndrome, a cluster of risk factors including abdominal adiposity (assessed through waist circumference), insulin resistance, high blood pressure and disturbance in lipid profile. The prevalence of the metabolic syndrome is around 4% in teenagers and 24% in adults in the USA, indicating that it is widespread in the population (American Heart Association, 2005). People with multiple risk factors have an increased probability of developing CHD. However, a substantial proportion of individuals who experience acute cardiac events are at relatively low risk according to standard risk factors. This is illustrated by an analysis of data from more than 122,000 patients in 14 international randomized controlled trials (Khot et al., 2003), which found that 43% of male and 32% of female CHD patients had only one of the major conventional risk factors (hypertension, hyperlipidemia, diabetes, or smoking), and a further third had only two. This means that relatively few patients could be regarded as very “high risk” on conventional risk factors. Furthermore, international studies of trends over time in cardiac events have estimated that only about 40% of the variance in men and 15% in women is explained by trends in conventional risk factors, even when appropriate time lags are taken into account (Kuulasmaa et al., 2000). Findings like these indicate that other factors contribute to disease risk and have prompted the search for psychosocial and immune/inflammatory determinants. It is the combination of the psychosocial and immunological processes that is the main topic of this chapter. People who have survived an ACS are several times more likely to suffer an early death or major disability than the general population. It has been estimated that within 6 years of an MI, 18% of men and 35% of women will have another ACS, 6–7% will experience sudden cardiac death, about 10% will have a stroke, and more than 20% will go on to develop disabling congestive heart failure. Great efforts in clinical care and research are therefore directed towards secondary prevention,
or reducing risk in patients with established CHD. Many of the risk factors that are involved in the primary etiology of coronary atherosclerosis also affect people with advanced CHD. Psychosocial and immunological processes may be relevant at this stage as well. The role of psychoneuroimmunology in CHD has only become widely recognized in the last decade, and research is rapidly evolving as the contribution of immunological processes to disease becomes better understood (Steptoe and Brydon, 2005b). This chapter summarizes current understanding of this field and addresses two basic issues. The first is whether emotional and behavioral factors stimulate the inflammatory and immunological processes that contribute to coronary atherosclerosis and CHD morbidity. The second question is whether psychoneuroimmunological pathways mediate links between psychosocial risk factors and CHD. In investigating this field, it is important to distinguish three stages of disease at which psychoneuroimmunological processes may be relevant: 1. The long term development of coronary atherosclerosis and CHD in initially healthy people in the general population. 2. The induction or triggering of clinical manifestations of CHD in patients with coronary advanced atherosclerosis. 3. The risk of adverse health outcomes and further cardiac events in patients with CHD who have survived an ACS. This chapter has three major sections. The next section, “Psychosocial Factors in CHD,” describes the psychosocial risk factors for CHD and the evidence that they are associated with the etiology and prognosis of the disease. The following section, “Pathophysiology of CHD,” summarizes current knowledge of the pathophysiology of CHD, focusing on the contribution of inflammatory and immune processes. Then in the section titled “Psychobiological Studies,” we draw these strands together by discussing how psychosocial and immunological processes contribute to cardiovascular pathology and how these pathways may mediate the impact of depression and other psychological factors on prognosis.
II. PSYCHOSOCIAL FACTORS IN CHD There is an extensive literature relating psychological and social (or psychosocial) factors with the development of CHD, and this has been reviewed in detail by Kuper et al. (2005) and by Everson-Rose and Lewis (2005). Important findings about psychosocial factors
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have been obtained from cross-sectional case-control research such as the INTERHEART study, which analyzed cardiovascular risk in more than 11,000 patients from 52 countries and observed associations between CHD and general stress, financial stress, depression, and stressful life events (Rosengren et al., 2004a). However, stronger evidence about the etiology of CHD derives from prospective observational epidemiological studies in which risk factors are assessed in apparently healthy samples that are then tracked over time for the development of clinical disease. Measurement of standard risk factors helps determine the pathways through which psychosocial variables may operate, since psychosocial influences may be mediated by behavioral and biological risk factors, or else act independently through distinct mechanisms. Most prospective observational studies have used clinical CHD as the disease endpoint. However, there has also been work on relationships with subclinical atherosclerosis, as indexed by ultrasound scanning of the intima-medial thickness of the carotid artery walls (carotid IMT) or by electron beam–computed tomographic assessment of coronary artery calcification. These studies of subclinical disease are important, since they indicate whether psychosocial factors influence the clinical manifestation of CHD or the progression of the underlying disease process. Research into the acute triggering of cardiac events requires a different study design. By their very nature, ACS and sudden cardiac death are unpredictable, so it is difficult to carry out prospective studies. More commonly, people who have survived an ACS are interviewed about their experience prior to symptom onset. The case–crossover approach to statistical analysis has been developed to analyze these data, comparing hazard periods with control periods of similar duration on a within-subject basis (Strike and Steptoe, 2005). Such studies are, of course, limited to people who have survived their cardiac event, unless information can be collected from bystanders or the families of fatalities, so findings relating to sudden cardiac death are sparse. Prognostic research on psychosocial factors in patients who have survived an ACS generally involves clinical cohort studies. One of the key issues in such investigations is adequate assessment of clinical status and clinical risk, so as to ensure that any associations with psychosocial factors such as depression are not due to covariation with high cardiological risk. In later parts of this section, we describe evidence related to all three stages of CHD, where the relevance of these different research strategies will become apparent. The psychosocial factors that contribute to CHD can be divided into four broad categories: sociodemo-
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graphic factors, exposure to life stress, protective social factors, and psychological factors such as depression and hostility.
A. Sociodemographic Factors Perhaps the most consistent sociodemographic determinant of CHD is socioeconomic status (SES). It has repeatedly been shown in epidemiological studies in the USA and Western Europe that CHD is more common among people of lower than higher SES. This relationship is observed when SES is defined by occupational grade, educational attainment, or income, and there is a gradient in risk rather than a simple difference between rich and poor. For example, analyses of two large American Cancer Society cohorts (each more than one million persons) showed that death rates from CHD reduced progressively with greater educational attainment, even after controlling for smoking, body mass index (BMI), diet, alcohol, hypertension, and menopausal status in women (Steenland et al., 2002). An association is also present with carotid IMT, suggesting an influence on the underlying disease process (Lynch et al., 1995). SES gradients are observed not only in affluent Western countries, but also in other parts of the world. For example, a study in Novosibirsk, Siberia, showed a robust relationship between educational attainment and death from cardiovascular causes in both men and women (Malyutina et al., 2004). The SES gradient is partly due to differences in risk factors such as smoking and hypertension, and the effectiveness of clinical care and risk factor management. However, a proportion of the variance in CHD remains unexplained once these factors are taken into account, and psychoneuroimmunological processes may contribute to this pattern. In addition to SES, there are important ethnic disparities in CHD, though these vary by country. For instance, in the USA, the number of premature cardiac deaths is higher among American Indians, Alaska Natives, and Blacks compared with people of White European origin, with an intermediate rate among Hispanics. However, in the UK, people of South Asian (India, Bangladesh, Pakistan, and Sri Lanka) origin have substantially greater premature death rates from CHD than do White Europeans, while Afro-Caribbean people do not.
B. Exposure to Life Stress Work stress is the form of chronic life stress that has been studied in most detail. The reason is partly that working people are easier to track over time than some other populations. In addition, people in paid
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employment are exposed to working conditions over many years of their adult lives, so adverse effects may be more readily detected than for other forms of life stress. Work stress has many facets, but two models have proved particularly valuable in studies of CHD. The first is the demand-control model, in which strain is thought to be greatest when high demands are coupled with low control over the work environment. Separate analyses have been carried out on each component and on the demand/control balance. Second, the effort-reward imbalance model postulates that adverse health effects arise when the effort put into work is not matched by appropriate rewards. This lack of reciprocity between effort spent and rewards received is thought to stimulate emotional distress and biological activation. Work stress measured with both models has been associated with increased CHD independently of standard risk factors (Everson-Rose and Lewis, 2005; Kuper et al., 2005). For instance, Kivimaki et al. (2002) followed up factory employees for an average of 25 years for cardiovascular mortality. After adjustment for age and gender, those reporting high demands/low control had more than twice the cardiovascular mortality risk, while those with high effortreward imbalance showed a relative risk of 2.4. These effects remain significant after controlling for SES, smoking, physical activity, blood pressure, cholesterol, and BMI. Other forms of chronic stress have been investigated less thoroughly than work stress. However, there is evidence that people are at increased risk if they live in more threatening neighborhoods that lack social cohesion (Diez Roux et al., 2001), that poor marital quality and strained domestic relationships predict subclinical atherosclerosis, and that caring for demented relatives may increase coronary risk (Lee et al., 2003). Most of these effects have been observed in relation to the long-term development of coronary atherosclerosis. In people who already have advanced disease, various types of acute stress may become more important and trigger cardiac events such as ACS and sudden cardiac death (Strike and Steptoe, 2005). Some of the most compelling evidence has come from studies of people living through severe natural disasters such as earthquakes, where increased admissions for ACS and rates of sudden cardiac death have been observed that appear to be attributable to the terrifying nature of the experience rather than to physical exertion or injury. Other studies have shown heightened rates in people exposed to war and terrorism. For instance, Shedd et al. (2004) assessed the rates of discharge of implantable cardioverter-defibrillators (ICDs) in the period surrounding the World Trade Center attacks on
September 11, 2001. ICDs are implanted in people with advanced heart disease and discharge when potentially dangerous cardiac arrhythmias are detected. Discharges may therefore act as proxies for cardiac activation prior to sudden death. The rates of ICD discharge increased substantially in the 30 days after the terrorist attacks compared with before. Interview studies with patients who have survived an ACS have identified more mundane forms of severe emotional distress as short-term triggers, including conflict at work or serious arguments with neighbors. Studies of sudden cardiac death are inevitably rare. However, one relevant study involved detailed interviews with the relatives of 100 men aged less than 70 who died suddenly, exploring the circumstances surrounding the cardiac arrest (Myers and Dewar, 1975). The coronary risk profiles of these individuals did not differ from those of MI survivors, but the men who suffered sudden death were significantly more likely to experience moderate or severe stress in the 30 minutes before symptom onset (23% vs. 8%). Still less is known about the influence of life stress on the prognosis of patients who have survived an ACS. Work stress appears to have stronger associations with the primary etiology of CHD in apparently healthy populations than it does with prognosis in people with established disease. One reason for this may be that after an ACS, many people change their working patterns. However, other forms of chronic stress are less easy to avoid. For instance, one study of female survivors of ACS showed that marital stress was associated with a nearly three-fold increase in risk of recurrent coronary events over the next few years, after controlling for clinical variables (Orth-Gomér et al., 2000).
C. Protective Social Factors Protective social factors that are relevant to CHD include social networks or ties and social support. Social supports are interactions that provide emotional, confiding, and practical support for the individual and may help to buffer the impact of exposure to life stress. Social network refers to the number and density of social contacts, and socially isolated individuals are people with small social networks who have few personal, family, or social ties. There is good evidence that individuals who have small networks and are isolated are at higher risk for CHD. Rosengren et al. (2004b) derived a social integration measure from reports about the quality and quantity of daily social interactions and found that less integrated men were at substantially higher CHD risk over the next 15 years.
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The same study also found that close emotional support was a protective factor. There is no evidence at present about the role of social factors in the acute triggering of cardiac events, although it is certainly true that acute emotional stress may arise from conflict with close family and friends. However, social support is a significant prognostic factor for people with established CHD. One study of more than 1,300 patients with angiographically confirmed coronary atherosclerosis showed a three-fold increase in cardiovascular mortality over a 9-year follow-up in patients who were unmarried and without a confidant, compared with those who were either married or had a close confidant (Williams et al., 1992).
D. Psychological Factors Psychological characteristics are the third group of psychosocial factors relevant to CHD. The bulk of evidence relates to negative traits such as depression, anxiety or distress, and hostility and anger. Although these are generally investigated separately, there are suggestions that together they all reflect an underlying dimension of negative affectivity (Suls and Bunde, 2005). Most attention over recent years has focused on depression. A positive association between depressive symptoms and CHD has been documented in more than 15 prospective observational cohort studies (Steptoe, in press). For instance, one study assessed the association between depressive symptoms and CHD over an 8-year period in nearly 9,000 men and women. Depressed men had a more than two-fold increase in risk of fatal CHD after adjusting for age, race, smoking, hypertension, BMI, diabetes, and poverty, while the relative risk of non-fatal CHD in women was 1.73. In the INTERHEART case-control study, depressive symptoms over the past year were associated with acute MI in almost all regions of the world, with an estimated population attributable risk of 9% (Rosengren et al., 2004a). Depressive symptoms overlap with other indicators of anxiety and psychological distress that also predict future CHD. Relationships with subclinical atherosclerosis are present, with at least 10 population studies relating carotid IMT or coronary artery calcification with depression or psychological distress (Steptoe, in press). Depression is significant in the aftermath of ACS. Up to 20% of individuals have an episode of major depression within a few weeks of ACS, while a further 25% experience minor depression or dysthymia. Depressed patients experience more social problems during the first years of recovery, report impaired
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quality of life, and are less adherent to treatment advice than are non-depressed patients (DiMatteo et al., 2000). A number of studies have shown that depression following ACS is associated with an increased risk of future cardiac events and with greater mortality, with adjusted risks of two to three (Lett et al., in press). This issue has stimulated intense interest in the relationship between depression and immune function in CHD patients (described in the section titled “Morbidity Following Acute Coronary Syndromes”), together with efforts to ameliorate depression using behavioral and pharmacological interventions. The literature investigating links between hostility, anger, and CHD spans several decades. Hostility is characterized by a suspicious and mistrustful attitude towards other people and the wider environment, while anger is an emotion that is triggered in response to frustration or perceptions of unjust or hostile actions. Hostile individuals are more likely than others to experience anger in everyday life, since they perceive a wide range of situations as threatening. Hostility is one of the key dimensions of Type A behavior, and although that construct has fallen out of favor in recent years, hostile dispositions have continued to be studied. Nevertheless, findings relating hostility with the longterm development of CHD are mixed. Kuper et al. (2005) concluded from their systematic review of longitudinal observational studies that there was little supportive evidence, while a more positive conclusion was drawn by Everson-Rose and Lewis (2005) from a wider literature. Most studies have been limited to White men, and there is less evidence from women or other ethnic groups. Another difficulty is the broad range of measures and constructs of hostility that have been investigated, making it hard to draw general conclusions. Hostility may also be significant in patients with existing CHD, since it has been found to predict recurrent coronary events (Haas et al., 2005). There is a small but nevertheless intriguing literature relating anger with the long-term development of CHD, though the extent to which this association is independent of hostility is not clear. Additionally, there is good evidence that anger may act as an acute trigger of ACS onset. Studies involving interviews with patients who have survived an ACS indicate that a proportion of them report having experienced severe anger in the 2 hours before symptom onset. Using case-crossover methods, the increase in risk of symptom onset is more than two-fold following an episode of acute anger (Strike and Steptoe, 2005). Interestingly, this relationship is greater in lower SES people, suggesting an interaction between long-term and acute psychosocial factors in promoting risk.
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E. Mechanisms Linking Psychosocial Factors with CHD A central issue in the investigation of psychosocial factors in CHD is understanding the pathways through which such associations are mediated. Theoretically, there are a number of possibilities. One is that genetic factors are involved. CHD has a strong hereditary component, and there also appear to be genetic influences on some of the psychosocial factors that relate to cardiovascular risk such as aggressive disposition. Thus, it is possible that polymorphisms which confer increased CHD risk also lead to expression of a heightened psychosocial risk profile. Direct evidence for common genetic pathways is limited, and the strongest case to date can probably be made for genes regulating central nervous system serotonin synthesis. Polymorphisms of these genes are associated with aggressive traits, the presence of the metabolic syndrome, and heightened cardiovascular stress reactivity (Manuck et al., 2004). A second possibility is that there are common environmental determinants of psychosocial factors and CHD, such as early life experiences in childhood and the perinatal period. Early life adversity predicts some aspects of adults’ psychosocial experience as well as potentially influencing physiological regulation. Psychosocial factors such as SES might also influence exposure to infectious agents that in turn contribute to CHD risk. The role of infection in determining chronic low-level inflammation is described further in the section titled “Pathophysiology of CHD.” However, it is generally agreed that two sets of processes are most likely to link psychosocial factors with CHD: direct behavioral pathways and psychobiological processes. The behaviors that may be relevant are lifestyle factors that contribute to CHD risk such as smoking, alcohol consumption, food choice, and leisure time physical activity, all of which vary in their occurrence with psychosocial risk. For instance, there are pronounced SES gradients in smoking, diet, and physical activity, with more smoking, less fruit and vegetable consumption, and less leisure time physical activity in lower SES groups. Psychosocial risk factors such as chronic work stress and depression are also linked to several health behaviors. Yet, the extent to which these pathways mediate long-term psychosocial influences on CHD is unclear. Estimates from a range of studies have suggested that 30–60% of the SES gradient in mortality may be attributed to health behaviors, but their role in mediating other psychosocial processes has not been studied systematically. It should be noted that many prospective observational studies of psychosocial factors have also measured health
behaviors such as smoking, alcohol consumption, and BMI (reflecting the balance of energy intake and expenditure). Since the psychosocial influence on cardiovascular risk remained significant after controlling for covariates, it is unlikely to have been mediated entirely by behavioral pathways. Behavioral pathways are more strongly implicated as mediators of the association between psychosocial factors and morbidity in patients with existing CHD. For example, depression leads to reduced levels of physical activity and to reduced adherence to treatment advice and medication (DiMatteo et al., 2000). It is likely, therefore, that lapses in adherence and failure to maintain physical activity are responsible in part for the association between depression and morbidity in patients following ACS. Psychobiological processes are the pathways through which psychosocial factors stimulate biological systems directly via central nervous system activation of autonomic, neuroendocrine, immune, and inflammatory responses. Structures in the limbic system (notably the amygdala and hippocampus) operate in conjunction with the prefrontal cortex to control lower brain processes regulating peripheral physiological activity. The biological responses that are particularly relevant to CHD are organized through two pathways: the sympathoadrenal axis, involving stimulation of the sympathetic branch of the autonomic nervous system in conjunction with hormones such as epinephrine and norepinephrine, and the hypothalamic-pituitary-adrenocortical (HPA) axis, leading to release of hormones such as cortisol. These pathways have a range of effects on the cardiovascular system, metabolic processes, adipose tissue, hemostatic factors, and arterial vessel wall biology. If these pathways are activated by acute or chronic psychosocial factors, they may contribute directly to CHD pathology, as detailed in “Psychobiological Studies.”
III. PATHOPHYSIOLOGY OF CHD A. The Atherosclerotic Process An understanding of the potential influence of psychoneuroimmunological factors on atherosclerosis starts with the structure of the artery, which is illustrated in Figure 1. The outer layer of the artery, known as the adventitia, consists of connective tissue with interspersed fibroblasts and smooth muscle cells. This is followed by the media, the middle layer, consisting of smooth muscle cells, and then the intimal layer consisting of extracellular connective tissue matrix, primarily collagen and proteoglycans. The intima is
44. Psychosocial Factors and Coronary Heart Disease: The Role of Psychoneuroimmunological Processes
Internal elastic lamina
Adventitia Media Intima
Lumen Monocyte
T-cell
Platelet
Endothelium
Blood
FIGURE 1 The structure of the artery.
bound by a sheet of elastic fibers, the internal elastic lamina, on its peripheral side. Finally, the innermost lining of the arterial wall is the endothelium, a single layer of cells. This protective layer plays a pivotal role in the atherosclerotic process. Blood, containing red blood cells, white blood cells (leukocytes) such as monocytes and T lymphocytes, and platelets, circulates through the vascular lumen. As atherosclerosis progresses, each of the different layers of the arterial wall becomes affected. 1. Initiation of Atherosclerosis (Endothelial Dysfunction) Research in the past 3 decades has dramatically modified our understanding of the atherosclerotic process. The original “response to injury” hypothesis proposed that the first step in atherosclerosis was endothelial denudation and that the principal events in the development of atherosclerotic plaques were accumulation of lipids within the artery wall and proliferation of smooth muscle cells. However, we now know that atherosclerosis is a much more complex process, in which inflammation plays a pivotal role (Ross, 1999). The primary initiating factor in atherosclerosis is a breakdown in the normal properties of the endothelium, termed endothelial dysfunction. The endothelium is an active tissue which normally promotes cardiovascular health by producing antiplatelet, anti-clotting, and fibrinolytic factors that prevent cells adhering to its surface, and regulating vascular tone through the production of molecules such as nitric oxide. Endothelial dysfunction, caused by a variety of factors, including high levels of circu-
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lating modified low-density lipoprotein (LDL)cholesterol, physical shear stress at points of arterial occlusion, elevated levels of homocysteine, free radicals, vasoactive amines, and infectious microorganisms, leads to a breakdown in these cardioprotective properties and development of a pro-inflammatory and pro-thrombotic environment. This is more common at specific atherosclerosis-prone sites of the artery including arterial branches, bifurcations and curvatures, where there are characteristic alterations in the flow of blood, including decreased shear stress and increased turbulence. Dysfunctional endothelium becomes more permeable to lipoproteins such as LDL-cholesterol, which accumulate in the subendothelial matrix (Figure 2). Oxidative modification of LDL-cholesterol by reactive oxygen species produced by vascular cells results in minimally oxidized LDL species (mOx LDL) with proinflammatory activity. mOxLDL stimulates overlying endothelial cells to express cell adhesion molecules (CAMs), which bind to complementary molecules on leukocytes and platelets, thereby promoting their recruitment to the vessel wall. Other factors that stimulate CAM expression include pro-inflammatory cytokines and chemo-attractant molecules (chemokines) produced by the endothelium, platelets, leukocytes and smooth muscle cells, changes in blood flow at atherosclerosis-prone sites of the artery, and lowered production of endothelium-derived nitric oxide, an anti-inflammatory, vasodilator molecule that normally limits CAM expression. ApoE-deficient mice, which have elevated cholesterol and acquire widespread arterial lesions with a pathomorphology similar to humans, are an invaluable model for studying atherosclerosis. In vivo fluorescence microscopy studies of the common carotid artery of these mice showed that platelets are one of the first blood cells to arrive at the scene of endothelial dysfunction and that they adhere directly to the intact endothelial monolayer even in the absence of endothelial disruption (Massberg et al., 2002). The initial tethering (rolling) of platelets on dysfunctional endothelium is mediated through platelet glycoprotein (GP) Ibα binding to von Willebrand factor and the adhesion molecule P-selectin, expressed on activated endothelial cells. Subsequently, ligation of the GPIbIX-V complex during platelet tethering leads to activation of platelet GPIIb-IIIa and firm, shear resistant, adhesion of platelets to the endothelium. Sulfatides expressed on the platelet surface are also thought to contribute to platelet adhesion since they are major ligands for P-selectin. Upon binding to dysfunctional endothelium, platelets become activated and surface express P-selectin.
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Lumen Monocyte
Platelet
Platelet-leukocyte binding
T-cell LDL
GPIbα P-selectin
vWF
Endothelial cell
VLA-4
PSGL P-selectin
CD11a VCAM-1
VCAM-1
cytokines chemokines
Oxidative modification
Intima
ICAM-1
ICAM-1
cytokines chemokines
mOxLDL
Smooth muscle cell
Media Adventitia FIGURE 2
Initiation of atherosclerosis.
Interaction between platelet P-selectin and the leukocyte receptor P-selectin glycoprotein ligand-1 (PSGL1) results in the formation of platelet-leukocyte aggregates (Figure 2). PSGL-1 also mediates leukocyte rolling on activated endothelium through binding to endothelial P-selectin (Merten and Thiagarajan, 2004). Platelet-leukocyte binding is important for targeting leukocytes to the lesion site. When ApoE-deficient mice are repeatedly injected with activated platelets, the resultant increase in platelet-leukocyte aggregates promotes increased leukocyte arrest on the lesion surface and increases the size of lesions (Huo et al., 2003). In contrast, inhibition of platelet interactions with endothelium and leukocytes, by removing platelet P-selectin or using monoclonal antibodies against platelet glycoproteins, substantially reduces leukocyte recruitment and progression of atherosclerosis in these mice (Huo et al., 2003; Massberg et al., 2002). Interaction between other complementary adhesion molecules expressed on leukocytes, platelets, and
endothelial cells ensures firm adhesion of leukocytes to the vessel wall and their subsequent transmigration into the intima. The initial association between leukocyte PSGL-1 and P-selectin, expressed on activated adherent platelets or activated endothelium, leads to an increased expression of β2 integrins (including CD11a and VLA-4) on leukocytes. These bind to immunoglobulin-related adhesion molecules ICAM-1 (intercellular adhesion molecule-1) and VCAM-1 (vascular cell adhesion molecule-1) that are expressed on endothelium. Specifically, ICAM-1 binds to CD11a on T lymphocytes and VCAM-1 binds to VLA-4 on monocytes. 2. Platelet-Leukocyte Interactions Upon entering the intimal layer, platelets, monocytes, and T lymphocytes participate in and perpetuate a local pro-inflammatory, pro-thrombotic response that develops the lesion (Figure 3). Activated platelets
44. Psychosocial Factors and Coronary Heart Disease: The Role of Psychoneuroimmunological Processes
953
Lumen
Monocyte
T-cell Platelet
LDL CD11a
VLA-4 GPIbα VCAM-1
P-selectin
vWF
ICAM-1
VCAM-1
ICAM-1
CD40 CD40L
MIP-1α RANTES PF-4 PDGF
MCP-1 M-CSF
IL-1β PF-4 free radicals
OxLDL
IFNγ IL-2
CD4+
Th1
IL-1β IL-8 MCP-1
Intima Smooth muscle cell
Macrophageous foam cell
IL-1β IL-8 MCP-1
Media Adventitia FIGURE 3
Platelet-leukocyte interactions during plaque development.
release a wealth of adhesive and pro-inflammatory factors, including cytokines, chemokines, vasoactive amines, and growth factors, which they deposit on the surface of leukocytes and endothelial cells through P-selectin–mediated interactions (Huo and Ley, 2004). Platelet-secreted chemokines including macrophage inflammatory protein (MIP)-1α, platelet factor 4 (PF4), and RANTES are powerful attractants of leukocytes and stimulate their migration to the endothelium. Platelet-derived growth factor (PGDF) is chemotactic for monocytes, fibroblasts, and vascular smooth muscle cells and also stimulates their proliferation within the arterial lesion. The pro-inflammatory cytokine interleukin (IL)-1β and PF-4, secreted by activated platelets, further promote leukocyte recruitment by upregulating endothelial cell expression of CAMs and stimulating endothelial release of the chemokine monocyte chemotactic protein (MCP)-1, which recruits and activates monocytes. In addition, activated platelets
surface express the molecule CD40 ligand (CD40L), which binds to CD40 on endothelial cells and promotes leukocyte binding by upregulating endothelial cell secretion of chemokines and expression of CAMs. Supporting a significant role for CD40L in atherosclerosis, lesion formation in Apo-E–deficient mice was substantially reduced by blocking the CD40/CD40L pathway (Huo and Ley, 2004). Monocytes, activated by the chemokines MCP-1 and macrophage colony stimulating factor (M-CSF), rapidly proliferate and differentiate into macrophages (Hansson, 2005). Macrophages express endocytosing scavenger receptors, which allow them to ingest highly oxidized LDL (Ox LDL), leading to formation of macrophageous foam cells, thus promoting the accumulation of LDL in the arterial lesion. The chemokine PF-4, released by activated platelets, stimulates uptake and esterification of oxidized LDL by macrophages. Activated macrophages also release toxic products of lipid
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oxidation known as free radicals, which damage the intima, and platelet-monocyte interactions promote this response. Exposure to platelet P-selectin and the platelet-derived chemokine RANTES induces monocyte-macrophages to express inflammatory cytokines interleukin-1β, interleukin-8, and MCP-1, which further promote their activity. With time the macrophageous foam cells die, contributing their lipid-filled contents to the necrotic core of the lesion. Activated T lymphocytes are also important contributors to the progression of atherosclerosis and are present at all stages of plaque development (Hansson, 2005). The predominant type of T-cells found in plaques is CD4+ type 1 helper (Th1) cells. These cells become activated upon recognition of protein antigens, which are processed and presented to them by macrophages or dendritic cells (a special type of macrophage). Such antigens include oxidized lipoproteins, bacterial endotoxins, and apoptotic cell fragments. In turn, activated Th1 cells secrete the cytokines IFN-γ, IL-2, TNF-α, and TNF-β, which stimulate macrophage production of oxygen-free radicals and pro-inflammatory cytokines and upregulate CAM expression on endothelial cells, thereby accelerating the inflammatory process. The early stage of atherosclerosis, characterized by an accumulation of lipid-laden macrophages, together with some platelets and T lymphocytes beneath the endothelium, is often referred to as a fatty streak. 3. Plaque Progression: Smooth Muscle Cell Migration and Proliferation The transition from fatty streak to a more complex lesion is characterized by migration of smooth muscle cells from the medial layer of the blood vessel wall into the intima. Intimal smooth muscle cells proliferate, and some take up modified lipoproteins contributing to foam cell formation. Their migration and proliferation are stimulated by cytokines, chemokynes, and growth fac-tors released by activated platelets, monocytesmacrophages, T-cells, and endothelial cells. These factors also promote smooth muscle cell production of fibrous elements (collagen and fibrin), leading to the formation of a dense extracellular matrix of fibrous tissue known as a fibrous cap (Figure 4). Other inflammatory substances that play an active role in atherosclerotic plaque development are Creactive protein (CRP) and fibrinogen. These proteins are generated by the liver during the acute phase hepatic response, which can be activated by the inflammatory cytokines IL-6 and TNF-α. In turn, CRP stimulates monocyte-macrophage production of proinflammatory cytokines, upregulates expression of adhesion molecules, enhances production of MCP-1,
and induces monocyte recruitment into the arterial wall. It also binds to modified LDL and facilitates its uptake by macrophages. Fibrinogen promotes atherosclerosis by stimulating smooth muscle cell proliferation and upregulating expression of CAMs. It also plays a major role in thrombosis, as explained below. 4. Advanced Atherosclerosis and ACS As these inflammatory processes continue throughout adult life, the atherosclerotic plaque grows into an advanced lesion. A few lesions are stenotic, meaning that the plaque protrudes into the arterial lumen and obstructs the flow of blood to the working heart muscle, resulting in ischemia. However, the majority of lesions are non-stenotic, because the artery compensates by dilating or remodeling so that the thickening of the arterial wall does not immediately result in narrowing of the vessel lumen. Eventually, however, the artery can no longer compensate by dilation, and the lesion may then intrude into the lumen and inhibit blood flow. Non-stenotic lesions are typically highly infiltrated with inflammatory cells and lipids, are covered with a thin fibrous cap, and are vulnerable to rupture. Acute cardiac events occur when the supply of blood through the coronary arteries to the working muscle of the heart is reduced or stopped altogether. This can happen with progressive narrowing of the lumen of the artery, but more commonly, acute cardiac events involve rupture of vulnerable plaque, exposing the underlying layers to circulating platelets, which then aggregate to form a blood clot (thrombus). Unfortunately, since non-stenotic vulnerable lesions do not immediately cause ischemia, they are often difficult to detect until they reach an advanced stage. Inflammatory processes are also pivotal at this time (Hansson, 2005) (Figure 5). Indeed, it appears that the degree of inflammatory activity and associated morphologic instability of a plaque, rather than the amount of stenosis, defines its propensity to cause an ACS. As outlined above, interactions between platelets, leukocytes, and endothelial cells stimulate a number of proinflammatory, pro-thrombotic processes, and these also contribute to plaque rupture and thrombosis in ACS (Freedman and Loscalzo, 2002). In addition and particularly relevant to ACS, activated T-cells and platelets stimulate macrophages to produce enzymes called matrix metalloproteinases (MMPs), which degrade the extracellular matrix that lends strength to the plaque’s protective fibrous cap, thereby rendering the cap weak and prone to rupture. IFN-γ produced by activated T-cells inhibits collagen synthesis by smooth muscle cells, limiting their capacity to renew the collagen that stabilizes the plaque, and platelet binding
44. Psychosocial Factors and Coronary Heart Disease: The Role of Psychoneuroimmunological Processes
955
Lumen CRP
Monocyte
T-cell
Fibrinogen
Platelet VLA-4 GPIbα VCAM-1
P-selectin
VCAM-1
LDL
CD11a
ICAM-1
vWF
ICAM-1
fibrous cap (collagen, fibrin)
OxLDL CRP
cytokines chemokines growth factors
Intima
cytokines chemokines growth factors
Macrophageous foam cell
CRP
Smooth muscle cell
Media Adventitia FIGURE 4
Migration and proliferation of smooth muscle cells.
stimulates production of tissue factor and plasminogen activator inhibitor (PAI)-1 by monocytes/macrophages, thus promoting thrombus formation. Tissue factor is one of the primary initiators of blood coagulation/clotting in ACS. PAI-1 is the principal inhibitor of tissue plasminogen activator (t-PA), an important circulating fibrinolytic component of plasma. PAI-1 promotes the extension and stability of newly formed thrombus, by forming ternary complexes with t-PA and fibrin on the clot surface, thus preventing the fibrinolytic activities of t-PA and stabilizing the thrombus from premature lysis. The acute phase inflammatory proteins CRP and fibrinogen are also important in advanced atherosclerosis. CRP stimulates the expression of tissue factor on macrophages, smooth muscle cells, and endothelial cells in and around coronary artery plaques. Meanwhile, fibrinogen is cleaved by thrombin to produce fibrin, the most abundant component of clots. It also plays a pivotal role in platelet
aggregation, through binding to receptors on adjacent platelets, and increases plasma and whole blood viscosity.
B. Empirical Evidence Relating Immune Factors with CHD and ACS The growing appreciation of the role of inflammation in atherogenesis has focused attention on the clinical utility of inflammatory biomarkers as predictors of cardiovascular risk and as therapeutic targets for cardiovascular disease prevention. The marker that has been most extensively studied in this respect is the acute phase reactant CRP (Koenig, 2005; Pai et al., 2004). Several large-scale prospective studies have shown that baseline level of high sensitivity (hs)CRP in apparently healthy individuals is a strong independent predictor of future cardiovascular disease and acute coronary syndromes. Elevated CRP levels are
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Lumen Platelets
Fibrinogen fibrin fibrous cap
PAI-1 Tissue factor
MMPs MMPs IFNγ
Intima
cytokines chemokines growth factors
CRP
Media Adventitia FIGURE 5
Advanced atherosclerosis; plaque rupture and thrombosis.
most prominent in patients with unstable angina, and CRP concentrations at the time of hospital admission predict new coronary events and poor clinical outcome in ACS patients. Another acute-phase reactant, serum amyloid A, is also elevated in CHD patients compared with healthy controls, and is predictive of mortality in patients with unstable angina (Fichtlscherer et al., 2004). The principal inducers of CRP production by the liver are the inflammatory cytokines, IL-6 and TNF-α. Prospective studies have shown that elevated plasma IL-6 is associated with an increased risk of CHD in apparently healthy middle-aged and elderly men and women (Yudkin et al., 2000). TNF-α has a limited halflife and is more difficult to measure than IL-6. Nevertheless, one study found an association between elevated plasma TNF-α and future risk of coronary events in apparently healthy elderly people (Cesari et al., 2003). The effects of TNF-α are mediated by two
receptors, which circulate in soluble forms (type 1 and type 2, sTNF-R1 and sTNF-R2), are easier to measure than TNF-α itself, and may better reflect long-term average circulating levels of TNF-α. Relevant to this, a recent report found that elevated plasma levels of sTNF-R1 and sTNF-R2 were associated with an increased risk of CHD in middle-aged women without previous cardiovascular disease (Pai et al., 2004). Raised circulating levels of IL-6 and TNF-α have been consistently reported in patients with acute coronary syndromes and are predictive of future cardiac events and mortality in these patients (Biasucci et al., 1999; Ridker et al., 2000). Other cytokines elevated in ACS patients include IL-1β, IL-1Ra, and IL-18. Raised hospital admission levels of IL-1Ra are associated with a higher risk of future coronary events in ACS patients (Biasucci et al., 1999), and serum IL-18 levels were recently identified as a strong independent predictor of death from cardiovascular causes in patients with
44. Psychosocial Factors and Coronary Heart Disease: The Role of Psychoneuroimmunological Processes
CHD, regardless of the clinical status at admission (Blankenberg et al., 2002). Conversely, elevated circulating levels of the anti-inflammatory cytokine IL-10 are associated with a more favorable prognosis in ACS patients (Fichtlscherer et al., 2004). Other inflammatory markers associated with cardiovascular risk include circulating soluble adhesion molecules and heat shock proteins. Several groups have reported a significant association between sICAM-1 levels and future cardiovascular events in initially healthy people, and elevated levels of sPselectin were found to predict major cardiovascular events in apparently healthy women (Blankenberg et al., 2003; Merten and Thiagarajan, 2004). Similarly, sVCAM-1, sICAM-1, and sP-selectin levels are predictive of future cardiovascular events in patients with established coronary artery disease. ACS patients often have elevated levels of sICAM-1, sVCAM-1, and sPselectin compared to patients with stable CHD or healthy individuals, and elevated sVCAM-1 was associated with an increased risk of subsequent cardiac events in these patients. The presence of soluble adhesion molecules, likely shed from activated leukocytes, endothelial, and/or smooth muscle cells, is thought to be indicative of an ongoing inflammatory process. Heat shock proteins (HSPs) are abundantly expressed in atherosclerotic lesions, and both HSPs and anti-HSP antibodies stimulate the production of pro-inflammatory cytokines. Circulating antibodies against HSP60 and HSP65 are elevated in patients with coronary artery disease and have been shown to be significantly associated with both the presence and severity of atherosclerosis. Levels of anti-HSP60 and anti-HSP65 antibodies were also found independently to predict future cardiovascular morbidity and mortality in patients with documented coronary artery disease (CAD). In contrast, high levels of human HSP70 were associated with low coronary risk, suggesting a more complex role for these proteins in coronary atherosclerosis (Mandal et al., 2005). More simple measures of immune function such as leukocyte counts are also related to the development of CHD (Coller, 2005). A meta-analysis of 19 prospective studies conducted between 1974 and 1996 reported a CHD risk ratio of 1.5 for healthy people with total leukocyte counts in the top compared with bottom third of the population distribution. Since then, additional studies of leukocyte numbers and cardiovascular risk involving more than 350,000 patients have been reported, and nearly all of these studies found a significant relationship between leukocyte numbers and vascular disease morbidity and mortality. There is strong evidence that leukocytosis at the time of onset of an acute vascular event predicts short-term morbid-
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ity and mortality. In the two largest studies of acute MI patients, examining 268,486 patients in total, the in-hospital mortality rates for those in the group with highest admission leukocyte counts were 11.5% and 19.6% higher than those in the lowest leukocyte count group. Leukocyte count is also predictive of long-term cardiovascular outcomes. For example, the GISSIPrevenzione study on 11,324 MI survivors found that mortality rate over a 4-year period was 17.7% in those with leukocyte counts ≥9000/μl, compared to 6.9% in those with leukocyte counts of <6000/μl. Evidence to date suggests that, among the leukocytes, cardiovascular morbidity and mortality are most closely associated with neutrophil numbers and to a lesser extent monocytes (Coller, 2005). In addition, circulating levels of platelet-leukocyte aggregates appear to correlate with the severity of cardiovascular disease (Freedman and Loscalzo, 2002). Circulating platelet-monocyte and platelet-neutrophil aggregates are more frequent in unstable angina and MI patients compared to patients with stable coronary disease. Similarly, elevated numbers of circulating platelet-leukocyte aggregates have been reported in patients with stable coronary artery disease compared with healthy people. However, so far, little work has been done evaluating their prognostic value. A number of investigators have examined the relationship between hemostatic factors linked with inflammation and cardiovascular risk. The best studied of these is the acute phase reactant fibrinogen. A recent meta-analysis of data from 31 prospective studies covering 125,211 participants found significant associations between plasma fibrinogen level and the risks of CHD, stroke, other vascular mortality, and nonvascular mortality in healthy middle-aged adults. The hazard ratios per 1-g/L increase in usual fibrinogen were 1.8 for CHD and stroke, after adjustment for age, sex, and established vascular risk factors (Danesh et al., 2005). Similarly, fibrin D-dimer has been consistently and independently associated with atherosclerosis and coronary events across multiple studies (Saigo et al., 2004). Meta-analysis indicates that von Willebrand factor is a predictor of future CHD (Whincup et al., 2002), while population studies have shown less consistent associations between cardiovascular risk and Factors VIII, IX, and XI; tissue plasminogen activator; and plasminogen activator inhibitor-1 (PAI-1). Variations in results are likely due to the complexity of the coagulation/fibrinolytic system, wherein each factor is intimately interrelated with another, meaning that it is sometimes difficult to assess the impact of a single factor (Saigo et al., 2004). Finally, results emerging in the past few years have highlighted a number of novel inflammatory markers
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relevant to cardiovascular risk, including soluble CD40 ligand (sCD40L), myeloperoxidase (MPO), the metalloproteinases MMP-9 and pregnancy-associated plasma protein-A (PAPP-A), and lipoprotein phospholipase A2 (Lp-PLA2) (Fichtlscherer et al., 2004). sCD40L is a powerful biochemical marker of thrombotic inflammatory activation in patients with acute coronary syndromes and has been used to identify patients with ACS that are at highest risk for future ischemic events as well as to predict which patients will benefit from anti-platelet treatment. The enzyme MPO, secreted during degranulation of polymorphonuclear neutrophils, displays potent pro-atherogenic properties including oxidation of LDL, catalytic consumption of nitric oxide, and activation of metalloproteinases, and was recently shown to be a strong predictor of adverse outcome in ACS patients. In addition, plasma levels of the metalloproteinases MMP-9 and PAPP-A, which are predominantly expressed in unstable plaques, were found to correlate with atherosclerosis severity and predict poor cardiovascular outcomes in CAD patients. Also currently under investigation is the phospholipase A2 superfamily member, Lp-PLA2. Lp-PLA2 is a macrophage-derived enzyme that plays a key role in atherosclerosis, by hydrolyzing oxidized LDL to pro-atherogenic products: oxidized fatty acids, and lysophosphatidylcholine. Recent epidemiological studies have shown that an elevated circulating level of Lp-PLA2 is an independent predictor for coronary risk in apparently healthy people and predicts adverse cardiovascular outcomes in patients with documented CHD (Sudhir, 2005). Not surprisingly, research interest is now focused on developing anti-inflammatory therapies directed at these atherosclerotic biomarkers. Drugs targeting novel putative markers are in various stages of investigational or clinical evaluation. The role of established treatments such as anti-platelet drugs (aspirin) and statins (3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors) is also being re-evaluated and expanded. Interestingly, in addition to their lipid-lowering effects, statins have numerous anti-inflammatory properties and were recently shown to inhibit vascular smooth muscle cell proliferation and production of IL-6.
C. Potential Role of Infection One of the factors thought to provoke endothelial dysfunction in atherosclerosis is a bacterial or viral infection. An association of viral infection with atherosclerosis was first reported in the 1970s when experimental infection of germ-free chickens with an avian herpesvirus was found to induce arterial disease
(Fabricant et al., 1978). Since then, data from numerous cross-sectional epidemiological studies in humans have demonstrated a higher incidence of coronary atherosclerosis in adults with serological evidence of prior infection with intracellular pathogens including Chlamydia pneumoniae (C. pneumoniae), Helicobacter pylori (H. pylori), herpesviruses (cytomegalovirus and herpes simplex virus), hepatitis A virus, and influenza, supporting an association between infection and risk of developing atherosclerosis (Gurevich, 2005; Liuba and Pesonen, 2005). In addition, a number of these microorganisms have been detected in human atherosclerotic plaques and linked with vascular inflammation. However, so far, no causal relationship has been established, and different studies have provided conflicting results. A meta-analysis of 10 studies of C. pneumoniae antibodies found at best a modest association with CHD, and analyses of H. pylori have also been negative (Danesh and Peto, 1998; Danesh et al., 2002). Possible reasons for inconsistent findings are that the tools used to diagnose infection are largely serology based and cannot distinguish between past and ongoing chronic infections. Furthermore, the atherogenic potential of infections may be dependent on the presence of additional risk factors with which infections synergistically react, such as genetic background, diet, and social class, which are not always controlled for in clinical studies. Most studies to date have focused on the contribution of infection to the advanced stages of atherosclerosis in adults. Since the greatest burden of infection occurs in childhood, infection may play a more important role during the pre-clinical phase (Charakida et al., 2005). Prospective studies have demonstrated an increased risk of cardiovascular events in patients with serological evidence of prior infection. A significant association was found between chronic H. pylori infection and increased risk of ischemic stroke in Japanese patients (Sawayama et al., 2005). Influenza infection is associated with a raised incidence of cardiovascular events, and concordantly, influenza vaccination seems to prevent myocardial infarction during influenza season (Marchesi et al., 2005). In addition, a recent study of over 39,000 patients showed that acute lower respiratory tract infections and urinary tract infections are associated with a significant transient increase in the risk of heart attack or stroke (Smeeth et al., 2004). These results indicate that the effect of infections on cardiovascular risk may be generic and not linked to specific types of infection. Various hypotheses of how infection promotes atherosclerosis have been proposed. First, certain microorganisms and/or their components might directly invade cells in the arterial wall, leading to a local
44. Psychosocial Factors and Coronary Heart Disease: The Role of Psychoneuroimmunological Processes
inflammatory reaction that stimulates atherogenesis. Second, chronic infection elsewhere in the body may lead to a systemic inflammatory state with increases in circulating cytokines, acute phase reactants, leukocytes, and other factors that activate endothelial cells and promote arterial damage. An extended hypothesis proposed by Epstein and colleagues is that instead of a particular infectious organism being important, the crucial factor is total pathogen burden, or the number of pathogens to which people have been exposed in their lifetimes. Thus, development of atherosclerosis would result from cumulative arterial injuries by short-lasting acute infections, disease severity increasing with the number of infections, and ultimately leading to the formation of a mature vulnerable plaque (Epstein et al., 1999). Supporting an additive effect of infection, atherosclerotic changes are more likely to occur in animals with repeated pathogen exposure (Liuba and Pesonen, 2005). Cross-sectional studies in humans with CAD have shown that the risk for coronary endothelial dysfunction and the extent of angiographically documented atherosclerosis increase with the number of pathogens to which an individual is exposed (Espinola-Klein et al., 2002; Zhu et al., 2001). Furthermore, prospective studies in cohorts of patients with angiographically documented CAD have found a graded dose-response relationship of increasing relative hazards for myocardial infarction or death with increasing pathogen burden, after controlling for other risk factors. For example, Espinola-Klein et al. (2002) found that over 3 years, cardiovascular mortality rate was 7.0% in patients with advanced atherosclerosis and seropositive for 0 to 3 pathogens, compared with 20% in those seropositive for 6 to 8 pathogens. Despite the evidence linking infection with atherosclerosis, large clinical trials of antibiotic therapy have found no overall beneficial effect of antibiotics in reducing mortality or cardiovascular events in CAD patients (Andraws et al., 2005). One explanation for these negative findings is that most trials have targeted specific infectious agents. If the overall pathogen load is important, then anti-microbial therapy directed against a single pathogen is likely to be ineffective. Another reason could be that microorganisms within infected cells are resistant to antibiotics. For example, C. pneumoniae within monocytes has been shown to resist anti-chlamydial therapy (Gieffers et al., 2001). Furthermore, experimental studies of infection have shown that bacterial antigens such as lipopolysaccharide may persist in the arterial wall, even in the absence of the viable pathogens. Thus, although antibiotics may kill bacteria, bacterial antigens might remain and continue to provoke inflammation.
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Laboratory studies have provided some insight into the biochemical mechanisms through which infection might promote atherosclerosis (Epstein et al., 1999). First, microorganism infection of cultured endothelial cells stimulates the production of inflammatory cytokines and the expression of adhesion molecules and tissue factor. Second, Gram negative bacteria such as E. coli, C. pneumoniae, and H. pylori may release lipopolysaccharide endotoxins, which cause arterial damage. Third, an autoimmune response may be induced due to cross-reactivity between antigens that are common to vascular cells and pathogens. For example, Chlamydia organisms are rich in HSP60, and there is a high degree of sequence homology between microbial and mammalian HSP60 due to evolutionary conservation (Mandal et al., 2005). This molecular mimicry could result in misdirected autoimmunity against HSPs expressed on vascular endothelium. Supporting this idea, simultaneously high levels of antibodies to human HSP60 and C. pneumoniae have been associated with an increased risk of atherosclerosis and disease severity in cardiac patients (Hoshida et al., 2005). Fourth, there is evidence that infection alters lipid metabolism. Increased oxidative modification of LDL-cholesterol and reduced circulating levels of high-density lipoprotein (HDL)-cholesterol have been observed during acute and chronic infections (Khovidhunkit et al., 2004). Since HDL mediates reverse cholesterol transport, as well as clearance of oxidative products and inflammatory mediators, it is considered anti-atherogenic, whereas oxidized LDL-cholesterol has pro-atherogenic effects. A final mechanism that has generated much recent interest is the activation of Tolllike receptors (TLR) by infectious pathogens (Rattazzi et al., 2005). TLRs are mainly expressed on the surface of macrophages and are able to recognize molecular patterns commonly found on pathogens, such as bacterial endotoxin. Inside atherosclerotic lesions, both endothelial cells and macrophages express TLRs, and receptor expression can be upregulated by oxidized LDL. Activation of TLRs by bacterial products is accompanied by activation of NFkB and MAPK pathways, with subsequent synthesis of pro-inflammatory mediators (endothelial production of cytokines, adhesion molecules, endothelin-1, chemokines, and reactive oxygen species). In addition, activation of macrophage TLRs by bacterial toxins induces macrophage expression of aP2 (a fatty acid-binding protein important for lipid transport) and increases macrophage LDL uptake and cholesterol content (Kazemi et al., 2005). Thus, TLRs offer a potential link between bacterial infection, foam cell formation, activation of the inflammatory response, and atherosclerosis progression.
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Evidence from animal and human studies supports a role for infection in endothelial dysfunction. In ApoE knockout mice, repeated intranasal administration of C. pneumoniae caused progressive impairment of aortic endothelial vasomotor function, and similar detrimental effects were observed in young piglets (Liuba and Pesonen, 2005). A recent study investigating the effect of common infections on endothelial function in 600 10-year-old children found that those who were currently infected or who had an infection in the past 2 weeks had markedly lower brachial artery flow-mediated dilation (a measure of endothelial function) than healthy controls (Charakida et al., 2005). Similarly, in healthy adults, typhoid (Salmonella typhi) vaccination induces temporary but profound brachial endothelial dysfunction, and this response is associated with increases in total white blood cells and serum levels of the inflammatory cytokines IL-6 and IL-1Ra (Hingorani et al., 2000). Another group found that endothelial function was significantly lower and circulating levels of inflammatory markers CRP and sICAM-1 higher in healthy male subjects with seropositive antibodies to H. pylori compared to those with seronegative antibodies (Oshima et al., 2005), and comparable findings were reported in a small group of men infected with influenza, where increases in serum CRP and sICAM-1 were positively associated with endothelial impairment (Marchesi et al., 2005). Together, these results suggest that the inflammation induced by microbial infection may contribute to endothelial dysfunction and ultimately atherosclerosis.
D. Conclusion There is robust evidence that inflammation plays a crucial role in the initiation, progression, and complications of atherosclerosis. Although an independent causal role of infection in atherosclerosis has yet to be established, there is general consensus that infection could additively interact with other conventional, genetic, and environmental risk factors in the development of atherosclerosis and occurrence of ischemic events. Increasing knowledge of the inflammatory and thrombotic components of atherosclerosis is expected to facilitate assessment of patients’ cardiovascular risk and thereby optimize diagnostic and therapeutic efforts in those most vulnerable. The way in which psychosocial and biological processes are thought to influence the progression of CHD is summarized in Figure 6. The task of psychobiological studies is to discover how these processes are interrelated.
IV. PSYCHOBIOLOGICAL STUDIES Several different types of psychobiological study have been conducted that provide evidence for the role of psychoneuroimmunological processes in CHD. These include cross-sectional observational studies, acute stress experiments, clinical investigations of patients with established CHD, and longitudinal studies of the prediction of future cardiovascular risk. There is also extensive work in animals on the impact of behavioral stimuli on inflammatory processes relevant to atherosclerosis that is not detailed here. Each type of study has both advantages and limitations, and it is only by integrating findings from different approaches that a comprehensive picture can be obtained of the extent to which inflammatory and immune processes mediate psychosocial influences on CHD.
A. Cross-sectional Studies of Psychosocial Factors Cross-sectional associations between psychosocial factors and fibrinogen, CRP, inflammatory cytokines, and other markers can be readily obtained through analyzing blood samples collected during clinical screening in epidemiological surveys. Since these measures are relatively inexpensive, it is possible to obtain data from large samples, allowing quite small associations to be detected. Associations can be modest in absolute terms but important as far as population health is concerned; thus, relationships between inflammation and SES or depressive symptoms may be modest but have considerable impact in the light of the high prevalence of these factors in the population at large. Additionally, population sampling can be employed, avoiding the selection factors that operate when small convenience samples are recruited. It is sometimes also possible to follow up participants longitudinally so that relationships with health outcomes can be determined. Cross-sectional observational studies have their limitations. The causal sequence cannot be determined in such a study, and it is impossible to conclude that psychosocial factors directly lead to differences in biological activity. Biological data are typically analyzed from a single blood sample, and the representativeness and reliability of the measure for the individual may not be known. Measures of inflammation are influenced by a host of factors that need to be taken into account, ranging from demographic characteristics (age, ethnicity, gender), lifestyle factors (smoking, alcohol consumption, physical activity), and anthropo-
44. Psychosocial Factors and Coronary Heart Disease: The Role of Psychoneuroimmunological Processes
PSYCHOSOCIAL Chronic Stressors Low SES Work stress Neighborhood stress Marital stress Care- giving Social isolation
Psychological Traits Depression Anxiety Hostility
Acute Triggers Earthquakes War and terrorism Conflict with colleague, spouse, or neighbor Anger
Depression Exhaustion
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BIOLOGICAL Fatty streak Bacterial/Viral Infection
Long-term development of atherosclerosis
Advanced Plaque
Inflammation Platelets and leukocytes Cytokines Chemokines Growth factors Ox LDL CAMs CD40L/CD40 Free radicals CRP and fibrinogen Metalloproteinases HSP60/65 MPO Lp-PLA2
Triggering of cardiac event
ACS Risk of further cardiac event
Thrombosis Platelets Tissue factor PAI-1 Fibrinogen Fibrin-D-dimer vWF Factors VIII, IX, XI
Poor Cardiac Outcome
FIGURE 6 Schematic diagram illustrating the hypothesized role of psychosocial and biological factors at various stages of CHD.
metric characteristics (body mass, abdominal adiposity). Therefore, an association between psychosocial factors and an inflammatory response may be secondary to other influences. Finally, data are typically collected in population studies when people are resting or sitting quietly in the clinic, so dynamic associations between biological factors and behavioral or emotional stimuli are not assessed.
(Brunner et al., 1996; Hemingway et al., 2003; Wamala et al., 1999). A relationship between lower SES and hemostatic measures such as Factor VII antigen and Factor VIII activity has also been described (Steptoe et al., 2003b; Wamala et al., 1999). Data relating sICAM-1 levels with SES have been less consistent (Hemingway et al., 2003), but Malik et al. (2001) showed that people in non-manual jobs had lower levels than those working in manual occupations.
1. Socioeconomic Status The most consistent evidence from population studies relates many of the biological measures detailed in “Pathophysiology of CHD” with low SES. For example, individuals with lower income from a working population were more than three times more likely to have high plasma HSP60 than more affluent groups after controlling for age, gender, and body mass (Lewthwaite et al., 2002). Lower SES defined by occupational grade is associated with higher plasma fibrinogen, plasma CRP and IL-6, and level of von Willebrand factor antigen, after adjusting for age, adiposity, smoking, blood pressure, and other covariates
2. Work Stress and Other Forms of Chronic Stress There is consistent evidence that plasma fibrinogen concentration is related to chronic work stress (Brunner et al., 1996). For example, a study of nearly 900 healthy Belgian men found that job control was inversely associated with fibrinogen after adjusting for age, education, body mass, smoking, alcohol consumption, and treatment of high blood pressure and hyperlipidemia (Clays et al., 2005). Associations between high work stress and von Willebrand factor and Factor VIII have been described in healthy Swedish women (Wamala et al., 1999). Population studies have found
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no significant relationship between IL-6 or CRP and work stress (Clays et al., 2005; Hemingway et al., 2003), but IL-6 has been associated with other chronic forms of stress. Some of the most striking effects have emerged from investigations of informal carers for dementing relatives. Kiecolt-Glaser et al. (2003) monitored caregivers and matched controls over a 6-year period. Caregivers showed a progressive increase in plasma IL-6 over the years that was some four times larger than that recorded from controls. This effect was not due to differences in body mass, smoking, sleep quality, physical activity, or alcohol consumption, even though these factors also influenced IL-6. It is not clear why work stress does not show associations, but one possibility is that more severe forms of life stress are needed before changes in CRP or IL-6 emerge. 3. Protective Social Factors Few findings linking protective social factors with immune and inflammatory markers relevant to CHD have been published to date (von Kanel et al., 2001). In their study of healthy Swedish women, Wamala et al. (1999) recorded higher levels of fibrinogen and von Willebrand factor in socially isolated than integrated participants. The association with fibrinogen has been confirmed in other samples such as the Whitehall II cohort (Steptoe et al., 2003a). Socially isolated individuals are also more likely to have high HSP60 levels in their blood (Lewthwaite et al., 2002). Unfortunately, relationships with social support have been little studied in this context and merit fuller investigation. 4. Psychological Characteristics The greatest amount of evidence in population studies is for associations between depression or depressed mood and inflammatory markers, much of which is detailed elsewhere in this book. Thus, analysis of the Coronary Artery Risk Development in Young Adults (CARDIA) study established associations between fibrinogen and depression that have been confirmed in other cohorts (Folsom et al., 1993). Penninx et al. (2003) showed in a sample of 3,000 older adults that depressed mood was positively associated with elevated CRP, IL-6, and TNF-α after adjustment for gender, age, adiposity, current disease, smoking, alcohol use, and other factors. Other studies indicate that the association of depression with CRP is stronger among men than women (Ford and Erlinger, 2004). A small study with a convenience sample demonstrated positive associations between depressive symptoms and expression of IL-1β, TNF-α, and MCP-1 following in vitro stimulation with lipopolysaccharide (Suarez et al., 2003). Endothelial function, assessed non-
invasively in humans with the flow-mediated dilation technique, is impaired in depressed patients, again suggesting an influence on vascular processes involved in atherosclerosis (Broadley et al., 2002). There has also been great interest in whether platelet activation is heightened in depression. Several studies have shown positive associations using measures of platelet aggregation in response to receptor agonists like ADP, plasma concentration of platelet products PF-4 and β-thromboglobulin, and expression of platelet activation markers. However, a systematic review of this literature showed that results were quite inconsistent, with many studies using small samples and failing to control for relevant confounders (von Kanel, 2004). Hostility has received less attention, but Miller et al. (2003) have argued from a small study of community volunteers that hostility is associated with elevated IL-6 and TNF-α in adults with low but not high depression levels.
B. Acute Stress Effects The second approach to the investigation of links between psychosocial factors and biological variables implicated in atherosclerosis involves measuring responses to acute stress. Laboratory mental stress testing involves the measurement of physiological responses to standardized stimuli such as problemsolving tasks or emotionally demanding social interactions. In children, tasks based on computer games are frequently used. The crucial element is that conditions are perceived as stressful, challenging, and involving. Two aspects of the physiological responses elicited by mental stress tests are important: reactivity (the magnitude of changes elicited) and recovery (the length of time taken before measures return to reference levels after the tasks are completed). For most physiological variables, high reactivity and delayed recovery are believed to be pathogenic, since they are indicative of dysfunction in physiological regulatory processes. However, there are circumstances in which low physiological reactivity may be characteristic of people experiencing chronic life stress (Charmandari et al., 2005). When applied carefully, mental stress testing induces consistent physiological responses with good test-retest reliability. Sophisticated measures of cardiovascular, metabolic, inflammatory, and hemostatic variables can be carried out repeatedly. Confounding factors can be monitored or eliminated, while the experimental manipulation of stimuli allows the causal factors responsible for the physiological responses to be determined. The disadvantages of mental stress testing are that studies are acute, so that only short-
44. Psychosocial Factors and Coronary Heart Disease: The Role of Psychoneuroimmunological Processes
term responses are observed, and typically involve reactions to artificial stimuli that rarely occur in the real world. Evidence suggests that several biological factors central to inflammation and atherosclerosis are sensitive to acute psychological stress. 1. Cytokines Studies in humans and animals have shown that circulating levels of inflammatory cytokines are altered by psychological stress. For example, one study found that acute psychological stress induced by two challenging mental tasks, a color-word interference task and mirror tracing, lead to significant increases in plasma levels of the inflammatory cytokines IL-6 and IL-1Ra, in healthy humans (Steptoe et al., 2001). These responses were delayed, with maximal plasma cytokine levels detected 2 hours following stress exposure. More recently, another group also reported delayed plasma IL-6 responses to the Trier Social Stress Test, in healthy volunteers. Notably, the IL-6 stress responses persisted when volunteers carried out the same tasks 1 and 2 weeks later and showed no adaptation to repeated stress (von Kanel et al., 2005b). In addition, stressful speech tasks have been shown to increase circulating levels of IL-1β in healthy volunteers (Heinz et al., 2003). The cellular origin of these stress-responsive cytokines is currently unknown. However, acute psychological stress has been shown to activate IL-1β gene expression in peripheral blood mononuclear cells of healthy humans (Brydon et al., 2005a). IL-1β stimulates IL-6 production, and increases in IL-1β gene expression were positively correlated with plasma IL-6 responses to stress. This suggests that stress-induced increases in mononuclear IL-1β may contribute to the plasma IL-6 response. Supporting results in humans, various stressors, including physical restraint, social disruption, and open-field exposure, have been consistently shown to increase circulating levels of IL-6 in rats, and restraint stress was also found to stimulate IL-1 and TNF-α secretion in these animals (Black and Garbutt, 2002). 2. Hemostatic Factors Acute mental stress activates both coagulation (i.e., fibrinogen, clotting factors VII and VIII, von Willebrand factor, thrombin) and fibrinolysis (i.e., tissuetype plasminogen activator) in healthy individuals (von Kanel et al., 2001). There is some debate as to whether these effects are a true phenomenon or whether they merely result from stress-induced changes in hemoconcentration, resulting from a loss of plasma volume within the intravascular space and concomitant concentration of non-diffusable blood
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constituents. Supporting a true effect, Zgraggen and colleagues (2005) recently showed that increases in several plasma coagulation factors in response to the Trier Social Stress Task in healthy men were independent of changes in plasma volume. The magnitude of coagulation responses to acute mental stress remains unaltered when volunteers are exposed to the same stressor 2 weeks later (von Kanel et al., 2004b). The apparent incapacity of the coagulation system to adapt to repeated stress could contribute to increased coronary risk, particularly in cardiovascular disease patients. 3. Leukocytosis, Adhesion Molecules, and Chemotaxis Various acute psychological stressors such as public speaking tasks stimulate a redistribution of leukocytes in the peripheral circulation of healthy individuals, resulting in a marked increase in the number of circulating leukocytes, the most pronounced increases occurring in cytotoxic T-cell and natural killer cell subsets (Benschop et al., 1996). The exact mechanisms underlying this rapid leukocytosis are unclear. However, it is likely that altered expression of cell adhesion molecules on the surface of leukocytes is involved. Acute psychological stress in humans stimulates a preferential increase in the number of lymphocytes not expressing L-selectin (CD62L−) versus CD62L+ cells (especially among cytotoxic CD8+ T-cells and natural killer cells), a reduction in the lymphocyte cell surface density of L-selectin, and an increase in the lymphocyte cell surface density of the integrins CD11a and Mac-1 (macrophage-associated antigen-1) (Goebel and Mills, 2000; Redwine et al., 2003). Leukocyte expression of ICAM-1 is also upregulated by acute psychological stress (Goebel and Mills, 2000). The increase in CD62L− leukocytes observed following acute stress is thought to be predominantly due to a preferential release of CD62L− cells into the circulation (Dopp et al., 2000; Mills et al., 2000). However, shedding of L-selectin from the leukocyte cell surface may also be involved. For example, Redwine et al. (2003) found that acute stress increased plasma levels of soluble L-selectin and also increased the number of circulating CD62L− cells. Supporting a shedding mechanism, a stressful oral presentation stimulated increases in circulating levels of soluble ICAM-1 levels in healthy volunteers (Heinz et al., 2003). Selective attraction of leukocytes by chemokines (chemotaxis) is also thought to play an important role in stress-induced leukocytosis. Redwine and colleagues (2003) demonstrated that an acute speech stressor increases chemotaxis of peripheral blood
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mononuclear cells to the chemokines FMLP and SDF-1 in healthy humans. Similarly, Bosch et al. (2003) showed that public speaking induces a selective mobilization of T lymphocytes that express receptors for chemokines known to be secreted by activated endothelial cells. This indicates that acute stress can mobilize immune cells that are primed to respond to inflamed endothelium. More recently, Viswanathan and Dhabhar (2005) reported that restraint stress in mice led to a 200–300% increase in infiltration of all leukocyte subtypes into a surgically implanted sponge. Importantly, when sponges were pre-treated with a predominantly lymphocyte-specific chemokine, lymphotactin, there was preferential recruitment of natural killer cells and T-cells to the site of injury, whereas sponges treated with the pro-inflammatory cytokine TNF-α stimulated increases in neutrophil infiltration, and treatment with both chemokines led to preferential recruitment of macrophages. Thus, acute stress may selectively mobilize specific leukocyte subtypes into sites of injury or immune activation, depending on the primary chemoattractants present. Stressinduced activation of leukocyte trafficking is likely to be beneficial in the context of wound healing, vaccination, or resistance to infection. However, it may also precipitate stress-induced exacerbations of inflammatory diseases such as CAD. 4. Platelets Platelet activation has been observed following a variety of acute stressors, including public speaking, mental arithmetic, and color/word interference tasks (Brydon et al., 2005b). However, there have been many inconsistent results, with the same behavioral challenge producing different responses from healthy individuals in different studies. Many studies have assessed platelet activity by measuring platelet aggregation in response to various agonists in vitro (aggregometry) or by assessing plasma levels of platelet activation products such as platelet factor 4 or β-thromboglobulin with enzyme-linked immunoassays (ELISAs). Since aggregometry and ELISA techniques involve a degree of sample manipulation, i.e., plasma separation prior to analysis, which can lead to artifactual platelet activation, this might explain the observed variation in results. Furthermore, the timing of stress-induced platelet activation in humans has not been well established, so measures may not have been made at the appropriate points. Recent evidence suggests that measurement of platelet-leukocyte aggregates (PLAs) by flow cytometry is a more accurate assessment of platelet activity. This method has the advantage of requiring little
sample manipulation, maintaining cells in their native milieu, and reducing in vitro artifactual activation. PLA measurement has yet to be used extensively to assess stress-induced platelet activation. However, our group used this method to show that acute mental stress leads to significant increases in circulating levels of PLAs in healthy middle-aged men. Increases were substantial, with an average rise of 21% in the most stress-sensitive subpopulation (platelet-monocyte aggregates), and a mean increase of 13% in PLAs overall (Steptoe et al., 2003c). 5. Lipids Mammals have evolved so that in times of stress, extra energy is supplied to the blood in the form of metabolic fuels, namely fatty acids and glucose. Relevant to this, a number of studies have documented an effect of acute psychological stress on blood lipid concentrations in healthy humans. The majority of these found that acute stress induces small but significant increases in the concentration of total and LDLcholesterol, with less consistent rises in high density lipoprotein (HDL) cholesterol (Bachen et al., 2002; Black and Garbutt, 2002). There is ongoing debate as to whether these effects occur due to a stress-induced increase in lipid biosynthesis and/or release into circulation, or are in fact secondary to stress-induced reductions in plasma volume resulting in increased concentrations of plasma proteins. Some studies found that increases in lipid levels observed following stress were no longer significant after correcting for changes in hemoconcentration, whereas others continued to observe significant effects of stress on lipids, after adjusting for this factor (Bachen et al., 2002; Black and Garbutt, 2002). 6. Endothelial Dysfunction Flow-mediated brachial arterial vasodilation has been established as a measure of arterial endothelial function. Mental stress induced by a variety of challenges, including anger recall, speech tasks, and mental arithmetic has been shown to significantly reduce brachial artery flow mediated dilation in healthy humans (Broadley et al., 2005; Ghiadoni et al., 2000; Gottdiener et al., 2003). This mental stress–induced inhibition of endothelial function can last for up to 1.5 hours poststress, and the effect may be attenuated by a hypnotic relaxation intervention (Jambrik et al., 2005).
C. Potential Mediating Pathways Psychological stress activates the sympathetic nervous system (SNS), which regulates blood pressure, heart rate, and release of catecholamines; and the
44. Psychosocial Factors and Coronary Heart Disease: The Role of Psychoneuroimmunological Processes
hypothalamic-pituitary-adrenal (HPA) axis, which regulates release of corticosteroids. Immune cells possess receptors for both catecholamines and glucocorticoids, and there is substantial evidence that these hormones modulate immune function, as noted elsewhere in this volume. Supporting a role for the SNS, the effects of acute stress on leukocytosis, adhesion molecule expression, inflammatory cytokines, and platelets can be mimicked by infusion of β-adrenergic agonists, whereas infusion of β-blockers inhibits many of these effects (Benschop et al., 1996; Mills et al., 2000; von Kanel and Dimsdale, 2000). Furthermore, stress-induced increases in leukocytosis, inflammatory cytokines, and plateletleukocyte aggregates were found to correlate with blood pressure and/or heart rate stress responses, and stress-induced alterations in hemostatic factors and lymphocyte adhesion molecule expression are positively correlated with increases in catecholamines (Brydon et al., 2005a; Redwine et al., 2003; Steptoe et al., 2003c; von Kanel et al., 2001). Glucocorticoids are best known for their antiinflammatory and immunosuppressive effects, and several studies in humans and animals have shown an inhibitory effect of glucocorticoids on the synthesis of inflammatory cytokines (Black and Garbutt, 2002). Accordingly, a recent investigation of healthy middleaged men and women showed that people with large cortisol responses to an acute stressor had lower plasma levels of inflammatory cytokines as well as smaller cytokine responses to acute stress than people with small cortisol responses (Kunz-Ebrecht et al., 2003). However, glucocorticoids may also have permissive effects. For example, while they inhibit the synthesis of inflammatory cytokines, glucocorticoids also increase the expression of certain cytokine receptors (i.e., IFN-γ, IL-1, and IL-6 receptors). Increases in plasma fibrin following the Trier Social Stress Test in healthy middle-aged men were positively associated with stress-induced elevations in cortisol, indicating that activation of the HPA axis contributes to hemostatic stress responses (von Kanel et al., 2005a). Similarly, stress-related endothelial dysfunction and impaired baroreflex sensitivity in healthy volunteers can be prevented by blocking cortisol production with metyrapone, demonstrating a direct or facilitative role for cortisol in these phenomena (Broadley et al., 2005). Stress-induced hypercortisolemia in mice causes a redistribution of leukocytes, with a reduction in the number of circulating monocytes and lymphocytes, and similar effects were observed following the awakening cortisol rise in humans. Leukocytes are thought to exit the peripheral blood to enter sites of injury and inflammation. Relevant to this, glucocorticoids stimu-
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late vascular cell adhesion molecule expression, thereby promoting leukocyte adhesion to inflamed endothelium (Black and Garbutt, 2002). Variations in glucocorticoid responses are thought to depend on their concentration, their physiological context (healthy or disease state), and whether they are activated on an acute or chronic basis. A further mechanism thought to be involved in inflammatory stress responses is the activation of nuclear factor-κB (NF-κB). NF-κB is a transcription factor which upregulates the expression of a number of inflammatory molecules, including cytokines. Acute psychological stress upregulates NF-κB expression in peripheral blood mononuclear cells of healthy volunteers. Increases in NF-κB expression paralleled stressinduced increases in catecholamines and cortisol, suggesting that both sympathetic and HPA pathways were involved in this response (Bierhaus et al., 2003). Lastly, a novel pathway that inhibits macrophage production of inflammatory cytokines, termed the cholinergic anti-inflammatory pathway, has been recently identified (Czura and Tracey, 2005). The central nervous system receives sensory input from the immune system via the vagus nerve, which innervates a number of organs that act as entry routes or filters for pathogens. Efferent vagal activity leads to release of acetylcholine (ACh), which specifically binds to α7 subunits of nicotinic ACh receptors on macrophages and inhibits NF-κB signaling and inflammatory cytokine release. Notably, human vascular endothelial cells also surface express the α7 subunit of nicotinic ACh receptors, and ACh was shown to inhibit cytokine-induced adhesion molecule expression and chemokine release by these cells.
D. Psychosocial Risk Factors and Acute Stress Responses Repeated or chronic exposure to stress may prime the immune and cardiovascular systems so that subsequent exposure to challenge results in an exaggerated or more prolonged inflammatory/cardiovascular response. In agreement with this, prior stress exposure in rats results in a more rapid induction of proinflammatory cytokines following administration of the bacterial endotoxin lipopolysaccharide (LPS) (Johnson et al., 2002). In humans, psychosocial factors associated with chronic psychological stress and increased coronary risk have also been shown to influence acute stress responses. For example, people of low SES have prolonged increases in plasma IL-6, clotting Factor VIII, and blood viscosity in response to acute mental stress compared with their higher status counterparts (Brydon et al., 2004; Steptoe et al., 2003b).
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Similarly, low SES individuals were found to have prolonged increases in blood pressure and heart rate variability following an acute stressor (Steptoe et al., 2002). So far, there are no reported effects of low SES on stress-induced platelet activation; however, our group found a positive correlation between low SES and basal levels of platelet-leukocyte aggregates in a group of healthy middle-aged men (Steptoe et al., 2003c). Psychological factors related to chronic stress include depression, anxiety, and hostility. Elderly people with high levels of anxiety and depression were found to have larger fibrin D-dimer responses to a laboratory speech stressor task (von Kanel et al., 2004a). Similarly, hostility and aggression were associated with increased LPS-stimulated monocyte expression of TNF-α in blood samples from healthy men (Suarez et al., 2002), while Gottdiener et al. (2003) found that stress-induced inhibition of endothelial function was greater in more hostile individuals. Other psychosocial factors have also been shown to modulate the impact of acute stress on inflammatory processes. One study showed that men reporting low job control had larger stress-induced increases in fibrinogen than those with high control at work (Steptoe et al., 2003a), while another found that agoniststimulated platelet aggregation was elevated in blood samples taken from accountants tested during a period of high work demand (end of the fiscal year), compared with samples taken during a more tranquil period (Frimerman et al., 1997). There is some evidence of increased mobilization and cytotoxicity of natural killer cells during marital conflict as well (Dopp et al., 2000). More recently, a study of individuals from the Whitehall II cohort found that loneliness, a psychological experience related to social isolation and perceived lack of companionship, was associated with heightened fibrinogen and natural killer cell responses to an acute laboratory stressor, independently of covariates (Steptoe et al., 2004). These findings all demonstrate enhanced or prolonged reactivity in chronically stressed individuals. However, there is evidence to suggest that chronic stress can also attenuate acute biological responses. For example, lymphocyte chemotaxis in response to a public speaking task was blunted in Alzheimer caregivers compared with non-caregiver controls (Redwine et al., 2004), and NK cell reactivity to a mental arithmetic task was blunted in mothers with post-traumatic stress symptoms (Glover et al., 2005). It is conceivable that repeated stress may lead to a downregulation or desensitization of certain pathways. Supporting this idea, chronic stress has been shown to dilute the suppressive effects of glucocorticoids and induce an
immunoenhancing effect of these hormones in animal studies (Black and Garbutt, 2002). Similarly, Miller and colleagues (2002) found that the capacity of a synthetic glucocorticoid hormone to suppress in vitro production of IL-6 was significantly reduced in blood samples taken from adults under serious stress (parents of children with cancer) compared with controls, suggesting that chronic stress can desensitize the body’s response to glucocorticoids. Thus, biological responses driven by the HPA axis may be attenuated by repeated stress, whereas inflammatory responses that are normally regulated by glucocorticoids may become exaggerated. Figure 7 summarizes the connections between acute stress, chronic stress, and the inflammatory and thrombotic responses described in this section.
E. Longitudinal Studies of Psychobiological Responses The clinical significance of acute responses to laboratory stress has been a topic of considerable debate. Psychosocial factors associated with chronic psychological stress such as low SES, job strain, hostility, depression, and anxiety are associated with increased blood pressure responses to acute laboratory stress as well as with elevated ambulatory blood pressure readings measured throughout the day (Steptoe and Marmot, 2002). An individual’s response to acute stress in a laboratory setting may therefore be indicative of how he/she typically responds to stress in real life. Acute laboratory responses tend to be relatively small in magnitude and duration. However, the stressors used are often mild compared to everyday life stress. Furthermore, although these responses may not necessarily be significant in themselves, they could well become clinically relevant, particularly if repeated regularly on a long-term basis. There is a growing body of evidence that cardiovascular reactivity to acute laboratory stress is predictive of both pre-clinical and clinical cardiovascular disease states in humans (Treiber et al., 2003). Epidemiological studies have shown that heightened blood pressure reactivity to acute laboratory stressors is related to ambulatory blood pressure measured in a naturalistic setting and predicts future hypertension in initially normotensive samples. Similarly, a number of prospective studies have found positive associations between acute blood pressure stress responses and progression of other pre-clinical disease states, namely carotid IMT and increased left ventricular mass. Stressrelated cardiovascular reactivity has been consistently shown to predict elevations in blood pressure in
44. Psychosocial Factors and Coronary Heart Disease: The Role of Psychoneuroimmunological Processes Cholinergic anti-inflammatory pathway
Acute stressors Public speaking Mental arithmetic
SNS/HPA activation
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Inflammation/thrombosis Fibrinogen, Factors VII, VIII, vWF, thrombin
Chronic stressors Work stress
HSP60
Social isolation
CRP
Low SES
Inflammatory cytokines
Care giving
Anger recall
Endothelial dysfunction
Color/word puzzle
Platelet activation and PLAs
Mirror tracing
CAM expression and sCAMs Leukocytosis (selective chemotaxis)
Psychological traits Depression Hostility
Total and LDL-cholesterol
FIGURE 7 Proposed links between stress, psychosocial, and biological factors in CHD.
normotensive children and adolescents over a period of 1–6 years, whereas evidence for such a relationship in adults has been variable (Treiber et al., 2003). Notably, several of the studies which failed to find a consistent association between cardiovascular stress reactivity and future blood pressure in adults did not include post-stress recovery in their analysis. Poststress recovery is likely to be particularly relevant in older age, since young people tend to have more rapid and efficient cardiovascular recovery, and impairment in post-stress recovery may emerge only after prolonged and repeated stress exposure over many decades (McEwen, 1998). In agreement with this, a study of middle-aged men and women from the UK found that impaired recovery of systolic and diastolic blood pressure following acute mental stress was predictive of higher ambulatory blood pressure measured 3 years later (Steptoe and Marmot, 2005). Furthermore, real-life stressors have been shown to have prolonged effects on blood pressure. Gerin et al. (2005) found that the attacks on the New York City World Trade Center on September 11, 2001, led to a substantial and sustained increase in blood pressure in individuals participating in clinical monitoring at four USA sites. There is less evidence relating exaggerated cardiovascular reactivity with clinical CHD. Most prospective investigations in healthy individuals have found no relationship between acute blood pressure stress responses and future cardiac events or mortality (Treiber et al., 2003). In contrast, some studies have found a significant relationship between cardiovascular reactivity and clinical events in patients with preexisting essential hypertension and/or documented
CHD. For example, Krantz et al. (1999) showed that CHD patients with larger diastolic blood pressure responses to mental arithmetic and public speaking tasks were more likely to have a recurrent cardiac event, and Alderman et al. (1990) found that untreated hypertensive patients with larger BP responses to an acute stressor were more than twice as likely to suffer an MI over a 14-year follow-up period. So far, most studies looking at the long-term relevance of acute stress responses have focused on cardiovascular reactivity. However, evidence supporting the prognostic value of other biological stress responses is also emerging. In a recent longitudinal study of 153 individuals from the Whitehall II cohort, we found a positive association between individual differences in inflammatory responses to an acute laboratory stressor and future blood pressure (Brydon and Steptoe, 2005). Specifically, larger increases in ambulatory systolic pressure over 3 years were predicted by larger acute fibrinogen and IL-6 stress responses, independently of previous ambulatory blood pressure, acute blood pressure stress responses, age, sex, body mass, and smoking. As outlined in the section titled “The Atherosclerotic Process,” IL-6 and fibrinogen play an important role in the arterial remodeling that underlies hypertension. Thus, stress could conceivably promote hypertension through stimulating these proteins. As both psychological stress and hypertension are risk factors for CAD, this response may also contribute to the association between stress and coronary risk. A separate analysis of 199 middle-aged men and women showed that acute lipid responses to stress were predictive of fasting lipid levels 3 years later
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(Steptoe and Brydon, 2005a). Individual differences in LDL and HDL-cholesterol stress responses and in total/HDL ratio responses predicted 3-year fasting HDL-cholesterol and total/HDL cholesterol ratio, respectively, independently of baseline serum cholesterol levels, gender, age, hormone replacement, change in BMI, smoking, and alcohol consumption at both time-points. Since elevated blood cholesterol levels are consistently associated with cardiovascular risk, this stress-related response could also be clinically significant.
F. Studies of Patients with Established CAD Although cardiovascular and neuroendocrine responses to psychological stress have been extensively studied in CHD patients, rather less is known about psychoneuroimmunological processes. Studies of heart disease patients are complicated by the fact that these patients already have activated inflammatory systems by virtue of their clinical condition, and are often medicated with anti-inflammatory drugs such as aspirin or statins and β-blockers which reduce sympathetic activation. This makes it difficult to discriminate the influence of psychological factors on immune responses in these individuals. Platelets and leukocytes play a central role in the inflammatory processes that promote plaque rupture and thrombosis in ACS. If activation of these cells contributes to emotional triggering of ACS, one would predict that patients with coronary disease would be more prone to stress-induced platelet/leukocyte activation than healthy controls. Studies examining the relationship between psychosocial factors and platelet activation in CAD patients have yielded variable results, with greater or more prolonged responses from CAD patients compared to healthy controls in some studies but not in others (Brydon et al., 2005b). This variation may relate to the different methods used to assess platelet function, the procedures used for controlling medication effects, and the timing of platelet measurements. Flow cytometry measurements of PLAs have begun to be used in this context. Patients with acute MI have higher levels of circulating platelet-monocyte aggregates than non-infarcted patients with acute chest pain or healthy controls, supporting the sensitivity of PLA measures as an index of disease severity (Brydon et al., 2005b). We recently used this method to compare stress-induced platelet activation in male patients with established coronary disease and healthy age-matched controls (Strike et al., 2004). We found no difference between the two groups in baseline PLA counts, but
there were significant differences in stress responses. Stress induced significant increases in PLAs in all participants. However, in the cardiac group, PLAs continued to increase between 30 and 75 minutes post-stress, whereas they returned to baseline levels by 75 minutes in controls. Compared with baseline, the number of PLAs was an average 18.1% higher at 75 minutes poststress in patients but had decreased by 9.3% in controls. The observed difference in the duration but not magnitude of stress-induced platelet responses might explain the inconsistency in results from previous comparisons of platelet activation in cardiac patients and healthy controls. These findings are consistent with other studies suggesting that psychosocial risk factors for CAD are related to delayed post-stress recovery in biological responses (Steptoe et al., 2003b). Among the PLA populations, platelet-monocyte aggregates appear to be particularly sensitive to acute psychological stress. Interestingly, Gidron and colleagues (2003) found that blood monocyte levels of ACS patients measured at the time of hospital admission were positively correlated with adverse psychological characteristics (hostility and life events) and negatively correlated with protective characteristics (perceived control and emotional support). Heightened or prolonged stress-induced activation of platelets and leukocytes may be significant in the emotional triggering of ACS in patients with advanced coronary atherosclerosis. Supporting this idea, clinical studies have demonstrated that the onset of acute MI and other forms of ACS may be triggered by acute episodes of anger and severe emotional stress in susceptible individuals, with a critical time window of about 2 hours (Strike and Steptoe, 2005). In a small study, our group recently showed that patients who had experienced an acute negative emotion during the 2-hour period prior to onset of ACS had significantly larger increases in monocyte-platelet, leukocyte-platelet, and neutrophil-platelet aggregates in response to an acute laboratory stressor than patients who had not experienced any negative emotion (Strike et al., 2006). Heightened stress-induced platelet activation may thus be a mechanism underlying susceptibility to emotional triggering of ACS in certain cardiac patients.
G. Morbidity Following Acute Coronary Syndromes It was noted in “Psychosocial Factors in CHD” that depression, low emotional support, and chronic life stress all appear to influence cardiac morbidity following ACS. The strongest evidence is for depression. Lett et al. (in press) reviewed 15 studies in which depression was measured soon after hospital admission with
44. Psychosocial Factors and Coronary Heart Disease: The Role of Psychoneuroimmunological Processes
an acute MI or ACS. Over follow-up periods ranging from 6 months to 5 years, there was typically between a two- and three-fold increased risk of cardiac death or serious cardiac event in depressed participants. Similar findings have been reported for patients undergoing coronary artery bypass graft, and effects appear to be independent of measures of cardiac disease severity. Importantly, subclinical levels of depressive symptoms as well as diagnosed major depression confer increased risk. Several mechanisms may underlie these associations. Traditional risk factors such as hypertension, diabetes, and metabolic syndrome may contribute, since they are themselves associated with depression (Lett et al., in press). Depressed individuals may be less likely to take medications reliably and are more likely to become sedentary, with consequent increases in cardiovascular morbidity (DiMatteo et al., 2000). Direct biological pathways have also been postulated, including imbalance in sympathovagal control of the heart, leading to electrical instability and heightened cortisol release. Depression has been associated with impaired endothelial function that in turn increases cardiac risk. For instance, Sherwood et al. (2005) reported greater impairment in endothelial function assessed using flow-mediated dilation in depressed compared with non-depressed CHD patients. In addition, there is some evidence that disturbances in inflammatory processes may mediate links between depression or other psychosocial factors and morbidity in patients following ACS. One early study involved a small group of patients undergoing coronary angioplasty (Appels et al., 2000). Only three patients were clinically depressed, but patients were also assessed for vital exhaustion, a related construct that emphasizes feelings of fatigue and physical exhaustion. The more exhausted patients had significantly higher plasma IL-1β and TNF-α than the non-exhausted group, and the trend in IL-6 approached significance. More recently, a larger study of mixed CHD patients again showed no association with depression, but a positive relationship between plasma IL-6 and vital exhaustion that was independent of clinical status and other covariates (Janszky et al., 2005). Lespérance et al. (2004) found that ACS patients who were depressed had heightened levels of sICAM-1, but raised CRP was recorded only in those who were not taking statins and there was no association with IL-6. Another comparison of matched depressed and non-depressed MI patients found no differences in CRP, IL-6, TNF-α, or soluble TNF receptors (Schins et al., 2005), while Miller et al. (2005) showed no relationship between depressive symptoms and IL-1β, IL-6, or TNF-α in a sample of 41 CHD patients.
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Effects may be stronger in heart failure, where depressive symptoms have been positively associated with TNF-α levels (Ferketich et al., 2005). This finding was confirmed in a second study of heart failure patients, in which depressive symptoms also correlated with soluble apoptosis mediators (Fas/Fas ligand) and negatively with the anti-inflammatory cytokine IL-10 (Parissis et al., 2004). Cytokines have also been implicated in associations between cardiovascular morbidity and another psychological construct, namely Type D personality. Type D is a psychological trait identified by Denollet as relevant to CHD and heart failure. It consists of a tendency to experience negative emotions coupled with the inhibition of self-expression. Denollet et al. (2003) showed that Type D personality was associated with increased circulating levels of TNF-α and TNF-α receptors in patients with congestive heart failure. Taken together, these findings suggest that negative psychological states may stimulate higher levels of vascular inflammatory activity in patients with established cardiovascular disease, though effects are stronger for exhaustion and Type D personality than for depression. Theoretically, these responses could contribute to the greater morbidity and mortality of depressed individuals, but such a relationship has yet to be established. It is also important to consider the possibility that the relationship between inflammatory activity and dysphoric mood may be reversed, so that negative mood states are in fact secondary to inflammation. There is a growing literature on sickness behavior and the cytokine theory of disease, and the influence of inflammatory processes on mood is detailed in chapter 14 of this book. It is conceivable that inflammatory processes present in patients with active CHD stimulate both negative mood states and future cardiac pathology. Shimbo et al. (2005) have described this as the depression-epiphenomenon model in the context of CHD. Almost all the evidence to date is cross-sectional and non-experimental, so causality is uncertain. If this reverse model is correct, then interventions targeting inflammation might be expected to produce a reduction in negative mood states in cardiac patients. There is some evidence that statins confer cardiovascular benefits in part by reducing inflammation, and preliminary findings suggest that statins are associated with reduced risk of depression (Yang et al., 2003). However, any such effect might be secondary to improved physical health and quality of life due to reduced cardiovascular disease risk. The importance of the influence of statins on depression must await results of randomized control trials specifically designed to assess impact on non-cardiac outcomes (Golomb et al., 2004). Trials involving other
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anti-inflammatory agents will also help to evaluate the importance of this reverse pathway.
V. CONCLUSIONS Research on psychoneuroimmunological aspects of CHD is advancing at a rapid pace, with many new developments since the third edition of Psychoneuroimmunology was published in 2001. This has been stimulated by a growing understanding of the involvement of inflammation and immune processes in the etiology of CHD and in the prognosis of patients with established disease. The close interaction between inflammatory processes and hemostatic mechanisms governing thrombosis development is also better appreciated. At the same time, population-based studies of inflammatory factors are starting to be analyzed for associations with psychosocial determinants, while clinical and experimental research is being used to document the dynamic influence of emotions and behaviors on immunological factors relevant to CHD. The one branch of research that has been limited thus far is the use of intervention studies to improve patient well-being and tease out causal pathways. However, it is likely that behavioral and pharmacological interventions will be increasingly used in this field over the next decade and will further enhance our knowledge of the role of immunological processes in linking psychosocial factors with cardiovascular outcomes.
Acknowledgement The preparation of this chapter was supported by the British Heart Foundation.
References Alderman, M. H., Ooi, W. L., Madhavan, S., and Cohen, H. (1990). Blood pressure reactivity predicts myocardial infarction among treated hypertensive patients. Journal of Clinical Epidemiology, 43, 859–866. American Heart Association. (2005). Heart and stroke statistical—2005 update. Dallas: Author. Andraws, R., Berger, J. S., and Brown, D. L. (2005). Effects of antibiotic therapy on outcomes of patients with coronary artery disease: a meta-analysis of randomized controlled trials. Journal of the American Medical Association, 293, 2641–2647. Appels, A., Bar, F. W., Bar, J., Bruggeman, C., and de Baets, M. (2000). Inflammation, depressive symptomatology, and coronary artery disease. Psychosomatic Medicine, 62, 601–605. Bachen, E. A., Muldoon, M. F., Matthews, K. A., and Manuck, S. B. (2002). Effects of hemoconcentration and sympathetic activation on serum lipid responses to brief mental stress. Psychosomatic Medicine, 64, 587–594. Benschop, R. J., Rodriguez-Feuerhahn, M., and Schedlowski, M. (1996). Catecholamine-induced leukocytosis: early observations,
current research, and future directions. Brain, Behavior and Immunity, 10, 77–91. Biasucci, L. M., Liuzzo, G., Fantuzzi, G., Caligiuri, G., Rebuzzi, A. G., Ginnetti, F., Dinarello, C. A., and Maseri, A. (1999). Increasing levels of interleukin (IL)-1Ra and IL-6 during the first 2 days of hospitalization in unstable angina are associated with increased risk of in-hospital coronary events. Circulation, 99, 2079–2084. Bierhaus, A., Wolf, J., Andrassy, M., Rohleder, N., Humpert, P. M., Petrov, D., Ferstl, R., von Eynatten, M., Wendt, T., Rudofsky, G., Joswig, M., Morcos, M., Schwaninger, M., McEwen, B., Kirschbaum, C., and Nawroth, P. P. (2003). A mechanism converting psychosocial stress into mononuclear cell activation. Proceedings of the National Academy of Sciences USA 100, 1920–1925. Black, P. H., and Garbutt, L. D. (2002). Stress, inflammation and cardiovascular disease. Journal of Psychosomatic Research 52, 1–23. Blankenberg, S., Barbaux, S., and Tiret, L. (2003). Adhesion molecules and atherosclerosis. Atherosclerosis, 170, 191–203. Blankenberg, S., Tiret, L., Bickel, C., Peetz, D., Cambien, F., Meyer, J., and Rupprecht, H. J. (2002). Interleukin-18 is a strong predictor of cardiovascular death in stable and unstable angina. Circulation, 106, 24–30. Bosch, J. A., Berntson, G. G., Cacioppo, J. T., Dhabhar, F. S., and Marucha, P. T. (2003). Acute stress evokes selective mobilization of T cells that differ in chemokine receptor expression: a potential pathway linking immunologic reactivity to cardiovascular disease. Brain, Behavior and Immunity, 17, 251–259. British Heart Foundation. (2004). Coronary heart disease statistics. London: Author. Broadley, A. J., Korszun, A., Abdelaal, E., Moskvina, V., Jones, C. J., Nash, G. B., Ray, C., Deanfield, J., and Frenneaux, M. P. (2005). Inhibition of cortisol production with metyrapone prevents mental stress-induced endothelial dysfunction and baroreflex impairment. Journal of the American College of Cardiology, 46, 344–350. Broadley, A. J., Korszun, A., Jones, C. J., and Frenneaux, M. P. (2002). Arterial endothelial function is impaired in treated depression. Heart, 88, 521–523. Brunner, E., Davey Smith, G., Marmot, M., Canner, R., Beksinska, M., and O’Brien, J. (1996). Childhood social circumstances and psychosocial and behavioural factors as determinants of plasma fibrinogen. Lancet, 347, 1008–1013. Brydon, L., Edwards, S., Jia, H., Mohamed-Ali, V., Zachary, I., Martin, J. F., and Steptoe, A. (2005a). Psychological stress activates interleukin-1beta gene expression in human mononuclear cells. Brain, Behavior and Immunity, 19, 540–546. Brydon, L., Edwards, S., Mohamed-Ali, V., and Steptoe, A. (2004). Socioeconomic status and stress-induced increases in interleukin-6. Brain, Behavior and Immunity, 18, 281–290. Brydon, L., Magid, K., and Steptoe, A. (2005b). Platelets, coronary heart disease, and stress. Brain, Behavior and Immunity, 20 (2), 113–119. Brydon, L., and Steptoe, A. (2005). Stress-induced increases in interleukin-6 and fibrinogen predict ambulatory blood pressure at 3-year follow-up. Journal of Hypertension, 23, 1001–1007. Cesari, M., Penninx, B. W., Newman, A. B., Kritchevsky, S. B., Nicklas, B. J., Sutton-Tyrrell, K., Rubin, S. M., Ding, J., Simonsick, E. M., Harris, T. B., and Pahor, M. (2003). Inflammatory markers and onset of cardiovascular events: results from the Health ABC study. Circulation, 108, 2317–2322. Charakida, M., Donald, A. E., Terese, M., Leary, S., Halcox, J. P., Ness, A., Davey Smith, G., Golding, J., Friberg, P., Klein, N. J., and Deanfield, J. E. (2005). Endothelial dysfunction in childhood infection. Circulation, 111, 1660–1665.
44. Psychosocial Factors and Coronary Heart Disease: The Role of Psychoneuroimmunological Processes Charmandari, E., Tsigos, C., and Chrousos, G. (2005). Endocrinology of the stress response. Annual Review of Physiology, 67, 259– 284. Clays, E., De Bacquer, D., Delanghe, J., Kittel, F., Van Renterghem, L., and De Backer, G. (2005). Associations between dimensions of job stress and biomarkers of inflammation and infection. Journal of Occupational and Environmental Medicine, 47, 878–883. Coller, B. S. (2005). Leukocytosis and ischemic vascular disease morbidity and mortality: is it time to intervene? Arteriosclerosis, Thrombosis and Vascular Biology, 25, 658–670. Czura, C. J., and Tracey, K. J. (2005). Autonomic neural regulation of immunity. Journal of Internal Medicine, 257, 156–166. Danesh, J., Lewington, S., Thompson, S. G., Lowe, G. D., Collins, R., Kostis, J. B., Wilson, A. C., Folsom, A. R., Wu, K., Benderly, M., Goldbourt, U., Willeit, J., Kiechl, S., Yarnell, J. W., Sweetnam, P. M., Elwood, P. C., Cushman, M., Psaty, B. M., Tracy, R. P., Tybjaerg-Hansen, A., Haverkate, F., de Maat, M. P., Fowkes, F. G., Lee, A. J., Smith, F. B., Salomaa, V., Harald, K., Rasi, R., Vahtera, E., Jousilahti, P., Pekkanen, J., D’Agostino, R., Kannel, W. B., Wilson, P. W., Tofler, G., Arocha-Pinango, C. L., Rodriguez-Larralde, A., Nagy, E., Mijares, M., Espinosa, R., Rodriquez-Roa, E., Ryder, E., Diez-Ewald, M. P., Campos, G., Fernandez, V., Torres, E., Coll, E., Marchioli, R., Valagussa, F., Rosengren, A., Wilhelmsen, L., Lappas, G., Eriksson, H., Cremer, P., Nagel, D., Curb, J. D., Rodriguez, B., Yano, K., Salonen, J. T., Nyyssonen, K., Tuomainen, T. P., Hedblad, B., Lind, P., Loewel, H., Koenig, W., Meade, T. W., Cooper, J. A., De Stavola, B., Knottenbelt, C., Miller, G. J., Bauer, K. A., Rosenberg, R. D., Sato, S., Kitamura, A., Naito, Y., Iso, H., Rasi, V., Palosuo, T., Ducimetiere, P., Amouyel, P., Arveiler, D., Evans, A. E., Ferrieres, J., Juhan-Vague, I., Bingham, A., Schulte, H., Assmann, G., Cantin, B., Lamarche, B., Despres, J. P., Dagenais, G. R., Tunstall-Pedoe, H., Woodward, M., Ben-Shlomo, Y., Davey Smith, G., Palmieri, V., Yeh, J. L., Rudnicka, A., Ridker, P., Rodeghiero, F., Tosetto, A., Shepherd, J., Ford, I., Robertson, M., Brunner, E., Shipley, M., Feskens, E. J., and Kromhout, D. (2005). Plasma fibrinogen level and the risk of major cardiovascular diseases and nonvascular mortality: an individual participant meta-analysis. Journal of the American Medical Association, 294, 1799–1809. Danesh, J., and Peto, R. (1998). Risk factors for coronary heart disease and infection with Helicobacter pylori: meta-analysis of 18 studies. British Medical Journal, 316, 1130–1132. Danesh, J., Whincup, P., Lewington, S., Walker, M., Lennon, L., Thomson, A., Wong, Y. K., Zhou, X., and Ward, M. (2002). Chlamydia pneumoniae IgA titres and coronary heart disease; prospective study and meta-analysis. European Heart Journal, 23, 371–375. Denollet, J., Conraads, V. M., Brutsaert, D. L., De Clerck, L. S., Stevens, W. J., and Vrints, C. J. (2003). Cytokines and immune activation in systolic heart failure: the role of Type D personality. Brain, Behavior and Immunity, 17, 304–309. Diez Roux, A. V., Merkin, S. S., Arnett, D., Chambless, L., Massing, M., Nieto, F. J., Sorlie, P., Szklo, M., Tyroler, H. A., and Watson, R. L. (2001). Neighborhood of residence and incidence of coronary heart disease. New England Journal of Medicine, 345, 99–106. DiMatteo, M. R., Lepper, H. S., and Croghan, T. W. (2000). Depression is a risk factor for noncompliance with medical treatment: meta-analysis of the effects of anxiety and depression on patient adherence. Archives of Internal Medicine, 160, 2101–2107. Dopp, J. M., Miller, G. E., Myers, H. F., and Fahey, J. L. (2000). Increased natural killer-cell mobilization and cytotoxicity during marital conflict. Brain, Behavior and Immunity, 14, 10–26.
971
Epstein, S. E., Zhou, Y. F., and Zhu, J. (1999). Infection and atherosclerosis: emerging mechanistic paradigms. Circulation, 100, e20–28. Espinola-Klein, C., Rupprecht, H. J., Blankenberg, S., Bickel, C., Kopp, H., Rippin, G., Victor, A., Hafner, G., Schlumberger, W., and Meyer, J. (2002). Impact of infectious burden on extent and long-term prognosis of atherosclerosis. Circulation, 105, 15–21. Everson-Rose, S. A., and Lewis, T. T. (2005). Psychosocial factors and cardiovascular diseases. Annual Review of Public Health, 26, 469–500. Fabricant, C. G., Fabricant, J., Litrenta, M. M., and Minick, C. R. (1978). Virus-induced atherosclerosis. Journal of Experimental Medicine, 148, 335–340. Ferketich, A. K., Ferguson, J. P., and Binkley, P. F. (2005). Depressive symptoms and inflammation among heart failure patients. American Heart Journal, 150, 132–136. Fichtlscherer, S., Heeschen, C., and Zeiher, A. M. (2004). Inflammatory markers and coronary artery disease. Current Opinion in Pharmacology, 4, 124–131. Folsom, A. R., Qamhieh, H. T., Flack, J. M., Hilner, J. E., Liu, K., Howard, B. V., and Tracy, R. P. (1993). Plasma fibrinogen: levels and correlates in young adults. The Coronary Artery Risk Development in Young Adults (CARDIA) Study. American Journal of Epidemiology, 138, 1023–1036. Ford, D. E., and Erlinger, T. P. (2004). Depression and C-reactive protein in US adults: data from the Third National Health and Nutrition Examination Survey. Archives of Internal Medicine, 164, 1010–1014. Fox, C. S., Evans, J. C., Larson, M. G., Kannel, W. B., and Levy, D. (2004). Temporal trends in coronary heart disease mortality and sudden cardiac death from 1950 to 1999: the Framingham Heart Study. Circulation, 110, 522–527. Freedman, J. E., and Loscalzo, J. (2002). Platelet-monocyte aggregates: bridging thrombosis and inflammation. Circulation, 105, 2130–2132. Frimerman, A., Miller, H. I., Laniado, S., and Keren, G. (1997). Changes in hemostatic function at times of cyclic variation in occupational stress. American Journal of Cardiology, 79, 72–75. Gerin, W., Chaplin, W., Schwartz, J. E., Holland, J., Alter, R., Wheeler, R., Duong, D., and Pickering, T. G. (2005). Sustained blood pressure increase after an acute stressor: the effects of the 11 September 2001 attack on the New York City World Trade Center. Journal of Hypertension, 23, 279–284. Ghiadoni, L., Donald, A., Cropley, M., Mullen, M. J., Oakley, G., Taylor, M., O’Connor, G., Betteridge, J., Klein, N., Steptoe, A., and Deanfield, J. E. (2000). Mental stress induces transient endothelial dysfunction in humans. Circulation, 102, 2473–2478. Gidron, Y., Armon, T., Gilutz, H., and Huleihel, M. (2003). Psychological factors correlate meaningfully with percent-monocytes among acute coronary syndrome patients. Brain, Behavior and Immunity, 17, 310–315. Gieffers, J., Fullgraf, H., Jahn, J., Klinger, M., Dalhoff, K., Katus, H. A., Solbach, W., and Maass, M. (2001). Chlamydia pneumoniae infection in circulating human monocytes is refractory to antibiotic treatment. Circulation, 103, 351–356. Glover, D. A., Steele, A. C., Stuber, M. L., and Fahey, J. L. (2005). Preliminary evidence for lymphocyte distribution differences at rest and after acute psychological stress in PTSD-symptomatic women. Brain, Behavior and Immunity, 19, 243–251. Goebel, M. U., and Mills, P. J. (2000). Acute psychological stress and exercise and changes in peripheral leukocyte adhesion molecule expression and density. Psychosomatic Medicine, 62, 664–670. Golomb, B. A., Criqui, M. H., White, H., and Dimsdale, J. E. (2004). Conceptual foundations of the UCSD Statin Study: a randomized
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controlled trial assessing the impact of statins on cognition, behavior, and biochemistry. Archives of Internal Medicine, 164, 153–162. Gottdiener, J. S., Kop, W. J., Hausner, E., McCeney, M. K., Herrington, D., and Krantz, D. S. (2003). Effects of mental stress on flow-mediated brachial arterial dilation and influence of behavioral factors and hypercholesterolemia in subjects without cardiovascular disease. American Journal of Cardiology, 92, 687–691. Gurevich, V. S. (2005). Influenza, autoimmunity and atherogenesis. Autoimmunity Reviews, 4, 101–105. Haas, D. C., Chaplin, W. F., Shimbo, D., Pickering, T. G., Burg, M., and Davidson, K. W. (2005). Hostility is an independent predictor of recurrent coronary heart disease events in men but not women: results from a population based study. Heart, 91, 1609–1610. Hansson, G. K. (2005). Inflammation, atherosclerosis, and coronary artery disease. New England Journal of Medicine, 352, 1685–1695. Heinz, A., Hermann, D., Smolka, M. N., Rieks, M., Graf, K. J., Pohlau, D., Kuhn, W., and Bauer, M. (2003). Effects of acute psychological stress on adhesion molecules, interleukins and sex hormones: implications for coronary heart disease. Psychopharmacology (Berlin), 165, 111–117. Hemingway, H., Shipley, M., Mullen, M. J., Kumari, M., Brunner, E., Taylor, M., Donald, A. E., Deanfield, J. E., and Marmot, M. (2003). Social and psychosocial influences on inflammatory markers and vascular function in civil servants (the Whitehall II study). American Journal of Cardiology, 92, 984–987. Hingorani, A. D., Cross, J., Kharbanda, R. K., Mullen, M. J., Bhagat, K., Taylor, M., Donald, A. E., Palacios, M., Griffin, G. E., Deanfield, J. E., MacAllister, R. J., and Vallance, P. (2000). Acute systemic inflammation impairs endothelium-dependent dilatation in humans. Circulation, 102, 994–999. Hoshida, S., Nishino, M., Tanouchi, J., Kishimoto, T., and Yamada, Y. (2005). Acute Chlamydia pneumoniae infection with heat shock protein 60–related response in patients with acute coronary syndrome. Atherosclerosis, 183, 109–112. Huo, Y., and Ley, K. F. (2004). Role of platelets in the development of atherosclerosis. Trends in Cardiovascular Medicine, 14, 18–22. Huo, Y., Schober, A., Forlow, S. B., Smith, D. F., Hyman, M. C., Jung, S., Littman, D. R., Weber, C., and Ley, K. (2003). Circulating activated platelets exacerbate atherosclerosis in mice deficient in apolipoprotein E. Nature Medicine, 9, 61–67. Jambrik, Z., Sebastiani, L., Picano, E., Ghelarducci, B., and Santarcangelo, E. L. (2005). Hypnotic modulation of flowmediated endothelial response to mental stress. International Journal of Psychophysiology, 55, 221–227. Janszky, I., Lekander, M., Blom, M., Georgiades, A., and Ahnve, S. (2005). Self-rated health and vital exhaustion, but not depression, is related to inflammation in women with coronary heart disease. Brain, Behavior and Immunity, 19, 555–563. Johnson, J. D., O’Connor, K. A., Deak, T., Stark, M., Watkins, L. R., and Maier, S. F. (2002). Prior stressor exposure sensitizes LPSinduced cytokine production. Brain, Behavior and Immunity, 16, 461–476. Kazemi, M. R., McDonald, C. M., Shigenaga, J. K., Grunfeld, C., and Feingold, K. R. (2005). Adipocyte fatty acid-binding protein expression and lipid accumulation are increased during activation of murine macrophages by toll-like receptor agonists. Arteriosclerosis, Thrombosis and Vascular Biology, 25, 1220–1224. Khot, U. N., Khot, M. B., Bajzer, C. T., Sapp, S. K., Ohman, E. M., Brener, S. J., Ellis, S. G., Lincoff, A. M., and Topol, E. J. (2003). Prevalence of conventional risk factors in patients with coronary heart disease. Journal of the American Medical Association, 290, 898–904.
Khovidhunkit, W., Kim, M. S., Memon, R. A., Shigenaga, J. K., Moser, A. H., Feingold, K. R., and Grunfeld, C. (2004). Effects of infection and inflammation on lipid and lipoprotein metabolism: mechanisms and consequences to the host. Journal of Lipid Research, 45, 1169–1196. Kiecolt-Glaser, J. K., Preacher, K. J., MacCallum, R. C., Atkinson, C., Malarkey, W. B., and Glaser, R. (2003). Chronic stress and agerelated increases in the proinflammatory cytokine IL-6. Proceedings of the National Academy of Sciences USA, 100, 9090–9095. Kivimaki, M., Leino-Arjas, P., Luukkonen, R., Riihimaki, H., Vahtera, J., and Kirjonen, J. (2002). Work stress and risk of cardiovascular mortality: prospective cohort study of industrial employees. British Medical Journal, 325, 857. Koenig, W. (2005). Predicting risk and treatment benefit in atherosclerosis: the role of C-reactive protein. Int. J. Cardiol., 98 (2), 199–206. Krantz, D. S., Santiago, H. T., Kop, W. J., Merz, C. N. B., Rozanski, A., and Gottdiener, J. S. (1999). Prognostic value of mental stress testing in coronary artery disease. American Journal of Cardiology, 84, 1292–1297. Kunz-Ebrecht, S. R., Mohamed-Ali, V., Feldman, P. J., Kirschbaum, C., and Steptoe, A. (2003). Cortisol responses to mild psychological stress are inversely associated with proinflammatory cytokines. Brain, Behavior and Immunity, 17, 373–383. Kuper, H., Marmot, M., and Hemingway, H. (2005). Systematic review of prospective cohort studies of psychosocial factors in the aetiology and prognosis of coronary heart disease. In P. Elliott and M. Marmot (Eds.), Coronary heart disease epidemiology (2nd ed., pp. 363–413). Oxford: Oxford University Press. Kuulasmaa, K., Tunstall-Pedoe, H., Dobson, A., Fortmann, S., Sans, S., Tolonen, H., Evans, A., Ferrario, M., and Tuomilehto, J. (2000). Estimation of contribution of changes in classic risk factors to trends in coronary-event rates across the WHO MONICA Project populations. Lancet, 355, 675–687. Lee, S., Colditz, G. A., Berkman, L. F., and Kawachi, I. (2003). Caregiving and risk of coronary heart disease in U.S. women: a prospective study. American Journal Preventive Medicine, 24, 113–119. Lesperance, F., Frasure-Smith, N., Theroux, P., and Irwin, M. (2004). The association between major depression and levels of soluble intercellular adhesion molecule 1, interleukin-6, and C-reactive protein in patients with recent acute coronary syndromes. American Journal of Psychiatry, 161, 271–277. Lett, H. S., Sherwood, A., Watkins, L., and Blumenthal, J. (In press). Depression and prognosis in cardiac patients. In A. Steptoe (Ed.), Depression and physical illness. Cambridge: Cambridge University Press. Lewthwaite, J., Owen, N., Coates, A., Henderson, B., and Steptoe, A. (2002). Circulating human heat shock protein 60 in the plasma of British civil servants: relationship to physiological and psychosocial stress. Circulation, 106, 196–201. Liuba, P., and Pesonen, E. (2005). Infection and early atherosclerosis: does the evidence support causation? Acta Paediatrica, 94, 643–651. Lynch, J., Kaplan, G. A., Salonen, R., Cohen, R. D., and Salonen, J. T. (1995). Socioeconomic status and carotid atherosclerosis. Circulation, 92, 1786–1792. Malik, I., Danesh, J., Whincup, P., Bhatia, V., Papacosta, O., Walker, M., Lennon, L., Thomson, A., and Haskard, D. (2001). Soluble adhesion molecules and prediction of coronary heart disease: a prospective study and meta-analysis. Lancet, 358, 971–976. Malyutina, S., Bobak, M., Simonova, G., Gafarov, V., Nikitin, Y., and Marmot, M. (2004). Education, marital status, and total and cardiovascular mortality in Novosibirsk, Russia: a prospective cohort study. Annals of Epidemiology, 14, 244–249.
44. Psychosocial Factors and Coronary Heart Disease: The Role of Psychoneuroimmunological Processes Mandal, K., Foteinos, G., Jahangiri, M., and Xu, Q. (2005). Role of antiheat shock protein 60 autoantibodies in atherosclerosis. Lupus, 14, 742–746. Manuck, S. B., Flory, J. D., Ferrell, R. E., and Muldoon, M. F. (2004). Socio-economic status covaries with central nervous system serotonergic responsivity as a function of allelic variation in the serotonin transporter gene-linked polymorphic region. Psychoneuroendocrinology, 29, 651–668. Marchesi, S., Lupattelli, G., Lombardini, R., Sensini, A., Siepi, D., Mannarino, M., Vaudo, G., and Mannarino, E. (2005). Acute inflammatory state during influenza infection and endothelial function. Atherosclerosis, 178, 345–350. Massberg, S., Brand, K., Gruner, S., Page, S., Muller, E., Muller, I., Bergmeier, W., Richter, T., Lorenz, M., Konrad, I., Nieswandt, B., and Gawaz, M. (2002). A critical role of platelet adhesion in the initiation of atherosclerotic lesion formation. Journal of Experimental Medicine, 196, 887–896. McEwen, B. S. (1998). Protective and damaging effects of stress mediators. New England Journal of Medicine, 338, 171– 179. Merten, M., and Thiagarajan, P. (2004). P-selectin in arterial thrombosis. Zeitschrift für Kardiologie 93, 855–863. Miller, G. E., Cohen, S., and Ritchey, A. K. (2002). Chronic psychological stress and the regulation of pro-inflammatory cytokines: a glucocorticoid-resistance model. Health Psychology, 21, 531–541. Miller, G. E., Freedland, K. E., and Carney, R. M. (2005). Depressive symptoms and the regulation of proinflammatory cytokine expression in patients with coronary heart disease. Journal of Psychosomatic Research, 59, 231–236. Miller, G. E., Freedland, K. E., Carney, R. M., Stetler, C. A., and Banks, W. A. (2003). Cynical hostility, depressive symptoms, and the expression of inflammatory risk markers for coronary heart disease. Journal of Behavioral Medicine, 26, 501–515. Mills, P. J., Goebel, M., Rehman, J., Irwin, M. R., and Maisel, A. S. (2000). Leukocyte adhesion molecule expression and T cell naive/memory status following isoproterenol infusion. Journal of Neuroimmunology, 102, 137–144. Myers, A., and Dewar, H. A. (1975). Circumstances attending 100 sudden deaths from coronary artery disease with coroner’s necropsies. British Heart Journal, 37, 1133–1143. Orth-Gomér, K., Wamala, S. P., Horsten, M., Schenck-Gustafsson, K., Schneiderman, N., and Mittleman, M. A. (2000). Marital stress worsens prognosis in women with coronary heart disease: The Stockholm Female Coronary Risk Study. Journal of the American Medical Association, 284, 3008–3014. Oshima, T., Ozono, R., Yano, Y., Oishi, Y., Teragawa, H., Higashi, Y., Yoshizumi, M., and Kambe, M. (2005). Association of Helicobacter pylori infection with systemic inflammation and endothelial dysfunction in healthy male subjects. Journal of the American College of Cardiology, 45, 1219–1222. Pai, J. K., Pischon, T., Ma, J., Manson, J. E., Hankinson, S. E., Joshipura, K., Curhan, G. C., Rifai, N., Cannuscio, C. C., Stampfer, M. J., and Rimm, E. B. (2004). Inflammatory markers and the risk of coronary heart disease in men and women. New England Journal of Medicine, 351, 2599–2610. Parissis, J. T., Adamopoulos, S., Rigas, A., Kostakis, G., Karatzas, D., Venetsanou, K., and Kremastinos, D. T. (2004). Comparison of circulating proinflammatory cytokines and soluble apoptosis mediators in patients with chronic heart failure with versus without symptoms of depression. American Journal of Cardiology, 94, 1326–1328. Penninx, B. W., Kritchevsky, S. B., Yaffe, K., Newman, A. B., Simonsick, E. M., Rubin, S., Ferrucci, L., Harris, T., and Pahor, M. (2003). Inflammatory markers and depressed mood in older
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persons: results from the Health, Aging and Body Composition Study. Biological Psychiatry, 54, 566–572. Rattazzi, M., Faggin, E., Bertipaglia, B., and Pauletto, P. (2005). Innate immunity and atherogenesis. Lupus, 14, 747–751. Redwine, L., Mills, P. J., Sada, M., Dimsdale, J., Patterson, T., and Grant, I. (2004). Differential immune cell chemotaxis responses to acute psychological stress in Alzheimer caregivers compared to non-caregiver controls. Psychosomatic Medicine, 66, 770– 775. Redwine, L., Snow, S., Mills, P., and Irwin, M. (2003). Acute psychological stress: effects on chemotaxis and cellular adhesion molecule expression. Psychosomatic Medicine, 65, 598–603. Ridker, P. M., Rifai, N., Pfeffer, M., Sacks, F., Lepage, S., and Braunwald, E. (2000). Elevation of tumor necrosis factor-alpha and increased risk of recurrent coronary events after myocardial infarction. Circulation, 101, 2149–2153. Rosengren, A., Hawken, S., Ounpuu, S., Sliwa, K., Zubaid, M., Almahmeed, W. A., Blackett, K. N., Sitthi-amorn, C., Sato, H., and Yusuf, S. (2004a). Association of psychosocial risk factors with risk of acute myocardial infarction in 11119 cases and 13648 controls from 52 countries (the INTERHEART study): casecontrol study. Lancet, 364, 953–962. Rosengren, A., Wilhelmsen, L., and Orth-Gomer, K. (2004b). Coronary disease in relation to social support and social class in Swedish men. A 15 year follow-up in the study of men born in 1933. European Heart Journal, 25, 56–63. Ross, R. (1999). Atherosclerosis—an inflammatory disease. New England Journal of Medicine, 340, 115–126. Saigo, M., Hsue, P. Y., and Waters, D. D. (2004). Role of thrombotic and fibrinolytic factors in acute coronary syndromes. Progress in Cardiovascular Diseases, 46, 524–538. Sawayama, Y., Ariyama, I., Hamada, M., Otaguro, S., Machi, T., Taira, Y., and Hayashi, J. (2005). Association between chronic Helicobacter pylori infection and acute ischemic stroke: Fukuoka Harasanshin Atherosclerosis Trial (FHAT). Atherosclerosis, 178, 303–309. Schins, A., Tulner, D., Lousberg, R., Kenis, G., Delanghe, J., Crijns, H. J., Grauls, G., Stassen, F., Maes, M., and Honig, A. (2005). Inflammatory markers in depressed post-myocardial infarction patients. Journal of Psychiatric Research, 39, 137–144. Shedd, O. L., Sears, S. F., Jr., Harvill, J. L., Arshad, A., Conti, J. B., Steinberg, J. S., and Curtis, A. B. (2004). The World Trade Center attack: increased frequency of defibrillator shocks for ventricular arrhythmias in patients living remotely from New York City. Journal of the American College of Cardiology, 44, 1265–1267. Sherwood, A., Hinderliter, A. L., Watkins, L. L., Waugh, R. A., and Blumenthal, J. A. (2005). Impaired endothelial function in coronary heart disease patients with depressive symptomatology. Journal of the American College of Cardiology, 46, 656–659. Shimbo, D., Chaplin, W., Crossman, D., Haas, D., and Davidson, K. W. (2005). Role of depression and inflammation in incident coronary heart disease events. American Journal of Cardiology, 96, 1016–1021. Smeeth, L., Thomas, S. L., Hall, A. J., Hubbard, R., Farrington, P., and Vallance, P. (2004). Risk of myocardial infarction and stroke after acute infection or vaccination. New England Journal of Medicine, 351, 2611–2618. Steenland, K., Henley, J., and Thun, M. (2002). All-cause and causespecific death rates by educational status for two million people in two American Cancer Society cohorts, 1959–1996. American Journal Epidemiology, 156, 11–21. Steptoe, A. (In press). Depression and the development of coronary heart disease. In A. Steptoe (Ed.), Depression and physical illness. Cambridge: Cambridge University Press.
974
V. Psychoneuroimmunology and Pathophysiology
Steptoe, A., and Brydon, L. (2005a). Associations between acute lipid stress responses and fasting lipid levels 3 years later. Health Psychology, 24, 601–607. Steptoe, A., and Brydon, L. (2005b). Psychoneuroimmunology and coronary heart disease. In K. Vedhara and M. R. Irwin (Eds.), Human psychoneuroimmunology (pp. 107–135). Oxford: Oxford University Press. Steptoe, A., Feldman, P. M., Kunz, S., Owen, N., Willemsen, G., and Marmot, M. (2002). Stress responsivity and socioeconomic status: A mechanism for increased cardiovascular disease risk? European Heart Journal, 23, 1757–1763. Steptoe, A., Kunz-Ebrecht, S., Owen, N., Feldman, P. J., Rumley, A., Lowe, G. D., and Marmot, M. (2003a). Influence of socioeconomic status and job control on plasma fibrinogen responses to acute mental stress. Psychosomatic Medicine, 65, 137–144. Steptoe, A., Kunz-Ebrecht, S., Rumley, A., and Lowe, G. D. (2003b). Prolonged elevations in haemostatic and rheological responses following psychological stress in low socioeconomic status men and women. Thrombosis and Haemostasis, 89, 83–90. Steptoe, A., Magid, K., Edwards, S., Brydon, L., Hong, Y., and Erusalimsky, J. (2003c). The influence of psychological stress and socioeconomic status on platelet activation in men. Atherosclerosis, 168, 57–63. Steptoe, A., and Marmot, M. (2002). The role of psychobiological pathways in socio-economic inequalities in cardiovascular disease risk. European Heart Journal, 23, 13–25. Steptoe, A., and Marmot, M. (2005). Impaired cardiovascular recovery following stress predicts 3-year increases in blood pressure. Journal of Hypertension, 23, 529–536. Steptoe, A., Owen, N., Kunz-Ebrecht, S., and Brydon, L. (2004). Loneliness and neuroendocrine, cardiovascular, and inflammatory stress responses in middle-aged men and women. Psychoneuroendocrinology, 29, 593–611. Steptoe, A., Willemsen, G., Owen, N., Flower, L., and Mohamed-Ali, V. (2001). Acute mental stress elicits delayed increases in circulating inflammatory cytokine levels. Clinical Science, 101, 185–192. Strike, P. C., Magid, K., Brydon, L., Edwards, S., McEwan, J. R., and Steptoe, A. (2004). Exaggerated platelet and hemodynamic reactivity to mental stress in men with coronary artery disease. Psychosomatic Medicine, 66, 492–500. Strike, P. C., and Steptoe, A. (2005). Behavioral and emotional triggers of acute coronary syndromes: a systematic review and critique. Psychosomatic Medicine, 67, 179–186. Strike, P. C., Magid, K., Whitehead, D. L., Brydon, L., Bhattacharyya, M. R., and Steptoe, A. (2006). Pathophysiological processes underlying emotional triggering of acute cardiac events, PNAS, 103(11), 4322–4327. Suarez, E. C., Krishnan, R. R., and Lewis, J. G. (2003). The relation of severity of depressive symptoms to monocyte-associated proinflammatory cytokines and chemokines in apparently healthy men. Psychosomatic Medicine, 65, 362–368. Suarez, E. C., Lewis, J. G., and Kuhn, C. (2002). The relation of aggression, hostility, and anger to lipopolysaccharide-stimulated tumor necrosis factor (TNF)-alpha by blood monocytes from normal men. Brain, Behavior and Immunity, 16, 675–684. Sudhir, K. (2005). Clinical review: lipoprotein-associated phospholipase A2, a novel inflammatory biomarker and independent risk predictor for cardiovascular disease. Journal of Clinical Endocrinology and Metabolism, 90, 3100–3105. Suls, J., and Bunde, J. (2005). Anger, anxiety, and depression as risk factors for cardiovascular disease: the problems and implications of overlapping affective dispositions. Psychological Bulletin, 131, 260–300.
Treiber, F. A., Kamarck, T., Schneiderman, N., Sheffield, D., Kapuku, G., and Taylor, T. (2003). Cardiovascular reactivity and development of preclinical and clinical disease states. Psychosomatic Medicine, 65, 46–62. Viswanathan, K., and Dhabhar, F. S. (2005). Stress-induced enhancement of leukocyte trafficking into sites of surgery or immune activation. Proceedings of the National Academy of Sciences USA, 102, 5808–5813. von Kanel, R. (2004). Platelet hyperactivity in clinical depression and the beneficial effect of antidepressant drug treatment: how strong is the evidence? Acta Psychiatrica Scandinavia, 110, 163–177. von Kanel, R., and Dimsdale, J. E. (2000). Effects of sympathetic activation by adrenergic infusions on hemostasis in vivo. European Journal of Haematology, 65, 357–369. von Kanel, R., Dimsdale, J. E., Adler, K. A., Patterson, T. L., Mills, P. J., and Grant, I. (2004a). Effects of depressive symptoms and anxiety on hemostatic responses to acute mental stress and recovery in the elderly. Psychiatry Research, 126, 253–264. von Kanel, R., Kudielka, B. M., Hanebuth, D., Preckel, D., and Fischer, J. E. (2005a). Different contribution of interleukin-6 and cortisol activity to total plasma fibrin concentration and to acute mental stress-induced fibrin formation. Clinical Science (London), 109, 61–67. von Kanel, R., Kudielka, B. M., Preckel, D., Hanebuth, D., and Fischer, J. E. (2005b). Delayed response and lack of habituation in plasma interleukin-6 to acute mental stress in men. Brain, Behavior and Immunity, 20 (1), 37–39. von Kanel, R., Mills, P. J., Fainman, C., and Dimsdale, J. E. (2001). Effects of psychological stress and psychiatric disorders on blood coagulation and fibrinolysis: a biobehavioral pathway to coronary artery disease? Psychosomatic Medicine, 63, 531–544. von Kanel, R., Preckel, D., Zgraggen, L., Mischler, K., Kudielka, B. M., Haeberli, A., and Fischer, J. E. (2004b). The effect of natural habituation on coagulation responses to acute mental stress and recovery in men. Thrombosis and Haemostasis, 92, 1327–1335. Wamala, S. P., Murray, M. A., Horsten, M., Eriksson, M., Schenck-Gustafsson, K., Hamsten, A., Silveira, A., and Orth-Gomér, K. (1999). Socioeconomic status and determinants of hemostatic function in healthy women. Arteriosclerosis, Thrombosis and Vascular Biology, 19, 485–492. Whincup, P. H., Danesh, J., Walker, M., Lennon, L., Thomson, A., Appleby, P., Rumley, A., and Lowe, G. D. (2002). von Willebrand factor and coronary heart disease: prospective study and metaanalysis. European Heart Journal, 23, 1764–1770. Williams, R. B., Barefoot, J. C., Califf, R. M., Haney, T. L., Saunders, W. B., Pryor, D. B., Hlatky, M. A., Siegler, I. C., and Mark, D. B. (1992). Prognostic importance of social and economic resources among medically treated patients with angiographically documented coronary artery disease. Journal of the American Medical Association, 267, 520–524. Yang, C. C., Jick, S. S., and Jick, H. (2003). Lipid-lowering drugs and the risk of depression and suicidal behavior. Archives of Internal Medicine, 163, 1926–1932. Yudkin, J. S., Kumari, M., Humphries, S. E., and Mohamed-Ali, V. (2000). Inflammation, obesity, stress and coronary heart disease: is interleukin-6 the link? Atherosclerosis, 148, 209–214. Zgraggen, L., Fischer, J. E., Mischler, K., Preckel, D., Kudielka, B. M., and von Kanel, R. (2005). Relationship between hemoconcentration and blood coagulation responses to acute mental stress. Thrombosis Research, 115, 175–183. Zhu, J., Nieto, F. J., Horne, B. D., Anderson, J. L., Muhlestein, J. B., and Epstein, S. E. (2001). Prospective study of pathogen burden and risk of myocardial infarction or death. Circulation, 103, 45–51.
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45 Endocrine and Immune Responses to Stress in Chronic Inflammatory Skin Disorder (Atopic Dermatitis) A. BUSKE-KIRSCHBAUM
I. GENERAL ASPECTS OF ATOPIC DERMATITIS II. ENDOCRINE AND IMMUNE RESPONSES TO STRESS IN AD 980 III. SUMMARY AND FUTURE DIRECTIONS 986
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is proposed, trying to integrate the existing data and highlight potential future research strategies in this field. This may lead to a better understanding of psychodermatological processes in AD and, more general, in chronic inflammatory skin disorders.
ABSTRACT I. GENERAL ASPECTS OF ATOPIC DERMATITIS
Psychodermatological research of the last decades has emphasized the significant role of psychological factors such as stress in the onset and exacerbation of various skin disorders. Of the various skin diseases, atopic dermatitis (AD) has received particular interest. AD is a chronic, pruritic inflammatory disease characterized by eczematous inflammation of the skin, a chronically relapsing course, and severe pruritus. Although it is well accepted that exacerbation of skin condition in AD is closely linked to emotional stress, the underlying mechanisms of stress-induced exacerbation of AD are rarely understood. Recent studies suggest an aberrant responsiveness of the hypothalamus-pituitary-adrenal (HPA) axis and the sympatho-adreno-medullary (SAM) system to stress in AD patients. Further, atopy-relevant immunological changes after stress have been reported. This chapter summarizes the role of immunological and psychological factors on AD and discusses the potential role of a dysfunctional HPA axis and SAM system responsiveness for the maintenance and aggravation of the allergic inflammatory process in AD. A psycho-neuro-endocrine-immunological model of AD PSYCHONEUROIMMUNOLOGY, 4E VOLUME II
A. Psychodermatology of AD— A Historical Perspective The skin is the largest organ of the human body, separating the external world from the internal homeostasis. However, the skin is not a static barrier, but is a complex organ communicating with the other systems of the body—i.e., the central nervous system (CNS), the endocrine system (ES), and the immune system (IS)—to maintain and protect internal homeostasis. Moreover, the skin has profound psychological implications, playing a pivotal role as a sensory organ being responsive to various tactile and social stimuli and determining the individual’s body image. It is also an organ of social communication. For example, blushing associated with strong emotions or pallor due to fear and anxiety are well known and are typical signs of a CNS-cutaneous relationship. The close relation between the CNS and the skin is further underlined by their common origin since the epidermis and the neural plate derive from the embryonic ectoderm (Goldsmith,
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1983). Moreover, the CNS and the skin share several hormones, neurotransmitters, and receptors (Raap and Kapp, 2005). Regarding the close functional neurocutaneous network, it is not surprising that the existence of a relationship between psychological factors and skin disorders has long been noticed and discussed (Wilson, 1857). For example, the wide acceptance of a close relationship between psychological factors and the skin is reflected by common expressions such as “things get under our skin” or “something makes our skin crawl.” Moreover, a large body of anecdotal literature attests to the relevance of emotions, unconscious conflicts, or distinct personality pattern in skin disease (Engels, 1982; Panconesi, 2000). Of the various skin diseases, atopic dermatitis (AD) has received particular attention as a psychosomatic disorder. In the 1940s, Alexander and French (1948), leading an influential school of psychosomatic thought, postulated that for each of seven classical psychosomatic illnesses (and AD was considered to be one of these), there was a distinct emotional conflict triggering the onset and maintenance of the disease. They postulated that the AD child is characterized by increased emotional stress, which was felt to revolve around the child’s failure to express anger and hostility stemming from maternal rejection. The psychosomatic approach to document a specific personality pattern in AD has been extensively criticized (Fritz, 1979). Accordingly, in more recent years, psychodermatological research has focused more on the effect of psychological factors such as major life events or emotional stress on the onset and course of AD (Picardi and Abeni, 2001). Another reason why psychodermatological research has focused on AD is that AD provides a good model in which to examine the effects of stress on inflammatory skin disease. AD is a condition characterized by periods of exacerbation and remission which can be clearly observed. To study the influence of psychological factors on the periodic course of the disease (and its underlying immunological mechanisms) is one challenge of psycho-(neuro)-dermatological research. Further, AD has an important behavioral component, that is, scratching, which is a key event in exacerbation of skin lesion. It has been shown that psychological factors such as stress can affect scratching that, in turn, can initiate the inflammatory cascade in the skin. Thus, there may be a direct psycho-neuro-immuno-cutaneous link in AD. A final but important reason to focus on AD is that AD is the most common chronic inflammatory dermatosis with significantly increasing prevalence during the last decade. Regarding the historical and actual relevance of AD in psychodermatological research, the present chapter
will focus on this inflammatory skin disease. A specific goal will be to summarize relevant immunological and psychological factors in AD and to outline the potential psychoneuroimmunological pathways that may be involved in stress-induced aggravation of skin condition in AD. Based on these data, a psycho-neuroendocrine-immunological model of AD will be proposed.
B. Atopic Dermatitis—Multiple Factors in One Disease Atopic dermatitis is a chronic, relapsing, inflammatory skin disorder which is observed most frequently in patients with a personal or family history of atopy. The term atopy refers to a familial or hereditary tendency to become sensitized to certain environmental or food substances such as dust mites, pollen, mold, or animal dander and to develop hypersensitivity reactions with an excessive production of immunoglobulin-E (IgE). Atopic status is determined using total and/or specific IgE levels and/or skin prick testing. The three major clinical manifestations of atopy, also called the atopic triad, are allergic asthma, allergic rhinitis, and atopic dermatitis (Gold and Kemp, 2005; Nimmagadda and Evans, 1999). Atopic dermatitis (AD), the skin manifestation of atopy, is one of the most frequent chronic diseases in early infancy and is estimated to affect 5–21% of the children in the industrialized Western countries. It accounts for up to 20% of all patients treated in dermatology departments. AD occurs slightly more frequently in females than males by a ratio about 1.5 : 1 (Mortz et al., 2001; Van Moerbeke, 1997). AD usually begins in early infancy with an initial disease onset before the age of 5 in approximately 90% of patients. In the beginning, the child shows acute, often exudative and intensely itchy eczema on the face, the forearms, and the flexural regions. Later, the main symptoms of AD are dry, crusted, and lichenified eruptions of the skin and erythema with a broad distribution across the body. AD symptomatology can be recurrent or chronic (Donnell and Tripathi, 2004; Sturgill and Bernard, 2004). Severe itching is considered to be a hallmark of AD, and some authors describe it as the primary symptom of AD. The intense pruritus is further assumed to be a central event in the maintenance and exacerbation of AD, triggering a vicious circle of itching, scratching, and aggravation of the disease. The symptomatology may vary with age (Boguniewicz, 2004). Although AD is not a lethal disease, it has a considerable impact on the daily life and the overall wellbeing of the patient. AD symptomatology, particularly
45. Endocrine and Immune Responses to Stress in Chronic Inflammatory Skin Disorder
the unpredictability of the disease, the torturing pruritus, and the feeling of being cosmetically disfigured, imposes a psychological burden on AD sufferers which often leads to depression, tension, and anxiety (Evers et al., 2005; Wittkowski et al., 2004). The economic costs accrued by the health care of AD patients are considerable. In a recent report, it is estimated that AD treatment in the United States—i.e., medication and hospitalization—costs on average $219 US per year and per patient, while the health care costs in Europe vary from $71 US (Netherlands) to $2,559 US (Germany) (Verboom et al., 2002; Weinmann et al., 2003). There is general agreement that AD is a multifactorial, hereditary disease triggered by multiple factors such as allergens, climate, microbial organisms (i.e., Staphylococcus aureus), deficient antigen exposure in early life (hygiene hypothesis), environmental pollution, altered vascular reactivity, or stress (Abramovits, 2005; Sturgill and Bernard, 2004). The pathological relevance of these different factors may vary from one patient to another and possibly during the course of the disease. They also may influence each other in a synergistic way. In general, AD is described as a hereditary skin disease. This idea is strongly supported by family studies suggesting that 56% of the children with a parent suffering from AD develop AD (Coleman et al., 1997). Interestingly, the atopic mothers had a higher incidence of atopic offspring than atopic fathers (Ruiz et al., 1992). The significance of genetics in AD is further underlined by twin studies with concordance rates for AD of 77% and 15% in monozygotic and dizygotic twins, respectively (Feijen et al., 2000). Although the molecular genetic mechanisms of AD are still obscure, substantial evidence supports a linkage of AD and the chromosome 5q31-33, which contains genes for the TH2 cytokines (IL-4, IL-5, IL-13) and the chromosome 11q13 encoding for the β chain of the FcεRI receptor (Feijen et al., 2000; Folster-Holst et al., 1998; Forrest et al., 1999). Although various potential contributory genes are currently discussed, it is assumed that AD is likely to result from a multifactorial inheritance with a complex interaction between genetic and environmental factors. In this model, environmental factors seem necessary to provoke or exacerbate the disease. The role of allergens as important trigger factors of AD has often been emphasized. For example, house dust mite, the most important aeroallergen in AD has been shown to induce and exacerbate eczematous skin lesions in AD sufferers (patch test) (Katoh et al., 2004). Moreover, climate was found to modulate the disease outcome. UV exposure during the summer seems to be benefi-
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cial, while low air humidity during the winter months can worsen skin condition in AD patients (Weiland et al., 2004). In recent years, there is a growing interest in the potential significance of microbial agents in AD pathology. In AD patients, a significant overgrowth of Staphylococcus aureus, probably due to a diminished anti-bacterial function of the skin, has been found in a majority of patients (Boguniewicz, 2004). S. aureus, cultured from patients with AD, can secrete endotoxins with superantigenic properties that strongly induce T helper type 2 (TH2) response known to be mainly involved in chronic allergic inflammation in AD. Superantigens derived from S. aureus have further been found to stimulate toxin-specific IgE that can activate mast or other IgE receptor-bearing cells which may initiate or promote allergic inflammation (Leung et al., 1993; Roll et al., 2004). In recent years, a concept known as the “hygiene” hypothesis has gained considerable interest (Bresciani et al., 2005; Gehring et al., 2001). In this model, exposure to infection during early childhood is assumed to affect the vulnerability to develop AD by stimulating maturation of TH0 cells to differentiate into TH1 cells rather than into TH2 cells. To this model, a reduced number of infections due to decreased exposure to infectious agents, a greater use of antibiotics, or a more urban lifestyle may consolidate a predominant TH2 immune response and may increase the risk of developing AD. The factors described above are the most important provocation factors of AD which may critically determine the individual course of AD. There is increasing evidence, however, that immunoregulatory abnormalities underlie AD pathogenesis and play a crucial role in the development, recurrence, and exacerbation of the disease.
C. Dysregulation of the Immune System—A Key Factor in Atopic Dermatitis In AD patients, initial allergen exposure results in activation of allergen-specific B-cells, followed by profound secretion of IgE by these cells (sensitization). Subsequent cross-binding of IgE molecules on basophils and mast cells by the allergen leads to the release of vasoactive and pro-inflammatory mediators (i.e., histamine, leukotrienes). These substances are responsible for the hypersensitivity reaction of the skin including redness, erythema, and itching (Allam et al., 2005; Jelinek, 2000). The immediate hypersensitivity reaction (IHR) is assumed to play a crucial role in AD, triggering the onset of the disease. However, the IHR, beginning rapidly within minutes after allergen challenge and then gradually subsiding over 24 hours, can
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only partly explain the more prolonged and chronic symptomatology of AD. It was found that the IHR is part of a more complex immune response that leads to local inflammation characterized by infiltration of activated T-cells and eosinophils. AD patients show increased (allergenspecific) IgE levels that have been found to induce expression of the high-affinity receptor for IgE FcεRI on epidermal Langerhans cells (LCs) and inflammatory dendritic epidermal cells (IDECs). LCs and IDECs are found to be significantly increased in AD subjects (Bieber et al., 1992; Wollenberg et al., 1996). Surfacebound IgE enables LCs and IDECs to present allergen fragments to T helper cells initiating an IgE-dependent late-phase (inflammatory) allergic response (Mudde et al., 1990). It was found that allergen-specific T helper cells that are cloned from AD skin lesions secrete high amounts of interleukin-4 (IL-4), interleukin-5 (IL-5), interleukin-10 (IL-10), and interleukin-13 (IL-13), but not interferon-γ (IFN-γ), reflecting a predominantly T helper type 2 (TH2) cytokine-secreting profile (Allam et al., 2005; Boguniewicz, 2004). TH1 and TH2 responses are mutually inhibitory (Romagnani, 2000). Thus, a generally increased frequency of allergen-specific Tcells producing a TH2-specific cytokine pattern, as it has been identified in AD subjects (Van Reijsen et al., 1992), may consolidate a TH2 immune response by suppressing the TH1 response. Moreover, a preferential apoptosis of circulating TH1 cells in AD subjects has been identified which might also contribute to the TH2 dominance observed in AD sufferers (Adkis et al., 2003). The predominant release of TH2-like cytokines plays a pivotal role in the maintenance and chronification of AD. IL-4 and IL-13 stimulate IgE synthesis and induce B-cells to switch from other Ig isotypes to IgE. They further induce expression of VCAM-1, an adhesion molecule involved in the adhesion and recruitment of eosinophils into sites of allergic tissue inflammation (Boguniewicz, 2004; Leung et al., 2004). IL-4 and IL-10 trigger mast cell proliferation. IL-5 plays a central role in the recruitment and activation of eosinophils, which is a major event to initiate the local inflammatory process. IL-5–induced stimulation of eosinophils leads to the secretion of toxic proteins such as major basic protein or eosinophilic cationic protein (ECP), which are known to contribute to tissue injury through their cytotoxic properties and by their ability to stimulate basophil and mast cell degranulation (Kapp, 1993). IL5 further is involved in the prolonged survival of eosinophils observed in AD patients (Trautmann et al., 2000). It is important to note that the natural course of AD flares show an acute and a chronic stage, with different
immunological processes being involved. Analyses of cytokines in AD skin lesions provided evidence that in acute skin lesion, mRNA of TH2-derived cytokines such as IL-4, IL-5, and IL-13 was significantly elevated, while mRNA for the TH1-derived cytokines IFN-γ and IL-12 was low. In chronic skin lesion, however, increased expression of mRNA for IFN-γ and IL-12 was detected (Hamid et al., 1994). Comparable data were reported using a patch test consisting of the application of an allergen to the skin to provoke an eczematous skin reaction. Sequential analyses of skin biopsies obtained from atopy patch test sites in AD sufferers yielded comparable results. Initially, a TH2 response with elevated levels of IL-4 was found, followed by a shift toward a TH1 secretion pattern with high amounts of IFN-γ 24 hours later (Thepen et al., 1996). Based on these findings, a model of a biphasic course with a sequential TH cell activation has been proposed in that during the acute allergic response, local inflammation is initiated by IL-4 and IL-5 (TH2 response), whereas the consolidation and aggravation of AD are dominated by a secretion of IFN-γ (TH1 response) (Grewe et al., 1998). There is evidence that IL-12, mainly produced by activated eosinophils and macrophages, may induce the switch from the early TH2 dominance to the TH1 predominance of the later chronic stage (Boguniewicz, 2004; Grewe et al., 1998). There is broad acceptance that immunological abnormalities with a complex hereditary background underlie AD pathogenesis. However, over the years clinical wisdom and experience, as well as a wealth of anecdotal observations, have emphasized the potential influence of emotional stress on AD. To date, an increasing number of papers strongly suggest that emotional stress may precede AD onset and/or may exert a negative influence on the disease course (BuskeKirschbaum et al., 2001). With this in mind, stress may be an important piece in the pathophysiological puzzle of AD and should be taken into account.
D. Stress—A Triggering Factor in Atopic Dermatitis The relevance of psychological factors such as emotional stress on the course of AD has long been postulated. In the 1940s, Alexander and French (1948) proposed that the AD child is characterized by increased stress due to the child’s failure to express anger and hostility. Although some studies have explored this hypothesis (Pauli-Pott et al., 1999), the maternal rejection/suppressed hostility hypothesis could not be conclusively supported. In more recent years, the role of stressful life events on AD pathology
45. Endocrine and Immune Responses to Stress in Chronic Inflammatory Skin Disorder
had been the focus of psychodermatological research. A central premise underlying much of this research is that elevated stress levels (1) may increase the organism’s vulnerability to develop AD and/or (2) exacerbate AD symptomatology. A number of reports suggest that emotional stress associated with a major life event is related to the development of AD (Picardi and Abeni, 2001). In these studies, assessment of critical life events was done by questionnaires or standardized interviews in adult patients and included parental separation by divorce, death of a family member, or profound family problems during childhood. It was reported that in 55–86% of the AD patients investigated, a stressful emotional event was a precipitating factor of the disease onset (Brown, 1972; Picardi and Abeni, 2001). It should be noted, however, that these early findings are mainly based on uncontrolled studies that did not include appropriate control groups. Most of the data are further retrospective and limited in that the accuracy of the subjects’ ability to recall events from childhood may be too unreliable for accurate data to be obtained. In their more recent, well-controlled study, Kodama and co-workers (1999) investigated the impact of a catastrophic life event such as the Hanshin earthquake in 1,457 diagnosed AD patients. It was reported that the percentage of patients experiencing exacerbation of skin condition 1 month after the earthquake was significantly higher in severely destroyed areas than in a mildly damaged or in a control area. Multi-variate analyses showed that the subjective emotional stress was the factor most strongly associated with the aggravation of AD symptoms. The studies showing a link between major critical life events and AD certainly deserve credit for having emphasized stress as a relevant factor in AD pathology. However, to better explore the hypothesized relation of emotional stress and the disease course characterized by episodes of recurrence and remissions, it may be advisable (and clinically more important) not to focus on one single critical life event but rather on the stressors of the everyday life. Using a diary technique, King and Wilson (1991) could demonstrate a significant positive relationship between emotional stress levels on day one and symptom severity 24 hours later. In this study, it was reported that this relationship is reciprocal in that exacerbation of AD also indicated the stress level experienced by the patients. This latter observation is most important, indicating that AD patients may suffer from generally increased daily life stress due to the chronic disease itself. For example, AD children have been found to experience increased levels of distress because of their chronic disease and, further, that the amount of stress
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is positively correlated with the skin condition, intensity of scratching, or medication taken (Gil et al., 1987). Thus, a circulus vitiosus can be assumed in that increased everyday life stress may trigger AD exacerbation, leading to worsening of skin condition and increased pruritus. Aggravation of these symptoms may then result in cosmetic disfigurement, social stigma, and sleep disturbances, and subsequently to profound body image problems, depression, anxiety, and social retreat. Increased anxiety and depression combined with inadequate coping skills, which have been described in AD patients (Scheich et al., 1993), may render AD subjects more liable to be stressed by various situations they have to face in their everyday life. The importance of stress in the clinical course of AD is further strongly supported by the effectiveness of psychotherapeutic interventions, including stress management or relaxation techniques, which have been shown to lead to significant improvement of AD symptomatology (Shenefelt, 2003). For example, Ehlers and co-workers (1995) could demonstrate that psychological treatments such as autogenic training (AT), cognitive behavioral treatment (BT), or a combined AT/BT intervention led to a significant improvement of skin condition and were more effective in reducing scratching and steroid medication than a standard dermatological treatment. Later, it was reported that the improvement by the psychological treatments could be predicted by high pre-treatment levels of scratching, low serum IgE, and a high frequency of copingrelated cognitions (Stangier et al., 2004). Other reports have emphasized a positive effect of hypnotherapy on skin condition in AD children and adults (Stewart and Thomas, 1995). In sum, there is strong evidence suggesting that psychosocial stress and skin condition in AD are bidirectionally related. It is important to keep in mind, however, that most of the studies pointing to a psychocutaneous relationship in AD suffer from shortcomings that have already been mentioned in this chapter. Most of the findings are retrospective or are based on cross-sectional correlational studies and, accordingly, are difficult to interpret. Does increased emotional stress aggravate skin condition, or does increased symptom severity lower the individual stress threshold? Is the positive relationship due to some additional factor? Moreover, most of the studies summarized here do not aim to delineate how stress may influence the course of AD. As previously discussed, AD is an immune-related disorder characterized by chronic inflammatory processes of the skin. Psychological processes such as stress (or relaxation) can modify the disease outcome. But how are psychological and
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immunological processes in AD linked together? Which neuro-immuno-dermatological pathways are activated under stressful conditions leading to stressinduced worsening of AD symptoms, and further, which are the communicating molecules of this interplay?
II. ENDOCRINE AND IMMUNE RESPONSES TO STRESS IN AD As extensively reviewed in this book, there is considerable evidence showing that the CNS and the immune system are intimately connected, each regulating the other. Although several communication channels between the CNS and the immune system have been evaluated, two pathways through which the CNS exerts control over the immune system are most frequently discussed. The CNS is capable of regulating immune functioning via the neuroendocrine system, such as the hypothalamus-pituitary-adrenal (HPA) axis or the sympathetic-adreno-medullary (SAM) system. Further, the CNS can regulate immunity via direct efferent autonomic nervous connections. Nerve terminals form a close anatomical contact with immunocompetent cells and regulate immune activity by the release of neuroactive substances. Both pathways, the autonomic and the neuroendocrine outflow, may change in response to psychosocial stress, leading to autonomic and (neuro)endocrine alterations and, accordingly, to a modulation of the immune response. Regarding these data, it is intriguing to postulate that the influence of stress on AD may be mediated by “classical” psychoneuroimmunological pathways, e.g., the regulation of atopy-relevant effector cells by (neuro)endocrine outflow or by neural input. Investigating the neuroendocrine-immune network in AD patients and, moreover, studying potential aberrations in the functional interplay between these systems under stressful conditions may help to elucidate how emotional stress impacts the skin condition in these subjects.
A. Endocrine Responses to Stress in Atopic Dermatitis 1. The Hypothalamus-Pituitary-Adrenal (HPA) Axis—A Relevant Regulatory System in (Allergic) Inflammation One major neuroendocrine stress pathway by which the CNS exerts control on immune function is via the activation of the HPA axis. During acute stress, corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP), the principal hypothalamic regulators
of the pituitary-adrenal axis, are released. CRH stimulates the secretion of the adrenocorticotropin hormone (ACTH) from the anterior pituitary into the hypophyseal portal system via collateral fibers and the systemic circulation. ACTH stimulates the secretion of glucocorticoids (GCs) from the adrenal cortex, the main target of ACTH. GCs are the final effectors of the HPA axis (Chrousos, 2002). GCs have profound immunosuppressive effects, including immune functions known to be critically involved in chronic allergic inflammation (Franchimont et al., 2002). For example, GCs inhibit dendritic cell maturation, leading to reduced allergen presentation to T-cells (Piemonti et al., 1999). GCs further induce apoptosis of eosinophils and basophils, the main effector cells of the chronic allergic response (Meagher et al., 1996). Moreover, GCs have been shown to inhibit transmigration of basophils and eosinophils to the inflammatory side by downregulating leukocyte adhesion molecules, such as leukocyte factor adhesion-1 (LFA-1) or ICAM-1 (Cronstein et al., 1995). Due to their immunosuppressive and anti-inflammatory properties, it has been proposed that an appropriate responsiveness of the HPA axis may be essential to control inflammation and to prevent an overshooting of the immune response, which may be damaging for the host. In turn, a chronic failure to mount an adequate GC response, especially under stress when the two systems are activated, may contribute to the development of pathology (Chrousos, 1995). The latter assumption is strongly supported by animal data showing that disruption or attenuation of the HPA axis activity is associated with increased susceptibility to inflammatory disease. Lewis (LEW/N) rats, which show a genetically blunted HPA axis reactivity in response to various stimuli such as IL-1, hCRH, or quipazin, are found to be highly vulnerable to proinflammatory stimuli when compared to histocompatible in-bred Fischer (F344/N) rats (Sternberg et al., 1989). Interestingly, treatment of the F344 rats with the GC receptor antagonist RU 486 rendered these otherwise resistant animals highly susceptible to inflammatory disease, whereas replacement of GCs by dexamethasone in LEW/N rats resulted in decreased susceptibility to inflammation in the former highly vulnerable rat strain. A dysfunctional HPA axis responsiveness has also been reported in other species prone to develop chronic inflammatory diseases such as the obese strain chicken (thyroiditis) or the NZB × NZW F1 lupus-prone mouse (lupus erythematosus) (Eskandari and Sternberg, 2002). In humans, comparable findings were reported. For example, patients with rheumatoid arthritis (RA) were found to show an attenuated cortisol response to surgical stress despite
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2. The HPA Axis Response to Stress in AD Following this line of reasoning, we investigated HPA axis function under psychosocial stress in AD sufferers. In a first study (Buske-Kirschbaum et al., 1997), AD children were exposed to a standardized laboratory stressor, the “Trier Social Stress Test for Children” (TSST-C), which mainly consists of public speaking (finishing a story in as exciting a manner as possible) and mental arithmetic tasks (serial subtraction) in front of an audience. The TSST-C represents an adapted version of the “Trier Social Stress Test” (TSST), which has been shown in numerous studies to significantly activate the HPA axis and the SAM system (Kirschbaum et al., 1993). When being exposed to the TSST-C, AD children showed increased cortisol levels; however, the cortisol response in AD children was found to be significantly attenuated when compared to a non-atopic control group (see Figure 1). Interest-
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significant post-operative elevations of IL-1 and IL-6 (Chikanza et al., 1992). Moreover, a significantly blunted cortisol response to CRH stimulation was reported in this patient group (Cash et al., 1992). The regulatory and anti-inflammatory role of GCs has also been suggested for the chronic allergic inflammatory process. For example, the circadian rhythm of cortisol closely corresponds with changes in basophil and eosinophil levels, supporting a close link between GCs and the effector cells of the acute allergic response (Schleimer, 2000). Further, Herrscher and co-workers (1992) reported that after treatment with the cortisol synthesis inhibitor methyrapone, AD subjects showed a significantly larger allergic skin response to a cutaneous allergen challenge, supporting the idea that the endogenous cortisol level may regulate/suppress the late-phase response. The protective role of GCs in allergic inflammation is further strongly emphasized by an incidental observation by Laue and co-workers (1990). They observed that healthy volunteers treated with the glucocorticoid receptor antagonist RU 486 for 7–14 days developed AD symptomatology including erythema or eruptions of the skin. None of the subjects had a prior history of atopy. In sum, there is growing evidence that the ability of an individual to raise an appropriate HPA axis response may be critical in regulating the immune response and in preventing an overshooting of the system. Regarding the fact that AD is an immunopathological condition characterized by an ongoing (overshooting) inflammatory process that often exacerbates under stressful conditions, one may ask whether in AD an aberrant HPA axis response may be of pathological relevance.
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FIGURE 1 Changes of cortisol levels in response to psychosocial stress (TSST-C) in children with atopic dermatitis (AD) and in non-atopic controls (means ± SEM). [Adapted with permission from Buske-Kirschbaum et al. (1997). Psychosom. Med., 59, 419–426.]
ingly, no differences in basal cortisol levels between the two experimental groups could be identified, suggesting that the HPA axis response dysfunction in AD patients may become apparent only under stimulated conditions. Further, AD and control children did not differ in heart rate responses to the stress test or in personality aspects such as emotional excitability, anxiety, self-conviction, or ambition in school. These findings suggested that the adrenocortical response to stress may be attenuated in patients with AD, which is in line with previous work by Rupprecht and co-workers (1991, 1995). They reported reduced cortisol levels to a CRH challenge as well as an increased number of GC receptors on peripheral lymphocytes in adults with AD. These data support the idea of a hyporesponsive HPA axis and a compensatory upregulation of GC binding sites due to a potentially long-term reduced action of endogenous cortisol in subjects with AD. Regarding the observation of attenuated cortisol responses in AD patients, the question arises whether a hyporesponsive HPA axis is a characteristic feature of skin atopy, or whether it is generally linked to chronic allergic inflammation. Following this question, HPA axis responsiveness in children with allergic asthma (AA) was investigated. AA is a chronic inflammatory disorder of the airways characterized by airway inflammation and airflow obstruction. The immunopathology of AA parallels the immunopathology of AD in that IgE-mediated inflammation, TH2-cellpredominance, and eosinophila have been described
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(Maddox and Schwarz, 2002). As in AD, AA is considered a chronic inflammatory condition of the atopic triad with a manifestation in the airway system (Gold and Kemp, 2005). When studying AA children with the TSST-C, we again found a significantly blunted cortisol response to the stressor in this patient group (Buske-Kirschbaum et al., 2003). Again, no betweengroup differences could be determined in heart rate responses to the stressor or in psychological variables such as the subjective stress experience. These data give evidence that reduced HPA axis reactivity as found in patients with AD probably does not reflect a specific phenomenon linked to skin atopy, but rather is a general phenomenon associated with allergic inflammation regardless of the target organ. This idea is also supported by Wamboldt and co-workers (2003), who reported significantly reduced cortisol responses to a laboratory stressor in atopic adolescents with different manifestations of atopy such as AD and AA. Given a blunted cortisol response to stress in AD patients, it may be of interest to further clarify at which level the HPA axis may be dysfunctional. In a recent study we found that in adult AD subjects, a reduced cortisol level and, concomitantly, a significantly blunted ACTH response to psychosocial stress (TSST) can be observed (Buske-Kirschbaum et al., 2002a) (see Figure 2). The finding of a pituitary ACTH hyporesponsiveness in AD patients supports the idea of a dysfunction of the HPA axis at the suprapituitary side. This would be in line with animal data showing
that a deficient CRH synthesis and secretion in the PVN may be responsible for attenuated HPA axis reactivity in animals (LEW/N rats) prone to develop inflammation (Calogero et al., 1992; Sternberg et al., 1989). It is important to keep in mind, however, that the data linking attenuated HPA axis responsiveness to chronic allergic inflammation in AD are of correlational nature. It still remains to be determined whether attenuated reactivity of the HPA axis in patients with AD represents a (genetically determined) predisposition of the individual that may contribute to the development of atopy, or alternatively, whether attenuated HPA axis reactivity in AD is a consequence of a long-term chronic inflammation of the skin. The latter assumption would be supported by findings demonstrating activation of the HPA axis by proinflammatory cytokines with a later downregulation of the system in chronic inflammatory conditions (Turnbull and Rivier, 1999). With this in mind, we studied newborns with atopic predisposition as defined by a positive family history of atopy (at least one parent atopic) and elevated IgE levels (IgE < 0.5 kU/l) in cord blood. The specific goal of the study was to investigate whether a hyporeactive HPA axis can be observed early in life before the onset of a (potential) allergic inflammation and therefore may be of etiological significance. In contrast to our expectations, a significantly elevated cortisol response to venipuncture stress was observed in newborns with an
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FIGURE 2 Changes in cortisol and ACTH levels in response to psychosocial stress (TSST) in patients with atopic dermatitis (AD) and in non-atopic controls (means ± SEM). [Adapted with permission from Buske-Kirschbaum et al. (Copyright 2002, The Endocrine Society). J. Clin. Endocrinol. Metabol., 87, 4245–4251.]
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45. Endocrine and Immune Responses to Stress in Chronic Inflammatory Skin Disorder
atopic predisposition when compared to a control group (Buske-Kirschbaum et al., 2004). Combining these findings with the existing data of HPA axis responsiveness in AD patients may be puzzling. One may wonder what the potential link might be between the previous observation of a hyporeactivity of the HPA axis in patients with long-term AD and the observation of a hyperreactivity of the system in newborns with atopic predisposition. To fit the two findings together, it could be speculated that with the onset of the disease and/or its becoming chronic, the HPA axis may switch from a hyper- to a hyporeactive state. To date, no convincing data are available to support this hypothesis. However, there are reports suggesting that the long-term release of pro-inflammatory cytokines (as observed after the onset of allergic inflammation) can diminish HPA axis responsiveness due to increased negative feedback produced by persistently increased endogenous cortisol concentrations (Mastorakos et al., 1993; Turnbull and Rivier, 1999). Alternatively, psychological factors such as chronic stress or altered maternal behavior have been emphasized to be linked to a blunted HPA axis responsiveness in animals (Francis and Meaney, 1999; Murison and Milde, 1999). Although these animal data are difficult to transfer to human beings, they provide evidence that the magnitude of the HPA axis response may be associated with the experience of chronic stress or a distinct (overprotective) mother-child interaction. Both factors, however—an increased everyday stress level and an altered mother-child interaction characterized by overprotection—have been described for the AD patient (Wallander and Varni, 1998). 3. The Sympatho-Adreno-Medullary (SAM) System and (Allergic) Inflammation There is general agreement that, besides the HPA axis, the SAM system functionally separable into the sympathetic nervous system (SNS) and the adrenal medulla (AM) represent another major immunoregulatory system. Activation of the SNS causes increased release of norepinephrine (NE) and neuropeptide-Y (NPY) from sympathetic nerve terminals and of NE, epinephrine (E), and dihydroxyphenylalanine (DOPA) from the AM. Systemic NE and E significantly affect a variety of (atopy-relevant) immune responses such as leukocyte trafficking, macrophage activity, or antibody production (Elenkov et al., 2000). It is well documented that CAs acutely mobilize leukocytes, mainly NK cells, monocytes, granulocytes, and neutrophils (Benschop et al., 1996). This process may optimize immunoprotection in the case of wounding or infection. Catecholamines (CAs) further have a stimulatory effect on
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B-cell antibody production (Sanders, 1995). In the last decade, the effect of the SAM system on immunity has been further specified in that CAs shape the immune response in modulating the TH1/TH2 balance. CAs drive a TH2 shift by suppressing IL-12, the main TH1 inducer, while the secretion of IL-10, a potent promoter of the TH2 response, is stimulated (Elenkov and Chrousos, 2002). In conjunction with their ability to suppress IL-12, CAs have been shown to inhibit the development of TH1 cells, while promoting maturation and differentiation of TH2 cells. The finding that TH1 but not TH2 cells express β-adrenergic receptors may represent another mechanistic basis of the differential effect of CAs on the TH1/TH2 immune response (Elenkov et al., 2000b; Elenkov and Chrousos, 2002). Analogous to the HPA axis, it can be assumed that the SAM response has important regulatory functions in countering the tissue-damaging effects of an excessive TH1 response, for example an overshooting of activated macrophages and their tissue-damaging potential. Thus, a hypo- or hyperreactive SAM system may increase the risk of an aberrant immune response that may facilitate or sustain TH1 (autoimmune) or TH2 (allergy/atopy) mediated inflammatory reactions, respectively. 4. The SAM System Response to Stress in AD There is evidence suggesting that AD patients show irregularities in the SAM system. Ionescu and Kiehl (1988) reported increased plasma NE levels under resting conditions in adult AD patients. Others found significantly elevated NE levels in AD subjects in response to standing (Crespi et al., 1982). In a more recent study, we investigated the SAM system response to psychosocial stress (TSST) in adult AD sufferers (Buske-Kirschbaum et al., 2002). In this study, AD patients showed elevated basal NE and E levels, supporting the previous findings of a hyperactive SAM system in this patient group. Moreover, when exposed to the stressor, NE and E responses in AD subjects were found to be significantly increased, pointing to an over(re)active SAM system in AD (see Figure 3). It is important to note, however, that elevated circulating CA levels do not necessarily implicate an increased adrenergic signaling, i.e., an overstimulation of the target cell. In a most recent study, a significantly decreased density of β-adrenergic receptors on peripheral mononuclear cells of AD patients was demonstrated (Niemeier et al., 1996). Moreover, a number of studies have shown that AD patients show a diminished β-adrenergic responsiveness due to disturbances in the cyclic adenosine monophosphate (cAMP) system. This was first introduced by Szentivanyi (1968),
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FIGURE 3 Changes in epinephrine and norepinephrine in response to psychosocial stress (TSST) in patients with atopic dermatitis (AD) and in non-atopic controls (means ± SEM). [Adapted with permission from Buske-Kirschbaum et al. (Copyright 2002 , The Endocrine Society). J. Clin. Endocrinol. Metabol., 87, 4245–4251.]
proposing the β-adrenoceptor blockade theory of atopy. Since it is known that β-adrenoceptor stimulation and subsequent cAMP secretion suppress immune activity, the hyper-releasability of mast cells and basophils found in AD patients has been contributed to the dysfunctional cAMP system in these patients. Evidence supporting Szentivanyi’s pathogenic concept came from more recent studies demonstrating reduced plasma cAMP levels and reduced leukocyte cAMP after stimulation with β-adrenergic agonists in AD patients (Safko et al., 1981; Salpietro et al., 1998). It is assumed that the reduced cAMP concentration in leukocytes of AD patients is due to a rapid enzymatic breakdown of cAMP by increased cAMP-phosphodiesterase (sAMP-PDE) activity in these patients (Grewe et al., 1982). Since increased cAMP-PDE activity has also been observed in cord blood leukocytes from newborns with atopic disposition, it is likely that increased cAMP-PDE is a primary, gene-associated abnormality of the adrenergic system (Hanifin et al., 1991). These findings of second messenger defects in AD may point to an impaired adrenergic signaling for the target (inflammatory) cell despite a potentially strong stimulus. Thus, a more complex dysfunction of the SAM system on different regulatory levels such as the CA secretion pattern, receptor density, or intracellular signal transduction should be considered when studying the SAM-immune-cutaneous axis under stress in AD.
B. Immune Responses to Stress in AD Regarding the findings of an aberrant responsiveness of the HPA axis and the SAM system to stress in AD patients, the question arises what the pathological relevance of these endocrine dysfunctions might be? Does stress affect atopy-relevant immune functions in AD subjects, and if so, are the stress-induced immunological changes linked to a dysfunctional HPA axis or SAM system? Following this line of reasoning, we investigated the impact of stress on atopy-relevant immune responses to a standardized stress test (TSST) in adult AD patients (Buske-Kirschbaum et al., 2002b). In this study, a significant rise of eosinophil number to the stressor was found in AD (see Figure 4A), but not in the control subjects, which is in line with data by Schmid-Ott and co-workers (2001a). The observation of a stress-induced eosinophilia may be of clinical relevance. As mentioned earlier in this chapter, eosinophils play a key role in the late-phase response of AD. It has been shown that recruitment and infiltration of eosinophils precede exacerbation of skin lesions. Further, eosinophils have been found to be mainly responsible for tissue injury through their ability to release cytotoxic mediators, which are found to be elevated in sera of patients with AD and are positively correlated with disease severity (Abramovits, 2005; Kapp, 1993). The observation of an increased eosinophil number after
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stress in AD sufferers may point to an increased sensitivity of this inflammatory cell to stress influences in AD subjects and may represent one potential mechanism of stress-induced worsening of skin condition in AD. This idea would be supported by the finding of an increased migratory responsiveness of eosinophils to various stimuli in AD sufferers (Bruijnzeel et al., 1993). Besides changes in eosinophil number, SchmidOtt and his group (2001b) reported a significant increase of CLA+ cells, as well as T-cells expressing intracellular IL-5 and IFN-γ. The membrane molecule CLA (cutaneous lymphocyte-associated antigen) is expressed on activated T-cells and is found to be involved in selective homing of these cells into inflamed skin by binding to E-selectin (Akdis et al., 2000). The stress-induced distribution of CLA+ cells as well as IL-5+ and IFN-γ+ T-cells from other sites of the body into the circulation may facilitate the onset/aggrava-
tion of inflammation and, thus, could be another piece of the puzzle indicating how stress may contribute to AD pathology. Interestingly, a re-analysis of the data revealed that the increase of CLA+, IL-5+, and IFN-γ+ cells after stress could only be identified in AD patients with high serum IgE levels (<1,000 kU/L), suggesting that the immunological changes described before can be found only in the allergic subtype of AD (Stephan et al., 2004). Besides a redistribution of atopy-relevant leukocyte subsets, an increase of total IgE levels in AD, but not in non-atopic control subjects, was found 24 hours after psychosocial stress (see Figure 4B). It is widely accepted that IgE represents a key molecule in AD. IgE stimulates basophils and mast cells and is of major importance in the propagation of the IHR. IgE further enables LCs and IDECs to present allergen to TH2 cells, initiating the chronic inflammatory response in AD (Abramovits, 2005; Allam et al., 2005). While our
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FIGURE 4 Changes in eosinophil number (A), total IgE (B), IFN-γ (C), and IL-4 (D) in response to psychosocial stress (TSST) in patients with atopic dermatitis (AD) and in non-atopic controls (means ± SEM). [Adapted with permission from Buske-Kirschbaum et al. (2002). J. Neuroimmunol., 129, 161–167.]
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knowledge of how stress may be involved in IgE synthesis is still very limited, there are some data linking the HPA axis to IgE regulation. For instance, Ray and co-workers (1987) found a stimulating effect of GCs on IgE production by mononuclear cells in vitro. Most interestingly, only in AD subjects treatment of mononuclear cells led to increased IgE concentrations, suggesting altered sensitivity of IgE-producing B-cells to GCs in AD patients. A growing number of reports suggest that stress can influence the TH1/TH2 balance probably via the release of GCs and CAs, which have been shown to suppress TH1 and to promote a TH2-dominant immune response (Elenkov et al., 2000a; Elenkov and Chrousos, 2002). For example, a polarization of the immune response with elevated IL-10, IL-1β, and IL-6 and concomitantly decreased IFN-γ levels was reported in response to examination stress (Kang and Fox, 2001; Paik et al., 2000). A stress-induced selective upregulation of TH2 cells may favor an atopy-relevant cytokine milieu and, thus, may trigger or worsen skin lesions in AD. In contrast to these findings, increased IFN-γ and decreased IL-4 levels in response to the TSST were found in AD patients, suggesting a stress-induced shift to a TH1-like rather than to a TH2-like immune response (Buske-Kirschbaum et al., 2002; see Figure 4C and D). It is important to note, however, that most of the data of a stress-induced shift to a predominantly TH2 cell response pattern were obtained in healthy individuals. The effect of stress on the TH1/TH2 balance in an already immunocompromised host suffering from an ongoing allergic inflammation may be different. Moreover, as previously discussed, a biphasic immune response with a sequential TH1 and TH2 cell activation dependent on the chronicity of the disease has been reported in AD patients (Thepen et al., 1996). Thus, the timing of the stress exposure may be important and may critically modulate the (sequential) activation of the TH1/TH2 response, respectively.
III. SUMMARY AND FUTURE DIRECTIONS This chapter described important immunological and psychological factors related to the pathogenesis of AD. It has been become clear that immunological abnormalities, such as IgE hypersecretion, a dysfunctional TH1/TH2 immune response pattern, and eosinophilia, play key roles in the onset and maintenance of the disease. On the other hand, stress has been found to be an important trigger of skin worsening in AD. Regarding the stress-AD relationship, it is important to keep in mind that stress can trigger exacerbation of the disease but, in turn, may be a consequence of a
worsening of skin condition and the discomfort related to an exacerbation of the disease. This may lead to a circulus vitiousus that is often difficult to interrupt. In this overview, potential psycho-neuroimmunological pathways, which may be involved in the close relationship of stress and exacerbation of allergic skin inflammation, were discussed. Due to their functional relevance in the adaptive stress response and, further, their immunoregulatory properties, this chapter focused on the two major endocrine stress systems, the HPA axis and the SAM system, and a psycho-neuro-endocrine-immunological model of AD was outlined (Figure 5). In this model, it is proposed that in AD patients, a hyporeactive HPA axis and a concomitantly hyperreactive SAM system may lead to an immunological milieu that may render the (genetically disposed) individual more vulnerable to develop and/or exacerbate allergic inflammation. The dysfunctional responsiveness of the HPA axis and the SAM system may be of specific pathological relevance when the organism is challenged by a stressor, and an adaptive regulatory control of the immune system is required. It is of note, however, that although this model is built on experimental evidence, several parts of it are still speculative, awaiting validation by future research. It has been shown that GCs drive the immune systems towards a TH2-type response pattern by suppressing IL-12 (Elenkov et al., 2000; Elenkov and Chrousos, 2002). Thus, one might expect that an attenuated GC level under stress, as it has been found in AD, would then be beneficial rather than detrimental to the patient. Regarding the biphasic immune response in AD with a sequential TH1/TH2 activation, one might argue that stress may especially trigger the disease when occurring during the chronic, TH1-dominant inflammatory state. To date, however, no such data are available, and additional studies are required to support this idea. Further, it may be of interest whether altered endocrine stress responses in AD, i.e., a hyporeactive HPA axis or a hyperreactive SAM system, may be a transient (state) or permanent (trait) variable? Is an aberrant endocrine responsiveness linked to the severity of the allergic disease, and does the reactivity of the HPA axis and the SAM system normalize under remission? Does a blunted HPA axis responsiveness and/or an increased SAM system response in an AD subject really predict a higher risk to show skin exacerbation under stress? There is some evidence in animals that the HPA axis response to a foot shock stress alone does not predict the susceptibility to develop inflammation (Chover-Gonzalez et al., 2000). Further, animal data give evidence that the HPA axis responsiveness to stress as well as the susceptibility to inflammation in
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Stress
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Allergic Inflammation FIGURE 5
Psycho-neuro-endocrine-immunological model of AD.
hyporeactive animals can be manipulated by simply altering housing or nurturing (Harbuz et al., 2003), suggesting that there is certain plasticity in the interplay between HPA axis responsiveness and susceptibility to inflammation. It remains to be determined, however, whether these observations are also true in human inflammatory disease, i.e., AD. Finally, there are other psychobiological pathways that may be involved in stress-induced exacerbation of AD that are not included in this model. For example, stress may affect atopy-relevant effector cells via direct neural connection. A growing number of immunohistochemical studies show a high density of nerve fibers positive for NE, substance P, calcitonin gene-related peptide (CGRP), or neuropeptide Y (NPY). It has been found that neuropeptide-positive nerve fibers are increased in AD skin lesions and, further, that the peripheral nerve endings are in an active state of excitation. These neuropeptides can manifest immunomodulatory activity and have shown to contribute to the cross-talk between the autonomic and sensory
nervous system and pro-inflammatory cells such as mast cells or eosinophils in the skin. Consequently, an activation of these direct neuropeptide-cutaneous communication pathways under stress may trigger local inflammation in the skin and, thus, may also be involved in stress-induced worsening of skin condition (Legat et al., 2002; Panconesi and Hautmann, 1996; Raap and Kapp, 2005). Besides the modulation of atopy-relevant immune processes via direct neural input, stress may trigger allergic inflammation indirectly by behavioral processes. As mentioned earlier in this chapter, pruritus and subsequent scratching are key events maintaining skin inflammation in AD. Some studies give evidence that stress may lower the itch threshold and, further, may sharpen the awareness of different itch stimuli, leading to increased pruritus perception and scratching (Cormia, 1952; Edwards et al., 1976). Scratching causes trauma and further insult to the already compromised skin. More importantly, scratching stimulates keratinocytes to secrete a variety of
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pro-inflammatory cytokines such as IL-1, TNF-α, and IL-4 that trigger local allergic inflammation (Leung and Soter, 2001). Scratching-induced disruption of the skin barrier also allows entry of microbes such as S. aureus, leading to inflammatory reactions due to their superantigenic properties (Leung et al., 1993; Roll et al., 2004). In a most recent study, it has also been shown that stress may directly affect skin barrier function by altering skin barrier homeostasis (i.e., epidermis cell proliferation and differentiation) and by delaying barrier recovery from acute disruption (Choi et al., 2005), which may additionally compromise skin barrier function in AD. Trying to integrate existing facts and promising working hypotheses into a model of psycho-neuroimmuno-cutaneous communication and, further, to validate such a working model in future research is a challenge for the field of psychodermatology which may lead to new disease concepts and therapeutic regimens for chronic allergic skin disorder.
References Abramovits., V. (2005). Atopic dermatitis. J. Am. Acad. Dermatol., 53, S86–S93. Akdis, M., Klunker, S., Schliz, M., Blaser, K., and Akdis, C. A. (2000). Expression of cutaneous lymphocyte-associated antigen on human CD4(+) and CD8(+) TH2 cells. Eur. J. Immunol., 30, 3533–3541. Akdis, M., Trautmann, A., Klunker, S., Daigle, I., Kucuksezer, U. C., Deglmann, W., Disch, R., Blaser, K., and Akdis, C. A. (2003). T helper (Th) 2 predominance in atopic diseases is due to preferential apoptosis of circulating memory/effector TH1 cells. FASEB, 17, 1026–1035. Alexander, F., and French, T. M. (1948). Studies in psychosomatic medicine. New York: Ronald Press. Allam, J. P., Bieber, T., and Novak, N. (2005). Recent highlights in the pathophysiology of atopic eczema. Int. Arch. Allergy Immunol., 136, 191–197. Benschop, R. J., Rodriguez-Feuerhahn, M., and Schedlowski, M. (1996). Catecholamine-induced leukocytosis: early observations, current research, and future directions. Brain, Behav. Immun., 10, 77–91. Bieber, T., de la Salle, H., Wollenberg, A., Hakimi, J., Chizzonite, R., Ring, J., Hanau, D., and de la Salle, C. (1992). Human epidermal Langerhans cells express the high affinity receptor of immunoglobulin-E (Fc epsilon RI). J. Exp. Med., 175, 1285–1290. Boguniewicz, M. (2004). Update on atopic dermatitis: insights into pathogenesis and new treatment paradigms. Allergy Asthma Proc., 25, 279–282. Bresciani, M., Parisi, C., Menghi, G., and Bonini, S. (2005). The hygiene hypothesis: does it function worldwide? Curr. Opin. Allergy Clin. Immunol., 5, 147–151. Brown, D. G. (1972). Stress as a precipitant factor of eczema. J. Psychosom. Res., 16, 321–327. Bruijnzeel, P. L., Juijper, P. H., Rihs, S., Betz, S., Waringa, R. A., and Koenderman, L. (1993). Eosinophil migration in atopic dermatitis: increased migratory responses to N-formyl-methionyl-
leucyl-phenylalanine, neutrophil-activating factor, plateletactivating factor and platelet factor 4. J. Invest. Dermatol., 100, 137–142. Buske-Kirschbaum, A., Fischbach, S., Rauh, W., Hanker, J., and Hellhammer, D. H. (2004). Increased responsiveness of the hypothalamus-pituitary-adrenal (HPA) axis to stress in newborns with atopic disposition. Psychoneuroendocrinol., 29, 705–711. Buske-Kirschbaum, A., Geiben, A., and Hellhammer, D. H. (2001). Psychobiological aspects of atopic dermatitis: an overview. Psychother. Psychosom., 70, 6–16. Buske-Kirschbaum, A., Geiben, A., Höllig, H., Morschhäuser, E., and Hellhammer, D. H. (2002a). Altered responsiveness of the hypothalamus-pituitary-adrenal axis and the sympathetic adrenomedullary system to stress in patients with atopic dermatitis. J. Clin. Edocrinol. Metab., 87, 4245–4251. Buske-Kirschbaum, A., Gierens, A., Höllig, H., and Hellhammer, D. H. (2002b). Stress-induced immunomodulation is altered in patients with atopic dermatitis. J. Neuroimmunol., 129, 161– 167. Buske-Kirschbaum, A., Jobst, S., Wustmans, A., Kirschbaum, C., Rauh, W., and Hellhammer, D. H. (1997). Attenuated free cortisol response to psychosocial stress in children with atopic dermatitis. Psychosom. Med., 59, 419–426. Buske-Kirschbaum, A., von Auer, K., Krieger, S., Weis, S., Rauh, W., and Hellhammer, D. H. (2003). Blunted cortisol responses to psychosocial stress in asthmatic children: a general feature of atopic disease? Psychosom. Med., 65, 806–810. Calogero, A. E., Sternberg, E. M., Bagdy, G., Smith, C., Bernardini, R., Aksentijevich, S., Wilder, R. L., Gold, P. W., and Chrousos, G. P. (1992). Neurotransmitter-induced hypothalamic-pituitaryadrenal axis responsiveness is defective in inflammatory diseasesusceptible Lewis rats: in vivo and in vitro studies suggesting globally defective hypothalamic secretion of corticotropinreleasing hormone. Neuroendocrinol., 55, 600–608. Cash, J. M., Crofford, L. J, Gallucci, W. T., Sternberg, E. M., Gold, P. W., and Wilder, R. S. (1992). Pituitary-adrenal axis responsiveness to ovine CRH in patients with rheumatoid arthritis treated with low-dose prednisolone. J. Rheumatol., 19, 1692–1696. Chover-Gonzalez, A. J., Jessops, D. S., Tejedor-Real, P., GibertRahola, J., and Harbuz, M. S. (2000). Onset and severity of inflammation in rats exposed to the learned helplessness paradigm. Rheumatol., 39, 764–771. Chrousos, G. P. (1995). The hypothalamic-pituitary-adrenal axis and immune mediated inflammation. N. Engl. J. Med., 332, 1351–1362. Chrousos, G. P. (2002). Organization and integration of the endocrine system. In J. Sperling (Ed.), Pediatric endocrinology (pp. 1– 14). Philadelphia: Saunders. Coleman, R., Trembath, R. C., and Harper, J. I. (1997). Genetic studies of atopy and atopic dermatitis. Br. J. Dermatol., 136, 1–5. Chikanza, I. C., Petrou, P., Kingsley, G., Chrousos, G., and Panayi, G. S. (1992). Defective hypothalamic response to immune and inflammatory stimuli in patients with rheumatoid arthritis. Arthritis Rheum., 35, 1281–1288. Choi, E. H., Brown, B. E., Crumrine, D., Chang, S., Man, M. Q., Elias, P. M., and Feingold, K. R. (2005). Mechanisms by which psychologic stress alters cutaneous permeability barrier homeostasis and stratum corneum integrity. J. Invest. Dermatol., 124, 587– 595. Cormia, F. E. (1952). Experimental histamine pruritus. I. Influence of physical and psychological factors on threshold reactivity. J. Invest. Dermatol., 19, 21–34. Crespi, H., Armando, I., Tumilasci, O., Levin, G., Massimo, J., Barontini, M., and Perec, C. (1982). Catecholamine levels and
45. Endocrine and Immune Responses to Stress in Chronic Inflammatory Skin Disorder parotid secretion in children with chronic atopic dermatitis. J. Invest. Dermatol., 78, 493–497. Cronstein, B. N., Kimmel, S. C., Levin, R. I., Martiniuk, F., and Weissmann, G. (1995). A mechanisms for the anti-inflammatory effects of corticosteroids: the glucocorticoid receptor regulates leukocyte adhesion to endothelial cells and expression of endothelial-leukocyte adhesion molecule 1, and intercellular adhesion molecule. Proc. Natl. Acad. Sci. USA, 89, 9991–9995. Donnell, A. T., and Tripathi, A. (2004). Atopic dermatitis. Allergy Asthma Proc., 25, S42–S43. Edwards, A. E., Shellow, W. V. R., Wright, E. T., and Dignam, T. F. (1976). Pruritic skin disease, psychological stress and the itch sensation. Arch. Dermatol., 112, 339–343. Ehlers, A., Stangier, U., and Gieler, U. (1995). Treatment of atopic dermatitis: a comparison of psychological and dermatological approaches to relapse prevention. J. Consult. Clin. Psychol., 63, 624–635. Eichenfield, L. F., Hanifin, J. M., Beck, L. A., Lemanske, R. F., Sampson, H. A., Weis, S. T., and Leung, D. Y. (2003). Atopic dermatitis and asthma: parallels in the evolution of treatment. Pediatrics, 111, 608–616. Elenkov, I. J., and Chrousos, G. P. (2002). Stress hormones, proinflammatory and anti-inflammatory cytokines, and autoimmunity. Ann. N. Y. Acad. Sci., 966, 290–303. Elenkov, I. J., Chrousos, G. P., and Wilder, R. L. (2000a). Neuroendocrine regulation of IL-12 and TNF-alpha/IL-10 balance. Clinical implications. Ann. N. Y. Acad. Sci., 917, 94–105. Elenkov, I. J., Wilder, R. L., Chrousos, G. P., and Vizi, E. S. (2000b). The sympathetic nerve—an integrative interface between the two supersystems: the brain and the immune system. Pharmacol. Rev., 52, 595–638. Engels, W. D. (1982). Dermatologic disorders. Psychosom., 23, 1209–1219. Eskandari, F., and Sternberg, E. M. (2002). Neural-immune interactions in health and disease. Ann. N. Y. Acad. Sci., 966, 20–27. Evers, A. W., Lu, Y., Duller, P., van der Alk, P. G., Kraaimaat, F. W., and van der Kerkhof, P. C. (2005). Common burden of chronic skin disease? Contributors to psychological distress in adults with psoriasis and atopic dermatitis. Br. J. Dermatol., 152, 1275–1281. Feijen, M., Gerritsen, J., and Postma, D. S. (2000). Genetics of allergic disease. Br. Med. Bull., 56, 894–907. Folster-Holst, R., Moises, H. W., Yang, L., Fritsch, W., Weissenbach, J., and Christophers, E. (1998). Linkage between atopy and the IgE high-affinity receptor gene at 11q13 in atopic dermatitis families. Hum. Genet., 102, 236–239. Forrest, S., Dunn K., Eliott, K., Fitzpatrick, E., Fullerton, J., McCarthy, M., Brown, J., Hill, D., and Williamson, R. (1999). Identifying genes predisposing to atopic eczema. J. Allergy Clin. Immunol., 104, 1066–1070. Franchimont, D., Kino, T., Galon, J., Meduri, G. U. and Chrousos, G. (2002). Glucocorticoids and inflammation revisited: the state of the art. Neuroimmunomodulation, 10, 247–260. Francis, D. D., and Meaney, M. J. (1999). Maternal care and the development of stress responses. Curr. Opin. Neurobiol., 9, 128–134. Fritz, G. K. (1979). Psychological aspects of atopic dermatitis. Clin. Ped., 18, 360–364. Gehring, U., Bolte, G., Borte, M., Bischof, W., Fahlbusch, B., Wichmann, H. E., and Heinrich, J. (2001). Exposure to endotoxin decreases the risk of atopic eczema in infancy: a cohort study. J. Allergy Clin. Immunol., 108, 847–854. Gil, K. M., Keef, F. J., Sampson, H. A., McCashill, C. C., Rodin, J., and Crisson, J. E. (1987). The relationship to stress and family
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environment to atopic dermatitis symptoms in children. J. Psychosom. Res., 31, 673–684. Gold, M. S., and Kemp, A. S. (2005). Atopic disorders in childhood. Med. J. Aust., 182, 298–304. Goldsmith, L. A. (1983). Biochemistry and physiology of the skin. New York: Oxford University Press. Grewe, M., Bruijnzeel-Koomen, C. A. F. M., Schöpf, E., Thepen, T., Langeveld-Wildschut, A. G., Ruzicka, T., and Krutman, J. (1998). A role for Th1 and Th2 cells in the immunopathogenesis of atopic dermatitis. Immunol. Today, 19, 359–361. Grewe, S. R., Chan, S. C., and Hanifin, J. M. (1982). Elevated leukocyte cyclic AMP-phosphodiesterase in atopic disease: a possible mechanism for cyclic AMP-agonist hyporesponsiveness. J. Allergy Clin. Immunol., 70, 452–457. Hamid, Q., Boguniewicz, M., and Leung, D. Y. (1994). Differential in situ cytokine gene expression in acute versus chronic atopic dermatitis. J. Clin. Invest., 94, 870–876. Hanifin, J. M., and Chan, S. C. (1991). Role of cyclic nucleotide metabolism in the pathophysiology of atopic eczema. In T. Ruzicka, J. Ring, and B. Przybilla (Eds.), Handbook of atopic eczema (pp. 232–244). Berlin: Springer. Harbuz, M. S., Chover-Gonzalez, A. J., and Jessop, D. S. (2003). Hypothalamo-pituitary-adrenal axis and chronic immune activation. Ann. N. Y. Acad. Sci., 992, 99–106. Herrscher, R. F., Kasper, C., and Sullivan, T. J. (1992). Endogenous cortisol regulates immunoglobulin E-dependent late phase reactions. J. Clin. Invest., 90, 596–603. Ionescu, G., and Kiehl, R. (1988). Plasma catecholamine levels in severe atopic dermatitis. Allergy, 43, 614–616. Jelinek, D. F. (2000). Regulation of B lymphocyte differentiation. Ann. Allergy Asthma Immunol., 84, 375–385. Kang, D. H., and Fox, C. (2001). Th1 and Th2 cytokine responses to academic stress. Res. Nurs. Health, 24, 245–257. Kapp, A. (1993). The role of eosinophils in the pathogenesis of atopic dermatitis-eosinophil granule proteins as markers of disease activity. Allergy, 48, 1–5. Katoh, N., Hirano, S., Suehiro, M., Masuda, K., and Kishimoto, S. (2004). The characteristics of patients with atopic dermatitis demonstrating a positive reaction in a scratch test after 48 hours against house dust mite antigen. J. Dermatol., 31, 720–726. King, R. M., and Wilson, G. V. (1991). Use of a diary technique to investigate psychosomatic relations in atopic dermatitis. J. Psychosom. Res., 35, 697–706. Kirschbaum, C., Pirke, K. M., and Hellhammer, D. H. (1993). The “Trier Social Stress Test”: a tool for investigating psychobiological stress responses in a laboratory setting. Neuropsychobiol., 28, 76–81. Kodama, A., Horikawa, T., Suzuki, T., Ajiki, W., Takashima, T., Harada, S., and Ichihashi, M. (1999). Effect of stress on atopic dermatitis: investigation in patients after the great Hanshin earthquake. J. Allergy Clin. Immunol., 104, 173–176. Laue, L., Lotze, M. T., Chrousos, G. P., Barnes, K., Loriaux, D. L., and Fleisher, T. A. (1990). Effect of chronic treatment with the glucocorticoid antagonist RU 486 in man: toxicity, immunological and hormonal aspects. J. Clin. Endocrinol. Metab., 71, 1474–1480. Legat, F. J., Armstrong, C. A., and Ansel, J. C. (2002). The cutaneous neurosensory system in skin disease. Adv. Dermatol., 18, 91–109. Leung, D. Y., Boguniewicz, M., Howell, M. D., Nomura, I., and Hamid, Q. A. (2004). New insights into atopic dermatitis. J. Clin. Invest., 113, 651–657. Leung, D. Y. M., Harbeck, R., Bina, P., Reiser R. F., Yang, E., Noris, D. A., Hanifin, J. M., and Sampson, H. A. (1993). Presence of IgE antibodies to staphylococcal exotoxins on the skin of patients
990
V. Psychoneuroimmunology and Pathophysiology
with atopic dermatitis: evidence for a new group of allergens. J. Clin. Invest., 92, 1374–1380. Leung, D. Y. M., and Soter, N. A. (2001). Cellular and immunologic mechanisms in atopic dermatitis. J. Am. Acad. Dermatol., 44, S1–S12. Maddox, L., and Schwarz, D. A. (2002). The pathophysiology of asthma. Ann. Rev. Med., 53, 477–498. Mastorakos, G., Chrousos, G. P., and Weber, J. S. (1993). Recombinant interleukin-6 activates the hypothalamus-pituitary-adrenal axis in humans. J. Clin. Endocrinol. Metab., 77, 1690–1694. Meagher, L. C., Cousin, J. M., Seckl, J. R., and Haslett, C. (1996). Opposing effects of glucocorticoids on the rate of apoptosis in neutrophilic and eosinophilic granulocytes. J. Immunol., 156, 4422–4428. Mortz, C. G., Lauritsen, J. M., Bindslev-Jensen, C., and Andersen, K. E. (2001). Prevalence of atopic dermatitis, asthma, allergic rhinitis, and hand and contact dermatitis in adolescents. The Odense Adolescence Cohort Study on Atopic Diseases and Dermatitis. Br. J. Dermatol., 144, 523–532. Mudde, G. C., van Reijsen, F. C., Boland, G. J., De Gast, G. C., Ruijnzeel, P. L. B., and Bruijnzeel, C. A. F. M. (1990). Allergen presentation by Langerhans cells from patients with atopic dermatitis is mediated by IgE. Immunol., 69, 335–341. Murison, R., and Milde, A. M. (1999). Long-term effects of two animal stress procedures on corticosterone: models for PTSD. Int. Soc. Psychoneuroendocrinol. (Abstract). Niemeier, V., Gieler, U., Baerwald, C., Kupfer, J., Schill, W. B., and Happle, R. (1996). Decreased density of β-adrenergic receptors on peripheral blood mononuclear cells in patients with atopic dermatitis. Eur. J. Dermatol., 6, 377–380. Nimmagadda, S. R., and Evans, R. (1999). Allergy. Etiology and epidemiology. Ped. Rev., 20, 111–115. Paik, I. H., Toh, K. Y., Lee, C., Kim, J. J., and Lee, S. J. (2000). Psychological stress may induce increased humoral and decreased cellular immunity. Behav. Med., 26, 139–141. Panconesi, E. (2000). Psychosomatic dermatology: past and future. Int. J. Dermatol., 39, 732–734. Panconesi, E., and Hautmann, G. (1996). Psychophysiology of stress in dermatology. Dermatol. Clin., 14, 399–421. Pauli-Pott, U., Darui, A., and Beckmann, D. (1999). Infants with atopic dermatitis: maternal hopelessness, child-rearing attitudes and perceived infant temperament. Pychother. Psychosom., 68, 39–45. Picardi, A., and Abeni, D. (2001). Stressful live events and skin diseases: disentangling evidence from myth. Psychother. Psychosom., 70, 118–136. Piemonti, L., Monti, P., Allavena, P., Sironi, M., Soldini, L., Leone, B. E., Socci, C., and Di Carlo, V. (1999). Glucocorticoids affect human dendritic cell differentiation and maturation. J. Immunol., 162, 6473–6481. Raap, U., and Kapp, A. (2005). Neuroimmunological findings in allergic skin disease. Curr. Opin. Allergy Clin. Immunol., 5, 419–424. Ray, A., Hemady, Z., and Rocklin, R. E. (1987). Glucocorticoidinduced enhancement of IgE-synthesis. Allergy Proc., 8, 81– 84. Roll, A., Cozzio, A., Fischer, B., and Schmid-Grendelmeier, P. (2004). Microbial colonization and atopic dermatitis. Curr. Opin. Allergy Clin. Immunol., 4, 373–378. Romagnani, S. (2000). T-cell subsets (TH1 versus TH2). Ann. Allergy Asthma Immunol., 85, 9–21. Ruiz, R. G. G., Kemeny, D. M., and Price, J. F. (1992). Higher risk of infantile atopic dermatitis from maternal atopy than from paternal atopy. Clin. Exp. Allergy, 22, 762–766.
Rupprecht, M., Hornstein, O. P., Schlüter, D., Schafers, H. J., Koch, H. U., Beck, G., Rupprecht, R. (1995). Cortisol, corticotropin, and beta-endorphin responses to corticotropin-releasing hormone in patients with atopic eczema. Psychoneuroendocrinol. 20, 543–551. Rupprecht, M., Rupprecht, R., Kornhuber, J., Wodarz, N., Koch, H. U., Riederer, P., and Hornstein, O. P. (1991). Elevated glucocorticoid receptor concentrations before and after glucocorticoid therapy in peripheral mononuclear leukocytes of patients with atopic dermatitis. Dermatol., 183, 100–105. Safko, M. J., Chan, S. C., Cooper, K. D., and Hanifin, J. M. (1981). Heterologous desensitization of leukocytes: a possible mechanism of beta adrenergic blockade in atopic dermatis. J. Allergy Clin. Immuno., 68, 218–225. Salpietro, D. C., Naccari, F., Polimeni, I., and Pellegrino, C. (1998). Reduced plasma c-AMP levels in children with atopic dermatitis. Pediatr. Allergy Immunol., 9, 130–132. Sanders, V. M. (1995). The role of adrenoceptor-mediated signals in the modulation of lymphocyte function. Adv. Neuroimmunol., 5, 283–298. Scheich, G., Florin, I., Rudolph, R., and Wilhelm, S. (1993). Personality characteristics and serum IgE levels in patients with atopic dermatitis. J. Psychosom. Res., 37, 637–642. Schleimer, R. P. (2000). Interactions between the hypothalamicpituitary-adrenal axis and allergic inflammation. J. Allergy Clin. Immunol., 106, S270–S274. Schmid-Ott, G., Jaeger, B., Adamek, C., Koch, H., Lamprecht, F., Kapp, A., and Werfel, T. (2001a). Levels of circulating CD8+ cells, and eosinophils increase upon acute psychosocial stress in patients with atopic dermatitis. J. Allergy Clin. Immunol., 107, 171–177. Schmid-Ott, G., Jaeger, B., Meyer, S., Stephan, E., Kapp, A., and Werfel, T. (2001b). Different expression of cytokine and membrane molecules by circulating lymphocytes on mental stress in patients with atopic dermatitis in comparison with healthy controls. J. Allergy Clin. Immunol., 108, 455–462. Shenefelt, P. D. (2003). Biofeedback, cognitive-behavioral methods, and hypnosis in dermatology: is it all in your mind? Dermatol. Ther., 16, 114–122. Stangier, U., Ehlers, A., and Gieler, U. (2004). Predicting long-term outcome in group treatment of atopic dermatitis. Psychother. Psychosom., 73, 293–301. Stephan, M., Jaeger, B., Lamprecht, F., Kapp, A., Werfel, T., and Schmid-Ott, G. (2004). Alteration of stress-induced expression of membrane molecules and intracellular cytokine levels in patients with atopic dermatitis depend on serum IgE levels. J. Allergy Clin. Immunol., 114, 977–978. Sternberg, E. M., Hill, J. M., Chrousos, G. P., Kamilaris, T., Listwak, S. J., Gold, P. W., and Wilder, R. L. (1989). Inflammatory mediator-induced hypothalamic-pituitary-adrenal axis activation is defective in streptococcal cell wall arthritis-susceptible Lewis rats. Proc. Natl. Acad. Sci. USA, 86, 2374–2378. Sternberg, E. M., Young, W. S., Bernardini, R., Calogero, A. E., Chrousos, G. P., Gold, P. W., and Wilder, R. L. (1989). A central nervous system defect in biosynthesis of corticotropin releasing hormone is associated with susceptibility to streptococcal cell wall-induced arthritis in Lewis rats. Proc. Natl. Acad. Sci., 86, 4771–4775. Stewart, A. C., and Thomas, S. E. (1995). Hypnotherapy as a treatment for atopic dermatitis in adults and children. Br. J. Dermatol., 132, 778–783. Sturgill, S., and Bernard, L. A. (2004). Atopic dermatitis update. Curr. Opin. Pediatr., 16, 396–401. Szentivanyi, A. (1968). The beta adrenergic theory of the atopic abnormality in bronchial asthma, J. Allergy, 42, 203–210.
45. Endocrine and Immune Responses to Stress in Chronic Inflammatory Skin Disorder Thepen, T., Langeveld-Wildschut, G., Bihari, I. C., van Wichen, D. F., van Reijsen, F. C., Mudde, G. C., and Bruijnzeel-Koomen, C. A. F. M. (1996). Biphasic response against aeroallergen in atopic dermatitis showing a switch from an initial TH2 response to a TH1 response in situ: an immunocytochemical study. J. Allergy Clin. Immunol., 97, 828–837. Trautmann, A., Akdis, M., Blaser, K., and Akdis, C. A. (2000). Role of dysregulated apoptosis in atopic dermatitis. Apoptosis, 5, 425–429. Turnbull, A. V., and Rivier, C. L. (1999). Regulation of the hypothalamus-pituitary-adrenal axis by cytokines: actions and mechanisms of action. Physiol. Rev., 79, 1–71. Van Moerbeke, D. (1997). European white paper. Allergic diseases as a public health problem in Europe. Brussels: UCB Institute of Allergy. Van Reijsen, F. C., Bruijnzeel-Koomen, C. A., Kalthoff, F. S., Maggi, E., Romagnani, S., Westland, J. K., and Mudde, G. C. (1992). Skinderived aeroallergen-specific T-cell clones of Th2 phenotype in patients with atopic dermatitis. J. Allergy Clin. Immunol. 90, 184–193. Verboom, P., Hekkart Van, L., Sturkenboom, M., De Zeeuw, R., Menke, H., and Rutten, F. (2002). The costs of atopic dermatitis in the Netherlands: an international comparison. Br. J. Dermatol., 147, 716–724. Wallander, J. L., and Varui, J. W. (1998). Effects of pediatric chronic physical disorders on child and family adjustment. J. Child Psychol. Psychiatry, 39, 29–46.
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Wamboldt, M. Z., Laudenslager, M., Wamboldt, F. S., Kelsay, K., and Hewitt, J. (2003). Adolescents with atopic disorders have an attenuated cortisol response to laboratory stress. J. Allergy Clin. Immunol., 111, 509–514. Weiland, S. K., Husing, A., Strachan, D. P., Rzehak, P., and Pearce, N. (2004). ISAAC Phase One Study Group. Climate and the prevalence of symptoms of asthma, allergic rhinitis, and atopic eczema in children. Occup. Environ. Med., 61, 609–615. Weinmann, S., Kamtsirius, P., Henke, K. D., Wickman, M., Jenner, A., and Wahn, U. (2003). The costs of atopy and asthma in children: assessment of direct costs and their determinants in a birth cohort. Pediatr. Allergy Immunol., 14, 18–26. Wilson, E. (1857). Diseases of the skin. London: Churchill. Wittkowski, A., Richards, H. L., Griffith, C. E., and Main, C. J. (2004). The impact of psychological and clinical factors on quality of life in individuals with atopic dermatitis. J. Psychosom. Res., 57, 195–200. Wollenberg, A., Kraft, S., Hanau, D., and Bieber, T. (1996). Immunomorphological and ultrastructural characterization of Langerhans cells and a novel, inflammatory dendritic epidermal cell (IDEC) population in lesional skin of atopic eczema. J. Invest. Dermatol., 106, 446–453.
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C H A P T E R
46 Obesity and Immunity CHRISTOPHER B. GUEST, YAN GAO, JASON C. O’CONNOR, AND GREGORY G. FREUND
I. OBESITY AND IMMUNITY 993 II. OBESITY IS CHARACTERIZED BY INFLAMMATION 993 III. OVERNUTRITION AND CHRONIC ACTIVATION OF THE INNATE IMMUNE SYSTEM 998 IV. IMMUNE DISORDERS AND OBESITY 999 V. CONCLUSIONS 1003
quences. In the United States, there are an estimated 60 million obese adults (Flegal et al., 2002) and 300 million worldwide (Cummings and Schwartz, 2003). Obesity is characterized by a ratio greater than 29.9 of body mass in kilograms divided by height in meters squared. Much of this mass is adipose tissue. Recently, our view of adipose tissue as an inert depot for excess energy has shifted. Adipose tissue is now recognized as a dynamic organ with important roles in modulating satiety, reproduction, immunity, and metabolism. Importantly, the obese exhibit increased markers of inflammation including macrophage infiltration (Cancello et al., 2005), C-reactive protein (CRP) (Santos et al., 2005), and tissue factor (TF) (Samad et al., 2001). These markers may shed light on the pathologies associated with obesity. Finally, obesity is associated with a number of serious pathologies including type 2 diabetes, cardiovascular disease, hypertension, stroke (Pischon et al., 2004), sepsis, impaired wound healing, asthma, inflammatory bowel disease, certain forms of cancer, and increased mortality (Tataranni and Ortega, 2005).
I. OBESITY AND IMMUNITY Throughout the course of evolution, organisms have conserved systems that contribute to their survival. Metabolism balances the synthesis and consumption of energy and nutrients. The immune system protects the organism from invading pathogenic microorganisms or intrinsic defects like cancer or senescent cells. The efficiency of evolution is exemplified by the interdependence of these two critical pathways. From the membrane to the nucleus, numerous components critical to the function of metabolism and immunity are shared, including cytokines, hormones, scavenger receptors, enzymes, and transcription factors. A shift in the balance in either metabolism or immunity will set into motion a complex cascade of functions with ramifications that are felt by the entire organism and tightly controlled by the brain. Industrialization has rapidly changed the availability of food and the manner we live our lives. The physically demanding lifestyle of an agrarian society has given way to a largely sedentary one. In much of the world, cheap energy-dense foods have become common, but this availability has had some unintended consePSYCHONEUROIMMUNOLOGY, 4E VOLUME II
II. OBESITY IS CHARACTERIZED BY INFLAMMATION A. Adipocytes and Macrophages—A Link between Immunity and Metabolism One of the obvious characteristics of obesity is adipose tissue. There are two types of adipose tissue: white and brown. Brown adipose tissue is
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predominantly found in rodents and newborns and is important for generating heat. White adipose tissue is the primary storage repository of energy and is the type of adipose tissue reviewed here. In addition, there is another distinction based on the area of deposition, either subcutaneous or visceral. There are a number of differences between subcutaneous and visceral fat (Einstein et al., 2005). In general, visceral fat is more active and contributes more to the pathologies associated with obesity (Smith et al., 2001). With the discovery of the gene-encoding leptin in 1994 by Zhang et al., the role of adipose tissue began to change from one of a passive homogenous storage depot of energy to that of a complex, integrated organ containing several cell types that modulate satiety, reproduction, immunity, and metabolism. To get a better understanding of these differences, we need to take a closer look at the composition of adipose tissue. Adipose tissue is a collection of organized, vascularized, and innervated cells. Two important constituents are the adipocyte and the macrophage. Interestingly, these cells share many characteristics. Macrophages express a number of adipocyte genes including PPARγ (Ricote et al., 1998) and fatty acid binding protein aP2 (Linton and Fazio, 2003; Makowski et al., 2005). Macrophages are also known for their ability to store lipids, as is exemplified by the primary constituent of the atherosclerotic plaque, the foam cell (Li et al., 2002). Adipocytes have been shown to take on a number of macrophage-like characteristics. Hotamisligil showed in 1993 that adipocytes produced tumor necrosis factor-alpha (TNF-α). Adipocytes also displayed macrophage-like capabilities such as phagocytosis and microbicidal activity (Villena et al., 2001). Most surprisingly, preadipocytes can differentiate into macrophage-like cells (Cousin et al., 1999). The important point to be taken from these comparisons is that the former view of adipocytes occupying only the realm of energy storage and macrophages as solely immune cells is one-dimensional. Indeed, these cells are excellent examples of the synchronization between metabolism and immunity. Adipose tissue secretes a number of potent signaling molecules that act locally and systemically, including bioactive lipids, TNF-α, interleukin-6 (IL-6), interleukin-1 beta (IL-1β), leptin, IL-1 receptor antagonist (IL-1Ra), vascular endothelial growth factor (VEGF), and plasminogen activator inhibitor (PAI). The effects elicited by these signaling molecules can be roughly split into two categories: pro-inflammatory or anti-inflammatory. They are important in understanding the link between metabolism and the immune system and differences exhibited by the obesityassociated chronic inflammation.
B. Pro-inflammatory 1. Leptin Part of the elegant interplay between the immune system and metabolism is beginning to emerge with a greater understanding of leptin. Leptin was discovered after a series of studies in cross-circulation. In an example of such a study, the plasma from the hyperleptinemic mice (db/db) was infused into lean wildtype mice and produced profound anorexia leading to starvation and death (Coleman, 1973). Studies like this one led to the eventual cloning of the ob gene (Zhang et al., 1994), which encodes the 167 amino acid–secreted protein called leptin (from the Greek leptos meaning thin) as well as the discovery of the receptor encoding the db gene (Leiter et al., 1980). Zhang solved the crystal structure of leptin to reveal a 16 kDa, four-helix bundle similar to that of the long-chain helical cytokine family containing IL-6 (Zhang et al., 1997). There are six leptin receptors derived from alternative splicing (reviewed by Friedman and Halaas, 1998). The dominant and most well-characterized leptin-signaling cascade is transduced through only one receptor commonly called the “long form.” Leptin mediates most of its effects through Janus kinase-2 and signal transducer and activator of transcription-3 (JAK-2/STAT-3) (Baumann et al., 1996). Interestingly, targeted disruption of STAT-3 in the central nervous system induces a similar phenotype to those with leptin deficiency (Gao et al., 2004). Importantly, leptin has been shown to act through other metabolic/immune pathways, including insulin receptor substrate (IRS), phosphatidylinositide 3-kinase (PI3K), and mitogen-activated protein kinase (MAPK) in peripheral blood mononuclear cells (Martin-Romero and Sanchez-Margalet, 2001). Leptin plays many roles. Most leptin is secreted by adipose tissue, but numerous other tissues and the gut also produce it, including macrophages and the placenta. Leptin is most well known for its metabolic role in regulating satiety and energy stores in the form of fat. It is released by adipocytes when energy levels are high and enters circulation. In blood, leptin is bound to a splice variant of the receptor and crosses the blood-brain barrier in this form. Leptin receptors are richly expressed in the centers of the brain responsible for maintaining energy homeostasis (Friedman and Halaas, 1998), and leptin exerts most of its classical regulatory roles through this system. When energy levels are low, leptin secretion decreases and various orexigenic neuropeptides are released, causing feelings of hunger. It has been speculated that the satietyinducing function of leptin could be blunted in obesity because of permeability issues. As with leptin’s
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structural cousin, IL-6, leptin resistance in the obese may be caused in part by a central deficiency, and not systemic excess. Other contributors of leptin resistance in obesity have been speculated to include IL-1Ra (Somm et al., 2005), TNF-α, and IL-6. A potential link to this resistance can be found when examining insulin resistance, which shares some of the same signaling machinery and is counter-regulated by suppressor of cytokine signaling (Senn et al., 2003). In addition to its role in satiety, leptin also plays a number of roles in metabolism and immunity. Valuable information about these roles has been garnered by investigating phenotypic changes found in transgenic animals lacking either functional leptin or receptors. Mice lacking a functional leptin system display defects in temperature regulation (Trayhurn, 1979), hyperphagia, diabetes, infertility (Coleman, 1978), reduction in peripheral B-cells and CD4 T-cells (Bennett et al., 1996), and macrophage expansion (Gainsford et al., 1996). Interestingly, macrophages from leptindeficient mice display enhanced and diminished particle uptake, depending on the particle. Macrophages from leptin-deficient mice have increased uptake of lipids like modified LDL (Liang et al., 2004), while leptin-deficient macrophages display defective phagocytosis of bacteria (Mancuso et al., 2002). Leptin may also directly modulate genes important for regulating fatty acid oxidation, adipogenesis (Wang et al., 2005b), and fertility (de Luca et al., 2005). Leptin is a molecule with a myriad of functions necessary for maintaining homeostasis of energy and balancing immune function. Leptin resistance is a common characteristic of obesity, and it has profound effects on energy balance and immunity and will no doubt contribute more to our understanding of their interplay. 2. TNF-a Carswell et al. first identified TNF-α as a “serum factor that causes necrosis of tumors” (Carswell et al., 1975). TNF-α is synthesized as a 27 kDa protein that is cleaved to the 17 kDa biologically active form. It acts through two receptors, which can be membrane bound or soluble, to exert many functions in both metabolism and immunity, including activating the release of acute phase proteins (Gresser et al., 1987), activating dendritic cell migration to lymph nodes (Cumberbatch and Kimber, 1995), and decreasing social exploration (Bluthe et al., 1994). Torti was among the first to describe the interaction between TNF-α produced by macrophages and adipocytes. The administration of TNF-α inhibited the activity of fat-producing (lipogenic) enzymes in cultured adipocytes (Torti et al., 1985). This report illustrated a mechanism by which
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the macrophage can express a powerful influence on energy homeostasis and was the beginning of the cytokine era. TNF-α was found to reduce peripheral glucose disposal and hepatic glucose output (Lang et al., 1992). This meshed with Hotamisligil’s finding that adipose tissue expressed TNF-α and that TNF-α inhibited insulin signaling (Hotamisligil et al., 1993; Hotamisligil et al., 1994; Hotamisligil et al., 1995). Notably, adipose tissue concentrations of TNF-α are increased in the obese. In addition, mice with targeted mutations in either TNF-α or its receptors had lower levels of circulating free fatty acids and were protected from the obesity-related reduction in insulin receptor signaling in muscle and fat tissues (Uysal et al., 1997). TNF-α has been shown to significantly downregulate a number of genes involved in lipid metabolism, including hormone sensitive lipase; long-chain fatty acyl-CoA synthase; adipocyte complement-related protein of 30 kDa; and transcription factors CCAAT/enhancer-binding protein-alpha, receptor retinoid X receptor-alpha, and peroxisome proliferator-activated receptor gamma (PPAR-γ) (Ruan et al., 2002). The intriguing effects of TNF-α and its early discovery have made it the most thoroughly researched cytokine. 3. IL-6 IL-6 is part of the pro-inflammatory trinity consisting of TNF-α, IL-6, and IL-1β. It is an extensively glycosylated protein of approximately 27-kDa playing a crucial role in initiating the acute phase response of the liver by strongly inducing protein synthesis of serum amyloid A, C-reactive protein, haptoglobin, alpha 1antichymotrypsin, and fibrinogen (Castell et al., 1988). IL-6 released at the periphery and/or in the central nervous system impacts the behavioral response to LPS and IL-1 (Bluthe et al., 2000) and induces fever following intracerebroventricular administration (Lenczowski et al., 1999). IL-6 is secreted by adipose tissue, and adipose tissue expresses receptors for IL-6. IL-6 secretion in adipose tissue and plasma is increased in obesity and has autocrine and endocrine roles (Fain et al., 2004). The role of IL-6 in obesity is multi-faceted, as indicated by transgenic animal models that either overexpress IL-6 or express none at all. Interestingly, overexpression of IL-6 induced a general growth defect in mice that was mediated through a reduction in IGF1. The decrease in IGF-1 was mimicked by chronic administration of IL-6 to non-transgenic mice and partially blocked by anti–IL-6 receptor antibodies (De Benedetti et al., 1997). IL-6 has been shown to induce hypertriglyceridemia (Nonogaki et al., 1996) and insulin resistance via STAT-3 (Senn et al., 2003). Cai recently showed that insulin resistance caused by
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chronic low-level inflammation induced by overactivation of NFκB could be improved by systemic neutralization of IL-6 (Cai et al., 2005). Rotter Sopasokis showed that the acute effects of IL-6, associated with STAT-3 induction, do not lead to whole-body insulin resistance and underscore the importance of the tissuespecific effects of IL-6 on insulin signaling and action (Rotter Sopasakis et al., 2004). IL-6 has also been found to decrease adiponectin levels (Fernandez-Real et al., 2003; Keller et al., 2003). With these mechanistic correlations between IL-6 and obesity, one would imagine that part of the pathological complications of obesity would be obviated by neutralizing IL-6. IL-6 knockout mice have provided some interesting insights into the multi-functional role of IL-6. Surprisingly, IL-6– deficient mice developed mature-onset diabetes characterized by glucose intolerance, hyperleptinemia, leptin resistance, and an increase in fat pad mass of 50–60%. Wallenius speculates that IL-6 acts upon the central nervous system to increase energy expenditure and decrease food intake and thereby decrease the deleterious effects seen in the IL-6 knockout animals. Indeed, this view was supported by an 18-day treatment with IL-6 in the knockout animals that significantly reduced bodyweight but had no effect on the body weight of wild-type animals (Wallenius et al., 2002). 4. IL-1b Interleukin-1β is a 17.4-kDa protein derived from a 33-kilodalton inactive precursor (Black et al., 1989). It is cleaved to the active form by interleukin-1β– converting enzyme, first cloned by Cerretti et al. (1992). IL-1β has two receptor types. One receptor is capable of activating NFκB through the MyD88 pathway, and the other receptor is a decoy that acts as a competitive inhibitor. IL-1β is produced by a handful of tissues, including macrophages, adipose, and neurons. Importantly, counter-regulation of IL-1β is altered in obesity (O’Connor et al., 2005). IL-1β is known to induce sickness behavior, fever, and the production of other cytokines (Bluthe et al., 2000). IL-1β has been found to have powerful effects on both the immune system and
TABLE 1
metabolism. Like TNF-α and IL-6, it has been found to induce anorexia when administered intracerebroventricularly or peripherally, though at a much higher dose (Plata-Salaman, 1994; Plata-Salaman and Ilyin, 1997). Although it is primarily produced by macrophages, IL-1β and its receptors are expressed throughout the nervous system, including the energy regulatory centers of the hypothalamus. Vagotomy blocks the induction of IL-1β mRNA in the brain of rats in response to systemic IL-1β, indicating an important point of cross-regulation between metabolism and immunity mediated by the vagus nerve (Hansen et al., 1998). Our lab has further shown the relevance of this link by finding that inhibition of vagally mediated immune-to-brain signaling by vanadyl sulfate speeds recovery from sickness (Johnson et al., 2005) and that IL-1β–mediated innate immunity is amplified in the db/db mouse model of type 2 diabetes (O’Connor et al., 2005). Significantly, IL-1β has been found to induce pancreatic beta cell apoptosis (Bendtzen et al., 1986; Papaccio et al., 2002). This suggests that IL-1β acts as a potential cause of the eventual loss of beta cell mass that is found when insulin resistance finally gives way to frank diabetes and profound dysregulation of glucose metabolism. 5. IL-18 Interestingly, another pro-inflammatory cytokine is activated by interleukin-1β–converting enzyme. Interleukin 18 is synthesized as a 24 kDa protein and is cleaved to a biologically active 18 kDa form. IL-18 secretion is increased in obesity. It is expressed in adipose tissue and strongly upregulated by TNF-α in human adipocytes (Wood et al., 2005). It is also associated with insulin resistance (Fischer et al., 2005), cardiovascular disease (Blankenberg et al., 2002), and numerous other inflammatory pathologies (Skurk et al., 2005). 6. Others Many other markers of inflammation are increased in obesity. An incomplete list can be found in Table 1.
Markers of Inflammation in Obesity
Leptin
TNF-a
IL-6
IL-1b
IL-18
IL-8
IL-1Ra
Resistin
C-reactive protein
Tissue factor
MCP-1
M-CSF
MIF
Vascular endothelial growth factor
TGF-β
Plasminogen activator inhibitor Soluble TNFR
Visfatin
IL-4
IL-10
Adiponectin
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C. Anti-inflammatory 1. IL-1Ra The counter-regulation of IL-1β is important for modulating its action, and defects in this modulation are found in pathological states like diabetes and obesity. An important mode of regulation is through IL-1Ra (Arend, 2002). IL-1Ra levels are highly elevated in human obesity, indicating an attempt to offset chronic inflammatory signals (Meier et al., 2002). Since IL-1Ra is tightly correlated to insulin and leptin sensitivity, it is speculated to play a causal role in insulin and leptin resistance (Somm et al., 2005). Notably, the secretion of IL-1Ra has been found to be directly stimulated by leptin (Gabay et al., 2001), and the mechanism was refined by the finding that leptin directly induced the secretion of IL-1Ra in human monocytes (Dreyer et al., 2003), providing another link between immunity and metabolism. Transgenic, IL-1 Ra deficient mice had a lean phenotype with decreased adipogenesis and food intake and increased energy expenditure. 2. Adiponectin Adiponectin is a 30 kDa protein produced by mature adipocytes and macrophages. It has a complex structure with a collagen-like domain and globular domain. In addition to this unmodified form, adiponectin circulates in complexes consisting of multiple trimers with unique properties (Pajvani et al., 2003) and a truncated version containing the globular form. A number of studies have shown an inverse correlation between adiponectin and the comorbidities of obesity. Adiponectin is critical in sustaining insulin sensitivity in obese subjects (Kantartzis et al., 2005). It is inversely correlated with cardiovascular disease (Hotta et al., 2000). It has been shown to inhibit the production of inflammatory cytokines (Yokota et al., 2000) and decrease hyperlipidemia (Xu et al., 2004). In fact, mice with a targeted deletion of adiponectin display many of the same phenotypic characteristics of leptindeficient mice, including defective insulin signaling and hyperglycemia (Nawrocki et al., 2005). Surprisingly, the globular form has structural similarity to TNF-α and elicits the production of inflammatory cytokines from macrophages. This somewhat paradoxical relationship is speculated to be important to the attenuation and counter-regulation of inflammatory signals (Tsatsanis et al., 2005). Adiponectin is a fast-expanding area of research, with the number of publications referring to it nearly doubling each year for the last 3 years. It is likely that other important findings relating immunity and metabolism will involve adiponectin.
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3. IL-4 IL-4 is a potent anti-inflammatory cytokine that drives macrophages toward an “alternative activation phenotype.” An absence of nitric oxide production and generation of IL-10 and IL-1Ra (Mosser, 2003) characterize this IL-4–dependent macrophage activation. Additionally, IL-4 inhibits the release of the proinflammatory cytokines IL-1β, TNF-α, and IL-6 from macrophages (McBride et al., 1990; Mijatovic et al., 1997; Opal and DePalo, 2000). This inhibitory effect appears to be part of a shift from Th1 immunity to Th2 immunity during the course of an inflammatory response (Tracey, 2002). Further, efferent nervous signals stimulated by pro-inflammatory cytokines in the brain act as counter-regulatory stimuli to initiate this shift in inflammatory status (Bernik et al., 2002; Borovikova et al., 2000; Tracey, 2002). The participation of β-adrenoceptors in modulating cytokine production is consistent with their direct effect on increasing the cAMP-level in the cell (Elenkov et al., 1995; Hu et al., 1991; Severn et al., 1992; Szabo et al., 1997; van der Poll et al., 1994), resulting in the suppression of LPS-induced TNF-α production. Although the ligand binding of both β1- and β2-adrenoceptors results in the increased level of cAMP, they display distinct mechanisms of action in the signaling system by which they stimulate cAMP production in the brain (Morin et al., 2000). Activation of β-adrenoceptors suppresses the production of inflammatory cytokines and increases the level of the anti-inflammatory cytokines. Accumulation of cAMP was shown to reduce the synthesis of TNF-α (Elenkov et al., 1995; Katakami et al., 1988; Renz et al., 1988), IL-2 (Novogrodsky et al., 1983), IFN-α (Ivashkiv et al., 1994), and IL-12 (Hasko et al., 1998; van der Pouw Kraan et al., 1995), while stimulating IL-4 (Lacour et al., 1994), IL-5 (Siegel et al., 1995), and IL-10 (Platzer et al., 1995; Szabo et al., 1997). Thus, activation of neurotransmitter receptors that induce adenylate-cyclase leads to a shift toward an “anti-inflammatory” Th2 immunophenotype, whereas downregulation of intracellular cAMP stimulates a T helper 1 (Th1)-type response, resulting in an inflammatory/cell destructive phenotype. The significance of these findings is that they reveal the complex mechanism by which differently localized adrenoceptors may control the course of immune response through the regulation of Th1/Th2 balance. The IL-4 receptor (IL-4R) is expressed ubiquitously on myeloid cells (Ohara and Paul, 1987; Wagteveld et al., 1991), and it lacks intrinsic kinase activity, requiring receptor-associated kinases for initiation of intracellular signaling (Kirken et al., 1994; Yin et al., 1994). The IL-4R complex consists of a 140 kDa α-chain and
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the gamma common (γc) chain of the IL-2 receptor (Nelms et al., 1999). Upon binding of IL-4, heterodimerization of the IL-4Rα and the γc chain occurs, resulting in transphosphorylation of JAK1 and JAK3 (Jiang et al., 2000) and activation of downstream signaling cascades (Kammer et al., 1996). The IL-4 system initiates the JAK-STAT pathway to induce signaling. Following receptor phosphorylation by JAK1 and JAK3, STAT6 associates with the IL-4R and is phosphorylated at a C-terminal tyrosine residue (Darnell, 1997; Mikita et al., 1996). This results in homodimerization of phosphorylated STAT6 molecules, translocation to the nucleus, and activation of gene transcription. One or both of the receptor-associated JAKs phosphorylate the IL-4α chain on residue Tyr497, which is within the insulin/IL-4 receptor motif responsible for IRS-2 recruitment (Nelms et al., 1999). JAK phosphorylation of IRS leads to activation of the IRS/ PI3-kinase system. IL-4 is produced by adipose tissue, T-cells, and macrophages. IL-4 secretion is increased in obesity (Hotta et al., 2000). Importantly, our lab has shown that obese mice display IL-4 resistance (Hartman et al., 2004). This is consistent with other findings indicating that obesity is associated with IRS-dependent cytokine resistance (Cengel and Freund, 1999). Thus, cytokine resistance may be an important defect in the regulation of inflammation and a potential pharmacological target for therapeutic intervention.
III. OVERNUTRITION AND CHRONIC ACTIVATION OF THE INNATE IMMUNE SYSTEM A. Reactive Oxygen Species A number of interesting findings on calorie restriction, longevity, and reactive oxygen species (ROS) have been published in the last 60 years and have recently been reviewed by Gredilla and Barja (2005). These findings indicate that damaging ROS are produced by normal flux through the mitochondrial respiratory chain. Recently, a unifying mechanism has emerged regarding overnutrition and chronic inflammation. This system revolves around the central theory that excessive nutrients such as glucose and fat cause increased flux through the mitochondrial electron transport chain and increase the production of ROS (Du et al., 2000; Nishikawa et al., 2000; Yang et al., 2000). The increase in ROS, in turn, leads to activation of the innate immune system and chronic inflammation, creating a feed-forward loop. Inhibition of ROS production has been shown to greatly diminish many
of the pathological changes found in models of obesity (Furukawa et al., 2004b). Four essential conduits implicated in the complications of obesity and diabetes include the polyol, advanced glycation end product (AGE), protein kinase C (PKC), and hexosamine (Brownlee, 2005) pathways. 1. Polyol Pathway One pathway linking oxidative stress induced by excess nutrients is the polyol pathway. In brief, in certain tissues, at high concentrations, glucose is reduced by aldose reductase to sorbitol. NADPH is an essential co-factor for this reaction as well as for the reaction that replenishes reduced glutathione. Since reduced glutathione is an important antioxidant, the oxidative stress within the cell is increased and, in turn, increases activation of the innate immune system (Lee and Chung, 1999). 2. Advanced Glycation End Products AGEs are formed by a several mechanisms including non-enzymatic addition of glucose molecules to native proteins. AGEs are speculated to damage cells by a number of mechanisms, including the modification of proteins involved in gene regulation (Giardino et al., 1994; Mercer et al., 2004) and activation of the receptor of advanced glycation end products (RAGE). Activation of RAGE causes the release of inflammatory cytokines and has been associated with a number of morbidities, including diabetes and cardiovascular disease (Schmidt et al., 1996; Takeda et al., 2005). 3. Protein Kinase C Another pathway linking nutrient abundance and immunity is the protein kinase C (PKC) pathway and its downstream targets JNK and IKK. PKC has several isoforms and has many tasks in metabolism and immunity, including the regulation of lipid uptake (Kruth et al., 2005), cellular growth and proliferation (Liu et al., 1998; Sugimoto et al., 2005), ROS production (Quagliaro et al., 2005), and activation of transcription factors associated with inflammation (Inoguchi et al., 2003). Some of the classical isoforms of PKC are activated by diacylglycerol (DAG). Endogenous DAG levels are increased by overnutrition by the shunting of excess glycolytic substrates to create dihydroxyacetone phosphate (DHAP), a precursor of DAG (Rossi et al., 1991). In addition, bioactive lipids that act as agonists for PKCs may be directly involved in activation of the innate immune system (Roche et al., 1999). Atypical PKCs also present an interesting point of regulation. PKC-ζ is not stimulated by DAG but is
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stimulated directly by insulin (Liu et al., 2001) and transduces its signal through PI3K (Hirai and Chida, 2003). Importantly, this pathway is still active in diabetes and may play a critical part in lipid-induced insulin resistance (Farese et al., 2005; Standaert et al., 2004). 4. Hexosamine Increased flux through glycolysis once again leads to the shuttling of substrates into alternative pathways. A product of the hexosamine pathway is N-acetyl glucosamine. This molecule is added to proteins and affects their activity, much in the same manner as phosphorylation. Interestingly, this process has been shown to induce the expression of factors that contribute to cardiovascular disease, including PAI and TGFβ (Du et al., 2000). TGF-β has been shown to stimulate further production of ROS and PAI, further compounding this cycle (Lee et al., 2005).
B. Other Pathways 1. Endoplasmic Reticulum Stress Another intriguing pathway involved in metabolism, immunity, and chronic inflammation is the endoplasmic reticulum (ER) stress pathway. When there is an abundance of nutrients, this pathway is activated and triggers the activation of a number of downstream responses, including activation of c-Jun-NH2-terminal kinase (JNK) and NFκB (Liu and Rondinone, 2005). The ER stress system has been found to be highly activated in models of obesity (Ozcan et al., 2004; Wang et al., 2005a). Furthermore, overactivation of this system can induce diabetes (Oyadomari et al., 2002). An excellent review of this pathway and its link to obesity and immunity was recently done by Hotamisligil, and exciting findings based on this new paradigm are sure to follow (Hotamisligil, 2005). 2. Peroxisome Proliferator-activated Receptor One of the most promising classes of anti-diabetic drugs is the peroxisome proliferator-activated receptor (PPAR) agonist. There are many subcategories, but the two most well studied are the fibrates (PPAR-α) and the thiazolidinediones (PPAR-γ). Briefly, both classes have been shown to improve the symptoms of obesity and diabetes. Fibrates improve lipid profiles, and thiazolidinediones have been shown to decrease blood glucose and decrease inflammation. Recently, they have been shown to synergize to improve obesityinduced insulin resistance (Tsuchida et al., 2005). Lately, the scavenger receptor, CD36, has been
identified as a co-stimulatory molecule for Toll-likereceptors (TLR) responsible for sensing DAG and lipotechoic acid (LTA) (Hoebe et al., 2005). Liang showed that CD36 is upregulated in insulin resistance (Liang et al., 2004). Interestingly, PPAR-γ was found to be required for basal expression of CD36 (Moore et al., 2001). This provides yet another area of overlap between the immune system and metabolism that has the potential for further important discoveries. Scavenger receptors may be regulated by metabolic factors and be linked to the TLR signaling (Platt et al., 2002).
IV. IMMUNE DISORDERS AND OBESITY Thus far, we have detailed some of the global differences that exist in obesity, the key molecules and pathways, and how they lead to chronic inflammation. Now we will focus specifically on immune disorders that are associated with obesity, with attention to proposed mechanisms of dysregulation between immunity and metabolism.
A. Type 2 Diabetes The number of people affected by this disease is estimated to be more than 150 million worldwide and quickly rising (Matthaei et al., 2000). The increase in people with type 2 diabetes is coincident with the obesity epidemic. It has long been suggested that there is a link between obesity and insulin resistance. Several adipokines and cytokines produced by white adipose tissue have been shown to alter insulin sensitivity and glucose metabolism. TNF-α interferes with insulin signaling by directly decreasing the insulin-stimulated autophosphorylation of the insulin receptor (IR) and thereby leading to a dramatic decrease in the phosphorylation of IR substrate 1 (IRS-1) (Hotamisligil et al., 1994). TNF-α can also induce insulin resistance through serine phosphorylation of IRS-1. Serine phosphorylated IRS-1 acts as an inhibitor of IR tyrosine kinase activity, blocking insulin signaling (Hotamisligil et al., 1996). Adipose fatty acid binding protein (FABP)–deficient mice do not express TNF-α and may be a key to uncoupling obesity and inflammation (Hotamisligil et al., 1996). A different mechanism linking inflammatory pathways and insulin resistance emerged when IRS-1 was found to be a direct substrate of IKK. Phosphorylation of IRS-1 by IKK at Ser(312) and other sites augments insulin resistance (Gao et al., 2002). The expression of a TNF-α target gene, SOCS-3, is elevated during obesity (Emanuelli et al., 2001). The increase in SOCS-3 leads to insulin resistance by antagonizing IRS-1 tyrosine phosphorylation (Emanuelli et al., 2001). Findings
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demonstrate that the upstream activator of NFκB, IKKβ, is activated in obesity and leads to liver and myeloid cell insulin resistance (Arkan et al., 2005). Obesity also causes increased hepatic production of NFκB and proinflammatory cytokines, including IL-6, IL-1β, and TNF-α. Fat accumulation in the liver creates subacute hepatic inflammation that could lead to insulin resistance both locally in the liver and systemically (Cai et al., 2005). In obese diabetic db/db mice, IL-1Ra and type 2 IL-1 receptor expression fail to increase in response to LPS, leading to amplified inflammation (O’Connor et al., 2005). Obesity leads to lowered adiponectin, and low adiponectin levels have been associated with insulin resistance and type 2 diabetes. Low plasma adiponectin concentrations precede a decrease in insulin sensitivity and predict type 2 diabetes (Hotta et al., 2000; Spranger et al., 2003). In cross-sectional analyses, the association between plasma adiponectin and insulin sensitivity, adjusted for age, gender, and PFAT, depended on whether subjects were lean or obese (Kantartzis et al., 2005). The diabetic medication class, thiazolidinediones (TZDs), increases adiponectin level and slightly reduces blood pressure (Bailey, 2005). In Pima Indians, individuals with high concentrations of adiponectin are less likely to develop type 2 diabetes later in life (Lindsay et al., 2002). Similar studies conducted among Asian Indians and Japanese have shown that a low concentration of plasma adiponectin is a predictor for development of type 2 diabetes (Daimon et al., 2003; Snehalatha et al., 2003). Adiponectin seems to have autocrine action on human fat cells and prevents the release of insulin resistance-inducing factors. Impaired insulin signaling is normalized upon addition of globular domain of adiponectin to a co-culture of human skeletal muscle cells and human fat cells (Dietze-Schroeder et al., 2005). Polymorphisms in the gene-encoding adiponectin receptor 1 are associated with lower insulin sensitivity, higher HbA(1)c levels, and higher liver fat (Stefan et al., 2005). There is an inverse association between adiponectin and inflammatory markers such as TNF-α, IL-6, and C-reactive protein (Engeli et al., 2003; Kern et al., 2003). Adiponectin/ACRP30-knockout (KO) mice have delayed clearance of free fatty acid in plasma, low levels of fatty-acid transport protein 1 (FATP-1) mRNA in muscle, high levels of TNF-α mRNA in adipose tissue, and high plasma TNF-α concentrations (Maeda et al., 2002). The KO mice exhibit severe diet-induced insulin resistance with reduced IRS-1– associated PI3K activity in muscle (Maeda et al., 2002). Adiponectin is currently under intensive research to learn how this adipose-derived protein affects insulin sensitivity. As more data are generated, the exact role
of adiponectin would become clearer, but mixed results are reported from clinical trials to increase adiponectin level through diet and exercise. Employing 51 middleaged, overweight, insulin-resistant and non-diabetic individuals, modest improvements in fitness, body composition, and insulin sensitivity were observed, but these changes were not associated with decreased CRP or increased adiponectin levels (Marcell et al., 2005). In a different clinical trial, weight reduction significantly elevated plasma adiponectin levels in diabetic subjects, as well as in non-diabetic subjects (Hotta et al., 2000). Finally, studies for the roles of other adipokines in type 2 diabetes are scarce. Data on visfatin and resistin levels in insulin resistance are currently inconclusive (Koerner et al., 2005; Sethi and Vidal-Puig, 2005). A novel protein, serum retinol-binding protein 4 (RBP4), is an adipocyte-derived “signal” that may contribute to the pathogenesis of type 2 diabetes (Yang et al., 2005). RBP4 levels are elevated in insulin-resistant mice and humans with obesity and type 2 diabetes; genetic deletion of RBP4 enhances insulin sensitivity (Yang et al., 2005).
B. Cardiovascular Disease Obesity has long been known as a risk factor for cardiovascular disease (CVD). Several adipokines increase with obesity progression, including TNF-α, plasminogen activator inhibitor type 1 (PAI-1), resistin, and leptin, and they contribute to type 2 diabetes and atherosclerosis (Lau et al., 1994). Adiponectin, on the other hand, decreases with visceral fat accumulation, and the level of this adipokine seems to be very important in the development of cardiovascular disease (Dunajska et al., 2004; Hotta et al., 2000; Kato et al., 2005; Ouchi et al., 1999). There is emerging data linking leptin to CVD. Leptin receptors are expressed on human endothelial cells (Sierra-Honigmann et al., 1998). Leptin induces neovascularization in corneas in normal rats but not in leptin receptor-deficient rats, suggesting leptin is an angiogenic factor (Sierra-Honigmann et al., 1998). The leptin-induced angiogenic process is mediated through a tyrosine kinase-dependent intracellular pathway (Bouloumie et al., 1998). Under high glucose conditions, leptin reduces hydrolysis of cholesterol esters in macrophages contributing to foam cell formation (O’Rourke et al., 2002). Moreover, a higher leptin concentration is associated with impaired arterial distension (Singhal et al., 2002). Platelets also express the leptin receptor, and leptin increases the aggregation of platelets and arterial thrombosis through a leptin receptor-dependent pathway (Konstantinides et al.,
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2001). Inhibition of circulating leptin using leptinneutralizing antibodies protects against arterial and venous thrombosis in mice, suggesting a potential approach to treat hyperleptinemic obese individuals (Konstantinides et al., 2004). Low plasma adiponectin level is connected with atherogenic lipid profile (Dunajska et al., 2004). Plasma adiponectin levels correlate negatively with BMI, waist, percentage of total fat, total cholesterol and triglycerides, and positively with HDL cholesterol, total testosterone, and total testosterone/estradiol ratio (Dunajska et al., 2004). Low levels of adiponectin are also associated with higher levels of hs-CRP and IL-6, two inflammatory mediators and markers of increased cardiovascular risk (Engeli et al., 2003). The reciprocal association of adiponectin and CRP levels in both human plasma and adipose tissue might signal a tolerant environment for the development of atherosclerosis (Ouchi et al., 2003). A prospective study employing men without previous CVD history shows that a high plasma adiponectin level is protective against future myocardial infarction (MI) (Pischon et al., 2004). Male patients with hypoadiponectinemia had a significant two-fold increase in coronary artery disease (CAD) prevalence, independent of well-known CAD risk factors (Kumada et al., 2003). Similar low plasma concentrations of adiponectin are found in patients with acute coronary syndrome (ACS) or CAD (Nakamura et al., 2004). Study with Japanese subjects with no history of CVD shows that the level of endothelial function impairment is in proportion to the severity of obesity and plasma adiponectin levels (Shimabukuro et al., 2003). Another study shows that impaired endothelium-dependent vasodilation is also associated with low plasma adiponectin levels (Tan et al., 2004). Furthermore, low adiponectin levels lead to enhanced thrombus formation and platelet aggregation (Kato et al., 2005). Globular adiponectin transgenic apoEdeficient mice demonstrate amelioration of atherosclerosis, which is associated with decreased expression of class A macrophage scavenger receptor (SR-A) and TNF-α (Yamauchi et al., 2003). This is the first demonstration that globular adiponectin can protect against atherosclerosis in vivo (Yamauchi et al., 2003). How does adiponectin affect the process of atherosclerosis? One of the initial steps in atherogenesis is adherence of monocytes to endothelial cells and their migration into the subendothelial space, where they take up oxidized lipoproteins and transform into foam cells. Recent studies show physiological concentrations of adiponectin inhibit TNF-α–induced monocyte cell line THP-1 adhesion and expression of vascular cell adhesion molecule-1 (VCAM-1), E-selectin, and intercellular adhesion molecule-1 (ICAM-1) on human
aortic endothelial cells (Ouchi et al., 1999). Studies demonstrate that suppression of TNF-α signaling acts only on IKK-α phosphorylation and subsequent NFκB activation without affecting other TNF-α–mediated phosphorylation signals, including Jun N-terminal kinase, p38 kinase, and Akt kinase (Ouchi et al., 2000). Adenovirus-induced expression of human adiponectin in aortic tissue significantly suppresses TNF-α and the mRNAs for VCAM-1 and SR-A (Okamoto et al., 2002). Acyl-coenzyme A : cholesterol acyltransferase-1 (ACAT-1) catalyzes the formation of cholesteryl esters (CE) for storage by macrophages. Excessive lipid accumulation in macrophages is important to atherogenesis (Furukawa et al., 2004a). Adiponectin has an inhibitory effect on ACAT-1 expression in human macrophages (Furukawa et al., 2004a). Adiponectin dosedependently suppresses SR-A and lipoprotein lipase (Ouchi et al., 2004). Taken together, macrophage-tofoam cell transformation is inhibited by adiponectin. Vascular smooth muscle cell proliferation plays an important role in the development of atherosclerosis. Adiponectin inhibits cell proliferation and may be a mode of vascular remodeling (Arita et al., 2002). In cultured endothelial cells, adiponectin attenuates heparin-binding epidermal growth factor–like growth factor (HB-EGF) expression stimulated by TNF-α (Matsuda et al., 2002). Physiological concentrations of adiponectin suppress both proliferation and migration of human aortic smooth muscle cells stimulated with platelet-derived growth factor (PDGF)-BB through direct binding (Arita et al., 2002). Furthermore, in bovine endothelial cells, globular adiponectin inhibits cell proliferation and superoxide release induced by oxidized LDL (Motoshima et al., 2004). Adiponectin also ameliorates the suppression of eNOS activity after treatment of endothelial cells with oxidized LDL (Motoshima et al., 2004). Globular adiponectin also inhibits basal and oxidized LDL-induced superoxide release and suppresses the activation of p42/p44 MAP kinase by oxidized LDL (Motoshima et al., 2004). Adiponectin can directly stimulate production of NO in endothelial cells through the PI3K pathway involving phosphorylation of eNOS at Ser1179 by AMPK (Chen et al., 2003; Tan et al., 2004). Adiponectin also stimulates differentiation of human endothelial cells into capillary-like structures in vitro (Ouchi et al., 2004).
C. Asthma Asthma has reached epidemic proportions in the developed world. Although there is an abundance of reports on the incidence association between obesity and asthma, there is debate as to a causal relationship
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between the two (Chinn, 2005; Weiss, 2005). A prospective cohort study of female U.S. registered nurses conducted in Nurses’ Health Study II shows women who gained weight after age 18 are at significantly increased risk of developing asthma during the 4-year follow-up period (Camargo et al., 1999). Among individuals from a British Cohort Study, the prevalence of asthma increases with increasing adult BMI (Shaheen et al., 1999). Several studies attempt to uncover how adipose tissue could modulate asthma susceptibility and symptoms. One reports ozoneinduced airway hyper-responsiveness and inflammation in obese ob/ob mice (Shore et al., 2003). Using animal models of obesity, ovalbumin induced asthma in obese mice. These mice had a higher sensitivity of antigen-induced T-cell responses, and increased INF-γ production from splenocytes with phytohemagglutinin stimulation (Mito et al., 2002). Mast cell numbers in the tracheal mucosa are increased in obese mice upon sensitization by ovalbumin (Mito et al., 2002). There are also reports on enhanced Th2 cytokine production in obese individuals during allergic reactions (Shore et al., 2005; Vieira et al., 2005). Higher levels of leptin have been observed in asthmatics with similar BMI (Guler et al., 2004; Gurkan et al., 2004). Leptin might be involved in the pathogenesis of asthma in overweight children since its level seems to increase during asthmatic episodes (Mai et al., 2004). Furthermore, there is a positive correlation between levels of leptin and levels of IFN-γ, indicating IFN-γ may play a role in leptin-induced inflammation (Mai et al., 2004). Other causes of asthma in obese individuals are also proposed, including differences in lung mechanics, genetics, diet, and endocrinology (Weiss, 2005).
D. Sepsis Obesity is linked with significant increases in the incidence of nosocomial infections (Choban et al., 1995). Higher rates of intensive care unit complications such as sepsis among morbidly obese patients have been observed (Yaegashi et al., 2005). The increased morbidity and sepsis in obesity may result from exaggerated microvascular inflammatory and thrombogenic responses that include the activation of endothelial cells with subsequent expression of adhesion molecules, such as P-selectin, CD18, or ICAM-1 (Vachharajani et al., 2005). In the brain, analysis of gene expression after LPS injection shows clear differences between lean and obese animals in coagulation, lipid transport, and neuroendocrine and insulin signaling (Scott et al., 2004). In obese animals treated with LPS, liver gene expression is significantly different when compared to lean animals (Scott et al., 2005). In fact, the short forms
of leptin receptors in db/db mice offer protection against endotoxin-induced lethality by preventing acute renal failure (Wang et al., 2004).
E. Wound Healing Obese patients have a higher incidence of woundhealing complications calling for special equipment, special techniques of handling, and careful nutritional planning (Armstrong, 1998; Derzie et al., 2000; Gallagher and Gates, 2004; Johnson et al., 1997; Pinchofsky-Devin, 1997; Wilson and Clark, 2004). The type of complications include infection, wound dehiscence, hematoma/seroma formation, pressure and venous ulcers, and constipation (Wilson and Clark, 2004). The risk of trocar-site herniation is greater in obese and bariatric patients, because of the larger preperitoneal space and elevated intra-abdominal pressure (Eid and Collins, 2005). A specialized trocar wound closure system is designed for use on obese and bariatric patients to reduce risk of complications (Eid and Collins, 2005). Adipose tissue is poorly vascularized and known to be less tolerant of ischemia and hypoxia (Maklebust and Sieggreen, 1996). Adipogenesis and angiogenesis are intimately integrated in soft tissue wound healing. In cell culture, endothelial cells release a soluble factor that sustains preadipocytes’ viability under hypoxic conditions (Frye et al., 2005). Leptin increases lesion growth and cellular proliferation in injured arteries, which may contribute to cardiovascular complications (Schafer et al., 2004).
F. Inflammatory Bowel Disease There is serum leptin in the acute stage of ulcerative colitis, and this increase may contribute to anorexia and weight loss (Tuzun et al., 2004). In mesenteric adipose tissue, overexpression of leptin mRNA likely leads to enhanced mesenteric TNF-α expression in Crohn’s disease. Thus, increased anorexia is frequently observed with inflammatory bowel disease (IBD) (Barbier et al., 2003). Colonic epithelial cells can express and release leptin into the intestinal lumen (Sitaraman et al., 2004). Intrarectal administration of leptin induces epithelial wall damage and neutrophil infiltration that is the hallmark of histological findings in acute intestinal inflammation (Sitaraman et al., 2004). In an immune experimental model of mice with chronic intestinal inflammation, the impact of leptin appears on Th1 lymphocytes mediated through the long receptor isoform (Siegmund et al., 2004a). Leptin, however, does not seem to play a role in the spontaneous colitis of IL-10–deficient mice (Siegmund et al., 2004b). Moreover, there are several reports showing no increase in leptin levels in IBD (Ballinger et al., 1998; Hoppin
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et al., 1998). Adiponectin is secreted in high amounts from adipocytes in hypertrophied mesenteric adipose tissue and has been suggested to regulate intestinal inflammation associated with Crohn’s disease (Yamamoto et al., 2005).
G. Rheumatoid Arthritis Rheumatoid arthritis (RA) is a chronic cytokinemediated inflammatory disease. One of the risk factors for rheumatoid arthritis is obesity (Symmons, 2005). RA patients have enhanced leptin production systemically, but the level in the synovial fluid is significantly lower, suggesting in situ consumption of this molecule (Bokarewa et al., 2003). There is a significant inverse correlation between inflammation and leptin in patients with active RA, suggesting active chronic inflammation may lower leptin levels (Popa et al., 2005). Both resistin and adiponectin may be involved in RA (Bokarewa et al., 2005; Schaffler et al., 2003). Resistin is shown to specifically accumulate in inflamed joints, and its level correlates positively with CRP (Bokarewa et al., 2005; Schaffler et al., 2003). The involvement of leptin, adiponectin, and resistin suggests that white adipose tissue is necessary to RA. Interestingly, a current therapy for RA is recombinant IL-1Ra (Kineret®, Amgen). Since, as we noted earlier, IL-1Ra is increased in obesity, an unanswered question is how RA develops in obesity.
H. Multiple Sclerosis Surging of leptin may serve as a marker of disease activity in individuals with multiple sclerosis (MS) (Batocchi et al., 2003; Sanna et al., 2003). Leptin secretion by activated T-cells sustains their proliferation in an autocrine loop (Sanna et al., 2003). In relapsing MS, leptin enhances production of TNF-α, IL-6, and IL-10 production by blood mononuclear cells (Frisullo et al., 2004). Moreover, there is an inverse relationship between leptin secretion, T-cells, and relapsingremitting MS (Matarese et al., 2005). Treating mice with soluble leptin receptor ameliorates clinical course and progression of MS (Matarese et al., 2005). Finally, in MS patients undergoing IFN-β-1b treatment, leptin and IL-6 levels are decreased in those who have no progression during treatment (Angelucci et al., 2005).
V. CONCLUSIONS Given the vast array of data linking chronic inflammation and obesity, examining the balance between metabolism and immunity was a natural step. At one
end of the continuum is calorie restriction. A large body of evidence suggests that reducing overall caloric intake improves many health factors, most importantly longevity (Gredilla and Barja, 2005). On the other end of the continuum is obesity and diabetes. Two important general mechanisms have emerged. First is the theory put forth by Brownlee (2005) that increased flux through metabolic pathways leads to increased ROS and tissue damage. The second posit, put forth by Hotamisligil (2005) and perhaps linked to the first, is that an overabundance of nutrients causes ER stress, which subsequently activates inflammatory cascades integral to the innate immune system. These viewpoints offer attractive targets for more focused therapeutic intervention. Through the last 2 decades the direction of obesity research has been toward understanding basic pathways on why people become fat and how fatness adversely affects health. In that same time, the search for an easy obesity fix through pharmaceutical-derived or medically implemented thinness technologies has also emerged. However, with the newer view of obesity as a condition impacting immunity, later-in-life reductions in weight may provide less-than-expected health benefits to individuals who have likely had long-term dysregulation of their immune systems. Like smoking, obesity may have taken its toll either in the form of explicit disease like diabetes, heart disease, and cancer or in more subtle and nefarious conditions negatively impacting fertility, self-image, life satisfaction, well-being, and life span. Future research will need to concentrate on obesity prevention, especially in children, adolescents, and young adults.
References Angelucci, F., Mirabella, M., Caggiula, M., Frisullo, G., Patanella, K., Sancricca, C., Nociti, V., Tonali, P. A., and Batocchi, A. P. (2005). Evidence of involvement of leptin and IL-6 peptides in the action of interferon-beta in secondary progressive multiple sclerosis. Peptides, 26, 2289–2293. Arend, W. P. (2002). The balance between IL-1 and IL-1Ra in disease. Cytokine Growth Factor Rev., 13 (4–5), 323–340. Arita, Y., Kihara, S., Ouchi, N., Maeda, K., Kuriyama, H., Okamoto, Y., Kumada, M., Hotta, K., Nishida, M., Takahashi, M., Nakamura, T., Shimomura, I., Muraguchi, M., Ohmoto, Y. T. F., and Matsuzawa, Y. (2002). Adipocyte-derived plasma protein adiponectin acts as a platelet-derived growth factor-BB-binding protein and regulates growth factor-induced common postreceptor signal in vascular smooth muscle cell. Circulation, 105, 2893–2898. Arkan, M. C., Hevener, A. L., Greten, F. R., Maeda, S., Li, Z. W., Long, J. M., Wynshaw-Boris, A., Poli, G., Olefsky, J., and Karin, M. (2005). IKK-beta links inflammation to obesity-induced insulin resistance. Nature Medicine, 11, 191–198. Armstrong, M. (1998). Obesity as an intrinsic factor affecting wound healing. Journal of Wound Care, 7, 220–221.
1004
V. Psychoneuroimmunology and Pathophysiology
Bailey, C. J. (2005). Treating insulin resistance in type 2 diabetes with metformin and thiazolidinediones. Diabetes Obesity and Metabolism, 7, 675–691. Ballinger, A., Kelly, P., Hallyburton, E., Besser, R., and Farthing, M. (1998). Plasma leptin in chronic inflammatory bowel disease and HIV: implications for the pathogenesis of anorexia and weight loss. Clinical Science, 94, 479–483. Barbier, M., Vidal, H., Desreumaux, P., Dubuquoy, L., Bourreille, A., Colombel, J. F., Cherbut, C., and Galmiche, J. P. (2003). Overexpression of leptin mRNA in mesenteric adipose tissue in inflammatory bowel diseases. Gastroenterol Clinical Biology, 27, 987–991. Batocchi, A. P., Rotondi, M., Caggiula, M., Frisullo, G., Odoardi, F., Nociti, V., Carella, C., Tonali, P. A., and Mirabella, M. (2003). Leptin as a marker of multiple sclerosis activity in patients treated with interferon-beta. Journal of Neuroimmunology, 139, 150–154. Baumann, H., Morella, K. K., White, D. W., Dembski, M., Bailon, P. S., Kim, H., Lai, C. F., and Tartaglia, L. A. (1996). The fulllength leptin receptor has signaling capabilities of interleukin 6–type cytokine receptors. Proc. Natl. Acad. Sci. USA, 93 (16), 8374–8378. Bendtzen, K., Mandrup-Poulsen, T., Nerup, J., Nielsen, J. H., Dinarello, C. A., and Svenson, M. (1986). Cytotoxicity of human pI 7 interleukin-1 for pancreatic islets of Langerhans. Science, 232 (4757), 1545–1547. Bennett, B. D., Solar, G. P., Yuan, J. Q., Mathias, J., Thomas, G. R., and Matthews, W. (1996). A role for leptin and its cognate receptor in hematopoiesis. Curr. Biol., 6 (9), 1170–1180. Bernik, T. R., Friedman, S. G., Ochani, M., DiRaimo, R., Ulloa, L., Yang, H., Sudan, S., Czura, C. J., Ivanova, S. M., and Tracey, K. J. (2002). Pharmacological stimulation of the cholinergic antiinflammatory pathway. J. Exp. Med., 195 (6), 781–788. Black, R. A., Kronheim, S. R., Merriam, J. E., March, C. J., and Hopp, T. P. (1989). A pre-aspartate–specific protease from human leukocytes that cleaves pro-interleukin-1 beta. Journal of Biological Chemistry, 264 (10), 5323–5326. Blankenberg, S., Tiret, L., Bickel, C., Peetz, D., Cambien, F., Meyer, J., and Rupprecht, H. J. (2002). Interleukin-18 is a strong predictor of cardiovascular death in stable and unstable angina. Circulation, 106 (1), 24–30. Bluthe, R. M., Michaud, B., Poli, V., and Dantzer, R. (2000). Role of IL-6 in cytokine-induced sickness behavior: a study with IL-6 deficient mice. Physiol. Behav., 70 (3–4), 367–373. Bluthe, R. M., Pawlowski, M., Suarez, S., Parnet, P., Pittman, Q., Kelley, K. W., and Dantzer, R. (1994). Synergy between tumor necrosis factor alpha and interleukin-1 in the induction of sickness behavior in mice. Psychoneuroendocrinology, 19 (2), 197–207. Bokarewa, M., Bokarew, D., Hultgren, O., and Tarkowski, A. (2003). Leptin consumption in the inflamed joints of patients with rheumatoid arthritis. Annals of the Rheumatic Diseases, 62, 952–956. Bokarewa, M., Nagaev, I., Dahlberg, L., Smith, U., and Tarkowski, A. (2005). Resistin, an adipokine with potent proinflammatory properties. Journal of Immunology, 174, 5789–5795. Borovikova, L. V., Ivanova, S., Zhang, M., Yang, H., Botchkina, G. I., Watkins, L. R., Wang, H., Abumrad, N., Eaton, J. W., and Tracey, K. J. (2000). Vagus nerve stimulation attenuates the systemic inflammatory response to endotoxin. Nature, 405 (6785), 458–462. Bouloumie, A., Drexler, H. C., Lafontan, M., and Busse, R. (1998). Leptin, the product of Ob gene, promotes angiogenesis. Circulation Research, 83, 1059–1066. Brownlee, M. (2005). The pathobiology of diabetic complications: a unifying mechanism. Diabetes, 54 (6), 1615–1625.
Cai, D., Yuan, M., Frantz, D. F., Melendez, P. A., Hansen, L., Lee, J., and Shoelson, S. E. (2005). Local and systemic insulin resistance resulting from hepatic activation of IKK-beta and NF-kappa B. Nat. Med., 11 (2), 183–190. Camargo, C. A. J., Weiss, S. T., Zhang, S., et al. (1999). Prospective study of body mass index, weight change, and risk of adult-onset asthma in women. Archives of Internal Medicine, 159 (21), 2582–2588. Cancello, R., Henegar, C., Viguerie, N., Taleb, S., Poitou, C., Rouault, C., Coupaye, M., Pelloux, V., Hugol, D., Bouillot, J. L., Bouloumie, A., Barbatelli, G., Cinti, S., Svensson, P. A., Barsh, G. S., Zucker, J. D., Basdevant, A., Langin, D., and Clement, K. (2005). Reduction of macrophage infiltration and chemoattractant gene expression changes in white adipose tissue of morbidly obese subjects after surgery-induced weight loss. Diabetes, 54 (8), 2277–2286. Carswell, E. A., Old, L. J., Kassel, R. L., Green, S., Fiore, N., and Williamson, B. (1975). An endotoxin-induced serum factor that causes necrosis of tumors. Proc. Natl. Acad. Sci. USA, 72 (9), 3666–3670. Castell, J. V., Gomez-Lechon, M. J., David, M., Hirano, T., Kishimoto, T., and Heinrich, P. C. (1988). Recombinant human interleukin-6 (IL-6/BSF-2/HSF) regulates the synthesis of acute phase proteins in human hepatocytes. FEBS Lett., 232 (2), 347–350. Cengel, K. A., and Freund, G. G. (1999). JAK1-dependent phosphorylation of insulin receptor substrate-1 (IRS-1) is inhibited by IRS-1 serine phosphorylation. Journal of Biological Chemistry, 274 (39), 27969–27974. Cerretti, D. P., Kozlosky, C. J., Mosley, B., Nelson, N., Van Ness, K., Greenstreet, T. A., March, C. J., Kronheim, S. R., Druck, T., Cannizzaro, L. A., et al. (1992). Molecular cloning of the interleukin-1 beta converting enzyme. Science, 256 (5053), 97–100. Chen, H., Montagnani, M., Funahashi, T., Shimomura, I., and Quon, M. J. (2003). Adiponectin stimulates production of nitric oxide in vascular endothelial cells. Journal of Biological Chemistry, 278, 45021–45026. Chinn, S. (2005). Concurrent trends in asthma and obesity. Thorax, 60, 3–4. Choban, P. S., Heckler, R., Burge, J. C., and Flancbaum, L. (1995). Increased incidence of nosocomial infections in obese surgical patients. American Surgeon, 61, 1001–1005. Coleman, D. L. (1973). Effects of parabiosis of obese with diabetes and normal mice. Diabetologia, 9 (4), 294–298. Coleman, D. L. (1978). Obese and diabetes: two mutant genes causing diabetes-obesity syndromes in mice. Diabetologia, 14 (3), 141–148. Cousin, B., Munoz, O., Andre, M., Fontanilles, A. M., Dani, C., Cousin, J. L., Laharrague, P., Casteilla, L., and Penicaud, L. (1999). A role for preadipocytes as macrophage-like cells. FASEB J., 13 (2), 305–312. Cumberbatch, M., and Kimber, I. (1995). Tumour necrosis factoralpha is required for accumulation of dendritic cells in draining lymph nodes and for optimal contact sensitization. Immunology, 84 (1), 31–35. Cummings, D. E., and Schwartz, M. W. (2003). Genetics and pathophysiology of human obesity. Annu. Rev. Med., 54, 453–471. Daimon, M., Oizumi, T., Saitoh, T., Kameda, W., Hirata, A., Yamaguchi, H., Ohnuma, H., Igarashi, M., and Kato, T. (2003). Decreased serum levels of adiponectin are a risk factor for the progression to type 2 diabetes in the Japanese population: the Funagata study. Diabetes Care, 26, 2015–2020. Darnell, J. E., Jr. (1997). STATs and gene regulation. Science, 277 (5332), 1630–1635.
46. Obesity and Immunity De Benedetti, F., Alonzi, T., Moretta, A., Lazzaro, D., Costa, P., Poli, V., Martini, A., Ciliberto, G., and Fattori, E. (1997). Interleukin 6 causes growth impairment in transgenic mice through a decrease in insulin-like growth factor-I. A model for stunted growth in children with chronic inflammation. J. Clin. Invest., 99 (4), 643–650. de Luca, C., Kowalski, T. J., Zhang, Y., Elmquist, J. K., Lee, C., Kilimann, M. W., Ludwig, T., Liu, S. M., and Chua, S. C. (2005). Complete rescue of obesity, diabetes, and infertility in db/db mice by neuron-specific LEPR-B transgenes. J. Clin. Invest., 115 (12), 3484–3493. Derzie, A. J., Silvestri, F., Liriano, E., and Benotti, P. (2000). Wound closure technique and acute wound complications in gastric surgery for morbid obesity: a prospective randomized trial. Journal of the American College of Surgeons, 191, 238–243. Dietze-Schroeder, D., Sell, H., Uhlig, M., Koenen, M., and Eckel, J. (2005). Autocrine action of adiponectin on human fat cells prevents the release of insulin resistance-inducing factors. Diabetes, 54, 2003–2011. Dreyer, M. G., Juge-Aubry, C. E., Gabay, C., Lang, U., RohnerJeanrenaud, F., Dayer, J. M., and Meier, C. A. (2003). Leptin activates the promoter of the interleukin-1 receptor antagonist through p42/44 mitogen-activated protein kinase and a composite nuclear factor kappa B/PU.1 binding site. Biochem. J., 370 (Pt 2), 591–599. Du, X. L., Edelstein, D., Rossetti, L., Fantus, I. G., Goldberg, H., Ziyadeh, F., Wu, J., and Brownlee, M. (2000). Hyperglycemiainduced mitochondrial superoxide overproduction activates the hexosamine pathway and induces plasminogen activator inhibitor-1 expression by increasing Sp1 glycosylation. Proc. Natl. Acad. Sci. USA, 97 (22), 12222–12226. Dunajska, K., Milewicz, A., Jedrzejuk, D., Szymczak, J., Kuliczkowski, W., Salomon, P., Bialy, D., Poczatek, K., and Nowicki, P. (2004). Plasma adiponectin concentration in relation to severity of coronary atherosclerosis and cardiovascular risk factors in middle-aged men. Endocrine, 25, 215–221. Eid, G. M., and Collins, J. (2005). Application of a trocar wound closure system designed for laparoscopic procedures in morbidly obese patients. Obesity Surgery, 15, 871–873. Einstein, F. H., Atzmon, G., Yang, X. M., Ma, X. H., Rincon, M., Rudin, E., Muzumdar, R., and Barzilai, N. (2005). Differential responses of visceral and subcutaneous fat depots to nutrients. Diabetes, 54 (3), 672–678. Elenkov, I. J., Hasko, G., Kovacs, K. J., and Vizi, E. S. (1995). Modulation of lipopolysaccharide-induced tumor necrosis factor-alpha production by selective alpha- and beta-adrenergic drugs in mice. J. Neuroimmunol., 61 (2), 123–131. Emanuelli, B., Peraldi, P., Filloux, C., Chavey, C., Freidinger, K., Hilton, D. J., Hotamisligil, G. S., and Van Obberghen, E. (2001). SOCS-3 inhibits insulin signaling and is up-regulated in response to tumor necrosis factor-alpha in the adipose tissue of obese mice. Journal of Biological Chemistry, 276, 47944–47949. Engeli, S., Feldpausch, M., Gorzelniak, K., Hartwig, F., Heintze, U., Janke, J., Mohlig, M., Pfeiffer, A. F., Luft, F. C., and Sharma, A. M. (2003). Association between adiponectin and mediators of inflammation in obese women. Diabetes, 52, 942–947. Fain, J. N., Madan, A. K., Hiler, M. L., Cheema, P., and Bahouth, S. W. (2004). Comparison of the release of adipokines by adipose tissue, adipose tissue matrix, and adipocytes from visceral and subcutaneous abdominal adipose tissues of obese humans. Endocrinology, 145 (5), 2273–2282. Farese, R. V., Sajan, M. P., and Standaert, M. L. (2005). Atypical protein kinase C in insulin action and insulin resistance. Biochem. Soc. Trans., 33 (Pt 2), 350–353.
1005
Fernandez-Real, J. M., Lopez-Bermejo, A., Casamitjana, R., and Ricart, W. (2003). Novel interactions of adiponectin with the endocrine system and inflammatory parameters. J. Clin. Endocrinol. Metab., 88 (6), 2714–2718. Fischer, C. P., Perstrup, L. B., Berntsen, A., Eskildsen, P., and Pedersen, B. K. (2005). Elevated plasma interleukin-18 is a marker of insulin-resistance in type 2 diabetic and non-diabetic humans. Clin. Immunol., 117 (2), 152–160. Flegal, K. M., Carroll, M. D., Ogden, C. L., and Johnson, C. L. (2002). Prevalence and trends in obesity among US adults, 1999–2000. JAMA, 288 (14), 1723–1727. Friedman, J. M., and Halaas, J. L. (1998). Leptin and the regulation of body weight in mammals. Nature, 395 (6704), 763–770. Frisullo, G., Angelucci, F., Mirabella, M., Caggiula, M., Patanella, K., Nociti, V., Tonali, P. A., and Batocchi, A. P. (2004). Leptin enhances the release of cytokines by peripheral blood mononuclear cells from relapsing multiple sclerosis patients. Journal of Clinical Immunology, 24, 287–293. Frye, C. A., Wu, X., and Patrick, C. W. (2005). Microvascular endothelial cells sustain preadipocyte viability under hypoxic conditions. In Vitro Cellular and Developmental Biology—Animal, 41, 160–164. Furukawa, K., Hori, M., Ouchi, N., Kihara, S., Funahashi, T., Matsuzawa, Y., Miyazaki, A., Nakayama, H., and Horiuchi, S. (2004a). Adiponectin down-regulates acyl-coenzyme A : cholesterol acyltransferase-1 in cultured human monocyte-derived macrophages. Biochemical and Biophysical Research Communications, 317, 831–836. Furukawa, S., Fujita, T., Shimabukuro, M., Iwaki, M., Yamada, Y., Nakajima, Y., Nakayama, O., Makishima, M., Matsuda, M., and Shimomura, I. (2004b). Increased oxidative stress in obesity and its impact on metabolic syndrome. J. Clin. Invest., 114 (12), 1752–1761. Gabay, C., Dreyer, M., Pellegrinelli, N., Chicheportiche, R., and Meier, C. A. (2001). Leptin directly induces the secretion of interleukin 1 receptor antagonist in human monocytes. J. Clin. Endocrinol. Metab., 86 (2), 783–791. Gainsford, T., Willson, T. A., Metcalf, D., Handman, E., McFarlane, C., Ng, A., Nicola, N. A., Alexander, W. S., and Hilton, D. J. (1996). Leptin can induce proliferation, differentiation, and functional activation of hemopoietic cells. Proc. Natl. Acad. Sci. USA, 93 (25), 14564–14568. Gallagher, S., and Gates, J. (2004). Challenges of ostomy care and obesity. Ostomy Wound Manage, 50, 38–40, 44, 46 passim. Gao, Q., Wolfgang, M. J., Neschen, S., Morino, K., Horvath, T. L., Shulman, G. I., and Fu, X. Y. (2004). Disruption of neural signal transducer and activator of transcription 3 causes obesity, diabetes, infertility, and thermal dysregulation. Proc. Natl. Acad. Sci. USA, 101 (13), 4661–4666. Gao, Z., Hwang, D., Bataille, F., Lefevre, M., York, D., Quon, M. J., and Ye, J. (2002). Serine phosphorylation of insulin receptor substrate 1 by inhibitor kappa B kinase complex. Journal of Biological Chemistry, 277, 48115–48121. Giardino, I., Edelstein, D., and Brownlee, M. (1994). Nonenzymatic glycosylation in vitro and in bovine endothelial cells alters basic fibroblast growth factor activity. A model for intracellular glycosylation in diabetes. J. Clin. Invest., 94 (1), 110–117. Gredilla, R., and Barja, G. (2005). Minireview: the role of oxidative stress in relation to caloric restriction and longevity. Endocrinology, 146 (9), 3713–3717. Gresser, I., Delers, F., Tran Quangs, N., Marion, S., Engler, R., Maury, C., Soria, C., Soria, J., Fiers, W., and Tavernier, J. (1987). Tumor necrosis factor induces acute phase proteins in rats. J. Biol. Regul. Homeost. Agents, 1 (4), 173–176.
1006
V. Psychoneuroimmunology and Pathophysiology
Guler, N., Kirerleri, E., Ones, U., Tamay, Z., Salmayenli, N., and Darendeliler, F. (2004). Leptin: does it have any role in childhood asthma? Journal of Allergy Clinical Immunology, 114, 254–259. Gurkan, F., Atamer, Y., Ece, A., Kocyigit, Y., Tuzun, H., and Mete, N. (2004). Serum leptin levels in asthmatic children treated with an inhaled corticosteroid. Annals of Allergy, Asthma and Immunology, 93 (3), 277–280. Hansen, M. K., Taishi, P., Chen, Z., and Krueger, J. M. (1998). Vagotomy blocks the induction of interleukin-1 beta (IL-1 beta) mRNA in the brain of rats in response to systemic IL-1 beta. J. Neurosci., 18 (6), 2247–2253. Hartman, M. E., O’Connor, J. C., Godbout, J. P., Minor, K. D., Mazzocco, V. R., and Freund, G. G. (2004). Insulin receptor substrate-2–dependent interleukin-4 signaling in macrophages is impaired in two models of type 2 diabetes mellitus. Journal of Biological Chemistry, 279 (27), 28045–28050. Hasko, G., Szabo, C., Nemeth, Z. H., Salzman, A. L., and Vizi, E. S. (1998). Stimulation of beta-adrenoceptors inhibits endotoxininduced IL-12 production in normal and IL-10 deficient mice. J. Neuroimmunol., 88 (1–2), 57–61. Hirai, T., and Chida, K. (2003). Protein kinase Czeta (PKCzeta): activation mechanisms and cellular functions. J. Biochem. (Tokyo), 133 (1), 1–7. Hoebe, K., Georgel, P., Rutschmann, S., Du, X., Mudd, S., Crozat, K., Sovath, S., Shamel, L., Hartung, T., Zahringer, U., and Beutler, B. (2005). CD36 is a sensor of diacylglycerides. Nature, 433 (7025), 523–527. Hoppin, A. G., Kaplan, L. M., Zurakowski, D., Leichtner, A. M., and Bousvaros, A. (1998). Serum leptin in children and young adults with inflammatory bowel disease. Journal of Pediatric Gastroenterology and Nutrition, 26, 500–505. Hotamisligil, G. S. (2005). Role of endoplasmic reticulum stress and c-Jun NH2-terminal kinase pathways in inflammation and origin of obesity and diabetes. Diabetes, 54 (Suppl 2), S73–S78. Hotamisligil, G. S., Arner, P., Caro, J. F., Atkinson, R. L., and Spiegelman, B. M. (1995). Increased adipose tissue expression of tumor necrosis factor-alpha in human obesity and insulin resistance. J. Clin. Invest., 95 (5), 2409–2415. Hotamisligil, G. S., Murray, D. L., Choy, L. N., and Spiegelman, B. M. (1994). Tumor necrosis factor alpha inhibits signaling from the insulin receptor. Proc. Natl. Acad. Sci. USA, 91 (11), 4854–4858. Hotamisligil, G. S., Peraldi, P., A, B., Ellis, R., White, M. F., and Spiegelman, B. M. (1996). IRS-1–mediated inhibition of insulin receptor tyrosine kinase activity in TNF-alpha and obesityinduced insulin resistance. Science, 271, 665–668. Hotamisligil, G. S., Shargill, N. S., and Spiegelman, B. M. (1993). Adipose expression of tumor necrosis factor-alpha: direct role in obesity-linked insulin resistance. Science, 259 (5091), 87–91. Hotta, K., Funahashi, T., Arita, Y., Takahashi, M., Matsuda, M., Okamoto, Y., Iwahashi, H., Kuriyama, H., Ouchi, N., Maeda, K., Nishida, M., Kihara, S., Sakai, N., Nakajima, T., Hasegawa, K., Muraguchi, M., Ohmoto, Y., Nakamura, T., Yamashita, S., Hanafusa, T., and Matsuzawa, Y. (2000). Plasma concentrations of a novel, adipose-specific protein, adiponectin, in type 2 diabetic patients. Arterioscler. Thromb. Vasc. Biol., 20 (6), 1595–1599. Hu, X. X., Goldmuntz, E. A., and Brosnan, C. F. (1991). The effect of norepinephrine on endotoxin-mediated macrophage activation. J. Neuroimmunol., 31 (1), 35–42. Inoguchi, T., Sonta, T., Tsubouchi, H., Etoh, T., Kakimoto, M., Sonoda, N., Sato, N., Sekiguchi, N., Kobayashi, K., Sumimoto, H., Utsumi, H., and Nawata, H. (2003). Protein kinase C-dependent
increase in reactive oxygen species (ROS) production in vascular tissues of diabetes: role of vascular NAD(P)H oxidase. J. Am. Soc. Nephrol., 14 (8 Suppl 3), S227–S232. Ivashkiv, L. B., Ayres, A., and Glimcher, L. H. (1994). Inhibition of IFN-gamma induction of class II MHC genes by cAMP and prostaglandins. Immunopharmacology, 27 (1), 67–77. Jiang, H., Harris, M. B., and Rothman, P. (2000). IL-4/IL-13 signaling beyond JAK/STAT. J. Allergy Clin. Immunol., 105 (6 Pt 1), 1063–1070. Johnson, D. R., O’Connor, J. C., Dantzer, R., and Freund, G. G. (2005). Inhibition of vagally mediated immune-to-brain signaling by vanadyl sulfate speeds recovery from sickness. Proc. Natl. Acad. Sci. USA, 102 (42), 15184–15189. Johnson, R. G., Cohn, W. E., Thurer, R. L., McCarthy, J. R., Sirois, C. A., and Weintraub, R. M. (1997). Cutaneous closure after cardiac operations: a controlled, randomized, prospective, comparison of intra-dermal versus staple closures. Annals of Surgery, 226, 606–612. Kammer, W., Lischke, A., Moriggl, R., Groner, B., Ziemiecki, A., Gurniak, C. B., Berg, L. J., and Friedrich, K. (1996). Homodimerization of interleukin-4 receptor alpha chain can induce intracellular signaling. Journal of Biological Chemistry, 271 (39), 23634–23637. Kantartzis, K., Fritsche, A., Tschritter, O., Thamer, C., Haap, M., Schafer, S., Stumvoll, M., Haring, H. U., and Stefan, N. (2005). The association between plasma adiponectin and insulin sensitivity in humans depends on obesity. Obes. Res., 13 (10), 1683–1691. Katakami, Y., Nakao, Y., Koizumi, T., Katakami, N., Ogawa, R., and Fujita, T. (1988). Regulation of tumour necrosis factor production by mouse peritoneal macrophages: the role of cellular cyclic AMP. Immunology, 64 (4), 719–724. Kato, H., Kashiwagi, H., Shiraga, M., Tadokoro, S., Kamae, T., Ujiie, H., Honda, S., Miyata, S., Ijiri, Y., Yamamoto, J., Maeda, N., Funahashi, T., Kurata, Y., Shimomura, I., Tomiyama, Y., and Kanakura, Y. (2006). Adiponectin acts as an endogenous antithrombotic factor. Arteriosclerosis, Thrombosis, and Vascular Biology, 261, 224–230. Keller, P., Moller, K., Krabbe, K. S., and Pedersen, B. K. (2003). Circulating adiponectin levels during human endotoxaemia. Clin. Exp. Immunol., 134 (1), 107–110. Kern, P. A., Di Gregorio, B., Lu, T., Rassouli, N., and Ranganathan, G. (2003). Adiponectin expression from human adipose tissue: relation to obesity, insulin resistance, and tumor necrosis factoralpha expression. Diabetes, 52, 1779–1785. Kirken, R. A., Rui, H., Malabarba, M. G., and Farrar, W. L. (1994). Identification of interleukin-2 receptor-associated tyrosine kinase p116 as novel leukocyte-specific Janus kinase. Journal of Biological Chemistry, 269 (29), 19136–19141. Koerner A., Kratzsch, J., Kiess W. (2005). Adipocytokines: leptin— the classical, resistin—the controversial, adiponectin—the promising, and more to come. Best Practice & Research Clinical Endocrinology & Metabolism, 4, 525–546. Konstantinides, S., Schafer, K., Koschnick, S., and Loskutoff, D. J. (2001). Leptin-dependent platelet aggregation and arterial thrombosis suggests a mechanism for atherothrombotic disease in obesity. Journal of Clinical Investigation, 108, 1533–1540. Konstantinides, S., Schafer, K., Neels, J. G., Dellas, C., and Loskutoff, D. J. (2004). Inhibition of endogenous leptin protects mice from arterial and venous thrombosis. Arteriosclerosis, Thrombosis, and Vascular Biology, 24(11), 2196–201. Kruth, H. S., Jones, N. L., Huang, W., Zhao, B., Ishii, I., Chang, J., Combs, C. A., Malide, D., and Zhang, W. Y. (2005). Macropinocytosis is the endocytic pathway that mediates macrophage foam
46. Obesity and Immunity cell formation with native low density lipoprotein. Journal of Biological Chemistry, 280 (3), 2352–2360. Kumada, M., Kihara, S., Sumitsuji, S., Kawamoto, T., Matsumoto, S., Ouchi, N., Arita, Y., Okamoto, Y., Shimomura, I., Hiraoka, H., Nakamura, T., Funahashi, T., and Matsuzawa, Y. (2003). Association of hypoadiponectinemia with coronary artery disease in men. Arteriosclerosis, Thrombosis, and Vascular Biology, 23, 85–89. Lacour, M., Arrighi, J. F., Muller, K. M., Carlberg, C., Saurat, J. H., and Hauser, C. (1994). cAMP up-regulates IL-4 and IL-5 production from activated CD4+ T cells while decreasing IL-2 release and NF-AT induction. Int. Immunol., 6 (9), 1333–1343. Lang, C. H., Dobrescu, C., and Bagby, G. J. (1992). Tumor necrosis factor impairs insulin action on peripheral glucose disposal and hepatic glucose output. Endocrinology, 130 (1), 43–52. Lau, D. C., Dhillon, B., Yan, H., Szmitko, P. E., and Verma, S. (1994). Adipokines: molecular links between obesity and atherosclerosis. American Journal of Physiology Heart and Circulatory Physiology, 288, 2031–2041. Lee, A. Y., and Chung, S. S. (1999). Contributions of polyol pathway to oxidative stress in diabetic cataract. FASEB J., 13 (1), 23–30. Lee, E. A., Seo, J. Y., Jiang, Z., Yu, M. R., Kwon, M. K., Ha, H., and Lee, H. B. (2005). Reactive oxygen species mediate high glucoseinduced plasminogen activator inhibitor-1 up-regulation in mesangial cells and in diabetic kidney. Kidney Int., 67 (5), 1762–1771. Leiter, E. H., Coleman, D. L., Eisenstein, A. B., and Strack, I. (1980). A new mutation (db3J) at the diabetes locus in strain 129/J mice. I. Physiological and histological characterization. Diabetologia, 19 (1), 58–65. Lenczowski, M. J., Bluthe, R. M., Roth, J., Rees, G. S., Rushforth, D. A., van Dam, A. M., Tilders, F. J., Dantzer, R., Rothwell, N. J., and Luheshi, G. N. (1999). Central administration of rat IL-6 induces HPA activation and fever but not sickness behavior in rats. Am. J. Physiol., 276 (3 Pt 2), R652–658. Li, D. Y., Chen, H. J., Staples, E. D., Ozaki, K., Annex, B., Singh, B. K., Vermani, R., and Mehta, J. L. (2002). Oxidized low-density lipoprotein receptor LOX-1 and apoptosis in human atherosclerotic lesions. J. Cardiovasc. Pharmacol. Ther., 7 (3), 147–153. Liang, C. P., Han, S., Okamoto, H., Carnemolla, R., Tabas, I., Accili, D., and Tall, A. R. (2004). Increased CD36 protein as a response to defective insulin signaling in macrophages. J. Clin. Invest., 113 (5), 764–773. Lindsay, R. S., Funahashi, T., Hanson, R. L., Matsuzawa, Y., Tanaka, S., Tataranni, P. A., Knowler, W. C., and Krakoff, J. (2002). Adiponectin and development of type 2 diabetes in the Pima Indian population. Lancet, 360, 57–58. Linton, M. F., and Fazio, S. (2003). Macrophages, inflammation, and atherosclerosis. Int. J. Obes. Relat. Metab. Disord., 27 (Suppl 3), S35–S40. Liu, G., and Rondinone, C. M. (2005). JNK: bridging the insulin signaling and inflammatory pathway. Curr. Opin. Investig. Drugs, 6 (10), 979–987. Liu, Q., Ning, W., Dantzer, R., Freund, G. G., and Kelley, K. W. (1998). Activation of protein kinase C-zeta and phosphatidylinositol 3′-kinase and promotion of macrophage differentiation by insulin-like growth factor-I. J. Immunol., 160 (3), 1393–1401. Liu, Y. F., Paz, K., Herschkovitz, A., Alt, A., Tennenbaum, T., Sampson, S. R., Ohba, M., Kuroki, T., LeRoith, D., and Zick, Y. (2001). Insulin stimulates PKCzeta-mediated phosphorylation of insulin receptor substrate-1 (IRS-1). A self-attenuated mechanism to negatively regulate the function of IRS proteins. Journal of Biological Chemistry, 276 (17), 14459–14465. Maeda, N., Shimomura, I., Kishida, K., Nishizawa, H., Matsuda, M., Nagaretani, H., Furuyama, N., Kondo, H., Takahashi, M., Arita,
1007
Y., Komuro, R., Ouchi, N., Kihara, S., Tochino, Y., Okutomi, K., Horie, M., Takeda, S., Aoyama, T., Funahashi, T., and Matsuzawa, Y. (2002). Diet-induced insulin resistance in mice lacking adiponectin/ACRP30. Nature Medicine, 8, 731–737. Mai, X. M., Bottcher, M. F., and Leijon, I. (2004). Leptin and asthma in overweight children at 12 years of age. Pediatric Allergy and Immunology, 15 (6), 523–530. Maklebust, J., and Sieggreen, M. Y. (1996). Pressure ulcers: guidelines for prevention and nursing management (2nd ed.). Springhouse, PA: Springhouse Corporation. Makowski, L., Brittingham, K. C., Reynolds, J. M., Suttles, J., and Hotamisligil, G. S. (2005). The fatty acid-binding protein, aP2, coordinates macrophage cholesterol trafficking and inflammatory activity. Macrophage expression of aP2 impacts peroxisome proliferator-activated receptor gamma and I kappa B kinase activities. Journal of Biological Chemistry, 280 (13), 12888–12895. Mancuso, P., Gottschalk, A., Phare, S. M., Peters-Golden, M., Lukacs, N. W., and Huffnagle, G. B. (2002). Leptin-deficient mice exhibit impaired host defense in gram-negative pneumonia. J. Immunol., 168 (8), 4018–4024. Marcell, T. J., McAuley, K. A., Traustadottir, T., and Reaven, P. D. (2005). Exercise training is not associated with improved levels of C-reactive protein or adiponectin. Metabolism, 54, 533–541. Martin-Romero, C., and Sanchez-Margalet, V. (2001). Human leptin activates PI3K and MAPK pathways in human peripheral blood mononuclear cells: possible role of Sam68. Cell Immunol., 212 (2), 83–91. Matarese, G., Carrieri, P. B., La Cava, A., Perna, F., Sanna, V., De Rosa, V., Aufiero, D., Fontana, S., and Zappacosta, S. (2005). Leptin increase in multiple sclerosis associates with reduced number of CD4(+)CD25+ regulatory T cells. Proceedings of the National Academy of Sciences, 102, 5150–5155. Matsuda, M., Shimomura, I., Sata, M., Arita, Y., Nishida, M., Maeda, N., Kumada, M., Okamoto, Y., Nagaretani, H., Nishizawa, H., Kishida, K., Komuro, R., Ouchi, N., Kihara, S., Nagai, R., Funahashi, T., and Matsuzawa, Y. (2002). Role of adiponectin in preventing vascular stenosis. The missing link of adipovascular axis. Journal of Biological Chemistry, 277, 37487–37491. Matthaei, A., Stumvoll, M., Kellerer, M., and Haring, H. U. (2000). Pathophysiology and pharmacological treatment of insulin resistance. Endocrine Reviews, 21, 585–618. McBride, W. H., Economou, J. S., Nayersina, R., Comora, S., and Essner, R. (1990). Influences of interleukins 2 and 4 on tumor necrosis factor production by murine mononuclear phagocytes. Cancer Res., 50 (10), 2949–2952. Meier, C. A., Bobbioni, E., Gabay, C., Assimacopoulos-Jeannet, F., Golay, A., and Dayer, J. M. (2002). IL-1 receptor antagonist serum levels are increased in human obesity: a possible link to the resistance to leptin? J. Clin. Endocrinol. Metab., 87 (3), 1184– 1188. Mercer, N., Ahmed, H., McCarthy, A. D., Etcheverry, S. B., Vasta, G. R., and Cortizo, A. M. (2004). AGE-R3/galectin-3 expression in osteoblast-like cells: regulation by AGEs. Mol. Cell Biochem., 266 (1–2), 17–24. Mijatovic, T., Kruys, V., Caput, D., Defrance, P., and Huez, G. (1997). Interleukin-4 and -13 inhibit tumor necrosis factor-alpha mRNA translational activation in lipopolysaccharide-induced mouse macrophages. Journal of Biological Chemistry, 272 (22), 14394–14398. Mikita, T., Campbell, D., Wu, P., Williamson, K., and Schindler, U. (1996). Requirements for interleukin-4–induced gene expression and functional characterization of Stat6. Mol. Cell Biol., 16 (10), 5811–5820.
1008
V. Psychoneuroimmunology and Pathophysiology
Mito, N., Kitada, C., Hosoda, T., and Sato, K. (2002). Effect of dietinduced obesity on ovalbumin-specific immune response in a murine asthma model. Metabolism, 51 (10), 1241–1246. Moore, K. J., Rosen, E. D., Fitzgerald, M. L., Randow, F., Andersson, L. P., Altshuler, D., Milstone, D. S., Mortensen, R. M., Spiegelman, B. M., and Freeman, M. W. (2001). The role of PPARgamma in macrophage differentiation and cholesterol uptake. Nat Med., 7 (1), 41–47. Morin, D., Sapena, R., Tillement, J. P., and Urien, S. (2000). Evidence for different interactions between beta(1)- and beta(2)adrenoceptor subtypes with adenylyl cyclase in the rat brain: a concentration-response study using forskolin. Pharmacol. Res., 41 (4), 435–443. Mosser, D. M. (2003). The many faces of macrophage activation. J. Leukoc. Biol., 73 (2), 209–212. Motoshima, H., Wu, X., Mahadev, K., and Goldstein, B. J. (2004). Adiponectin suppresses proliferation and superoxide generation and enhances eNOS activity in endothelial cells treated with oxidized LDL. Biochemical and Biophysical Research Communications, 315, 264–271. Nakamura, Y., Shimada, K., Fukuda, D., Shimada, Y., Ehara, S., Hirose, M., Kataoka, T., Kamimori, K., Shimodozono, S., Kobayashi, Y., Yoshiyama, M., Takeuchi, K., and Yoshikawa, J. (2004). Implications of plasma concentrations of adiponectin in patients with coronary artery disease. Heart, 90, 528–533. Nawrocki, A. R., Rajala, M. W., Tomas, E., Pajvani, U. B., Saha, A. K., Trumbauer, M. E., Pang, Z., Chen, A. S., Ruderman, N. B., Chen, H., Rossetti, L., and Scherer, P. E. (2006). Mice lacking adiponectin show decreased hepatic insulin sensitivity and reduced responsiveness to PPARgamma-agonists. Journal of Biological Chemistry, 281 (5), 2654–2660. Nelms, K., Keegan, A. D., Zamorano, J., Ryan, J. J., and Paul, W. E. (1999). The IL-4 receptor: signaling mechanisms and biologic functions. Annu. Rev. Immunol., 17, 701–738. Nishikawa, T., Edelstein, D., Du, X. L., Yamagishi, S., Matsumura, T., Kaneda, Y., Yorek, M. A., Beebe, D., Oates, P. J., Hammes, H. P., Giardino, I., and Brownlee, M. (2000). Normalizing mitochondrial superoxide production blocks three pathways of hyperglycaemic damage. Nature, 404 (6779), 787–790. Nonogaki, K., Pan, X. M., Moser, A. H., Shigenaga, J., Staprans, I., Sakamoto, N., Grunfeld, C., and Feingold, K. R. (1996). LIF and CNTF, which share the gp130 transduction system, stimulate hepatic lipid metabolism in rats. Am. J. Physiol., 271 (3 Pt 1), E521–528. Novogrodsky, A., Patya, M., Rubin, A. L., and Stenzel, K. H. (1983). Agents that increase cellular cAMP inhibit production of interleukin-2, but not its activity. Biochem. Biophys. Res. Commun., 114 (1), 93–98. O’Connor, J. C., Satpathy, A., Hartman, M. E., Horvath, E. M., Kelley, K. W., Dantzer, R., Johnson, R. W., and Freund, G. G. (2005). IL-1beta–mediated innate immunity is amplified in the db/db mouse model of type 2 diabetes. J. Immunol., 174 (8), 4991–4997. Ohara, J., and Paul, W. E. (1987). Receptors for B-cell stimulatory factor-1 expressed on cells of haematopoietic lineage. Nature, 325 (6104), 537–540. Okamoto, Y., Kihara, S., Ouchi, N., Nishida, M., Arita, Y., Kumada, M., Ohashi, K., Sakai, N., Shimomura, I., Kobayashi, H., Terasaka, N., Inaba, T., Funahashi, T., and Matsuzawa, Y. (2002). Adiponectin reduces atherosclerosis in apolipoprotein E deficient mice. Circulation, 106, 2767–2770. Opal, S. M., and DePalo, V. A. (2000). Anti-inflammatory cytokines. Chest, 117 (4), 1162–1172.
O’Rourke, L., Gronning, L. M., Yeaman, S. J., and Shepherd, P. R. (2002). Glucose-dependent regulation of cholesterol ester metabolism in macrophages by insulin and leptin. Journal of Biological Chemistry, 277, 42557–42562. Ouchi, N., Kihara, S., Arita, Y., Maeda, K., Kuriyama, H., Okamoto, Y., Hotta, K., Nishida, M., Takahashi, M., Nakamura, T., Yamashita, S., Funahashi, T., and Matsuzawa, Y. (1999). Novel modulator of endothelial adhesion molecules: adipocyte-derived plasma protein adiponectin. Circulation, 100, 2473–2476. Ouchi, N., Kihara, S., Arita, Y., Okamoto, Y., Maeda, K., Kuriyama, H., Hotta, K., Nishida, M., Takahashi, M., Muraguchi, M., Ohmoto, Y., Nakamura, T., Yamashita, S., Funahashi, T., and Matsuzawa, Y. (2000). Adiponectin, an adipocyte-derived plasma protein, inhibits endothelial NF-kappa B signaling through a cAMP-dependent pathway. Circulation, 102, 1296–1301. Ouchi, N., Kihara, S., Funahashi, T., Nakamura, T., Nishida, M., Kumada, M., Okamoto, Y., Ohashi, K., Nagaretani, H., Kishida, K., Nishizawa, H., Maeda, N., Kobayashi, H., Hiraoka, H., and Matsuzawa, Y. (2003). Reciprocal association of C-reactive protein with adiponectin in blood stream and adipose tissue. Circulation, 107, 671–674. Ouchi, N., Kobayashi, H., Kihara, S., Kumada, M., Sato, K., Inoue, T., Funahashi, T., and Walsh, K. (2004). Adiponectin stimulates angiogenesis by promoting cross-talk between AMP-activated protein kinase and Akt signaling in endothelial cells. Journal of Biological Chemistry, 279, 1304–1309. Oyadomari, S., Koizumi, A., Takeda, K., Gotoh, T., Akira, S., Araki, E., and Mori, M. (2002). Targeted disruption of the Chop gene delays endoplasmic reticulum stress-mediated diabetes. J. Clin. Invest., 109 (4), 525–532. Ozcan, U., Cao, Q., Yilmaz, E., Lee, A. H., Iwakoshi, N. N., Ozdelen, E., Tuncman, G., Gorgun, C., Glimcher, L. H., and Hotamisligil, G. S. (2004). Endoplasmic reticulum stress links obesity, insulin action, and type 2 diabetes. Science, 306 (5695), 457–461. Pajvani, U. B., Du, X., Combs, T. P., Berg, A. H., Rajala, M. W., Schulthess, T., Engel, J., Brownlee, M., and Scherer, P. E. (2003). Structure-function studies of the adipocyte-secreted hormone Acrp30/adiponectin. Implications for metabolic regulation and bioactivity. Journal of Biological Chemistry, 278 (11), 9073–9085. Papaccio, G., Nicoletti, F., Pisanti, F. A., Galdieri, M., and Bendtzen, K. (2002). An imidazoline compound completely counteracts interleukin-1[beta] toxic effects to rat pancreatic islet [beta] cells. Mol. Med., 8 (9), 536–545. Pinchofsky-Devin, G. (1997). Nutritional assessment and intervention. In D. Krasner and D. Kane (Eds.), Chronic wound care: a clinical source book for professionals (2nd ed., pp. 73–83). Wayne, PA: Health Management Publications Inc. Pischon, T., Girman, C. J., Hotamisligil, G. S., Rifai, N., Hu, F. B., and Rimm, E. B. (2004). Plasma adiponectin levels and risk of myocardial infarction in men. JAMA, 291 (14), 1730–1737. Plata-Salaman, C. R. (1994). Meal patterns in response to the intracerebroventricular administration of interleukin-1 beta in rats. Physiol. Behav., 55 (4), 727–733. Plata-Salaman, C. R., and Ilyin, S. E. (1997). Interleukin-1 beta (IL-1 beta)-induced modulation of the hypothalamic IL-1 beta system, tumor necrosis factor-alpha, and transforming growth factorbeta 1 mRNAs in obese (fa/fa) and lean (Fa/Fa) Zucker rats: implications to IL-1 beta feedback systems and cytokine-cytokine interactions. J. Neurosci. Res., 49 (5), 541–550. Platt, N., Haworth, R., Darley, L., and Gordon, S. (2002). The many roles of the class A macrophage scavenger receptor. Int. Rev. Cytol., 212, 1–40.
46. Obesity and Immunity Platzer, C., Meisel, C., Vogt, K., Platzer, M., and Volk, H. D. (1995). Up-regulation of monocytic IL-10 by tumor necrosis factoralpha and cAMP elevating drugs. Int. Immunol., 7 (4), 517– 523. Popa, C., Netea, M. G., Radstake, T. R., van Riel, P. L., Barrera, P., and van der Meer, J. W. (2005). Markers of inflammation are negatively correlated with serum leptin in rheumatoid arthritis. Annals of the Rheumatic Diseases, 64, 1195–1198. Quagliaro, L., Piconi, L., Assaloni, R., Da Ros, R., Maier, A., Zuodar, G., and Ceriello, A. (2005). Intermittent high glucose enhances ICAM-1, VCAM-1 and E-selectin expression in human umbilical vein endothelial cells in culture: the distinct role of protein kinase C and mitochondrial superoxide production. Atherosclerosis, 183 (2), 259–267. Renz, H., Gong, J. H., Schmidt, A., Nain, M., and Gemsa, D. (1988). Release of tumor necrosis factor-alpha from macrophages. Enhancement and suppression are dose-dependently regulated by prostaglandin E2 and cyclic nucleotides. J. Immunol., 141 (7), 2388–2393. Ricote, M., Li, A. C., Willson, T. M., Kelly, C. J., and Glass, C. K. (1998). The peroxisome proliferator-activated receptor-gamma is a negative regulator of macrophage activation. Nature, 391 (6662), 79–82. Roche, E., Buteau, J., Aniento, I., Reig, J. A., Soria, B., and Prentki, M. (1999). Palmitate and oleate induce the immediate-early response genes c-fos and nur-77 in the pancreatic beta-cell line INS-1. Diabetes, 48 (10), 2007–2014. Rossi, F., Grzeskowiak, M., Della Bianca, V., and Sbarbati, A. (1991). De novo synthesis of diacylglycerol from glucose. A new pathway of signal transduction in human neutrophils stimulated during phagocytosis of beta-glucan particles. Journal of Biological Chemistry, 266 (13), 8034–8038. Rotter Sopasakis, V., Larsson, B. M., Johansson, A., Holmang, A., and Smith, U. (2004). Short-term infusion of interleukin-6 does not induce insulin resistance in vivo or impair insulin signalling in rats. Diabetologia, 47 (11), 1879–1887. Ruan, H., Hacohen, N., Golub, T. R., Van Parijs, L., and Lodish, H. F. (2002). Tumor necrosis factor-alpha suppresses adipocytespecific genes and activates expression of preadipocyte genes in 3T3–L1 adipocytes: nuclear factor-kappa B activation by TNFalpha is obligatory. Diabetes, 51 (5), 1319–1336. Samad, F., Pandey, M., and Loskutoff, D. J. (2001). Regulation of tissue factor gene expression in obesity. Blood, 98 (12), 3353– 3358. Sanna, V., Di Giacomo, A., La Cava, A., Lechler, R. I., Fontana, S., Zappacosta, S., and Matarese, G. (2003). Leptin surge precedes onset of autoimmune encephalomyelitis and correlates with development of pathogenic T cell responses. The Journal of Clinical Investigation, 111, 241–250. Santos, A. C., Lopes, C., Guimaraes, J. T., and Barros, H. (2005). Central obesity as a major determinant of increased highsensitivity C-reactive protein in metabolic syndrome. Int. J. Obes. (Lond.), 29 (12), 1452–1456. Schafer, K., Halle, M., Goeschen, C., Dellas, C., Pynn, M., Loskutoff, D. J., and Konstantinides, S. (2004). Leptin promotes vascular remodeling and neointimal growth in mice. Arteriosclerosis, Thrombosis, and Vascular Biology, 24, 112–117. Schaffler, A., Ehling, A., Neumann, E., Herfarth, H., Tarner, I., Scholmerich, J., Muller-Ladner, U., and Gay, S. (2003). Adipocytokines in synovial fluid. The Journal of the American Medical Association, 290, 1709–1710. Schmidt, A. M., Hori, O., Cao, R., Yan, S. D., Brett, J., Wautier, J. L., Ogawa, S., Kuwabara, K., Matsumoto, M., and Stern, D. (1996).
1009
RAGE: a novel cellular receptor for advanced glycation end products. Diabetes, 45 (Suppl 3), S77–80. Scott, L. K., Vachharajani, V., Minagar, A., Mynatt, R. L., and Conrad, S. A. (2005). Differential RNA expression of hepatic tissue in lean and obese mice after LPS-induced systemic inflammation. Frontiers in Bioscience, 10, 1828–1834. Scott, L. K., Vachharajani, V., Mynatt, R. L., Minagar, A., and Conrad, S. A. (2004). Brain RNA expression in obese vs lean mice after LPS-induced systemic inflammation. Frontiers in Bioscience, 9, 2686–2696. Senn, J. J., Klover, P. J., Nowak, I. A., Zimmers, T. A., Koniaris, L. G., Furlanetto, R. W., and Mooney, R. A. (2003). Suppressor of cytokine signaling-3 (SOCS-3), a potential mediator of interleukin-6–dependent insulin resistance in hepatocytes. Journal of Biological Chemistry, 278 (16), 13740–13746. Sethi, J. K., and Vidal-Puig, A. (2005). Visfatin: the missing link between intra-abdominal obesity and diabetes? Trends in Molecular Medicine, 11, 344–347. Severn, A., Rapson, N. T., Hunter, C. A., and Liew, F. Y. (1992). Regulation of tumor necrosis factor production by adrenaline and beta-adrenergic agonists. J. Immunol., 148 (11), 3441–3445. Shaheen, S. O., Sterne, J. A., Montgomery, S. M., and Azima, H. (1999). Birth weight, body mass index and asthma in young adults. Thorax, 54, 396–402. Shimabukuro, M., Higa, N., Asahi, T., Oshiro, Y., Takasu, N., Tagawa, T., Ueda, S., Shimomura, I., Funahashi, T., and Matsuzawa, Y. (2003). Hypoadiponectinemia is closely linked to endothelial dysfunction in man. Journal of Clinical Endocrinology & Metabolism, 88, 3236–3240. Shore, S. A., Rivera-Sanchez, Y. M., Schwartzman, I. N., and Johnston, R. A. (2003). Responses to ozone are increased in obese mice. Journal of Applied Physiology, 95 (3), 938–945. Shore, S. A., Schwartzman, I. N., Mellema, M. S., Flynt, L., Imrich, A., and Johnston, R. A. (2005). Effect of leptin on allergic airway responses in mice. Journal of Allergy and Clinical Immunology, 115, 103–109. Siegel, M. D., Zhang, D. H., Ray, P., and Ray, A. (1995). Activation of the interleukin-5 promoter by cAMP in murine EL-4 cells requires the GATA-3 and CLE0 elements. Journal of Biological Chemistry, 270 (41), 24548–24555. Siegmund, B., Sennello, J. A., Jones-Carson, J., Gamboni-Robertson, F., Lehr, H. A., Batra, A., Fedke, I., Zeitz, M., and Fantuzzi, G. (2004a). Leptin receptor expression on T lymphocytes modulates chronic intestinal inflammation in mice. Gut, 53, 965–972. Siegmund, B., Sennello, J. A., Lehr, H. A., Batra, A., Fedke, I., Zeitz, M., and Fantuzzi, G. (2004b). Development of intestinal inflammation in double IL-10– and leptin-deficient mice. Journal of Leukocyte Biology, 76, 782–786. Sierra-Honigmann, M. R., Nath, A. K., Murakami, C., Garcia-Cardena, G., Papapetropoulos, A., Sessa, W. C., Madge, L. A., Schechner, J. S., Schwabb, M. B., Polverini, P. J., and Flores-Riveros, J. R. (1998). Biological action of leptin as an angiogenic factor. Science, 281, 1683–1686. Singhal, A., Farooqi, I. S., Cole, T. J., O’Rahilly, S., Fewtrell, M., Kattenhorn, M., Lucas, A., and Deanfield, J. (2002). Influence of leptin on arterial distensibility: a novel link between obesity and cardiovascular disease? Circulation, 106, 1919–1924. Sitaraman, S., Liu, X., Charrier, L., Gu, L. H., Ziegler, T. R., Gewirtz, A., and Merlin, D. (2004). Colonic leptin: source of a novel proinflammatory cytokine involved in IBD. FASEB J., 18, 696–698. Skurk, T., Kolb, H., Muller-Scholze, S., Rohrig, K., Hauner, H., and Herder, C. (2005). The proatherogenic cytokine interleukin-18 is
1010
V. Psychoneuroimmunology and Pathophysiology
secreted by human adipocytes. Eur. J. Endocrinol., 152 (6), 863–868. Smith, S. R., Lovejoy, J. C., Greenway, F., Ryan, D., deJonge, L., de la Bretonne, J., Volafova, J., and Bray, G. A. (2001). Contributions of total body fat, abdominal subcutaneous adipose tissue compartments, and visceral adipose tissue to the metabolic complications of obesity. Metabolism, 50 (4), 425–435. Snehalatha, C., Mukesh, B., Simon, M., Viswanathan, V., Haffner, S. M., and Ramachandran, A. (2003). Plasma adiponectin is an independent predictor of type 2 diabetes in Asian Indians. Diabetes Care, 26, 3226–3229. Somm, E., Henrichot, E., Pernin, A., Juge-Aubry, C. E., Muzzin, P., Dayer, J. M., Nicklin, M. J., and Meier, C. A. (2005). Decreased fat mass in interleukin-1 receptor antagonist-deficient mice: impact on adipogenesis, food intake, and energy expenditure. Diabetes, 54 (12), 3503–3509. Spranger, J., Kroke, A., Mohlig, M., Bergmann, M. M., Ristow, M., Boeing, H., and Pfeiffer, A. F. (2003). Adiponectin and protection against type 2 diabetes mellitus. Lancet, 361, 226–228. Standaert, M. L., Sajan, M. P., Miura, A., Kanoh, Y., Chen, H. C., Farese, R. V., Jr., and Farese, R. V. (2004). Insulin-induced activation of atypical protein kinase C, but not protein kinase B, is maintained in diabetic (ob/ob and Goto-Kakazaki) liver. Contrasting insulin signaling patterns in liver versus muscle define phenotypes of type 2 diabetic and high fat-induced insulinresistant states. Journal of Biological Chemistry, 279 (24), 24929– 24934. Stefan, N., Machicao, F., Staiger, H., Machann, J., Schick, F., Tschritter, O., Spieth, C., Weigert, C., Fritsche, A., Stumvoll, M., and Haring, H. U. (2005). Polymorphisms in the gene encoding adiponectin receptor 1 are associated with insulin resistance and high liver fat. Diabetologia, 48, 2282–2291. Sugimoto, R., Enjoji, M., Kohjima, M., Tsuruta, S., Fukushima, M., Iwao, M., Sonta, T., Kotoh, K., Inoguchi, T., and Nakamuta, M. (2005). High glucose stimulates hepatic stellate cells to proliferate and to produce collagen through free radical production and activation of mitogen-activated protein kinase. Liver Int., 25 (5), 1018–1026. Symmons, D. P. (2005). Looking back: rheumatoid arthritis— aetiology, occurrence and mortality. In Rheumatology (pp. 44; Suppl 4: iv14–iv17). Oxford. Szabo, C., Hasko, G., Zingarelli, B., Nemeth, Z. H., Salzman, A. L., Kvetan, V., Pastores, S. M., and Vizi, E. S. (1997). Isoproterenol regulates tumour necrosis factor, interleukin-10, interleukin-6 and nitric oxide production and protects against the development of vascular hyporeactivity in endotoxaemia. Immunology, 90 (1), 95–100. Takeda, R., Suzuki, E., Satonaka, H., Oba, S., Nishimatsu, H., Omata, M., Fujita, T., Nagai, R., and Hirata, Y. (2005). Blockade of endogenous cytokines mitigates neointimal formation in obese Zucker rats. Circulation, 111 (11), 1398–1406. Tan, K. C., Xu, A., Chow, W. S., Lam, M. C., Ai, V. H., Tam, S. C., and Lam, K. S. (2004). Hypoadiponectinemia is associated with impaired endothelium-dependent vasodilation. Journal of Clinical Endocrinology & Metabolism, 89, 765–769. Tataranni, P. A., and Ortega, E. (2005). A burning question: does an adipokine-induced activation of the immune system mediate the effect of overnutrition on type 2 diabetes? Diabetes, 54 (4), 917–927. Torti, F. M., Dieckmann, B., Beutler, B., Cerami, A., and Ringold, G. M. (1985). A macrophage factor inhibits adipocyte gene expression: an in vitro model of cachexia. Science, 229 (4716), 867–869.
Tracey, K. J. (2002). The inflammatory reflex. Nature, 420 (6917), 853–859. Trayhurn, P. (1979). Thermoregulation in the diabetic-obese (db/db) mouse. The role of non-shivering thermogenesis in energy balance. Pflugers Arch, 380 (3), 227–232. Tsatsanis, C., Zacharioudaki, V., Androulidaki, A., Dermitzaki, E., Charalampopoulos, I., Minas, V., Gravanis, A., and Margioris, A. N. (2005). Adiponectin induces TNF-alpha and IL-6 in macrophages and promotes tolerance to itself and other proinflammatory stimuli. Biochem. Biophys. Res. Commun., 335 (4), 1254–1263. Tsuchida, A., Yamauchi, T., Takekawa, S., Hada, Y., Ito, Y., Maki, T., and Kadowaki, T. (2005). Peroxisome proliferator-activated receptor (PPAR)α activation increases adiponectin receptors and reduces obesity-related inflammation in adipose tissue: comparison of activation of PPARα, PPARγ, and their combination. Diabetes, 54 (12), 3358–3370. Tuzun, A., Uygun, A., Yesilova, Z., Ozel, A. M., Erdil, A., Yaman, H., Bagci, S., Gulsen, M., Karaeren, N., and Dagalp, K. (2004). Leptin levels in the acute stage of ulcerative colitis. Journal of Gastroenterology & Hepatology, 19, 428–432. Uysal, K. T., Wiesbrock, S. M., Marino, M. W., and Hotamisligil, G. S. (1997). Protection from obesity-induced insulin resistance in mice lacking TNF-alpha function. Nature, 389 (6651), 610– 614. Vachharajani, V., Russell, J. M., Scott, K. L., Conrad, S., Stokes, K. Y., Tallam, L., Hall, J., and Granger, D. N. (2005). Obesity exacerbates sepsis-induced inflammation and microvascular dysfunction in mouse brain. Microcirculation, 12, 183–194. van der Poll, T., Jansen, J., Endert, E., Sauerwein, H. P., and van Deventer, S. J. (1994). Noradrenaline inhibits lipopolysaccharide-induced tumor necrosis factor and interleukin 6 production in human whole blood. Infect. Immun., 62 (5), 2046–2050. van der Pouw Kraan, T. C., Boeije, L. C., Smeenk, R. J., Wijdenes, J., and Aarden, L. A. (1995). Prostaglandin-E2 is a potent inhibitor of human interleukin 12 production. J. Exp. Med., 181 (2), 775–779. Vieira, V. J., Ronan, A. M., Windt, M. R., and Tagliaferro, A. R. (2005). Elevated atopy in healthy obese women. American Journal of Clinical Nutrition, 82 (3), 504–509. Villena, J. A., Cousin, B., Penicaud, L., and Casteilla, L. (2001). Adipose tissues display differential phagocytic and microbicidal activities depending on their localization. Int. J. Obes. Relat. Metab. Disord., 25 (9), 1275–1280. Wagteveld, A. J., van Zanten, A. K., Esselink, M. T., Halie, M. R., and Vellenga, E. (1991). Expression and regulation of IL-4 receptors on human monocytes and acute myeloblastic leukemic cells. Leukemia, 5 (9), 782–788. Wallenius, V., Wallenius, K., Ahren, B., Rudling, M., Carlsten, H., Dickson, S. L., Ohlsson, C., and Jansson, J. O. (2002). Interleukin6–deficient mice develop mature-onset obesity. Nat. Med., 8 (1), 75–79. Wang, D., Wei, Y., and Pagliassotti, M. J. (2006). Saturated fatty acids promote endoplasmic reticulum stress and liver injury in rats with hepatic steatosis. Endocrinology, 147 (2), 943–951. Wang, M. Y., Orci, L., Ravazzola, M., and Unger, R. H. (2005). Fat storage in adipocytes requires inactivation of leptin’s paracrine activity: implications for treatment of human obesity. Proc. Natl. Acad. Sci. USA, 102 (50), 18011–18016. Wang, W., Poole, B., Mitra, A., Falk, S., Fantuzzi, G., Lucia, S., and Schrier, R. (2004). Role of leptin deficiency in early acute renal failure during endotoxemia in ob/ob mice. Journal of American Society of Nephrology, 15, 645–649.
46. Obesity and Immunity Weiss, S. T. (2005). Obesity: insight into the origins of asthma. Nature Immunology, 6, 537–539. Wilson, J. A., and Clark, J. J. (2004). Obesity: impediment to postsurgical wound healing. Advances in Skin & Wound Care, 17, 426–435. Wood, I. S., Wang, B., Jenkins, J. R., and Trayhurn, P. (2005). The pro-inflammatory cytokine IL-18 is expressed in human adipose tissue and strongly upregulated by TNF-alpha in human adipocytes. Biochem. Biophys. Res. Commun., 337 (2), 422–429. Xu, A., Yin, S., Wong, L., Chan, K. W., and Lam, K. S. (2004). Adiponectin ameliorates dyslipidemia induced by the human immunodeficiency virus protease inhibitor ritonavir in mice. Endocrinology, 145 (2), 487–494. Yaegashi, M., Jean, R., Zuriqat, M., Noack, S., and Homel, P. (2005). Outcome of morbid obesity in the intensive care unit. Journal of Intensive Care Medicine, 20, 147–154. Yamamoto, K., Kiyohara, T., Murayama, Y., Kihara, S., Okamoto, Y., Funahashi, T., Ito, T., Nezu, R., Tsutsui, S., Miyagawa, J. I., Tamura, S., Matsuzawa, Y., Shimomura, I., and Shinomura, Y. (2005). Production of adiponectin, an anti-inflammatory protein, in mesenteric adipose tissue in Crohn’s disease. Gut, 54, 789–796. Yamauchi, T., Kamon, J., Waki, H., Imai, Y., Shimozawa, N., Hioki, K., Uchida, S., Ito, Y., Takakuwa, K., Matsui, J., Takata, M., Eto, K., Terauchi, Y., Komeda, K., Tsunoda, M., Murakami, K., Ohnishi, Y., Naitoh, T., Yamamura, K., Ueyama, Y., Froguel, P., Kimura, S., Nagai, R., and Kadowaki, T. (2003). Globular adiponectin protected ob/ob mice from diabetes and ApoE-deficient
1011
mice from atherosclerosis. Journal of Biological Chemistry, 278, 2461–2468. Yang, Q., Graham, T. E., Mody, N., Preitner, F., Peroni, O. D., Zabolotny, J. M., Kotani, K., Quadro, L., and Kahn, B. B. (2005). Serum retinol binding protein 4 contributes to insulin resistance in obesity and type 2 diabetes. Nature, 436, 356–362. Yang, S., Zhu, H., Li, Y., Lin, H., Gabrielson, K., Trush, M. A., and Diehl, A. M. (2000). Mitochondrial adaptations to obesity-related oxidant stress. Arch. Biochem. Biophys., 378 (2), 259–268. Yin, T., Tsang, M. L., and Yang, Y. C. (1994). JAK1 kinase forms complexes with interleukin-4 receptor and 4PS/insulin receptor substrate-1–like protein and is activated by interleukin-4 and interleukin-9 in T lymphocytes. Journal of Biological Chemistry, 269 (43), 26614–26617. Yokota, T., Oritani, K., Takahashi, I., Ishikawa, J., Matsuyama, A., Ouchi, N., Kihara, S., Funahashi, T., Tenner, A. J., Tomiyama, Y., and Matsuzawa, Y. (2000). Adiponectin, a new member of the family of soluble defense collagens, negatively regulates the growth of myelomonocytic progenitors and the functions of macrophages. Blood, 96 (5), 1723–1732. Zhang, F., Basinski, M. B., Beals, J. M., Briggs, S. L., Churgay, L. M., Clawson, D. K., DiMarchi, R. D., Furman, T. C., Hale, J. E., Hsiung, H. M., Schoner, B. E., Smith, D. P., Zhang, X. Y., Wery, J. P., and Schevitz, R. W. (1997). Crystal structure of the obese protein leptin-E100. Nature, 387 (6629), 206–209. Zhang, Y., Proenca, R., Maffei, M., Barone, M., Leopold, L., and Friedman, J. M. (1994). Positional cloning of the mouse obese gene and its human homologue. Nature, 372 (6505), 425–432.
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47 Endogenous Extracellular Hsp72 Release Is an Adaptive Feature of the Acute Stress Response MONIKA FLESHNER, CRAIG M. SHARKEY, MOLLY NICKERSON, AND JOHN D. JOHNSON
I. INTRODUCTION 1013 II. STRESS AND INTRACELLULAR HEAT SHOCK PROTEIN 72 (HSP72) 1014 III. STRESS AND ENDOGENOUS EXTRACELLULAR HEAT SHOCK PROTEINS 1015 IV. RELEASING SIGNAL(S), AND CELLULAR SOURCE(S) OF STRESS-INDUCED EXTRACELLULAR HSP72 1016 V. IMMUNOLOGICAL FUNCTION(S) OF EXTRACELLULAR HSP72 1023 VI. CONCLUSIONS AND IMPLICATIONS 1027
response, and that eHsp72 may function as an endogenous “danger signal” leading to the facilitation of immune responses during times of acute stress.
I. INTRODUCTION A. Overview The release of endogenous eHsp72 may be a previously unrecognized feature of the acute stress response. The generalizability, releasing signal(s), cellular source(s), and in vivo function(s) of endogenous eHsp72 have only recently been explored. In the current chapter we describe results from our research that endogenous eHsp72 release is indeed a generalized response such that eHsp72 increases in the blood of males and females, and rodents and humans after exposure to a variety of stressors, including conditioned contextual fear, predatory stress, tailshock stress, exhaustive exercise stress, and hand shock stress. Furthermore, we report that eHsp72 is rapidly (<15 minutes) released into the blood via an α1-adrenergic receptor (ADR)– mediated releasing signal. Specifically, α1-ADR blockade (prazosin) prevents stress-induced increases of eHsp72 in the blood, and an α1-ADR agonist (phenylephrine) in the absence of stress releases eHsp72 into the blood (Fleshner and Johnson, 2005; Johnson et al., 2005). The cellular source or sources of eHsp72 released into the circulation remain a topic of ongoing
ABSTRACT Exposure to acute (<4 hours) mental or physical stressors stimulates a cascade of behavioral and physiological responses that facilitate fight/flight responses and improve an organism’s chances of survival. At the cellular level, one important and highly conserved response to stress is upregulation of heat shock proteins, specifically heat shock protein 72 (Hsp72). Although the mechanisms of induction and functions of intracellular Hsp72 have been thoroughly studied, only recently has it been discovered that extracellular Hsp72 (eHsp72) can be rapidly released into the blood after exposure to either mental or physical stressors, and that this response is conserved across gender and species. Based on these experimental results, we hypothesize that endogenous eHsp72 release may be a previously unrecognized feature of the acute stress PSYCHONEUROIMMUNOLOGY, 4E VOLUME II
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Copyright © 2007 by Elsevier, Inc. All rights of reproduction in any form reserved.
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investigation. We have tested the effect of acute tailshock stressor exposure on intracellular Hsp72 in a variety of tissues, including the pituitary, adrenal glands, spleen, liver, mesenteric lymph nodes and brown adipose tissue. Here, we present data that each of these tissues is stress responsive and robustly upregulates intracellular Hsp72 content. To date, however, a single tissue or single cellular source of the eHsp72 detected in the blood after acute stressor exposure remains unidentified. Finally, we hypothesize that endogenous eHsp72 functions in vivo to facilitate immune responses. This is based on several observations. First, in vivo injection of eHsp72 at the site of bacterial challenge facilitates inflammation recovery (Campisi et al., 2003a). Second, both blockade of eHsp72 release and extravasation from the blood into the inflammatory site prevent the positive effects of stress on host anti-microbial responses. The goal of this chapter, therefore, is to develop the hypothesis that elevations of endogenous eHsp72 are an adaptive feature of the acute stress response. Once released into the circulation via an α1-ADR–mediated signal, eHsp72 may function as an endogenous “danger signal” for the immune system. Hence, in the presence of bacterial challenge or at a site of inflammation, endogenous eHsp72 potentiates the release of antimicrobial products such as nitric oxide (NO) from macrophages/neutrophils resulting in facilitated killing of, and recovery from, in vivo bacterial challenge. It is important to note that the immune effects of Hsps vary depending on several factors, including the specific Hsp family (e.g., Hsp60, Hsp70, Hsp90), the cellular source of the Hsp (e.g., normal self, cancerous self, viral infected self, bacterial), the cellular location of the Hsp (e.g., intracellular, cell surface, circulating), and the physiological circumstances of the Hsp expression (oxidative stress, bacterial infection, viral infection, psychological stress, physical stress, whole organism vs. localized cellular stress). Thus, our hypothesis does not encompass every immunological function of Hsps and may be specific for the immunomodulatory function of endogenous eHsp72 released after exposure to an acute whole organism stressor.
II. STRESS AND INTRACELLULAR HEAT SHOCK PROTEIN 72 (HSP72) A. Induction Signals Heat shock proteins (Hsp) consist of several families of highly conserved proteins that play a role in a number of important cellular functions (Morimoto,
1994). The first observations demonstrating the induction of intracellular heat shock proteins were reported in 1962 when Ritossa and colleagues noted that Drosophila exposed to temperature shock demonstrated an unusual gene expression profile (Ritossa, 1962). In 1974, the term heat shock protein was first coined (Tissieres et al., 1974). The focus of the current review is on one member of the 70-kDa Hsp (Hsp70) family of proteins, Hsp72. The Hsp70 family of proteins includes the constitutive 73-kDa protein (HSC73) and a highly stress-inducible 72-kDa protein (Hsp72) (Hartl, 1996; Morimoto, 1994). Intracellular Hsp72 is found in nearly every cell of the body and can be upregulated after exposure to a variety of cellular and whole organism stressors (Hartl, 1996; Morimoto, 1994). Although basal concentrations of Hsp72 are low in most tissues, high concentrations of intracellular Hsp72 can be found in the absence of stressors in some tissues such as the frontal cortex (Heneka et al., 2003), pituitary (Campisi et al., 2003b), adrenal (Campisi et al., 2003), and brown fat (Matz et al., 1996a; Matz et al., 1996b). Intracellular Hsp72 induction has been reported after exposure to a variety of whole organism physical stressors including heat (Kregel, 2002), tailshock stress (Campisi et al., 2003a), and restraint (Udelsman, 1991; Udelsman et al., 1993). Interestingly, induction of intracellular Hsp72 is not restricted to physical stressors. We recently reported that the experience of predatory fear, exposure of rats to a cat with no physical contact, increases intracellular Hsp72 in the brain (Fleshner et al., 2004). A great deal is understood about intracellular Hsp72 protein induction signals and synthesis. The gene for Hsp72 contains at least two regulatory elements that interact with heat shock transcription factors (HSFs) (Wu, 1995; Wu et al., 1986). Specifically, the induction of Hsp72 protein requires HSF1 binding to the heat shock element (HSE) in the promoter region of the Hsp70 gene (Pirkkala et al., 2001). Hsp70 mRNA is transcribed, resulting in the synthesis and accumulation of cytosolic Hsp72 protein (Kregel, 2002). Many factors induce transcription and translation of intracellular Hsp72 protein and vary depending on the tissue examined. Stress-induced signals reported to increase intracellular Hsp72 concentrations include the following: (1) adrenocorticotropin hormone (ACTH) (Blake, 1994; Blake et al., 1991), (2) corticosterone (CORT) (Cvoro and Matic, 2002; Sun et al., 2000; Valen et al., 2000), (3) glycogen deprivation (Febbraio et al., 2002b; Santoro, 2000), (4) norepinephrine (NE) or epinephrine (E) (Heneka et al., 2003; Matz et al., 1996a; Matz et al., 1996b; Maloyan and Horowitz, 2002; Paroo and Noble, 1999; Udelsman et al., 1994a; Udelsman et al., 1994b), and (5) heat or hyperthermia (Cvoro and Matic, 2002;
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King et al., 2002; Kregel and Moseley, 1996; Redaelli et al., 2001; Thomas et al., 2002).
B. Intracellular Hsp72 Function The cellular functions of intracellular Hsp72 have been thoroughly studied and include limiting protein aggregation, facilitating protein refolding, and chaperoning proteins (Hartl, 1996; Morimoto, 1994). These cellular functions en masse serve to improve cell survival in the face of a broad array of cellular stressors (Hartl, 1996; Morimoto, 1994). There are many examples from the literature that convincingly demonstrate that induction of Hsp72 is not simply a consequence of cellular stress, but rather clearly improves resistance to death after cellular insult. It has been recently reported, for example, that Hsp72 induction protects neurons (Arieli et al., 2003; Kelly et al., 2002), heart (Hamilton et al., 2003; Paroo et al., 2002b), kidney (Mao et al., 2003; Ruchalski et al., 2003), intestine (Liu et al., 2003), and liver (Kregel, 2002), from heat and/or ischemia-induced apoptosis and cell death. In addition to basic cell survival functions, the induction of intracellular Hsp72 in monocytes can directly impact immune function. The induction of Hsp72 gene transcription can suppress inflammatory cytokine gene transcription (Cahill et al., 1996; Cahill et al., 1997; Housby et al., 1999). Thus, intracellular Hsp72 induction in macrophages has been postulated to serve as a negative regulator of inflammatory cytokines (Ding et al., 2001; Ianaro et al., 2001; Xie et al., 2002a; Xie et al., 2002b). The downregulation of inflammatory cytokines protects the cell from high levels of inflammatory cytokines that can result in injury or death to innocent bystander cells during inflammation (Lindquist and Craig, 1988; Yoo et al., 2000; Zugel and Kaufmann, 1999). One extreme example of this function can be found in HSF-1–deficient mice. These mice lack the ability to upregulate intracellular Hsp72 and have reduced survival and excessive TNF-α after a single injection of LPS compared to wild-type controls (Xiao et al., 1999). In addition to limiting inflammatory cytokine transcription, intracellular Hsps also chaperone peptides for immune presentation in major histocampatibility (MHCI) molecules (Srivastava, 2002), contributing to cross-priming or the loading of vesicular peptides into MHCI molecules (Martin et al., 2003). More recently, it has been established that cell surface Hsps also modulate immunity. For example, it has been reported that Hsps can be recognized by natural killer (NK) cells and cytotoxic T lymphocytes (CTLs) when expressed on the surface of stressed cells (Gastpar et al., 2005; Hickman-Miller and Hildebrand, 2004; Lehner et al.,
2004; Multhoff, 2002; Multhoff and Botzler, 1998; Multhoff et al., 1995; Multhoff et al., 1999; Wang et al., 2005). This recognition appears to be direct and may not involve the MHCI pathway. The immunological function of Hsps in this context has been suggested to stimulate anti-cancer immunity (Ciocca and Calderwood, 2005; Srivastava and Heike, 1991), exacerbate chronic inflammatory disease states (Pockley, 2003; Prohaszka and Fust, 2004), and/or inhibit chronic inflammation (van Eden, 1998; van Eden et al., 2003; van Eden et al., 2005). In addition, there is evidence that extracellular and cell surface expression of Hsps, especially Hsp60, can contribute to autoimmune responses due to infection-induced molecular mimicry or cross-recognition between mammalian and microbial Hsps (Kaufmann, 1990a; Kaufmann, 1990b). Thus, the immunological function of intracellular and cell surface Hsp72 is complex. Finally, there is evidence that secreted extracellular Hsps can directly activate macrophage, neutrophil, and dendritic cells through Toll-like receptors (TLR) (Asea et al., 2000b; Asea et al., 2002; Heine and Lien, 2003; Prohaszka and Fust, 2004; Vabulas et al., 2002), as well as activate the complement cascade (Prohaszka et al., 2002). The focus of the current review is on the immunophysiology of Hsp72 in this specific context, i.e., secreted and extracellular. In the remainder of the chapter, we will describe the generalizability, releasing signal(s), cellular source(s), and in vivo function(s) of stress-induced endogenous eHsp72.
III. STRESS AND ENDOGENOUS EXTRACELLULAR HEAT SHOCK PROTEINS A. Introduction Clearly, a great deal is already understood about intracellular and cell surface function(s) of Hsp72; however, the focus of the current proposal is stressinduced release of eHsp72. We have chosen to focus on eHsp72 because stress-induced release of endogenous eHsp72 into the blood has only recently been documented and very little is understood about its unique regulation. Understanding more about the stress-induced eHsp72 response is important because it may contribute to a variety of stress effects. In fact, we and others have proposed that the function of in vivo endogenous eHsp72 is likely context dependent. For example, in a normal physiological state eHsp72 facilitates immunity, whereas in a pathophysiological state eHsp72 may exacerbate inflammatory diseases like atherosclerosis, inflammatory bowel disease, and Alzheimer’s disease. This idea requires additional
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investigation because, depending on the circumstances, eHsp72 can also stimulate anti-inflammatory cytokines (Pockley, 2003; van Eden et al., 2005; Wang et al., 2005). The first reports that eHsp72 was detectable in the circulation of humans were published by Pockley and colleagues in 2000. This group reported that people suffering from a variety of disease states such as renal disease (Wright et al., 2000), hypertension (Pockley et al., 2002), and atherosclerosis (Pockley et al., 2003) have chronically elevated basal levels of eHsp72 relative to healthy age-matched controls. In addition to elevated basal eHsp72 associated with disease pathology, Dybdahl et al. (2002) reported that patients with coronary artery disease have an acute increase in eHsp72 in response to the stress of coronary bypass surgery. Not long after these reports, we (Campisi and Fleshner, 2003; Campisi et al., 2003a; Fleshner et al., 2003) and Febbraio et al. (Febbraio et al., 2002a; Walsh et al., 2001) reported that organisms in the absence of clinical disease states also rapidly increase the concentration of eHsp72 in blood after exposure to acute stressors. These papers first demonstrated that an increase of endogenous eHsp72 in the blood occurs in healthy organisms after exposure to acute stressors, and led us to suggest that stress-induced eHsp72 release may be a previously unrecognized feature of the normal stress response. It should be noted that there are some reports in the literature that eHsp60 (another species of Hsp) may also increase with chronic stress in humans (Lewthwaite et al., 2002), bind to the surface of macrophages (Habich et al., 2002), and stimulate proinflammatory cytokines (Kol et al., 2000). Based on our preliminary studies, however, exposure to acute stressors does not increase eHsp60 in the blood. In fact, eHsp60 is not detectable in the blood of pathogen-free rats in normal physiological conditions (unpublished observations). Our research, therefore, has focused on acute stress-induced release of endogenous eHsp72.
1. Stressor Exposure Releases eHsp72 in Both Males and Females The first supposition is that the eHsp72 response should occur in both males and females. No previous research has examined the effect of gender on acute stress-induced release of extracellular Hsp72. There is, however, evidence that the intracellular Hsp72 induction in cardiac (Paroo et al., 2002b) and skeletal muscle (Paroo et al., 1999; Paroo et al., 2002) is reduced in female compared to male rodents, and that estrogen may be responsible. We recently completed a series of studies testing the effect of our standard tailshock stressor (100, 1.6mA, 5-second tailshocks with ∼60-second random inter-trial interval) on eHsp72 increases in adult female F344 rats. Male and female F344 rats were exposed to either no stress or tailshock. Immediately after stressor exposure, blood samples were collected and plasma levels of eHsp72 were measured using ELISA (StressGen). Clearly, tailshock increased eHsp72 equally in both male and female rats (Figure 1). It is possible, however, given the reported interactions between estrogen and Hsp72, that eHsp72 may be affected by the stage of estrus in females. Thus, in the next study, the phase of estrus was staged in the female rats prior to stressor exposure by examining vaginal smears. A vaginal smear contains cells whose morphology changes in relationship to the estrous cycle. The accuracy of staging was verified by measuring blood levels of estrogen. Estrogen levels spike at the end of proestrus, are lowest during estrus, and slowly rise during diestrus. Figure 2 depicts the
B. Generalizability of Stress-induced eHsp72 Release Since these initial publications, we have characterized the stress-induced increase in endogenous eHsp72. We propose that eHsp72 release is a common and important feature of the acute stress response. If this is true, then one would expect that the eHsp72 response (1) will occur in males and females, (2) should be generalizable across acute stressors and express temporal dynamics that are associated with stressor onset/ offset, and (3) should be common across animal species including humans. Our experimental findings support these suppositions.
FIGURE 1 Adult male and female Fischer 344 rats (n = 12 per group) were either left in their home cage (No Stress) or exposed to 100, 5 s, 1.6 mA tailshocks with a random inter-trial interval of 60 seconds (Stress). Immediately after stressor exposure, animals were rapidly decapitated; blood was collected and spun down. Measurement of plasma via ELISA (StressGen) reveals a robust and similar effect of stress on the presence of eHsp72 in both male and female rats (P < .0001).
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FIGURE 2 Adult female Fischer 344 rats (n = 4–10 per group) were either left in their home cage (No Stress) or exposed to 100, 5 s, 1.6 mA tailshocks with a random intertrial interval of 60 seconds (Stress) and immediately decapitated after stressor termination. Phase of estrous was determined using vaginal smear. Blood was collected with EDTA, spun, and plasma Hsp72 was assessed using ELISA (StressGen). There was a significant effect of stress on the expression of Hsp72 (P < .0001), but there was neither a main effect of estrous phase (P = .3332) nor an interaction between stress and estrous phase (P = .1199).
stress-induced eHsp72 response across the estrous cycle. Stress elevated eHsp72 in every phase of the cycle with a slightly greater increase during estrus than during proestrus and diestrus. These data demonstrate that stress-induced release of eHsp72 is not restricted to gender and remains relatively constant across the estrous cycle. 2. The Generalizability and Kinetics of Stress-induced eHsp72 Release The next issues to consider are the generalizability across stressors and the kinetics of the eHsp72 response. Evidence suggests that stress-induced release of eHsp72 does occur after exposure to a variety of acute psychological and/or physical stressors. We have conducted two studies that activate the stress response after exposure to fear-evoking stimuli using specifically the conditioned contextual fear and predatory stress paradigms. The conditioned contextual fear paradigm involves exposing rats to five, 1.8 mA, 2-second footshocks delivered in a specific environment or context (Barrientos et al., 2002; Fleshner et al., 1997; Pugh, 1997; Rudy, 1993; Rudy, 1994; Rudy and Morledge, 1994; Rudy and O’Reilly, 1999). As a consequence of this experience, rats will develop a conditioned fear response to cues in that environment or context. Seven days after conditioning, the fear response can be initiated by re-exposing the rats to the original context with no additional footshocks. The fear-evoking memory of the context is very resilient
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and persists for many days after the initial conditioning experience. In collaboration with Dr. Jerry Rudy (University of Colorado), we have generated preliminary data (not shown) that conditioned contextual fear induces the release of eHsp72 into the blood after reexposure to the context (20 minutes) in the absence of footshocks. These animals also show clear evidence of conditioned contextual fear or freezing behavior when placed in the context. These results demonstrate that exposure to a psychologically fear-evoking situation is sufficient to stimulate eHsp72. A second example that exposure to a fear-evoking stimulus can release eHsp72 comes from a study using a predatory-fear paradigm. In collaboration with Dr. David Diamond (University of South Florida), we report that rats exposed to a cat (90 minutes with no physical contact) release eHsp72 into the circulation (Fleshner et al., 2004). We previously documented that exposure to the predatory stress paradigm is sufficient to stimulate a three- to five-fold elevation in circulating corticosterone (Diamond et al., 1999; Fleshner et al., 2004; Mesches et al., 1999; Park et al., 2001). Thus, these studies suggest that exposure to fear-evoking stimuli will trigger the acute stress response in the absence of physical challenge, including the release of eHsp72 into the blood. We recently completed a study that extends our previous kinetics studies (Campisi et al., 2003a; Fleshner and Johnson, 2005) and examines the duration of tailshock-induced eHsp72 elevations in the blood. In this study, adult male F344 rats were exposed to either no stress or tailshock stress. Rats were sacrificed and trunk blood collected immediately after, 1 hour, 3 hours, 24 hours, and 72 hours after tailshock termination. As shown in Figure 3, eHsp72 concentration in the blood is highest immediately after 100, 1.6mA, 5-second tailshocks and remains reliably elevated above basal concentrations 1, 3, and 24 hours, and returning to basal levels 72 hours after stressor termination. It remains unknown if the immunological or functional consequences of eHsp72 are dependent on prolonged elevations of eHsp72 or if transient increases in eHsp72 will have long-lived immunological effects. Our evidence, to date, suggests that both may be true. Hsp72 must be present in the circulation at the time of pathogenic challenge to affect innate host defense (Campisi et al., 2003a), but such changes result in long-term improvements in acquired immunity that are detectable many days after eHsp72 concentration have returned to basal levels. 3. eHsp72 Release Is Not Species Specific If eHsp72 is a common feature of the acute stress response, one might expect this response to be found
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IV. RELEASING SIGNAL(S), AND CELLULAR SOURCE(S) OF STRESSINDUCED EXTRACELLULAR HSP72 A. Introduction
FIGURE 3 Adult male Fischer 344 rats (n = 8 per group) were either left in their home cage (No Stress) or exposed to 100, 5 s, 1.6 mA tailshocks with a random inter-trial interval of 60 seconds (Stress). Animals were sacrificed at various time-points following stressor termination: Immediately, 1 hour, 3 hours, 24 hours, or 72 hours. All animals except those that were sacrificed immediately were returned to their home cages. Animals were rapidly decapitated and trunk blood was collected over EDTA, spun, and plasma was assayed via ELISA for Hsp72. Circulating Hsp72 was significantly elevated above No Stress animals immediately following stressor (p = .0004), at 1 hour (p = .0321), 3 hours (p = .05), 24 hours (p = .0266) and returned to No Stress levels by 72 hours.
across animal species, including humans. Based on the literature and our published work, exposure to either intense acute exercise stress (120 minutes) or intermittent shock stress (90 minutes) increases eHsp72 in both humans (Febbraio et al., 2002a) and rodents (Campisi and Fleshner, 2003; Campisi et al., 2003a). In addition, we have preliminary data (not shown) collected in collaboration with Dr. Roger Enoka (University of Colorado) that eHsp72 is rapidly increased in the blood of humans after exposure to an acute stressor. Humans (19–86 years, n = 36/grp) exposed to uncontrollable, unpredictable handshocks (25, 50–200msec, ∼90–100 V) delivered over 20 minutes had elevated levels of circulating eHsp72 in response to the stressor. This stressor also produced reliable (p < 0.05) elevations in selfreported stress (Visual Analog Scale and Speilburger State/Trait Anxiety Inventory), NE, E, and ACTH (Christou et al., 2004). Interestingly, the increase in eHsp72 produced by stress is significantly correlated with increases in plasma NE (r = 0.46, p = 0.001), and not E or ACTH.
The search for the releasing signals and cellular sources of eHsp72 released into the blood after exposure to acute stress is still ongoing. We have made some progress in our pursuit and, based on the literature and our current data, we hypothesize that exposure to an acute stressor stimulates the release of eHsp72 into the blood via an α1-adrenergic receptor (ADR)–mediated pathway from possibly the mesenteric lymph nodes and/or the vascular endothelial cells, and not from pituitary, adrenal, spleen, liver, or brown adipose tissue.
B. Releasing Signals: Necrosis versus Exocytosis There are currently two potential mechanisms for extracellular Hsp72 release. The first is that eHsp72 is released from the intracellular pool after necrotic or lytic cell death. The second is that eHsp72 is released via a receptor-mediated exocytotic mechanism. 1. Hsp72 Is Released after Necrotic/Lytic Cell Death Gallucci, Loema, and Matzinger (1999) first suggested that Hsp72 is released only in pathological circumstances such as those that result in necrotic/lytic death, and not after apoptosis or programmed cell death. More recently, Basu et al. (2000), Sauter et al. (2000), and Berwin et al. (2001) supported these ideas and demonstrated that, indeed, Hsp72 was released after necrotic/lytic, but not apoptotic, cell death. In these studies, cellular necrosis was induced in vitro by either repeated freeze/thaw exposures (Basu et al., 2000; Berwin et al., 2001; Sauter et al., 2000), hypotonic lysis (Sauter et al., 2000), or viral lysis (Berwin et al., 2001), and necrosis was measured using flow cytometric assessment of Annexin V (AV) + propridium iodide (PI) staining (Del Bino et al., 1999; Hammill et al., 1999; Honda et al., 2000; Lecoeur et al., 2001). The percentage of cells that are necrotic (AV+PI+), apoptotic (AV+PI-) or viable (AV-PI-) can be determined using flow cytometry. Apoptosis was induced by exposure to UV (Basu et al., 2000; Sauter et al., 2000) or serum-depleted culture media (Berwin et al., 2001) and verified using flow cytometric assessment of AV and PI staining. Clearly, the release of eHsp72 via necrotic cell death does occur; however, it likely results in a local, restricted, and tissue-specific increase in eHsp72 at the site of injury. In this local fashion, eHsp72 released
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from necrotic cells likely functions to facilitate local innate immune responses. 2. Hsp72 Is Released by a Receptor-mediated Exocytotic Mechanism In contrast to necrotic/lytic release of eHsp72, we propose that eHsp72 released after exposure to a whole organism psychological and/or physical stressor most likely occurs via an exocytosis pathway in the absence of necrosis. This hypothesis is based on the following observations. First, there is precedent in the literature for an exocytotic mechanism. Glia cells (Guzhova et al., 2001), B-cells (Clayton et al., 2005), and tumors (Gastpar et al., 2005), for example, have been shown to exocytotically release eHsp72. The releasing pathway is independent of the classical protein transport pathway (Broquet et al., 2003; Gastpar et al., 2005; Hightower and Guidon, 1989; Lancaster and Febbraio, 2005) and may involve exosomal packaging of Hsp72 (Clayton et al., 2005; Guzhova et al., 2001; Lancaster and Febbraio, 2005). The details associated with these releasing pathways have been recently reviewed (Johnson and Fleshner, 2006) and will not be, therefore, discussed further here. Second, eHsp72 is elevated in the blood within 10–25 minutes of tailshock onset (Fleshner and Johnson, 2005). The speed of the response suggests the classic protein induction/necrosis release pathway is not likely. Third, as previously described, eHsp72 is increased in the blood after exposure to psychological stressors such as conditioned contextual fear and predatory stress, stressors that are not likely to induce necrosis. Fourth, Febbraio and colleagues (Febbraio et al., 2002a; Walsh et al., 2001) reported that intense exercise (∼65% V02max) increases eHsp72 in blood within 30 minutes of exercise onset and that this occurs in the absence of cellular necrosis (Febbraio et al., 2002a). And fifth, the increases in concentrations of eHsp72 released into the blood are two- to six-fold above baseline (pre-stress) levels, and if necrotic/lytic cell death were the source of eHsp72 in the blood, it would require a large number of cells to simultaneously die a necrotic/lytic death. Although it remains unknown at this time, we hypothesize that the observed increased circulating eHsp72 following exposure to a whole organism stressor is not due to necrosis and is more likely due to a receptor-mediated exocytotic releasing mechanism. 3. Stress-induced eHsp72 Release Involves Norepinephrine and α1-ADRs We are making progress in the search for the stressinduced releasing signal(s) for eHsp72 after exposure to acute stress. The approach we took in our studies
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designed to address this issue was to examine stress hormones that have been both shown to modulate intracellular Hsp72 levels (see above) and are commonly elevated after exposure to most stressors (Cacioppo et al., 1998; Carrasco and Van de Kar, 2003; Fleshner, 1995; Greenwood et al., 2003). Our initial studies, therefore, examined if the pituitary-adrenal and/or the sympathetic nervous system responses to stress were responsible for eHsp72 release. The results of these studies were that neither hypophysectomy (removal of the pituitary) nor adrenalectomy (removal of the adrenal) reduced the effect of tailshock-induced release of eHsp72 (Johnson et al., 2005). Completeness of our surgical dissections was verified by measuring circulation ACTH and corticosterone. These data suggest that neither pituitary (ACTH, etc.) nor adrenal (corticosterone, epinephrine [E], etc.) hormones are necessary for eHsp72 release into the blood. We then examined the role of the sympathetic nervous system and, specifically, norepinephrine (NE) in the stress-induced release of eHsp72. Using pharmacological blockade of adrenergic receptors, we completed a series of studies that tested the effect of labetalol (α1- and β-ADR antagonist), propranolol (βADR antagonist), and prazosin (α1-ADR antagonist) on tailshock-induced release of eHsp72. The results reported in Johnson et al. (2005) were that labetalol and prazosin, but not propranolol, blocked the effect of tailshock on eHsp72. In addition, administration of phenylephrine (α1-ADR agonist) but not isoproterenol (β-ADR agonist) in the absence of stress is sufficient to increase blood concentration of eHsp72. These data support our hypothesis that eHsp72 is being induced and/or released via an α1-ADR–mediated mechanism. We hypothesize that NE released from sympathetic nerve terminals binds to α1-ADRs and stimulates Hsp72 release. We propose that NE, and not E, is responsible because NE binds with a higher affinity to α1-ADRs than does E (Hardman and Limbird, 2001), and adrenalectomy depletes ∼95–99% of E (Hessman et al., 1976; Vollmer et al., 1995) yet has no effect on eHsp72 release after tailshock stress (Johnson et al., 2005). Interestingly, the correlational findings with our human data are also consistent with this idea. Recall, eHsp72 was increased in the blood of hand-shocked stressed humans and that the increase in eHsp72 correlated with elevated NE but not E or ACTH.
C. Cellular Source(s) of Extracellular Hsp72 The cellular source or sources of eHsp72 released into the blood after exposure to acute stress remain unknown. Increases in intracellular Hsp72 after
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exposure to stressors occurs in many tissues in the body although, in most circumstances, intracellular Hsp72 is not released and remains intracellular (Morimoto, 1994; Morimoto, 1998). It is possible, therefore, that no single tissue is the source of eHsp72 released after stress. In addition, the speed of eHsp72 release (within 15 minutes) suggests that whatever tissue or tissues are the source or sources of eHsp72, they must contain high basal concentrations of intracellular Hsp72 protein and/or mRNA, allowing for rapid protein translation. Although it remains a mystery as to which tissue is the cellular source of eHsp72 released into the blood after stressor exposure, several possibilities have been eliminated. The approach we took to address this question was to conduct a series of studies to determine (1) the basal concentrations of intracellular Hsp72 in stress-responsive or secretory tissues, (2) if such tissues upregulated intracellular Hsp72 after exposure to tailshock, and (3) the kinetics of intracellular Hsp72 upregulation. After identifying likely candidates, we then conducted studies to determine if that tissue was the source of Hsp72 that is released into the blood after stress.
were dissected and tissues were processed. Hsp72 protein concentrations are expressed as pg of Hsp72 per μg of protein (Bradford). As shown in Figure 4, basal concentrations of Hsp72 were highest in the adrenals and lowest in the mesenteric lymph nodes. It is important to remember that we are reporting tissue concentration. If we consider basal content per entire organ/gland, however, the liver would likely have the greatest total Hsp72 content simply due to the mass of this organ relative the other tissues like the adrenals or pituitary. Clearly, tailshock stress elevated intracellular Hsp72 content in every tissue examined, with the most rapid and greatest increases occurring in the adrenal, spleen, and mesenteric lymph nodes. The duration of intracellular Hsp72 upregulation after stressor termination also varied. Every tissue returned to basal levels 72 hours after stressor termination except the mesenteric lymph nodes. We did not conduct a kinetics analyses of Hsp72 responses in brown adipose tissue (BAT), but we did assess basal and stress-induced increases in this tissue immediately after tailshock stressor termination (Figure 5). Clearly, BAT has a high concentration of basal intracellular Hsp72, and Hsp72 concentration after tailshock stress was upregulated.
1. Pituitary, Adrenal, Spleen, Mesenteric Lymph Nodes, Liver, and Brown Adipose Tissue Are Potential Sources of eHsp72
2. Pituitary, Adrenal, Spleen, Liver, and Brown Adipose Tissue Are Not Sole Sources of eHsp72
Adult male F344 rats were exposed to either no stress or our standard tailshock procedure. Rats were sacrificed either immediately, 1 hour, 3 hours, 24 hours, or 48 hours after stressor termination. Pituitary, adrenal, spleen, mesenteric lymph nodes, and liver
In view of these results, any or all of the tissues tested could possibly contribute to the pool of eHsp72 found in the blood after stress. We can, however, already exclude the pituitary and the adrenal for further consideration because, as previously described,
FIGURE 4 Adult male Fischer 344 rats (n = 8 per group) were either left in their home cage (No Stress) or exposed to 100, 5 s, 1.6 mA tailshocks with a random inter-trial interval of 60 seconds (Stress). Animals were sacrificed at various time-points following stressor termination: Immediately, 1 hour, 3 hours, 24 hours, or 72 hours. All animals except those that were sacrificed immediately were returned to their home cages. Animals were rapidly decapitated and pituitary, adrenal glands, spleen, mesenteric lymph nodes, and liver were dissected out within 5 minutes, placed in a 1.5 mL eppendorf snap cap tube, and flash frozen in liquid nitrogen and stored at −80°C until time of assay. Prior to assay, tissues were sonicated in sonication buffer, spun in the centrifuge, and the supernatant was collected. Supernatant was assayed using Hsp72 ELISA (StressGen) per manufacturer’s guidelines. In all graphs, *signifies a significant increase in Hsp72 compared to the No Stress group. (A) In the pituitary gland, Hsp72 was significantly elevated above the No Stress group by 1 hour (p = .0031) and at 24 hours (p = .0488). (B) In the adrenal gland, Hsp72 was significantly elevated above the No Stress group immediately following stressor (p < .0001) and sustained at 1 hour (p < .0001), 3 hours (p < .0001), 24 hours (p = .0012), and was no longer significantly elevated at 72 hours. (C) In the spleen, Hsp72 was significantly elevated immediately following stressor (p = .0079) and at 3 hours (p = .0296). Spleen Hsp72 was no longer significantly elevated at 24 hours (p = .10). (D) In the mesenteric lymph nodes, Hsp72 was significantly elevated immediately following stressor (p = .0048) and remained elevated at 1 hour (p = .0006), 3 hours (p = .0007), 24 hours (p = .0029), and 72 hours (p = .0027). (E) In the liver, Hsp72 was significantly elevated above No Stress at 1 hour (p = .0001), 3 hours (p < .0001), 24 hours (p = .0037), and returned to No Stress levels by 72 hours.
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FIGURE 5 Adult male Fischer 344 rats (n = 8 per group) were either left in their home cage (No Stress) or exposed to 100, 5 s, 1.6 mA tailshocks with a random inter-trial interval of 60 seconds (Stress). Animals were sacrificed immediately following termination of stressor via decapitation, and brown adipose tissue located between the scapulae was dissected, placed in a 1.5 mL eppendorf snap tube, flash frozen in liquid nitrogen, and stored at −80°C until time of assay. Prior to assay, tissues were sonicated in sonication buffer, spun in a centrifuge, and supernatant was collected. Supernatant was assayed using Hsp72 ELISA (StressGen) per manufacturer’s guidelines. Fischer PLSD revealed that Hsp72 was significantly elevated in the Stress group compared to No Stress (*p < .05).
neither the removal of the pituitary nor the adrenal reduced the release of eHsp72 after tailshock (Johnson et al., 2005). Thus, we will discuss the possible contribution of the liver, spleen, BAT, and mesenteric lymph nodes. There is evidence in the literature that exercise stress stimulates the rapid release of Hsp72 into the circulation from hepatosplanchnic tissue (Febbraio et al., 2002a). Febbraio et al. (2002a) cannulated the left brachial artery and the hepatic vein of young (22–25 years), healthy males. Blood samples were collected 0, 30, 60, and 120 minutes after the onset of intense exercise on a semi-recumbent cycle ergometer (65% VO2max). Net hepatosplanchnic Hsp72 was calculated by multiplying the hepatosplanchnic venous-arterial Hsp72 difference by the net hepatic blood flow. Reliable increases in hepatosplanchnic eHsp72 were detected by 30 minutes after exercise onset and persisted at 60 and 120 minutes. The authors excluded the muscle as a source of exercise-induced circulating eHsp72 because eHsp72 in the blood can be detected prior to intracellular induction in muscle (Febbraio and Koukoulas, 2000; Febbraio et al., 2002a). We conducted two studies designed to investigate if the hepaticsplanchnic tissue, specifically the spleen and the liver, contributes to stress-induced eHsp72
release from rats. To test the possibility that the spleen was contributing to stress-induced eHsp72, rats were either splenectomized (spleen removed) or sham operated. After 1 week of recovery, rats were exposed to tailshock stress or no stress, sacrificed immediately after stressor termination, and serum levels of eHsp72 measured. Splenectomy had no effect on stress-induced eHsp72 release. To test the possibility that the liver releases eHsp72 into the circulation in response to stress, rats were deeply anesthetized after 0, 10, or 25 tailshocks. Blood samples were collected from a cardiac puncture, the hepatic portal artery (entering liver), and vena cava (exiting liver). If eHsp72 is released from the liver in response to tailshock stress, then after the onset of stress, we should detect a greater concentration of eHsp72 in the vena cava sample than the hepatic portal sample or cardiac sample. Tailshock stress rapidly (after 10 shocks, ∼10 minutes) increased eHsp72, and the increase was equal for all sources suggesting that, in rats under these circumstances, the liver does not release eHsp72. Several observations led to the hypothesis that BAT may be an important cellular source of eHsp72. First, BAT has a high resting concentration of intracellular Hsp72 prior to stressor exposure (∼1.5 μg/g) and would not, therefore, require transcription of mRNA and/or translation of new Hsp72 protein prior to release into the circulation. Second, BAT is densely sympathetically innervated (Foster et al., 1982a; Foster et al., 1982b), making it “wired” to respond very quickly to stress via release of NE from sympathetic nerves. Third, BAT expresses a high concentration of α1-ADRs (Cannon et al., 1996; Granneman et al., 1997; Kikuchi-Utsumi et al., 1997; Raasmaja et al., 1984), the receptor previously shown to mediate stress-induced increases in circulating eHsp72 (Johnson et al., 2005). Fourth, exposure to some types of stress upregulates α1-ADRs in BAT (Kikuchi-Utsumi et al., 1997). Rapid upregulation of α1-ADRs would make brown fat even more responsive to NE. And finally, aging results in a decline of both BAT content in humans (Collins and Surwit, 2001) and blood concentrations of basal eHsp72 in humans (Rea et al., 2001). Thus, with high hopes of success, we conducted the following study. Adult male F344 rats had either their interscapular (between the shoulder blades) BAT removed or had sham surgery. Interscapular BAT in the adult rat is the primary depot of BAT (Foster et al., 1982a; Foster et al., 1982b). After 1 week of recovery, rats were exposed to our standard tailshock procedure, and blood samples were collected immediately after stressor termination. Tailshock stress once again increased plasma eHsp72 concentrations, but removal
47. Extracellular Hsp72 and Immunity
of BAT did not reduce either basal or stress-induced eHsp72 concentrations. Thus, BAT is not the cellular source of eHsp72 released into the blood after stressor exposure. 3. The Search Continues: Mesenteric Lymph Nodes and Vascular Endothelial Cells Remain Potential Sources of eHsp72 The final tissues to be discussed are the mesenteric lymph nodes and vascular endothelium. As shown in Figure 4, the mesenteric lymph nodes have a rapid and persistent upregulation of intracellular Hsp72. In addition, the mesenteric lymph nodes are densely sympathetically innervated (Gulati et al., 1980) and are associated with a rich vasculature, making them possible cellular sources. Other possible cellular sources are endothelial cells of the vasculature. These cells are candidates because they express α1-ADR, are abundant in number, upregulate intracellular Hsp72 after exposure to stressors (Lucas et al., 2000), and have a high secretory capacity (Krishnaswamy et al., 1999). We are continuing to develop approaches to test the possible role of these tissues in stress-induced eHsp72 elevations, and future work will address these possibilities. Until such studies are completed, the search for a cellular source of endogenous eHsp72 continues.
V. IMMUNOLOGICAL FUNCTION(S) OF EXTRACELLULAR HSP72 A. In Vitro Evidence and Potential Controversy Much needs to be learned about the function of eHsp72, especially in vivo. While intracellular Hsp72 induction decreases cytokine production (see above), extracellular Hsp72 can robustly stimulate inflammatory cytokine production and other innate immune responses (Asea et al., 2000a; Breloer et al., 2001; Multhoff et al., 1999). We and others have recently reported that eHsp72 in vitro stimulates inducible NO synthase (Panjwani et al., 2002), NO (Campisi and Fleshner, 2003), TNF-α (Asea et al., 2000b; Campisi and Fleshner, 2003), IL-1β (Asea et al., 2000b; Campisi and Fleshner, 2003), and IL-6 (Asea et al., 2000b; Campisi and Fleshner, 2003) production from macrophages and neutrophils. Hsp72 also stimulates DC cytokines and chemokine production as well as DC maturation. In a series of elegant studies by Thomas Lehner and colleagues, unique immunological consequences of Hsp72 can be localized to specific domains of the Hsp72 molecule. For example, the C-terminal portion
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of Hsp72 (aa359-610) stimulates production of chemokines, IL-12, TNF-α, and NO; induces Th1 polarization; and stimulates the maturation of DC. The N-terminal ATPase portion (aa 1-358) largely lacks these functions (Lehner et al., 2000; Lehner et al., 2004; Wang et al., 2002; Wang et al., 2005). The C-terminal portion of several species of Hsp72 (microbial and human) binds to CD14, TLR4, and CD40 on antigenpresenting cells (Wang et al., 2001). CD40-CD40L interactions made between antigen-presenting cells (APC) and T-cells serve an important co-stimulatory role. Thus, Hsp72 may function to both stimulate innate immunity via CD14 and TLRs and facilitate Tcell responses via activation of CD40+ APCs. This makes Hsp72 a molecule positioned to play an important role at the interface between innate and adaptive immunity (Wang et al., 2005). 1. The Controversial Role of Endotoxin or Lipopolysaccharide in Hsp72 Immune Stimulation One issue that remains a source of debate is whether in vitro macrophage activation and/or inflammatory cytokine stimulation induced by Hsp72 reported in earlier studies is actually due to Hsp72 or is, instead, a result of LPS contamination inherent in the recombinant protein used. Many studies have carefully demonstrated that (1) stimulation of inflammatory cytokines and NO by eHsp72 in vitro is specific to eHsp72 and is not due to non-specific effects of endotoxin contamination in the recombinant Hsp72 protein, and (2) that the intracellular signaling pathways used by lipopolysaccharide (LPS) versus Hsp72 are unique and distinguishable (Asea et al., 2000a; Campisi and Fleshner, 2003; Panjwani et al., 2002). Nonetheless, this issue deserves discussion. Gao and Tsuan (2003a, 2003b; Tsan and Gao, 2004) have published several articles warning that researchers must consider the contribution of LPS contamination inherent in recombinant Hsp when testing the immune function of these proteins in vitro. One observation that is reported to support this idea is that endotoxin-free recombinant human Hsp70 (rhHsp70) does not stimulate inflammatory cytokines from murine macrophages in vitro (Gao and Tsan, 2003a). We have replicated theses observations and agree with their conclusion that in vitro testing of the immunological function of rhHsp70 must be conducted with caution. These results, however, do not diminish our hypothesis that endogenous Hsp72 released into the blood during an acute stress response has in vivo immunomodulatory functions. In fact, these findings have stimulated a new series of studies that will investigate which peptides are
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associated with the Hsp72 released into the circulation and if those peptides work in concert with the Hsp72 to stimulate immune function. It seems clear that endogenous Hsp72 released into the blood is likely not “naked.” In fact, it has been previously suggested that considering the complex forming ability and chaperoning function of Hsp72, in vivo “endotoxin-free” Hsp is probably non-existent (Prohaszka and Fust, 2004). This observation, and the fact that exposure to a variety of physical and psychological stressors stimulates commensal bacterial translocation from the gut (Deitch and Berg, 1987; Horton, 1994; Katafuchi et al., 2003; Nazli et al., 2004; Nettelbladt et al., 2003; Velin et al., 2004), has led us to speculate that perhaps some or all of the endogenous eHsp72 released by acute stress into the blood may be, in fact, associated with LPS released from endogenous gut bacterial flora. Perhaps it is this Hsp72/LPS complex that extravasates across the leaky vasculature or is transported from the blood into the inflamed tissues that facilitates host anti-microbial defenses. Future research will test these ideas. Interestingly, Quintana and Cohen (2005) recently reviewed this issue and concluded that the results of Gao and Tsan do not negate the hypothesis that endogenous Hsps manifest innate immune activities that are not due to bacterial contaminants. They suggest that endogenous eHsps may perform diverse functions in two alternative modes of inflammation: sterile inflammation, which results from endogenous stimuli and is necessary for body maintenance, and septic inflammation, which protects us from environmental pathogens. Here, they offer the intriguing idea that eHsp72/LPS complexes may augment immune responses by facilitating the transfer of LPS to the TLR4-MD2, leading to improved signal transduction and inflammatory cytokines responses. In our model, we have evidence supporting both functions of eHsp72. The release of eHsp72 by psychological/physical stressors in the absence of an infectious agent could be an example of sterile inflammation, whereas the accumulation of eHsp72 at the site of bacterial inflammation and its role in facilitating host anti-microbial responses could be an example of septic inflammation. The role of endogenous extracellular Hsps as immune modulators has grasped the attention of mainstream immunologists. We anticipate that this work will continue to be in the forefront in the field of psychoneuroimmunology.
B. Hsp72 and the “Danger Theory” Endogenous eHsp72 released during times of stress can stimulate innate immunity leading to improvement in acquired immunity. In fact it has been proposed that eHsp72 released during stress may function
as a “messenger of stress” or “danger signal” to the immune system. Matzinger (1994, 1998) first proposed the hypothesis that the body may release endogenous danger signals capable of stimulating immunity. In brief, the danger theory states that immune activation involves danger/non-danger molecular recognition schemas. The danger theory postulates that innate immune cells are activated by danger/alarm signals that are derived from stressed or damaged self. Although the danger theory is controversial when viewed as exclusionary, the suggested ideas are intriguing when viewed as complementary to other schemas. Clearly, innate immunity has evolved several strategies of activation. Consequently, it is reasonable to propose that innate immune cells can be activated by both exogenous antigens (i.e., LPS) binding to a limited number of germ-line encoded receptors (i.e., CD14 [Janeway and Medzhitov 2002]) and also by endogenous molecules that are released during times of cellular stress or danger. One important and unresolved issue for the danger theory is which molecules serve as “danger signals” to the immune system. We (Campisi and Fleshner 2003; Campisi et al., 2003a; Fleshner et al., 2002) and others (Asea et al., 2000a; Bethke et al., 2002; Breloer et al., 2001; Chen et al., 1999; Colaco 1998; Habich et al., 2002; Moseley 1998; Ohashi et al., 2000; Todryk et al., 2000; Vabulas et al., 2002) have suggested that eHsps may serve this function. Although Hsps fit the theoretical framework proposed by Matzinger, there is currently little supporting in vivo experimental evidence. Pittet et al. (2002) reported that humans who experienced trauma had increased serum levels of eHsp72 and that higher levels of eHsp72 correlated with improved survival. Based on the danger theory, it would follow that if a danger signal serves to facilitate or target immune function and eHsp72 acts as a danger signal, then organisms with increased eHsp72 should have improved immune responses and facilitated host defense to some types of pathogenic challenges.
C. Innate Immune Cell Activation: Toll-like Receptors Bind eHsp72 The search for the eHsp72 receptor is a topic of intense investigation and debate. There is evidence of a cell surface receptor for Hsp70 on macrophages/ neutrophils (Asea et al., 2000b; Asea et al., 2002; Reed and Nicchitta, 2000; Sondermann et al., 2000), B-cells (Arnold-Schild et al., 1999), and NK cells (Gross et al., 2003; Multhoff et al., 2001). A number of cell-surface binding proteins for eHsp72 have been implicated. Most research to date, however, suggests that eHsp72 transduces an inflammatory signal to innate immune
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cells (macrophages/dendritic/neutrophils) by binding to either Toll-like receptor-2 (TLR2) and/or TLR4 in a CD14-dependent fashion (Asea et al., 2000b; Asea et al., 2002; Vabulas et al., 2002; Visintin et al., 2001). Mammalian Toll-like receptors (TLR) are transmembrane proteins that are evolutionarily conserved between very primitive organisms (such as insects) and humans (Akira et al., 2001). It has been suggested that, just as released eHsps may function as “danger signals” or “messengers of stress” to the immune system, the TLRs may function as surveillance receptors for those signals (Johnson et al., 2003). In addition, exposure to prior injury stress was recently reported to produce a long-term (1–7 days) potentiation of TLR2- and TLR4-induced IL-1β, IL-6 and TNF-α production by spleen cells (Paterson et al., 2003), and chronic social stress (Avitsur et al., 2003) modulates TLR4-mediated responses. These data support the hypothesis that stress-induced modulation of innate immune function may involve TLR2 and TLR4. Extracellular Hsp72 exerts its effects on innate immune cells by stimulating the inflammatory MyD88/IRAK/NFkappaΒ signal transduction pathway (Vabulas et al., 2002). A rapid intracellular Ca2+ flux ensues within 10 seconds of eHsp72 binding with high affinity to monocytes or macrophages (Asea et al., 2000). This is important because it distinguishes eHsp72 signaling from LPS signaling, which does not induce Ca2+ flux (McLeish et al., 1989). Based on work by Asea and colleagues (2000a, 2000b, 2002), eHsp72-induction of NF-kappaΒ and inflammatory cytokines requires the expression of CD14 in addition to TLR2 and TLR4. Asea and colleagues have proposed that CD14 could function as a co-receptor for eHsp72 (Asea et al., 2000b). One implication of these results is that eHsp72 released into the blood after exposure to psychological and/or physical stressors may result in optimal stimulation of the inflammatory cascade only in the presence of CD14 activation. Interestingly, binding CD14 plus either TLR2 and/or TLR4 with selective receptor agonists (Pam3Cys binds TLR2 or Taxol binds TLR4) resulted in synergistic increases in NF-kappaΒ (Asea et al., 2002). Thus, facilitation of innate immune responses by eHsp72 after exposure to stress may be restricted to cells that express CD14 and/or are binding bacteria, LPS, or eHsp72 complexed to endogenous LPS released from the gut microflora. In many instances, therefore, we hypothesize that acute stressinduced release of eHsp72 may have little or no effect on innate immune cell production of NO and/or inflammatory cytokines. If, however, the host is challenged with a pathogen (e.g., bacteria) or already suffers from chronic inflammatory disease (e.g.,
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atherosclerosis, Alzheimer’s disease, inflammatory bowel disease), eHsp72 could extravasate from the blood into the inflamed tissues and bind to macrophages and/or neutrophils. Cells that are binding bacteria (LPS) and eHsp72 via CD14 and/or TLR2 or TLR4 could have potentiated NO and/or cytokine responses, resulting in facilitated bacterial killing and/or exacerbation of chronic inflammatory disease.
D. Stress and Innate Immunity Several measures of innate immunity are optimized following exposure to an acute stressor in a healthy organism and include the following: the acute phase response (APR), neutrophil and macrophage cellular function, local in vivo inflammatory responses, and recovery from bacterial challenge. The APR is a constellation of physiological changes initiated at a site of infection or trauma that collectively act to help clear the pathogen in a non-selective manner. Several components of the APR are triggered by exposure to acute. For example, uncontrollable tailshock stress increases levels of acute phase proteins such as haptoglobulin (Deak et al., 1997) and α1-acid glycoprotein (Deak et al., 1997). In addition, circulating IL-6 (Takaki et al., 1994), complement function (Coe et al., 1988; Fleshner et al., 2002), and circulating neutrophils (Fleshner et al., 2002) are increased following exposure to acute tailshock stress. Each of these responses can facilitate the development and resolution of the local inflammatory response (Baumann and Gauldie, 1994). In fact, Noursadighi et al. (2002) recently reported that prior pharmacological stimulation of the acute phase response protected animals from lethal E. coli infection, and this protection was due to enhanced early bacterial clearance, phagocytosis, and neutrophil oxidative burst. At the cellular level, acute stressor exposure increases the neutrophil oxidative burst (Smith and Pyne, 1997) and phagocytosis activity (Harmsen and Turney, 1985; Lyte et al., 1990). In addition, LPSstimulated leukocyte nitric oxide (NO) (Fleshner et al., 1998) and IL-1β (Moraska et al., 2002) responses are potentiated after tailshock exposure. Similar effects on antigen-stimulated NO production after exposure to a variety of acute stressors have also been reported (Coussons-Read et al., 1994; Fecho et al., 1994; Lysle et al., 1995). Neutrophil oxidative burst, phagocytosis, NO production, TNF-α production, and IL-1β production each play an important role in local inflammation (Ali et al., 1997; Bellingan et al., 1996; Dinarello, 2000; Ianaro et al., 1994; Mac Micking 1997). Many of the cellular products secreted by activated macrophages/ neutrophils are potent, non-specific suppressors of
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pathogen growth (Zidel, 1998). For example, NO, prostaglandin (PGE2), and superoxide radicals are all toxic to cells and function in a non-specific fashion to kill pathogens (Tomioka, 1992). Importantly, we are hypothesizing that eHsp72 contributes to, but is not solely responsible for, the beneficial effects of stress on innate immunity and bacterial recovery. This is reasonable given the variety of changes in immune responses produced by stress. 1. Does Stress Impact Host Defense by Modulating the Immune System or by Directly Modulating Bacterial Growth? Stress hormones, such as E, have been reported to directly influence the growth and molecular fingerprint of E. coli (Lyte, 1991; Lyte and Nguyen, 1997). It is possible, therefore, that the effect of tailshock stress on bacterial inflammation is due to stress hormone effects on bacterial growth, rather than eHsp72 effects on innate immunity. This seems unlikely because exposure to catecholamines increases E. coli growth, whereas exposure to tailshock decreases bacterial load (Campisi et al., 2003). In addition, adrenalectomy, which depletes 80–90% of circulating epinephrine, has no effect on stress-induced facilitation of bacterial inflammation resolution (Deak et al., 1999).
E. Stress Facilitates Recovery from Subcutaneous E. coli Challenge— A Role for NO Using subcutaneous E. coli, we tested if exposure to acute tailshock prior to bacterial challenge would improve host defense due to potentiation of innate immunity (Campisi and Fleshner, 2003; Campisi et al., 2002; Campisi et al., 2003a). Rats exposed to tailshock stress and subcutaneously injected immediately after stressor termination with ∼108 colony forming units (CFUs) of freshly grown E. coli resolve their inflammation 10–14 days faster (Campisi and Fleshner, 2003; Campisi et al., 2002; Campisi et al., 2003a), experience less bacterial-induced body weight loss (Campisi et al., 2002), and release 300% more NO at the inflammatory site compared to bacterially injected, non-stressed controls (Campisi et al., 2003a). Stress-induced potentiation of NO is important in anti-microbial host defense. This is supported by the observation that inhibition of NO at the inflammatory site with L-NIO (NOS inhibitor) reduces the effect of stress on facilitation of recovery from bacterial challenge (Campisi et al., 2003a). NO contributes to almost every stage of inflammation by impacting leukocyte migration, adherence, antimicrobial activities, and phagocytic ability and, in fact,
can act to restrict the development of inflammation (Ali et al., 1997). One beneficial effect of stress on recovery from bacterial challenge could be greater NO-mediated bacterial killing. Consistent with this idea is that rats challenged with E. coli after stress have fewer E. coli CFUs retrieved from the inflammatory site 2, 4, and 6 hours after challenge compared to nonstressed E. coli–challenged controls (Campisi et al., 2003a). The enhanced release of NO appears to be an important mediator; however, the mechanisms involved in stress-induced facilitation of NO and recovery from bacterial inflammation remain unknown. We propose that eHsp72, possibly associated with LPS, binds to TLR2 and/or TLR4 on the surface of macrophages and results in a greater and more rapid NO at the site of bacterial inflammation. The release of eHsp72 in response to a global stressor such as tailshock, therefore, facilitates innate immune function only in the presence of pathogenic challenge. This is consistent with previous literature on the priming effects of stress on innate immunity (Johnson et al., 2002a; Johnson et al., 2002b; Johnson et al., 2003).
F. Stress Facilitates Recovery from Subcutaneous E. coli Challenge— A Role for eHsp72 A series of published studies lend support to the hypothesis that stress-induced elevation in eHsp72 facilitates innate immunity in the presence of pathogenic challenge (E. coli). For example, rats exposed to tailshock and challenged with subcutaneous E. coli have an increase in eHsp72 at the site of inflammation, and eHsp72 administered to the site of inflammation in the absence of stress improves recovery from bacterial challenge (Campisi et al., 2003a). We recently completed additional studies further testing this idea. We have clearly established that exposure to stress increases endogenous eHsp72 concentrations in the blood. We hypothesize that the Hsp72 in the blood interacts with immune cells only if it accumulates in tissue. In our experimental model, we produced an inflammatory site by injecting subcutaneous E. coli. We hypothesize that increased vascular leaking at the site of inflammation, due to histamine release from mast cells, allows eHsp72 to extravasate from the blood vessels into the tissue. To test this hypothesis, we conducted the following study. Adult male F344 rats were pre-treated with vehicle or ketotifen (a selective histamine type-1 receptor antagonist that prevents vascular leaking (Martin and Roemer, 1977; Yokoyama et al., 1993) and exposed to either stress or no stress. Immediately after stressor
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exposure, all rats were injected subcutaneously with E. coli, the inflammatory sites were removed, and eHsp72 concentration (Figure 6) and the number of live E. coli in the subcutaneous tissue (Figure 7) were assessed. Replicating our previous work (Campisi et al., 2003a), eHsp72 tissue concentration was increased, and the number of E. coli was decreased only in animals that were exposed to tailshock stress (and hence had elevated blood eHsp72) and that were injected with E. coli and vehicle (and hence had vascular leaking). Importantly, in vivo ketotifen blocked both the stress-induced increase of eHsp72 (Figure 6) and the stress-induced decrease in bacterial load (Figure 7) at the inflammatory site. These data support our hypothesis that eHsp72 can extravasate from the blood into inflamed tissue via a type-1 histamine receptordependent mechanism, and suggest that eHsp72 may participate in improved anti-microbial responses associated with acute activation of the stress response.
FIGURE 6 Adult male Fischer F344 rats (n = 8 per group) received either sodium chloride (Vehicle) or 40 mg/kg body weight of (ketotifen, sigma) intraperitoneal injection 30 minutes before being left undisturbed in their home cages (No Stress) or exposed to 100, 5 s, 1.6 mA tailshocks with a random inter-trial interval of 60 seconds (Stress). Following termination of stressor, all animals were injected subcutaneously on their dorsum with E. coli bacteria (2.5 × 108 CFU ATCC 15756). Animals were replaced in their home cages and 90 minutes later were sacrificed via decapitation. Samples were obtained by removing the skin from the dorsum, excising a sample of subcutaneous tissue with heat-sterilized scissors. Samples were homogenized with a smooth mortar and pestle in normal saline, spun in a centrifuge, and the supernatant was frozen at −20°C until assay by ELISA (StressGen). Two-way ANOVA revealed that there was a main effect of Stress (p = .0073). Fisher PLSD post-hoc revealed that the Stress/Vehicle group was significantly higher compared to all other groups (*p < .0285).
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VI. CONCLUSIONS AND IMPLICATIONS As depicted in Figure 8, we hypothesize that stressinduced release of eHsp72 acts in concert with other aspects of the APR (neutrophilia, NO/O2−, complement activation, etc.) to facilitate host defense. Specifically, we propose that one previously unrecognized and adaptive feature of the acute stress response is the release of endogenous eHsp72 into the circulation. If an organism is subsequently challenged with a pathogen such as E. coli, eHsp72 possibly complexed to LPS from intestinal bacteria extravasates from the blood into the subcutaneous space across blood vessels that are rendered leaky due to bacterial-stimulated histamine release from mast cells (Ali et al., 1997). Extracellular Hsp72 and/or Hsp72/LPS complexes accumulate at the inflammatory site and bind to TLR2 and TLR4
FIGURE 7 Adult male Fischer F344 rats (n = 8 per group) received either sodium chloride (Vehicle) or 40 mg/kg body weight of (ketotifen, sigma) intraperitoneal injection 30 minutes before being left undisturbed in their home cages (No Stress) or exposed to 100, 5 s, 1.6 mA tailshocks with a random inter-trial interval of 60 seconds (Stress). Following termination of stressor, all animals were injected subcutaneously on their dorsum with E. coli bacteria (2.5 × 108 CFU ATCC 15756). Animals were replaced in their home cages and 90 minutes later were sacrificed via decapitation. Samples were obtained by removing the skin from the dorsum, excising a sample of subcutaneous tissue with heat-sterilized scissors. Samples were homogenized with a smooth mortar and pestle in normal saline; aliquots were diluted in normal saline and plated onto McConkey agar plates (VWR). Plates were incubated at 37°C for 16 hrs in 5% CO2 and then counted. Two-way ANOVA revealed a significant main effect for stress (p = .009) and bacterial challenge (p = .0006). Fisher PLSD revealed that the Stress/ Vehicle group was significantly lower compared to all other groups (*p < .0032).
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E.coli Subcutaneous Space E.coli NO
NO
E.coli
Hsp72
N
Hsp72
E.coli
Hsp72
Macrophage N
Hsp72
NO
E.coli
DC T
Hsp72 Hsp72
Exosomal Hsp72 Hsp72
N = Neutrophil = LPS = Hsp72 T = T-cell = Hsp72+LPS
N
Hsp72
Mast Cell Vascular leaking
Blood Vessel
= CD14 = TLR2/4 NO = Nitric Oxide = H1 Receptor
FIGURE 8 This is a schematic representation of the immunological function of eHsp72 at the site of subcutaneous bacterial inflammation. We hypothesize that stress-induced release of eHsp72 acts in concert with other aspects of the acute phase response (neutrophilia, NO/O2−, complement activation) to facilitate host defense. If an organism is exposed to stress or danger and is subsequently challenged with a pathogen such as E. coli, eHsp72 possibly complexed to LPS from intestinal bacteria, extravasates from the blood into the subcutaneous space across blood vessels that are rendered leaky due to bacterial-stimulated histamine release from mast cell acting on histamine type 1 (H1) receptors on blood vessels. Extracellular Hsp72 and/or Hsp72/LPS complexes accumulate at the inflammatory site and bind to TLR2 and TLR4 on macrophages, neutrophils (N), and/or dendritic cells (DC). Macrophages and/or neutrophils that have received a stimulatory signal via CD14 binding to LPS will mount potentiated innate immune responses (i.e., NO, TNF, IL-1, IL-6) that result in an immediate optimal bacterial killing. eHsp72 and/or eHsp72/LPS complexes that interact with DC may also produce increased stimulation of anti-microbial Tcells and a long-lasting beneficial anti-microbial effect of stress to subsequent E. coli challenges.
on macrophages, neutrophils, and/or dendritic cells. Macrophages and/or neutrophils that have received a stimulatory signal via CD14 binding to LPS will mount potentiated innate immune responses (i.e., NO, TNF, IL-1, IL-6) that result in an immediate optimal bacterial killing. The acute stress response includes a complex cascade of behavioral, neural, endocrine, and immunological responses that are designed to facilitate fight/flight responses and host survival. Our work has revealed that the release of endogenous eHsp72 is an additional feature of the acute stress response that may have important implications for aiding host defense. Thus, for example, if a gazelle were running across the savanna being chased by a lion, the acute stress response would be activated to facilitate escape. If that gazelle manages a successful escape but is wounded
during the attack, perhaps the released eHsp72 in the circulation would accumulate in the wounded and possibly infected tissue and facilitate a faster immune response that also improves the gazelle’s chances of survival. Although we have emphasized the adaptive aspects of the acute stress response, including eHsp72 release, it is important to remember that inappropriate stimulation or excessive stimulation of the response due to intense emotional distress, anxiety, or chronic physical stressors, or stimulation of the response in the presence of inflammatory diseases, such as atherosclerosis, inflammatory bowel disease, or Alzheimer’s disease, could be maladaptive to host survival. Thus, more work needs to be done to fully characterize and appreciate the function of this newly recognized immunomodulatory endogenous protein in host immunity.
47. Extracellular Hsp72 and Immunity
References Akira, S., Takeda, K., and Kaisho, T. (2001). Toll-like receptors: critical proteins linking innate and acquired immunity. Nature Immunology, 2, 675–680. Ali, H., Haribabu, B., Richardson, R. M., and Snyderman, R. (1997). Mechanisms of inflammation and leukocyte activation. Med. Clin. North Am., 81, 1–28. Arieli, Y., Eynan, M., Gancz, H., Arieli, R., and Kashi, Y. (2003). Heat acclimation prolongs the time to central nervous system oxygen toxicity in the rat. Possible involvement of Hsp72. Brain Res., 962, 15–20. Arnold-Schild, D., Hanau, D., Spehner, D., Schmid, C., Rammensee, H. G., de la Salle, H., and Schild, H. (1999). Cutting edge: receptor-mediated endocytosis of heat shock proteins by professional antigen-presenting cells. J. Immunol., 162, 3757– 3760. Asea, A., Kabingu, E., Stevenson, M. A., and Calderwood, S. K. (2000a). Hsp70 peptide-bearing and peptide-negative preparations act as chaperokines. Cell Stress Chaperones, 5, 425–431. Asea, A., Kraeft, S. K., Kurt-Jones, E. A., Stevenson, M. A., Chen, L. B., Finberg, R. W., Koo, G. C., and Calderwood, S. K. (2000b). Hsp70 stimulates cytokine production through a CD14dependant pathway, demonstrating its dual role as a chaperone and cytokine. Nat. Med., 6, 435–442. Asea, A., Rehli, M., Kabingu, E., Boch, J. A., Bare, O., Auron, P. E., Stevenson, M. A., and Calderwood, S. K. (2002). Novel signal transduction pathway utilized by extracellular Hsp70: role of toll-like receptor (TLR) 2 and TLR4. J. Biol. Chem., 277, 15028–15034. Avitsur, R., Padgett, D. A., Dhabhar, F. S., Stark, J. L., Kramer, K. A., Engler, H., and Sheridan, J. F. (2003). Expression of glucocorticoid resistance following social stress requires a second signal. J. Leukoc. Biol., 74, 507–513. Barrientos, R. M., O’Reilly, R. C., and Rudy, J. W. (2002). Memory for context is impaired by injecting anisomycin into dorsal hippocampus following context exploration. Behav. Brain Res., 134, 299–306. Basu, S., Binder, R. J., Suto, R., Anderson, K. M., and Srivastava, P. K. (2000). Necrotic but not apoptotic cell death releases heat shock proteins, which deliver a partial maturation signal to dendritic cells and activate the NF-kappa B pathway. Int. Immunol., 12, 1539–1546. Baumann, H., and Gauldie, J. (1994). The acute phase response. Immunol. Today, 15, 74–80. Bellingan, G. J., Caldwell, H., Howie, S. E., Dransfield, I., and Haslett, C. (1996). In vivo fate of the inflammatory macrophage during the resolution of inflammation: inflammatory macrophages do not die locally, but emigrate to the draining lymph nodes. J. Immunol., 157, 2577–2585. Berwin, B., Reed, R. C., and Nicchitta, C. V. (2001). Virally induced lytic cell death elicits the release of immunogenic GRP94/gp96. J. Biol. Chem., 276, 21083–21088. Bethke, K., Staib, F., Distler, M., Schmitt, U., Jonuleit, H., Enk, A. H., Galle, P. R., and Heike, M. (2002). Different efficiency of heat shock proteins (Hsp) to activate human monocytes and dendritic cells: superiority of Hsp60. J. Immunol., 169, 6141–6148. Blake, M. J., Buckley, A. R., LaVoi, K. P. and Bartlett, T. (1994). Neural and endocrine mechanisms of cocaine-induced 70k-Da heat shock protein expression in aorta and adrenal gland. Journal of Pharmacological Experimental Therapy, 268, 522–529. Blake, M. J., Udelsman, R., Feulner, G. J., Norton, D. D., and Holbrook, N. J. (1991). Stress-induced heat shock protein 70 expression in adrenal cortex: an adrenocorticotropic hormone-
1029
sensitive, age-dependent response. Proc. Natl. Acad. Sci. USA, 88, 9873–9877. Breloer, M., Dorner, B., More, S. H., Roderian, T., Fleischer, B., and von Bonin, A. (2001). Heat shock proteins as “danger signals”: eukaryotic Hsp60 enhances and accelerates antigen-specific IFNgamma production in T cells. Eur. J. Immunol., 31, 2051–2059. Broquet, A. H., Thomas, G., Masliah, J., Trugnan, G., and Bachelet, M. (2003). Expression of the molecular chaperone Hsp70 in detergent-resistant microdomains correlates with its membrane delivery and release. J. Biol. Chem., 278, 21601–21606. Cacioppo, J. T., Berntson, G. G., Malarkey, W. B., Kiecolt-Glaser, J. K., Sheridan, J. F., Poehlmann, K. M., Burleson, M. H., Ernst, J. M., Hawkley, L. C., and Glaser, R. (1998). Autonomic, neuroendocrine, and immune responses to psychological stress: the reactivity hypothesis. Ann. N. Y. Acad. Sci., 840, 664–673. Cahill, C. M., Lin, H. S., Price, B. D., Bruce, J. L., and Calderwood, S. K. (1997). Potential role of heat shock transcription factor in the expression of inflammatory cytokines. Adv. Exp. Med. Biol., 400, 625–630. Cahill, C. M., Waterman, W. R., Xie, Y., Auron, P. E., and Calderwood, S. K. (1996). Transcriptional repression of the prointerleukin 1beta gene by heat shock factor 1. J. Biol. Chem., 271, 24874–24879. Campisi, J., and Fleshner, M. (2003). The role of extracellular Hsp72 in acute stress-induced potentiation of innate immunity in physically active rats. Journal of Applied Physiology, 94, 43–52. Campisi, J., Leem, T. H., and Fleshner, M. (2002). Acute stress decreases inflammation at the site of infection. A role for nitric oxide. Physiology and Behavior, 77, 291–299. Campisi, J., Leem, T. H., and Fleshner, M. (2003a). Stress-induced extracellular Hsp72 is a functionally significant danger signal to the immune system. Cell, Stress and Chaperones, 8, 272–286. Campisi, J., Leem, T. H., Greenwood, B. N., Hansen, M. K., Moraska, A., Higgins, K., Smith, T. P., and Fleshner, M. (2003b). Habitual physical activity facilitates stress-induced Hsp72 induction in brain, peripheral and immune tissues. American Journal of Physiology, 284, 520–530. Cannon, B., Jacobsson, A., Rehnmark, S., and Nedergaard, J. (1996). Signal transduction in brown adipose tissue recruitment: noradrenaline and beyond. Int. J. Obes. Relat. Metab. Disord., 20, S36–42. Carrasco, G. A., and Van de Kar, L. D. (2003). Neuroendocrine pharmacology of stress. Eur. J. Pharmacol., 463, 235–272. Chen, W., Syldath, U., Bellmann, K., Burkart, V., and Kolb, H. (1999). Human 60-kDa heat-shock protein: a danger signal to the innate immune system. J. Immunol., 162, 3212–3219. Christou, E. A., Jakobi, J., Critchlow, A., Fleshner, M., and Enoka, R. (2004). The 1-2 Hz oscillations in force are exacerbated by stress, especially in older adults. J. Appl. Phys., 97, 225–235, Ciocca, D. R., and Calderwood, S. K. (2005). Heat shock proteins in cancer: diagnostic, prognostic, predictive, and treatment implications. Cell Stress Chaperones, 10, 86–103. Clayton, A., Turkes, A., Navabi, H., Mason, M. D., and Tabi, Z. (2005). Induction of heat shock proteins in B-cell exosomes. J. Cell Sci., 118, 3631–3638. Coe, C. L., Rosenberg, L. T., and Levine, S. (1988). Effect of maternal separation on the complement system and antibody responses in infant primates. Int. J. Neurosci., 40, 289–302. Colaco, C. A. (1998). Towards a unified theory of immunity: dendritic cells, stress proteins and antigen capture. Cell Mol. Biol. (Noisy-le-grand), 44, 883–890. Collins, S., and Surwit, R. S. (2001). The beta-adrenergic receptors and the control of adipose tissue metabolism and thermogenesis. Recent. Prog. Horm. Res., 56, 309–328.
1030
V. Psychoneuroimmunology and Pathophysiology
Coussons-Read, M. E., Maslonek, K. A., Fecho, K., Perez, L., and Lysle, D. T. (1994). Evidence for the involvement of macrophagederived nitric oxide in the modulation of immune status by a conditioned aversive stimulus. J. Neuroimmunol., 50, 51–58. Cvoro, A., and Matic, G. (2002). Hyperthermic stress stimulates the association of both constitutive and inducible isoforms of 70 kDa heat shock protein with rat liver glucocorticoid receptor. Int. J. Biochem. Cell Biol., 34, 279–285. Deak, T., Meriwether, J. L., Fleshner, M., Spencer, R. L., Abouhamze, A., Moldawer, L. L., Grahn, R. E., Watkins, L. R., and Maier, S. F. (1997). Evidence that brief stress may induce the acute phase response in rats. Am. J. Physiol., 273, R1998–2004. Deak, T., Nguyen, K. T., Fleshner, M., Watkins, L. R., and Maier, S. F. (1999). Acute stress may facilitate recovery from a subcutaneous bacterial challenge. Neuroimmunomodulation, 6, 344–354. Deitch, E. A., and Berg, R. (1987). Bacterial translocation from the gut: a mechanism of infection. J. Burn. Care. Rehabil., 8, 475– 482. Del Bino, G., Darzynkiewicz, Z., Degraef, C., Mosselmans, R., Fokan, D., and Galand, P. (1999). Comparison of methods based on annexin-V binding, DNA content or TUNEL for evaluating cell death in HL-60 and adherent MCF-7 cells. Cell Prolif., 32, 25–37. Diamond, D. M., Park, C. R., Heman, K. L., and Rose, G. M. (1999). Exposing rats to a predator impairs spatial working memory in the radial arm water maze. Hippocampus, 9, 542–552. Dinarello, C. A. (2000). Proinflammatory cytokines. Chest., 118, 503–508. Ding, X. Z., Fernandez-Prada, C. M., Bhattacharjee, A. K., and Hoover, D. L. (2001). Overexpression of Hsp-70 inhibits bacterial lipopolysaccharide-induced production of cytokines in human monocyte-derived macrophages. Cytokine, 16, 210–219. Febbraio, M. A., and Koukoulas, I. (2000). Hsp72 gene expression progressively increases in human skeletal muscle during prolonged, exhaustive exercise. J. Appl. Physiol., 89, 1055–1060. Febbraio, M. A., Ott, P., Nielsen, H. B., Steensberg, A., Keller, C., Krustrup, P., Secher, N. H., and Pedersen, B. K. (2002a). Exercise induces hepatosplanchnic release of heat shock protein 72 in humans. J. Physiol., 544, 957–962. Febbraio, M. A., Steensberg, A., Walsh, R., Koukoulas, I., van Hall, G., Saltin, B., and Pedersen, B. K. (2002b). Reduced glycogen availability is associated with an elevation in Hsp72 in contracting human skeletal muscle. J. Physiol., 538, 911–917. Fecho, K., Maslonek, K. A., Coussons-Read, M. E., Dykstra, L. A., and Lysle, D. T. (1994). Macrophage-derived nitric oxide is involved in the depressed concanavalin A responsiveness of splenic lymphocytes from rats administered morphine in vivo. J. Immunol., 152, 5845–5852. Fleshner, M., Campisi, J., Amiri, L., and Diamond, D. M. (2004). Cat exposure induces both intra- & extra-cellular Hsp72: the role of adrenal hormones. Psychoneuroendocrinology, 29, 1142–1152. Fleshner, M., Campisi, J., Deak, T., Greenwood, B. N., Kintzel, J. A., Leem, T. H., Smith, T. P., and Sorensen, B. (2002). Acute stressor exposure facilitates innate immunity more in physically active than in sedentary rats. Am. J. Physiol. Regul. Integr. Comp. Physiol., 282, R1680–1686. Fleshner, M., Campisi, J., and Johnson, J. D. (2003). Can exercise stress facilitate innate immunity? A functional role for stressinduced extracellular Hsp72. Exercise Immunology Review, 9, 6–24. Fleshner, M., Deak, T., Spencer, R. L., Laudenslauger, M. L., Watkins, L. R. and Maier, S. F. (1995). A long term increase in basal levels of corticosterone and a decrease in corticosteroid-binding globulin after acute stressor exposure. Endocrinology, 136, 5336–5342.
Fleshner, M., and Johnson, J. D. (2005). Exogenous extra-cellular heat shock protein 72: releasing signal(s) and function. International Journal of Hyperthermia, 21, 457–471. Fleshner, M., Nguyen, K. T., Cotter, C. S., Watkins, L. R., and Maier, S. F. (1998). Acute stressor exposure both suppresses acquired immunity and potentiates innate immunity. Am. J. Physiol., 275, R870–878. Fleshner, M., Pugh, C. R., Tremblay, D., and Rudy, J. W. (1997). DHEA-S selectively impairs contextual-fear conditioning: support for the antiglucocorticoid hypothesis. Behav. Neurosci., 111, 512–517. Foster, D. O., Depocas, F., and Zaror-Behrens, G. (1982a). Unilaterality of the sympathetic innervation of each pad of rat interscapular brown adipose tissue. Can. J. Physiol. Pharmacol., 60, 107– 113. Foster, D. O., Depocas, F., and Zuker, M. (1982b). Heterogeneity of the sympathetic innervation of rat interscapular brown adipose tissue via intercostal nerves. Can. J. Physiol. Pharmacol., 60, 747–754. Gallucci, S., Lolkema, M., and Matzinger, P. (1999). Natural adjuvants: endogenous activators of dendritic cells. Nat. Med., 5, 1249–1255. Gao, B., and Tsan, M. F. (2003a). Endotoxin contamination in recombinant human heat shock protein 70 (Hsp70) preparation is responsible for the induction of tumor necrosis factor alpha release by murine macrophages. J. Biol. Chem., 278, 174–179. Gao, B., and Tsan, M. F. (2003b). Recombinant human heat shock protein 60 does not induce the release of tumor necrosis factor alpha from murine macrophages. J. Biol. Chem., 278, 22523– 22529. Gastpar, R., Gehrmann, M., Bausero, M. A., Asea, A., Gross, C., Schroeder, J. A., and Multhoff, G. (2005). Heat shock protein 70 surface-positive tumor exosomes stimulate migratory and cytolytic activity of natural killer cells. Cancer Res., 65, 5238–5247. Granneman, J. G., Zhai, Y., and Lahners, K. N. (1997). Selective upregulation of alpha1a-adrenergic receptor protein and mRNA in brown adipose tissue by neural and beta3-adrenergic stimulation. Mol. Pharmacol., 51, 644–650. Greenwood, B. N., Kennedy, S., Smith, T. P., Campeau, S., Day, H. E., and Fleshner, M. (2003). Voluntary freewheel running selectively modulates catecholamine content in peripheral tissue and c-Fos expression in the central sympathetic circuit following exposure to uncontrollable stress in rats. Neuroscience, 120, 269–281. Gross, C., Hansch, D., Gastpar, R., and Multhoff, G. (2003). Interaction of heat shock protein 70 peptide with NK cells involves the NK receptor CD94. Biol. Chem., 384, 267–279. Gulati, N., Huggel, H., and Gulati, O. P. (1980). Effect of labetalol on adrenoceptors in the isolated perfused rat mesentery. Arch. Int. Pharmacodyn. Ther., 246, 251–256. Guzhova, I., Kislyakova, K., Moskaliova, O., Fridlanskaya, I., Tytell, M., Cheetham, M., and Margulis, B. (2001). In vitro studies show that Hsp70 can be released by glia and that exogenous Hsp70 can enhance neuronal stress tolerance. Brain Res., 914, 66–73. Habich, C., Baumgart, K., Kolb, H., and Burkart, V. (2002). The receptor for heat shock protein 60 on macrophages is saturable, specific, and distinct from receptors for other heat shock proteins. J. Immunol., 168, 569–576. Hamilton, K. L., Staib, J. L., Phillips, T., Hess, A., Lennon, S. L., and Powers, S. K. (2003). Exercise, antioxidants, and Hsp72: protection against myocardial ischemia/reperfusion. Free Radic. Biol. Med., 34, 800–809. Hammill, A. K., Uhr, J. W., and Scheuermann, R. H. (1999). Annexin V staining due to loss of membrane asymmetry can be reversible
47. Extracellular Hsp72 and Immunity and precede commitment to apoptotic death. Exp. Cell Res., 251, 16–21. Hardman, J. G., and Limbird, L. E. (Eds.) (2001). Goodman & Gilman’s: The pharmacological basis of therapeutics (10th ed.). New York: McGraw-Hill. Harmsen, A. G., and Turney, T. H. (1985). Inhibition of in vivo neutrophil accumulation by stress. Possible role of neutrophil adherence. Inflammation, 9, 9–20. Hartl, F. U. (1996). Molecular chaperones in cellular protein folding. Nature, 381, 571–579. Heine, H., and Lien, E. (2003). Toll-like receptors and their function in innate and adaptive immunity. Int. Arch. Allergy. Immunol., 130, 180–192. Heneka, M. T., Gavrilyuk, V., Landreth, G. E., O’Banion, M. K., Weinberg, G., and Feinstein, D. L. (2003). Noradrenergic depletion increases inflammatory responses in brain: effects on IkappaB and Hsp70 expression. J. Neurochem., 85, 387– 398. Hessman, Y., Rentzhog, L., and Ekbohm, G. (1976). Effect of adrenal demedullation on urinary excretion of catecholamines in thermal trauma in rats. Acta. Chir. Scand., 142, 291–295. Hickman-Miller, H. D., and Hildebrand, W. H. (2004). The immune response under stress: the role of Hsp-derived peptides. Trends. Immunol., 25, 427–433. Hightower, L. E., and Guidon, P. T., Jr. (1989). Selective release from cultured mammalian cells of heat-shock (stress) proteins that resemble glia-axon transfer proteins. J. Cell Physiol., 138, 257–266. Honda, O., Kuroda, M., Joja, I., Asaumi, J., Takeda, Y., Akaki, S., Togami, I., Kanazawa, S., Kawasaki, S., and Hiraki, Y. (2000). Assessment of secondary necrosis of Jurkat cells using a new microscopic system and double staining method with annexin V and propidium iodide. Int. J. Oncol., 16, 283–288. Horton, J. W. (1994). Bacterial translocation after burn injury: the contribution of ischemia and permeability changes. Shock, 1, 286–290. Housby, J. N., Cahill, C. M., Chu, B., Prevelige, R., Bickford, K., Stevenson, M. A., and Calderwood, S. K. (1999). Non-steroidal anti-inflammatory drugs inhibit the expression of cytokines and induce Hsp70 in human monocytes. Cytokine., 11, 347– 358. Ianaro, A., Ialenti, A., Maffia, P., Pisano, B., and Di Rosa, M. (2001). HSF1/hsp72 pathway as an endogenous anti-inflammatory system. FEBS Lett., 499, 239–244. Ianaro, A., O’Donnell, C. A., Di Rosa, M., and Liew, F. Y. (1994). A nitric oxide synthase inhibitor reduces inflammation, downregulates inflammatory cytokines and enhances interleukin-10 production in carrageenin-induced oedema in mice. Immunology., 82, 370–375. Janeway, C. A., Jr., and Medzhitov, R. (2002). Innate immune recognition. Annu. Rev. Immunol., 20, 197–216. Johnson, G. B., Brunn, G. J., Tang, A. H., and Platt, J. L. (2003). Evolutionary clues to the functions of the Toll-like family as surveillance receptors. Trends Immunol., 24, 19–24. Johnson, J. D., Campisi, J., Sharkey, C. M., Kennedy, S., Nickerson, M., and Fleshner, M. (2005). Adrenergic receptors mediate stressinduced elevation in endogenous extracellular Hsp72. Journal of Applied Physiology, 99(5), 1789–1795. Johnson, J. D., and Fleshner, M. (2006). Releasing signals, secretory pathways and immunological function of endogenous extracellular Hsp72. Journal of Leukocyte Biology, 79(3), 425–434. Johnson, J. D., O’Connor, K. A., Deak, T., Spencer, R. L., Watkins, L. R., and Maier, S. F. (2002a). Prior stressor exposure primes the HPA axis. Psychoneuroendocrinology, 27, 353–365.
1031
Johnson, J. D., O’Connor, K. A., Deak, T., Stark, M., Watkins, L. R., and Maier, S. F. (2002b). Prior stressor exposure sensitizes LPSinduced cytokine production. Brain Behav. Immun., 16, 461–476. Johnson, J. D., O’Connor, K. A., Hansen, M. K., Watkins, L. R., and Maier, S. F. (2003). Effects of prior stress on LPS-induced cytokine and sickness responses. Am. J. Physiol. Regul. Integr. Comp. Physiol., 284, 422–432. Katafuchi, T., Takaki, A., Take, S., Kondo, T., and Yoshimura, M. (2003). Endotoxin inhibitor blocks heat exposure-induced expression of brain cytokine mRNA in aged rats. Brain Res. Mol. Brain Res., 118, 24–32. Kaufmann, S. H. (1990a). Heat shock proteins and the immune response. Immunol. Today, 11, 129–136. Kaufmann, S. H. (1990b). Heat-shock proteins: a link between rheumatoid arthritis and infection? Curr. Opin. Rheumatol., 2, 430– 435. Kelly, S., Zhang, Z. J., Zhao, H., Xu, L., Giffard, R. G., Sapolsky, R. M., Yenari, M. A., and Steinberg, G. K. (2002). Gene transfer of Hsp72 protects cornu ammonis 1 region of the hippocampus neurons from global ischemia: influence of Bcl-2. Ann. Neurol., 52, 160–167. Kikuchi-Utsumi, K., Kikuchi-Utsumi, M., Cannon, B., and Nedergaard, J. (1997). Differential regulation of the expression of alpha1-adrenergic receptor subtype genes in brown adipose tissue. Biochem. J., 322 (Pt 2), 417–424. King, Y. T., Lin, C. S., Lin, J. H., and Lee, W. C. (2002). Whole-body hyperthermia-induced thermotolerance is associated with the induction of heat shock protein 70 in mice. J. Exp. Biol., 205, 273–278. Kol, A., Lichtman, A. H., Finberg, R. W., Libby, P., and Kurt-Jones, E. A. (2000). Cutting edge: heat shock protein (Hsp) 60 activates the innate immune response: CD14 is an essential receptor for Hsp60 activation of mononuclear cells. J. Immunol., 164, 13–17. Kregel, K. C. (2002). Invited review: heat shock proteins: modifying factors in physiological stress responses and acquired thermotolerance. J. Appl. Physiol., 92, 2177–2186. Kregel, K. C., and Moseley, P. L. (1996). Differential effects of exercise and heat stress on liver Hsp70 accumulation with aging. J. Appl. Physiol., 80, 547–551. Krishnaswamy, G., Kelley, J., Yerra, L., Smith, J. K., and Chi, D. S. (1999). Human endothelium as a source of multifunctional cytokines: molecular regulation and possible role in human disease. J. Interferon Cytokine Res., 19, 91–104. Lancaster, G. I., and Febbraio, M. A. (2005). Exosome-dependent trafficking of Hsp70: a novel secretory pathway for cellular stress proteins. J. Biol. Chem., 280, 23349–23355. Lecoeur, H., Prevost, M. C., and Gougeon, M. L. (2001). Oncosis is associated with exposure of phosphatidylserine residues on the outside layer of the plasma membrane: a reconsideration of the specificity of the annexin V/propidium iodide assay. Cytometry., 44, 65–72. Lehner, T., Bergmeier, L. A., Wang, Y., Tao, L., Sing, M., Spallek, R., and van der Zee, R. (2000). Heat shock proteins generate betachemokines which function as innate adjuvants enhancing adaptive immunity. Eur. J. Immunol., 30, 594–603. Lehner, T., Wang, Y., Whittall, T., McGowan, E., Kelly, C. G., and Singh, M. (2004). Functional domains of Hsp70 stimulate generation of cytokines and chemokines, maturation of dendritic cells and adjuvanticity. Biochem. Soc. Trans., 32, 629–632. Lewthwaite, J., Owen, N., Coates, A., Henderson, B., and Steptoe, A. (2002). Circulating human heat shock protein 60 in the plasma of British civil servants: relationship to physiological and psychosocial stress. Circulation, 106, 196–201.
1032
V. Psychoneuroimmunology and Pathophysiology
Lindquist, S., and Craig, E. A. (1988). The heat-shock proteins. Annu. Rev. Genet., 22, 631–677. Liu, T. S., Musch, M. W., Sugi, K., Walsh-Reitz, M. M., Ropeleski, M. J., Hendrickson, B. A., Pothoulakis, C., Lamont, J. T., and Chang, E. B. (2003). Protective role of Hsp72 against Clostridium difficile toxin A-induced intestinal epithelial cell dysfunction. Am. J. Physiol. Cell Physiol., 284, C1073–1082. Lucas, M., Rose, P. E., and Morris, A. G. (2000). Contrasting effects of Hsp72 expression on apoptosis in human umbilical vein endothelial cells and an angiogenic cell line, ECV304. Br. J. Haematol., 110, 957–964. Lysle, D. T., Fecho, K., Maslonek, K. A., and Dykstra, L. A. (1995). Evidence for the involvement of macrophage-derived nitric oxide in the immunomodulatory effect of morphine and aversive Pavlovian conditioning. Adv. Exp. Med. Biol., 373, 141–147. Lyte, M., and Ernst, S. (1991). Catecholamine induced growth of gram negative bacteria. Life Sciences, 50, 203–212. Lyte, M., Nelson, S. G., and Thompson, M. L. (1990). Innate and adaptive immune responses in a social conflict paradigm. Clin. Immunol. Immunopathol., 57, 137–147. Lyte, M., and Nguyen, K. T. (1997). Alteration of Escherichia coli O157:H7 growth and molecular fingerprint by the neuroendocrine hormone noradrenaline. Microbios, 89, 197–213. Mac Micking, J., Xie, Q. W. and Nathan, C. (1997). Nitric oxide and macrophage function. Annual Review of Immunology, 15, 323–350. Maloyan, A., and Horowitz, M. (2002). Beta-adrenergic signaling and thyroid hormones affect Hsp72 expression during heat acclimation. J. Appl. Physiol., 93, 107–115. Mao, H., Li, F., Ruchalski, K., Mosser, D. D., Schwartz, J. H., Wang, Y., and Borkan, S. C. (2003). Hsp72 inhibits focal adhesion kinase degradation in ATP-depleted renal epithelial cells. J. Biol. Chem., 278, 18214–18220. Martin, C. A., Carsons, S. E., Kowalewski, R., Bernstein, D., Valentino, M., and Santiago-Schwarz, F. (2003). Aberrant extracellular and dendritic cell (DC) surface expression of heat shock protein (hsp)70 in the rheumatoid joint: possible mechanisms of hsp/DC-mediated cross-priming. J. Immunol., 171, 5736–5742. Martin, U., and Roemer, D. (1977). Ketotifen: a histamine release inhibitor. Monogr. Allergy, 12, 145–149. Matz, J. M., LaVoi, K. P., and Blake, M. J. (1996a). Adrenergic regulation of the heat shock response in brown adipose tissue. J. Pharmacol. Exp. Ther., 277, 1751–1758. Matz, J. M., LaVoi, K. P., Moen, R. J., and Blake, M. J. (1996b). Coldinduced heat shock protein expression in rat aorta and brown adipose tissue. Physiol. Behav., 60, 1369–1374. Matzinger, P. (1994). Tolerance, danger, and the extended family. Annu. Rev. Immunol., 12, 991–1045. Matzinger, P. (1998). An innate sense of danger. Semin. Immunol., 10, 399–415. McLeish, K. R., Dean, W. L., Wellhausen, S. R., and Stelzer, G. T. (1989). Role of intracellular calcium in priming of human peripheral blood monocytes by bacterial lipopolysaccharide. Inflammation, 13, 681–692. Mesches, M. H., Fleshner, M., Heman, K. L., Rose, G. M., and Diamond, D. M. (1999). Exposing rats to a predator blocks primed burst potentiation in the hippocampus in vitro. J. Neurosci., 19, RC18. Moraska, A., Campisi, J., Nguyen, K. T., Maier, S. F., Watkins, L. R., and Fleshner, M. (2002). Elevated IL-1beta contributes to antibody suppression produced by stress. J. Appl. Physiol., 93, 207–215.
Morimoto, R. I. (1994). The biology of heat shock proteins and molecular chaperones. Cold Spring Harbor, NY: Cold Spring Harbor Laboratory. Morimoto, R. I. (1998). Regulation of the heat shock transcriptional response: cross talk between a family of heat shock factors, molecular chaperones, and negative regulators. Genes. Dev., 12, 3788–3796. Moseley, P. L. (1998). Heat shock proteins and the inflammatory response. Ann. N. Y. Acad. Sci., 856, 206–213. Multhoff, G. (2002). Activation of natural killer cells by heat shock protein 70. Int. J. Hyperthermia., 18, 576–585. Multhoff, G., and Botzler, C. (1998). Heat-shock proteins and the immune response. Ann. N. Y. Acad. Sci., 851, 86–93. Multhoff, G., Botzler, C., Wiesnet, M., Muller, E., Meier, T., Wilmanns, W., and Issels, R. D. (1995). A stress-inducible 72-kDa heat-shock protein (Hsp72) is expressed on the surface of human tumor cells, but not on normal cells. Int. J. Cancer, 61, 272–279. Multhoff, G., Mizzen, L., Winchester, C. C., Milner, C. M., Wenk, S., Eissner, G., Kampinga, H. H., Laumbacher, B., and Johnson, J. (1999). Heat shock protein 70 (Hsp70) stimulates proliferation and cytolytic activity of natural killer cells. Exp. Hematol., 27, 1627–1636. Multhoff, G., Pfister, K., Gehrmann, M., Hantschel, M., Gross, C., Hafner, M., and Hiddemann, W. (2001). A 14-mer Hsp70 peptide stimulates natural killer (NK) cell activity. Cell Stress Chaperones, 6, 337–344. Nazli, A., Yang, P. C., Jury, J., Howe, K., Watson, J. L., Soderholm, J. D., Sherman, P. M., Perdue, M. H., and McKay, D. M. (2004). Epithelia under metabolic stress perceive commensal bacteria as a threat. Am. J. Pathol., 164, 947–957. Nettelbladt, C. G., Katouli, M., Bark, T., Svenberg, T., Mollby, R., and Ljungqvist, O. (2003). Orally inoculated Escherichia coli strains colonize the gut and increase bacterial translocation after stress in rats. Shock, 20, 251–256. Ohashi, K., Burkart, V., Flohe, S., and Kolb, H. (2000). Cutting edge: heat shock protein 60 is a putative endogenous ligand of the toll-like receptor-4 complex. J. Immunol., 164, 558–561. Panjwani, N. N., Popova, L., and Srivastava, P. K. (2002). Heat shock proteins gp96 and Hsp70 activate the release of nitric oxide by APCs. J. Immunol., 168, 2997–3003. Park, C. R., Campbell, A. M., and Diamond, D. M. (2001). Chronic psychosocial stress impairs learning and memory and increases sensitivity to yohimbine in adult rats. Biol. Psychiatry, 50, 994–1004. Paroo, Z., Dipchand, E. S., and Noble, E. G. (2002a). Estrogen attenuates postexercise Hsp70 expression in skeletal muscle. Am. J. Physiol. Cell Physiol., 282, C245–251. Paroo, Z., Haist, J. V., Karmazyn, M., and Noble, E. G. (2002b). Exercise improves postischemic cardiac function in males but not females: consequences of a novel sex-specific heat shock protein 70 response. Circ. Res., 90, 911–917. Paroo, Z., and Noble, E. G. (1999). Isoproterenol potentiates exerciseinduction of Hsp70 in cardiac and skeletal muscle. Cell Stress Chaperones, 4, 199–204. Paroo, Z., Tiidus, P. M., and Noble, E. G. (1999). Estrogen attenuates Hsp72 expression in acutely exercised male rodents. Eur. J. Appl. Physiol. Occup. Physiol., 80, 180–184. Paterson, H. M., Murphy, T. J., Purcell, E. J., Shelley, O., Kriynovich, S. J., Lien, E., Mannick, J. A., and Lederer, J. A. (2003). Injury primes the innate immune system for enhanced Toll-like receptor reactivity. J. Immunol., 171, 1473–1483. Pirkkala, L., Nykanen, P., and Sistonen, L. (2001). Roles of the heat shock transcription factors in regulation of the heat shock response and beyond. FASEB J., 15, 1118–1131.
47. Extracellular Hsp72 and Immunity Pittet, J. F., Lee, H., Morabito, D., Howard, M. B., Welch, W. J., and Mackersie, R. C. (2002). Serum levels of Hsp 72 measured early after trauma correlate with survival. J. Trauma., 52, 611–617. Pockley, A. G. (2003). Heat shock proteins as regulators of the immune response. Lancet, 362, 469–476. Pockley, A. G., De Faire, U., Kiessling, R., Lemne, C., Thulin, T., and Frostegard, J. (2002). Circulating heat shock protein and heat shock protein antibody levels in established hypertension. J. Hypertens., 20, 1815–1820. Pockley, A. G., Georgiades, A., Thulin, T., de Faire, U., and Frostegard, J. (2003). Serum heat shock protein 70 levels predict the development of atherosclerosis in subjects with established hypertension. Hypertension, 42, 235–238. Prohaszka, Z., and Fust, G. (2004). Immunological aspects of heatshock proteins—the optimum stress of life. Mol. Immunol., 41, 29–44. Prohaszka, Z., Singh, M., Nagy, K., Kiss, E., Lakos, G., Duba, J., and Fust, G. (2002). Heat shock protein 70 is a potent activator of the human complement system. Cell Stress Chaperones, 7, 17–22. Pugh, C. R., Fleshner, M., Tremblay, D. and Rudy, J. W. (1997). A selective role for corticosterone in contextual fear conditioning. Behavioral Neuroscience, 111, 503–511. Quintana, F. J., and Cohen, I. R. (2005). Heat shock proteins as endogenous adjuvants in sterile and septic inflammation. J. Immunol., 175, 2777–2782. Raasmaja, A., Mohell, N., and Nedergaard, J. (1984). Increased alpha 1-adrenergic receptor density in brown adipose tissue of coldacclimated rats and hamsters. Eur. J. Pharmacol., 106, 489–498. Rea, I. M., McNerlan, S., and Pockley, A. G. (2001). Serum heat shock protein and anti-heat shock protein antibody levels in aging. Exp. Gerontol., 36, 341–352. Redaelli, C. A., Wagner, M., Kulli, C., Tian, Y. H., Kubulus, D., Mazzucchelli, L., Wagner, A. C., and Schilling, M. K. (2001). Hyperthermia-induced Hsp expression correlates with improved rat renal isograft viability and survival in kidneys harvested from non–heart-beating donors. Transpl. Int., 14, 351–360. Reed, R. C., and Nicchitta, C. V. (2000). Chaperone-mediated crosspriming: a hitchhiker’s guide to vesicle transport (review). Int. J. Mol. Med., 6, 259–264. Ritossa, F. (1962). A new puffing pattern induced by temperature shock and DNP in Drosophila. Experientia., 15, 571–573. Ruchalski, K., Mao, H., Singh, S. K., Wang, Y. D., Mosser, D., Li, F. H., Schwartz, J. H., and Borkan, S. C. (2003). Hsp72 inhibits apoptosis-inducing factor release in ATP depleted renal epithelial cells. Am. J. Physiol. Cell Physiol., 285, 1483–1493. Rudy, J. W. (1993). Contextual conditioning and auditory cue conditioning dissociate during development. Behav. Neurosci., 107, 887–891. Rudy, J. W. (1994). Ontogeny of context-specific latent inhibition of conditioned fear: implications for configural associations theory and hippocampal formation development. Dev. Psychobiol., 27, 367–379. Rudy, J. W., and Morledge, P. (1994). Ontogeny of contextual fear conditioning in rats: implications for consolidation, infantile amnesia, and hippocampal system function. Behav. Neurosci., 108, 227–234. Rudy, J. W., and O’Reilly, R. C. (1999). Contextual fear conditioning, conjunctive representations, pattern completion, and the hippocampus. Behav. Neurosci., 113, 867–880. Santoro, M. G. (2000). Heat shock factors and the control of the stress response. Biochem. Pharmacol., 59, 55–63. Sauter, B., Albert, M. L., Francisco, L., Larsson, M., Somersan, S., and Bhardwaj, N. (2000). Consequences of cell death: exposure to necrotic tumor cells, but not primary tissue cells or apoptotic
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cells, induces the maturation of immunostimulatory dendritic cells. J. Exp. Med., 191, 423–434. Smith, J. A., and Pyne, D. B. (1997). Exercise, training, and neutrophil function. Exerc. Immunol. Rev., 3, 96–116. Sondermann, H., Becker, T., Mayhew, M., Wieland, F., and Hartl, F. U. (2000). Characterization of a receptor for heat shock protein 70 on macrophages and monocytes. Biol. Chem., 381, 1165–1174. Srivastava, P. (2002). Interaction of heat shock proteins with peptides and antigen presenting cells: chaperoning of the innate and adaptive immune responses. Ann. Rev. Immunol., 20, 395–425. Srivastava, P. K., and Heike, M. (1991). Tumor-specific immunogenicity of stress-induced proteins: convergence of two evolutionary pathways of antigen presentation? Semin. Immunol., 3, 57–64. Sun, L., Chang, J., Kirchhoff, S. R., and Knowlton, A. A. (2000). Activation of HSF and selective increase in heat-shock proteins by acute dexamethasone treatment. Am. J. Physiol. Heart Circ. Physiol., 278, H1091–1097. Takaki, A., Huang, Q. H., Somogyvari-Vigh, A., and Arimura, A. (1994). Immobilization stress may increase plasma interleukin-6 via central and peripheral catecholamines. Neuroimmunomodulation, 1, 335–342. Thomas, G., Souil, E., Richard, M. J., Saunier, B., Polla, B. S., and Bachelet, M. (2002). Hyperthermia assists survival of astrocytes from oxidative-mediated necrotic cell death. Cell Mol. Biol. (Noisy-le-grand), 48, 191–198. Tissieres, A., Mitchell, H. K., and Tracy, U. (1974). Protein synthesis in salivary glands of Drosophila melanogaster: relation to chromosome puffs. Journal of Molecular Biology, 84, 389–398. Todryk, S. M., Melcher, A. A., Dalgleish, A. G., and Vile, R. G. (2000). Heat shock proteins refine the danger theory. Immunology, 99, 334–337. Tomioka, H., and Saito, H. (1992). Characterization of immunosuppressive functions of murine peritoneal macrophages induced with various agents. Journal of Leukocyte Biology, 51, 24–31. Tsan, M. F., and Gao, B. (2004). Endotoxin contamination in recombinant human heat shock protein 70 (Hsp70) preparation is responsible for the induction of tumor necrosis factor alpha release by murine macrophages. Journal of Biological Chemistry, 278, 174–179. Udelsman, R., Blake, M. J., and Holbrook, N. J. (1991). Molecular response to surgical stress: specific and simultaneous heat shock protein induction in the adrenal cortex, aorta, and vena cava. Surgery, 110, 1125–1131. Udelsman, R., Blake, M. J., Stagg, C. A., and Holbrook, N. J. (1994a). Endocrine control of stress-induced heat shock protein 70 expression in vivo. Surgery, 115, 611–616. Udelsman, R., Blake, M. J., Stagg, C. A., Li, D. G., Putney, D. J., and Holbrook, N. J. (1993). Vascular heat shock protein expression in response to stress. Endocrine and autonomic regulation of this age-dependent response. J. Clin. Invest., 91, 465–473. Udelsman, R., Li, D. G., Stagg, C. A., Gordon, C. B., and Kvetnansky, R. (1994b). Adrenergic regulation of adrenal and aortic heat shock protein. Surgery, 116, 177–182. Vabulas, R. M., Ahmad-Nejad, P., Ghose, S., Kirschning, C. J., Issels, R. D., and Wagner, H. (2002). Hsp70 as endogenous stimulus of the Toll/interleukin-1 receptor signal pathway. J. Biol. Chem., 277, 15107–15112. Valen, G., Kawakami, T., Tahepold, P., Dumitrescu, A., Lowbeer, C., and Vaage, J. (2000). Glucocorticoid pretreatment protects cardiac function and induces cardiac heat shock protein 72. Am. J. Physiol. Heart Circ. Physiol., 279, H836–843. van Eden, W., Koets, A., van Kooten, P., Prakken, B., and van der Zee, R. (2003). Immunopotentiating heat shock proteins:
1034
V. Psychoneuroimmunology and Pathophysiology
negotiators between innate danger and control of autoimmunity. Vaccine, 21, 897–901. van Eden, W., van der Zee, R., Paul, A. G., Prakken, B. J., Wendling, U., Anderton, S. M., and Wauben M. H. (1998). Do heat shock proteins control the balance of T-cell regulation in inflammatory diseases? Immunol. Today, 19, 303–307. van Eden, W., van der Zee, R., and Prakken, B. (2005). Heat-shock proteins induce T-cell regulation of chronic inflammation. Nat. Rev. Immunol., 5, 318–330. Velin, A. K., Ericson, A. C., Braaf, Y., Wallon, C., and Soderholm, J. D. (2004). Increased antigen and bacterial uptake in follicle associated epithelium induced by chronic psychological stress in rats. Gut, 53, 494–500. Visintin, A., Mazzoni, A., Spitzer, J. H., Wyllie, D. H., Dower, S. K., and Segal, D. M. (2001). Regulation of Toll-like receptors in human monocytes and dendritic cells. J. Immunol., 166, 249– 255. Vollmer, R. R., Meyers-Schoy, S. A., Kolibal-Pegher, S. S., and Edwards, D. J. (1995). The role of the adrenal medulla in neural control of blood pressure in rats. Clin. Exp. Hypertens., 17, 649–667. Walsh, R. C., Koukoulas, I., Garnham, A., Moseley, P. L., Hargreaves, M., and Febbraio, M. A. (2001). Exercise increases serum Hsp72 in humans. Cell Stress Chaperones, 6, 386–393. Wang, Y., Kelly, C. G., Karttunen, J. T., Whittall, T., Lehner, P. J., Duncan, L., MacAry, P., Younson, J. S., Singh, M., Oehlmann, W., Cheng, G., Bergmeier, L., and Lehner, T. (2001). CD40 is a cellular receptor mediating mycobacterial heat shock protein 70 stimulation of CC-chemokines. Immunity, 15, 971–983. Wang, Y., Kelly, C. G., Singh, M., McGowan, E. G., Carrara, A. S., Bergmeier, L. A., and Lehner, T. (2002). Stimulation of Th1polarizing cytokines, C-C chemokines, maturation of dendritic cells, and adjuvant function by the peptide binding fragment of heat shock protein 70. J. Immunol., 169, 2422–2429. Wang, Y., Whittall, T., McGowan, E., Younson, J., Kelly, C., Bergmeier, L. A., Singh, M., and Lehner, T. (2005). Identification of stimulating and inhibitory epitopes within the heat shock protein 70 molecule that modulate cytokine production and maturation of dendritic cells. J. Immunol., 174, 3306–3316.
Wright, B. H., Corton, J. M., El-Nahas, A. M., Wood, R. F., and Pockley, A. G. (2000). Elevated levels of circulating heat shock protein 70 (Hsp70) in peripheral and renal vascular disease. Heart Vessels, 15, 18–22. Wu, B. J., Kingston, R. E., and Morimoto, R. I. (1986). Human Hsp70 promoter contains at least two distinct regulatory domains. Proc. Natl. Acad. Sci. USA, 83, 629–633. Wu, C. (1995). Heat shock transcription factors: structure and regulation. Annu. Rev. Cell Dev. Biol., 11, 441–469. Xiao, X., Zuo, X., Davis, A. A., McMillan, D. R., Curry, B. B., Richardson, J. A., and Benjamin, I. J. (1999). HSF1 is required for extra-embryonic development, postnatal growth and protection during inflammatory responses in mice. Embo. J., 18, 5943–5952. Xie, Y., Chen, C., Stevenson, M. A., Auron, P. E., and Calderwood, S. K. (2002a). Heat shock factor 1 represses transcription of the IL-1beta gene through physical interaction with the nuclear factor of interleukin 6. J. Biol. Chem., 277, 11802–11810. Xie, Y., Chen, C., Stevenson, M. A., Hume, D. A., Auron, P. E., and Calderwood, S. K. (2002b). NF-IL6 and HSF1 have mutually antagonistic effects on transcription in monocytic cells. Biochem. Biophys. Res. Commun., 291, 1071–1080. Yokoyama, H., Iinuma, K., Yanai, K., Watanabe, T., Sakurai, E., and Onodera, K. (1993). Proconvulsant effect of ketotifen, a histamine H1 antagonist, confirmed by the use of d-chlorpheniramine with monitoring electroencephalography. Methods Find Exp. Clin. Pharmacol., 15, 183–188. Yoo, C. G., Lee, S., Lee, C. T., Kim, Y. W., Han, S. K., and Shim, Y. S. (2000). Anti-inflammatory effect of heat shock protein induction is related to stabilization of I kappa B alpha through preventing I kappa B kinase activation in respiratory epithelial cells. J. Immunol., 164, 5416–5423. Zidel, Z., and Masek, K. (1998). Erratic behavior of nitric oxide within the immune system: illustrative review of conflicting data and their immunopharmacological aspects. International Journal of Immunopharmacology, 20, 319–343. Zugel, U., and Kaufmann, S. H. (1999). Role of heat shock proteins in protection from and pathogenesis of infectious diseases. Clin. Microbiol. Rev., 12, 19–39.
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48 Cold-Restraint-induced Immune and Biochemical Changes Inhibit Host Resistance to Listeria REBECCA T. EMENY AND DAVID A. LAWRENCE
I. INTRODUCTION: NEUROIMMUNE INTERACTIONS AND HOST DEFENSES 1035 II. SHORT-TERM COLD-RESTRAINT TREATMENT: A MODEL FOR STRESS-RELATED IMMUNOSUPPRESSION 1036 III. HOST RESISTANCE TO LISTERIA MONOCYTOGENES INFECTION IS IMPAIRED BY COLD-RESTRAINT TREATMENT 1037 IV. β-ADRENERGIC RECEPTOR EXPRESSION AND SIGNALING IN IMMUNE AND NONIMMUNE CELLS 1042
frequent occurrences in everyday life, namely, psychological or physical stressors and exposure to common infectious agents. Our studies have demonstrated that the psychological stress of inescapable restraint, combined with the physiological stress of cold (4° C) exposure for 1 hour, suppresses host defenses against a low-dose infection with the facultative, intracellular, Gram-positive bacterium Listeria monocytogenes (LM) (17). Studies from our laboratory and others have provided evidence for an immunosuppressive role of the peripheral sympathetic nervous system (SNS) during experimental LM infection. A current research focus is on understanding the β-adrenergic receptor (βAR) mechanisms that regulate host-pathogen interactions under normal or stressful conditions. This chapter reviews the use of the cold-restraint model to investigate stress-induced inhibition of host defenses against a bacterial infection. A summary of evidence for the role of sympathetic mediators of the stress response, particularly the β1and β2-adrenergic receptors (β1AR and β2AR), in immune regulation will be presented, followed by a review of the known and postulated consequences of adrenergic signaling in immune cells. Finally, the importance of understanding cellular and molecular mechanisms that regulate neuroimmune interactions will be addressed, in the context of public health and clinical practice.
I. INTRODUCTION: NEUROIMMUNE INTERACTIONS AND HOST DEFENSES The nervous system and the immune system rival one another in terms of both complexity and adaptive potential. Both systems can influence and regulate themselves and one another; in individuals who experience excessive stress, disrupted neuroimmune homeostasis can cause sickness. A focus of our research is on the underlying mechanisms of neuroimmune interactions, specifically those processes that influence an individual’s susceptibility to infections. The paradigm of short-term cold-restraint stress has been used to assess effects on host defenses of mice infected with a low dose of bacteria. This model attempts to simulate PSYCHONEUROIMMUNOLOGY, 4E VOLUME II
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Copyright © 2007 by Elsevier, Inc. All rights of reproduction in any form reserved.
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II. SHORT-TERM COLD-RESTRAINT TREATMENT: A MODEL FOR STRESSRELATED IMMUNOSUPPRESSION In general medical terms, stress is considered to be any condition resulting in perturbation of the body’s homeostasis (Gr, homeo—stable/same + Gr. -stasis— state) (23). The term allostasis (Gr. allos—other/different) is used to define a normally beneficial process that maintains stability under abnormal or “stressful” conditions (122). Physiologic responses to stress include increased heart rate and subsequently elevated blood pressure, increased glycogenolysis in the liver, increased lipolysis in adipose tissue, and relaxation of smooth muscle in the lungs. The crucial basis for the existence (i.e., the raison d’etre) of this evolutionarily programmed process is to mobilize glucose and the oxygen needed to generate ATP, the energy source required to adapt and respond to an environmental stressor. The unregulated or excessive production of stress response mediators that induce these organspecific changes is termed allostatic load, and heightened or prolonged allostatic load can have damaging effects, leading to disease and susceptibility to infection (83, 84). When mice undergo a 1-hour cold-restraint treatment, increased allostatic load (or stress mediators) renders the mice more susceptible to a low-dose bacterial infection (17). The combined psychological and physiological changes elicited by cold-restraint treatment cause a biochemical response characteristic of the fight/flight and freezing/hide reactions observed in dominant and subordinate animals, respectively, when confronted with an environmental stressor (61). For our cold-restraint model, mice are contained in well-ventilated 50-ml conical tubes for 1 hour at 4° C, in the dark. Cold-restraint is a very acute stressor, in that corticosterone (a common indicator of stress) is immediately elevated for a transient period. Historically, cold-restraint treatment has been used to characterize neurogastric interactions, since short-term cold-restraint treatment can cause ulcers in rats (96). Many other stress-inducing models, such as shortterm restraint (2–6 hours), repeat restraint (14 hours daily for 7 consecutive days), forced swimming, social confrontation, and inescapable foot shock, are known to cause immunologic alterations. It is important to note that systemic changes differ for each acute (29) or chronic (100) stressor studied. For example, 40-minute swimming and 1-hour cold treatment (both considered to be physical, metabolic stressors) as well as 1-hour restraint, a psychological stressor, cause an increase in
corticosterone, but only restraint induces significant increases in serum homocysteine (29), a stress-induced cardiovascular risk factor that is also implicated in immune dysfunction (28,116). Therefore, direct comparison of the stress-induced immunologic changes that arise within different stress paradigms is challenging. In the following discussion of stress-induced neuroimmune interactions, we will focus only on consequences of short-term restraint or cold-restraint treatment. For a better understanding of the neuroimmune interactions that accompany cold-restraint inhibition of immunity against LM, a review of the systemic changes induced by cold-restraint treatment will be presented in section III. LM infection is a widely utilized model of host-pathogen interaction that has been extensively studied (129). Section IIIB and Section IIIC will introduce the host defense mechanisms that are known to contribute to a successful anti-LM response, followed by an analysis of the neuroimmune interactions that likely influence host defenses during LM infection.
A. Neuroendocrine and Biochemical Changes Associated with Cold-Restraint Treatment Upon perception of a challenge or threat, initial sensory impulses arising in the cortex are relayed through brain stem nuclei (i.e., the dorsal vagal complex and adrenergic cell groups) and the limbic region to stimulate the paraventricular nucleus of the hypothalamus to produce corticotropin-releasing factor (CRF), a critical mediator of the stress response (7,12,61). Cold-restraint stress has been shown to cause alterations of norepinephrine (NE) levels in limbic regions (92); as a consequence of neurotransmitter signaling, CRF is released and the hypothalamicpituitary-adrenal (HPA) axis and the sympathoadreno-medullary system (SAS) are activated. Glucocorticoids (corticosterone in the mouse and cortisol in humans), the hallmark products of HPA activation, are released by the adrenal cortex, while sympathetic neurons that synapse with cells of the inner adrenal medulla release the catecholamines NE and epinephrine (Epi) directly into the blood stream. Post-ganglionic sympathetic neurons also release NE as a neurotransmitter directly into innervated tissue. Both the primary and secondary lymph organs are innervated by sympathetic neurons (15,36,40,107,123). Our studies show that cold-restraint treatment induces the HPA axis, the SNS, and oxidative stress in
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mice. Significant increases in the levels of plasma corticosterone and splenic NE are measured in stresstreated mice, relative to controls (Figure 1A and B). As previously mentioned, this biochemical response is acute, in that corticosterone levels return to baseline by 3–4 hours post-stress treatment (18, 20). In addition to neuroendocrine changes, cold-restraint treatment induces a mild hypothermic state, which likely contributes to the oxidative stress commonly observed in this model (Figure 1C).
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Cellular oxidation is characterized by a loss of free sulfhydryls or thiols (R-SH), due to the conversion of these groups to intra- or inter-chain disulfides (R-S-SR) on or between proteins. Immediately following a 1-hour cold-restraint treatment, total cellular thiols increase and extracellular surface thiols decrease, as measured by the thiol-specific compounds coumarinyl-phenyl maleimide and alexa-488 maleimide, respectively (5,67) (Figure 2). A loss of surface thiols on peripheral blood lymphocytes, particularly those of the natural killer (NK) cell subset, occurs after the coldrestraint treatment (Figure 2A). The marked decreases of extracellular thiols with concomitant increases in total cellular thiols induced by cold-restraint have been observed for blood, but not splenic, lymphocytes (Figure 2B). In support of our findings, others have demonstrated that cold-restraint–induced oxidative stress, reported as increased gastric mucosal myeloperoxidase activity (102), superoxide dismutase activity, and lipid peroxidation (127), resulted in damaged gastric mucosal surfaces and ulceration. Not surprisingly, increased lipid peroxidation in the serum of clinical peptic ulceration and gastric carcinoma patients has been reported (127). Additionally, hepatic glutathione (GSH) levels are decreased following cold-restraint, which indicates an oxidized microenvironment in liver tissue following this stress treatment (120). Oxidative stress is known to specifically affect immune cell function. For example, the activation and proliferation of lymphocytes depend on the redox state of the cellular microenvironment (38,67). Macrophage (Mφ) function is also redox-dependent (2,99,104). An increase in free radicals following 4hour cold restraint was recently shown to be associated with altered Mφ activity, as well as decreased chemotaxis and phagocytosis (51). Furthermore, the intracellular thiol content of activated Mφ in vitro is known to influence the Th1/Th2 generation of cytokines (89).
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FIGURE 1 Cold-restraint treatment (1 hour) is associated with increased HPA (A) and SNS (B) activity and decreased core body temperature (C). Immediately following treatment with cold, restraint, or combined cold restraint for 1 hour, core body temperatures were measured before BALB/c mice (n = 12) were sacrificed, to yield blood that was processed for serum CORT analysis by EIA and spleens that were immediately frozen and stored for HPLC analysis of NE. Data are presented as mean ± Std. Dev. *Significant differences (p < 0.05) between treatment groups were evaluated using one-way ANOVA and Tukey’s post hoc test (R. T. Emeny, J. Hornickel, D. A. Lawrence).
III. HOST RESISTANCE TO LISTERIA MONOCYTOGENES INFECTION IS IMPAIRED BY COLD-RESTRAINT TREATMENT To identify the deleterious effects of cold-restraint stress on host resistance to LM, it is critical that we understand the pathology of an infection with LM. Primary infection with LM activates both innate and adaptive immune mechanisms. Early host responses
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V. Psychoneuroimmunology and Pathophysiology
A
CD3+
Mean Fluorescence Intensity
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FIGURE 2 Intracellular and cell-surface changes in thiol content measured in peripheral blood lymphocytes and splenocytes obtained from 6–8-week-old male mice. (A) Changes in the quantity of free surface sulfhydryls on blood lymphocyte populations (B-cells, NKs, and T-cells, expressing CD19+, CD3−, and CD3+, respectively) were measured by fluorescent labeling with the impermeable alexa-488 maleimide compound immediately following 1-hour cold-restraint (CR) treatment of BALB/c mice (n = 12 control, n = 14 CR). Similar results were obtained using FVB/NJ mice (data not shown). (B) Numeration of total thiols of serum, white blood cells (wbc), and splenic lymphocytes obtained from FVB/NJ mice (n = 3) were detected after 1-hour cold-restraint treatment using the thiol-specific compound coumarinyl-phenyl maleimide. Data are presented as mean ± Std. Dev. *Significant differences (p < 0.05) between treatment groups were evaluated using one-way ANOVA and Tukey’s post hoc test (R. T. Emeny, J. Hornickel, D. A. Lawrence).
are characterized by the recruitment of neutrophils, macrophages, and NK cells to sites of infection. Once activated, these innate cells produce bactericidal oxidants and immune-modulating cytokines (101). Cytokine production is greatly influenced by the bacterial load (55), in that an increase in LM colonization elicits an inflammatory-stress response and subsequent upregulation of the cytokines IL-1, IL-6, and TNF-α, through a process termed neurogenic inflammation (12). Essential to the non-specific host response to LM is the early recruitment of monocytes to sites of bacterial infection (26). Activated macrophages are thought to be the main effectors of bacterial clearance (60);
however, NK cells and recruited CD8+ T-cells are also involved in mediating successful bacterial clearance, which occurs on about day 3 after the initial infection, the time at which innate responses begin to convert to adaptive immune mechanisms (91,129). Whether an experimental infection is administered intraperitoneal (i.p.) or intravenous (i.v.), the liver is thought to be the organ primarily responsible for LM clearance (87). Since a successful host response against primary LM infection is dependent upon the coordination of both innate and T-cell (but not B-cell) defense mechanisms, it is a useful infectious model for the analysis of neuroimmune effects on host innate and cell-mediated immunity.
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48. Cold-Restraint-induced Immune and Biochemical Changes Inhibit Host Resistance to Listeria
Cold-restraint treatment administered just before a low-dose infection with LM (i.v.) inhibits host resistance (Table 1, Figure 3). Cold-restraint treated BALB/ c mice had significantly increased LM colonization in the liver and spleen on day 3 as compared to control mice (17, 19). The increased bacterial burden was associated with significantly higher levels of IL-6 and TNFα in the spleen, measured on days 1 and 2, and with higher levels of IL-6 and IFN-γ in the serum on day 3 (20). Cytokine mRNA evaluated 1 day after LM infection by RNase protection assay showed significant increases in IL-1β, IL-1α, IL-1Ra, and IL-6 expression in spleens from cold-restraint treated mice, in comparison to those from control mice (20). In general, the absolute numbers of splenic and blood immune cell subsets (B-, T-, and NK cells; Mφ; neutrophils) do not change over the course of initial infection (days 1–3); however, cold-restraint treatment was observed to cause a significant increase on day 1 of activated (CD69+) CD4+ and CD8+ T-cells and non-T (CD3−) cells in the spleen (19). To further evaluate specific immune cell subsets that may be negatively affected by cold-restraint–induced immunosuppression, studies with SCID mice (18) and mice deficient in CD4 T-cells were conducted (19). Neither SCID mice nor CD4−/− mice were immunocompromised by coldrestraint treatment; in fact, anti-LM responses were enhanced overall in these immunodeficient mice as compared to wild-type BALB/c mice. These experiments suggest that CD4+ T-cells, possibly regulatory T-cells, or downstream CD8+ T-cell effectors are involved in stress-induced immunosuppression. TABLE 1 Pharmacologic treatment or genetic deficiency Intrastriatal 6-OHDA Intracerebroventricular 6-OHDA DA β hydroxylase−/− i.p. 6-OHDA i.p. 6-OHDA in IFN-γ−/− i.p. 6-OHDA in IL-10−/− i.p. 6-OHDA Metyrapone Phentolamine Propranolol Nadolol Atenolol ICI118,551 CD4−/− SCID IL-6−/−
However, both CD4−/− and SCID mouse strains have robust innate immunity to compensate for the lack of adaptive cell populations, which suggests that the allostatic load induced by 1-hour cold-restraint is not suppressive of such vigorous innate defenses.
A. Host Resistance to Listeria monocytogenes Infection Is Regulated by Sympathetic Activity Although cold-restraint influences both SNS and HPA activities, pharmacological studies from our laboratory have demonstrated that sympathetic activity mediates the observed stress-induced immunosuppression (Table 1). To delineate the impact of stressinduced SNS activity during an anti-LM response, the neurotoxin 6-OHDA was used to selectively and temporarily ablate dopaminergic nerves (thereby depleting peripheral tissues of catecholamines, since dopamine [DA] is the precursor to NE and Epi). Metyrapone was used to inhibit corticosterone biosynthesis, thus blocking the predominant mediator of HPA activity. Mice treated with 6-OHDA prior to coldrestraint treatment and subsequent LM-infection were protected from the negative effects of cold-restraint treatment, while the administration of metyrapone exacerbated stress-induced immunosuppression (17). In fact, mice that received chemical ablation of their peripheral SNS cleared LM more effectively than did their control litter mates, whether or not they were treated with cold-restraint. This indicates that peripherally released catecholamines are potent
Neuroimmune Mediators of Anti-listerial Host Resistance Stress treatment No stress No stress No stress No stress No stress No stress Cold-restraint Cold-restraint Cold-restraint Cold-restraint Cold-restraint Cold-restraint Cold-restraint Cold-restraint Cold-restraint Cold-restraint
Neuroimmune component disrupted
Anti-listerial response*
Ref.
Systemic catecholamines Systemic catecholamines Systemic catecholamines Peripheral catecholamines IFN-γ synthesis IL-10 synthesis Peripheral catecholamines Corticosterone Peripheral αARs Peripheral and central βARs Peripheral βARs β1ARs β2ARs CD4+ and CD8+ lymphocytes CD4+ and CD8+ lymphocytes IL-6 synthesis
Impaired Impaired Impaired Enhanced Equal to control Equal to control Enhanced Impaired Impaired Enhanced Enhanced Enhanced Impaired Enhanced Enhanced Impaired
(39) (94) (3) (17; 88; 108; 109) (88) (88) (18) (18) (18) (18) (18) (18) (18) (19) (18) (20)
*Outcome of infection as compared to control (i.e., no drug treatment or genetic alteration).
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FIGURE 3 Viable LM numbers in organs of cold-restraint (acute cold-restraint stress, ACRS) and control mice during primary infection. Male BALB/c mice (10–12-week-old; n = 3–7 mice per group) subjected to ACRS (triangles) or undisturbed (circles) were infected with LM (5–6 × 103 CFU/ mouse, i.v.) immediately after 1-hour cold restraint or an undisturbed period. Kinetics of viable LM numbers per spleen (A) and liver (B) were determined at day 0 (7 hours), or day 1, 2, 3, 5, 7, or 9 after infection. Bacteria were counted in serial dilutions of organ homogenates using blood-agar plates. Data are presented as mean ± S.E.M. ANOVA was followed by SNK post hoc analysis to compare different treatment groups; *indicates p < 0.05, and **indicates p < 0.01, when non-stressed control and cold-restraint groups are compared at the same time-point. (From L. Cao and D. A. Lawrence, 2002; with permission from the publisher.)
immunosuppressive agents against anti-LM immunity. Overall, our cold-restraint studies suggest an immunoprotective effect of corticosteroids during an LM-specific inflammatory response, whereas the activation of adrenergic receptors by stress-induced catecholamines has immunosuppressive consequences. For over 3 decades, the influences of the SNS, particularly NE and the adrenergic receptor family, have been researched and have been shown to exert modulatory effects on immune functions, with some detrimental clinical outcomes (121,128). Many of the early
studies on SNS-immune interactions evaluated phenotypic changes in cell populations or antigen-specific responses in vitro after pharmacologic or mechanical sympathectomy (75–78,133). As mentioned, studies in the last 5 years have provided ample evidence for the importance of sympathetic activity in regulation of host susceptibility to infectious organisms, in particular LM. Along with our lab, others have shown that in a normal experimental infection, host defenses against LM are enhanced by treatment with 6-OHDA: the LM colonization of livers and spleens in sympathectomized mice is significantly reduced around days 3–5 of the infection as compared to the colonization in control mice (18,88,108,109). The reduced bacterial load in mice with denervation of peripheral organs was correlated with increased numbers of splenic neutrophils (108) and activated peritoneal Mφs (109) during the first 3 days of an i.p. infection. Conversely, 6-OHDA treatment decreased splenic leukocyte numbers between days 5–7 in LM-infected mice (108), a result similar to that observed in a model of HSV infection in which 6-OHDA was shown to suppress the generation of both primary and secondary virusspecific cytotoxic T lymphocytes (CTLs) (70). It is important to note that all observed effects of 6-OHDA reported in the cited papers were reduced if mice were pre-treated with the catecholamine uptake blocker desipramine, which prevents the destruction of dopaminergic neurons by blockage of 6-OHDA uptake into NE nerve terminals (18,39,88,108,109). Interestingly, the peripheral injection of 6-OHDA does not affect the central nervous system since this molecule cannot pass the blood-brain barrier (133). However, central ablation of dopaminergic neurons by intra-striatal injection of 6-OHDA (39), bilateral injection of 6-OHDA into the lateral ventricles (94), or genetic removal of DA β-hydroxylase (an enzyme required for the production of dopamine [3]) impairs cellular immunity (Table 1). Therefore, blockage of the stimulation of ARs in the brain has immunosuppressive effects, while the peripheral loss of adrenergic signaling is immunoenhancing. How the elimination of catecholamine signaling in the brain functions to suppress peripheral immune activity is as of yet unresolved, but it likely involves inappropriate HPA axis activation (39), and dysregulation of peripheral catecholamines essential for immune homeostasis (94). The positive outcome of sympathectomy on host resistance to LM infection is thought to be a consequence of increased production of inflammatory cytokines, including IL-12, TNF-α, and IFN-γ, given that 6-OHDA treatments increased production of these cytokines by dendritic cells (DC) and splenic cultures. No immunoenhancing effect of 6-OHDA treatment was observed
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48. Cold-Restraint-induced Immune and Biochemical Changes Inhibit Host Resistance to Listeria
B. Cold-Restraint-induced Immunosuppression of Host Immunity against Listeria monocytogenes Is Mediated by b-adrenergic Receptors; Pharmacologic Studies Reveal a Role for b1-adrenergic Receptors in Neuroimmune Interactions The catecholamines NE and Epi bind both αARs and βARs. The AR family is composed of three types of 7 transmembrane, G-protein–coupled receptors, α1ARs, α2ARs, and βARs, and each type has three subtypes, namely, α1A/D, 1B, and 1C; α2A, B, and C; and β1, 2, and 3, respectively. This review focuses on the βAR subtypes; however, information from αARs that is pertinent to the functional biology of ARs in general is included. Pharmacologic studies that used αAR and βAR subtype blocking and stimulating agents identified β1AR as the predominant neurotransmitter signaling receptor through which host resistance to LM is inhibited by the cold-restraint treatment (Table 1) (18). When mice were given phentolamine, an αAR antagonist, before being subjected to LM infection either with or without cold-restraint pre-treatment, their anti-LM responses were diminished. In fact, blockage of NE signaling through αARs made even non-stressed mice sicker than their control littermates. However, mice treated with the non-selective βAR blocker propranolol showed improved host resistance, regardless of stress treatment. Mice treated with propanolol, but not phentolamine, had decreased IL-6 and IFN-γ levels in their sera and spleens on day 3 postinfection; these levels were comparable to the levels observed in non–stress-treated control mice. In splenic samples, IL-1β and TNF-α were decreased by βblockers, but not by α-blockers (18). Further βAR blocking studies using β1AR- and β2AR-specific antagonists were conducted, in order to delineate the effects of catecholamine signaling through two of the three known βARs. Administration of the β2AR-specific blocker ICI118,551 caused increased bacterial burden in both liver and spleen, whereas mice that received the β1-specific antagonist atenolol
had overall improved host defenses against the LM infection. Cold-restraint–treated mice with atenolol pre-treatment had bacterial colonization in liver and spleen almost equal to that in control mice. Therefore, the elimination of catecholamine signaling through β1ARs completely blocked the deleterious effects of cold-restraint treatment. Combined, these data suggest that a key immunomodulatory role for cold-restraint– induced signaling is through β1ARs since β2AR antagonists worsen, while β1AR antagonists improve, host resistance against LM.
C. Immunosuppression of Cold-Restraint Treatment in b2-adrenergic Receptor Deficient but Not b1-adrenergic Receptor Deficient Mice Studies performed with βAR deficient mice (24,110) have substantiated the pharmacologic evidence that signaling of NE and Epi through β1ARs affects host responses to an LM infection differently than does signaling of catecholamines through β2ARs. Our results have shown that the immunosuppressive effect of cold-restraint treatment is abolished in β1AR−/− mice, while β2AR−/− and wild-type mice succumb to LM infection when they have been immunoimpaired by cold-restraint stress pre-treatment (Figure 4). Further studies have demonstrated that on day 3 of a low-dose infection, β1AR−/− mice treated or not treated with cold restraint had lower bacterial loads in their spleen and liver homogenates than those of wild-type (FVB/NJ) control mice (34). In contrast, the splenic and liver LM colonization was increased by approximately 1 log in the cold-restraint–treated FVB/NJ and β2AR−/− mice, compared to the LM colonization of non-stressed control mice. Based on bacterial burden and mortality data, cold-restraint treatment administered before 100 80
% Survival
in studies with IFN-γ−/− and TNFα−/− mice (88). Taken together, these studies support the hypothesis that the presence of NE during an infection diminishes innate mechanisms of host defense, specifically, the recruitment of and cytokine secretion by innate immune cells. In our model of cold-restraint–induced alterations of host-pathogen interactions, the detrimental consequences of catecholamine signaling of cell subtypes, either immune or non-immune, remain uncertain; the possible mechanisms will be discussed later.
FVB/NJ FVB/NJ, Cold restraint B1AR-/B1AR-/-, Cold restraint B2AR-/B2AR-/-, Cold restraint
60 40 20 0 1
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FIGURE 4 The survival of wild-type FVB/NJ and βARdeficient mice (age 6–8 weeks, n = 4–6 per group) following a low-dose LM infection (3 × 103 colony-forming units, i.v.) with or without cold-restraint pre-treatment (R. T. Emeny and D. A. Lawrence).
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bacterial infection was clearly immunosuppresive for both wild-type and β2AR−/− mice, whereas such treatment was not harmful for the β1AR−/− mice. The beneficial effects for the latter may be due to the positive influences of corticosterone in the absence of catecholamine signaling through the β1AR. Additionally, the limitation of β1AR activity may boost immunity. Our observation that β2AR−/− and FVB wild-type mice respond similarly to the LM infection, with or without stress treatment, is supported by recent evidence that β2AR−/− mice do not differ from wild-type mice in their ability to mount contact hypersensitivity responses or T-cell–dependent antibody responses. Nonetheless, β2AR−/− B-cells are unable to mount an antigenspecific antibody response in the presence of IL-4 in vitro (115).
IV. b-ADRENERGIC RECEPTOR EXPRESSION AND SIGNALING IN IMMUNE AND NON-IMMUNE CELLS Subclasses of βARs were first discerned based on the order of pharmacological potencies of three classi-
cal catecholamines—isoproterenol (Iso), Epi, and NE (64). Kidney and adipose tissue were found to express β1ARs with binding affinities of Epi greater than or equal to those of NE, while skeletal muscle, liver, lung, and trachea expressed β2ARs and bound Epi to an extent approximately 10 times greater than for NE (64). Heart tissue has been shown to express both β1AR and β2AR (14). β3AR was found predominantly on adipocytes along with moderate levels of β1AR and with low levels of α1A+DARs (22). Pharmacologic expression studies that used Chinese hamster ovary cells indicated that β3ARs have a higher affinity for NE than for Epi, in contrast to the affinity of β2ARs (124). Because little is known about the β3AR in immune function, this chapter will focus mainly on the β1- and β2ARs. The murine β1AR and β2AR structures are shown in Figure 5. Both receptors are palmitylated, indicating localization in lipid rafts that could, hypothetically, place them in close proximity to T-cell receptors on lymphocytes. Differences occur in both the amino- and carboxy-ends of the proteins that dictate unique activities. The β1AR has a cysteine on the extracellular Nterminus and one potential serine phosphorylation site on its intracellular cytoplasmic end, whereas the N-
-NH3+
-NH3+
b2AR
b1AR
-COO-
-COO-
CHO Cysteine Palmitate FIGURE 5 The structures of murine β1AR and β2ARs are depicted. Indicated are the 7transmembrane spanning regions through the lipid bilayer of the cell surface membrane, the extracellular amino-terminal (—NH3+), the intracellular carboxyl-terminal (—COO−), glycosylation sites (—CHO), the location of the amino acid cysteine, and a palmitate moiety (16-carbon saturated fatty acid).
48. Cold-Restraint-induced Immune and Biochemical Changes Inhibit Host Resistance to Listeria
terminus of β2AR is devoid of sulfhydryls and the Cterminus has four possible phosphorylation sites; it is hypothesized that these structural differences affect susceptibility to redox modulations that could affect configuration, and thus binding of ligands and intracellular signaling. As an example, the intracellular tail of human kidney-derived β2AR binds to an Na+/H+ exchanger regulatory factor protein that is involved in the regulation of cellular pH (46). Furthermore, recent studies that used hamster kidney cells transfected with wild-type or chimeric human βARs implicate the Cterminus of the βAR in the regulation of receptor internalization and in lysosomal degradation (71). In these studies, wild-type β1ARs and chimeric β2ARs with β1AR C-termini were resistant to agonist-mediated downregulation. Results of such research not only emphasize functional differences between these two receptors, but also illuminate actions of βAR signaling that are independent of G-protein interactions. The next section will describe the actions of βAR signaling that have been characterized in non-immune cells and in immune cells, with a review of the detection of βARs on immune cell subsets.
A. Non-immune Consequences of b-adrenergic Receptor Signaling Intrinsic to catecholamine binding by cell-surface βARs of all types is the immediate activation of Gprotein coupling to the intracellular effector adenylate cyclase (AC). This enzyme then acts to produce the second messenger cAMP, and to activate downstream molecules, such as protein kinase A (PKA) and extracellular signal-regulated kinase (ERK2). Globally, it is understood that βAR signaling increases cAMP through binding of Gs, which stimulates AC, while αARs decrease cAMP through their association with Gi, which inhibits AC, or Gq, which in turn stimulates phospholipase C (65). Furthermore, the αARs have been shown to increase protein synthesis in a fashion similar to insulin (86), while βAR signaling generally decreases protein synthesis. In myeloid cells (rat myeloid leukemia cell line IPC-81), cardiomyocytes, and adipocytes, the βAR agonist isoproterenol increases phosphorylation of eukaryotic elongation factor 2 (eEF2) (41,48,85). Phosphorylation of eEF2 inhibits its activity that is required for translocation in peptidechain elongation. Therefore, stress-induced catecholamines shut down protein synthesis in order to make ATP available for fight or flight responses such as cardiac contraction. In many tissues, the functions of βAR subtypes have been described. β1AR signaling in the heart increases the strength of contractions, and in the kidney it stimu-
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lates the release of rennin so as to increase blood pressure. Stimulation of β2AR can have vasodilating effects on blood vessels in cardiac and skeletal muscles, and can cause the relaxation of smooth muscles in the GI tract. The β3ARs mediate lipolysis and thermogenesis in adipose tissue (124). The activation of each specific βAR subset may result in either regional or localized intracellular changes. In neurons and in the myocardium, the signaling effects of β1ARs appear to have widespread cellular consequences as a result of PKA activation, whereas signaling by β2ARs appears to be spatially restricted. Immunoprecipitation and electrophysiological studies have shown that the cytoplasmic C-terminus of β2AR co-localizes with the pore-forming subunit of the predominant L-type Ca++ channel, in the rat hippocampus (27). In immune cells, this could hypothetically translate to T-cell receptor (TCR)–linked modulation (local) that affects antigen-specific activation or actin mobilization and diapedesis (regional).
B. Expression of b-adrenergic Receptors on Immune Cell Subsets Because it was known pharmacologically that the synthetic non-specific agonist isoproterenol and the natural ligands NE and Epi stimulated βARs to increase cAMP and AC activity, the first indication of βAR expression on human lymphocytes was demonstrated by catecholamine-induced lymphoblast transformation (44) and AC activity (13,82). Thereafter, radioisotype-labeled ligand-binding studies that used a heterologous mixture of cells purified from human blood provided direct evidence for the presence of βARs on mononuclear cells, polynuclear cells, and lymphocytes (134). In these studies, isoproterenol was shown to be the most potent agonist, followed by Epi and then NE. Studies of both lymphocytes and neurons have shown that Epi binds βARs with a 10-fold greater affinity than NE (4,54,134). The distribution of βARs in immune cell subpopulations is influenced by cell type. The highest receptor densities have been shown by radioligand-binding studies to be on NK cells and B-cells, followed by CD8+ T-cells and monocytes, while the lowest numbers were measured on T helper cells (Th) (11,54,74,81,100,130). Approximate receptor densities averaged between 1000 and 2000 receptors/cell, depending upon the cell type examined, but regardless of whether intact cells or isolated membranes were measured (14). Not only does receptor expression vary for each lymphocyte subset, but receptor affinities also differ, in that NKs, CTLs, and monocytes appear to have greater βAR coupling capacities than do Th and B-cells, with regard to cAMP production (56,80). For example, subsets of
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human lymphocytes were shown to bind the radioligand [125I]-cyanopindolol (ICYP) differentially, with the binding affinity of T suppressor cells (Ts; Leu2+, 9.3−) > T cytolytic cells (Tc; Leu2+, 9.3+) > Th cells (Leu3+) (54). The number of binding sites on each T lymphocyte subset (Ts∼2900, Tc∼1800, Th∼750), the affinity of agonist for βAR, and the biological activity (as measured by cAMP production or AC activity) appear to correlate (53,54,68,134). Similar to the differentiation between β1AR and β2AR expression on cells of other tissue types, the expression of these receptors on lymphocyte subsets has been determined largely by the pharmacologic activities of non-specific or specific agonists and antagonists. For example, β2ARs have been thought to be the primary βAR on rat peritoneal macrophages since a non-specific βAR antagonist (bufetolol) was shown to block Epi-induced cAMP production, while the selective β1AR antagonist failed to do so (49). Similarly, because Epi demonstrates greater binding affinities towards the βARs on T lymphocyte subsets than NE, it was concluded that β2ARs are the majority of βARs present (54). Recently, RT-PCR analysis has partially substantiated this, by demonstrating expression of β2AR mRNA by Th0 and Th1 clones, but not Th2 clones, implicating the receptor in differential regulation of Th1 and Th2 functions (105,113,115). Early radioligand binding studies demonstrated the presence of β2ARs, but not β1ARs, on NK cells (81,130). Competitive radioligand-binding assays also demonstrated that a 20-minute infusion of Epi (but not NE) into healthy volunteers decreased the expression of β2AR and α1AR on the CD16+ peripheral lymphocyte populations (which includes all FcRγIII+ cell subsets), and increased β2AR densities on the CD4+ and CD8+ peripheral blood leukocyte subsets (52). More recently, however, RT-PCR analysis identified mRNA expression of β1ARs and β2ARs as well as α1AAR on murine Langerhans cells (117), and β1-, β2-, α1-, α2A-, and α2CARs on bone marrow–derived dendritic cells (BMDCs, CD11c+) (79). Freshly isolated human peripheral blood monocytes express mRNA for β2AR and α2ARs, but stimulation with dexamethasone or the β2AR-specific agonist terbutaline can induce expression of α1B- and α1DARs (112). The expression and activity of a particular βAR on lymphoid and myeloid cells is likely to be complex, regulated by the microenvironment of the cell as well as by the surface expression and activity of other βARs (22), αARs (52), GCs (1,112) and prostaglandins (8) (to name only a few among perhaps many other molecules that can affect βAR function). An indication of the potential complexities has been demonstrated by analyses of mRNA expression in brown adipocytes.
Although mature adipocytes express β1-, β3-, α1A-, and α1DARs, mRNA expression of ARs is altered by NE such that β1ARs increase, β3ARs decrease, and β2ARs are transiently expressed (9). Additionally, NEmediated glucose uptake appears to function normally in β3AR−/− mice, which indicates that β1AR, perhaps β2AR, and α1AR signaling can compensate for β3AR deficiencies in these mice (22). The degree to which lymphocytes can be activated by catecholamines is thought to change over time, which provides a mechanism for SNS modulation throughout the development of host immunity. For example, the differentiation state of Th1 cells appears to determine the influence of βAR signaling on IFN-γ production, in that naïve T-cells produce more IFN-γ following NE exposure and antigenic stimulation, while mature Th1 clones produce less IFN-γ (113,125). Studies that used in vitro stimulated cell lines suggest that activated Mφ can be less sensitive and mature T-cells more sensitive to βAR-mediated sympathetic stimuli (103). It has long been proposed that cAMP promotes differentiation of immature lymphocytes but inhibits the function of mature lymphocytes (25). Thus, the classical methodologies that have defined βAR expression patterns of immune cells based upon pharmacological analysis may be inconclusive. Determination of β1AR and β2AR expression on immune cells has mainly relied on ligand-binding variations and on the extent of functional responsiveness to these ligands (i.e., cAMP production or AC activity), but these parameters may not be directly interrelated. For example, ligand-binding studies of β2AR distribution in respiratory-tract smooth-muscle tissue have shown the presence of β2ARs to be segment-specific, and AC coupling activity to be inversely correlated with receptor density (134). Additionally, ligand binding likely depends on cell surface topography, as well as on the expression of other surface molecules that influence receptor activity. In any case, a comprehensive analysis of βAR subsets on naïve, resting, and activated immune cells, including quantification of mRNA and protein expression, is warranted.
C. Immunologic Consequences of b-adrenergic Receptor Signaling Catecholamine signaling through βARs is known to modulate a wide range of immune functions, including altered peripheral cytokine levels (126), activation of virus-specific effectors (47), increased DTH responses (31), decreased Mφ IL-1 production (57), increased lymphocyte trafficking (especially of NK cells [30] and monocytes [35]), and decreased splenic and thymic lymphocyte chemotaxis (42). It is well documented
48. Cold-Restraint-induced Immune and Biochemical Changes Inhibit Host Resistance to Listeria
that βAR stimulation on immune cells inhibits production of pro-inflammatory cytokines (TNF-α, IL-12, and IFN-γ) and enhances the production of IL-6 and IL-10. For example, Epi and NE have both been shown to inhibit IL-12 by T-cells and to enhance IL-10 production by Mφ (32). Catecholamine signaling through β2ARs has been found to be associated with functional changes in Bcells, CD4+ lymphocytes, Mφs, NKs, and DCs. β2ARs promote T-cell-dependent antibody responses (115) and mediate antigen-specific follicular cell expansion and germinal center formation in the spleen (58). Overexpression of β2AR in a macrophage cell line significantly reduced IL-12 mRNA and protein expression following lipopolysaccharide (LPS) stimulation (50); interestingly, the β2AR inhibition of IL-12 expression by peritoneal macrophages was eliminated by exercise training of mice, which suggests that exercise downregulates β2AR activity. Other studies that utilize β2AR-specific agonists or antagonists have shown β2AR-associated inhibition of antigen-presentation by Langerhans cells (117) and β2AR-specific inhibition of IL-10 production early in LPS activation of DCs, whereas inhibition of IL-12 appeared to be mediated by both α2AR and β2ARs (79). In studies of human immune cells, the β2AR-specific agonist salbutamol blocked IL-12, but not IL-1α, IL-1β, IL-6, or IL-10, production by LPS-stimulated monocytes in vitro (95). The effects of β2AR signaling on Th1 cell function are reported to be both suppressive and enhancing, depending upon the mode of activation (i.e., LPS [95] or antigen-bound MHC class II [125], respectively), or on the developmental stage of the Th cell studied (i.e., naïve [125] or mature [114]). While these studies provide strong evidence for a role of β2ARs in many immune cell subsets, analyses of β1AR regulation of immune responses have been less intensively investigated. Furthermore, the mutual effects of β1AR and β2AR on immunity have been largely unexplored.
D. Proposed Mechanisms of b-adrenergic Receptor-Mediated Immunosuppression and Future Research Directions Both tissue-specific and cell type-specific mechanisms can account for cold-restraint–induced immunosuppression, and both β1AR- and β2AR-signaling pathways are likely to be involved. Based upon LM colonization results, cold-restraint treatment induces a more dramatic influence on host immunosuppression in liver than in spleen (Figure 3). It is possible that the expression of βARs differs between these tissues, or that the blood supply (supplying Epi) and sympathetic innervation (supplying NE) differs between
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these tissues, thereby altering the impact of catecholamine actions following cold-restraint stress. In fact, it was shown recently that β2AR mRNAs are more abundant in bovine hepatic tissue than are mRNAs of either β1AR or β3AR (with β2AR > β1AR > β3AR) (21). Furthermore, immunologic regulation in the liver is unique (131) and neuroimmune interactions in hepatic tissue require further study in a cold-restraint stress model. Since it is well documented that NK cells are required for efficient LM clearance, a simple explanation for the enhanced immunity observed in β1AR−/− mice with or without cold-restraint treatment may be that blockade or elimination of β1ARs has no impact on NK function, if NK cells do not normally express this receptor subtype (52). Our studies show that β2AR−/− mice succumb to cold-restraint treatment to an extent equal to or worse than that for wild-type mice. Perhaps, in mice lacking β2AR signaling, the beneficial stress-induced activation of NKs (via β2AR) is eliminated; inadequate activation of NK cells would be detrimental to defensive mechanisms against LM. Alternatively, β1AR-dependent mechanisms may directly influence immune cell subsets that likely express β1ARs, namely the monocyte (33,56,134) and DC populations (79). It is reported that βAR stimulation by an effective agonist requires the reduction of a disulfide bond in the active binding site, in order to initiate optimal coupling to AC (62,98,135). This activation is controlled by thiol-disulfide redox reactions, which can be disrupted by oxidative stress. In fact, oxidative stress of heart tissue has been shown to reduce βAR functioning by decreasing levels of cAMP production (45). We hypothesize that βAR activity is altered by and may contribute to stress-induced oxidation, the consequences of which are detrimental to host innate immune defenses. An association between oxygen radicals and β2AR expression by human T lymphocytes has been demonstrated; combined isoproterenol and H2O2 treatment caused a 70% reduction in sequestration of β2ARs (72). In these studies, H2O2 treatment reduced G-protein–coupled receptor kinase 2 (GRK2) protein levels and activity, but not mRNA. Expression of GRK2 is known to regulate G-protein–coupled receptor desensitization and re-sensitization. Thus, an oxidative environment may promote more β2AR expression on lymphocyte surfaces in times of stress, thereby subjecting cells to prolonged β2AR activation. In a homeostatic environment, oxidation is required to activate resting lymphocytes (37); the source of the immunoenhancing oxygen radicals is typically activated Mφ and neutrophils. Too much of a good thing
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can turn bad, in that excessive oxidation and a critical loss of surface thiols can alter CD8+ cytotoxic activity (106) and prevent T-cell activation (90). Intracellular redox regulation is also critical for lymphocyte trafficking or scavenging. For example, selective oxidation of Rho GTPase (but not Rac), by the arsenical compound PAO, causes the inhibition of stress-fiber formation and membrane ruffling, two essential processes for phagocytosis and cell migration (43). Finally, it has been proposed that the redox state of the Mφ is decisive in promoting either a cell-mediated or a humoral immune response (89,99). Resting Mφs are known to contain high levels of oxidant scavengers such as GSH and thioredoxin so as to maintain a reduced microenvironment for optimal activation of nearby lymphocytes since, as stated previously, an oxidized lymphocyte surface is associated with inhibited activation (90). A Mφ with greater reducing potential promotes Th1 responses through regulated production of NO and the cytokines IFN-γ and IL-12, whereas a Mφ with lowered reducing potential has diminished GSH and promotes a Th2-mediated host response, due to the elevated synthesis of IL-10 and IL-4 (89). We believe that the critical effect of cold restraint with our LM model is to alter the redox state of the resting macrophage, promoting a Th2-mediating phenotype, which weakens host defenses against LM. The initial cause of the altered redox state and whether βARs play a direct role are uncertain. A possible scenario is that βAR-induced inhibition of protein synthesis alters available GSH for the intracellular and extracellular maintenance of the optimal redox status. Whether the βAR-specific immunosuppressive effects of cold restraint are a consequence of βAR activity in immune or non-immune cells is poorly understood. Nonetheless, cold-restraint activation of stress mediators followed by the initiation of a systemic inflammatory response (LM infection) impairs host innate and/or adaptive immune responses. An increased understanding of several factors is crucial, if we are to attain a more comprehensive knowledge of βAR expression and function on immune cell subsets. First, molecular analysis of mRNA transcription and surface expression of all βAR subsets on immune cells would shed light on βAR-induced immunologic changes. While many years of study have elucidated the functional consequences of β2AR signaling on immune cells, little knowledge exists for β1AR and almost none for β3ARs. A single study has reported immune alterations induced by β3AR agonists in obese rats (63). Oral administration of the β3AR agonist trecadrine, which is an effective anti-obesity agent, caused an increase of CD4+ and CD8+ T-cells, yet it caused a decrease in lympho-proliferative activity.
Additional studies are needed to clarify the association between βAR subsets and redox changes of immune cells under various states of activation. Finally, a more detailed conception of an individual’s ability to manage allostatic load must be considered in stressresponse studies, for it is well documented that individuals perceive stress differently, depending upon genetic and/or behavioral characteristics (6,61,119). Generally, it appears that dominant or subordinate behavioral patterns can influence the sensitivity of an individual to a stressor, possibly through different inactivation mechanisms of stress factors (61). The mediation of allostatic load, the way an individual manages stress, is also a process relevant to aging and the associated immunosuppression that can occur in some individuals. In fact, diminished immunocompetence that is associated with aging has been linked to altered redox regulation (59,97,111); the relationships among these three parameters require further exploration.
E. The Implications of Short-term Stress for Sickness and Health A thorough understanding of the direct action of βAR signaling on immune cells will have broad therapeutic application in human health and disease. For example, a β2AR-induced increase in cAMP was shown to be coincident with decreases in TNF-α in rheumatoid arthritis patients, but not in controls (73). Therapeutic strategies for the inhibition or stimulation of specific βARs may therefore prove useful in treatment of inflammatory disorders such as arthritis, sepsis (93), allergic asthma (69), and multiple sclerosis (132), as well as in prevention of tumor metastasis (since βAR stimulation has been shown to alter NK activity and resistance to tumor metastasis in rats [118]). Prophylactic strategies like psychological counseling, which are procedures that can induce SNS activity, can improve the outcome of patients undergoing invasive surgeries. Pre-surgical psychosocial intervention has been shown to positively affect breast cancer patients’ post-operative psychological status, as well as their immune responsiveness (66). In terms of host susceptibility to infectious pathogens, stressful conditions that occur at or near the time of antigen exposure have been shown to significantly lower host immunity and to increase susceptibility to infectious disease (10,137). Furthermore, an individual’s self-perceived stress level may influence the ability of that person to mount an optimal response to vaccination (16,138). Since βARs are polymorphic, there may be clinical consequences of altered βAR signaling and susceptibility to tumor growth, pathogenic
48. Cold-Restraint-induced Immune and Biochemical Changes Inhibit Host Resistance to Listeria
infection, or chronic inflammatory disease (136). Our studies and those of many others indicate that βAR signaling influences innate and cellular immune function and survival during systemic inflammation. Delineation of the multi-faceted nature of βAR signaling, through analysis of the effects of cold-restraint stress during an LM infection, should continue to provide insights into the complex interactions between the nervous system and the immune system.
References 1. Abraham, G., Gottschalk, J., and Ungemach, F. R. (2004). Possible role of dexamethasone in sensitizing the beta-2– adrenergic receptor system in vivo in calves during concomitant treatment with clenbuterol. Pharmacology, 72, 196–204. 2. Ahmed, A. E., Aronson, J., and Jacob, S. (2000). Induction of oxidative stress and TNF-alpha secretion by dichloracetonitrile, a water disinfectant by-product, as possible mediators of apoptosis or necrosis in a murine macrophage cell line (raw). Toxicol. in vitro, 14, 199–210. 3. Alaniz, R. C., Thomas, S. A., Perez-Melgosa, M., Mueller, K., Farr, A. G., Palmitter, R. D., and Wilson, C. B. (1999). Dopamine beta-hydroxylase deficiency impairs cellular immunity. PNAS, 96, 2274–2278. 4. Ariens, E. J., and Simonis, A. M. (1983). Physiological and pharmacological aspects of adrenergic receptor classification. Biochemical Pharmacology, 32, 1539–1545. 5. Ayers, F. C., Warner, G. L., Smith, K. L., and Lawrence, D. A. (1986). Fluorometric quantitation of cellular and nonprotein thiols. Anal. Biochem., 154, 186–193. 6. Bailey, M. T., Avitsur, R., Engler, H., Padgett, D. A., and Sheridan, J. F. (2004). Physical defeat reduces the sensitivity of murine splenocytes to the suppressive effects of corticosterone. Brain, Behavior and Immunity 18, 416–424. 7. Banks, W. A. (2004). Neuroimmune networks and communication pathways: the importance of location. Brain, Behavior and Immunity, 18, 120–122. 8. Bartik, M. M., Brooks, W. H., and Roszman, T. L. (1993). Modulation of T cell proliferation by stimulation of the β-adrenergic receptor: lack of correlation between inhibition of T cell proliferation and cAMP accumulation. Cell Immunol., 148, 408–421. 9. Bengtsson, T., Cannon, B., and Nedergaard, J. (2000). Differential adrenergic regulation of the gene expression of the βadrenoceptor subtypes β1, β2, and β3 in brown adipocytes. Biochem. J., 347, 643–651. 10. Biondi, M., and Zannino, L.-G. (1997). Psychological stress, neuroimmunomodulation, and susceptibility to infectious diseases in animals and man; a review. Psychother. Psychosom., 66, 3–26. 11. Bishopric, N. H., Cohen, H. J., and Lefkowitz, R. J. (1980). Adrenergic receptors in lymphocyte subpopulations. J. Allergy Clin. Immunol., 65, 29–33. 12. Black, P. H. (2002). Stress and the inflammatory response: a review of neurogenic inflammation. Brain, Behavior and Immunity, 16, 622–653. 13. Bourne, H. R., and Melmon, K. L. (1971). Adenyl cyclase in human leukocytes: evidence for activation by separate βadrenergic and prostaglandin receptors. J. Pharmacol. Exp. Ther., 178, 1–7.
1047
14. Brodde, O.-E., Beckeringh, J. J., and Michel, M. C. (1987). Human heart β-adrenoceptors: a fair comparison with lymphocyte β-adrenoceptors? Trends in Pharmacol. Sci., 8, 403–407. 15. Bulloch, K. (1985). Neuroanatomy of lymphoid tissues. In R. Guillemin, M. Cohn, and T. Melnechuk (Eds.), Neural modulation of immunity (pp. 111–141). New York: Raven Press. 16. Burns, V. E., Carroll, D., Drayson, M., Whitham, M., and Ring, C. (2003). Life events, perceived stress and antibody response to influenza vaccination in young, healthy adults. J. Psychosom. Res., 55, 569–572. 17. Cao, L., Filipov, N. M., and Lawrence, D. A. (2002). Sympathetic nervous system plays a major role in acute cold/restraint stress inhibition of host resistance to Listeria monocytogenes. J. Neuroimmunol., 125, 94–102. 18. Cao, L., Hudson, C. A., and Lawrence, D. A. (2003). Acute cold/restraint stress inhibits host resistance to Listeria monocytogenes via β1-adrenergic receptors. Brain, Behavior and Immunity, 17, 121–133. 19. Cao, L., Hudson, C. A., and Lawrence, D. A. (2003). Immune changes during acute cold/restraint stress-induced inhibition of host resistance to Listeria. Toxicol. Sci., 74, 325–334. 20. Cao, L., and Lawrence, D. A. (2002). Suppression of host resistance to Listeria monocytogenes by acute cold/restraint stress: lack of direct IL-6 involvement. J. Neuroimmunol., 133, 132–143. 21. Carron, J., Morel, C., Hammon, H. M., and Blum, J. W. (2005). Ontogenetic development of mRNA levels and binding sites of hepatic β-adrenergic receptors in cattle. Domestic Animal Endocrinology, 28, 320–330. 22. Chernogubova, E., Hutchinson, D. S., Nedergaard, J., and Bengtsson, T. (2005). α1- and β1-adrenoceptor signaling fully compensates for β3-adrenoceptor deficiency in brown adipocyte norepinephrine-stimulated glucose uptake. Endocrinology, 146, 2271–2284. 23. Chrousos, G. P., and Gold, P. W. (1992). The concepts of stress and stress system disorders. Overview of physical and behavioral homeostasis. JAMA, 267, 1244–1252. 24. Chruscinski, A. J., Rohrer, D. K., Schauble, E., Desai, K. H., Bernstein, D., and Kobilka, B. K. (1999). Targeted disruption of the β2 adrenergic receptor gene. J. Biolog. Chem., 274, 16694–16700. 25. Coffey, R. G., and Hadden, J. W. (1985). Neurotransmitters, hormones and cyclic nucleotides in lymphocyte regulation. Fed. Proc., 44, 112–117. 26. Czuprynski, C. J., Canono, B. P., Henson, P. M., and Campbell, P. A. (1985). Genetically determined resistance to listeriosis is associated with increased accumulation of inflammatory neutrophils and macrophages, which have enhanced listericidal activity. Immunology, 55, 511–518. 27. Davare, M., Avdonin, V., Hall, D. D., Peden, E. M., Burette, A., Weinberg, R. J., Horne, M. C., Hoshi, T., and Hell, J. W. (2001). A β2 adrenergic receptor signaling complex assembled with the Ca2+ Channel Cav1.2. Science, 293. 28. Dawson, H., Collins, G., Pyle, R., Deep-Dixit, V., and Taub, D. D. (2004). The immunoregulatory effects of homocysteine and its intermediates on T-lymphocyte function. Mech. Aging Dev., 125, 107–110. 29. de Oliveira, A. C., Suchecki, D., Cohen, S., and D’Almeida, V. (2004). Acute stressor-selective effect on total plasma homocysteine concentration in rats. Pharmacol. Biochem. Behav., 77, 269–273. 30. Dhabhar, F. S., Miller, A. H., McEwen, B. S., and Spencer, R. L. (1995). Effects of stress on immune cell distribution, dynamics and hormonal mechanisms. J. Immunol., 154, 5511–5527.
1048
V. Psychoneuroimmunology and Pathophysiology
31. Dhabhar, F. S., Miller, A. H., McEwen, B. S., and Spencer, R. L. (1996). Stress-induced changes in blood leukocytes distribution, role of adrenal steroid hormones. J. Immunol., 157, 1638–1644. 32. Elenkov, I. J., Papanicolau, D. A., Wilder, R. L., and Chrousos, G. P. (1996). Modulatory effects of glucocorticoids and catecholamines on human interleukin-12 and interleukin-10 production; clinical implications. P. Assoc. Am. Physicians, 108, 1–8. 33. Elenkov, I. J., Wilder, R. L., Chrousos, G. P., and Sylvester Vizi, E. (2000). The sympathetic nerve—an integrative interface between two supersystems: the brain and the immune system. Pharmacol. Rev., 595–638. 34. Emeny, R. T., Ault, J. G., and Lawrence, D. A. (2006). Innate mechanisms modified by stress-induced catecholamines increase host susceptibility to Listeria. Immunology Annual Meeting, Abstract 5138, Boston, MA. 35. Engler, H., Dawils, L., Hoves, S., Kurth, S., Stevenson, J. R, Schauenstein, K., and Stefanski, V. (2004). Effects of social stress on blood leukocyte distribution: the role of α- and β-adrenergic mechanisms. J. Neuroimmunol., 156, 153–162. 36. Felten, S. Y., Madden, J. A., Bellinger, S. L., Kruszewska, B., Moynihan, J. A., and Felten, D. L. (1998). The role of the sympathetic nervous system in the modulation of immune response. Adv. Pharmacol., 42, 583–587. 37. Fidelus, R. K. (1988). The generation of oxygen radicals: a positive signal for lymphocyte activation. Cell Immunol., 113, 175–182. 38. Fidelus, R. K., Ginouves, P., Lawrence, D., and Tsan, M. F. (1987). Modulation of intracellular glutathione concentrations alters lymphocyte activation and proliferation. Exp. Cell Res., 170, 269–275. 39. Filipov, N. M., Cao, L., Seegal, R. F., and Lawrence, D. A. (2002). Compromised peripheral immunity of mice injected intrastriatally with six-hydroxydopamine. J. Neuroimmunol, 132, 129–139. 40. Friedman, E. M., and Irwin, M. R. (1997). Modulation of immune cell function by the autonomic nervous system. Pharmacol. Ther., 74, 27–38. 41. Fuller, S. J., and Sugden, P. H. (1988). Acute inhibition of rat heart protein synthesis in vitro during beta-adrenergic stimulation or hypoxia. Am. J. Physiol., 255, E537–E547. 42. Garcia, J. J., del Carmen Saez, M., de la Fuente, M., and Ortega, E. (2003). Noradrenaline and its end metabolite 3-methoxy4-hydroxyphenylglycol inhibit lymphocyte chemotaxis: role of α- and β-adrenoreceptors. Mol. Cell Biochemistry, 254, 305–309. 43. Gerhard, R., Harald, J., Aktories, K., and Just, I. (2003). Thiolmodifying phenylarsine oxide inhibits guanine nucleotide binding of Rho but not of Rac GTPases. Molecular Pharmacology, 63, 1349–1355. 44. Hadden, J. W., Hadden, E. M., and Middleton, E. (1970). Lymphocyte blast transformation. I. Demonstration of adrenergic receptors in human peripheral lymphocytes. Cell Immunol., 1, 583–595. 45. Haenen, G. R., Veerman, M., and Bast, A. (1990). Reduction of β-adrenoceptor function by oxidative stress in the heart. Free Radic. Biol. Med., 9, 279–288. 46. Hall, R. A., Premonet, R. T., Chow, C.-W., Blitzer, J. T., Pitcher, J. A., Claing, A., Stoffel, R. H., Barak, L. S., Shenolikar, S., Weinman, E. J., Grinstein, S., and Lefkowitz, R. J. (1998). The β2-adrenergic receptor interacts with the Na+/H+-exchanger regulatory factor to control Na+/H+ exchange. Nature, 392, 626–630.
47. Hermann, G., Beck, F. M., Tovar, C. A., Malarkey, W. B., Allen, C., and Sheridan, J. F. (1994). Stress-induced changes attributable to the sympathetic nervous system during experimental influenza viral infection in DAB/2 inbred mouse strain. J. Neuroimmunol., 53, 173–180. 48. Hovland, R., Eikhom, T. S., Proud, C. G., Cressey, L. I., Lanotte, M., Doskeland, S. O., and Houge, G. (1999). cAMP inhibits translation by inducing Ca2+/calmodulin-independent elongation factor 2 kinase activity in IPC-81 cells. FEBS Lett., 444, 97–101. 49. Ikegami, K. (1977). Modulation of adenosine 3’5’-monophosphate contents of rat peritoneal macrophages mediated by β2adrenergic receptors. Biochem. Pharmacol., 26, 1813–1816. 50. Itoh, C. E., Kizaki, T., Hitomi, Y., Hanawa, T., Kamiya, S., Ookawara, T., Suzuki, K., Izawa, T., Saitoh, D., Haga, S., and Ohno, H. (2004). Down-regulation of β2-adrenergic receptor expression by exercise training increases IL-12 production by macrophages following LPS stimulation. Biochem. Biophys. Res. Commun., 322, 979–984. 51. Izgut-Uysal, V. N., Tan, R., Bulbul, M., and Derin, N. (2004). Effect of stress-induced lipid peroxidation on functions of rat peritoneal macrophages. Cell Biol. Int., 28, 517–521. 52. Jetschmann, J.-U., Benscop, R. J., Jacobs, R., Kemper, A., Oberbeck, R., Schmidt, R. E., and Schedlowski, M. (1997). Expression and in vivo modulation of alpha- and betaadrenoceptors on human natural killer (CD16+) cells. J. Neuroimmunol., 74, 159–164. 53. Kahn, M. M., Sansoni, P., Engleman, E. G., and Melmon, K. L. (1985). Pharmacologic effects of autacoids on subsets of T cells. Regulation of expression/function of histamine-2 receptors by a subset of suppressor cells. J. Clin. Invest., 75, 1578. 54. Kahn, M. M., Sansoni, P., Silverman, E. D., Engleman, E. G., and Melmon, K. L. (1986). Beta-adrenergic receptors on human suppressor, helper, and cytolytic lymphocytes. Biochem. Pharmacol., 35, 1137–1142. 55. Kim, D., Reilly, A., and Lawrence, D. A. (2001). Relationships between IFNγ, IL-6, corticosterone, and Listeria monocytogenes pathogenesis in BALB/c mice. Cellular Immunology, 207, 13–18. 56. Knudsen, J. H., Kjaersgaard, E., and Christensen, N. J. (1995). Individual lymphocyte subset composition determines cAMP response to isoproterenol in mononuclear cell preparations from peripheral blood. Scand J. Clin. Lab. Invest., 55, 9–14. 57. Koff, W. C., Fann, A. V., Dunegan, M. A., and Lachman, L. B. (1986). Catecholamine-induced suppression of interleukin-1 production. Lymphokine Res., 5, 239–247. 58. Kohm, A. P., and Sanders, V. M. (1999). Suppression of antigenspecific Th2 cell-dependant IgM and IgG1 production following norepinephrine depletion in vivo. J. Immunol., 162, 5299–5308. 59. Kohut, M. L., and Senchina, D. S. (2004). Reversing ageassociated immunosenescence via exercise. Exerc. Immunol. Rev., 10, 6–41. 60. Kongshavn, P. (1985). Genetic control of murine listeriosis is expressed in the macrophage response. Immunol. Lett., 11, 181–188. 61. Korte, S. M., Koolhaas, J. M., Wingfield, J. C., and McEwen, B. S. (2005). The Darwinian concept of stress; benefits of allostasis and costs of allostatic load and the trade-offs in health and disease. Neuroscience and Biobehavioral Reviews, 29, 3–38. 62. Kuhl, P. W. (1985). A redox cycling model for the action of β-adrenoceptor agonists. Experientia, 41, 1118–1122.
48. Cold-Restraint-induced Immune and Biochemical Changes Inhibit Host Resistance to Listeria 63. Lamas, O., Martinez, J. A., and Marti, A. (2003). Effects of a β3-adrenergic agonist on the immune response in diet-induced (cafeteria) obese animals. J. Physiol. & Biochem., 59, 183–191. 64. Lands, A. M., Arnold, A., McAuliff, J. P., Luduena, F. P., and Brown, T. G. (1967). Differentiation of receptor systems activated by sympathomimetic amines. Nature, 214, 597– 598. 65. Landsberg, L., and Young, J. B. (1991). Physiology and pharmacology of the autonomic nervous system. In J. D. Wilson, E. Braunwald, and K. J. Isselbacher (Eds.), Harrison’s principles of internal medicine (pp. 380–392). New York: McGraw Hill. 66. Larson, M. R., Duberstein, P. R., Talbot, N. L., Caldwell C., and Moynihan, J. A. (2000). A presurgical psychosocial intervention for breast cancer patients: psychological distress and the immune response. J. Psychosom. Res., 48, 187–194. 67. Lawrence, D. A., Song, R., and Weber, P. (1996). Surface thiols of human lymphocytes and their changes after in vitro and in vivo activation. J. Leukoc. Biol., 60, 611–618. 68. Lefkowitz, R. J. (1975). Heterogeneity of adenylate cyclasecoupled β-adrenergic receptors. Biochem. Pharmacol., 24, 583–590. 69. Lehrer, P., Isenberg, S., and Hochron, S. M. (1993). Asthma and emotion: a review. J. Asthma, 30, 5–21. 70. Leo, N. A., and Bonneau, R. H. (2000). Mechanisms underlying chemical sympathectomy-induced suppression of herpes simplex virus-specific cytotoxic T lymphocyte activation and function. J. Neuroimmunol., 110, 45–56. 71. Liang, W., Austin, S., Hoang, Q., and Fishman, P. H. (2003). Resistance of the human β1 adrenergic receptor to agonistmediated down-regulation. Role of the C terminus in determining βAR-subtype degradation. J. Biolog. Chem., 278, 39773–39781. 72. Lombardi, M. S., Kavelaars, A., Petronila, P., Scholtens, E. J., Roccio, M., Schmidt, R. E., Schedlowski, M., Mayor Jr. F., and Heijnen, C. J. (2002). Oxidative stress decreases G proteincoupled receptor kinase 2 in lymphocytes via a calpaindependent mechanism. Mol. Pharmacol., 62, 379–388. 73. Lombardi, M. S., Kavelaars, A., Schedlowski, M., Bijlsma, J. W. J., Okihara, K. L., van de Pol, M., Ochsmann, S., Pawlak, C., Schmidt, R. E., and Heijnen, C. J. (1999). Decreased expression and activity of G-protein–coupled receptor kinases in peripheral blood mononuclear cells of patients with rheumatoid arthritis. FASEB, 13, 715–725. 74. Loveland, B. E., Jarrott, B., and McKenzie, I. F. C. (1981). The detection of β-adrenoceptors on murine lymphocytes. Int. J. Immunopharmacol., 3, 45–55. 75. Lyte, M., Ernst, S., Driemeyer, J., and Baissa, B. (1991). Strain-specific enhancement of splenic T cell mitogenesis and macrophage phagocytocysis following peripheral axotomy. J. Neuroimmunology, 31, 1–8. 76. Madden, K., Felten, S., Felten, D., Hardy, C., and Livnat, S. (1994). Sympathetic nervous system modulation of the immune system. II. Induction of lymphocyte proliferation and migration in vivo by chemical sympathectomy. J. Immunology, 49, 67–75. 77. Madden, K., Felten, S., Felten, D., Sundaresan, P., and Livnat, S. (1989). Sympathetic neural modulation of immune system: I. Depression of T cell immunity in vivo and in vitro following chemical sympathectomy. Brain, Behavior and Immunity, 3, 72–89. 78. Madden, K., Moynihan, J. A., Brenner, G. J., Felten, S., Felten, D., and Livnat, S. (1994). Sympathetic nervous system modulation of the immune system. III. Alterations in T and B cell
79.
80.
81.
82. 83. 84.
85.
86.
87.
88.
89.
90.
91. 92.
93.
94.
95.
1049
proliferation and differentiation in vitro following sympathectomy. J. Immunology, 49, 77–87. Maestroni, G. J. M., and Mazzola, P. (2003). Langerhans cells β2-adrenoceptors: role in migration, cytokine production, Th priming and contact hypersensitivity. J. Neuroimmunol., 144, 91–99. Maisel, A. S., Fowler, P., Rearden, A., Motulsky, H. J., and Michel, M. C. (1989). A new method for isolation of human lymphocyte subsets reveals differential regulation of βadrenergic receptors by terbutaline treatment. Clin. Pharmacol. Ther., 46, 429–439. Maisel, A. S., Harris, T., Reardon, A., and Martin, M. F. (1990). β-adrenergic receptors in lymphocyte subsets after exercise: alteration in normal individuals and patients with congestive heart failure. Circulation, 82, 2003–2010. Makman, M. H. (1971). Properties of adenylate cyclase of lymphoid cells. PNAS, 68, 885–889. McEwen, B. S. (1998). Protective and damaging effects of stress. N. Engl. J. Med., 338, 171–179. McEwen, B. S., and Steller, E. (1993). Stress and the individual: mechanisms leading to disease. Arch. Int. Med., 1153, 2093–2101. McLeod, L. E., Wang, L., and Proud, C. G. (2001). Betaadrenergic agonists increase phosphorylation of elongation factor 2 in cardiomyocytes without eliciting calciumindependent eEF2 kinase activity. FEBS Letters, 489, 225– 228. Meidell, R. S., Sen, A., Henderson, S. A., Slahetka, M. F., and Chien, K. R. (1986). Alpha 1-adrenergic stimulation of rat myocardial cells increases protein synthesis. Am. J. Physiology, 251, H1076–H1084. Mielke, M., Ehlers, S., and Hahn, H. (1993). The role of cytokines in experimental listeriosis. Immunobiology, 189, 285–315. Miura, T., Kudo, T., Matsuki, A., Sekikawa, K., Tagawa, Y-I., Iwakura, Y., and Nakane, A. (2001). Effect of 6hydroxydopamine on host resistance against Listeria monocytogenes infection. Infection and Immunity, 69, 7234–7241. Murata, Y., Shimamura, T., and Hamuro, J. (2002). The polarization of Th1/Th2 balance is dependent on the intracellular thiol redox status of macrophages due to the distinctive cytokine production. International Immunology, 14, 201–212. Noelle, R. J., and Lawrence, D. A. (1981). Modulation of T cell function. II. Chemical basis for the involvement of cell surface thiol reactive sites in control of T-cell proliferation. Cell Immunol., 60, 453–469. North, R. J., and Conlan, J. W. (1998). Immunity to Listeria monocytogenes. Chem. Immunol., 70, 1–20. Nukina, I., Glavin, G. B., and LaBella, F. S. (1987). Acute coldrestraint stress affects α2-adrenoceptors in specific brain regions of the rat. Brain Res., 401, 30–33. Oberbeck, R., Schmidtz, D., Wilsenack, K., Schuler, M., Pehle, B., Schedlowski, M., and Exton, M. S. (2004). Adrenergic modulation of survival and cellular immune functions during polymicrobial sepsis. Neuroimmunomod., 11, 214–223. Pacheco-Lopez, G., Niemi, M.-B., Kou, W., Bildhauser, A., Gross, C. M., Goebel, M. U., del Rey, A., Besedovsky, H. O., and Schedlowski, M. (2003). Central catecholamine depletion inhibits peripheral lymphocyte responsiveness in spleen and blood. J. Neurochem., 86, 1024–1031. Panina-Bordignon, P., Mazzeo, D., Di Lucia, P., D’Ambrosio, D., Lang, R., Fabbri, L., Self, C., and Sinigaglia, F. (1997). β2agonists prevent Th1 development by selective inhibition of interleukin 12. J. Clin. Invest., 100, 1513–1519.
1050
V. Psychoneuroimmunology and Pathophysiology
96. Pare, W. P., and Glavin, G. B. (1986). Restraint stress in biomedical research: a review. Neuroscience & Biobehavioral Reviews, 10, 339–370. 97. Petersen, A. M., and Pedersen, B. K. (2005). The antiinflammatory effect of exercise. J. Appl. Physiol., 98, 1154– 1162. 98. Peterson, D. A., and Gerrard, J. M. (1987). Reduction of a disulfide bond by β-adrenergic agonists: evidence in support of a general “reductive activation” hypothesis for the mechanism of action of adrenergic agents. Med. Hypotheses, 22, 45–49. 99. Peterson, J. D., Herzenberg, L. A., Vasquze, K., and Waltenbaugh, C. (1998). Glutathione levels in antigenpresenting cells modulate Th1 versus Th2 response patterns. PNAS, 95, 3071–3076. 100. Pochet, R., Delespesse, G., Gausset, P. W., and Collet, H. (1979). Distribution of βAR on human lymphocyte subpopulations. Clin. Expl. Immunol., 38, 578. 101. Poston, R. M., and Kurlander, R. J. (1992). Cytokine expression in vivo during murine listeriosis. J. Immunol., 149, 3040–3044. 102. Qui, B. S., Mei, Q. B., Liu, L., and Tchou-Wong, K. M. (2004). Effects of nitric oxide on gastric ulceration induced by nicotine and cold-restraint stress. World J. Gastroenterol., 15, 594–597. 103. Radojcic, T., Baird, S., Darko, D., Smith, D., and Bulloch, K. (1991). Changes in β-adrenergic receptor distribution on immunocytes during differentiation: an analysis of T cells and macrophages. J. Neurosci. Res., 30, 328–335. 104. Raley, M. J., and Loegering, D. J. (1999). Role of an oxidative stress in the macrophage dysfunction caused by eythrophagocytosis. Free Radic. Biol. Med., 27, 1455–1464. 105. Ramer-Quinn, D. S., Baker, R. A., and Sanders, V. M. (1997). Activated T helper 1 and T helper 2 cells differentially express the β2-adrenergic receptor, 99, 1569–1575. 106. Redelman D., and Hudig, D. (1980). The mechanism of cellmediated cytotoxicity. I. Killing by murine cytotoxic T lymphocytes requires cell surface thiols and activated proteases. J. Immunol., 124, 870–878. 107. Reilly, F. D., McCuskey, R. S., and Meineke, H. A. (1976). Studies of the hemopoietic microenvironment. VIII. Adrenergic and cholinergic innervation of the murine spleen. Anat. Rec., 105, 100. 108. Rice, P. A., Boehm, G. W., Moynihan, J. A., Bellinger, D. L., and Stevens, S. Y. (2001). Chemical sympathectomy increases the innate immune response and decreases the specific immune response in the spleen to infection with Listeria monocytogenes. J. Neuroimmunol., 114, 19–27. 109. Rice, P. A., Boehm, G. W., Moynihan, J. A., Bellinger, D. L., and Stevens, S. Y. (2002). Chemical sympathectomy increases numbers of inflammatory cells in the peritoneum early in murine listeriosis. Brain, Behavior and Immunity, 16, 654–662. 110. Rohrer, D. K., Desai, K. H., Jasper, J. R., Stevens, Jr., M. E., Regula, D. P., Barsh, G. S., Bernstein, D., and Kobilka, B. K. (1996). Targeted disruption of the mouse β1-adrenergic receptor gene: developmental and cardiovascular effects. PNAS, 93, 7375–7380. 111. Rosa, E. F., Silva, A. C., Ihara, S. S., Mora, O. A., Aboulafia, J., and Nouailhetas, V. L. (2005). Habitual exercise program protects murine intestinal, skeletal, and cardiac muscles against aging. J. Appl. Physiol.: A mechanism for selective modulation of the Th1 cell cytokine production. J. Immunol., 159, 4857– 4867. 112. Rouppe van der Voort, C., Kavelaars, A., van de Pol, M., and Heijnen, C. J. (1999). Neuroendocrine mediators up-regulate α1b- and α1d-adrenergic receptor subtypes in human monocytes. J. Neuroimmunol., 95, 165–173.
113. Sanders, V. M. (1998). The role of norepinephrine and β2adrenergic receptor stimulation in the modulation of Th1, Th2 and B lymphocyte function. Adv. Exp. Med. Biol., 437, 269–278. 114. Sanders, V. M., Baker, R. A., Ramer-Quinn, S., Kasprowicz, D. J., Fuchs, B. A., and Street, N. E. (1997). Differential expression of the β2-adrenergic receptor by Th1 and Th2 clones. J. Immunol., 158, 4200–4210. 115. Sanders, V. M., Kasprowicz, D. J., Swanson-Mungerson, M. A., Podojil, J. R., and Kohm, A. P. (2003). Adaptive immunity in mice lacking the β2-adrenergic receptor. Brain, Behavior Immunity, 17, 55–67. 116. Schroecksnadel, K., Frick, B., Wirleitner, B., Winkler, C., Schennach, H., and Fuchs, D. (2004). Moderate hyperhomocysteinemia and immune activation. Curr. Pharm. Biotechnol., 5, 107–118. 117. Seiffert, C., Hosoi, J., Torij, H., Ding, W., Campton, K., Wagner, J. A. A., and Granstein, R. D. (2002). Catecholamines inhibit the antigen-presenting capability of epidermal Langerhans cells. J. Immunol., 168, 6128–6135. 118. Shakhar, G., and Ben-Eliyahu., S. (1998). In vivo β-adrenergic stimulation suppresses natural killer activity and compromises resistance to tumor metastasis in rats. J. Immunol. 160, 3251–3258. 119. Shalyapina, V. G., and Rakitskaya, V. V. (2004). Reactivity of the hypophyseal-adrenocortical system to stress in rats with active and passive behavioral strategies. Neurosci. Behav. Physiol., 34, 821–824. 120. Simmons, H. F., James, R. C., Harbison, R. D., Patel, R. D., and Roberts, S. M. (1991). Examination of the role of catecholamines in hepatic glutathione suppression by cold-restraint in mice. Toxicology, 67, 29–40. 121. Smith, I. M., Kennedy, L. R., Regne-Karlsson, M. H., Johnson, V. L., and Burgmeister, L. F. (1977). Adrenergic mechanisms in infection. III. Alpha and beta-receptor blocking agents in treatment. American J. Clinical Nutrition, 30, 1285–1288. 122. Sterling P., and Eyer, J. (1988). Allostasis: a new paradigm to explain arousal pathology. In S. Fisher and J. Reason (Eds.), Handbook of life stress, cognition and health (pp. 629–649). New York: Wiley. 123. Stevens-Felten, S. Y., and Bellinger, D. L. (1997). Noradrenergic and peptidergic innervation of lymphoid organs. Chem. Immunol., 69, 99–131. 124. Strosberg, A. D., and Pietri-Rouxel, F. (1996). Function and regulation of the β3-adrenoceptor. Trends Pharmacol. Sci., 17, 373–380. 125. Swanson, M. A., Lee, W. T., and Sanders, V. M. (2001). IFNγ production by Th1 cells generated from naive CD4+ T cells exposed to norepinephrine. J. Immunol., 166, 232–240. 126. Takaki, A., Hyuang, Q.-H., Somogyvari-Vigh, A., and Arimura, A. (1994). Immobilization stress may increase plasma IL-6 via central and peripheral catecholamines. Neuroimmunomodulation, 1, 335–342. 127. Tandon, R., Khanna, H. D., Dorababu, M., and Goel, R. K. (2004). Oxidative stress and antioxidants status in peptic ulcer and gastric carcinoma. Indian J. Physiol. Pharmacol., 48, 115–118. 128. Tran, D. T., Miller, S. H., Burk, D., Imatani, J., Demuth, R. J., and Miller, M. A. (1985). Potentiation of infection by epinephrine. Plastic Reconstructive Surgery, 76, 933–934. 129. Unanue, E. R. (1997). Inter-relationship among macrophages, natural killer cells and neutrophils in early stages of Listeria resistance. Curr. Opinion Immunol., 9, 35–43.
48. Cold-Restraint-induced Immune and Biochemical Changes Inhibit Host Resistance to Listeria 130. van Tits, L., Michel, M., Grosse-Wilde, H., Happel, H., Eigler, F., Soliman, A., and Brodde, O. (1990). Catecholamines increase lymphocyte β2-adrenergic receptors via a β2-adrenergic, spleen-dependent process. Am. J. Physiology, 258, E191–E202. 131. Weiler-Normann, C., and Rehermann, B. (2004). The liver as an immunological organ. J. Gastroenterol. Hepatol., 19, S279–S283. 132. Wiegmann, K., Muthyala, S., Kim, D. K., Arnason, B. G. W., and Chelmicka-Schorr, E. (1995). Beta-adrenergic agonists suppress chronic/relapsing experimental allergic encephalomyelitis in Lewis rats. J. NeuroImmunol., 56, 201–206. 133. Williams, J. M., Peterson, R. G., Shea, P. A., Schnedtje, J. F., Bauer, D. C., and Felten, D. (1981). Sympathetic innervation of murine thymus and spleen: evidence for a functional link between the nervous and immune systems. Brain Research Bulletin, 6, 83–94. 134. Williams, L. T., Snyderman, R., and Lefkowitz, R. J. (1976). Identification of β-adrenergic receptors in human lymphocytes by (−) (3H) alprenolol binding. J. Clin. Invest., 57, 149.
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135. Wong A., Hwang, S. M., Cheng, H. Y., and Crooke, S. T. (1987). Structure-activity relationships of β-adrenergic receptorcoupled adenylate cyclase: implications of a redox mechanism for the action of agonists at beta-adrenergic receptors. Mol. Pharmacol., 31, 368–376. 136. Xu, B. (2001). The importance of β-adrenergic receptors in immune regulation: a link between neuroendocrine and immune system. Medical Hypotheses, 56, 273–276. 137. Yang, E. V., and Glaser, R. (2000). Stress-induced immunomodulation: impact on immune defenses against infectious disease. Biomed Pharmacother, 54, 245–250. 138. Yang, E. V., and Glaser, R. (2003). Stress-associated immunomodulation and its implications for responses to vaccination. Expert Rev. Vaccines, 1, 453–459.
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C H A P T E R
49 Psychobiology of HIV Infection ERICA SLOAN, ALICIA COLLADO-HIDALGO, AND STEVE COLE
I. INTRODUCTION 1053 II. HIV PATHOGENESIS 1053 III. NEUROENDOCRINE INFLUENCES ON HIV PATHOGENESIS 1055 IV. PSYCHOSOCIAL INFLUENCES ON HIV PROGRESSION 1059 V. PROSPECTS 1064
Chapter 61 of Psychoneuroimmunology, 3rd edition, and Chapter 32 by Antoni and colleagues in this volume). However, the biological processes mediating those effects remain poorly understood. This chapter reviews data on the role of the nervous and endocrine systems as biological signaling pathways that convey the effects of psychosocial factors to the cellular and molecular processes involved in HIV pathogenesis. In addition to studies that link neuroendocrine function to viral biology, we also consider the broader relationship between psychosocial characteristics and clinical disease outcomes in an effort to understand the behavioral ecology of those relationships. To provide a framework for this inquiry, we begin by summarizing some key pathogenetic characteristics of HIV infection.
I. INTRODUCTION Infection with human immunodeficiency virus type 1 (HIV-1) has a highly variable course, with some individuals progressing rapidly to AIDS, while others remain asymptomatic for 2 decades or more (Munoz et al., 1989; Phair et al., 1992; Sheppard et al., 1991). Factors influencing the rate of HIV-1 disease progression include the strain of virus contracted, the route and quantity of viral exposure (Koot et al., 1993; Levy, 1993), age, gender (Melnick et al., 1994, Phillips et al., 1991; Quinn and Overbaugh, 2005; Saah et al., 1994), drug abuse (Munoz et al., 1988), co-infection with other pathogens (Bentwich et al., 1995, Lusso and Gallo, 1995), and host genetic characteristics such as HLA alleles and chemokine receptor gene polymorphisms (Carrington and O’Brien, 2003; Dean et al., 1996). However, all these factors together account for only a fraction of the total variability in HIV disease progression. Much research has focused on identifying other influences, and biobehavioral factors have received particular attention due to their known impact other viral infections (see Chapters 40, 50, 51, and 52 in this volume); (Cohen et al., 1997; Padgett et al., 1998). A large body of research has linked psychosocial factors to variations in HIV disease progression (see PSYCHONEUROIMMUNOLOGY, 4E VOLUME II
II. HIV PATHOGENESIS A. Acute Infection HIV-1 is a primate lentivirus that primarily infects cells expressing the CD4 protein, including CD4+ T lymphocytes, monocytes/macrophages, and glial cells of the central nervous system (CNS) (Levy et al., 1996; Nielsen et al., 2005). Cells expressing the DC-SIGN molecule can also bind viral particles (virions) and convey them to CD4+ cells (Engering et al., 2002; Geijtenbeek et al., 2000; Geijtenbeek et al., 2002; Pohlmann et al., 2001; Snyder et al., 2005). Infection is initiated by attachment of the HIV-1 surface glycoprotein gp120 to CD4, which tethers virions to the cell surface and facilitates interaction with co-receptor molecules. The chemokine receptors CXCR4 and CCR5 are the
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Copyright © 2007 by Elsevier, Inc. All rights of reproduction in any form reserved.
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most prevalent co-receptors, and their binding to gp120 initiates fusion of the viral envelope with the cell membrane by exposing the viral glycoprotein gp41. HIV-1 RNA is then released into the cell, where the viral reverse transcriptase (RT) enzyme begins converting the viral RNA genome into a proviral doubled-stranded cDNA. A “pre-integration complex” of viral proteins and nucleic acids migrates to the nucleus, where the provirus is integrated into cellular DNA by the viral integrase enzyme. Transcription of the integrated provirus is regulated by the HIV-1 5’ long terminal repeat (LTR), which contains DNA motifs that facilitate binding of cellular transcription factors such as NF-κB and Sp1 (Garcia and Gaynor, 1994; Nabel and Baltimore, 1987; Rohr et al., 2003; Trkola, 2004). The HIV-1 Tat protein also plays a key role in facilitating viral transcription, and the viral Rev protein shuttles large viral RNAs back into the cytoplasm (Trkola, 2004). The HIV-1 protease splices translated viral gene products into active proteins for the production of new viral particles. HIV-1 structural proteins, enzymes, and genomic RNA then associate with viral envelope proteins at the plasma membrane to produce virions that bud from the cell surface to infect new targets. HIV-1 infection spreads quickly among CD4+ cells due to its short replication cycle (∼2 days) (Ho et al., 1995; Perelson et al., 1996; Wei et al., 1995) and the viral genome’s sensitivity to inflammatory signaling pathways (Fauci, 1988, 1996). Following primary infection, systemic viral load shows an acute spike, and CD4+ T lymphocytes are rapidly depleted as infection disseminates through lymphoid organs (Haase, 1999; Pantaleo et al., 1993a; Pantaleo et al., 1993b; Schacker et al., 2000). Within a week or two of primary infection, a vigorous cytotoxic T-cell (CTL) response begins to suppress viral replication, and CD4+ T lymphocyte numbers generally rebound (Alimonti et al., 2003). HIV-1 replication may also be controlled by production of HIV-1–specific antibodies (Aasa-Chapman et al., 2005; Borrow et al., 1994; Gloster et al., 2004; Pantaleo et al., 1994), chemokines (Graziosi et al., 1996; Levy, 2001; Levy et al., 1996; Mackewicz et al., 1996; Pomerantz and Hirsch, 1987), and other soluble factors that inhibit HIV-1 replication without destroying virally infected cells (Levy et al., 1996), as well as by innate anti-viral responses generated by type I interferons (IFNs). The acute anti-viral response is sometimes accompanied by a mononucleosis-like syndrome of clinical symptoms that typically resolves within 2–4 weeks. As antigen-driven anti-viral responses strengthen, plasma viral load and CD4+ T-cell levels come into a quasi-stable equilibrium, and the resulting plasma viral load “set point” can persist for many years. However, there are substantial individual dif-
ferences in the level of this set point, and those with high viral replication equilibria show more rapid progression to AIDS (Mellors et al., 1996).
B. Clinical Latency Following the establishment of set point, an infected individual may remain healthy for many years, with 10 being the median time to the onset of AIDS-defining clinical conditions (Munoz et al., 1989). Despite the lack of overt symptoms during “clinical latency” or CDC Category A infection, HIV-1 continues to replicate and establish latent infection in the lymph nodes, spleen, and thymus (Embretson et al., 1993; Pantaleo et al., 1993a). Lymphoid organs show progressive structural alterations that can produce mild immunodysregulation even during the earliest stages of infection (Frost and McLean, 1994; Heeney, 1995; Helbert et al., 1993). Other physiologic systems can also be dysregulated to produce changes in cognitive function, peripheral neuropathy, hypothalamic dysregulation, and metabolic lipodystrophy (Cohen and Laudenslager, 1989; Heaton et al., 1994; Kaul et al., 2005; Kino and Chrousos, 2004; Kumar et al., 1991; Mattson et al., 2005; Merenich et al., 1990). Soon after infection, HIV-1 can also enter the CNS to infect microglia and astrocytes (Kaul et al., 2005; Mattson et al., 2005). Neurons are rarely infected, but they sustain indirect damage from neurotoxins, cytokines, and chemokines that cross the blood-brain barrier from peripheral circulation or are produced by locally activated glial cells (Banks et al., 2005; Kaul et al., 2005). Consequences of CNS infection range from mild and focal impairments of specific memory systems to frank dementia (Manji and Miller, 2004; Mattson et al., 2005). From a long-term health standpoint, the most significant physiologic dynamic during clinical latency involves the slow progressive decline in CD4+ T-cell levels as the immune system struggles to replace cells continuously lost to infection. Viral replication and CD4+ T-cell declines are accelerated by immunologic activation and inflammatory cytokine signals, which enhance NF-κB signaling and thereby stimulate the HIV-1 LTR. Intercurrent infections, vaccinations, and even the anti-HIV-1 immune response itself can enhance immunologic activation and accelerate viral replication (Levy, 1993; Pantaleo et al., 1993b). As a result of continuing CD4+ T-cell loss, the immune system gradually loses “helper” T-cell function for a growing range of pathogens, including the HIV virus itself.
C. AIDS Once the absolute number of CD4+ T-cells count falls below ∼200 per mm3 of peripheral blood, the body
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becomes vulnerable to a variety of AIDS-defining opportunistic infections and malignancies (RowlandJones, 2003). Declining CD4+ T-cell levels are often accompanied by increased plasma viral load and declining HIV antibody production as T-cell help for the humoral immune response fails (Alimonti et al., 2003). In the absence of effective treatment, patients typically die within 2 years of an AIDS diagnosis. The development of combination anti-retroviral therapies (ART) using drugs that target multiple stages of the viral replication cycle have dramatically reduced the incidence of AIDS in developed countries (Fauci, 2003; Quinn and Overbaugh, 2005). Economic, political, and social barriers often impede access to long-term ART in developing countries (Forsythe, 1998; Jaffar et al., 2005; Rabkin et al., 2002), although short-term ART regimens have seen increasing use to block motherchild transmission during birth (Cooper et al., 2002; Dorenbaum et al., 2002). However, even the most effective long-term ART regimens cannot fully eradicate HIV-1 from latently infected cells, and low levels of viral replication continue in lymphoid organs and the CNS. HIV-1 thus constitutes a chronic infection, and the virus will generally mutate over time to evade any specific therapeutic regimen. Continued development of new therapeutic agents and maximal suppression of residual viral replication during ART is key to long-term management of HIV-1 infection.
III. NEUROENDOCRINE INFLUENCES ON HIV PATHOGENESIS As a chronic infection of lymphoid cells, HIV-1 is subject to direct neuroendocrine regulation of its host cell and indirect regulation via neuro-immune interactions that modulate the anti-viral immune response. The hypothalamic-pituitary-adrenal (HPA) axis and the autonomic nervous system (ANS) have both received intensive focus as possible physiologic signaling pathways that might mediate psychosocial influences on HIV-1 pathogenesis.
A. The Hypothalamus-PituitaryAdrenal Axis 1. Disease Progression Physical and mental stress, anxiety, depression, and a variety of other psychological and physiological conditions can influence leukocyte function by modulating HPA production of cortisol (Sapolsky, 1993; Weiner, 1992). Cortisol inhibits cellular immune responses and modulates cytokine production profiles
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and leukocyte trafficking (Clerici et al., 1997; Norbiato et al., 1997; Vago et al., 1994; and Chapter 1 in Volume I). As such, the HPA axis represents one major pathway by which psychological dynamics could conceivably influence HIV pathogenesis. However, HIV disease progression can also influence activity of the HPA axis, so it is difficult to determine whether differential HPA activity represents a cause or a consequence of HIV disease progression. Approximately one-third of AIDS patients show adrenal gland alterations postmortem, and many studies have documented a progressive rise in circulating cortisol levels and failure of HPA homeostatic processes as HIV infection progresses (Antoni et al., 1991b; Azar and Melby, 1993; Bhansali et al., 2000; Biglino et al., 1995; Catania et al., 1992; Christeff et al., 1992; Christeff et al., 1997; Christeff et al., 2000; Clerici et al., 2000; de la Torre et al., 1997; Eledrisi and Verghese, 2001; Findling et al., 1994; Fontes et al., 2003; Freda and Bilezikian, 1999; Kumar et al., 1993; Kumar et al., 2002; Laudat et al., 1995; Lortholary et al., 1996; Martin et al., 1992; Mayo et al., 2002; Merenich et al., 1990; Norbiato et al., 1997; Phillips et al., 1997; Rondanelli et al., 1997; Stolarczyk et al., 1998; Verges et al., 1989; Villette et al., 1990; Wisniewski et al., 1993; Wolff et al., 2001). One large longitudinal study of cortisol levels in HIV+ individuals found increasing HPA activity to predict AIDS onset and mortality independently of psychosocial risk factors and biological markers of HIV disease progression at study entry (Leserman et al., 2000; Leserman et al., 2002). Shortterm studies have also documented relationships between cortisol levels and various immune parameters (Antoni et al., 1991a; Antoni et al., 2005; Goodkin et al., 1996; Delahanty et al., 2004; Petitto et al., 2000), as well as extended survival following an AIDS diagnosis (Ironson et al., 2002). However, all of these results emerge from correlational natural history studies, so it is unclear whether effects reflect HPA mediation of psychosocial influences on HIV pathogenesis, or effects of disease progression on neuroendocrine function; e.g., HPA adaptation to inflammatory signaling (Hofbauer and Heufelder, 1996; Kumar et al., 2002), effects of ART on neuroendocrine function (Collazos et al., 2004; Hatano et al., 2000; Miller et al., 1999; Yanovski et al., 1999), or opportunistic infections of the adrenal gland (Mulhall et al., 1988; Pulakhandam and Dincsoy, 1990). Some studies have found altered cortisol levels in stressed or depressed HIV+ individuals even after controlling for measures of disease progression (Cruess et al., 1999), and behavioral interventions have been shown to reduce cortisol levels in HIV+ individuals (Antoni et al., 2000a; Antoni et al., 2000b; Antoni et al., 2005; Cruess et al., 1999; Cruess et al., 2000a; Cruess et al., 2000b; Ironson et al., 1996). Uncon-
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trolled clinical studies have also found accelerated HIV-1 disease progression following pharmacologic glucocorticoid (GC) therapy, which engages the same glucocorticoid receptor (GR)-mediated signaling pathway as cortisol (Laurence et al., 1989; Pedersen et al., 1989; Shafer et al., 1985). However, no studies have shown that behavioral or pharmacologic interventions to reduce HPA activity can significantly impact HIV-1 viral load or clinical disease progression in humans. One experimental study of rhesus macaques infected with the simian immunodeficiency virus (SIV) found elevated plasma viral load in animals subjected to stressful social reorganization, but this was associated with a paradoxical decrease in basal cortisol levels (Capitanio and Lerche, 1998). Thus, some clinical studies have linked psychosocial factors to HPA activity in the context of HIV or SIV infection, and other studies have linked HPA activity to lentiviral pathogenesis, but no study has shown that variations in HPA activity mediate relationships between behavioral risk factors and individual differences in plasma viral load or clinical disease progression. The only potential exception to this general conclusion comes from a study reporting statistical mediation analyses that support individual differences in HPA activity as a potential mediator of relationships between religious practice and status as a long-term survivor of AIDS (Ironson et al., 2002). However, the interpretation of these results is complicated by baseline differences in disease characteristics between long-term survivors and members of the control group. No study of a homogenous group of HIV+ individuals has found baseline individual differences in HPA activity to forecast disease progression. 2. Viral Replication In vitro studies have identified several ways in which GC signaling could potentially impact the molecular processes driving HIV-1 pathogenesis. Early studies found that addition of low GC concentrations to cell cultures could modestly enhance replication of CXCR4-tropic strains of HIV-1 in activated human leukocytes (Markham et al., 1985; Markham et al., 1986; Soudeyns et al., 1993; Swanson et al., 1998). GCs were subsequently found to elevate cell surface expression of CXCR4 both in vitro and in vivo (Caulfield et al., 2002; Curnow et al., 2004; Okutsu et al., 2005; Wang et al., 1998). Low GC concentrations may enhance HIV-1 replication by stimulating the viral LTR (Kolesnitchenko and Snart, 1992; Spandidos et al., 1990) or arresting T lymphocytes in the G2 phase of the cell cycle, which favors viral gene expression (Emerman, 1996; Chowdhury et al., 2003; Goh et al.,
2004; He et al., 1995). The HIV-1 Vpr protein can exert similar effects by interacting with the GR (Ayyavoo et al., 1997; He et al., 1995; Re et al., 1995; Zhao et al., 1996; Zhao et al., 2005) to regulate cellular gene expression (Fakruddin and Laurence, 2005; Kino and Chrousos, 2004) and vulnerability to apoptosis (Lu et al., 1995; Nair et al., 2000). Mutations in the Vpr gene that impair interactions with the GR are associated with retarded disease progression (Lum et al., 2003). Thus, the cellular GC response system appears to benefit HIV-1 sufficiently for the virus to evolve its own means for activating that pathway. In contrast to results for low GC concentrations, high pharmacologic levels of GC activity have consistently inhibited HIV-1 gene expression by suppressing T-cell activation and blocking transcriptional activation of the viral LTR (Mitra et al., 1995; Russo et al., 1999). 3. Immune Response Physiologic GC activity can suppress production of IFN-γ, IL-12, and other Th1 cytokines that support cellular immune response (Elenkov and Chrousos, 1999). These effects are mediated in large part by GR inhibition of the NF-kB signaling pathway via proteinprotein interactions and induction of the IκB inhibitor gene (Almawi and Melemedjian, 2002; Ayyavoo et al., 1997; Hayashi et al., 2004). Local cortisol production in the thymus may also regulate thymocyte apoptosis and tailor the breadth of the T-cell receptor repertoire (Ashwell et al., 2000). In the context of HIV infection, normal HPA regulation of anti-viral cytokine production appears to diminish as disease progresses (Kawa and Thompson, 1996; Norbiato et al., 1998). In vitro studies also suggest that HIV-1 Vpr protein might interact with the GR to synergistically repress IL-12 production and modulate other immune response genes (Mirani et al., 2002; Refaeli et al., 1995). Given these dynamics, physiologic HPA activity could plausibly influence HIV pathogenesis by undermining CTL containment of viral replication or hampering the provision of cytokine “help” by the waning CD4+ T-cell population. However, no clinical studies have directly assessed relationships between HPA activity and CTL activity in HIV-infected individuals. Clinical studies have linked high cortisol levels to other immunologic parameters such as circulating levels of CD4+CD45RA+CD29− naive T lymphocytes or NK cell cytotoxic activity (Antoni et al., 2005; Goodkin et al., 1996; Petitto et al., 2000), but these cell types are not believed to play a major role in controlling HIV-1 disease progression. Thus, HPA regulation of the antiHIV immune response remains a plausible hypothesis with little empirical support.
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Given the complexities of assessing HPA axis activity and the multiple physiologic systems that regulate its function in addition to psychosocial factors (Weiner, 1992), pharmacologic blockade studies will likely be required to clearly define the status of this system as a physiologic mediator of psychosocial influences on lentiviral pathogenesis. In vitro studies suggest several potential mechanisms by which HPA activity might impact HIV replication, but no studies have directly evaluated those dynamics in vivo. Results from experimental studies of SIV infection (Capitanio and Lerche, 1991) have shown that stress can accelerate lentiviral pathogenesis in the absence of elevated HPA activity, suggesting that other biological signaling pathways can play a decisive role even in the absence of significant HPA alterations.
B. The Autonomic Nervous System 1. Disease Progression The autonomic nervous system (ANS) mediates physiologic adaptations to a broad range of physical, psychological, and social stimuli, and it is controlled by functional and neurobiological influences very different from those regulating the HPA axis (Chrousos and Gold, 1992; Sapolsky, 1998; Weiner, 1992). The sympathetic division of the ANS (SNS) has long been known to modulate leukocyte function by releasing catecholamines from the adrenal medulla and sympathetic neurons in lymphoid organs (Castrillon et al., 2000; Downing and Miyan, 2000; Felten et al., 1984; Felten et al., 1987; Madden et al., 1995a; Madden et al., 1995b; Sanders and Straub, 2002; Stebbing et al., 2004). Recent data suggest that the parasympathetic division of the ANS may also play a role in regulating inflammatory signals (Tracey, 2002). Early hints that ANS activity might influence HIV-1 pathogenesis came from natural history studies showing accelerated clinical disease progression in HIV+ individuals with socially inhibited temperament, which is associated with elevated ANS activity (Cole et al., 1996; Cole et al., 1998). Similar socio-temperamental risk factors have emerged in studies of SIV-infected rhesus macaques (Capitanio and Lerche, 1998). Subsequent studies directly assessed autonomic activity and found elevated plasma viral load and impaired virologic and immunologic response to ART in HIV+ individuals with constitutively high levels of ANS activity (Antoni et al., 2000a; Cole et al., 2001). Statistical mediation analyses have also found that individual differences in ANS activity could account for much of the temperament-related variation in HIV-1 viral load set point and biological responses to ART (Cole et al., 2003).
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Moreover, methodological controls ruled out several potential counter-explanations for associations between temperament, ANS activity, and biological indicators of HIV pathogenesis. Reverse causation of high ANS activity by accelerated HIV disease progression is less likely than in the case of the HPA axis because ANS activity is not substantially altered until AIDS onset, when ANS activity shows mild blunting (rather than the increased responsiveness that was prospectively linked to HIV pathogenesis in this study) (Brownley et al., 2001; da Silva et al., 1999; Hengge et al., 2003; Kumar et al., 1991; Larsson et al., 1991; Schifitto et al., 2002; Sondergaard et al., 1999; Sondergaard et al., 2000a; Sondergaard et al., 2002). No clinical studies have evaluated the effects of pharmacologic manipulation of ANS activity on HIV disease progression. One randomized trial has shown that behavioral intervention can reduce indicators of ANS activity in HIV+ individuals (Antoni et al., 2000a), but this did not significantly affect plasma viral load or other markers of disease progression. It thus remains unclear whether experimental manipulation of ANS activity might have any clinical impact on HIV-1 pathogenesis, but ANS activity is clearly implicated as a potential mediator of biobehavioral influence on HIV-1 biomarkers. 2. Viral Replication Consistent with clinical indications that ANS activity might influence HIV pathogenesis, several in vitro studies have shown that the catecholamine neurotransmitters released by the ANS can accelerate HIV-1 replication in activated T lymphocytes (Cole et al., 1998; Cole et al., 2001). Those effects are mediated by several molecular mechanisms including suppression of antiviral cytokines (Cole et al., 1998), enhanced cell surface expression of CXCR4 and CCR5 (Cole et al., 1999a; Cole et al., 2001), and activation of the viral LTR (Cole et al., 2001). Catecholamines regulate leukocyte function by ligating cell surface adrenoreceptors linked to the cAMP/PKA second messenger system (Lefkowitz et al., 1983). Other pharmacologic and physiologic activators of PKA can also accelerate HIV-1 replication in vitro (Chowdhury et al., 1993; Nokta and Pollard, 1992), and pharmacologic agents that elevate cAMP in T lymphocytes have been shown to increase plasma viral load in vivo (Hofmann et al., 1996). In vitro studies have identified several aspects of the HIV-1 replication cycle that are sensitive to cAMP/PKA signaling, including virion binding to target cells (Cole et al., 1999a), synthesis of proviral DNA (Amella et al., 2005), activation of the viral LTR (Chowdhury et al., 1993; Krebs et al., 1998; Nokta and Pollard, 1992; Rabbi et al., 1997b; Rabbi et al., 1998; Rabkin et al., 1997; Rohr
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et al., 2003; Schwartz et al., 1997), phosphorylation of the viral Nef protein (Li et al., 2005), and production of infectious viral particles (Cartier et al., 2003). Some of these dynamics are qualified by the particular type of cell infected. For example, PKA upregulates cell surface expression of CXCR4 and CCR5 on T lymphocytes (Cole et al., 1999a; Cole et al., 2001), but it inhibits CCR5 expression on monocytes (Thivierge et al., 1998). PKA enhances HIV-1 LTR activity in T lymphoid cells (Nokta and Pollard, 1992) and in some monocytic cell lines (Chowdhury et al., 1993), but it inhibits LTR activity in primary macrophages (Hayes et al., 2002). CD4+ T lymphocytes represent the primary contributors to systemic viral load, and PKA generally facilitates HIV1 replication in this cell type. Consistent with those principles, systemic inhibition of PKA has been shown to suppress plasma viral load in vivo (Hofmann et al., 1996) and increase circulating CD4+ T-cell levels (Eugen-Olsen et al., 2000). PKA activity is so beneficial for HIV-1 replication that the virus has acquired the capacity to activate cAMP/PKA signaling in the absence of physiologic hormone/receptor interactions (Gibellini et al., 1998; Hofmann et al., 1993a; Hofmann et al., 1993b; Nokta and Pollard, 1991; Rabbi et al., 1997a). The viral Tat and gp120 proteins both stimulate cAMP/PKA signaling in vitro (Haraguchi et al., 1995; Misse et al., 2005), and aberrant PKA activity contributes to several functional deficits observed in HIVinfected leukocytes (Aandahl et al., 1998; Eugen-Olsen et al., 1997; Hofmann et al., 1993a; Hofmann et al., 1993b; Thomas et al., 1997). Given the clear involvement of cAMP/PKA signaling in HIV-1 replication and immunopathogenesis, activation of this signaling pathway by the ANS represents a plausible mechanism by which biobehavioral processes could influence HIV disease pathogenesis. Experimental studies have shown that PKA inhibitors can help normalize HIV-1 biomarkers (Eugen-Olsen et al., 2000; Hofmann et al., 1996), but no studies have sought to suppress HIV-1 replication by targeting ANS activity per se. However, a recent study documenting increased SIV gene expression in the vicinity of catehcolaminergic neurons within primate lymph nodes (Sloan et al., 2006) suggests that ANS activity might significantly enhance lentiviral replication in vivo. 3. Immune Response The ANS regulates immune system function by releasing catecholamines from the adrenal gland and from sympathetic neural processes innervating lymphoid organs (Felten and Felten, 1988; Ottaway and Husband, 1994). Catecholamine ligation of leukocyte α- and β-adrenergic receptors can regulate several leukocyte functions including cellular activation, cytokine
production, and cell trafficking (Dantzer et al., 1998; Kammer, 1988; Maier et al., 1998; Ottaway and Husband, 1994; Sanders and Straub, 2002). Catecholamines and other physiologic PKA activators can selectively inhibit production of Th1 cytokines that support anti-viral CTL responses (Tokoyoda et al., 2004). PKA activators can also inhibit CTL activity at the level of target cell binding and lysis (Kalinichenko et al., 1999; Sugiyama et al., 1992). Such results suggest that ANS activity could undermine CTL control of HIV-1 replication, but no studies have directly examined this hypothesis. One study of a behavioral stress management intervention has linked decreases in 24-hour norepinephrine output to increased CD8+ T lymphocyte counts 6–12 months later (Antoni et al., 2000a). However, HIV-specific CTLs were not measured, and no change in plasma viral load was reported that might indicate a change in immune control of the virus. Several studies have examined peripheral blood leukocyte responses to transient catecholamine infusions in HIV+ individuals (Hengge et al., 2003; Sondergaard et al., 1999; Sondergaard et al., 2000b; Sondergaard et al., 2002), but no data were reported on HIV-specific immune responses. It thus remains unclear whether ANS activity can significantly impact the anti-viral immune response in vivo. In vitro studies have shown that catecholamines and the cAMP/PKA signaling pathway can suppress production of HIV-inhibitory cytokines (Cole et al., 1998; Johansson et al., 2004), reduce T-cell activation (Aandahl et al., 1998; Eugen-Olsen et al., 1997; Hofmann et al., 1993a; Hofmann et al., 1993b; Thomas et al., 1997), and alter leukocyte interactions with the vascular endothelium (Sundstrom et al., 2001; Sundstrom et al., 2003). However, the clinical significance of those dynamics has not been assessed in vivo, and no studies have directly targeted ANS activity in an effort to enhance immune responses to HIV-1. As with HPA axis function, pharmacologic blockade studies will likely be required to clearly define the role of ANS activity in HIV pathogenesis. However, data from in vitro mechanistic studies, in vivo clinical studies, and pharmacologic manipulations of cAMP/ PKA signaling all converge in suggesting that ANS activity might plausibly impact HIV-1 (Munoz et al., 1989) pathogenesis in vivo. Several studies are currently evaluating the pharmacologic inhibition of catecholamine signaling in the context of HIV and SIV infections, and the contribution of the ANS to lentiviral pathogenesis in vivo should soon be clarified.
C. Other Neuroendocrine Influences The HPA and ANS represent the most widely studied mediators of biobehavioral influences on immune function, but psychological processes can
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regulate a variety of other neuroendocrine molecules that could potentially influence HIV pathogenesis. In vitro studies show that the neurotransmitter Substance P (SP) can accelerate HIV-1 replication and impair T-cell proliferation (Covas et al., 1994; Ho and Douglas, 2004, Ho et al., 1996; Lai et al., 2001; Li et al., 2001). The viral gp120 envelope glycoprotein can also induce SP production by monocytes in vitro (Ho et al., 2002), and circulating SP levels are elevated in the blood of HIV+ individuals in vivo (Douglas et al., 2001; Ho and Douglas, 2004). These data suggest that SP could constitute an autocrine accelerator of HIV-1 replication, and biobehavioral factors could conceivably exacerbate this dynamic by elevating SP in circulation (DeVane, 2001). However, no clinical studies have evaluated this hypothesis in vivo. Production of human growth hormone (GH) can be modulated by stress (Weiner, 1992), and GH can increase production of pro-inflammatory cytokines and HIV-1 replication in vitro (Laurence et al., 1992). However, several clinical trials of pharmacologic GH therapy for HIV-associated wasting have not shown any significant alteration in plasma viral load (e.g., Schambelan et al., 1996). Reproductive hormones are also sensitive to psychosocial influences (Sapolsky, 1993; Weiner, 1992), and in vitro studies suggest that estrogen and progesterone can modulate HIV-1 replication and LTR-driven gene expression (Bourinbaiar et al., 1992; Laurence et al., 1990; Lee et al., 1997). In vivo studies have documented changes in plasma viral load over the course of the menstrual cycle (Benki et al., 2004) and during pharmacologic hormone treatment (Clemetson et al., 1993; Mostad et al., 1997; Sagar et al., 2004), but no studies have evaluated the relationship between biobehavioral factors and reproductive hormone levels in HIV+ women. Adrenal androgens have received a great deal of attention as possible influences on HIV pathogenesis following the observation that circulating dehydroepiandosterone (DHEA) declines precipitously over the course of disease progression (Centurelli and Abate, 1997). DHEA can suppress HIV-1 replication in vitro (Henderson et al., 1992; Yang et al., 1993, 1994), although clinical trials have not shown any effects in vivo (Dyner et al., 1993; Piketty et al., 2001). No clinical studies have linked any of the neuroendocrine parameters reviewed above to psychosocial characteristics of HIV+ individuals, so it is unclear what role these factors might play in mediating biobehavioral influences on HIV disease progression.
D. Virologic Mechanisms The studies reviewed above suggest that a variety of neuroendocrine signaling molecules might potentially influence HIV pathogenesis if they are released
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in physiologically significant quantities at appropriate tissue sites; e.g., in lymphoid organs, where most HIV-1 replication takes place (Haase, 1999; Kilby, 2001). Potential mechanisms with at least some empirical support include modulation of (1) cellular vulnerability to de novo infection (e.g., via chemokine receptor regulation and leukocyte trafficking), (2) establishment of proviral DNA structures, (3) cellular activation and cell cycle progression (e.g., modulating Nef or Vpr), (4) cytokine production (e.g., anti-viral cytokines such as IFN-α, IFN-γ, and IL-10, or HIVactivating cytokines such as TNF-α), (5) activation of the viral LTR, (6) HIV protein expression and posttranslational modification (e.g., Nef phosphorylation), (7) assembly and release of infectious viral particles, (8) host cell survival, (9) infection-related deficits in leukocyte function (e.g., proliferation and cytokine production), (10) immunologic responses to HIV infection (e.g., CTL activity, soluble HIV-1 suppressor factors, or type I interferon responses), (11) immunologic responses to other pathogens, which may indirectly facilitate HIV pathogenesis by enhancing immunologic activation (Rosenberg and Fauci, 1989), and (12) activation of opportunistic pathogens that directly induce AIDS-defining clinical conditions (e.g., catecholamines can activate lytic replication of the Kaposi’s sarcoma-associated herpesvirus [Chang et al., 2005]). Most of the mechanistic interactions outlined above have been documented in vitro, and it is unclear whether they exert clinically significant effects in vivo. One way of gauging the potential relevance of such interactions is to examine relationships between HIV-1 disease progression and psychosocial characteristics that modulate neuroendocrine function in vivo.
IV. PSYCHOSOCIAL INFLUENCES ON HIV PROGRESSION Over 70 published studies have examined relationships between psychosocial characteristics and HIV progression, but only a small minority have included direct measures of potential neuroendocrine mediators. Moreover, most of these data come from correlational natural history analyses, which cannot definitively identify causal effects of behavioral risk factors or neuroendocrine mediators because those parameters are not experimentally manipulated. Despite these caveats, it may be possible to “borrow interpretive power” from the broader biobehavioral research literature by analyzing relationships between psychosocial risk factors and HIV pathogenesis in the context of more general psychoneuroendocrinologic and psychoneuroimmunologic principles. This interpretive process cannot provide decisive conclusions,
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but it can be heuristically valuable in shaping the design and analysis of future studies, and in prioritizing hypotheses for empirical analysis. We begin by summarizing data on several broad psychosocial parameters that have been related to HIV pathogenesis and then consider what those results might tell us about potential neuroendocrine mediators.
A. Stress and Coping 1. Stressful Life Events Events that dramatically alter an individual’s life circumstances (e.g., change in health status, bereavement, divorce, unemployment, disability) can change neuroendocrine function and increase the risk of morbidity and mortality (Sapolsky, 1993; Weiner, 1992). However, physiologic responses depend crucially on the individual’s subjective psychological experience of the event—the degree of threat perceived and the coping strategies that are mobilized in response. Studies measuring the objective incidence of negative life events in HIV+ individuals found little impact on biological indicators of disease progression (Goodkin et al., 1992b; Kessler et al., 1991; Perry et al., 1992; Rabkin et al., 1991). However, several studies assessing the subjective experience of stressful life events have documented significant accelerations in the decline of CD4+ T lymphocyte levels and onset of AIDS-defining clinical conditions (Evans et al., 1997; Golub et al., 2003; Leserman et al., 1999; Leserman et al., 2000; Leserman et al., 2002; Moss et al., 1998; Patterson et al., 1995; Vedhara et al., 1997). Bereavement of close friends or intimate partners is the only “objective” negative event that has been linked to biological markers of HIV disease progression (Kemeny and Dean, 1995; Martin and Dean, 1993), perhaps because bereavement is so consistently experienced as traumatic. Some studies have also documented associations between subjective distress and immunologic parameters such as CD8+ or CD57+ T-cell levels, memory CD4+ T-cell levels, B-cell levels, and NK cell levels or cytotoxic activity (Evans et al., 1995; Motivala et al., 2003; Patterson et al., 1995; Petitto et al., 2000). However, no studies have identified neuroendocrine changes that mediate relationships between subjective stress and HIV disease progression. Well-controlled natural history studies have found stressful life events and elevated HPA activity to be independent predictors of clinical disease progression, but HPA alterations could not account for the increased disease progression risk associated with stressful life events in mediational analyses (Leserman et al., 1999; Leserman et al., 2000; Leserman et al., 2002). One behavioral intervention that sought to buffer the stress of bereave-
ment induced favorable changes in CD4+ T lymphocyte levels, plasma viral load, and cortisol levels among treated participants versus controls (Goodkin et al., 1998; Goodkin et al., 2001), and stressful social manipulations have also been shown to accelerate SIV disease progression and alter HPA activity in experimentally infected rhesus macaques (Capitanio et al., 1998). However, no study has reported mediational analyses that identify HPA alterations as potential mechanisms of virologic or immunologic changes (as opposed to consequences of disease progression or independent contributors to pathogenesis as in Leserman et al., 2000; Leserman et al., 2002). 2. Coping Responses Psychological processes play a key role in shaping biological stress responses (Sapolsky, 1993), and several studies have linked differential HIV disease progression to individual variations in psychological responses to stressful events (coping). Variations in coping responses to bereavement (Bower et al., 1998; Kemeny et al., 1994; Kemeny and Dean, 1995; Reed et al., 1994; Reed et al., 1999) and the stress of HIV infection (Goodkin et al., 1992a; Mulder et al., 1995a; Mulder et al., 1999; Reed et al., 1994; Reed et al., 1999; Segerstrom et al., 1996; Solano et al., 1993) have been especially prognostic. Several studies have found contradictory results regarding specific coping strategies such as active versus passive coping (Goodkin et al., 1992a; Ironson et al., 1994; Keet et al., 1994; Leserman et al., 2000; Mulder et al., 1995a; Mulder et al., 1999; Patterson et al., 1996), psychological hardiness (Perry et al., 1992; Solano et al., 1993; Solomon et al., 1987), and hopelessness versus positive affect, optimism, or fighting spirit (Moskowitz, 2003; Perry et al., 1992; Rabkin et al., 1991; Reed et al., 1994; Reed et al., 1999; Solano et al., 1993; Thornton et al., 2000; Tomakowsky et al., 2001). Some of these differences may be due to variations in the effects of psychological responses in different contexts (e.g., at different stages of infection or in different social ecologies, as suggested by theoretical analyses of the effects of optimism in the context of infectious disease [Auld, 2003]). Two studies have linked religious practice (e.g., attending worship, prayer, or reading religious literature) to increased CD4+ T-cell levels, long-term survival after AIDS diagnosis, and reduced cortisol levels (Ironson et al., 2002; Woods et al., 1999). Among all the coping responses studied, religious practice is distinctive in showing neuroendocrine correlates that meet statistical criteria as a potential mediator of group differences in longterm survival following an AIDS diagnosis (Ironson, 2002). Despite the central role of coping processes in
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shaping neuroendocrine responses to stress, no other studies have identified neuroendocrine correlates of coping in HIV+ individuals. 3. Stress Reduction Interventions Several clinical trials have sought to reduce stress in HIV+ individuals through behavioral interventions such as cognitive-behavioral stress management (CBSM) (Antoni et al., 1991a; Ironson et al., 1994; Ironson et al., 2005a; Mulder et al., 1995b), mindfulness-based stress reduction (MBSR) (Robinson et al., 2003), cognitive-behavioral grief resolution (Goodkin et al., 1998; Goodkin et al., 2001), relaxation (Coates et al., 1989; Eller, 1995; Taylor, 1995), and massage therapy (Diego et al., 2001; Shor-Posner et al., 2004). These studies are reviewed in detail by Antoni and colleagues in this volume (Chapter 32). Effects on HIV pathogenesis are mixed, and no effectively controlled intervention study has induced clear changes in longterm plasma viral load or clinical disease progression. (Goodkin and colleagues have reported significant effects of a cognitive-behavioral bereavement support intervention on plasma viral load, but baseline differences between treatment and control groups in viral load and CD4+ T-cell levels complicate the interpretation of those data [Goodkin et al., 2001]). Several studies have documented beneficial effects of behavioral interventions on neuroendocrine parameters (Antoni et al., 2000a; Antoni et al., 2005; Cruess et al., 1999; Goodkin et al., 1998) and immunologic parameters (Antoni et al., 1991a; Eller, 1995; Goodkin et al., 2001; Ironson et al., 1994; Taylor, 1995), but no mediational analyses have identified specific neuroendocrine parameters as mediators of immunologic alterations.
B. Depression Depression can refer to dysphoric mood or a formally defined clinical syndrome including affective, behavioral, and physiologic components (clinical depression). Clinical depression often involves disturbances in sleep, eating, and neuroendocrine function, in addition to dysphoric affect, and both HPA and ANS function can be affected (Delgado and Moreno, 2000; Gold et al., 1995; Ressler and Nemeroff, 2000). The prevalence of depression in the HIV+ population is estimated to range between 19–45% (Morrison et al., 2002; Penzak et al., 2000), which is considerably higher than in the general population. 1. Depressive States Studies using one-time measures of clinical depression or depressive mood have found mixed results,
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with some showing more rapid declines in circulating CD4+ T-cell numbers (Burack et al., 1993; Gruzelier et al., 1996; Page-Shafer et al., 1996; Patterson et al., 1995; Vedhara et al., 1997), increased plasma viral load (Kalichman et al., 2002; Lyon and Munro, 2001), and accelerated times to AIDS-related clinical conditions (Page-Shafer et al., 1996; Patterson et al., 1995), whereas others failed to find such relationships (Lyketsos et al., 1993; Lyketsos et al., 1996; Perry et al., 1992; Rabkin et al., 1991). Differences in sample size, follow-up duration, and the measurement of depression likely contributed to the variation in results. However, studies are consistent in finding that any disease progression risk associated with a one-time measure of depression is small (less than 10% acceleration in disease progression). One-time measures of depression have also been linked to immunologic parameters such as circulating CD8+ T lymphocyte levels and NK cell numbers and lytic activity (Cruess et al., 2003; Evans et al., 2002; Leserman et al., 1997; see Sahs et al., 1994, for an exception). Behavioral interventions that reduce one-time measures of depressive affect have also suppressed cortisol production (Antoni et al., 2005), although those changes were not associated with decreases in viral load or CD4+ T-cell levels. 2. Chronic Depression In contrast to one-time depression measures, chronic depression assessed repeatedly over time has been consistently linked to accelerated HIV disease progression (Ickovics et al., 2001; Leserman et al., 2002; Mayne et al., 1996). Chronic depression is associated with a substantially greater disease progression risk than are one-time measures of depression, and several studies have sought to exclude the possibility that advancing disease progression might be a cause of chronic depression (Kalichman et al., 2002; Leserman, 2003). However, the causal significance of depression remains unclear because several short-term studies of antidepressant therapy have successfully reduced depression in HIV+ individuals without impacting CD4+ T-cell levels or plasma viral load (Rabkin et al., 1994a; Rabkin et al., 1994b; Rabkin et al., 1994c; Rabkin et al., 1999). No studies have evaluated the long-term impact of antidepressant therapy on HIV disease progression, and intervention studies have not distinguished transient “reactive” depression from chronic depression. Even if antidepressant interventions were found to slow HIV disease progression, it is not clear that such effects would be mediated by neuroendocrine alterations as opposed to potential effects of improved mood on ART adherence or other behavioral risk factors (Elliott et al., 2002; Mayne et al., 1998). Only one long-term
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study has evaluated the neuroendocrine correlates of depression in HIV+ individuals, and it found HPA axis activity to be an independent risk-factor for AIDS onset that did not mediate the effects of depressive symptoms (Leserman et al., 2000; Leserman et al., 2002). Despite the availability of effective pharmacologic and behavioral therapies for depression, the paucity of long-term follow-up studies leaves it unclear whether depressive states or their neuroendocrine correlates exert a significant causal impact on HIV pathogenesis.
C. Social Support Positive social relationships can support physical health by providing instrumental resources (e.g., financial support, health information, or physical assistance) and by buffering physiologic responses to stress (Cohen et al., 2000). However, recent studies have also identified potential detrimental health effects of social relationships (Kiecolt-Glaser and Newton, 2001; Kiecolt-Glaser et al., 1998). Analyses of social support in the context of HIV infection reflect that complexity, with some studies showing more favorable disease course in people with high social support (Burgoyne, 2005; Leserman et al., 2000; Leserman et al., 2002; Persson et al., 2002; Solano et al., 1993; Theorell et al., 1995) and others suggesting significant detrimental effects (Blomkvist et al., 1994; Miller et al., 1997; Patterson et al., 1996; Persson et al., 1994). Variable results appear to stem in part from differences in the extent to which social relationships constitute potential psychological burdens or physical disease transmission pathways. Negative effects of social relationships were most often found in early studies of HIV+ gay men, who may have faced greater exposure to AIDS-related bereavement, care-giving burdens, and sexual HIV transmission than would socially integrated members of other populations (Miller et al., 1997). Social interactions may also serve as markers of negative health events if they reflect changes in the capacity for independent living or social visitations associated with illness. For example, one study found that male hemophiliacs with late-stage HIV infection who anticipated high levels of social interaction in the near future showed significantly increased mortality risk (Blomkvist et al., 1994). Social relationships may also qualify the effects of other factors by enhancing the intensity of self-relevant emotional states or defending individuals against negative social judgments. For example, one study found gay men’s public expression of homosexual identity was associated with high CD4+ T lymphocyte counts when individuals had high levels
of social support, but not when they had low levels of social support (Ullrich et al., 2003). In this context, variations in social support could reflect differences in the acceptability of a gay identity in different social reference groups. Much of the complexity in the HIV social support literature may stem from the fact that social relationships have diverse motivational and evaluative impacts on the individual in addition to their stress-buffering and instrumental support properties. The clearest indication that social relationships can impact the biology of lentiviral pathogenesis comes from studies of rhesus macaques experimentally infected with SIV. Several parameters of a young primate’s social history have been linked to variations in SIV disease progression, including separation from mother or peers, frequency of cage changes, and housing relocations or social separations in the vicinity of SIV inoculation (Capitanio and Lerche, 1991, 1998). Underscoring the potential negative effects of social relationships, these studies found that animals housed together after SIV inoculation experienced shorter survival times than did those housed individually (Capitanio and Lerche, 1998). Primates randomly assigned to social interactions with unfamiliar monkeys displayed more antagonistic social behavior, less affiliative social behavior, and (unexpectedly) lower basal cortisol levels than did animals assigned to stable social hierarchies (Capitanio et al., 1998). Macaques most frequently targeted by social threats showed increased plasma SIV RNA levels and decreased antiSIV IgG levels (Capitanio et al., 1998). Affiliative animals showed reduced plasma viral load, and animals randomly assigned to unstable social hierarchies showed significantly shorter survival times than did those housed in stable hierarchies (Capitanio et al., 1998). These experimental studies demonstrate causal effects of social conditions on neuroendocrine function, SIV replication, and lentiviral disease progression, and they underscore the central role of relationship content in shaping social influences on individual health (e.g., effects of stable vs. unstable social networks and antagonistic vs. affiliative interactions). No studies of human HIV infection have examined relationship content or its neuroendocrine correlates as potential influences on disease progression. Such studies are complicated by the possibility that social relationships may impact HIV disease progression through behavioral or pharmacologic pathways not available in the SIV model (e.g., effects of social support on health care utilization or medication adherence [Catz et al., 1999; Catz et al., 2000; Gonzalez et al., 2004]).
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D. Psychological Inhibition Inhibiting the expression of subjectively significant thoughts, feelings, or social behaviors can heighten SNS activity (Gross and Levenson, 1993; Miller et al., 1999; Pennebaker and Chew, 1985), alter immunologic responses (Petrie et al., 1995), and increase the risk of physical illness (Pennebaker et al., 1988). Studies have also documented a heightened incidence of immunologically mediated disorders (Bell et al., 1990; Gauci et al., 1993; Kagan et al., 1991), altered immune responses (Cole et al., 1999b), increased vulnerability to viral infections (Broadbent et al., 1984; Cohen et al., 1997; Cohen et al., 2003; Totman et al., 1980), and differential patterns of CNS activity (Sutton and Davidson, 1997) and ANS activity (Block, 1957; Cole et al., 2003; Kagan et al., 1991; Miller et al., 1999) among individuals who manifest socially inhibited personality characteristics. Similar alterations in immunologic and neuroendocrine function have been found in animal models of inhibited social behavior (Capitanio and Lerche, 1991; Petitto et al., 1994; Suomi, 1991). In the context of HIV infection, one early study took gay men’s concealment of their homosexual identity as a model of psychological inhibition and found accelerated declines in CD4+ T-cell levels, accelerated AIDS onset, and accelerated HIV-specific mortality among “closeted” gay men (Cole et al., 1996). A follow-up study of the same cohort found closeted individuals to be especially sensitive to social rejection, and rejectionsensitivity emerged as an even stronger predictor of HIV disease progression (Cole et al., 1997). Consistent with a critical role for the social environment in driving inhibition-related health dynamics, subsequent studies of closeting in a different cohort found concealmentrelated decreases in CD4+ T lymphocyte levels to be most pronounced in gay men who were most strongly enmeshed in their social environment (Ullrich et al., 2003). Decreased CD4+ T lymphocyte levels were also found in HIV+ women who used inhibition-related words frequently in describing their personal approach to coping with HIV infection (Eisenberger et al., 2003). A study of gay men in early- to mid-stage HIV infection also found elevated plasma viral load set points and impaired virologic and immunologic responses to ART initiation among socially inhibited individuals (Cole et al., 2003). The same study also linked social inhibition to elevated ANS activity and found that individual differences in ANS activity could potentially account for most of the association between social inhibition and HIV biomarkers (Cole et al., 2003). Studies of SIV-infected rhesus macaques revealed similar sociobehavioral dynamics, although ANS
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mediation was not directly assessed. In the SIV studies, macaques that rated as showing low levels of sociability prior to infection were subsequently found to have increased plasma SIV RNA levels and decreased IgG response to rhesus cytomegalovirus within the first 10 weeks following inoculation (Capitanio et al., 1999). Given the confluence of data from animal models, human natural history studies, clinical studies of ANS mediation, and in vitro molecular analyses of catecholamine effects on viral replication, socially inhibited temperament represents one of the most broadly supported biobehavioral risk factors for HIV pathogenesis.
E. Neuroendocrine Mediation of Psychosocial Influences Several broad conclusions emerge from existing studies on the psychobiology of HIV infection. In vitro mechanistic analyses have identified a variety of biological signaling pathways by which psychosocial factors might impact viral pathogenesis, and correlational natural history studies suggest that such dynamics could be clinically relevant. Chronic depression, perceptual orientations (e.g., expectancies or attributional styles), coping strategies (e.g., religious practice), cumulative life stress, and socially inhibited temperament have all emerged as prognostic parameters in multiple studies involving reasonably large samples and control of at least some potential confounders. Several of these characteristics have been linked to neuroendocrine function in the general population, and some of those relationships have been verified in HIV+ samples (e.g., elevated ANS activity in people with socially inhibited temperament [Cole et al., 2003; Kagan, 1994]). Correlational natural history studies have also demonstrated transitive associations between socially inhibited temperament, ANS activity, and biological markers of HIV pathogenesis (Cole et al., 2003), and between variations in religious practice, HPA activity, and pre-existing group differences in clinical disease trajectory (Ironson et al., 2002; Woods et al., 1999). Other studies have identified psychosocial risk factors for AIDS onset and SIV pathogenesis that do not appear to operate through HPA alterations but could plausibly involve other neuroendocrine pathways (Capitanio et al., 1998; Leserman et al., 2000; Leserman et al., 2002). However, no existing study has experimentally manipulated neuroendocrine function to formally demonstrate a causal impact on HIV pathogenesis or to block the association between a psychosocial risk factor and disease progression. Neuroendocrine mediation of psychosocial influences on
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HIV disease progression thus represents a plausible hypothesis with some empirical support, but not one that has been rigorously established in vivo. Experimental manipulations of social stress in the SIV model have clearly shown that psychosocial variables can casually impact lentiviral pathogenesis. The challenge that remains is mapping the specific biological signaling pathways by which socio-environmental influences “get inside the body” to impact viral pathogenesis.
V. PROSPECTS Despite the complexity of the current literature and the scientific challenges that remain, several broad themes have emerged from studies on the psychobiology of HIV. Perhaps the most salient message involves the key role of stable individual differences. One-time measures of stressful events or emotional states have rarely emerged as significant predictors of disease progression in more than one study. However, chronic individual differences in depression, generalized perceptual orientation (e.g., expectancies or attributional styles), coping strategies (e.g., religious practice), cumulative life stress, and socially inhibited temperament have all emerged as significant predictors of HIV pathogenesis in multiple studies involving reasonably large samples and efforts to control potential confounders. In the context of a chronic viral infection that unfolds over decades, it seems reasonable that enduring psychological characteristics would exert the greatest biological impact. However, this implies that neuroendocrine parameters may also need to be measured over extended periods to provide valid information on their mediational role. The two clinical studies that have most successfully documented relationships between neuroendocrine function and HIV pathogenesis have both involved repeated longitudinal assessment of neuroendocrine parameters and HIV outcomes (Cole et al., 2001; Cole et al., 2003; Leserman et al., 2000; Leserman et al., 2002). If the clinical impact of psychobiological interactions is dominated by long-term regulatory interactions, this could explain why so few studies have succeeded in identifying potential neuroendocrine mediators in vivo—because few studies have sought to assess neuroendocrine parameters over such durations. Among the few that have taken an extended approach to the psychobiology of HIV progression, several have found results supporting a potential impact of ANS or HPA activity. Much remains to be learned about neuroendocrine mediation in vivo, but the existing literature provides a clear clinical impetus for further mechanistic studies. The key challenge now is to formally demonstrate the causal impact of
neuroendocrine mediators and define their clinical significance. As mediational analyses progress, several methodological strategies show particular promise for resolving outstanding questions regarding the psychobiology of HIV. The SIV model of lentiviral infection in rhesus macaques provides unique opportunities for experimentally manipulating social and physiologic parameters in the context of a behaviorally rich animal model. This approach might be combined with pharmacologic antagonists (e.g., beta-blockers or GR antagonists) to clamp putative mediators and provide epistemologically sound demonstrations of their importance. Behavioral scientists often accept transitive associations as evidence of mediation (Baron and Kenny, 1986), but many biomedical scientists would reject such claims until experimental blockade of a putative mediator is shown to attenuate relationships between psychosocial factors and disease progression. New analytic opportunities have also emerged from a burgeoning array of imaging technologies that can track infectious viral particles, endocrine dynamics, inflammatory/immune responses, and neural activity over a broad range of scales from cellular to systemic. Functional neural imaging in particular provides unprecedented opportunities for mapping the relationships between external stimuli; CNS processes; and peripheral neural, endocrine, and immune dynamics. Microarray approaches for global gene expression analysis are encouraging a more integrative “systems biology” approach to understanding genome function and the upstream signaling pathways that shape those dynamics. Genomics-based approaches can be further leveraged by new techniques for accessing the lymphoid tissue structures that constitute the organizing physical environment of lentiviral pathogenesis as well as largely unexplored sites of neural interaction with virally infected lymphocytes (e.g., laser-capture microdissection, vector/reporter systems for assessing molecular dynamics in vivo, flow-FISH and immunomagnetic strategies for separating cells based on molecular or virologic properties, and laser optical microscopy systems that can resolve planar images within three-dimensional tissue structures). These in situ molecular approaches provide an opportunity to move beyond simple analyses of circulating hormone levels to assess post-receptor signaling dynamics and their subsequent functional impact on viral and immunologic dynamics. Applied in conjunction, these technologies can provide an integrative portrait of psychobiology that is at once more detailed and broader in scope than current empirical analyses. In addition to technological advances, the evolution of the AIDS epidemic may also broaden our under-
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standing of psychobiological dynamics in HIV infection. ART has so dramatically reduced the incidence of AIDS that HIV infection is now a manageable chronic disease in economically developed environments. However, social and economic barriers have hampered the spread of therapy to the poor and disenfranchised. As a result, psychobiological dynamics will continue to be relevant on a global level and may also continue to affect health even in economically privileged environments. Several studies have shown that psychosocial characteristics and neuroendocrine parameters have prognostic significance above and beyond the effects of anti-retroviral treatment (Cole et al., 2001; Cole et al., 2003; Ironson et al., 2005b; Leserman et al., 2000; Leserman et al., 2002), and one study suggests that biobehavioral factors may even modulate the biological efficacy of ART (Cole et al., 2001; Cole et al., 2003). In the absence of ART, biobehavioral dynamics are likely to become increasingly significant because the same social conditions that impede access to therapy are also associated with increased exposure to stress and reduced access to coping resources. The fundamental relationships between threatening events, psychological responses, and their neuroendocrine consequences are likely to be general, but the specific factors that trigger those dynamics may vary significantly across socio-cultural contexts. Research has just begun to explore the psychological dynamics of HIV infection outside gay male populations in the West (Chan et al., 2005; Molassiotis et al., 2002; Shor-Posner et al., 2004). Biobehavioral studies have begun to track the shifting demographics of AIDS (Ironson et al., 2005b; Prado et al., 2004; Wyatt et al., 2002), but no study has systematically compared the content or structure of psychobiological dynamics across social, economic, or cultural contexts. The growing diversity of the AIDS epidemic has enhanced both the opportunity and the need to develop comprehensive analytic frameworks that explicitly incorporate the socio-cultural context in understanding individual biology (Dickerson and Kemeny, 2004). Cross-cultural studies provide a ready framework for such analyses, but the same issues can be analyzed in other ways that might offer unique advantages. For example, the impact of the social ecology is clearly evident in experimental studies of SIV disease progression (Capitanio and Lerche, 1998, Capitanio et al., 1998), and primate hierarchies provide a compelling model system in which to analyze cultural dynamics and their biological effects (Sapolsky, 1998). Given the socio-economic dynamics of ART, the best hope for halting the AIDS epidemic lies in the development of an effective prophylactic vaccine (Letvin et al., 2002). It is generally believed that such
a vaccine would need to induce strong and persistent CTL responses against a diverse array of HIV epitopes without involving a replicating HIV genome. This is an unprecedented requirement for an anti-viral vaccine, and progress has been slow as a result. No current vaccine candidate has induced strong CTL responses to HIV-1 in uninfected humans, and it is unclear how such responses might be maintained over the durations that would be required for effective protection. As reviewed above, nothing is known about psychobiological influences on the HIV-specific CTL response. However, animal models of other viral infections have shown that stress-related neuroendocrine dynamics can profoundly undermine anti-viral CTL responses (Glaser and Kiecolt-Glaser, 2005; Padgett et al., 1998), and in vitro studies have defined several of the molecular mechanisms involved (Kalinichenko et al., 1999; Padgett et al., 1998; Valitutti et al., 1993). Biobehavioral factors are well known to modulate the efficacy of vaccine-induced antibody responses (Glaser et al., 1992; Glaser et al., 1998; Jabaaij et al., 1993; Jabaaij et al., 1996; Marsland et al., 2001), and new measurement technologies are available to extend these analyses to anti-viral CTLs (e.g., ELISPOT and intracellular cytokine detection by flow cytometry, and MHC tetramers for identification of specific antigen-responsive cells). Given the unprecedented technical demands of an HIV vaccine, progress in this area is likely to be incremental. If ever there were a setting in which basic immunology needs all the help it can get from PNI, this is certainly one. Ongoing HIV vaccine trials provide a rich technical infrastructure for analyzing biobehavioral influences on anti-viral CTL responses in humans. Beyond their methodological advantages, biobehavioral analyses of vaccine-induced CTL responses to HIV-1 also provide a rich opportunity for demonstrating the clinical significance of psychoneuroimmunology in the context of a globally significant health threat.
References Aandahl, E. M., Aukrust, P., Skalhegg, B. S., Muller, F., Froland, S. S., Hansson, V., and Tasken, K. (1998). Protein kinase A type I antagonist restores immune responses of T cells from HIVinfected patients. FASEB J., 12 (10), 855–862. Aasa-Chapman, M. M., Holuigue, S., Aubin, K., Wong, M., Jones, N. A., Cornforth, D., Pellegrino, P., Newton, P., Williams, I., Borrow, P., and McKnight, A. (2005). Detection of antibodydependent complement-mediated inactivation of both autologous and heterologous virus in primary human immunodeficiency virus type 1 infection. J. Virol., 79 (5), 2823–2830. Alimonti, J. B., Ball, T. B., and Fowke, K. R. (2003). Mechanisms of CD4+ T lymphocyte cell death in human immunodeficiency virus infection and AIDS. J. Gen. Virol., 84 (Pt 7), 1649–1661.
1066
V. Psychoneuroimmunology and Pathophysiology
Almawi, W. Y., and Melemedjian, O. K. (2002). Negative regulation of nuclear factor-kappaB activation and function by glucocorticoids. J. Mol. Endocrinol., 28 (2), 69–78. Amella, C. A., Sherry, B., Shepp, D. H., and Schmidtmayerova, H. (2005). Macrophage inflammatory protein 1alpha inhibits postentry steps of human immunodeficiency virus type 1 infection via suppression of intracellular cyclic AMP. J. Virol., 79 (9), 5625–5631. Antoni, M. H., Baggett, L., Ironson, G., LaPerriere, A., August, S., Klimas, N., Schneiderman, N., and Fletcher, M. A. (1991a). Cognitive-behavioral stress management intervention buffers distress responses and immunologic changes following notification of HIV-1 seropositivity. J. Consult. Clin. Psychol., 59 (6), 906–915. Antoni, M. H., Cruess, D. G., Cruess, S., Lutgendorf, S., Kumar, M., Ironson, G., Klimas, N., Fletcher, M. A., and Schneiderman, N. (2000a). Cognitive-behavioral stress management intervention effects on anxiety, 24-hr urinary norepinephrine output, and T-cytotoxic/suppressor cells over time among symptomatic HIV-infected gay men. J. Consult. Clin. Psychol., 68 (1), 31– 45. Antoni, M. H., Cruess, D. G., Klimas, N., Carrico, A. W., Maher, K., Cruess, S., Lechner, S. C., Kumar, M., Lutgendorf, S., Ironson, G., Fletcher, M. A., and Schneiderman, N. (2005). Increases in a marker of immune system reconstitution are predated by decreases in 24-h urinary cortisol output and depressed mood during a 10-week stress management intervention in symptomatic HIV-infected men. J. Psychosom. Res., 58 (1), 3–13. Antoni, M. H., Cruess, S., Cruess, D. G., Kumar, M., Lutgendorf, S., Ironson, G., Dettmer, E., Williams, J., Klimas, N., Fletcher, M. A., and Schneiderman, N. (2000b). Cognitive-behavioral stress management reduces distress and 24-hour urinary free cortisol output among symptomatic HIV-infected gay men. Ann. Behav. Med., 22 (1), 29–37. Antoni, M. H., Schneiderman, N., Klimas, N., LaPerriere, A., Ironson, G., and Fletcher, M. A. (1991b). Disparities in psychological, neuroendocrine, and immunologic patterns in asymptomatic HIV-1 seropositive and seronegative gay men. Biol. Psychiatry, 29 (10), 1023–1041. Ashwell, J. D., Lu, F. W., and Vacchio, M. S. (2000). Glucocorticoids in T cell development and function. Annu. Rev. Immunol., 18, 309–345. Auld, M. C. (2003). Choices, beliefs, and infectious disease dynamics. J. Health Econ., 22 (3), 361–377. Ayyavoo, V., Mahboubi, A., Mahalingam, S., Ramalingam, R., Kudchodkar, S., Williams, W. V., Green, D. R., and Weiner, D. B. (1997). HIV-1 Vpr suppresses immune activation and apoptosis through regulation of nuclear factor kappa B. Nat. Med., 3 (10), 1117–1123. Azar, S. T., and Melby, J. C. (1993). Hypothalamic-pituitary-adrenal function in non-AIDS patients with advanced HIV infection. Am. J. Med. Sci., 305 (5), 321–325. Banks, W. A., Robinson, S. M., and Nath, A. (2005). Permeability of the blood-brain barrier to HIV-1 Tat. Exp. Neurol., 193 (1), 218–227. Baron, R. M., and Kenny, D. A. (1986). The moderator-mediator variable distinction in social psychological research: conceptual, strategic, and statistical considerations. J. Pers. Soc. Psychol., 51 (6), 1173–1182. Bell, I. R., Jasnoski, M. L., Kagan, J., and King, D. S. (1990). Is allergic rhinitis more frequent in young adults with extreme shyness? A preliminary survey. Psychosom. Med., 52 (5), 517–525. Benki, S., Mostad, S. B., Richardson, B. A., Mandaliya, K., Kreiss, J. K., and Overbaugh, J. (2004). Cyclic shedding of HIV-1 RNA
in cervical secretions during the menstrual cycle. J. Infect. Dis., 189 (12), 2192–2201. Bentwich, Z., Kalinkovich, A., and Weisman, Z. (1995). Immune activation is a dominant factor in the pathogenesis of African AIDS. Immunol. Today, 16 (4), 187–191. Bhansali, A., Dash, R. J., Sud, A., Bhadada, S., Sehgal, S., and Sharma, B. R. (2000). A preliminary report on basal & stimulated plasma cortisol in patients with acquired immunodeficiency syndrome. Indian J. Med. Res., 112, 173–177. Biglino, A., Limone, P., Forno, B., Pollono, A., Cariti, G., Molinatti, G. M., and Gioannini, P. (1995). Altered adrenocorticotropin and cortisol response to corticotropin-releasing hormone in HIV-1 infection. Eur. J. Endocrinol., 133 (2), 173–179. Block, J. (1957). A study of affective responsiveness in a lie-detection situation. J Abnorm. Psychol., 55 (1), 11–15. Blomkvist, V., Theorell, T., Jonsson, H., Schulman, S., Berntorp, E., and Stiegendal, L. (1994). Psychosocial self-prognosis in relation to mortality and morbidity in hemophiliacs with HIV infection. Psychother Psychosom., 62 (3–4), 185–192. Borrow, P., Lewicki, H., Hahn, B. H., Shaw, G. M., and Oldstone, M. B. (1994). Virus-specific CD8+ cytotoxic T-lymphocyte activity associated with control of viremia in primary human immunodeficiency virus type 1 infection. J. Virol., 68 (9), 6103–6110. Bourinbaiar, A. S., Nagorny, R., and Tan, X. (1992). Pregnancy hormones, estrogen and progesterone prevent HIV-1 synthesis in monocytes but not in lymphocytes. FEBS Lett., 302 (3), 206–208. Bower, J. E., Kemeny, M. E., Taylor, S. E., and Fahey, J. L. (1998). Cognitive processing, discovery of meaning, CD4 decline, and AIDS-related mortality among bereaved HIV-seropositive men. J. Consult. Clin. Psychol., 66 (6), 979–986. Broadbent, D. E., Broadbent, M. H., Phillpotts, R. J., and Wallace, J. (1984). Some further studies on the prediction of experimental colds in volunteers by psychological factors. J. Psychosom. Res., 28 (6), 511–523. Brownley, K. A., Milanovich, J. R., Motivala, S. J., Schneiderman, N., Fillion, L., Graves, J. A., Klimas, N. G., Fletcher, M. A., and Hurwitz, B. E. (2001). Autonomic and cardiovascular function in HIV spectrum disease: early indications of cardiac pathophysiology. Clin. Auton. Res., 11 (5), 319–326. Burack, J. H., Barrett, D. C., Stall, R. D., Chesney, M. A., Ekstrand, M. L., and Coates, T. J. (1993). Depressive symptoms and CD4 lymphocyte decline among HIV-infected men. JAMA, 270 (21), 2568–2573. Burgoyne, R. W. (2005). Exploring direction of causation between social support and clinical outcome for HIV-positive adults in the context of highly active antiretroviral therapy. AIDS Care, 17 (1), 111–124. Capitanio, J. P., and Lerche, N. W. (1991). Psychosocial factors and disease progression in simian AIDS: a preliminary report. AIDS, 5 (9), 1103–1106. Capitanio, J. P., and Lerche, N. W. (1998). Social separation, housing relocation, and survival in simian AIDS: a retrospective analysis. Psychosom. Med., 60 (3), 235–244. Capitanio, J. P., Mendoza, S. P., and Baroncelli, S. (1999). The relationship of personality dimensions in adult male rhesus macaques to progression of simian immunodeficiency virus disease. Brain Behav. Immun., 13 (2), 138–154. Capitanio, J. P., Mendoza, S. P., Lerche, N. W., and Mason, W. A. (1998). Social stress results in altered glucocorticoid regulation and shorter survival in simian acquired immune deficiency syndrome. Proc. Natl. Acad. Sci. U.S.A., 95 (8), 4714–4719. Carrington, M., and O’Brien, S. J. (2003). The influence of HLA genotype on AIDS. Annu. Rev. Med., 54, 535–551.
49. Psychobiology of HIV Infection Cartier, C., Hemonnot, B., Gay, B., Bardy, M., Sanchiz, C., Devaux, C., and Briant, L. (2003). Active cAMP-dependent protein kinase incorporated within highly purified HIV-1 particles is required for viral infectivity and interacts with viral capsid protein. J. Biol. Chem., 278 (37), 35211–35219. Castrillon, P. O., Cardinali, D. P., Arce, A., Cutrera, R. A., and Esquifino, A. I. (2000). Interferon-gamma release in sympathetically denervated rat submaxillary lymph nodes. Neuroimmunomodulation, 8 (4), 197–202. Catania, A., Manfredi, M. G., Airaghi, L., Vivirito, M. C., Milazzo, F., Lipton, J. M., and Zanussi, C. (1992). Delayed cortisol response to antigenic challenge in patients with acquired immunodeficiency syndrome. Ann. N. Y. Acad. Sci., 650, 202–204. Catz, S. L., Kelly, J. A., Bogart, L. M., Benotsch, E. G., and McAuliffe, T. L. (2000). Patterns, correlates, and barriers to medication adherence among persons prescribed new treatments for HIV disease. Health Psychol., 19 (2), 124–133. Catz, S. L., McClure, J. B., Jones, G. N., and Brantley, P. J. (1999). Predictors of outpatient medical appointment attendance among persons with HIV. AIDS Care, 11 (3), 361–373. Caulfield, J., Fernandez, M., Snetkov, V., Lee, T., and Hawrylowicz, C. (2002). CXCR4 expression on monocytes is up-regulated by dexamethasone and is modulated by autologous CD3+ T cells. Immunology, 105 (2), 155–162. Centurelli, M. A., and Abate, M. A. (1997). The role of dehydroepiandrosterone in AIDS. Ann. Pharmacother, 31 (5), 639–642. Chan, I., Kong, P., Leung, P., Au, A., Li, P., Chung, R., Po, L. M., and Yu, P. (2005). Cognitive-behavioral group program for Chinese heterosexual HIV-infected men in Hong Kong. Patient Educ. Couns., 56 (1), 78–84. Chang, M., Brown, H. J., Collado-Hidalgo, A., Arevalo, J. M., Galic, Z., Symensma, T. L., and Tanaka, L. (2005). Beta-adrenoreceptors reactivate KSHV lytic replication via PKA-dependent control of viral RTA. Journal of Virology, 79, 13538–13547. Chowdhury, I. H., Wang, X. F., Landau, N. R., Robb, M. L., Polonis, V. R., Birx, D. L., and Kim, J. H. (2003). HIV-1 Vpr activates cell cycle inhibitor p21/Waf1/Cip1, a potential mechanism of G2/M cell cycle arrest. Virology, 305 (2), 371–377. Chowdhury, M. I., Koyanagi, Y., Horiuchi, S., Hazeki, O., Ui, M., Kitano, K., Golde, D. W., Takada, K., and Yamamoto, N. (1993). cAMP stimulates human immunodeficiency virus (HIV-1) from latently infected cells of monocyte-macrophage lineage: synergism with TNF-alpha. Virology, 194 (1), 345–349. Christeff, N., Gharakhanian, S., Thobie, N., Rozenbaum, W., and Nunez, E. A. (1992). Evidence for changes in adrenal and testicular steroids during HIV infection. J. Acquir. Immune Defic. Syndr., 5 (8), 841–846. Christeff, N., Gherbi, N., Mammes, O., Dalle, M. T., Gharakhanian, S., Lortholary, O., Melchior, J. C., and Nunez, E. A. (1997). Serum cortisol and DHEA concentrations during HIV infection. Psychoneuroendocrinology, 22 (Suppl 1), S11–18. Christeff, N., Nunez, E. A., and Gougeon, M. L. (2000). Changes in cortisol/DHEA ratio in HIV-infected men are related to immunological and metabolic perturbations leading to malnutrition and lipodystrophy. Ann. N. Y. Acad. Sci., 917, 962–970. Chrousos, G. P., and Gold, P. W. (1992). The concepts of stress and stress system disorders. Overview of physical and behavioral homeostasis. JAMA, 267 (9), 1244–1252. Clemetson, D. B., Moss, G. B., Willerford, D. M., Hensel, M., Emonyi, W., Holmes, K. K., Plummer, F., Ndinya-Achola, J., Roberts, P. L., Hillier, S. et al. (1993). Detection of HIV DNA in cervical and vaginal secretions. Prevalence and correlates among women in Nairobi, Kenya. JAMA, 269 (22), 2860–2864.
1067
Clerici, M., Galli, M., Bosis, S., Gervasoni, C., Moroni, M., and Norbiato, G. (2000). Immunoendocrinologic abnormalities in human immunodeficiency virus infection. Ann. N. Y. Acad. Sci., 917, 956–961. Clerici, M., Trabattoni, D., Piconi, S., Fusi, M. L., Ruzzante, S., Clerici, C., and Villa, M. L. (1997). A possible role for the cortisol/ anticortisol imbalance in the progression of human immunodeficiency virus. Psychoneuroendocrinology, 22 (Suppl 1), S27–31. Coates, T. J., McKusick, L., Kuno, R., and Stites, D. P. (1989). Stress reduction training changed number of sexual partners but not immune function in men with HIV. Am. J. Public Health, 79 (7), 885–887. Cohen, J. A., and Laudenslager, M. (1989). Autonomic nervous system involvement in patients with human immunodeficiency virus infection. Neurology, 39 (8), 1111–1112. Cohen, S., Doyle, W. J., Skoner, D. P., Rabin, B. S., and Gwaltney, J. M., Jr. (1997). Social ties and susceptibility to the common cold. JAMA, 277 (24), 1940–1944. Cohen, S., Doyle, W. J., Turner, R., Alper, C. M., and Skoner, D. P. (2003). Sociability and susceptibility to the common cold. Psychol. Sci., 14 (5), 389–395. Cohen, S., Gottlieb, B., and Underwood, L. (2000). Social relationships and health. In S. Cohen, L. Underwood, and B. Gottlieb (Eds.), Social support measurement and interventions: a guide for health and social scientists (pp. 3–25). New York: Oxford University Press. Cole, S. W., Jamieson, B. D., and Zack, J. A. (1999a). cAMP upregulates cell surface expression of lymphocyte CXCR4, implications for chemotaxis and HIV-1 infection. J. Immunol., 162 (3), 1392–1400. Cole, S. W., Kemeny, M. E., Fahey, J. L., Zack, J. A., and Naliboff, B. D. (2003). Psychological risk factors for HIV pathogenesis: mediation by the autonomic nervous system. Biol. Psychiatry, 54 (12), 1444–1456. Cole, S. W., Kemeny, M. E., and Taylor, S. E. (1997). Social identity and physical health: accelerated HIV progression in rejectionsensitive gay men. J. Pers. Soc. Psychol., 72 (2), 320–335. Cole, S. W., Kemeny, M. E., Taylor, S. E., Visscher, B. R., and Fahey, J. L. (1996). Accelerated course of human immunodeficiency virus infection in gay men who conceal their homosexual identity. Psychosom. Med., 58 (3), 219–231. Cole, S. W., Kemeny, M. E., Weitzman, O. B., Schoen, M., and Anton, P. A. (1999b). Socially inhibited individuals show heightened DTH response during intense social engagement. Brain Behav. Immun., 13 (2), 187–200. Cole, S. W., Korin, Y. D., Fahey, J. L., and Zack, J. A. (1998). Norepinephrine accelerates HIV replication via protein kinase Adependent effects on cytokine production. J. Immunol., 161 (2), 610–616. Cole, S. W., Naliboff, B. D., Kemeny, M. E., Griswold, M. P., Fahey, J. L., and Zack, J. A. (2001). Impaired response to HAART in HIV-infected individuals with high autonomic nervous system activity. Proc. Natl. Acad. Sci. U.S.A., 98 (22), 12695–12700. Collazos, J., Ibarra, S., and Loureiro, M. (2004). Cortisol serum levels and their relationship to certain antiretroviral drugs. Scand. J. Infect. Dis., 36 (6–7), 480–482. Cooper, E. R., Charurat, M., Mofenson, L., Hanson, I. C., Pitt, J., Diaz, C., Hayani, K., Handelsman, E., Smeriglio, V., Hoff, R., and Blattner, W. (2002). Combination antiretroviral strategies for the treatment of pregnant HIV-1–infected women and prevention of perinatal HIV-1 transmission. J. Acquir. Immune Defic. Syndr., 29 (5), 484–494. Covas, M. J., Pinto, L. A., and Victorino, R. M. (1994). Disturbed immunoregulatory properties of the neuropeptide substance P
1068
V. Psychoneuroimmunology and Pathophysiology
on lymphocyte proliferation in HIV infection. Clin. Exp. Immunol., 96 (3), 384–388. Cruess, D. G., Antoni, M. H., Kumar, M., Ironson, G., McCabe, P., Fernandez, J. B., Fletcher, M., and Schneiderman, N. (1999). Cognitive-behavioral stress management buffers decreases in dehydroepiandrosterone sulfate (DHEA-S) and increases in the cortisol/DHEA-S ratio and reduces mood disturbance and perceived stress among HIV-seropositive men. Psychoneuroendocrinology, 24 (5), 537–549. Cruess, D. G., Antoni, M. H., Kumar, M., and Schneiderman, N. (2000a). Reductions in salivary cortisol are associated with mood improvement during relaxation training among HIVseropositive men. J. Behav. Med., 23 (2), 107–122. Cruess, D. G., Antoni, M. H., McGregor, B. A., Kilbourn, K. M., Boyers, A. E., Alferi, S. M., Carver, C. S., and Kumar, M. (2000b). Cognitive-behavioral stress management reduces serum cortisol by enhancing benefit finding among women being treated for early stage breast cancer. Psychosom. Med., 62 (3), 304–308. Cruess, D. G., Douglas, S. D., Petitto, J. M., Leserman, J., Ten Have, T., Gettes, D., Dube, B., and Evans, D. L. (2003). Association of depression, CD8+ T lymphocytes, and natural killer cell activity: implications for morbidity and mortality in human immunodeficiency virus disease. Curr. Psychiatry Rep., 5 (6), 445–450. Curnow, S. J., Wloka, K., Faint, J. M., Amft, N., Cheung, C. M., Savant, V., Lord, J., Akbar, A. N., Buckley, C. D., Murray, P. I., and Salmon, M. (2004). Topical glucocorticoid therapy directly induces up-regulation of functional CXCR4 on primed T lymphocytes in the aqueous humor of patients with uveitis. J. Immunol., 172 (11), 7154–7161. Dantzer, R., Bluthe, R. M., Laye, S., Bret-Dibat, J. L., Parnet, P., and Kelley, K. W. (1998). Cytokines and sickness behavior. Ann. N. Y. Acad. Sci., 840, 586–590. da Silva, B., Singer, W., Fong, I. W., and Ottaway, C. A. (1999). In vivo cytokine and neuroendocrine responses to endotoxin in human immunodeficiency virus-infected subjects. J. Infect. Dis., 180 (1), 106–115. Dean, M., Carrington, M., Winkler, C., Huttley, G. A., Smith, M. W., Allikmets, R., Goedert, J. J., Buchbinder, S. P., Vittinghoff, E., Gomperts, E., Donfield, S., Vlahov, D., Kaslow, R., Saah, A., Rinaldo, C., Detels, R., and O’Brien, S. J. (1996). Genetic restriction of HIV-1 infection and progression to AIDS by a deletion allele of the CKR5 structural gene. Hemophilia Growth and Development Study, Multicenter AIDS Cohort Study, Multicenter Hemophilia Cohort Study, San Francisco City Cohort, ALIVE Study. Science, 273 (5283), 1856–1862. Delahanty, D. L., Bogart, L. M., and Figler, J. L. (2004). Posttraumatic stress disorder symptoms, salivary cortisol, medication adherence, and CD4 levels in HIV-positive individuals. AIDS Care, 16 (2), 247–260. de la Torre, B., von Krogh, G., Svensson, M., and Holmberg, V. (1997). Blood cortisol and dehydroepiandrosterone sulphate (DHEAS) levels and CD4 T cell counts in HIV infection. Clin. Exp. Rheumatol., 15 (1), 87–90. Delgado, P. L., and Moreno, F. A. (2000). Role of norepinephrine in depression. J. Clin. Psychiatry, 61 (Suppl 1), 5–12. DeVane, C. L. (2001). Substance P: a new era, a new role. Pharmacotherapy, 21 (9), 1061–1069. Dickerson, S. S., and Kemeny, M. E. (2004). Acute stressors and cortisol responses: a theoretical integration and synthesis of laboratory research. Psychol. Bull, 130 (3), 355–391. Diego, M. A., Field, T., Hernandez-Reif, M., Shaw, K., Friedman, L., and Ironson, G. (2001). HIV adolescents show improved immune function following massage therapy. Int J. Neurosci., 106 (1–2), 35–45.
Dorenbaum, A., Cunningham, C. K., Gelber, R. D., Culnane, M., Mofenson, L., Britto, P., Rekacewicz, C., Newell, M. L., Delfraissy, J. F., Cunningham-Schrader, B., Mirochnick, M., and Sullivan, J. L. (2002). Two-dose intrapartum/newborn nevirapine and standard antiretroviral therapy to reduce perinatal HIV transmission: a randomized trial. JAMA, 288 (2), 189–198. Douglas, S. D., Ho, W. Z., Gettes, D. R., Cnaan, A., Zhao, H., Leserman, J., Petitto, J. M., Golden, R. N., and Evans, D. L. (2001). Elevated substance P levels in HIV-infected men. AIDS, 15 (15), 2043–2045. Downing, J. E., and Miyan, J. A. (2000). Neural immunoregulation: emerging roles for nerves in immune homeostasis and disease. Immunol. Today, 21 (6), 281–289. Dyner, T. S., Lang, W., Geaga, J., Golub, A., Stites, D., Winger, E., Galmarini, M., Masterson, J., and Jacobson, M. A. (1993). An open-label dose-escalation trial of oral dehydroepiandrosterone tolerance and pharmacokinetics in patients with HIV disease. J. Acquir. Immune Defic. Syndr., 6 (5), 459–465. Eisenberger, N. I., Kemeny, M. E., and Wyatt, G. E. (2003). Psychological inhibition and CD4 T-cell levels in HIV-seropositive women. J. Psychosom. Res., 54 (3), 213–224. Eledrisi, M. S., and Verghese, A. C. (2001). Adrenal insufficiency in HIV infection: a review and recommendations. Am. J. Med. Sci., 321 (2), 137–144. Elenkov, I. J., and Chrousos, G. P. (1999). Stress hormones, Th1/Th2 patterns, pro/anti-inflammatory cytokines and susceptibility to disease. Trends Endocrinol. Metab., 10 (9), 359–368. Eller, L. S. (1995). Effects of two cognitive-behavioral interventions on immunity and symptoms in persons with HIV. Annals of Behavioral Medicine, 17, 339. Elliott, A. J., Russo, J., and Roy-Byrne, P. P. (2002). The effect of changes in depression on health related quality of life (HRQoL) in HIV infection. Gen. Hosp. Psychiatry, 24 (1), 43–47. Embretson, J., Zupancic, M., Ribas, J. L., Burke, A., Racz, P., Tenner-Racz, K., and Haase, A. T. (1993). Massive covert infection of helper T lymphocytes and macrophages by HIV during the incubation period of AIDS. Nature, 362 (6418), 359–362. Emerman, M. (1996). HIV-1, Vpr and the cell cycle. Curr. Biol., 6 (9), 1096–1103. Engering, A., Van Vliet, S. J., Geijtenbeek, T. B., and Van Kooyk, Y. (2002). Subset of DC-SIGN(+) dendritic cells in human blood transmits HIV-1 to T lymphocytes. Blood, 100 (5), 1780–1786. Eugen-Olsen, J., Afzelius, P., Andresen, L., Iversen, J., Kronborg, G., Aabech, P., Nielsen, J. O., and Hofmann, B. (1997). Serotonin modulates immune function in T cells from HIV-seropositive subjects. Clin. Immunol. Immunopathol., 84 (2), 115–121. Eugen-Olsen, J., Benfield, T., Axen, T. E., Parner, J., Iversen, J., Pedersen, C., and Nielsen, J. O. (2000). Effect of the serotonin receptor agonist, buspirone, on immune function in HIV-infected individuals: a six-month randomized, double-blind, placebocontrolled trial. HIV Clin. Trials, 1 (1), 20–26. Evans, D. L., Leserman, J., Perkins, D. O., Stern, R. A., Murphy, C., Tamul, K., Liao, D., van der Horst, C. M., Hall, C. D., Folds, J. D. et al. (1995). Stress-associated reductions of cytotoxic T lymphocytes and natural killer cells in asymptomatic HIV infection. Am. J. Psychiatry, 152 (4), 543–550. Evans, D. L., Leserman, J., Perkins, D. O., Stern, R. A., Murphy, C., Zheng, B., Gettes, D., Longmate, J. A., Silva, S. G., van der Horst, C. M., Hall, C. D., Folds, J. D., Golden, R. N., and Petitto, J. M. (1997). Severe life stress as a predictor of early disease progression in HIV infection. Am. J. Psychiatry, 154 (5), 630–634. Evans, D. L., Ten Have, T. R., Douglas, S. D., Gettes, D. R., Morrison, M., Chiappini, M. S., Brinker-Spence, P., Job, C., Mercer, D. E., Wang, Y. L., Cruess, D., Dube, B., Dalen, E. A., Brown, T., Bauer,
49. Psychobiology of HIV Infection R., and Petitto, J. M. (2002). Association of depression with viral load, CD8 T lymphocytes, and natural killer cells in women with HIV infection. Am. J. Psychiatry, 159 (10), 1752–1759. Fakruddin, J. M., and Laurence, J. (2005). HIV-1 Vpr enhances production of receptor of activated NF-kappaB ligand (RANKL) via potentiation of glucocorticoid receptor activity. Arch. Virol., 150 (1), 67–78. Fauci, A. S. (1988). The human immunodeficiency virus: infectivity and mechanisms of pathogenesis. Science, 239 (4840), 617– 622. Fauci, A. S. (1996). Host factors in the pathogenesis of HIV disease. Antibiot. Chemother, 48, 4–12. Fauci, A. S. (2003). HIV and AIDS: 20 years of science. Nat. Med., 9 (7), 839–843. Felten, D. L., and Felten, S. Y. (1988). Sympathetic noradrenergic innervation of immune organs. Brain Behav. Immun., 2 (4), 293–300. Felten, D. L., Felten, S. Y., Bellinger, D. L., Carlson, S. L., Ackerman, K. D., Madden, K. S., Olschowki, J. A., and Livnat, S. (1987). Noradrenergic sympathetic neural interactions with the immune system: structure and function. Immunol. Rev., 100, 225–260. Felten, D. L., Livnat, S., Felten, S. Y., Carlson, S. L., Bellinger, D. L., and Yeh, P. (1984). Sympathetic innervation of lymph nodes in mice. Brain Res. Bull, 13 (6), 693–699. Findling, J. W., Buggy, B. P., Gilson, I. H., Brummitt, C. F., Bernstein, B. M., and Raff, H. (1994). Longitudinal evaluation of adrenocortical function in patients infected with the human immunodeficiency virus. J. Clin. Endocrinol. Metab., 79 (4), 1091–1096. Fontes, R., Vangeloti, A., Pires, M. L., Lima, M. B., Dimetz, T., Faulhaber, M., Faria, R., Jr., and Meirelles, R. M. (2003). Endocrine disorders in Brazilian patients with acquired immune deficiency syndrome. Clin. Infect. Dis., 37 (Suppl 2), S137–141. Forsythe, S. S. (1998). The affordability of antiretroviral therapy in developing countries: what policymakers need to know. AIDS, 12 (Suppl 2), S11–18. Freda, P. U., and Bilezikian, J. P. (1999). The hypothalamuspituitary-adrenal axis in HIV disease. AIDS Read, 9 (1), 43–50. Frost, S. D., and McLean, A. R. (1994). Germinal centre destruction as a major pathway of HIV pathogenesis. J. Acquir. Immune Defic. Syndr., 7 (3), 236–244. Garcia, J. A., and Gaynor, R. B. (1994). The human immunodeficiency virus type-1 long terminal repeat and its role in gene expression. Prog. Nucleic Acid Res. Mol. Biol., 49, 157–196. Gauci, M., King, M. G., Saxarra, H., Tulloch, B. J., and Husband, A. J. (1993). A Minnesota Multiphasic Personality Inventory profile of women with allergic rhinitis. Psychosom. Med., 55 (6), 533–540. Geijtenbeek, T. B., Kwon, D. S., Torensma, R., van Vliet, S. J., van Duijnhoven, G. C., Middel, J., Cornelissen, I. L., Nottet, H. S., KewalRamani, V. N., Littman, D. R., Figdor, C. G., and van Kooyk, Y. (2000). DC-SIGN, a dendritic cell-specific HIV-1– binding protein that enhances trans-infection of T cells. Cell, 100 (5), 587–597. Geijtenbeek, T. B., van Duijnhoven, G. C., van Vliet, S. J., Krieger, E., Vriend, G., Figdor, C. G., and van Kooyk, Y. (2002). Identification of different binding sites in the dendritic cell-specific receptor DC-SIGN for intercellular adhesion molecule 3 and HIV-1. J. Biol. Chem., 277 (13), 11314–11320. Gibellini, D., Bassini, A., Pierpaoli, S., Bertolaso, L., Milani, D., Capitani, S., La Placa, M., and Zauli, G. (1998). Extracellular HIV1 Tat protein induces the rapid Ser133 phosphorylation and activation of CREB transcription factor in both Jurkat lymphoblastoid T cells and primary peripheral blood mononuclear cells. J. Immunol., 160 (8), 3891–3898.
1069
Glaser, R., and Kiecolt-Glaser, J. K. (2005). Stress-induced immune dysfunction: implications for health. Nat. Rev. Immunol., 5 (3), 243–251. Glaser, R., Kiecolt-Glaser, J. K., Bonneau, R. H., Malarkey, W., Kennedy, S., and Hughes, J. (1992). Stress-induced modulation of the immune response to recombinant hepatitis B vaccine. Psychosom. Med., 54 (1), 22–29. Glaser, R., Kiecolt-Glaser, J. K., Malarkey, W. B., and Sheridan, J. F. (1998). The influence of psychological stress on the immune response to vaccines. Ann. N. Y. Acad. Sci., 840, 649–655. Gloster, S. E., Newton, P., Cornforth, D., Lifson, J. D., Williams, I., Shaw, G. M., and Borrow, P. (2004). Association of strong virusspecific CD4 T cell responses with efficient natural control of primary HIV-1 infection. AIDS, 18 (5), 749–755. Goh, W. C., Manel, N., and Emerman, M. (2004). The human immunodeficiency virus Vpr protein binds Cdc25C: implications for G2 arrest. Virology, 318 (1), 337–349. Gold, P. W., Licinio, J., Wong, M. L., and Chrousos, G. P. (1995). Corticotropin releasing hormone in the pathophysiology of melancholic and atypical depression and in the mechanism of action of antidepressant drugs. Ann. N. Y. Acad. Sci., 771, 716–729. Golub, E. T., Astemborski, J. A., Hoover, D. R., Anthony, J. C., Vlahov, D., and Strathdee, S. A. (2003). Psychological distress and progression to AIDS in a cohort of injection drug users. J. Acquir. Immune Defic. Syndr., 32 (4), 429–434. Gonzalez, J. S., Penedo, F. J., Antoni, M. H., Duran, R. E., McPhersonBaker, S., Ironson, G., Isabel Fernandez, M., Klimas, N. G., Fletcher, M. A., and Schneiderman, N. (2004). Social support, positive states of mind, and HIV treatment adherence in men and women living with HIV/AIDS. Health Psychol., 23 (4), 413–418. Goodkin, K., Baldewicz, T. T., Asthana, D., Khamis, I., Blaney, N. T., Kumar, M., Burkhalter, J. E., Leeds, B., and Shapshak, P. (2001). A bereavement support group intervention affects plasma burden of human immunodeficiency virus type 1. Report of a randomized controlled trial. J. Hum. Virol., 4 (1), 44–54. Goodkin, K., Blaney, N. T., Feaster, D., Fletcher, M. A., Baum, M. K., Mantero-Atienza, E., Klimas, N. G., Millon, C., Szapocznik, J., and Eisdorfer, C. (1992a). Active coping style is associated with natural killer cell cytotoxicity in asymptomatic HIV-1 seropositive homosexual men. J. Psychosom. Res., 36 (7), 635–650. Goodkin, K., Feaster, D. J., Asthana, D., Blaney, N. T., Kumar, M., Baldewicz, T., Tuttle, R. S., Maher, K. J., Baum, M. K., Shapshak, P., and Fletcher, M. A. (1998). A bereavement support group intervention is longitudinally associated with salutary effects on the CD4 cell count and number of physician visits. Clin. Diagn. Lab. Immunol., 5 (3), 382–391. Goodkin, K., Feaster, D. J., Tuttle, R., Blaney, N. T., Kumar, M., Baum, M. K., Shapshak, P., and Fletcher, M. A. (1996). Bereavement is associated with time-dependent decrements in cellular immune function in asymptomatic human immunodeficiency virus type 1–seropositive homosexual men. Clin. Diagn. Lab. Immunol., 3 (1), 109–118. Goodkin, K., Fuchs, I., Feaster, D., Leeka, J., and Rishel, D. D. (1992b). Life stressors and coping style are associated with immune measures in HIV-1 infection—a preliminary report. Int. J. Psychiatry Med., 22 (2), 155–172. Graziosi, C., Gantt, K. R., Vaccarezza, M., Demarest, J. F., Daucher, M., Saag, M. S., Shaw, G. M., Quinn, T. C., Cohen, O. J., Welbon, C. C., Pantaleo, G., and Fauci, A. S. (1996). Kinetics of cytokine expression during primary human immunodeficiency virus type 1 infection. Proc. Natl. Acad. Sci. U.S.A., 93 (9), 4386–4391. Gross, J. J., and Levenson, R. W. (1993). Emotional suppression: physiology, self-report, and expressive behavior. J. Pers. Soc. Psychol., 64 (6), 970–986.
1070
V. Psychoneuroimmunology and Pathophysiology
Gruzelier, J., Burgess, A., Baldeweg, T., Riccio, M., Hawkins, D., Stygall, J., Catt, S., Irving, G., and Catalan, J. (1996). Prospective associations between lateralised brain function and immune status in HIV infection: analysis of EEG, cognition and mood over 30 months. Int. J. Psychophysiol., 23 (3), 215–224. Haase, A. T. (1999). Population biology of HIV-1 infection: viral and CD4+ T cell demographics and dynamics in lymphatic tissues. Annu. Rev. Immunol., 17, 625–656. Haraguchi, S., Good, R. A., James-Yarish, M., Cianciolo, G. J., and Day, N. K. (1995). Induction of intracellular cAMP by a synthetic retroviral envelope peptide: a possible mechanism of immunopathogenesis in retroviral infections. Proc. Natl. Acad. Sci. U.S.A., 92 (12), 5568–5571. Hatano, H., Miller, K. D., Yoder, C. P., Yanovski, J. A., Sebring, N. G., Jones, E. C., and Davey, R. T., Jr. (2000). Metabolic and anthropometric consequences of interruption of highly active antiretroviral therapy. AIDS, 14 (13), 1935–1942. Hayashi, R., Wada, H., Ito, K., and Adcock, I. M. (2004). Effects of glucocorticoids on gene transcription. Eur. J. Pharmacol., 500 (1–3), 51–62. Hayes, M. M., Lane, B. R., King, S. R., Markovitz, D. M., and Coffey, M. J. (2002). Prostaglandin E(2) inhibits replication of HIV-1 in macrophages through activation of protein kinase A. Cell Immunol., 215 (1), 61–71. He, J., Choe, S., Walker, R., Di Marzio, P., Morgan, D. O., and Landau, N. R. (1995). Human immunodeficiency virus type 1 viral protein R (Vpr) arrests cells in the G2 phase of the cell cycle by inhibiting p34cdc2 activity. J. Virol., 69 (11), 6705–6711. Heaton, R. K., Velin, R. A., McCutchan, J. A., Gulevich, S. J., Atkinson, J. H., Wallace, M. R., Godfrey, H. P., Kirson, D. A., and Grant, I. (1994). Neuropsychological impairment in human immunodeficiency virus-infection: implications for employment. HNRC Group. HIV Neurobehavioral Research Center. Psychosom. Med., 56 (1), 8–17. Heeney, J. L. (1995). AIDS: a disease of impaired Th-cell renewal? Immunol. Today, 16 (11), 515–520. Helbert, M. R., L’Age-Stehr, J., and Mitchison, N. A. (1993). Antigen presentation, loss of immunological memory and AIDS. Immunol. Today, 14 (7), 340–344. Henderson, E., Yang, J. Y., and Schwartz, A. (1992). Dehydroepiandrosterone (DHEA) and synthetic DHEA analogs are modest inhibitors of HIV-1 IIIB replication. AIDS Res. Hum. Retroviruses, 8 (5), 625–631. Hengge, U. R., Reimann, G., Schafer, A., and Goos, M. (2003). HIVpositive men differ in immunologic but not catecholamine response to an acute psychological stressor. Psychoneuroendocrinology, 28 (5), 643–656. Ho, D. D., Neumann, A. U., Perelson, A. S., Chen, W., Leonard, J. M., and Markowitz, M. (1995). Rapid turnover of plasma virions and CD4 lymphocytes in HIV-1 infection. Nature, 373 (6510), 123–126. Ho, W. Z., Cnaan, A., Li, Y. H., Zhao, H., Lee, H. R., Song, L., and Douglas, S. D. (1996). Substance P modulates human immunodeficiency virus replication in human peripheral blood monocyte-derived macrophages. AIDS Research and Human Retroviruses, 12 (3), 195–198. Ho, W. Z., and Douglas, S. D. (2004). Substance P and neurokinin-1 receptor modulation of HIV. J. Neuroimmunol., 157 (1–2), 48– 55. Ho, W. Z., Lai, J. P., Li, Y., and Douglas, S. D. (2002). HIV enhances substance P expression in human immune cells. FASEB J., 16 (6), 616–618. Hofbauer, L. C., and Heufelder, A. E. (1996). Endocrine implications of human immunodeficiency virus infection. Medicine (Baltimore), 75 (5), 262–278.
Hofmann, B., Afzelius, P., Iversen, J., Kronborg, G., Aabech, P., Benfield, T., Dybkjaer, E., and Nielsen, J. O. (1996). Buspirone, a serotonin receptor agonist, increases CD4 T-cell counts and modulates the immune system in HIV-seropositive subjects. AIDS, 10 (12), 1339–1347. Hofmann, B., Nishanian, P., Nguyen, T., Insixiengmay, P., and Fahey, J. L. (1993a). Human immunodeficiency virus proteins induce the inhibitory cAMP/protein kinase A pathway in normal lymphocytes. Proc. Natl. Acad. Sci. U.S.A., 90 (14), 6676–6680. Hofmann, B., Nishanian, P., Nguyen, T., Liu, M., and Fahey, J. L. (1993b). Restoration of T-cell function in HIV infection by reduction of intracellular cAMP levels with adenosine analogues. AIDS, 7 (5), 659–664. Ickovics, J. R., Hamburger, M. E., Vlahov, D., Schoenbaum, E. E., Schuman, P., Boland, R. J., and Moore, J. (2001). Mortality, CD4 cell count decline, and depressive symptoms among HIVseropositive women: longitudinal analysis from the HIV Epidemiology Research Study. JAMA, 285 (11), 1466–1474. Ironson, G., Balbin, E., Stuetzle, R., Fletcher, M. A., O’Cleirigh, C., Laurenceau, J. P., Schneiderman, N., and Solomon, G. (2005a). Dispositional optimism and the mechanisms by which it predicts slower disease progression in HIV: proactive behavior, avoidant coping, and depression. Int. J. Behav. Med., 12 (2), 86–97. Ironson, G., Field, T., Scafidi, F., Hashimoto, M., Kumar, M., Kumar, A., Price, A., Goncalves, A., Burman, I., Tetenman, C., Patarca, R., and Fletcher, M. A. (1996). Massage therapy is associated with enhancement of the immune system’s cytotoxic capacity. Int. J. Neurosci., 84 (1–4), 205–217. Ironson, G., Friedman, A., Klimas, N., Antoni, M., Fletcher, M. A., LaPerrier, A., Simoneau, J., and Schneiderman, N. (1994). Distress, denial and low adherence to behavioral interventions predict faster disease progression in gay men infected with human immunodeficiency virus. International Journal of Behavioral Medicine, 1, 90. Ironson, G., Solomon, G. F., Balbin, E. G., O’Cleirigh, C., George, A., Kumar, M., Larson, D., and Woods, T. E. (2002). The IronsonWoods Spirituality/Religiousness Index is associated with long survival, health behaviors, less distress, and low cortisol in people with HIV/AIDS. Ann. Behav. Med., 24 (1), 34–48. Ironson, G., Weiss, S., Lydston, D., Ishii, M., Jones, D., Asthana, D., Tobin, J., Lechner, S., Laperriere, A., Schneiderman, N., and Antoni, M. (2005b). The impact of improved self-efficacy on HIV viral load and distress in culturally diverse women living with AIDS: the SMART/EST Women’s Project. AIDS Care, 17 (2), 222–236. Jabaaij, L., Grosheide, P. M., Heijtink, R. A., Duivenvoorden, H. J., Ballieux, R. E., and Vingerhoets, A. J. (1993). Influence of perceived psychological stress and distress on antibody response to low dose rDNA hepatitis B vaccine. J. Psychosom. Res., 37 (4), 361–369. Jabaaij, L., van Hattum, J., Vingerhoets, J. J., Oostveen, F. G., Duivenvoorden, H. J., and Ballieux, R. E. (1996). Modulation of immune response to rDNA hepatitis B vaccination by psychological stress. J. Psychosom. Res., 41 (2), 129–137. Jaffar, S., Govender, T., Garrib, A., Welz, T., Grosskurth, H., Smith, P. G., Whittle, H., and Bennish, M. L. (2005). Antiretroviral treatment in resource-poor settings: public health research priorities. Trop Med. Int. Health, 10 (4), 295–299. Johansson, C. C., Bryn, T., Yndestad, A., Eiken, H. G., Bjerkeli, V., Froland, S. S., Aukrust, P., and Tasken, K. (2004). Cytokine networks are pre-activated in T cells from HIV-infected patients on HAART and are under the control of cAMP. AIDS, 18 (2), 171–179. Kagan, J. (1994). Galen’s prophecy: temperament in human nature. New York: Basic Books.
49. Psychobiology of HIV Infection Kagan, J., Snidman, N., Julia-Sellers, M., and Johnson, M. O. (1991). Temperament and allergic symptoms. Psychosom. Med., 53 (3), 332–340. Kalichman, S. C., Difonzo, K., Austin, J., Luke, W., and Rompa, D. (2002). Prospective study of emotional reactions to changes in HIV viral load. AIDS Patient Care STDS, 16 (3), 113–120. Kalinichenko, V. V., Mokyr, M. B., Graf, L. H., Jr., Cohen, R. L., and Chambers, D. A. (1999). Norepinephrine-mediated inhibition of antitumor cytotoxic T lymphocyte generation involves a betaadrenergic receptor mechanism and decreased TNF-alpha gene expression. J. Immunol., 163 (5), 2492–2499. Kammer, G. M. (1988). The adenylate cyclase-cAMP-protein kinase A pathway and regulation of the immune response. Immunol. Today, 9 (7–8), 222–229. Kaul, M., Zheng, J., Okamoto, S., Gendelman, H. E., and Lipton, S. A. (2005). HIV-1 infection and AIDS: consequences for the central nervous system. Cell Death Differ, 12 (Suppl 1), 878–892. Kawa, S. K., and Thompson, E. B. (1996). Lymphoid cell resistance to glucocorticoids in HIV infection. J. Steroid Biochem. Mol. Biol., 57 (5–6), 259–263. Keet, I. P., Krol, A., Klein, M. R., Veugelers, P., de Wit, J., Roos, M., Koot, M., Goudsmit, J., Miedema, F., and Coutinho, R. A. (1994). Characteristics of long-term asymptomatic infection with human immunodeficiency virus type 1 in men with normal and low CD4+ cell counts. J. Infect. Dis., 169 (6), 1236–1243. Kemeny, M. E., and Dean, L. (1995). Effects of AIDS-related bereavement on HIV progression among New York City gay men. AIDS Educ. Prev., 7 (5 Suppl), 36–47. Kemeny, M. E., Weiner, H., Taylor, S. E., Schneider, S., Visscher, B., and Fahey, J. L. (1994). Repeated bereavement, depressed mood, and immune parameters in HIV seropositive and seronegative gay men. Health Psychol., 13 (1), 14–24. Kessler, R. C., Foster, C., Joseph, J., Ostrow, D., Wortman, C., Phair, J., and Chmiel, J. (1991). Stressful life events and symptom onset in HIV infection. Am. J. Psychiatry, 148 (6), 733–738. Kiecolt-Glaser, J. K., Glaser, R., Cacioppo, J. T., and Malarkey, W. B. (1998). Marital stress: immunologic, neuroendocrine, and autonomic correlates. Ann. N. Y. Acad. Sci., 840, 656–663. Kiecolt-Glaser, J. K., and Newton, T. L. (2001). Marriage and health: his and hers. Psychol. Bull, 127 (4), 472–503. Kilby, J. M. (2001). Human immunodeficiency virus pathogenesis: insights from studies of lymphoid cells and tissues. Clin. Infect. Dis., 33 (6), 873–884. Kino, T., and Chrousos, G. P. (2004). Human immunodeficiency virus type-1 accessory protein Vpr: a causative agent of the AIDS-related insulin resistance/lipodystrophy syndrome? Ann. N. Y. Acad. Sci., 1024, 153–167. Kolesnitchenko, V., and Snart, R. S. (1992). Regulatory elements in the human immunodeficiency virus type 1 long terminal repeat LTR (HIV-1) responsive to steroid hormone stimulation. AIDS Res. Hum. Retroviruses, 8 (12), 1977–1980. Koot, M., Keet, I. P., Vos, A. H., de Goede, R. E., Roos, M. T., Coutinho, R. A., Miedema, F., Schellekens, P. T., and Tersmette, M. (1993). Prognostic value of HIV-1 syncytium-inducing phenotype for rate of CD4+ cell depletion and progression to AIDS. Ann. Intern. Med., 118 (9), 681–688. Krebs, F. C., Mehrens, D., Pomeroy, S., Goodenow, M. M., and Wigdahl, B. (1998). Human immunodeficiency virus type 1 long terminal repeat quasispecies differ in basal transcription and nuclear factor recruitment in human glial cells and lymphocytes. J. Biomed. Sci., 5 (1), 31–44. Kumar, M., Kumar, A. M., Morgan, R., Szapocznik, J., and Eisdorfer, C. (1993). Abnormal pituitary-adrenocortical response in early HIV-1 infection. J. Acquir. Immune Defic. Syndr., 6 (1), 61–65.
1071
Kumar, M., Kumar, A. M., Waldrop, D., Antoni, M. H., Schneiderman, N., and Eisdorfer, C. (2002). The HPA axis in HIV-1 infection. J. Acquir. Immune Defic. Syndr., 31 (Suppl 2), S89–93. Kumar, M., Morgan, R., Szapocznik, J., and Eisdorfer, C. (1991). Norepinephrine response in early HIV infection. J. Acquir. Immune Defic. Syndr., 4 (8), 782–786. Lai, J. P., Ho, W. Z., Zhan, G. X., Yi, Y., Collman, R. G., and Douglas, S. D. (2001). Substance P antagonist (CP-96,345) inhibits HIV-1 replication in human mononuclear phagocytes. Proc. Natl. Acad. Sci. U.S.A., 98 (7), 3970–3975. Larsson, M., Hagberg, L., Forsman, A., and Norkrans, G. (1991). Cerebrospinal fluid catecholamine metabolites in HIV-infected patients. J. Neurosci. Res., 28 (3), 406–409. Laudat, A., Blum, L., Guechot, J., Picard, O., Cabane, J., Imbert, J. C., and Giboudeau, J. (1995). Changes in systemic gonadal and adrenal steroids in asymptomatic human immunodeficiency virus-infected men: relationship with the CD4 cell counts. Eur. J. Endocrinol., 133 (4), 418–424. Laurence, J., Cooke, H., and Sikder, S. K. (1990). Effect of tamoxifen on regulation of viral replication and human immunodeficiency virus (HIV) long terminal repeat-directed transcription in cells chronically infected with HIV-1. Blood, 75 (3), 696–703. Laurence, J., Grimison, B., and Gonenne, A. (1992). Effect of recombinant human growth hormone on acute and chronic human immunodeficiency virus infection in vitro. Blood, 79 (2), 467–472. Laurence, J., Sellers, M. B., and Sikder, S. K. (1989). Effect of glucocorticoids on chronic human immunodeficiency virus (HIV) infection and HIV promoter-mediated transcription. Blood, 74 (1), 291–297. Lee, A. W., Mitra, D., and Laurence, J. (1997). Interaction of pregnancy steroid hormones and zidovudine in inhibition of HIV type 1 replication in monocytoid and placental Hofbauer cells: implications for the prevention of maternal-fetal transmission of HIV. AIDS Res. Hum. Retroviruses, 13 (14), 1235–1242. Lefkowitz, R. J., Stadel, J. M., and Caron, M. G. (1983). Adenylate cyclase-coupled beta-adrenergic receptors: structure and mechanisms of activation and desensitization. Annu. Rev. Biochem., 52, 159–186. Leserman, J. (2003). HIV disease progression: depression, stress, and possible mechanisms. Biol. Psychiatry, 54 (3), 295–306. Leserman, J., Jackson, E. D., Petitto, J. M., Golden, R. N., Silva, S. G., Perkins, D. O., Cai, J., Folds, J. D., and Evans, D. L. (1999). Progression to AIDS: the effects of stress, depressive symptoms, and social support. Psychosom. Med., 61 (3), 397–406. Leserman, J., Petitto, J. M., Golden, R. N., Gaynes, B. N., Gu, H., Perkins, D. O., Silva, S. G., Folds, J. D., and Evans, D. L. (2000). Impact of stressful life events, depression, social support, coping, and cortisol on progression to AIDS. Am. J. Psychiatry, 157 (8), 1221–1228. Leserman, J., Petitto, J. M., Gu, H., Gaynes, B. N., Barroso, J., Golden, R. N., Perkins, D. O., Folds, J. D., and Evans, D. L. (2002). Progression to AIDS, a clinical AIDS condition and mortality: psychosocial and physiological predictors. Psychol. Med., 32 (6), 1059–1073. Leserman, J., Petitto, J. M., Perkins, D. O., Folds, J. D., Golden, R. N., and Evans, D. L. (1997). Severe stress, depressive symptoms, and changes in lymphocyte subsets in human immunodeficiency virus-infected men. A 2-year follow-up study. Arch. Gen. Psychiatry, 54 (3), 279–285. Letvin, N. L., Barouch, D. H., and Montefiori, D. C. (2002). Prospects for vaccine protection against HIV-1 infection and AIDS. Annu. Rev. Immunol., 20, 73–99. Levy, J. A. (1993). Pathogenesis of human immunodeficiency virus infection. Microbiol. Rev., 57 (1), 183–289.
1072
V. Psychoneuroimmunology and Pathophysiology
Levy, J. A. (2001). The importance of the innate immune system in controlling HIV infection and disease. Trends Immunol., 22 (6), 312–316. Levy, J. A., Mackewicz, C. E., and Barker, E. (1996). Controlling HIV pathogenesis: the role of the noncytotoxic anti-HIV response of CD8+ T cells. Immunol. Today, 17 (5), 217–224. Li, P. L., Wang, T., Buckley, K. A., Chenine, A. L., Popov, S., and Ruprecht, R. M. (2005). Phosphorylation of HIV Nef by cAMPdependent protein kinase. Virology, 331 (2), 367–374. Li, Y., Douglas, S. D., Song, L., Sun, S., and Ho, W. Z. (2001). Substance P enhances HIV-1 replication in latently infected human immune cells. J. Neuroimmunol., 121 (1–2), 67–75. Lortholary, O., Christeff, N., Casassus, P., Thobie, N., Veyssier, P., Trogoff, B., Torri, O., Brauner, M., Nunez, E. A., and Guillevin, L. (1996). Hypothalamo-pituitary-adrenal function in human immunodeficiency virus-infected men. J. Clin. Endocrinol. Metab., 81 (2), 791–796. Lu, W., Salerno-Goncalves, R., Yuan, J., Sylvie, D., Han, D. S. et al. (1995). Glucocorticoids rescue CD4+ T lymphocytes from activation-induced apoptosis triggered by HIV-1, implications for pathogenesis and therapy. AIDS, 9 (1), 35–42. Lum, J. J., Cohen, O. J., Nie, Z., Weaver, J. G., Gomez, T. S., Yao, X. J., Lynch, D., Pilon, A. A., Hawley, N., Kim, J. E., Chen, Z., Montpetit, M., Sanchez-Dardon, J., Cohen, E. A., and Badley, A. D. (2003). Vpr R77Q is associated with long-term nonprogressive HIV infection and impaired induction of apoptosis. J. Clin. Invest., 111 (10), 1547–1554. Lusso, P., and Gallo, R. C. (1995). Human herpesvirus 6 in AIDS. Immunol. Today, 16 (2), 67–71. Lyketsos, C. G., Hoover, D. R., Guccione, M., Dew, M. A., Wesch, J. E., Bing, E. G., and Treisman, G. J. (1996). Changes in depressive symptoms as AIDS develops. The Multicenter AIDS Cohort Study. Am. J. Psychiatry, 153 (11), 1430–1437. Lyketsos, C. G., Hoover, D. R., Guccione, M., Senterfitt, W., Dew, M. A., Wesch, J., VanRaden, M. J., Treisman, G. J., and Morgenstern, H. (1993). Depressive symptoms as predictors of medical outcomes in HIV infection. Multicenter AIDS Cohort Study. JAMA, 270 (21), 2563–2567. Lyon, D. E., and Munro, C. (2001). Disease severity and symptoms of depression in Black Americans infected with HIV. Appl. Nurs. Res., 14 (1), 3–10. Mackewicz, C. E., Barker, E., and Levy, J. A. (1996). Role of betachemokines in suppressing HIV replication. Science, 274 (5291), 1393–1395. Madden, K. S., Felten, S. Y., Felten, D. L., and Bellinger, D. L. (1995a). Sympathetic nervous system–immune system interactions in young and old Fischer 344 rats. Ann. N. Y. Acad. Sci., 771, 523–534. Madden, K. S., Sanders, V. M., and Felten, D. L. (1995b). Catecholamine influences and sympathetic neural modulation of immune responsiveness. Annu. Rev. Pharmacol. Toxicol., 35, 417–448. Maier, S. F., Goehler, L. E., Fleshner, M., and Watkins, L. R. (1998). The role of the vagus nerve in cytokine-to-brain communication. Ann. N. Y. Acad. Sci., 840, 289–300. Manji, H., and Miller, R. (2004). The neurology of HIV infection. J. Neurol. Neurosurg. Psychiatry, 75 (Suppl 1), S129–135. Markham, P. D., Salahuddin, S. Z., Popovic, M., Patel, A., Veren, K., Fladager, A., Orndorff, S., and Gallo, R. C. (1985). Advances in the isolation of HTLV-III from patients with AIDS and AIDSrelated complex and from donors at risk. Cancer Res., 45 (9 Suppl), 4588s–4591s. Markham, P. D., Salahuddin, S. Z., Veren, K., Orndorff, S., and Gallo, R. C. (1986). Hydrocortisone and some other hormones enhance the expression of HTLV-III. Int. J. Cancer, 37 (1), 67–72.
Marsland, A. L., Cohen, S., Rabin, B. S., and Manuck, S. B. (2001). Associations between stress, trait negative affect, acute immune reactivity, and antibody response to hepatitis B injection in healthy young adults. Health Psychol., 20 (1), 4–11. Martin, J. L., and Dean, L. (1993). Effects of AIDS-related bereavement and HIV-related illness on psychological distress among gay men: a 7-year longitudinal study, 1985–1991. J. Consult. Clin. Psychol., 61 (1), 94–103. Martin, M. E., Benassayag, C., Amiel, C., Canton, P., and Nunez, E. A. (1992). Alterations in the concentrations and binding properties of sex steroid binding protein and corticosteroidbinding globulin in HIV+ patients. J. Endocrinol. Invest., 15 (8), 597–603. Mattson, M. P., Haughey, N. J., and Nath, A. (2005). Cell death in HIV dementia. Cell Death Differ, 12 (Suppl 1), 893–904. Mayne, T. J., Acree, M., Chesney, M. A., and Folkman, S. (1998). HIV sexual risk behavior following bereavement in gay men. Health Psychol., 17 (5), 403–411. Mayne, T. J., Vittinghoff, E., Chesney, M. A., Barrett, D. C., and Coates, T. J. (1996). Depressive affect and survival among gay and bisexual men infected with HIV. Arch. Intern. Med., 156 (19), 2233–2238. Mayo, J., Collazos, J., Martinez, E., and Ibarra, S. (2002). Adrenal function in the human immunodeficiency virus-infected patient. Arch. Intern. Med., 162 (10), 1095–1098. Mellors, J. W., Rinaldo, C. R., Jr., Gupta, P., White, R. M., Todd, J. A., and Kingsley, L. A. (1996). Prognosis in HIV-1 infection predicted by the quantity of virus in plasma. Science, 272 (5265), 1167–1170. Melnick, S. L., Sherer, R., Louis, T. A., Hillman, D., Rodriguez, E. M., Lackman, C., Capps, L., Brown, L. S., Jr., Carlyn, M., Korvick, J. A. et al. (1994). Survival and disease progression according to gender of patients with HIV infection. The Terry Beirn Community Programs for Clinical Research on AIDS. JAMA, 272 (24), 1915–1921. Merenich, J. A., McDermott, M. T., Asp, A. A., Harrison, S. M., and Kidd, G. S. (1990). Evidence of endocrine involvement early in the course of human immunodeficiency virus infection. J. Clin. Endocrinol. Metab., 70 (3), 566–571. Miller, G. E., Cohen, S., Rabin, B. S., Skoner, D. P., and Doyle, W. J. (1999). Personality and tonic cardiovascular, neuroendocrine, and immune parameters. Brain Behav. Immun., 13 (2), 109–123. Miller, G. E., Kemeny, M. E., Taylor, S. E., Cole, S. W., and Visscher, B. R. (1997). Social relationships and immune processes in HIV seropositive gay and bisexual men. Ann. Behav. Med., 19 (2), 139–151. Mirani, M., Elenkov, I., Volpi, S., Hiroi, N., Chrousos, G. P., and Kino, T. (2002). HIV-1 protein Vpr suppresses IL-12 production from human monocytes by enhancing glucocorticoid action: potential implications of Vpr coactivator activity for the innate and cellular immunity deficits observed in HIV-1 infection. J. Immunol., 169 (11), 6361–6368. Misse, D., Gajardo, J., Oblet, C., Religa, A., Riquet, N., Mathieu, D., Yssel, H., and Veas, F. (2005). Soluble HIV-1 gp120 enhances HIV-1 replication in non-dividing CD4+ T cells, mediated via cell signaling and Tat cofactor overexpression. AIDS, 19 (9), 897–905. Mitra, D., Sikder, S. K., and Laurence, J. (1995). Role of glucocorticoid receptor binding sites in the human immunodeficiency virus type 1 long terminal repeat in steroid-mediated suppression of HIV gene expression. Virology, 214 (2), 512–521. Molassiotis, A., Callaghan, P., Twinn, S. F., Lam, S. W., Chung, W. Y., and Li, C. K. (2002). A pilot study of the effects of cognitive-behavioral group therapy and peer support/counseling in
49. Psychobiology of HIV Infection decreasing psychologic distress and improving quality of life in Chinese patients with symptomatic HIV disease. AIDS Patient Care STDS, 16 (2), 83–96. Morrison, M. F., Petitto, J. M., Ten Have, T., Gettes, D. R., Chiappini, M. S., Weber, A. L., Brinker-Spence, P., Bauer, R. M., Douglas, S. D., and Evans, D. L. (2002). Depressive and anxiety disorders in women with HIV infection. Am. J. Psychiatry, 159 (5), 789–796. Moskowitz, J. T. (2003). Positive affect predicts lower risk of AIDS mortality. Psychosom. Med., 65 (4), 620–626. Moss, H., Bose, S., Wolters, P., and Brouwers, P. (1998). A preliminary study of factors associated with psychological adjustment and disease course in school-age children infected with the human immunodeficiency virus. J. Dev. Behav. Pediatr., 19 (1), 18–25. Mostad, S. B., Overbaugh, J., DeVange, D. M., Welch, M. J., Chohan, B., Mandaliya, K., Nyange, P., Martin, H. L., Jr., Ndinya-Achola, J., Bwayo, J. J., and Kreiss, J. K. (1997). Hormonal contraception, vitamin A deficiency, and other risk factors for shedding of HIV1 infected cells from the cervix and vagina. Lancet, 350 (9082), 922–927. Motivala, S. J., Hurwitz, B. E., Llabre, M. M., Klimas, N. G., Fletcher, M. A., Antoni, M. H., LeBlanc, W. G., and Schneiderman, N. (2003). Psychological distress is associated with decreased memory helper T-cell and B-cell counts in pre-AIDS HIV seropositive men and women but only in those with low viral load. Psychosom. Med., 65 (4), 627–635. Mulder, C. L., Antoni, M. H., Duivenvoorden, H. J., Kauffmann, R. H., and Goodkin, K. (1995a). Active confrontational coping predicts decreased clinical progression over a one-year period in HIV-infected homosexual men. J. Psychosom. Res., 39 (8), 957–965. Mulder, C. L., Antoni, M. H., Emmelkamp, P. M., Veugelers, P. J., Sandfort, T. G., van de Vijver, F. A., and de Vries, M. J. (1995b). Psychosocial group intervention and the rate of decline of immunological parameters in asymptomatic HIV-infected homosexual men. Psychother Psychosom., 63 (3–4), 185–192. Mulder, C. L., de Vroome, E. M., van Griensven, G. J., Antoni, M. H., and Sandfort, T. G. (1999). Avoidance as a predictor of the biological course of HIV infection over a 7-year period in gay men. Health Psychol., 18 (2), 107–113. Mulhall, B. P., Fieldhouse, S., Deam, D., Verges, B., Chavanet, P., Kisterman, J. P., Vaillant, G., Waldner, A., B. J. M., and Protier, H. (1988). Adrenocortical lesions and HIV infection [letter]. Lancet, 1 (8598), 1345. Munoz, A., Carey, V., Saah, A. J., Phair, J. P., Kingsley, L. A., Fahey, J. L., Ginzburg, H. M., and Polk, B. F. (1988). Predictors of decline in CD4 lymphocytes in a cohort of homosexual men infected with human immunodeficiency virus. J. Acquir. Immune Defic. Syndr., 1 (4), 396–404. Munoz, A., Wang, M. C., Bass, S., Taylor, J. M., Kingsley, L. A., Chmiel, J. S., and Polk, B. F. (1989). Acquired immunodeficiency syndrome (AIDS)-free time after human immunodeficiency virus type 1 (HIV-1) seroconversion in homosexual men. Multicenter AIDS Cohort Study Group. Am. J. Epidemiol., 130 (3), 530–539. Nabel, G., and Baltimore, D. (1987). An inducible transcription factor activates expression of human immunodeficiency virus in T cells. Nature, 326 (6114), 711–713. Nair, M. P. N., Mahajan, S., Hou, J., Sweet, A. M., and Schwartz, S. A. (2000). The stress hormone, cortisol, synergizes with HIV-1 gp-120 to induce apoptosis of normal human peripheral blood mononuclear cells. Cell Mol. Biol. (Noisy-le-grand), 46 (7), 1227–1238.
1073
Nielsen, M. H., Pedersen, F. S., and Kjems, J. (2005). Molecular strategies to inhibit HIV-1 replication. Retrovirology, 2 (1), 10. Nokta, M., and Pollard, R. (1991). Human immunodeficiency virus infection: association with altered intracellular levels of cAMP and cGMP in MT-4 cells. Virology, 181 (1), 211–217. Nokta, M. A., and Pollard, R. B. (1992). Human immunodeficiency virus replication: modulation by cellular levels of cAMP. AIDS Res. Hum. Retroviruses, 8 (7), 1255–1261. Norbiato, G., Bevilacqua, M., Vago, T., and Clerici, M. (1998). Glucocorticoid resistance and the immune function in the immunodeficiency syndrome. Ann. N. Y. Acad. Sci., 840, 835–847. Norbiato, G., Bevilacqua, M., Vago, T., Taddei, A., and Clerici, M. (1997). Glucocorticoids and the immune function in the human immunodeficiency virus infection: a study in hypercortisolemic and cortisol-resistant patients. J. Clin. Endocrinol. Metab., 82 (10), 3260–3263. Okutsu, M., Ishii, K., Niu, K. J., and Nagatomi, R. (2005). Cortisolinduced CXCR4 augmentation mobilizes T lymphocytes after acute physical stress. Am. J. Physiol. Regul. Integr. Comp. Physiol., 288 (3), R591–599. Ottaway, C. A., and Husband, A. J. (1994). The influence of neuroendocrine pathways on lymphocyte migration. Immunol. Today, 15 (11), 511–517. Padgett, D. A., Sheridan, J. F., Dorne, J., Berntson, G. G., Candelora, J., and Glaser, R. (1998). Social stress and the reactivation of latent herpes simplex virus type 1. Proc. Natl. Acad. Sci. U.S.A., 95 (12), 7231–7235. Page-Shafer, K., Delorenze, G. N., Satariano, W. A., and Winkelstein, W., Jr. (1996). Comorbidity and survival in HIV-infected men in the San Francisco Men’s Health Survey. Ann. Epidemiol., 6 (5), 420–430. Pantaleo, G., Demarest, J. F., Soudeyns, H., Graziosi, C., Denis, F., Adelsberger, J. W., Borrow, P., Saag, M. S., Shaw, G. M., Sekaly, R. P. et al. (1994). Major expansion of CD8+ T cells with a predominant V beta usage during the primary immune response to HIV. Nature, 370 (6489), 463–467. Pantaleo, G., Graziosi, C., Demarest, J. F., Butini, L., Montroni, M., Fox, C. H., Orenstein, J. M., Kotler, D. P., and Fauci, A. S. (1993a). HIV infection is active and progressive in lymphoid tissue during the clinically latent stage of disease. Nature, 362 (6418), 355–358. Pantaleo, G., Graziosi, C., and Fauci, A. S. (1993b). The role of lymphoid organs in the pathogenesis of HIV infection. Semin. Immunol., 5 (3), 157–163. Patterson, T. L., Semple, S. J., Temoshok, L. R., Atkinson, J. H., McCutchan, J. A., Straits-Troster, K., Chandler, J. L., Grant, I., and H. N. R. C. Group. (1995). Stress and depressive symptoms prospectively predict immune change among HIV-seropositive men. Psychiatry, 58 (4), 299–312. Patterson, T. L., Shaw, W. S., Semple, S. J., Cherner, M., McCutchan, A., and Atkinson, J. H. E. A. (1996). Relationship of psychosocial factors to HIV disease progression. Annals of Behavioral Medicine, 18, 30. Pedersen, C., Nielsen, J. O., Dickmeis, E., and Jordal, R. (1989). Early progression to AIDS following primary HIV infection. AIDS, 3 (1), 45–47. Pennebaker, J. W., and Chew, C. H. (1985). Behavioral inhibition and electrodermal activity during deception. J. Pers. Soc. Psychol., 49 (5), 1427–1433. Pennebaker, J. W., Kiecolt-Glaser, J. K., and Glaser, R. (1988). Disclosure of traumas and immune function: health implications for psychotherapy. J. Consult. Clin. Psychol., 56 (2), 239–245. Penzak, S. R., Reddy, Y. S., and Grimsley, S. R. (2000). Depression in patients with HIV infection. Am. J. Health Syst. Pharm., 57 (4), 376–386; quiz, 387–389.
1074
V. Psychoneuroimmunology and Pathophysiology
Perelson, A. S., Neumann, A. U., Markowitz, M., Leonard, J. M., and Ho, D. D. (1996). HIV-1 dynamics in vivo: virion clearance rate, infected cell life-span, and viral generation time. Science, 271 (5255), 1582–1586. Perry, S., Fishman, B., Jacobsberg, L., and Frances, A. (1992). Relationships over 1 year between lymphocyte subsets and psychosocial variables among adults with infection by human immunodeficiency virus. Arch. Gen. Psychiatry, 49 (5), 396–401. Persson, L., Gullberg, B., Hanson, B. S., Moestrup, T., and Ostergren, P. O. (1994). HIV infection: social network, social support, and CD4 lymphocyte values in infected homosexual men in Malmo, Sweden. J. Epidemiol. Community Health, 48 (6), 580–585. Persson, L., Ostergren, P. O., Hanson, B. S., Lindgren, A., and Naucler, A. (2002). Social network, social support and the rate of decline of CD4 lymphocytes in asymptomatic HIV-positive homosexual men. Scand. J. Public Health, 30 (3), 184–190. Petitto, J. M., Leserman, J., Perkins, D. O., Stern, R. A., Silva, S. G., Gettes, D., Zheng, B., Folds, J. D., Golden, R. N., and Evans, D. L. (2000). High versus low basal cortisol secretion in asymptomatic, medication-free HIV-infected men: differential effects of severe life stress on parameters of immune status. Behav. Med., 25 (4), 143–151. Petitto, J. M., Lysle, D. T., Gariepy, J. L., and Lewis, M. H. (1994). Association of genetic differences in social behavior and cellular immune responsiveness: effects of social experience. Brain Behav. Immun., 8 (2), 111–122. Petrie, K. J., Booth, R. J., Pennebaker, J. W., Davison, K. P., and Thomas, M. G. (1995). Disclosure of trauma and immune response to a hepatitis B vaccination program. J. Consult. Clin. Psychol., 63 (5), 787–792. Phair, J., Jacobson, L., Detels, R., Rinaldo, C., Saah, A., Schrager, L., and Munoz, A. (1992). Acquired immune deficiency syndrome occurring within 5 years of infection with human immunodeficiency virus type-1, the Multicenter AIDS Cohort Study. J. Acquir. Immune Defic. Syndr., 5 (5), 490–496. Phillips, A. N., Lee, C. A., Elford, J., Webster, A., Janossy, G., Timms, A., Bofill, M., and Kernoff, P. B. (1991). More rapid progression to AIDS in older HIV-infected people: the role of CD4+ T-cell counts. J. Acquir. Immune Defic. Syndr., 4 (10), 970–975. Phillips, E. J., Ottaway, C. A., Freedman, J., Kardish, M., Li, J., Singer, W., and Fong, I. W. (1997). The effect of exercise on lymphocyte redistribution and leukocyte function in asymptomatic HIVinfected subjects. Brain Behav. Immun., 11 (3), 217–227. Piketty, C., Jayle, D., Leplege, A., Castiel, P., Ecosse, E., GonzalezCanali, G., Sabatier, B., Boulle, N., Debuire, B., Le Bouc, Y., Baulieu, E. E., and Kazatchkine, M. D. (2001). Double-blind placebo-controlled trial of oral dehydroepiandrosterone in patients with advanced HIV disease. Clin. Endocrinol. (Oxf.), 55 (3), 325–330. Pohlmann, S., Baribaud, F., and Doms, R. W. (2001). DC-SIGN and DC-SIGNR: helping hands for HIV. Trends Immunol., 22 (12), 643–646. Pomerantz, R. J., and Hirsch, M. S. (1987). Interferon and human immunodeficiency virus infection. Interferon, 9, 113–127. Prado, G., Feaster, D. J., Schwartz, S. J., Pratt, I. A., Smith, L., and Szapocznik, J. (2004). Religious involvement, coping, social support, and psychological distress in HIV-seropositive African American mothers. AIDS Behav., 8 (3), 221–235. Pulakhandam, U., and Dincsoy, H. P. (1990). Cytomegaloviral adrenalitis and adrenal insufficiency in AIDS. Am. J. Clin. Pathol., 93 (5), 651–656. Quinn, T. C., and Overbaugh, J. (2005). HIV/AIDS in women: an expanding epidemic. Science, 308 (5728), 1582–1583. Rabbi, M. F., Al-Harthi, L., and Roebuck, K. A. (1997a). TNFalpha cooperates with the protein kinase A pathway to synergistically
increase HIV-1 LTR transcription via downstream TRE-like cAMP response elements. Virology, 237 (2), 422–429. Rabbi, M. F., Al-Harthi, L., Saifuddin, M., and Roebuck, K. A. (1998). The cAMP-dependent protein kinase A and protein kinase Cbeta pathways synergistically interact to activate HIV-1 transcription in latently infected cells of monocyte/macrophage lineage. Virology, 245 (2), 257–269. Rabbi, M. F., Saifuddin, M., Gu, D. S., Kagnoff, M. F., and Roebuck, K. A. (1997b). U5 region of the human immunodeficiency virus type 1 long terminal repeat contains TRE-like cAMP-responsive elements that bind both AP-1 and CREB/ATF proteins. Virology, 233 (1), 235–245. Rabkin, J. G., Goetz, R. R., Remien, R. H., Williams, J. B., Todak, G., and Gorman, J. M. (1997). Stability of mood despite HIV illness progression in a group of homosexual men. Am. J. Psychiatry, 154 (2), 231–238. Rabkin, J. G., Rabkin, R., Harrison, W., and Wagner, G. (1994a). Effect of imipramine on mood and enumerative measures of immune status in depressed patients with HIV illness. Am. J. Psychiatry, 151 (4), 516–523. Rabkin, J. G., Rabkin, R., and Wagner, G. (1994b). Effects of fluoxetine on mood and immune status in depressed patients with HIV illness. J. Clin. Psychiatry, 55 (3), 92–97. Rabkin, J. G., Wagner, G., and Rabkin, R. (1994c). Effects of sertraline on mood and immune status in patients with major depression and HIV illness: an open trial. J. Clin. Psychiatry, 55 (10), 433–439. Rabkin, J. G., Wagner, G. J., and Rabkin, R. (1999). Fluoxetine treatment for depression in patients with HIV and AIDS: a randomized, placebo-controlled trial. Am. J. Psychiatry, 156 (1), 101–107. Rabkin, J. G., Williams, J. B., Remien, R. H., Goetz, R., Kertzner, R., and Gorman, J. M. (1991). Depression, distress, lymphocyte subsets, and human immunodeficiency virus symptoms on two occasions in HIV-positive homosexual men. Arch. Gen. Psychiatry, 48 (2), 111–119. Rabkin, M., El-Sadr, W., Katzenstein, D. A., Mukherjee, J., Masur, H., Mugyenyi, P., Munderi, P., and Darbyshire, J. (2002). Antiretroviral treatment in resource-poor settings: clinical research priorities. Lancet, 360 (9344), 1503–1505. Re, F., Braaten, D., Franke, E. K., and Luban, J. (1995). Human immunodeficiency virus type 1 Vpr arrests the cell cycle in G2 by inhibiting the activation of p34cdc2-cyclin B. J. Virol., 69 (11), 6859–6864. Reed, G. M., Kemeny, M. E., Taylor, S. E., and Visscher, B. R. (1999). Negative HIV-specific expectancies and AIDS-related bereavement as predictors of symptom onset in asymptomatic HIVpositive gay men. Health Psychol., 18 (4), 354–363. Reed, G. M., Kemeny, M. E., Taylor, S. E., Wang, H. Y., and Visscher, B. R. (1994). Realistic acceptance as a predictor of decreased survival time in gay men with AIDS. Health Psychol., 13 (4), 299–307. Refaeli, Y., Levy, D. N., and Weiner, D. B. (1995). The glucocorticoid receptor type II complex is a target of the HIV-1 vpr gene product. Proc. Natl. Acad. Sci. U.S.A., 92 (8), 3621–3625. Ressler, K. J., and Nemeroff, C. B. (2000). Role of serotonergic and noradrenergic systems in the pathophysiology of depression and anxiety disorders. Depress Anxiety, 12 (Suppl 1), 2–19. Robinson, F. P., Mathews, H. L., and Witek-Janusek, L. (2003). Psycho-endocrine-immune response to mindfulness-based stress reduction in individuals infected with the human immunodeficiency virus: a quasiexperimental study. J. Altern. Complement. Med., 9 (5), 683–694. Rohr, O., Marban, C., Aunis, D., and Schaeffer, E. (2003). Regulation of HIV-1 gene transcription: from lymphocytes to microglial cells. J. Leukoc. Biol., 74 (5), 736–749.
49. Psychobiology of HIV Infection Rondanelli, M., Solerte, S. B., Fioravanti, M., Scevola, D., Locatelli, M., Minoli, L., and Ferrari, E. (1997). Circadian secretory pattern of growth hormone, insulin-like growth factor type I, cortisol, adrenocorticotropic hormone, thyroid-stimulating hormone, and prolactin during HIV infection. AIDS Res. Hum. Retroviruses, 13 (14), 1243–1249. Rosenberg, Z. F., and Fauci, A. S. (1989). Induction of expression of HIV in latently or chronically infected cells. AIDS Res. Hum. Retroviruses, 5 (1), 1–4. Rowland-Jones, S. L. (2003). Timeline: AIDS pathogenesis: what have two decades of HIV research taught us? Nat. Rev. Immunol., 3 (4), 343–348. Russo, F. O., Patel, P. C., Ventura, A. M., and Pereira, C. A. (1999). HIV-1 long terminal repeat modulation by glucocorticoids in monocytic and lymphocytic cell lines. Virus Res., 64 (1), 87–94. Saah, A. J., Hoover, D. R., He, Y., Kingsley, L. A., and Phair, J. P. (1994). Factors influencing survival after AIDS: report from the Multicenter AIDS Cohort Study (MACS). J. Acquir. Immune Defic. Syndr., 7 (3), 287–295. Sagar, M., Lavreys, L., Baeten, J. M., Richardson, B. A., Mandaliya, K., Ndinya-Achola, J. O., Kreiss, J. K., and Overbaugh, J. (2004). Identification of modifiable factors that affect the genetic diversity of the transmitted HIV-1 population. AIDS, 18 (4), 615–619. Sahs, J. A., Goetz, R., Reddy, M., Rabkin, J. G., Williams, J. B., Kertzner, R., and Gorman, J. M. (1994). Psychological distress and natural killer cells in gay men with and without HIV infection. Am. J. Psychiatry, 151 (10), 1479–1484. Sanders, V. M., and Straub, R. H. (2002). Norepinephrine, the betaadrenergic receptor, and immunity. Brain Behav. Immun., 16 (4), 290–332. Sapolsky, R. M. (1993). Potential behavioral modification of glucocorticoid damage to the hippocampus. Behav. Brain Res., 57 (2), 175–182. Sapolsky, R. M. (1998). Why zebras don’t get ulcers: an updated guide to stress, stress related diseases, and coping. New York: W. H. Freeman. Schacker, T., Little, S., Connick, E., Gebhard-Mitchell, K., Zhang, Z. Q., Krieger, J., Pryor, J., Havlir, D., Wong, J. K., Richman, D., Corey, L., and Haase, A. T. (2000). Rapid accumulation of human immunodeficiency virus (HIV) in lymphatic tissue reservoirs during acute and early HIV infection: implications for timing of antiretroviral therapy. J. Infect. Dis., 181 (1), 354–357. Schambelan, M., Mulligan, K., Grunfeld, C., Daar, E. S., LaMarca, A., Kotler, D. P., Wang, J., Bozzette, S. A., and Breitmeyer, J. B. (1996). Recombinant human growth hormone in patients with HIV-associated wasting. A randomized, placebo-controlled trial. Serostim Study Group. Ann. Intern. Med., 125 (11), 873–882. Schifitto, G., McDermott, M. P., McArthur, J. C., Marder, K., Sacktor, N., Epstein, L., and Kieburtz, K. (2002). Incidence of and risk factors for HIV-associated distal sensory polyneuropathy. Neurology, 58 (12), 1764–1768. Schwartz, C., Canonne-Hergaux, F., Aunis, D., and Schaeffer, E. (1997). Characterization of nuclear proteins that bind to the regulatory TGATTGGC motif in the human immunodeficiency virus type 1 long terminal repeat. Nucleic Acids Res., 25 (6), 1177–1184. Segerstrom, S. C., Taylor, S. E., Kemeny, M. E., Reed, G. M., and Visscher, B. R. (1996). Causal attributions predict rate of immune decline in HIV-seropositive gay men. Health Psychol., 15 (6), 485–493. Shafer, R. W., Offit, K., Macris, N. T., Horbar, G. M., Ancona, L., and Hoffman, I. R. (1985). Possible risk of steroid administration in patients at risk for AIDS. Lancet, 1 (8434), 934–935.
1075
Sheppard, H. W., Ascher, M. S., McRae, B., Anderson, R. E., Lang, W., and Allain, J. P. (1991). The initial immune response to HIV and immune system activation determine the outcome of HIV disease. J. Acquir. Immune Defic. Syndr., 4 (7), 704–712. Shor-Posner, G., Miguez, M. J., Hernandez-Reif, M., Perez-Then, E., and Fletcher, M. (2004). Massage treatment in HIV-1 infected Dominican children: a preliminary report on the efficacy of massage therapy to preserve the immune system in children without antiretroviral medication. J. Altern. Complement. Med., 10 (6), 1093–1095. Sloan, E. K., Tarara, R. P., Capitanio, J. P., and Cole, S. W. (2006). Enhanced SIV replication adjacent to catecholaminergic varicosities in primate lymph nodes. Journal of Virology, 80 (9), 4326–4335. Snyder, G. A., Ford, J., Torabi-Parizi, P., Arthos, J. A., Schuck, P., Colonna, M., and Sun, P. D. (2005). Characterization of DCSIGN/R interaction with human immunodeficiency virus type 1 gp120 and ICAM molecules favors the receptor’s role as an antigen-capturing rather than an adhesion receptor. J. Virol., 79 (8), 4589–4598. Solano, L., Costa, M., Salvati, S., Coda, R., Aiuti, F., Mezzaroma, I., and Bertini, M. (1993). Psychosocial factors and clinical evolution in HIV-1 infection: a longitudinal study. J. Psychosom. Res., 37 (1), 39–51. Solomon, G. F., Temoshok, L., O’Leary, A., and Zich, J. (1987). An intensive psychoimmunologic study of long-surviving persons with AIDS. Pilot work, background studies, hypotheses, and methods. Ann. N. Y. Acad. Sci., 496, 647–655. Sondergaard, S. R., Cozzi Lepri, A., Ullum, H., Wiis, J., Hermann, C. K., Laursen, S. B., Qvist, J., Gerstoft, J., Skinhoj, P., and Pedersen, B. K. (2000a). Adrenaline-induced mobilization of T cells in HIV-infected patients. Clin. Exp. Immunol., 119 (1), 115–122. Sondergaard, S. R., Essen, M. V., Schjerling, P., Ullum, H., and Pedersen, B. K. (2002). Proliferation and telomere length in acutely mobilized blood mononuclear cells in HIV infected patients. Clin. Exp. Immunol., 127 (3), 499–506. Sondergaard, S. R., Ullum, H., and Pedersen, B. K. (2000b). Proliferative and cytotoxic capabilities of CD16+CD56- and CD16+/CD56+ natural killer cells. APMIS, 108 (12), 831–837. Sondergaard, S. R., Ullum, H., Skinhoj, P., and Pedersen, B. K. (1999). Epinephrine-induced mobilization of natural killer (NK) cells and NK-like T cells in HIV-infected patients. Cell Immunol., 197 (2), 91–98. Soudeyns, H., Geleziunas, R., Shyamala, G., Hiscott, J., and Wainberg, M. A. (1993). Identification of a novel glucocorticoid response element within the genome of the human immunodeficiency virus type 1. Virology, 194 (2), 758–768. Spandidos, D. A., Zoumpourlis, V., Kotsinas, A., Tsiriyotis, C., and Sekeris, C. E. (1990). Response of human immunodeficiency virus long terminal repeat to growth factors and hormones. Anticancer Res., 10 (5A), 1241–1245. Stebbing, J., Gazzard, B., and Douek, D. C. (2004). Where does HIV live? N. Engl. J. Med., 350 (18), 1872–1880. Stolarczyk, R., Rubio, S. I., Smolyar, D., Young, I. S., and Poretsky, L. (1998). Twenty-four-hour urinary free cortisol in patients with acquired immunodeficiency syndrome. Metabolism, 47 (6), 690–694. Sugiyama, H., Chen, P., Hunter, M., Taffs, R., and Sitkovsky, M. (1992). The dual role of the cAMP-dependent protein kinase C alpha subunit in T-cell receptor-triggered T-lymphocytes effector functions. J. Biol. Chem., 267 (35), 25256–25263. Sundstrom, J. B., Martinson, D. E., Mosunjac, M., Bostik, P., McMullan, L. K., Donahoe, R. M., Gravanis, M. B., and Ansari, A. A. (2003). Norepinephrine enhances adhesion of HIV-1–
1076
V. Psychoneuroimmunology and Pathophysiology
infected leukocytes to cardiac microvascular endothelial cells. Exp. Biol. Med. (Maywood), 228 (6), 730–740. Sundstrom, J. B., Mosunjac, M., Martinson, D. E., Bostik, P., Donahoe, R. M., Gravanis, M. B., and Ansari, A. A. (2001). Effects of norepinephrine, HIV type 1 infection, and leukocyte interactions with endothelial cells on the expression of matrix metalloproteinases. AIDS Res. Hum. Retroviruses, 17 (17), 1605–1614. Suomi, S. J. (1991). Uptight and laid-back monkeys: individual differences in the response to social challenges. In S. Branch, W. Hall, and E. Dooling (Eds.) pp. 27–55, Plasticity of development. Cambridge, MA: MIT Press. Sutton, S. K., and Davidson, R. J. (1997). Prefrontal brain asymmetry: a biological substrate of the behavioral approach and inhibition systems. Psychological Reports, 76, 451. Swanson, B., Zeller, J. M., and Spear, G. T. (1998). Cortisol upregulates HIV p24 antigen production in cultured human monocyte-derived macrophages. J. Assoc. Nurses AIDS Care, 9 (4), 78–83. Taylor, D. N. (1995). Effects of a behavioral stress-management program on anxiety, mood, self-esteem, and T-cell count in HIV positive men. Psychol. Rep., 76 (2), 451–457. Theorell, T., Blomkvist, V., Jonsson, H., Schulman, S., Berntorp, E., and Stigendal, L. (1995). Social support and the development of immune function in human immunodeficiency virus infection. Psychosom. Med., 57 (1), 32–36. Thivierge, M., Le Gouill, C., Tremblay, M. J., Stankova, J., and Rola-Pleszczynski, M. (1998). Prostaglandin E2 induces resistance to human immunodeficiency virus-1 infection in monocyte-derived macrophages: downregulation of CCR5 expression by cyclic adenosine monophosphate. Blood, 92 (1), 40–45. Thomas, C. A., Weinberger, O. K., Ziegler, B. L., Greenberg, S., Schieren, I., Silverstein, S. C., and El Khoury, J. (1997). Human immunodeficiency virus-1 env impairs Fc receptor-mediated phagocytosis via a cyclic adenosine monophosphate-dependent mechanism. Blood, 90 (9), 3760–3765. Thornton, S. T., Troop, M., Burgess, A. P., Button, J., Goodall, R., Flynn, R., Gazzard, B. G., Catalan, J., and Easterbrook, P. J. (2000). The relationship of psychological variables and disease progression among long-term HIV-infected men. Int. J. STD. AIDS, 11 (11), 734–742. Tokoyoda, K., Tsujikawa, K., Matsushita, H., Ono, Y., Hayashi, T., Harada, Y., Abe, R., Kubo, M., and Yamamoto, H. (2004). Up-regulation of IL-4 production by the activated cAMP/ cAMP-dependent protein kinase (protein kinase A) pathway in CD3/CD28-stimulated naive T cells. Int. Immunol., 16 (5), 643–653. Tomakowsky, J., Lumley, M. A., Markowitz, N., and Frank, C. (2001). Optimistic explanatory style and dispositional optimism in HIV-infected men. J. Psychosom. Res., 51 (4), 577–587. Totman, R., Kiff, J., Reed, S. E., and Craig, J. W. (1980). Predicting experimental colds in volunteers from different measures of recent life stress. J. Psychosom. Res., 24 (3–4), 155–163. Tracey, K. J. (2002). The inflammatory reflex. Nature, 420 (6917), 853–859. Trkola, A. (2004). HIV-host interactions: vital to the virus and key to its inhibition. Curr. Opin. Microbiol., 7 (4), 407–411. Ullrich, P. M., Lutgendorf, S. K., and Stapleton, J. T. (2003). Concealment of homosexual identity, social support and CD4 cell count among HIV-seropositive gay men. J. Psychosom. Res., 54 (3), 205–212. Vago, T., Clerici, M., and Norbiato, G. (1994). Glucocorticoids and the immune system in AIDS. Baillieres Clin. Endocrinol. Metab., 8 (4), 789–802.
Valitutti, S., Dessing, M., and Lanzavecchia, A. (1993). Role of cAMP in regulating cytotoxic T lymphocyte adhesion and motility. Eur. J. Immunol., 23 (4), 790–795. Vedhara, K., Nott, K. H., Bradbeer, C. S., Davidson, E. A., Ong, E. L., Snow, M. H., Palmer, D., and Nayagam, A. T. (1997). Greater emotional distress is associated with accelerated CD4+ cell decline in HIV infection. J. Psychosom. Res., 42 (4), 379–390. Verges, B., Chavanet, P., Desgres, J., Vaillant, G., Waldner, A., Brun, J. M., and Putelat, R. (1989). Adrenal function in HIV infected patients. Acta. Endocrinol. (Copenh.), 121 (5), 633–637. Villette, J. M., Bourin, P., Doinel, C., Mansour, I., Fiet, J., Boudou, P., Dreux, C., Roue, R., Debord, M., and Levi, F. (1990). Circadian variations in plasma levels of hypophyseal, adrenocortical and testicular hormones in men infected with human immunodeficiency virus. J. Clin. Endocrinol. Metab., 70 (3), 572–577. Wang, J., Harada, A., Matsushita, S., Matsumi, S., Zhang, Y., Shioda, T., Nagai, Y., and Matsushima, K. (1998). IL-4 and a glucocorticoid up-regulate CXCR4 expression on human CD4+ T lymphocytes and enhance HIV-1 replication. J. Leukoc. Biol., 64 (5), 642–649. Wei, X., Ghosh, S. K., Taylor, M. E., Johnson, V. A., Emini, E. A., Deutsch, P., Lifson, J. D., Bonhoeffer, S., Nowak, M. A., Hahn, B. H. et al. (1995). Viral dynamics in human immunodeficiency virus type 1 infection. Nature, 373 (6510), 117–122. Weiner, H. (1992). Perturbing the organism: the biology of stressful experience. Chicago: University of Chicago Press. Wisniewski, T. L., Hilton, C. W., Morse, E. V., and Svec, F. (1993). The relationship of serum DHEA-S and cortisol levels to measures of immune function in human immunodeficiency virus– related illness. Am. J. Med. Sci., 305 (2), 79–83. Wolff, F. H., Nhuch, C., Cadore, L. P., Glitz, C. L., Lhullier, F., and Furlanetto, T. W. (2001). Low-dose adrenocorticotropin test in patients with the acquired immunodeficiency syndrome. Braz. J. Infect. Dis., 5 (2), 53–59. Woods, T. E., Antoni, M. H., Ironson, G. H., and Kling, D. W. (1999). Religiosity is associated with affective and immune status in symptomatic HIV-infected gay men. J. Psychosom. Res., 46 (2), 165–176. Wyatt, G. E., Myers, H. F., Williams, J. K., Kitchen, C. R., Loeb, T., Carmona, J. V., Wyatt, L. E., Chin, D., and Presley, N. (2002). Does a history of trauma contribute to HIV risk for women of color? Implications for prevention and policy. Am. J. Public Health, 92 (4), 660–665. Yang, J. Y., Schwartz, A., and Henderson, E. E. (1993). Inhibition of HIV-1 latency reactivation by dehydroepiandrosterone (DHEA) and an analog of DHEA. AIDS Res. Hum. Retroviruses, 9 (8), 747–754. Yang, J. Y., Schwartz, A., and Henderson, E. E. (1994). Inhibition of 3′azido-3′deoxythymidine-resistant HIV-1 infection by dehydroepiandrosterone in vitro. Biochem. Biophys. Res. Commun., 201 (3), 1424–1432. Yanovski, J. A., Miller, K. D., Kino, T., Friedman, T. C., Chrousos, G. P., Tsigos, C., and Falloon, J. (1999). Endocrine and metabolic evaluation of human immunodeficiency virus–infected patients with evidence of protease inhibitor-associated lipodystrophy. J. Clin. Endocrinol. Metab., 84 (6), 1925–1931. Zhao, R. Y., Bukrinsky, M., and Elder, R. T. (2005). HIV-1 viral protein R (Vpr) & host cellular responses. Indian J. Med. Res., 121 (4), 270–286. Zhao, Y., Cao, J., O’Gorman, M. R., Yu, M., and Yogev, R. (1996). Effect of human immunodeficiency virus type 1 protein R (vpr) gene expression on basic cellular function of fission yeast Schizosaccharomyces pombe. J. Virol., 70 (9), 5821–5826.
C H A P T E R
50 Stress-induced Modulation of the Immune Response to Herpes Simplex Virus Infections ROBERT H. BONNEAU AND JOHN T. HUNZEKER
I. INTRODUCTION TO STRESS-HSV INTERACTIONS 1077 II. INTRODUCTION TO HSV 1078 III. IMMUNITY TO HSV INFECTION 1079 IV. PSYCHOLOGICAL STRESS AND IMMUNITY— A BRIEF OVERVIEW 1080 V. STRESS AND THE INNATE IMMUNE RESPONSE TO HSV 1081 VI. STRESS AND THE ADAPTIVE IMMUNE RESPONSE TO HSV 1082 VII. THE IMPACT OF STRESS ON THE PATHOGENESIS OF HSV INFECTION 1086 VIII. PREVENTING HSV INFECTIONS— THE POTENTIAL ROLE OF STRESS 1088 IX. DECIPHERING THE STRESS-HSV RELATIONSHIP—FUTURE RESEARCH DIRECTIONS 1089 X. CONCLUDING REMARKS 1092
skin lesions. Obviously, the notion of infectious pathogenic microorganisms, including herpesviruses, was not even conceptualized during this period in history, and the lesions observed may have actually been caused by a variety of other pathogens or were the result of some cutaneous malignancies that had yet to be defined. However, it is quite likely that at least some of these lesions were caused by viruses belonging to the Herpesviridae family of viruses, of which the herpes simplex viruses types 1 and 2 (HSV-1 and HSV-2) are two of the most recognized members today. Descriptions of lesions resembling those that we now suspect as being caused by herpes simplex viruses have also been found on a Sumerian tablet dating from the 3rd millennium b.c. as well as on the Ebers papyrus, which dates from approximately 1500 b.c. Descriptions of clinical observations that are now known to be commonly associated with herpetic-based infections were also made by Herodotus, the Greek historian known as the “Father of History,” as well as by Galen, one of the most prominent ancient physicians and philosophers. As is reviewed in depth elsewhere (Roizman and Whitley, 2001), these and many other historical references to disease conditions resembling those caused by herpesviruses have been made throughout the previous two millennia and precede the beginning of the age of scientific experimentation in the late nineteenth and early twentieth centuries. Through the use of both human subjects and animal models of infection and immunity, scientific research has provided mankind with a plethora of knowledge regarding the pathogenesis of and immune-based host
I. INTRODUCTION TO STRESS-HSV INTERACTIONS . . .O’er ladies lips, who straight on kisses dream, Which oft the angry Mab with blisters plagues, Because their breaths with sweetmeats tainted are . . . Mercutio to Romeo in Romeo and Juliet, Act I, Scene IV, William Shakespeare
Historical references to herpes-like virus infections in humans date back to the time of ancient Greece. In fact, it was the Greeks who, during this time, first coined the word herpes, which means to “creep or crawl,” and was the word Hippocrates used to describe the characteristic spreading nature of herpetic-like PSYCHONEUROIMMUNOLOGY, 4E VOLUME II
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Copyright © 2007 by Elsevier, Inc. All rights of reproduction in any form reserved.
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defense against a wide range of bacterial, viral, and parasital pathogens—the herpes simplex viruses (HSV) are no exception. The result of these research efforts has led to determining the causative agents of these herpes-like diseases (i.e., HSV-1 and HSV-2), defining the unique characteristics of HSV-1 and HSV-2 infections (i.e., distinct primary and latent stages of infection), identifying the mode of HSV-1 and HSV-2 transmission (typically oral and genital, respectively), deciphering the naturally occurring immunologicalbased means of defense (e.g., innate and adaptive immune components), developing pharmacologicalbased strategies to treat active herpes simplex virus infections (e.g., acyclovir), and attempting to design immune-based prophylactic strategies (e.g., vaccines) to prevent HSV infections altogether. As is illustrated at the beginning of this chapter, Shakespeare was familiar not only with recurrent herpes simplex virus lesions and their mode of personto-person transmission but perhaps also the psychological factors (in this case, anger) which could aid in contributing to their development. As noted above, extensive research efforts during the previous 100 or so years have been successful in defining the causative agent of herpes-like lesions and the myriad of immune components that play critical roles in a host’s ability to resolve an HSV infection. However, the precise role played by psychological factors—psychological factors even recognized by Shakespeare—in modulating these immune components and thus altering the host resistance to infection has yet to be thoroughly defined. One area that is of particular interest is psychological stress, given its long-term anecdotal and recently proven association with the development of recurrent HSV infections. Although stress can be broadly defined as a state of altered homeostasis, resulting from either an external or an internal stimulus and resulting in a restoration of homeostasis through a variety of adaptive neuroendocrine mechanisms (Ramsey, 1982), the concept of psychological stress is far more complex than this rather simple definition. However, a comprehensive discussion of this complexity is clearly beyond the scope of this chapter. The reader is referred to the more complete and thorough discussions of psychological stress that are presented in other sections within this volume. There has been extensive anecdotal evidence supporting an association between psychological stress and one’s susceptibility to a variety of infectious pathogens. These pathogens include a number of viruses with significant short- and long-term health consequences. Infections with one such group of viruses, the herpes simplex viruses, have long been recognized to be linked to a variety of life stressors. These HSV infec-
tions, both primary and recurrent, have been thought to be, in part, a function of decreased immune surveillance and suppression of anti-viral immune defense mechanisms. Such stress-induced alterations in immune capacity may be mediated by one or more products of the nervous and endocrine systems. A number of human and animal studies have provided data to support this hypothesis and represent a subset of a larger group of studies that have established a solid link among psychological stress, immune function, and diseases that are caused by pathogenic microorganisms (reviewed in Bailey et al., 2003; Bonneau et al., 2001; Moynihan and Ader, 1996; Moynihan and Stevens, 2001; Sheridan et al., 1998). Recent advances in experimental immunology have broadened our overall knowledge of immunological processes, which, in turn, have facilitated the design of studies to better examine the interactions among the nervous, endocrine, and immune systems at both the cellular and molecular level. The primary goal of the information in this chapter is to provide the reader with a better understanding of the relationship between psychological stress and the immune response to and pathogenesis of HSV infection. Following a brief description of the HSV itself, a review of the experimental evidence illustrating the impact of stress on both the innate and adaptive components of anti-HSV immunity will be presented. This review will incorporate studies from our own laboratories as well as from other laboratories that have sought to define the stress-immune-HSV relationship at both the cellular and molecular levels. How this stress-induced modulation of immunity alters the pathogenesis of HSV infection and possibly plays a role in current and yet-to-be-developed strategies to prevent HSV infection will also be discussed. Given our rapidly expanding knowledge in the fields of virology, immunology, and neuroscience (among others), we will outline how possible areas of future research could better define this relationship. Overall, the information provided in this chapter will review some of the studies that have established a link between stress and HSV infection, and will discuss the impact of this link on human health.
II. INTRODUCTION TO HSV HSV is an icosahedral, double-stranded DNA virus belonging to the Herpesviridae family of viruses. This well-known family of viruses is composed of eight members including herpes simplex virus type 1 (HSV-1), herpes simplex virus type 2 (HSV-2), varicella-zoster virus (VZV), Epstein-Barr Virus (EBV),
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cytomegalovirus (CMV), and the somewhat lessrecognized members roseolovirus (human herpesvirus-6; HHV-6), HHV-7, and rhadinovirus (HHV-8). Although the contents of this chapter focus specifically on the relationship between psychological stress and infections caused by HSV-1 and HSV-2, it is worth noting that stress has also been shown to be associated with diseases caused by VZV, EBV, and CMV (Cacioppo et al., 2002; Glaser et al., 1999; Glaser et al., 2005; Irwin et al., 1998; Larson et al., 2001; Laudenslager et al., 1999; Mehta et al., 2000a; Mehta et al., 2000b; Mehta et al., 2004; Stowe et al., 2000; Stowe et al., 2001; Zorilla et al., 2001; reviewed in Glaser and Kiecolt-Glaser, 1998). The role that stress plays in the immune response to HHV-6, HHV-7, and HHV-8 infections and the pathogenic conditions caused by each of these viruses remain to be determined. HSV-1 and HSV-2 represent two commonly recognized and antigenically distinct serotypes of HSV. Although HSV-1 is generally considered to be associated with orofacial infections and HSV-2 with genital infections, both serotypes can affect any region of the body. Both HSV-1 and HSV-2 cause a wide variety of clinical syndromes in humans (e.g., herpes labialis, gingivostomatitis, keratoconjunctivitis, herpes genitalis) with the basic lesion being an intraepithelial vesicle from which infectious progeny virus is shed. It is during the primary infection that virus particles first enter sensory nerve endings, which innervate the lesion and are then transported to the local sensory ganglia. For oral lesions, this site is the trigeminal ganglia; for genital infections, the dorsal root ganglia. Once it reaches these sensory ganglia, the virus may either produce an acute infection resulting in subsequent neuronal cell death, or enter a dormant or latent phase (reviewed in Jones, 2003). During this latent state, there is restricted viral gene expression that is limited to the production of what are referred to as latency-associated transcripts or LATs (Block and Hill, 1997). There is an absence of, or only minimal, expression of any viral proteins during this stage. The primary lesions generally resolve once antibody- and cellmediated immune responses develop; however, it is in these ganglia where the virus remains for the lifetime of the host. In some of the neurons harboring latent HSV, the virus periodically reactivates. The resulting infectious HSV virion is then transported via an intraaxonal route to the cells at or near the site of the initial infection (Holland et al., 1999). This viral reactivation may be asymptomatic or, in some cases, may result in debilitating lesions (Stanberry et al., 2000). Although the precise mechanisms underlying latent HSV reactivation and the development of recurrent herpetic disease are poorly understood, there is evidence that
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a variety of forms of psychological stress play a role in this recurrent disease. It had long been believed, and there is now experimental evidence to support the notion, that stress contributes to recurrent HSV disease by altering the infected host’s overall immune competency.
III. IMMUNITY TO HSV INFECTION The role of the immune response in controlling HSV infections is multi-faceted and complex. This complexity is a function, in part, of HSV being distributed in both neuronal and extraneuronal sites during the primary and latent stages of infection. In addition, HSV persists within the host despite the presence of concomitant adaptive and humoral HSV-specific immunity. This persistence is achieved by the unique ability of HSV to establish itself as a latent infection within sensory neurons that innervate the sites of peripheral infection. Despite these challenges, considerable progress has been made in defining the immune components that play a key role in the resolution of an HSV infection. In the case of adaptive immune responses, identifying the specific virus-encoded epitopes that are recognized by the B and T lymphocytes represents one of the more important recent advances in studies of HSV-associated immunity. Since a comprehensive discussion of the immune response to HSV infections is beyond the scope to this chapter, the reader is directed to recent reviews on this topic for more detailed information (Khanna et al., 2004; Koelle and Corey, 2003). Both the innate and adaptive arms of the immune response have been shown to play a role in immunity to HSV in both immune and naive individuals. Furthermore, both arms have been shown to function not only at the site of the primary infection in the periphery but also in the initial control of HSV-1 replication in the sensory ganglia and the establishment of a latent infection in the nervous system of the infected host. Although the immune response at the primary site of HSV infection has been well characterized, less had been known about the immunological events that occur in the sensory ganglia during latency. However, as described below, there is now evidence of a role for T lymphocytes in controlling HSV-1 latency (Khanna et al., 2003, Khanna et al., 2004; Liu et al., 2000). Such findings challenge the long-held view that HSV is able to “hide” from the immune system during latency and suggest that the immune system controls recurrent herpetic disease not only during active infection in the periphery, but also during latent infection in the nervous system. Latency represents the critical stage
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of infection during which stress, in part, may be associated with HSV reactivation and recurrent disease. The other specific components of innate and adaptive immunity that contribute to one’s defense against HSV infection, and that also may be affected by stress, are described in detail below in the context of discussing the effects of psychological stress on anti-HSV immunity.
IV. PSYCHOLOGICAL STRESS AND IMMUNITY—A BRIEF OVERVIEW Stress can be generally defined as a state of altered homeostasis resulting from either an external or an internal stimulus. The host’s response to stress is designed to restore homeostasis through a variety of adaptive neuroendocrine-mediated mechanisms (Ramsey, 1982). This restoration of homeostasis is accomplished, in part, through the increased synthesis of a variety of neuroendocrine-derived peptides and hormones. For example, the perception of a psychological stressor activates the hypothalamic-pituitaryadrenal (HPA) axis and the sympathetic branch of the autonomic nervous system. This activation culminates in the synthesis of both cortisol (corticosterone in rodents) by the adrenal glands and epinephrine and norepinephrine (catecholamines) by the sympathetic nervous system. Interestingly, in addition to their roles in maintaining physiological homeostasis, these and other products of the nervous and endocrine system pathways can also modulate immune function through their binding to specific receptors that are expressed by the many cell types that comprise the immune system. As a result, most aspects of immune function, including immunity to HSV, have the potential to be modulated under conditions of psychological stress. A complete assessment of all the mechanisms and pathways underlying stress-associated, neuroendocrinemediated modulation of immunity would include those that are associated directly with not only the HPA axis and the sympathetic nervous system, but also with the parasympathetics, neuropeptides, and endogenous opioid systems. However, to date, the majority of studies, including those in our own laboratory, have focused on the corticosteroids and the catecholamines. Although studies in humans have established a clear relationship between stress and susceptibility to HSV infection, these studies have not been able to address each of the components of the immune response that potentially underlie this relationship. As is discussed further below, the limitations of such studies are rooted in the obvious inability to deliber-
ately induce HSV infections in human subjects and to assess immune responses in tissues other than the peripheral blood. However, the use of animal models— models which closely approximate human HSV infections with respect to both pathogenesis and the host immune response—has provided an opportunity to determine these immune components given the ability to establish an HSV infection and to assess the immune responses at various sites throughout the body. Using a murine model, the effects of stress on susceptibility to HSV infections have been known for nearly 50 years (Rasmussen et al., 1957). Although these studies were important in establishing an association between stress and viral infection, they were unable to identify specific anti-viral immune defense mechanisms that were modulated by stress and that contributed to viral pathogenesis since the components and mechanisms of anti-viral immune responses were virtually unknown at that time. Since then, however, significant progress has been made in understanding the complex immune interactions that are necessary for the development of protective immunity to viral infections, including HSV. Thus, it is now possible to study the effects of stress on well-defined components of the anti-viral immune response. A number of animal-based studies have been conducted in an attempt to decipher the impact of psychological stress on immune function. Although many of the early studies had simply focused on aspects of non-specific immune function such as lymphocyte proliferation and cytokine production, more recent studies have examined the effects of stress on the specific immune response to viral pathogens including HSV (Anglen et al., 2003; Bonneau, 1996; Bonneau et al., 1991a; Bonneau et al., 1991b; Bonneau et al., 1993; Bonneau et al., 1997; Bonneau et al., 1998; Brenner and Moynihan, 1997; Buske-Kirschbaum et al., 2001; Carr et al., 1998; Cruess et al., 2000; Delano and Mallery, 1998; Dobbs et al., 1993; Glaser and Kiecolt-Glaser, 1997; Karp et al., 1997; Kriesel et al., 1997; Kusnecov et al., 1992; Leo and Bonneau, 2000a; Leo and Bonneau, 2000b; Leo et al., 1998; Noisakran et al., 1998; Ortiz et al., 2003; Padgett et al., 1998b; Pariante et al., 1997; Wonnacott and Bonneau, 2002; Yorty and Bonneau, 2003; Yorty and Bonneau, 2004a; Yorty and Bonneau, 2004b; Yorty et al., 2004), influenza virus (Cohen et al., 1999; Dobbs et al., 1996; Feng et al., 1991; Hermann et al., 1993; Hermann et al., 1994a; Hermann et al., 1994b; Hermann et al., 1995; Hunzeker et al., 2004; Konstantinos and Sheridan, 2001; Padgett et al., 1998a; Sheridan et al., 1991; Sheridan et al., 2000), adenovirus (Cohen et al., 1997), pseudorabies virus (de Groot et al., 1999a; de Groot et al., 1999b), and Theiler’s virus (Johnson et al., 2004; Mi et al., 2004; Sieve et al., 2004;
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Welsh et al., 2004). Some of these studies have also focused on determining the contribution of both glucocorticoids and products of the sympathetic nervous system to the qualitative and quantitative aspects of anti-viral immunity. Furthermore, a variety of stressors including physical restraint, social reorganization, social disruption, hypothermia, and acoustic stress have been used to achieve the increased levels of immunomodulatory neuroendocrine-derived peptides and hormones that are typically associated with psychological stress in humans. Despite the wellrecognized effects of stress on immunity to a variety of viral infections (as noted above), the studies described in this chapter focus specifically on the impact of stress on immunity to HSV.
V. STRESS AND THE INNATE IMMUNE RESPONSE TO HSV A. Introduction The innate immune system possesses two primary functions in mediating a defense against pathogenic microorganisms: the direct destruction of the pathogens and the initiation of specific components of adaptive immunity that immediately follow. Studies in both humans and animals have been valuable in deciphering the components of the innate immune response that play important roles in defense against HSV. The innate immune components that are elicited in response to HSV-1 infection include the activation of the complement cascade; the activation of macrophages; and the recruitment, activation, and maturation of natural killer (NK) cells, dendritic cells, and γ/δ extrathymicderived T-cells. Activation of the innate immune response also results in the synthesis and secretion of a variety of cytokines and chemokines that orchestrate the above activities. These responses are designed to primarily limit the initial infection and to abrogate further virus propagation. Equally important is the role of these responses in the generation of the adaptive immune components—components that are composed of the activation of both HSV-specific helper and cytotoxic T-cells as well as the maturation of Bcells for HSV-specific antibody production.
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tumor necrosis factor-α), and alterations in leukocyte trafficking. Numerous studies have examined the influence of psychological stress on the early inflammatory events that are initiated shortly following HSV infection. For example, using a murine model, restraint stress was shown to decrease both type I and II interferon production in response to a primary, HSV-1 dermal infection (Ortiz et al., 2003). From a clinical perspective, it is important to note that this decrease in interferon production correlated with an increase in virus titer at the site of primary infection. In another study using a different model, hyperthermic stress was shown to increase the levels of both IL-6 mRNA and the IL-6 protein itself in the trigeminal ganglia of HSV-1 latently infected mice (Noisakran et al., 1998). The stress-induced increase in the expression of this pro-inflammatory cytokine was shown to be mediated by glucocorticoids since the administration of cyanoketone, a corticosterone synthesis inhibitor, blocked this stress-induced increase in IL-6 (Noisakran et al., 1998). More importantly, additional studies had demonstrated a potential role for stress-induced increases in IL-6 in HSV pathogenesis. In these studies, mice that had been previously infected with HSV via a corneal route and harboring latent HSV in their nervous system, demonstrated reactivated HSV following exposure to hyperthermic stress (Kriesel et al., 1997), and this reactivation was due, in part, to the presence of IL-6. In contrast, other studies (Bonneau et al., 1998) have shown that stress, administered in the form of restraint during the primary footpad HSV infection, actually suppresses splenic IL-6 production in an adrenal-dependent manner. The above studies suggest that psychological stress can modulate the pro-inflammatory response to an HSV infection. Furthermore, the precise effects of stress on this response may depend on a number of variables including the location (peripheral, lymphoid, central nervous system) and the stage of infection (primary, latent) at which the response is being measured. However, it is important to note that in some circumstances an inflammatory response may be desirable to the host for the resolution of infection, whereas in other circumstances it may result in immunemediated pathology and thus be detrimental to the host.
B. Inflammatory Response The inflammatory response to most infectious pathogens is generally characterized by symptoms of redness, swelling, heat, and pain at the site of infection. These symptoms depend on a constellation of immunological events including, but not limited to, the synthesis of pro-inflammatory cytokines (e.g., IL-1, IL-6,
C. Leukocyte Trafficking and Recruitment Leukocyte recruitment to sites of inflammation is crucial for initiating immune-mediated control of a viral infection. Inhibition of this early leukocyte trafficking may ultimately impair the ability of the immune system to control viral replication, thus leading to an
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increase in the pathology that is often associated with viral replication. Restraint stress has been shown to alter the pattern of leukocyte recruitment and retention. For example, during a primary intranasal HSV infection, restraint stress delays both CD4+ and CD8+ T-cell recruitment into the brain of mice with symptoms of HSV encephalitis (Anglen et al., 2003). In a corneal infection model, hyperthermic stress was found to reduce the numbers of NK cells in the trigeminal ganglia of mice that were latently infected with HSV-1 (Noisakran et al., 1998). Restraint stress was found to suppress lymphadenopathy in HSV-1– infected mice in a glucocorticoid-dependent manner given that receptor blockade with the glucocorticoid receptor antagonist RU-486 was shown to restore lymph node cellularity in these stressed mice (Sheridan et al., 1998). In contrast, studies by Dhabhar and colleagues (Dhabhar and McEwen, 1997, 1999) have demonstrated that an acute restraint stress session (2 hours) can actually enhance a lymphocyte traffickingdependent delayed-type hypersensitivity (DTH) response in an adrenal-dependent manner. However, such a stress-induced enhancement of cell trafficking has yet to be demonstrated in an HSV infection model and may depend greatly on the physical site to which trafficking is being measured. Psychological stressinduced alterations in leukocyte trafficking may also have a profound impact on controlling viral replication and disease pathogenesis by altering the available pool of responding cells (e.g., CD8+ T-cells) to the site of virus infection. A smaller pool of these cells and/or their delayed trafficking to key sites of infection could lead to prolonged viral replication and increased morbidity and mortality. However, additional studies are needed to support this hypothesis.
D. Cells of the Innate Immune System The non-specific innate immune response to a viral infection consists of a variety of different cell types that contribute to the early defenses against infection. Despite the well-known functions of cells of the innate immune system, only a few studies to date have examined the impact of psychological stress on these cells in the context of an HSV infection. Macrophages possess a number of functions that may either alone, or in concert with the function of other cells of the immune system, serve to mediate a powerful component of the overall anti-viral immune response. For example, macrophages may produce cytokines that influence the nature and magnitude of the adaptive immune response, present virus-encoded antigen to virus-specific B and T lymphocytes, and eliminate virus-infected cells. Although the precise role of macrophages during a primary HSV infection
is not completely understood, both adoptive transfer and depletion studies have shown that macrophages can indeed contribute to host resistance to an HSV infection (Morahan and Morse, 1979; Pinto et al., 1991). In an ex vivo activation assay, Koff and Dunegan (1986) demonstrated that products of the sympathetic nervous system (epinephrine and norepinephrine) can reduce the ability of macrophages to lyse HSV-1–infected target cells. In support of these early in vitro findings, Davis and colleagues have recently shown that exercise stress can reduce the anti-HSV activity of macrophages (Davis et al., 2004). However, the effects of stress-induced alterations in macrophage activity on HSV pathogenesis in vivo have not yet been determined. Natural killer (NK) cells serve as a bridge between the innate and adaptive arms of the immune response by limiting viral replication as well as producing cytokines that aid in generating the adaptive immune response. As with macrophages, the role of the NK cell during a primary HSV infection is not completely understood. For example, some studies have suggested that NK cells are not necessary for the resolution of an HSV infection (Bukowski and Welsh, 1986), while others have shown that NK cells are required (Biron et al., 1989). The differences between these apparently conflicting studies may be due primarily to differences in the species that were being examined in these two studies (human vs. mouse). Consistent with these reports, stress has been shown to have differing effects on NK cell activity during a primary HSV infection. For example, restraint stress has been shown to reduce splenic NK cell lytic activity following an intradermal HSV-1 infection (Bonneau et al., 1991b). However, in a model of exercise stress, running to a state of fatigue did not have any effect on splenic NK cell activity (Davis et al., 2004). It is important that additional studies be conducted to better elucidate the role of NK cells during a primary infection and how stress may affect their widespread anti-viral activities. In interpreting the findings of these and other studies, it is important not to generalize such findings to all situations, but instead to consider differences such as the species being examined, the site of HSV infection, and the stage of the infection (e.g., primary, latent, recurrent) during which the immune response to HSV infection or HSV pathogenesis itself is being examined.
VI. STRESS AND THE ADAPTIVE IMMUNE RESPONSE TO HSV A. Introduction The adaptive immune response to HSV infection has been shown to play a key role in primary and,
50. Stress-induced Modulation of the Immune Response to Herpes Simplex Virus Infections
more recently, in latent HSV infections. The production of HSV-specific antibodies has been known for quite some time, long before it was even recognized that HSV establishes itself in a latent state within the nervous system of the infected host. These antibodies function by neutralizing infectious HSV and, in conjunction with other cell types (e.g., polymorphonuclear leukocytes, monocytes, and NK-like cells), in mediating antibody-dependent cell-mediated cytotoxicity (ADCC) for the destruction of HSV-infected cells. There is also compelling evidence that antibody alone is able to provide protection against primary HSV infection in neonates exposed to HSV at or near the time of birth (Brown et al., 1991). However, despite the presence of high levels of circulating HSV-specific antibodies in a latently infected host, HSV reactivation and recrudescent herpetic disease appear to go unchecked in most individuals. More recently, a number of studies have focused on the specific roles of CD4+ and CD8+ T lymphocytes in anti-HSV immunity and the antigenic specificity of these T lymphocyte responses. There are several lines of evidence indicating that both of these subsets of T lymphocytes are functionally important in controlling HSV infections. CD8+ T-cells mediate their protective ability via their cytotoxic effects on virus-infected target cells and their synthesis of cytokines—cytokines which may be able to inhibit viral replication. The recent finding of a role for CD8+ T-cells for controlling HSV reactivation in latently infected ganglia (Khanna et al., 2003; Khanna et al., 2004) is intriguing since it has long been thought that latently infected cells were essentially hidden from immunosurveillance mechanisms. CD4+ T-cells are important in that they release numerous cytokines which can both orchestrate the inflammatory response that is associated with HSV infection as well as play a key role in determining the magnitude of the CD8+ Tcell response. Overall, one or more components of the adaptive immune response have the potential to control HSV infections and thus may form the basis for developing an effective vaccine against HSV.
B. Humoral Immunity As noted above, antibodies play a role in clearing HSV infections in a direct manner by neutralizing infectious viruses and by acting in concert with other cells (e.g., NK cells) to reduce the viral load. Although they may not be able to prevent HSV infection altogether, antibodies have the potential to significantly reduce the extent of viral spread and pathogenesis, thus lessening the burden of other components of the adaptive immune response in clearing the infection. To date, most of the studies that have examined the influence of psychological stress on the B-cells during
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an HSV infection have focused on simply measuring antibody titers and isotypes. For example, as compared to individually housed mice, group-housed mice were shown to produce lower levels of some, but not all, cytokines in response to HSV-1 infection. However, these differences were shown not to be due simply to the kinetics of the cytokine response in the two groups of mice. Despite producing lower levels of cytokines, these group housing conditions, which apparently resulted in different levels of stress than individual housing conditions, were shown not to alter the levels of circulating IgM and IgG antibodies (Karp et al., 1997). In contrast, another study showed that the stress induced by electric footshock also altered cytokine production but did not increase circulating anti-HSV IgM titers in response to a subcutaneous HSV challenge (Brenner and Moynihan, 1997). These electric footshock stress-induced increases in antibody titers were found in both BALB/c and C57BL/6 mice. In contrast, yet another study showed that electric footshock stress administered at the time of HSV-1 infection via footpad scarification actually reduced IgM titers (Kusnecov et al., 1992). The differences in the results obtained among these studies may be primarily due to differences in shock intensity, duration, and/or frequency, suggesting that the more stressful the event, the more likely that immunosuppression is to occur. Such differences observed in these and other studies may also be a function of the strain of mice used in the studies since strains of mice may vary in not only in their inherent susceptibility to HSV infection, but also in their neuroendocrine response to stress. Together, these factors may contribute to differences in viral antigenic load which, in turn, may alter the overall immune response that is generated in response to infection. The observed relationship between stress and anti-HSV antibodies in murine models has also been extended to studies in humans. For example, Glaser and Kiecolt-Glaser (1997) demonstrated that caregivers of individuals suffering from dementia had increased antibody titers to HSV antigen but exhibited no difference in neutralizing antibody titers to a latent HSV-1 infection. The ability of an individual to generate HSVspecific antibodies following a primary infection may be important, to a limited extent, in protecting the host against re-infection from either peripheral re-exposure to HSV or reactivation of the latent virus from within the nervous system. Although a less-common route of HSV transmission, the acquisition of HSV by a neonate, most often from his/her mother during delivery, is still a significant health concern and results in a number of Cesarean sections annually in the United States, particularly if the mother is experiencing a genital HSV infection near the time of expected delivery. In
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the case of these neonatally acquired HSV infections, the transfer of HSV-specific antibody from mother to child is extremely important in protecting the health of the newborn infant. This antibody is potentially transferred by placental (prenatal transfer) or transmammary (postnatal transfer) routes and obviously plays a greater role in protecting the neonate if his/her mother has a history of HSV infection and thus already possesses high levels of transferable antibody. This is in contrast to a situation in which a mother is experiencing her first infection with HSV at or near the time of delivery and thus has either absent or only a low level of HSV-specific antibody. As would be expected, any reduction in this antibody transfer from mother to fetus (prenatal via the placenta) or neonate (postnatal via the milk) could compromise the resistance of the newborn to maternally derived herpetic infection. Using a murine model, recent studies from our laboratory provide evidence that a previous HSV-2 infection in female mice protects their offspring against HSV-2 infection (Yorty and Bonneau, 2003; Yorty and Bonneau, 2004a) and that this protection is associated with the transfer of high titers of HSV-specific antibodies. Furthermore, these studies demonstrated that an acute stressor does not affect either the transmammary (Yorty and Bonneau, 2004b) or placental transfer of anti-HSV antibodies to newborn mice despite high circulating levels of corticosterone (Yorty and Bonneau, 2004a). In contrast, sustained elevated levels of corticosterone in the mother immediately following parturition diminishes the maternal serum and milk levels of HSV-2 antibodies and thus reduces the amount of antibody available to the neonates to ward off infection. As we had predicted, this corticosteronemediated reduction in antibody transfer is accompanied by an increased HSV-2 susceptibility in neonatal mice who were nursed by these mothers (Yorty et al., 2004). The above findings illustrate that both the active production of HSV-specific antibodies in response to HSV infection as well as their passive transfer to an uninfected host may be modulated by stress or stressassociated hormones. However, exactly how stress modulates these and humoral immune responses to infectious pathogens may greatly depend on a variety of factors, including the type of stressor as well as the stage of infection (e.g., primary, latent, recurrent) during which the stressor is experienced by the HSVinfected host.
C. Cellular Immunity As is evident from information presented above, there have been relatively few studies of the effects of
psychological stress on the humoral or antibodymediated immune response to HSV infection. In contrast, a greater number of studies have attempted to determine the effects of stress on the cellular or T lymphocyte-based component of the adaptive immune response. One reason for this focus on T-cell–mediated immunity is the essential role that T-cells are known to play in controlling viral replication during HSV infection, as noted above. The initial studies of the effect of stress on the primary cellular immune response to HSV infection were conducted in a well-established mouse model of HSV infection. Using this model, stress, applied in the form of physical restraint, was shown to suppress the lymphoproliferative response in the draining popliteal lymph nodes following footpad infection with HSV (Bonneau et al., 1991b; Dobbs et al., 1993). Using this same model, it was also shown that stress suppresses the extent of HSVspecific CTL and natural killer (NK) cell activity generated in response to local HSV infection (Bonneau et al., 1991b). This suppression in the generation of CTL was shown to occur early in the sequence of events that are involved in the differentiation and maturation of HSVspecific precursor CTL (CTLp) to a phenotypically lytic state (Bonneau et al., 1991b). A similar stressinduced suppression of lymphoproliferation and HSVspecific CTL activity was also observed in studies in which an electric footshock model of stress was employed (Kusnecov et al., 1992), thus further supporting a role for stress in the suppression of the T-cell response to HSV infection. Having shown an effect of stress on the HSVspecific cellular immune response, the next logical step was to determine the stress-induced neuroendocrinemediated mechanisms underlying this observation. By using a combination of surgical (adrenalectomy) and pharmacological approaches (β-adrenergic and glucocorticoid receptor antagonists, corticosteronereleasing pellets), a role for both adrenal-dependent and catecholamine-mediated mechanisms in stressinduced suppression of the primary cellular immune response to HSV infection was defined (Bonneau et al., 1993; Dobbs et al., 1993). Lymphocyte trafficking was found to be corticosterone dependent as the administration of RU-486 restored the accumulation of lymphoid cells in the draining lymphoid tissues. In addition, CD8+ T-cell lytic activity was restored by treatment of mice of nadalol, a non-specific adrenergic receptor antagonist. Together, these results demonstrate that psychological stress can affect all aspects of T-cell function, including proliferation, trafficking, and lytic activity. Given the key role that T-cells play in controlling HSV infection, stress-induced modulation of their function would be expected to result in
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prolonged viral replication. Paradoxically, one could also expect to see a decreased level of HSV pathogenesis associated with stress since the immune response itself has the potential to contribute significantly to the virus-associated tissue damage within the HSV infected host. The development of such immunopathology may, in part, be a function of the stage of infection during which the T-cell response is activated. Recent studies in our laboratory have begun to examine the impact of corticosterone, a major stressassociated hormone, on dendritic cell function. Dendritic cells are specialized for the uptake, transport, processing, and MHC class I-restricted presentation of antigen to naive CD8+ T-cells—critical events that are an absolute requirement for the generation of both effector and memory CD8+ CTL responses. Dendritic cells play a pivotal role in generating these CD8+ T-cell immune responses by presenting MHC class I-peptide complexes on their surface. We have shown (Truckenmiller et al., 2005) that physiologically relevant stress levels of corticosterone, acting via the glucocorticoid receptor, suppress the formation of specific peptideMHC class I complexes on the surface of virus-infected dendritic cells. We have also determined that the mechanism of this suppression is via the action of corticosterone on components of the class I pathway involved in the processing of protein to form the antigenic peptides. This corticosterone-mediated suppression of complexes on dendritic cells also results in a marked reduction in the ability of these dendritic cells to activate an antigen-specific T-cell hybridoma, thus suggesting that a suppression of complex formation may have a functional effect in vivo by suppressing the induction of HSV-specific CTL. These studies represent the first attempt to examine the effects of stress on the adaptive immune response at the level of dendritic cell function. More importantly, they provide the foundation for elucidating the effects of stress on dendritic cell maturation and function in vivo in the context of a viral infection, such as HSV. As illustrated above, the impact of stress on the functioning of dendritic cells and other antigen presenting cells in T-cell activation is an important component in our understanding of stressneuroendocrine-immune interactions. The notion that stress mediates effects on T-cell activation has been expanded by recent studies from our laboratory in which we have examined the effects of stress and corticosterone on the proliferation and function of microglia in the brains of both non-infected and HSV-infected mice (Nair and Bonneau, 2006). Microglia are thought to function as a type of antigen-presenting cell with the brain and thus may contribute to T-cell activation and function. In one component of these studies, we have
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demonstrated that stress-associated corticosterone increases the numbers and activation status of microglia in the brain. This finding suggests that stress may be able to induce a pro-inflammatory response within the central nervous system, which, in turn, may be a contributing factor in the development of various stress-induced inflammatory conditions in the central nervous system, including those caused by HSV infection. A better understanding of the interrelationship between antigen presentation and T-cell activation in secondary lymphoid tissues (e.g., spleen, lymph nodes) and the brain, but also in other sites of HSV infection within the body, will provide the knowledge to better define the mechanisms underlying stress-induced, neuroendocrine-mediated modulation of the cellular immune response.
D. Immunological Memory An individual who has previously recovered from a primary HSV infection exhibits an adaptive, T lymphocyte-based immune response upon HSV reinfection that differs primarily in its rapidity and magnitude as compared to an individual who has never been infected. This memory component of the immune response plays a key role in one’s ability to quickly ward off not only recurrent HSV infections, but also infections with other pathogens to which they have previously been exposed and that are immunologically resisted. It is the generation and utilization of this immunological memory that forms the basis for vaccination strategies. Given the relative insignificance of high titers of HSV-specific antibody in preventing the development of recurrent herpetic diseases in adults, most attention has focused on memory T lymphocyte responses, particularly the CTL responses, as a means by which individuals quickly respond to and destroy HSV-infected cells soon after HSV reactivation. Memory cytotoxic T lymphocytes (CTLm) play an important role in mediating long-term protective immunity against a variety of intracellular pathogens (reviewed in Ahmed, 1994; Doherty et al., 1992; Gray, 1993; Mackay, 1993; Pamer, 1993; Sher and Coffman, 1992; Sprent, 1994). While these CTLm do not prevent recurrence or reinfection per se, they do limit the severity of infection/disease by becoming activated in an accelerated fashion following re-exposure to the particular pathogen (Ahmed, 1994; Gray, 1993; Mackay, 1993; Sprent, 1994). This activation occurs as memory T-cells move continually from blood to tissues, scanning cell surfaces for the appropriate antigen to which they are programmed to recognize. Upon an encounter with this antigen, CTLm are readily triggered to become effector CTL. In the case of viral infections, the
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encounter of the CTLm with a virus-specific peptide/ MHC complex triggers these memory CTL to proliferate rapidly, differentiate into effector cells, and localize to the site of infection. It is here where these CTL destroy virus-infected cells, thus eliminating the virus “factories” that produce infectious viral progeny. These CTL may also synthesize cytokines such as IFNγ and TNF-α, which have both a direct anti-viral activity as well as the ability to enhance components of antigen processing and presentation. A role for CTLm in mediating protection against recurrent HSV infections has been documented in both humans and in animals (Ashley et al., 1994; Koelle et al., 1998; Rinaldo and Torpey, 1993; Schmid and Rouse, 1992). Although HSV reactivation occurs quite frequently, it usually does not lead to an apparent clinical infection (Wald et al., 1995; Wald et al., 1997), especially when the immune system is intact. Our knowledge of CTL-mediated defense against HSV infection has grown significantly in recent years. This knowledge, driven by advances in experimental immunology, has provided a solid foundation on which to decipher the mechanisms underlying the impact of stress on the immunity to not only HSV, but also to other viral pathogens. Immunological memory is a key component of the overall immune response and is important in reducing the severity of recurrent HSV infection. Because recovery from recurrent HSV infections is largely controlled by T lymphocytes, the ability to generate a population of HSV-specific CTLm during a primary infection with HSV is thought to be critical for the long-term defense against recurrent HSV infection. The psychological stress that is often associated with these primary episodes of infection, as well as the development of recurrent disease, emphasizes the potential significance of the effect of stress on the development of HSV-specific T-cell–mediated immunity. In studies to date, restraint stress of mice has been shown not to suppress the generation of CTLm in response to systemic HSV infection. However, in contrast, such a stressor has been shown to be effective at inhibiting the activation of CTLm (Bonneau et al., 1991a; Bonneau, 1996, Leo et al., 1998) and their migration to the site of recurrent HSV infection (Bonneau et al., 1991a). Further studies into the mechanisms underlying the suppression of CTLm activation revealed that stress does not suppress the expression of the Tcell receptor, IL-2 receptor, and other accessory molecules that are required for T lymphocyte activation. However, stress does suppress the production of cytokines that are involved in HSV-specific CTLm activation—a suppression which is likely to be the mechanism underlying stress-induced suppression of CTLm acti-
vation (Bonneau et al., 1996). These studies were later extended to show that products of adrenal function associated with stress are responsible for suppression of cytokine production and the development of lytic activity, but that they do not affect splenic cellularity (Bonneau et al., 1997). Similar to the studies of the primary immune response, adrenal-dependent mechanisms do not appear to be solely responsible for stressinduced suppression of memory responses to HSV infection. Although much has been learned about the effects of stress on the generation and activation of CTLm, there is little known about the effects of stress, either acute or chronic, on the long-term maintenance of memory T-cells in vivo and their ability to thoroughly survey the body for sites of HSV infection. The recent identification of two distinct phenotypes of CD8+ memory T-cells, the central and effector memory cells (Lanzavecchia and Sallusto, 2005; Sallusto et al., 1999; Sallusto et al., 2004), provides an opportunity to determine the effects of stress on the generation, location, and function of these specific memory cell subsets. The recent development of experimental models and novel in vivo strategies to both track and determine the number and function of relatively low numbers of CTLm at various sites throughout the body also provides an opportunity to extend our knowledge of stress-neuroendocrine-immune interactions to a new level.
VII. THE IMPACT OF STRESS ON THE PATHOGENESIS OF HSV INFECTION A. Introduction HSV is a natural pathogen of humans and, as noted above, is characterized by its ability to cause an acute infection at a peripheral site and to establish a latent infection in the local sensory ganglia which innervate the sites of the initial infection (Blyth and Hill, 1984). The hallmark of HSV is its ability to spontaneously reactivate from this quiescent, non-infectious latent state and cause a recurrent infection in the periphery, at, or near the site of the original infection (Hill, 1985). In humans, HSV reactivation and recurrent infections typically occur spontaneously, although infrequently. However, even as long as 30 years ago, correlations had been made between reactivation and physical or emotional stress, fever, exposure to ultraviolet light, tissue damage, and immune suppression (Hill, 1985; Stevens, 1975). As is described above, more recent efforts by us and others have used mouse models of HSV infection, immune responsiveness, and patho-
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genesis to begin to decipher the roles of psychological stress and its associated neuroendocrine components in the development of both primary and recurrent HSV infection. Together, these models have provided a foundation for obtaining a better understanding of the effects of stress on the pathogenesis of HSV infection.
B. The Impact of Stress on Primary HSV Infection The ability of the innate and adaptive components of the immune system to curb the amount of HSV replication during a primary infection may, in turn, limit the amount of latent virus that colonizes the local sensory ganglia (Bonneau and Jennings, 1989). Destroying HSV-infected cells before progeny virions can be produced may not only control the extent of neuronal involvement and the associated pathological consequences during a primary HSV infection, but may also reduce the amount of latent virus that ultimately colonizes the ganglia. Therefore, the impact of psychological stress on the immune response during a primary HSV infection may have consequences on not only one’s resistance to and recovery from his/her initial encounter with HSV, but also on the development of recurrent HSV infection, as a consequence of latent HSV reactivation, throughout his/her entire lifetime. Studies in humans have indicated that stress can affect the frequency, severity, and duration of HSV infection. However, a number of murine-based studies during the past 15 years have substantiated these findings by providing compelling experimental evidence that stress and stress-induced, neuroendocrine-derived products increase the development and severity of HSV infection in both the periphery (Bonneau et al., 1991b; Bonneau et al., 1997; Brenner and Moynihan, 1997; Kusnecov et al., 1992; Wonnacott and Bonneau, 2002) and the central nervous system (Anglen et al., 2003). For example, experiments in which either restraint (Bonneau et al., 1991b, Ortiz et al., 2003; Wonnacott and Bonneau, 2002) or electric footshock (Kusnecov et al., 1992) models of stress were used were shown to result in increased HSV titers at a site of local HSV infection. Stress was also shown to suppress the ability of adoptively transferred lymphocytes with HSV-specific lytic activity to confer protection against lethal HSV infection in an immunocompromised host as well as to inhibit the restoration of immune responsiveness to HSV infection following sublethal gamma irradiation (Bonneau et al., 1997). These latter findings are particularly important since adoptive immunotherapy represents a potentially
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effective approach by which to control the extent of viral infections in an immunocompromised host. Other studies have used the glucocorticoid antagonist androstenediol (AED) to show that AED can significantly improve the survival of mice with HSV-1 induced encephalitis, thus suggesting that glucocorticoids are a mediator of stress-induced immunosuppression. Moreover, it was shown that this increased level of protection was associated with an augmentation in type I interferon production (Daigle and Carr, 1998). As noted above, recent studies from our own laboratory have focused on the impact of maternal stress on the transfer of antibody from mother to fetus/neonate. In these studies, we have demonstrated that increased levels of postpartum maternal corticosterone increases neonatal susceptibility to HSV-2–associated infection by reducing the amount of HSV-specific antibody transferred via the transmammary route (Yorty and Bonneau, 2004b). As was described earlier, a number of animal model studies have shown that stress suppresses components of the primary (Bonneau et al., 1991b; Bonneau et al., 1993; Bonneau, 1997; Brenner and Moynihan, 1997; Dobbs et al., 1993; Kusnecov et al., 1992; Leo and Bonneau, 2000a; Leo et al., 1998) and memory (Bonneau, 1996; Bonneau et al., 1991a; Bonneau et al., 1998; Leo and Bonneau, 2000a; Leo et al., 1998, Wonnacott and Bonneau, 2002) cytotoxic T lymphocyte (CTL) responses to HSV infection. By using a combination of surgical and pharmacological approaches, a role for both the hypothalamic-pituitary-adrenal (HPA) axis (Bonneau et al., 1993; Bonneau et al., 1998) and the sympathetic nervous system (Leo and Bonneau, 2000b) has clearly been demonstrated as one of the underlying mechanisms mediating this stress-induced modulation of immunity and HSV-associated pathology. However, the precise role of these neuroendocrine-mediated mechanisms in HSV pathogenesis in humans remains to be elucidated but is likely to be involved in mediating components of innate and/or adaptive immunity.
C. The Impact of Stress on HSV Reactivation and Recurrent HSV Infection 1. Human Subject Studies In all but a small number of cases, a primary infection with HSV resolves within a few weeks and without any long-term consequences in the infected human host. However, the ability of HSV to establish itself in a latent state and, more importantly, to reactivate periodically during the lifetime of this host and cause recurrent lesions is a significant challenge to the development of therapeutic strategies against HSV
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infection. There has long been evidence that acute and chronic psychosocial stress trigger recurrences of both oral and genital infections. Support for this hypothesis has been provided by studies in humans which have demonstrated that emotional stress is associated with the development of recurrent HSV infections (Bierman, 1983; Friedmann et al., 1977; Glaser et al., 1987; Katcher et al., 1973; Schmidt et al., 1985; Young et al., 1976) and that personality may play a role in the frequency of these recurrences (Stout and Bloom, 1986). The severity of HSV infection has also been correlated with psychosocial factors (Longo and Clum, 1989; Silver et al., 1986), which suggests that the control and resolution of recurrent HSV lesions by the memory components of the immune response may be compromised. There is also evidence that social support can moderate the impact of stress on HSV infection (Cruess et al., 2000; Glaser et al., 1985; VanderPlate et al., 1988) and that high levels of depressive mood may result in a higher rate of HSV recurrence (Kemeny et al., 1989). More recent studies have shown that stress may be a significant predictor of recurrent genital herpes in HIVinfected women (Pereira et al., 2003)—a population that may already be immunosuppressed as a consequence of the HIV infection alone. Together, these studies in humans strongly support the existence of a relationship between psychological stress and the development of HSV infections. 2. Animal Model Studies It has long been known that psychological stress in humans is often associated with the spontaneous bouts of recurrent HSV infection that occur as consequence of latent virus reactivation. Unfortunately, the lack of a reliable mouse model of spontaneous reactivation has somewhat limited the usefulness of mice in studying HSV reactivation and the associated immune response. However, the immune system of the mouse is very well characterized and is similar in many respects to that of humans. This reason, and the fact that there is a wide and continually expanding variety of reagents for studying detailed immune responses in mice, has led to mice being the species of choice for most immunological studies, including those studies which seek to better decipher the nature of stressneuroendocrine-immune interactions. For many years, it has been known that local trauma (e.g., hair plucking, tape stripping, chemical-induced trauma, ultraviolet light) administered to a previously infected area can result in HSV reactivation and recurrent disease. However, the ability of each of these methods to consistently induce recurrent disease is quite low (Harbour et al., 1983; Hill et al., 1978; Hill
et al., 1983; Hurd and Robinson, 1977). Whether or not the above methods elicited reactivation and recurrent infection simply due to trauma on nerve endings innervating the site or whether the animal perceived the trauma as a psychological stressor is not known. However, two additional recent and reliable models of psychological stress in mice have been shown to be effective in inducing HSV reactivation and recurrent disease and, in turn, have allowed for better studies of the immunological and neuroendocrine mechanisms underlying behaviorally mediated reactivation of latent HSV and the development of recrudescent HSV infection in mice. For example, the use of a hyperthermic stress model (Sawtell, 1998; Sawtell and Thompson, 1992; Thompson and Sawtell, 1997) has been used to show that HPA axis activation plays an important role in HSV-1 reactivation in the trigeminal ganglion and that this reactivation may be associated with an increase in IL-6 expression in the ganglia itself (Noisakran et al., 1998). In addition, the use of a social stress model in mice has been shown to be effective in causing recurrent HSV infection in mice (Padgett et al., 1998b). This correlation between neuroendocrine activity, immune function, and latent HSV reactivation (Carr et al., 1998; Halford et al., 1996; Noisakran et al., 1998; Padgett et al., 1998b) is particularly interesting in light of recent findings that HSV-specific memory CD8+ T-cells are selectively activated and retained in latently infected sensory ganglia (Khanna et al., 2003). Studies are in progress to determine if stress-induced, neuroendocrine-mediated mechanisms are able to play a role in the activation of ganglia-resident CD8+ T-cells and the impact of this activation on latent HSV reactivation and recurrent infection.
VIII. PREVENTING HSV INFECTIONS— THE POTENTIAL ROLE OF STRESS Given the various roles that the immune system plays in the resistance to many viral infections, including HSV, vaccination typically remains the desired strategy by which to confer protection. However, in the case of HSV, identifying the salient immune components that are involved in this protection may represent an obstacle to the design of an effective vaccine. The complex nature of HSV infections may also provide a formidable challenge to the development of a vaccine that would be effective at all stages of infection and against infections at multiple sites within the body. Even if a vaccine were to be developed, the fact that stress has been shown to suppress the induction of vaccine-induced immunity (Burns et al., 2002; Glaser et al., 1992; Glaser et al., 2000; Kiecolt-Glaser et al.,
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1996; Miller et al., 2004; Vedhara et al., 1999) suggests that not all individuals who are vaccinated may necessarily be protected. Moreover, the potential impact of stress on the reactivation of immunological memory may also suppress vaccine-mediated protection against infection. Despite long-term and continual efforts, there currently is no vaccine to prevent either a primary HSV infection or an infection arising from reactivation of HSV from the latent state. However, various therapeutic agents have been designed to interfere directly with viral replication (e.g., acyclovir, penciclovir), are converted in vivo to acyclovir or penciclovir (e.g., valacyclovir HCl and famciclovir, respectively), or prevent the virus from fusing to cell membranes, thus barring virus entry into the cell (e.g., docosanol). These drugs may be beneficial by reducing the severity and shortening the course of recurrent infections and may aid in lowering the incidence of future outbreaks by reducing the amount of latent virus in the neural ganglia. However, they do not prevent recurrences entirely and therefore do not eliminate the possibility of spreading an HSV infection from one individual to another. However, a reduced viral load and shorter duration of infection may reduce this possibility to some extent. The effectiveness of these drugs may be enhanced by an effectively functioning immune system. Thus, the effects of stress on immune function may be important even when drug therapy is the only available treatment strategy. Any effective strategy to eliminate HSV infections from the general population will need to not only prevent a primary infection, but also prevent the establishment of a latent infection. For those individuals already harboring latent HSV, the ability of this strategy to either eliminate the latent virus, inhibit its reactivation, and/or block the development of recrudescent disease following reactivation is desirable. However, it is unlikely that any one treatment strategy will be effective in accomplishing these objectives. What role could controlling the degree of stress play in the prevention of recurrent HSV? First, despite the many facets of an HSV infection, it is clear that the immune system plays a role, to some degree, in one’s ability to prevent and/or recover from infection. Second, psychological stress has been shown to be intimately linked to the development of recurrent HSV infections—most likely through the suppression of both HSV-specific and non-specific immune defense mechanisms. As is outlined above, a number of life events, some of which are inherently stressful, have been shown to be associated with outbreaks of recurrent HSV infection. Such events may, in part, dictate why some individuals experience frequent reactiva-
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tion events and other individuals experience relatively few. Therefore, limiting the degree of psychological stress may, in some cases, be adequate for maintaining a sufficient immune defense against HSV infection. This limiting of stress may be accomplished though a variety of behavioral modification and social support mechanisms.
IX. DECIPHERING THE STRESS-HSV RELATIONSHIP—FUTURE RESEARCH DIRECTIONS As is outlined above, significant progress has been made in determining the impact of psychological stress on the immune response to HSV infection and, in turn, its effect on the pathological consequences in the infected host. Despite this progress, the cellular and molecular mechanisms underlying the relationship among stress, neuroendocrine activation, immune function, and HSV pathogenesis have not yet been fully realized. Such mechanisms are often able to be determined only as the experimental tools are developed to learn more about the basic immunological processes that are involved in responding to and warding off infectious pathogens such as HSV. In addition, there is often an inherent delay in the use of such tools for studying neuroendocrine-immune interactions to determine how the neuroendocrine system specifically affects some of these basic immunological processes. The information in this section offers some opinions as to future research directions in both humans and animals in order to better define the link between stress and immunity to HSV infection. The advantages and limitations of conducting studies in humans and animals are also discussed, as are some of the challenges in conducting stateof-the-art research in the burgeoning field of psychoneuroimmunology.
A. Human Subject Studies Although deciphering the impact of stress on immune function in humans is obviously more clinically relevant than the use of animal models, the ability to conduct well-controlled, mechanistic-based studies in humans is limited. For example, for obvious practical and ethical considerations, human subjects are not able to be infected experimentally with HSV. Thus, there are limitations in determining the impact of stress on one’s susceptibility to a primary HSV infection unless, of course, a natural exposure to HSV is known to have already occurred. Given the large percentage of the population that is infected with HSV
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and the frequency with which many of these individuals experience recurrent outbreaks, there are certainly many opportunities to determine the relationship among the nature, severity, duration, and timing of a stressor relative to HSV reactivation and the development of recurrent lesions. A major constraint in using human subjects to study anti-HSV immune responses is the limited ability to assess specific components of the HSV-specific immune response. First, and perhaps most importantly, is the ability to examine only cells of the peripheral blood and to use these cells as a broad measure of anti-viral immunity. However, HSV-specific immune responses in the local draining lymph nodes, spleen, and HSVinfected tissues (e.g., oral cavity, skin, genital tract, nervous system) are more clinically relevant and provide a better experimental approach to determine, at the mechanistic level, the relationship among stress, immune function, and viral pathogenesis. However, the ability to obtain a sufficient number of immune cells for assessing immunological function is a clearly recognized limitation of human-based studies. An even more significant limiting factor is the inability to assess antigen-specific responses, particularly T-cell– based responses, at these sites. Not only is there is a high level of diversity in the HLA class I and class II molecules within the human population, but also the HSV-encoded antigenic peptides that associate with these molecules and that form the antigenic recognition sites for T-cell receptors have yet to be defined. The lack of information regarding these epitopes, in turn, prevents both a quantitative and functional analysis of HSV-specific immune responses due to the lack of reagents (tetramers, synthetic peptides) on which such antigen-specific analyses greatly depend. Within the past decade, the quantitative and qualitative analysis of the pathogen-specific immune responses at various anatomical locations has been well deciphered, but only in a variety of non-human animal models. A quick review of the literature supports the fact that studies of neuroendocrine-mediated modulation of immune response to HSV and other pathogens in humans in locations other than the peripheral blood are lacking. Furthermore, although the number of available reagents to study these responses in animals (particularly mice) has increased substantially in recent years, the reagents to study these responses in humans have continued to be extremely limited. Despite the limited ability to assess HSV-specific, immunological-based studies in humans, there are still a number of advantages to performing behavioral/ psychological-based studies in humans that are worth considering. For example, one of the clear advantages of human subject studies is the detailed psychological
profiles that can be obtained from humans but obviously not from animal-based studies, particularly those studies which use rodents. Human subject studies also provide a means to measure the impact of naturally occurring stressors (e.g., academic stress, divorce, caregiving, spaceflight) on immune responses to viral pathogens, including HSV. A better understanding of the nature of these and other stressors and the neuroendocrine responses that they invoke will encourage the design of intervention studies in an attempt to counteract the effects of stress on immune function. Lastly, these studies also present an opportunity to include aging as a variable in stress-induced immunomodulation—a particularly important variable given the relatively large number of individuals who are not only aging but who are also living to an age that was once achieved by only a small percentage of the population.
B. Animal Model Studies A wide variety of animal species have long been used in biomedical research. Mice have especially been valuable in studying viral immunology given the remarkable similarity of the murine immune system to that of humans. Equally important is the fact that animals have played a key role in advancing our understanding of the immunobiology of HSV infections—an understanding that has been incorporated into some of the studies that have been described in this chapter. Another essential element to using murine models is the finding that similar, if not identical, immune mechanisms provide protection against HSV infection in both humans and mice. However, similar to the human studies and as outlined below, there are also significant advantages and disadvantages to the use of murine and other animal models. Unlike human studies, the use of animals provides an opportunity to design studies that incorporate a variety of experimental variables associated with both the HSV infection itself and the immune responses that will be measured. One of the obvious advantages of using animal models is the ability to deliberately induce an HSV infection. The routes of infection can be varied and can often be designed to model the natural sites of HSV infection in humans. Unfortunately, some studies have been reported using not only HSV, but also other pathogens, in which the experimentally induced infection sites poorly represent the natural sites of infection normally observed in humans. Studies should also be designed so that the exposure levels of animals to HSV mimic those levels which humans naturally encounter or which represent levels that at least elicit an immune response that is
50. Stress-induced Modulation of the Immune Response to Herpes Simplex Virus Infections
comparable to the magnitude of the immune response typically observed in humans. The use of supraphysiological infecting doses and/or laboratory-adapted strains of HSV may often be useful for deciphering the immunological mechanisms that are involved in antiHSV immunity. However, one should be cautious in extrapolating the findings of such studies to the human condition. In addition to being able to carefully control the HSV infection, animal models also provide an excellent opportunity to assess immune responses in lymphoid tissues which drain the site of infection and in which critical interactions among the myriad of cell types (e.g., cytotoxic T lymphocytes, helper T lymphocytes, antigen-presenting cells) that are necessary for generation of an effective immune response. These models also allow one to assess the migration and homing of antigen-activated lymphocytes to sites of infection both in the nervous system as well as in the periphery. As noted above, the accessibility of a variety of both lymphoid and non-lymphoid tissues in animals for assessing immune function has been and will continue to be critical in advancing our knowledge of stress-neuroendocrine-immune interactions. Equally important is the development of new technologies/ methodologies for determining the location, magnitude, and specificity of immune responses. Typically, these developments first surface in more “mainstream” immunological research arenas and are supported by a large number of commercially available products from a number of vendors. For example, during the past decade, advances in measuring T lymphocyte function both in vitro (tetramer analysis, intracellular cytokine staining) and in vivo (in vivo cytolysis and proliferation) have taken experimental immunology to a new level. These and other advances have been particularly supported by the development of multi-parameter/multi-color flow cytometric technology—technology that allows for the assessment of a wide variety of cell surface and intracellular phenotypic and functional lymphocyte markers on a single cell. These newer methods have been useful in both supplementing and, in some cases, replacing somewhat older immunological methods such as the 51 Cr release assay, ELISPOT, and ELISA. The use of microarray analyses as well as other genomic and proteomic methodologies will also continue to advance our knowledge of neuroimmunology. As a result of recent research efforts that have taken advantage of some of the above methods, the field of psychoneuroimmunology has been advanced to a higher level. However, it may also be important for investigators in psychoneuroimmunology to develop additional novel experimental strategies to examine the intricate inter-
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actions among the nervous, endocrine, and immune systems. One can only imagine what technological advances will be developed in the future and how these advances will propel our knowledge of all biological systems, including psychoneuroimmunology, to a new and exciting dimension. Along with some of these technological advances has already come additional knowledge which can be utilized in further advancing our understanding of stress-neuroendocrine-immune interactions. For example, the recent discovery of two distinct subsets of CD8+ memory T-cells, the effector and central memory T-cells (Lanzavecchia and Sallusto, 2005; Sallusto et al., 1999; Sallusto et al., 2004), provides a new avenue of study particularly in defining the effects of stress on the immune responses to intracellular pathogens such as HSV. The recent “re-birth” of the regulatory T-cells (Treg) also begs the question of how stress-associated, neuroendocrine-derived hormones and peptides regulate immune function by acting through these Treg cells. Even the recent discovery of at least seven individual dendritic cell subsets in mice (Kelsall et al., 2002; Serbina et al., 2003) provides a challenge to determine the neuroendocrine effects on their number and function. In the case of studies of HSV, additional details on the structure and function of the virion itself, including viral gene expression and virus particle maturation, assembly, egress, and infection of other cells of various origins, may be useful in our understanding of how stress affects the immune response to HSV infection. Overall, the emerging technologies in each of the fields related to psychoneuroimmunology will contribute to our understanding of the relationship among the nervous, endocrine, and immune systems. The information presented in this chapter has focused exclusively on the effects of stress on HSV infection. However, it is important to remember that stress and its associated neuroendocrine products represent only one of many factors that can modulate immune function and, thus, one’s susceptibility to HSV infection. Therefore, other products of the nervous and endocrine systems, such as those associated with gender and metabolic disease conditions (e.g., diabetes), should be evaluated for their effects on immune function. The impact of genetics on neuroendocrineimmune interactions also remains a largely unexplored area that could have a significant impact on our overall understanding of the effects of stress on anti-viral immunity. Technological advances in the areas of genomics and proteomics also provide an impetus to better understanding the relationship among psychological stress, neuroendocrine activation, and immune function.
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C. Stress-Neuroendocrine-Immune Interactions—The Challenges of Conducting Interdisciplinary Research The contents of this chapter, and others throughout this volume, center around the theme of interdisciplinary research. Such research is critical to fully understand the functioning of the nervous, endocrine, and immune systems since each of these systems obviously do not exist autonomously within the body. However, we are also quite aware that, in some venues, educating students in the structure and function of the immune system is often attempted without ever mentioning the potential influence of both the nervous and endocrine systems. This deficit in the teaching of immunology is a function of the fact that most modern immunology textbooks never discuss, or even mention, the concept of neuroendocrine-immune interactions. Indeed, the teaching and study of immunology from an autonomous perspective are alone a formidable challenge given its complexity. Moreover, this challenge often extends from the classroom into the research laboratory. However, the authors of the chapters within this volume (i.e., the “students and scholars of psychoneuroimmunology”) have embraced this challenge in their research endeavors and have attempted to educate the research personnel in their laboratories on the many components and functions of the immune system from a neuroendocrine-immune perspective. The rapidly expanding field of psychoneuroimmunology and its foundational disciplines of neuroscience and immunology (among others) significantly adds to the challenge of conducting state-of-the-art research in this exciting and relatively new area of research. Even incorporating a specific pathogen (e.g., HSV, influenza virus, Theiler’s virus, human immunodeficiency virus [HIV]) or disease (e.g., autoimmunity, allergy, cancer) adds another level of complexity to the many difficult equations that psychoneuroimmunologists are attempting to solve. However, at the same time, these individuals have recognized that the breadth and depth of each of the various disciplines that comprise the field of psychoneuroimmunology perhaps challenge both their ability to fully comprehend or, at the very least, to remain up-to-date in their knowledge in each of these disciplines. As a result, some of these “students and scholars” have formed scientific partnerships at both the local, national, and international levels. It is these partnerships, and the resulting collaborative research efforts, that will be instrumental in further advancing the highly interdisciplinary and integrated field of psychoneuroimmunology.
X. CONCLUDING REMARKS Much has been learned about how various components of immune function serve to either eliminate or control many viral infections. Although a role for most components of the immune response have been shown to contribute to the control of HSV, how each of these components function in a coordinated fashion to prevent and/or eliminate HSV infections remains to be fully elucidated. This is particularly true as the components of the immune system become better defined (e.g., subsets of T helper cells and memory CD8+ T-cells), enjoy renewed attention (e.g., regulatory T-cells), or are dissected at a molecular level (e.g., Tcell activation). New methodologies in detecting and quantifying antigen-specific immune responses will also make it possible to better define the components of the immune system that are activated in response to HSV infection and their roles in either preventing or, in some cases, eliciting the pathology that is associated with HSV infections. Together, an increased knowledge of both innate and adaptive immune components will also allow us to further define the relationship between psychological stress and the interactions among the nervous, endocrine, and immune systems. The impact of stress on the immune response to and pathogenesis of HSV infection represents only one small component of the widespread interest and need to decipher the cellular and molecular mechanisms underlying stress-neuroendocrine-immune interactions. A better understanding of these mechanisms will allow us to understand this relationship as it pertains to other diseases that may be immunologically resisted, such as those caused by various pathogenic microorganisms or malignant diseases.
References Ahmed, R. (1994). Viral persistence and immune memory. Semin. Virol., 5, 319–324. Anglen, C. S., Truckenmiller, M. E., Schell, T. D., and Bonneau, R. H. (2003). The dual role of CD8+ T lymphocytes in the development of stress-induced herpes simplex virus encephalitis. J. Neuroimmunol., 140, 13–27. Ashley, R., Wald, A., and Corey, L. (1994). Cervical antibodies in patients with oral herpes simplex virus type-1 (HSV-1) infection: local anamnestic responses after genital HSV-2 infection. J. Virol., 68, 5284–5286. Bailey, M., Engler, H., Hunzeker, J., and Sheridan, J. F. (2003). The hypothalamic-pituitary-adrenal axis and viral infection. Viral Immunol., 16, 141–157. Bierman, S. M. (1983). A proposed biologic cure for recurrent genital herpes simplex through injection of neurolytic agents into cutaneous sensory nerves. Med. Hypotheses, 10, 97–103.
50. Stress-induced Modulation of the Immune Response to Herpes Simplex Virus Infections Biron, C. A., Byron, K. S., and Sullivan, J. L. (1989). Severe herpesvirus infections in an adolescent without natural killer cells. N. Engl. J. Med., 320, 1731–1735. Block, T. M., and Hill, J. M. (1997). The latency associated transcripts (LAT) of herpes simplex virus: still no end in sight. J. Neurovirol., 3, 313–321. Blyth, W. A., and Hill, T. J. (1984). Establishment, maintenance, and control of herpes simplex virus (HSV). Latency. In B.T. Rouse and C. Lopez (Eds.), Immunobiology of herpes simplex virus infection (pp. 9–32). Boca Raton, FL: CRC Press. Bonneau, R. H. (1996). Stress-induced effects on integral immune components involved in herpes simplex virus (HSV)-specific memory cytotoxic T lymphocyte activation. Brain, Behav. Immun., 10, 139–163. Bonneau, R. H., Brehm, M. A., and Kern, A. M. (1997). The impact of psychological stress on the efficacy of anti-viral adoptive immunotherapy in an immunocompromised host. J. Neuroimmunol., 78, 19–33. Bonneau, R. H., and Jennings, S. R. (1989). Modulation of acute and latent herpes simplex virus infection in C57BL/6 mice by adoptive transfer of immune lymphocytes with cytolytic activity. J. Virol., 63, 1480–1484. Bonneau, R. H., Padgett, D. A., and Sheridan, J. F. (2001). Psychoneuroimmune interactions in infectious disease: studies in animals. In R. Ader, D. L. Felten, and N. Cohen (Eds.), Psychoneuroimmunology (3rd ed., pp. 483–497). San Diego: Academic Press. Bonneau, R. H., Sheridan, J. F., Feng, N., and Glaser, R. (1991a). Stress-induced effects on cell-mediated innate and adaptive memory components of the murine immune response to local and systemic herpes simplex virus (HSV) infection. Brain, Behav. Immun., 5, 274–295. Bonneau, R. H., Sheridan, J. F., Feng, N., and Glaser, R. (1991b). Stress-induced suppression of herpes simplex virus (HSV)specific cytotoxic T lymphocyte and natural killer cell activity and enhancement of acute pathogenesis following local HSV infection. Brain, Behav. Immun., 5, 170–192. Bonneau, R. H., Sheridan, J. F., Feng, N., and Glaser, R. (1993). Stressinduced modulation of the primary cellular immune response to herpes simplex virus infection is mediated by both adrenaldependent and adrenal-independent mechanisms. J. Neuroimmunol., 42, 167–176. Bonneau, R. H., Zimmerman, K. M., Ikeda, S. C., and Jones, B. C. (1998). Differential effects of stress-induced adrenal function on components of the herpes simplex virus-specific memory cytotoxic T lymphocyte response. J. Neuroimmunol., 82, 199– 207. Brenner, G. J., and Moynihan, J. A. (1997). Stressor-induced alterations in immune response and viral clearance following infection with herpes simplex virus-type 1 in BALB/c and C57BL/6 mice. Brain, Behav. Immun., 11, 9–23. Brown, Z. A., Benedetti, J., Ashley, R., Burchett, S., Selke, S., Berry, S., Vontver, L. A., and Corey, L. (1991). Neonatal herpes simplex virus infection in relation to asymptomatic maternal infection at the time of labor. N. Engl. J. Med., 324, 1247–1252. Bukowski, J. F., and Welsh, R. M. (1986). The role of natural killer cells and interferon in resistance to acute infection of mice with herpes simplex virus type 1. J. Immunol., 136, 3481–3485. Burns, V. E., Drayson, M., Ring, C., and Carroll, D. (2002). Perceived stress and psychological well-being are associated with antibody status after meningitis C conjugate vaccination. Psychosom. Med., 64, 963–970. Buske-Kirschbaum, A., Geiben, A., Wermke, C., Pirke, K. M., and Hellhammer, D. (2001). Preliminary evidence for Herpes labialis
1093
recurrence following experimentally induced disgust. Psychother. Psychosom., 70, 86–91. Cacioppo, J. T., Kiecolt-Glaser, J. K., Malarkey, W. B., Laskowski, B. F., Rozlog, L. A., Poehlmann, K. M., Burleson, M. H., and Glaser, R. (2002). Autonomic and glucocorticoid associations with the steady-state expression of latent Epstein-Barr virus. Hormones Behav., 42, 32–41. Carr, D. J., Noisakran, S., Halford, W. P., Lukacs, N., Asensio, V., and Campbell, I. L. (1998). Cytokine and chemokine production in HSV-1 latently infected trigeminal ganglion cell cultures: effects of hyperthermic stress J. Neuroimmunol., 85, 111–121. Cohen, S., Doyle, W. J., and Skoner, D. P. (1999). Psychological stress, cytokine production, and severity of upper respiratory illness. Psychosom. Med., 61, 175–180. Cohen, S., Line, S., Manuck, S. B., Rabin, B. S., Heise, E. R., and Kaplan, J. R. (1997). Chronic social stress, social status, and susceptibility to upper respiratory infections in nonhuman primates. Psychosom. Med., 59, 213–221. Cruess, S. M., Antoni, M., Cruess, D., Fletcher, M. A., Ironson, G., Kumar, M., Lutgendorf, S., Hayes, A., Klimas, N., and Schneiderman, N. (2000). Reductions in herpes simplex virus type 2 antibody titers after cognitive behavioral stress management and relationships with neuroendocrine function, relaxation skills, and social support in HIV-positive men. Psychosom. Med., 62, 828–837. Daigle, J., and Carr, D. J. (1998). Androstenediol antagonizes herpes simplex virus type 1–induced encephalitis through the augmentation of type I IFN production. J. Immunol., 160, 3060–3066. Davis, J. M., Murphy, E. A., Brown, A. S., Carmichael, M. D., Ghaffar, A., and Mayer, E. P. (2004). Effects of oat beta-glucan on innate immunity and infection after exercise stress. Medicine and Science in Sports and Exercise, 36, 1321–1327. de Groot, J., Moonen-Leusen, H. W., Thomas, G., Bianchi, A. T., Koolhaas, J. M., and van Milligen, F. J. (1999a). Effects of mild stress on the immune response against pseudorabies virus in mice. Vet. Immunol. Immunopathol., 67, 153–160. de Groot, J., van Milligen, F. J., Moonen-Leusen, B. W., Thomas, G., and Koolhaas, J. M. (1999b). A single social defeat transiently suppresses the anti-viral immune response in mice. J. Neuroimmunol., 95, 143–151. DeLano, R. M., and Mallery, S. R. (1998). Stress-related modulation of central nervous system immunity in a murine model of herpes simplex encephalitis. J. Neuroimmunol., 89, 51–58. Dhabhar, F. S., and McEwen, B. S. (1997). Acute stress enhances while chronic stress suppresses cell-mediated immunity in vivo: a potential role for leukocyte trafficking. Brain, Behav. Immun., 4, 286–306. Dhabhar, F. S., and McEwen, B. S. (1999). Enhancing versus suppressive effects of stress hormones on skin immune function. Proc. Nat. Acad. Sci., USA, 96, 1059–1064. Dobbs, C. M., Feng, N., Beck, F. M., and Sheridan, J. F. (1996). Neuroendocrine regulation of cytokine production during experimental influenza viral infection: effects of restraint stress-induced elevation in endogenous corticosterone. J. Immunol., 157, 1870–1877. Dobbs, C. M., Vasquez, M., Glaser, R., and Sheridan, J. F. (1993). Mechanisms of stress-induced modulation of viral pathogenesis and immunity. J. Neuroimmunol., 48, 151–160. Doherty, P. C., Allan, W., Eichelberger, M., and Carding, S. R. (1992). Roles of α, β, and γ/δ T cell subsets in viral immunity. Ann. Rev. Immunol., 10, 123–151. Feng, N., Pagniano, R., Tovar, C. A., Bonneau, R. H., Glaser, R., and Sheridan, J. F. (1991). The effect of restraint stress on the kinetics,
1094
V. Psychoneuroimmunology and Pathophysiology
magnitude, and isotype of the humoral immune response to influenza virus infection. Brain Behav. Immun., 5, 370–382. Friedman, E., Katcher, A. H., and Brightman, V. J. (1977). Incidence of recurrent herpes labialis and upper respiratory infection: a prospective study of the influence of biological, social and psychological predictors. Oral Surg. Oral Med. Oral Pathol., 43, 873–878. Glaser R., Friedman, S. B., Smyth, J., Ader, R., Bijur, P., Brunell, P., Cohen, N., Krilov, L. R., Lifrak, S. T., Stone, A., and Toffler, P. (1999). The differential impact of training stress and final examination stress on herpesvirus latency at the United States Military Academy at West Point. Brain Behav. Immun., 13, 240–251. Glaser, R., and Kiecolt-Glaser, J. K. (1997). Chronic stress modulates the virus-specific immune response to latent herpes simplex virus type 1. Annal. Behav. Med., 19, 78–82. Glaser, R., and Kiecolt-Glaser, J. K. (1998). Stress-associated immune modulation: relevance to viral infections and chronic fatigue syndrome. Amer. J. Med., 105, 35S–42S. Glaser, R., Kiecolt-Glaser, J. K., Bonneau, R. H., Malarkey, W., and Hughes, J. (1992). Stress-induced modulation of the immune response to recombinant hepatitis B vaccine. Psychosom. Med., 54, 22–29. Glaser, R., Kiecolt-Glaser, J. K., Speicher, C. E., and Holliday, J. E. (1985). Stress, loneliness, and changes in herpesvirus latency. J. Behav. Med., 8, 249–260. Glaser R., Padgett, D. A., Litsky, M. L., Baiocchi, R. A., Yang, E. V., Chen, M., Yeh, P. E., Klimas, N. G., Marshall, G. D., Whiteside, T., Herberman, R., Kiecolt-Glaser, J., and Williams, M. V. (2005). Stress-associated changes in the steady-state expression of latent Epstein-Barr virus: implications for chronic fatigue syndrome and cancer. Brain Behav. Immun., 19, 91–103. Glaser, R., Rice, J., Sheridan, J., Fertel, R., Stout, J., Speicher, C., Pinsky, D., Kotur, M., Post, A., Beck, M., and Kiecolt-Glaser, J. K. (1987). Stress-related immune suppression: health implications. Brain Behav. Immun., 1, 7–20. Glaser, R., Sheridan, J. F., Malarkey, W. B., MacCallum, R. C., and Kiecolt-Glaser, J. K. (2000). Chronic stress modulates the immune response to a pneumococcal pneumonia vaccine. Psychosom. Med., 62, 804–807. Gray, D. (1993). Immunological memory. Ann. Rev. Immunol., 11, 49–77. Halford, W. P., Gebhardt, B. M., and Carr, D. J. (1996). Mechanisms of herpes simplex virus type 1 reactivation. J Virol. 70, 5051–5060. Harbour, D. A., Hill, T. J., and Blyth, W. A. (1983). Recurrent herpes simplex in the mouse: inflammation in the skin and activation of virus in the ganglia following peripheral stimulation. J. Gen. Virol., 64, 1491–1498. Hermann, G., Beck, F. M., and Sheridan, J. F. (1995). Stress-induced glucocorticoid response modulates mononuclear cell trafficking during an experimental influenza viral infection. J. Neuroimmunol., 56, 179–186. Hermann, G., Beck, F. M., Tovar, C. A., Malarkey, W. B., Allen, C., and Sheridan, J. F. (1994a). Stress-induced changes attributable to the sympathetic nervous system during experimental influenza viral infection in DBA/2 inbred mouse strain. J. Neuroimmunol., 53, 173–180. Hermann, G., Tovar, C. A., Beck, F. M., Allen, C., and Sheridan, J. F. (1993). Restraint stress differentially affects the pathogenesis of an experimental influenza viral infection in three inbred strains of mice. J. Neuroimmunol., 47, 83–94. Hermann, G., Tovar, C. A., Beck, F. M., and Sheridan, J. F. (1994b). Kinetics of glucocorticoid response to restraint stress and/or experimental influenza viral infection in two inbred strains of mice. J. Neuroimmunol., 49, 25–33.
Hill, T. J. (1985). Herpes simplex virus latency. In B. Roizman (Ed.), The herpesviruses (pp. 175–240). New York: Plenum. Hill, T. J., Blyth, W. A., and Harbour, D. A. (1978). Trauma to the skin causes recurrence of herpes simplex in the mouse. J. Gen. Virol., 39, 21–28. Hill, T. J., Blyth, W. A., Harbour, D. A., Berrie, E. L., and Tullo, A. B. (1983). Latency and other consequences of infection of the nervous system with herpes simplex virus. Prog. Brain Res., 59, 173–184. Holland, D. J., Miranda-Saksena, M., Boadle, R. A., Armati, P., and Cunningham, A. L. (1999). Anterograde transport of herpes simplex virus proteins in axons of peripheral human fetal neurons: an immunoelectron microscopy study. J. Virol., 73, 8503–8511. Hunzeker, J., Padgett, D. A., Sheridan, P. A., Dhabhar, F. S., and Sheridan, J. F. (2004). Modulation of natural killer cell activity by restraint stress during an influenza A/PR8 infection in mice. Brain Behav. Immun., 18, 526–535. Hurd, J., and Robinson, T. W. (1977). Herpes virus reactivation in a mouse model. J. Antimicrob. Chemother., 3, 99–106. Irwin, M., Costlow, C., Williams, H., Artin, K. H., Chan, C. Y., Stinson, D. L., Levin, M. J., Hayward, A. R., and Oxman, M. N. (1998). Cellular immunity to varicella-zoster virus in patients with major depression. J. Infect. Dis., 178 (Suppl 1), S104–108. Johnson, R. R., Storts, R., Welsh, Jr., T. H., Welsh, C. J., and Meagher, M. W. (2004). Social stress alters the severity of acute Theiler’s virus infection. J. Neuroimmunol., 148, 74–85. Jones, C. (2003). Herpes simplex virus type 1 and bovine herpesvirus 1 latency. Clin. Microbiol. Rev., 6, 79–95. Karp, J. D., Moynihan, J. A., and Ader, R. (1997). Psychosocial influences on immune responses to HSV-1 infection in BALB/c mice. Brain, Behav. Immun., 11, 47–62. Katcher, A. H., Brightman, V., Luborsky, L., and Ship, I. (1973). Prediction of the incidence of recurrent herpes labialis and systemic illness from psychological measurements. J. Dent Res., 52, 49–58. Kelsall, B. L., Biron, C. A., Sharma, O., and Kaye, P. M. (2002). Dendritic cells at the host-pathogen interface. Nat. Immunol., 3, 699–702. Kemeny, M. E., Cohen, F., Zegans, L. S., and Conant, M. A. (1989). Psychological and immunological predictors of genital herpes recurrence. Psychosom. Med., 51, 195–208. Khanna, K. M., Bonneau, R. H., Kinchington, P. R., and Hendricks, R. L. (2003). Herpes simplex virus-specific memory CD8+ T cells are selectively activated and retained in latently infected sensory ganglia. Immunity, 18, 593–603. Khanna, K. M., Lepisto, A. J., Decman, V., and Hendricks, R. L. (2004). Immune control of herpes simplex virus during latency. Curr. Opin. Immunol., 16, 463–469. Kiecolt-Glaser, J. K., Glaser, R., Gravenstein, S., Malarkey, W. B., and Sheridan, J. (1996). Chronic stress alters the immune response to influenza virus vaccine in older adults. Proc. Nat. Acad. Sci. USA, 93, 3043–3047. Koelle, D. M., and Corey, L. (2003). Recent progress in herpes simplex virus immunobiology and vaccine research. Clin. Microbiol. Rev., 16, 96–113. Koelle, D. M., Posavad, C. M., Barnum, G. R., Johnson, M. L., Frank, J. M., and Corey, L. (1998). Clearance of HSV-2 from recurrent genital lesions correlates with infiltration of HSVspecific cytotoxic T lymphocytes. J. Clin. Inves., 101, 1500– 1508. Koff, W. C., and Dunegan, M. A. (1986). Neuroendocrine hormones suppress macrophage-mediated lysis of herpes simplex virusinfected cells. J. Immun., 136, 705–709.
50. Stress-induced Modulation of the Immune Response to Herpes Simplex Virus Infections Konstantinos, A. P., and Sheridan, J. F. (2001). Stress and influenza viral infection: modulation of proinflammatory cytokine responses in the lung. Respir. Physiol., 128, 71–77. Kriesel, J. D., Gebhardt, B. M., Hill, J. M., Maulden, S. A., Hwang, I. P., Clinch, T. E., Cao, X., Spruance, S. L., and Araneo, B. A. (1997). Anti-interleukin-6 antibodies inhibit herpes simplex virus reactivation. J. Infect. Dis., 175, 821–827. Kusnecov, A. V., Grota, L. J., Schmidt, S. G., Bonneau, R. H., Sheridan, J. F., Glaser, R., and Moynihan, J. A. (1992). Decreased herpes simplex virus immunity and enhanced pathogenesis following stressor administration in mice. J. Neuroimmunol., 38, 129–138. Lanzavecchia, A., and Sallusto, F. (2005). Understanding the generation and function of memory T cell subsets. Curr. Opin. Immunol., 17, 326–332. Larson, M. R., Ader, R., and Moynihan, J. A. (2001). Heart rate, neuroendocrine, and immunological reactivity in response to an acute laboratory stressor. Psychosom. Med., 63, 493–501. Laudenslager, M. L., Rasmussen, K. L., Berman, C. M., Lilly, A. A., Shelton, S. E., Kalin, N. H., and Suomi, S. J. (1999). A preliminary description of responses of free-ranging rhesus monkeys to brief capture experiences: behavior, endocrine, immune, and health relationships. Brain Behav. Immun., 13, 124–137. Leo, N. A., and Bonneau, R. H. (2000a). Chemical sympathectomy alters cytotoxic T lymphocyte responses to herpes simplex virus infection. Annal. New York Acad. Sci., 840, 803–808. Leo, N. A., and Bonneau, R. H. (2000b). Mechanisms underlying chemical sympathectomy-induced suppression of herpes simplex virus-specific cytotoxic T lymphocyte activation and function. J. Neuroimmunol., 110, 45–56. Leo, N. A., Callahan, T. A., and Bonneau, R. H. (1998). Peripheral sympathetic denervation alters both the primary and memory cellular immune response to herpes simplex virus infection. Neuroimmunomod., 5, 22–35. Liu, T., Khanna, K. M., Chen, X., Fink, D. J., and Hendricks, R. L. (2000). CD8(+) T cells can block herpes simplex virus type 1 (HSV-1) reactivation from latency in sensory neurons. J. Exp. Med., 191, 1459–1466. Longo, D. J., and Clum, G. A. (1989). Psychosocial factors affecting genital herpes recurrences: linear vs mediating models. J. Psychosom Res., 33, 161–166. Mackay, C. R. (1993). Immunological memory. Adv. Immunol., 53, 217–265. Mehta, S. K., Cohrs, R. J., Forghani, B., Zerbe, G., Gilden, D. H., and Pierson, D. L. (2004). Stress-induced subclinical reactivation of varicella zoster virus in astronauts. J. Med. Virol., 72, 174–179. Mehta, S. K., Pierson, D. L., Cooley, H., Dubow, R., and Lugg, D. (2000a). Epstein-Barr virus reactivation associated with diminished cell-mediated immunity in Antarctic expeditioners. J. Med. Virol., 61, 235–240. Mehta, S. K., Stowe, R. P., Feiveson, A. H., Tyring, S. K., and Pierson, D. L. (2000b). Reactivation and shedding of cytomegalovirus in astronauts during spaceflight. J. Infect. Dis., 182, 1761–1764. Mi, W., Belyavskyi, M., Johnson, R. R., Sieve, A. N., Storts, R., Meagher, M. W., and Welsh, C. J. (2004). Alterations in chemokine expression following Theiler’s virus infection and restraint stress. J. Neuroimmunol., 151, 103–115. Miller, G. E., Cohen, S., Pressman, S., Barkin, A., Rabin, B. S., and Treanor, J. J. (2004). Psychological stress and antibody response to influenza vaccination: when is the critical period for stress, and how does it get inside the body? Psychosom. Med., 66, 215–223. Morahan, P. S., and Morse, S. (1979). Macrophage-virus interactions. In M. Proffitt (Ed.), Virus-lymphocyte interactions: implications for disease (pp. 17–35). New York: Elsevier.
1095
Moynihan, J. A., and Ader, R. (1996). Psychoneuroimmunology: animal models of disease. Psychosom. Med., 58, 546–558. Moynihan, J. A., and Stevens, S. Y. (2001). Mechanisms of stressinduced modulation in animals In R. Ader, D. L. Felten, and N. Cohen (Eds.), Psychoneuroimmunology (3rd ed., pp. 227–250). San Diego: Academic Press. Nair, A., and Bonneau, R. H. (2006). Stress-induced elevation of glucocorticoids increases microglia proliferation through NMDA receptor activation. J. Neuroimmunol., 171, 72–85. Noisakran, S., Halford, W. P., and Carr, D. J. (1998). Role of the hypothalamic pituitary adrenal axis and IL-6 in stress-induced reactivation of latent herpes simplex virus type 1. J. Immunol., 160, 5441–5447. Ortiz, G. C., Sheridan, J. F., and Marucha, P. T. (2003). Stress-induced changes in pathophysiology and interferon gene expression during primary HSV-1 infection. Brain Behav. Immun., 17, 329–338. Padgett, D. A., MacCallum, R. C., and Sheridan, J. F. (1998a). Stress exacerbates age-related decrements in the immune response to an experimental influenza viral infection. J. Gerontol. A Biol. Sci. Med. Sci., 53, B347–353. Padgett, D. A., Sheridan, J. F., Dorne, J., Berntson, G. G., Candelora, J., and Glaser, R. (1998b). Social stress and the reactivation of latent herpes simplex virus type 1. Proc. Natl. Acad. Sci. USA, 95, 7231–7235. Pamer, E. G. (1993). Cellular immunity to intracellular bacteria. Curr. Opin. Immunol., 5, 492–496. Pariante, C. M., Carpiniello, B., Orru, M. G., Sitzia, R., Piras, A., Farci, A. M., DelGiacco, G. S., Piludu, G., and Miller, A. H. (1997). Chronic caregiving stress alters peripheral blood immune parameters: the role of age and severity of stress. Psychother. Psychosom., 66, 199–207. Pereira, D. B., Antoni, M. H., Danielson, A., Simon, T., Efantis-Potter, J., Carver, C. S., Duran, R. E., Ironson, G., Klimas, N., Fletcher, M. A., and O’Sullivan, M. J. (2003). Stress as a predictor of symptomatic genital herpes virus recurrence in women with human immunodeficiency virus. J. Psychosom. Res., 54, 237– 244. Pinto, A. J., Stewart, D., van Rooijen, N., and Morahan, P. S. (1991). Selective depletion of liver and splenic macrophages using liposomes encapsulating the drug dichloromethylene diphosphonate: effects on antimicrobial resistance. J. Leukoc. Biol., 49, 579–586. Ramsey, J. M. (1982). Basic pathophysiology: modern stress and the disease process (pp. 30–73). Menlo Park, CA: Addison-Wesley. Rasmussen, A. F., Marsh, J. T., and Brill, N. O. (1957). Increased susceptibility to herpes simplex in mice subjected to avoidancelearning stress or restraint. Proc. Soc. Exp. Biol. Med., 96, 183–189. Rinaldo, C. R., and Torpey, D. J. (1993). Cell-mediated immunity and immunosuppression in herpes simplex virus infection. Immunodef., 5, 33–90. Roizman, B., and Whitley, R. J. (2001). The nine ages of herpes simplex virus. Herpes., 8, 23–27. Sallusto, F., Geginat, J., and Lanzavecchia, A. (2004). Central memory and effector memory T cell subsets: function, generation, and maintenance. Ann. Rev. Immunol., 22, 745–763. Sallusto, F., Lenig, D., Forster, R., Lipp, M., and Lanzavecchia, A. (1999). Two subsets of memory T lymphocytes with distinct homing potentials and effector functions. Nature, 401, 708–712. Sawtell, N. M. (1998). The probability of in vivo reaction herpes simplex virus type 1 increases with the number of latently infected neurons in the ganglia. J. Virol. 72, 6888–6892. Sawtell, N. M., and Thompson, R. L. (1992). Rapid in vivo reactivation of herpes simplex virus type 1 in latently infected murine
1096
V. Psychoneuroimmunology and Pathophysiology
ganglionic neurons after transient hyperthermia. J. Virol., 66, 2150–2156. Schmid, D. S., and Rouse, B. T. (1992). The role of T cell immunity in control of herpes simplex virus. Cur. Top. Microbiol. Immunol., 179, 57–74. Schmidt, D. D., Zyzanski, S., Ellner, J., Kumar, M. L., and Arno, J. (1985). Stress as a precipitating factor in subjects with recurrent herpes labialis. J. Fam. Pract., 20, 359–366. Serbina, N. V., Salazar-Mather, P. T., Biron, C. A., Kuziel, W. A., and Pamer. E. G. (2003). TNF/iNOS-producing dendritic cells mediate innate immune defense against bacterial infection. Immunity, 19, 59–70. Sher, A., and Coffman, R. L. (1992). Regulation of immunity to parasites by T cells and T cell-derived cytokines. Ann. Rev. Immunol., 10, 385–409. Sheridan, J. F., Dobbs, C., Jung, J., Chu, X., Konstantinos, A., Padgett, D., and Glaser, R. (1998). Stress-induced neuroendocrine modulation of viral pathogenesis and immunity. Annal. New York Acad. Sci., 840, 803–808. Sheridan, J. F., Feng, N. G., Bonneau, R. H., Allen, C. M., Huneycutt, B. S., and Glaser, R. (1991). Restraint stress differentially affects anti-viral cellular and humoral immune responses in mice. J. Neuroimmunol., 31, 245–255. Sheridan, J. F., Stark, J. L., Avitsur, R., and Padgett, D. A. (2000). Social disruption, immunity, and susceptibility to viral infection. Role of glucocorticoid insensitivity and NGF. Annal. N. Y. Acad. Sci., 917, 894–905. Sieve, A. N., Steelman, A. J., Young, C. R., Storts, R., Welsh, T. H., Welsh, C. J., and Meagher, M. W. (2004). Chronic restraint stress during early Theiler’s virus infection exacerbates the subsequent demyelinating disease in SJL mice. J. Neuroimmunol., 155, 103–118. Silver, P. S., Auerbach, S. M., Vishniavsky, N., and Kaplowitz, L. G. (1986). Psychological factors in recurrent genital herpes infection: stress, coping style, social support, emotional dysfunction, and symptom recurrence. J. Psychosom. Res., 30, 163–171. Sprent, J. (1994). T and B memory cells. Cell, 76, 315–322. Stanberry, L. R., Cunningham, A. L., Mindell, A., Scott, L. L., Spruance, S. L., Aoki, F. Y., and Lacey, C. J. (2000). Prospects for control of herpes simplex virus disease through immunization. Clin. Infect. Dis., 30, 549–566. Stevens, J. G. (1975). Latent herpes simplex virus and the nervous system. Curr. Top. Microbiol. Immunol., 70, 31–50. Stout, C. W., and Bloom L. J. (1986). Genital herpes and personality. J. Human Stress., 12, 119–124. Stowe, R. P., Pierson, D. L., and Barrett, A. D. (2001). Elevated stress hormone levels relate to Epstein-Barr virus reactivation in astronauts. Psychosom. Med., 63, 891–895. Stowe, R. P., Pierson, D. L., Feeback, D. L., and Barrett, A. D. (2000). Stress-induced reactivation of Epstein-Barr virus in astronauts. Neuroimmunomod., 8, 51–58. Thompson, R. L., and Sawtell, N. M. (1997). The herpes simplex virus and type 1 latency-associated transcript gene regulates the establishment of latency. J. Virol., 71, 5432–5440.
Truckenmiller, M. E., Princiotta, M. F., Norbury, C. C., and Bonneau, R. H. (2005). Corticosterone impairs MHC class I antigen presentation by dendritic cells via reduction of peptide generation. J. Neuroimmunol., 160, 48–60. VanderPlate, C., Aral, S. O., and Magder, L. (1988). The relationship among genital herpes simplex virus, stress, and social support. Health Psychol., 7, 159–168. Vedhara, K. Cox, N. K., Wilcox, G. K., Perks, P., Hunt, M., Anderson, S., Lightman, S. L., and Shanks, N. M. (1999). Chronic stress in elderly caregivers of dementia patients and antibody response to influenza vaccination. Lancet, 353, 627–631. Wald, A., Corey, L., Cone, R., Hobson, A., Davis, G., and Zeh, J. (1997). Frequent genital herpes simplex virus 2 shedding in immunocompetent women: effect of acyclovir treatment. J. Clin. Invest., 99, 1092–1097. Wald, A., Zeh, J., Selke, S., Ashley, R. L., and Corey, L. (1995). Virologic characteristics of subclinical and symptomatic genital herpes infections. N. Eng. J. Med., 333, 770–775. Welsh, C. J., Bustamante, L., Nayak, M., Welsh, T. H., Dean, D. D., and Meagher, M. W. (2004). The effects of restraint stress on the neuropathogenesis of Theiler’s virus infection II: NK cell function and cytokine levels in acute disease. Brain Behav. Immun., 18, 166–174. Wonnacott, K. M., and Bonneau, R. H. (2002). The effects of stress on memory cytotoxic T lymphocyte (CTLm)-mediated protection against herpes simplex virus (HSV) infection at mucosal sites. Brain, Behav. Immun., 16, 104–117. Yorty, J. L., and Bonneau, R. H. (2003). Transplacental transfer and subsequent neonate utilization of herpes simplex virus-specific immunity is resilient to acute maternal stress. J. Virol., 77, 6613–6619. Yorty, J. L., and Bonneau, R. H. (2004a). Prenatal transfer of low amounts of herpes simplex virus (HSV)-specific antibody protects newborn mice against HSV infection during acute maternal stress. Brain, Behav. Immun., 18, 15–23. Yorty, J. L., and Bonneau, R. H. (2004b). The impact of maternal stress on the transmammary transfer and protective capacity of herpes simplex virus-specific immunity. Amer. J. Physiol. Regulat., Integrat. Compar. Physiol., 287, R1316–1324. Yorty, J. L., Schultz, S. A., and Bonneau, R. H. (2004). Postpartum maternal corticosterone decreases maternal and neonatal antibody levels and increases susceptibility of newborn mice to herpes simplex virus-associated mortality. J. Neuroimmunol., 150, 48–58. Young, E .J., Killam, A. P., and Greene, J. F., Jr. (1976). Disseminated herpesvirus infection. Association with primary genital herpes in pregnancy. JAMA, 235, 2731–2733. Zorrilla, E. P., Luborsky, L., McKay, J. R., Rosenthal, R., Houldin, A., Tax, A., McCorkle, R., Seligman, D. A., and Schmidt, K. (2001). The relationship of depression and stressors to immunological assays: a meta-analytic review. Brain Behav. Immun., 15, 199–226.
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51 Stress-induced Modulation of Innate Resistance and Adaptive Immunity to Influenza Viral Infection MICHAEL T. BAILEY, DAVID A. PADGETT, AND JOHN F. SHERIDAN
I. INTRODUCTION 1097 II. RODENT STRESSORS AND THE STRESS RESPONSE 1098 III. GLUCOCORTICOIDS, GLUCOCORTICOID RECEPTORS, AND LEUKOCYTES 1098 IV. IMPACT OF STRESS ON ANTI-INFLUENZA IMMUNITY 1099 V. ANTI-INFLAMMATORY GLUCOCORTICOID RESPONSE: FRIEND OR FOE? 1103 VI. SUMMARY 1103
immune cells, is significantly suppressed upon stressinduced elevation of the adrenal hormone corticosterone. Other measures of innate immunity, such as NK cell cytotoxicity, are not affected by corticosterone but, rather, are suppressed during restraint through an opioid-dependent mechanism. As the infection progresses, acquired immunity is needed to eliminate infectious virus from the host. Exposure to stress, however, significantly suppresses and delays the development of acquired immunity, including the Bcell antibody response, the production of T-cell–derived cytokines, and T-cell cytotoxicity. These effects are dependent upon stress-induced elevations in corticosterone (antibody and cytokine production), as well as stress-induced catecholamines (T-cell cytotoxicity). This approach to studying stressors and infections that have been extensively documented in the extant literature has provided valuable insight into the impact of these alterations on host health.
ABSTRACT Mind-body interactions affect multiple aspects of the immune response through behavioral, neural, and endocrine responses to stimuli. Many of the mechanisms through which this occurs have already been defined, but the overall impact on host health during infectious challenge has remained elusive. Thus, we have been using a well-established rodent stressor to experimentally activate stress-reactive neuroendocrine pathways to determine the impact on host resistance to influenza virus challenge. The series of studies presented in this chapter demonstrate that stress-induced elevations in corticosterone, as well as epinephrine and norepinephrine, affect the host response to influenza infection at all levels of the immune response. For example, the early inflammatory phase of infection, such as the production of pro-inflammatory cytokines and chemokines, as well as the trafficking of innate PSYCHONEUROIMMUNOLOGY, 4E VOLUME II
I. INTRODUCTION It is now common knowledge that mind-body interactions influence the ability of the immune system to respond to infectious challenge. This realization has led to efforts to identify points of intersection between the nervous, endocrine, and immune systems at the cellular and molecular levels. The many receptors and ligands shared by these systems have been shown to allow for bi-directional communication between
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systems. Because the immune system’s primary function is to protect the host from infectious challenge, many researchers have been studying how neuroendocrine hormones modulate the pathophysiology of acute viral infection. The most efficient way to study these systems is to do so when they are activated by external stimuli; thus studies of immune function are often carried out during states of stress-induced neuroendocrine activation. For example, studies in our laboratories have focused on a well-characterized rodent stressor, i.e., physical restraint, and a viral pathogen, i.e., influenza virus A/PR8, with wellcharacterized pathogenesis and anti-viral immunity. The studies outlined in this chapter illustrate the delicate balance that occurs between nervous, endocrine, and immune system functioning during stressful and quiescent periods.
II. RODENT STRESSORS AND THE STRESS RESPONSE Mammalian responses to stressors have been studied for over 100 years, and it is now known that, when organisms encounter potentially threatening stimuli, an integrated physiological and behavioral response to the stimulus occurs. The stress response begins when stimuli are appraised as being benign or potentially harmful. Benign stimuli can simply be ignored and no response ensues. However, if the stimuli are appraised as threatening, the adaptive capacity of the individual is assessed in terms of whether the organism is able to cope with the demand. If the demands are appraised as exceeding coping resources, the demands will be perceived as taxing or “stressful,” and behavioral and physiological responses to the demand will follow. Within this framework, a stressor is defined as a stimulus that disrupts homeostasis, while the physiological and behavioral responses to that stressor are referred to as the stress response. The stress response is regulated by the hypothalamus, which integrates inputs from many different cortical and subcortical brain regions. Although many behavioral and physiological responses to the stressor may ensue, the two main physiological responses to stressors involve activation of the hypothalamicpituitary-adrenal (HPA) axis and the sympathetic nervous system (SNS). Plasma levels of glucocorticoid hormones, namely cortisol in human and non-human primates and corticosterone in rodents, are significantly elevated during the stress response as a result of HPA activation; plasma and tissue levels of catecholamines, i.e., epinephrine and norepinephrine, are
elevated upon activation of the SNS. Over the past 15 years, research in this laboratory has primarily been focused on the role of glucocorticoids in immunoregulation during influenza viral infection, with some studies examining the role of catecholamines. To experimentally elevate glucocorticoid levels, mice are placed into well-ventilated, 50-millimeter conical tubes for 12–18 hours, on up to 10 consecutive days during their active phase. Although this model is not as ethologically sensitive as some other murine stressors, it has been very useful in dissecting the impact of stressinduced glucocorticoids on immune functioning, because it results in reproducible elevations in corticosterone. For example, restraining mice for 12 hours during the active cycle reproducibly increases plasma corticosterone levels approximately five-fold in comparison to non-stress values (Hermann et al., 1994; Padgett and Sheridan, 1999; Sheridan et al., 1991). This effect is evident after a single cycle of restraint and does not habituate after repeated cycles (Padgett and Sheridan, 1999). Infection during this stressor further increases glucocorticoid levels (Hermann et al., 1994; Sheridan et al., 1991), illustrating the bi-directional communications between the immune and nervous systems.
III. GLUCOCORTICOIDS, GLUCOCORTICOID RECEPTORS, AND LEUKOCYTES Glucocorticoids exert their actions by binding to cytoplasmic receptors in target tissues. The activated receptor translocates to the nucleus, where it acts as a ligand-dependent transcription factor to modulate the expression of glucocorticoid-responsive genes (Bamberger and Chrousos, 1995; Hache et al., 1999) or modifies the activity of other transcription factors, such as NF-κB or AP-1 (Ashwell et al., 2000; Scheinman et al., 1995). There are two types of glucocorticoid receptors. The type I glucocorticoid receptor has a sixfold to ten-fold higher affinity for glucocorticoid hormones and, thus, is occupied even when glucocorticoid levels are relatively low. The type II receptor, on the other hand, is occupied only when glucocorticoid levels are elevated, such as after a stress response. Interestingly, both subclasses of corticosteroid receptors are widely expressed on cells of the immune system, but their level of expression is markedly different depending upon leukocyte subtype. Monocytes, for example, have relatively high levels of type II receptors, but neutrophils express low numbers. Lymphocytes have an intermediate expression of type II
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receptors but also express type I receptors (Bailey et al., 2003; McEwen et al., 1997). This chapter will discuss the antiviral immune response to influenza, which is heavily dependent upon monocytes, NK cells, and T and B lymphocytes. Given that all these cell types express receptors for glucocorticoids, it is not surprising that stress-induced HPA activation noticeably affects immune cell function.
IV. IMPACT OF STRESS ON ANTI-INFLUENZA IMMUNITY A. Influenza Virus Background Influenza viral infection is a leading global cause of morbidity and mortality. In the U.S. alone, 20–30 thousand people will die from influenza viral infection each year, with significant illness occurring in countless others. This may seem somewhat surprising, given that there are several commercially available vaccines. However, it is now known that people undergoing chronic stress do not always mount protective antibody responses upon vaccination. For example, human studies of chronic stress, in which the subjects were caring for spouses with dementia, demonstrated that chronically stressed caregivers responded less well to a number of different commercially prepared vaccines (Glaser et al., 1998; Glaser et al., 2000; Kiecolt-Glaser et al., 1996). The percentage of caregivers who seroconverted (defined as a four-fold rise in antibody titers determined by ELISA and HAI) was lower than controls at 1 month post-vaccination. Moreover, the IL-2 responses of peripheral blood lymphocytes from controls stimulated with influenza vaccine antigen was significantly higher at 30, 90, and 180 days postvaccination in comparison to the caregiver subjects (Kiecolt-Glaser et al., 1996). These human studies have provided copious amounts of data on how adverse life events can affect immune functioning. However, sufficient data have not been available to assess the state of protective immunity in naturally acquired influenza virus infection in stressed human subjects, leading to the development of animal models of stress and infection. We have used influenza virus A/Puerto Rico/ 8/ 34 (A/ PR8) because infection with this virus results in a respiratory disease that is well characterized, with innate and adaptive immune responses that have been clearly described in the extant murine literature. Thus, our strategy has been to combine this viral infection with restraint stress to produce data on the impact of stress-induced neruoendocrine activation on viral pathogenesis and anti-viral immunity.
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B. Stress-induced Alterations in the Innate Immune Response to Influenza Viral Infection The influenza A/PR8 virus enters the body through the respiratory tract by attaching to respiratory epithelial cells (Matrosovich et al., 2004). After attachment to the host cell, the virus is endocytosed, with uncoating of the genetic material (eight single-stranded RNA molecules) occurring in the endosome. This release of the genetic material stimulates toll-like receptors (primarily TLR-3, TLR-7, and TLR-9) (Barchet et al., 2005; Hornung et al., 2004; Lund et al., 2004) that trigger the initial inflammatory response. The first host response to occur is the production of type 1 interferons (IFN), IFN-α and IFN-β, which cause neighboring cells to destroy RNA molecules and shut down protein synthesis, ultimately halting viral replication. In mice infected with influenza A/PR8, gene expression for IFN-α and IFN-β was detected in the lungs as early as 1 day post-infection, with peak expression occurring between days 3 and 7 post-infection. This expression was significantly increased when the mice were exposed to restraint stress during infection. The expression of IFN-α and IFN-β in the lungs of restrained mice was over five-fold higher than the expression in the non-stressed infected controls on day 7 post-infection (Hunzeker et al., 2004). This finding was confirmed in a separate study using high-density oligonucleotide microarrays to demonstrate a significant increase in IFN-β in mice restrained during influenza infection (Engler et al., 2005a). Interestingly, the expression of the influenza virus matrix gene, M1, which was used as a surrogate measure of viral replication, was significantly higher in the lungs of mice exposed to restraint in comparison to the non-stressed infected controls on day 5 post-infection (Hunzeker et al., 2004). Thus, it is possible that the stress-induced increase in type 1 IFN gene expression on day 7 post-infection was in response to higher viral titers and not due to a direct effect of the stressor on cytokine-producing cells. Regardless of whether the effect is direct or indirect, it is evident that restraint stress affects the initial inflammatory response in the lungs to an influenza viral infection. As the inflammatory response to viral infection progresses, a variety of leukocytes (i.e., macrophages, NK cells, and B and T lymphocytes) traffic to and infiltrate the lungs and regional draining lymph nodes (both the cervical and mediastinal lymph nodes). Proinflammatory cytokines, such as IL-1α and TNF-α, play key roles in the infiltration of these leukocytes into infected tissue by inducing the development of a
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reactive endothelium. In response to these pro-inflammatory cytokines, endothelial cells that line the blood vessels adjacent to the site of viral replication augment their expression of intracellular adhesion molecule-1 (ICAM-1) and vascular adhesion molecule-1 (VCAM1) (McHale et al., 1999; Strieter et al., 2003). Because these molecules are expressed on the circulatory side of the blood vessels, cells in the general circulation that express the appropriate ligands become tethered to the vessel wall. Once tethered, exposure to proinflammatory cytokines induces these cells to express chemokine receptors (Rosseau et al., 2000; Weber et al., 1999a; Weber et al., 1999b). This is an important step in the inflammatory response, allowing the tethered cells to maturate and leave the circulation to migrate toward the loci of infection. This migration is directed by chemokines (the secretion of which produces a chemotactic gradient) that emanate from the point of infection (Nieto et al., 1999; Randolph and Furie, 1995). An influenza viral infection results in the secretion of multiple chemokines, including MIP-1α, MIP-1β, RANTES, MCP-1, MCP-3, MIP-3α, and IP-10 (Julkunen et al., 2000; Kaufmann et al., 2001), to initially recruit macrophages and NK cells into the tissue parenchyma, where viral replication is occurring. This inflammatory response is important in controlling early viral replication but also in setting the stage for an optimal adaptive response that ultimately will resolve the infection. Restraint stress had a dramatic effect on several aspects of this initial inflammatory response to influenza viral infection. Interleukin-1α levels in the lungs of infected, non-stressed mice were significantly elevated within 48 hours post-infection. Exposure to restraint stress during infection significantly reduced the IL-1α response in the lungs, to levels found in uninfected controls (Konstantinos and Sheridan, 2001). Interleukin-6 levels were also significantly elevated in the lungs of non-stressed, influenza-infected mice within 24 hours after infection with influenza virus. However, in contrast to IL-1α, IL-6 levels were not affected by exposure to restraint stress (Konstantinos and Sheridan, 2001), suggesting that there is a differential regulation of pro-inflammatory cytokines by stress-induced mediators, such that some cytokines (i.e., IL-1α) are altered during stress exposure, but other cytokines (i.e., IL-6) remain unaffected. Indeed, an additional study indicated that cells derived from the mediastinal lymph nodes of infected, restrained mice actually produced more IL-6 upon in vitro stimulation with influenza virus than did cells derived from non-stressed, infected controls. Treating the mice with the type II glucocorticoid receptor antagonist, RU486, abolished this effect (Dobbs et al., 1996), suggesting
that the increase was due to the effects of restraintinduced increases of glucocorticoid hormones. In addition to affecting the production of proinflammatory cytokines, restraint stress also significantly affected the expression of chemokines that recruit mononuclear and NK cells during influenza A/PR8 viral infection (Hunzeker et al., 2004). Infection of non-stressed mice with influenza A/PR8 resulted in a significant enhancement of the genes encoding for MIP-1α and MCP-1. This expression could be significantly decreased by exposure to restraint stress prior to influenza A/PR8 infection. In non-stressed, infected control mice, MCP-1 gene expression peaked on day 3 post-infection, with a nearly 400-fold increase in expression compared to uninfected controls. Restraint stress, however, significantly delayed peak expression until day 5 post-infection. Although the mean level of this peak expression was lower than in the controls (300- versus 400-fold increase in comparison to controls), this difference was not quite statistically significant (Hunzeker et al., 2004). A similar pattern of gene expression was evident when MIP-1α was investigated in the lungs. Infecting non-stressed control mice significantly increased the expression of MIP-1α. But here, the peak expression was bimodal with the initial peak occurring on day 3 post-infection and a second peak occurring on day 7. Again, exposure to restraint significantly delayed the peak expression of MIP-1α to day 5. No secondary peak was evident in the restrained mice. In addition to affecting the kinetics, peak expression levels were lower in the restrained mice in comparison to the nonstressed controls (40- versus 70-fold increase, respectively) (Hunzeker et al., 2004). These studies indicating that restraint stress affected the production of pro-inflammatory cytokines and chemokines were consistent with previous results showing that restraint stress also reduced cellularity in the lungs and draining lymph nodes during influenza A/PR8 infection (Hermann et al., 1995; Sheridan et al., 1991). During an influenza viral infection, an interstitial pneumonia develops that is characterized by the presence of inflammatory cells in the lung parenchyma. These cells are primarily macrophages and T lymphocytes (Beck and Sheridan, 1989), but NK cells also traffic to the site of infection and play a prominent role in limiting viral replication. Exposure to restraint stress during A/PR8 infection significantly reduced this inflammatory response in the lungs 7 days postinfection, as indicated by significantly reduced infiltration of mononuclear cells, alveolar hemorrhage, and lung consolidation (Sheridan et al., 1991). Inflammation and cell trafficking during influenza viral infection is not limited to the lungs. In fact, mice
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infected with influenza A/PR8 show a pronounced lymphadenopathy in the mediastinal lymph nodes during the week following infection. As with trafficking to the lungs, exposure to restraint stress during influenza A/PR8 infection significantly diminished the trafficking of cells to the mediastinal lymph nodes (reducing the development of lymphadenopathy) (Hermann et al., 1995). This effect proved to be dependent upon stress-induced elevations in corticosterone, since treating the mice with the type II glucocorticoid receptor antagonist RU486 restored the development of lymphadenopathy (Hermann et al., 1995). Although the primary cells trafficking to the lungs and lymph nodes during influenza infection are macrophages and T lymphocytes, NK cells also traffic to loci of infection and play an important role in the early innate defense. And, infecting mice with influenza A/ PR8 results in a significant increase in the number of NK cells found in the lungs. Peak NK cell numbers occur 1 day post-infection with a return to baseline by 5 days post-infection (Hunzeker et al., 2004). Exposing mice to restraint during infection significantly reduced NK cell trafficking, such that there was no significant increase in the number of NK cells found in the lungs during infection (Hunzeker et al., 2004). In addition to affecting trafficking, restraint stress also suppressed the capacity of the lung-derived NK cells to kill target cells (Hunzeker et al., 2004). These effects were most likely due to a loss of regulatory signals provided by the cytokines IL-12 and IL-15. In the non-stressed, infected control mice, gene expression for IL-15 and IL-12 was significantly increased 1 and 3 days postinfluenza-infection, respectively. As hypothesized, the expression of these cytokines was significantly suppressed in the restrained mice (Hunzeker et al., 2004). In addition to reducing the number of NK cells that traffic to the lungs, restraint during influenza virus infection also reduced the number of NK cells found in the spleen on day 3 post-infection (Tseng et al., 2005). As with NK cells in the lung, cytotoxicity was significantly reduced in the spleens of restrained mice during influenza infection. Interestingly, administering RU486 to block the effects of stress-induced increases in corticosterone restored the trafficking of NK cells to the spleen, but NK cytotoxicity remained suppressed in the restrained mice (Tseng et al., 2005). Previous studies indicated that opioids, in addition to glucocorticoids, can affect NK functioning (Adelson et al., 1994; Carr and Serou, 1995; Carr et al., 1996a; Carr et al., 1996b; Fiatarone et al., 1988). Thus, additional studies were conducted in which opioid receptors were pharmacologically blocked using naltrexone. As hypothesized, blocking opioid receptors abolished
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the stress-induced decrease in NK cytotoxicity (Tseng et al., 2005). This was found to be specifically due to the actions on μ-opioid receptors, since blocking μ-, but not δ- or κ-opioid receptors, restored NK cytotoxicity (Tseng et al., 2005). It is currently unclear whether this effect on NK cells during an influenza infection is mediated centrally or peripherally, but it must be noted that centrally mediated mechanisms for opioidassociated modulation of immune function have been described (Mellon and Bayer, 1998a; Mellon and Bayer, 1998b; Nelson et al., 2000; Nelson and Lysle, 2001). Moreover, administration of the dopamine D2 receptor antagonist, 7-hydroxy-N, N-di-n-propyl-2aminotetralin (7-OH-DPAT), either centrally or peripherally abolished the suppressive effects of morphine on NK cell activity (Saurer et al., 2004). Thus, it is apparent that the effects of opioids on NK cell activity can be mediated by other neurotransmitter systems. Taken together, the data indicate that restraint stress alters three major components of natural resistance to viral infection: the proinflammatory cytokine response, the β-chemokine response, and the NK cell response. These responses were altered at the site of virus replication, as well as in secondary lymphoid tissues, and were primarily due to the activation of the HPA axis and the resultant increased levels of glucocorticoid and opioid hormones. Alterations in the initial inflammatory response not only affect the ability of the virus to replicate in respiratory epithelial cells but also affect the development of adaptive immunity linked to the microenvironment created by a successful innate response.
C. Stress-induced Alteration of the Adaptive Immune Response to Influenza Virus Infection Both T and B lymphocytes are involved in recovery from influenza infection and in protection against re-infection with the same strain of the virus. Unlike cells of the innate immune system that respond to generalized inflammatory stimuli, T- and B-cells are selected for activation based on their antigen specificity. As they arrive in the lymph nodes draining the influenza-infected lungs—i.e., the mediastinal, superficial cervical, and the deep cervical lymph nodes—the lymphocytes are driven to proliferate and mature so that they are competent to mediate their respective effector functions. It is here that the CD4+ helper T-cells, which are the first antigen-specific cells activated in response to influenza virus, help to drive the clonal expansion of CD8+ T-cells and the antibodyproducing B-cells. The immune response generated in the lymph nodes may vary dramatically depending on
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the type of antigen encountered and the microenvironment in which the antigen is processed and presented. If an antigen is encountered by the CD4+ cell in the presence of IL-12 and IFN-γ, naïve CD4+ cells differentiate into T helper 1 (Th1) cells that primarily produce IFN-γ, IL-2, and TNF-α (Deng et al., 2004). On the other hand, if the naïve CD4+ cells are activated in the presence of IL-4, Th2 cells will develop and produce IL-4, IL-5, and IL-13 (Oran and Robinson, 2004). Although both types of cells can be produced, viral infections such as influenza A/PR8 predominantly induce Th1 or type 1 immunity during infection (Cella et al., 2000; Lopez et al., 2001; Lopez et al., 2002). Clonal expansion of influenza virus–specific CD4+ T-cells of the Th1 subtype promotes the activation of cytotoxic CD8+ T-cells (Fonteneau et al., 2003). These antigen-specific CD8+ T-cells are responsible for terminating influenza replication through MHC class I-dependent cytotoxic mechanisms involving perforin and Fas (Topham et al., 1997). The Th1 CD4+ T-cells also drive B-cell differentiation and expansion into antibody-secreting plasma cells. Although antibodies play a minor role in terminating viral replication during a primary infection with influenza, the antigenspecific antibody response is a key component in longlasting virus-specific immunological memory. There are now several studies indicating that, in addition to affecting innate resistance to an influenza viral infection, restraint stress also modulates virusspecific T- and B-cell responses. For example, it was demonstrated that restraint stress during a primary A/PR8 infection significantly reduced the number of IL-2 secreting cells found in the mediastinal lymph nodes and spleen when compared to the number found in non-stressed, infected controls (Dobbs et al., 1996). Moreover, mononuclear cells from both the mediastinal lymph nodes and the spleen that were cultured and stimulated with A/PR8 antigen produced lower levels of Th1 cytokines (IL-2, IFN-γ, and IL-6) as well as Th2 cytokines (IL-10) if the mice were restrained during the influenza infection (Dobbs et al., 1996; Sheridan et al., 1991). Interestingly, this effect was abolished when the mice were given RU486, suggesting that the stress-induced effects on cytokine production were due to elevations in corticosterone (Dobbs et al., 1996). In fact, many of these effects of restraint could be reversed by administering the steroid hormone androstenediol (AED), which is thought to counteract the effects of corticosterone. Administering AED to mice exposed to restraint stress significantly suppressed corticosterone levels, restored the development of lymphadenopathy in draining lymph nodes, enhanced IFN-γ production, and elevated IL-10 gene expression on day 7 post-infection (Dobbs et al., 1996;
Padgett et al., 2000; Padgett and Sheridan, 1999). The importance of corticosterone in mediating these effects was further demonstrated by an in vitro experiment in which the addition of corticosterone to splenocyte cultures from mice infected with influenza A/PR8 significantly reduced virus-specific Th1 and Th2 type cytokines in a dose-dependent manner (Dobbs et al., 1996). Since the antibody response is largely dependent upon the cytokine environment during antigen stimulation of B-cells, it is not surprising that, in addition to affecting cytokine production, restraint stress also affects the humoral immune response to influenza virus. Overall, it does not appear that restraint affects either the isotype or the magnitude of the mature antibody response during the plateau phase (Feng et al., 1991; Sheridan et al., 1991). However, restraint stress does have significant effects on the kinetics of the antibody response. Influenza A/PR8 infection in nonstressed controls results in an antibody response characterized by a peak in IgM on day 14 that begins to decline by day 21. IgG reaches high levels by day 10 and plateaus through day 21 post-infection. This pattern is similar for IgA levels that reach high plateau levels by 14 days (Feng et al., 1991). Exposure to restraint stress during influenza A/PR8 infection significantly affected the kinetics, such that IgM levels peaked on day 10 and then returned to baseline levels by day 21. The kinetics for the IgG and IgM responses were delayed, and high plateau levels were not reached until day 14 (IgG) or day 21 (IgA). However, the restraint did not affect the plateau levels of antibodies (Feng et al., 1991). Thus, there is now ample evidence that the adaptive immune response to influenza A/PR8 infection is significantly affected by restraining the mice during infection. As with the innate response to influenza, trafficking of lymphocytes and the production of proinflammatory cytokines are reduced by the restraintinduced elevations in corticosterone. However, it is likely that the sympathetic nervous system also plays a role in alterations of adaptive immunity during stress. An initial study involving herpes simplex virus (HSV) infection of adrenalectomized mice clearly demonstrated that adrenal-dependent and adrenalindependent mechanisms were responsible for the restraint stress–induced decrease in the cellular immune response to experimental virus infection (Bonneau et al., 1993). In a followup study, the contributions of the HPA and SNS to this immunosuppression were further delineated by demonstrating that the type II glucocorticoid receptor antagonist RU486 restored cellularity and cytokine responses but failed to restore cytolytic T-cell responses. In contrast, the use
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of RU486 along with the β-adrenergic receptor antagonist nadolol resulted in the abrogation of restraintinduced suppression of cytolytic T-cell activity (Dobbs et al., 1993). Interestingly, restraint stress can actually enhance survival in certain mouse strains, such as DBA/2, during influenza viral infection (Hermann et al., 1994). This was found to be primarily due to sympathetic innervation of secondary lymphoid organs, since chemical sympathectomy using 6-hydroxydopamine enhanced mortality in infected mice exposed to restraint stress (Hermann et al., 1994). These findings have led to the belief that, unlike stress-induced alterations of cell trafficking and cytokine production, antigen-specific T-cell activation during influenza virus infection is, in part, dependent upon SNS activity.
V. ANTI-INFLAMMATORY GLUCOCORTICOID RESPONSE: FRIEND OR FOE? It is well known that pro-inflammatory cytokines produced during infection activate the HPA axis. Thus, a severe viral infection has been considered to be a stressor. Infection of mice with influenza A/PR8 is no exception and is a potent activator of the HPA axis. During this infection, the corticosterone response is biphasic, with an initial peak occurring at 48–72 hrs, the time when pro-inflammatory cytokine production peaks; a secondary peak occurs at 5–6 days postinfection, when leukocyte infiltration is maximal and lung consolidation begins to make respiration difficult (Hermann et al., 1994). Although the previous sections provide ample evidence that stress-induced increases in glucocorticoid levels have deleterious effects on the immune response, the fact that organisms evolved to produce glucocorticoids upon infection, as well as the fact that virtually all leukocytes contain glucocorticoid receptors, suggests that glucocorticoids must provide an adaptive advantage during infection. Leukocytes from mice exposed to social stressors, such as social reorganization (SRO) or social disruption (SDR), become resistant to the suppressive effects of corticosterone (Avitsur et al., 2002; Avitsur et al., 2003; Avitsur et al., 2001; Bailey et al., 2004; Engler et al., 2005b; Sheridan et al., 2000; Stark et al., 2001). This was first realized when mice were exposed to SRO and then infected with influenza virus. Splenocytes from these socially stressed mice proliferated when stimulated with Conconavalin A, even when high pharmacological doses of corticosterone were applied to the cultures (Sheridan et al., 2000). This finding was in stark contrast to splenocytes from control mice having a significant reduction in prolif-
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eration when the same doses of corticosterone were used. Because corticosterone has potent anti-inflammatory effects, it was hypothesized that infectioninduced elevations in corticosterone served to regulate leukocyte proliferation and perhaps trafficking to the lungs. If true, it would mean that disrupting this regulation, through the development of stress-induced functional glucocorticoid resistance, would enhance inflammation during infection. As predicted, mice exposed to SRO (to induce glucocorticoid resistance prior to influenza A/PR8 infection) had significantly higher lung cellularity and were more likely to die from lung consolidation than were the non-stressed control mice (Sheridan et al., 2000). This study indicates that there is a delicate balance between glucocorticoid levels and optimal immune functioning and suggests that, in addition to affecting the immune response during stress, the nervous system may have a more direct role in immunoregulation. Loss of glucocorticoid sensitivity of immune cell function during social stress is a current topic of study in this laboratory, and it has yet to be determined whether glucocorticoid resistance is maladaptive, or whether this response to stress can have beneficial effects. For example, it is possible that reduced sensitivity to glucocorticoids allows the immune system to contend with insults likely to be incurred during this type of stress, such as bite wounds and opportunistic microbial infection, even when the stressor induces high levels of glucocorticoids. Additional studies, using different types of stressors and different infectious challenges, will provide the data necessary to determine the impact of functional glucocorticoid resistance on resistance to infectious challenge.
VI. SUMMARY It is now widely accepted that brain/mind-body interactions affect multiple aspects of the immune response through behavioral, neural, and endocrine responses to stimuli. And, as research progresses, the shared receptors and ligands, as well as the molecular mechanisms linking these diverse organ systems, are becoming better defined. However, we remain on the cusp of fully knowing the extent of the impact of this neuroimmunomodulation on susceptibility and resistance to infectious diseases. The application of wellcharacterized stressors during microbial challenges with pathogenic bacteria and viruses, for which there is detailed knowledge of the pathogenesis and antimicrobial immunity, has been a very useful approach for determining the impact of stress-induced neuroendocrine activation on resistance to infectious diseases.
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Utilization of stressors that differ in their nature (e.g., social vs. physical), duration (e.g., hours vs. days), and predominant physiological response (e.g., HPA axis vs. SNS) will provide a fuller understanding of the harmful, and potentially beneficial, effects of stress on anti-microbial immunity.
References Adelson, M. O., Novick, D. M., Khuri, E., Albeck, H., Hahn, E. F., and Kreek, M. J. (1994). Effects of the opioid antagonist naloxone on human natural killer cell activity in vitro. Isr. J. Med. Sci., 30, 679–684. Ashwell, J. D., Lu, F. W., and Vacchio, M. S. (2000). Glucocorticoids in T cell development and function. Annu. Rev. Immunol., 18, 309–345. Avitsur, R., Padgett, D. A., Dhabhar, F. S., Stark, J. L., Kramer, K. A., Engler, H., and Sheridan, J. F. (2003). Expression of glucocorticoid resistance following social stress requires a second signal. J. Leukoc. Biol., 74, 507–513. Avitsur, R., Stark, J. L., Dhabhar, F. S., Padgett, D. A., and Sheridan, J. F. (2002). Social disruption-induced glucocorticoid resistance: kinetics and site specificity. J. Neuroimmunol., 124, 54–61. Avitsur, R., Stark, J. L., and Sheridan, J. F. (2001). Social stress induces glucocorticoid resistance in subordinate animals. Horm. Behav., 39, 247–257. Bailey, M., Engler, H., Hunzeker, J., and Sheridan, J. F. (2003). The hypothalamic-pituitary-adrenal axis and viral infection. Viral Immunol., 16, 141–157. Bailey, M. T., Avitsur, R., Engler, H., Padgett, D. A., and Sheridan, J. F. (2004). Physical defeat reduces the sensitivity of murine splenocytes to the suppressive effects of corticosterone. Brain Behav. Immun., 18, 416–424. Bamberger, C. M., and Chrousos, G. P. (1995). The glucocorticoid receptor and RU 486 in man. Ann. N. Y. Acad. Sci., 761, 296–310. Barchet, W., Krug, A., Cella, M., Newby, C., Fischer, J. A., Dzionek, A., Pekosz, A., and Colonna, M. (2005). Dendritic cells respond to influenza virus through. Eur. J. Immunol., 35, 236–242. Beck, M. A., and Sheridan, J. F. (1989). Regulation of lymphokine response during reinfection by influenza virus. Production of a factor that inhibits lymphokine activity. J. Immunol., 142, 3560–3567. Bonneau, R. H., Sheridan, J. F., Feng, N., and Glaser, R. (1993). Stressinduced modulation of the primary cellular immune response to herpes simplex virus infection is mediated by both adrenaldependent and independent mechanisms. J. Neuroimmunol., 42, 167–176. Carr, D. J., Brockunier, L. L., Scott, M., Bagley, J. R., and France, C. P. (1996a). Mirfentanil antagonizes morphine-induced suppression of splenic NK activity in mice. Immunopharmacology, 34, 9–16. Carr, D. J., Scott, M., Brockunier, L. L., Bagely, J. R., and France, C. P. (1996b). The effect of novel opioids on natural killer activity and tumor surveillance in vivo. Adv. Exp. Med. Biol., 402, 5–11. Carr, D. J., and Serou, M. (1995). Exogenous and endogenous opioids as biological response modifiers. Immunopharmacology, 31, 59–71. Cella, M., Facchetti, F., Lanzavecchia, A., and Colonna, M. (2000). Plasmacytoid dendritic cells activated by influenza virus and CD40L drive a potent TH1 polarization. Nat. Immunol., 1, 305–310.
Deng, Y., Jing, Y., Campbell, A. E., and Gravenstein, S. (2004). Agerelated impaired type 1 T cell responses to influenza: reduced activation ex vivo, decreased expansion in CTL culture in vitro, and blunted response to influenza vaccination in vivo in the elderly. J. Immunol., 172, 3437–3446. Dobbs, C. M., Feng, N., Beck, F. M., and Sheridan, J. F. (1996). Neuroendocrine regulation of cytokine production during experimental influenza viral infection: effects of restraint stressinduced elevation in endogenous corticosterone. J. Immunol., 157, 1870–1877. Dobbs, C. M., Vasquez, M., Glaser, R., and Sheridan, J. F. (1993). Mechanisms of stress-induced modulation of viral pathogenesis and immunity. J. Neuroimmunol., 48, 151–160. Engler, A., Roy, S., Sen, C. K., Padgett, D. A., and Sheridan, J. F. (2005a). Restraint stress alters lung gene expression in an experimental influenza A viral infection. J. Neuroimmunol., 162, 103–111. Engler, H., Engler, A., Bailey, M. T., and Sheridan, J. F. (2005b). Tissue-specific alterations in the glucocorticoid sensitivity of immune cells following repeated social defeat in mice. J. Neuroimmunol., 163, 110–119. Feng, N., Pagniano, R., Tovar, C. A., Bonneau, R. H., Glaser, R., and Sheridan, J. F. (1991). The effect of restraint stress on the kinetics, magnitude, and isotype of the humoral immune response to influenza virus infection. Brain Behav. Immun., 5, 370–382. Fiatarone, M. A., Morley, J. E., Bloom, E. T., Benton, D., Makinodan, T., and Solomon, G. F. (1988). Endogenous opioids and the exercise-induced augmentation of natural killer cell activity. J. Lab. Clin. Med., 112, 544–552. Fonteneau, J. F., Gilliet, M., Larsson, M., Dasilva, I., Munz, C., Liu, Y. J., and Bhardwaj, N. (2003). Activation of influenza virus-specific CD4+ and CD8+ T cells: a new role for plasmacytoid dendritic cells in adaptive immunity. Blood, 101, 3520–3526. Glaser, R., Kiecolt-Glaser, J. K., Malarkey, W. B., and Sheridan, J. F. (1998). The influence of psychological stress on the immune response to vaccines. Ann. N. Y. Acad. Sci., 840, 649–655. Glaser, R., Sheridan, J., Malarkey, W. B., MacCallum, R. C., and Kiecolt-Glaser, J. K. (2000). Chronic stress modulates the immune response to a pneumococcal pneumonia vaccine. Psychosom. Med., 62, 804–807. Hache, R. J. G., Savory, R. G. A., and Lefebvre, Y. A. (1999). Nucleocytoplasmic trafficking and glucocorticoid receptor function. Gene Ther. Mol. Biol., 4, 99–107. Hermann, G., Beck, F. M., and Sheridan, J. F. (1995). Stress-induced glucocorticoid response modulates mononuclear cell trafficking during an experimental influenza viral infection. J. Neuroimmunol., 56, 179–186. Hermann, G., Tovar, C. A., Beck, F. M., and Sheridan, J. F. (1994). Kinetics of glucocorticoid response to restraint stress and/or experimental influenza viral infection in two inbred strains of mice. J. Neuroimmunol., 49, 25–33. Hornung, V., Schlender, J., Guenthner-Biller, M., Rothenfusser, S., Endres, S., Conzelmann, K. K., and Hartmann, G. (2004). Replication-dependent potent IFN-alpha induction in human plasmacytoid dendritic cells by a single-stranded RNA virus. J. Immunol., 173, 5935–5943. Hunzeker, J., Padgett, D. A., Sheridan, P. A., Dhabhar, F. S., and Sheridan, J. F. (2004). Modulation of natural killer cell activity by restraint stress during an influenza A/PR8 infection in mice. Brain Behav. Immun., 18, 526–535. Julkunen, I., Melen, K., Nyqvist, M., Pirhonen, J., Sareneva, T., and Matikainen, S. (2000). Inflammatory responses in influenza A virus infection. Vaccine, 19 (1), S32–S37.
51. Stress-induced Modulation of Innate Resistance and Adaptive Immunity to Influenza Viral Infection Kaufmann, A., Salentin, R., Meyer, R. G., Bussfeld, D., Pauligk, C., Fesq, H., Hofmann, P., Nain, M., Gemsa, D., and Sprenger, H. (2001). Defense against influenza A virus infection: essential role of the chemokine system. Immunobiology, 204, 603–613. Kiecolt-Glaser, J. K., Glaser, R., Gravenstein, S., Malarkey, W. B., and Sheridan, J. (1996). Chronic stress alters the immune response to influenza virus vaccine in older adults. Proc. Natl. Acad. Sci. U. S. A., 93, 3043–3047. Konstantinos, A. P., and Sheridan, J. F. (2001). Stress and influenza viral infection: modulation of proinflammatory cytokine responses in the lung. Respir. Physiol., 128, 71–77. Lopez, C. B., Fernandez-Sesma, A., Schulman, J. L., and Moran, T. M. (2001). Myeloid dendritic cells stimulate both Th1 and Th2 immune responses depending on the nature of the antigen. J. Interferon Cytokine Res., 21, 763–773. Lopez, C. B., Moran, T. M., Schulman, J. L., and Fernandez-Sesma, A. (2002). Antiviral immunity and the role of dendritic cells. Int. Rev. Immunol., 21, 339–353. Lund, J. M., Alexopoulou, L., Sato, A., Karow, M., Adams, N. C., Gale, N. W., Iwasaki, A., and Flavell, R. A. (2004). Recognition of single-stranded RNA viruses by Toll-like receptor 7. Proc. Natl. Acad. Sci. U. S. A., 101, 5598–5603. Matrosovich, M. N., Matrosovich, T. Y., Gray, T., Roberts, N. A., and Klenk, H. D. (2004). Human and avian influenza viruses target different cell types in cultures of human airway epithelium. Proc. Natl. Acad. Sci. U. S. A., 101, 4620–4624. McEwen, B. S., Biron, C. A., Brunson, K. W., Bulloch, K., Chambers, W. H., Dhabhar, F. S., Goldfarb, R. H., Kitson, R. P., Miller, A. H., Spencer, R. L., and Weiss, J. M. (1997). The role of adrenocorticoids as modulators of immune function in health and disease: neural, endocrine and immune interactions. Brain Res. Brain Res. Rev., 23, 79–133. McHale, J. F., Harari, O. A., Marshall, D., and Haskard, D. O. (1999). TNF-alpha and IL-1 sequentially induce endothelial ICAM-1 and VCAM-1 expression in MRL/lpr lupus-prone mice. J. Immunol., 163, 3993–4000. Mellon, R. D., and Bayer, B. M. (1998a). Evidence for central opioid receptors in the immunomodulatory effects of morphine: review of potential mechanism(s) of action. J. Neuroimmunol., 83, 19–28. Mellon, R. D., and Bayer, B. M. (1998b). Role of central opioid receptor subtypes in morphine-induced alterations in peripheral lymphocyte activity. Brain Res., 789, 56–67. Nelson, C. J., and Lysle, D. T. (2001). Involvement of substance P and central opioid receptors in morphine modulation of the CHS response. J. Neuroimmunol., 115, 101–110. Nelson, C. J., Schneider, G. M., and Lysle, D. T. (2000). Involvement of central mu- but not delta- or kappa-opioid receptors in immunomodulation. Brain Behav. Immun., 14, 170–184. Nieto, M., Rodriguez-Fernandez, J. L., Navarro, F., Sancho, D., Frade, J. M., Mellado, M., Martinez, A., Cabanas, C., and SanchezMadrid, F. (1999). Signaling through CD43 induces natural killer cell activation, chemokine release, and PYK-2 activation. Blood, 94, 2767–2777. Oran, A. E., and Robinson, H. L. (2004). DNA vaccines: influenza virus challenge of a Th2/Tc2 immune response results in a Th2/ Tc1 response in the lung. J. Virol., 78, 4376–4380.
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Padgett, D. A., MacCallum, R. C., Loria, R. M., and Sheridan, J. F. (2000). Androstenediol-induced restoration of responsiveness to influenza vaccination in mice. J. Gerontol. A Biol. Sci. Med. Sci., 55, B418–B424. Padgett, D. A., and Sheridan, J. F. (1999). Androstenediol (AED) prevents neuroendocrine-mediated suppression of the immune response to an influenza viral infection. J. Neuroimmunol., 98, 121–129. Randolph, G. J., and Furie, M. B. (1995). A soluble gradient of endogenous monocyte chemoattractant protein-1 promotes the transendothelial migration of monocytes in vitro. J. Immunol., 155, 3610–3618. Rosseau, S., Selhorst, J., Wiechmann, K., Leissner, K., Maus, U., Mayer, K., Grimminger, F., Seeger, W., and Lohmeyer, J. (2000). Monocyte migration through the alveolar epithelial barrier: adhesion molecule mechanisms and impact of chemokines. J. Immunol., 164, 427–435. Saurer, T. B., Carrigan, K. A., Ijames, S. G., and Lysle, D. T. (2004). Morphine-induced alterations of immune status are blocked by the dopamine D2-like receptor agonist 7-OH-DPAT. J. Neuroimmunol., 148, 54–62. Scheinman, R. I., Gualberto, A., Jewell, C. M., Cidlowski, J. A., and Baldwin, A. S., Jr. (1995). Characterization of mechanisms involved in transrepression of NF-kappa B by activated glucocorticoid receptors. Mol. Cell Biol., 15, 943–953. Sheridan, J. F., Feng, N. G., Bonneau, R. H., Allen, C. M., Huneycutt, B. S., and Glaser, R. (1991). Restraint stress differentially affects anti-viral cellular and humoral immune responses in mice. J. Neuroimmunol., 31, 245–255. Sheridan, J. F., Stark, J. L., Avitsur, R., and Padgett, D. A. (2000). Social disruption, immunity, and susceptibility to viral infection. Role of glucocorticoid insensitivity and NGF. Ann. N. Y. Acad. Sci., 917, 894–905. Stark, J. L., Avitsur, R., Padgett, D. A., Campbell, K. A., Beck, F. M., and Sheridan, J. F. (2001). Social stress induces glucocorticoid resistance in macrophages. Am. J. Physiol. Regul. Integr. Comp. Physiol., 280, R1799–R1805. Strieter, R. M., Belperio, J. A., and Keane, M. P. (2003). Host innate defenses in the lung: the role of cytokines. Curr. Opin. Infect. Dis., 16, 193–198. Topham, D. J., Tripp, R. A., and Doherty, P. C. (1997). CD8+ T cells clear influenza virus by perforin or Fas-dependent processes. J. Immunol., 159, 5197–5200. Tseng, R. J., Padgett, D. A., Dhabhar, F. S., Engler, H., and Sheridan, J. F. (2005). Stress-induced modulation of NK activity during influenza viral infection: role of glucocorticoids and opioids. Brain Behav. Immun., 19, 153–164. Weber, K. S., Draude, G., Erl, W., de Martin, R., and Weber, C. (1999a). Monocyte arrest and transmigration on inflamed endothelium in shear flow is inhibited by adenovirus-mediated gene transfer of IkappaB-alpha. Blood, 93, 3685–3693. Weber, K. S., von Hundelshausen, P., Clark-Lewis, I., Weber, P. C., and Weber, C. (1999b). Differential immobilization and hierarchical involvement of chemokines in monocyte arrest and transmigration on inflamed endothelium in shear flow. Eur. J. Immunol., 29, 700–712.
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C H A P T E R
52 Social Stress Alters the Severity of a Virally Initiated Model of Multiple Sclerosis MARY W. MEAGHER, ROBIN JOHNSON, ELISABETH GOOD, AND C. JANE WELSH
I. INTRODUCTION 1107 II. MULTIPLE SCLEROSIS 1107 III. THEILER’S VIRUS INFECTION AS A MODEL FOR MS 1109 IV. STRESS AND MS 1110 V. SOCIAL STRESS AND IMMUNE CHALLENGE 1111 VI. THE IMPACT OF SOCIAL DISRUPTION STRESS ON TMEV INFECTION 1112 VII. GENERAL CONCLUSIONS 1118
development of MS (Acheson, 1977; Gilden, 2005; Kurtzke and Hyllested, 1987; Sospedra and Martin, 2005). A growing body of literature also suggests that exposure to psychological and physical stressors increases the risk for disease onset and exacerbation of MS. Importantly, recent animal studies have shown that the environmental risk factors of viral infection and stress interact to determine disease severity (Campbell et al., 2001; Sieve et al., 2004; Johnson et al., 2004b, 2005, In press). This chapter will focus on the interaction between viral infection and stress in MS and in an animal model of MS. We will begin by briefly reviewing the pathophysiology of MS, including evidence for a viral etiology in humans and in animal models of MS. Next, we examine the literature on stress in MS as well as evidence that social stress can alter immune function. Finally, we review evidence that exposure to social stress alters the course of Theiler’s murine encephalomyelitis virus (TMEV) infection, an animal model for MS.
I. INTRODUCTION Multiple sclerosis (MS) is a primary inflammatory demyelinating disease of the central nervous system (CNS) affecting approximately 1 in 350,000 of the U.S. population (Anderson et al., 1992; Jacobson et al., 1997; Noonan et al., 2002; Sospedra & Martin, 2005). MS develops between the ages of 15 and 50 and results in significant disability through loss of motor, sensory, autonomic, and neurological function. Clinical symptoms include loss of motor control or sensation in the limbs, loss of bowel or bladder control, pain, optic neuritis, sexual dysfunction, and cognitive dysfunction. Although the etiology of MS is uncertain, research indicates that several environmental factors interact with genetic factors to cause disease (Kurtzke and Hyllested, 1987; Noseworthy et al., 2000; Sospedra and Martin, 2005). Potential environmental risk factors include, but are not limited to, viral infection and stress. Epidemiological studies suggest that adolescent exposure to certain viruses is associated with later PSYCHONEUROIMMUNOLOGY, 4E VOLUME II
II. MULTIPLE SCLEROSIS MS is a heterogeneous disease that can follow a relapsing remitting, secondary progressive, or chronic progressive disease course (Sospedra and Martin, 2005). Relapsing remitting (RR) MS is the most common presentation (85–90%), characterized by episodes of symptom exacerbations followed by periods of
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Copyright © 2007 by Elsevier, Inc. All rights of reproduction in any form reserved.
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complete remission. Over time, the majority of RR-MS patients develop secondary progressive MS, with steady symptom progression between episodes of clinical relapse. About 10–15% of MS patients present with a chronic primary progressive disease course, which is characterized by steady disease progression without periods of remission. The factors determining differences in disease course remain poorly understood. However, individual differences in complex genetic traits, as well as individual differences in environmental risk factors, may result in differential susceptibility to viral infections and dysregulation of the immune response to CNS inflammatory insults. Current research suggests that MS develops in genetically susceptible individuals exposed to an environmental trigger (Dyment et al., 2004; Sospedra and Martin, 2005). Family and twin studies indicate that genetic susceptibility is necessary but not sufficient for disease vulnerability. Although the risk of disease is substantially increased among relatives of MS patients, modest concordance rates (approximately 25%) for monozygotic twins suggest that environmental influences must be involved. Considerable evidence indicates that MS is a cellmediated autoimmune disease in which immune responses are directed against the myelin sheath surrounding the axons of neurons. MS lesions are characterized by plaques throughout the white matter of the brain and spinal cord. Demyelination is accompanied by inflammatory cell infiltrates consisting of plasma cells, macrophages/microglia, T and B lymphocytes. Autoimmune responses to myelin components myelin basic protein (MBP), proteolipid protein (PLP), and myelin-oligodendrocyte glycoprotein (MOG) have been detected in MS patients, suggesting an autoimmune etiology for MS (Stinissen et al., 1997).
A. A Viral Etiology for MS Viral infection is considered a likely environmental trigger of MS (Gilden, 2005; Sospedra and Martin, 2005). A number of viral agents have been isolated from the brains of MS patients at postmortem, including measles, mumps, parainfluenza type I (Allen and Brankin, 1993), and human herpes virus simplex type 6 (Challoner et al., 1995). Additionally, disease exacerbations are frequently preceded by viral infections (Sibley et al., 1985). Although no single viral culprit has been found, it is plausible that several viruses may be capable of initiating and/or aggravating the autoimmune processes leading to MS (Gilden, 2005; Sospedra and Martin, 2005). Supporting this line of reasoning, several viruses have been shown to initiate demyelinating diseases in humans (Johnson, 1994;
Soldan and Jacobson, 2001) and animals (Dal Canto and Rabinowitz, 1982; Johnson, 1994; Soldan and Jacobson, 2001). Ubiquitous viruses that induce persistent infections are likely candidates in human MS. Recent research implicates two common human herpes viruses: human herpes virus 6 (HHV-6) and Epstein-Barr Virus (EBV). Both viruses are widespread, with seroprevalence rates of 80% and 90%, respectively (Martyn et al., 1993; Moore et al., 2002; Soldan et al., 2000; Wandinger et al., 2000). Importantly, seroconversion for both viruses tends to occur during adolescence, which corresponds to epidemiological evidence for exposure to an infectious agent during adolescence as a trigger for MS. HHV-6 and EBV are considered likely culprits due to their neurotrophic properties (Majid et al., 2002). In addition, there is evidence that HHV-6 can induce encephalitis, can infect astrocytes, and is found in the oligodendrocytes of MS plaques (Challoner et al., 1995). Although controversial, other research indicates that HHV-6 DNA and antibodies are found in the serum and CSF of MS patients (Moore and Wolfson, 2002). Likewise, EBV antibodies are elevated in MS patients, especially during relapses (Wandinger et al., 2000). Finally, human herpes virus 1, varicella zoster virus, and retroviruses have been implicated as initiating agents for MS on the basis of markers in plasma and CRF of MS patients. However, further epidemiological research is needed to clarify the relationship between these viruses and MS.
B. Animal Models of Virus-induced Demyelination Animal models provide experimental evidence that viruses can induce demyelination in the CNS. While TMEV infection provides the best characterized model of virus-induced CNS demyelination in mice, demyelination is also observed after infection with mouse hepatitis virus, Semliki Forest virus, canine distemper virus, Visna virus, caprine arthritis-encephalitis virus, and measles virus. In each case, the virus establishes a persistent infection that subsequently triggers virus and/or autoimmune-mediated demyelination. Animal studies indicate that viruses may trigger demyelination through mechanisms of molecular mimicry and/ or bystander activation (Olson et al., 2001, 2002, 2004; Sospedra and Martin, 2005). Molecular mimicry involves T- and B-cells that cross-react with either virus, antigenic determinants, or peptides of selfantigens, such as MBP, MOG, and PLP. In contrast, bystander activation involves the activation of autoreactive T-cells by non-specific inflammatory responses triggered by infection (e.g., cytokines activation). Thus,
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52. Social Stress Alters the Severity of a Virally Initiated Model of Multiple Sclerosis
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TMEV induces a biphasic disease (Figure 1). The acute phase of the disease (first month) is primarily a gray matter disease similar to poliomyelitis. The later chronic disease occurs several months post-infection and is characterized by primary inflammatory demyelination. Immunosuppressive regimens during the acute phase of disease are detrimental because an intact immune system is required to control infection. In contrast, immunosuppression during chronic disease is beneficial because it ameliorates inflammation as the immune response becomes pathogenic (Welsh et al., 1987). The early immune events that occur during TMEV infection are crucial in the effective clearance of the virus from the CNS. Failure to clear the virus results in persistent infection of the CNS and subsequent demyelination (Brahic et al., 1981; Rodriguez et al., 1996). Innate cytokine responses to infection play an important role in shaping downstream innate and adaptive immune responses (Biron, 1998). For example, the cytokines IFN-α and IFN-β appear to play a pivotal role in the early immune response to TMEV. Supporting this, IFN-α/IFN-β receptor knockout mice die within 10 days of infection, indicating the critical
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Early polio-like disease of the gray matter
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Virus replicates in motor neurons
Virus in oligodendrocytes, astrocytes, and macrophages/microglia
Lesion characterized by necrosis of ventral horn cells
A. The Immune Response in TMEV Infection
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Theiler’s murine encephalomyelitis virus (TMEV) is a Picornavirus and a natural pathogen of mice, which causes an asymptomatic gastrointestinal infection and occasionally paralysis (Theiler, 1934). Following intracerebral infection with either the BeAn or DA strains of TMEV, susceptible strains of mice develop a primary inflammatory demyelinating disease that is remarkably similar to MS (Lipton, 1975; Oleszak et al., 2004). TMEV must establish a persistent infection of the CNS in order to cause demyelination (Aubert et al., 1987). Resistant strains of mice, which are able to clear the virus from the CNS during the first month of infection, do not develop the demyelination.
ANTI-VIRAL IgG titer (log 2 )
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III. THEILER’S VIRUS INFECTION AS A MODEL FOR MS
DTH TO VIRUS
LOG
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THEILER'S VIRUS INFECTION (p.f.u./g spinal cord)
in order to understand the pathogenesis of MS, it is important to study an animal model of virus-induced demyelination such as TMEV infection. TMEV infection not only represents an excellent model for the study of the pathogenesis of MS, it also provides a model for studying disease susceptibility factors, CNS viral persistence, and virus-induced autoimmune disease.
Lesion characterized by lymphocytic infiltrate surrounding zone of demyelination
FIGURE 1 Disease course of Theiler’s virus-induced demyelination. Intracerebral infection of CBA mice with 5 × 104 p.f.u. of the BeAn strain of Theiler’s virus results in high levels of virus in the spinal cord (top panel). The viral titers decrease at 4 weeks post-infection when neutralizing antiviral antibodies, and viral T-cell responses are detected (middle panel). During late disease, T- and B-cell responses are detected in TMEV-infected mice (lower panel).
nature of the type I IFN response (Fiette et al., 1995). Natural killer (NK) cells are also activated early in viral infections and play an important role in natural resistance. When resistant mice are depleted of NK cells and then infected with TMEV, they develop severe gray matter disease. Conversely, the highly susceptible SJL mouse strain has a differentiation defect in the thymus that impairs the responsiveness of NK cells to stimulation by IFN-β, which results in a low NK response to infection (Kaminsky et al., 1987). Thus, NK cells are critical in the early TMEV clearance. Both CD8+ and CD4+ T-cells play an important role in acute viral clearance (Borrow et al., 1992; Dethlefs et al., 1997; Murray et al., 1998; Welsh et al., 1987), but in chronic disease these T-cell subsets have been implicated in the demyelinating process (Clatch et al., 1987;
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Rodriguez et al., 1988; Welsh et al., 1989). In early disease, CD4+ T-cells are required for B-cells to produce antibodies, which are probably the most important mediators of Picornavirus clearance (Borrow et al., 1993; Welsh et al., 1987). In addition, CD4+ T-cells secrete IFN-α, which inhibits the replication of TMEV in vitro (Welsh et al., 1995) and has a protective role in vivo (Kohanawa et al., 1993; Rodriguez et al., 1995). Additional evidence that CD8+ T-cells are clearly important in viral clearance comes from in vivo depletion experiments (Borrow et al., 1992) and studies with gene knockout mice (Fiette et al., 1993; Pullen et al., 1993). CD8+ depleted mice fail to clear the virus from the CNS and develop severe demyelinating disease (Borrow et al., 1992). Reduced cytotoxic T lymphocyte (CTL) activity has been detected in TMEV-infected SJL/J mice (Lindsley et al., 1991; Rossi et al., 1991) when compared with TVID-resistant strains of mice. The CTLs may be important in either recognizing viral determinants or inhibiting delayed type hypersensitivity (DTH) responses (Borrow et al., 1992; Lipton et al., 1995).
B. Theiler’s Virus-induced Demyelination (TVID) The mechanisms of demyelination induced by TMEV are complex and not fully understood. Demyelination is partly mediated by (a) direct viral lysis of oligodendrocytes (Roos and Wollmann, 1984) and (b) CD4+ T-cell–mediated CNS demyelination consisting of anti-virus and anti-myelin autoimmune responses (Borrow et al., 1998; Dal Canto et al., 2000; Miller et al., 1997; Welsh et al., 1987, 1989, 1990). Susceptibility to inflammation and demyelination of the spinal cord are strongly related to the ability of the mouse to mount a delayed-type hypersensitivity response to viral antigen. Other evidence suggests that demyelination is initiated by virus-specific T-cells that target the virus presented by persistently infected macrophages/microglia in the CNS. This leads to initial myelin destruction due to pro-inflammatory cytokines produced by TMEVspecific Th1 cells that target CNS-persistent virus. As the disease progresses, myelin destruction induces epitope spreading, characterized by the development of myelin-epitope–specific autoreactive Th1 cells (Croxford et al., 2002; Miller et al., 2001; Olson et al., 2004). The autoimmune aspects of this disease enhance bystander demyelination mediated by virus-specific DTH T-cells (Clatch et al., 1987; Gerety et al., 1991) and cytotoxic T-cell reactivity (Rodriguez and Sriram, 1988). In summary, TMEV infection provides an excellent animal model of MS in which to study the effects of
social stress on disease course. Our laboratory has investigated the effects of restraint stress in this model in order to gain a better understanding of how stress impacts the human disease (for a recent review, see Welsh et al., In press). In the following sections, we focus our discussion on social stress and MS, and on our more recent experiments investigating the effect of social disruption stress on the early disease induced by TMEV, as a model of MS disease onset.
IV. STRESS AND MS MS patients frequently report elevated levels of stress prior to initial diagnosis and/or disease exacerbation (Ackerman et al., 2000; Grant et al., 1989; Mohr et al., 2000; Mohr et al., 2004; Warren et al., 1982). A recent meta-analysis conducted on 14 studies investigating the impact of stressful life events on MS exacerbation found that stress significantly increased the risk of disease exacerbation (Mohr et al., 2004). Although the effects size was modest (d = .53), it is as large or larger than the effect sizes for one of the most common medical treatments, interferon β, which is estimated to yield an effect size of d = .30–.36 (Filippinni et al., 2003). It should be noted that 13 of the 14 studies measured common stressful life events, including interpersonal stressors with family and work. However, not all of the studies reported negative outcomes associated with stress and MS. One study, examining a traumatic stressor (missile attacks during the Gulf War), found reduced relapse rates and no impact on lesion development (Nisipeanu and Korczyn, 1993). Taken together, these findings suggest that stressor characteristics may alter the impact of stress on initial susceptibility and disease course in MS. Because most studies examining the relationship between stress and MS rely on self-reports of symptoms and/or neurologist ratings that are derived from patient reports, it is possible that reports of exacerbations during periods of stress may be biased by the patient’s mood. Therefore, studies are needed that use more objective markers of disease exacerbation. Only one human study meets this criterion. Using a longitudinal design, Mohr et al. (2000) examined the relationship of stressful life events and lesion development in MS patients. The patients received a monthly gadolinium (Gd+) MRI to detect changes in blood-brain barrier (BBB) disruption that are linked to CNS inflammation in MS. During the MRI scan, Gd+ is injected peripherally and then crosses the BBB at sites of MS inflammation, allowing the quantification of active focal lesions. Their results indicated that patient reports
52. Social Stress Alters the Severity of a Virally Initiated Model of Multiple Sclerosis
of stressful life events preceded and predicted the development of new Gd+ brain lesions. Importantly, chronic social stressors at home and at work were implicated, as well as disruptions in daily routine. Although prospective human MS studies suggest that social stress is associated with later disease exacerbation, experimental studies are needed to determine whether there is a causal relationship and to elucidate the mechanisms mediating the effects of social stress on MS. Currently, little is known about the underlying neuroendocrine and immune mechanisms. Indeed, no studies have examined the immune or endocrine effects of chronic stressors in MS patients. Because MS patients are likely to vary in their genetic and psychological vulnerability to stress, as well as in their stage of disease, clinical studies will be especially challenging and quasi experimental in nature. Moreover, experimental studies examining the relationship between chronic stress and MS in humans raise ethical concerns. Given this, animal models are needed to elucidate the mechanisms mediating the effects of chronic stress on disease course. Animal studies are advantageous because the stressor can be experimentally manipulated, and its impact on disease course can be quantified using objective behavioral and physiological markers of disease progression.
V. SOCIAL STRESS AND IMMUNE CHALLENGE Recent research indicates that the nature of a stressful event determines its biobehavioral consequences in both human and animal studies. For example, social stress, but not restraint stress, can lead to the reactivation of a latent herpes virus infection (Padgett et al., 1998) resulting in increased inflammatory responses to a lipopolysaccharide (LPS) challenge (Quan et al., 2001) and increased CNS inflammation during acute TMEV infection (Johnson et al., 2004b). Because virtually all mammals experience chronic or recurrent social stress, there is a strong rationale for examining the consequences of social conflict in both human and animal studies (Blanchard et al., 2001).
A. Social Stress and Immunity in Humans Human studies indicate that chronic social stress is immunosuppressive and associated with increased risk for infectious illnesses. For example, studies of the chronic stress of caring for spouses with Alzheimer’s disease indicate that caregivers show suppressed antibody responses to vaccination challenge (Glaser et al., 2000; Kiecolt-Glaser et al., 1996). Likewise, prospective
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viral challenge studies have shown that chronic social stress increases the risk for upper respiratory viral infection (Cohen et al., 1991, 1993). Although these clinical studies suggest that social stress is associated with adverse immunological and health effects, it is possible that this correlation may be due to a third variable, such as a personality variable that is linked to both stress and illness. To resolve this issue, animal studies have been conducted to experimentally investigate the effects of social stress on susceptibility to infection as well as the underlying mechanisms that mediate these effects.
B. Social Stress and Immunity in Animals The majority of animal studies examining the impact of social stress on infectious disease vulnerability have used male rodents exposed to repeated social defeat. Similar to most mammals, male rodents establish dominance hierarchies that influence a wide range of observable aggressive behaviors such as posturing, fighting, and wounding. Several social conflict models have been developed that involve social defeat and disruption of the social hierarchy. One variant is known as the social disruption (SDR) model, in which an aggressive male intruder is introduced into the residence of a group of younger male mice. The introduction of the dominant intruder elicits aggressive confrontations and defeat of the resident mice. Several studies suggest that repeated exposure to social stress has profound effects on neuroendocrine and immune function (Avitsur et al., 2001; Johnson et al., 2004b; Padgett et al., 1998; Quan et al., 2001). For example, social stress has been shown to produce an increase in circulating levels of the stress hormones corticosterone (Avitsur, 2001), while also increasing susceptibility to influenza virus infection and endotoxin challenge in mice (Avitsur et al., 2001; Padgett and Sheridan, 1998; Quan et al., 2001). Likewise, studies in non-human primates have experimentally evaluated the effects of chronic social stress on T-cell immune responses and the risk of upper respiratory infections. Exposure to chronic social stress resulted in a suppression of T-cell function (Cohen et al., 1992) and an increased risk of upper respiratory infections in monkeys with lower social status (Cohen et al., 1997).
C. Glucocorticoid Resistance and Social Stress A growing body of research indicates that chronic social stress can induce glucocorticoid (GC) resistance in animals and humans. GC resistance refers to a decrease in the immune system’s capacity to respond
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to the inhibitory effects of corticosterone in terminating inflammatory responses. For example, when mice are exposed to SDR, their splenocytes become less sensitive to corticosterone when stimulated with LPS, exhibiting enhanced proliferation and viability compared to control splenocyte cultures (Avitsur et al., 2001). These animals also exhibit splenomegaly, an increased number of CD11b+ monocytes, and elevated levels of the pro-inflammatory cytokines TNF-α, IL-6, and IL-1β (Avitsur et al., 2002, 2003; Quan et al., 2001; Stark et al., 2002). When challenged with LPS in vivo, socially stressed mice show heightened susceptibility to endotoxic shock; inflammatory organ damage; and exaggerated pro-inflammatory cytokine responses in lung, spleen, liver, and brain compared to controls (Quan et al., 2001). Collectively, these findings suggest that the development of glucocorticoid resistance and elevated pro-inflammatory cytokine expression mediate the increase in susceptibility to endotoxic shock observed after repeated social defeat. Humans who experience chronic stressors also show increased levels of circulating cortisol (McEwen, 1998) and develop glucocorticoid resistance (Lowy et al., 1984; Miller et al., 2002; Stratakis et al., 1994). For example, GC resistance is seen in the parents of children undergoing treatment for cancer (Miller et al., 2002). These parents reported higher levels of psychological distress and exhibited flatter diurnal cortisol rhythms compared to the parents of healthy children. Moreover, the immune systems of these parents showed reduced sensitivity to the anti-inflammatory action of a synthetic glucocorticoid, dexamethasone. Specifically, the capacity of dexamethasone to inhibit in vitro production of pro-inflammatory cytokine IL-6 was suppressed among the parents of cancer patients compared to parents of healthy children.
D. Glucocorticoid Resistance and MS Recently, Mohr provided evidence that social stress is associated with increased exacerbations and new lesions in multiple sclerosis patients (Mohr et al., 2000) and suggested that the development of GC resistance is one potential mechanism explaining the link between stress and exacerbation of MS (Mohr, In press). Supporting this line of reasoning, several clinical studies have provided evidence that immune cells of MS patients are less sensitive to the regulatory effects of GC when compared to healthy controls (DeRijk et al., 2004; Stefferl et al., 2001; van Winsen et al., 2005). Moreover, GC resistance has been observed in other inflammatory and autoimmune diseases (lupus, rheumatoid arthritis, asthma, Crohn’s disease, ulcerative colitis) and is hypothesized to contribute to the patho-
genesis of these diseases. For example, reduced sensitivity to in vitro corticosteroid is correlated with poor clinical response to steroid therapy in lupus patients (Tanaka et al., 1992), suggesting that GC resistance may be one factor associated with susceptibility to autoimmune disease. The mechanism mediating GC resistance in autoimmune disease remains unknown. Although it has been suggested that GC resistance may develop due to frequent administration of exogenous GC, a recent study of MS patients demonstrated that GC resistance was unrelated to the frequency or interval of prior treatment with exogenous GC (van Winsen et al., 2005). Given the important role that endogenous GCs play in immune regulation, a reduction in tissue sensitivity to GCs induced by chronic social stress could be one mechanism that increases vulnerability to infectious and autoimmune diseases. To experimentally test this hypothesis, our laboratory has examined the impact of SDR-induced GC resistance on acute and chronic TMEV infection.
VI. THE IMPACT OF SOCIAL DISRUPTION STRESS ON TMEV INFECTION A. SDR during Acute TMEV Infection Our first set of experiments examined the impact of SDR during the acute phase of Theiler’s virus infection. We hypothesized that exposure to SDR prior to infection (PRE-SDR) would induce GC resistance and that this would lead to an increase in CNS inflammation and behavioral signs of infection compared to infected/non-stressed mice. This hypothesis was based on the studies reviewed above that found SDR induced GC resistance and enhanced inflammation induced by LPS, whereas restraint stress did not (Avisur et al., 2001; Quan et al., 2001). We also examined the impact of SDR applied concurrent with infection (CON-SDR), a procedure that mirrors the timing of an alternative stressor (restraint) used in our previous studies (Campbell, et al., 2001; Sieve et al., 2004; Welsh et al., 2004). We found that when restraint stress was applied concurrent with infection, it led to a decrease in CNS inflammation during acute TMEV infection. Given this, concurrent SDR could have a beneficial effect. Alternatively, the impact of a concurrent stressor may vary depending upon the nature of the stress paradigm; restraint may reduce CNS inflammation, while SDR may enhance inflammation. To resolve this issue, we began by evaluating the impact of SDR applied either before or concurrent with TMEV infection. Figure 2 provides a timeline of
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A.
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FIGURE 2 Timeline showing the timing of procedures and data collection for the acute Theiler’s virus infection studies (2A). The effects of SDR on hind limb impairment (2B), stride length (2C), and spinal cord inflammatory markers at day 21 post-infection (2D).
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the experimental procedures (panel A). Mice in the PRE-SDR condition received six sessions of SDR 1 week prior to infection, the CON-SDR mice received six sessions of SDR concurrent with infection, and the NON-SDR mice remained undisturbed. Mice in the PRE-SDR condition were infected intracranially with TMEV 2 hours after the last SDR session, whereas mice in the CON-SDR condition were infected 2 hours after their first session. Following infection, the mice were monitored for the development of motoric impairment and illness behavior before being sacrificed at days 7 or 21 post-infection. Unlike other susceptible mouse strains, BALBc/J mice exhibit significant motor impairment during acute TMEV infection. To quantify these motor changes, we developed a scoring system based on the natural progression of hind limb impairment across time in infected BALBc/J mice. Raters who were blind to experimental condition used this scale to measure changes in weakness and motor coordination. Additional measures of motor function were provided by the foot print (stride length) and grid hang latencies. To make comparisons with our previous research on restraint stress (Campbell et al., 2001), we also assessed encephalitis-like symptoms. To evaluate the physiological effects of SDR on acute TMEV infection, we examined the impact on CNS inflammation and CNS viral clearance. Half of the brains and spinal cords were sectioned and stained with hematoxylin and eosin (H&E) for histological assessment of CNS inflammatory markers for acute TMEV infection. The markers evaluated included perivascular cuffing (accumulation of lymphocytes and macrophages around blood vessels), meningitis (accumulation of lymphocytes and macrophages in the meninges), and microgliosis (presence of increased microglia/macrophages within the parenchyma of the brain and spinal cord). Prior studies have shown that viral titers in CNS are maximal at 1–2 weeks postinfection, and by 3–4 weeks post-infection they have apparently cleared to non-detectable levels (Welsh et al., 1987, 1989). Thus, to evaluate the impact of SDR on CNS viral clearance, half of the brains and spinal cords were used to determine viral titer at days 7 and 21 post-infection using a plaque assay. Intruders for the SDR manipulation were older male breeders, which were selected based on latency to attack both peers and adolescents. During an SDR session, intruders were introduced into the cage of resident mice during the beginning of their dark cycle onset for a period of 2 hours for a total of six SDR sessions. Stressed mice received three consecutive SDR sessions, with one night off, followed by an additional three consecutive SDR sessions. The NON-SDR mice remained undisturbed in their home cage.
We found that when social disruption occurred prior to infection (PRE-SDR) it led to a more severe disease course, while social disruption presented concurrent with infection (CON-SDR) resulted in a less severe disease course (Figure 2, panels B–D). The PRESDR mice exhibited greater hind limb impairment, reduced stride length, and reduced grid hang time compared to the non-stressed controls and CON-SDR. Postmortem histological analyses of H&E stained sections of spinal cord and brain revealed that mice exposed to SDR prior to infection exhibited increased levels of inflammation in spinal cord and brain compared to the no-stress control and CON-SDR mice. Although we observed significant increases in microgliosis, perivascular cuffing, and meningitis in both spinal cord and brain, these effects were most pronounced in spinal cord and most prominent at day 21 (Figure 2, panel D). We also examined whether the timing of SDR altered viral load on days 7 and 21 post-infection. As expected, the non-stressed animals showed a significant reduction in viral load over time, indicating that they were effectively clearing the virus from the CNS to low levels. In comparison, the CONSDR group showed even greater clearance over time, while the PRE-SDR animals showed no reduction over time. This is important because as noted earlier, a failure to clear the virus during the acute phase of TMEV increases the risk of developing the chronic demyelinating phase. Taken together, these findings suggest that the effects of SDR on acute TMEV infection are dependent upon the timing of SDR application in relation to infection, with PRE-SDR resulting in more severe disease course and CON-SDR resulting in less severe disease course.
B. SDR, GC Resistance, and Exacerbation of Acute TMEV The divergent effects of PRE-SDR and CON-SDR on behavioral signs of infection, CNS inflammation, and viral clearance may be attributable to the differential development of GC resistance between groups. Consistent with prior studies conducted using C57BL/6 mice (Avitsur, 2001; Stark et al., 2001), we found that exposure to SDR increased circulating levels of corticosterone and induced GC resistance in the uninfected BALBc/J mice. Although SDR-induced increases in corticosterone would normally be expected to decrease inflammation, the development of GC resistance in the PRE-SDR mice prior to infection would be expected to amplify the CNS inflammatory response during TMEV infection. We propose that the development of GC resistance prior to infection may account for the increase in CNS inflammation and motor impairment
52. Social Stress Alters the Severity of a Virally Initiated Model of Multiple Sclerosis
observed in the infected PRE-SDR mice. Interestingly, GC resistance was not observed following infection in either the CON-SDR or the PRE-SDR mice at 7 days post-infection. Because the non-infected PRE-SDR and infected PRE-SDR were treated exactly the same prior to infection, it is reasonable to assume that both groups developed GC resistance prior to infection and that this would have been maintained in the infected PRESDR mice in the absence of infection. Therefore, it appears that the presence of GC resistance at the time of infection in the PRE-SDR mice resulted in a more robust inflammatory CNS response. In contrast, the inflammatory response to infection was not amplified in the CON-SDR mice due to the absence of GC resistance at the time of infection. Rather, it appears that SDR-induced increases in corticosterone in the CONSDR mice attenuated the CNS inflammatory response to infection relative to the NON-SDR–infected control mice. These findings suggest that the induction of GC resistance by social stress may be one factor that increases the severity of CNS inflammatory responses to TMEV immune challenge.
C. The Role of IL-6 in Mediating the Adverse Effects of SDR We have previously shown that mice subjected to SDR have elevated circulating levels of IL-6 following infection compared to non-stressed controls (Johnson et al., 2005c). IL-6 is a pro-inflammatory cytokine that functions as a central regulator of acute phase, immune, fever, and HPA-axis responses (Akira et al., 1990). Therefore, we examined whether the induction of CNS cytokine production by social stress prior to infection mediates the adverse effects of SDR on acute TMEV. We chose to examine the role of IL-6 because both SDR and TMEV infection have been shown to elevate IL-6. Sheridan’s laboratory has shown that IL-6 is significantly elevated following SDR (Avitsur et al., 2001; Stark et al., 2002). Specifically, SDR enhanced IL-6 responses in plasma and in LPS-stimulated splenocytes. The fact that plasma IL-6 levels are elevated after several cycles of SDR is consistent with other research indicating that circulating levels of IL-6 are increased following stress in animals (Nukina et al., 1998; Zhou et al., 1993) and in humans suffering from major depression (Maes et al., 1997). Other work indicates that IL-6 levels are elevated during Theiler’s virus infection (Mi et al., In review; Palma et al., 2003; Theil et al., 2000). Importantly, recent evidence also suggests that IL-6 is implicated in MS because IL-6–deficient mice do not develop experimental allergic encephalomyelitis
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(EAE), an autoimmune model of MS mediated by Th1 cells (DeRijk et al., 2004; Eugster et al, 1998; Mendel et al., 1998; Samoilova et al., 2000). Moreover, clinical studies indicate that IL-6 is expressed in the lesions and CSF of human MS patients (Padberg et al., 1999; Schonrock et al., 2000). In light of these findings, it seems plausible that SDR-induced increases in central IL-6 prior to infection could enhance the IL-6 response to TMEV infection, thereby exacerbating TMEV-induced inflammation and acute disease course. Importantly, prior studies indicate that exposure to stress prior to LPS immune challenge can sensitize pro-inflammatory cytokine expression, a phenomenon known as crosssensitization (Chancellor-Freeland et al., 1995; Johnson et al., 2002; Persoons et al., 1995; Tilder and Schmidt, 1999; Zhu et al., 1995). This suggests that the increase in histological signs of CNS inflammation observed in mice exposed to social stress prior to TMEV infection may be due to the cross-sensitization of central proinflammatory cytokine activity. If SDR-induced increases in central IL-6 mediate the adverse effects of PRE-SDR, then blocking its effects during the stress exposure period should prevent the exacerbation of acute disease. To test this hypothesis, we recently examined whether the adverse effects of SDR during acute TMEV infection could be reversed by intracranial administration of a neutralizing antibody to IL-6 (Johnson et al., 2005a; Johnson et al., 2005b). Prior to each SDR session, mice in the PRE-SDR or no stress groups received either an intracranial injection of a neutralizing antibody to IL-6 or the vehicle. Thereafter, mice were infected with TMEV and monitored for the development of motor impairment and illness behaviors (see Figure 3). As expected, exposure to social disruption prior to infection led to greater hind limb impairment (3A), decreased locomotor activity (3B), reduced stride length, loss of sucrose preference (3C), allodynia, and a loss of body weight in the vehicle control group. In contrast, pre-treatment with the IL-6 neutralizing antibody blocked the effects of SDR on illness behavior and motor function. In addition, preliminary histological data indicate that PRE-SDR–induced increases in meningitis (3D), perivascular cuffing, and microgliosis observed in the spinal cord were reversed by administration of the neutralizing antibody to IL-6. Collectively, these findings suggest that SDR-induced increases in central IL-6 contribute to the adverse effects of social stress during acute TMEV infection. It must be acknowledged, however, that on some behavioral measures, only a partial reversal was observed in the PRE-SDR mice treated with the IL-6 antibody. Partial reversal suggests that social stress may increase
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FIGURE 3 Intracranial administration of a neutralizing antibody to IL-6 reverses the adverse effects of PRE-SDR during acute TMEV infection. The IL-6 antibody reversed the effects of PRESDR on hind limb impairment (3A), horizontal locomotor activity (3B), sucrose intake (3C), and meningitis in spinal cord at day 21 post-infection (3D).
the central expression of other pro-inflammatory cytokines. Therefore, we are currently investigating whether the adverse effects of social stress on acute TMEV infection also depend on the release of TNF-α and IL-1β in CNS.
D. Clinical Significance of Acute SDR Effects Our findings suggest that PRE-SDR exacerbates acute TMEV infection in adolescent mice. These findings are especially significant given epidemiological evidence suggesting that MS may be triggered by viral infection in adolescence or early adulthood (Acheson, 1977; Kurtzke, 1993). We propose that systemic conditions at the time of infection play an important role in modulating immune processes leading to the development of MS. Specifically, we hypothesize that the induction of GC resistance and the release of proinflammatory cytokines by social stress exacerbates acute infection, which in turn would be expected to have cascading adverse effects during the demyelinating phase of disease.
E. The Impact of SDR on Chronic TMEV Infection To evaluate whether the timing of SDR during early infection alters the development of late disease, we used a longitudinal design to examine the impact of SDR on several behavioral and immunological measures (Johnson et al., 2005c). In this study, TMEVinfected mice received SDR either immediately prior to (PRE-SDR) infection, concurrent with (CONSDR) infection, or they remained undisturbed (NONSDR). During early infection, mice were examined regularly for behavioral signs of the acute disease. In addition, we measured circulating levels of the proinflammatory cytokine IL-6 at day 9 post-infection. After the resolution of the acute phase (4 weeks), mice were monitored monthly until they exhibited behavioral signs of the chronic disease. Thereafter, weekly behavioral measures were taken to examine the development of chronic phase disease. During this period, blood samples were taken on a monthly basis to determine whether SDR altered the development of circulating levels of antibodies to TMEV and several myelin
52. Social Stress Alters the Severity of a Virally Initiated Model of Multiple Sclerosis
components [myelin basic protein (MBP), myelin oligodendrocyte glycoprotein peptide (MOG), and proteolipid protein peptide (PLP)]. The results replicate and extend our prior research by showing that the PRE-SDR condition exacerbated disease course in both the acute and chronic phase of TMEV infection. Consistent with past studies, the PRE-
SDR group developed more severe behavioral signs of acute infection, including hind limb impairment, reduced stride length, and reduced spontaneous locomotor activity compared to both CON-SDR and NONSDR groups. In addition, the PRE-SDR group developed earlier and more severe behavioral signs of chronic disease (Figure 4), including hind limb impairment
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FIGURE 4 The effect of SDR on behavioral measures of motor impairment during chronic Theiler’s virus infection. PRE-SDR animals had earlier onset (day 138 post-infection) and significantly greater hind limb impairment over time (4A). In addition, horizontal locomotor activity (4B), motor coordination on the rotarod test (4C), and stride length (4D) were significantly reduced in the PRE-SDR mice compared to the NON-SDR and CON-SDR groups. In contrast, the CON-SDR mice did not develop significant hind limb impairment until day 165 post-infection and they showed less impairment over time. The CON-SDR mice also showed increased horizontal locomotor activity, improved rotarod performance, and increased stride length relative to the infected NON-SDR controls and PRE-SDR mice. CONSDR stride length was similar to age-matched controls. Average age-matched control data are subtracted from all data points prior to analysis for stride length. Asterisks indicate significant differences.
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(4A), reduced spontaneous locomotor activity (4B), impaired motor coordination on the rotarod (4C) and inclined plane tests, reduced stride length (4D), and reduced sensitivity to von Frey mechanical stimulation. In contrast, exposure to the CON–SDR during the first week of TMEV infection reduced the severity of functional impairments during both the acute and chronic phase of disease. Interestingly, several acute phase behavioral and immunological measures were found to predict the severity of the chronic phase measures. For example, behavioral measures taken on day 7 post-infection (hind limb impairment and spontaneous locomotor activity) predicted the level of behavioral impairment during the chronic phase (hind limb impairment, footprint stride length, and spontaneous locomotor activity at day 136 pi; significant r values ranged from 0.33 to 0.72). In addition, several acute phase physiological measures (IL-6 at day 9 pi; antibody to TMEV, MOG, and MBP at day 42 pi; and body weights) also predicted the level of behavioral impairment during the chronic phase. These correlations between the acute and chronic phase were found for both the onset of the chronic phase and the later time-points. These converging lines of evidence suggest that social stress applied prior to infection leads to more severe acute phase symptomology and increases the risk for developing more severe behavioral symptoms during the chronic phase of disease.
F. Neonatal Experience Alters the Impact of SDR on TMEV Infection More recently, we have examined whether exposure to brief daily maternal separation during the first 2 weeks of life alters the subsequent impact of SDR on TMEV infection. Several laboratories have previously shown that exposure to brief maternal separation leads to a hypoactive HPA-axis, with long-term protective effects (for a review, see Meaney, 2001). In contrast, we found that brief maternal separation may not be protective when paired with later social stress (Johnson et al., 2004a, 2005a). In this study, mouse pups were exposed to either brief maternal separation for 15 minutes each day or to an undisturbed control condition during the first 2 weeks of life and infected with TMEV during adolescence. Typically, when SDR occurs prior to TMEV infection, the outcome is detrimental, while SDR stress concurrent with infection reduces disease severity (Johnson et al., 2004b, Johnson et al., 2005b). However, when the brief maternal separation mice were socially stressed later in life (either prior to or concurrent with infection), they developed more severe behavioral
signs of impairment compared to mice that were not separated as neonates (Figure 5). In contrast, the brief maternal separation mice that were not socially stressed showed a trend of protection, with less severe levels of impairment on some measures. These effects were observed during both the acute and chronic phase of infection on several functional measures, including hind limb impairment (5A), open field horizontal activity measures (5B), corticosterone (5C), IL-6 (5D), antibody to MOG (5E), and antibody to TMEV (5F). Additionally, the brief maternal separation mice that were not socially stressed exhibited lower antibody to virus during late disease, suggesting that neonatal experience influenced disease activity. We also observed blunted CORT responses in the brief maternally separated mice exposed to SDR before or concurrent with infection (5C). It is tempting to speculate that blunted HPA function creates a permissive environment that increases acute CNS inflammation, which in turn alters the immune response to the virus and the development of GC resistance following SDR. Consistent with this notion, elevated circulating levels of IL-6, antibody to TMEV virus, antibody to myelin, as well as greater motor impairment during late disease, were observed in the brief maternal separation mice subjected to SDR prior to infection. Collectively, these results suggest that, while brief maternal separation may be protective against some types of later stressors, it can make animals more vulnerable to the adverse effects of later social stressors on TMEV infection (Laban et al. 1995; Shank and Lightman, 2001).
VII. GENERAL CONCLUSIONS This chapter focused on evidence that two environmental factors, viral infection and stress, may contribute to the development of MS in genetically susceptible humans and animals. A growing body of correlational research suggests that MS is triggered by viral infection. Similarly, evidence for a relationship between stressful life events and MS exacerbation is mounting, including prospective studies indicating that naturally occurring stressors predict the occurrence of new lesions. Because these human studies are correlational, a spurious third variable that influences both stress and disease may be responsible for the association. For example, a personality variable such as pessimism may inflate self-reports of stressful life events while also influencing disease course by increasing a range of health-compromising behaviors (medication nonadherence, substance abuse, poor diet, etc.). To understand the relationship between chronic stress and viral infection in MS, experimental studies
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are needed which allow researchers to randomly assign individuals to stress and virus conditions. Obviously, it would be unethical to conduct such studies in humans. Consequently, we have used an animal model of MS to determine the effects of chronic stress on disease course. Using this approach, we have shown that social stress interacts with TMEV infection to determine the severity of behavioral impairment and
CNS inflammation. We have also found that the timing of the stressor in relation to infection plays a critical role in determining disease course and that neonatal experience alters the impact of social stress during adolescence on TMEV disease course. Additionally, we have begun to examine the underlying endocrine and immune mechanisms whereby social stress exacerbates CNS inflammation and disease course,
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including the induction of GC resistance and crosssensitization of central pro-inflammatory cytokine activity (IL-6). Importantly, we found that adolescent mice exposed to social stress prior to TMEV infection developed more severe behavioral and physiological manifestations of acute and chronic disease. This finding is clinically significant given epidemiological evidence that MS may be initiated by viral infection in adolescence or early adulthood (Acheson, 1977; Kurtzke, 1993). It is tempting to speculate that systemic conditions at the time of infection play an important role in shaping both immune and autoimmune responses leading to the development of MS. Our results provide the first experimental evidence that the induction of GC resistance and the sensitization of central proinflammatory cytokine expression by social stress contribute to the exacerbation of acute TMEV infection. Future studies will need to examine whether the induction of GC resistance and central sensitization of IL-6 by social stress have cascading effects that exacerbate the demyelinating phase of disease. In conclusion, we have presented a mouse model that is designed to resolve issues regarding the relationship between social stress and viral infection in MS. Although mice are not men, they share many behavioral and biological similarities with humans that make them a reasonable model for investigating the relationships between social conflict and virally initiated inflammatory diseases. Our results may have implications for understanding the development of multiple sclerosis and other autoimmune diseases. We propose that exposure to chronic social stress prior to infection may result in increased CNS inflammation and a dysregulation of the early immune response infection. Because early immune responses shape the specific immune response to infection, dysregulation of this response may contribute to the failure to eliminate the pathogen and exacerbation during late disease. The establishment of a persistent infection, combined with a heightened inflammatory environment in the CNS, may contribute to the development of autoimmune diseases such as multiple sclerosis.
Acknowledgments This research was supported by an NSF Fellowship and NIH/ NRSA to RRJ and funded by grants to C.J.R.W. and M.W.M. from the National Multiple Sclerosis Society RG 3128 and NIH/NINDS R01 39569.
References Acheson, E. D. (1977). Epidemiology of multiple sclerosis. Brit. Med. Bull., 33, 9–14.
Ackerman, K. D., Rabin, B. S., Heyman, R., and Baum, A. (2000). Stressful life events and disease activity in multiple sclerosis. Brain Behav. Immun., 14, 77. Akira, S., Hirano, T., Taga, T., and Kishimoto, T. (1990). Biology of multifunctional cytokines: IL-6 and related molecules (IL1 and TNF). FASEB J., 4, 2860–2867. Allen, I., and Brankin, B. J. (1993). Pathogenesis of multiple sclerosis—the immune diathesis and the role of viruses. Neuropathol. and Exp. Neurol., 52, 95. Anderson, D. W., Ellenberg., J. H., Leventhal, C. M., Reingold, S. C., Rodriguez, M., and Silberberg, D. H. (1992). Revised estimate of the prevalence of multiple sclerosis in the United States. Ann. Neurol., 31, 333–336. Aubert, C., Chamorro, M. and Brahic, M. (1987). Identification of Theiler’s infected cells in the central nervous system of the mouse during demyelinating disease. Microbial Pathogenesis, 3, 319– 326. Avitsur, R., Padgett, D. A., Dhabhar, F. S., Stark, J. L., Kramer, K. A., Engler, H., and Sheridan, J. F. (2003a). Expression of glucocorticoid resistance following social stress requires a second signal. J. Leukocyte Biology, 74, 507–513. Avitsur, R., Stark, J. L., Dhabhar, F. S., Kramer, K. A., and Sheridan, J. F. (2003b). Social experience alters the response to social stress in mice. Brain Behav. Immun., 17, 426–437. Avitsur, R., Stark, J. L., Dhabhar, F. S., Padgett, D. A., and Sheridan, J. F. (2002). Social disruption-induced glucocorticoid resistance: kinetics and site specificity. J. Neuroimmunol., 124 (1–2), 54–61. Avitsur, R., Stark, J. L., and Sheridan, J. F. (2001). Social stress induces glucocorticoid resistance in subordinate animals. Hormones and Behavior, 39, 247–257. Barak, O., Goshen, I., Ben-Hur, T., Weidenfeld, J., Taylor, A. N., and Yirmiya, R. (2002a). Involvement of brain cytokines in the neurobehavioral disturbances induced by HIV-1 glycoprotein120. Brain Res., 933, 98–108. Barak, O., Weidenfeld, J., Goshen, I., Ben-Hur, T., Taylor, A. N., and Yirmiya, R. (2002b). Intracerebral HIV-1 glycoprotein 120 produces sickness behavior and pituitary-adrenal activation in rats: role of prostaglandins. Brain Behav. Immun., 16, 720–735. Biron, C. A. (1998). Role of early cytokines, including alpha and beta interferons ((IFN-α/β), in innate and adaptive immune responses to viral infections. Seminars in Immunology, 10, 383–390. Blanchard, R. J., McKittrick, C. R., and Blanchard, D. C. (2001). Animal models of social stress: effects on behavior and brain neurochemical systems. Neurosciences and Biobehavioral. Reviews, 73, 261–271. Borrow, P., Tonks, P., Welsh, C. J. R., and Nash, A. A. (1992). The role of CD8+ T cells in the acute and chronic phases of Theiler’s virus-induced disease in mice. J. Gen. Virol., 73, 1861–1865. Borrow, P., Welsh, C. J. R., Dean, D., Tonks, P., Blakemore, W. F., and Nash, A. A. (1998). Investigation of the role of autoimmune responses to myelin in the pathogenesis of TMEV-induced demyelinating disease. Immunol., 93, 478–484. Borrow, P., Welsh, C. J. R., and Nash, A. A. (1993). Study of the mechanisms by which CD4+ T cells contribute to protection in Theiler’s murine encephalomyelitis. Immunol., 80, 502–506. Brahic, M., Stroop, W. G., and Baringer, J. R. (1981). Theiler’s virus persists in glial cells during demyelinating disease. Cell, 26, 123–128. Campbell, T., Meagher, M. W., Sieve, A., Scott, B., Storts, R., Welsh, T. H., and Welsh, C. J. (2001). The effects of restraint stress on the neuropathogenesis of Theiler’s virus infection: I. Acute disease. Brain Behav. Immun., 15, 235–254. Challoner, P. B., Smith, K. T., Parker, J. D., MacLeod, D. L., Coulter, S. N., et al. (1995). Plaque-associated expression of human her-
52. Social Stress Alters the Severity of a Virally Initiated Model of Multiple Sclerosis pesvirus 6 in multiple sclerosis. Proc. Natl. Acad. Sci. USA, 92, 7440–7444. Chancellor-Freeland, C., Zhu, G., Kage, R., Beller, D., Leeman, S., and Black, P. (1995). Substance P and stress-induced changes in macrophages. Ann. N. Y. Acad. Sci., 771, 472–484. Chrousos, G. P. (1995). The hypothalamic-pituitary-adrenal axis and immune-mediated inflammation. N. Engl. J. Med., 332 (20), 1351–1362. Clatch, R. J., Lipton, H. L., and Miller, S. D. (1987) Class II-restricted T cell responses in Theiler’s murine encephalomyelitis virus (TMEV)-induced demyelinating disease. II. Survey of host immune responses and central nervous system virus titers in inbred mouse strains. Microbial Pathogenesis, 3, 327–337. Clatch, R. J., Miller, S. D., Metzner, R., Dal Canto, M. C., and Lipton, H. L. (1990). Monocytes/macrophages isolated from the mouse central nervous system contain infectious Theiler’s murine encephalomyelitis virus (TMEV). Virol., 176, 244–254. Cohen, S., Doyle, W. J., Skoner, D. P., Rabin, B. S., and Gwaltney, J. M. Jr. (1997a). Social ties and susceptibility to the common cold. JAMA, 277, 1940–1944. Cohen, S., Kaplan, J. R., Cunnick, J. E., Manuck, S. B., and Rabin, B. S. (1992). Chronic social stress, affiliation and cellular immune response in nonhuman primates. Psychological Science, 3, 301–304. Cohen, S., Line, S., Manuck, S. B., Rabin, B. S., Heise, E., and Kaplan, J. R. (1997b). Chronic social stress, social status and susceptibility to upper respiratory infections in nonhuman primates. Psychosomatic Medicine, 59, 213–221. Cohen, S., Tyrrell, D. A. J., and Smith, A. P. (1991). Psychological stress in humans and susceptibility to the common cold. N. Engl. J. Med., 325, 606–612. Cohen, S., Tyrrell, D. A. J., and Smith, A. P. (1993). Life events, perceived stress, negative affect and susceptibility to the common cold. Journal of Personality and Social Psychology, 64, 131–140. Croxford, J. L., Olson, J. K., and Miller, S. D. (2002). Epitope spreading and molecular mimicry as triggers of autoimmunity in the Theiler’s virus-induced demyelinating disease model of multiple sclerosis. Autoimmunity Reviews, 1, 251–260. Dal Canto, M. C., Calenoff, M. A., Miller, S. D., and Vanderlugt, C. L. (2000). Lymphocytes from mice chronically infected with Theiler’s murine encephalomyelitis virus produce demyelination of organotypic cultures after stimulation with the major encephalitic epitope of myelin proteolipid protein. Epitope spreading in TMEV infection has functional activity. J. Neuroimmunol., 104, 79–84. Dal Canto, M. C., and Rabinowitz, S. G. (1982). Experimental models of virus-induced demyelination of the central nervous system. Ann. Neurol., 11, 109–127. DeRijk, R. H., Eskandari, F., and Sternberg, E. M. (2004). Corticosteroid resistance in a subpopulation of multiple sclerosis patients as measured by ex vivo dexamethasone inhibition of LPS induced IL-6 production. J. Neuroimmunol., 151 (1–2), 180–188. Dethlefs, S., Brahic, M., and Larsson-Sciard, E. L. (1997). An early abundant cytotoxic T-lymphocyte response against Theiler’s virus is critical for preventing for viral persistence. J. Virol., 71, 8875–8878. Dyment, D. A., Ebers, G. C., and Sadovnick, A. D. (2004). Genetics of multiple sclerosis. Lancet Neurol., 3, 104–110. Elenkov, I. J., and Chrousos, G. P. (2002). Stress hormones, proinflammatory and antiinflammatory cytokines, and autoimmunity. Ann. N. Y. Acad. Sci., 966, 290–303. Eugster, H. P., Frei, K., Kopf, M., Lassmann, H., and Fontana, A. (1998). IL-6–deficient mice resist myelin oligodendrocyte glyco-
1121
protein-induced autoimmune encephalomyelitis. Eur. J. Immunol., 28, 2178–2187. Fiette, L., Aubert, C., Brahic, M., and Ross, C. P. (1993). Theiler’s virus infection of β2-microglobulin deficient mice. J. Virol., 67, 589–592. Fiette, L., Aubert, C., Ulrike, M., Huang, S., Aguet, M., Brahic, M., and Bureau, J. F. (1995). Theiler’s virus infection of 129Sv mice that lack the interferon αβ or IFN-γ receptors. J. Exp. Med., 181, 2069–2076. Filippini, G., Munari, L., Incorvaia, B., Ebers, G. C., Polman, C., D’Amico, R., et al. (2003). Interferons in relapsing remitting multiple sclerosis: a systematic review. Lancet, 361 (9357), 545–552. Gerety, S. J., Clatch, R. J., Lipton, H. L., Goswami, R. G., Rundell, M. K., and Miller, S. D. (1991). Class II-restricted T cell responses in Theiler’s murine encephalomyelitis virus-induced demyelinating disease. IV. Identification of an immunodominant T cell determinant, on the N-terminal end of the VP-2 capsid protein in susceptible SJL/J mice. J. Immunol., 146, 4322–4326. Gilden, D. H. (2005). Infectious causes of multiple sclerosis. Lancet Neurol., 4, 195–202. Glaser, R., Kiecolt-Glaser, J. K., Bonneau, R., Malarkey, W. and Hughes, J. (1992). Stress-induced modulation of the immune response to recombinant hepatitis B vaccine. Psychosomatic Medicine, 54, 22–29. Glaser, R., Sheridan, J. F., Malarkey, W. B., MacCallum, R. C., and Kiecolt-Glaser, J. K. (2000). Chronic stress modulates the immune response to a pneumococcal pneumonia vaccine. Psychosomatic Medicine, 62, 804–807. Grant, I., Brown, G. W., Harris, T., McDonald, W. I., Patterson, T., and Trimble, M. R. (1989). Severely threatening events and marked life difficulties preceding onset or exacerbation of multiple sclerosis. J. Neurol. Neurosurg. Psychiatry, 52, 8–13. Gutierrez, J., Vergara, M. J., Guerrero, M., Fernandez, O., Piedrola, G., Morales, P., and Maroto, M. C. (2002). Multiple sclerosis and human herpesvirus 6. Infection, 30, 145–149. Hernan, M. A., Zhang, S. M., Lipworth, L., Olek, M. J., and Ascherio, A. (2001). Multiple sclerosis and age at infection with common viruses. Epidemiology, 12, 301–306. Jacobson, D. L., Gange, S. J., Rose, N. R., and Graham, N. M. (1997). Epidemiology and estimated population burden of selected autoimmune diseases in the United States. Clin. Immunol. Immunopathol., 84 (3), 223–243. Johnson, J. D., O’Connor, K. A., Deak, T., Stark, M., Watkins, L. R., and Maier, S. F. (2002). Prior stressor exposure sensitizes LPSinduced cytokine production. Brain Behav. Immunol., 16, 461–476. Johnson, R. R., Bridegam, P., Prentice, T. W., Welsh, T. H., Welsh, C. J. R., and Meagher, M. W. (2004a). Early life experience interacts with later social stress in the development of Theiler’s virus infection. Society for Neuroscience Abstracts. Johnson, R. R., Bridegam, P., Prentice, T. W., Welsh, T. H., Welsh, C. J. R., and Meagher, M. W. (2005a, In preparation). Early life experience interacts with later social stress in the development of acute and chronic Theiler’s virus infection. Johnson, R. R., Good, E. A., Hardin, E. A., Connoer, M. A., Prentice, T. W., Welsh, C. J. R., and Meagher, M. W. (2005b). Necessity of IL-6 in effects of social stress in acute Theiler’s virus infection. Society for Neuroscience Abstracts 31, 1012. 20. Johnson, R. R., Prentice, T. W., Bridegam, P., Welsh, T. H., Welsh, C. J. R., and Meagher, M. W. (In press). Social stress alters the severity and onset of the chronic phase of Theiler’s virus infection. Brain Beh. Immun. Johnson, R. R., Prentice, T. W., Bridegam, P., Young, C. R., Steelman, A. J., Welsh, T. H., Welsh, C. J. R., and Meagher, M. W. (2005c,
1122
V. Psychoneuroimmunology and Pathophysiology
In review). Social stress alters the severity and onset of the chronic phase of Theiler’s virus infection. Johnson, R. R., Storts, R., Welsh, T. H., Jr., Welsh, C. J., and Meagher, M. W. (2004b). Social stress alters the severity of acute Theiler’s virus infection. J. Neuroimmunol., 148, 74–85. Johnson, R. T. (1994). The virology of demyelinating diseases. Ann. Neurol., 36 (Suppl.), S54–60. Kaminsky, S. G., Nakamura, I., and Cudkowicz, G. (1987). Defective differentiation of natural killer cells in SJL mice. Role of the thymus. J. Immunol., 138, 1020–1025. Kiecolt-Glaser, J., Glaser, R., Gravenstein, S., Malarkey, W. B., and Sheridan, J. F. (1996). Chronic stress alters the immune response to influenza virus vaccine in older adults. Proc. Natl. Acad. Sci. USA, 93, 3043–3047. Kohanawa, M., Nakane, A., and Minagawa, T. (1993). Endogenous gamma interferon produced in central nervous system by systemic infection with Theiler’s virus in mice. J. Neuroimmunol., 48, 205–211. Kurtzke, J. F. (1993). Epidemiologic evidence for multiple sclerosis as an infection. Clin. Microbiol. Rev., 6, 382–427. Kurtzke, J. F., and Hyllested, K. (1987). MS epidemiology in Faroe Islands. Rev. Neurol., 57, 77–87. Laban, O., Dimitrijevic, M., von Hoersten, S., Markovic, B. M., and Jankovic, B. D. (1995). Experimental allergic encephalomyelitis in adult DA rats subjected to neonatal handling or gentling. Brain Res., 676, 133–140. Levin, L. I., Munger, K. L., Rubertone, M. V., Peck, C. A., Lennette, E. T., Spiegelman, D., and Ascherio, A. (2003). Multiple sclerosis and Epstein-Barr virus. JAMA, 289, 1533–1536. Lindsley, M. D., Thiemann R., and Rodriguez, M. (1991). Cytotoxic T cells isolated from the central nervous system of mice infected with Theiler’s virus. J. Virol., 65, 6612–6620. Lipton, H. L. (1975). Theiler’s virus infection in mice: an unusual biphasic disease process leading to demyelination. Infect. Immun., 11, 1147–1155. Lipton, H. L., Twaddle, G., and Jelachich, M. L. (1995). The predominant virus antigen burden is present in macrophages in Theiler’s murine encephalomyelitis virus-induced demyelinating disease. J. Virol., 69, 2525–2533. Lowy, M. T., Reder, A. T., Antel, J. P., and Meltzer, H. Y. (1984). Glucocorticoid resistance in depression: the dexamethasone suppression test and lymphocyte sensitivity to dexamethasone. Am. J. Psychiatry, 141, 1365–1370. Mack, C. L., Vanderlugt-Castaneda, C. L., Neville, K. L., and Miller, S. D. (2003). Microglia are activated to become competent antigen presenting and effector cells in the inflammatory environment of the Theiler’s virus model of multiple sclerosis. J. Neuroimmunol., 144, 68–79. Maes, M., Bosmans, E., De Jongh, R., Kenis, G., Vandoolaeghe, E., and Neels, H. (1997). Increased serum IL-6 and IL-1 receptor antagonist concentrations in major depression and treatment resistant depression. Cytokine, 9, 853–858. Majid, A., Galetta, S. L., Sweeney, C. J., et al. (2002). Epstein-Barr virus myeloradiculitis and encephalomyeloradiculitis. Brain, 125, 1–7. Martyn, C. N., Cruddas, M., and Compston, D. A. (1993). Symptomatic Epstein-Barr virus infection and multiple sclerosis. J. Neurol. Neurosurg. Psychiatry, 56, 167–168. McEwen, B. S. (1998). Protective and damaging effects of stress mediators. N. Engl. J. Med., 338, 171–179. McGavern, D. B., Zoecklein, L., Drescher, K. M., and Rodriguez, M. (1999). Quantitative assessment of neurologic deficits in a chronic progressive murine model of CNS demyelination. Exp. Neurol., 158, 171–181.
McGavern, D. B., Zoecklein, L., Sathornsumetee, S., and Rodriguez, M. (2000). Assessment of hindlimb gait as a powerful indicator of axonal loss in a murine model of progressive CNS demyelination. Brain Res., 877, 396–400. Meaney, M. J. (2001). Maternal care, gene expression, and the transmission of individual differences in stress reactivity across generations. Annu. Rev. Neurosci., 24, 1161–1192. Mendel, I., Katz, A., Kozak, N., Ben-Nun, A., and Revel, M. (1998). Interleukin-6 functions in autoimmune encephalomyelitis: a study in gene-targeted mice. Eur. J. Immunol., 28, 1727–1737. Mi, W., Prentice, T., Johnson, R. R., Sieve, A. N., Storts, R., Meagher, M. W., and Welsh, C. J. (In preparation). Alterations in cytokine expression following Theiler’s virus infection and restraint stress. Miller, G. E., Cohen, S., and Ritchey, A. K. (2002). Chronic psychological stress and the regulation of pro-inflammatory cytokines: a glucocorticoid-resistance model. Health Psychol., 21 (6), 531–541. Miller, S. D., Olson, J. K., and Croxford, J. L. (2001). Multiple pathways to induction of virus-induced autoimmune demyelination: lessons from Theiler’s virus infection. J. Autoimmunology, 16, 219–227. Miller, S. D., VanDerlugt, C. L., Begolka, W. S., Pao, W., Yauch, R. L., Neville, K. L., Katz-Levy, Y., Carrizosa, A., and Kim, B. S. (1997). Persistent infection with Theiler’s virus leads to CNS autoimmunity via epitope spreading. Nat. Med., 3, 1133–1136. Mohr, D. C. (In press). The relationship between stressful life events and inflammation among patients with multiple sclerosis. In C. J. R. Welsh, M. W. Meagher, and E. M. Sternberg (Eds.), Host defense and autoimmunity: neural and neuroendocrine mechanisms in disease. New York: Kluwer Publishers. Mohr, D. C., Goodkin, D. E., Bacchetti, P., Boudewyn, A. C., Huang, L., Marrietta, P., Cheuk, W., and Dee, B. (2000). Psychological stress and the subsequent appearance of new brain MRI lesions in MS. Neurology, 55, 55–61. Mohr, D. C., Goodkin, D. E., Nelson, S., Cox, D., and Weiner, M. (2002). Moderating effects of coping on the relationship between stress and the development of new brain lesions in multiple sclerosis. Psychosomatic Medicine, 64 (5), 803–809. Mohr, D. C., Hart, S. L., Julian, L., Cox, D., and Pelletier, D. (2004). Association between stressful life events and exacerbation in multiple sclerosis: a meta-analysis. British Medical Journal, 328 (7442), 731–735. Mohr, D. C., and Pelletier, D. (In press). A temporal framework for understanding the effects of stressful life events on inflammation in patients with multiple sclerosis. Brain Behav. Immun. Moore F. G., and Wolfson, C. (2002). Human herpes virus 6 and multiple sclerosis. Acta Neurol. Scand., 106, 63–83. Murray, P. D., Pavelko, K. D., Leibowitz, J., Lin, X., and Rodriguez, M. (1998). CD4 (+) and CD8 (+) T cells make discrete contributions to demyelination and neurologic disease in a viral model of multiple sclerosis. J. Virol., 72, 7320–7329. Nicholson, S. M., Peterson, J. D., Miller, S. D., Wang, K., Dal Canto, M. C., and Melvold, R. W. (1994). BALB/c substrain differences in susceptibility to Theiler’s murine encephalomyelitis virusinduced demyelinating disease. J. Neuroimmunol., 52, 19–24. Nisipeanu, P., and Korczyn, A. D. (1993). Psychological stress as risk factor for exacerbations in multiple sclerosis. Neurology, 43, 1311–1312. Noonan, C. W., Kathman, S. J., and White, M. C. (2002). Prevalence estimates for MS in the United States and evidence of an increasing trend for women. Neurology, 58 (1), 136–138. Noseworthy, J. H., Lucchinetti, C., Rodriguez, M., and Weinshenker, B. G. (2000). Multiple sclerosis. N. Engl. J. Med., 343, 938–952.
52. Social Stress Alters the Severity of a Virally Initiated Model of Multiple Sclerosis Oleszak, E. L., Chang, J. R., Friedman, H., Katsetos, C. D., and Platsoucas, C. D. (2004). Theiler’s virus infection: a model for multiple sclerosis. Clin. Microbiol. Rev., 17, 174–207. Olson, J. K., Eagar, T. N., and Miller, S. D. (2002). Functional activation of myelin specific T cells by virus-induced molecular mimicry. J. Immunol., 169, 2719–2726. Olson, J. K., Girvin, A. M., and Miller, S. D. (2001). Direct activation of innate and antigen-presenting functions of microglia following infection with Theiler’s virus. J. Virol., 75, 9780–9789. Olson, J. K., Ludovic Croxford, J., and Miller, S. D. (2004). Innate and adaptive immune requirements for induction of autoimmune demyelinating disease by molecular mimicry. Mol. Immunol., 40, 1103–1108. Padberg, F., Feneberg, W., Schmidt, S., Schwarz, M. J., Korschenhausen, D., Greenberg, B. D., Nolde, T., Muller, N., Trapmann, H., Konig, N., Moller, H. J., and Hampel, H. (1999). CSF and serum levels of soluble interleukin-6 receptors (sIL-6R and sgp130), but not of interleukin-6 are altered in multiple sclerosis. J. Neuroimmunol., 99, 218–223. Padgett, D. A., Sheridan, J. F., Dorne, J., Berntson, G. G., Candelora, J., and Glaser, R. (1998). Social stress and the reactivation of latent herpes simplex virus type 1. Proc. Natl. Acad. Sci. USA, 95, 7231–7235. Palma, J. P., Kwon, D., Clipstone, N. A., and Kim, B. S. (2003). Infection with Theiler’s murine encephalomyelitis virus directly induces proinflammatory cytokines in primary astrocytes via NF-kappaB activation: potential role for the initiation of demyelinating disease. J. Virol., 77, 6322–6331. Persoons, J. H., Schornagel, K., Breve, J., Berkenbosch, F., and Kaal, G. (1995). Acute stress affects cytokines and nitric oxide production by alveolar macrophages differently. Am. J. Respir. Crit. Care Med., 152, 619–624. Pollak, Y., Ovadia, H., Goshen, I., Gurevich, R., Monsa, K., Avitsur, R., and Yirmiya, R. (2000). Behavioral aspects of experimental autoimmune encephalomyelitis. J. Neuroimmunol., 104, 31–36. Pullen, L. C., Miller, S. D., Dal Canto, M. C., and Kim, B. S. (1993). Class I-deficient resistant mice intracerebrally inoculated with Theiler’s virus show an increased T cell response to viral antigens and susceptibility to demyelination. Eur. J. Immunol., 23, 2287–2293. Quan, N., Avitsur, R., Stark, J. L., He, L., Lai, W., Dhabhar, F. S., and Sheridan, J. F. (2003). Molecular mechanisms of glucocorticoid resistance in splenocytes of socially stressed male mice. J. Neuroimmunol., 137, 51–58. Quan, N., Avitsur, R., Stark, J. L., He, L., Shah, M., Caliguiri, M., Padgett, D. A., Marucha, P. T., and Sheridan, J. F. (2001). Social stress increases the susceptibility to endotoxic shock. J. Neuroimmunol., 115, 36–45. Rodriguez, M., Pavelko, K., and Coffman, R. L. (1995). Gamma interferon is critical for resistance to Theiler’s virus-induced demyelination. J. Virol., 69, 7286–7290. Rodriguez, M., Pavelko, K. D., Njenga, M. K., Logan., W. C., and Wettstein, P. J. (1996). The balance between persistent virus infection and immune cells determines demyelination. J. Immunol., 157, 5699–5709. Rodriguez, M., and Sriram, S. (1988). Successful therapy of Theiler’s virus-induced demyelination (DA strain) with monoclonal antiLyt2 antibody. J. Immunol., 140, 2950–2955. Roos, R. P., and Wollmann, R. (1984). DA strain of Theiler’s murine encephalomyelitis virus induces demyelination in nude mice. Ann. Neurol., 15, 494–499. Rossi, P. C., McAllister, A., Fiette, L., and Brahic, M. (1991). Theiler’s virus infection induces a specific cytotoxic T lymphocyte response. Cell. Immunol., 138, 341–348.
1123
Samoilova, E. B., Horton, J. L., Hilliard, B., Liu, T. S., and Chen, Y. (1998). IL-6–deficient mice are resistant to experimental autoimmune encephalomyelitis: roles of IL-6 in the activation and differentiation of autoreactive T cells. J. Immunol., 161, 6480–6486. Schonrock, L. M., Gawlowski, G., and Bruck, W. (2000). Interleukin6 expression in human multiple sclerosis lesions. Neurosci. Lett., 294, 45–48. Shanks, N. and Lightman, S. L. (2001). The maternal-neonatal neuroimmune interface: Are there long-term implications for inflammatory or stress-related disease? J. Clin. Invest., 108, 1567–1573. Sibley, W. A., Bamford, C. R., and Clark, K. (1985). Clinical viral infections and multiple sclerosis. Lancet, 1, 1313–1315. Sieve, A. N., Steelman, A. J., Young, C. R., Storts, R., Welsh, T. H., Welsh, C. J., and Meagher, M. W. (2004). Chronic restraint stress during early Theiler’s virus infection exacerbates the subsequent demyelinating disease in SJL mice. J. Neuroimmunol., 155, 103–118. Soldan, S. S., and Jacobson S. (2001). Role of viruses in etiology and pathogenesis of multiple sclerosis. Adv. Virus Res., 56, 517–555. Soldan, S. S., Leist, T. P., Juhng, K. N., McFarland, H. F., and Jacobson, S. (2000). Increased lymphoproliferative response to human herpesvirus type 6A variant in multiple sclerosis patients. Ann. Neurol., 47, 306–313. Sospedra, M., and Martin, R. (2005). Immunology of multiple sclerosis. Annu. Rev. Immunol., 23, 683–747. Stark, J. L., Avitsur, R., Hunzeker, J., Padgett, D. A., and Sheridan, J. F. (2002). Interleukin-6 and the development of social disruption-induced glucocorticoid resistance. J. Neuroimmunol., 124 (1– 2), 9–15. Stark, J. L., Avitsur, R., Padgett, D. A., Campbell, K. A., Beck, F. M., and Sheridan, J. F. (2001). Social stress induces glucocorticoid resistance in macrophages. Am. J. Physiol. Regul. Integr. Comp. Physiol., 280 (6), R1799–1805. Stefferl, A., Storch, M. K., Linington, C., Stadelmann, C., Lassmann, H., Pohl, T., et al. (2001). Disease progression in chronic relapsing experimental allergic encephalomyelitis is associated with reduced inflammation-driven production of corticosterone. Endocrinology, 142 (8), 3616–3624. Stininssen, P., Raus, J., and Zhang, J. (1997). Autoimmune pathogenesis of multiple sclerosis: role of autoreactive T lymphocytes and new immunotherapeutic strategies. Crit. Rev. Immunol., 17, 33–75. Stratakis, C. A., Karl, M., Schulte, H. M., and Chrousos, G. P. (1994). Glucocorticosteroid resistance in humans. Elucidation of the molecular mechanisms and implications for pathophysiology. Ann. N. Y. Acad. Sci., 746, 362–374. Tanaka, H., Akama, H., Ichikawa, Y., Makino, I., and Homma, M. (1992). Glucocorticoid receptor in patients with lupus nephritis: relationship between receptor levels in mononuclear leukocytes and effect of glucocorticoid therapy. J. Rheumatol., 19, 878– 883. Theil, D. J., Tsunoda, I., Libbey, J. E., Derfuss, T. J., and Fujinami, R. S. (2000). Alterations in cytokine but not chemokine mRNA expression during three distinct Theiler’s virus infections. J. Neuroimmunol., 104, 22–30. Theiler, M. (1934). Spontaneous encephalomyelitis of mice—a new virus. Science, 80, 122. Tilder, F. J., and Schmidt, E. D. (1999). Cross-sensitization between immune and non-immune stressors. A role in depression? Adv. Exp. Med. Biol., 461, 179–197. van Winsen, L. M., Muris, D. F., Polman, C. H., Dijkstra, C. D., van den Berg, T. K., and Uitdehaag, B. M. (2005). Sensitivity to glucocorticoids is decreased in relapsing remitting multiple sclerosis. J. Clin. Endocrinol. Metab., 90 (2), 734–740.
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V. Psychoneuroimmunology and Pathophysiology
Wandinger, K. P., Jabs, W., Siekhaus, A., Bubel, S., Trillenberg, P., et al. (2000). Association between clinical disease activity and Epstein-Barr virus reactivation in MS. Neurology, 55, 178–184. Warren, S., Greenhill, S., and Warren, K. G. (1982). Emotional stress and the development of multiple sclerosis: case-control evidence of a relationship. J. Chronic Dis., 35, 821–831. Welsh, C. J. R., Blakemore, W. F., Tonks, P., Borrow, P., and Nash, A. A. (1989). Theiler’s murine encephalomyelitis virus infection in mice: a persistent viral infection of the central nervous system which induces demyelination. In Nigel Dimmock (Ed.), Immune responses, virus infection and disease (pp. 125–147). Oxford: Oxford University Press. Welsh, C. J. R., Mi, W., Sieve, A. N., Steelman, A. J., Johnson, R. R, Young, C. R., Prentice, T., Storts, R., Welsh T. W., and Meagher, M. W. (In press). Stress effects on the neuropathogenesis of Theiler’s virus-induced demyelination as a model for multiple sclerosis. In C. J. R., Welsh, M. W. Meagher, and E. M. Sternberg (Eds.), Host defense and autoimmunity: neural and neuroendocrine mechanisms in disease. New York: Kluwer Publishers. Welsh, C. J. R., Sapatino, B. V., Rosenbaum, B., and Smith, R. (1995). Characteristics of cloned cerebrovascular endothelial cells fol-
lowing infection with Theiler’s virus. I. Acute infection. J. Neuroimmunol., 62, 119–125. Welsh, C. J. R., Tonks, P., Borrow, P., and Nash, A. A. (1990). Theiler’s virus: an experimental model of virus-induced demyelination. Autoimmunity, 6, 105–112. Welsh, C. J. R., Tonks, P., Nash, A. A., and Blakemore, W. F. (1987). The effect of L3T4 T cell depletion on the pathogenesis of Theiler’s murine encephalomyelitis virus infection in CBA mice. J. Gen. Virol., 68, 1659–1667. Zhou, D., Kusnecov, A. W., Shurin, M. R., DePaoli, M., and Rabin, B. S. (1993). Exposure to physical and psychological stressors elevates plasma interleukin 6: relationship to the activation of hypothalamic-pituitary-adrenal axis. Endocrinology, 133, 2523–2530. Zhu, G., Chancellor-Freeland, C., Berman, A., Kage, R., Leeman, S., Beller, D., and Black, P. (1995). Endogenous substance P mediates cold-water-stress induced increase in interleukin-6 section from peritoneal macrophages. J. Neurosci., 16, 3745–3752.
Author Index
Aabech, P., 1057, 1058 Aandahl, E. M., 1058 Aarden, L. A., 54, 997 Aaronson, N. K., 875 Aarseth, J., 420 Aasa-Chapman, M. M., 1054 Aasal, R., 490 Abad, C., 104, 133, 135, 139, 143, 144, 146, 195 Abad, L. W., 361 Abate, M. A., 1059 Abbas, A. K., 47, 66, 222 Abbas Helmy, A., 362 Abbott, D. H., 491 Abboud, F. M., 603 Abdel Shafy, S., 362 Abdelaal, E., 964, 965 Abd-ElGawad, H. M., 303 Abdel-Naseer, M., 362 Abdul-Khaliq, H., 566 Abdullah, A., 174 Abdullah, K. M., 174 Abdulrazzaq, Y. M., 807 Abe, M., 100, 329, 330, 554 Abe, R., 830, 1058 Abe, S., 522 Abel, S., 565 Abela, G. S., 922, 930 Abell, K. M., 728 Abelli, L., 115, 117 Abello, J., 109, 114 Abeloff, M. D., 771 Abelson, J. L., 539 Abendroth, A., 859 Abeni, D., 976, 979 Abercrombie, H., 884 Abercrombie, H. C., 884 Abidi, A., 736 Abitri, N., 255 Abney, E., 143 Abo, T., 605, 744 Aboud, M., 237
Abouhamze, A., 733, 1025 Aboulafi a, J., 1046 Abraham, C. R., 384 Abraham, G., 1044 Abraham, J., 304, 384, 385, 386, 387, 444 Abramovitch, R., 239 Abramovits, V., 977, 984, 985 Abrams, G. M., 745 Abrams, T., 631, 632 Abramsky, O., 364, 419 Abramson, J. H., 870 Abramson, M., 816 Abrass, C. K., 100 Abrass, I. B., 100 Abrous, D. N., 465 Abudarham, N., 76, 256, 257, 259 Abulafia, O., 881 Abumrad, N., 105, 605, 997 Accardo, S., 209, 212, 222 Accili, D., 174, 995, 999 Achermann, P., 585 Acheson, E. D., 1107, 1116, 1120 Ackenheil, M., 365, 568, 570, 572 Ackerman, G. A., 746 Ackerman, K., 678 Ackerman, K. D., 64, 70, 77, 115, 621, 725, 726, 733, 744, 746, 1057, 1110 Ackerman, S., 789 Acree, M., 1061 Acs, G., 102, 109 Acs, P., 102, 109 Acton, R. T., 365, 366 Adachi, A., 88 Adachi, M., 52 Adair, L. S., 462 Adam, E., 927 Adamek, C., 984 Adami, C., 565 Adami, N., 103 Adamopoulos, S., 969 Adams, D. O., 925, 930
1125
Adams, E., 736 Adams, F., 802 Adams, H. G., 551 Adams, L., 717 Adams, M. M., 184 Adams, M. R., 483 Adams, N. C., 1099 Adams, P., 804 Adams, R. J., 811 Adams, S., 901, 907, 912, 914 Adams, V., 800 Adamson, J. D., 733 Adashi, E. Y., 219 Adcock, I., 741, 842 Adcock, I. M., 54, 842, 1056 Adelman, D. C., 109 Adelsberger, J. W., 1054 Adelson, M. O., 1101 Adem, R., 589 Ader, H. J., 872 Ader, R., 63, 64, 97, 255, 450, 453, 456, 469, 476, 499, 632, 636, 637, 643, 644, 645, 646, 649, 650, 651, 652, 654, 678, 724, 725, 731, 732, 734, 761, 900, 903, 907, 914, 934, 1078, 1079, 1080, 1083 Ader, Robert, 710, 718 Aderka, D., 212 Adkins, B., 462 Adler, G., 106 Adler, K. A., 606, 966 Adler, L., 490, 534, 535 Adler, M. W., 557, 713 Adler, N. E., 498, 499, 500, 734, 790 Adorini, L., 142 Adorni, A., 570 Adriaesen, D., 105 Advenier, C., 102, 103 Adzick, N. S., 842 Aferiat, D. H., 539 Affleck, G., 198, 681, 771 Afleri, S., 687, 691
1126 Afzelius, P., 1057, 1058 Agarwal, S., 801, 811, 812, 814, 816 Agarwal, S. K., 73, 801, 811, 812, 884 Agathanggelou, A., 856 Agelaki, S., 108 Aggarwal, B. B., 274 Aggleton, J. P., 350 Agneletti, A. L., 565 Agnello, D., 434 Ago, T., 420 Agostinelli, E., 635 Agras, W. S., 789 Agrawal, B., 218 Agrawal, D. K., 108 Agro, A., 101, 107 Agrp. A., 200 Aguet, M., 1109 Aguilera, G., 196, 304 Agulnick, A. D., 420 Aguzzi, A., 440 Ahern, G. L., 620 Ahle, J. C., 663 Ahleman, S., 763, 764 Ahlm, K., 554 Ahlman, H., 133 Ahlquist, R. P., 526 Ahmadiyeh, N., 305 Ahmad-Nejad, P., 1015, 1024, 1025 Ahmed, A., 663, 669 Ahmed, A. A., 110 Ahmed, A. E., 1037 Ahmed, H., 998 Ahmed, N., 845 Ahmed, R., 1085 Ahmed, S., 195 Ahn, M. W., 400 Ahn, S. H., 400 Ahnve, S., 969 Aho, K., 193 Ahokas, A., 569 Ahokas, R. A., 321 Ahren, B., 996 Ahrens, B., 469 Ah-See, A., 684 Ahuja, S. S., 55 Ai, V. H., 1001 Aiba, Y., 238 Aikawa, T., 110, 647 Aikens, J. E., 93 Ailon, K., 362, 366 Airaghi, L., 1055 Aisen, P. S., 440 Aiso, S., 357 Aitken, D. H., 491 Aiuti, F., 688, 790, 1060, 1062 Aiyar, N. V., 417 Ajiki, W., 979 Ajmone-Cat, M. A., 147, 276 Ak, D., 146
Author Index Akahoshi, T., 736 Akaike, N., 186 Akaji, K., 353 Akaki, S., 1018 Akama, H., 1112 Akaneya, Y., 359 Akassoglou, K., 352, 354, 360 Akbar, A. N., 1056 Akbar, S. M., 554 Akbari, O., 800 Akdis, C. A., 978, 985 Akdis, M., 803, 978, 985 Akerlind, I., 769 Akiko, M., 785 Akil, H., 160, 161 Akins, P. T., 160 Akira, S., 54, 99, 322, 337, 365, 381, 999, 1025, 1115 Akiyama, H., 361, 439, 440 Akiyama, M., 858 Akkaraju, G. R., 46 Aksentijevich, S., 739, 982 Aktas, O., 307 Aktories, K., 1046 Akwa, Y., 284 Al Abed, Y., 105, 106 Al Rashed, S., 110 Al Shammari, K., 829, 830 Al’Abadie, M. S., 725, 726, 733, 745 al’Absi, M., 625, 772 Aladjem, Z., 364 Alafuzoff, I., 364 Alam, M. N., 586 Alamanos, Y., 193 Alani, M. D., 736 Alani, S. D., 736 Alaniz, R. C., 69, 71, 1039, 1040 Alard, P., 113 Albeck, H., 1101 Albeggiani, G., 273 Albensi, B. C., 357 Alberati-Giani, D., 307 Albert, D., 522 Albert, M., 361, 380 Albert, M. L., 1018 Albert, M. S., 366 Albert, P. R., 51 Albert, Z., 236 Alberti, A., 588 Alberts, S. C., 488 Albitar, M., 519 Alblas, J., 272 Albrecht, M., 239 Albrecht, P., 566 Alcocer-Varela, J., 213 Aldag, J. C., 199, 228 Alderman, M. H., 967 Aldskogius, H., 403 Alegiani, F., 385
Aleman, A., 186 Alexacos, N., 110, 117 Alexander, D. A., 533, 538 Alexander, F., 976, 978 Alexander, H. M., 933 Alexander, R. C., 567 Alexander, W. C., 854 Alexander, W. S., 995 Alexandre, C., 853, 863 Alexandre, H., 458 Alexopoulos, D., 923 Alexopoulou, L., 46, 352, 1099 Alferes, L., 117 Alferi, S., 687, 691, 876, 877, 881 Alferi, S. M., 1055 Alford, C. A., 863 Alfrey, C. P., 853 Algarra, I., 879 Algazi, M., 242 Al-Harthi, L., 1057, 1058 Alheim, K., 345 Ali, C., 276, 277, 420 Ali, H., 109, 1025, 1026, 1027 Aliakbar, J., 133 Alimonti, J. B., 1054, 1055 Aliprandi, M., 186 Allain, J. P., 1053 Allam, J. P., 977, 978, 985 Allan, J. S., 603 Allan, S. M., 355, 415, 422, 430, 433 Allan, W., 1085 Allansmith, M., 459 Allavena, P., 142, 217, 219, 980 Allchorne, A., 165, 405 Allegrini, P. R., 434 Allen, C., 1044, 1080 Allen, C. M., 1080, 1098, 1100, 1102 Allen, H., 419 Allen, I., 1108 Allen, J., 518, 927 Allen, J. B., 740 Allen, J. I., 551 Allen, L. H., 466 Allen, R. M., 66, 72 Allen, S. H., 201 Alleva, E., 284, 285, 352, 354, 360, 621 Alley, P. G., 828, 842 Allgayer, H., 662 Allikmets, R., 1053 Allison, A. C., 55, 300, 542, 738, 741 Allport, G. W., 484 Alm, P., 115 Almahmeed, W. A., 947, 949 Almawi, W. Y., 55, 56, 772, 828, 1056 Almberg, K., 220 Almeida, S. A., 241 Almer, G., 147 Almlof, T., 49–50 Almonti, S., 440
Author Index Aloe, L., 106, 284, 352, 354, 360 Aloisi, A. M., 350, 351 Aloisi, F., 404, 430, 432 Aloisi, R., 681 Alonso, G., 565 Alonso, M., 344, 346, 347 Alonzi, T., 995 Alonzo, A. A., 921 Alper, C. M., 504, 768, 769, 770, 771, 772, 782, 1063 Alpers, J., 736 Al-Ragaiey, K., 173 Al-Shamli, E., 458, 459 al-Shekhlee, A., 294 Alt, A., 999 Alt, J., 605 Altamura, C., 570 Altamura, V., 219 Altar, C. A., 106 Altares, M., 360 Altavilla, D., 86, 88, 89 Altemus, M., 485, 534, 535, 570, 680, 694, 727, 729, 735 Alter, A., 716 Alter, R., 967 Altman, B., 541 Altmann, J., 488 Altshuler, D., 999 Alvarez, G., 816 Alvarez, V., 366, 421 Alvarez, X. A., 361 Alvarez-Borda, B., 644, 645, 646, 653 Alvarez-Mon, M., 550, 551, 553 Alvind, K., 109 Alvir, J., 564 Amano, Y., 55, 741 Ambrogi Lorenzini, C. G., 342 Ambrosch, A., 161 Ambrose, C. T., 735 Ambrose, J. A., 923 Ambrosini, E., 404 Amedee, T., 274, 292, 294, 295 Amella, C. A., 1057 Amelung, P. J., 814 Amenta, F., 635 Amento, E. P., 224 American Cancer Society., 888 American Heart Association., 945, 946 American Psychiatric Association, 519, 533 Amerlla, C. A., 105, 106 Ames, B. N., 383 Amft, N., 1056 Amiel, C., 1055 Amindari, S., 292 Amiri, L., 1014 Amkraut, A., 236 Amkraut, A. A., 725, 726, 799 Ammatuna, M., 256
Amoli, M. M., 198 Amor, B., 209, 210 Amorati, P., 549, 551 Amoruso, A., 108 Amouyel, P., 957 Amraoui, Z., 135 Amuchastegui, S., 142 Amyx, H. L., 585 An, S., 133 An, X., 713 Anastassiou, E. D., 724, 736 Anaya, J. M., 609 Ancoli-Israel, S., 579, 607, 771 Ancona, L., 1056 Anda, R. F., 713 Andell-Jonsson, S., 418 Anderlini, R., 784, 792 Ander-Peciva, S, 929 Andersen, B., 682, 687, 691, 786, 869, 870, 875, 877, 881, 888 Andersen, B. L., 734 Andersen, K. E., 976 Andersen, M., 684 Andersen, P., 386 Andersen-Ranberg, K., 362 Anderson, B., 686, 692, 787, 875, 876, 877, 881, 882, 885 Anderson, B. N., 668 Anderson, B. P., 725, 726, 733, 744, 746 Anderson, C. M., 50 Anderson, D. R., 714, 717 Anderson, D. W., 1120 Anderson, J. L., 927, 959 Anderson, K., 290, 339, 633, 646, 693 Anderson, K. M., 1018 Anderson, M., 639 Anderson, N. B., 498, 623 Anderson, N. R., 201 Anderson, P. A., 326 Anderson, R. E., 1053 Anderson, S., 687, 790, 900, 902, 907, 909, 911, 914, 915, 1089 Anderson, S. M., 241 Anderson, W. J., 813 Andersson, B., 417 Andersson, I. M., 322 Andersson, J., 89 Andersson, L. C., 569 Andersson, L. P., 999 Andersson, P. B., 272, 433, 434 Anderton, S. M., 218, 1015 Andervont, H., 236 Andia, I., 838, 839 Ando, T., 296, 521–22, 524 Andrassy, M., 72, 965 Andraws, R., 959 Andre, M., 994 Andreasen, N., 361
1127 Andreasson, K. I., 322, 358 Andrecht, S., 53 Andrei, C., 321 Andreis, P. G., 101 Andreoli, A., 514, 516 Andreoni, M., 683 Andreotti, F., 937 Andres, P., 383 Andresen, K., 417 Andresen, L., 1058 Andrew, D. P., 142 Andrews, H. N., 233 Andrews, M., 930 Andrews, W. W., 711 Androsova, L. V., 570 Androulidaki, A., 997 Andrykowski, M. A., 234, 871, 872 Andus, T., 224 Anello, G., 363, 364, 365, 366 Ang, V. T., 241 Angel, P., 53 Angeli, A., 603 Angelico, M., 237 Angelina, A., 184 Angell, K., 790 Angelucci, F., 284, 352, 354, 1003 Angelucci, L., 241, 352, 359 Anger, H. A., 149 Anghelescu, I., 553 Anglen, C. S., 1080, 1082, 1087 Angold, A., 858 Aniento, I., 998 Anisman, H., 303–4, 304, 305, 306, 343, 347, 511, 514, 522, 523, 652, 733, 743 Anitua, E., 838, 839 Anker-Lugtenburg, P. J., 100, 115 Annex, B., 994 Annoni, G., 361, 363, 364, 365, 366, 421 Annunziato, F., 212, 637, 800 Anrather, J., 55 Ansari, A. A., 1058 Anscher, M. S., 885 Ansel, J., 103 Ansel, J. C., 98, 109, 112, 113, 987 Ansell, S. M., 883 Antel, J. P., 436, 1112 Antelman, S. M., 743 Anthenelli, R. M., 552 Anthony, D., 344, 346, 347 Anthony, D. C., 272, 417, 422, 429, 433, 434, 435, 437, 438 Anthony, J. C., 383, 553, 1060 Antinescu-Dimitriu, O., 636 Antolin, M., 112 Anton, P. A., 497, 1063 Antonelli, L. R., 555 Antoni, F., 197, 739, 740 Antoni, F. A., 357
1128 Antoni, M., 233, 242, 532, 535, 537, 538, 677, 679, 686, 687, 688, 689, 691, 693, 694, 791, 876, 877, 881, 883, 884, 1060, 1061, 1065, 1080, 1088 Antoni, M. H., 235, 237, 453, 676, 677, 679, 680, 682, 683, 684, 685, 686, 687, 688, 689, 690, 691, 692, 693, 695, 773, 774, 791, 883, 888, 1055, 1056, 1057, 1058, 1060, 1061, 1062, 1063, 1088 Antoni, Michael H., 675 Antropova, E. A., 855 Antunes, E., 252 Antunez, E., 550 Antuono, P., 363, 364, 421 Anzano, M. A., 829 Anzo, M., 174 Aoki, F. Y., 1079 Aoki, M., 623 Aoki, S., 252, 253 Aoki, T., 258 Aou, S., 329, 358 Aoyama, T., 1000 Appel, E., 106 Appelberg, K., 789 Appelboom, T., 556 Appels, A., 681, 682, 694, 931, 932, 933, 935, 937, 969 Appels, A. P., 931, 935 Appleby, P., 957 Appleton, C. L., 380 Apte, R. N., 430 Apter, A. J., 771 Arabatzis, K., 664, 665, 666, 667 Arad, M., 255 Aragane, Y., 273 Arai, H., 365 Arai, K., 73 Arai, N., 73 Arai, T., 361 Arakawa, S., 420 Araki, E., 999 Araki, K., 565 Aral, S. O., 1088 Aramaki, H., 523 Aramrattana, A., 200 Arancibia, S., 717 Araneo, B. A., 380, 731, 732, 735, 740, 855, 1080, 1081 Araoz, C., 361 Araque, A., 403, 404, 406 Araujo, L. M., 98 Arbel, Y., 933 Arbustini, E., 109 Arce, A., 1057 Arch, R. H., 736 Archer, J., 477, 478 Archer, S., 408 Archer, T. K., 51
Author Index Archi, D., 364 Arck, P. C., 113 Ardanza, B., 838, 839 Arena, P., 691 Arend, W. P., 997 Arendash, G. W., 351, 354 Arendt, G., 523 Arendt, J., 603 Arendt-Nielsen, L., 625, 763 Arenzana-Seisdedos, F., 275 Arevalo, J. M., 1059 Arevalo-Martin, A., 569 Argov, S., 430 Arias, C., 87, 320, 321, 323, 328, 329 Arieli, R., 1015 Arieli, Y., 1015 Ariens, E. J., 1043 Arima, M., 55 Arimura, A., 103, 133, 296, 321, 736, 1025, 1044 Arita, Y., 997, 1000, 1001 Ariwodola, O. J., 184 Ariyama, I., 958 Arizono, N., 98, 109, 115 Arkan, M. C., 1000 Arkins, S., 171, 174, 175, 603 Arkinstall, S. J., 103 Arlehag, L., 65 Arling, G. L., 479 Armando, I., 238, 983 Armanini, M. P., 360 Armario, A., 284, 339 Armati, P., 1079 Armendariz-Borunda, J., 212, 214 Armisen, M., 554 Armon, T., 930, 968 Armour, C. L., 55 Armstrong, C. A., 109, 112, 113, 987 Armstrong, C. B., 398, 399 Armstrong, G. L., 380 Armstrong, M., 1002 Arnarson, A., 109 Arnason, B. G., 63 Arnason, B. G. W., 70, 1046 Arndt, S., 785 Arner, P., 995 Arnett, D., 948 Arnett, H. A., 421 Arno, J., 1088 Arnold, A., 1042 Arnold, M. C., 363 Arnold, R., 871 Arnold, S. E., 564, 565 Arnold-Schild, D., 1024 Arnston, B. A., 662 Arocha-Pinango, C. L., 957 Aroldt, V., 451 Arolt, V., 510, 511, 565, 566, 567, 568, 569, 570
Arolt, Volker, 563 Aron, A., 793 Aron, B. S., 252 Aron, E. N., 793 Arons, M. M., 93 Aronson, J., 1037 Aronsson, F., 277 Arora, C. P., 711 Arora, P. K., 552 Arosio, A., 421 Arosio, B., 365 Arpey, C. J., 846 Arranz, A., 135, 143, 144, 146 Arrenbrecht, S., 64 Arria, A. M., 549 Arrighi, J., 73 Arrighi, J. F., 997 Arrigoni, E., 332 Arshad, A., 948 Arshad, H., 470 Arshad, S. H., 807 Artes, R., 711 Arthos, J. A., 1053 Artico, M., 635 Artiges, E., 523 Artin, K. H., 1079 Artuc, M., 838 Arveiler, D, 932 Arveiler, D., 957 Arvidsson, P., 419 Arvin, A. M., 859, 861 Arvin, B., 419 Arya, S. K., 736 Arzt, E., 54 Asa, S. L., 200 Asaba, K., 195 Asadullah, K., 254 Asahi, T., 1001 Asahina, A., 104, 107, 108, 113, 114, 134 Asai, K., 116 Asai, M., 357, 571 Asai, T., 143, 200 Asakawa, M., 294 Asano, M., 274, 419, 433 Asano, Y., 859 Asante, M., 516 Asaumi, J., 1018 Asch, F., 934 Ascher, M. S., 1053 Ascioti, C., 523 Asea, A., 1015, 1019, 1023, 1024, 1025 Asensio, V., 1080, 1088 Asensio, V. C., 284 Aserinsky, E., 580 Ashcroft, G. S., 825, 828, 829, 830, 831, 837 Ashdown, H., 640 Asher, R. A., 421 Ashkanani, L., 458, 459
1129
Author Index Ashleigh, E. A., 682 Ashley, E., 667, 668 Ashley, R., 1083, 1086 Ashley, R. L., 1086 Ashmore, R. C., 74 Ashtana, D., 687, 688 Ashwell, J. D., 54, 843, 1056, 1098 Ashworth, J. J., 828, 829, 830, 831, 837 Askenase, P. W., 110 Askenasy, A. R., 788 Asnis, G. M., 295, 512, 522 Asosina, S., 623 Asp, A. A., 1054, 1055 Assal, R., 534, 535 Assaloni, R., 998 Assenmacher, I., 736 Assimacopoulos-Jeannet, F., 997 Assman, M., 937 Assmann, G., 957 Aste-Amezaga, M., 137 Astemborski, J. A., 1060 Asthana, D., 773, 792, 883, 1060, 1061, 1065 Astolfi, G. M., 117 Asuaki, N., 533, 535, 536, 537 Atamer, Y., 1002 Atamura, C. A., 570, 571 Atchison, M., 531 Atkins, A. B., 92 Atkins, E., 380 Atkinson, C., 512, 790, 858, 863, 882, 888, 962 Atkinson, J. H., 792, 1054, 1060, 1061 Atkinson, J. H. E. A., 1060, 1062 Atkinson, J. P., 46 Atkinson, M., 763, 764 Atkinson, R. L., 995 Atkov, O., 853 Atolfi, M., 404 Atreya, R., 144 Attar, B. K., 498 Atterwill, C. K., 97, 100, 106, 109 Attrep, J., 199 Attwell, D., 433 Atwood, C., 609 Atzeni, F., 224 Atzil, S., 255 Atzmon, G., 994 Au, A., 1065 Auberger, P., 73 Aubert, A., 283, 286, 287, 302, 306, 344, 347, 422, 431, 514 Aubert, C., 1109, 1110 Aubin, K., 1054 Auclair, M. C., 222 Audhya, T., 100 Audino, M. G., 523 Audoly, L. P., 322 Auerbach, J. E., 684
Auerbach, R., 237 Auerbach, S. M., 1088 Auerbach, W., 237 Auernhammer, C. J., 603 Auewarakul, P., 237 Aufiero, D., 1003 August, S., 687, 689, 1055, 1061 Aukrust, P., 1058 Auld, M. C., 1060 Ault, J. G., 1041 Aunis, D., 1054, 1057, 1058 Auphan, N., 53, 741 Aurer, A., 532, 536 Aurer-Kozelj, J., 532, 536 Auron, P. E., 1015, 1024, 1025 Aussel, C., 73 Austad, S. N., 220 Austejuler, R., 212 Austen, K. F., 46, 74 Austin, C. P., 101 Austin, D. F., 873 Austin, J., 1061 Austin, M. D., 663, 666, 667 Austin, S., 1043 Autio-Harmainen, H., 459 Autschbach, F., 144 Avanzini, P., 772, 784, 792 Avdonin, V., 1043 Avelino, A., 102 Averner, M., 851 Avery, D. H., 717 Avery, J. K., 223 Avila, J. J., 552 Avital, A., 345, 346, 348, 349, 355, 358, 646 Avitsur, R., 172, 259, 284, 294, 297, 302, 305, 339, 358, 480, 621, 622, 842, 1025, 1046, 1080, 1103, 1111, 1112, 1114, 1115 Avraham, R., 42, 251, 255, 257, 258 Avraham, S., 534, 536 Avron, M., 345, 346 Aw, S. E., 257 Axelson, M., 184 Axen, T. E., 1058 Ayala, J., 72, 301 Ayata, C., 419 Ayers, F. C., 1036 Ayres, A., 997 Ayroldi, E., 54 Ayyavoo, V., 1056 Azad, N., 607 Azar, S. T., 1053 Aze, Y., 326 Azieh, F., 458, 459 Azima, H., 1002 Aziz, N., 519, 608, 624, 625, 885 Azorin, J. M., 570 Azrieli, Y., 727
az-Ruiz, O., 586 Azuma, Y., 322 Azzari, C., 855 Azzawi, M., 55 Azzolina, A., 273 Ba, Z. F., 65 Baba, A., 522 Baba, H., 365, 395, 396 Babenko, V., 53 Baber, M. A., 55 Babulas, V., 569 Babyak, M., 772 Babyak, M. A., 517, 937 Bacanu, S. A., 485 Bacchetti, P., 1110, 1112 Bach, J. F., 98, 570 Bacharier, L., 803 Bacharier, L. B., 502, 503 Bachelet, M., 1015, 1019 Bachen, E. A, 934 Bachen, E. A., 730, 766, 772, 964 Bacher, M., 736 Bachinger, H. P., 137 Bachmann, S., 567 Baciu, I., 636 Backhauss, C., 420 Backlund, E., 781, 783 Backlund, J., 197 Backman, C., 420 Bacon, B. R., 303 Bacon, S. L., 772 Badia, E., 554 Badie, B., 551 Badimon, J. J., 922 Badimon, L., 922 Badino, G. R., 235, 239 Badley, A. D., 1056 Badr, N., 289 Baecher-Allan, C., 149 Baelum, V., 830 Baer, J. D., 184 Baerwald, C., 200, 983 Baerwald, C. G., 76, 198 Baeten, J. M., 1059 Baetjer, A. M., 662 Baeuerle, P., 53 Bagby, G. J., 554, 995 Bagci, S., 1002 Bagdade, J. D., 715 Bagdy, G., 982 Bagely, J. R., 1101 Baggett, L., 687, 689, 773, 774, 1055, 1061 Baggliolini, M., 55, 142 Bagley, C., 771 Bagley, J. R., 1101 Bagli, M., 364, 365, 421 Baglioni, C., 54
1130 Bagnall, A. M., 928 Bahk, W. M., 571 Bahouth, S. W., 995 Bail, M., 587 Baile, W. F., 812 Bailery, E. M., 664 Bailey, C. J., 1000 Bailey, J., 845 Bailey, M., 637, 1078, 1099 Bailey, M. T., 306, 463, 464, 480, 1046, 1103 Bailey, Michael T., 1097 Bailey, N., 604 Bailleux, F., 859 Bailon, P. S., 994 Baiocchi, R., 883 Baiocchi, R. A., 1079 Bairati, I., 242 Baird, A., 416, 417 Baird, A. W., 110, 115 Baird, S., 66, 104, 1044 Bairey Merz, C. N., 932, 935 Baissa, B., 637, 731, 732, 1040 Bajetto, A., 275, 430, 435 Bajzer, C. T., 946 Baker, A. H., 842 Baker, A. J., 420 Baker, D. G., 533, 536, 543 Baker, G. H., 76 Baker, J., 184 Baker, K. H., 762, 763 Baker, M. S., 663 Baker, R. A., 66, 73, 99, 293, 1044, 1045 Bakhiet, M., 359 Bakiri, L., 53 Bakke, O., 542 Bal, E. T., 923 Balague, C., 256 Balasko, M., 290, 320 Balbin, E., 683, 1061 Balbin, E. G., 1055, 1056, 1060, 1063 Balbo, P., 108 Balboa, J. L., 255 Balcerzak, S. P., 133, 134, 746 Baldaro, B., 772 Baldeweg, T., 1061 Baldewicz, T., 687, 688, 773, 792, 1060, 1061 Baldewicz, T. T., 1060, 1061 Baldi, E., 117, 342 Baldi, G., 487 Baldo, C., 361 Baldwin, A. S. J., 741 Baldwin, A. S., Jr., 52, 53, 54, 1098 Baldwin, G. C., 555, 557 Baldwin, R. L., 399 Bales, K. R., 363, 364 Balk-Lamberton, A. J., 667 Balkowski, G., 284
Author Index Balkwill, F. R., 882 Ball, C., 300 Ball, T. B., 1054, 1055 Ballam, L., 928 Ballanger, J. C., 531 Ballantyne, C. M., 927, 935 Ballarino, P., 199 Ballas, C. B., 846 Ballas, M., 362, 366 Ballas, Z. K., 549, 550, 551 Balleari, E., 222 Ballieux, R., 652 Ballieux, R. E., 67, 68, 164, 729, 768, 900, 901, 903, 904, 914, 1065 Ballinari, D., 652 Ballinger, A., 1002 Ballou, L. R., 274, 322 Balow, J. E., 603, 724, 736, 826 Balraj, V., 859 Balschun, D., 275, 350, 351, 355, 356, 646 Balthasar, N., 332 Baltimore, D., 383, 1054 Baltuch, G., 136, 148 Baluk, P., 101, 103, 110 Baluyut, A. R., 74 Bamberger, A. M., 198, 934 Bamberger, C. M., 198, 934, 1098 Bamford, C. R., 272, 385, 386, 436, 1108 Ban, C. R., 419 Ban, E., 292, 302, 381, 638, 641, 642 Banati, R. B., 437 Banchereau, J., 98, 142 Bandinelli, S., 361 Bandler, R., 294 Bando, H., 881, 882 Bando, T., 321 Bandura, A., 677 Bandyopadhyay, B., 845 Bane, C. M., 882 Banerjee, K., 186 Banerjee, S., 419 Bangale, Y., 133, 134, 140 Banis, P. L., 884 Bankhurst, A. D., 70, 257 Banks, W. A., 87, 194, 272, 287, 338, 343, 347, 381, 509, 511, 512, 514, 516, 622, 932, 937, 962, 1036, 1054 Banning, A., 419 Bannon, M. J., 103 Banos, M. A., 417 Bar, F., 937 Bar, F. W., 681, 682, 694, 931, 932, 935, 969 Bar, J., 681, 682, 694, 932, 969 Baragar, F. D., 733 Barak, L. S., 1043 Barak, O., 259, 300, 302, 339 Barak, V., 570
Barak, Y., 570 Baraniuk, J. N., 110 Baras, M., 532, 535, 536, 538 Barbacanne, M. A., 829, 830 Barbagli, G., 117 Barbanel, G., 736 Barbara, G., 101, 116 Barbatelli, G., 993 Barbaux, S., 957 Barbazanges, A., 711 Barber, D., 863 Barber, W. D., 88 Barberan, E. M., 434 Barbero, S., 275, 430, 435 Barbier, M., 1002 Barbier, Y., 257 Barbieri, I., 420 Barch, D. M., 523 Barchet, W., 1099 Bardana, E. J. J., 736, 737 Barde, Y. A., 106, 359, 386 Bardelli, C., 108 Barden, N., 514 Bardwell, W. A., 771 Bardy, M., 1058 Bare, O., 1015, 1024, 1025 Barefoot, J., 931 Barefoot, J. C., 498, 694, 929, 930, 949 Bar-Eli, M., 239 Barer, A. S., 853 Barger, B. A., 417 Barger, S., 439, 440 Barger, S. W., 361 Baribaud, F., 1053 Baringer, J. R., 1109 Barja, G., 998, 1003 Bark, T., 1024 Barkans, J., 502 Barker, D. J., 712 Barker, D. J. P., 456, 469, 498 Barker, E., 1053, 1054 Barker, R., 456, 462 Barkin, A., 512, 782, 787, 792, 900, 903, 904, 912, 913, 914, 1089 Barkow, K., 364, 421 Barlow, C. E., 666 Barlozzari, T., 255, 257, 878 Barnard, C. J., 482 Barnes, C. A., 322 Barnes, K., 738, 981 Barnes, P. J., 52, 54, 55, 106, 108, 110, 115, 502, 741, 809 Barnes, R. F., 682 Barnes, S., 399 Barnett, E. V., 729 Barnett, P. A., 716 Barnum, G. R., 1086 Barnum, S., 439, 440 Baron, H., 585
Author Index Baron, J., 769 Baron, R., 676 Baron, R. M., 1064 Baron, R. S., 785 Baroncelli, S., 487, 1063 Barone, F. C., 417, 419, 420 Barone, M., 994 Barontini, M., 983 Baron-Van Evercooren, A., 273 Barouch, D. H., 1065 Barouch, R., 106 Barquero, M., 361 Barr, C. S., 485 Barra, A., 224 Barraclough, J., 234, 692, 870 Barraso, J., 689 Barreau, F., 464, 469 Barrera, M., 715, 788 Barrera, P., 193, 1003 Barrett, A. D., 236, 853, 854, 856, 862, 863, 1079 Barrett, A. D. T., 856, 857, 861 Barrett, D. C., 689, 1061 Barrett, W. L., 252 Barrientos, R., 399 Barrientos, R. M., 197, 200, 343, 347, 360, 384, 385, 406, 1017 Barriga, C., 745, 746 Barron, D., 878 Barros, H., 993 Barroso, J., 1055, 1060, 1061, 1062, 1063, 1065 Barrow, R. E., 603 Barrows, E., 771 Barry, C., 353 Barry, C. P., 714 Barry, R. A., 732 Barsh, G. S., 993, 1041 Bartesaghi, S., 405 Bartfai, T., 274, 275, 287, 291, 321, 345, 358, 405, 418, 432 Bartfei, T., 345 Barth, J., 934 Barthelmas, R., 741 Barthlow, H., 110 Bartholdi, D., 136, 147, 148 Bartholomew, J. S., 237, 683 Bartik, M. M., 1044 Bartke, A., 173 Bartke, I., 106 Bartlett, J. A., 514, 516, 623 Bartlett, T., 1014 Bartolazzi, A., 184 Bartolomucci, A., 480, 482 Barton, C., 814 Barton, G. M., 282 Bartova, L., 566 Bartrop, R., 676, 734, 784 Bartsch, B., 144
Bartter, F. C., 744 Bartzokis, G., 564 Baruch, J., 691 Barve, S. S., 711 Bar-Yosef, S., 256, 257 Barzilai, N., 994 Basbaum, A. I., 69, 110, 200, 407, 408, 801 Basdevant, A., 993 Baserga, R., 174, 180 Bashir, T., 586 Basinski, M. B., 994 Baskin, D. G., 293 Bass, R., 419 Bass, S., 1053, 1054, 1058 Bass, T. A., 937 Bassant, M. H., 585 Bassett, S. S., 366 Bassini, A., 1058 Basso, A. M., 733 Basso, A. S., 649, 653 Bast, A., 1045 Basta-Kaim, A., 305, 515 Basterra, J., 115 Bastidas-Ramirez, B. E., 212, 214 Basu, A., 419 Basu, M. K., 840 Basu, S., 242, 1018 Basudev, H., 420 Bataille, F., 999 Bataller, R., 554 Bate, C., 276 Bateman, E. D., 664, 669 Bates, M. D., 458, 459 Batocchi, A. P., 1003 Batra, A., 1002 Batshake, B., 329 Battey, J. F., 87 Battisa Tura, G. J., 570, 571 Battisti, M., 224 Battistini, L., 184 Bauch, J., 652 Baud, V., 177 Bauer, D. C., 1040 Bauer, D. E., 275 Bauer, J., 108, 291, 361, 381, 439, 440, 511, 570, 592, 594 Bauer, K. A., 957 Bauer, M., 162, 166, 963 Bauer, M. E., 730 Bauer, R., 1061 Bauer, R. M., 1061 Baulieu, E. E., 49, 1059 Baum, A., 518, 532, 535, 537, 538, 539, 541, 542, 607, 676, 695, 725, 726, 733, 744, 746, 772, 884, 934, 1110 Baum, A. E., 305 Baum, A. S., 541 Baum, C. L., 846
1131 Baum, M. K., 773, 784, 792, 1055, 1056, 1060, 1061 Baumann, D., 434 Baumann, H., 736, 994, 1025 Baumann, N., 273 Baumgart, K., 1016, 1024 Baumgarten, C. R., 131 Baumgartner, J. D., 146 Baumi, A., 236 Baur, M., 219 Baura, G. D., 287 Bausero, M. A., 1015, 1019 Baxevanis, C., 692 Baxevanis, C. N., 570 Baxter, J. D., 48 Bayer, B. M., 555, 556, 1101 Bayer, T. A., 421, 565, 567, 568, 569, 570 Bayer, T. M., 365 Baylis, W., 583 Bayne, M. L., 101, 175 Bazan, N. G., 275, 359 Bazin, I., 219 Bazzarre, T. L., 714, 717 Bazzocchi, G., 361 Bazzoni, F., 839 Beach, J. E., 357 Beach, R. S., 466 Beacock-Sharp, H., 800 Bealer, S. L., 321 Beall, S., 908 Beals, J. M., 994 Beard, C. M., 440 Beard, J. L., 466 Beard, S., 563 Beasley, C. R., 55 Beasley, R., 456, 470, 808 Beattie, E. C., 357, 359, 405 Beattie, M. S., 357, 359 Beaufour, C., 167 Beaune, J., 209, 210 Becerra, R. M., 787 Bechara, A., 620 Becher, H., 422 Bechter, K., 567 Becich, M. J., 110 Beck, A., 686 Beck, A. T., 686 Beck, F. M., 843, 1044, 1080, 1098, 1100, 1102, 1103, 1114 Beck, G., 981 Beck, J., 927 Beck, J. M., 103, 115, 131, 133 Beck, K. D., 346, 347, 348, 349, 351, 353, 354 Beck, L. A., 54, 55, 979 Beck, L. Jr., 692 Beck, M., 676, 858, 863, 1088 Beck, M. A., 462, 1100 Beck, N., 687
1132 Beck, N. C., 198, 609 Becker, C., 144 Becker, D., 570 Becker, H. D., 254 Becker, K., 365 Becker, M. L., 485 Becker, T., 1024 Beckeringh, J. J., 1042, 1043 Beckman, K. B., 383 Beckman, M., 117 Beckmann, D., 978 Bedard, P. J., 522 Beebe, D., 998 Beekman, A. T., 509 Beer, H. D., 841, 843 Befus, D., 107, 116 Beg, A. A., 52 Begely, A. E., 580 Begg, M. D., 277 Begolka, W. S., 1110 Behi, M. E., 148 Behnisch, A., 510 Behnke, J. M., 482 Behrendsen, S. C., 213 Behrens, L., 106 Behrens, M. M., 274, 405 Behrmann, I., 338 Beilin, B., 255, 256, 362, 366, 710 Beilke, M. A., 567 Beiqing, L., 74 Beiske, K., 74 Beissert, S., 114 Beiter, T., 254 Beksinska, M., 961 Bektas, H., 109 Belagaje, R., 55 Belch, R., 606 Beldjord, C., 362 Belin, T. R., 885 Bell, D. R., 873 Bell, G. J., 661 Bell, I. R., 1063 Bell, J., 440, 646, 713 Bell, M., 876 Bell, P. A., 741 Bell, R., 872 Bellavia, V., 209, 210 Belle, S., 364, 365 Beller, D., 1115 Beller, D. I., 108, 734 Bellerose, G., 554 Bellezzo, J. M., 303 Bellibas, S. E., 108 Bellingan, G. J., 1025 Bellinger, D., 678, 888 Bellinger, D. L., 64, 68, 70, 77, 106, 115, 132, 133, 194, 200, 226, 772, 1036, 1039, 1040, 1057 Bellinger, F. P., 353, 354, 356
Author Index Bellinger, S. L., 1036 Bellmann, K., 1024 Bellmann, R., 107 Bellone, C. J., 735 Bellone, G., 222 Bellucci, F., 107 Bellward, G. D., 236, 884 Belmonte, A., 255 Belmonte, C., 223 Belmonte-de-Abreu, P., 566 Belo, L., 458 Beloni, L., 212 Belowski, D., 570 Belperio, J. A., 1100 Belvisi, M. G., 48, 106 Belyavskyi, M., 1080 Belyea, M., 714 Ben Eliyahu, D. L., 76 Ben Eliyahu, S., 251, 726, 734, 745, 1046 Benali, N., 100 Benassayag, C., 222, 1055 Benavides, J., 136, 147, 148 Benca, R. M., 607 Bence-Hanulec, K. K., 184 Benchenane, K., 276 Benda, J., 764, 767, 900, 906 Bendelac, A., 800 Bender, B., 816 Bender, C. E., 736 Bender, J. R., 46 Benderly, M., 957 Bendtzen, K., 996 Benedetti, F., 710 Benedetti, J., 1083 Benedetti, P., 882 Benedict, C., 594, 596, 598 Benediktsdottir, I. S., 830 Beneforti, P., 117 Ben-Eliyahu, S., 42, 235, 238, 252, 253, 255, 256, 257, 258, 259, 555, 606, 621, 873, 878, 880 Bener, A., 807 Benetato, G., 636 Beneytout, J., 208, 211 Benfenati, F., 356 Benfield, T., 1057, 1058 Bengtsson, T., 1042, 1044 Benham, C. D., 102 Ben-Hur, T., 300, 302, 361 Beni, S. M., 418 Benice, T., 523 Benicke, M., 542 Benight, C., 490, 532, 535, 537, 538, 539, 541, 676 Benigni, F., 434 Benito, M., 171, 172 Benjamin, I. J., 1015 Benjamin, L., 692 Ben-Jonathan, N., 241
Benki, S., 1059 Ben-Menachem, O., 361 Ben-Neriah, Y., 52 Bennet, J. T., 842 Bennet, M. C., 357 Bennett, B. D., 995 Bennett, C., 174 Bennett, M. C., 745 Bennett, P. D., 901, 909, 910, 911 Bennett, S. A., 184 Bennett, T. L., 787 Bennish, M. L., 1055 Ben-Nun, A., 1115 Benoit, G., 253 Benotsch, E. G., 930, 1062 Benotti, P., 1002 Benovic, J. L., 69 Benowitz, N. L., 110 Benschop, R. J., 65, 67, 68, 70, 605, 728, 729, 811, 929, 934, 963, 965, 983 Benscop, R. J., 1044, 1045 Ben-Shlomo, Y., 712, 957 Benson, E., 870 Benson, H., 678 Benson, J., 419 Benson, J. A., Jr., 557 Bentivoglio, M., 585 Benton, D., 729, 1101 Benton, T., 549, 550, 551, 552 Bentson, K. L., 484, 485, 486 Bentwich, Z., 1053 Benveniste, E. N., 137, 273, 276, 565 Benyamin, R., 556 Benyon, R. C., 109 Benzur, H., 532, 535, 536, 538 Beraki, S., 277 Berard, F., 725, 732 Berard, J. D., 489 Berberich, S. L., 764, 767 Berciano, J., 363, 364, 366, 421 Bercovitch, F. B., 491 Berczi, I., 301 Berek, J. S., 882 Berg, A., 666 Berg, A. H., 997 Berg, B. M., 303, 304, 384, 385, 386, 387, 444 Berg, E. L., 839 Berg, L. J., 998 Berg, M., 813 Berg, R., 1024 Berg, T., 460 Berga, S. L., 71, 623 Bergamasco, B., 710 Berge, B., 585 Berge-Landry H., 874 Berger, C. B., 488 Berger, C. L., 484, 485, 490, 491, 534, 535
Author Index Berger, J. R., 523 Berger, J. S., 959 Berger, M., 108, 361, 511, 570, 592, 594 Berger, R., 859 Bergers, G., 692, 882 Berghmans, R., 570 Berglin, E., 218 Bergman, E., 106 Bergman, R. N., 287 Bergmann, B. M., 596, 597 Bergmann, M., 54, 200 Bergmann, M. M., 1000 Bergmann, M. W., 55 Bergmeier, L., 1023 Bergmeier, L. A., 1015, 1016, 1023 Bergmeier, W., 951, 952 Bergquist, J., 73 Bergren, D., 809 Berho, M., 555 Berin, M. C., 115 Berk, L. S., 625, 763, 764, 765, 772 Berkelman, R. L., 380 Berkenbosch, F., 291, 293, 322, 357, 381, 439, 678, 732, 1115 Berkhof, H., 711, 772 Berkin, A., 904, 912 Berking, C., 842 Berkman, L., 771 Berkman, L. F., 695, 714, 771, 781, 782, 783, 937, 948 Berman, A., 1115 Berman, A. S., 108 Berman, C. M., 488, 1079 Berman, D., 632 Berman, J. W., 136 Berman, N. E., 382, 430 Bermúdez-Rattoni, F., 632, 644, 645, 646, 649, 653 Bernabei, R., 365, 421 Bernadini, R., 739 Bernaerts, C., 134 Bernal, G. A. A., 683 Bernard, D., 275 Bernard, G. R., 93 Bernard, H. U., 237 Bernard, L. A., 976, 977 Bernardini, R., 54, 197, 982 Bernard-Medina, G., 212, 214 Bernardone, I. S., 108 Bernhagen, J., 736 Bernheim, H. A., 273, 321 Bernier, L., 632 Bernik, T. R., 86, 88, 92, 997 Bernstein, B., 683 Bernstein, B. M., 1055 Bernstein, D., 566, 1015, 1041 Bernstein, D. E., 531 Bernstein, I., 632, 639 Bernstein, I. S., 478
Bernston, G. G., 787 Bernton, E. W., 357 Berntorp, E., 689, 1062 Berntsen, A., 996 Berntson, G. G., 799, 934, 964, 1019, 1053, 1065, 1080, 1088, 1111 Berria, M. I., 565 Berrie, E. L., 1088 Berry, C. C., 729, 771, 934 Berry, D. S., 771 Berry, G., 502 Berry, H., 870, 871 Berry, M., 416, 417 Berry, S., 1083 Bert, A. G., 54 Bert, J., 586 Berthelot, P., 554 Berthouze, S. E., 666 Berti, R., 417 Bertin, P., 208, 211 Bertini, M., 790, 1060, 1062 Bertini, R., 301, 738 Bertipaglia, B., 959 Bertles, J. S., 338 Bertolaso, L., 1058 Berton, M. T., 74, 75 Bertora, P., 487 Bertrand, D., 90 Bertz, A. L., 418 Berwin, B., 1018 Berzi, I., 200 Beschmann, K., 164, 166 Besedovsky, H., 40, 64, 65, 70, 97, 273, 282, 344, 346, 347, 357, 637, 646, 650, 651, 652, 653, 678, 738 Besedovsky, H. O., 64, 73, 217, 220, 222, 275, 300, 338, 350, 351, 355, 356, 357, 380, 516, 518, 520, 601, 603, 605, 733, 1039, 1040 Besser, R., 1002 Bessis, A., 275 Bessle, H., 710 Bessler, H., 256, 362, 366, 515 Best-Aguilera, C. R., 212, 214 Betancur, C., 302 Bethea, C. L., 485 Bethea, J. R., 408 Bethke, K., 1024 Bethus, J., 523 Betmouni, S., 440 Betteridge, J., 964 Bettinger, T., 482, 483, 854 Bettinotti, M. P., 879 Betz, A. L., 418, 419 Betz, M., 73 Betz, S., 985 Beuckmann, C. T., 321, 322, 331 Beuscher, K., 687 Beutler, B., 431, 738, 843, 995, 999
1133 Bevan, S., 102 Bevilacqua, M., 487, 1055, 1056 Bevilacqua, M. P., 926 Beyhum, H. N., 56, 772, 828 Beylin, A., 340, 637 Bhadada, S., 1055 Bhagat, K., 960 Bhan, A., 144 Bhansali, A., 1055 Bhardwaj, N., 1018, 1102 Bhat, N. R., 136 Bhatia, M., 110 Bhatia, V., 961 Bhatnagar, S., 491 Bhatt, A., 360 Bhatt, H., 173 Bhatt, S., 294 Bhattacharjee, A. K., 1015 Bhattacharyya, M. R., 968 Bhatti, T., 307 Bhatty, R., 240, 882 Bhojak, T. J., 365 Bhopale, G. M., 237 Biagi, P. L., 553 Biagiotti, R., 212 Bialy, D., 1000, 1001 Bian, D., 161 Bianca, V. D., 841 Bianchi, A. T., 1080 Bianchi, E., 46 Bianchi, G., 142 Bianchi, M., 85, 92, 256, 284, 301, 346, 349, 350, 351, 738 Bianchi, S., 422, 587 Bianco, F., 291 Biasucci, L. M., 923, 925, 926, 956 Bickel, C., 55, 957, 959, 996 Bickel, M., 54 Bickford, K., 1015 Bickford, P. C., 383 Bidlack, J. M., 408 Bidlingmaier, M., 603 Bieber, T., 805, 977, 978, 985 Biedenkapp, J., 406, 407 Biedenkapp, J. C., 384, 385 Bielas, H., 113 Bielfeld, P., 359 Biemann, K., 584 Bienen, T., 637 Bienenstock, J., 40, 97, 98, 101, 102, 106, 107, 109, 110, 110.109, 115, 116, 647, 648, 653 Bienstock, R. J., 48 Bienvenu, J., 257 Bienvenu, T., 362 Bierer, L. M., 539 Bierhaus, A., 72, 965 Bierman, S. M., 1088 Biernacki, K., 436
1134 Bierwolf, C., 601 Biewenga-Booji, C. M., 199 Biglino, A., 1055 Bignante, A. E., 480 Bignotti, S., 570, 571 Bihari, I. C., 978, 986 Bijlsma, J. W., 69, 76, 198, 199 Bijlsma, J. W. J., 207, 208, 733, 737, 1046 Bijman, J. T., 239 Bijur, P., 1079 Bikowsky, J., 828 Bilbo, S. D., 303, 456, 732 Bilder, R., 564 Bildhauser, A., 1039, 1040 Bileviciute, I., 200 Bilezikian, J. P., 1055 Bilfinger, T. V., 921, 930 Bilker, W., 564 Billack, B., 712 Billet, S., 405 Billiard, M., 609 Billman, M. A., 403 Bills, A. R., 710 Bilski, J. J., 174 Bina, P., 977, 988 Binaglia, M., 405 Binder, R. J., 1018 Binder, W., 164, 165, 166 Binder-Brynes, K., 539 Bindon, J. R., 501 Bindslev-Jensen, C., 976 Binetti, G., 363, 364, 421 Bing, E. G., 1061 Bingham, A., 957 Bingham, S. F., 553 Bingle, L., 840 Binkley, N., 361 Binkley, P. F., 969 Binnekade, R., 304 Biondi, M., 77, 785, 814, 1046 Birder, L. A., 102 Birk, T. J., 814 Birkhead, J. R., 253 Birkhead, T. R., 285 Birkle, D. L., 712 Birmaher, B., 541 Birnbacher, R., 106 Biro, T., 102, 109 Biron, C. A., 98, 172, 516, 724, 745, 1082, 1091, 1099, 1109 Biron, G., 688 Birx, D. L., 1056 Bischof, W., 977 Bischoff, S. C., 106, 109 Bishopric, N. H., 200, 1043 Bissell, M. G., 793 Bissell, M. J., 239 Bisser, S., 586 Bissette, G., 305
Author Index Bistoni, F., 565 Bistrian, B. R., 273 Biswas, A., 873 Bitar, M. S., 846 Bito, H., 329 Bittinger, F., 100, 105 Bittman, B. B., 763, 764, 765 Bittman, M., 786 Bittman, M. E., 786 Biunno, I., 363, 364, 365, 366, 421 Bixler, E. O., 588, 589, 591, 594, 599, 606, 608 Bjerkeli, V., 1058 Bjerregard, K., 609 Bjerring, P., 625, 763, 766 Bjork, S. K., 115 Bjorklund, H., 113 Bjorling, D. E., 117 Bjorntorp, P., 715 Bjoro, T., 74 Bjugstad, K. B., 351, 354, 710 Black, B. E., 50 Black, P., 1115 Black, P. H., 100, 108, 112, 733, 734, 763, 765, 766, 772, 801, 881, 932, 963, 964, 965, 966, 1036, 1038 Black, R. A., 996 Black, S., 110 Black, S. A., 769 Blackburn, E. H., 734, 790 Blackburn, G. L., 273 Blackburn, W. D., 543 Blackburn-Munro, G., 199 Blackburn-Munro, R. E., 199 Blacker, D., 366 Blackett, K. N., 947, 949 Blacklow, R. S., 234, 873 Blackwell, P., 565 Blada, P., 570 Blaese, R. M., 732, 735, 855 Blair, L. A., 184 Blair, M., 637 Blaiss, M., 816 Blaiss, M. S., 805, 813 Blajchman, M. A., 258 Blake, H., 580 Blake, M. J., 1014 Blakely, B., 585 Blakely, W. P., 256, 257 Blakemore, W. F., 1109, 1110, 1114 Blake-Mortimer, J., 884 Blake-Mortimer, J. S., 879 Blakey, G. H., 830 Blalock, E. M., 384 Blalock, J., 633, 646 Blalock, J. E., 39, 87, 97, 98, 100, 162, 603, 725, 732 Blalock, S. J., 199 Blamire, A. M., 422, 438
Blanc, A., 585 Blanchard, D. C., 478, 479, 480, 481, 1111 Blanchard, E. B., 93, 541, 542 Blanchard, R. J., 478, 479, 480, 481, 1111 Blanchet, P., 253 Blanchette, J. O., 881 Blaney, N., 677, 687, 688, 689 Blaney, N. T., 773, 784, 792, 1055, 1056, 1060, 1061 Blaney, P., 682, 883 Blank, S. E., 553 Blankenberg, S., 957, 959, 996 Bläß, S., 222 Blascovich, J., 793 Blaser, K., 811, 978, 985 Blasi, E., 565 Blasi, F., 46 Blasig, I. E., 566 Blasko, I., 382 Blatteis, C. M., 274, 286, 320, 321, 322 Blattner, W., 1055 Blattner, W. A., 552, 556 Blau, H. M., 842 Blau, K., 485 Blauw, G. J., 362 Blayney, M., 359 Blazer, D. G., 579, 607, 782, 882 Ble, A., 361 Blecha, F., 732 Bleich, A., 534, 536 Bleiker, E. M., 872 Blenk, K. H., 109 Blennerhassett, M. G., 102, 106, 109, 110 Blennerhassett, P., 101 Blennow, K., 361 Blichington, T. F., 540 Blieszner, R., 786 Bliss, J., 691, 692 Bliss, J. M., 871, 872 Bliss, T. V., 340, 353 Bliss, T. V. P., 340 Blitzer, J. T., 1043 Blix, G. G., 667, 668 Bloch, A., 181 Bloch, D. A, 923 Bloch, E. F., 461 Block, F., 417 Block, G., 851 Block, J., 1063 Block, T. M., 1079 Bloem, B. R., 147 Bloemen, P. G., 72 Blohmke, M., 871, 873 Blois, M. S., 871, 876 Blom, M., 652, 969 Blomberg, B., 687, 691, 876, 877, 881 Blomgren, H., 875
Author Index Blomgren, K., 419 Blomhoff, H. K., 74 Blomhoff, R., 74 Blomjous, F. J., 72 Blomkvist, V., 689, 1062 Blomquist, P., 51, 827 Blomqvist, A., 273, 274, 293, 294, 320, 322, 332 Blomstrand, C., 417, 420 Blond, D., 272 Bloom, B. R., 509 Bloom, D., 653 Bloom, E., 512, 516, 625, 676, 784 Bloom, E. T., 622, 729, 785, 1101 Bloom, F. E., 520 Bloom, G., 873 Bloom, J., 687, 692 Bloom, L. J., 1088 Bloom, O., 92, 419 Bloom, S. R., 104, 132 Bloomberg, G. R., 811, 812 Bloomfield, L., 713 Blosser, R. L., 490 Blotta, M. H., 55, 56 Blough, D., 710 Blount, J. D., 285 Blount, P., 103 Bluethmann, H., 284, 339, 725, 732 Bluhm, E. J., 186 Blum, A., 104 Blum, A. M., 100, 101, 103, 104, 107, 108, 133 Blum, J. W., 1045 Blum, L., 1055 Blumbenberg, M., 52 Blumberg, D., 201 Blumberg, J. B., 669 Blumberg, P. M., 102, 109 Blumberg, R. S., 144 Blum-Degen, D., 361 Blumenthal, J., 695, 937, 949 Blumenthal, J. A., 517, 681, 695, 716, 772, 921, 928, 929, 930, 933, 935, 937, 969 Blumenthal, M., 809, 816 Blumhardt, L. D., 437 Bluthe, R., 622 Bluthe, R. M., 99, 171, 223, 273, 274, 277, 282, 283, 286, 288, 289, 290, 295, 296, 297, 298, 300, 304, 320, 337, 338, 339, 344, 345, 382, 397, 422, 430, 431, 432, 518, 995, 996, 1058 Bluthé, R. M., 171, 172, 184, 185, 186, 187, 281 Blyth, W. A., 1086, 1088 Bo, L., 436 Bo, M., 364 Boadle, R. A., 1079 Bobak, M., 947
Bobbioni, E., 997 Bocchio Chiavetto, L., 570, 571 Boccia, M. L., 468, 483, 484, 485, 491 Boccio, D., 117 Boch, J. A., 1015, 1024, 1025 Boche, D., 384, 420, 430, 440, 443 Bockaert, J., 101, 133, 290, 337, 339 Bockermann, R., 197 Boddeke, H., 291 Boddeke, H. W., 416, 417 Bode, C., 552 Bodey, B., 462 Bodine, S. C., 181, 182 Bodles, A. M., 361 Bodnar, J., 676, 685, 786, 789, 790 Bodnoff, S. R., 491 Bodwell, J. E., 49, 50 Boe, D. M., 554 Boeckh, C., 360 Boehm, G., 644, 645, 646 Boehm, G. W., 68, 97, 342, 1039, 1040 Boehm, T., 253 Boeije, L. C., 997 Boeing, H., 1000 Boerbooms, A. M., 193 Boettner, A., 45, 55 Bofill, M., 1053 Bogart, L. M., 1055, 1062 Bogdan, C., 85, 142 Bogdanov, A., 882 Bogenrieder, T., 842 Bogerts, B., 565 Bogomolov, V. V., 853 Bogui, P., 585, 586 Boguniewicz, M., 976, 977, 978 Bogyo, M., 47 Bohatschek, M., 402 Bohle, B., 462 Bohm, S., 103 Boichot, E., 102, 103 Boin, F., 571 Boin, R., 570, 571 Boinski, S., 484, 485 Boisoneau, D., 540 Boissin, J., 736 Bokarew, D., 1003 Bokarewa, M., 1003 Bokos, P., 557 Boksa, P., 640 Bol, G. F., 553 Bol, J. G., 304 Bolado, J., 53 Boland, G. J., 978 Boland, R. J., 1061 Boldogkoi, Z., 323, 326 Bolger, N., 782 Boling, W., 419 Bolles, R. C., 285 Bologna, C., 222
1135 Bolte, G., 977 Bolte, M. A., 717 Bolton, M. R., 663, 666 Bolton, S. J., 429, 433, 434 Bonaccorso, S., 304, 521, 539 Bonafe, M., 361, 364, 365, 421 Bonanno, G. A., 785 Bonaventre, J. V., 405 Bonavia, R., 275, 430, 435 Bonavida, B., 71 Boncz, I., 361 Bond, R. N., 510, 514, 551, 552, 743 Bond, S., 237 Bonde, S., 359, 386 Bondiolotti, G. P., 284 Bondjers, L., 712 Bondy, B., 365 Bondy, C. A., 185 Bondy, P. K., 110 Bondy, S. C., 352 Bonecchi, R., 142 Bongartz, T., 193 Bongiorno, P. B., 292, 294, 299 Bongiovanni, A., 273 Bonhoeffer, S., 1054 Bonini, C., 142 Bonini, S., 106, 977 Bonneau, R., 676, 694 Bonneau, R. H., 236, 237, 238, 461, 512, 676, 734, 785, 858, 863, 899, 900, 904, 1040, 1065, 1078, 1079, 1080, 1081, 1082, 1083, 1084, 1085, 1086, 1087, 1088, 1098, 1100, 1102 Bonneau, Robert H., 1077 Bonnefoy, J. Y., 219 Bonnefoy, M., 666 Bonni, A., 360 Bonni, A.., 360 Bonus, K., 622, 901, 909, 910, 913 Bonvicini, C., 363, 364, 421 Booji, A., 199 Bookwala, J., 872, 887 Boone, E., 53, 566 Booth, A., 854 Booth, B. M., 550 Booth, R. J., 625, 685, 694, 766, 767, 791, 828, 842, 901, 908, 914, 1063 Bootsma-van der Wiel, A., 362 Bopaiah, C. P., 161, 164, 165, 166 Boraldi, F., 844 Borand, T., 693 Borawski, E., 712 Borawski-Clark, E. A., 785 Borbély, A. A., 582, 583, 584 Borda, E. S., 66 Borda, T., 565, 567 Borden, E. C., 521, 522 Bordignon, P. P., 142 Bordoli, L., 142
1136 Bordoni, A., 553 Borenstein, M., 603 Borger, P., 66, 73 Borhani, N. O., 931 Bori, Z., 422 Borisov, A. S., 521 Borkan, S. C., 1015 Borkoski, J. P., 283, 297 Borkovec, T., 683 Borman, P., 769 Born, J., 224, 452, 585, 590, 591, 592, 593, 594, 596, 597, 598, 599, 600, 601, 603, 603ÿ, 604, 605, 606, 607, 913 Born, Jan., 579 Born, T. L., 338 Borne, B. V., 233, 870 Borner, C., 161 Bornstein, J. C., 103 Bornstein, S., 594, 605 Bornstein, S. R., 45, 55, 224 Boronow, J. J., 566, 567 Borovikova, L. V., 85, 86, 88, 89, 105, 605, 772, 997 Borregaard, N., 839, 841 Borrell, J., 302, 569 Borrow, P., 1054, 1109, 1110, 1114 Borsatti, A., 142 Borsody, M. K., 290 Borte, M., 977 Borthwick, L. A., 360 Borysenko, J., 678, 724, 733 Borysenko, M., 678, 724, 733 Borysiewicz, L. K., 901, 911 Borzotta, A., 256 Bos, J. D., 604 Boscarino, J. A., 531, 534, 535, 537, 538, 539, 542 Bosch, J. A., 830, 831, 832, 934, 964 Bosch, P. V., 789 Bosco, P., 363, 364, 365, 366 Bosco, S., 635 Bose, S., 1060 Bosis, S., 570, 1055 Bosmans, E., 304, 510, 515, 533, 536, 537, 538, 551, 568, 570, 571, 622, 1115 Bossche, B. V., 622 Bosset, S., 725, 732 Bossy-Wetzel, E., 53 Bost, K. L., 102, 103, 104, 107, 108 Bostik, P., 1058 Bostock, J., 802 Botana, M. A., 198 Botchkarev, N. V., 106 Botchkarev, V. A., 106 Botchkina, G. I., 92, 105, 419, 605, 772, 997 Botham, M. S., 434
Author Index Bottcher, M. F., 1002 Bottcher, T., 352, 353, 354 Botteri, F., 74 Botting, R. M., 329 Bottomley, M. J., 224 Botvinick, M. M., 523 Botzler, C., 1015 Bouaboula, M., 557 Bouchard, C., 148 Boucher, W., 110, 117 Boucher, W. S., 113 Bouchier-Hayes, D. J., 256 Boudewyn, A. C., 1110, 1112 Boudon, A., 103 Boudou, P., 1055 Boudreau, N., 239 Boufidou, F., 551 Bouillot, J. L., 993 Boukhris, W., 69 Bouletreau, P., 257 Boulle, N., 1059 Bouloumie, A., 993, 1000 Bouman, A., 458 Boumpas, D. T., 55, 73, 724, 736 Bourassa, M. G., 681, 792 Bourdon, L., 585, 586 Bourgeois, C., 47, 48 Bourin, P., 1055 Bourinbaiar, A. S., 1059 Bourne, H. R., 1043 Bourreille, A., 1002 Bousquet, J., 103, 813, 842 Bousseau, A., 72, 301 Bousvaros, A., 1002 Bouteille, B., 585, 586 Boutin, H., 274, 418, 419, 433 Bovberg, D. H., 900, 903 Bovbjerg, D., 633, 649, 650, 652, 682, 692, 874, 875 Bovbjerg, D. H., 764, 767, 874 Bovolenta, P., 148 Bowden, J. J., 101, 103 Bowen, D. L., 737 Bowen, J., 876 Bower, J. E., 519, 608, 713, 885, 1060 Bowers, D., 870 Bowles, C. A., 676 Boyajyan, A., 568 Boyce, T., 498, 499 Boyce, W. T., 901, 907, 912, 914 Boyd, J. C., 239 Boyd, J. E., 592 Boyd, P. T., 234, 871, 873 Boyd, R. L., 462 Boyd, S., 692 Boyer, C. M., 882 Boyers, A., 687, 691, 876, 877, 881 Boyers, A. E., 1055 Boynton, S., 632
Boyson, J. E., 457 Boyum, A., 599 Bozzette, S. A., 1059 Bozzola, M., 603 Braaf, Y., 1024 Braaten, D., 1056 Brabet, P., 146 Bracci-Laudiero, L., 106 Brack, A., 110, 160, 162, 164, 165, 166 Bradbeer, C. S., 1060, 1061 Bradding, P., 70 Bradley, A. J., 534, 535 Bradley, B., 55 Bradley, K. A., 531 Bradley, S., 253, 261, 882, 885 Bradlow, H. L., 208, 209 Bradshaw, A., 715 Bradt, B., 439, 440 Brady, M., 353 Brady, M. J., 234, 871, 872 Brady, S. S., 498 Bragulat, V., 523 Brahic, M., 1109, 1110 Braida, D., 350, 351 Brain, S. D., 110, 113, 195, 200 Braithwaite, V. A., 342 Brambilla, D., 422, 587 Brambilla, F., 772, 784, 792 Brammer, G. L., 477 Bramson, J., 99 Bramwell, N. H., 116 Branch, D. W., 212 Branchi, I., 352, 354 Brand, K., 951, 952 Brand, R. J., 771, 781 Brandeis, R., 341 Brandenberger, G., 585, 601, 603 Brandes, C., 632 Brandon, D., 482 Brandon, D. D., 738 Brandt, R., 184 Brandwein, M., 856 Brandys, Y., 341 Branigan, C., 772 Brankin, B. J., 1108 Brannan, S. K., 710 Brantley, P., 811 Brantley, P. J., 198, 726, 733, 745, 1062 Brar, J. S., 571, 572 Brashler, J. R., 385, 441 Brasseur, M., 664, 666 Brath, P. C., 679 Bratton, D., 440 Bratton, D. L., 440 Brau, P., 305 Brauchle, M., 826, 843, 845 Brauer, R., 210 Braun, A., 106, 107, 108, 113, 360 Braun, H., 161
Author Index Braun, J., 76 Braun, J. S., 400 Brauner, M., 1055 Braunstahl, G. J., 812 Braunwald, E., 921, 926, 956 Braver, T. S., 523 Bray, G. A., 994 Braz, J., 167 Breathnach, R., 53 Breckling, U., 597, 601, 603 Breder, C. D., 291, 294, 321, 322, 432, 438 Bredow, S., 882 Breeding, S. A., 104 Breedveld, F. C., 193, 199 Breeze, R. E., 710 Brehm, B. J., 715 Brehm, M. A., 1080, 1086, 1087 Breier, A., 567 Breitbart, W., 694 Breitmeyer, J. B., 1059 Breitner, J. C., 383 Breittmayer, J. P., 142 Breivogel, C. S., 161 Brekken, R., 882 Breloer, M., 1023, 1024 Brem, H., 843, 845 Bremner, D., 539, 540 Brener, S. J., 946 Brener, W., 531 Brennan, F. M., 69, 195, 542 Brennan, F. X., 346, 347, 348, 349, 351, 353, 354 Brennan, K., 305 Brennan, P., 199 Brennan, R. G., 137 Brenneman, D. E., 134, 135, 137, 139, 149 Brenner, B., 690 Brenner, D. A., 53, 554 Brenner, G. J., 194, 734, 1040, 1080, 1083, 1087 Bresciani, M., 977 Breslau, I., 539 Breslau, N., 539 Breslin, M. B., 48 Breslow, L., 771 Bresnahan, J. C., 357, 359 Bresnahan, M., 277 Bressler, J. P., 828 Bressot, N., 222 Bret-Dibat, J. L., 283, 288, 297, 1058 Breteler, M. M., 439 Bretscher, P., 47 Brett, J., 998 Breuninger, H., 258 Breve, J., 1115 Brew, B. J., 307, 522 Breyer, M. D., 332
Breyer, R. M., 332 Brezinschek, H. P., 738 Breznitz, S., 532, 535, 536, 538 Briant, L., 1058 Brickley, D. R., 241 Bridegam, P., 1107, 1115, 1116, 1118 Bridges, M. W., 497, 713 Brien, T. G., 746 Briend-Sutren, M. M., 235 Briere, F., 142 Briet, D., 585 Brigelius-Flohe, R., 383 Briggs, S. L., 994 Brightman, V., 1088 Brightman, V. J., 1088 Brightwell, D., 738 Brill, N. O., 1080 Brincat, M. P., 829 Brinker-Spence, P., 1061 Brinklov, M. M., 67, 728 Brinton, R. D., 300 Brionne, T., 420 Brisson, J., 234, 870, 873 Bristow, A., 273, 274, 293, 294, 300 Bristow, A. F., 417, 736 Bristow, M., 624, 764, 765, 766 British Heart Foundation., 945 Brittain, R., 632 Britten, K. M., 70 Brittenden, J., 252 Brittingham, K. C., 994 Britto, L. R. G., 649, 653 Britto, P., 1055 Britton, K. T., 515, 516, 555 Britton, R. S., 303 Brivio, F., 594, 604 Brivio, O., 594, 604 Brizel, D. M., 885 Broadbent, D. E., 773, 1063 Broadbent, E., 828, 842 Broadbent, M. H., 1063 Broadbent, M. H. P., 773 Broadley, A. J., 681, 962, 964, 965 Broadwell, R. D., 381 Broadwell, S. D., 521 Broady, R., 585 Brock, C. D., 531 Brocke, S., 438 Brocker, E. B., 841 Brockmann, A., 653 Brockunier, L. L., 1101 Brodan, V., 599 Brodanova, M., 599 Brodde, O., 1044 Brodde, O. E., 766 Brodde, O.-E., 1042, 1043 Broder, S. R., 239 Broderick, P. A., 306 Brodie, C., 102, 106, 109
1137 Brodin, E., 112, 115 Brodin, K., 112 Brody, E., 787 Brody, S., 815 Broghammer, C. L. W., 882 Brokelmann, M., 881, 882 Broman, J. E., 518, 579, 606 Bromberg-White, J. L., 237 Bromet, E., 538 Bromley, L. J., 482 Brondolo, E., 687, 689 Bronner, C., 101 Bronnikov, G. E., 240 Brook, U., 813 Brooke, S. M., 261 Brooks, E., 910, 911 Brooks, G. R., 687 Brooks, P. M., 208 Brooks, W. H., 70, 1044 Brooks, W. S., 364, 365 Broom, K. A., 438 Broome, C., 635 Broquet, A. H., 1019 Brosnan, C. F., 136, 997 Bross, T., 73 Brossay, L., 98 Brosschot, J. F., 729, 934 Brostjan, C., 55 Broug-Holub, E., 733 Brouns, M., 291, 322, 381, 439 Broussard, C. L., 483, 491 Broussard, S. R., 171, 172, 177, 180, 181, 182, 183, 184, 422 Broussard, Suzanne R., 171 Brouwenstyn, N., 693 Brouwers, P., 1060 Brouxhon, S., 115, 132, 133 Brower, K., 549, 551 Brown, A., 166, 663, 668 Brown, A. S., 277, 459, 569, 1082 Brown, B. E., 813, 988 Brown, D., 254 Brown, D. A., 440 Brown, D. G., 978 Brown, D. H., 734 Brown, D. L., 959 Brown, D. M., 74 Brown, E. R., 195, 328, 843 Brown, G., 338 Brown, G. W., 1110 Brown, H., 482 Brown, H. C., 429 Brown, H. J., 1059 Brown, J., 717, 977 Brown, J. E., 771, 872 Brown, J. R., 113 Brown, L., 882 Brown, L. L., 713, 793 Brown, L. M., 552, 556
1138 Brown, L. S., Jr., 1053 Brown, M., 55, 515, 693 Brown, M. A., 113 Brown, M. B., 603 Brown, M. H., 272 Brown, M. R., 881 Brown, N. J., 840 Brown, R., 600, 650, 651 Brown, R. R., 521, 522 Brown, S., 517, 538, 551, 553, 677 Brown, S. A., 724 Brown, S. J., 586 Brown, S. L., 579, 607, 790 Brown, S. M., 557 Brown, T., 1061 Brown, T. G., 1042 Brown, T. J., 48 Brown, V. A., 667 Brown, Z. A., 1083 Brownlee, M., 997, 998, 999, 1003 Brownlee-Duffeck, M., 609 Brownley, K. A., 1057 Brownschidle, L. A., 103 Bru, E., 716 Bruce, A. J., 419 Bruce, A. T., 874, 878, 879 Bruce, E. C., 931 Bruce, J. L., 1015 Bruce, L. C., 569 Bruce, M. E., 440, 443 Bruce-Keller, A. J., 419 Bruck, W., 1115 Brugg, B., 385 Bruggeman, C., 681, 682, 694, 932, 969 Bruijnzeel, C. A. F. M., 978 Bruijnzeel, P. L., 985 Bruijnzeel-Koomen, C. A., 978 Bruijnzeel-Koomen, C. A. F. M., 978, 986 Brukner, P., 663 Brull, S. J., 400 Brummet, M., 54, 55 Brummitt, C. F., 1055 Brun, J. M., 1055 Brun, V., 142 Brunell, P., 1079 Brunelleschi, S., 108, 114 Brunetti, A., 174 Brunke-Reese, D., 292 Brunke-Reese, D. L., 175 Brunn, G. J., 1025 Brunner, E., 501, 957, 961, 962 Brunner, E. J., 501, 505 Brunner, J., 89 Brunner, R., 744 Bruns, C., 100 Brunsch, R., 554 Brunso-Bechtold, J. K., 184 Brunson, K. W., 516, 724, 745, 1099
Author Index Brunsvold, M. A., 830 Brusa, R., 420 Bruschke, A. V., 923 Bruscoli, S., 54 Brutkiewicz, R. R., 252 Brutsaert, D. L., 497, 938, 969 Bruunsgaard, H., 361, 362, 363, 662, 663 Bryant, F. B., 763, 764, 765, 766 Bryant, P. A., 579, 586 Bryant, R. A., 542 Brydon, L., 305, 502, 503, 918, 935, 946, 963, 964, 965, 966, 967, 968 Brydon, Lena, 945 Bryn, T., 1058 Brzezinski, A., 603 Bu, D. F., 408 Bu, J. Y., 103 Bubel, S., 1108 Bucala, R., 736 Buccheri, G., 234, 871 Bucci, D. J., 342 Bucciarelli, P., 365, 421 Buchanan, R. W., 567 Buchanan, T. W., 625, 772 Buchbinder, S. P., 1053 Bucherelli, C., 342 Bucholz, K. K., 552 Buchschacher, G. L. J., 236 Buchwald, D., 695 Buck, C., 842 Buck, J. M., 900, 902 Buck, S. H., 101 Buckle, S., 771 Buckley, A. R., 1014 Buckley, C. D., 1056 Buckley, D. M., 555, 557 Buckley, K. A., 1058 Buckley, K. S., 663 Buckley, P., 568 Buckley, T. C., 541, 542 Buckley, T. L., 110, 115 Buckner, C. K., 115 Buckwalter, K., 882 Buddeberg, C., 872 Budelmann, B. U., 398, 399 Bue, M. C., 356 Buell, G., 103, 132 Bueno, L., 273 Bueno, M., 212, 214 Bueono, L., 464, 469 Bueso-Ramos, C., 557 Buggle, F., 422 Buggy, B. P., 1055 Buguet, A., 585, 586 Buhl, A. E., 385, 441 Buhler, F. R., 727, 934 Buijs, R. M., 843 Buisson, A., 276, 277, 420
Buitelaar, J. K., 711 Buka, L. C., 566 Buka, S. L., 498 Bukantz, S., 802 Bukhari, M., 224 Bukowski, J. F., 1082 Bukrinsky, M., 1056 Bulbul, M., 1037 Bulian, D., 637, 638, 640, 652 Buljevac, D., 437 Bulla, G. A., 303 Buller, H. R., 54 Buller, K. M., 294 Buller, R., 686, 692, 882 Buller, R. E., 786, 787, 882 Bulloch, K., 66, 104, 724, 745, 1036, 1044, 1099 Bullock, B., 273 Bullock, E. D., 106 Bullock, G. R., 101, 104, 115 Bultz, B. D., 791 Bulzebruck, H., 234, 871 Bunde, J., 921, 928, 935, 949 Bundlie, S. R., 609 Bunjes, D., 871 Bunkowski, S., 352, 353, 354 Bunnett, N. W., 101, 102, 103, 109, 112, 113, 116 Bunney, W., 692 Bunney, W. E., Jr., 477 Buno, W., 184 Bunse, J., 307 Burack, J. H., 689, 1061 Burbaeva, O. A., 570 Burbridge, J., 534, 537 Burcher, E., 101, 103, 131 Burchett, S., 1083 Burdick, M., 841 Bureau, J. F., 1109 Bures, J., 342 Burette, A., 1043 Burg, M., 695, 937, 949 Burg, M. M., 695 Burg, N. D., 839 Burge, C., 869 Burge, J. C., 1002 Burger, A., 542 Burger, K., 365, 591, 594, 598, 605, 606 Burger, P. C., 838 Burgess, A., 1061 Burgess, A. P., 1060 Burgess, E. D., 771 Burgess, H. J., 605 Burgess, W., 174, 298, 384 Burges-Watson, I. P., 534, 535 Burges-Watson, P., 539 Burgmeister, L. F., 1040 Burgos, I., 606 Burgoyne, R. W., 1062
Author Index Burguete, M. C., 420 Burhol, P. G., 133 Buriani, A., 106 Buring, J. E., 502–3 Burk, D., 1040 Burk, R. D., 237 Burkart, V., 1016, 1024 Burke, A., 1054 Burke, J. G., 400 Burke, L., 538 Burke, N. E., 102 Burke, S. K., 47 Burke, T. F., 54, 55 Burke, W. J., 514 Burket, R. C., 812 Burkhalter, J., 687, 688 Burkhalter, J. E., 1060, 1061 Burkhardt, H., 222 Bürkle, H., 565 Burks, T. F., 101 Burleson, M., 858, 884 Burleson, M. H., 784, 788, 811, 861, 1019, 1079 Burman, B., 783 Burman, I., 1055 Burman, R., 684, 689 Burmester, G. R., 200, 210, 222 Burnett, F. M., 217 Burnett, R., 789 Burney, M. W., 295 Burns, A. R., 839 Burns, J. L., 173, 174 Burns, V. E., 762, 763, 900, 901, 905, 907, 912, 913, 914, 1046, 1088 Burnside, S., 199 Burnstein, K. L., 49, 50 Burnstock, G., 115 Burri, R., 40, 64, 678 Burrows, L., 784, 788 Burrows, S. J., 186 Burton, J. L., 847 Burton, L. E., 461 Burudi, E. M., 307 Buruma, O. J., 147 Burwell, R. D., 342 Busby, W. H., 175 Buscail, L., 100 Busch, C. R., 284 Buscher, R., 816 Bush, G., 523 Bush, K. R., 531 Bush, M. R., 55 Busiguina, S., 186 Buske-Kirschbaum, A., 637, 652, 725, 726, 739, 741, 742, 812, 813, 918, 975, 978, 981, 982, 983, 984, 985, 986, 1080 Buslei, R., 565 Busquet, P., 274
Busse, R., 1000 Busse, W., 695 Busse, W. W., 502 Busse-Grawitz, M., 108 Bussfeld, D., 1100 Bussing, R., 812 Bussolati, G., 241 Bustamante, L., 1081 Butch, A. W., 554 Butchart, A. G., 272, 434, 435 Buteau, J., 998 Buter, J., 519 Butfiloski, E. J., 438 Butini, L., 1054 Butler, D., 419 Butler, L. D., 301, 542, 738 Butler, M. P., 357 Butlin, D. J., 101 Butow, P., 869, 871, 872 Butow, P. N., 234, 771, 870, 871, 872, 873 Butrimiene, I., 196 Bütschli, O., 636 Butt, S., 344, 346 Butterfield, D. A., 383 Butterworth, D. E., 662, 663, 664, 665, 667, 668, 669 Butterworth, M., 459 Buttgereit, F., 198, 211 Buttiglieri, S., 604 Buttini, M., 291, 416, 417 Button, J., 1060 Buunk, B. P., 790 Buwalda, B., 480 Buynak, E. B., 859 Buysse, D., 676 Buysse, D. J., 518, 580, 607 Bwayo, J. J., 1059 Bychkova, E., 643 Bydder, G., 437 Byers, V. S., 744 Bylund, D. L., 237 Byne, W., 564 Bynoe, M. S., 149, 199 Byrd, E. K., 770 Byrd, P. K., 103, 115, 131, 133 Byrne, G. I., 522 Byrnes, D., 683, 883 Byron, K., 688 Byron, K. S., 1082 Byrum, C. E., 540 Byszewski, A., 607 Bywaters, E. G., 76 Cabanas, C., 1100 Cabane, J., 1055 Cabot, P. J., 162, 164, 165, 166 Cacabelos, R., 361 Caccavari, R., 772
1139 Cacioppo, J., 677, 884 Cacioppo, J. T., 236, 623, 771, 785, 787, 789, 799, 830, 831, 832, 858, 861, 863, 912, 934, 964, 1019, 1062, 1079 Cadahia, A., 112 Cadepond, F., 49 Cadet, P., 299, 586 Cadore, L. P., 1055 Cadoret, R. J., 517 Cady, A. B., 588 Café, C., 356 Caggiula, A. R., 71, 516, 556, 623, 743 Caggiula, M., 1003 Cagnin, A., 437 Cahill, C. M., 402, 1015 Cahill, L., 340 Cai, D., 996, 1000 Cai, J., 790, 1060 Cai, T.-Q., 747 Caillot-Augusseau, A., 853, 863 Cainazzo, M. M., 86, 88, 89 Cairns, N. J., 365, 366, 421 Cakar, L., 599 Calabrese, J., 677 Calabrese, V. P., 566 Calabresi, C., 364, 365, 421 Calabresi, P. A., 148 Calandra, T., 146, 736 Calapai, G., 295, 300 Caldenhoven, E., 55, 741 Calderas, T., 644, 646 Calderwood, S. K., 1015, 1023, 1024, 1025 Caldji, C., 491 Caldwell, C., 514, 517, 538, 551, 553, 622, 691, 724, 1046 Caldwell, H., 1025 Calenoff, M. A., 1110 Calhoun, M. E., 382, 386 Califf, R. M., 694, 949 Caligiuri, G., 925, 926, 956 Caligiuri, M., 302 Caliguiri, M., 1111 Calissano, P., 184 Callaghan, J. T., 556 Callaghan, P., 1065 Callahan, T., 555 Callahan, T. A., 1080, 1086, 1087 Callaway, E., 647, 648, 653 Callewaert, D. M., 728 Calogero, A. E., 54, 197, 739, 982 Calvano, S. E., 254 Calvia, Alessandro, 207 Calvin, M., 829 Calvo, J. R., 103, 131, 134, 135, 146 Calzetti, F., 108, 839 Calzia, A., 41, 207 Camacho, T., 769 Camacho-Hubner, C., 175
1140 Camacho-Hubner, R. C., 174 Camargo, C. A. J., 1002 Camats, J., 419 Cambien, F., 957, 996 Cambier, J., 160, 165 Camenisch, T., 326 Camerino, M., 784 Cameron, J. L., 485 Cameron, R. G., 554 Camm, A. J., 937 Cammarota, G., 927 Campagna, J. A., 407 Campbell, A. E., 1102 Campbell, A. M., 1017 Campbell, C. A., 407 Campbell, D., 998 Campbell, D. E., 599 Campbell, I. J., 419 Campbell, I. K., 197 Campbell, I. L., 284, 349, 350, 351, 354, 356, 360, 384, 1080, 1088 Campbell, J., 553 Campbell, K. A., 1103, 1114 Campbell, K. S., 65, 70, 100 Campbell, P. A., 1038 Campbell, R. D., 366 Campbell, S., 422, 434 Campbell, S. J., 272, 417, 434, 435 Campbell, S. S., 581 Campbell, T., 1112, 1114 Campeau, S., 343, 347, 360, 1019 Campion, D. R., 173, 175 Campion, S., 444 Campisi, J., 71, 407, 408, 1013, 1014, 1016, 1017, 1018, 1019, 1022, 1023, 1024, 1025, 1026, 1027 Campos, G., 957 Campton, K., 68, 69, 219, 1044, 1045 Camrack, T., 785 Canada, A., 692 Canada, A. L., 873, 881 Canal, N., 363, 364, 365, 366, 421 Canbay, A. E., 654 Cancela, L., 733 Cancello, R., 993 Candelora, J., 1053, 1065, 1080, 1088, 1111 Candenas, M. L., 101 Candore, G., 421 Canevari, L., 353 Canli, T., 620 Cannarile, L., 54 Canner, R., 961 Canning, B., 810 Canning, B. J., 809 Cannizzaro, L. A., 996 Cannon, B., 1022, 1044 Cannon, C. P., 937 Cannon, G. W., 193
Author Index Cannon, J. G., 273, 669, 829 Cannon, J. T., 160, 165 Cannon, T., 564 Cannon, T. D., 569 Cannon, Walter, 917, 918 Cannuscio, C. C., 956 Cano, G., 326 Canonne-Hergaux, F., 1058 Canono, B. P., 1038 Cantagrel, A., 110 Canteras, N. S., 330 Canteros, G., 294 Cantin, B., 957 Canton, P., 1055 Cao, C., 294, 322 Cao, G., 383 Cao, J., 113, 1056 Cao, L., 68, 77, 238, 1036, 1039, 1040, 1041 Cao, L. Y., 570, 571 Cao, Q., 999 Cao, R., 998 Cao, T., 110 Cao, X., 1080, 1081 Cao, Y., 253 Cao, Y. L., 842 Capasso, G., 663 Capelli, S., 549, 551 Capellino, S., 208, 211 Capin, L., 826 Capitani, S., 1058 Capitanio, J. P., 469, 479, 484, 485, 486, 487, 1056, 1057, 1058, 1060, 1062, 1063, 1065 Caplan, A. I., 55 Capo, C., 570 Cappalonga, J. L., 182 Cappellari, L., 871 Capps, L., 1053 Capsoni, F., 100 Capuron, L., 277, 296, 304, 305, 307, 422, 451, 509, 519, 520, 521, 522, 523, 608, 622, 885 Capurso, A., 365 Capurso, C., 365 Capurso, S. A., 365 Caput, D., 997 Caputi, A. P., 295, 300 Caputo, L., 366 Caraci, F., 363, 364, 365, 366 Caragine, T., 85 Caralis, P., 688 Caramori, G., 842 Caravalho, J., Jr., 932, 935 Carayanniotis, K., 587 Carayon, P., 557 Carbin, L., 747 Carbonari, M., 688 Carbone, G., 652
Carbone, K. M., 567 Card, J. P., 326 Cardinali, D. P., 1057 Carding, S. R., 1085 Cardona, A., 362 Cardone, F., 440 Carella, C., 361, 1003 Carew, T., 631, 632 Carey, M., 885 Carey, V., 1053 Caricco, A., 690, 696 Carignola, R., 603 Carini, F., 107 Cariti, G., 1055 Carlander, B., 609 Carlberg, C., 73, 997 Carli, A., 222 Carlin, J. M., 307 Carlino, J. A., 438 Carlquist, J. F., 927 Carlson, C. S., 174 Carlson, L. E., 791, 877 Carlson, M. A., 845 Carlson, R. W., 879 Carlson, S., 678 Carlson, S. L., 64, 70, 103, 115, 728, 772, 1057 Carlson, W., 687, 691 Carlstedt-Duke, J., 50, 51 Carlsten, H., 996 Carlstrom, K., 199, 209 Carlton, S. M., 397 Carlyn, M., 1053 Carman-Kzran, M., 421 Carmeliet, P., 842 Carmichael, M. D., 1082 Carmo-Fonseca, M., 223 Carmona, J. V., 1065 Carnalley, K. B., 785 Carnelli, V., 361 Carnemolla, R., 995, 999 Carnevale, D., 91 Carney, C., 785 Carney, D. S., 539, 540 Carney, R. M., 509, 511, 512, 514, 516, 622, 681, 695, 931, 932, 937, 962, 969 Carney, W. P., 858 Caro, J. F., 995 Caron, M. G., 69, 76, 1057 Carpen, O., 416, 417 Carpene, E., 361 Carpenter, A. B., 484 Carpenter, C. B., 74 Carpenter, C. R., 476 Carpenter, J., 691, 877 Carpenter, J. R., 476 Carpenter, M. K., 419 Carpenter, W. T., 567 Carpentier, P. A., 149
Author Index Carpiniello, B., 361, 1080 Carr, D., 816 Carr, D. J., 69, 97, 725, 732, 1080, 1081, 1082, 1087, 1088, 1101 Carr, R. W., 223 Carrabba, M., 224, 879 Carrara, A. S., 1023 Carrasco, G. A., 1019 Carrasco, J., 419 Carraway, R., 109 Carraway, R. E., 115 Carrico, A., 689, 696 Carrico, A. W., 1055, 1056, 1061 Carrie, A., 362 Carriere, D., 557 Carrieri, P. B., 1003 Carrigan, K. A., 256, 1101 Carrington, D., 937 Carrington, M., 1053 Carrizosa, A., 1110 Carro, E., 184, 186 Carroll, B., 510 Carroll, B. J., 512, 516, 682 Carroll, D., 396, 762, 763, 765, 900, 901, 905, 907, 912, 913, 914, 1046, 1088 Carroll, M. C., 47 Carroll, M. D., 993 Carro-Muino, I., 100, 104, 107, 219 Carron, J., 1045 Carruba, G., 209, 210, 224 Carruette, A., 117 Carruthers, M., 716 Carson, D. A., 108, 223 Carson, J., 663, 668 Carson, P., 361 Carson, R. W., 873 Carsons, S. E., 1015 Carswell, E. A., 995 Carta, M. G., 361 Cartar, L., 712 Cartei, G., 234, 871, 872, 873 Carter, A., 419 Carter, C. S., 174, 523 Carter, D., 881, 882 Carter, D. A., 133 Carter, D. B., 87, 385, 441 Carter, D. L., 490 Carter, G., 303 Carter, J. J., 256, 258 Carter, L., 162, 164, 165, 166, 554 Carter, S. M., 70, 727 Carthy, D., 193 Cartier, C., 1058 Carucci, J. A., 108 Caruso, C., 77, 421 Carver, C., 683, 685, 687, 689, 876, 877, 881 Carver, C. S., 682, 683, 687, 691, 713, 773, 1055, 1088
Carvery, P. M., 348, 359 Casadei, V., 361, 364, 366 Casadei, V. M., 363, 364, 365, 366, 421 Casale, T., 807 Casamijana, R., 554 Casamitjana, R., 996 Casanova, P., 275 Casas, R., 462 Casassus, P., 1055 Casati, C., 420 Cascieri, M. A., 101, 175 Case, N., 694 Case, R. B., 694 Casellas, P., 557 Casey, K. L., 710 Casey, R., 554 Cash, J. M., 981 Caslake, M., 458 Caso, V., 417, 420 Casolaro, V., 54, 55, 814 Casolini, P., 241, 352, 359 Casorati, M., 142 Caspi, D., 436, 515 Cassatella, M. A., 108, 839 Cassayre, P., 460 Casscells, S. W., 921 Cassell, C., 715 Cassileth, B. R., 869, 872 Cassoni, P., 241 Castagliuolo, I., 110, 112, 115, 116 Castagna, A., 586 Castagnetta, L., 209, 210 Castagnetta, L. A., 209, 210, 224 Castanon, N., 273, 277, 281, 284, 300, 305, 307, 308, 514, 622, 651 Casteilla, L., 994 Castell, J. V., 995 Castell, L. M., 664, 665, 666 Castellazzo, G., 500 Castelli, C., 879 Castelli, E., 553 Castiel, P., 1059 Castillo, J., 417, 421 Castillo, S., 682 Castle, S. C., 380 Castriconi, R., 107 Castrillon, P. O., 1057 Castro, G. A., 398, 399 Castro, L., 199 Castro, L. C., 711 Castro, M., 502 Castro, V. A., 851, 852, 855 Castro, W. L., 788 Catalan, J., 1060, 1061 Cataland, S., 133 Catalani, C., 107 Catalani, Z., 352, 359 Catalano, D., 85, 551, 553 Catania, A., 100, 143, 1055
1141 Catellier, D, 937 Catellier, D., 695 Caterina, M., 400 Caterina, M. J., 102 Cathala, F., 585 Catley, D., 854 Cato, A. C. B., 772 Catt, S., 1061 Cattaneo, M., 364 Catts, S. V., 570 Catz, S. L., 1062 Caughey, G. H., 109 Caughman, S. W., 112 Caulfield, J., 1056 Caulfield, L. E., 466, 469 Caulfield, M. J., 863 Cauvet, N., 622 Caux, C., 108, 142 Cavalcantede Albuquerque, A., 810 Cavallone, L., 77, 365, 421 Cavallotti, C., 635 Cavigelli, S. A., 236 Cawthon, R. M., 734, 790 Cazaux, C. A., 66 Cazzaniga, S., 142 Cazzullo, C. L., 365, 421, 568, 570 Cebra, J. J., 456, 463, 464 Cecchini, A., 568 Cech, A. C., 254 Cederqvist, L. L., 461 Celadon, M., 553 Celiker, R., 769 Cella, D., 885 Cella, M., 1099, 1102 Cellary, A., 252 Cengel, K. A., 998 Centers for Disease Control, 689 Centurelli, M. A., 1059 Cerami, A., 54, 736, 738, 843, 995 Cercek, B., 928 Cerhan, J. R., 870, 873 Ceriello, A., 998 Cerillo, G., 210 Cermak, J., 664, 665, 666 Cerretti, D. P., 996 Cervera, A., 421 Cervera-Enguix, S., 510 Cervero, F., 161 Cesano, A., 222 Cesari, M., 924, 926, 956 Ceska, M., 108 Cespuglio, R., 585, 586 Cesselin, F., 167 Cesura, A. M., 307 Cetrulo, C. L., 113 Cetta, G., 844 Cezilly, F., 285 Cha, Y., 137 Chacon, M. E., 466
1142 Chacur, M., 399, 405, 406, 407 Chadwick, R., 643, 644 Chae, J. H., 571 Chai, C. Y., 847 Chai, T. C., 117 Chaiworapongsa, T., 458 Chakos, M., 564 Chakrabarty, S., 174 Chakraborty, P., 840 Chakravarty, S., 272 Chakroborty, D., 242 Chalikonda, I., 863 Challoner, P. B., 1108 Chalmers, D., 292 Chambers, A. F., 238 Chambers, D. A., 74, 1058, 1065 Chambers, W. H., 724, 745, 1099 Chambless, L., 948 Chambrier, C., 257 Chamorro, A., 417, 421 Chamorro, M., 1109 Champoux, M., 485 Chan, B., 134 Chan, C. Y., 863, 1079 Chan, H., 300, 542, 738, 741 Chan, I., 1065 Chan I., 863 Chan, K., 443 Chan, K. W., 997 Chan, R. C., 103 Chan, R. K., 195, 328, 843 Chan, S. C., 984 Chan, S. H., 93 Chan, S. T., 257 Chan, W., 133 Chanaud, B., 223 Chancellor-Freeland, C., 108, 1115 Chandler, J. L., 1060, 1061 Chandra, R. K., 456 Chanez, P., 103 Chang, C. F., 420 Chang, E. B., 1015 Chang, F. C., 583, 589 Chang, J., 531, 534, 535, 537, 538, 998, 1014 Chang, J. R., 1109 Chang, J. W., 358 Chang, L., 53, 667, 668 Chang, L. C., 847 Chang, M., 237, 1059 Chang, M. S., 142 Chang, N., 827 Chang, P. P., 714 Chang, S., 988 Chang, T. L., 47 Chang, Y. H., 570 Chan-Yeung, M., 814 Chao, C. C., 136, 361, 408, 734 Chao, H., 638, 641, 642
Author Index Chao, H. J., 68 Chao, M. F., 683 Chaouat, G., 463 Chapais, B., 489 Chaplin, D. D., 46, 47, 421 Chaplin, D. J., 260 Chaplin, W., 967, 969 Chaplin, W. F., 949 Chapman, G., 407 Chapman, G. A., 407 Chaponnier, C., 844 Chapotot, F., 585, 586 Chappel, M. R., 736 Chappell, P., 540 Chapple, C. R., 117 Charakida, M., 958, 960 Charalampopoulos, I., 997 Chard, K. M., 543 Charlotte, F., 149 Charmandari, E., 235, 962 Charney, D. S., 307, 521, 541, 570, 747 Charnley, R. M., 879 Charnock-Jones, S., 359 Charpentier, B., 551 Charra, M., 551 Charrier, L., 1002 Chartier-Harlin, M. C., 364, 365 Charurat, M., 1055 Chassard, D., 257 Chatenoud, L., 570 Chatterjee, T. K., 133 Chatters, L. M., 714 Chatterton, R. T., 199, 228 Chaturvede, U. C., 567 Chatzipanagiotou, S., 551 Chaudhuri, S., 241 Chaudry, I. H., 65 Chauvet, N., 291 Chavagnac, C., 725, 732 Chavanet, P., 1055 Chaveau, C., 74 Chavey, C., 999 Chavez, R., 405 Chavez, R. A., 405 Chayama, K., 237 Chazalviel, L., 420 Chebat, E., 487 Checchia De, A. C., 420 Checinski, M., 70 Chediak, A. D., 586 Chedid, L., 380, 584 Chedid, M., 826 Chee, M., 623, 683, 789, 863 Cheema, P., 995 Cheetham, M., 1019 Chelly, J., 362 Chelmicka-Schorr, E., 70, 1046 Chen, A. S., 997 Chen, C., 253, 275, 359, 1015
Chen, C. C., 233, 289, 870, 871 Chen, D., 75, 364 Chen, E., 451, 498, 499, 500, 502, 503, 800, 811, 812 Chen, Edith, 497 Chen, F. J., 417 Chen, H., 997, 1001 Chen, H. C., 999 Chen, H. J., 994 Chen, H. L., 240, 882 Chen, J., 148, 304, 384, 385, 386, 387, 444, 499, 644, 645, 653 Chen, J. P., 855 Chen, J. T., 167 Chen, K. C., 384 Chen, K. S., 360 Chen, L. B., 1015, 1023, 1024, 1025 Chen, M., 845, 883, 1079 Chen, M. J., 717 Chen, M. Y., 683 Chen, N., 241 Chen, P., 1058 Chen, Q., 565 Chen, R., 54, 55 Chen, S., 638, 641, 646 Chen, V. W., 871, 873 Chen, W., 1024, 1054 Chen, W. Y., 241 Chen, X., 1079 Chen, Z., 287, 996, 1056 Chen, Z. J., 46 Cheney, D., 695 Cheng, B., 184 Cheng, C. M., 185 Cheng, F., 641 Cheng, G., 1023 Cheng, G. J., 734 Cheng, H., 143 Cheng, H. Y., 1045 Cheng, J. G., 338, 359 Cheng, L., 884 Cheng, P. P., 109 Chengappa, K. N. R., 571, 572 Chenine, A. L., 1058 Cherbut, C., 1002 Cherichi, M., 688 Cheriff, A. D., 624, 764 Cherin, E., 710 Cherkaoui, J., 344 Chernajovsky, Y., 736 Cherner, M., 1060, 1062 Chernogubova, E., 1042, 1044 Chertoff, M., 434, 435 Chesebro, J. H., 922 Chesney, M., 686 Chesney, M. A., 498, 499, 689, 1061 Chesnut, J., 104 Chetboun, I., 933 Cheuk, W., 1110, 1112
Author Index Cheung, C. M., 1056 Cheung, S. W., 106 Chevrier, C., 585 Chew, C. H., 1063 Chew, L. J., 133 Chi, D. S., 1023 Chiang, S., 572 Chiang, Y. P., 683 Chiappelli, F., 288 Chiappelli, M., 361, 364, 421 Chiappini, M. S., 1061 Chiarelli, F., 855 Chiarotti, F., 284 Chiavetto, L. B., 571 Chicchi, G. G., 101 Chicheportiche, R., 997 Chicz-DeMet, A., 711 Chida, D., 274 Chida, K., 999 Chie, E. T., 400 Chiego, D. J., Jr., 223 Chien, K. R., 1043 Chikanza, I. C., 193, 197, 198, 201, 603, 604, 739, 981 Childers, S. R., 161 Chi-Mei Hsueh, 651 Chin, D., 1065 Chin, J. E., 385, 441 Chinn, S., 1002 Chiorazzi, N., 557 Chiovenda, P., 385 Chiozzi, P., 291 Chirigos, M., 678 Chitnis, D., 841 Chiu, H. F., 364, 421 Chiu, R., 53 Chizzolini, C., 142 Chizzonite, R., 56, 345, 978 Chizzonite, R. A., 292 Chmiel, J., 1060 Chmiel, J. S., 1053, 1054, 1058 Cho, C., 434 Cho, C. S., 76 Cho, E., 712, 713 Cho, M. L., 76 Cho, Y. W., 400 Choban, P. S., 1002 Choe, S., 1056 Chohan, B., 1059 Choi, B., 567 Choi, B. M., 553 Choi, C., 565 Choi, E. H., 813, 988 Choi, I. S., 800 Choi, S. H., 571 Choi, W. S., 331 Chojkier, M., 53 Chollet-Martin, S., 554 Chopra, V., 882
Chorine, V., 635, 636 Chornia, L., 716 Chorny, A., 143, 148, 149 Chou, A. K., 167 Chou, C. K., 237 Chou, K. B., 103 Chou, T. C., 321, 322, 327, 330 Chover-Gonzalez, A. J., 681, 739, 980, 987 Chow, C.-W., 1043 Chow, P. K., 257 Chow, W. S., 1001 Chowdari, K. V., 571 Chowdhury, I. H., 1056 Chowdhury, M. I., 1057, 1058 Chowdrey, H. S., 101, 112 Choy, L. N., 995, 999 Chretien, J. L., 853 Chretien, M., 110 Christeff, N., 222, 1055 Christen, U., 817 Christenfeld, N., 715 Christensen, A. J., 930 Christensen, N. J., 67, 222, 727, 728, 729, 1043 Christensen, T., 417 Christian, G. J., 606, 607 Christian, Lisa, 706 Christian, Lisa M., 781 Christmas, T. J., 117 Christodoulou, G., 932 Christoffels, V. M., 48 Christofides, N. D., 132 Christopher, N. C., 541 Christophers, E., 977 Christou, E. A., 1018 Chritton, D. B. W., 667 Chrivia, J. C., 137 Chrouses, G. P., 784 Chrousos, G., 110, 197, 201, 635, 679, 695, 881, 962, 980, 981 Chrousos, G. P., 45, 54, 55, 65, 67, 72, 73, 100, 110, 116, 194, 196, 197, 198, 200, 219, 222, 235, 254, 482, 521, 533, 536, 542, 543, 588, 589, 591, 594, 599, 605, 606, 608, 669, 711, 712, 737, 738, 739, 740, 741, 799, 812, 843, 855, 871, 881, 931, 932, 935, 980, 981, 982, 983, 986, 1036, 1045, 1054, 1055, 1056, 1057, 1061, 1098, 1112 Chruscinski, A. J., 74, 75, 1041 Chrysohoou, C., 932 Chrysohoou, C. A., 501, 505 Chu, B., 1015 Chu, E., 770 Chu, X., 70, 71, 1078 Chua, S. C., 995 Chua, S. C., Jr., 332
1143 Chuang, C. Y., 683 Chuang, L., 690 Chumlea, W. C., 715 Chun, T., 882 Chung, C., 882 Chung, J. H., 571 Chung, K. F., 502 Chung, L., 641 Chung, R., 1065 Chung, S. S., 998 Chung, W. Y., 1065 Chuo, L. J., 364 Church, D., 173, 174 Church, M. K., 109, 113, 417 Churgay, L. M., 994 Chute, D. J., 564 Cialic, R., 302 Ciallella, J., 104 Cianciolo, G. J., 1058 Ciccarelli, E., 133 Cicognani, G., 549, 551 Cid, A., 237 Cid, M. C., 224 Cidlowski, J., 198 Cidlowski, J. A., 41, 45, 48, 49, 50, 53, 55, 300, 521, 524, 1098 Cifone, M. G., 54 Cilia, M., 295 Ciliberto, G., 995 Cimadevilla, J. M., 342 Cinader, B., 380, 732 Cintado, C. G., 101 Cinti, S., 993 Cintron, N. M., 853, 862 Ciocca, D. R., 1015 Cioffi Dagger, R. P., 420 Ciotti, M. T., 184 Cira, D., 727, 743 Cirulli, F., 284, 285, 621 Ciudad, J., 550, 551, 553 Civin, W. H., 382 Cizza, G., 196, 198, 199 Claasen, J. H., 359, 386 Claes, S. J., 716 Claffey, K., 882 Claing, A., 1043 Claman, H. N., 724, 726, 728, 732, 737, 740 Clarencon, D., 585 Claria, J., 260–61 Clark, A. J., 100 Clark, B., 66 Clark, B. D., 286 Clark, C., 307, 510, 518, 606, 607 Clark, C. J., 815 Clark, D., 464, 878 Clark, J. J., 1002 Clark, J. V., 45 Clark, J. W., 552
1144 Clark, K., 272, 385, 386, 436, 681, 1108 Clark, L., 93 Clark, L. A., 622, 761, 762, 771 Clark, M., 662 Clark, R., 110 Clark, R. A., 223, 837, 838, 845 Clark, R. A. F., 826 Clark, R. E., 340 Clark, R. K., 417 Clark, S., 901, 909 Clark, W. M., 419 Clarke, A. S., 484, 485, 712 Clarke, B. A., 181, 182 Clarke, D., 814 Clarke, H., 437 Clarke, M. J., 380 Clarke, R. W., 394 Clark-Lewis, I., 1100 Clarkson, P. M., 669 Clarkson, T. B., 483 Classen, C., 687 Clatch, R. J., 1109, 1110 Clatworthy, A., 653 Clatworthy, A. L., 398, 399 Claudy, A., 109, 114 Claussen, C., 771 Clavenna, A., 349, 350, 351 Clawson, D. K., 994 Clay, W. C., 53 Clays, E., 961, 962 Clayton, A., 1019 Cleeland, C. S., 520 Clement, H. W., 599 Clement, K., 993 Clements, G. B., 901, 911 Clements, J. E., 490 Clements, M. K., 101 Clements, P. J., 729 Clemetson, D. B., 1059 Clemmons, D. R., 175 Clergue, F., 815 Clerici, C., 487, 1055 Clerici, E., 211, 212, 214 Clerici, M., 211, 212, 214, 365, 421, 487, 568, 570, 1055, 1056 Cleven, K., 687, 689 Clevenger, C. V., 241 Clifford, D. B., 166 Clifford, G. M., 237 Clinch, T. E., 1080, 1081 Clipstone, N. A., 1115 Clodi, M., 520 Cloitre, M., 534, 535 Cloninger, C. R., 550, 552 Clough, G. F., 417 Clout, D. E., 48 Clow, A., 624, 762, 763, 764, 765, 766, 912 Clum, G. A., 1088
Author Index Clutterbuck, E. J., 55 Cnaan, A., 1059 Coates, A., 501, 505, 961, 962, 1016 Coates, A. S., 771, 872, 873 Coates, B., 405 Coates, T., 686 Coates, T. J., 689, 1061 Coats, S. R., 101 Cobb, M. H., 137 Cobbold, S. P., 736 Cobelens, P. M., 68, 69, 76 Cobelli, C., 287 Cocchiara, R., 273 Cocco, L., 635 Cochran, D. L., 830 Cochrane, D. E., 109 Cochrane, L. M., 815 Cocke, R., 725, 731, 732 Cockerill, P. N., 54 Cockroft, K. M., 419 Coda, B., 710 Coda, R., 790, 1060, 1062 Coderre, T. J., 69, 402 Codispoti, M., 772 Cody, M., 931 Coe, C., 695, 786 Coe, C. C., 622, 773, 913 Coe, C. L., 383, 450, 460, 461, 463, 464, 465, 467, 468, 469, 470, 482, 483, 491, 497, 539, 622, 712, 787, 801, 1025 Coe, Christopher L., 455 Coelho, A. M., 273 Coelho, M. M., 302 Coffey, M. J., 1058 Coffey, R., 678 Coffey, R. G., 1044 Coffin, J., 253, 261, 882, 885 Coffman, R. L., 47, 73, 732, 735, 810, 1085, 1110 Coffman, T. M., 326 Coggeshall, R. E., 407 Coghlan, M. J., 48 Cogne, M., 74 Cogswell, J. P., 53 Cogswell, P. C., 53, 741 Cohard, M., 554 Cohen, B. A., 166 Cohen, D. H., 87 Cohen, D. P., 74 Cohen, E., 284, 339 Cohen, E. A., 1056 Cohen, F., 713, 901, 907, 912, 914, 1088 Cohen, H., 967 Cohen, H. J., 186, 200, 380, 782, 1043 Cohen, I. R., 148, 1024 Cohen, J., 146, 510, 514, 551, 552, 738, 745
Cohen, J. A., 1054 Cohen, J. D., 523, 710, 928 Cohen, J. I., 856, 864 Cohen, J. J., 468, 485, 728, 741 Cohen, J. L., 149 Cohen, L., 801, 811, 812, 884 Cohen, M., 874, 880 Cohen, N., 63, 64, 97, 453, 476, 499, 632, 636, 643, 644, 645, 646, 649, 650, 651, 652, 724, 725, 731, 732, 734, 761, 921, 934, 936, 1079 Cohen, O., 363 Cohen, O. J., 1054, 1056 Cohen, P., 174 Cohen, P. S., 92 Cohen, R. B., 54 Cohen, R. D., 781, 782, 947 Cohen, R. J., 239 Cohen, R. L., 74, 236, 1058, 1065 Cohen, R. T., 456, 461, 469, 801, 807, 811, 812, 816 Cohen, S., 56, 234, 236, 237, 257, 456, 461, 469, 483, 484, 486, 497, 498, 499, 503, 504, 505, 509, 510, 512, 516, 517, 551, 553, 622, 625, 676, 677, 681, 682, 694, 724, 726, 727, 729, 730, 734, 761, 762, 764, 766, 768, 769, 770, 771, 772, 773, 775, 781, 782, 783, 785, 786, 787, 791, 792, 793, 827, 872, 881, 888, 899, 900, 901, 903, 904, 911, 912, 913, 914, 932, 934, 966, 1036, 1053, 1055, 1062, 1063, 1065, 1080, 1089, 1111, 1112 Cohen SG, Z.-Q. M., 802 Cohen, Sheldon, 706, 761 Cohen, T., 224 Cohn, M. A., 586 Cohn, W. E., 1002 Cohnert, T., 254, 257 Cohrs, R. J., 859, 860, 1079 Coker, A. L., 237 Colacchio, T. A., 254, 257 Colacicco, A. M., 365 Colaco, C. A., 1024 Colantoni, A., 553 Colantonio, A., 714 Colas, D., 284 Colbert, L. H., 663 Colditz, G. A., 948 Cole, G. M., 439, 440 Cole, J. C., 517 Cole, S., 233, 235, 240, 241, 242, 253, 261, 497, 678, 679, 692, 790, 882, 885, 1053 Cole, S. W., 74, 233, 237, 261, 497, 624, 682, 683, 692, 790, 1057, 1058, 1062, 1063, 1064, 1065 Cole, T. J., 462, 1000
Author Index Coleman, D. L., 994, 995 Coleman, K., 485 Coleman, M. E., 181 Coleman, P. D., 358 Coleman, R., 977 Coleman, R. E., 933, 937 Coleman-Mesches, K., 645, 649 Coles, A., 436 Coley, W. B., 252 Coll, E., 957 Colla, M., 887 Collado-Hidalgo, A., 1053, 1059 Collart, M. A., 53 Collazos, J., 1055 Collector, M. I., 743 Coller, B. S., 957 Collet, H., 1036, 1043 Collingridge, D. R., 260 Collingridge, G. L., 340 Collins, B., 433 Collins, C., 498 Collins, G., 1036 Collins, J., 1002 Collins, J. S., 365, 366 Collins, J. V., 55 Collins, M., 639, 736 Collins, R., 921, 923, 927, 957 Collins, S., 235, 1022 Collins, S. M., 101, 116 Collins, T., 137 Collman, R. G., 1059 Colloca, L., 710 Colombel, J. F., 1002 Colombo, A., 291 Colombo, F., 570 Colombo, M., 652 Colombo, R., 716 Colonna, M., 1053, 1099, 1102 Colonna-Romano, G., 421 Coltrini, D., 842 Combarros, O., 363, 364, 366, 421 Combe, C., 274, 288, 291, 292, 294, 298, 301, 302, 382, 589 Combrinck, M. I., 304, 385, 441, 443 Combs, C. A., 998 Combs, T. P., 997 Comijs, H. C., 361, 362 Commins, S., 358, 359 Comora, S., 997 Comp, P. C., 199 Compas, B., 872 Compston, A., 436 Compston, D. A., 1108 Compton, C. C., 845 Comstock, G., 784 Comstock, G. W., 517, 871 Con, A. H., 716 Conant, M. A., 1088 Conboy, I. M., 173
Concina, P., 829, 830 Conde, G. L., 196, 739 Cone, R., 1086 Conejo-Garcia, J. R., 881 Conlan, J. W., 1038 Conley, R., 564 Conn, C. A., 298, 302, 303 Conn, L. A., 380 Connell, J., 804 Conner, J. R., 466 Connick, E., 1054 Connoer, M. A., 1115, 1118 Connor, K. A., 859 Connor, S. J., 136 Connor, T. J., 295, 305, 306, 557 Conraads, V. M., 497, 938, 969 Conrad, C. D., 348, 357 Conrad, D. H., 74 Conrad, S., 1002 Conrad, S. A., 1002 Conrad, S. M., 830 Consensus, 174 Conte, F., 603 Content, J., 736 Conti, B., 321, 736 Conti, F., 565 Conti, J. B., 948 Conti, P., 113 Conti, S., 115 Contoreggi, C., 197, 200 Contrada, R., 762, 789 Converse, P. J., 881 Conzelmann, K. K., 1099 Conzen, S. D., 236 Coogan, A., 353 Coogan, A. N., 353, 355, 359 Cook, B. L., 549, 550, 551 Cook, D. N., 840, 841 Cook, E., 816 Cook. G. A., 100, 103 Cook, J. L., 831 Cook, K., 690 Cook, K. S., 788 Cook, P., 585 Cook, R. T., 549, 550, 551, 554 Cooke, H., 1059 Cooke, H. J., 105, 116 Cooke, J. P., 842 Cooke, J. R., 579 Cook-Mills, J. M., 74, 236 Cooley, H., 855, 862, 863, 1079 Coolican, S. A., 182 Cooney, J., 458 Cooper, B., 240, 786 Cooper B., 882 Cooper, B. C., 882 Cooper, C., 456 Cooper, C. L., 872 Cooper, E. R., 1055
1145 Cooper, H., 761, 773 Cooper, J. A., 957 Cooper, K. D., 984 Cooper, L., 839 Cooper, M., 931 Cooper, M. D., 735 Cooper, M. L., 788 Cooper, N. R., 439, 440 Coppack, S. W., 512 Coppari, R., 332 Corbett, A. H., 50 Corcoran, L. M., 74 Corey, L., 1054, 1079, 1083, 1086 Corinaldesi, R., 116 Corkill, A. R., 762, 763 Corlu, A., 237 Cormia, F. E., 987 Corn, B., 233, 869 Cornelissen, I. L., 1053 Cornelius, C., 199 Cornforth, D., 1054 Corre, F., 556 Corrigan, C. J., 55, 502 Corringham, R., 885 Corsi, M. M., 361 Corsi, M. P., 380, 595 Corsini, E., 405 Cortelli, P., 585 Cortizo, A. M., 998 Corton, J. M., 1016 Cortright, D. N., 102 Corvera, C. U., 109 Costa, M., 133, 771, 790, 1060, 1062 Costa, P., 995 Costanzo, E., 235, 240, 241, 679, 692, 882, 885 Costanzo, E. S., 234, 240, 253, 255, 261, 764, 767, 881, 882, 885, 900, 906 Costanzo, Erin, 707, 869 Costa-Pinto, F. A., 649, 653 Costello, A. H., 165 Costello, E. J., 858 Costello, N., 686 Costigan, M., 407 Costlow, C., 512, 514, 598, 1079 Cosyns, P., 622 Coto, E., 366, 421 Cotter, C. S., 1025 Cottral, G. E., 927 Cottrell, D., 830, 831 Cottrell, G. S., 116 Cottrez, F., 142 Coudurier, S., 801 Coughlin, M. D., 109 Coull, J. M., 49 Coulter, S. N., 1108 Counil, F. P., 815 Counter, C. M., 235 Coupaye, M., 993
1146 Coupland, N. C., 542 Courneya, K. S., 661 Courouce, A. M., 554 Court, L., 585 Courtney, M., 691 Courtney, M. E., 734, 875 Cousin, B., 994 Cousin, J. L., 994 Cousin, J. M., 980 Cousineau, A., 733 Cousins, N., 624, 691, 692, 773, 774, 877, 881 Coussens, L. M., 879, 881 Coussons-Read, M., 459 Coussons-Read, M. E., 588, 1017, 1025 Coutaux, A., 167 Coutinho, R. A., 1053, 1060 Couvert, P., 362 Covas, M. J., 107, 1059 Cover, H., 514, 517, 607 Cowan, A., 400, 557 Cowan, M. J., 695, 937 Cowan, W. M., 330 Cowell, P., 564 Cowen, T., 805 Cox, D., 681, 695, 1110 Cox, D. S., 624, 625, 762, 764, 766 Cox, J. H., 728, 729, 730 Cox, M. E., 239 Cox, N. K., 512, 1089 Cox, N. K. M., 790, 900, 902, 907, 909, 911, 914, 915 Coyle, D. A., 681 Coyle, J. T., 184 Coyne, J. C., 782 Coyne, L., 871 Cozzarelli, C., 788 Cozzi Lepri, A., 70, 1057 Cozzio, A., 988 Crabtree, G. R., 53, 55 Craft, T. K., 842 Craig, E. A., 1015 Craig, J. W., 773, 1063 Craig, K. J., 532, 535 Craig, T., 692 Craig, T. K., 870 Cramer, I., 871, 873 Crampin, A., 859 Crane, J., 456, 470, 808 Crane, M. L., 197 Cranston, T., 668 Crary, B., 678 Craske, M. G., 623 Craven, T. E., 664, 665 Cravioto, M. C., 210 Craviotto, C., 199, 207, 208 Creed, F., 609 Creel, S., 491 Cremaschi, G. A., 66, 77
Author Index Cremer, P., 957 Cremon, C., 116 Cremona, S., 291, 298, 302, 430, 431 Crespi, H., 983 Crespin, T., 687, 691 Crespin, T. R., 877, 881 Cressey, L. I., 1043 Crestani, F., 273, 284, 295, 296 Cretney, E., 47 Creusvaux, H., 859 Criado, J., 586 Cribier, B., 237 Crider, A. B., 93 Crijns, H. J., 969 Crimmins, E. M., 380 Criqui, M. H., 769, 813, 969 Crisi, G. M., 438 Crispen, H., 461 Crisson, J. E., 979 Cristoforoni, P., 690 Critchlow, A., 1018 Crivello, A., 421 Crnic, L. S., 304, 523 Croce, M. A., 844 Crocker, I. C., 73 Crofford, L. J., 222, 981 Croft, C. S., 219 Croghan, T. W., 949, 950, 969 Crombleholme, T. M., 842 Cromi, A., 462 Cromlish, J. A., 110 Cron, K. C., 360 Cronstein, B. N., 55, 980 Crook, R., 364 Crooke, S. T., 1045 Cropley, M., 680, 694, 964 Crosby, W., 855 Cross, J., 960 Cross, R. J., 70 Cross, S. E., 789 Crossman, D., 969 Cross-Mellor, S. K., 284, 306, 307 Crouse, D., 600 Crowe, N. Y., 252 Crowley, C., 360 Crowley-Nowick, P., 876 Crowson, C. S., 199 Crowther, J. H., 687 Crowther, S. D., 815 Croxford, J. L., 1110 Croxson, T. S., 557 Crozat, K., 999 Crucian, B. E., 854, 855 Cruddas, M., 234, 692, 870, 1108 Cruess, D., 539, 541, 679, 686, 687, 689, 691, 694, 884, 1061, 1080, 1088 Cruess, D. G., 235, 687, 691, 1055, 1056, 1057, 1058, 1061 Cruess, Dean, 531
Cruess, S., 235, 679, 686, 687, 689, 1055, 1056, 1057, 1058, 1061 Cruess, S. M., 1080, 1088 Crum, R. M., 553 Crumeyrolle-Arias, M., 292, 358 Crumrine, D., 988 Crusazk, C. A., 403 Cruttenden, K. A., 901, 908 Cruz, C., 102 Cruz, F., 102, 117 Cruz, P. E., 405 Csako, G., 501 Csaky, K. G., 826 Csizmadia, V., 55 Cuadros, M. A., 401 Cuan, N., 136 Cucchi, P., 107 Cudkowicz, G., 1109 Cuello, C., 104 Cuffel, B., 812 Cui, K., 180 Cuijpers, P., 509 Culhane, J., 711 Culhane, J. F., 458, 711 Culjak, G., 771, 872 Cullinan, E. B., 345 Cullinan, W. E., 328, 329 Culnane, M., 1055 Culpan, D., 365, 366, 421 Culpepper, J. A., 55 Culver, J., 691 Culver, S., 710 Cumberbatch, M., 995 Cumberland, J. E., 54, 55 Cumiskey, D., 357 Cumming, A., 365 Cummings, D. E., 297, 993 Cummings, S., 695 Cummins, R. W., 647, 648, 653 Cunha, F. Q., 160, 165 Cunnick, J. E., 70, 483, 484, 662, 733, 743, 775, 787, 792, 1111 Cunningham, A. J., 353, 357, 873 Cunningham, A. L., 1079 Cunningham, B. R., 101 Cunningham, C., 272, 276, 304, 361, 384, 385, 386, 420, 430, 439, 440, 441, 443, 444 Cunningham, C. E., 717 Cunningham, C. K., 1055 Cunningham, E. T., 338 Cunningham, E. T., Jr., 87 Cunningham, L. A., 272 Cunningham-Schrader, B., 1055 Cuoco, L., 927 Cupps, T., 678 Cupps, T. R., 724, 737 Curb, J. D., 957 Curhan, G. C., 956
Author Index Curnow, S. J., 1056 Curran, B., 357 Curran, B. P., 353, 357 Curran, E., 160, 161 Curran, J. F., 568 Curran, M., 854 Curran, M. D., 366 Currie, G. P., 815 Currie, M. S., 882 Curry, B. B., 1015 Curtis, A. B., 948 Curtis, A. L., 710 Curtis, N., 579, 586 Curtis, S. E., 461 Cury, Y., 399 Cushion, M. T., 729 Cushman, M., 923, 926, 957 Cusmai, A., 241 Cuthbert, A. W., 110, 115 Cutolo, M., 41, 198, 199, 200, 207, 208, 209, 210, 211, 212, 213, 214, 222, 223, 224, 226, 733, 737 Cutrera, R. A., 1057 Cutrona, C., 676 Cutrona, C. E., 785 Cutz, E., 133 Cuzner, M. L., 437, 739 Cuzzocrea, S., 300 Cvoro, A., 1014 Cypess, A. M., 108 Czaja, J., 144 Czaja, S., 553 Czajkowski, S. M., 695 Czeh, B., 465, 712 Czeisler, C. A., 603 Czerwenka, K., 690 Czeslick, E., 543 Czlonkowski, A., 165 Czuprynski, C. J., 1038 Czura, C., 635 Czura, C. J., 40, 85, 88, 105, 106, 965, 997 D’ Aigle, T., 385 Da Costa, M. L., 256 Da Ros, R., 998 da Silva, B., 1057 da Silva, J. A., 198, 199 Daar, E. S., 1059 Dababneh, A., 198 D’Adamio, F., 54 D’Addario, V., 462 Daffertshofer, M., 420 Dafny, N., 409 Dagalp, K., 1002 Dagenais, G. R., 957 D’Agostino, R., 957 Dahinden, C. A., 106 Dahlberg, L., 1003
Dahlen SE, H. P., 802 Dahlgren, C., 839 Dahlman, K., 50 Dahlstrom, A., 133 Dahlstrom, M., 322 Dahlstrom, W. G., 498, 929 Dahme, B., 771 Dahmen, N., 553 Dahn, J., 693 Dahn, J. R., 693 Dai, A., 211 Daida, H., 937 Daigle, I., 978 Daigle, J., 1087 D’Aigle, T., 444 Daimon, M., 1000 Dakay, E. B., 727 Dakhama, A., 810 Dal Canto, M. C., 1108, 1110 Dal Cin, E., 142 Dal, F. G., 421 Dal Forno, G., 363, 364 Dal Piaz, F., 109 Dal Toso, R., 106 Dalal, M., 594, 598 Dale, D. C., 603, 727, 728, 729, 826 Dale, J., 695 Dale, J. K., 363 Dalen, E. A., 1061 Dalerba, P., 879 Dalgalarrondo, P., 570 Dalgleish, A. G., 1024 Dalhoff, K., 959 Dallal, G. E., 361 Dalla-Vorgia, P., 933 Dalle, M. T., 1055 Dallman, M. F., 110 D’Almeida, V., 1036 Dalsgaard, C. J., 113, 115, 223 Dalton, D., 184 Dalton, K. M., 913 Daly, J. M., 254 Daly, M., 869 Daly, R. J., 570 Damasio, A. R., 620 Damasio, H., 620 D’Ambrosio, D., 72, 73, 142, 1045 D’Ambrosio, S., 883 Damert, A., 885 D’Amico, M., 432 D’Amico, R., 1110 Dammann, O., 459 Damoiseaux, J. G., 740 D’Amore, P. A., 692 Danesh, J., 501, 921, 923, 924, 926, 927, 957, 958, 961 Dang, J., 518, 553, 554, 595, 598, 599, 607, 608, 609 D’Angelo, T., 869, 874, 876
1147 Dani, C., 994 Daniel, J. A., 605 Daniel, K. W., 235 Daniel, N., 566 Daniel, S., 522 Daniel, V., 645–46 Daniele, A., 363, 364, 421 Daniels, M., 199, 512, 516, 622, 625, 676, 784, 785 Daniels, S., 290 Danielson, A., 237, 683, 1088 Danis, V. A., 208 Dankbar, B., 882 Danner, R. L., 146 Danoff-Burg, S., 685 Danon, Y. L., 712 Danton, G. H., 433 D’Antuono, M., 356 Dantzer, R., 87, 99, 112, 113, 171, 172, 174, 175, 177, 180, 181, 182, 183, 184, 185, 186, 187, 223, 267, 268, 271, 272, 273, 274, 277, 281, 282, 283, 284, 286, 287, 288, 290, 291, 292, 294, 295, 296, 297, 298, 300, 301, 302, 304, 305, 306, 307, 308, 309, 320, 321, 337, 338, 339, 344, 345, 347, 381, 382, 384, 397, 422, 430, 431, 432, 480, 481, 482, 514, 518, 519, 521, 522, 589, 603, 622, 651, 681, 693, 694, 923, 934, 935, 936, 995, 996, 998, 1000, 1058 Dao, M., 876 DaPrada, M., 40, 64, 65, 70, 678 Darby, I., 844 Darbyshire, J., 1055 D’Arcangelo, G., 356, 357 Dardenne, M., 462, 603 Dardick, S. J., 200 Daremberg CH, G. C., 802 Darendeliler, F., 1002 Dark, K., 647, 648 Dark, K. A., 647, 648, 653 Darko, D., 66, 1044 Darko, D. F., 586 Darley, L., 999 Darnell, J. E., Jr., 137, 998 Darsaud, A., 585 Darui, A., 978 Darzynkiewicz, Z., 1018 Das, A. T., 48 Das, K. M., 116 Das, M. P., 140 Dasgupta, D., 840 Dash, R. J., 1055 Dashevsky, B. A., 533, 536, 543 Dasilva, I., 1102 Datson, N. A., 198 Datta, S. P., 521 Dattore, P. J., 871
1148 Daucher, M., 1054 Daugherty, C., 725, 731, 732, 743, 745, 750 Daun, J. M., 296 D’Aunno, D., 855 Davalli, A. M., 142 Davalos, A., 417, 421 Davare, M., 1043 Dave, J. R., 241, 417 Davey, M., 830, 831 Davey, R. T., Jr., 1055 Davey Smith, G., 957, 958, 960, 961 David, A. S., 233, 870, 871 David, D., 538 David, J. R., 725, 732, 745 David, M., 995 David, S., 148, 565 Davidson, B. L., 418, 419 Davidson, E. A., 1060, 1061 Davidson, J., 540, 692, 871, 872 Davidson, J. M., 846 Davidson, J. R., 599 Davidson, K. P., 685, 694 Davidson, K. W., 949, 969 Davidson, L. M., 538 Davidson, N., 498 Davidson, R. I., 622 Davidson, R. J., 497, 620, 622, 710, 713, 773, 901, 909, 910, 913, 1063 Davidsson, P., 361 Davies, A., 679 Davies, A. A., 712 Davies, B. D., 882 Davies, C. A., 416, 417 Davies, D., 804 Davies, J. L., 348, 361, 380 Davies, M. J., 922 Davies, R., 433 Davis, A. A., 1015 Davis, D. G., 363, 364, 421 Davis, G., 1086 Davis, H., 580 Davis, H. M., 885 Davis, J. B., 102 Davis, J. M., 663, 664, 665, 666, 668, 669, 1082 Davis, K. L., 510, 622 Davis, L. J., 366 Davis, M., 501 Davis, M. C., 199 Davis, P. A., 580 Davis, S., 511 Davis, T. M., 531 Davison, K. P., 791, 901, 908, 914, 1063 Davis-Smyth, T., 240 Davis-Street, J. E., 851 Davis-Vogal, A., 554 Davoust, J., 142 Dawils, L., 1044
Author Index Dawson, D., 594 Dawson, D. A., 419, 554 Dawson, H., 1036 Dawson, J. L., 870, 871 Day, C. L. Jr., 837 Day, H. E., 1019 Day, I. N., 364 Day, M. J., 740 Day, N. K., 1058 Day, R., 653 Day, T. A., 294 Dayan, K. I., 933 Dayer, J. M., 142, 273, 274, 995, 997 Daynes, R., 747 Daynes, R. A., 361, 380, 383, 731, 732, 735, 740, 747, 855 Dazin, P., 134 Dazin, P. F., 65, 72 De, A., 605 De, A. M., 603 De Acetis, L., 284, 285, 621 De, B. F., 603 De, B. G., 421 De Backer, G., 961, 962 De Bacquer, D., 961, 962 De Baets, M., 932 de Baets, M., 969 de Bates, M, 681, 682, 694 De Beaurepaire, R., 695 De Benedetti, F., 995 De Berardinis, M. A., 147, 276 de Bock, F., 186 De Boer, A. G., 293 De Boer, S. F., 479, 480, 484 de Boo, T. M., 199 De Bosscher, K., 53 de Brabander, J. M., 386 de Bracco, M. M., 66 De Carli, M., 106, 800 de Caro, G., 103 de Castro, M., 198, 521 De Cecco, L., 828 de Champlain, J., 716 De Clerck, L. S., 497, 938, 969 de Coupade, C., 65, 72 de Craen, A. J., 362 de Crescenzo, G., 109 De Deyn, P. P., 341 de Faire, U., 1016 de Felipe, C., 219 de Filipe, C., 100, 104, 107 De Gast, G. C., 978 De Giorgio, R., 116 de Goede, R. E., 1053 de Graeff, A., 679 de Groat, W. C., 102 De Groot, C. J., 439 de Groot, J., 1080 de Groot, P. G., 811
de Haan, E. H., 186 de Jager, S. C., 109 De Jager, T., 211 de Jong, B. A., 218 de Jong, E. C., 219 de Jong, J. B., 541 de Jong, J. G., 480 De Jong, R., 551, 570 de Jong-de Vos van Steenwijk, T., 739 de Jonge, W. J., 89 de Jongh, R., 570, 571, 1115 de Keyser, J., 184 de Kloet, E. R., 198, 338, 342, 347, 349, 357, 604, 733, 735, 745 de la Bretonne, J., 994 De La F. M., 133 de la Fuente, M., 855, 1044 De La Fuente, R. L., 923 De La Garza, R., 2nd, 295 De La Pena, S., 64 de la Salle, C., 978 de la Salle, H., 978, 1024 de la Torre, B., 1055 de la Torre, R., 557 de Lavalette, C. R., 272 de Leij, L. F., 458 de Leon-Casasola, O., 556 De Ley, M., 570 De los Santos, M. J., 359 de Luca, C., 995 De Luigi, A., 434 De, M. C., V, 603 De, M. M., 595, 607 de Maat, M. P., 957 de Martin, R., 1100 De Martinis, M., 380 De Martino, M., 855 De Mees, C., 458 De Mello, V., 937 de Neef, P., 133 de Oliveira, A. C., 1036 de Oliveira Massoco, C., 828 De Paredes, E. S. O., 872 De Paulis, A., 109 De Preval, C., 110, 200 de Rooij, J., 239 De Rosa, V., 1003 De Saint Hilaire, Z., 330 De Sarro, A., 300 De Sarro, G. B., 523 De Seau, V., 855 de Seau, V., 735 De Seze, J., 148 De Simone, R., 147, 276 De Simoni, M. G., 186, 434 De Smet, M., 729 De Smet, M. B., 934 De Souza, E., 104 De Souza, E. B., 87, 292, 294, 338
Author Index De Souza, G. E., 288 De Souza Silva, M. A., 305 De, SR., 91 De Stavola, B., 957 de Stefano, G., 637, 638, 640, 652 De Swart, H., 931 De Swart, H. B, 931 De Swart, H. B., 935 De Swert, K. O., 107 De Veerman, M., 100, 104, 107, 219 de Vellis, J., 148 de Vries, E. G., 519 De Vries, H. E., 293 de Vries, M., 679, 689 de Vries, M. J., 1061 De Vries, T. J., 304 de Vries, W. R., 186 de Vroome, E., 689 de Vroome, E. M., 1060 De Waal, F. B. M., 479 de Wit, J., 1060 De Zeeuw, R., 977 Deacon, R., 384, 440, 443 Deacon, R. M., 443 Deaglio, S., 241 Deak, T., 301, 344, 357, 481, 732, 733, 854, 965, 1019, 1025, 1026, 1115 Deakins, S., 551 Deal, M., 934 Deam, D., 1055 Dean, D., 1110 Dean, D. D., 1081 Dean, L., 784, 1060 Dean, L. M., 734 Dean, M., 1053 Dean, T. P., 502 Dean, W. L., 1025 Deanfield, J., 964, 965, 1000 Deanfield, J. E., 958, 960, 961, 962, 964 Dearman, R., 732 Deary, I. J., 380 Debakey, M. E., 927 De-Bellis, G., 363, 364, 365, 366 DeBellis, M. D., 538, 541 Deboer, T., 422, 585 Debord, M., 1055 DeBruin, J. P. C., 713 Debuire, B., 1059 Debus, S., 841 DeBusk, R., 695 deChatel, R., 422 Decicco, C. P., 419 Decker, K., 241 Decman, V., 1079, 1083 Decourt, C., 74 Decroly, E., 132 Dedert, E. A., 884 Dedousis, G., 692 Dee, B., 1110, 1112
Deeble, P. D., 239 Deeg, D. J., 186, 509 Deep-Dixit, V., 1036 Defea, K., 109 Defrance, P., 997 DeGaetano, J. S., 859 Degli-Esposti, M. A., 47 Deglmann, W., 978 Degraef, C., 1018 Deguchi, M., 254 Dehen, H., 160, 165 Dehoff, M. H., 175 Deijen, J. B., 186 Deisseroth, A. B., 137 Deitch, E. A., 1024 DeJong, G. M., 790 deJonge, L., 994 Dekaris, D., 532, 535, 536, 537, 538 DeKeyser, F. G., 881 Dekker, E., 647 DeKosky, S. T., 364, 365 DeKruyff, R. H., 55, 56, 502, 800 Del Bianco, E., 115 Del Bino, G., 1018 Del Bo, R., 434 Del Boca, E., 108 del Carmen Saez, M., 1044 del Castillo, J., 727 Del Giacco, G. S., 361 del Prete, F., 184 Del Prete, G., 855 Del, R. G., 603 Del Rey, A., 40, 64, 65, 70, 73, 217, 222, 224, 273, 275, 282, 300, 338, 344, 346, 347, 350, 351, 355, 356, 357, 380, 516, 518, 520, 601, 603, 605, 637, 646, 650, 651, 652, 678, 738, 1039, 1040 del Zoppo, G. J., 434 Delahanty, D. L., 532, 535, 541, 542, 1055 Delahaye, F., 49 Delaney, C. A., 223 Delanghe, J., 961, 962, 969 DeLano, R. M., 1080 Delarmarter, J., 132 Delbono, O., 90 Delcroix, I., 354, 355, 646 Delea, C. S., 744 Delemarre-van de Waal, H. A., 186 DeLeo, J. A., 405, 406, 408, 409 Delers, F., 995 Delespesse, G., 73, 732, 1036, 1043 Delfraissy, J. F., 1055 Delgado, M., 40, 99, 103, 104, 131, 133, 134, 135, 136, 137, 139, 140, 141, 142, 143, 144, 146, 147, 148, 149, 195 Delgado, P. G., 521 Delgado, P. L., 1061
1149 DelGiacco, G. S., 1080 Delhaye-Bouchaud, N., 304, 385 D’Elios, M. M., 106 Delisi, L. E., 564, 567 Della Bianca, V., 998 Della, C. M., 107 Dellas, C., 1001, 1002 Dellow, K., 359 Dellu, F., 344, 712 Delmiere, L., 533, 536, 537, 538, 539 Delneste, Y., 219 Delorenze, G. N., 1061 Delporte, C., 133 Delrahim, K. K., 568 Delsignore, R., 772 DeLuca, D., 105 Del-Val, M., 47 Delville, Y., 478 Demarest, J. F., 1054 Demas, G. E., 481 DeMayo, F., 181 Dembinski, S., 510 Dembroski, T. M., 929 Dembski, M., 994 Dement, W., 582 Demetrashvili, M., 304, 523 Demissie, S., 638, 640, 641, 642, 651 Demitrack, M., 695 Demodena, A., 512, 607 Demoly, P., 842 Dempster, R., 434, 435 Dempster-McClain, D., 782 Demuth, R. J., 1040 Denburg, J., 98, 116 Denburg, J. A., 109, 116 DeNeve, K. M., 761, 773 Deng, J., 184 Deng, L., 46 Deng, Y., 1102 Deng, Y. S., 400 Denhardt, G. H., 55 Denicoff, K. D., 519 Denis, F., 1054 Denisova, N. A., 383 Dennis, J., 92 Dennis, T., 104 Denny, T. N., 139 Denny, W. B., 482 Denollet, J., 497, 938, 969 Dentino, A. N., 882 Denton, J., 224 Denzinger, R., 871 DePalo, V. A., 997 DePaoli, M., 301, 1115 Depaulis, A., 556 Depboylu, C., 365 Depiante-Depaoli, M., 733 Depino, A. M., 344, 346, 347, 422, 434 Depner, M., 887
1150 Depocas, F., 1022 Der, G., 800, 814 Derad, I., 597, 601, 603 Derby, L. E., 242 D’Ercole, A. J., 173, 184 Derendorf, H., 851 Derevenco, V., 636 Derfuss, T. J., 1115 DeRijk, R., 734, 745 Derijk, R., 732 DeRijk, R. H., 198, 1112, 1115 Derin, N., 1037 Dermitzaki, E., 997 Derogatis, L. R., 771 Deroo, B. J., 51 DeRose, V., 109 Derr, R. F., 842 Derrick, B. E., 356 Dery, O., 109 Derzie, A. J., 1002 Des Roches, A., 807 Desai, B. B., 56 Desai, K. H., 1041 Deschenes, L., 234, 870, 873 Descotes, J., 69 Desgres, J., 1055 Desmond, J. E., 620 Desmonts, J. M., 815 Desmouliere, A., 844 Desnyder, R., 570 Despres, J. P., 957 Desreumaux, P., 1002 Dessing, M., 1065 Dessy, L. A., 568 Detels, R., 1053 Deten, A., 542 Detera-Wadleigh, S. D., 48 DeTeresa, R., 386 Dethlefs, S., 1109 Detillion, C. E., 842 Detmar, M., 842, 882 Detrano, R. C., 923 Detry, O., 252 Dettmer, E., 689, 1055 Detweiler, J. B., 761 Deusch, E., 557 Deuschle, M., 884, 887 Deuster, P. A., 669 Deutsch, C., 73 Deutsch, P., 1054 DeVald, B. L., 735 DeVane, C. L., 815, 1059 DeVange, D. M., 1059 Devata, S., 348, 382 Devaux, C., 1058 DeVellis, R. F., 199 Devenport, L., 745 Devereux, G., 456, 462, 816 Devillier, P., 101
Author Index Devine, E. C., 828 Devins, G. M., 771 DeVita, V. T. J., 236 Devlin, B. J., 485 Devogelaer, J. P., 213 Devor, M., 110 DeVries, A. C., 842 Devries, A. C., 480, 842 deVries, M., 691 Dew, M. A., 518, 580, 1061 Dewald, B., 55 Dewar, D., 363, 364, 365, 366, 421 Dewar, H. A., 948 Dewey, K. G., 466 DeWilde, S., 771 DeWit, L., 736 DeWitt, D., 135, 294, 321, 322, 438 DeWitt, D. L., 321 DeWitt, J., 273 Dey, R. D., 133 Deykin, A., 809 Dhabhar, F., 637, 680, 682, 683, 692, 694, 706 Dhabhar, F. S., 68, 112, 198, 222, 469, 480, 512, 516, 534, 535, 555, 620, 621, 723, 724, 725, 726, 727, 728, 729, 730, 731, 732, 733, 734, 735, 737, 739, 741, 742, 743, 744, 745, 747, 750, 790, 934, 964, 1025, 1044, 1080, 1082, 1099, 1100, 1101, 1103, 1112 Dhabhar, Firdaus S., 723 Dhalla, H. S., 235 Dhalla, K. S., 235 Dhillon, B., 1000 D’Hondt, P., 622 D’Hooge, R., 341 Di Bello, C., 132 Di Bello, M. G., 838 Di, C. V., 142 Di Carlo, S., 557 Di Carlo, V., 980 Di Falco, M., 209, 210 Di Giacomo, A., 1003 Di Gregorio, B., 1000 Di Lucia, P., 1045 Di Maria, G. U., 103 Di Marzio, P., 1056 Di Naro, E., 462 Di, R. F., 420 Di Rosa, M., 1015, 1025 Di, S. E., 419 di Sant’Agnese, P. A., 239 Di Santo, E., 434 Di Scala, G., 639, 646 Di Virgilio, F., 291 Diabetes Prevention Research Group, 716 Diamantstein, T., 74 Diamond, B., 199
Diamond, D. M., 357, 745, 1014, 1017 Diamond, S., 687, 790 Diana, A., 274 Diaz, A., 711 Diaz, C., 1055 Diaz, G., 361 Diaz-Mitoma, F., 858 Dick, E. C., 115, 668 Dickens, P., 361 Dicker, D., 716 Dickerson, C., 841 Dickerson, F. B., 566, 567 Dickerson, S. S., 621, 624, 625, 1065 Dickey, C. C., 564 Dickey, R. F., 45 Dickhaus, B., 599 Dickinson, A. G., 443 Dickmeis, E., 1056 Dickson, D. W., 136 Dickson, J. F., 199 Dickson, S. L., 996 Dickstein, J. B., 592 DiClemente, R. J., 871, 876 DiDonato, J. A., 53, 741 Dieckmann, B., 995 Diedrich, J. P., 552 Diedrich, M., 565 Diefenbacher, A., 566 Diegelmann, R. F., 842 Diego, M. A., 1061 Diehl, A. M., 554, 998 Diem, G., 710 Diem, S., 98 Diemer, N. H., 416, 417 Dienberg Love, G., 625, 764, 771, 772, 900, 902 Diener, E., 761, 762, 771, 773 Dierschke, D. J., 467, 483, 491 Dierse, J. K., 358 Dietrich, H., 739 Dietrich, W. D., 433 Dietze-Schroeder, D., 1000 Dietzschold, B., 567 Dieu-Nosjean, M. C., 108 Diez, E., 692 Diez Roux, A. V., 948 Diez-Ewald, M. P., 957 Difonzo, K., 1061 Dighe, A. S., 878 Dignam, T. F., 987 Dijkstra, C., 678 Dijkstra, C. D., 272, 438, 439, 740, 1112 Dik, M. G., 186, 361, 362 Dilley, R. J., 211 Dillon, E., 930 Dillon, K. M., 762, 763 Dillon, S., 710 DiLuca, M., 405 DiMaggio, D., 103
Author Index DiMaggio, D. A., 110 DiMarchi, R. D., 994 DiMatteo, M. A., 258 DiMatteo, M. R., 949, 950, 969 Dimetz, T., 1055 DiMicco, J. A., 74 Dimitriadou, V., 109, 111 Dimitrijevic, M., 632, 649, 1118 Dimitrov, S., 224, 594, 596, 598, 603, 604 Dimsdale, J., 966 Dimsdale, J. E., 70, 606, 729, 730, 771, 930, 931, 934, 962, 963, 965, 966, 969 Dinarello, C., 222 Dinarello, C. A., 85, 273, 274, 282, 295, 297, 303, 321, 337, 338, 358, 361, 380, 419, 542, 584, 738, 844, 845, 956, 996, 1025 Dincsoy, H. P., 1055 Dineley, K. E., 102 Ding, A., 85 Ding, J., 956 Ding, W., 68, 69, 219, 680, 694, 727, 729, 735, 1044, 1045 Ding, X. F., 50 Ding, X. Z., 1015 Dinges, D. F., 598, 599 Dingman, C. W., 567 Dinh, T. V., 882 Diniz, C. P., 384, 440, 443 Dinkel, K., 186 D’Introno, A., 365 Diorio, J., 491 Diot, C., 237 DiPauli, R., 652 Dipchand, E. S., 1015, 1016 DiPietro, L. A., 830, 831, 840, 841, 846 DiPiro, J. T., 586 DiRaimo, R., 997 Dirdal, I., 716 Dirnagl, U., 76, 433 Disch, R., 978 Distelhorst, C. W., 49, 241 Distler, M., 1024 Diwa, A., 104 Dixon, M. F., 116 Dixon, R. A., 235 Djaldetti, M., 515 Djaldetti, R., 147 Djukanovic, R., 55 Djuric, V., 649, 653 Dloughy, S., 184 Do, M., 164 Dobbleing, U., 735 Dobbs, C., 70, 71, 254, 811, 1078 Dobbs, C. M., 70, 862, 1080, 1084, 1087, 1100, 1102, 1103 Dobie, D. J., 531
Dobos, G., 646 Dobrescu, C., 995 Dobrina, A., 363, 364, 421 Dobson, A., 946 Dobson, A. J., 933 Docagne, F., 276, 277, 417, 420, 434, 435 Docherty, J., 692 Docke, W., 254 Docke, W. D., 198, 254 Dockray, G. J., 117, 200 Dodel, R. C., 363, 364, 365 Dodsworth, J., 829, 830 Dodsworth, R. O., 479 Dodt, C., 597, 601, 603, 607 Doeberitz, M. V. K., 740 Dofferhoff, A. S., 146 Dogterom, G., 304 Doherty, D., 875 Doherty, J. M., 878 Doherty, P. C., 1085, 1102 Dohi, K., 416, 417 Dohi, T., 404 Dohrenwend, B. P., 788 Dohrenwend, B. S., 788 Doi, K., 882 Doi, S., 55 Doi, T., 769 Doinel, C., 1055 Dolan, S., 539 Dolganiuc, A., 554 Dolganov, G., 141 Dolin, A., 643 Dollman, M., 420 Dolnak, D., 568 Dolovich, M., 110 Dolski, I., 497, 622, 773, 913 Dominguez-Santalla, M. J., 550, 552, 554 Dominici, R., 364 Domjan, M., 631, 634 Doms, R. W., 1053 Donahoe, F., 557 Donahoe, R. M., 557, 1058 Donald, A., 964 Donald, A. E., 680, 694, 958, 960, 961, 962 Donaldson, D. J., 826 Donaldson, M. R., 853 Donato, R., 565 Donelan, J. M., 113 Donfield, S., 1053 Dong, Y., 273, 565 Donini, M., 841 Donnell, A. T., 976 Donnelley, T., 736 Donnelly, P. K., 256 Donnelly, R. J., 53 Donnelly, S., 141
1151 Donnelly, T. M., 236, 884 Donner, D. B., 338 Donnerer, J., 105, 106 Donney, E. C., 516 Donny, E. C., 556 D’Onofrio, F., 361 Donovan, K., 855 Donovan, S. M., 175 Donzella, B., 497, 622, 773 Doogan, J., 844, 845 Dooley, N. J., 732, 735 Dooley, W., 881 Dopp, E. A., 438, 740 Dopp, E. D., 439 Dopp, J. M., 497, 724, 789, 966 Doppler, H., 181 Dorababu, M., 1037 Doran, M. F., 199 Dore, S., 184 Dorenbaum, A., 1055 Dorfman, M., 235 Doria, A., 210, 213, 214 Doring, A., 932, 937 Dornan, B., 769 Dornand, J., 186 Dorne, J., 238, 1053, 1065, 1080, 1088, 1111 Dorner, B., 1023, 1024 Dorrucci, M., 683 Dorsam, G., 103, 134, 140, 141 Dorst, K., 652 Doskeland, S. O., 1043 Dossi, R., 842 D’Ostilio, A., 595, 607 Dostrovsky, J. O., 405 Dotson, R. C., 662, 665, 667 Dotzlaw, H., 198 Dou, P., 88 Doua, F., 585, 586 Douek, D. C., 1057 Dougados, M., 209, 210 Dougall, A. L., 532, 535, 542 Dougherty, P. M., 397, 409 Dougherty, R. F., 727, 728 Dougherty, T. F., 724, 738 Douglas, K. M., 932, 937 Douglas, S. D., 112, 509, 510, 512, 554, 598, 599, 606, 1059, 1061 Douglas, W. W., 109 Doutremepuich, J. D., 109, 114 Douville, C. C., 878 Dovi, J. V., 831, 846 Dowd, M., 184 Dowdell, K., 739 Dower, S. K., 1025 Dowling, F. E., 400 Downing, J., 635 Downing, J. E., 100, 1057 Doyle, M. P., 934
1152 Doyle, W. J., 486, 497, 504, 505, 768, 769, 770, 771, 772, 773, 782, 783, 1053, 1055, 1063, 1080, 1111 Drake, C. L., 587 Dranoff, G., 180, 181, 885 Dransfield, I., 1025 Draude, G., 1100 Dray, A., 402 Drayson, M., 762, 763, 900, 901, 905, 907, 912, 913, 914, 1046, 1088 Drazen, D. L., 303, 481 Drazen, J. M., 101 Drell, T. L, T., 261 Drell, T. Lt., 239, 240 Drenth, J. P., 664 Dreschel, N. A., 456 Dresner-Pollak, R., 364 Dressler, W. W., 501 Dreux, C., 1055 Drew, B. C., 662 Drewes, A. M., 609 Drexler, H. C., 1000 Dreyer, M., 997 Dreyer, M. G., 997 Driemeyer, J., 1040 Drings, P., 234, 871 Dripps, D., 88, 290, 381 Driscoll, L., 386 Driss, F., 554 Droppleman, L. F., 762 Drosos, A. A., 193 Drossaers-Bakker, K. W., 199 Drouet, M., 74 Druck, T., 996 Drugea, I. A., 840, 841 Druley, J. A., 791 Dry, J., 736 Drzonek, H., 740 D’Sa, C., 275 D’sa, C., 103 D’Souza, D., 839 D’Souza, M. J., 92 Du, X., 997, 999 Du, X. L., 998, 999 Du, Y., 363, 364, 365 Duan, J. J., 419 Duan, W., 383 Duan, X., 644, 645, 653 Duarte-Risselin, C., 736 Duba, J., 1015 Dubas-Slemp, H., 570, 571 Dube, B., 1061 Dube, M. G., 297 Duberstein, P., 691 Duberstein, P. R., 900, 903, 914, 1046 Dubey, D. P., 829 Dubinett, S. M., 555, 557 Dubner, R., 165 Dubois, A., 789
Author Index Dubois, F., 853, 863 Dubois, R. N., 260, 261 Dubois-Dalq, M., 275 Dubow, R., 855, 862, 863, 1079 Dubreuil, Y. L., 385 Dubrow, N., 498 Dubs, R., 417 Dubs, R.Gemsa, D., 584 Dubucquoi, S., 148 Dubuquoy, L., 1002 Duchateau, J., 664, 666 Ducimetiere, P., 957 Duckett, S., 108 Duda, E., 182, 738 Dudai, Y., 632 Dudek, F. E., 88 Dudley, D. J., 735 Duff, G. W., 366 Duffner, L. A., 553, 554, 840, 841 Dugas, B., 801 Dugue, B., 934 Duijts, S. F., 233 Duijts, S. F. A., 870 Duivenvoorden, H., 689, 691 Duivenvoorden, H. J., 768, 900, 901, 903, 904, 914, 937, 1060, 1065 Duke, R. C., 741 Dukic-Stefanovic, S., 386 Duller, P., 977 Dulloog, L., 479, 480 Dumas, F., 253 Dumas, M., 585, 586 Dumitrescu, A., 1014 Dumke, C. L., 663, 665, 666, 668 DuMouchel, W., 710 Dunajska, K., 1000, 1001 Dunbar-Jacob, J., 623 Duncan, D. A., 553 Duncan, L., 208, 211, 1023 Duncan, L. G., 208, 211 Duncan, M., 678 Duncliffe, K. N., 54 Dunegan, M. A., 1044, 1082 Dunger, D. B., 174 Dunkel-Schetter, C., 711, 787 Dunlap, A., 66 Dunlop, O., 741 Dunn, A. J., 233, 290, 295, 296, 297, 305, 338, 339, 487, 518, 521–22, 523, 524, 691 Dunn, A. L., 666 Dunn, G. P., 874, 878, 879 Dunn K., 977 Dunn, K. L., 555 Dunn, L. A., 237 Dunn, N., 386, 440, 444 Dunn, R. L., 714, 717 Dunn, S. M., 771, 872, 873 Dunne, A., 274
Dunphy, J. E., 826 Duntley, S., 511, 932 DuNuoy, P. L., 831 Dunzendorfer, S., 108 Duong, D., 967 Dupont, J., 175 Duquette, P., 436 Dura, J., 632 Dura, J. R., 676, 786, 790 Duraisamy, Y., 845 Duran, R., 625, 682, 683, 687, 690, 693, 784, 884 Duran, R. E., 1062, 1088 Durand, D. B., 53, 55 Durand-Gasselin, I., 213 Durham, S. R., 55, 807 Durst, M., 237 Durum, S. K., 53 Dusi, S., 841 Dusseldorp, E., 694 Dussossoy, D., 557 Dutra, W. O., 555 Duval, S., 93 Dux, M., 110 Dvorak, A. M., 882 Dvoskin, R. L., 485 Dwyer, J., 586 Dy, M., 98 Dybkjaer, E., 1057, 1058 Dyck, D. G., 284 Dyer, H. R., 198, 726, 733, 745 Dyken, M. E., 603 Dykstra, L. A., 1017, 1025 Dyment, D. A., 1108 Dynan, K. B., 366 Dyne, K., 844 Dyner, T. S., 1059 Dyson, M., 829, 842 Dzionek, A., 1099 Dzubow, L. M., 831 Eagar, T. N., 1108 Earle, J., 277 Earle, M. L., 399 Earls, F. J., 498 Easterbrook, P. J., 1060 Eastwood, B. J., 363, 364 Eastwood, C., 116 Eastwood, S. L., 564 Eaton, J. W., 105, 605, 997 Eberhardt, B., 254 Eberle, R., 490 Eberly, S., 694 Ebers, G., 802 Ebers, G. C., 1108, 1110 Ebert, T., 594 Ebisui, O., 432 Ebner, C., 462 Ebner, K., 479, 481
Author Index Ebrecht, M., 827, 842 Eby, W. C., 625, 772 Ece, A., 1002 Eck, S. L., 842 Eckel, J., 1000 Eckenstein, F., 419 Eckhardt, L. A., 74 Eckhardt, M. J., 549, 550, 551, 552, 553 Eckhoff, D., 565, 569, 570 Eckholdt, H. M., 549 Eckstein, D. J., 436 Economou, E., 937 Economou, J. S., 997 Economou, M., 570 Ecosse, E., 1059 Eda, S., 924, 926 Eddy, D. E., 668 Edelman, S., 873 Edelstein, D., 998, 999 Edgar, V. A., 77 Edin, R., 133 Edinger, M., 149 Edington, D. W., 717 Edjeback, M., 274 Edmonds, C. V., 873 Edoff, K., 359 Edwards, A., 556 Edwards, A. E., 987 Edwards, A. G., 814 Edwards, C. K., III, 603 Edwards, C. L., 716 Edwards, D. J., 1019 Edwards, D. L., 930 Edwards, E. A., 734 Edwards, J. C., 826 Edwards, J. L., 741 Edwards, J. R., 872 Edwards, S., 437, 502, 503, 963, 964, 965, 966, 968 Edwards, V., 713 Efantis-Potter, J., 682, 683, 883, 1088 Efstratiadis, A., 172, 184 Egan, C. L., 104, 107, 108, 113, 114 Egan, D., 927, 928, 935 Egekvist, H., 625, 763, 766 Egert, J., 554 Eggens, U., 76 Eggers, V., 554 Eggert, M., 198 Eglen, R. M., 161 Egorov, A. D., 853 Eguchi, N., 320, 322 Ehara, S., 1001 Ehl, C., 364 Ehlers, A., 979 Ehlers, C., 608, 609 Ehlers, C. L., 512, 518, 607, 608 Ehlers, S., 1038 Ehlert, U., 195
Ehling, A., 1003 Ehrenreich, H., 554 Ehrhard, P. B., 106 Ehrhart-Bornstein, M., 45, 55, 224 Ehrlich, L., 136 Ehrlich, P., 878 Ehya, H., 238 Eibl, M., 690 Eichelberger, M., 1085 Eichenbaum, H., 340, 344, 346 Eichenfield, L. F., 979 Eid, G. M., 1002 Eidelberg, D., 710 Eiden, L. E., 342 Eigler, F., 1044 Eigler, F. W., 766 Eijkelkamp, N., 68 Eikelboom, R., 633, 635 Eikelenboom, P., 276, 361, 362, 382, 386, 439, 440 Eiken, H. G., 1058 Eikhom, T. S., 1043 Eil, C., 482 Einen, M., 588 Einstein, F. H., 994 Eiriksdottir, G, 924, 926 Eisdorfer, C., 276, 1054, 1055, 1057, 1060 Eisen, J., 587 Eisenberger, N. I., 1063 Eisenhofer, G., 241 Eisenstein, A. B., 994 Eisenstein, T. K., 556, 557 Eisenthal, S., 885 Eissner, G., 1015, 1023 Ek, E., 715 Ek, M., 88, 290, 320, 322, 323, 329, 332 Ekblad, E., 103 Ekblom, A., 200 Ekbohm, G., 1019 Ekdahl, C. T., 359, 386 Ekelun, L., 461 Ekenstedt, K., 174 Ekhator, N. N., 533, 536, 543 Ekholm, S., 417, 420 Ekman, M. R., 927 Ekman, P., 620, 623, 625, 762 Ekman, R., 73, 103 Ekstrand, M. L., 689, 1061 El Faiuomy, N., 362 El Khoury, J., 1058 el Lati, S., 113 El Mahmoudy, A. M., 133 Elashoff, R., 624, 691, 692, 773, 774, 872, 873, 877, 881 Elbadawi, A., 117 El-Benna, J., 71 Elberson, K., 931 Elde, R., 161 El-Deiry, W. S., 842
1153 Elder, G. H., 531 Elder, J. H., 586 Elder, R. T., 1056 Eldrup, E., 625, 763 Eledrisi, M. S., 1055 Elenkov, I., 635, 1056 Elenkov, I. J., 55, 56, 65, 67, 72, 73, 110, 194, 212, 254, 605, 732, 735, 740, 801, 811, 812, 816, 843, 855, 881, 983, 986, 997, 1045, 1056 Elford, J., 1053 Elhage, R., 829, 830 Elhassan, A., 589 El-Hilali, R., 554 Elias, C. G., III, 142 Elias, P. M., 988 Elin, R. J., 146 Eliott, K., 977 Elkayam, O., 436 Elkis, H., 565 Ell, K., 786, 789, 790 Ellenberg, J. H., 1120 Eller, L. S., 1061 Ellgring, J. H., 710 Elliott, A. J., 1061 Elliott, D., 100, 103 Elliott, D. E., 100, 101, 103, 107, 108 Elliott, P. J., 417 Elliott, T. R., 198, 609 Ellis, J., 810 Ellis, R., 999 Ellis, S. D., 385 Ellis, S. G., 946 Ellison, C., 782 Ellison, J. A., 420 Ellison, M. C., 603 Ellman, G., 647, 648, 653 Ellner, J., 1088 Ellwanger, U., 258 Elmadjian, F., 727, 729 El-Mallakh, R. S., 570 Elmore, S. W., 48 Elmquist, J. K., 293, 294, 321, 322, 323, 324, 325, 326, 327, 328, 329, 330, 332, 438, 995 Elmsley, H. C., 422, 423, 434 El-Nahas, A. M., 1016 Elo, I. T., 458 El-Okl, M., 272, 276, 361, 385, 386, 440, 444 Elorza, F. L., 134 El-Sadr, W., 1055 Elsasser, T. H., 605 Elsen, H., 934 Elston, M. A., 498 Elsworth, G. R., 875 Elton, R. A., 592 Elwan, F., 362 Elwan, O., 362
1154 Elwood, M., 869, 870 Elwood, P. C., 957 Ely, E. W., 385 Emamian, E. S., 277 Emanuelli, B., 999 Embretson, J., 1054 Emeny, R. T., 1041 Emeny, Rebecca T., 1035 Emerman, J. T., 884 Emerman, M., 1055, 1056 Emery, C., 687, 691 Emery, C. F., 877, 881 Emery, G., 686 Emilie, D., 213 Emini, E. A., 1054 Emmanual, J., 733 Emmel, E. A., 53 Emmelkamp, P., 689 Emmelkamp, P. M., 1061 Emmerling, M., 439, 440 Emmons, R. A., 762, 773 Emonyi, W., 1059 Emorine, L. J., 235 Emoto, M., 98 Empana, J. P., 511, 932 Empl, M., 570 Emr, S. D., 275 Emsley, H. C., 434 Enault, G., 110, 200 Encinas, J., 149 Encio, I. J., 48 Endert, E., 72, 997 Endler, G., 421 Endo, H., 73 Endo, Y., 647, 648 Endres, M., 419 Endres, S., 1099 Eneroth, P., 112 Engblom, D., 320, 322, 332 Engebretson, T. O., 929 Engel, G., 725, 726, 745 Engel, H., 876 Engel, J., 997 Engel, J. M., 222 Engel, R., 514 Engeland, C. G., 828, 830, 831, 832 Engeland, Christopher, 707, 825 Engelhardt, E., 841 Engeli, S., 1000, 1001 Engelman, E. G., 252 Engelmann, M., 479, 481 Engelmann, M. D. M., 464 Engels, F., 72 Engels, W. D., 976 Engering, A., 1053 Engeset, A., 592 Engfors, C., 345 England, G. T., 827 England, R., 609
Author Index Engleman, C., 380 Engleman, E. G., 66, 1043, 1044 Engler, A., 637, 1099, 1103 Engler, H., 255, 453, 480, 481, 637, 1025, 1044, 1046, 1078, 1099, 1101, 1103, 1112 Engler, Harald, 631 Engler, R., 995 English, J. A., 342 Engstrom, A., 222 Engstrom, C., 693 Engstrom, G., 926 Engstrom, L., 322 Enioutina, E., 855 Enjoji, M., 998 Enk, A. H., 1024 Ennis, M., 115, 330, 687 Ennix, M. E. A., 873 Enoka, R., 1018 Enokida, M., 197 Enright, T., 788 Enright, T. M., 871 Enserink, J. K., 240 Entingh, A. J., 174 Entman, M. L., 927, 935 Entschladen, F., 261 Epel, E., 734 Epel, E. S., 500, 790, 884 Epperly, T. D., 859 Epping-Jordan, J., 872 Epplen, C., 162, 166 Epstein, A. L., 167 Epstein, G. N., 814 Epstein, L., 1057 Epstein, L. H., 743 Epstein, S. E, 927 Epstein, S. E., 927, 959 Erb, K., 142 Erb, K. J., 456 Erb, P., 106, 142 Erbagci, A. B., 570, 571 Erdil, A., 1002 Erdman, R., 937 Erdman, R. A. M., 771 Erhardt, J. A., 417 Ericcson, A., 195 Erickson, C., 468, 469 Ericson, A. C., 1024 Ericsson, A., 87, 88, 290, 292, 293, 320, 321, 328, 329, 843 Ericsson-Dahlstrand, A., 320, 322, 323, 329, 332 Eriksson, A., 554 Eriksson, E., 934 Eriksson, H., 957 Eriksson, J. G., 712 Eriksson, K., 419 Eriksson, M., 961, 962 Eriksson, M. A., 49
Eriksson, P., 882 Eriksson, P. S., 408 Erl, W., 1100 Erlinger, T. P., 962 Ermann, J., 149 Erne, P., 727, 934 Ernerudh, J., 361 Ernst, J., 884 Ernst, J. M., 1019 Ernst, M. K., 52 Ernst, R. K., 431 Ernst, S., 1026, 1040 Ersbool, A. K., 464 Erschler, W. B., 712 Ershler, W. B., 361, 380, 463, 467, 483, 491, 622, 913 Ersoz, A., 383 Ertel, W., 254, 257 Ertl, R. F., 109 Erusalimsky, J., 503, 964, 965, 966 Ervin, E., 632 Erwin, J. M., 476, 477 Esaki, K., 623 Esato, K., 258 Eschenbach, D. A., 711 Eschwege, P., 253 Escobar, J., 384 Esiri, M. M., 363, 364, 421, 436 Eskandari, F., 980, 1112, 1115 Eskelson, C., 549, 551 Eskildsen, P., 996 Eskola, J., 744 Esparza, E. M., 736 Espejo, E. F., 303 Espel, E., 736 Espinola-Klein, C., 959 Espinosa, E., 644, 645, 646 Espinosa, R., 957 Espinoza, J., 235 Esquifino, A. I., 1057 Esselink, M. T., 66, 997 Essen, M. V., 1057, 1058 Essex, M. J., 712, 713 Essner, R., 997 Esterling, B., 676, 685, 686, 687, 689 Esterling, B. A., 786, 790, 791, 858, 863 Esteve, A., 421 Estey, E., 519 Estruch, R., 550, 554 Etcheverry, S. B., 998 Etherington, M. D., 501, 505 Eto, K., 1001 Etoh, T., 998 Eton, D. V., 693 Eugen-Olsen, J., 1058 Eugster, H. P., 419, 1115 Eugui, E. M., 300, 542, 738, 741 Eun, H. C., 830, 831 Eusebi, F., 357
Author Index Evans, A., 946 Evans, A. E., 957 Evans, C. C., 810 Evans, C. H., 135, 400 Evans, D., 689 Evans, D. L., 307, 509, 510, 512, 514, 518, 790, 1055, 1056, 1059, 1060, 1061, 1062, 1063, 1064, 1065 Evans, G. W., 498 Evans, J. C., 945 Evans, J. T., 149 Evans, M. C., 842 Evans, P., 624, 764, 765, 766, 800, 814 Evans, P. D., 624, 762, 763, 765, 766, 912 Evans, R., 49, 976 Evans, R. M., 49, 53, 363, 364, 741 Evans, R. W, 923, 926 Evans, S. L., 241 Evans, T. G., 901, 908 Everaert, E. G., 100, 104, 107, 219 Everett, R., 236 Everitt, B. J., 360 Evermann, J. F., 733 Evers, A. W., 977 Everson, C. A., 596, 597 Everson, M. P., 543 Everson, S. A., 234 Everson-Rose, S. A., 946, 949 Ewart, C. K., 789 Ewing, A., 73 Ewton, D. Z., 182 Exploring the biological contributions to human health: Does sex matter?, 199 Exton, M. S., 654, 1046 Eyer, J., 1036 Eynan, M., 1015 Eysselein, V. E., 106 Ezekowitz, R. A. B., 337 Faas, M. M., 458 Fabbri, L., 72, 73, 1045 Fabricant, C. G., 958 Fabricant, J., 958 Fabriek, B. O., 439 Fabris, M., 106 Fabris, N., 637, 638, 640, 652 Fabrizio, K. R., 295 Fabry, Z., 107, 108, 383, 417 Facchetti, F., 1102 Facciola, G., 300 Fadeel, B., 839 Faden, A. I., 416, 420 Fadok, V. A., 440 Faessler, R., 738 Fagerberg, B., 712 Fagerlin, A., 769 Faggin, E., 959
Faggioni, R., 297 Fagoaga, O. R., 663, 664, 665, 666, 667, 668, 669 Fahdi, I. E., 921 Fahey, J., 532, 535, 537, 676, 678, 683, 692, 784 Fahey, J. L., 74, 237, 261, 497, 519, 537, 608, 623, 624, 625, 713, 724, 729, 763, 765, 766, 772, 773, 774, 784, 789, 872, 873, 877, 881, 885, 966, 1053, 1057, 1058, 1060, 1063, 1064, 1065 Fahlbusch, B., 977 Fahn, S., 710 Fahrig, T., 147 Fain, J. N., 995 Fainman, C., 931, 962, 963, 965 Faint, J. M., 1056 Fair, W. R., 877 Fairbanks, L. A., 483, 485 Fairey, A. S., 661 Faist, E., 254, 257 Faith, R. E., 724, 733 Faivre, B., 285 Fakruddin, J. M., 1056 Faldella, G., 361 Falek, A., 557 Falger, P., 682 Falger, P. R., 931, 935 Falk, A., 67, 68, 728, 729 Falk, E., 921, 922, 923 Falk, S., 1002 Falk, W., 68, 224, 605 Falkai, P., 565 Falke, E., 565 Faller, H., 234, 871 Falloon, J., 1055 Falsetti, S. A., 531 Faltraco, F., 365 Falus, A., 181 Falzoni, S., 291 Famaey, J. P., 556 Fan, J., 605, 738, 845 Fan, L., 416 Fan, R., 259, 737, 745 Fandrey, J., 645 Faneslow, M., 631 Fang, G., 101 Fang, J., 331, 583, 584, 586, 587, 588, 589, 601 Fann, A. V., 1044 Fanselow, M. S., 341 Fantozzi, R., 114 Fantus, I. G., 998, 999 Fantuzzi, G., 297, 956, 1002 Farag, N. H., 729, 934 Farci, A. M., 1080 Fardon, J., 910, 911 Farese, R. V., 999
1155 Farese, R. V. Jr., 999 Farhan, A., 193 Farhangmehr, M., 669 Farhoody, N., 743 Faria, R., Jr., 1055 Farina, A. R., 53, 55 Farkkila, M., 859 Farlow, M. R., 363, 364 Farmer, R. G., 116 Farmerie, W. G., 297 Farook, T., 846 Farooqi, I. S., 1000 Farquhar, C. F., 440 Farr, A. G., 69, 71, 1039, 1040 Farr, R. S., 460 Farr, S. A., 287, 343, 347 Farrar, D. J., 586 Farrar, W., 687, 691 Farrar, W. B., 734, 875, 877, 881 Farrar, W. L., 997 Farre, M., 557 Farries, T. C., 46 Farrington, P., 958 Farthing, M., 1002 Fasano, F., 365, 421 Fasano, f., 365 Fassbender, K., 48, 420, 589, 594 Fassler, R., 843, 845 Fässler, R., 826 Fatemi, S. H., 277, 459 Fathman, C. G., 66, 149, 438 Fatjo, F., 554 Fattori, E., 995 Fattori, R., 937 Faucher, I., 479 Fauchere, J. L., 103 Fauci, A., 678 Fauci, A. S., 74, 224, 603, 724, 727, 728, 729, 735, 737, 745, 826, 1054, 1055, 1059 Faulds, G., 365, 512 Faulhaber, M., 1055 Faunce, D. E., 553, 554 Favagehi, M., 724, 734, 745, 842, 846 Favoreel, H. W., 490 Fawcett, J. W., 421 Fawzy, F., 690, 691, 692 Fawzy, F. I., 624, 773, 774, 872, 873, 877, 881 Fawzy, N., 690, 691, 692 Fawzy, N. W., 624, 773, 774, 872, 873, 877, 881 Fawzy, R. N., 873, 881 Fawzy, S., 691, 692 Fazio, S., 994 Fazio, V. M., 363, 364, 421 Fearn, S., 382, 433, 434, 444 Fearon, D. T., 46, 47 Feaster, D., 677, 689, 1060
1156 Feaster, D. J., 773, 784, 792, 1055, 1056, 1060, 1061, 1065 Febbraio, M. A., 1014, 1016, 1018, 1019, 1022 Fecho, K., 1017, 1025 Feder, M., 379 Federlin, K., 197 Fedke, I., 1002 Fedynyshyn, J. P., 277 Fee, D. B., 417 Feeback, D. L., 853, 854, 855, 856, 857, 858, 859, 862, 863, 1079 Fehder, W. P., 112 Feher, E., 115 Fehlman, M., 73 Fehm, H. L., 224, 585, 590, 591, 592, 593, 594, 597, 598, 599, 600, 601, 603, 604, 606, 607, 913 Feibelkorn, J. C., 714 Feierl, G., 469 Feige, B., 606 Feigenbaum, S. L., 198, 199 Feijen, M., 977 Fein, H. G., 357 Feinberg, B. B., 679 Feinglos, M. N., 683, 716 Feingold, K. R., 284, 297, 959, 988, 995 Feinleib, M., 921 Feinstein, D. L., 1014 Feinstein, J. S., 523 Feiveson, A. H., 853, 854, 858, 859, 862, 863, 1079 Fejes-Toth, A. N., 736 Felder, R. B., 306 Feldman, C., 222 Feldman, E. L., 174, 184, 186 Feldman, J., 814 Feldman, P. J., 503, 505, 962, 963, 965, 966 Feldman, R. D., 73 Feldman, S. Y., 64 Feldmann, B., 882 Feldmann, H., 567 Feldmann, M., 69, 143, 193, 195, 542, 736 Feldmeier, H., 603 Feldon, J., 344, 346 Feldpausch, M., 1000, 1001 Felitti, V. J., 713 Felix, D., 64, 97 Felix, E., 883 Fellander-Tsai, L., 209 Felli, M. P., 53, 55 Felten, D., 499, 534, 637, 677, 678, 888, 934, 1040 Felten, D. L., 64, 66, 69, 70, 77, 97, 98, 103, 106, 115, 132, 133, 139, 194, 200, 222, 226, 476, 605, 761, 763, 764, 765, 772, 1036, 1057, 1058
Author Index Felten, S., 115, 132, 133, 678, 1040 Felten, S. Y., 66, 69, 70, 77, 97, 103, 106, 110.109, 115, 116, 132, 139, 194, 200, 222, 497, 534, 772, 789, 1036, 1057, 1058 Felton, D. L., 724 Felton, L. M., 270, 276, 429, 430, 443 Felzien, L. K., 430 Fencl, V., 584 Feneberg, W., 1115 Feng, D., 882 Feng, G., 565 Feng, G. S., 522 Feng, G. Y., 571 Feng, N., 734, 1080, 1082, 1084, 1086, 1087, 1100, 1102 Feng, N. G., 238, 1080, 1098, 1100, 1102 Feng, Q. F., 885 Feng, X., 223, 845 Fenske, N. A., 831 Fent, T., 422 Fentiman, I., 692 Fentiman, I. S., 870 Fenton, A. A., 342 Fenu, G., 568 Fenzel, T., 570, 591 Ferdinand, K., 553 Ferguson, A., 321 Ferguson, A. V., 274, 300 Ferguson, B., 436 Ferguson, D. M., 456, 470 Ferguson, J. P., 969 Ferguson, M. A, 934 Ferguson, M. W., 829, 830, 831 Ferguson, S. A., 594 Ferguson, S. S., 69 Fergusson, D. M., 817 Ferini-Strambi, L., 586 Ferjoux, G., 100 Ferketich, A. K., 969 Fernandez, J., 66 Fernandez, J. B., 1055, 1061 Fernandez, L., 104 Fernandez, M., 1056 Fernandez, O., 830 Fernandez, S., 115 Fernandez, V., 957 Fernandez-Luna, J. L., 421 Fernandez-Martin, A., 143, 148, 149 Fernandez-Monreal, M., 276 Fernandez-Prada, C. M., 1015 Fernandez-Real, J. M., 996 Fernandez-Redondo, V., 737 Fernandez-Rial, J. C., 255 Fernandez-Sesma, A., 1102 Fernandez-Sola, J., 550, 554 Fernstrom, J. D., 307 Ferrandez, M. D., 855
Ferrando, A. A., 853, 854, 856, 857, 858, 859, 863 Ferrara, A., 859 Ferrara, F., 361 Ferrara, N., 223, 224, 240, 842 Ferrari, C., 344, 346, 347 Ferrari, C. C., 422, 434 Ferrari, D., 291 Ferrari, E., 1055 Ferrario, M., 946 Ferrario, P., 349, 350, 351 Ferraris, L., 104 Ferreira, R. F., 711 Ferreira, S. H., 160, 165 Ferrell, R. E., 950 Ferrero, M., 364 Ferri, C., 361, 363, 364, 365, 366, 421 Ferri, C. C., 274, 300 Ferri, R., 363, 364, 365, 366 Ferrier, K. E., 662 Ferrier, L., 464, 469 Ferrieres, J., 932, 957 Ferrucci, L., 361, 870, 873, 962 Ferry, B., 639, 646 Ferson, M., 556 Ferstl, R., 72, 965 Fertel, R., 676, 858, 863, 1088 Fertomani, G., 772 Feskens, E. J., 957 Fesq, H., 1100 Feuerstein, G. Z., 417, 419, 420 Feulner, G. J., 1014 Feussner, J. R., 714 Fewkes, J., 837 Fewtrell, M., 1000 Fey, M. F., 55 Fiala, M., 858 Fiatarone, M. A., 669, 1101 Fichtlscherer, S., 957, 958 Fidani, L., 364 Fidelus, R. K., 1037, 1045 Fidler, I. J., 237, 238, 239, 257, 879, 880 Fiebich, B., 606 Fiebich, B. L., 108, 439, 440 Fiedling, R. A., 669 Field, C. J., 661 Field, S., 195 Field, T., 684, 689, 828, 1055, 1061 Fieldhouse, S., 1055 Fielding, L. P., 258 Fields, H. L., 710 Fields, J. Z., 551 Fiers, W., 995 Fiet, J., 1055 Fiette, L., 1109, 1110 Fifield, J., 198, 531 Figdor, C., 693 Figdor, C. G., 1053 Figini, M., 101
Author Index Figler, J. L., 1055 Filaci, G., 828 Filice, G. A., 734 Filipov, N. M., 68, 238, 1036, 1039, 1040 Filippi, M., 148 Filippini, G., 1110 Fillion, G., 292, 302 Fillion, L., 1057 Filloux, C., 999 Finberg, R. W., 1015, 1016, 1023, 1024, 1025 Finch, C. E., 186, 379, 380, 382, 384, 439, 440 Finch, J. F., 788 Finck, B. N., 297, 384 Finckh, U., 553 Findling, J. W., 1055 Fineman, S. M., 813 Fingerle, J., 925 Finiasz, M., 66 Fink, D. J., 1079 Fink, K. B., 419 Fink, M., 646 Fink, T., 132 Finkelstein, E. A., 714 Finn, P., 812 Finn, R., 802 Finotto, S., 144 Finsen, B., 416, 417 Fintelmann, S., 715 Fiocchi, C., 104, 116 Fioramonti, J., 273, 464, 469 Fioravanti, M., 1055 Fiore, M., 284, 352, 354, 360 Fiore, N., 995 Fiorilli, M., 688 Fireman, P., 497 Firestein, G. S., 69 First, M. R., 252 Fischbach, S., 983 Fischer, A., 103, 110, 113, 810 Fischer, B., 988 Fischer, C. P., 996 Fischer, H. G., 107 Fischer, I., 149 Fischer, J. A., 104, 1099 Fischer, J. E., 512, 963, 965 Fischer, M., 554, 585 Fischer-Colbrie, R., 107 Fischler, B., 586 Fischman, H. K., 236 Fiserova, A., 238 Fisher, E. B., 800 Fisher, E. B., Jr., 502, 503 Fisher, H., 793 Fisher, L., 676, 677, 784, 788, 874 Fisher, L. D., 782, 783, 784, 788, 792 Fisher, R. A., 133 Fisher, S., 106
Fisher, S. G., 553 Fishman, B., 687, 790, 792, 1060, 1061 Fishman, D., 365, 512 Fishman, J., 209 Fishman, M. C., 419 Fishman, P. H., 1043 Fisler, R., 534, 537 Fisson, S., 149 Fitch, F. W., 73, 732, 735 Fitzgerald, A. J., 859 Fitzgerald, G. A., 322 Fitzgerald, G. B., 241 Fitzgerald, K. A., 320 Fitzgerald, L. W., 815 Fitzgerald, M., 223 Fitzgerald, M. L., 999 Fitzpatrick, E., 977 Fitzpatrick, F., 302 Fitzpatrick, J. M., 400 Fitzpatrick, P., 875 Flach, H. Z., 437 Flachskamm, C., 296 Flack, J. M., 962 Flackhskamm, C., 522 Fladager, A., 1056 Flagel, S. B., 539 Flahault, A., 242 Flamig, G., 106 Flamm, U., 937 Flanagan, D. E., 712 Flancbaum, L., 1002 Flanders, K. C., 829 Flannery, D., 712 Flavell, R. A., 46, 419, 840, 1099 Flaxman, B. A., 239 Flegal, K. M., 993 Fleischer, B., 1023, 1024 Fleischhacker, W. W., 569 Fleisher, T. A., 981 Fleming, K. A., 744 Fleming, M. A., 419 Fleming, R., 538 Flerov, B., 643 Fleshner, M., 71, 87, 88, 100, 112, 194, 288–89, 342, 343, 344, 345, 347, 348, 357, 407, 408, 517, 621, 662, 677, 683, 724, 729, 732, 733, 734, 745, 854, 1013, 1014, 1016, 1017, 1018, 1019, 1022, 1023, 1024, 1025, 1026, 1027, 1058 Fleshner, M. R., 475, 481, 482, 483, 486, 489 Fletcher, B., 872 Fletcher, M., 676, 679, 685, 686, 687, 689, 1055, 1061, 1065 Fletcher, M. A., 677, 680, 683, 684, 685, 686, 687, 688, 689, 690, 695, 773, 774, 784, 791, 792, 1055, 1056, 1057, 1058, 1060, 1061, 1062, 1080, 1088
1157 Fletcher, M. N., 532, 535, 537, 538 Flex, A., 365, 421 Flinders, J. B., 788, 792 Flitter, W. D., 351, 354 Flohe, L., 383 Flohe, S., 1024 Flor, H., 405 Flore, R., 421 Flores, C., 101 Flores, G., 386 Floresco, S. B., 344 Flores-Muciño, O., 644, 646 Flores-Riveros, J. R., 1000 Floridi, A., 417, 420, 588 Florijn, Y., 685 Florin, I., 771, 979 Florini, J. R., 182 Florin-Lechner, S. M., 710 Florio, T., 275, 399, 430, 435 Florquin, S., 88, 92 Floru, S., 570 Flory, J. D., 71, 623, 773, 950 Flotte, T. R., 405 Flower, L., 680, 694, 963 Flower, R. J., 100, 432 Floyd, N., 294 Floyd, R., 600 Floyd, R. A., 600 Flugel, A., 106 Flugge, G., 241 Flynn, E., 253 Flynn, R., 1060 Flynt, L., 1002 Flyvbjerg, A., 173, 180 Fodor, M., 115 Foey, A. D., 195 Fogal, B., 275 Fogelsanger, L. N., 358 Fogliarino, S., 366 Fokan, D., 1018 Folbre, Nancy, 786 Folds, J., 689 Folds, J. D., 510, 514, 790, 1055, 1056, 1060, 1061, 1062, 1063, 1064, 1065 Foley, D. J., 579, 607 Folkerts, G., 115 Folkman, J., 237, 253, 261, 881, 882 Folkman, S., 498, 499, 619, 620, 686, 772, 781, 1061 Folks, D. G., 725, 726 Follenius, M., 601, 603 Follett, H., 599 Follin, P., 839, 841 Folmar, S., 385 Folomeev, M., 209, 210 Folsch, U. R., 144 Folsom, A. R., 957, 962 Folster-Holst, R., 977 Fonanilla, I., 685
1158 Fong, I. W., 1055, 1057 Fong, L., 252 Fong, Y., 54 Fonseca, M., 566 Fontana, A., 273, 274, 360, 422, 584, 693, 1115 Fontana, S., 1003 Fontanarosa, P., 675 Fontanilla, C. V., 553 Fontanilles, A. M., 994 Fonteneau, J. F., 692, 1102 Fontenot, M. B., 485 Fontes, R., 1055 Fook-Chong, S. M., 257 Foppiani, L., 199 Forbes, M. E., 184 Ford, D. E., 714, 962 Ford, E. S., 664, 665, 812 Ford, G. M., 567 Ford, I., 957 Ford, J., 50, 1053 Ford, J. M., 365, 366, 421 Ford, W. L., 728, 729, 730 Foreman, J. C., 109 Forghani, B., 860, 1079 Forgue, D. F., 541 Forlenza, M. J., 236, 884 Forleo, C., 716 Forloni, G., 366, 434 Forlow, S. B., 952 Forner, M. A., 745, 746 Forno, B., 1055 Forrest, S., 977 Forrester, L., 458 Forsayeth, J. R., 405 Forsen, T., 712 Forsey, R. J., 361 Forsman, A., 1057 Forster, R., 1086, 1091 Forstl, H., 365, 366, 421 Forstrom, L., 736 Forsythe, P., 115 Forsythe, S. S., 1055 Fortier, M., 640 Fortmann, S., 946 Fortmann, S. P., 500, 931 Fortner, M., 514, 598 Forunier, S., 732 Foschi, F. G., 553 Foster, A. C., 407 Foster, C., 1060 Foster, D. M., 287 Foster, D. O., 1022 Foster, M. L., 48 Foster, T. C., 384 Foteinos, G., 957, 959 Fotev, Z., 925 Foti, E., 882 Foulstone, E., 173, 174
Author Index Founds, H., 386 Fournial, G., 829, 830 Fournier, A., 104 Fournier, N., 142 Fourrier, B. M., 213 Fowell, D. J., 212, 855 Fowke, K. R., 1054, 1055 Fowkes, F. G., 957 Fowler, C., 910, 911 Fowler, C. J., 117 Fowler, P., 1043 Fowler, R. S., 713 Fox, A., 405 Fox, A. J., 106 Fox, B., 692 Fox, B. H., 682, 763, 765, 766, 772, 873 Fox, B. S., 73 Fox, C., 986 Fox, C. H., 1054 Fox, C. M., 871 Fox, C. S., 945 Fox, E. S., 303 Fox, H. S., 307 Fox, J., 116 Fox, J. D., 901, 911 Fox, P., 105 Fox, S., 728 Foy, D. W., 541 Frade, J. M., 1100 Fraga, E., 218 Frahnert, C., 364 France, C. P., 1101 Francel, P. C., 838 Frances, A., 359, 1060, 1061 Franceschi, C., 77, 361, 364, 365, 379, 380, 421, 653, 784, 792 Franceschi, M., 363, 364, 365, 366, 421 Franchimont, D., 45, 55, 980 Franchini, D., 772 Franci, J. A., 241 Francis, D., 491 Francis, D. D., 983 Francis, I. M., 846 Francis, J., 297, 306 Francisco, L., 1018 Franco, D., 551 Francoys, I., 133 Frank, C., 713, 1060 Frank, D. A., 360 Frank, E., 500, 504, 505, 725, 726, 733, 744, 746, 931 Frank, J. M., 1086 Frank, M., 148 Frank, M. G., 273, 384, 405, 406, 407, 408, 514 Frank, R., 687 Frank, R. G., 198, 609 Franke, E. K., 1056 Franke, T., 184
Franks, P., 787 Franti, C. E., 931 Frantz, D. F., 996, 1000 Franz, B. R., 565 Fraser, H., 440, 443 Fraser, J., 233, 651 Fraser, J. M., 870 Fraser, J. R., 440 Frassanito, M. A., 241 Frasure-Smith, N., 509, 511, 512, 514, 516, 518, 607, 681, 694, 792, 931, 932, 937 Frati, L., 53, 55 Fraticelli, P., 142 Fraulin, A., 511, 570 Fraumeni, J. F., Jr., 923 Frautschy, S., 439, 440 Frautschy, S. A., 416, 417 Frayo, R. S., 297 Frazier, T. W., 772 Freda, P. U., 1055 Frede, S., 654 Frederich, R. C., 297 Frederick, J., 50 Fredrickson, B. L., 626, 772 Fredrikson, M., 875, 877 Fredriksson, J. M., 240 Freed, C. R., 710 Freed, P. W., 440 Freedberg, I. M., 52 Freedberg, K. A., 554 Freedland, K. E., 509, 511, 512, 514, 516, 622, 681, 931, 932, 937, 962, 969 Freedman, J., 1055 Freedman, J. E., 954, 957 Freedman, L., 678 Freedman, L. P., 49 Freedman, N. D., 49 Freedman, R., 876, 879 Freedman, S., 542 Freedson, P. S., 666 Freeman, A., 491 Freeman, J., 802 Freeman, L. W., 814 Freeman, M. W., 999 Freemont, A. J., 224 Frei, K., 360, 1115 Freidinger, K., 999 Freire-Garabal, M., 255 Freitas, A. A., 456 French, L., 693 French, M. T., 717 French, T. M., 976, 978 French-Mullen, J. M. B., 283, 297 Frenkel, D., 420 Frenneaux, M. P., 681, 962, 964, 965 Frenois, F., 186, 187, 300 Fresno, M., 359 Freudenberg, G., 771
1159
Author Index Freund, B., 543 Freund, G. G., 175, 177, 180, 181, 182, 183, 996, 998, 1000 Freund, Gregory G., 993 Frewin, M. R., 736 Frey, G., 45, 55 Frey, H., 361, 744 Friberg, P., 958, 960 Fricchione, G. L., 921, 930 Frick, B., 1036 Frick, O. L., 109 Fricker, P. A., 663 Frid, D. J., 933, 937 Fridkin, M., 134, 135, 137, 139 Fridlanskaya, I., 1019 Fried, G., 874, 880 Fried, L. P., 932 Friedlander, R. M., 419 Friedman, A., 685, 689, 1060, 1061 Friedman, E., 1088 Friedman, E. M., 515, 607, 1036 Friedman, H., 342, 344, 347, 1109 Friedman, H. S., 713, 769 Friedman, J. M., 994 Friedman, L., 1061 Friedman, M., 695, 929, 937 Friedman, M. J., 531 Friedman, S. B., 1079 Friedman, S. G., 86, 88, 92, 456, 469, 997 Friedman, T. C., 1055 Friedrich, K., 998 Frielle, T., 235 Friend, K. E., 173, 180 Frieri, M., 815, 817 Fries, D., 551 Fries, J. F., 76, 923 Friesen, W. V., 620, 625 Frilli, S., 117 Friman, G., 662, 663, 668 Frimerman, A., 966 Frints, S., 362 Frisullo, G., 1003 Fritsch, W., 977 Fritsche, A., 997, 1000 Fritsche, M., 106 Fritsch-Montero, R., 592, 594 Fritz, G. K., 976 Froelich, C. J., 70 Froguel, P., 1001 Froland, S. S., 1058 Frolich, M., 362 Frommberger, U. H., 511, 570 Frossard, J. L., 110 Frost, R. A., 172, 173, 605 Frost, R. O., 762 Frost, S. D., 1054 Frostegard, J., 1016 Frostick, S. P., 149
Fruchter, R., 682 Frucht-Pery, J., 106 Fruhauf, S., 566 Frumin, M., 564 Fry, W. F., 625, 772 Frye, C. A., 1002 Fryer, A. D., 810 Fryns, J., 362 Frystyk, J., 171 Fu, L., 885 Fu, X. Y., 994 Fu, Z. F., 567 Fuccillo, D. A., 863 Fuchs, B. A., 65, 66, 70, 73, 99, 100, 1045 Fuchs, D., 307, 522, 1036 Fuchs, E., 465, 712 Fuchs, E. J., 252 Fuchs, I., 1060 Fudenberg, H., 678 Fudenberg, H. H., 740, 744 Fujihara, N., 296, 523 Fujii, T., 88, 105, 255 Fujii, Y., 571 Fujikawa, T., 479, 480, 481 Fujimori, J., 763, 765, 766 Fujimori, K., 322 Fujimoto, J. M., 408 Fujimoto, M., 107 Fujimoto, T., 252 Fujimura, R., 276 Fujinami, R. S., 1115 Fujino, H., 605 Fujita, T., 997, 998 Fujitani, Y., 320, 322 Fujiwara, H., 879 Fujiwara, K., 554 Fujiyama, F., 326 Fukai, N., 253 Fukata, J., 432 Fukuda, D., 1001 Fukuda, R., 567, 569 Fukuda, S., 859 Fukuda, T., 55 Fukuda, Y., 329, 858 Fukuhara, K., 238 Fukui, H., 109 Fukui, T., 73 Fukunaga, K., 184 Fukunaga, Y., 882 Fukunishi, I., 785 Fukushima, M., 998 Fukuyama, T., 197 Fuller, J., 297 Fuller, P. J., 482 Fuller, S. J., 1043 Fullerton, J., 977 Fullgraf, H., 959 Fumagalli, F., 305 Fumagalli, L., 594, 604
Funahashi, T., 997, 1000, 1001, 1003 Funata, N., 881, 882 Funch, D. P., 234, 873 Funderud, S., 74 Fundin, B. T., 106 Furie, M. B., 1100 Furio, M., 117 Furkert, J., 131 Furlanetto, R. W., 995 Furlanetto, T. W., 1055 Furman, T. C., 994 Furness, J. B., 103, 105, 133 Furness, L., 329, 678 Furnkranz, A., 72 Furst, C., 875 Furst, C. J., 875, 877 Furst, D., 193 Furth, P. A., 241 Furudoi, S., 842 Furukawa, K., 1001 Furukawa, S., 106, 998 Furukawa, Y., 106 Furuno, T., 101, 109, 110 Furusho, K., 73 Furuta, Y., 859 Furuya, Y., 344, 352 Furuyama, N., 1000 Furuyama, S., 53 Furuyashiki, T., 329 Fusco, B., 117 Fusenig, N. E., 53, 238 Fusi, M. L., 487, 1055 Fuss, I. J., 143 Fust, G., 1015, 1024 Fuster, V., 922, 923 Futamura, M., 252, 253 Futrell, N., 417 Futterman, A. D., 625, 763, 765, 766, 772 Fyhrquist, F., 934 Gabant, P., 458 Gabardino, J., 498 Gabay, C., 997 Gabay, E., 339 Gabbiani, G., 844 Gabellec, M. M., 292 Gabriel, H., 663 Gabriel, S. E., 199 Gabrieli, J. D., 620 Gabrielson, K., 998 Gabrilovich, D., 240 Gabrilovich, D. I., 240, 241, 882 Gabry, K. E., 197, 200 Gaczynska, M., 47 Gad, M. Z., 303 Gaddam, V., 921 Gadducci, A., 882 Gadient, R. A., 338, 359, 360
1160 Gadin, K. G., 713 Gaetani, E., 365, 421 Gafarov, V., 947 Gaffney, J., 845 Gage, A. R., 482 Gage, F. H., 340, 359, 360 Gagliardini, V., 419 Gagliardo, R., 842 Gagnerault, M. C., 603 Gahmberg, C. G., 46 Gaiddon, C., 162, 164 Gaillard, R. C., 828 Gainsford, T., 995 Gajardo, J., 1058 Gajdusek, D. C., 53 Gajendrareddy, P. K., 828, 832, 842, 845 Gajewski, T. F., 73, 732, 735 Gala, R. R., 603, 914 Galanaud, P., 213 Galand, P., 1018 Galanos, C., 48, 589, 590, 601, 605 Galasso, F., 219 Galbo, H., 67 Galbraith, A., 747 Galdieri, M., 996 Gale, M., 929 Gale, N. W., 1099 Gale, R., 712 Gale, R. P., 256, 556, 726, 734, 745 Galea, B., 219 Galea, I., 439 Galetta, S. L., 1108 Galey, D., 276 Galic, Z., 1059 Galicia, O., 586 Galiegue, S., 557 Galimberti, L., 365, 421 Galindo, M., 143, 200 Galinowski, A., 570 Gallacher, F., 564 Gallagher, H., 254 Gallagher, M., 386, 646 Gallagher, S., 1002 Gallahan, D., 237 Gallai, V., 417, 420, 588 Gallant, E. M., 93 Gallar, J., 223 Galle, P. R., 144, 1024 Galley, H. F., 256, 258 Galli, C. L., 405 Galli, L., 855 Galli, M., 1055 Galli, S. J., 98, 109, 110, 115, 116, 133 Gallily, R., 419 Gallimore, J. R., 501, 923, 926 Gallin, J. I., 826 Gallinella, E., 588 Galliven, E., 196 Gallmeier, E., 106
Author Index Gallo, L. C., 498 Gallo, R. C., 736, 1053, 1056 Gallucci, S., 272, 1018 Gallucci, W. T., 981 Galluzzo, A., 570 Galmarini, M., 1059 Galmiche, J. P., 1002 Galobardes, B., 498 Galon, J., 45, 55, 980 Galvez, A., 235, 238 Gama, C. S., 566 Gama, R., 201 Gambardella, A., 361 Gambari, P. F., 210, 213, 214 Gambetti, P., 585 Gamble, J. R., 839 Gamboni-Robertson, F., 1002 Gamelli, R. L., 553, 554 Gamp, P. D., 103 Gan, X., 71 Gancz, H., 1015 Gandy, S. E., 364, 365 Ganea, D., 40, 99, 100, 103, 104, 131, 133, 134, 135, 136, 137, 139, 140, 141, 142, 143, 146, 147, 148, 149 Ganem, D., 236 Ganesh, S., 90 Gange, S. J., 1107 Ganguli, M., 364, 365 Ganguli, R., 571, 572, 775 Ganguly, E. K., 878 Ganter, U., 361, 592, 594 Gantt, K. R., 1054 Ganz, P., 934 Ganz, P. A., 519, 608, 885 Gao, B., 554, 1023 Gao, F., 363, 364 Gao, G., 101 Gao, H. M., 523 Gao, P. Q., 137 Gao, Q., 994 Gao, Y., 143 Gao, Yan, 993 Gao, Z., 999 Gapski, R., 829, 830 Garabedian, B. V., 438, 439 Garabedian, M. J., 50 Garand, L., 882 Garaud, J. J., 554 Garbarg, M., 109, 111 Garbe, C., 258 Garber, R. A., 792, 937 Garbutt, L. D., 963, 964, 965, 966 Garcia, A. K., 342 Garcia, J., 632, 646 Garcia, J. A., 1054 Garcia, J. H., 418 Garcia, J. J., 1044 Garcia, P., 361
Garcia, R., 927 Garcia-Calderat, M. S., 184 Garcia-Cardena, G., 1000 Garcia-Carranca, A., 237 Garcia-Echeverria, C., 173, 174 Garcia-Galloway, E., 184 Garcia-Gomez, M., 146 Garcia-Iglesias, T., 212, 214 Garcia-Lora, A., 879 Garcia-Porrua, C., 198 Garde, K., 871 Gardi, J., 605 Gardiner, S. M., 101 Gardner, C. O., 514 Gardner, J. D., 297 Gardner, R., 510 Gardner, R. J., 362 Gardoni, F., 405 Gareus, I., 646 Garey, L. J., 565 Garfield, S., 686 Garfinkel, L., 579, 586, 606 Gariepy, J. L., 1063 Garite, T. J., 459, 711 Garka, K. E., 338 Garland, M. R., 875 Garland, W. A., 351, 354 Garner, E. B., 668 Garner, J. L., 554 Garner, W., 677, 686, 734, 787, 792, 814, 845, 878 Garner, W. L., 838, 841 Garnham, A., 1016 Garofalo, A., 842 Garot, N., 213 Garovoy, M. R., 74 Garret, C., 117 Garrett, V., 811 Garrib, A., 1055 Garrido, E., 133 Garrido, F., 879 Garrido, T., 133 Garrigue, C., 257 Garrison, C. J., 397 Garrone, G., 514 Garrud, P., 340, 341 Garry, R. F., 567 Garside, P., 115 Garssen, B., 679, 870, 871 Garssen, J., 104 Gartner, L., 400 Garvey, J. S., 735 Garvey, M. J., 550 Garvin, B. J., 931 Gary, D. S., 419 Garza, L., 921 Gasbarrini, A, 927 Gasbarrini, G., 549, 551 Gasc, J. M., 49
Author Index Gascon, P., 139 Gasic-Milenkovic, J., 386 Gaspani, L., 160, 256 Gasparotto, O. C., 482 Gasperini, S., 839 Gasser, T., 363, 364, 365 Gastel, A. V., 533, 536, 537, 538 Gastpar, R., 1015, 1019, 1024 Gately, M. K., 56 Gatenbeck, L., 693 Gates, J., 1002 Gates, S., 541 Gattaz, W. F., 565, 570 Gatti, G., 603 Gatti, S., 287, 291, 358, 432 Gauci, M., 801, 1063 Gaufo, G. O., 134 Gaughran, F., 570 Gauldie, J., 110, 360, 420, 736, 1025 Gauquelin, G., 853 Gaur, A., 438 Gaurtam, A., 438 Gaus, S. E., 322, 327, 585 Gausset, P. W., 1036, 1043 Gauthier, S., 307 Gavazzi, A., 364 Gaveriaux-Ruff, C., 160 Gavin, C. M., 434 Gavin, L., 806 Gavish, B., 716 Gavrilyuk, V., 1014 Gawaz, M., 951, 952 Gawkrodger, D. J., 725, 726, 733, 745 Gawlowski, G., 1115 Gay, B., 1058 Gay, S., 1003 Gaya, A., 550 Gaykema, R., 633, 646 Gaykema, R. P., 99, 288–89, 289, 290, 320, 339, 381, 398 Gaynes, B. N., 1055, 1060, 1061, 1062, 1063, 1064, 1065 Gaynor, R. B., 1054 Gayo, A., 56 Gazda, L., 399 Gazel, A., 52 Gazenko, O. G., 853 Gazit, A., 184 Gazzard, B., 1057 Gazzard, B. G., 1060 Geaga, J., 1059 Gear, R. W., 65, 72 Gebhard-Mitchell, K., 1054 Gebhardt, B. M., 1080, 1081, 1088 Gebhart, G. F., 394, 395 Geelen, G., 853 Geenen, R., 811, 934 Geerling, I., 106 Geerlings, S. W., 509
Geginat, J., 1086, 1091 Geha, R. S., 502 Gehlert, S., 236 Gehring, U., 977 Gehrmann, J., 416 Gehrmann, M., 1015, 1019, 1024 Geiben, A., 725, 726, 739, 741, 978, 982, 983, 984, 985, 986, 1080 Geiger, A., 685 Geiger, K. K., 73 Geijtenbeek, T. B., 1053 Geinitz, H., 885 Geisler, J. P., 240 Gekker, G., 408 Gelato, M. C., 605 Gelb, L., 859, 861 Gelber, R. D., 1055 Geleziunas, R., 1056 Gelfand, A. N., 531 Gelfand, E. W., 855 Geller, E. B., 557 Gemma, C., 586 Gemou-Engesaeth, V., 55 Gemsa, D., 733, 997, 1100 Genain, C. P., 106 Genaro, A. M., 70, 77 Gendelman, H. E., 1054 Geng, C. D., 48 Geng, Y., 556 Gennarelli, M., 363, 364, 421, 571 Gennaro-Ruggles, M. M., 485 Gentile, D. A., 770 Gentleman, S. M., 565 Gentry, M. J., 551 Georas, S. N., 54, 55 George, A., 1055, 1056, 1060, 1063 George, A. J. T., 461 George, C., 771 George, J., 677, 686, 787, 792 George, J. K., 148 George, L., 782 George, L. K., 782 Georgel, P., 999 Georgescu, H. I., 400 Georgiades, A., 716, 969, 1016 Georgiev, O., 74 Georgiou, R. F., 423, 434 Georgopoulos, K., 53 Geppetti, P., 101, 102, 110, 115, 117 Geraci, D., 273 Geracioti, T. D., 533, 536, 543 Gerard, C., 101, 102, 117 Gerard, N., 101, 107, 108, 110 Gerard, N. P., 102, 117 Gerard, R. W., 580 Gerardino, L., 365, 421 Gerashchenko, D., 321, 331 Gerber, D., 540 Gerber, D. K., 541
1161 Gerber, J., 352, 353, 354 Gerety, S. J., 1110 Gerhard, R., 1046 Gerin, W., 715, 874, 967 Gerlach, I., 147 Gerlach, M., 361 German, D. F., 744 Germonpre, P. R., 100, 101, 102, 104, 107, 111, 115, 219 Gerosa, F., 137 Gerozissis, K., 330 Gerra, G., 772, 784, 792 Gerrard, J. M., 1045 Gerrie, L. M., 256 Gerritsen, J., 977 Gerritsen, M. E., 137 Gershenson, D., 883 Gershon, A. A., 859, 861 Gershon, E. S., 567 Gershon, M. D., 105 Gershwin, M. E., 466 Gerson, B., 273 Gerspach, J., 172 Gerstberger, R., 323, 326 Gerstein, A. D., 831 Gerstmayr, M., 462 Gerstoft, J., 70, 1057 Gervasi, M. T., 458 Gervasoni, C., 1055 Gervois, N., 692 Gerwin, N., 359 Geske, R., 181 Gettes, D., 1055, 1056, 1060, 1061 Gettes, D. R., 1059, 1061 Getting, S. J., 100 Getty, T., 296 Geuna, M., 604 Gewirtz, A., 1002 Geyer, S., 233, 870 Ghaffar, A., 663, 1082 Ghahary, A., 844 Ghali, V., 557 Ghanta, V., 638, 639, 640, 641, 642, 643, 651, 652 Ghanta, V. K., 640, 641, 651 Gharakhanian, S., 1055 Gharib, C., 853 Ghatei, M. A., 104 Ghayur, T., 291, 321, 419, 432 Ghelarducci, B., 964 Gherbi, N., 1055 Ghetti, B., 184 Gheusi, G., 185, 286, 287, 291, 298, 300, 381, 430, 431 Ghezzi, F., 462 Ghezzi, P., 301, 419, 434, 738 Ghiadoni, L., 680, 694, 964 Ghiani, A., 361 Ghiasuddin, S. M., 603
1162 Ghilchic, M. W., 208, 211 Ghiorzo, P., 211 Ghirardello, A., 210, 213, 214 Ghisletti, S., 210 Ghosal, K., 238 Ghose, S., 1015, 1024, 1025 Ghosh, S., 137, 274, 292, 295, 741 Ghosh, S. K., 1054 Giannarini, L., 212 Giannini, E., 161 Giannò, V., 637 Giardino, I., 998 Giavazzi, R., 842 Gibbons, L., 829, 830 Gibbs, C. J., Jr., 585 Gibbs, L., 100 Gibellini, D., 1058 Gibert- Rahola, J., 980 Gibertini, M., 342, 343, 344, 345, 347, 348 Giboudeau, J., 1055 Gibson, S. J., 200 Gibson-Berry, K., 139 Gides, J. J., 430 Gidron, Y., 930, 968 Giebelen, I. A., 88, 92 Giedraitas, V., 416, 417 Gieffers, J., 959 Giefing, J., 166 Gieler, U., 979, 983 Giembycz, M. A., 108 Giercksky, K. E., 133 Gierens, A., 812, 983, 984, 985, 986 Giese, S., 588 Giese-Davis, J., 233, 234, 884 Giffard, R. G., 1015 Giffin, W., 49 Giftochristos, N., 148 Giglio, T., 828 Gijbels, K., 438 Gil, K. M., 979 Gil-Ad, I., 184, 534, 536 Gilbert, S. S., 594 Gilboa, A., 361 Gilboa, E., 252 Gilchrest, B. A., 831 Gildea, E. F., 729 Gildehaus, D., 358 Gilden, D. H., 859, 860, 1079, 1107, 1108 Gill, H., 651 Gill, J., 695 Gill, J. J., 937 Gillan, D. J., 735 Gillazpy, S. R., 807 Gillen, T., 830, 831 Giller, E. L., 539, 540, 542 Gillespie, C. F., 801, 812
Author Index Gillett, N., 184 Gilliet, M., 99, 1102 Gilliland, M. A., 596, 597 Gillin, C., 538 Gillin, C. J., 724 Gillin, J. C., 510, 512, 514, 517, 518, 551, 553, 594, 595, 598, 603, 607, 608, 885 Gillitzer, R., 840, 841 Gilliver, S. C., 828, 829, 830 Gilman, R., 543 Gilman-Sachs, A., 534, 535, 538 Gilmore, H. J., 569 Gilmore, J. H., 459 Gilmore, S. L., 729 Gilson, I. H., 1055 Gilutz, H., 930, 968 Gimbrone, M. A., Jr., 926 Gimotty, P. A., 881 Ginaldi, L., 380, 595, 607 Ginestet, D., 570 Ginn, E. M., 663 Ginnetti, F., 956 Ginouves, P., 1037 Ginsberg, B. I., 734, 745 Ginsburg, D., 52 Ginzberg, D., 363 Ginzburg, H. M., 1053 Ginzler, E., 208 Gioannini, P., 1055 Giorelli, M., 76 Giorgi, L. V., 937 Giorgi, R. G., 763, 765, 766, 772 Giotti, A., 114 Giovanietti, S., 365, 421 Giovannoni, G., 437 Giovedi, S., 356 Giraldi, T., 234, 871, 872, 873 Giralt, M., 419 Girard, M. T., 736 Girardi, C., 235, 239 Girdler, S. S., 927 Girgis, K. R., 240, 882 Girman, C. J., 993, 1001 Girnita, A., 184 Girnita, L., 184 Giron, J. A., 551, 553 Girouard, L., 551 Giroud, D., 923 Giroud, J. P., 223 Girvin, A. M., 1108 Gisslinger, H., 520 Giucastro, G., 772 Giudizi, M. G., 212 Giugliano, D., 361 Giulian, D., 148, 385 Giuliani, Piccari, G., 635 Giuliani, S., 107, 117
Giusano, B., 570 Giusti, M., 222 Givalois, L., 717, 736 Given, B. A., 234, 869, 871 Given, C. W., 234, 869, 871 Glac, W., 555 Gladwell, R. T., 101 Glafkides, M., 687 Glantz, L. A., 564 Glanzman, D., 632 Glaros, A. G., 93 Glaser, B., 532, 535, 536, 538 Glaser, R., 63, 70, 71, 77, 236, 237, 380, 490, 499, 501, 512, 514, 538, 623, 676, 677, 682, 684, 685, 686, 687, 688, 691, 694, 705, 723, 724, 726, 733, 734, 745, 747, 768, 771, 774, 782, 783, 784, 785, 786, 787, 788, 789, 790, 792, 793, 799, 811, 812, 817, 827, 842, 846, 856, 858, 861, 862, 863, 869, 870, 874, 877, 881, 882, 883, 884, 888, 899, 900, 901, 902, 904, 906, 907, 908, 910, 913, 962, 1019, 1046, 1053, 1062, 1063, 1065, 1078, 1079, 1080, 1082, 1083, 1084, 1086, 1087, 1088, 1098, 1099, 1100, 1102, 1103, 1111 Glaser R., 1079 Glaser, T., 566 Glasgow, R. E., 715 Glasper, E. R., 480, 842 Glass, C. K., 50, 137, 997 Glass, D. C., 762 Glass, D. J., 181, 182 Glass, P., 791 Glass, T., 782 Glass, T. A., 714 Glassman, A. H., 622 Glauser, M. P., 146, 738, 745 Glavin, G. B., 1036 Glaving, G. B., 241 Gleason, S. M., 430 Gleeson, M., 77, 815 Gleich, G. J., 817 Glenn, N. D., 781, 783 Glenville, S., 237 Glezerson, G., 239 Glickman, J., 144 Glimcher, L. H., 140, 144, 997, 999 Glitz, C. L., 1055 Globerson, A., 379 Glockner, F., 254 Gloss, B., 137, 237 Gloster, S. E., 1054 Glover, D. A., 623, 966 Glowa, J., 739 Glowa, J. R., 305 Glowacki, J., 555
Author Index Gluck, T., 68 Gluckman, S. J., 551, 552 Gluhoski, V. L., 790, 792 Glumoff, V., 459 Glynn, L., 711 Glynn, R. J., 926 Go, H. J., 553 Go, R. C., 365, 366 Goberna, R., 134 Gocke, P., 365 Godaert, G. L., 67, 68, 729, 934 Godal, T., 74 Godard, P., 103 Godbout, J. P., 269, 273, 303, 304, 348, 379, 380, 384, 385, 386, 387, 444, 998 Goddard, R., 272 Godfrey, D. I., 252, 261, 462 Godfrey, H. P., 1054 Godlevski, M. M., 53 Godlowski, Z. Z., 741 Godowski, P. J., 49 Godt, S. M., 73 Goebel, M., 646, 651, 965 Goebel, M. U., 76, 654, 680, 730, 963, 1039, 1040 Goebeler, M., 840, 841 Goeddel, D. V., 338 Goedegebuure, P. S., 878 Goedert, J. J., 1053 Goedert, M., 147 Goehler, L., 633, 646, 678 Goehler, L. E., 87, 88, 99, 100, 112, 284, 288–89, 289, 290, 320, 329, 338, 339, 381, 1058 Goeken, J. A., 550 Goel, K., 771 Goel, R. K., 1037 Goellner, J. J., 358 Goenjian, A. K., 539 Goephert, H., 878 Goeschen, C., 1002 Goetz, R., 1060, 1061 Goetz, R. R., 1057 Goetzel, R. Z., 714, 717 Goetzl, E. J., 100, 102, 103, 109, 110, 115, 131, 133, 134, 140, 141 Goetzsche, J. M., 665, 666, 669 Goh, D. Y., 809 Goh, W. C., 1056 Goh, Y., 331 Goichot, B., 603 Goin, J. C., 66 Goiny, M., 306 Golan, H., 352, 354, 359, 360 Golay, A., 997 Gold, D. R., 811 Gold, L. H., 349, 350, 351, 384
Gold, M. S., 161, 975–76, 982 Gold, P., 677, 679, 695 Gold, P. W., 54, 100, 196, 197, 222, 235, 594, 599, 737, 739, 741, 784, 799, 871, 884, 931, 932, 935, 980, 981, 982, 1036, 1057, 1061 Goldbach, M., 99, 290 Goldberg, D. E., 234 Goldberg, H., 998, 999 Goldberg, N., 678 Goldberg, S., 713, 937 Goldberg, T. E., 366 Goldblatt, M. W., 320 Goldbourt, U., 789, 957 Golde, D. W., 1057, 1058 Golden, R., 689 Golden, R. N., 307, 790, 1055, 1056, 1059, 1060, 1061, 1062, 1063, 1064, 1065 Goldenberg, R. L., 711 Golden-Kreutz, D., 687, 691, 734, 875 Golden-Kreutz, D. M., 877, 881 Golden-Mason, L., 875 Goldfarb, R. H., 724, 745, 1099 Goldfarb, Y., 284, 651 Goldfine, I. D., 48, 174 Goldgaber, D., 53 Goldin, L. R., 567 Golding, J., 958, 960 Goldman, A. S., 464 Goldman, J. E., 403 Goldman, J. M., 872 Goldman, M., 135, 213 Goldman, P. R., 238 Goldman, P. S., 137 Goldman, S. A., 422 Goldman-Rakic, P. S., 564 Goldmuntz, E. A., 997 Goldrich, M. S., 131 Goldsmith, L. A., 975 Goldsteen, K., 783 Goldstein, A., 685 Goldstein, A. L., 70, 222, 604, 828 Goldstein, B. J., 1001 Goldstein, D., 688 Goldstein, D. S., 195, 934 Goldstein, G., 55 Goldstein, R. A., 737 Goleva, E., 66, 521 Golier, J., 539, 541 Golier, J. A., 533, 535, 536, 537 Gollob, K. J., 555 Golomb, B. A., 969 Golombeck, B., 931 Golos, T. G., 457 Golub, A., 1059 Golub, E. T., 1060 Golub, T. R., 995
1163 Gomariz, R. P., 103, 104, 131, 133, 134, 135, 137, 139, 140, 141, 143, 144, 146, 195 Gomez, M., 197 Gomez, R., 565 Gomez, R. M., 567 Gomez, T. S., 1056 Gomez-Chavarin, M., 586 Gomez-Flores, R., 557 Gomez-Isla, T., 186 Gomez-Lechon, M. J., 995 Gomi, K., 106, 110 Gomperts, E., 1053 Gompertz, D., 814 Goncalves, A., 684, 689, 1055 Goncalves, C. A., 565, 566 Goncalves, S., 482 Goncalves, V., 386 Gonenne, A., 1059 Gong, C., 418 Gong, J. H., 997 Gong, S., 74 Gong, X. Q., 738 Gonik, B., 459, 679 Gonyea, J. L., 343, 345, 347, 348, 357 Gonzalez, A. M., 416, 417 Gonzalez, C., 712 Gonzalez- Canali, G., 1059 Gonzalez de la Vega, A., 184 Gonzalez, J., 693 Gonzalez, J. S., 693, 1062 Gonzalez, P., 366, 421 Gonzalez-Amaro, R., 46 Gonzalez-Bahillo, J., 255 Gonzalez-Garcia, A., 738 Gonzalez-García, A., 651 Gonzalez-Gay, M. A., 198 Gonzalez-Quintela, A., 550, 552, 554 Gonzalez-Rey, E., 134, 141, 142, 143, 148, 149 Gonzalez-Sarmiento, R., 552 Gonzalez-Scarano, F., 136, 148 Gonzalo, J., 651 Gonzalo, J. A., 738 Good, E., 1107 Good, E. A., 1115, 1118 Good, R., 678 Good, R. A., 1058 Goodall, G., 283, 286, 287, 302, 344, 347, 422, 514, 523, 622 Goodall, R., 1060 Goodenow, M. M., 1057 Goodey, E., 877 Goodhart, M., 639 Goodkin, D. E., 1110, 1112 Goodkin, K., 677, 679, 682, 683, 687, 688, 689, 773, 784, 792, 869, 883, 932, 933, 1055, 1056, 1060, 1061
1164 Goodkin, R. S., 199 Goodman, R. H., 50, 137 Goodrich, C. A., 584 Goodson III, W. H., 831 Goodson, J., 771 Goodson, W. H., 827 Goodson, W. H., III, 827 Goodwin, F. K., 931, 932, 935 Goodwin, J. M., 785, 786 Goodwin, J. S., 713, 769, 770, 773, 785, 786 Goodwin, P., 687 Goodwin, P. J., 791, 873 Goodwin, R. D., 815 Goodwin, S., 789 Goorha, S., 274 Goormastic, M., 923 Goos, M., 1057, 1058 Gopalakrishnan, M., 90 Gopez, J. J., 358 Gorby, H. E., 41, 193 Gorczynski, R., 587, 599, 640, 650, 651 Gorczynski, R. M., 380, 587ÿ Gordon, A. S., 741 Gordon, C. B., 1014 Gordon, H. S., 783 Gordon, J. I., 464 Gordon, J. L., 440 Gordon, M. A., 74 Gordon, N. C., 710 Gordon, S., 401, 402, 408, 433, 434, 999 Gordon, S. M., 385 Gordon, T. P., 468 Gorelik, G., 66 Gorgun, C., 999 Gorin, A. A., 854 Gorman, J. M., 307, 569, 1057, 1060, 1061 Gormley, E. A., 93 Gormley, G. J., 512 Gorzelniak, K., 1000, 1001 Gosain, A., 831 Goshen, I., 269, 300, 337, 339, 345, 346, 347, 348, 349, 352, 355, 357, 358, 408, 556, 646 Gosling, S. D., 484 Goswami, R. G., 1110 Goth, A., 133 Gotliebsen, K., 625, 763 Gotlieb-Stemansky, T., 570 Gotoh, T., 999 Gottdiener, J. S., 921, 929, 932, 933, 934, 964, 966, 967 Gotthardt, U., 884 Gottheil, E., 687, 692, 873 Gottlieb, B., 1062 Gottlieb, K., 137 Gottlieb-Stamatsky, T. E., 501
Author Index Gottrup, F., 89, 830 Gottschalk, A., 995 Gottschalk, J., 1044 Gottschall, P. E., 321, 736 Goudsmit, J., 1060 Gougat, C., 842 Gougeon, M. L., 1018, 1055 Goujon, E., 287, 288, 291, 292, 298, 301, 302, 381, 430, 432, 514, 589 Goulas, A., 364 Gould, E., 340, 359, 465, 637, 712, 745 Gould, J. B., 585 Goulding, N. J., 197 Gourgoulianis, K. I., 815 Gourlet, P., 135 Gourmelon, P., 585 Govaerts, A., 556 Govender, T., 1055 Govindarajan, A., 356 Govitrapong, P., 557 Govoni, M., 361, 364 Gowing, G., 385, 444 Goymann, W., 491 Gozes, I., 133, 134, 135, 136, 137, 139, 149 Gozukirmizi, E., 599 Graafsma, S. J., 239 Grabbe, J., 106 Grabbe, S., 104, 107, 108, 113, 114, 134 Graber, J. M., 380 Grabowski, T. J., 620 Grace, E., 197 Grady, E. F., 101, 103, 109, 116 Grady, K. E., 531 Graebe, A., 851 Graeber, M. B., 147–48 Graef, V., 197 Graefe, C., 198, 200 Graf, B., 74 Graf, K. J., 963 Graf, L. H., Jr., 74, 236, 1058, 1065 Grafe, M., 386 Grafe, P., 399 Grafman, J., 363 Graham, D. I., 363, 364, 421 Graham, J. E., 791, 793 Graham, Jennifer, 706 Graham, Jennifer, E., 781 Graham, N., 385 Graham, N. M., 1107 Graham, T. E., 1000 Graham-Bermann, S., 816 Grahn, R. E., 733, 1025 Grammas, P., 422 Gramsch, C., 165, 166 Granata, O., 209, 210 Granata, O. M., 209, 210, 224 Granger, D. A., 456, 854 Granger, D. N., 1002
Granger, H. J., 224 Granneman, J. G., 1022 Granner, D. K., 48, 50 Granstein, R., 680, 694, 727, 729, 735 Granstein, R. D., 68, 69, 103, 104, 107, 108, 113, 114, 134, 219, 1044, 1045 Grant, D. S., 224 Grant, I., 515, 693, 724, 966, 1054, 1060, 1061, 1110 Grants, I. S., 74 Grasbeck, R., 934 Grasemann H, Y. C., 809 Grassi, B., 568, 570 Grassi, F., 357 Grassi, L., 871, 872, 873 Grathwohl, D., 666 Gratziou, C., 70 Grau, A. J., 422 Graul, J., 873, 887 Grauls, G., 969 Graumann, U., 106 Gravanis, A., 108, 997 Gravanis, M. B., 1058 Gravenstein, S., 277, 361, 724, 726, 734, 900, 902, 907, 908, 1088, 1099, 1102, 1111 Graves, C. N., 461 Graves, D. T., 830, 831 Graves, J. A., 1057 Graves, W. L., 827 Gravina, C., 363, 364, 421 Gray, A., 715 Gray, D., 1085 Gray, J., 885 Gray, J. D., 213 Gray, J. G., 53 Gray, P., 274 Gray, P. A., 142 Gray, P. W., 142 Gray, T., 1099 Grayson, J., 732, 735 Grayston, J. T., 928 Grazioli, L., 652 Graziosi, C., 1054 Grazul-Bilska, A. T., 174 Greco, A., 440 Greden, J., 510, 512, 516, 549, 551 Greden, J. F., 682 Gredilla, R., 998, 1003 Green, B., 113 Green, B. L., 531 Green, D. R., 1056 Green, E. K., 364 Green, J. E., 180 Green, M. L., 762 Green, M. R., 137 Green, P., 407, 408 Green, P. G., 65, 72, 194 Green, S., 995
Author Index Greenberg, A. H., 64, 284, 288, 320, 419 Greenberg, B. D., 1115 Greenberg, D., 885 Greenberg, G. R., 103, 134 Greenberg, M. E., 53, 360 Greenberg, R. S., 873 Greenberg, S., 1058 Greenblatt, M. Y., 787 Greene, J. F., Jr., 1088 Greene, J. R., 101 Greene, P., 710 Greene, P. E., 710 Greene, R. W., 332 Greenfeld, K., 255 Greenfelder, S. A., 292 Greenfield, R. E., 733 Greenhill, S., 1110 Greensburg, D. L., 540 Greenstein, J. I., 713 Greenstreet, T. A., 996 Greenwald, G., 235 Greenway, F., 994 Greenwell-Wild, T., 829, 830 Greenwood, B. N., 1014, 1019, 1025 Greenwood, D., 532, 535, 537, 538, 539, 541, 676 Greer, S., 234, 691, 692, 869, 871, 872, 873, 875 Gregoire, A., 285 Gregori, S., 142 Gregory, M. S., 554 Greig, P. C., 212 Greisenegger, S., 421 Grenader, T., 364 Gress, R. E., 461 Gresser, I., 995 Greten, F. R., 1000 Grewe, M., 978 Grewe, S. R., 984 Grey, C., 901, 910 Gri, G., 137 Grider, J. R., 133 Griebler, C., 197 Griffais, R., 292 Griffey, K., 85 Griffin, A., 695 Griffin, A. C., 734, 735, 739, 744 Griffin, G. E., 960 Griffin, J. D., 323, 326, 328 Griffin, W. S., 361, 363, 364, 365, 366, 421, 439, 440, 444 Griffin, W. S. T., 361, 564 Griffith, C. E., 977 Griffith, M., 637 Griffiths, J., 511, 514 Griffiths, M. M., 193 Grigoriev, A., 853 Grigoriev, A. I., 853 Grigoryev, A. I., 853
Grilli, M., 420 Grilli, T., 361 Grillo, R. L., 923, 926, 927 Grimaldi, C. M., 199 Grimaldi, L., 364 Grimaldi, L. M., 361, 363, 364, 365, 366, 421 Grimaldi, M., 399 Grimison, B., 1059 Grimm, E. A., 853, 854, 855 Grimm, M. C., 136 Grimm, P. C., 64 Grimminger, F., 1100 Grimsley, S. R., 1061 Grimwood, P. D., 340 Grinevich, G., 362, 366 Grinninger, C., 133, 134, 140 Grinstein, S., 1043 Gripon, P., 237 Grippo, A. J., 306 Griswold, M. P., 261, 497, 1057, 1058, 1064, 1065 Gritzapis, A., 692 Gritzapis, A. D., 570 Grobbelaar, B., 665, 666, 669 Groen, J., 647 Groenman, N. H., 790 Groer, M., 501 Grohr, P., 532, 535, 537, 676 Grolms, M., 76 Gronbaek, M., 931 Grondal, G., 213 Groner, B., 998 Gronning, L. M., 1000 Groom, A. C., 238 Grose, E., 398 Grose, R., 839, 841, 845ÿ Grosheide, P. M., 236, 237, 768, 900, 903, 904, 914, 1065 Grosjean, M. B., 419 Gross, C., 1015, 1019, 1024 Gross, C. G., 340, 359 Gross, C. M., 1039, 1040 Gross, J., 620 Gross, J. J., 1063 Gross, P. A., 900, 903 Gross, P. M., 87 Gross, S. J., 663, 665, 666 Gross, V., 224 Grosse-Wilde, H., 1044 Grosskurth, H., 1055 Grossman, A. B., 294 Grossman, C., 461 Grossman, C. J., 550 Grossman, P., 709 Grossman, R., 533, 535, 536, 537 Grossman, S. P., 342 Gross-Wilde, H., 766 Grota, L., 632, 637, 644, 645, 646, 651
1165 Grota, L. J., 97, 725, 731, 732, 1080, 1083, 1084, 1087 Groth, D. M., 364, 365 Groux, H., 142 Grover, N. B., 532, 535, 536, 538 Grubb, B. D., 223 Grubeck-Loebenstein, B., 382 Gruber, B., 691, 877 Gruber, R., 568 Gruenewald, T. L., 621, 624, 713 Grunblatt, E., 147 Grundy, D., 116 Gruner, S., 951, 952 Grunfeld, C., 284, 297, 959, 995, 1059 Gruss, C. J., 842 Grutzkau, A., 106, 273, 838 Gruzelier, J., 1061 Grzeskowiak, M., 998 Gu, D. S., 1057 Gu, H., 1055, 1060, 1061, 1062, 1063, 1064, 1065 Gu, H. X., 567 Gu, L. H., 1002 Gu, N., 565 Gu, N. F., 571 Gu, Y., 89, 167, 419 Gualberto, A., 53, 1098 Gualco, G., 64 Gualde, N., 304 Guan, G., 210 Guan, Y., 332 Guarini, S., 86, 88, 89 Guaza, C., 302, 417, 569 Guccione, M., 1061 Gudbjornsson, B., 197 Gude, F., 554 Gudewill, S., 48, 589, 594 Gueant, J. L., 363, 364, 365, 366 Gueant-Rodriguez, R. M., 363, 364, 365, 366 Guechot, J., 1055 Guell, A., 853 Guenthner-Biller, M., 1099 Guerra, N. G., 498 Guerra, S., 813 Guerrero, J. M., 134, 195 Guess, H. A., 859 Guest, C. B., 918 Guest, Christopher B., 993 Guida, L., 89, 736 Guidicini, G., 361 Guidon, P. T., Jr., 1019 Guijarro, M. L., 497, 623 Guilbert, L., 212, 457 Guiliani, S., 117 Guillemin, G. J., 307, 522 Guillevin, L., 1055 Guimaraes, J. T., 993 Guimarães, R., 648, 649, 653
1166 Guisasola, L. M., 366, 421 Gulati, N., 1023 Gulati, O. P., 1023 Guler, N., 1002 Gulevich, G., 582 Gulevich, S. J., 1054 Gulino, A., 53, 55 Gulko, P. S., 193 Gullberg, B., 790, 1062 Gullette, E. C. D., 716 Gulsen, M., 1002 Gumnick, J. F., 199, 519, 520, 608, 885 Gunella, G., 108 Gunn, R. N., 437 Gunnar, M. R., 901, 907, 912, 914 Gunnarson, I., 213 Gunnon, C., 770, 773 Gunzler, C., 200, 223, 224 Guo, C. J., 554 Guo, L. S., 540 Guo, P., 419 Guo, S. S., 715 Guo, T., 565 Guo, Y., 645 Guo, Z., 383 Gupta, A. K., 567, 813 Gupta, M. A., 813 Gupta, P., 1054 Gupta, S., 937 Gur, R. C., 564 Gur, R. E., 564, 565, 569 Guralnik, J. M., 234, 361, 870, 873 Gurevich, V. S., 958 Gurfinkel, E. P., 923 Gurkan, F., 1002 Gurklis, B. S. J., 570 Gurniak, C. B., 998 Gurvitis, T. V., 540 Gusewitch, G., 662, 665, 667, 668 Gussekloo, J., 362 Gust, D. A., 468 Gustafson, D., 383 Gustafson, E. L., 101 Gustafson, J. A., 49–50, 50, 55 Gustafsson, J. A., 55 Gustafsson, J.-A., 741 Gustavsson, E., 599 Guthrie, D., 624, 692, 872, 873, 877, 881 Guthrie, R. M., 542 Gutierrez, C., 56 Gutierrez, E. G., 381 Gutierrez, J. M., 399 Gutierrez-Canas, I., 143, 200 Gutierrez-Ramos, J. C., 359 Gutstein, H., 160, 161 Guyre, P. M., 724, 731, 736, 737, 738, 747 Guzhova, I., 1019 Gwaltney, J. M., 486, 773, 782, 783
Author Index Gwaltney, J. M., Jr., 497, 504, 505, 1053, 1063, 1111 H. N. R. C. Group., 1060, 1061 Ha, B. K., 357, 359 Ha, H., 999 Haack, M., 222, 223, 305, 362, 363, 570, 585, 594, 598, 601, 609 Haan, J., 147 Haan, S., 338 Haap, M., 997, 1000 Haas, D., 969 Haas, D. C., 949 Haas, H., 64, 97 Haas, H. S., 523 Haase, A. T., 1054, 1059 Haban, V, 532, 536 Habets, P. E., 48 Habich, C., 1016, 1024 Habrioux, G., 208, 211 Habu, S., 481 Hacham, M., 430 Hache, R. J., 49 Hache, R. J. G., 1098 Hack, C. E., 54, 361, 362 Hack, M., 712 Hacke, W., 422 Hacohen, N., 995 Haczku, A., 55 Hada, Y., 999 Hadad, D., 184 Hadberg, H., 419 Haddad, J. J., 303 Hadden, E., 678 Hadden, E. M., 1043 Hadden, J., 678 Hadden, J. W., 1043, 1044 Haddox, M., 678 Hädike, A., 727, 729, 730 Hadjamu, M., 568 Hadro, E. T., 55 Haeberli, A., 963 Haegeman, G., 53 Haenen, G. R., 1045 Haering, D., 421 Haffejee, Z., 239 Haffner, S. M., 1000 Haffty, B. G., 881, 882 Hafler, D. A., 149 Hafner, G., 959 Hafner, M., 1024 Hafstrom, I., 199, 209 Haga, C., 361 Haga, S., 1045 Hagberg, H., 419 Hagberg, L., 1057 Hagedoorn, M., 790 Hagelstein, M. T., 241
Hagen, E., 113 Hager, G. L., 51 Hager, K., 361 Haggerty, R. J., 456 Hagino, H., 197 Hagiwara, E., 196 Hagiwara, M., 137 Hahn, B. H., 1054 Hahn, E., 803 Hahn, E. F., 1101 Hahn, H., 1038 Hahn, M., 352, 353, 354 Hahn, P. Y., 65 Hahn, R. C., 871 Hahn, S., 142 Hahn, W. C., 235 Hahne, M., 693 Haidich, A. B., 166 Haifang, L., 793 Hailey, S., 814 Haines, G. K., 224 Haist, J. V., 1016 Hajeer, A. H., 198 Hajjar, A. M., 431 Hakanson, R., 103 Hake, A., 363, 364 Hakimi, J., 978 Hakobyan, P. J., 568 Halaas, J. L., 994 Halazonetis, T. D., 53 Halberg, F., 744 Halbreich, U., 512 Halbur, L., 348, 382 Halcox, J., 501 Halcox, J. P., 927, 958, 960 Hale, J. E., 994 Hale, S. L., 417 Halford, K. W., 791 Halford, W. P., 1080, 1081, 1082, 1088 Halie, M. R., 997 Halkjaer-Kristensen, J., 669 Hall, A. J., 958 Hall, C. D., 1060 Hall, D. D., 1043 Hall, G. M., 199 Hall, J., 197, 360, 1002 Hall, M., 518, 553, 580, 595, 599, 607, 608, 676, 784, 785 Hall, N., 691, 877 Hall, N. R., 70, 222, 604 Hall, N. R. S., 461 Hall, R. A., 1043 Halle, E., 76 Halle, M., 1002 Hallelmo, M. E., 340, 344, 346 Hallenbeck, J. M., 417, 419, 434 Hallet, A. J., 497, 623 Hallgren, R., 197
Author Index Halliday, W. G., 440 Halliday, W. J., 735 Hallman, M., 459 Hallmans, G., 218 Hallmayer, J., 364, 365 Hallyburton, E., 1002 Halper, J. P., 814 Halpern, G. M., 736 Halpern, J. H., 555 Halter, J. B., 682 Hamada, A., 106 Hamada, M., 958 Hamaker, S., 771 Hamamr, J. A., 461 Hamaoka, T., 879 Hamarman, S., 598, 599 Hamashima, Y., 70 Hamatani, T., 223 Hamazaki, T., 303 Hamburger, M. E., 1061 Hamel, B., 362 Hamelin, J., 110 Hamid, Q., 55, 103, 978 Hamid, Q. A., 978 Hamill, E., 637, 732, 743 Hamilton, C., 647 Hamilton, K. L., 1015 Hamilton, T. A., 137 Hammack, S. E., 405 Hammarestrom, A., 713 Hammarstrom, S., 802 Hammerschlag, M., 859 Hammes, E., 744 Hammes, H. P., 998 Hammes, S., 552 Hammill, A. K., 1018 Hammon, H. M., 1045 Hammond, E. C., 606 Hammond, E. H., 927 Hammond, G. L., 746, 747 Hammond, S., 885 Hammond, T. G., 117 Hamon, M., 167 Hamovit, J. R., 567 Hamovitch, M., 786 Hampel, H., 365, 439, 440, 1115 Hamrick, N., 782 Hamsten, A., 961, 962 Hamulyak, K., 682, 931, 932 Hamuro, J., 1037, 1046 Han, B., 143 Han, C. S., 571 Han, D. S., 1056 Han, H., 571 Han, J. N., 709 Han, L. Y., 565 Han, M., 184 Han, S., 995, 999
Han, S. K., 1015 Hanada, T., 177, 404 Hanafusa, T., 997, 1000 Hanahan, D., 235, 882 Hanashi, H., 223 Hanau, D., 978, 1024 Hanau, S., 291 Hanauer, S. B., 144 Hanawa, T., 1045 Hancock, C., 712 Hancock, W. W., 420 Handelsman, E., 1055 Handjiski, B., 113 Handley, D., 926 Handman, E., 995 Handwerker, H. O., 110 Hanebuth, D., 963, 965 Haney, T. L., 694, 929, 930, 949 Hangai, N., 258 Hanifin, J. M., 977, 979, 984, 988 Hanini, M., 400 Hank, J. A., 521 Hanker, J., 983 Hankinson, S. E., 241, 956 Hann, D., 691, 694 Hanna, C., 539, 540 Hannapel, A. C., 859 Hannigan, E., 882 Hanninen, L., 113 Hans, V. H., 417 Hansch, D., 1024 Hansen, B., 609 Hansen, C., 740 Hansen, G., 502 Hansen, J. B., 684 Hansen, K., 224, 591, 592, 593, 594, 598, 599, 606 Hansen, L., 386, 996, 1000 Hansen, M., 633, 646 Hansen, M. K., 88, 287–88, 288–89, 290, 301, 339, 357, 996, 1014, 1026 Hansen, N. B., 792 Hanson, B., 808 Hanson, B. S., 790, 1062 Hanson, I. C., 1055 Hanson, N. D., 521 Hanson, R. L., 715, 1000 Hansson, B., 769 Hansson, E., 408 Hansson, G. K., 921, 922, 925, 927, 953, 954 Hansson, P., 200 Hansson, S., 241 Hansson, V., 257, 1058 Hantschel, M., 1024 Hao, A. J., 402 Hao, L., 555 Haour, F., 292, 304, 358, 381, 739
1167 Happel, H., 1044 Happel, M., 766 Happle, R., 983 Haque, I. U., 923 Haque, M. S., 365 Hara, A., 71 Hara, H., 419 Harada, A., 1056 Harada, S., 979 Harada, Y., 1058 Haraguchi, S., 1058 Harald, J., 1046 Harald, K., 957 Harari, O. A., 1100 Harbeck, R., 977, 988 Harbeck, R. J., 468, 745, 855 Harben, M. B., 50 Harbison, R. D., 1037 Harbour, D. A., 1088 Harbour-McMenamin, D., 39 Harbuz, M., 63 Harbuz, M. S., 101, 112, 196, 197, 681, 739, 980, 987 Hardin, E. A., 1115, 1118 Harding, H., 606 Harding, M. W., 419 Hardison, A. M., 193 Hardman, J. G., 1019 Hardoy, M. C., 361 Hardwick, A. J., 286, 298 Hardy, C., 1040 Hardy, C. A., 194 Hardy, I., 859 Hardy, J., 364 Hare, G. M., 420 Hare, W. S., 400 Harel, F., 242 Hargreaves, K. M., 165 Hargreaves, M., 1016 Haribabu, B., 1025, 1026, 1027 Haring, H. U., 997, 999, 1000 Harkin, A., 305 Harkness, L., 540 Harlacher, R., 284 Harle, P., 69, 76, 193, 209, 210, 224 Harley, E. J., 768 Harlow, H. F., 479 Harlow, L. A., 224 Harlow, M. K., 479 Harman, P., 745 Harmar, A. J., 106, 133, 134, 140 Harmsen, A. G., 1025 Harper, A. P., 871 Harper, D. M., 237 Harper, J., 173, 174 Harper, J. I., 977 Harper, M., 490 Harper, R. A., 239
1168 Harrell, F. E., Jr., 929, 930 Harrell, L. E., 365, 366 Harreman, M. T., 50 Harrington, A., 622, 901, 909, 910, 913 Harris, A. H., 814 Harris, C. L., 46 Harris, H. W., 53 Harris, J., 365, 394 Harris, J. M., 364 Harris, J. R., 773 Harris, J. W., 459 Harris, M. B., 998 Harris, M. H., 275 Harris, S., 691 Harris, T., 361, 380, 882, 962, 1043, 1044, 1110 Harris, T. B., 361, 782, 783, 956 Harris, T. J., 727 Harrison, C. M., 762, 763 Harrison, D., 407 Harrison, J., 786 Harrison, L. C., 592, 594, 595, 603, 604, 817 Harrison, L. K., 762, 763, 900, 905, 907, 913 Harrison, P. J., 564 Harrison, R., 511 Harrison, S., 110 Harrison, S. M., 1054, 1055 Harrison, W., 1061 Hart, B. L., 285, 339, 396, 431 Hart, D. J., 567 Hart, J., 838, 839, 841 Hart, L. K., 567 Hart, M. N., 417 Hart, R., 783, 787 Hart, R. P., 100, 134, 136, 292, 293, 385 Hart, S. L., 681, 695, 1110 Härting, M., 637, 645, 650, 651, 652 Hartkopp, A., 663 Hartl, F. U., 1014, 1015, 1024 Hartman, A., 921, 930 Hartman, M. E., 297, 304, 996, 998, 1000 Hartmann, B., 549, 551 Hartmann, G., 1099 Hartung, H. P., 108, 416, 417 Hartung, T., 999 Hartwig, A., 764, 767 Hartwig, F., 1000, 1001 Harvey, E. N., 580 Harvey, J. H., 764, 767 Harvill, J. L., 948 Hasegawa, H., 323, 326 Hasegawa, K., 997, 1000 Haselbauer, P., 511, 570 Hashimoto, K., 321, 338 Hashimoto, M., 321, 684, 689, 1055 Hashimoto, R., 523
Author Index Hashiramoto, A., 197 Haskard, D., 961 Haskard, D. O., 1100 Haskett, R., 771 Hasko, G., 997 Haslett, C., 980, 1025 Hassan, A. B., 173, 174 Hassan, A. H. S., 162, 164, 166 Hassanain, M., 294 Hasse, C., 599 Hasselbach, H., 464 Hasset, J., 727, 743 Hassiakos, D., 257 Hassid, J., 240 Hassim, Z., 136 Hassner, A., 109 Hastings, N., 340, 359 Hastings, S. L., 400 Hata, K., 831 Hatakeyama, R., 348, 382 Hatanaka, H., 359 Hatano, H., 1055 Hatano, M., 862 Hatfield, S. M., 74 Hatfield, T., 646 Hatton, G. I., 400, 401 Hattori, A., 106 Hattori, N., 147 Hattori, T., 98, 109, 115 Hauck, S., 566 Hauer, P., 166 Haugen, A. H., 599 Hauger, R., 512, 515, 555, 693 Hauger, R. L., 515, 516, 594, 595, 598, 603, 608, 885 Haughey, N., 420 Haughey, N. J., 1054 Hauner, H., 996 Haus, E., 592 Hausen, H. Z., 740 Hauser, C., 73, 997 Hauser, C. J., 85 Hauser, S. L., 106 Hausner, E., 964, 966 Haussler, A., 252 Hauss-Wegrzyniak, B., 386 Haut, A. E., 198, 609 Hautanen, A., 931 Hauth, J. C., 711 Hautmann, G., 987 Hauw, J. J., 585 Havas, L., 565 Haverkate, F., 923, 926, 957 Haviland, J., 692 Haviland, J. S., 234, 871, 872 Havlir, D., 1054 Hawk, L. W., 542 Hawken, S., 947, 949 Hawkins, D., 1061
Hawkins, G. A., 814 Hawkins, R., 631, 632 Hawkley, L., 884 Hawkley, L. C., 787, 1019 Hawley, N., 1056 Haworth, R., 999 Hawrylowicz, C., 1056 Hawrylowicz, C. M., 736, 817 Hay, E., 239 Hay, F., 502, 503 Hay, F. C., 931 Hay, J. B., 592 Hay, N., 177 Hayaishi, O., 87, 320, 321, 322, 330, 331 Hayakata, T., 417 Hayakawa, Y., 47, 252 Hayani, K., 1055 Hayano, J., 772 Hayasha, Y., 382 Hayashi, J., 958 Hayashi, K., 106, 360, 882 Hayashi, N., 419 Hayashi, R., 54, 842, 1056 Hayashi, T., 1058 Hayashi, Y., 305, 348 Haybittle, J., 692, 871, 872 Haybittle, J. L., 692, 871, 872, 887 Haydon, P. G., 403, 404, 406 Hayduk, R., 586 Hayes, A., 365, 679, 686, 687, 1080, 1088 Hayes, M. M., 1058 Hayes, N. A., 109 Hayley, S., 303–4, 304 Haynes, L. T., 786 Haynes, R. C. J., 737 Haynesworth, S. E., 55 Hayney, M. S., 900, 902 Hays, J. C., 782 Haythornthwaite, J. A., 93 Hayward, A. R., 863, 1079 Hazeki, O., 1057, 1058 Hazel, K., 419 Hazenburg, M. P., 100 Hazes, J. M., 199 Hazuka, C., 291, 321, 432 He, F., 110 He, G., 565 He, J., 1056 He, L., 293, 302, 303, 405, 565, 571, 1111 He, L. K., 831 He, Y., 1053 Heald, N., 106 Healy, M., 851, 852 Heaney, L. G., 115 Heard, R. H., 830 Heath, G. W., 664, 665 Heath, R. G., 567 Heaton, R. K., 1054 Hebb, D. O., 340
Author Index Heberer, G., 254, 257 Heberman, R. B., 255, 257 Hebert, J. R., 666 Hebert, P., 555, 737, 745 Hecht, G., 934 Heckler, R., 1002 Heckman, H. M., 397, 399 Hedblad, B., 926, 957 Hediger, M. L., 712 Hedley, R., 364, 365 Hedman, L. A., 728 Hedrich, H. J., 925 Hedrick, J. A., 101 Hedtjarn, M., 419 Heemann, U., 654 Heeney, J. L., 1054 Heeren, T. C., 763, 765, 766, 772 Heeschen, C., 957, 958 Heffner, K. L., 786 Hegadoren, K. M., 542 Hegyesi, H., 181 Hehlgans, T., 172 Heijink, I. H., 66 Heijnen, C., 172, 679, 691, 694 Heijnen, C. J., 39, 43, 63, 65, 68, 69, 72, 76, 164, 200, 726, 729, 739, 1044, 1045, 1046 Heijtink, R. A., 236, 237, 768, 900, 903, 904, 914, 1065 Heike, M., 1015, 1024 Heiker, H., 726 Heikkila, K., 769, 770, 789 Heilman, C. A., 855 Heils, A., 522 Heim, C., 521 Heimendinger, P., 859 Heine, H., 1015 Heinegard, D., 193 Heineman, M. J., 458 Heinrich, J., 977 Heinrich, K., 386 Heinrich, P. C., 598, 995 Heinrich, P. D., 338 Heintze, U., 1000, 1001 Heinz, A., 963 Heinzel, T., 137 Heise, E., 1111 Heise, E. R., 483, 486, 1080 Heise, S. R., 478 Heisel, S. J., 901, 907 Heiser, P., 599 Heiske, A., 567 Heiss, G., 927 Heit, S., 521 Hejna, M. J., 103 Hekkart Van, L., 977 Helbert, M. R., 1054 Helbo-Hansen, H. S., 222 Held, P. E., 468, 485
Helder, L., 883 Helders, P. J., 739 Helenius, H., 870 Helenius, M., 383 Helgeson, V. S., 693, 792 Heliovaara, M., 870 Helisalmi, S., 364 Hell, J. W., 1043 Hellekson, C., 717 Heller, B., 871, 876 Heller, P., 194 Heller, P. H., 110 Hellerstein, M. K., 295, 303 Hellhammer, D., 637, 652, 725, 726, 739, 741, 1080 Hellhammer, D. H., 302, 739, 741, 742, 772, 811, 813, 854, 884, 978, 981, 982, 983, 984, 985, 986 Hellhammer, D. J., 514 Hellings, P. W., 812 Hellman, S., 236 Hellstrand, K., 71 Helman, L., 173, 180, 184 Helmberg, A., 53, 741 Helmchen, F., 402, 406 Helmert, U., 800 Helms, C., 69, 110, 200 Helsen, M. M., 143 Helsing, K., 784 Hemady, Z., 986 Heman, K. L., 1017 Hemingway, H., 501, 946, 949, 961, 962 Hemmann, U., 598 Hemmings, C. P., 570 Hemmings, G. P., 348, 361, 380, 568 Hemonnot, B., 1058 Hench, P. S., 737 Henderson, B., 501, 505, 961, 962, 1016 Henderson, E., 1059 Henderson, E. E., 1055, 1059 Henderson, M. A, 937 Henderson, S. A., 1043 Hendricks, R. L., 1079, 1083, 1088 Hendricks, S. E., 514 Hendrickson, B. A., 1015 Hendrickson, R. B., 462 Hendrickx, A., 462 Hendrickx, A. G., 462 Hendrie, H. C., 733 Hendriks, J. H., 872 Hendrix, M., 692 Henegar, C., 993 Heneka, M. T., 1014 Hengel, H., 422 Hengemihle, J., 386 Hengge, U. R., 1057, 1058 Heninger, G. R., 521, 541 Henke, A., 733 Henke, H., 104
1169 Henke, K. D., 977 Henle, G., 856 Henle, W., 856 Henley, J., 947 Henna, J., 565 Hennebold, J., 747, 855 Hennebold, J. D., 747 Henne-Bruns, D., 873, 887 Hennekens, C. H., 502–3, 518, 923, 926, 927 Hennerici, M., 420 Henney, A., 882 Hennig, J., 599, 652 Hennighausen, L., 180 Henning, S. J., 746 Henrich-Noack, P., 420 Henrichot, E., 995, 997 Henricks, P. A., 72 Henriksen, S. J., 586 Henriques, J. B., 913 Henriquet, C., 842 Henry, G., 838, 841, 845 Henry, J. L., 101 Hens, J., 105 Hensel, M., 1059 Henslee-Downey, P. J., 234, 871, 872 Henson, D. A., 662, 663, 664, 665, 666, 667, 668, 669 Henson, P. M., 440, 1038 Henz, B. M., 106, 273, 838 Heo, D., 879 Heppner, F., 437 Herbault, N., 219 Herbelin, A., 98 Herberman, R., 678, 686, 869, 874, 876, 878, 879, 1079 Herberman, R. B., 786, 787, 792 Herbert, M. K., 104 Herbert, R. B., 724 Herbert, T., 676, 677 Herbert, T. B., 257, 499, 510, 516, 517, 551, 553, 622, 724, 727, 729, 761, 766, 785, 793, 932, 934 Herbert, W. N., 212 Herbreman, R., 878 Herbst, H., 856 Herbst-Damm, K. L., 787 Herchuelz, A., 133 Herder, C., 996 Herfarth, H., 224, 1003 Herken, H., 570, 571 Herkenham, M., 272, 293, 294, 321, 401 Herlyn, M., 842 Herman, J. P., 328, 329, 384 Herman, S., 517 Herman, Z. S., 570 Hermann, C., 93 Hermann, C. K., 70, 1057 Hermann, D., 591, 963
1170 Hermann, D. M., 589, 590, 601, 605 Hermann, G., 843, 1044, 1080, 1098, 1100, 1103 Hermann, G. E., 88 Hermanns, H. M., 338 Hermanowski-Vosatka, A., 747 Hermanson, K., 790 Hermansson, A., 113 Hermanussen, S., 164 Hermes, B., 838 Hermida, R. C., 594, 599 Hermina, N. S., 134 Hermodsson, S., 71 Hermoso, M. A., 55 Hernandez, J., 284, 339, 419 Hernandez, M. C., 555 Hernandez-Pando, R., 603, 855 Hernandez-Reif, M., 684, 1061, 1065 Hernanz, A., 133 Herndon, D. N., 69, 603 Herndon, J., 2nd, 234 Herold, M., 739 Heron, I., 663 Herr, I., 241 Herrald, M. M., 620 Herregodts, P., 417 Herrington, D., 964, 966 Herrmann, G, 934 Herrmann, M., 76, 198, 223 Herrscher, R. F., 981 Herschkovitz, A., 999 Hersey, P., 556 Hersh, S., 691, 877 Hertel-Wulff, B., 66 Hertenstein, B., 871 Hertzog, C., 768 Herz, A., 162, 165, 166 Herz, L. R., 541 Herz, U., 469 Herzenberg, L. A., 1037, 1043 Herzer, K., 241 Herzog, L., 419 Herzog, R., 785 Herzog, S., 567 Herzog, Y., 224 Hess, A., 692, 1015 Hesse, D. G., 54 Hesselbrock, V. M., 552 Hessman, Y., 1019 Hetier, E., 72, 301 Hetta, J., 518, 579, 606 Hettich, M., 511 Hetzel, G., 565, 566 Heufelder, A. E., 1055 Heumann, D., 146 Heun, R., 364, 365, 421 Heuser, I., 887 Heusser, C., 732 Heuven-Nolsen, D., 109
Author Index Hevener, A. L., 1000 Heward, C. B., 663, 669 Hewett, J. A., 275 Hewett, J. E., 198 Hewett, S. J., 275 Hewitt, H. B., 257 Hewitt, J., 982 Hewson, A. K., 437 Hextall, J., 827, 842 Heyes, M., 276 Heyman, R., 621, 725, 726, 733, 744, 746, 1110 Heyman, R. A., 137 Heys, S., 684 Heyser, C. J., 349, 350, 351, 384 Hibbard, J. H., 789 Hichwa, R. D., 620 Hickey, W. F., 272, 294, 322, 438 Hickfang, K., 161 Hickie, C., 512 Hickie, I., 512 Hicklin, D., 676, 785 Hickling, E. J., 541, 542 Hickling, P., 198 Hickman-Miller, H. D., 1015 Hickok, J. T., 520 Hicks, E., 326 Hicks, J. T., 566 Hidalgo, J., 284, 339, 419 Hiddemann, W., 1024 Hidderley, M., 684 Hide, I., 404 Hiemke, C., 553, 744 Hieta, N., 840 Higa, N., 1001 Higashi, M., 329 Higashi, Y., 960 Higashino, K., 419 Higgins, E. A., 343, 347, 360, 385 Higgins, J. T., 683 Higgins, K., 1014 Higgins, P., 681 Hightower, L. E., 1019 Higley, J. D., 479, 485 Higuchi, H., 522, 523 Higuchi, S., 523 Hijazi, A. S., 483, 484, 491 Hijdra, D., 437 Hilbe, W., 569 Hildebrand, W. H., 1015 Hildebrandt, L. W., 254, 257 Hildemann, W. H., 738 Hiler, M. L., 995 Hilgers, J., 652 Hilkins, J., 652 Hill, A., 875 Hill, D., 977 Hill, E., 549, 551 Hill, E. E., 603
Hill, J. K., 419 Hill, J. M., 54, 56, 197, 737, 739, 741, 980, 1079, 1080, 1081 Hill, K. K., 533, 536, 543 Hill, M., 815 Hill, R. H., 585 Hill, S. A., 90, 260 Hill, T. J., 1086, 1088 Hillard, J., 490 Hillburger, M. E., 556 Hilleman, M. R., 859 Hiller, A., 186 Hiller, J. E., 234, 870, 871 Hillhouse, J., 858, 863 Hillier, S., 711, 1059 Hillier, S. L., 458 Hillis, S. L., 764, 767 Hillman, D., 1053 Hilner, J. E., 962 Hilton, C. W., 1055 Hilton, D. J., 995, 999 Hiltunen, M., 364 Himmelstein, S. A., 669 Hinde, R. A., 476 Hinderliter, A. L., 772, 927, 969 Hinderliter, C., 639 Hindmarch, F., 515 Hingorani, A. D., 960 Hino, S., 663 Hinrichsen, H., 592 Hinson, J. P., 224 Hintze, H., 830 Hintzen, R. Q., 437 Hinuma, S., 744 Hinze-Selch, D., 331, 570, 585, 586, 589, 590, 591 Hioki, H., 326 Hioki, K., 1001 Hirai, H., 512 Hirai, K., 878 Hirai, T., 999 Hirai, Y., 301, 353, 858 Hiraki, Y., 1018 Hiramoto, N., 638, 639, 640, 641, 642, 651, 652 Hiramoto, N. S., 651 Hiramoto, R., 638, 639, 640, 641, 642, 643, 651, 652 Hiramoto, R. N., 640, 641, 651 Hirano, S., 977 Hirano, T., 54, 995, 1115 Hiraoka, H., 1001 Hirasawa, N., 322 Hirata, A., 1000 Hirata, F., 731 Hirata, Y., 54, 998 Hiremagalur, B., 235 Hirofumi, I., 785 Hiroi, N., 45, 55, 198, 1056
Author Index Hirose, M., 326, 663, 1001 Hirose, S., 859 Hirsch, M., 609 Hirsch, M. S., 1054 Hirsch, S., 565 Hirschfeld, R. M., 307 Hirschfield, G. M., 924, 926 Hirshfeld, J. W., 937 Hirst, E. M., 55 Hirst, S., 804 Hirt, R., 532, 535, 536, 538 Hirte, H., 878 Hiscott, J., 1056 Hisey, C. L., 663 Hislop, T. G., 786 Hitomi, Y., 1045 Hizaki, H., 326 Hizawa, N., 814, 816 Hjaltadottir, S., 736 Hjemdahl- Monsen, C. E., 923 Hjemdahl, P., 712 Hjertman, J. M. E., 663, 666 Hla, T., 53, 54 Hlatky, M. A., 694, 949 Ho, D. D., 1054 Ho, W. Z., 554, 1059 Hoagland, H., 727, 729 Hoang, Q., 1043 Hobart, G., 580 Hobart, G. A., III, 580 Hobel, C., 711 Hobel, C. J., 711 Hoberman, H., 785 Hoberman, H. M., 785 Hobson, A., 1086 Hoch, C. C., 518, 580 Hochhaus, G., 408 Hochron, S. M., 1046 Hochwald, G. M., 438 Hockings, C. G., 342 Hodel, A. E., 50 Hodgson, D. M., 456 Hoebe, K., 999 Hoehe, M. R., 161 Hoek, R. M., 272 Hoekstra, Y., 66 Hoelzl, J., 166 Hoesli, L., 584 Hoetzel, A., 73 Hoey, T., 53 Hof, P. R., 476, 477 Hofbauer, B., 110 Hofbauer, L. C., 1055 Hoff, A. L., 807 Hoff, R., 1055 Hoffer, B. J., 420 Hoffman, C., 878 Hoffman, G., 651, 710, 711 Hoffman, G. E., 710
Hoffman, G. S., 224 Hoffman, H. G., 710 Hoffman, I. R., 1056 Hoffman, J., 199 Hoffman, J. M., 788 Hoffman, L., 534, 539 Hoffman, R. E., 564 Hoffman, R. R., 908 Hoffman-Goetz, L., 661, 663 Hoffmann, E., 564 Hoffmann, J., 212 Hoffmann, J. A., 337 Hoffmann, P., 149 Hofland, L. J., 100 Hoflich, C., 76, 554 Hofman, A., 439 Hofman, F. M., 419 Hofmann, B., 1057, 1058 Hofmann, F, 173, 174 Hofmann, P., 733, 1100 Hofmeister, M., 110 Hogan, B. E., 792 Hogan, D., 422, 588 Hogan, E. L., 136 Hogan, V., 458, 711 Hohagen, F., 592, 594 Hohenegger, M., 557 Hohle, K. D., 89 Hohlfeld, R., 106 Hohman, R. J., 131 Hohne, R., 566 Hokelt, T., 161 Hokfelt, T., 104, 107, 109, 133 Holaday, J. W., 357 Holan, V., 305 Holaska, J. M., 50 Holbeck, J. C., 663 Holbrook, N. J., 724, 737, 738, 747, 1014 Holden, H., 678 Holden-Lund, C., 828 Holgate, S., 103, 804, 807 Holgate, S. T., 55, 70 Holguin, A., 398 Holla, A., 808 Hollaender, J., 771 Holland, D. J., 1079 Holland, J., 967 Holland, J. C., 875 Holland, P. J., 133 Hollander, C. S., 100 Hollander, G., 859 Hollander, H., 166 Hollenberg, S. M., 49 Holliday, J., 684, 734, 787 Holliday, J. E., 856, 858, 863, 1088 Höllig, H., 982, 983, 984, 985, 986 Holligan, S., 193 Hollingshead, P., 184 Hollis, J., 714
1171 Hollon, S. D., 686 Holloway, B. R., 182 Höllt, V., 161 Holly, J. M., 181, 182 Holm, J., 925 Holm, S., 925 Holmang, A., 996 Holmberg, D., 789 Holmberg, V., 1055 Holmdahl, R., 197, 222 Holmes, C., 361, 364, 385, 386, 440, 444 Holmes, E., 272, 276 Holmes, K. K., 1059 Holmes, R., 686, 692 Holmgren, L., 253 Holmlund, A., 200 Holmlund, L., 339 Holsboe, R. F., 733, 735, 746 Holsboer, F., 48, 133, 296, 338, 516, 522, 540, 589, 590, 591, 594, 598, 601, 605, 724, 733, 735, 745 Holst, C., 931 Holst, K., 873, 887 Holst, P. A., 106 Holt, A. C., 46 Holt, L., 224 Holt, M., 684 Holt, P. G., 816 Holt, W., 341 Holte, H., 74 Holth, P., 344 Holt-Lunstad, J., 788, 792 Holtmann, M., 144 Holtsberg, F. W., 419 Holtsclaw, L. I., 196 Holtzman, M. J., 502 Holuigue, S., 1054 Holzer, P., 100, 101, 102, 104 Holzman, A., 686 Homberg, M., 568 Homburger, V., 290 Homel, P., 1002 Homer, L. D., 320 Homma, M., 1112 Hommes, D., 92 Homo-Delarche, F., 304, 570 Honda, A., 830 Honda, K., 331 Honda, O., 1018 Honda, S., 1000, 1001 Honda, Y., 360 Honegger, C., 40, 64, 678 Honer, W. G., 565 Hong, C. J., 364 Hong, H., 50 Hong, J. S., 523 Hong, M., 46 Hong, M. S., 571 Hong, S., 136, 606, 729, 882, 934
1172 Hong, S-Y, 764, 767 Hong, Y., 503, 964, 965, 966 Hong-Brown, L., 172 Honig, A., 307, 682, 969 Honing, H., 272 Honkanen, R., 769, 770 Honkaniemi, J., 186 Honkasaol, M. L., 789 Honma, S., 211 Honore, P., 252 Hons, R. B., 771 Hontebeyrie-Joskowicz, M., 399 Hoo, B. S., 487 Hood, K. E., 456 Hoogendijk, W. J., 386 Hooghe, R., 417 Hooghe-Peters, E. L., 417 Hoon, E. F., 855 Hooper, D. C., 567 Hooper, L. G., 464 Hooper, S., 663 Hooper, S. L., 670 Hoopes, P., 885 Hooton, J., 569 Hoover, D. L., 1015 Hoover, D. R., 1053, 1060, 1061 Hoover, R., 419, 736 Hoover, R. N., 556 Hoozemans, J. J., 276 Hop, W. C., 437 Hopf, H. W., 827 Hopf, J., 554 Hopkins, R. O., 385 Hopkins, S. J., 320, 423, 434 Hopp, T. P., 996 Hoppe, E., 106 Hoppin, A. G., 1002 Hoppu, U., 815 Hopster, H., 479, 480, 484 Horai, R., 419, 433 Horan, M. A., 829, 830, 831 Horan, M. P., 828, 832, 842, 845 Horbar, G. M., 1056 Horgan, K., 233, 870 Hori, M., 1001 Hori, O., 998 Hori, T., 64, 100, 274, 356, 358, 522, 635 Hori, Y., 71 Horie, M., 1000 Horigome, K., 106 Horiguchi, S., 881, 882 Horiike, N., 554 Horikawa, N., 522 Horikawa, T., 296, 523, 979 Hori,T., 325, 329, 330 Horiuchi, S., 1001, 1057, 1058 Horn, T., 323 Horne, B. D., 927, 959 Horne, M. C., 1043
Author Index Horner, H. C., 261 Horner, J., 93 Horney, B., 238 Horn-Muller, J., 181 Hornquist, J. O., 769 Hornstein, O. P., 981 Hornung, V., 1099 Horowitz, D. A., 213 Horowitz, M., 1014 Horrobin, D., 342, 343, 347, 348, 358, 359 Horrobin, D. F., 303, 344, 358, 359 Horst, H. J., 592 Horsten, M., 948, 961, 962 Horton, J. W., 1024 Horton, N. J., 554 Horuk, R., 148 Horvath, E., 147 Horvath, E. M., 297, 304, 996, 1000 Horvath, T. L., 994 Horwath, C. C., 715 Horwitz, R. I., 491, 932 Horwood, N., 456, 470 Hosaka, T., 878 Hoshi, T., 1043 Hoshida, S., 959 Hoshino, K., 381 Hosking, C. S., 460 Hosking, J., 695 Hosoda, T., 1002 Hosoi, J., 68, 69, 104, 107, 108, 113, 114, 134, 219, 1044, 1045 Hosoi, M., 100, 329, 330, 358 Hosoi, T., 297, 605 Hosokawa, H., 923 Hosomi, N., 419 Hosotubo, H., 417 Hossain, A., 533, 536, 537 Hosseini, J. M., 146 Hossmann, K. A., 416 Hotamisligil, G., 817 Hotamisligil, G. S., 172, 993, 994, 995, 999, 1001, 1003 Hotta, K., 997, 1000, 1001 Hou, J., 679, 1056 Houck, P. R., 580, 725, 726, 733, 744, 746 Houge, G., 1043 Houldin, A., 553, 932, 1079 Hoult, J. R., 110 Houri, J. M., 201 Housby, J. N., 1015 House, A., 870 House, J. D., 512, 516 House, J. S., 499, 500, 781, 782, 783, 872 Housley, P. R., 49 Houssiau, F. A., 213 Houx, P., 362 Hoves, S., 1044
Hovland, R., 1043 Howard, B. V., 962 Howard, K. J., 49 Howard, L. M., 148 Howard, M. B., 1024 Howard, V., 382 Howarth, P., 103 Howarth, P. H., 70 Howarth, R. H., 55 Howe, G., 788 Howe, K., 1024 Howell, D., 872 Howell, E. A., 669 Howell, G. R., 362 Howell, M. D., 978 Howell, R. H., 932, 934, 935 Howie, S. E., 1025 Howley, P. M., 236 Hoyle, G., 106 Hoyle, J. R., 826 Hoyt, W. T., 782 Hrelia, S., 553 Hromchak, R., 181 Hrupka, B. J., 289 Hseu, S. S., 93 Hsiao, K., 419 Hsieh, F., 579 Hsiung, H. M., 994 Hsu, B., 49 Hsu, K. S., 717 Hsu, M. Y., 842, 879 Hsu, Y., 638, 642 Hsu, Y. C., 68 Hsue, P. Y., 957 Hsueh, C., 638, 639, 640, 641, 642 Hsueh, C. -M., 639, 640 Hsueh, C. M., 68 Hu, F., 521 Hu, F. B., 993, 1001 Hu, J., 404 Hu, J. M., 49, 50 Hu, S., 70, 136, 361, 408 Hu, X. X., 997 Hu, Y., 739, 839 Hua, C. S., 364, 365, 366 Hua, X. Y., 109 Huang, C. C., 717 Huang, H., 532, 535, 537, 538, 638, 641, 676, 858 Huang, H. M., 364 Huang, H. Y., 359 Huang, J., 644, 645 Huang, L., 651, 1110, 1112 Huang, L. M., 683 Huang, L. Y., 167 Huang, M. H., 361, 380 Huang, P., 885 Huang, Q. H., 1025 Huang, Q.-H., 736
Author Index Huang, S., 882 Huang, T.-Y., 400 Huang, W., 998 Huang, Y., 177 Huang, Y. M., 416, 417 Huang, Z., 296, 419, 420 Huang, Z. L., 331 Hubbard, R., 958 Hubbard, R. W., 625, 772 Hübell, D., 651 Huber, B. T., 73 Huber, C., 252 Huber, G., 385 Huber, K., 72 Huber, M. G., 73 Huber, P., 254, 257 Huber, V., 879 Huber, V. C., 77 Huber-Bruning, O., 199 Huberty, G., 405 Hubner, G., 826, 843 Hubschle, T., 323, 326 Hucklebridge, F., 624, 632, 762, 763, 764, 765, 766, 912 Hudgson, P., 400 Hudig, D., 1045 Hudson, C. A., 77, 1036, 1039, 1040, 1041 Huez, G., 997 Huff, A., 485 Huffnagle, G. B., 995 Huggel, H., 1023 Hughes, A., 365, 366, 421 Hughes, G. A., 237 Hughes, J., 512, 694, 734, 785, 899, 900, 904, 1065, 1088 Hughes, J. M., 55 Hughes, M., 538 Hughes, P. M., 434, 435, 437 Hughes, T., 405 Hughes, T. K., 557 Hughes, T. K., Jr., 299, 586, 588 Huginin, M., 291, 321, 432 Hugli, T. E., 101 Hugol, D., 993 Hugunin, M., 419 Huhman, K. L., 481 Hui, L. Y., 875 Huisman, A. M., 198 Huitinga, I., 740 Huizink, A. C., 711 Hukuda, S., 208 Huleihel, M., 352, 354, 359, 360, 930, 968 Hull, M., 108, 439, 440 Hulse, R. E., 277 Hulsmann, A. R., 101, 107, 115 Hultgren, O., 1003 Hultner, L., 254
Humar, M., 73 Humbert, M., 502 Humbert, P. O., 74 Hume, D. A., 401, 402, 1015 Hume, P. D., 744 Humes, D., 163 Humpert, P. M., 72, 965 Humphrey, J. H., 110 Humphrey, P. P., 116 Humphreys, S., 100, 104 Humphries, S., 365 Humphries, S. E., 514, 542, 956 Huneycutt, B. S., 1080, 1098, 1100, 1102 Hung, Y. Y., 485 Hunninghake, G. W., 73 Hunsaker, B. N., 301, 357 Hunstiger, M., 510 Hunt, B., 716 Hunt, J., 416, 417 Hunt, J. S., 828 Hunt, M., 790, 900, 902, 907, 909, 911, 914, 915, 1089 Hunt, M. A., 901, 909 Hunt, P. R., 350 Hunt, S. P., 100, 104, 107, 219 Hunt, T. K., 254, 827, 831, 832 Hunter, C. A., 543, 997 Hunter, D., 872 Hunter, J. C., 161 Hunter, J. R., 199 Hunter, M., 1058 Hunter, W. S., 320, 321 Huntley, A., 814 Hunzeker, J., 1078, 1080, 1099, 1100, 1101, 1112, 1115 Hunzeker, John T., 1077 Huo, Y., 952, 953 Huovinen, E., 812 Hurd, J., 1088 Hurewitz, A., 685, 791 Hurley, L. S., 466 Hurley, S., 234, 871, 873 Hurley, S. D., 136 Hurst, M. W., 901, 907 Hurst, T. L., 361 Hursti, T. J., 877 Hurwitz, B., 680 Hurwitz, B. E., 1057, 1060 Hurwitz, E. L., 812 Husband, A., 650, 651 Husband, A. J., 600, 603, 605, 621, 644, 645, 653, 1058, 1063 Husing, A., 977 Huskisson, E. C., 199 Husted, J., 661 Huston, J. P., 305 Hutchinson, A., 393 Hutchinson, D., 533, 538 Hutchinson, D. S., 1042, 1044
1173 Hutchinson, J. S., 110 Hutchinson, M. R., 269, 275, 408, 409 Huttley, G. A., 1053 Huttunen, H. J., 386 Huttunen, J. K., 422 Huttunen, M. O., 712 Hwang, C. B., 859 Hwang, D., 999 Hwang, I. P., 1080, 1081 Hwang, S. M., 1045 Hyjek, E. M., 855 Hyllested, K., 1107 Hyman, M. C., 952 Hyner, G. C., 871 Hynes, R. O., 239 Hyslop, D. E., 237 Hyuang, Q.-H., 1044 Hyun, C., 692 Hyun, C. S., 624, 872, 873, 877, 881 Iadecola, C., 433 Ialenti, A., 1015 Ianaro, A., 1015, 1025 Ibarra, S., 1055 Ibayashi, S., 420 Ibfelt, T., 669 Ibrahim, N. B., 200 Icaza, E., 599 Ichihashi, M., 979 Ichijo, T., 635 Ichikawa, A., 322, 323, 326, 327, 328 Ichikawa, S., 103, 115, 131, 133 Ichikawa, Y., 1112 Ichinose, M., 115 Ickovics, J. R., 500, 1061 Idsoe, T., 716 Igarashi, H., 199 Igarashi, M., 1000 Igase, K., 350 Iglesias, M. C., 551 Iglesias-Osma, C., 551 Ignacio, Z. M., 482 Ignarro, L. J., 136 Ignatius, R., 108 Ihara, S. S., 1046 Iida, M., 420 Iida, R., 339, 352, 353, 354 Iijima, H., 144, 255 Iinuma, K., 1026 Iivanainen, M., 422 Iivonen, S., 364 Ijames, S. G., 256, 1101 Ijiri, Y., 1000, 1001 Ikebe, S., 147 Ikeda, H., 874, 878, 879 Ikeda, K., 361 Ikeda, M., 432 Ikeda, S. C., 1081, 1087 Ikegami, K., 1044
1174 Ikegawa, H., 417 Ikegaya, Y., 354, 355, 646 Ikeno, Y., 174 Ikoma, K., 404 Ikonomidis, I., 937 Ikushima, H., 830 Ikuta, K., 342, 567 Il’enko, V., 646 Illes, Z., 149 Illias, I., 711 Illich, P. A., 399 Illman, J., 885 Ilyin, S. E., 297, 996 Im, M., 843, 845 Im, S. Y., 383 Imafuku, H., 252 Imai, C., 565 Imai, T., 142 Imai, Y., 1001 Imamura, M., 109 Imatani, J., 1040 Imbert, J. C., 1055 Imeri, L., 422, 586, 587, 589 Imperato, A., 241 Impola, U., 840 Imrich, A., 1002 Imro, M., 828 Imura, H., 432 Inaba, K., 99 Inaba, T., 1001 Inagaki, C., 115 Inagaki, M., 565 Inagaki, N., 73 Inan, S., 400 Inbar, S., 255, 256 Incorvaia, B., 1110 Infante, J., 363, 364, 366, 421 Ingeman, J. E., 148 Ingham, C., 440 Inglis, J. D., 384 Ingram, D. A., 103, 115, 131, 133 Ingram, D. K., 382, 386 Ingram, R., 174 Ingram, S. L., 161 Ingvar, M., 710 Inners, L. D., 853 Inoguchi, T., 998 Inoue, A., 400, 404 Inoue, H., 53, 54, 115 Inoue, J., 46 Inoue, K., 199, 208, 407 Inoue, M., 882 Inoue, S., 331, 584 Inoue, T., 1001 Inoue, W., 322 Inoue, Y., 110, 417, 830 Inoue-Sakurai, C., 533, 535 Insixiengmay, P., 1058 Institute of Medicine, 449
Author Index Inthorn, D., 254, 257 Intiso, D., 420 Introini-Collison, I., 645, 649 Inuyama, Y., 859 Iny, L. J., 491 Ioannides, C., 879 Iodice, G., 241 Ionescu, G., 983 Ionescu, M., 725, 732 Iosue, S., 350, 351 Iredale, J. P., 434, 435 Irie, M., 647, 648, 653 Iriki, M., 321, 584 Iritani, S., 565 Ironson, G., 532, 535, 537, 538, 539, 541, 543, 676, 679, 680, 682, 683, 684, 685, 686, 687, 688, 689, 690, 695, 773, 774, 1055, 1056, 1057, 1058, 1060, 1061, 1062, 1063, 1065, 1080, 1088 Ironson, G. H., 1060, 1063 Ironson, Gail, 531 Irving, G., 1061 Irving, W., 437 Irving, W. L., 459 Irwin, C., 531 Irwin, C. R., 844, 845 Irwin, I., 147 Irwin, M., 509, 510, 511, 512, 514, 515, 516, 517, 518, 538, 549, 551, 552, 553, 554, 555, 556, 594, 595, 598, 599, 603, 604, 605, 606, 607, 608, 609, 622, 625, 676, 680, 681, 693, 694, 724, 730, 733, 734, 784, 785, 874, 885, 888, 932, 963, 965, 1079 Irwin, M. R., 449, 451, 452, 511, 512, 514, 515, 516, 518, 554, 607, 622, 932, 965, 1036 Irwin, Michael R., 449, 579 Irwin, W., 913 Isaac, A., 553 Isaac, M. G., 197, 200 Isabel Fernandez, M., 1062 Isakov, N., 73 Isakson, P., 358 Isakson, P. C., 358 Iscovich, J., 233, 870 Isenberg, S., 1046 Ishibashi, T., 830 Ishida, K., 106, 360 Ishida, T., 240 Ishihara, H., 571 Ishihara, Y., 255 Ishii, D. N., 186 Ishii, I., 998 Ishii, K., 1056 Ishii, M., 519, 687, 689, 1065 Ishii, T., 322
Ishii-Kuntz, M., 787 Ishikawa, J., 997 Ishikawa, T., 99, 785 Ishikawa, Y., 295, 322, 741 Ishimori, K., 583, 584 Ishioka, C., 101, 115 Ishizaka, K., 802 Ishizaka, T., 802 Ishizuka, T., 365 Isles, A., 804 Ismail, K., 716 Iso, H., 957 Isobe, Y., 254 Isovich, E., 241 Issekutz, T. B., 731 Issels, R. D., 1015, 1024, 1025 Italian Seroconversion Study, 683 Itano, N., 831 Ito, A., 110, 148, 294 Ito, H., 144 Ito, K., 54, 842, 1056 Ito, T., 70, 830, 1003 Ito, Y., 999, 1001 Itoh, C. E., 1045 Itoh, H., 882 Itoh, K., 623, 744 Itoh, M., 567 Itoh, N., 132 Itoh, T., 882 Itohara, S., 882 Itoyama, Y., 418 Itzik, A., 302 Ivanov, A. I., 290, 320, 321, 322 Ivanova, S., 86, 88, 89, 105, 605, 772, 997 Ivanova, S. M., 997 Ivashkiv, L. B., 997 Iverfeldt, K., 339, 345, 346, 348, 349, 355, 357, 358, 418, 646 Ivers, H., 518, 606 Iversen, J., 1057, 1058 Ives, D. G., 923, 926 Ivic-Kardum, M., 532, 536 Iwahashi, H., 997, 1000 Iwahashi, K., 223, 567 Iwakabe, K., 238, 481 Iwaki, M., 998 Iwakoshi, N. N., 999 Iwakura, Y., 274, 344, 354, 355, 419, 433, 646, 1039, 1040, 1041 Iwao, M., 998 Iwasaki, A., 1099 Iwata, M., 139, 481 Iwatsubo, T., 364, 365 Ixart, G., 736 Izard, C. E., 762 Izard, K. M., 460 Izawa, T., 736, 1045 Izgut-Uysal, V. N., 1037
1175
Author Index Jabaaij, L., 236, 237, 652, 768, 900, 901, 903, 904, 914, 1065 Jabbari, S., 253, 261, 882, 885 Jabbur, S., 300 Jaber, R., 806 Jabrane-Ferrat, N., 134 Jabs, J., 715 Jabs, W., 1108 Jackson, D. A., 663 Jackson, D. C., 773, 913 Jackson, E., 511 Jackson, E. D., 790, 1060 Jackson, J., 871, 873 Jackson, J. C., 70, 385, 549, 551 Jackson, J. S., 873 Jackson, K. L., 664, 665 Jackson, L. A., 928 Jackson, S. T., 180, 181 Jackson-Lewis, V., 147 Jacob, R., 235 Jacob, S., 1037 Jacob-Hirsch, J., 239 Jacobi, J., 842 Jacobowitz, D., 551 Jacobowitz, D. M., 112 Jacobs, B., 386 Jacobs, C., 173, 174 Jacobs, D. A., 551 Jacobs, J. W., 198, 199 Jacobs, R., 65, 67, 68, 70, 726, 727, 728, 729, 730, 739, 1044, 1045 Jacobs, R. A., 294 Jacobs, S. C., 933 Jacobsberg, L., 1060, 1061 Jacobsen, J. S., 53 Jacobsen, P., 691, 694 Jacobson, C. D., 293, 322, 332 Jacobson, D. L., 1107 Jacobson, L., 1053 Jacobson, M. A., 1059 Jacobson, S., 1108 Jacobsson, A., 1022 Jacoby, R. K., 198 Jacque, C., 273, 290, 337, 339 Jacques, T. J., 417 Jacquet, N., 252 Jadad, A. R., 396 Jaddoe, V. W., 712 Jaeger, B., 984, 985 Jafarian-Tehrani, M., 292, 304, 739 Jaffar, S., 1055 Jaffe, A., 695 Jaffe, A. S., 681, 695, 931, 932 Jaffe, R. B., 223 Jaffer, A., 115 Jaffuel. D., 842 Jager, H., 685 Jagodzinski, P. P., 855 Jahangiri, M., 957, 959
Jahn, J., 959 Jahng, J. W., 736 Jail, A., 423 Jain, A., 143, 195 Jain, N., 803, 805 Jain, R., 100 Jain, S., 732, 733, 736, 741 Jain, V. V., 807 Jakobi, J., 1018 Jakobsson, P. J., 320, 322 Jambrik, Z., 964 James, A., 804, 878 James, D. K., 459 James, G. D., 874 James, K., 592 James, R. C., 1037 James, S. L., 85 James-Yarish, M., 1058 Jamieson, B. D., 237, 1057, 1058 Jamison, J. R., 815 Jancso, G., 102, 110 Jancso, N., 102 Jancso-Gabor, A., 102 Jander, S., 148, 419 Jandorf, L., 624, 625, 762, 764, 766 Janeway, C., 636, 637, 651 Janeway, C. A., Jr., 46, 52, 149, 217, 272, 337, 1024 Jang, S. H., 400 Janig, W., 76, 109, 110, 194 Janiszewski, J., 110 Janka, Z., 361 Janke, J., 1000, 1001 Janknecht, R., 137 Jankovic, B., 632, 649, 653 Jankovic, B. D., 1118 Jankowsky, J. L., 356 Janney, R. P., 855 Janoff, E. N., 361 Janoff-Bulman, R., 769 Janossy, G., 1053 Jansen, J., 72, 997 Jansen, S. A., 358 Janson, W., 110 Janssen, J. A., 174 Janssen, O., 646, 651 Janssen-Heininger, Y. M., 182 Janssens, J. P., 385 Jansson, J. O., 996 Janszky, I., 969 Janus, M., 713 Janzer, R., 104 Janzon, L., 926 Jara, G., 830 Jardanhazy, T., 361 Jardin, A., 253 Jareo, P. W., 551 Jarmalaite, S., 196 Jaroch, S., 198
Jarrard, L. E., 186 Jarrott, B., 1043 Jarskog, L. F., 459, 569 Jarvelin, M. R., 470 Jarvenpaa, S., 813 Jarvinen, A., 859 Jarvis, M. J., 771 Jasiuleviciute, L., 196 Jaskowiak, N. T., 297 Jasnoski, M. L., 1063 Jasnow, A. M., 481 Jasper, J. R., 1041 Jatulis, D. E., 500, 931 Jaunin, F., 73 Javed, N. H., 116 Jay, G., 237 Jayaraman, S., 175, 502 Jayle, D., 1059 Jayson, M. I., 609 Jazwinska, E., 592 Jean, D., 239 Jean, R., 1002 Jeanjean, A. P., 161 Jean-Louis, G., 579 Jeanmonod, P., 512 Jeannin, P., 219 Jedrzejuk, D., 1000, 1001 Jefferies, C., 274 Jefferies, W. M., 734, 736, 741, 745 Jefferson, W. E., 222 Jeffery, D. R., 437 Jeffery, P. K., 55 Jeffery, R., 365, 512 Jeffrey, M., 440 Jekich, B., 400–401, 405 Jekich, B. M., 402, 407 Jekrich, B. M., 406 Jelachich, M. L., 1110 Jelicic, M., 769 Jelinek, D. F., 977 Jemmott, J. B., III, 907 Jenkins, F. J., 532, 535 Jenkins, G. P., 873 Jenkins, J. R., 996 Jenkins, J. S., 241 Jenkins, P., 643, 644 Jenkins, P. L., 871 Jenner, A., 977 Jenner, E., 898 Jenner, P., 147 Jennings, J. R., 714, 715 Jennings, N., 240, 883 Jennings, R., 855, 862 Jennings, S. R., 1087 Jensen, A. B., 786 Jensen, C., 417, 420 Jensen, G., 931 Jensen, J. A., 827 Jensen, M., 692
1176 Jensen, M. M., 236, 727, 729 Jensen, M. R., 871 Jenssen, T. G., 133 Jeong, J., 553 Jeong, M. J., 829, 830 Jephthah-Ochola, J., 587 Jeppesen, D. L., 462, 464 Jepson, C., 769 Jerabek, P. A., 710 Jerant, A. F., 859 Jeren, T., 532, 535, 537 Jern, C., 934 Jern, S., 934 Jeron, A., 926 Jerragard, H., 359 Jerrells, T., 456, 465 Jerrells, T. R., 553 Jessen, F., 364, 365, 421 Jessen, J., 667, 668 Jessop, D. S., 101, 112, 196, 681, 739, 740, 987 Jessops, D. S., 980 Jetschmann, G., 554 Jetschmann, J. U., 65 Jetschmann, J.-U., 1044, 1045 Jeune, B., 362 Jewell, C. M., 48, 49, 50, 53, 1098 Jhou, T., 294 Ji, R., 161, 162, 166 Ji, R. R., 161 Jia, G. Q., 359 Jia, H., 963, 965 Jia, Y., 88 Jia, Y.-P., 400 Jiang, H., 638, 642, 998 Jiang, H. S., 68 Jiang, J., 523 Jiang, W., 116, 933, 937 Jiang, X., 133, 139, 142 Jiang, X. M., 139 Jiang, Y., 101 Jiang, Z., 999 Jibard, N., 49 Jick, H., 969 Jick, S. S., 199, 242, 969 Jimenez, J., 134 Jimenez-Anguiano, A., 586 Jin, H., 362 Jin, J., 117 Jin, J. G., 133 Jin, S., 148 Jin, S. Y., 571 Jing, H., 142 Jing, Y., 1102 jmone-Cat, M. A., 91 Joachi, R., 469 Joachim, R., 113 Joachim, R. A., 813, 817
Author Index Job, C., 1061 Jobst, S., 739, 741, 813, 981 Joe, E. H., 136 Joels, M., 357, 604, 745 Joensen, L., 567 Joffe, B., 222 Joh, T. H., 736 Johannsen, L., 588 Johansen, C., 871 Johanson, S., 359 Johanssen, L. M., 664, 665, 666 Johansson, A., 996 Johansson, B., 361 Johansson, C. C., 1058 Johansson, O., 112 Johansson, S. G., 805 John, T. J., 859 Johns, M. W., 727 Johnsen, E., 686, 692, 882 Johnsen, E. L., 240, 786 Johnson, A. K., 87, 306 Johnson, C. C., 809 Johnson, C. L., 993 Johnson, D., 541, 686 Johnson, D. A., 110 Johnson, D. E., 241 Johnson, D. L., 74 Johnson, D. R., 514, 996 Johnson, E. M., Jr., 106 Johnson, G. B., 1025 Johnson, G. L., 53 Johnson, G. R., 512 Johnson, H. M., 438 Johnson, H. R., 461 Johnson, J., 1015, 1023 Johnson, J. C., 198 Johnson, J. D., 71, 342, 344, 357, 965, 1013, 1016, 1017, 1019, 1022, 1024, 1026, 1115 Johnson, J. H., 855 Johnson, K., 405 Johnson, K. W., 405, 409 Johnson, L., 582 Johnson, L. J., 297 Johnson, M., 72, 76, 814 Johnson, M. C., 103, 104, 134 Johnson, M. L., 174, 1086 Johnson, M. O., 1063 Johnson, M. S., 133 Johnson, N., 564 Johnson, N. J., 781, 783 Johnson, P. C., 854, 855 Johnson, P. J., 103 Johnson, P. M., 295, 458, 459 Johnson, P. R., 487 Johnson, R. G., 1002 Johnson, R. R., 1080, 1107, 1110, 1111, 1115, 1116, 1118
Johnson, R. T., 1107 Johnson, R. W., 171, 172, 180, 181, 182, 183, 184, 185, 269, 273, 297, 298, 300, 302, 303, 304, 321, 348, 379, 380, 381, 382, 383, 384, 385, 386, 387, 422, 444, 996, 1000 Johnson, V. A., 1054 Johnson, V. L., 1040 Johnson, W. L, 937 Johnston, A. R., 440 Johnston, I. N., 407, 408 Johnston, M., 385 Johnston, R. A., 1002 Johnstone, D., 200 Johnston-Wilson, N., 565 Joja, I., 1018 Joksimovic, L., 540, 542 Jolly, C. J., 485 Jonakait, G. M., 134, 136 Jonas, D., 200 Joncas, G., 185 Jones, A. C., 456, 462, 469 Jones, B. C., 1081, 1087 Jones, B. M., 213 Jones, C., 1079 Jones, C. A., 456, 462, 469 Jones, C. J., 681, 962, 964, 965 Jones, C. T., 273 Jones, D., 1065 Jones, D. B., 679 Jones, E. C., 1055 Jones, G. N., 198, 726, 733, 745, 1062 Jones, H. E., 712 Jones, I. H., 534, 535 Jones, J. F., 87, 236, 858, 863 Jones, L., 515, 516 Jones, L. B., 564 Jones, L. L., 402 Jones, L. W., 661 Jones, M., 901, 911 Jones, M. L., 854, 855 Jones, N. A., 1054 Jones, N. L., 998 Jones, R., 901, 911 Jones, R. F., 236 Jones, R. W., 901, 909 Jones, S. A., 338, 594, 596, 598 Jones, S. B., 65, 222 Jones, S. L., 330 Jones, T., 437 Jones, T. H., 605 Jones, W. K., 175 Jones-Carson, J., 1002 Jongh, R. D., 533, 536, 537, 538 Jonker, C., 186, 361, 362, 386 Jonsson, C. E., 113 Jonsson, H., 689, 1062 Jonsson, K., 827
Author Index Jonuleit, H., 1024 Joos, G., 810 Joos, G. F., 100, 101, 102, 104, 107, 111, 115, 219 Joos, S., 645–46 Joosten, L. A., 143 Jordal, R., 1056 Jordan, C., 551 Jordan, D., 87 Jordan, M. C., 856 Jorgensen, C., 222 Jorgensen, L. N., 830 Jorgensen, M. J., 485 Jorgensen, M. M., 625, 763, 766 Jormsjo, S., 882 Josenando, T., 586 Joseph, J., 240, 1060 Joseph, J. A., 383 Joseph, L. E., 665, 669 Joshipura, K., 956 Josipovic, D. B., 222 Jostock, T., 144 Joswig, M., 72, 965 Jotereau, F., 692 Jou, I., 136 Joubert, D., 565 Jouret, B., 603 Journot, L., 133 Jousilahti, P., 957 Joy, J. E., 557 Joyce, 715 Ju, G., 292, 644, 645, 653 Juarez, I., 386 Juarranz, M. G., 104, 143, 144, 146, 200 Juarranz, Y., 135, 146 Jucker, M., 382, 386 Judovish, R., 515 Juge-Aubry, C. E., 995, 997 Juhan-Vague, I., 932, 957 Juhasz, A., 361 Juhng, K. N., 1108 Juijper, P. H., 985 Julian, L., 681, 695, 1110 Julia-Sellers, M., 1063 Julien, J. P., 385, 444 Julius, D., 102, 394 Julkunen, I., 1100 Jun, L., 362 Jun, T. Y., 571 Juneau, M., 792, 937 Jung, C., 877 Jung, J., 70, 71, 1078 Jung, S., 136, 952 Jung, W., 516, 556 Jungk, C., 684, 691 Juric, D. M., 421 Jurkowlaniec, E., 555 Jurkowski, M. K., 555
Jury, J., 1024 Just, I., 1046 Justen, H. P., 200, 223 Justice, A., 233, 236 Justicia, C., 420 Kaal, G., 1115 Kabat-Zinn, J., 622, 901, 909, 910, 913 Kabesch, M., 816 Kabiersch, A., 73, 222 Kabingu, E., 1015, 1023, 1024, 1025 Kademian, S. M., 480 Kadowaki, T., 999, 1001 Kadoya, C., 419 Kaechele, H., 871 Kaell, A., 685, 791 Kaemingk, K., 485 Kaestner, F., 511 Kafatos, F. C., 337 Kagan, B. L., 399 Kagan, J., 485, 713, 1063 Kagan, V. E., 839 Kagawa, J., 255 Kage, R., 108, 1115 Kagiwada, K., 274 Kagnoff, M. F., 1057 Kagoura, M., 109 Kahana, E., 364 Kahanna, B., 539 Kahari, V. M., 840 Kahler, C. M., 107 Kahn, A., 362 Kahn, B. B., 1000 Kahn, C. R., 174 Kahn, M. M., 1043, 1044 Kahn, R. L., 498, 499 Kahn, R. S., 522 Kahn, S., 553 Kahn, S. E., 287 Kahneman, D., 626 Kai, Y., 293 Kaibara, A., 297 Kaiser, M., 164, 165, 166 Kaiser, T., 926 Kaiserlian, D., 240, 725, 732 Kaisho, T., 99, 337, 1025 Kaissling, B., 400 Kajander, K. C., 397 Kajekar, R., 809 Kaji, R., 364, 365 Kakihara, K., 554 Kakimoto, M., 998 Kakita, A., 565, 569 Kakizaki, M., 142 Kakucska, I., 286 Kakumu, S., 554 Kakuta, S., 274 Kalden, J. R., 193, 222
1177 Kaldi, K., 882 Kaleda, V. G., 567 Kalehua, A. N., 430 Kalenic, S., 532, 536 Kales, A., 588, 594, 599, 606, 608 Kalichman, S. C., 1061 Kalin, N. H., 488, 712, 713, 773, 913, 1079 Kaliner, M., 74 Kaliner, M. A., 110, 131 Kalinichenko, V. V., 74, 236, 1058, 1065 Kalinkovich, A., 1053 Kalinski, P., 219 Kalita, A., 186 Kalkers, N. F., 148 Kallehave, F., 830 Kallenbach, J. M., 222 Kalman, B. A., 724, 727, 734, 745 Kalman, J., 361 Kalogeras, K. T., 222 Kalra, P. S., 297 Kalra, R., 89 Kalso, E., 405, 710 Kalthoff, F. S., 978 Kaltreider, H. B., 103, 115, 131, 133 Kaltsas, G. A., 294 Kaltschmidt, C., 261 Kamachi, M., 212, 214 Kamae, T., 1000, 1001 Kamarck, T., 788, 966, 967 Kamarck, T. W., 714, 715 Kamata, M., 522, 523 Kambe, M., 960 Kamboh, M. I., 364, 365 Kameda, W., 1000 Kamei, D., 322 Kamei, Y., 137 Kamen, R., 419 Kameyama, T., 623, 859 Kamfar, H. Z., 502 Kamijima, K., 519 Kamilaris, T., 54, 197, 737, 739, 741, 980 Kamimori, K., 1001 Kaminska, T., 570, 571 Kaminsky, D. E., 663 Kaminsky, L., 668 Kaminsky, L. A., 668 Kaminsky, S. G., 1109 Kamitani, W., 342 Kamiya, S., 862, 1045 Kammer, G. M., 1058 Kammer, T., 420 Kammer, W., 998 Kamon, J., 1001 Kamoske, G., 361 Kamouchi, M., 420 Kampert, J. B., 666 Kampinga, H. H., 1015, 1023
1178 Kamradt, M. C., 237 Kamsler, A., 345, 346, 348, 349, 355, 358, 646 Kamtsirius, P., 977 Kan, L., 786 Kan, Y., 134, 135, 136, 137 Kanaan, S. A., 300 Kanabrocki, E. L., 594 Kanada, S., 303 Kanai, A. J., 102 Kanaka-Gantenbein, C., 712 Kanakura, Y., 1000, 1001 Kanazawa, S., 1018 Kanba, S., 357 Kanbour, A., 879 Kanda, N., 209 Kandefer-Szerszen, M., 570, 571 Kandel, E., 631, 632 Kane, J., 563 Kaneda, Y., 258, 998 Kaneko, A., 143, 200 Kaneko, H., 522 Kaneko, T., 52, 321, 323, 326, 327, 331 Kanemoto, T., 106 Kaneta, T., 300, 306 Kang, D. H., 622, 815, 913, 986 Kang, D.-H., 786 Kang, E., 620 Kang, J., 361 Kang, J. D., 400 Kanik, K. S., 196, 197, 222 Kannan, Y., 106 Kannel, W. B., 945, 957 Kanodia, R., 277 Kanoh, Y., 999 Kanosue, K., 323, 326, 330 Kant, J., 53 Kantartzis, K., 997, 1000 Kantrowitz, F. G., 586 Kanzler, H., 99 Kao, R., 710 Kapas, L., 601 Kapás, L., 587, 589 Kaplan, B. H., 694 Kaplan, D., 184, 360 Kaplan, G. A., 234, 498, 499, 500, 769, 781, 782, 872, 947 Kaplan, J., 681, 921, 928, 935 Kaplan, J. P., 483 Kaplan, J. R., 483, 484, 485, 486, 787, 792, 929, 1080, 1111 Kaplan, L. M., 1002 Kaplan, M. D., 358 Kaplan, M. S., 744 Kaplan, R. M., 623 Kaplan, S., 637, 732, 743 Kaplan, S. B., 197 Kaplowitz, L. G., 1088 Kapoor, S., 598, 599
Author Index Kapoor, S. C., 599 Kapp, A., 976, 978, 984, 985, 987 Kappel, M., 67 Kaprio, J., 193, 233, 769, 770, 812, 870 Kapsenberg, M. L., 219, 604, 735 Kapuku, G., 966, 967 Kar, S., 184 Karacay, B., 134 Karadeniz, D., 599 Karadi, I., 422 Karaeren, N., 1002 Karagounis, L. A., 927 Karalis, K., 112, 200, 740 Karaszewski, J., 463 Karaszewski, J. W., 712 Karaszweski, J., 786 Karatzas, D., 969 Kardish, M., 1055 Karim, A. S., 811 Karin, L. D., 516 Karin, M., 52, 53, 177, 383, 741, 1000 Kariya, K., 419 Kariya, Y., 252 Karjalainen, J., 662, 663, 668 Karjalainen-Lindsberg, M. L., 416, 417 Kark, R. M., 741 Karl, M., 1112 Karlsen, B., 716 Karlsson, A., 839 Karlsson, H., 277, 567 Karmacharya, J., 842 Karmaus, W., 470 Karmazyn, M., 1016 Karnovsky, M. L., 584, 584ÿ Karol, M. H., 725, 732 Karoly, P., 788 Karow, M., 1099 Karp, J., 645 Karp, J. D., 1080, 1083 Karre, K., 217 Karson, C. N., 564 Karst, M., 646 Karstadt, L., 713 Karttunen, J. T., 1023 Karvelas, M., 74 Kasahara, K., 70 Kasahara, T., 741 Kasahara-Orita, K., 330 Kasckow, J. W., 533, 536, 543 Kaseda, S., 258 Kaser, A., 108 Kashani, J. H., 198, 609 Kashi, Y., 1015 Kashiba, H., 109 Kashiwagi, H., 1000, 1001 Kaski, J. C., 937 Kasl, S. V., 714, 769 Kaslow, R., 1053 Kasper, C., 981
Kasper, D. L., 464 Kasprowicz, D. J., 65, 66, 73, 74, 75, 99, 1042, 1044, 1045 Kassam, N., 142 Kassel, R. L., 995 Kassiotis, G., 47, 48, 352, 354, 360 Kassotakis, L., 161 Kast, W., 878 Kaste, M., 416, 417, 422 Kasten-Jolly, J., 77 Kastin, A. J., 87, 381 Kastl, S. P., 72 Kataeva, G., 107 Katafuchi, T., 274, 356, 635, 1024 Katakami, N., 997 Katakami, Y., 997 Katamura, K., 73 Kataoka, T., 1001 Kataoka, Y., 296, 523 Katayama, M., 97 Katcher, A. H., 1088 Kathman, S. J., 1107 Kato, H., 116, 148, 1000, 1001 Kato, K., 863 Kato, R., 357, 859 Kato, T., 1000 Katoh, H., 323, 326, 327 Katoh, N., 977 Katon, W. J., 531, 815 Katouli, M., 1024 Katsarava, Z., 651 Katsaros, D., 881 Katsetos, C. D., 1109 Katsikis, P. D., 143 Katsouyanni, K., 933 Katsuki, H., 353 Katsumata, S., 87 Katsumata, U., 115 Katsumata, Y., 223 Katsuura, G., 321 Katsuyama, M., 326 Kattenhorn, M., 1000 Katus, H. A., 959 Katz, A., 1115 Katz, G. G., 554 Katz, J., 181, 380 Katzenstein, D., 166 Katzenstein, D. A., 1055 Katzer, L., 715 Katz-Levy, Y., 1110 Kauffman, H. F., 66, 73 Kauffmann, R., 689 Kauffmann, R. H., 1060 Kaufhold, R. M., 863 Kaufman, I. C., 479, 485 Kaufman, S., 539 Kaufmann, A., 1100 Kaufmann, P. G., 695 Kaufmann, S. H., 98, 1015
Author Index Kaufmann, W. E., 322, 358 Kaul, M., 1054 Kaulbach, H. C., 131 Kaun, C., 72 Kaur, C., 402 Kaur, I., 853, 854, 855 Kaushansky, K., 741, 858 Kavaliers, M., 284, 306, 307, 828 Kavanagh, T., 303, 662 Kavelaars, A., 40, 41, 63, 65, 68, 69, 72, 76, 164, 172, 200, 242, 679, 726, 739, 1044, 1045, 1046 Kaveri, S., 220 Kawa, S. K., 1056 Kawachi, I., 497, 498, 500, 623, 713, 714, 948 Kawaguchi, H., 322 Kawahito, Y., 116, 193 Kawai, S., 738 Kawai, T., 381 Kawakami, H., 364, 365 Kawakami, M., 400 Kawakami, T., 1014 Kawamoto, R., 769 Kawamoto, T., 1001 Kawamura, A., 235 Kawamura, M., 565 Kawamura, N., 99, 533, 535, 536, 537, 785 Kawamura, T., 605 Kawano, M., 87 Kawano, T., 184 Kawanokuchi, J., 148 Kawasaki, H., 239 Kawasaki, S., 1018 Kawasaki, T., 208 Kawashima, E., 103, 132 Kawashima, K., 88, 105 Kawashima, N., 306 Kawate, T., 569, 744 Kay, A., 199 Kay, A. B., 55 Kay, D. R., 609 Kay, G., 456, 712 Kayahara, T., 329 Kaye, D., 623 Kaye, J., 134 Kaye, P. M., 1091 Kayhko, K., 736 Kaynak, H., 599 Kazamtsuri, H., 569 Kazatchkine, M. D., 220, 1059 Kazemi, M. R., 959 Kazimirsky, G., 106 Kean, R., 567 Keane, M. P., 1100 Kearney, K. A., 713 Kearns, G., 523 Keates, A. C., 115
Keay, K. A., 294 Keck, C., 419 Keeble, J. E., 195, 200 Keef, F. J., 979 Keegan, A. D., 998 Keegan, B. P., 241 Keet, I. P., 1053, 1060 Kehoe, P. G., 365, 366, 421 Kehrl, J. H., 74 Keiser, J. A., 736 Keisler, D., 201 Keith, I. M., 117 Kel, A., 53 Kelders, M. C., 182 Kelleher, R. J., 3rd., 356 Keller, C., 662, 1016, 1018, 1022 Keller, E. T., 380 Keller, H. H., 64, 65, 70 Keller, P., 662, 996 Keller, P. M., 863 Keller, S., 784 Keller, S. E., 510, 514, 516, 549, 550, 551, 552, 553, 622, 623, 727, 743 Kellerer, M., 999 Kelley, J., 1023 Kelley, K., 171, 186, 187, 291, 292, 298, 382 Kelley, K. W., 41, 66, 171, 172, 174, 175, 177, 180, 181, 182, 183, 184, 185, 223, 273, 274, 277, 281, 282, 283, 284, 286, 288, 290, 294, 296, 297, 298, 300, 301, 302, 303, 304, 305, 307, 308, 320, 337, 338, 339, 381, 382, 384, 385, 386, 387, 397, 422, 430, 431, 432, 444, 456, 518, 603, 622, 732, 733, 734, 923, 934, 935, 936, 995, 996, 998, 1000, 1058 Kelley, M. E., 570 Kellner, A., 768 Kellner, M., 540 Kelly, A., 353 Kelly, C., 1015, 1016, 1023 Kelly, C. G., 1015, 1023 Kelly, C. J., 997 Kelly, C. P., 115 Kelly, D. D., 236 Kelly, J. A., 1062 Kelly, J. F., 323, 324, 325, 326, 328, 329, 330 Kelly, J. M., 47 Kelly, J. P., 295, 305 Kelly, K., 632, 651 Kelly, M., 662 Kelly, O., 304 Kelly, P., 1002 Kelly, S., 1015 Kelly, T., 586 Kellyey, Keith W., 281 Kel-Margoulis, O., 53
1179 Kelsall, B. L., 1091 Kelsay, K., 982 Kelsey, M. E., 531 Kelsey, S. F., 717 Kelsoe, J., 307 Keltikangas-Jarvinen, L., 931 Kemeny, A. E., 453 Kemeny, D. M., 977 Kemeny, M., 532, 535, 537, 676, 678, 689, 691, 692, 784, 790 Kemeny, M. E., 237, 261, 497, 537, 619, 620, 621, 622, 623, 624, 625, 688, 713, 763, 765, 766, 772, 773, 774, 784, 790, 877, 881, 1057, 1058, 1060, 1062, 1063, 1064, 1065, 1088 Kemeny, Margaret E., 619 Kemmler, G., 569 Kemnitz, J. W., 468 Kemp, A. S., 975–76, 982 Kemp, G. J., 149 Kempen, G. I. J. M., 769 Kemper, A., 65, 1044, 1045 Kemper, P., 384 Kempermann, G., 340, 359 Kempthorne-Rawson, J., 871 Kempuraj, D., 113 Kenchappa, P., 186 Kendall, E. C., 737 Kendall, G., 407 Kendall, M. D., 461 Kendler, K. S., 514 Kenis, G., 422, 515, 533, 536, 537, 538, 551, 570, 571, 969, 1115 Kennedy, B., 510, 518, 606, 607 Kennedy, B. P., 500, 729, 934 Kennedy, J. L., 113 Kennedy, L. R., 1040 Kennedy, M., 650, 651 Kennedy, R. L., 605 Kennedy, S., 450, 482, 512, 676, 734, 784, 785, 788, 858, 863, 869, 871, 872, 884, 899, 900, 904, 1013, 1019, 1022, 1065 Kennedy, S. L., 71, 517, 662 Kennedy, S. T., 714, 717 Kennedy, Sarah, 475 Kennedy-Moore, E., 624, 764, 766 Kenny, C. D., 332 Kenny, D. A., 1064 Kent, G. G., 725, 726, 733, 745 Kent, S., 282, 283, 286, 288, 294, 297, 298, 337, 338, 339, 382, 518, 640 Kent, W. D., 306 Kenyon, C., 173, 174 Keranen, T., 186 Kercher, C., 554 Keren, G., 966 Kern, A. M., 1080, 1086, 1087 Kern, P. A., 1000
1180 Kern, W., 590, 599 Kernoff, P. B., 1053 Kerns, R., 686 Kerns, R. D., 790 Kerr, I. M., 137 Kerr, L. R., 233 Kerr, P. E., 805 Kerschensteiner, M., 106 Kertzner, R., 1060, 1061 Kerza-Kwiatecki, A. P., 436 Keshavarzian, A., 551 Keshet, G. I., 712 Kessler, J., 569 Kessler, J. A., 359 Kessler, M. J., 476 Kessler, O., 224 Kessler, R. C., 538, 553, 762, 785, 1060 Kester, M. H., 72 Ketchem, R. R., 338 Keuning, F. J., 727 Keverne, E. B., 491 KewalRamani, V. N., 1053 Kewenter, J., 133 Keys, M., 727 Keyser, L. A., 712 Keystone, E., 587 Khachaturian, A. S., 383 Khalsa, J., 554, 555 Khamis, I., 1060, 1061 Khamlichi, A. A., 74 Khan, M. M., 66, 73 Khandwala, H. M., 173, 180 Khanis, I., 687, 688 Khanna, H. D., 1037 Khanna, K. M., 1079, 1083, 1088 Khansari, D. N., 724, 733 Kharazmi, A., 89 Kharbanda, R. K., 960 Khare, S., 237 Khavari, P., 252 Kheir-Eldin, A. A., 303 Khew-Goodall, Y., 839 Khong, H. T., 879 Khoruts, A., 551 Khot, M. B., 946 Khot, U. N., 946 Khovidhunkit, W., 959 Khuri, E., 1101 Ki, C. S., 364 Kibler, J. L., 931 Kidd, B. L., 200 Kidd, G. S., 1054, 1055 Kidman, A. D., 873 Kieburtz, K., 1057 Kiechl, S., 957 Kiechle, R., 290, 381 Kiecolt-Glaser, J., 676, 677, 682, 683, 684, 685, 686, 688, 694, 695, 869, 870, 874, 883, 888, 1079
Author Index Kiecolt-Glaser, J. K., 63, 77, 112, 236, 237, 380, 499, 512, 514, 538, 623, 677, 682, 685, 723, 724, 726, 733, 734, 745, 747, 768, 771, 774, 781, 782, 783, 784, 785, 786, 787, 788, 789, 790, 792, 793, 801, 811, 812, 814, 816, 827, 842, 846, 856, 858, 861, 863, 881, 882, 883, 884, 888, 899, 900, 901, 902, 904, 906, 907, 908, 910, 913, 934, 962, 1019, 1062, 1063, 1065, 1079, 1080, 1083, 1088, 1099, 1111 Kiecolt-Glaser, Janice, 705, 706 Kiecolt-Glaser, Janice K., 781 Kiefer, R., 416, 417 Kiefer, S., 646 Kieff, E., 236 Kieffer, B. L., 160, 167 Kiehl, R., 983 Kieko, F., 417 Kiel, M., 586 Kielty, C. M., 831 Kienast, J., 923, 926 Kiess W., 1000 Kiessling, R., 1016 Kiff, J., 773, 1063 Kihara, S., 997, 1000, 1001, 1003 Kihara, T., 432 Kikkawa, F., 882 Kikkawa, H., 252 Kikuchi, Y, 55 Kikuchi-Utsumi, K., 1022 Kikuchi-Utsumi, M., 1022 Kilbinger, H., 100, 105 Kilbourn, K., 687, 691 Kilbourn, K. M., 1055 Kilby, J. M., 1059 Kilimann, M. W., 995 Killam, A. P., 1088 Killebrew, D., 237, 683 Killeen, N., 338 Killestein, J., 148 Killion, J. J., 257 Kiloh, L., 676 Kiloh, L. G., 734, 784 Kilpelainen, M., 807 Kim, B. S., 1110, 1115 Kim, C., 727, 743, 789 Kim, C. J., 879 Kim, C. K., 813 Kim, D., 149, 1038 Kim, D. J., 553 Kim, D. K., 364, 1046 Kim, D. S., 213 Kim, H., 511, 515, 571, 994 Kim. H. B., 842 Kim, H. J., 364 Kim, H. S., 400 Kim, H. Y., 76
Kim, J. E., 1056 Kim, J. H., 1056 Kim, J. J., 357, 568, 986 Kim, J. S., 553 Kim, J. W., 364, 571 Kim, K. H., 624, 625 Kim, K. S., 571 Kim, L., 294 Kim, M. K., 571 Kim, M. S., 959 Kim, S. J., 571 Kim, S. U., 147 Kim, U., 74 Kim, W., 553 Kim, W. K., 134, 136 Kim, W. U., 76 Kim, Y., 533, 535, 536, 537, 605, 879 Kim, Y. K., 511, 515, 553, 571 Kim, Y. S., 812 Kim, Y. W., 1015 Kimata, H., 101, 107, 115, 625, 766, 813 Kimata, K., 831 Kimber, I., 732, 995 Kimmel, S. C., 55, 980 Kimmerling, R., 531 Kim-Miller, M., 107, 108 Kimura, H., 272, 863 Kimura, K., 115 Kimura, M., 598 Kimura, S., 116, 1001 Kimzey, S. L., 855 Kin, N. W., 75, 77 Kincade, P. W., 199 Kinchington, P. R., 1079, 1083, 1088 Kindermann, W., 663 Kindlon, D. J., 498 Kindy, M. S., 419 King, D. S., 1063 King, L., 761 King, M., 650, 651 King, M. G., 600, 644, 645, 653, 801, 1063 King, R. M., 979 King, S. M., 837 King, S. R., 1058 King, Y. T., 1015 Kingsley, G., 193, 197, 201, 981 Kingsley, L. A., 487, 1053, 1054, 1058 Kingston, R. E., 1014 Kingwell, B. A., 662 Kinne, R. W., 210 Kinney, F. C., 725, 726 Kinney, K. S., 854 Kinnunen, E., 859 Kino, T., 980, 1054, 1055, 1056 Kinon, B. J., 564 Kinouchi, K., 338 Kinsley, C. H., 712 Kintzel, J. A., 1025
Author Index Kinzler, K. W., 235, 237 Kiraly, E., 102 Kirby, J. A., 879 Kirch, D. G., 566, 570 Kirch, W., 592 Kirchhoff, F., 402, 406 Kirchhoff, S. R., 1014 Kirchner, H., 510, 565, 566, 568, 569, 570 Kirerleri, E., 1002 Kirjonen, J., 717, 948 Kirken, R. A., 997 Kirkpatrick B., 567 Kirkpatrick, C., 802 Kirkpatrick, C. H., 745 Kirkpatrick, C. J., 89, 100, 105 Kirkup, A. J., 116 Kirkwood, J., 786, 787, 792, 876 Kirkwood, T. B., 220, 379 Kirschbaum, C., 72, 302, 465, 514, 540, 542, 637, 652, 712, 772, 854, 884, 965, 981 Kirschbaum, J. G., 522 Kirschboum, C., 912 Kirschning, C. J., 68, 1015, 1024, 1025 Kirsner, R. S., 845 Kirson, D. A., 1054 Kirtley, L. G., 827, 842 Kirwan, J. R., 198 Kishi, M., 567 Kishida, K., 1000, 1001 Kishihara, K., 352 Kishimoto, S., 977 Kishimoto, T., 54, 144, 338, 365, 959, 995, 1115 Kishiyama, J. L., 103, 115, 131, 133 Kisich, K. O., 521 Kisiel, W., 926 Kislyakova, K., 1019 Kiso, Y., 106, 353 Kiss, A., 196 Kiss, E., 1015 Kiss, H., 462 Kiss, S., 102 Kist, D., 277 Kisterman, J. P., 1055 Kita, H., 817 Kita, M., 198 Kitada, C., 1002 Kitagaki, K., 807 Kitagami, T., 523 Kitagawa, A., 197 Kitajima, I., 344, 352 Kitamura, A., 957 Kitamura, T., 174 Kitamura, Y., 106, 110, 605 Kitano, K., 1057, 1058 Kitasako, J. T., 401 Kitazawa, T., 104
Kitazono,T., 420 Kitchen, C. R., 1065 Kitson, R. P., 724, 745, 1099 Kittel, F., 961, 962 Kiviat, N. B., 711 Kivimaki, M., 717, 948 Kivisakk, P., 436 Kivlahan, D. R., 531 Kiyohara, T., 1003 Kiyono, H., 107 Kizaki, T., 736, 1045 Kizer, D., 717 Kjaeldgaard, A., 359 Kjaersgaard, E., 1043 Kjems, J., 1053 Klaassen, T., 307 Klag, M. J., 714 Klapp, B. F., 113 Klatzmann, D., 149 Klauber, M. R., 579, 586 Klebanoff, M. A., 566 Klee, M., 584 Klein, C., 435 Klein, E., 874, 880 Klein, H. G., 256, 258 Klein, J. S., 104 Klein, M. H., 712, 713 Klein, M. R., 1060 Klein, N., 712, 964 Klein, N. J., 958, 960 Klein, N. K., 466 Klein, R. M., 430 Klein, S. L., 236, 456 Klein, T., 606 Klein, T. W., 342, 344, 347 Kleinman, H. K., 224, 831 Kleinschmidt-DeMasters, B. K., 859 Kleitman, N., 580 Klenk, H. D., 1099 Kliewer, S., 53 Klimas, N., 532, 535, 537, 538, 676, 679, 680, 682, 683, 685, 686, 687, 688, 689, 690, 695, 1055, 1056, 1057, 1058, 1060, 1061, 1080, 1088 Klimas, N. G., 773, 774, 1057, 1060, 1062, 1079 Kline, T. M., 50 Kling, A. S., 727 Kling, D. W., 1060, 1063 Kling, M., 677 Klingenberg, C. P., 379 Klinger, M., 959 Klinkert, W. E., 106, 733, 735, 746 Klinman, D., 405 Klinman, D. M., 196, 859 Klinnert, M. D., 469, 799 Klionsky, D. J., 275 Klir, J. J., 286, 302 Kliushnik, T. P., 567
1181 Klockgether, T., 365 Klonoff-Cohen, H., 770 Kloodt, A. R., 359 Klopp, R. G., 361, 467 Kloss, C. U. A., 402 Klosterman, L. L., 482 Klover, P. J., 995 Klug, C., 291, 321, 432 Klug, L. A., 380 Kluger, M. J., 282, 285, 298, 299, 301, 302, 303, 556, 736 Klunker, S., 978, 985 Kluter, A., 198 Klutke, C. G., 110 Klyushnik, T. P., 567 Knable, M. B., 565 Knapp, J. E., 872, 887 Knapp, M., 365 Knapp, P. H., 763, 765, 766, 772 Knazek, R. A., 738 Knehans, A., 745 Knekt, P., 870 Knight, K. R., 399 Knight, R. A., 740 Knighton, D. R., 827 Knoblach, S. M., 416, 420 Knook, M. M., 256 Knopf, G., 479 Knopf, M. A., 115 Knopf, S., 516, 556, 743 Knott, B., 456 Knottenbelt, C., 957 Knowler, W. C., 715, 1000 Knowlton, A. A., 1014 Knowlton, B. J., 340 Knox, R. M., 882 Knox, S., 769 Knudsen, J. H., 1043 Knudsen, P. J., 85, 542 Knudsen, S., 839, 841 Ko, G. N., 541 Kobasa, S., 686 Kobayashi, H., 69, 133, 432, 1001 Kobayashi, J., 73 Kobayashi, K., 998 Kobayashi, M., 69, 237 Kobayashi, N., 223 Kobayashi, S., 97, 273, 321, 322, 326, 327, 328 Kobayashi, T., 326, 329, 342 Kobayashi, Y., 840, 1001 Kobilka, B. K., 235, 1041 Kobzik, L., 810 Kocevar, V. S., 813 Koch, A. E., 142, 224 Koch, H., 984 Koch, H. U., 981 Koch, S., 740 Kochman, A., 792
1182 Kochwa, S., 557 Kocijan-Hergigonja, D., 532, 535, 537 Kockerling, F., 107 Kockler, M., 364, 421 Kocyigit, Y., 1002 Kodama, A., 979 Kodama, K. T., 100 Kodys, K., 85, 554 Koehl, M., 465 Koehler, K. M., 669 Koek, G. H., 277 Koelle, D. M., 1079, 1086 Koelling, R., 632 Koenderman, L., 55, 741, 985 Koenen, M., 1000 Koenig, H. G., 714, 782 Koenig, W., 932, 937, 955, 957 Koerner A., 1000 Koethe, D., 594, 598 Koets, A., 1015 Koff, W. C., 1044, 1082 Kofler, S., 817 Koga, C., 623 Koga, Y., 71 Kogevinas, M., 498 Kogon, M. M., 873 Kogure, K., 418, 432 Koh, K. B., 623 Koh, Y. I., 800 Koh, Y. Y., 813 Kohanawa, M., 1110 Kohda, M., 763, 765, 766 Kohjima, M., 998 Kohler, C., 307 Kohler, P. C., 521 Kohler, P. F., 460 Kohm, A., 635 Kohm, A. P., 63, 64, 65, 66, 67, 70, 74, 75, 77, 149, 194, 222, 1042, 1044, 1045 Kohman, R. A., 342 Kohn, E. C., 881 Kohn, R., 870 Kohn. R., 233 Kohno, M., 106, 419 Kohno, T., 344, 357 Kohsaka, S., 407 Kohut, M. L., 70, 517, 662, 663, 764, 767, 900, 906, 1046 Koivisto, A. M., 364 Koivumaa-Honkanen, H., 769, 770 Koizumi, A., 999 Koizumi, S., 407 Koizumi, T., 997 Kojima, S., 863 Kojima, Y., 98, 109, 115 Kokaia, Z., 359, 386 Kokka, R. P., 487 Kokkinidis, L., 305
Author Index Kokmen, E., 440 Kokovay, E., 272 Koksvik, H. S., 220 Kokunai, T., 235 Kol, A., 926, 927, 938, 1016 Kolb, H., 996, 1016, 1024 Kolb, L. C., 541 Kolbeck, R., 106 Kolbus, A., 53 Koldzic, D. N., 420 Kolesnitchenko, V., 1056 Kolhagen, H., 876 Koliaskina, G. I., 570 Kolibal-Pegher, S. S., 1019 Koller, B. H., 326 Koller, T., 222 Kollias, G., 284, 352, 354, 360, 440 Kolsch, H., 364, 421 Koma, Y., 110 Komeda, K., 1001 Komesaroff, P. A., 211 Komesli, S., 420 Komi, J., 219 Komori, S., 133 Komori, T., 842 Komuro, R., 1000, 1001 Konan, K. V., 522 Kondo, H., 361, 1000 Kondo, M., 116 Kondo, T., 841, 842, 1024 Kong, M., 275 Kong, P., 1065 Kong, W., 109 Kong, Y., 133, 134, 140, 141 Kongshavn, P., 1037 Koniaris, L. G., 995 Konig, D., 666 Konig, M., 323, 326 Konig, N., 1115 Konig, W., 161 Konishi, M., 330 Konowal, A., 440 Konrad, I., 951, 952 Konradsen, H., 663 Konsman, J., 622 Konsman, J. P., 99, 112, 272, 273, 274, 277, 281, 288, 290, 291, 292, 293, 294, 295, 320, 321, 338, 382, 422, 431, 432 Konstantinides, S., 1000, 1001, 1002 Konstantinos, A., 70, 71, 1078 Konstantinos, A. P., 1080, 1100 Konstantinova, I., 855, 862 Konstantinova, I. V., 855 Kontogeorgos, G., 352 Koo, G. C., 1015, 1023, 1024, 1025 Koo, H. G., 571 Koob, G. F., 520, 522, 555 Koochesfahani, K. M., 273
Kool, M., 109 Koolhaas, J., 745 Koolhaas, J. M., 479, 480, 484, 1036, 1046, 1080 Koopman, C., 783, 790, 876, 884 Koopman, C. F., 826 Koot, M., 1053, 1060 Kop, W., 937 Kop, W. J., 917, 918, 921, 928, 929, 931, 932, 933, 934, 935, 936, 964, 966, 967 Kopf, M., 1115 Kopinsky, K. L., 688, 811 Kopp, H., 959 Kopp, M. S., 931 Koppeschaar, H. P., 186 Koprowski, H., 567 Kops, S. K., 110 Korczyn, A. D., 1110 Korhonen, P., 383 Korin, Y. D., 74, 237, 261, 1057, 1058 Korn, H., 274 Kornely, E., 198 Korner, A., 884 Kornhuber, J., 981 Kornmüller, A., 584 Koropchak, C. M., 861 Korschenhausen, D., 1115 Korszun, A., 681, 962, 964, 965 Kort, M. E., 48 Kort, W. J., 724, 733 Korte, S., 745 Korte, S. M., 479, 480, 484, 1036, 1046 Korth, C., 586, 589, 590, 601, 605 Korvick, J. A., 1053 Korzun, A., 234 Koschnick, S., 1000 Kosco-Vilbois, M. H., 74 Koshak, E. E., 502 Koshorek, G., 587 Koskenvuo, M., 193, 769, 770, 789, 807 Koskenvuo, M. S., 870 Koski, G., 584 Koski, I. R., 732, 735 Koskikallio, E., 186 Koskiniemi, M., 859 Koskiniemi, S., 859 Kosno-Kruszewska, E., 565 Koss, M. P., 531, 713 Kosslyn, S. M., 710 Kossmann, T., 148, 417, 419 Kossoff, M., 869, 871, 872 Kostakis, G., 969 Kostelny, K., 498 Kosten, T. R., 539, 540 Kostis, J. B., 957 Kostka, T., 666 Kostulas, N., 416, 417 Kostulas, V., 416, 417
Author Index Kotani, K., 1000 Kotanidou, A., 816 Kotchabhakdi, N., 557 Kotler, D. P., 1054, 1059 Kotler, S., 543 Kotoh, K., 998 Kotsinas, A., 1056 Kottapalli, V., 551 Kotur, M., 676, 858, 863, 1088 Kou, W., 637, 645, 646, 650, 651, 652, 1039, 1040 Kouassi, E., 69, 74 Koukoulas, I., 1014, 1016, 1022 Kouro, T., 199 Kouyoumdjian, J. C., 209, 210 Kovacs, E. J., 552, 553, 554, 840, 841 Kovacs, K., 200 Kovacs, K. J., 293, 321, 328, 329, 843, 997 Kovacs, M., 686, 815 Kovacs, W. J., 462 Kovak, N., 1115 Kovaleva, G., 646 Koverola, C., 539, 540 Koves, K., 321, 736 Kowalczyk, D. W., 879 Kowalewski, R., 1015 Kowalski, J., 570 Kowalski, M. L., 110 Kowalski, T. J., 995 Kowal-Vern, A., 553 Kox, W. J., 553, 554 Koyama, N., 223 Koyama, S., 88, 109 Koyama, Y., 51 Koyanagi, S., 523 Koyanagi, Y., 1057, 1058 Koyluoglu, O., 570, 571 Kozak, A., 89 Kozak, W., 298, 299, 303, 516, 556 Kozak, W. M., 110 Kozbor, D., 855 Kozlosky, C. J., 996 Kozlova, E. N., 403 Kozlovskaya, I. B., 853 Kozma, A., 769 Kozora, E., 362 Kraaij, V., 694 Kraaimaat, F. W., 977 Kraal, G., 725, 732, 733 Krabbe, K. S., 361, 363, 996 Kradin, R., 108, 534, 537 Krady, J. K., 419 Kraeft, S. K., 1015, 1023, 1024, 1025 Kraemer, H. C., 687, 692, 724, 725, 726, 747, 789, 879, 884 Kraemer, P. J., 419 Kraetsch, H. G., 222 Kraft, B., 557
Kraft, J. K., 461 Kraft, K., 235 Kraft, M., 603 Kraft, S., 978 Kraig, R. P., 277, 321 Krakenes, J., 420 Krakoff, J., 1000 Krakowski, M., 307 Kramer, J., 873 Kramer, J. R., Jr., 923 Kramer, K. A., 480, 1025, 1103, 1112 Kramer, M., 465, 712 Kramer, P. R., 210 Kramer, S. F., 210 Kramers, R. J., 386 Kraneveld, A. D., 109 Krantz, D. S., 762, 921, 929, 932, 933, 934, 935, 937, 964, 966, 967 Krasnoff, L., 788 Krasnolobova, S. A., 567 Kraszpulski, M., 712 Kratzsch, J., 1000 Krauhs, J. M., 853, 854 Kraus, J., 161 Kraus, J. F., 931 Kraus, L., 901, 907 Kraus, T., 223, 305, 362, 363, 570, 585, 594, 598, 609 Krause, A., 198, 200 Krause, D. S., 73 Krause, J. E., 103, 110 Krause, K. H., 385 Krause, N., 785, 787 Krause, P. R., 859 Kream, R. M., 303 Krebs, F. C., 1057 Kreek, M. J., 557, 1101 Kregel, K. C., 1014, 1015 Kreiker, C., 592 Kreis, M. E., 116 Kreisel, T., 345, 346 Kreiss, J. K., 1059 Kremastinos, D. T., 969 Kremsner, P. G., 470 Krenning, E. P., 100, 115 Kress, H. G., 557 Kreutzberg, G. W., 147–48, 402, 416, 433, 437 Kreutzer, D., 693 Krey, L. C., 832 Kricker, A., 870, 871 Krieg, J. C., 599 Krieg, M., 885 Kriegel, W., 789 Krieger, E., 1053 Krieger, J., 1054 Krieger, N., 500 Krieger, S., 361, 592, 594, 739, 741, 982 Krieglstein, J., 420
1183 Kriesel, J. D., 1080, 1081 Kriete, M. F., 485 Krilov, L. R., 1079 Kripke, D. F., 579, 586, 606 Krishnan, A. V., 239 Krishnan, K. R., 307, 540 Krishnan, R., 695 Krishnan, R. R., 962 Krishnaswamy, G., 1023 Kriss, J. P., 218 Kristensen, F., 584 Kristensen, J. H., 670 Kristensson, K., 277, 585 Kritchevsky, S., 361 Kritchevsky, S. B., 511, 924, 926, 956, 962 Kritschmann, E., 570 Kriynovich, S. J., 1025 Krochin, N., 738, 843 Kroegel, C., 108 Kroemer, G., 571, 572, 651, 738 Krohn, M., 711 Kroke, A., 1000 Krol, A., 1060 Kroll, P., 549, 551 Kromhout, D., 957 Krommydas, G., 815 Kronborg, G., 1057, 1058 Kronfol, Z., 422, 510, 512, 516, 549, 551, 603, 771 Kronheim, S. R., 996 Krönig, H., 568 Kronke, M., 352 Kronmal, R. A., 928 Kroonenberg, P. M., 813 Kropff, M., 882 Krouse, E. M., 712 Krueger, J., 584, 600 Krueger, J. M., 287–88, 331, 380, 583, 584, 585, 586, 587, 588, 589, 591, 600, 601, 605, 996 Kruesi, M., 695 Kruessel, J. S., 359 Krug, A., 1099 Kruger-Krasagakes, S., 273 Krugman, S., 828 Krupitza, G., 181 Krupp, L. B., 586 Kruse, M. L., 109 Kruse, S., 814 Krustrup, P., 1016, 1018, 1022 Kruszewska, B., 64, 69, 555, 1036 Kruth, H. S., 998 Krutman, J., 978 Kruys, V., 997 Krylov, V., 643 Krystal, J. H., 539, 540, 541, 570 Krzesicki, R. F., 385, 441 Krzych, U., 828
1184 Krzyszton, C., 384 Ku, G., 419 Kuang, F., 644, 645, 653 Kubata, B. K., 320, 322 Kubera, M., 305, 515 Kubin, M., 213, 338 Kubista, E., 690 Kubo, C., 329, 330 Kubo, K., 88 Kubo, M., 1058 Kubota, T., 331, 583, 586, 587, 601 Kubota, Y., 116 Kubulus, D., 1015 Kubzansky, L. D., 497, 498, 623, 713 Kuchler, T., 873, 887 Kuchroo, V. K., 140, 149 Kucia, K., 570 Kucia, M., 926 Kucinski, B. J., 743 Kucuk, O., 534, 535, 538 Kucuksezer, U. C., 978 Kudchodkar, S., 1056 Kudielka, B. M., 302, 963, 965 Kudler, H., 540 Kudo, I., 322 Kudo, T., 1039, 1040, 1041 Kudo, Y., 416, 417 Kudoh, A., 571 Kuhbacker, T., 144 Kuhl, P. W., 1045 Kuhla, B., 386 Kuhlmei, A., 113 Kuhlwein, E., 603, 604 Kuhn, C., 966 Kuhn, C. M., 497, 929, 930, 935 Kuhn, E., 599 Kühn, M., 570 Kuhn, R. W., 746 Kuhn, W., 361, 963 Kuhne, A. A., 540 Kuhns, A. J., 382 Kuida, K., 419 Kuijer, R. G., 790 Kuiper, J., 293 Kuiper, J. P., 831 Kuiper, S., 199 Kuiperij, H. B., 240 Kuis, W., 65, 72, 739 Kuitert, L. M., 54 Kuji, N., 223 Kukutsch, N. A., 142 Kulacki, R., 359 Kulchitsky, V. A., 290, 320 Kuldova, M., 238 Kulick-Bell, R., 538, 541 Kuliczkowski, W., 1000, 1001 Kulik, J. A., 787 Kuller, L., 361, 931 Kuller, L. H., 717, 923
Author Index Kulli, C., 1015 Kullmer, J., 241, 885 Kumada, M., 1001 Kumagai, K., 404, 744 Kumagawa, K., 342, 344 Kumagi, T., 554 Kumai, Y., 420 Kumanyika, S., 623 Kumar, A., 541, 684, 689, 1055 Kumar, A. M., 1055 Kumar, M., 539, 541, 677, 679, 680, 684, 686, 687, 688, 689, 691, 773, 784, 791, 792, 884, 1054, 1055, 1056, 1057, 1058, 1060, 1061, 1063, 1080, 1088 Kumar, M. L., 1088 Kumar, Mahendra, 531 Kumar, R. K., 131 Kumar, S., 586 Kumari, M., 501, 514, 542, 956, 961, 962 Kummer, W., 103, 110 Kundig, T. M., 352 Kung, L., 564 Kunicka, J. E., 55 Kunkel, G., 131 Kunkel, H. G., 209 Kunkel, S. L., 66, 72, 736, 841 Kunkel, S. R., 769 Kunkler, P. E., 277 Kuno, R., 1061 Kunugi, H., 567, 569 Kunz, J., 691, 877 Kunze, W. A., 105 Kunz-Ebrecht, S., 503, 505, 961, 962, 963, 965, 966, 968 Kunz-Ebrecht, S. R., 912, 965 Kuo, C. J., 842 Kuo, J., 638, 641 Kuo, K. W., 847 Kuo, T. B., 93 Kuo, Y., 105 Kuo, Y. M., 364 Kuper, H., 717, 946, 949 Kupfer, D., 676 Kupfer, D. J., 518, 607 Kupfer, J., 983 Kupfermine, M. J., 212 Kupper, D. J., 580 Kuraishi, Y., 186, 301 Kuramoto, N., 97 Kurata, Y., 1000, 1001 Kurcrock, R., 885, 886 Kuribayashi, K., 400 Kurimoto, M., 419 Kuriyama, H., 997, 1000, 1001 Kurlander, R. J., 1038 Kuroda, K., 330 Kuroda, M., 1018 Kuroiwa, H., 522
Kurokawa, R., 137 Kurokawa, Y., 663 Kuroki, T., 999 Kurosaka, K., 840 Kurosawa, M., 88, 290, 320 Kurth, D., 386 Kurth, S., 1044 Kurt-Jones, E. A., 1015, 1016, 1023, 1024, 1025 Kurtz, M. M., 101 Kurtzke, J. F., 1107, 1116, 1120 Kurtzman, S., 693 Kurumaji, A., 294 Kurumbail, R. G., 358 Kuruvilla, A. P., 193 Kurz, A., 363, 364, 365, 366, 421 Kushida, C. A., 596, 597 Kushikata, T., 588 Kushner, P. J., 50 Kushner, S. G., 570 Kushwaha, N., 51 Kusiak, J. W., 430 Kusnecov, A., 637, 651, 732, 733, 743 Kusnecov, A. V., 1080, 1083, 1084, 1087 Kusnecov, A. W., 238, 284, 300, 301, 306, 555, 725, 732, 1115 Kusunoki, Y., 858 Kuten, A., 874, 880 Kuter, B. J., 859 Kutz, I., 678, 933 Kutz, L., 691 Kutz, L. A., 236, 734, 856, 861, 875 Kuulasmaa, K., 946 Kuwabara, K., 998 Kuwabara, Y., 937 Kuwahara, M., 109 Kuzawa, C. W., 462 Kuziel, W. A., 1091 Kuzushima, K., 863 Kverno, K., 691 Kvetan, V., 997 Kvetnansky, R., 235, 238, 727, 729, 730, 732, 853, 1014 Kvikstad, A., 870 Kwee, L., 292 Kwekkeboom, D. J., 100, 115 Kwidzinski, E., 307 Kwiecien, O., 407 Kwok, R. P., 137 Kwon, D., 1115 Kwon, D. S., 1053 Kwon, M. K., 999 Kym, P. R., 48 Kyrou, I., 219 La Cava, A., 1003 La, M., 432 La Perriere, A., 532, 535, 537, 538 La Placa, M., 1058
Author Index La Scola, M. E., 287, 343, 347 Laakso, M., 364 Laakso, R.-L., 733, 745 Laban, O., 1118 Labbok, M. H., 464 LaBella, F. S., 1036 Labeur, M. S., 112, 733, 735, 746 LaBine, M., 729 Labott, S. M., 763, 764 Labouvie, E., 789 Labow, M., 292, 345 LaBrecque, D. R., 549, 550, 551 Laburthe, M., 133 Labuz, D., 162, 165, 166 Lacey, C. J., 1079 Lacher, U., 514, 622 Lachman, L. B., 1044 Laciak, M., 515 Lack, G., 801, 855 Lackman, C., 1053 Lackner, C., 512 Lacosta, S., 343, 347, 523, 652 Lacour, B., 253 Lacour, J., 666 Lacour, M., 73, 997 Lacroix, K., 668 Lacroix, S., 87, 294, 328, 432, 438 Lacroix-Desmazes, S., 220 Ladenius, A. R., 115 Ladogana, A., 440 Laduron, P. M., 161 Ladwig, K. H., 932, 937 Lafage-Proust, M.-H., 853, 863 Lafeber, F. P., 198 Laflamme, N., 386, 438 LaFleur, B., 93 Lafontan, M., 1000 LaForge, K. S., 741 Laforgia, A., 89 Lafuse, W. P., 65, 676 Lagente, V., 102, 103 Lager, D., 579 L’Age-Stehr, J., 1054 Lagioia, G., 420 Lago, A. D., 365, 421 Lago, C. T., 224 Lago, N., 419 Lagoo, A., 85 Lagoo, S., 85 LaGuardia, J. J., 859 Laharrague, P., 994 Lahita, R., 208, 828 Lahita, R. G., 207, 208, 209, 211, 212, 213 Lahners, K. N., 1022 Lahoz, C. H., 366, 421 Lai, C. F., 994 Lai, C. T., 241 Lai, J., 161
Lai, J. P., 1059 Lai, O. F., 257 Lai, P., 876 Lai, W., 293 Laidlaw, T. M., 625, 766, 767 Laird, G., 361 Laird, J. M., 161 Laitinen, J., 715 Lakdawala, V. S., 521 Lakhani, S., 239 Lakier Smith, L., 815 Lakos, G., 1015 Laliberte, C., 184 Lallemand, D., 53 Lalouschek, W., 421 Lam, K. S., 997, 1001 Lam, L. C., 364, 421 Lam, M. C., 1001 Lam, S. W., 1065 Laman, J. D., 437 LaMarca, A., 1059 Lamarche, B., 957 LaMarco, K., 379 Lamas, M., 736 Lamas, O., 1046 Lamb, N., 137 Lambert, J. C., 364, 365 Lambert, K. G., 712 Lambert, N., 110, 200 Lambert, N. K., 624, 763, 764 Lambert, R. B., 624, 763, 764 Lambert, S., 624, 762, 763, 765, 766 Lamberts, S. W., 100, 115, 174 Lambiase, A., 106 Lambracht-Hall, M., 109 Lambrecht, B. N., 100, 101, 104, 107, 219 Lambrechts, J., 510 Lamers, W. H., 48 Lamont, J. T., 1015 Lamprecht, F., 984, 985 Lancaster, G. I., 1019 Landau, N. R., 1056 Landen, C., 882 Landen, C. N., Jr., 240 Landfield, P. W., 380, 384 Landgraf, R., 323, 479, 481 Landis, C. A., 609 Landis, K. R., 782, 783, 872 Landmann, R., 727, 728 Landmann, R. M., 934 Landolfi, E., 399 Landolt, H. P., 307 Landolt-Ritter, C., 872 Landreth, G., 439, 440 Landreth, G. E., 1014 Landry, D. W., 93 Landry, Y., 101 Lands, A. M., 1042 Landsberg, L., 1043
1185 Lane, B. R., 1058 Lane, H. W., 853 Lane, J. D., 716 Lane, R. D., 620 Lane, W. S., 253 Lang, B., 224 Lang, C. H., 172, 173, 605, 995 Lang, H., 871 Lang, K., 239, 240, 261 Lang, R., 72, 73, 142, 1045 Lang, S., 254 Lang, U., 997 Lang, W., 421, 1053, 1059 Lange, P., 805 Lange, R. D., 855 Lange, T., 224, 585, 591, 592, 593, 594, 596, 597, 598, 599, 600, 603, 604, 913 Langen, R. C., 182 Langenbach, R., 332, 358 Langer, D. A., 498, 499 Langer, R. D., 813 Langer, S., 405, 407, 408 Langer, S. J., 405 Langeveld-Wildschut, A. G., 978 Langeveld-Wildschut, G., 978, 986 Langhans, W., 284, 289 Langin, D., 993 Langley, R., 882 Langston, J. W., 147 Laniado, S., 966 Laniece, P., 292 Lanksch, W. R., 254 Lanotte, M., 710, 1043 Lansman, J. B., 109 Lantz, P. M., 499 Lanza, G. A., 926 Lanzavecchia, A., 142, 800, 1065, 1086, 1091, 1102 Laoont, J. T., 115 Laor, A., 712 Laor, N., 515 Laorden, M. L., 711 Lapadat, R., 53 LaPerrier, A., 1060, 1061 LaPerriere, A., 676, 684, 685, 687, 688, 689, 773, 774, 1055, 1061 Laperriere, A., 1065 Lapidus, C. S., 800, 805 Lapinet-Vera, J. A., 839 Lappas, G., 957 Laquian, I. R., 49 Lara, D. R., 565, 566 Lara, H. E., 235 Larabee, J., 422 Lara-Marquez, M. L., 134 Lardone, P., 480 Large, R. G., 625, 766, 767 Larina, I., 853
1186 Larkin, E., 855 Laroche, L., 518, 606 Larocque, S., 456, 491 Larrick, J. W., 276 Larsen, C. S., 625, 763 Larsen, G. L., 810 Larsen, P. J., 101, 112 Larsen, R. J., 762, 773 Larson, D., 1055, 1056, 1060, 1063 Larson, D. B., 714, 782 Larson, L. J., 681 Larson, M., 691 Larson, M. G., 945 Larson, M. R., 900, 903, 907, 914, 1046, 1079 Larson, S. J., 305, 339 Larsson, B., 929 Larsson, B. M., 996 Larsson, J., 769, 839 Larsson, M., 1018, 1057, 1102 Larsson, O., 184 Larsson-Sciard, E. L., 1109 LaRussa, P., 859 Lasho, D. J., 830 Lasker, J., 937 Laskin, D. L., 135 Lasko, N. B., 540, 541 Laskowski, B. F., 77, 842, 861, 1079 Lasley, E., 654 Laso, F. J., 550, 551, 552, 553 Lason, W., 162, 166 Lassila, O., 219 Lassila, R., 931 Lassmann, H., 106, 1112, 1115 Laszt, A., 716 Lathey, J. L., 862 Latimer, J. J., 236, 884 Lau, C. S., 198 Lau, D. C., 1000 Lau, M. M., 173 Laub, O., 237 Laudat, A., 1055 Laudenslager, M., 362, 619, 620, 622, 813, 982, 1054 Laudenslager, M. L., 194, 450, 468, 475, 476, 481, 482, 483, 484, 485, 486, 487, 488, 489, 490, 491, 497, 534, 535, 619, 621, 729, 734, 854, 1019, 1079 Laudenslager, Mark L., 475 Lauder, J. M., 459 Laue, L., 738, 981 Lauerma, A., 736 Laughlin, T. M., 408 Laumbacher, B., 1015, 1023 Launer, L., 361 Launer, L. J., 439 Laurence, J., 1056, 1059 Laurenceau, J. P., 1061
Author Index Lauretani, F., 361 Lauritsen, J. M., 976 Laursen, S. B., 70, 1057 Lauterbach, R., 303 Lauwerys, B. R., 213 Lavelle, E., 875 Laverty, M., 101 Lavi, E., 147 Lavine, S. D., 419 LaVoi, K. P., 1014 Lavoie, J. F., 436 Lavreys, L., 1059 Law, M., 691 Law, M. R., 928 Law, P. Y., 161 Lawlor, K. E., 197 Lawniczek, T., 570 Lawrence, D., 1037 Lawrence, D. A., 68, 77, 238, 1036, 1037, 1038, 1039, 1040, 1041, 1045, 1046 Lawrence, David A., 1035 Lawrence, L. L., 669 Laws, S. M., 365, 366, 421 Lawson, D. H., 199, 521, 523, 608, 885 Lawson, L. J., 402, 440 Laye, S., 273, 277, 281, 287, 288, 289, 291, 292, 294, 298, 301, 302, 381, 382, 430, 431, 432, 589, 622, 1058 Lazar, G., 738 Lazar, G., Jr., 738 Lazarevic, M., 649, 653 Lazarini, F., 275 Lazar-Molnar, E., 181 Lazarus, L., 676, 734, 784 Lazarus, M., 268, 273, 274, 319, 320, 321, 322, 331 Lazarus, R. S., 499, 619, 620, 772, 781 Lazovic, J., 419 Lazure, C., 132 Lazzarin, A., 586 Lazzaro, D., 995 Lazzeri, M., 117 Le Bail, J., 208, 211 Le Bert, M., 74 Le Bouc, Y., 1059 Le Cras, A. E., 256 Le Drean, E., 692 Le Fur, G., 557 Le Gouill, C., 1058 Le Grand, C. B., 747 Le Guiner, S., 692 Le Hir, M., 400 Le Maire, V., 253 Le Moal, M., 273, 284, 344, 465, 711, 712 Le Morvan, C., 74 Le, Y., 136 Leach, C. S., 853, 854, 855, 862 Leach Huntoon, C. S., 853, 862
Leadbeater, J., 566 Leads, B., 687, 688 Leal, V. V., 106 Leal-Cardose, J., 810 Leary, S., 958, 960 Leary, T., 872, 930 Leatham, E. W., 937 Leavy, J., 923 Lebecque, S., 108, 142 LeBlanc, F., 306 LeBlanc, W. G., 1060 Lebman, D. A., 810 LeBold, D., 419 Lecam, L. N., 744 Lecci, A., 100, 101, 107 Leceta, J., 103, 104, 131, 133, 134, 135, 136, 139, 140, 141, 143, 144, 146, 195 Lechan, R. M., 286 Lechler, R. I., 1003 Lechner, O., 738, 739 Lechner, S., 687, 689, 1065 Lechner, S. C., 1055, 1056, 1061 Lechowicz, W., 565 Leclercq, R., 664, 666 Lecoeur, H., 1018 Lecour, H., 386 Ledda, F., 114 Ledeboer, A., 269, 273, 275, 393, 405, 406, 409 Leder, K., 164, 165 Leder, P., 53 Lederer, J. A., 1025 Ledochowski, M., 307, 522 Ledoux, J. E., 294 Lee, A. F., 585 Lee, A. H., 999 Lee, A. J., 957 Lee, A. W., 1059 Lee, A. Y., 998 Lee, B., 342, 843, 845 Lee, B. J., 342 Lee, B. N., 599 Lee, C., 323, 324, 325, 326, 328, 329, 330, 885, 986, 995 Lee, C. A., 1053 Lee, C. C., 364, 365, 366 Lee, C. H., 213 Lee, C. K., 384 Lee, C. M., 131, 332, 521, 522 Lee, C. T., 1015 Lee, C. U., 568 Lee, D., 733 Lee, D. J., 663, 930 Lee, D. K., 815 Lee, E. A., 999 Lee, F., 55 Lee, G. R., 787 Lee, H., 134, 140, 141, 1024 Lee, H. B., 999
Author Index Lee, H. G., 830, 831 Lee, H. H., 551 Lee, H. J., 571 Lee, H. M., 181 Lee, H. R., 1059 Lee, H. S., 110 Lee, H. Y., 293 Lee, J., 213, 771, 786, 787, 792, 869, 874, 876, 996, 1000 Lee, J. C., 403 Lee, J. E., 99, 290, 320, 381 Lee, J. M., 103, 604 Lee, J. W., 625, 664, 665, 666, 667, 772 Lee, K., 172 Lee, K. A., 531 Lee, K. H., 879 Lee, K. U., 571 Lee, K. Y., 878 Lee, L. C., 93 Lee, L. Y., 110 Lee, N. R., 531 Lee, R. S., 792 Lee, S., 174, 644, 646, 948, 1015 Lee, S. C., 97, 136 Lee, S. J., 568, 986 Lee, S. K., 213 Lee, S. W., 55, 300, 542, 738, 741 Lee, T., 551, 1056 Lee, T. Y., 93 Lee, W., 70, 517, 662 Lee, W. C., 1015 Lee, W. H., 184, 185 Lee, W. J., 663, 668 Lee, W. T., 66, 71, 73, 76, 1044, 1045 Lee, W.-S., 710, 711 Lee, Y., 623 Leech, M., 54 Leeds, B., 1060, 1061 Leeka, J., 761, 1060 Leem, T. H., 1014, 1016, 1017, 1018, 1024, 1025, 1026, 1027 Leeman, S., 1115 Leeman, S. E., 108, 109, 112, 115, 116 Leesnitzer, L. M., 53 Leevy, C. M., 554 Lefebvre, C., 213 Lefebvre, J., 239 Lefebvre, P., 51 Lefebvre, R. A., 115 Lefebvre, Y. A., 49, 1098 LeFeuvre, R., 274, 418 LeFeuvre, R. A., 419, 433 Lefevre, M., 999 Lefevre, P. M., 103 Leff, A. R., 102, 111 Lefkowitz, R., 679 Lefkowitz, R. J., 69, 200, 235, 1043, 1044, 1057 Lefort, J., 98
Lefranc, D., 148 Lefvert, A. K., 65 Legat, F. J., 987 Legendre, R., 583 Legos, J. J., 417 Legraverend, C., 565 Lehman, J., 691 Lehmann, L. K., 522 Lehmann-Facius, H., 566 Lehner, P. J., 1023 Lehner, T., 1015, 1016, 1023 Lehnert, H., 652 Lehr, H. A., 144, 1002 Lehrberger, K., 166 Lehrer, P., 93, 814, 1046 Lehrer, P. M., 814 Lehrmann, E., 416, 417 Lehtimaki, K. A., 186 Lehtinen, V., 870 Lehtovirta, M., 364 Lei, D. L., 382 Lei, K., 829, 830 Leibovich, S. J., 839, 842 Leibowitz, J., 1109 Leibowitz-Amit, R., 148 Leichtner, A. M., 1002 Leigh, J. P., 784, 792 Leijon, I., 1002 Leineweber, K., 816 Leingang, K. A., 303 Leinninger, G. M., 174, 184 Leino-Arjas, P., 717, 948 Leinonen, M., 927 Leinwand, L., 405, 407, 408 Leinwand, L. A., 405 Leirisalo-Repo, M., 197, 222, 223, 224 Leissner, K., 1100 Leist, T. P., 360, 1108 Leite-de-Moraes, M. C., 98 Leiter, E. H., 994 Lekander, M., 875, 877, 969 Leker, R. R., 419 Lellouch, J., 556 Lemaigre-Dubreuil, Y., 438, 439 Lemaire, V., 465 Lemaitre, R. N., 923, 926 Lemanske, R. F., 502, 979 LeMay, L. G., 301 Lemercier, G., 585 Lemere, C., 386 Lemieux, A., 362 Lemieux, A. M., 497, 539 Lemmon, H., 364, 365 Lemne, C., 1016 Lemon, J., 873 Lenardo, M. J., 338 Lenczowski, M. J., 283, 298, 995 Lendon, C. L., 364, 365 Lendrum, B., 717
1187 Lendvay, J., 342 Lenig, D., 1086, 1091 Lennard, T. W., 256 Lennette, E. T., 856 Lennon, L., 957, 958, 961 Lennon, S. L., 1015 Lenoir, M., 223 Lensing, P., 851 Lenstra, R., 381 Lenszowski, M. J. P., 320 Lentz, M. J., 609 Lenz, J. W., 716 Lenzlinger, P. M., 417, 419 Leo, N. A., 1040, 1080, 1086, 1087 Leo, R., 882 Leon, A., 106 Leon, L. R., 298, 299 Leonard, B., 346, 358, 677, 812 Leonard, B. E., 236, 277, 303, 305, 306, 344, 358, 359, 514 Leonard, J. I., 853 Leonard, J. M., 1054 Leonard, J. P., 739 Leonard, S., 90 Leone, B. E., 142, 980 Leonhardt, J., 255, 257, 878 Leopold, K., 885 Leopold, L., 994 Lepage, S., 926, 956 Lepisto, A. J., 1079, 1083 Lepkowski, J. M., 499 Leplege, A., 1059 Lepore, S. J., 693 Leppanen, E. A., 934 Lepper, H. S., 949, 950, 969 Leproult, R., 607 Lerche, N. W., 469, 487, 1056, 1057, 1060, 1062, 1063, 1065 Lerer, B., 504, 901, 904 Lerner, E. A., 104, 107, 108, 114 LeRoith, D., 173, 175, 180, 181, 184, 186, 999 Leroith, D., 175 Lesch, K. P., 485, 522 Lescoulie, P. L., 110, 200 Leserman, J., 509, 512, 689, 790, 1055, 1056, 1059, 1060, 1061, 1062, 1063, 1064, 1065 Leski, M. L., 184 Leskiw, M. J., 853, 855 Lesko, L. M., 875 Leslie, C. A., 829 Lesne, S., 276, 277 Lesnyak, A. T., 855 Lesperance, F., 607, 681, 694, 792, 931, 932, 937 Lesperance, G., 509, 511, 512, 514, 516, 518 Lessing, J. B., 212
1188 Lessov, N. S., 419 Lestage, J., 281, 288, 289, 291, 300, 307, 308, 344, 345, 522 Leszcz, M., 687, 873 Letourneau, P. K., 771 Letourneau, R., 110, 117 Lett, H. S., 949 Letvin, N. L., 1065 Leu, C. H., 193 Leu, S. L., 218 Leung, D. Y., 66, 521, 803, 805, 855, 978, 979 Leung, D. Y. M., 977, 988 Leung, K. B., 109 Leung, P., 1065 Levatrovsky, D., 515 Levav, I., 233, 870 Levav, T., 352, 354, 359, 360 Levengood, R., 540 Levengood, R. A., 539, 540, 541 Levenson, R. W., 620, 625, 1063 Levenstein, S., 789, 811 Leventhal, C. M., 1120 Leverin, A. L., 419 Levi, F., 884, 885, 1055 Levi, G., 404, 440 Levi, R., 109 Levi-Montalcini, R., 106 Levin, A. S., 744 Levin, G., 983 Levin, H. R., 93 Levin, J. S., 714 Levin, M. J., 512, 863, 1079 Levin, R. I., 55, 980 Levine, J., 570 Levine, J. D., 65, 69, 72, 102, 103, 110, 161, 194, 200, 710, 801 Levine, S., 460, 461, 468, 469, 677, 734, 745, 762, 773, 1025 Levings, M. K., 142 Levinson, Y., 256 Levi-Schaffer, F., 106, 109 Levisohn, D., 330 Levison, S. W., 419 Levite, M., 107, 855 Leviton, A., 459 Levitsky, H. I., 880 Levitt, L., 741 Levitt, P., 564 Levitzki, A., 184 Levkoff, L. H., 456 Levo, Y., 745 Levy, B. R., 769 Levy, D., 945 Levy, D. N., 1056 Levy, E. M., 734, 763, 765, 766, 772 Levy, F. O., 257 Levy, H., 222 Levy, J., 729
Author Index Levy, J. A., 1053, 1054 Levy, S., 686, 869, 874, 876 Levy, S. M., 771, 786, 787, 792 Levy, W. C., 938 Lew, R. A., 837 Lewandoski, M., 332 Lewandowska, E., 565 Lewandowski, L., 693 Lewicki, H., 1054 Lewin, D., 690 Lewin, G. R., 106, 107 Lewin, M., 882 Lewin, N. E., 102, 109 Lewington, S., 957, 958 Lewis, C., 260 Lewis, C. E., 554, 840 Lewis, D. A., 564 Lewis, J., 647 Lewis, J. E., 625, 772 Lewis, J. G., 497, 962, 966 Lewis, J. L., 741 Lewis, J. W., 160, 165 Lewis, L., 307 Lewis, M. H., 1063 Lewis, N., 682 Lewis, S., 358 Lewis, S. E., 407 Lewis, S. F., 105 Lewis, S. L., 669 Lewis, T. T., 946, 949 Lewthwaite, J., 501, 505, 961, 962, 1016 Ley, K., 89, 952 Ley, K. F., 953 Leynadier, F., 736 Leyton, V., 235, 238 L’Faqihi, F. E., 840 Lhullier, F., 1055 Li, A. C., 997 Li, A. J., 356 Li, B., 645 Li, C., 275 Li, C. I., 242 Li, C. K., 1065 Li, C. L., 875 Li, C.-Y., 883 Li, D. G., 1014 Li, D. J. J. S. F. Wang, W., 863 Li, D. Y., 994 Li, F., 549, 551, 1015 Li, F. H., 1015 Li, G., 842 Li, G. M., 567 Li, G. W., 167 Li, G. Y., 883 Li, G. Z., 380 Li, H., 400 Li, H. L., 416, 417 Li, H. M., 51 Li, H. Y., 195, 328, 843
Li, J., 107, 108, 845, 1055 Li, J. H., 105, 106, 567 Li, J. M., 923 Li, M., 184 Li, M. O., 840 Li, N., 383 Li, P., 1065 Li, P. L., 1058 Li, Q., 51 Li, R., 879 Li, S., 274, 320, 322 Li, S. T., 342 Li, T., 571 Li, W., 276, 419, 845 Li, X., 565 Li, X. Q., 364 Li, Y., 361, 554, 998, 1059 Li, Y. H., 1059 Li, Y. M., 175, 603 Li, Y. P., 182 Li, Y. S., 69, 74 Li, Z., 181 Li, Z. G., 208 Li, Z. W., 1000 Liagre, B., 208, 211 Liang, C. P., 995, 999 Liang, R., 306 Liang, W., 1043 Liao, D., 1060 Liao, H., 86, 88, 89, 90, 91 Liao, J., 736 Liao, P. C., 364 Liao, Y. C., 364, 365, 366 Liappas, I. A., 551 Libbey, J. E., 1115 Libby, P., 502, 679, 695, 921, 923, 925, 926, 927, 928, 935, 938, 1016 Liberatore, G., 147 Libermann, T. A., 383 Liberzon, I., 539 Libin, M., 213 Libing, C., 110 Liby, K., 241 Licastro, F., 361, 363, 364, 365, 366, 421 Lichtenauer-Kaligis, E. G., 100 Lichtenstein, G. R., 440 Lichtenwalner, R. J., 184 Lichtman, A. H., 47, 1016 Lichtman, R. R., 790 Liciano, J., 292, 299 Licinio, J., 570, 571, 594, 599, 884, 1061 Lideman, R. R., 567 Liden, J., 55, 741 Liden, S., 110 Lieb, J., 242 Lieb, K., 106, 108, 606 Lieberman, H. H., 237 Lieberman, J. A., 459, 564 Liebert, B., 570
Author Index Liebeskind, J. C., 160, 165, 235, 238, 256, 556, 726, 734, 745 Liechty, K. W., 842 Lien, E., 1015, 1025 Lienard, D., 693 Liew, F., 651 Liew, F. Y., 115, 997, 1025 Lifrak, S. T., 1079 Lifson, J. D., 1054 Light, K. C., 927 Lightman, S. L., 112, 196, 197, 241, 603, 730, 739, 740, 790, 855, 900, 901, 902, 907, 909, 910, 911, 914, 915, 1089, 1118 Ligier, S., 197, 200 Ligon, R. W., 937 Ligris, K., 117 Likos, A., 456 Liljeroth, A. M., 361 Lillberg, K., 233, 870 Lillenhoj, E. P., 567 Lillevang, S. T., 222 Lilly, A., 101 Lilly, A. A., 479, 488, 1079 Lilly, C. M., 810 Lilly, J., 764, 767 Lim, C. S., 571 Lima, M. B., 1055 Limbird, L. E., 1019 Limiroli, E., 160 Limmroth, V., 76, 651 Limone, P., 1055 Limuris, G., 257 Lin, A., 533, 536, 537, 538, 539, 551, 570 Lin, C., 364 Lin, C. C., 364 Lin, C. S., 1015 Lin, E., 254 Lin, H., 212, 457, 998 Lin, H. I., 360 Lin, H. M., 237, 589, 591, 594, 599, 606 Lin, H. S., 1015 Lin, J., 143, 734, 790 Lin, J. H., 1015 Lin, K., 482 Lin, L., 588 Lin, R., 641 Lin, S. C., 137 Lin, S. H., 167 Lin, W., 644, 645, 653 Lin, X., 1109 Lin, Y. C., 799 Linares, O. A., 682 Lincoff, A. M., 946 Lind, A., 556 Lind, J., 200 Lind, P., 926, 957 Lind, R. H., 663, 665, 666
Lindauer, M., 252 Lindburg, D. G., 485 Linde, F., 664, 665 Linde, H. J., 68 Lindecke, A., 239, 261 Lindell, S., 485 Lindell, S. G., 485 Lindemann, C., 876 Linden, W., 694, 715, 716, 792, 937 Linder, J., 116 Lindgren, A., 1062 Lindholm, D., 416 Lindquist, J. M., 240 Lindquist, K., 361 Lindquist, S., 1015 Lindsay, R. D., 382 Lindsay, R. M., 106 Lindsay, R. S., 1000 Lindsberg, P. J., 416, 417 Lindsley, M. D., 1110 Lindsten, T., 275 Lindvall, O., 359, 386 Line, S., 486, 1080, 1111 Linehan, D. C., 878 Ling, C., 361 Ling, E. A., 402 Ling, S., 211 Ling, Z. D., 348, 359 Lininger, J., 842 Linington, C., 1112 Link, H., 416, 417 Linkins, R. W., 517, 871 Linnavuori, K., 859 Linnemann, K., 594 Linsner, J. P., 579 Linthorst, A. C., 112, 296, 522, 735 Linton, M. F., 994 Linville, M. C., 184 Lio, D., 77, 421 Liotta, A. S., 743 Liotta, L. A., 238, 240 Lipetz, P. D., 236, 884 Lipman, M. L., 55 Lipp, M., 1086, 1091 Lipper, S., 540 Lippert, U., 273 Lippman, M., 771, 869, 874, 876 Lips, P., 186 Lipsky, P. E., 73 Lipton, H. L., 1109, 1110 Lipton, J. M., 100, 143, 1055 Lipton, J. W., 348, 359 Lipton, S. A., 136, 147, 1054 Liriano, E., 1002 Lis, S., 594 Lischke, A., 998 Lischner, H. W., 855 Lissandrini, D., 841 Lissoni, P., 594, 604
1189 Listwak, S., 197, 200, 695, 740 Listwak, S. J., 54, 197, 737, 739, 741, 980 Liszewski, M. K., 46 Litchfield, P., 712 Litovsky, S, 921 Litrenta, M. M., 958 Litsky, M., 883 Litsky, M. L., 1079 Little, S., 1054 Littman, D. R., 952, 1053 Litwin, D. K., 114 Litwin, S. D., 461 Liu, A., 808 Liu, B., 523 Liu, B.-G., 400 Liu, C., 292, 293, 338 Liu, D., 491 Liu, G., 999 Liu, H., 565 Liu, H. C., 364 Liu, J., 565, 885 Liu, J. P., 184 Liu, K., 962 Liu, K. F., 418 Liu, K. J., 605 Liu, L., 76, 101, 361, 1037 Liu, L. Y., 801 Liu, M., 1058 Liu, Q., 101, 174, 175, 839, 998 Liu, R. Q., 419 Liu, S. M., 332, 995 Liu, T., 399, 409, 417, 1079 Liu, T. F., 213 Liu, T. S., 1015 Liu, T. Y., 364 Liu, W., 136, 646, 842 Liu, X., 1002 Liu, X. H., 419 Liu, Y., 149, 921, 930 Liu, Y. F., 999 Liu, Y. J., 99, 142, 1102 Liu, Y. P., 360 Liu, Z., 173 Liu, Z. G., 177 Liu, Z. J., 571, 842 Liuba, P., 958, 959, 960 Liu-Chen, L. Y., 713 Liuzzo, G., 923, 925, 926, 956 Livi, C., 212 Livingston, D. J., 419 Livingstone, J. N., 900, 906 Livnat, S., 64, 66, 69, 70, 103, 115, 194, 222, 678, 772, 1040, 1057 Livrea, P., 76 Livshits, D., 339, 408, 556 Ljungberg, A., 110 Ljunggren, H. G., 217 Ljungqvist, O., 1024 Llabre, M. M., 1060
1190 Llanas, J. N., 554 Llanos, Q. J., 321 Lledo, A., 302 Llewelyn, M. B., 901, 911 Llorca, J., 363, 364, 366, 421 Llorente, L., 213 Llorente, M., 603 Lloyd, A., 512, 570 Lloyd, A. J., 859 Lloyd, A. R., 136 Lloyd, M., 240, 883 Lloyd, R. V., 883 Lobel, M., 711, 791 Lober, C. W., 831 Lobert, H., 711 LoBuglio, A. F., 746 Locatelli, M., 1055 Locati, M., 217, 219 Lochner, K., 500 Locke, S. E., 586, 901, 907 Locksley, r. M., 338 Lockwood, G. A., 873 Lockwood, L. L., 729 Loddick, S. A., 338, 416, 417, 418, 419, 433 Lodish, H., 662 Lodish, H. F., 995 Loeb, T., 1065 Loeffler, J. P., 162, 164 Loegering, D. J., 1037 Loehr, L. R., 385 Loeser, R. F., 174 Loetscher, M., 142 Loetscher, P., 142 Loewel, H., 957 Loewenstein, G., 769 Lofquist, A. K., 53, 741 Loftenius, A., 417 Loftin, C. D., 332 Logan, A., 416, 417 Logan, G., 551 Logan, H. L., 764, 767 Logan, W. C., 1109 Logsdon, C. D., 48 Lohmeyer, J., 1100 Lohmuller, F., 363, 364, 365 Lohse, A. W., 744 Loibichler, C., 462 Loidi, L., 552 Lojo, S., 554 Lokshina, I., 791 Lolkema, M., 1018 Lombardi, M. S., 63, 69, 76, 726, 739, 1045, 1046 Lombardini, R., 958, 960 Lombart, C., 747 Lomecky, M. Z., 186 Lommatzsch, M., 106, 107, 360 Lomo, T., 340
Author Index Lomthaisong, K., 101 Lonergan, P. E., 303 Long, E. O., 252 Long, J. M., 382, 386, 1000 Long, L., 814 Long, W., 863 Longaker, M. T., 841, 845 Longmate, J. A., 1060 Longo, D. J., 1088 Lonne-Rahm, S., 813 Lonnerdal, B., 466 Lonsdorfer, J., 586 Loo, H., 570 Look, D. C., 502 Looker, H. C., 715 Loomis, A. L., 580 Loop, T., 73 Loos, W. R., 541, 542 Loosen, P. T., 713 Lopes, C., 993 Lopez, A., 550, 551, 553 Lopez, C. B., 1102 Lopez, D., 47 Lopez, R., 830 Lopez-Atalaya, J. P., 276 Lopez-Bermejo, A., 996 Lopez-Briones, L. G., 223 Lopez-Figueroa, M. O., 809 Lopez-Otin, C., 840 Lopez-Sobaler, A. M., 383 Lopiano, L., 710 Loppnow, H., 926 LoPreste, G., 273 Lord, J., 1056 Lorden, J., 639, 640, 641 Loredo, J. S., 606 Lorence, R. M., 603 Lorens, J. B., 103 Lorens, S. A., 103 Lorentz, A., 109 Lorenz, B., 74 Lorenz, M., 951, 952 Lorenzo, M., 171, 172 Loreto, M. F., 380, 595, 607 Lorettu, L., 568 Loria, R. M., 1102 Loriaux, D. L., 482, 738, 981 Loric, S., 253 Lorr, M., 762 Lortholary, O., 1055 Lorton, D., 106, 115, 132, 133, 194, 200, 226, 817, 888 Loscalzo, J., 954, 957 Loscalzo, M., 687 Loscher, C. E., 353, 355 Loskutoff, D. J., 926, 993, 1000, 1001, 1002 Losy, J., 420, 421 Lotsikas, A., 363, 594, 599
Lotz, M., 108, 223, 605 Lotze, M. T., 981 Lotzova, E., 690, 876 Lou, J. S., 523 Loudon, A. S., 297 Loue, L., 695 Louis Harris and Associates, 396 Louis, S. M., 200 Louis, T. A., 1053 Louisse, S., 291, 381, 439 Loureiro, M., 1055 Louridas, C., 257 Lousberg, R., 682, 790, 969 Louthrenoo, W., 200 Loutsch, J. M., 56 Lovallo, W. R., 625, 772, 788 Love, S., 363, 364, 421 Lovejoy, J. C., 994 Loveland, B. E., 1043 Loveless, C. A., 781, 783 Loverra, G., 462 Lovett, M., 101 Loving, T. J., 786 Low, A., 110 Low, H. H., 161 Low, Q. E., 840, 841 Lowbeer, C., 1014 Lowe, D., 763, 764 Lowe, G. D., 957, 961, 962, 963, 965, 966, 968 Lowe, G. D. O., 503, 505 Lowel, H., 932, 937 Lowell, B. B., 332 Lowenberg, B., 100, 115 Lowery, M., 490 Lowman, M. A., 109 Lowry, M. T., 1112 Lowry, P. J., 101 Lowry, S. F., 54, 72, 254 Lowy, M. T., 512, 540, 801 Lozoff, B., 466 Lozza, G., 420 Lu, B., 102, 107, 108, 117 Lu, C. Y., 167 Lu, D., 934 Lu, F. W., 843, 1056, 1098 Lu, J., 321, 322, 323, 327, 328, 330, 332 Lu, N. Z., 48 Lu, T., 1000 Lu, W., 1056 Lu, Y., 977 Lu, Y. F., 342 Lubach, G. L., 450 Lubach, G. R., 460, 461, 463, 464, 465, 467, 470, 483, 491, 712 Lubach, Gabriele R., 455 Lubahn, C., 194, 817, 888 Luban, J., 1056 Lubaroff, D., 676, 875, 877, 882
Author Index Lubaroff, D. M., 764, 767, 785, 787, 881, 882, 885 Lubbers, E., 143 Luber-Narod, J., 382 Lublin, D. M., 46 Luborsky, L., 509, 510, 511, 553, 874, 932, 1079, 1088 Lubowski, D. Z., 131 Luc, G., 511, 932 Lucas, A., 1000 Lucas, M., 1023 Lucas, M. J., 89 Lucas, P., 603 Lucca, U., 366 Lucchinetti, C., 1107 Lucero, L., 105 Lucey, D. R., 855 Lucia, P. D., 72, 73 Lucia, S., 1002 Luckhurst, E., 676, 734, 784 Ludlow, A. M., 342 Ludovic Croxford, J., 1108, 1110 Luduena, F. P., 1042 Ludwig, E., 417 Ludwig, T., 995 Lue, F. A., 587, 592, 599, 609 Lue, L., 439, 440 Luedke, C., 738, 843 Luffau, G., 109, 111 Lufgendorf, S., 682, 683, 692 Luft, F. C., 1000, 1001 Lugaresi, E., 585 Luger, T., 98 Luger, T. A., 98, 109, 113 Lugg, D., 855, 862, 863, 1079 Lugg, D. J., 236, 853, 855, 856, 857, 862, 863 Luheshi, G., 274, 397, 640 Luheshi, G. N., 99, 290, 297, 337, 338, 417, 418, 419, 432, 433, 995 Lui, C. H., 464 Luise Rao, M., 365 Luisi, B. F., 49 Lukacs, N., 1080, 1088 Lukacs, N. W., 995 Lukas, R. J., 105 Luke, D., 605 Luke, W., 1061 Luk’ianenko, V., 635, 636, 643 Lum, J. J., 275, 1056 Lumley, M. A., 713, 814, 1060 Lund, J. M., 1099 Lundberg, A. S., 235 Lundberg, G., 675 Lundberg, J. M., 104, 109, 110, 115, 133 Lundblad, J. R., 137 Lundeberg, T., 88, 200, 290, 320 Lundin, P. M., 728, 737
Lundkvist, G. B., 585 Lundkvist, J., 345, 418 Lundy, J., 551 Lunnon, K., 444 Luo, J., 101 Luo, Y., 74 Luo, Z., 662 Luoto, R., 771 Lupattelli, G., 958, 960 Lupien, S. B., 186 Lupien, S. J., 348, 357 Lupu, F., 172 Lush, R., 240 Lusk, E. J., 872 Lusle, D. T., 775 Lusso, P., 1053 Luster, A. D., 136 Lutgendorf, S., 233, 242, 677, 679, 680, 684, 686, 687, 689, 692, 695, 707, 782, 783, 786, 882, 1055, 1056, 1057, 1058, 1061, 1080, 1088 Lutgendorf, S. K., 233, 234, 235, 240, 241, 253, 255, 261, 764, 767, 773, 787, 790, 876, 881, 882, 885, 900, 906, 1062, 1063 Lutgendorf, Susan K., 869 Luthringer, R., 601 Luts, A., 115 Lutz, E. M., 133 Lutz, M., 217 Lutz, M. B., 142 Luu, P., 523 Luukkainen, R., 219 Luukkonen, R., 717, 948 Lux, H., 584 Luyten, V. W. H., 101, 104 Lyakh, L. A., 829 Lydiard, R. B., 531 Lydston, D., 687, 689, 1065 Lyerly, H. K., 252 Lygren, I., 133 Lyketsos, C. G., 1061 Lyle, R. M., 871 Lynch, A., 353 Lynch, C. D., 184 Lynch, D., 1056 Lynch, J., 947 Lynch, J. W., 498, 499, 500 Lynch, M. A., 275, 303, 353, 355, 356, 357, 384 Lynch, R., 100, 103 Lynn, D. L., 273 Lyon, D. E., 1061 Lyon, S. M., 554 Lyons, P. D., 162 Lyseng, Williamson, K. A., 148 Lysko, P. G., 419 Lysle, D. T., 256, 556, 733, 743, 1017, 1025, 1063, 1101
1191 Lyte, M., 306, 637, 731, 732, 1025, 1026, 1040 Lyubomirsky, S., 761 Ma, C., 571 Ma, D., 109 Ma, G., 297 Ma, h., 50 Ma, J., 956 Ma, M., 931 Ma, S. L., 364, 421 Ma, X., 137 Ma, X. H., 994 Maass, M., 959 Maas-Szabowski, N., 53 Mabbott, N. A., 440 Mabry, T. R., 663, 930 Mac Micking, J., 1025 MacAllister, R. J., 960 Macari-Hinson, M. M., 681 MacAry, P., 1023 MacCallum, R., 691, 734, 875 MacCallum, R. C., 77, 236, 512, 789, 790, 792, 817, 842, 846, 856, 861, 863, 882, 888, 900, 906, 907, 908, 962, 1080, 1088, 1099, 1102, 1111 Maccari, S., 711, 712 Macdiarmid, F., 208, 211 MacDonald, G., 419 MacDonald, I. C., 238 MacDonald, R. G., 937 Macera, C. A., 664, 665 Macey, T., 469 Macfarlane, P. W., 362 MacGowan, S., 363, 364, 421 MacGowan, S. H., 365, 366, 421 MacGregor, A. J., 193 MacGregor, R. R., 551, 552 Machado-Neto, R., 461 Machann, J., 1000 Machein, M., 885 Machein, M. R., 241 Machein, U., 361, 885 Machelska, H., 41, 159, 160, 161, 162, 164, 165, 166 Machelska, Halina, 159 Macher, J. P., 601 Machi, T., 958 Machicao, F., 1000 Macho, L., 853 Maciag, T., 53 Mackall, C. L., 461 Mackay, C. R., 142, 163, 1085 MacKenzie, A., 419 MacKenzie, C. J., 133 MacKenzie, E. T., 276, 277, 420 MacKenzie, F. J., 739 Mackenzie, I. R., 439, 440 MacKenzie, J., 646
1192 Mackerlova, L., 273, 274, 293, 294 Mackersie, R. C., 1024 Mackewicz, C. E., 1053, 1054 Mackey, J. R., 661 Mackiewicz, A., 515 Mackinnon, L. T., 663, 670 MacLean, D. A., 670 Maclean, D. B., 105 MacLean, J., 108 MacLean, M., 459 MacLeod, D. L., 1108 MacLeod, N. K., 440 MacLeod, V., 361 Maclure, M., 933 MacLusky, I., 713 MacMahon, J., 115 MacManus, J. P., 735, 745 Macnamee, M., 359 MacNaughton, W., 105 MacPhee, I., 197, 739, 740 MacPhee, I. A. M., 740 MacPherson, A., 186 MacQueen, G., 110, 647, 648, 653 Macrae, S., 650, 651 Macris, N. T., 1056 Madamba, S., 353 Madamba, S. G., 354, 356 Madan, A. K., 995 Madden, C. J., 327 Madden, J. A., 1036 Madden, J. J., 557 Madden, K., 555, 644, 646, 678, 1040 Madden, K. S., 64, 66, 69, 70, 77, 97, 98, 115, 194, 222, 226, 605, 1057 Maddi, S., 686 Maddox, L., 649, 982 Maddux, B. A., 48, 174 Madeira, M. D., 386 Madej, A., 570 Madeleine, M. M., 237 Madge, L. A., 1000 Madhavan, N., 549, 551 Madhavan, S., 967 Madkour, O., 362 Madlener, M., 826, 840, 843 Madruga, J. I., 550, 551, 553 Madsen, G., 644, 645, 653 Madsen, S. A., 847 Madson, L., 789 Maeda, K., 997, 1000, 1001 Maeda, M., 647, 648, 653 Maeda, N., 1000, 1001 Maeda, S., 299, 1000 Maeda, T., 98, 109, 115 Maes, M., 172, 277, 304, 305, 307, 422, 510, 511, 515, 516, 521, 533, 536, 537, 538, 539, 551, 568, 570, 571, 622, 682, 932, 969, 1115 Maes, S., 694
Author Index Maestri, D., 772 Maestroni, G., 207, 635 Maestroni, G. J., 63, 65, 69, 72, 73, 235 Maestroni, G. J. M., 1044, 1045 Maeyama, S., 554 Maffei, M., 994 Maffia, P., 1015 Maffulli, N., 663 Magarinos, A. M., 745 Magder, L., 1088 Magee, J. C., 359 Magee, W., 637 Magerl, W., 110 Maggi, A., 210 Maggi, C. A., 100, 101, 103, 104, 107, 110, 114, 115, 117 Maggi, E., 637, 811, 978 Magiakou, M. A., 196, 222 Magid, K., 503, 964, 965, 966, 968 Magistrelli, G., 219 Maglione, D., 224 Magnus, P., 773 Magnuson, D. J., 103 Magnuson, M. A., 332 Magovern, G. J., 713 Magovern, G. J., Sr., 497 Maguire, P., 786 Magy, N., 237 Mahadev, K., 1001 Mahajan, S., 1056 Mahalingam, R., 859 Mahalingam, S., 1056 Mahan, J. T., 826 Mahboubi, A., 1056 Mahendran, R., 570 Maher, K., 687, 689, 1055, 1056, 1061 Maher, K. G., 773 Maher, K. J., 792, 1060, 1061 Mahoney, J., 405 Mahoney, J. H., 456 Mahony, J. H., 273, 405, 406 Mahony, N., 815 Mahowald, M. L., 609 Mahowald, M. W., 609 Mahurin, R. K., 710 Mai, X. M., 1002 Maier, A., 224, 998 Maier, H., 592, 769 Maier, L. A., 875 Maier, S., 400–401, 405, 633, 646, 678, 815, 885 Maier, S. F., 87, 88, 99, 100, 112, 194, 273, 281, 284, 288, 289, 290, 304, 320, 329, 337, 338, 339, 342, 343, 344, 345, 347, 348, 357, 360, 381, 384, 385, 393, 395, 396, 397, 398, 399, 400, 401, 402, 405, 406, 407, 408, 409, 456, 475, 481, 482, 486, 504, 518, 520, 524, 556, 620, 621,
677, 681, 683, 724, 729, 732, 733, 734, 854, 965, 1019, 1025, 1026, 1058, 1115 Maier, W., 364, 365, 421, 565 Maik, G., 685 Maillot, M. C., 213 Maiman, M., 682 Main, C. J., 977 Maini, R. N., 69, 143, 193, 542 Mainka, C., 861 Mains, D. A., 694 Maisel, A. S., 70, 605, 727, 965, 1043, 1044 Maiseri, H., 876 Maiwald, M., 422 Majde, J. A., 331, 584, 586, 587, 589 Majid, A., 1108 Majka, M., 926 Major, B., 788 Major, P., 685 Majtenyi, C., 565 Mak, T. W., 352 Makela, P. H., 927 Makhsee, M., 458, 459 Maki, R., 292, 839 Maki, T., 999 Makifuchi, T., 565 Makino, I., 1112 Makino, R., 416, 417 Makino, S., 55, 196 Makino, T., 109 Makinodan, T., 729, 1101 Makishima, M., 998 Makkos, Z., 565 Maklebust, J., 1002 Makman, M. H., 1043 Makowski, L., 994 Maksimova, E., 357 Makukhin, I. I., 635 Malabarba, M. G., 997 Malagelada, J. R., 112 Malamet, R. L., 199 Malarkey, W., 512, 677, 683, 694, 734, 785, 789, 792, 884, 899, 900, 904, 1065, 1088 Malarkey, W. B., 77, 236, 512, 623, 724, 726, 734, 745, 786, 789, 790, 792, 793, 842, 856, 858, 861, 863, 882, 883, 888, 900, 901, 902, 906, 907, 908, 910, 962, 1019, 1044, 1062, 1065, 1079, 1080, 1088, 1099, 1111 Malarky, W. B., 842, 846 Malaval, F., 736 Malcolm, J. A., 933 Malec, P. H., 605 Malendowicz, L. K., 101 Malenka, R. C., 357, 359, 405 Maler, B. A., 49 Malferrari, G., 364
Author Index Maliarik, M. J., 809 Malide, D., 998 Malik, A. S., 358 Malik, I., 961 Malipiero, U. V., 360 Malissen, B., 725 Malkoff, S., 676, 784, 788 Mallard, C., 419 Mallery, S. R., 1080 Mallmann, P., 876 Mallon, E., 653 Mallon, L., 518, 579, 606 Malloy, P. J., 239 Malone, K. E., 242 Maloney, C., 380 Maloney, J. R., 459 Maloney, T. M., 236 Maloteaux, J.-M., 161 Malouf, N. N., 326 Maloyan, A., 1014 Malt, U. F., 875 Malucelli, B. E., 649, 653 Maluish, A., 874, 876 Maly, F. E., 512 Malyutina, S., 947 Mamakos, J., 874 Mammes, O., 1055 Man, A. H. W., 322 Man, M. Q., 988 Manatunga, A. K., 199 Manca, E., 361 Manchanda, N., 210 Mancini, J. A., 786 Manconi, P. E., 361 Mancuso, P., 995 Mancuso, R. A., 711, 772 Mandai, M., 330 Mandal, K., 957, 959 Mandaliya, K., 1059 Mandel, S., 147 Mandin, H., 771 Mandoza, L. M., 538 Mandrekar, P., 551, 553, 554 Mandrup-Poulsen, T., 996 Manel, N., 1056 Manetti, R., 212, 637 Manfield, L. E., 71 Manfredi, B., 256 Manfredi, M. G., 1055 Manfridi, A., 422, 434, 587 Mangan, C. E., 606 Mangat, H., 589 Mangge, H., 727, 729, 730, 732 Mani, V., 90 Manickasundari, M., 218 Maninger, N., 486 Manios, Y., 501, 505 Manji, H., 1054 Mankowski, J., 273
Mankowski, J. L., 490 Mann, D. L., 556 Mann, D. M., 364, 365 Mann, J., 771 Mann, J. J., 485 Mannaioni, P. F., 838 Mannarini, A., 716 Mannarino, E., 958, 960 Mannarino, M., 958, 960 Manne, S. L., 900, 903 Mannermaa, A., 364 Mannhalter, C., 421 Mannick, J. A., 1025 Mannion, R. J., 407 Mannix, C., 885 Mannonen, L., 859 Manns, M. P., 109, 435 Manogue, K. R., 54 Manson, J. C., 585 Manson, J. E., 956 Mansour, I., 1055 Mansson, P., 839 Mantecon, A. G., 101 Mantell, J., 786 Mantero-Atienza, E., 1060 Mantovani, A., 142, 217, 219, 434 Mantovani, G., 876 Mantyh, P. W., 101, 103, 107 Manuck, S. B., 483, 484, 485, 486, 497, 712, 714, 715, 730, 764, 766, 768, 769, 772, 773, 787, 792, 901, 911, 912, 929, 950, 964, 1065, 1080, 1111 Manuel, M., 466 Manuelpillai, W., 307 Manyonda, I. T., 101 Manzini, S., 115, 404 Mao, H., 789, 1015 Mao, H. Y., 623, 858, 863 Mao, L., 600 Mao, Y., 418, 419 Mao, Z., 184 Mapp, P. I., 200 Marano, M., 804 Marban, C., 1054, 1057 Marcell, T. J., 1000 Marcenaro, E., 107 March, C. J., 996 Marchalonis, J. J., 220 Marchand, F., 398, 401, 405 Marchand, J., 557 Marcheselli, V., 275 Marchesi, S., 958, 960 Marchetti, B., 239 Marchetti, C., 54 Marchioli, R., 957 Marciani, R. D., 830 Marciano, M. C., 300 Marcinkiewicz, M., 110 Marcondes, M. C., 307
1193 Marder, K., 1057 Marecos, E., 882 Maren, S., 341 Marenco, S., 564 Margioris, A. N., 108, 997 Margolese, R., 690 Margolin, G., 783 Margolis, D. J., 842 Marguet, C., 502 Margulies, S., 685, 791 Margulis, B., 1019 Mariani, C., 363, 364, 365, 366, 421 Mariani, E., 607 Mariani, J., 304, 385, 438, 439 Mariani, R. A., 361 Marietta, C., 553 Mariggio, M. A., 89 Marin, P., 516 Marinetti, G. V., 65, 66 Marini, L., 595, 607 Marino, M., 421 Marino, M. W., 352, 354, 419, 420, 995 Marino, V., 521 Marinovich, M., 405 Marion, D., 462 Marion, S., 995 Mariotti, M., 422, 587 Mark, A. L., 603 Mark, D. B., 694, 949 Mark, T. L., 717 Markesbery, W. R., 70 Markewitz, A., 254 Markham, A. W., 815 Markham, P. D., 1056 Markides, K. S., 713, 769, 770, 773 Markiewicz, K., 605 Markin, R. S., 116 Marklund, N., 419 Markoff, P. A., 667 Markovic, B., 632, 649, 653 Markovic, B. M., 1118 Markovitz, D. M., 1058 Markovitz, J. H., 930 Markowitz, M., 1054 Markowitz, N., 713, 1060 Markowska, A., 101 Markowska, A. L., 358 Marks, C., 554 Marks, G., 764, 767 Marks, J. S., 713 Marks, R., 90 Markus, A. M., 107 Markusse, R., 931 Marler, M. R., 579, 586 Marlin, R., 877 Marmot, M., 717, 772, 946, 947, 949, 961, 962, 963, 966, 967 Marmot, M. G., 498, 501, 505, 716, 717, 931
1194 Marmurowska-Michalowska, H., 570, 571 Maroder, M., 53, 55 Maron, R., 420 Marone, G., 109 Marquart, M. E., 56 Marques-Deak, A., 196, 198, 199 Marquette, C., 292, 302 Marrietta, P., 1110, 1112 Marriott, I., 102, 103, 107, 108 Marrocco, T., 241 Marsh, J. T., 1080 Marsh, L., 564 Marshall, D., 1100 Marshall, G., 769 Marshall, G. D., 800, 801, 807, 811, 812, 814, 815, 1079 Marshall, G. D., Jr., 73, 801, 811, 812, 816, 884 Marshall, Gailen, 707, 799 Marshall, J., 110, 184, 647, 648, 653, 873 Marshall, J. R., 234 Marshall, J. S., 97, 106, 110 Marshall, L., 591, 598, 601, 606 Marshall, P., 804 Marsland, A. L., 236, 237, 483, 485, 497, 764, 766, 768, 769, 772, 773, 901, 911, 912, 929, 934, 1065 Marsland, Anna, 706 Marsland, Anna L., 761 Marson, A. L., 880 Marten-Mittag, B., 932, 937 Marth, T., 143 Marti, A., 1046 Marti, O., 196, 739 Martikainen, P., 233, 870 Martin, A., 383, 517 Martin, B., 551 Martin, C. A., 1015 Martin, D., 329, 342, 344, 398, 399, 405, 406, 407, 408, 418, 419 Martin, D. E., 236 Martin, E., 137, 645–46 Martin, F. C., 556 Martin, G. S., 180 Martin, H. L., Jr., 1059 Martin, J., 148, 839 Martin, J. D., 101 Martin, J. F., 963, 965 Martin, J. L., 1060 Martin, M. E., 1055 Martin, M. F., 1043, 1044 Martin, P., 839 Martin, R., 1107, 1108 Martin, R. A., 774 Martin, R. B., 763, 764 Martin, R. J., 603 Martin, S. A., 584 Martin, S. J., 340
Author Index Martin, T. J., 557 Martin, U., 1026 Martina, C., 365, 421 Martinelli Boneschi, F., 364 Martinelli, G., 878 Martinez, A., 605, 1100 Martinez, A. C., 738 Martinez, C., 103, 104, 131, 133, 134, 135, 139, 143, 144, 146, 195, 366, 421, 571, 572, 603 Martínez, C., 651 Martinez, E., 1055 Martinez, J., 329, 678 Martinez, J. A., 1046 Martinez, M., 195 Martinez, M. C., 133 Martínez, R., 645 Martinez-Bonilla, G., 212, 214 Martinez-Lopez, E., 212, 214 Martinez-Maza, O., 882 Martini, A., 995 Martiniuk, F., 55, 980 Martino, M., 621 Martinot, M., 523 Martinotti, S., 53, 55 Martin-Parras, L., 736 Martin-Romero, C., 994 Martins, R. N., 364, 365, 366, 421 Martinson, D. E., 1058 Martling, C. R., 110, 115 Martorelli, V., 607 Martyn, C. N., 1108 Marucco, E., 200 Marucha, P., 694 Marucha, P. T., 77, 724, 734, 745, 790, 792, 827, 828, 830, 831, 832, 842, 843, 844, 845, 846, 934, 964, 1080, 1081, 1087, 1111 Marucha, Philip, 707, 825, 837 Marued, M., 912 Marullo, S., 235 Maruyama, S., 533, 535 Marvel, F. A., 289 Marx, J., 737 Mary, D., 73 Mary, S., 557 Marynen, P., 362 Marz, P., 338, 359 Marzi, M., 211, 212, 214 Marziniak, M., 399 Mascarenhas, P., 829, 830 Mascart-Lemone, F., 213 Mascovich, A., 514, 515, 538, 598, 607, 693 Masek, K., 679, 1026 Maseri, A., 502, 679, 695, 925, 956 Masferrer, J., 321 Mashburn, T. A., Jr., 321 Mashek, D. J., 793
Masi, A. T., 198, 199, 207, 208, 209, 212, 219, 222, 228 Masini, E., 838 Maskimova, E., 408 Maslankiewicz, K., 926 Masliah, E., 349, 350, 351, 364, 365, 384, 386, 420, 421 Masliah, J., 1019 Maslonek, K. A., 1017, 1025 Mason, A., 691 Mason, D., 197, 212, 732, 735, 738, 739, 740, 742, 855 Mason, D. K., 727, 729 Mason, D. W., 740 Mason, J., 421, 539 Mason, J. L., 421 Mason, J. W., 539, 540 Mason, M. D., 1019 Mason, S. A., 49 Mason, W. A., 485, 486, 487, 1060, 1063, 1065 Masood, N., 523 Massari, F., 716 Massberg, S., 951, 952 Massey, J. K., 855 Massi, M., 103 Massimo, J., 983 Massing, M., 948 Massobrio, M., 881 Masson, S., 110, 116 Masternak, M. M., 173 Masters, B., 533, 536, 537 Masterson, J., 1059 Mastorakos, G., 222, 254, 594, 599, 711, 712, 983 Mastropasqua, F., 716 Masuda, K., 977 Masuda, Y., 523 Masullo, C., 363, 364, 421 Masur, H., 1055 Masur, K., 240 Mata, I. F., 366, 421 Matarese, G., 1003 Matchar, D. B., 714 Matera, L., 222, 604 Matera, M. G., 363, 364, 421 Matetzky, S., 928 Mathes, S. J., 827 Matheson, George, 786 Mathews, H. L., 77, 1061 Mathews, P. M., 70 Mathias, J., 995 Mathiesen, T., 417 Mathieu, D., 1058 Mathieu, M., 842 Mathur, J., 715 Matic, G., 1014 Matijevic, L., 532, 535, 537 Matikainen, S., 1100
Author Index Matire, L. M., 791 Matran, R., 109 Matre, R., 875 Matrosovich, M. N., 1099 Matrosovich, T. Y., 1099 Matsubara, T., 923 Matsubara, Y., 365 Matsuda, H., 98, 106, 109 Matsuda, I., 184 Matsuda, M., 997, 998, 1000, 1001 Matsuda, S., 98, 109, 115, 350 Matsuguchi, T., 55 Matsui, H., 342 Matsui, J., 1001 Matsukawa, S., 254 Matsuki, A., 571, 1039, 1040, 1041 Matsuki, N., 354, 355, 646 Matsumi, S., 1056 Matsumoto, I., 110 Matsumoto, M., 998 Matsumoto, S., 1001 Matsumoto, T., 400 Matsumoto, Y., 344, 347, 352, 354, 359 Matsumura, H., 321, 326, 330, 331 Matsumura, K., 87, 273, 294, 322, 323, 326, 327 Matsumura, T., 998 Matsumuro, K., 106 Matsunaga, K., 255 Matsuno, H., 110 Matsuo, A., 383 Matsuo, S., 554 Matsuo, Y., 432 Matsuoka, T., 326 Matsuoka, Y., 329 Matsushima, G. K., 421 Matsushima, K., 142, 736, 741, 1056 Matsushita, H., 1058 Matsushita, M., 342 Matsushita, S., 1056 Matsuura, N., 418 Matsuyama, A., 997 Matsuyama, H., 133 Matsuyama, T., 352, 863 Matsuzawa, Y., 997, 1000, 1001, 1003 Matt, K. S., 199, 784, 788 Matteoli, M., 291 Mattes, J., 470 Matthaei, A., 999 Matthews, C. E., 666 Matthews, D. A., 714 Matthews, K. A., 497, 498, 499, 623, 713, 717, 773, 929, 930, 964 Matthews, P. M., 71 Matthews, W., 995 Matthias, P., 74 Mattila, K., 927 Mattson, M. P., 184, 275, 276, 357, 380, 383, 419, 420, 1054
Maturana, P., 534, 535, 538 Matute, C., 565 Matyszak, M. K., 344, 382, 436, 438, 444 Matz, J. M., 1014 Matzinger, P., 217, 252, 272, 879, 1018, 1024 Maucione, A., 256 Mauger, D. T., 419 Maulden, S. A., 1080, 1081 Maule, S., 200 Maunsell, E., 234, 870, 873 Maurel, D., 736 Maurer, G., 72 Maurer, M., 102, 109 Mauri, C., 143 Maurice, J., 694, 937 Maury, C., 995 Maury, K., 103 Maus, U., 1100 Mautner, B., 923 Maxwell, M. E., 567 May, M. J., 274, 292, 295, 741 May, W., 209 Mayberg, H. S., 710 Mayburd, E., 710 Mayer, B., 103 Mayer, E. P., 663, 1082 Mayer, K., 1100 Mayer, P., 161 Mayer-Proschel, M., 403 Mayhew, M., 1024 Maymon, E., 458 Maynar, M., 855 Maynard, C., 531 Mayne, T. J., 789, 1061 Mayo, J., 1055 Mayo, W., 344, 712 Mayor, F., Jr., 1045 Mayr, T., 329 Mayumi, M., 73 Mazaeva, N. A., 567 Mazieres, B., 110, 200 Mazmanian, S. K., 464 Mazumdar, S., 116 Mazuran, R., 532, 535, 536, 537, 538 Mazurowa, A., 605 Mazzaglia, G., 295 Mazzarella, G., 103 Mazzarello, V., 568 Mazzeo, D., 72, 73, 1045 Mazzetti, M., 549, 551 Mazzi, P., 841 Mazziotti, G., 361 Mazzocco, V. R., 998 Mazzola, P., 63, 69, 72, 1044, 1045 Mazzone, S. B., 809 Mazzoni, A., 1025 Mazzotta, G., 417, 420, 588
1195 Mazzucchelli, L., 1015 McAdam, H. M., 342 McAllen, R. M., 327 McAllister, A., 1110 McAllister, C. G., 71, 570, 623, 743, 934 McAllister-Sistilli, C. G., 516, 556 McAlpine, B. E., 109 McAnulty, L., 669 McAnulty, L. S., 663, 668, 669 McAnulty, S. R., 663, 668, 669 McArdle, W., 73 McArthur, J., 567 McArthur, J. C., 166, 1057 McAuley, K. A., 1000 McAuliff, J. P., 1042 McAuliffe, T. L., 1062 McBride, W. H., 997 McBrides, P. A., 585 McBurnie, M. A., 932 McCabe, C. H., 937 McCabe, P., 687, 688, 689, 1055, 1061 Mccabe, P. M., 483 McCadden, J. D., 880 McCann, S. M., 292, 294, 299 McCarley, R. W., 564 McCarson, K., 103 McCarson, K. E., 110 McCarthy, A. D., 998 McCarthy, D. B., 296 McCarthy, D. O., 296, 786, 815 McCarthy, J. R., 1002 McCarthy, K. D., 403 McCarthy, M., 977 McCarty, M., 882 McCashill, C. C., 979 McCaskill, C. C., 716 McCeney, M. K., 964, 966 McClain, C. J., 551 McClane, S. J., 542 McClellan, B. H., 459 McClellan, J. L., 286, 302 McClelland, D. C., 624, 764 McCleskey, E. W., 160 McClintick, J., 512, 514, 598 McClintock, M., 884 McClintock, M. K., 236 McClish, D. K., 466 McClure, J., 487 McClure, J. B., 1062 McClure, J. E., 70 McColl, B. W., 269, 274, 276, 415 McCollum, K. F., 458 McConaghy, N., 570 McConahay, D. R., 937 McConnell, I., 443 McCook, E. C., 305 McCorkle, R., 553, 1079 McCormack, D., 400 McCormack, R. J., 100
1196 McCormick, C., 491 McCormick, C. M., 712 McCoy, G. C., 541 McCoy, J. L., 252 McCrady, B., 789 McCraty, R., 763, 764 McCullagh, C. D., 366 McCulley, M. C., 364 McCulloch, D. A., 133 McCullough, M. E., 782 McCune, W. J., 734, 745 McCurry, C., 647 McCusker, R., 41 McCusker, R. H., 171, 172, 173, 174, 175, 180, 181, 182, 183 McCusker, R. H., Jr., 175 McCusker, Robert H., 171 McCusker, S. M., 366 McCuskey, R. S., 1036 McCutchan, A., 1060, 1062 McCutchan, J. A., 1054, 1060, 1061 McCutcheon, I. E., 173, 180 McDade, T. W., 462, 501, 800, 858 McDermott, M., 694 McDermott, M. P., 901, 908, 1057 McDermott, M. T., 1054, 1055 McDevitt, H. O., 366 McDonald, A. R., 48 McDonald, C. M., 959 McDonald, D. M., 101, 103 McDonald, J. J., 358 McDonald, J. S., 256 McDonald, J. T., 430 McDonald, P. G., 682, 683, 692 McDonald, P. H., 235 McDonald, P. P., 440 McDonald, W. A., 663 McDonald, W. I., 1110 McDonell, N., 362 McDonnell, P. C., 417 McDowell, I., 761 McDowell, T. L., 366 McDyer, J. F., 56 McElhaney, J., 662 McElhaney, J. E., 764, 767, 900, 906 McEwan, B., 235 McEwan, I. J., 50 McEwan, J. R., 966, 968 McEwen, B., 72, 195, 479, 481, 654, 677, 679, 745, 965 McEwen, B. S., 68, 104, 112, 222, 348, 357, 469, 480, 481, 491, 499, 516, 531, 620, 621, 715, 723, 724, 725, 726, 727, 728, 729, 730, 731, 732, 733, 734, 737, 739, 741, 742, 743, 744, 745, 747, 748, 750, 832, 932, 967, 1036, 1044, 1046, 1082, 1099, 1112 McEwen, Bruce, 706 McEwen, Bruce S., 723
Author Index McFall, J. R., 540 McFall, M. E., 541 McFarland, H. F., 1108 McFarland, M., 241 McFarlane, A. C., 531, 541 McFarlane, C., 995 McFeeley, S., 786, 787, 876 McFerran, B., 485 McGarvey, L. P., 115 McGaugh, J., 645, 649 McGaugh, J. L., 340 McGee, R., 869, 870 McGeer, E. G., 361, 421, 439 McGeer, P. L., 361, 383, 421, 439, 440 McGhee, J. R., 107 McGill, V., 553 McGillis, J. P., 100, 104, 115 McGinn, S., 876 McGinnis, S., 710 McGinty, D., 586 McGlashan, T. H., 564 McGlone, J. J., 727, 729, 744 McGorry, M. M., 88 McGovern, R. A., 332 McGowan, E., 1015, 1016, 1023 McGowan, E. G., 1023 McGrady, A., 93, 683, 814 McGrath, C. M., 236 McGregor, B., 687, 691, 876, 877, 881 McGregor, B. A., 687, 691, 1055 McGregor, G. P., 110 McGue, M., 808 McGuire, L., 380, 514, 768, 774, 792 McGuire, M. T., 477, 485 McHale, J. F., 1100 McHutchison, J. G., 237 McIlroy, S. P., 366 McInnis, M. G., 366 McIntosh, J., 717 McIntosh, T. K., 352, 354, 419, 420 McIntyre, C. W., 771 McIntyre, K. W., 345 McIntyre, L. A., 400 McIntyre, T. D., 552 McKay, D. M., 98, 101, 109, 115, 116, 1024 McKay, J. R., 509, 510, 511, 553, 874, 932, 1079 McKay, L. I., 53, 524 McKean, K. A., 828ÿ McKelvey, L., 930 McKenna, M., 869 McKenna, M. C., 233 McKenzie, I. F. C., 1043 McKercher, S. R., 839 McKinley, D. D., 385, 441 McKinney, C., 688 McKinney, W. T., Jr., 477 McKinnon, W., 532, 537, 538, 676
McKittrick, C. R., 479, 1111 McKnight, A., 1054 McKusick, L., 686, 1061 McLachlan, E. M., 400 McLean, A. A., 859 McLean, A. R., 1054 McLeish, K. R., 1025 McLeod, L. E., 1043 McLeod TM, L.-F. A., 809 McLoon, L. K., 165 McMahon, G., 882 McMahon, L. J., 744 McMahon, S. B., 398, 401, 405 McMann, J. M., 599 McManus, C. M., 136 McMenamin, P. G., 400 McMillan, D. R., 1015 McMinn, J., 332 McMullan, L. K., 1058 McMurray, R. W., 201, 209 McNair, D. M., 762 McNair, P., 592, 594 McNerlan, S., 1022 McNinch, J., 142 McPherson, G. A., 66 McPherson-Baker, S., 1062 McQuay, H. J., 396 McQuid, D. R., 540 McRae, B., 1053 McRae, B. L., 552 McRae, C., 710 McSharry, C., 106 McSorley, S. J., 115 McSweeney, J. C., 931 McTiernan, A., 668 McTigue, D. M., 88 McVay, J., 531 McWade, F. J., 182 Mdzewski, B., 875 Meade, C. S., 792 Meade, T. W., 957 Meadows, G. G., 553, 554 Meagher, L. C., 980 Meagher, M. W., 1080, 1081, 1107, 1110, 1111, 1112, 1114, 1115, 1116, 1118 Meaney, M. J., 491, 712, 829, 983, 1118 Meany, M. J., 456 Mears, B., 786 Mease, P., 586 Mecacci, F., 462 Meck, J. V., 855 Meco, D., 53, 55 Meda, C., 210 Medalie, J. H., 789 Medbak, S., 197 Medberry, P., 136 Mediansky, L., 786 Medina, C., 288, 382 Médina, C., 651
Author Index Medina, J. H., 344, 346, 347 Meduri, G. U., 980 Medzhitov, R., 46, 52, 98, 217, 272, 282, 337, 1024 Meehan, R., 854 Meehan, R. T., 663, 930 Meenhard, H., 879 Meesters, C. M., 929, 931 Meetz, G., 678 Meffert, R. M., 830 Mege, J. L., 570 Megel, M. E., 811 Mehal, W. Z., 840 Mehler, M. F., 359 Mehlman, P. T., 479 Mehrens, D., 1057 Mehta, B., 85 Mehta, J. L., 921, 994 Mehta, P. D., 361 Mehta, S., 184 Mehta, S. K., 236, 853, 854, 855, 856, 857, 858, 859, 860, 862, 863, 1079 Mehta, Satish, 707, 851 Mei, Q. B., 1037 Meidel, A., 510 Meidell, R. S., 1043 Meier, B., 923 Meier, C. A., 995, 997 Meier, C. R., 242 Meier, F., 879 Meier, R., 55 Meier, T., 1015 Meierhofer, C., 108 Meilahn, E. N., 717, 923 Meineke, H. A., 1036 Meiner, Z., 364 Meini, S., 107 Meirelles, R. M., 1055 Meisel, A., 76 Meisel, C., 76, 997 Meisel, S. R., 933 Meissler, J. J., Jr., 557 Meissner, J., 109 Meistrell, M. E., III, 92, 419 Mei-Tal, V., 725, 726, 745 Mekaouche, M., 736 Melamed, B., 790 Melamed, E., 184 Melamed, R., 76, 236, 255, 256, 257, 258, 259 Melames, S., 817 Melby, J. C., 1053 Melcarne, A., 710 Melcher, A. A., 1024 Melchior, J. C., 1055 Melega, W. P., 485 Melemedjian, O. K., 1056 Melen, K., 1100 Melendez, P. A., 996, 1000
Meli, A., 117 Melief, C., 693, 878, 879 Melief, C. J., 252 Melief, M. J., 100 Melisaratos, N., 771 Mellado, M., 603, 1100 Mellema, M. S., 1002 Melling, J., 604 Mellman, T., 695 Mellman, T. A., 538, 541 Mello, N. K., 555 Mellon, R. D., 555, 556, 1101 Mellonig, J. T., 830 Mellor, A. L., 522 Mellors, J. W., 487, 1054 Melmon, K. L., 66, 1043, 1044 Melnick, J. L., 927 Melnick, S. L., 1053 Melone, M., 565 Meltzer, E. O., 803, 806 Meltzer, H., 565 Meltzer, H. Y., 304, 511, 512, 516, 568, 570, 622, 1112 Meltzer, J. C., 64 Memon, R. A., 959 Mencia-Huerta, J. M., 801 Mendall, M. A., 516, 928, 937 Mendel, C. M., 747 Mendel, I., 1115 Mendelsohn, A., 352, 354, 359, 360 Mendelson, J. H., 555 Mendelson, S. C., 745 Mendenhall, C. L., 550 Mendes de Leon, C. F., 694, 931, 935 Mendes, W. B., 793 Mendiola, M., 693 Mendiz, O., 923 Mendoza, S. P., 482, 484, 485, 486, 487, 491, 1060, 1063, 1065 Mendoza-Fuentes, A., 210 Menetski, J. P., 52 Meng, Y. G., 223 Menges, M., 142 Menghi, G., 977 Menke, H., 977 Menninger, K. A., 566 Menoyo, E., 557 Menz, G., 502 Menzel, R., 632 Meoni, L. A., 714 Merali, Z., 304, 305, 306, 343, 347, 511, 514, 522, 523, 652 Mercader, A., 359 Mercado, A., 694 Mercado, A. M., 790, 792, 832, 842, 843, 844, 845, 846 Mercanti, D., 184 Mercer, D. E., 1061 Mercer, N., 998
1197 Mercer, W. D., 557 Mercier, F., 400, 401 Mercier, S., 585 Mercurio, A. M., 239 Mercurio, F., 741 Merenich, J. A., 1054, 1055 Merialdi, M., 466, 469 Merida, A., 101 Meridith-Middleton, J., 407 Meriwether, J. L., 733, 1025 Merkin, S. S., 948 Merlin, D., 1002 Merlo, D., 184 Merlot, E., 480, 481, 482 Mermelstein, R., 785 Mero, R. P., 499 Merriam, J. E., 996 Merriam, P. A., 666 Merrick, N., 714, 717 Merrill, J. E., 136 Merrill, J. P., 74 Merrow, M., 73 Merryman, J., 260 Merten, M., 952, 957 Mertens, D. J., 662 Merz, C. N. B., 967 Mesches, M. H., 1017 Messi, M. L., 90 Messick, C. H., 385 Messick, G., 677, 686, 787, 792 Messingham, K. A., 552, 553 Mester, R., 534, 536 Mesters, R., 882 Metalnikov, S., 635, 636 Metcalf, D., 995 Metcalfe, N. B., 285 Metchnikov, E., 636 Mete, N., 1002 Methi, T., 240 Metwali, A., 100, 101, 103, 104, 107, 108 Metz, C., 85 Metz, C. N., 736, 844 Metzger, D. S., 554 Metzger, L. J., 541 Metzler, H., 72 Metzner, H. L., 781 Meulman, J., 694 Meurisse, M., 252 Meydani, M., 295, 303, 669 Meydani, S. N., 295, 303, 669 Meyer, J., 957, 959, 996 Meyer, L., 885 Meyer, R. G., 1100 Meyer, R. J., 456 Meyer, S., 985 Meyer, T., 51 Meyer Zum Büschenfelde, K.-H., 744 Meyerowitz, S., 725, 726, 745 Meyers, C., 237
1198 Meyers, C. A., 519 Meyerson, A. T., 510, 622 Meyers-Schoy, S. A., 1019 Mezey, E., 241 Mezzapesa, D. M., 148 Mezzaroma, I., 688, 790, 1060, 1062 Mi, W., 1080, 1110, 1115 Miao, F. J., 110, 194 Miaskowski, C., 693 Micera, A., 352, 354, 360 Michaelis, M., 109 Michaels, J., 105 Michaelsen, K. F., 464 Michalowska, A., 926 Michaud, B., 288, 296, 298, 304, 320, 382, 996 Michaud, C. M., 509 Michel, F. B., 812 Michel, M., 1044 Michel, M. C., 70, 605, 654, 766, 1042, 1043 Michelato, A., 571 Michelen, V., 736 Michell, M., 870, 871 Michelson, D., 200 Michitaka, K., 554 Mickerson, J. N., 736 Micklem, H. S., 592 Miczek, K. A., 303, 621 Middaugh, S. J., 93 Middel, J., 1053 Middleton, D., 366 Middleton, E., 678, 745, 1043 Middleton, F. A., 564 Middleton, R. A., 770 Miedema, F., 1053, 1060 Miele, M., 209, 210, 224 Mielke, M., 1038 Mier, J., 92 Mier, J. W., 273 Miesfeld, R., 49 Miesfeld, R. L., 48 Miettinen, K., 569 Migliorati, G., 54 Mignini, F., 635 Mignot, E., 588 Miguel, B. G., 135, 146 Miguel-Hidalgo, J. J., 565 Miguez, M. J., 1061, 1065 Mihalek, R., 632 Mijares, M., 957 Mijatovic, T., 997 Mijnster, M. J., 241 Mikami-Nakanishi, M., 322 Mikawa, H., 101, 115 Mikeska, E., 726, 739 Mikita, T., 998 Milaat, W. A., 502 Milanes, M. V., 711
Author Index Milani, D., 1058 Milanovich, J. R., 1057 Milazzo, F., 1055 Milde, A. M., 983 Miles, B. A., 65 Miles, J., 910, 911 Miles, K., 70 Miles, T. A., 933 Mileusnic, D., 103 Milewicz, A., 1000, 1001 Milford, H. G., 50 Milgrom, H., 816 Millar, D., 637 Millar, D. B., 732 Millard, D. K., 384 Millard, M., 419 Miller, A., 274, 418, 419, 451 Miller, A. H., 172, 222, 296, 304, 305, 307, 481, 509, 511, 512, 516, 519, 520, 521, 524, 542, 608, 723, 724, 725, 726, 727, 728, 729, 730, 731, 739, 741, 742, 743, 744, 745, 747, 750, 932, 1044, 1080, 1099 Miller, A. L., 71, 516, 556, 570, 623, 815 Miller, C., 510, 512, 514, 552, 603, 607 Miller, D., 652 Miller, D. B., 305 Miller, D. H., 437 Miller, D. R., 859 Miller, G., 509, 512, 782, 787, 790, 792 Miller, G. E., 451, 497, 499, 503, 509, 511, 512, 516, 534, 535, 536, 537, 543, 619, 622, 624, 625, 681, 682, 694, 724, 761, 766, 768, 773, 789, 881, 899, 900, 903, 904, 912, 913, 914, 929, 932, 937, 962, 966, 969, 1055, 1062, 1063, 1089, 1112 Miller, G. J., 957 Miller, Gregory E., 497 Miller, H. I., 966 Miller, H. L., 521 Miller, H. R., 109, 111 Miller, I., 684 Miller, J., 566 Miller, J. B., 182 Miller, J. C., 358, 586 Miller, K., 236 Miller, K. D., 1055 Miller, L., 693, 828, 856 Miller, L. E., 200, 223, 224 Miller, M. A., 1040 Miller, N. E., 285, 727, 743, 762 Miller, R., 1054 Miller, R. A., 887 Miller, R. C., 136 Miller, R. J., 434, 533, 538 Miller, S. C., 196 Miller, S. D., 87, 103, 148, 149, 1108, 1109, 1110
Miller, S. H., 1040 Miller, S. I., 431 Miller, S. M., 606 Miller, T. B., 584 Miller, T. Q., 497, 623 Miller-Graziano, C. L., 85 Millest, A. J., 200 Milligan, D. W., 872 Milligan, E., 405 Milligan, E. D., 88, 269, 273, 275, 395, 397, 398, 399, 401, 402, 405, 406, 407, 408, 409, 524 Millon, C., 1060 Mills, C. M., 90 Mills, K. H., 353, 355 Mills, M., 606 Mills, P, 680 Mills, P., 148, 730, 963, 965 Mills, P. J., 70, 606, 680, 729, 730, 855, 930, 931, 934, 962, 963, 965, 966 Mills, S. J., 825, 829, 830, 831, 837 Milner, C. M., 1015, 1023 Milon, G., 292, 302 Milroy, E. J., 117 Milsark, I. W., 738, 843 Milstone, D. S., 999 Milton, A. S., 323 Milton, G. V., 92 Milton, G. W., 556 Min, D. J., 76 Minagar, A., 276, 1002 Minagawa, T., 1111 Minakuchi, R., 73 Minami, M., 87, 186, 301 Minamitani, M., 859 Minas, V., 997 Minchoff, B., 762, 763 Mindell, A., 1079 Mindlin, R., 716 Mine, K., 330 Minghetti, L., 91, 147, 276, 358, 404, 440 Minick, C. R., 958 Minner, B., 515 Minoli, L., 1055 Minonzio, F., 100 Minopoli, G., 109 Minor, K. D., 998 Minshall, C., 171, 175 Minster, R. L., 364, 365 Minthon, L., 361 Minton, J., 878 Miorner, G., 736, 745 Mir, A. K., 434 Mirabella, M., 1003 Miranda-Saksena, M., 1079 Mirani, M., 1056 Mirante, D., 200 Mirkes, S. J., 485 Mirnics, K., 564
Author Index Mirochnick, M., 1055 Mirowsky, J., 783 Mirsalim, P., 554 Mirtsou, V., 364 Mirzayans, F., 858 Misanin, J., 639 Misawa, H., 88, 105 Mischler, K., 963 Misery, L., 109, 113, 114 Misgeld, T., 106 Mishima, K., 115 Misiewicz, B., 197 Misse, D., 1058 Missitzis, I., 692 Missler, U., 565, 566 Missotten, M., 103 Mistretta, A., 103 Mitamura, K., 519 Mitani, M., 197 Mitchell, D. M., 76, 923 Mitchell, H. K., 1014 Mitchell, P., 695 Mitchell, P. J., 305 Mitchell, R., 133 Mitchell, W. M., 164, 294 Mitchison, N. A., 1054 Mitler, M. M., 586 Mito, N., 1002 Mitra, A., 1002 Mitra, D., 1056, 1059 Mitra, R. B., 242 Mittal, R., 237 Mittelstadt, P. R., 54 Mittendorfer-Rutz, E., 712 Mittleman, M. A., 933, 948 Mittwoch-Jaffe, T., 625, 763, 765 Miura, A., 999 Miura, H., 523 Miura, M., 115, 810 Miura, T., 652, 1039, 1040, 1041 Miura, Y., 197 Miyachi, Y., 198 Miyagawa, J. I., 1003 Miyake, K., 106 Miyakoshi, K., 223 Miyamoto, Y., 339, 352, 353, 354 Miyan, J., 635 Miyan, J. A., 100, 1057 Miyaoka, H., 519 Miyashiro, J. M., 358 Miyata, S., 1000, 1001 Miyaura, H., 139, 481 Miyawaki, T., 592 Miyazaki, A., 1001 Miyazaki, H., 348, 382 Miyazaki, K., 74 Miyazaki, T., 223, 785 Miyoshi, K., 180 Mizoguchi, A., 144, 321, 329, 331
Mizoguchi, E., 144 Mizoi, Y., 522 Mizokoshi, A., 407 Mizuma, H., 106 Mizuno, K., 736 Mizuno, N., 321, 331 Mizuno, T., 147, 148 Mizzen, L., 1015, 1023 Mo, Z. L., 274 Moalem, G., 148, 399 Moberg, G. P., 482 Moberg, P. J., 565 Mobius, D., 69 Mobley, B. C., 186 Mobley, D., 549, 551 Mobley, W. C., 106 Mocellin, S., 172, 177, 178 Mochida, S., 554 Mochizuki, H., 147 Mochizuki, N., 239 Mochizuki, T., 331 Modarres, S., 102, 109 Moday, H., 481, 727 Modesti, M., 380 Mody, N., 1000 Moe, K., 606 Moen, P., 782 Moen, R. J., 1014 Moes, H., 458 Moessner, R., 485 Moestrup, T., 790, 1062 Mofenson, L., 1055 Moffett, J. R., 417 Mohamed-Ali, V., 365, 502, 503, 512, 514, 542, 680, 694, 931, 956, 963, 965 Mohammed, A. H., 306 MohanKumar, P. S., 296, 297 MohanKumar, S. M., 296, 297 Mohar, G., 744 Mohell, N., 1022 Mohideen, N., 237 Mohlig, M., 1000, 1001 Mohlig, T., 89 Mohr, D. C., 681, 695, 1110, 1112 Mohr, T., 663 Mohri, I., 321, 331 Moinuddin, A., 87 Moises, H. W., 977 Mojsov, S., 108 Mojtabhai, R., 808 Mok, C. C., 198 Mokyr, M. B., 74, 236, 1058, 1065 Molassiotis, A., 872, 1065 Moldawer, L. L., 273, 297, 345, 733, 1025 Moldofsky, H., 586, 587, 592, 599, 609 Molina, V., 733 Molina-Holgado, E., 569
1199 Molinatti, G. M., 1055 Molinero, A., 419 Molinero, P., 134 Molitor, T. W., 136 Mollby, R., 1024 Molle, M., 224, 592, 593, 594, 598, 599 Moller, A., 273 Moller, H. J., 365, 568, 1115 Moller, K., 996 Moller, T., 291 Molton, I., 693 Molvig, J., 364 Monachesi, M., 222 Moncada, S., 738 Monchy, J. G., 66 Mondal, T. K., 77 Mondor, M., 234, 870 Moneta, D., 186 Mongini, P. K., 56 Monica, C., 772 Monjan, A. A., 579, 607, 743 Monje, M. L., 359, 360, 386 Monk, T. H., 580 Monma, I., 198 Monma, M., 512 Monnier, M., 584 Monsen, C. E., 923 Montagna, P., 208, 211, 585 Montagnani, M., 1001 Montebarocci, O., 772 Montefiori, D. C., 1065 Montella, A., 568 Montgomery, C., 181 Montgomery, G., 874 Montgomery, J., 539 Montgomery, P. T., 490, 534, 535 Montgomery, S. M., 1002 Monti, D., 380, 784, 792 Monti, P., 142, 980 Montier, F., 117 Montminy, M. R., 137 Montpetit, M., 1056 Montreggia, L. M., 90 Montroni, M., 1054 Moo, L., 166 Moody, C. A., 103 Moody, T. W., 133 Moonen-Leusen, B. W., 1080 Moonen-Leusen, H. W., 1080 Mooney, R. A., 995 Mooney-Heiberger, K., 329, 678 Moore, A., 396 Moore, B., 105 Moore, D. D., 237 Moore, F. G., 1108 Moore, J., 1061 Moore, K. A., 405 Moore, K. J., 999 Moore, P., 307
1200 Moore, P. M., 196 Moore, S., 137 Moore, T., 174 Moores, K., 407 Moorey, S., 691 Moorhead, J. W., 728, 732 Moorman, A. F., 48 Moos, R., 761 Moos, R. H., 726, 733, 745 Moqbel, R., 55 Mora, O. A., 1046 Morabito, D., 1024 Morag, A., 223, 259, 284, 305, 339, 504, 609, 622, 901, 904 Morag, M., 259, 284, 305, 339, 504, 622, 901, 904 Morahan, P. S., 1082 Moraine, C., 362 Morales, M., 420 Moran, T. M., 1102 Morand, E. F., 54, 197 Moraska, A., 1014, 1025 Morato, E. F., 552 Morato, G. S., 552 Morbidelli, L., 224 Morcos, M., 72, 965 Mordashev, B., 710 Mordhorst, C. H., 663 More, S. H., 1023, 1024 Moreau, M., 307, 308, 522 Moreb, J., 234, 871 Morel, C., 1045 Morel, P. A., 855 Morella, K. K., 994 Morelock, S., 585 Moreno, F. A., 1061 Moreno-Coutino, G., 210 Moreno-Flores, M. T., 148 Moretta, A., 107, 995 Morey, M., 386 Morgan, B. P., 46 Morgan, C. A., 541 Morgan, D. O., 1056 Morgan, R., 1054, 1055, 1057 Morgan, T. E., 384 Morgan, W., 684 Morganti-Kossmann, M. C., 148, 417, 419 Morgenstern, H., 812, 1061 Morgenstern, R., 322 Morham, S. G., 322 Mori, M., 604, 999 Mori, N., 109 Moriggl, R., 998 Morikawa, O., 521, 522 Morikawa, Y., 109 Morimoto, A., 321 Morimoto, K., 533, 535 Morimoto, R. I., 1014, 1015, 1020
Author Index Morin, C. M., 518, 579, 606 Morin, D., 997 Morino, K., 994 Morioka, N., 404 Morishima, T., 863 Morishima, Y., 254 Morishita, W., 357, 359 Morita, F., 350 Morita, M., 741, 863 Moriwaki, A., 342 Moriya, H., 405 Mork, S., 436 Morledge, P., 1017 Morley, J. E., 87, 287, 343, 347, 729, 1101 Mormede, C., 284, 305, 307, 308, 651 Mormont, M., 884, 885 Morohashi, M., 109 Moroni, M., 1055 Morozova, M. A., 570 Morri, H., 53 Morris, A. G., 1023 Morris, C., 511 Morris, J. J, 933 Morris, J. K., 928 Morris, J. L., 198, 726, 733, 745 Morris, M., 690 Morris, M. J., 223 Morris, R., 341 Morris, R. G., 340, 741 Morris, R. G. M., 340, 341 Morris, T., 692, 871, 872, 873, 875, 887 Morrison, C. F., 134, 140 Morrison, J. M., 768 Morrison, M., 1061 Morrison, M. F., 1061 Morrison, S. F., 326, 327 Morrow, D., 937 Morrow, D. A., 681 Morrow, G. R., 520 Morrow, J. D., 339, 422, 588, 663, 669, 734, 790 Morrow, L. E., 302 Morrow-Tesch, J. L., 727, 729, 734, 744 Morschhäuser, E., 982, 983, 984, 985, 986 Morse, E. V., 1055 Morse, S., 1082 Morselli-Labate, A. M., 116 Morteau, O., 102 Mortensen, R. M., 999 Morton, D., 624, 691, 692, 773, 774, 877, 881 Morton, D. L., 624 Morton, G. J., 297 Mortz, C. G., 976 Moseley, P. L., 1015, 1016, 1024 Moser, A., 297 Moser, A. H., 959, 995 Moser, B., 142, 435
Moser, D. K., 931 Moser, M., 585 Moser, M. B., 386 Moses, M., 253 Mosimann, B. L., 131 Moskaliova, O., 1019 Moskowitz, J. T., 771, 1060 Moskowitz, M. A., 110, 199, 419, 420, 433 Moskvina, V., 964, 965 Mosley, B., 996 Mosmann, T. R., 47, 56, 212, 457, 732, 735 Mosnaim, A. D., 534, 535, 538 Mosnaim, G., 534, 535, 538 Moss, A. J., 694 Moss, G. B., 1059 Moss, H., 1060 Moss, H. B., 764, 767 Moss, N. E., 500 Moss, R. B., 764, 767 Moss, T., 363, 364, 421 Mosselmans, R., 1018 Mosser, D., 1015 Mosser, D. D., 1015 Mosser, D. M., 997 Moss-Moriss, R., 901, 910 Mossner, R., 522 Mostad, S. B., 1059 Mostafa, M., 362 Mosunjac, M., 1058 Mota-Miranda, A., 386 Motawi, T. K., 303 Motivala, S., 608, 609 Motivala, S. J., 511, 514, 516, 518, 554, 607, 1057, 1060 Motojima, S., 55 Motoshima, H., 1001 Mottonen, M., 219 Motulsky, H. J., 1043 Moudgil, V. K., 728 Moulds, M. L., 542 Moulton, R. J., 420 Mourelle, M., 112 Mousa, A., 359 Mousa, S. A., 110, 160, 161, 162, 164, 165, 166, 554 Mousli, M., 101 Moussaoui, S., 117 Moussaoui, S. M., 161 Mouton, P. R., 382, 386 Moyna, N. M., 621 Moynagh, P. N., 357 Moynihan, J., 555, 632, 637, 645, 651, 691 Moynihan, J. A., 64, 68, 69, 194, 255, 516, 725, 731, 732, 734, 900, 903, 914, 1036, 1039, 1040, 1046, 1078, 1079, 1080, 1083, 1084, 1087
Author Index Mozaffarian, A., 75 Moze, E., 480, 481, 482 Mozo, L., 56 Mrak, R., 439, 440 Mrak, R. E., 361, 363, 364, 421, 444, 564 Mrazek, D. A., 469 Mrazek, P., 469 Mtandabari, T., 913 Mu, H. H., 747, 855 Muanga, G., 585 Mucke, L., 384 Mudd, S., 999 Mudde, G. C., 978, 986 Muders, F., 926 Mudipalli, A., 181 Mudter, J., 144 Muegge, K., 53 Muehrcke, R. C., 741 Mueller, K., 69, 71, 1039, 1040 Mueller, M. M., 238 Muglia, L. J., 295 Mugyenyi, P., 1055 Muhammad, R., 167 Muhl, C., 198, 200 Muhlbauer, E., 553 Muhlblock, O., 236 Muhlestein, J. B., 927, 928, 959 Mui, A., 241 Muir, J., 501 Muis, T., 115 Mukai, S., 116 Mukaida, N., 741 Mukesh, B., 1000 Mukherjee, J., 1055 Mulcahy, N., 99, 290, 418 Mulder, C., 689 Mulder, C. L., 1060, 1061 Mulder, E. J., 711 Mulder, N., 679, 689 Mulder, N. H., 519 Mulder, P., 931 Mulderry, P., 104 Muldoon, M. F., 730, 766, 773, 934, 950, 964 Mulhall, B. P., 1055 Mullberg, J., 144 Mulle, G., 181 Mullee, M., 386, 440, 444 Mullen, M. J., 501, 960, 961, 962, 964 Mullen, P. D., 694 Muller, A., 238 Muller, C., 554, 690 Muller, D., 622, 900, 901, 902, 909, 910, 913 Muller, E., 951, 952, 1015 Muller, F., 1058 Muller, F. B., 727, 934 Müller, H., 744 Muller, H. K., 236, 534, 535, 855, 862
Muller, I., 951, 952 Muller, J. E., 922, 930 Müller, K., 569 Muller, K. M., 73, 997 Muller, M. J., 553 Muller, N., 568, 570, 572, 1115 Muller, O. A., 54 Muller, T., 361 Muller, U., 363, 364, 365, 366, 421 Muller-Ladner, U., 193, 1003 Muller-Newen, G., 338 Muller-Preuss, P., 296 Muller-Scholze, S., 996 Muller-Werden, U., 542 Mulligan, K., 1059 Mullington, J., 222, 585, 586, 589, 590, 591, 601, 605 Mullington, J. M., 331, 594, 599, 601 Mullins, M. W., 104 Mullooly, J., 714 Mulry, R. P., 933 Multhoff, G., 1015, 1019, 1023, 1024 Munajj, J., 683 Munari, L., 1110 Munch, G., 386 Munck, A., 49, 50, 235, 724, 731, 737, 738, 745, 747 Munck, A. U., 723, 724, 737, 745, 747 Mundel, P., 103 Munderi, P., 1055 Munford, R. S., 254 Munn, D. H., 522 Munnoch, K., 910, 911 Munoz, A., 1053, 1054, 1058 Munoz, C., 342 Munoz, D., 399 Munoz, E., 73 Munoz, O., 994 Munoz-Elias, E. J., 104 Munoz-Elias, J., 134, 135, 137, 140 Munoz-Fernandez, M. A., 359 Munoz-Valle, J. F., 212, 214 Munro, C., 1061 Müns, G., 663 Munson, A. E., 65, 66, 70, 74, 100 Munster, A. M., 841 Muntaner, O., 223 Muntner, S. E., 802 Muntoni, F., 362 Munz, C., 1102 Muragachi, A., 74 Muraguchi, M., 997, 1000, 1001 Murai, J. T., 482, 746 Murakami, C., 1000 Murakami, K., 882, 1001 Murakami, M., 322 Murakami, N., 321 Muramami, N., 432 Muraro, N., 422, 434
1201 Murase, K., 360 Murasko, D., 623 Murata, J., 882 Murata, T., 326 Murata, Y., 1037, 1046 Murayama, T., 305, 348, 382 Murayama, Y., 1003 Murburg, M. M., 541, 682 Murdoch, C., 260 Murdoch, D., 148 Murgo, A. J., 724, 733 Murgolo, N. J., 101 Murillo-Rodriguez, E., 586 Muris, D. F., 1112 Murison, R., 983 Muro, S., 329, 432 Murphy, C., 1060 Murphy, C. A., 272 Murphy, D., 133 Murphy, E. A., 1082 Murphy, G. E., 686 Murphy, G. F., 104, 107, 108, 113, 114 Murphy, J., 808 Murphy, K. C., 871 Murphy, K. M., 66, 222 Murphy, P. G., 360 Murphy, P. J., 901, 909 Murphy, S., 609 Murphy, T. J., 1025 Murphy, W. J., 174 Murray, C. A., 275, 353, 356, 357, 384 Murray, C. J., 509 Murray, D., 605 Murray, D. L., 995, 999 Murray, E. A., 342 Murray, H. J., 353, 357 Murray, J. S., 219 Murray, L., 284 Murray, L. S., 363, 364, 421 Murray, M., 149 Murray, M. A., 961, 962 Murray, P. D., 1109 Murray, P. I., 1056 Murray, R., 668 Murrieta-Aguttes, M., 736 Musaro, A., 181 Muscat-Baron, Y., 829 Musch, M. W., 1015 Musich, S. A., 717 Musick, M. A., 499 Musselman, D. L., 199, 511, 519, 520, 521, 522, 608, 885, 931 Mustafa, A., 589 Mustafa, A. S., 800 Mustafa, M., 589 Mutchnick, M. G., 551 Muthusamy, N., 74 Muthyala, S., 1046 Mutlu, L., 307
1202 Muttilainen, M., 859 Muzet, A., 601 Muzumdar, R., 994 Muzzin, P., 995, 997 Muzzioli, M., 637, 638, 640, 652 Myers, A., 810, 948 Myers, A. C., 110 Myers, D., 809 Myers, D. G., 771 Myers, H. F., 497, 724, 789, 966, 1065 Myers, J. K., 681 Myers, L. P., 737, 745 Myers, P., 142 Myers, R., 437 Myers, R. R., 397, 399, 405 Myhr, K. M., 420 Myles, K., 211 Mynatt, R. L., 1002 Myrillas, T., 844, 845 Na, D. L., 364 Nabekura, J., 186 Nabel, G., 1054 Nabeshima, T., 339, 352, 353, 354, 523 Naccari, F., 984 Naccasha, N., 458 Nadal-Vicens, M., 360 Nadeau, A., 302 Nadeau, R., 716 Nadeau, S., 438 Nadel, E. M., 735 Nadel, L., 566 Nadjar, A., 274, 292, 294, 295 Naeve, G. S., 407 Nagaev, I., 1003 Nagai, H., 73 Nagai, J., 322 Nagai, R., 998, 1001 Nagai, Y., 1056 Nagamatsu, S., 223 Nagano, I., 195 Nagao, M., 365 Nagao, T., 73 Nagaoki, T., 592 Nagaretani, H., 1000, 1001 Nagasaki, H., 584 Nagashima, K., 330, 859 Nagata, K., 565 Nagata, S., 647, 648, 653 Nagata, T., 522 Nagatomi, R., 1056 Nagatsu, T., 147 Nagel, D., 957 Nagel, J. E., 430 Naghavi, M., 921 Nagira, M., 142 Nagorny, R., 1059 Nagy, E., 200, 957 Nagy, I., 102
Author Index Nagy, J. A., 242, 882 Nagy, K., 1015 Nagy, L. M., 541 Nagy, Z., 422 Nahlik, G., 557 Nahori, M. A., 98 Nahoul, K., 209, 210 Nain, M., 997, 1100 Nair, A., 1085 Nair, M., 603, 771 Nair, M. P. N., 1056 Nair, S. K., 252 Naito, Y., 73, 957 Naitoh, T., 1001 Najafi, M., 912 Najarian, B., 792 Najjar, S. M., 55 Naka, T., 338 Nakabayashi, H., 51 Nakagawa-Hattori, Y., 147 Nakagawara, G., 254 Nakai, S., 301, 353 Nakajima, N., 254 Nakajima, T., 330, 997, 1000 Nakajima, Y., 998 Nakaki, T., 357 Nakamachi, T., 416, 417 Nakamori, T., 321 Nakamura, I., 1109 Nakamura, K., 323, 326, 327 Nakamura, M., 352, 354, 419, 420, 432 Nakamura, R., 565 Nakamura, T., 997, 1000, 1001 Nakamura, Y., 223, 326, 1001 Nakamuta, M., 998 Nakane, A., 1039, 1040, 1041, 1111 Nakane, H., 64 Nakane, T., 235 Nakanishi, H., 186 Nakanishi, K., 419 Nakanishi, M., 101, 109, 110 Nakano, K., 222, 738 Nakao, K., 329, 432 Nakao, S., 53 Nakao, T., 73 Nakao, Y., 997 Nakashima, K., 275 Nakata, A., 99 Nakata, Y., 400, 404 Nakatani, Y., 322 Nakayama, H., 859, 1001 Nakayama, K., 512 Nakayama, O., 998 Nakshatri, H., 92 Naliboff, B., 678 Naliboff, B. D., 237, 261, 497, 624, 729, 934, 1057, 1058, 1063, 1064, 1065 Nalpas, B., 554 Nambu, A., 274
Namiki, M., 295, 296 Namour, B., 363, 364, 365, 366 Nan, K., 875 Nanamiya, W., 195 Nance, D. M., 64, 284, 288, 320 Nanda, R. K., 237 Nandakumar, K. S., 222 Nandan, S., 186 Nanko, S., 567, 569 Nankova, B., 235 Nantel, F., 323, 324, 325, 326, 328, 329, 330 Napier, B. J., 625, 772 Napoli, A., 624, 764, 766 Narayan, R. K., 358 Naray-Fejes-Toth, A., 745 Narko, K., 54 Nartucci, R., 882 Narumiya, S., 322, 325, 326, 327, 328, 329 Nasatzky, E., 181 Nash, A. A., 1109, 1110, 1114 Nash, G. B., 964, 965 Nash, T. P., 393 Nasrallah, H., 510 Nassenstein, C., 360 Natarajan, G., 55 Natarajan, L., 770 Natelson, B. H., 483 Nath, A., 276, 1054 Nath, A. K., 1000 Nathan, C., 85, 137, 271, 1025 Nathans, D., 53 Nau, G., 732, 735 Nau, R., 352, 353, 354 Naucler, A., 1062 Naudin, J., 570 Naumann, E., 554 Nauwynck, H. J., 490 Nava, F., 300 Navabi, H., 1019 Navarro, A. D., 212, 214 Navarro, F., 1100 Navarro, L., 586 Navascues, J., 401 Navia, B., 383 Nawa, H., 565, 569 Nawashiro, H., 419 Nawata, H., 998 Nawrocki, A. R., 997 Nawroth, P., 926 Nawroth, P. P., 72, 965 Naya, T., 419 Nayagam, A. T., 1060, 1061 Nayak, M., 1081 Nayersina, R., 997 Naylor, M. S., 882 Nazli, A., 1024 Ndinya-Achola, J., 1059
Author Index Ndinya-Achola, J. O., 1059 Neal, M. S., 844, 845 Neale, J. M., 624, 625, 762, 764, 766 Nealen, M. L., 102 Nealey-Moore, J. B., 788 Nedelec, B., 844 Nedergaard, J., 1022, 1042, 1044 Nedergaard, M., 422 Neeck, G., 197, 198 Needleman, P., 321 Neelamegham, S., 839 Neels, H., 1115 Neels, J. G., 1001 Neff, B. J., 859 Neggers, Y. H., 501 Negishi, M., 323, 326, 327 Nehlsen-Cannarella, S. L., 662, 663, 664, 665, 666, 667, 668, 669 Neiman, D. C., 661, 662, 663, 667, 668 Neish, A. S., 137 Nelesen, R. A., 729, 930 Nelms, K., 998 Nelson, C. B., 538, 553 Nelson, C. J., 256, 556, 1101 Nelson, D. A., 102, 107 Nelson, E. C., 466 Nelson, H. S., 71, 799, 800 Nelson, L., 651 Nelson, N., 996 Nelson, P., 763, 764 Nelson, P. T., 147 Nelson, R. J., 303, 481, 732 Nelson, S., 554, 637 Nelson, S. G., 731, 732, 1025 Nelsso, V., 74 Nemeroff, C. B., 299, 307, 485, 486, 509, 515, 520, 521, 524, 608, 801, 812, 885, 1061 Nemeth, Z. H., 997 Nenchausky, B. M., 594 Nerad, L., 645 Nerup, J., 364, 996 Nerzon, Y., 532, 535, 536, 538 Nesbit, M., 842 Neschen, S., 994 Ness, A., 958, 960 Nesse, R. M., 790 Nestel, P., 662 Nestler, D., 254 Nesto, R. W., 922, 930 Netea, M. G., 1003 Nettelbladt, C. G., 1024 Netter, C., 465 Neubort, A. S. L., 745 Neufeld, G., 224 Neugebauer, E., 352, 354, 419, 420 Neuhaus, J. M., 713 Neuhuber, W. L., 107 Neuland, C. Y., 552
Neuman, M. G., 554 Neumann, A. U., 1054 Neumann, E., 1003 Neumann, H., 106, 359, 386 Neumann, M., 211 Neumann, S. A., 772 Neurath, M. F., 143, 144 Neurauter, G., 521, 522 Neure, L., 76 Neveu, P. J., 304, 307, 480, 481, 482, 514, 521 Neville, K. L., 1110 Nevin, J., 643, 644 Nevines, E., 669 New, M., 208 Newby, C., 1099 Newcomb, P. V., 181, 182 Newcomb, R. W., 735 Newcombe, J., 437 Newell, C., 761 Newell, M. L., 1055 Newhouse, Y. G., 74 Newlands, G. J., 109, 111 Newman, A. B., 924, 926, 956, 962 Newman, M. E., 259 Newman, R., 136, 883 Newman, T. A., 304, 361, 384, 430, 437, 439, 441, 444 Newman, T. K., 485 Newport, D. J., 521 Newsholme, E. A., 664, 665, 666 Newsholme, P., 71 Newsom, J. T., 497 Newton, C., 342, 344, 347 Newton, P., 201, 1054 Newton, R., 54, 55 Newton, T., 623, 781, 783, 784, 786, 788, 789, 793, 863 Newton, T. L., 789, 1062 Nezu, R., 1003 Ng, A., 995 Ngoc, L. P., 811 Nguyen, K. T., 88, 99, 288–89, 290, 301, 320, 343, 344, 345, 347, 348, 357, 381, 398, 732, 1025, 1026 Nguyen, M., 326 Nguyen, M. D., 385, 444 Nguyen, M. M., 479, 480, 481 Nguyen, N. B., 117 Nguyen, T., 1058 Nguyen, V. T., 137, 276, 747 Nhuch, C., 1055 Ni, R. X., 727 Nicassio, P. M., 512, 609 Nicchitta, C. V., 1018, 1024 Nichol, K., 361 Nichols, J., 458 Nicholson, J. K., 557 Nicholson, L., 149
1203 Nickel, E. J., 553 Nickel, T., 817 Nickerson, M., 71, 1013, 1019, 1022 Nicklas, B. J., 662, 924, 926, 956 Nicklin, M. J., 995, 997 Nicola, N. A., 995 Nicolaidis, S., 330 Nicolaou, A., 541 Nicolaou, C., 551 Nicolas, J. F., 725, 732 Nicolas, J. M., 554 Nicolau, I., 636 Nicolaus, S., 662 Nicole, O., 276, 277, 420 Nicoletti, F., 996 Nicoll, J. A., 363, 364, 365, 366, 421 Nicolson, N., 711, 772 Nicolson, N. A., 307 Nictistico, G., 523 Nie, Z., 1056 Nieber, K., 131 Niederhofer, H., 712 Niedobitek, G., 856 Niedzwiecki, D., 875 Nielsen, H. B., 89, 1016, 1018, 1022 Nielsen, J. H., 996 Nielsen, J. O., 1056, 1057, 1058 Nielsen, K. D., 609 Nielsen, L., 106 Nielsen, M. H., 1053 Nielsen, P. J., 74 Nielsen, T., 625, 763 Nieman, D. C., 77, 452, 453, 662, 663, 664, 665, 666, 667, 668, 669, 670, 815 Nieman, David C., 661 Niemeier, V., 983 Niemi, M., 637, 645, 650, 651, 652 Niemi, Maj-Britt, 631 Niemi, M.-B., 453, 1039, 1040 Nieminen, M. S., 927 Nieswandt, B., 951, 952 Nieto, F. J., 927, 948, 959 Nieto, M., 1100 Nieto-Sampedro, M., 148 Nieuwenhuis, E., 144 Nieuwenhuis, E. E., 67, 68 Niggemann, B., 240, 261 Nihoyannopoulos, P., 937 Niijima, A., 635 Niizeki, H., 113 Nijkamp, F. P., 72, 104, 109, 110, 115 Nikitin, Y., 947 Nikkalä, H., 569 Nikolaus, S., 144 Nikulasson, S., 115 Nikulasson, S. T., 112 Nikulina, E., 303 Nilsson, A., 361
1204 Nilsson, B. O., 361 Nilsson, C., 329 Nilsson, G., 133 Nilsson, J., 223 Nilsson, L., 49 Nilsson, P., 712 Nimgaonkar, V. L., 571, 572 Nimmagadda, S. R., 976 Nimmerjahn, A., 402, 406 Ning, W., 175, 998 Ninomiya, M., 432 Nishanian, P., 1058 Nishi, S., 51 Nishida, M., 997, 1000, 1001 Nishida, T., 830 Nishihira, J., 830 Nishikawa, H., 937 Nishikawa, T., 294, 523, 998 Nishimatsu, H., 998 Nishimori, T., 54 Nishimoto, M., 931 Nishimoto, N., 144, 338 Nishimoto, R., 786 Nishimura, M., 142, 364, 365 Nishimura, M. C., 360 Nishimura, T., 326 Nishino, M., 959 Nishino, Y., 567 Nishioka, J., 199 Nishiyama, M., 195 Nishiyama, N., 354, 355, 646 Nishizawa, H., 1000, 1001 Nisipeanu, P., 1110 Niskanen, P., 712 Nisker, J. A., 746 Nisly, N., 764, 767, 900, 906 Nisman, B., 570 Nissen, R. M., 53 Nissley, P., 175 Nitschke, W., 763, 764, 765, 766 Nitta, A., 106, 184 Nitti, D., 172, 177, 178 Niu, K. J., 1056 Niven, J. S., 110 Nizamani, R., 554 Njenga, M. K., 1109 Njus, D. M., 763, 764, 765, 766 Noack, S., 1002 Noah, N., 859 Noakes, T. D., 665, 666, 669 Noble, E. G., 1014, 1015, 1016 Noc, M., 928 Nociti, V., 1003 Nockleby, K. J., 165 Noda, M., 186 Noel, M., 550 Noelle, R. J., 1045, 1046 Noelpp, B., 647 Noelpp-Eschenhagen, I., 647
Author Index Noggle, R. M., 801 Nogueira, F., 711 Nogueiras, C., 112 Noisakran, S., 1080, 1081, 1082, 1088 Nokta, M., 1058 Nokta, M. A., 1057, 1058 Nolan, B., 541 Nolan, Y., 295, 353 Nolde, T., 1115 Nolden-Koch, M., 417 Noldus, L. P. J. J., 477 Noll, D., 523 Nomoto, H., 106 Nomura, A., 322 Nomura, I., 978 Nomura, J., 605 Nomura, K. S., 321, 331 Nomura, Y., 297, 348, 382, 605 Nong, Y. H., 113 Nonogaki, K., 995 Nooh, N., 830, 831 Noon, L., 802 Noonan, C. W., 1107 Noponen, M., 148 Norbiato, G., 487, 1055, 1056 Norbury, C. C., 1085 Nordberg, J., 104 Nordenberg, D., 713 Nordheim, A., 137 Nordlind, K., 110 Nordstrom, M. L., 768 Norin, A. J., 512 Noris, D. A., 977, 988 Norkrans, G., 1057 Norman, J., 695 Norman, R. L., 727, 729, 744 Norman, S. E., 586 Norris, D. A., 826 North, R. J., 1038 North, W., 692 North, W. R., 870 North, W. R. S., 716 Northfield, T. C., 928 Northoff, H., 666 Norton, D. D., 1014 Norton, M. C., 383 Norusis, M., 929 Nosaka, S., 87 Noseworthy, J. H., 1107 Noskov, V., 853 Nott, K. H., 1060, 1061 Nottet, H. S., 1053 Notti, I., 515 Nouailhetas, V. L., 1046 Novak, N., 977, 978, 985 Novak, P., 716 Novak, T. J., 73 Novak, V., 716 Novakofski, J. E., 173, 182, 183
Novakovic, S., 161 Novelli, A., 235, 239 Novellino, L., 879 Noverr, M. C., 801 Novick, D., 419 Novick, D. M., 557, 1101 Novogrodsky, A., 997 Nowak, I. A., 995 Nowak, M. A., 1054 Nowell, M. A., 594, 596, 598 Nowell, P., 736 Nowicki, P., 1000, 1001 Nugent, C. C., 744 Nugent, N. R., 541 Nukina, H., 238 Nukina, I., 1036 Numao, T., 108 Numazaki, M., 102 Nunes, P., 292, 345 Nunes, S. O., 811 Nunez, A., 184 Nunez, E. A., 222, 747, 1055 Nunez, L., 181, 182 Nunez, M. J., 255 Nunnerley, H., 233 Nunnerleym, H., 870, 871 Nunninghoff, D., 607 Nuovo, G., 856 Nurden, A. T., 838, 839 Nurden, P., 838, 839 Nussbaum, G., 539 Nussdorfer, G. G., 101 Nussenzweig, M., 74 Nutt, J., 523 Nyange, P., 1059 Nyberg, F., 589 Nye, B. A., 396 Nykanen, P., 1014 Nyqvist, M., 1100 Nyyssonen, K., 957 Oakley, G., 964 Oates, P. J., 998 Oba, S., 998 Obach, V., 421 Obal, F., 591, 601 Obal, F. J., 583, 586, 587, 601 Obal, F., Jr., 331, 583, 589, 605 Obana, S., 99 O’Banion, M. K., 321, 329, 358, 439, 440, 1014 Obara, H., 521, 522 Obata, K., 132 Obata, N. H., 882 Oberbeck, R., 65, 1044, 1045, 1046 Oberg, K., 197 Oberholtzer, E., 222 Obermeyer, W. H., 607 Oblet, C., 1058
Author Index Obradovic, T., 554 Obrams, G. I., 869 O’Brien, C. P., 554 O’Brien, J., 961 O’Brien, J. R., 501, 505 O’Brien, J. T., 511 O’Brien, P. C., 440 O’Brien, S., 715 O’Brien, S. J., 1053 O’Callaghan, E., 459 Ochani, M., 86, 88, 89, 90, 91, 92, 105, 106, 997 Ochieng, J., 241 Ochs, H. D., 606 Ochshorn, M., 557 Ochsmann, S., 69, 76, 726, 739, 1046 Ockene, I. S., 666 Ockenfels, M. C., 772, 854 O’Cleirigh, C., 1055, 1056, 1060, 1061, 1063 O’Conell, M., 783, 786 O’Connor, C. M., 826 O’Connor, G., 964 O’Connor, J. C., 297, 304, 996, 998, 1000 O’Connor, J. J., 353, 355, 357, 359 O’Connor, Jason C., 993 O’Connor, K., 405, 406 O’Connor, K. A., 357, 398, 407, 965, 1026, 1115 O’Connor, S. W., 100 Oda, S., 356 Oda, T., 223 Odoardi, F., 1003 O’Donnell, C. A., 1025 O’Donnell, E., 353, 356, 384 O’Donnell, K., 197 O’Donnell, M. C, 570 O’Donnell, T., 542 O’Dorisio, M., 134 O’Dorisio, M. S., 133, 134 O’Dorisio, T., 134 O’Dorisio, T. M., 133, 134, 532, 535, 536, 538 O’Dowd, Y. M., 71 Oehlmann, W., 1023 Oehme, P., 131 Oeki, S., 344, 352 Oelkers, W., 554 Oertel, W. H., 363, 364 Oesch, B., 585 Oesterling, E., 693 Oesterling, J. E., 693 Oettgen, H. F., 551 Oettinger, C. W., 92 O’Fallon, W. M., 199 Offen, D., 184 Offenbacher, S., 927 Offit, K., 1056 Offord, E., 669
Offord, K. P., 90 Offringa, R., 252 O’Flaherty, E., 879 Ofosu, F. A., 838 Oftung, F., 800 O’Garra, A., 137, 800, 817 Ogasawara, M., 882 Ogawa, M., 828 Ogawa, R., 115, 997 Ogawa, S., 998 Ogawa, T., 381, 881, 882 Ogden, C. L., 993 Ogden, J., 913 Ogimoto, K., 297 Ogletree, M. L., 419 O’Gorman, M. R., 1056 O’Grady, J. A., 363 O’Grady, M. P., 461 Ogren, S. O., 277 Ogrocki, P., 676, 677, 782, 783, 784, 788, 792, 874 Ogston, K., 684 Ogtata, Y., 53 Oguchi, Y., 255 Ogura, H., 862 Ogura, T., 862 Oh, C., 222, 738 Oh, H. S., 139 Oh, Y. M., 812 O’Hara, C., 804 Ohara, J., 997 Ohara, K., 931 O’Hara, M., 53 Oharazawa, A., 522 Ohashi, K., 1001, 1024 Ohashi, P. S., 352 Ohata, M., 554 Ohayon, M., 579 Ohayon, M. M., 579 Ohba, M., 999 Ohdo, S., 523 O’Heeron, R. C., 792 Oh-Ishi, S., 322, 736 Ohlsson, C., 996 Ohlsson, R., 74 Ohm, J. E., 241, 882 Ohman, E. M., 946 Ohmi, Y., 481 Ohmori, Y., 137 Ohmoto, Y., 997, 1000, 1001 Ohmoto, Y. T. F., 1001 Ohnishi, K., 554 Ohnishi, Y., 1001 Ohno, H., 736, 1045 Ohno, M., 344, 352 Ohnuma, H., 1000 Ohnuma, T., 365 Ohrmann, P., 565 Ohshima, T., 841, 842
1205 Ohshima, Y., 73 Ohta, A., 238, 481 Ohta, T., 523 Ohtaki, H., 416, 417 Ohtani, F., 859 Ohtomo, H., 106 Ohtori, S., 405 Ohtsuka, K., 213 Ohtsuka, M., 365 Ohuchi, K., 322 Ohyashiki, T., 184 Oida, H., 326 Oishi, R., 296, 523 Oishi, Y., 960 Oitzl, M. S., 342, 347, 349, 357, 604 Oizumi, T., 1000 Ojaniemi, M., 459 Ojika, K., 148 Ojio, S., 923 Oka, K., 100, 322, 323, 324, 325, 326, 327, 328, 329, 330, 663 Oka, M., 842 Oka, T., 100, 322, 323, 324, 325, 326, 327, 328, 329, 330, 358 Okada, T., 331 Okamoto, A., 101 Okamoto, H., 132, 995, 999 Okamoto, M., 342 Okamoto, N., 252 Okamoto, S., 741, 1054 Okamoto, Y., 997, 1000, 1001, 1003 Okamura, H., 419 Okamura, K., 295 Okano, T., 197 Okayama, Y., 113 Okayli, G., 622 O’Keane, J. C., 115 O’Keefe, G. M., 276 O’Keefe, J., 340, 341 Oken, B., 523 Oker, M., 827 Okihara, K. L., 69, 76, 1046 Okimura, T., 828 Okladnova, O., 522 Okret, S., 55, 741 Oku, N., 252 Okubo, Y., 88 Okuma, Y., 297, 305, 348, 382, 605 Okumura, T., 295 Okun, M., 459 Okun, M. A., 733, 788 Okun, M. L., 588 O’Kusky, J. R., 173 Okutomi, K., 1000 Okutsu, M., 1056 Okuyama, T., 878 Olanow, C. W., 147, 386 Olariu, R., 554 Old, L. J., 874, 878, 879, 995
1206 Oldani, A., 586 Olding, L. B., 463 Oldstone, M. B., 384, 1054 Oldstone, M. B. A., 858 O’Leary, A., 606, 677, 789, 799, 1060 Olefsky, J., 1000 Olerud, J. E., 109, 112, 113 Oleson, T. D., 684 Oleszak, E. L., 1109 Oleszko, W. R., 768 Olff, M., 729, 934 Olivieri, F., 361, 364, 365, 421 Ollier, B., 198 Olmarker, K., 400 Olmos, L., 511, 514, 516, 518, 607 Olschowka, J., 678, 772 Olschowka, J. A., 64, 103, 115, 132, 1057 Olsen, B. R., 253 Olsen, J. H., 871 Olsen, N. J., 462 Olson, G., 462 Olson, J. K., 87, 103, 1108, 1110 Olson-Cerny, C., 788 Olsson, G., 712 Olsson, Y., 399 Olszewski, W. L., 592 Omachonu, V. K., 717 O’Malley, B. W., 50 O’Malley, P. G., 932, 937 O’Mara, S. M., 358, 359 Omata, M., 998 Omholt, S., 379 Omu, A., 458, 459 Omvidvari, K., 554 O’Neil, L. A. J., 353, 357, 359 O’Neill, B., 677 O’Neill, D., 109 O’Neill, E., 570 O’Neill, L. A., 274 O’Neill, L. A. J., 320 Ones, U., 1002 Ong, E. L., 1060, 1061 Ong, J., 74 Ongini, E., 420 Ongur, D., 713 Onji, M., 554 Ono, E., 342 Ono, Y., 1058 Onodera, H., 418, 432 Onodera, K., 1026 Onodera, T., 305 Onoe, H., 87, 331 Onofri, F., 356 Onsrud, M., 727 Onuki, M., 519 Ooboshi, H., 420 Ooi, W. L., 967 Ookawara, T., 736, 1045 Oomura, Y., 293, 356
Author Index Oostveen, F. G., 68, 901, 1065 Opal, S. M., 997 Opiela, S. J., 669 Opp, M. R., 299, 339, 422, 452, 583, 584, 586, 587, 588, 589, 591, 600, 601 Opp, Mark. R., 579 Oppenheim, J. J., 136, 400, 736 Opper, C., 599 Oprica, M., 306, 418 Opsjon, S. L., 212 Opstad, P. K., 599 Oradia, H., 419 O’Rahilly, S., 1000 Oran, A. E., 1102 Orci, L., 995, 999 O’Reilly, M. S., 253 O’Reilly, R. C., 1017 Orencole, S. F., 669 Orenstein, J. M., 1054 Orfao, A., 550, 551, 553 Origoni, A. E., 566, 567 Oriss, T. B., 855 Oritani, K., 997 Orloff, M., 260 Orlovskaia, D. D., 565 Orlowski, W., 856 Ormsby, C., 645 Orndorff, S., 1056 Orne, E. C., 599 Orne, M. T., 599 Ornish, D., 877 Oronsky, A., 724, 726, 737 Oropeza-Wekerle, R. L., 106 Orosco, M., 330 O’Rourke, L., 1000 Orozco-Barocio, G., 212, 214 Orr, S. P., 539, 540, 541 Orru, M. G., 1080 Orson, F. M., 735 Ortega, E., 745, 746, 993, 1044 Ortega, N., 840 Ortega, R. M., 383 Orth, A., 589, 590, 601, 605 Orth, D. N., 713 Orth-Gomer, K., 781, 948, 961, 962 Orti, E., 49 Ortiz, G. C., 1080, 1081, 1087 Ortiz, L., 381 Ortuno, F., 510 Ortuno, J., 557 Ory, M., 908 Osanto, S., 693 Osborne, R. H., 875 Osburn, B., 462 Osburn, B. I., 462 O’Shea, J. J., 45, 55 Oshima, T., 960 Oshiro, Y., 1001 Oshita, K., 400
Oskoui, K. B., 133 Osmond, C., 692, 712, 870 Ossendorp, F., 252 Ossenkopp, K. P., 284, 306, 307, 828 Ossipov, M. H., 161 Ostensen, M., 220 Ostergren, P. O., 790, 1062 Ostfeld, A. M., 234, 714, 929 Ostir, G. V., 713, 769, 770, 773 Ostlere, L., 805 Ostlund, P., 345 Ostravskaya, O., 646 Ostroff, R. B., 539, 540 Ostroukhova, M., 800 Ostrow, D., 1060 Ostrowski, K., 669 O’Sullivan, J., 295 O’Sullivan, M. J., 682, 683, 1088 O’Sullivan, P., 931 Oswald, I., 592 Oswald, I. P., 85 Otaguro, S., 958 Otani, H., 115 Otsubo, T., 519 Otsuka, H., 350 Ott, C. M., 851, 852, 855 Ott, P., 1016, 1018, 1022 Ottaviani, E., 653 Ottaway, C. A., 103, 116, 134, 603, 605, 621, 1055, 1057, 1058 Otten, F., 931 Otten, U., 106, 338, 359, 360 Ottenberg, P., 647 Ottman, T., 422 Otto, V. I., 419 Otwinowski, Z., 49 Ou, D. W., 113 Ou, X. M., 51 Ouchi, N., 997, 1000, 1001 Ounpuu, S., 947, 949 Ovadia, H., 259, 339 Overbaugh, J., 1053, 1055, 1059 Overholser, J., 565 Overpeck, M. D., 712 Overstreet, D. H., 306 Owen, N., 501, 502, 503, 505, 680, 694, 931, 961, 962, 963, 966, 1016 Owens, C., 160, 161 Owens, J. F., 71, 497, 623, 713 Owens, M. J., 299, 307, 485, 515, 520, 521, 524 Owens, S. M., 344, 357 Owens, T., 148, 307 Ownby, R., 276 Oxman, M. N., 512, 517, 856, 888, 1079 Oyadomari, S., 999 Oyama, T., 240 Ozaki, K., 858, 994 Ozaki, M., 53
Author Index Ozaki, Y., 521 Ozawa, A., 174 Ozawa, H., 68, 69, 219 Ozawa, T., 147 Ozcan, U., 999 Ozdelen, E., 999 Ozel, A. M., 1002 Ozminkowski, R. J., 714, 717 Ozono, R., 960 Öztürk, L., 599 Pablos, J. L., 143 Pacak, K., 238 Pacheco, N., 637 Pacheco, N. D., 732 Pacheco-Lopez, G., 453, 637, 645, 646, 650, 651, 652, 1039, 1040 Pacheco-Lopez, Gustavo, 631 Pachter, J., 439, 440 Paci, L., 551 Paciaroni, M., 417, 420 Pacifici, R., 557 Packard, M. G., 340, 359 Packer, L., 383 Pacora, P., 458 Padawer, J., 741 Padberg, F., 1115 Padgett, D., 70, 71, 707, 883, 1078 Padgett, D. A., 238, 480, 828, 832, 842, 843, 844, 845, 846, 917, 1025, 1046, 1053, 1065, 1078, 1079, 1080, 1088, 1097, 1098, 1099, 1100, 1101, 1102, 1103, 1111, 1112, 1114, 1115 Padgett, David. A., 837 Padro, T., 882 Padron, J., 115 Pae, C. U., 571 Paetau, A., 416, 417 Pagani, S., 603 Page, G., 878 Page, G. G., 77, 238, 255, 256, 257, 555, 606, 792, 816, 842, 846, 878 Page, M. E., 710 Page, N. M., 101 Page, S., 951, 952 Pagenstecher, A., 284 Pager, C. K., 93 Page-Shafer, K., 1061 Paget, S., 238 Pagliogianni, F., 73 Pagniano, R., 1080, 1102 Pagnoni, G., 523 Pahl, H. L., 73 Pahor, M., 234, 361, 870, 873, 956, 962 Pai, J. K., 956 Pai, M. P., 827, 832 Paige, C. J., 101, 107 Paik, I. H., 568, 986 Paimela, L., 197, 222, 223, 224
Pajack, B., 458 Pajvani, U. B., 997 Pak, J. Y., 358 Pal, S., 242 Palacios, M., 960 Palanza, P., 480 Palao, G., 143, 200 Paleolog, E., 736 Palermo, M. T., 363, 364, 421 Palermo-Neto, J., 648, 649, 653, 828 Palestro, G., 604 Palican, H., 885 Palin, K., 284, 291, 305, 307, 308, 344, 345, 522 Paliogianni, F., 55, 724, 736 Palladino, M., 772 Palladino, M. A., 193 Palladino, M. A., Jr., 54, 193 Palm, S., 592 Palma, C., 404 Palma, J. P., 1115 Palmer, D., 1060, 1061 Palmer, J. R., 242 Palmer, R. M. J., 738 Palmer, T. D., 359, 360, 386 Palmi, I., 557 Palmieri, G., 237, 357 Palmieri, V., 957 Palmiter, R. D., 69, 71 Palmitter, R. D., 1039, 1040 Palombo-Kinne, E., 210 Palosuo, T., 957 Palucka, K., 142 Pamer, E. G., 1085, 1091 Pan, H., 105 Pan, X. M., 995 Panagiotakos, D. B., 501, 505, 932 Panariello, A., 570 Panayi, G. S., 193, 197, 201, 981 Panconesi, E., 976, 987 Pandey, H. P., 330 Pandey, M., 993 Pandey, R. S., 567 Pandurangi, A. K., 566 Panelli, M. C., 879 Panerai, A. E., 256, 284, 346, 349, 350, 351, 480, 784, 792 Pang, G., 600 Pang, K., 845 Pang, P. K. T., 727, 729 Pang, S., 208 Pang, X., 109, 110, 117 Pang, Z., 997 Panikashvili, D., 358 Panina-Bordignon, P., 72, 73, 1045 Panitch, H. S., 437 Panjwani, N. N., 1023 Pankhaniya, R., 134 Pankiw-Trost, L., 552, 556
1207 Pannen, B. H., 73 Panocka, I., 103 Panosian, J. O., 65, 66 Pantaleo, G., 1054 Pantaloni, C., 133 Panula, P., 109 Panuncio, A. L., 64 Panz, V. R., 222 Panza, F., 365 Pao, W., 1110 Paoletti, I., 224 Paolisso, G., 361 Papa, M. Z., 519 Papaccio, G., 996 Papacosta, O., 961 Papademetriou, V., 934 Papadogianniakis, N., 463 Papadopoulou, N., 113 Papageorgiou, C., 932 Papaleo, P., 421 Papamichail, M., 692 Papamichail, M. P., 570 Papanicolaou, D. A., 55, 72, 73, 219, 363, 588, 594, 599, 606, 608, 669, 801, 816, 855 Papanicolau, D. A., 1045 Papapetropoulos, A., 1000 Papassotiropoulos, A., 364, 365, 421 Papay, P., 531 Papconstantinou, J., 383 Papiris, S., 816 Pappenheimer, J. R., 584 Pappin, D. J., 49 Paradis, L., 807 Parasekvas, R., 733 Pardi, R., 46 Pardridge, W. M., 287 Pare, W. P., 483, 1036 Paredes, A., 235, 238 Parekh, P., 716 Pariante, C. M., 520, 521, 524, 1080 Parillo, J. E., 146, 724 Paris, A. H., 531 Parise, G., 224 Parish, S. M., 733 Parisi, A. F., 928 Parisi, C., 977 Parissis, J. T., 969 Park, A. N., 555, 557 Park, C. R., 1017 Park, H. J., 571 Park, H. K., 571 Park, J. H., 741 Park, P. G., 260 Park, S. H., 76 Park, W., 76 Park, Y. B., 213 Parker, C., 485 Parker, C. W., 73
1208 Parker, D. E., 533, 536, 537 Parker, J., 236, 687 Parker, J. C., 198, 609 Parker, J. D., 1108 Parker, L., 274, 418 Parker, L. C., 417, 433 Parker, M. G., 768 Parker, S., 663 Parkhurst, M. R., 800 Parkinson, J. F., 136 Parks, W. C., 840 Parlani, M., 117 Parlesak, A., 552 Parmiani, G., 652 Parmigiani, S., 480 Parner, J., 805, 1058 Parnet, P., 112, 184, 223, 272, 274, 281, 283, 287, 288, 289, 291, 292, 294, 295, 298, 301, 302, 320, 321, 338, 381, 382, 397, 422, 430, 431, 432, 514, 589, 622, 995, 1058 Paroo, Z., 1014, 1015, 1016 Parpura, V., 403, 404, 406 Parrillo, J. E., 146 Parronchi, P., 212, 637, 800 Parrott, R. F., 87, 325 Parry, S., 143 Parry-Jones, W. L., 361 Parsian, A., 306 Parsons, A. A., 417 Partners Against Pain, 396 Parvizi, J., 620 Pasare, C., 46, 98 Pasceri, V., 927 Paschal, B. M., 50 Paschen, C., 554 Pascual, D. W., 102, 103, 104, 107 Pasennik, E., 565 Pasha, A., 112, 115 Pasi, P., 853 Pasic, J., 938 Pasinetti, G., 439, 440 Pasinetti, G. M., 440 Paskind, M., 419 Pasparakis, M., 352, 440 Pasquali Ronchetti, I., 844 Pasquinelli, G., 116 Passantino, A., 716 Passegue, E., 53 Passerin, A. M., 326 Passmore, A. P., 366 Pasternak, G., 338 Pastor, I., 551 Pastor, I. J., 552 Pastores, S. M., 997 Patacchini, R., 100, 101, 107, 117 Patak, E., 101 Patanella, K., 1003 Patarca, R., 680, 684, 689, 1055
Author Index Pate, R. R., 664, 665 Patel, A., 1056 Patel, C., 716 Patel, H. J., 106 Patel, K. D., 877 Patel, M., 551, 716 Patel, P., 516, 928 Patel, P. C., 1056 Patel, P. J., 554 Patel, R. D., 1037 Patel, S., 405, 830, 831, 912 Patel, S. C., 185 Pater, A., 237 Pater, C., 409 Pater, M. M., 237 Paterson, B. M., 109 Paterson, H. M., 1025 Paterson, J., 927 Paterson, N. A. M., 747 Patestas, M., 400 Paton, J. Y., 815 Patrao, M. T., 239 Patrick, C. W., 1002 Patricot, M., 853 Patten, S. B., 480 Patterson, C. C., 366 Patterson, P. H., 277, 338, 356, 359, 459 Patterson, S., 934 Patterson, S. M., 934 Patterson, T., 515, 693, 724, 792, 966, 1110 Patterson, T. L., 510, 512, 514, 966, 1060, 1061, 1062 Patti, G., 927 Paturel, B., 257 Paty, P. B., 827 Patya, M., 997 Pau, F. K. Y., 485 Paul, A. G., 1015 Paul, G. L., 668 Paul, I. A., 342 Paul, L. A., 745 Paul, L. C., 771 Paul, O., 929 Paul, S., 133, 134, 140, 141 Paul, S. M., 363, 364, 570 Paul, W. E., 56, 997, 998 Paula, 786 Paula-Barbosa, M. M., 386 Pauletto, P., 959 Paul-Eugene, N., 801 Pauli, S., 296 Pauligk, C., 1100 Pauli-Pott, U., 978 Paulus, H. E., 729 Paulus, M. P., 523 Paulus, S. B., 552 Pauly, T., 553 Paus, R., 102, 106, 109, 113
Paus, T., 523 Pauwels, R. A., 100, 101, 102, 104, 107, 111, 115, 219 Pauzner, H., 933 Pav, D., 681 Pavcovich, L. A., 710 Pavelko, K., 1110 Pavelko, K. D., 1109 Pavelko, M., 712 Pavlides, C., 745 Pavlidis, N., 678 Pavlov, I., 631, 632 Pavlov, V., 635 Pavlov, V. A., 88, 273, 434 Pawelec, G., 253 Pawlak, C., 69, 76, 726, 1046 Pawlak, C. R., 726, 739 Pawlowski, M., 223, 283, 995 Payan, D. G., 101, 103, 113 Payne, D., 694 Payne, D. A., 236, 856, 863 Payne, D. W., 219 Payne, M. E., 540 Paz, I., 712 Paz, K., 999 Pazos, A., 711 Peaceman, A. M., 212 Pearce, B. D., 172, 521, 524, 727 Pearce, F. L., 109 Pearce, J., 631 Pearce, N., 977 Pearl, D., 789, 792, 863, 873 Pearl, D. K., 745, 858, 883 Pearl, S. G., 872 Pearlson, G. D., 564 Pearlstein, G. R., 143 Pearman, T., 234 Pearman, T. P., 871 Pearson, G., 676 Pearson, G. R., 236, 858, 863 Pease, J. E., 148 Pechnick, R. N., 556 Peck, M., 828 Peck, R., 108 Pecorini, G., 421 Peden, E. M., 1043 Pedersen, A., 565 Pedersen, A. N., 362 Pedersen, B. K., 67, 70, 77, 362, 363, 662, 663, 667, 669, 670, 816, 996, 1014, 1016, 1018, 1022, 1046, 1057, 1058 Pedersen, C., 1056, 1058 Pedersen, F. S., 1053 Pedersen, M., 361 Pedersen, S. S., 771 Pedrini, S., 361, 364, 366 Peduzzi, P. N., 93 Peebles, A. M. S., 569 Peek, M. K., 713, 770, 773
Author Index Peeke, H., 647, 648 Peeke, H. V., 647, 648, 653 Peeke, H. V. S., 647 Pe’er, J., 106 Peetz, D., 957, 996 Pegoraro, M., 570 Peguet-Navarro, J., 109, 114 Pehle, B., 1046 Peimonti, L., 142 Pek, M., 422 Pekkanen, J., 470, 957 Pekosz, A., 1099 Pela, I. R., 302 Peleman, R., 732 Pelin, Z., 599 Pellegrinelli, N., 997 Pellegrino, C., 984 Pellegrino, P., 1054 Pellegrino, T., 555 Pellegrino, T. C., 555 Peller, J. S., 736, 737 Pellerito, R. A., 200 Pelletier, D., 681, 695, 1110 Pelletier, G., 239 Pellicer, A., 359 Pelloux, V., 993 Pelonero, A. L., 566 Pelser, H., 647 Peltola, J., 186 Peltomaa, R., 197, 222, 223, 224 Pelzer, T., 211 Pena, J., 366, 421 Pendino, K. J., 135 Penedo, F., 453, 690, 695 Penedo, F. J., 693, 1062 Penedo, Frank, 675 Peng-Nemeroff, T., 86, 90, 91 Penicaud, L., 994 Penick, E. C., 553 Penkowa, M., 419 Penn, G. M., 734, 787 Penn, I., 252, 878 Penna, S., 199 Pennebaker, J., 685 Pennebaker, J. W., 677, 685, 694, 791, 792, 901, 908, 914, 1063 Pennefather, J. N., 101 Penning, M. J., 783, 787 Penning, T. D., 358 Penninx, B. W., 234, 361, 509, 511, 870, 873, 924, 926, 956, 962 Penny, R., 676, 734, 784 Pensaert, M. B., 490 Penzak, S. R., 1061 Pepine, C. J., 937 Peppel, K., 54 Pepys, M. B., 501, 923, 926 Pequeux, C., 241 Peraldi, P., 999
Peraldi, P. A. B., 999 Perdue, M., 110, 116, 647, 648, 653 Perdue, M. H., 110, 115, 116, 1024 Perea, G., 403 Perea, J. M., 383 Perec, C., 983 Perego, C., 186 Pereira, C. A., 1056 Pereira, D., 682, 683 Pereira, D. B., 237, 1088 Pereira da Silva, J. A., 223 Pereira-Leite, L., 458 Perelson, A. S., 1054 Perera, S., 763, 764 Perez, D., 419 Perez, D. M., 826 Perez, E., 223 Perez, L., 1025 Perez, L. F., 550, 552 Perez Rivera, R., 567 Perez-Asensio, F. J., 420 Pérez-García, G., 644, 646 Perez-Melgosa, M., 69, 71, 1039, 1040 Pérez-Montfort, R., 644, 645, 646, 653 Perez-Polo, J. R., 383 Perez-Then, E., 1061, 1065 Peri, T., 541 Perianin, A., 71 Perini, C., 934 Perini, C. H., 727 Perissin, L., 238 Peritt, D., 553 Perkin, G. D., 437 Perkins, A. S., 184 Perkins, D., 689 Perkins, D. O., 790, 1055, 1056, 1060, 1061, 1062, 1063, 1064, 1065 Perkins, K., 743 Perks, P., 196, 730, 790, 900, 901, 902, 907, 909, 911, 914, 915, 1089 Perlick, D., 579 Perlman, R. L., 74, 236 Perna, F., 1003 Perneczky, R., 365, 366, 421 Pernin, A., 995, 997 Pernod, J., 853, 863 Pernot, K., 931, 932 Pernow, B., 107 Peroni, D. G., 799 Peroni, O. D., 1000 Perper, J., 931 Perras, B., 585, 591, 597, 600, 607, 913 Perretti, F., 115 Perretti, M., 100, 398, 401, 405, 432 Perrin, M., 569 Perron, L., 242 Perrot, L. J., 361 Perry, B. D., 542 Perry, C., 363
1209 Perry, L., 197 Perry, L. A., 199 Perry, M., 692, 870 Perry, R. T., 365, 366 Perry, S., 1060, 1061 Perry, S. W., 790, 792 Perry, V. H., 270, 272, 276, 304, 344, 361, 382, 384, 385, 386, 401, 402, 408, 417, 420, 422, 429, 430, 433, 434, 435, 436, 437, 438, 439, 440, 441, 443, 444 Perryman, E. K., 556 Perryman, L. E., 733 Persico, M. G., 224 Persky, V. W., 871 Persoons, J. H., 1115 Persoons, J. H. A., 725, 732 Persson, L., 790, 1062 Persson, P. A., 408 Perstrup, L. B., 996 Pert, A., 556 Pert, C. B., 223 Peruzzi, F., 180 Pesare, M., 710 Peschon, J., 419 Peskind, E. R., 682 Pesman, G. J., 664 Pesonen, E., 958, 959, 960 Pession, A., 361, 364 Pestov, I. D., 853 Petenusci, S. O., 241 Peter, A. S., 113 Peter, J. B., 729 Peter, K., 166 Petermann, J. B., 104 Peters, A., 386 Peters, E. M., 106, 113, 664, 665, 666, 669 Peters, J. L., 570 Peters, K., 89 Peters, M., 417, 511, 565, 566 Petersen, A. M., 662, 1046 Petersen, B. H., 556 Petersen, E. W., 669 Petersen, J. K., 830 Petersen, R. C., 364 Peters-Futre, E. M., 665, 666, 669 Peters-Golden, M., 995 Peterson, 695 Peterson, B. H., 74 Peterson, B. L., 498 Peterson, D. A., 1045 Peterson, J., 436 Peterson, J. D., 1037, 1043 Peterson, K. E., 100 Peterson, P. K., 136, 361, 408, 734 Peterson, R., 764, 767 Peterson, R. G., 1040 Petersson, K. M., 710
1210 Petit, L., 607 Petitti, D. B., 871 Petitto, J., 689 Petitto, J. M., 296, 510, 514, 518, 552, 790, 1055, 1056, 1059, 1060, 1061, 1062, 1063, 1064, 1065 Petkova, E., 569 Peto, R., 921, 923, 927, 958 Petrangeli, E., 53, 55 Petras, R. E., 116 Petrenko, A. B., 395, 396 Petrie, K., 300, 542, 685, 738, 741 Petrie, K. J., 685, 694, 791, 828, 842, 901, 908, 910, 914, 1063 Petro, T. M., 89 Petronila, P., 1045 Petros, J. A., 252 Petroski, G. F., 198 Petrou, P., 197, 201, 981 Petrov, D., 72, 965 Petrova, T. V., 404 Petrovic, P., 710 Petrovicky, P., 679 Petrovsky, N., 592, 594, 595, 603, 604, 605 Petruzzelli, L., 163 Petry, J., 900, 906 Pettengill, E. B., 877 Pettepher, C., 332 Petterson, T., 440 Pettersson, G., 133 Petticrew, M., 233, 870, 872 Pettingale, K., 692, 871, 872, 875 Pettingale, K. W., 692, 869, 871, 872, 887 Pettit, S., 879 Petty, P. G., 400 Petzoldt, S., 73, 222 Peyron, E., 725, 732 Peyron, J.-F., 73 Peyser, M. R., 212 Pezeshki, G., 598 Pezzone, K. M., 710 Pezzone, M. A., 555, 710, 711 Pfaffenberger, S., 72 Pfeffer, K., 172, 352 Pfeffer, M., 926, 956 Pfeifer-Ohlsson, S., 74 Pfeiffer, A. F., 1000, 1001 Pfeiffer, C., 198 Pfeiffer, C. A., 769 Pfeilschifter, J., 360 Pfeuffer, I., 741 Pfister, K., 1024 Pfister, R., 502 Pfizenmaier, K., 172, 181, 338 Pflüger, M., 166 Phair, J., 1053, 1060 Phair, J. P., 1053
Author Index Pham, T. M., 306 Phan, J., 184 Phanuphak, P., 732 Phare, S. M., 995 Phelps, E. A., 294 Philip, J. M. D., 901, 909 Philippin, B., 103, 110 Philippopoulos, G. S., 733 Phillips, A. G., 344, 346, 358, 359 Phillips, A. N., 1053 Phillips, C., 830 Phillips, D. I., 712 Phillips, E., 518, 607, 608 Phillips, E. J., 1055 Phillips, H. S., 360 Phillips, L., 687 Phillips, R. E., 879 Phillips, R. S., 115 Phillips, T., 1015 Phillips, T. J., 831 Phillips, T. M., 853, 855, 856, 857, 862, 863 Phillips-Conroy, J. E., 485 Phillpotts, R. J., 773, 1063 Phinney, A. L., 386 Phipps, R. P., 74 Phyliksy, R. L., 883 Piacentini, G. L., 799 Piascik, M. T., 826 Piaskowski, S., 417 Piazza, P. V., 711 Picano, E., 964 Picard, O., 1055 Picardi, A., 976, 979 Piccini, A., 237 Piccini, M. P., 462 Piccinini, G., 549, 551 Piccinni, M. P., 212 Piccoli, F., 366 Pichini, S., 557 Pichler, J., 462 Pickar, D., 570 Pickering, M., 357 Pickering, T., 874 Pickering, T. G., 715, 949, 967 Pickford, G. E., 727, 729 Piconi, L., 998 Piconi, S., 487, 1055 Piemonti, L., 980 Piepenbrock, S., 646 Pieper, C. F., 882 Pieraggi, M. T., 829, 830 Piercy, C., 438 Piéron, H., 583 Pierotti, M., 652 Pierpaoli, S., 1058 Pierson, D. L., 236, 851, 852, 853, 854, 855, 856, 857, 858, 859, 860, 861, 862, 863, 1079
Pierson, Duane, 707, 851 Pietraszek, M. H., 931 Pietri-Rouxel, F., 1042, 1043 Pietrowsky, R., 598 Pifl, C., 239 Pigareva, N., 305 Piiparinen, H., 859 Pike, J., 538, 598, 607, 888 Pike, J. L., 511, 512, 514, 516, 517, 932 Pike, S., 735 Pike, S. E., 855 Piketty, C., 1059 Pilati, P., 172, 177, 178 Pillinger, M. H., 839 Pilon, A. A., 1056 Piludu, G., 1080 Pinaud, E., 74 Pinchofsky-Devin, G., 1002 Pincus, G., 727, 729 Pinder, P., 234, 692, 870 Pinessi, L., 364 Pinkney, J. H., 512 Pinner, R. W., 380 Pinsky, D., 676, 858, 863, 1088 Pinter, E., 110 Pinto, A., 647 Pinto, A. J., 1082 Pinto, C., 108 Pinto, F. M., 101 Pinto, L. A., 107, 1059 Pintucci, G., 52 Pioli, R., 570, 571 Piotrowski, W., 109 Piras, A., 1080 Pires, M. L., 1055 Pirhonen, J., 1100 Pirke, K. M., 981, 1080 Pirkkala, L., 1014 Pirskanen, M., 364 Pirttila, T., 361 Pisano, B., 1015 Pisanti, F. A., 996 Pischon, T., 956, 993, 1001 Pisegna, J. R., 133 Pisell, T. L., 521, 727 Pitceathly, C., 786 Pitcher, G. M., 101 Pitcher, J. A., 1043 Pitcher, L. A., 47 Pitman, R. K., 540, 541 Pitossi, F., 275, 344, 346, 347, 350, 351, 355, 356, 646 Pitossi, F. J., 422, 434, 435 Pitsavos, C., 501, 505, 932 Pitson, S. M., 839 Pitt, J., 1055 Pittet, J. F., 1024 Pittman, Q., 223, 283, 995 Pittman, Q. J., 321, 323
Author Index Pittman, R. K., 539, 541 Pitts-Meek, S., 184 Pitzalis, M. V., 716 Piva, T., 937 Pizzorni, C., 199, 207, 208 Plaeger, S., 727 Plaisance, S., 53 Planas, A. M., 420, 421 Plasse, T., 92 Plat, L., 607 Plata-Salaman, C., 439, 440 Plata-Salaman, C. R., 283, 288, 289, 293, 297, 996 Platsoucas, C., 879 Platsoucas, C. D., 1109 Platt, D., 361 Platt, J. L., 1025 Platt, N., 999 Platzer, C., 254, 997 Platzer, M., 997 Plaut, M., 98, 735 Plitt, J., 55 Ploegh, H. L., 47 Plotkin, S. R., 87, 381 Plotsky, P., 357, 738, 933 Plouet, J., 840 Plowden, J., 380 Plu-Bureau, G., 242 Pluijm, S. M., 186 Plummer, F., 1059 Plummer, S., 901, 908, 910, 911 Pluzanska, A., 605 Pluznik, D. H., 54 Po, L. M., 1065 Pocchiari, M., 440 Pochet, R., 73, 1036, 1043 Pociot, F., 364 Pockley, A. G., 1015, 1016, 1022 Poczatek, K., 1000, 1001 Podd, L., 539 Podhajcer, O., 422, 434 Podliszewski, E., 515 Podojil, J., 75 Podojil, J. R., 74, 75, 77, 1042, 1044, 1045 Poehlmann, K. M., 811, 861, 1019, 1079 Pogady, J., 566 Pohl, M., 167 Pohl, T., 598, 1112 Pohlau, D., 963 Pohlmann, S., 1053 Poirier, J., 436 Poitou, C., 993 Pol, S., 554 Pola, P., 365, 421 Pola, R., 365, 421 Polak, J. M., 103, 104, 132 Polan, M. L., 359 Polesel, J., 237 Polfliet, M. M., 438, 439
Poli, G., 1000 Poli, V., 298, 995, 996 Poliakov, V., 853 Polimeni, I., 984 Polk, B. F., 1053, 1054, 1058 Polk, D. E., 772 Polla, B. S., 1015 Pollack, H., 873 Pollack, S., 874, 880 Pollak, C. P., 579 Pollak, M., 181 Pollak, U., 622 Pollak, Y., 259, 284, 294, 297, 305, 339, 361, 515, 519 Pollard, M. S., 783, 787 Pollard, R., 1058 Pollard, R. B., 69, 1057, 1058 Pollard, V., 605 Polley, H., 737 Pollina, D. A., 586 Pollmacher, T., 48, 222, 223, 259, 305, 331, 362, 363, 570, 585, 586, 589, 590, 591, 594, 598, 601, 605, 609 Pollono, A., 1055 Polman, C., 1110 Polman, C. H., 148, 1112 Poloczek, P., 133 Polonis, V. R., 1056 Polonsky, W., 625, 763, 765, 766 Poltorak, M., 197 Poltyrev, T., 712 Polverini, P. J., 1000 Polyakov, V. V., 853 Polychronopoulos, E., 501, 505 Polydefkis, M., 166 Polyrevt, T., 456 Pomerantz, R. J., 1054 Pomeroy, C., 734 Pomeroy, S., 1057 Ponath, G., 565, 566 Pongratz, G., 68 Ponnudurai, R., 237 Pons, S., 184 Ponti, W., 361 Ponto, L. L., 620 Pool, J., 937 Poole, B., 1002 Poole, S., 165, 291, 292, 297, 300, 320, 399, 405, 406, 407, 417, 640 Poortmans, J. R., 664, 665, 666 Poosch, M. S., 103 Popa, C., 1003 Pope, C., 714 Pope, C. R., 789 Pope, M., 108 Pope, R., 679 Pope, R. M., 224 Popoli, M., 571 Popov, S., 1058
1211 Popova, L., 1023 Popovic, M., 1056 Popovich, P. G., 136 Porcile, A., 235 Poretsky, L., 1055 Porras, J., 859 Porreca, F., 161 Porszasz, J., 102 Porta, S., 727, 729, 730, 732 Portbury, A. L., 103 Porte, D., Jr., 287, 293 Portel, L. V., 565 Portela, L. V. C., 566 Portenoy, R., 693 Porter, J. T., 403 Porter, L., 772 Porter, L. S., 854 Porter, M. H., 289 Porter, M. R., 511, 519 Porter, N. M., 380, 384 Porter, R. R., 46 Portier, P., 802 Porto, M., 711 Portoles, E., 359 Porzsolt, F., 594, 605 Posavad, C. M., 1086 Posner, E., 362, 366 Posner, M. I., 523 Post, A., 676, 858, 863, 1088 Post, R. M., 303 Postel-Vinay, M. C., 603 Postler, E., 592, 594 Postma, D. S., 66, 73, 977 Poston, R. M., 1038 Potapova, T., 93 Pothoulakis, C., 110, 112, 115, 116, 1015 Potter, E. D., 348, 359 Potter, J., 683 Potter, J. D., 668 Potter, P., 199 Potter, P. T., 198, 788 Poulos, A., 631 Poulos, A. M., 341 Poulsen, T. D., 67 Poulton, T., 502, 503, 931 Pournajafi-Nazarloo, H., 290 Pousset, F., 300, 302, 359, 622 Powell, B. J., 553 Powell, H. C., 397 Powell, L. H., 694, 695, 937 Powell-Braxton, L., 184 Power, A., 900, 903, 914 Power, B., 607 Powers, R. E., 564 Powers, S. K., 1015 Poynard, T., 554 Poynter, M. E., 383 Pozo, D., 103, 131, 134, 135, 146, 148, 149, 195
1212 Prada, F., 422, 434 Prado, G., 1065 Prager, K. J., 787 Pragst, F., 554 Prakken, B., 739, 1015, 1016 Prakken, B. J., 1015 Prasad, A., 927 Prasad, P. D., 521 Prass, K., 76 Prass, W. A., 236 Prat, A., 436 Pratera, C., 811 Pratt, A., 110 Pratt, I. A., 1065 Pratt, K. R., 735, 745 Pratt, W. B., 49 Prattala, R., 771 Pravettoni, E., 291 Preacher, K. J., 512, 790, 811, 814, 882, 888, 962 Preat, T., 632 Preault, M., 285 Prechel, M. M., 348, 382 Preckel, D., 963, 965 Prefontaine, K., 53, 54 Preheim, L. C., 551 Prehn, J. H., 420 Preiksaitis, J. K., 858 Preissler, U., 103 Preitner, F., 1000 Premonet, R. T., 1043 Prendergast, B. J., 842 Prentice, T., 1110, 1115 Prentice, T. W., 1107, 1115, 1116, 1118 Prentki, M., 998 Prescott, E., 931 Present, D. H., 144 Presley, N., 1065 Pressman, S., 512, 761, 762, 769, 770, 771, 772, 782, 787, 792, 900, 903, 904, 912, 913, 914, 1089 Pressman, S. D., 625, 904, 912 Pressman, Sarah, 706, 761 Presta, M., 842 Prete, C., 199 Preut, R., 815 Prevelige, R., 1015 Prevost, M. C., 1018 Preynat-Seauve, O., 801 Price, A., 684, 689, 691, 1055 Price, B. D., 1015 Price, G., 437 Price, J., 294 Price, J. F., 977 Price, J. L., 713 Price, L. H., 521 Price, L. S., 240 Price, M., 869, 871, 872 Price, M. A., 234, 870, 871
Author Index Price, N. J., 599 Price, V. A., 937 Prieto, J. C., 134 Prigerson, G., 676 Prigerson, H. G., 518, 607 Priller, J., 76 Priluck, R., 716 Prin, L., 148 Prince, L. A., 55 Prince, R., 792, 937 Prince, R. H., 937 Prince, S., 173, 174 Princiotta, M. F., 1085 Pringle, A. K., 417 Prins, A., 541 Prinz, P. N., 606 Prior, R. L., 383 Pritchard, A., 365 Probert, L., 284, 352, 354, 360 Prochiantz, A., 72, 301 Prodinger, W. M., 107 Proenca, R., 994 Proft, T., 651 Prohaszka, Z., 1015, 1024 Proia, A. S., 421 Prolla, T. A., 384 Prolo, P., 594, 599, 606 Prop, N., 727 Properzi, F., 352, 354, 360 Prosch, S., 254 Proskocil, B. J., 88 Prospero-Garcia, O., 586 Protheroe, D., 233, 870 Prothrow-Stith, D., 500 Protier, H., 1055 Proud, C. G., 1043 Proud, D., 810 Proud, G., 256 Prough, D. S., 605 Provencio, M., 515, 516 Provinciali, M., 637, 638, 640, 652 Prudhomme, N., 292 Pruessner, J. C., 811, 884 Pruett, S. B., 259, 555, 737, 745 Prusiner, S. B., 440 Pryor, D. B., 694, 929, 930, 949 Pryor, J., 1054 Pryor, J. C., 106 Przedborski, S., 147 Przewlocki, R., 162, 166 Przuntek, H., 361 Psaty, B. M., 923, 926, 957 Psych, D., 739, 741 Ptok, U., 364, 365, 421 Puccetti, M., 686 Pucci, P., 109 Puente, E., 100 Puente, J., 534, 535, 538 Pugeat, M., 482
Pugh, C. R., 342, 343, 344, 345, 347, 348, 357, 1017 Pugin, J., 254 Pukkala, E., 870 Puklavec, M., 212, 855 Pulakhandam, U., 1055 Pulendran, B., 142 Pullan, R. D., 90 Pullen, L. C., 1110 Pulvirenti, L., 555 Punzi, L., 210, 213, 214 Puolakkainen, M., 859 Puopolo, M., 440 Puppo, F., 828 Pupupakkam, R. K., 801 Purcell, E. J., 1025 Purcell, W. M., 97, 100, 106, 109 Purohit, A., 208, 211 Purohit, B., 554, 555 Purton, J. F., 462 Puska, P., 771, 781 Putcha, L., 851 Putelat, R., 1055 Putnam, F. W., 538 Putney, D. J., 1014 Puttfarcken, P., 89 Puzella, A., 521 Pyke, S. D., 923, 926 Pyle, R., 1036 Pyne, D. B., 663, 815, 1025 Pynn, M., 1002 Pynoos, R. S., 539 Pyo, H., 136 Pyrdol, J., 149 Pyter, L. M., 303 Qadir, K., 107, 108 Qamhieh, H. T., 962 Qi, Y., 286 Qin, S., 142 Qin, X. F., 74 Qin, Z., 418 Qiu, B., 101, 115 Qiu, P., 605 Qu, Q. M., 364 Qu, W. -M., 331 Quadri, P., 366 Quadri, R., 200 Quadri, S. K., 296, 297 Quadro, L., 1000 Quagliaro, L., 998 Quaglino, D., 595, 607 Quaglino, D. Jr., 844 Qualls, C. R., 669 Quan, N., 293, 294, 302, 303, 321, 401, 842, 844, 845, 846, 1111 Quantin, B., 53 Quarcoo, D., 106, 360, 817 Quartara, L., 107
Author Index Quenby, S., 458, 459 Qui, B. S., 1037 Quillian, R., 680 Quinlan, K. L., 112 Quinn, D., 855, 862 Quinn, D. G., 840, 841 Quinn, P. M., 56 Quinn, T. C., 1053, 1054, 1055 Quinonez, G., 97, 109, 110.109, 115, 116 Quintal, L., 419 Quintana, A., 419 Quintana, F. J., 1024 Quintanilha, A., 458 Quintans, J., 70 Quinteiro, C., 552 Quinton, L., 554 Quirinia, A., 831 Quirion, R., 104, 176, 184 Quirk, G. J., 341 Quon, M. J., 999, 1001 Qureshi, S., 662 Quyyumi, A. A., 501, 927 Qvist, J., 70, 1057 Raab, J. R., 67, 68, 70 Raabe, T., 92 Raaf, J. H., 551 Raaijmakers, J., 55, 741 Raap, U., 976, 987 Raasmaja, A., 1022 Rabaeus, M., 514, 516 Rabatic, S., 532, 535, 536, 537, 538 Rabbani, Z. N., 885 Rabbi, M. F., 1057, 1058 Rabe-Hesketh, S., 716 Raber, J., 520 Rabert, D. K., 161 Rabin, B., 637, 888 Rabin, B. S., 236, 237, 301, 483, 484, 486, 497, 499, 504, 505, 512, 555, 571, 572, 621, 710, 711, 714, 718, 725, 726, 732, 733, 743, 744, 746, 764, 766, 768, 769, 772, 773, 775, 782, 783, 787, 792, 898, 899, 900, 901, 903, 904, 911, 912, 913, 914, 934, 1053, 1055, 1063, 1065, 1080, 1089, 1110, 1111, 1115 Rabin, Bruce, 706, 709 Rabinovitz, I., 239 Rabinowich, H., 876 Rabinowitz, J., 783, 876 Rabinowitz, S. G., 1108 Rabkin, J. G., 1057, 1060, 1061 Rabkin, J. M., 827 Rabkin, M., 1055 Rabkin, R., 1061 Racz, P., 1054 Raczynski, J. M., 695 Radbruch, A., 76, 469
Radcliff, G., 728 Raddatz, R., 103 Radeke, H., 360 Radewicz, K., 565 Radicke, E., 927 Radinsky, R., 257 Radka, S. F., 106 Radoi, G. E., 295 Radojcic, T., 66, 1044 Radomski, M. W., 585, 586, 738 Radstake, T. R., 1003 Raducanu, N., 636 Rady, J. J., 408 Rady, P. L., 299, 557, 586 Raedler, A., 144 Rafalowicz, E., 531 Raff, H., 1055 Raffin, J., 853 Rafter, I., 55 Rage, F., 717 Rager, D. R., 456 Raggi, M. A., 772 Raghavendra, V., 405, 406, 408, 409 Raghow, R., 846 Raghupathi, R., 352, 354, 419, 420 Raghupathy, R., 457, 458, 459 Ragland, D. R., 929 Rahim, R. T., 557 Rahman, S. U., 288 Rahme, A. A., 56, 772, 828 Rai, R., 457 Raible, R., 766 Raiha, K., 859 Raikkonen, K., 931 Raimonde, A. J., 542 Raine-Fenning, N. J., 829 Rainero, I., 364 Rainwater, K., 253, 261 Raio, L., 462 Raisin, C. J., 877 Raison, C. L., 304, 511, 512, 520, 521, 542 Raitasalo, R., 870 Raith, K., 408 Raivich, G., 402 Rajagopalan, B., 422 Rajala, M. W., 997 Rajcani, J., 566 Rajkowska, G., 565 Rajora, N., 100 Rakic, P., 340, 840 Rakitskaya, V. V., 1046 Raleigh, M. J., 477 Raley, M. J., 1037 Raley-Susman, K., 236 Raley-Susman, K. M., 261 Ram, A., 330 Ram, S., 201 Ramachandra, R. N., 301
1213 Ramachandran, A., 1000 Ramakrishna, V., 380 Ramalingam, R., 1056 Ramamoorthy, J. D., 521 Ramamoorthy, P., 241 Ramamoorthy, S., 521 Rambaut, P. C., 853 Ramchand, C. N., 568 Ramchand, R., 568 Ramer, M., 856 Ramer-Quinn, D. S., 66, 73, 99, 1044 Ramer-Quinn, S., 1045 Rameshwar, P., 139, 254 Ramirez, A., 692 Ramirez, A. J., 870 Ramirez, F., 212, 855 Ramirez, R., 134 Ramírez-Amaya, V., 644, 645, 646, 653 Rammensee, H. G., 1024 Ramsden, V., 716 Ramsey, J. M., 1078, 1080 Ramsey, M. M., 174, 184 Rancan, M., 148, 419 Ranceva, J., 196 Ranchalis, J., 487 Rand, K. H., 855 Randal, H. W., 827 Randolf, A., 355, 356 Randolph, G. J., 1100 Randow, F., 999 Ranganathan, G., 1000 Rangarajan, P., 53 Rangarajan, S., 240 Ranger, A. M., 140 Rangnekar, V., 104 Rangoni, A., 361 Ranjan, R., 570 Ranke, M. B., 174 Rankine, E. L., 430, 434, 443 Ransohoff, R. M., 436 Ransom, B., 422 Ransone, L. J., 53 Rantalaiho, T., 859 Rantapaa-Dahlquist, S. B., 65 Rantapää-Dahlqvist, S., 218 Rao, B., 680, 694, 727, 729, 735 Rao, J. S., 842 Rao, L. S., 52 Rao, M. K., 882 Rao, M. L., 364, 365, 421 Rao, M. S., 403 Rao, R. S., 242 Rapaport, M. H., 533, 535, 536, 537, 568, 570 Raphaelson, Y. E., 498, 499 Rapier, S. H., 196 Rapozzi, V., 238 Rapp, F., 236 Rapp, K. L., 739
1214 Rapp, P. R., 386 Rappat, S., 873, 887 Rapson, N. T., 543, 997 Raptis, A., 55 Raptis, S. A., 219 Rasanen, J., 459 Rashed, S., 879 Rasi, R., 957 Rasi, V., 957 Raskin, M. J., 510, 622 Raskind, M. A., 682 Rasley, A., 103 Rasmussen, A. F., 1080 Rasmussen, F., 712 Rasmussen, J. P., 670 Rasmussen, J. W., 222, 727, 729 Rasmussen, K. L., 1079 Rasmussen, K. L. R., 488, 489, 490 Rasmussen, T., 386 Rassner, G., 258 Rassnick, S., 637, 710, 733, 743 Rassouli, N., 1000 Rassu, M., 568 Rasta, K., 677 Rastinejad, F., 50 Rathsack, R., 131 Ratliff, T. L., 110, 142 Rattazzi, M., 959 Rau, M. T., 783, 784 Raud, J., 839 Raudenbush, S. W., 498 Rauh, V., 458, 711 Rauh, W., 739, 741, 981, 982, 983 Raus, J., 515 Rausch, D. M., 342, 688 Ravaud, A., 304, 305, 307, 519, 521 Ravazzola, M., 995, 999 Ravindran, A. V., 511, 514 Ravizza, T., 186, 273 Rawlings, R., 566 Rawlings, S. R., 133 Rawlins, J. N., 344, 346, 350, 384, 440, 443 Rawlins, J. N. P., 340, 341 Rawlins, R. G., 476 Rawson, H., 859 Ray, A., 53, 54, 741, 800, 986, 997 Ray, C., 964, 965 Ray, O., 811 Ray, P., 997 Raybourne, R., 197 Raybourne, R. B., 197 Raymoure, W. J., 746 Raynor, W. J., Jr., 234 Rayter, Z., 910, 911 Raz, A., 321 Raz, J., 539 Razga, Z., 182 Re, F., 1056
Author Index Rea, I. M., 1022 Read, A. F., 342 Reali, N., 772 Rearden, A., 605, 1043 Reardon, A., 1043, 1044 Reaven, P. D., 1000 Rebeck, G. W., 364, 421 Rebeiz, N., 175 Rebelo, I., 458 Rebuzzi, A. G., 923, 926, 956 Rechtschaffen, A., 596, 597 Reclos, G., 692 Redaelli, C. A., 419, 1015 Redd, W. H., 875 Reddy, A. P., 485 Reddy, J., 149 Reddy, M., 1061 Reddy, Y. S., 1061 Redegeld, F. A., 109 Redei, E. E., 305 Redelman D., 1045 Redelmeier, D. A., 626 Reder, A. T., 512, 1112 Redington, A., 103 Redington, T. J., 729 Redish, D., 236 Redish, D. M., 261 Redman, B., 92 Redman, C., 458 Redmer, D. A., 174 Redmond, P., 256 Reduta, A., 134, 139, 140 Redwine, J., 200, 740 Redwine, L., 518, 553, 594, 595, 598, 599, 603, 608, 609, 680, 730, 885, 963, 965, 966 Reed, C. L., 236 Reed, G., 689 Reed, G. L., 837 Reed, G. M., 497, 713, 1060 Reed, J., 736 Reed, R. C., 1018, 1024 Reed, S. E., 773, 1063 Reemsnyder, A., 608, 885 Rees, A., 210 Rees, G. S., 283, 298, 995 Rees, P. H., 109 Rees, P. J., 815 Rees, R. G., 197 Reeve, A. J., 405 Reeves, A., 340 Reeves, A. J., 465, 712 Refaeli, Y., 1056 Refinetti, R., 584 Regan, M., 233 Regan, M. F., 870 Regauer, S., 845 Regnani, G., 881 Regne-Karlsson, M. H., 1040
Regnier, J. A., 734 Regoli, D., 103, 223 Regula, D. P., 1041 Rehailia, M., 585 Reheiser, E. C., 623 Rehermann, B., 554, 1045 Rehg, J. E., 584 Rehli, M., 1015, 1024, 1025 Rehman, J., 70, 965 Rehn, T. J., 570 Rehnmark, S., 1022 Rehnqvist, N., 712 Reich, J. W., 788 Reich, P., 734, 745 Reich, T., 49 Reichart, B., 254 Reiche, E. M., 811 Reichenberg, A., 223, 259, 305, 339, 362, 363, 609, 901, 904 Reichlin, S., 799 Reichmann, G., 107 Reid, K. B., 46 Reid, M. B., 182 Reid, S., 100, 586 Reidler, M., 643 Reifman, A., 714 Reig, J. A., 998 Reilly, A., 1038 Reilly, F. D., 1036 Reilly, J. M., 146 Reiman, E. M., 620 Reimann, G., 1057, 1058 Reimann-Philipp, U., 422 Rein, G., 763, 764 Reinberg, M., 682 Reinders, F. X., 420 Reingold, S. C., 1120 Reinhardt, R. R., 185 Reinheimer, T., 89 Reinisch, N., 107 Reinshagen, M., 106 Reis, H. T., 787 Reiser R. F., 977, 988 Reisine, S. T., 531, 771 Reiss, D., 871 Reiss, K., 180 Reissenweber, N., 64 Reitamo, S., 736 Reite, M. L., 468, 484, 485, 491, 534, 535 Reite, M. R., 468 Reiter, A., 712 Rekacewicz, C., 1055 Religa, A., 1058 Relton, J., 284 Relton, J. K., 88, 290, 381, 418, 433 Remarque, E. J., 362 Remick, D. G., 66, 72, 422 Remien, R. H., 1057, 1060, 1061
Author Index Remington, J. W., 738 Remmers, E. F., 193 Remohi, J., 359 Remold, H. G., 113 Remschmidt, H., 599 Renardel de Lavalette, C., 438 Renauld, J. C., 213 Renegar, K. B., 584, 600 Renganathan, M., 90 Rengaraju, M., 213 Rennard, S., 72, 76 Rennard, S. I., 109 Rennke, H. G., 734 Renno, T., 307 Renquist, D., 482 Renshaw, B. R., 338 Renshaw, D., 101 Renshaw-Hoelscher, M., 380 Rentzhog, L., 1019 Renz, H., 106, 107, 108, 360, 469, 733, 997 Renzi, D., 117 Reod, M. R., 553 Replogle, R. E., 55 Requejo, A. M., 383 Rescorla, R., 631, 632, 634, 653 Reseland, J., 599 Resnich, H. S., 541 Resnick, C. E., 219 Ressler, K. J., 521, 1061 Restifo, N. P., 879 Reszka, R., 166 Rettig, J., 553 Rettori, V., 292, 294, 299 Reuben, J. M., 599 Reubi, J. C., 100, 115, 134 Reul, J. H. M., 724 Reul, J. M., 56, 112, 296, 516, 522, 598, 733, 735, 746 Reul, J. M. H. M., 733, 735, 736, 745 Reus, V., 647 Revel, M., 1115 Revell, P. A., 200 Revhaug, A., 133 Revilla, M., 421 Revillard, J. P., 69, 74 Revillion, F., 239 Rex, J., 93 Rey, Mendez, M., 255 Reyes, T. M., 293, 383, 465 Reyes-Vazquez, C., 409 Reynold, C. F., 580 Reynolds, C., 676, 878 Reynolds, C. F., 607 Reynolds, C. P., 676 Reynolds, C. W., 255, 257, 260 Reynolds, D. W., 863 Reynolds, I. J., 102 Reynolds, J. M., 994
Reynolds, L. P., 174 Reynolds, M. L., 223 Reynolds, P., 234, 871, 872, 873 Reynolds, R., 565 Reynolds, R. M., 712 Reznick, J. S., 713 Reznikoff, M., 236 Rezvani, A. H., 306 Rezza, G., 683 Rhee, R., 727, 743 Rhee, S. H., 198 Rhinehart, J. J., 746 Rhode, H. K., 809 Rhode, T., 670 Rhodes, J., 90 Ribas, J. L., 1054 Ribatti, D., 224 Ribeiro, J. M., 113 Ribeiro, M. C., 711 Ricart, W., 996 Riccardi, C., 54 Ricci, R., 107 Ricciardi-Castagnoli, P., 307 Riccio, M., 810, 1061 Rice, B. L., 851 Rice, C., 844, 845 Rice, E., 788 Rice, G. P. A., 858 Rice, J., 676, 811, 858, 863, 1088 Rice, N., 741 Rice, N. R., 52 Rice, P. A., 68, 1039, 1040 Rich, M. W., 681, 931, 932 Richard, M. J., 1015 Richards, A. L., 710 Richards, C., 788 Richards, E., 878 Richards, H. L., 977 Richards, J. P., 137 Richards, P. J., 338 Richards, T. L., 710 Richardson, B. A., 1059 Richardson, F. C., 687 Richardson, J. A., 1015 Richardson, L., 815 Richardson, P. M., 360 Richardson, R. M., 1025, 1026, 1027 Richaud-Patin, Y., 213 Richelle, M., 669 Richert, M. M., 241 Richet, C. R., 802 Richichi, C., 186 Richman, D., 1054 Richt, J. A., 567 Richter, A., 563 Richter, D., 307, 872 Richter, L., 606 Richter, S., 727, 729, 730 Richter, T., 951, 952
1215 Richter-Levin, G., 345, 346, 348, 349, 353, 355, 358, 646 Richwine, A. F., 304, 384, 385, 386, 387, 444 Rickenbach, M., 237 Ricker, D., 677, 686, 787, 792 Ricketts, S. W., 727, 729 Ricksten, A., 361 Ricote, M., 997 Riddell, R. H., 116 Riddle, D. R., 184 Ridker, P., 957 Ridker, P. M., 502–3, 511, 518, 606, 679, 681, 695, 923, 926, 927, 937, 956 Riechman, S., 637 Riedel, M., 568, 570 Riedel, W. J., 307 Rieder, H., 685 Rieder, M. J., 56, 772, 828 Riederer, P., 361, 386, 981 Riegger, G. A., 926 Rieks, M., 963 Riemann, D., 511, 570, 606 Riemenschneider, M., 365, 366, 421 Riesenny, K. R., 553 Rifai, N., 502–3, 518, 926, 937, 956, 993, 1001 Rigas, A., 969 Rigas, J., 885 Rigby, A. S., 193 Rihanek, M., 142 Rihs, S., 985 Riihimaki, H., 717, 948 Riis, J., 769 Rijavec, M., 532, 535, 537 Riker, A. I., 879 Riley, J., 802 Riley, J. P., 800 Riley, V., 233, 236, 724, 873 Rilling, J. K., 710 Rimanoczy, A., 361 Rime, B., 791, 792 Rimm, E. B., 956, 993, 1001 Rimoldi, D., 693 Rimon, R., 733, 745 Rimón, R., 569 Rinaldo, C., 1053 Rinaldo, C. R., 1086 Rinaldo, C. R., Jr., 487, 1054 Rincon, M., 994 Rinetti, G., 608, 609 Ring, C., 762, 763, 765, 900, 901, 905, 907, 912, 913, 914, 1046, 1088 Ring, J., 978 Ringel, N., 929 Ringeling, M., 76 Ringold, G. M., 995 Ringvolt, E., 607 Rini, C. M., 711
1216 Rink, L., 510 Rinker, C. M., 296 Rinker, L. G., 419 Rinne, M., 815 Rinner, I., 727, 729, 730, 732 Rio, M. E., 117 Rippin, G., 959 Riquet, N., 1058 Risberg, B., 934 Risch, S. C., 512, 516 Rish, M., 652 Rishel, D. D., 1060 Riskin, I., 635 Ristimaki, A., 54 Ristow, M., 1000 Ritchey, A. K., 503, 512, 681, 682, 694, 881, 966, 1112 Ritchie, A. W., 592 Ritchie, J. C., 540 Ritchie, J. M., 253, 261, 882 Ritossa, F., 1014 Ritter, M. A., 461 Ritter, S. Y., 815 Rittner, H. L., 110, 160, 162, 164, 165, 166 Ritz, T., 771, 814 Rivas, D., 56 Rivera-Sanchez, Y. M., 1002 Riveros-Moreno, V., 103 Rivest, S., 87, 272, 274, 291, 294, 302, 320, 325, 328, 330, 339, 385, 386, 432, 438, 440, 444, 682 Rivier, C., 357, 605, 738, 933 Rivier, C. L., 259, 338, 357, 516, 982, 983 Rivier, J., 104 Rivoltini, L., 879 Rixon, R. H., 745 Rizvi, T. A., 330 Rizzo, L. V., 800 Rizzo, M. R., 361 Rizzon, P., 716 Robaeys, G., 277 Robatscher, P., 382 Robb, M. L., 1056 Robb, R., 736 Robberecht, P., 133, 135 Robbins, C., 781 Robbins, P. D., 842 Robbins, R. A., 109 Robergs, R. A., 669 Roberts, D., 875, 877 Roberts, J. A., 70 Roberts, J. C., 102 Roberts, L. J., 787 Roberts, N. A., 1099 Roberts, P. L., 1059 Roberts, R., 937 Roberts, R. A., 93
Author Index Roberts, R. C., 564 Roberts, R. G., 223, 362 Roberts, S., 284, 858 Roberts, S. G., 137 Roberts, S. M., 1037 Robertson, B., 691 Robertson, C., 803 Robertson, D. M., 460 Robertson, D. N., 133 Robertson, E. J., 184 Robertson, M., 957 Robinette, B. L., 212 Robinette, C. D., 923 Robins, P., 837 Robinson, C., 663, 930 Robinson, C. M., 307 Robinson, D., 564 Robinson, D. J., 885 Robinson, F. P., 77, 1061 Robinson, H. L., 1102 Robinson, M. E., 790 Robinson, S. E., 733 Robinson, S. M., 1054 Robinson, T. W., 1088 Robles de Medina, P. G., 711 Robles, F., 383 Robles, T. F., 380, 514, 682, 768, 774, 792, 793, 811, 901, 910 Robson, M. C., 828, 846 Robson, N. C., 800 Roccio, M., 1045 Rocha, A., 458 Rocha, B., 47, 48 Rocha, B. B., 456 Roch-Arveiller, M., 223 Roche, E., 998 Roche, W. R., 55 Rocklin, R. E., 986 Rodabaugh, K., 882 Rodani, M. G., 234, 871, 872, 873 Rode, J., 117 Rodeghiero, F., 957 Roden, M. M., 879 Roder, I., 813 Roderian, T., 1023, 1024 Rodin, J., 979 Rodrigo, J., 104 Rodrigue, J., 234 Rodrigue, J. R., 871 Rodriguez, A. B., 745, 746 Rodriguez, B., 957 Rodriguez, E. M., 1053 Rodriguez, F., 294 Rodriguez, M., 397, 399, 532, 535, 537, 538, 782, 1107, 1109, 1110, 1120 Rodriguez, R., 99, 103, 139, 140, 141, 142 Rodriguez, R. E., 552 Rodriguez-Fernandez, J. L., 1100
Rodriguez-Feuerhahn, M., 67, 68, 605, 728, 729, 929, 963, 965, 983 Rodriguez-Frade, J. M., 603 Rodriguez-Henche, N., 146 Rodriguez-Larralde, A., 957 Rodriquez, M., 676, 680 Rodriquez-Roa, E., 957 Roebuck, K. A., 1057, 1058 Roecker, E. B., 361 Roeder, R. G., 74 Roehrs, T. A., 587 Roemer, D., 1026 Roesch, S. C., 711 Roess, D. A., 735 Roffel, M., 186 Rogatsky, I., 53 Rogentine, G., 692 Rogers, A. M., 142 Rogers, C., 638, 639, 640, 641, 642 Rogers, C. F., 651 Rogers, G. S., 831 Rogers, J., 382, 439, 440, 485 Rogers, M. P., 734, 745 Rogers, N. E., 136 Rogers, P., 307 Rogers, R. C., 88 Rogers, T. J., 400, 557 Rogerson, F. M., 482 Rogg, J. M., 148 Rohde, T., 816 Rohde, W., 554 Rohleder, N., 72, 302, 514, 540, 542, 815, 965 Rohm, H., 106 Rohne, A., 67, 68, 728, 729 Rohner-Jeanrenaud, F., 997 Rohr, O., 1054, 1057 Rohrer, D. K., 1041 Rohrig, K., 996 Roisman, I., 570 Roitman-Johnson, B., 518, 594, 927 Roizen, M. F., 200, 827 Roizman, B., 1077 Rojas, D., 386 Rojas, I. G., 828, 832, 842, 843, 846 Rojas, S., 419 Rokne Hanestad, B., 716 Roland, B. L., 195, 328, 843 Rola-Pleszczynski, M., 1058 Rolf, C., 662, 663, 668 Rolfe, F. G., 55 Rolink, A., 74 Roll, A., 988 Rollins, B. J., 136, 840, 841 Rollwagen, F., 637 Rollwagen, F. M., 732 Rolstad, B., 257 Romagnani, P., 800, 811, 812, 813, 817 Romagnani, S., 66, 637, 978
Author Index Roman, A., 305 Romanello, S., 106 Romano, A., 363, 364, 365, 366 Romano, F. D., 222 Romano, M., 260–61 Romano, T. D., 132 Romanoff, R. L., 305 Romanos, M., 237 Romanov, K., 789 Romanovsky, A. A., 290, 320, 321, 322 Rombeau, J. L., 542 Romeo, F., 921 Romeo, H. E., 288, 289 Romero, L., 236 Romero, L. M., 235, 261, 723, 724, 737, 745, 747 Romero, P., 693 Romero, R., 458 Romero-Diaz, J., 210 Romics, L., 554 Romine, M. F., 137 Rommel, C., 181, 182 Rommelspacher, H., 553 Rompa, D., 1061 Ronaldson, E., 133 Ronan, A. M., 1002 Ronan, P. J., 332 Ronca, R., 842 Roncarolo, M. G., 142 Rondanelli, M., 1055 Rondinone, C. M., 999 Rondo, P. H., 711 Rondouin, G., 186 Ronicke, V., 241, 885 Ronk, E. C., 745 Ronnback, L., 408 Ronnelid, J., 213 Rontgen, P., 543 Ronzoni, E., 729 Roodell, M. M., 594 Roof, S. L., 182 Rook, G. A., 603, 800, 855 Rook, K. S., 781, 788 Rooney, I. A., 46 Roos, B., 693 Roos, M., 1060 Roos, M. T., 1053 Roos, R. A., 147 Roos, R. P., 1110 Ropeleski, M. J., 1015 Roper, R. L., 74 Roper Starch Worldwide, 396 Ropers, H. H., 362 Rosa, E. F., 1046 Rosal, M. C., 666 Rosas, M., 40, 85 Roscoe, J. A., 520 Rose, C. A., 516, 556 Rose, D. W., 137
Rose, G., 717, 931 Rose, G. M., 357, 745, 1017 Rose, H., 303 Rose, L., 693, 881 Rose, L. M., 937 Rose, N. R., 1107 Rose, P. E., 1023 Rose, R. M., 710 Roseboom, K., 764, 767 Rosecrans, J. A., 516 Rose-John, S., 144, 338, 359, 594, 596, 598 Roselle, G. A., 550 Rosen, A., 112 Rosen, E. D., 999 Rosen, T. A., 102 Rosenbaum, B., 1110 Rosenbaum, E., 583 Rosenberg, D., 106 Rosenberg, L., 242 Rosenberg, L. T., 460, 468, 469, 1025 Rosenberg, R., 790 Rosenberg, R. D., 957 Rosenberg, S. A., 236, 252 Rosenberg, Z. F., 1059 Rosenberger, P., 553 Rosenblatt, J., 692 Rosenbloom, D., 717 Rosenblum, G. A., 737 Rosenblum, L. A., 479, 485 Rosenfeld, M. G., 50, 137 Rosenfeld, R. G., 174 Rosenfield, R. E., 557 Rosengren, A., 947, 948, 949, 957 Rosengren, L., 417, 420 Rosenkranz, K., 359, 386 Rosenkranz, M., 622, 901, 909, 910, 913 Rosenkranz, M. A., 913 Rosenman, R., 929 Rosenmann, H., 364 Rosenne, E., 76, 236, 255, 256, 257, 258, 259 Rosenthal, G. E., 783 Rosenthal, N., 181 Rosenthal, R., 553, 932, 1079 Rosenthal, R. A., 253 Roset, P. N., 557 Rosette, C., 53, 741 Rosewicz, S., 48 Rosier, M., 663 Rosignoli, F., 135, 146 Rosmond, R., 715 Ross, A. H., 116 Ross, C. E., 783 Ross, C. P., 1110 Ross, F. M., 355 Ross, J., 418 Ross, M., 789 Ross, M. T., 362
1217 Ross, P. C., 222, 604 Ross, R., 502, 679, 694, 839, 842, 921, 922, 923, 926, 927, 951 Rossano, F., 637, 638, 640, 652 Rosseau, S., 1100 Rossetti, L., 997, 998, 999 Rossi, C. R., 172, 177, 178 Rossi, D., 136, 841 Rossi, E. L., 815 Rossi, F., 841, 998 Rossi, J. F., 885 Rossi, M., 855 Rossi, P. C., 1110 Rossi, R., 112 Rossi-George, A., 284, 306 Rossman, R., 181, 182 Rossner, S., 142 Rossol, S., 420 Ross-Petersen, L., 871 Rostene, W., 745 Roszman, T. L., 70, 1044 Rot, A., 435 Roth, J., 283, 288, 298, 323, 326, 995 Roth, K. A., 275 Roth, M. D., 555, 557 Roth, S., 784, 788 Roth, S. H., 733 Roth, T., 587 Rothenberg, E. V., 73, 75 Rothenberger, C. A., 859 Rothenfusser, S., 1099 Rothermel, J., 609 Rothermundt, M., 451, 511, 565, 566, 567, 568, 569, 570 Rothermundt, Matthias, 563 Rothman, A. J., 761 Rothman, P., 998 Rothstein, R. P., 419 Rothstein, T. L., 74 Rothwell, N., 274 Rothwell, N. J., 269, 276, 286, 297, 298, 320, 337, 338, 355, 361, 397, 415, 416, 417, 418, 419, 422, 423, 430, 432, 433, 434, 995 Rotondi, M., 361, 1003 Rotstein, S., 875, 877 Rott, D., 501 Rott, R., 567 Rotter Sopasakis, V., 996 Rottman, J. B., 142 Rotwein, P., 173, 182 Rouault, C., 993 Roubenoff, R., 361 Rouch, C., 330 Roue, R., 1055 Rouleau, A., 109, 111 Rounds, J., 869 Rounioja, S., 459 Rouot, B., 101
1218 Rouppe van der Voort, C., 65, 72, 200, 1044 Rourke, K. M., 715 Rouse, B. T., 1086 Rousseau, G. G., 48 Roussel, S., 420 Rovaris, M., 148 Rovelli, F., 594, 604 Rowden, L., 691 Rowe, J. W., 361, 380, 491, 932 Rowe, R., 712 Rowland-Jones, S. L., 1055 Rowse, D. L., 884 Rowse, G. L., 236 Roy, S., 235, 808, 1099 Roy, Sitesh R., 707, 799 Roy-Byrne, P. P., 1061 Royer, D. K., 542 Royer, H., 587 Roysamb, E., 773 Rozanski, A., 681, 921, 928, 935, 967 Rozeboom, K., 662, 900, 906 Rozemuller, J. M., 276 Rozen, F., 181 Rozenbaum, W., 1055 Rozlog, L. A., 77, 861, 1079 Rozniecki, J. J., 109 Rozovsky, I., 360, 384 Ruan, H., 995 Ruan, W. J., 712 Rubens, R., 692 Rubens, R. D., 870 Rubin, A. L., 997 Rubin, J. S., 826 Rubin, S., 361, 962 Rubin, S. A., 567 Rubin, S. M., 956 Rubinow, D. R., 519 Rubinstein, I., 109 Rubinstein, M., 419 Rubio, S. I., 1055 Rubio-Trujillo, M., 732 Ruchalski, K., 1015 Rucker, R., 252 Ruddin, M., 434 Ruderman, N. B., 662, 997 Rudert, W. A., 571 Rudick, R., 436 Rudin, E., 994 Rudin, M., 434 Rudisch, B., 509 Rudling, M., 996 Rudnicka, A., 957 Rudofsky, G., 72, 965 Rudolf, S., 566 Rudolph, K., 299, 303 Rudolph, R., 979 Rudy, J. W., 342, 343, 344, 345, 347, 348, 357, 360, 384, 385, 456, 1017
Author Index Rueckert, T., 646 Ruehlman, L. S., 788 Ruela, C., 386 Ruff, M. R., 223 Ruggieri, R. M., 366 Rugulies, R., 681 Ruh, M. F., 735 Ruh, T. S., 735 Rui, H., 997 Ruijnzeel, P. L. B., 978 Ruitenberg, A., 439 Ruiz, P., 555 Ruiz, R. G. G., 977 Rülicke, T., 585 Rumberger, J., 921 Rumley, A., 503, 505, 924, 926, 957, 961, 962, 963, 965, 966, 968 Rundell, M. K., 1110 Ruocco, A., 420 Rupp, H., 235 Rupprecht, H. J., 957, 959, 996 Rupprecht, M., 981 Rupprecht, R., 981 Ruprecht, R. M., 1058 Rusch, D., 197 Ruschen, S., 572 Ruscher, K., 76 Rüschoff, J., 733 Ruscica, M., 361 Ruscio, M. A., 712 Rusconi, S., 735 Rush, A. J., 686 Rush, K. A., 555 Rush, R. A., 400 Rushanan, S., 639 Rushforth, D., 99, 290 Rushforth, D. A., 283, 297, 298, 417, 995 Rusiniak, K., 646 Ruslanova, I., 566, 567 Russel, D., 676 Russell, A. S., 212 Russell, D., 782, 783 Russell, D. A., 418 Russell, D. W., 785 Russell, J. A., 762 Russell, J. H., 110, 142 Russell, J. M., 1002 Russell, M., 647, 648, 653 Russell, M. A., 771 Russell, N. J., 200 Russo, F. O., 1056 Russo, J., 1061 Russo, M., 649, 653 Russo, T., 109 Russo-Marie, F., 843 Russo-Neustadt, A. A., 717 Rusu, V. M., 735 Rutherford, B. D., 937 Rutishauer, W., 923
Rutkowski, M. D., 405, 408 Rutschmann, S., 999 Ruttanaumpawan, P., 200 Rutten, F., 977 Ruttinger, D., 879 Ruud, E., 74 Ruuls, S. R., 272 Ruwe, W. D., 533, 536, 537 Ruysschaert, J. M., 132 Ruzicka, T., 978 Ruzzante, S., 487, 1055 Ryan, A. S., 662 Ryan, D., 994 Ryan, I. P., 223 Ryan, J. J., 998 Ryan, N. D., 485, 541 Ryan, T. J., Jr., 934 Rybakowski, J. K., 515 Rydel, R., 439, 440 Rydel, T., 340, 359 Ryder, E., 957 Ryder, K., 53 Rydevik, B., 400 Ryff, C. D., 625, 761, 764, 771, 772, 900, 902, 913 Rykova, M. P., 855 Rymer, J., 829 Rymeski, B. A., 483 Rysanek, K., 599 Ryu, S. Y., 380, 747 Rzehak, P., 977 Sa, M. J., 386 Saab, P., 687 Saade, N. E., 300, 303 Saag, K. G., 198 Saag, M. S., 1054 Saah, A., 1053 Saah, A. J., 1053 Saarialho-Kere, U., 840 Saatman, K. E., 352, 354, 419, 420 Saavedra, J. M., 238 Saban, M. R., 117 Saban, R., 117 Sabatier, B., 1059 Sabin, E., 763, 764 Sabioncello, A., 532, 535, 536, 537, 538 Sabiston, B. H., 732 Sablone, M., 434 Sablotzki, A., 543 Sacanella, E., 550, 554 Sacchetti, B., 342 Sacchetti, E., 570 Sacedon, R., 462 Sacerdote, P., 160, 256, 346, 349, 350, 351, 480, 784, 792 Sachais, B. S., 103 Sachot, C., 297 Sachs, J., 112
Author Index Sackett, G., 482, 483, 854 Sacks, F., 926, 956 Sacks, G., 457, 458 Sackstein, R., 603 Sacktor, N., 1057 Sad, S., 56 Sada, M., 966 Saddoris, M. P., 342 Sadeghi, R., 736 Sadlik, J., 678 Sadovnick, A. D., 1108 Sadovsky, R., 768 Saeed, R. W., 86, 90, 91 Saelan, H., 871 Safieh-Garabedian, B., 165, 300, 303 Safko, M. J., 984 Sagach, V., 813 Sagar, M., 1059 Sagawa, M., 522 Sage, E. H., 253 Sagebiel, R. W., 871, 876 Sagone, A. L., 746 Sagvolden, T., 344 Saha, A. K., 662, 997 Saha, N., 571 Saha, S., 320, 322 Sahar, T., 542 Saheki, Y., 342 Sahinturk, V., 146 Sahley, C., 631 Sahs, J. A., 1061 Said, G., 399 Said, S., 133 Said, S. I., 114, 132, 133 Saifuddin, M., 1057 Saigo, M., 957 Saikku, P., 927 Saini, J., 603, 681 Saint-Mezard, P., 725, 732 Sainz, B., 56 Sairanen, T., 416, 417 Saito, H., 211, 1026 Saito, K., 339, 352, 353, 354 Saito, M., 858 Saito, N., 521, 522 Saito, S., 554 Saitoh, D., 1045 Saitoh, T., 1000 Sajan, M. P., 999 Saji, S., 252, 253 Sajithlal, G., 386 Sakabe, K., 462 Sakaguchi, S., 800 Sakai, K., 110 Sakai, M., 51 Sakai, N., 521, 522, 997, 1000, 1001 Sakai, R. R., 479, 481, 745 Sakai, T., 331, 571 Sakamoto, N., 995
Sakamoto, T., 364, 365 Sakanaka, M., 350 Sakane, T., 143, 200 Sakatani, T., 274 Sakurai, E., 1026 Sala, M., 350, 351 Salahuddin, S. Z., 1056 Salak-Johnson, J., 136 Salazar-Mather, P. T., 1091 Saldanha, C., 197 Salentin, R., 1100 Salerno-Goncalves, R., 1056 Salfi, M., 647, 648 Sali, A., 875 Saliou, C., 383 Saliou, P., 554 Salkeld, D. J., 342 Sallusto, F., 142, 800, 1086, 1091 Salm, A. K., 712 Salmayenli, N., 1002 Salminen, A., 383 Salmon, M., 1056 Salmon, P. G., 884 Salom, J. B., 420 Salomaa, V., 957 Salomen, J. T., 781 Salomon, B. L., 149 Salomon, P., 1000, 1001 Salomonsson, M., 827 Salonen, E. M., 859 Salonen, J. T., 498, 499, 947, 957 Salonen, R., 947 Salovey, P., 623, 761 Salpietro, D. C., 984 Salter, M. W., 160, 396, 398, 407 Saltin, B., 1014, 1022 Saltzman, A., 734 Saltzman, W., 491 Saluja, A. K., 110 Salvaggio, A., 211, 212, 214 Salvati, S., 790, 1060, 1062 Salzet, M., 653 Salzman, A. L., 997 Sama, A., 85 Samad, F., 993 Samad, T. A., 405 Samara, M. M., 713 Sambhara, S., 380 Samet, J. H., 554 Samimi, A., 349, 350, 351, 384 Sammon, A., 910, 911 Sammons, N. W., 382 Sampath, D., 502 Sampliner, R., 549, 551 Sampognaro, S., 212, 462 Sampson, H., 803 Sampson, H. A., 977, 979, 988 Sampson, S. R., 999 Sams, C., 854
1219 Sams, C. F., 854, 855, 856 Samuel, D. S., 182 Samuelsson, A. R., 303 Samuelsson, B., 322, 802 Samulski, T. V., 885 San Miguel, J. F., 550, 551, 553 Sanborn, C. K., 584 Sanchez, M. D., 711 Sanchez- Madrid, F., 1100 Sanchez, R. L., 485 Sanchez-Alavez, M., 586 Sanchez-Dardon, J., 1056 Sanchez-Guerra, M., 363, 364 Sanchez-Guerrero, J., 210 Sanchez-Madrid, F., 46 Sanchez-Margalet, V., 994 Sanchez-Narvaez, F., 586 Sanchiz, C., 1058 Sancho, D., 1100 Sancricca, C., 1003 Sandberg, E., 534, 535 Sandberg, S., 813, 815 Sandborn, W. J., 90 Sander, M., 554 Sanderman, R., 790 Sanders, A., 438 Sanders, M., 715 Sanders, V., 75, 635 Sanders, V. M., 40, 41, 63, 64, 65, 66, 67, 68, 70, 71, 73, 74, 75, 76, 77, 98, 99, 194, 222, 515, 516, 605, 826, 983, 1042, 1044, 1045, 1057, 1058 Sanderson, C. J., 55 Sandfort, T., 689 Sandfort, T. G., 1060, 1061 Sandman, C. A., 459, 711 Sandnas, A. M., 165 Sandner, G., 646 Sandor, M., 100, 103 Sang, N., 275 Sangameswaran, L., 161 Sanger, J., 490 Sanjo, H., 381 Sann, H., 109, 110 Sanna, V., 1003 Sano, H., 116, 200, 740 Sans, S., 946 Sansone, L. A., 714 Sansone, R. A., 714 Sansoni, P., 1043, 1044 Sant, G. R., 117 Santambrogio, L., 438 Santarcangelo, E. L., 964 Santema, J., 458 Santiago, B., 143, 200 Santiago, H. T., 921, 929, 933, 934, 967 Santiago-Schwarz, F., 1015 Santicioli, P., 117
1220 Santini, D., 116 Santoni, A., 357 Santorelli, S. F., 622 Santorelli, S. K., 901, 909, 910, 913 Santoro, M. G., 1014 Santos, A. C., 993 Santos, J., 112, 116 Santoso, D. I., 307 Santos-Silva, A., 458 Sany, J., 222, 609 Sanz, C., 421 Sanz, E., 736 Sanzgiri, R. P., 403, 404, 406 Sanzo, K., 792 Sapatino, B. V., 1110 Sapena, R., 997 Saper, C., 331 Saper, C. B., 268, 273, 274, 293, 294, 319, 321, 322, 323, 324, 325, 326, 327, 328, 329, 330, 332, 432, 438 Saperas, E., 112 Sapirstein, A., 405 Sapolsky, R., 235, 357, 738, 933 Sapolsky, R. M., 186, 235, 236, 261, 357, 482, 487, 488, 489, 491, 540, 620, 716, 723, 724, 737, 745, 747, 832, 879, 884, 911, 1015, 1055, 1057, 1059, 1060, 1065 Sapp, S. K., 946 Sar, M., 49, 50 Sarazan, F. F., 607 Sarchielli, P., 417, 420, 588 Sareneva, T., 1100 Sarfati, M., 732, 812 Sarfatti, A., 511, 514, 516, 518, 607 Sargent, I., 458 Saria, A., 110, 115 Sarkar, C., 242 Sarkar, S., 237 Sarkisian, M. R., 840 Sarraf, P., 297 Sarrieau, A., 302 Sartin, J. L., 605 Sary, G., 583 Sarzi-Puttini, P., 224 Sasaki, C. T., 881, 882 Sasaki, H., 512, 647 Sasaki, T., 567, 569 Sasso, D. A., 305 Sata, M., 1001 Satariano, W. A., 1061 Satchitanantham, S., 257 Sato, A., 1099 Sato, E., 88 Sato, H., 862, 947, 949 Sato, K., 357, 1001, 1002 Sato, N., 998 Sato, S., 957 Sato, V., 419
Author Index Sato, Y., 331, 841, 842 Satoh, M., 87, 186, 301, 353 Satoh, N., 329 Satoh, S., 330 Satonaka, H., 998 Satoskar, A. R., 725, 732 Satpathy, A., 297, 304, 996, 1000 Satta, M. A., 294 Satterwhite, B. B., 811 Satyamoorthy, K., 842 Saudin, F., 257 Sauer, J., 54 Sauerwein, H. P., 72, 997 Saul, A., 732 Saunders, W. B., 694, 949 Saunier, B., 1015 Saura, R., 197 Saurat, J., 73 Saurat, J. H., 997 Saurer, T. B., 256, 1101 Sauter, A., 416, 417 Sauter, B., 1018 Sauter, N. P., 73 Sautner, T., 200 Sautter, J. J., Jr., 567 Savage, A., 482 Savage, M. O., 174 Savage, S. M., 556 Savant, V., 1056 Savard, J., 518, 579, 606 Savary, C., 876 Savelkoul, H. F., 437 Savina, I., 304 Savino, W., 240, 462 Saviolakis, G. A., 241 Savonenko, A., 358 Savory, J. G., 49 Savory, R. G. A., 1098 Savu, L., 747 Sawa, H., 223 Sawada, M., 147 Sawayama, Y., 958 Sawchenko, P., 321, 323, 328, 329 Sawchenko, P. E., 87, 195, 292, 293, 320, 321, 322, 328, 329, 360, 438, 439, 843 Sawtell, N. M., 1088 Sawyer, R., 462 Sawyer, R. H., 462 Saxarra, H., 1063 Saxne, T., 193 Sayer, A. A., 456 Sayer, Liana, 786 Sayers, A. R., 440 Saylor, S., 743 Sbano, E., 219 Sbarbati, A., 998 Scafidi, F., 684, 689, 1055 Scala, G., 399
Scales, W. E., 736 Scambia, G., 882 Scammell, J. G., 482 Scammell, T., 331 Scammell, T. E., 293, 294, 322, 323, 324, 325, 326, 328, 329, 330, 332, 438 Scanlan, J. M., 484, 491, 606 Scapini, P., 839 Scarisbrick, P., 609 Scarone, S., 568, 570 Scarpace, P. J., 100 Scarparo, A. C., 239 Scevola, D., 1055 Schaaf, M., 198 Schaaf, M. J., 198 Schaal, M., 876 Schachter, S. C., 540 Schacke, H., 198 Schacker, T., 1054 Schaefer, C. A., 277, 569 Schaeffer, E., 1054, 1057, 1058 Schaeffer, M. A., 539 Schaer, D. A., 108 Schafe, G., 632, 639 Schafer, A., 1057, 1058 Schafer, C., 552 Schafer, K., 1000, 1001, 1002 Schafer, M., 110, 160, 161, 162, 164, 165, 166, 554 Schafer, S., 997, 1000 Schafers, H. J., 981 Schafers, M., 399 Schaffer, M., 254 Schaffler, A., 1003 Schaffner, W., 74 Schaible, H. G., 223 Schaible, H.-G., 330 Schaider, H., 842 Schall, M., 386 Schaltenbrand, N., 601 Schambelan, M., 1059 Schanberg, S. M., 929, 930, 935 Schantz, S., 878 Schaper, F., 338 Schapira, A. H., 383 Schapiro, I. R., 871 Scharf, B. A., 485 Scharpe, S., 277, 511, 516, 551, 568, 570, 622 Scharrer, E., 284 Schatz, M., 816 Schaub, J., 109 Schauble, E., 1041 Schauenstein, K., 523, 727, 729, 730, 732, 738, 1044 Schechner, J. S., 1000 Scheck, A. C., 322 Schedel, J., 209, 210
Author Index Schedlowski, M., 65, 67, 68, 69, 70, 76, 453, 605, 637, 645, 646, 650, 651, 652, 653, 654, 684, 691, 724, 726, 727, 728, 729, 730, 733, 737, 739, 877, 929, 963, 965, 983, 1039, 1040, 1044, 1045, 1046 Schedlowski, Manfred, 631 Scheerens, H., 115 Scheibel, A. B., 382 Scheibel, M. E., 382 Scheich, G., 979 Scheier, M., 872, 887 Scheier, M. F., 497, 713, 773 Scheinichen, D., 646 Scheinman, R. I., 53, 741, 1098 Schell, S. R., 73, 732, 735 Schell, T. D., 1080, 1082, 1087 Schellekens, P. T., 1053 Scheller, J., 338, 594, 596, 598 Schemann, M., 109, 110 Schenck-Gustafsson, K., 948, 961, 962 Schenk, B., 741 Schenk, U., 291 Schenker, S., 554 Schennach, H., 1036 Schepers, R., 709 Scherbaum, W. A., 224 Scherbel, U., 352, 354, 419, 420 Scherer, P. E., 997 Scherg, H., 871, 873 Schetter, C. D., 711 Schettini, G., 275, 430, 435 Schettini, G. M., 399 Scheuermann, R. H., 1018 Scheurich, P., 338 Scheving, L. E., 594 Schevitz, R. W., 994 Schick, F., 1000 Schick, G., 566 Schiepers, O. J., 172, 307 Schieren, I., 1058 Schiff, M. H., 193 Schiffenbauer, J., 438 Schifitto, G., 166, 901, 908, 1057 Schild, H., 1024 Schill, S., 200, 223, 224 Schill, W. B., 983 Schilling, B. K., 663, 666 Schilling, M. K., 1015 Schillinger, M., 421 Schiltz, A., 166 Schiltz, J. C., 293, 326, 438, 439 Schimanski, G., 684, 691, 877 Schimpl, G., 469 Schindler, H., 142 Schindler, U., 998 Schinkel, C., 254 Schins, A., 969 Schirrmacher, V., 253
Schjerling, P., 1057, 1058 Schlaak, J. F., 144 Schlaak, M., 592, 594ÿ Schlagenhauff, B., 258 Schlaghecke, R., 198 Schlatter, J., 510 Schleef, R. R., 926 Schlegel, P., 361 Schleifer, S., 784 Schleifer, S. J., 452, 510, 514, 549, 550, 551, 552, 553, 622, 623, 681, 727, 743 Schleifer, Steven J., 549 Schleimer, R. P., 55, 724, 726, 737, 806, 981 Schlein, B., 874, 876 Schleinger, K., 863 Schlender, J., 1099 Schlenzig, C., 685 Schlichter, L. C., 420 Schliemann, T., 386 Schlitz, J. C., 321, 322 Schliz, M., 985 Schlosser, R., 364 Schluchterm, M., 712 Schlumberger, W., 959 Schlüter, D., 981 Schluter, M. D., 853, 855 Schluterman, K. O., 564 Schmees, N., 198 Schmeidler, J., 440, 539, 540, 541 Schmelz, M., 98 Schmid, C., 1024 Schmid, D. S., 1086 Schmider, J., 884 Schmid-Grendelmeier, P., 988 Schmid-Hempel, P., 653 Schmidlin, F., 109 Schmid-Ott, G., 984, 985 Schmidt, A., 53, 733, 997 Schmidt, A. J., 790 Schmidt, A. M., 998 Schmidt, C., 235 Schmidt, D. D., 1088 Schmidt, D. K., 110 Schmidt, E. D., 304, 1115 Schmidt, F., 591, 598, 606 Schmidt, K., 553, 1079 Schmidt, K. L., 197 Schmidt, M., 209, 210, 224 Schmidt, R., 73 Schmidt, R. E., 65, 67, 68, 69, 70, 76, 726, 727, 728, 729, 730, 739, 1044, 1045, 1046 Schmidt, S., 1115 Schmidt, S. G., 1080, 1083, 1084, 1087 Schmidt, W. E., 109 Schmidt-Choudury, A., 109 Schmidtmayer, J., 109 Schmidtmayerova, H., 1057
1221 Schmidt-Sidor, B., 565 Schmidt-Weber, C. B., 811 Schmidtz, D., 1046 Schmitt, A., 522 Schmitt, C., 237 Schmitt, D., 109, 114 Schmitt, J. A., 307 Schmitt, R. L., 664, 666 Schmitt, T. K., 110 Schmitt, U., 1024 Schmitz, G., 652 Schmitz, S., 364, 421 Schmoll, H., 684, 691 Schmoll, H. J., 877 Schmutz, B., 106 Schnaper, H. W., 224 Schnedtje, J. F., 1040 Schneeberger, E. E., 108 Schneider, A., 332 Schneider, G. M., 556, 1101 Schneider, H., 275, 350, 351, 355, 356, 646 Schneider, M. L., 467, 468, 483, 485, 491, 712 Schneider, P., 693 Schneider, S., 625, 784, 1060 Schneiderman, N., 453, 532, 535, 537, 538, 539, 541, 676, 677, 679, 680, 683, 684, 685, 686, 687, 688, 689, 690, 693, 695, 773, 774, 791, 884, 948, 966, 967, 1055, 1056, 1057, 1058, 1060, 1061, 1062, 1065, 1080, 1088 Schneiderman, Neil, 675 Schnohr, P., 931 Schnurr, P. P., 531 Schober, A., 952 Schobitz, B., 338, 342, 347, 349, 516, 598, 724 Schoen, M., 497, 1063 Schoenbaum, E. E., 1061 Schoeniger, D., 406, 407 Schoffelmeer, A. N., 304 Scholmerich, J., 68, 69, 76, 193, 197, 198, 200, 209, 210, 222, 223, 224, 226, 605, 1003 Schols, A. M., 182 Scholtens, E. J., 1045 Scholz, J., 395, 398 Scholzen, T., 109, 113 Schommer, N. C., 514 Schondorf, T., 876 Schoner, B. E., 994 Schoneveld, O., 41, 45 Schoning, B., 254 Schonrock, L. M., 1115 Schoolmann, D., 598 Schöpf, E., 978 Schopohl, J. K., 160, 162, 164, 165, 166
1222 Schor, S. L., 844, 845 Schornagel, K., 725, 732, 1115 Schorpp-Kistner, M., 53 Schorr, E. C., 63 Schorr, S., 771 Schott, C., 645–46 Schott, E., 112 Schottelius, A., 198 Schouten, E. G., 935 Schrager, L., 1053 Schramm, J., 565 Schramm, R., 839 Schratzberger, P., 107 Schreiber, C. A., 626 Schreiber, R. D., 874, 878, 879 Schreiber, S., 144 Schreiber, W., 48, 589, 590, 594, 599 Schreiber-Kounine, C., 910, 911 Schreier, M., 693 Schreiter-Gasser, U., 361 Schrezenmeier, H., 591, 594, 598, 605, 606 Schrieber, S., 662 Schrier, P., 693 Schrier, R., 1002 Schrier, R. D., 858 Schröder, H. C., 570 Schroder, J., 567 Schroder, T., 554 Schroecksnadel, K., 1036 Schroeder, J. A., 1015, 1019 Schroeter, M., 148, 419 Schroeter, M. L., 566 Schroter, M., 693 Schubart, D. B., 74 Schuck, E. L., 851 Schuck, P., 1053 Schuckit, M., 538 Schuckit, M. A., 517, 552 Schuld, A., 222, 223, 305, 362, 363, 570, 585, 591, 594, 598, 609 Schule, R., 53, 741 Schulenbe, J., 553 Schuler, G., 142, 217 Schuler, M., 1046 Schuligoi, R., 105, 106 Schuller, H. M., 260 Schulman, J. L., 1102 Schulman, S., 689, 1062 Schulte, H., 957 Schulte, H. M., 934, 1112 Schulte-Herbruggen, O., 106, 360 Schulthess, T., 997 Schultz, G. S., 829, 830 Schultz, S. A., 1080, 1084 Schultzberg, M., 117, 274, 275, 292, 345 Schultzenberg, M., 418 Schulz, D., 305 Schulz, M. F., 103
Author Index Schulz, R., 497, 693, 713, 783, 784, 792, 872, 887, 908 Schulz, S., 479 Schulze, P., 172 Schulzer, M., 439, 816 Schulzhenko, E. B., 853 Schumacher, H. R., 196, 197 Schumacher, J., 622, 901, 909, 910, 913 Schumacher, M. A., 102 Schumacher, W. A., 419 Schuman, P., 1061 Schumann, M., 211 Schunemann, S., 861 Schurmann, G., 144 Schurmeyer, T. H., 67, 68, 70 Schurr, T., 668 Schuttler, R., 567 Schutz, M., 144 Schuurs, A. H. W. M., 828 Schwab, C. L., 737, 745 Schwab, M. E., 136, 147, 148, 360 Schwabb, M. B., 1000 Schwaber, J. S., 87 Schwakenhofer, H., 590 Schwandt, M., 485 Schwaninger, M., 72, 965 Schwarts, A. L., 523 Schwartsburd, P. M., 888 Schwartz, A., 1055, 1059 Schwartz, B. D., 567 Schwartz, C., 1058 Schwartz, D., 556, 649 Schwartz, E., 385 Schwartz, E. B., 854 Schwartz, G. E., 620, 625 Schwartz, G. J., 289 Schwartz, J., 632 Schwartz, J. C., 109, 111 Schwartz, J. E., 769, 967 Schwartz, J. H., 1015 Schwartz, M., 148 Schwartz, M. W., 287, 297, 993 Schwartz, R. H., 800 Schwartz, R. J., 181, 182 Schwartz, S., 771 Schwartz, S. A., 1056 Schwartz, S. J., 1065 Schwartz, Y., 76, 256, 257, 258, 259 Schwartzman, I. N., 1002 Schwarz, D. A., 982 Schwarz, M. J., 568, 570, 572, 1115 Schwarz, M. W., 293 Schwarz, S., 739 Schwarz, T., 273 Schweiger, U., 884 Schweigreiter, R., 359, 386 Schweizer-Groyer, G., 49 Schwengberg, S., 109 Schwyzer, M., 584
Sciacca, F. L., 361, 364 Scicchitano, R., 98 Sciolla, A. D., 792 Sciorio, S., 635 Scola, L., 421 Scott, B., 1112, 1114 Scott, D. K., 48 Scott, D. W., 321 Scott, H., 384, 440, 443 Scott, J. L., 791 Scott, K. L., 1002 Scott, L. K., 1002 Scott, L. L., 1079 Scott, M., 1101 Scott, P. G., 844 Screpanti, I., 53, 55 Scudeletti, M., 828 Seagal, J. D., 792 Seals, C. M., 70 Seamans, J. K., 344 Sears, S. F., Jr., 948 Seaton, A., 456, 462, 816 Sebastiani, L., 964 Sebring, N. G., 1055 Secher, N. H., 1016, 1018, 1022 Seckl, J. R., 980 Seder, R. A., 56 Sederer, L. I., 717 Seebeck, J., 109 Seeburg, P. H., 133 Seedorf, K., 237 Seefried, G., 361 Seegal, R. F., 1039, 1040 Seeger, W., 1100 Seeley, R. J., 293 Seeliger, S., 98 Seeman, T., 235 Seeman, T. E., 361, 380, 491, 932 Seftel, H. C., 222 Seftor, E., 692 Seftor, R., 692 Segal, A., 642 Segal, B. M., 148 Segal, D. M., 1025 Segal, M., 345, 346, 348, 349, 355, 358, 646 Segal, S., 430 Segall, M. A., 304 Segard-Maurel, I., 49 Segawa, H., 432 Segerstrom, S., 676 Segerstrom, S. C., 497, 511, 532, 534, 535, 536, 537, 543, 619, 620, 622, 623, 624, 625, 713, 724, 761, 766, 773, 880, 929, 932, 1060 Seghal, P. B., 741 Segi, E., 326 Segreti, J., 381 Segreti, S., 381
Author Index Segura, J., 557 Seguy, F., 295 Sehgal, S., 1055 Sehic, E., 320 Sehon, A. H., 301 Seibert, K., 321, 358 Seibyl, J. P., 570 Seich, J. D., 715 Seidah, N. G., 110, 132 Seidler, F. J., 305 Seidman, D. S., 712 Seifert, G. J., 668 Seifert, H., 104 Seifert, J., 679 Seiffert, C., 1044, 1045 Seiffert, K., 68, 69, 103, 219 Seifritz, E., 307 Seiger, A., 359 Seiki, K., 462 Seishima, M., 339, 352, 353, 354 Seitz, M., 55 Sekaly, R. P., 1054 Sekeris, C. E., 1056 Sekhon, H. S., 88 Seki, H., 592 Sekiguchi, M., 88 Sekiguchi, N., 998 Sekikawa, K., 339, 352, 353, 354, 1039, 1040, 1041 Sekirina, T. P., 570 Sekiya, C., 295, 296 Sekizawa, K., 647 Sekizawa, S., 109 Sekut, L., 419 Selemon, L. D., 564 Self, C., 72, 73, 1045 Selhorst, J., 1100 Seligman, D. A., 553, 1079 Seligman, M. E., 771 Selke, S., 1083, 1086 Sell, H., 1000 Sellers, M. B., 1056 Selley, D. E., 161 Selner-O’Hagan, M. B., 498 Selvey, L. A., 237 Selye, H., 462, 843, 907, 931, 935 Semmyo, N., 322 Semple, S. J., 1060, 1061, 1062 Semple-Rowland, S. L., 136 Sempowski, G. D., 241, 882 Sen, A., 1043 Sen, C. K., 828, 832, 1099 Senba, E., 109 Senchina, D. S., 662, 1046 Senecal, J. L., 198 Seng, J., 816 Seng-Jaw Soong, 651 Senior, J. R., 551, 552 Senn, J. J., 995
Sennello, J. A., 1002 Sennino, B., 842 Sensi, M., 652 Sensini, A., 958, 960 Senterfitt, W., 1061 Seo, J. Y., 357, 405, 999 Sephton, E., 687 Sephton, S., 876, 879, 884, 885 Sephton, S. E., 682, 683, 692, 724, 747, 783, 876, 879, 884 Sepulveda, R. S., 579 Sequeira, W., 110 Serafetinides, E. A., 787 Serbina, N. V., 1091 Serfling, E., 211, 741 Serge, G. V., 172 Sergeant, E., 456 Sergeyev, N., 882 Seriolo, B., 199, 207, 208, 209, 212 Seripa, D., 363, 364, 421 Seror, D., 362, 366 Serou, M., 1101 Serra, M. C., 108 Serra, P., 361 Serrano, A., 136, 147, 148 Serrano, J., 554, 555 Serretti, A., 571 Serricchio, M., 421 Servatius, R. J., 346, 347, 348, 349, 351, 353, 354 Sessa, W. C., 1000 Sesso, H. D., 713 Sestini, P., 110 Sethi, J. K., 1000 Sethi, S., 110 Sethuraman, G., 715 Setiawan, T., 100, 101 Setser, J., 180 Settipane, G. A., 801 Sevelda, P., 690 Severn, A., 115, 543, 997 Sevin, B., 682, 883 Sewell, D. L., 417 Sewell, W. A., 55 Sexton, G., 523 Seybold, J., 54 Seyer, J. M., 589 Seyle, H., 491 Seymour, G. J., 663 Seymour, K., 879 Sfikas, N., 144 Sgonc, R., 738, 739 Sha, L. X., 113 Shade, E. D., 668 Shaefer, C. A., 459 Shafer, R. W., 1056 Shaffer, A., 358 Shaffer, D., 540 Shah, M., 134, 302, 1111
1223 Shah, P. K., 922, 923, 928 Shah, R., 193 Shahani, N., 184 Shaheen, S. O., 1002 Shahinian, A., 352 Shakhar, G., 252, 253, 255, 256, 257, 258, 259, 606, 878, 1046 Shakhar, K., 76, 236, 255, 256, 257, 606, 878 Shakibaei, M., 162, 164 Shalev, A. Y., 541, 542 Shalit, F., 625, 763, 765 Shalita-Chesner, M., 181 Shalyapina, V. G., 1046 Sham, P., 459, 570 Shamel, L., 999 Shanahan, F., 109, 116, 570 Shani, J., 305 Shankar, A. H., 466, 469 Shankaran, V., 878 Shanks, N., 196, 456, 491, 651, 730, 1118 Shanks, N. M., 790, 900, 901, 902, 907, 909, 911, 914, 915, 1089 Shannon, C., 485 Shannon, H. S., 717 Shannon, M., 663, 666 Shannon, W. A., Jr., 133 Shao, F., 644, 645, 653 Shapira, I., 716 Shapira-Lichter, I., 362, 366 Shapiro, C., 687, 691 Shapiro, D., 625, 763, 765, 766, 772 Shapiro, E., 859 Shapiro, P. A., 622 Shapshak, P., 276, 687, 688, 773, 784, 792, 1055, 1056, 1060, 1061 Shaqura, M., 166 Shaqura, M. A., 161, 166 Sharar, S. R., 710 Share, L. J., 488 Sharer, L. R., 342 Shargill, N. S., 995 Shark, K. B., 408 Sharkey, A. M., 359 Sharkey, C., 71 Sharkey, C. M., 1013, 1019, 1022 Sharkey, K. A., 112, 117 Sharma, A. M., 1000, 1001 Sharma, B. R., 1055 Sharma, O., 1091 Sharma, R. V., 133 Sharma, S., 491, 712 Sharma, V., 134, 139, 140, 141 Sharman, E. H., 352 Sharman, K. G., 352 Sharp, B. M., 160, 734 Sharp, C. W., 549 Sharp, G. C., 201 Sharp, P. A., 74
1224 Sharpe, A. H., 74, 75 Sharrow, K., 384 Shaten, J., 923 Shatney, C. H., 93 Shaul, Y., 237 Shaver, J. L., 609 Shavit, Y., 160, 165, 256, 259, 339, 362, 408, 556, 710 Shaw A., 863 Shaw, G. M., 1054 Shaw, J., 813 Shaw, J. P., 53, 55 Shaw, K., 1061 Shaw, K. N., 358, 359 Shaw, M., 901, 910 Shaw, S., 901, 909 Shaw, W. S., 1060, 1062 Shcherbakova, I. V., 567 Shea, P. A., 1040 Shea, S., 800 Sheahan, P., 810 Shear, N. H., 554 Shearer, G. M., 607 Shearer, W. T., 599 Shedd, O. L., 948 Sheffield, D., 966, 967 Sheffield, L. G., 382 Sheffold, A., 469 Sheikh, M. S., 177 Sheitman, B. B., 564 Shek, P. N., 668, 815 Shekelle, R. B., 234, 871, 929 Shelhaas, J., 738 Shelley, O., 1025 Shellhaas, J., 301, 542 Shellito, J. E., 554 Shellow, W. V. R., 987 Shelton, S. E., 488, 1079 Shema, S. J., 782 Shemer, J., 181 Shen, H. M., 113 Shen, S., 134, 140 Shen, W. H., 172, 177, 180, 181, 182, 183, 184, 422 Shen, Y., 439, 440 Shen, Y. C., 570 Shenefelt, P. D., 979 Sheng, J. G., 361, 444, 564 Sheng, W. S., 408 Shenolikar, S., 1043 Shenton, B. K., 256 Shenton, M. E., 564 Shephard, R. J., 662, 668, 730, 815 Shepherd, A. G., 604 Shepherd, J., 957 Shepherd, P. R., 1000 Shepp, D. H., 1057 Sheppard, H. W., 1053 Sher, A., 66, 85, 222, 1085
Author Index Sherer, D., 881 Sherer, R., 1053 Sheridan, J., 637, 676, 707, 724, 726, 734, 811, 858, 863, 900, 901, 902, 906, 907, 908, 910, 1088, 1099 Sheridan, J. F., 70, 71, 77, 172, 238, 254, 480, 483, 585, 600, 621, 622, 724, 726, 734, 745, 790, 792, 828, 832, 842, 843, 844, 845, 846, 862, 900, 901, 909, 910, 913, 917, 1019, 1025, 1044, 1046, 1053, 1065, 1078, 1080, 1081, 1082, 1083, 1084, 1086, 1087, 1088, 1097, 1098, 1099, 1100, 1101, 1102, 1103, 1111, 1112, 1114, 1115 Sheridan, John F., 837 Sheridan, P. A., 1080, 1099, 1100, 1101 Sherin, J. E., 294, 322, 438 Sherman, N. A., 745 Sherman, P. M., 1024 Sherrill, D. L., 813 Sherry, B., 85, 1057 Sherwood, A., 517, 716, 772, 927, 949, 969 Sherwood, J. B., 933 Sherwood, N., 624, 762, 763, 765, 766 Sheu, H. M., 847 Shi, L., 184, 277, 459 Shi, Y., 137, 565 Shi, Y. Y., 571 Shibata, K., 882 Shibata, N., 365 Shichi, H., 329 Shichita, T., 420 Shieh, T. M., 490 Shiflett, S. C., 549, 550, 551, 552 Shifren, J. L., 223 Shifteh, S., 52 Shiga, Y., 432 Shigemoto-Mogami, Y., 407 Shigenaga, J., 995 Shigenaga, J. K., 959 Shih, H. M., 683 Shillitoe, E. J., 859 Shim, Y. S., 1015 Shimabukuro, M., 998, 1001 Shimada, K., 1001 Shimada, M., 238, 481 Shimada, T., 110 Shimada, Y., 1001 Shimamura, T., 1037, 1046 Shimazu, T., 417 Shimbo, D., 949, 969 Shimizu, E., 53 Shimizu, K., 258 Shimizu, N., 64, 635 Shimizu, T., 522, 523, 830 Shimizu, Y., 211 Shimizu-Sasamata, M., 419 Shimoda, M., 523
Shimodaira, K., 211 Shimodozono, S., 1001 Shimoji, K., 395, 396 Shimomura, I., 998, 1000, 1001, 1003 Shimozawa, N., 1001 Shin, D. H., 571 Shinar, O., 785, 787 Shing, Y., 253 Shinkai, S., 663 Shinkawa, M., 512 Shinomura, Y., 1003 Shinozawa, Y., 344 Shintaku, N., 73 Shintani, F., 357, 571 Shioda, S., 416, 417 Shioda, T., 1056 Shiokawa, S., 223 Shiomi, H., 404 Shiozaki, T., 417 Shiozawa, M., 357 Ship, I., 1088 Shipley, M., 501, 957, 961, 962 Shipley, M. J., 717, 931 Shipley, M. T., 330 Shiraga, M., 1000, 1001 Shiraishi, H., 522 Shiraishi, S., 663 Shirakawa, T., 842 Shiraki, T., 322 Shiramizu, B., 237, 683 Shirazi, L., 515 Shire, D., 557 Shires, G. T., 54 Shirey, K. A., 307 Shirom, A., 817 Shiromani, P., 322, 327 Shishodia, S., 274 Shively, C. A., 483, 491 Shlomchik, M., 636, 637, 651 Shlomo-David, Y., 570 Shoelson, S. E., 996, 1000 Shohami, E., 358, 418, 419 Shohat, B., 534, 536 Sholar, M. B., 555 Shontz, F. C., 871 Shooter, L. R., 663, 665, 666 Shore, B., 900, 903, 914 Shore, S. A., 101, 1002 Shor-Posner, G., 1061, 1065 Shors, T., 637 Shors, T. J., 340 Shou, J., 254 Shozuhara, H., 418 Shraga, N., 224 Shriver, S., 166 Shtaif, B., 184 Shuck, A., 52 Shuckit, M. A., 551, 553 Shugars, D. A., 830
Author Index Shugars D. A., Jr., 830 Shukitt-Hale, B., 383 Shull, J., 482 Shulman, G. I., 994 Shulzhenko, Y. B., 853 Shumilla, J. A., 409 Shurin, G., 306, 651 Shurin, M., 637 Shurin, M. R., 238, 301, 732, 733, 743, 1115 Shuster, D., 345 Shuster, J., 695 Shuster, L., 621 Shute, M., 663, 668 Shuto, H., 296, 523 Shyamala, G., 1056 Si, L. S., 879 Siaud, P., 736 Sibbald, W. J., 747 Sibbitt, W. L., 70 Sibley, J. T., 923 Sibley, W. A., 272, 385, 386, 436, 1108 Sibson, N. R., 422, 437, 438 Sica, A., 217, 219 Sicherer, S., 803 Sidhu, M., 105 Sidwell, R. W., 277, 459 Siebenlist, U., 53 Sieber, M., 872 Sieber, W., 770 Siegel, A., 294 Siegel, A. J., 555 Siegel, M. D., 997 Siegel, S., 110, 647, 648, 653 Siegel, Scott, 707, 869 Siegert, S., 76 Sieggreen, M. Y., 1002 Siegler, I. C., 498, 606, 694, 949 Siegman, A. W., 929 Siegmund, A., 565 Siegmund, B., 1002 Siegrist, J., 717 Siekhaus, A., 1108 Siemer, A., 352, 353, 354 Sieper, J., 76 Siepi, D., 958, 960 Sierra-Honigmann, M. R., 1000 Sietses, C., 258 Sieve, A., 1112, 1114 Sieve, A. N., 1080, 1107, 1110, 1112, 1115 Siever, L. J., 539, 541 Siewertsz Van Reesema, D. R., 198 Siggins, G. R., 353, 354, 356 Sigler, C., 440 Sigler, P. B., 49 Siiteri, P., 458 Siiteri, P. K., 482, 746 Sikder, S. K., 1056, 1059 Sikkema, K. J., 792
Silber, J. L., 863 Silber, R. E., 543 Silberberg, D. H., 1120 Silberman, D. M., 70, 77 Silberstein, D. S., 882 Silberstein, F. C., 404 Silman, A., 199 Silman, A. J., 193, 199 Silove, D., 512 Silva, A., 710 Silva, A. C., 1046 Silva, A. G., 736 Silva, C., 117 Silva, J., 510, 512, 516 Silva, S. G., 790, 1055, 1056, 1060, 1062, 1063, 1064, 1065 Silva-Gomez, A. B., 386 Silveira, A., 961, 962 Silver, I. A., 827 Silver, P. S., 1088 Silverman, E., 66 Silverman, E. D., 1043, 1044 Silverman, M. N., 172 Silverstein, S., 859 Silverstein, S. C., 1058 Silvestri, F., 1002 Sim, R. B., 46, 568 Simandle, S., 663 Simard, A. R., 272 Simard, S., 434, 518, 606 Simbirtsev, A., 305 Simerly, R. B., 330 Simm, A., 543 Simmens, S., 788 Simmens, S. J., 871 Simmonds, S., 212, 855 Simmons, A., 523 Simmons, D. A., 306 Simmons, H. F., 1037 Simmons, P., 858 Simmons, R. J., 713 Simmons, T., 783, 786 Simms, S., 459 Simon, A. B., 921 Simon, C., 359 Simon, D. I., 927 Simon, G. T., 97, 109, 110.109, 115, 116 Simon, H., 344, 712, 803 Simon, M., 1000 Simon, M. W., 856 Simon, S. I., 839 Simon, T., 682, 683, 883, 1088 Simon, W. E., 239 Simone, P., 420 Simoneau, J., 688, 1060, 1061 Simonin, F., 167 Simonis, A. M., 1043 Simonitsch, I., 181 Simonova, G., 947
1225 Simons, A. D., 686 Simons, C. T., 290, 320, 321 Simons, E. R., 855 Simons, L., 475, 481, 482, 486, 621, 734 Simons, R. N., 606 Simonsen, L., 380 Simonsick, E. M., 361, 579, 607, 956, 962 Simpson, C. R., 813 Simpson, D. M., 166 Simpson, H. W., 744 Sims, J. E., 338 Sims, S. H., 137 Sinclair, A. J., 875 Sing, M., 1023 Singal, B. M., 931 Singel, D. J., 136, 147 Singer, A. J., 837 Singer, B., 900, 902 Singer, B. H., 491, 625, 764, 771, 772, 913, 932 Singer, J. A., 625 Singer, W., 1055, 1057 Singh, A., 669 Singh, B., 218 Singh, B. K., 994 Singh, G., 186 Singh, J., 461 Singh, L. K., 110 Singh, M., 1015, 1016, 1023 Singh, S. K., 1015 Singh, S. P., 89 Singh, V. K., 740 Singhal, A., 420, 1000 Singh-Manoux, A., 717 Sinha, P., 553, 554 Sinigaglia, F., 72, 73, 142, 1045 Sinnema, G., 739 Sipe, J. D., 434 Siren, A. L., 417 Siriachonko, T. M., 567 Sirlin, S., 74 Sirois, C. A., 1002 Sironi, M., 142, 434, 980 Siryachenko, T. M., 567 Sisk, D., 284 Sistonen, L., 1014 Sitaraman, S., 1002 Sitkovsky, M., 1058 Sitkovsky, M. V., 74 Sitte, B. A., 107 Sitte, N., 161, 162, 164, 165, 166 Sitthi-amorn, C., 947, 949 Sitzia, R., 1080 Sivori, S., 107 Sjogren, H., 554 Sjostrand, J., 397 Skalhegg, B. S., 1058 Skalli, O., 844 Skanse, B., 736, 745
1226 Skarlatos, S., 927, 928, 935 Skiba, I. A., 853 Skinhoj, P., 70, 362, 1057, 1058 Sklar, L. S., 733 Skobe, M., 842 Skofitsch, G., 112 Skogseid, B., 197 Skolnick, P., 552 Skoner, D. P., 486, 497, 504, 505, 768, 769, 770, 771, 772, 773, 782, 783, 1053, 1055, 1063, 1080, 1111 Skopal, J., 422 Skrobanski, P., 420 Skurk, T., 996 Skyba, D., 409 Slade, M. D., 769 Slahetka, M. F., 1043 Slavin, B. M., 501, 505 Sleijfer, D. T., 519 Slevin, M., 845 Slicher, A. M., 727, 729 Sliwa, K., 947, 949 Sloan, E. K., 1058 Sloane, E., 405, 406, 1053 Sloane, E. M., 273, 393, 399, 405, 406 Slocumb, C. H., 737 Slone, J. L., 305 Slotkin, T. A., 305 Slotnik, A., 841 Sloviter, R. S., 745 Slukvin, I., 457 Sluzewska, A., 515 Sly, L. M., 385, 441 Smagin, G. N., 297 Smallridge, R. C., 357 Smarr, K., 687 Smarr, K. L., 198 Smed, A., 363 Smeenk, R. J., 997 Smeeth, L., 958 Smeland, E. B., 74 Smeriglio, V., 1055 Smetankin, A., 93 Smeyne, R. J., 147 Smialik, J., 564 Smid, C., 853, 854, 855 Smirne, S., 586 Smirnov, G., 256 Smiroldo, S., 142 Smit, F., 509 Smit, J. H., 361, 362 Smith, A., 585 Smith, A. M., 770, 773 Smith, A. P., 56, 486, 694, 726, 734, 741, 771, 901, 911, 1111 Smith, A. W., 772 Smith, B., 199 Smith, B. D., 881, 882 Smith, B. J., 482
Author Index Smith, B. N., 88 Smith, C., 845, 982 Smith, C. J., 423, 434 Smith, C. L., 747 Smith, C. W., 839 Smith, D., 66, 1044 Smith, D. E., 338 Smith, D. F., 482, 952 Smith, D. M., 790 Smith, D. P., 994 Smith, E., 554, 609, 687, 815, 885 Smith, E. E., 710 Smith, E. L. P., 485 Smith, E. M., 39, 162, 299, 422, 557, 586, 588 Smith, E. O., 599 Smith, F. B., 957 Smith, G. D., 498, 500, 712 Smith, G. E., 440 Smith, G. L., 881, 882 Smith, I. M., 1040 Smith, J., 769 Smith, J. A., 663, 1025 Smith, J. C., 910 Smith, J. E., 557 Smith, J. G., 863 Smith, J. K., 1023 Smith, K., 678 Smith, K. L., 1036 Smith, K. P., 329 Smith, K. T., 1108 Smith, L., 1065 Smith, L. I., 49 Smith, L. L., 663 Smith, M., 93, 739 Smith, M. A., 196, 540 Smith, M. B., 419 Smith, M. L., 663, 930 Smith, M. W., 1053 Smith, N., 845 Smith, N. C., 109 Smith, P., 321 Smith, P. G., 1055 Smith, R., 459, 869, 871, 872, 1110 Smith, R. C., 234 Smith, R. J., 430 Smith, R. S., 745 Smith, S. B., 567 Smith, S. K., 359 Smith, S. M., 851, 853, 854 Smith, S. R., 438, 994 Smith, T., 437, 538, 676 Smith, T. L., 510, 512, 514, 517, 551, 553, 598, 607, 625, 724, 784, 785 Smith, T. P., 71, 517, 662, 1014, 1019, 1025 Smith, T. W., 497, 623, 788 Smith, U., 996, 1003 Smith, W. L., 321, 358
Smithurst, P. R., 482 Smitz, J., 458 Smoak, K., 55 Smoak, K. A., 300, 521 Smola, H., 826, 843 Smolen, J. S., 193 Smolensky, M. H., 592 Smolka, M. N., 963 Smollan, D., 793 Smolyar, D., 1055 Smulders, J., 929 Smuts, B. B., 484 Smyth, J., 772, 1079 Smyth, J. M., 685, 791, 814, 854 Smyth, M., 844, 845 Smyth, M. J., 47, 98, 142, 252, 261 Smythe, G., 307, 522 Smythe, H., 609 Smythe, H. A., 609 Smythe, J. W., 712 Snart, R. S., 1056 Snehalatha, C., 1000 Snetkov, V., 1056 Snider, R. M., 109, 115 Snidman, N., 485, 713, 1063 Snieder, H., 193 Snijdewint, F. G., 604, 735 Snouwaert, J. N., 326 Snow, D. H., 727, 729 Snow, G. E., 556 Snow, M. H., 1060, 1061 Snow, S., 680, 730, 963, 965 Snyder, D. S., 843 Snyder, G. A., 1053 Snyder, S. H., 405 Snyderman, R., 1025, 1026, 1027, 1043, 1044 Snydersmith, M., 789 Snyers, L., 736 Sobczak, S., 307 Sobel, B. E., 937 Sobel, R. A., 149 Sobieska, M., 515 Sobrian, S. K., 461 Socci, C., 980 Socol, M. L., 212 Soderholm, J. D., 116, 1024 Soeharto, R., 727 Sohn, Y. K., 400 Soininen, H., 364 Sokolik, A., 710 Sokolowski, J., 592 Solal, A. C., 565 Solana, R., 607 Solano, L., 790, 1060, 1062 Solar, G. P., 995 Solbach, W., 959 Solberg, L. C., 305 Soldan, S. S., 1108
Author Index Soldini, L., 980 Soler, C., 853, 863 Solerte, S. B., 1055 Solfrizzi, V., 365 Soliman, A., 766, 1044 Sollars, S., 632, 639 Sollas, A. I., 745 Solomon, A., 106 Solomon, C. F., 725, 726 Solomon, G., 676, 683, 689, 1061 Solomon, G. F., 71, 236, 461, 532, 535, 537, 623, 684, 726, 727, 729, 732, 733, 745, 761, 1055, 1056, 1060, 1063, 1101 Solomon, G. J., 799 Solomon, George, 718 Solomon, M. J., 93 Solomon, Z., 541 Solorzano, C., 345 Soloski, M. J., 252 Solov’eva, Z. V., 565 Soltesz, K., 419 Solvason, B., 640, 641, 652 Solvason, H., 638, 639, 640, 641, 643, 652 Solway, J., 102, 111 Soma, L. A., 147 Somers, V. K., 603 Somersan, S., 1018 Somm, E., 995, 997 Somma, V., 115, 117 Sommer, B., 67, 68, 70 Sommer, C., 399 Somogyvari-Vigh, A., 736, 1025, 1044 Son, J. H., 736 Sondel, P. M., 521 Sondergaard, S. R., 70, 1057, 1058 Sondermann, H., 1024 Song, C., 303, 306, 342, 343, 344, 346, 347, 348, 358, 359, 522, 551 Song, C. H., 213 Song, I., 112 Song, I. C., 257 Song, J. Y., 571 Song, L., 554, 1059 Song, P., 408 Song, R., 1037 Song, X. Y., 419 Song, Z., 814 Sonnega, A., 538 Sonnenfeld, G., 854, 855, 862 Sonntag, W. E., 174, 184 Sonoda, N., 998 Sonta, T., 998 Sonti, G., 283, 297 Soo, K. C., 257 Sood, A., 682, 683, 686, 692, 882 Sood, A. K., 42, 233, 240, 253, 261, 786, 876, 881, 882, 885
Soong, S., 639, 640, 652 Soong, S.-J., 639, 640 Soos, J. M., 438 Sopori, M., 556 Sopori, M. L., 89, 516, 556 Soppi, E., 744 Sorbi, S., 363, 364, 365, 366, 421 Sorci, G., 285, 565 Sordello, S., 829, 830 Soreide, J. A., 875 Sorensen, B., 1025 Sorensen, C. M., 288, 320 Sorensen, J. C., 386 Sorensen, L. T., 89, 830 Soreq, H., 361, 362, 363, 366 Soria, B., 998 Soria, C., 995 Soria, J., 995 Sorkin, E., 40, 64, 65, 70, 97, 222, 273, 282, 380, 678, 738 Sorkin, L. S., 397, 399 Sorlie, P., 948 Sorlie, P. D., 781, 783 Sorosky, J., 686, 692, 881, 882, 885 Sorosky, J. I., 786, 787, 882 Sospedra, M., 1107, 1108 Soszynski, D., 298, 303, 556 Soter, N. A., 988 Sothern, R. B., 594 Soto, H., 238 Sotuz, V., 636 Soucy, G., 386 Soudeyns, H., 1054, 1056 Souil, E., 1015 Soukanov, J., 853 Soumelis, V., 99 Souslova, V., 161 Southern, D. L., 568 Southwick, S., 540 Southwick, S. M., 539, 540, 541, 542 Souza, A. L., 555 Souza, D. O., 565, 566 Souza, G. E., 302 Sovath, S., 999 Sovio, U., 715 Sozzani, S., 142, 217, 219 Spackman, S., 236 Spada, R. S., 363, 364, 365, 366 Spahn, G., 646 Spahn, J. D., 806 Spain, D. M., 727, 728 Spallek, R., 1023 Spanakos, G., 570 Spandidos, D. A., 1056 Spangelo, B. L., 222, 604 Spangler, Z., 419 Spanos, C., 117 Sparber, S., 295 Sparkman, N. L., 342
1227 Sparks, D. L., 70, 382 Sparrow, D., 497, 498, 623, 713, 714 Spataro, L., 269, 275, 393, 402, 405, 406 Spate, U., 172 Späth-Schwalbe, E., 590, 591, 594, 598, 599, 605, 606 Spear, C., 551 Spear, G. T., 1056 Speca, M., 877 Specker, C., 198 Spector, N., 637, 638, 639, 640, 652 Spector, S. A., 862 Spector, T. D., 199 Speer, P., 89 Spehner, D., 1024 Speicher, C., 676, 677, 684, 686, 734, 787, 858, 863, 874, 1088 Speicher, C. E., 236, 676, 782, 783, 784, 786, 787, 788, 790, 792, 856, 858, 863, 884, 1088 Speidl, W. S., 72 Speigel, D., 879, 884 Speilberger, C. D., 623 Spence, J. D., 716 Spencer, N. F., 383 Spencer, R. L., 112, 222, 479, 481, 516, 723, 724, 725, 726, 727, 728, 729, 730, 731, 733, 734, 739, 741, 742, 743, 744, 745, 747, 750, 854, 1019, 1025, 1026, 1044, 1099 Spencer, S. D., 360 Spengler, D., 133 Spengler, R. N., 66, 72 Spera, P. A., 420 Sperber, J., 813 Sperisen, P., 736 Sperner-Unterweger, B., 569 Spicuzza, L., 103 Spiegel, D., 233, 234, 687, 692, 724, 747, 783, 790, 873, 876, 879, 884, 885 Spiegel, K., 585, 600, 601 Spiegel, L. A., 736 Spiegelman, B. M., 995, 999 Spiel, M., 422 Spies, C. D., 553, 554 Spieth, C., 1000 Spinedi, E., 828 Spinelli, M., 117 Spinola, P. G., 239 Spiro, A., III, 531, 714 Spitsin, S., 567 Spittler, A., 239 Spitz, A. M., 713 Spitzer, J. A., 552 Spitzer, J. H., 1025 Spitzer, S., 690 Spitznagel, E., 554 Spivak, B., 534, 536 Spona, J., 690
1228 Spooner, S., 764, 767, 900, 906 Spoonster, E., 542 Sporn, M., 85 Sporn, M. B., 416, 417 Spranger, J., 1000 Sprenger, H., 1100 Sprent, J., 726, 1085 Springall, D. R., 103 Springett, G. M., 239 Spruance, S. L., 1079, 1080, 1081 Spruijt, K., 831 Sprung, C. L., 93 Sprunger, D. B., 343, 347, 360, 385, 402 Spry, C. J. F., 728, 729, 730 Spurgeon, A., 814 Spurlock, M. E., 284 Spurzem, J. R., 109 Squadrito, F., 295 Squire, L. R., 340 Squitti, R., 363, 364, 421 Sreedharan, S. P., 100, 103, 109, 115, 131, 133, 134 Srendi, B., 625, 763, 765 Sriram, S., 135, 140, 1110 Sriram, V., 252 Srivastava, A. K., 727, 729 Srivastava, P., 1015 Srivastava, P. K., 1015, 1018, 1023 Sroussi, H. Y., 65, 72 St Clair, D., 364, 365 St Pierre, B. A., 136, 829 St Pierre, S., 104 Staab, J. P., 518 Staal, J. A., 937 Stadel, J. M., 1057 Stadelmann, C., 106, 1112 Stafford, J. M., 50 Stagg, C. A., 1014 Stagno, S., 863 Stahel, P. F., 148, 419 Stahl, N., 360 Stahnke, L., 551 Staib, F., 1024 Staib, J. L., 1015 Staiger, H., 1000 Stalder, A. K., 284 Stalder, T., 142 Stall, R. D., 689, 1061 Stalla, G. K., 54 Stallcup, M. R., 50 Stallings, C., 566, 567 Stallings, J. F., 858 Stallings, W. C., 358 Stamler, J. S., 136, 147 Stamp, G. W., 882 Stampfer, M. J., 518, 923, 926, 927, 956 Stampfer-Kountchev, M., 382 Stanberry, L. R., 1079 Standaert, M. L., 999
Author Index Stander, S., 98 Stange, K. C., 789 Stanghellini, A., 585 Stanghellini, V., 116 Stangier, U., 979 Staniek, V., 109, 114 Stanislawski, T., 252 Stanisz, A., 98, 101 Stanisz, A. M., 107, 200 Stankova, J., 1058 Stanley, H., 687, 689 Stanley, L. C., 361 Stans, G., 570 Stanton, A., 685 Staples, E. D., 994 Staples, K. J., 55 Stapleton, J. T., 790, 1062, 1063 Staprans, I., 995 Star, R. A., 100 Starace, G., 106 Starec, M., 238 Stark, C. E., 340 Stark, G. R., 137 Stark, J. L., 302, 480, 621, 1025, 1080, 1103, 1111, 1112, 1114, 1115 Stark, M., 965, 1026, 1115 Starling, E., 583 Starr, D. B., 51 Starr, J. M., 380 Starr, K., 680, 686, 687, 689 Stassen, F., 969 Stauder, A., 815 Stavenow, L., 926 Stavljenic-Rukavina, A., 532, 536 Stavnezer-Nordgren, J., 74 Ste Rose, J. E. M., 732 Stead, R., 98 Stead, R. H., 97, 106, 109, 110, 110.109, 115, 116 Stebbing, J., 1057 Stec, I. E., 733, 735, 746 Steckelings, U. M., 838 Steed, D. L., 839, 844, 846 Steele, A. C., 966 Steele, B., 605 Steele, B. W., 555 Steele, K., 501 Steele, P. L., 933 Steelman, A. J., 1080, 1107, 1110, 1112, 1115, 1116 Steenland, K., 947 Steensberg, A., 1014, 1016, 1018, 1022 Steer, M. L., 110 Steers, W. D., 117 Steeves, J. D., 273 Stefan, N., 997, 1000 Stefanadis, C., 501, 505, 937 Stefanek, M., 682, 683, 692, 693 Stefanini, G. F., 549, 551, 553
Stefanis, C. N., 570 Stefano, G. B., 921, 930 Stefano, R., 224 Stefanski, V., 255, 256, 479, 480, 481, 482, 606, 621, 727, 878, 1044 Steffek, A. J., 462 Steffens, D. C., 540 Stefferl, A., 1112 Stegeman, R. A., 358 Stegen, K., 709 Steiger, A., 583, 601 Steike, P. C., 968 Steimel, L. F., 556 Stein, B. N., 839 Stein, C., 41, 105, 106, 110, 159, 160, 161, 162, 164, 165, 166, 554 Stein, Christoph, 159 Stein, M., 510, 512, 514, 551, 552, 622, 647, 723, 724, 726, 727, 728, 729, 730, 731, 742, 743, 744, 750, 784, 932 Stein, M. B., 523, 539, 540 Stein, S. H., 74, 403 Stein, T. P., 853, 855 Steinbach, S. F., 813 Steinberg, A. D., 855 Steinberg, A. M., 539 Steinberg, B., 878 Steinberg, G. K., 1015 Steinberg, J. S., 948 Steinberg, S., 859 Steinberg, S. P., 859, 861 Steiner, J., 654 Steiner, P., 360 Steiner, R., 872 Steinhauer, S. R., 772 Steinhoff, M., 98, 109 Steinkamp, M., 106 Steinman, L., 63, 142, 148, 438, 740 Steinman, R. M., 98, 99, 108, 142 Steinwender, G., 469 Stellar, E., 832 Stellato, C., 55 Stellberg, W., 572 Steller, E., 1036 Stellfeldt, A., 715 Stellwagen, D., 357, 359 Stellwagen, G., 405 Stelzer, G. T., 1025 Stenlund, H., 218 Stenzel, K. H., 997 Stenzel-Poore, M., 419 Stepanovic-Racic, M., 400 Stephan, E., 985 Stephan, M., 985 Stephanou, A., 740 Stephens, M. A. P., 791 Stephens, R. E., 236, 801, 884 Stephenson, J. R., 604
Author Index Stepheson, T., 459 Steplewski, Z., 238 Steptoe, A., 305, 501, 502, 503, 505, 680, 694, 771, 772, 814, 901, 910, 912, 918, 931, 935, 945, 946, 947, 949, 959, 961, 962, 963, 964, 965, 966, 967, 968, 1016 Sterin-Borda, L., 66, 565, 567 Sterling P., 1036 Stern, D., 926, 998 Stern, E. L., 321 Stern, L., 235 Stern, R. A., 1055, 1056, 1060 Sternberg, E., 196, 198, 199, 299, 695, 739 Sternberg, E. M., 41, 54, 193, 194, 195, 196, 197, 198, 737, 738, 739, 741, 784, 843, 980, 981, 982, 1112, 1115 Sterne, J. A., 1002 Stetler, C. A., 509, 511, 512, 514, 516, 622, 932, 937, 962 Stetler-Stevenson, W. G., 240 Stetlow, R. B., 883 Stevens, A. C., 55 Stevens, A. M., 358 Stevens, C. E., 768 Stevens, J. G., 1086 Stevens, M., 213, 807 Stevens, M. E., Jr., 1041 Stevens, S., 74 Stevens, S. Y., 68, 69, 77, 516, 1039, 1040, 1078 Stevens, W. J., 497, 938, 969 Stevens-Felten, S. Y., 1036 Stevenson, D. K., 712 Stevenson, J. R, 1044 Stevenson, J. R., 732, 733, 736, 741 Stevenson, M. A., 1015, 1023, 1024, 1025 Stevenson, R., 639, 640 Stevenson-Hinde, J., 484, 488 Steward, B. R., 407 Steward, W. T., 761 Stewart, A. C., 979 Stewart, B., 550 Stewart, B. C., 550 Stewart, C. E., 173, 181, 182 Stewart, C. L., 173 Stewart, D., 1082 Stewart, J., 363, 364, 421, 633, 635 Stewart, T. A., 184 Stiegendal, L., 1062 Stierle, H., 652 Stigendal, L., 689, 1062 Stijnen, T., 439 Stimler-Gerard, N. P., 101 Stimmel, B., 557 Stimpel, M., 211 Stinson, D. L., 1079 Stinus, L., 523
Stirling, D. P., 273 Stites, D., 678, 879, 1059 Stites, D. P., 458, 713, 1061 Stitt, J. T., 321 Stitt, T. N., 181, 182 Stivers, M., 689 Stober, G., 522 Stobo, J., 678 Stock, C. J., 269, 276, 415 Stockinger, B., 47, 48 Stockmeier, C., 565 Stockmeier, C. A., 307 Stoff, D. M., 688, 811 Stoffel, R. H., 1043 Stoica, N., 636 Stojadinovic, O., 843, 845 Stokes, B. T., 136 Stokes, F., 385 Stokes, K. Y., 1002 Stolarczyk, R., 1055 Stoll, G., 148, 419 Stoll, P., 885 Stommel, M., 234, 869, 871 Stone, A., 1079 Stone, A. A., 624, 625, 685, 762, 764, 766, 772, 791, 814, 854 Stone, G. W., 937 Stone, L., 196 Stone, S. V., 383 Stones, M. J., 769 Storch, M. K., 1112 Storer, B. E., 521 Storey, A., 237 Storm, T., 362 Storm Van’s Gravesande, K., 809 Storring, J. M., 51 Storts, R., 1080, 1107, 1110, 1111, 1112, 1114, 1115, 1118 Story, M. E., 101 Storz, P., 181 Stossel, C., 694, 937 Stout, C. W., 1088 Stout, J., 676, 677, 684, 858, 863, 874, 1088 Stout, J. C., 782, 783, 784, 788, 792, 856, 858 Stout, S. C., 524 Stouthart, P. J., 186 Stowe, R. P., 236, 853, 854, 855, 856, 857, 858, 859, 861, 862, 863, 1079 Stowe, Raymond, 707, 851 Stoyan, T., 338, 359 Strachan, D., 928 Strachan, D. P., 977 Strack, I., 994 Strader, D. J., 235 Straface, G., 421 Strain, E., 684 Straits-Troster, K., 1060, 1061
1229 Stralzko, S., 223 Strand, D., 144 Strange, K. S., 233 Strannegard, O., 71 Strasburger, C. J., 603 Strasner, A., 666 Strasser, R. H., 69 Strassnig, M., 568 Stratakis, C. A., 799, 1112 Strathdee, S. A., 1060 Stratigos, A., 114 Stratman, G., 727, 729, 730 Stratmann, M., 646 Straub, R., 195, 207, 208, 635, 653 Straub, R. H., 42, 65, 68, 69, 76, 193, 197, 198, 200, 207, 208, 209, 210, 211, 217, 220, 223, 224, 226, 515, 516, 605, 724, 733, 737, 826, 926, 1057, 1058 Strauch, A. R., 842, 845 Strauman, T. J., 497 Straus, S., 361, 695 Straus, S. E., 363 Strausbaugh, H., 194 Strauss, J., 543 Strauss, K. I., 358 Strauss, M. E., 772 Strauss, R. S., 712 Strauss, S., 361 Strausser, H. R., 828 Strawbridge, W. J., 782 Strebel, R., 745 Streccioni, V., 635 Street, N. E., 66, 73, 99, 1045 Street, S. E., 47 Streetz, K. L., 435 Strehlke, P., 198 Streicher, J. M., 485 Streilein, J. W., 104, 113 Streit, W., 439, 440 Streit, W. J., 136, 147–48, 382 Strelau, J., 184 Stricker, B. H., 439 Strieter, R. M., 66, 72, 841, 1100 Strijbos, P. J. L. M., 407 Strik, J. J. M. H., 682 Strike, P. C., 305, 901, 910, 935, 947, 959, 966, 968 Strindall, J., 361 Strine, T. W., 812 Strle, K., 171, 180, 181, 182, 183 Strle, Klemen, 171 Stroback, R. S., 116 Strober, S., 66, 149 Strober, W., 143, 144 Stroebel, W., 258 Stroemer, R. P., 416, 417, 418 Strohl, R., 693 Strohmeyer, R., 439, 440 Strom, T. B., 55, 74, 85, 542
1230 Stromberg, I., 359 Stromstedt, P. E., 48 Strong, G., 793 Stroop, W. G., 1109 Strosberg, A. D., 1042, 1043 Strunk, R. C., 502, 503 Struve, K., 601 Strycker, L. A., 715 Stuart, M. J., 770, 773 Stubb, S., 736 Stuber, M. L., 966 Studts, J. L., 884 Stuetzle, R., 1061 Stuhlmuller, B., 210 Stumvoll, M., 997, 999, 1000 Sturgill, S., 976, 977 Sturiale, S., 101 Sturk, A., 54 Sturkenboom, M., 977 Sturner, W. Q., 564 Stygall, J., 1061 Styles, P., 422, 438 Styren, S. D., 382 Su, G. C., 351, 354 Su, M. S., 419 Suarez, A., 56 Suarez, E. C., 497, 793, 929, 930, 935, 937, 962, 966 Suarez, S., 223, 283, 995 Subakir, S. B., 307 Subbarao, B., 74 Subramaniam, S., 184 Subramanian, S. V., 842, 845 Suchecki, D., 1036 Sud, A., 1055 Sudan, S., 997 Suddath, R. L., 570 Sudhir, K., 211, 958 Sudie, K., 252 Sudo, N., 238 Suefuji, Y., 623 Suehiro, M., 977 Sueoka, K., 223 Sugai, T., 565 Sugano, S., 109 Sugden, P. H., 1043 Sugerman, A. A., 568 Sugi, K., 258, 1015 Sugimori, H., 420 Sugimoto, H., 417 Sugimoto, K., 113 Sugimoto, N., 321 Sugimoto, R., 998 Sugimoto, Y., 322, 325, 326, 327, 328 Sugiura, H., 322 Sugiya, H., 53 Sugiyama, H., 1058 Sugiyama, Y., 878 Sugust, S., 773, 774
Author Index Suh, I. B., 511, 515, 571 Suh, Y. H., 352, 354 Sui, C. G., 875 Suinn, R. M., 623 Sujaku, C., 859 Suki, W. N., 853 Sukiennik, L., 555 Sukitawut, W., 200 Suligoi, B., 683 Sulke, A. N., 679 Sulli, A., 199, 207, 208, 209, 210, 211, 212, 213, 214 Sullivan, B. M., 144 Sullivan, J., 688 Sullivan, J. L., 1055, 1082 Sullivan, J. P., 90 Sullivan, M. D., 938 Sullivan, T. J., 981 Sulon, J., 711, 772 Suls, J., 788, 872, 921, 928, 935, 949 Sumida, D. H., 239 Sumimoto, H., 998 Sumitsuji, S., 1001 Summerfelt, A., 567 Summers, J., 792 Summers, R. J., 66 Sun, L., 1014 Sun, L. Y., 173 Sun, P. D., 1053 Sun, R., 174, 400 Sun, S., 1059 Sun, W., 139 Sun, W. H., 361 Sun, Y., 360 Sun, Y. L., 53 Sunami, M., 523 Sundaresan, P., 1040 Sundaresan, P. R., 66, 69, 70, 222 Sundelin, J., 329 Sunden, A., 212 Sundgren-Andersson, A. K., 345 Sundin, U., 218 Sundler, F., 103, 115 Sundram, U., 842 Sundstrom, A., 745 Sundstrom, C., 109 Sundstrom, J. B., 1058 Suomi, S. J., 485, 488, 489, 490, 1063, 1079 Surai, P. F., 285 Surwit, R. S., 683, 716, 1022 Susarla, S., 105, 106 Susini, C., 100 Suslow, T., 565 Susser, E. S., 569 Sutanto, W., 338 Sutherland, A. G., 533, 538 Sutherland, D., 678 Sutherland, D. E., 403
Sutherland, E. R., 603 Suthers, K., 361 Suto, R., 1018 Suttitum, T., 557 Suttles, J., 663, 994 Sutton, S. K., 1063 Sutton, W., 487 Sutton-Tyrrell, K., 924, 926, 956 Suy, E., 515, 568 Suyama, H., 523 Suzuki, E., 357, 998 Suzuki, F., 69, 603 Suzuki, H., 106 Suzuki, K., 322, 421, 1045 Suzuki, N., 143, 200 Suzuki, R., 101, 109 Suzuki, S., 222, 738 Suzuki, T., 522, 923, 979 Suzuki, Y., 592 Suzumura, A., 148 Svardsudd, K., 929 Svec, F., 1055 Sved, A. F., 326, 710 Svenberg, T., 1024 Svend-Aage, J., 463 Svendsen, L., 609 Svendsen, P., 727, 729 Svenson, M., 996 Svensson, J., 769 Svensson, M., 1055 Svensson, P. A., 993 Svoboda, M., 133 Svoboda, T., 520 Svoboda-Beusan, N. L., 532, 535, 536, 537, 538 Swain, M. G., 101 Swanson, B., 1056 Swanson, L. W., 330 Swanson, M. A., 65, 66, 71, 73, 76, 1044, 1045 Swanson, P. E., 878 Swanson-Mungerson, M. A., 1042, 1044, 1045 Sweeney, C. J., 1108 Sweet, A. M., 1056 Sweet, D. M., 871, 876 Sweetnam, P. M., 957 Swerdlow, N. R., 555 Swick, N. S., 669 Swiergiel, A. H., 290, 295, 297 Swift, F., 49 Swift, M. E., 831 Swingle, W. W., 738 Swinkels, H. L., 199 Swoboda, R., 741 Sworowski, L. A., 685 Sydeman, S. J., 623 Sykes, D. H., 511, 932 Syldath, U., 1024
1231
Author Index Sylvester Vizi, E., 1045 Sylvia, C. J., 839 Sylvie, D., 1056 Symbirtsev, A., 515 Syme, L., 781, 783 Syme, S. L., 498, 781 Symensma, T. L., 1059 Symmons, D. P., 1003 Symons, J. A., 366 Syrjänen, J., 422 Szabo, C., 997 Szabo, G., 551, 553, 554 Szabo, S., 241 Szabo, S. J., 144 Szabowski, A., 53 Szalay, K., 182 Szallasi, A., 102 Szapocznik, J., 1054, 1055, 1057, 1060, 1065 Szatkowski, M., 433 Szavo, G., 85 Szedmak, S., 931 Szefler, S. J., 521 Szegedi, A., 553 Szekely, M., 290, 320 Szentendrei, T., 235 Szentivanyi, A., 983 Szepfalusi, Z., 462 Szklo, M., 784, 948 Szmit, E., 800 Szmitko, P. E., 1000 Szmuness, W., 768 Szolcsanyi, J., 110 Szpaderska, A. M., 830, 831, 846 Szpirer, J., 458 Szuba, M. P., 599 Szymczak, J., 1000, 1001 Szymusiak, R., 586 t’ Veld, B. A., 439 Taagholt, S. J., 609 Taban, C., 514 Tabaraud, F., 586 Tabarean, I., 321 Tabarean, I. V., 274 Tabarowski, Z., 139 Tabas, I., 995, 999 Tabi, Z., 1019 Tabilio, A., 54 Tada, T., 653 Taddei, A., 1055 Tadokoro, S., 1000, 1001 Taenzer, P., 716 Taffe, M. A., 307 Taffs, R., 1058 Tafti, M., 609 Taga, K., 592 Taga, T., 54, 275, 365, 1115 Tagawa, T., 1001
Tagawa, Y-I., 1039, 1040, 1041 Tagaya, Y., 98 Tagliaferro, A. R., 1002 Taglialatela, G., 383 Tagliamonte, M. R., 361 Taharaguchi, S., 342 Tahepold, P., 1014 Tai, C. L., 847 Taieb, J., 554 Tailor, A., 432 Taira, Y., 958 Taishi, P., 287–88, 331, 583, 586, 587, 601, 605, 996 Takada, A., 931 Takada, J., 420 Takada, K., 1057, 1058 Takada, Y., 931 Takadera, T., 184 Takagi, K., 106, 254, 603 Takagi, S., 142 Takagi, Y., 252, 253 Takahashi, H., 69, 565 Takahashi, I., 997 Takahashi, J., 223 Takahashi, K., 405 Takahashi, L. K., 461, 712 Takahashi, M., 359, 365, 840, 997, 1000, 1001 Takahashi, S., 329, 587, 589, 601 Takahashi, T., 365, 419 Takahashi, Y., 321 Takahata, R., 330 Takaki, A., 736, 1024, 1025, 1044 Takakuwa, K., 458, 459, 1001 Takamatsu, M., 554 Takami, M., 163 Takamoto, T., 71 Takano, M., 322 Takao, T., 195, 294, 338 Takashima, T., 979 Takasu, N., 1001 Takasugi, Y., 295, 296 Takata, M., 1001 Takatsu, F, 937 Takatsu, H., 923 Takatsu, K., 55 Takayama, H., 74 Takayama, M., 859 Takayama, N., 859 Take, S., 635, 1024 Takeba, Y., 143, 200 Takeda, J., 103 Takeda, K., 47, 99, 252, 337, 339, 381, 404, 419, 999, 1025 Takeda, R., 998 Takeda, S., 1000 Takeda, Y., 103, 381, 1018 Takegoshi, Y., 322 Takehara, K., 842
Takei, N., 459 Takekawa, S., 999 Takemura, T., 195 Takenaka, M., 303 Takeo, S., 106 Takeuchi, K., 1001 Takeuchi, O., 381 Takewaki, T., 133 Takikawa, O., 307, 522 Takishima, T., 115 Tal, M., 339 Talabot, F., 103 Talajic, M., 681, 694 Talal, N., 193 Talanian, R., 419 Talbot, N., 691 Talbot, N. L., 1046 Taleb, S., 993 Tall, A. R., 995, 999 Tallam, L., 1002 Talle, M. A., 55 Tallon, D., 901, 908, 909, 910, 911 Talluto, C., 685 Tam, B. Y., 842 Tam, S. C., 1001 Tamaki, K., 52, 209, 219, 882 Tamaki, N., 235 Tamaki, T., 400 Tamakoshi, K., 882 Tamarkin, L., 570 Tamashiro, K. L., 479, 480, 481 Tamay, Z., 1002 Tambs, K., 773 Tamir, A., 73 Tamul, K., 1060 Tamura, H., 99 Tamura, S., 1003 Tamura, Y., 404 Tan, K. C., 1001 Tan, N. S., 679 Tan, R., 1037 Tan, S., 257 Tan, S. A., 625, 763, 764, 765, 772 Tan, X., 1059 Tanabe, T., 53, 115 Tanaka, H., 73, 417, 1112 Tanaka, J., 862 Tanaka, K. F., 571 Tanaka, L., 1059 Tanaka, M., 147, 223, 327 Tanaka, S., 70, 1000 Tanaka, T., 326, 882 Tanaka, Y., 329 Tanami, M., 294 Tanapat, P., 340, 359, 727 Tanchot, C., 47, 48 Tancredi, V., 356, 357 Tandon, R., 1037 Tang, A. H., 1025
1232 Tang, C., 645 Tang, H., 74 Tang, H. B., 400 Tang, J., 565 Tang, N. L., 364, 421 Tang, Q., 174 Tang, S. C., 237 Tang, V., 332 Tang, X., 184 Tang, Y., 65 Tanga, F., 406, 408, 409 Tangalos, E., 364 Tangen, C. M., 932 Taniguchi, C. M., 174 Taniguchi, E., 830 Taniguchi, M., 829, 830 Taniguchi, N., 592 Tanimoto, T., 419 Tanioka, T., 322 Taniyama, H., 342 Tannenbaum, B., 491 Tannenbaum, M. A., 923 Tanno, E., 361 Tanouchi, J., 959 Tanovic, M., 105, 106 Tanzawa, K., 882 Tanzi, R. E., 366 Tao, L., 1023 Tao, M. L., 885 Tao, T. W., 218 Taogoshi, T., 322 Tapia-Arancibia, L., 717 Tapie, P., 585, 586 Tarakcioglu, M., 570, 571 Tarara, R. P., 1058 Taravosh-Lahn, K., 478 Tarcic, N., 456, 532, 535, 536, 538 Tare, S., 70 Targorona, E. M., 256 Tarkowski, A., 73, 361, 417, 420, 1003 Tarkowski, E., 361, 417, 420 Tarner, I., 1003 Tarnuzzer, R. W., 829, 830 Tarr, K., 684, 883 Tarr, K. L., 236, 856, 858 Tarroni, P., 357 Tartaglia, L. A., 338, 994 Tartaglia, N., 284, 290, 381 Tarter, R. E., 549 Tartter, P., 878 Tasaki, O., 417 Tashiro, T., 254 Tashjian, M., 539 Tashkin, D. P., 555, 557 Tasken, K., 257, 1058 Tassoni, G., 342 Tataranni, P. A., 993, 1000 Tate, S., 407 Tato, F., 737
Author Index Tatsuno, I., 736 Taub, D. D., 430, 1036 Taub, D. M., 479 Taub, K., 771 Taub, R., 419 Taub, R. N., 557 Tauber, M., 603 Taupin, V., 136, 147, 148, 307 Tavadia, H. B., 744 Tavassoli, M., 855 Tavernier, J., 995 Tavor, E., 239 Tax, A., 553, 932, 1079 Taylor, A., 662, 827, 842 Taylor, A. E., 541, 542 Taylor, A. H., 241 Taylor, A. J., 932, 937 Taylor, A. N., 255, 256, 257, 288, 289, 300, 555, 726, 734, 745 Taylor, C. B., 695, 789 Taylor, D. N., 684, 1061 Taylor, G. R., 854, 855, 862 Taylor, H. G., 712 Taylor, I., 692, 870 Taylor, J. M., 1053, 1054, 1058 Taylor, L., 160, 161 Taylor, M., 501, 960, 961, 962, 964 Taylor, M. E., 1054 Taylor, M. W., 522 Taylor, R. M., 256 Taylor, R. N., 223 Taylor, S., 678, 790 Taylor, S. E., 497, 624, 625, 689, 713, 773, 784, 790, 1057, 1060, 1062, 1063 Taylor, T., 966, 967 Taylor-Robinson, A. W., 115 Tazi, A., 273, 284 Tchorzewski, H., 605 Tchou-Wong, K. M., 1037 Teather, L. A., 359 Tedjarati, S., 882 Tehranian, R., 418 Teicher, M. H., 539, 541 Teipel, S. J., 365 Teixeira, M. M., 555 Tejedor-Real, P., 980 Tekell, J. L., 710 Telia, M., 636 Tellegen, A., 762, 773 Temoshok, L., 871, 876, 1060 Temoshok, L. R., 1060, 1061 ten Bokum, A. M., 100 ten Cate, J. W., 54 Ten Have, T., 1061 Ten Have, T. R., 509, 510, 512, 1061 Tendera, M., 926 Teng, M., 321, 432 Tengborn, L., 934 Tengstrand, B., 199, 209
Tennant, C., 869, 871, 872 Tennant, C. C., 234, 870, 871 Tennen, H., 198, 681 Tennen, H. A., 771 Tennenbaum, T., 999 Tenner, A. J., 997 Tenner-Racz, K., 1054 Tennstedt, S., 908 Teot, L. A., 212 Tepper, I., 813 Teppo, A. M., 934 Teppo, L., 870 Terada, H., 342 Teragawa, H., 960 Terai, K., 383 Terano, Y., 321 Terao, A., 330 Terasaka, N., 1001 Terauchi, Y., 1001 Terayama, H., 567 Terenius, L., 133 Terese, M., 958, 960 Terman, G. W., 160, 165, 556 Terno, G., 256 Terr, A., 876 Terr, A. I., 783 Terrell, T., 462 Terrell, T. G., 462 Terreni, L., 366 Terry, D. J., 716 Terry, J. M., 200 Terry, R., 345, 386 Tersmette, M., 1053 Terwilliger, J. D., 172 Terzi, A., 553 Terzioglu, E., 380 Tesfaigzi, J., 89 Teshima, R., 101, 109, 197 Tesseur, I., 420 Tessler, A., 149 Testa, U., 882 Testa, V., 663 Tetenman, C., 684, 689, 1055 Tetrud, J. W., 147 Tettamanti, M., 366 Tetzlaff, W., 273 Teunis, M. A., 242 Teutsch, S. M., 380 Tevelde, A., 681 Tewes, U., 67, 68, 684, 691, 727, 728, 729, 730, 877 Tha, K. K., 305, 348, 382 Thackway, S. V., 870, 871 Thaker, P., 882, 883 Thaker, P. H., 240 Thaker, U., 365 Thaler, J., 569 Thalhimer, W., 727, 728 Tham, T. N., 275
1233
Author Index Thamer, C., 997, 1000 Thapaliya, S., 133 Thayer, C. A., 771 Theil, D. J., 1115 Theilbaard-Monch, K., 839, 841 Theiler, M., 1109 Theobald, M., 252 Theodorescu, D., 239 Theodoropoulou, S., 570 Theodorsson, E., 117, 200 Theoharides, T. C., 109, 110, 113, 117 Theorell, T., 689, 769, 1062 Thepen, T., 725, 732, 978, 986 Thepot, V., 554 Theroux, P., 509, 511, 512, 514, 516, 518, 607, 681, 694, 921, 923, 932 Thiagarajan, P., 952, 957 Thieda, P., 563 Thiel, H. J., 323, 326 Thiele, G. M., 109 Thielemans, K., 100, 104, 107, 219 Thiemann, R., 1110 Thieringer, R., 747 Thisted, R. A., 607 Thivierge, M., 1058 Thobie, N., 1055 Thoma, M. S., 109 Thomas, A., 922 Thomas, A. J., 511 Thomas, C. A., 1058 Thomas, D. R., 831 Thomas, E., 693 Thomas, G., 1015, 1019, 1080 Thomas, G. A., 90 Thomas, G. R., 995 Thomas, J., 300, 542, 637, 727, 738, 741 Thomas, J. R., 732 Thomas, K. L., 360 Thomas, M., 813 Thomas, M. G., 685, 694, 791, 901, 908, 914, 1063 Thomas, N., 741 Thomas, P. D., 785, 786 Thomas, S. A., 69, 71, 1039, 1040 Thomas, S. E., 979 Thomas, S. L., 958 Thomas, T., 745 Thomason, B. T., 198, 726, 733, 745 Thomassen, L., 420 Thompson, B., 93 Thompson, C. B., 275 Thompson, E. B., 1056 Thompson, J., 603, 728 Thompson, J. A., 523 Thompson, J. M., 361 Thompson, J. R., 70 Thompson, M., 76 Thompson, M. A., 332 Thompson, M. L., 621, 732, 1025
Thompson, M. M., 669 Thompson, R. C., 418 Thompson, R. F., 340 Thompson, R. L., 1088 Thompson, S. G., 923, 926, 957 Thompson, S. P., 744 Thomson, A., 957, 958, 961 Thomson, M. J., 927 Thomson, W., 193 Thorbecke, G. J., 193, 438 Thoren, S., 322 Thoresen, C., 782, 876 Thoresen, C. E., 695, 814, 937 Thorlacius, H., 839 Thorlin, T., 408 Thorn, B., 883 Thorn, B. E., 236 Thornton, L. M., 514 Thornton, S. T., 1060 Thorpe, P., 882 Thorpe, R., 666 Thorsby, E., 727 Thorslund, M., 768 Thorton, J. C., 784 Thrasher, A. N., 851, 852 Thulin, T., 1016 Thun, M., 947 Thurer, R. L., 1002 Thyagarajan, S., 69, 194, 226 Tian, Y., 103 Tian, Y. H., 1015 Tibblin, B., 929 Tibblin, G., 929 Tichatschek, E., 690 Tickly, M., 198 Tieken, S., 224, 603, 604 Tiidus, P. M., 1016 Tilders, F., 357, 678 Tilders, F. J., 99, 290, 291, 292, 293, 304, 320, 381, 995, 1115 Tilders, F. J. H., 320 Tilg, H., 108, 554 Tillement, J. P., 997 Timerding, B. L., 385 Timmer, J., 592, 594 Timmermans, J. P., 105 Timms, A., 1053 Tims, F., 688 Tindle, R. W., 237 Ting, J. P., 421 Tingate, T. R., 236 Tingsborg, S., 345 Tingslad, S., 212 Tinti, C., 736 Tio, D. L., 288, 289 Tiozzo, R., 844 Tipp, J., 552 Tirassa, P., 354 Tiret, L., 957, 996
Tirloni, G., 586 Tischler, G. L., 681 Tisone, G., 237 Tissieres, A., 1014 Titinchi, S., 66 Titus, R. G., 113 Tjemsland, L., 875 Tjurmina, O. A., 238 Tntipopipats, S., 212 Tobias, C., 149 Tobias, E., 554 Tobin, B., 811 Tobin, J., 687, 689, 1065 Tobler, A., 55 Tobler, I., 422, 581, 584, 585 Tobler, P. H., 104 Tocco-Bradley, R., 273 Tochino, Y., 1000 Toda, G., 554 Toda, H., 359, 360, 386 Todak, G., 1057 Todd, J. A., 487, 1054 Todryk, S. M., 1024 Toelboell, T., 847 Toes, R. E., 252 Toescu, E. C., 380 Toffler, P., 1079 Tofler, G., 957 Tofler, G. H., 922, 930, 933 Toft, D. O., 49 Toft, P., 222, 727, 729 Togami, I., 1018 Togias, A., 812 Toh, K. Y., 568, 986 Tohmi, M., 569 Tohya, K., 598 Tohyama, M., 110 Tokarski, J., 555 Tokoyoda, K., 1058 Toksoy, A., 841 Tokuda, Y., 878 Tolan, P. H., 498 Toliver-Kinsky, T., 383 Toller, W. G., 72 Tollerud, D. J., 552, 556 Tolley, E. A., 585, 586, 601 Tolonen, H., 946 Tomac, A. C., 420 Tomaka, J., 620 Tomakowsky, J., 713, 1060 Tomarken, A. J., 622, 713, 913 Tomas, E., 662, 997 Tomasevic, L., 637 Tomasi, T. B., 458 Tomasic, J., 532, 535, 536, 537, 538 Tome, S., 737 Tomei, L. D., 884 Tomic-Canic, M., 843, 845 Tomihara, H., 937
1234 Tominaga, M., 102 Tomioka, H., 1026 Tomioka, M., 97, 98, 109, 110.109, 115, 116 Tomiyama, Y., 997, 1000, 1001 Tomiyasu, U., 382 Tomizawa, K., 342 Tomlinson-Keasey, C., 769 Tomoda, Y., 882 Tomonaga, K., 342 Tonali, P., 420 Tonali, P. A., 1003 Tondi, P., 421 Tone, M., 736 Tone, Y., 736 Tonegawa, S., 356 Tonelli, L., 194, 195, 198, 737, 739 Tonks, P., 1109, 1110, 1114 Tonnesen, E., 67, 222, 727, 728, 729 Tonnesen, H., 554 Tonnesen, M. G., 223, 845 Toobert, D. J., 715 Toole, J. J., 53 Tooley, D. D., 589 Tooyoma, I., 439, 440 Topham, D. J., 1102 Topic, B., 305 Topol, E. J., 946 Topper, R., 416 Torabi-Parizi, P., 1053 Torchia, J., 137 Tore, F., 146 Torensma, R., 1053 Torgersen, K. M., 257 Torii, H., 68, 69, 104, 107, 114, 219 Torii, J., 663 Torij, H., 1044, 1045 Torjesen, P., 74 Torkvist, L., 839 Torok-Storb, B., 858 Torpey, D. J., 1086 Torpy, D. J., 739 Torre, E., 710 Torres, E., 957 Torres, K. C., 555 Torres, M., 234, 871, 873 Torres-Aleman, I., 184, 186 Torrey, E. F., 566, 567 Torrey, W. C., 531 Torri, O., 1055 Torroba, M., 143, 146, 200 Tort, A. B., 565 Tortella, F. C., 417 Torti, F. M., 995 Tosato, G., 855 Tosatti, M. P., 842 Tosetto, A., 957 Toshima, H., 71 Toshiyuki, F., 417
Author Index Tosi, M. F., 98 Toth, I., 323, 326 Toth, L. A., 584, 585, 586, 587, 588, 597, 600, 601 Toth, M., 422 Toth, S., 181 Totman, R., 773, 1063 Tougas, G., 197 Tough, D. F., 726 Toulmond, S., 136, 147, 148, 337, 416, 417 Toutouzas, P., 937 Touzani, O., 274, 276, 418, 419 Tovar, C. A., 843, 1044, 1080, 1098, 1102, 1103 Townley, R. G., 73 Townsend, P., 498 Toyka, K. V., 417 Toyoda, M., 109 Trabattoni, D., 211, 212, 214, 365, 421, 487, 568, 570, 1055 Trabekin, E., 710 Traber, D. L., 605 Traber, L. D., 605 Traber, M. G., 383 Tracey, D., 419 Tracey, D. E., 87, 294 Tracey, D. J., 399 Tracey, K., 406, 635 Tracey, K. J., 40, 54, 64, 85, 88, 92, 105, 106, 194, 273, 399, 419, 434, 605, 772, 932, 933, 965, 997, 1057 Trachsel, L., 589 Track, N. S., 133 Tracy, R. P., 923, 926, 934, 957, 962 Tracy, U., 1014 Traenor, J. J., 900, 903, 904, 912, 913, 914 Trainin, N., 461 Trakada, G., 589, 591, 594 Tramer, M., 396 Tramontana, M., 107 Trams, G., 239 Tran, D. T., 1040 Tran Quangs, N., 995 Tran, V. K., 137 Trannoy, E., 859 Trapani, J. A., 261 Traphagen, E. T., 554 Trapmann, H., 1115 Trapp, B. D., 436 Trask, O. J., 676, 786, 790 Traustadottir, T., 1000 Trautman, R. P., 533, 536, 537 Trautmann, A., 978 Trautwein, C., 435 Travaglino, P., 603 Travers, P., 636, 637, 651 Travis, B., 487
Trayhurn, P., 995, 996 Treanor, J., 782, 787, 792, 900, 903, 914 Treanor, J. J., 512, 900, 901, 904, 907, 908, 912, 1089 Trebst, A. E., 654 Trebst, C., 436 Tredget, E. E., 844 Treiber, F. A., 966, 967 Treisman, G. J., 1061 Trejo, J., 184 Trejo, J. L., 186 Tremaine, W. J., 90 Trembath, R. C., 977 Tremblay, D., 1017 Tremblay, M. J., 1058 Trenado, A., 149 Trenn, G., 74 Trentham, D. E., 734, 745 Trentz, O., 417, 419 Tresoldi, E., 142 Trestman, R. L., 512, 539, 932 Trew, G., 457 Triadafilopoulous, G., 117 Trias, M., 256 Trichopoulos, D., 933 Trickett, P. K., 538 Tridon, V., 274, 290, 292, 294, 295, 344, 345 Triest, W., 881 Triggle, C. R., 399 Trijsburg, W., 937 Trillenberg, P., 1108 Triller, A., 275 Trimble, M. R., 1110 Trinchieri, G., 56, 137, 213, 800, 855 Trinder, J., 579, 586, 605 Tringali, G., 363, 364, 365, 366 Tripathi, A., 976 Tripp, R. A., 1102 Tripp-Reimer, T., 764, 767, 882 Trkola, A., 1054 Troendle, J. F., 712 Trogoff, B., 1055 Trojano, M., 76 Trojanowski, I. Q., 565 Trojanowski, J. Q., 113, 352, 354, 419, 420, 710 Trommald, M., 386 Tromp, E. A., 67, 68 Troop, M., 1060 Tross, S., 234 Trucco, M., 571 Truckenmiller, M. E., 1080, 1082, 1085, 1087 Trugnan, G., 1019 Trumbauer, M. E., 997 Trung, T., 109, 111 Trush, M. A., 998 Truss, M., 55
1235
Author Index Trzonkowski, P., 800 Tsacopoulos, M., 403 Tsai, F. J., 364, 365, 366 Tsai, J. H., 431 Tsai, M. J., 50 Tsai, P., 638, 641 Tsai, S. J., 364 Tsai, S. Y., 50 Tsai, W. Y., 710, 870 Tsan, M. F., 1023, 1037 Tsang, M. L., 997 Tsang, Y. T., 839 Tsao, T. S., 662 Tsatas, O., 148 Tsatsanis, C., 108, 997 Tschann, J. M., 901, 907, 912, 914 Tschanz, J. T., 383 Tschopp, F. A., 104 Tschritter, O., 997, 1000 Tschuschke, V., 871 Tseng, J., 142 Tseng, J. F., 223 Tseng, R. J., 1101 Tsetsekou, E., 932 Tsiang, H., 585 Tsiantos, A., 863 Tsiftsoglou, S. A., 46 Tsigos, C., 219, 235, 711, 738, 843, 962, 1055 Tsiriyotis, C., 1056 Tsoi, W. F., 571 Tsou, A. P., 300, 542, 738, 741 Tsubone, H., 109 Tsubota, A., 237 Tsubouchi, H., 998 Tsuchida, A., 999 Tsuchida, T., 209 Tsuchiya, N., 211 Tsuda, M., 407 Tsuda, N., 569 Tsuda, Y., 69 Tsuji, H., 110 Tsujikawa, K., 1058 Tsujimoto, M., 321 Tsujimoto, S., 344 Tsukada, H., 252 Tsukada, T., 432 Tsunawaki, S., 85 Tsunoda, I., 1115 Tsunoda, M., 1001 Tsuruta, S., 998 Tsutsui, H., 419 Tsutsui, S., 1003 Tsutsumi, K., 237 Tubb, G., 199 Tubbs, R. R., 116 Tuboi, K., 326 Tucci, M., 224 Tuchel, T., 828
Tuchinda, M., 735 Tucker, E. W., 184 Tucker, J. S., 769 Tucker, P., 533, 536, 537 Tugade, M. M., 772 Tuimala, R., 461 Tullo, A. B., 1088 Tulloch, B. J., 1063 Tulloch-Reid, M. K., 715 Tully, T., 632 Tulner, D., 969 Tuma, R. F., 417 Tumilasci, O., 983 Tuncel, N., 146 Tuncman, G., 999 Tunstall-Pedoe, H., 946, 957 Tuomainen, T. P., 957 Tuomilehto, J., 712, 946 Tura, G. B., 571 Tura, G. J. B., 570 Turbucz, P., 422 Turck, C. W., 133 Tureckova, J., 182 Turetsky, B. I., 564 Turgeman, H., 237 Turini, D., 117 Turk, D., 686 Turk, D. C., 790 Tur-Kaspa, R., 237 Turkes, A., 1019 Turkheimer, F., 437 Turnay, J., 222 Turnbull, A. V., 259, 338, 357, 419, 433, 516, 605, 982, 983 Turnbull, J., 647 Turner, B. B., 196 Turner, C. W., 497, 623 Turner, E. M., 297 Turner, G., 198 Turner, J. G., 712 Turner, M. W., 46 Turner, R., 510, 1063 Turner, R. B., 504, 587, 768, 769, 770, 771, 772, 782 Turner-Cobb, J., 876 Turner-Cobb, J. M., 783, 884 Turner-Warwick, R. T., 117 Turney, T. H., 1025 Turpeinen, U., 416, 417 Turrin, N., 283, 304 Turrin, N. P., 304 Turrini, P., 354 Turvey, C., 785 Turvey, K., 233, 870 Tuttle, R., 784, 1055, 1056 Tuttle, R. S., 773, 792, 1060, 1061 Tuzun, A., 1002 Tuzun, H., 1002 Twaddle, G., 1110
Tweedy, D., 716 Twentyman, O. P., 55 Twining, C., 398, 406 Twinn, S. F., 1065 Tybjaerg-Hansen, A., 957 Tyden, P., 926 Tyrell, D., 811 Tyrell, D. A. J., 1111 Tyring, S., 639, 640, 652 Tyring, S. K., 236, 299, 586, 853, 854, 856, 858, 859, 862, 863, 1079 Tyroler, H. A., 948 Tyrrell, D. A., 56, 694, 771 Tyrrell, D. A. J., 486, 726, 734 Tyrrell, D. L., 858 Tyrrell, P. J., 422, 423, 433, 434 Tyson, K., 588, 608 Tytell, M., 1019 Tzavellas, E. O., 551 Tzeng, S. F., 360 Tzianabos, A. O., 464 Tzivos, D., 551 Tzonou, A., 933 Tzotcheva, I., 816 Ubel, P. A., 769 Uccella, I., 683 Uccella, S., 462 Uchakin, P. N., 811 Uchida, A., 252 Uchida, K., 344 Uchida, S., 1001 Uchikoshi, T., 554 Uchino, B. N., 771, 785, 788, 792 Uchizono, K., 584 Ucur, E., 241 Uddman, R., 115 Udelsman, R., 1014 Ueda, M., 831 Ueda, R., 148 Ueda, S., 1001 Uehara, A., 295, 296 Uehara, T., 348, 382, 605 Ueki, A., 365 Ueki, S., 344, 352 Uematsu, S., 322 Ueno, R., 331 Ueshiba, H., 198 Uesugi, A., 321, 331 Ueyama, Y., 1001 Uguccioni, M., 142 Uhlig, M., 1000 Uhr, J. W., 1018 Uhrlaub, J., 273 Uht, R. M., 50 Ui, M., 1057, 1058 Uitdehaag, B. M., 1112 Ujiie, H., 1000, 1001 Ukkonen, P., 859
1236 Ulett, G., 645 Ulfhake, B., 106 Ulich, T. R., 727 Ulloa, L., 105, 106, 997 Ullrich, P., 782, 783 Ullrich, P. M., 790, 1062, 1063 Ullum, H., 70, 670, 1057, 1058 Ulmer, A., 74 Ulmer, D., 695, 937 Ulrich, C. M., 668 Ulrich, P., 92 Ulrichs, T., 200 Ulrike, M., 1109 Ulvestad, E., 420 Umberson, D., 782, 783, 786, 872 Umesono, K., 49 Umetsu, D. T., 55, 56, 502, 800 Umino, A., 294 Unanue, E. R., 843, 1036, 1038, 1043 Undem, B., 810 Undem, B. J., 110, 115 Underhill, C. M., 747 Underwood, Gordon L., 762 Underwood, L., 1062 Uneklabh, T., 557 Unemori, E. N., 224 Ungar, A. L., 320 Ungemach, F. R., 1044 Unger, J., 106 Unger, R., 100, 105, 662 Unger, R. E., 89 Unger, R. H., 995, 999 Unno, T., 133 Uno, D., 788, 792 Unsicker, K., 184 Upham, J. W., 816 Upton, R. A., 827 Urade, Y., 320, 321, 322, 331 Urakami, T., 330 Urakubo, A., 459 Urbach, D., 284, 306 Urban, L., 405 Urban, P., 923 Urbanke, R., 462 Urbano-Marquez, A., 550 Urbanowski, F., 622, 901, 909, 910, 913 Urien, S., 997 Uris, P., 93 Urquhart, D. D., 366 Urrows, S., 681 Ursano, R. J., 542 Ursin, H., 855 Urso, M. L., 669 Usala, P. D., 768 Usami, E., 73 Ushikubi, F., 322, 325, 326, 327, 328, 329 Ushio, H., 106 Ushiyama, T., 199, 208 Uthgenannt, D., 598, 599, 607
Author Index Uthman, I., 198 Utsumi, H., 998 Utsuyama, M., 815 Utter, A. C., 663, 665, 666, 667, 668, 669 Utz, P. J., 53 Uutela, A., 771 Uvaydova, M., 112 Uvnas-Wallensten, K., 133 Uygun, A., 1002 Uylings, H. B., 386 Uysal, K. T., 995 Vaage, J., 1014 Vaage, J. T., 257 Vabulas, R. M., 1015, 1024, 1025 Vacca, A., 53, 55 Vaccarezza, M., 1054 Vacchio, M. S., 843, 1056, 1098 Vachharajani, V., 1002 Vadas, M. A., 54, 839 Vadlamudi, S., 459, 569 Vago, T., 487, 1055, 1056 Vaheri, A., 859 Vahtera, E., 957 Vahtera, J., 717, 948 Vaidya, A. M., 348, 382 Vail, A., 434 Vaillant, G., 1055 Vaillant, G. E., 531, 622 Valagussa, F., 957 Valdimarsdottir, H., 624, 625, 692, 762, 764, 766, 874 Valdimarsdottir, H. B., 764, 767, 874 Vale, W., 104, 357, 738, 933 Vale, W. W., 307 Valen, G., 1014 Valenick, L., 115 Valensin, S., 653 Valentine, D. L., 482 Valentine, S. L., 184 Valentino, M., 1015 Valentino, R. J., 710 Valevski, A., 534, 536 Valfre, W., 364 Valiant, G. E., 509 Valiquett, G., 745 Valitutti, S., 1065 Valkonen, T., 233, 870 Vallance, P., 958, 960 Vallee, M., 712 Vallejo, L. G., 255 Vallejo, R., 556 Vallejo-Illarramendi, A., 565 Vallieres, L., 274, 291, 328, 360, 438 Valtonen, V., 859 Valtonen, V. V., 422 Valverde, A. M., 171, 172 Vamvakas, E. C., 258 Van Acker, A., 478
Van Arsdall, M., 882 Van Bergen, B., 831 van Boxtel, E., 829, 830 Van Buggenhout, G., 362 Van, C. E., 585, 600 Van Cauter, E., 607 Van, D. V., 101, 104 Van, D. V. V., 101, 107, 115 Van Dam, A. M., 76, 274, 283, 291, 292, 293, 298, 320, 322, 381, 418, 439, 995 van Dam, P. S., 186 Van de Kar, L. D., 1019 van de Kerkhof, P. C., 831 Van De Loo, J. C., 923, 926 van de Loo, P. G., 72 van de Pol, M., 65, 69, 72, 76, 200, 1044, 1046 van de Putte, L. B., 193 Van de Stolpe, A., 55, 741 van de Vijver, F. A., 1061 Van de Woestijne, K. P., 709 Van Deist, R., 682 Van den Akker, O. B. A., 872 van den, B. B., 92 Van den Berg, B. R., 711 van den Berg, T. K., 272, 438, 439, 1112 van den Berg, W. B., 143 Van den Bergh, O., 709 van den Brand, M. J. B. M., 771 van den Brink, H. R., 199 Van Den Broek, A. A., 727 van den Heuvel, C. J., 594 Van Den Heuvel, M. M., 439 van den Tweel, M. C., 72 van der Alk, P. G., 977 Van der Does, A. J., 307 van der Horst, C. M., 1060 van der Kerkhof, P. C., 977 Van der Kleij, H., 40, 97 van der Kleij, H. P., 106, 109 Van der Kolk, B., 534, 537 van der Linde, H. J., 115 van der, M. P., 416, 417 van Der Meche, F. G., 437 van der Meer, J. W., 146, 193, 1003 Van Der Meer, J. W. M., 664 van der Net, J., 72 Van Der, P. G., 937 Van der Ploeg, H. M., 872 van der Poll, T., 72, 438, 997 Van der Pompe, G., 679, 691, 694 van der Pouw Kraan, T. C., 997 Van der Saag, P. T., 55, 741 van Der Valk, P., 439 van der Veen, E. A., 186 van der Vegt, B. J., 479, 480, 484 Van Der Ven, A., 682
Author Index Van Der VenJongekrijg, J., 664 van der Vijver, F., 689 van der Zanden, E. P., 89 van der Zee, R., 76, 1015, 1016, 1023 Van Deuren, M., 664 van Deuren, M., 146 van Deventer, S. J., 54, 72, 997 Van Dixhoorn, J., 937 van Domburg, R. T., 771 van Dommelen, S. L., 47 Van Dongen, H. P., 599 van Doorn, P. A., 437 van Doornen, L. J., 67, 68 van Duijn, C. M., 439 van Duijnhoven, G. C., 1053 Van Duren Schmidt, K., 462 van Eck, M., 711, 772 Van Eden, C. G., 843 van Eden, W., 76, 1015, 1016 van Eijk, J. T., 509 van Elderen, T., 694 Van Eldik, L. J., 404 Van Everdingen, A. A., 198, 199 van Exel, E., 362 van Falck, B., 715 van Furth, A. M., 438 Van Furth, R., 728 van Gastel, A., 539 van Gestel, A. M., 199 van Ginkel, F. W., 103 Van Gool, W. A., 276 van Griensven, G., 689 van Griensven, G. J., 1060 Van Haastert, E. S., 439 van Hagen, P. M., 100, 115 van Hall, G., 1014, 1022 van Hattum, J., 236, 237, 1065 van Houwelingen, A. H., 109 van Hunsel, F., 539 van Kammen, D. P., 570 van Kesteren-Hendrikx, E. M., 438 van Koetsveld, P. M., 100 van Kooten, P., 1015 Van Kooyk, Y., 1053 Van Krammen, D., 692 van Loveren, H., 115 van Milligen, F. J., 1080 Van Moerbeke, D., 976 Van Muiswinkel, F. L., 439, 440 Van Ness, K., 996 Van Obberghen, E., 999 van Oers, H., 342, 347, 349 Van Oers, J., 357, 678 van Oers, N. S., 47 Van Parijs, L., 995 van Praag, H. M., 522 Van Rampelbergh, J., 133 van Ree, R., 470 Van Reenen, C. G., 479, 480, 484
van Reesema, S., 198 Van Reeth, T., 458 Van Reijsen, F. C., 978, 986 Van Renterghem, L., 961, 962 van Riel, P. L., 199, 1003 van Rooijen, N., 438, 1082 van Roon, M. A., 48 Van Rossum, E. F., 814 Van Snick, J., 135 Van Thiel, D. H., 549 Van Tilburg, M. A. L., 716 van Tilburg, W., 386, 509 van Tits, L., 1044 van Tits, L. J. H., 766 Van Umm, S. H. M., 664 Van V, D., 104 van Venrooij, W. J., 218 van Vliet, S. J., 1053 Van Vugt, E., 104 van Westerloo, D. J., 88, 92 van Wichen, D. F., 978, 986 van Wijk, M. J., 199 van Winsen, L. M., 1112 van Zanten, A. K., 997 van Zeben, D., 199 Vancheri, C., 110 Vanden Berghe, M., 213 Vanden Berghe, W., 53 Vander, A. J., 301 Vanderbilt, J., 678 Vanderlugt, C. L., 1110 VanderPlate, C., 1088 Vandersteen, D., 549, 550, 551 Vandewalle, B., 239 Vandoolaeghe, E., 551, 570, 1115 Vane, J. R., 320, 321, 329 Vane, John, 320 Vanegas, H., 330 Vange, J., 830 Vangeloti, A., 1055 vanHattum, J., 901 VanHoy, R., 174, 302 Vanner, S., 105 Vanni, L., 114 Vannice, J. L., 286, 298 VanRaden, M. J., 1061 VanRiel, F., 695 Varas, A., 462 Varcoe, J. J., 306 Varela de Seijas, E., 361 Vargaftig, B. B., 98 Vargas, M., 421 Vargot, S., 934 Varma, S., 86, 90, 91 Varray, A., 815 Varricchio, M., 361 Varsaldi, F., 108 Varui, J. W., 983 Vaschillo, E., 814
1237 Vasey, D., 149 Vasil’eva, E. F., 570 Vasios, G., 253 Vasquez, M., 70, 862, 1084, 1087, 1103 Vasquze, K., 1037, 1043 Vassalli, P., 53, 135 Vassiliou, E., 133 Vasta, G. R., 998 Vastag, M., 422 Vasudevan, R., 358 Vatten, L. J., 870 Vaudo, G., 958, 960 Vaughan, A. T., 237 Vaughan, J. H., 108, 223 Vaughn, V. T., 461 Vaula, G., 364 Vaysse, P. J. J., 403 Vazquez, M., 859 Vázquez-Camacho, A., 644, 646 Vazquez-Del Mercado, M., 212, 214 Veas, F., 1058 Vecchi, A., 217, 219 Vedder, H., 48, 589, 594 Vedeckis, W. V., 48 Vedeler, C. A., 420 Vedhara, K., 512, 708, 790, 897, 900, 901, 902, 907, 908, 909, 910, 911, 914, 915, 1060, 1061, 1089 Veenstra van Nieuwenhoven, A. L., 458 Veerhuis, R., 276, 382, 439, 440 Veerman, M., 1045 Vega, C., 344, 347, 422 Vegeto, E., 210 Veglia, F., 361, 363, 364, 365, 366, 421 Veiby, O. P., 599 Veith, R. C., 541, 682, 695, 931 Vekshtein, V. I., 934 Vela, J. M., 569 Vela-Bueno, A., 606 Velarde, L. C., 417 Velazquez, O., 842 Velez, R., 694 Velin, A. K., 1024 Velin, R. A., 1054 Vellenga, E., 66, 73, 997 Vellucci, S. V., 87, 325 Venalis, A., 196 Venditti, A., 361 Venegas, M., 235 Venetsanou, K., 969 Ventura, A. M., 1056 Verboom, P., 977 Verbrugge, L. M., 781, 783 Verderio, C., 291 Vereker, E., 353, 356, 384 Veren, K., 1056 Vergani, C., 365, 421 Verge, G. M., 407
1238 Verge, M., 609 Verges, B., 1055 Verghese, A. C., 1055 Vergne, P., 208, 211 Verhage, F., 937 Verheijen, M. H., 239 Verheul, H. A. M., 828 Verkasalo, P. K., 233, 870 Verkerk, R., 277 Verkhratsky, A., 355, 380 Verma, B., 553 Verma, I. M., 53 Verma, S., 1000 Vermani, R., 994 Vermersch, P., 148 Vermeulen, L., 53 Verreault, R., 870 Verrier, D., 288, 289, 291, 307, 308, 344, 345, 522 Verrier, P., 792, 937 Verrier, R. L., 933, 934 Vertongen, P., 133, 135 Vescovi, F., 210, 213 Vessen, N., 693 Vessey, S. J. R., 863 Veugelers, P., 689, 1060 Veugelers, P. J., 1061 Veyssier, P., 1055 Vezzani, A., 186, 273, 405 Vgontzas, A. N., 588, 589, 591, 594, 599, 606, 608 Viau, V., 829 Vicari, A., 108 Vicente, A., 462 Vickers, J., 479 Victor, A., 959 Victorino, R. M., 107, 1059 Victorov, I. V., 76 Vidal, C., 550, 554, 737 Vidal, H., 1002 Vidal-Puig, A., 1000 Vidensky, S., 358 Vieau, D., 653 Vieira, P., 800 Vieira, P. L., 219 Vieira, V. J., 1002 Vierucci, A., 855 Vigano, A., 211, 212, 214 Vigdorovich, D., 870 Vige, X., 421 Vigersky, R., 482 Viglietta, V., 149 Viglietto, G., 224 Viglione-Schneck, M. J., 113 Vignola, A. M., 813 Viguerie, N., 993 Vigues, S., 273, 274, 293, 294, 417 Viidik, A., 831 Viinamaki, H., 769, 770
Author Index Vila, M., 147 Vila, N., 417, 421 Vile, R. G., 1024 Vilhardt, F., 565 Villa, M. L., 211, 212, 214, 1055 Villacres, E. C., 682 Villaggio, B., 199, 207, 208, 209, 211 Villanueva, I., 199, 509, 511, 512 Villegas, A., 210 Villella, A., 632 Villemain, F., 570 Villena, J. A., 994 Villette, J. M., 1055 Villoslada, P., 106 Vince, G. M., 458, 459 Vincendeau, P., 586 Vincent, A. M., 186 Vincentelli, G. M., 385 Vincenti, V., 224 Vinci, D. M., 663, 665, 666, 668, 669 Vinci, J. M., 54 Vinet, M., 362 Vingerhoets, A. J., 1065 Vingerhoets, A. J. J. M., 768, 900, 901, 903, 904, 914 Vingerhoets, J. J., 236, 237, 1065 Vinokur, A. D., 790 Vinson, G. P., 224 Vinuela, J., 550 Virchow, J. C., 106, 107 Viret, C., 149 Virgin, C. E., 488 Visa, K., 736 Vischer, T. L., 74 Viselli, S. M., 462 Vishniavsky, N., 1088 Vishnubhakat, J. M., 419 Vishwanath, R., 653 Visintin, A., 1025 Viskoper, R., 716 Vismara, C., 568, 570 Visscher, B., 625, 678, 689, 784, 790, 1060 Visscher, B. R., 497, 1057, 1060, 1062, 1063 Visser, A., 691 Visser, G. H., 711 Viswanathan, K., 637, 723, 724, 725, 729, 730, 731, 732, 733, 743, 745, 747, 750, 964 Viswanathan, V., 1000 Viswesvaraiah, R., 362 Vita, J. A., 934 Vitale, M., 635 Vitaliano, P. P., 606 Vitebski, V., 636 Vitek, M. P., 53 Viticchi, C., 637, 638, 640, 652 Vitkovic, L., 290, 299, 337, 339
Vitoratos, N., 257 Vitterso, J., 773 Vittinghoff, E., 1053, 1061 Vives, V., 565 Viviani, B., 405 Vivien, D., 276, 277, 420 Vivier, E., 725 Vivirito, M. C., 1055 Vizi, E., 635 Vizi, E. S., 65, 67, 110, 254, 605, 801, 983, 986, 997 Vlad, T., 295 Vlahov, D., 1053, 1060, 1061 Vo, A. H., 710 Vo, N., 50 Voderholzer, U., 594, 606 Vodovotz, Y., 85 Voelker, T., 273 Voest, E., 242 Vogel, C., 109 Vogel, S. N., 736 Vogel, W. H., 238 Vogelstein, B., 235, 237 Voget, G., 599 Vogl, D., 224 Vogt, G. J., 524 Vogt, K., 997 Vogt, S. K., 295 Vogt, T., 714 Voice, J., 141 Voice, J. K., 133, 134, 140, 141 Voigtlander, C., 142 Vokonas, P., 497, 498, 713, 714 Vokonas, P. S., 713, 927 Volafova, J., 994 Volk, B., 386 Volk, H., 254 Volk, H. D., 76, 254, 997 Volk, M. J., 361 Voll, R. E., 137 Vollmer, A., 541, 542 Vollmer, R. R., 1019 Volosin, M., 480 Volpi, S., 1056 von Andrian, U. H., 163, 435 von Auer, K., 739, 741, 982 von Bonin, A., 1023, 1024 von Bonsdorff, C. H., 859 von Borell, E., 321 von Degenfeld, G., 842 von Dossow, V., 554 Von Ehrenstein, O. S., 808 Von Essen, S. G., 109 von Euler, A. M., 223 von Euler, U. S., 320 von Eynatten, M., 72, 965 Von Herbay, A., 106 von Herrath, M. G., 817 von Hoersten, S., 1118
1239
Author Index von Holst, H., 417 von Hundelshausen, P., 1100 Von, K. R., 931 von Kanel, R., 512, 962, 963, 965, 966 Von Korff, M., 531 von Krogh, G., 1055 Von Mutius, E., 808 von Pirquet, C., 802 Von Rucker, A., 876 von Smitten, K., 827 Von Wichert, P., 198, 200 von Wichert, P., 200 Von Zastrow, M., 357, 359 Vonderhaar, B. K., 241 vonHolst, D., 486 Vontver, L. A., 1083 Voorhuis, D. A., 338 Vorobyev, Y. I., 853 Voronov, A., 635 Vos, A. H., 1053 Vouthounis, C., 843, 845 Vreugdenhil, E., 198, 604 Vriend, G., 1053 Vrints, C. J., 497, 938, 969 Vroon, A., 76 Vu, T. H., 882 Vuillier, D., 859 Vuitton, D., 551 Vujaskovic, Z., 885 Vukosavic, S., 147 Waage, A., 542 Waager, A., 212 Wacholtz, M. C., 73 Waclawiw, M. A., 927 Wada, E., 87 Wada, H., 54, 842, 1056 Wada, M., 109 Wada, S., 297 Waddell, I. D., 182 Wade, E., 772 Wade, S. L., 813 Wadell, G., 218 Wadenvik, H., 934 Wadhwa, P. D., 459, 711 Waeber, C., 108, 133 Waelbroeck, M., 133 Waelli, T., 380 Wagener, D. J., 239 Wagenpfeil, S., 365, 366, 421 Wager, T. D., 710 Wagers, A. J., 173 Wagner, A., 275, 355, 631 Wagner, A. C., 1015 Wagner, D. D., 838 Wagner, E. F., 53 Wagner, G., 1061 Wagner, G. J., 1061 Wagner, H., 1015, 1024, 1025
Wagner, J. A., 68, 69, 219 Wagner, J. A. A., 1044, 1045 Wagner, M., 1015 Wagner, R., 397, 399 Wagner, S., 689 Wagner, T., 607, 646 Wagner, T. O., 67, 68 Wagner, T. O. F., 727, 728, 729, 730 Wagteveld, A. J., 997 Wahby, V., 539 Wahid, S., 846 Wahl, S. M., 223, 829, 830 Wahlberg, L. J., 534, 535 Wahle, M., 76, 200 Wahn, U., 977 Wahren, J., 107 Wainberg, M. A., 1056 Wainstock, J. M., 881 Wainwright, C., 804 Waite, R., 728 Wajant, H., 172, 274, 338 Waje-Andreassen, U., 420 Wakefield, D., 512, 570 Wakeham, A., 352 Wakeling, A., 385 Waki, H., 1001 Wakikawa, A., 815 Wakkach, A., 142 Walberg-Rankin, J., 663, 668 Wald, A., 1086 Wald, M. R., 70 Wald, N. J., 928 Walder, J., 104 Walder, R., 104 Waldmann, H., 736 Waldmann, T. A., 98 Waldner, A., 1055 Waldner, A. B. J. M., 1055 Waldorf, H., 837 Waldrop, D., 1055 Waldschmidt, T. J., 550 Waldstein, S. R., 772 Waletzky, L., 691, 877 Walker, B. R., 712 Walker, D., 307, 439, 440 Walker, E. A., 531 Walker, F. R., 456 Walker, K., 405 Walker, L., 222 Walker, L. G., 684 Walker, M., 684, 957, 958, 961 Walker, R., 1056 Walker, S. E., 201 Walker, S. M., 807 Wall, P., 303–4 Wall, P. M., 478 Wallace, A. D., 50 Wallace, E. M., 307 Wallace, J., 773, 1063
Wallace, M. E., 98 Wallace, M. R., 1054 Wallace, R., 782, 783 Wallace, R. B., 579, 607, 785 Wallach, D., 212, 419 Wallander, J. L., 983 Wallenius, K., 996 Wallenius, V., 996 Wallenstein, G. V., 340, 344, 346 Waller, D., 769 Wallin, A., 361 Wallis, W. J., 199 Wallon, C., 1024 Walls, A. F., 70 Wallsten, S. M., 902 Wallston, K. A., 609 Walmsley, M., 143 Walport, M., 636, 637, 651 Walsh, D. T., 440 Walsh, J. H., 101 Walsh, K., 1001 Walsh, L. J., 113 Walsh, M., 541 Walsh, M. G., 400 Walsh, R., 1014, 1022 Walsh, R. C., 1016 Walsh, R. M., 810 Walsh, S. W., 679 Walsh, W. P., 872 Walsh-Reitz, M. M., 1015 Walston, J., 932 Waltenbaugh, C., 1037, 1043 Walter, E. T., 398 Walter, J., 380, 584 Walter, V., 288, 289 Walters, E. T., 398, 399 Walters, J. A., 816 Walters, J. R., 477 Walters, N., 624, 764, 766 Waltman, T. J., 727 Waltrip, R. W., 567 Waltz, M., 789 Walzer, P. D., 729 Wamala, S. P., 948, 961, 962 Wamboldt, F. S., 982 Wamboldt, M., 806, 812 Wamboldt, M. Z., 813, 982 Wan, C. K., 788 Wan, M. X., 839 Wan, W., 288, 320 Wan, Y., 99 Wandinger, K. P., 565, 566, 1108 Wanebo, H. J., 551 Wang, B., 644, 645, 653, 996 Wang, C., 46 Wang, C. C., 110, 115 Wang, D., 208, 211, 260, 261, 568 Wang, D. R., 842 Wang, D. Y., 809
1240 Wang, E. C. Y., 901, 911 Wang, G., 714 Wang, H., 85, 86, 88, 89, 90, 91, 92, 105, 106, 399, 419, 605, 997 Wang, H. J., 689 Wang, H. L., 829, 830 Wang, H. Y., 139, 497, 1060 Wang, J., 142, 173, 296, 338, 518, 521–22, 524, 1056, 1059 Wang, J. C., 48, 50 Wang, J. M., 136, 400 Wang, K., 56 Wang, K. Y., 364 Wang, L., 1043 Wang, L. H., 237 Wang, M. C., 1053, 1054, 1058 Wang, M. Y., 995, 999 Wang, N. Y., 714 Wang, P., 65, 693 Wang, R., 101, 142 Wang, T., 1058 Wang, W., 133, 644, 645, 653, 1002 Wang, W. F., 364, 365, 366 Wang, X., 184, 417, 419, 521, 554 Wang, X. F., 568, 1056 Wang, X. G., 853 Wang, Y., 87, 89, 238, 322, 420, 587, 588, 839, 1015, 1016, 1023 Wang, Y. D., 1015 Wang, Y. L., 879, 1061 Wang, Y. Z., 105, 116 Wang, Z., 50 Wang, Z. J., 605 Wank, S. A., 133 Wara, D., 901, 907, 912, 914 Warburton, C., 184 Warburton, D. M., 624, 762, 763, 765, 766 Ward, B. G., 791 Ward, J. M., 260 Ward, M., 501, 958 Ward, M. M., 784, 792 Ward, P. B., 570 Wardeh, G., 304 Wardlaw, A. J., 55 Wardle, J., 305, 772, 901, 910 Waringa, R. A., 985 Warnatz, H., 572 Warner, G. L., 74, 1036 Warner, J. A., 456, 462, 469 Warner, J. O., 456, 462, 469, 502 Warner, L. A., 553 Warner, L. J., 814 Warnock, M. L., 103, 115, 131, 133 Warr, D., 873 Warren, B. J., 662, 663, 664, 665, 667, 668, 669 Warren, D. L., 734, 735 Warren, K. G., 1110
Author Index Warren, M. K., 736 Warren, S., 1110 Waschek, J. A., 133 Washington, J., 713 Wasik, T. J., 855 Wasserman, D., 712 Wasserman, J., 714, 717 Wasserman, S., 97 Watabe, K., 110 Watanabe, H., 830 Watanabe, N., 106, 840 Watanabe, S., 73, 344, 347, 352, 354, 359, 663 Watanabe, T., 663, 1026 Watanabe, Y., 53, 87, 88, 105, 294, 303, 305, 321, 322, 569, 745 Waterman, W. R., 1015 Waters, D. D., 957 Waters, R. J., 421 Waters, S., 384, 430, 434, 435, 438, 440, 443 Waters, W. W., 855 Wathen, S. T., 142 Watkins, A. D., 763, 764, 815 Watkins, D. R., 457 Watkins, L., 400–401, 633, 646, 677, 678, 683, 885, 949 Watkins, L. L., 772, 969 Watkins, L. R., 64, 87, 88, 99, 100, 105, 112, 194, 269, 273, 275, 281, 284, 288–89, 289, 290, 320, 329, 338, 339, 342, 343, 344, 345, 347, 348, 357, 360, 381, 384, 385, 393, 395, 396, 397, 398, 399, 400, 401, 402, 405, 406, 407, 408, 409, 456, 481, 504, 518, 520, 524, 556, 605, 620, 681, 724, 729, 732, 733, 772, 815, 854, 965, 997, 1019, 1025, 1026, 1058, 1115 Watkins, S., 102 Watry, D. D., 307 Watson, A., 487 Watson, B., Jr., 366 Watson, C. J., 224 Watson, D., 622, 761, 762, 771, 773 Watson, H. M., 882 Watson, J., 74, 692 Watson, J. L., 1024 Watson, J. M., 882 Watson, J. P., 870 Watson, M., 234, 691, 692, 869, 871, 872 Watson, R. L., 948 Watson, R. R., 549, 551, 553 Watson, R. W., 400 Watson, S., 160, 161 Watson, S. J., 557 Watt, A., 458 Watt, R., 74 Watts, D. H., 711
Watzl, B., 553 Wauben M. H., 1015 Wauben-Penris, P. J., 604 Wauben-Penris, P. J. J., 735 Waugh, R., 772 Waugh, R. A., 933, 969 Wautier, J. L., 998 Waxler-Morrison, N., 786 Ways, J. P., 53 Weatherbee, J. A., 594 Weaver, C. N., 781, 783 Weaver, J. D., 361, 380 Weaver, J. G., 1056 Webb, A., 148 Webb, C. L., 419 Webb, N. J., 224 Weber, A. L., 1061 Weber, B., 884, 887 Weber, C., 952, 1100 Weber, E., 273, 274, 584 Weber, J. S., 254, 983 Weber, K. S., 1100 Weber, P., 1037 Weber, P. C., 1100 Weber, P. S., 847 Weber, R. J., 556, 557 Webster, A., 1053 Webster, E., 110 Webster, E. L., 197, 200 Webster, J. C., 49, 50 Webster, J. I., 194, 195, 198, 737, 739, 843 Webster, M. J., 565 Webster, N. R., 256, 258 Webster, R. G., 584 Webster, S., 439, 440 Webster, W., 712 Webster’s encyclopedic unabridged dictionary of the English language, 340 Weems, L. B., 900, 906 Weesner, R. E., 550 Wegert, S., 161 Wegmann, T. G., 212, 457 Wegner, F., 437 Wegrzyn, L., 438 Wegrzyniak, B., 439, 440 Wei, J., 348, 361, 380, 568, 570 Wei, Q., 884 Wei, X., 645, 1054 Wei, Y., 108, 875 Weibel, R. E., 859 Weich, H. A., 881, 882 Weidenfeld, J., 259, 284, 300, 302, 305, 339, 357, 358, 515, 519, 622 Weidler, C., 68, 209, 210 Weidner, G., 877 Weidner, T., 668 Weidner, T. G., 668 Weigel, N. L., 50
1241
Author Index Weigel, P. H., 422 Weigert, C., 1000 Weigl, B. A., 726 Weigl, L., 557 Weigmann, B., 144 Weihe, E., 132 Weihold, C., 254 Weihs, K., 788 Weihs, K. L., 871 Weil, C. M., 813 Weil, J., 926 Weiland, S. K., 977 Weiler-Normann, C., 1045 Weinberg, G., 1014 Weinberg, J., 236, 456, 465, 884 Weinberg, R. A., 235 Weinberg, R. J., 1043 Weinberger, D. A., 625 Weinberger, D. R., 366, 564 Weinberger, N. M., 340 Weinberger, O. K., 1058 Weinblatt, M., 142 Weindl, A., 87 Weindruch, R., 361, 384 Weiner, D. B., 1056 Weiner, H., 235, 512, 516, 620, 622, 625, 676, 784, 785, 1055, 1057, 1059, 1060 Weiner, H. L., 149, 420 Weiner, J. L., 184 Weiner, P., 623 Weinman, E. J., 1043 Weinman, J., 842 Weinmann, S., 977 Weinreich, D., 110 Weinshenker, B. G., 1107 Weinstock, C., 666 Weinstock, J. V., 100, 101, 102, 103, 104, 107, 108, 110, 133 Weinstock, M., 456, 465, 712 Weintraub, R. M., 1002 Weis, S., 739, 741, 982 Weis, S. T., 979 Weisel, J. W., 838 Weisman, A. D., 761 Weisman, M. H., 193 Weisman, Z., 1053 Weiss, D., 695 Weiss, D. W., 532, 535, 536, 538 Weiss, G., 569 Weiss, J. M., 290, 483, 727, 743, 1099 Weiss, M., 923 Weiss, N. S., 242 Weiss, R. M., 306 Weiss, R. S., 784 Weiss, S., 687, 689, 691, 1065 Weiss, S. M., 479, 481 Weiss, S. T., 714, 1002 Weiss, T. W., 72 Weissbecker, I., 884
Weisse, C., 677 Weisse, C. S., 532, 537, 538, 676, 932 Weissenbach, J., 977 Weissenburger, J., 686 Weissleder, R., 882 Weissman, J., 518, 607, 608 Weissman, M. M., 681 Weissmann, C., 440 Weissmann, G., 55, 980 Weissmuller, T., 553 Weitzman, O., 624 Weitzman, O. B., 497, 1063 Weitzsch, C., 569, 570 Weizman, A., 184, 534, 536 Weizman, R., 515 Wekerle, H., 106, 359, 386 Wekstein, D. R., 363, 364, 421 Welbon, C. C., 1054 Welch, H. J., 109 Welch, M. J., 1059 Welch, W. J., 1024 Welin, L., 929 Welker, P., 106 Wellen, K., 817 Wellhausen, S. R., 1025 Wells, B. W., 258 Wells, H., 384, 440, 443 Wells, J., 222, 678 Wells, M., 771 Wells, V. E., 509, 622 Welniak, L. A., 174 Welsh, C. J., 1080, 1081, 1107, 1111, 1112, 1114, 1115, 1118 Welsh, C. J. R., 1107, 1109, 1110, 1114, 1115, 1116, 1118 Welsh, R. M., 1082 Welsh, T. H., 1080, 1081, 1107, 1112, 1114, 1115, 1116, 1118 Welsh, T. H., Jr., 1080, 1107, 1111, 1118 Welsh, T. W., 1110 Welsh-Bohmer, K. A., 383 Welte, C., 166 Welte, M., 110 Weltman, J. K., 811 Welton, D., 814 Welz, T., 1055 Wen, H. J., 799 Wen, T. C., 350 Wen, Y., 359 Wendlandt, S., 323 Wendling, U., 1015 Wendt, T., 72, 965 Wener, M. H., 668 Wenk, E., 745 Wenk, G., 439, 440 Wenk, G. L., 386 Wenk, S., 1015, 1023 Wenner, M., 99, 785 Wenston, J., 579
Wenting, M. J., 198 Wenzel, A., 830 Wenzel, S. E., 804 Wenzyl, H. H., 469 Werb, Z., 879, 881, 882 Werden, K., 542 Werfel, T., 984, 985 Werle, E., 422 Wermke, C., 1080 Wernecke, K. D., 553, 554 Werner, A., 402 Werner, H., 181 Werner, S., 826, 840, 841, 843, 845 Wershil, B. K., 109, 110, 112, 116 Wertman, E., 364 Wery, J. P., 994 Wesch, J., 1061 Wesch, J. E., 1061 Wesemann, W., 599 Weshil, B. K., 133 Wesley, R. A., 146 Wesp, M., 727, 934 Wesslen, L., 662, 663, 668 Wessler, I., 89, 100, 105 West, G. B., 802 West, J. M., 827 West, K. M., 134, 140 West, M. J., 386 West, S. G., 362 Westcott, J. Y., 440 Westendorp, R. G., 362, 379 Westengard, J., 763, 764, 765 Westenhoefer, J., 715 Westerman, R. A., 110, 223 Westermann, J., 605 Westgate, C., 106 Westland, J. K., 978 Westman, M., 322 Weston, W. L., 826 Westphal, H., 420 Westphal, O., 380 Westwood, J. A., 47 Wether, N. C., 212 Wetherall, M., 708, 897 Wetmore, L., 288, 320 Wetstone, S. L., 769 Wettstein, P. J., 1109 Wetzel, H., 553 Wetzel, W., 350, 351, 356, 646 Weyerbrock, A., 592, 594 Weyhenmeyer, J. A., 292 Whalen, G., 735, 745 Whalen, M. M., 257 Whalley, L. J., 380 Whartenby, K. A., 148 Wharton, J., 690 Whatling, C., 882 Wheeler, A. P., 93 Wheeler, F. B., 105
1242 Wheeler, J., 690 Wheeler, J. G., 924, 926 Wheeler, R., 967 Wheeler, R. D., 148, 419 Wheeler, R. E., 913 Wheeler, R. W., 622 Whelan, A., 551 Whelchel, L. M., 430 Whetton, A., 635 Whincup, P., 958, 961 Whincup, P. H., 957 Whisler, R. L., 74 Whitacre, C., 695 Whitacre, C. C., 734, 735, 739, 744 Whitaker-Menezes, D., 113 White, A., 727, 728 White, A. R., 814 White, B., 554 White, C. L, 3rd, 361 White, D. W., 994 White, H., 969 White, I. R., 501, 505 White, J., 514, 598 White, J. L., 586 White, J. M., 408, 878 White, L., 361 White, M., 256 White, M. C., 1107 White, M. F., 176, 999 White, M. V., 131 White, P. D., 923 White, R. F., 417, 419 White, R. J., 851 White, R. M., 430, 1054 White, R. P., 830 White, R. P., Jr., 830 Whitehead, D. L., 968 Whitehead, L., 856 Whitehouse, W. G., 599 Whiteside, M., 294, 401 Whiteside, M. B., 321 Whiteside, T., 686, 786, 787, 792, 876, 878, 879, 1079 Whitfield, J. F., 735, 745 Whitham, M., 900, 1046 Whitley, R. J., 1077 Whitlock, B. K., 605 Whitmer, R. W., 714, 717 Whitmore, R. G., 417 Whitmore, S. E., 737 Whitney, J. D., 827 Whitson, P., 854 Whittaker, A., 362 Whittaker, J. A., 871 Whittall, T., 1015, 1016, 1023 Whittle, H., 1055 Whitty, C. J., 103 Whitworth, A., 569 Whorwood, C. B., 712
Author Index Wichers, M. C., 172, 277, 307 Wichmann, H. E., 977 Wick, G., 738, 739 Wick, M. M., 241 Wickman, M., 977 Wicks, I. P., 197 Wicks, S., 48 Widaman, K. F., 484 Wide, L., 197 Widner, B., 307, 522 Wiebe, J. S., 930 Wiechmann, K., 1100 Wieczorek, M., 290 Wiedemann, K., 48, 540, 589 Wiedenfeld, S., 677 Wiederman, M. W., 714 Wiedermann, C. J., 107, 108 Wiedmann, M., 184 Wiedswang, G., 212 Wiegers, G. J., 56, 112, 733, 735, 736, 745, 746 Wiegmann, K., 352, 1046 Wieland, F., 1024 Wieland, S., 735 Wiener, N., 632 Wientjes, C. J., 709 Wiertelak, E., 678 Wiertelak, E. P., 329, 397 Wierzba-Bobrowicz, T., 565 Wiesbrock, S. M., 995 Wiese, B., 646, 726 Wiese-Bjornstal, D. M., 770, 773 Wieseler, J. L., 514 Wieseler-Frank, J., 269, 275, 393, 399, 400–401, 402, 405, 406, 407, 408 Wieseler-Frank, J. L., 357, 408 Wiesmann, M., 565, 566 Wiesnet, M., 1015 Wiess, S. T., 623 Wiessner, C., 416, 434 Wiest, R., 224 Wietek, C., 274 Wiffen, P., 396 Wigdahl, B., 1057 Wiig, K. A., 342 Wiik, P., 599 Wiis, J., 70, 1057 Wijdenes, J., 213, 997 Wikby, A., 361 Wikkelso, C., 417, 420 Wiktorowicz, K., 515 Wilckens, T., 734, 745 Wilcock, G., 363, 364, 421 Wilcock, G. K., 365, 366, 421, 512, 790, 900, 901, 902, 907, 909, 911, 914, 915 Wilcockson, D., 272, 276, 361, 385, 386 Wilcockson, D. C., 434, 435, 440, 444 Wilcox, G. K., 1089 Wilcox, G. L., 408
Wilczak, N., 184 Wilder, R., 635 Wilder, R. L., 54, 55, 65, 67, 72, 73, 110, 116, 193, 196, 197, 200, 212, 222, 254, 605, 737, 739, 740, 741, 784, 855, 881, 980, 982, 983, 986, 1045 Wilder, R. S., 981 Wiley, C. A., 386 Wilhelm, M. C., 872 Wilhelm, S., 979 Wilhelmsen, L., 948, 957 Wilke, I., 568 Wilkins, R. T., 534, 535 Wilkinson, C. W., 297 Wilkinson, J. M., 815 Wilkinson, M. F., 323, 399 Wilkinson, R. G., 500 Wilkinson, S. M., 736, 737 Will, M. J., 301, 357 Willard, A., 771 Willard, L. B., 386 Willeit, J., 957 Willems, F., 135 Willemse, P. H., 519 Willemsen, G., 680, 694, 963 Willemson, G., 765 Willer, J. C., 160, 165 Willerford, D. M., 1059 Willette, R. N., 419 William, D. C., 768 Williams, A., 276, 440 Williams, A. E., 440 Williams, A. J., 137, 417 Williams, A. L., 272, 276, 361, 385, 386, 440, 444 Williams, C. A., 923 Williams, D. E., 715 Williams, D. R., 498, 499, 500, 851 Williams, H., 512, 803, 1079 Williams, H. C., 801 Williams, I., 1054 Williams, J., 543, 689, 1055 Williams, J. B., 1057, 1060, 1061 Williams, J. I., 873, 887 Williams, J. K., 483, 485, 929, 1065 Williams, J. M., 98, 1040 Williams, J. T., 161 Williams, L. T., 1043, 1044 Williams LK, O. D., 809 Williams, M., 901, 907 Williams, M. E., 47 Williams, M. R., 211 Williams, M. V., 1079 Williams, P., 716 Williams, R. B., 498, 694, 929, 930, 935, 949 Williams, R. G., 117 Williams, R. M., 109 Williams, R. M., Jr., 782
Author Index Williams, R. O., 143, 193 Williams, S., 869, 870 Williams, T. J., 113, 738 Williams, T. M., 53 Williams, W. V., 1056 Williamson, B., 995 Williamson, D., 790 Williamson, D. E., 485 Williamson, D. F., 713 Williamson, G. M., 499, 872, 887 Williamson, K., 53, 998 Williamson, R., 977 Williger, D., 684 Willimann, K., 435 Willingham, J. K., 771 Willis, P. W., 927 Willis, T. A., 234 Willner, P., 305 Willoughby, R., 514, 538, 598, 607 Wills, T., 872 Wills, T. A., 785, 787 Wills-Karp, M., 817 Willson, T. A., 995 Willson, T. M., 997 Wilmanns, W., 1015 Wilsenack, K., 1046 Wilson, A. C., 957 Wilson, A. G., 366 Wilson, A. K., 114 Wilson, B., 523 Wilson, C. B., 69, 71, 431, 1039, 1040 Wilson, C. D., 283, 297 Wilson, C. J., 186, 380 Wilson, D., 639, 640 Wilson, D. H., 811 Wilson, E., 976 Wilson, E. M., 182 Wilson, G., 534, 539 Wilson, G. V., 979 Wilson, J. A., 1002 Wilson, J. M., 842 Wilson, J. W., 55 Wilson, M. E., 483, 811 Wilson, P. W., 361, 957 Wilson, S., 70, 540 Wilson, S. N., 534, 537 Wilterdink, J. L., 148 Wiltrout, R., 878 Wiltrout, R. H., 255, 257 Winand, J., 133 Winblad, B., 274, 306, 418 Winchester, C. C., 1015, 1023 Winchurch, R. A., 841 Windt, M. R., 1002 Winfield, H., 710 Winfrey, C. J., 566 Wing, R. R., 717 Wingard, D. L., 579, 586, 769, 771 Wingender, E., 53
Winger, E., 1059 Wingfield, J., 745 Wingfield, J. C., 480, 491, 1036, 1046 Winkel, K., 584 Winkelstein, W., Jr., 1061 Winkleby, M. A., 500, 931 Winkler, C., 1036, 1053 Winkler, H., 55, 107 Winkley, K., 716 Winocur, G., 345, 346, 347, 348, 349 Winokur, A., 606 Winokur, G., 510 Winship, D., 551 Winter, C. D., 417 Winter, J., 165 Winter, J. B., 596 Winther, C., 103 Wirleitner, B., 1036 Wirth, S., 73, 420, 639 Wirtschafter, J. D., 165 Wirtz, S., 144 Wise, B. C., 421 Wise, R. A., 304 Wisely, G. B., 53 Wiskott, L., 340, 359 Wisnieski, B. J., 399 Wisniewski, H. M., 361 Wisniewski, T. L., 1055 Wison, M. E., 468 Wisse, B. E., 297 Wissink, S., 55, 741 Wistar, R., 738 Witek-Janusek, L., 77, 1061 Witkin, S., 711 Witt, I., 361 Witte, T., 726 Wittek, A. E., 861 Wittersheim, G., 603 Wittkower, E. D., 733 Wittkowski, A., 977 Wjst, M., 814 Wloka, K., 1056 Wobbes, T., 790 Wodarz, N., 981 Woerner, M., 683 Wofford, J. L., 385 Wogensen, L., 364 Woiciechowsky, C., 254 Woitsch, B., 816 Wojakowski, W., 926 Wojciechowski, F. L., 682 Wojno, W. C., 791 Wojta, J., 72 Wolburg, H., 148 Wolever, M. E., 763, 764 Wolf, C., 872 Wolf, G., 339, 408, 556 Wolf, H., 690 Wolf, J., 72, 965
1243 Wolf, J. M., 302, 540, 542, 815 Wolf, M. E., 534, 535, 538 Wolf, S. E., 603 Wolf, T., 76 Wolfe, F., 923 Wolff, F. H., 1055 Wolff, K., 785 Wolff, L. J., 733 Wolff, M. H., 861 Wolff, S. M., 273, 380, 584, 738 Wolfgang, M. J., 994 Wolford, R. G., 51 Wolfson, C., 792, 1108 Wolitzky, A. G., 56 Wolke, D., 713 Wollenberg, A., 978 Wollenhaupt, J., 198 Wollman, E., 432 Wollman, E. E., 385 Wollmann, R., 1110 Wolny, A. C., 734, 735 Wolters, P., 1060 Wolvers, D., 101, 109 Wolvers, D. A., 732 Wong A., 1045 Wong, B., 747 Wong, C. M., 533, 535, 536, 537 Wong, H., 103 Wong, J. K., 1054 Wong, J. L., 136 Wong, K. Y., 174 Wong, L., 997 Wong, M., 1054 Wong, M. L., 292, 294, 299, 594, 599, 884, 1061 Wong, N. C., 51 Wong, W., 419 Wong, W. L., 224 Wong, Y. K., 501, 958 Wong-Staal, F., 236, 736 Wonnacott, K. M., 1080, 1087 Woo, P., 365 Wood, B., 668 Wood, G., 637 Wood, I. S., 996 Wood, J., 571 Wood, J. D., 105 Wood, J. N., 161 Wood, J. V., 790 Wood, P. G., 555, 725, 732 Wood, P. J., 679, 712 Wood, R. F., 1016 Woodley, D. T., 845 Woods, B. T., 564 Woods, R. J., 101 Woods, S., 713 Woods, S. C., 293, 479, 480, 481 Woods, T. E., 1055, 1056, 1060, 1063 Woodward, C. A., 717
1244 Woodward, M., 957 Wooley, S. T., 437 Woolf, C. J., 160, 165, 395, 396, 398, 405, 407 Woolley, C. S., 745 Woolley, T. W., 725, 732 Wordsworth, B. P., 198 Worlein, J. M., 476 Worley, P. F., 322, 358 Worsaae, H., 364 Worthman, C. M., 858 Wortman, C., 1060 Wortman, C. B., 785 Wotjak, C. T., 479, 481 Wouters, E. F., 182 Wouters, S., 132 Wrange, O., 51 Wright, A. P., 49–50, 50 Wright, B. H., 1016 Wright, C. E., 305, 935 Wright, D. H., 856 Wright, E. T., 987 Wright, G. J., 272 Wright, R., 456, 461, 469 Wright, R. J., 801, 807, 812, 813, 814, 816 Wright, S. C., 276 Wright, S. D., 747 Wright-Hardesty, K. J., 385 Wrona, D., 555 Wu, B. J., 1014 Wu, C., 292, 364, 812, 1014 Wu, C. H., 402 Wu, C. L., 167 Wu, C. Y., 56, 732 Wu, D., 184, 287 Wu, F., 828, 829, 830 Wu, G. Y., 570, 571 Wu, H., 501, 521, 564 Wu, H. Y., 342 Wu, J., 738, 998, 999 Wu, K., 295, 303, 957 Wu, P., 167, 998 Wu, P. C., 167 Wu, S., 882 Wu, S. L., 364, 365, 366 Wu, W., 241, 873, 882 Wu, X., 1001, 1002 Wu, Y., 180 Wu, Y. P., 811 Wu, Z., 783, 787 Wu, Z. X., 110 Wucherpfennig, A. L., 223 Wucherpfennig, K. W., 149 Wulffraat, N., 65, 72 Wulsin, L. R., 509, 622, 931 Wurtman, R. J., 307 Wust, S., 814 Wustefeld, T., 435
Author Index Wustmans, A., 739, 741, 981 Wustner, J., 855 Wyatt, D. B., 533, 536, 537 Wyatt, G. E., 1063, 1065 Wyatt, L. E., 1065 Wyatt, R. J., 277, 459, 570 Wybran, J., 556 Wylie, A. H., 741 Wyllie, D. H., 1025 Wynings, C., 532, 535, 537, 538, 539, 541, 676 Wynn, T. A., 85 Wynshaw-Boris, A., 1000 Wysocka, A., 570, 571 Wysocka, M., 800 Wyss-Coray, T., 420, 439, 440 Xia, M., 109 Xian, C. J., 400 Xiang, X., 662 Xiao, B. G., 416, 417 Xiao, W. H., 399 Xiao, X., 1015 Xie, B. Y., 571 Xie, Q. W., 137, 1025 Xie, Y., 1015 Xie, Y. F., 654 Xie, Z., 384 Xin, Z., 135, 140 Xu, A., 997, 1001 Xu, B., 297, 470, 1047 Xu, B. Y., 65 Xu, D., 115 Xu, G. Y., 167 Xu, H., 348, 361, 380 Xu, H. M., 570 Xu, K., 571 Xu, L., 137, 419, 1015 Xu, Q., 957, 959 Xu, R.-B., 738 Xu, T., 479, 480, 481 Xu, W. X., 49 Xu, X., 53 Xu, Y., 167 Xue, Q., 400 Yablonsky, F., 420 Yabuki, Y., 862 Yabuta, Y., 863 Yabuuchi, K., 87 Yada, T., 605 Yadav, A., 186 Yaegashi, M., 1002 Yaffe, K., 361, 511, 962 Yagello, M., 149 Yager, J. G., 594 Yagi, G., 357, 571 Yagita, H., 47, 252 Yagita, M., 252
Yahata, T., 481 Yakar, I., 257 Yakar, S., 180 Yaksh, T. L., 109 Yakushiji, F., 198 Yalom, I., 687 Yamada, H., 197 Yamada, K., 339, 352, 353, 354 Yamada, Y., 831, 959, 998 Yamagata, K., 294, 322 Yamagishi, S., 998 Yamaguchi, A., 254 Yamaguchi, E., 814, 816 Yamaguchi, H., 1000 Yamaguchi, K., 252, 253, 321, 344 Yamaguchi, T., 301, 344, 347, 359 Yamakawa, K., 322 Yamakura, T., 395, 396 Yamamori, H., 254 Yamamoto, G., 357, 738, 933 Yamamoto, H., 99, 330, 1058 Yamamoto, J., 1000, 1001 Yamamoto, K., 678, 1003 Yamamoto, K. R., 49, 53 Yamamoto, M., 144, 736 Yamamoto, N., 1057, 1058 Yamamoto, S., 859 Yamamoto, T., 344, 347, 352, 354, 359, 522 Yamamura, H. I., 101 Yamamura, K., 1001 Yamamura, Y., 116 Yaman, H., 1002 Yamasa, K., 523 Yamasaki, A., 326 Yamasaki, D., 197 Yamasaki, Y., 418 Yamashita, K., 738 Yamashita, M., 342 Yamashita, S., 997, 1000, 1001 Yamashita, T., 359, 386, 417 Yamashita, Y., 323, 326 Yamatodani, A., 331 Yamauchi, H., 810 Yamauchi, M., 554 Yamauchi, T., 828, 999, 1001 Yamauchi, Y., 73 Yamazaki, F., 73 Yamazaki, M., 53 Yamazaki, T., 522 Yamazaki, T. G., 710 Yamin, A., 419 Yamura, T., 882 Yan, H., 1000 Yan, H. Q., 417 Yan, S. D., 998 Yan, Z., 104, 107, 114 Yanai, K., 1026 Yanai, M., 647
Author Index Yanaihara, N., 132 Yanaihara, T., 211 Yancopoulos, G. D., 181, 182, 360 Yang, A. Y., 567 Yang, C., 638, 641 Yang, C. C., 969 Yang, C. H., 167, 717 Yang, E., 352, 694, 882, 883, 884, 977, 988 Yang, E. V., 799, 1046, 1079 Yang, G. Y., 418, 419 Yang, H., 105, 106, 605, 667, 772, 997 Yang, J., 133, 174, 287, 644, 645, 653 Yang, J. D., 571 Yang, J. Y., 1055, 1059 Yang, L., 977 Yang, L. C., 167 Yang, M., 253, 261 Yang, M. S., 571 Yang, N., 53 Yang, P. C., 1024 Yang, Q., 1000 Yang, R. K., 537, 539, 541 Yang, S., 998 Yang, X. M., 994 Yang, Y., 565 Yang, Y. C., 997 Yang, Y. X., 436 Yang, Z. W., 571, 572 Yaniv, M., 53 Yano, K., 957 Yano, Y., 960 Yanovski, J. A., 1055 Yao, B. S. J., 570 Yao, C., 417 Yao, J., 298, 302 Yao, J. H., 384 Yao, K. T., 883 Yao, W., 184 Yao, X. J., 1056 Yarboro, C. H., 196, 197 Yarchoan, R., 855 Yarnell, J. W., 957 Yaron, I., 515 Yaron, M., 436, 515 Yarwood, H., 738 Yasko, J., 792 Yassine-Diab, B., 110, 200 Yassouridis, A., 166, 540 Yasuda, K., 291, 321, 432 Yasuda, S., 322 Yasui, H., 322 Yasui, Y., 668 Yasunaga, K., 87 Yates, S. F., 736 Yatsiv, I., 418, 419 Yatsugi, S., 344, 352 Yauch, R. L., 1110 Yazaki, T., 859
Yazdanbakhsh, M., 470 Ye, F., 646 Ye, J., 999 Ye, P., 173, 184 Ye, S., 882 Ye, S. M., 348, 382, 383, 384 Ye, W., 418 Yeager, M. P., 254, 257 Yeaman, S. J., 1000 Yee, J. L., 908 Yegorov, A. D., 853 Yeh, J. L., 957 Yeh, P., 1057 Yeh, P. E., 1079 Yehuda, R., 485, 533, 535, 536, 537, 539, 540, 541 Yehuda, S., 341, 625, 763, 765 Yellon, S. M., 732 Yenari, M. A., 1015 Yerra, L., 1023 Yesilova, Z., 1002 Yeung, A. C., 934 Yezierski, R. P., 408 Yi, Y., 1059 Yiannoutsos, C. T., 166 Yien, H. W., 93 Yilmaz, E., 999 Yilmaz, N., 570, 571 Yin, H., 143 Yin, K. C., 181 Yin, L., 416, 417 Yin, Q., 149 Yin, S., 997 Yin, T., 997 Yin, Y., 101, 181 Yin, Z., 76 Ying, S., 55, 502 Yirmiya, R., 223, 235, 238, 255, 257, 259, 269, 284, 294, 297, 300, 302, 305, 337, 339, 345, 346, 347, 348, 349, 352, 355, 357, 358, 361, 362, 363, 366, 408, 504, 514, 515, 518, 519, 555, 556, 609, 622, 646, 726, 734, 745, 901, 904 Ylikorkala, F. O., 461 Yndestad, A., 1058 Yocum, D., 199, 788 Yocum, D. C., 199, 509, 511, 512 Yoder, C. P., 1055 Yogev, R., 1056 Yokoi, H., 937 Yokosuka, O., 237 Yokota, T., 199, 997 Yokoya, K., 923 Yokoyama, H., 1026 Yokoyama, M. M., 71, 97 Yokozaki, H., 110 Yolk, B., 361 Yolken, R. H., 565, 566, 567
1245 Yoneda, H., 330 Yong, V. W., 148 Yoo, C. G., 1015 Yoo, P., 65 Yoon, B. H., 458 Yoon, K. J., 662 Yoon, S. H., 571 Yoon, S. J., 553 Yorek, M. A., 998 York, D., 999 Yorogi, A., 523 Yorty, J. L., 461, 1080, 1084, 1087 Yoshida, A., 101, 115 Yoshida, K., 323, 326, 330, 522, 523 Yoshida, M., 344, 347, 360, 623 Yoshida, N., 326 Yoshida, Y., 330 Yoshie, O., 142 Yoshie, T., 862 Yoshii, T., 842 Yoshikawa, J., 1001 Yoshikawa, T., 113 Yoshimoto, M., 522, 523 Yoshimura, A., 177 Yoshimura, H., 350 Yoshimura, M., 1024 Yoshimura, N., 360 Yoshimura, T., 73 Yoshimura, Y., 223 Yoshinaga, S., 678 Yoshino, S., 342, 763, 765, 766 Yoshiyama, M., 1001 Yoshizaki, K., 144 Yoshizumi, M., 960 Youdim, M. B., 147 Youn, J., 76 Young, C. R., 1080, 1107, 1110, 1112, 1115, 1116 Young, E. A., 539, 541 Young, E .J., 1088 Young, H. A., 53 Young, I. S., 1055 Young, J. B., 1043 Young, L. S., 856 Young, M. R., 348, 382, 594 Young, P. R., 417 Young, S. N., 307 Young, S. R., 829 Young, W. S., 739, 982 Young, W. S. 3rd, 241 Young, W. S., 3rd, 54, 197 Youngblood, M. E., 695 Youngstrom, E. A., 712 Younis, F. M., 419 Younson, J., 1015, 1016, 1023 Younson, J. S., 1023 Yount, S., 691 Yssel, H., 1058 Ytterberg, S. R., 609
1246 Yu, D. T. Y., 729 Yu, H. S., 847 Yu, L., 571 Yu, M., 86, 88, 89, 105, 106, 143, 1056 Yu, M. R., 999 Yu, P., 1065 Yu, P. H., 241 Yu, W. K., 257 Yuan, H., 638, 642 Yuan, H. P., 68 Yuan, J., 419, 1056 Yuan, J. Q., 995 Yuan, M., 996, 1000 Yucha, C. B., 93 Yudkin, J. S., 365, 514, 542, 956 Yudko, E., 479, 480 Yudt, M. R., 48 Yue, H., 358 Yuill, E. A., 274, 300 Yu-Lee, L. Y., 603 Yumiba, T., 830 Yun Ma, L., 479, 480, 481 Yunger, L. M., 603 Yusuf, S., 947, 949 Zaagsma, J., 66 Zabel, P., 592, 594 Zabolotny, J. M., 1000 Zaccheo, O., 173, 174 Zachariae, C., 625, 763 Zachariae, R., 625, 763, 766 Zacharieae, R., 684 Zacharioudaki, V., 997 Zachary, I., 963, 965 Zachary, J. F., 384 Zachman, K., 594, 599 Zack, J., 678 Zack, J. A., 74, 237, 261, 497, 624, 1057, 1058, 1063, 1064, 1065 Zaenker, K. S., 261 Zagans, L. S., 713 Zagliani, A., 570 Zahger, D., 928 Zaho, J., 571 Zahringer, U., 999 Zaidel, A., 256 Zaimovic, A., 772, 784, 792 Zakaria, D., 854 Zakowski, S. G., 874, 934 Zalc, B., 273 Zalcman, S., 284, 294, 304, 743 Zalcman, S. S., 284, 304 Zaloudek, C. J., 223 Zaman, M., 197 Zamorano, J., 56, 998 Zamorano-Rojas, H., 645 Zampieri, S., 210, 213 Zanardini, R., 571 Zandi, P. P., 383
Author Index Zandonatti, M., 307 Zane, C. J., 556 Zang, E. A., 768 Zanker, B., 55 Zanker, K. S., 240 Zannino, L. G., 814 Zannino, L.-G., 77, 1046 Zanollo, A., 117 Zanussi, C., 1055 Zapata, V., 407, 408 Zappacosta, S., 1003 Zaremba, J., 420, 421 Zarember, K. A., 53 Zarifan, E., 570 Zarius, S., 741 Zarkin, G. A., 717 Zaror-Behrens, G., 1022 Zarrelli, M. M., 420 Zatz, M. M., 727, 728 Zaugg, L., 514, 598, 599 Zauli, G., 1058 Zautra, A. J., 198, 199, 509, 511, 512, 733, 761, 784, 788 Zavala, F., 136, 147, 148, 292 Zavala, S. K., 717 Zavaleta, N., 466, 469 Zavitsanos, X., 933 Zech, E., 791, 792 Zeegers, M. P., 233 Zeegers, M. P. A., 870 Zegans, L. S., 1088 Zeh, J., 1086 Zeidel, A., 256, 710 Zeigler, M. G., 855 Zeiher, A. M., 957, 958 Zeitlenok, N., 643 Zeitz, M., 1002 Zelazowska, E., 197 Zelenka, M., 399 Zeller, J. M., 1056 Zeman, K., 605 Zemni, R., 362 Zeng, X. T., 115 Zenker, W., 400 Zephir, H., 148 Zerbe, G., 860, 1079 Zerhouni, Elias, 705 Zerwekh, J. E., 851 Zetterman, R. K., 116 Zetterstorm, M., 345 Zevon, M., 869 Zevon, M. A., 233 Zeymer, U., 928 Zezula, J., 239 Zgraggen, L., 963 Zhai, Q. H., 417 Zhai, Y., 1022 Zhan, G. X., 1059 Zhang, B., 882
Zhang, D. H., 997 Zhang, F., 143, 571, 994 Zhang, F. M., 567 Zhang, H., 569 Zhang, J., 181, 275, 305, 325, 328, 330, 438, 440 Zhang, J. M., 400 Zhang, J. W., 364 Zhang, L., 71, 881 Zhang, M., 85, 86, 88, 89, 105, 605, 772, 997 Zhang, N., 400 Zhang, P., 136, 552, 554 Zhang, P. Y., 570, 571 Zhang, Q., 161, 162, 164, 165, 166, 554, 603 Zhang, S., 89, 1002 Zhang, W., 523 Zhang, W. Y., 998 Zhang, X., 149 Zhang, X. Y., 570, 571, 994 Zhang, Y., 89, 101, 107, 332, 358, 365, 420, 994, 995, 1056 Zhang, Y. H., 321, 322, 323, 327 Zhang, Y. P., 845 Zhang, Y.-F., 738 Zhang, Y.-H., 322, 328, 330, 332 Zhang, Z. J., 1015 Zhang, Z. Q., 1054 Zhang, Z. X., 364 Zhao, B., 998 Zhao, H., 1015, 1059 Zhao, L., 300 Zhao, R. Y., 1056 Zhao, X., 565 Zhao, X. Y., 239 Zhao, X. Z., 571 Zhao, Y., 1056 Zhao, Y. J., 419 Zhao, Z., 620 Zhao, Z. Q., 408 Zheng, B., 1055, 1056, 1060 Zheng, J., 1054 Zheng, Q., 259, 737, 745 Zheng, W. F., 679 Zheng, W. H., 176, 184 Zhengbin, L., 880 Zhong, H., 137 Zhong, J., 184 Zhong, J. H., 400 Zhou, D., 238, 301, 637, 710, 733, 743, 1115 Zhou, D. F., 570, 571 Zhou, F. L., 875 Zhou, G., 880 Zhou, J., 174 Zhou, J. H., 172, 177, 180, 181, 184, 422 Zhou, X., 830, 958
Author Index Zhou, X. F., 400 Zhou, Y. F., 959 Zhu, G., 108, 139, 1115 Zhu, G. F., 108 Zhu, H., 998 Zhu, J., 501, 927, 934, 959 Zhu, L., 143 Zhu, R., 98 Zhu, S., 306, 565, 814 Zhu, W., 568 Ziccone, S., 101 Zich, J., 1060 Ziche, M., 224 Zick, Y., 999 Zidel, Z., 1026 Zieg, G., 801, 855 Ziegler, B. L., 1058 Ziegler, M., 510, 518, 603, 606, 607 Ziegler, M. G., 70, 729, 934 Ziegler, T. R., 1002 Ziegter, G., 219 Zieher, L. M., 77 Zielinski, C., 690 Zielinski, M., 409 Ziemiecki, A., 998 Zietz, B., 226 Zijlstra, F. J., 293 Zijlstra, J., 72 Zill, P., 365 Zimmer, D., 490 Zimmer, H. G., 542 Zimmer, J., 386, 416, 417 Zimmer, R., 363, 364, 365 Zimmer, S., 254 Zimmerman, E., 422 Zimmerman, E. A., 930, 935
Zimmerman, E. H., 929, 930, 935 Zimmerman, K. M., 1081, 1087 Zimmermann, E. M., 105 Zimmermann, F., 885 Zimmermann, R. R., 479 Zimmermann, S., 89 Zimmers, T. A., 995 Zinder, O., 874, 880 Zingarelli, B., 295, 997 Zink, M. C., 273, 490 Zinkernagel, R. M., 360 Zipp, F., 307 Zisook, S., 792 Ziyadeh, F., 998, 999 Zlokovic, B. V., 419 Zlotnik, A., 136, 142 Zola, M., 686 Zola-Morgan, S., 340 Zöllner, C., 161, 166 Zollo, O., 54 Zona, C., 184 Zorilla, E. P., 569, 874 Zorn, M., 422 Zorrilla, E. P., 509, 510, 511, 553, 932, 1079 Zorzet, S., 238 Zou, H., 645–46 Zoumakis, E., 533, 536, 543, 589, 591, 599 Zoumakis, M., 606 Zoumpourlis, V., 1056 Zourlas, P. A., 257 Zsuang, M. T., 566 Zubaid, M., 947, 949 Zubek, J. M., 788 Zubiaga, A. M., 73
1247 Zuccaro, P., 557 Zucconi, M., 586 Zucker, J. D., 993 Zucker, N., 716 Zuckerman, J. D., 830, 831 Zuckerman, M., 686, 687 Zuckerman, S., 476 Zuckerman, S. H., 301, 542, 738 Zuena, A. R., 352, 359 Zugel, U., 1015 Zuk, M., 828 Zuker, M., 1022 Zukervar, P., 69 Zunarelli, P., 549, 551 Zunz, M., 484, 488 Zuo, X., 1015 Zuodar, G., 998 Zupancic, M., 1054 zur Hausen, H., 236 Zurakowski, D., 1002 Zurawski, S. M., 272 Zuriqat, M., 1002 Zuschratter, W., 350, 351, 356, 646 ZuWallack, R. L., 771 Zvartau, M., 437 Zvirbliene, A., 196 Zwart, S. R., 851 Zwartkruis, F. J., 239 Zweig, L., 534, 535 Zweit, J., 845 Zwijnenburg, P. J., 438 Zwilling, B., 254, 695, 733 Zwilling, B. S., 65, 734 Zwinderman, A. H., 199 Zyanski, S. J., 789 Zyzanski, S., 1088
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Subject Index
A AA. See Allergic asthma Accumulation theory, CDIDs and, 220 Acetylcholine (ACh), 97, 100, 105, 112, 809, 965 as neurotransmitter, 194 sleep and, 583 Acetylcholinesterase (AChE), 22 ACh. See Acetylcholine AChE. See Acetylcholinesterase Acquired immune deficiency syndrome (AIDS), 275, 624, 675, 790. See also Human immunodeficiency virus ART and, 1065 behavioral interventions and, 688–689 epidemic of, 1065 HIV and, 1053, 1054–1055 sleep and, 586 vaccine for, 1065 ACS. See Acute coronary syndrome ACTH. See Adrenocorticotrophic hormone Activator protein-1 (AP-1), 300 Active avoidance, 341–342 Acupuncture, 815 Acute coronary syndrome (ACS), 945 adiponectin and, 1001 atherosclerosis and, 954–955 depression and, 949, 968–969 IL-1 and, 956 IL-10 and, 957 leukocytes and, 968 morbidity and, 968–969 platelets and, 968 unpredictability of, 947 Acute phase proteins (APPs), 435 CAD and, 926 Acute phase response (APR), 1025 Acyclovir, 1089
AD. See Alzheimer’s disease; Atopic dermatitis ADCC. See Antibody-dependent cellular cytotoxic Adhesion, in tumor cells, 239 Adhesion molecules. See also Intercellular adhesion molecules CAD and, 926–927 Adiponectin, 997 ACS and, 1001 MI and, 1001 obesity and, 1000 Adipose tissue, 918 brown, 993–994 eHSP in, 1020–1021 HSP in, 1020–1021 IL-1 and, 994, 996 IL-4 and, 997–998 IL-6 and, 994, 995–996 macrophages and, 994 obesity and, 993–994 PAI and, 994 TNF and, 994, 995 VEGF and, 994 white, 993–994 Adrenal gland, 727 Adrenal medulla (AM), 983 Adrenalectomy (ADX), 195, 300–301 Cushing’s disease and, 197 LPS and, 301 Adrenaline, 100 Adrenocorticotrophic hormone (ACTH), 3, 23, 48, 54, 97, 195, 328, 357, 521, 729, 843, 980 aggression and, 481 CRF and, 826 eHSP and, 1019 GCs and, 933 HSP and, 1014 IL-1 and, 933 infant immunity and, 463
1249
sleep and, 589, 601 stress and, 196 TSST and, 982 vagus nerve and, 87 β-adrenogenic receptors, 1041–1045 Advanced glycation end product (AGE), 998 Adventitia, 950 ADX. See Adrenalectomy AED. See Androstenediol; Antagonist androstenediol Affective disorders, 620 Affective traits, 620 AFP. See Alpha-fetoprotein AGE. See Advanced glycation end product Aggression, 476. See also Anger; Dominance ACTH and, 481 competitive, 477 parental, 477 protective, 477 Aging alcohol and, 552 cancer and, 887–888 cognition and, 269 deterioration and, 379–380 free radicals and, 383 immune senescence and, 662 neuroinflammation and, 382–384 RA and, 219 sleep and, 606–607 wound healing and, 831–832 α7 agonists, 90–92 AICD. See Antigen-induced cell death AIDS. See Acquired immune deficiency syndrome Alcohol, 452, 499, 550 African Americans and, 513, 552 aging and, 552 cancer and, 554–555
1250 Alcohol (continued) childhood development and, 713 cytokines and, 608 depression and, 516, 517, 553 gender and, 552, 554 HBC and, 554 HIV and, 554 immunity and, 549, 552 lymphocytes and, 550 maternal, 456 NK cells and, 517, 551 PMN and, 52 sleep and, 607–609 Alcoholic hepatitis, 549, 554 Alcoholic patients without liver disease (AWLDs), 550–551, 552 Aldosterone, 18 Allergic asthma (AA), 981 Allergic rhinitis (AR), 801–802, 803– 804, 805–806 asthma and, 813 corticosteroids for, 806 sleep and, 805 stress and, 812–813 tobacco smoke and, 805 URTI and, 806 Allergies. See also Asthma; Atopic dermatitis; Hay fever anxiety and, 815 atopic dermatitis and, 977 depression and, 714, 812 to food, 801–803 genetics and, 807–808 history of, 801–802 infants and, 456 inflammation and, 810 to insect stings, 801–802 prevalence of, 799–800 at risk for, 816 stress and, 812 therapies for, 806–807 Allodynia, 273 Allostasis, 1036 Allostatic load, 491, 1036 Alpha-fetoprotein (AFP), 458 Alprazolam, 514 ALS. See Amyotrophic lateral sclerosis Alzheimer’s disease (AD), 147, 185– 186, 275, 276, 382, 386, 421, 430, 439 caregivers for, 827 cytokines and, 270 marriage and, 789–790 polymorphisms and, 364 AM. See Adrenal medulla Amphetamines, 555 Amphibians, 12–20 Amygdala, 88, 112
Subject Index Amyotrophic lateral sclerosis (ALS), 444 Anabolic steroids, 557 Anakinra, 524 Analgesics, 256 Anaphylactic response, 646–649 Anaphylaxis, 802 Androgen, 207 HIV and, 1059 wound healing and, 828 Androstenediol (AED), 1102 Anemia, 466 Anesthesia, 691, 880 immunity and, 692 stress and, 729 Anesthetics, 256 Anger, 921 CAD and, 929 cancer and, 624 CHD and, 623, 949 coronary disease and, 933 heart disease and, 714 HSV and, 1078 immunity and, 623–624 management of, 686 as risk factor, 917–918 vaccination and, 907 Angina, symptoms of, 922 Angina pectoris, 945 Angiogenesis, 881 for cancer progression, 42 IL-6 and, 882 MMPs and, 882–883 regulation of, 881–882 Angiopeptin, 937 Animal dander, 803 Anorexia, 87, 305 ANS. See Autonomic nervous system Antagonist androstenediol (AED), 1087 Antibodies, vs. neurotropic viruses, 566–567 Antibody titer index (ATI), 861 Antibody-dependent cellular cytotoxic (ADCC), 538, 730 HSV and, 1083 Antidepressants, 815 Antigen-induced cell death (AICD), 141 Antigen-presenting cells (APCs), 137, 149, 217, 252, 463, 803 CDIDs and, 226 Antihistamines, 806–807 Antioxidants, 303, 668 exercise and, 669–670 Anti-retroviral therapies (ART), 1055, 1057 AIDS and, 1065
Anxiety, 761 allergies and, 815 asthma, 815 and CHD and, 949 cytokines and, 304 fetal development and, 712 immunity and, 77, 622–623 stress and, 966 vaccination and, 907 AP-1. See Activator protein-1 APCs. See Antigen-presenting cells Apollo Program, 851 Apoptosis, 179 cytokines and, 275 Applied kinesiology, 815 APPs. See Acute phase proteins APR. See Acute phase response AR. See Allergic rhinitis ARDs. See Autoimmune rheumatic diseases Arginine vasopressin (AVP), 112, 980 Arrhythmia, 933, 945–946 ART. See Anti-retroviral therapies Arteries, structure of, 950–951 Aspirin, 320, 937, 958 Assertiveness training, 686 Association, 632, 633 Asthma, 93, 801–802, 804–805. See also Allergic asthma anxiety and, 815 AR and, 813 biofeedback and, 814 corticosteroids for, 806 cytokines and, 809 depression and, 714, 802 emotions and, 804 exertion, 816 and expressive writing and, 814 genetics and, 807–808 infants and, 456 influenza and, 806 massage and, 814 menses and, 806 NO and, 809 obesity and, 1001–1002 PA and, 771 placebo, 815 and prevalence of, 799–800 SES and, 501–502 stress and, 812–813 symptoms of, 806 Astroglia, schizophrenia and, 565 Astronauts. See Space flight Atheromata, 922 Atherosclerosis, 679–680, 918 ACS and, 954–955 HSP and, 957 infection and, 958–959 inflammation and, 921, 951
Subject Index initiation of, 952 progression of, 923 ATI. See Antibody titer index Atopic dermatitis (AD), 803, 805 eosinophil and, 984–985 heredity of, 977 HPA and, 975, 981 hypersensitivity and, 976 IHR and, 977 infancy and, 976 pruritus and, 976–977 as psychosomatic disorder, 976 SAM and, 975, 983–984 self-esteem and, 805 stress and, 813, 918, 975, 978–979 Atopic triad, 976, 982 Atopy, 976 Auditory Verbal Learning Test, 362 Autoimmune rheumatic diseases (ARDs), 213 Autoimmunity, vasoactive intestinal peptide and, 143 Autonomic motor system, 86 Autonomic nervous system (ANS) catecholamines and, 1058 HIV and, 1055, 1058 leukocytes and, 1057 Autophagy, cytokines and, 275 Avoidance, 341–342 AVP. See Arginine vasopressin AWLDs. See Alcoholic patients without liver disease Azelastine, 806–807
B B lymphocytes, 106–107 Baboon endogenous virus (BaEV), 567 Bacteria CAD and, 927–928 gram-negative, 146 in gut, 464 in space flight, 852 wound healing and, 828 Bacterial vaginosis (BV), 458 B-adrenergic antagonist, 257 BaEV. See Baboon endogenous virus BBB. See Blood brain barrier B-cells, 47, 66, 70–71, 74–75 proliferation of, 380 BDNF. See Brain-derived neurotrophic factor BDV. See Borna disease virus Bed nucleus of stria terminalis (BST), 329 Behavioral disengagement, 621 Behavioral immunoconditioning, 632, 633 Behavioral recuperation, 621
Behaviors disorders of, 451 maternal, 467 socially patterned, 450 Benzodiazepine, 815 Bereavement, 784–785 cancer and, 870 emotions and, 792 HIV and, 1060 immunity and, 792 Beta-blockers, 1064 Biofeedback, 93–94, 684 asthma and, 814 cancer and, 877 Birds, 22–25 Blood brain barrier (BBB), 93, 429 cytokines and, 194, 286, 520 MS and, 437, 1110 schizophrenia and, 568 TNF and, 338 Blood loss, 256 Blood transfusions, 880 BMI. See Body mass index; Ideal body mass Body mass index (BMI), 947 Bone marrow transplantation, 149 Borna disease virus (BDV), 567 Bovine spongiform encephalopathy (BSE), 440 Brain. See also Blood brain barrier cytokines and, 267, 268, 291, 415, 520–523 deterioration of, 379–380 development of, 274–275 immune system and, 273, 913 injury to, 269 macrophages in, 272 size of, 172–173 stress and, 710 trauma to, 147–148, 416, 420–421 Brain-derived neurotrophic factor (BDNF), 105–106 BSE. See Bovine spongiform encephalopathy BST. See Bed nucleus of stria terminalis Bullying, 713 Burkitt’s lymphoma, 883 BV. See Bacterial vaginosis
C CAD. See Coronary artery disease Caenorhabditiis elegans, 173 Caffeine, 557 Calcitonin gene-related peptide (CGRP), 22, 40, 99, 103, 104, 107, 114, 116, 131, 143, 810, 855 RA and, 200
1251 Calor, 288 CAM. See Complementary and alternative medicine CAMP. See Cyclic adenosine monophosphate CAMP responsive element-binding (CREB), 239 Campylobacter jejuni, 306 CAMs. See Cell adhesion molecules Cancer aging and, 887–888 alcohol and, 554–555 anger and, 624 benefits of, 876–877 bereavement and, 870 biofeedback and, 877 CBSM and, 687 cell proliferation and, 179–180 childhood development and, 713 circadian rhythms and, 884 coping and, 872 counseling and, 873 cytokines and, 179, 180 death of spouse and, 870 denial and, 872 depression and, 234, 304, 869, 870–871 emotions and, 871 exercise and, 877 fighting spirit and, 871 guided imagery and, 877 hopelessness and, 871–872 HPA and, 884 IGF and, 174, 180 initiation of, 235–237 medical treatment and, 690–692 meditation and, 877 metastasis of, 237–238 perceived marital support and, 786 pessimism and, 871–872 progression of, 233 psychosocial factors in, 233 QOL and, 692, 693 recurrence of, 692 relaxation therapy and, 877 sickness behavior and, 693–694 social ties and, 786, 872–873, 875–876 stress and, 233, 234–235, 734, 869 stress management and, 877 survival from, 871 tobacco and, 870 tumor progression in, 652–653 windows of opportunity with, 880 yoga and, 877 CanCOPE, 791 Canine distemper virus, 1108 Caprine arthritis-encephalitis virus, 1108
1252 Capsaicin, 102 Carbohydrates, 661 exercise and, 668–669 Carcinogenesis. See Cancer CARDIA. See Coronary Artery Risk Development in Young Adults Cardiovascular disease (CVD), 681 obesity and, 1000–1001 Caregivers, 902, 903, 906 Alzheimer’s disease and, 827 HSV and, 1083 IL-6 and, 962 immunity and, 910 influenza and, 1099 stress and, 910 vaccination and, 1111 CART. See Cocaine and amphetamineregulated transcript CAs. See Catecholamines Caste systems, 491 Castration, vasopressin and, 300 Catecholamines (CAs), 12, 22, 255, 603, 679, 727–728, 801, 983. See also Epinephrine; Norepinephrine amphetamines and, 555 ANS and, 1058 CAD and, 930 cocaine and, 555 depression and, 515 NKCC and, 678 PTSD and, 541 sleep and, 601–603 space flight and, 854 wound healing and, 826–827 CBG. See Corticosteroid-binding globulin; Corticosterone-binding globulin CBP. See CREB-binding protein CCK. See Cholecystokinin CCP. See Cyclic-citrullinated peptide CD. See Complementarity domain CDIDs. See Chronic disabling inflammatory diseases CE. See Cholesteryl esters Cell adhesion molecules (CAMs), 433, 680 Cell-mediated immunity (CMI), 252, 649, 734–735 PTSD and, 535 stress and, 731–732 surgery and, 257–258 tumors and, 253 Cell-mediated lympholysis (CML), 538 Central nervous system (CNS), 65 acute inflammation of, 433–435 alerts by, 100 cytokines and, 321 disease of, 270 HPA and, 980
Subject Index immune system and, 434–435 immunity and, 97 inflammation of, 433–435 MS and, 1107 plasticity in, 275 SAM and, 980 skin and, 975–976 Cerebrospinal fluid (CSF), 361, 465, 572 Cervical intraepithelial neoplasia (CIN), 682, 883 Cetirizine, 806 CFIDS. See Chronic fatigue and immune dysfunction syndrome CGRP. See Calcitonin gene-related peptide CH. See Corticosteroid hormones Challenge tests, 540 CHD. See Coronary heart disease Chemokines, 275 inflammation and, 271 leukocytes and, 963 wound healing and, 840–841 Chemotherapy, 691 immunity and, 691, 875 stress and, 875 Chest pain, 922 Chiropractic, 815 Cholecystokinin (CCK), neuropeptides and, 296 Cholesterol. See also High-density lipoprotein; Low-density lipoprotein CHD and, 946 fetal development and, 712 stress and, 967–968 Cholesteryl esters (CE), 1001 Cholinergic anti-inflammatory pathway, 88–89, 105, 932, 965 dysfunction of, 93 Cholinergic inflammatory reflex, 194 Chorine, V., 635–636 Choroid plexus, 292 IL-1 and, 382 Chronic, 225–226 Chronic disabling inflammatory diseases (CDIDs), 217 accumulation theory and, 220 antigen-presenting cells and, 226 evolution and, 219–220 homeostasis and, 220–222 Chronic fatigue and immune dysfunction syndrome (CFIDS), 586 etiology of, 911 marriage and, 788–789 Chronic idiopathic urticaria (CIU), 813
Chronic neurodegenerative disease, 270 Chronic obstructive pulmonary disease (COPD), 76 CIA. See Collagen-induced arthritis Ciliary neurotrophic factor (CNTF), 297 signaling and, 338 CIN. See Cervical intraepithelial neoplasia Circadian rhythms, 11 cancer and, 884 cortisol and, 197 immunity and, 591–595 leukocytes and, 744 sleep and, 581 Circumventricular organs (CVOs), 272, 290, 321 IL-1 and, 382 Cirrhosis, 549, 554 CIU. See Chronic idiopathic urticaria CJD. See Creutzfeldt-Jakob disease Class switch recombination (CSR), 74 Classical conditioning, 631, 653 Classical neuroendocrine mediators, 39 Clinical latency, of HIV, 1054 Clotting, 838 CMI. See Cell-mediated immunity CML. See Cell-mediated lympholysis CMV, 932 CNS. See Central nervous system CNTF. See Ciliary neurotrophic factor Cocaine, 555 Cocaine and amphetamine-regulated transcript (CART), 293 Cognition, aging and, 269 Cognitive behavioral stress management (CBSM), 686–687 HIV and, 1061 Cold restraint, 1035–1039 Colitis, 116 Collagen, 829, 844–845, 950 Collagen-induced arthritis (CIA), 143, 144 Complementarity domain (CD), 47 Complementary and alternative medicine (CAM), 688, 888 Con A. See Concanavalin A Concanavalin A (Con A), 481 Conditioned stimulus (CS), 631 kinetics of, 640 neutrality of, 639, 642 specificity of, 640 Conditioning protocol, 637–639, 642, 644, 648, 650 Congestive heart failure, 946 MI and, 946 Contentment, 761
Subject Index Contingencies, 632 Contraceptives, RA and, 199 COPD. See Chronic obstructive pulmonary disease Coping, 677, 686 vs. avoidance, 872 cancer and, 872 HIV and, 1060 by substance abuse, 913 Copper, 668 Coronary artery disease (CAD). See also Myocardial infarction anger and, 929 APPs and, 926 bacterial infection and, 927–928 catecholamines and, 930 CMV and, 927 cytokines and, 925–926 depression and, 929, 931 dyslipidemia and, 921 fatigue and, 931 fatty streaks with, 922 HSP and, 957 hypertension and, 921, 929, 930 immunity and, 923, 930 lipids and, 929 lymphocytes and, 925 macrophages with, 924–925 obesity and, 921, 929 risk factors in, 921, 924 SES and, 929 tobacco and, 921, 929 viral infection and, 927–928 Coronary Artery Risk Development in Young Adults (CARDIA), 962 Coronary heart disease (CHD). See also Atherosclerosis anger and, 623, 933, 949 anxiety and, 949 cholesterol and, 946 CRP and, 955–956 death and, 945 depression and, 949 diabetes and, 946 diet and, 947 genetics and, 950 hypertension and, 946 immunity and, 955–958 leukocytes and, 957 PNI and, 918 prevalence of, 945 risk factors for, 917–918, 936 SES and, 501, 947, 961 social ties and, 948–949 sociodemographic factors of, 947 stress and, 717 tobacco and, 946 type D personality and, 969
vitamin E and, 937 work stress and, 947–948 CORT. See Corticosterone Corticosteroid hormones (CH), 17–18, 679 Corticosteroid-binding globulin (CBG), 746–747, 854 Corticosteroids, 806, 937 for asthma, 806 Corticosterone (CORT), 23 eHSP and, 1019 HSPand, 1014 influenza and, 1097 stress and, 1036 Corticosterone-binding globulin (CBG), 480, 482 Corticotropin releasing factor (CRF), 48, 328, 357, 459, 520, 524 ACTH and, 826 HPA and, 1036 Corticotropin releasing hormone (CRH), 100, 111, 112, 195, 200, 294, 304, 740, 980 depression and, 515, 931 neuropeptides and, 296 sleep and, 601 Cortisol, 10, 222 CBSM and, 687 depression and, 516, 884 fetal development and, 712 levels of, 225 loneliness and, 884 norepinephrine and, 224 obesity and, 715 personality and, 713 PTSD and, 539–540 sleep and, 589, 603 space flight and, 853–854 stress and, 235, 884, 912, 1098 TSST and, 982 tumor cells and, 885 vaccination and, 912 Counseling, cancer and, 873 COX. See Cyclooxygenase C-reactive protein (CRP), 538, 568, 681, 926, 955 CHD and, 955–956 exhaustion and, 932 heart disease and, 923–924 plaque and, 954 SES and, 961 CREB. See CAMP responsive element-binding CREB-binding protein (CBP), 53 Creutzfeldt-Jakob disease (CJD), 440 CRF. See Corticotropin releasing factor CRH. See Corticotropin releasing hormone
1253 Crohn’s disease, 116 as autoimmune disease, 144–146 CRP. See C-reactive protein Cryogens, 299 CS. See Conditioned stimulus CSF. See Cerebrospinal fluid CSR. See Class switch recombination CTL. See Cytotoxic T lymphocytes Cushing’s disease, 197 CVD. See Cardiovascular disease CVOs. See Circumventricular organs CY. See Cyclophosphamide Cyclic adenosine monophosphate (cAMP), 66, 72, 73, 161, 322, 325, 983–984 Cyclic-citrullinated peptide (CCP), 218 Cyclooxygenase (COX), 87, 282, 295 Cyclophosphamide (CY), 649 Cyclosporine A, 166 Cytokines, 52, 651. See also Interleukin 1; Interleukin 6; Tumor necrosis factor alcohol and, 608 anti-inflammatory, 299, 300, 419– 420, 842 anxiety and, 304 apoptosis and, 275 asthma and, 809 autophagy and, 275 BBB and, 194, 286 behavioral effects of, 287 brain and, 267, 268, 291, 415, 520–523 brain development and, 274–275 breast cancer and, 180 CAD and, 925–926 cancer cells and, 179, 181 CNS and, 321 depression and, 268, 304, 518, 523– 524, 622, 932 emotions and, 624, 765 estrogen and, 208 exercise and, 662 fatigue and, 936 fever and, 269 GCs and, 300, 302 growth and, 300 HPA and, 520–521 hypothalamus and, 274, 681 IGF resistance and, 179, 182–184 inflammation and, 271 ingestive behavior and, 283 insomnia and, 606 lipids and, 284 mechanisms of, 422 memory and, 269, 360–366 muscle and, 182, 183 necrosis and, 275 network of, 291
1254
Subject Index
Cytokines (continued) neural processes and, 338 neuroendocrine effects of, 520–521 neuropeptides and, 296 neurotransmitters and, 296, 521 nitric oxide and, 294 NREM and, 587 overexpression of, 416 PGs and, 294 pluses and minuses, 298 production of, 55 pro-inflammatory, 25, 171, 267, 268, 298, 299, 337, 418–419, 536, 694, 841 PTSD and, 535–537 RA and, 194 receptors for, 56 in repair and recovery, 421 schizophrenia and, 277, 569–571 sensitization of, 303–304 SES and, 504 sickness behavior and, 281, 294, 339, 384 signaling of, 177, 179, 338 sleep and, 586–591 stress and, 694, 963 systemic lupus erythematosus and, 213 targets of, 292, 293 therapies with, 519 wound healing and, 841 Cytomegalovirus (CMV), 538, 566–567, 706, 859, 1079 CAD and, 927 space flight and, 858 Cytostasis, 179 Cytotoxic T lymphocytes (CTL), 878– 879, 1040 HSP and, 1015 HSV and, 1084, 1085–1086 Cytoxic T-cells, 142
D DA. See Dopamine DAG. See Diacylglycerol Danger signals, 919 HSP and, 1024 DC. See Dendritic cells DD. See Death domain D-dimer, 957 Death domain (DD), 177 Dehydroepiandrosterone (DHEA), 462, 1059 Delayed-type hypersensitivity (DTH), 344–345, 437, 438, 512, 649–651, 732 HSV and, 1082 PTSD and, 535
social network and, 783, 876 space flight and, 855 Demyelination, 1107, 1108 Theiler’s virus and, 1110 Dendritic cells (DC), 68, 72–73 homeostasis and, 142 HSP and, 1023 HSV and, 1081 infections and, 107 innate immunity and, 98 VEGF and, 240 Denial, cancer and, 872 Dennie Morgan lines, 805 Dentate gyrus (DG), 340 Deoxycorticosterone, 212 Depression, 93, 452, 761, 874, 921 ACS and, 949, 968–969 age and, 513 alcohol and, 516, 517, 553 allergies and, 714, 812 asthma and, 714, 802 CAD and, 929, 931 cancer and, 234, 304, 869, 870–871 catecholamines and, 515 CHD and, 949 childhood development and, 713 cortisol and, 884 CRH and, 931 cytokines and, 268, 304, 518, 523– 524, 622, 932 fetal development and, 712 gender and, 513 GR and, 521 health care costs of, 714 heart disease and, 681–682 HIV and, 1061–1062 hypercortisolemia and, 801, 812 IL-1 and, 510, 511 immunity and, 77, 622 immunological changes with, 509–512 infectious disease and, 511–512 inflammation and, 305, 511, 681–682, 960 influenza and, 910–911 insomnia and, 607 leukocytes and, 932 lymphocytes and, 510, 932 in medically ill, 518–519 morbidity and, 509 NE and, 932 NK and, 932 obesity and, 715, 937 parasympathetic nervous system and, 932 platelets and, 962 RA and, 198–199, 509 reactive vs. chronic, 1061 as risk factor, 918
sleep and, 516, 517, 607 SNS and, 515 stress and, 716–717, 966 symptoms of, 519 T-cells and, 512 TNF and, 511 tobacco and, 870 treatments for, 514–515 vaccination and, 907 Dermatitis, 726, 801. See also Atopic dermatitis topical steroids for, 806 Descending pain inhibitory pathways, 160 Desloratadine, 806 Desynchronization, of systems, 224 Detergents, 805 DEX. See Glucocorticoid dexamethasone Dex. See Dexamethasone Dexamethasone (Dex), 461 Dexamethasone suppression test (DST), 465, 540 DG. See Dentate gyrus DHAP. See Dihydroxyacetone phosphate DHEA. See Dehydroepiandrosterone Diabetes, 93, 817 CHD and, 946 fetal development and, 712 IGF and, 174 obesity and, 715, 998–1000 PTSD and, 531 stress and, 715–716 Diacylglycerol (DAG), 998 Diet CHD and, 947 death and, 452 infants and, 456 SES and, 950 unhealthy, 452 Dihydroxyacetone phosphate (DHAP), 998 Dihydroxyphenylalanine (DOPA), 983 Dinitrochlorobenzene (DNCB), 469 Disk-over-water method, 596 Distress, 747 DMH. See Dorsomedial hypothalamus DMV. See Dorsal motor nucleus of the vagus DNCB. See Dinitrochlorobenzene Docosanol, 1089 Dolor, 288 Dominance, 475 aggression and, 477–479 HPA and, 480 learning of, 478 linear, 479
1255
Subject Index matrilineal, 488–489 personality and, 484 reproductive maturation and, 482 SES and, 491 transitive, 479 DOPA. See Dihydroxyphenylalanine Dopamine (DA), 3, 241, 523, 1039 sleep and, 583 Dorsal motor nucleus of the vagus (DMV), 88 Dorsomedial hypothalamus (DMH), 327 Down syndrome (DS), 361 Drugs, 557. See also Pharmaceuticals; Substance abuse DS. See Down syndrome DST. See Dexamethasone suppression test DTH. See Delayed-type hypersensitivity Dust mites, 803 Dyslipidemia, CAD and, 921
E E. coli. See Escherichia coli E type prostaglandin receptors (EPRs), 322, 323, 324, 325 EA. See Early antigen EAE. See Experimental autoimmune encephalomyelitis Early antigen (EA), 856 EBV. See Epstein-Barr virus Ecstasy (MDMA), 557 Ectotherms. See Reptiles Eczematous lesions, 805 EEG. See Electroencephalogram Eggs, 803 EHSP. See Endogenous heat shock protein EIA. See Enzyme immunoassay Eicosanoids, inflammation and, 271 ELAM-1. See Endothelial-leukocyte adhesion molecule 1 Electroencephalogram (EEG), 579 Electromyogram (EMG), 582 Electrooculogram (EOG), 582 ELISA. See Enzyme-linked immunosorbent assay EMG. See Electromyogram Emotional disclosure, 908 Emotions, 620. See also Negative affect; Positive affect asthma and, 804 bereavement and, 792 cancer and, 871 cytokines and, 624, 765 expression of, 453 immunity and, 761
NK cells and, 625 suppression of, 871 Endocrine system common ancestor and, 24 immune system and, 171 versatility of, 222 Endogenous heat shock protein (eHSP), 1013 ACTH and, 1019 in adipose tissue, 1020–1021 CORT and, 1019 immune response and, 1014 in liver, 1020–1021 in lymph nodes, 1020–1021 lymph nodes and, 1023 NE and, 1019 NO and, 1023 in pituitary gland, 1020–1021 in spleen, 1020–1021 stress and, 1015–1018, 1019, 1026–1027 TLR and, 1024–1025 vascular endothelial cells and, 1023 Endoplasmic reticulum (ER), 164 stress and, 999 Endorphins, 164, 166 Endothelial dysfunction, 951–952, 964 infection and, 958–960 Endothelial-leukocyte adhesion molecule 1 (ELAM-1), 55 Endothelium layer, 91, 951 Endotoxemia, 91 Endotoxins, 87, 591 Enhancing Recovery in Coronary Heart Disease (ENRICHD), 695 ENRICHD. See Enhancing Recovery in Coronary Heart Disease ENS. See Enteric nervous system Enteric nervous system (ENS), 105 Enthusiasm, 761 Environmental tobacco smoke (ETS), 804 Enzyme immunoassay (EIA), 860 Enzyme-linked immunosorbent assay (ELISA), 899, 902, 964, 1099 EOG. See Electrooculogram Eosinophil chemotaxis, 108 Eosinophils, 108–109 atopic dermatitis and, 984–985 stress and, 984–985 Ephedrine, 76 EPI. See Epinephrine Epinephrine (EPI), 2, 20, 63–65 aggression and, 480–481 atopic dermatitis and, 984 influenza and, 1097 natural killer cells and, 67–68 NK and, 67–68
stress and, 235 wound healing and, 827 EPRs. See E type prostaglandin receptors Epstein-Barr virus (EBV), 236, 676, 677, 682, 706, 707, 783, 883, 1078 MS and, 1108 schizophrenia and, 567 SES and, 501 sleep and, 585–586 space flight and, 856 ER. See Endoplasmic reticulum Escherichia coli, 92 E-selectin, 163 Esquirol, 564 Estrogen, 207 antibodies and, 208 cytokines and, 208 menopause and, 829 pregnancy and, 212 RA and, 197, 199 as risk factor, 210 wound healing and, 828–829 Etanercept, 524 ETS. See Environmental tobacco smoke Eustress, 747 Excitotoxic insults, 184 Exercise. See also Exertion antioxidants and, 669–670 carbohydrates and, 668–669 cytokines and, 662 depression and, 516, 517 excessive, 662 HIV and, 684–685 immunity and, 77 inadequate, 452 morbidity and, 662–663 PA and, 771 prostate cancer and, 877 SES and, 950 URTI and, 661, 666–667 Exertion asthma and, 816 URTI and, 664 vitamin C and, 665–666 Experimental autoimmune encephalomyelitis (EAE), 145, 148–149, 734, 739 Exposure, 501 immunity and, 498 Expressive writing, 685–686 asthma and, 814 Extinction, 632, 635 Extroversion, 773, 871
F FABP. See Fatty acid binding protein Factor S, 584
1256
Subject Index
Famciclovir, 1089 Fatigue. See also Chronic fatigue and immune dysfunction syndrome; Post-viral fatigue syndrome CAD and, 931 cytokines and, 936 Fatty acid binding protein (FABP), 999, 1000 Fear, 620 Fear conditioning, 341 Fever, 87 cytokines and, 269 endogenous pyrogens and, 273 IL-6 and, 274 immune system and, 319 inflammation and, 322 TNF and, 282 Fexofenadine, 806 FGF. See Fibroblast growth factor Fibrin clot, 838 Fibrinogen, 954 hypertension and, 967 SES and, 961 social ties and, 962 stress and, 961–962 Fibroblast growth factor (FGF), 842 Fibromyalgia, 586 Fibroplasia, 844 Fight or flight response, 64, 747, 1036 SNS and, 620 Fighting spirit, 875 cancer and, 871 Fish, 6–12 5HT. See Serotonin Fluoxetine, 514, 515 Food allergies, 801–803 Forkhead proteins, 173 Free radicals, 953–954 exertion and, 669 hypothesis of aging, 383
G GALT. See Gut-associated lymphoid tissue Gamma-aminobutyric acid, 583 Gastrointestinal tract, 115–117 GCR. See Glucocorticoid resistance GCs. See Glucocorticoids G-CSF. See Granulocyte-colony stimulating factor Gender alcohol and, 552, 554 depression and, 513 social integration and, 783 wound healing and, 830 Genes, transrepression of, 51 GFAP. See Glial fibrillary acid protein GH. See Growth hormone
GHRH. See Growth hormonereleasing hormone GILZ. See Glucocorticoid-induced leucine zipper GIM. See Guided imagery in music Gingivitis, 725, 726 heart disease and, 927 Glial fibrillary acid protein (GFAP), 565 Glucocorticoid dexamethasone (DEX), 7, 17, 23 Glucocorticoid receptor interacting protein-1 (GRIP-1), 53 Glucocorticoid receptors (GR), 41, 45, 521, 1098–1099 antagonists to, 1064 expression of, 48 inflammation and, 198 inhibition effects of, 300 modifications of, 49–50 protein structure of, 49 PTSD and, 540 sleep and, 604 Glucocorticoid resistance (GCR), 621 Glucocorticoid-induced leucine zipper (GILZ), 54 Glucocorticoid-induced TNF receptor (GITR), 736 Glucocorticoid-response elements (GREs), 50, 54 Glucocorticoids (GCs), 48, 194, 197, 267, 734, 737, 980, 1098–1099 ACTH and, 933 anti-inflammatory, 965, 1103 cytokines and, 300, 302 HIV and, 1056 HPA and, 826 humoral immunity and, 735 IL-1 and, 302 immunosuppressive effects of, 9 inhibitory effects of, 54–56 MS and, 1112 as pharmaceuticals, 45 PTSD and, 540 resistance to, 1111–1112, 1114–1115 SDR and, 1114–1115 sensitivity to, 1103 sepsis and, 738 stress responses and, 357–358 therapy with, 1056 TMEV and, 1114–1115 wound healing and, 826, 843 Glutamate, 583 Glutamine, 670 Glycosaminoglycan, 844 GM-CSF. See Granulocytemacrophage-colony stimulating factor Golgi apparatus, 164
G-protein-related kinase 2 (GRK2), 69 GR. See Glucocorticoid receptor; Glucocorticoid receptors Graft-versus-host reaction (GVHR), 149 Graft-versus-tumor (GVT), 149 Gram-negative bacterial infections, 146 Granulocyte-colony stimulating factor (G-CSF), 591, 736 Granulocyte-macrophage-colony stimulating factor (GM-CSF), 458 GREs. See Glucocorticoid-response elements GRIP-1. See Glucocorticoid receptor interacting protein-1 GRK2. See G-protein-related kinase 2 Growth hormone (GH), 18–19, 171, 604 replacement therapy with, 186 sleep and, 601, 603 Growth hormone-releasing hormone (GHRH), 601 Guided imagery, 684, 687 cancer and, 877 stress and, 828 Guided imagery in music (GIM), 688 Gut-associated lymphoid tissue (GALT), 464 GVHR. See Graft-versus-host reaction GVT. See Graft-versus-tumor
H HA. See Hyaluronic acid HAART. See Highly active antiretroviral therapy HAI. See Hemagglutination Inhibition Happiness, 761 Hay fever, 802 HBO. See Hyperbaric oxygen therapy HBV. See Hepatitis B Virus HCV. See Hepatitis C Virus HDL. See High-density lipoprotein Healing. See Wound healing Healing touch, 688 Health maintenance equilibrium, 747 Heart. See Coronary Heat shock protein (HSP), 568 ACTH and, 1014 in adipose tissue, 1020–1021 CAD and, 957 cellular functions of, 1015 CORT and, 1014 CTLs and, 1015 as danger signal, 919 danger signals and, 1024 DC and, 1023 in liver, 1020–1021 LPS and, 1023
Subject Index in lymph nodes, 1020–1021 MHC and, 1015 NE and, 1014 NKC and, 1015 in pituitary gland, 1020–1021 in spleen, 1020–1021 stress and, 1013, 1014 HEL. See Hen egg lysozyme Helicobacter pylori, 927 Hemagglutination inhibition (HAI), 898, 902, 907, 1099 Hematopoiesis, vasoactive intestinal peptide and, 139 Hemocytes, 2 Hemokinin, 101–102 Hemostasis, in wound healing, 838 Hen egg lysozyme (HEL), 646 HEPA. See High-efficiency particulate air Hepaticsplanchnic tissue, 1022 Hepatitis B virus (HBV), 237, 694 PA and, 768 stress and, 907 vaccination for, 768, 902, 904–905, 906–907 Hepatitis C Virus (HBC), 237 alcohol and, 554 Herpes simplex virus (HSV), 56, 70, 303, 538, 676, 706, 803, 919. See also Cytomegalovirus; Epstein-Barr virus; VaricellaZoster virus ADCC and, 1083 anger and, 1078 caregivers and, 1083 CTL and, 1084, 1085–1086 DC and, 1081 divorce and, 676 drugs for, 1089 DTH and, 1082 history of, 1077–1078 HPA and, 1088 IL-6 and, 1081 immune response and, 1079, 1082–1083 immunological memory and, 1085 inflammation and, 1081 innate immune system and, 1081 lesions with, 1077, 1088 LPS and, 1111 lymphocytes and, 1079 macrophages and, 1081 neonates and, 1083–1084 NK and, 1081 pregnancy and, 461 reactivation of, 1080, 1083 schizophrenia and, 566 space flight and, 856
stress and, 1078, 1086–1088, 1089, 1111 vaccine for, 1083, 1088–1089 Hexosamine, 998, 999 High-density lipoprotein (HDL), 959 stress and, 964 High-efficiency particulate air (HEPA), 852 Highly active anti-retroviral therapy (HAART), 690 Hippocampal-dependent memory, 269 Hippocampus, 184 kainate and, 186 Histamine inflammation and, 270 sleep and, 583 Histocompatibility epitopes, 207 HIV. See Human immuno-deficiency virus Hives, 813 HLA-G. See Human leukocyte antigen Homeostasis, 171 allostasis and, 491 CDIDs and, 220–222 dendritic cells and, 142 hormonal, 710 stress and, 1036, 1080 Homology, 477 Hopelessness, 874 cancer and, 871–872 Hormone replacement therapy, 199 Hormone resistance, 172 Hostility. See also Anger CHD and, 949 IL-6 and, 962 stress and, 966 TNF and, 962 HPA. See Hypothalamic-pituitaryadrenal gland axis HPG. See Hypothalamic-pituitarygonadal axis HPV. See Human Papilloma Viruses; Human papillomavirus HSP. See Heat shock protein HSV. See Herpes simplex virus Human immuno-deficiency virus (HIV), 77, 415, 624, 919 AIDS and, 1053, 1054–1055 alcohol and, 554 androgens and, 1059 ANS and, 1055, 1058 behavioral interventions and, 688–689 bereavement and, 1060 CBSM and, 1061 clinical latency of, 1054 cocaine and, 555 coping and, 1060 depression and, 1061–1062
1257 GCs and, 1056 HAART and, 690 HPA and, 1055 HPG and, 679 individual differences with, 1064 MBSR and, 1061 neural imaging and, 1064 optimism and, 713–714, 1060 pathogenesis of, 1053–1055 personality and, 487 progression of, 1055–1056 psychological inhibition and, 1063 religious services and, 1060 replication cycle of, 1054 sleep and, 585 social support and, 790, 1062 stress and, 1060 stress reduction and, 1061 T-cells and, 74 Human leukocyte antigen (HLA-G), 457 Human Papilloma Viruses (HPV), 237, 682, 883 Humoral efferent pathway, 635, 641 Humoral immunity, 568 GCs and, 735 Humoral innate immunity, 642–643 Hyaluronic acid (HA), 844, 846 Hyperalgesia, 281 inflammation and, 329 LPS and, 290 Hyperbaric oxygen therapy (HBO), 828, 832 Hypercholesterolemia, 922 Hypercortisolemia, 801 depression and, 812 Hyperlipidemia, 945 Hyperphagia, 932 Hypersensitivity disease, 800 Hypersomnia, 932 Hypertension, 93 CAD and, 921, 929, 930 CBSM and, 687 CHD and, 946 fetal development and, 712 fibrinogen and, 967 IL-6 and, 967 leukocytes and, 934 MI and, 967 obesity and, 715 stress and, 716, 966 Hypnosis, 111, 684, 766 Hypophysectomy, 195 Hypothalamic ventromedial nucleus (VMH), 293, 294 Hypothalamic-pituitary-adrenal gland axis (HPA), 48, 54, 76, 87, 111, 195, 207, 274, 337, 456 activation of, 329
1258
Subject Index
Hypothalamic-pituitary-adrenal gland axis (HPA) (continued) atopic dermatitis and, 975, 981 autoimmune disorders and, 197 cancer and, 884 CNS and, 980 CRF and, 1036 cytokines and, 520–521 depression and, 516 differences in, 741–742 dominance and, 480 dysregulation of, 516 GC and, 826 GCs, 826 HIV and, 1055 HSV and, 1088 IL-1 and, 933 immune response and, 911–913 immunity and, 932 lymphocytes and, 934 nicotine and, 516 pregnancy and, 711 PTSD and, 539 RA and, 197–198 sleep and, 589, 601 SNS and, 228 stress and, 826, 853, 917, 1080, 1098 surgery and, 254 sympathetic nervous system and, 228 TNF and, 933 Hypothalamic-pituitary-gonadal axis (HPG), 207 HIV and, 679 Hypothalamus, 64 cytokines and, 274, 681 as gatekeeper, 86 paraventricular nucleus of, 293 stress reaction by, 710 Hypothermia, 256, 880, 1081
I IBAT. See Intrascapular brown adipose tissue IBD. See Inflammatory bowel disease IC. See Interstitial cystitis ICAMs. See Intercellular adhesion molecules ICDs. See Implantable cardioverter-defibrillators ICE. See Interleukin converting enzyme ICH. See Immunocompetence handicap hypothesis ICV. See Intracerebroventricular administration Ideal body mass (BMI), 718
IDECs. See Inflammatory dendritic epidermal cells IDO. See Indoleamine dioxygenase IFN. See Interferon IGF. See Insulin-like growth factor IgM. See Immunoglobulin M IHC. See Immunohistochemical analyses IHR. See Immediate hypersensitivity reaction IL-1. See Interleukin 1 IL-1 a, CVOs and, 382 IL-2. See Interleukin 2 IL-4. See Interleukin 4 IL-5. See Interleukin 5 IL-6. See Interleukin 6 IL-10. See Interleukin 10 IL-13. See Interleukin 13 Imipramine, 515 Immediate hypersensitivity reaction (IHR), 977 Immune response, 46 adaptive, 1082–1083 eHSP and, 1014 HPA and, 911–913 HSV and, 1079 to infectious diseases, 337 innate vs. adaptive, 636–637 NK and, 1082 to TMEV, 1109–1110 to vaccination, 897 Immune senescence, aging and, 662 Immune system adaptive, 534 brain and, 273, 913 CNS and, 434–435 common ancestor and, 25 deterioration of, 380 fever and, 319 innate, 534, 1081, 1082 sickness behavior and, 319 versatility of, 222 Immune-to-brain signaling, 291 Immunity ACTH and, 463 adaptive, 46–48, 69–70, 73–75 alcohol and, 549, 552 anesthesia and, 692 anger and, 623–624 anxiety and, 77, 622–623 bereavement and, 792 CAD and, 923, 930 caregivers and, 910 cellular, 569 CHD and, 955–958 chemotherapy and, 691, 875 circadian rhythms and, 591–595 CNS and, 97 depression and, 77, 622
emotions and, 761 exercise and, 77, 684–685 exposure and, 498 expressive writing and, 685 of fetus, 461 HPA and, 932 humoral, 568, 735 infants and, 455, 462 innate, 46, 67, 135 marriage and, 788 massage and, 684 moods and, 677 nicotine and, 556 obesity and, 993 opiates and, 556 PA and, 771–772 parasympathetic nervous system and, 605 PTSD and, 543 QOL and, 885–886 radiation therapy and, 692 schizophrenia and, 563 sleep and, 517, 595–600 SNS and, 605, 1035 space flight and, 854–856 stress and, 881 surgery and, 591 vulnerability and, 498 Immunocompetence handicap hypothesis (ICH), 24 Immunogenic potential, 879 Immunoglobulin M (IgM), 568 Immunoglobulins, 550 Immunohistochemical (IHC) analyses, 417 Immunological memory, 1085–1086 Immunoselection, 879 Immunostimulation, 258–260 Immunosurveillance, 878–879 hypothesis of, 879 Immunotherapy (IT), 258–260, 807 Impetigo, 803 Implantable cardioverter-defibrillators (ICDs), 948 In situ hybridization (ISH), 417 In utero, environment of, 711–713 Incontinence, 93 Individual differences, social context and, 497 Indoleamine dioxygenase (IDO), 307, 308, 522 Infants ACTH and, 463 allergies in, 456 asthma and, 456 diet and, 456 immunity and, 455, 462 Inflammation of airway, 805
1259
Subject Index allergies and, 810 atherosclerosis and, 921, 951 axonal reflexes and, 810 of CNS, 433–435 components of, 288 depression and, 305, 511, 681–682, 960 fever and, 322 GR and, 198 histamine and, 270 HSV and, 1081 hyperalgesia and, 329 leukocytes and, 968 MMPs and, 869–870 neurogenic, 1038 NO and, 113 obesity and, 996 platelets and, 968 as response, 271 SAM and, 983 SES and, 960 signs of, 679 SP and, 110 stress and, 680–681 tumors and, 881 Inflammatory bowel disease (IBD), 144 obesity and, 1002–1003 Inflammatory dendritic epidermal cells (IDECs), 978 Inflammatory markers circulating levels of, 511 depression and, 520 Inflammatory phase stress and, 842 of wound healing, 837–840 Inflammatory reflex, 85–86 Infliximab, 524 Influenza, 1092 asthma and, 806 caregivers and, 1099 CORT and, 1097 depression and, 910–911 EPI and, 1089 ICAMs and, 1100 lymphocytes and, 1101 NE and, 1097 psychosis and, 277 stress and, 908, 1099–1103 vaccination for, 902, 903, 906 VCAM-1 and, 1100 Insect sting allergies, 801–802 Insomnia, 579 cytokines and, 606 depression and, 607 primary, 606 Insulin receptor (IR), 999 Insulin receptor substrate (IRS), 994, 999
Insulin resistance, 715 Insulin-like growth factor (IGF), 171, 267, 282, 300 binding proteins and, 173, 175, 182 cancer and, 174, 180 diabetes and, 174 life span and, 173 muscles and, 181–182 osteoporosis and, 174 sickness behavior and, 184–185 signaling of, 175, 176 spatial learning and, 185–186 system of, 172–175 therapeutic uses for, 174 Intercellular adhesion molecules (ICAMs), 46, 55, 91, 163, 730 influenza and, 1100 Interferon (IFN), 515, 519, 676, 954 serotonin and, 521 sleep and, 584, 591 therapy with, 519 Interleukin, 273–274 Interleukin 1 (IL-1), 52, 85, 97, 267, 282, 456, 524, 571, 682, 997 accessory protein of, 292 ACS and, 956 ACTH and, 933 adipose tissue and, 994, 996 choroid plexus and, 382 circumventricular organs and, 382 depression and, 510, 511 5HT and, 521 GCs and, 302 HPA and, 933 LPS and, 288, 355 memory and, 342–348 neural plasticity and, 353–356 PGs and, 358 pregnancy and, 458–459 pro-inflammatory, 337 signal diffusion of, 292 sleep and, 584, 588 SWS and, 587 Interleukin 2 (IL-2), 569–570 Interleukin 4 (IL-4), 299 adipose tissue and, 997–998 Interleukin 5 (IL-5), 55 Interleukin 6 (IL-6), 275, 298, 365, 570, 682 adipose tissue and, 994, 995–996 angiogenesis and, 882 caregivers and, 962 depression and, 512, 515 exercise and, 662 fever and, 274 heart disease and, 923 hostility and, 962 HSV and, 1081
hypertension and, 967 memory and, 342, 348–350 neural plasticity and, 356 PTSD and, 536 SDR and, 1115 SES and, 961 sleep and, 518, 588, 591 tobacco and, 516 Interleukin 10 (IL-10), 299, 300, 417 ACS and, 957 Interleukin 13 (IL-13), 299 Interleukin 18 (IL-18), 996 Interleukin converting enzyme (ICE), 291, 301–302, 419 International Space Station (ISS), 851, 854 Inter-stimulus interval, 634, 639 Interstitial cystitis (IC), 117 Intima layer, 951 free radicals and, 954 Intimacy, social integration and, 787–788 Intimal layer, 950 Intracerebroventricular (ICV) administration, 304 Intraperitoneal (IP) administration, 304 Intrascapular brown adipose tissue (IBAT), 326 Intrinsic primary afferent neurons (IPANs), 105 Invertebrates, 2–7 IP. See Intraperitoneal administration IPANs. See Intrinsic primary afferent neurons IR. See Insulin receptor Iron, 668 deficiency of, 466 IRS. See Insulin receptor substrate Ischemic insults, 184 Ischemic stroke, 416 ISH. See In situ hybridization ISS. See International Space Station IT. See Immunotherapy
J Joy, 761
K Kainate (KA), 186 spatial memory and, 187 Kaposi’s sarcoma, 235, 237 Keratinocyte growth factor (KGF), 826, 845 Keratosis pilaris, 805 Keyhole limpet hemocyanin (KLH), 69, 468, 481, 487–488, 643, 732
1260
Subject Index
KGF. See Keratinocyte growth factor Kinesiology, 815 KLH. See Keyhole limpet hemocyanin Kupffer cells, 320
L Lactate dehydrogenase (LDH), 728 Lactobacilli, 464 LAL. See Long attack latency Langerhans cells (LC), 98, 104, 114, 803, 978 Latent inhibition, 632 LC. See Langerhans cells LDH. See Lactate dehydrogenase LDL. See Low-density lipoprotein Learned helplessness, 480 Learning trajectory, 470 Legionella pneumophilia, 90, 344 Leptin, 994–995 Leukemia, 883 Leukemia inhibitory factor (LIF), 297 Leukocytes, 39, 1098–1099 ACS and, 968 ANS and, 1057 CHD and, 957 chemokines and, 963 circadian rhythms and, 744 depression and, 932 hypertension and, 934 inflammation and, 968 PTSD and, 537 recruitment of, 163, 1081–1082 redistribution of, 728, 742–744 schizophrenia and, 569 stress and, 726–731, 963 trafficking of, 1081–1082 Levodopa, 523 Lichenification, 805 LIF. See Leukemia inhibitory factor Lifestyles improvement of, 718 sedentary, 452, 499 Lipopolysaccharides (LPS), 4, 7–8, 46, 68, 99, 104, 184, 272, 274, 281, 286, 287, 306, 381, 431, 432, 456, 965 adrenalectomy and, 301 HSP and, 1023 HSV and, 1111 hyperalgesia and, 290 IL-1 and, 288, 355 as immune stimulant, 320 NA and, 296 sickness and, 284 vagotomy and, 289 Listeria monocytogenes (LM), 68, 69, 919, 1035 cold and, 1035–1039
Little brain. See Enteric nervous system LM. See Listeria monocytogenes Loneliness, 677, 874, 904 cortisol and, 884 social integration and, 787–788 Long attack latency (LAL), 479 Long-term potential (LTP), 275, 340 Loratidine, 806 Low-density lipoprotein (LDL), 679– 680, 922, 951, 953 stress and, 964 LPS. See Lipopolysaccharides L-selectin, 163 LTP. See Long-term potential Lupus, 76 Lymphocytes, 106–107, 878–879, 1040 alcohol and, 550 CAD and, 925 depression and, 510, 932 HPA and, 934 HSV and, 1079 influenza and, 1101 neuropeptides and, 104 PTSD and, 537 SAM and, 934 schizophrenia and, 569 sleep and, 598
M Macrophage chemoattractant protein (MCP), 841, 1100 Macrophage colony stimulating factor (M-CSF), 953 Macrophage inflammatory protein (MIP), 953, 1100 Macrophages, 68 adipose tissue and, 994 α7 agonists and, 90 in brain, 272 with CAD, 924–925 cytokines and, 72 functions of, 108 in healthy brain, 272 HSV and, 1081 wound healing and, 839 Major histocompatibility complex (MHC), 2, 430, 457, 565, 878, 879 HSP and, 1015 Malaria, 415 Mammalians, 1 MAPK. See Mitogen-activated protein kinase Marijuana, 557 Marriage, 781 Alzheimer’s disease and, 789–790 conflict in, 788–789 immunity and, 788
morbidity and, 783 mortality and, 783–784 RA and, 784 same sex, 786–787 Mason-Pfizer monkey virus (MPMV), 567 Massage, 684 asthma and, 814 stress and, 828 Mast cells, 40 in brain, 273 in GI tract, 116–117 neurons and, 109 Pavlovian conditioning and, 111 skin and, 113–114 stimulation of, 109–110 Matrix metalloproteases (MMPs), 72, 200, 882–883, 954 inflammation and, 869–870 MBP. See Myelin basic protein MBSR. See Mindfulness-based stress reduction MCAO. See Middle cerebral artery occlusion MCP. See Macrophage chemoattractant protein; Monocyte chemotactic protein M-CSF. See Macrophage colony stimulating factor MDMA. See Ecstasy Measles, 415, 567, 1108 Media layer, 950 Medial preoptic area (MPO), 325 Meditation, 684 cancer and, 877 Melatonin, 604 Memory, 340 cytokines and, 269, 360–366 IL-1 and, 342–348 IL-6 and, 342, 348–350 testing of, 340 tumor necrosis factor and, 342, 350–353 Meningeal macrophages (MMs), 438 Meninges, 292 Meningitis C, vaccination for, 905 Menopause estrogen and, 829 wound healing and, 829 Mental Adjustment to Cancer scale, 875 MET. See Methionine-enkephalin Metastasis in cancer, 237–238 surgery and, 253 Methionine-enkephalin (MET), 535 Methylprednisolone, 937 MHC. See Major histocompatibility complex
Subject Index MI. See Myocardial infarction Microglia, 91, 136, 147 of brain blood vessels, 273 schizophrenia and, 564–565 Middle cerebral artery occlusion (MCAO), 92 MIF. See Migration inhibitory factor Migration inhibitory factor (MIF), 829 Milk, 803 bacteria and, 464 Mindfulness-based stress reduction (MBSR), HIV and, 1061 Mineralocorticoid receptors (MR), 604 Minimal residual disease (MRD), 252 MIP. See Macrophage inflammatory protein Mitogen-activated protein kinase (MAPK), 47, 274, 282, 994 pathway of, 175, 176, 177, 181 MMPs. See Matrix metalloproteases MMs. See Meningeal macrophages MMTV. See Mouse mammary tumor virus gene MNC. See Mononuclear cells MOG. See Myelin oligodendrocyte Molds, 803 Monocyte chemotactic protein (MCP), 953 Mononuclear cells (MNC), 463 Montelukast, 807 Mood induction studies, 762–766 Moods, 620 immunity and, 677 vaccination and, 910 Morphine, 166 Motivational state competition of, 286 sickness behavior and, 285 Mouse mammary tumor virus gene (MMTV), 50 MPMV. See Mason-Pfizer monkey virus MPO. See Medial preoptic area (MPO); Myeloperoxidase MR. See Mineralocorticoid receptors MRD. See Minimal residual disease MS. See Multiple sclerosis Multiple sclerosis (MS), 147, 148, 270, 386, 429, 430, 726, 817 BBB and, 437, 1110 CNS and, 1107 demyelination and, 1107 EBV and, 1108 environment and, 1108 GCs and, 1112 genetics and, 1108 as inflammatory disease, 435–439 obesity and, 1003 relapse of, 436
relapsing remitting, 1107 stress and, 1100–1110, 1107 Theiler’s virus and, 1109 viruses and, 1107, 1108 Mumps, 467 Music therapy, 688 Mycobacterium tuberculosis, 69 Myelin basic protein (MBP), 1117 Myelin oligodendrocyte (MOG), 1117 Myeloperoxidase (MPO), 958 Myoblasts, 173–174, 182 Myocardial infarction (MI), 927, 945 adiponectin and, 1001 congestive heart failure and, 946 deaths and, 946 hypertension and, 967 risk factors for, 929 stroke and, 946 Myofibers, 182
N NA. See Negative affect Nafazodone, 514 NANC. See Non-adrenergic, non-cholinergic Narcolepsy, 587–588 NASA. See National Aeronautics and Space Administration National Aeronautics and Space Administration (NASA), 851 National Health and Nutrition Examination Survey, 715 National Sleep Foundation, 452 Natural cytotoxic cells (NCC), 9 Natural killer cell cytotoxicity (NKCC), 676 Natural killer (NK) cells, 19, 23, 42, 47, 65, 71, 75, 257, 534, 637–639, 676 alcohol and, 551 depression and, 510, 932 emotions and, 625 epinephrine and, 67–68 HSP and, 1015 HSV and, 1081 immune response and, 1082 innate immunity and, 98 pregnancy and, 457 PTSD and, 537 schizophrenia and, 569 sleep and, 598 space flight and, 855 stress and, 874 surgery and, 254–257 tobacco and, 516 tumors and, 256 Natural killer T-cells (NKT), 98 NCC. See Natural cytotoxic cells NE. See Norepinephrine
1261 Necrosis, cytokines and, 275 Negative affect (NA), 621–622, 762 NEP. See Neutral endopeptidase Nepotistic hierarchy, 489 Nerve growth factor (NGF), 102, 105– 106, 567 mast cells and, 109 skin and, 113 Neural efferent pathway, 635, 641 Neural imaging, 1064 Neural pathways, 290 Neural plasticity IL-1 and, 353–356 IL-6 and, 356 TNF and, 357 Neurodegenerative hypothesis, 564 Neurodevelopmental hypothesis, 563 Neurogenesis, 359–360 Neurogenic inflammation, 111, 1038 Neuroinflammation, 147, 270 Neurokinin A, 101 in GI tract, 115 Neurokinin B, 101 in GI tract, 115 Neurokinins, receptors for, 102–103 Neuropeptides, 100–105 cholecystokinin and, 296 communication of, 106–110 CRH and, 296 cytokines and, 296 depression and, 515 lymphocytes and, 104 skin and, 113–114 space flight and, 862 Neuropeptide-Y (NPY), 983 Neuroticism, 871 Neurotransmitters ACh as, 194 cytokines and, 296, 521 SP as, 103 Neurotrophins, 105–106, 359–360 Neutral endopeptidase (NEP), 101 Neutrophils, 108–109, 642 depression and, 510 infection control and, 839 scarring and, 846 space flight and, 855 wound healing and, 839 New Caledonian viral strain, 903–904 NF-AT. See Nuclear factor of activated T-cells NGF. See Nerve growth factor Nicotine, 90 immunity and, 556 Nipple eczema, 805 Nippostrongylus brasiliensis, 110 Nitric oxide (NO), 100, 103, 115, 1025 asthma and, 809 cytokines and, 294
1262 Nitric oxide (NO) (continued) eHSP and, 1023 inflammation and, 113 stress and, 1026 Nitric oxide synthase (NOS), 4, 26, 282, 294 Nitrogen dioxide, 804 NK. See Natural killer (NK) cells NKCC. See Natural killer cell cytotoxicity NKT. See Natural killer T-cells NL1. See Nuclear-localization signal NMDA. See N-methyl-d-aspartate N-methyl-d-aspartate (NMDA), 276 NO. See Nitric oxide Nociception, 256 Nociceptive thresholds, 329–330 Non-adrenergic, non-cholinergic (NANC), 100, 103, 109, 810 in airways, 115 Non-rapid eye movement (NREM), 580, 581 infections and, 584–585 Non-steroidal anti-inflammatory drugs (NSAIDs), 54, 439 Noradrenaline (NA), 100, 165 LPS and, 296 Noradrenergic receptors, PTSD and, 542 Norepinephrine (NE), 2, 14, 63–65, 100, 200, 222, 983 aggression and, 481 atopic dermatitis and, 984 B-cells and, 70–71 cold and, 1036 cortisol and, 224 depression and, 932 eHSP and, 1019 HSP and, 1014 influenza and, 1097 regulation by, 66–71 relevance of, 75–77 sleep and, 583 stress and, 112, 235 tumor cells and, 240 Nortriptyline, 514 NOS. See Nitric oxide synthase NPY. See Neuropeptide-Y NREM. See Non-rapid eye movement NRM. See Nucleus raphe magnus NSAIDS. See Non-steroidal antiinflammatory drugs NTS. See Nucleus of solitary tract; Nucleus tractus solitaries Nuclear factor of activated T-cells (NF-AT), 52, 53 Nuclear-localization signal (NL1), 49
Subject Index Nucleus of solitary tract (NTS), 322 Nucleus raphe magnus (NRM), 330 Nucleus tractus solitaries (NTS), 88 Nutrition. See Diet Nuts, 803
O Obesity, 452, 587–588, 918. See also Weight management adiponectin and, 1000 adipose tissue and, 993–994 asthma and, 1001–1002 CAD and, 921, 929 cortisol and, 715 CVD and, 1000–1001 depression and, 715, 937 diabetes and, 715, 998–1000 heart disease and, 714 hypertension and, 715 immunity and, 993 inflammation and, 996 inflammatory bowel disease and, 1002–1003 liver and, 1000 MS and, 1003 osteoarthritis and, 715 RA and, 1003 sepsis and, 1002 wound healing and, 1002 OCA-B, 75 OD. See Optical density Oligodendrocytes, 26 Omalizumab, 807 Omega-3 fatty acids, 303 Open window theory, 663 Opiates, immunity and, 556 Opioid peptides analgesia and, 165 clinical implications of, 166 migration of, 163 release of, 164 Opioid receptors, 159 analgesic effects of, 161 inflammation and, 162 peripheral, 160 signaling and, 160–161 structure of, 161 Optical density (OD), 899 Optimism, 713–714, 761, 773 HIV and, 1060 Organum vasculosum of the lamina terminalis (OVLT), 286, 321, 323, 324, 325, 327 Osteoporosis, 174 OVA. See Ovalbumin Ovalbumin (OVA), 645 OVLT. See Organum vasculosum of the lamina terminalis
Oxygen therapy with, 828 wound healing and, 827 Oxytocin, 241 Ozone, 804
P PA. See Positive affect PACAP. See Pituitary adenylate cyclase-activating polypeptide PAF. See Platelet-activating factor PAI. See Plasminogen activator inhibitor Pain, 256, 626 inflammation and, 166 purpose of, 159 stress and, 165 Palmar hyperlinearity, 805 PALS. See Periarteriolar lymphoid sheath PAMPs. See Pathogen-associated molecular patterns PANAS. See Positive and Negative Affect Schedule Panic disorder (PD), 623 Papules, 805 Paracrine, 207, 210 Parasympathetic nervous system, 86 depression and, 932 immune responses and, 194 immunity and, 605 RA and, 200 Paraventricular hypothalamic nucleus (PVH), 322, 328 stress reaction by, 710 Paraventricular nucleus (PVN), 112, 293, 294 Parkinson’s disease, 147, 184, 275, 523, 710 depression and, 518 Paroxetine, 514 Passive avoidance, 341–342 Pathogen-associated molecular patterns (PAMPs), 307, 309 PBMC. See Peripheral blood mononuclear cells PD. See Panic disorder; Phosphodiesterase PDGF. See Platelet-derived growth factor PDQ-R. See Personality Diagnostic QuestionnaireRevised Penciclovir, 1089 PENK. See Proenkephalin PEP. See Pre-ejection period Peptidergic nerves, 103 Perceived marital support, 783, 786–787
Subject Index Perceived social support, 785–786 Periarteriolar lymphoid sheath (PALS), 64 Periodontal disease, sex hormones and, 830 Peripheral blood mononuclear cells (PBMC), 210, 730 Peritonitis, 91 Perivascular macrophages (PVMs), 438 Peroxisome proliferator-activated receptor (PPAR), 999 Personality descriptions of, 484 health and, 713–715 HIV and, 487 immune modulation and, 484 as risk factor, 917–918 type C, 871 type D, 969 Personality Diagnostic QuestionnaireRevised (PDQ-R), 714 Pessimism, cancer and, 871–872 PET. See Positron-emission tomography Peyer’s patches, 103, 107, 133 PFC. See Plaque-forming cells PGE2. See Prostaglandin E2 PGs. See Prostaglandins PG-synthesis inhibitor, 257 PHA. See Phytohemagglutinin Phagocytosis, 26, 551 Pharmaceuticals, GCs as, 45 Phorbol myrisate acetate (PMA), 468 Phosphodiesterase (PD), 807 Phospholipase C (PLC), 133 Phospholipase D (PLD), 133 Phosphorylation, 50 Physiological resilience, 747–748 Phytohemagglutinin (PHA), 462, 510, 535, 677 PIGF. See Placental growth factor Pituitary adenylate cyclase-activating polypeptide (PACAP), 99, 103, 810 discovery of, 133 receptor cells and, 134 Pityriasis alba, 805 PKC. See Protein kinase C Placebo, 633, 710–711 asthma and, 815 Placental growth factor (PIGF), 224 Plaque, 921 atherosclerotic, 922 development of, 953 progression of, 954 Plaque-forming cells (PFCs), 6 PLAs. See Platelet-leukocyte aggregates
Plasminogen activator inhibitor (PAI), 994 Platelet-activating factor (PAF), 108 Platelet-derived growth factor (PDGF), 829, 838–839, 841, 953 Platelet-leukocyte aggregates (PLAs), 964 Platelets ACS and, 968 depression and, 962 inflammation and, 968 stress and, 964 in wound healing, 838 PLC. See Phospholipase C PLD. See Phospholipase D Pleasure, 761 Pleiotropic transcription factor, 137 PMA. See Phorbol myrisate acetate PMN. See Polymorphonuclear cells PMR. See Progressive muscle relaxation Pneumococcal meningitis, 438–439 Pneumonia, vaccination for, 906 Pollen, 803 Polymerase chain reaction after reverse transcription (RT-PCR), 291, 294 Polymorphisms, Alzheimer’s disease and, 364 Polymorphonuclear cells (PMN), 65, 68–69, 71–72 alcohol and, 52 Polyol, 998 POMC. See Pro-opiomelanocortin POMS. See Profile of Mood States Positive affect (PA), 624–625, 761 asthma and, 771 emotional states of, 766 emotional traits of, 767 exercise and, 771 hepatitis B and, 768 immunity and, 771–772 morbidity and, 768–770 mortality and, 769 NKCC and, 767 sleep and, 771 as stress buffer, 772 survival and, 770–771 tobacco and, 771 URTI and, 770 Positive and Negative Affect Schedule (PANAS), 762 Positron-emission tomography (PET), 437 Post-traumatic stress disorder (PTSD), 451, 452 CAs and, 541 chronic disease and, 531 CMI and, 535
1263 of combat veterans, 490 cortisol and, 539–540 cytokines and, 535–537 diabetes and, 531 diagnosis of, 532–533 DTH and, 535 endocrine-immune interactions and, 542–543 GCs and, 540 GR and, 540 HPA and, 539 IL-6 and, 536 immunity and, 543 leukocytes and, 537 lymphocytes and, 537 morbidity and, 531 NK and, 537 noradrenergic receptors and, 542 RA and, 531 SAM and, 541–542 sleep and, 538 sympathetic nervous system and, 534 trauma and, 531–532 Post-viral fatigue syndrome, 663 PPAR. See Peroxisome proliferatoractivated receptor Prednisolone, RA and, 198 Pre-ejection period (PEP), 912 Pregnancy antibodies and, 459–461 autoimmunity and, 211–214 bacteria and, 464 estrogen and, 212 HPA and, 711 HSV and, 461 IL-1 and, 458–459 miscarriage and, 457 NK and, 457 PRL and, 212 progesterone and, 211 SLE and, 212 stress during, 711 systemic lupus erythematosus and, 212 TNF and, 458–459 viral infections and, 459 Prion diseases, 270 PRL. See Prolactin Probucol, 937 Prodynorphin, 161 Proenkephalin (PENK), 161 in immune cells, 162 Profile of Mood States (POMS), 762, 767, 768 Progesterone, 207, 211 pregnancy and, 211, 458 wound healing and, 829
1264
Subject Index
Progressive muscle relaxation (PMR), 683, 687 Prolactin (PRL), 18, 171, 200–201, 222, 241, 604 pregnancy and, 212 sleep and, 603 Proliferative phase stress and, 845 of wound healing, 840, 844–845 Pro-opiomelanocortin (POMC), 2, 15, 161, 293 in immune cells, 162 Prostaglandin E2 (PGE2), 85, 87, 274, 320, 329 central production of, 321–322 as immune system-brain link, 319 Prostaglandin receptors, 268 Prostaglandins (PGs), 286, 320, 432 cytokines and, 274, 294 IL-1 and, 358 sickness behavior and, 295 surgery and, 257 Prostate cancer, 693 Prostate-specific antigen (PSA), 693, 877 Proteases, inflammation and, 271 Protein kinase C (PKC), 998–999 Proteoglycans, 950 Pruritus, atopic dermatitis and, 976–977 PSA. See Prostate-specific antigen P-selectin, 163, 954 Pseudomonas aeruginosa, 68 Psychological resilience, 747 Psycho-physiological states, 748 Psychosis, influenza and, 277 Psychosomatic medicine, 917 PTSD. See Post-traumatic stress disorder Purkinje cells, 292 Pustules, 805 PVH. See Paraventricular hypothalamic nucleus PVMs. See Perivascular macrophages PVN. See Paraventricular nucleus
Q Quality of life (QOL), 675, 761 cancer and, 692, 694 immunity and, 885–886
R RA. See Rheumatoid arthritis Radiation therapy, 692 RAGE. See Receptor of advanced glycation end products Raphe pallidus nucleus (RP), 326
Rapid eye movement (REM), 330, 331, 514, 581 discovery of, 580 Rapidly progressive periodontitis (RPP), 536 Rat mast cell protease (RMCP), 647 Raynaud disease, 93, 826 Reactive nitrogen species (RNS), 8 Reactive oxygen species (ROS), 8, 353, 383, 998 exercise and, 669 Recall, 635, 639–640 Received support, 787 Receptor of advanced glycation end products (RAGE), 998 Receptors adrenergic, 65–66 shared, 41 Relapsing remitting (RR) MS, 1107 Relaxation therapy, 814 cancer and, 877 Religious services, 782 HIV and, 1060 REM. See Rapid eye movement Remodeling phase stress and, 846 of wound healing, 840, 846 Reptiles, 20–22 Rest interval, 632, 639 Rhadinovirus, 1079 Rheumatoid arthritis (RA), 41, 817 aging and, 219 animal models of, 196–197 as autoimmune disease, 143 calcitonin gene-related peptide and, 200 CBSM and, 687 contraceptives and, 199 cytokines and, 194 depression and, 198–199, 509 endocrine system and, 193 estrogen and, 197, 199 HPA and, 197–198 interpersonal stress and, 788 marriage and, 784 nervous system and, 193 obesity and, 1003 parasympathetic nervous system and, 200 prednisolone and, 198 PTSD and, 531 sex hormones and, 199 sleep and, 609 stress and, 198, 733 substance P and, 200 sympathetic nervous system and, 76, 199–200 symptoms of, 193 testosterone and, 208
vasoactive intestinal peptide and, 200 Rhinitis. See Allergic rhinitis Rhinovirus, 806 RMCP. See Rat mast cell protease RNS. See Reactive nitrogen species ROS. See Reactive oxygen species Roseolovirus, 1079 RP. See Raphe pallidus nucleus RPP. See Rapidly progressive periodontitis RR. See Relapsing remitting MS RT-PCR. See Polymerase chain reaction after reverse transcription Rubella, 504, 567
S S100B, 565–566 SAA. See Serum amyloid A protein SAM. See Sympathetic-adrenalmedullary system SAPK. See Stress-activated protein kinase Scarring, 825, 828 neutrophils and, 846 SCE. See Sister chromatid exchange SCF. See Stem cell factor Schizophrenia, 451 autoimmune process and, 566, 572 BBB and, 568 cytokines and, 277, 569–571 EBV and, 567 fetal development and, 712 HSV and, 566 immunity and, 563 infection and, 571–572 leukocytes and, 569 NK and, 569 Th1 and, 572–573 Seafood, 803 Secretin, 583 Secretory immunoglobulin A (slgA), 762, 765 Secretory leukocyte protease inhibitor (SLPI), 54 Selenium, 668 Self-conscious emotions, 624 Self-esteem, 761 atopic dermatitis and, 805 social support and, 790 Semliki Forest virus, 1108 Sepsis, 91 GCs and, 738 obesity and, 1002 Septic shock syndrome, 146–147 Serotonin (5HT), 112, 521 IFN and, 521
Subject Index IL-1 and, 521 sleep and, 583 Sertraline, 514 Serum amyloid A protein (SAA), 435 SES. See Socioeconomic status SET. See Supportive-expressive therapy Sex hormones autoimmune diseases and, 207–208 metabolism of, 208 periodontal disease and, 830 RA and, 199 wound healing and, 828–830 Sexual behavior, sickness and, 284 SF. See Synovial fluid SgIGSF. See Spermatogenic Ig superfamily Shame, 624 Shortness of breath, 922 SICAM. See Soluble intercellular adhesion molecule Sickness behavior, 184–185, 431, 682 acute infectious disease and, 223 brain aging and, 380 cancer and, 693–694 changes with, 432 cytokines and, 268, 294, 339, 384, 518, 621 depression and, 518 diet and, 303 IGF and, 185 motivational state and, 285 PGs and, 295 reversibility of, 282 sex and, 284 symptoms of, 519 TNF and, 185 Silencer of Death Domain (SODD), 177 Simian B virus, 490 Simian immunodeficiency virus (SIV), 1056, 1058, 1062, 1063 SIRS. See Systemic inflammatory response syndrome Sister chromatid exchange (SCE), 883 SIV. See Simian immunodeficiency virus Skin, 113 Skinner box, 297 SLE. See Systemic lupus erythematosus Sleep, 330–331. See also Insomnia ACh and, 583 ACTH and, 589, 601 aging and, 606–607 AIDS and, 586 alcohol and, 607–609 apnea, 587–588 AR and, 805
CAs and, 601–603 circadian rhythms and, 581 cortisol and, 589 CRH and, 601 DA and, 583 decrease in, 579 depression and, 516, 517, 607 deprivation of, 595–600 disordered, 606 EBV and, 585–586 GH and, 601, 603 GR and, 604 histamine and, 583 HIV and, 585 HPA and, 589 IL-1 and, 584, 588 IL-6 and, 518, 588, 591 immunity and, 517, 595–600 infections and, 579–580, 584–586, 600–601 interferon (IFN) and, 584, 591 latency in, 579 lymphocytes and, 598 monophasic, 581 mortality and, 579 NE and, 583 neuroendocrine mechanisms of, 601–605 NK and, 598 PA and, 771 polyphasic, 581 PRL and, 603 problems with, 452, 579 PTSD and, 538 RA and, 609 serotonin and, 583 sICAM and, 518 slow-wave, 580, 587 stress and, 913–914 TNF and, 588 vapors and, 583 Sleeping sickness, 585, 586 SlgA. See Secretory immunoglobulin A Slow-wave sleep (SWS), 580 IL-1 and, 587 SLPI. See Secretory leukocyte protease inhibitor Smallpox, 898 SMI. See Stress-management intervention Smoking. See Tobacco SNS. See Sympathetic nervous system Soap, 805 Social disruption (SDR), 1103 GCs and, 1114–1115 IL-6 and, 1115 neonates and, 1118 TMEV and, 1112–1114, 1116–1118
1265 Social dominance. See also Dominance infectious illness and, 486 instability in, 483–484 morbidity and, 492 Social exchange theory, 788 Social gradient, 498 Social integration, 781 gender and, 783 interventions for, 791–792 intimacy and, 787–788 loneliness and, 787–788 network size in, 782–783 Social reorganization (SRO), 486–487, 1103 Social support. See Social ties Social systems, 450 Social ties, 781, 785–788, 904 cancer and, 786, 872–873, 875–876 CHD and, 948–949 DTH and, 783, 876 fibrinogen and, 962 HIV and, 1062 negative aspects of, 788–791 Socioeconomic status (SES), 450–451, 497–498 anemia and, 466–467 asthma and, 501–502 blood pressure and, 966 CAD and, 929 CHD and, 947, 961 chronic stress and, 503 coping mechanisms and, 500 CRP and, 961 cytokines and, 504 determinants of, 498 diet and, 950 dominance and, 491 EBV and, 501 exercise and, 950 fibrinogen and, 961 health and, 498 IL-6 and, 961 immune functions and, 498–500 inflammation and, 960 measurement of, 500 social ties and, 785 stress and, 499 tobacco and, 950 vaccination and, 504 SODD. See Silencer of Death Domain Soluble intercellular adhesion molecule (sICAM), 511 depression and, 607 Soluble TNF receptors (sTNFR), 594 SOM. See Somatostatin Somatic motor system, 86 Somatostatin (SOM), 100, 107 Soy, 803 SP. See Substance P
1266 Space flight catecholamines and, 854 DTH and, 855 EBV and, 856 environment for, 852 HSV and, 856 immunity and, 854–856 neutrophils and, 855 NK and, 855 stress and, 853 white blood cells and, 855 Spermatogenic Ig superfamily (SgIGSF), 110 Spermine, 85 SPG. See Sucrose-potassium phosphate-glyoxylic acid-induced Spleen HSP in, 1020–1021 immune activation of, 40 Splenic anti-sheep red blood cells (SRBC), 6, 20, 481 Splenocytes, 1103 Sprouting, 161 SRBC. See Splenic anti-sheep red blood cells SRO. See Social reorganization Staphyloccocus aureus, 803, 828, 843 State PA, 762 Stem cell factor (SCF), 109 Steroids, 20–21 Stimulation tests, 540, 541–542 STNFR. See Soluble TNF receptors Stress, 761. See also Anger; Anxiety; Depression acoustic, 1081 ACTH and, 196 acute, 680–681, 723, 724–726, 744– 745, 816 acute vs. chronic, 112–113 as adaptive response, 724–726 allergies and, 812 anesthesia and, 729 animal models and, 238 anxiety and, 966 AR and, 812–813 asthma and, 812–813 atopic dermatitis and, 813, 918, 975, 978–979 brain and, 710 cancer and, 233, 234–235, 734, 869 caregivers and, 910 chemotherapy and, 875 cholesterol and, 967–968 chronic, 196, 503, 681, 694, 723, 744– 745, 816 CMI and, 731–732 cognitive function and, 637 cold as, 1035 CORT and, 1036
Subject Index cortisol and, 235, 884, 912 cumulative, 499 cytokines and, 694, 963 definition of, 195 depression and, 716–717, 966 diabetes and, 715–716 DNA repair and, 883 in early life, 713 eHSP and, 1015–1118, 1019, 1026–1027 enhancement from, 731–733, 742–747 environmental, 19, 27 eosinophil and, 984–985 epinephrine and, 235 ER and, 999 fibrinogen and, 961–962 financial, 947 GCs and, 357–358 by group, 491 HDL and, 964 hepatitis B and, 907 HIV and, 1060, 1061 homeostasis and, 1036, 1080 hostility and, 966 HPA and, 826, 853, 917, 1080, 1098 HSP and, 1013, 1014 HSV and, 1078, 1086–1088, 1089, 1111 hypertension and, 716, 966 immune response and, 56, 637 immunity and, 881 inflammation and, 680–681 inflammatory phase and, 842 influenza and, 908, 1099–1103 LDL and, 964 leukocytes and, 726–731, 963 life experiences and, 503 loss of job as, 476 MS and, 1107, 1110–1111 NK and, 874 NO and, 1026 norepinephrine and, 235 PA and, 772 pain and, 165 paradoxes with, 726 from physical restraint, 1081 physiological, 816 platelets and, 964 poverty as, 476 during pregnancy, 711 prenatal, 465 proliferative phase and, 845 psychological, 816 RA and, 198, 733 remodeling phase and, 846 response to, 195–196, 235 from restraint, 1100 SAM and, 912, 983–984 from SDR, 1081 SES and, 499
sleep and, 913–914 SNS and, 826, 964–965, 1098 socioeconomic status and, 499 space flight and, 853 from SRO, 1081 as stimulant, 723 with surgery, 255 Th1 and, 811–812 Th2 and, 811–812 vaccination and, 899–900, 903, 907, 909 viral activation and, 883 viral susceptibility and, 486 weight management and, 715 from work, 947–948, 962–963 in workplace, 717 wound healing and, 827–828 Stress hormones, 236 space flight and, 853, 862 Stress management, cancer and, 877 Stress responses, 686 Stress spectrum, 747–748 Stress-activated protein kinase (SAPK), 175 Stress-management intervention (SMI), 909 Stroke, 416, 420–421 MI and, 946 Subdiaphragmatic vagus nerve, 100 Substance abuse childhood development and, 713 coping with, 913 depression and, 516 disease and, 549 Substance P (SP), 40, 42, 97, 101, 109, 131, 195, 223, 855 in GI tract, 107, 115 inflammation and, 110 in lungs, 107 as neurotransmitter, 103 RA and, 200 skin and, 113 Sucrose-potassium phosphateglyoxylic acid-induced (SPG), 6 Sulfur dioxide, 804 Supportive-expressive therapy (SET), 687–688 with cancer patients, 692 Surgery, 691 cell-mediated immunity and, 257–258 for esthetics, 832 hypothalamic-pituitary-adrenal gland axis and, 254 metastasis and, 253 natural killer (NK) cells and, 254–257 PGs and, 257 stress with, 255
Subject Index SWS. See Slow-wave sleep Sympathetic nervous system (SNS), 64, 86, 207, 254 acute mental arousal and, 933–934 depression and, 515 fight or flight response and, 620 HPA and, 228 immunity and, 605, 1035 RA and, 199–200 stress and, 826, 964–965, 1098 Sympathetic-adrenal-medullary (SAM) system, 677 atopic dermatitis and, 975, 983 CNS and, 980 inflammation and, 983 lymphocytes and, 934 PTSD and, 541–542 stress and, 912, 983–984 TSST and, 983 Synaptic cell adhesion molecule (SynCAM), 109–110 SynCAM. See Synaptic cell adhesion molecule Synchronization, of systems, 224 Synovial fluid (SF), 207, 209 Systemic inflammatory response syndrome (SIRS), 181 Systemic lupus erythematosus (SLE), 207 cytokines and, 213 pregnancy and, 212
T T helper cells, 56, 139, 569 T lymphocytes, 106–107 T regulatory cells (Treg), 99 T suppresser cells, 569 TAAs. See Tumor-associated antigens Tachykinins. See Neurokinin A; Neurokinin B; Substance P TBI. See Traumatic brain injury T-cells, 66, 73, 651 activation of, 139, 735 adaptive immunity and, 69–70 autoimmune activation of, 40 depression and, 512 differentiation of, 140 HIV and, 74 recruitment of, 142 Temperament, 484–485 Temporomandibular joint disorders, 93 Testosterone, 21, 207 RA and, 208 wound healing and, 829 Tetanous toxoid (TT), 484 TGF. See Transforming growth factors TH. See Tyrosine hydroxylase
Th1. See Type 1 helper cells Th2. See Type 2 helper cells Theiler’s murine encephalomyelitis virus (TMEV), 1092, 1109 GCs and, 1114–1115 immune response to, 1109–1110 MS and, 1109 SDR and, 1112, 1114–1115, 1116–1118 Theiler’s virus-induced demyelination (TVID), 1110 Theophylline, 807 Thiazolidinediones (TZDs), 1000 Thrombolysis, 945 Thymus, development of, 461–462 Thyroid hormone deficiency, 24 Thyroid stimulating hormone (TSH), 603 Thyrotropin-releasing hormone (TRH), 24 Thyroxine, 17 TLR. See Toll-like receptors TMEV. See Theiler’s murine encephalomyelitis virus TNCB. See Trinitrochlorobenzene TNF. See Tumor necrosis factor Tobacco, 499. See also Environmental tobacco smoke; Nicotine AR and, 805 CAD and, 921, 929 cancer and, 870 CHD and, 946 death and, 452 depression and, 516, 870 heart disease and, 714 IL-6 and, 516 NK cells and, 516 PA and, 771 SES and, 950 white blood cells and, 516 Toll-like receptors (TLR), 46, 87, 98, 135, 272, 274, 282, 320, 924–925, 959 eHSP and, 1024–1025 Topical steroids, 806 Trait PA, 761–762 Transcription factors, 50, 54 Transforming growth factors (TGF), 838–839, 841–842 Transfusions, 256, 258, 880 Transient ambulatory ischemia, 933 Transient receptor potential (TRP), 102 Transmissible spongiform encephalopathies (TSEs), 440 Transrepression, of genes, 51 Trauma, PTSD and, 531–532 Traumatic brain injury (TBI), 416, 420–421 Treg. See T regulatory cells
1267 TRH. See Thyrotropin-releasing hormone Trials, 632 Trier Social Stress Test (TSST), 963, 981, 982 ACTH and, 982 cortisol and, 982 SAM and, 983 Trier Social Stress Test for Children (TSST-C), 981 Triiodothyronine, 17, 24 Trinitrochlorobenzene (TNCB), 70 TRP. See Transient receptor potential Trypanosomes, 585 Tryptophan, depression and, 521 TSC. See Tuberous sclerosis TSEs. See Transmissible spongiform encephalopathies TSH. See Thyroid stimulating hormone TSST. See Trier Social Stress Test TSST-C. See Trier Social Stress Test for Children TT. See Tetanous toxoid Tuberous sclerosis (TSC), 177 Tumor(s) angiogenesis and, 881 inflammation and, 881 natural killer cells and, 256 stress and, 260–261 windows of opportunity with, 880 Tumor cells adhesion to, 239 cell-mediated immunity and, 253 cortisol and, 885 hormones and, 241 migration of, 240 norepinephrine and, 240 Tumor escape mechanisms, 879 Tumor necrosis factor (TNF), 85, 92, 177, 209, 240, 267, 282, 365–366, 571, 682 adipose tissue and, 994, 995 BBB and, 338 fever and, 282 heart disease and, 923 hostility and, 962 HPA and, 933 memory and, 342, 350–353 neural plasticity and, 357 pro-inflammatory, 337 sickness behavior and, 185 signaling of, 178, 338 sleep and, 588 Tumor-associated antigens (TAAs), 252 TVID. See Theiler’s virus-induced demyelination
1268
Subject Index
Type 1 helper cells (Th1), 570, 572–573, 586–588 schizophrenia and, 572–573 stress and, 811–812 Type 2 helper cells (Th2), 570, 586–588 stress and, 811–812 Type C personality, 871 Type D personality, 969 Typhoid, 910 Tyrosine hydroxylase (TH), 12, 642 TZDs. See Thiazolidinediones
U Ucn. See Urocortin Ultraviolet B (UVB) radiation, 113 Unconditioned stimulus (US), 631 Upper respiratory tract infection (URTI), 661, 694 AR and, 806 exercise during, 668 frequency of, 662 PA and, 770 Upregulation, 161 Urinary tract, 117 Urocortin (Ucn), 117 URTI. See Upper respiratory tract infection US. See Unconditioned stimulus UV radiation, as environmental stressor, 53 UVB. See Ultraviolet B radiation
V Vaccination for AIDS, 1065 anger and, 907 anxiety and, 907 caregivers and, 1111 cortisol and, 912 depression and, 907 for hepatitis B, 902, 904–905, 906–907 for HSV, 1083, 1088–1089 immune outcome with, 898–899 immune response to, 897 for influenza, 902, 903 for meningitis C, 905 mood and, 910 mutation with, 898 New Caledonian viral strain and, 903–904 for overseas travel, 910 for pneumonia, 906 response to, 694 SES and, 504 for smallpox, 898
stress and, 899–900, 903, 907, 909 for typhoid, 910 Vagotomy, 288 LPS and, 289 Vagus nerve ACTH and, 87 anatomy of, 86–87 cytokines and, 194 electrical stimulation of, 89 immune signals and, 320 sensory role of, 88 Valacyclovir, 1089 Vanilloids, 109 Variable number of tandem repeat (VNTR), 364–365 Varicella-Zoster virus (VZV), 859–860, 1078 Vascular cell adhesion molecule-1 (VCAM-1), 46 influenza and, 1100 Vascular endothelial growth factor (VEGF), 223, 224, 240, 261, 679, 692–693, 786, 842 adipose tissue and, 994 angiogenesis and, 881–882 dendritic cells and, 240 wound healing and, 829 Vasoactive intestinal peptide (VIP), 40, 97, 99, 100, 103, 107, 810, 855 autoimmunity and, 143 discovery of, 131 hematopoiesis and, 139 by immune cells, 133 immunoregulatory effects of, 135 inflammation and, 195 in lymphoid organs, 132 neuronal, 132 RA and, 200 receptor cells and, 134 T-cell activation and, 139 Vasoconstriction, wound healing and, 827 Vasopressin (VP), 300 castration and, 300 VCA. See Virus capsid antigen VCAM, 91 VCAM-1. See Vascular cell adhesion molecule-1 VEGF. See Vascular endothelial growth factor Venlafaxine, 514, 515 Ventrolateral medulla (VLM), 322 Ventrolateral preoptic area (VLPO), 330 Ventromedial pre-optic area of hypothalamus (VMPO), 293, 322, 323, 324, 327 VIP. See Vasoactive intestinal peptide Viral infection, CAD and, 927–928
Viral oncogenesis, 236 Virus capsid antigen (VCA), 856 Visna virus, 1108 Vitamin A, 668 Vitamin B6, 668 Vitamin C, 665–666, 668, 669, 815 Vitamin E, 668, 669–670, 815 coronary disease and, 937 VLM. See Ventrolateral medulla VLPO. See Ventrolateral preoptic area VMH. See Hypothalamic ventromedial nucleus VMPO. See Ventromedial pre-optic area of hypothalamus VNTR. See Variable number of tandem repeat Von Willebrand factor, 957 VP. See Vasopressin VPAC, 134 Vulnerability, 499, 501 immunity and, 498 SES and, 502 to viruses, 503–504 VZV. See Varicella-Zoster virus
W Water maze, 340–341 Weight management, stress and, 715 Wheat, 803 White blood cells. See also Leukocytes depression and, 510 space flight and, 855 tobacco and, 516 Wool, 805 Worry, 623 Wound healing, 223, 694 aging and, 825, 831–832 androgen and, 828–829 bacteria and, 828 catecholamines, 826–827 and chemokines and, 840–841 cytokines and, 841 dermal, 830–831 EP and, 827 estrogen and, 828–829 GCs and, 826, 843 gender and, 825, 830 hemostasis in, 838 inflammatory phase of, 837–840 macrophages and, 839 menopause and, 829 mucosal, 830–831 neutrophils and, 839 obesity and, 1002 oxygen, 827 and perfection of, 825, 832 platelets in, 838 progesterone, 829 and
1269
Subject Index proliferative phase of, 837, 840 remodeling phase of, 837, 840 scarring and, 825, 828 sex hormones, 828–830 and stress and, 827–828 testosterone, 829 and vasoconstriction and, 827 VEGF and, 829
Y Yellow fever, 910 Yoga, 688 cancer and, 877
Z Zafirlukast, 807 Zinc, 668